Regulation of MTP expression in developing swine

Abstract

To define the developmental expression of microsomal triglyceride transfer protein (MTP) large subunit mRNA and protein, samples of small intestine and liver were collected from 40-day gestation fetal, 2-day-old newborn, 3-week-old suckling, and 2-month-old weanling swine. In fetal animals, MTP mRNA expression was high in intestine and liver. Postnatally, jejunal expression paralleled the intake of a high-fat breast milk diet and declined after weaning. Ileal expression was comparable with that of jejunum in 2-day-old animals, but declined to low levels afterward. Hepatic expression declined postnatally and remained low. MTP protein expression generally paralleled mRNA expression, except in fetal intestine in which no 97 kDa protein was detected. In 2-day-old piglets, a high-triacylglycerol diet increased jejunal and ileal MTP mRNA levels, as compared to a low-triacylglycerol diet. To test the roles of glucocorticoids and fatty acids in MTP regulation, a newborn swine enterocyte cell line (IPEC-1) was used. Except at day 2 of differentiation, dexamethasone did not influence MTP expression. Fatty acids either up-regulated or down-regulated MTP expression, depending on the specific fatty acid and duration of exposure.Although programmed genetic cues regulate MTP expression during development, clearly the amount and fatty acid composition of dietary lipid also play regulatory roles.

A non‐synonymous mutation in a conserved site of the MTTP gene is strongly associated with protein activity and fatty acid profile in pigs

“…2007). In addition, the amount and composition of dietary fatty acids play an important role in MTTP expression in developing swine (Lu et al. 2002) and this effect could also be maintained in growing pigs.…”

Developmental expression and nutritional regulation of a zebrafish gene homologous to mammalian microsomal triglyceride transfer protein large subunit

“…In mammals, Mttp is expressed during embryonic and fetal development (Terasawa et al,1999; Shelton et al,2000; Levy et al,2001; Lu et al,2002). Mouse Mttp mRNA has been detected in the YS at embryonic day E9.5 (Terasawa et al,1999; Shelton et al,2000) and MTP large subunit has been immunodetected in the YS of 9‐day chicken embryos (Hermann et al,2000).…”

“…Mammalian MTP large subunit gene ( Mttp ) is expressed during development (Terasawa et al,1999; Shelton et al,2000; Levy et al,2001; Lu et al,2002) and seems to be essential, as all homozygous Mttp knockout mice have been reported to die during embryonic development (Raabe et al,1998). Genetic mutations of human Mttp causing the absence or length modifications of the protein are responsible for abetalipoproteinemia (Shoulders et al,1993; Sharp et al,1993).…”

Assignment of the microsomal triglyceride transfer protein large subunit (MTP ) gene to porcine chromosome 8

“…MTP plays a key role in the transfer of lipids during lipoprotein assembly in liver and the intestine 1 . In swine, it has been shown that the MTP gene expression is regulated by dietary fatty acids 2 . Although deleterious mutations in MTP lead to abetalipoproteineamia, a recessive disorder characterized by the absence of plasma apolipoprotein B and the accumulation of triglycerides in the cytoplasm of liver and intestinal cells, it has been suggested that nucleotide variation in the MTP gene can predict hepatic secretion levels of lipoproteins in healthy men 3…”

“…Nucleotide sequence: Pig genomic DNA was isolated from blood using a phenol–chloroform extraction. MTP porcine mRNA sequence 2 (GenBank accession no. ) was used to design primers in exon 17 (MTPe17‐FW) and exon 18 (MTPe18‐RV), assuming conservation with the previously described human MTP gene structure (GenBank , region: 24990685–25039330).…”