PYRUVATE AND HEPATIC PYRUVATE-DEHYDROGENASE LEVELS IN RAT STRAINS SENSITIVE AND RESISTANT TO DIETARY OBESITY

This study compared the effects of exogenous pyruvate and lactate on t he serum levels of pyruvate, lactate, glucose, alanine, and insulin, a s well as the activity of hepatic pyruvate dehydrogenase (PDH) in stra ins of rat that were either sensitive [Osborne-Mendel (OM)] or resista nt (S5B/Pl) to high-fat diet-induced obesity. Serum pyruvate and lacta te were significantly higher and glucose lower in ad libitum-fed OM ra ts, but these differences disappeared after an 18-h fast. The increase in pyruvate and lactate after exogenous pyruvate administration was s ignificantly greater in S5B/Pl rats than OM rats. There were no differ ences in serum alanine with strain or diet. The total PDH activity was similar across strains and diets but the proportion of PDH in its act ivated form (PDH,) was decreased in ad libitum-fed S5B/Pl rats. Pyruva te injection increased insulin and hepatic PDH, activity in OM rats fe d both high- and low-fat diets, but these responses were greatly atten uated or absent in S5B/Pl rats, The data are consistent with the hypot hesis that modulation of carbohydrate oxidation by PDH may be related to susceptibility to obesity when rats are fed a high-fat diet.