Sibling-based association study of the PPARgamma2 Pro12Ala polymorphism and metabolic variables in Chinese and Japanese hypertension families: a SAPPHIRe study. Stanford Asian-Pacific Program in Hypertension and Insulin Resistance

Association of PPAR Alpha Intron 7 G/C, PPAR Gamma 2 Pro12Ala, and C161T Polymorphisms with Serum Fetuin-A Concentrations

BACKGROUND

Both peroxisome activator proteins (PPARs) and fetuin-A play a role in lipid and glucose metabolism.

AIMS

We investigated whether PPARα intron 7 G2468/C and PPARγ2 Pro12Ala and PPARγ exon 6 C161T polymorphisms are associated with serum fetuin-A concentrations.

PATIENTS AND METHODS

The PPARα intron 7 G/C polymorphism was studied in cohort 1 (79 reference individuals, 165 postinfarction patients). The two PPARγ polymorphisms were investigated in cohort 2 (162 reference individuals, 165 postinfarction patients). Fetuin-A levels and PPAR polymorphisms were determined by radial immunodiffusion and polymerase chain reaction-restriction fragment length polymorphism techniques.

RESULTS

The C allele variant of PPARα intron 7 G2467C was associated with higher fetuin-A levels (p = 0.018). Postinfarction status (p = 0.001), PPARα intron 7 GG/GC/CC genotypes (p = 0.032), and the C allele (p = 0.021) were the strongest determinants of fetuin-A concentration in a multiple regression model. Higher fetuin-A levels were associated with the Pro variant of PPARγ2 (p = 0.047). Postinfarction status (p = 0.041) and BMI (p < 0.001) but not PPARγ2 Pro were the strongest determinants of fetuin-A concentrations. PPARγ exon 6 C161T genotypes were not associated with fetuin-A levels.

CONCLUSIONS

Fetuin-A was determined mainly by the PPARα intron 7C allele and postinfarction status in cohort 1 and the BMI and postinfarction in cohort 2. The PPARα intron 7C and PPARγ2 Pro variants are associated with fetuin-A levels.

Nutrigenomics at the Interface of Aging, Lifespan, and Cancer Prevention

The percentage of elderly people with associated age-related health deterioration, including cancer, has been increasing for decades. Among age-related diseases, the incidence of cancer has grown substantially, in part because of the overlap of some molecular pathways between cancer and aging. Studies with model organisms suggest that aging and age-related conditions are manipulable processes that can be modified by both genetic and environmental factors, including dietary habits. Variations in genetic backgrounds likely lead to differential responses to dietary changes and account for some of the inconsistencies found in the literature. The intricacies of the aging process, coupled with the interrelational role of bioactive food components on gene expression, make this review a complex undertaking. Nevertheless, intriguing evidence suggests that dietary habits can manipulate the aging process and/or its consequences and potentially may have unprecedented health benefits. The present review focuses on 4 cellular events: telomerase activity, bioenergetics, DNA repair, and oxidative stress. These processes are linked to both aging and cancer risk, and their alteration in animal models by selected food components is evident.

Pro12Ala variant of the PPARG2 gene increases body mass index: An updated meta-analysis encompassing 49,092 subjects

OBJECTIVE

The peroxisome proliferator-activated receptor gamma 2 (PPARG2) gene has been intensively studied with relation to obesity and metabolic disorders. Indeed, a large number of studies assessing the association between the PPARG2 polymorphism Pro12Ala (rs1801282) and body mass index (BMI) have been published with some controversial results. In this meta-analysis, the effects of Pro12Ala polymorphism of the PPARG2 gene on BMI were investigated.

DESIGN AND METHODS

Externally published data were collected and we included our own novel data from a study in the elderly participants (>55 years) of a Mediterranean cohort, the SUN ("Seguimiento Universidad de Navarra") Project (n = 972). A total of 75 independent studies with 49,092 subjects (39,806 with the genotype Pro12Pro and 9,286 carrier subjects of the Ala allele) were included.

RESULTS

The meta-analysis revealed a higher BMI with an overall estimation of +0.065 kg/m(2) (95%CI = 0.026-0.103, P = 0.001) for homo-/heterozygous carriers of the Ala allele of the PPARG2 gene in comparison to non-carriers. The analysis also showed that there was heterogeneity (P for heterogeneity <0.001), but funnel plots did not suggest apparent publication bias. Furthermore, the association between the Pro12Ala polymorphism of the PPARG2 gene and increased BMI was stronger in Caucasian. Thus, carriers of the Ala allele had significantly higher BMI than non-carriers in a subsample of 6,528 Caucasian male subjects (standardized mean difference = 0.090, 95%CI=0.032-0.148, P = 0.002, P for heterogeneity = 0.121).

CONCLUSION

This updated meta-analysis showed that carriers of the Ala12 allele of the PPARG2 gene had a higher average BMI.

Endothelin Type A Receptor Genotype is a Determinant of Quantitative Traits of Metabolic Syndrome in Asian Hypertensive Families: A SAPPHIRe Study

Co-heritability of hypertension and insulin resistance (IR) within families not only implies genetic susceptibility may be responsible for these complex traits but also suggests a rational that biological candidate genes for hypertension may serve as markers for features of the metabolic syndrome (MetS). Thus we determined whether the T323C polymorphism (rs5333) of endothelin type A (ETA) receptor, a predominant receptor evoking potent vasoconstrictive action of endothelin-1, contributes to susceptibility to IR-associated hypertension in 1694 subjects of Chinese and Japanese origins. Blood pressures (BPs) and biochemistries were measured. Fasting insulin level, insulin-resistance homeostasis model assessment (HOMAIR) score, and area under curve of insulin concentration (AUCINS) were selected for assessing insulin sensitivity. Genotypes were obtained by methods of polymerase chain reaction-restriction fragment length polymorphism. Foremost findings were that minor allele frequency of the T323C polymorphism was noticeable lower in our overall Asian subjects compared to multi-national population reported in gene database; moreover both the genotypic and allelic frequencies of the polymorphism were significantly different between the two ethnic groups we studied. The genotype distributions at TT/TC/CC were 65, 31, 4% in Chinese and 51, 41, 8% in Japanese, respectively (p < 0.0001). Additionally, carriers of the C homozygote revealed characteristics of IR, namely significantly higher levels of fasting insulin, HOMAIR score, and AUCINS at 29.3, 35.3, and 39.3%, respectively, when compared to their counterparts with TT/TC genotypes in Chinese. Meanwhile, the CC genotype was associated with a higher level of high density lipoprotein cholesterol in Japanese. No association of the polymorphism with BP was observed. This study demonstrated for the first time that T323C polymorphism of ETA receptor gene was associated with an adverse insulin response in Chinese and a favorite atherogenic index in Japanese.

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSION

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

Association of serum lipid/lipoprotein with Pro12Ala polymorphism in PPAR-γ2 among Chinese nonagenarians/centenarians

BACKGROUND AND AIMS

In previous studies, the Pro12Ala polymorphism in the peroxisome proliferator-activated receptor gamma 2 (PPAR-γ2) was shown to be associated with both lipid metabolism and longevity. We examined whether the polymorphism continued to be associated with abnormal levels of serum lipid/lipoprotein among elderly subjects (≥90 years).

METHODS

The Pro12Ala variant was examined using polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP). Abnormal levels of serum lipid/lipoprotein were defined according to the criteria provided by the Chinese Medical Association (2004). Abnormal criteria were triglyceride (TG) >5.18 mmol/l, total cholesterol (TC) >1.7 mmol/l, low-density lipoprotein cholesterol (LDL-C) >3.37 mmol/l and high-density lipoprotein cholesterol (HDL-C) <1.04 mmol/l).

RESULTS

The sample included 673 unrelated Chinese individuals aged 90-108 years (mean age: 93.54 ± 3.54 years) and 67.3% females. Genotype frequencies of the Pro12Ala polymorphism were 0% Ala12Ala, 8.9% Pro12Ala, 91.1% Pro12Pro. Neither differences in the levels of serum lipid/lipoprotein nor the prevalence of their abnormal levels was significant between subjects who were or were not 12Ala carriers. Unadjusted and adjusted multiple logistic regressions showed that the odds ratios (OR) for abnormal levels of serum lipid/lipoprotein were not associated with the Pro12Ala polymorphism in PPAR-γ2.

CONCLUSIONS

Levels of serum lipid/lipoprotein were not associated with the Pro12Ala polymorphism in PPAR-γ2 among Chinese nonagenarians and centenarians, which was different from the general population.

Association of PPAR polymorphisms with cytokine levels in allergic rhinitis

Our aim was to study the association of Pro12Ala and exon6 C161T polymorphisms of PPARgamma and intron7 G/C polymorphisms of PPAR-alpha with clinical symptoms, peak nasal inspiratory flow values, serum soluble TNF-alpha, TNF-R1, Fas, Fas ligand and IgE concentrations in patients with seasonal allergic rhinitis during and after pollen season. We performed a follow-up study of 66 Hungarian patients with seasonal allergic rhinitis and 180 healthy referent subjects. We used PCR-RFLP technique and ELISA. The distribution of mutant alleles of PPAR-gamma and -alpha did not differ in patients and referent subjects. Patients carrying the mutant 12Ala, exon6 161T alleles of PPAR-gamma and intron7 C allele of PPAR-alpha had significantly higher clinical symptom score values, TNF-alpha and IgE levels and lower peak nasal inspiratory flow values during and after pollen season. The results indicated that nuclear receptors PPAR-gamma and PPAR-alpha are involved in the regulation of inflammatory mediator production in patients with seasonal allergic rhinitis and polymorphisms of the receptors are very likely to contribute to the heterogeneity of clinical and immunological parameters of allergic patients.

PPAR Genomics and Pharmacogenomics: Implications for Cardiovascular Disease

The peroxisome proliferator-activated receptors (PPARs) consist of three related transcription factors that serve to regulate a number of cellular processes that are central to cardiovascular health and disease. Numerous pharmacologic studies have assessed the effects of specific PPAR agonists in clinical trials and have provided insight into the clinical effects of these genes while genetic studies have demonstrated clinical associations between PPAR polymorphisms and abnormal cardiovascular phenotypes. With the abundance of data available from these studies as a background, PPAR pharmacogenetics has become a promising and rapidly advancing field. This review focuses on summarizing the current state of understanding of PPAR genetics and pharmacogenetics and the important implications for the individualization of therapy for patients with cardiovascular diseases.

Pro12Ala polymorphism in PPAR-gamma2 and dementia in Chinese nonagenarians/centenarians

We examined the existence of a relationship between polymorphism and dementia in subjects aged 90 years and above. The sample included 732 unrelated Chinese nonagenarians/centenarians (aged 90-108 years, mean age 93.68 years; 67.5% women). The Pro12Ala variant was examined using polymerase chain reaction restriction fragment length polymorphism. Cognitive function was measured with 30-item mini-mental state examination. The genotype frequencies of the Pro12Ala polymorphism were 0% Ala12Ala, 9.1% Pro12Ala, and 90.9% Pro12Pro. The prevalence rates of dementia were 64.9% in the whole sample (45.0% for men and 74.5% for women). In both men and women, between subjects with and without 12Ala carriers, there was no significant difference in cognitive function scores and also no significant difference in prevalence of dementia; there was no significant difference in frequency of 12Ala carriers between subjects with and without dementia. Multiple logistic regression was performed by adjusting clinical factors that are thought to be associated with cognitive function or with 12Ala carriers. We found that 12Ala is not a risk factor for dementia. We found that Pro12Ala polymorphism in PPAR-gamma2 was not directly correlated with dementia among Chinese nonagenarians and centenarians.

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.

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.

Association of peroxisome proliferator-activated receptorgamma gene Pro12Ala and C161T polymorphisms with metabolic syndrome

BACKGROUND Peroxisome proliferator-activated receptor gamma (PPARgamma) is involved mainly in adipocyte differentiation and has been suggested to play an important role in the pathogenesis of insulin resistance (IR) and atherosclerosis. The frequencies of 2 common polymorphisms of the PPARgamma gene, Pro12Ala single nucleotide polymorphism (SNP) in exon B and C161T SNP in exon 6, were investigated in 792 subjects and the correlations between the different genotypes, IR and metabolic syndrome (MS) were analyzed.

METHODS AND RESULTS

Anthropometric measurements, fasting glucose, insulin and lipid profiles were measured in 792 people of the Han population in Beijing, China. Homeostatic model assessments and quantitative insulin sensitivity check indices were calculated. MS was diagnosed according to the IDF guidelines (2005) for a Chinese population. Polymerase chain reaction - restriction fragment length polymorphism were performed for DNA genotyping. For the C161T polymorphism, allele frequencies were 0.804 for the C allele and 0.196 for the T allele. For Pro12Ala, allele frequencies were 0.947 for proline and 0.053 for alanine. There was no Ala12Ala homozygote in the population. No differences were seen in the mean values of age, body mass index (BMI), blood pressure or fasting blood glucose level among different genotypes when analyzed as a whole. Subjects with an A or T allele had lower fasting insulin levels, HOMA-IR levels, and a lower level QUICKI trend. Further analysis by age was conducted, and A or T allele carriers in the <60 year group showed a trend of lower triglyceride and a higher high-density lipoprotein-cholesterol level, but this was not statistically significant. When subjects were divided into 4 groups according to the combination of genetic alleles of the 2 polymorphisms, the subjects with Pro12Ala and a T allele simultaneously showed a significantly higher BMI than those without the Ala allele. The presence of a T allele in the C161T polymorphism and Pro12Ala polymorphism seems to affect body weight, which is similar to the results found in previous studies.

CONCLUSIONS

Both polymorphisms showed a significant association with IR, but failed to show an association with MS components. Those with an A allele of Pro12Ala and a T allele of the C161T polymorphism showed a higher BMI, which requires further investigation.

Pathogenic potential of adipose tissue and metabolic consequences of adipocyte hypertrophy and increased visceral adiposity

When caloric intake exceeds caloric expenditure, the positive caloric balance and storage of energy in adipose tissue often causes adipocyte hypertrophy and visceral adipose tissue accumulation. These pathogenic anatomic abnormalities may incite metabolic and immune responses that promote Type 2 diabetes mellitus, hypertension and dyslipidemia. These are the most common metabolic diseases managed by clinicians and are all major cardiovascular disease risk factors. 'Disease' is traditionally characterized as anatomic and physiologic abnormalities of an organ or organ system that contributes to adverse health consequences. Using this definition, pathogenic adipose tissue is no less a disease than diseases of other body organs. This review describes the consequences of pathogenic fat cell hypertrophy and visceral adiposity, emphasizing the mechanistic contributions of genetic and environmental predispositions, adipogenesis, fat storage, free fatty acid metabolism, adipocyte factors and inflammation. Appreciating the full pathogenic potential of adipose tissue requires an integrated perspective, recognizing the importance of 'cross-talk' and interactions between adipose tissue and other body systems. Thus, the adverse metabolic consequences that accompany fat cell hypertrophy and visceral adiposity are best viewed as a pathologic partnership between the pathogenic potential adipose tissue and the inherited or acquired limitations and/or impairments of other body organs. A better understanding of the physiological and pathological interplay of pathogenic adipose tissue with other organs and organ systems may assist in developing better strategies in treating metabolic disease and reducing cardiovascular disease risk.

Vascular risk factors in South Asians

South Asians originate from the Indian sub-continent (India, Pakistan, Bangladesh, Sri Lanka and Nepal) and represent one fifth of the world's population. Several studies suggested that South Asians have an increased risk of developing coronary heart disease (CHD) when compared with European populations. We review the role of traditional and emerging risk factors in the increased CHD risk in South Asians. The high prevalence of insulin resistance and type 2 diabetes mellitus in South Asians may be a major cause for their elevated vascular risk. However, other established and emerging risk factors are also overrepresented in South Asians. Large-scale prospective studies could determine the relative contribution of established and emerging vascular risk factors in South Asians. There is an urgent need for trials in South Asians that will evaluate clinical outcomes following treatment of these risk factors.

Pharmacogenetics of the PPAR genes and cardiovascular disease

The goal of pharmacogenetics is to define the genetic determinants of individual drug responsiveness, and thereby provide personalized treatment to each individual. The peroxisome proliferator-activated receptors (PPARs) are polypeptide products of a set of related genes functioning to regulate several cellular processes that are central to cardiovascular health and disease. Given their pleiotropic roles in lipid and glucose homeostasis, cardiac energy balance and regulation of adipocyte release of circulating inflammatory factors, it is not surprising that PPARs represent an attractive target for clinical investigation and intervention in disease states, such as diabetes, obesity, atherosclerosis, cardiomyopathy, cardiac hypertrophy and heart failure. Research into the manipulation of PPAR function by pharmacologic agents has already resulted in important advances in the treatment of diabetes mellitus and cardiovascular disease. It follows that PPAR pharmacogenetics promises important advances in the personalized treatment of cardiovascular disease.

PPARG locus haplotype variation and exacerbations in asthma

The peroxisome proliferator-activated receptor gamma (PPARgamma) regulates inflammation and may play a role in asthma. Using mouthwash-derived DNA and clinical interviews and measurements, we investigated the association of previously characterized single-nucleotide polymorphisms in the PPARG gene (Pro12Ala, C1431T, and C-681G) with asthma exacerbations in patients aged 3-22 years (n=569). The common homozygous haplotype combination of the Pro12 and C1431 alleles was associated with increased risk for asthma exacerbations (ProC, odds ratio (OR) 1.87, 95% confidence interval 1.25-2.79; P=0.002). The ProC genotype was associated with increased school absences (OR 1.82, 95% confidence interval 1.21-2.76; P=0.004) and hospital admissions (OR 2.32, 95% confidence interval 1.18-4.58; P=0.015) over the preceding 6 months. The population-attributable risk of this genotype was 33%. Common genetic variation at the PPARG locus may play an important role in modulating the long-term control of asthma in children and young adults.

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.

The influence of the Pro12Ala mutation of PPARγ2 receptor gene on β-cells restoration and insulin resistance in type 2 diabetes with hypertension

The aim of this investigation was to determine whether a PPARgamma2 Pro12Ala polymorphism was associated with insulin resistance, beta-cell function and hypertension in Chinese populations. 289 unrelated Chinese subjects first diagnosed Type 2 diabetes (HbAC1 < 6.0) were investigated, including 132 hypertensive diabetic (HTD) subjects, 157 normotensive diabetic (NTD) subjects. Blood pressure and anthropometric measurements were collected from all participants, as well as several venous blood samples during oral glucose tolerance test (OGTT). Biochemical measurements (high-density lipoprotein (HDL) and low-density lipoprotein-cholesterol (LDL), triglycerides) and PPARgamma2 Pro12Ala genotype were also determined. And insulin resistance and beta-cells function was assessed by HOMA-IR and HOMA-beta respectively. The frequency of subjects bearing the Pro12Ala was lower in the hypertension group (3.03%) than in the non-hypertension group (5.7%) (P < 0.05) after adjusted for age, BMI and gender. Hypertensive diabetic Pro12Ala subjects had lower fasting plasma glucose level (P = 0.0127), and better glucose tolerance 60 min after oral glucose (P = 0.0361). Moreover, plasma insulin concentrations at 60 min was lower than those without A variant (P = 0.0275), and both hypertensive Ala/Pro in HOMA-beta (P = 0.0455) and AUC for insulin (P = 0.0473) were higher, and HOMA-IR was lower (P = 0.0375) as compared with hypertensive Pro/Pro subjects. No association was observed between Pro12Ala genotype and BMI, total cholesterol, HDL- cholesterol or triglycerides in either group. Our findings suggested that the Ala 12 allele of the PPARgamma2 gene may improve insulin resistance and ameliorate beta-cell function reserves in T2DM with hypertension, and protect patients from hypertension in T2DM. As an important thrifty gene, environment factors may exerts an effect of PPAR gamma2 on glucose homeostasis and insulin resistance.

Inverse effects of the PPAR(gamma)2 Pro12Ala polymorphism on measures of adiposity over 15 years in African Americans and whites. The CARDIA study

Few studies have addressed the association of the Pro12Ala polymorphism of the peroxisome proliferator-activated receptor gamma 2 (PPAR gamma 2) gene with longitudinal measures of adiposity and insulin sensitivity during young adulthood, or reported on its relationship with these outcomes in African Americans. These issues were examined in the biracial Coronary Artery Risk Development in Young Adults (CARDIA) cohort, a population-based sample of 5115 African Americans and whites followed prospectively over 15 years. Frequency of the Ala12 allele was 2.1% in African Americans and 12.8% in whites, consistent with previous reports. A generalized estimating equation method was used to simultaneously examine the cross-sectional and longitudinal relationships between the Pro12Ala polymorphism and the measures of adiposity and insulin sensitivity. The Pro12Ala polymorphism was significantly associated with mean 15-year levels of adiposity, but these associations were in opposite direction in the 2 racial groups. On average, African Americans carrying the Ala12 allele had a 1.1 kg/m2 lower body mass index (BMI) ( P = .02) and whites a 0.6 kg/m2 higher BMI ( P = .01), as compared to Pro12 homozygotes. The Ala12 allele was also significantly associated with a decreased risk of incident insulin resistance syndrome in each race (OR = 0.44, P = .04 in African Americans; OR = 0.61, P = .01 in whites) and lower mean 15-year levels of fasting insulin ( P = .02), glucose ( P = .02), and homeostasis model assessment ( P = .01) in African Americans but not in whites. Important roles of BMI and ethnic background in influencing the complex relationships among PPAR gamma gene variation, adiposity, and insulin resistance are suggested.

Analysis of separate and combined effects of common variation in KCNJ11 and PPARG on risk of type 2 diabetes

The separate and combined effects of the PPARG Pro(12)Ala polymorphism and the KCNJ11 Glu(23)Lys polymorphisms on risk of type 2 diabetes were investigated in relatively large-scale, case-control studies. Separate effects of the variants were examined among 1187/1461 type 2 diabetic patients and 4791/4986 middle-aged, glucose-tolerant subjects. The combined analysis involved 1164 type 2 diabetic patients and 4733 middle-aged, glucose-tolerant subjects. In the separate analyses, the K allele of the KCNJ11 Glu(23)Lys associated with type 2 diabetes (odds ratio, 1.19; P = 0.0002), whereas the PPARG Pro(12)Ala showed no significant association with type 2 diabetes. The combined analysis indicated that the two polymorphisms acted in an additive manner to increase the risk of type 2 diabetes, and we found no evidence for a synergistic interaction between them. Analysis of a model with equal additive effects of the two variants showed that the odds ratio for type 2 diabetes increased with 1.14/risk allele (P = 0.003). Together, the two polymorphisms conferred a population-attributable risk for type 2 diabetes of 28%. In conclusion, our results showed no evidence of a synergistic interaction between the KCNJ11 Glu(23)Lys and PPARG Pro(12)Ala polymorphisms, but indicated that they may act in an additive manner to increase the risk of type 2 diabetes.

Peroxisome proliferator-activated receptor-??2 Pro12Ala and endothelial nitric oxide synthase-4a/b gene polymorphisms are not associated with hypertension in diabetes mellitus type 2

OBJECTIVE AND DESIGN

The Pro12Ala and the 4a/b polymorphisms of the peroxisome proliferator-activated receptor gamma (PPARgamma) and the endothelial nitric oxide-synthase (eNOS) genes, respectively, have been associated with hypertension in some but not all studies. The purpose of this study was to investigate the association between these polymorphisms and hypertension in patients with diabetes mellitus type 2 (DM2).

METHODS

We determined, by polymerase chain reaction (PCR), the Pro12Ala PPARgamma2 and the eNOS 4a/b gene polymorphisms in a total of 395 patients with diabetes mellitus 2 (DM2) (225 men and 170 women) from the LIANCO (Lipid-Analytic-Cologne) study. Hypertension was defined as known or newly diagnosed hypertension according to current national guidelines. Associations were determined using chi-square statistics. The influence of genotype and other parameters on blood pressure was determined by analysis of variance (ANOVA) and multivariate analyses.

RESULTS

The genotype frequencies of the Pro12Ala polymorphism were 3% AlaAla, 23% ProAla and 74% ProPro and of the eNOS 4a/b polymorphism 3% a/a, 25% b/a and 72% b/b. There were 65% patients with, and 35% without hypertension. A total of 77% of the patients with hypertension were under pharmacological treatment. The mean systolic and diastolic blood pressure (SBP, DBP) was 148 +/- 22 and 84 +/- 11 mmHg in patients with, and 131 +/- 12 and 79 +/- 8 mmHg in patients without, hypertension. There was no difference in the occurrence of hypertension among ProAla and AlaAla subjects compared with ProPro subjects (P = 0.98). There was also no difference between a-allele carriers and non-carriers of the eNOS polymorphism (P = 0.42). There were no differences between men and women in the associations. Analysis of variance did neither identify an influence on systolic or diastolic blood pressure by the presence of the Ala or the a-allele of the respective genotypes nor a significant interaction of the two.

CONCLUSIONS

In DM2 the Pro12Ala and 4a/b gene polymorphisms of the PPARgamma2 and eNOS genes, respectively, are not associated with systolic or diastolic blood pressure, either in men or in women. Our results in a large cohort fail to confirm reports of recent studies suggesting an association of lower blood pressure in patients with DM2 and carriers of Pro12Ala polymorphism.

Impact of genetic variation of PPARgamma in humans

Peroxisome proliferator-activated receptor gamma (PPARgamma) is a transcription factor with a key role in adipocyte differentiation. Since 1997, studies of rare mutations and common polymorphisms of the PPARgamma gene have enabled us to expand our knowledge of the role of this transcription factor in humans. Rare monogenic mutations in PPARgamma have a limited impact on the health of the population due to their low frequency but are associated with severe phenotypes such as severe insulin resistance, partial lipodystrophy, type 2 diabetes and hypertension. Conversely, common polymorphisms of PPARgamma with a relatively high frequency can have a significant impact on the general population. Although they may modulate the risk of developing type 2 diabetes, obesity and cardiovascular diseases, the data remains controversial. This review details and discusses results obtained for PPARgamma variants, whose effects sometimes appear discordant.

Tree-structured supervised learning and the genetics of hypertension

This paper is about an algorithm, FlexTree, for general supervised learning. It extends the binary tree-structured approach (Classification and Regression Trees, CART) although it differs greatly in its selection and combination of predictors. It is particularly applicable to assessing interactions: gene by gene and gene by environment as they bear on complex disease. One model for predisposition to complex disease involves many genes. Of them, most are pure noise; each of the values that is not the prevalent genotype for the minority of genes that contribute to the signal carries a "score." Scores add. Individuals with scores above an unknown threshold are predisposed to the disease. For the additive score problem and simulated data, FlexTree has cross-validated risk better than many cutting-edge technologies to which it was compared when small fractions of candidate genes carry the signal. For the model where only a precise list of aberrant genotypes is predisposing, there is not a systematic pattern of absolute superiority; however, overall, FlexTree seems better than the other technologies. We tried the algorithm on data from 563 Chinese women, 206 hypotensive, 357 hypertensive, with information on ethnicity, menopausal status, insulin-resistant status, and 21 loci. FlexTree and Logic Regression appear better than the others in terms of Bayes risk. However, the differences are not significant in the usual statistical sense.

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

We investigated the association of C1431T and Pro12Ala polymorphisms at the peroxisome proliferator-activated receptor gamma (PPARgamma) locus with plasma lipids and insulin resistance-related variables, according to diabetes status, in a large and representative Asian population from Singapore consisting of 2,730 Chinese, 740 Malays, and 568 Indians. Moreover, we estimated the diabetes risk and examined gene-nutrient interactions between these variants and the ratio of polyunsaturated fatty acid to saturated fat (SFA) in determining body mass index (BMI) and fasting insulin. We found differential effects of these gene variants. The Pro12Ala polymorphism was more associated with plasma lipids and fasting glucose concentrations, whereas the C1431T polymorphism was related to the risk of diabetes. Carriers of the 12Ala allele had higher HDL-cholesterol than did Pro12Pro homozygotes (P < 0.05), and the effect of the 12Ala allele on fasting glucose was modified by diabetes status (P < 0.001). After controlling for confounders, carriers of the T allele had decreased risk of diabetes compared with CC homozygotes [odds ratio (OR) 0.73, 95% confidence interval (CI) 0.58-0.93; P = 0.011]; this effect was stronger in Indians (OR 0.38, 95% CI 0.15-0.92; P = 0.032). For both polymorphisms, normal subjects carrying the less prevalent allele had higher BMI (P < 0.05). The PUFA/SFA did not modify the effect of these polymorphisms on BMI or insulin.

Estudios sobre la obesidad en genes candidatos

There are more than 430 chromosomic regions with gene variants involved in body weight regulation and obesity development. Polymorphisms in genes related to energy expenditure--uncoupling proteins (UCPs), related to adipogenesis and insulin resistance--hormone-sensitive lipase (HLS), peroxisome proliferator-activated receptor gamma (PPAR gamma), beta adrenergic receptors (ADRB2,3), and alfa tumor necrosis factor (TNF-alpha), and related to food intake--ghrelin (GHRL)--appear to be associated with obesity phenotypes. Obesity risk depends on two factors: a) genetic variants in candidate genes, and b) biographical exposure to environmental risk factors. It is necessary to perform new studies, with appropriate control groups and designs, in order to reach relevant conclusions with regard to gene/environmental (diet, lifestyle) interactions.

Pro12Ala of the peroxisome proliferator-activated receptor-gamma2 gene is associated with lower serum insulin levels in nonobese African Americans: the Atherosclerosis Risk in Communities Study

Recent research suggests that the Pro12Ala variant in peroxisome proliferator-activated receptor-gamma2 (PPAR-gamma2) is associated with diabetes- and obesity-related traits, and that its effects may be modified by obesity status. We characterized this variant in a population-based sample of 1,441 middle-aged African-American individuals with respect to diabetes-, obesity-, and other cardiovascular-related traits, both cross-sectionally and prospectively. The overall frequency of Ala12 was 1.9% (95% CI 1.5-2.5%), significantly lower than in Caucasian populations. Consistent with previous findings in Caucasians, African Americans with type 2 diabetes tended to be less likely to have the Pro/Ala genotype than those without (odds ratio [OR] 0.64, 95% CI 0.34-1.20); however, this OR was not statistically significant. Among nonobese individuals, the Pro/Ala genotype was associated with significantly lower ln(insulin) (P = 0.001), lower ln(HOMA-IR) (homeostasis model assessment of insulin resistance) (P = 0.002), higher fasting glucose-to-insulin ratio (P = 0.005), and lower diastolic blood pressure (P = 0.02). Among overweight individuals (BMI 25-29.9 kg/m(2)), the Pro/Ala genotype was associated with greater BMI (P = 0.02), waist-to-hip ratio (P = 0.01), and waist circumference (P = 0.04). Among obese individuals, there was no association between any of the diabetes- or obesity-related traits and the Pro12Ala PPAR-gamma2 variant. We conclude that among nonobese African Americans, the Pro/Ala genotype is associated with markers of greater insulin sensitivity.

The peroxisome proliferator-activated receptor-gamma2 gene polymorphism (Pro12Ala) beneficially influences insulin resistance and its tracking from childhood to adulthood: the Bogalusa Heart Study

The peroxisome proliferator-activated receptor (PPAR)-gamma2 gene polymorphism Pro12Ala has been associated with increased insulin sensitivity in some but not all studies. Little is known about its effect on the tracking of insulin resistance status over time. These aspects were examined in a community-based sample of 686 white young adults, aged 20-38 years, and 426 white children, aged 4-17 years, and a subsample of a cohort (n = 362) who participated both as children and adults, with an average follow-up period of 13.4 years. Insulin resistance was measured by the homeostasis model assessment of insulin resistance (HOMA-IR) using fasting insulin and glucose. The frequency of the variant Ala12 allele was 0.104 in whites vs. 0.017 in blacks. After adjusting for sex, age, and BMI, adult subjects with the genotype Pro/Pro, Pro/Ala, and Ala/Ala, respectively, showed significant decreasing trends in fasting insulin (11.7, 10.3, and 8.8 micro U/ml; P = 0.002) and HOMA-IR (2.4, 2.1, and 1.7; P = 0.006). Similar but nonsignificant trends were noted in childhood. A significant genotype-BMI interaction effect on insulin (P = 0.020), glucose (P = 0.007), and HOMA-IR (P = 0.001) was found in adulthood, with carriers versus noncarriers showing attenuated association with BMI. The genotype-BMI interaction effect on these variables tended to be similar in childhood. With respect to tracking over time, of individuals in the top age- and sex-specific quartile of HOMA-IR in childhood, 48.7% (38/78) of noncarriers vs. 16.7% (2/12) of the carriers (P = 0.035) remained in the same quartile in adulthood. A similar trend was observed for insulin (2/13 vs. 35/77, P = 0.037). In conclusion, the Pro12Ala polymorphism of the PPAR-gamma2 gene beneficially influences insulin resistance and its tracking from childhood to adulthood. Further, the Ala12 allele attenuates the adverse association between adiposity and insulin resistance measures.

The human obesity gene map: the 2002 update

This is the ninth update of the human obesity gene map, incorporating published results through October 2002 and continuing the previous format. Evidence from single-gene mutation obesity cases, Mendelian disorders exhibiting obesity as a clinical feature, quantitative trait loci (QTLs) from human genome-wide scans and various animal crossbreeding experiments, and association and linkage studies with candidate genes and other markers is reviewed. For the first time, transgenic and knockout murine models exhibiting obesity as a phenotype are incorporated (N = 38). As of October 2002, 33 Mendelian syndromes relevant to human obesity have been mapped to a genomic region, and the causal genes or strong candidates have been identified for 23 of these syndromes. QTLs reported from animal models currently number 168; there are 68 human QTLs for obesity phenotypes from genome-wide scans. Additionally, significant linkage peaks with candidate genes have been identified in targeted studies. Seven genomic regions harbor QTLs replicated among two to five studies. Attempts to relate DNA sequence variation in specific genes to obesity phenotypes continue to grow, with 222 studies reporting positive associations with 71 candidate genes. Fifteen such candidate genes are supported by at least five positive studies. The obesity gene map shows putative loci on all chromosomes except Y. More than 300 genes, markers, and chromosomal regions have been associated or linked with human obesity phenotypes. The electronic version of the map with links to useful sites can be found at http://obesitygene.pbrc.edu.

Haplotype analysis of the PPARgamma Pro12Ala and C1431T variants reveals opposing associations with body weight

BACKGROUND

Variation at the PPARG locus may influence susceptibility to type 2 diabetes and related traits. The Pro12Ala polymorphism may modulate receptor activity and is associated with protection from type 2 diabetes. However, there have been inconsistent reports of its association with obesity. The silent C1431T polymorphism has not been as extensively studied, but the rare T allele has also been inconsistently linked to increases in weight. Both rare alleles are in linkage disequilibrium and the independent associations of these two polymorphisms have not been addressed.

RESULTS

We have genotyped a large population with type 2 diabetes (n = 1107), two populations of non-diabetics from Glasgow (n = 186) and Dundee (n = 254) and also a healthy group undergoing physical training (n = 148) and investigated the association of genotype with body mass index. This analysis has demonstrated that the Ala12 and T1431 alleles are present together in approximately 70% of the carriers. By considering the other 30% of individuals with haplotypes that only carry one of these polymorphisms, we have demonstrated that the Ala12 allele is consistently associated with a lower BMI, whilst the T1431 allele is consistently associated with higher BMI.

CONCLUSION

This study has therefore revealed an opposing interaction of these polymorphisms, which may help to explain previous inconsistencies in the association of PPARG polymorphisms and body weight.

Lack of association of the codon 12 polymorphism of the peroxisome proliferator-activated receptor gamma gene with breast cancer and body mass

A principal hypothesized mechanism underlying breast carcinogenesis involves oestrogen-induced cell proliferation. In addition to its well-established role in the transcriptional regulation of genes required for adipocyte differentiation, the peroxisome proliferator-activated receptor gamma (PPARgamma) may be involved in transcriptional down-regulation of aromatase, a key enzyme in oestrogen biosynthesis. Furthermore, specific agonists for PPARgamma induce differentiation and suppress markers of malignancy in breast cancer cells in vitro. We investigated the association of the Pro12Ala PPARgamma polymorphism with breast cancer in a case-control study nested within the prospective Nurses' Health Study. Included were 725 incident cases of breast cancer diagnosed after blood collection through 1996 and 953 matched controls. In addition to breast cancer, the association of the PPARgamma Pro12Ala polymorphism with breast cancer risk factors, body mass index (BMI), weight gain since age 18 years, plasma hormones [oestrone sulphate, oestrone, oestradiol, androstenedione, testosterone, dehydroepiandrosterone (DHEA) and DHEA sulphate] and plasma lipids (total cholesterol and high density lipoprotein) was analysed. No significant association was observed between PPARgamma Pro12Ala polymorphism and either incident breast cancer (odds ratio = 1.08, 95% confidence interval = 0.85-1.38 for Ala allele carriers compared to non-carriers), plasma hormones, plasma cholesterol, BMI, weight gain since age 18 years or waist-to-hip ratio. To our knowledge, this is the first study to investigate the role of the Pro12Ala PPARgamma polymorphism in cancer. We did not find evidence to support a role for this polymorphism in breast cancer susceptibility. Furthermore, similar to others, we did not find evidence to suggest that Pro12Ala PPARgamma polymorphism is directly associated with body mass or weight gain.

The peroxisome proliferator-activated receptor-gamma2 Pro12Ala polymorphism

Peroxisome proliferator-activated receptor (PPAR)-gamma is a transcription factor with a key role in adipocyte differentiation. The Ala allele of the common Pro12Ala polymorphism in the isoform PPAR-gamma2 is associated with reduced risk for type 2 diabetes. The effect on the individual is weak, but because of a prevalence of >75% of the high-risk Pro allele, the population-attributable risk is enormous. The in vivo effects of the polymorphism are secondary to alterations in adipose tissue, where PPAR-gamma2 is predominantly expressed. Moderate reduction in transcriptional activity of PPAR-gamma as a result of the polymorphism modulates production and release of adipose-derived factors. Both decreased release of insulin-desensitizing free fatty acids, tumor necrosis factor-alpha, and resistin and increased release of the insulin-sensitizing hormone adiponectin result in secondary improvement of insulin sensitivity of glucose uptake and suppression of glucose production. The population effect of this polymorphism may be modulated by environmental or genetic factors such as obesity, ethnicity, ratio of unsaturated to saturated fatty acids, and genetic background. Once diabetes has developed, the protective effect of the Ala allele may be lost, since increased vascular complications and more pronounced beta-cell dysfunction have been reported. These observations, however, are currently unexplained. In conclusion, the Pro12Ala polymorphism in PPAR-gamma2 represents the first genetic variant with a broad impact on the risk of common type 2 diabetes. The precise understanding of its mechanism may lead to novel diagnostic, preventive, and therapeutic approaches for improving the management of type 2 diabetes.