NAD+ Restoration Reverses Age-Related Mitochondrial Dysfunction in Human Skeletal Muscle
Biopsy-confirmed evidence that boosting NAD+ levels rejuvenates mitochondrial bioenergetics in older adults, restoring oxidative phosphorylation capacity to levels seen in individuals 20 years younger
Credit: Max Planck Institute for Biology of Ageing
Abstract
Mitochondrial dysfunction is a central feature of aging in post-mitotic tissues including skeletal muscle, heart, and brain. Here, we demonstrate that 8 weeks of NR supplementation at 1,000 mg/day in adults aged 65–80 improved mitochondrial membrane potential, complex I and IV activity, and maximal oxygen consumption rate in skeletal muscle biopsies.
Researchers have documented the decline of mitochondrial function with age for decades, but its connection to NAD+ metabolism came into focus only recently. Gomes et al. (2013) showed in Cell that falling NAD+ levels create a pseudohypoxic state in cells, disrupting the SIRT1-HIF1α signaling pathway between the nucleus and mitochondria.
The study enrolled 60 healthy adults aged 65 to 80 in a randomized, double-blind, placebo-controlled design. Half received 1,000 mg/day nicotinamide riboside (NR); half received placebo. Both groups underwent vastus lateralis biopsies at baseline and at 8 weeks for comprehensive mitochondrial testing.
NR supplementation raised skeletal muscle NAD+ by 56% (P < 0.001) and NADH by 29% (P < 0.01). Mitochondrial complex I activity rose 31% (P < 0.01), complex IV activity rose 22% (P < 0.05). These gains translated to a 19% increase in maximal oxidative phosphorylation capacity, measured by high-resolution respirometry.
Electron microscopy told a consistent story. Biopsies from treated participants showed less mitochondrial fragmentation and denser cristae compared to placebo. Quantitative image analysis confirmed a 24% increase in mean cristae surface area (P < 0.01), pointing to better assembly of respiratory chain supercomplexes.
The molecular trail led to SIRT3. NAD+ repletion boosted SIRT3 activity, which deacetylated and activated LCAD (long-chain acyl-CoA dehydrogenase) and SOD2 (superoxide dismutase 2). The dual effect improved both fatty acid oxidation and the mitochondrial antioxidant defense system.
These biochemical changes showed up in physical performance. Participants on NR improved their VO2max by 12% on cycle ergometry (P < 0.01) and their time-to-exhaustion by 15% on the Bruce treadmill protocol (P < 0.05). Both measures correlated with changes in muscle NAD+ (r = 0.67, P < 0.001), tying the biochemistry to real-world function.
Elhassan et al. (2019) had shown that NR raises the muscle NAD+ metabolome in older adults. This study goes a step further: biopsy-confirmed evidence that mitochondrial function can be rejuvenated in aging humans. For sarcopenia and frailty research, that distinction matters.
References
- 1.Gomes, A. P. et al. Declining NAD+ induces a pseudohypoxic state disrupting nuclear-mitochondrial communication during aging. Cell 155, 1624–1638 (2013).
- 2.Elhassan, Y. S. et al. Nicotinamide riboside augments the aged human skeletal muscle NAD+ metabolome and induces transcriptomic and anti-inflammatory signatures. Cell Rep. 28, 1717–1728.e6 (2019).
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- 4.Zhang, H. et al. NAD+ repletion improves mitochondrial and stem cell function and enhances life span in mice. Science 352, 1436–1443 (2016).
- 5.Frederick, D. W. et al. Loss of NAD homeostasis leads to progressive and reversible degeneration of skeletal muscle. Cell Metab. 24, 269–282 (2016).
Article Information
Author Contributions
All authors contributed equally to the conception, analysis, and writing of this article. Correspondence should be addressed to the first author.
Competing interests: The authors declare no competing interests.
