VLDL-triglyceride production after alcohol ingestion, studied using [2-13C1] glycerol.
We used [2-13C1]glycerol to characterize very low density lipoprotein (VLDL)-triglyceride kinetics and intrahepatic glycerol metabolism in normal men (n = 4) after alcohol (EtOH) ingestion. [2-13C1]glycerol was infused before and after the consumption of 48 g EtOH or a placebo. Three additional subjects also received [1-13C1]acetate in addition to the [2-13C1]glycerol with EtOH treatment. Incorporation of tracer into the glycerol or fatty acid moiety of VLDL-triglyceride was measured by gas chromatography-mass spectrometry and used to calculate VLDL-triglyceride production rates. Intrahepatic triose-phosphate enrichments were also calculated based on mass isotopomer distribution analysis of plasma glucose. There was no difference in VLDL-triglyceride production rates after 48 g EtOH (11.9 +/- 3.7 mg/kg/h) or placebo (14.7 +/- 3. 3 mg/kg/h). The VLDL-triglyceride rate constants calculated by kinetic modeling using the glycerol and acetate tracers in the combined isotope infusion subjects were very closely correlated (r 2 = 0.94). The peak VLDL-glycerol enrichments after EtOH were 22.5 +/- 3.3% versus 7.6 +/- 0.8% after placebo (P < 0.001), while intrahepatic triose-phosphate enrichments were 19.8 +/- 1.3% and 13. 1 +/- 1.2% (P < 0.001), respectively. Moreover, the calculated asymptotic VLDL-glycerol enrichments (representing the hepatic alpha-glycerol phosphate enrichment) were significantly higher after EtOH than placebo. The higher ratio of VLDL-glycerol to triose-phosphate labeling after EtOH suggests a metabolic block at glycerol 3-phosphate dehydrogenase. We conclude that consumption of 48 g EtOH does not increase VLDL-triglyceride production in normal men but does cause accumulation of tracer in hepatic alpha-glycerol phosphate.
Siler
S Q
SQ
Department of Nutritional Sciences, 309 Morgan Hall, University of California at Berkeley, CA 94720-3104, USA.
Neese
R A
RA
Parks
E J
EJ
Hellerstein
M K
MK
D000328:Adult; D000428:Alcohol Drinking / Q000378:metabolism*; D002247:Carbon Isotopes; D005990:Glycerol / Q000097:blood / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008079:Lipoproteins, VLDL / Q000096:biosynthesis*; D008099:Liver / Q000378:metabolism; D008297:Male; D014280:Triglycerides / Q000096:biosynthesis*; D014306:Trioses / Q000378:metabolism
D002247:Carbon Isotopes; D008079:Lipoproteins, VLDL; D014280:Triglycerides; D014306:Trioses; D005990:Glycerol