[Role of brown adipose tissue in the development of genetic obesity in the obese Zucker rat (fa/fa)].

The lipogenic capacity and thermogenic activity (assessed by GDP binding to mitochondrial) of brown adipose tissue was studied in lean (Fa/fa) and obese (fa/fa) suckling Zucker rat pups 2 and 10 days old. By 10 days of age, fat deposition, lipogenesis in vivo and fatty acid synthetase activity were 1.5 to 2-fold higher, whereas GDP binding to mitochondria was 40% lower in pre obese than in lean pups. Compared with lean pups, 2-day old fa/fa pups showed a 60% increase in triglyceride accumulation in interscapular brown adipose tissue and a 30% decrease in GDP binding to mitochondria, while no change occurred in fatty acid synthetase activity. These results strongly suggest that an impaired thermogenic activity in the brown adipose tissue of fa/fa pups could play a key role in the development of obesity. However, the concomitant increase in fat content in the brown adipose tissue of 2-day old pre-obese pups raises the question of the causal relationship between these two disorders.