Homocysteine levels during fasting and after methionine loading in adolescents with diabetic retinopathy and nephropathy

Objective: To assess plasma homocysteine levels in adolescents and young adults with type 1 (insulin-dependent) diabetes with and without microvascular complications. Study design: Homocysteine levels were measured during fasting and after methionine loading in plasma of 61 patients with onset of diabetes before the age of 12 years and duration of disease longer than 7 years. They had an albumin excretion rate (AER) between 20 and 200 mu g/min in 2 of 3 overnight urine collections in a period of 6 months and/or retinopathy. Patients with persistent microalbuminuria were divided into 2 groups: subjects with AER of 20 to 70 mu g/min and patients with AER of 70 to 200 mu g/min. Adolescents (n = 54) without signs of diabetic retinopathy or nephropathy and matched control subjects (n = 63) were also studied. Results: Homocysteine concentrations before and after methionine load were higher in adolescents with diabetic complications than in healthy subjects (fasting values: 12.4 +/- 7.9 mu mol/L vs 7.8 +/- 4.2 mu mol/L; P < .01; after methionine load: 28.1 +/- 13.2 mu mol/L vs 16.6 +/- 7.3 mu mol/L; P < .005). Values of 11.9 mu mol/L or higher were considered to constitute fasting hyperhomocysteinemia. The increase of homocysteine concentrations was particularly evident in young diabetic patients with AER >70 mu g/min (fasting values: 14.7 +/- 5.6 mu mol/L; after methionine load: 34.2 +/- 12.6 mu mol/L) and in patients with proliferative retinopathy (fasting values: 15.1 +/- 5.0 mu mol/L; after methionine load: 36.8 +/- 12.5 mu mol/L). Conclusions: Increased plasma homocysteine concentrations may contribute to increased morbidity and death from cardiovascular disease in adolescents and young adults with diabetic retinopathy and nephropathy.