The peroxisome proliferator-activated receptor-gamma2 Pro12Ala polymorphism

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

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

New type 2 diabetes risk genes provide new insights in insulin secretion mechanisms

Type 2 diabetes results from the inability of beta cells to increase insulin secretion sufficiently to compensate for insulin resistance. Insulin resistance is thought to result mainly from environmental factors, such as obesity. However, there is compelling evidence that the decline of both insulin sensitivity and insulin secretion have also a genetic component. Recent genome-wide association studies identified several novel risk genes for type 2 diabetes. The vast majority of these genes affect beta cell function by molecular mechanisms that remain unknown in detail. Nevertheless, we and others could show that a group of genes affect glucose-stimulated insulin secretion, a group incretin-stimulated insulin secretion (incretin sensitivity or secretion) and a group proinsulin-to-insulin conversion. The most important so far type 2 diabetes risk gene, TCF7L2, interferes with all three mechanisms. In addition to advancing knowledge in the pathophysiology of type 2 diabetes, the discovery of novel genetic determinants of diabetes susceptibility may help understanding of gene-environment, gene-therapy and gene-gene interactions. It was also hoped that it could make determination of the individual risk for type 2 diabetes feasible. However, the allelic relative risks of most genetic variants discovered so far are relatively low. Thus, at present, clinical criteria assess the risk for type 2 diabetes with greater sensitivity and specificity than the combination of all known genetic variants.

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

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

PPARs in Alzheimer's Disease

Peroxisome proliferator-activated receptors (PPARs) are well studied for their peripheral physiological and pathological impact, but they also play an important role for the pathogenesis of various disorders of the central nervous system (CNS) like multiple sclerosis, amyotrophic lateral sclerosis, Alzheimer's, and Parkinson's disease. The observation that PPARs are able to suppress the inflammatory response in peripheral macrophages and in several models of human autoimmune diseases lead to the idea that PPARs might be beneficial for CNS disorders possessing an inflammatory component. The neuroinflammatory response during the course of Alzheimer's disease (AD) is triggered by the neurodegeneration and the deposition of the β-amyloid peptide in extracellular plaques. Nonsteroidal anti-inflammatory drugs (NSAIDs) have been considered to delay the onset and reduce the risk to develop Alzheimer's disease, while they also directly activate PPARγ. This led to the hypothesis that NSAID protection in AD may be partly mediated by PPARγ. Several lines of evidence have supported this hypothesis, using AD-related transgenic cellular and animal models. Stimulation of PPARγ receptors by synthetic agonist (thiazolidinediones) inducing anti-inflammatory, anti-amyloidogenic, and insulin sensitising effects may account for the observed effects. Several clinical trials already revealed promising results using PPAR agonists, therefore PPARs represent an attractive therapeutic target for the treatment of AD.

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

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

PPAR Gamma: Coordinating Metabolic and Immune Contributions to Female Fertility

Peroxisome proliferator-activated receptor gamma (PPARG) regulates cellular functions such as adipogenesis and immune cell activation. However, new information has indicated additional roles of PPARG directing the cyclic changes that occur within ovarian tissue of female mammals, including those that facilitate the release of oocytes each estrous cycle. In addition to ovarian PPARG expression and function, many PPARG actions within adipocytes and macrophages have additional direct and indirect implications for ovarian function and female fertility. This encompasses the regulation of lipid uptake and transport, insulin sensitivity, glucose metabolism, and the regulation of inflammatory mediator synthesis and release. This review discusses the developing links between PPARG activity and female reproductive function, and highlights several mechanisms that may facilitate such a relationship.

The Genetics of PPARG and the Skeleton

Osteoporosis is a complex metabolic bone disorder. Recently it has been appreciated that the “obesity in bone” phenomenon occurs at the expense of bone formation, and that is a key component of the pathology of this disease. Mouse models with altered bone expression levels of peroxisome proliferator-activated receptor gamma (PPARG) impact bone formation, but genetic studies connecting PPARG polymorphisms to skeletal phenotypes in humans have proven to be less than satisfactory. One missense polymorphism in exon one has been linked to low bone mineral density (BMD), but the most studied polymorphism, Pro12Ala, has not yet been examined in the context of skeletal phenotype. The studies to date are a promising start in leading to our understanding of the genetic contribution of PPARG to the phenotypes of BMD and fracture risk.

D2 Thr92Ala and PPARγ2 Pro12Ala polymorphisms interact in the modulation of insulin resistance in type 2 diabetic patients

Type 2 deiodinase (D2) converts T4 into its active metabolite T3, an essential step in thyroid metabolism. A Thr92Ala polymorphism in the gene encoding D2 has been inconsistently associated with insulin resistance (IR). Recently, it was reported that the D2 Thr92Ala (rs225014) and the peroxisome proliferator-activated receptor (PPAR) γ2 Pro12Ala (rs1801282) polymorphisms interact in the modulation of metabolic syndrome in nondiabetic subjects. Here, we investigated the effect of both polymorphisms, isolated or in combination, on IR in patients with type 2 diabetes mellitus (DM2). The D2 Thr92Ala and PPARγ2 Pro12Ala polymorphisms were genotyped in 721 DM2 patients. IR was evaluated using the homeostasis model assessment-IR (HOMA(IR)) index in a subgroup of 246 DM2 subjects. The frequencies of D2 Ala92 and PPARγ2 Ala12 variants were 0.390 and 0.074, respectively. Patients carrying D2 Ala/Ala genotype had a higher fasting plasma insulin and HOMA(IR) index as compared to patients carrying Thr/Ala or Thr/Thr genotypes (P = 0.022 and P = 0.001, respectively). A significant synergistic effect was observed between D2 Thr92Ala and PPARγ2 Pro12Ala polymorphisms on HOMA(IR) index, with carriers of both D2 Ala/Ala genotype and PPARγ2 Ala12 allele showing the highest HOMA(IR) values, after adjusting for age, gender, BMI, and use of medication for DM2 (P = 0.010). In conclusion, DM2 patients harboring both D2 Ala/Ala genotype and PPARγ2 Ala12 allele seem to present more severe IR than those with other D2/PPARγ2 genotype combinations. These findings suggest that these polymorphisms interact in the IR modulation, which may constitute a potential therapeutic target.

Erythrocyte membrane phospholipid polyunsaturated fatty acids are related to plasma C-reactive protein and adiponectin in middle-aged German women and men

PURPOSE

Modulation of circulating inflammatory markers and adiponectin may link PUFA to risk of diabetes and cardiovascular diseases. We investigated erythrocyte n-6 and n-3 PUFA in relation to plasma C-reactive protein (CRP) and adiponectin, and whether the Pro12Ala polymorphism in the PPARγ2 gene (PPARG2) modified these associations.

METHODS

We conducted a cross-sectional analysis among 1,222 women and 758 men participating in the EPIC-Potsdam study.

RESULTS

Most notably, in both sexes, higher linoleic acid (LA) was related to lower CRP (geometric mean outcome [mg/L], quintile 1, quintile 5, p for trend ≤ 0.01 unless otherwise stated: 0.95, 0.61 [women], 0.67, 0.51 [men]) and higher adiponectin (7.9, 9.1 [women], 5.3, 6.1 [men]), whereas higher γ-linolenic acid (GLA) and dihomo-γ-linolenic acid (DGLA) were related to higher CRP (GLA: 0.63, 0.92 [women], 0.55, 0.70, p = 0.08 [men], DGLA: 0.55, 1.07 [women], 0.52, 0.76 [men]) and lower adiponectin (GLA: 8.6, 8.0 [women], 5.8, 5.4, p = 0.08 [men], DGLA: 9.2, 7.9 [women], 5.9, 5.4, p = 0.08 [men]) adjusting for age and lifestyle. The associations mostly did neither strongly nor significantly vary by PPARG2 genotype. In women, Pro12Ala appeared to interact with arachidonic acid on CRP (p = 0.04), as well as with docosatetraenoic acid on CRP (p = 0.08) and adiponectin (p = 0.02).

CONCLUSIONS

Our findings suggest that erythrocyte PUFA, particularly LA and n-6 higher unsaturated fatty acids, are related to circulating CRP and adiponectin. They do not indicate that PUFA strongly interact with the PPARG2 Pro12Ala variant on these risk markers.

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.

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

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

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

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

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

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

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

Peroxisome proliferator-activated receptor gamma polymorphism and periodontitis in pregnant Japanese women

BACKGROUND

Recent studies suggest an association between maternal periodontitis and preterm birth, although the association remains controversial. It was suggested that mechanisms such as a genetic predisposition for a hyperinflammatory response cause periodontitis and preterm births. Peroxisome proliferator-activated receptor gamma (PPARgamma) is a nuclear hormone receptor and ligand-dependent transcription factor. PPARgamma inhibits the transcriptional activity of the genes that produce proinflammatory mediators and repress periodontitis. Recently, a common polymorphism, proline(PRO)-to-alanine(ALA) mutation at codon12 in exonB (Pro12Ala: rs 1801282) PPARgamma, was reported to reduce the ability to transactivate responsive promoters. In this study, we tested whether the PPARgammaPro12Ala polymorphism was associated with maternal periodontitis and/or preterm birth.

METHODS

Genomic DNA was isolated from the venous blood of pregnant Japanese women (term birth: n = 72; preterm birth: n = 58). The PPARgammaPro12Ala genotype was determined by polymerase chain reaction (PCR)-restriction fragment length polymorphism. Within 5 days after labor, clinical periodontal parameters were evaluated, and periodontopathic bacteria from the subgingival plaque were detected by species-specific PCR.

RESULTS

The mean clinical attachment level (P = 0.012), mean probing depth (P = 0.031), mean gingival index (P = 0.037), and percentages of sites with bleeding on probing (P = 0.041) in women with the PPARgammaPro12Ala genotype were significantly higher than in women with the PPARgammaPro12Pro genotype. However, there was no association between preterm birth and periodontitis.

CONCLUSION

We suggest that the PPARgammaPro12Ala polymorphism may represent a genetic susceptibility factor for the clinical measurements of periodontitis in a limited number of pregnant Japanese women, but it probably cannot influence the relationship between periodontitis and preterm birth.

Peroxisome proliferator-activated receptor gamma in osteoarthritis

Osteoarthritis (OA) is among the most prevalent chronic human health disorders and the most common form of arthritis. It is a leading cause of disability in developed countries. This disease is characterized by cartilage deterioration, synovitis, and remodeling of the subchondral bone. There is not yet a satisfactory treatment to stop or arrest this disease process. Although several candidates for therapeutic approaches have been put forward, recent studies suggest that activation of the transcription factor peroxisome proliferator-activated receptor gamma (PPARγ) is an interesting target for this disease. PPARγ is a ligand-activated transcription factor and member of the nuclear receptor superfamily. Agonists of PPARγ inhibit inflammation and reduce synthesis of cartilage degradation products both in vitro and in vivo, and reduce the development/progression of cartilage lesions in OA animal models. This review will highlight the recent experimental studies on the presence of PPARγ in articular tissues and its effect on inflammatory and catabolic responses in chondrocytes and synovial fibroblasts, as well as the protective effects of PPARγ ligands in arthritis experimental models. Finally, the role of PPARγ polymorphism in the pathogenesis of OA and related musculoskeletal diseases will also be discussed.

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

AIMS/HYPOTHESIS

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

METHODS

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

RESULTS

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

CONCLUSIONS/INTERPRETATION

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

Three novel SNPs in the coding region of PPARγ gene and their associations with meat quality traits in cattle

The peroxisome proliferator-activated receptor γ (PPARγ) is a nuclear hormone receptor that regulates adipogenesis and many other biological processes. In the present study, we carried out PCR-SSCP and DNA sequencing analyses to examine SNPs in coding region of the PPARγ gene. A total of 660 individuals from five Chinese cattle breeds were genotyped. We identified three SNPs and their associations with meat quality traits were analyzed in 108 Qinchuan cattle. Two missense mutations and one synonymous mutation were found: 200 A>G (genotypes AA, AB and BB) resulting in D7G change, the silent substitution 42895 C>T (genotypes JJ and JI) and 72472 G>T (genotypes CC, DC and DD) producing Q448H change, respectively. The frequencies of PPARγ-A allele were 0.86, 0.83, 0.80, 0.72 and 0.87 for Qinchuan, Nanyang, Jiaxian, Luxi and Xianan populations, respectively. The frequencies of PPARγ-J allele varied from 0.87 to 0.96 in the five populations. In the 72472 G>T locus, the frequencies of PPARγ-C allele were higher than PPARγ-D allele in the five populations, and ranged from 0.58 to 0.82. Least squares analysis revealed that in 42895 C>T locus, there was a significant effect on tenderness in 18-20 months Qinchuan cattle (P<0.01), and in the 72472 G>T locus, animals with the genotype DC had lower mean values than these with genotype CC (P<0.01) for back fat thickness in 18-20 months, and animals with the genotype DD had lower mean values than these with genotypes CC and DC (P<0.01) for water holding capacity in 21-24 months (P<0.01). The SNPs we have identified may contribute to establishing a more efficient selection program for improving of genetic characteristics in indigenous Chinese cattle.

Nutritional genomics era: opportunities toward a genome-tailored nutritional regimen

There is increasing evidence indicating that nutritional genomics represents a promise to improve public health. This goal will be reached by highlighting the mechanisms through which diet can reduce the risk of monogenic and common polygenic diseases. Indeed, nutrition is a very relevant environmental factor involved in the development and progression of metabolic disorders, as well as other kind of diseases. The revolutionary changes in the field of genomics have led to the development and implementation of new technologies and molecular tools. These technologies have a useful application in the nutritional sciences, since they allow a more precise and accurate analysis of biochemical alterations, in addition to filling fundamental gaps in the knowledge of nutrient-genome interactions in both health and disease. Overall, these advances will open undiscovered ways in genome-customized diets for disease prevention and therapy. This review summarizes the recent knowledge concerning this novel nutritional approach, paying attention to the human genome variations, such as single-nucleotide polymorphisms and copy number variations, gene expression and innovative molecular tools to reveal them.

The role of genetic variation in peroxisome proliferator-activated receptors in the polycystic ovary syndrome (PCOS): an original case-control study followed by systematic review and meta-analysis of existing evidence

OBJECTIVE

To study the association of polymorphisms in the genes encoding peroxisome proliferator-activated receptors (PPARs) with the polycystic ovary syndrome (PCOS).

DESIGN

Case-control study and meta-analysis of published evidence.

PATIENTS

One hundred and sixty-one polycystic ovary syndrome patients and 113 non-hyperandrogenic women.

MEASUREMENTS

Genotyping for PPAR-gamma coactivator-1 gene (PPARGC1A) Gly482Ser, PPAR-alpha Leu162Val, PPAR-delta rs2267668A/G, PPAR-delta-87T/C, PPAR-gamma2 Pro12Ala and PPAR-gamma2 -681C/G variants and systematic review of the literature using the Entrez-PubMed search engine, followed by meta-analysis whenever possible.

RESULTS

Polycystic ovary syndrome patients carried the Gly482Ser variant in PPARGC1A more frequently than controls (72%vs. 58%, chi(2 )=( )5.54 P = 0.019), whereas carriers of the PPAR-alpha Leu162Val, PPAR-delta rs2267668A/G, PPAR-delta-87T/C, PPAR-gamma2 Pro12Ala and PPAR-gamma2 -681C/G variants were distributed similarly among both groups. The interaction between the PPARGC1A Gly482Ser and PPAR-delta-87T/C variants was also associated with PCOS (OR = 1.24, 95% CI 1.05-1.50, P = 0.008). The systematic review identified 31 studies addressing associations between PPARs variants and PCOS; meta-analysis was possible for nine studies focusing on the PPAR-gamma2 Pro12Ala variant. Although the individual studies did not reveal any statistically significant association, meta-analysis uncovered that carrying the PPAR-gamma2 Pro12Ala variant was associated with a reduced probability of having PCOS (OR = 0.77, 95% CI 0.61-0.96, P = 0.025), and that this association may be mediated by an effect on insulin sensitivity.

CONCLUSIONS

Common polymorphisms in the PPARGC1A, PPAR-delta and PPAR-gamma2 loci are associated with PCOS.

Recurrent miscarriage: current concepts in diagnosis and treatment

Although recurrent miscarriage (RM) affects only 1-3% of couples, it has a major influence on the wellbeing and psychosocial status of patients. Therefore, research into improved diagnosis and development of new treatment strategies is essential. In this review, we summarize current concepts on diagnosis and treatment in RM, drawing upon research reports and international guidelines to provide insights into the pathophysiology of pregnancy disrupted by repeated miscarriage. Anatomical malformations, infectious diseases, endocrine disorders, autoimmune defects as well as acquired and inherited thrombophilia are established risk factors in RM. In addition, our recent findings indicate an impact on miscarriage incidence of glycoproteins such as glycodelin, and nuclear hormone receptors such as the peroxisome proliferator-activated receptors (PPARs). Significantly reduced glycodelin expression is associated with miscarriage, whereas up-regulation of PPARs appears to compensate for either the activated immune response or the disturbed cytotrophoblast differentiation in RM patients. There is also evidence that circulating placental microparticles are increased in a subgroup of RM patients, indicating an acquired procoagulant state even outside pregnancy. Treatment strategies like aspirin and low molecular weight heparin (LMWH) are standard medications in RM, although only a few placebo-controlled trials have proven their benefit in respect to live birth rate. There is emerging evidence that new treatment options, including drugs like TNFalpha inhibitors and granulocyte colony-stimulating factor (G-CSF) might be beneficial in some cases of RM. However, larger clinical trials must be completed to further prove or disprove benefits of these drugs in the treatment of RM patients.

Pro12Ala polymorphism in the PPARG gene contributes to the development of diabetic nephropathy in Chinese type 2 diabetic patients

OBJECTIVE

Oxidative stress is a major contributing factor in the development of diabetic nephropathy. Peroxisome proliferator-activated receptor gamma heterozygous mice and Pro12Ala polymorphism in PPARG exhibited increased resistance to oxidative stress. Smoking increases the production of reactive oxygen species, which accelerates oxidative stress under hyperglycemia. To determine whether the Pro12Ala polymorphism, alone or in combination with smoking, contributes to the development of diabetic nephropathy, a case-control study was performed in 760 Chinese patients with type 2 diabetes.

RESEARCH DESIGN AND METHODS

Among patients, 532 had diabetic nephropathy with microalbuminuria (n = 245) or overt albuminuria (n = 287), and 228 did not show either of these symptoms but had had diabetes for > or =10 years and were not undergoing anti-hypertension treatment.

RESULTS

After adjustment for confounders, the Pro/Pro genotype was significantly associated with diabetic nephropathy (odds ratio 2.30 [95% CI 1.18-4.45], P = 0.014); smoking was also an independent risk factor for diabetic nephropathy (1.99 [1.08-3.68], P = 0.029). In addition, we identified possible synergistic effects; i.e., the high-risk group (smokers with the Pro/Pro genotype) showed 4.52 times higher risk (1.78-11.48, P = 0.002) of diabetic nephropathy than the low-risk group (nonsmokers with the Pro/Ala genotype) in a multiple logistic regression analysis controlled for the confounders.

CONCLUSIONS

Our results indicated that the Pro/Pro genotype and smoking were significant independent risk factors for diabetic nephropathy. The possible synergistic effects of genotype and smoking may aggravate oxidative stress and contribute to the development of diabetic nephropathy.

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.

The association of olanzapine-induced weight gain with peroxisome proliferator-activated receptor-gamma2 Pro12Ala polymorphism in patients with schizophrenia

Olanzapine is a second-generation antipsychotic that may cause weight gain and metabolic syndrome in some cases. The peroxisome proliferator-activated receptor (PPAR)-gamma is an important gene in the progress of type II diabetes and metabolic syndrome. In recent studies the polymorphism of the PPAR-gamma has been studied in type II diabetes mellitus, polycystic ovary syndrome, and insulin resistance syndrome. It is aimed to evaluate the association between polymorphism of PPAR-gamma gene and olanzapine-induced weight gain. Our study comprised 95 unrelated subjects who strictly met Diagnostic and Statistical Manual of Mental Disorders, 4th edition (DSM-IV) criteria for schizophrenia, and all were of Turkish origin. All patients were evaluated with rating scales, and genetic analyses were performed. We found statistically significant differences between pretreatment and posttreatment body mass index and weight change in Pro12Ala polymorphism of PPAR-gamma2. Our results suggest that genetic polymorphism of PPAR might be important in olanzapine-induced weight gain and that genetic variance of people might be considered in antipsychotic medication selection.

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

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

No association of multiple type 2 diabetes loci with type 1 diabetes

AIMS/HYPOTHESIS

We used recently confirmed type 2 diabetes gene regions to investigate the genetic relationship between type 1 and type 2 diabetes, in an average of 7,606 type 1 diabetic individuals and 8,218 controls, providing >80% power to detect effects as small as an OR of 1.11 at a false-positive rate of 0.003.

METHODS

The single nucleotide polymorphisms (SNPs) with the most convincing evidence of association in 12 type 2 diabetes-associated gene regions, PPARG, CDKAL1, HNF1B, WFS1, SLC30A8, CDKN2A-CDKN2B, IGF2BP2, KCNJ11, TCF7L2, FTO, HHEX-IDE and THADA, were analysed in type 1 diabetes cases and controls. PPARG and HHEX-IDE were additionally tested for association in 3,851 type 1 diabetes families. Tests for interaction with HLA class II genotypes, autoantibody status, sex, and age-at-diagnosis of type 1 diabetes were performed with all 12 gene regions.

RESULTS

Only PPARG and HHEX-IDE showed any evidence of association with type 1 diabetes cases and controls (p = 0.004 and p = 0.003, respectively; p > 0.05 for other SNPs). The potential association of PPARG was supported by family analyses (p = 0.003; p (combined) = 1.0 x 10(-4)). No SNPs showed evidence of interaction with any covariate (p > 0.05).

CONCLUSIONS/INTERPRETATION

We found no convincing genetic link between type 1 and type 2 diabetes. An association of PPARG (rs1801282/Pro12Ala) could be consistent with its known function in inflammation. Hence, our results reinforce evidence suggesting that type 1 diabetes is a disease of the immune system, rather than being due to inherited defects in beta cell function or regeneration or insulin resistance.

Pro12Ala polymorphism of the peroxisome proliferatoractivated receptor-gamma gene is associated with metabolic syndrome and surrogate measures of insulin resistance in healthy men: interaction with smoking status

BACKGROUND

The Pro12Ala polymorphism (rs1801282), a nonsynonymous substitution of peroxisome proliferator-activated receptor-gamma (PPARG), has been robustly associated with type 2 diabetes. However, its role in metabolic syndrome (MetS) remains poorly understood. The associations among rs1801282, MetS and surrogate measures of insulin resistance (IR) were investigated in the present study.

METHODS AND RESULTS

A cross-sectional population-based survey of 572 unrelated healthy male Argentinian blood donors with normal findings on medical examination and not taking any medication was conducted. MetS was assessed using the National Cholesterol Education Program/Adult Treatment Panel III (NCEP/ATP III) criteria, and the HOMA-IR, and QUICKI were calculated. Genotyping of rs1801282 was performed using RFLP-PCR. The prevalence of MetS was 26.2%. The Pro/Ala genotype (and the Ala12 allele) was associated with a high risk for MetS (odds ratio (OR) 1.67 [95% confidence interval (CI) 1.03-2.72], P=0.0394). This was highlighted among nonsmokers (OR 2.20 [95%CI 1.25-3.88], P=0.0059). ANCOVA confirmed an interaction between smoking status and this association (P=0.031). Ala12 carriers had a higher waist circumference than noncarriers (P=0.0065). Among nonsmokers, surrogates of IR, such as HOMA-IR, were significantly higher in Ala12 carriers than in noncarriers (P<0.05).

CONCLUSIONS

Healthy men, in particular nonsmokers, carrying the Ala12 allele of PPARG rs1801282 polymorphism, have a high risk for MetS and IR.

Retinoid X receptor heterodimer variants and cardiovascular risk factors

Nuclear receptors are transcription factors that can be activated by specific ligands. Recent progress has shown that retinoid X receptor (RXR) and its heterodimerization partners, including peroxisome proliferator-activated receptors, regulate many important genes involved in energy homeostasis and atherosclerosis, and should be promising therapeutic targets of metabolic syndrome. RXR heterodimers regulate a number of complex cellular processes, and genetic studies of RXR heterodimers have provided important clinical information in addition to knowledge gained from basic research. Genetic variants of RXR heterodimers were screened and investigated, and some variants were shown to have a considerable impact on metabolic disorders, including phenotypic components of familial combined hyperlipidemia. The combined efforts of basic and clinical science regarding nuclear receptors have achieved significant progress in unraveling the inextricably linked control system of energy expenditure, lipid and glucose homeostasis, inflammation, and atherosclerosis.This review summarizes the current understanding regarding RXR heterodimers based on their human genetic variants, which will provide new clues to uncover the background of multifactorial disease, such as metabolic syndrome or familial combined hyperlipidemia.

Papel dos lipídeos da dieta na nefropatia diabética

O objetivo do presente manuscrito foi revisar o possível papel dos lipídeos dietéticos na nefropatia diabética (ND), considerando as alterações do perfil lipídico associadas e a interação entre aspectos dietéticos e genéticos. Os lipídeos dietéticos podem ter um papel importante no desenvolvimento e na progressão da ND. A composição das gorduras da dieta tem sido associada com a ND, particularmente à microalbuminúria e às anormalidades lipídicas e de função endotelial. Entretanto, ainda não está comprovado o benefício da modificação da ingestão de gorduras em pacientes com ND, em especial sobre desfechos definitivos, como incidência e progressão da ND, insuficiência renal e morte. Além disso, a resposta do perfil lipídico à ingestão de gorduras pode ser influenciada por fatores genéticos. A identificação de polimorfismos genéticos específicos associados a essa interação poderá permitir a individualização de estratégias nutricionais na ND.

Interação entre gene e nutriente e sua associação à obesidade e ao diabetes melito

A genômica nutricional avalia o efeito da variação genética na interação entre dieta e doenças crônicas. O objetivo deste manuscrito foi revisar os principais polimorfismos associados à obesidade, ao diabetes melito e também aos fatores da dieta. As principais interações entre polimorfismos genéticos e dieta foram: para obesidade: interleucina-6 (IL-6) com consumo energético; receptor ativado por proliferador de peroxissoma gama 2 (PPAR-gama2) e fat mass and obesity associated (FTO) com consumo de gorduras; receptor β-adrenérgico 2 (ADRB2) e receptor da melanocortina-4 (MCR4) com consumo de carboidratos; para perda de peso: proteínas desacopladoras (UCPs) com restrição calórica; para leptinemia: receptor da leptina (LEPR) com restrição calórica; para diabetes melito: PPAR-gama2 com consumo de gordura; para hipertrigliceridemia: proteína transportadora de ácidos graxos 2 (FABP2) com consumo de gordura. Os dados apresentados sugerem que a genômica nutricional é importante ao desenvolvimento da obesidade e do diabetes melito.

PPARgamma Pro12Ala polymorphism and risk of acute coronary syndrome in a prospective study of Danes

Background

Acute coronary syndrome (ACS) is a major cause of morbidity and mortality in the western world. Peroxisome proliferator-activated receptor γ (PPARγ) plays a key role in the regulation of the energy balance, adipocyte differentiation and lipid biosynthesis. The aim was to investigate if the polymorphism PPARγ2 Pro¹²Ala, which encodes a less efficient transcription factor, was associated with risk of acute coronary disease and if there were interactions between this polymorphism and factors that modify PPARγ activity, such as alcohol intake, smoking, and use of non-steroidal anti-inflammatory medicine.

Methods

A case-cohort study including 1031 ACS cases and a sub-cohort of 1703 persons was nested within the population-based prospective study Diet, Cancer and Health of 57,053 individuals.

Results

Homozygous male variant allele carriers of PPARγ2 Pro¹²Ala were at higher risk of ACS (HR = 2.12, 95% CI: 1.00–4.48) than homozygous carriers of the Pro-allele. Among men, there was a statistically significant interaction between genotypes and alcohol intake such that homozygous variant allele carriers with a low alcohol intake were at higher risk of ACS (HR = 25.3, CI: 16.5–38.7) compared to homozygous common allele carriers (p for interaction < 0.0001). Overall, the association was only observed among homozygous variant allele carriers. Thus, all the observed associations were obtained in subgroups including small numbers of cases. It is therefore possible that the observed associations were due to chance.

Conclusion

In the present study, there were no consistent associations between PPARγ Pro¹²Ala and risk of ACS, and no consistent interaction with alcohol, BMI, NSAID or smoking in relation to ACS.

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.

Type 2 Diabetes Mellitus: New Genetic Insights will Lead to New Therapeutics

Type 2 diabetes is a disorder of dysregulated glucose homeostasis. Normal glucose homeostasis is a complex process involving several interacting mechanisms, such as insulin secretion, insulin sensitivity, glucose production, and glucose uptake. The dysregulation of one or more of these mechanisms due to environmental and/or genetic factors, can lead to a defective glucose homeostasis. Hyperglycemia is managed by augmenting insulin secretion and/or interaction with hepatic glucose production, as well as by decreasing dietary caloric intake and raising glucose metabolism through exercise. Although these interventions can delay disease progression and correct blood glucose levels, they are not able to cure the disease or stop its progression entirely. Better management of type 2 diabetes is sorely needed. Advances in genotyping techniques and the availability of large patient cohorts have made it possible to identify common genetic variants associated with type 2 diabetes through genome-wide association studies (GWAS). So far, genetic variants on 19 loci have been identified. Most of these loci contain or lie close to genes that were not previously linked to diabetes and they may thus harbor targets for new drugs. It is also hoped that further genetic studies will pave the way for predictive genetic screening. The newly discovered type 2 diabetes genes can be classified based on their presumed molecular function, and we discuss the relation between these gene classes and current treatments. We go on to consider whether the new genes provide opportunities for developing alternative drug therapies.

Causes and metabolic consequences of Fatty liver

Type 2 diabetes and cardiovascular disease represent a serious threat to the health of the population worldwide. Although overall adiposity and particularly visceral adiposity are established risk factors for these diseases, in the recent years fatty liver emerged as an additional and independent factor. However, the pathophysiology of fat accumulation in the liver and the cross-talk of fatty liver with other tissues involved in metabolism in humans are not fully understood. Here we discuss the mechanisms involved in the pathogenesis of hepatic fat accumulation, particularly the roles of body fat distribution, nutrition, exercise, genetics, and gene-environment interaction. Furthermore, the effects of fatty liver on glucose and lipid metabolism, specifically via induction of subclinical inflammation and secretion of humoral factors, are highlighted. Finally, new aspects regarding the dissociation of fatty liver and insulin resistance are addressed.

Birth weight and blood lipid levels in Spanish adolescents: influence of selected APOE, APOC3 and PPARgamma2 gene polymorphisms. The AVENA Study

Background

There is increasing evidence indicating that genes involved in certain metabolic processes of cardiovascular diseases may be of particular influence in people with low body weight at birth. We examined whether the apolipoprotein (APO) E, APOC3 and the peroxisome proliferator-activated receptor-γ-2 (PPARγ2) polymorphisms influence the association between low birth weight and blood lipid levels in healthy adolescents aged 13–18.5 years.

Methods

A cross-sectional study of 502 Spanish adolescents born at term was conducted. Total (TC) and high density lipoprotein cholesterol (HDLc), triglycerides (TG), apolipoprotein (apo) A and B, and lipoprotein(a) [Lp(a)] were measured. Low density lipoprotein cholesterol (LDLc), TC-HDLc, TC/HDLc and apoB/apoA were calculated.

Results

Low birth weight was associated with higher levels of TC, LDLc, apoB, Lp(a), TC-HDLc, TC/HDLc and apoB/apoA in males with the APOE ε3ε4 genotype, whereas in females, it was associated with lower HDLc and higher TG levels. In males with the APOC3 S1/S2 genotype, low birth weight was associated with lower apoA and higher Lp(a), yet this association was not observed in females. There were no associations between low birth weight and blood lipids in any of the PPARγ2 genotypes.

Conclusion

The results indicate that low birth weight has a deleterious influence on lipid profile particularly in adolescents with the APOE ε3/ε4 genotype. These findings suggest that intrauterine environment interact with the genetic background affecting the lipid profile in later life.

LG839: anti-obesity effects and polymorphic gene correlates of reward deficiency syndrome

INTRODUCTION

This study systematically assessed the weight management effects of a novel experimental DNA-customized nutraceutical, LG839 (LifeGen, Inc., La Jolla, CA, USA).

METHODS

A total of 1058 subjects who participated in the overall D.I.E.T. study were genotyped and administered an LG839 variant based on polymorphic outcomes. A subset of 27 self-identified obese subjects of Dutch descent, having the same DNA pattern of four out of the five candidate genes tested (chi-square analysis) as the entire data set, was subsequently evaluated. Simple t tests comparing a number of weight management parameters before and after 80 days of treatment with LG839 were performed.

RESULTS

Significant results were observed for weight loss, sugar craving reduction, appetite suppression, snack reduction, reduction of late night eating (all P<0.01), increased perception of overeating, enhanced quality of sleep, increased happiness (all P<0.05), and increased energy (P<0.001). Polymorphic correlates were obtained for a number of genes (LEP, PPAR-gamma2, MTHFR, 5-HT2A, and DRD2 genes) with positive clinical parameters tested in this study. Of all the outcomes and gene polymorphisms, only the DRD2 gene polymorphism (A1 allele) had a significant Pearson correlation with days on treatment (r=0.42, P=0.045).

CONCLUSION

If these results are confirmed in additional rigorous, controlled studies, we carefully suggest that DNA-directed targeting of certain regulator genes, along with customized nutraceutical intervention, provides a unique framework and strategic modality to combat obesity.

Interaction between genes and lifestyle factors on obesity

Obesity originates from a failure of the body-weight control systems, which may be affected by changing environmental influences. Basically, the obesity risk depends on two important mutually-interacting factors: (1) genetic variants (single-nucleotide polymorphisms, haplotypes); (2) exposure to environmental risks (diet, physical activity etc.). Common single-nucleotide polymorphisms at candidate genes for obesity may act as effect modifiers for environmental factors. More than 127 candidate genes for obesity have been reported and there is evidence to support the role of twenty-two genes in at least five different populations. Gene-environment interactions imply that the synergy between genotype and environment deviates from either the additive or multiplicative effect (the underlying model needs to be specified to appraise the nature of the interaction). Unravelling the details of these interactions is a complex task. Emphasis should be placed on the accuracy of the assessment methods for both genotype and lifestyle factors. Appropriate study design (sample size) is crucial in avoiding false positives and ensuring that studies have enough power to detect significant interactions, the ideal design being a nested case-control study within a cohort. A growing number of studies are examining the influence of gene-environmental interactions on obesity in either epidemiological observational or intervention studies. Positive evidence has been obtained for genes involved in adiposity, lipid metabolism or energy regulation such as PPARgamma2 (Pro12Ala), beta-adrenoceptor 2 (Gln27Glu) or uncoupling proteins 1, 2 and 3. Variants on other genes relating to appetite regulation such as melanocortin and leptin receptors have also been investigated. Examples of some recently-identified interactions are discussed.

Impaired adiponectin-AMPK signalling in insulin-sensitive tissues of hypertensive rats

AIMS

Adiponectin improves insulin sensitivity by decreasing lipid accumulation in insulin-sensitive tissues. The aim of this study was to investigate whether these effects are altered in hypertension.

MAIN METHODS

Adiponectin receptors (AdipoR1 and AdipoR2) and adiponectin-related enzymes were measured by real-time PCR and Western-blot in insulin-sensitive tissues of 10-week-old male spontaneously hypertensive rats (SHR). Intrahepatic and intramyocellular triglycerides were determined by enzymatic methods.

KEY FINDINGS

SHR showed overweight, dyslipidemia, glucose intolerance and insulin resistance. Circulating concentrations of adiponectin as well as the mRNA and protein expression of adiponectin in epididymal and subcutaneous fat depots were significantly increased in hypertensive rats. Adiponectin mRNA levels were strongly associated with PPARgamma mRNA levels in both epididymal (r=0.54, P<0.05) and subcutaneous (r=0.93, P<0.0001) fat. The expression of AdipoR1 and AdipoR2, acetyl-CoA carboxylase (ACC), as well as carnitine palmitoyl transferase 1 (CPT1), were increased in skeletal muscle of SHR. These changes were not observed in the liver of SHR. In addition, in spite of the hyperadiponectinemia, SHR showed similar activation of AMP-activated protein kinase (AMPK) and a lower phosphorylation degree of its downstream ACC in liver and skeletal muscle. Accordingly, SHR exhibited a significant increase in intrahepatic (approximately 40%) and intramyocellular (approximately 60%) lipid accumulation.

SIGNIFICANCE

These findings suggest that dysregulation of the adiponectin downstream effectors contributes to increased intrahepatic and intramyocellular triglycerides in SHR. Hyperadiponectinemia together with overexpression of adiponectin receptors in skeletal muscle may reflect a defective compensatory mechanism to overcome adiponectin resistance in hypertensive rats.

The Pro12Ala polymorphism of the PPARG gene is not associated with the metabolic syndrome in an urban population of middle-aged Swedish individuals

BACKGROUND

To determine if the common Pro12Ala polymorphism (rs1801282) of the peroxisome proliferator-activated receptor (PPARG) gene is associated with the metabolic syndrome (MetS) or with its individual components in middle-aged Swedish individuals.

METHODS

MetS was defined according to the National Cholesterol Education Program/Adult Panel III (NCEP/ATP III), the International Diabetes Federation (IDF) and the European Group for the Study of Insulin Resistance (EGIR) criteria in a population-based sample of nearly 5000 subjects participating in the Malmö Diet and Cancer-cardiovascular arm.

RESULTS

Of the subjects included in the analysis, 21.8, 29.4 and 20.4% had MetS according to the NCEP/ATP III, IDF and EGIR (only in subjects without diabetes) definitions, respectively. The Pro12Ala was not associated with MetS or with its individual components. These results were similar when patients with diabetes were excluded. Hypertensive and obese ala-carriers had lower fasting glucose and hypertensive ala-carriers also had lower level triglycerides (P < 0.05).

CONCLUSIONS

Our data do not support a major role for the Pro12Ala variant of the PPARG gene in MetS and its individual components. The modest difference in triglyceride and glucose levels, restricted to hypertensive and obese subjects in our cohort, suggests that the polymorphism has a minor effect on glucose and lipid metabolism, particularly in individuals at risk for gluco-metabolic disturbances.

[Peroxisome proliferator-activated receptor gamma (PPARgamma): molecular study in glucose homeostasis, lipid metabolism and therapeutic approach]

The peroxisome proliferators-activated receptors (PPARs) are transcription factors belonging to the family of nuclear receptors that regulate glucose homeostasis, lipid metabolism and inflammation. Three proteins, encoded by distinct genes, have been identified: PPARalpha, PPARbeta and PPARgamma, which control gene expression by binding to specific response elements (PPREs) in the promoters. Recent studies suggest that activation of PPARgamma might decrease atherosclerosis progression and increase the insulin sensitivity, might be a potential therapeutic target for the treatment of a diverse array of disorders, including type 2 diabetes and dyslipidaemia. This review highlights recent studies, which have advanced our understanding of the pivotal role that this receptor plays in metabolism, with particular reference to the molecular mechanisms and therapeutic efficacy.

Variation within the PPARG gene is associated with residual beta-cell function and glycemic control in children and adolescents during the first year of clinical type 1 diabetes

CONTEXT

Conflicting evidence exists as to whether the Pro12Ala single nucleotide polymorphism of the type 2 diabetes susceptibility gene peroxisome proliferator-activated receptor gamma (PPARG) also confers risk for type 1 diabetes (T1D).

OBJECTIVE

The objective of this study was to investigate the PPARG gene in relation to residual beta-cell function and glycemic control in newly diagnosed T1D.

DESIGN

Prospective, non-interventional, 12-month follow-up study, conducted in 18 centers in 15 countries.

PATIENTS

Two hundred and fifty-seven children and adolescents (aged <16 yr) with newly diagnosed T1D.

MAIN OUTCOME MEASURES

Beta-cell function was determined as 90-min meal-stimulated C-peptide (Boost test) 1, 6, and 12 months after diagnosis. Hemoglobin A1c (HbA1c) and daily insulin dose (IU/kg/d) were recorded at 1, 3, 6, 9, and 12 months after diagnosis. Haplotypes within PPARG were estimated by SNPHap program. Statistical analyses were performed in a repeated measurements model.

RESULTS

Five haplotypes within PPARG were generated (h1, 68.4%; h2, 16.3%; h3, 8.3%; h4, 3.5%; and hx, 3.5%). Compared with the most frequent h1 haplotype, the haplotypes h3 and h4 of the PPARG associated with residual beta-cell function during the first year of clinical disease: h3 with a 27% lower C-peptide (p = 0.02) and h4 with a 39% lower C-peptide (p = 0.01). Haplotype h4 also associated with a 0.86% (absolute) higher HbA1c, after adjustment for the insulin dose (p = 0.02).

CONCLUSION

Variation in the PPARG locus may influence disease progression during the first year after the presentation of T1D.

Analysis of Pro12Ala PPAR gamma polymorphism and Helicobacter pylori infection in gastric adenocarcinoma and peptic ulcer disease

BACKGROUND

Peroxisome proliferator-activated receptor gamma (PPARgamma) is a ligand-dependent transcription factor involved in various disease processes including inflammation and carcinogenesis. We investigated the association of Pro12Ala PPARgamma polymorphism and Helicobacter pylori infection with gastric cancer and peptic ulcer disease (PUD).

PATIENTS AND METHODS

In total, 348 adult patients [62 gastric adenocarcinoma, 45 PUD and 241 nonulcer dyspepsia (NUD)] who underwent an upper gastrointestinal endoscopy were enrolled. PPARgamma polymorphism was analyzed by PCR-based restriction fragment length polymorphism. H. pylori infection was diagnosed by rapid urease test, culture, histopathology and PCR.

RESULTS

PPARgamma G carrier had significant association with gastric adenocarcinoma [P = 0.023, odds ratio (OR) = 2.136, 95% CI = 1.112-4.104] and PUD (P = 0.028, OR = 2.165, 95% CI = 1.008-4.306) when compared with NUD. Combination of G carrier and H. pylori infection further increased the risk of gastric adenocarcinoma (OR = 3.054, 95% CI = 1.195-7.807) and PUD (OR = 11.161, 95% CI = 3.495-35.644). PPARgamma polymorphism did not increase the risk of gastric adenocarcinoma and PUD in H. pylori-negative subjects.

CONCLUSIONS

The study suggests that Pro12Ala PPARgamma polymorphism is associated with gastric adenocarcinoma and PUD, and is a potential marker for genetic susceptibility to these two diseases in the presence of H. pylori infection.

Lack of association between the Pro12Ala polymorphism of the PPAR-gamma 2 gene and type 2 diabetes mellitus in the Qatari consanguineous population

Peroxisome proliferators-activated receptor gamma (PPAR gamma) is a nuclear hormone receptor that serves as a master regulator for adipocytes-specific genes contributing to adipocytes differentiation, insulin sensitivity and lipid metabolism. The substitution of proline to alanine at codon 12 of the PPAR gamma 2 gene (Pro12Ala polymorphism) is most widely studied, and the associations with diabetes, obesity, and other clinical parameters have been reported and discussed in several ethnic groups. Among native Qatar ethnicity, however, there is no report about this polymorphism. The aim of this study was to estimate the allele frequency of the Pro12Ala polymorphism of PPAR gamma 2 gene among Qatari population and investigate the association between this polymorphism and obesity or type 2 diabetes. This is a matched case-control study. It was carried out among diabetic patients and healthy subjects at the Primary Healthcare Clinics, and the survey was conducted from February 2003 to March 2006 in Qatari male and female nationals aged 35 to 60 years. The study was based on matched age, sex, and ethnicity of 400 cases (with diabetes) and 450 controls (without diabetes). Face-to-face interviews were based on a questionnaire that included variables such as age, sex, sociodemographic status, body mass index (BMI), and obesity. Their health status was assessed by medical conditions, family history, and blood pressure measurements. The allele frequency of Pro12Ala polymorphism in PPAR gamma 2 gene among Qataris is lower than that in many Caucasian ethnic groups. No association is seen between the Pro12Ala and type 2 Diabetes (0.055 vs 0.059, OR = 1.1311, P = 0.669). Nearly half of the diabetic type 2 patients (48.5%) were obese (BMI > 30) compared to nondiabetic subjects (29.8%) (P < 0.001). In this study, no association is seen between the Pro12Ala polymorphism in PPAR gamma 2 gene and the type 2 diabetes in Qatar.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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