IL-18 Production from the NLRP1 Inflammasome Prevents Obesity and Metabolic Syndrome

Interleukin-18 (IL-18) is activated by Caspase-1 in inflammasome complexes and has anti-obesity effects; however, it is not known which inflammasome regulates this process. We found that mice lacking the NLRP1 inflammasome phenocopy mice lacking IL-18, with spontaneous obesity due to intrinsic lipid accumulation. This is exacerbated when the mice are fed a high-fat diet (HFD) or a high-protein diet, but not when mice are fed a HFD with low energy density (high fiber). Furthermore, mice with an activating mutation in NLRP1, and hence increased IL-18, have decreased adiposity and are resistant to diet-induced metabolic dysfunction. Feeding these mice a HFD further increased plasma IL-18 concentrations and strikingly resulted in loss of adipose tissue mass and fatal cachexia, which could be prevented by genetic deletion of IL-18. Thus, NLRP1 is an innate immune sensor that functions in the context of metabolic stress to produce IL-18, preventing obesity and metabolic syndrome. [Display omitted] •Deletion of NLRP1 in mice leads to obesity and metabolic syndrome•NLRP1 obesity phenotype is related to the energy quotient of the diet•Loss of NLRP1 decreased IL-18 production and lipolysis•NLRP1 activation increased IL-18, prevented obesity, but was fatal on the high-fat diet Murphy et al. link the NLRP1 inflammasome to IL-18 production and show that mice lacking NLRP1 have defective lipolysis and become obese, as seen with IL-18 deficiency. NLRP1 activation prevents obesity but results in fatal fat loss and cachexia on a high-fat diet, which is rescued by deletion of IL-18.