Association of IL-6, TNF-α and IL-10 gene polymorphisms with type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is a metabolic pro-inflammatory disorder characterized by chronic hyperglycemia and increased levels of circulating cytokines suggesting a causal role of inflammation in its etiology. Polymorphism of cytokine genes including interleukin-6 (IL-6), tumour necrosis factor-α (TNF-α) and interleukin-10 (IL-10) were studied in T2DM patients as well as in normal healthy controls. Genomic DNA was isolated from both T2DM patients and controls followed by quantification and genotyping by polymerase chain reaction–restriction fragment length polymorphism (PCR–RFLP) using suitable primers. The genotypic, allelic and carriage rate frequency distribution in patients and controls were analyzed by SPSS (version 15.0). Odd ratios with 95 % confidence interval was determined to describe the strength of association by logistic regression model. Double and triple combinations of genotypes were analyzed by χ² test. Gene–gene interaction and linkage disequilibrium tests were performed using SHEsis software. Individually, IL-6, TNF-α and IL-10 did not show any association. In double combination, IL-6 ?597 GA and TNF-α ?308 GG genotypes increased the risk up to 21 times and in triple combination IL-6 ?597 AA, TNF-α ?308 GG and IL-10 ?592 CA increased the risk of T2DM up to 314 times. In gene–gene interaction allele ‘A’ of all studied polymorphisms increased the risk of T2DM up to 1.41 times. Our results suggest that individuals having a haplotype combination of AA, GG and CA for IL-6, TNF-α and IL-10 gene polymorphisms will have higher susceptibility and be at greater risk of developing T2DM.     

Association between the −11377 C/G and −11391 G/A polymorphisms of adiponectin gene and adiponectin levels with susceptibility to type 1 and type 2 diabetes mellitus in population from the west of Iran,correlation with lipid profile

Adipose tissue, an endocrine organ, secretes bioactive factors including adiponectin. Adiponectin is a protein hormone that enhances insulin sensitivity through increased fatty acid oxidation and inhibition of hepatic glucose production. We assessed the association of the adiponectin promoter region polymorphisms −11391 G/A and −11377 C/G with susceptibility to type 1 (T1DM) and type 2 (T2DM) diabetes mellitus in the population of west Iran. Also, we investigated the effect of adiponectin level and lipid profile on T1DM and T2DM development. In this case-control study, we recruited 189 patients with diabetes (100 T2DM and 89 T1DM) and 161 sex and age-matched unrelated healthy controls. Adiponectin mutations were detected by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), and the protein level was measured by the enzyme-linked immunosorbent assay. Other biochemical parameters were determined by routine laboratory methods. The G allele of adiponectin gene at −11377 position (C/G) significantly increased the risk of T1DM. With respect to genotype models, codominant (2.97 times), dominant (3.6-fold), and over-codominant (2.9-fold) patients with T1DM who carried −11377 C > G single-nucleotide polymorphisms were significantly susceptible to the development of the disease. A significantly higher level of adiponectin in T1DM was oberved compared with the control group. In contrast, patients with T2DM had lower adiponectin levels compared with healthy controls. The genotype distributions of −11391 G/A polymorphisms were the same for patients with diabetes and control groups. The presence of G allele at −11377 C/G adiponectin gene significantly increased serum adiponectin level and may be a risk factor for T1DM susceptibility among the western Iranian population.     

Association studies of CTLA-4, CD28, and ICOS gene polymorphisms with type 1 diabetes in the Japanese population

Co-stimulatory molecules of CD28, cytotoxic T lymphocyte-associated antigen-4 (CTLA-4), and the newly identified inducible co-stimulator (ICOS) are expressed on cell surfaces and provide regulatory signals for T-cell activation. Their genes are candidate susceptibility genes for type 1 diabetes because they co-localize to Chromosome 2q33 with the IDDM12 locus. After determining the genomic structure and screening for polymorphisms of the ICOS gene, we performed association studies between newly identified polymorphisms of the ICOS gene, together with known polymorphisms of CD28 and CTLA-4 genes, and type 1 diabetes. The 49A/G dimorphism in exon 1 and the (AT)n in the 3' untranslated region of the CTLA-4 gene were significantly associated with type 1 diabetes. Evaluation of the CTLA-4 49A-3'(AT)n 86-bp haplotype frequency in patients and controls confirmed the results from the analysis of each polymorphic site. Dimorphism in intron 3 of the CD28 gene was associated with type 1 diabetes only in the early-onset group. In contrast, there was no association with the microsatellite polymorphisms in the ICOS gene or dimorphisms in the promotor region of CTLA-4. Of the three genes encoding co-stimulatory molecules, the CTLA-4 gene appears to confer risks for the development of type 1 diabetes.     

Molecular & biochemical analysis of Pro12Ala variant of PPAR-γ2 gene in type 2 diabetes mellitus

Diabetes has emerged as a major threat to human life globally. Genomic studies have found a significant link between the Pro12Ala polymorphism of the PPAR-γ2 gene with incidence as well as occurrence of the risk of metabolic syndrome. The present study was aimed at assessing the PPAR-γ2 variant in an Asian Indian cohort of type 2 diabetes patients and its correlation with metabolic parameters. The present case-control study involved 100 type 2 diabetic patients and 100 asymptomatic healthy volunteers enrolled in random. Assessment of demographic factors and biochemical parameters were done for all enrolled. In addition, genotyping for the Pro12Ala (CCA to GCA) polymorphism was done by polymerase chain reaction - restriction fragment length polymorphism (PCR-RFLP) technology. The genotyping study detected the frequency of the CC genotype (Pro12Pro) to be higher in frequency in comparison to the heterozygous CG genotype in both, cases and controls. The homozygous GG genotype (Ala12Ala) was not detected in any of the cases or controls assessed. Biochemical analysis of the levels of malondialdehyde (MDA) detected a significant increase (p < 0.0001). Additionally, increase in levels of fasting and postprandial glucose, total cholesterol, triglycerides, and parameters of the liver and renal function tests were detected. This study detected the PPAR-γ2 to be a significant biomarker for type 2 diabetes mellitus.     

Association of peroxisome proliferator activated receptor-γ gene with non-alcoholic fatty liver disease in Asian Indians residing in north India

Background

Genetics of non-alcoholic fatty liver (NAFLD) in Asian Indians has been inadequately studied. We investigated the association of polymorphisms C161T and Pro12Ala of peroxisome proliferator-activated receptor gamma (PPARγ) with clinical and biochemical parameters in Asian Indians with NAFLD.

Methods

In this case–control study, 162 NAFLD cases and 173 controls were recruited. Abdominal ultrasound, clinical and biochemical profiles, fasting insulin levels and value of homeostasis model assessment of insulin resistance were determined. Polymerase chain reaction–restriction fragment length polymorphisms of two polymorphisms were performed. The association of these polymorphisms with clinical and biochemical parameters was analysed.

Results

Higher frequency of Ala and T alleles of PPARγ was obtained in cases. Ala/Ala genotype of PPARγ (Pro12Ala) was associated with significantly higher serum triglycerides (TG), alkaline phosphatase (ALK) and waist–hip ratio in cases as compared to controls. In C161T polymorphism, TT genotype was significantly increased TG (p = 0.04), total cholesterol (p = 0.01), ALK (p = 0.04) and gamma-glutamyl transpeptidase (p = 0.007) in cases. The linkage disequilibrium for these two single-nucleotide polymorphisms of PPARγ was differed in cases (D1 = 0.1; p = 0.006) and controls (D1 = 0.07; p = 0.1). Using a multivariate analysis after adjusting for age, sex and body mass index, the presence of NAFLD was linked to these two polymorphisms (odds ratio 1.64 (95% CI: 1.09–2.45, p = 0.05)].

Conclusion

Asian Indians in north India carrying the alleles Ala and T of PPARγ (Pro12Ala and C161T) polymorphisms are predisposed to develop NAFLD.     

Screening of mitochondrial mutations and insertion–deletion polymorphism in gestational diabetes mellitus in the Asian Indian population

In this study we scrutinized the association between the A8344G/A3243G mutations and a 9-bp deletion polymorphism with gestational diabetes mellitus (GDM) in an Asian Indian population. The A3243G mutation in the mitochondrial tRNA^Leu(UUR) causes mitochondrial encephalopathy myopathy, lactic acidosis, and stroke-like episodes (MELAS), while the A8344G mutation in tRNA^Lys causes myoclonus epilepsy with ragged red fibers (MERRF). We screened 140 pregnant women diagnosed with GDM and 140 non-GDM participants for these mutations by PCR-RFLP analysis. Both A3243G and A8344G were associated with GDM (A3243: OR-3.667, 95% CI = 1.001–13.43, p = 0.03; A8344G: OR-11.00, 95% CI = 0.6026–200.8, p = 0.04). Mitochondrial DNA mutations contribute to the development of GDM. Our results conclude that mitochondrial mutations are associated with the GDM women in our population. Thus it is important to screen other mitochondrial mutations in the GDM women.     

Association of ��2-adrenergic receptor and insulin receptor substrate-1 polymorphisms with obesity in a Northern Indian population

BACKGROUND:

Imbalance in hormonal levels, regulated by host genetic factors, are known to be a major cause of obesity. Therefore, we aimed to evaluate association of genetic polymorphisms of β₂-adrenergic receptor (β₂-AR) and insulin receptor substrate-1 (IRS-1) with hormonal levels in northern Indian obese.

METHODS:

A total of 111 obese and 89 age matched non-obese subjects were studied after taking detailed clinical profile. Hormonal assays in serum/plasma for different hormones were done using IRMA and RIA kits. Genetic analysis of β₂-AR (-47 and -20, T to C) and IRS-1 (Arg972Gly) was done using PCR-RFLP.

STATISTICAL ANALYSIS:

Statistical analysis was performed by SPSS (version 11.5) software. All continuous variables were expressed as mean ± SD and tested by ANOVA test. Comparisons of categorical variables were assessed using X² tests or Fisher''s exact test. P-value <0.05 was considered as significant.

RESULTS:

Analysis showed that obese subjects had significantly higher value of blood pressure (systolic), WHR, leptin insulin and glucagon and lower value of GH. In β₂-AR (-47) T/C and IRS-1 Gly972Arg gene polymorphisms we did not found significant differences in genotype or allele frequencies. Moreover, none of the studied hormonal or metabolic parameters showed any association with the gene polymorphisms.

CONCLUSIONS:

Study reveals no significant association of β₂-AR (-47 and -20, T to C) and IRS-1 Gly 972 Arg polymorphisms with obesity in northern Indians.     

Three single nucleotide variants of the HDAC gene are associated with type 2 diabetes mellitus in a Chinese population: A community-based case–control study

Objectives

There are no data regarding the possible role of the single nucleotide polymorphism (SNP) of class I histone deacetylases (HDACs) in type 2 diabetes mellitus (DM). We designed this study to examine whether polymorphisms of HDACs can be implicated in that disease.

Methods

A community-based, case–control study was conducted, with a total of 568 subjects (284 patients and 284 controls) enrolled. Four polymorphisms of HDAC1 (rs1741981) and HDAC3 (rs11741808, rs2547547, rs2530223) were examined by the use of TaqMan technology.

Results

We found a significant association with risk of type 2 DM for three SNPs of HDAC3, including rs11741808 [odds ratio (OR) = 0.53, 95% confidence interval (CI): 0.35–0.81], rs2547547 [OR = 1.72, 95% CI: 1.13–2.64], and rs2530223 [OR = 1.39; 95% CI: 1.01–1.91]. Subgroup analysis showed that BMI ≥ 23 kg/m², high triglyceride and high blood pressure, together with the rs11741808AG genotype, were associated with a significantly decreased risk for type 2 DM, with ORs of 0.50 (95% CI: 0.27–0.91), 0.38 (95% CI: 0.20–0.71) and 0.43 (95% CI: 0.24–0.76) compared with the AA genotype, respectively. In a population with normal total cholesterol, the AG genotype yielded a significantly decreased risk of type 2 DM risk, with an OR of 0.42 (95% CI: 0.25–0.70) when compared with the persons of the AA genotype. For rs2547547, in a population with normal total cholesterol and triglyceride, the AG genotype was associated with a significantly increased risk of type 2 DM, with ORs of 1.92 (95% CI: 1.17–3.15) and 2.24 (95% CI: 1.28–3.94) when compared with the population carrying the AA genotype.

Conclusions

The results suggest that variants of HDAC3 contribute to an increased prevalence of type 2 DM in the Chinese Han population.     

Association of IL1β and IL4 gene polymorphisms with nasal polyps in a Polish population

Imbalance between proinflammatory and anti-inflammatory cytokines may regulate the inflammatory reaction in the nasal polyps. Polymorphisms in the regulatory regions of the cytokines genes may influence their expression. The aim of this study was to investigate the relationship between an IL-1β and IL-4 promoter polymorphisms and nasal polyps. The C-511T promoter polymorphism of the IL-1β gene and C-590T promoter polymorphism of the IL-4 gene were genotyped by polymerase chain reaction-restriction fragment length polymorphism analysis in 208 Polish patients with nasal polyps and 200 healthy Polish subjects. The risk of susceptibility to NP was significantly higher in patients with NP who had ?511 T/T genotype of IL1β than in controls (OR 3.07; 95 % CI 1.18–7.99). No statistically significant differences were found between NP patients and the control group with regard to genotype distribution and allele frequencies of C/T polymorphism of IL4 gene. Our study demonstrated that the TT genotype for C-511T mutation associated with the risk of developing NP in a Polish population.     

Association of PPARγ2 polymorphisms with carcass and meat quality traits in a Pietrain x Jinhua F2 population

The PPARγ2 gene is a key regulator of both proliferation and preadipocyte differentiation in mammals. Herein its genotype and allele frequencies were analyzed using PCR-SSCP in eight pig breeds (N = 416). Two kinds of polymorphisms of the PPARγ2 gene were detected, including a previously reported shift SNP A177G (Met59Val) in exon 1 and a novel silent mutation G876A in exon 5. The results revealed that European pig breeds carry a higher allele A frequency at the A177G locus and a fixed GG genotype at the G876A locus. Allele A at the G876A locus was only found in Jinhua pigs. The association between haplotype (A177G/G876A) and carcass and meat quality traits was analyzed in a Pietrain x Jinhua F2 population (N = 248). The PPARγ2 gene was found to be significantly associated with backfat thickness at the shoulder (p < 0.05), 6-7(th) ribs (p < 0.01), last rib (p < 0.01), gluteus medius (p <0.05) and ham weight (p < 0.01). Significant effects of different haplotypes on ham weight and backfat thickness at the 6-7(th) ribs, last rib, and gluteus medius were also observed.     

Adiponectin and peroxisome proliferator-activated receptor-γ gene polymorphisms and gene-gene interactions with type 2 diabetes

Aims

To investigate whether gene polymorphisms of both adiponectin and peroxisome proliferator-activated receptor gamma (PPARγ) influence type 2 diabetes mellitus (T2DM) respectively in the Han people of the Wenzhou region of China and whether the interaction of gene polymorphism between adiponectin and PPARγ influences T2DM in the same subjects.

Main methods

This study included 198 patients with T2DM and 255 healthy individuals. Polymerase chain reaction–restriction fragment length polymorphism analyses were used to detect single nucleotide polymorphisms (SNPs). Logistic regression and multifactor dimensionality reduction (MDR) methods were used to analyze gene–gene interactions.

Key findings

The frequency distribution of adiponectin SNP11377 was not different (p = 0.792), but the frequency of CC, CG and GG genotypes showed the difference between two groups (T2DM: 57.1%, 33.3%, and 9.6%; control: 53.7%, 41.6%, and 4.7%, respectively; p = 0.047). Adiponectin SNP45, SNP276 and PPAR γ SNPp12a were equally distributed between the two groups (p = 0.586, 0.119, 0.437, respectively), and there were no significant differences in genotype frequencies between the two groups (p = 0.751, 0.144, 0.479, respectively). Linkage disequilibrium existed between SNP11377 and SNP45 (p < 0.001) and SNP45 and SNP276 (p < 0.001). Haplotype analyses showed no significant differences between the T2DM and control groups. According to the logistic regression and MDR gene–gene interaction analyses, SNP11377GG and SNP276GT interactions increased the risk of T2DM (odds ratio = 6.984, p = 0.012).

Significance

Adiponectin SNP11377 and SNP276 gene–gene interactions are associated with the increased risk of T2DM in this population.     

TNF-α gene expression is increased following zinc supplementation in type 2 diabetes mellitus

Chronic low-grade inflammation in type 2 diabetes mellitus (DM) can elicit changes in whole-body zinc metabolism. The interaction among the expression of inflammatory cytokines, zinc transporter and metallothionein (MT) genes in peripheral blood mononuclear cells in type 2 DM remains unclear. In a 12-week randomized controlled trial, the effects of zinc (40 mg/day) supplementation on the gene expression of cytokines, zinc transporters and MT in women with type 2 DM were examined. In the zinc-supplemented group, gene expression of tumour necrosis factor (TNF)-α tended to be upregulated by 27 ± 10 % at week 12 compared to baseline (P = 0.053). TNF-α fold change in the zinc-treated group was higher than in those without zinc supplementation (P < 0.05). No significant changes were observed in the expression or fold change of interleukin (IL)-1β or IL-6. Numerous bivariate relationships were observed between the fold changes of cytokines and zinc transporters, including ZnT7 with IL-1β (P < 0.01), IL-6 (P < 0.01) and TNF-α (P < 0.01). In multiple regression analysis, IL-1β expression was predicted by the expression of all zinc transporters and MT measured at baseline (r ² = 0.495, P < 0.05) and at week 12 (r ² = 0.532, P < 0.03). The current study presents preliminary evidence that zinc supplementation increases cytokine gene expression in type 2 DM. The relationships found among zinc transporters, MT and cytokines suggest close  interactions between zinc homeostasis and inflammation.     

Are variants in the CAPN10 gene related to risk of type 2 diabetes? A quantitative assessment of population and family-based association studies

The calpain-10 gene (CAPN10) on chromosome 2q37.3 was the first candidate gene for type 2 diabetes (T2D) identified through a genomewide screen and positional cloning. One polymorphism (UCSNP-43: G-->A) and a specific haplotype combination defined by three polymorphisms (UCSNP-43, -19, and -63) were linked to an increased risk of T2D in several populations. To quantitatively assess the collective evidence for the effects of CAPN10 on risk of T2D, we conducted a meta-analysis of both population-based and family-based association studies. We retrieved data from the MEDLINE, PubMed, and Online Mendelian Inheritance in Man databases, as well as from other relevant reports and abstracts published up to July 2003. From a total of 26 studies with primary data (21 population-based studies: 5,013 cases and 5,876 controls; 5 family-based studies: 487 parent-offspring trios), we developed a summary database that contains variables of study design, study population/ethnicity, specific polymorphisms and haplotype combinations in CAPN10, and diabetes-related metabolic phenotypes. For population-based studies, we used both fixed-effects and random-effects models to calculate the pooled odds ratio (OR) and 95% confidence interval (CI) for the associations of CAPN10 genotypes with the risk of T2D. We also calculated weighted mean differences for the associations between CAPN10 and diabetes-related quantitative traits. Under either an additive or a dominant effect model, we found no statistically significant relation between CAPN10 genotypes in the UCSNP-43 locus and T2D risk. However, under a recessive model, individuals homozygous for the common G allele had a statistically significant 19% higher risk of T2D than carriers of the A allele (OR 1.19; 95% CI 1.07-1.33). The association between the 112/121 haplotype combination and T2D risk appeared to be overestimated by several initial small studies with positive findings (OR 1.38; 95% CI 1.04-1.84). After we removed these initial studies, this association became nonsignificant (OR 1.11; 95% CI 0.91-1.35). Moreover, we found no evidence for the associations between the UCSNP-43 G/G genotype and the 112/121 haplotype combination and metabolic phenotypes. Our meta-analysis of family-based studies showed only an overtransmission of the rare allele C in UCSNP-44 from heterozygous parents to their affected offspring with T2D. Our analysis indicates that inadequate statistical power, racial/ethnic differences in frequencies of alleles, haplotypes and haplotype combinations, potential gene-gene or gene-environment interactions, publication bias, and multiple hypothesis testing may contribute to the significant heterogeneity in previous studies of CAPN10 and T2D. Our findings also suggest that both large-scale, well-designed association studies and functional studies are warranted to either reliably confirm or conclusively refute the initial hypothesis regarding the role of CAPN10 in T2D risk.     

Association analysis of GABAA β2 and γ2 gene polymorphisms with event-related prefrontal activity in man

Gamma-aminobutyric acid (GABA)A-receptors play a crucial role in the generation of electroencephalogram (EEG) oscillations and evoked potentials (ERPs). The present association study was designed to test whether EEG and ERPs are modulated by genetic variations of the human GABAA beta2 (GABRB2) and gamma2 (GABRG2) genes on chromosome 5q33. The genotypes of two nucleotide substitution polymorphisms of the GABRB2 and GABRG2 genes were assessed in 95 psychiatrically healthy subjects of German descent. Neurophysiological phenotyping was performed with four factorized EEG/ERP parameters: EEG activation, anterior and posterior EEG synchronization, and event-related activity (N100/ P200-complex). No genotypic association was found for the GABRB2 nucleotide exchange polymorphism with any electrophysiological parameter. A significant association was found between the genotype of the intronic GABRG2 G-->A nucleotide exchange and the event-related N100/P200 (ANOVA: F=3.81; df=2; P=0.026). A comparison of homozygous subjects carrying either the G/G or A/A genotype of the GABRG2 polymorphism consistently revealed an even stronger difference in the effect-size (ANOVA: F=11.13; df=1; P=0.002). Post hoc analysis of this association with current density analysis in three-dimensional neuroanatomic Talairach space-time showed a reduction in the event-related signal power after 120 ms in the right dorsolateral prefrontal cortex. Taking into account the risk of false-positive association findings attributable to multiple testing, our results encourage further replication studies to examine the phenotype-genotype relationship of GABRG2 gene variants and event-related prefrontal activity.