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

Interaction between the dietary indices and PPAR-γ Pro12Ala gene variants on cardiovascular risk factors in patients with type 2 diabetes mellitus

AIMS

We investigated the interaction between peroxisome proliferator-activated receptor gamma (PPAR-γ) Pro12Ala polymorphism and healthy eating index (HEI), Dietary Quality Index-International (DQI-I), and dietary phytochemical index (DPI) on cardiovascular disease (CVD) risk factors in patients with type 2 diabetes mellitus (T2DM).

METHODS

This cross-sectional study was conducted on 393 diabetic patients. PPAR-γ Pro12Ala was genotyped by the PCR-RFLP method. Biochemical markers including total cholesterol (TC), low-density lipoprotein (LDL), high-density lipoprotein (HDL), triglyceride (TG), superoxide dismutase (SOD), C-reactive protein (CRP), total antioxidant capacity (TAC), pentraxin-3 (PTX3), isoprostaneF2α (PGF2α). Interleukin 18 (IL18), leptin, and ghrelin were measured by standard protocol. Food-frequency questionnaires (FFQ) were used for dietary indices (DQI-I, DPI, HEI) calculation.

RESULTS

Homozygous carriers of the rs1801282 C allele showed higher leptin compared G allele carriers (P = .015). The rs1801282-DQI-I interactions were significant on waist circumference (WC) (P = .019). Thus, C-allele carriers in the higher tertile of DQI-I had higher WC compared with GG homozygous. Further, an interaction was observed between PPAR rs1801282 polymorphism and DQI-I on serum IL-18 level (P = .032). Besides, a significant rs1801282-DPI interaction was shown on HDL concentration (P = .041), G allele carriers who were in the highest tertile of DPI, had lower HDL. Moreover, there were significant rs1801282-HEI interactions on serum leptin (P = .021). Individuals with (CC, CG) genotypes in the higher tertile of HEI, had lower leptin concentration.

CONCLUSION

Higher dietary indices (DQI-I, DPI, HEI) may affect the relationship between PPAR-γ Pro12Ala polymorphism and WC, ghrelin, leptin, HDL, and IL-18 concentration in patients with T2DM.

Evolutionary forces in diabetes and hypertension pathogenesis in Africans

Rates of type 2 diabetes (T2D) and hypertension are increasing rapidly in urbanizing sub-Saharan Africa (SSA). While lifestyle factors drive the increases in T2D and hypertension prevalence, evidence across populations shows that genetic variation, which is driven by evolutionary forces including a natural selection that shaped the human genome, also plays a role. Here we report the evidence for the effect of selection in African genomes on mechanisms underlying T2D and hypertension, including energy metabolism, adipose tissue biology, insulin action and salt retention. Selection effects found for variants in genes PPARA and TCF7L2 may have enabled Africans to respond to nutritional challenges by altering carbohydrate and lipid metabolism. Likewise, African-ancestry-specific characteristics of adipose tissue biology (low visceral adipose tissue [VAT], high intermuscular adipose tissue and a strong association between VAT and adiponectin) may have been selected for in response to nutritional and infectious disease challenges in the African environment. Evidence for selection effects on insulin action, including insulin resistance and secretion, has been found for several genes including MPHOSPH9, TMEM127, ZRANB3 and MC3R. These effects may have been historically adaptive in critical conditions, such as famine and inflammation. A strong correlation between hypertension susceptibility variants and latitude supports the hypothesis of selection for salt retention mechanisms in warm, humid climates. Nevertheless, adaptive genomics studies in African populations are scarce. More work is needed, particularly genomics studies covering the wide diversity of African populations in SSA and Africans in diaspora, as well as further functional assessment of established risk loci.

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

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

Prevalence of the rs1801282 single nucleotide polymorphism of the PPARG gene in patients with metabolic syndrome

OBJECTIVE

This study aimed to get the genotypic and allelic frequencies of rs1801282 in 179 volunteer donors and 154 patients with Metabolic syndrome (MetS) in Brasilia, Brazil and also examine the association with anthropometric, biochemical and hemodynamic variables in the latter group. MetS comprises a group of diseases resulting from insulin resistance, in-creased risk of type 2 diabetes and atherosclerotic cardiovascular disease. MetS is defined by the presence of increased visceral fat, atherogenic dyslipidemia (elevated triglycerides (TGL)), with decreased high density lipoprotein (HDL) and increased low density lipoprotein (LDL) levels, hypertension (BPH) and disturbances in glucose homeostasis representing a significant burden across the world due to the alarming increase in the incidence over the last decades besides their significant morbidity and mortality. Peroxisome proliferator activated receptor-gamma (PPARg) has been mentioned as a candidate gene for determining the risk of MetS. It is a member of the nuclear receptors superfamily and a ligand-activated transcription factor, which regulates the expression of genes involved in the network lipogenesis and adipogenesis, insulin sensitivity, energy balance, inflammation, angiogenesis and atherosclerosis. Among the PPARG genetic variants, single nucleotide polymorphism rs1801282 has been the most extensively studied one since it was first described by Yen and cols. in 1997. This polymorphism is characterized by the replacement of a proline (CCC) to an alanine (GCA) at codon 12 of exon B, due to the exchange of a cytosine with a guanine. The Ala allele frequency varies in different ethnic groups.

MATERIALS AND METHODS

DNA was extracted using Chelex-100 method and determinations of genotypes were performed by allele-specific chain reaction.

RESULTS

The distribution of genotype frequency of the MetS group was not statistically different from the frequency in the donor population at large. In the first group, genotype frequency was CC to 0.869 and 0.103 for CG, while allelic frequencies were 0.948 for C and 0.052 for G allele. In the group of donors, the genotype and allele frequencies were 0.882 for CC, 0.117 to CG; and 0.941 to 0.059 for G and C, respectively. GG genotype was not found in any of the two groups. The genotype distribution and allele frequencies were in Hardy-Weinberg equilibrium. No marker could be detected from the analysis of anthropometric, biochemical and hemodynamic variables in the MetS group.

CONCLUSION

Our data suggest that this polymorphism is not correlated with predisposition to MetS. The results obtained on a small sample of the population of Brasilia, corroborate the data reported in the literature on the prevalence of this polymorphism in PPAR in populations of different ethnic origins.

Association of the Pro12Ala Polymorphism with the Metabolic Parameters in Women with Polycystic Ovary Syndrome

AIM:

To investigate the association of peroxisome proliferator-activated receptor gamma (PPARG) Pro12Ala polymorphism with polycystic ovary syndrome (PCOS) and its effect on the metabolic parameters in PCOS women.

METHODS:

The study used PCR to identify the presence of the PPARG Pro12Ala polymorphism in 100 PCOS women and 120 age-matched healthy women. All participants were subjected to anthropometry, biochemical and metabolic evaluation.

RESULTS:

Significant difference in the genotypes distributions of PPARG Pro12Ala polymorphism was observed among PCOS women and controls (p = 0.03). The frequency of the polymorphic allele Ala was significantly higher in PCOS cases than that in the controls (OR = 2.01, p = 0.01). The carries of the variant allele Ala in PCOS women showed significant higher values in body mass index (BMI), systolic and diastolic blood pressure, waist circumference, waist to hip ratio, sum of skin folds, fasting blood glucose, fasting blood insulin, HOMA-IR, fasting triglycerides, total cholesterol and low-density lipoprotein than non-carriers.

CONCLUSION:

The PPARG Pro12Ala polymorphism might contribute to the risk of PCOS and abnormal metabolic parameters and could be considered as a biomarker for early diagnosis and clinic prediction of metabolic complications.

Cardiovascular risk in Gullah African Americans with high familial risk of type 2 diabetes mellitus: project SuGAR

OBJECTIVES

To determine the prevalence of cardiovascular disease, levels of cardiovascular risk factors, and extent of preventive care in Gullah African Americans with a high familial risk of type 2 diabetes mellitus.

METHODS

Between 1995 and 2003, 1321 Gullah African Americans with a high prevalence of diabetes mellitus from the South Carolina Sea Islands consented to and enrolled in the Sea Islands Genetic African American Registry (Project SuGAR). A cross-sectional analysis of cardiometabolic risk, preventive care, and self-reported cardiovascular disease was conducted.

RESULTS

Cardiometabolic risk factor levels were high and vascular disease was prevalent. Among the subjects with diabetes mellitus, the mean disease duration was 10.5 years; approximately one-third reported reduced vision or blindness; and >80% reported numbness, pain, or burning in their feet. Preventive diabetes care was limited, with <60%, <25%, and <40% seeing an ophthalmologist, podiatrist, and dentist, respectively, within the past year. Only 54.4% of women and 39.3% of men reported daily glucose monitoring.

CONCLUSIONS

As the largest existing study of Gullah individuals, our study offers insight into not only the level of cardiovascular risk in this population but also the pathophysiological mechanisms central to ancestral differences in cardiometabolic risk in the broader African American population.

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

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

The Pro12Ala Polymorphism of PPAR-γ Gene Is Associated with Sepsis Disease Severity and Outcome in Chinese Han Population

Peroxisome proliferator-activated receptor-γ (PPAR-γ) is a ligand-binding nuclear receptor, and its activation plays a prominent role in regulating the inflammatory response. Therefore, PPAR-γ has been suggested as a candidate gene for sepsis. In the present study, we investigated the association between the Pro12Ala polymorphism of PPAR-γ and sepsis in a Han Chinese population. A total of 308 patients with sepsis and 345 healthy controls were enrolled in this study. Genotyping was performed using the polymerase chain reaction-ligation detection reaction (PCR-LDR) method. No significant differences were detected in the allele and genotype distributions of the PPAR-γ Pro12Ala SNP between septic patients and controls (P = 0.622 for genotype; P = 0.629 for allele). However, stratification by subtypes (sepsis, septic shock, and severe sepsis) revealed a statistically significant difference in the frequency of the Ala allele and Ala-carrier genotype between the patients with the sepsis subtype and the healthy controls (P = 0.014 for allele and P = 0.012, for genotype). Moreover, significant differences were found in the frequency of the Ala allele and genotype between the sepsis survivors and nonsurvivors (all P = 0.002). In the survivors, the PPAR-γ Pro12Ala genotype was significantly associated with decreased disease severity and recovery time (all P < 0.001). Thus, genetic polymorphism is thought to play a role in the development and outcome of sepsis.

Association of PPARG Pro12Ala polymorphism with insulin sensitivity and body mass index in patients with polycystic ovary syndrome

Insulin resistance is one of the key factors in the pathogenesis of polycystic ovary syndrome (PCOS). The peroxisome proliferator-activated receptor gamma (PPARG) plays a role in the regulation of insulin sensitivity. The aim of the present study was to establish a possible association of the PPARG Pro12Ala polymorphism with PCOS and its effect on family and personal history, as well as on the metabolic and endocrine parameters in PCOS patients. A total of 151 PCOS patients and 179 healthy women of reproductive age were enrolled. History, body mass index (BMI), waist-to-hip ratio and the presence of phenotypic hyperandrogenism were recorded. Hormonal, metabolic and biochemical profiles were assessed. A molecular analysis for the genetic polymorphism was performed. One third (29.8%) of the PCOS patients were found to be carriers of at least one variant of the Ala allele (X/Ala), while 70.2% carried two wild-type Pro alleles (Pro/Pro), with an equal distribution observed in the control group. The PCOS patients carrying the X/Ala alleles exhibited lower serum fasting insulin levels, homeostatic model assessment of insulin resistance (HOMA-IR) and BMI compared to Pro/Pro carriers. This finding was significant only in the lean PCOS group. The polymorphic genotype exerted no effect on history, hormonal and clinical hyperandrogenism, lipid status or C-reactive protein, leptin, adiponectin, resistin and ghrelin serum levels in women with PCOS. In conclusion, although the PPARG Pro12Ala polymorphism is not a major determinant of PCOS in the Croatian population, it may exert a positive effect on insulin sensitivity and BMI. As these associations were recorded exclusively in the lean group of patients with PCOS, this polymorphism potentially contributes to a protective role against hyperinsulinemia and obesity.

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

BACKGROUND

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

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

Background

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

Methods and Findings

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

Conclusion

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

The Human Obesity Gene Map: The 2003 Update

This is the tenth update of the human obesity gene map, incorporating published results up to the end of October 2003 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 animal crossbreeding experiments, and association and linkage studies with candidate genes and other markers is reviewed. Transgenic and knockout murine models relevant to obesity are also incorporated (N = 55). As of October 2003, 41 Mendelian syndromes relevant to human obesity have been mapped to a genomic region, and causal genes or strong candidates have been identified for most of these syndromes. QTLs reported from animal models currently number 183. There are 208 human QTLs for obesity phenotypes from genome-wide scans and candidate regions in targeted studies. A total of 35 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 272 studies reporting positive associations with 90 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. Overall, more than 430 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.

The Human Obesity Gene Map: The 2004 Update

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

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

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

PPAR-gamma2 pro12Ala polymorphism is associated with post-challenge abnormalities of glucose homeostasis in children and adolescents with obesity

AIM

The aim of the study was to investigate the association between PPAR-gamma2 Pro12Ala polymorphism and laboratory characteristics of carbohydrate metabolism in children and adolescents with obesity. In addition, serum levels of tumor necrosis factor (TNF)-alpha, and soluble form of its receptors (sTNFR1 and sTNFR2) were assessed.

METHODS

In a cross-sectional study, 79 obese children and adolescents of Caucasian origin were investigated. PPAR-gamma2 Pro12Ala polymorphism was determined using polymerase chain reaction--restriction fragment length polymorphism technique. Serum levels of TNF-alpha, sTNFR1 and sTNFR2 were measured by enzyme amplified sensitivity immunoassay.

RESULTS

The minor Ala allele frequency was found to be 14.56% in our cohort. No significant differences in age, BMI, waist circumference, blood pressure, serum lipid, uric acid, TNF-alpha, sTNFR1 and sTNFR2 values were found between carriers of the Ala allele (Pro/Ala and Ala/Ala; n=21) vs. homozygous carriers of the Pro allele (Pro/Pro; n=58). However, post-challenge (120 min) plasma glucose and insulin values were significantly lower in Ala allele carriers vs. homozygous Pro allele carriers (6.56 +/- 0.26 vs. 7.36 +/- 0.25 mmol/L and 65.9 +/- 13.8 vs. 111.8 +/- 20.7 microU/mL, respectively; p < 0.05); while no significant differences were found at fasting state.

CONCLUSIONS

The association between PPAR-gamma2 Prol2Ala polymorphism and glucose metabolism is already present in children and adolescents with obesity who might be at the very beginning of the natural course of type 2 diabetes. At this stage, higher insulin sensitivity can be detected in Ala allele carriers compared to homozygous Pro subjects at post-challenge but not in fasting state; however, the TNF-system seems not to be involved in the alteration of glucose homeostasis due to PPAR-gamma2 Pro12Ala polymorphism.

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

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.

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

Purpose

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

Methods

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

Results

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

Conclusions

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

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.

An analysis of peroxisome proliferator-activated receptor gamma (PPAR-gamma 2) Pro12Ala polymorphism distribution and prevalence of type 2 diabetes mellitus (T2DM) in world populations in relation to dietary habits

BACKGROUND AND AIM

The human peroxisome proliferator-activated receptor gamma (PPAR-gamma) is involved in lipid storage, glucose homeostasis and adipocyte differentiation. The Ala allele of the Pro12Ala polymorphism has been associated with a protective effect against T2DM. Ala allele frequencies are known for many populations, but data are absent for other interesting human groups.

METHODS AND RESULTS

We examined samples from Ethiopia, Benin, Ecuador and Italy. In addition, we performed an analysis of the Pro12Ala polymorphism distribution in world populations, also in relation to T2DM prevalence and the diet lipid content. In the European populations, the Ala allele frequencies are distributed according to a latitudinal trend, with the highest in the northern and central European populations and the lowest in the Mediterranean populations. Considering the world populations, a significant inverse relationship between Ala frequency and T2DM prevalence was observed mainly in populations where energy from lipids exceeded 30% of the total energy intake.

CONCLUSION

Northern Europe's cold climate has been hypothesised to have played a role in contributing to the present pattern. Moreover our analysis appears to confirm, at a population level, the protective effect of Ala allele against T2DM, already observed in case-control studies, but only in populations with a diet rich in lipids.

Validation of steady-state insulin sensitivity indices in chronic kidney disease

OBJECTIVE

Insulin resistance may contribute to cardiovascular disease and the progression of renal insufficiency in patients with chronic kidney disease (CKD). However, feasible methods for estimating insulin sensitivity in large-population CKD studies have not been validated. The purpose of this study was to attempt to validate several commonly used steady-state insulin sensitivity (SI-SS) indices in a CKD population.

RESEARCH DESIGN AND METHODS

Twenty-seven subjects with estimated glomerular filtration rate (eGFR) ranging from 70 to <10 ml/min per 1.73 m2 (median eGFR = 48) underwent a frequently sampled intravenous glucose tolerance test (FSIVGTT) on a single occasion. Correlations were obtained between the minimal model-derived insulin sensitivity parameter from the FSIVGTT (SI-FSIVGTT) and seven SI-SS indices derived from fasting insulin and glucose data obtained just before the FSIVGTT.

RESULTS

Each of the seven steady-state indices was significantly correlated with SI-FSIVGTT. For indices obtained using the mean of four fasting insulin and glucose values over 15 min, Pearson correlation coefficients (|r|) ranged from 0.51 to 0.87 (P < 0.01 for each). For indices using single fasting insulin and glucose values, |r| ranged from 0.51 to 0.72 (P < 0.01 for each). By both the four and one time point approaches, 1/I(0) had the highest correlation with SI-FSIVGTT. The correlation with SI-FSIVGTT did not change significantly according to eGFR level for any of the SI-SS indices.

CONCLUSIONS

SI-SS indices are valid surrogates for SI-FSIVGTT in the CKD population. Their use will expand the range of testable hypotheses in CKD cohort studies.

Evaluation of polymorphisms known to contribute to risk for diabetes in African and African-American populations

PURPOSE OF REVIEW

Populations of direct African ancestry have much greater genetic diversity than do other populations. African-American populations exhibit twice the prevalence of type 2 diabetes as compared with their Caucasian counterparts. African-American populations are likely to have unique genetic susceptibility to type 2 diabetes. This review addresses current knowledge of susceptibility genes that are shared with other groups and those that are unique to populations of African descent.

RECENT FINDINGS

When compared with the plethora of Caucasian studies, relatively few studies have been conducted in African or African-American populations. The most exciting findings have been family-based linkage studies, which point to multiple regions that may harbor susceptibility genes. Recent work suggests that the major Caucasian locus, TCF7L2, plays a role in some African-based populations, whereas unique factors remain to be confirmed.

SUMMARY

Although progress has been made in finding the genetic cause of type 2 diabetes in African and African-American populations, at this time no variant can be considered unequivocally confirmed as a diabetes susceptibility locus.

Complexity of type 2 diabetes mellitus data sets emerging from nutrigenomic research: a case for dimensionality reduction?

Nutrigenomics promises personalized nutrition and an improvement in preventing, delaying, and reducing the symptoms of chronic diseases such as diabetes. Nutritional genomics is the study of how foods affect the expression of genetic information in an individual and how an individual's genetic makeup affects the metabolism and response to nutrients and other bioactive components in food. The path to those promises has significant challenges, from experimental designs that include analysis of genetic heterogeneity to the complexities of food and environmental factors. One of the more significant complications in developing the knowledge base and potential applications is how to analyze high-dimensional datasets of genetic, nutrient, metabolomic (clinical), and other variables influencing health and disease processes. Type 2 diabetes mellitus (T2DM) is used as an illustration of the challenges in studying complex phenotypes with nutrigenomics concepts and approaches.

Pro12Ala polymorphism of the PPARgamma2 locus modulates the relationship between energy intake and body weight in type 2 diabetic patients

OBJECTIVE

We explore the relationship among BMI, habitual diet, and the Pro12Ala polymorphism in the peroxisome proliferator-activated receptor (PPAR)gamma2.

RESEARCH DESIGN AND METHODS

The Pro12Ala variant was characterized in 343 unrelated type 2 diabetic patients who were consecutively seen at the outpatient clinic of a health district of the province of Naples. Anthropometric and laboratory parameters were measured; habitual diet was assessed by a validated semiquantitative food frequency questionnaire.

RESULTS

The overall frequency of Ala12 was 12% (n = 42). BMI was significantly higher in Ala carriers than non-Ala carriers, whereas total daily energy intake or macronutrient composition of the diet were similar in the two groups. For further analysis, participants were stratified according to genotype and sex-specific quartiles of energy intake. BMI increased in both genotype groups with increasing energy intake (P < 0.03). BMI was similar in Ala carriers and non-Ala carriers (30.0 vs. 30.1 kg/m2, P > 0.10) in the lower quartile of energy intake but significantly higher in Ala carriers in the upper quartile (36.0 vs. 32.1 kg/m2, P < 0.001). Average daily energy intake and diet composition were comparable within each quartile for carriers or noncarriers of the Ala allele. Relative to the noncarriers, Ala carriers had a significantly lower energy intake per kilogram body weight, thus suggesting that the Ala allele is associated with a higher food efficiency. The confounding role of medications, glucose control, and physical exercise was ruled out.

CONCLUSIONS

This study provides evidence of a differential susceptibility to fat accumulation, and, hence, weight gain, in response to habitual high energy intake for Ala carriers compared with Pro/Pro homozygotes.

Heterogeneous effect of peroxisome proliferator-activated receptor gamma2 Ala12 variant on type 2 diabetes risk

Conflicting results have been reported regarding whether the PPARgamma2 Pro12Ala polymorphism plays a role in the risk of type 2 diabetes (T2D), suggesting genetic heterogeneity. To investigate this issue, a meta-analysis of 41 published and 2 unpublished studies (a total of 42,910 subjects) was conducted. Ala12 carriers had a 19% T2D risk reduction, but this association was highly heterogeneous (p = 0.005). A great proportion (48%) of heterogeneity was explained by the controls' BMI, with risk reduction being greater when BMI was lower. Risk reduction of Ala12 carriers in Asia (35%) was higher than in Europe (15%, p = 0.02) and tended to be higher than in North America (18%, p = 0.10). Difference between Asians and Europeans was no longer significant (p = 0.15) after adjusting for the controls' BMI. Studies from Europe were still heterogeneous (p = 0.02) with risk reduction in Ala12 carriers being progressively smaller (test for trend in the odds ratios, p = 0.02) from Northern (26% reduction, p < 0.0001) to Central (10%, p = 0.04) and Southern (0%, p = 0.94) Europe. In conclusion, in our meta-analysis, the reduced risk of T2D in Ala12 carriers is not homogeneous. It is greater in Asia than in Europe and, among Europeans, it is higher in Northern Europe, barely significant in Central Europe, and nonexistent in Southern Europe.

Family history of diabetes, awareness of risk factors, and health behaviors among African Americans

OBJECTIVES

We examined the role of family history of diabetes in awareness of diabetes risk factors and engaging in health behaviors.

METHODS

We conducted a cross-sectional analysis of 1122 African American adults without diabetes who were participants in Project DIRECT (Diabetes Interventions Reaching and Educating Communities Together).

RESULTS

After adjustment for age, gender, income, education, body mass index, and perceived health status, African Americans with a family history of diabetes were more aware than those without such a history of several diabetes risk factors: having a family member with the disease (relative risk [RR]=1.09; 95% confidence interval [CI]=1.03, 1.15), being overweight (RR=1.12; 95% CI=1.05, 1.18), not exercising (RR=1.17; 95% CI=1.07, 1.27), and consuming energy-dense foods (RR=1.10; 95% CI=1.00, 1.17). Also, they were more likely to consume 5 or more servings of fruits and vegetables per day (RR=1.31; 95% CI=1.02, 1.66) and to have been screened for diabetes (RR=1.21; 95% CI=1.12, 1.29).

CONCLUSIONS

African Americans with a family history of diabetes were more aware of diabetes risk factors and more likely to engage in certain health behaviors than were African Americans without a family history of the disease.

Association of the peroxisome proliferator-activated receptor gamma gene with type 2 diabetes mellitus varies by physical activity among non-Hispanic whites from Colorado

The objective of the study was to test for an association between type 2 diabetes mellitus (T2DM) and the Pro12Ala polymorphism in the peroxisome proliferator-activated receptor gamma gene (PPAR-gamma) in families from Colorado. We were also interested in whether there was any modification by diet or physical activity. We studied 216 Hispanic pedigrees (1850 nuclear families) and 236 non-Hispanic white (NHW) pedigrees (1240 families) from the San Luis Valley and Denver, CO. We genotyped the Pro12Ala polymorphism of the PPAR-gamma gene. Historical physical activity (average metabolic equivalent task units per week) as well as average dietary intake over the past year was assessed by self-report. Using the family-based association test, we found that in NHWs the Pro12 allele was associated with T2DM only among those with low physical activity (P = .006), or with high polyunsaturated fat intake (P = .034). A significant interaction between low physical activity and the Pro12 allele in association with T2DM was also detected using generalized estimating equations models (P = .022). Furthermore, after stratifying by physical activity similar to the family-based association test, we found the Pro12 allele was significantly associated with T2DM in those with low physical activity (odds ratio, 2.37; 95% confidence interval, 1.14-4.94). There may be a gene-environment interaction between the Pro12 allele of the PPAR-gamma gene and physical activity that results in increased risk of T2DM in NHWs.

Application of nutrigenomic concepts to Type 2 diabetes mellitus

The genetic makeup that individuals inherit from their ancestors is responsible for variation in responses to food and susceptibility to chronic diseases such as Type 2 diabetes mellitus (T2DM). Common variations in gene sequences, such as single nucleotide polymorphisms, produce differences in complex traits such as height or weight potential, food metabolism, food-gene interactions, and disease susceptibilities. Nutritional genomics, or nutrigenomics, is the study of how foods affect the expression of genetic information in an individual and how an individual's genetic makeup affects the metabolism and response to nutrients and other bioactive components in food. Since both diet and genes alter one's health and susceptibility to disease, identifying genes that are regulated by diet and that cause or contribute to chronic diseases could result in the development of diagnostic tools, individualized intervention, and eventually strategies for maintaining health. Translating this research through clinical studies promises contributions to the development of personalized medicine that includes nutritional as well as drug interventions. Reviewed here are the key nutrigenomic concepts that help explain aspects of the development and complexity of T2DM.

No Association of Pro12Ala Polymorphism of PPAR-.GAMMA. Gene With Coronary Artery Disease in Korean Subjects

BACKGROUND

Peroxisome proliferator-activated receptor (PPAR)-gamma, a member of the nuclear hormone receptor family, which is involved in the differentiation of adipose tissue, is reported to be associated with the pathogenesis of type 2 diabetes mellitus, insulin resistance and atherosclerosis. Whether the prevalence of coronary artery disease (CAD) is associated with Pro12Ala polymorphism in exon B of PPAR-gamma was investigated in Korean adults.

METHODS AND RESULTS

The study was conducted in 267 subjects (158 males, 109 females, mean age 58 years) who underwent coronary angiography because of chest pain. Cardiovascular risk factors, such as blood pressure, body mass index (BMI), fasting blood sugar and serum lipid profiles, were assessed in all subjects, who were divided into 4 groups according to the number of stenosed coronary arteries: normal, 1-vessel, 2-vessel and 3-vessel disease. Genotyping of Pro12Ala polymorphism was done with real-time polymerase chain reaction. Allelic frequency for proline was 0.955 and 0.045 for alanine, which was in Hardy-Weinberg equilibrium (p=0.74). One hundred and seventeen subjects (43.8%) had normal coronary arteries, 88 (33%) had 1-vessel disease, 39 (14.6%) had 2-vessel disease and 23 (8.6%) had 3-vessel disease. When the cardiovascular risk factors were compared among the 4 groups, there were no meaningful differences except for age and FBG levels, which were significant even after adjustment for age and BMI. There were no significant differences in the prevalence or severity of CAD according to the different genotypes of Pro12Ala, and in logistic regression analysis Pro12Ala polymorphism was not a predictor for CAD.

CONCLUSIONS

There was no significant association between Pro12Ala polymorphism in exon B of PPAR-gamma and prevalence or severity of CAD in Korean adults. Further studies on the correlation between Pro12Ala polymorphism and CAD should be carried out in a larger Korean population in the future.

Lack of association between the Pro12Ala polymorphism in PPAR-gamma2 gene and body weight changes, insulin resistance and chronic diabetic complications in obese patients with type 2 diabetes

BACKGROUND

It is generally accepted that the Pro12Ala polymorphism in peroxisome proliferator-activated receptor-gamma2 (PPAR-gamma2) is associated with an increased risk of type 2 diabetes. However, studies on an association between the polymorphism and obesity have yielded inconsistent findings. Also, a role of PPAR-gamma receptors in development of chronic diabetic complications cannot be excluded. The aim of this study was to investigate an association between Pro12Ala polymorphism and body weight changes, insulin resistance, insulin secretion and incidence of diabetic complications in obese patients with long-lasting type 2 diabetes.

METHODS

In 216 obese patients with at least a 10-year history of type 2 diabetes, a detailed medical history was taken and a physical examination with assessment of diabetic complications was performed as well as evaluation of insulin resistance (homeostatic model assessment-HOMA), insulin secretion and other biochemical parameters. PCR-RFLP was used to assess Pro12Ala polymorphism. Two subgroups of patients were compared: homozygotic Pro/Pro and Ala allele carriers (Ala/Ala + Ala/Pro).

RESULTS

No differences between the analyzed groups in body weight changes, insulin resistance and insulin secretion were found, but Ala allele was significantly more frequent in males than in females. There was no difference in incidence and progression of diabetic complications with only a trend towards higher incidence of diabetic retinopathy in patients with Ala allele.

CONCLUSIONS

There is no association between Pro12Ala PPAR-gamma2 polymorphism and body mass changes observed during a course of type 2 diabetes, differences in peripheral insulin resistance and incidence and progression of diabetic complications in obese patients with long-lasting type 2 diabetes.

PPAR-gamma Pro12Ala genotype and risk of cognitive decline in elders

BACKGROUND

The Pro12Ala polymorphism of peroxisome proliferator-activated receptor-gamma (PPAR-gamma) has been associated with decreased risk of diabetes and obesity, both disorders linked to cognitive impairment. We tested whether this polymorphism is associated with cognition.

METHODS

Two thousand nine hundred sixty-one participants (mean age, 74.1; 41% Black; 52% women) were administered the Modified Mini-Mental State Examination (3MS) and Digit Symbol Substitution Test (DSST) at baseline and 4 year follow-up. Test scores were adjusted for age, sex, education, cerebrovascular disease, depression and APOE genotype and additionally for race. We determined the association between Ala allele and development of cognitive decline (3MS decline of > or = 5 points).

RESULTS

At baseline, unadjusted scores on both cognitive tests were higher for Ala carriers compared to non-carriers (3MS, 94.2 versus 92.5, p<0.001; DSST, 40.2 versus 34.5, p<0.001). Similarly, follow-up scores were higher for Ala carriers. Multivariable adjustment led to similar results; additional adjustment for race attenuated the baseline 3MS results. After 4 years, 17.5% of Ala carriers developed cognitive decline compared to 25% among non-carriers (unadjusted OR=0.61; 95%CI, 0.46-0.82; adjusted OR=0.75; 95%CI, 0.55-1.02). Further adjustment for metabolic variables including fasting blood glucose and lipid level did not change the results.

CONCLUSIONS

The PPAR-gamma Ala12 allele carriers may have less risk of developing cognitive decline.

PPAR-gamma2 Pro12Ala polymorphism is associated with weight gain in women with gestational diabetes mellitus

OBJECTIVE

The polymorphisms of peroxisome proliferator-activator receptor-gamma2 (PPAR-gamma2) have been suggested to affect glucose metabolism and weight gain. Both conditions show great variations during pregnancy that makes pregnancy a suitable condition to detect any metabolic abnormalities related to PPAR-gamma2 polymorphisms. The objective of this study is to investigate the prevalence and metabolic impacts of PPAR-gamma2 polymorphism in control pregnant women and in patients with gestational diabetes mellitus (GDM).

METHODS

In this case-control study, anthropometric and metabolic variables of 100 non-diabetic pregnant women and of 62 women who were diagnosed as having GDM according to 100 g oral glucose tolerance test (OGTT) were compared on the basis of PPAR-gamma2 polymorphism by univariate analysis of covariance.

RESULTS

There were no statistically significant differences in baseline characteristics and the mean 50 g glucose challenge test values of pregnant women in both groups on the basis of PPAR-gamma2 genotype, although patients with Pro12Ala polymorphism were significantly taller in GDM group. The Pro12Ala polymorphism had no effect on 100 g OGTT results of patients with GDM. However, patients with GDM who had Pro12Ala polymorphism gained significantly more weight during their pregnancy.

CONCLUSION

The PPAR-gamma2 Pro12Ala polymorphism was observed to have no effect on glucose metabolism in normal pregnant women and women with GDM. However, only the patients with GDM who had this polymorphism gained significantly more weight during their pregnancy. It seems that Pro12Ala polymorphism plays a dynamic and interactive role in the regulation of BMI and glucose homeostasis.

The human obesity gene map: the 2005 update

This paper presents the 12th update of the human obesity gene map, which incorporates published results up to the end of October 2005. Evidence from single-gene mutation obesity cases, Mendelian disorders exhibiting obesity as a clinical feature, transgenic and knockout murine models relevant to obesity, quantitative trait loci (QTL) from animal cross-breeding experiments, association studies with candidate genes, and linkages from genome scans is reviewed. As of October 2005, 176 human obesity cases due to single-gene mutations in 11 different genes have been reported, 50 loci related to Mendelian syndromes relevant to human obesity have been mapped to a genomic region, and causal genes or strong candidates have been identified for most of these syndromes. There are 244 genes that, when mutated or expressed as transgenes in the mouse, result in phenotypes that affect body weight and adiposity. The number of QTLs reported from animal models currently reaches 408. The number of human obesity QTLs derived from genome scans continues to grow, and we now have 253 QTLs for obesity-related phenotypes from 61 genome-wide scans. A total of 52 genomic regions harbor QTLs supported by two or more studies. The number of studies reporting associations between DNA sequence variation in specific genes and obesity phenotypes has also increased considerably, with 426 findings of positive associations with 127 candidate genes. A promising observation is that 22 genes are each supported by at least five positive studies. The obesity gene map shows putative loci on all chromosomes except Y. The electronic version of the map with links to useful publications and relevant sites can be found at http://obesitygene.pbrc.edu.

The PPARG Pro12Ala polymorphism is associated with a decreased risk of developing hyperglycemia over 6 years and combines with the effect of the APM1 G-11391A single nucleotide polymorphism: the Data From an Epidemiological Study on the Insulin Resistance Syndrome (DESIR) study

Although cross-sectional studies have associated the Pro12Ala polymorphism of PPARG with type 2 diabetes, prospective studies offer more opportunities to investigate genetic variants. Associations between PPARG polymorphisms with insulin resistance parameters and with the 6-year incidence of impaired fasting glucose or type 2 diabetes were tested in 3,914 French Caucasians from the DESIR (Data From an Epidemiological Study on the Insulin Resistance Syndrome) cohort. In subjects normoglycemic at baseline (n = 3,498), the 6-year risk of hyperglycemia was lower in PPARG Ala carriers (odds ratio [OR] vs. ProPro = 0.66 [95% CI 0.44-0.99], P = 0.046 adjusted for sex, age, and BMI). Similar results were found with the PPARG C1431T single nucleotide polymorphism (SNP; adjusted OR = 0.65 [0.44-0.96], P = 0.036). Both alleles are in strong linkage disequilibrium (D' = 0.669, P < 0.001). The baseline mean fasting insulin and homeostasis model assessment of insulin resistance (HOMA-IR) were lower in Ala carriers compared with ProPro homozygotes (P = 0.001 for both), with smaller increases in mean insulin and HOMA-IR during follow-up (P = 0.007 and 0.018, respectively). No association with insulin levels or HOMA-IR was found with C1431T. In this cohort, the APM1 G-11391A SNP is associated with the development of hyperglycemia. The combined effects of PPARG Pro12Ala and APM1 G-11391A SNPs showed no interaction on the risk of 6-year hyperglycemia. The PPARG Ala allele showed a relatively high protective effect in developing hyperglycemia and hyperinsulinemia during a 6-year period. Cumulative rather than synergistic effects of PPARG Pro12Ala and APM1 SNPs on diabetes risk are suggested.

Genetics of leptin and obesity: a HuGE review

Leptin is an important regulator of the mass of adipose tissue and of body weight; it operates by inhibiting food intake and stimulating energy expenditure. Some polymorphic genes involved in the regulation of leptin-the leptin gene (LEP A19G), the leptin receptor gene (LEPR Q223R, K109R, and K656N), and the peroxisome proliferator-activated receptor-gamma gene (PPARG P12A and C161T)--have been investigated as possible factors associated with obesity. Allelic frequencies of these polymorphisms show ethnic variation. The authors performed a meta-analysis of the available data on the association between these polymorphisms and obesity based on case-control studies. Odds ratios and 95% confidence intervals for obesity associated with leptin polymorphisms were calculated by using both fixed- and random-effects models. Results suggest no evidence of association between the genes under study and obesity. The lack of association could be due to the complex pathogenesis of obesity, which involves a number of genetic and environmental factors. Large studies including testing of multiple genes in both obese and lean subjects, with epidemiologic data on dietary habits in different ethnic groups, are necessary to better understand the role of leptin in regulating weight in human populations.

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.

The genetics of human obesity

Obesity is an important cause of morbidity and mortality in developed countries, and is also becoming increasingly prevalent in the developing world. Although environmental factors are important, there is considerable evidence that genes also have a significant role in its pathogenesis. The identification of genes that are involved in monogenic, syndromic and polygenic obesity has greatly increased our knowledge of the mechanisms that underlie this condition. In the future, dissection of the complex genetic architecture of obesity will provide new avenues for treatment and prevention, and will increase our understanding of the regulation of energy balance in humans.

Evaluation of glucose metabolism and reproductive hormones in polycystic ovary syndrome on the basis of peroxisome proliferator-activated receptor (PPAR)-γ2 Pro12Ala genotype

BACKGROUND

Peroxisome proliferator-activated receptor (PPAR)-gamma2 Pro12Ala polymorphism has been suggested as a protective factor for polycystic ovary syndrome (PCOS). In this study, we aimed to investigate metabolic features and reproductive hormones in women with PCOS and compare these features with control women on the basis of Pro12Ala genotype.

METHODS

This study involved 60 randomly selected women with PCOS and 60 controls. Main outcome measures were anthropometric measures, variables of glucose metabolism and reproductive hormones. All the patients were genotyped for Pro12Ala variant of PPAR-gamma2 gene.

RESULTS

Patients with Pro12Ala polymorphism were more obese in both groups. Furthermore, they had lower fasting insulin levels, were less insulin-resistant and were less glucose-intolerant as demonstrated by 2 h glucose concentrations. However, there was no difference in reproductive hormone levels on the basis of Pro12Ala genotype.

CONCLUSIONS

Both control women and women with PCOS had significant differences in glucose metabolism on the basis of PPAR-gamma2 Pro12Ala polymorphism. Pro12Ala variant may break the process that leads to PCOS in susceptible women, instead of being a direct causal relationship between Pro12Ala polymorphism and PCOS.

Comparison of Gene Expression in Intra-Abdominal and Subcutaneous Fat: A Study of Men with Morbid Obesity and Nonobese Men Using Microarray and Proteomics

Extent of intra-abdominal fat had significant linear relations with six metabolic coronary risk factors: systolic and diastolic blood pressure, fasting blood concentrations of glucose, high density lipoprotein (HDL) cholesterol, triglyceride, and plasminogen activator inhibitor-1. Tumor necrosis factor-alpha and adiponectin can be biological mediators from the intra-abdominal fat to the metabolic coronary risk factors. Complementarily, we describe a new study that will analyze the gene expression in intra-abdominal and subcutaneous fat on mRNA and protein level using high throughput methods. The study will elucidate further whether intra-abdominal obesity is the common denominator for the different components of the metabolic syndrome.

Transcription suppression of peroxisome proliferator-activated receptor gamma2 gene expression by tumor necrosis factor alpha via an inhibition of CCAAT/ enhancer-binding protein delta during the early stage of adipocyte differentiation

TNFalpha is known to inhibit adipocyte differentiation and induce insulin resistance. Moreover, TNFalpha is known to down-regulate peroxisome proliferator-activated receptor (PPAR)gamma2, an adipocyte-specific nuclear receptor of insulin-sensitizer thiazolidinediones. To clarify molecular mechanisms of TNFalpha- mediated PPARgamma2 down-regulation, we here examined the effect of TNFalpha on transcription regulation of PPARgamma2 gene expression during the early stage of adipocyte differentiation. 3T3-L1 preadipocytes (2 d after 100% confluent) were incubated in a differentiation mixture (dexamethasone, insulin, 3-isobutyl-1-methlxanthine), with or without 50 ng/ml TNFalpha, for 24 h. TNFalpha significantly decreased PPARgamma2 expression both at mRNA and protein levels (to approximately 40%), as well as aP2 mRNA expression. The mouse PPARgamma2 gene promoter region (2.2-kb) was isolated and was used for luciferase reporter assays by transient transfection. TNFalpha significantly suppressed PPARgamma2 gene transcription (to approximately 50%), and deletion analyses demonstrated that the suppression was mediated via CCAAT/enhancer-binding protein (C/EBP) binding elements at the -320/-340 region of the promoter. Moreover, TNFalpha significantly decreased expression of C/EBPdelta mRNA and protein levels (to approximately 40%). EMSA, using 3T3-L1 cells nuclear extracts with the -320/-340 region as a probe, demonstrated the binding of C/EBPdelta to the element, which was significantly decreased by TNFalpha treatment. Overexpression of CEBP/delta prevented the TNFalpha-mediated suppression of PPARgamma2 transactivation. Taken together, TNFalpha suppresses PPARgamma2 gene transcription by the inhibition of C/EBPdelta expression and its DNA binding during the early stage of adipocyte differentiation, which may contribute to the inhibition of adipocyte differentiation, as well as the induction of insulin resistance.

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.