Insulin secretion impairment and insulin sensitivity improvement in adult rats undernourished during early lactation.

In order to study the effect of undernutrition on the onset of disturbances in insulin secretion and insulin resistance, we compared the effects of a low protein diet containing 4% of protein (LPD) and a normal diet containing 25% of protein (NPD) supplied to the dams during the first 10 days of lactation when the pups turn into adults (90 days). We studies, in these rats, the insulin secretion, the glucose tolerance test (GTT) and, using the glucose clamp technique, the insulin resistance. The GTT showed a delay of the response of LPD group to the glucose challenge (1 mg/kg body weight) at 10 minutes (NPD = 450 +/- 27 mg/dl; LPD = 650 +/- 32 mg/dl, p < 0.01). The insulin secretion, four minutes after stimulation was found reduced in the LPD group (LPD = 1.1 +/- 0.08 microU/islet/min; NPD = 1.85 +/- 0.02 microU/islet/min, p < 0.01). Using the glucose clamp technique the plasma glucose concentration was raised during the first 20 minutes after the glucose stimulation with 10 mg/Kg-1.min-1 (NPD = 200 +/- 32 mg/dl and; LPD = 160 +/- 14 mg/dl., p < 0.01). Afterwards, the hyperglycemia was subsequently maintained (NPD = 154 +/- 9 mg/dl; LPD = 149 +/- 12 mg/dl) and the insulinemia was unchanged by infusion of glucose in the LPD group. In a similar experiment, the administration of glucose (10 mg/Kg-1. min-1) plus insulin (1.67 mU/Kg-1. min-1), the LPD group when compared with the NPD group, displayed an accentuated decreasing of glucose concentration level (LPD = 90 +/- 7 mg/dl; NPD = 130 +/- mg/dl., p < 0.01), 30 minutes after the infusion. The data suggest that undernutrition induces an adaptive process of insulin sensitivity which occurs together with an insulin secretion first phase blockage.