Effects of oleic acid and chicken serum on the expression of adipogenic transcription factors and adipogenic differentiation in hen preadipocytes

Differences in Lipid Metabolism between the Perirenal Adipose Tissue of Chinese Simmental Cattle and Angus Cattle (Bos taurus) Based on Metabolomics Analysis

The aim of this experiment was to investigate the differences in metabolites in perirenal fat (PF) between Chinese Simmental cattle and Angus cattle. Six healthy 18-month-old male Angus cattle and Chinese Simmental cattle were selected, and the perirenal adipose tissue was collected after slaughtering. HE staining, a triglyceride assay kit, and liquid chromatography-tandem mass spectrometry (LC-MS/MS) technology were used to compare and analyze the differences in the cell morphology, lipid accumulation, and metabolites of the two types of PF. The results showed that the PF of Angus cattle had a larger cell area and stronger lipid deposition ability than that of Simmental cattle. A total of 567 metabolites were detected by LC-MS/MS technology, of which 119 were significantly upregulated in Angus cattle PF and 129 were significantly upregulated in Simmental cattle PF. Differential metabolites were enriched in pathways such as fatty acid biosynthesis, polyunsaturated fatty acid biosynthesis, regulation of adipocyte lipolysis, and oxidative phosphorylation. Finally, 12 metabolites that may cause phenotypic differences between the two types of perirenal adipose tissue were screened out from these pathways. This study has preliminarily screened out biomarkers that may affect lipid metabolism in PF, providing basic data for the further exploration of the metabolic characteristics of PF.

Insulin interacts with PPARγ agonists to promote bovine adipocyte differentiation

Insulin is a potent adipogenic hormone that triggers a series of transcription factors that regulate the differentiation of preadipocytes into mature adipocytes. Ciglitazone specifically binds to peroxisome proliferator-activated receptor-γ (PPARγ), thereby promoting adipocyte differentiation. As a natural ligand of PPARγ, oleic acid (OA) can promote the translocation of PPARγ into the nucleus, regulate the expression of downstream genes, and promote adipocyte differentiation. We hypothesized that ciglitazone and oleic acid interact with insulin to enhance bovine preadipocyte differentiation. Preadipocytes were cultured 96 h in differentiation medium containing 10 mg/L insulin (I), 10 mg/L insulin + 10 µM cycloglitazone (IC), 10 mg/L insulin + 100 µM oleic acid (IO), or 10 mg/L insulin + 10 µM cycloglitazone+100 µM oleic acid (ICO). Control preadipocytes (CON) were cultured in differentiation medium (containing 5% fetal calf serum). The effects on the differentiation of Yanbian cattle preadipocytes were examined using molecular and transcriptomic techniques, including differentially expressed genes (DEGs) and Kyoto Encyclopaedia of Genes and Genomes (KEGG) pathway analysis. I, IC, IO, and ICO treatments produced higher concentrations of triglycerides (TAG) and lipid droplet accumulation in preadipocytes compared with CON treatment (P < 0.05). Co-treatment of insulin and PPARγ agonists significantly increased the expression of genes involved in regulating adipogenesis and fatty acid synthesis. (P < 0.05). Differential expression analysis identified 1488, 1764, 1974 and 1368 DEGs in the I, IC, IO and ICO groups, respectively. KEGG pathway analysis revealed DEGs mainly enriched in PPAR signalling, FOXO signaling pathway and fatty acid metabolism. These results indicate that OA, as PPARγ agonist, can more effectively promote the expression of bovine lipogenesis genes and the content of TAG and adiponectin when working together with insulin, and stimulate the differentiation of bovine preadipocytes. These findings provide a basis for further screening of relevant genes and transcription factors in intramuscular fat deposition and meat quality to enhance breeding programs.

Single-nucleus RNA sequencing and lipidomics reveal characteristics of transcriptional and lipid composition in porcine longissimus dorsi muscle

BACKGROUND

Global per capita meat consumption continues to rise, especially pork. Meat quality is influenced by the content of intramuscular fat (IMF) as a key factor. The longissimus dorsi muscle of Dahe pigs (DHM, IMF: 7.98% ± 1.96%) and Dahe black pigs (DHBM, IMF: 3.30% ± 0.64%) was studied to explore cellular heterogeneity and differentially expressed genes (DEGs) associated with IMF deposition using single-nucleus RNA sequencing (snRNA-seq). The lipid composition was then analyzed using non-targeted lipidomics.

RESULTS

A total of seven cell subpopulations were identified, including myocytes, fibroblast/fibro/adipogenic progenitors (FAPs), satellite cells, endothelial cells, macrophages, pericytes, and adipocytes. Among them, FAPs and adipocytes were more focused because they could be associated with lipid deposition. 1623 DEGs in the FAPs subpopulation of DHBM were up-regulated compared with DHM, while 1535 were down-regulated. These DEGs enriched in the glycolysis/gluconeogenesis pathway. 109 DEGs were up-regulated and 806 were down-regulated in the adipocyte subpopulation of DHBM compared with DHM, which were mainly enriched in the PPAR signaling pathway and fatty acid (FA) biosynthesis. The expression level of PPARG, ABP4, LEP, and ACSL1 genes in DHM was higher than that in DHBM. Lipidomics reveals porcine lipid composition characteristics of muscle tissue. A total of 41 lipid classes and 2699 lipid species were identified in DHM and DHBM groups. The top ten relative peak areas of lipid classes in DHM and DHBM were triglyceride (TG), phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylserine (PS), diglyceride (DG), cardiolipin (CL), ceramides (Cer), Simple Glc series (Hex1Cer), sphingomyelin (phSM), and phosphatidylinositol (PI). The relative peak areas of 35 lipid species in DHM were lower than DHBM, and 28 lipid species that were higher. There was a significant increase in the TG fatty acyl chains C6:0, C17:0, and C11:4, and a significant decrease in C16:0, C18:1, C18:2, and C22:4 in DHBM (p < 0.05).

CONCLUSIONS

C16:0 FA may downregulate the expression level of PPARG gene, which leads to the downregulation of fat metabolism-related genes such as ACSL, PLIN2, and FABP4 in DHBM compared with DHM. This may be the reason that the lipid deposition ability of Dahe pigs is stronger than that of Dahe black pigs, which need further investigation.

Unravelling the anti-inflammatory and antioxidant effects of standardized green and black caffeinated coffee, tea, and their mixtures in an obese male rat model: Insights from biochemical, metabolomic, and histopathological analyses

Obesity is one of the major metabolic syndrome risk factors upon which altered metabolic pathways follow. This study aimed to discern altered metabolic pathways associated with obesity and to pinpoint metabolite biomarkers in serum of obese rats fed on high fructose diet using metabolomics. Further, the effect of standardized green versus black caffeinated aqueous extracts (tea and coffee) in controlling obesity and its comorbidities through monitoring relevant serum biomarkers viz. Leptin, adiponectin, spexin, malondialdehyde, total antioxidant capacity. Liver tissue oxidative stress (catalase, super oxide dismutase and glutathione) and inflammation (IL-1β and IL-6) markers were assessed for green coffee and its mixture with green tea. Results revealed improvement of all parameters upon treatments with more prominence for those treated with green caffeinated extract (coffee and tea) especially in mixture. Upon comparing with obese rat group, the green mixture of coffee and tea exhibited anti-hyperlipidemic action through lowering serum triglycerides by 35.0% and elevating high density lipoprotein by 71.0%. Black tea was likewise effective in lowering serum cholesterol and low density lipoprotein by 28.0 and 50.6%, respectively. GC-MS- based metabolomics of rat serum led to the identification of 34 metabolites with obese rat serum enriched in fatty acids (oleamide).

Endoplasmic reticulum stress is involved in lipid accumulation induced by oleic acid in adipocytes of grass carp (Ctenopharyngodon idella): focusing on the transcriptional level

It has been extensively claimed that endoplasmic reticulum stress (ER stress) is related to lipid accumulation in mammals, but little is known in fish. This study aims at elucidating the role of ER stress in mediating lipid accumulation induced by monounsaturated oleic acid (OA) with a focus on the transcriptional level. We treated the adipocytes of grass carp with 200 μM and 400 μM OA, respectively, while the control group was treated with 2% bovine serum albumin (BSA). The results showed that cell viability was significantly improved, while 400 μM OA treatment promoted neutral lipid accumulation along with stimulating ER stress more obviously. Although lipolysis and fatty acid β-oxidation were activated simultaneously, the primary effect of OA seems to be promotion of lipid accumulation. To further explore whether ER stress affects lipid accumulation, 4-phenyl butyric acid (4-PBA), an effective inhibitor of ER stress, was used to pretreat the cells for 4 h. Unsurprisingly, it was found that the mRNA expressions of genes linked with ER stress were decreased. Intracellular triglyceride (TG) content was also decreased, which was in accordance with the mRNA expressions of adipogenic and lipogenic transcription factors as well as their target genes. Collectively, our data shows that ER stress may take part in OA-induced lipid accumulation in adipocytes via activating adipogenesis and lipogenesis. Based on this, strategies for protecting ER could be used to alleviate excessive accumulation of lipid in grass carp adipose tissue.

Dietary Germinated Paddy Rice and Stocking Density Affect Egg Performance, Serum Biochemical Properties, and Proteomic and Transcriptomic Response of Laying Hens Exposed to Chronic Heat Stress

Germinated paddy rice (GPR) could be a good alternative feed source for poultry with stocking density and heat stress problems. A total of 72 Hy-line Brown laying hens raised under low (LSD, 0.12 m2/bird) and high stocking densities (HSD, 0.06 m2/bird) were investigated. Three dietary GPR levels (0, 74 and 148 g/kg) were used. It was found that average daily feed intake, hen-day egg production, and egg mass significantly decreased in the HSD group. The levels of serum glucose (GLU), phosphorous (P), corticosterone (CORT), total Ig, lysozyme (LZY), and superoxide dismutase activities (SOD) in the HSD group were higher than those in the LSD group. Dietary GPR significantly affected GLU, P, alternative complement haemolytic 50 (ACH50), total Ig, and LZY. Moreover, CORT level significantly decreased in 74 and 148 g/kg dietary GPR groups, whereas SOD significantly increased only in the 148 g/kg dietary GPR group. Serum samples were analyzed using liquid chromatography-tandem mass spectrometry, and 8607 proteins were identified. Proteome analysis revealed 19 proteins which were enriched in different stocking densities and dietary GPR levels. Quantitative real-time reverse transcription-PCR technique was successfully used to verify the differentiated abundant protein profile changes. The proteins identified in this study could serve as appropriate biomarkers.

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.

Bovine Stearoyl-CoA Desaturase 1 Promotes Adipogenesis by Activating the PPARγ Receptor

Stearoyl-CoA desaturase 1 (SCD1) is a rate-limiting enzyme that mainly catalyzes the saturated fatty acids (SFAs) into the monounsaturated fatty acids (MUFAs). The expression level of SCD1 is positively correlated with the marbling score. However, the functional mechanism of SCD1 in adipogenesis is still unclear. In this study, we identified SCD1 as highly expressed in subcutaneous and visceral fat, peaking at 2 days after differentiation in bovine stromal vascular fraction (SVF) cells. When the SCD1 was overexpressed in bovine SVF cells, lipid droplets accumulation was increased from 142.46 ± 21.77 to 254.89 ± 11.75 μg/mg (P < 0.01). Further, the expression levels of FABP4, FASN, and ACCα were increased (P < 0.01), while the expression of PPARγ or C/EBPα was not changed at mRNA or protein level (P > 0.05). Dual-luciferase reporter assay showed that the activity of the PPARγ receptor was enhanced by 3.69 times (P < 0.01). Moreover, the contents of palmitoleate (C16:1) and oleate (C18:1) were significantly increased (P < 0.05). Furthermore, 100 μM exogenous oleate increased the lipid accumulation by 22.28 times (P < 0.01). These results suggest that oleate is probably a strong ligand of the PPARγ receptor to enhance adipogenesis.

Metabolic Differences between Subcutaneous and Visceral Adipocytes Differentiated with an Excess of Saturated and Monounsaturated Fatty Acids

Obesity is a major health problem in highly industrialized countries. High-fat diet (HFD) is one of the most common causes of obesity and obesity-related disorders. There are considerable differences between fat depots and the corresponding risks of metabolic disorders. We investigated the various effects of an excess of fatty acids (palmitic 16:0, stearic 18:0, and oleic acids 18:1n-9) on adipogenesis of subcutaneous- and visceral-derived mesenchymal stem cells (MSCs) and phenotypes of mature adipocytes. MSCs of white adipose tissue were acquired from adipose tissue biopsies obtained from subcutaneous and visceral fat depots from patients undergoing abdominal surgery. The MSCs were extracted and differentiated in vitro with the addition of fatty acids. Oleic acid stimulated adipogenesis, resulting in higher lipid content and larger adipocytes. Furthermore, oleic acid stimulated adipogenesis by increasing the expression of CCAAT enhancer binding protein β (CEBPB) and peroxisome proliferator activated receptor γ (PPARG). All of the examined fatty acids attenuated the insulin-signaling pathway and radically reduced glucose uptake following insulin stimulation. Visceral adipose tissue was shown to be more prone to generate inflammatory stages. The subcutaneous adipose tissue secreted a greater quantity of adipokines. To summarize, oleic acid showed the strongest effect on adipogenesis. Furthermore, all of the examined fatty acids attenuated insulin signaling and secretion of cytokines and adipokines.

Oleic acid influences the adipogenesis of 3T3-L1 cells via DNA Methylation and may predispose to obesity and obesity-related disorders

BACKGROUND

Adipogenesis is the process of adipocytes formation from unspecialized progenitor cells called mesenchymal stromal cells. Numerous mechanisms including epigenetic regulation modulate the correct progress of this process. Dietary exposures occurring over a specific period of time might cause long-lasting and even permanent changes in gene expression regulated by epigenetic mechanisms. For that reason, we investigated the adipogenesis of 3 T3-L1 cells with the excess of saturated and monounsaturated fatty acids and their influence on global and site-specific DNA methylation in these cells.

MATERIALS AND METHODS

3T3-L1 cells were cultured in vitro to obtain 100% of confluence, then the adipogenesis was induced by a differentiation cocktail with the addition of the excess of 0.25 mM and 0.5 mM of palmitic (16:0), stearic (18:0) and oleic (18:1n-9) acids. DNA and RNA were extracted at five-time points to assess the adipogenesis process. The phenotype of mature adipocytes (insulin sensitivity, adipokines secretion, fat content) was estimated in fully mature adipocytes. DNA methylation was investigated both during adipogenesis and in mature adipocytes.

RESULTS

Oleic acids stimulated expression of C/ebpα and Pparγ, which was correlated with lower methylation levels at promoters sites. Furthermore, cells cultured with an excess of oleic acid were characterized by higher lipid accumulation rate, higher leptin, and lower adiponectin secretion. Moreover, in all experimental cells, insulin signaling and glucose utilization were impaired.

CONCLUSION

Oleic acid affected the methylation of Pparγ and C/ebpα promoters, what correlated with higher expression. Furthermore, examined free fatty acids influenced the phenotype of mature adipocytes, especially insulin signaling pathway and adipokine secretion.

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.

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.

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 Regulation of Adipogenesis and Potential Anti-Adipogenic Bioactive Molecules

Adipogenesis is the process by which precursor stem cells differentiate into lipid laden adipocytes. Adipogenesis is regulated by a complex and highly orchestrated gene expression program. In mammalian cells, the peroxisome proliferator-activated receptor γ (PPARγ), and the CCAAT/enhancer binding proteins (C/EBPs) such as C/EBPα, β and δ are considered the key early regulators of adipogenesis, while fatty acid binding protein 4 (FABP4), adiponectin, and fatty acid synthase (FAS) are responsible for the formation of mature adipocytes. Excess accumulation of lipids in the adipose tissue leads to obesity, which is associated with cardiovascular diseases, type II diabetes and other pathologies. Thus, investigating adipose tissue development and the underlying molecular mechanisms is vital to develop therapeutic agents capable of curbing the increasing incidence of obesity and related pathologies. In this review, we address the process of adipogenic differentiation, key transcription factors and proteins involved, adipogenic regulators and potential anti-adipogenic bioactive molecules.

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.

Fasting for 21days leads to changes in adipose tissue and liver physiology in juvenile checkered garter snakes (Thamnophis marcianus)

Snakes often undergo periods of prolonged fasting and, under certain conditions, can survive years without food. Despite this unique phenomenon, there are relatively few reports of the physiological adaptations to fasting in snakes. At post-prandial day 1 (fed) or 21 (fasting), brain, liver, and adipose tissues were collected from juvenile checkered garter snakes (Thamnophis marcianus). There was greater glycerol-3-phosphate dehydrogenase (G3PDH)-specific activity in the liver of fasted than fed snakes (P=0.01). The mRNA abundance of various fat metabolism-associated factors was measured in brain, liver, and adipose tissue. Lipoprotein lipase (LPL) mRNA was greater in fasted than fed snakes in the brain (P=0.04). Adipose triglyceride lipase (ATGL; P=0.006) mRNA was greater in the liver of fasted than fed snakes. In adipose tissue, expression of peroxisome proliferator-activated receptor (PPAR)γ (P=0.01), and fatty acid binding protein 4 (P=0.03) was greater in fed than fasted snakes. Analysis of adipocyte morphology revealed that cross-sectional area (P=0.095) and diameter (P=0.27) were not significantly different between fed and fasted snakes. Results suggest that mean adipocyte area can be preserved during fasting by dampening lipid biosynthesis while not changing rates of lipid hydrolysis. In the liver, however, extensive lipid remodeling may provide energy and lipoproteins to maintain lipid structural integrity during energy restriction. Because the duration of fasting was not sufficient to change adipocyte size, results suggest that the liver is important as a short-term provider of energy in the snake.

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.

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.