Expression of porcine adipocyte transcripts: tissue distribution and differentiation in vitro and in vivo

Bacoside-A repressed the differentiation and lipid accumulation of 3T3-L1 preadipocytes by modulating the expression of adipogenic genes

Obesity is one of the more complicated diseases, it can induce numerous life-threatening diseases mainly diabetes mellitus, cardiovascular disease, hypertension, and certain cancers. In this study, we assessed the efficacy of bacoside-A (a dammarane-type triterpenoid saponin derived from the plant Bacopa monniera Linn.) on the adipogenesis of 3T3-L1 preadipocytes. Results of this study illustrated that bacoside-A decreased the differentiation of 3T3-L1 cell, as evidenced by diminution of lipid droplets, which contains triglycerides and other lipids. During the differentiation process, transcription factors, which are mainly participating in adipogenesis such us CCAAT/enhancer-binding protein α (C/EBPα) and C/EBPβ, peroxisome proliferator-activated receptor-γ (PPARγ), and sterol regulatory element-binding protein-1c (SREBP-1c), expressions were significantly suppressed by bacoside-A. In addition, bacoside-A showed a potent reduction in genes precise to adipocytes such as lipoprotein lipase (LPL), fatty acid synthase (FAS), adipocyte fatty acid-binding protein (FABP4), and leptin expressions. Further, bacoside-A stimulated the phosphorylation of acetyl CoA carboxylase (ACC) and AMP-activated protein kinase (AMPK). These results demonstrated that bacoside-A has anti-adipogenic effects by regulating the transcription factors involved in adipocyte differentiation. Therefore, bacoside-A might be considered as a potent therapeutic agent for alleviating obesity and hyperlipidemia.

Dietary dibutyryl cAMP supplementation regulates the fat deposition in adipose tissues of finishing pigs via cAMP/PKA pathway

This study investigated potential mechanism of dibutyryl-cAMP (db-cAMP) on porcine fat deposition. (1) Exp.1, 72 finishing pigs were allotted to 3 treatments (0, 10 or 20 mg/kg dbcAMP) with 6 replicates. dbcAMP increased the hormone sensitive lipase (HSL) activity and expression of β-adrenergic receptor (β-AR) and growth hormone receptor (GHR), but decreased expression of peroxisome proliferator-activated receptor gamma 2 (PPAR-γ2) and adipocyte fatty acid binding protein (A-FABP) in back fat. dbcAMP upregulated expression of β-AR, GHR, PPAR-γ2 and A-FABP, but decreased insulin receptor (INSR) expression in abdominal fat. Dietary dbcAMP increased HSL activity and expression of G protein-coupled receptor (GPCR), cAMP-response element-binding protein (CREB) and insulin-like growth factor-1 (IGF-1), but decreased fatty acid synthase (FAS) and lipoprotein lipase (LPL) activities, and expression of INSR, cAMP-response element-binding protein (C/EBP-α) and A-FABP in perirenal fat. (2) Exp. 2, dbcAMP suppressed the proliferation and differentiation of porcine preadipocytes in a time- and dose-dependent manner, which might be associated with increased activities of cAMP and protein kinase A (PKA), and expression of GPCR, β-AR, GHR and CREB via inhibiting C/EBP-α and PPAR-γ2 expression. Collectively, dbcAMP treatment may reduce fat deposition by regulating gene expression related to adipocyte differentiation and fat metabolism partially via cAMP-PKA pathway.

Circular RNAs in metabolism and metabolic disorders

Metabolic syndrome (MetS) is a serious health condition triggered by hyperglycemia, dyslipidemia, and abnormal adipose deposition. Recently, circular RNAs (circRNAs) have been proposed as key molecular players in metabolic homeostasis due to their regulatory effects on genes linked to the modulation of multiple aspects of metabolism, including glucose and lipid homeostasis. Dysregulation of circRNAs can lead to metabolic disorders, indicating that circRNAs represent plausible potential targets to alleviate metabolic abnormalities. More recently, a series of circulating circRNAs have been identified to act as both essential regulatory molecules and biomarkers for the progression of metabolism-related disorders, including type 2 diabetes mellitus (T2DM or T2D) and cardiovascular disease (CVD). The findings of this study highlight the function of circRNAs in signaling pathways implicated in metabolic diseases and their potential as future therapeutics and disease biomarkers.

CircRNA expression profiles in human visceral preadipocytes and adipocytes

Circular RNAs (circRNAs) regulate several physiological and pathological processes, but their role in visceral lipid deposition has not been explored. In the present study, human preadipocytes from visceral fat tissue (HPA-v) were induced to form adipocytes, and the circRNA expression profiles in HPA-v and adipocytes were detected using circRNA microarrays. The microarray data revealed that 2,215 and 1,865 circRNAs were significantly up- and downregulated, respectively, in adipocytes compared with HPA-v. Moreover, the parental genes of differentially expressed circRNAs were associated with fatty acid metabolism based on Kyoto Encyclopedia of Genes and Genomes analysis. Three circRNAs (hsa_circ_0136134, hsa_circ_0017650, and hsa-circRNA9227-1) were selected for quantitative PCR (qPCR) validation, and the qPCR results were consistent with the microarray results. Furthermore, MiRanda software was used to predict the microRNAs (miRNAs) potentially targeting the top 10 up- and downregulated circRNAs, and 14 miRNAs with more than two miRNA response elements targeting these circRNAs. This is the first study of the expression profiles of circRNAs in HPA-v and adipocytes and may suggest potential therapeutic targets for the visceral obesity.

Original Research: Orexins A and B stimulate proliferation and differentiation of porcine preadipocytes

Orexin A (OXA) and B (OXB) are neuropeptides which regulate appetite, energy expenditure, and arousal via G-protein coupled receptors termed as OXR1 and OXR2. The aim of this study was to characterize the effects of OXA and OXB on proliferation and differentiation of porcine preadipocytes. Porcine preadipocytes express both OXRs. OXA and OXB enhance porcine preadipocyte proliferation by 54.8% or 63.2 %, respectively. OXA and OXB potentiate differentiation of porcine preadipocytes, as judged by the increased lipid accumulation and expression of proadipogenic genes. Cellular lipid content after exposure of preadipocytes for six days to 100 nM OXA or OXB increased by 82.2% or 59.2%, respectively. OXA and OXB suppressed glycerol release by 23.9% or 24.9% in preadipocytes differentiated for six days. OXA (100 nM) increased peroxisome proliferator-activated receptor gamma (PPARγ) expression in cells differentiated for 24 h by 100.5%. PPARγ expression was also stimulated in preadipocytes differentiated in the presence of 10 nM (58.3%) or 100 nM OXA (50.6%) for three days. OXB potentiated PPARγ mRNA expression at 1 nM (59%), 10 nM (53.2%), and 100 nM (73.9%) in cells differentiated for three days. OXA increased CCAAT/enhancer binding protein alpha expression in preadipocytes differentiated for six days by 65%. OXB stimulated CCAAT/enhancer binding protein beta expression in preadipocytes differentiated for three days at 10 nM (149.5%) as well as 100 nM (207.2%). Lipoprotein lipase mRNA expression increased in cells treated with 10 nM OXA by 152.6% and 100 nM OXA by 162%. Lipoprotein lipase expression increased by 134% at 100 nM OXB. Furthermore, OXA (100 nM) and OXB (100 nM) increased leptin mRNA expression in preadipocytes differentiated for three days by 49.9% or 71.3%, respectively. These data indicate that orexin receptors may be relevant in the context of white adipose tissue formation.

Insulin: pancreatic secretion and adipocyte regulation

Insulin is the primary acute anabolic coordinator of nutrient partitioning. Hyperglycemia is the main stimulant of insulin secretion, but other nutrients such as specific amino acids, fatty acids, and ketoacids can potentiate pancreatic insulin release. Incretins are intestinal hormones with insulinotropic activity and are secreted in response to food ingestion, thus integrating diet chemical composition with the regulation of insulin release. In addition, prolactin is required for proper islet development, and it stimulates β-cell proliferation. Counterintuitively, bacterial components appear to signal insulin secretion. In vivo lipopolysaccharide infusion acutely increases circulating insulin, which is paradoxical as endotoxemia is a potent catabolic condition. Insulin is a potent anabolic orchestrator of nutrient partitioning, and this is particularly true in adipocytes. Insulin dictates lipid accretion in a dose-dependent manner during preadipocyte development in adipose tissue-derived stromal vascular cell culture. However, in vivo studies focused on insulin's role in regulating adipose tissue metabolism from growing, and market weight pigs are sometimes inconsistent, and this variability appears to be animal, age and depot dependent. Additionally, porcine adipose tissue synthesizes and secretes a number of adipokines (leptin, adiponectin, and so forth) that directly or indirectly influence insulin action. Therefore, because insulin has an enormous impact on agriculturally important phenotypes, it is critical to have a better understanding of how insulin homeostasis is governed.

Preadipocyte and adipose tissue differentiation in meat animals: influence of species and anatomical location

Early in porcine adipose tissue development, the stromal-vascular (SV) elements control and dictate the extent of adipogenesis in a depot-dependent manner. The vasculature and collagen matrix differentiate before overt adipocyte differentiation. In the fetal pig, subcutaneous (SQ) layer development is predictive of adipocyte development, as the outer, middle, and inner layers of dorsal SQ adipose tissue develop and maintain layered morphology throughout postnatal growth of SQ adipose tissue. Bovine and ovine fetuses contain brown adipose tissue but SQ white adipose tissue is poorly developed structurally. Fetal adipose tissue differentiation is associated with the precocious expression of several genes encoding secreted factors and key transcription factors like peroxisome proliferator activated receptor (PPAR)γ and CCAAT/-enhancer-binding protein. Identification of adipocyte-associated genes differentially expressed by age, depot, and species in vivo and in vitro has been achieved using single-gene analysis, microarrays, suppressive subtraction hybridization, and next-generation sequencing applications. Gene polymorphisms in PPARγ, cathepsins, and uncoupling protein 3 have been associated with back fat accumulation. Genome scans have mapped several quantitative trait loci (QTL) predictive of adipose tissue-deposition phenotypes in cattle and pigs.

Hesperetin inhibit adipocyte differentiation and enhance Bax- and p21-mediated adipolysis in human mesenchymal stem cell adipogenesis

We aimed to explore the antiadipogenic and adipolysis effect of hesperetin in human mesenchymal stem cells (hMSCs)-induced adipogenesis. IC50 value of hesperetin was higher for hMSCs such as 149.2 ± 13.2 μmol for 24 h and 89.4 ± 11.4 μmol in 48 h, whereas in preadipocytes was 87.6 ± 9.5 μmol and 72.4 ± 5.6 μmol in 24 h and 48 h, respectively. Hesperetin treatment (5, 10, and 20 μmol) to adipogenesis-induced hMSCs (Group 1) and preadipocytes (Group 2) resulted in a significantly (p < 0.05) increased lipolysis. The treatment with hesperetin decreased the expression of resistin, adiponectin, aP2, LPL, PPAR-γ, and TNF-α in Groups 1 and 2, whereas a significant increase was observed in Bcl, Bax, and p21 expression in Group 2 compared to untreated preadipocytes. hMSCs cultured in adipogenic medium along with hesperetin significantly inhibited adipocyte differentiation and increased the proapoptotic gene expression levels in preadipocyte. Our result indicates the antiadipogenic and adipolysis effects of hesperetin.

The proliferation and differentiation of primary pig preadipocytes is suppressed when cultures are incubated at 37°Celsius compared to euthermic conditions in pigs

Given similarities in metabolic parameters and cardiovascular physiology, the pig is well positioned as a biomedical model for metabolic disease and obesity in humans. Better understanding molecular mechanisms governing porcine adipocyte hyperplasia may provide insight into the regulation of adipose tissue development that is useful both when considering the pig as a commodity and when extrapolating porcine data to human disease. Primary cultures of pig stromal-vascular cells have served as a useful tool for investigating factors that regulate preadipocyte proliferation and differentiation. However, such cultures have generally been maintained at 37°C in vitro despite euthermia being 39°C in pigs. To address potential concerns about the physiological relevance of culturing primary pig preadipocytes under what would be hypothermic conditions in vivo, the objective of this study was to investigate the effect of culture temperature on the proliferation and differentiation of pig preadipocytes in primary culture. Culturing primary preadipocytes at 37 rather than 39°C decreases their proliferation rates based upon cleavage of the tetrazolium salt, MTT (P < 0.001), reduction of resazurin (P < 0.001), and daily cell counts (P < 0.001). Likewise, culturing primary porcine preadipocytes at 37°C suppressed their adipogenic potential based upon monitoring adipogenesis morphologically, biochemically, and via the expression of mRNA encoding adipogenic marker genes. Collectively, these data indicate the proliferation and differentiation of primary pig preadipocytes is suppressed when cultures are incubated at 37°C compared to normal body temperature of pigs. This may confound investigation of factors that impact adipocyte hyperplasia in the pig.

Spontaneous intra-uterine growth restriction modulates the endocrine status and the developmental expression of genes in porcine fetal and neonatal adipose tissue

Low birth weight is correlated with low adiposity at birth, a phenotype that influences neonatal survival and later adiposity. A better understanding of events affecting the fetal adipose tissue development and its functionality around birth is thus needed. This study was undertaken to examine the impact of spontaneous intra-uterine growth restriction (IUGR) on circulating concentrations of hormones and nutrients together with the developmental expression patterns of various genes in subcutaneous adipose tissue of pig fetus during the last third of pregnancy and just after birth. At 71 and 112 days post-conception and 2 days postnatal, pairs of same-sex piglets were chosen within litters to have either a medium (MBW) or a low (LBW) weight (n=6 pairs at each stage). The results indicate that IUGR counteracts the temporal fall of DLK1 gene expression in developing adipose tissue across gestation. It also attenuates the time-dependent increase in expression levels of many genes promoting adipocyte differentiation (PPARG, CEBPA) and lipogenesis (LPL, SREBF1, FASN, FABP4). Opposite responses to IUGR were observed for the IGF system, so that IGF1 mRNA levels were lower (P<0.001) but IGF2 mRNA levels were greater in adipose tissue of LBW piglets compared with MBW piglets. The plasma insulin concentration and the mRNA levels of insulin receptor (INSR) and insulin-responsive glucose transporter (GLUT4) in adipose tissue were also greater in LBW piglets at day 2 postnatal. The data indicate that IUGR delays the normal ontogeny of adipose tissue across gestation and affects the insulin and IGF axes around birth.

The suckling piglet as an agrimedical model for the study of pediatric nutrition and metabolism

The neonatal pig ranks among the most prominent research models for the study of pediatric nutrition and metabolism. Its precocial development at birth affords ready adaptation to artificial rearing systems, and research using this model spans a wide array of nutrients. Sophisticated in vitro and in vivo methodologies supporting both invasive, reduction-science research as well as whole-animal preclinical investigations have been developed. Potential applications may dually benefit both agricultural and medical sciences (e.g., "agrimedical research"). The broad scope of this review is to outline the fundamental elements of the piglet model and to highlight key aspects of relevance to various macronutrients, including lipids, carbohydrates, proteins/amino acids, and calcium/phosphorus. The review examines similarities between piglets and infants and also piglet idiosyncrasies, concluding that, overall, the piglet represents an adaptable and robust model for pediatric nutrition and metabolism research.

Calcium ions released from mineral trioxide aggregate convert the differentiation pathway of C2C12 cells into osteoblast lineage

INTRODUCTION

The purpose of this study was to examine the effect of mineral trioxide aggregate (MTA) on pluripotent-mesenchymal cell differentiation.

METHODS

The pluripotent-mesenchymal cell line C2C12 was cultured in a 5% serum medium to induce cell differentiation with or without MTA. The differentiation to myoblasts was analyzed by the immunocytochemical staining of myosin heavy chains. The cellular phenotype-specific markers characterizing the osteoblasts (Runx2 and osterix), chondroblasts (Sox9), myoblasts (MyoD), and adipocytes (LPL) were estimated with mRNA and protein levels by using real-time polymerase chain reaction and Western blot analysis, respectively. To verify that the effect of MTA was caused by the released calcium ions, the mRNA levels were analyzed in the presence or absence of MTA with ethylene glycol tetraacetic acid, calcium chloride, or verapamil.

RESULTS

C2C12 cells cultured without MTA altered their phenotype to myoblasts, exhibiting positive reactions to myosin heavy chains. However, the cells cultured with MTA were strongly inhibited from developing into myoblasts. The mRNA and protein expressions of Runx2, osterix, and Sox9 significantly increased with MTA; the expressions of MyoD and LPL decreased significantly. Calcium chloride addition without MTA presented a significant increase of mRNA levels of Runx2, osterix, and Sox9; ethylene glycol tetraacetic acid addition with MTA presented a significant increase of mRNA levels of MyoD and LPL. Verapamil blocked the stimulating or suppressing effect of MTA on these transcription factors.

CONCLUSIONS

Our study showed that MTA converted the differentiation pathway of C2C12 cells into osteoblast and/or chondroblast lineages as a result of elution components such as calcium ions from MTA.

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.

Gene expression profiling in developing pig adipose tissue: non-secreted regulatory proteins

The expression of many genes encoding secreted and non-secreted factors have been studied in human and rodent adipose tissue with cDNA microarrays, but few such studies in adipose tissue from growing pigs have been reported. Total RNA was collected at slaughter from outer subcutaneous adipose tissue (OSQ) and middle subcutaneous adipose tissue (MSQ) samples from gilts at 90, 150 and 210 days (n = 5/age). Dye-labeled cDNA probes were hybridized to custom microarrays (70-mer oligonucleotides) representing about 600 pig genes involved in growth and reproduction. Gene expression intensity ratios changed little with age for 100 transcription factors, nuclear receptors, enzymes and other regulatory proteins in OSQ and MSQ from pigs between 90 and 210 days of age. However, the relative expression of 13 genes distinguished OSQ and MSQ depots in growing pigs. The expression of several genes were influenced by age including an increase in CCND3, HSF1 and PTGR1 expression in MSQ and a decrease in UCP2 and REA (prohibitin-2) expression in OSQ. These studies demonstrate for the first time the expression of several key regulatory genes in pig adipose tissue. Simple linear regression analysis showed that leptin gene expression was associated with expression of some of these regulatory genes. Negative associations between expression of some regulatory factors and leptin gene expression indicated that local leptin may decrease or antagonize adipogenesis.

Expression of lipogenic genes during porcine intramuscular preadipocyte differentiation

Intramuscular fat (IMF) content plays an important role in meat quality. Triglyceride (TG) metabolism in intramuscular adipocytes is strongly associated with the intramuscular fat deposition. To better understand the mechanisms leading to IMF deposition we compared the expression levels of genes related to preadipocyte differentiation and lipogenesis in the intramuscular preadipocytes isolated from the longissimus muscle of Wujin and Landrace pigs. The results showed that the intramuscular preadipocytes could differentiate into mature adipocytes in vitro. Triglyceride content in adipocytes isolated from Wujin pigs was higher than Landrace pigs during the middle and later phases of preadipocyte differentiation. The expression levels of genes related to preadipocyte differentiation such as PPARG and CEBPA showed differential expression between Wujin and Landrace porcine adipocytes during the early stage of differentiation. The expression levels of lipogenic genes such as FASN and SREBF1 were significantly higher in Wujin porcine intramuscular preadipocytes than in Landrace intramuscular preadipocytes at the middle and the later stages of differentiation. This suggests that preadipocyte differentiation and lipogenesis exhibited breed-related scheduling.

Aloe-emodin inhibits adipocyte differentiation and maturation during in vitro human mesenchymal stem cell adipogenesis

In this study, we examined the effects of Aloe-emodin (AE) on the inhibition of adipocyte differentiation during 3-isobutyl-1-methylxanthine (IBMX)-induced adipocyte differentiation in human mesenchymal stem cells (hMSCs). AE treatment (5, 10, and 20 µM) of preadipocyte cells resulted in a significant (p < 0.05) decrease in glycerol phosphate dehydrogenase and triglyceride levels as well as an increase in lactate dehydrogenase activity and attenuated lipid accumulation compared with untreated differentiated adipocytes. Using quantitative reverse transcription polymerase chain reaction, we studied the mRNA expression levels of resistin, adiponectin, aP(2), lipoprotein lipase, PPARγ, and tumor necrosis factor-α in hMSCs undergoing adipocyte differentiation; treatment with AE decreased the expression of these adipogenic genes and decreased adipocyte differentiation. In addition, AE suppresses the differentiation of hMSCs into adipocytes by downregulating PPARγ and C/EBPα expressions. AE significantly inhibited hMSCs proliferation and preadipocyte differentiation within the first 2 days of treatment, indicating that the antiadipogenic effect.

Feeding docosahexaenoic acid to pigs reduces blood triglycerides and induces gene expression for fat oxidation

Meadus, W. J., Duff, P., Rolland, D., Aalhus, J. L., Uttaro, B., and Dugan, M. E. R. 2011. Feeding docosahexaenoic acid to pigs reduces triglycerides in blood and induces gene expression for fat oxidation in liver and adipose but not in muscle. Can. J. Anim. Sci. 91: 601–612. The essential fatty acids required in diets of humans are linoleic acid (18:2n-6:LA) and α-linolenic acid (18:3n-3: ALA), and these can be elongated and desaturated to form long-chain omega-6 or omega-3, respectively. Even though not considered essential, consumption of long-chain omega-3 fatty acid is recommended for health benefits, including protection against cardiovascular disease. The omega-3 fatty acid, docosahexanoic acid (DHA), was supplemented in pig diets as a dried biomass of the microalgae Schizochytrium to see if there are unique physiological changes associated with DHA feeding. Pigs were fed a diet with 330 mg (low), 3600 mg (medium) or 9400 mg (high) DHA per day for the last 25 d before slaughter at market weight (∼110 kg). Blood triglycerides (TG) were assayed colormetrically and tissue samples were analyzed for gene expression patterns of RNA by quantitative real-time polymerase chain reaction. Fatty acids were analyzed by gas chromatography. Animal performance appeared to increase with DHA, as shown by a 14% improved feed:gain ratio of 2.74±0.27 (P<0.05). Blood triglycerides were reduced significantly from 0.40±0.23 mM to 0.20±0.09 mM. Pigs accumulated 14 times more DHA in their subcutaneous fat (SQ) (10.67 mg g−1) on the high diet compared with the control diet (0.75 mg g−1). Gene analysis showed that the expression of the fat oxidation biomarkers acyl CoA oxidase 1 (ACOX1), peroxisome proliferator-activated receptors alpha (PPARα) and gamma (PPARγ) were stimulated in the SQ and liver. The delta-6 desaturase (D6D) and elongase (Elov5), which are genes involved in the endogenous synthesis of DHA, were unchanged. Fatty acid synthase (FASN) was stimulated in the liver and muscle of pigs on the high DHA diet. Analysis of gene transcription activity suggested fat metabolism was stimulated in the liver and SQ fat, but the genes involved in the endogenous production of DHA remained unchanged.

Regulation of lipoprotein lipase gene expression by insulin and troglitazone in rainbow trout (Oncorhynchus mykiss) adipocyte cells in culture

Adipose tissue plays a central role regulating the balance between deposition and mobilization of lipid reserves. Lipoprotein lipase (LPL) is a key enzyme controlling lipid accumulation in mammals and fish. In the present study, we have examined the expression of LPL in rainbow trout cultured adipocytes and we have investigated the effect of troglitazone, a member of thiazolidinediones (TZDs), and insulin on its expression. LPL gene expression increased from day 1 until day 12 of culture, and the level was maintained up to day 21. The addition of insulin at 10 nM and 1.7 μM increased significantly LPL gene expression in undifferentiated cells (days 7 to 12 maintained in growth medium). Nevertheless, treatment of day 7 cells incubated in growth medium with troglitazone (5 μM) or troglitazone plus insulin (1 μM each), tended to enhance LPL expression. In addition, LPL mRNA levels increased significantly in the presence of 1 μM and 5 μM of troglitazone (days 7 to 12) when the cells were induced to differentiate by addition of differentiation medium. Although troglitazone alone (1 μM) did not stimulate lipid accumulation in the cells neither in growth nor in differentiation medium, the simultaneous presence of troglitazone (1 μM) and insulin (1 μM) increased significantly the content of triglycerides in adipocyte cells maintained in growth medium (days 7 to 12). These results indicate that insulin and troglitazone regulate LPL gene expression during adipocyte differentiation and suggest that both factors may have combined effects in the modulation of adipogenesis.

Visfatin regulates genes related to lipid metabolism in porcine adipocytes

Visfatin is a visceral adipose tissue-specific adipocytokine that plays a positive role in attenuating insulin resistance by binding to the insulin receptor. Visfatin has been suggested to play a role in the regulation of lipid metabolism and inflammation; however, the mechanism remains unclear. We investigated the effects of visfatin on the regulation of gene expression in cultured porcine preadipocytes and differentiated adipocytes. In preadipocytes, the mRNA abundance of lipoprotein lipase and PPARgamma were significantly increased by visfatin or insulin treatment after 8 d (all P < 0.05). In the presence of insulin, the mRNA abundance of adipocyte fatty acid-binding protein was 24.7-fold greater than in the untreated group (P < 0.05), whereas visfatin alone had no effect on adipocyte fatty acid-binding protein mRNA abundance. Adipocyte differentiation was induced by insulin treatment for 8 d. In differentiated porcine adipocytes, exposure to insulin or visfatin for 24 h increased (P < 0.05) fatty acid synthase mRNA abundance but had no effect on the expression of sterol regulatory element binding-protein 1c mRNA. We also found a 5.8-fold upregulation of IL-6 expression in porcine adipocytes after 24 h of treatment with visfatin (P < 0.05). These results demonstrated that visfatin upregulated lipoprotein lipase expression in preadipocytes, potentially facilitating lipid uptake, and increased the gene expression of fatty acid synthase in differentiated adipocytes to potentially enhance lipogenic activity. Furthermore, visfatin can upregulate IL-6 expression in differentiated porcine adipocytes. The information presented in this study provides insights into the roles of visfatin in lipid metabolism in pigs.

Docosahexaenoic acid regulates serum amyloid A protein to promote lipolysis through down regulation of perilipin

Docosahexaenoic acid (DHA) increases lipolysis and decreases lipogenesis through several pathways. DHA also enhances the expression of serum amyloid A protein (SAA), a possible lipid metabolism related gene. The question of whether DHA regulates the expression of SAA to affect lipid metabolism and increase lipolysis needs to be demonstrated in human adipocytes. We designed experiments to determine the role of SAA in regulating lipid metabolism in HepG2 cells using microarray technology. In human hepatocytes, recombinant human SAA1 (hSAA1) inhibited the expression of genes related to lipogenesis and promoted the expression of those involved in lipolysis. When human breast adipocytes were treated with hSAA1 or DHA in vitro, the expression of peroxisome proliferator-activated receptor gamma and other lipogenic genes was decreased, whereas the expression of several lipolytic genes was increased. Glycerol release was increased by both SAA and DHA treatments, suggesting that they increased lipolytic activity in human adipocytes. The expression of perilipin, a lipid droplet-protective protein, was decreased, and hormone-sensitive lipase was increased by both of hSAA1 and DHA treatment. We speculate that the mechanism of lipolysis by DHA or SAA is at least partially the result of increased expression of hormone-sensitive lipase and decreased expression of perilipin. Whereas DHA treatment increased expression of hSAA1 in human adipocytes, the DHA-mediated reduction in expression of lipogenesis genes and enhancement of lipolysis may be through the activity of hSAA1. These results may be useful in developing new approaches to reduce body fat deposition.

Identification of differentially expressed genes in a porcine in vivo model of adipogenesis using suppression subtractive hybridization

Although they provide valuable information, in vitro models of adipocyte development often require high doses of hormones and growth factors, which may influence gene expression and adipocyte differentiation patterns. To overcome these problems, a novel in vivo model of adipose tissue development was used to characterize genes involved in adipogenesis. The suppression subtractive hybridization technique was used to identify genes showing differential expression between the adipose tissue of a day 90 gestating sow, which is enriched in adipocytes, and day 90 fetal adipose tissue, which is enriched in preadipocytes. A total of 149 expressed sequence tags corresponding to identified genes and tentative consensus sequences emerged. Thirty-seven clones matched expressed sequence tags or genomic DNA sequences and six novel sequences were also identified. Adipogenesis-related genes were identified, many of which have never been reported to be expressed in mammalian adipose tissue, and may play a role in regulation of adipose tissue differentiation. Validation of differentially expressed genes was confirmed for perilipin, monocyte to macrophage differentiation-associated, myocilin, paraoxonase 3, stearoyl-CoA desaturase, angiotensinogen and adiponectin genes using real-time RT-PCR.

Identification of genes downregulated during differentiation of porcine mesenteric adipocytes

Adipose tissue development is a process that comprises not only hypertrophy, but also hyperplasia, of adipocytes. Although the proliferation of undifferentiated preadipocytes plays an important part in hyperplasia, this process is less well understood than the post-proliferation differentiation process. Despite the potential importance of porcine visceral adipose tissue to both meat production and biomedical research, there has been little study of this tissue and, in particular, its development and differentiation. To detect the genes involved in the maintenance of porcine visceral preadipocytes in an undifferentiated state or in the inhibition of adipocyte differentiation, we performed suppression subtractive hybridization using mesenteric preadipocytes in which fragments of the genes that are downregulated at 2 d of differentiation were enriched. We selected 672 clones and subjected them to differential screening and semiquantitative reverse transcription (RT)-PCR. As a result, we identified 34 downregulated genes. Among these, the detailed expression patterns of 6 genes were examined using real-time RT-PCR in both preadipocytes during in vitro differentiation and cell fractions directly isolated from pig mesenteric adipose tissue. The expressions of connective tissue growth factor, AXL receptor tyrosine kinase, stromal membrane-associated protein 1-like, and retinoic acid-induced 14 were significantly downregulated during adipocyte differentiation in vitro (P < 0.05), and the expressions of Rho/Rac guanine nucleotide exchange factor 2 and secreted frizzled-related protein 4 also tended to be decreased, although not significantly. Furthermore, all 6 genes showed significantly greater expression in stromal vascular cells, which contain preadipocytes, than in mature adipocytes (P < 0.05), raising the possibility that these genes are involved in adipocyte differentiation in vivo as well as in vitro.

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.

Serum amyloid A protein regulates the expression of porcine genes related to lipid metabolism

Serum amyloid A protein (SAA) is an apolipoprotein that can replace apolipoprotein A1 (apoA1) as the major apolipoprotein of HDL. Porcine hepatic SAA mRNA is increased by dietary docosahexaenoic acid (DHA) treatment. The purpose of this study was to investigate the role of SAA protein in regulating gene expression related to lipid metabolism in pigs. First, we demonstrated that the 100-micromol/L DHA treatment increased SAA and apoA1 mRNA expression in porcine hepatic cell cultures (P < 0.05). Secondly, we produced porcine SAA recombinant protein and found that the addition of SAA to porcine preadipocytes in culture stimulated interleukin-6 (IL-6) mRNA expression (P < 0.05), indicating a similar biological function of porcine SAA and human SAA. We also found PPARalpha and PPARgamma mRNA were decreased (40 and 60%, respectively) in differentiated adipocytes after treatment with 2 mumol/L SAA. SAA treatment also increased inflammatory cytokine gene expression (IL-6 and tumor necrosis factor alpha) and glycerol release (P < 0.05), indicating increased lipolysis. Because the expression of perilipin, a lipid droplet-protective protein, was reduced by the SAA treatment, we hypothesized that SAA increased lipolysis by decreasing the expression of perilipin, which would then allow an increase in hormone sensitive lipase activity. In conclusion, we demonstrated that the DHA-induced SAA gene expression decreased PPAR expression and consequently downregulated the expression of several genes involved in lipid metabolism. Accordingly, SAA may play a critical role in mediating the function of dietary DHA on lipid metabolism and could be a factor in regulating obesity.

Porcine peroxisome proliferator-activated receptor gamma induces transdifferentiation of myocytes into adipocytes

Peroxisome proliferator-activated receptor gamma2 (PPARgamma) is a nuclear transcription factor that regulates adipocyte differentiation and lipogenic genes during adipogenesis. The activity of rodent PPARgamma is regulated by phosphorylation of serine 112. The current experiment was designed to study the ability of porcine PPARgamma to stimulate transdifferentiation of myoblasts to adipocytes by overexpressing wild-type PPARgamma or mutated PPARgamma (serine 112 was mutated to alanine) in mouse myoblast cells. The expression of adipogenic marker genes (adipocyte fatty acid binding protein, lipoprotein lipase, and glycerol-3 phosphate dehydrogenase) in cells stably expressing mutated porcine PPARgamma was greater than in cells with wild-type PPARgamma, indicating that the mutated PPARgamma has greater adipogenic capability than the wild-type PPARgamma. Under treatment with a ligand, both wild-type and mutant porcine PPARgamma-expressing C2C12 myoblasts differentiated into adipocytes in 10 d. The expression of myogenic marker genes (myogenin, myogenic regulatory factor-4) was suppressed in cells transfected with the mutated PPARgamma or wild-type PPARgamma. Moreover, wild-type and mutant PPARgamma were able to inhibit myogenesis without addition of a ligand. Our results suggest that porcine wild-type PPARgamma and mutated PPARgamma can both convert myoblast cells into adipocytes, and also that the ability to transdifferentiate was greater in cells containing the mutated PPARgamma than in cells containing the wild-type PPARgamma. Therefore, the existence of serine 112 in PPARgamma may have a role in regulating adipocyte differentiation.

Abundantly expressed genes in pig adipose tissue: an expressed sequence tag approach

Adipose tissue plays a critical role in metabolism, storage, and release of fatty acids in mammals. Construction of a full-length cDNA library is an effective way to understand the functional expression of genes in adipose tissue, and in addition, novel genes for further research can be found in the library. In this study, adipose tissue RNA was extracted from three 18-mo-old Lee-Sung pigs. The mRNA was isolated, reverse transcribed, and used to construct a cDNA library. After transformation, 2,880 clones were selected and sequenced. Cluster analysis was performed, and the assembled contig of each cluster was subjected to search against DNA sequences in the nucleotide databases (NCBINR/TIGRGI). These sequences were clustered into 1,527 unique sequences; 80% of the sequences were categorized as known genes, and 20% of the sequences were categorized as unknown genes. In this adipose tissue cDNA library, approximately 16% of the genes contained full-length sequences with start and stop codons. Gene ontology analysis was performed to indicate the possible functions of these genes. Genes associated with mitochondrial function were abundant and represented 10% of the total. Several fatty acid transport genes and stearoyl coenzyme A desaturase were among the most abundant genes expressed. Tissue distribution of several abundant genes was analyzed by northern analysis, and many of these genes were transcribed in porcine adipose tissue in high copy number. Our full-length sequence data and tissue distribution data can be used to decipher the functional roles exhibited by the adipocyte under various perturbations via endocrine, environmental, genetic, nutritional, pharmacological, or physiological manipulations.

Isomer-specific regulation of differentiating pig preadipocytes by conjugated linoleic acids

Conjugated linoleic acids are a group of geometric and positional isomers of linoleic acid that decrease body fat in growing animals by a poorly understood mechanism. The objective of this study was to investigate the isomer-specific effect of CLA on the proliferation and differentiation of pig preadipocytes in primary culture. The effect of CLA on preadipocyte proliferation was determined using cleavage of the tetrazolium salt, WST-1, as a marker for proliferation. Preadipocyte number was decreased in a dose-dependent fashion by trans-12,cis-10 CLA (P < 0.05). No other fatty acid affected preadipocyte number. Differentiation was monitored on d 10 after induction morphologically, enzymatically, and by measuring the mRNA abundance of key adipogenic transcription factors. Both a crude CLA preparation containing a mixture of CLA isomers (CLA-mix) and the pure trans-10,cis-12 CLA isomer inhibited glycerol-3-phosphate dehydrogenase (GPDH) activity in a dose-dependent fashion, with trans-10,cis-12 CLA being more potent (P < 0.01) than the CLA-mix. Cis-9,trans-11 CLA failed to decrease GPDH activity; however, increasing concentrations of cis-9,trans-11 CLA tended to blunt the inhibitory effect of trans-10,cis-12 CLA on GPDH activity (P < 0.09), suggesting that cis-9,trans-11 CLA may antagonize the action of trans-10,cis-12 CLA in porcine adipocytes. Finally, the isomer-specific effect of CLA on adipogenic transcription factor gene expression was investigated. Trans-10,cis-12 CLA decreased expression of peroxisome proliferator-activated receptor gamma (PPAR gamma; P < 0.01) and sterol regulatory element-binding protein-1c (SREBP-1c; P < 0.05) mRNA, while failing to alter the expression of CCAAT/enhancer binding protein alpha (C/EBPalpha) mRNA. Interestingly, both the CLA-mix and the trans-10,cis-12 CLA isomer increased the mRNA abundance of chicken ovalbumin upstream promoter transcription factor 1 (COUP-TF; P < 0.002). No other fatty acid affected COUP-TF mRNA levels. Collectively these data support the concept that CLA decreases fat accretion in pigs, in part by inhibiting preadipocyte proliferation and differentiation, with trans-10,cis-12 CLA being an active isomer eliciting these effects. Furthermore, trans-10,cis-12 CLA inhibits porcine preadipocyte differentiation by a mechanism that involves the down-regulation of PPARgamma and SREBP-1c mRNA. This mechanism is independent of changes in C/EBPalpha mRNA abundance and may involve COUP-TF.

PPARgamma and GLUT-4 expression as developmental regulators/markers for preadipocyte differentiation into an adipocyte

In this document, we have integrated knowledge about two major cellular markers found in cells of the adipocyte lineage (an adipogenic marker and a metabolic marker). This review provides information as to how differentiation of a cell (such as an adipofibroblast, fibroblast or preadipocyte) to become a viable (and new) adipocyte is under different regulation than that experienced by an immature adipocyte that is just beginning to accumulate lipid. The differentiation, prior to lipid-filling, involves PPARgamma. Subsequently, lipid-filling of the adipocyte relies on a late subset of genes and, depending on depot specificity, involves GLUT-4 or any number of other metabolic markers.

Clofibrate causes an upregulation of PPAR-α target genes but does not alter expression of SREBP target genes in liver and adipose tissue of pigs

This study investigated the effect of clofibrate treatment on expression of target genes of peroxisome proliferator-activated receptor (PPAR)-α and various genes of the lipid metabolism in liver and adipose tissue of pigs. An experiment with 18 pigs was performed in which pigs were fed either a control diet or the same diet supplemented with 5 g clofibrate/kg for 28 days. Pigs treated with clofibrate had heavier livers, moderately increased mRNA concentrations of various PPAR-α target genes in liver and adipose tissue, a higher concentration of 3-hydroxybutyrate, and markedly lower concentrations of triglycerides and cholesterol in plasma and lipoproteins than control pigs ( P < 0.05). mRNA concentrations of sterol regulatory element-binding proteins (SREBP)-1 and -2, insulin-induced genes ( Insig) -1 and Insig-2, and the SREBP target genes acetyl-CoA carboxylase, 3-methyl-3-hydroxyglutaryl-CoA reductase, and low-density lipoprotein receptor in liver and adipose tissue and mRNA concentrations of apolipoproteins A-I, A-II, and C-III in the liver were not different between both groups of pigs. In conclusion, this study shows that clofibrate treatment activates PPAR-α in liver and adipose tissue and has a strong hypotriglyceridemic and hypocholesterolemic effect in pigs. The finding that mRNA concentrations of some proteins responsible for the hypolipidemic action of fibrates in humans were not altered suggests that there were certain differences in the mode of action compared with humans. It is also shown that PPAR-α activation by clofibrate does not affect hepatic expression of SREBP target genes involved in synthesis of triglycerides and cholesterol homeostasis in liver and adipose tissue of pigs.

Effects of RXRalpha gene silencing on the porcine adipocyte differentiation in vitro

The elucidation of the molecular mechanism of porcine adipocyte differentiation is important not only to domestic animal industry, but also to medical science because of the similarities in the trait of body lipid deposition between human and pigs. In this study, we investigated the roles of RXRalpha in porcine (Sus scrofa) adipocyte differentiation by using RNAi method and primary cultured porcine adipocytes. With the transfection of RXRalpha-siRNA, the gene and protein expressions of RXRalpha were successfully inhibited in differentiating porcine adipocytes. By the RXRalpha gene silencing, the adipocyte differentiation, as characterized by lipid accumulation and GPDH activity, was suppressed. Furthermore, in association with the decrease in RXRalpha gene expression level, PPARgamma and C/EBPalpha genes expression level also decreased, suggesting that RXRalpha is involved in their expression. Thus, our study clearly demonstrated the pivotal roles of RXRalpha in porcine adipocyte differentiation.

Heart fatty acid binding protein is upregulated during porcine adipocyte development

Heart fatty acid binding protein (H-FABP) has been associated with intramuscular fat content in pigs. In the current study, we showed that expression of H-FABP mRNA in adipose tissue of adult pigs was 8.5% of that in heart and 30% of that in skeletal muscle, and that H-FABP mRNA level was more than 10% of that of adipocyte fatty acid binding protein mRNA in adipose tissue. Levels of H-FABP mRNA reached a maximum in adipose tissue from 7-d neonates, with no further increase in the adult. Also, H-FABP mRNA was induced during adipogenic differentiation of stromal-vascular cells derived from adipose tissue and skeletal muscle. In conclusion, H-FABP may play a role in adipose tissue development and function in the pig.

Myostatin inhibits differentiation of bovine preadipocyte

We investigated the effect of myostatin on the differentiation of bovine preadipocyte. Stromal-vascular cells containing preadipocytes were prepared from perirenal adipose tissue of approximately 30-month-old Japanese Black steers. After confluence, the differentiation was induced by 1-methyl-3-isobutyl-xanthine, dexamethasone, insulin, and troglitasone for 2 days, and then subsequently cultured for 6 days. The cells were treated with myostatin during the induction of differentiation (the early phase of differentiation) or throughout the differentiation period. We measured the terminal differentiation markers such as glycerol-3-phosphate dehydrogenase activity, lipid accumulation, and the expression of adipocyte fatty acid-binding protein mRNA at the end of cultures. The treatment with myostatin throughout the differentiation period severely suppressed the induction of all differentiation markers. The treatment with myostatin in the early phase of differentiation also suppressed the induction of terminal differentiation markers but three-fold higher dose of myostatin was required for the suppression compared with its treatment throughout the differentiation period. Myostatin treatment reduced the expression of peroxisome proliferator-activated receptor (PPAR) gamma mRNA and interfered with the induction of CCAAT/enhancer binding protein (C/EBP) alpha mRNA. We also observed that follistatin stimulates preadipocyte differentiation in the presence of myostatin. These results suggest that myostatin inhibits bovine preadiopocyte differentiation through suppressing PPARgamma and C/EBPalpha mRNA expressions and that follistatin counteracts the suppressive effect of myostatin.

Modulation of peroxisome proliferator-activated receptor delta and gamma transcripts in swine endometrial tissue during early gestation

Recent evidence points to a role for peroxisome proliferator-activated receptors (PPARs) delta and gamma in embryo implantation and survival. In this study, we report the porcine PPARdelta complete coding sequence and mRNA abundance of PPARdelta, PPARgamma1 and gamma2, angiopoietin-like protein 4 (ANGPTL4) and adipocyte determination and differentiation-dependent factor 1 (ADD1) genes in the pregnant sow endometrium. Real-time PCR analysis was used to study the effect of parity (Yorkshire-Landrace multiparous (YL) and nulliparous (YLn)), site of endometrial tissue sampling (between and at embryo attachment sites) in crossbred DurocxYorkshire-Landrace (DYL) sows and stages of pregnancy (non-pregnant, day 15 and day 25 after mating) in Meishan-Landrace (ML) on mRNA levels. Parity effects were observed for PPARdelta, ANGPTL4, and ADD1, with higher mRNA levels in YL than YLn sows. In DYL sows, lower mRNA levels were present at attachment sites compared to between attachment sites for PPARdelta, PPARgamma1, and ANGPTL4. Finally, day 15 pregnant ML sows had lower PPARdelta mRNA levels compared to day 15 cycling ML sows. A significant increase of PPARgamma1 mRNA levels was found on day 25 pregnant ML and DYL sows relative to day 15 ML or DYL pregnant sows. PPARdelta and gamma immunostaining was detected in endometrial tissue of day 15 cycling sows, day 15 and 25 pregnant sows and epithelial cells of day 25 embryos. Collectively, our results suggest a role for PPARdelta, PPARgamma1, and ANGPTL4, but not PPARgamma2, during the peri-implantation period in pregnant sows.

Alternative splicing of delta-like 1 homolog (DLK1) in the pig and human

Delta-like homolog 1 (DLK1), a paternally imprinted gene with several alternative splicing isoforms, is an important regulator of fetal and postnatal development. We report the sequence of porcine DLK1 (pDLK1) and examine the expression and alternative splicing isoforms in the pig (Sus scrofa) and human. DLK1-A was the sole isoform identified in human tissues and has been shown to be present in mouse and cattle. Surprisingly, DLK1-A was undetected in various tissues from fetal and postnatal pigs. Instead, DLK1-C2 was the most abundant isoform while DLK1-B was expressed to a lesser extent. In fractionated adipose tissue, pDLK1 was most highly expressed in the stromal-vascular cell fraction. In addition, total pDLK1 was highly expressed in fetal adipose tissue but dramatically decreased postnatally. Our data suggests that expression of DLK1-B and -C2 isoforms is sufficient for normal pig development. Furthermore, human and pig samples showed no alterations in species-specific splicing, but expression levels decreased with age, suggesting that regulation of expression, not splicing, is the most likely mechanism controlling the biological function of DLK1.

Cloning and expression of porcine adiponectin and adiponectin receptor 1 and 2 genes in pigs

In mice, adiponectin receptors (AdipoR) have been found to mediate the effect of adiponectin in muscle and liver in regulation of glucose and fatty acid metabolism. The purposes of this study were to clone these receptors from pig tissues by reverse transcription PCR using mRNA from skeletal muscle and adipose tissue and to investigate the expression of these genes in various pig tissues. Sequences of adiponectin, AdipoR1, and AdipoR2 were determined and found to be highly homologous to those of the human and mouse. The AA sequences predicted for the full-length cDNA of porcine adiponectin, AdipoR1, and AdipoR2 were similar to those of the human and mouse, ranging from 81 to 97% homology, suggesting similar functions of these genes in pigs as in other species. Transcripts for adiponectin were abundant in s.c. adipose tissue in Lee-Sung pigs and in crossbred pigs. Transcripts for AdipoR1 were abundant in heart and skeletal muscle and also detected to a lesser extent (P < 0.05) in adipose tissue, liver, and spleen of the Lee-Sung pigs. Transcripts for AdipoR2 were abundant in s.c. adipose tissue and present to a lesser extent (P < 0.05) in the liver, heart, skeletal muscle, and spleen. These results indicate that the effect of adiponectin may be mediated through these receptors in various porcine tissues. Fasting for 8 h did not have a significant effect on the expression of adiponectin and AdipoR1 mRNA, but it increased (P < 0.05) the AdipoR2 mRNA in the s.c. adipose tissue of crossbred pigs. These results indicate that the AdipoR2-mediated fatty acid oxidation may be responsible at least in part for the fasted state fatty acid oxidation in porcine adipose tissues. The successful cloning of pig adiponectin and adiponectin receptors will enhance the understanding of the involvement of these genes in regulating energy metabolism in pigs.

The expression of genes related to adipocyte differentiation in pigs1

The purpose of this study was to detect differential expression of genes related to adipocyte differentiation in pigs by suppression subtractive hybridization. Adipocytes and stromal vascular cells (a fraction containing preadipocytes) from pig adipose tissue were isolated for mRNA extraction. The cDNA from preadipocytes was subtracted from the cDNA from adipocytes. The subtracted gene fragments were cloned into pGEM-T Easy TA cloning vector. We selected 384 clones for gene sequence determination and for further analysis. These genes were subjected to a differential screening procedure to confirm the differential expression of genes between the 2 cell types. We found that at least 36 genes were highly expressed in the adipocytes compared with preadipocytes. Among these, 6 genes including 2 novel genes with the greatest differences were selected and confirmed by Northern analysis. We found that angiotensin I-converting enzyme (ACE), ataxia-telangiectasia mutated protein (ATM), calpain 1, and stearoyl coenzyme A desaturase 1 (SCD1) were highly expressed in adipocytes compared with preadipocytes (P < 0.05). The relative mRNA abundance of ACE, ATM, calpain 1, SCD1, and 2 novel genes discovered in the current study was increased at the later stages of adipocyte differentiation (P < 0.05). The results confirmed that the genes involved in lipid metabolism and adipocyte differentiation were highly expressed in porcine adipocytes. However, further investigation is needed to demonstrate specific functions of the novel genes discovered in the current study.

Low Birth Weight and Male Reproductive Function

Scientific interest in morbidity in children born small for gestational age (SGA) has increased considerably over the last few decades. The elevated risk of cardiovascular and metabolic diseases in adulthood in individuals born SGA has been well documented, whereas data on gonadal development are limited. Prospective studies, case-control investigations and registry surveys show that impaired intrauterine growth increases the risks of congenital hypospadias, cryptorchidism and testicular cancer approximately two- to threefold. Although few studies focus on the effect of intrauterine growth on male pubertal development, testicular hormone production or sperm quality, available evidence points towards a subtle impairment of both Sertoli cell and Leydig cell function. Animal studies support the hypothesis that impaired perinatal growth restriction, depending on the timing, can affect postnatal testis size and function into adulthood. Current human data, however, are often based on highly selected hospital populations and lack precise distinctions between low birth weight, SGA, timing of growth restriction and a differentiation of catch-up growth patterns. Despite the methodological inadequacies of individual study results, the combined evidence from all data leaves little doubt that fetal growth restriction is associated with increased risk of male reproductive health problems, including hypospadias, cryptorchidism and testicular cancer.

Identification and characterization of novel peroxisome proliferator-activated receptor-gamma (PPAR-gamma) transcriptional variants in pig and human

The peroxisome proliferator-activated receptor-gamma (PPAR-gamma) is a member of the steroid/thyroid/retinoid receptor superfamily, and is primarily expressed in fat tissue. To date, two major PPAR-gamma isoforms have been identified in pig, PPAR-gamma1 and PPAR-gamma2. Porcine PPAR-gamma1a consists of two leader exons, designated A1 and A2, followed by six exons containing the open reading frame. Here, we report the isolation and characterization of three novel PPAR-gamma1 transcripts. PPAR-gamma1b is derived from exon A1, with exon A2 spliced out. PPAR-gamma1c and PPAR-gamma1d are derived from the new exon, A', containing exon A2 (gamma1c) or without exon A2 (gamma1d). Based on PCR analysis of PAC clones that included sequences from the 5'-untranslated region of the PPAR-gamma gene, the new A' exon is located between the known exons A1 and A2. We also isolated the human homologue to exon A', as well as the two new PPAR-gamma1c and -gamma1d splice variants, from human adipose tissue. Studies of the expression of porcine PPAR-gamma by real time reverse transcription-polymerase chain reaction analysis show that transcripts derived from exon A1 were not expressed at significantly different levels in visceral fat (lamina subserosa) or subcutaneous fat (back fat, inner and outer layer). In contrast, exon A'-derived transcripts were expressed at progressively higher levels in the inner and outer layers of subcutaneous fat than in visceral fat. The same expression pattern was also observed for PPAR-gamma2. We hypothesize that there are three promoters, which differentially regulate PPAR-gamma1 and PPAR-gamma2 gene expression, depending on the specific localization of the fat tissue.

Effect of docosahexaenoic acid and arachidonic acid on the expression of adipocyte determination and differentiation-dependent factor 1 in differentiating porcine adipocytes1

Adipocyte determination and differentiation-dependent factor 1 (ADD1) drives the expression of several lipogenic genes in mammals. Polyunsaturated fatty acids decrease ADD1 mRNA abundance in differentiating porcine adipocytes. The current study was designed to explore the mechanisms by which PUFA inhibit the expression of ADD1 in porcine adipocytes. Porcine preadipocytes were differentiated for 24 h with 0 or 100 microM of docosahexaenoic acid (DHA) and mixtures of different concentrations of antioxidants to investigate the effect of DHA and antioxidants on the ADD1 mRNA abundance. We found the relative mRNA abundance was decreased by the addition of 100 microM DHA to the medium for porcine differentiating adipocytes, and adding an antioxidant mixture to the medium prevented part of the decrease in ADD1 mRNA abundance. These data suggest that DHA decreased the steady-state transcription factor ADD1 mRNA through a mechanism related to fatty acid peroxidation. Indeed, adding 7.5 microM vitamin E (a natural antioxidant) also restored the concentrations of ADD1 and fatty acid synthase mRNA, which were decreased by DHA treatment; however, the DHA or the antioxidant treatment did not change the expression of antioxidation genes (superoxide dismutase 1 and glutathione peroxidase 1) in porcine stromal vascular cells. When supplemented with the eicosanoid synthesis pathway inhibitors, the inhibition of the expression of ADD1 by arachidonic acid was partially recovered. These results suggest that the mechanism by which PUFA decrease ADD1 mRNA is due to the metabolic product of eicosanoids and peroxidation of these PUFA.