Implication of the Pro12Ala polymorphism of the PPAR-gamma 2 gene in type 2 diabetes and obesity in the French population

PPARγ2 Pro12Ala Polymorphism is Associated in Children With Traits Related to Susceptibility to Type 2 Diabetes

Peroxisome proliferator-activated receptor gamma (PPARγ) is a ligand-activated nuclear receptor that regulates glucose and lipid metabolism. Pharmacological activators of PPARγ are being used as a treatment of obesity related disorders such as dyslipidaemia and type 2 diabetes, but questions remain open regarding the effects of PPARγ on traits related to the development of type 2 diabetes. In our study, we have analyzed the relationship of the common variant Pro12Ala in the human PPARγ2 gene with the presence of obesity and with insulin, HOMA and lipid profile in a representative sample of 6-to 8-year-old children free from the confounding factors associated with adults. We found that Ala12Ala genotype was significantly more frequent in females with obesity than in those without obesity, with Ala12Ala carriers having significantly higher weight and body mass index (BMI), however the association disappeared when adjusting by leptin concentrations. The Ala12Ala genotype was associated with significantly higher HDL-cholesterol and apoA-I levels in males but not in females, independently of BMI. In a recessive model, in females, leptin levels appeared higher in Ala12Ala carriers. Although no apparent differences were observed in any sex when analyzing insulin levels and HOMA among genotypes without adjusting, lower insulin levels and lower HOMA appeared associated with Ala12Ala carriers when adjusting for BMI and leptin levels. In summary, our data showed that leptin seems to be having an effect on the association between the PPARγ2 Pro12Ala and BMI. Besides, after controlling for BMI and leptin, a protective effect of the Ala12Ala variant of the PPARγ2 Pro12Ala polymorphism on insulin sensitivity is evident already in prepubertal children.

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.

Association study of rs1801282 PPARG gene polymorphism and immune cells and cytokine levels in a Spanish pregnant women cohort and their offspring

Background

Peroxisome proliferator activated receptor gamma (PPARG) belongs to the nuclear receptor superfamily functioning as transcription factors to regulate cellular differentiation, development and metabolism. Moreover, it has been implicated in the regulation of lipid metabolism, as well as the maturation of monocytes/macrophages and the control of inflammatory reactions. The aim of this study was to evaluate the relationship between the Pro12Ala (rs1808212) PPARG gene polymorphism on immune molecular and cellular components in mothers and their offspring participating in the PREOBE study.

Methods

DNA from maternal venous blood samples at 24, 34 and 40 gestational weeks, plus cord blood samples was extracted. Pro12Ala PPARG polymorphism genotyping was performed, and immune system markers were analyzed by flow cytometry.

Results

Study findings revealed no effect of rs1808212 PPARG genotypes on innate immune parameters in mothers and their offspring; however, CD4 + /CD8 + ratio were decreased at 24 and 34 weeks in pregnant women carrying the CG (Pro12Ala) rs1808212 polymorphism, (p = 0,012 and p = 0,030; respectively). Only CD19 levels in peripheral blood were significantly higher at delivery in pregnant women carrying the CC (Pro12Pro) genotype (p ≤ 0.001). Moreover, there were statistically significant differences in leukocytes and neutrophils maternal levels at 34 weeks of gestation, being lower in carriers of Pro12Ala genotype (p = 0.028 and p = 0.031, respectively).

Conclusions

Results suggest that Pro12Ala PPARG polymorphism may have an effect on some cell and immune parameters in pregnant women during pregnancy and at time of delivery. However, newborn innate immune system does not seems to be influenced by PPARG Pro12Ala polymorphism in cord blood.

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.

Genetic predisposition in type 2 diabetes: A promising approach toward a personalized management of diabetes

Diabetes mellitus, also known simply as diabetes, has been described as a chronic and complex endocrine metabolic disorder that is a leading cause of death across the globe. It is considered a key public health problem worldwide and one of four important non-communicable diseases prioritized for intervention through world health campaigns by various international foundations. Among its four categories, Type 2 diabetes (T2D) is the commonest form of diabetes accounting for over 90% of worldwide cases. Unlike monogenic inherited disorders that are passed on in a simple pattern, T2D is a multifactorial disease with a complex etiology, where a mixture of genetic and environmental factors are strong candidates for the development of the clinical condition and pathology. The genetic factors are believed to be key predisposing determinants in individual susceptibility to T2D. Therefore, identifying the predisposing genetic variants could be a crucial step in T2D management as it may ameliorate the clinical condition and preclude complications. Through an understanding the unique genetic and environmental factors that influence the development of this chronic disease individuals can benefit from personalized approaches to treatment. We searched the literature published in three electronic databases: PubMed, Scopus and ISI Web of Science for the current status of T2D and its associated genetic risk variants and discus promising approaches toward a personalized management of this chronic, non-communicable disorder.

Genetic Background of Hypertension in Connective Tissue Diseases

Peroxisome proliferator-activated receptors (PPAR gamma-2) and beta-3-adrenergic receptors (ADRB3) are involved in the risk of hypertension. But their exact role in blood pressure modulation in patients with connective tissue diseases (CTD) is still not well defined. In this study, 104 patients with CTD and 103 gender- and age-matched controls were genotyped for Pro12Ala and C1431T polymorphisms of the PPAR gamma-2 gene and Trp64Arg polymorphism of the ADRB gene. Anthropometric and biochemical measurements were evaluated, followed by genotyping using TaqMan® SNP genotyping assays and polymerase chain reaction-restriction fragment length polymorphism. The prevalence of analyzed genotypes and alleles was comparable between patients with CTD and the control group, as well as hypertensive and normotensive subjects. Patients with CTD have lower body fat and higher body water amount, serum glucose, and triglyceride (TG) levels. Hypertensive subjects are older and have higher body mass, BMI, waist circumference (WC), body water content, glucose, and TG concentration. The multivariate analysis revealed that hypertensive subjects with Ala12/X or Trp64Trp have higher body mass and WC when compared to normotensive subjects. Trp64Trp polymorphism was also characterized by a higher TG level, while T1431/X subjects had higher WC. The presence of CTD, visceral fat distribution, and increased age are the predictors of hypertension development. Hypertensive patients with CTD and Trp64Trp polymorphism have an increased risk of visceral obesity development and metabolic complications, which in turn affects the value of blood pressure. In addition, either Ala12/X or T1431/X predicts the visceral body fat distribution in hypertensive subjects.

ASSOCIATION OF THE HUMAN PPARγ2 PRO12ALA POLYMORPHISM WITH OBESITY IN A POPULATION FROM TURKEY

BACKGROUND

There have been a number of reports on the relationship between the PPARγ2 Pro12Ala genotype and the development of obesity.

OBJECTIVE

A case-control survey was designed to investigate the potential association between a Pro12Ala polymorphism in the PPARγ2 gene and obesity and/or obesity-related phenotypes in a population from Turkey.

MATERIALS AND METHODS

The polymerase chain reaction and restriction enzyme digestion were used to genotype the Pro12Ala polymorphism of the PPARγ2 gene in 149 unrelated obese and 105 non-obese control subjects from Turkey. The data were analyzed statistically.

RESULTS

We found that the overall minor allele frequency was 0.12 in cases and 0.095 in controls. In terms of genotype distribution and allele frequencies among the cases versus controls in the population studied, only the gender-stratified analysis revealed a significantly higher frequency of Pro/Ala genotype within males. The polymorphism was associated with significantly higher weight, height, waist circumference, central adiposity (waist-to-hip ratio, WHR), lean body weight as well as dry body weight, but not overall adiposity (total body fat percentage, TBF) in cases carrying Ala allele (Pro/Ala or Ala/Ala). However, in the subjects carrying Ala allele of the control group, WHR values were found significantly lower.

CONCLUSION

Our results showed that the Pro12Ala polymorphism in the PPARγ2 gene is associated with obesity in the studied adult population from Turkey. These data suggest that the Pro12Ala polymorphism in PPARγ2 may be a potential genetic risk factor for central obesity.

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.

Peroxisome proliferator-activated receptor-γ polymorphism (rs1801282) is associated with obesity in Egyptian patients with coronary artery disease and type 2 diabetes mellitus

OBJECTIVE

Peroxisome Proliferator-Activated Receptor-γ (PPAR-γ) gene is one of the possible genes linking diabetes mellitus (DM) with coronary artery disease (CAD). The aim of this study is to clarify whether PPAR-γ Pro12Ala polymorphism is associated with the development of CAD in type 2 diabetic patients and to evaluate PPAR-γ Pro12Ala polymorphism genetic distribution in type 2 DM (T2DM) Egyptian subjects.

METHODS

PPAR-γ Pro12Ala polymorphism was determined by Real-Time PCR in serum of 405 subjects classified into 4 groups; T2DM patients (n = 105), T2DM with CAD (n = 100), CAD patients (n = 100) and healthy controls (n = 100).

RESULTS

The PPAR-γ Pro12Ala polymorphism was associated significantly with T2DM with CAD (group2) (OR = 3, 95% CI = (1.5-6); p = 0.001). In this study, T2DM with CAD complications carrying the PPAR-γ Pro12Ala polymorphism had higher BMI than those without the PPAR-γ Pro12Ala polymorphism (p < 0.0001). CAD patients carrying PPAR-γ Pro12Ala polymorphism had considerable insulin resistance features. Plasma paraoxanase 1(PON1) level was considerably reduced among our 3 studied groups in comparison to control group (p < 0.001).

CONCLUSIONS

PPAR-γ Pro12Ala polymorphism might represent a novel risk factor for CAD in T2DM.

Effect of the Pro12Ala Polymorphism of the Peroxisome Proliferator-activated Receptor γ2 Gene on Lipid Profile and Adipokines Levels in Obese Subjects

Peroxisome proliferator-activated receptor γ (PPARγ) is a key regulator of metabolism, adipokines production and secretion. The aim of this study was to investigate the association between the PPARγ2 gene Pro12Ala polymorphism in obesity in terms of body mass index (BMI), lipid parameters, homeostasis model assessment of insulin resistance (HOMA-IR), serum lipid, leptin, adiponectin, resistin and chemerin levels. The study included 160 obese and 140 non obese subjects. The Pro12Ala polymorphism was determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Serum lipid, leptin, adiponectin, resistin and chemerin levels were measured. No association was found between the Pro12Ala polymorphism and BMI. Strikingly, in the study group, obese subjects with the AA genotype had significantly higher triglycerides (p = 0.046) and resistin (p <0.001) levels than those with the wild-type PP and heterozygous PA genotypes. Serum leptin and chemerin levels were significantly associated with Pro-12Ala poymorphism in the obese and non obese groups (p <0.01). In the obese group, subjects with the homozygous AA genotype had significantly lower adiponectin (p = 0.010) activity than the PP genotype. Our results suggest that the PPARγ2 gene Pro12Ala polymorphism has no direct association with obesity but does have significant influences on lipid profiles and adipokines levels.

Polymorphisms FTO rs9939609, PPARG rs1801282 and ADIPOQ rs4632532 and rs182052 but not lifestyle are associated with obesity related-traits in Mexican children

Concerning the genetic factors of obesity, no consistent association between populations has been reported, which may be due to the frequency of polymorphisms, the lifestyle of studied populations and its interaction with other factors. We studied a possible association of polymorphisms FTO rs9939609, PPARG rs1801282, and ADIPOQ rs4632532 and rs182052 with obesity phenotypes in 215 Mexican children. Glucose, triglycerides, cholesterol, HDL and LDL were measured. In addition, weight, height, waist circumference and triceps skin thickness were recorded. High-energy diets and sedentary behavior were evaluated with a validated questionnaire. In contrast with other reports, only FTO rs9939609 was associated with obesity related-traits, including BMI (p = 0.03), waist circumference (p = 0.02), triceps skinfold (p = 0.03) and waist/height ratio (p = 0.01), and also with cholesterol levels (p = 0.02) and LDL (p = 0.009). Lower levels of triglycerides (p=0.04) were related with presence of PPARG rs1801282, while ADIPOQ rs4632532 showed an effect on HDL (p = 0.03) levels. On the other hand, diet, physical activity and screen time were not related with obesity. In summary, only FTO rs9939609 was associated with obesity related-traits, while PPARG2 rs1801282 and ADIPOQ rs4632532 were involved in lipid metabolism.

Genetic polymorphisms associated with overweight and obesity in uncontrolled Type 2 diabetes mellitus

Generally, obese and overweight individuals display higher free fatty acid levels, which stimulate insulin resistance. The combination of overweight or obesity with insulin resistance can trigger Type 2 diabetes mellitus (T2DM) and are primary contributing factors to the development of uncontrolled T2DM. Genetic polymorphisms also play an important role as they can impact a population's susceptibility to becoming overweight or obese and developing related chronic complications, such as uncontrolled T2DM. This review specifically examines the genetic polymorphisms associated with overweight and obesity in patients with uncontrolled T2DM. Particularly, gene polymorphisms in ADIPOQ (rs1501299 and rs17300539), LepR (rs1137101 and rs1045895), IRS2 (rs1805092), GRB14 (rs10195252 and rs3923113) and PPARG (rs1801282) have been associated with overweight and obesity in uncontrolled T2DM.

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.

The Pro12Ala polymorphism in the peroxisome proliferator-activated receptor gamma (PPARG) gene in relation to obesity and metabolic phenotypes in a Taiwanese population

Obesity is considered as an important public health problem in the world. Although the association of a common single nucleotide polymorphism (SNP), rs1801282 (Pro12Ala), in the peroxisome proliferator-activated receptor gamma (PPARG) gene with obesity has been reported in various populations, these data are not conclusive. This study aimed to reassess whether the PPARG rs1801282 SNP is linked with obesity and obesity-related metabolic traits in a Taiwanese population. A total of 674 Taiwanese subjects with general health examinations were genotyped. The rs1801282 genotype was determined by the Taqman SNP genotyping assay. Obesity-related metabolic traits such as triglyceride, waist circumference, systolic and diastolic blood pressure, total cholesterol, and fasting glucose were measured. The PPARG rs1801282 SNP did not exhibit any significant association with obesity among the complete sample population. However, sex-stratified analyses revealed an effect on overweight in female participants where the carriers of the combined CG and GG genotypes had a higher risk to overweight than those with the CC homozygotes (OR=4.05; 95% CI=1.28-12.83; P=0.017). Compared to the carriers of CC homozygotes, BMI was significantly higher for the carriers of the combined CG and GG genotypes in the female subjects (24.4±3.7 vs. 23.5±3.8 kg/m2; P=0.033). In addition, the carriers of the CC homozygotes had a higher total cholesterol level than those with the combined CG and GG genotypes in the female subjects (197.0±37.3 vs. 180.7±33.7 mg/dl; P=0.026). Our study indicates that PPARG rs1801282 may significantly predict overweight, BMI, and total cholesterol in female but not male Taiwanese subjects.

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 between PPAR-γ2 Pro12Ala polymorphism and obesity: a meta-analysis

The peroxisome proliferator-activated receptor-γ2 (PPAR-γ2) gene has been reported in the pathogeny of obesity. However, the results have been inconsistent. The purpose of this meta-analysis was to acquire a more accurate assessment of the association between PPAR-γ2 Pro12Ala polymorphism and obesity. PubMed, Wan Fang (Chinese) databases, Chinese Biomedical Medical databases, and Chinese National Knowledge Infrastructure were searched to identify eligible studies. Finally, 25 studies (6491 cases and 8242 controls) were enrolled in this meta-analysis. The effect summary odds ratio (OR) with 95 % confidence interval (CI) was applied. Random-effects or fixed-effects model was performed based on the heterogeneity. STATA 12.0 was applied for this meta-analysis. The combined results showed that PPAR-γ Pro12Ala polymorphism was associated with the obesity risk (Ala vs. Pro: OR = 1.55, 95 % CI 1.34-1.80; Pro/Ala vs. Pro/Pro: OR = 1.54, 95 % CI 1.31-1.82; Ala/Ala + Pro/Ala vs. Pro/Pro: OR = 1.61, 95 % CI 1.36-1.90). Subgroup analysis by ethnicity showed that there were significant associations between PPAR-γ Pro12Ala polymorphism and obesity risk in Caucasians, Asians, and Mixed population. Subgroup analysis by obesity's cutoff points showed that the associations were found among the patients with the cutoff point of BMI ≥24 and BMI ≥30 but not among the patients with the cutoff point of BMI ≥95th percentile. These results suggested that PPAR-γ Pro12Ala polymorphism might be a risk factor for obesity susceptibility.

Association of IRS1, CAPN10, and PPARG gene polymorphisms with type 2 diabetes mellitus in the high-risk population of Hyderabad, India

BACKGROUND

We attempted to validate earlier findings on the nature of the association of the IRS1, CAPN10, and PPARG genes with type 2 diabetes mellitus (T2DM) in the high-risk population of Hyderabad, India.

METHODS

A sample of 1379 subjects (758 T2DM patients, 621 controls) was genotyped for single nucleotide polymorphisms (SNPs) of the IRS1 (rs1801278), CAPN10 (rs3792267, rs5030952), and PPARG (rs1801282) genes.

RESULTS

The allele and genotype frequencies of IRS1 (rs1801278) and CAPN10 (rs3792267) SNPs differed significantly between the patient and control groups. Logistic regression analysis suggested a significant association of these two SNPs (P ≤ 0.007) with T2DM and the strength of association did not alter when adjusted for age, gender, body mass index, and the waist : hip ratio as covariates. The same two SNPs showed significant association in multivariate logistic regression analyses, even after Bonferroni correction for multiple testing, suggesting an independent nature of the role of these genes in the manifestation of T2DM in our population.

CONCLUSIONS

We replicated the significant association of rs1801278 and rs3792267 SNPs of the IRS1 and CAPN10 genes with T2DM in the population of Hyderabad. Despite the known biological significance of the PPARG gene and a sufficient statistical power of the present study, we could not replicate the association of PPARG with T2DM in our high-risk population. Given the vast ethnic, geographic, and genetic heterogeneity of the Indian population, many more studies are needed covering the ethnic and geographic heterogeneity of India to enable identification of an Indian-specific profile of genes associated with T2DM.

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.

IRS1, TCF7L2, ADRB1, PPARG, and HHEX polymorphisms associated with atherogenic risk in Mexican population

Objective. We aimed to explore the association between polymorphisms of IRS1 (rs1801278), TCF7L2 (rs7903146 and rs12255372), ADRB1 (rs1801253), PPARG (rs1801282), and HHEX (rs5015480) genes with atherogenic risk (AI = Total cholesterol/HDL) in MetS, T2D, and healthy populations from the Mexican Social Security Institute. Methodology and Results. Four hundred thirty-five MetS, 517 T2D, and 547 healthy individuals were selected. The association between the SNPs and the atherogenic index was evaluated by multiple linear regression and multinomial logistic regression models. The ADRB1 gene showed a statistically significant association with high-risk atherogenic index, OR = 2.94 (IC 95% 1.64-5.24; P < 0.0001) for the Arg/Gly variant, under the dominant model an OR = 2.96 (IC 95% 1.67-5.25; P < 0.0001), and under the Log additive model an OR = 2.52 (IC 95% 1.54-4.15; P < 0.0001). Conclusions. The Arg389Gly polymorphism of the ADRB1 gene may be a worthy biological marker to predict the risk of developing cardiovascular diseases given a high-risk atherogenic index.

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.

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?

ACE I/D and MTHFR C677T polymorphisms are significantly associated with type 2 diabetes in Arab ethnicity: a meta-analysis

In this meta-analysis study, SNPs were investigated for their association with type 2 diabetes (T2D) in both Arab and Caucasian ethnicities. A total of 55 SNPs were analyzed, of which 11 fulfilled the selection criteria, and were used for analysis. It was found that TCF7L2 rs7903146 was significantly associated with a pooled OR of 1.155 (95%C.I.=1.059-1.259), p<0.0001 and I(2)=78.30% among the Arab population, whereas among Caucasians, the pooled OR was 1.45 (95%C.I.=1.386-1.516), p<0.0001 and I(2)=77.20%. KCNJ11 rs5219 was significantly associated in both the populations with a pooled OR of 1.176(1.092-1.268), p<0.0001 and I(2)=32.40% in Caucasians and a pooled OR of 1.28(1.111-1.475), p=0.001 among Arabs. The ACE I/D polymorphism was found to be significantly associated with a pooled OR of 1.992 (95%C.I.=1.774-2.236), p<0.0001 and I(2)=83.20% among the Arab population, whereas among Caucasians, the pooled OR was 1.078 (95%C.I.=0.993-1.17), p=0.073 and I(2)=0%. Similarly, MTHFR C677T polymorphism was also found to be significantly associated among Arabs with a pooled OR of 1.924 (95%C.I.=1.606-2.304), p<0.0001 and I(2)=27.20%, whereas among Caucasians, the pooled OR was 0.986 (95%C.I.=0.868-1.122), p=0.835 and I(2)=0%. Meanwhile PPARG-2 Pro12Ala, CDKN2A/2B rs10811661, IGF2BP2 rs4402960, HHEX rs7923837, CDKAL1 rs7754840, EXT2 rs1113132 and SLC30A8 rs13266634 were found to have no significant association with T2D among Arabs. In conclusion, it seems from this study that both Arabs and Caucasians have different SNPs associated with T2D. Moreover, this study sheds light on the profound necessity for further investigations addressing the question of the genetic components of T2D in Arabs.

Nutrigenetics and metabolic disease: current status and implications for personalised nutrition

Obesity, particularly central adiposity, is the primary causal factor in the development of insulin resistance, the hallmark of the metabolic syndrome (MetS), a common condition characterized by dyslipidaemia and hypertension, which is associated with increased risk of cardiovascular disease (CVD) and type 2 diabetes (T2DM). Interactions between genetic and environmental factors such as diet and lifestyle, particularly over-nutrition and sedentary behavior, promote the progression and pathogenesis of these polygenic diet-related diseases. Their current prevalence is increasing dramatically to epidemic proportions. Nutrition is probably the most important environmental factor that modulates expression of genes involved in metabolic pathways and the variety of phenotypes associated with obesity, the MetS and T2DM. Furthermore, the health effects of nutrients may be modulated by genetic variants. Nutrigenomics and nutrigenetics require an understanding of nutrition, genetics, biochemistry and a range of “omic” technologies to investigate the complex interaction between genetic and environmental factors relevant to metabolic health and disease. These rapidly developing fields of nutritional science hold much promise in improving nutrition for optimal personal and public health. This review presents the current state of the art in nutrigenetic research illustrating the significance of gene-nutrient interactions in the context of metabolic disease.

Association of FTO and PPARG polymorphisms with obesity in Portuguese women

PURPOSE

We evaluated the association between risk of obesity in the Portuguese population and two obesity-related single-nucleotide gene polymorphisms: fat-mass and obesity-associated (FTO) rs9939609 and peroxisome proliferator-activated receptor gamma (PPARG) rs1801282.

PATIENTS AND METHODS

A total of 194 Portuguese premenopausal female Caucasians aged between 18 and 50 years (95 with body mass index [BMI] ≥30 g/m(2), 99 controls with BMI 18.5-24.9 kg/m(2)) participated in this study. The association of the single-nucleotide polymorphisms with obesity was determined by odds ratio calculation with 95% confidence intervals.

RESULTS

Significant differences in allelic expression of FTO rs9939609 (P<0.05) were found between control and case groups, indicating a 2.5-higher risk for obesity in the presence of both risk alleles when comparing the control group with the entire obese group. A fourfold-higher risk was found for subjects with class III obesity compared to those with classes I and II. No significant differences in BMI were found between the control and case groups for PPARG rs1801282 (P>0.05).

CONCLUSION

For the first time, a study involving an adult Portuguese population shows that individuals harboring both risk alleles in the FTO gene locus are at higher risk for obesity, which is in agreement to what has been reported for other European populations.

Association of MTHFR and PPARγ2 gene polymorphisms in relation to type 2 diabetes mellitus cases among north Indian population

BACKGROUND

Type 2 diabetes mellitus is a multifactorial and polygenic disease, which is considered as a major life threatening problem all over the world. There has been a worldwide effort in the identification of susceptibility genes for type 2 diabetes mellitus and its complications. At present, adequate data is not available dealing with MTHFR (rs1801133) and PPARγ2 (rs1801282) gene polymorphisms and its association with type 2 diabetes mellitus cases among north Indian populations. Thus, we conceived the need for further studies to investigate MTHFR and PPARγ2 gene polymorphisms and their susceptibility to type 2 diabetes mellitus in north Indian population.

MATERIALS AND METHODS

In this study, a total 175 subjects including 87 type 2 diabetes mellitus cases and 88 controls were enrolled. MTHFR and PPARγ2 gene polymorphisms in the cases and controls were evaluated by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP).

RESULTS

The MTHFR gene CC, CT, TT genotype frequencies obtained were 40%, 43%, and 17% in type 2 diabetes mellitus cases and 56%, 29%, and 15% in healthy controls respectively. The OR for CC was 0.54 (95%CI 0.29-0.98, P=0.041, χ(2)=4.18, power=0.98), for CT 1.76 (95%CI 0.94-3.30, P=0.07, χ(2)=3.2, power=0.96), and for TT 1.2 (95%CI 0.53-2.70, P=0.66, χ(2)=0.198, power=0.76). The PPARγ2 gene GG CG, CC genotype frequencies obtained were 28%, 41%, and 31% in cases and 40%, 39%, and 21% in healthy controls respectively. OR for GG was 0.58 (95%CI 0.30-1.09, P=0.08, χ(2)=2.9, power=0.96), for CG 1.12 (95%CI 0.61-2.05, P=0.71, χ(2)=0.137, power=0.778), and for CC 1.63 (95%CI 0.82-3.23, P=0.156, χ(2)=2.01, power=0.92).

CONCLUSION

It might be recommended that MTHFR CC genotype seems to be a good marker for the early identification of population at risk of type 2 diabetes mellitus. While we have detected significant difference in allelic frequencies of PPARγ2 C (Proline) and G (Alanine), but at genotypic level significant difference was not detected in this case-control study. Further study with larger groups may be required to validate the study.

Effect of the PPARG2 Pro12Ala polymorphism and clinical risk factors for diabetes mellitus on HbA1c in the Japanese general population

Background

Although the peroxisome proliferator-activated receptor-γ2 (PPARG2) Pro12Ala gene variant is associated with diabetes mellitus, the associations and interactions of this polymorphism and known clinical risk factors with glycated hemoglobin (HbA1c) remain poorly understood. We investigated if carrying the Ala allele was inversely associated with HbA1c level and examined possible interactions.

Methods

This cross-sectional analysis used data collected from 1281 men and 1356 women aged 40 to 69 years who completed the baseline survey of the Japan Multi-Institutional Collaborative Cohort Study. PPARG2 polymorphism was determined by multiplex polymerase chain reaction (PCR)-based Invader assay. Multiple linear regression and ANCOVA were used to control for confounding variables (age, body mass index [BMI], energy intake, alcohol, smoking, physical activity, and family history of diabetes) and examine possible interactions.

Results

After adjustment, the Ala allele was significantly inversely associated with HbA1c in women but not in men. Older age, BMI, and family history of diabetes were associated with higher HbA1c in both sexes. When stratified by PPARG2 genotype, these associations were observed in subjects with the Pro12Pro genotype but not in Ala allele carriers. A significant interaction of genotype and BMI on HbA1c was observed in women. Older age, BMI, and family history of diabetes were significantly associated with high-normal HbA1c (≥5.7% NGSP), whereas PPARG2 polymorphism was not.

Conclusions

Although PPARG2 Pro12Ala polymorphism might attenuate associations between known risk factors and HbA1c level, it had a small effect on high-normal HbA1c, as compared with clinical risk factors, in the general population.

Association between PPARγ2 Pro12Ala polymorphism and myocardial infarction and obesity in Han Chinese in Hohhot, China

Activation of the peroxisome proliferator-activated receptor g (PPARg) improves insulin sensitivity and inhibits atherosclerosis. Whether PPARg2 Pro12Ala polymorphism affects myocardial infarction is not clearly understood. We investigated a possible association of PPARg2 Pro12Ala polymorphism with obesity and myocardial infarction in Han Chinese in Hohhot, Inner Mongolia, China. We included 121 subjects with myocardial infarction and 137 healthy controls in our study. Triglycerides, total cholesterol, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol were measured. The following information was recorded for each subject: age, gender, body height, body weight, systolic blood pressure, and diastolic blood pressure; the body mass index was calculated. PCR-RFLP was used to examine Pro12Ala polymorphism. There were significant differences in clinical characteristics between myocardial infarction patients and healthy controls, except for diastolic blood pressure and triglycerides. The PP, PA/AA genotype frequencies were 88.4 and 11.6% in myocardial infarction patients and 95.6 and 4.4% in controls, respectively (P = 0.031). Individuals with the A allele had a significantly higher risk of myocardial infarction. The A allele was not an independent risk factor for obesity. We conclude that PPARg2 Pro12Ala polymorphisms are associated with increased risk for myocardial infarction in Han Chinese in Hohhot.

Angiotensinogen gene polymorphisms and food-intake behavior in young, normal female subjects in Japan

OBJECTIVE

We examined whether angiotensinogen (AGT) gene polymorphisms are associated with food preferences in young, normal female subjects.

METHODS

Fifty-two young, normal female subjects (21-22 y old) were recruited. After a 12-h fast, blood samples were obtained to examine the AGT gene polymorphisms (rs699 and rs7079), angiotensin-converting enzyme (ACE) insertion (I)/deletion (D), and adrenergic β3 receptor (ADRB3) gene polymorphisms (rs4994). A trained dietitian interviewed the participants to determine the portion size and frequency of food eaten for 1 wk by using the established questionnaire FFQg 3.0.

RESULTS

The genotypes of the AGT Met235Thr polymorphisms were TT:TC:CC = 2:19:31 (T:C = 0.22:0.78). The genotypes of AGT rs7079 were CC:CA:AA = 26:21:5 (C:A = 0.70:0.30), and those of ACE were DD:DI:II = 5:28:19 (D/I = 0.37:0.63). The genotypes of ADRB3 Trp64Arg were TT:TC:CC = 38:11:3 (T:C = 0.84:0.16). The total caloric intake was greater for those with the MM/MT genotype of AGT Met235Thr than for those with the TT genotype (1993 versus 1698 kcal/d, P < 0.05). The consumption of total lipids, cholesterol, and unsaturated free fatty acids was also higher in those with the MM/MT genotype of AGT Met235Thr than in those with the TT genotype. However, the AGT polymorphism (rs7079) and the ACE I/D were not associated with food preferences. In contrast, the subjects with ADRB3 Trp64 tended to show a high energy intake and preferences for proteins and lipids including fatty acids and cholesterol. They ate more fish and meat. Multiple regression analysis showed that the energy intake in subjects with the MM/MT genotype was independently determined by total lipids (B = 11.7, P < 0.0001) and carbohydrates (B = 4.6, P < 0.0001).

CONCLUSIONS

The AGT Met235Thr polymorphism was significantly associated with a higher caloric intake owing to total fat and carbohydrate consumption.

Common variants of IL6, LEPR, and PBEF1 are associated with obesity in Indian children

The increasing prevalence of obesity in urban Indian children is indicative of an impending crisis of metabolic disorders. Although perturbations in the secretion of adipokines and inflammatory molecules in childhood obesity are well documented, the contribution of common variants of genes encoding them is not well investigated. We assessed the association of 125 common variants from 21 genes, encoding adipocytokines and inflammatory markers in 1,325 urban Indian children (862 normal weight [NW group] and 463 overweight/obese [OW/OB group]) and replicated top loci in 1,843 Indian children (1,399 NW children and 444 OW/OB children). Variants of four genes (PBEF1 [rs3801266] [P = 4.5 × 10(-4)], IL6 [rs2069845] [P = 8.7 × 10(-4)], LEPR [rs1137100] [P = 1.8 × 10(-3)], and IL6R [rs7514452] [P = 2.1 × 10(-3)]) were top signals in the discovery sample. Associations of rs2069845, rs1137100, and rs3801266 were replicated (P = 7.9 × 10(-4), 8.3 × 10(-3), and 0.036, respectively) and corroborated in meta-analysis (P = 2.3 × 10(-6), 3.9 × 10(-5), and 4.3 × 10(-4), respectively) that remained significant after multiple testing corrections. These variants also were associated with quantitative measures of adiposity (weight, BMI, and waist and hip circumferences). Allele dosage analysis of rs2069845, rs1137100, and rs3801266 revealed that children with five to six risk alleles had an approximately four times increased risk of obesity than children with less than two risk alleles (P = 1.2 × 10(-7)). In conclusion, our results demonstrate the association of the common variants of IL6, LEPR, and PBEF1 with obesity in Indian children.

Oxidative stress and inflammation interactions in human obesity

Obesity is often characterized by increased oxidative stress and exacerbated inflammatory outcomes accompanying infiltration of immune cells in adipocytes. The oxidative stress machinery and inflammatory signaling are not only interrelated, but their impairment can lead to an inhibition of insulin responses as well as a higher risk of cardiovascular diseases and associated features. Mitochondria, in addition to energy transformation, play a role in apoptosis, cellular proliferation, as well as in the cellular redox state control. Under certain circumstances, protons are able to re-enter the mitochondrial matrix via different uncoupling proteins, disturbing free radical production by mitochondria. Disorders of the mitochondrial electron transport chain, over-generation of reactive oxygen species, and lipoperoxides or alterations in antioxidant defenses have been reported in situations of obesity and type-2 diabetes. On the other hand, obesity has been linked to a low grade pro-inflammatory state, in which impairments in the oxidative stress and antioxidant mechanism could be involved. The current scientific evidence highlights the need of investigating the interplay between oxidative stress and inflammation with obesity/diabetes onset as well as the interactions of such factors either as a cause or consequence of obesity. The signaling mediated by the activation of inflammatory markers or nuclear factor kappa β and other transcription factors as central regulators of inflammation are key issues to understanding oxidative stress responses in obesity. This review aims at summarizing the main mechanisms and interplay factors between oxidative stress and inflammation in human obesity according to the last 10 years of research in the field.

Nuclear receptor variants in liver disease

This review aims to provide a snapshot of the actual state of knowledge on genetic variants of nuclear receptors (NR) involved in regulating important aspects of liver metabolism. It recapitulates recent evidence for the application of NR in genetic diagnosis of monogenic ("Mendelian") liver disease and their use in clinical diagnosis. Genetic analysis of multifactorial liver diseases such as viral hepatitis or fatty liver disease identifies key players in disease predisposition and progression. Evidence from these analyses points towards a role of NR polymorphisms in common diseases, linking regulatory networks to complex and variable phenotypes. The new insights into NR variants also offer perspectives and cautionary advice for their use as handles towards diagnosis and treatment.

Nuclear receptor variants in liver disease

This review aims to provide a snapshot of the actual state of knowledge on genetic variants of nuclear receptors (NR) involved in regulating important aspects of liver metabolism. It recapitulates recent evidence for the application of NR in genetic diagnosis of monogenic (“Mendelian”) liver disease and their use in clinical diagnosis. Genetic analysis of multifactorial liver diseases such as viral hepatitis or fatty liver disease identifies key players in disease predisposition and progression. Evidence from these analyses points towards a role of NR polymorphisms in common diseases, linking regulatory networks to complex and variable phenotypes. The new insights into NR variants also offer perspectives and cautionary advice for their use as handles towards diagnosis and treatment.

Association study of candidate gene polymorphisms and obesity in a young Mexican-American population from South Texas

BACKGROUND AND AIMS

Obesity is increasingly a health problem and a risk factor for diabetes in young Mexican-American populations. Genetic association studies in older, mostly non-Hispanic populations have reported that polymorphisms in the candidate genes HSD11B1, CRP, ADIPOQ, PPARG, ANKK1, ABCC8 and SERPINF1 are associated with obesity or diabetes. We analyzed the polymorphisms rs846910, rs1205, rs1501299, rs1801282, rs1800497, rs757110 and rs1136287 in these candidate genes, for association with obesity and metabolic traits in a young Mexican-American population from south Texas.

METHODS

Genotyping of the seven common SNPs were performed by allelic discrimination assays in 448 unrelated Mexican Americans (median age = 16 years) from south Texas. χ(2) tests and regression analyses using additive models were used for genetic association analyses adjusting for covariates; p values were corrected for multiple testing by permutation analyses.

RESULTS

rs1800497 (ANKK1) shows association with waist circumference (p = 0.009) and retains the association (p = 0.03) after permutation testing. Analysis of metabolic quantitative traits shows that rs846910 (HSD11B1) was associated with HOMA-IR (p = 0.04) and triglycerides (p = 0.03), and rs1205 (CRP) with HOMA-IR (p = 0.03) and fasting glucose levels (p = 0.007). However, the quantitative traits associations are not maintained after permutation analysis. None of the other SNPs in this study showed associations with obesity or metabolic traits in this young Mexican-American population.

CONCLUSIONS

We report a potential association between rs1800497 (linked to changes in brain dopamine receptor levels) and central obesity in a young Mexican-American 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.

Genotyping of peroxisome proliferator-activated receptor gamma (PPAR-γ) polymorphism (Pro12Ala) in Iranian population

BACKGROUND

The peroxisome proliferator-activated receptor-γ (PPAR-γ) is a nuclear hormone receptor. It is predominantly expressed in adipose tissue and as a receptor for thiazolidinediones, it has drawn attentions towards itself as a key molecule to trigger pathways involving in some diseases such as cancers, type 2 diabetes, inflammations and osteoporosis. A proline changed to alanine in codon 12 of PPAR-γ gene (Pro12Ala) has been known to be responsible for decreased risk of type 2 diabetes. The aim of the present study is to investigate the frequency of Pro12Ala polymorphism in PPAR-γ in healthy Iranian population to compare with other populations. Understanding this polymorphism may help us in better diagnosis, prevention, and therapeutic approaches toward a better management of diseases such as type 2 diabetes and osteoporosis.

METHODS

128 healthy volunteers were enrolled in this study. To determine single nucleotide polymorphisms (SNPs), we did real time polymerase chain reaction (RT-PCR), using TaqMan allelic discrimination assays.

RESULTS

Genotype frequencies for PPAR-γ gene Pro12Ala (rs1801282) polymorphism were 0.86 for CC, 0.14 for CG, 0.00 for GG while allelic frequencies were 0.93 and 0.0.07 for C and G, respectively.

CONCLUSIONS

There are statistical differences between the distribution of the PPAR-γ-2 Pro12Ala polymorphism in other populations and Iranian population.

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.

Pro12Ala polymorphism of the peroxisome proliferator-activated receptor γ2 in patients with fatty liver diseases

AIM: To test the occurrence of the Pro12Ala mutation of the peroxisome proliferator-activated receptor-γ (PPARγ)2-gene in patients with non-alcoholic fatty liver disease (NAFLD) or alcoholic fatty liver disease (AFLD).

METHODS: DNA from a total of 622 specimens including 259 blood samples of healthy blood donors and 363 histologically categorized liver biopsies of patients with NAFLD (n = 263) and AFLD (n = 100) were analyzed by Real-time polymerase chain reaction using allele-specific probes.

RESULTS: In the NAFLD and the AFLD collective, 3% of the patients showed homozygous occurrence of the Ala12 PPARγ2-allele, differing from only 1.5% cases in the healthy population. In NAFLD patients, a high incidence of the Ala12 mutant was not associated with the progression of fatty liver disease. However, we observed a significantly higher risk (odds ratio = 2.50, CI: 1.05-5.90, P = 0.028) in AFLD patients carrying the mutated Ala12 allele to develop inflammatory alterations. The linkage of the malfunctioning Ala12-positive PPARγ2 isoform to an increased risk in patients with AFLD to develop severe steatohepatitis and fibrosis indicates a more prominent anti-inflammatory impact of PPARγ2 in progression of AFLD than of NAFLD.

CONCLUSION: In AFLD patients, the Pro12Ala single nuclear polymorphism should be studied more extensively in order to serve as a novel candidate in biomarker screening for improved prognosis.

Evidences on three relevant obesogenes: MC4R, FTO and PPARγ. Approaches for personalized nutrition

Obesity is a complex disease that results from the interaction between lifestyle (dietary patterns and sedentary habits) and genetic factors. The recognition of a genetic basis for human obesity has driven to identify putative causal genes to understand the pathways that control body mass and fat deposition in humans as well as to provide personalized treatments and prevention strategies to fight against obesity. More than 120 candidate genes have been associated with obesity-related traits. Genome-wide association study has so far identified over 20 novel loci convincingly associated with adiposity. This review is specifically focused on the study of the effects of melanocortin 4 receptor, Peroxisome proliferator-activated receptor γ and fat mass and obesity associated (FTO) gene variants and their interactions with dietary intake, physical activity or drug administration on body weight control. The advances in this field are expected to open new ways in genome-customized diets for obesity prevention and therapy following personalized approaches.

Relationships of dietary patterns with body composition in older adults differ by gender and PPAR-γ Pro12Ala genotype

Purpose

Dietary patterns may better capture the multifaceted effects of diet on body composition than individual nutrients or foods. The objective of this study was to investigate the dietary patterns of a cohort of older adults, and examine relationships of dietary patterns with body composition. The influence of a polymorphism in the peroxisome proliferator-activated receptor-γ (PPAR-γ) gene was considered.

Methods

The Health, Aging and Body Composition (Health ABC) Study is a prospective cohort study of 3,075 older adults. Participants’ body composition and genetic variation were measured in detail. Food intake was assessed with a semi-quantitative food frequency questionnaire (Block Dietary Data Systems, Berkeley, CA), and dietary patterns of 1,809 participants with complete data were derived by cluster analysis.

Results

Six clusters were identified, including a ‘Healthy foods’ cluster characterized by higher intake of low-fat dairy products, fruit, whole grains, poultry, fish and vegetables. An interaction was found between dietary patterns and PPAR-γ Pro12Ala genotype in relation to body composition. While Pro/Pro homozygous men and women in the ‘Healthy foods’ cluster did not differ significantly in body composition from those in other clusters, men with the Ala allele in the ‘Healthy foods’ cluster had significantly lower levels of adiposity than those in other clusters. Women with the Ala allele in the ‘Healthy foods’ cluster differed only in right thigh intermuscular fat from those in other clusters.

Conclusions

Relationships between diet and body composition in older adults may differ by gender and by genetic factors such as PPAR-γ Pro12Ala genotype.

The PPARgamma Pro12Ala variant is associated with insulin sensitivity in Russian normoglycaemic and type 2 diabetic subjects

The second isoform of the PPARgamma2 is specific for adipose tissue. In adipocytes, this isoform is involved in the regulation of adipogenesis and lipid storage, insulin and glucose metabolism. Pro12Ala, a missense mutation in exon 2 of PPARG, reduces transcriptional activity of PPARgamma2 and is shown to be associated with increased insulin sensitivity and protection from T2D. Previously, this polymorphism has never been assessed in a Russian population for its relationship to T2D, insulin resistance, and diabetes-related metabolic traits. In this study, we tested 588 Russian T2D patients and 597 normoglycaemic controls. Carriers of the Pro12 allele and subjects homozygous for Pro/Pro had significantly increased risk of developing T2D (OR 1.43 and 2.04, respectively). In Pro/Pro homozygotes, adjustment for potential confounding risk factors resulted in reducing the OR value from 2.04 to 1.69, but the association remained significant (p=0.046).The Pro/Pro genotype also showed association with increased levels of fasting insulin (p=0.019) in non-diabetic controls and elevated serum triglycerides (p=0.019) in T2D patients. Compared with other genotypes, non-diabetic and diabetic subjects homozygous for Pro/Pro had a significantly higher HOMA-IR score and reduced ISI value. This observation strongly supports the implication of the PPARG Pro12Ala in insulin resistance and T2D in a Russian population.

Association between type 2 diabetes loci and measures of fatness

Background

Type 2 diabetes (T2D) is a metabolic disorder characterized by disturbances of carbohydrate, fat and protein metabolism and insulin resistance. The majority of T2D patients are obese and obesity by itself may be a cause of insulin resistance. Our aim was to evaluate whether the recently identified T2D risk alleles are associated with human measures of fatness as characterized with Dual Energy X-ray Absorptiometry (DEXA).

Methodology/Principal Findings

Genotypes and phenotypes of approximately 3,000 participants from cross-sectional ERF study were analyzed. Nine single nucleotide polymorphisms (SNPs) in CDKN2AB, CDKAL1, FTO, HHEX, IGF2BP2, KCNJ11, PPARG, SLC30A8 and TCF7L2 were genotyped. We used linear regression to study association between individual SNPs and the combined allelic risk score with body mass index (BMI), fat mass index (FMI), fat percentage (FAT), waist circumference (WC) and waist to hip ratio (WHR). Significant association was observed between rs8050136 (FTO) and BMI (p = 0.003), FMI (p = 0.007) and WC (p = 0.03); fat percentage was borderline significant (p = 0.053). No other SNPs alone or combined in a risk score demonstrated significant association to the measures of fatness.

Conclusions/Significance

From the recently identified T2D risk variants only the risk variant of the FTO gene (rs8050136) showed statistically significant association with BMI, FMI, and WC.

Impact of the Pro12Ala polymorphism of the PPAR-Gamma 2 gene on metabolic and clinical characteristics in the Palestinian type 2 diabetic patients

Peroxisome proliferators activated receptor-gamma2 (PPARγ2) represents the transcriptional master regulator of adipocyte differentiation and therefore has been suggested as a candidate gene for obesity, insulin resistance, and dyslipidemia. The objective of the study was to investigate for the first time the potential association of the most common variant Pro12Ala (p.P12A) substitution of the PPARγ2 gene with body mass index (BMI), blood pressure, fasting plasma glucose, plasma total cholesterol, LDL and HDL cholesterol, and plasma triglyceride in a sample of 202 (138 females and 64 male) type 2 diabetic Palestinians. Genotyping of the PPARγ2 p.P12A polymorphism was determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis. The A12 allele was associated with lower fasting plasma glucose (P = .03) but had no influence on blood pressure, BMI, or other metabolic parameters. In obese patients, the p.P12A substitution was associated with elevated total plasma cholesterol levels (P = .02) and a tendency toward increased LDL cholesterol level (P = .06). In conclusion, the p.P12A variant of the PPARγ2 may influence cardiovascular risk through effects on lipid metabolism in obese T2D Palestinian patients.