Adipocyte and erythrocyte plasma membrane phospholipid composition and hyperinsulinemia: a study in nondiabetic and diabetic obese women

BACKGROUND: The cell functions involved in the action of insulin-receptor b inding, enzyme and transporter activities-are controlled by membrane proper ties. We have previously shown that the fasting plasma insulin (FPI) concen tration and the homeostasis model assessment (HOMA) estimate of insulin res istance are associated with the sphingomyelin concentration in the erythroc yte membranes of obese women. OBJECTIVES: (1) To study the distribution of phospholipid classes in the pl asma membrane and their association with insulin resistance markers in the adipocyte, an insulin-sensitive cell in obese women. (2) To investigate the influence of diabetes in a small group of obese women treated by diet alon e. (3) To compare the distribution of phospholipids in erythrocyte membrane s in a subgroup of obese nondiabetic and diabetic women. SUBJECTS: Subcutaneous fat biopsies were taken from the abdominal region of 19 obese non-diabetic and seven obese type 2 diabetic women. Erythrocyte m embrane assessment was performed in a subgroup of 10 of the 19 obese nondia betic and in the seven diabetic patients. METHODS: The phospholipid composition of adipocyte and erythrocyte plasma m embranes was analyzed by high performance liquid chromatography. RESULTS: FPI was positively correlated with the adipocyte membrane contents of sphingomyelin (P <0.001), phosphatidylethanolamine (P <0.05), and phosp hatidylcholine (P <0.01) in the obese nondiabetic women. Similar correlatio ns were obtained with HOMA. A stepwise multiple regression analysis indicat ed that sphingomyelin accounted for 45.6 and 43.8% of the variance in FPI a nd HOMA values as an independent predictor. There was a similar positive in dependent association between FPI and SM in the erythrocyte membranes of th e studied subgroup. Diabetes per se did not influence the independent assoc iation between SM membrane contents and FPI in both cell types. CONCLUSION: These results suggest a link between membrane phospholipid comp osition, especially SM, and hyperinsulinemia in obese women.