Effects of a Mixed Meal on Hemodynamics and Autonomic Control of the Heart in Patients with Type 1 Diabetes

Context: Food intake induces relevant cardiovascular changes together with parallel increases in cardiac sympathetic activity and insulin plasma levels in man. Objective: We evaluated hemodynamics, neurohormones, and cardiac autonomic control after eating in patients with type 1 diabetes, a disease characterized by the absence of basal and stimulated insulin production. Design and Setting: Fifteen type 1 diabetic patients and 15 healthy controls underwent blood sampling, electrocardiogram, blood pressure and respiration recordings, and heart rate variability analysis while recumbent, during the 70° head-up tilt, and 20 min after a mixed meal; on another occasion, diabetic patients were also studied 20 min after a mixed meal preceded by their scheduled bolus of exogenous insulin. Spectrum analysis of RR interval provided the indices of sympathetic (LFRR) and vagal (HFRR) modulation of the sinoatrial node. Results: At baseline, no significant differences were found between groups, except for metabolic parameters. Compared with baseline, heart rate, plasma catecholamines, and LFRR significantly (P < 0.005) increased, whereas HFRR significantly (P < 0.0001) decreased during the tilt in all subjects. Compared with baseline, plasma norepinephrine, heart rate, and LFRR significantly (P < 0.05) increased, whereas HFRR significantly (P < 0.02) decreased after eating in controls but not in diabetic patients (with and without insulin administered before eating). In both controls and diabetic patients, no relationship between postprandial changes of insulin and LFRR and HFRR was found. Conclusions: Hemodynamic, neurohormonal, and cardiac neural responses to eating are abnormal in type 1 diabetic patients, independently of insulin.