Oleate induces transdifferentiation of chicken fibroblasts into adipocyte-like cells

A Novel DNA Methyltransferase Dnmt3a3 Splice Variant Represses Preadipocyte Proliferation and Differentiation

Proliferation and differentiation of preadipocyte are essential for the formation of fat tissues. However, the genes that regulate the early stage of preadipocyte differentiation in chicken have remained elusive. Here we identify a novel spliced variant of the DNA methyltransferase Dnmt3a gene, named Dnmt3a3, that controls early preadipocyte differentiation. Dnmt3a3 expression is increased at the onset of preadipocyte differentiation and remains elevated during differentiation. Overexpression of Dnmt3a3 in preadipocytes markedly inhibits proliferation and cell-cycle progression, and this is accompanied by inhibition of the mRNA and protein level of cell-cycle control genes, such as p21 and p27. In addition, forced expression of Dnmt3a3 in differentiating preadipocytes represses early preadipocyte differentiation, and this was found to be accompanied by inhibition of the mRNA expression levels of early preadipocyte differentiation markers, such as GATA2, GATA3, C/EBPα, C/EBPβ, AP2, and PPARγ, or the protein levels of GATA3, C/EBPβ, and PPARγ. Taken together, these data demonstrate the participation of Dnmt3a3 in the proliferation and differentiation process of chicken primary preadipocyte cells.

Factors affecting adipose tissue development in chickens: A review

The intense genetic selection for rapid growth in broilers has resulted in an increase in voluntary feed intake and growth rate, accompanied by increased fat deposition in adipose tissue depots throughout the body. Adipose tissue expansion is a result of the formation of adipocytes (several processes collectively referred to as adipogenesis) and cellular accumulation of triacylglycerols inside lipid droplets. In mammals, different anatomical depots are metabolically distinct. The molecular and cellular mechanisms underlying adipose tissue development have been characterized in mammalian models, whereas information in avian species is scarce. The purpose of this review is to describe factors regulating adipogenesis in chickens, with an emphasis on dietary factors and the broiler. Results from many studies have demonstrated effects of dietary nutrient composition on adipose tissue development and lipid metabolism. Transcription factors, such as peroxisome proliferator-activated receptor γ, CCAAT/enhancer-binding proteins α and β, and sterol regulatory element binding proteins orchestrate a series of cellular events that lead to an increase in activity of fatty acid transport proteins and enzymes that are responsible for triacylglycerol synthesis. Understanding the mechanisms underlying adipose tissue development may provide a practical strategy to affect body composition of the commercial broiler while providing insights on diets that maximize conversion into muscle rather than fat and affect depot-dependent deposition of lipids. Because of the propensity to overeat and become obese, the broiler chicken also represents an attractive biomedical model for eating disorders and obesity in humans.

Specific Physical Exercise Improves Energetic Metabolism in the Skeletal Muscle of Amyotrophic-Lateral- Sclerosis Mice

Amyotrophic Lateral Sclerosis is an adult-onset neurodegenerative disease characterized by the specific loss of motor neurons, leading to muscle paralysis and death. Although the cellular mechanisms underlying amyotrophic lateral sclerosis (ALS)-induced toxicity for motor neurons remain poorly understood, growing evidence suggest a defective energetic metabolism in skeletal muscles participating in ALS-induced motor neuron death ultimately destabilizing neuromuscular junctions. In the present study, we report that a specific exercise paradigm, based on a high intensity and amplitude swimming exercise, significantly improves glucose metabolism in ALS mice. Using physiological tests and a biophysics approach based on nuclear magnetic resonance (NMR), we unexpectedly found that SOD1(G93A) ALS mice suffered from severe glucose intolerance, which was counteracted by high intensity swimming but not moderate intensity running exercise. Furthermore, swimming exercise restored the highly ALS-sensitive tibialis muscle through an autophagy-linked mechanism involving the expression of key glucose transporters and metabolic enzymes, including GLUT4 and glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Importantly, GLUT4 and GAPDH expression defects were also found in muscles from ALS patients. Moreover, we report that swimming exercise induced a triglyceride accumulation in ALS tibialis, likely resulting from an increase in the expression levels of lipid transporters and biosynthesis enzymes, notably DGAT1 and related proteins. All these data provide the first molecular basis for the differential effects of specific exercise type and intensity in ALS, calling for the use of physical exercise as an appropriate intervention to alleviate symptoms in this debilitating disease.

Expression and regulation of C/EBPα in normal myelopoiesis and in malignant transformation

One of the most studied transcription factors in hematopoiesis is the leucine zipper CCAAT-enhancer binding protein α (C/EBPα), which is mainly involved in cell fate decisions for myeloid differentiation. Its involvement in acute myeloid leukemia (AML) is diverse, with patients frequently exhibiting mutations, deregulation of gene expression, or alterations in the function of C/EBPα. In this review, we emphasize the importance of C/EBPα for neutrophil maturation, its role in myeloid priming of hematopoietic stem and progenitor cells, and its indispensable requirement for AML development. We discuss that mutations in the open reading frame of CEBPA lead to an altered C/EBPα function, affecting the expression of downstream genes and consequently deregulating myelopoiesis. The emerging transcriptional mechanisms of CEBPA are discussed based on recent studies. Novel insights on how these mechanisms may be deregulated by oncoproteins or mutations/variants in CEBPA enhancers are suggested in principal to reveal novel mechanisms of how CEBPA is deregulated at the transcriptional level.

Integrated analysis of microRNA and mRNA expression profiles in abdominal adipose tissues in chickens

Excessive fat accretion is a crucial problem during broiler production. Abdominal fat weight (AbFW) and abdominal fat percentage (AbFP) are major phenotypic indices of fat traits. The present study used F2 females derived from a cross between Beijing-You and Cobb-Vantress chickens. Cohorts with extreme AbFP and AbFW phenotypes were chosen to construct high- and low-abdominal fat libraries (HAbF and LAbF, respectively) to investigate the expression profiles by RNA-sequencing and microRNA (miRNA)-sequencing. Compared with the LAbF library, 62 differentially expressed miRNAs (DEMs) and 303 differentially expressed genes (DEGs) were identified in the HAbF birds. Integrated analysis of DEMs and DEGs showed that a total of 106 DEGs were identified as target genes for the 62 DEMs. These genes were designated as intersection genes, and 11 of these genes are involved in lipid metabolism pathways. The miRNA gga-miR-19b-3p accelerated the proliferation of preadipocytes, as well as adipocyte differentiation, by down- regulating ACSL1. These findings suggest that some strong candidate miRNAs and genes, important in relation to abdominal adipose deposition, were identified by the integrated analysis of DEMs and DEGs. These findings add to our current understanding of the molecular genetic controls underlying abdominal adipose accumulation in chickens.

Brain Natriuretic Peptide Stimulates Lipid Metabolism through Its Receptor NPR1 and the Glycerolipid Metabolism Pathway in Chicken Adipocytes

Brain natriuretic peptide (BNP) is related to lipid metabolism in mammals, but its effect and the molecular mechanisms underlying it in chickens are incompletely understood. We found that the level of natriuretic peptide precursor B (NPPB, which encodes BNP) mRNA expression in high-abdominal-fat chicken groups was significantly higher than that of low-abdominal-fat groups. Partial correlations indicated that changes in the weight of abdominal fat were positively correlated with NPPB mRNA expression level. In vitro, compared with the control group, preadipocytes with NPPB interference showed reduced levels of proliferation, differentiation, and glycerin in media. Treatments of cells with BNP led to enhanced proliferation and differentiation of cells and glycerin concentration, and mRNA expression of its receptor natriuretic peptide receptor 1 (NPR1) was upregulated significantly. In cells exposed to BNP, 482 differentially expressed genes were identified compared with controls without BNP. Four genes known to be related to lipid metabolism (diacylglycerol kinase; lipase, endothelial; 1-acylglycerol-3-phosphate O-acyltransferase 1; and 1-acylglycerol-3-phosphate O-acyltransferase 2) were enriched in the glycerolipid metabolism pathway and expressed differentially. In conclusion, BNP stimulates the proliferation, differentiation, and lipolysis of preadipocytes through upregulation of the levels of expression of its receptor NPR1 and key genes enriched in the glycerolipid metabolic pathway.

Folate supplementation modifies CCAAT/enhancer-binding protein α methylation to mediate differentiation of preadipocytes in chickens

Folate, an essential vitamin participating in 1-carbon metabolism leading to a methyl donor function, is a key factor inducing epigenetic changes. This study sought to determine if folate influences the methylation level of cytosine-guanine (CpG) islands in the promoters of critical adipogenic genes in chickens, and how this might affect gene expression and differentiation of preadipocytes in vitro. Preadipocytes were treated with 0 to 16 mg/L of folate during the induction of differentiation, and cell proliferation and lipid accumulation were assessed. The folate supplementation resulted in enhanced cell proliferation and decreased content of lipid per adipocyte at d 6 of differentiation. The effects of folate on relative expression of genes critical for adipocyte differentiation and 1-carbon metabolism were measured by quantitative reverse-transcription PCR. Folate caused a dose-dependent decrease in transcript abundance of peroxisome proliferator-activated receptor γ (PPARγ), CCAAT/enhancer-binding protein α (C/EBPα) gene expression, and the downstream enzyme fatty acid synthase; in contrast, expression of DNA (cytosine-5)-methyltransferase and methylenetetrahydrofolate reductase was obviously upregulated at d 6 of differentiation (P < 0.05). The DNA methylation was examined with the bisulfite sequencing PCR method. Overall CpG methylation in the C/EBPα gene promoter region was 21.8% lower (P < 0.05) and the gene's expression was 2.7-fold higher in the absence of folate, compared with cells treated with 16 mg/L of folate, whereas methylation of the PPARγ promoter was not affected. Overall, the results show that folate increased the proliferation of adipocytes but reduced per-cell lipid accumulation, thereby influencing differentiation; it increased expression of genes involved in 1-carbon metabolism resulting in greater methylation of the C/EBPα promoter during differentiation and decreased that gene's expression, perhaps accounting for decreased expression of PPARγ.

Isolation, culture and differentiation of duck (Anas platyrhynchos) preadipocytes

In the present study, we isolated preadipocytes from the adipose tissue of Peking duck and subsequently cultured them in vitro. Cell counting kit-8 assay was employed to establish the growth curve of duck primary preadipocytes. Meanwhile, after the cells reaching full confluency, they were induced to differentiate into mature adipocytes by the addition of a cocktail containing dexamethasone, insulin, 3-isobutyl-1-methylxanthine, and oleic acid for 8 days. Successful differentiation was demonstrated by the development of lipid droplets and the expression of key marker genes including peroxisome proliferator-activated receptor-γ (PPARγ), CCAAT/enhancer binding protein-α (CEBP/α) and adipocyte fatty acid-binding protein (FABP4). Our results showed that duck primary preadipocytes began to adhere 12 h after seeding as short spindle shapes or litter triangles, which grew quickly 3 days post attachment and maintained stable after day 7. After 8 days the preadipocytes were induced to differentiate into mature adipocytes, which were stained red by oil red O. Additionally, it showed that during preadipocyte differentiation PPARγ mRNA was highly expressed at day 3, while CEBP/α and FABP4 mRNA peaked at day 5 and 8, respectively. These results indicate that we have successfully isolated and cultured Peking duck preadipocytes and successfully induced them to differentiate into mature adipocytes. This work could lay a foundation for further research into waterfowl adipogenesis.

Oleate promotes differentiation of chicken primary preadipocytes in vitro

In addition to providing energy and constituting cell membrane, fatty acids also play an important role in adipocyte differentiation and lipid metabolism. As an important member of monounsaturated fatty acids, oleate, together with other components, is widely used to induce chicken preadipocyte differentiation. However, it is not clear whether oleate alone can induce chicken preadipocyte differentiation. In the present study, four different treatments were designed to test this question: basal medium, IDX [insulin, dexamethasone and IBMX (isobutylmethylxanthine)], oleate and IDX plus oleate. Cytoplasmic lipid droplet accumulation and mRNA expression for adipogenesis-related genes were monitored. After treatment of oleate on chicken preadipocytes, apparent lipid droplet formation and lipid accumulation were observed, accompanied by increasing expression of PPARγ (peroxisome proliferator-activated receptor-γ) and AFABP (adipocyte fatty acid-binding protein), but decreasing level of GATA2 (GATA-binding protein 2). In contrast, for cells cultured in the basal medium with or without IDX supplementation, lipid droplet barely occurred. These results suggest that exogenous oleate alone can act as an inducer of preadipocyte differentiation into adipocytes.

Our results suggest that oleate alone can act as a direct inducer of chicken preadipocyte differentiation by elevating expression of key positive regulators and suppressing expression of negative regulator of adipogenesis.

Solubilization and identification of hen eggshell membrane proteins during different times of chicken embryo development using the proteomic approach

A fertilized chicken egg is a unit of life. During hatching, transport of nutrients, including calcium, have been reported from the egg components to the developing embryo. Calcium is mobilized from the eggshell with the involvement of Ca(2+)-binding proteins. In addition, other unknown proteins may also play some important roles during embryo developing process. Therefore identification and prediction of biological functions of eggshell membrane (ESM) proteins during chick embryo development was conducted by proteome analysis. Comparison of different lysis solutions indicated that the highest ability to extract ESM proteins could be obtained with 1 % sodium dodecyl sulfate in 5 mM Tris-HCl buffer pH 8.8 containing 0.1 % 2-mercaptoethanol. In this study fertilized Cornish chicken eggs were incubated at 37 °C in humidified incubators for up to 21 days. At selected times (days 1, 9, 15 and 21), samples were taken and the ESMs were carefully separated by hand, washed with distilled water, and air-dried at room temperature. The ESM proteins were then solubilized and analyzed by proteome analysis. Sodium dodecyl sulfate polyacrylamide gel electrophoresis combined with high performance liquid chromatography and mass spectrometry revealed 62 proteins in the ESM; only keratin is known ESM protein, 8 of which are egg white proteins and related while 53 others have not previously been reported. Some differences in the types of proteins and their molecular functions were noted in ESM at different incubation times. One protein which was present only at days 15 and 21 of egg incubation was identified as a calcium binding protein i.e. EGF like repeats and discoidin I like domain 3 (EDIL3 homologous protein).

Direct conversion of tenocytes into chondrocytes by Sox9

Sox9 is a high-mobility group box-containing transcription factor that functions as a key regulator of chondrogenesis. We here report that Sox9 mediates the direct conversion of tenocytes to chondrocytes through an intermediate state in which both differentiation programs are active. Sox9 is abundantly expressed in cartilage but is undetectable in limb tendons that express Scleraxis (Scx) and Tenomodulin (Tnmd), tendon-specific early and late molecular markers, respectively. Upon forced expression of Sox9 in the chick forelimb, ectopic cartilage formation is preferentially observed in fibrous tissues including the tendons, ligaments, perichondrium/periosteum, dermis, and muscle connective tissues. Tnmd expression in tenocytes isolated from leg tendons was markedly upregulated by forced expression of basic helix-loop-helix (b-HLH) activators including Scx, Paraxis, Twist1 and Twist2. In contrast, the overexpression of Sox9 in monolayer tenocytes resulted in the downregulation of Tnmd and Scx expressions during passaging in culture, and the induction of cartilage molecular markers such as type II collagen (Col2a1) and Chondromodulin-I (ChM-I). This Sox9-driven switching from a tenocytic to a chondrocytic gene expression profile was associated with a dramatic change from a spindle to a polygonal cellular morphology. The extracellular accumulation of cartilage-characteristic proteoglycans was also observed. These data suggest that tenocytes have a strong potential for conversion into chondrocytes through the activities of Sox9 both in vitro and in vivo.

FSH stimulates lipid biosynthesis in chicken adipose tissue by upregulating the expression of its receptor FSHR

Transcripts and protein for follicle-stimulating hormone receptor (FSHR) were demonstrated in abdominal adipose tissue of female chickens. There was no expression of the Fsh gene, but FSH and FSHR colocalized, suggesting that FSH was receptor bound. Partial correlations indicted that changes in abdominal fat (AF) content were most directly correlated with Fshr mRNA expression, and the latter was directly correlated with tissue FSH content. These relationships were consistent with FSH inducing Fshr mRNA expression and with the finding that FSH influenced the accumulation of AF in chickens, a novel role for the hormone. Chicken preadipocytes responded linearly to doubling concentrations of FSH in Fshr mRNA expression and quantities of FSHR and lipid, without discernable effect on proliferation. Cells exposed to FSH more rapidly acquired adipocyte morphology. Treatment of young chickens with chicken FSH (4 mIU/day, subcutaneous, days 7-13) did not significantly decrease live weight but increased AF weight by 54.61%, AF as a percentage of live weight by 55.45%, and FSHR transcripts in AF by 222.15% (2 h after injection). In cells stimulated by FSH, genes related to lipid metabolism, including Rdh10, Dci, RarB, Lpl, Acsl3, and Dgat2, were expressed differentially, compared with no FSH. Several pathways of retinal and fatty acid metabolism, and peroxisome proliferator-activated receptor (PPAR) signaling changed. In conclusion, FSH stimulates lipid biosynthesis by upregulating Fshr mRNA expression in abdominal adipose tissue of chickens. Several genes involved in fatty acid and retinal metabolism and the PPAR signaling pathway mediate this novel function of FSH.

Transdifferentiation of fibroblasts into adipocyte-like cells by chicken adipogenic transcription factors

Adipocyte differentiation is a complex process that is regulated mainly by a cascade of transcription factors. Among these, CCAAT/enhancer binding protein (C/EBP)alpha, peroxisome proliferator-activated receptor (PPAR)gamma and sterol regulatory element-binding protein-1 (SREBP-1) have been identified as key regulators of adipocyte differentiation. In mammals, ectopic expression of adipogenic transcription factors C/EBPalpha, PPARgamma and SREBP-1 can induce transdifferentiation of a variety of different cell types into adipocyte-like cells. However, in birds, whether C/EBPalpha, PPARgamma and SREBP-1 can induce transdifferentiation is unknown. The current study was designed to investigate whether chicken embryo fibroblasts (CEFs) can be induced to transdifferentiate into adipocyte-like cells by the ectopic expression of chicken C/EBPalpha, PPARgamma and SREBP-1 via retrovirus-mediated gene transfer. The results showed that any one of these three adipogenic transcription factors was sufficient to trigger the adipogenic program in CEFs, as demonstrated by accumulation of cytoplasmic lipid droplets and expression of the adipocyte marker gene (adipocyte fatty acid binding protein, A-FABP). This suggests that C/EBPalpha, PPARgamma and SREBP-1 play a crucial role in chicken adipogenesis.