Transcriptional regulation of adipogenic marker genes for the improvement of intramuscular fat in Qinchuan beef cattle

A review of the role of transcription factors in regulating adipogenesis and lipogenesis in beef cattle

In the past few decades, genomic selection and other refined strategies have been used to increase the growth rate and lean meat production of beef cattle. Nevertheless, the fast growth rates of cattle breeds are often accompanied by a reduction in intramuscular fat (IMF) deposition, impairing meat quality. Transcription factors play vital roles in regulating adipogenesis and lipogenesis in beef cattle. Meanwhile, understanding the role of transcription factors in regulating adipogenesis and lipogenesis in beef cattle has gained significant attention to increase IMF deposition and meat quality. Therefore, the aim of this paper was to provide a comprehensive summary and valuable insight into the complex role of transcription factors in adipogenesis and lipogenesis in beef cattle. This review summarizes the contemporary studies in transcription factors in adipogenesis and lipogenesis, genome-wide analysis of transcription factors, epigenetic regulation of transcription factors, nutritional regulation of transcription factors, metabolic signalling pathways, functional genomics methods, transcriptomic profiling of adipose tissues, transcription factors and meat quality and comparative genomics with other livestock species. In conclusion, transcription factors play a crucial role in promoting adipocyte development and fatty acid biosynthesis in beef cattle. They control adipose tissue formation and metabolism, thereby improving meat quality and maintaining metabolic balance. Understanding the processes by which these transcription factors regulate adipose tissue deposition and lipid metabolism will simplify the development of marbling or IMF composition in beef cattle.

Verification of Key Target Molecules for Intramuscular Fat Deposition and Screening of SNP Sites in Sheep from Small-Tail Han Sheep Breed and Its Cross with Suffolk

Intramuscular fat (IMF) is vital for meat tenderness and juiciness. This study aims to explore the IMF deposition mechanism and the related molecular markers in sheep. Two populations, Small-tail Han Sheep (STH) and STH × Suffolk (SFK) F1 (SFK × STH), were used as the research object. Histological staining techniques compared the differences in the longissimus dorsi muscle among populations. A combination of transcriptome sequencing and biological information analysis screened and identified IMF-related target genes. Further, sequencing technology was employed to detect SNP loci of target genes to evaluate their potential as genetic markers. Histological staining revealed that the muscle fiber gap in the SFK × STH F1 was larger and the IMF content was higher. Transcriptome analysis revealed that PIK3R1 and PPARA were candidate genes. Histological experiments revealed that the expressions of PIK3R1 mRNA and PPARA mRNA were lower in SFK × STH F1 compared with the STH. Meanwhile, PIK3R1 and PPARA proteins were located in intramuscular adipocytes and co-located with the lipid metabolism marker molecule (FASN). SNP locus analysis revealed a mutation site in exon 7 of the PIK3R1 gene, which served as a potential genetic marker for IMF deposition. This study's findings will provide a new direction for meat quality breeding in sheep.

Molecular and Cellular Mechanisms of Intramuscular Fat Development and Growth in Cattle

Intramuscular fat, also referred to as marbling fat, is the white fat deposited within skeletal muscle tissue. The content of intramuscular fat in the skeletal muscle, particularly the longissimus dorsi muscle, of cattle is a critical determinant of beef quality and value. In this review, we summarize the process of intramuscular fat development and growth, the factors that affect this process, and the molecular and epigenetic mechanisms that mediate this process in cattle. Compared to other species, cattle have a remarkable ability to accumulate intramuscular fat, partly attributed to the abundance of sources of fatty acids for synthesizing triglycerides. Compared to other adipose depots such as subcutaneous fat, intramuscular fat develops later and grows more slowly. The commitment and differentiation of adipose precursor cells into adipocytes as well as the maturation of adipocytes are crucial steps in intramuscular fat development and growth in cattle. Each of these steps is controlled by various factors, underscoring the complexity of the regulatory network governing adipogenesis in the skeletal muscle. These factors include genetics, epigenetics, nutrition (including maternal nutrition), rumen microbiome, vitamins, hormones, weaning age, slaughter age, slaughter weight, and stress. Many of these factors seem to affect intramuscular fat deposition through the transcriptional or epigenetic regulation of genes directly involved in the development and growth of intramuscular fat. A better understanding of the molecular and cellular mechanisms by which intramuscular fat develops and grows in cattle will help us develop more effective strategies to optimize intramuscular fat deposition in cattle, thereby maximizing the quality and value of beef meat.

Comparative alternative polyadenylation profiles in differentiated adipocytes of subcutaneous and intramuscular fat tissue in cattle

Alternative polyadenylation (APA) is a key molecular mechanism involved in the post-transcriptional regulation of gene expression, which has been proven to play a critical role in cell differentiation. In the present study, we performed IVT-SAPAS sequencing to profile the dynamic changes of APA sites in bovine subcutaneous preadipocytes and intramuscular preadipocytes during adipogenesis. A total of 52621 high quality APA sites were identified in preadipocytes and adipocytes. Compared with preadipocytes, the increased usage of canonical AATAAA was observed in the cell-biased APA sites of adipocytes. Furthermore, 1933 and 2140 differentially expressed APA (DE-APA) sites, as well as 341 and 337 untranslated region-APA (UTR-APA) switching genes were identified in subcutaneous preadipocytes and intramuscular preadipocytes during adipogenesis, respectively. The UTR-APA switching genes showed divergent trends in preadipocytes, among which UTR-APA switching genes in intramuscular preadipocytes tended to use shorter 3'UTR for differentiation into mature adipocytes. APA events mediated by UTR-APA switching in intramuscular adipocytes were enriched in lipid synthesis and adipocyte differentiation. TRIB3, WWTR1, and INSIG1 played important roles in the differentiation of intramuscular preadipocytes. Briefly, our results provided new insights into understanding the mechanisms of bovine adipocyte differentiation.

Goat miR-92a-3p Targets APOL6 Gene to Regulate the Differentiation of Intramuscular Precursor Adipocytes

The quality of lamb meat is positively correlated with intramuscular fat content. In recent years, a large number of studies have shown that miRNAs play an important role in the proliferation and differentiation of adipocytes. In this study, we aimed to explore the effect of miR-92a-3p on the differentiation of goat intramuscular preadipocytes. The results showed that the expression level of miR-92a-3p was low in the early stage of differentiation, reached the highest level on the third day of differentiation, and then decreased. And miR-92a-3p can inhibit the accumulation of lipid droplets and down-regulate the determinants of adipogenic differentiation. Mechanistically, by predicting target genes, we found that miR-92a-3p affects the differentiation of goat intramuscular preadipocytes and the accumulation of lipid droplets by regulating the expression of goat gene APOL6. This study provides important new information to better understand the relationship between miRNAs and the differentiation of goat intramuscular preadipocytes, thus providing a new reference for goat intramuscular adipogenesis.

Lambs supplemented with Amazonian oilseed co-products: Meat quality and fatty acid profile

The Amazon has a wide variety of oilseeds that generate a huge amount of co-products with potential for use in animal nutrition. The objective was to use alternative resources (oilseed cakes) in the feeding of lambs to assign a sustainable destination to this biomass, and evaluate its influence on the quality and fatty acid (FA) profile of the meat. Twenty-four lambs, male, castrated, crossbred Dorper × Santa Inês, weighing 30 ± 1.3 kg of initial body weight, were distributed in a completely randomized design in 4 treatments (diets) with six replications (animals). The control diet (Control) contained corn and soybean meal as main ingredients, which were partially replaced in the other diets by cupuassu cake diet (Cup), palm kernel cake diet (Palm) and tucuma cake diet (Tuc). The inclusion of Amazon cakes influences the lipid (P = 0.02) and protein (P < 0.01) composition of meat (longissimus lumborum); reduces cooking losses (P < 0.01); influences the colors (L, a, b), chroma, and Hue Angle (P < 0.01); promotes changes in total FA composition and FA profile (P < 0.05); reduces hypocholesterolemic FA (h) (P = 0.01), but does not influence hypercholesterolemic (H) and indices h:H, AI and TI (P > 0.05). The inclusion of oilseed cakes influences the chemical composition, physical parameters, composition and fatty acid profile of the meat, but does not influence the indicators of atherogenicity, thrombogenicity and cholesterolemia.

Roles of MEF2A and HOXA5 in the transcriptional regulation of the bovine FoxO1 gene

The Forkhead box factor 1 (FoxO1) gene plays a vital role in the growth and development of skeletal muscle. In the present study, expression analysis of the bovine FoxO1 gene exhibited the highest expression in longissimus dorsi muscle followed by its expression in adipose tissue. Moreover, high mRNA expression of FoxO1 gene was found in differentiated bovine myoblasts and adipocytes at day 6 of induced differentiation (p < 0.05). The regulatory pattern of the bovine FoxO1 gene was investigated through screening and dual-luciferase activity of the 1.7 kb 5'UTR (untranslated region) within pGL3-basic vector and a core promoter region was explored at (-285/-27) upstream of the transcription start site. The transcription factors (TFs) MEF2A and HOXA5 within the core promoter region (-285/-27) were found as the regulatory cis-acting element. The siRNA interference of the TFs, chromatin immunoprecipitation (ChIP) assay, and site-directed mutation validated that MEF2A and HOXA5 binding occurs in the region -285/-27 bp and performs an essential role in the transcriptional regulation of bovine FoxO1 gene. These findings explored the regulatory network mechanism of the FoxO1 gene in skeletal muscle development and adipogenesis for the bovine breed improvement program.

The body weight heritability and the effect of non-genetic factors on the body measurement traits in Qinchuan cattle

This study aimed to understand the influence of the non-genetic factors that include breeding year, season, and sex of growth and development traits of Qinchuan cattle and to estimate the heritability of body weight at different growth stages. The Qinchuan cattle measurement records were by the Experiment farm of the National Beef Cattle Improvement Center (Yangling, China) from 2000 to 2017. SPSS and R software were used to analyze the influence of non-genetic factors on body size traits that include body weight (BW), withers height (WH), hip height (HH), body length (BL), chest circumference (CC), abdominal girth (AG), and calf girth (CG), at birth, 6, 12, 18, and 24 months of age. Meanwhile, the single-trait animal model of DMU software was used to estimate the variance component and the heritability of body weight. The results of GLM analysis showed as follows: sex, birth year, and birth season had effects on the body size traits of Qinchuan cattle at different growth stages. Respectively, the heritability of body weight at birth, 6, 12, 18, and 24 months of age were 0.43, 0.32, 0.37, 0.32, and 0.38.

Bioinformatics and genetic variants analysis of FGF10 gene promoter with their association at carcass quality and body measurement traits in Qinchuan beef cattle

The fibroblast growth factor 10 (FGF10) gene regulates adipogenesis and myogensis. In this study, sequencing of FGF10 prompter region identified three SNPs at loci g.78G > A, g.116C > T and g.201A > T. Each SNP yields three genotypes as GG, GA and AA at loci g.78G > A, CC, CT and TT at loci g.116C > T and AA, AT and TT at loci g.201A > T. Allelic and genotypic frequencies of all three SNPs deviated from the Hardy-Weinberg equilibrium (HWE) (P < 0.05) and were found highly polymorphic as PIC (0.25 < PIC < 0.50). Moreover, we found highest LD (D'/γ2) between SNP2 and SNP3 (0.989/0.909), followed by SNP1 and SNP3 (0.944/0.796). Moreover, three variants of FGF10 gene promoter exhibited significant (P < 0.05) association with body measurement and carcass quality traits in Qinchuan beef cattle. At loci g.78G > A, the genotype GG showed significantly (P < 0.01) larger body length (BL), rump length (RL), chest depth (CD), chest circumference (CC) and ultrasound loin area (ULA). The genotype TC at loci g.116C > T showed significantly (P < 0.01 and 0.05) larger body measurement and intramuscular fat, and ultrasound loin area (ULA). In addition to that, at loci g.201A > T, genotype TT showed significantly (P < 0.01 and P < 0.05) larger body length (BL), rump length (RL), hip width (HW), chest circumference (CC) and ultrasound loin area (ULA). Additionally, screening of promoter sequence of FGF10 gene explored loss of four TFs binding sites (KLF3, ZNF37α, GLIS2 and BCL11A) at g.116C > T because of SNP2. However, a single TF binding site was lost at g.202A > T due to SNP3. Interestingly, none of TF binding site was lost at g.78G > A in SNP1; however, one new TF binding site was gained at this location due to SNP1. These findings conclude that genotype GG, TC and TT could be used as genetic markers of FGF10 gene for body measurement and carcass quality traits in Qinchuan beef cattle.

Rapid direct conversion of bovine non-adipogenic fibroblasts into adipocyte-like cells by a small-molecule cocktail

Introduction: The molecular regulation mechanism of fat deposition in bovine and its improvement on beef quality are important research directions in the livestock industry. The research of molecular mechanisms that govern the regulation and differentiation of adipocytes may conduct to understand the mechanism of obesity, lipid disorders, and fat deposition. In the recent decade, small-molecule compounds have been widely used in reprogramming and transdifferentiation fields, which can promote the induction efficiency, replace exogenous genes, or even induce cell fate conversion alone. Furthermore, small-molecule compound induction is expected to be a novel approach to generate new cell types from somatic cells in vitro and in vivo. Methods: In this study, we established rapid chemically induced platform for transdifferentiation of bovine ear fibroblasts into adipocyte-like cells using a small-molecule cocktail (Repsox, VPA, TTNPB). The chemically induced adipocytes (CiADCs) were characterized by lipid staining, qRT-PCR and WB. Bovine natural adipocytes were used as positive control, and the expression of adipocyte-related marker genes in CiADCs were analyzed. Moreover, RNA-Seq explore the mechanism of RVB in the regulation of Bovine adipocyte transdifferentiation. Results: In this study, the chemically induced adipocytes (CiADCs) could be identified as early as day 6. The CiADCs appeared to be circular and rich of lipid droplets. The adipocyte-specific genes of LPL, PPARγ, IGF1, GPD1, C/EBPδ, ADIPOQ, PCK2, FAS, C/EBPβ, PPARGC1A, C/EBPα, and CFD were detected to be significantly upregulated in both CiADCs and natural adipocytes. Western blot analysis also confirmed the increase C/EBPα and PPARγ protein level in induced adipocytes (CiADCs-6d) treated with RVB. In addition, we also found that the signaling pathways (PPAR signaling pathway, PI3K-Akt signaling pathway, p53 signaling pathway, MAPK signaling pathway, and ECM-receptor interaction) regulated by the DEGs played a vital role in adipogenesis. Discussion: In the present study, a combination of small-molecule compounds RVB was used to transdifferentiate bovine ear fibroblasts into the chemically-induced adipocyte cells (CiADCs) that have a large number of lipid droplets. Importantly, the small-molecule cocktail significantly shortened the reprogramming turnaround time. The morphology of CiADCs is close to the "ring type" of natural differentiated adipocytes on sixth day. And, the CiADCs showed similar adipocyte-specific gene expression patterns to natural adipocytes. Furthermore, RVB increased protein expression of PPARγ and C/EBPα in the chemically-induced adipocytes (CiADCs-6d). Our findings reveal that the signaling pathways of C/EBPα and PPARγ play pivotal roles in this transdifferentiation process. In addition, we also found that the signaling pathways (PPAR signaling pathway, PI3K-Akt signaling pathway, p53 signaling pathway, MAPK signaling pathway, and ECM-receptor interaction) regulated by the DEGs played a vital role in adipogenesis. In general, this study provides valuable evidence to deepen our understanding of the molecular mechanism of small molecule cocktails in regulating adipogenesis.