Fig 1.
Vitamin A (retinol) handling during health and disease.
(A) During homeostasis, gut bacteria suppress the conversion of dietary retinol into RA and promote its storage. Retinol transporter RBP4 is the main transporter of retinol to and from the liver. (B) During infection, RBP4 amounts drop, reducing retinol transport and storage in the liver. Acute-phase RBPs, such as SAAs, increase in the intestinal tissue and up-regulate local immune response to infection. RA, retinoic acid; RBP, retinol-binding protein; SAA, serum amyloid A.