EFFECTS OF PYRUVATE ON THE METABOLISM AND INSULIN-RESISTANCE OF OBESEZUCKER RATS

Female obese Zucker rats aged 5 wk were randomly assigned to a control diet or one of two experimental diets. Experimental diets contained 6 % of energy as pyruvate in the form of calcium-pyruvate (Ca-pyr) or 6% pyruvylglycine (pyrgly). Diets were pair-fed according to the experim ental group with the lowest food consumption. During the 3 wk of dieta ry treatment, Ca-pyr- and pyr-gly-fed rats gained significantly less w eight, had a lower food-conversion efficiency, and maintained a higher resting oxygen consumption (mL.min(-1).kg(-0.67)) than control rats. Ca-pyr and pyr-gly also lowered the respiratory exchange ratio of the rats resulting in a 90% increase in their lipid oxidation and a 50% de crease in their carbohydrate oxidation. Glucose tolerance, assessed by an oral glucose load, was not different among treatments, but the ins ulin response of the pyr-gly-fed rats was significantly less than that of the control rats despite elevated plasma triglyceride concentratio ns in the pyr-gly-fed rats (control, 1.43 +/- 0.16 vs pyr-gly, 3.76 +/ - 0.87 mmol/L). These results suggest that pyr-gly, like Ca-pyr, favor ably alters the metabolism of obese Zucker rats. In addition, pyrgly a ppeared to reduce the insulin resistance that develops spontaneously i n obese rats.