TREM2−/− mice fed a high-fat diet (HFD) exhibited a reduction of infiltrating F4/80+CD11c+ macrophages in adipose tissue but displayed augmentation of pro-inflammatory cytokines IL-1β, IL-6, and inducible nitric oxide synthase (iNOS), adipocyte hypertrophy, hepatic steatosis, and insulin resistance compared with WT controls (86). This evidence concerns the gene NOS2 and fatty liver disease.