Expression of porcine adipocyte transcripts during differentiation in vitro and in vivo

Association Between BMP2 Functional Polymorphisms and Sheep Tail Type

Bone morphogenetic protein 2 (BMP2) is strongly selected in both fat-tailed and thin-tailed sheep and may be a candidate gene for sheep tail type selection. However, the mechanism of action of BMP2 in sheep tail fat deposition remains unclear. This study investigated genetic variation and haplotype combinations of the BMP2 gene in sheep with different tail types, aiming to reveal the molecular mechanism of BMP2 in sheep tail fat deposition. We detected a total of three single nucleotide polymorphisms (SNPs) (g.48401619 T > A, g.48401272 C > A, and g.48401136 C > T) among 533 sheep. The alleles and genotype frequencies of these SNPs were in Hardy-Weinberg equilibrium and showed significant correlations with tail length. Linkage disequilibrium existed between the g.48401272 C > A and g.48401136 C > T sites, where CACT was the predominant genotype. At the cellular level, the expression levels of peroxisome proliferator-activated receptor gamma (PPARγ) and lipoprotein lipase (LPL) were upregulated after BMP2 overexpression; there were significantly higher levels of PPARγ than controls at 0 d and 1 d, and of LPL than controls at 1 d and 7 d. These results indicate that the BMP2 gene may participate in sheep tail fat deposition and could be used for molecular-marker-assisted selection of sheep tail type.

Lipid Deposition and Metabolism in Local and Modern Pig Breeds: A Review

Modern pig breeds, which have been genetically improved to achieve fast growth and a lean meat deposition, differ from local pig breeds with respect to fat deposition, fat specific metabolic characteristics and various other properties. The present review aimed to elucidate the mechanisms underlying the differences between fatty local and modern lean pig breeds in adipose tissue deposition and lipid metabolism, taking into consideration morphological, cellular, biochemical, transcriptomic and proteomic perspectives. Compared to modern breeds, local pig breeds accumulate larger amounts of fat, which generally contains more monounsaturated and saturated fatty acids; they exhibit a higher adipocyte size and higher activity of lipogenic enzymes. Studies using transcriptomic and proteomic approaches highlighted several processes like immune response, fatty-acid turn-over, oxidoreductase activity, mitochondrial function, etc. which differ between local and modern pig breeds.

Transcriptome Modifications in the Porcine Intramuscular Adipocytes during Differentiation and Exogenous Stimulation with TNF-α and Serotonin

Adipocytes are dynamic cells that have critical functions to maintain body energy homeostasis. Adipocyte physiology is affected by the adipogenic differentiation, cell program, as well as by the exogenous stimulation of biochemical factors, such as serotonin and TNF-α. In this work, we investigated the global transcriptome modifications when porcine intramuscular preadipocyte (PIP) was differentiated into porcine mature adipocyte (pMA). Moreover, we studied transcriptome changes in pMA after stimulation with serotonin or TNF-α by using a microarray approach. Transcriptome analysis revealed that the expression of 270, 261, and 249 genes were modified after differentiation, or after serotonin and TNF-α stimulation, respectively. Expression changes in APP, HNF4A, ESR1, EGR1, SRC, HNF1A, FN1, ALB, STAT3, CBL, CEBPB, AR, FOS, CFTR, PAN2, PTPN6, VDR, PPARG, STAT5A and NCOA3 genes which are enriched in the ‘PPAR signaling’ and ‘insulin resistance’ pathways were found in adipocytes during the differentiation process. Dose-dependent serotonin stimulation resulted in a decreased fat accumulation in pMAs. Serotonin-induced differentially expressed genes in pMAs were found to be involved in the significant enrichment of ′GPCR ligand-binding′, ‘cell chemotaxis’, ‘blood coagulation and complement’, ‘metabolism of lipid and lipoproteins’, ‘regulation of lipid metabolism by PPARA’, and ‘lipid digestion, mobilization and transport’ pathways. TNF-α stimulation also resulted in transcriptome modifications linked with proinflammatory responses in the pMA of intramuscular origin. Our results provide a landscape of transcriptome modifications and their linked-biological pathways in response to adipogenesis, and exogenous stimulation of serotonin- and TNF-α to the pMA of intramuscular origin.

The history of adipocyte and adipose tissue research in meat animals

Research in growth and development, accumulation of lean, and fat metabolism in farm animals was gaining attention principally from a carcass perspective by meat scientists and animal nutritionists about a century ago. Under the auspices of the USDA Cooperative State Research Service, State Agricultural Experiment Stations, and the Land Grant University system, researchers from various universities embarked on forming combined regional research projects (across states) with unifying specific aims. In the North Central region, this included states in the upper and lower Mid-West region. For those interested in improving production and eating quality of meats, initially a single multistate committee was formed in the North Central region which was active for many years. However, these efforts were later split into two committees with one addressing lipids and the other muscle biology. Herein we reviewed research of workers in the North Central region in the 1940s and 1950s and to a limited extent in the 2000s on meat animal's lipid metabolism. We further reviewed the history of meat animal carcass composition research and the influence of the Word War II (WWII) period on porcine carcass composition. The development and utilization of adipocyte cellularity research methodology in meat animals was demonstrated. The history of the progression of adipose tissue metabolism research in meat animals was also reviewed. Finally, the history of research on lipid deposition in muscle that ultimately precipitated the expanded marbling and the intramuscular research was delineated. By the 1970s, great interest had emerged on how to curtail excessive fat deposition in meat-producing animals. Thus, for some segments of the animal lipid metabolism community, the focus then shifted to exploring the processes of lipogenesis and lipolysis in farm animals. These efforts morphed into research efforts in fat cell biology and cellularity. Today adipocyte biology is studied by many in the biomedical and agricultural-life sciences communities. In this article, we present a history of this research and notable achievements up to the 1980s. Herein we revisit these research efforts and results that have become an important knowledge base for growth and development, nutrition, and meat science research.

Expression of genes involved in lipid droplet formation (BSCL2, SNAP23 and COPA) during porcine in vitro adipogenesis

Adipogenesis is a complex process of fat cells development driven by the expression of numerous genes. Differentiation of progenitor cells into mature adipocytes is accompanied by changes in cell shape, as a result of lipid accumulation. In the present study, expression of three genes involved in lipid droplet formation (SNAP23, BSCL2 and COPA) was evaluated during porcine adipogenesis. It was found that mRNA levels of BSCL2 and SNAP23, but not COPA, increased during differentiation. Redistribution of SNAP23 protein to different cellular compartments was observed when comparing undifferentiated mesenchymal stem cells and differentiated adipocytes. The BSCL2 protein was found to be highly specific to cells with accumulated lipids, while COPA protein coated the lipid droplets. Obtained results indicated that the studied genes may be considered as candidates for fatness traits in pigs. Moreover, this study has shown that the porcine in vitro adipogenesis system provides a useful tool for the characterisation of novel genes involved in adipose tissue accumulation.

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.

Ontogenetic development of adipose tissue in grass carp (Ctenopharyngodon idellus)

To investigate the adipose tissue development process during the early stages of grass carp (Ctenopharyngodon idellus) development, samples were collected from fertilized eggs to 30 days post-fertilization (dpf) of fish. Paraffin and frozen sections were taken to observe the characteristics of adipocytes in vivo by different staining methods, including hematoxylin and eosin (H&E), Oil red O, and BODIPY. The expression of lipogenesis-related genes of the samples at different time points was detected by real-time qPCR. In addition, protein expression level of peroxisome proliferator-activated receptors γ (PPAR γ) was detected by immunohistochemistry. The results showed that the neutral lipid droplets accumulated first in the hepatocytes of 14-dpf fish larvae, and visceral adipocytes appeared around the hepatopancreas on 16 dpf. As grass carp grew, the adipocytes increased in number and spread to other tissues. In 20-dpf fish larvae, the intestine was observed to be covered by adipose tissue. However, there was no significant change in the average size (30.40-40.01 μm) of adipocytes during this period. Accordingly, the gene expression level of PPAR γ and CCAAT/enhancer-binding proteins α (C/EBP α) was significantly elevated after fertilization for 12 days (p < 0.05), but C/EBP α declined at 20 dpf. Expression of lipoprotein lipase (LPL) increased from 2 to 16 dpf and then declined. In addition, immunoreaction of PPAR γ was positive on hepatocytes after fertilization for 15 days. These results implied that the early developmental stage of adipose tissue is caused by active recruitment of adipocytes as opposed to hypertrophy of the cell. In addition, our study indicated that lipogenesis-related genes might regulate the ongoing development of adipose tissue.

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.

Polymorphisms within angiotensin II receptor type 1 gene associated with essential hypertension in Chinese Hani and Yi minorities

INTRODUCTION

Angiotensin II receptor type 1 mediates the major cardiovascular effects of angiotensin II to regulate blood pressure. Polymorphisms of angiotensin II receptor type 1 are associated with essential hypertension, but the results are inconsistent and conflicting. The aim of the present study is to assess the association between angiotensin II receptor type 1 polymorphisms and essential hypertension risk in Chinese Hani and Yi minorities.

METHODS

This study recruited 692 unrelated Chinese Hani subjects (case vs. control = 346:346) and 615 unrelated Chinese Yi subjects (case vs. control = 303:312). Twelve selected single nucleotide polymorphisms in the angiotensin II receptor type 1 gene were genotyped using a polymerase chain reaction-restriction fragment length polymorphism method.

RESULTS

Statistical analysis indicated that the GC+CC genotype of rs387967 was significantly associated with the decreased susceptibility to essential hypertension compared with GG in a Yi population (odds ratio = 0.58, 95% confidence intervals 0.41-0.83, P = 0.003). Allele C was a protective allele for essential hypertension (odds ratio = 0.78, 95% confidence intervals 0.61-0.99, P = 0.040). This association was confirmed respectively by comparing systolic blood pressure and diastolic blood pressure between different genotypes and between different alleles, which indicated that the genotype (GC+CC) had a tendency of lower systolic blood pressure and diastolic blood pressure than GG (PSBP = 3.716 × 10(-4), PDBP = 1.187 × 10(-3)); Carriers with C had lower systolic blood pressure and diastolic blood pressure (PSBP = 7.301 × 10(-3), PDBP = 9.142 × 10(-4)). Another single nucleotide polymorphism (rs2638360) was analysed in a Hani minority, then replicated in a Yi minority. The C allele showed a consistent risk trend for essential hypertension in two independent populations (Hani: odds ratio = 1.74, 95% confidence intervals 1.01-2.99, P = 0.046; Yi: odds ratio = 1.27, 95% confidence intervals 0.82-1.96, P = 0.277). Meta-analysis revealed that the C allele could significantly increase the risk of essential hypertension (odds ratio = 1.44, 95% confidence intervals 1.02-2.02, P = 0.037).

CONCLUSION

Our findings suggest that rs387967 is associated with the susceptibility to essential hypertension in a Yi population and the tendency was replicated in systolic blood pressure and diastolic blood pressure detection. Meta-analysis revealed that C allele of rs2638360 could significantly increase the risk of essential hypertension. The two single nucleotide polymorphisms maybe play a role in the pathology of essential hypertension.

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.

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.

Towards candidate genes affecting body fatness at the SSC7 QTL by expression analyses

A quantitative trait locus (QTL) affecting fatness in a way opposite to expectations based on breed means was mapped to swine chromosome 7 (SSC7) using crosses between Large White (LW) and Meishan (MS) founders. Defining the molecular fatness trait more explicitly would allow deducing positional candidate genes, for which expression differences must be analysed in experimental populations. First, mRNA levels of genes representing sequential steps in adipogenesis or involved in lipid metabolism were studied in backfat of pigs having homozygous LW(QTL7)/LW(QTL7) or heterozygous LW(QTL7)/MS(QTL7) alleles and considered at two ages. mRNA level of DLK1 expressed in preadipocytes was greater in MS(QTL7)/LW(QTL7) pigs than in homozygous pigs at 28 days. Transcript abundances of CEBPA involved in differentiation, the prolipogenic FASN gene and the adipocyte-specific marker FABP4 were lower in MS(QTL7)/LW(QTL7) pigs compared with LW(QTL7)/LW(QTL7) pigs at 150 days. Because these results suggest a lag time in terminal differentiation associated with the MS allele, seven genes in the QTL interval were deduced as promising candidates for the QTL effect by bioinformatics analysis. Among them, PPARD and CDKN1A had lower expression levels in MS(QTL7)/LW(QTL7) pigs at both ages. Genotype-related differences were observed in mRNA levels of PPARD target genes involved in cell differentiation (FZD7) or fatty acid oxidation (ACADL and ACOX1) at 150 days. These results re-evaluate the potential of PPARD to explain part of variation in pig adiposity.

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.

Mapping quantitative trait loci for metabolic and cytological fatness traits of connected F2 crosses in pigs

In the present study 3 connected F(2) crosses were used to map QTL for classical fat traits as well as fat-related metabolic and cytological traits in pigs. The founder breeds were Chinese Meishan, European Wild Boar, and Pietrain with to some extent the same founder animals in the different crosses. The different selection history of the breeds for fatness traits as well as the connectedness of the crosses led to a high statistical power. The total number of F(2) animals varied between 694 and 966, depending on the trait. The animals were genotyped for around 250 genetic markers, mostly microsatellites. The statistical model was a multi-allele, multi-QTL model that accounted for imprinting. The model was previously introduced from plant breeding experiments. The traits investigated were backfat depth and fat area as well as relative number of fat cells with different sizes and 2 metabolic traits (i.e., soluble protein content as an indicator for the level of metabolic turnover and NADP-malate dehydrogenase as an indicator for enzyme activity). The results revealed in total 37 significant QTL on chromosomes 1, 2, 4, 5, 6, 7, 8, 9, 14, 17, and 18, with often an overlap of confidence intervals of several traits. These confidence intervals were in some cases remarkably small, which is due to the high statistical power of the design. In total, 18 QTL showed significant imprinting effects. The small and overlapping confidence intervals for the classical fatness traits as well as for the cytological and metabolic traits enabled positional and functional candidate gene identification for several mapped QTL.

Differential gene expressions in subcutaneous adipose tissue pointed to a delayed adipocytic differentiation in small pig fetuses compared to their heavier siblings

Intra-uterine growth retardation in piglets is associated to neonatal losses and a greater susceptibility to fat deposition in the long term. Dietary l-arginine supplementation to gilts during early gestation has been proposed as a way to enhance fetal survival. This study aims to investigate the effects of variation in fetal growth within litters and dietary l-arginine treatment during early gestation in pregnant sows on expression levels of several genes involved in early adipose tissue development and lipid deposition in the fetuses. At day 75 of pregnancy, sows fed a standard gestation diet throughout pregnancy and sows fed 26g L-arginine daily from days 14 to 28 of gestation in supplement to the standard diet were sacrificed. Six pairs of littermates in each dietary group with the smallest or the heaviest fetal weights within each litter were collected (total: 24 fetuses). Expression levels of DLK1/PREF1 and FZD7 were significantly greater in subcutaneous backfat of the smallest fetuses. Conversely, transcriptional adipogenic regulators PPARG, SREBP1, and CEBPA, and genes involved in terminal adipocytic differentiation LPL, ME1, and FABP4 were less expressed in those piglets. Fetal weight has no effect on expression levels of genes involved in cell cycle progression and DNA content in subcutaneous adipose tissue. Maternal dietary L-arginine treatment did not affect subcutaneous adipose tissue features in 75-day old fetuses. The gene expression changes observed in the smallest fetuses are likely associated to a lower body fat content at birth, and could predispose to catch-up fat growth during the postnatal period.

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.

Developmental, hormonal, and nutritional regulation of porcine adipose triglyceride lipase (ATGL)

Adipose triglyceride lipase (ATGL) is a newly identified lipase. We report for the first time the porcine ATGL sequence and characterize ATGL gene and protein expression in vitro and in vivo. Adult pig tissue expresses ATGL at high levels in the white adipose and muscle tissue relative to other tested tissues. We show that within the white adipose tissue ATGL is expressed at higher levels in the adipocyte than in the stromal-vascular fraction. Additionally, ATGL expression increases dramatically in the subcutaneous adipose during adipose development and maturation, as well as during in vitro adipogenesis. Peroxisome proliferator-activated receptor gamma transcript levels increased concomitant with ATGL gene expression, suggesting a possible role in the regulation of ATGL by adipogenic regulators. In vitro treatment of differentiated primary pig preadipocytes with insulin and forskolin decreased ATGL gene expression in a dose-dependent manner, suggesting ATGL transcript levels are hormone sensitive. In vivo experimentation showed that calorie-restriction in gilts resulted in increased ATGL mRNA and protein levels in subcutaneous and peri-renal fat tissues. Our data demonstrate that ATGL expression reacts to hormonal stimuli and plays a role in catecholamine-induced lipolysis in porcine adipose tissue.

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.

Effects of 1,25-dihydroxyvitamin D3 on proliferation and differentiation of porcine preadipocyte in vitro

1,25-Dihydroxyvitamin D3, the physiologically active form of vitamin D3, exerts its functions through a receptor-mediated mechanism and plays an important role in the cell differentiation. This study investigated the effects of 1,25-dihydroxyvitamin D3 on the proliferation and differentiation of porcine preadipocyte. Stromal-vascular cells containing preadipocytes were prepared from dorsal subcutaneous adipose tissue of approximately 3-day-old Chinese male crossbred pigs. After confluence, the differentiation was induced by transferrin, dexamethasone and insulin for 2 days, and then subsequently cultured for 6 days. The cells were treated with 1,25-dihydroxyvitamin D3 during the induction of differentiation (the early phase of differentiation) or throughout the differentiation period. The terminal differentiation markers, such as glycerol-3-phosphate dehydrogenase activity and lipid accumulation were measured during the process of cultures. The treatment with 1,25-dihydroxyvitamin D3 severely affected the induction of all differentiation markers throughout the differentiation period. 1,25-Dihydroxyvitamin D3 suppressed the expression of peroxisome proliferator-activated receptor gamma mRNA and interfered with the induction of retinoid X receptor alpha mRNA. The mRNAs of the adipogenesis-related genes, lipoprotein lipase, stearoyl-CoA desaturase, phosphoenolpyruvate carboxykinase, glycerol-3-phosphate dehydrogenase and glucose transporter 4 were reduced when 1,25-dihydroxyvitamin D3 was added into differentiation medium. Also, 1,25-dihydroxyvitamin D3 inhibited preadipocyte differentiation in dose-dependent manner. These results suggested that 1,25-dihydroxyvitamin D3 inhibited porcine preadipocyte differentiation through suppressing PPAR gamma and RXR alpha mRNA expressions and then down regulating the expression of adipogenesis-related genes.

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.

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.

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.

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.

Effects of insulin, triiodothyronine and fat soluble vitamins on adipocyte differentiation and LPL gene expression in the stromal-vascular cells of red sea bream, Pagrus major

Various kinds of hormones including insulin, triiodothyronine (T(3)) and fat-soluble vitamins have been proposed as mediators of adipocyte differentiation in mammals. To investigate the factors which are responsible for fish adipocyte differentiation, we developed a serum-free culture system of stromal-vascular cells of red sea bream adipose tissue and examined the effects of bovine insulin, T(3), and fat-soluble vitamins (all-trans retinoic acid, retinyl acetate and 1,25-dihydroxyvitamin D(3)) on the differentiation-linked expression of the lipoprotein lipase (LPL) gene. As assessed by the increase in LPL gene expression after 3 day cultivation, like in mammalian adipocytes, insulin enhanced the adipocyte differentiation in a concentration-dependent manner. During 2 week cultivation, bovine insulin promoted lipid accumulation in differentiating adipocytes concentration-dependently until the terminal differentiation. These results indicate that the differentiation of fish adipocytes is inducible by insulin alone. T(3) alone had no effect but enhanced the differentiation-linked LPL gene expression in the presence of insulin. Fat-soluble vitamins, unlike in mammalian adipocytes, did not show any significant effects. The method developed in this study should be of interest for the characterization of factors involved in fish adipocyte differentiation.

Regulation of differentiating pig preadipocytes by retinoic acid

All-trans retinoic acid (ATRA) potently inhibits the differentiation of porcine preadipocytes in primary culture; however, the mechanism by which ATRA exerts this effect in pigs is poorly understood. The objective of this study was to use retinoid receptor-specific ligands to investigate the mechanism underlying the antiadipogenic action of retinoids in cultured pig preadipocytes by identifying the retinoid receptor mediating this action and examining the effect of retinoids on the expression of key adipogenic transcription factors. Stromal-vascular cells were harvested from porcine adipose tissue and cultured in serum-free medium. Glycerol-3-phoshphate dehydrogenase (GPDH) activity, a late marker of preadipocyte differentiation, was decreased (P < 0.01) by the addition of 0 to 10 microM of either ATRA, a nonspecific agonist for both the retinoic acid receptor (RAR) and the retinoid X receptor (RXR) or the selective RAR agonist, 4-(E-2-[5,6,7,8-tet-rahydro-5,5,8,8-tetramethyl-2-naphthalenyl]-1-propenyl) benzoic acid (TTNPB). Addition of increasing amounts of Ro-61, a RAR-specific antagonist (0 to 10 microM) prevented ATRA and TTNBP from decreasing GPDH activity. Addition of methoprene acid, an RXR-specific agonist, increased (P < 0.01) GPDH activity. Preadipocytes were then continuously treated with 10 nM of TTNPB in the presence or absence of 1 microM Ro-61, and mRNA was isolated on d 2 and 8. Addition of TTNPB decreased (P < 0.001) the expression of peroxisome proliferator-activated receptor gamma (PPARgamma), sterol regulatory element-binding protein-1c (SREBP-1c), retinoid X receptor alpha (RXRalpha), and adipocyte fatty acid binding protein (aP2) mRNA transcripts, whereas these effects were prevented by the presence of Ro-61. Interestingly, TTNBP increased (P < 0.001) the mRNA abundance of the orphan nuclear receptor chicken ovalbumin upstream promoter-transcription factor 1 (COUP-TF1), whereas Ro-61 prevented this increase. These changes were independent of alterations in the mRNA abundances of the retinoic acid receptor alpha, and CCAAT/enhancer binding protein alpha and beta (C/EBPbeta; C/EBPalpha) genes. These results indicate that retinoic acid inhibits porcine preadipocyte differentiation by a mechanism that involves activation of the RAR and downregulation of PPARgamma, RXRalpha, and SREBP-1C mRNA. This mechanism is independent of changes in C/EBPbeta and C/EBPalpha mRNA abundance and may involve COUP-TF.

Regulation of development and metabolism of adipose tissue by growth hormone and the insulin-like growth factor system

White adipose tissue plays a key role in the regulation of the energy balance of vertebrates. This tissue is also now recognized to secrete a variety of factors such as leptin, which is thought to be involved in the modulation of adipose mass. Unlike other tissues, adipose tissue mass has considerable capacity to expand. The review deals primarily on the regulation of development and metabolism of adipose tissue by growth hormone (GH) and the insulin-like growth factor (IGF) system, with a special focus on the pig. The anti-insulin effects of GH are well-documented in pigs as in other species. In vitro exposure of adipose precursor cells to GH leads to a decrease in differentiation of those cells in pigs, in contrast to data obtained in murine cell lines. In vivo treatment and prolonged in vitro incubation of adipose tissue or isolated adipocytes with GH result in a decrease in glucose transport and lipogenesis, especially at the level of the fatty acid synthase gene, resulting in a reduction of the lipid content and adipose tissue mass. The mechanism by which GH antagonizes insulin stimulation of lipogenesis is still unresolved, as it is not mediated by protein kinase A, protein kinase C and Janus kinase-2 at the signaling level, or upstream stimulatory factor 1 or sterol regulatory element binding protein-1 at the transcriptional level. GH is apparently the main regulator of IGF-I mRNA expression in adipose tissue, however, the effects of IGF-I on this tissue are rather unclear.

Role of fatty acids in adipocyte growth and development1,2

Fat is typically added to diets as a source of energy. The alternative aspects considered here are the use of specific fats to alter the fatty acid profile of adipose tissue toward creation of value-added products and the potential for individual fatty acids to alter gene expression and control adipose tissue development. Emphasis is placed on the omega-3 fatty acids, such as those found in fish oil, and on CLA. The most common association of fatty acids with adipose tissue is related to their storage as triglycerides in mature adipocytes and the consequences of excess accumulation in obesity. Fatty acids and their derivatives also can have hormone-like effects and have been be shown to regulate gene expression in preadipocytes, which ultimately effects their proliferation and differentiation. Long-chain, saturated, and polyunsaturated fatty acids have been shown to regulate transcription factors, such as CCAAT/enhancer binding protein, peroxisome proliferator activated receptor, and other adipose-specific genes, very early in adipocyte development. These effects have the potential to affect fat cell number at maturity. Specifically, there is evidence that the fatty acids in fish oil, such as docosahexaenoic and eicosopentaenoic acids, and fatty acids in the CLA series, decrease preadipocyte proliferation in cell lines and reduce adiposity in rodents. There is little direct evidence of the ability of fatty acids to manipulate adipocyte development in non-rodent species. The genetic, nutritional, and pharmacological manipulation of adipose tissue in meat animals has long been of interest to animal scientists. An understanding of the ability of fatty acids to regulate factors such as adipocyte size and number, particularly in meat animals, would be of great interest. The evidence for regulatory roles of fatty acids in development from rodent and in vitro studies and their potential application to meat animals are reviewed.

The effect of dietary docosahexaenoic acid on the expression of porcine lipid metabolism-related genes1

To study the effect of dietary docosahexaenoic acid (DHA) on the expression of adipocyte determination and differentiation-dependent factor 1 (ADD1) mRNA in pig tissues, weaned, crossbred pigs (30 d of age) were fed either 2% (as-fed basis) tallow or DHA oil for 18 d. Body weight of the pigs was not affected by different dietary fatty acid (FA) compositions. The plasma and liver FA composition reflected the composition of the diet. The adipose tissue and skeletal muscle FA composition only partially reflected the diet, indicating either a slower FA turnover or that a greater proportion of the FA in these tissues is from endogenous FA synthesis. The ADD1 is an important transcription factor that modulates transcription of FA synthase to regulate the endogenous FA synthesis in the liver and adipose tissue. The ADD1 mRNA was decreased (P < 0.05) in the liver of DHA-treated pigs compared with that of the tallow-treated pigs. The diets did not have an effect on the ADD1 mRNA in pig adipose tissue. The ADD1 transcript was not detected in pig skeletal muscle. These results indicate that significant enrichment of liver DHA content inhibits the expression of ADD1 mRNA. Such an effect is similar to that reported in porcine differentiating adipocytes cultured with DHA. The liver and muscle acyl CoA oxidase mRNA concentration was increased (P < 0.05) by DHA oil treatment, suggesting that DHA treatment may increase peroxisomal fatty acid oxidation in these two tissues. Our present observations demonstrate that dietary DHA enrichment not only affects tissue DHA concentration but also mildly modifies the expression of genes related to fatty acid metabolism in the porcine liver and skeletal muscle.

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Dexamethasone induced preadipocyte recruitment and expression of CCAAT/enhancing binding protein alpha and peroxisome proliferator activated receptor-gamma proteins in porcine stromal-vascular (S-V) cell cultures obtained before and after the onset of fetal adipogenesis

The present study examined the influence of dexamethasone (DEX) treatment on preadipocyte recruitment and expression of transcription factor proteins in adipose tissue stromal-vascular (S-V) cell cultures from 50 and 75 day old pig fetuses and young pigs. C/EBPalpha, C/EBPdelta, and PPARgamma immunoreactive cells had evenly reactive nuclei and unreactive nucleoli. DEX recruited many more preadipocytes in 75 day than in 50 day fetal S-V cultures. However, DEX did not increase the number of differentiated preadipocytes (lipid+, C/EBPalpha+) in 50 day S-V cultures and only slightly increased this number in 75 day fetal S-V cultures. In fetal cultures, extensive, precocious increases in C/EBPalpha expression (number of reactive cells) by day three were followed by extensive decreases in expression. However, PPARgamma expression was not expressed precociously since preadipocyte lipid accretion and PPARgamma immunoreactivity were strongly linked in fetal and pig S-V cultures. Nevertheless, all cells with lipid in fetal S-V cultures were C/EBPalpha and PPARgamma reactive. DEX increases preadipocyte differentiation in pig S-V cultures and in this study DEX increased PPARgamma expression to a much greater degree in pig than in fetal S-V cultures. These studies suggest that restricted adipogenesis in the pig fetus is attributable to limited DEX induced PPARgamma expression.

Effects of isomers of conjugated linoleic acid on porcine adipocyte growth and differentiation

Conjugated linoleic acids (CLAs) decrease fat deposition in mammals, including pigs. To determine mechanisms for CLA effects on adipocyte growth, porcine stromal-vascular cells (preadipocytes) were isolated and plated in medium containing 10% fetal bovine serum. After 24 h, differentiation factors (insulin + hydrocortisone + transferrin) were added. Oleic acid (200 microM) was added to some plates as a positive control. One of two isomers of CLA (50 microM cis 9, trans 11 or >50 microM trans 10, cis 12), or a mixture of the two isomers (25 microM each) was added to other plates. The cell number increased 7+ times in 7 days after initiation of differentiation, and was not different among treatment groups. By 7 days, Oil Red O-stained material (OROSM), expressed per cell, increased 10+ times in control cells and 64 times in oleic acid-treated cells. Addition of either isomer of CLA or the mixture caused OROSM/cell to increase 10+ times at 2 days, with no further increase at later times. In CLA-treated cells there was no increase in peroxisome proliferator-activated receptor gamma (PPARgamma) or lipoprotein lipase mRNA concentrations. The increased OROSM/cell may represent triacylglycerol synthesis from medium CLA using existing biosynthetic capacity or provision of a limiting ligand for PPARgamma already present. The results are different from those observed with rodent-derived clonal cells (3T3-L1 cells), wherein proliferation and differentiation are inhibited by CLAs, and the active isomer is trans 10, cis 12-CLA. The results suggest distinctions between clonal and primary preadipocytes, or species differences.

Dietary fat has minimal effects on fatty acid metabolism transcript concentrations in pigs

Young, crossbred pigs were fed either a low-fat, corn-based diet; a high-fat, tallow-based diet with a considerable saturated fatty acid (FA) content; or a high-fat, fish oil-based diet with a considerable polyunsaturated FA content, for 14 d. There were six pigs per dietary group (approximately 4-wk-old with a body weight of 6.16 kg). The plasma and adipose tissue FA composition reflected the composition of the diet to a large extent, but also reflected de novo FA synthesis coupled with chain elongation and desaturation. The liver and skeletal muscle FA composition reflected the diet and endogenous synthesis, but the indications for preferential incorporation or exclusion of specific FA were greater in these tissues than in plasma or adipose tissue. An important transcription factor for adipocyte differentiation and other aspects of lipid metabolism is adipocyte determination and differentiation-dependent factor 1 (ADD1). Liver ADD1 messenger RNA (mRNA) tended to be decreased (P = 0.06) in the fish oil-fed group, as well as in the combined high-fat-fed groups (tallow + fish oil) compared to the low-fat-fed group (P = 0.06). The muscle acyl-CoA oxidase mRNA tended to be increased in the tallow-fed group and decreased in fish oil-fed groups (P = 0.06). The muscle carnitine palmitoyltransferase mRNA tended to be elevated in both fat-fed groups (P = 0.07). None of the adipose tissue mRNA were changed by the diet (P > 0.20). The observations suggest there are major differences between rodents and pigs in modulation of transcripts associated with lipid metabolism by the dietary FA composition or concentration. Also, in porcine adipose tissue, as well as in liver and skeletal muscle, these transcripts are rather refractory to modification by dietary FA.

ISOMERS OF CONJUGATED LINOLEIC ACID MODULATE HUMAN PREADIPOCYTE DIFFERENTIATION

Conjugated linoleic acids (CLAs) reduce fat deposition in several mammalian species. Among the proposed mechanisms for this effect are reduced preadipocyte proliferation and differentiation. We measured proliferation and differentiation of cultured human preadipocytes treated with CLAs. Preadipocytes were differentiated with insulin, hydrocortisone, transferrin, and 10% fetal bovine serum, with isobutyl-methylxanthine included for the first 2 d. The differentiation medium contained 200 microM oleic acid (C18:1), 50 microM cis-9,trans-11-CLA (9,11-CLA), or 50 microM trans-10,cis-12-CLA (10,12-CLA); the negative control medium contained no added fatty acid, and the cells did not differentiate. Cell number increased three to four times during the 17 d of differentiation, but was 30-35% lower in the CLA-treated cells than in the negative control cells. Compared with the negative control cells, differentiation was increased in the cells treated with C18:1 (increased Oil Red O-stained material [OROSM], triacylglycerol, glycerol 3-phosphate dehydrogenase activity [GPDH], peroxisome proliferator-activated receptor-gamma [PPAR gamma] messenger ribonucleic acid [mRNA], and lipoprotein lipase [LPL] mRNA). In effect, the C18:1-treated cells act as a positive control to demonstrate the differentiation capacity of each cell lot. Both 9,11-CLA- and 10,12-CLA-treated cells had increased differentiation (increased OROSM, triacylglycerol, GPDH, PPAR gamma, and LPL) compared with the negative control cells. The data suggest that early in differentiation when de novo fatty acid (FA) synthesis is limited and competition for FAs by membrane and triacylglycerol synthetic pathways is great, human preadipocytes do not differentiate unless a PPAR gamma ligand is added. Either CLA isomer or C18:1 can provide such a ligand.

Modulation of adipocyte determination and differentiation-dependent factor 1 by selected polyunsaturated fatty acids

The transcription factor, sterol regulatory binding protein 1c (also called adipocyte determination and differentiation-dependent factor 1), stimulates transcription of the messenger ribonucleic acids (mRNAs) for lipid synthesis enzymes. Hepatic ADD1 transcripts are reduced by polyunsaturated fatty acids (PUFAs). The ADD1 transcripts are expressed to a considerable extent in porcine adipocytes. Consequently, it was of interest to examine the effects of several PUFAs on ADD1 in a tissue wherein several long-chain fatty acids (FAs) increase adipocyte differentiation. The effects of arachidonic acid (C20:4), docosahexaenoic acid (C22:6), and cis 9, trans 11-conjugated linoleic acid (9,11-CLA) on differentiating preadipocyte ADD1 mRNA and protein and on preadipocyte differentiation were determined. Porcine stromal-vascular cells were plated in serum-containing medium and differentiated in serum-free medium containing insulin, hydrocortisone, and transferrin +/- an individual FA. After 24-h differentiation +/- FA, plates were stained with Oil Red O as an indicator of differentiation or total RNA was extracted or a nuclear fraction was isolated for protein measurement. Addition of C20:4 or 9,11-CLA increased the number of Oil Red O-stained cells or the Oil Red O-stained material, whereas C22:6 did not. Addition of C20:4, C22:6, or 9,11-CLA decreased the concentration of the mRNA and protein for ADD1. Thus, although all three FAs decreased the ADD1 mRNA and protein concentrations, C20:4 and 9,11-CLA increased differentiation, measured by Oil Red O staining, whereas C22:6 did not. The data suggest that the regulation of differentiation and mRNAs by individual FAs may involve distinct mechanisms.