Genomic Insights into Molecular Regulation Mechanisms of Intramuscular Fat Deposition in Chicken.

Intramuscular fat (IMF) plays an important role in the tenderness, water-holding capacity, and flavor of chicken meat, which directly affect meat quality. In recent years, regulatory mechanisms underlying IMF deposition and the development of effective molecular markers have been hot topics in poultry genetic breeding. Therefore, this review focuses on the current understanding of regulatory mechanisms underlying IMF deposition in chickens, which were identified by multiple genomic approaches, including genome-wide association studies, whole transcriptome sequencing, proteome sequencing, single-cell RNA sequencing (scRNA-seq), high-throughput chromosome conformation capture (HiC), DNA methylation sequencing, and m6A methylation sequencing. This review comprehensively and systematically describes genetic and epigenetic factors associated with IMF deposition, which provides a fundamental resource for biomarkers of IMF deposition and provides promising applications for genetic improvement of meat quality in chicken.

RNA sequencing analysis of the longissimus dorsi to identify candidate genes underlying the intramuscular fat content in Anqing Six-end-white pigs.

Intramuscular fat (IMF) is a significant marker for pork quality. The Anqing Six-end-white pig has the characteristics of high meat quality and IMF content. Owing to the influence of European commercial pigs and a late start in resource conservation, the IMF content within local populations varies between individuals. This study analyzed the longissimus dorsi transcriptome of purebred Anqing Six-end-white pigs with varying IMF content to recognize differentially expressed genes. We identified 1528 differentially expressed genes between the pigs with high (H) and low (L) IMF content. Based on these data, 1775 Gene Ontology terms were significantly enriched, including lipid metabolism, modification and storage, and regulation of lipid biosynthesis. Pathway analysis revealed 79 significantly enriched pathways, including the Peroxisome proliferator-activated receptor and mitogen-activated protein kinase signaling pathways. Moreover, gene set enrichment analysis indicated that the L group had increased the expression of genes related to ribosome function. Additionally, the protein-protein interaction network analyses revealed that VEGFA, KDR, LEP, IRS1, IGF1R, FLT1 and FLT4 were promising candidate genes associated with the IMF content. Our study identified the candidate genes and pathways involved in IMF deposition and lipid metabolism and provides data for developing local pig germplasm resources.

Functional study and epigenetic targets analyses of SIRT1 in intramuscular preadipocytes via ChIP-seq and mRNA-seq.

The SIRT1 epigenetic regulator is involved in hepatic lipid homoeostasis. However, the role of SIRT1 in regulating intramuscular fat deposition as well as the pathways and potential epigenetic targets involved remain unknown. Herein, we investigate SIRT1 function, its genome-wide epigenetic target profile, and transcriptomic changes under SIRT1 overexpression during yak intramuscular preadipocytes differentiation. To this end, we analysed the relationship between SIRT1 and intramuscular fat content as well as lipid metabolism-related genes in longissimus dorsi tissue. We found that SIRT1 expression negatively correlates with intramuscular fat content as well as with the expression of genes related to lipid synthesis, while positively correlating with that of fatty acid oxidation-involved genes. SIRT1 overexpression in intramuscular preadipocytes significantly reduced adipose differentiation marker expression, intracellular triacylglycerol content, and lipid deposition. Chromatin immunoprecipitation coupled with high-throughput sequencing of H3K4ac (a known direct target of SIRT1) and high-throughput mRNA sequencing results revealed that SIRT1 may regulate intramuscular fat deposition via three potential new transcription factors (NRF1, NKX3.1, and EGR1) and four genes (MAPK1, RXRA, AGPAT1, and HADH) implicated in protein processing within the endoplasmic reticulum pathway and the MAPK signalling pathway in yaks. Our study provides novel insights into the role of SIRT1 in regulating yak intramuscular fat deposition and may help clarify the mechanistic determinants of yak meat characteristics.

Transcriptome analysis reveals the molecular regulatory network of muscle development and meat quality in Sunit lamb supplemented with dietary probiotic.

Supplementing animal feed with probiotic additives can promote muscle production and improve meat quality. The study aimed to explore the effects of dietary probiotics supplementation on the performance, meat quality and muscle transcriptome profile in Sunit lamb. Overall, feeding probiotics significantly increased the body length, LT area, pH24h and intramuscular fat (IMF) content, but decreased cooking loss and meat shear force compared to the control group (P < .05). A total of 651 differentially expressed genes (DEGs) were found in probiotic supplemented lambs. Pathway analysis revealed that DEGs were involved in multiple pathways related to muscle development and fat deposition, such as the ECM-receptor interactions, the MAPK signaling pathway and the FoxO signaling pathway. Therefore, dietary probiotic supplementation can improve muscle development and final meat quality in Sunit lambs by altering gene expression profiles associated with key pathways, providing unique insights into the molecular mechanisms by which dietary probiotics regulate muscle development in the lamb industry.

miR-381-3p Inhibits Intramuscular Fat Deposition through Targeting FABP3 by ceRNA Regulatory Network.

Intramuscular fat (IMF) deposition is an important determinant of pork quality and a complex process facilitated by non-coding ceRNAs. In this study, 52 Berkshire × Anqing Sixwhite crossbred pigs were slaughtered to measure eight carcass and pork quality traits. Whole-transcriptome sequencing analysis was performed using longissimus dorsi samples of six low- and high-IMF samples; 34 ceRNA networks, based on 881, 394, 158 differentially expressed (DE) lncRNAs, miRNAs, and mRNAs, were constructed. Following weighted gene co-expression network analysis between the low and high IMF, only one ceRNA, lncRNA4789/miR-381-3p/FABP3, that showed similar DE trend in longissimus dorsi tissue was retained. Dual-luciferase reporter assays further indicated that FABP3 was a direct, functional target of miR-381-3p, where miR-381-3p overexpression inhibited the mRNA and protein expression of FABP3. In addition, overexpressed lncRNA4789 attenuated the effect of miR-381-3p on FABP3 by sponging miR-381-3p. Cell function verification experiment demonstrated that miR-381-3p suppressed IMF deposition by inhibiting preadipocyte cell differentiation and lipid droplet deposition via the suppression of FABP3 expression in the peroxisome proliferator-activated receptor signalling pathway, whereas lncRNA4789 rescued FABP3 expression by sponging miR-381-3p. Our study may aid in identifying novel molecular markers for its optimization in IMF which is of importance in breeding for improving pork quality.

Evaluation of the association between plasma glucose-dependent insulinotropic polypeptide, respiratory quotient, and intramuscular fat deposition in feedlot cattle fed different levels of dry matter intake.

The objectives of this trial were to evaluate the association between different levels of dry matter intake (DMI) on gas exchange, plasma glucose-dependent insulinotropic polypeptide (GIP) concentration, and intramuscular (IM) fat deposition. We used 60 individually fed backgrounded Angus × SimAngus-crossbred steers (n = 30) in a randomized complete block design. Steers (paired by body weight [BW] and gain to feed ratio [G:F]) were randomly allocated to one of the following treatments: ad libitum intake (AI) or restricted intake (RI; the same diet fed at 85% of the AI) of a finishing diet. The diet contained 61% cracked corn, 9% corn silage, 15% distillers' dried grains with solubles, 5% soyhulls, and 10% of a protein-mineral-vitamin premix. Measurements of CO2 emission and consumption of O2, and respiratory quotient (RQ) were taken using the GreenFeed system (n = 15/treatment). Plasma and gas samples were collected 10 d before slaughter, 1 h before and 2 h after feeding. Plasma glucose, non-esterified fatty acids, GIP, and insulin concentration and gasses (O2, CO2, and RQ) were analyzed using the MIXED procedure of SAS evaluating the fixed effect of treatment, time (repeated measurement) and their interaction, and the random effect of the block. Final BW and carcass characteristics were analyzed with a similar model, without the time statement and its interaction. Compared with RI, AI steers had greater (P < 0.01) DMI and average daily gain (ADG). Steers on AI had greater final BW (P = 0.02), tended to have a greater ribeye area (P = 0.09), and had lower plasma GIP concentration (P = 0.04). There was no treatment effect (P ≥ 0.11) on G:F, subcutaneous backfat (BF), and IM fat, O2 consumption, CO2 emission, and RQ. Plasma glucose concentration of AI steers was greater before and after feeding than RI (P < 0.05). In conclusion, feeding steers ad libitum increased DMI, ADG, and plasma glucose and GIP concentration but does not affect G:F, BF, IM fat, CO2 emission, and O2 consumption. Plasma GIP concentration and RQ are not associated with IM fat deposition.

FATP1 Exerts Variable Effects on Adipogenic Differentiation and Proliferation in Cells Derived From Muscle and Adipose Tissue.

In livestock, intramuscular adipose tissue is highly valued whereas adipose tissue in other depots is considered as waste. Thus, genetic factors that favor fat deposition in intramuscular compartments over that in other adipose depots are highly desirable in meat-producing animals. Fatty acid transport 1 (FATP1) has been demonstrated to promote cellular fatty acid uptake and metabolism; however, whether it also influences cellular lipid accumulation remains unclear. In the present study, we investigated the effects of FATP1 on the differentiation and proliferation of adipocytes in five types of cells derived from muscle and adipose tissue and estimated the effects of FATP1 on intramuscular fat (IMF) deposition. We showed that FATP1 is mainly expressed in heart and muscle tissue in buffaloes as well as cells undergoing adipogenic differentiation. Importantly, we found that FATP1 promoted the adipogenic differentiation of muscle-derived cells (buffalo myocytes and intramuscular preadipocytes and mouse C2C12 cells) but did not affect, or even inhibited, that of adipose-derived cells (buffalo subcutaneous preadipocytes and mouse 3T3-L1 cells, respectively). Correspondingly, our results further indicated that FATP1 promotes IMF deposition in mice in vivo. Meanwhile, FATP1 was found to enhance the proliferative activity of all the assessed cells, except murine 3T3-L1 cells. These results provide new insights into the potential effects of FATP1 on IMF deposition, especially regarding its positive effects on meat quality in buffaloes and other livestock.

RNA-Seq Analysis Reveals the Potential Molecular Mechanisms of Puerarin on Intramuscular Fat Deposition in Heat-Stressed Beef Cattle.

To investigate the effect of Puerarin on intramuscular fat deposition in heat-stressed beef cattle and its underlying mechanism. Thirty-two healthy Jinjiang bulls were randomly divided into four groups and dietary with 0 (Control), 200 (Pue200), 400 (Pue400), and 800 (Pue800) mg/kg Puerarin in the feed concentrate. The results showed that Puerarin treatment enhanced the concentration of crude fat, fatty acid (C14:1 and C17:1), and the activity of fatty acid synthase in Longissimus thoracis (LT), but decreased the levels of blood leptin (P < 0.05). High-throughput sequencing of mRNA technology (RNA-Seq) was used and the analysis showed that 492 genes were down-regulated and 341 genes were up-regulated in LT, and these genes were significantly enriched to the pathways related to lipid metabolism. These results indicated that dietary supplemental with Puerarin enhanced intramuscular fat deposition by regulating lipid metabolism of heat-stressed beef cattle.

miR-34a Regulates Lipid Droplet Deposition in 3T3-L1 and C2C12 Cells by Targeting LEF1.

Intramuscular fat (IMF) content plays a key role in improving the flavor and palatability of pork. The IMF content varies between species, breeds, and individuals of the same breed. Hence, it is necessary to elucidate the mechanisms of IMF deposition to improve pork quality. Herein, the IMF content in the longissimus dorsi muscles of 29 Laiwu pigs was detected and divided into two groups, the H group (IMF > 12%) and the L group (IMF < 5%). RNA sequencing analysis showed 24 differentially expressed (DE) miRNA, and GO and KEGG analysis demonstrated that the DE miRNAs were significantly enriched in lipid metabolic process, lipid storage, Wnt, mTOR, and PPAR signaling pathways. miR-34a was found to be increased in the H group and 3T3-L1-derived adipocytes, while Lef1 was decreased. Luciferase reporter assays demonstrated that Lef1 was a potential target of miR-34a. Mechanism analysis revealed that miR-34a could increase lipid droplet deposition in 3T3-L1 and C2C12 cells by dampening the suppressive function of Lef1 on the transcription of adipogenic markers (i.e., Pparg, Cebpa, Fabp4, and Plin1). Moreover, overexpression of miR-34a could enhance the lipid deposition in the co-culture system of 3T3-L1 and C2C12 cells as well as in C2C12 cells cultured with conditioned medium from the progress of adipocyte differentiation. Taken together, our study indicated that miR-34a was an important positive modulator in the regulation of fatty metabolism and fat deposition by inhibiting the suppressive function of Lef1. These results might provide insight for the exploration of potential strategies to promote intramuscular fat deposition in livestock.

C/EBPb converts bovine fibroblasts to adipocytes without hormone cocktail induction

BACKGROUND: Adipogenesis and fibrogenesis can be considered as a competitive process in muscle, which may affect the intramuscular fat deposition. The CCAAT/enhancer-binding protein beta (C/EBPb) plays an important role in adipogenesis, which is well-characterized in mice, but little known in bovine so far. RESULTS: In this study, real-time qPCR revealed that the level of C/EBPb was increased during the developmental stages of bovine and adipogenesis process of preadipocytes. Overexpression of C/EBPb promoted bovine fibroblast proliferation through mitotic clonal expansion (MCE), a necessary process for initiating adipogenesis, by significantly downregulating levels of p21 and p27 (p < 0.01). Also, the PPARc expression was inhibited during the MCE stage (p < 0.01). 31.28% of transfected fibroblasts adopted lipid-laden adipocyte morphology after 8 d. Real-time qPCR showed that C/EBPb activated the transcription of early stage adipogenesis markers C/EBPa and PPARc. Expression of ACCa, FASN, FABP4 and LPL was also significantly upregulated, while the expression of LEPR was weakened. CONCLUSIONS: It was concluded C/EBPb can convert bovine fibroblasts into adipocytes without hormone induction by initiating the MCE process and promoting adipogenic genes expression, which may provide new insights into the potential functions of C/EBPb in regulating intramuscular fat deposition in beef cattle.

Comprehensive analysis of differentially expressed circRNAs and ceRNA regulatory network in porcine skeletal muscle.

BACKGROUND: Circular RNA (circRNA), a novel class of non-coding RNA, has a closed-loop structure with important functions in skeletal muscle growth. The purpose of this study was to investigate the role of differentially expressed circRNAs (DEcircRNAs), as well as the DEcircRNA-miRNA-mRNA regulatory network, at different stages of porcine skeletal muscle development. Here, we present a panoramic view of circRNA expression in porcine skeletal muscle from Large White and Mashen pigs at 1, 90, and 180 days of age. RESULTS: We identified a total of 5819 circRNAs. DEcircRNA analysis at different stages showed 327 DEcircRNAs present in both breeds. DEcircRNA host genes were concentrated predominately in TGF-ß, MAPK, FoxO, and other signaling pathways related to skeletal muscle growth and fat deposition. Further prediction showed that 128 DEcircRNAs could bind to 253 miRNAs, while miRNAs could target 945 mRNAs. The constructed ceRNA network plays a vital role in skeletal muscle growth and development, and fat deposition. Circ_0015885/miR-23b/SESN3 in the ceRNA network attracted our attention. miR-23b and SESN3 were found to participate in skeletal muscle growth regulation, also playing an important role in fat deposition. Using convergent and divergent primer amplification, RNase R digestion, and qRT-PCR, circ_0015885, an exonic circRNA derived from Homer Scaffold Protein 1 (HOMER1), was confirmed to be differentially expressed during skeletal muscle growth. In summary, circ_0015885 may further regulate SESN3 expression by interacting with miR-23b to function in skeletal muscle. CONCLUSIONS: This study not only enriched the circRNA library in pigs, but also laid a solid foundation for the screening of key circRNAs during skeletal muscle growth and intramural fat deposition. In addition, circ_0015885/miR-23b/SESN3, a new network regulating skeletal muscle growth and fat deposition, was identified as important for increasing the growth rate of pigs and improving meat quality.

Treatment of Hepatitis C Virus Infection with Direct-acting Antiviral Agents Elevates the Serum Small-dense Low-density Lipoprotein Cholesterol Level.

Objective The low-density lipoprotein cholesterol (LDL) level is known to increase following the treatment of hepatitis C virus (HCV) infection using direct-acting antiviral agents (DAAs). This study aimed to investigate the changes in the lipid profiles, including small-dense LDL cholesterol (sdLDL), in HCV patients treated with DAAs. Patients We retrospectively assessed 67 HCV patients who achieved sustained virological response with DAA administration and were observed for more than 2 years, of whom 32 were on daclatasvir/asunaprevir, 14 were on sofosbuvir/ledipasvir, and 21 were on sofosbuvir/ribavirin. Methods We evaluated the lipid profiles, including sdLDL, every 6 months until 2 years after the start of treatment and analyzed the factors related to changes in the sdLDL level. Results The median sdLDL value at baseline was 12.8 mg/dL, which increased to 19.5 mg/dL at 6 months (p<0.001) and remained elevated at 25.4 mg/dL at 2 years later (p<0.001). The Kaplan-Meier curve indicated that patients with high values of LDL, albumin, muscle attenuation and visceral to subcutaneous adipose tissue area ratio were at increased risk for elevation of sdLDL over 35 mg/dL (log-rank test: p<0.001; p=0.008, p=0.002 and p=0.042, respectively). A multivariate analysis performed on the factors contributing to elevation of sdLDL 2 years after DAA treatment (≥35.0 mg/dL) revealed pretreatment LDL (≥91.0 mg/dL) and muscle attenuation (≥33.7 HU) as significant factors (p=0.007 and p=0.032, respectively). Conclusion SdLDL increased continuously after DAA treatment, and high LDL levels and low intramuscular fat deposition before treatment contributed to elevated sdLDL levels after treatment.

Effect of Excessive or Restrictive Energy on Growth Performance, Meat Quality, and Intramuscular Fat Deposition in Finishing Ningxiang Pigs.

This study investigated the effects of excessive or restrictive energy on growth performance, meat quality, intramuscular fat (IMF) deposition, and related gene expression in finishing Ningxiang pigs. A total of 36 Ningxiang pigs (43.26 ± 3.21 kg) were randomly assigned to three treatments (6 pens of 2 piglets per treatment) and fed by one of three dietary treatments until the pigs of each treatment weighed approximately 75 kg equally. The three treatments were control diet (digestible energy, DE:13.02 MJ/kg, CON), excessive energy diet (DE 15.22 MJ/kg, EE), and restrictive energy diet (DE 10.84 MJ/kg, RE). Results showed that EE improved average daily gain (ADG) and feed conversion ratio (FCR) (p < 0.01), while nothing significantly changed by RE except FCR increasing (p < 0.01). EE increased the content of IMF and triglycerides (TG) (p < 0.05), L*24h and b*45min (p < 0.01), while decreasing cooking loss and meat tenderness in longissimus thoracis (LT) (p < 0.05). b*24h was significantly increased with the increase of energy level (p < 0.01). Meanwhile, EE increased the cross-sectional area (CSA) of muscle fiber and the mRNA expression of myosin heavy chain (MyHC) IIb, acetyl CoA carboxylase (ACC), fatty acid synthase (FAS), and adipocyte fatty-acid binding protein (FABP4) (p < 0.05). In addition, throughout: A diet supplemented with excessive energy promoted IMF deposition by positively changing lipogenic potential while decreasing tenderness by increasing glycolytic muscle fibers, which together affected meat quality. In terms of growth performance and meat quality, the present study suggests that the low-energy diet is suitable for finishing Ningxiang pigs.

Skeletal muscle quality affects patient outcomes in acute type A aortic dissection.

OBJECTIVES: Although skeletal muscle quantity is linked to surgical outcomes, quality remains unexamined. In this study, we evaluated whether skeletal muscle quality and quantity could predict surgical outcomes in acute type A aortic dissection (ATAAD). METHODS: Skeletal muscle quality and quantity were evaluated using computed tomography (CT) values and the psoas muscle mass index, respectively. From May 2004 to December 2017, 324 ATAAD patients underwent aortic replacement after CT scans and psoas muscle mass index measurements. Patients were grouped into intramuscular fat (IMF; n = 55) and non-IMF (n = 269) deposition groups. RESULTS: The mean ages of the patients were 72.3 ± 9.7 and 66.8 ± 12.1 years (P = 0.002), and hospital mortality rates were 3.6% (2/55) and 7.4% (20/269; P = 0.393) for IMF and non-IMF deposition groups, respectively. IMF deposition was a risk factor for a deterioration in activities of daily living at discharge by multivariable analysis [odds ratio 0.33, 95% confidence interval (CI) 0.16-0.69; P = 0.003]. The mean follow-up was 43.9 ± 36.8 months. The 5-year survival was significantly worse for the IMF deposition group (IMF 73.8% vs non-IMF 88.2%; P = 0.010). The multivariable Cox proportional hazard analysis showed that IMF deposition significantly predicted poor survival (hazard ratio 3.26, 95% CI 1.47-7.24; P = 0.004), unlike psoas muscle mass index and age. CONCLUSIONS: Skeletal muscle quality, defined by IMF deposition, was an independent predictor of overall survival and postoperative activities of daily living dependence risk in patients undergoing surgery for ATAAD. Thus, IMF deposition may be an additional risk factor for estimating late outcomes of ATAAD surgery.

miRNA-223 targets the GPAM gene and regulates the differentiation of intramuscular adipocytes.

Intramuscular fat (IMF) has significant effects on the tenderness, juiciness, and flavor of chicken, which are important determinants of poultry meat quality. Although many studies have focused on microRNAs (miRNAs) involved in adipogenesis, little is known about miRNAs associated with poultry IMF deposition or intramuscular adipocyte differentiation. Bioinformatic analysis identified mitochondrial glycerol­3­phosphate acyltransferase (GPAM) as a putative target of miR-223. To explore the role of miR-223 in the process of chicken IMF deposition, loss and gain of function experiments were performed in primary intramuscular preadipocytes using miR-223 mimics, miR-223 inhibitor, and si-GPAM. Our results showed that miR-223 is significantly down-regulated in the breast muscle tissues of Gushi hens at the later-laying period in comparison with hens at the pre-laying period. Using qRT-PCR, we found that miR-223 expression in chicken tissues and intramuscular adipocytes correlates negatively with GPAM expression. Cell transfection experiments suggest that miR-223 inhibits intramuscular adipocyte differentiation via targeting GPAM. Experiments using a dual luciferase reporter system show that GPAM is a direct target of miR-223. Taken together, our results support the hypothesis that miR-223 regulates intramuscular fat deposition in chickens.

Decreased Psoas Muscle Computed Tomography Value Predicts Poor Outcome in Peripheral Artery Disease.

BACKGROUND: The prognosis of peripheral artery disease (PAD) and comorbid sarcopenia is poor. Some reports indicate that the computed tomography (CT) value of skeletal muscle, which reflects intramuscular fat deposition as well as skeletal muscle mass, is considered a marker of sarcopenia. However, it remains unclear if skeletal muscle area and CT value are associated with poor outcomes in patients with PAD. Methods and Results: Psoas muscle area and CT value were measured by manual trace at the level of the third lumbar vertebral body in 327 consecutive patients with PAD undergoing endovascular therapy (EVT). The endpoint was major adverse cardiovascular and limb events (MACLE). There were 60 MACLE during the follow-up period. Patients with MACLE had lower mean psoas muscle CT value than those without. However, there was no significant difference in total psoas muscle area between patients with and without MACLE. Kaplan-Meier analysis demonstrated that the lowest tertile of psoas muscle CT value was associated with the highest risk of MACLE. Multivariate Cox hazard analysis revealed that psoas muscle CT value was associated with MACLE after adjustment for Fontaine class, previous ischemic heart disease, prevalence of diabetes mellitus, brain natriuretic peptide, and serum albumin. CONCLUSIONS: Psoas muscle CT value is a feasible predictor of MACLE in patients with PAD.

Genetic, management, and nutritional factors affecting intramuscular fat deposition in beef cattle - A review.

Intramuscular fat (IMF) content in skeletal muscle including the longissimus dorsi muscle (LM), also known as marbling fat, is one of the most important factors determining beef quality in several countries including Korea, Japan, Australia, and the United States. Genetics and breed, management, and nutrition affect IMF deposition. Japanese Black cattle breed has the highest IMF content in the world, and Korean cattle (also called Hanwoo) the second highest. Here, we review results of research on genetic factors (breed and sex differences and heritability) that affect IMF deposition. Cattle management factors are also important for IMF deposition. Castration of bulls increases IMF deposition in most cattle breeds. The effects of several management factors, including weaning age, castration, slaughter weight and age, and environmental conditions on IMF deposition are also reviewed. Nutritional factors, including fat metabolism, digestion and absorption of feed, glucose/starch availability, and vitamin A, D, and C levels are important for IMF deposition. Manipulating IMF deposition through developmental programming via metabolic imprinting is a recently proposed nutritional method to change potential IMF deposition during the fetal and neonatal periods in rodents and domestic animals. Application of fetal nutritional programming to increase IMF deposition of progeny in later life is reviewed. The coordination of several factors affects IMF deposition. Thus, a combination of several strategies may be needed to manipulate IMF deposition, depending on the consumer's beef preference. In particular, stage-specific feeding programs with concentrate-based diets developed by Japan and Korea are described in this article.

The regulation of IMF deposition in pectoralis major of fast- and slow- growing chickens at hatching.

BACKGROUND: The lipid from egg yolk is largely consumed in supplying the energy for embryonic growth until hatching. The remaining lipid in the yolk sac is transported into the hatchling's tissues. The gene expression profiles of fast- and slow-growing chickens, Arbor Acres (AA) and Beijing-You (BJY), were determined to identify global differentially expressed genes and enriched pathways related to lipid metabolism in the pectoralis major at hatching. RESULTS: Between these two breeds, the absolute and weight-specific amounts of total yolk energy (TYE) and intramuscular fat (IMF) content in pectoralis major of fast-growing chickens were significantly higher (P < 0.01, P < 0.01, P < 0.05, respectively) than those of the slow-growing breed. IMF content and u-TYE were significantly related (r = 0.9047, P < 0.01). Microarray analysis revealed that gene transcripts related to lipogenesis, including PPARG, RBP7, LPL, FABP4, THRSP, ACACA, ACSS1, DGAT2, and GK, were significantly more abundant in breast muscle of fast-growing chickens than in slow-growing chickens. Conversely, the abundance of transcripts of genes involved in fatty acid degradation and glycometabolism, including ACAT1, ACOX2, ACOX3, CPT1A, CPT2, DAK, APOO, FUT9, GCNT1, and B4GALT3, was significantly lower in fast-growing chickens. The results further indicated that the PPAR signaling pathway was directly involved in fat deposition in pectoralis major, and other upstream pathways (Hedgehog, TGF-beta, and cytokine-cytokine receptor interaction signaling pathways) play roles in its regulation of the expression of related genes. CONCLUSIONS: Additional energy from the yolk sac is transported and deposited as IMF in the pectoralis major of chickens at hatching. Genes and pathways related to lipid metabolism (such as PPAR, Hedgehog, TGF-beta, and cytokine-cytokine receptor interaction signaling pathways) promote the deposition of IMF in the pectoralis major of fast-growing chickens compared with those that grow more slowly. These findings provide new insights into the molecular mechanisms underlying lipid metabolism and deposition in hatchling chickens.

Genome-wide study on intramuscular fat in Italian Large White pig breed using the PorcineSNP60 BeadChip.

Genome-wide association study results are presented for intramuscular fat in Italian Large White pig breed. A total of 886 individuals were genotyped with PorcineSNP60 BeadChip. After quality control performed with plink software and in R environment, 49 208 markers remained for the association analysis. The genome-wide association studies was conducted using linear mixed model implemented in GenABEL. We detected seven new SNPs of genes till now not found associated to intramuscular fat (IMF). Three markers map in a wide intergenic region rich of QTL linked to fat traits, one map 388 kb upstream the gene SDK1, one map inside PPP3CA gene, one inside SCPEP1 gene and the last is not mapped in the porcine genome yet. Associations here presented indicate a moderate effect of these genes on IMF. In particular, PPP3CA, that is involved in the oxidative metabolism of skeletal muscle, could be considerated as an interesting candidate gene for IMF content in pigs. However, further studies are needed to clarify the role of these genes on the physiological processes involved in IMF regulation. These results may be useful to control this trait that is important in terms of nutritional, technological and organoleptic characteristics of fresh meat and processed products.