Effect of Leptin on Insulin
Resistance of Muscle – Direct or Indirect?
K.O. DOH1, J.O. PARK2, Y.W. KIM2,
S.Y. PARK2, J.H. JEONG3, J.R. JEON2,
S.K. LEE2, J.Y. KIM2
1Department of Physiology, Dongguk University College
of Medicine, 2Department of Physiology, 3Plastic
Surgery, Yeungnam University College of Medicine, Daegu, Korea
Received April 20, 2005
Accepted August 8, 2005
On-line available October 17, 2005
Summary
We examined the effect of leptin on the insulin resistance in
skeletal muscles by measuring glucose transport. Male Wistar
rats were fed rat chow or high-fat diets for 30 days. Before
sacrifice, rats fed high-fat diet were subcutaneously injected
with leptin (1 mg/kg b.w.) for 3 days. The glucose transport in
epitrochlearis and soleus muscles did not differ in the
experimental groups under basal conditions, however these values
decreased significantly in the rats fed high-fat diet under
insulin stimulation (p<0.01). Leptin treatment recovered the
decreased glucose transport in epitrochlearis (p<0.05) and
soleus muscles (p=0.08). Triglyceride concentrations in soleus
muscles were increased significantly in the rats fed high-fat
diet as compared to rats fed chow diet (p<0.01), and were
decreased significantly by leptin treatment (p<0.01). The
glucose transport was measured under basal conditions and after
60 μU/ml of insulin treatment with or without 50 ng/ml of
leptin. Leptin had no direct stimulatory effect on glucose
transport under both basal and insulin-stimulated conditions in
vitro. These results demonstrate that leptin injection to rats
fed high-fat diet recovered impaired insulin responsiveness of
skeletal muscles and muscle triglyceride concentrations.
However, there was no direct stimulatory effect of leptin on
insulin sensitivity of skeletal muscles in vitro.
Key words
Leptin • Glucose transport • Insulin • Skeletal muscle
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