Identification and characterization of novel peroxisome proliferator-activated receptor-gamma (PPAR-gamma) transcriptional variants in pig and human

The Influence of the Differentiation of Genes Encoding Peroxisome Proliferator-Activated Receptors and Their Coactivators on Nutrient and Energy Metabolism

Genetic components may play an important role in the regulation of nutrient and energy metabolism. In the presence of specific genetic variants, metabolic dysregulation may occur, especially in relation to the processes of digestion, assimilation, and the physiological utilization of nutrients supplied to the body, as well as the regulation of various metabolic pathways and the balance of metabolic changes, which may consequently affect the effectiveness of applied reduction diets and weight loss after training. There are many well-documented studies showing that the presence of certain polymorphic variants in some genes can be associated with specific changes in nutrient and energy metabolism, and consequently, with more or less desirable effects of applied caloric reduction and/or exercise intervention. This systematic review focused on the role of genes encoding peroxisome proliferator-activated receptors (PPARs) and their coactivators in nutrient and energy metabolism. The literature review prepared showed that there is a link between the presence of specific alleles described at different polymorphic points in PPAR genes and various human body characteristics that are crucial for the efficacy of nutritional and/or exercise interventions. Genetic analysis can be a valuable element that complements the work of a dietitian or trainer, allowing for the planning of a personalized diet or training that makes the best use of the innate metabolic characteristics of the person who is the subject of their interventions.

Plant Compounds for the Treatment of Diabetes, a Metabolic Disorder: NF-κB as a Therapeutic Target

Background:

The prevalence of diabetes in the world population hás reached 8.8 % and is expected to rise to 10.4% by 2040. Hence, there is an urgent need for the discovery of drugs against therapeutic targets to sojourn its prevalence. Previous studies proved that NF-κB serves as a central agent in the development of diabetic complications.

Objectives:

This review intended to list the natural plant compounds that would act as inhibitors of NF-κB signalling in different organs under the diabetic condition with their possible mechanism of action.

Methods:

Information on NF-κB, diabetes, natural products, and relation in between them, was gathered from scientific literature databases such as Pubmed, Medline, Google scholar, Science Direct, Springer, Wiley online library.

Results and Conclusion:

NF-κB plays a crucial role in the development of diabetic complications because of its link in the expression of genes that are responsible for organs damage such as kidney, brain, eye, liver, heart, muscle, endothelium, adipose tissue and pancreas by inflammation, apoptosis and oxidative stress. Activation of PPAR-α, SIRT3/1, and FXR through many cascades by plant compounds such as terpenoids, iridoids, flavonoids, alkaloids, phenols, tannins, carbohydrates, and phytocannabinoids recovers diabetic complications. These compounds also exhibit the prevention of NF-κB translocation into the nucleus by inhibiting NF-κB activators, such as VEGFR, RAGE and TLR4 receptors, which in turn, prevent the activation of many genes involved in tissue damage. Current knowledge on the treatment of diabetes by targeting NF-κB is limited, so future studies would enlighten accordingly.

Evidences for diabetes and insulin mimetic activity of medicinal plants: Present status and future prospects

Diabetes mellitus (DM) is a considerable systemic metabolic disorder to exhibit various metabolic and cardiovascular disorders, mainly hyperglycemia. The global projected estimate of diabetes in 2030 will be about 439 million adults, out of which 300 million expected are of type-2 diabetes mellitus (T2DM). The present knowledge revealed responsible factors, occurrence and mechanism of these factors involved in the DM diseases. Hence, the aim of this review is to address and summarize the causes, plant resources, importance, present status and future programmes for diabetes control. The present review answers the contemporary present questions raised in the scientific field on DM. Two major problems are explained in detail about the autoimmune attack or dysfunction of β-cell and insulin resistance involved for Type 1 and Type 2 DM, respectively. Though there are various approaches to reduce the ill effects of diabetes and its secondary complications, many preferred herbal formulations due to lesser side effects and low cost. For this reason still it is getting increased attention in searching antidiabetic medicinal plants for hot research and to develop targeted medicine. Recurrence of islet autoimmunity lesson from pancreatic islet cell transplantation to cure T1D was outlined. With these highlights, the review summarizes the current knowledge on diabetes occurrence, factors (environmental and genetics), and types (I, II, gestation, and secondary DM), antidiabetic plants, sources for insulin mimetic plant principle compounds and their target mechanism with current and future trusted research areas for controlling of DM.

Study on quantitative expression of PPARγ and ADRP in muscle and its association with intramuscular fat deposition of pig

Background

Intramuscular fat (intramuscular fat, IMF) is one of the important traits of pork quality. How to reasonably improve the intramuscular fat content is the most focus researchers. Some possible regulation of intramuscular fat deposition of candidate genes to cause the attention of people. The objective of this study was to elucidate the relationship between peroxisome proliferator-activated receptor γ (PPARγ) and adipose differentiation-related protein (ADRP) mRNA expression and intramuscular fat (IMF) deposition in the muscle tissue of three breeds of pig: Laiwu (LW), Lulai Black (LL), and Large White (LY).

Results

qPCR analysis of the PPARγ and ADRP genes in the three breeds of pig revealed PPARγ and ADRP mRNA expression profiles of LW > LL > LY and LL > LW > LY, respectively. PPARγ mRNA expression was significantly and positively correlated with IMF deposition (p < 0.05). There were significant correlations between PPARγ and ADRP mRNA expression levels (p < 0.01).

Conclusions

These results suggest correlations between PPARγ and ADRP in fat deposition and regulation in pigs, PPARγ gene may be a main effector of IMF content and play an important role during adipocyte differentiation in pigs, thereby providing new information to further elucidate molecular mechanisms associated with intramuscular fat deposition in Laiwu pigs and provides new data for further molecular studies of mechanisms underlying intramuscular fat deposition in human obesity. The continued elucidation of specific genetic mechanisms between PPARγ and ADRP warrants further studies.

MyoD promotes porcine PPARγ gene expression through an E-box and a MyoD-binding site in the PPARγ promoter region

Peroxisome proliferator-activated receptor γ (PPARγ) is a key transcription factor in adipogenesis and can be regulated by adipogenesis-related factors. However, little information is available regarding its regulation by myogenic factors. In this study, we found that over-expression of MyoD enhanced porcine adipocyte differentiation and up-regulated PPARγ expression, whereas small interfering RNA against MyoD significantly attenuated porcine adipocyte differentiation and inhibited PPARγ expression. The MyoD-binding sites in the PPARγ promoter region at -412 to -396 and -155 to -150 were identified by promoter deletion analysis and site-directed mutagenesis. Electrophoretic mobility shift assays and chromatin immunoprecipitation further showed that these two regions are MyoD-binding sites, both in vitro and in vivo, indicating that MyoD directly interacts with the porcine PPARγ promoter. Thus, our results demonstrate that an Enhancer box and a binding site for a cooperative co-activator of MyoD are present in the promoter region of porcine PPARγ; furthermore, MyoD up-regulates PPARγ expression and promotes porcine adipocyte differentiation.

Swine PPAR-γ2 expression upregulated in skeletal muscle of transgenic mice via the swine Myozenin-1 gene promoter

Myozenin-1 (Myoz1) gene-encoded calsarcin-2 protein was expressed exclusively in fast-twitch muscles. Peroxisome proliferator-activated receptor γ2 (PPAR-γ2) is a key regulator of adipocyte differentiation, fatty acid uptake and storage in mammals. In this study, transgenic (TG) mice were generated by injecting linearized DNA that contained mouse creatine kinase M-type enhancer, Myoz1 core promoter, swine PPAR-γ2 (sPPAR-γ2) and SV40 polyadenylation sequences into pronuclei of fertilized FVB/NJ mouse embryos using microinjection technology. Then, the TG mice were used to identify whether swine Myoz1 (sMyoz1) promoter could upregulate sPPAR-γ2 expression in skeletal muscle in a TG mouse model. The results showed that the sMyoz1 promoter indeed upregulated sPPAR-γ2 expression on both the RNA and protein levels. The target genes of PPAR-γ in fat formation pathways, such as fatty acid-binding protein 4 (FABP4) and lipoprotein lipase (LPL), were also overexpressed on the RNA level. Meanwhile, the level of skeletal muscle triacylglycerol in TG mice was increased (P < 0.05), and the result of Oil Red-O staining in the skeletal muscle sections also showed that the number of lipid droplets was significantly increased in TG mice compared to wild-type mice, which might improve the intramuscular fat (IMF) content. For pork, the quality was mostly influenced by the IMF; the identification of swine muscle-specific promoter, sMyoz1, could further serve to develop transgenic pigs with higher intramuscular fat contents and improve pork quality.

A Novel Splicing Variant of Peroxisome Proliferator-Activated Receptor-γ (Pparγ1sv) Cooperatively Regulates Adipocyte Differentiation with Pparγ2

Peroxisome proliferator-activated receptors (PPARs) are nuclear receptors that regulate expression of a number of genes associated with the cellular differentiation and development. Here, we show the abundant and ubiquitous expression of a newly identified splicing variant of mouse Pparγ (Pparγ1sv) that encodes PPARγ1 protein, and its importance in adipogenesis. The novel splicing variant has a unique 5′-UTR sequence, relative to those of Pparγ1 and Pparγ2 mRNAs, indicating the presence of a novel transcriptional initiation site and promoter for Pparγ expression. Pparγ1sv was highly expressed in the white and brown adipose tissues at levels comparable to Pparγ2. Pparγ1sv was synergistically up-regulated with Pparγ2 during adipocyte differentiation of 3T3-L1 cells and mouse primary cultured preadipocytes. Inhibition of Pparγ1sv by specific siRNAs completely abolished the induced adipogenesis in 3T3-L1 cells. C/EBPβ and C/EBPδ activated both the Pparγ1sv and Pparγ2 promoters in 3T3-L1 preadipocytes. These findings suggest that Pparγ1sv and Pparγ2 synergistically regulate the early stage of the adipocyte differentiation.

Peroxisome proliferator activated receptor (PPAR)-gamma concentrations in childhood obesity

BACKGROUND

Peroxisome proliferator-activated receptors (PPARs) are nuclear proteins that regulate transcriptional responses to peroxisome proliferators. There has been limited research concerned with the childhood expression of these receptors. In this study, we aimed to evaluate PPAR-gamma (PPAR-γ) concentrations and their relationship to body mass index (BMI), ratio of waist and hip, blood pressure levels, insulin resistance and lipid profile in obese children and adolescents.

SUBJECTS AND METHODS

Children aged 8-16 years old were included in the study; 44 obese children and 25 healthy children were taken into the study. Blood pressure and waist-hip circumference of obese patients were measured. Following a 12-hour nighttime fasting, venous blood samples were taken, including blood glucose, insulin, lipid profile, liver function tests and PPAR-γ concentrations, and all samples were analyzed at the same time.

FINDINGS

PPAR-γ concentrations were 0.226 + 0.128 in obese children and 0.547 + 0.546 in the control group. PPAR-γ concentrations were lower in obese children and this difference was statistically significant (p = 0.008). PPAR-γ concentrations of control children were 2.42-fold higher than obese children. There was a negative correlation between PPAR-γ concentrations and waist circumference, and a positive correlation between birth weight and PPAR-γ concentrations in obese children.

CONCLUSION

In our study we found that PPAR-γ concentrations were low in obese children. In adults, treatment modalities aimed at enhancing the activation of PPAR in obesity lead to a decrease in obesity, insulin resistance, dyslipidemia and cardiovascular disease and this gives hope that similar treatment modalities can be used for children.

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.

Role of peroxisome proliferator-activated receptor gamma and its ligands in the treatment of hematological malignancies

Peroxisome proliferator-activated receptor gamma (PPARgamma) is a multifunctional transcription factor with important regulatory roles in inflammation, cellular growth, differentiation, and apoptosis. PPARgamma is expressed in a variety of immune cells as well as in numerous leukemias and lymphomas. Here, we review recent studies that provide new insights into the mechanisms by which PPARgamma ligands influence hematological malignant cell growth, differentiation, and survival. Understanding the diverse properties of PPARgamma ligands is crucial for the development of new therapeutic approaches for hematological malignancies.

Association of PPARγ2 polymorphisms with carcass and meat quality traits in a Pietrain x Jinhua F2 population

The PPARγ2 gene is a key regulator of both proliferation and preadipocyte differentiation in mammals. Herein its genotype and allele frequencies were analyzed using PCR-SSCP in eight pig breeds (N = 416). Two kinds of polymorphisms of the PPARγ2 gene were detected, including a previously reported shift SNP A177G (Met59Val) in exon 1 and a novel silent mutation G876A in exon 5. The results revealed that European pig breeds carry a higher allele A frequency at the A177G locus and a fixed GG genotype at the G876A locus. Allele A at the G876A locus was only found in Jinhua pigs. The association between haplotype (A177G/G876A) and carcass and meat quality traits was analyzed in a Pietrain x Jinhua F2 population (N = 248). The PPARγ2 gene was found to be significantly associated with backfat thickness at the shoulder (p < 0.05), 6–7^th ribs (p < 0.01), last rib (p < 0.01), gluteus medius (p <0.05) and ham weight (p < 0.01). Significant effects of different haplotypes on ham weight and backfat thickness at the 6–7^th ribs, last rib, and gluteus medius were also observed.

Peripartal feeding strategy with different n-6:n-3 ratios in sows: effect on gene expression in backfat white adipose tissue postpartum

The aim of this study was to describe the effects of two diets differing in n-6:n-3 ratio and prepartal feeding regime on gene expression of PPARgamma1a/1b, PPARgamma1c/1d, PPARgamma2, PPARgamma coactivator 1A (PPARGC1A), GLUT4, TNFalpha, adiponectin, leptin, leptin receptor (LEPR), fatty acid binding protein 4 (FABP4), lipoprotein lipase (LPL) in sows' white adipose tissue on the first day of lactation. The relationship between mRNA expression of these genes and circulating insulin, leptin and thyroid hormones was also considered. Diets contained a low (supplemented with fish oil; f group) or a high (supplemented with sunflower oil; s group) n-6:n-3 ratio and were provided from 8 (f8, s8) or 3d (f3, s3) before parturition (onset day 8 or 3). A low n-6:n-3 ratio reduced the 1d postpartum expression of PPARgamma2 and PPARGC1A but only when applied from 3 d before parturition. Circulating leptin was negatively correlated with mRNA expression of adiponectin, LEPR and LPL, whereas thyroxine was positively correlated with levels of PPARGC1A. In conclusion, the effect of dietary treatments, e.g. altering the n-6:n-3 ratio, around parturition on the expression of crucial genes in nutrient metabolism can be modulated by the duration of application before parturition.

Patterns of gene expression in pig adipose tissue: Transforming growth factors, interferons, interleukins, and apolipoproteins1

Although cDNA microarray studies have indicated the expression of unique and unexpected genes and their products in human and rodent adipose tissue, cDNA microarray studies of adipose tissue from growing pigs have not been reported. Total RNA was collected at slaughter from outer s.c. adipose tissue (OSQ), middle s.c. adipose tissue (MSQ), ovary, uterus, hypothalamus, and pituitary tissue samples from gilts at 90, 150, and 210 d (n = 5/age). Dye-labeled cDNA probes were hybridized to custom microarrays (70 mer oligonucleotides) representing approximately 600 pig genes involved in growth and reproduction. Expression intensity ratios revealed little change in expression of 27 cytokines and 4 apolipoproteins with age in OSQ and MSQ from pigs at 90, 150, and 210 d of age. Distinct patterns of relative gene expression were evident within apolipoproteins, IL, interferons, and transforming growth factor beta family members in adipose tissue from growing pigs (90-, 150-, and 210-d-old pigs). Patterns of gene expression within apolipoproteins, IL, interferons, and transforming growth factor beta family members distinguished OSQ and MSQ depots in growing pigs. We also demonstrated, for the first time, the expression of several major cytokine and apolipoprotein genes in pig adipose tissue, including small inducible cytokine A5 (RANTES), IL-1B, IL-1A, IL-12A, IL-1 receptor antagonist, and apolipoproteins A1 and E with microarray and reverse transcription-PCR assays or reverse transcription-PCR assays alone. These studies demonstrate that expression of major cytokine and apolipoprotein genes in pig adipose tissue are not influenced by age in growing pigs but may be influenced by location or depot.

Peroxisome proliferator-activated receptor gamma in the human pituitary gland: expression and splicing pattern in adenomas versus normal pituitary

Pituitary adenomas are slow-growing tumours arising within the pituitary gland. If secreting, they give rise to well-known syndromes such as Cushing's disease or acromegaly; when hormonally inactive, they come to clinical attention often with local mass effects or pituitary deficiency. Peroxisome proliferator-activated receptor gamma (PPARgamma), a nuclear hormone receptor with a key role in fat and glucose metabolism, but also involved in several neoplasia, has recently been detected in pituitary adenomas. In the present study, we evaluated the occurrence and splicing profile of PPARgamma in 43 cases of pituitary adenoma of different subtypes and compared it to 12 normal pituitary glands. By real-time polymerase chain reaction, PPARgamma was expressed as much in adrenocorticotrophic hormone (ACTH)-secreting and ACTH-silent adenomas as in controls, with a moderate underexpression in somatotrophinomas and prolactinomas and overexpression in 54% of nonfunctioning pituitary adenomas (NFPA). There was no apparent qualitative change in the splicing profile of pathological pituitary glands, nor was the presence of specific isoforms with dominant negative effects against PPARgamma detected. Western blotting revealed similar expression levels in the different subgroups of pituitary adenomas and normal glands. Immunohistochemistry confirmed PPARgamma expression in approximately one-half of analysed samples. The intra- and intergroup differences observed in pituitary adenomas may represent new elements in the process of understanding the different clinical responses of Cushing's and Nelson patients to PPARgamma-ligand treatment. Moreover, the higher level of PPARgamma expression detected in the NFPA subgroup may suggest its possible role as a molecular target in these pituitary adenomas, paving the way for investigations on the effectiveness of treatment with thiazolidinediones in such patients.

Development of a new set of reference genes for normalization of real-time RT-PCR data of porcine backfat and longissimus dorsi muscle, and evaluation with PPARGC1A

Background

An essential part of using real-time RT-PCR is that expression results have to be normalized before any conclusions can be drawn. This can be done by using one or multiple, validated reference genes, depending on the desired accuracy of the results. In the pig however, very little information is available on the expression stability of reference genes. The aim of this study was therefore to develop a new set of reference genes which can be used for normalization of mRNA expression data of genes expressed in porcine backfat and longissimus dorsi muscle, both representing an economically important part of a pig's carcass. Because of its multiple functions in fat metabolism and muscle fibre type composition, peroxisome proliferative activated receptor γ coactivator 1α (PPARGC1A) is a very interesting candidate gene for meat quality, and was an ideal gene to evaluate our developed set of reference genes for normalization of mRNA expression data of both tissue types.

Results

The mRNA expression stability of 10 reference genes was determined. The expression of RPL13A and SDHA appeared to be highly unstable. After normalization to the geometric mean of the three most stably expressed reference genes (ACTB, TBP and TOP2B), the results not only showed that the mRNA expression of PPARGC1A was significantly higher in each of the longissimus dorsi muscle samples than in backfat (P < 0.05), but also that the expression was significantly higher in the most cranial of the three muscle samples (P < 0.05).

Conclusion

This study provides a new set of reference genes (ACTB, TBP and TOP2B) suitable for normalization of real-time RT-PCR data of backfat and longissimus dorsi muscle in the pig. The obtained PPARGC1A expression results, after application of this set of reference genes, are a first step in unravelling the PPARGC1A expression pattern in the pig and provide a basis for possible selection towards improved meat quality while maintaining a lean carcass.

Peroxisome proliferator-activated receptors (PPARs) and ovarian function--implications for regulating steroidogenesis, differentiation, and tissue remodeling

The peroxisome proliferator-activated receptors (PPARs) are a family of transcription factors involved in varied and diverse processes such as steroidogenesis, angiogenesis, tissue remodeling, cell cycle, apoptosis, and lipid metabolism. These processes are critical for normal ovarian function, and all three PPAR family members--alpha, delta, and gamma, are expressed in the ovary. Most notably, the expression of PPARgamma is limited primarily to granulosa cells in developing follicles, and is regulated by luteinizing hormone (LH). Although much has been learned about the PPARs since their initial discovery, very little is known regarding their function in ovarian tissue. This review highlights what is known about the roles of PPARs in ovarian cells, and discusses potential mechanisms by which PPARs could influence ovarian function. Because PPARs are activated by drugs currently in clinical use (fibrates and thiazolidinediones), it is important to understand their role in the ovary, and how manipulation of their activity may impact ovarian physiology as well as ovarian pathology.