Effects of caloric restriction and exercise on insulin receptors in obesity: association with changes in membrane...

We have studied the effects of supervised caloric restriction and exercise on mononuclear leukocyte lipid composition, membrane fluidity, and insulin receptors in ten nondiabetic obese adults, (175 +/- 9.3% of ideal body weight) and ten normal adult subjects. In a second study, we examined the effects of caloric restriction alone using a very low calorie liquid diet in the treatment of another ten obese adults. In both groups of obese adults, fasting insulin levels were elevated and fell to normal levels following treatment. Insulin binding to monocytes, which was reduced in obese subjects, increased toward normal after short-term treatment; this was due to the restoration of total insulin binding capacity to levels one half of that seen in the normal adult group. Obese subjects undergoing either treatment had elevated membrane cholesterol/phospholipid ratios prior to treatment (0.499 +/- 0.050 and 0.446 +/- 0.011 v 0.400 +/- 0.025 mol/mol in normal adults P less than 0.005 by ANOVA). Prior to treatment, for all subjects there was a significant inverse correlation between insulin tracer binding and membrane cholesterol/phospholipid ratios (r = .484, n = 34, P less than 0.005). This relationship did not change significantly in obese subjects in either treatment group. Cell membrane microviscosity was determined by fluorescence polarization (FP) using DPH (2 X 10(-6) mol/L). Prior to weight loss, obese subjects had significantly higher FP values than controls (0.304 +/- 0.006 and 0.319 v 0.259 +/- 0.009, P less than 0.005, by ANOVA) indicating greater microviscosity.(ABSTRACT TRUNCATED AT 250 WORDS)