The role of bariatric surgery on beta-cell function and insulin resistance in patients with nonalcoholic fatty liver disease and steatohepatitis

Background: Nonalcoholic fatty liver disease (NAFLD) and steatohepatitis (NASH) are strongly associated with obesity, metabolic syndrome, and insulin resistance (IR). Objective: The aim of this study was to investigate the effects of metabolic surgery on pancreatic beta cell function and IR in patients with obesity and NAFLD. Setting: University Hospital, Germany. Methods: Liver biopsies were taken intraoperatively from 112 patients undergoing sleeve gastrectomy (n = 68) or Roux-en-Y gastric bypass (n = 44) and analyzed histologically for the presence of simple steatosis (NAFL) or NASH. Clinical and biochemical parameters were collected over up to 2 years. Beta cell function and IR were assessed using the homeostasis model assessment of beta-cell function (HOMA2-%B) and insulin resistance (HOMA2-IR) index. Results: NASH was present in 53.6% (n = 60) of the patients and NAFL in 25.9% (n = 29). Liver enzymes, adiponectin/leptin ratio, triglycerides, and HbA1C were improved at 6 months, 1, and 2 years after surgery. HOMA2-IR was significantly lower in patients without NAFLD while HOMA2-IR did not differ between patients with NAFL and/or NASH. HOMA2-%B was highest in the NAFLD group and lowest in patients with NASH. While there was no change in HOMA2-%B and HOMA2-IR in the No-NAFLD group, HOMA2-%B decreased and IR improved in the NAFL and NASH groups. Conclusion: Insufficient compensatory beta-cell function may contribute to the progression from NAFL alongside with IR to NASH. Our findings suggest that bariatric surgery decreases IR while at the same time reducing compensatory insulin oversecretion. These results are associated with beneficial changes in adipose tissue function after bariatric surgery. (Surg Obes Relat Dis 2023;19:1421-1434.) (c) 2023 American Society for Metabolic and Bariatric Surgery. Published by Elsevier Inc. All rights reserved.