Cardiovascular Autonomic Dysfunction as a Link Between Insulin Resistance and Nocturnal Blood Pressure Elevation
To the Editor:
I read with interest the article by Lurbe et al1 on the relationship between insulin resistance and the ambulatory blood pressure components in obese children and adolescents. The authors have observed that nocturnal systolic blood pressure and heart rate were significantly higher in subjects in the highest homeostasis model assessment index tertile. They conclude that the increased nocturnal blood pressure and heart rate associated with hyperinsulinemia may contribute to heightened cardiovascular risk associated with this condition. I agree with the authors, and I want suggest cardiovascular autonomic function as a possible link between insulin resistance and increased nocturnal blood pressure.
This hypothesis is supported by several pieces of evidence. Scherrer and Sartori2 have observed that hyperinsulinemia activates the central sympathetic drive. Several studies performed by spectral analysis of heart rate variability have shown sympathetic hyperactivity in insulin-resistant subjects with normoglycemia.3,4 In a previous study performed in adult subjects, Perciaccante et al5 have reported a relationship between insulin resistance and cardiovascular autonomic dysfunction, characterized by an impaired circadian rhythm of heart rate variability with a sympathetic hyperactivity at nighttime. Moreover, the authors have reported that this hyperactivity of sympathetic component at nighttime (evaluated by heart rate variability analysis in the frequency domain as low frequency expressed in normalized units and the low frequency:high frequency ratio) is correlated with the highest homeostasis model assessment index.
I conclude that insulin resistance has an impact on nocturnal blood pressure and heart rate, and this may be because of the effect of the insulin resistance on the cardiovascular autonomic activity.
Lurbe E, Torro I, Aguilar F, Alvarez J, Alcon J, Pascual MJ, Redon J. Added impact of obesity and insulin resistance in nocturnal blood pressure elevation in children and adolescent. Hypertension. 2008; 51: 635–641.
Scherrer U, Sartori C. Insulin as a vascular and sympathoexcitatory hormone. Implications for blood pressure regulation, insulin sensitivity and cardiovascular morbidity. Circulation. 1997; 96: 4104–4114.
Laitinen T, Vauhkonen IK, Niskanen LK, Hartikainen JE, Lansimies EA, Uusitupa MI, Laakso M. Power spectral analysis of heart rate variability during hyperinsulinemia in nondiabetic offspring of type 2 diabetic patients: evidence for possible early autonomic dysfunction in insulin-resistant subjects. Diabetes. 1999; 48: 1295–1299.
Perciaccante A, Fiorentini A, Paris A, Serra P, Tubani L. Circadian rhythm of the autonomic nervous system in insulin resistant subjects with normoglycemia, impaired fasting glycemia, impaired glucose tolerance, type 2 diabetes mellitus. BMC Cardiovasc Disord. 2006; 2: 6: 19–28.