Impaired autonomic control of heart rate and blood pressure in obesity: role of age and of insulin-resistance

Abstract

The objectives of this study were to investigate cardiac and peripheral autonomic nervous system changes in normotensive overweight or obese subjects and the possible relation between these changes and insulin resistance independent of age. The authors used spectral analysis to measure simultaneously the short-term variability of heart rate (HR) and blood pressure (BP) using a Finapres device, in 67 normotensive overweight or obese patients (age 37 +/- 12 y, body mass index [BMI] = 37 +/- 9 kg/m2) and 45 never-obese subjects (controls; age 41 +/- 13 y, BMI 22 +/- 2 kg/m2). The spectral density was determined in three situations: subjects in the supine position, spontaneously breathing; subjects in the supine with controlled breathing; and subjects standing. The insulin sensitivity of overweight and obese subjects was determined from homeostatic model assessment (HOMA). The variability of normalized low-frequency (LF) spectral analysis of both HR and BP was lower in overweight or obese subjects than in controls, in the supine and standing positions (p <0.01). Normalized LF spectral analysis was negatively correlated to BMI independent of age, whatever the position. Homeostatic model assessment values were negatively correlated to the normalized LF spectral of HR, systolic BP and diastolic BP, in the standing position independent of BMI and age (p <0.05). Normalized high frequency (HF) of HR during controlled breathing decreased with age but not with BMI. In normotensive overweight or obese subjects, changes in sympathetic nervous system modulation are strongly correlated to insulin resistance. Decreased HR and BP variability could partly account for the higher cardiovascular risk and incidence of sudden death in obese persons.

The effects of a glucose load and sympathetic challenge on autonomic function in obese women with and without type 2 diabetes mellitus

“…Both obesity and hyperinsulinemia (4,6,25,26) have been shown to cause alterations in HRV, however, the potential additive effects are unknown and differences between obese women with and without type 2 diabetes are not clear. Consistent with earlier findings (4), we observed that sympathovagal balance (Ln LF/HF) is higher in obese women than in non-obese women, but there was no difference between the obese women with and without type 2 diabetes.…”

“…The very low frequency (VLF) power was obtained for the region below 0.040 Hz and was subtracted from the total power when the data were normalized. Sympathetic modulation of the heart has been associated with the LF spontaneous oscillations of the spectral period (24), whereas the HF component has been shown to be primarily influenced by the efferent vagal activity (6). As an indirect measure of sympathovagal balance the LF/HF ratio has been used.…”

“…Dysfunction of the autonomic system (e.g. increased sympathetic and decreased parasympathetic activity) are related to increased mortality (1,2), and this dysfunction has been reported in obese individuals (3)(4)(5)(6). Additionally, perturbations to the ANS occur with both changes in body position and with food ingestion (7).…”

Effect of Combination Therapy of Benidipine Hydrochloride and Candesartan Cilexetil on Serum Lipid Metabolism and Blood Pressure in Elderly Hypertensive Patients with Type 2 Diabetes Mellitus

“…From our previous reports [21][22][23][24][25][26][27] , low preheparin LPL mass could be consistent with increased insulin resistance. It is known that the sympathetic nerve is activated under the condition of insulin resistance [31][32][33][34] and that blood vessels contract by activation of the sympathetic nerve. So, it is expected that the tonus of the sympathetic nerve in patients with systolic hypertension might be higher than that in patients with non-systolic hypertension before benidipine hydrochloride administration, because preheparin LPL mass levels were significantly lower in patients with systolic hypertension than in patients with nonsystolic hypertension before benidipine hydrochloride administration.…”

Blood pressure and lipid profile in young women: the role of anthropometric measurement

“…While the sympathetic activation is demonstrated at the level of the kidneys and skeletal muscles, cardiac sympathetic activity does not seem to be increased 11 . However, cardiac autonomic disturbances such as decreased vagal tonus, with or without sympathetic activation, are documented in obesity 12 .…”