Localization and regulation of the putative membrane fatty-acid transporter (FAT) in the small intestine. Comparison with fatty acid-binding proteins (FABP).
The expression of the putative membrane fatty-acid transporter (FAT) was investigated in the small intestine. The FAT mRNA level was higher in the jejunum than in the duodenum and was lower in the ileum, as observed for cytosolic fatty-acid-binding proteins (FABP) expressed in this tissue. No FAT transcript was found in the stomach or colon. FAT mRNA was constitutively expressed in the epithelial cells located in the upper two thirds of villi, while it was undetectable in the crypt cells and submucosal cells. In jejunal mucosa, immunochemical studies showed that FAT protein was limited to the brush border of enterocytes. No fluorescence was found in the goblet cells. To determine whether FAT responded to changes in fat intake, as reported for FABP, the effect of two high-fat diets, which essentially contained either medium-chain fatty acids or long-chain fatty acids (sunflower-oil diet), was investigated. The sunflower-oil diet greatly increased FAT mRNA abundance throughout the small intestine. In contrast, a weak effect of medium-chain fatty acids was observed only in the jejunum. As found for FABP expression, treatment with the hypolipidemic drug bezafibrate affected FAT expression. These data demonstrate that FAT and FABP are co-expressed in enterocytes, as has been shown in adipocytes, myocytes and mammary cells. The data suggest that these membrane and cytosolic proteins might have complementary functions during dietary-fat absorption.
Poirier
H
H
Laboratoire de Physiologie de la Nutrition, Ecole Nationale Supérieure de Biologie Appliquée a la Nutrition et à l'Alimentation, Université de Bourgogne, Dijon, France.
Degrace
P
P
Niot
I
I
Bernard
A
A
Besnard
P
P
D000818:Animals; D001629:Bezafibrate / Q000494:pharmacology; D001692:Biological Transport; D015152:Blotting, Northern; D015153:Blotting, Western; D002352:Carrier Proteins / Q000032:analysis / Q000378:metabolism*; D004041:Dietary Fats / Q000008:administration & dosage; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D005227:Fatty Acids / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000235:genetics; D000960:Hypolipidemic Agents / Q000494:pharmacology; D007150:Immunohistochemistry; D007413:Intestinal Mucosa / Q000737:chemistry / Q000378:metabolism*; D007421:Intestine, Small / Q000737:chemistry / Q000378:metabolism*; D008297:Male; D008565:Membrane Proteins / Q000032:analysis / Q000378:metabolism*; D018996:Myelin P2 Protein / Q000378:metabolism*; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar
D002352:Carrier Proteins; D004041:Dietary Fats; C490174:Fabp7 protein, rat; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D005227:Fatty Acids; D000960:Hypolipidemic Agents; D008565:Membrane Proteins; D018996:Myelin P2 Protein; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D012333:RNA, Messenger; D001629:Bezafibrate