Association of peroxisome proliferator-activated receptor α/δ/γ with obesity, and gene-gene interaction, in the Chinese Han population

NBF2, an Algal Fiber-Rich Formula, Reverses Diabetic Dyslipidemia and Hyperglycemia In Vivo

Ulva prolifera, known as Aonori in Japan, is an edible alga species that is mass-cultivated in Japan. Supplementation with Aonori-derived biomaterials has been reported to enhance metabolic health in previous studies. This was an experimental study that evaluated the metabolic health effects of NBF2, a formula made of algal and junos Tanaka citrus-derived biomaterials, on obesity and type 2 diabetes (T2DM). We used 18 obese and hyperglycemic Otsuka Long-Evans Tokushima Fatty (OLETF) rats that were assigned randomly to three groups of six animals: a high-dose NBF2 drink (20 mg/kg) group, a low-dose (10 mg/kg) NBF2 drink group and the control group that received 2 mL of tap water daily for a total of six weeks. We also used eight LETO rats as the normal control group. In addition to the glucose tolerance test (OGTT), ELISA and real-time PCR assays were performed. High-dose and lowdose NBF2 improved insulin sensitivity, as well as glycemic and lipid profiles, as compared with control rats. The OGTT showed that both NBF2 groups and LETO rats had normalized glycemia by the 90-min time-point. NBF2 up-regulated PPARα/γ-mRNA and Sirt2-mRNA gene expressions in BAT and improved the blood pressure profile. These findings suggest that the NBF2 formula, which activates PPAR-α/γ mRNA and Sirt2-mRNA, may reverse dyslipidemia and hyperglycemia in T2DM.

Genome-wide DNA methylation analysis of body composition in Chinese monozygotic twins

BACKGROUND

Little is currently known about epigenetic alterations associated with body composition in obesity. Thus, we aimed to explore epigenetic relationships between genome-wide DNA methylation levels and three common traits of body composition as measured by body fat percentage (BF%), fat mass (FM) and lean body mass (LBM) among Chinese monozygotic twins.

METHODS

Generalized estimated equation model was used to regress the methylation level of CpG sites on body composition. Inference about Causation Through Examination Of Familial Confounding was used to explore the evidence of a causal relationship. Gene expression analysis was further performed to validate the results of differentially methylated genes.

RESULTS

We identified 32, 22 and 28 differentially methylated CpG sites (p < 10-5 ) as well as 20, 17 and eight differentially methylated regions (slk-corrected p < 0.05) significantly associated with BF%, FM and LBM which were annotated to 65 genes, showing partially overlapping. Causal inference demonstrated bidirectional causality between DNA methylation and body composition (p < 0.05). Gene expression analysis revealed significant correlations between expression levels of five differentially methylated genes and body composition (p < 0.05).

CONCLUSIONS

These DNA methylation signatures will contribute to increased knowledge about the epigenetic basis of body composition and provide new strategies for early prevention and treatment of obesity and its related diseases.

Contribution of gene polymorphisms on 3p25 to salivary gland carcinoma, ameloblastoma, and odontogenic keratocyst in the Chinese Han population

OBJECTIVE

This study aimed to investigate the contribution of gene polymorphisms in 3p25 to salivary gland carcinoma (SGC), ameloblastoma (AM), and odontogenic keratocyst (OKC) in the Chinese Han population.

STUDY DESIGN

Sixteen tag-single nucleotide polymorphisms (SNPs) within 5 genes (SYN2, TIMP4, PPARG, RAF1, and IQSEC1) in 3p25 were genotyped in 411 individuals with or without SGC, AM, and OKC. Genotype, clinical phenotype, and bioinformatics analyses were performed to evaluate the function of candidate SNPs.

RESULTS

SYN2-rs3773364, TIMP4-rs3755724, PPARG-rs10865710, and PPARG-rs1175544 were related to decreased SGC susceptibility, whereas IQSEC1-rs2600322 and IQSEC1-rs2686742 decreased and increased AM risk, respectively. Stratification analysis revealed that the significance of the identified SNPs was stronger in females or individuals younger than 46 years in SGC. PPARG-rs10865710 and PPARG-rs1175544 were associated with lower lymph node metastasis. SYN2-rs3773364 and PPARG-rs1175544 were associated with favorable SGC patient survival. Functional assessments linked PPARG-rs1175544 to PPARG expression regulation. Linkage disequilibrium analysis revealed a haplotype (SYN2-rs3773364-A, TIMP4-rs3817004-A, and TIMP4-rs3755724-C) associated with decreased susceptibility to SGC. Generalized multifactor dimensionality reduction analysis indicated the gene-gene interactions among IQSEC1, TIMP4, and PPARG in SGC, AM, and OKC progression.

CONCLUSIONS

These variants play important roles in the progression of SGC, AM, and OKC in the Chinese Han population and may be considered biomarkers for early diagnosis and prognosis prediction.

Haplotype of ESR1 and PPARD Genes Is Associated with Higher Anthropometric Changes in Han Chinese Obesity by Adjusting Dietary Factors-An 18-Month Follow-Up

The obesity genetic effect may play a major role in obesogenic environment. A combined case-control and an 18-month follow-up were carried out, including a total of 311 controls and 118 obese cases. All participants were aged in the range of 20-55 y/o. The body mass index (BMI) of obese cases and normal controls was in the range of 27.0-34.9 and 18.5-23.9 kg/m², respectively. The rs712221 on Estrogen receptor1 (ESR1) and rs2016520 on Peroxisome proliferator-activated receptor delta (PPARD) showed significant associations with obesity. The TT (odds ratio (OR): 2.42; 95% confidence interval (CI): 1.46-4.01) and TT/TC (OR: 2.80; 95% CI: 1.14-6.85) genotypes on rs712221 and rs2016520 had significantly higher obesity risks, respectively. Moreover, the synergic effect of these two risk SNPs (2-RGH) exhibited an almost geometrical increase in obesity risk (OR: 7.00; 95% CI: 2.23-21.99). Obese individuals with 2-RGH had apparently higher changes in BMI increase, body weight gain and dietary fiber intake but a lower total energy intake within the 18-month follow-up.

Association of PPARG rs3856806 C>T polymorphism with body mass index, glycaemia and lipid parameters in Serbian adolescents

Background/Aim: Peroxisome proliferator-activated receptor gamma (PPARg) belongs to a family of nuclear hormone receptors and ligand-activated transcription factors. PPARG gene is expressed in many tissues including adipose tissue where it plays a crucial role in differentiation of adipocyte, insulin resistance, blood glucose levels and lipid metabolism. The aim of the study was to examine the association of rs3856806 polymorphism with the body mass index (BMI), fasting glucose levels and lipid parameters in Serbian adolescents. Methods: This research included 287 adolescents of both genders (143 boys and 144 girls), 14-15 years of age. Genotype detection was done by polymerase chain reaction-restriction fragment length polymorphism (RFLP) assay. Results: Results showed statistically significant difference in terms of fasting glucose levels among girls (p = 0.013) depending on their genotype. Female carriers of CC genotype had significantly higher level of fasting glucose levels. Also, results showed that in the group of overweight and obese girls, carriers of CT or TT genotype had statistically significant lower values of HDL cholesterol compared to girls - carriers of CC genotype (p = 0.000). However, this result was not confirmed by multiple regression analysis. Statistically significant association of rs3856806 polymorphism was not observed with BMI nor with other lipid parameters. Conclusion: This polymorphism is associated with fasting glucose level and HDL cholesterol among girls. To draw definite conclusions, further research should be conducted including non-genetic factors and other polymorphisms among this gene.

Pro12Ala PPAR-γ2 and +294T/C PPAR-δ Polymorphisms and Association with Metabolic Traits in Teenagers from Northern Mexico

Peroxisome proliferator-activated receptors (PPARs) play roles in glucose and lipid metabolism regulation. Pro12Ala PPAR-γ2 and +294T/C PPAR-δ have been associated with dyslipidemia, hyperglycemia and high body mass index (BMI). We compared metabolic traits and determined associations with Pro12Ala PPAR-γ2 or +294T/C PPAR-δ polymorphism among teenagers from different ethnicity. Four hundred and twelve samples with previous biochemical and biometric measurements were used. Genomic DNA from peripheral blood was extracted and analyzed by end-point PCR for Pro12Ala PPAR-γ2. The +294T/C PPAR-δ PCR product was also digested with Bsl I. Two genotype groups were formed: major allele homozygous and minor allele carriers. Pro12Ala PPAR-γ2 G minor allele frequencies were: 10% in Mestizo-1, 19% in Mestizo-2, 23% in Tarahumara, 12% in Mennonite, and 17% in the total studied population. The +294T/C PPAR-δ C minor allele frequencies were: 18% in Mestizo-1, 20% in Mestizo-2, 6% in Tarahumara, 13% in Mennonite, and 12% in the total studied population. Teenagers with PPAR-γ2 G allele showed a greater risk for either high waist/height ratio or low high-density lipoprotein; and, also had lower total cholesterol. Whereas, PPAR-γ2 G allele showed lower overweight/obesity phenotype (BMI Z-score) frequency, PPAR-δ C allele was a risk factor for it. Metabolic traits were associated with both PPAR polymorphisms.

PPARG Polymorphisms Are Associated with Unexplained Mild Vision Loss in Patients with Type 2 Diabetes Mellitus

Objectives

To investigate whether the presence of peroxisome proliferator-activated receptor gamma (PPARG) gene polymorphisms is associated with unexplained mild visual impairment (UMVI) in patients with type 2 diabetes mellitus (T2DM).

Methods

A total of 135 T2DM residents with UMVI and 133 with normal vision (NV; best-corrected visual acuity ≥ 20/25 in both eyes) were enrolled. UMVI was defined as best-corrected visual acuity (BCVA) < 20/25 and ≥ 20/63 in both eyes, with no visual impairment-causing diseases found. Four PPARG gene single-nucleotide polymorphisms (SNPs) (rs3856806, rs1801282, rs709158, and rs10865710) were assessed with the HAPLOVIEW 4.0 software to examine the statistical association of PPARG polymorphisms and UMVI in patients with T2DM.

Results

Four SNPs qualified the Hardy-Weinberg equilibrium (p > 0.05). The frequency of genotype GC at SNP rs10865710 was significantly higher in the UMVI group than in the NV group (p < 0.001; GG + GC versus CC) (OR = 8.94, 95% CI: 4.90-16.31), whereas genotype CC decreased the risk (OR = 0.07, 95% CI: 0.03-0.14). Genotype TT at SNP rs3856806 was strongly associated with UMVI (p < 0.0001, TT + TC versus CC) (OR = 4.74, 95% CI: 2.68-8.54), whereas genotype CC appeared to be protective for UMVI (OR = 0.55, 95% CI: 0.37-0.82).

Conclusions

Susceptibilities of PPARG variants may lead to differences in PPARG transcription, result in early function loss of retinal photoreceptor cells, and eventually cause UMVI.

Polymorphisms of peroxisome proliferator-activated receptor γ (PPARγ) and cluster of differentiation 36 (CD36) associated with valproate-induced obesity in epileptic patients

RATIONALE

Valproate (VPA) is a choice for the treatment of primary generalized epilepsies and partial epilepsies. Unfortunately, weight gain or obesity is one of the most frequent adverse effects of VPA treatment. Genetic factors were shown to be involved in the effect.

OBJECTIVE

The aim of this study was to investigate the association of selected single nucleotide polymorphisms (SNPs) of cluster of differentiation 36 (CD36) and peroxisome proliferator-activated receptor γ (PPARγ) with VPA-induced weight gain and obesity in epileptic patients.

METHODS

A total of 225 Chinese Han epilepsy patients receiving VPA treatment were recruited in the study. Height and weight for the calculation of body mass index (BMI) were measured at the initiation of VPA therapy and in the follow-up examination. A BMI of 25 kg/m² or higher was defined as obesity on the basis of the World Health Organization (WHO) criteria for Asian populations. Four SNPs in CD36 (rs1194197, rs7807607) and PPARγ (rs10865710, rs2920502) were genotyped using the Sequenom^® MassArray iPlex platform.

RESULTS

About 19.6% of epileptic patients receiving VPA therapy were found to become obese. After covariate analysis of age, gender, sex, height, initial BMI, and VPA dosage, the CD36 rs1194197 C allele and rs7807607 T allele (OR, 0.31; 95%CI, 0.13-0.72; P = 0.009 and OR, 0.38; 95%CI; 0.18-0.83; P = 0.02, respectively) were identified as protective factors for VPA-induced obesity. The PPARγ rs10865710 C allele carriers were found to be less likely to suffer from VPA-induced obesity compared with GG genotype carriers (OR, 0.04; 95%CI, 0.01-0.12; P < 0.001). After a Bonferroni correction for multiple comparisons, the genotypic associations of CD36 rs1194197 and PPARγ rs10865710 and the allelic association of CD36 rs7807607 with obesity remained statistically significant.

CONCLUSIONS

Our data first indicated that CD36 and PPARγ polymorphisms may be associated with VPA-induced obesity and weight gain, suggesting that CD36 and PPARγ may have potential value in predicting VPA-induced obesity in Chinese Han epileptic patients.

Single-nucleotide polymorphisms of peroxisome proliferator-activated receptor-γ are associated with systemic lupus erythematosus in a Chinese Han population

BACKGROUND

Evidence has indicated that peroxisome-proliferator activated receptor-γ (PPAR-γ) agonists could be used in the prevention and treatment of murine systemic lupus erythematosus (SLE). However, to our knowledge, just one previous study has focused on the association between PPAR-γ polymorphisms and SLE in humans.

AIM

To investigate the association between PPAR-γ polymorphisms and SLE in a Chinese population and on additional gene-gene interaction between multiple single nucleotide polymorphisms (SNPs) in PPAR-γ.

METHODS

Three SNPs of PPAR-γ were selected for genotyping in this case-control study: rs1805192, rs10865710 and rs709158. Logistic regression was used to examine the association between the three SNPs and SLE, and the odds ratio (OR) and 95% CI were calculated. Generalized multifactor dimensionality reduction (GMDR) was used to investigate additional interaction.

RESULTS

All genotypes were distributed according to Hardy-Weinberg equilibrium. Logistic regression analysis showed a significant association between genotypes of rs1805192 variants and decreased SLE risk, after adjustment for sex, age, smoking, high-fat diet, low-fibre diet, alcohol status, body mass index and waist circumference. Participants with Ala allesles had a lower SLE risk than those homozygous for the wild-type allele (OR = 0.78; 95% CI 0.69-0.92). GMDR analysis indicated that there was a significant two-locus model (P = 0.001) involving rs1805192 and rs10865710, indicating a potential gene-gene interaction between them. Overall, the two-locus models had a cross-validation consistency of 10 out of 10 and a testing accuracy of 60.72%.

CONCLUSIONS

There was a significant association between PPAR-γ rs1805192 genotypes and decreased SLE risk, and a potential gene-gene interaction between rs1805192 and rs10865710.

Association of peroxisome proliferator-activated receptor delta and additional gene-smoking interaction on cardiovascular disease

AIMS

To investigate the impact of peroxisome proliferator-activator receptor delta (PPARD) gene polymorphism and additional gene-smoking interaction on cardiovascular disease (CVD) risk based on this Chinese population.

METHODS

A total of 1048 subjects (617 males, 431 females) with a mean age of 52.9 ± 14.1 years old were selected, including 520 CVD patients and 528 normal control subjects. The logistic regression model was used to examine the association between three SNPs and CVD risk, odds ratio (OR), and 95% confident interval (95%CI) were calculated. Generalized multifactor dimensionality reduction (GMDR) was employed to investigate the gene-smoking interaction.

RESULTS

Genotypes of variants in rs2016520 and rs9794 were associated with decreased CVD risk, and CVD risk was significantly lower in carriers of C allele of the rs2016520 polymorphism than those with the TT genotype (TC+CC versus TT), adjusted OR (95%CI) = 0.71 (0.56-0.86). In addition, we also found that CVD risk was also significantly lower in carriers of the G allele of the rs9794 polymorphism than those with the CC genotype (CG+ GG versus CC), adjusted OR (95%CI) = 0.69 (0.53-0.86). GMDR analysis suggested a potential gene-environment interaction between rs2016520 and smoking. Overall, the two-locus models had a cross-validation consistency of 10 of 10, and had the testing accuracy of 62.17%, and never smokers with TC or CC of the rs2016520 genotype have the lowest CVD risk, compared to smokers with TT of rs2016520, OR (95%CI) was 0.42 (0.23-0.66).

CONCLUSIONS

The minor allele of rs2016520 and rs9794 in PPAR-δ and interaction between rs2016520 and non-smoking were associated with decreased risk of CVD.

PPARD rs2016520 polymorphism is associated with metabolic traits in a large population of Chinese adults

AIMS

Polymorphism of rs2016520 in gene PPARD has been associated with lipid metabolism, obesity, metabolic syndrome and type 2 diabetes mellitus (T2DM). We aimed to study the association of rs2016520 with common metabolic traits in a large population of Han Chinese adults.

METHODS

The polymorphism was genotyped in 1409 subjects using Matrix-Assisted Laser Desorption/Ionization Time of Flight Mass Spectrometry (MALDI-TOF MS); all participants underwent standard clinical examination and a 75g oral glucose tolerance test (OGTT); associations between the polymorphism and metabolic traits and indices of insulin resistance and insulin sensitivity were analyzed.

RESULTS

There was no significant difference in genotypes between the normal glucose tolerance (NGT) and the prediabetes group (χ(2)=3.17, P=0.2), except a nominal difference of allele frequency (χ(2)=3.07, P=0.07). The G carrier presented lower fasting plasma glucose (FPG, P=0.03), lower 2h plasma glucose (Pdom=0.04) and lower fasting insulin (P=0.02), lower systolic blood pressure (SBP, P=0.03), lower HOMA-IR (P=0.02) and higher QUICKI (P=0.01). Moreover, rs2016520 polymorphism was associated with FPG (β=-0.09, P=0.05), it was also associated with indices of insulin resistance (HOMA-IR, β=-0.06, Pdom=0.02; fasting insulin, β=-0.04, P=0.02) and indices of insulin sensitivity (QUICKI, β=-0.01, P=0.004). In addition, we observed that the allele G was also associated with lower SBP (β=-1.29, P=0.04) and diastolic blood pressure (DBP, β=-0.09, P=0.01). However, the minor allele G was not associated with risk of metabolic disorders including prediabetes, overweight, hypertension and metabolic syndrome.

CONCLUSIONS

Polymorphism of rs2016520 in gene PPARD was associated with benign metabolic traits in a large cohort of Chinese adults. The G allele may confer protection from type 2 diabetes and hypertension in Han Chinese.

Gene-gene interaction of erythropoietin gene polymorphisms and diabetic retinopathy in Chinese Han

The aim of this study was to investigate the association of three single nucleotide polymorphisms in the erythropoietin gene polymorphisms with diabetic retinopathy and additional role of gene-gene interaction on diabetic retinopathy risk. A total of 1193 patients (579 men, 614 women) with type 2 diabetes mellitus were selected, including 397 diabetic retinopathy patients and 796 controls (type 2 diabetes mellitus patients without diabetic retinopathy); the mean age of all participants was 56.7 ± 13.9 years. Three single nucleotide polymorphisms were selected: rs507392, rs1617640, and rs551238. The t-test was used for comparison of erythropoietin protein level erythropoietin levels in patients having different erythropoietin genotypes. Logistic regression model was used to examine the association between three single nucleotide polymorphisms and diabetic retinopathy. Odds ratio (OR) and 95% confident interval (95% CI) were calculated. Generalized multifactor dimensionality reduction was employed to analyze the impact of interaction among three single nucleotide polymorphisms on CVD risk. After covariates adjustment, the carriers of homozygous mutant of three single nucleotide polymorphisms have higher diabetic retinopathy risk than those with wild-type homozygotes, OR (95% CI) were 2.04 (1.12-2.35), 1.87 (1.10-2.41) and 1.15 (1.06-1.76), respectively. Generalized multifactor dimensionality reduction model indicated a significant three-locus model (p = 0.0010) involving rs507392, rs1617640, and rs551238. Overall, the three-locus models had a cross-validation consistency of 10 of 10, and had the testing accuracy of 60.72%. Subjects with TC or CC-TG or GG-AC or CC genotype have the highest diabetic retinopathy risk. In conclusion, our results support an important association of rs507392, rs1617640 and rs551238 minor allele of erythropoietin with increased diabetic retinopathy risk, and additional interaction among three single nucleotide polymorphisms.

Influence of SNP*SNP interaction on BMI in European American adolescents: findings from the National Longitudinal Study of Adolescent Health

BACKGROUND

Adolescent obesity is predictive of future weight gain, obesity and adult onset severe obesity (body mass index [BMI] ≥40 kg m(-2) ). Despite successful efforts to identify Single Nucleotide Polymorphisms (SNPs) influencing BMI, <5% of the 40-80% heritability of the phenotype has been explained. Identification of gene-gene (G-G) interactions between known variants can help explain this hidden heritability as well as identify potential biological mechanisms affecting weight gain during this critical developmental period.

OBJECTIVE

We have recently shown distinct genetic effects on BMI across the life course, and thus it is important to examine the evidence for epistasis in adolescence.

METHODS

In adolescent participants of European descent from wave II of the National Longitudinal Study of Adolescent Health (Add Health, n = 5072, ages 12-21, 52.5% female), we tested 34 established BMI-related SNPs for G-G interaction effects on BMI z-score. We used mixed-effects regression, assuming multiplicative interaction models adjusting for age, sex and geographic region, with random effects for family and school.

RESULTS

For 28 G-G interactions that were nominally significant (P < 0.05), we attempted to replicate our results in an adolescent sample from the Childhood European American Cohort from Philadelphia. In the replication study, one interaction (PRKD1-FTO) was significant after correction for multiple testing.

CONCLUSIONS

Our results are suggestive of epistatic effects on BMI during adolescence and point to potentially interactive effects between genes in biological pathways important in obesity.

Sports genetics: the PPARA gene and athletes' high ability in endurance sports. A systematic review and meta-analysis

A meta-analysis was performed with the aim of re-evaluating the role of the peroxisome proliferator activated receptor alpha (PPARA) gene intron 7 G/C polymorphism (rs4253778) in athletes’ high ability in endurance sports. Design: A meta-analysis of case control studies assessing the association between the G/C polymorphisms of the PPARA gene and endurance sports was conducted. The Cochrane Review Manager software was used to compare the genotype and allele frequencies between endurance athletes and controls to determine whether a genetic variant is more common in athletes than in the general population. Five studies, encompassing 760 endurance athletes and 1792 controls, fulfilled our inclusion criteria. The pooled odds ratio (and confidence intervals, CIs) for the G allele compared to the C allele was 1.65 (95% CI 1.39-1.96). The pooled OR for the GG genotype compared to the GC genotype was 1.79 (95% CI 1.44-2.22), and for the GG genotype compared to the CC genotype 2.37 (95% CI 1.40-3.99). There was no evidence of heterogeneity (I² =0%) or of publication bias. Athletes with high ability in endurance sports had a higher frequency of the GG genotype and G allele.

Screening of Peroxisome Proliferator-Activated Receptors (PPARs) α, γ and α Gene Polymorphisms for Obesity and Metabolic Syndrome Association in the Multi-Ethnic Malaysian Population

OBJECTIVE

This study aimed to investigate the association of peroxisome proliferator-activated receptor (PPAR) genes PPARα L162V, PPARγ2 C161T and PPARδ T294C single nucleotide polymorphisms (SNPs) with obesity and metabolic syndrome (Met-S) in a multi-ethnic population in Kampar, Malaysia.

METHODS

Socio-demographic data, anthropometric and biochemical measurements (plasma lipid profile, adiponectin and interleukin-6 [IL-6] levels) were taken from 307 participants (124 males; 180 obese; 249 Met-S; 97 Malays, 85 ethnic Chinese, 55 ethnic Indians).

RESULTS

The overall minor allele frequencies were .08, .22 and .30 for PPAR α L162V, γ C161T, δ T294C, respectively. All SNPs were not associated with obesity, Met-S and obesity with/without Met-S by χ(2) analysis, ethnicity-stratified and logistic regression analyses. Nevertheless, participants with V162 allele of PPARα had significantly higher IL-6, while those with T161 allele of PPARγ2 had significantly lower HOMA-IR.

CONCLUSIONS

All PPAR SNPs were not associated with obesity and Met-S in the suburban population of Kampar, Malaysia, where only PPARα V162 and PPARγ2 T161 alleles were associated with plasma IL-6 and HOMA-IR, respectively.

A roadmap to multifactor dimensionality reduction methods

Complex diseases are defined to be determined by multiple genetic and environmental factors alone as well as in interactions. To analyze interactions in genetic data, many statistical methods have been suggested, with most of them relying on statistical regression models. Given the known limitations of classical methods, approaches from the machine-learning community have also become attractive. From this latter family, a fast-growing collection of methods emerged that are based on the Multifactor Dimensionality Reduction (MDR) approach. Since its first introduction, MDR has enjoyed great popularity in applications and has been extended and modified multiple times. Based on a literature search, we here provide a systematic and comprehensive overview of these suggested methods. The methods are described in detail, and the availability of implementations is listed. Most recent approaches offer to deal with large-scale data sets and rare variants, which is why we expect these methods to even gain in popularity.

A population association study of PPAR δ gene rs2016520 and rs9794 polymorphisms and haplotypes with body mass index and waist circumference in a Chinese population

BACKGROUND

Peroxisome proliferator-activated receptor (PPAR) gene plays an important role in obesity and PPAR δ protein is a potent inhibitor; however, few previous studies have focused on this gene.

AIM

To investigate the association of haplotypes of PPAR δ gene rs2016520 and rs9794 with abnormal weight (BMI ≥ 24 kg/m(2)) and abdominal obesity (WC ≥ 90 cm for males and ≥ 80 cm for females) in a Chinese Han population.

SUBJECTS AND METHODS

In total, 820 subjects (270 men, 550 women) were randomly selected from the PMMJS cohort population and no individuals were related. rs2016520 and rs9794 were detected by TaqMan fluorescence probe. Hardy-Weinberg equilibrium (HWE) was used to detect genotype typing errors by Fisher's exact test. Linkage disequilibrium (LD) between polymorphisms was estimated by using SHEsis. Two PPAR δ SNPs (rs2016520 and rs9794) were analysed by using the logistic regression model.

RESULTS

After adjustment for covariates, the haplotype containing the rs1026520-C and rs9794-C alleles was associated with a statistically significant decreased risk of obesity (OR = 0.64; 95% CI = 0.48-0.84, p = 0.0015). Coincidentally, the haplotype containing the rs1026520-C and rs9794-C alleles was also associated with a statistically decreased risk of abdominal obesity after covariate adjustment (OR = 0.59, 95% CI = 0.45-0.77, p < 0.001).

CONCLUSION

C-C haplotype, constructed from rs2016520 and rs9794 alleles, showed a significant protective effect for both abnormal weight and abdominal obesity.

Role of peroxisome proliferator-activated receptors gene polymorphisms in type 2 diabetes and metabolic syndrome

Metabolic syndrome (MetS) and type 2 diabetes mellitus (T2DM) are the serious public health problems worldwide. Moreover, it is estimated that MetS patients have about five-fold greater risk of the T2DM development compared with people without the syndrome. Peroxisome proliferator-activated receptors are a subgroup of the nuclear hormone receptor superfamily of ligand-activated transcription factors which play an important role in the pathogenesis of MetS and T2DM. All three members of the peroxisome proliferator-activated receptor (PPAR) nuclear receptor subfamily, PPARα, PPARβ/δ and PPARγ are critical in regulating insulin sensitivity, adipogenesis, lipid metabolism, and blood pressure. Recently, more and more studies indicated that the gene polymorphism of PPARs, such as Leu¹⁶²Val and Val²²⁷Ala of PPARα, +294T > C of PPARβ/δ, Pro¹²Ala and C1431T of PPARγ, are significantly associated with the onset and progressing of MetS and T2DM in different population worldwide. Furthermore, a large body of evidence demonstrated that the glucose metabolism and lipid metabolism were influenced by gene-gene interaction among PPARs genes. However, given the complexity pathogenesis of metabolic disease, it is unlikely that genetic variation of a single locus would provide an adequate explanation of inter-individual differences which results in diverse clinical syndromes. Thus, gene-gene interactions and gene-environment interactions associated with T2DM and MetS need future comprehensive studies.

Integrative and systemic approaches for evaluating PPARβ/δ (PPARD) function

The peroxisome proliferator-activated receptors (PPARs) are a group of nuclear receptors that function as transcription factors regulating the expression of genes involved in cellular differentiation, development, metabolism and also tumorigenesis. Three PPAR isotypes (α, β/δ and γ) have been identified, among which PPARβ/δ is the most difficult to functionally examine due to its tissue-specific diversity in cell fate determination, energy metabolism and housekeeping activities. PPARβ/δ acts both in a ligand-dependent and -independent manner. The specific type of regulation, activation or repression, is determined by many factors, among which the type of ligand, the presence/absence of PPARβ/δ-interacting corepressor or coactivator complexes and PPARβ/δ protein post-translational modifications play major roles. Recently, new global approaches to the study of nuclear receptors have made it possible to evaluate their molecular activity in a more systemic fashion, rather than deeply digging into a single pathway/function. This systemic approach is ideally suited for studying PPARβ/δ, due to its ubiquitous expression in various organs and its overlapping and tissue-specific transcriptomic signatures. The aim of the present review is to present in detail the diversity of PPARβ/δ function, focusing on the different information gained at the systemic level, and describing the global and unbiased approaches that combine a systems view with molecular understanding.

Obesity and genomics: role of technology in unraveling the complex genetic architecture of obesity

Obesity is a complex and multifactorial disease that occurs as a result of the interaction between "obesogenic" environmental factors and genetic components. Although the genetic component of obesity is clear from the heritability studies, the genetic basis remains largely elusive. Successes have been achieved in identifying the causal genes for monogenic obesity using animal models and linkage studies, but these approaches are not fruitful for polygenic obesity. The developments of genome-wide association approach have brought breakthrough discovery of genetic variants for polygenic obesity where tens of new susceptibility loci were identified. However, the common SNPs only accounted for a proportion of heritability. The arrival of NGS technologies and completion of 1000 Genomes Project have brought other new methods to dissect the genetic architecture of obesity, for example, the use of exome genotyping arrays and deep sequencing of candidate loci identified from GWAS to study rare variants. In this review, we summarize and discuss the developments of these genetic approaches in human obesity.

Analysis on the association between PPARα/γ polymorphisms and lipoprotein(a) in a Chinese Han population

Lipoprotein(a) [Lp(a)], a low-density lipoprotein-like particle, is recognized as an independent risk factor for atherosclerosis, cardiovascular diseases, and diabetic vascular diseases. Our recent studies revealed that the single nucleotide polymorphisms (SNPs) of peroxisome proliferator-activated receptors (PPARα/δ/γ) gene are involved in the regulation of lipid storage and metabolism. In order to investigate the relationships between the SNPs of PPARα/γ gene and plasma levels of Lp(a), 644 participants were randomly selected from Chinese Han population in the present study. As the results shown, Lp(a) was significantly associated with L162V (rs1800206) in PPARα. Compared with those subjects with widetype (LL), significantly higher Lp(a) concentration was determined in the individuals with mutant (LV + VV) (mean difference: 49.07 mg/l, 95% CI 23.32-74.82 mg/l, p = 0.0002). Moreover, with generalized multifactor dimensionality reduction analysis, our present results indicated that there was a significant association between plasma Lp(a) level and gene-gene interaction among the polymorphisms rs1800206, rs135539 in PPARα and rs10865710, rs1805192, and rs4684847 in PPARγ. Therefore, our presented study indicated that PPARα/γ polymorphisms should be involved in the regulation of plasma Lp(a) in independently and/or in an interactive manner, suggesting that PPARα/γ gene may influence the risk of hypertension, cardiovascular diseases, and dyslipidemia by regulating Lp(a) level.

Rare mutations of peroxisome proliferator-activated receptor gamma: frequencies and relationship with insulin resistance and diabetes risk in the mixed ancestry population from South Africa

Background. Genetic variants in the nuclear transcription receptor, PPARG, are associated with cardiometabolic traits, but reports remain conflicting. We determined the frequency and the clinical relevance of PPARG SNPs in an African mixed ancestry population. Methods. In a cross-sectional study, 820 participants were genotyped for rs1800571, rs72551362, rs72551363, rs72551364, and rs3856806, using allele-specific TaqMan technology. The homeostatic model assessment of insulin (HOMA-IR), β-cells function (HOMA-B%), fasting insulin resistance index (FIRI), and the quantitative insulin-sensitivity check index (QUICKI) were calculated. Results. No sequence variants were found except for the rs3856806. The frequency of the PPARG-His447His variant was 23.8% in the overall population group, with no difference by diabetes status (P = 0.215). The His447His allele T was associated with none of the markers of insulin resistance overall and by diabetes status. In models adjusted for 2-hour insulin, the T allele was associated with lower prevalent diabetes risk (odds ratio 0.56 (95% CI 0.31-0.95)). Conclusion. Our study confirms the almost zero occurrences of known rare PPARG SNPs and has shown for the first time in an African population that one of the common SNPs, His447His, may be protective against type 2 diabetes.