Chronic Supplementation with L-Isoleucine Alone or in Combination with Exercise Reduces Hepatic Cholesterol Levels with No Effect on Serum Glucose, Insulin, or Lipids in Rats Fed a High Fructose Diet

Abstract

The thought of using branched-chain amino acids (BCAA) in the prevention and treatment of certain disorders is becoming increasingly popular. Indi vidual BCAA use has been associated with improving glucose tolerance and liver disease. Previous studies have cited improvements in glucose metabol ism with a single dose of L-isoleucine (ILE). However, it is still unclear whether chronic consumption of ILE has any direct benefit. The objective of this study was to examine the influence of chronic ILE supplementation alone or in combination with exercise on fasting serum glucose, insulin, lipids, and lipoprotein cholesterol levels; glucose tolerance; and hepatic lipids in rats. Male Sprague-Dawley rats (n = 40) were divided into Control (low fructose diet); High Fructose diet (HF); HF plus 1.5% ILE (HF + ILE); HF plus exercise (HF + EX); and HF plus 1.5% ILE and exercise (HF + ILE + EX). The HF diets consisted of 70% kcalories from fructose. After 6 weeks of treatment, no significant differences were observed between groups for changes in fasting serum glucose, insulin, lipids, or lipoprotein cholesterol levels. However, hepatic total cholesterol was significantly lower in the HF + ILE + EX compared to the Control and HF, while, the HF + ILE had significantly lower hepatic free cholesterol compared to the HF. We also found no differences between groups for serum glucose response following an oral glucose tolerance test. In conclusion, our study shows that ILE supplementation in rats does not influence serum glucose and lipid biomarkers but may have an influence on lipid metabolic pathways within the liver.