Fetal MTHFR C677T polymorphism confers no susceptibility to Down syndrome: Evidence from meta-analysis

Evaluation of the Relationship Between Dopamine Receptor D2 Gene TaqIA1 Polymorphism and Alcohol Dependence Risk

Several studies are published, that investigated dopamine receptor 2 (DRD2) gene TaqIA polymorphism as a risk factor for alcohol dependence (AD) with positive and negative associations. To derive a more precise estimation of the relationship, a meta-analysis of case-control studies that examined the association between DRD2 gene Taq1A polymorphism and alcohol dependence was performed. Eligible articles were identified through a search of databases including PubMed, Science Direct, Springer link, and Google Scholar. The association between the DRD2 TaqIA polymorphism and AD susceptibility was conducted using odds ratios (ORs) and 95% confidence intervals (95% CIs) as association measures. A total of 69 studies with 9125 cases and 9123 healthy controls were included in the current meta-analysis. Results of the present analysis showed significant association between DRD2 TaqIA polymorphism and AD risk using five genetic modes (allele contrast model-OR 1.22, 95% CI 1.13-1.32, p < 0.0001; homozygote model-OR 1.35, 95%CI 1.18-1.55; p ≤ 0.0001; dominant model-OR 1.29; 95% CI 1.20-1.39; p < 0.0001; recessive model-OR 1.21; 95% CI 1.08-1.36; p = 0.0006). There was no significant association found in subgroup analysis, TaqIA polymorphism was not significantly associated with AD risk in the Asian population under all genetic models, but in the Caucasian population, TaqIA polymorphism was significantly associated with AD risk. Overall, results support the hypothesis that DRD2 Taq1A polymorphism plays a role in alcohol dependence.

Relation Between Methylenetetrahydrofolate Reductase Polymorphisms (C677T and A1298C) and Migraine Susceptibility

Migraine is a neurological disorder which impairs the patient's quality of life. Several association studies investigating the association between MTHFR gene C677T and A1298C polymorphisms and susceptibility to migraine were published. But the results were conflicting, so authors performed a meta-analysis of published case control studies to find out the exact association between MTHFR polymorphism and migraine susceptibility. Four databases were searched for suitable studies up to December, 2018. Odds ratios (OR) with 95% confidence intervals (CI) was calculated adopting additive, homozygote, co-dominant, dominant, and recessive genetic models. Results of MTHFR C677T polymorphism studies meta-analysis showed significant association with migraine risk using allele contrast, homozygote, dominant and recessive genetic models (T vs. C: OR = 1.18, 95% CI = 1.00-1.26, p = 0.05; TT vs. CC: OR = 1.24, 95% CI = 1.0-1.5, p = 0.04; CT vs. CC: OR = 1.08, 95% CI = 0.97-1.07, p = 0.25; TT + CT vs. CC: OR = 1.15, 95% CI = 1.0-1.29, p = 0.04; TT vs. CT + CC: OR = 1.97, 95% CI = 1.28-3.42, p = 0.002). However, results of MTHFR A1298 polymorphism studies meta-analysis did not show any association with migraine. Subgroup analysis based on ethnicity and migraine types i.e. migraine with aura (MA) and without aura (MO) were also performed. Results of present meta-analysis indicate overall association between MTHFR C677T polymorphism with migraine in total 24 studies, in Asian population and in MA cases but did not show any association with Caucasian population and MO cases.

Catechol-O-methyltransferase (COMT) Val158Met Polymorphism and Susceptibility to Alcohol Dependence

Catechol-O-methyl transferase (COMT) enzyme catalyzes the metabolism of dopamine and other catechols in the brain. Several articles investigated catechol-O-methyltransferase (COMT) Val158Met polymorphism as risk factor for alcohol dependence (AD) but the results were inconclusive. The aim of present meta-analysis was to evaluate the association of Val158Met (COMT) polymorphism with AD. Authors performed keyword search of the 4 electronic databases-Pubmed, Google Scholar, Springer Link and Science Direct databases up to December 31, 2019. Total eighteen studies that investigated the association of Val158Met polymorphism with AD were retrieved. The pooled results from the meta-analysis (2278 AD cases and 3717 healthy controls) did not show association with AD using all 5 genetic models (allele contrast model: OR = 1.02, 95% CI = 0.90-1.14, p = 0.03; homozygote model: OR = 1.06, 95% CI = 0.81-1.38, p = 0.69; dominant model: OR = 0.99, 95% CI = 0.85-1.14, p = 0.87; co-dominant model: OR = 0.97, 95% CI = 0.86-1.11, p = 0.71; recessive model: OR = 1.05;95% CI = 0.85-1.29, p = 0.61). Results of subgroup analysis showed that Val158Met is not risk for AD in Asian and Caucasian population. In conclusion, COMT Val158Met is not a risk factor for alcohol dependence.

FokI polymorphism of the vitamin D receptor (VDR) gene and susceptibility to tuberculosis: Evidence through a meta-analysis

BACKGROUND

Tuberculosis is one of the top ten causes of deaths worldwide. The deficiency of vitamin D was reported to be associated with the increased susceptibility of tuberculosis. Various previous reports were published to check the association of FokI polymorphism of the vitamin D receptor gene with tuberculosis risk. But their results were inconsistent so, we performed a meta-analysis to know the exact relation of the two.

METHODS

Different databases were screened up to November 2020 with the keywords "Vitamin D receptor", "VDR", and "FokI", along with "Tuberculosis" and "TB" to find the suitable articles. All the statistical analyses were performed by the Open Meta-Analyst program and all p-values were two-tailed with a significance level of 0.05.

RESULTS

No statistically significant association was observed in the allele contrast model (OR_fvs.F = 1.11, 95%CI = 0.99-1.24, p = 0.05, I² = 73.46%), in the dominant model (OR_ff+Ffvs.FF = 1.11, 95%CI = 0.96-1.28, p = 0.14, I² = 71.39%), and in the co-dominant model (OR_Ffvs.FF = 1.05, 95%CI = 0.92-1.21, p = 0.41, I² = 65.97%). However, a significant association was found in the homozygote model (OR_ffvs.FF = 1.32, 95%CI = 1.03-1.69, p = 0.02, I² = 67.02%) and in the recessive model (OR_{FF+Ff vs.ff} = 1.26, 95%CI = 1.03-1.54, p = 0.02, I² = 58.01%). Further analysis was performed on the bases of the ethnicity. In Asian population a significant association was found in the homozygote model (OR_ffvs.FF = 1.57, 95%CI = 1.12-2.21, p = 0.008, I² = 70.37%) and in the recessive model (OR_{FF+Ff vs.ff} = 1.43, 95%CI = 1.08-1.89, p = 0.01, I² = 63.13%).

CONCLUSION

In conclusion, a significant association of FokI with tuberculosis susceptibility was found in the overall analysis and in the Asian population.

Methylenetetrahydrofolate reductase (MTHFR) gene C677T (rs1801133) polymorphism and risk of alcohol dependence: a meta-analysis

Alcohol dependence is a complex neuropsychiatric disorder. Numerous studies investigated association between MTHFR gene C677T (rs1801133) polymorphism and alcohol dependence (AD), but the results of this association remain conflicting. Accordingly, authors conducted a meta-analysis to further investigate such an association. PubMed, Elsevier Science Direct and Springer Link databases were searched for studies on the association between the MTHFRC677T polymorphism and AD. Pooled odds ratio (OR) with 95% confidence interval (CI) was calculated using the fixed- or random-effects model. Statistical analysis was performed with the software program MetaAnayst and MIX.A total of 11 articles were identified through a search of electronic databases, up to February 28, 2020. The results of the present meta-analysis did not show any association between MTHFR C677T polymorphisms and AD risk (for T vs. C: OR = 1.04, 95% CI = 0.88-1.24; CT vs. CC: OR = 1.02, 95% CI = 0.62-1.68; for TT+CT vs. CC: OR = 1.10, 95% CI = 0.94-1.29; for TT vs. CC: OR = 1.01, 95% CI = 0.66-1.51; for TT vs. CT+CC: OR = 0.97, 95% CI = 0.66-1.40). Results of subgroup analysis showed no significant association between MTHFR C677T polymorphism with AD in Asian as well as in Caucasian population. In conclusion, C677T polymorphism is not a risk factor for alcohol dependence.

Catechol-O-methyltransferase gene Val158Met polymorphism and obsessive compulsive disorder susceptibility: a meta-analysis

Obsessive-compulsive disorder (OCD) is a common psychiatric disorder that affects approximately 1-3% of the general population. It is characterized by disabling obsessions (intrusive unwanted thoughts) and/or compulsions (ritualized repetitive behaviors). Catechol-O-methyltransferase (COMT) enzyme has an important role in inactivation of dopamine and higher dopamine levels may be implicated in OCD, hence COMT gene is a suitable candidate for OCD. Several case-control studies have evaluated the role of COMT Val 158Met (rs4680;472G- > A) polymorphism as a risk factor for OCD but the results remained inconclusive, hence present meta-analysis was designed to find out correct assessment. All studies that investigated the association of COMT gene Val158Met polymorphism with OCD risk, were considered in the present meta-analysis. Statistical analysis was performed with the software program MetaAnalyst. In the current meta-analysis, 14 case-control studies with 1435 OCD cases and 2753 healthy controls were included. The results indicated significant association between COMT Val158Met polymorphism and OCD risk using allele contrast, homozygote and dominant models (OR_{A vs G} = 1.14; 95% CI = 1.02-1.27; p = 0.01; OR_AAvs.GG = 1.33; 95% CI = 1.09-1.62, p = 0.004; OR_{AA + AGvs.GG} = 1.14; 95% CI = 1.0-1.32; p = 0.04). In subgroup analysis based on case gender, meta-analysis of male cases showed significant association using all five genetic models (OR_AAvsGG = 1.99; 95%CI = 1.42-2.59; p = <0.001; OR_{AA + AGvs.GG} = 1.59; 95% CI = 1.20-2.10; p = 0.001), but did not show any association between COMT Val 158Met polymorphism and OCD risk in females. In conclusion, results of present meta-analysis supports that the COMT Val158Met polymorphism is a risk factor for OCD especially for males.