Regulation of Glucose Transport and Transporter 4 (GLUT-4) in Muscle and Adipocytes of Sucrose-Fed Rats: Effects of N-3 Poly- and Monounsaturated Fatty Acids

Abstract

The goal of this study was to compare the short-term effects of dietary n-3 polyunsaturated (fish oil) and monounsaturated (olive oil) fatty acids on glucose transport, plasma glucose and lipid controls in a dietary insulin resistance model using sucrose-fed rats. The underlying cellular and molecular mechanisms were also determined in the muscle and adipose tissue. Male Sprague-Dawley rats (5 weeks old) were randomized for diets containing 57.5 % (w/w) sucrose and 14 % lipids as either fish oil (SF), olive oil (SO) or a mixture of standard oils (SC) for 3 weeks. A fourth control group (C) was fed a diet containing 57.5 % starch and 14 % standard oils. After three weeks on the diet, body weight was comparable in the four groups. The sucrose-fed rats were hyperglycemic and hyperinsulinemic in response to glucose load. The presence of fish oil in the sucrose diet prevented sucrose-induced hyperinsulinemia and hypertriglyceridemia, but had no effect on plasma glucose levels. Insulin-stimulated glucose transport in adipocytes increased after feeding with fish oil (p < 0.005). These modifications were associated with increased Glut-4 protein (p < 0.05) and mRNA levels in adipocytes. In the muscle, no effect was found on Glut-4 protein levels. Olive oil, however, could not bring about any improvement in plasma insulin, plasma lipids or Glut-4 protein levels. We therefore conclude that the presence of fish oil, in contrast to olive oil, prevents insulin resistance and hypertriglyceridemia in rats on a sucrose diet, and restores Glut-4 protein quantity in adipocytes but not in muscle at basal levels. Dietary regulation of Glut-4 proteins appears to be tissue specific and might depend on insulin stimulation and/or duration of dietary interventions.

Reduction in Plasma Glucose after Lipid Changes in Mice Fed Fish Oil, Docosahexaenoic Acid, and Eicosapentaenoic Acid Diets

“…It is reported that n-3 PUFA causes an increase in insulin sensitivity and/or enzyme activities of carbohydrate metabolism, such as hexokinase, lactate dehydrogenase and glucose-6-phosphate dehydrogenase [24,25] . There is a report on muscle glucose transporter-4 content of rats fed fi sh oil which is similar to that of control rats [26,27] . The decrease in plasma glucose concentrations of mice fed fi sh oil and DHA+EPA or either of these components alone always occurred subsequent to similar changes in total cholesterol and phospholipid concentrations.…”

n-3 long chain polyunsaturated fatty acids: a nutritional tool to prevent insulin resistance associated to type 2 diabetes and obesity?

“…Fish oil also prevents sucrose-induced insulin resistance in rats [41][42][43]. However, the results are controversial as to the capacity of fish oil to reverse insulin resistance once installed after a high sucrose diet.…”

Anti-inflammatory effects of EPA and DHA are dependent upon time and dose-response elements associated with LPS stimulation in THP-1-derived macrophages

“…Fish oils have a variety of potential cardioprotective effects, including reduction of plasma triacylglycerol concentrations, regulation of blood pressure, amelioration of cardiac arrythmia and reduction in incidence of sudden cardiac death [1][2][3][4][5][6][7]. LC n-3 PUFA supplementation improved insulin sensitivity in normal and insulinresistant rodents [8][9][10][11]. High concentrations of LC n-3 PUFA in plasma and muscle membranes are inversely associated with insulin resistance and protect against the metabolic syndrome in obese human subjects [12,13].…”