Relation between Insulin Resistance Improvement Mechanisms by Fish Oil Feeding and Circulating Leptin Concentrations

2004 Fiscal Year Final Research Report Summary

• Project/Area Number: 15590215
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Environmental physiology (including Physical medicine and Nutritional physiology)
• Research Institution: Ochanomizu University
• Principal Investigator: IKEMOTO Shinji Ochanomizu University, Faculty of Human Life and Environmental Sciences, Associate Professor (10176117)
• Co-Investigator(Kenkyū-buntansha): KIM Hyoun-Ju Josai University, Faculty of Pharmaceutical Sciences, Lecturer (70348176)
• Project Period (FY): 2003 – 2004
• Keywords: Fish Oil / Anti-obesity Effect / Improvement of Glucose Metabolism / Improvement in blood lipid levels / Leptin / Insulin

Research Abstract

Fish oil improved obesity and lipid metabolism relative to other dietary oils. Although n-3 polyunsaturated fatty acid rontained in fish oil has various advantages for glucose and lipid metabolism, it is also easily be oxidized and lipidperoxidation induces tissue damages in many organs. Therefore, concern remains whether much fish oil feeding is better than low dose of fish oil feeding. In this study, we investigated the effect of fish oil at different doses on glucose and lipid metabolism on 3 days, 1 week, 2 weeks and 2 months after feeding in C57BL/BL6J mice. Mice were fed the four diets each, 20 en% fish oil, 50 en% fish oil, 20 en% safflower oil and 50 en% safflower (HC-Fish, HF-Fish, HC-Saff and HF-Saff groups). Body weight, WAT weight, plasma leptin and insulin levels were most decreased in HF-Fish group compared to other groups, whereas plasma TC and TG levels in HC-Fish and HF-Fish groups were lower than that in HC-Saff and HF-Saff group respectively. Lipidperoxidation in liver in HF-Fish group was remarkably highest in all groups. Uncoupling protein 2 (UCP2) mRNA in liver and uncoupling protein 3 (UCP3) mENA in muscle, which are reported the association with lipidperoxidation disappears and decease of insulin contents in pancreas, were increased in HF-Fish group only. Although high close of fish oil decreases body weight and plasma lipid levels, that is induced lipidperoxidation and UCP2, 3 mRNA at the same time. These results suggest that low dose of fish oil is suitable (around 20 en%).