The Pro12 -->Ala substitution in PPAR-gamma is associated with resistance to development of diabetes in the general population: possible involvement in impairment of insulin secretion in individuals with type 2 diabetes

Peroxisome proliferator-activated receptor γ Pro12 ala polymorphism and risk of cerebral stroke in type 2 diabetes mellitus egyptian patients

Objectives

This study aimed to analyze the association of the peroxisome proliferator activated receptor gamma (PPARγ) P12A (rs1801282) polymorphism with development of cerebral stroke in patients with type 2 diabetes mellitus.

Methods

We included 224 patients with diabetes, they were categorized into116 patients with ischemic stroke (IS) and 108 without IS, in addition to 148 healthy controls in this study. respectively. Anthropometric parameters and laboratory tests were measured. The polymorphism was detected by a PCR-RFLP method.

Results

A12 allele and A12 containing genotypes show significant higher percentage in patients with diabetes and IS in comparison to diabetes patients without IS (9.1 vs. 4.2%,16.4 vs7.4%; P = 0.044,0.044) with OR of 2.29 and 2. 449 respectively (95% CI: 1.024-5.115, 1.024-5.856) but does not withstand Bonferroni correction.

Conclusion

A12 containing genotypes and A12 allele are not associated with IR, diabetes and risk of IS development, however, significant higher BMI were observed in A12 allele carriers in the studied patients with diabetes as well as those with IS.

Evidence Linking PPARG Genetic Variants with Periodontitis and Type 2 Diabetes Mellitus in a Brazilian Population

The peroxisome proliferator-activated receptor gamma (PPARG) gene encodes a transcription factor involved in the regulation of complex metabolic and inflammatory diseases. We investigated whether single nucleotide polymorphisms (SNPs) and haplotypes of the PPARG gene could contribute with susceptibility to develop periodontitis alone or together with type 2 diabetes mellitus (T2DM). Moreover, we evaluated the gene-phenotype association by assessing the subjects' biochemical and periodontal parameters, and the expression of PPARG and other immune response-related genes. We examined 345 subjects with a healthy periodontium and without T2DM, 349 subjects with moderate or severe periodontitis but without T2DM, and 202 subjects with moderate or severe periodontitis and T2DM. PPARG SNPs rs12495364, rs1801282, rs1373640, and rs1151999 were investigated. Multiple logistic regressions adjusted for age, sex, and smoking status showed that individuals carrying rs1151999-GG had a 64% lower chance of developing periodontitis together with T2DM. The CCGT haplotype increased the risk of developing periodontitis together with T2DM. The rs1151999-GG and rs12495364-TC were associated with reduced risk of obesity, periodontitis, elevated triglycerides, and elevated glycated hemoglobin, but there was no association with gene expression. Polymorphisms of the PPARG gene were associated with developing periodontitis together with T2DM, and with obesity, lipid, glycemic, and periodontal characteristics.

Decoding type 2 diabetes mellitus genetic risk variants in Pakistani Pashtun ethnic population using the nascent whole exome sequencing and MassARRAY genotyping: A case-control association study

Genome-wide association studies have greatly increased the number of T2DM associated risk variants but most of them have focused on populations of European origin. There is scarcity of such studies in developing countries including Pakistan. High prevalence of T2DM in Pakistani population prompted us to design this study. We have devised a two stage (the discovery stage and validation stage) case-control study in Pashtun ethnic population in which 500 T2DM cases and controls each have been recruited to investigate T2DM genetic risk variants. In discovery stage Whole Exome Sequencing (WES) was used to identify and suggest T2DM pathogenic SNPs, based on SIFT and Polyphen scores; whereas in validation stage the selected variants were confirmed for T2DM association using MassARRAY genotyping and appropriate statistical tests. Results of the study showed the target positive association of rs1801282/PPARG (OR = 1.24, 95%Cl = 1.20-1.46, P = 0.010), rs745975/HNF4A (OR = 1.30, 95%Cl = 1.06-1.38, P = 0.004), rs806052/GLIS3 (OR = 1.32, 95%Cl = 1.07-1.66, P = 0.016), rs8192552/MTNR1B (OR = 1.53, 95%Cl = 0.56-1.95, P = 0.012) and rs1805097/IRS-2 (OR = 1.27, 95%Cl = 1.36-1.92, P = 0.045), with T2DM; whereas rs6415788/GLIS3, rs61788900/NOTCH2, rs61788901/NOTCH2 and rs11810554/NOTCH2 (P>0.05) showed no significant association. Identification of genetic risk factors/variants can be used in defining high risk subjects assessment, and disease prevention.

Ethnic disparities attributed to the manifestation in and response to type 2 diabetes: insights from metabolomics

Type 2 diabetes (T2D) associated health disparities among different ethnicities have long been known. Ethnic variations also exist in T2D related comorbidities including insulin resistance, vascular complications and drug response. Genetic heterogeneity, dietary patterns, nutrient metabolism and gut microbiome composition attribute to ethnic disparities in both manifestation and progression of T2D. These factors differentially regulate the rate of metabolism and metabolic health. Metabolomics studies have indicated significant differences in carbohydrate, lipid and amino acid metabolism among ethnicities. Interestingly, genetic variations regulating lipid and amino acid metabolism might also contribute to inter-ethnic differences in T2D. Comprehensive and comparative metabolomics analysis between ethnicities might help to design personalized dietary regimen and newer therapeutic strategies. In the present review, we explore population based metabolomics data to identify inter-ethnic differences in metabolites and discuss how (a) genetic variations, (b) dietary patterns and (c) microbiome composition may attribute for such differences in T2D.

G Allele of the rs1801282 Polymorphism in PPARγ Gene Confers an Increased Risk of Obesity and Hypercholesterolemia, While T Allele of the rs3856806 Polymorphism Displays a Protective Role Against Dyslipidemia: A Systematic Review and Meta-Analysis

BACKGROUND

The relationships between the rs1801282 and rs3856806 polymorphisms in nuclear receptor peroxisome proliferator-activated receptor gamma (PPARγ) gene and obesity indexes as well as serum lipid levels have been extensively investigated in various studies, but the results were inconsistent and even contradictory.

METHODS

PubMed, Google Scholar, Embase, Cochrane Library, Web of Science, Wanfang, CNKI and VIP databases were searched for eligible studies. The random-effTPDEects model was used, and standardized mean difference (SMD) with 95% confidence interval (CI) was calculated to estimate the differences in obesity indexes and serum lipid levels between the subjects with different genotypes in a dominant model. Heterogeneity among studies was assessed by Cochran's x²-based Q-statistic test. Publication bias was identified by using Begg's test.

RESULTS

One hundred and twenty studies (70,317 subjects) and 33 studies (18,353 subjects) were identified in the analyses for the rs1801282 and rs3856806 polymorphisms, respectively. The G allele carriers of the rs1801282 polymorphism had higher levels of body mass index (SMD = 0.08 kg/m², 95% CI = 0.04 to 0.12 kg/m², p < 0.001), waist circumference (SMD = 0.12 cm, 95% CI = 0.06 to 0.18 cm, p < 0.001) and total cholesterol (SMD = 0.07 mmol/L, 95% CI = 0.02 to 0.11 mmol/L, p < 0.01) than the CC homozygotes. The T allele carriers of the rs3856806 polymorphism had lower levels of low-density lipoprotein cholesterol (SMD = -0.09 mmol/L, 95% CI = -0.15 to -0.03 mmol/L, p < 0.01) and higher levels of high-density lipoprotein cholesterol (SMD = 0.06 mmol/L, 95% CI = 0.02 to 0.10 mmol/L, p < 0.01) than the CC homozygotes.

CONCLUSIONS

The meta-analysis suggests that the G allele of the rs1801282 polymorphism confers an increased risk of obesity and hypercholesterolemia, while the T allele of the rs3856806 polymorphism displays a protective role against dyslipidemia, which can partly explain the associations between these polymorphisms and cardiovascular disease.

SYSTEMATIC REVIEW REGISTRATION

https://www.crd.york.ac.uk/prospero/, identifier [CRD42022319347].

PPARγ and Diabetes: Beyond the Genome and Towards Personalized Medicine

PURPOSE OF REVIEW

Full and partial synthetic agonists targeting the transcription factor PPARγ are contained in FDA-approved insulin-sensitizing drugs and used for the treatment of metabolic syndrome-related dysfunctions. Here, we discuss the association between PPARG genetic variants and drug efficacy, as well as the role of alternative splicing and post-translational modifications as contributors to the complexity of PPARγ signaling and to the effects of synthetic PPARγ ligands.

RECENT FINDINGS

PPARγ regulates the transcription of several target genes governing adipocyte differentiation and glucose and lipid metabolism, as well as insulin sensitivity and inflammatory pathways. These pleiotropic functions confer great relevance to PPARγ in physiological regulation of whole-body metabolism, as well as in the etiology of metabolic disorders. Accordingly, PPARG gene mutations, nucleotide variations, and post-translational modifications have been associated with adipose tissue disorders and the related risk of insulin resistance and type 2 diabetes (T2D). Moreover, PPARγ alternative splicing isoforms-generating dominant-negative isoforms mainly expressed in human adipose tissue-have been related to impaired PPARγ activity and adipose tissue dysfunctions. Thus, multiple regulatory levels that contribute to PPARγ signaling complexity may account for the beneficial as well as adverse effects of PPARγ agonists. Further targeted analyses, taking into account all these aspects, are needed for better deciphering the role of PPARγ in human pathophysiology, especially in insulin resistance and T2D. The therapeutic potential of full and partial PPARγ synthetic agonists underlines the clinical significance of this nuclear receptor. PPARG mutations, polymorphisms, alternative splicing isoforms, and post-translational modifications may contribute to the pathogenesis of metabolic disorders, also influencing the responsiveness of pharmacological therapy. Therefore, in the context of the current evidence-based trend to personalized diabetes management, we highlight the need to decipher the intricate regulation of PPARγ signaling to pave the way to tailored therapies in patients with insulin resistance and T2D.

The Pro12Ala polymorphism of PPARγ2 modulates beta cell function and failure to oral glucose-lowering drugs in patients with type 2 diabetes

BACKGROUND

We evaluate whether the Pro12Ala polymorphism of peroxisome proliferator-activated receptor γ2 (PPARγ2) has a role in the progression of diabetes by modulating the occurrence of treatment failure to glucose-lowering drugs.

METHODS

We studied 215 patients with type 2 diabetes participating in the Thiazolidinediones Or Sulphonylureas and Cardiovascular Accidents Intervention Trial study. All participants were insufficiently controlled (glycated haemoglobin [HbA_1c ] 7.0%-9.0%) with metformin 2 g/day and were randomly allocated to add-on pioglitazone or a sulfonylurea. Treatment failure was defined as HbA_1c ≥8% on two consecutive visits, 3 months apart.

RESULTS

Carriers or non-carriers of the polymorphism had similar age, body mass index, and diabetes duration. Ala carriers had lower fasting plasma insulin, better insulin sensitivity (Homeostasis Model Assessment [HOMA]2-%S), and worse beta cell secretion (HOMA2-%B) than non-carriers. During 24 months of follow-up, 32.5% among the Ala carriers and 8.6% among non-carriers (P < 0.001) developed treatment failure with a cumulative incidence of 18.6 vs 4.6/100 person-years. Those patients who developed treatment failure were older, had a younger age at diabetes diagnosis (48 ± 10 vs 52 ± 7 years; P = 0.032), higher HbA_1c (8.1 ± 0.5 vs 7.7 ± 0.5%; P < 0.001), and lower HOMA2-%B (30 ± 12 vs 46 ± 29; P = 0.015) at study entry, as compared to those who did not develop treatment failure. At multivariate analysis, the Pro12Ala polymorphism was significantly associated with treatment failure (hazard ratio [HR] 4.45; 95% confidence interval [CI] 1.79-11.1; P < 0.001); HbA_1c at study entry was the other independent predictor of failure in this study population.

CONCLUSION

The Pro12Ala polymorphism is associated with a greater insulin sensitivity, reduced beta cell function and a substantially increased risk of treatment failure.

Association between PPAR-γ2 gene polymorphisms and diabetic retinopathy risk: a meta-analysis

A close association between peroxisome proliferator-activated receptor-γ2 (PPAR-γ2) and the development of diabetic retinopathy (DR) has been previously suggested. Herein, a meta-analysis was conducted to explore the association between PPAR-γ2 polymorphisms and DR risk by performing a systematic search and quantitative analysis. Overall, fourteen articles involving 10,527 subjects were included. The pooled results did not reveal an association between PPAR-γ2 rs1801282 C/G and DR susceptibility in the overall population (e.g., the dominant model: CG+GG vs. CC, OR=0.85, 95% CI=0.69-1.06, P=0.15, I²=62.9%). Furthermore, heterogeneity tests, cumulative analyses, sensitivity analyses, and publication bias analyses were conducted and showed that the results were robust. Similarly, race-based subgroup analyses and other subgroup analyses did not reveal an association between the rs1801282 C/G and DR susceptibility. In addition, no significant association was observed between PPAR-γ2 rs3856806 C/T polymorphism and DR risk (e.g., the dominant model: CT+TT vs. CC, OR=1.12, 95%CI=0.91-1.37, P=0.28, I²=27.0%). Overall, based on the current sample size and the level of evidence presented in the study, the results suggest that PPAR-γ2 gene polymorphisms are not associated with DR risk.

Relationship of the Pro12Ala Polymorphism on the PPARy2 Gene With the Body Composition of Practitioners of Cyclic Exercises

This study aimed to verify the association between the genotypic of the receptor gene activated by peroxisome proliferators gamma 2 (PPARy2) and the body composition and the specific indicators of adiposity in practitioners physical exercises, considering nutritional intake, age, and training load as influencing factors. It was conducted a cross-sectional study with 335 adults (47.9 ± 12.7 years, 138 men, body mass index/BMI = 27.0 ± 4.9 kg/m²), practitioners of aerobic exercises in cyclical modalities (running, walking and/or cycling, who spent 328.3 ± 193.6 kcal/day on physical training). The genotyping of the Pro12Ala polymorphism was performed using the PCR-RFLP technique and the body composition measured by bioimpedance (InBody 720). Energy expenditure was based on the compendium of physical activities and caloric intake was measured by 24 h recall questionnaire. The higher prevalence was for the Pro/Pro genotype (76.1% vs. 23.9% of Pro/Ala). Pro/Pro genotypic group showed significant higher mean values for body mass (BM) (p < 0.03 for men and p < 0.02 for women) and BMI (p < 0.00 for men and p < 0.02 for women) and %FAT (p < 0.00), waist-hip ratio (WHR) (p < 0.04), and visceral fat (VF) (p < 0.00) only in men compared to Pro/Ala. Higher frequency of Pro/Pro was observed in the category indicating BMI (p < 0.00 for men and p < 0.03 for women), WRH (p < 0.03 for men and p < 0.00 for women), and %FAT (p < 0.03) (in the latter case, only among men. It was also observed that the frequency of distribution of Pro/Ala in the eutrophic category of the BMI remained independent of all influencers, while WHR and %FAT were independent of the training load, but influenced by nutritional intake and age. In women, the frequency of Pro/Ala distribution at the lowest BMI and WHR values remained independent of all confounding variables. It is concluded that the Pro12Ala polymorphism in the PPARy2 gene consistently influences indicators of body composition and adiposity, regardless of the practitioners of physical training, but the relationship needs to be considered according to age and nutritional intake.

High Expression Level of PPARγ in CD24 Knockout Mice and Gender-Specific Metabolic Changes: A Model of Insulin-Sensitive Obesity

Background: The heat-stable HSA/CD24 gene encodes a protein that shows high expression levels in adipocyte precursor cells but low levels in terminally differentiated adipocytes. Its high expression in many types of human cancer suggests an association between cancer, diabetes, and obesity, which is currently unclear. In addition, peroxisome proliferator-activated receptor gamma (PPARγ) is a regulator of adipogenesis that plays a role in insulin sensitivity, lipid metabolism, and adipokine expression in adipocytes. Aim: To assess gender-dependent changes in CD24 KO and its association with PPARγ expression. Experimental approach: WT and CD24 KO mice were monitored from birth up to 12 months, and various physiological and molecular characteristics were analysed. Mean body weight and adipose mass were higher in KO mice than in WT mice. Male, but not female, KO mice showed increased insulin sensitivity, glucose uptake, adipocyte size, and PPARγ expression than WT mice. In addition, enteric bacterial populations, assessed through high-throughput sequencing of stool 16S rRNA genes, were significantly different between male KO and WT mice. Conclusions: CD24 may negatively regulate PPARγ expression in male mice. Furthermore, the association between the CD24 and insulin sensitivity suggests a possible mechanism for diabetes as a cancer risk factor. Finally, CD24 KO male mice may serve as a model of obesity and insulin hyper-sensitivity.

Molecular & biochemical analysis of Pro12Ala variant of PPAR-γ2 gene in type 2 diabetes mellitus

Diabetes has emerged as a major threat to human life globally. Genomic studies have found a significant link between the Pro12Ala polymorphism of the PPAR-γ2 gene with incidence as well as occurrence of the risk of metabolic syndrome. The present study was aimed at assessing the PPAR-γ2 variant in an Asian Indian cohort of type 2 diabetes patients and its correlation with metabolic parameters. The present case-control study involved 100 type 2 diabetic patients and 100 asymptomatic healthy volunteers enrolled in random. Assessment of demographic factors and biochemical parameters were done for all enrolled. In addition, genotyping for the Pro12Ala (CCA to GCA) polymorphism was done by polymerase chain reaction - restriction fragment length polymorphism (PCR-RFLP) technology. The genotyping study detected the frequency of the CC genotype (Pro12Pro) to be higher in frequency in comparison to the heterozygous CG genotype in both, cases and controls. The homozygous GG genotype (Ala12Ala) was not detected in any of the cases or controls assessed. Biochemical analysis of the levels of malondialdehyde (MDA) detected a significant increase (p < 0.0001). Additionally, increase in levels of fasting and postprandial glucose, total cholesterol, triglycerides, and parameters of the liver and renal function tests were detected. This study detected the PPAR-γ2 to be a significant biomarker for type 2 diabetes mellitus.

PPARG (Pro12Ala) genetic variant and risk of T2DM: a systematic review and meta-analysis

Type 2 diabetes mellitus (T2DM) is a complex disease caused by the interaction between genetic and environmental factors. A growing number of evidence suggests that the peroxisome proliferator-activated receptor gamma (PPARG) gene plays a major role in T2DM development. Meta-analysis of genetic association studies is an efficient tool to gain a better understanding of multifactorial diseases and potentially to provide valuable insights into gene-disease interactions. The present study was focused on assessing the association between Pro12Ala variation in the PPARG and T2DM risk through a comprehensive meta-analysis. We searched PubMed, WoS, Embase, Scopus and ProQuest from 1990 to 2017. The fixed-effect or random-effect model was used to evaluate the pooled odds ratios (ORs) and 95% confidence intervals (CIs) depending on the heterogeneity among studies. The sources of heterogeneity and publication bias among the included studies were assessed using I² statistics and Egger's tests. A total of 73 studies, involving 62,250 cases and 69,613 controls were included. The results showed that the minor allele (G) of the rs1801282 variant was associated with the decreased risk of T2DM under different genetic models. Moreover, the protective effect of minor allele was detected to be significantly more in some ethnicities including the European (18%), East Asian (20%), and South East Asian (18%). And the reduction of T2DM risk in Ala12 carriers was stronger in individuals from North Europe rather than Central and South Europe. Our findings indicated that the rs1801282 variant may contribute to decrease of T2DM susceptibility in different ancestries.

Association between Pro12Ala polymorphism and albuminuria in type 2 diabetic nephropathy

AIMS/INTRODUCTION

Diabetic nephropathy (DN) is a complication of diabetes mellitus that is characterized by the gradual loss of kidney function, which results in increased levels of albumin in the urine. The Pro12Ala polymorphism in the peroxisome proliferator-activated receptor-γ2 gene has been confirmed to improve insulin sensitivity, but its association with susceptibility to DN in patients with type 2 diabetes remains inconclusive.

MATERIALS AND METHODS

To examine whether the Pro12Ala polymorphism leads to the development of DN, a case-control study was carried out in 554 patients with type 2 diabetes. The genotypes of Pro12Ala polymorphism of the peroxisome proliferator-activated receptor gamma 2 gene were analyzed by real-time polymerase chain reaction with TaqMan® probe genotyping assay in all patients.

RESULTS

The mean age of the study population was 57.7 ± 8.8 years, with average diabetes duration of 12.8 ± 6.9 years. The prevalence of albuminuria was 43.5%. The frequency of genotype Pro12Pro, Pro12Ala and Ala12Ala genotype were 92.6%, 7.0%, 0.4% in our study population, and 90.4%, 8.9% and 0.7% in normal urinary albumin-to-creatinine ratio group, respectively. The Ala carriers (Pro12Ala + Ala12Ala) had significantly lower urinary albumin-to-creatinine ratio (15.0 vs 20.5 mg/g, P = 0.001) and better renal function (estimated glomerular filtration rate 81.8 [69.8-97.6] vs 78.7 mL/min/1.73 m2 [61.6-96.2]; P = 0.05) compared with those with the genotype Pro12Pro. After adjustment for age, sex and other confounders, the odds ratio of albuminuria for the Ala12 allele was 0.428 (95% confidence interval 0.195-0.940, P = 0.034]).

CONCLUSIONS

Our results suggest that the peroxisome proliferator-activated receptor gamma 2 Ala12 variant has significant protective effects against albuminuria and DN.

Association between PPARγrs1801282 polymorphism with diabetic nephropathy and type-2 diabetes mellitus susceptibility in south India and a meta-analysis

BACKGROUND

Diabetic Nephropathy (DN) is a major complication of Type 2 Diabetes Mellitus (T2DM) with high morbidity rates worldwide.

OBJECTIVE

To determine the association of PPARγ rs1801282 polymorphism in T2DM and DN in south Indian population.

METHODS

We have conducted a case-control study to test the association of rs1801282 polymorphism with T2DM and DN in 424 subjects (DN=128; T2DM=148 and controls=148) belonging to the south Indian population using ARMS-PCR and Sanger sequencing method. Further, a meta-analysis was performed for rs1801282 polymorphism from the published literature retrieved from various electronic databases to determine the susceptibility among T2DM and DN across various ethnic populations under five genetic models.

RESULTS

The genotyping of rs1801282 polymorphism showed significant (p-value<0.05) association with DN and T2DM compared to controls. In the meta-analysis, no significant association (p-value>0.05) was noticed for rs1801282 with DN vs. controls in homozygote, heterozygote, allelic, recessive and dominant genetic models. However, a significant association was observed between rs1801282 SNP and T2DM under heterozygote (Jj vs JJ) genetic model with OR=0.56, (95%CI [0.43-0.74]), p≤0.0001 of Asian and Caucasian populations.

CONCLUSION

Overall analysis suggests that the rs1801282 polymorphism might be associated with DN and T2DM. More case-control studies on the PPARγ gene with a larger sample size including all the confounding factors are required to corroborate the findings from this meta-analysis.

Association between PPARγrs1801282 polymorphism with diabetic nephropathy and type-2 diabetes mellitus susceptibility in south India and a meta-analysis

BACKGROUND

Diabetic Nephropathy (DN) is a major complication of Type 2 Diabetes Mellitus (T2DM) with high morbidity rates worldwide.

OBJECTIVE

To determine the association of PPARγ rs1801282 polymorphism in T2DM and DN in south Indian population.

METHODS

We have conducted a case-control study to test the association of rs1801282 polymorphism with T2DM and DN in 424 subjects (DN=128; T2DM=148 and controls=148) belonging to the south Indian population using ARMS-PCR and Sanger sequencing method. Further, a meta-analysis was performed for rs1801282 polymorphism from the published literature retrieved from various electronic databases to determine the susceptibility among T2DM and DN across various ethnic populations under five genetic models.

RESULTS

The genotyping of rs1801282 polymorphism showed significant (p-value<0.05) association with DN and T2DM compared to controls. In the meta-analysis, no significant association (p-value>0.05) was noticed for rs1801282 with DN vs. controls in homozygote, heterozygote, allelic, recessive and dominant genetic models. However, a significant association was observed between rs1801282 SNP and T2DM under heterozygote (Jj vs JJ) genetic model with OR=0.56, (95%CI [0.43-0.74]), p≤0.0001 of Asian and Caucasian populations.

CONCLUSION

Overall analysis suggests that the rs1801282 polymorphism might be associated with DN and T2DM. More case-control studies on the PPARγ gene with a larger sample size including all the confounding factors are required to corroborate the findings from this meta-analysis.

Peroxisome Proliferator-Activated Receptor-γ Gene Polymorphism in Psoriasis and Its Relation to Obesity, Metabolic Syndrome, and Narrowband Ultraviolet B Response: A Case-Control Study in Egyptian Patients

Background:

Psoriasis is a common dermatologic disease with multifactorial etiology in which genetic factors play a major role. Peroxisome proliferator-activated receptor (PPAR)-γ is expressed in keratinocytes and is known to affect cell maturation and differentiation in addition to its role in inflammation.

Aim:

To study the association between PPAR-γ gene polymorphism and psoriasis vulgaris in Egyptian patients to explore if this polymorphism influenced disease risk or clinical presentation.

Methods:

Forty-five patients with psoriasis vulgaris and 45 age, sex and body mass index matched healthy volunteers who have no present, past or family history of psoriasis as a control group were enrolled. Selected cases included obese and nonobese participants. Detection of PPAR-γ gene polymorphism was done with restriction fragment length polymorphism polymerase chain reaction. Narrow-band ultraviolet B (NBUVB) was given for every case three times/week for 12 weeks.

Results:

Homopolymorphism, heteropolymorphism, and Ala allele were significantly associated with cases (P = 0.01, P = 0.01, and P = 0.004, respectively) and increased risk of occurrence of psoriasis by 5.25, 3.65, and 3.37 folds, respectively. Heteropolymorphism was significantly associated with nonobese cases compared to obese ones (P = 0.01). Ala allele was significantly associated with obese cases (P = 0.001) and increased risk of occurrence of psoriasis in obese participants by 1.14 folds. Homopolymorphism, heteropolymorphism, and Ala allele were more prevalent among obese cases without metabolic syndrome (MS) than obese cases with MS but without statistical significance. Percentage of decrease of mean Psoriasis Area and Severity Index score before and after 3 months of treatment with NBUVB was higher in cases with heteropolymorphism with no significant difference between homo- and heteropolymorphism.

Conclusion:

PPAR-γ gene polymorphism is associated with and increased the risk of psoriasis and its associated obesity in Egyptian patients. It has no role in NBUVB response in those patients. Future large-scale studies on different populations are recommended.

Maternal urinary phthalate metabolites in relation to gestational diabetes and glucose intolerance during pregnancy

BACKGROUND

Phthalates are common plasticizer chemicals that have been linked to glucose intolerance in the general population, but there is only limited research on their association with gestational diabetes (GDM).

OBJECTIVE

We evaluated the association between 11 urinary phthalate metabolites and GDM, impaired glucose tolerance (IGT), and continuous blood glucose concentration during pregnancy in The Infant Development and Environment Study (TIDES). Based on prior study results, our primary analyses focused on monoethyl phthalate (MEP) in relation to our outcomes of interest.

STUDY DESIGN

We used multi-variable logistic regression to examine the odds of GDM and IGT in relation to an interquartile-range (IQR) increase in natural log (ln)-transformed, specific gravity (SG)-adjusted first trimester (T1) and average of T1 and third trimester (T3) ("T1T3avg") phthalate metabolite concentrations. We fit linear regression models to examine the percent change in blood glucose per IQR increase in ln-transformed, SG-adjusted T1 and T1T3avg phthalates. In sensitivity analyses, we examined interactions between exposure and race. We adjusted for maternal age, maternal body mass index, study center, race/ethnicity, parity, and gestational age at glucose testing.

RESULTS

In our sample of 705 pregnant women, we observed 60 cases of GDM, 90 cases of IGT, and an average GLT blood glucose of 113.6 ± 27.7 mg/dL. In our primary analysis, T1T3avg MEP was positively associated with GDM ([OR (95% CI) per IQR increase] T1T3avg MEP: 1.61 (1.10, 2.36)). In secondary analyses, most other phthalates were not found to be related to study outcomes, though some associations were noted. Sensitivity analyses indicated possible strong race-specific associations in Asians, though these results are based on a small sample size (n = 35).

CONCLUSION

In alignment with our a priori selection, we documented an association between T1T3avg MEP and GDM. Additional phthalate metabolites were also found to be linked to glucose intolerance, with possible stronger associations in certain racial/ethnic subgroups. Given the prevalence of phthalate exposures and the growing evidence of associations with metabolic outcomes, future studies should continue to examine this question in diverse cohorts of pregnant women, particularly in those who may be at higher risk for GDM and IGT.

Relationship of PPARG, PPARGC1A, and PPARGC1B polymorphisms with susceptibility to hepatocellular carcinoma in an eastern Chinese Han population

Background

PPARG, PPARGC1A, and PPARGC1B polymorphisms may be implicated in the development of cancer.

Participants and methods

In this study, we selected PPARG rs1801282 C>G and rs3856806 C>T, PPARGC1A rs2970847 C>T, and PPARGC1B rs7732671 G>C and rs17572019 G>A single-nucleotide polymorphisms to explore the relationship between these polymorphisms and hepatocellular carcinoma (HCC) risk. A total of 584 HCC patients and 923 controls were enrolled.

Results

We found that PPARG rs1801282 C>G polymorphism was correlated with a decreased susceptibility of HCC (CG vs CC, adjusted OR 0.47, 95% CI 0.27-0.82, P=0.007; CG/GG vs CC, adjusted OR 0.52, 95% CI 0.31-0.88, P=0.015). However, PPARG rs3856806 C>T polymorphism was a risk factor for HCC (TT vs CC, adjusted OR 2.33, 95% CI 1.25-4.36, P=0.008; TT vs CT/CC, adjusted OR 2.26, 95% CI 1.22-4.17, P=0.010). In a subgroup analysis by chronic hepatitis B virus (HBV)-infection status, age, sex, alcohol use, and smoking status, a significant association between PPARG rs1801282 C>G polymorphism and a decreased risk of HCC in male, ≥53 years, never-smoking, never-drinking, and nonchronic HBV-infection-status subgroups was found. However, we found PPARG rs3856806 C>T polymorphism increased the risk of HCC in never-smoking, never-drinking, and nonchronic HBV-infection-status subgroups. Haplotype-comparison analysis indicated that C_rs1801282T_rs3856806C_rs2970847G_rs7732671G_rs17572019, C_rs1801282T_rs3856806T_rs2970847G_rs7732671G_rs17572019, and C_rs1801282C_rs3856806C_rs2970847C_rs7732671A_rs17572019 haplotypes increased the risk of HCC. PPARG C_rs1801282T_rs3856806 and G_rs1801282C_rs3856806 haplotypes also influenced the risk of HCC.

Conclusion

In conclusion, our findings suggest PPARG polymorphisms may influence the susceptibility of HCC. The PPARG, PPARGC1A, and PPARGC1B haplotypes might be associated with HCC risk.

Assessment of the Pro12Ala Polymorphism in the PPAR-γ2 Gene among Type 2 Diabetes Patients in a Nigerian Population

The association between the Pro12Ala polymorphism of the PPARγ2 gene, type 2 diabetes (T2D), and obesity in certain ethnic populations has been reported. However, this relationship has not yet been described among diabetes patients in Nigeria. This study investigated the relationship between the Pro12Ala polymorphism in the PPARγ2 gene, obesity, and lipid abnormalities characterizing T2D among patients in Nigeria. This case-control study recruited 73 T2D and 75 non-diabetic (ND) patients. Demographic and clinical data were collected and blood glucose levels together with serum lipid profile for patients were measured. Pro12Ala polymorphism in the PPARγ2 gene was genotyped by restriction fragment length-Polymerase Chain Reaction (RFLP-PCR). The PPAR-γ2 gene (amplicon size = 270 base pair) was successfully amplified for all samples. Following restriction enzyme digestion and analysis by agarose gel electrophoresis, amplicons from samples showed a band of size 270 bp and were of the wild homozygous Pro/Pro genotype. Ala12 variant was totally absent from the study population. Obesity, estimated using Body Mass Index (BMI) and waist circumference (WC), was significantly higher (p < 0.05) in T2D patients compared to the non-diabetic patients. More so, the prevalence of lipid abnormalities; hypercholesterolaemia (TC > 200 mg/dL), hypertriglyceridaemia (TG > 150 mg/dL), high HDL (>100 mg/dL), and low HDL (<50 mg/dL) was significantly greater (p < 0.001) in T2D patients compared to non-diabetic patients. Results obtained further indicated lack of significant association between PPAR-γ2 gene polymorphism, T2D, and obesity. However, obesity and dyslipidaemia were strongly associated in T2D patients.

Is the rs1801282 (G/C) Polymorphism of PPAR - Gamma Gene Associated with T2DM in Iraqi People?

BACKGROUND

Pro12Ala (rs1801282) is a common polymorphism of the human PPAR-γ gene. Studies have demonstrated conflicting results about its association with T2DM worldwide. There are no reports about such possible association among Iraqi people.

OBJECTIVES

This study aims at finding out whether having the mutant allele (Ala12) might be associated with T2DM among Iraqi people.

METHODS

One hundred and ninety-two Arabic Iraqi adult subjects (97 with T2DM and 95 controls) were genotyped using PCR- RFLP. Clinical, anthropometrical and biochemical variables were compared regarding the Pro12Ala genotypes.

RESULTS

About 5.67% of people with diabetes were carriers of the (Ala12) allele versus 9.47% of controls. Allelic and genotypic frequencies were not statistically different among diabetics and controls [(χ2= 1.99, p= 0.16) and (χ2= 2.17, p= 0.14)]. Age, BMI and smoking- but not Pro12Ala - were independent risk factors for T2DM in our subjects. Pro12Ala was not associated with T2DM (Odd's ratio 0.55, 95% CI 0.23- 1.32, p= 0.14).

CONCLUSIONS

Our study revealed a relatively high frequency of the Ala12 allele among Arabic Iraqis. These frequencies did not significantly differ between diabetics and controls indicating the absence of association of Pro12Ala with T2DM among Iraqis.

Single-nucleotide polymorphisms of peroxisome proliferator-activated receptor-γ are associated with systemic lupus erythematosus in a Chinese Han population

BACKGROUND

Evidence has indicated that peroxisome-proliferator activated receptor-γ (PPAR-γ) agonists could be used in the prevention and treatment of murine systemic lupus erythematosus (SLE). However, to our knowledge, just one previous study has focused on the association between PPAR-γ polymorphisms and SLE in humans.

AIM

To investigate the association between PPAR-γ polymorphisms and SLE in a Chinese population and on additional gene-gene interaction between multiple single nucleotide polymorphisms (SNPs) in PPAR-γ.

METHODS

Three SNPs of PPAR-γ were selected for genotyping in this case-control study: rs1805192, rs10865710 and rs709158. Logistic regression was used to examine the association between the three SNPs and SLE, and the odds ratio (OR) and 95% CI were calculated. Generalized multifactor dimensionality reduction (GMDR) was used to investigate additional interaction.

RESULTS

All genotypes were distributed according to Hardy-Weinberg equilibrium. Logistic regression analysis showed a significant association between genotypes of rs1805192 variants and decreased SLE risk, after adjustment for sex, age, smoking, high-fat diet, low-fibre diet, alcohol status, body mass index and waist circumference. Participants with Ala allesles had a lower SLE risk than those homozygous for the wild-type allele (OR = 0.78; 95% CI 0.69-0.92). GMDR analysis indicated that there was a significant two-locus model (P = 0.001) involving rs1805192 and rs10865710, indicating a potential gene-gene interaction between them. Overall, the two-locus models had a cross-validation consistency of 10 out of 10 and a testing accuracy of 60.72%.

CONCLUSIONS

There was a significant association between PPAR-γ rs1805192 genotypes and decreased SLE risk, and a potential gene-gene interaction between rs1805192 and rs10865710.

Association of PPARG rs 1801282 C>G polymorphism with risk of colorectal cancer: from a case-control study to a meta-analysis

The functional single nucleotide polymorphisms in peroxisome proliferator-activated receptor gamma (PPARG) gene were predicted to be correlated with the susceptibility of colorectal cancer (CRC). The aim of the present study was to explore the relationship between PPARG rs1801282 C>G polymorphism and the risk of CRC. First, we conducted a case-control study with 387 CRC cases and 1,536 controls. We used the SNPscan method to determine the genotypes of PPARG rs1801282 C>G polymorphism. We found PPARG rs1801282 C>G polymorphism had a tendency of decreased risk to CRC risk (CG vs. CC: adjusted OR, 0.67, 95% CI = 0.43–1.04 for CG vs. CC, P = 0.073; GG vs. CC: adjusted OR, 0.68; 95% CI, 0.44–1.05; P = 0.078). The stratified analysis revealed PPARG rs1801282 C>G polymorphism also had a tendency of decreased risk to colon cancer (CG vs. CC: adjusted OR = 0.54, 95% CI = 0.27–1.08, P = 0.083). The results of subsequent meta-analysis suggested that PPARG rs1801282 C>G polymorphism might be a protective factor for CRC, especially in Asians, colon cancer and rectum cancer subgroups. In conclusion, our study indicates that PPARG rs1801282 C>G polymorphism might decrease the risk of overall CRC. Larger sample size and well-designed case-control studies are needed to confirm the potential association.

Thiazolidinedione-induced effects beyond glycaemic control

The thiazolidinediones exert their insulin sensitising effect by binding to the nuclear receptors (transcription factors) peroxisome proliferator activated receptor (PPAR) γ and, to varying degrees, to PPARα. Several different genes are activated by thiazolidinediones, many of which contribute to the increase in insulin sensitivity (eg. an increase in glucose uptake and utilisation, a decrease in gluconeogenesis and in insulin-antagonistic cytokines, such as tumour necrosis factor α). Activation of other genes indirectly reduces insulin resistance by, for example, increasing free fatty acid (FFA) uptake and oxidation resulting in lower circulating FFA levels. The action of thiazolidinediones at PPARγ is generally responsible for their insulin sensitising effects while action at PPARα contributes to their lipid lowering effects. Therefore, the relative affinities of the different thiazolidinediones for PPARγ and PPARα will also lead to a different spectrum of actions for each agent.

Molecular Mechanism of Insulin Resistance and Obesity

Obesity and insulin resistance have been recognized as leading causes of major health issues. We have endeavored to depict the molecular mechanism of insulin resistance, focusing on the function of adipocyte. We have investigated a role of PPARgamma on the pathogenesis of Type II diabetes. Heterozygous PPARgamma-deficient mice were protected from the development of insulin resistance due to adipocyte hypertrophy under a high-fat diet. Moreover, a Pro12Ala polymorphism in the human PPARgamma2 gene was associated with decreased risk of Type II diabetes in Japanese. Taken together with these results, PPARgamma is proved to be a thrifty gene mediating Type II diabetes. Pharmacological inhibitors of PPARgamma/RXR ameliorate high-fat diet-induced insulin resistance in animal models of Type II diabetes. We have performed a genome-wide scan of Japanese Type 2 diabetic families using affected sib pair analysis. Our genome scan reveals at least 9 chromosomal regions potentially harbor susceptibility genes of Type II diabetes in Japanese. Among these regions, 3q26-q28 appeared to be very attractive one, because of the gene encoding adiponectin, the expression of which we had found enhanced in insulin-sensitive PPARgamma-deficient mice. Indeed, the subjects with the G/G genotype of SNP276 in the adiponectin gene were at increased risk for Type II diabetes compared with those having the T/T genotype. The plasma adiponectin levels were lower in the subjects with the G allele, suggesting that genetically inherited decrease in adiponectin levels predispose subjects to insulin resistance and Type II diabetes. Our work also confirmed that replenishment of adiponectin represents a novel treatment strategy for insulin resistance and Type II diabetes using animal models. Further investigation will be needed to clarify how adiponectin exerts its effect and to discover the molecular target of therapies.

The Role of PPARγ in Cardiovascular Diseases

The peroxisome proliferator-activated receptors (PPAR) belong to the nuclear superfamily of ligand-activated transcription factors. PPARγ acts as a nutrient sensor that regulates several homeostatic functions. Its disruption can lead to vascular pathologies, disorders of fatty acid/lipid metabolism and insulin resistance. PPARγ can modulate several signaling pathways connected with blood pressure regulation. Firstly, it affects the insulin signaling pathway and endothelial dysfunction by modulation of expression and/or phosphorylation of signaling molecules through the PI3K/Akt/eNOS or MAPK/ET-1 pathways. Secondly, it can modulate gene expression of the renin- angiotensin system – cascade proteins, which potentially slow down the progression of atherosclerosis and hypertension. Thirdly, it can modulate oxidative stress response either directly through PPAR or indirectly through Nrf2 activation. In this context, activation and functioning of PPARγ is very important in the regulation of several disorders such as diabetes mellitus, hypertension and/or metabolic syndrome.

Association of Pro12Ala Polymorphism of Peroxisome Proliferator-Activated Receptor gamma 2 (PPARγ2) Gene with Type 2 Diabetes Mellitus in Ethnic Kashmiri Population

Type 2 diabetes mellitus (T2DM) is characterized by chronic hyperglycemia associated with insulin resistance and relative insulin deficiency. T2DM is believed to be attributable to the combined effect of genetic and environmental factors. Peroxisome proliferator-activated receptor gamma 2 (PPARγ2) is one of the main candidate genes that are implicated in T2DM. A common proline 12 alanine (Pro12Ala) polymorphism in PPARγ2 has been shown to be associated with T2DM. The aim of this work was to investigate the possible role of PPARγ2 gene polymorphism, as a genetic risk factor for T2DM. The study comprised 200 ethnic unrelated subjects (100 T2DM patients and 100 controls). PCR-RFLP technique was used for genotyping analysis. The frequency of the Pro allele was 79 and 91.5 % for controls and cases, respectively (P < 0.05; OR 3.2; 95 % CI 1.64-6.3). The Pro12Ala polymorphism was in Hardy-Weinberg equilibrium in both patients and controls (χ ² = 0.13, P > 0.05). We found a significant association of Pro12Ala polymorphism of PPARγ2 gene with T2DM, however the genotypes showed statistically significant association only with few clinical parameters including body mass index, total cholesterol, and low-density lipoprotein (P < 0.05). The study signifies that Pro allele in PPARγ2 may be a genotypic risk factor that confers susceptibility to T2DM in ethnic Kashmiri population.

Catalase and PPARg2 genotype and risk of systemic lupus erythematosus in Koreans

Catalase (CAT) and peroxisome proliferator activated receptor-g2 (PPARg2) are important regulators of oxidative stress and inflammation, which may contribute to the development of systemic lupus erythematosus (SLE). The objective of this study was to investigate the effects of genetic polymorphisms of CAT and PPARg2 on risk and severity of SLE in a Korean population. DNA was isolated from blood samples collected from 345 patients with SLE and 400 controls. Genotyping for the 2262C!T polymorphism of CAT and the Pro12Ala polymorphism of PPARg2 were performed by PCR-RFLP analysis. The severity of SLE was assessed using the Systemic Lupus International Collaborating Clinics/American College of Rheumatology (SLICC/ACR) damage index (SDI). No association was observed between genotypes for any of the clinical manifestations of SLE. CAT and PPARg2 genotypes were not associated with either risk or severity of SLE. For subjects who were carriers of the high activity Tallele for CATand have the Pro/Pro genotype for PPARg2, the odds ratio (95% confidence interval) for risk of SLE was 0.45 (0.23-1.08). Our results suggest that genetic polymorphisms of CAT and PPARg2 do not play a significant role in the development of SLE in a Korean population. A possible protective effect of a combined genotype warrants further investigation.

The Pro12Ala polymorphism in the PPAR-γ2 gene is not associated to obesity and type 2 diabetes mellitus in a Cameroonian population

Background

Peroxisome proliferator-activated receptor gamma 2 (PPAR-γ2) is a transcription factor with a key role in adipocyte differentiation, lipid storage and glucose homeostasis. The Ala allele of the common Pro12Ala polymorphism in the isoform PPAR-γ2 is at the center of many controversies because in some populations, it has been observed to be associated with T2DM or obesity but, not in others. The aim of this study was to investigate the association of Pro12Ala polymorphism in the PPAR-γ2 gene with susceptibility to obesity or T2DM in a Cameroonian population.

Methods

This case-control study included 62 obese, 60 T2DM patients and 120 controls (60 non obese and 60 patients without T2DM), all unrelated and of Cameroonian origin. PPAR-γ2 was examined by genotyping for Pro12Ala using the Restriction Fragment Length Polymorphism - Polymerase Chain Reaction (PCR - RFLP).

Results

A portion of the 270 base pair bands of the PPAR-γ2 gene was successfully amplified. The Ala12 variant was totally absent from the study population, all participants being homozygote Pro/Pro.

Conclusion

PPAR-γ2 Pro12Ala gene polymorphism may not be associated with obesity and T2DM. These results suggest that, PPAR-γ2 is unlikely a major gene for obesity or T2DM in the study population.

Variation in Association Between Thiazolidinediones and Heart Failure Across Ethnic Groups: Retrospective analysis of Large Healthcare Claims Databases in Six Countries

INTRODUCTION

The prevalence of polymorphisms among the metabolising enzymes and pharmacodynamic receptors relevant for the thiazolidinediones differs by ethnic group, a factor that may modify risk of adverse drug events.

OBJECTIVE

The aim of the study was to determine if the risk of oedema or heart failure associated with the thiazolidinediones varies in populations in Australia, Canada, Hong Kong, Japan, Korea and Taiwan.

METHODS

Sequence symmetry analyses were undertaken to investigate the risk of peripheral oedema, as measured by incident furosemide dispensing, and risk of hospitalisations for heart failure. Results were pooled, with Australia and Canada representing predominantly Caucasian population and all other countries contributing to Asian population estimates.

RESULTS

Pooled estimates of risk for furosemide initiation in the Caucasian populations were significantly increased for pioglitazone [adjusted sequence ratio (ASR) 1.47; 95 % confidence interval (CI) 1.14-1.91] and rosiglitazone (ASR 1.65; 95 % CI 1.58-1.72), while in the Asian populations, the pooled risk estimates were lower (ASR 1.11; 95 % CI 0.93-1.32 and ASR 1.21; 95 % CI 1.01-1.45 for pioglitazone and rosiglitazone, respectively). Results for hospitalisation for heart failure showed a similar trend, with elevated risk in the Australian data (ASR 1.88; 95 % CI 1.01-3.5 and ASR 1.25; 95 % CI 0.76-2.05 for pioglitazone and rosiglitazone, respectively), while no increased risk was found in the pooled results for the Asian populations.

CONCLUSION

The risk of both oedema and heart failure with thiazolidinediones was higher in predominantly Caucasian countries than in the Asian countries assessed. Assessment of adverse events by ethnicity may support safer medicine use.

Small heterodimer partner-interacting leucine zipper protein inhibits adipogenesis by regulating peroxisome proliferator-activated receptor γ activity

AIMS

Adipocytes play a critical role in energy balance. Growth of fat tissue is achieved via an increase in adipocyte mass and the formation of newly differentiated adipocytes from precursor cells. Understanding the cellular and molecular mechanisms of adipocyte differentiation is crucial for the study of obesity- and fat-related diseases. The present study was designed to study whether small heterodimer partner-interacting leucine zipper protein (SMILE), a novel co-repressor, could regulate differentiation of adipocyte in 3T3-L1 cells.

MATERIALS AND METHODS

Treatment of endoplasmic stress inducers, thapsigargin and tunicamycin, inhibited adipocyte differentiation, stimulated Smile mRNA expression, and repressed the expression of adiponectin (Adipoq) in 3T3-L1 pre-adipocyte. Overexpression of SMILE in 3T3-L1 cells decreased the expression of the mRNA encoding Adipoq, a major marker of adipocytes, significantly. Furthermore, knockdown of SMILE recovered the thapsigargin-mediated repression of Adipoq transcription. Co-immunoprecipitation experiments revealed that SMILE interacted physically with PPARγ in 3T3-L1 cells. In addition, chromatin immunoprecipitation experiments revealed that SMILE suppressed the binding affinity of PPARγ for the Adipoq promoter.

KEY FINDINGS

We demonstrate that SMILE controls adipocyte differentiation by regulating the transactivity of peroxisome proliferator-activated receptor γ (PPARγ).

SIGNIFICANCE

These findings demonstrate that SMILE represses adipocyte differentiation by regulating PPARγ transactivity; hence, SMILE is a potential regulator of PPARγ-related diseases.

A meta-analysis of the association of PPARγ rs1801282 polymorphism and NSAID usage with the risk of developing cancer

Use of nonsteroidal anti-inflammatory drugs (NSAIDs) is correlated with a reduced risk of cancer through the reduction of inflammation, which is an important risk factor. Several studies have investigated polymorphisms in the peroxisome proliferator-activated receptor gamma (PPARγ) gene and NSAID use in association with cancer risk. However, these studies yielded mixed results. Therefore, we performed a meta-analysis to evaluate the association of PPARγ polymorphisms and NSAID usage with cancer risk. We conducted a comprehensive search of PubMed through May 2013. Odds ratios (ORs) with corresponding 95% confidence intervals (CIs) were calculated using the fixed-effect or random-effect model. A comprehensive search of the database revealed 6 studies that fulfilled the inclusion criteria. NSAID use was significantly associated with decreased cancer risk regardless of PPARγ rs1801282 genotypes. In a stratified analysis by cancer type, NSAID users who were minor allele carriers had significantly decreased colon cancer risk compared to non-NSAID users (OR=0.73, 95% CI=0.57-0.93), whereas NSAID users homozygous for the major allele had significantly decreased risk for cancers other than colon cancer compared to non-NSAID users (OR=0.79, 95% CI=0.69-0.91). Our results suggest that the association of PPARγ rs1801282 polymorphism and NSAID use with the risk of cancer may differ according to cancer type.

Impact of the Pro12Ala polymorphism of the PPARγ2 gene on diabetes and obesity in a highly consanguineous population

BACKGROUND

The peroxisome proliferator-activated receptors (PPARs) are members of the nuclear hormone receptor subfamily of transcription factors. It has been reported that they play important roles in obesity and the development of type 2 diabetes mellitus (T2DM).

MATERIALS AND METHODS

This case-control study was carried out among 764 Qatari patients with diabetes and 764 healthy subjects above 20 years of age at Primary Healthcare Clinics (PHCs) from January 2011 to December 2012. Face-to-face interviews were based on a questionnaire that included variables such as age, sex, sociodemographic status, body mass index (BMI) and other clinical parameters. The Pro12Ala in the PPARγ2 gene was detected on the LightCycler using two specific probes. Univariate and multivariate statistical analysis were performed.

RESULTS

The study revealed that in the diabetes group, Pro/(10.2% vs 9.4%; P = 0.606) and Ala/Ala (1.4% vs 0.9%; P = 0.343) were higher than in controls, whereas Pro/Pro (88.4% vs 89.7%;P = 0.413) was lower in diabetes patients, but no significant difference was observed among the genotype groups. In obese patients with diabetes, Pro/Pro (89% vs 89.9%;P = 0.792) and Pro/Ala (8.9% vs 10.1%;P = 0.671) were lower than in obese healthy subjects. No homozygous Ala/Ala was found in obese healthy subjects, whereas 6 Ala/Ala homozygotes were in obese diabetes group. But in diabetes group, obese patients had higher homozygous of Pro/Pro (89.3% vs 87.8%;P = 0.523) and Ala/Ala (1.8% vs 1.2%;P = 0.771) compared to non-obese patients.

CONCLUSION

The current study did not reveal an association between the Pro12Ala polymorphism of the PPAR γ2 gene and type 2 diabetes (T2D) in Qatari's population.

Association of the variants in the PPARG gene and serum lipid levels: a meta-analysis of 74 studies

Considerable studies have been carried out to investigate the relationship between the polymorphisms of PPARG (Pro12Ala, C161T and C1431T) and serum lipid levels, but the results were inconclusive. Hence, we conducted a meta-analysis to clarify the association. MEDLINE, EMBASE and the Cochrane Library databases were searched systematically. The subgroup analysis was performed based on ethnicity. Seventy-four studies with 54,953 subjects were included in this meta-analysis. In Pro12Ala, the group with the ‘PP’ (C/C genotype) genotype group had lower levels of total cholesterol (TC) (mean difference, MD: −0.02, P < 0.00001; I² = 28%), low-density lipoprotein cholesterol (LDL-C) (MD: −0.02, P < 0.00001; I² = 30%) and higher levels of triglyceride (TG) (MD: 0.06, P < 0.00001; I² = 30%) than the combined ‘PA+AA’ (PA = C/G genotype, AA = G/G genotype) genotype group in Asian population, and the group with the ‘PP’ genotype had higher levels of TG (MD: 0.07, P < 0.02; I² = 67%) than the combined ‘PA+AA’ genotype group in non-Asian population. No statistically significant differences in the levels of TC, TG, high-density lipoprotein cholesterol, LDL-C were detected between different genotypes in C161T(Asian or non-Asian) and C1431T(Asian) polymorphisms. This meta-analysis was a renewed and confirmed study to assess the association between PPARG polymorphisms and serum lipid levels in Asian and non-Asian populations. There is a prominent association between Pro12Ala polymorphism and the levels of TC, LDL-C and TG in Asian population. No statistically significant differences in serum lipid levels were detected between different genotypes in C161T and C1431T polymorphisms.

Association of peroxisome proliferator-activated receptorγ gene Pro12Ala and C161T polymorphisms with cardiovascular risk factors in maintenance hemodialysis patients

The Pro12Ala and C161T polymorphisms in peroxisome proliferator-activated receptor γ (PPARγ) have been shown to be associated with carotid artery atherosclerosis. It remains unclear whether these two polymorphisms are associated with risk factors for cardiovascular disease (CVD) in hemodialysis (HD) patients. Therefore, the PPARγ genotypes in 99 HD patients and 149 controls were determined, and clinical characteristics among the different genotypes were compared. We found that the frequency of the Pro12Ala and C161T polymorphisms in HD patients was similar to that in healthy controls, but C161T polymorphism and T allele frequencies in HD patients with CVD were lower than that in HD patients without CVD. Carotid artery plaque (CAP) and carotid intima-media thickness (CIMT) in HD patients with CT + TT or Pro12Ala genotypes were also less than that in patients with CCor Pro12Pro genotypes, respectively. HD patients with CT + TT genotype had lower serum C reactive protein (CRP) levels, as well as higher triceps skin fold (TSF) thickness, mid arm circumference (MAC) and mean mid arm circumference (MMAC) than HD patients with CC genotype (P < 0.05). Moreover, CIMT of the Pro12Ala-CT161 subgroup was less than the Pro12Pro-CC161 and Pro12Pro-CT161 subgroup, and, CAP amounts of the Pro12Ala-CT161 subgroup was less than the Pro12Pro-CC161 subgroup. Our results indicate that the Pro12Ala and C161T polymorphisms were associated with some important risk factors for CVD in HD patients in the Han Chinese population.

PPARG in Human Adipogenesis: Differential Contribution of Canonical Transcripts and Dominant Negative Isoforms

The nuclear receptor PPARγ is a key regulator of adipogenesis, and alterations of its function are associated with different pathological processes related to metabolic syndrome. We recently identified two PPARG transcripts encoding dominant negative PPARγ isoforms. The existence of different PPARG variants suggests that alternative splicing is crucial to modulate PPARγ function, underlying some underestimated aspects of its regulation. Here we investigate PPARG expression in different tissues and cells affected in metabolic syndrome and, in particular, during adipocyte differentiation of human mesenchymal stem cells. We defined the transcript-specific expression pattern of PPARG variants encoding both canonical and dominant negative isoforms and identified a novel PPARG transcript, γ1ORF4. Our analysis indicated that, during adipogenesis, the transcription of alternative PPARG variants is regulated in a time-specific manner through differential usage of distinct promoters. In addition, our analysis describes—for the first time—the differential contribution of three ORF4 variants to this process, suggesting a still unexplored role for these dominant negative isoforms during adipogenesis. Therefore, our results highlight crucial aspects of PPARG regulation, suggesting the need of further investigation to rule out the differential impact of all PPARG transcripts in both physiologic and pathologic conditions, such as metabolism-related disorders.

Role of peroxisome proliferator-activated receptor gamma gene polymorphisms in type 2 diabetes mellitus patients of West Bengal, India

AIMS/INTRODUCTION

Peroxisome proliferator activated receptor gamma (PPARG) is a nuclear hormone receptor of the ligand-dependent transcription factor involved in adipogenesis, and a molecular target of the insulin sensitizer, thiazolidinediones. The present study aimed to investigate whether the PPARG gene is associated with type 2 diabetes mellitus and its related traits within the population of West Bengal, India.

MATERIALS AND METHODS

The study participants (200 type 2 diabetes mellitus and 200 normal individuals) were chosen randomly, and the variants were screened by direct sequencing.

RESULTS

The results showed that rs1801282 (odds ratio 0.66; 95% confidence interval 0.15-2.96; P = 0.57) and rs3856806 (odds ratio 1.23; 95% confidence interval 0.73-2.06; P = 0.44) variants of the PPARG gene were not associated with type 2 diabetes mellitus.

CONCLUSIONS

The results showed that the PPARG gene was not associated with type 2 diabetes mellitus in our study population. As the lack of association might come from the small sample size, further studies with larger sample size are required to verify the present observation.

The Rate of Decline of Glomerular Filtration Rate May Not Be Associated with Polymorphism of the PPARγ2 Gene in Patients with Type 1 Diabetes and Nephropathy

The aim of the study was to investigate whether a Pro12Ala polymorphism in the peroxisome proliferator-activated receptor gamma 2 (PPARγ2) gene is associated with the progress of diabetic nephropathy in patients with type 1 diabetes. 197 Caucasian patients with type 1 diabetes and ethnically matched 151 normal healthy controls were genotyped for this polymorphism. Results showed that there were no significant differences in the frequencies of the genotypes and alleles of the polymorphism between groups. Multiple regression analysis in 77 patients demonstrated that the rate of decline in renal function in terms of glomerular filtration rate was significantly correlated to the baseline level of cholesterol (P = 0.0014), mean diastolic blood pressure during follow-up period (P = 0.019), and baseline level of HbA1c (P = 0.022) adjusting for the effect of diabetes duration and gender, but no significant association was found between the polymorphism and the progression of diabetic nephropathy in our studied population. In summary, our results show that the PPARγ2 polymorphism is unlikely to be associated with the development and progression of the diabetic nephropathy in patients with type 1 diabetes. Further studies in different populations may be warranted to confirm our findings as the sample size in our study was relatively small.

Proliferator-activated receptor gamma Pro12Ala interacts with the insulin receptor substrate 1 Gly972Arg and increase the risk of insulin resistance and diabetes in the mixed ancestry population from South Africa

BACKGROUND

The peroxisome proliferator-activated receptor gamma (PPARG), Pro12Ala and the insulin receptor substrate (IRS1), Gly972Arg confer opposite effects on insulin resistance and type 2 diabetes mellitus (T2DM). We investigated the independent and joint effects of PPARG Pro12Ala and IRS1 Gly972Arg on markers of insulin resistance and T2DM in an African population with elevated risk of T2DM. In all 787 (176 men) mixed-ancestry adults from the Bellville-South community in Cape Town were genotyped for PPARG Pro12Ala and IRS1 Gly972Arg by two independent laboratories. Glucose tolerance status and insulin resistance/sensitivity were assessed.

RESULTS

Genotype frequencies were 10.4% (PPARG Pro12Ala) and 7.7% (IRS1 Gly972Arg). Alone, none of the polymorphisms predicted prevalent T2DM, but in regression models containing both alleles and their interaction term, PPARG Pro12 conferred a 64% higher risk of T2DM. Furthermore PPARG Pro12 was positively associated in adjusted linear regressions with increased 2-hour post-load insulin in non-diabetic but not in diabetic participants.

CONCLUSION

The PPARG Pro12 is associated with insulin resistance and this polymorphism interacts with IRS1 Gly972Arg, to increase the risk of T2DM in the mixed-ancestry population of South Africa. Our findings require replication in a larger study before any generalisation and possible application for risk stratification.

Association of genetic polymorphism of PPARγ-2, ACE, MTHFR, FABP-2 and FTO genes in risk prediction of type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is a non-autoimmune, complex, heterogeneous and polygenic metabolic disease condition characterized by persistent elevated blood glucose levels (hyperglycemia). India as said to be the diabetic capital of the world is likely to experience the largest increase in T2DM and a greater number of diabetic individuals in the world by the year 2030. Identification of specific genetic variations in a particular ethnic group has a critical role in understanding the risk of developing T2DM in a much efficient way in future. These genetic variations include numerous types of polymorphisms among which single nucleotide polymorphisms (SNPs) is the most frequent. SNPs are basically located within the regulatory elements of several gene sequences. There are scores of genes interacting with various environmental factors affecting various pathways and sometimes even the whole signalling network that cause diseases like T2DM. This review discusses the biomarkers for early risk prediction of T2DM. Such predictions could be used in order to understand the pathogenesis of T2DM and to better diagnostics, treatment, and eventually prevention.

Association of PPARγ2 gene variant Pro12Ala polymorphism with hypertension and obesity in the aboriginal Qatari population known for being consanguineous

AIM

The aim of this study was to investigate the association of the Pro12Ala polymorphism of the human peroxisome proliferator-activated receptor gamma 2 (PPARγ2) gene with hypertension and obesity in a highly consanguineous aboriginal Qatari population.

DESIGN

A cross-sectional survey conducted from January 2011-December 2012.

SETTING

Primary health care clinics.

SUBJECTS

A random sample of 1,528 Qatari male and female population older than 20 years of age.

MATERIALS AND METHODS

Data on age, sex, income, level of education, occupation status, body mass index, and blood pressure and lipid profile were obtained. The Pro12Ala in the PPARγ2 gene was detected on the LightCycler® using two specific probes: (Sensor [G] 5'-CTC CTA TTG ACG CAG AAA GCG-FL and PPAR Anchor 5' LC Red 640- TCC TTC ACT GAT ACA CTG TCT GCA AAC ATA TC-PH). Univariate and multivariate logistic regression were performed.

RESULT

Out of a total 1,528 participants, 220 were diagnosed with essential hypertension, and 420 were obese. Participants with consanguinity were significantly higher among hypertensive than normotensive (41.9% versus 30.8%; P=0.001). Altogether, more than three-fourths (89%) of the participants had a wild genotype (Pro12Pro), 9.8% were heterozygous with Pro12Ala, and only 1.2% was homozygous with the Ala12Ala genotype. The frequency of the Pro allele was 94.5% in normotensive versus 90.5% in hypertensive, while the distribution of the Ala allele was 5.5% in normotensive versus 9.5% in the hypertensive group (P=0.001). The odds of hypertension were 1.7 times higher among the participants with the Ala allele as compared to those with the Pro, while adjusting for other potential confounders (adjusted odds ratio 1.69; 95% confidence interval 1.12-2.55; P=0.012). There was no association between the PPARγ2Ala allele and obesity (P=0.740).

CONCLUSION

The current study revealed an association between the PPARγ2Ala allele and hypertension in Qatar's population. On the other hand, this study found no association between the Ala allele and obesity.

Association between PRO12ALA polymorphism of the PPAR-γ2 gene and type 2 diabetes mellitus in Iranian patients

BACKGROUND:

Peroxisome proliferator-activated receptor (PPARs) have been identified as ligand-activated transcription factors that belong to the nuclear receptor superfamily. It has been shown that an association exists between Proline 12 alanine (Pro12Ala) polymorphism of PPAR-GAMMA2 (PPAR-γ2) gene and increased risk of type 2 diabetes mellitus (T2DM) in different populations. Therefore, the present study was designed to investigate the association between Pro12Ala polymorphism of PPAR-γ2 gene and T2DM in an Iranian population.

MATERIALS AND METHODS:

Two hundred unrelated people, including 100 healthy controls and 100 diabetic patients were recruited diagnosed based on American Diabetes Association criteria. Blood samples were used for isolation of genomic deoxyribonucleic acid (DNA). Having extracted the genomic DNA from human blood leukocytes by means of High Pure polymerase chain reaction (PCR) Template preparation kit, we carried out polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) on each blood sample. Then, Genomic DNA was digested by BstU-I restriction enzyme. Thereafter, restriction products were analyzed by means of Polyacrylamide gel electrophoresis and stained by Ethidium Bromide.

RESULTS:

We found that the frequency of Ala allele in healthy subjects was significantly higher than in diabetic subjects (P = 0003). Moreover, the genotype frequency of Ala/Ala in healthy subjects was significantly higher than in diabetic subjects (P < 0.001). However, the genotype frequency of Ala/Pro in diabetic subjects was significantly higher than in healthy subjects (P < 0.001).

CONCLUSION:

The present study suggests that polymorphism of PPAR-γ2 gene is associated with T2DM. Furthermore, Ala allele is significantly found in non-diabetic individual’s Iranian population.

The association between the Pro12Ala variant in the PPARγ2 gene and type 2 diabetes mellitus and obesity in a Chinese population

Background

Conflicting results have been reported on the association of the Pro12Ala polymorphism of the PPARγ2 gene with the risk of type 2 diabetes or obesity.

Methods and Findings

A total of 3146 subjects with 1145 cases of type 2 diabetes and 2001 healthy controls were included in the study. Genomic DNA was obtained from blood samples and the screening for the gene polymorphisms was done using an allelic discrimination assay-by-design TaqMan method. Overall, the Ala allele frequency was 5.6% in control subjects and 3.9% in diabetes subjects (P = 0.023). We found a statistically significant association of carriers of the Ala allele with greater homoeostasis model assessment of beta cell function index in all subjects (P = 0.046). After controlling for confounders, carriers of the Ala allele had a decreased risk of diabetes compared with noncarriers [odds ratio (OR) 0.64, 95% confidence interval (CI) 0.49–0.83; P = 0.001]. A beneficial effect of the Ala allele was also observed for obesity (OR 0.64, 95% CI 0.42–0.96; P = 0.030).

Conclusion

Our results suggested that the presence of the Ala allele may contribute to improved insulin secretory capacity and may confer protection from type 2 diabetes and obesity in the Chinese population.

Gender-specific association between FSHR and PPARG common variants and human longevity

Men and women have different life expectancies. Not unexpectedly, several genes involved in life span determination have been found to influence the probability of achieving longevity differently in men and women. This investigation examines the association between longevity and polymorphisms of follicle-stimulating hormone receptor (FSHR, Asn680Ser polymorphism) and peroxisome proliferator-activated receptor gamma (PPARG, Pro12Ala polymorphism), two genes that previous investigations suggested may exert a gender-specific influence on human longevity. A sample of 277 individuals (mean age, 82.9±5.7years) was recruited in 2000. On the basis of mortality data collected in 2009, the sample was divided into two groups of subjects surviving over 90 years (long-lived) or not (controls). The frequency of the FSHR 680 Ser/Ser genotype was significantly higher in the sample of long-lived women compared to controls, indicating that the FSHR 680 Ser/Ser genotype may favor survival to more than 90 years of age only in women (odds ratio [OR]=4.21; 95% confidence interval [CI], 1.10-16.10, p=0.036). In contrast, the frequency of the PPARG Pro/Ala genotype was significantly higher in the sample of male subjects who died before 90 years of age than in the long-lived, suggesting that carrying the PPARG Pro/Ala genotype may prevent the attainment of advanced age only in men (OR=0.13; 95% CI, 0.02-0.79; p=0.03). We then searched the literature for studies reporting a differential role for the genetic component in male and female longevity. To do this, we selected longevity genes with a gender-specific effect. A review of the studies showed that genetic factors tend to have a greater relevance in determining longevity in men than in women. The possible impact of this phenomenon is discussed.

Does Pro(12)Ala Polymorphism Enhance the Physiological Role of PPARγ2?

Obesity and type 2 diabetes mellitus (T2D) are two major public health problems that have motivated the scientific community to investigate the high contribution of genetic factors to these disorders. The peroxisome proliferator activated by gamma 2 (PPARγ2) plays an important role in the lipid metabolism. Since PPARγ2 is expressed mainly in adipose tissue, a moderate reduction of its activity influences the sensitivity to insulin, diabetes, and other metabolic parameters. The present study aims to contribute to the elucidation of the impact of the Pro(12)Ala polymorphism associated with T2D and obesity through a meta-analysis study of the literature that included approximately 11500 individuals, from which 3870 were obese and 7625 were diabetic. Statistical evidence supports protective effect in T2D of polymorphism Pro(12)Ala of PPARγ2 (OR = 0.702 with 95% CI: 0.622; 0.791, P < 0.01). Conversely the same polymorphism Pro(12)Ala of PPARγ2 seems to favor obesity since 1.196 more chance than nonobese was found (OR = 1.196 with 95% CI: 1.009; 1.417, P < 0.004). Our results suggest that Pro(12)Ala polymorphism enhances both adipogenic and antidiabetogenic physiological role of PPARγ. Does Pro(12)Ala polymorphism represent an evolutionary step towards the stabilization of the molecular function of PPARγ transcription factor signaling pathway?

Peroxisome proliferator-activated receptors alpha and gamma2 polymorphisms in nonalcoholic fatty liver disease: a study in Brazilian patients

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) refers to the accumulation of hepatic steatosis in the absence of excess alcohol consumption. The pathogenesis of fatty liver disease and steatohepatitis (NASH) is not fully elucidated, but the common association with visceral obesity, hyperlipidemia, hypertension and type 2 diabetes mellitus (T2DM) suggests that it is the hepatic manifestation of metabolic syndrome. Peroxisome proliferator-activated receptor PPARα and PPARγ are members of a family of nuclear receptors involved in the metabolism of lipids and carbohydrates, adipogenesis and sensitivity to insulin. The objective of this study was to analyze the polymorphisms Leu162Val of PPARα and Pro12Ala of PPARγ as genetic risk factors for the development and progression of NAFLD.

METHODS

One hundred and three NAFLD patients (89 NASH, 14 pure steatosis) and 103 healthy volunteers were included. Single nucleotide polymorphisms (SNPs) Leu162Val and Pro12Ala were analyzed by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP).

RESULTS

NASH patients presented higher BMI, AST and prevalence of T2DM than patients with pure steatosis. A higher prevalence of 12Ala allele was observed in the NASH Subgroup when compared to Control Group. When we grouped NASH and Steatosis Subgroups (NAFLD), we found lower serum glucose and more advanced fibrosis in the Leu162Val SNP. On the other hand, there was no statistical difference in clinical, laboratorial and histological parameters according to the Pro12Ala SNP.

CONCLUSIONS

We documented a lower prevalence of 12Ala allele of gene PPARγ in the NASH Subgroup when compared to Control Group. In NAFLD patients, there were no associations among the occurrence of Pro12Ala SNP with clinical, laboratorial and histological parameters. We also documented more advanced fibrosis in the Leu162Val SNP. The obtained data suggest that Pro12Ala SNP may result in protection against liver injury and that Leu162Val SNP may be involved in the progression of NAFLD.