Fat-related Traits Research Articles

Comparative analysis on gene expression profiles in cattle subcutaneous fat tissues

Fat related carcass traits are important to the beef industry due to their association with value of the meat. In this study, we attempted to discover the genes that are associated with fat metabolism by identification of differentially expressed genes in subcutaneous adipose tissues of beef steers with different backfat thicknesses. Microarray analysis was performed using a bovine specific oligo-platform containing 8329 probes. In total, 360 differentially expressed genes were identified and their functions were characterized by bioinformatical tools to elucidate molecular pathways. 45 out of 360 differentially expressed genes were found to be involved in 82 KEGG pathways. Validation of 6 selected differentially expressed genes by quantitative real-time PCR revealed correlations between backfat thickness and their expression levels. Our results suggest that expression differences of novel genes and the genes that have been known as genetic markers for fat related traits may be associated with backfat development in beef cattle. Moreover, the gene expression differences were also compared between two cattle crossbreds. The observed different association between the expression of selected genes and breed types suggested that the mechanisms of fat metabolism may differ in response to genotypes.

The g.763G>C SNP of the bovineFASNgene affects its promoter activity via Sp-mediated regulation: implications for the bovine lactating mammary gland

Fatty acid synthase (FASN) is an enzyme that catalyzes de novo synthesis of fatty acids in cells. The bovine FASN gene maps to BTA 19, where several quantitative trait loci for fat-related traits have been described. Our group recently reported the identification of a single nucleotide polymorphism (SNP), g.763G>C, in the bovine FASN 5' flanking region that was significantly associated with milk fat content in dairy cattle. The g.763G>C SNP was part of a GC-rich region that may constitute a cis element for members of the Sp transcription factor family. Thus the SNP could alter the transcription factor binding ability of the FASN promoter and consequently affect the promoter activity of the gene. However, the functional consequences of the SNP on FASN gene expression are unknown. The present study was therefore directed at elucidating the underlying molecular mechanism that could explain the association of the SNP with milk fat content. Three cellular lines (3T3L1, HepG2, and MCF-7) were used to test the promoter and the transcription factor binding activities by luciferase reporter assays and electrophoretic mobility shift assays, respectively. Band shift assays were also carried out with nuclear extracts from lactating mammary gland (LMG) to further investigate the role of the SNP in this tissue. Our results demonstrate that the SNP alters the bovine FASN promoter activity in vitro and the Sp1/Sp3 binding ability of the sequence. In bovine LMG, the specific binding of Sp3 may account for the association with milk fat content.

Identification of 14 new single nucleotide polymorphisms in the bovineSLC27A1gene and evaluation of their association with milk fat content

The solute carrier family 27 member 1 (SLC27A1) is an integral membrane protein involved in the transport of long-chain fatty acids across the plasma membrane. This protein has been implicated in diet-induced obesity and is thought to be important in the control of energy homeostasis. In previous reports, our group described the isolation and characterization of the bovine SLC27A1 gene. The bovine gene is organized in 13 exons spanning over more than 40 kb of genomic DNA and maps in BTA 7 where several quantitative trait loci for fat related traits have been described. Because of its key role in lipid metabolism and its genomic localization, in the present work the search for variability in the bovine SLC27A1 gene was carried out with the aim of evaluating its potential association with milk fat content in dairy cattle. By sequencing analysis of all exons and flanking regions 14 new single nucleotide polymorphisms (SNPs) were identified: 1 in the promoter, 7 in introns and 6 in exons. Allele frequencies of all the SNPs were calculated by minisequencing analysis in two groups of Holstein-Friesian animals with highest and lowest milk-fat content estimated breeding values as well as in animals of two Spanish cattle breeds, Asturiana de los Valles and Menorquina. In the conditions assayed, no significant differences between Holstein-Friesian groups were found for any of the SNPs, suggesting that the SLC27A1 gene may have a poor or null effect on milk fat content. In Asturiana and Menorquina breeds all the positions were polymorphic with the exception of SNPs 1 and 8 in which C allele was fixed in both of them.

Mapping and association studies of diabetes related genes in the pig

The mitogen-activated protein kinase 8 (MAPK8), resistin (RETN), 11 beta hydroxysteroid dehydrogenase isoform 1 (HSD11B1) and protein kinase B Akt2 (AKT2) genes are all genes known to affect insulin signalling and have been implicated in the progression of obesity and type 2 diabetes in humans. In this study, polymorphisms in the porcine diabetes related MAPK8, RETN, HSD11B1 and AKT2 genes were identified, mapped and their associations with phenotypic measurements in swine were analysed. Polymorphisms detected in the MAPK8, RETN and HSD11B1 loci were used to genotype a Berkshire-Yorkshire pig breed reference family. Using linkage analysis, RETN, HSD11B1 and MAPK8 genes were mapped to pig chromosomes 2, 9 and 14, respectively, while the AKT2 gene was physically mapped to pig chromosome 6q21. Results presented here suggest associations between the polymorphisms in the MAPK8, RETN and HSD11B1 genes with several phenotypic measurements, including fat deposition traits in the pig. Because these genes have been implicated in obesity and diabetes in humans, and this study suggests associations with fat related traits, further research on these genes in swine may provide useful information on genetic factors underlying lean pork production.

Genetic variation and prediction of additive and nonadditive genetic effects for six carcass traits in an Angus-Brahman multibreed herd.

Estimates of covariances and sire expected progeny differences of additive and nonadditive genetic effects for six carcass traits were obtained using records from 486 straightbred and crossbred steers from 121 sires born between 1989 and 1995 in the Angus-Brahman multibreed herd of the University of Florida. Steers were slaughtered at a similar carcass composition end point. Covariances were estimated by REML procedures, using a generalized expectation-maximization algorithm applied to multibreed populations. Straightbred and crossbred estimates of heritabilities and additive genetic correlations were within ranges found in the literature for steers slaughtered on an age- or weight-constant basis for hot carcass weight, longissimus muscle area, and shear force but equal to or less than the lower bound of these ranges for fat-related traits. Maximum values of interactibilities (i.e., ratios of nonadditive variances to phenotypic variances in the F1) and nonadditive genetic correlations were smaller than heritabilities and additive genetic correlations in straightbreds and crossbred groups. Sire additive and total direct genetic predictions for longissimus muscle area, marbling, and shear force tended to decrease with the fraction of Brahman alleles, whereas those for hot carcass weight and fat thickness over the longissimus were higher, and those for kidney fat were lower in straightbreds and F1 than in other crossbred groups. Nonadditive genetic predictions were similar across sire groups of all Angus and Brahman fractions. These results suggest that slaughtering steers on a similar carcass composition basis reduces variability of fat-related traits while retaining variability for non-fat-related traits comparable to slaughtering steers on a similar age or weight basis. Selection for carcass traits within desirable (narrow) ranges and slaughter of steers at similar compositional end point seems to be a good combination to help produce meat products of consistent quality.

Heritabilities of morphological and body composition characteristics in a Spanish population

Different estimates of heritability are presented for a set of anthropometric characteristics taken in 844 individuals from 261 families living in the Madrid city area (Spain). The data include measurements of 10 craniofacial, 11 body skeletal (4 lengths and 7 breadths), and 13 fat-related characteristics (weight, 3 circumferences, 6 skinfold thicknesses, body mass index and arm fat and arm muscle areas). The estimates computed from parent and offspring data show a clear defined pattern (higher heritabilities for longitudinal traits, followed by breadths, circumferences, and skinfolds, respectively). Heritabilities estimated from sib-sib correlation do not show such pattern and are generally higher than those assessed through parent-offspring data, mainly for fat related traits, which is attributed to common environment effects.