Abstract

Meal consumption leads to an increase in sympathetic output to compensate for hemodynamic changes and maintain blood pressure (BP). Obesity is associated with a blunting of the sympathetic response to meal ingestion, but interpretation of studies investigating these responses is compromised by their failure to account for the rate of gastric emptying, which is an important determinant of postprandial cardiovascular and sympathetic responses and, in both health and obesity, exhibits a wide interindividual variation. We sought to determine the effects of intraduodenal glucose infusion, bypassing gastric emptying, on BP, heart rate (HR), and noradrenaline responses in obese and healthy control subjects. 12 obese subjects (age 36.6 ± 3.9 years, body mass index (BMI) 36.1 ± 1.3 kg/m2) and 23 controls (age 27.8 ± 2.4 years, BMI 22.4 ± 0.5 kg/m2) received intraduodenal infusions of glucose at 1 or 3 kcal/min, or saline, for 60 min (t = 0–60 min), followed by intraduodenal saline (t = 60–120 min). BP and HR were measured with an automatic cuff, and blood samples collected for measurement of plasma noradrenaline. Intraduodenal glucose at 1 kcal/min was associated with a fall in diastolic BP in the control subjects only (P < 0.01), with no change in systolic BP, HR or noradrenaline in either group. In both groups, intraduodenal glucose at 3 kcal/min was associated with a fall in diastolic (P < 0.01), but not systolic, BP, and rises in HR (P < 0.001) and plasma noradrenaline (P < 0.01), with no difference in responses between the groups. We conclude that cardiovascular and sympathetic responses to intraduodenal glucose infusion are comparable between obese and control subjects, and dependent on the rate of glucose delivery.

Highlights

  • The postprandial cardiovascular response in health involves splanchnic blood pooling compensated for by increases in cardiac output and heart rate (HR), along with vasoconstriction in skeletal muscle and the peripheral vasculature, so there is minimal change in blood pressure (BP) (Sidery et al 1991; Waaler and Eriksen 1992)

  • The aim of this study was to determine the effects of intraduodenal glucose infusion at two rates within the normal range of gastric emptying on BP, HR and noradrenaline responses in obese and healthy control subjects

  • Our study has evaluated the effects of intraduodenal glucose infusion at two rates within the physiological range of gastric emptying on BP, HR and plasma noradrenaline in obese adults and compared these responses to those in healthy lean subjects

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Summary

Introduction

The postprandial cardiovascular response in health involves splanchnic blood pooling compensated for by increases in cardiac output and heart rate (HR), along with vasoconstriction in skeletal muscle and the peripheral vasculature, so there is minimal change in blood pressure (BP) (Sidery et al 1991; Waaler and Eriksen 1992). These responses are driven by barostat activation and autonomic pathways (Kearney et al 1995), and in healthy subjects, meal ingestion is associated with an increase in sympathetic nerve activity and plasma noradrenaline concentrations (Fagius and Berne 1994; Fagius et al 1996).

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