Role of the Autonomic Nervous System in Mechanism of Energy and Glucose Regulation Post Bariatric Surgery

Abstract

Even though lifestyle changes are the mainstay approach to address obesity, Sleeve gastrectomy (SG) and Roux-en-Y gastric bypass (RYGB) are the most effective and durable treatments facing this pandemic and its associated metabolic conditions. The traditional classifications of bariatric surgeries labeled them as “restrictive,” “malabsorptive,” or “mixed” types of procedures depending on the anatomical rearrangement of each one of them. This conventional categorization of bariatric surgeries assumed that the “restrictive” procedures induce their weight loss and metabolic effects by reducing gastric content and therefore having a smaller reservoir. Similarly, the “malabsorptive” procedures were thought to induce their main energy homeostatic effects from fecal calorie loss due to intestinal malabsorption. Observational data from human subjects and several studies from rodent models of bariatric surgery showed that neither of those concepts is completely true, at least in explaining the multiple metabolic changes and the alteration in energy balance that those two surgeries induce. Rather, neuro-hormonal mechanisms have been postulated to underly the physiologic effects of those two most performed bariatric procedures. In this review, we go over the role the autonomic nervous system plays- through its parasympathetic and sympathetic branches- in regulating weight balance and glucose homeostasis after SG and RYGB.

Neurohormonal Changes in the Gut–Brain Axis and Underlying Neuroendocrine Mechanisms following Bariatric Surgery

“…BS, especially RYGB, has been hypothesized to potentially reduce SNS activity while increasing splanchnic selective sympathetic nerve activity, activating thermogenesis through BAT and increasing energy expenditure; however, findings from previous studies are contradictory [ 108 ]. Hankir et al used 18F-FDG PET-CT imaging to measure BAT 18F-FDG uptake in control and RYGB animals and reported no difference in BAT thermogenesis between groups as well as no difference in UCP-1 mRNA expression [ 109 ].…”

“…The gut–brain axis is a complex, bidirectional communication network that involves signaling between the gastrointestinal system and the brain. This network is regulated at the neural, hormonal and immunological levels, and its main components are the CNS, the neuroendocrine and neuroimmune systems, the ANS, the ENS and the gut microbiota [ 108 , 118 , 119 , 120 ]. At the gut level, the EECs, which lie in the intestinal epithelium, play a major role in gut–brain signaling through the secretion of multiple gut hormones in response to pre-absorptive nutrients [ 121 ].…”

Examining weight bias before and/or after bariatric surgery: A systematic review

“…people who receive Roux-en-Y gastric bypass for the first time; 16.7% compared with 17.8%. 1 The mechanisms of bariatric surgery are complex and multifactorial, [6][7][8] yet not understood fully. Several preoperative and postoperative modifiable (e.g., eating and physical activity) and nonmodifiable (e.g., age and race) features have been examined as prognostic indicators for bariatric surgery outcomes.…”

Progressive Additive Benefits of Prehabilitation and Subsequent Bariatric Surgery on Cardiac Autonomic Regulation as Assessed by Means of a Simple Unitary Composite Index: Preliminary Data from an Observational Study

“…Notably, exercise training was seen to sustain or even enhance the benefits of BS on the cardiac autonomic regulation (CAR) [ 12 ]. Furthermore, increased parasympathetic activity following BS could, in turn, contribute to mitigate food intake [ 33 ]. However, there was high heterogeneity among studies both in the HRV assessment timing (ranging from 7 days to 12 months after BS procedure) and methods employed (e.g., Holter electrocardiograms, plethysmography, Polar RS800CX HR monitor, VariaCardio T4 device, and echocardiography).…”