Aging is the greatest risk factor for many diseases. Intracellular concentrations of nicotinamide adenine dinucleotide (NAD+) and the NAD+-coupled redox state have been proposed to moderate many aging-related processes, yet the specific mechanisms remain unclear. The concentration of NAD+ falls with age in skeletal muscle, yet there is no consensus on whether aging will increase or decrease the redox potential of NAD+/NADH. Oxidized flavin groups (Fp) (e.g. FAD, i.e., flavin adenine dinucleotide, contained in flavoproteins) and NADH are intrinsic fluorescent indicators of oxidation and reduction status of tissue, respectively. The redox ratio, i.e., the ratio of Fp to NADH, may be a surrogate indicator of the NAD+/NADH redox potential. In this study we used the Chance redox scanner (NADH/Fp fluorescence imaging at low temperature) to investigate the effect of aging on the redox state of mitochondria in skeletal muscles. The results showed that there are borderline significant differences in nominal concentrations of Fp and NADH, but not in the redox ratios when comparing 3.5-month and 13-month old muscles of mice (n = 6). It may be necessary to increase the number of muscle samples and study mice of more advanced age.
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We appreciate Dr. Yu Wen and Dr. He N. Xu for their assistance with the paper revision. This work was supported by the NIH grant R01CA155348 and R01CA191207 (PI: L.Z. Li), the Center for Magnetic Resonance and Optical Imaging (CMROI) – an NIH supported research resource (P41EB015893, PI: R. Reddy).
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