The Absorption of Cholesterol and Plant Sterols by the Intestine

This chapter explores the evidence contained in works in an attempt to define the rate-limiting steps in the absorptive process, the factors influencing absorption, and the molecular interactions involved. It deals with lumenal, membrane, cytosolic, and enzymatic aspects of sterol absorption. The chapter considers the influence of each of the major transformations on the absorption of cholesterol itself, on the ability of the intestine to selectively absorb cholesterol over other sterol analogs, and on the hypocholesterolemic effect of plant sterols. Sterols, along with the glycerolipids, are absorbed primarily by the proximal V₃ of the small intestine. The greater absorption in the jejunal region of the small intestine may be expected from its position in the intestinal tract, but D. G. Thompson has reported structural differences between the jejunal and ileal epithelium. The process of chylomicron formation apparently represents a major rate-limiting step in the transport of sterol.