Meta-analysis of association studies between five candidate genes and type 2 diabetes in Chinese Han population

Correlation Between PPARGC1A Gene Rs8192678 G>A Polymorphism and Susceptibility To Type-2 Diabetes

Objective

To systematically investigate the correlation between the G>A polymorphism of the peroxisome proliferator-activated receptor γ coactivator 1α (PPARGC1A or PGC-1alpha) gene rs8192678 locus and the susceptibility to type-2 diabetes mellitus (T2DM).

Methods

The inclusion and exclusion criteria and retrieval strategies of original literatures were formulated. Then, subjects and free words “PPARGC1A”,”gene polymorphism”, and “T2DM” were retrieved from the PubMed, EMBASE, and Cochrane Library databases. Case-control studies on the G>A polymorphism of the PPARGC1A gene rs8192678 locus and susceptibility to T2DM were included for the meta-analysis.

Results

The number of cases in the T2DM group and control group was 5,607 and 7,596, respectively. The meta-analysis revealed that the PPARGC1A gene rs8192678 locus G>A polymorphism is associated with susceptibility to T2DM. There are differences in each group of genetic models, of which three groups of genetic models are highly significant. In the allele model, OR=1.249, 95% CI: 1.099-1.419, and P=0.001. In the dominant inheritance model, OR=1.364, 95% CI: 1.152-1.614, and P=0.000. In the additive inheritance model, OR=0.828, 95% CI: 0.726-0.945, and P=0.005. And one group is significant, in the recessive inheritance model, OR=1.187, 95% CI: 1.021-1.381, and P=0.026.

Conclusion

In Western Asian, South Asian, European and African populations, the A allele of the PPARGC1A gene rs8192678 locus may be one of the risk factors for T2DM.

Interactions among moderate/severe periodontitis, ADIPOQ-rs1501299, and LEPR-rs1137100 polymorphisms on the risk of type 2 diabetes in a Chinese population

OBJECTIVE

Type 2 diabetes mellitus (T2DM) is a complex disease influenced by genes and the environment. Periodontitis a demonstrated risk factor of T2DM. Previous studies related to gene-environment interactions on the risk of T2DM mainly focused on gene-obesity interactions. However, the impact of gene-periodontitis interaction on the risk of T2DM has not yet been investigated. This study aimed to investigate gene-environment interactions among moderate/severe periodontitis, polymorphisms of adiponectin (ADIPOQ)-rs1501299, and leptin receptor (LEPR)-rs1137100 on T2DM risk in Chinese subjects.

DESIGN

A case-control study was conducted in 239 Chinese participants from Beijing Hypertension Association Institute (BHAL). After full-mouth periodontal examinations, the participants underwent bilateral buccal swabs for DNA testing. ADIPOQ-rs1501299 and LEPR-rs1137100 were used for genotyping. Generalised multifactor dimensionality reduction (GMDR) and logistic regression were used to examine the interactions among single nucleotide polymorphisms (SNPs) and moderate/severe periodontitis on the risk of T2DM.

RESULTS

The risk of T2DM was higher in moderate/severe periodontitis [adjusted odds ratio (AOR) = 3.67, 95% confidence interval (95%CI): 1.26-10.71] in ADIPOQ-rs1501299 GG genotype (AOR = 3.42, 95%CI: 1.81-6.46) and LEPR-rs1137100 GG genotype (AOR = 3.16, 95%CI: 1.56-6.39). The GMDR model indicated that there was a significant three-factor model (p = 0.001) involving rs1501299, rs1137100, and moderate/severe periodontitis, demonstrating a potential gene-environment interaction among periodontitis, polymorphisms of rs1501299, and rs1137100 influencing the risk of T2DM. Moderate/severe periodontitis patients with rs1501299-GG and rs1137100-GG have the highest T2DM risk after adjusting for age, gender, BMI, WHR, smoking status, alcohol consumption, economic status, and hypertension (AOR = 20.39, 95%CI: 2.64-157.26).

CONCLUSIONS

Interactions among moderate/severe periodontitis, rs1501299-GG, and rs1137100-GG were associated with an increased risk of T2DM. This study may provide a new insight into the effect of gene-environment interactions on T2DM.

Association of common polymorphisms in the VEGFA and SIRT1 genes with type 2 diabetes-related traits in Mexicans

INTRODUCTION

Genetic variants have been replicated for association with type 2 diabetes mellitus (T2D) and many of them with diabetes-related traits. Because T2D is highly prevalent in Mexico, this study aimed to test the association of CDKN2A/B, PPARGC1A, VEGFA, SIRT1 and UCP2 gene polymorphisms (rs10811661, rs8192678, rs2010963, rs7896005 and rs659366 respectively) with metabolic traits in 415 unrelated Mexican mestizos with T2D under three models of inheritance.

MATERIAL AND METHODS

A total of 415 unrelated Mexican mestizos were genotyped by TaqMan assays. Triglycerides, cholesterol, glucose, high-density lipoprotein cholesterol (HDL-C), insulin and anthropometric measurements were determined and the HOMA-IR was calculated. Association studies were tested by the Kruskal-Wallis test, linear regression, statistical power analysis, Bonferroni correction, paired SNP analysis, and physical interaction by GeneMANIA.

RESULTS

All polymorphisms were in Hardy-Weinberg equilibrium, and the association by genotype with T2D-related traits displayed nominal significance for rs8192678 with glucose (p = 0.023) and triglycerides (p = 0.013); rs2010963 with diastolic blood pressure (DBP) (p = 0.012) and cholesterol (p = 0.013); rs7896005 with DBP (p = 0.012) and insulin (p = 0.011); and rs659366 with cholesterol (p = 0.034), glucose (p = 0.031) and triglycerides (p = 0.028); and the association of rs2010963 with HDL-C (p = 0.0007) was significant. Linear regression performed with three models of inheritance, adjusted by age + sex + BMI and corrected with Bonferroni, showed a significant association of rs2010963 with HDL-C in an additive model (p = 0.007); and rs7896005 was significantly associated with DBP in the recessive model (p = 0.006).

CONCLUSIONS

Rigorous analysis evidenced the association of VEGFA rs2010963 and SIRT1 rs7896005 with HDL-C and DBP respectively; these traits are known predictors of cardiovascular complications, which increase the risk of cardiovascular diseases in this population.

Association and in silico studies of ENPP1 gene variants with type 2 diabetes mellitus in a Northern Iranian population

In the current study, a sample population of Northern Iranians was selected to investigate the association of K121Q, rs1799774, rs7754561, and rs997509 ENPP1 gene variants and their haplotypes with T2DM. Genomic DNAs of 978 samples were extracted by Salting Out standard technique and then genotyped by the TaqMan assay. The results show significant differences between study groups for K121Q (p = 0.0004) under a Dominant and rs7754561 (p = 0.002) under a co-dominant hereditary model. Based on allele frequency, there was a significant difference between two study groups at K121Q and rs7754561 variants (p = 0.010 and p = 0.01, respectively). There was no evidence for an association between ENPP1 haplotypes and overall risk of T2DM. Genotype-phenotype sub-analyses showed no significant relationship of four studied polymorphisms with age, gender, FBS, and systolic and diastolic blood pressures. Homology modeling and molecular docking of ENPP1 in K173 and Q173 models with ATP, AMP, and 2'3'-cGAMP as ligands revealed that all ligands had a more binding affinity to Lys173 protein model, and 2'3'-cGAMP had a higher affinity to both ENPP1 protein models compared to ATP and AMP. These findings suggest that ENPP1 gene variants may have a potential impact on the occurrence of T2DM in Northern Iranians.

Linking Metabolic Disease With the PGC-1α Gly482Ser Polymorphism

Peroxisome proliferator-activated receptor γ coactivator 1-α (PGC-1α) is a highly conserved transcriptional coactivator enriched in metabolically active tissues including liver, adipose, pancreas, and muscle. It plays a role in regulating whole body energy metabolism and its deregulation has been implicated in type 2 diabetes (T2D). A single nucleotide variant of the PPARGC1A gene (rs8192678) is associated with T2D susceptibility, relative risk of obesity and insulin resistance, and lower indices of β cell function. This common polymorphism is within a highly conserved region of the bioactive protein and leads to a single amino acid substitution (glycine 482 to serine). Its prevalence and effects on metabolic parameters appear to vary depending on factors including ethnicity and sex, suggesting important interactions between genetics and cultural/environmental factors and associated disease risk. Interestingly, carriers of the serine allele respond better to some T2D interventions, illustrating the importance of understanding functional impacts of genetic variance on PGC-1α when targeting this pathway for personalized medicine. This review summarizes a growing body of literature surrounding possible links between the PGC-1α Gly482Ser single nucleotide polymorphism and diabetes, with focus on key clinical findings, affected metabolic systems, potential molecular mechanisms, and the influence of geographical or ethnic background on associated risk.

The ENPP1 K121Q polymorphism modulates developing of bone disorders in type 2 diabetes: A cross sectional study

BACKGROUND

Osteoporosis and osteopenia are common diseases in every population. Type 2 diabetes mellitus (T2DM) can lead to the development of various complications, such as bone disorders especially among elderly individuals. Studies suggested that ectonucleotide pyrophosphatase/phosphodiesterase1 (ENPP1) is contributed in insulin resistance and also the inhibition of bone mineralization. In this study, association of K121Q (rs1044498) polymorphism of the ENPP1 gene with T2DM and bone disorders is evaluated.

METHODS

Four-hundred-and-ninety females who were classified based on bone mineral density (BMD) at lumbar spine and femur were included in this study. In addition, participants were classified according to their diabetes status. K121Q polymorphism was evaluated by the PCR-PFLF technique. One-way ANOVA was used for comparison of various analyzed factors in diseases subgroups and K121Q genotypes. Association of K121Q polymorphism with diabetes and bone disorders was evaluated by logistic regression.

RESULTS

Significant association was observed between K121Q polymorphism with osteoporosis and osteopenia (p=0.041, p=0.029, respectively), but a similar pattern was not observed in T2DM status (p=0.723). Moreover, in diabetic patients, K121Q polymorphism showed a better prediction potential for the development of bone disorders in comparison to non-diabetic subjects (p=0.018; OR=4.63, p=0.540; OR=1.31). There were no significant differences between K121Q genotypes with FBS, Ca, P, vitamin D, PTH and BMD status.

CONCLUSIONS

The present study implies that K121Q polymorphism of ENPP1 gene is able to modulate the development of bone disorders in T2DM. Therefore in diabetic patients screening of this polymorphism is suggested for the monitoring of these persons.

Association between 28 single nucleotide polymorphisms and type 2 diabetes mellitus in the Kazakh population: a case-control study

Background

We evaluated the associations between single nucleotide polymorphisms and different clinical parameters related to type 2 diabetes mellitus (T2DM), obesity risk, and metabolic syndrome (MS) in a Kazakh cohort.

Methods

A total of 1336 subjects, including 408 T2DM patients and 928 control subjects, were recruited from an outpatient clinic and genotyped for 32 polymorphisms previously associated with T2DM and obesity-related phenotypes in other ethnic groups. For association studies, the chi-squared test or Fisher’s exact test for binomial variables were used. Logistic regression was conducted to explore associations between the studied SNPs and the risk of developing T2DM, obesity, and MS, after adjustments for age and sex.

Results

After excluding four SNPs due to Hardy-Weinberg disequilibrium, significant associations in age-matched cohorts were found betweenT2DM and the following SNPs: rs9939609 (FTO), rs13266634 (SLC30A8), rs7961581 (TSPAN8/LGR5), and rs1799883 (FABP2). In addition, examination of general unmatched T2DM and control cohorts revealed significant associations between T2DM and SNPsrs1799883 (FABP2) and rs9939609 (FTO). Furthermore, polymorphisms in the FTO gene were associated with increased obesity risk, whereas polymorphisms in the FTO and FABP2 genes were also associated with the risk of developing MS in general unmatched cohorts.

Conclusion

We confirmed associations between polymorphisms within the SLC30A8, TSPAN8/LGR5, FABP2, and FTO genes and susceptibility to T2DM in a Kazakh cohort, and revealed significant associations with anthropometric and metabolic traits. In particular, FTO and FABP2 gene polymorphisms were significantly associated with susceptibility to MS and obesity in this cohort.

Electronic supplementary material

The online version of this article (doi:10.1186/s12881-017-0443-2) contains supplementary material, which is available to authorized users.

The ENPP1 K121Q polymorphism is associated with type 2 diabetes and related metabolic phenotypes in a Taiwanese population

Increased risk of developing type 2 diabetes (T2D) has been associated with a single nucleotide polymorphism (SNP), rs1044498 (K121Q), in the ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1) gene, but this association is unclear among Asians. In this replication study, we reassessed whether the ENPP1 rs1044498 SNP is associated with T2D, obesity, and T2D/obesity-related metabolic traits in a Taiwanese population. A total of 1513 Taiwanese subjects were assessed in this study. The ENPP1 rs1044498 SNP was genotyped by the Taqman assay. T2D/Obesity-related quantitative traits, such as waist circumference and fasting glucose, were measured. Our data showed a significant association of the ENPP1 rs1044498 SNP with T2D (P < 0.001) among the subjects. Moreover, the ENPP1 rs1044498 SNP was significantly associated with T2D/obesity-related metabolic traits, such as waist circumference (P = 0.002) and fasting glucose (P < 0.001), among the subjects. However, we found no association of ENPP1 rs1044498 with obesity (BMI ≧ 27 kg/m(2)). Our study indicates that the ENPP1 rs1044498 SNP is associated with T2D, waist circumference, and fasting glucose in Taiwanese subjects.

Central and peripheral pathogenetic forms of type 2 diabetes: a proof-of-concept study

HYPOTHESIS

Previous studies provide evidence that glycated haemoglobin (HbA1c) and fasting plasma glucose (FPG) should not be considered as interchangeable alternatives in the diagnosis of the same type 2 diabetes, but as indicators of its different pathogenetic subtypes. This study was conducted to determine whether a particularly high amount of glucose in either HbA1c form or in fasting plasma would be found in diabetic patients genetically predisposed for either intensive cognitive or intensive muscle metabolic activity, respectively.

METHODS

HbA1c and FPG levels, polymorphisms of genes indicating the predisposition to different cognitive activity (the dopamine D2 receptor (DRD2/ANKK1)), muscle activity (peroxisome proliferator-activated receptor gamma, coactivator 1 alpha (PGC1A(PPARGC1A))), and vascular regulation of general metabolic activity (the angiotensin 1 converting enzyme (ACE)) were assessed in diabetic patients and nondiabetic controls.

RESULTS

DRD2/ANKK1 polymorphism that affects baseline central arousal determined HbA1c variations uncorrelated with FPG in total and clinical groups. The mutation of PGC1A mainly affecting peripheral glucose metabolism had an effect on FPG correlated or uncorrelated with HbA1c depending on the effect assessment in the total sample or in the nondiabetic group, respectively. ACE insertion/deletion (I/D) gene polymorphism was associated with both HbA1c and FPG fluctuations, but only in diabetic patients.

CONCLUSION

The findings provide evidence that the HbA1c and FPG may predict the risks for different subtypes of type 2 diabetes associated with either brain or muscle metabolic activity in genetically vulnerable people.

Genetic Associations of PPARGC1A with Type 2 Diabetes: Differences among Populations with African Origins

The aim of this study was to assess the differences in correlation of PPARGC1A polymorphisms with type 2 diabetes (T2D) risk in adults of African origins: African Americans and Haitian Americans. The case-control study consisted of >30 years old, self-identified Haitian Americans (n = 110 cases and n = 116 controls) and African Americans (n = 124 cases and n = 122 controls) living in South Florida with and without T2D. Adjusted logistic regression indicated that both SNP rs7656250 (OR = 0.22, P = 0.005) and rs4235308 (OR = 0.42, P = 0.026) showed protective association with T2D in Haitian Americans. In African Americans, however, rs4235308 showed significant risk association with T2D (OR = 2.53, P = 0.028). After stratification with sex, in Haitian Americans, both rs4235308 (OR = 0.38, P = 0.026) and rs7656250 (OR = 0.23, P = 0.006) showed protective association with T2D in females whereas in African American males rs7656250 had statistically significant protective effect on T2D (OR = 0.37, P = 0.043). The trends observed for genetic association of PPARGC1A SNPs, rs4235308, and rs7656250 for T2D between Haitian Americans and African Americans point out differences in Black race and warrant replicative study with larger sample size.

Association between the ENPP1 K121Q polymorphism and risk of diabetic kidney disease: a systematic review and meta-analysis

The potential association between the K121Q (A/C, rs1044498) polymorphism in the ectonucleotide pyrophosphatase/phosphodiesterase (ENPP1) gene and risk of diabetic kidney disease (DKD) has been investigated. Nevertheless, the effect of this variant on DKD risk is still under debate, and conflicting results have been reported. To this date, no meta-analysis has evaluated the association of the K121Q polymorphism with DKD. This paper describes the first meta-analysis conducted to evaluate whether the ENPP1K121Q polymorphism is associated with DKD. A literature search was conducted to identify all case-control or cross-sectional studies that evaluated associations between the ENPP1K121Q polymorphism and DKD. Pooled odds ratios (OR) and 95% confidence intervals (95% CI) were calculated for allele contrast, additive, dominant and recessive inheritance models. Seven studies were eligible for inclusion in the meta-analysis, providing data on 3571 type 1 or type 2 diabetic patients (1606 cases with DKD and 1965 diabetic controls without this complication). No significant heterogeneity was observed among the studies included in the meta-analysis when assuming different inheritance models (I² < 50% or P > 0.10 for the entire sample and after stratification by ethnicity). Meta-analysis results revealed significant associations between the K121Q polymorphism and risk of DKD in Asians and Europeans when assuming the different inheritance models analyzed. The most powerful association was observed for the additive model (OR = 1.74, 95% CI 1.27-2.38 for the total sample). In conclusion, the present meta-analysis detected a significant association between the ENPP1K121Q polymorphism and increased susceptibility of DKD in European and Asian populations.

Calpain-10 SNP43 and SNP19 polymorphisms and colorectal cancer: a matched case-control study

OBJECTIVE

Insulin resistance (IR) is an established risk factor for colorectal cancer (CRC). Given that CRC and IR physiologically overlap and the calpain-10 gene (CAPN10) is a candidate for IR, we explored the association between CAPN10 and CRC risk.

METHODS

Blood samples of 400 case-control pairs were genotyped, and the lifestyle and dietary habits of these pairs were recorded and collected. Unconditional logistic regression (LR) was used to assess the effects of CAPN10 SNP43 and SNP19, and environmental factors. Both generalized multifactor dimensionality reduction (GMDR) and the classification and regression tree (CART) were used to test gene-environment interactions for CRC risk.

RESULTS

The GA+AA genotype of SNP43 and the Del/Ins+Ins/Ins genotype of SNP19 were marginally related to CRC risk (GA+AA: OR = 1.35, 95% CI = 0.92-1.99; Del/Ins+Ins/ Ins: OR = 1.31, 95% CI = 0.84-2.04). Notably, a high-order interaction was consistently identified by GMDR and CART analyses. In GMDR, the four-factor interaction model of SNP43, SNP19, red meat consumption, and smoked meat consumption was the best model, with a maximum cross-validation consistency of 10/10 and testing balance accuracy of 0.61 (P < 0.01). In LR, subjects with high red and smoked meat consumption and two risk genotypes had a 6.17-fold CRC risk (95% CI = 2.44-15.6) relative to that of subjects with low red and smoked meat consumption and null risk genotypes. In CART, individuals with high smoked and red meat consumption, SNP19 Del/Ins+Ins/Ins, and SNP43 GA+AA had higher CRC risk (OR = 4.56, 95%CI = 1.94-10.75) than those with low smoked and red meat consumption.

CONCLUSIONS

Though the single loci of CAPN10 SNP43 and SNP19 are not enough to significantly increase the CRC susceptibility, the combination of SNP43, SNP19, red meat consumption, and smoked meat consumption is associated with elevated risk.

Meta-analysis of the association of ADIPOQ G276T polymorphism with insulin resistance and blood glucose

Insulin resistance (IR) is a major risk for the development of type 2 diabetes (T2D). Numerous studies have been conducted to determine the relationship of ADIPOQ G276T with IR and blood glucose, but the results are conflicting. We conducted a meta-analysis in this work to further investigate such an association. Published works were retrieved from PubMed and Embase databases. A pooled standardized mean difference (SMD) with 95 % confidence interval (CI) was calculated under a dominant model using a random effect model. Twenty-five studies involving 7,480 subjects were included in the meta-analysis. A significant association of G276T polymorphism with homeostasis model assessment insulin resistance index (HOMA-IR) was observed after excluding studies with obvious heterogeneity by performing influence analysis (SMD = -0. 08, 95 % CI -0.15 to -0.01, p = 0.019) and Galbraith plot analysis (SMD = -0.08, 95 % CI -0.14 to -0.02, p = 0.005). In the subgroup analysis, Asians with TG/TT genotypes were found to have a significantly decreased degree of HOMA-IR (SMD = -0.13, 95 % CI -0.20 to -0.07, p < 0.001). The association of G276T with IR or blood glucose for the subgroups (obese, male, and T2D) was also significant. However, the results may not be reliable for small sample sizes. The current meta-analysis suggested that the G276T polymorphism may genetically affect IR using HOMA-IR as an index, and the effect of this polymorphism on IR particularly exists in Asians.

Association between PGC-1alpha gene polymorphisms and type 2 diabetes risk: a case-control study of an Iranian population

OBJECTIVE

The peroxisome proliferator-activated receptor gamma coactivator-1alpha (PGC-1alpha) gene could play a role in the onset of type 2 diabetes mellitus. The aim of this study was to explore the possible associations among polymorphisms Gly482Ser, Thr394Thr and Thr528Thr of the PGC-1alpha gene and the risk of type 2 diabetes in Kurdish-Iranians.

METHODS

DNA specimens from all 173 type 2 diabetes subjects and 173 normoglycemic subjects were genotyped by the polymerase chain reaction-restriction fragment length polymorphism method. Genotypic and allelic frequencies were analyzed in each group. Serum lipids, fasting glucose, fasting serum insulin, homeostasis model assessment of insulin resistance and glycated hemoglobin levels were determined using the conventional methods. The data were analyzed using SPSS software.

RESULTS

The GA genotype of Gly482Ser was associated with a significant susceptibility for type 2 diabetes (odds ratio 5.23, p<0.000). Furthermore, the GA genotype of Thr528Thr had a higher risk for type 2 diabetes (odds ratio 2.37, p<0.002). Normoglycemic persons carrying the GA+AA genotypes of Gly482Ser variation had significantly lower high-density lipoprotein cholesterol in comparison with persons having GG genotype. In comparison with GG genotype carriers, normoglycemic subjects carrying the GA+AA genotypes of Thr394Thr variation had significantly higher fasting blood sugar, fasting serum insulin and homeostasis model assessment of insulin resistance. Normoglycemic subjects with the GA+AA genotypes of Thr528Thr variation had significantly higher levels of low-density lipoprotein cholesterol compared with subjects having the GG genotype. Type 2 diabetes subjects carrying the GA+AA genotypes of this polymorphism had significantly higher waist-hip ratio in comparison with the GG genotype carriers. We also found that haplotype 394-GG/482-GA/528-GG of PGC-1alpha was significantly associated with higher risk of type 2 diabetes.

CONCLUSIONS

Our findings revealed significant associations between PGC-1alpha Gly482Ser and Thr528Thr polymorphisms and type 2 diabetes in Kurdish-Iranians.

Adiponectin polymorphisms and non-alcoholic fatty liver disease risk: a meta-analysis

BACKGROUND AND AIM

The adiponectin polymorphism has been implicated in susceptibility to non-alcoholic fatty liver disease (NAFLD), but the results remain inconclusive. The aim of this meta-analysis is to investigate the association between adiponectin polymorphisms and NAFLD risk.

METHODS

All eligible case-control studies published up to September 2013 were identified by searching PubMed, Web of Science, and CNKI. Effect sizes of odds ratio (OR) and 95% confidence interval (95% CI) were calculated by using a fixed- or random-effect model.

RESULTS

A total of 10 case-control studies were included; of those, there were nine studies (1223 cases and 1580 controls) for +45T>G polymorphism, seven studies (876 cases and 989 controls) for +276G>T polymorphism, and three studies (299 cases and 383 controls) for -11337C>G polymorphism. Overall, a significantly increased risk was found for +45T>G and -11377C>G polymorphism (+45T>G: OR = 1.45, 95% CI: 1.06-2.00 for recessive model, OR = 1.48, 95% CI: 1.07-2.06 for GG vs TT; -11377C>G: OR = 1.52, 95% CI: 1.10-2.09 for dominant model, OR = 3.88, 95% CI: 1.29-11.68 for GG vs CC), while for +276G>T polymorphism, we found a significantly decreased risk between them (OR = 0.65, 95% CI: 0.45-0.94 for recessive model, OR = 0.58, 95% CI: 0.40-0.84 for TT vs GG). In subgroup analysis by ethnicity, significant association was detected among Asians for +276G>T polymorphism, but not for +45T>G polymorphism. Besides, none of the three adiponectin polymorphisms was associated with the serum adiponectin levels.

CONCLUSION

This meta-analysis suggests that adiponectin +45T>G and -11377C>G polymorphisms might be a risk factor for NAFLD, while +276G>T polymorphism may be a protective factor for NAFLD among Asians.

Current clinical evidence on pioglitazone pharmacogenomics

Pioglitazone is the most widely used thiazolidinedione and acts as an insulin-sensitizer through activation of the Peroxisome Proliferator-Activated Receptor-γ (PPARγ). Pioglitazone is approved for use in the management of type 2 diabetes mellitus (T2DM), but its use in other therapeutic areas is increasing due to pleiotropic effects. In this hypothesis article, the current clinical evidence on pioglitazone pharmacogenomics is summarized and related to variability in pioglitazone response. How genetic variation in the human genome affects the pharmacokinetics and pharmacodynamics of pioglitazone was examined. For pharmacodynamic effects, hypoglycemic and anti-atherosclerotic effects, risks of fracture or edema, and the increase in body mass index in response to pioglitazone based on genotype were examined. The genes CYP2C8 and PPARG are the most extensively studied to date and selected polymorphisms contribute to respective variability in pioglitazone pharmacokinetics and pharmacodynamics. We hypothesized that genetic variation in pioglitazone pathway genes contributes meaningfully to the clinically observed variability in drug response. To test the hypothesis that genetic variation in PPARG associates with variability in pioglitazone response, we conducted a meta-analysis to synthesize the currently available data on the PPARG p.Pro12Ala polymorphism. The results showed that PPARG 12Ala carriers had a more favorable change in fasting blood glucose from baseline as compared to patients with the wild-type Pro12Pro genotype (p = 0.018). Unfortunately, findings for many other genes lack replication in independent cohorts to confirm association; further studies are needed. Also, the biological functionality of these polymorphisms is unknown. Based on current evidence, we propose that pharmacogenomics may provide an important tool to individualize pioglitazone therapy and better optimize therapy in patients with T2DM or other conditions for which pioglitazone is being used.

Lack of Genetic Associations of PPAR-γ and PGC-1α with Alzheimer's Disease and Parkinson's Disease with Dementia

Background and Aims

Similar clinical and pathological features have been observed in Alzheimer's disease (AD) and Parkinson's disease with dementia (PDD). Both the peroxisome proliferator-activated receptor-γ (PPAR-γ) gene and the peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) gene are candidates modifying the risk for both diseases. The aim of this study was to clarify whether common single nucleotide polymorphisms (SNPs) of the PPAR-γ gene and the PGC-1α gene affect the onset of AD and PDD genetically.

Methods

Four exonic SNPs of both genes (rs1801282 and rs3856806 of the PPAR-γ gene, rs3736265 and rs8192678 of the PGC-1α gene) were genotyped in 171 AD patients, 136 age-matched controls and 53 PDD patients. Haplotype analysis and logistic regression analysis with apolipoprotein E (APO E) status were performed for AD.

Results

There was no statistical difference between AD cases and controls for the 4 SNPs, nor was there any statistical difference between PDD cases and controls for the 4 SNPs. We could not find any synergetic associations between these SNPs, APO E4 and AD.

Conclusions

The 4 SNPs studied here did not influence the risk for AD in a Japanese population. As the number of PDD cases was small, comprehensive genetic studies considering diabetes would be needed.

Association of genetic variants in the adiponectin gene with metabolic syndrome: a case-control study and a systematic meta-analysis in the Chinese population

Background

The prevalence of metabolic syndrome has been rising worldwide, including in China, but knowledge on specific genetic determinants of metabolic syndrome is very limited. A number of studies have reported that polymorphisms in the ADIPOQ gene are associated with metabolic syndrome in Chinese Han populations. However, data is still conflicting. The objective of this study was to examine the associations of the adiponectin genetic variants with metabolic syndrome by a case-control study and meta-analyses in Chinese.

Methods

We first investigated the association of ADIPOQ rs2241766 (+45T>G in exon 2), rs266729 (−11377C>G in promoter) and rs1501299 (+276G>T in intron 2) polymorphisms with metabolic syndrome in a Hubei Han Chinese population with 322 metabolic syndrome patients and 161 normal controls recruited from the Yichang, Hubei. Then we comprehensively reviewed the association between ADIPOQ rs2241766/rs266729/rs1501299 and metabolic syndrome in the Chinese populations via a meta-analysis. The strength of association was assessed by odds ratios (ORs) with 95% confidence intervals (CI).

Results

The G allele frequency of rs2241766 in metabolic syndrome patients was significantly higher than those of controls group (29.8% vs 23.3%, OR = 1.40, P = 0.033). The logistic regression analysis adjusted by gender and age showed a nominally significant association for rs2241766 GG+GT genotype (P = 0.065, OR = 1.55) and rs1501299 GG genotype in recessive model (OR = 1.54, P = 0.066). However, no association was observed for rs266729 in our sample. We identified thirteen studies for rs2241766 (2,684 metabolic syndrome patients and 2,864 controls), three studies for rs266729, and eleven studies for rs1501299 (2,889 metabolic syndrome patients and 3,304 controls) in Chinese. Meta-analysis indicated significant associations for the rs2241766 G allele (OR = 1.14, 95%CI = 1.05–1.24, P = 0.003), rs266729 GG+GT genotypes (OR = 0.80, 95%CI = 0.68–0.92, P = 0.003) and rs1501299 GG+TG genotypes (OR = 1.42, 95%CI 1.16–1.75, P = 0.001).

Conclusions

Our results demonstrated ADIPOQ as a pleiotropic locus for metabolic syndrome and its components in the Han Chinese population.