Interaction between malnutrition and ovarian hormones on the systemic IGF-I axis.

Abstract

In malnutrition both the GH-IGF and reproductive axes are greatly affected. Because the actions of IGF and sex steroids are inter-dependent in many tissues, we have examined how ovariectomy modulates the response of the systemic IGF system to undernutrition. Peripubertal (30 days of age) female rats were either sham operated or ovariectomized. Five days later half of each group was submitted to a protein-caloric restriction diet. All rats were killed at 60 days of age. Growth was decreased in all rats submitted to calorie restriction and this was consistent with a decrease in circulating IGF-I concentrations and liver IGF-I mRNA expression. While in normally fed rats ovariectomy had no significant effect on serum IGF-I concentrations, ovariectomized and underfed rats had significantly higher levels than intact underfed rats. In undernourished rats, serum IGF-binding proteins (IGFBP)-1, -2 and -3 concentrations were significantly reduced and this was not modified by ovariectomy. In contrast, liver mRNA concentrations of IGFBP-1 and -2 were increased and IGFBP-3 unchanged in intact undernourished animals, suggesting that undernutrition could be affecting the proteolysis of these binding proteins, and this response was significantly modulated by ovariectomy. These results indicate that the presence of circulating ovarian hormones significantly affects the response of the IGF system to undernutrition.