Modulation of in vivo insulin action by dietary protein during pregnancy.

Rats were provided with a standard 20% protein diet or an isocaloric 8% protein diet from day 1 of gestation and were studied on day 19 of pregnancy. Fetal numbers per dam were unchanged, but total fetal weight at day 19 of gestation was reduced by 10% (P < 0.001) in the 8% protein group. In the basal state, endogenous glucose production (Ra) and muscle glucose uptake/phosphorylation were not significantly affected by dietary protein content. The glucose infusion rate required to maintain glycemia and Ra during euglycemic-hyperinsulinemic clamp (insulin infusion rate of 4.17 mU.kg-1.min-1) were reduced in the 8% protein group by 17% (P < 0.05) and 76% (P < 0.001), respectively. Suppression of Ra by insulin was not significant in the 20% protein group. Insulin-stimulated glucose disappearance (Rd) was 24% lower (P < 0.001) in the 8% protein group (25.0 +/- 0.8 mg.min-1.kg-1) than in the 20% protein group (32.7 +/- 0.5 mg.min-1.kg-1). The overall increment in muscle glucose utilization index (mean of 6 muscles) elicited by insulin was impaired by 38.1 +/- 4.0%. Insulin suppressed nonesterified fatty acid concentration (NEFA) by 83% (P < 0.001) and plasma triacylglycerol concentration (TAG) by 67% (P < 0.05) in the 20% protein group but evoked only a 43% (P < 0.01) decline in plasma NEFA and did not significantly suppress plasma TAG in the 8% protein group.(ABSTRACT TRUNCATED AT 250 WORDS)