Retinol and alpha-tocopherol in serum of type 1 diabetic patients with intensive insulin therapy: a long term follow-up study

OBJECTIVE: We evaluated the effect of intensive insulin therapy and glycemic control in patients with type 1 diabetes on biochemical markers of vitamin A and E. METHODS: Fifty-seven patients with type 1 diabetes were enrolled in a follow-up study for 3 to 33 mo. At entrance, all patients were on conventional insulin therapy or recently had been diagnosed with the disease. Intensive insulin therapy (multiple daily glycemia records and at least three insulin doses daily) was established, and every 3 to 6 mo patients were screened for clinical, biochemical, and hematologic indexes. Biochemical markers of vitamin A and E nutrition status were measured at each visit by a quality-controlled high-performance liquid chromatography. RESULTS: At entrance, serum retinol concentrations, but not the ratio of alpha-tocopherol to cholesterol, showed a negative correlation with increasing values of HbA1c and insulin dose, neither of which was significant in multiple regression models. With intensive insulin therapy, a trend to normalize parameters of glycemic control (HbA1c and fructosamine) was observed within subjects and on a group level. However, no significant changes were observed in serum retinol or alpha-tocopherol:cholesterol ratio according to the metabolic control of the disease. CONCLUSIONS: Patients with type 1 diabetes under intensive insulin therapy tend to normalize the clinical parameters of glycemic control, although this improvement does not significantly affect biochemical markers of vitamin A and E status.