NAC and Glycine Prevents Decline of Aging and Prolongs Lifespan

NAC and Glycine Prevents Decline of Aging and Prolongs Lifespan by Jeffrey Dach MD

Over age of 50, we may experience age related fatigue, loss of muscle mass, slower recovery from injuries, brain fog, and greater risk for diabetes, cardiovascular disease, and inflammation. In previous newsletters, I have discussed Bioidentical Hormone replacement as our main way to prevent this decline. However, much of this aging process is due to reduced production Glutathione (GSH), our major intracellular anti-oxidant, which protects our cells from oxidative damage, supports energy production in mitochondria, reduces inflammation, and helps detoxify harmful substances.

Header Image: Nine mainhallmarks of biological aging: genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, deregulated nutrient sensing, mitochondrial dysfunction, cellular senescence, stem cell exhaustion, altered intercellular communication.Source: Author: Rebelo-Marques, De Sousa Lages, Andrade, Ribeiro, Mota-Pinto, Carrilho and Espregueira-Mendes. Courtesy of Wikimedia Commons. CC 4.0.

What is the Good News? Glycine and NAC.

The good news is we have two safe amino acid supplements, Glycine and N-acetylcysteine (NAC) which act synergistically. When used together, they restore glutathione levels, correct many age-related cellular problems, and give us improved vitality and sense of well being. This combination provides the two rate-limiting building blocks, glycine and cysteine, needed for us to make our own glutathione. Glycine also plays extra roles in DNA repair, methylation, and other processes, while cysteine supports mitochondrial energy pathways.

This combination of GlyNAC is synergistic, meaning faster and more complete benefits than taking either alone or trying to supplement glutathione directly.¹,⁴,⁵

Evidence from Animal Studies

Longevity Increased 24 Per Cent!

In mice, GlyNAC supplementation corrected glutathione deficiency, lowered oxidative stress, improved mitochondrial function, fixed problems with cellular cleanup (mitophagy), improved nutrient sensing, and reduced DNA damage. Remarkably, older mice given GlyNAC lived 24% longer than untreated controls.

Another study showed GlyNAC reversed age-related cognitive decline in old mice by restoring brain glutathione, reducing brain inflammation and oxidative stress, improving glucose uptake and mitochondrial health, and boosting protective neurotrophic factors. These findings suggest GlyNAC targets root causes of aging at the cellular level.²,⁶

Strong Evidence from Human Studies:

Clinical Trials in Older Adults Human studies, led by researchers at Baylor College of Medicine, provide compelling proof-of-concept.

In a 2021 pilot trial, older adults (around age 70) took GlyNAC for 24 weeks. They experienced restored glutathione levels, reduced oxidative stress, better mitochondrial function, lower inflammation and insulin resistance, improved blood vessel health, stronger grip, faster walking speed, better exercise capacity, sharper cognition, and reductions in body fat and waist size. Benefits faded after stopping supplementation, confirming the effect was due to GlyNAC.³

A larger 2023 randomized, double-blind, placebo-controlled trial confirmed these results. Older adults took 100 mg/kg/day of each glycine and NAC (about 7 grams each daily for a 70 kg person) for 16 weeks.

Key improvements included:

Glutathione levels increased dramatically (up to 225% in red blood cells) –

Oxidative stress markers dropped 70%+

Inflammation markers (IL-6, TNF-α, hsCRP) reduced 41–78%

Better physical function including improved gait speed, strength, 6-minute walk test with some measures actually returning to that of matched younger adults. There was improved insulin sensitivity, blood pressure, waist circumference and correction of multiple “hallmarks of aging”, mitochondrial dysfunction, inflammation, genomic instability, and cellular senescence.

Improvements started within 2 weeks and grew stronger over time. The supplement was safe and well-tolerated.⁷,⁸

Benefits Beyond Aging Because GlyNAC addresses oxidative stress, mitochondrial health, and inflammation, it shows promise in other areas:

Type 2 Diabetes

A pilot study found GlyNAC improved mitochondrial fat burning and lowered insulin resistance.⁹

Type 1 Diabetes (animal models)

NAC helped protect skeletal muscle, heart tissue, nerves, retina, and reduced inflammation and thrombosis.

Chronic kidney disease

NAC (a key part of GlyNAC) slowed progression of chronic kidney disease in meta-analysis reviews and human cohort studies.

Cardiovascular health

NAC reduces oxidative damage and inflammation linked to atherosclerosis, heart injury, and surgical complications.

Lung conditions

NAC is a mucolytic and is already used for COPD, cystic fibrosis, and other chronic respiratory diseases due to its antioxidant and mucolytic effects.

Nerve protection and injury

Animal data show GlyNAC reduces oxidative stress (OxS) after spinal cord injury and supports nerve health in diabetes.

Glycine and NAC for the Nine Hallmarks of Aging

The nine hallmarks of aging driving age-related decline are outlined in the widely cited 2013 study by by López-Otín. GlyNAC primarily acts upstream to these nine factors by addressing GSH deficiency and OxS (Oxidative Stress). Reference: López-Otín, C., Blasco, M. A., Partridge, L., Serrano, M., & Kroemer, G.(2013). The hallmarks of aging153(6), 1194–1217.

Key Human Evidence

Key human evidence comes from a 2022 randomized, double-blind, placebo-controlled trial (published 2023) showing 16 weeks of GlyNAC supplementation (100 mg/kg/day each of glycine and NAC) in older adults reversed multiple defects toward youthful levels. Here’s a breakdown of GlyNAC’s documented impacts on the hallmarks, with inline citations to primary sources:

1. Genomic instability: GlyNAC reduces genomic damage (e.g., genotoxicity markers) by lowering OxS and boosting GSH, which shields DNA from reactive oxygen species (ROS). Improvements in genomic damage were noted in human trials

Kumar, Premranjan, et al. “Supplementing glycine and N-acetylcysteine (GlyNAC) in older adults improves glutathione deficiency, oxidative stress, mitochondrial dysfunction, inflammation, physical function, and aging hallmarks: a randomized clinical trial.” The Journals of Gerontology: Series A 78.1 (2023): 75-89. https://pubmed.ncbi.nlm.nih.gov/35975308/

2. Telomere attrition: Direct evidence is limited in human GlyNAC studies, but reduced overall OxS and cellular protection could indirectly support telomere maintenance.

3. Epigenetic alterations: Not a primary endpoint, though benefits via lowered inflammation and improved mitochondrial health may contribute indirectly.

4. Loss of proteostasis: GlyNAC enhances proteostasis by improving mitochondrial function and reducing OxS, aiding protein quality control and folding. Reference: BCM news on reversing hallmarks of aging: https://www.bcm.edu/news/glynac-supplementation-reverses-aging-hallmarks-in-aging-humans

5. Deregulated nutrient sensing: GlyNAC corrects abnormalities in nutrient-sensing pathways (e.g., improved insulin sensitivity and metabolic regulation), addressing insulin resistance common in aging. reference: https://pmc.ncbi.nlm.nih.gov/articles/PMC9879756/
BCM blog August 23, 2022: https://blogs.bcm.edu/2022/08/23/from-the-labs-glynac-reverses-aging-hallmarks-in-older-adults/

6. Mitochondrial dysfunction: Among the strongest effects: GlyNAC significantly boosts mitochondrial fatty-acid oxidation, energy production, biogenesis, and function while correcting GSH-linked damage. This hallmark improved markedly in the RCT. ([PubMed 35975308](https://pubmed.ncbi.nlm.nih.gov/35975308/); [BCM announcement](https://www.bcm.edu/news/glynac-supplementation-reverses-aging-hallmarks-in-aging-humans)).

7. Cellular senescence: Indirect benefits via reduced inflammation (“inflammaging”) and OxS; studies show lowered pro-inflammatory cytokines like IL-6, TNF-α, and hsCRP. Reference: https://pubmed.ncbi.nlm.nih.gov/35975308/

8. Stem cell exhaustion: Not directly quantified in most trials, but overall reductions in damage and improved cellular health support stem cell maintenance. https://pmc.ncbi.nlm.nih.gov/articles/PMC9879756/

9. Altered intercellular communication: GlyNAC reduces chronic inflammation—a core driver—by lowering cytokines and improving endothelial function ([BCM news](https://www.bcm.edu/news/glynac-supplementation-reverses-aging-hallmarks-in-aging-humans). https://pubmed.ncbi.nlm.nih.gov/35975308/

In the 2022-2023 RCT, GlyNAC improved at least 7 of the nine hallmarks of aging, alongside better physical function (muscle strength, gait speed), cognition, body composition, and metabolic health. References:

https://pubmed.ncbi.nlm.nih.gov/35975308/

https://pmc.ncbi.nlm.nih.gov/articles/PMC9879756/)).

Earlier pilot trials showed similar reversals of age-related defects after 24 weeks. Clinical and Translational Medicine, 2021: https://onlinelibrary.wiley.com/doi/full/10.1002/ctm2.372

Preclinical mouse studies provide additional context:

GlyNAC extended lifespan by 24% while correcting GSH deficiency, OxS, mitochondrial dysfunction, abnormal mitophagy, nutrient sensing issues, and genomic damage—further supporting its role in addressing aging biology. References: Nutrients 2022 mouse study:
https://www.mdpi.com/2072-6643/14/5/1114
BCM mouse lifespan news:https://www.bcm.edu/news/glynac-supplementation-extends-life-span-in-mice.

Kumar, Premranjan, et al. “Supplementing Glycine and N-Acetylcysteine (GlyNAC) in Older Adults Improves Glutathione Deficiency, Oxidative Stress, Mitochondrial Dysfunction, Inflammation, Physical Function, and Aging Hallmarks: A Randomized Clinical Trial.” The Journals of Gerontology: Series A, vol. 78, no. 1, Jan. 2023, pp. 75–89. PubMed,

https://doi.org/10.1093/gerona/glac135.

(covers every instance of BCM news on reversing hallmarks, BCM announcement, and BCM news)

Shalchi, Homa. “GlyNAC Supplementation Reverses Aging Hallmarks in Aging Humans.” Baylor College of Medicine, 17 Aug. 2022, www.bcm.edu/news/glynac-supplementation-reverses-aging-hallmarks-in-aging-humans. Accessed 17 Mar. 2026.BCM blog post

(covers the single instance of BCM blog)

Rodríguez, Ana María. “GlyNAC Reverses Aging Hallmarks in Older Adults.” Baylor College of Medicine Blogs, 23 Aug. 2022, blogs.bcm.edu/2022/08/23/from-the-labs-glynac-reverses-aging-hallmarks-in-older-adults/.

GlyNAC was safe and well-tolerated in these studies, with benefits declining after discontinuation—suggesting ongoing supplementation may be needed.

Practical Dosing and Where to Find Quality Supplements

The successful human trials used 100 mg/kg/day of each of glycine and NAC. For a 70 kg (154 lb) person, that’s roughly 7 grams per day of each. Powder forms make high doses easier and more affordable than dozens of capsules. This reputable brand is known for purity, third-party testing, and clinician trust:

Buy glycine and NAC from Pure Encapsulations: Hypoallergenic, professional-grade. The combined NAC + Glycine powder is currently out of stock. You can buy separately:

Buy NAC from Pure Encapsulations

Buy Glycine from Pure Encapsulations

Always consult your doctor before starting Gycine/NAC, especially if you have medical conditions, take medications, or are pregnant/breastfeeding.

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Conclusion: Supplementing with Glycine and NAC gives your body the building blocks to make more glutathione, reversing cellular signs of aging, boosting energy and ability to function, and improves well being and vitality. For anyone over 50 interested in healthy aging, GlyNAC stands out as one of the most evidence-based, affordable, and straightforward nutritional strategies available.

Jeffrey Dach MD
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References:

1. Kumar P, Osahon OW, Sekhar RV. GlyNAC supplementation in mice increases length of life… *Nutrients*. 2022;14(5):1114.

2. Kumar P, et al. GlyNAC supplementation in old mice improves brain glutathione… *Antioxidants*. 2023;12(5):1042.

3. Kumar P, et al. Glycine and N-acetylcysteine (GlyNAC) supplementation in older adults… pilot clinical trial. *Clin Transl Med*. 2021;11(3):e372.

4. Sekhar RV, et al. Deficient synthesis of glutathione underlies oxidative stress in aging… *Am J Clin Nutr*. 2011;94(3):847-853.

5. Sekhar RV, et al. Glutathione Synthesis Is Diminished in Patients With Uncontrolled Diabetes… *Diabetes Care*. 2011;34(1):162-167.

6. Additional mouse lifespan and brain health details from Kumar et al. (2022) and related reviews.

7. Kumar P, et al. Supplementing glycine and N-acetylcysteine (GlyNAC) in older adults… randomized clinical trial. *J Gerontol A Biol Sci Med Sci*. 2023;78(1):75-89.

8. Natural Health Research summary of Kumar et al. 2023 RCT (April 2024). 9. Sekhar RV. GlyNAC supplementation improves impaired mitochondrial fuel oxidation… in type 2 diabetes: pilot study. *Antioxidants*. 2022;11(1):154.

Links and references:

glycine and N acetylcysteine

Mouse Study: 2022 Prolongs life span.

Kumar, Premranjan, Ob W. Osahon, and Rajagopal V. Sekhar. “GlyNAC (glycine and N-acetylcysteine) supplementation in mice increases length of life by correcting glutathione deficiency, oxidative stress, mitochondrial dysfunction, abnormalities in mitophagy and nutrient sensing, and genomic damage.” Nutrients 14.5 (2022): 1114.

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1002/ctm2.372
Kumar, Premranjan, et al. “Glycine and N‐acetylcysteine (GlyNAC) supplementation in older adults improves glutathione deficiency, oxidative stress, mitochondrial dysfunction, inflammation, insulin resistance, endothelial dysfunction, genotoxicity, muscle strength, and cognition: results of a pilot clinical trial.” Clinical and translational medicine 11.3 (2021): e372.

https://pmc.ncbi.nlm.nih.gov/articles/PMC9879756/
Kumar, Premranjan, et al. “Supplementing glycine and N-acetylcysteine (GlyNAC) in older adults improves glutathione deficiency, oxidative stress, mitochondrial dysfunction, inflammation, physical function, and aging hallmarks: a randomized clinical trial.” The Journals of Gerontology: Series A 78.1 (2023): 75-89.

This RCT provides evidence to show that GlyNAC supplementation in OA improves GSH deficiency, OxS, mitochondrial impairment, mitophagy, inflammation, insulin resistance, endothelial dysfunction, physical function and strength, exercise capacity, waist circumference, state systolic blood pressure, and multiple hallmarks of aging (mitochondrial dysfunction, altered intercellular communication, dysregulated nutrient sensing, loss of proteostasis, genomic toxicity, stem-cell exhaustion, and cellular senescence). GlyNAC supplementation begins to improve age-associated declines within 2-weeks but a longer duration of supplementation is needed for a greater magnitude of improvement. This RCT provides proof-of-concept that GlyNAC supplementation represents a novel, simple, safe, and effective nutritional approach in humans to promote and improve healthy aging.

Why glycine is needed (particularly in GlyNAC):

Glutathione (GSH) is the body’s primary intracellular antioxidant tripeptide, synthesized in two steps from three amino acids: glutamate + cysteine → γ-glutamylcysteine (via glutamate cysteine ligase), then + glycine → GSH (via glutathione synthetase). In aging, GSH deficiency arises primarily from impaired synthesis due to low availability of its rate-limiting precursor amino acids, glycine and cysteine (not glutamate).Glycine is specifically rate-limiting for GSH synthesis in older adults/aging contexts.
Supplementing NAC alone provides cysteine but not glycine, limiting GSH production if glycine is deficient.
GlyNAC supplies both glycine and cysteine (as NAC), enabling full, physiologic GSH synthesis (cells autoregulate to produce needed amounts, avoiding risks like reductive stress from excess exogenous GSH or NAC alone).
Glycine also supports other benefits (e.g., 1-carbon metabolism for DNA/methylation, potential longevity effects seen in animal models).

The “power of 3” (glycine + cysteine/NAC + resulting GSH) explains why GlyNAC outperforms single precursors or direct GSH attempts, as it corrects the root cause of GSH deficiency and downstream aging defects more effectively. This trial builds on prior work showing similar benefits in rodents and pilot human studies.

In the randomized clinical trial by Kumar et al. (2023) published in The Journals of Gerontology: Series A, the daily dosage for GlyNAC supplementation in older adults (the intervention group, n=12) was:100 mg/kg/day of glycine
100 mg/kg/day of N-acetylcysteine (NAC)

For a practical example, a 70 kg person would take approximately 7 grams per day of each (glycine and NAC).

Here are **three top-quality, reputable supplement companies** that offer high-purity **glycine** and **N-acetylcysteine (NAC)** products suitable for achieving approximately **7 grams per day** of each (as referenced from the study dosing example for a ~70 kg person). These brands are frequently highlighted in independent reviews (e.g., ConsumerLab approvals, third-party testing mentions), practitioner-recommended sources, and recent evaluations for quality, purity, and transparency.

1. **Thorne Research**

Thorne is widely regarded as a premium, high-end brand with rigorous third-party testing, GMP certification, and a strong reputation among clinicians for purity and bioavailability. They offer standalone **NAC capsules** (e.g., 500 mg per capsule, odorless and stable) and **glycine capsules** (often 1,000 mg). For higher daily doses like 7 g, you’d need multiple capsules (e.g., 14 NAC capsules or mix with powder if available), but their products are excellent for quality-focused users. Available via their site, iHerb, or professional channels.

2. **Pure Encapsulations**

A professional-grade brand (hypoallergenic, free of unnecessary additives, third-party verified) trusted in functional medicine. They sell a dedicated **NAC + Glycine Powder** (flavored peach-ginger, providing ~1.8 g each per serving), as well as separate pure glycine and NAC options. This makes scaling to 7 g/day straightforward with powder form for easier high-dose mixing (e.g., in water or smoothies). Highly recommended for clean formulations and glutathione-support protocols.

3. **BulkSupplements.com (or PureBulk)**

For cost-effective, high-volume needs, these bulk-focused companies excel in pure powders (often ConsumerLab-approved or third-party tested). They offer **pure glycine powder** and **NAC powder** (e.g., NAC at 600–750 mg per serving scoops, with large bags for 250 g+). This is ideal for 7 g/day dosing—simply measure out scoops (inexpensive per gram, unflavored, vegan). Great for those preferring bulk to minimize capsules and maximize value while maintaining quality.

**Notes**:
– For doses this high (7 g each), **powder forms** are often more practical and economical than capsules to avoid swallowing dozens daily. Always start lower if new to these, and consult a healthcare provider (e.g., for potential GI tolerance or interactions).

– Look for third-party testing certificates on the brand sites for heavy metals/purity. Availability can vary by region (e.g., US-based shipping common), and check retailers like iHerb, Amazon, or direct sites for current stock. These brands align with evidence-based, high-quality sourcing for GlyNAC-related use.

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GlyNAC supplementation in OA older adults for 16-weeks was safe and well-tolerated. By combining the benefits of glycine, NAC and GSH, GlyNAC is an effective nutritional supplement that improves and reverses multiple age-associated abnormalities to promote health in aging humans.

Supplement Details

Glycine and N-acetylcysteine and alanine were purchased commercially, and quality verified via certificates of analyses. These supplements are filled into capsules by a pharmacist, and provided monthly to study participants at doses of 100 mg/kg/d each of glycine and NAC, and 200 mg/kg/d of alanine.

This RCT found that GlyNAC supplementation in OA significantly improved/corrected GSH deficiency, OxS, mitochondrial dysfunction, physical function, waist circumference, endothelial function, SBP, and 7 hallmarks of aging affecting mitochondria, inflammation, IR, mitophagy, genomic damage, cellular senescence, and stem cells.

GlyNAC provides the precursor amino acids glycine and cysteine (from N-acetylcysteine) for GSH synthesis. Glycine, cysteine, and GSH make independent and important contributions toward cellular health and organ function (22,56,57). Their combination represents a “Power of 3” to indicate that benefits occur due to the combined effects of all three components. It is not just GSH alone. Glycine is a rate-limiting amino acid for GSH synthesis (57). It is an important donor of the 1-carbon methyl-group essential for multiple cellular reactions, including purines for deoxyribonucleic acid (DNA) synthesis. Glycine and GlyNAC supplementation in mice significantly increase life span (55,58). Glycine supplementation is shown to lower the incidence of pulmonary adenocarcinoma (58). NAC donates cysteine and which provides the critically essential thiol (SH) groups needed for multiple cellular reactions. This is especially true for mitochondrial energy metabolism. Thiol groups play important roles in cellular reactions, and are a component of peptides, proteins and lipids. GSH is considered a “master antioxidant” based on its abundant presence within cells, its ability to neutralize harmful OxS, support mitochondrial function, and detoxification via glutathionylation. The “power of 3” refers to the combined action of glycine, NAC, and GSH, and could explain the speed and magnitude of GlyNAC-mediated improvement of the age-associated decline in cellular function, reversal of aging hallmarks, and health improvement in aging.
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Mouse study

https://pmc.ncbi.nlm.nih.gov/articles/PMC8002905/

Kumar, Premranjan, et al. “Glycine and N‐acetylcysteine (GlyNAC) supplementation in older adults improves glutathione deficiency, oxidative stress, mitochondrial dysfunction, inflammation, insulin resistance, endothelial dysfunction, genotoxicity, muscle strength, and cognition: results of a pilot clinical trial.” Clinical and translational medicine 11.3 (2021): e372.

Oxidative stress (OxS) and mitochondrial dysfunction are implicated as causative factors for aging. Older adults (OAs) have an increased prevalence of elevated OxS, impaired mitochondrial fuel‐oxidation (MFO), elevated inflammation, endothelial dysfunction, insulin resistance, cognitive decline, muscle weakness, and sarcopenia, but contributing mechanisms are unknown, and interventions are limited/lacking. We previously reported that inducing deficiency of the antioxidant tripeptide glutathione (GSH) in young mice results in mitochondrial dysfunction, and that supplementing GlyNAC (combination of glycine and N‐acetylcysteine [NAC]) in aged mice improves naturally‐occurring GSH deficiency, mitochondrial impairment, OxS, and insulin resistance. This pilot trial in OA was conducted to test the effect of GlyNAC supplementation and withdrawal on intracellular GSH concentrations, OxS, MFO, inflammation, endothelial function, genotoxicity, muscle and glucose metabolism, body composition, strength, and cognition.
Methods

A 36‐week open‐label clinical trial was conducted in eight OAs and eight young adults (YAs). After all the participants underwent an initial (pre‐supplementation) study, the YAs were released from the study. OAs were studied again after GlyNAC supplementation for 24 weeks, and GlyNAC withdrawal for 12 weeks. Measurements included red‐blood cell (RBC) GSH, MFO; plasma biomarkers of OxS, inflammation, endothelial function, glucose, and insulin; gait‐speed, grip‐strength, 6‐min walk test; cognitive tests; genomic‐damage; glucose‐production and muscle‐protein breakdown rates; and body‐composition.
Results

GlyNAC supplementation for 24 weeks in OA corrected RBC‐GSH deficiency, OxS, and mitochondrial dysfunction; and improved inflammation, endothelial dysfunction, insulin‐resistance, genomic‐damage, cognition, strength, gait‐speed, and exercise capacity; and lowered body‐fat and waist‐circumference. However, benefits declined after stopping GlyNAC supplementation for 12 weeks.
Conclusions

GlyNAC supplementation for 24‐weeks in OA was well tolerated and lowered OxS, corrected intracellular GSH deficiency and mitochondrial dysfunction, decreased inflammation, insulin‐resistance and endothelial dysfunction, and genomic‐damage, and improved strength, gait‐speed, cognition, and body composition. Supplementing GlyNAC in aging humans could be a simple and viable method to promote health and warrants additional investigation.

Mouse Study 2023

https://pmc.ncbi.nlm.nih.gov/articles/PMC10215265/
Kumar, Premranjan, Ob W. Osahon, and Rajagopal V. Sekhar. “GlyNAC (glycine and N-acetylcysteine) supplementation in old mice improves brain glutathione deficiency, oxidative stress, glucose uptake, mitochondrial dysfunction, genomic damage, inflammation and neurotrophic factors to reverse age-associated cognitive decline: Implications for improving brain health in aging.” Antioxidants 12.5 (2023): 1042.

To test whether these defects occur in the brain in association with age-associated cognitive decline (ACD)ACD, and could be improved/reversed with GlyNAC supplementation, we studied young (20-week) and old (90-week) C57BL/6J mice. Old mice received either regular or GlyNAC supplemented diets for 8 weeks, while young mice received the regular diet. Cognition and brain outcomes (GSH, OxS, mitochondrial energetics, autophagy/mitophagy, glucose transporters, inflammation, genomic damage and neurotrophic factors) were measured. Compared to young mice, the old-control mice had significant cognitive impairment and multiple brain defects. GlyNAC supplementation improved/corrected the brain defects and reversed ACD. This study finds that naturally-occurring ACD is associated with multiple abnormalities in the brain, and provides proof-of-concept that GlyNAC supplementation corrects these defects and improves cognitive function in aging.

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A Combination of NAC and Glycine Promotes Healthy Aging in Older Adults

A Combination of NAC and Glycine Promotes Healthy Aging in Older Adults. April 10, 2024
Written by Taylor Woosley, Science Writer.

16-week supplementation with 100 mg/kg of glycine and 100 mg/kg of NAC significantly improved glutathione concentrations by 164% and resulted in a significant reduction in IL-6 by 78%, TNF-α by 54%, and hsCRP by 41% in older adults.

Aging is a complex process that affects humans at the molecular, cellular, tissue, and systemic levels1. An important aspect of aging is the presence of inflammageing, a low-grade chronic inflammation that progressively increases with age, contributing to age-related diseases and frailty2. Furthermore, cellular senescence, associated with the pro-inflammatory senescence-associated secretory phenotype, interlinks with inflammation and acts as an important driver for organismal aging3.

Glycine is a simple non-essential amino acid which acts as a vital building block for glutathione (GSH), a robust antioxidant that becomes less abundant as we age4. Additionally, N-acetylcysteine (NAC) is a synthetic derivative of the endogenous amino acid L-cysteine which is a precursor of GSH that plays a role in modulating oxidative stress5. Previous research on supplementation with a combination of glycine and NAC (GlyNAC) shows a significant improvement in correcting GSH deficiency, oxidative stress, mitochondrial dysfunction, inflammation, and endothelial dysfunction6.

Kumar et al. conducted a double-blind, placebo-controlled randomized controlled trial to examine the effect of a GlyNAC supplementation on GSH concentrations, oxidative stress (OxS), mitochondrial fatty-acid oxidation (MFO), insulin resistance (IR), inflammation, endothelial function, physical function, and body composition. Subject inclusion consisted of young adults (aged 21-40 years) and older adults (aged 61-80 years), with body mass index (BMI) >27, who had stopped all nonvitamin nutritional supplements for 4-weeks prior to the trial beginning. Fasted blood samples were obtained to measure plasma lipids, liver profile, BUN, creatinine, thyroid stimulating hormone (TSH), free T4, glucose, HbA1c, and complete blood counts. Furthermore, all subjects completed baseline studies of glucose tolerance test, physical function tests (gait speed, upper and lower extremity strength, and rapid 6-minute walk test), DEXA and liver scans, calorimetry, tracer studies, and muscle biopsy.

23 participants were randomized to receive either GlyNAC (n=11) or placebo (alanine) (n=12) for a 16-week intervention. Those in the GlyNAC group consumed 100 mg/kg/d each of glycine and NAC daily. The placebo group consumed 200 mg/kg/d of alanine daily. Studies were repeated 2 weeks after beginning supplementation and young adult subjects were released at the end of 2 weeks. The older adults returned at the end of weeks 4, 8, and 12 to measure liver transaminases and creatinine and then underwent a final study at the end of the 16-weeks of supplementation. OxS and oxidative damage were measured using ELISA assays as plasma concentrations thiobarbituric acid reducing substances (TBARS) and 8-Iso-Prostaglandin-F2a. Biomarkers of inflammation and endothelial function assessed included interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-α) interleukin-10 (IL-10), human soluble intercellular adhesion molecule 1 (sICAM1), soluble vascular cell adhesion molecule 1 (sVCAM1), and high-sensitivity human C-reactive protein.

Physical function measures, body composition, blood pressure, and lipids were compared between 3 cohorts at baseline, change in response at 16-weeks versus baseline among older adults receiving placebo (OAP) and older adults receiving GlyNAC (OAG), 16-week OAP/OAG versus young adults at baseline, and OAP versus OAG at 16-weeks.

Young adult subjects (7 men, 5 women) were 25.6 years ± 2.5 years of age, OAG (8 men, 4 women) were 71.4 ± 4.2 years, and OAP (4 men, 8 women) were 70.8 ± 3.9 years. Significant findings of the study are as follows:

At 0 weeks, both the OAG and OAP group had 66% lower muscle GSH concentrations compared to the YA group. Only the OAG group experienced significantly improved GSH concentrations by 121% after 2-weeks and by 164% after 16-weeks.
Only the OAG group had a significant improvement in total RBC-GSH (tGSH) (by 173% after 2-weeks and 225% after 16-weeks) and in reduced RBC-GSH (rGSH) (by 195% after 2-weeks and 225% after 16-weeks).
Changes in oxidative stress measured by plasma TBARS concentrations and F2-I concentrations show that only the OAG group had significantly lower markers after 2-weeks (TBARS 42% lower; F2-I 44% lower) and 16-weeks (TBARS 72% lower; F2-I 72% lower) to levels not different from the YA group at baseline.

Results of the 16-week double-blind, placebo-controlled randomized controlled trial show that Gly-NAC supplementation significantly improved glutathione concentrations and reduced oxidative stress and inflammatory markers in older adult subjects. Findings suggest a combination of glycine and NAC may be beneficial to improve markers of aging. Study limitations include the use of only healthy older adult subjects.

Source: Kumar, Premranjan, Chun Liu, James Suliburk, Jean W. Hsu, Raja Muthupillai, Farook Jahoor, Charles G. Minard, George E. Taffet, and Rajagopal V. Sekhar. “Supplementing glycine and N-acetylcysteine (GlyNAC) in older adults improves glutathione deficiency, oxidative stress, mitochondrial dysfunction, inflammation, physical function, and aging hallmarks: a randomized clinical trial.” The Journals of Gerontology: Series A 78, no. 1 (2023): 75-89.

© The Author(s) 2022. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please e-mail: jo******************@*up.com.
Posted April 10, 2024.
Taylor Woosley studied biology at Purdue University before becoming a 2016 graduate of Columbia College Chicago with a major in Writing. She currently resides in Glen Ellyn, IL.

References:

Baechle JJ, Chen N, Makhijani P, Winer S, Furman D, Winer DA. Chronic inflammation and the hallmarks of aging. Mol Metab. Aug 2023;74:101755. doi:10.1016/j.molmet.2023.101755
Teissier T, Boulanger E, Cox LS. Interconnections between Inflammageing and Immunosenescence during Ageing. Cells. Jan 21 2022;11(3)doi:10.3390/cells11030359
Schmauck-Medina T, Molière A, Lautrup S, et al. New hallmarks of ageing: a 2022 Copenhagen ageing meeting summary. Aging (Albany NY). Aug 29 2022;14(16):6829-6839. doi:10.18632/aging.204248
Johnson AA, Cuellar TL. Glycine and aging: Evidence and mechanisms. Ageing Res Rev. Jun 2023;87:101922. doi:10.1016/j.arr.2023.101922
Raghu G, Berk M, Campochiaro PA, et al. The Multifaceted Therapeutic Role of N-Acetylcysteine (NAC) in Disorders Characterized by Oxidative Stress. Curr Neuropharmacol. 2021;19(8):1202-1224. doi:10.2174/1570159×19666201230144109
Kumar P, Liu C, Hsu JW, et al. Glycine and N-acetylcysteine (GlyNAC) supplementation in older adults improves glutathione deficiency, oxidative stress, mitochondrial dysfunction, inflammation, insulin resistance, endothelial dysfunction, genotoxicity, muscle strength, and cognition: Results of a pilot clinical trial. Clinical and translational medicine. Mar 2021;11(3):e372. doi:10.1002/ctm2.372

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https://pmc.ncbi.nlm.nih.gov/articles/PMC3155927/
Sekhar, Rajagopal V., et al. “Deficient synthesis of glutathione underlies oxidative stress in aging and can be corrected by dietary cysteine and glycine supplementation.” The American journal of clinical nutrition 94.3 (2011): 847-853.

https://pmc.ncbi.nlm.nih.gov/articles/PMC3005481/
Sekhar, Rajagopal V., et al. “Glutathione Synthesis Is Diminished in Patients With Uncontrolled Diabetes and Restored by Dietary Supplementation With Cysteine and Glycine.” Diabetes Care 34.1 (2010): 162.

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### Summary of the First Article: Sekhar et al. (2011) – “Deficient synthesis of glutathione underlies oxidative stress in aging and can be corrected by dietary cysteine and glycine supplementation” (The American Journal of Clinical Nutrition)

#### Abstract
Aging is associated with oxidative stress, but the underlying mechanisms are not fully understood. Glutathione (GSH) is the most abundant intracellular antioxidant. The study tested whether GSH deficiency in aging is due to diminished synthesis and contributes to oxidative stress, and if supplementing with the GSH precursors cysteine and glycine could correct this deficiency and reduce oxidative stress. Eight elderly humans (60-80 years) and 10 younger controls (20-40 years) were studied using stable isotope methods to measure erythrocyte (RBC) GSH synthesis and concentrations, plasma markers of oxidant damage (F2-isoprostanes), and oxidative stress. Elderly subjects were restudied after 2 weeks of supplementation with cysteine (as N-acetylcysteine) and glycine.

#### Introduction
Oxidative stress increases with age and is implicated in age-related diseases such as cardiovascular disease, diabetes, neurodegenerative disorders, and cancer. Reactive oxygen species (ROS) cause damage to lipids, proteins, and DNA. GSH plays a critical role in detoxifying ROS and maintaining cellular redox balance. GSH is synthesized from glutamate, cysteine, and glycine in two steps catalyzed by glutamate-cysteine ligase and GSH synthetase. Previous studies show lower GSH levels in aged animals and humans, but the cause—whether due to decreased synthesis, increased consumption, or impaired recycling—is unclear. The hypothesis was that GSH deficiency in elderly humans results from reduced synthesis due to limited availability of cysteine and glycine (rate-limiting precursors), and that dietary supplementation could restore GSH levels and lower oxidative stress. The study used in vivo kinetic measurements with stable isotopes to quantify GSH synthesis rates in RBCs, as they reflect systemic GSH status and lack nuclei/mitochondria, simplifying interpretation.

#### Methods
The study was approved by the Baylor College of Medicine Institutional Review Board. Participants included 8 healthy elderly adults (age 71 ± 4 years) and 10 younger controls (age 31 ± 7 years), matched for sex and BMI, with no chronic illnesses, normal lab values, sedentary lifestyles, and no recent supplements or unusual diets. After baseline assessments (blood counts, glucose, liver/renal function), subjects underwent an 8-hour primed constant intravenous infusion of [²H₂]-glycine to measure GSH synthesis. Blood samples were collected for RBC GSH concentration (using high-performance liquid chromatography after derivatization with monobromobimane), fractional synthesis rate (FSR, using precursor-product labeling), and absolute synthesis rate (ASR = FSR × GSH concentration). Plasma oxidative stress was measured via reactive oxygen metabolites (d-ROMs test, in Carratelli units), and oxidant damage via F2-isoprostanes (enzyme immunoassay). RBC free amino acids (glycine, cysteine, glutamate) were quantified by gas chromatography-mass spectrometry. Elderly subjects received oral supplementation (cysteine 0.81 mmol/kg/d as N-acetylcysteine; glycine 1.33 mmol/kg/d) for 2 weeks while maintaining usual diets, then were restudied. Statistics used unpaired t-tests for group comparisons and paired t-tests for pre/post-supplementation changes (P < 0.05 significant).

#### Results
At baseline, elderly subjects had significantly lower RBC concentrations of glycine (218.0 ± 23.7 vs. 486.7 ± 28.3 μmol/L; P < 0.01), cysteine (19.8 ± 1.3 vs. 26.2 ± 1.4 μmol/L; P < 0.05), and GSH (1.12 ± 0.18 vs. 2.08 ± 0.12 mmol/L RBC; P < 0.05) compared to younger controls; glutamate levels were similar. GSH FSR was lower in elderly (45.80 ± 5.69%/d vs. 83.14 ± 6.43%/d; P < 0.01), as was ASR (0.55 ± 0.12 vs. 1.73 ± 0.16 mmol/L RBC/d; P < 0.01). Plasma oxidative stress was higher in elderly (346 ± 20 vs. 304 ± 16 Carratelli units; P < 0.05), as were F2-isoprostanes (136.3 ± 11.3 vs. 97.7 ± 8.3 pg/mL; P < 0.05). After supplementation, elderly subjects showed increased RBC glycine (to 458.2 ± 20.1 μmol/L; P < 0.01) and cysteine (to 25.9 ± 1.2 μmol/L; P < 0.05), with GSH concentration rising 94.6% (to 2.08 ± 0.15 mmol/L RBC; P < 0.01), FSR 78.8% (to 81.9 ± 4.2%/d; P < 0.01), and ASR 230.9% (to 1.70 ± 0.14 mmol/L RBC/d; P < 0.01). Post-supplementation values matched younger controls. Plasma oxidative stress decreased (to 298 ± 18 Carratelli units; P < 0.05), and F2-isoprostanes decreased (to 99.2 ± 9.1 pg/mL; P < 0.05), normalizing to control levels. No changes in body weight, diet, or other parameters.

#### Discussion
The findings confirm GSH deficiency in healthy elderly humans due to markedly reduced synthesis rates, linked to lower intracellular availability of cysteine and glycine despite normal glutamate. This leads to elevated oxidative stress and lipid peroxidation. Supplementation fully restored precursor levels, GSH synthesis, and concentrations, eliminating differences from younger adults and reducing oxidative stress markers. The mechanism may involve age-related declines in protein turnover or increased amino acid utilization, limiting precursors. Unlike diabetes (where similar deficiencies occur), aging shows no hyperglycemia, suggesting a primary synthetic defect. Animal studies support precursor limitation causing GSH decline. The study rules out increased consumption or recycling issues as primary causes, as supplementation corrected the deficit without affecting GSSG levels. This simple, safe intervention could mitigate age-related oxidative damage and diseases, warranting larger trials.

#### Conclusions
Glutathione deficiency in elderly humans occurs because of a marked reduction in synthesis. Supplementation with the glutathione precursors cysteine and glycine fully restores glutathione synthesis and concentrations and lowers levels of oxidative stress and oxidant damages. These findings suggest a practical approach to decreasing oxidative stress in aging.
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Uncontrolled Type II Diabetes

### Summary of the Second Article: Sekhar et al. (2010) – “Glutathione Synthesis Is Diminished in Patients With Uncontrolled Diabetes and Restored by Dietary Supplementation With Cysteine and Glycine” (Diabetes Care)

#### Abstract
Sustained hyperglycemia is associated with low cellular levels of the antioxidant glutathione (GSH), leading to tissue damage from oxidative stress. The study tested the hypothesis that diminished GSH in adult patients with uncontrolled type 2 diabetes is due to decreased synthesis and evaluated the effect of dietary supplementation with cysteine and glycine on GSH synthesis rate and oxidative stress. Twelve diabetic patients and 12 nondiabetic controls were infused with [²H₂]-glycine to measure GSH synthesis. Intracellular GSH concentrations, reactive oxygen metabolites, and lipid peroxides were also measured. Diabetic patients were restudied after 2 weeks of supplementation with cysteine and glycine. Diabetic subjects had higher fasting glucose, lower erythrocyte glycine and cysteine, lower GSH concentrations, diminished GSH synthesis rates (fractional and absolute), and higher reactive oxygen metabolites and lipid peroxides compared to controls. Supplementation in diabetics increased GSH synthesis and concentrations, and decreased oxidative stress and lipid peroxides. Conclusions: Uncontrolled type 2 diabetes features deficient GSH synthesis due to limited precursor availability; supplementation restores synthesis and lowers oxidative stress despite persistent hyperglycemia.

#### Introduction
Diabetes is the leading cause of blindness, renal failure, and amputations, and increases risk of macrovascular complications like myocardial ischemia and strokes. Multiple pathways contribute to tissue damage, including polyol pathway, advanced glycation end products, protein kinase C activation, and hexosamine pathway, all featuring increased oxidative stress from reactive oxygen species (ROS). GSH, the most abundant antioxidant, resists oxidative damage. GSH is synthesized from glutamate, cysteine, and glycine. Diabetes is associated with decreased cellular GSH, but the cause is unknown. Uncontrolled hyperglycemia increases ROS; lowering glucose reduces oxidative stress, potentially diminishing complications, but many patients fail to achieve glycemic goals (e.g., A1C <7%). Thus, novel strategies to reduce oxidative stress in uncontrolled diabetes are needed. The study hypothesized that GSH deficiency in uncontrolled diabetes results from diminished synthesis due to limited precursors, and that supplementing glycine and cysteine would increase GSH synthesis, concentrations, and reduce oxidative stress despite hyperglycemia. Stable isotope methods compared GSH synthesis and concentrations in erythrocytes, and plasma oxidant markers, in diabetic patients matched to nondiabetic controls, before and after 14 days of cysteine and glycine supplementation.

#### Methods
The study was approved by the institutional review board at Baylor College of Medicine. Twelve adults with uncontrolled type 2 diabetes (A1C 8–10%) and 12 nondiabetic controls matched for age, sex, and BMI were recruited, excluding those with thyroid disorders, hypercortisolemia, liver/renal impairment, malignancy, infections, or illnesses in the prior 6 months. Subjects had sedentary lifestyles, no unusual diets or supplements, and abstained from alcohol. Diabetics were treated with lifestyle or oral agents (no insulin to avoid glucose swings), and matched for glycemic levels pre- and post-supplementation. After baseline measurements (blood counts, glucose, A1C, liver/renal profiles), subjects fasted for 10 hours and underwent intravenous infusion of [²H₂]-glycine (prime: 20 μmol/kg; infusion: 15 μmol/kg/h for 8 hours) in the GCRC to measure GSH synthesis. Blood samples were taken at baseline and 2–8 hours for erythrocyte GSH-bound glycine enrichment. Diabetic subjects received oral supplementation (0.81 mmol/kg/day cysteine as N-acetylcysteine; 1.33 mmol/kg/day glycine) for 14 days, then restudied similarly, while maintaining habitual diets.

Erythrocyte GSH concentration was measured by lysing cells with monobromobimane (MBB) for reduced GSH, and total GSH after reduction; GSSG was calculated as total minus reduced. GSH synthesis rates: fractional synthesis rate (FSR) using precursor-product equation with steady-state free glycine; absolute synthesis rate (ASR) as GSH concentration × FSR. Erythrocyte free amino acids (glycine, cysteine, glutamate) were analyzed by gas chromatography-mass spectrometry after derivatization and HPLC. Plasma oxidative stress: reactive oxygen metabolites (DROMs) via spectrophotometric assay; lipid peroxides via ferrous ion oxidation with xylenol orange. Statistics: unpaired t-tests for group differences; paired t-tests for pre-post supplementation; significance at P < 0.05.

#### Results
Baseline characteristics: Diabetics had higher fasting glucose (10.7 ± 0.5 vs. 5.0 ± 0.1 mmol/l; P < 0.001) and A1C (9.1 ± 0.2% vs. 5.5 ± 0.1%; P < 0.001) than controls; no differences in age, BMI, hemoglobin, renal/liver functions. Erythrocyte glycine (403.2 ± 18.2 vs. 514.7 ± 33.1 μmol/l; P < 0.01) and cysteine (17.8 ± 1.5 vs. 25.2 ± 1.5 μmol/l; P < 0.01) were lower in diabetics; glutamate similar. GSH concentrations (1.65 ± 0.16 vs. 6.75 ± 0.47 μmol/g Hb; P < 0.001), FSR (44.86 ± 2.87% vs. 79.21 ± 5.75%/day; P < 0.001), and ASR (0.74 ± 0.10 vs. 5.26 ± 0.61 μmol/g Hb/day; P < 0.001) were lower in diabetics. Oxidized GSSG higher (0.33 ± 0.07 vs. 0.10 ± 0.01 μmol/g Hb; P < 0.05); GSH:GSSG ratio lower (6.30 ± 1.30 vs. 59.15 ± 4.12; P < 0.001). Plasma DROMs (403 ± 11 vs. 286 ± 10 UCarr; P < 0.001) and lipid peroxides (10.8 ± 1.2 vs. 2.6 ± 0.4 pg/ml; P < 0.001) higher in diabetics.

Post-supplementation in diabetics: GSH FSR increased 85.1% (83.03 ± 3.66%/day; P < 0.001), reaching control levels; ASR increased 193.8% (2.17 ± 0.17 μmol/g Hb/day; P < 0.001); GSH concentrations increased 64.4% (2.72 ± 0.15 μmol/g Hb; P < 0.001). However, post-supplementation GSH concentrations (2.72 ± 0.15 vs. 6.75 ± 0.47 μmol/g Hb; P < 0.001) and ASR remained lower than controls. Glycine and cysteine concentrations normalized (521.6 ± 19.4 and 25.5 ± 1.9 μmol/l; P < 0.01 vs. pre). DROMs decreased (359 ± 10 UCarr; P < 0.05 vs. pre; P < 0.01 vs. controls); lipid peroxides decreased (6.2 ± 0.9 pg/ml; P < 0.01 vs. pre; P < 0.05 vs. controls). GSSG and GSH:GSSG ratio unchanged.

#### Discussion
Diabetics had lower erythrocyte GSH, cysteine, glycine, and synthesis rates, with higher oxidative stress markers, confirming GSH deficiency due to reduced synthesis from precursor limitation. Supplementation restored FSR to control levels and increased concentrations/ASR, reducing oxidative stress, though not fully to controls, suggesting ongoing GSH consumption. Glutamate levels unchanged, indicating cysteine/glycine specificity. Diabetes may impair protein turnover or increase amino acid needs due to hyperglycemia, reducing precursor availability. GSH deficiency exacerbates oxidative stress, activating damage pathways; increasing GSH via precursors could mitigate this despite poor glycemic control. Animal studies support precursor deficiency causing GSH loss; human data align. Total GSH measurement rules out impaired redox cycling. Glycemic control reduces ROS, but many patients fail; precursor supplementation offers a safe, inexpensive adjunct.

#### Conclusions
Uncontrolled type 2 diabetes causes severely deficient GSH synthesis due to limited cysteine and glycine availability, leading to oxidative stress and damage. Dietary supplementation with these precursors restores GSH synthesis rates, increases concentrations, and reduces oxidative stress and lipid peroxides, even with persistent hyperglycemia. This approach could prevent chronic complications as a nutritional intervention alongside standard management.

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Type I Diabetes

https://www.sciencedirect.com/science/article/abs/pii/S0024320523006100
Ding, Qingyu, et al. “N-acetylcysteine alleviates oxidative stress and apoptosis and prevents skeletal muscle atrophy in type 1 diabetes mellitus through the NRF2/HO-1 pathway.” Life sciences 329 (2023): 121975.

https://doi.org/10.1016/j.lfs.2023.121975

•
N-acetylcysteine reduced the expression levels of Atrogin-1 and MuRF-1.
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N-acetylcysteine activates the NRF2/HO-1 signaling pathway.
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N-acetylcysteine inhibits oxidative stress and apoptosis in skeletal muscle.
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N-acetylcysteine and insulin prevent skeletal muscle atrophy in type 1 diabetes.

Abstract
Aims
Type 1 diabetes mellitus (T1DM) has been linked to the occurrence of skeletal muscle atrophy. Insulin monotherapy may lead to excessive blood glucose fluctuations. N-acetylcysteine (NAC), a clinically employed antioxidant, possesses cytoprotective, anti-inflammatory, and antioxidant properties. The objective of our study was to evaluate the viability of NAC as a supplementary treatment for T1DM, specifically regarding its therapeutic and preventative impacts on skeletal muscle.
Main methods
Here, we used beagles as T1DM model for 120d to explore the mechanism of NRF2/HO-1-mediated skeletal muscle oxidative stress and apoptosis and the therapeutic effects of NAC. Oxidative stress and apoptosis related factors were analyzed by immunohistochemistry, immunofluorescence, western blotting, and RT-qPCR assay.
Key findings
The findings indicated that the co-administration of NAC and insulin led to a reduction in creatine kinase levels, preventing weight loss and skeletal muscle atrophy. Improvement in the reduction of muscle fiber cross-sectional area. The expression of Atrogin-1, MuRF-1 and MyoD1 was downregulated, while Myh2 and MyoG were upregulated. In addition, CAT and GSH-Px levels were increased, MDA levels were decreased, and redox was maintained at a steady state. The decreased of key factors in the NRF2/HO-1 pathway, including NRF2, HO-1, NQO1, and SOD1, while KEAP1 increased. In addition, the apoptosis key factors Caspase-3, Bax, and Bak1 were found to be downregulated, while Bcl-2, Bcl-2/Bax, and CytC were upregulated.

Significance Our findings demonstrated that NAC and insulin mitigate oxidative stress and apoptosis in T1DM skeletal muscle and prevent skeletal muscle atrophy by activating the NRF2/HO-1 pathway.

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Beagles with type 1 Diabetes

https://www.sciencedirect.com/science/article/abs/pii/S0040816624002167
Wu, Haitong, et al. “N-acetylcysteine combined with insulin therapy can reduce myocardial injury induced by type 1 diabetes through the endoplasmic reticulum pathway.” Tissue and Cell 90 (2024): 102515.
A canine model of T1DM was established by the combination of alloxan and streptozotocin.
•
NAC combined with insulin therapy maintained glucose stability better than insulin therapy alone.
•
NAC can reduce myocardial injury by regulating ERs and apoptosis in diabetes myocardium.
•
NAC can be used as an adjuvant drug for the treatment of T1DM to alleviate the complications of T1DM.

These findings suggest that NAC has a phylactic effect on myocardial injury in beagles with T1DM, and the mechanism may be related to the improvement of endoplasmic reticulum stress-induced apoptosis.

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2022

https://pmc.ncbi.nlm.nih.gov/articles/PMC8773349/
Sekhar, Rajagopal V. “GlyNAC (glycine and N-acetylcysteine) supplementation improves impaired mitochondrial fuel oxidation and lowers insulin resistance in patients with type 2 diabetes: results of a pilot study.” Antioxidants 11.1 (2022): 154.

Type 2 diabetes (T2D) is associated with mitochondrial dysfunction [1,2] which involves the impaired oxidation of fatty-acids (FA) [3,4,5,6,7,8,9,10,11,12,13]. Mitochondria are the source of energy generation and reactive oxygen species in cells, and mitochondrial dysfunction has been linked to diabetic complications [14,15] involving the heart [15,16,17,18,19,20], skeletal muscle [3,4,5,6,7,20], kidneys [21,22] and liver [23,24], and is also associated with inflammation [25], aging [26], cognitive disorders [27,28] and insulin resistance (IR) [29,30]. During the process of energy generation, mitochondria generate toxic reactive oxygen species (ROS) which induce a harmful state known as oxidative stress (OxS). To defend against OxS, mitochondria critically depend on antioxidants for protection, and glutathione (GSH, γ-glutamyl-cysteinyl-glycine) is the most abundant endogenous intracellular antioxidant [31,32]. Acute depletion of intracellular GSH concentrations result in mitochondrial injury or irreversible cell damage [16,33], suggesting that GSH is important for mitochondrial function and survival. GSH is a tripeptide synthesized from glutamic acid, cysteine and glycine in two steps catalyzed by the enzymes glutamate cysteine ligase (GCL, also known as γ-glutamylcysteine synthetase) and γ-l-glutamyl-l-cysteine:glycine ligase (also known as glutathione synthetase), and is important in health and disease [31,32]. Patients with T2D are reported to have GSH deficiency [34,35,36,37,38,39]. In a pilot study conducted earlier, we investigated the mechanisms contributing to GSH deficiency in T2D and reported that diminished synthesis contributes to GSH deficiency, and that this occurs due to decreased availability of the GSH precursor amino acids glycine and cysteine, and not glutamic acid [39]. We also reported that supplementing these patients with T2D with glycine and cysteine (provided as N-acetylcysteine, NAC) for a short duration of 2 weeks corrected the impaired GSH synthesis, improved intracellular GSH concentrations, and lowered OxS, without a decrease in fasting blood glucose concentrations [39]. This combination of glycine and NAC is abbreviated as GlyNAC. In rodent studies, we discovered that depleting GSH in young healthy mice results in impaired mitochondrial fatty-acid oxidation (MFO) [40], and that supplementing GlyNAC in old mice corrected GSH deficiency, reversed impaired MFO and lowered IR [40]. The results of these rodent studies suggest that GSH adequacy is critically important for optimal and efficient mitochondrial function, and that GlyNAC supplementation could be important for improving mitochondrial dysfunction and lowering IR. We tested this in human clinical trials involving older humans and in HIV-infected patients, and found that GlyNAC supplementation for a short duration of 2 weeks was sufficient to improve mitochondrial dysfunction and lower IR in both trials [41,42], but also that GlyNAC supplementation over longer durations ranging from 12–24 weeks reversed, corrected and normalized mitochondrial dysfunction compared to controls, also further improved IR [43,44]. However, stopping GlyNAC supplementation in both trials resulted in a recurrence of mitochondrial dysfunction and worsening of IR [43,44]. These observations indicate causality where defects improve with GlyNAC supplementation, and recur after stopping GlyNAC. Next, we tested and found that GlyNAC supplementation in old mice reversed impaired MFO in the heart and improved cardiac function [45]. However, whether GlyNAC supplementation can improve mitochondrial dysfunction or IR in patients with T2D remains unknown.

Reversing mitochondrial impairment is a key focus in T2D [46]. The effect of GlyNAC on mitochondrial function in patients with T2D has not been previously reported in the medical literature. This manuscript reports unpublished data on mitochondrial fuel oxidation, insulin resistance and free-fatty acid (FFA) concentrations from a previous study investigating the effect of supplementing GlyNAC in patients with T2D [39].

The results of this exploratory pilot study suggest that supplementing GlyNAC in patients with T2D could improve defects in mitochondrial function, lower insulin resistance and circulating plasma fatty-acid concentrations. These results could have important implications for improving health in diabetes, and support the need for a randomized clinical trial to confirm these findings and to understand the impact of GlyNAC supplementation on defects linked to mitochondrial dysfunction in diabetes.

4.4. Why GlyNAC Works—The ‘Power of Three’

GlyNAC supplementation provides glycine, cysteine (from NAC) and GSH (from glycine and cysteine) [39,41,42]. Glycine is of vital importance to cellular health as a 1-carbon metabolite and methyl (CH3) group donor [58,59]. Glycine and methyl groups are required by multiple cellular pathways for the synthesis of important metabolites and metabolic intermediates, such as purines for DNA synthesis [58,59,60,61]. Glycine acts as a neurotransmitter in the brain [62,63,64,65,66] and is an important component of cartilage [67]. Cysteine contains a sulfhydryl (SH) group donor and is an important thiol in antioxidant systems [68] and for multiple cellular processes, especially in mitochondria [69,70,71]. For example, coenzyme A (CoA-SH) is an important intermediate in the mitochondrial β-oxidation of fatty-acids and for pyruvate metabolism in the Krebs’ cycle, and requires cysteine for its synthesis [72]. Cysteine is also important in maintaining protein structure, iron metabolism and other reactions in the body [71,73,74]. A key function of both glycine and cysteine is to serve as precursors for the synthesis of glutathione, the most abundant endogenous, intracellular tripeptide antioxidant [31,32]. GSH is commonly referred to as the ‘master antioxidant’, both for its abundance and for the multitude of biological functions that it supports [31,32,75,76]. GSH combats OxS, provides cellular protection, is required for efficient mitochondrial function, participates in detoxification of harmful metabolites, supports glutathionylation function, and is important for multiple and varied cellular processes [31,32,76,77]. We have termed the beneficial effects of the combination of glycine, cysteine and glutathione as the ‘power of three’ [43,44,78] because they act rapidly (after 2 weeks of GlyNAC supplementation in this study) to provide a powerful biological effect toward cellular protection, correcting cellular defects and improving cell, organ and organism health.

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Beneficial in Chronic Kidney Disease

Click to access ajtr0013-2472.pdf

Ye, Minyuan, et al. “N-acetylcysteine for chronic kidney disease: a systematic review and meta-analysis.” American Journal of Translational Research 13.4 (2021): 2472.

https://www.mdpi.com/1648-9144/59/11/1983
Chiu, Ai-Hua, et al. “N-acetylcysteine alleviates the progression of chronic kidney disease: a three-year cohort study.” Medicina 59.11 (2023): 1983.
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Cardio-Renal Disease

https://www.sciencedirect.com/science/article/pii/S2213231724003185
Lumpuy-Castillo, Jairo, et al. “Role of mitochondria in reno-cardiac diseases: A study of bioenergetics, biogenesis, and GSH signaling in disease transition.” Redox Biology 76 (2024): 103340.
On the other hand, N-acetylcysteine (NAC), a thiol-containing antioxidant known to replenish intracellular GSH [34], has shown promise in addressing oxidative stress and mitochondrial dysfunction in renal, cardiac, and cardio-renal diseases [34,35]

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Spinal cord injury mice

https://pmc.ncbi.nlm.nih.gov/articles/PMC11074018/
Xu, Xin, et al. “The effect of Glycine and N-acetylcysteine on oxidative stress in the spinal cord and skeletal muscle after spinal cord injury.” Inflammation 47.2 (2024): 557-571.

Oxidative stress is a frequently occurring pathophysiological feature of spinal cord injury (SCI) and can result in secondary injury to the spinal cord and skeletal muscle atrophy. Studies have reported that glycine and N-acetylcysteine (GlyNAC) have anti-aging and anti-oxidative stress properties; however, to date, no study has assessed the effect of GlyNAC in the treatment of SCI. In the present work, we established a rat model of SCI and then administered GlyNAC to the animals by gavage at a dose of 200 mg/kg for four consecutive weeks. The BBB scores of the rats were significantly elevated from the first to the eighth week after GlyNAC intervention, suggesting that GlyNAC promoted the recovery of motor function; it also promoted the significant recovery of body weight of the rats. Meanwhile, the 4-week heat pain results also suggested that GlyNAC intervention could promote the recovery of sensory function in rats to some extent. Additionally, after 4 weeks, the levels of glutathione and superoxide dismutase in spinal cord tissues were significantly elevated, whereas that of malondialdehyde was significantly decreased in GlyNAC-treated animals. The gastrocnemius wet weight ratio and total antioxidant capacity were also significantly increased. After 8 weeks, the malondialdehyde level had decreased significantly in spinal cord tissue, while reactive oxygen species accumulation in skeletal muscle had decreased. These findings suggested that GlyNAC can protect spinal cord tissue, delay skeletal muscle atrophy, and promote functional recovery in rats after SCI.

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https://theamericanchiropractor.com/article/2023/12/1/the-truth-about-n-acetylcysteine
The Truth About N-Acetylcysteine Guy R. Schenker December 1 2023

“Glycine and NAC supplementation resulted in significant improvement in both cognitive performance and physical function tests”.

Glycine and NAC supplementation resulted in significant improvement in both cognitive performance and physical function tests. All measured cognitive functional assessments improved. The slower gate speed improved enough to match the younger control group, and hand grip strength and six-minute rapid walk test perfonnance significantly improved.

With the improvements in respiratory quotient (fat burning versus sugar burning in the mitochondria), there was a signifi-

cant reduction m total body fat and waist circumference, showing prefened fat loss in the abdomen, which is an indication of improved insulin sensitivity.

These researchers did a follow-up on mice to see if glycine and NAC supplementation could increase lifespan. Compared to the placebo, they found that mice supplemented with glycine and NAC lived 24% longer than control mice, improved/ corrected impaired glutathione synthesis, glutathione deficiency, oxidative stress, mitochondrial dysfunction, abnormal mitophagy, nutrient-sensing, and genomic damage.

No supplementation even compares to what you will achieve with glycine and NAC, along with the inducers alpha lipoic acid, carnosine, and quercetin, to produce intracellular glutathione in defense against inflam-aging.

Dr. Guy Schenker, a Pennsylvania chiropractor

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11. McCarty MF. Practical prospects for boosting hepatic production of the “pro-longevity” hormone FGF21. F[orm Mol Biol Clin Investig. 2015 Dec 19;30(2):/j/hmbci.2017.30.issue-2/hmbci-2015-0057/hmbci-2015-005 7. xml. doi: 10.1515/limbci-2015-0057. PMID: 26741352.

12. Chapela SP. Burgos HI, Stella CA. N-acetylcysteine improves cellular growth in respiratory-deficient yeast. Braz J Microbiol. 2022 Jun;53(2):791-794. doi: 10.1007/s42770-022-00705-5. Epub 2022 Feb 5. PMID: 35122656; PMCID: PMC9151961.

13. Albera C, Ferrero C, Rindone E, Zanotto S, Rizza E. Where do we stand with IPF treatment? Respir Res. 2013;14 Suppl l(Suppl 1):S7. doi: 10.1186/1465-9921-14-S1-S7. Epub 2013 Apr 16. PMID: 23734956; PMCID: PMC3 643087.

14. Carvalho DP. Ferreira AC, Coelho SM, Moraes JM, Camacho MA, Rosenthal D. Thyroid peroxidase activity is inhibited by amino acids. Braz J Med Biol Res. 2000 Mar;33(3):355-61. doi: 10.1590/s0100879x2000000300015. PMID:10719389.

15. Gusarov I, Shamovsky I, Pani B. Gautier L, Eremina S. Katkova-Zhukotskaya O, Mironov A, Makarov AA, Nudler E. Dietary thiols accelerate aging of C. elegans. Nat Commun. 2021 Jul 15;12(1):4336. doi: 10.1038/s41467021-24634-3. Erratum in: Nat Commun. 2021 Dec 6;12(1):7220. PMID: 34267196; PMCID: PMC8282788. EJ3
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Peripheral Neuropathy

Click to access s13098-025-01624-9.pdf

Emara, Sherien Mohamed, et al. “Effect of high-dose N-acetyl cysteine on the clinical outcome of patients with diabetic peripheral neuropathy: a randomized controlled study.” Diabetology & Metabolic Syndrome 17.1 (2025): 79.

Click to access article_397116_8757b42d5ae6560a642122bc577ac913.pdf

Emara, Sherien M., et al. “Role of N-Acetyl Cysteine in the Management of Diabetic Peripheral Neuropathy: A Systematic Review.” Archives of Pharmaceutical Sciences Ain Shams University 8.2 (2024): 455-468.
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Cardiovascular

https://www.mdpi.com/2076-3921/12/12/2073
Cui, Yuqi, et al. “N-acetylcysteine and atherosclerosis: promises and challenges.” Antioxidants 12.12 (2023): 2073.

N-Acetylcysteine (NAC) is approved by the Food and Drug Administration (FDA) for the treatment of acetaminophen overdose.
Although not approved for use as a dietary supplement, NAC has been widely used for acute respiratory distress syndrome, bronchitis, chemotherapy-induced toxicity, human immunodeficiency virus/acquired immune deficiency syndrome, radio-contrast-induced nephropathy, heavy metal toxicity, psychiatric disorders, and as an over-the-counter nutritional supplement [5,6]. In the cardiovascular area, NAC has been used off label for doxorubicin-induced cardiotoxicity, stable angina pectoris, and cardiac ischemia-reperfusion injury [6,7].

The primary mechanisms for the actions of NAC are considered to relate to its antioxidative effects via increasing intracellular glutathione (GSH) levels (crucial for cellular redox balance) and its anti-inflammatory effect through suppressing nuclear factor kappa B (NF-κB)-mediated expression of a variety of inflammatory mediators, including tumor necrosis factor-alpha (TNF-α) and interleukins (IL-6 and IL-1β) [5]. In this review, we summarize the data on the effects of NAC on atherosclerosis from both pre-clinical and clinical studies and discuss the potential mechanisms of the effects of NAC on atherosclerosis development and progression, as well as controversies and challenges concerning NAC and atherosclerosis.

N-acetylcysteine (NAC) has been used as a mucolytic agent and an antidote for acetaminophen overdose with a well-established safety profile. NAC has antioxidant and anti-inflammatory effects through multiple mechanisms, including an increase in the intracellular glutathione level and an attenuation of the nuclear factor kappa-B mediated production of inflammatory cytokines like tumor necrosis factor-alpha and interleukins.

NAC has been reported to protect against coronary artery diseases (CAD), myocardial infarction (AMI), myocardial injuries, and cardiomyopathy [15,16,17,18,19,20] (Table 2). In patients with cardiac surgery, NAC decreases diabetes-associated cardiovascular, cardiopulmonary bypass, and cardiac surgery complications, including early reperfusion injury, pump-induced inflammatory response, and myocardial stress [21,22,23].

NAC was also shown to potentiate the effects of NTG on the treatment of patients with unstable angina pectoris and other CAD patients [39,80]. A review of data from clinical studies has shown that NAC has cardioprotective effects in patients who had ischemic heart disease and underwent CABG and PCI [81].
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Chronic Lung Disease 2023

https://pmc.ncbi.nlm.nih.gov/articles/PMC10526097/
Mokra, Daniela, et al. “Advances in the use of N-acetylcysteine in chronic respiratory diseases.” Antioxidants 12.9 (2023): 1713.

However, because of the anticoagulant properties and inhibition of platelet aggregation, NAC should be used with caution in patients with bleeding disorders and anemia [26].

N-acetylcysteine (NAC) is widely used because of its mucolytic effects, taking part in the therapeutic protocols of cystic fibrosis. NAC is also administered as an antidote in acetaminophen (paracetamol) overdosing. Thanks to its wide antioxidative and anti-inflammatory effects, NAC may also be of benefit in other chronic inflammatory and fibrotizing respiratory diseases, such as chronic obstructive pulmonary disease, bronchial asthma, idiopathic lung fibrosis, or lung silicosis. In addition, NAC exerts low toxicity and rare adverse effects even in combination with other treatments, and it is cheap and easily accessible. This article brings a review of information on the mechanisms of inflammation and oxidative stress in selected chronic respiratory diseases and discusses the use of NAC in these disorders.

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OCD

Click to access Narrative-Review-N-acetylcysteine-An-Innovative-Approach-to-Obsessive-Compulsive-Disorder-Treatment-A-Narrative-Review.pdf

Sonia, Sadia Binte Anwar, et al. “N-acetylcysteine: An innovative approach to obsessive-compulsive disorder treatment: A narrative review.” Advances in Human Biology 15.2 (2025): 167-176.

NAC’s clinical effectiveness has not been identified despite pre-clinical
research suggesting that it improves the animal models of OCD.

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NAC and Glycine Prevents Decline of Aging and Prolongs Lifespan

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