Effects of lipid on basal carbohydrate metabolism in normal men.

We investigated the effects of infusion of a 20% triglyceride emulsion plus heparin (LH) on carbohydrate (CHO) metabolism during basal insulin and glucose turnover conditions in normal male subjects. In study 1, LH or saline was infused at 0.5 and 1.5 ml/min for 2 h each. Plasma free fatty acids rose from approximately 0.4 to 0.8 mM with the low rate and to between 1.6 and 2.1 mM with the high rate. Similar increases occurred in plasma concentrations of glycerol, acetoacetate, and beta-hydroxybutyrate. LH infusions resulted in significant increases in C-peptide concentrations but had no effects on any of the other measured parameters of CHO metabolism. In study 2, LH or saline was infused as in study 1, but the compensatory insulin release was prevented by intravenous infusion of somatostatin and replacement of basal insulin and glucagon concentrations. This resulted in significant increases in plasma glucose (from 4.5 +/- 0.2 to 7.1 +/- 0.6 mM, P less than 0.001) and hepatic glucose output (from 9.0 +/- 1.5 to 11.3 +/- 1.4 mumol.kg-1.min-1, P less than 0.05) and a decrease in glucose clearance (from 2.32 +/- 0.13 to 1.44 +/- 0.11 ml.kg-1.min-1, P less than 0.05). We conclude that lipids can have adverse effects on CHO metabolism under basal conditions and that healthy individuals can compensate for these effects with additional secretion of insulin.