Free Fatty Acid Increases the Expression of NLRP3-Caspase1 in Adipose Tissue Macrophages in Obese Severe Acute Pancreatitis

Background and aims: Obesity is an important risk factor for severe acute pancreatitis. The necrosis of epididymal adipose tissue occurs in severe acute pancreatitis. Adipose tissue macrophages play an important role in metabolic related inflammation. Therefore, we explored the potential mechanisms between adipose tissue macrophages and obesity-related severe acute pancreatitis.

Methods: Severe acute pancreatitis mice model was induced by caerulein with lipopolysaccharide. The severity of severe acute pancreatitis was evaluated according to the morphological, general, and biochemical change. We assessed the injury of epididymal white adipose tissue, pancreas, and adipose tissue macrophages in obese mice and lean mice with severe acute pancreatitis. Outcomes of caerulein-induced severe acute pancreatitis were studied in lean and obese mice with or without Lipase inhibitor orlistat.

Results: Fat necrosis and pancreatic injury increased in the SAP groups. High levels of serum free fatty acid and triglyceride were increased significantly in the SAP group. The NLRP3-caspase1 inflammasome signal pathway in adipose tissue macrophages markedly enhanced in the SAP groups compared with control group. Free fatty acid can trigger macrophages inflammation through NLRP3-caspase1. Lipase inhibited by orlistat remarkably decreased in adipose tissue necrosis, and the levels of serum Lipase, amylase, and pancreatic tissue damage decreased in the orlistat group compared with the SAP group. The NLRP3-caspase1 inflammasome pathway in adipose tissue macrophages markedly decreased in the orlistat groups compared with SAP group. The levels of serum free fatty acid and triglyceride were decreased significantly in the orlistat group.

Conclusions: Inflammation increases in adipose tissue macrophages of obese mice with severe acute pancreatitis. Free fatty acid generated via adipocyte lipolysis worsens inflammation in adipose tissue macrophages and the outcome of severe acute pancreatitis in obese mice through the NLRP3-caspase1 inflammasome pathway.