Age Related Changes in NAD+ Metabolism Oxidative Stress and Sirt1 Activity in Wistar Rats

Abstract

The cofactor nicotinamide adenine dinucleotide (NAD+) has emerged as a key regulator of metabolism, stress resistance and longevity. Apart from its role as an important redox carrier, NAD+ also serves as the sole substrate for NAD-dependent enzymes, including poly(ADP-ribose) polymerase (PARP), an important DNA nick sensor, and NAD-dependent histone deacetylases, Sirtuins which play an important role in a wide variety of processes, including senescence, apoptosis, differentiation, and aging. We examined the effect of aging on intracellular NAD+ metabolism in the whole heart, lung, liver and kidney of female wistar rats. Our results are the first to show a significant decline in intracellular NAD+ levels and NAD∶NADH ratio in all organs by middle age (i.e.12 months) compared to young (i.e. 3 month old) rats. These changes in [NAD(H)] occurred in parallel with an increase in lipid peroxidation and protein carbonyls (o- and m- tyrosine) formation and decline in total antioxidant capacity in these organs. An age dependent increase in DNA damage (phosphorylated H2AX) was also observed in these same organs. Decreased Sirt1 activity and increased acetylated p53 were observed in organ tissues in parallel with the drop in NAD+ and moderate over-expression of Sirt1 protein. Reduced mitochondrial activity of complex I–IV was also observed in aging animals, impacting both redox status and ATP production. The strong positive correlation observed between DNA damage associated NAD+ depletion and Sirt1 activity suggests that adequate NAD+ concentrations may be an important longevity assurance factor.

Changes in mitochondrial energy utilization in young and old worker honeybees (Apis mellifera)

“…The NAD + /NADH ratio was decreased with advancing age in the trophocytes and fat cells of workers. This finding is consistent with previous studies showing that the NAD + /NADH ratio decreases with advancing age in pancreatic β cells and neurons of mice (Ramsey et al 2008;Imai 2009), as well as in the livers, hearts, kidneys, and lungs of rats (Braidy et al 2011;Son et al 2012). These findings are also related to the differences in ΔΨm level observed in the current study.…”

“…This result is in agreement with previous studies showing that NAD + levels decrease with advancing age in pancreatic β cells and neurons of mice (Ramsey et al 2008;Imai 2009), as well as in the livers, hearts, kidneys, and lungs of rats (Braidy et al 2011;Son et al 2012). NADH concentration was not significantly different with advancing age in the trophocytes and fat cells of workers.…”

Reductive carboxylation is a major metabolic pathway in the retinal pigment epithelium

“…NAD + declines with age (47,51), and supplementation with NAD + precursors can delay aging, liver disease, and vascular dysfunction (52)(53)(54). NAD + precursors, such as nicotinamide riboside, can be used safely in humans (55,56).…”

Redox-regulating sirtuins in aging, caloric restriction, and exercise

“…Metabolic challenges, such as hypoxemia-ischemia and reoxygenation, result in deceased NAD and nicotinamide phosphoribosyltransferase (NAMPT) levels and decreased activity of sirtuins [32][33][34][35]. It was recently shown that treatment with glycated low-density lipoprotein resulted in increased ROS production in vascular endothelial cells and in lowered mitochondrial membrane potential, the NAD:NADH ratio [36].…”

“…In sporadic inclusion-body myositis, which is an agingassociated muscle disease, it was found that deacetylation of p53 was decreased [111]. Aging results in decreased intracellular levels of NADþ and NAD:NADH ratio in various organs of old rats, and this finding was associated with decreased activity of SIRT1 and increased acetylation of p53 [33]. Moreover, aging processes resulted in a lower activity of complexes I-IV in the mitochondria and enhanced oxidative DNA damage [33].…”