Beta-endorphin plasma levels and their dependence on gender during an enteral glucose load in lean subjects as well as in obese patients before and after weight reduction

It is speculated that endogenous opioid peptides are involved in glucose metabolism and that their homeostasis might be disturbed in obesity. Despite a different response of the pancreatic beta-cells after beta-endorphin and naloxone injections between obese patients and normal weight controls, there is little knowledge concerning the direct influence of a glucose load on beta-endorphin plasma levels, especially with respect to various nutrition states. During exploration of this topic we gained further insight on the difference of basal beta-endorphin plasma levels between normal and overweight persons. We compared beta-endorphin plasma levels during an oral glucose load in 60 obese, non-diabetic patients and in 20 normal weight controls. We also studied 40 of the obese patients after a weight reduction of 2.1 kg/m2. The following results were obtained: (1) Normal weight females have significantly lower (P less than 0.05) basal beta-endorphin levels compared to the male controls. This difference in gender is abolished in obesity where female and male patients do not differ in basal beta-endorphin plasma levels. Therefore, the difference between normal and overweight persons in beta-endorphin plasma levels was restricted to the subgroup of females. We suppose that former neglect of this difference in gender explains most of the so far reported discrepant results. (2) During the oral glucose tolerance test the beta-endorphin plasma values remained constant in the obese group. Despite improved insulin sensitivity after weight reduction there was still no change of beta-endorphin plasma levels both during the OGTT and when compared to the values before weight reduction.(ABSTRACT TRUNCATED AT 250 WORDS)