Insulin resistance in diabetic microangiopathies

To investigate whether insulin resistance is associated with diabetic microangiopathies in type 2 diabetes mellitus, insulin sensitivity was measured in 133 type 2 diabetic subjects with or without diabetic retinopathy and/or nephropathy. Insulin sensitivity was measured by steady-state plasma glucose method or euglycemic glucose clamp method. Regarding retinopathy, in the insulin-resistant group, advanced retinopathy (preproliferative and proliferative retinopathy) was more frequently observed compared with the insulin-sensitive group (significance: p<0.02). Similarly, as for nephropathy, the occurrence of continuous proteinuria in the insulin-resistant group was significantly (p<0.01) more frequent compared with the insulin-sensitive group. Insulin sensitivity expressed as glucose utilization and glucose clearance was significantly (p<0.05) lower in diabetic subjects with retinopathy (without nephropathy) compared with subjects without the microangiopathies after adjustment for age, body mass index (BMI), fasting blood glucose (FBS), and diabetic duration. Similarly, insulin sensitivity in subjects with nephropathy (without retinopathy) was significantly (p<0.05) decreased compared with those without microangiopathies. Furthermore, insulin resistance was significantly (p<0.01) severe in the subjects with both retinopathy and nephropathy than in those without the two microangiopathies. Insulin resistance of type 2 diabetes is closely associated with the progression of microangiopathies, and causal relationship between insulin resistance and microangiopathies has remained to be solved.