Cardiac autonomic regulation in response to a mixed meal is impaired in obese children and adolescents: the role played by insulin resistance.

CONTEXT: Obesity in children/adolescents has been associated with subtle cardiac abnormalities, including myocardial dysfunction and cardiac autonomic dysregulation at rest, both likely responsible for a higher mortality in adulthood. Food intake induces remarkable adjustments of cardiovascular autonomic activity in healthy subjects.

OBJECTIVE

The objective of the study was to evaluate in obese children/adolescents meal-induced cardiac autonomic response and the role played by insulin resistance.

DESIGN AND

SETTING

Sixty-eight obese and 30 matched normal-weight children/adolescents underwent blood sampling and cardiovascular autonomic analysis while recumbent and 20 minutes after a mixed meal ingestion. Spectrum analysis of the R-R interval and systolic blood pressure (SBP) variability provided the indices of sympathetic [low frequency (LFRR)] and vagal [high frequency (HFRR)] modulation of the sinoatrial node and the low frequency component of SBP. The homeostasis model assessment of insulin resistance served to separate insulin resistant (n = 35) from non insulin resistant (n = 33) obese children/adolescents.

RESULTS

At baseline, C-reactive protein, the LFRR to HFRR ratio, SBP, and low frequency oscillatory component of SBP variability in obese children/adolescents were significantly (P < .05) greater than in referent subjects, whereas high-density lipoprotein cholesterol and HFRR were lower; meal-induced increase in the LFRR to HFRR ratio was significantly less than in controls and exaggeratedly scanty (or opposite) among insulin resistant subjects. The homeostasis model assessment of insulin resistance index strongly and inversely correlated (r = -0.871; P < .001) with meal-induced changes in the LFRR to HFRR ratio among obese subjects.

CONCLUSIONS

Autonomic modulation of the heart was impaired after eating in obese children/adolescents. This abnormality was exaggerated among insulin resistant subjects and strongly correlated with the degree of insulin resistance.