Reply to letter: "Concerning the article: assessment of different bariatric surgeries in the treatment of obesity and insulin resistance in mice".

OBJECTIVE To assess the effects of different bariatric surgical procedures on the treatment of obesity and insulin resistance in high fat diet-induced obese (DIO) mice. BACKGROUND Bariatric surgery is currently considered the most effective treatment for morbid obesity and its comorbidities; however, a systematic study of their mechanisms is still lacking. METHODS We developed bariatric surgery models, including gastric banding, sleeve gastrectomy, Roux-en-Y gastric bypass (RYGB), modified RYGB (mRYGB) and biliopancreatic diversion (BPD), in DIO mice. Body weight, body fat and lean mass, liver steatosis, glucose tolerance and pancreatic beta cell function were examined. RESULTS All bariatric surgeries resulted in significant weight loss, reduced body fat and improved glucose tolerance in the short term (4 weeks), compared with mice with sham surgery. Of the bariatric surgery models, sleeve gastrectomy and mRYGB had higher success rates and lower mortalities and represent reliable restrictive and gastrointestinal (GI) bypass mouse bariatric surgery models, respectively. In the long term, the GI bypass procedure produced more profound weight loss, significant improvement of glucose tolerance and liver steatosis than the restrictive procedure. DIO mice had increased insulin promoter activity, suggesting overactivation of pancreatic beta cells, which was regulated by the mRYGB procedure. Compared with the restrictive procedure, the GI bypass procedure showed more severe symptoms of malnutrition following bariatric surgery. DISCUSSIONS Both restrictive and GI bypass procedures provide positive effects on weight loss, fat composition, liver steatosis and glucose tolerance; however, in the long term, the GI bypass shows better results than restrictive procedures.