Fatty Acid-Binding Protein in Small Intestine IDENTIFICATION, ISOLATION, AND EVIDENCE FOR ITS ROLE IN CELLULAR FATTY ACID TRANSPORT

Abstract

A B S T R A C T A soluble fatty acid-binding protein (FABP), mol wt 12,000 is present in intestinal mucosa and other tissues that utilize fatty acids, including liver, myocardium, adipose, and kidney. This protein binds long chain fatty acids both in vivo and in vitro.FABP was isolated from rat intestine by gel filtration and isoelectric focusing. It showed a reaction of complete -immunochemical identity with proteins in the 12,000 mol wt fatty acid-binding fractions of liver, myocardium, and adipose tissue supernates. (The presence of immunochemically nonidentical 12,000 mol wt FABP in these tissues is not excluded.) By quantitative radial immunodiffusion, supernatant FABP concentration in mucosa from proximal and middle thirds of jejuno-ileum significantly exceeded that in distal third, duodenum, and liver, expressed as micrograms per milligram soluble protein, micrograms per gram DNA, and micrograms per gram tissue. FABP concentration in villi was approximately three times greater than in crypts. Small quantities of FABP were present in washed nuclei-cell membrane, mitochondrial and microsomal fractions. However, the amount of FABP solubilized per milligram membrane protein was similar for all particulate fractions, and total membrane-associated FABP was only about 16% of supernatant FABP. Intestinal FABP concentration was significantly greater in animals maintained on high fat diets than on low fat; saturated and unsaturated fat diets did not differ greatly in this regard.The preponderance of FABP in villi from proximal and middle intestine, its ability to bind fatty acids in vivo as well as in vitro, and its response to changes in dietary fat intake support the concept that this protein participates in cellular fatty acid transport during fat

Tissue distribution and subcellular localization of phosphatidylcholine transfer protein in rats as determined by radioimmunoassay

“…It is, therefore, possible that PC-transfer protein in the cell is associated with subcellular organelles. Such associations have been observed for the cellular retinol-and fatty acid-binding proteins in rat [20,21]. In order to determine the levels of PC-transfer protein on membranes we modified our radioimmunoassay.…”

“…Two other cellular binding proteins, i.e., the fatty acid-binding protein from rat intestinal mucosa and the cellular retinol-binding protein, have also been shown to be partly associated with particulate fractions [20,21]. As shown in Table I, liver contains the highest amount of PC-transfer protein, followed by the intestinal mucosa, kidney and spleen.…”

Evidence for a Role of the Gut Hormone PYY in the Regulation of Intestinal Fatty Acid-binding Protein Transcripts in Differentiated Subpopulations of Intestinal Epithelial Cell Hybrids

“…Fatty acid binding-proteins (FABPs) are 14 -15-kDa cytosolic proteins that bind fatty acids with affinities in the nanomolar range (16). An extensive number of cytosolic binding proteins have been grouped into the FABP gene family, including liver fatty acid-binding protein L-FABP (found in the liver and intestine) (17), I-FABP (found only in the intestine) (17,18), ileal gastrotropin (19), cellular retinol-binding proteins I and II (20,21), cellular retinoic acid-binding proteins I and II (20), adipocyte and myelin FABP (22), and heart and epidermal FABP (23,24). The intestine abundantly expresses both I-and L-FABP, each as 2-3% of total cytosolic protein (25).…”

Effects of dihydroxy bile acids and hydroxy fatty acids on the absorption of oleic acid in the human jejunum.

“…Since net absorption of fatty acids is the result of uptake from micellar solutions, possible binding to a cytoplasmic fatty acid binding protein (31), resynthesis to triglycerides, chylomicron formation, and subsequent release of the chylomicrons into the lymphatics (32), the later steps in this sequence could become rate limiting in the presence of dihydroxy bile acids or hydroxy fatty acids. If saturation of a ratelimiting step or inhibition of an enzymatic reaction were the explanation for the reduced fatty acid absorption in the presence of hydroxy fatty acids or dihydroxy bile acids (33), absorption of OA from 3 mM OA plus 2 mM HSA should have been lower than from OA alone, not only in the presence of 10 mM TC but also in the presence of 7 mM TC plus 3 mM DC.…”