Dietary carbohydrate interacts with dietary fat to influence leptin responsiveness in rats

Abstract

Previously we showed that a 60% kcal fructose, and 10% kcal fat diet induces leptin resistance in rats. All rats fed the 60% kcal fructose diet were thinner than those fed a diet with 17% fructose and 10% fat (LFruc/LF), therefore, we tested leptin responsiveness in rats fed either a 40% kcal fructose and 30% kcal fat (MFruc/HF) or the LFruc/LF diet. An i.p injection of 2.0 mg/kg leptin inhibited food intake and weight gain of both MFruc/HF and LFruc/LF rats after days 7, 14, and 21 on diet. On day 36, leptin inhibited 14‐hour energy intake only in LFruc/LF fed rats. To determine whether changes in leptin responsiveness were due to fructose specifically or increased dietary monosaccharide, a second study tested leptin responsiveness in rats fed a 50% kcal glucose and 30% kcal fat diet (HGluc/HF), MFruc/HF or LFruc/HF diet. After 10.5 weeks, i.p. injections of 2.0 mg/kg leptin inhibited 14 hour weight gain and food intake in MFruc/HF and HGluc/HF groups but not LFruc/HF rats. These data suggest that dietary fat and carbohydrate have independent effects on leptin responsiveness and monosaccharides may reverse dietary fat‐induced leptin resistance. Supported by NIH grant DK053903.