Adipocyte- and heart-type fatty acid binding proteins are both expressed in subcutaneous and intramuscular porcine ( Sus scrofa ) adipocytes

Promotion effect of salt on intramuscular neutral lipid hydrolysis during dry-salting process of porcine (biceps femoris) muscles by inducing phosphorylation of ATGL, HSL and their regulatory proteins of Perilipin1, ABHD5 and G0S2

Towards a better understanding of the formation mechanism of salt on intramuscular triglyceride (TG) hydrolysis occurring in biceps femoris (BF) muscles during dry-salting process, the changes of TG hydrolysis, TG hydrolysis activity and phosphorylation of adipose triglyceride lipase (ATGL) and hormone sensitive lipase (HSL) as well as their regulatory proteins (Perilipin1, ABHD5, G0S2) with different salt content (0%, 1%, 3%, 5%) and salting time (the first and third day) were analyzed. The results showed that dry-salting significantly increased the TG hydrolase activity and hydrolysis extent with salting process proceed (P < 0.05), especially upon the treatment with 3% amount of salt. The SDS-PAGE and Western-blot results further demonstrated that the promotion of salt on TG hydrolysis in intramuscular adipocytes was mainly attributed to the activation of protein kinase activity and protein phosphorylation process. Accordingly, the ATGL and HSL were activated, and meanwhile, the TG hydrolysis pivotal switch perilipin1 was also turned on by phosphorylation modification.

Association of A-FABP gene polymorphism and mRNA expression with intramuscular fat content (IMF) in Baicheng-You chicken

This study aims to assess the association of polymorphisms and mRNA expression of adipocyte-type fatty acid-binding protein (A-FABP) with intramuscular fat (IMF) in the breast muscle (BM) and leg muscle (LM) of Baicheng-You chickens (BYCs). A total of 180 chickens, including sixty black Baicheng-You chickens (BBYCs), sixty silky Baicheng-You chickens (SBYCs) and sixty white Baicheng-You chickens (WBYCs), were reared from 1 to 120 day. A polymerase chain reaction-single-strand conformation polymorphism strategy (PCR-SSCP) was used to detect the polymorphism of the A-FABP gene in the first exon, and the C51T silent mutational site was found. The IMF content with the AA genotype was significantly higher than that with the AG genotype (p = 0.0473) in the LM of WBYC. Thus, this site could be taken as a molecular marker in selecting a higher IMF content of LM in WBYC. A-FABP gene mRNA expression in the BM and LM of BYCs was detected, and a significant positive correlation was observed in the LM of WBYC. These findings provide fundamental data that might be useful in further study of the role of the A-FABP gene in IMF content and fatty metabolism in chickens.

Expression patterns of PPARγ2, PGC-1α, and MEF2C and their association with intramuscular fat content and skeletal muscle tenderness of crossbred Simmental bulls

PPARγ2, PGC-1α, and MEF2C play an important role in skeletal muscle development and fat deposition. This study aimed to determine their mRNA expression levels in longissimus dorsi (Ld), semitendinosus (Se), and soleus (Sol) muscles of crossbred Simmental bulls and estimate their association with intramuscular fat (IMF) content and meat shear force (MSF). We measured the muscle fiber (MF) density and area, IMF content, and MSF of 6-, 12-, and 36-mo-old bulls. We found that the expression patterns differed with age: the PPARγ2 expression in the three muscles of 36-mo-old bulls was greater than that in the muscles of 6- and 12-mo-old bulls (P < 0.05). Furthermore, PGC-1α expression in Sol of 36-mo-old and MEF2C expression in Ld of 12-mo-old bulls were higher than those in the respective muscles of 6- and 12-mo-old bulls, and 6- and 36-mo-old bulls, respectively (P < 0.05). The MF area, IMF content, and MSF increased with age (P < 0.05). The PPARγ2 mRNA expression in Ld, Se, and Sol was positively correlated with MF area and IMF content (P < 0.05) and negatively correlated with MF density (P < 0.05). Thus, PPARγ2 might be a candidate marker, which is positively correlated with IMF content and MF area.

miR-17-5p Regulates Differential Expression of NCOA3 in Pig Intramuscular and Subcutaneous Adipose Tissue

Fat distribution affects economic value in pork production. Intramuscular adipose tissue (IMAT) improves meat quality, whereas subcutaneous adipose tissue (SCAT) is usually regarded as waste. In the present study, we analyzed IMAT/SCAT (I/S) ratios in each pig. Individuals selected from a population of 1200 Suhuai pigs were divided into two cohorts; those with high I/S ratios and those with low I/S ratios, and correlations between nuclear Receptor Co-activator 3 (NCOA3), a critical gene involved in regulating fat accumulation, and fat distribution were investigated. The ratio of IMAT NCOA3 to SCAT NCOA3 expression levels (NCOA3_I/NCOA3_S) was higher in the high I/S group compared with the low I/S group. The NCOA3 expression level in fat tissue was positively correlated with fat deposition. miR-17-5p was identified as a putative regulator of NCOA3 based on bioinformatics prediction analysis followed by gene expression analysis. The miR-17-5p_I/miR-17-5p_S ratio was negatively correlated with the NCOA3_I/NCOA3_S ratio. The predicted relationship between miR-17-5p and NCOA3 was further verified by dual luciferase activity assays, qPCR, and western blots. Overexpression of miR-17-5p in intramuscular preadipocytes inhibited NCOA3 expression and reduced preadipocyte differentiation. FABP4 and PPARG expression were also significantly decreased, as was triglyceride content. Meanwhile, knockdown of miR-17-5p significantly increased NCOA3 expression and promoted intramuscular preadipocyte differentiation. Based on these results, we propose that differential expression of NCOA3 in pig intramuscular and subcutaneous adipose tissue is regulated by miR-17-5p.

Correlation between Heart-type Fatty Acid-binding Protein Gene Polymorphism and mRNA Expression with Intramuscular Fat in Baicheng-oil Chicken

This study aims to determine the polymorphism and mRNA expression pattern of the heart-type fatty acid-binding protein (H-FABP) gene and their association with intramuscular fat (IMF) content in the breast and leg muscles of Baicheng oil chicken (BOC). A total of 720 chickens, including 240 black Baicheng oil chicken (BBOC), 240 silky Baicheng oil chicken (SBOC), and 240 white Baicheng oil chicken (WBOC) were raised. Three genotypes of H-FABP gene second extron following AA, AB, and BB were detected by polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) strategy. The G939A site created AA genotype and G956A site created BB genotype. The content of IMF in AA genotype in breast muscle of BBOC was significantly higher than that of AB (p = 0.0176) and the genotype in leg muscle of WBOC was significantly higher than that of AB (p = 0.0145). The G939A site could be taken as genetic marker for higher IMF content selecting for breast muscle of BBOC and leg muscle of WBOC. The relative mRNA expression of H-FABP was measured by real-time PCR at 30, 60, 90, and 120 d. The IMF content significantly increased with age in both muscles. The mRNA expression level of H-FABP significantly decreased with age in both muscles of the three types of chickens. Moreover, a significant negative correlation between H-FABP abundance and IMF content in the leg muscles of WBOC (p = 0.035) was observed. The mRNA expression of H-FABP negatively correlated with the IMF content in both breast and leg muscles of BOC sat slaughter time.

Molecular characterization and different expression patterns of the FABP gene family during goat skeletal muscle development

The FABP (adipocyte fatty acid-binding protein) genes play an important role in intracellular fatty acid transport and considered to be candidate genes for fatness traits in domestic animal. In this study, we cloned the cDNA sequences of goat FABP family genes and their expression patterns were detected by semi-quantitative RT-PCR and quantitative real time RT-PCR. Expression analysis showed that goat FABP1 gene was predominantly expressed in liver, kidney and large intestine. While FABP4 was widely expressed in many tissues with a high expression level was observed in the fat, skeletal muscle, stomach and lung. Notably, FABP2 gene was expressed specifically in small intestine. Moreover, goat FABP3 was expressed at 60 day with the highest level, then significantly (p < 0.01) decreased at the 90 day. No significant expression differences were observed in longissimus dorsi muscles among 3 day, 30 day and 60 day. Goat FABP4 was expressed at 3 day with the lowest level, then significantly (p < 0.01) increased to a peak at the 60 day. In addition, a significant relationship between FABP3 mRNA expression levels and intramuscular fat (IMF) content was observed. These results suggest that the FABP3 and FABP4 may be important genes for meat quality and provides useful information for further studies on their roles in skeletal muscle IMF deposit.

Comparison of the adipogenesis in intramuscular and subcutaneous adipocytes from Bamei and Landrace pigs

Fat deposition is a complex process involving proliferation, differentiation, and lipogenesis of adipocytes. Bamei and Landrace are considered to represent fat- and lean-type pig breeds. Subcutaneous (SC) and intramuscular (IM) pre-adipocytes were cultured to compare the proliferation and lipogenesis in these breeds. The differentiated adipocytes were exposed to glucose or insulin to evaluate their effects on lipogenesis and lipogenic gene expression. Pre-adipocytes proliferated dramatically faster in SC vs. IM cells, and in Bamei vs. Landrace breeds. Lipogenesis and lipogenic gene expression had a greater increase in Bamei than in Landrace, and in SC vs. IM in the process of differentiation. Glucose markedly promoted lipogenesis and lipogenic gene expression in differentiated adipocytes. The stimulation of high-glucose levels on lipogenesis and ChREBP and lipogenic gene expression was higher in SC than IM adipocytes, and in Bamei vs. Landrace. Insulin largely increased SREBP-1c expression, however it modestly stimulated lipogenesis and lipogenic gene expression, and there was no difference between cell populationsor between breeds. These data demonstrated that regional and varietal differences obviously existed in the development of porcine adipocytes. The proliferation and differentiation capacity of pre-adipocytes, and the adipocyte lipogenesis stimulated by glucose, are stronger in Bamei than Landrace, and in SC vs. IM adipocytes independent of breed.

RNA-seq analysis of bovine intramuscular, subcutaneous and perirenal adipose tissues

The deposition of intramuscular fat is an important factor affecting the beef quality, such as flavour and palatability. In this study, for further identifying the differential molecular mechanisms regulating the deposition of fat between intramuscular and external adipose tissues, particularly subcutaneous and perirenal adipose tissues, it was designed to obtain transcript sequence data and compare the transcriptomes among intramuscular, subcutaneous, and perirenal adipose tissues by RNA-Seq. A total of 66,206,912, 55,114,070 and 67,320,426 fragments were sequenced for the intramuscular (IAT), subcutaneous (SAT), and perirenal adipose tissue (PAT) respectively. Among them, total 953, 1,534, 2,026 genes showing differential expression between IAT and SAT, IAT and PAT, SAT and PAT, were identified respectively (FDR < 0.05). When these data had been mixed and analyzed together, 110 genes were differentially expressed among these three adipose tissues. Using GO enrichment analysis, multiple biological pathways were found to be significantly enriched for differentially expressed genes (FDR < 0.01), including cellular process, biological regulation, and metabolic process. In addition, total 4,625, 4,775 and 4,147 alternative splicing events occurred in IAT, SAT, and PAT, had also been detected respectively. Thus, our results logically provide the evidence for further understanding the bovine fat deposition, especially intramuscular fat, at a fine scale.

Identification of microRNA and bioinformatics target gene analysis in beef cattle intramuscular fat and subcutaneous fat

MicroRNA (miRNA) is endogenous non-coding RNA that has been proposed to play an important role in the formation of body fat. However, the differential expression of miRNA and the role of these miRNAs in bovine intramuscular and subcutaneous fat tissue are still unknown. In this study, the profile of differentially expressed miRNA and the target gene analysis in intramuscular adipose and subcutaneous adipose of adult beef cattle were investigated by microarray and bioinformatics. The data identified 88 differentially expressed miRNAs in 213 miRNAs which were detected on the microarray, and 30 miRNAs among these 88 miRNAs were changed significantly between intramuscular and subcutaneous fat (fold change >1, P < 0.001). miR-143, miR-145, miR-26a, miR-2373-5p and miR-23b-3p were highly expressed in intramuscular fat, whilst miR-26a, miR-2373-5p, miR-2325c, miR-3613 and miR-2361 showed highest abundance in subcutaneous fat. Bioinformatics of KEGG pathway analysis and GO term enrichment suggested that these differentially expressed miRNAs involved in different pathways and target genes may regulate differently the fat deposition. Taken together, our study provides the first evidence for better understanding the differential expression and mechanisms of miRNA in bovine fat deposition, and provides thinking to improve the quality of beef by reducing subcutaneous fat and increasing intramuscular fat of beef cattle.

Distinctive genes determine different intramuscular fat and muscle fiber ratios of the longissimus dorsi muscles in Jinhua and landrace pigs

Meat quality is determined by properties such as carcass color, tenderness and drip loss. These properties are closely associated with meat composition, which includes the types of muscle fiber and content of intramuscular fat (IMF). Muscle fibers are the main contributors to meat mass, while IMF not only contributes to the sensory properties but also to the plethora of physical, chemical and technological properties of meat. However, little is known about the molecular mechanisms that determine meat composition in different pig breeds. In this report we show that Jinhua pigs, a Chinese breed, contains much higher levels of IMF than do Landrace pigs, a Danish breed. We analyzed global gene expression profiles in the longissimus dorsi muscles in Jinhua and Landrace breeds at the ages of 30, 90 and 150 days. Cross-comparison analysis revealed that genes that regulate fatty acid biosynthesis (e.g., fatty acid synthase and stearoyl-CoA desaturase) are expressed at higher levels in Jinhua pigs whereas those that regulate myogenesis (e.g., myogenic factor 6 and forkhead box O1) are expressed at higher levels in Landrace pigs. Among those genes which are highly expressed in Jinhua pigs at 90 days (d90), we identified a novel gene porcine FLJ36031 (pFLJ), which functions as a positive regulator of fat deposition in cultured intramuscular adipocytes. In summary, our data showed that the up-regulation of fatty acid biosynthesis regulatory genes such as pFLJ and myogenesis inhibitory genes such as myostatin in the longissimus dorsi muscles of Jinhua pigs could explain why this local breed produces meat with high levels of IMF.

Association between subcutaneous and intramuscular fat content in porcine ham and loin depending on age, breed and FABP3 and LEPR genes transcript abundance

The objective of the present study was to analyze the level of intramuscular fat (IMF) in loin (musculus longissimus dorsi) and ham (musculus semimembranosus) and the level of subcutaneous fat in these cuts depending on breed, age and the expression level of FABP3 and LEPR genes. The results obtained showed that only the breed influenced on the level of both intramuscular and subcutaneous fat to the same extent (P ≤ 0.001). The age of animals had an effect on fat content of the cuts (P ≤ 0.001) and to a lower extent on the level of IMF in both muscles (P ≤ 0.05). We confirmed highly significant effect of breed and age on the LEPR mRNA abundance—the expression of the this gene increased significantly (P ≤ 0.01) with age and the highest expression was found for the Puławska breed in m. longissimus dorsi and for the Polish Landrace breed in m. semimembranosus. We observed the high correlations between the transcript level of the LEPR gene and the fat content of individual cuts (P ≤ 0.01). The expression level of FABP3 gene influenced the level of IMF (P ≤ 0.01), but not the level of subcutaneous fat in loin and ham.

Expression levels of candidate genes for intramuscular fat deposition in two Banna mini-pig inbred lines divergently selected for fatness traits

Intramuscular fat (IMF) content plays an important role in meat quality. Many genes involved in lipid and energy metabolism were identified as candidate genes for IMF deposition, since genetic polymorphisms within these genes were associated with IMF content. However, there is less information on the expression levels of these genes in the muscle tissue. This study aimed at investigating the expression levels of sterol regulating element binding protein-1c (SREBP-1c), diacylglycerol acyltransferase (DGAT-1), heart-fatty acids binding protein (H-FABP), leptin receptor (LEPR) and melanocortin 4 receptor (MC4R) genes and proteins in two divergent Banna mini-pig inbred lines (BMIL). A similar growth performance was found in both the fat and the lean BMIL. The fat meat and IMF content in the fat BMIL were significantly higher than in the lean BMIL, but the lean meat content was lower. The serum triacylglycerol (TAG) and free fatty acid (FFA) contents were significantly higher in the fat than in the lean BMIL. The expression levels of SREBP-1c, DGAT-1 and H-FABP genes and proteins in fat BMIL were increased compared to the lean BMIL. However, the expression levels of LEPR and MC4R genes and proteins were lower.

Heart-type fatty acid-binding protein and its relation with morphological changes in rat myocardial damage model induced by isoproterenol

We have investigated heart type fatty acid binding protein (H-FABP) rat serum values at different time point following subcutaneous (s.c) isoproterenol (ISO) administration and their correlation with severity of myocardial lesion. Thirty adult, male, Wistar rats were used for this study. Six rats per group were treated with a single dose of either ISO (ISO groups, dose 100 mg/kg, s.c.) at different time point (30', 60', 120', 240') or with saline (control group). Serum H-FABP was determined by enzyme-linked immunosorbent assay (ELISA) and histological analysis was performed by hematoxylin-eosin (HE) method of staining. The first serum H-FABP increase was obtained 30' following ISO administration, but maximal value was reached after 240'. Myocardial histological changes were time-dependent and correlated with serum H-FABP values (p<0.001). The results of the study suggest that H-FABP is sensitive marker for acute rat myocardial injury and its possible inclusion in myocardial injury screening studies in rats.

Investigation of four porcine candidate genes (H-FABP, MYOD1, UCP3 and MASTR) for meat quality traits in Large White pigs

Meat quality traits are economically important traits of swine, and are controlled by multiple genes as complex quantitative traits. In the present study four genes, H-FABP (heart fatty acid-binding protein), MASTR (MEF2 activating motif and SAP domain containing transcriptional regulator), UCP3 (uncoupling protein 3) and MYOD1 (myogenic differentiation 1) were researched in Large White pigs. The polymorphisms H-FABP T/C of 5'UTR, MYOD1 g.257 A>C, UCP3 g.1406 G>A in exon 3 and MASTR c.187 C>T have been reported to be associated with meat quality traits in pigs. The aim of this study was to analyze the effect of single and multiple markers for single traits in Large White pigs. The single marker association analysis showed that the H-FABP and MASTR genes were associated with IMF (intramuscular fat content) (P < 0.05), and that the g.257 A>C of MYOD1 gene was most significantly related to muscle pH value (P < 0.01). The multiple markers for IMF were analyzed by combining the markers and quantitative trait modes into the linear regression. The results revealed that H-FABP and MASTR integrate gene networks for IMF. Thus, our study results suggested that H-FABP and MASTR polymorphisms could be used as genetic markers in the marker-assisted selection towards the improvement of IMF in Large White pigs.

Association of A-FABP gene polymorphism in intron 1 with meat quality traits in Junmu No. 1 white swine

This study was designed to investigate the single nucleotide polymorphism (SNP) in intron 1 of the gene A-FABP in 127 Junmu No. 1 white swine using PCR-SSCP. The association between the polymorphism and meat quality traits was also studied. The cloning and sequencing results indicated that the polymorphism of intron 1 was due to a point mutation in position 3481bp of A-FABP, giving 3 genotypes (CC, CD and DD). Association analysis indicated that the polymorphism had a significant effect on marbling (P<0.05). Genotype DD had higher marbling than CD and CC, but the difference between CD and CC was no significant. Polymorphism had a highly significant effect on intramuscular fat (IMF) content (P<0.01). DD was higher than CD, which was higher than CC. No significant conclusions can be drawn regarding other traits. Immunoblot analysis of A-FABP levels was carried out on 3 different genotype individuals. Expression was markedly reduced in DD compared with genotype CC. Thus A-FABP may be a candidate gene or a quantitative trait locus-linked gene associated with meat quality traits.

Effects of microRNA-143 in the differentiation and proliferation of bovine intramuscular preadipocytes

MicroRNAs (miRNAs) are short non-coding RNA that post-transcriptionally regulates gene expression. miRNA-143 has been proposed to play a role in the differentiation of preadipocytes. However, effects and mechanism of miRNA-143 in the differentiation of mammals intramuscular adipocytes is unknown. In this study, the fibroblast-like preadipocytes were cultured from the marbling muscle tissue of holstein steers by the ceiling culture method. The in vitro studies showed that the fibroblast-like preadipocytes could differentiated into mature adipocytes with up-regulated expression of miRNA-143. Furthermore, the transfection of the fibroblast-like preadipocytes with miRNA-143 antisense inhibitor induced a significant suppression of differentiation, and indicated by decreased storage of lipid droplets and down-regulated expression of key adipocytes regulatory genes such as CCAAT/enhancer-binding protein-α (C/EBPα) and fatty acid binding proteins-4 (FABP-4). On the contrary, cells proliferation were increased with miRNA-143 inhibitor transfection. Taken together, our study provide the first evidence for stimulation of endogenous miRNA-143 in the differentiation of bovine intramuscular fat, which in part contribute to the regulated expression of adipocyte genes.

Bovine adipose triglyceride lipase is not altered and adipocyte fatty acid-binding protein is increased by dietary flaxseed

In this paper, we report the full-length coding sequence of bovine ATGL cDNA and analyze its expression in bovine tissues. Similar to human, mouse, and pig ATGL sequences, bovine ATGL has a highly conserved patatin domain that is necessary for lipolytic function in mice and humans. This suggests that ATGL is functionally intact as a triglyceride lipase in cattle. Tissue distribution of ATGL gene expression was highest in fat and muscle (skeletal and cardiac) tissue, while protein expression was solely detectible in the adipose tissue. The effect of 109 days of flaxseed supplementation on ATGL and adipocyte fatty acid-binding protein (FABP4 or A-FABP, E-FABP or FABP5) expression was examined in Angus steers. Supplemented steers had greater triacylglycerol (TAG) content in the muscle compared with unsupplemented ones. Additionally, supplementation increased A-FABP expression and decreased stearoyl-CoA desaturase 1 (SCD-1) expression in muscle, while total ATGL expression was unaffected. In summary, supplementation of cattle rations with flaxseed increased muscle TAG concentrations attributed in part to increased expression of key enzymes involved in lipid trafficking (A-FABP) and metabolism (SCD-1).

Global comparison of gene expression profiles between intramuscular and subcutaneous adipocytes of neonatal landrace pig using microarray

The objective of this study was to compare the differences of gene expression profiles between intramuscular and subcutaneous adipocytes originated from the isolated preadipocytes in vitro. Cytosolic triglyceride determination indicated that subcutaneous adipocytes accumulated more lipid than intramuscular adipocytes did at the late stage of differentiation. Microarray assay revealed that 172 probes representing 133 genes were differentially expressed, among which 46 genes were highly expressed in intramuscular adipocytes and the other 87 genes were highly expressed in subcutaneous adipocytes. Real-time PCR confirmed that genes related to lipid metabolism, such as LPL, FABP4, FABP5 and OSBPL10, were predominantly expressed in subcutaneous adipocytes, whereas BMP4 and BMP7 were highly expressed in intramuscular adipocytes. The results indicated that the accumulation of lipid mass in subcutaneous adipocytes might be due to the highly expressed genes related to lipid metabolism, and the high levels of BMP4 and BMP7 in intramuscular adipocytes suggested that BMPs might be involved in the differentiation of intramuscular adipocytes.

Influence of birth weight on gene regulators of lipid metabolism and utilization in subcutaneous adipose tissue and skeletal muscle of neonatal pigs

Epidemiological studies suggest that low-birth weight infants show poor neonatal growth and increased susceptibility to metabolic syndrome, in particular, obesity and diabetes. Adipose tissue development is regulated by many genes, including members of the peroxisome proliferator-activated receptor (PPAR) and the fatty acid-binding protein (FABP) families. The aim of this study was to determine the influence of birth weight on key adipose and skeletal muscle tissue regulating genes. Piglets from 11 litters were ranked according to birth weight and 3 from each litter assigned to small, normal, or large-birth weight groups. Tissue samples were collected on day 7 or 14. Plasma metabolite concentrations and the expression ofPPARG2,PPARA,FABP3, andFABP4genes were determined in subcutaneous adipose tissue and skeletal muscle. Adipocyte number and area were determined histologically. Expression ofFABP3and4was significantly reduced in small and large, compared with normal, piglets in adipose tissue on day 7 and in skeletal muscle on day 14. On day 7,PPARAandPPARG2were significantly reduced in adipose tissue from small and large piglets. Adipose tissue from small piglets contained more adipocytes than normal or large piglets. Birth weight had no effect on adipose tissue and skeletal muscle lipid content. Low-birth weight is associated with tissue-specific and time-dependent effects on lipid-regulating genes as well as morphological changes in adipose tissue. It remains to be seen whether these developmental changes alter an individual's susceptibility to metabolic syndrome.

Differential gene expression of fatty acid binding proteins during porcine adipogenesis

Four different subtypes of fatty acid binding proteins i.e. liver-type FABP1, heart/muscle-type FABP3, adipocyte-type FABP4 and epithelial/epidermal-type FABP5 are expressed in adipose tissue. However, only the regulatory role of FABP4 in adipogenesis has been thoroughly investigated. To increase the knowledge on possible roles of these FABP subtypes in preadipocyte differentiation, gene expression patterns were examined during adipogenesis in pig (Sus scrofa). FABP1 expression was induced in proliferating cells, whereas FABP3, FABP4 and FABP5 expression increased throughout preadipocyte differentiation. Interestingly, the FABP4 and FABP5 expression increased early in the differentiation, followed by FABP3 later in the differentiation process. This indicates a role of FABP4 and FABP5 in intracellular fatty acid transport during initiation of differentiation, whereas, FABP3 likely is involved in the transport of fatty acids during intermediate stages of adipogenesis. In this study we demonstrate that FABP3, FABP4 and FABP5 expression is correlated with that of the peroxisome proliferator-activated receptors alpha and gamma (PPARA and PPARG). Altogether, this suggests a role of FABP1 during cell proliferation, whereas a coordinated expression of FABP3, FABP4 and FABP5 together with that of PPARA, PPARG1 and PPARG2 might be critical for the metabolic regulation during porcine adipogenesis.

A combination of octanoate and oleate promotes in vitro differentiation of porcine intramuscular adipocytes

To understand the relationship between intramuscular adipogenesis in the pig and the supply fatty acids, we established a clonal porcine intramuscular preadipocyte (PIP) line from the marbling muscle tissue of female Duroc pig. Confluent PIP cells exhibited a fibroblastic appearance. Their adipogenic ability was investigated using confluent PIP cells after exchanging growth medium for adipogenic medium containing 50 ng/mL insulin, 0.25 microM dexamethasone, 2 mM octanoate, and 200 microM oleate. Appropriate concentrations of octanoate and oleate for the induction of adipogenesis were determined from the ability of cells to accumulate lipid and the toxicity of fatty acids. When cells were cultured in differentiation medium for 8 days, large numbers of lipid droplets were observed in differentiated PIP cells, and their cytosolic TG content increased in a time-dependent manner. While oleate only induced the expression of PPARgamma mRNA, but not that of C/EBPalpha, octanoate significantly induced the expression of both PPARgamma and C/EBPalpha mRNA. Octanoate and oleate accelerated the inducing effect of insulin and dexamethasone on the expression of aP2 mRNA. These results indicate that a combination of octanoate and oleate synergistically induced PIP adipogenesis, and that the stimulation of octanoate was essential to the trigger for the adipogenesis in PIP cells.