The physiology underlying Roux-en-Y gastric bypass: a status report

Abstract

Lutz TA, Bueter M. The physiology underlying Roux-en-Y gastric bypass: a status report. Am J Physiol Regul Integr Comp Physiol 307: R1275-R1291, 2014. First published September 24, 2014 doi:10.1152/ajpregu.00185.2014.-Obesity and its related comorbidities can be detrimental for the affected individual and challenge public health systems worldwide. Currently, the only available treatment options leading to clinically significant and maintained body weight loss and reduction in obesity-related morbidity and mortality are based on surgical interventions. This review will focus on two main clinical effects of Roux-en-Y gastric bypass (RYGB), namely body weight loss and change in eating behavior. Animal experiments designed to understand the underlying physiological mechanisms of these post-gastric bypass effects will be discussed. Where appropriate, reference will also be made to vertical sleeve gastrectomy. While caloric malabsorption and mechanical restriction seem not to be major factors in this respect, alterations in gut hormone levels are invariably found after RYGB. However, their causal role in RYGB effects on eating and body weight has recently been challenged. Other potential factors contributing to the RYGB effects include increased bile acid concentrations and an altered composition of gut microbiota. RYGB is further associated with remarkable changes in preference for different dietary components, such as a decrease in the preference for high fat or sugar. It needs to be noted, however, that in many cases, the question about the necessity of these alterations for the success of bariatric surgery procedures remains unanswered.Roux-en-Y gastric bypass; vertical sleeve gastrectomy; gut hormones; restriction; malabsorption; energy expenditure THE OBESITY EPIDEMIC AND ITS related comorbidities constitute a major challenge for both personal health and public health systems worldwide. The enormous increase in knowledge about the physiological mechanisms that control eating and body weight contrasts with the lack of available pharmacological therapies leading to safe, efficient, and long-lasting body weight reductions and amelioration of obesity-related comorbidities. However, recent insights into underlying mechanisms of obesity and bariatric surgery have led to promising perspectives in respect to gut hormone-based strategies against obesity. Nevertheless, best results for maintained weight reduction and improvement of comorbidities are still achieved by surgical means (22,88,121,135,136). This review aims to summarize key findings in respect to underlying physiological mechanisms of the Roux-en-Y gastric bypass (RYGB) procedure, which is the most commonly performed bariatric operation worldwide and thus, by many is considered as the gold standard in bariatric surgery. Sporadic reference will also be made to vertical sleeve gastrectomy (VSG) when appropriate. Both operations reduce eating at least temporarily (19,140,143) and lead to changes in food preferences (20,27,72). The majority of data collected with...

Current and Emerging Treatment Options in Diabetes Care

“…Studies using genetic animal models have indicated that neither factor alone is crucial for the metabolic benefits Wilson-Perez et al 2013). Recent, preclinical reports imply that coordinated alteration in multiple systems including bile homeostasis, microbiota, and gut-brain communication functions in concert with humoral alterations to mediate the metabolic effects of surgery (Berthoud et al 2011;Furet et al 2010;Lutz and Bueter 2014;Ryan et al 2014). Identification of these mechanisms could lead to the development of a pharmacological strategy that may reproduce the glycemic control of surgery and render such invasive surgical procedures obsolete.…”

Early Weight Loss Independent Effects of Sleeve Gastrectomy on Diet-Induced Cardiac Dysfunction in Obese, Wistar Rats

“…These post-operative changes are likely to impact energy expenditure, food intake, satiety, glucose, and lipid homeostasis in a weight-loss independent manner [16]. We predict in this exploratory study that performance of a SG has weight-loss independent effects on cardiac dysfunction induced by diet-induced obesity.…”

Effects of high-fat diet and gastric bypass on neurons in the caudal solitary nucleus

“…The explanations for its efficacy likely include complex interactions between the peripheral and central nervous system (Berthoud, Shin et al 2011; Lutz and Bueter 2014). Proposed mechanisms for weight loss include increased energy expenditure, enhanced satiety signals, and changes in the preference for certain foods.…”

“…It receives neural and hormonal satiety signals from the gut (Dockray 2009; de Lartigue, de La Serre et al 2011), projects to brainstem structures involved in regulating metabolism, e.g. (Zechner, Mirshahi et al 2013; Lutz and Bueter 2014), and has reciprocal connections with forebrain structures involved in food regulation and preference (Rinaman 2010; Rinaman 2011). Moreover, it shows demonstrable plasticity in response to short-term changes in energy balance (Rinaman, Baker et al 1998) as well as changes associated with diet (Covasa, Grahn et al 2000).…”