Myeloid-specific fatty acid transport protein 4 deficiency induces a sex- dimorphic susceptibility for nonalcoholic steatohepatitis in mice fed a high-fat, high-cholesterol diet

Newborns with FATP4 mutations exhibit ichthyosis prematurity syndrome (IPS), and adult patients show skin hyperkeratosis, allergies, and eosinophilia. We have previously shown that the polarization of macrophages is altered by FATP4 deficiency; however, the role of myeloid FATP4 in the pathogenesis of nonalcoholic steatohepatitis (NASH) is not known. We herein phenotyped myeloid-specific Fatp4-deficient (Fatp4M-/-) mice under chow and high-fat, high-cholesterol (HFHC) diet. Bone-marrow-derived macrophages (BMDMs) from Fatp4M-/- mice showed significant reduction in cellular sphingolipids in males and females, and additionally phospho-lipids in females. BMDMs and Kupffer cells from Fatp4M-/- mice exhibited increased LPS-dependent activation of proinflammatory cytokines and transcription factors PPARc, CEBPa, and p-FoxO1. Correspondingly, these mutants under chow diet displayed throm-bocytopenia, splenomegaly, and elevated liver enzymes. After HFHC feeding, Fatp4M-/- mice showed increased MCP-1 expression in livers and subcutaneous fat. Plasma MCP-1, IL4, and IL13 levels were elevated in male and female mutants, and female mutants additionally showed elevation of IL5 and IL6. After HFHC feeding, male mutants showed an increase in hepatic steatosis and inflam-mation, whereas female mutants showed a greater severity in hepatic fibrosis associated with immune cell infiltration. Thus, myeloid-FATP4 deficiency led to steatotic and inflammatory NASH in males and females, respectively. Our work offers some implications for patients with FATP4 mutations and also highlights considerations in the design of sex-targeted therapies for NASH treatment. NEW & NOTEWORTHY FATP4 deficiency in BMDMs and Kupffer cells led to increased proinflammatory response. Fatp4M-/- mice displayed thrombocytopenia, splenomegaly, and elevated liver enzymes. In response to HFHC feeding, male mutants were prone to hepatic steatosis, whereas female mutants showed exaggerated fibrosis. Our study provides insights into a sex -dimor-to NASH