TY - JOUR
T1 - Blood glycerol is an important precursor for intramuscular triacylglycerol synthesis
AU - Guo, Zeng Kui
AU - Jensen, Michael D.
PY - 1999/8/20
Y1 - 1999/8/20
N2 - The utilization of blood glycerol and glucose as precursors for intramuscular triglyceride synthesis was examined in rats using an intravenous infusion of [2-14C]g-lycerol and [6-3H]glucose or [6- 14C]glucose. In 24-h fasted rats, more glycerol than glucose was incorporated into intramuscular triglyceride glycerol in soleus (69 ± 23 versus 4 ± 1 nmol/μmol triglyceride/h, respectively, p = 0.02 glycerol versus glucose) and in gastrocnemius (25 ± 5 versus 9 ± 2 nmol/μmol 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/μmol triglyceride/h) were similar (p > 0.3) to those of glucose (5 ± 2, 9 ± 2, and 5 ± 2 nmol/μmol triglyceride/h for quadriceps, gastrocnemius, and soleus muscle, respectively). Glucose incorporation into intramuscular triglycerides was less with [6-3H]glucose than with [6- 14C]glucose, suggesting an indirect pathway for glucose carbon entry into muscle triglyceride. The isotopic equilibrium between plasma and intramuscular free glycerol ([U-13C]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.
AB - The utilization of blood glycerol and glucose as precursors for intramuscular triglyceride synthesis was examined in rats using an intravenous infusion of [2-14C]g-lycerol and [6-3H]glucose or [6- 14C]glucose. In 24-h fasted rats, more glycerol than glucose was incorporated into intramuscular triglyceride glycerol in soleus (69 ± 23 versus 4 ± 1 nmol/μmol triglyceride/h, respectively, p = 0.02 glycerol versus glucose) and in gastrocnemius (25 ± 5 versus 9 ± 2 nmol/μmol 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/μmol triglyceride/h) were similar (p > 0.3) to those of glucose (5 ± 2, 9 ± 2, and 5 ± 2 nmol/μmol triglyceride/h for quadriceps, gastrocnemius, and soleus muscle, respectively). Glucose incorporation into intramuscular triglycerides was less with [6-3H]glucose than with [6- 14C]glucose, suggesting an indirect pathway for glucose carbon entry into muscle triglyceride. The isotopic equilibrium between plasma and intramuscular free glycerol ([U-13C]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.
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U2 - 10.1074/jbc.274.34.23702
DO - 10.1074/jbc.274.34.23702
M3 - Article
C2 - 10446128
AN - SCOPUS:0033588373
SN - 0021-9258
VL - 274
SP - 23702
EP - 23706
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 34
ER -