EFFECT OF ACUTE GLYCEROL ADMINISTRATION WITH OR WITHOUT A MIXED MEAL IN HUMANS

We explored the effects of oral glycerol administration (20 g) alone o r in combination with a mixed meal on postprandial lipids, free fatty acids, high-density lipoprotein cholesterol and retinyl palmitate. We also tested the meal alone as a control. The metabolic behavior of C-1 3-labelled glycerol, mainly its incorporation into triglycerides and g lucose, was also investigated. The tests were performed on 13 healthy subjects aged 20-56 years (mean 32.1 +/- 10.8). Glycerol administratio n alone induced a decrease in plasma free fatty acid levels. When glyc erol was given with the meal, it was absorbed faster and postprandial triglyceride levels were higher compared to the meal alone (p < 0.05). An earlier and higher peak of retinyl palmitate was also observed whe n comparing the glycerol and mixed meal test to the mixed meal alone. No significant effect was observed on total, high-density and low-dens ity lipoprotein cholesterol. These results suggest that the glycerol-i nduced increase in postprandial triglyceride levels is probably due to an increase in chylomicron synthesis and perhaps to the stimulation o f intestinal glycerol kinase activity. C-13-labelled glycerol administ ration showed a more important glycerol incorporation in lipoproteins with a density range of <1.006 during the test with glycerol alone as compared to the test with glycerol and a mixed meal, suggesting that t he rate of glycerol incorporation into lipoproteins depends on the ava ilability of other substrates.