Myricetin, a naturally occurring flavonol, ameliorates insulin resistance induced by a high-fructose diet in rats.

Abstract

The present study was conducted to explore the effects of myricetin on insulin resistance in rats fed for 6 weeks with a diet containing 60% fructose. Repeated intravenous (i.v.) injection of myricetin (1 mg/kg per injection, 3 times daily) for 14 days was found to significantly decrease the high glucose and triglyceride levels in plasma of fructose chow-fed rats. Also, the higher degree of insulin resistance in fructose chow-fed rats as measured by homeostasis model assessment of basal insulin resistance was significantly decreased by myricetin treatment. Myricetin increased the whole-body insulin sensitivity in fructose chow-fed rats, as evidenced by the marked elevation of composite whole-body insulin sensitivity index during the oral glucose tolerance test. Myricetin was found to reverse the defect in expression of insulin receptor substrate-1 (IRS-1) and the p85 regulatory subunit of phosphatidylinositol 3-kinase (PI 3-kinase) in soleus muscle of fructose chow-fed rats under the basal state, despite the protein expression of insulin receptor (IR). Increased basal phosphorylation of IR and IRS-1 as well as Akt was observed in parallel. The reduced level of insulin action on phosphorylation of IR, IRS-1 and Akt in soleus muscle of fructose chow-fed rats was reversed by myricetin treatment. Furthermore, myricetin treatment improved the defective insulin action on the translocation of glucose transporter subtype 4 (GLUT 4) in insulin-resistant soleus muscle. These findings indicate that myricetin improves insulin sensitivity through the enhancement of insulin action on IRS-1-associated PI 3-kinase and GLUT 4 activity in soleus muscles of animals exhibiting insulin resistance.

• Authors: I-Min Liu, Thing-Fong Tzeng, Shorong-Shii Liou, Ting-Wei Lan
• Journal: Life sciences (Life Sci) Vol. 81 Issue 21-22 Pg. 1479-88 (Nov 10 2007) ISSN: 0024-3205 [Print] Netherlands
• PMID: 17976658 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Blood Glucose
• Flavonoids
• Flavonols
• Glucose Transporter Type 4
• Hypoglycemic Agents
• Insulin
• Thiazolidinediones
• Triglycerides
• Rosiglitazone
• Fructose
• myricetin
• Glycogen
• Cholesterol
• Phosphatidylinositol 3-Kinases
• Receptor, Insulin

Topics

• Animals
• Blood Glucose (metabolism)
• Blotting, Western
• Cholesterol (blood)
• Diet (adverse effects)
• Electrophoresis, Polyacrylamide Gel
• Flavonoids (pharmacology)
• Flavonols (pharmacology)
• Fructose (pharmacology)
• Glucose Transporter Type 4 (metabolism)
• Glycogen (biosynthesis)
• Hepatocytes (drug effects, metabolism)
• Hypoglycemic Agents (pharmacology)
• Immunoprecipitation
• Insulin (blood)
• Insulin Resistance (physiology)
• Male
• Muscle, Skeletal (drug effects)
• Phosphatidylinositol 3-Kinases (metabolism)
• Phosphorylation
• Rats
• Rats, Wistar
• Receptor, Insulin (drug effects)
• Rosiglitazone
• Thiazolidinediones (pharmacology)
• Triglycerides (blood)