Age-associated changes in oxidative stress and NAD+ metabolism in human tissue.
Level 4 - case-series / case-control
Cross-sectional observational human tissue study
PubMed 22848760 · doi:10.1371/journal.pone.0042357
What was done
Human pelvic skin samples were obtained from consenting patients aged between 15 and 77 years and newborn infants (0-1 year old) scheduled for unrelated surgical procedures (total n = 49). Researchers measured DNA damage, lipid oxidation (malondialdehyde), PARP activity, tissue NAD+ levels, and SIRT1 activity across age and sex groups.
What was found
DNA damage correlated positively with age in males (r = 0.490, p = 0.029) and females (r = 0.600, p = 0.003). Tissue NAD+ levels correlated negatively with age in both males (r = -0.706, p = 0.001) and females (r = -0.537, p = 0.01). Lipid oxidation increased with age in males (r = 0.623, p = 0.004) but not females (r = 0.200, p = 0.3734). In males, PARP activity rose with age (r = 0.768, p < 0.0001) and inversely correlated with NAD+ levels (r = -0.639, p = 0.0003), while SIRT1 activity declined with age (r = -0.612, p = 0.007); these associations were less evident in females. In post-pubescent males, lipid peroxidation correlated with DNA damage (r = 0.4962, p < 0.0001), and PARP activity correlated with NAD+ levels (r = 0.5241, p = 0.0213).
Why it matters
This study provides direct human tissue data confirming that NAD+ levels decline and DNA damage increases across the human lifespan, showing prominent sex-specific patterns in oxidative stress and sirtuin activity.
Limits
The study is cross-sectional and observational, which cannot prove causality. The sample size is modest (n = 49), contains an unrepresented age gap between 1 and 15 years, and is limited to pelvic skin from surgical patients, which may not represent systemic NAD+ metabolism across other vital organs.
Cited by
- supports NAD+ levels decline by approximately 50% by the time a person reaches middle age.