title: Blood glycerol is an important precursor for intramuscular triacylglycerol synthesis.
abstract: The utilization of blood glycerol and glucose as precursors for intramuscular triglyceride synthesis was examined in rats using an intravenous infusion of [2-(14)C]glycerol and [6-(3)H]glucose or [6-(14)C]glucose. In 24-h fasted rats, more glycerol than glucose was incorporated into intramuscular triglyceride glycerol in soleus (69 +/- 23 versus 4 +/- 1 nmol/micromol triglyceride/h, respectively, p = 0.02 glycerol versus glucose) and in gastrocnemius (25 +/- 5 versus 9 +/- 2 nmol/micromol triglyceride/h, respectively, p = 0.02). Blood glucose was utilized more than blood glycerol for triglyceride glycerol synthesis in quadriceps. In fed rats, the blood glycerol incorporation rates (4 +/- 2, 8 +/- 3, and 9 +/- 3 nmol/micromol triglyceride/h) were similar (p > 0.3) to those of glucose (5 +/- 2, 8 +/- 2, and 5 +/- 2 nmol/micromol triglyceride/h for quadriceps, gastrocnemius, and soleus muscle, respectively). Glucose incorporation into intramuscular triglycerides was less with [6-(3)H]glucose than with [6-(14)C]glucose, suggesting an indirect pathway for glucose carbon entry into muscle triglyceride. The isotopic equilibrium between plasma and intramuscular free glycerol ([U-(13)C]glycerol) was complete in quadriceps and gastrocnemius, but not soleus, within 2 h after beginning the tracer infusion. We conclude that blood glycerol is a direct and important precursor for muscle triglyceride synthesis in rats, confirming the presence of functionally important amounts of glycerol kinase in skeletal muscle.
authors.affiliation: Endocrine Research Unit, Mayo Clinic, Rochester, Minnesota 55905, USA.
authors.forename: Z
authors.initials: Z
authors.lastname: Guo
authors.forename: M D
authors.initials: MD
authors.lastname: Jensen
mesh_terms: D000818:Animals; D002250:Carbon Radioisotopes; D005947:Glucose / Q000378:metabolism; D005990:Glycerol / Q000097:blood* / Q000378:metabolism; D005991:Glycerol Kinase / Q000378:metabolism; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014280:Triglycerides / Q000096:biosynthesis*; D014316:Tritium
chemical_list: D002250:Carbon Radioisotopes; D014280:Triglycerides; D014316:Tritium; D005991:Glycerol Kinase; D005947:Glucose; D005990:Glycerol