Lysine supplementation increases fat oxidation in high‐fat diet fed mice

It is suggested that amino acids influence lipid and glucose metabolism, e.g., infusion of glutamine increases glucose uptake in muscle and liver in dogs (Borel M.J. et. al. 1998), dietary L‐arginine supplementation reduces fat mass in Zucker diabetic fatty rats (Fu W.J. et. al. 2005), and L‐taurine improves cholesterol metabolism (Murakami S. et. al. 1999). We investigated the effect of L‐lysine on lipid‐energy metabolism using indirect calorimetry and 13 C labeled trigriceride in high‐fat diet fed mice. Male 14 weeks old C57BL/6J mice were fed high‐fat diet (25% w/w) or the high‐fat diet supplemented L‐lysine (2.4% w/w), both diets contain 13 C 3 ‐triolein and 13 C 3 ‐tripalmitin, for 8 hours in dark period after 18 hours fasting. Respiratory gas exchanges and expired 13 CO 2 were measured by an open‐circuit metabolic gas analysis system connected directly to a mass spectrometer (ARCO SYSTEM, Japan). The respiratory quotient decreased in the L‐lysine supplemented group compared with the high‐fat diet group. The recovery rate of 13 C in expired gas for 24 hours increased by 30% in high fat diet with lysine group (65.0±6.4%) compared to high fat diet group (50.4±10.2%). These results suggest that supplementation of L‐lysine increases fat oxidation in mice fed high‐fat diet.