Pyruvate dehydrogenase activity in several tissues of genetically obese hyperglycemic mice

The active form (PDHa) and total activity of pyruvate dehydrogenase (PDH) were measured in homogenates from heart muscle, epididymal fat pads and liver of genetically obese hyperglycemic mice and compared with similar data derived from lean controls or Swiss albino mice. Both PDHa and total PDH activities were similar in heart muscle from all mice with a precipitous decrease in the PDHa upon fasting. Adipose tissue and liver of obese mice had a PDHa level that was almost two-fold higher than either lean control or Swiss albino mice. Fasting for 24 hours decreased the elevated activity of PDHa in adipose tissue and liver in obese mice to a value that was comparable to lean control or Swiss albino mice, fasted similarly. The elevation in both the active form and total activity of pyruvate dehydrogenase in livers from obese mice could explain the increased provision of acetyl-CoA units necessary for the accelerated hepatic lipogenesis observed with this mouse, a model for human obesity and insulin resistance.