Effects of breed, parity, and folic acid supplement on the expression of leptin and its receptors' genes in embryonic and endometrial tissues from pigs at day 25 of gestation

Novel porcine housekeeping genes for real-time RT-PCR experiments normalization in adipose tissue: assessment of leptin mRNA quantity in different pig breeds

The main function of adipose tissue is energy storage and production of various cytokines and hormones, such as leptin. Leptin is a protein hormone synthesized and secreted by adipose tissue. The expression of leptin is strongly dependent on growth and luteinizing hormones, which play an important role in the brain-pituitary axis. The concentration of leptin in blood plasma increases with age and obesity and is associated with the level of leptin mRNA in adipose tissue. Selection of appropriate internal control gene (ICG) for normalization of quantitative PCR data for genes of interest is critical for interpretation of results. The estimation of leptin mRNA is important in the research on regulation of feed intake and metabolic and energy balance. Therefore, the objective of this study was to evaluate the stability of mRNA expression for a number of candidate housekeeping genes in the porcine backfat tissue across different breeds. In our study we used a freeware computer program (geNorm) to evaluate the most stable among eight ICG genes (β-actin, hypoxanthine phosphoribosyltransferase 1, TATA binding protein, glyceraldehyde-3-phosphate dehydrogenase, ornithine decarboxylase antizyme 1, 60S ribosomal protein L27, 40S ribosomal protein S29, eukaryotic elongation factor (1) in 90 mRNA samples of backfat tissue. In the study we used three breeds differing in muscling: Polish Large White (n=30), Polish Landrace (n=30) and Pietrain (n=30). The results showed that the three most stable genes were ornithine decarboxylase antizyme 1 (OAZ1), 60S ribosomal protein L27 (RPL27) and β-actin (M=0.579, 0.602 and 0.607, respectively). In order to evaluate the abundance of leptin mRNA, the two most stable genes were used. The highest level of mRNA expression was obtained for PL and the lowest for Pietrain pigs. These results confirmed previous studies which showed that pigs with lean carcass were characterized by a lower level of leptin transcript compared to pigs with large fat deposit. Moreover, we analyzed relationship between C3469T Lep polymorphism and level of leptin mRNA, but did not find significant associations. Our study provides a new panel of housekeeping genes for normalization of the expression of a gene of interest in adipose tissue.

Early programming of adipose tissue function: a large-animal perspective

The emerging role of adipose tissue as a dynamic endocrine organ with an extent of anatomical and physiological plasticity has generated numerous studies linking early-life events with long-term alterations in adipose tissue structure and function. Coupled with increasing rates of human obesity, which cannot be explained without some genetic component, the role of early programming of adipose tissue may provide an insight into potential mechanisms. The developmental origins of health and disease hypothesis investigates the potential association between a compromised fetal and postnatal environment and later disease, such as obesity and type 2 diabetes, in the offspring. A number of animal models have been developed to examine potential mechanisms that drive these physiological changes, including rodent and large-mammal models that provide mechanistic insights into the epidemiological findings. In utero challenges such as under- or over-provision of nutrients, placental insufficiency and glucocorticoid infusion, as well as postnatal nutritional challenges, can all result in the long-term programming of adipose tissue abundance and function. A range of hormones, enzymes, transcription factors and other metabolic signalling molecules have been implicated in adverse adipose tissue development, including leptin, glucocorticoids, members of the PPAR family, fatty acid-binding proteins and adipokines. The long-term structural and physiological consequences associated with these molecular and cellular changes are less well described. The experimental models, potential mechanisms and regulators of the early programming of adipose tissue in large mammalian species will be summarised in the present review.

Modulation of peroxisome proliferator-activated receptor delta and gamma transcripts in swine endometrial tissue during early gestation

Recent evidence points to a role for peroxisome proliferator-activated receptors (PPARs) delta and gamma in embryo implantation and survival. In this study, we report the porcine PPARdelta complete coding sequence and mRNA abundance of PPARdelta, PPARgamma1 and gamma2, angiopoietin-like protein 4 (ANGPTL4) and adipocyte determination and differentiation-dependent factor 1 (ADD1) genes in the pregnant sow endometrium. Real-time PCR analysis was used to study the effect of parity (Yorkshire-Landrace multiparous (YL) and nulliparous (YLn)), site of endometrial tissue sampling (between and at embryo attachment sites) in crossbred DurocxYorkshire-Landrace (DYL) sows and stages of pregnancy (non-pregnant, day 15 and day 25 after mating) in Meishan-Landrace (ML) on mRNA levels. Parity effects were observed for PPARdelta, ANGPTL4, and ADD1, with higher mRNA levels in YL than YLn sows. In DYL sows, lower mRNA levels were present at attachment sites compared to between attachment sites for PPARdelta, PPARgamma1, and ANGPTL4. Finally, day 15 pregnant ML sows had lower PPARdelta mRNA levels compared to day 15 cycling ML sows. A significant increase of PPARgamma1 mRNA levels was found on day 25 pregnant ML and DYL sows relative to day 15 ML or DYL pregnant sows. PPARdelta and gamma immunostaining was detected in endometrial tissue of day 15 cycling sows, day 15 and 25 pregnant sows and epithelial cells of day 25 embryos. Collectively, our results suggest a role for PPARdelta, PPARgamma1, and ANGPTL4, but not PPARgamma2, during the peri-implantation period in pregnant sows.

Genetic polymorphisms in porcine leptin gene and their association with reproduction and production traits

Leptin (LEP), the product of the leptin gene, is a 16-kDa protein synthesised by adipose tissue and is involved in regulation of feed intake, energy balance, fertility, and immune functions. Using bi-directional polymerase chain reaction amplification of specific alleles (bi-PASA) and PCR-restriction fragment length polymorphisms (PCR-RFLP), we have successfully detected genetic polymorphisms of LEP intron 1 and exon 3, respectively, in Landrace, Yorkshire, and Duroc. Chi-square statistics were used to calculate homogeneity of genotypic frequencies of 2 candidate genes for 3 breeds of animals. Effects of exon 3 polymorphisms on reproduction traits such as litter sizes of sows in the first parity and 1–4 parities were evident (P < 0.05) in Landrace, and 1–4 parities in Yorkshire. Polymorphisms of intron 1 affected (P < 0.05) only litter sizes of the first parity in Duroc. Effects of exon 3 polymorphisms on production traits such as average daily gain and feed efficiency were evident (P < 0.05) in Landrace and Yorkshire, respectively. Polymorphisms of intron 1 affected (P < 0.05) only backfat thickness in Duroc. Our data also show that the higher the reproduction traits, the lower the genotypic frequencies. Further, the better the production traits, the higher the genotypic frequencies were. These data suggest that the long-term selection of favourable traits in pig production may be partially attributed to the effects of LEP polymorphisms on reproduction and production traits.

Effects of Breed, Parity, and Folic Acid Supplement on the Expression of Folate Metabolism Genes in Endometrial and Embryonic Tissues from Sows in Early Pregnancy1

Folic acid and glycine are factors of great importance in early gestation. In sows, folic acid supplement can increase litter size through a decrease in embryonic mortality, while glycine, the most abundant amino acid in the sow oviduct, uterine, and allantoic fluids, is reported to act as an organic osmoregulator. In this study, we report the characterization of cytoplasmic serine hydroxymethyltransferase (cSHMT), T-protein, and vT-protein (variant T-protein) mRNA expression levels in endometrial and embryonic tissues in gestating sows on Day 25 of gestation according to the breed, parity, and folic acid + glycine supplementation. Expression levels of cSHMT, T-protein, and vT-protein mRNA in endometrial and embryonic tissues were performed using semiquantitative reverse transcription-polymerase chain reaction. We also report, for the first time, an alternative splicing event in the porcine T-protein gene. Results showed that a T-protein splice variant, vT-protein, is present in all the tested sow populations. Further characterizations revealed that this T-protein splice variant contains a coding intron that can adopt a secondary structure. Results demonstrated that cSHMT mRNA expression levels were significantly higher in sows receiving the folic acid + glycine supplementation, independently of the breed or parity and in both endometrial and embryonic tissues. Upon receiving the same treatment, the vT-protein and T-protein mRNA expression levels were significantly reduced in the endometrial tissue of Yorkshire-Landrace sows only. These results indicate that modulation of specific gene expression levels in endometrial and embryonic tissues of sows in early gestation could be one of the mechanism involved with the role of folic acid on improving swine reproduction traits.