MFGE8 links absorption of dietary fatty acids with catabolism of enterocyte lipid stores through HNF4 γ- dependent transcription of CES enzymes

Abstract

Enterocytes modulate the extent of postprandial lipemia, a potent risk factor for developing atherosclerotic disease, by storing dietary fats in cytoplasmic lipid droplets (cLDs). We have previously demonstrated that the integrin ligand MFGE8 links absorption of dietary fats with activation of triglyceride (TG) hydrolases that catabolize cLDs for chylomicron production. The hydrolase(s) responsible for mobilization of TG from diet-derived cLDs is unknown though recent evidence indicates that this process is independent of the canonical pathway of TG hydrolysis mediated by ATGL. Here we identify CES1D as the key hydrolase downstream of the MFGE8-v{beta}5 integrin pathway that regulates catabolism of diet-drive cLDs. Mfge8 KO enterocytes have reduced CES1D transcript and protein levels and reduced protein levels of the transcription factor HNF4{gamma}. Mice KO for Ces1d or Hnf4{gamma} have decreased enterocyte TG hydrolase activity coupled with retention of TG in cLDs. Mechanistically, MFGE8-dependent fatty acid uptake through CD36 leads to stabilization of HNF4{gamma} protein levels; HNF4{gamma} then increases Ces1d transcription. Our work identifies a regulatory network by which MFGE8 and v{beta}5 regulate the severity of postprandial lipemia by linking dietary fat absorption with protein stabilization of a transcription factor that increases expression of enterocyte TG hydrolases that catabolize diet-derived cLDs.