Further observations on serum viscosity changes in diabetes mellitus.

The 8% increase in serum viscosity in diabetes mellitus, more striking in diabetics with evidence of microangiopathy, has been further investigated. Methodology has been developed to eliminate the effect of fluctuating levels of glucose, lipids and protein. This was accomplished first by dialysis of fresh serum and later by ultracentrifugation to remove lipoprotein followed by dialysis. The distinction between diabetic and nondiabetic viscosity levels was improved by removing glucose and correcting for fluctuations in serum protein level, principally because variation between observations on the same subject was substantially reduced. Two methods were utilized to adjust for protein concentration differences. Ether technique increased the statistical significance of the viscosity increase in diabetes. Without lipoprotein removal the regression of specific fluidity (1-1/relative viscosity) with concentration differed between the sexes. When lipoprotein was removed the sex difference disappeared and the regression line passed through the origin. Removal of lipoprotein also further increased the discrimination between diabetic and normal serum. Even without lipoprotein removal elevated serum viscosity was readily detected in advanced glucose intolerance. In both studies, viscosity was higher in diabetics with microangiopathic sequelae, increasing progressively with more evidence of microangiopathy. No effect of severity of hyperglycemia or duration of diabetes could be demonstrated. Increased serum viscosity' association with microvascular sequelae and its presence early in the disorder suggest that the protein changes responsible for its elevation may play a role in the development of diabetic microangiopathy.