Dietary Lipid Metabolism Overview

Lipids are a heterogeneous group of water-insoluble (hydrophobic) organic molecules (Fig. 1). Because of their insolubility in aqueous solutions, body lipids are generally found compartmentalized, as in the case of membraneassociated lipids or droplets of triacylglycerol in adipocytes, or transported in blood in association with protein, as in lipoprotein particles or on albumin. Lipids are a major source of energy for the body, and they also provide the hydrophobic barrier that permits partitioning of the aqueous contents of cells and subcellular structures. Lipids serve additional functions in the body (for example, some fat-soluble vitamins have regulatory or coenzyme functions, and the prostaglandins and steroid hormones play major roles in the control of the body’s homeostasis). Deficiencies or imbalances of lipid metabolism can lead to some of the major clinical problems encountered by physicians, such as atherosclerosis, diabetes, and obesity.

Figure 1: Structures of some common classes of lipids. Hydrophobic portions of the molecules are shown in orange.