Intestine lipids

ABR Thomson, JM Dietschy. (1981). Intestinal lipid absorption Major extracellular and intracellular events. In LR Johnson, J Christensen, SL Schultz, eds. Physiology of the Gastrointestinal Tract. New York Raven Press, p 1146. 

Following oral administration of a lipophilic drug, the main route for the drug to access into the intestinal lymphatics is transcellular, by tracking the same pathway as the lipidic nutrients in food, which use the physiological intestinal lipid transport system. Hence, a brief description of this process is described. 

Kemp, P. and Smith, M.F. (1970). Effect of temperature acclimatization on the fatty acid composition of goldfish intestinal lipids. Biochemical Journal 117,9-15. 

Hui, D. Y., Labonte, E. D., and Howies, P. N. (2008) Development and physiological regulation of intestinal lipid absorption III. Intestinal transporters and cholesterol absorption. Am. J. Physiol. Gastrointest. Liver Physiol. 294, 839-843. 

P. Tso, Intestinal lipid absorption, Physiology of the Gastrointestinal Tract (L. R. Johnson, chief ed.), Raven Press, New York, 1994, pp. 1867-1908. 

The synthetic vitamin K3 is water soluble and absorbed irrespective of the presence of intestinal lipids and bile. Since the vitamin K2 form is synthesized by intestinal bacteria, deficiency of the vitamin in adults is rare. 

The extensive, multigenic family of fatty acid and retinoid binding proteins is clearly described by Leonard Banaszak and co-workers in their elegant third chapter. The products of hydrolysis of the intestinal lipids, including fatty acids, cholesterol, monoglycerides, and lysophos-... 

Phan CT and Tso P. Intestinal Lipid Absorption and Transport. Front Biosci 2001 6 D299-D319. 

Roles of bile acids in intestinal lipid digestion... 

Brief outline of intestinal lipid digestion and absorption... 

The relative content of the dietary fat components varies with different sources but generally the physico-chemical properties are rather similar. For absorption to take place the physico-chemical properties of the fat have to be changed. This takes place as a consequence of the lipolytic activity in the intestinal tract and the addition of bile to chyme. Through lipolytic enzymes the dietary lipids are converted to more polar products. Bile contributes bile salt-phospholipid-cholesterol aggregates to the intestinal content (cf. Chapter 13). The concerted action of these agents is the formation of lipid products in a physical state which allows them to be transported into the enterocyte membrane and onwards for further metabolism in the cell. Bile salts are involved in the proper function of some of these enzymatic reactions and in the formation of product phases on which a normal uptake process is based. Little is known at present of the importance of bile salts for the intracellular reactions following uptake of fat into the enterocyte. Different aspects of intestinal lipid absorption have been reviewed in recent years by Patton [7], Thomson and Dietschy [8], Carey [9], Carey et al. [10], Wells and Direnzo [11], and Grundy [12]. The role of bile acids in fat absorption has been discussed by Holt [13]. 

The enterocytes of the small intestine can be isolated and used for study of intracellular aspects of intestinal lipid transport like triglyceride synthesis [52]. The disappearance of the mucus barrier during isolation of the epithelial cells results in plasma membrane disintegration and loss of cellular integrity when the cells are exposed to bile salts. As is the case for brush border vesicles, the system of isolated cells does not allow study of interaction between enterocytes and lipids dispersed in a form that resembles physiological conditions, i.e. solubilized in mixed bile salt micelles. 

What is the role of micellar solubilization for intestinal lipid absorption ... 

Up till now intestinal lipid absorption from mixed micellar solutions has been studied in detail. The existence of non-micellar dispersions of lipolytic products in intestinal contents during fat digestion has recently been proposed [18,47], but so far only little information regarding the importance of these phases for the lipid... 

Phan, C.T., and Tso, P. (2001) Intestin Lipid Absorption and Transport, Front. Biosci. 6, D299-D319. 

Murase, T., Aoki, M., Wakisaka, T., Hase, T., and Tokimitsu, I. (2002) Anti-Obesity Effect of Dietary Diacylglycerol in C57BL/6J Mice Dietary Diacylglycerol Stimulates Intestinal Lipid Metabolism, J. Lipid Res. 43,1312-1319. 

Intestine > lipid degradation -Release o probiotic -Immune signaling... 

Lehner, R., Kuksis, A. and Itabashi, Y. (1993) Chiral phase HPLC analysis of the stereospecificity of mono- and diacylglycerol acyltransferases from rat intestine. Lipids, 28, 29-34. 

After synthesis in enterocytes (increasing in response to intestinal lipid absorption) Apo A-IV is secreted as a major apoprotein component of chylomicrons and is transported in the lymph ducts (for review see [17]). Upon entry into the blood plasma compartment, it rapidly dissociates from chylomicrons and is found in the lipoprotein-free plasma fraction. Weinberg und Spector [38] showed a difference in isoform distribution between lymph and plasma Apo A-IV. Treatment of lymph Apo A-IV with neuraminidase could not mimic the isopeptide change seen upon entry into the plasma compartment [38]. The authors showed that changes in Apo A-IV isoform... 

IQBAL, J. HUSSAIN, M. M. 2009. Intestinal lipid absorption. Am J Physiol Endocrinol Metab, 296, El 183-94. 

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