Insulin enhances the gain of arterial baroreflex control of muscle sympathetic nerve activity in humans

Abstract

Recent animal studies indicate that insulin increases arterial baroreflex control of lumbar sympathetic nerve activity; however, the extent to which these findings can be extrapolated to humans is unknown. To begin to address this, muscle sympathetic nerve activity (MSNA) and arterial blood pressure were measured in 19 healthy subjects (27 ± 1 years) before, and for 120 min following, two common methodologies used to evoke sustained increases in plasma insulin: a mixed meal and a hyperinsulinaemic euglycaemic clamp. Weighted linear regression analysis between MSNA and diastolic blood pressure was used to determine the gain (i.e. sensitivity) of arterial baroreflex control of MSNA. Plasma insulin was significantly elevated within 30 min following meal intake ( 34 ± 6 uIU ml −1 ; P < 0.05) and remained above baseline for up to 120 min. Similarly, after meal intake, arterial baroreflex-MSNA gain for burst incidence and total MSNA was increased and remained elevated for the duration of the protocol (e.g. burst incidence gain: −3.29 ± 0.54 baseline vs. −5.64 ± 0.67 bursts (100 heart beats) −1 mmHg −1 at 120 min; P < 0.05). During the hyperinsulinaemic euglycaemic clamp, in which insulin was elevated to postprandial concentrations ( 42 ± 6 μIU ml −1 ; P < 0.05), while glucose was maintained constant, arterial baroreflex-MSNA gain was similarly enhanced (e.g. burst incidence gain: −2.44 ± 0.29 baseline vs. −4.74 ± 0.71 bursts (100 heart beats)at 120 min; P < 0.05). Importantly, during time control experiments, with sustained fasting insulin concentrations, the arterial baroreflex-MSNA gain remained unchanged. These findings demonstrate, for the first time in healthy humans, that increases in plasma insulin enhance the gain of arterial baroreflex control of MSNA.

Blood Pressure Decreases More after High-Carbohydrate Meals Than after High-Protein Meals in Overweight Adults with Elevated Blood Pressure, but There Is No Difference after 4 Weeks of Consuming a Carbohydrate-Rich or Protein-Rich Diet

“…This is in agreement with the finding that cardiac baroreflex sensitivity was reduced in middle-aged men and women with central obesity after a 75-g glucose load (18). However, it is in contrast with the finding that insulin increases baroreflex sensitivity in young men (19). Reduced baroreflex sensitivity may be a characteristic of our relatively old participants.…”

Resting sympathetic activity is associated with the sympathetically mediated component of energy expenditure following a meal

“…2005; Young et al. 2010), the attenuated rise in insulin could have contributed to both a lower increase in MSNA and lower β ‐REE/ β ‐TEF. Importantly, when we examined the MSNA : Insulin ratio, we found it to be unaffected by propranolol.…”

Influence of age and sex on the pressor response following a spontaneous burst of muscle sympathetic nerve activity

“…of Bioengineering, University of Iowa, Iowa City, IA), bandpass filtered (bandwidth 700 -2,000 Hz), rectified, and integrated (time constant, 0.1 s) to obtain a mean voltage neurogram. Muscle SNA recordings were identified by their characteristic pulse-synchronous burst pattern and increased neural activity in response to an end-expiratory apnea or Valsalva maneuver, without any response to arousal stimuli or stroking of the skin (31,42,50).…”

“…Studies were performed in a clinical research laboratory at the Mayo Clinic [n ϭ 56; 30 young (16 men) and 26 older (13 men) subjects] and at the University of Missouri [n ϭ 24; 10 young (4 men) and 14 older (7 men) subjects]. The records used were retrospectively analyzed from previous (13)(14)(15)50) and ongoing studies in the respective laboratories. Of note, all data were taken during an initial baseline period before any type of intervention.…”