Effects of high protein diets and leucine supplementation on body weight regulation and energy metabolism in mice

Abstract

High dietary protein (P) intake can improve glucose homeostasis, decrease body weight gain, and increase energy expenditure (EE). Leucine (Leu) was suggested to be involved in the regulation of genes stimulating energy metabolism. Therefore, we aimed to study the effects of high P and a high Leu containing adipogenic diets in mice. Male C57BL/6 mice were fed for 20 wks high fat diets (20%) containing either 10% (AP, control) or 50% whey P (HP). A third group was exposed to AP supplemented with L‐Leu (AP+L) as contained in HP. HP feeding and Leu supplementation resulted in significantly (P<0.05) lower food intake, reduced body weight gain (20.7±0.8, 14.8±1.4 and 9.7±0.8 g for AP, AP+L and HP, respectively), lower food energy efficiency (2.14±0.08, 1.57±0.11 and 1.11±0.08 g/MJ for AP, AP+L and HP, respectively), lower body fat mass (quantitative nuclear resonance), lower liver triacylglycerol concentrations, and higher lean body mass as well as higher weights of m. quadriceps and higher postabsorptive 15N‐lysine incorporation into skeletal muscle. EE (indirect calorimetry) was not different between groups. Parameters of glucose homeostasis were significantly (P<0.05) improved in HP and AP+L fed mice. Effects of Leu supplementation are generally intermediate to those of the HP as compared to AP. We suggest a role of Leu at the increase of EE; however, an expected higher uncoupling protein gene expression was not detected.