Cinnamon extract prevents the insulin resistance induced by a high-fructose diet.
The aim of this study was to determine whether cinnamon extract (CE) would improve the glucose utilization in normal male Wistar rats fed a high-fructose diet (HFD) for three weeks with or without CE added to the drinking water (300 mg/kg/day). In vivo glucose utilization was measured by the euglycemic clamp technique. Further analyses on the possible changes in insulin signaling occurring in skeletal muscle were performed afterwards by Western blotting. At 3 mU/kg/min insulin infusions, the decreased glucose infusion rate (GIR) in HFD-fed rats (60 % of controls, p < 0.01) was improved by CE administration to the same level of controls (normal chow diet) and the improving effect of CE on the GIR of HFD-fed rats was blocked by approximately 50 % by N-monometyl-L-arginine. The same tendency was found during the 30 mU/kg/min insulin infusions. There were no differences in skeletal muscle insulin receptor (IR)-beta, IR substrate (IRS)-1, or phosphatidylinositol (PI) 3-kinase protein content in any groups. However, the muscular insulin-stimulated IR-beta and IRS-1 tyrosine phosphorylation levels and IRS-1 associated with PI 3-kinase in HFD-fed rats were only 70 +/- 9 %, 76 +/- 5 %, and 72 +/- 6 % of controls (p < 0.05), respectively, and these decreases were significantly improved by CE treatment. These results suggest that early CE administration to HFD-fed rats would prevent the development of insulin resistance at least in part by enhancing insulin signaling and possibly via the NO pathway in skeletal muscle.
Department of Sports Medicine, Graduate School of Medicine, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan.
B
B
Qin
M
M
Nagasaki
M
M
Ren
G
G
Bajotto
Y
Y
Oshida
Y
Y
Sato
D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D001835:Body Weight; D002935:Cinnamomum zeylanicum / Q000737:chemistry*; D004032:Diet; D004305:Dose-Response Relationship, Drug; D004435:Eating; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005632:Fructose / Q000008:administration & dosage*; D005947:Glucose / Q000008:administration & dosage / Q000378:metabolism; D015309:Glucose Clamp Technique; D007328:Insulin / Q000097:blood; D055504:Insulin Receptor Substrate Proteins; D007333:Insulin Resistance; D008297:Male; D010750:Phosphoproteins; D010766:Phosphorylation / Q000187:drug effects; D010936:Plant Extracts / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D011972:Receptor, Insulin / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism
D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; C526296:Irs1 protein, rat; D010750:Phosphoproteins; D010936:Plant Extracts; D005632:Fructose; D014443:Tyrosine; D011972:Receptor, Insulin; D005947:Glucose