Effects of simmondsin on food intake, growth, and metabolic variables in lean (+/?) and obese(fa/fa) Zucker rats

Incorporation of 2.5 g/kg of the anorexigen, simmondsin, in the diet result ed in food intake reduction in both lean and obese Zucker rats; however, th e obese rats were much more sensitive to the food intake-reducing activity of simmondsin. In both obese and lean simmondsin-treated Zucker rats, growt h was slower than in control rats, but was the same as that in pair-fed ani mals. The 24 h heat production pattern showed a smaller diurnal variation a nd a lower mean in obese rats than in lean rats. Food intake reduction, as a result of either simmondsin treatment or pair feeding, caused a decrease in mean heat production. Simmondsin treatment, but not pair feeding, caused a decrease in the diurnal variation of heat production. Plasma total chole sterol levels were increased in both simmondsin-treated and pair-fed obese and lean Zucker rats compared with control animals; this increase was mainl y due to an increase in HDL-cholesterol levels. Blood leptin levels in both obese and lean rats decreased with decreased food intake and decreased fat deposition, but in obese rats, simmondsin treatment resulted in an additio nal decrease in leptin levels. It is concluded that the food intake-reducin g effect of simmondsin is more pronounced in obese Zucker rats than in thei r lean littermates, and except for the simmondsin-specific effects on lepti n and total cholesterol values in obese littermates, the effects of simmond sin are related to food intake restriction in obese and lean Zucker rats.