Effect of dietary protein on in vivo insulin action and liver glycogen repletion

Abstract

To investigate the influence of dietary manipulation on in vivo glucose metabolism, we pair fed normal rats for 10 days with one of three diets: 1) high protein-low carbohydrate (Hi-PN) (n = 20); 2) intermediate protein (I-PN) (n = 11); and 3) low protein-high carbohydrate (Lo-PN) (n = 18). Fasting glucose, postmeal plasma glucose, and insulin concentrations were as follows: 118 +/- 2 mg/dl, 138 +/- 2 mg/dl, and 4.0 +/- 0.2 ng/ml in Hi-PN; 111 +/- 3 mg/dl, 147 +/- 3 mg/dl, and 5.1 +/- 0.3 ng/ml in I-PN; 102 +/- 2 mg/dl, 162 +/- 2 mg/dl, and 6.0 +/- 0.2 ng/ml in Lo-PN, respectively. Basic hepatic glucose production (HGP) was 6.6 +/- 0.2 in Hi-PN, 6.1 +/- 0.2 in I-PN, and 5.6 +/- 0.1 mg.kg-1.min-1 in Lo-PN. Insulin sensitivity was assessed with the euglycemic clamp using two insulin infusion rates: 2 and 4 mU.kg-1.min-1. The rate of glucose disappearance was 14.8 +/- 0.4 and 25.3 +/- 0.7 in Hi-PN, 15.3 +/- 0.4 and 26.9 +/- 0.5 in I-PN, and 16.1 +/- 0.6 and 31.5 +/- 0.5 mg.kg-1.min-1 in Lo-PN, respectively. HGP was suppressed by 86 in the 2- and by 90% in the 4-mU insulin clamp in the Lo-PN, whereas HGP was suppressed by 45 and by 79% in the two steps in the Hi-PN group.(ABSTRACT TRUNCATED AT 250 WORDS)