Abstract
Deacetylases such as sirtuins convert nicotinamide adenine dinucleotide (NAD) to nicotinamide (NAM). NAM must be reconverted to NAD by nicotinamide phosphoribosyltransferase (Nampt) to ensure maintenance of deacetylase activity. We employed murine models of reduced skeletal muscle activity of AMP‐activated protein kinase (AMPK) to determine whether exercise‐mediated increases in skeletal muscle Nampt are dependent on AMPK activity.A single bout of acute exercise (90 min, 10 – 17 m/s, 10% slope) increased skeletal muscle Nampt mRNA to similar degrees in both wild type (WT) and AMPKα2 knockout (KO) mice three hours after exercise cessation (WT sedentary vs. exercise, 1.00±0.17 vs. 1.55±0.23 arbitrary units [AU, mean ± SEM], KO sedentary vs. exercise, 0.97±0.22 vs. 1.29±0.19, n=6–7, p<0.05). Nampt protein in quadriceps muscle of AMPKα2 kinase dead (KD) mice was reduced relative to WT mice (p<0.05), and 6.5 weeks of combined voluntary wheel cage (7 d/week) and forced treadmill (5 d/week) exercise training increased quadriceps Nampt protein content of WT and KD animals to a similar degree (WT sedentary vs. trained 1.00±0.07 vs. 1.24±0.08 p<0.05, KD sedentary vs. trained, 0.89±0.05 vs. 1.05±0.07 AU, n=12–15, p<0.05).Despite reduced Nampt protein concentrations in skeletal muscle lacking a functional AMPKα2 subunit, exercise‐mediated Nampt protein gains do not appear to be dependent on α2 AMPK activity.
Published Version
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