Effects of Bariatric Surgery on Change of Brown Adipocyte Tissue and Energy Metabolism in Obese Mice

Bariatric surgery is an effective treatment for obesity causing changes in energy expenditure. Brown adipose tissue (BAT) is an energy-related organ, and the potential effects of bariatric surgery are yet to be investigated. We aimed to study the effects of different bariatric surgeries on growth hormone/insulin-like growth factor-1 (GH/IGF-1) axis, brown adipocyte differentiation, and energy metabolism in obese mice and explore the underlying mechanisms. Mice were fed a high-fat diet for 12 weeks and subjected to different bariatric procedures: adjustable gastric band (AGB), sleeve gastrectomy (SG), Roux-en-Y gastric bypass (RYGB), and sham operation (SO). Pre- and postoperative weight, a metabolic index, content, and metabolic activity of BAT was recorded by micro-positron emission tomography/computed tomography (micro-PET/CT). Altered energy metabolism was estimated by metabolic cage technology. Serum GH/IGF-1 level and the brown adipose cell differentiation-related gene expression were estimated. By postoperative week 4, serum GH and IGF-1 levels, as well as the content and metabolic activity of BAT increased postoperatively. The differentiation factors of the brown adipose cell were significantly stronger, energy consumption increased, and respiratory exchange frequency decreased postoperative. The effect was predominant in RYGB; SG demonstrated superior result to ABG. With weight regain 8-week postoperation, these parameters deteriorated in the operation groups, significantly in the GB group; the RYGB group seemed superior to the SG group. Bariatric surgery elevated the GH/IGF-1 levels and increased BAT volume and activity, meanwhile decreasing the respiratory exchange frequency. This may help us better understand the mechanisms of bariatric surgery.