Glucose homeostasis is altered by a reduction in calorie intake and this relationship has important implications because calorie restriction is a common treatment for obesity and diabetes II (American Diabetes Association, 1998). Calorie restriction alters insulin action and glucose transport in skeletal muscle. Previous work has shown that ovarian steroids are able to modulate insulin sensitivity (González et al. 2000; Livingstone et al. 2002). However, the relation between food restriction, insulin signalling and ovarian hormones is partially unknown.

In female food-restricted (50 %) rats (FR), we investigated the relation among ovarian hormones and insulin sensitivity, focusing on muscle insulin receptor (IR) and the possible influence of the food restriction time (5, 10 and 15 days). Analysis of variance and Student-Newman-Keuls tests were employed. P ²le³ 0.05 was considered significant.

Rats were anaesthetized (pentobarbital 45 mg kg^-1 intraperitoneal) and euglycaemic-hyperinsulinaemic clamp was performed (González et al. 2000). Insulin sensitivity was significantly higher in control (CD) than FR rats. The time of restriction determines the increase in insulin sensitivity (FR15 rats were more sensitivity than FR5 and FR10 rats). The amount and phosphorylation of IR in CD were significantly higher than FR. However, the time of food restriction determines only an increase in IR phosphorylation according to insulin sensitivity.

On the other hand, our food restriction model determinates a decrease in 17β-oestradiol plasma levels, while the progesterone levels does not change and we have shown that ovarian steroids are able to modulate insulin sensitivity involving IR (González et al. 2000, 2002a, b). Taken together these data show that a special ovarian hormonal millieu associated with food restriction could be related to changes in insulin sensitivity through a specific regulation of the muscle IR.

This study was partially supported by grant from the University of Oviedo (AYP-02-518).