Milk lipid globules from humans, cows and rats contain a protein identified as adipocyte differentiation-related protein (ADFP) associated with the globule surface membrane material. This protein, previously believed to be specific to adipocytes, was a major constituent of the globule surface and was present in a detergent-insoluble complex that contained stoichiometric amounts of butyrophilin and xanthine oxidase. ADFP (Adipophilin) occurs in a wide range of cultured cell lines, including fibroblasts, endothelial and epithelial cells. In tissues, however, expression of adipophilin is restricted to certain cell types, such as lactating mammary epithelial cells, adrenal cortex cells, Sertoli and Leydig cells of the male reproductive system, and steatosis or fatty change hepatocytes in alcoholic liver cirrhosis. ADFP may be a possible new marker for the identification of specialized differentiated cells containing lipid droplets and for diseases associated with fat-accumulating cells.
