Differential effects of the C1431T and Pro12Ala PPARgamma gene variants on plasma lipids and diabetes risk in an Asian population

Target gene variations of PPAR isoforms may contribute to MODY heterogeneity: A preliminary comparative study with type 2 diabetes

AIMS

The objective of this study was to evaluate the associations of several genetic variants of peroxisome proliferator-activated receptors (PPARs) on clinical and laboratory parameters in patients with maturity-onset diabetes of the young (MODY), and possible contribution to heterogeneity of the disease.

METHODS

The study groups comprised patients with MODY (genetically confirmed (n = 28), clinically relevant but genetically unconfirmed; MODYX (n = 56)), type 2 diabetes mellitus (T2DM; n = 94) and healthy controls (n = 153). PPARA-L162V-(rs1800206), PPARG-C161T-(rs3856806), P12A-(rs1801282), and PPARB/D + 294 T/C-(rs2016520) polymorphisms were genotyped by real-time-PCR.

RESULTS

The results demonstrated that the frequencies of PPARA-LL162 (p = 0.002), PPARG-CC161 (p = 0.002), and PPARG-ProPro (p = 0.012) genotypes were significantly higher in the MODY group compared to the controls. Furthermore, total-MODY and MODYX groups had a higher frequency of PPARA-LL162 genotype than T2DM (p = 0.005 and p = 0.006, respectively). The frequency of the PPARB/D + 294 T allele was significantly higher in individuals with T2DM than in genetically-determined MODY group (p = 0.019). The PPARA-LL162 genotype was associated with early-onset diabetes in total-MODY (p = 0.022) and T2DM (p < 0.05) groups.

CONCLUSIONS

The association of PPARA-L162V polymorphism with early-onset diabetes in both T2DM and MODY is a noteworthy finding. Considering these results, we suggested that genetic polymorphisms in PPAR isoforms may contribute to the clinical and metabolic heterogeneity of MODY.

Gene-Diet Interactions on Metabolic Disease-Related Outcomes in Southeast Asian Populations: A Systematic Review

Diabetes and obesity are chronic diseases that are a burden to low- and middle-income countries. We conducted this systematic review to understand gene-diet interactions affecting the Southeast Asian population's risk of obesity and diabetes. The literature search was performed on Google Scholar and MEDLINE (PubMed) search engines independently by four reviewers who evaluated the eligibility of articles based on inclusion criteria. Out of 19,031 articles, 20 articles examining gene-diet interactions on obesity and/or diabetes-related traits met the inclusion criteria. Three (Malaysia, Indonesia, and Singapore) out of eleven Association of Southeast Asian Nations (ASEAN) countries have conducted studies on gene-diet interactions on obesity and diabetes. From the 20 selected articles, the most common interactions were observed between macronutrients and genetic risk score (GRS) on metabolic disease-related traits in the Malay, Chinese, and Indian ethnicities. Overall, we identified 29 significant gene-diet interactions in the Southeast Asian population. The results of this systematic review demonstrate ethnic-specific gene-nutrient interactions on metabolic-disease-related traits in the Southeast Asian population. This is the first systematic review to explore gene-diet interactions on obesity and diabetes in the Southeast Asian population and further research using larger sample sizes is required for better understanding and framing nutrigenetic approaches for personalized nutrition.

Correlation between PPARG Pro12Ala Polymorphism and Therapeutic Responses to Thiazolidinediones in Patients with Type 2 Diabetes: A Meta-Analysis

Background: Thiazolidinediones (TZDs) are a type of oral drug that are utilized for the treatment of type 2 diabetes mellitus (T2DM). They function by acting as agonists for a nuclear transcription factor known as peroxisome proliferator-activated receptor-gamma (PPAR-γ). TZDs, such as pioglitazone and rosiglitazone, help enhance the regulation of metabolism in individuals with T2DM by improving their sensitivity to insulin. Previous studies have suggested a relationship between the therapeutic efficacy of TZDs and the PPARG Pro12Ala polymorphism (C > G, rs1801282). However, the small sample sizes of these studies may limit their applicability in clinical settings. To address this limitation, we conducted a meta-analysis assessing the influence of the PPARG Pro12Ala polymorphism on the responsiveness of TZDs. Method: We registered our study protocol with PROSPERO, number CRD42022354577. We conducted a comprehensive search of the PubMed, Web of Science, and Embase databases, including studies published up to August 2022. We examined studies investigating the association between the PPARG Pro12Ala polymorphism and metabolic parameters such as hemoglobin A1C (HbA1C), fasting plasma glucose (FPG), triglyceride (TG), low-density lipoprotein cholesterol (LDL), high-density lipoprotein cholesterol (HDL), and total cholesterol (TC). The mean difference (MD) and 95% confidence intervals (CIs) between pre- and post-drug administration were evaluated. The quality of the studies included in the meta-analysis was assessed by using the Newcastle-Ottawa Scale (NOS) tool for cohort studies. Heterogeneity across studies was assessed by using the I2 value. An I2 value greater than 50% indicated substantial heterogeneity, and a random-effects model was used for meta-analysis. If the I2 value was below 50%, a fixed-effects model was employed instead. Both Begg's rank correlation test and Egger's regression test were performed to detect publication bias, using R Studio software. Results: Our meta-analysis incorporated 6 studies with 777 patients for blood glucose levels and 5 studies with 747 patients for lipid levels. The included studies were published between 2003 and 2016, with the majority involving Asian populations. Five of the six studies utilized pioglitazone, while the remaining study employed rosiglitazone. The quality scores, as assessed with the NOS, ranged from 8 to 9. Patients carrying the G allele exhibited a significantly greater reduction in HbA1C (MD = -0.3; 95% CI = -0.55 to -0.05; p = 0.02) and FPG (MD = -10.91; 95% CI = -19.82 to -2.01; p = 0.02) levels compared to those with the CC genotype. Furthermore, individuals with the G allele experienced a significantly larger decrease in TG levels than those with the CC genotype (MD = -26.88; 95% CI = -41.30 to -12.46; p = 0.0003). No statistically significant differences were observed in LDL (MD = 6.69; 95% CI = -0.90 to 14.29; p = 0.08), HDL (MD = 0.31; 95% CI = -1.62 to 2.23; p = 0.75), and TC (MD = 6.4; 95% CI = -0.05 to 12.84; p = 0.05) levels. No evidence of publication bias was detected based on Begg's test and Egger's test results. Conclusions: This meta-analysis reveals that patients with the Ala12 variant in the PPARG Pro12Ala polymorphism are more likely to exhibit positive responses to TZD treatment in terms of HbA1C, FPG, and TG levels compared to those with the Pro12/Pro12 genotype. These findings suggest that genotyping the PPARG Pro12Ala in diabetic patients may be advantageous for devising personalized treatment strategies, particularly for identifying individuals who are likely to respond favorably to TZDs.

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.

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].

Associations between peroxisome proliferator-activated receptor γ (PPAR-γ) polymorphisms and serum lipids: Two cross-sectional studies of community-dwelling adults

Dyslipidemia is a well-established risk factor for cardiovascular disease. Experimental studies have reported that peroxisome proliferator-activated receptor γ (PPAR-γ) regulates adipocyte differentiation, lipid storage, and glucose metabolism. Therefore, we examined the associations between PPAR-γ polymorphisms (rs1801282, rs3856806, rs12497191, rs1151999, and rs1152003) and serum lipids in two cross-sectional studies. In the Shizuoka area of the Japan Multi-Institutional Collaborative Cohort Study, we examined 4,952 participants (3,356 men and 1,596 women) in a baseline survey and 2,245 participants (1,550 men and 695 women) in a second survey 5 years later. Outcome measures were the prevalence of dyslipidemia (low-density lipoprotein-cholesterol [LDL-C] ≥ 140 mg/dl, high-density lipoprotein-cholesterol < 40 mg/dl, triglycerides ≥ 150 mg/dl, and/or use of cholesterol-lowering drugs) and the prevalence of high LDL-C (LDL-C ≥ 140 mg/dl and/or use of cholesterol-lowering drugs). Multivariate odds ratios (ORs) were estimated by using unconditional logistic regression models. A total of 2,114 and 1,431 individuals (42.7% and 28.9%) had dyslipidemia and high LDL-C in the baseline survey, respectively, as did 933 and 716 (41.6% and 31.9%), respectively, in the second survey. In the baseline study, compared with major allele homozygotes, minor allele homozygotes of rs3856806 and rs12497191 had a 42% (OR, 0.58; 95% confidence interval (CI), 0.39-0.85) and 23% (OR, 0.77; 95% CI, 0.60-0.99) lower risk of dyslipidemia, respectively, after adjustment for potential confounding factors. In addition, minor allele homozygotes of rs3856806 had a 45% (OR, 0.55; 95% CI, 0.35-0.86) lower risk of high LDL-C. Similar risk reductions were found in the second survey. In conclusion, rs3856806 and rs12497191 polymorphisms may be related to a lower risk of dyslipidemia and high LDL-C.

Genotype-based recall to study metabolic effects of genetic variation: a pilot study of PPARG Pro12Ala carriers

AIM

To assess practical implications of genotype-based recall (GBR) studies, an increasingly popular approach for in-depth characterization of genotype-phenotype relationships.

METHODS

We genotyped 2500 participants from the Swedish EpiHealth cohort and considered loss-of-function and missense variants in genes with relation to cardiometabolic traits as the basis for our GBR study. Therefore, we focused on carriers and non-carriers of the PPARG Pro12Ala (rs1801282) variant, as it is a relatively common variant with a minor allele frequency (MAF) of 0.14. It has also been shown to affect ligand binding and transcription, and carriage of the minor allele (Ala12) is associated with a reduced risk of type 2 diabetes. We re-invited 39 Pro12Pro, 34 Pro12Ala, and 30 Ala12Ala carriers and performed detailed anthropometric and serological assessments.

RESULTS

The participation rates in the GBR study were 31%, 44%, and 40%, and accordingly we included 12, 15, and 13 individuals with Pro12Pro, Pro12Ala, and Ala12Ala variants, respectively. There were no differences in anthropometric or metabolic variables among the different genotype groups.

CONCLUSIONS

Our report highlights that from a practical perspective, GBR can be used to study genotype-phenotype relationships. This approach can prove to be a valuable tool for follow-up findings from large-scale genetic discovery studies by undertaking detailed phenotyping procedures that might not be feasible in large studies. However, our study also illustrates the need for a larger pool of genotyped or sequenced individuals to allow for selection of rare variants with larger effects that can be examined in a GBR study of the present size.

Impact of the PPAR gamma-2 gene polymorphisms on the metabolic state of postmenopausal women

The relationship Pro12Ala (rs1801282) and C1431T (rs3856806) polymorphisms of PPAR gamma-2 with glucose and lipid metabolism is not clear after menopause. We investigated the impact of the Pro12Ala and C1431T silent substitution in the 6th exon in PPAR gamma-2 gene on nutritional and metabolic status in 271 postmenopausal women (122 lean and 149 obese). The general linear model (GLM) approach to the two-way analysis of variance (ANOVA) was used to infer the interactions between the analysed genotypes. The frequency of the Pro-T haplotype was higher in obese than in lean women (p less than 0.0349). In the analysed GLM models according to obesity status, the C1431C genotype was related to a lower glucose concentration (beta=-0.2103) in lean women, and to higher folliculotropic hormone FSH levels (beta=0.1985) and lower waist circumferences (beta=-0.1511) in obese women. The influence of C1431C was present regardless of the occurrence of the Pro12Ala polymorphism. The co-existence of the C1431C and Pro12Pro genotypes was related to lower values for triceps skinfold thickness compared those for the T1241/X and Ala12/X polymorphisms (beta=-0.1425). The presence of C1431C decreased the differences between triceps values that were determined by Pro or Ala allele. In conclusion, C1431T polymorphism seems to have a more essential influence on anthropometric and biochemical parameters than is the case with Pro12Ala polymorphism.

Nutrigenomic Functions of PPARs in Obesogenic Environments

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors that mediate the effects of several nutrients or drugs through transcriptional regulation of their target genes in obesogenic environments. This review consists of three parts. First, we summarize current knowledge regarding the role of PPARs in governing the development of white and brown/beige adipocytes from uncommitted progenitor cells. Next, we discuss the interactions of dietary bioactive molecules, such as fatty acids and phytochemicals, with PPARs for the modulation of PPAR-dependent transcriptional activities and metabolic consequences. Lastly, the effects of PPAR polymorphism on obesity and metabolic outcomes are discussed. In this review, we aim to highlight the critical role of PPARs in the modulation of adiposity and subsequent metabolic adaptation in response to dietary challenges and genetic modifications. Understanding the changes in obesogenic environments as a consequence of PPARs/nutrient interactions may help expand the field of individualized nutrition to prevent obesity and obesity-associated metabolic comorbidities.

The C1431T polymorphism of peroxisome proliferator activated receptor γ (PPARγ) is associated with low risk of diabetes in a Pakistani cohort

BACKGROUND

Diabetes is a socioeconomic burden in Pakistan. International diabetes federation reported 6.9 million cases of diabetes and 87,548 deaths due to diabetes in Pakistan in 2014. Peroxisome proliferators-activated receptors are transcription factors, regulating several physiological processes.

AIM

The aim of the current study was to determine the prevalence of silent variant C1431T in exon 6 of PPAR-y and analyze its effect on various anthropometric and biochemical parameters in a Pakistani cohort.

METHODS

We collected 926 samples, 500 healthy controls (fasting blood sugar <99 mg/dL, random blood sugar <126 mg/dL) and 426 cases with diabetes (fasting blood sugar >99 mg/dL, random blood sugar >126 mg/dL). The genotyping was done by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) and serum biochemical parameters were determined by commercially available kits.

RESULTS

The genotyping results by RLFP showed allelic frequency C = 61.2 % and T = 38.8 % in controls while C = 74.5 % and T = 25.5 % in cases (OR 0.536, CI 0.439-0.655, p = 8.2 × 10(-10)) and genotypic frequency CC = 38.8 %, CT = 44.7 %, TT = 16.5 % in controls. While CC = 53.6 %, CT = 41.4 %, TT = 5.1 % in cases (OR 0.544, CI 0.408-0.726, p = 2.3 × 10(-10)). The rare T allele appeared to be a protective allele i.e., the presence of rare allele lowered the risk of diabetes in the studied cohort. The biochemical and anthropometric parameters were analyzed for any significant association with the SNP showing that C1431T variant has an association with BMI, weight, fasting glucose and LDLC. However, no significant association was found with age, gender, height, HDLC, TC, triglycerides and leptin.

CONCLUSION

In conclusion, the presence of minor allele lowers the risk of diabetes and the effect may involve modulating certain serum parameters.

Genetic predictors of obesity development

The most common reasons that cause obesity are eating disorders (overeating), genetic predisposition, sedentary lifestyle (lack of exercise), disorders of the endocrine system, and environmental factors. There is evidence of an obvious relationship of high consumption of sugary drinks and weight gain. Since 1990, there has been considerable growth in the number of obese people in the first place associated with the promotion of soft drinks. According to a study in Finnish diabetes prevention average physical activity and change of diet (1200-1800 kcal) of total fat intake with less than 30% saturated fat, including less than 10%, leading to long-term loss of excess weight (within 4 years). Many studies have demonstrated the impossibility of a single template approach to the determination of optimal diets for patients with overweight and obesity which has been shown in various studies on gene polymorphisms are associated with obesity, and their interaction. This article provides an overview of current data on the genetics of obesity covering the main provisions of the study of candidate genes, such as PPARG, FABP2, ADRB 2, ADRB3. The role nutrigenetics in the creation of individual programs of weight control and weight loss. But the question of the direct role of genetic factors in the development of obesity remains controversial, since one can not ignore the impact of environmental factors, such as lifestyle, diet, physical activity, stress, and harmful habits. To understand the mechanism of the relationship between genetic factors, environmental factors, and obesity, one needs to carry out research not only on the population level, but also in certain groups of people (ethnic, racial, age).

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.

Genotype Phenotype Correlation of Genetic Polymorphism of PPAR Gamma Gene and Therapeutic Response to Pioglitazone in Type 2 Diabetes Mellitus- A Pilot Study

INTRODUCTION

Pro12Ala polymorphism is a missense mutation at codon 12 in peroxisome proliferator-activated receptor γ gene (PPARG). This polymorphism is known to be associated with increased insulin sensitivity. Pioglitazone, a thiazolidinedione, is an anti-diabetic drug which acts as an agonist at PPAR γ receptor.

AIM

To determine the association between Pro12Ala polymorphism of the PPARG and variation in therapeutic response to the PPARγ agonist, pioglitazone.

MATERIALS AND METHODS

The study was done as a hospital based pilot project in 30 patients with type 2 diabetes mellitus, on treatment with sulfonylurea or metformin but without adequate glycaemic control. They were started on pioglitazone as add on therapy for a period of 12 weeks. The participants were categorized as responders and non-responders based on the change in HbA1C level after 12 weeks. Pro12Ala polymorphism was analysed by polymerase chain reaction-restriction fragment length polymorphism.

STATISTICAL ANALYSIS

Logistic regression analysis was done to evaluate the associations between age, baseline body weight, BMI, waist circumference, waist-hip ratio and Pro12Ala variants with the response to pioglitazone. The p-value< 0.05 was considered significant.

RESULTS

The frequency distributions of PPAR gamma genotypes were 80% for Pro/Pro and 20% for Pro/Ala in the study population. Among the study participants, 30% were non-responders and 70% responders to pioglitazone. A significantly higher frequency of the polymorphism was detected in the responders (p=0.005) compared to non-responders group.

CONCLUSION

Our study suggests that there is a potential association between Pro12Ala polymorphism and glycaemic response to pioglitazone.

Obesity and Pro12Ala Polymorphism of Peroxisome Proliferator-Activated Receptor-Gamma Gene in Healthy Adults: A Systematic Review and Meta-Analysis

BACKGROUND

The aim of this systematic review was to evaluate the relationship between obesity and peroxisome proliferator-activated receptor-gamma (PPARx03B3;) Pro12Ala polymorphism in healthy adults.

SUMMARY

Weighted mean differences (WMDs) of body mass index (BMI) were calculated for different inheritance models and subgroups. Fifty-six studies were eligible for inclusion in the meta-analysis. The result shows that the Ala allele of this polymorphism was associated with increased WMD in mean BMI (WMD = 0.29, 95% CI 0.10-0.48, p = 0.003). The Ala carriers were associated with increased WMD in mean BMI values in both genders and in the Caucasian subgroup. The associations were seen among people with higher levels of BMI (BMI ≥35).

MESSAGE

The Ala allele of the PPARx03B3; Pro12Ala polymorphism in healthy adults was associated with increased BMI under a dominant model of inheritance.

Nutrigenetics of cholesterol metabolism: observational and dietary intervention studies in the postgenomic era

Cholesterol metabolism is a well-defined responder to dietary intakes and a classic biomarker of cardiovascular health. For this reason, circulating cholesterol levels have become key in shaping nutritional recommendations by health authorities worldwide for better management of cardiovascular disease, a leading cause of mortality and one of the most costly health problems globally. Data from observational and dietary intervention studies, however, highlight a marked between-individual variability in the response of cholesterol metabolism to similar dietary protocols, a phenomenon linked to genetic heterogeneity. This review summarizes the postgenomic evidence of polymorphisms within cholesterol-associated genes relative to fasting circulating cholesterol levels under diverse nutritional conditions. A number of cholesterol-related gene-diet interactions are confirmed, which may have clinical importance, supporting a deeper look into the rapidly emerging field of nutrigenetics for meaningful conclusions that may eventually lead to genetically targeted dietary recommendations in the era of personalized nutrition.

Impact of the C1431T Polymorphism of the Peroxisome Proliferator Activated Receptor-Gamma (PPAR-γ) Gene on Fasted Serum Lipid Levels in Patients with Coronary Artery Disease

BACKGROUND/AIMS

The C1431T polymorphism of peroxisome proliferator activated receptor-γ (PPAR-γ) gene is related to diabetes and metabolic-syndrome. However, studies have been inconclusive about its association with coronary artery disease (CAD) and there have been no studies analyzing the association of this polymorphism with fasted-serum-lipid levels in Iranian-individuals with CAD. We investigated the association of PPAR-γ C1431T-polymorphism with CAD and dyslipidaemia in 787 individuals.

METHODS

Anthropometric-parameters and biochemical-measurements were evaluated, followed by genotyping. The association of the genetic-polymorphisms with CAD and lipid-profile was determined by univariate/multivariate-analyses.

RESULTS

Patients with CT or CT+TT genotype were at an increased-risk of CAD relative to CC-carriers (adjusted odds ratio: 2.03; 95% confidence interval, 1.01-4.09; p = 0.046). However, in the larger population, CT genotype was present at a higher frequency in the group with a positive angiogram. Furthermore, CT+TT genotypes were associated with an altered fasted-lipid-profile in the initial population sample of patients with a positive angiogram, compared to the group with a negative-angiogram. The angiogram-positive patients carrying the T allele had a significantly higher triglyceride, serum C-reactive protein and fasting-blood-glucose.

CONCLUSION

We have found the PPAR-γ C1431T polymorphism was significantly associated with fasted serum lipid profile in individuals with angiographically defined CAD. Since accumulating data support the role of PPAR-γ polymorphisms in CAD, further studies are required to investigate the association of this polymorphism with coronary artery disease.

Variation in PPARG is associated with longitudinal change in insulin resistance in Mexican Americans at risk for type 2 diabetes

CONTEXT

Peroxisome proliferator-activated receptor gamma (PPARG) is a susceptibility locus for type 2 diabetes mellitus (T2DM). Although cross-sectional associations have been reported, primarily for Pro12Ala, few longitudinal studies in nondiabetic populations have been conducted.

OBJECTIVE

This study aimed to examine whether and to what extent variation in PPARG is associated with longitudinal changes in anthropometric and metabolic traits in Mexican Americans at risk for T2DM.

SETTING AND DESIGN

Subjects were participants of BetaGene, a family-based study of obesity, insulin resistance, and β-cell function, who completed a baseline and follow-up study visit (n = 378; mean followup, 4.6 ± 1.5 y). Phenotypes included body fat assessed by dual-energy x-ray absorptiometry; insulin sensitivity (SI), acute insulin response, and β-cell function (disposition index; DI) were estimated from iv glucose tolerance tests with Minimal Model analysis. Eighteen tag single nucleotide polymorphisms (SNPs) capturing variation in a 156-kb region surrounding PPARG were tested for association with changes in longitudinal traits. P-values were Bonferroni-corrected for multiple testing.

RESULTS

Six SNPs (rs2972164, rs11128598, rs17793951, rs1151996, rs1175541, rs3856806) were significantly associated with rate of change in SI after adjustment for age, sex, and body fat percentage, but not with changes in adiposity. rs17793951 also had a significant effect on change in DI over time. Association between rs1175541 and change in SI varied by changes in adiposity such that only carriers of the minor allele who reduced body fat over followup improved SI. rs1306470 (captured Pro12Ala, r(2) = 0.9) was not associated with rates of change in any traits and its effects were not modified by changes in adiposity.

CONCLUSIONS

Variation in PPARG, but not Pro12Ala, contributes to declining SI and concomitant deterioration in β-cell function in Mexican Americans at risk for T2DM.

Docosahexaenoic Acid-Rich Fish Oil Supplementation Improves Body Composition without Influence of the PPAR&#947; Pro12Ala Polymorphism in Patients with Type 2 Diabetes: A Randomized, Double-Blind, Placebo-Controlled Clinical Trial

<b><i>Background:</i></b> The aims of this research were to investigate (1) the impact of docosahexaenoic acid (DHA)-rich fish oil supplementation on body composition, plasma adiponectin level, and peroxisome proliferator-activated receptor &#947; (PPAR&#947;) gene expression, and (2) whether the effect of DHA-rich fish oil supplementation on the aforementioned variables is modulated by PPAR&#947; Pro12Ala polymorphism. <b><i>Methods:</i></b> We genotyped PPAR&#947; Pro12Ala polymorphism in subjects with type 2 diabetes mellitus (T2DM). Ala carriers and non-Ala carriers were randomly assigned to DHA-rich fish oil or placebo intake for 8 weeks. <b><i>Results:</i></b> Glycemic control was not affected by the intervention. The supplementation with DHA-rich fish oil decreased waist circumference (p < 0.001), body fat mass (p = 0.01), body fat percent (p = 0.04), and visceral fat rating (p = 0.02) as well as trunk fat mass (p = 0.04). Weight, body mass index, fat-free mass, adiponectin level, and PPAR&#947; gene expression changes showed no significant difference. No gene-diet interaction was found on body composition, adiponectin level, and PPAR&#947; gene expression. <b><i>Conclusions:</i></b> DHA-rich fish oil supplementation favorably modulated body composition in patients with T2DM and could be useful to reduce visceral obesity. However, the PPAR&#947; Pro12Ala polymorphism did not influence the changes in the desired variables.

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.

Peroxisome proliferator‑activated receptor γ polymorphisms as risk factors for dyslipidemia

Peroxisome proliferator‑activated receptor γ (PPARγ) may play an important role in lipid metabolism directly or by inducing the transcription of target genes. The aim of the present study was to investigate the association between common variants at the PPARγ locus (C1431T and Pro12Ala polymorphisms) and lipid serum levels. The studied population consisted of 820 subjects randomly selected from the Prevention of Multiple Metabolic Disorders and Metabolic Syndrome in Jiangsu Province cohort population. All subjects were interviewed and blood samples were obtained for laboratory analysis and DNA extraction. The TaqMan single nucleotide polymorphism genotyping assay was used for polymorphism genotyping. Individual polymorphisms and haplotype data were available for analysis. The 12Ala allele was found to be associated with significantly increased levels of triglyceride (TG) (P<0.01), whilst the 1431T allele was found to be associated with significantly increased levels of TG, total cholesterol (TC) and non‑high‑density lipoprotein (non‑HDL) (P<0.01). When P‑C, the most common haplotype, was used as the reference group, the P‑T, A‑C and A‑T haplotypes were found to be associated with significantly increased levels of TG (P<0.01). In addition, the A‑T haplotype was shown to be associated with significantly increased levels of TC and non‑HDL (P<0.01). In conclusion these results suggest that PPARγ gene variability may increase the risk of dyslipidemia.

Associations between C1431T and Pro12Ala variants of PPARγ gene and their haplotypes with susceptibility to metabolic syndrome in an Iranian population

Peroxisome proliferator-activated receptor gamma (PPARγ) is a nuclear hormone receptor that regulates a number of genes involved in lipid and carbohydrate metabolism. The aim of this study was to investigate the association of C1431T and Pro12Ala polymorphisms of PPARγ gene and their haplotypes and diplotypes with risk of metabolic syndrome (MetS) in an Iranian population. A total of 340 unrelated Iranian subjects, including 175 MetS patients and 165 normal controls were enrolled. Each group was then divided into two subgroups according to the genotype (Pro/Pro and Pro/Ala+Ala/Ala for Pro12Ala, CC and CT+TT for C1431T). Genotypes were determined using a TaqMan method. Anthropometric indices, fasting plasma glucose and fasting lipid profile were measured by routine methods. A significant difference in the frequencies of the C1431T genotypes was observed between MetS and control subjects (P=0.014), whereas no association was found for the Pro12Ala. The T allele carriers had a significantly increased risk of MetS compared to the CC genotype (P=0.016) even after correction for multiple-testing and adjustment for age, sex and genotype. The T allele may therefore be considered as a risk factor for MetS (P=0.003). Analysis of combined groups showed that X/Ala-CC and Pro/Pro-X/T diplotypes were associated with a higher body weight, waist circumference and waist to hip ratio among the individuals with MetS. Moreover the Ala-T haplotype was weakly associated with a higher level of triglyceride and lower level of HDL, suggesting the possibility of an interaction between Ala and T alleles. This study suggests that the PPARγ C1431T polymorphism is related to an increased risk of MetS in an Iranian population and interacts with the Pro12Ala polymorphism, further increasing the risk of MetS.

Rare mutations of peroxisome proliferator-activated receptor gamma: frequencies and relationship with insulin resistance and diabetes risk in the mixed ancestry population from South Africa

Background. Genetic variants in the nuclear transcription receptor, PPARG, are associated with cardiometabolic traits, but reports remain conflicting. We determined the frequency and the clinical relevance of PPARG SNPs in an African mixed ancestry population. Methods. In a cross-sectional study, 820 participants were genotyped for rs1800571, rs72551362, rs72551363, rs72551364, and rs3856806, using allele-specific TaqMan technology. The homeostatic model assessment of insulin (HOMA-IR), β-cells function (HOMA-B%), fasting insulin resistance index (FIRI), and the quantitative insulin-sensitivity check index (QUICKI) were calculated. Results. No sequence variants were found except for the rs3856806. The frequency of the PPARG-His447His variant was 23.8% in the overall population group, with no difference by diabetes status (P = 0.215). The His447His allele T was associated with none of the markers of insulin resistance overall and by diabetes status. In models adjusted for 2-hour insulin, the T allele was associated with lower prevalent diabetes risk (odds ratio 0.56 (95% CI 0.31-0.95)). Conclusion. Our study confirms the almost zero occurrences of known rare PPARG SNPs and has shown for the first time in an African population that one of the common SNPs, His447His, may be protective against type 2 diabetes.

Distribution and genotype frequency of the C1431T and pro12ala polymorphisms of the peroxisome proliferator activator receptor gamma gene in an Iranian population

BACKGROUND

Peroxisome proliferator activator receptor gamma (PPARγ) is a nuclear transcription factor regulating multiple genes involved in cell growth, differentiation, carbohydrate and lipid metabolism and energy production. Several genetic variations in the PPARγ gene have been identified to be associated with diabetes, obesity, dyslipidemia, insulin resistance, metabolic syndrome and coronary artery disease. The present study was designed to explore the distribution of two common single nucleotide polymorphisms of the PPARγ gene (C1431T and Pro12Ala) in an Iranian population.

MATERIALS AND METHODS

Genotype frequencies for these two polymorphisms were compared for 160 healthy Iranian individuals with reports from other populations. The Genotyping was performed using real-time polymerase chain reaction.

RESULTS

The genotype distribution of the C1431T PPARγ polymorphism was 0.869 for the CC genotype, 0.119 for the CT genotype and 0.013 for uncommon TT genotype. Allelic frequencies were 0.93 for C and 0.07 for T allele respectively. For the Pro12Ala polymorphism of PPARγ gene, genotypic distributions and allelic frequencies were, 0.813 for CC, 0.181 for CG and 0.06 for GG and 0.903 for C and 0.097 for G respectively. Allelic and genotypic frequencies for both polymorphisms of PPARγ gene were in Hardy-Weinberg equilibrium.

CONCLUSIONS

Iran is a country with an ethnically diverse population and a comparison of allelic and genotypic frequencies of PPARγ C1431T and Pro12Ala polymorphisms between our population and others showed significant differences.

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.

Role of the ACE ID and PPARG P12A Polymorphisms in Genetic Susceptibility of Diabetic Nephropathy in a South Indian Population

BACKGROUND

Diabetic nephropathy (DN) is one of the life-threatening disorders characterized by persistent albuminuria, raised arterial blood pressure, a lowered glomerular filtration rate, and high risk of cardiovascular morbidity and mortality. The vascular genes ACE (Angiotensin-converting enzyme), and PPARG (peroxisome proliferator activated receptor gamma) are involved in alterations in vascular endothelium, and are suggested to play a role in the susceptibility of diabetic nephropathy.

OBJECTIVES

The aim of our study was to find out the role of ACE ID and PPARG P12A polymorphisms in genetic susceptibility of diabetic nephropathy in south Indian population.

PATIENTS AND METHODS

A total of 54 cases with diabetic nephropathy and 67 control subjects with diabetes were enrolled for our study. DNA was isolated from peripheral blood leucocytes, and genotyped using PCR-electrophoresis (ACE ID) or PCR-RFLP (PPARG P12A) methods.

RESULTS

ACE ID genotypes followed Hardy-Weinberg equilibrium in both cases and controls. But P12A genotypes deviated from Hardy-Weinberg equilibrium in diabetic controls. Chi(2) test was applied for the analysis of genotypic distributions in genotypic and dominant models. Odds ratios were also calculated. No significant differences in genotype frequencies of ACE ID and PPARG P12A polymorphisms were found on comparing patients with diabetic nephropathy with diabetic controls. The synergistic role of ACE ID* PPARG P12A interaction, did not show any association in patients with diabetic nephropathy when compared to diabetic controls.

CONCLUSIONS

In conclusion, the ACE and PPARG genes do not have a key role in conferring risk for diabetic nephropathy.

Effects of PPARγ and RBP4 gene variants on metabolic syndrome in HIV-infected patients with anti-retroviral therapy

Background

PPARγ and RBP4 are known to regulate lipid and glucose metabolism and insulin resistance. The influences of PPARγ (C1431T and Pro12Ala) and RBP4 (−803GA) polymorphisms on metabolic syndrome in HIV-infected patients receiving anti-retroviral therapy were examined in this study.

Materials and Methods

A cross-sectional study of HIV-1 infected adults with antiretroviral therapy for more than one year in the National Cheng Kung University Hospital was conducted. The gene polymorphisms were determined by quantitative PCR.

Results

Ninety-one patients were included in the study. Eighty-two (90.1%) patients were males with a mean age of 44.4 years. For the C1431T polymorphism in PPARγ, while patients with the T allele (48.4%) had trends toward lower rate of hypertriglyceridemia, the borderline significance together with insignificant power did not support the protective effect of the T allele against development of hypertriglyceridemia. For the Pro12Ala polymorphism in PPARγ, although patients with the Pro/Ala genotype (8.8%) had a higher level of serum LDL (138.0 vs. 111.5 mg/dl, P = 0.04) and trends toward higher rates of hypercholesterolemia and serum LDL>110 mg/dl, these variables were found to be independent of the Pro/Ala genotype in the multivariate analysis. For the −803GA polymorphism in RBP4, patients with the A allele (23.1%) more often had insulin resistance (HOMA>3.8; 33.3 vs. 8.7%, P = 0.01) and more often received anti-hypoglycemic drugs (14.3 vs. 1.4%, P = 0.04). The detrimental effect of the A allele in RBP4 −803GA polymorphism on development of insulin resistance was supported by the multivariate analysis adjusting for covariates.

Conclusion

The impacts of PPARγ C1431T and Pro12Ala polymorphisms on metabolism in HIV-infected patients are not significant. RBP4 −803GA polymorphism has increased risk of insulin resistance in HIV-infected patients with anti-retroviral therapy.

The Human Obesity Gene Map: The 2004 Update

This paper presents the eleventh update of the human obesity gene map, which incorporates published results up to the end of October 2004. Evidence from single-gene mutation obesity cases, Mendelian disorders exhibiting obesity as a clinical feature, transgenic and knockout murine models relevant to obesity, quantitative trait loci (QTLs) from animal cross-breeding experiments, association studies with candidate genes, and linkages from genome scans is reviewed. As of October 2004, 173 human obesity cases due to single-gene mutations in 10 different genes have been reported, and 49 loci related to Mendelian syndromes relevant to human obesity have been mapped to a genomic region, and causal genes or strong candidates have been identified for most of these syndromes. There are 166 genes which, when mutated or expressed as transgenes in the mouse, result in phenotypes that affect body weight and adiposity. The number of QTLs reported from animal models currently reaches 221. The number of human obesity QTLs derived from genome scans continues to grow, and we have now 204 QTLs for obesity-related phenotypes from 50 genome-wide scans. A total of 38 genomic regions harbor QTLs replicated among two to four studies. The number of studies reporting associations between DNA sequence variation in specific genes and obesity phenotypes has also increased considerably with 358 findings of positive associations with 113 candidate genes. Among them, 18 genes are supported by at least five positive studies. The obesity gene map shows putative loci on all chromosomes except Y. Overall, >600 genes, markers, and chromosomal regions have been associated or linked with human obesity phenotypes. The electronic version of the map with links to useful publications and genomic and other relevant sites can be found at http://obesitygene.pbrc.edu.

Association of PPAR-γ gene polymorphisms with obesity and obesity-associated phenotypes in North Indian population

OBJECTIVES

The worldwide increasing prevalence of obesity is considered as a major health problem. Peroxisome proliferator-activated receptor gamma (PPAR-γ) controls adipocyte differentiation and regulates a number of genes associated with energy homeostasis. In this study, we investigated the association of PPAR-γ gene Pro12Ala (rs1801282) and C1431T (rs3856806) polymorphisms with morbid obesity and related phenotypes, in north Indian population.

METHODS

A total of 6,42 subjects, 309, obese and 333 nonobese individuals were included in this case-control study. Insulin, adiponectin, glucose, and lipid levels were estimated using standard protocols. All subjects were genotyped by PCR restriction fragment length polymorphism (PCR-RFLP) method.

RESULTS

The ProAla+AlaAla genotypes of PPAR-γ Pro12Ala were significantly associated with higher risk of obesity while C1431T polymorphism did not show any significant association. None of the haplotypes showed association with morbid obesity. However, a strong association of variant genotypes was observed with higher levels of insulin, HOMA-IR, and lower serum adiponectin concentrations.

CONCLUSION

PPAR-γ gene polymorphisms influence obesity and obesity phenotype in a complex manner, probably involving insulin resistance in north Indian population.

Interactions between dietary n-3 fatty acids and genetic variants and risk of disease

Nutritional genomics has undergone rapid development and the concept is now very popular with the general public. Therefore, there is increasing demand for knowledge on adapting dietary composition to the genome. Our aim has been to undertake a systematic review so as to find out the level of evidence existing on whether the effects of n-3 fatty acids on health can be modulated by genetic variation. A systematic literature search was conducted on studies that jointly analyse the effect of one or more genetic variants in candidate genes and n-3 fatty acids. Both observational and experimental studies were included. Results are classified in accordance with whether the study was undertaken on intermediate phenotypes (plasma lipid concentrations, glucose, inflammation markers, anthropometric measurements) or disease phenotypes (cancer, cardiovascular diseases, metabolic syndrome, etc) and whether it was experimental or observational. A wide diversity of genetic variants and little consistency in the publication of replication studies was found. Greater consistency was observed in studies that involved the FADS1 and FADS2 locus in the determination of n-3 fatty acid concentrations in biological samples. Most of the studies were designed to measure gene-diet interactions and not diet-gene interactions. Despite the fact that multiple studies have shown statistically significant interactions between n-3 fatty acids and certain genetic variants on intermediate and disease phenotypes, the individual level of evidence is very low and recommendations cannot be made on increasing or reducing the intake of n-3 fatty acids based on each individual's genotype.

Peroxisome proliferator activating receptor alpha and gamma polymorphisms and metabolic abnormalities in HIV-infected patients receiving highly active antiretroviral therapy: the ANRS CO8 APROCO-COPILOTE study

Highly active antiretroviral therapy (HAART) is associated with fat redistribution and metabolic disorders. The present study was undertaken to evaluate the association between peroxisome proliferator activated receptor (PPAR)α and PPARγ polymorphisms, two genes involved in lipid metabolism and adipocyte differentiation, and elements of the metabolic syndrome, lipodystrophy, or carbohydrate metabolism abnormalities in patients receiving HAART. The frequency distribution of rare alleles for PPARα (L162V) and PPARγ (P12A and H449H) was compared using the chi square test in 363 HIV-1-infected patients classified according to the presence or absence of the metabolic syndrome after 48 months of follow-up on their first PI-containing regimen. The P12A rare g allele was present in 12% patients with normal glucose metabolism, 11% patients with impaired glucose tolerance or impaired fasting glucose, and 35% patients with diabetes (p=0.014). The rare g allele for L162V was present in 14% of patients free of hypertriglyceridemia and in 7% patients with hypertriglyceridemia (p=0.04). The rare g allele for L162V was found in 15% of patients free of any sign of lipodystrophy and 8% with at least one sign of lipodystrophy (p=0.04) and the rare t allele for H449H was found in 14% of patients free of any sign of lipodystrophy and 23% of patients with at least one sign of lipodystrophy (p=0.05). There was no convincing association between any polymorphism of PPARα and PPARγ and each individual component of the metabolic syndrome, except for the relationship of the P12A polymorphism with diabetes. Confirmatory studies on a larger number of individuals are needed.

Association between PPAR-γ and RXR-α gene polymorphism and metabolic syndrome risk: a case-control study of a Chinese Han population

BACKGROUND AND AIMS

Polymorphisms in peroxisome proliferator activated receptor-γ (PPAR-γ) and retinoid X receptor-α (RXR-α) gene may alter metabolic syndrome (MetS) risks by increasing or decreasing the human adiponectin promoter activity in cells. To test this statement, three potentially functional SNPs of PPAR-γ and four SNPs of RXR-α with minor allele frequency (MAF) ≥0.05 in the Chinese Han population were identified from NCBI dbSNPs database to evaluate their associations with MetS.

METHODS

TaqMan assay was performed to test the genotypes in MetS patients (n = 901) and normal controls (n = 1009). Serum adiponectin concentration was measured by ELISA kit.

RESULTS

The variant genotypes rs2920502CG and CG/CC, rs4240711GG and AG/GG, rs4842194CC and CT/CC, rs3132291CT, CC and CT/CC were associated with MetS. Furthermore, in the haplotype of PPAR-γ gene, compared with the most common haplotype GC, haplotype CC was associated with an increased risk of MetS (crude p = 0.017). In the haplotype of RXR-α gene, haplotype GCGC was associated with a significant protective effect for MetS [adjusted p = 0.002, OR (95% CI) = 0.718 (0.585-0.882)] compared with the most common haplotype GTAT. After taking smoking, alcohol consumption and physical activity as environmental adjustment factors into the analysis, the result showed A1 A2 A4 A5 A6 A7 B1 (rs3856806, rs2920502, rs180128, rs1045570, rs3132291, rs4240711, rs4842194) was the best model (cross-validation consistency 10/10, p = 0.0107).

CONCLUSIONS

The present study suggested that the variant genotypes in PPAR-γ gene could increase the risk of MetS; however, genotypes in RXR-α gene could decrease the risk of MetS in a Chinese Han population.

Application of back propagation artificial neural network on genetic variants in adiponectin ADIPOQ, peroxisome proliferator-activated receptor-γ, and retinoid X receptor-α genes and type 2 diabetes risk in a Chinese Han population

AIMS

Our study was designed to explore the applied characteristics of the back propagation artificial neural network (BPANN) on studying the genetic variants in adipnectin ADIPOQ, peroxisome proliferator-activated receptor (PPAR)-γ, and retinoid X receptor-α (RXR-α) genes and type 2 diabetes mellitus (T2DM) risks in a Chinese Han population.

SUBJECTS AND METHODS

We used BPANN as the fitting model based on data gathered from T2DM patients (n=913) and normal controls (n=1,001). The mean impact value (MIV) for each input variables were calculated, and the sequence of the factors according to their absolute MIVs was sorted.

RESULTS

The results from BPANN were compared with multiple logistic regression analysis, and the generalized multifactor dimensionality reduction (GMDR) method was used to calculate the joint effects of ADIPOQ, PPAR-γ, and RXR-α genes. By BPANN analysis, the sequence according to the importance of the T2DM risk factors was in the order of serum adiponectin level, rs3856806, rs7649121, hypertension, rs3821799, rs17827276, rs12495941, rs4240711, age, rs16861194, waist circumference, rs2241767, rs2920502, rs1063539, alcohol drinking, smoking, hyperlipoproteinemia, gender, rs3132291, T2DM family history, rs4842194, rs822394, rs1801282, rs1045570, rs16861205, rs6537944, body mass index, rs266729, and rs1801282. However, compared with multiple logistic regression analysis, only 11 factors were statistically significant. After overweight and obesity were taken as environment adjustment factors into the analysis, model A2 B4 C5 C6 C8 (rs3856806, rs4240711, rs7649121, rs3821799, rs12495941) was the best model (coefficient of variation consistency=10/10, P=0.0107) in the GMDR method.

CONCLUSIONS

These results suggested the interactions of ADIPOQ, PPAR-γ, and RXR-α genes might play a role in susceptibility to T2DM. BPANN could be used to analyze the risk factors of diseases and provide more complicated relationships between inputs and outputs.

HDL cholesterol and bone mineral density: is there a genetic link?

Overwhelming evidence has linked cardiovascular disease and osteoporosis, but the shared root cause of these two diseases of the elderly remains unknown. Low levels of high density lipoprotein cholesterol (HDL) and bone mineral density (BMD) are risk factors for cardiovascular disease and osteoporosis respectively. A number of correlation studies have attempted to determine if there is a relationship between serum HDL and BMD but these studies are confounded by a number of variables including age, diet, genetic background, gender and hormonal status. Collectively, these data suggest that there is a relationship between these two phenotypes, but that the nature of this relationship is context specific. Studies in mice plainly demonstrate that genetic loci for BMD and HDL co-map and transgenic mouse models have been used to show that a single gene can affect both serum HDL and BMD. Work completed to date has demonstrated that HDL can interact directly with both osteoblasts and osteoclasts, but no direct evidence links bone back to the regulation of HDL levels. Understanding the genetic relationship between BMD and HDL has huge implications for understanding the clinical relationship between CVD and osteoporosis and for the development of safe treatment options for both diseases.

Effects of the PPARG P12A and C161T gene variants on serum lipids in coronary heart disease patients with and without Type 2 diabetes

We investigated whether PPAR-γ2 gene polymorphisms are associated with serum lipids and the occurrence of coronary heart disease (CHD) prospectively characterised for the presence or absence of Type 2 diabetes in a Turkish population. Our study included 202 patients with CHD (102 with diabetes, 100 without diabetes) and 105 controls. PPARγ genotypes were determined by PCR-RFLP technique. The PPARγ-C161T CC homozygote genotype was associated with significantly increased CHD risk when compared with the T allele carriers (CT+TT) in CHD patients with diabetes (OR:1.951, 95%CI: 1.115-3.415, P = 0.019), whereas PPARγ-P12A polymorphism was not associated with CHD risk (P > 0.05). Serum HDL-C levels were significantly lower in controls with the P12A heterozygote when compared with the P12P homozygote (P = 0.002). In the CHD patients with diabetes, CT heterozygote genotype showed higher serum triglyceride than the CC homozygote genotype (CT:2.42 ± 1.89 vs. CC:1.61 ± 0.21, P = 0.015). Our findings shows the association of these two polymorphisms with serum triglyceride levels, which was increased in the order of P12P-CC < P12P-CT < P12A-CC < P12A-CT in the CHD patients with diabetes. Furthermore, we observed that the increasing effects of the CT genotype on serum triglyceride levels could be modified by PPARγ P12A polymorphism (P12A-CT:2.30 ± 1.75 vs. P12P-CC:1.79 ± 1.14, P = 0.028). We suggested that homozygote CC genotype of the PPARγ C161T polymorphism might be associated with an increased CHD risk especially in patients with diabetes. We observed that the C161T CT heterozygote genotype shows an unfavorable effect on serum lipid profile in CHD patients with diabetes and this effect was weaken with the presence of P12P homozygote genotype.

'Striking the Right Balance' in Targeting PPARgamma in the Metabolic Syndrome: Novel Insights from Human Genetic Studies

At a time when the twin epidemics of obesity and type 2 diabetes threaten to engulf even the most well-resourced Western healthcare systems, the nuclear receptor peroxisome proliferator-activated receptor γ (PPARγ) has emerged as a bona fide therapeutic target for treating human metabolic disease. The novel insulin-sensitizing antidiabetic thiazolidinediones (TZDs, e.g., rosiglitazone, pioglitazone), which are licensed for use in the treatment of type 2 diabetes, are high-affinity PPARγ ligands, whose beneficial effects extend beyond improvement in glycaemic control to include amelioration of dyslipidaemia, lowering of blood pressure, and favourable modulation of macrophage lipid handling and inflammatory responses. However, a major drawback to the clinical use of exisiting TZDs is weight gain, reflecting both enhanced adipogenesis and fluid retention, neither of which is desirable in a population that is already overweight and prone to cardiovascular disease. Accordingly, the “search is on” to identify the next generation of PPARγ modulators that will promote maximal clinical benefit by targeting specific facets of the metabolic syndrome (glucose intolerance/diabetes, dyslipidaemia, and hypertension), while simultaneously avoiding undesirable side effects of PPARγ activation (e.g., weight gain). This paper outlines the important clinical and laboratory observations made in human subjects harboring genetic variations in PPARγ that support such a therapeutic strategy.

Association between C1431T polymorphism in peroxisome proliferator-activated receptor-γ gene and coronary artery disease in Chinese Han population

The C1431T polymorphism in peroxisome proliferator-activated receptor-γ (PPARγ) has been shown to be associated with diabetes, obesity, and metabolic syndrome. However, it is unclear whether this polymorphism is associated with coronary artery disease (CAD). Therefore, we conducted a hospital-based case-control study with 864 CAD patients and 1008 controls to explore the association between the PPARγ C1431T polymorphism and risk of CAD in Chinese Han population. Subjects with the variant genotypes (CT + TT) had a 39% decreased risk of CAD relative to CC carriers (adjusted odds ratio, 0.61; 95% confidence interval, 0.49-0.76). Our results suggested that the C1431T polymorphism was associated with a higher body mass index in both CAD patients and controls. Moreover, this polymorphism was also found to be associated with a higher HDL cholesterol level and a lower blood glucose level in CAD patients. In stratified analyses, the T allele was significantly associated with reduced risk of CAD in males, subjects with age <62 years, and non-smokers. In conclusion, the PPARγ C1431T polymorphism is associated with decreased risk of CAD in Chinese Han population.

Studies of gene variants related to inflammation, oxidative stress, dyslipidemia, and obesity: implications for a nutrigenetic approach

Obesity is currently considered a serious public health issue due to its strong impact on health, economy, and quality of life. It is considered a chronic low-grade inflammation state and is directly involved in the genesis of metabolic disturbances, such as insulin resistance and dyslipidemia, which are well-known risk factors for cardiovascular disease. Furthermore, there is evidence that genetic variation that predisposes to inflammation and metabolic disturbances could interact with environmental factors, such as diet, modulating individual susceptibility to developing these conditions. This paper aims to review the possible interactions between diet and single-nucleotide polymorphisms (SNPs) in genes implicated on the inflammatory response, lipoprotein metabolism, and oxidative status. Therefore, the impact of genetic variants of the peroxisome proliferator-activated receptor-(PPAR-)gamma, tumor necrosis factor-(TNF-)alpha, interleukin (IL)-1, IL-6, apolipoprotein (Apo) A1, Apo A2, Apo A5, Apo E, glutathione peroxidases 1, 2, and 4, and selenoprotein P exposed to variations on diet composition is described.

PPARγ2 C1431T genotype increases metabolic syndrome risk in young men with low cardiorespiratory fitness

The peroxisome proliferator-activated receptor gamma 2 (PPARγ2) genotypes are related to obesity and the metabolic syndrome (MetS). A low level of cardiorespiratory fitness is also a strong determining factor in the development of MetS. This cross-sectional study was performed to investigate the influence of the interaction between the PPARγ2 genotype and cardiorespiratory fitness on the risk of MetS. Healthy Japanese men ( n = 211) and women ( n = 505) participated in this study. All subjects were divided into 8 groups according to sex, fitness level (high and low fitness groups), and age (younger, age < 40 yr; middle-aged/older, age ≥ 40 yr). The PPARγ2 genotypes (Pro12Ala and C1431T) were analyzed by real-time PCR with Taq-Man probes. Two-way ANCOVA with adjustment for age as a covariate indicated that fitness and the CC genotype of C1431T in the PPARγ2 gene interacted to produce a significant effect on MetS risk in younger men and that the risk of MetS in the CC genotype group with low cardiorespiratory fitness was significantly higher than that in the corresponding CT+TT genotypes or in the high fitness groups. There was no significant interaction between fitness and genotype in determining MetS risk in middle-aged/older men or in women in any group. With regard to the Pro12Ala genotype of the PPARγ2 gene, there were no significant differences in fitness or genotype effects nor were there any interactions between measurement variables. We concluded that the CC genotype of C1431T in the PPARγ2 gene together with low cardiorespiratory fitness may increase the risk of MetS in younger men (age < 40 yr), even with adjustment for age.

Genetic variants in peroxisome proliferator-activated receptor-γ and retinoid X receptor-α gene and type 2 diabetes risk: a case-control study of a Chinese Han population

BACKGROUND

The serum levels of adiponectin are paradoxically decreased in obesity and may play important roles in the development of type 2 diabetes mellitus (T2DM). Potentially functional polymorphisms in the peroxisome proliferator-activated receptor-γ (PPAR-γ) and retinoid X receptor-α (RXR-α) genes may alter T2DM risks by increasing the human adiponectin promoter activity in cells. Therefore, we hypothesized that single nucleotide polymorphisms (SNPs) in PPAR-γ and RXR-α were associated with risk of T2DM. To test this hypothesis, three potentially functional SNPs of PPAR-γ and four of RXR-α with a minor allele frequency of ≥ 0.05 in the Chinese Han population were identified from the National Center for Biotechnology Information dbSNPs database to evaluate their association with T2DM.

METHODS

Polymerase chain reaction-restriction fragment length polymorphism was performed to test the genotypes in T2DM patients (n = 540) and normal controls (n = 604).

RESULTS

The variant genotypes rs2920502CC, rs3856806CT, rs3856806CT/TT, and rs4240711AG/GG were associated with T2DM. Furthermore, the prevalences of haplotype GTC and CTG in PPAR-γ and GTAC in RXR-α were less frequent in cases (17.1%, 2.6%, and 2.4%, respectively) than in controls (22.3%, 3.8%, and 6.6%, respectively), whereas GTGT in RXR-α was more frequent in cases (6.9%) than in controls (4.4%) (P < 0.05 for both two-sided χ(2) test and thousand times permutation tests). Patients with genotype CT/TT of rs3856806 and genotype AG/GG of rs4240711 had higher levels of serum adiponectin than those with the genotype CC and genotype AA (P = 0.026 and 0.021, respectively). Model X2 X5 X6 X7 (rs3856806, rs3132291, rs4240711, and rs4842194) was the best model with the highest test balanced accuracy (0.5764) (cross-validation consistency = 10/10) in the multifactor dimensionality reduction method.

CONCLUSIONS

The PPAR-γ and RXR-α gene variants associated with the development of T2DM in this study must be investigated in a larger population to reveal any potential effects on metabolism.

Tagging single nucleotide polymorphisms in the PPAR-γ and RXR-α gene and type 2 diabetes risk: a case-control study of a Chinese Han population

Peroxisome proliferator-activated receptor (PPAR-γ),which is mainly involved in adipocyte differentiation, has been suggested to play an important role in the pathogenesis of insulin resistance and atherosclerosis. We investigated the frequencies of two common tagging polymorphisms of the PPAR-γ gene and two of PPAR-α with minor allele frequency (MAF) ≥0.05 in the Chinese Han population and analyzed the correlation between the different genotypes and the risk of type 2 diabetes mellitus (T2DM). TaqMan® assay was performed to test the genotypes in T2DM patients (n = 1,105) and normal controls (n = 1,107). Serum adiponectin concentration was measured by ELISA kit. The variant genotypes rs17817276GG, rs3856806CT and rs3856806CT/TT of PPAR-γ were associated with T2DM, P = 0.023,0.037 and 0.018, respectively. Furthermore, the prevalence of haplotype GT in PPAR-γ was less frequent in the case subjects (0.3%) than in the controls (1.9%) [P < 0.001,OR(95%CI)=0.13 (0.06-0.31)]. Patients with genotype TT of rs3856806 had a higher serum level of adiponectin than those with the genotype CC and CT (P = 0.031 and 0.038, respectively). There was no statistically significant difference between patients and controls in genotype distribution of rs6537944 and rs1045570 of the RXR-α gene. The present study suggests that the variant genotypes in the PPAR-γ gene could decrease the risk for the development of T2DM in the Chinese Han population.

Joint effect of peroxisome proliferator-activated receptor γ genetic polymorphisms and estrogen-related risk factors on breast cancer risk: results from a case-control study in Taiwan

Peroxisome proliferator-activated receptor γ (PPARγ) has been linked with possible antineoplastic effects in colorectal carcinogenesis. However, data for the possible link between PPARγ and breast cancer risk are sparse. We assessed the association of three polymorphisms in PPARγ (rs10865710 [C-681T], rs1805192 [Pro12Ala], and rs3856806 [C1431T]) with the risk of breast cancer in an ethnic Chinese female population in Taiwan. In addition, interactions with estrogen exposures were also explored. Genotypes for the PPARγ polymorphisms were determined on 291 incident breast cancer cases and 589 matched controls by fluorogenic 5'-nuclease assay. The at-risk haplotypes were defined according to the three polymorphisms in the following order: C-681T, Pro12Ala, and C1431T, which include CCT, GGT, and GGC. In addition, a critical period of estrogen exposure was estimated by the interval between age at menarche and age at first full-term pregnancy. Overall, there was no evidence of a significant impact of individual polymorphisms of PPARγ on breast cancer risk. However, the haplotype analysis revealed that women harboring at-risk haplotypes showed a significant 67% increase in breast cancer risk [adjusted odds ratio (OR) 1.67; 95% confidence interval (CI) 1.11-2.52]. Furthermore, there was a significant joint effect of estrogen exposure-related factors and at-risk haplotypes of PPARγ on breast cancer risk (adjusted OR 4.04; 95% CI 1.89-8.65), particularly in premenopausal women. The present study implicates a role for PPARγ in breast cancer risk. Mechanistic studies to fully elucidate the mechanisms underlying PPARγ's effects should be pursued in future investigations.

PPARG: Gene Expression Regulation and Next-Generation Sequencing for Unsolved Issues

Peroxisome proliferator-activated receptor gamma (PPARγ) is one of the most extensively studied ligand-inducible transcription factors (TFs), able to modulate its transcriptional activity through conformational changes. It is of particular interest because of its pleiotropic functions: it plays a crucial role in the expression of key genes involved in adipogenesis, lipid and glucid metabolism, atherosclerosis, inflammation, and cancer. Its protein isoforms, the wide number of PPARγ target genes, ligands, and coregulators contribute to determine the complexity of its function. In addition, the presence of genetic variants is likely to affect expression levels of target genes although the impact of PPARG gene variations on the expression of target genes is not fully understood. The introduction of massively parallel sequencing platforms-in the Next Generation Sequencing (NGS) era-has revolutionized the way of investigating the genetic causes of inherited diseases. In this context, DNA-Seq for identifying-within both coding and regulatory regions of PPARG gene-novel nucleotide variations and haplotypes associated to human diseases, ChIP-Seq for defining a PPARγ binding map, and RNA-Seq for unraveling the wide and intricate gene pathways regulated by PPARG, represent incredible steps toward the understanding of PPARγ in health and disease.

Associations for lipoprotein lipase and peroxisome proliferator-activated receptor-gamma gene and coronary artery disease in an Indian population

BACKGROUND AND AIMS

Peroxisome proliferator activated receptor-gamma (PPARgamma) and lipoprotein lipase (LPL) genes are important in pathways of triglyceride metabolism, insulin resistance and adipogenesis. We hypothesized that polymorphisms of PPARgamma Pro12Ala, LPL HindIII and LPL Ser447X influence severity of coronary artery disease (CAD) in an Indian population.

METHODS

PPARgamma Pro12Ala, LPL HindIII and LPL Ser447X polymorphisms were genotyped in 414 patients with CAD and matched with 424 controls. The study subjects were inducted after standard diagnostic procedures and analyzed statistically for the association of polymorphisms with clinical characteristics.

RESULTS

We found that PPARgamma alleles were not associated with CAD among Indians although proline carriers had significantly higher levels of HDL-cholesterol (p = 0.03) among CAD patients. The LPL HindIII also had no significant correlations for CAD or for any clinical characteristics. The Ser447X polymorphism (p = 0.015) influenced lower triglyceride levels among CAD patients with significant associations (OR = 0.66, 95% CI 0.483-0.915, p = 0.012). This protective effect of the 447X allele was more pronounced among the CAD patients without the risk factor of diabetes (OR = 0.60, 95% CI 0.403-0.907, p = 0.014) along with less progression of a severe atherosclerotic disease.

CONCLUSIONS

PPARgamma and LPL have intractable roles in pathways that lead to CAD, but their gene polymorphisms associate differently. Our results imply a significant correlation of Ser447X polymorphism and its protective effect on Indians against severity of CAD modified by the risk of diabetes, than LPL HindIII and PPARgamma Pro12Ala.