Obese gene expression: reduction by fasting and stimulation by insulin and glucose in lean mice, and persistent elevation in acquired (diet-induced) and genetic (yellow agouti) obesity

Targeted disruption of the melanocortin-4 receptor results in obesity in mice

The melanocortin-4 receptor (MC4-R) is a G protein-coupled, seven-transmembrane receptor expressed in the brain. Inactivation of this receptor by gene targeting results in mice that develop a maturity onset obesity syndrome associated with hyperphagia, hyperinsulinemia, and hyperglycemia. This syndrome recapitulates several of the characteristic features of the agouti obesity syndrome, which results from ectopic expression of agouti protein, a pigmentation factor normally expressed in the skin. Our data identify a novel signaling pathway in the mouse for body weight regulation and support a model in which the primary mechanism by which agouti induces obesity is chronic antagonism of the MC4-R.

Chronic ICV enterostatin preferentially reduced fat intake and lowered body weight

The pancreatic peptide enterostatin will acutely reduce fat intake in rats provided a choice of diets. Chronic ICV infusions of enterostatin suppress the intake of high fat diet. However, the effects of chronic ICV enterostatin on diet choice has not previously been studied. To investigate this, enterostatin (0.5 microgram/h) or artificial cerebrospinal fluid (CSF) was infused for 9 days into the lateral ventricle of rats adapted to a two-choice high-fat (HF) and low-fat (LF) diet regime. Enterostatin reduced intake of HF diet with the maximum depression at day 4, but there was no compensatory increase in LF intake. The body weight of enterostatin-infused rats declined. This was associated with a reduction in fat pad and liver weights compared to the CSF-infused control rats. Serum triglycerides and insulin were decreased and corticosterone was elevated in enterostatin-infused rats. The data show that enterostatin will chronically reduce fat intake and body weight and suggest that enterostatin may attenuate the appetite for fat.