Mitochondrial NAD Profile in a Rat Model of Attention-Deficit/Hyperactivity Disorder

Abstract

Mitochondria require nicotinamide adenine dinucleotide (NAD) to satisfy cellular energy needs. Mitochondrial stress has been reported in skeletal muscle tissue of humans with attention-deficit/hyperactivity disorder. NAD deficiency may indicate mitochondrial stress that can be assessed through NAD concentration assays and Western blotting of Nampt and Sirtuin 3 (SIRT3) proteins. Nampt is the rate-limiting enzyme in intracellular NAD recycling, while SIRT3 is an NAD-dependent protein deacetylase that regulates mitochondrial mass and activity. The objective of this study was to investigate skeletal muscle and liver tissues of rat strains that exhibit behaviors associated with ADHD. We hypothesized that tissues from rat models with ADHD-like behavior (Lewis and F344 strains) would have lower NAD concentrations and reduced Nampt and SIRT3 protein expression relative to the control strain (Sprague Dawley). To examine this hypothesis, we performed fluorescence tissue NAD concentration assays. We found a significant difference in liver NAD between Sprague Dawley and F344 rats (Sprague Dawley, 0.14 ± 0.07 mM/mg [mean ± standard deviation], F344, 0.22 ± 0.11; p < 0.05). Western blot analysis for Nampt and SIRT3 proteins revealed a significant difference between the F344 and Sprague Dawley rats for Nampt protein in the extensor digitorum longus (EDL) muscle (Sprague Dawley, 1043930 ± 303677 arbitrary units [AU], F344, 1729014 ± 553568 AU; p < 0.05). Our results indicate minor differences in tissue NAD concentration and Nampt protein expression in rat models with ADHD-like behaviors. This could be indicative of differential mitochondrial function in skeletal muscle or liver tissues. Further studies will examine the implications of increasing nicotinamide riboside in the skeletal muscles to observe the effects of NAD functioning. This work was supported by funds provided by the Cross-Disciplinary Science Institute at Gettysburg College (X-SIG) (HMS, JB) and a Gettysburg College Professional Development Grant (JB). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.