Intestinal Absorption of Fats.

Great progress in understanding the mechanisms of fat absorption by the mammalian intestine has been made in the past decade and a half. In contrast to the contentions of rival theorists of the century before this, it has been possible for many laboratories throughout the world to confirm observations made by use of the new tools available, and to come to agreement on current interpretations of the data. A brief survey of the historical background is presented to establish mainly a point of departure, after which some of the notable contributions of the postwar period and early Fifties are discussed in time sequence. In developing the review of advances during the past decade, however, I have chosen to focus upon metabolicevents occurring in the epithelial cells of the gut mucosa. For emphasis on these events a deviation has been made from the usual anatomic sequence of discussion in order to consider the glycerol moiety of the glycerides synthesized in the cells, the activation of fatty acids, and the pathway of direct esterification of monoglycerides. By this device I have attempted to underscore the importance of the components of the intraluminally formed micelles, and the intracellular partition based upon chain length and solubility. Also, it is hoped that the biochemical transformations may be borne in mind when considering the morphologic and fine structure changes associated with pinocytosis, possible micellar absorption of lipid, intracellular transport of the fat droplets, and the release of finished chylomicrons into the lacteal spaces. Finally, some of the structural determinants of glyceride synthesis and the energetics of the over-all process of triglyceride absorption are mentioned before a statement of the present position is offered.