Impaired glucose effectiveness in chronic progressive external ophthalmoplegia

Mitochondrial gene mutations have been recognized to be associated with diabetes mellitus. The incidence of diabetes mellitus in patients with other mitochondrial diseases, such as chronic progressive external ophthalmoplegia (CPEO), seems to be several times higher than in the normal population. The aim of the present investigation was to study insulin sensitivity index (SI), insulin secretion (AIR(Glucose)), and glucose effectiveness (Sg) in patients with CPEO. Six unrelated patients with CPEO and 6 matched-pair, unrelated, healthy control subjects underwent a modified intravenous glucose tolerance test (IVGTT) (Bergman's minimal model). Three patients demonstrated an impaired glucose tolerance (IGT), 1 patient already had diabetes mellitus. No significant difference between patients and controls could be demonstrated for SI, AIR(Glucose), or fasting insulin. However, there was a significant difference for glucose effectiveness Sg (P =.016) indicating an impaired glucose effectiveness in the CPEO patients. The diabetic patient showed insulin resistance, low AIR(Glucose), and low Sg. We conclude that there is a high incidence of IGT and diabetes mellitus in patients with CPEO. Impaired glucose effectiveness seems to play a major role in early pathogenesis. Overt diabetes in CPEO seems to be a combination of insulin resistance, an insulin secretion defect, and impaired glucose effectiveness.