RNA-Seq explores the functional role of the fibroblast growth factor 10 gene in bovine adipocytes differentiation

OBJECTIVE

The present study was executed to explore the molecular mechanism of fibroblast growth factor 10 (FGF10) gene in bovine adipogenesis.

METHODS

The bovine FGF10 gene was overexpressed through Ad-FGF10 or inhibited through siFGF10 and their negative control (NC) in bovine adipocytes, and the multiplicity of infection, transfection efficiency, interference efficiency were evaluated through quantitative real-time polymerase chain reaction, western blotting and fluorescence microscopy. The lipid droplets, triglycerides (TG) content and the expression levels of adipogenic marker genes were measured during preadipocytes differentiation. The differentially expressed genes were explored through deep RNA sequencing.

RESULTS

The highest mRNA level was found in omasum, subcutaneous fat, and intramuscular fat. Moreover, the highest mRNA level was found in adipocytes at day 4 of differentiation. The results of red-oil o staining showed that overexpression (Ad-FGF10) of the FGF10 gene significantly (p<0.05) reduced the lipid droplets and TG content, and their downregulation (siFGF10) increased the measurement of lipid droplets and TG in differentiated bovine adipocytes. Furthermore, the overexpression of the FGF10 gene down regulated the mRNA levels of adipogenic marker genes such as CCAAT enhancer binding protein alpha (C/EBPα), fatty acid binding protein (FABP4), peroxisome proliferator-activated receptor-γ (PPARγ), lipoprotein lipase (LPL), and Fas cell surface death receptor (FAS), similarly, down-regulation of the FGF10 gene enriched the mRNA levels of C/EBPα, PPARγ, FABP4, and LPL genes (p<0.01). Additionally, the protein levels of PPARγ and FABP4 were reduced (p<0.05) in adipocytes infected with Ad-FGF10 gene and enriched in adipocytes transfected with siFGF10. Moreover, a total of 1,774 differentially expressed genes (DEGs) including 157 up regulated and 1,617 down regulated genes were explored in adipocytes infected with Ad-FGF10 or Ad-NC through deep RNA-sequencing. The top Kyoto encyclopedia of genes and genomes pathways regulated through DEGs were the PPAR signaling pathway, cell cycle, base excision repair, DNA replication, apoptosis, and regulation of lipolysis in adipocytes.

CONCLUSION

Therefore, we can conclude that the FGF10 gene is a negative regulator of bovine adipogenesis and could be used as a candidate gene in marker-assisted selection.

GOT1 regulates adipocyte differentiation by altering NADPH content

Objective

This study was performed to examine whether the porcine glutamic-oxaloacetic transaminase 1 (GOT1) gene has important functions in regulating adipocyte differentiation.

Methods

Porcine GOT1 knockout and overexpression vectors were constructed and transfected into the mouse adipogenic 3T3-L1 cells. Lipid droplets levels were measured after 8 days of differentiation. The mechanisms through which GOT1 participated in lipid deposition were examined by measuring the expression of malate dehydrogenase 1 (MDH1) and malic enzyme (ME1) and the cellular nicotinamide adenine dinucleotide phosphate (NADPH) content.

Results

GOT1 knockout significantly decreased lipid deposition in the 3T3-L1 cells (p< 0.01), whereas GOT1 overexpression significantly increased lipid accumulation (p<0.01). At the same time, GOT1 knockout significantly decreased the NADPH content and the expression of MDH1 and ME1 in the 3T3-L1 cells. Overexpression of GOT1 significantly increased the NADPH content and the expression of MDH1 and ME1, suggesting that GOT1 regulated adipocyte differentiation by altering the NADPH content.

Conclusion

The results preliminarily revealed the effector mechanisms of GOT1 in regulating adipose differentiation. Thus, a theoretical basis is provided for improving the quality of pork and studies on diseases associated with lipid metabolism.

Identification and functional prediction of long noncoding RNAs related to intramuscular fat content in Laiwu pigs

Objective

Intramuscular fat (IMF) is a critical economic indicator of pork quality. Studies on IMF among different pig breeds have been performed via high-throughput sequencing, but comparisons within the same pig breed remain unreported.

Methods

This study was performed to explore the gene profile and identify candidate long noncoding RNA (lncRNAs) and mRNAs associated with IMF deposition among Laiwu pigs with different IMF contents. Based on the longissimus dorsi muscle IMF content, eight pigs from the same breed and management were selected and divided into two groups: a high IMF (>12%, H) and low IMF group (<5%, L). Whole-transcriptome sequencing was performed to explore the differentially expressed (DE) genes between these two groups.

Results

The IMF content varied greatly among Laiwu pig individuals (2.17% to 13.93%). Seventeen DE lncRNAs (11 upregulated and 6 downregulated) and 180 mRNAs (112 upregulated and 68 downregulated) were found. Gene Ontology analysis indicated that the following biological processes played an important role in IMF deposition: fatty acid and lipid biosynthetic processes; the extracellular signal-regulated kinase cascade; and white fat cell differentiation. In addition, the peroxisome proliferator-activated receptor, phosphatidylinositol-3-kinase-protein kinase B, and mammalian target of rapamycin pathways were enriched in the pathway analysis. Intersection analysis of the target genes of DE lncRNAs and mRNAs revealed seven candidate genes associated with IMF accumulation. Five DE lncRNAs and 20 DE mRNAs based on the pig quantitative trait locus database were identified and shown to be related to fat deposition. The expression of five DE lncRNAs and mRNAs was verified by quantitative real time polymerase chain reaction (qRT-PCR). The results of qRT-PCR and RNA-sequencing were consistent.

Conclusion

These results demonstrated that the different IMF contents among pig individuals may be due to the DE lncRNAs and mRNAs associated with lipid droplets and fat deposition.

Comparison of transcriptome between high- and low-marbling fineness in longissimus thoracis muscle of Korean cattle

Objective

This study compared differentially expressed genes (DEGs) between groups with high and low numbers of fine marbling particles (NFMP) in the longissimus thoracis muscle (LT) of Korean cattle to understand the molecular events associated with fine marbling particle formation.

Methods

The size and distribution of marbling particles in the LT were assessed with a computer image analysis method. Based on the NFMP, 10 LT samples were selected and assigned to either high- (n = 5) or low- (n = 5) NFMP groups. Using RNA sequencing, LT transcriptomic profiles were compared between the high- and low-NFMP groups. DEGs were selected at p<0.05 and |fold change| >2 and subjected to functional annotation.

Results

In total, 328 DEGs were identified, with 207 up-regulated and 121 down-regulated genes in the high-NFMP group. Pathway analysis of these DEGs revealed five significant (p<0.05) Kyoto encyclopedia of genes and genomes pathways; the significant terms included endocytosis (p = 0.023), protein processing in endoplasmic reticulum (p = 0.019), and adipocytokine signaling pathway (p = 0.024), which are thought to regulate adipocyte hypertrophy and hyperplasia. The expression of sirtuin4 (p<0.001) and insulin receptor substrate 2 (p = 0.043), which are associated with glucose uptake and adipocyte differentiation, was higher in the high-NFMP group than in the low-NFMP group.

Conclusion

Transcriptome differences between the high- and low-NFMP groups suggest that pathways regulating adipocyte hyperplasia and hypertrophy are involved in the marbling fineness of the LT.

Comparison of carcass and meat quality traits between lean and fat Pekin ducks

OBJECTIVE

According to market demand, meat duck breeding mainly includes 2 breeding directions: lean Pekin duck (LPD) and fat Pekin duck (FPD). The aim of the present study was to compare carcass and meat quality traits between 2 strains, and to provide basic data for guidelines of processing and meat quality improvement.

METHODS

A total of 62 female Pekin ducks (32 LPDs and 30 FPDs) were slaughtered at the age of 42 days. The live body weight and carcass traits were measured and calculated. Physical properties of breast muscle were determined by texture analyzer and muscle fibers were measured by paraffin sections. The content of inosine monophosphate (IMP), intramuscular fat (IMF) and fatty acids composition were measured by high-performance liquid chromatography, Soxhlet extraction method and automated gas chromatography respectively.

RESULTS

The results showed that the bodyweight of LPDs was higher than that of FPDs. FPDs were significantly higher than LPDs in subcutaneous fat thickness, subcutaneous fat weight, subcutaneous fat percentage, abdominal fat percentage and abdominal fat shear force (p<0.01). LPDs were significantly higher than FPDs in breast muscle thickness, breast muscle weight, breast muscle rate and breast muscle shear force (p<0.01). The muscle fiber average area and fiber diameter of LPDs were significantly higher than those of FPDs (p<0.01). The muscle fiber density of LPDs was significantly lower than that of FPDs (p<0.01). The IMF of LPDs in the breast muscle was significantly higher than that in the FPDs (p<0.01). There was no significant difference between the 2 strains in IMP content (p>0.05). The polyunsaturated fatty acid content of LPDs was significantly higher than that of FPDs (p<0.01), and FPDs had higher saturated fatty acid and monounsaturated fatty acid levels (p<0.05).

CONCLUSION

Long-term breeding work resulted in vast differences between the two strains Pekin ducks. This study provides a reference for differences between LPD and FPD that manifest as a result of long-term selection.

Expression of lipid metabolism genes provides new insights into intramuscular fat deposition in Laiwu pigs

Objective

The objective of this study was to measure the special expression pattern of lipid metabolism genes and investigate the molecular mechanisms underlying intramuscular fat (IMF) deposition in Longissimus dorsi muscle of Laiwu pigs.

Methods

Thirty-six pigs (Laiwu n = 18; Duroc×Landrace×Yorkshire n = 18) were used for the measurement of the backfat thickness, marbling score, IMF content, and expression of lipid metabolism genes.

Results

Significant correlations were found between IMF content and the mRNA expression of lipid metabolism genes. Of the 14 fat deposition genes measured, fatty acid synthase (FASN) showed the strongest correlation (r = 0.75, p = 0.001) with IMF content, and of the 6 fat removal genes, carnitine palmitoyl transferase 1B (CPT1B) exhibited the greatest negative correlation (r = −0.66, p = 0.003) with IMF content in Laiwu pig. Multiple regression analysis showed that CPT1B, FASN, solute carrier family 27 member 1 (SLC27A1), and fatty acid binding protein 3 (FABP3) contributed 38% of the prediction value for IMF content in Laiwu pigs. Of these four variables, CPT1B had the greatest contribution to IMF content (14%) followed by FASN (11%), SLC27A1 (9%), and FABP3 (4%).

Conclusion

Our results indicate that the combined effects of an upregulation in fat deposition genes and downregulation in fat removal genes promotes IMF deposition in Laiwu pigs.

Effect of visual marbling levels in pork loins on meat quality and Thai consumer acceptance and purchase intent

Objective

We investigated visual marbling level (VML) influence on pork loin physicochemical traits, consumer palatability responses, VML liking, purchase intent, and their relationships.

Methods

For each of five slaughtering dates, at 24-h postmortem, nine paired Duroc castrated male boneless Longissimus dorsi (LD) muscles were categorized into low (LM, score 1-2, n=3), medium (MM, score 3-4, n=3), and high (HM, score 5-6, n=3) VML. Meat physicochemical quality traits and consumer responses (n=389) on palatability and VML liking, and purchase intent were evaluated. The experiment was in RCBD. ANOVA, Duncan's multiple mean comparisons, and correlation coefficients were determined.

Results

VML correspond to crude fat (r=0.91, p<0.01), but both were reversely related to moisture content (r=-0.75 and -0.91, p<0.01, respectively). As VML increased, ash (p<0.05) and protein (p=0.072) decreased, pH and b* increased (p<0.05), but drip, cooking (p<0.05) and thawing (p=0.088) losses decreased. Among treatments, muscle fiber diameter, sarcomere length, total and insoluble collagen contents, L*, and a* did not differ (p>0.05). Compared to the others, HM had lower collagen solubility percentage (p<0.05), but similar (p>0.05) Warner-Bratzler Shear Force (WBSF). No differences (p>0.05) were found in juiciness, overall flavor, oiliness, and overall acceptability, but HM was more tender (p<0.05) than the others. Based on VML, consumers preferred MM to HM (p<0.05), while LM was similar to MM and HM (p>0.05). Corresponding to VML preference (r=0.45, p<0.01), consumers (83%) would (p<0.01) definitely and probably buy MM, over LM (74%), and HM (68%), respectively.

Conclusion

Increasing VML in pork LD altered its chemical composition, slightly increased pH, and improved WHC, thereby improving its tenderness acceptability. Marbling might reduce chewing resistance, as lower collagen solubility in HM did not impact tenderness acceptability and WBSF. While HM was rated as most tender, consumers visually preferred and would purchase MM.

Relationship between water-holding capacity and intramuscular fat content in Japanese commercial pork loin

OBJECTIVE

The relationship between water-holding capacity (WHC) and intermuscular fat (IMF) was studied in Japanese commercial pork.

METHODS

Longissimus muscles of pigs (n = 62), obtained from two meat packing plants, were analyzed for IMF content, moisture content, drip loss, cooking loss, and pH. Pairwise relationships among these traits were determined using correlation analyses.

RESULTS

IMF content was significantly correlated with moisture content (r = -0.88; p<0.01) and pH (r = 0.32; p<0.05), but not with drip loss (r = -0.23; p = 0.07) or cooking loss (r = -0.10; p = 0.42). In contrast, drip loss was significantly (and negatively) correlated with pH (r = -0.57; p<0.01).

CONCLUSION

IMF content was not significantly correlated with WHC in pork, and so ultimately, we consider pH to be one of the most important factors influencing WHC in pork meat.

Identification and characterization of novel single nucleotide polymorphism markers for fat deposition in muscle tissue of pigs using amplified fragment length polymorphism

Objective

This study was conducted to identify and evaluate the effective single nucleotide polymorphism (SNP) markers for fat deposition in the longissimus dorsi muscles of pigs using the amplified fragment length polymorphism (AFLP) approach.

Methods

Sixty-four selective primer combinations were used to identify the AFLP markers in the 20 highest- and 20 lowest-intramuscular fat (IMF) content phenotypes. Five AFLP fragments were converted into simple codominant SNP markers. These SNP markers were tested in terms of their association with IMF content and fatty acid (FA) composition traits in 620 commercially crossbred pigs.

Results

The SSC7 g.4937240C>G marker showed an association with IMF content (p<0.05). The SSC9 g.5496647_5496662insdel marker showed a significant association with IMF content and arachidonic levels (p<0.05). The SSC10 g.71225134G>A marker revealed an association with palmitoleic and ω9 FA levels (p<0.05), while the SSC17 g.61976696G>T marker showed a significant association with IMF content and FA levels of palmitoleic, eicosenoic, arachidonic, monounsaturated fatty acids, and ω9 FA levels. However, no significant association of SSC8 g.47338181G>A was observed with any IMF and FA levels in this study.

Conclusion

Four SNP markers (SSC7 g.4937240C>G, SSC9 g.5496647_5496662insdel, SSC10 g.71225134G>A, and SSC17 g.61976696G>T) were found to be associated with IMF and/or FA content traits in commercially crossbred pigs. These findings provide evidence of the novel SNP markers as being potentially useful for selecting pigs with the desirable IMF content and FA composition.

Accuracy of genomic breeding value prediction for intramuscular fat using different genomic relationship matrices in Hanwoo (Korean cattle)

Objective

Intramuscular fat is one of the meat quality traits that is considered in the selection strategies for Hanwoo (Korean cattle). Different methods are used to estimate the breeding value of selection candidates. In the present work we focused on accuracy of different genotype relationship matrices as described by forni and pedigree based relationship matrix.

Methods

The data set included a total of 778 animals that were genotyped for BovineSNP50 BeadChip. Among these 778 animals, 72 animals were sires for 706 reference animals and were used as a validation dataset. Single trait animal model (best linear unbiased prediction and genomic best linear unbiased prediction) was used to estimate the breeding values from genomic and pedigree information.

Results

The diagonal elements for the pedigree based coefficients were slightly higher for the genomic relationship matrices (GRM) based coefficients while off diagonal elements were considerably low for GRM based coefficients. The accuracy of breeding value for the pedigree based relationship matrix (A) was 13% while for GRM (GOF, G05, and Yang) it was 0.37, 0.45, and 0.38, respectively.

Conclusion

Accuracy of GRM was 1.5 times higher than A in this study. Therefore, genomic information will be more beneficial than pedigree information in the Hanwoo breeding program.

Trunk Muscle Size and Composition Assessment in Older Adults with Chronic Low Back Pain: An Intra-Examiner and Inter-Examiner Reliability Study

OBJECTIVE

To evaluate intra- and inter-examiner reliability for the assessment of relative cross-sectional area, muscle-to-fat infiltration indices, and relative muscle cross-sectional area, i.e., total cross-sectional area minus intramuscular fat, from T1-weighted magnetic resonance images obtained in older adults with chronic low back pain.

DESIGN

Reliability study.

SUBJECTS

n = 13 (69.3 ± 8.2 years old)

METHODS

After lumbar magnetic resonance imaging, two examiners produced relative cross-sectional area measurements of multifidi, erector spinae, psoas, and quadratus lumborum by tracing regions of interest just inside fascial borders. Pixel-intensity summaries were used to determine muscle-to-fat infiltration indices; relative muscle cross-sectional area was calculated. Intraclass correlation coefficients were used to estimate intra- and inter-examiner reliability; standard error of measurement was calculated.

RESULTS

Intra-examiner intraclass correlation coefficient point estimates for relative cross-sectional area, muscle-to-fat infiltration indices, and relative muscle cross-sectional area were excellent for multifidi and erector spinae across levels L2-L5 (ICC = 0.77-0.99). At L3, intra-examiner reliability was excellent for relative cross-sectional area, muscle-to-fat infiltration indices, and relative muscle cross-sectional area for both psoas and quadratus lumborum (ICC = 0.81-0.99). Inter-examiner intraclass correlation coefficients ranged from poor to excellent for relative cross-sectional area, muscle-to-fat infiltration indices, and relative muscle cross-sectional area.

CONCLUSIONS

Assessment of relative cross-sectional area, muscle-to-fat infiltration indices, and relative muscle cross-sectional area in older adults with chronic low back pain can be reliably determined by one examiner from T1-weighted images. Such assessments provide valuable information, as muscle-to-fat infiltration indices and relative muscle cross-sectional area indicate that a substantial amount of relative cross-sectional area may be magnetic resonance-visible intramuscular fat in older adults with chronic low back pain.

Gene Expression Patterns Associated with Peroxisome Proliferator-activated Receptor (PPAR) Signaling in the Longissimus dorsi of Hanwoo (Korean Cattle)

Adipose tissue deposited within muscle fibers, known as intramuscular fat (IMF or marbling), is a major determinant of meat quality and thereby affects its economic value. The biological mechanisms that determine IMF content are therefore of interest. In this study, 48 genes involved in the bovine peroxisome proliferator-activated receptor signaling pathway, which is involved in lipid metabolism, were investigated to identify candidate genes associated with IMF in the longissimus dorsi of Hanwoo (Korean cattle). Ten genes, retinoid X receptor alpha, peroxisome proliferator-activated receptor gamma (PPARG), phospholipid transfer protein, stearoyl-CoA desaturase, nuclear receptor subfamily 1 group H member 3, fatty acid binding protein 3 (FABP3), carnitine palmitoyltransferase II, acyl-Coenzyme A dehydrogenase long chain (ACADL), acyl-Coenzyme A oxidase 2 branched chain, and fatty acid binding protein 4, showed significant effects with regard to IMF and were differentially expressed between the low- and high-marbled groups (p<0.05). Analysis of the gene co-expression network based on Pearson’s correlation coefficients identified 10 up-regulated genes in the high-marbled group that formed a major cluster. Among these genes, the PPARG-FABP4 gene pair exhibited the strongest correlation in the network. Glycerol kinase was found to play a role in mediating activation of the differentially expressed genes. We categorized the 10 significantly differentially expressed genes into the corresponding downstream pathways and investigated the direct interactive relationships among these genes. We suggest that fatty acid oxidation is the major downstream pathway affecting IMF content. The PPARG/RXRA complex triggers activation of target genes involved in fatty acid oxidation resulting in increased triglyceride formation by ATP production. Our findings highlight candidate genes associated with the IMF content of the loin muscle of Korean cattle and provide insight into the biological mechanisms that determine adipose deposition within muscle.

Studies on Intramuscular Fat Percentage in Live Swine Using Real-time Ultrasound to Determine Pork Quality

In the modern pork industry, selection of high intramuscular fat (IMF) in pigs is necessary to improve pork quality. Ultrasound has been used previously to predict subcutaneous fat thickness and IMF in the longissimus muscles of line pigs and Real-time ultrasound has also been reported as a reliable method for estimating IMF in live pigs. So we estimate the correlation between meat quality traits and IMF percentage to investigate the possibility of utilizing real-time ultrasound technology for predicting IMF percentage in line pigs to improve pork quality. The genetic and phenotypic correlations for chemical intramuscular fat (CIMF) and ultrasound intramuscular fat (UIMF) were estimated to be 0.75 and 0.76, respectively. These results suggest that genetic factors strongly influence meat quality. The genetic and phenotypic correlation between UIMF and CIMF were 0.75, 0.76, respectively. The heritability of UIMF and CIMF were 0.48 and 0.50, respectively. So we concluded that CIMF can be replaced with UIMF and Ultrasound machines can be used to test IMF in live swine. In future, UIMF can be utilized to improve pork quality as an alternative to CIMF.

Association of DNA Methylation Levels with Tissue-specific Expression of Adipogenic and Lipogenic Genes in Longissimus dorsi Muscle of Korean Cattle

Epigenetic factors, such as DNA methylation status, may regulate adipogenesis and lipogenesis, thus affecting intramuscular fat (IMF) deposition in longissimus dorsi muscle (LM) of beef cattle. In Korean cattle steers, the LM consists mainly of muscle tissue. However, the LM tissue also contains IMF. We compared the gene expression levels between the IMF and muscle portions of the LM after tissue separation. Real-time polymerase chain reaction analysis showed that the mRNA levels of both adipogenic peroxisome proliferator-activated receptor gamma isoform 1 (PPARG1) and lipogenic fatty acid binding protein 4 (FABP4) were higher (p<0.01) in the IMF than in the muscle portion of the LM. We determined DNA methylation levels of regulatory regions of the PPARG1 and FABP4 genes by pyrosequencing of genomic DNA. DNA methylation levels of two of three CpG sites in the PPARG1 gene promoter region were lower (p<0.05) in the IMF than in the muscle portion of the LM. DNA methylation levels of all five CpG sites from the FABP4 gene promoter region were also lower (p<0.001) in the IMF than in the muscle portion. Thus, mRNA levels of both PPARG1 and FABP4 genes were inversely correlated with DNA methylation levels in regulatory regions of CpG sites of the corresponding gene. Our findings suggest that DNA methylation status regulates tissue-specific expression of adipogenic and lipogenic genes in the IMF and muscle portions of LM tissue in Korean cattle.

Detection of quantitative trait Loci affecting fat deposition traits in pigs

Quantitative trait loci (QTL) associated with fat deposition traits in pigs are important gene positions in a chromosome that influence meat quality of pork. For QTL study, a three generation resource population was constructed from a cross between Korean native boars and Landrace sows. A total of 240 F2 animals from intercross of F1 were produced. 80 microsatellite markers covering chromosomes 1 to 10 were selected to genotype the resource population. Intervals between adjacent markers were approximately 19 cM. Linkage analysis was performed using CRIMAP software version 2.4 with a FIXED option to obtain the map distances. For QTL analysis, the public web-based software, QTL express (http://www.qtl.cap.ed.ac.uk) was used. Two significant and two suggestive QTL were identified on SSC 6, 7, and 8 as affecting body fat and IMF traits. For QTL affecting IMF, the most significant association was detected between marker sw71 and sw1881 on SSC 6, and a suggestive QTL was identified between sw268 and sw205 on SSC8. These QTL accounted for 26.58% and 12.31% of the phenotypic variance, respectively. A significant QTL affecting IMF was detected at position 105 cM between markers sw71 and sw1881 on SSC 6.

Effects of dietary thiazolidinedione supplementation on growth performance, intramuscular fat and related genes mRNA abundance in the longissimus dorsi muscle of finishing pigs

The objective of this study was to investigate the effect of dietary supplementation with thiazolidinedione (TZD) on growth performance and meat quality of finishing pigs. In Experiment 1, 80 castrated finishing pigs (Large White×Landrace, BW = 54.34 kg) were randomly assigned to 2 treatments with 5 replicates of 8 pigs each. The experimental pigs in the 2 groups were respectively fed with a diet with or without a TZD supplementation (15 mg/kg). In Experiment 2, 80 castrated finishing pigs (Large White×Landrace, BW = 71.46 kg) were divided into 2 treatments as designed in Experiment 1, moreover, carcass evaluations were performed. The results from Experiment 1 showed that TZD supplementation could significantly decreased the average daily feed intake (ADFI) (p<0.05) during 0 to 28 d, without impairing the average daily gain (ADG) (p>0.05). In Experiment 2, the ADG was significantly increased by TZD supplementation during 14 to 28 d and 0 to 28 d (p<0.05) and the feed:gain ratio (F:G) was significantly decreased by TZD supplementation during 0 to 28 d (p<0.05). Compared with the control group, TZD group had significantly higher serum triglyceride (TG) concentration at 28h and serum high-density lipoprotein (HDL) levels at 14 d (p<0.05). Moreover, there was an apparent improvement in the marbling score (p<0.10) and intramuscular fat (IMF) content (p<0.10) of the longissimus dorsi muscle in pigs treated by TZD supplementation. Real-time RT-PCR analyses demonstrated that pigs of TZD group had higher mRNA abundance of PPARγ coactivator 1 (PGC-1) (p<0.05) and fatty acid-binding protein 3 (FABP3) (p<0.05) than pigs of control group. Taken together, these results suggested that dietary TZD supplementation could improve growth performance and increase the IMF content of finishing pigs through regulating the serum parameters and genes mRNA abundance involved in fat metabolism.