Abstract
Aging is characterized by extensive metabolic dysregulation. Redox coenzyme nicotinamide adenine dinucleotide (NAD) can exist in oxidized (NAD+) or reduced (NADH) states, which together form a key NADH/NAD+ redox pair. Total levels of NAD decline with age in a tissue-specific manner, thereby playing a significant role in the aging process. Supplementation with NAD precursors boosts total cellular NAD levels and provides some therapeutic benefits in human clinical trials. However, supplementation studies cannot determine tissue-specific effects of an altered NADH/NAD+ ratio. Here, we created transgenic Drosophila expressing a genetically encoded xenotopic tool LbNOX to directly manipulate the cellular NADH/NAD+ ratio. We found that LbNOX expression in Drosophila impacts both NAD(H) and NADP(H) metabolites in a sex-specific manner. LbNOX rescues neuronal cell death induced by the expression of mutated alpha-B crystallin in the Drosophila eye, a widely used system to study reductive stress. Utilizing LbNOX, we demonstrate that targeting redox NAD metabolism in different tissues may have drastically different outcomes, as the expression of LbNOX solely in the muscle is much more effective for rescuing paraquat-induced oxidative stress compared to whole-body expression. Excitingly, we demonstrate that perturbing NAD(P) metabolism in non-neuronal tissues is sufficient to rejuvenate sleep profiles in aged flies to a youthful state. In summary, we used xenotopic tool LbNOX to identify tissues and metabolic processes which benefited the most from the modulation of the NAD metabolism thereby highlighting important aspects of rebalancing the NAD and NADP pools, all of which can be translated into novel designs of NAD-related human clinical trials.
Significance statement Total levels of NAD decline with age in a tissue-specific manner, thereby playing a significant role in the aging process. Supplementation with NAD precursors boosts organismal NAD levels but cannot determine tissue-specific effects of altered NAD metabolism. Here, we created transgenic Drosophila expressing a genetically encoded xenotopic tool, LbNOX, to directly manipulate NAD metabolism. We demonstrate that targeting NAD metabolism in just one tissue may be more effective than altering whole-body metabolism and can reverse some aging-related manifestations in a sex-specific manner. We anticipate that our work will define the tissues that benefit the most from targeting NAD metabolism and aid in designing better human clinical trials.
Competing Interest Statement
The authors (except Dr. Valentin Cracan) have no conflicts of interest to declare. Dr. Valentin Cracan is listed as an inventor on a patent application on the therapeutic uses of LbNOX and TPNOX (US patent application US20190017034A1).
