Retinopathy, but not neuropathy, is influenced by the level of residual endogenous insulin secretion in type 2 diabetes.

The files of 132 patients with Type 2 diabetes were retrospectively studied to characterize the influence of metabolic control and residual insulin secretion on neuropathy and retinopathy, the two most frequent degenerative diabetic complications. Patients were classified according to their metabolic control (mean HbA1C either < or > or = 8%; reference values: 3-6%) and residual endogenous insulin secretion (fasting plasma C-peptide levels either < or > or = 0.600 nmol/l). Neuropathy was more frequent in patients with poor metabolic control (32/64 = 50%) than in those adequately controlled (17/68 = 25%; p < 0.005). In both subgroups, the level of endogenous insulin secretion did not influence the prevalence of neuropathy. Retinopathy was less effected than neuropathy by the degree of metabolic control (37.5% in the subgroup with HbA1C > or = 8% v.s. 25% in the subgroup with HbA1C < 8%; p < 0.10), but was influenced by residual insulin secretion. Indeed, in patients with inadequate metabolic control, the prevalence of retinopathy was significantly increased in those with higher endogenous insulin secretion (51.4 versus 20.6%, p < 0.02) and thus probably higher insulin resistance. Furthermore, higher systolic arterial blood pressure was observed in the subgroups with a higher prevalence of retinopathy. Such conclusions were confirmed using multivariate analysis. Thus, in Type 2 diabetes, neuropathy is essentially affected by the degree of metabolic control, whereas retinopathy is also influenced by the level of residual endogenous insulin secretion and the presence of systolic hypertension.