Primary Study On Molecular Mechanisms Of The Porcine GPIHBP1and ApoC â…¡ Genes

Lipoprotein lipase (LPL) is an essential enzyme in the lipid metabolism, and proper regulation of LPL is important for controlling the delivery of lipid nutrients to tissues. Recent studies have identified glycosylphosphatidylinositol-anchored high density lipoprotein-binding protein1(GPIHBP1) as the important regulation factor of LPL that serves as a binding platform for lipolysis on the vascular lumen and an endothelial cell transporter transporting LPL from the interstitial spaces to the capillary lumen. Apolipoprotein CII (ApoCII) is the activator of LPL, and can promote the lipid metabolism by improving the activity of LPL. Although the researches on GPIHBP1and ApoCII molecules of the mouse and human primarily revealed the physiological functions of the GPIHBP1and ApoCII in lipid metabolism, the molecular mechanism in vivo needs further investigation. Moreover, so far the molecular mechanisms of the procine GPIHBP1and ApoCII in lipid metabolism have not been reported. Using the molecular biology techniques, the DNA sequences, profiles of tissue expression and genetic diversities of GPIHBP1and ApoCII genes of pigs were investigated at the levels of molecules, individuals and groups. The results are as follows:(1) We obtained the procine1984bp of GPIHBP1and2061bp of ApoCII complete gene sequence. The procine GPIHBP1gene was composed of4exons and3introns, encoding184amino acid residues. At the amino acid level, the homology with human, mouse and bovine was53%,51%and65%, respectively. The procine ApoCII gene was composed of4exons and3introns, encoding101amino acid residues. At the amino acid level, the homology with human, mouse and bovine was62%,59%and75%, respectively.(2) The mRNA transcription levels of the porcine GPIHBP1and ApoCII genes were detected by quantitative real time PCR (qPCR) in seventeen tissues (heart, liver, spleen, lung, kidney, stomach, intestine, ovary, testicle, eye muscle, the psoas muscle, the outer layer of subcutaneous fat, the inner layer of subcutaneous fat, omentum, lesser omentum, abdominal subcutaneous fat and suet) at the180-day-old, and we also analyzed the sex effects on the two gene transcription levels. The results found that:the GPIHBP1and LPL genes transcriptional levels were similar in diffirent organizations, both transcription at high levels in adipose tissues and muscle tissues, but different transcription levels in other tissues. The GPIHBPI transcription levels were higher in the lung, but the LPL lower in the lung. Sex had a significant effect on transcription levels of the GPIHBPI gene, and the mRNA levels of sows were very significantly higer than that of boars in adipose tissues (P <0.01). The ApoCII transcription levels were high in the liver. Sex had a significant effect on transcription levels of the ApoCII gene, and the mRNA levels of sows were very significantly higer than that of boars in adipose and liver tissue (P<0.01).(3) We sequenced the GPIHBP1and ApoCII gene for266pigs from five breeds (Jinhua, Yanan, Yorkshire, Landrace and Duroc).37mutated sites of the procine GPIHBP1gene were found. The intron have31mutated sites, of which a single base insertion/deletion is at the1014site of the intron; five mutated sites are in exon, of which at695site is an arginine→tryptophan amino acid mutation; the mutated site is in the3’ untranslated region. There are13mutated sites of ApoCII gene. The intron has11mutated sites, of which a single base insertion/deletion is at the first intron of846site; exon3has two single mucleotide polymorphisms (SNPs).(4) In order to further analyze whether these polymorphic loci affect procine lipid metabolism, we carried on analysis the correlation between the GPIHBP1and ApoCII genes polymorphism loci and the intramuscular fat content and back fat thickness. The results showed that the255G>C and626T>G mutation sites of the procine GPIHBP1gene were significantly associated with intramuscular fat (P<0.05);1557T>C and1948G>A mutation sites were significantly correlated with backfat thick (P<0.01); genotype distribution of these four polymorphic loci have a very significant difference in the five breeds (P<0.01). The551T>C and610A>G mutation locus of the ApoCII gene were significantly related with backfat thickness (P<0.05); genotype distribution of two polymorphic loci have a very significant difference in five breeds (P<0.001).