Mechanisms underlying the efficacy of a rodent model of vertical sleeve gastrectomy — A focus on energy expenditure

Bariatric surgery remains the only effective and durable treatment option for morbid obesity. Vertical Sleeve Gastrectomy (VSG) is currently the most widely performed of these surgeries primarily because of its proven efficacy in generating rapid onset weight loss, improved glucose regulation and re...

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Published in:	Molecular metabolism (Germany) Vol. 73; p. 101739
Main Authors:	Stefanidis, A., Lee, C.M.C., Greaves, E., Montgomery, M.K., Arnold, M., Newn, S., Budin, A.J., Lemus, M.B., Foldi, C.J., Burton, P.R., Brown, W.A., Lutz, T.A., Watt, M.J., Oldfield, B.J.
Format:	Journal Article
Language:	English
Published:	Germany Elsevier GmbH 01-07-2023 Elsevier
Subjects:	Animal model Animals Bariatric surgery Body Weight - physiology Brown adipose tissue thermogenesis Energy expenditure Energy Metabolism Gastrectomy - methods Glucose Humans Male Metabolic surgery Original Oxidopamine Rats Rats, Sprague-Dawley Rodentia Vertical sleeve gastrectomy Weight Loss Animal model RVMM RYGB GTT Bariatric surgery UCP1 6-OHDA BeAT CNS OVLT WAT NTS GFP H129 BnST PRV Brown adipose tissue thermogenesis iBAT RFP Metabolic surgery GLP-1 POA RVLM Energy expenditure 2-DG DIO VSG FGF-19 Vertical sleeve gastrectomy PYY BAT DEXA LC VANs RER
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Summary:	Bariatric surgery remains the only effective and durable treatment option for morbid obesity. Vertical Sleeve Gastrectomy (VSG) is currently the most widely performed of these surgeries primarily because of its proven efficacy in generating rapid onset weight loss, improved glucose regulation and reduced mortality compared with other invasive procedures. VSG is associated with reduced appetite, however, the relative importance of energy expenditure to VSG-induced weight loss and changes in glucose regulation, particularly that in brown adipose tissue (BAT), remains unclear. The aim of this study was to investigate the role of BAT thermogenesis in the efficacy of VSG in a rodent model. Diet-induced obese male Sprague–Dawley rats were either sham-operated, underwent VSG surgery or were pair-fed to the food consumed by the VSG group. Rats were also implanted with biotelemetry devices between the interscapular lobes of BAT to assess local changes in BAT temperature as a surrogate measure of thermogenic activity. Metabolic parameters including food intake, body weight and changes in body composition were assessed. To further elucidate the contribution of energy expenditure via BAT thermogenesis to VSG-induced weight loss, a separate cohort of chow-fed rats underwent complete excision of the interscapular BAT (iBAT lipectomy) or chemical denervation using 6-hydroxydopamine (6-OHDA). To localize glucose uptake in specific tissues, an oral glucose tolerance test was combined with an intraperitoneal injection of 14C-2-deoxy-d-glucose (14C-2DG). Transneuronal viral tracing was used to identify 1) sensory neurons directed to the stomach or small intestine (H129-RFP) or 2) chains of polysynaptically linked neurons directed to BAT (PRV-GFP) in the same animals. Following VSG, there was a rapid reduction in body weight that was associated with reduced food intake, elevated BAT temperature and improved glucose regulation. Rats that underwent VSG had elevated glucose uptake into BAT compared to sham operated animals as well as elevated gene markers related to increased BAT activity (Ucp1, Dio2, Cpt1b, Cox8b, Ppargc) and markers of increased browning of white fat (Ucp1, Dio2, Cited1, Tbx1, Tnfrs9). Both iBAT lipectomy and 6-OHDA treatment significantly attenuated the impact of VSG on changes in body weight and adiposity in chow-fed animals. In addition, surgical excision of iBAT following VSG significantly reversed VSG-mediated improvements in glucose tolerance, an effect that was independent of circulating insulin levels. Viral tracing studies highlighted a patent neural link between the gut and BAT that included groups of premotor BAT-directed neurons in the dorsal raphe and raphe pallidus. Collectively, these data support a role for BAT in mediating the metabolic sequelae following VSG surgery, particularly the improvement in glucose regulation, and highlight the need to better understand the contribution from this tissue in human patients. [Display omitted] •VSG results in increased BAT temperature and glucose uptake into BAT as well as elevated gene markers of BAT activity and browning of white fat.•Removal of BAT substantially limits the positive impact of VSG on both body weight and glycemic control.•Combination of two neurotropic viruses highlights a patent neural circuit between the gut and BAT that may underpin this response.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	2212-8778 2212-8778
DOI:	10.1016/j.molmet.2023.101739