Early life nutrition influences physical activity level and the contractile and metabolic phenotype of the mouse plantaris (706.17)

Abstract

The objective was to determine the effects of postnatal nutrition on skeletal muscle composition and voluntary physical activity. Newborn FVB female pups (n=18) were fostered by dams fed a control (CON; 20% protein) or protein‐restricted (PR; 8% protein) diet. After 3 wks all pups were weaned to a CON diet and individually housed with locked (SEDentary) or free‐moving (EX) running wheels. After 3 wks the contractile and metabolic properties of the plantaris were characterized by immunohistochemistry for myosin heavy chain (MHC) isoforms and succinate dehydrogenase (SDH) enzyme. Compared to SED CON, SED PR pups had a 60% higher proportion of oxidative fibers (P=0.03), 16% more intermediate fibers (P=0.06), and fewer glycolytic fibers (P=0.01); SED PR mice had 11% fewer MHC IIB fibers (P=0.03), 40% more IIX fibers (P=0.001) and similar IIA fibers. In EX CON pups the proportion of oxidative (P=0.024) and IIA fibers increased by 70% and 75%, respectively (p=0.001), and glycolytic, IIB (p=0.003) and IIX (p=0.005) fibers decreased. There was no effect of EX on the metabolic composition of the fibers in PR mice, whereas the changes in MHC were similar to those of EX CON mice. PR mice ran less than CON pups (55.2±4.8 vs 130.1 ± 5.1 km, respectively; P<0.001).Thus, early postnatal PR appears to result in the dissociation between the metabolic and contractile properties of skeletal muscle that may contribute to impaired wheel running.Grant Funding Source: Supported by USDA