Changes in mRNA expression of regulatory factors involved in adipocyte differentiation during fatty acid induced adipogenesis in chicken

Embryonic Thermal Programming and Dietary Baicalein Supplementation Post-Hatch: Effects on Broiler Adipose Tissue Deposition

Optimization of growth performance and fat metabolism in broilers are critical for meat quality and overall production efficiency. This experiment investigated the effects of dietary baicalein supplementation and embryonic heat conditioning (EHC) on the growth performance and adipose tissue metabolism of 10-day old broilers. Fertile eggs were divided into control and EHC groups, with EHC eggs exposed to intermittent heating (39.5 °C) from day 7 to day 16 of incubation. Hatched chicks were further divided into four groups: CC (control control), CT (control treatment with baicalein), EC (embryonic heat control), and ET (embryonic heat treatment with baicalein), and were fed ad libitum. On day 10 post-hatch, blood and adipose tissue samples were collected for analysis. C/EBPα mRNA was lower in the ET group compared to the EC group and higher in the CT group compared to the CC group. PPARγ and HSL mRNAs were elevated in both the ET and CT groups relative to their controls. Additionally, plasma non-esterified fatty acid (NEFA) levels were significantly higher in the CT group compared to the CC group. These results indicate that baicalein supplementation, particularly when combined with embryonic heat conditioning, can modulate fat metabolism and potentially improve the growth performance of broilers, thereby offering insights into strategies for enhancing poultry production.

Chicken Embryo Fibroblast Viability and Trans-Differentiation Potential for Cultured Meat Production Across Passages

This study was conducted to analyze the viability of primary chicken embryo fibroblasts and the efficiency of adipogenic trans-differentiation for cultured meat production. In isolating chicken embryo fibroblasts (CEFs) from a heterogeneous cell pool containing chicken satellite cells (CSCs), over 90% of CEFs expressed CD29 and vimentin. The analysis of the proliferative capabilities of CEFs revealed no significant differences in EdU-positive cells (%), cumulative cell number, doubling time, and growth rate from passage 1 to passage 9 (p > 0.05). This indicates that CEFs can be isolated by 2 h of pre-plating and survive stably up to passage 9, and that primary fibroblasts can serve as a valuable cell source for the cultured meat industry. Adipogenic trans-differentiation was induced up to passage 9 of CEFs. As passages increased, lipid accumulation and adipocyte size significantly decreased (p < 0.05). The reduced differentiation rate of primary CEFs with increasing passages poses a major challenge to the cost and efficiency of cultured meat production. Thus, effective cell management and the maintenance of cellular characteristics for a long time are crucial for ensuring stable and efficient cultured fat production in the cultured meat industry.

E2F transcription factor 5, a new regulator in adipogenesis to mediate the role of Krüppel-like factor 7 in chicken preadipocyte differentiation and proliferation

E2F transcription factor 5 (E2F5) gene is a transcription factor, plays an important role in the development of a variety of cells. E2F5 is expressed in human and mouse adipocytes, but its specific function in adipogenesis is unclear. Krüppel-like factor 7 (KLF7) facilitates proliferation and inhibits differentiation in chicken preadipocytes. Our previous KLF7 chromatin immunoprecipitation-sequencing analysis revealed a KLF7-binding peak in the 3' flanking region of the E2F5, indicating a regulatory role of KLF7 in this region. In the present study, we investigated E2F5 potential role, the overexpression and knockdown analyses revealed that E2F5 inhibited the differentiation and promoted the proliferation of chicken preadipocytes. Moreover, we identified enhancer activity in the 3' flanking region (nucleotides +22661/+22900) of E2F5 and found that KLF7 overexpression increased E2F5 expression and luciferase activity in this region. Deleting the putative KLF7-binding site eliminated the promoting effect of KLF7 overexpression on E2F5 expression. Further, E2F5 reversed the KLF7-induced decrease in preadipocyte differentiation and increase in preadipocyte proliferation. Taken together, our findings demonstrate that KLF7 inhibits differentiation and promotes proliferation in preadipocytes by enhancing E2F5 transcription.

PU.1 interacts with KLF7 to suppress differentiation and promote proliferation in chicken preadipocytes

<p indent="0mm">Krüppel-like factor 7 (KLF7) is a negative regulator of preadipocyte differentiation. Our previous KLF7 ChIP-seq analysis showed that the binding motif of PU.1 was found among the KLF7 binding peaks, indicating that an interaction between KLF7 and PU.1 at preadipocyte gene promoters and other regulatory elements might be common. Here, Co-IP and FRET assays are used to confirm that PU.1 can directly bind to KLF7 and enhance the transcription activity of cyclin-dependent kinase inhibitor 3 ( <italic>CDKN3</italic>), which is a downstream target gene of KLF7. We show that the PU.1 expression level is decreased during preadipocyte differentiation. Furthermore, PU.1 overexpression and knockdown experiments reveal that PU.1 negatively regulates chicken preadipocyte differentiation, as evidenced by appropriate changes in lipid droplet accumulation and altered expressions of PPARγ, FAS, and PLIN. In addition, PU.1 overexpression promotes preadipocyte proliferation, while knockdown of <italic>PU</italic>. <italic>1</italic> inhibits preadipocyte proliferation. We further demonstrate that PU.1 inhibits differentiation and promotes proliferation in preadipocytes, in part by directly interacting with KLF7. </p>.

Resveratrol Inhibits Proliferation and Differentiation of Porcine Preadipocytes by a Novel LincRNA-ROFM/miR-133b/AdipoQ Pathway

Resveratrol (RES) has a wide range of biological and pharmacological activities with various health benefits for humans as a food additive. In animal production, RES has been considered a potential functional feed additive for producing high-quality pork. Long noncoding RNAs (lncRNAs) have emerged as essential regulators of fat metabolism, and phytochemicals can regulate fat metabolism through lncRNA. However, it is unclear whether RES can improve back-fat thickness by regulating lncRNA. In this study, we identified a novel lncRNA, which was named a long intergenic non-protein coding RNA, a regulator of fat metabolism (LincRNA-ROFM), from our previous lncRNA sequencing data. LincRNA-ROFM can inhibit adipocyte proliferation and differentiation. In-depth analyses showed that LincRNA-ROFM acts as a molecular sponge for miR-133b, and adiponectin (AdipoQ) is a direct target of miR-133b in porcine preadipocytes. In addition, the expression of LincRNA-ROFM was positively correlated with AdipoQ. RES can promote the expression of LincRNA-ROFM by PPARα and C/EBPα. Altogether, our research showed that LincRNA-ROFM acts as a ceRNA to sequester miR-133b and is upregulated by RES, leading to heightened AdipoQ expression, and thus decreased adipocyte proliferation and differentiation, which reduces back-fat thickness of pigs. Taken together, the RES/LincRNA-ROFM/miR-133b/AdipoQ regulatory network preliminarily explains the mechanism of action of RES in inhibiting fat deposition, which provides new insight into the downstream mechanism of RES inhibition of fat deposits by regulating the lncRNA.

Reassessment of adipocyte technology for cellular agriculture of alternative fat

Alternative proteins, such as cultivated meat, have recently attracted significant attention as novel and sustainable food. Fat tissue/cell is an important component of meat that makes organoleptic and nutritional contributions. Although adipocyte biology is relatively well investigated, there is limited focus on the specific techniques and strategies to produce cultivated fat from agricultural animals. In the assumed standard workflow, stem/progenitor cell lines are derived from tissues of animals, cultured for expansion, and differentiated into mature adipocytes. Here, we compile information from literature related to cell isolation, growth, differentiation, and analysis from bovine, porcine, chicken, other livestock, and seafood species. A diverse range of tissue sources, cell isolation methods, cell types, growth media, differentiation cocktails, and analytical methods for measuring adipogenic levels were used across species. Based on our analysis, we identify opportunities and challenges in advancing new technology era toward producing "alternative fat" that is suitable for human consumption.

Regulation of Δ6Fads2 Gene Involved in LC-PUFA Biosynthesis Subjected to Fatty Acid in Large Yellow Croaker (Larimichthys crocea) and Rainbow Trout (Oncorhynchus mykiss)

Δ6 fatty acyl desaturase (Δ6Fads2) is regarded as the first rate-limiting desaturase that catalyzes the biosynthesis of long-chain polyunsaturated fatty acids (LC-PUFA) from 18-carbon fatty acid in vertebrates, but the underlying regulatory mechanism of fads2 has not been comprehensively understood. This study aimed to investigate the regulation role of fads2 subjected to fatty acid in large yellow croaker and rainbow trout. In vivo, large yellow croaker and rainbow trout were fed a fish oil (FO) diet, a soybean oil (SO) diet or a linseed oil (LO) diet for 10 weeks. The results show that LO and SO can significantly increase fads2 expression (p < 0.05). In vitro experiments were conducted in HEK293T cells or primary hepatocytes to determine the transcriptional regulation of fads2. The results show that CCAAT/enhancer-binding protein α (C/EBPα) can up-regulate fads2 expression. GATA binding protein 3 (GATA3) can up-regulate fads2 expression in rainbow trout but showed opposite effect in large yellow croaker. Furthermore, C/EBPα protein levels were significantly increased by LO and SO (p < 0.05), gata3 expression was increased in rainbow trout by LO but decreased in large yellow croaker by LO and SO. In conclusion, we revealed that FO replaced by LO and SO increased fads2 expression through a C/EBPα and GATA3 dependent mechanism in large yellow croaker and rainbow trout. This study might provide critical insights into the regulatory mechanisms of fads2 expression and LC-PUFA biosynthesis.

The Full-Length Transcriptome Provides New Insights Into the Transcript Complexity of Abdominal Adipose and Subcutaneous Adipose in Pekin Ducks

Adipose tissues have a central role in organisms, and adipose content is a crucial economic trait of poultry. Pekin duck is an ideal model to study the mechanism of abdominal and subcutaneous adipose deposition for its high ability of adipose synthesis and deposition. Alternative splicing contributes to functional diversity in abdominal and subcutaneous adipose. However, there has been no systematic analysis of the dynamics of differential alternative splicing of abdominal and subcutaneous adipose in Pekin duck. In our study, the Pacific Biosciences (PacBio) Iso-Seq technology was applied to explore the transcriptional complexity of abdominal and subcutaneous adipose in Pekin ducks. In total, 143,931 and 111,337 full-length non-chimeric transcriptome sequences of abdominal and subcutaneous adipocytes were obtained from 41.78 GB raw data, respectively. These data led us to identify 19,212 long non-coding RNAs (lncRNAs) and 74,571 alternative splicing events. In addition, combined with the next-generation sequencing technology, we correlated the structure and function annotation with the differential expression profiles of abdominal and subcutaneous adipose transcripts. This study identified lots of novel alternative splicing events and major transcripts of transcription factors related to adipose synthesis. STAT3 was reported as a vital gene for adipogenesis, and we found that its major transcript is STAT3-1, which may play a considerable role in the process of adipose synthesis in Pekin duck. This study greatly increases our understanding of the gene models, genome annotations, genome structures, and the complexity and diversity of abdominal and subcutaneous adipose in Pekin duck. These data provide insights into the regulation of alternative splicing events, which form an essential part of transcript diversity during adipogenesis in poultry. The results of this study provide an invaluable resource for studying alternative splicing and tissue-specific expression.

Three chromosome-level duck genome assemblies provide insights into genomic variation during domestication

Domestic ducks are raised for meat, eggs and feather down, and almost all varieties are descended from the Mallard (Anas platyrhynchos). Here, we report chromosome-level high-quality genome assemblies for meat and laying duck breeds, and the Mallard. Our new genomic databases contain annotations for thousands of new protein-coding genes and recover a major percentage of the presumed "missing genes" in birds. We obtain the entire genomic sequences for the C-type lectin (CTL) family members that regulate eggshell biomineralization. Our population and comparative genomics analyses provide more than 36 million sequence variants between duck populations. Furthermore, a mutant cell line allows confirmation of the predicted anti-adipogenic function of NR2F2 in the duck, and uncovered mutations specific to Pekin duck that potentially affect adipose deposition. Our study provides insights into avian evolution and the genetics of oviparity, and will be a rich resource for the future genetic improvement of commercial traits in the duck.

Research Note: Potential usage of DF-1 cell line as a new cell model for avian adipogenesis

Current research of avian adipogenesis has been dependent on primary preadipocytes culture due to the lack of commercially available immortal preadipocyte cell lines in avian species. In addition to primary stromal vascular cells, primary chicken embryonic fibroblasts (CEF) were suggested as new in vitro models for adipogenesis study, because CEF can be differentiated into adipocytes by a combination of fatty acids and insulin (FI), or all-trans retinoic acid (atRA) alone in the media containing chicken serum (CS). However, there are decreases in differentiation of primary cells due to diverse population of cell types and low adipogenic potential of cells after passages. In the present study, adipogenic differentiation of DF-1 cells, immortal fibroblasts derived from an embryonic chicken, was tested with 4 different medium; 10% fetal bovine serum (FBS), 10% CS, 10% CS with FI, and 10% CS with FI and atRA. Lipid droplets stained with Oil Red O were not shown in DF-1 cells under 10% FBS, appeared with very small sizes under 10% CS, significantly increased under 10% CS with FI, and most significantly accumulated under 10% CS with FI and atRA. In addition, expressions of markers for adipogenesis (Znf423, C/ebpβ, Pparγ, and Fabp4), fatty acid uptake (CD36), triglyceride synthesis (Gpd1, Dgat2), and lipid droplet stabilization (Plin1) were significantly upregulated by supplementation of 10% CS with FI and atRA. Morphological evidence for formation of lipid droplets and dramatic induction of adipogenic marker genes support the adipogenic potential of DF-1 cells, offering DF-1 cells as a new cell model to investigate various research studies involving avian adipogenesis.

Increasing Fat Deposition Via Upregulates the Transcription of Peroxisome Proliferator-Activated Receptor Gamma in Native Crossbred Chickens

Simple Summary

Crossbreeding using exotic breeds is usually employed to improve the growth characteristics of indigenous chickens. This mating not only provides growth but adversely affects excess fat deposition as well. This deposition was regulated by a complicated cellular mechanism including peroxisome proliferator-activated receptors (PPARs) function. Thus, we hypothesized that native chickens breed percentage might be related to PPARs gene expression. This study aimed to study the role of PPARs on fat deposition in chickens which was the different native genetic background. Our results indicated that increasing commercial breed percentage in the chicken leads to increased fat deposition via the increasing of PPARG gene expression. Therefore, the PPARG gene notable as a major gene of cellular fat deposition and might be applied in further study.

Abstract

This study aimed to study the role of PPARs on fat deposition in native crossbred chicken. We studied the growth, abdominal, subcutaneous, and intramuscular fat, and mRNA expression of PPARA and PPARG in adipose and muscle tissues of four chicken breeds (CH breed (100% Thai native chicken), KM1 (50% CH background), KM2 (25% CH background), and broiler (BR)). The result shows that the BR chickens had higher abdominal fat than other breeds (p < 0.05) and the KM2 had an abdominal fat percentage higher than KM1 and CH respectively (p < 0.05). The intramuscular fat of BR was greater than KM1 and CH (p < 0.05). In adipose tissue, PPARA expression was different among the chicken breeds. However, there were breed differences in PPARG expression. Study of abdominal fat PPARG expression showed the BR breed, KM1, and KM2 breed significantly greater (p < 0.05) than CH. In 8 to 12 weeks of age, the PPARG expression of the CH breed is less than (p < 0.05) KM2. Crossbreeding improved the growth of the Thai native breed, there was also a corresponding increase in carcass fatness. However, there appears to be a relationship between PPARG expression and fat deposition traits. therefore, PPARG activity hypothesized to plays a key role in lipid accumulation by up-regulation.

Effect of 20(S)-Hydroxycholesterol on Multilineage Differentiation of Mesenchymal Stem Cells Isolated from Compact Bones in Chicken

Bone health and body weight gain have significant economic and welfare importance in the poultry industry. Mesenchymal stem cells (MSCs) are common progenitors of different cell lineages such as osteoblasts, adipocytes, and myocytes. Specific oxysterols have shown to be pro-osteogenic and anti-adipogenic in mouse and human MSCs. To determine the effect of 20(S)-hydroxycholesterol (20S) on osteogenic, adipogenic, and myogenic differentiation in chicken, mesenchymal stem cells isolated from compact bones of broiler chickens (cBMSCs) were subjected to various doses of 20S, and markers of lineage-specific mRNA were analyzed using real-time PCR and cell cytochemistry. Further studies were conducted to evaluate the molecular mechanisms involved in lineage-specific differentiation pathways. Like human and mouse MSCs, 20S oxysterol expressed pro-osteogenic, pro-myogenic, and anti-adipogenic differentiation potential in cBMSCs. Moreover, 20(S)-Hydroxycholesterol induced markers of osteogenic genes and myogenic regulatory factors when exposed to cBMSCs treated with their specific medium. In contrast, 20S oxysterol suppressed expression of adipogenic marker genes when exposed to cBMSCs treated with OA, an adipogenic precursor of cBMSCs. To elucidate the molecular mechanism by which 20S exerts its differentiation potential in all three lineages, we focused on the hedgehog signaling pathway. The hedgehog inhibitor, cyclopamine, completely reversed the effect of 20S induced expression of osteogenic and anti-adipogenic mRNA. However, there was no change in the mRNA expression of myogenic genes. The results showed that 20S oxysterol promotes osteogenic and myogenic differentiation and decreases adipocyte differentiation of cBMSCs. This study also showed that the induction of osteogenesis and adipogenesis inhibition in cBMSCs by 20S is mediated through the hedgehog signaling mechanism. The results indicated that 20(S) could play an important role in the differentiation of chicken-derived MSCs and provided the theory basis on developing an intervention strategy to regulate skeletal, myogenic, and adipogenic differentiation in chicken, which will contribute to improving chicken bone health and meat quality. The current results provide the rationale for the further study of regulatory mechanisms of bioactive molecules on the differentiation of MSCs in chicken, which can help to address skeletal health problems in poultry.

Investigation of the CEBPA gene expression pattern and association analysis of its polymorphisms with meat quality traits in chickens

Meat quality is closely related to the fat deposition which is regulated by a cascade of transcription factors. As a transcription factor, the CCAAT/enhancer binding protein alpha (CEBPA) is considered as one of the key molecules regulating adipogenesis. Therefore, the objective of this study was to detect the expression pattern of the CEBPA gene and evaluate whether its single nucleotide polymorphisms (SNPs) were associated with the meat quality traits in Wuliang Mountain Black-bone (WLMB) chickens. The results showed that the chicken CEBPA mRNA was widely expressed in the 11 tissues, and the expression pattern of it might be tissue- and time-specific different. The locus of g.74C > G was not significantly associated with chicken meat quality. For the locus of g.552G > A, chickens with the GG genotype showed higher pH (p < 0.01), lower drip loss (p < 0.01) and higher intramuscular fat (p < 0.05) than those with other genotypes. It suggested that polymorphisms of the CEBPA gene were significantly associated with the meat quality traits of WLMB chickens. The results of this study contribute to the functional research of the CEBPA gene and lay the foundation for improving meat quality based on the marker-assisted selection in chickens.

Obesity, insulin resistance, adiponectin, and PPAR-γ gene expression in broiler chicks fed diets supplemented with fat and green tea (Camellia sinensis) extract

Adipose tissue is an active endocrine organ secreting several adipokines, especially adiponectin, that play an important role in regulating insulin function in the body of mammals. Therefore, this study was aimed to investigate the association between abdominal fat deposit, insulin resistance, peroxisome proliferator-activated receptor gamma (PPAR-γ), and adiponectin gene (AG) expression in broiler chicks fed diets high in unsaturated fat supplemented with green tea extract (GTE). A total of 300 one-day-old female Ross 308 broiler chicks were allocated to 6 dietary treatments in a completely randomized design with a factorial arrangement of two levels of GTE (0 and 500 mg/kg diet) × three levels of fat inclusion [without fat (control group), soybean oil (SO), and tallow (Ta)]. Each treatment was replicated five times. At the end of the experiment (day 49), two chicks from each replicate weighing an average of pen weight were bled and then slaughtered for further analysis. Abdominal fat percentage, fasting concentration of blood glucose, triglyceride and insulin, glycogen reserves of breast and liver tissues, and PPAR-γ and AG expression were determined. The insulin resistance index of the Quantitative Insulin Sensitivity Check Index (QUICKI) was calculated using the fasting plasma glucose and insulin concentrations. The highest abdominal fat percentage and the lowest carcass yield were obtained in chicks fed SO-supplemented diet (P < 0.05). Chicks fed diet supplemented with SO showed the highest PPAR-γ gene expression (P < 0.05). SO-rich diets suppressed AG expression in chickens' abdominal fat tissue, and the birds fed with SO-supplemented diet showed a significant decrease in AG expression compared with the control (P < 0.05). Chicks fed diet supplemented with SO showed lower QUICKI and breast glycogen reserve compared with the control group (P < 0.05). A significant increase in blood glucose and triglyceride concentrations was observed in birds fed SO-supplemented diets (P < 0.05). AG and PPAR-γ expression increased and decreased by GTE, respectively. QUICKI tended (P = 0.09) to be greater in GTE-supplemented chicks; however, the effect of GTE supplementation on carcass yield, abdominal fat percentage, and blood insulin and glucose concentration was not significant. The findings of this study showed that SO-rich diets via increased PPAR-γ gene expression and decreased AG expression in abdominal fat may lead to insulin resistance in female broiler chicks.

ALDH1A1 Inhibits Chicken Preadipocytes' Proliferation and Differentiation via the PPARγ Pathway In Vitro and In Vivo

ALDH1A1 (aldehyde dehydrogenase 1A1) is a crucial protein in retinoids’ metabolism, and the lack of ALDH1A1 inhibits the fat deposition in mice. However, whether ALDH1A1 has a similar effect on chickens’ fat-depot is still unknown. In this study, we investigate the role of ALDH1A1 in chickens’ adipogenesis. The immortalized chicken preadipocyte 1 (ICP1) cell line and chicken primary preadipocytes isolated from abdominal fat were used to perform a series of experiments in vitro to elucidate the effects of ALDH1A1. In addition, lentivirus was used to verify the results of cell experiments in vivo. The data showed that overexpression of ALDH1A1 significantly weakened the proliferation of preadipocytes and suppressed the differentiation of preadipocytes through the PPARγ pathway, and the knockdown experiments had the opposite results. Moreover, chickens injected with overexpression lentivirus had higher abdominal fat percentage, a bigger size of lipid droplets, and higher triglyceride content in abdominal fat, and chickens injected with interfering lentivirus had the opposite situation. We proved that ALDH1A1 not only inhibited the proliferation and differentiation of chickens’ preadipocytes in vitro, but also inhibited the fat-depot of chickens in vivo, which was completely opposite the function of ALDH1A1 in mice, indicating that ALDH1A1 may have a different mechanism that is still unknown.

Short-Term Responses to Fatty Acids on Lipid Metabolism and Adipogenesis in Rainbow Trout (Oncorhynchus mykiss)

Fish are rich in n-3 long-chain polyunsaturated fatty acids (LC-PUFA) such as eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids. Due to the increasing use of vegetable oils (VO), their proportion in diets has lowered, affecting lipid metabolism and fillet composition. Rainbow trout cultured preadipocytes were treated with representative FA found in fish oils (EPA and DHA) or VO (linoleic, LA and alpha-linolenic, ALA acids), while EPA and LA were also orally administered, to evaluate their effects on adipogenesis and lipid metabolism. In vitro, all FA increased lipid internalization, with ALA producing the highest effect, together with upregulating the FA transporter fatp1. In vivo, EPA or LA increased peroxisome proliferator-activated receptors ppara and pparb transcripts abundance in adipose tissue, suggesting elevated β-oxidation, contrary to the results obtained in liver. Furthermore, the increased expression of FA synthase (fas) and the FA translocase/cluster of differentiation (cd36) in adipose tissue indicated an enhanced uptake of lipids and lipogenesis de novo, whereas stable or low hepatic expression of genes involved in lipid transport and turnover was found. Thus, fish showed a similar tissue metabolic response to the short-term availability of EPA or LA in vivo, while in vitro VO-derived FA demonstrated greater potential inducing fat accumulation.

Dynamics of transcriptome changes during subcutaneous preadipocyte differentiation in ducks

BACKGROUND

Pekin duck is an important animal model for its ability for fat synthesis and deposition. However, transcriptional dynamic regulation of adipose differentiation driven by complex signal cascades remains largely unexplored in this model. This study aimed to explore adipogenic transcriptional dynamics before (proliferation) and after (differentiation) initial preadipocyte differentiation in ducks.

RESULTS

Exogenous oleic acid alone successfully induced duck subcutaneous preadipocyte differentiation. We explored 36 mRNA-seq libraries in order to study transcriptome dynamics during proliferation and differentiation processes at 6 time points. Using robust statistical analysis, we identified 845, 652, 359, 2401 and 1933 genes differentially expressed between -48 h and 0 h, 0 h and 12 h, 12 h and 24 h, 24 h and 48 h, 48 h and 72 h, respectively (FDR < 0.05, FC > 1.5). At the proliferation stage, proliferation related pathways and basic cellular and metabolic processes were inhibited, while regulatory factors that initiate differentiation enter the ready-to-activate state, which provides a precondition for initiating adipose differentiation. According to weighted gene co-expression network analysis, pathways positively related to adipogenic differentiation are significantly activated at the differentiation stage, while WNT, FOXO and other pathways that inhibit preadipocyte differentiation are negatively regulated. Moreover, we identified and classified more than 100 transcription factors that showed significant changes during differentiation, and found novel transcription factors that were not reported to be related to preadipoctye differentiation. Finally, we manually assembled a proposed regulation network model of subcutaneous preadipocyte differentiation base on the expression data, and suggested that E2F1 may serve as an important link between the processes of duck subcutaneous preadipocyte proliferation and differentiation.

CONCLUSIONS

For the first time we comprehensively analyzed the transcriptome dynamics of duck subcutaneous preadipocyte proliferation and differentiation. The current study provides a solid basis for understanding the synthesis and deposition of subcutaneous fat in ducks. Furthermore, the information generated will allow future investigations of specific genes involved in particular stages of duck adipogenesis.

Fatty acids from fish or vegetable oils promote the adipogenic fate of mesenchymal stem cells derived from gilthead sea bream bone potentially through different pathways

Fish are rich in n-3 long-chain polyunsaturated fatty acids (LC-PUFA), such as eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids, thus they have a great nutritional value for human health. In this study, the adipogenic potential of fatty acids commonly found in fish oil (EPA and DHA) and vegetable oils (linoleic (LA) and alpha-linolenic (ALA) acids), was evaluated in bone-derived mesenchymal stem cells (MSCs) from gilthead sea bream. At a morphological level, cells adopted a round shape upon all treatments, losing their fibroblastic form and increasing lipid accumulation, especially in the presence of the n-6 PUFA, LA. The mRNA levels of the key transcription factor of osteogenesis, runx2 significantly diminished and those of relevant osteogenic genes remained stable after incubation with all fatty acids, suggesting that the osteogenic process might be compromised. On the other hand, transcript levels of the main adipogenesis-inducer factor, pparg increased in response to EPA. Nevertheless, the specific PPARγ antagonist T0070907 appeared to suppress the effects being caused by EPA over adipogenesis. Moreover, LA, ALA and their combinations, significantly up-regulated the fatty acid transporter and binding protein, fatp1 and fabp11, supporting the elevated lipid content found in the cells treated with those fatty acids. Overall, this study has demonstrated that fatty acids favor lipid storage in gilthead sea bream bone-derived MSCs inducing their fate into the adipogenic versus the osteogenic lineage. This process seems to be promoted via different pathways depending on the fatty acid source, being vegetable oils-derived fatty acids more prone to induce unhealthier metabolic phenotypes.

Isolation and Differentiation of Mesenchymal Stem Cells From Broiler Chicken Compact Bones

Chicken mesenchymal stem cells (MSCs) can be used as an avian culture model to better understand osteogenic, adipogenic, and myogenic pathways and to identify unique bioactive nutrients and molecules which can promote or inhibit these pathways. MSCs could also be used as a model to study various developmental, physiological, and therapeutic processes in avian and other species. MSCs are multipotent stem cells that are capable of differentiation into bone, muscle, fat, and closely related lineages and express unique and specific cell surface markers. MSCs have been isolated from numerous sources including human, mouse, rabbit, and chicken with potential clinical and agricultural applications. MSCs from chicken compact bones have not been isolated and characterized yet. In this study, MSCs were isolated from compact bones of the femur and tibia of day-old male broiler chicks to investigate the biological characteristics of the isolated cells. Isolated cells took 8–10 days to expand, demonstrated a monolayer growth pattern and were plastic adherent. Putative MSCs were spindle-shaped with elongated ends and showed rapid proliferation. MSCs demonstrated osteoblastic, adipocytic, and myogenic differentiation when induced with specific differentiation media. Cell surface markers for MSCs such as CD90, CD105, CD73, CD44 were detected positive and CD31, CD34, and CD45 cells were detected negative by PCR assay. The results suggest that MSCs isolated from broiler compact bones (cBMSCs) possess similar biological characteristics as MSCs isolated from other chicken tissue sources.

The differentiation of preadipocytes and gene expression related to adipogenesis in ducks (Anas platyrhynchos)

Meat quality is closely related to adipose tissues in ducks, and adipogenesis is controlled by a complex network of transcription factors tightly acting at different stages of differentiation especially in ducks. The aim of this study was to establish the preadipocyte in vitro culture system and understand the biological characteristics of expansion of duck adipocyte tissue at the cellular and molecular level. We isolated pre-adipocytes from the subcutaneous fat of three breeds of duck and differentiated them into mature adipocytes using a mixture of insulin, rosiglitazone, dexamethasone, 3-isobutyl-1-methylxanthine, and oleic acid over 0,2, 4, 6, and 8 days. Successful differentiation was confirmed from the development of lipid droplets and their response to Oil Red O, and increasing numbers of lipid droplets were stained red over time. The expression of key marker genes, including peroxisome proliferator activated receptor γ (PPARγ), CCAAT/enhancer binding protein-α (C/EBPα), adipocyte fatty acid binding protein 4 (FABP4), and fatty acid synthetase (FAS), gradually increased during pre-adipocyte differentiation. Furthermore, it was verified by interference experiments that the knockdown of PPARγ directly reduced lipid production. Meanwhile we analyzed the role of unsaturated fatty acids in the production of poultry fat using different concentrations of oleic acid and found that lipid droplet deposition was highest when the concentration of oleic acid was 300 μM. We also compared the level of differentiated pre-adipocytes that were isolated from Jianchang ducks (fatty-meat duck), Cherry Valley ducks (lean-meat duck) and White-crested ducks (egg-producing duck). The proliferation and differentiation rate of pre-adipocytes derived from Jianchang ducks was higher than that of White-crested ducks. These results provide the foundation for further research into waterfowl adipogenesis.

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.

A high fat diet enhances the sensitivity of chick adipose tissue to the effects of centrally injected neuropeptide Y on gene expression of adipogenesis-associated factors

The purpose of this study was to determine how dietary macronutrient composition and exogenous neuropeptide Y (NPY) affect mRNA abundance of factors associated with lipid metabolism in chick adipose tissue. Chicks were fed one of three isocaloric (3000kcal metabolizable energy (ME)/kg) diets after hatch: high carbohydrate (HC; control), high fat (HF; 30% of ME from soybean oil) or high protein (HP; 25% crude protein). On day 4 post-hatch, vehicle or 0.2nmol of NPY was injected intracerebroventricularly and abdominal and subcutaneous fat depots collected 1h later. In abdominal fat, mRNA abundance of peroxisome proliferator-activated receptor γ (PPARγ) and fatty acid binding protein 4 (FABP4) increased after NPY injection in HF diet-fed chicks. NPY injection decreased expression of PPARγ and sterol regulatory element-binding transcription factor 1 (SREBP1) in the subcutaneous fat of HC diet-fed chicks, whereas SREBP1 expression was increased in the subcutaneous fat of HF diet-fed chicks after NPY injection. An acutely increased central concentration of NPY in chicks affects adipose tissue physiology in a depot- and diet-dependent manner. The chick may serve as a model to understand the relationship between diet and the brain-fat axis' role in maintaining whole body energy homeostasis, as well as to understand metabolic distinctions among fat depots.

Fatty Acids Have Different Adipogenic Differentiation Potentials in Stromal Vascular Cells Isolated from Abdominal Fat in Laying Hens

This study was conducted to examine the effects of fatty acids (FA) with/without chicken serum (CS) on the expression of adipogenic transcripts and adipogenesis in chicken stromal vascular cells (SVC). In experiment 1, SVC were grown in DMEM containing 10% FBS (Control) and treated with 300 µM oleic acid (OLA) + FBS, linoleic acid (LNA) + FBS, palmitic acid (PAM) + FBS, or stearic acid (STA) + FBS for 48 h. In experiment 2, cells were grown in DMEM containing 5% CS and treated with 300 µM OLA (CS + OLA), PAM (CS + PAM), STA (CS + STA) or 200 µM LNA (CS + LNA) for 48 h. Adipogenesis was determined using Oil Red O staining and glycerol-3-phosphate dehydrogenase (GPDH) activity. The proportion of OLA, PAM, or STA was increased (P < 0.05) in SVC grown in either FBS or CS with OLA, PAM or STA. Adipogenesis was induced in FBS + OLA, FBS + LNA, FBS + PAM, FBS + STA, CS + OLA, CS + LNA, CS + PAM, or CS + SAT compared to FBS. GPDH activity was significantly higher in FBS + OLA and FBS + LNA than one in FBS. Compared to FBS, the expression of FABP4 mRNA increased (P < 0.05) in FBS + OLA, FBS + LNA, or FBS + PAM, whereas that of C/EBPα, C/EBPβ, and ATGL increased (P < 0.05) in FBS + OLA or FBS + LNA cells. Expression of FABP4 and C/EBPβ mRNA was higher in CS, CS + OLA, CS + LNA, CS + PAM, or CS + SAT compared with (FBS, whereas the expression of ATGL and C/EBPα was higher in CS, CS + OLA, or CS + LNA than FBS cells. In conclusion, these results showed that FA have different potentials to induce adipogenesis, LNA is the most potent among the tested FA, and these potentials can be improved in the presence of CS.

Immortalization of chicken preadipocytes by retroviral transduction of chicken TERT and TR

The chicken is an important agricultural animal and model for developmental biology, immunology and virology. Excess fat accumulation continues to be a serious problem for the chicken industry. However, chicken adipogenesis and obesity have not been well investigated, because no chicken preadipocyte cell lines have been generated thus far. Here, we successfully generated two immortalized chicken preadipocyte cell lines through transduction of either chicken telomerase reverse transcriptase (chTERT) alone or in combination with chicken telomerase RNA (chTR). Both of these cell lines have survived >100 population doublings in vitro, display high telomerase activity and have no sign of replicative senescence. Similar to primary chicken preadipocytes, these two cell lines display a fibroblast-like morphology, retain the capacity to differentiate into adipocytes, and do not display any signs of malignant transformation. Isoenzyme analysis and PCR-based analysis confirmed that these two cell lines are of chicken origin and are free from inter-species contamination. To our knowledge, this is the first report demonstrating the generation of immortal chicken cells by introduction of chTERT and chTR. Our established chicken preadipocyte cell lines show great promise as an in vitro model for the investigation of chicken adipogenesis, lipid metabolism, and obesity and its related diseases, and our results also provide clues for immortalizing other avian cell types.

Genome-Wide Analysis of lncRNA and mRNA Expression During Differentiation of Abdominal Preadipocytes in the Chicken

Long noncoding RNAs (lncRNAs) regulate adipogenesis and other processes associated with metabolic tissue development and function. However, little is known about the function and profile of lncRNAs during preadipocyte differentiation in the chicken (Gallus gallus). Herein, lncRNA and mRNA expression in preadipocytes at different stages of differentiation were analyzed using RNA sequencing. A total of 1,300,074,528 clean reads and 27,023 novel lncRNAs were obtained from 12 samples. The number of genes (1336 lncRNAs and 1759 mRNAs; 3095 in total) differentially expressed across various stages declined as differentiation progressed. Differentially expressed genes were found to be involved in several pathways related to preadipocyte differentiation that have been extensively studied, including glycerolipid metabolism, and the mammalian target of rapamycin, peroxisome proliferator-activated receptor, and mitogen-activated protein kinase signaling pathways. To our knowledge, some pathways are being reported for the first time, including the propanoate metabolism, fatty acid metabolism, and oxidative phosphorylation pathways. Furthermore, 3095 differentially expressed genes were clustered into eight clusters, and their expression patterns were determined through K-means clustering. Genes involved in the K2 cluster likely play important roles in preadipocyte differentiation. Six stage-specific modules related to A0 (day 0), A2 (day 2), and A6 (day 6) stages were identified, using weighted coexpression network analysis. Nine central, highly connected .genes in stage-specific modules were subsequently identified, including XLOC_068731, XLOC_022661, XLOC_045161, XLOC_070302, CHD6, LLGL1, NEURL1B, KLHL38, and ACTR6. This study provides a valuable resource for further study of chicken lncRNA and facilitates a better understanding of preadipocyte differentiation in the chicken

Cocktail supplement with rosiglitazone: a novel inducer for chicken preadipocyte differentiation in vitro

Chicken preadipocytes cultured in cocktail supplement with rosiglitazone resulted in a marked increase in lipid droplet accumulation, glycerol-3-phosphate dehydrogenase (GPDH) activity and mRNA expression of adipocyte fatty acid-binding protein (aP2), G₀/G₁ switch gene 2 (G0S2), peroxisome proliferator-activated receptor γ (PPARγ) and lipolysis. The present study provides a novel induction method for in vitro chicken preadipocyte differentiation.

The preadipocyte differentiation biological process involves a cascade of transcriptional events that culminates in the expression of peroxisome proliferator-activated receptor (PPAR) γ. The differentiation cocktail [insulin (INS), dexamethasone (DEX) and isobutylmethylxanthine (IBMX)] can induce preadipocyte differentiation in mammals, but it is insufficient for chicken (Gallus gallus) adipogenesis. Oleate can induce chicken preadipocyte differentiation, but these differentiated preadipocytes may not be fully functional. The objective of the current study was to evaluate whether chicken preadipocytes can be induced to mature adipocytes by a novel induction method using differentiation cocktail supplemented with PPARγ agonist(s). Chicken preadipocytes cultured in cocktail supplemented with rosiglitazone or troglitazone resulted in a marked increase in lipid droplet accumulation (P<0.05), glycerol-3-phosphate dehydrogenase (GPDH) activity (P<0.05), mRNA expression level of adipocyte fatty acid-binding protein (aP2; P<0.05), G₀/G₁ switch gene 2 (G0S2; P<0.05) and lipolysis (P<0.05). In addition, supplementation of the cocktail with rosiglitazone promoted PPARγ mRNA expression (P<0.05). In conclusion, our data indicated that chicken preadipocytes can be induced to mature adipocytes using differentiation cocktail supplemented with rosiglitazone. The results of the present study provide a novel induction method for in vitro chicken preadipocyte differentiation.

Phenamil enhances the adipogenic differentiation of hen preadipocytes

A study was conducted to examine the effect of phenamil on adipogenic differentiation and expression of key adipogenic transcripts in hen preadipocytes. Preadipocytes were isolated from 20-week old Single Comb White Leghorn hens (Gallas gallus, Lohman strain). The experiment lasted for 48 h and had six treatments. Non-treated control (C) cells, cells treated with dexamethasone, 3-isobutyl-1-methylxanthine, insulin, and oleic acid (DMIOA) (T1), DMIOA + 15 μM phenamil (T2), DMIOA + 30 μM phenamil (T3), 15 μM phenamil alone (T4), and 30 μM phenamil alone (T5). Neutral lipid accumulation and the mRNA expression of key adipogenic transcripts were measured in all treatments and compared. Lipid accumulation was detected in T1, T2, and T3 only. Expression of peroxisome proliferator receptor-activator gamma 2 (PPARγ2), the core enhancer binding protein α (C/EBPα), C/EBPβ, fatty acid binding protein 4 (FABP4), and lipoprotein lipase (LPL) as well as ETS variant 4 (ETV4) and 5 was higher (P < 0.05) in T2, T3, T4, and T5 compared to C. Expression of these transcripts was higher (P < 0.05) in T2 and T3 compared to T4 and T5. The core enhancer binding protein α, C/EBPβ, and FABP4 were highly expressed (P < 0.05) in T1 compared to C. However, the expression of PPARγ2, LPL, and ETV4 and ETV5 was not significantly different. Expression of C/EBPα, C/EBPβ, and FABP4 was higher (P < 0.05) in T2 and T3 compared to T1. Expression of sterol regulatory element binding protein 1 (SREBP1) and leptin receptor (LEPR) was not significantly different among the treatments. In conclusion, phenamil enhances DMIOA-induced adipogenic differentiation of hen preadipocytes but does not induce adipogenesis by itself.

Molecular nutrition: Interaction of nutrients, gene regulations and performances

Nutrition deals with ingestion of foods, digestion, absorption, transport of nutrients, intermediary metabolism, underlying anabolism and catabolism, and excretion of unabsorbed nutrients and metabolites. In addition, nutrition interacts with gene expressions, which are involved in the regulation of animal performances. Our laboratory is concerned with the improvement of animal productions, such as milks, meats and eggs, with molecular nutritional aspects. The present review shows overviews on the nutritional regulation of metabolism, physiological functions and gene expressions to improve animal production in chickens and dairy cows.

Broiler chicken adipose tissue dynamics during the first two weeks post-hatch

Selection of broiler chickens for growth has led to increased adipose tissue accretion. To investigate the post-hatch development of adipose tissue, the abdominal, clavicular, and subcutaneous adipose tissue depots were collected from broiler chicks at 4 and 14 days post-hatch. As a percent of body weight, abdominal fat increased (P<0.001) with age. At day 4, clavicular and subcutaneous fat depots were heavier (P<0.003) than abdominal fat whereas at day 14, abdominal and clavicular weighed more (P<0.003) than subcutaneous fat. Adipocyte area and diameter were greater in clavicular and subcutaneous than abdominal fat at 4 and 14 days post-hatch (P<0.001). Glycerol-3-phosphate dehydrogenase (G3PDH) activity increased (P<0.001) in all depots from day 4 to 14, and at both ages was greatest in subcutaneous, intermediate in clavicular, and lowest in abdominal fat (P<0.05). In clavicular fat, peroxisome proliferator-activated receptor-γ (PPARγ), CCAAT/enhancer binding protein (CEBP)α, CEBPβ, fatty acid synthase (FASN), fatty acid binding protein 4 (FABP4), lipoprotein lipase (LPL), neuropeptide Y (NPY), and NPY receptor 5 (NPYR5) mRNA increased and NPYR2 mRNA decreased from day 4 to 14 (P<0.001). Thus, there are site-specific differences in broiler chick adipose development, with larger adipocytes and greater G3PDH activity in subcutaneous fat at day 4, more rapid growth of abdominal fat, and clavicular fat intermediate for most traits. Adipose tissue expansion was accompanied by changes in gene expression of adipose-associated factors.

Effects of rosiglitazone on proliferation and differentiation of duck preadipocytes

Rosiglitazone (RSG), one member of the thiazolidinediones (TZDs), is a type of anti-diabetic drug in diabetic humans and animal models, whose function remains unknown in waterfowl. In this study, effects of RSG on duck preadipocyte differentiation were investigated. We detected cell viability using CCK method and measured the mRNA expression of key genes and protein contents involved in preadipocyte differentiation via qRT-PCR and ELISA kits, respectively. Lipid accumulation was determined via Oil Red O staining extraction, and lipolysis was measured by free fatty acid release in the culture medium. Results showed that high concentrations of RSG (50, 100 μM) significantly decreased cell viability. RSG (0-10 μM) enhanced preadipocyte differentiation in a dose-dependent manner and thus promoted lipid accumulation. With increasing RSG concentrations, cellular lipid content gradually decreased and preadipocyte differentiation was suppressed. mRNA expression of key genes involved in preadipocyte differentiation including FAS, ACC, SCD1, LPL, PLIN, SREBP1c, and ATGL were significantly upregulated by RSG, and the protein content of FAS, ACC, and ATGL were also increased in response to RSG. Meanwhile, RSG exposure increased free fatty acid release in the culture medium. Similar results were obtained in response to RSG plus oleate that was used to induce cell differentiation. These findings suggest that RSG does not promote duck preadipocyte viability, but it does induce duck preadipocyte differentiation, which might influence both lipogenesis and lipolysis pathways.

Transcriptome analysis of hen preadipocytes treated with an adipogenic cocktail (DMIOA) with or without 20(S)-hydroxylcholesterol

Background

20(S)-hydroxycholesterol (20(S)) potentially reduces adipogenesis in mammalian cells. The role of this oxysterol and molecular mechanisms underlying the adipogenesis of preadipocytes from laying hens have not been investigated. This study was conducted to 1. Analyze genes differentially expressed between preadipocytes treated with an adipogenic cocktail (DMIOA) containing 500 nM dexamethasone, 0.5 mM 3-isobutyl-1-methylxanthine, 20 μg/mL insulin and 300 μM oleic acid (OA) and control cells and 2. Analyze genes differentially expressed between preadipocytes treated with DMIOA and those treated with DMIOA + 20(S) using Affymetrix GeneChip® Chicken Genome Arrays.

Results

In experiment one, where we compared the gene expression profile of non-treated (control) cells with those treated with DMIOA, out of 1,221 differentially expressed genes, 755 were over-expressed in control cells, and 466 were over-expressed in cells treated with DMIOA. In experiment two, where we compared the gene expression profile of DMIOA treated cells with those treated with DMIOA+20(S), out of 212 differentially expressed genes, 90 were over-expressed in cells treated with DMIOA, and 122 were over-expressed in those treated with DMIOA+20(S).

Genes over-expressed in control cells compared to those treated with DMIOA include those involved in cell-to-cell signaling and interaction (IL6, CNN2, ITGB3), cellular assembly and organization (BMP6, IGF1, ACTB), and cell cycle (CD4, 9, 38). Genes over-expressed in DMIOA compared to control cells include those involved in cellular development (ADAM22, ADAMTS9, FIGF), lipid metabolism (FABP3, 4 and 5), and molecular transport (MAP3K8, PDK4, AGTR1). Genes over-expressed in cells treated with DMIOA compared with those treated with DMIOA+20(S) include those involved in lipid metabolism (ENPP2, DHCR7, DHCR24), molecular transport (FADS2, SLC6A2, CD36), and vitamin and mineral metabolism (BCMO1, AACS, AR). Genes over-expressed in cells treated with DMIOA+20(S) compared with those treated with DMIOA include those involved in cellular growth and proliferation (CD44, CDK6, IL1B), cellular development (ADORA2B, ATP6VOD2, TNFAIP3), and cell-to-cell signaling and interaction (VCAM1, SPON2, VLDLR).

Conclusion

We identified important adipogenic regulators and key pathways that would help to understand the molecular mechanism of the in vitro adipogenesis in laying hens and demonstrated that 20(S) is capable of suppressing DMIOA-induced adipogenesis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1231-z) contains supplementary material, which is available to authorized users.

Single injection of the β2-adrenergic receptor agonist, clenbuterol, into newly hatched chicks alters abdominal fat pad mass in growing birds

Excessive energy is stored in white adipose tissue as triacylglycerols in birds as well as in mammals. Although β2-adrenergic receptor agonists reduce adipose tissue mass in birds, the underlying mechanism remains unclear. The aim of the current study was to examine the effects of a single intraperitoneal injection of the β2-adrenergic receptor agonist, clenbuterol, on the abdominal fat pad tissue development. Thirty-three chicks at 1-day-old were given a single intraperitoneal injection of clenbuterol (0.1mg/kg body weight) or phosphate-buffered saline. At 2 weeks post-dose, the weight of the abdominal fat tissue was decreased in the clenbuterol-injected chicks, and small adipocyte-like cells were observed in the abdominal fat pad tissue of the clenbuterol-injected chicks. Then, the expression of mRNAs encoding genes related to avian adipogenesis was examined in the abdominal fat pat tissue. The expression of mRNAs encoding Krüppel-like zinc finger transcription factor 5 (KLF-5), KLF-15, and zinc finger protein 423 in the abdominal fat pad tissue of the clenbuterol-injected chicks was significantly lower (P<0.05) than that of the control chicks, while the expression of mRNA encoding peroxisome proliferator-activated receptor-gamma was not affected. In addition, both mRNA expression (P<0.05) and enzymatic activity (P<0.05) of fatty acid synthase (FAS) were decreased in the abdominal fat pad tissue of the clenbuterol-injected chicks, while clenbuterol injection did not affect FAS activity in liver. These results suggested that a single injection with clenbuterol into newly hatched chicks reduces their abdominal fat pad mass possibly via disrupting adipocyte development during later growth stages.

Neuropeptide Y promotes adipogenesis in chicken adipose cells in vitro

Neuropeptide Y is an evolutionarily conserved neurotransmitter that stimulates food intake in higher vertebrate species and promotes adipogenesis in mammals. The objective of this study was to determine if NPY also enhances adipogenesis in birds, using chickens as a model. The stromal-vascular fraction of cells was isolated from the abdominal fat of 14 day-old broiler chicks and effects of exogenous chicken NPY on proliferation and differentiation determined. Based on a thymidine analog incorporation assay and gene expression analysis, there was no effect of NPY on proliferation during the first 12 hours post-treatment in cells that were induced to proliferate. However, there were effects of NPY treatment on proliferation and lipid accumulation during the first 6 days post-induction of differentiation. Neuropeptide Y supplementation during induction of differentiation was associated with greater glycerol-3-phosphate dehydrogenase activity and staining for neutral lipids, indicative of augmented lipid accumulation. This was also accompanied by increased proliferation during differentiation, which was characterized by up-regulation of proliferation and preadipocyte marker mRNA, and a greater number of proliferating cells in groups that were treated with NPY. Additionally, NPY treatment was associated with increased expression of fatty acid binding protein 4 and lipoprotein lipase during differentiation. In conclusion, these results suggest that NPY plays a role in promoting adipogenesis in chickens and that the mechanisms involve an increase in the synthesis of new preadipocytes and increased lipid synthesis and storage.

Dietary Conjugated Linoleic Acid Supplementation Leads to Downregulation of PPAR Transcription in Broiler Chickens and Reduction of Adipocyte Cellularity

Conjugated linoleic acids (CLA) act as an important ligand for nuclear receptors in adipogenesis and fat deposition in mammals and avian species. This study aimed to determine whether similar effects are plausible on avian abdominal fat adipocyte size, as well as abdominal adipogenic transcriptional level. CLA was supplemented at different levels, namely, (i) basal diet without CLA (5% palm oil) (CON), (ii) basal diet with 2.5% CLA and 2.5% palm oil (LCLA), and (iii) basal diet with 5% CLA (HCLA).The content of cis-9, trans-11 CLA was between 1.69- and 2.3-fold greater (P < 0.05) than that of trans-10, cis-12 CLA in the abdominal fat of the LCLA and HCLA group. The adipogenic capacity of the abdominal fat depot in LCLA and HCLA fed chicken is associated with a decreased proportion of adipose cells and monounsaturated fatty acids (MUFA). The transcriptional level of adipocyte protein (aP2) and peroxisome proliferator-activated receptor gamma (PPARγ) was downregulated by 1.08- to 2.5-fold in CLA supplemented diets, respectively. It was speculated that feeding CLA to broiler chickens reduced adipocyte size and downregulated PPARγ and aP2 that control adipocyte cellularity. Elevation of CLA isomers into their adipose tissue provides a potential CLA-rich source for human consumption.

Lactobacillus brevis OPK-3 isolated from kimchi inhibits adipogenesis and exerts anti-inflammation in 3T3-L1 adipocyte

BACKGROUND

Kimchi is a traditional fermented food in Korea that contains various unique microorganisms. Diverse bacteria are involved in the process of Kimchi fermentation and the healthful advantages; one of the major species is Lactobacillus. We investigated whether lactic acid bacteria isolated from Kimchi (KLAB) are capable of reducing intracellular lipid accumulation by downregulating the expression of adipogenesis and lipogenesis promoting genes in differentiating 3T3-L1 cells.

RESULTS

KLAB (Lactobacillus brevis OPK-3) mediated dose-dependent inhibition of adipocyte differentiation, intracellular triglyceride accumulation and glycerol-3-phosphate dehydrogenase (GPDH) activity. The expression of transcription factors such as peroxisome proliferator-activated receptor γ and CCAAT/enhancer-binding protein α involved in adipogenesis was markedly decreased by the KLAB treatment. Terminal adipogenic marker, e.g. adipocyte fatty acid binding protein (aP2), lipoprotein lipase, liver X receptor α, leptin and GPDH were significantly downregulated by KLAB treatment compared to untreated control. Moreover, cytokine genes, such as tumor necrosis factor-α and interleukin-6 mRNA expressions level were also decreased, whereas adiponectin mRNA level was upregulated by KLAB.

CONCLUSION

These results suggest that the KLAB inhibits lipid accumulation in the differentiating adipocyte through downregulating the expression of adipogenic transcription factors and other specific genes involved in lipid metabolism.

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.

Hydrodynamic tail vein injection of SOCS3 eukaryotic expression vector in vivo promoted liver lipid metabolism and hepatocyte apoptosis in mouse

Suppressor of cytokine signaling 3 (SOCS3), a signal transduction cytokine, is involved in lipid metabolism as well as in cell proliferation, differentiation, apoptosis, and so on. To explore the effects of SOCS3 on apoptosis and lipid metabolism in liver, we used a simple effective method named hydrodynamic tail vein injection to overexpress SOCS3. Then orbital blood was obtained for the assessment of blood lipid after injection. Lipid metabolism related genes were detected by Western blot after the determination of serum lipids. Meanwhile, liver cell apoptosis was observed by Hoechst and TUNEL staining and the expression of apoptosis related proteins Bax, Bcl-2, and Caspase3 were detected as well as the JAK2/STAT3 signaling pathway. In addition, we also demonstrated the effect of SOCS3 in prime hepatocyte by overexpression or interference of SOCS3 along with SD1008, which is a specific inhibitor of the JAK2/STAT3 signaling pathway. Taken together, all the results indicated that SOCS3 promoted lipid synthesis in mice liver and promoted hepatocyte apoptosis by inhibiting the activation of the JAK2/STAT3 signaling pathway, however the detailed regulation mechanism had not yet been fully understood and needs further study.

Molecular and metabolic profiles suggest that increased lipid catabolism in adipose tissue contributes to leanness in domestic chickens

Domestic broiler chickens rapidly accumulate fat and are naturally hyperglycemic and insulin resistant, making them an attractive model for studies of human obesity. We previously demonstrated that short-term (5 h) fasting rapidly upregulates pathways of fatty acid oxidation in broiler chickens and proposed that activation of these pathways may promote leanness. The objective of the current study was to characterize adipose tissue from relatively lean and fatty lines of chickens and determine if heritable leanness in chickens is associated with activation of some of the same pathways induced by fasting. We compared adipose gene expression and metabolite profiles in white adipose tissue of lean Leghorn and Fayoumi breeds to those of fattier commercial broiler chickens. Both lipolysis and expression of genes involved in fatty acid oxidation were upregulated in lean chickens compared with broilers. Although there were strong similarities between the lean lines compared with broilers, distinct expression signatures were also found between Fayoumi and Leghorn, including differences in adipogenic genes. Similarities between genetically lean and fasted chickens suggest that fatty acid oxidation in white adipose tissue is adaptively coupled to lipolysis and plays a role in heritable differences in fatness. Unique signatures of leanness in Fayoumi and Leghorn lines highlight distinct pathways that may provide insight into the basis for leanness in humans. Collectively, our results provide a number of future directions through which to fully exploit chickens as unique models for the study of human obesity and adipose metabolism.

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.

Expression of Potential Regulatory Genes in Abdominal Adipose Tissue of Broiler Chickens during Early Development

The identities of genes that underlie population variation in adipose tissue development in farm animals are poorly understood. Previous studies in our laboratory have suggested that increased fat tissue involves the expression modulation of an array of genes in broiler chickens. Of special interest are eight genes, FGFR3, EPHB2, IGFBP2, GREM1, TNC, COL3A1, ACBD7, and SCD. To understand their expression regulation and response to dietary manipulation, we investigated their mRNA levels after dietary manipulation during early development. Chickens were fed either a recommended standard or a high caloric diet from hatch to eight weeks of age (WOA). The high caloric diet markedly affected bodyweight of the broiler birds. mRNA levels of the eight genes in the abdominal adipose tissue were assayed at 2, 4, 6, and 8 WOA using RT-qPCR. Results indicate that (1) FGFR3 mRNA level was affected significantly by diet, age, and diet:age interaction; (2) COL3A mRNA level was repressed by high caloric diet; (3) mRNA levels of EPHB2, ACBD7, and SCD were affected by age; (4) mRNA level of TNC was modulated by age:diet interaction; (5) changes in GREM1 and IGFBP2 mRNA levels were not statistically different.

Molecular cloning, expression and regulation analysis of the interleukin-6 (IL-6) gene in goose adipocytes

1. Interleukin-6 (IL-6) is a multifunctional cytokine involved in lipid metabolism in adipose tissue. The objective of the study was to identify and characterize the IL-6 gene in the goose. 2. A full-length coding sequence (CDS) of the goose (Anser anser) IL-6 gene was cloned that encoded a 234-amino acid peptide containing a 38-amino acid signal peptide, an IL-6/G-CSF/MGF family consensus pattern and four conserved α-helices. The mature goose IL-6 showed 74% and 39% identities to that of chicken and human, respectively. 3. Quantitative real-time PCR analysis showed that the goose IL-6 was predominantly expressed in liver and was up-regulated in adipocytes by lipopolysaccharide (LPS) and oleic acid.