Electron spin resonance study of the erythrocyte membrane fluidity changes in diabetes.

The membrane fluidity of intact erythrocytes from diabetic patients and sex-matched controls has been examined between 20 and 40 degrees C by electron spin resonance spectroscopy using the 5-doxyl palmitic acid spin label. In contrast to the normal erythrocytes, in both types of diabetes a significant non-linearity was found around 30 degrees C in the fluidity-temperature plots of the lipid bilayer. This was assigned to a phase transition normally absent in the 20-40 degrees C range. The magnitude of the bilayer fluidity showed a little decrease in insulin-dependent diabetes and an increasing trend vanishing around 37 degrees C in non-insulin-dependent diabetes. In addition, we observed two protein-immobilized lipid subpopulations, showing slightly higher apparent concentrations and modified fluidity in diabetes. Membrane composition alterations, mainly in the fatty acid concentrations, may explain the fluidity changes. Our results, although preliminary in a clinical sense because the number of investigated patients was too small, evidenced specific and complex changes of the erythrocyte membrane fluidity in diabetes and demonstrated the high potential of the spin label approach for the diabetic medicine.