Evidence for the role of insulin-like growth factor II (IGF-II) in the control of food intake

Highly purified insulin-like growth factors I and II and insulin (100 ng peptide/animal) were injected intracerebroventricularly in rats and the effect on 24 hour food consumption examined. IGF-II injections resulted in a 21% decrease in food intake and 4% body weight loss over the 24 hour period following peptide administration whereas IGF-I and insulin had no effect on either parameter. Increasing the amount of IGF-II injected also increased these responses with depressions of 22, 33 and 44% occurring in rats given 33, 100 and 300 ng IGF-II respectively. In addition, tissue concentrations of IGF-II were detected and found to be differentially distributed, via radioimmunoassay, in specific regions of the brain implicated in the regulation of food intake. IGF-I was not found in these same tissue punches despite radioimmunoassay sensitivity of 6 pg.