No association between retinopathy and insulin resistance in type 1 diabetes

Intact endothelial cell function has been suggested to be important for insulin action. An association between retinopathy and insulin resistance has been found in type 2 diabetes. To evaluate, whether insulin resistance is related to retinopathy in insulin dependent diabetes, we examined 36 type 1 diabetic patients with various degrees of retinopathy: 7 patients had proliferative, 15 had background and 14 patients had no retinopathy. The three groups were matched for age, sex, body weight and insulin dose. Compared with patients with no retinopathy, those with proliferative retinopathy had a longer (P less than 0.05) duration of diabetes (13 +/- 3 vs 22 +/- 3 years for no vs proliferative retinopathy), and higher (P less than 0.05) serum creatinine (74 +/- 4 vs 97 +/- 8 mumol/l), triglyceride (0.69 +/- 0.04 vs 1.02 +/- 0.17 mmol/l) and diastolic blood pressure (77 +/- 3 vs 90 +/- 10 mmHg) levels. The rate of insulin-mediated glucose metabolism (1 mU euglycaemic insulin clamp) was virtually identical in each diabetic group (4.80 +/- 0.42, 4.90 +/- 0.36 and 4.98 +/- 0.74 mg/kg/min) and 40% below that in 8 matched normal subjects (7.53 +/- 0.53 mg/kg/min, P less than 0.001). In conclusion, proliferative retinopathy is related to long duration of diabetes, incipient nephropathy and hypertension. Insulin resistance characterizes the majority of patients with type 1 diabetes but is unrelated to retinopathy.