Experimental basis of obesity.

The methods utilized in our laboratory for a biochemical approach of obesity include dietary manipulations, fatty acid analysis of tissue lipids, in vivo lipogenesis from [3H H2O and [1-14C] acetate, in vitro utilization of [3H] H2O, [U-14C] glucose, [U-14C] fructose, [U-14C] alanine and [1-14C] acetate by adipose tissue fragments, hormone sensitivity (to insulin and catecholamines), and the activity of enzymes such as fatty acid synthetase and adenylate cyclase in adipose tissue extracts. With these methods at hand, it is possible to estimate the major biochemical factors responsible for fat accumulation in adipose tissue. As an example, the case of obese (ob/ob) homozygotic animals of the C57BL/6J strain of Bar Harbor, which suffer from an autosomal recessive obese-hyperglycemic (O-H) syndrome, is compared to that of control nonobese (ob+/ob+) mice from the same strain. The hereditary O-H syndrome in ob/ob mice is characterized by obesity, resistance to the action of insulin, and hyperinsulinism. The development of obesity depends on high lipogenesis in fat depots. Contribute also to obesity a large influx of fatty acids of hepatic and dietary origin, and reduced lipolysis. In these mice, a high fat diet is more propitious to fat accretion than a high-carbohydrate diet.