Adding Carbohydrate to a Fat Meal Alters Post-Prandial Lipemia Without Changing Plasma Triglyceride Concentration

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1492 The insulin response to a meal containing both carbohydrate and fat can alter the lipemic response to the ingested fat through changes in muscle and adipose tissue lipoprotein lipase activity. PURPOSE: Determine the effect of adding carbohydrate to a fat meal on post-prandial triglyceride and fatty acid concentrations in the blood. METHODS: 5 healthy males ingested a lipid load (0.7g fat/kg body weight) on two separate occasions: 1) fat meal alone (F), and 2) fat meal co-ingested with glucose (GF; 1 g glucose/kg body weight). Blood samples were collected hourly for 8 h and were analyzed for concentrations of plasma insulin, fatty acid, glycerol, total plasma triglycerides (TG) and TG concentrations in the chylomicron and very-low density lipoprotein fractions (separated by density gradient centrifugation). Fat oxidation was measured using indirect calorimetry before the meal and 1.5, 3.5, 5.5, and 7.5 h after the meal. RESULTS: Despite a modest elevation in plasma insulin concentration in GF vs. F (insulin AUC: 74.9 ± 17.6 and 16.4 ± 4.3 μU/ml*min; P<0.05), plasma glycerol and total TG concentration, as well as the TG concentration in the chylomicron and VLDL fractions were not different between GF and F. In contrast, the elevation in plasma insulin concentration during GF was associated with a greater plasma fatty acid concentration (0.44 ± 0.02 and 0.26 ± .01 mM; P<0.05, average values during the 6–8 h period after the meal) and a lower rate of fat oxidation (73.6 ± 4.9 and 83.0 ± 2.8 μmol/min; P<0.05) during the 8 h period after the meal. CONCLUSION: The addition of carbohydrate to a fat meal and the resultant increase in plasma insulin concentration did not alter the net hydrolysis of the ingested lipids. However, the differential effects of insulin on lipoprotein lipase activity in adipose tissue and skeletal muscle may have reduced the uptake and oxidation of fatty acids derived from exogenous lipids.