Effect of leptin on insulin resistance of muscle--direct or indirect?
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 microU/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.
Doh
K O
KO
Department of Physiology, Dongguk University College of Medicine, Daegu, Korea.
Park
J O
JO
Kim
Y W
YW
Park
S Y
SY
Jeong
J H
JH
Jeon
J R
JR
Lee
S K
SK
Kim
J Y
JY
D050153:Abdominal Fat / Q000033:anatomy & histology / Q000378:metabolism; D000818:Animals; D001066:Appetite / Q000187:drug effects; D001786:Blood Glucose / Q000378:metabolism; D001835:Body Weight / Q000187:drug effects; D003847:Deoxyglucose / Q000493:pharmacokinetics; D004041:Dietary Fats / Q000494:pharmacology; D004435:Eating / Q000187:drug effects; D007333:Insulin Resistance / Q000502:physiology*; D020738:Leptin / Q000097:blood* / Q000494:pharmacology*; D008297:Male; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D014280:Triglycerides / Q000378:metabolism
D001786:Blood Glucose; D004041:Dietary Fats; D020738:Leptin; D014280:Triglycerides; D003847:Deoxyglucose