Cardiovascular autonomic responses to hyperinsulinemia in young adult males of normal and low body mass index

Abstract

Acute hyperinsulinemia increases sympathetic nervous system activity, it is unclear if individuals of low body mass index (BMI) have different responses from those of normal BMI. Approximately 30% of adults in India have a low BMI and are likely to become hyperinsulinemic as they transition to better nutritional planes. We evaluated whether individuals of low BMI had different autonomic nervous responses to acute hyperinsulinemia as compared with individuals of normal BMI. 51 young men were divided into 2 groups based on their BMI. All subjects underwent anthropometry, physical activity levels and a hyperinsulinemic euglycemic clamp (HEC). Lead II ECG and beat to beat blood pressure were recorded during the HEC. Basal insulin level and steady state plasma insulin values during HEC were significantly higher in the normal BMI. Insulin sensitivity and glucose disposal rates during the HEC were significantly higher in the low BMI group. LF-RR power (nu) increased and HF-RR power (nu) decreased with hyperinsulinemia, resulting in a significant increase in LF/HF ratio but with no between-group differences. There was a significant increase in low frequency systolic blood pressure variability and a significant reduction in baroreflex sensitivity in both the groups with hyperinsulinemia. However, there were no between-group differences in the magnitude of these responses. The present study indicates that insulin mediated activation of the autonomic nervous system was comparable between low and normal BMI groups in spite of differences in insulin sensitivity and body composition and suggests that insulin mediated autonomic nervous activation is affected by other factors.