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.
Qin
B
B
Department of Sports Medicine, Graduate School of Medicine, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan.
Nagasaki
M
M
Ren
M
M
Bajotto
G
G
Oshida
Y
Y
Sato
Y
Y
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