Overexpression of apolipoprotein A-IV enhances lipid transport in newborn swine intestinal epithelial cells.
Apolipoprotein A-IV (apoA-IV) has myriad functions, including roles as a post-prandial satiety factor and lipid antioxidant. ApoA-IV is expressed in mammalian small intestine and is up-regulated in response to lipid absorption. In newborn swine jejunum, a high fat diet acutely induces a 7-fold increase in apoA-IV expression. To determine whether apoA-IV plays a role in the transport of absorbed lipid, swine apoA-IV was overexpressed in a newborn swine enterocyte cell line, IPEC-1, followed by analysis of the expression of genes related to lipoprotein assembly and lipid transport, as well as quantitation of lipid synthesis and secretion. A full-length swine apoA-IV cDNA was cloned, sequenced, and inserted into a Vp and Rep gene-deficient adeno-associated viral vector, containing the cytomegalovirus immediate early promoter/enhancer and neomycin resistance gene, and was used to transfect IPEC-1 cells. Control cells were transfected with the same vector minus the apoA-IV insert. Using neomycin selection, apoA-IV-overexpressing (+AIV) and control (-AIV) clones were isolated for further study. Both undifferentiated (-D) and differentiated (+D) +AIV cells expressed 40- to 50-fold higher levels of apoA-IV mRNA and both intracellular and secreted apoA-IV protein compared with -AIV cells. Expression of other genes was not affected by apoA-IV overexpression in a manner that would contribute to enhanced lipid secretion. +D +AIV cells secreted 4.9-fold more labeled triacylglycerol (TG), 4.6-fold more labeled cholesteryl ester (CE), and 2-fold more labeled phospholipid (PL) as lipoproteins, mostly in the chylomicron/very low density lipoprotein (VLDL) density range. ApoA-IV overexpression in IPEC-1 cells enhances basolateral TG, CE, and PL secretion in chylomicron/VLDL particles. This enhancement is not associated with up-regulation of other genes involved in lipid transport. ApoA-IV may play a role in facilitating enterocyte lipid transport, particularly in the neonate receiving a diet of high fat breast milk.
Lu
Song
S
Children's Foundation Research Center at Le Bonheur Children's Medical Center, University of Tennessee Health Science Center, Memphis, Tennessee 38103, USA.
Yao
Ying
Y
Meng
Songmai
S
Cheng
Xiangying
X
Black
Dennis D
DD
D000595:Amino Acid Sequence; D000818:Animals; D000831:Animals, Newborn; D001054:Apolipoproteins A / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D001692:Biological Transport; D002460:Cell Line; D003001:Cloning, Molecular; D005786:Gene Expression Regulation; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism*; D050356:Lipid Metabolism; D008969:Molecular Sequence Data; D011994:Recombinant Proteins / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D013552:Swine; D014162:Transfection
D001054:Apolipoproteins A; D011994:Recombinant Proteins; C022205:apolipoprotein A-IV