Leptin and the lipostat model

The lipostat model proposes that adipose tissue is directly involved in the hormonal regulation of apetite and energy expenditure.

The 'obese' (ob) gene has been cloned in the mouse and human (1). Leptin is the ob gene product. Leptin is secreted by adipose tissue and results in:

• decresed food intake
• increased energy expenditure
• decreased insulin levels
• decreased cortisol levels

In the ob mouse there are mutations in the ob gene which abolish leptin activity and so interupt any negative feedback regulation. Ob mice suffer gross obesity and non-insulin dependent diabetes. No similar mutations have been found in humans.

Reference:

• ) Zhang, Y. et al. (1994). Positional cloning of the mouse obese gene and its human homologue. Nature, 372, 425-432. 2) Sorensen, T. et al. (1996). Leptin in obesity. BMJ, 313, 953-4.