Resting Energy Expenditure and Energetic Cost of Feeding Are Augmented after Roux-en-Y Gastric Bypass in Obese Mice

Abstract

Although the prevalence of obesity has increased dramatically throughout the world during the last 25 yr, its long-term control remains poor. Currently, only gastrointestinal weight loss surgery, especially Roux-en-Y gastric bypass (RYGB), is associated with substantial and sustained weight loss and resolution or significant improvement of diabetes mellitus and other metabolic obesity-induced complications. Clinical observations and recent studies have suggested that RYGB induces its effects by changing the physiology of weight regulation. Understanding the underlying mechanisms of these profound and sustainable effects could facilitate the development of novel and less invasive treatments against obesity and its complications. To study the physiological mechanisms of RYGB, we have developed a mouse RYGB model that replicates the human operation. The aims of this study were to develop a roadmap for assessing energy expenditure (EE) in animal models of weight loss surgery and to examine the effects of RYGB on EE. We first measured EE by indirect calorimetry in groups of animals that underwent RYGB or a sham operation. Calorimetry data were analyzed using three different methods: normalization by total body mass, allometric scaling, and analysis of covariance modeling. RYGB in mice induced a significant increase in EE that was independent of the method used. An energy balance analysis was then performed, which also confirmed that RYGB-treated animals have higher energy maintenance needs. Finally, we determined the EE components that account for the observed increase in EE, and we found that resting EE and postprandial thermogenesis are the major contributors to this increase.

Metagenomic sequencing of the human gut microbiome before and after bariatric surgery in obese patients with type 2 diabetes: correlation with inflammatory and metabolic parameters

“…24 Alternatively, clinical and experimental studies have clearly demonstrated that RYGB induces weight loss by altering physiological regulation of energy balance and metabolic function. 10,12,[25][26][27] Calorimetric measurements in a RYGB mice model revealed increased resting energy expenditure and postprandial thermogenesis as main causes for higher postoperative energy consumption. 27 Global metabolic changes in a non-obese rat model of RYGB were characterized by a decrease in faecal bile acids and a shift from protein degradation to putrefaction through decreased faecal tyrosine with concomitant increases in faecal putrescine and diaminoethane.…”

“…10,12,[25][26][27] Calorimetric measurements in a RYGB mice model revealed increased resting energy expenditure and postprandial thermogenesis as main causes for higher postoperative energy consumption. 27 Global metabolic changes in a non-obese rat model of RYGB were characterized by a decrease in faecal bile acids and a shift from protein degradation to putrefaction through decreased faecal tyrosine with concomitant increases in faecal putrescine and diaminoethane. 10 These data led to the suggestion that human gut microbiota and their cross talk with host metabolism may have an important role for the metabolic conversion in patients with T2D after RYGB.…”

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

“…A number of studies were published in recent years addressing the correct analysis of energy expenditure data in animals of markedly differing body weight and body adiposity (98). In the case of RYGB rats, when energy expenditure determined by indirect calorimetry is corrected for body weight, energy expenditure is usually higher in RYGB rats than in shamoperated ad libitum-fed and weight-matched controls (19).…”

Physiological Mechanisms behind Roux-en-Y Gastric Bypass Surgery

“…Dig Surg 2014;31:13-24 DOI: 10.1159/000354319 21 induced changes in energy expenditure [53,[55][56][57][58][59] . Some but not all studies report increases in energy expenditure, but energy expenditure was often measured only over short time periods and then extrapolated to a 24-hour period; hence, true effects induced by RYGB may have been overlooked.…”