Pro12Ala polymorphism in the peroxisome proliferator-activated receptor-gamma2 gene is associated with increased antilipolytic insulin sensitivity

A Personalized Diet Approach Study: Interaction between PPAR-γ Pro12Ala and Dietary Insulin Indices on Metabolic Markers in Diabetic Patients

BACKGROUND

The objectives were to investigate the effect of the interaction between peroxisome proliferator-activated receptor gamma (PPAR-γ) Pro12Ala polymorphisms and dietary insulin load and insulin index (DIL and DII) on Cardio-metabolic Markers among diabetic patients.

METHODS

This cross-sectional study was conducted on 393 diabetic patients. Food-frequency questionnaire (FFQ) was used for DIL and DII calculation. PPAR-γ Pro12Ala was genotyped by the PCR-RFLP method. Biochemical markers including TC, LDL, HDL, TG, SOD, CRP, TAC, PTX3, PGF2α. IL18, leptin and ghrelin were measured by standard protocol.

RESULT

Risk-allele carriers (CG, GG) had higher obesity indices WC (P _interaction =0.04), BMI (P _interaction =0.006) and, WC (P _interaction =0.04) compared with individuals with the CC genotype when they consumed a diet with higher DIL and DII respectively. Besides, carriers of the G allele who were in the highest tertile of DIL, had lower HDL (P _interaction =0.04) and higher PGF2α (P _interaction =0.03) and PTX3 (P _interaction =0.03). Moreover, the highest tertile of the DII, showed an increase in IL18 (P _interaction =0.01) and lower SOD (P _interaction =0.03) for risk allele carriers compared to those with CC homozygotes.

CONCLUSION

We revealed PPAR-γ Pro12Ala polymorphism was able to intensify the effect of DIL and DII on CVD risk factors; risk-allele carriers who consumed a diet with high DIL and DII score have more likely to be obese and have higher inflammatory markers. Also, protective factor against CVD risk factors were reduced significantly in this group compared to CC homozygotes. This article is protected by copyright. All rights reserved.

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.

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

Background:

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

Aim:

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

Methods:

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

Results:

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

Conclusion:

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

PPARG Pro12Ala Ala carriers exhibit greater improvements in peripheral insulin sensitivity in response to 12 weeks of aerobic exercise training

The Ala allele of PPARG Pro12Ala ( rs1801282 ) is associated with greater improvements to the glucose metabolism in exercise studies, but whether this extends to peripheral insulin sensitivity is unknown. Our objective was to investigate the effect of PPARG Pro12Ala on exercise-induced changes in peripheral insulin sensitivity. A total of 124 (91 Pro homozygotes and 33 Ala carriers) previously physically inactive healthy young men and women with overweight or class 1 obesity who completed a 12 wk aerobic exercise intervention were included in the analysis. All participants underwent a hyperinsulinemic euglycemic clamp before and after the 12 wk intervention. The prescribed exercise frequency was 5–7 days/wk, and the exercise energy expenditure was 2,100 4,200 kcal/wk for men and 1,600 kcal/wk for women. Insulin sensitivity improved significantly in both genotype groups. However, Ala carriers had a 1.13-fold (95% confidence interval 1.01; 1.26, P = 0.032) greater improvement in insulin sensitivity from baseline compared with Pro homozygotes. Our data support that PPARG Pro12Ala modifies the effect of aerobic exercise on peripheral insulin sensitivity.

Association between PPARG genetic polymorphisms and ischemic stroke risk in a northern Chinese Han population: a case-control study

Two common polymorphisms of the peroxisome proliferator-activated receptor gamma (PPARG) gene, rs1801282 and rs3856806, may be important candidate gene loci affecting the susceptibility to ischemic stroke. This case-control study sought to identify the relationship between these two single-nucleotide polymorphisms and ischemic stroke risk in a northern Chinese Han population. A total of 910 ischemic stroke participants were recruited from the First Hospital of China Medical University, Shenyang, China as a case group, of whom 895 completed the study. The 883 healthy controls were recruited from the Health Check Center of the First Hospital of China Medical University, Shenyang, China. All participants or family members provided informed consent. The study protocol was approved by the Ethics Committee of the First Hospital of China Medical University, China on February 20, 2012 (approval No. 2012-38-1). The protocol was registered with the Chinese Clinical Trial Registry (registration number: ChiCTR-COC-17013559). Plasma genomic DNA was extracted from all participants and analyzed for rs1801282 and rs3856806 single nucleotide polymorphisms using a SNaPshot Multiplex sequencing assay. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated using unconditional logistic regression to estimate the association between ischemic stroke and a particular genotype. Results demonstrated that the G allele frequency of the PPARG gene rs1801282 locus was significantly higher in the case group than in the control group (P < 0.001). Individuals carrying the G allele had a 1.844 fold increased risk of ischemic stroke (OR = 1.844, 95% CI: 1.286-2.645, P < 0.001). Individuals carrying the rs3856806 T allele had a 1.366 fold increased risk of ischemic stroke (OR = 1.366, 95% CI: 1.077-1.733, P = 0.010). The distribution frequencies of the PPARG gene haplotypes rs1801282-rs3856806 in the control and case groups were determined. The frequency of distribution in the G-T haplotype case group was significantly higher than that in the control group. The risk of ischemic stroke increased to 2.953 times in individuals carrying the G-T haplotype (OR = 2.953, 95% CI: 2.082-4.190, P < 0.001). The rs1801282 G allele and rs3856806 T allele had a multiplicative interaction (OR = 3.404, 95% CI: 1.631-7.102, P < 0.001) and additive interaction (RERI = 41.705, 95% CI: 14.586-68.824, AP = 0.860; 95% CI: 0.779-0.940; S = 8.170, 95% CI: 3.772-17.697) on ischemic stroke risk, showing a synergistic effect. Of all ischemic stroke cases, 86% were attributed to the interaction of the G allele of rs1801282 and the T allele of rs3856806. The effect of the PPARG rs1801282 G allele on ischemic stroke risk was enhanced in the presence of the rs3856806 T allele (OR = 8.001 vs. 1.844). The effect of the rs3856806 T allele on ischemic stroke risk was also enhanced in the presence of the rs1801282 G allele (OR = 2.546 vs. 1.366). Our results confirmed that the G allele of the PPARG gene rs1801282 locus and the T allele of the rs3856806 locus may be independent risk factors for ischemic stroke in the Han population of northern China, with a synergistic effect between the two alleles.

Precision medicine in diabetes prevention, classification and management

Diabetes has become a major burden of healthcare expenditure. Diabetes management following a uniform treatment algorithm is often associated with progressive treatment failure and development of diabetic complications. Recent advances in our understanding of the genomic architecture of diabetes and its complications have provided the framework for development of precision medicine to personalize diabetes prevention and management. In the present review, we summarized recent advances in the understanding of the genetic basis of diabetes and its complications. From a clinician's perspective, we attempted to provide a balanced perspective on the utility of genomic medicine in the field of diabetes. Using genetic information to guide management of monogenic forms of diabetes represents the best-known examples of genomic medicine for diabetes. Although major strides have been made in genetic research for diabetes, its complications and pharmacogenetics, ongoing efforts are required to translate these findings into practice by incorporating genetic information into a risk prediction model for prioritization of treatment strategies, as well as using multi-omic analyses to discover novel drug targets with companion diagnostics. Further research is also required to ensure the appropriate use of this information to empower individuals and healthcare professionals to make personalized decisions for achieving the optimal outcome.

Role of peroxisome proliferator-activated receptor gamma Pro12Ala polymorphism in human adipose tissue: assessment of adipogenesis and adipocyte glucose and lipid turnover

The protective mechanisms of peroxisome proliferator-activated receptor gamma (PPARγ) Pro12Ala polymorphism in type 2 diabetes (T2D) are unclear. We obtained subcutaneous adipose tissue (AT) before and 3 h after oral glucose (OGTT) in carriers and non-carriers of the Ala allele (12 Pro/Pro, 15 Pro/Ala, and 13 Ala/Ala). Adipogenesis, adipocyte glucose uptake and lipolysis as well as PPARγ target gene expression were investigated and compared between the genotype groups. During fasting and post-OGTT, neither basal nor insulin-stimulated adipocyte glucose uptake differed between genotypes. Compared to fasting, a decreased hormone-sensitive lipase gene expression in Pro/Pro (p < 0.05) was accompanied with a higher antilipolytic effect of insulin post-OGTT (p < 0.01). The adipocyte size was similar across groups. Preadipocyte differentiation rates between Pro/Pro and Ala/Ala were unchanged. In conclusion, no major differences in AT differentiation, glucose uptake, lipolysis or expression of PPARγ target genes were observed between different PPARγ Pro12Ala genotypes. Albeit small, our study may suggest that other pathways in AT or effects exerted in other tissues might contribute to the Pro12Ala-mediated protection against T2D.

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

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

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.

Obstacles to Translating Genotype-Phenotype Correlates in Metabolic Disease

Type 2 diabetes mellitus is a polygenic disease with a variable phenotype. Many genetic associations have been described; however, understanding their underlying pathophysiological role in Type 2 diabetes mellitus is important for development of future therapeutic targets. Here, we review the physiological mechanisms of diabetes-associated variants that affect glycemia.

Improvement of cardiometabolic markers after fish oil intervention in young Mexican adults and the role of PPARα L162V and PPARγ2 P12A

Polyunsaturated fatty acids (PUFA) contained in fish oil (FO) are ligands for peroxisome proliferator-activated receptors (PPAR) that may induce changes in cardiometabolic markers. Variation in PPAR genes may influence the beneficial responses linked to FO supplementation in young adults. The study aimed to analyze the effect of FO supplementation on glucose metabolism, circulating lipids and inflammation according to PPARα L162V and PPARγ2 P12A genotypes in young Mexican adults. 191 young, non-smoking subjects between 18 and 40 years were included in a one-arm study. Participants were supplemented with 2.7 g/day of EPA+DHA, during six weeks. Dietary analysis, body composition measurements and indicators for glucose metabolism, circulating lipids, and markers for inflammation were analyzed before and after intervention. An overall decrease in triglycerides (TG) and an increase in HS-ω3 index were observed in all subjects [-4.1 mg/dL, (SD:±51.7), P=.02 and 2.6%, (SD:±1.2), P<.001 respectively]. Mean fasting insulin and glycated hemoglobin (HbA1c%) were significantly decreased in all subjects [-0.547mlU/L, (SD:±10.29), P=.034 and-0.07%, (SD:±0.3), P<.001 respectively], whereas there was no change in body composition, fasting glucose, adiponectin and inflammatory markers. Subjects carrying the minor alleles of PPARα L162V and PPARγ2 P12A had higher responses in reduction of TG and fasting insulin respectively. Interestingly, doses below 2.7 g/day (1.8 g/day) were sufficient to induce a significant reduction in fasting insulin and HbA1c% from baseline (P=.019 and P<.001). The observed responses in triglycerides and fasting insulin in the Mexican population give further evidence of the importance of FO supplementation in young people as an early step towards the prevention of cardiometabolic disease.

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.

The Pro12Ala Polymorphism of the Peroxisome Proliferator-Activated Receptor Gamma Gene Modifies the Association of Physical Activity and Body Mass Changes in Polish Women

Peroxisome proliferator-activated receptor γ is a key regulator of adipogenesis, responsible for fatty acid storage and maintaining energy balance in the human body. Studies on the functional importance of the PPARG Pro12Ala polymorphic variants indicated that the observed alleles may influence body mass measurements; however, obtained results were inconsistent. We have decided to check if body mass changes observed in physically active participants will be modulated by the PPARG Pro12Ala genotype. The genotype distribution of the PPARG Pro12Ala allele was examined in a group of 201 Polish women measured for selected body mass variables before and after the completion of a 12-week training program. The results of our experiment suggest that PPARG genotype can modulate training-induced body mass measurements changes: after completion of the training program, Pro12/Pro12 homozygotes were characterised by a greater decrease of body fat mass measurements in comparison with 12Ala allele carriers. These results indicate that the PPARG 12Ala variant may impair the training-induced positive effects on body mass measurements; however, the detailed mechanism of such interaction remained unclear and observed correlation between PPARG genotype and body mass differential effects should be interpreted with caution.

Peroxisome proliferator-activated receptor gamma (PPARG) modulates free fatty acid receptor 1 (FFAR1) dependent insulin secretion in humans

Genetic variation in FFAR1 modulates insulin secretion dependent on non-esterified fatty acid (NEFA) concentrations. We previously demonstrated lower insulin secretion in minor allele carriers of PPARG Pro12Ala in high-NEFA environment, but the mode of action could not been revealed. We tested if this effect is mediated by FFAR1 in humans. Subjects with increased risk of diabetes who underwent oral glucose tolerance tests were genotyped for 7 tagging SNPs in FFAR1 and PPARG Pro12Ala. The FFAR1 SNPs rs12462800 and rs10422744 demonstrated interactions with PPARG on insulin secretion. FFAR1 rs12462800 (p = 0.0006) and rs10422744 (p = 0.001) were associated with reduced insulin secretion in participants concomitantly carrying the PPARG minor allele and having high fasting FFA. These results suggest that the minor allele of the PPARG SNP exposes its carriers to modulatory effects of FFAR1 on insulin secretion. This subphenotype may define altered responsiveness to FFAR1-agonists, and should be investigated in further studies.

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?

Association between the Pro12Ala polymorphism of the peroxisome proliferator-activated receptor gamma gene and strength athlete status

Background

The 12Ala allele of the Peroxisome Proliferator-Activated Receptor gamma gene (PPARG) Pro12Ala polymorphism produces a decreased binding affinity of the PPARγ2 protein, resulting in low activation of the target genes. The 12Ala allele carriers display a significantly improved insulin sensitivity that may result in better glucose utilisation in working skeletal muscles. We hypothesise that the PPARG 12Ala allele could be associated with strength athlete status in Polish athletes.

Methodology

The genotype distribution of PPARG Pro12Ala was examined in 660 Polish athletes. The athletes were stratified into four subgroups: endurance, strength-endurance, sprint-strength and strength. Control samples were prepared from 684 unrelated sedentary volunteers. A χ² test was used to compare the PPARG Pro12Ala allele and genotype frequencies between the different groups of athletes and control subjects. Bonferroni’s correction for multiple testing was applied.

Results

A statistically significant higher frequency of PPARG 12Ala alleles was observed in the subgroup of strength athletes performing short-term and very intense exertion characterised by predominant anaerobic energy production (13.2% vs. 7.5% in controls; P = 0.0007).

Conclusion

The PPARG 12Ala allele may be a relevant genetic factor favouring strength abilities in professional athletes, especially in terms of insulin-dependent metabolism, a shift of the energy balance towards glucose utilisation and the development of a favourable weight-to-strength ratio.

The effect of PPARG gene polymorphisms on the risk of coronary heart disease: a meta-analysis

The peroxisome proliferator-activated receptor-γ (PPARG) is a member of the nuclear hormone receptor superfamily that has attracted considerable attention as a candidate gene for coronary heart disease (CHD) based on its function as a key factor involved in the regulation of lipid and glucose metabolism. In the past decade, a number of case-control studies have been carried out to investigate the relationship between the PPARG polymorphisms and CHD. However, these studies have yielded contradictory results. To derive a more precise estimation of the relationship, a meta-analysis of 33 studies including a total of 12,340 cases and 17,471 controls on 3 PPARG polymorphisms (Pro12Ala, C161T and C1431T) was performed. In a combined analysis, the summary per-allele odds ratio for CHD was 1.02 (95 % CI: 0.93-1.13), 0.86 (95 % CI: 0.72-1.02), and 0.92 (95 % CI: 0.74-1.16) for PPARG 12Ala, 161T and 1431T alleles, respectively. No significant results were observed under dominant or recessive genetic models for these polymorphisms in almost all comparisons. In the stratified analyses according to ethnicity, sample size, CHD endpoints and HWE status, no evidence of any gene-disease association was obtained. Our results suggest that the Pro12Ala, C161T and C1431T polymorphisms of PPARG gene are not associated with CHD susceptibility.

Polymorphism of peroxisome proliferator-activated receptor γ (PPARγ) Pro12Ala in the Iranian population: relation with insulin resistance and response to treatment with pioglitazone in type 2 diabetes

The peroxisome proliferator-activated receptor γ (PPARγ) has important effects on insulin sensitivity, obesity and diabetes. Pioglitazone improves insulin sensitivity by activating PPARγ. In view of inter-individual variability in therapeutic response to pioglitazone, this study was designed to search for an association between type 2 diabetes mellitus and Pro12Ala single-nucleotide polymorphism (SNP) in PPARγ (SNP rs1801282) and to investigate whether these genetic variants affect pioglitazone response in an Iranian population. A total of 101 patients with type 2 diabetes were treated for 12 weeks with pioglitazone (15 mg/day). Paraclinical parameters were measured before and after therapy. We genotyped 128 control participants without diabetes and all patients with type 2 diabetes. The Pro12Ala polymorphism in PPARγ was detected with real-time PCR. The Ala allele was found in 7% of the control participants vs. 3% of those with type 2 diabetes (P=0.04). The genotypic frequencies of Pro/Ala were 14.06% in the former group vs. 5.94% in the latter (P=0.036). There were significant changes in some laboratory values and biochemical markers of insulin sensitivity after pioglitazone therapy. The Pro12Ala polymorphism was associated with significant changes in insulin-to-glucose ratio after treatment (P=0.015 and P=0.005). Our findings suggest that in carriers of the 12Ala variant, pioglitazone significantly reduced the risk of type 2 diabetes, and in diabetic patients with the Pro12Ala genotype, the therapeutic response to treatment was better than in patients with the Pro12Pro genotype, although the difference between groups did not reach statistical significance.

Genetics of adipose tissue biology

Adipose tissue morphology and release of free fatty acids, as well as peptide hormones, are believed to contribute to obesity and related metabolic disorders. These adipose tissue phenotypes are influenced by adiposity, but there is also a strong hereditary impact. Polymorphisms in numerous adipose-expressed genes have been evaluated for association with adipocyte and clinical phenotypes. In our opinion, some results are convincing. Thus ADRB2 and GPR74 genes are associated with adipocyte lipolysis, GPR74 also with BMI; PPARG and SREBP1, which promote adipogenesis and lipid storage, are associated with T2D and possible adiposity; ADIPOQ and ARL15 are associated with circulating levels of adiponectin, ARL15 also with coronary heart disease. We anticipate that the use of complementary approaches such as expression profiling and RNAi screening, and studies of additional levels of gene regulation, that is, miRNA and epigenetics, will be important to unravel the genetics of adipose tissue function.

Association of indices of liver and adipocyte insulin resistance with 19 confirmed susceptibility loci for type 2 diabetes in 6,733 non-diabetic Finnish men

AIMS/HYPOTHESIS

Of the confirmed type 2 diabetes susceptibility loci only a few are known to affect insulin sensitivity. We examined the association of indices of hepatic and adipocyte insulin resistance (IR) with 19 confirmed type 2 diabetes risk loci in a large population-based study.

METHODS

Non-diabetic participants (n = 8,460, age 57.3 ± 7.0 years, BMI 26.8 ± 3.8 kg/m(2); mean ± SD) from a population-based cohort underwent an OGTT. Of them, 6,733 non-diabetic men were genotyped for single nucleotide polymorphisms (SNPs) in or near PPARG2 (also known as PPARG), KCNJ11, TCF7L2, SLC30A8, HHEX, CDKN2B, IGF2BP2, CDKAL1, HNF1B, WFS1, JAZF1, CDC123, TSPAN8, THADA, ADAMTS9, NOTCH2, KCNQ1, MTNR1B and SNP rs7480010. We investigated hepatic IR with a new index of liver IR. The adipocyte IR index was defined as a product of fasting NEFA and plasma insulin levels.

RESULTS

Type 2 diabetes risk SNPs in or near KCNJ11 and HHEX were significantly (p < 0.0013), and those in or near CDKN2B, NOTCH2 and MTNR1B were nominally (p < 0.05), associated with decreased liver IR index. The Pro12 allele of PPARG2 was significantly associated with a high adipocyte IR index and nominally associated with high liver IR.

CONCLUSIONS/INTERPRETATION

The Pro12 allele of PPARG2 seems to impair insulin's antilipolytic effect, leading to high NEFA release in the fasting state and IR. In addition, the type 2 diabetes risk alleles of KCNJ11 and HHEX, which are known to impair insulin secretion, were associated with increased hepatic insulin sensitivity.

Body mass index and obesity- and diabetes-associated genotypes and risk for pancreatic cancer

BACKGROUND

The genetic factors predisposing individuals with obesity or diabetes to pancreatic cancer have not been identified.

AIMS

To investigate the hypothesis that obesity- and diabetes-related genes modify the risk of pancreatic cancer.

METHODS

We genotyped 15 single nucleotide polymorphisms of fat mass and obesity-associated (FTO), peroxisome proliferators-activated receptor gamma (PPARγ), nuclear receptor family 5 member 2 (NR5A2), AMPK, and ADIPOQ genes in 1,070 patients with pancreatic cancer and 1,175 cancer-free controls. Information on risk factors was collected by personal interview. Adjusted ORs (AOR) and 95% CIs were calculated using unconditional logistic regression.

RESULTS

The PPARγ P12A GG genotype was inversely associated with risk of pancreatic cancer (AOR, 0.21; 95% CI, 0.07-0.62). Three NR5A2 variants that were previously identified in a genome-wide association study were significantly associated with reduced risk of pancreatic cancer, AORs ranging from 0.57 to 0.79. Two FTO gene variants and one ADIPOQ variant were differentially associated with pancreatic cancer according to levels of body mass index (BMI; P(interaction) = 0.0001, 0.0015, and 0.03). For example, the AOR (95% CI) for FTO IVS1-2777AC/AA genotype was 0.72 (0.55-0.96) and 1.54 (1.14-2.09) in participants with a BMI of less than 25 or 25 kg/m(2) or more, respectively. We observed no significant association between AMPK genotype and pancreatic cancer and no genotype interactions with diabetes or smoking.

CONCLUSION

Our findings suggest the PPARγ P12A GG genotype and NR5A2 variants may reduce the risk for pancreatic cancer. A positive association of FTO and ADIPOQ gene variants with pancreatic cancer may be limited to persons who are overweight.

IMPACT

The discovery of genetic factors modifying the risk of pancreatic cancer may help to identify high-risk individuals for prevention efforts.

Body mass index and obesity- and diabetes-associated genotypes and risk for pancreatic cancer

BACKGROUND

The genetic factors predisposing individuals with obesity or diabetes to pancreatic cancer have not been identified.

AIMS

To investigate the hypothesis that obesity- and diabetes-related genes modify the risk of pancreatic cancer.

METHODS

We genotyped 15 single nucleotide polymorphisms of fat mass and obesity-associated (FTO), peroxisome proliferators-activated receptor gamma (PPARγ), nuclear receptor family 5 member 2 (NR5A2), AMPK, and ADIPOQ genes in 1,070 patients with pancreatic cancer and 1,175 cancer-free controls. Information on risk factors was collected by personal interview. Adjusted ORs (AOR) and 95% CIs were calculated using unconditional logistic regression.

RESULTS

The PPARγ P12A GG genotype was inversely associated with risk of pancreatic cancer (AOR, 0.21; 95% CI, 0.07-0.62). Three NR5A2 variants that were previously identified in a genome-wide association study were significantly associated with reduced risk of pancreatic cancer, AORs ranging from 0.57 to 0.79. Two FTO gene variants and one ADIPOQ variant were differentially associated with pancreatic cancer according to levels of body mass index (BMI; P(interaction) = 0.0001, 0.0015, and 0.03). For example, the AOR (95% CI) for FTO IVS1-2777AC/AA genotype was 0.72 (0.55-0.96) and 1.54 (1.14-2.09) in participants with a BMI of less than 25 or 25 kg/m(2) or more, respectively. We observed no significant association between AMPK genotype and pancreatic cancer and no genotype interactions with diabetes or smoking.

CONCLUSION

Our findings suggest the PPARγ P12A GG genotype and NR5A2 variants may reduce the risk for pancreatic cancer. A positive association of FTO and ADIPOQ gene variants with pancreatic cancer may be limited to persons who are overweight.

IMPACT

The discovery of genetic factors modifying the risk of pancreatic cancer may help to identify high-risk individuals for prevention efforts.

Polymorphisms in PPARD, PPARG and APM1 associated with four types of traditional Chinese medicine constitutions

Based on the theory of constitution of Traditional Chinese Medicine (TCM), the human population is divided into nine constitutions including one balanced constitution (Normality) and eight unbalanced constitutions (Yang-deficiency, Yin-deficiency, Phlegm-wetness, Qi-deficiency, Wetness-heat, Blood stasis, Depressed constitution, and Inherited special constitution). Different constitutions have specific metabolic features and different susceptibility to certain diseases. However, whether a genetic basis accounts for such constitution classification is yet to be determined. Here we performed a genetic study to assess the association between genetic variations of metabolic genes including PPARD, PPARG and APM1 and the constitutions. A total of 233 individuals of the Han population in China were classified into four groups, Normality, Yang-deficiency, Yin-deficiency and Phlegm-wetness with whom 23 single nucleotide polymorphisms (SNPs) in the three genes were genotyped using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. Biased distribution of PPARD rs2267669 and rs2076167, APM1 rs7627128 and rs1063539 in Yang-deficiency, PPARG Pro12Ala in Yin-deficiency and PPARD rs2076167, APM1 rs266729 and rs7627128 in Phlegm-wetness were observed. The frequencies of Haplotype13 (Hap13) of PPARG in Yin-deficiency, Hap25 of APM1 in Yang-deficiency and Hap2 of PPARD and Hap14 of PPARG in Phlegm-wetness, were significantly different from those in Normality, suggesting those might be group-associated haplotypes. These results suggested that single SNP and haplotypes of PPARD, PPARG and APM1 may underlie the genetic basis of the constitutions classified in TCM.

The Ala allele in the PPAR-gamma2 gene is associated with reduced risk of type 2 diabetes mellitus in Caucasians and improved insulin sensitivity in overweight subjects. Br J Nutr. 2010;104:488-497. [PMID: 20420754 DOI: 10.1017/s0007114510000851]

The purpose of the present study was to identify the association of the Pro12Ala polymorphism in the PPAR-gamma2 gene with diabetes, insulinaemia and insulin resistance. A meta-analysis study was carried out based on studies conducted in the last 10 years, using the databases PubMed, ISI Web of Knowledge, High Wire Press and Scielo, and the reference lists of the obtained articles. We included original studies that showed the relationship between the Pro12Ala polymorphism in the PPAR-gamma2 gene and type 2 diabetes mellitus (T2DM), insulinaemia and insulin resistance. Statistical analyses were conducted using the program RevMAn 5.0. The Mantel-Haenszel test was used to estimate the OR and the 95 % CI of the dichotomous variable, while the standardised effect size was used to estimate the average standardised mean difference and 95 % CI of continuous variables. The studies were subgrouped by ethnicity and overweight status. Forty-one studies were analysed, including a global sample of 30 612 subjects. We found a significant association of the Ala allele with the lowest risk of T2DM in Caucasians (OR 0.80; 95 % CI 0.65, 0.98), lower serum insulin (standardised effect size: - 0.05; 95 % CI - 0.09, - 0.00; P = 0.04), and greater sensitivity to insulin in overweight individuals (homeostasis model assessment of insulin resistance standardised effect size: - 0.07; 95 % CI - 0.13, - 0.01; P = 0.02). Considering that the Pro12Ala polymorphism in the PPAR-gamma2 gene is one of the factors related to insulin sensitivity, the present study demonstrated a significant effect of the Ala allele on lower development of T2DM in Caucasians and greater sensitivity to insulin in overweight subjects.

Improvements in glucose homeostasis in response to regular exercise are influenced by the PPARG Pro12Ala variant: results from the HERITAGE Family Study

AIMS/HYPOTHESIS

Exercise training improves glucose homeostasis, but large inter-individual differences are reported, suggesting a role of genetic factors. We investigated whether variants either confirmed or newly identified as diabetes susceptibility variants through genome-wide association studies (GWAS) modulate changes in phenotypes derived from an IVGTT in response to an endurance training programme.

METHODS

We analysed eight polymorphisms in seven type 2 diabetes genes (CDKAL1 rs7756992; CDKN2A and CDKN2B rs10811661 and rs564398; HHEX rs7923837; IGF2BP2 rs4402960; KCNJ11 rs5215; PPARG rs1801282; and TCF7L2 rs7903146) in a maximum of 481 sedentary, non-diabetic white individuals, who participated in a 20-week endurance training programme. Associations were tested between the variants and changes in IVGTT-derived phenotypes.

RESULTS

The only evidence of association with training response was found with PPARG rs1801282 (Pro12Ala). We observed that Ala carriers experienced greater increase in overall glucose tolerance (Deltaglucose disappearance index Ala/Ala 0.22 +/- 0.22, Pro/Ala 0.14 +/- 0.06, Pro/Pro 0.004 +/- 0.03; p = 0.0008), glucose effectiveness (Ala/Ala 0.28 +/- 0.41, Pro/Ala 0.44 +/- 0.14, Pro/Pro 0.09 +/- 0.06; p = 0.004), acute insulin response to glucose (Ala/Ala 64.21 +/- 37.73, Pro/Ala -11.92 +/- 40.30, Pro/Pro -46.30 +/- 14.70; p = 0.03) and disposition index (Ala/Ala 551.8 +/- 448.5, Pro/Ala 534.6 +/- 218.3, Pro/Pro -7.44 +/- 88.18; p = 0.003).

CONCLUSIONS/INTERPRETATION

Compared with Pro/Pro individuals, PPARG Ala carriers experienced greater improvements in glucose and insulin metabolism in response to regular endurance training. However, we did not find evidence of association between type 2 diabetes susceptibility variants recently identified through GWAS and glucose homeostasis response to exercise. Our results extend those of previous studies showing that Ala carriers appear to be more responsive to beneficial health effects of lifestyle interventions.

The PPAR-gamma Pro12Ala polymorphism associates with weight gain during GH-treatment in short children born small for gestational age

CONTEXT

Short children born small for gestational age (SGA) have a lean phenotype with lower insulin sensitivity and higher blood pressure. GH treatment results in weight gain, and a decrease in blood pressure and insulin sensitivity. However, not all children respond in the same way. The Pro12Ala polymorphism of the peroxisome proliferator-activated receptor (PPAR-gamma) gene is inversely associated with body mass index (BMI), changes in BMI and the risk to develop type 2 diabetes mellitus.

OBJECTIVE

To analyze the contribution of the PPAR-gamma Pro12Ala polymorphism to GH induced changes in determinants of metabolic and cardiovascular disease in short SGA children.

METHODS

PPAR-gamma was genotyped in 238 Caucasian short SGA children (mean age 7.5 years). Height, weight, blood pressure, and serum lipids were measured before start and during 4 years of GH treatment. In addition, glucose homeostasis by homeostasis model assessment insulin resistance ratio (HOMA-IR) (n=148) and by frequently sampled i.v. glucose tolerance test (n=51), and body composition by dual energy X-ray absorptiometry (n=79) were measured.

RESULTS

At baseline, the Ala12 allele was not associated with any determinant of metabolic and cardiovascular disease. After 4 years of GH treatment, the increase in weight for height SDS and BMI SDS was significantly greater in carriers of an Ala12 allele than in noncarriers. The change in all other parameters was not associated with Pro12Ala genotype.

CONCLUSION

The Ala12 variant of the PPAR-gamma gene is associated with higher weight gain during GH treatment but not with changes in determinants of metabolic and cardiovascular diseases in Caucasian subjects born SGA.

Pathomechanisms of type 2 diabetes genes

Type 2 diabetes mellitus is a complex metabolic disease that is caused by insulin resistance and beta-cell dysfunction. Furthermore, type 2 diabetes has an evident genetic component and represents a polygenic disease. During the last decade, considerable progress was made in the identification of type 2 diabetes risk genes. This was crucially influenced by the development of affordable high-density single nucleotide polymorphism (SNP) arrays that prompted several successful genome-wide association scans in large case-control cohorts. Subsequent to the identification of type 2 diabetes risk SNPs, cohorts thoroughly phenotyped for prediabetic traits with elaborate in vivo methods allowed an initial characterization of the pathomechanisms of these SNPs. Although the underlying molecular mechanisms are still incompletely understood, a surprising result of these pathomechanistic investigations was that most of the risk SNPs affect beta-cell function. This favors a beta-cell-centric view on the genetics of type 2 diabetes. The aim of this review is to summarize the current knowledge about the type 2 diabetes risk genes and their variants' pathomechanisms.

PPARγ2 polymorphism and human health

The nuclear hormone receptor peroxisome proliferator activated receptor gamma (PPARγ) is an important transcription factor regulating adipocyte differentiation, lipid and glucose homeostasis, and insulin sensitivity. Numerous genetic mutations of PPARγ have been identified and these mutations positively or negatively regulate insulin sensitivity. Among these, a relatively common polymorphism of PPARγ, Pro12Ala of PPARγ2, the isoform expressed only in adipose tissue has been shown to be associated with lower body mass index, enhanced insulin sensitivity, and resistance to the risk of type 2 diabetes in human subjects carrying this mutation. Subsequent studies in different ethnic populations, however, have revealed conflicting results, suggesting a complex interaction between the PPARγ2 Pro12Ala polymorphism and environmental factors such as the ratio of dietary unsaturated fatty acids to saturated fatty acids and/or between the PPARγ2 Pro12Ala polymorphism and genetic factors such as polymorphic mutations in other genes. In addition, this polymorphic mutation in PPARγ2 is associated with other aspects of human diseases, including cancers, polycystic ovary syndrome, Alzheimer disease and aging. This review will highlight findings from recent studies.

Effect of the Pro12Ala polymorphism of the PPAR gamma 2 gene on response to pioglitazone treatment in menopausal women

OBJECTIVE

To investigate the influence of the Pro12Ala polymorphism of the PPAR gamma 2 gene on metabolic and hormonal response to pioglitazone treatment in obese postmenopausal women.

DESIGN

We included 102 obese (body mass index [BMI] >or=30 kg/m2) and 97 nonobese (BMI <or=27 kg/m2) postmenopausal women. Anthropometric data were collected, and fasting glucose, insulin, leptin, follicle-stimulating hormone, luteinizing hormone, dehydroepiandrosterone, dehydroepiandrosterone sulfate, testosterone, estrone, estradiol, and adiponectin were measured and the PPAR gamma 2 Pro12Ala genotypes were determined. Eighty-three obese postmenopausal women were treated with pioglitazone 15 mg/day for 15 days, and hormone levels and insulin resistance (homeostasis model assessment of insulin resistance) were assessed before and after treatment.

RESULTS

Obese women had a higher BMI, waist-to-hip ratio, fasting glucose, insulin, homeostasis model assessment of insulin resistance, leptin, dehydroepiandrosterone, estradiol, testosterone, and adiponectin levels, whereas the follicle-stimulating hormone level was lower. Genotype frequencies were similar in obese and nonobese women. Analysis of the whole group showed that women with the Pro/Ala genotype had a higher BMI, waist-to-hip ratio, and fasting glucose (P < 0.04, P < 0.02, and P < 0.004, respectively) than the group with the Pro/Pro genotype. After pioglitazone treatment, glucose levels decreased in both genotypes, but at a greater amount in carriers of the Pro/Ala genotype (-15 mg/dL vs -7 mg/dL, P < 0.003). However, insulin and homeostasis model assessment of insulin resistance levels were lower in carriers of the Pro/Pro genotype (-4.0 vs 0.7 IU/L, P=0.009 and -1.0 vs -0.08, P = 0.03, respectively).

CONCLUSIONS

The Pro/Ala genotype of PPAR gamma 2 was associated with obesity and higher fasting glucose. Pioglitazone treatment in obese women with the Pro/Ala genotype induced a greater glucose decrease, and obese women may derive more benefit from this drug.

Personalized nutrition for the prevention of cardiovascular disease: a future perspective

Cardiovascular disease (CVD) is responsible for significant morbidity and mortality in the Western and developing world. This multi-factorial disease is influenced by many environmental and genetic factors. At present, public health advice involves prescribed population-based recommendations, which have been largely unsuccessful in reducing CVD risk. This is, in part, due to individual variability in response to dietary manipulations, that arises from nutrient-gene interactions (defined by the term 'nutrigenetics'). The shift towards personalized nutritional advice is a very attractive proposition, where, in principle, an individual can be given dietary advice specifically tailored to their genotype. However, the evidence-base for the impact of interactions between nutrients and fixed genetic variants on biomarkers of CVD risk is still very limited. This paper reviews the evidence for interactions between dietary fat and two common polymorphisms in the apolipoprotein E and peroxisome proliferator-activated receptor-gamma genes. Although an increased understanding of how these and other genes influence response to nutrients should facilitate the progression of personalized nutrition, the ethical issues surrounding its routine use need careful consideration.

Thiazolidinediones and the preservation of beta-cell function, cellular proliferation and apoptosis

The thiazolidinediones (TZDs) or glitazones are pharmaceutical agents that have profound effects on energy expenditure and conservation. They also exert significant anti-inflammatory effects and influence cell proliferation and cell death. The drugs are primarily used in clinical practice in the treatment of patients with type 2 diabetes mellitus, a disorder of insulin resistance that occurs when the pancreatic beta-cells are unable to produce adequate amounts of insulin to maintain euglycaemia. Loss of pancreatic beta-cell function in type 2 diabetes is progressive and often precedes overt diabetes by 10 years or more, as was shown by the United Kingdom Prospective Diabetes Study. Any therapeutic or preventive approach that would limit or reverse loss of beta-cell function in diabetes would have profound effects on the morbidity associated with this widespread disease. Evidence suggesting a potential role of TZDs in preserving beta-cell function in type 2 diabetes as well as the ability of these agents to exert anti-inflammatory and proapoptotic anticancer effects, and their ability to promote cellular proliferation in various organs is reviewed.

Nutrigenetics and CVD: what does the future hold?: Symposium on ‘Diet and CVD’

CVD is a common killer in both the Western world and the developing world. It is a multifactorial disease that is influenced by many environmental and genetic factors. Although public health advice to date has been principally in the form of prescribed population-based recommendations, this approach has been surprisingly unsuccessful in reducing CVD risk. This outcome may be explained, in part, by the extreme variability in response to dietary manipulations between individuals and interactions between diet and an individual's genetic background, which are defined by the term ‘nutrigenetics’. The shift towards personalised nutritional advice is a very attractive proposition. In principle an individual could be genotyped and given dietary advice specifically tailored to their genetic make-up. Evidence-based research into interactions between fixed genetic variants, nutrient intake and biomarkers of CVD risk is increasing, but still limited. The present paper will review the evidence for interactions between dietary fat and three common polymorphisms in theapoE,apoAIandPPARγgenes. Increased knowledge of how these and other genes influence dietary response should increase the understanding of personalised nutrition. While targeted dietary advice may have considerable potential for reducing CVD risk, the ethical issues associated with its routine use need careful consideration.

Impact of peroxisome proliferator-activated receptors gamma and delta on adiposity in toddlers and preschoolers in the GENESIS Study

Peroxisome proliferator-activated receptor gamma (PPAR gamma) and peroxisome proliferator-activated receptor delta (PPAR delta) are promising candidate genes for obesity. Associations between adiposity-related phenotypes and genetic variation in PPAR gamma (Pro12Ala and C1431T), as well as PPAR delta (T+294C) were assessed in 2,102 Greek children aged 1-6 years, as part of a large-scale epidemiological study (Growth, Exercise and Nutrition Epidemiological Study In preSchoolers). In girls aged 3-4 years, the Ala12 allele was associated with higher mid-upper arm (P = 0.010) and hip (P = 0.005) circumferences, as well as subscapular (P = 0.008) and total skinfolds (P = 0.011) that explained 2.0, 3.7, 2.1, and 1.9% of the phenotypic variance, respectively, while the T1431 allele was associated with higher mean values for waist circumference (P = 0.018) and suprailiac skinfold (P = 0.017), genotype accounting for 1.6% of the variance in both phenotypes. No significant effects of PPAR delta T+294C polymorphism or the interaction of the PPAR delta and PPAR gamma variants on adiposity-related phenotypes were observed in any age group or gender. Haplotype-based analysis including both PPAR gamma polymorphisms revealed that in girls aged 3-4 years, the Ala-T haplotype was associated with higher waist (P = 0.014) and hip (P = 0.007) circumferences compared to the common Pro-C haplotype. The PPAR gamma Pro12Ala and C1431T polymorphisms are associated with increased adiposity during early childhood in a gender- and age-specific manner and independently of the PPAR delta T+294C polymorphism.

Alanine variant of the Pro12Ala polymorphism of the PPARgamma gene might be associated with decreased risk of diabetic retinopathy in type 2 diabetes

OBJECTIVE

Molecular background of diabetic retinopathy (DR) remains unknown. An interesting group of candidate genes encode proteins involved in insulin resistance.

AIM

To search for association between the PPARgamma, calpain 10, PTPN1 genes and DR in type 2 diabetes mellitus (T2DM).

METHODS

We examined 238 T2DM subjects without DR (NDR) and 121 with DR (mean diabetes duration: 9.1+/-6.8 and 15.1+/-7.7, respectively). The subjects were genotyped for four markers: Pro12Ala of PPARgamma, SNP43 of calpain 10, rs3787345 and rs754118 of PTPN1. The distributions of the genotypes were compared using the chi(2)-test and Fisher exact test.

RESULTS

The alleles and genotypes were not associated with DR in non-stratified analysis. To investigate the impact of T2DM duration, we performed analysis that excluded short duration NDR subjects and long-duration DR subjects. It allowed obtaining groups with similar T2DM duration but different DR status (DR: 88 individuals, 11.4+/-5.3 years; NDR: 136 individuals, 13.2 years+/-6.2, respectively). This analysis suggested that the alanine variant of Pro12Ala might be associated with decreased risk of DR (p=0.026 for alleles, p=0.038 and p=0.014 for genotypes in additive and dominant models, respectively). In multivariable logistic regression that included non-genetic parameters, Pro12Ala was not an independent risk factor (p=0.28). Further analysis showed, however, that Pro12Ala remained significant when urea level was excluded from the model.

CONCLUSION

The alanine variant of the Pro12Ala polymorphism of PPARgamma might be associated with decreased risk of DR in T2DM. This effect may be indirect, at least in part, due to diabetic kidney disease.

Evidence of interaction between PPARG2 and HNF4A contributing to variation in insulin sensitivity in Mexican Americans

OBJECTIVE

We hypothesized that interaction between PPARG2 Pro12Ala and variants in the promoter region of HNF4A are associated with type 2 diabetes-related quantitative traits in Mexican-American families of a proband with previous gestational diabetes.

RESEARCH DESIGN AND METHODS

The BetaGene project genotyped PPARG2 Pro12Ala and nine HNF4A single nucleotide polymorphisms (SNPs) in 473 individuals in 89 families. Members of the proband generation had fasting glucose <126 mg/dl and were phenotyped by oral and intravenous glucose tolerance tests.

RESULTS

Neither PPARG2 Pro12Ala nor any of the nine HNF4A SNPs were independently associated with type 2 diabetes-related quantitative traits. However, the interaction between PPARG2 Pro12Ala and HNF4A rs2144908 was significantly associated with both insulin sensitivity (S(I)) (Bonferroni P = 0.0006) and 2-h insulin (Bonferroni P = 0.039). Subjects with at least one PPARG2 Ala allele and homozygous for the HNF4A rs2144908 A allele had 40% higher S(I) compared with individuals with at least one G allele. S(I) did not vary by rs2144908 genotype among PPARG2 Pro/Pro. The interaction result for S(I) was replicated by the Insulin Resistance Atherosclerosis Family Study (P = 0.018) in their San Antonio sample (n = 484) where subjects with at least one PPARG2 Ala allele and homozygous for the HNF4A rs2144908 A allele had a 29% higher S(I) compared with individuals with at least one G allele. However, the interaction was not replicated in their San Luis Valley sample (n = 496; P = 0.401).

CONCLUSIONS

Together, these results suggest that variation in PPARG2 and HNF4A may interact to regulate insulin sensitivity in Mexican Americans at risk for type 2 diabetes.

SNPs in PPARG associate with type 2 diabetes and interact with physical activity

PURPOSE

To study the associations of seven single-nucleotide polymorphisms (SNPs) in the peroxisome proliferator-activated receptor gamma (PPARG) gene with the conversion from impaired glucose tolerance (IGT) to type 2 diabetes (T2D), and the interactions of the SNPs with physical activity (PA).

METHODS

Overweight individuals with IGT who participated in the Finnish Diabetes Prevention Study (DPS) (N = 479) were followed, on average, 4.2 yr. PA was assessed yearly with a 12-month validated questionnaire.

RESULTS

In Cox regression analyses, the rare alleles of rs17036314 and rs1801282 (Pro12Ala) predicted conversion to T2D (P = 0.038 and 0.037, respectively), but only rs17036314 predicted T2D after adjustment for baseline fasting glucose (P = 0.030). The change in the total amount of PA, stratified by median, modified the association of rs17036314 and rs1801282 with the risk of T2D during the intervention (P = 0.002 and 0.031, respectively, for interaction between PA change and genotype); an increase in PA seemed to remove the effect of the risk alleles. The distinct rs1152003 polymorphism interacted with the study group on the conversion to T2D (P = 0.027) and tended to increase the risk of T2D in the intervention group (P = 0.050). No interaction between rs1152003 and the change in PA was found.

CONCLUSIONS

The rs17036314, rs1801282 (Pro12Ala), and rs1152003 were associated with the risk of T2D in the DPS. Increased PA seemed to decrease the effect of the risk alleles of rs17036314 and rs1801282 on the conversion to T2D. The effect of rs1152003 was modified by other lifestyle changes or the lifestyle intervention as a whole.

Adipose tissue-specific PPARgamma deficiency increases resistance to oxidative stress

The nuclear hormone receptor peroxisome proliferator activated receptor gamma (PPARgamma) critically regulates adipogenesis and lipogenesis. Obesity is closely associated with increased oxidative stress, and pharmacological activation of PPARgamma by its ligands significantly suppresses oxidative stress in cultured adipocytes. On the other hand, a PPARgamma2(Pro12Ala) polymorphism, which decreases receptor transcription activity, is associated with lower body mass index and increased insulin sensitivity in humans. This mutation is also found to be positively associated with increased human lifespan. Here we show that adipose tissue-specific PPARgamma heterozygous mice, which exhibit significant improvement in insulin sensitivity in skeletal muscle, show increased resistance to paraquat-induced oxidative stress. The enhanced oxidative stress tolerance is associated with significant upregulation of antioxidant genes in white adipose tissue and skeletal muscle whereas prooxidant genes are not changed. This is also associated with a significant increase in adipose tissue of Foxo3a, a transcription factor that is known to regulate clearance of reactive oxygen species. Consistently, Foxo3a dependent genes are significantly upregulated in adipose tissue. These data implicate adipose tissue PPARgamma in the regulation of oxidative stress, which may underlie extended lifespan in humans bearing PPARgamma2(Pro12Ala) mutation.

Association of pro12Ala polymorphism in the peroxisome proliferative-activated receptor gamma2 gene with obesity and hypertension in Korean women

This study examined whether the Pro12Ala polymorphism of the PPARgamma2 gene is associated with obesity, hypertension and cardiovascular risk profiles in Korean adult women. We studied 129 Korean women (aged 42.71 +/- 8.56 y) who were divided into 2 groups as a Pro12Pro homozygous group and a Pro12Ala heterozygous or Ala12Ala homozygous group based upon PPARy2 genotype. Anthropometric parameters, blood pressure, abdominal fat area and blood lipid profiles were compared between the 2 groups, and the association of Ala allele frequency in PPARgamma2 gene with obesity or hypertension was evaluated. Most anthropometric parameters and blood lipid profiles did not differ significantly between the genotypes. However, all variables of skinfold thickness, body circumference and abdominal fat area of Pro12Ala heterozygous were consistently higher compared to the Pro12Pro homozygous subjects without a significance differences. The hypertensive group had significantly higher (p = 0.004) Ala12 allele frequency than the normotensive group whereas allele frequencies did not differ significantly between the obese group and non-obese group. Ala allele carriers had a significantly higher risk of hypertension than non-carriers in logistic regression analysis. There was no evidence that the Ala allele can be regarded as an independent risk factor for obesity. In conclusion, all variables related to obesity showed a consistently higher trend in Pro12Ala heterozygous subjects compared to Pro12Pro homozygous subjects. Pro12Ala heterozygous subjects showed an increasing trend of elevated blood pressure compared to Pro12Pro homozygous subjects. Ala12 variant as well as BMI and TG were regarded as independent risk factors for hypertension in our subjects.

Ala12 variant of the peroxisome proliferator-activated receptor-gamma gene (PPARG) is associated with higher polyunsaturated fat in adipose tissue and attenuates the protective effect of polyunsaturated fat intake on the risk of myocardial infarction

BACKGROUND

Intake of polyunsaturated fat is protective against the development of coronary heart disease. Less is known about the genetic variation modulating this association. The Ala12 allele of the peroxisome proliferator-activated receptor-gamma gene (PPARG) decreases the lipolysis of triacylglycerols in adipose tissue, which results in the accumulation of fatty acids in adipocytes.

OBJECTIVE

We aimed to determine whether the Pro12Ala polymorphism interacts with polyunsaturated fat intake to affect the risk of myocardial infarction (MI).

DESIGN

Cases (n = 1805) with a first nonfatal acute MI and population-based controls matched by age, sex, and area of residence (n = 1805) living in Costa Rica were genotyped for the PPARG Pro12Ala genetic polymorphism. Polyunsaturated fat intake was determined by use of a validated food-frequency questionnaire and by gas chromatography analysis of adipose tissue. Odds ratios and 95% CIs for MI were estimated by use of logistic regression.

RESULTS

The relative allele frequencies of the Ala12 allele were 10% in controls and 11% in cases. Odds ratios (95% CI) for MI per each 5% increase in energy from polyunsaturated fat were 0.66 (0.53, 0.82) in Pro12/Pro12 subjects and 0.93 (0.61, 1.42) in carriers of the Ala12 allele (P for interaction = 0.03). Increments (95% CI) of polyunsaturated fat in adipose tissue per 5% increment in dietary intake were 5.4% (4.9%, 5.9%) in Pro12/Pro12 homozygotes, 6.9% (6.0%, 7.9%) in Pro12/Ala12 heterozygotes, and 7.7% (3.2%, 12.2%) in Ala12/Ala12 homozygotes (P for interaction = 0.016).

CONCLUSIONS

The protective effect of polyunsaturated fat intake on MI is attenuated in carriers of the Ala12 allele of PPARG.

The Pro12Ala polymorphism of the PPAR-gamma2 gene affects associations of fish intake and marine n-3 fatty acids with glucose metabolism

BACKGROUND/OBJECTIVES

Data on associations between marine n-3 fatty acids and glucose metabolism are inconsistent. Therefore, we explored effects of the Pro12Ala polymorphism in peroxisome proliferator-activated receptor (PPAR)-gamma2 gene on associations of fish intake and dietary and plasma eicosapentaenoic and docosahexaenoic acid with glucose metabolism. The design comprises of the cross-sectional analysis.

SUBJECTS/METHODS

The Pro12Ala variant in the PPAR-gamma2 (PPARG) gene was genotyped in 571 non-diabetic relatives of subjects with type II diabetes. The dietary intake was measured by a 3-day food record, and the plasma cholesterol ester fatty acid composition was analysed with gas chromatography. Associations of dietary and plasma variables with insulin resistance and fasting and 2-h glucose and free fatty acid concentrations were analysed with multiple linear regression analysis.

RESULTS

In men, there was a significant interaction between PPARG polymorphism and plasma docosahexaenoic acid on fasting free fatty acid concentration (P=0.036), and genotype-stratified models showed an inverse association in Pro homozygotes only (P=0.028). In women, the proportion of plasma eicosapentaenoic acid was higher in Ala-allele carriers compared to Pro homozygotes (1.67 vs 1.44% respectively, P=0.006). A significant interaction between PPARG polymorphism and fish intake on 2-h glucose was found in women (P=0.021), and genotype-stratified models suggested an inverse association in Ala-allele carriers only (P=0.039).

CONCLUSIONS

The findings suggest that PPARG polymorphism might affect the plasma proportion of eicosapentaenoic acid and modulate the associations of fish intake and marine n-3 fatty acids with glucose metabolism and fasting free fatty acids.

The role of the Pro12Ala polymorphism in peroxisome proliferator-activated receptor gamma in diabetes risk

PURPOSE OF REVIEW

To provide a timely update of the literature regarding the role of the Pro12Ala polymorphism of the peroxisome proliferator-activated receptor gamma gene in type 2 diabetes and related phenotypes.

RECENT FINDINGS

The adipocyte-specific gamma2 isoform of peroxisome proliferator-activated receptor gamma is now considered to be one of the best-replicated genetic risk factors of common type 2 diabetes. The effect is relatively weak (pooled odds ratio is about 1.2) but because of the high prevalence and population-attributable risk, this polymorphism becomes relevant for assessing genetic susceptibility for type 2 diabetes. Less clear is the association with prediabetes subphenotypes where effects were only detectable in selected subgroups. Furthermore this review gives an overview about possible mechanisms of peroxisome proliferator-activated receptor gamma effects, gene-environment interactions, relevance to the therapeutic response to thiazolidinediones and further clinical observations.

SUMMARY

In conclusion, the Pro12 allele of peroxisome proliferator-activated receptor gamma is a robust diabetes-risk allele, as confirmed by many replications. There are many more clinical observations related to the Pro12Ala genotype which could be interesting and these clearly need to be analyzed in future studies.

Lack of association between serum adiponectin levels and the Pro12Ala polymorphism in Asian Indians

AIMS

The aim of the study was to investigate the association of serum adiponectin levels with the Pro12Ala polymorphism of the peroxisome proliferator activated receptor-gamma (PPARG) gene in Asian Indians.

METHODS

We selected 400 diabetic subjects, 200 with the Pro12Pro genotype (100 male and 100 female) and 200 with the Pro12Ala genotype (100 male and 100 female) and 400 age- and sex-matched normal glucose tolerance subjects with similar genotype profiles from the Chennai Urban Rural Epidemiology Study. Fasting serum adiponection levels were measured using radioimmunoassay. The Pro12Ala polymorphism was genotyped by PCR-restriction fragment length polymorphism using BstUI.

RESULTS

All clinical and biochemical parameters were similar in the subjects with the Pro12Pro and Pro12Ala genotypes. There was no significant difference in serum adiponectin values between subjects with the Pro12Pro and Pro12Ala genotypes (males 5.4 vs. 5.8 microg/ml, P = 0.546; females 6.9 vs. 7.2 microg/ml, P = 0.748). Adiponectin values did not differ among these two genotypes even when categorized based on their diabetes status (normal glucose tolerance Pro12Pro 7.9 vs. Pro12Ala 7.7 microg/ml, P = 0.994; diabetes Pro12Pro 4.7 vs. Pro12Ala 5.4 microg/ml, P = 0.622).

CONCLUSION

The Pro12Ala polymorphism of the PPARG gene is not associated with serum adiponectin levels in Asian Indians.

Upstream transcription factor 1 gene polymorphisms are associated with high antilipolytic insulin sensitivity and show gene–gene interactions

Upstream transcription factor 1 (USF1) regulates the expression of many genes involved in lipid and glucose metabolism, among them genes regulating lipolysis. USF1 specifically regulates the expression of the hormone-sensitive lipase gene (HSL) in adipocytes and the hepatic lipase gene (LIPC) in the liver, which was found to be involved in liver fat accumulation. The usf1s1 C > T and usf1s2 G > A single-nucleotide polymorphisms (SNPs) in USF1 are associated with increased in vitro catecholamine-induced lipolysis in adipocytes. We investigated first whether SNPs in USF1 affect the lipolysis-suppressing action of insulin in vivo, and second, whether they interact with the -60C > G SNP in HSL on lipolysis and the -514C > T SNP in LIPC on liver fat. The usf1s1 C > T and usf1s2 G > A SNPs, together with the SNPs in HSL and LIPC, were determined in 407 Caucasians. Lipolysis was estimated as a change in free fatty acid (FFA) levels from baseline to 2 h of a 75-g oral glucose tolerance test (OGTT). Fifty-four subjects had data from a euglycemic hyperinsulinemic clamp with calculation of antilipolytic insulin sensitivity. Subjects carrying the minor alleles (T of usf1s1 and A of usf1s2) had lower 2 h FFA (p = 0.01) and a larger decrease in FFA concentrations during the OGTT (p = 0.02). Antilipolytic insulin sensitivity was higher in these individuals (p = 0.03). No interaction of the usf1s1 C > T and usf1s2 G > A SNPs with the -60C > G SNP in HSL on antilipolytic insulin sensitivity was detected. Liver fat, measured by (1)H magnetic resonance spectroscopy, was elevated only in subjects who were both homozygous for the major alleles of usf1s1 and usf1s2 and carriers of the T allele of the -514C > T SNP in LIPC (p = 0.01). In conclusion, subjects carrying the T allele of SNP usf1s1 and the A allele of SNP usf1s2 have a higher antilipolytic insulin sensitivity. Moreover, both SNPs may interact with the -514C > T SNP in LIPC to determine liver fat.

Patterns of association between PPARgamma genetic variation and indices of adiposity and insulin action in African-Americans and whites: the CARDIA Study

We performed a combination of single-variant- and haplotype-based analyses to investigate the association of peroxisome-proliferator-activated receptor gamma (PPARgamma) gene sequence variation with indices of adiposity, including body mass index (BMI) and waist girth, as well as insulin action, including fasting blood glucose and insulin levels. Nine polymorphisms, selected based on race-specific pairwise linkage disequilibrium relations and/or potential functional relevance, were assayed in 3,875 African-American and white young adults from the Coronary Artery Risk Development in Young Adults Study. These polymorphisms were C25819G (C-681G), C65746G (Pro12Ala), G67222A, A69208G, G81556T, T95872C, T115432G, C127599T, and C148157T (C1431T). They defined seven and six common haplotypes in African-Americans and whites, respectively. Patterns of associations of PPARgamma genetic variation with the metabolic traits differed between the two racial groups, with some exceptions. Haplotype CCGGCTCC was associated with a significant reduction in glucose levels in both racial groups (P<0.001 in each group), and the G69208 allele was associated with lower glucose levels in lean African-Americans and in whites (both P=0.02). Two haplotypes, relatively unique to whites, were associated with measures of adiposity and glucose levels. Two haplotypes, relatively unique to African-Americans, were associated with glucose levels. There were no significant effects of PPARgamma haplotypes on measures of body size in this racial group, but a novel polymorphism, G67222A, significantly modulated the relation between BMI and glucose levels (P interaction, 0.003). This study provides evidence that variants, other than Pro12Ala, influence variation in body size and indices of insulin action. It underscores the role of genetic and environmental contexts in shaping the patterns of associations of PPARgamma sequence variants with metabolic traits in human populations.