Structural Features and Transcriptional Activity of Chicken PPARs (α, β, and γ)

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.

Transcriptome of Chicken Liver Tissues Reveals the Candidate Genes and Pathways Responsible for Adaptation into Two Different Climatic Conditions

RNA sequencing was used to profile the liver transcriptome of a Korean commercial chicken (Hanhyup) at two different environments (Korea and Kyrgyzstan) to investigate their role during acclimatization into different climatic conditions. Ten samples from each location were analyzed to identify candidate genes that respond to environmental changes such as altitude, humidity, temperature, etc. Sequencing reads were preprocessed, aligned with the reference genome, assembled and expressions were estimated through bioinformatics approaches. At a false discovery rate (FDR) <0.05 and fold change (FC) ≥2, we found 315 genes were DE. Out of 315 DE genes, 174 and 141 were up- and down-regulated respectively in the Kyrgyz environment. Gene ontology (GO) enrichment analysis showed that the differentially expressed genes (DEGs) were associated with energy metabolism such as pyruvate and lactate metabolic processes, and glycerol catabolic process. Similarly, KEGG pathway analysis indicated pyruvate metabolism, glycolysis/gluconeogenesis, biosynthesis, citrate cycles were differentially enriched in the Kyrgyz environment. DEGs like TSKU, VTG1, SGK, CDK2, etc. in such pathways are highly involved in the adaptation of organisms into diverse climatic conditions. Our investigation may serve as a resource for the chicken industry, especially in exporting Hanhyup chicken from Korea to other countries.

Activation of peroxisome proliferator-activated receptor gamma induces anti-inflammatory properties in the chicken free avian respiratory macrophages

Background

Activation of peroxisome proliferator activated receptor gamma (PPAR γ) in the alveolar macrophages (AM) by selective synthetic PPAR γ ligands, improves the ability of the cells to resolve inflammation. In birds, respiratory macrophages are known as free avian respiratory macrophages (FARM) and show distinct functional differences from AM. The effects of treating FARM with PPAR γ ligands are unclear.

Methods

FARM were harvested by lavage of chicken respiratory tract and their morphology assessed at microscopic level. The effects of PPAR γ agonists on the FARM in vitro viability, phagocytic capacity and proinflammatory cytokine (TNF-α) production were assessed.

Results

FARM had eccentric nucleus and plasma membrane ruffled with filopodial extensions. Ultrastructurally, numerous vesicular bodies presumed to be lysosomes were present. FARM treated with troglitazone, a selective PPAR γ agonist, had similar in vitro viability with untreated FARM. However, treated FARM co-cultured with polystyrene particles, internalized more particles with a mean volume density of 41 % compared to that of untreated FARM of 21 %. Further, treated FARM significantly decreased LPS-induced TNF-α production in a dose dependent manner.

Conclusion

Results from this study show that PPAR γ synthetic ligands enhance phagocytic ability of FARM. Further the ligands attenuate production of proinflammatory cytokines in the FARM, suggesting potential therapeutic application of PPAR γ ligands in the management of respiratory inflammatory disorders in the poultry industry.

Identification and characterization of transcript variants of chicken peroxisome proliferator-activated receptor gamma

Peroxisome proliferator-activated receptor gamma regulates adipogenesis. The genomic structure of the chicken peroxisome proliferator-activated receptor gamma (cPPARγ) gene has not been fully characterized, and only one cPPARγ gene mRNA sequence has been reported in genetic databases. Using 5' rapid amplification of cDNA ends, we identified five different cPPARγ mRNAs that are transcribed from three transcription initiation sites. The open reading frame analysis showed that these five cPPARγ transcript variants (cPPARγ1 to 5) could encode two cPPARγ protein isoforms (cPPARγ1 and cPPARγ2), which differ only in their N-terminal region. Quantitative real-time RT-PCR analysis showed that, of these five cPPARγ transcript variants, cPPARγ1 was ubiquitously highly expressed in various chicken tissues, including adipose tissue, liver, kidney, spleen and duodenal; cPPARγ2 was exclusively highly expressed in adipose tissue; cPPARγ3 was highly expressed in adipose tissue, kidney, spleen and liver; cPPARγ4 and cPPARγ5 were ubiquitously weakly expressed in all the tested tissues, and comparatively, cPPARγ5 was highly expressed in adipose tissue, heart, liver and kidney. The comparison of the expression of the five cPPARγ transcript variants showed that adipose tissue cPPARγ1 expression was significantly higher in the fat line than in the lean line from 2 to 7 wk of age (P < 0.05 or P < 0.01). Adipose tissue cPPARγ3 expression was significantly higher in the fat line than in the lean line at 3, 5 and 6 wk of age (P < 0.01, P < 0.05), but lower at 4 wk of age (P < 0.05). Adipose tissue cPPARγ5 expression was significantly higher in the fat line than in the lean line at 3, 4, and 6 wk of age (P < 0.01) and at 2 and 7 wk of age (P < 0.05). This is the first report of transcript variants and protein isoforms of cPPARγ gene. Our findings provided a foundation for future investigations of the function and regulation of cPPARγ gene in adipose tissue development.

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.

Nuclear control of the inflammatory response in mammals by peroxisome proliferator-activated receptors

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors that play pivotal roles in the regulation of a very large number of biological processes including inflammation. Using specific examples, this paper focuses on the interplay between PPARs and innate immunity/inflammation and, when possible, compares it among species. We focus on recent discoveries establishing how inflammation and PPARs interact in the context of obesity-induced inflammation and type 2 diabetes, mostly in mouse and humans. We illustrate that PPAR γ ability to alleviate obesity-associated inflammation raises an interesting pharmacologic potential. In the light of recent findings, the protective role of PPAR α and PPAR β / δ against the hepatic inflammatory response is also addressed. While PPARs agonists are well-established agents that can treat numerous inflammatory issues in rodents and humans, surprisingly very little has been described in other species. We therefore also review the implication of PPARs in inflammatory bowel disease; acute-phase response; and central, cardiac, and endothelial inflammation and compare it along different species (mainly mouse, rat, human, and pig). In the light of the data available in the literature, there is no doubt that more studies concerning the impact of PPAR ligands in livestock should be undertaken because it may finally raise unconsidered health and sanitary benefits.