Metabolism of Adipose Tissue from Normal and Hypothyroid Rats1

Abstract

The metabolism of adipose tissue from normal and hypothyroid rats was studied in vitro. O2 consumption was reduced in fat cells obtained from thyroidectomized rats, but the oxidation of 14C-labeled glucose, pyruvate and acetate proceeded at normal rates. The oxidation of palmitate-l-14c to 14CO2, however, was significantly reduced following thyroidectomy. Synthesis of long-chain fatty acids from a variety of precursors was also reduced in the thyroprivic tissues. In addition to the well-known reduction in FFA release, thyroidectomy also reduced glycerol production by adipose tissue. Thus, thyroidectomy interferes with the conversion of 2 C units to long-chain fatty acids and with the conversion of long-chain fatty acids to 2 C fragments. Abnormalities in the function of mitochondrial membranes may account for the metabolic defects of thyroidectomy in adipose tissue.