T-allele Frequency Research Articles

Evaluation of the Association between the C677T Polymorphism of Methylenetetrahydrofolate Reductase Gene and Recurrent Spontaneous Abortion

Introduction: One factor known to cause thrombophilia in women with unexplained recurrent spontaneous abortion (RSA) is C677T polymorphism of methylenetetrahydrofolate reductase gene. This study aimed to determine the association between RSA and MTHFR C677T polymorphism in Iranian patients. Methods: In this case-control study, 30 patients with previous history of two or more consecutive unexplained abortions, and 10 women with at least two live births without a miscarriage were analyzed for MTHFR C677T polymorphism using PCR-RFLP (PCR-Restriction Fragment Length Polymorphism) method; the study was carried out on patients referring to Baqiyatallah Hospital and Avicenna Infertility Clinic. The results obtained via estimating the genotype of each polymorphism were analyzed by SPSS version 16. Results: Seventeen women (56.6 %) with recurrent spontaneous abortions and 5 women (50 %) from the control group were heterozygous for MTHFR C677T polymorphism. T-allele frequency in the experiment group was higher than the control group (28.4 % and 25 % for the experiment and control group, respectively). Conclusion: The prevalence of MTHFR C677T polymorphism was slightly higher in RSA patients compared with the controls. This finding failed to support the relationship between this polymorphism and the increasing risk of RSA in the evaluated Iranian women.

Adaptive developmental plasticity in methylene tetrahydrofolate reductase (MTHFR) C677T polymorphism limits its frequency in South Indians

Methylene tetrahydrofolate reductase (MTHFR) C677T polymorphism shows considerable heterogeneity in its distribution in humans worldwide. The current study was conducted to investigate whether this polymorphism exhibited adaptive developmental plasticity in the control of the TT-genotype frequency. We screened 1,818 South Indian subjects (895 males and 923 females) for MTHFR C677T polymorphism using PCR-restriction fragment length polymorphism approach. MTHFR 677T-allele frequency in males and females was 9.1 and 11.0%, respectively. Compared to females, males had lower frequency of TT-genotype [odds ratio 0.31, 95% confidence interval (CI) 0.08-1.01]. The frequency of MTHFR 677T-allele was highest in the age group of 20-40 years and it gradually decreased from 40-60 to 60-80 years (P trend<0.0001). MTHFR 677TT-genotype was associated with 7.02-folds (95% CI: 2.12-25.63, P<0.0001) cumulative risk for recurrent pregnancy loss (RPL), neural tube defects (NTDs) and deep vein thrombosis (DVT). Linear regression model suggested that male gender exhibited increased homocysteine levels by 9.35 μmol/L while each MTHFR 677T-allele contributed to 4.63 μmol/L increase in homocysteine. Plasma homocysteine showed inverse correlation with dietary folate (r=-0.17, P<0.0001), B2 (r=-0.14, P<0.0001) and B6 (r=-0.07, P=0.03). Examination of the spontaneously aborted fetuses (n=35) showed no significant association of fetal genotype on its in utero viability. From the current study, it was concluded that C677T seemed to have acquired adaptive developmental plasticity among South Indians due to environmental influences thus contributing to hyperhomocysteinemia and its associated complications such as RPL, NTDs, DVT, etc.

Т(-786) --&gt; С-поліморфізм промотора гена ендотеліальної NO-синтази та фізична працездатність у спорті

Given the significant impact of the T(-786) --> C-polymorphism of the eNOS gene in the process of adaptation to physical stress, we aimed to investigate the effect of this polymorphism on physical performance in sportsmen and establish the possibility of its use as a marker of predisposition to the sport. DNA of 516 people, of which 195 qualified athletes and 321 people who had no experience of regular exercise was investigated. The frequency of genotypes and alleles of the T(-786) --> C-polymorphism of the eNOS gene in groups of athletes of different sports, the distribution of genotypes and alleles among athletes and those who are not involved in sports were studied. T allele frequency in a group of athletes on 6.4% (r(chi)2 = 0.03) than in control group. The association of the T allele of the T(-786) --> C-polymorphism of the eNOS gene with a predisposition for speed and power was established. In the group of athletes in speed and power sports, the T-allele frequency was higher than that in the control group by 12% (r(chi)2 = 0.002) and than in group endurance sports by 10% (r(chi)2 = 0.004). We found that the T(-786) --> C-polymorphism of the eNOS gene influence the power and efficiency ofthe functioning of the cardiorespiratory system of athletes during exercise.

Ethnic variation of the C677T and A1298C polymorphisms in the methylenetetrahydrofolate-reductase (MTHFR) gene in southwestern Mexico.

In this study, we examined the distribution of genotype and allele frequencies of the C677T and A1298C polymorphisms in the methylenetetrahydrofolate-reductase gene (MTHFR) in two ethnic groups in the State of Guerrero, Mexico, which were compared with those of the Mestizo population of the region. A comparative study was conducted on 455 women from two ethnic groups and a group of Mestizo women of the State of Guerrero, Mexico: 135 Nahuas, 124 Mixtecas, and 196 Mestizas. Genotyping of both polymorphisms were performed by using polymerase chain reaction-restriction fragment length polymorphism methods. We found that the 677TT genotype was more frequent in Nahua and Mixteca women compared to Mestiza women (P = 0.008), and the most prevalent genotype in both ethnic groups was the 1298AA genotype (P < 0.001). We also compared the 677T allele frequency obtained from the groups studied with the frequencies reported in other ethnic groups of Mexico (Huichol, Tarahumara, and Purepecha). There were significant differences between the three ethnic groups compared to Nahuas (Huicholes, P = 0.004; Tarahumaras, P < 0.001; Purepechas, P = 0.042). Our results indicated significant differences in the frequencies of the C677T and A1298C polymorphisms between the two ethnic groups and the Mestizo population of the State of Guerrero. In addition, we found strong differences with other ethnic groups in Mexico. These results could be useful for future studies investigating diseases related to folate metabolism, and could help the government to design specific nutrition programs for different ethnic groups.

Associations between prefrontal γ-aminobutyric acid concentration and the tryptophan hydroxylase isoform 2 gene, a panic disorder risk allele in women

Associations between the central serotonergic and γ-aminobutyric acid (GABA) systems play key roles in the prefrontal cortical regulation of emotion and cognition and in the pathophysiology and pharmacotherapy of highly prevalent psychiatric disorders. The goal of this study was to test the effects of common variants of the tryptophan hydroxylase isoform 2 (TPH2) gene on GABA concentration in the prefrontal cortex (PFC) using magnetic resonance spectroscopy. In this study involving 64 individuals, we examined the associations between prefrontal cortical GABA concentration and 12 single nucleotide polymorphisms (SNPs) spanning the TPH2 gene, including rs4570625 (-703 G/T SNP), a potentially functional TPH2 polymorphism that has been associated with decreased TPH2 mRNA expression and panic disorder. Our results revealed a significant association between increased GABA concentration in the PFC and the T-allele frequencies of two TPH2 SNPs, namely rs4570625 (-703 G/T) and rs2129575 (p⩽0.0004) and the C-allele frequency of one TPH2 SNP, namely rs1386491 (p=0.0003) in female subjects. We concluded that rs4570625 (-703 G/T), rs2129575 and rs1386491 play a significant role in GABAergic neurotransmission and may contribute to the sex-specific dysfunction of the GABAergic system in the PFC.

Association of Hepatic Lipase -514T Allele with Coronary Artery Disease and Ankle-Brachial Index, Dependence on the Lipoprotein Phenotype: The GENES Study

ObjectivesRelationship between hepatic lipase (LIPC) polymorphism and coronary artery disease (CAD) has often led to contradictory results. We studied this relation by genotyping rs1800588 in the LIPC promoter in a case-control study on CAD (the GENES study). We also investigated the relationship between this polymorphism and the ankle-brachial index (ABI), which is predictive of atherosclerosis progression and complications in patients at high cardiovascular risk.Methods557 men aged 45–74 with stable coronary artery disease and 560 paired controls were genotyped for rs1800588. Medical data, clinical examination including determination of ABI and biological measurements related to cardiovascular risk factors enabled multivariate analyses and multiple adjustments.ResultsCAD cases showed a higher T-allele frequency than controls (0.246 vs 0.192, p = 0.003). An interaction has been found between LIPC polymorphism and triglycerides (TG) levels regarding risk of CAD: TT-homozigosity was associated with an Odds ratio (OR) of 6.4 (CI: 1.8–22.3) when TG were below 1.5 g/L, but no association was found at higher TG levels (OR = 1.34, CI: 0.3–5.9). The distribution of LIPC genotypes was compared between CAD patients with normal or abnormal ABI and impact of LIPC polymorphism on ABI was determined. Following multiple adjustments, association of the T-allele with pejorative ABI (<0.90) was significant for heterozygotes and for all T-carriers (OR = 1.55, CI: 1.07–2.25).ConclusionThe -514T LIPC allele is associated with CAD under normotriglyceridemic conditions and constitutes an independent determinant of pejorative ABI in coronary patients.

INFLUENCE OF THE POLYMORPHISM OF THE RENIN-ANGIOTENSIN SYSTEM GENES ON THE CARDIAC ARRHYTHMIAS IN CHILDREN WITH HYPERTROPHIC CARDIOMYOPATHY

Hypertrophic cardiomyopathy (HCMP) is a genetically determined myocardial disease, characterized by massive hypertrophy of the myocardium of the left and/or (rarely) the right ventricle, often associated with obstruction of the left ventricular outflow tract and diastolic dysfunction. The course of disease can be complicated by development of various cardiac arrhythmias. It was reported that severity of HCMP course depends at certain degree on polymorphism of candidate genes, including genes of the renin angiotensin system (RAS). Influence of RAS genes polymorphism on the frequency and character of cardiac arrhythmias in childhood is almost not studied. Aim : to determine the influence of RAS genes polymorphism on the prevalence and structure of cardiac arrhythmias in children with HCMP. Patients and methods : analysis of influence of RAS genes polymorphism on the prevalence and structure of cardiac arrhythmias was performed in 32 children with HCMP. All the patients were carried out ECG, cardiac ultrasound and ECG Holter monitoring. Polymorphism of the RAS genes (renin gene (REN) G83A, angiotensinogen gene (AGT) M235T, angiotensin-converting enzyme gene (ACE) I/D, angiotensin II receptor type 1 gene (AGTR1) A1166C). Results : in patients with HCMP was established a higher frequency of TT-genotype and T-alleles of angiotensinogen gene than in comparison group. In homozygous patients with T-allele of angiotensinogen gene ventricular arrhythmia was found reliably more often than in patients with MT- and MM-genotypes, which suggested that M235T polymorphism of angiotensinogen gene influenced on intensity of ventricular arrhythmias in children with HCMP. Conclusions : in children with HCMP and cardiac arrhythmias analysis of M235T polymorphism of angiotensinogen gene can be used as an additional criterion for revealing of patients with high risk of arrhythmic complications and for development of preventative measures.

ABCB1/MDR1 gene polymorphism and colorectal cancer risk: a meta‐analysis of case–control studies

ABCB1/MDR1 protein is found in high concentrations on the apical surfaces of colonic epithelial cells. It acts as an efflux pump by transporting toxic endogenous substances, drugs and xenobiotics out of cells. Polymorphisms in the ABCB1/MDR1 gene may either change expression of the ABCB1/MDR1 protein or alter its function, suggesting its possible association with colorectal cancer. Several studies have reported a relationship between ABCB1 gene polymorphisms and colorectal cancer risk, but no consistent conclusion has been reached. We therefore conducted a meta-analysis to identify any association between the ABCB1 gene and CRC risk. PubMed, Embase, Google Scholar, Cbmdisc and CNKI were searched for studies on the relationship of ABCB1/MDR1 gene SNPs and the incidence of colorectal cancer. Eligible articles were included for data extraction. The main outcome was the frequency of ABCB1/MDR1 gene SNPs among cases and controls. Comparison of the distribution of SNPs was performed mainly using Review Manager 5.0. Ten, four and two trials were identified that focussed on the ABCB1 gene SNPs rs1045642, rs2032582 and rs3789243, respectively. A total of 3175 cases and 3715 controls were included. The meta-analysis, stratified by ethnicity or population source, indicated no association between the ABCB1 gene rs1045642 polymorphism and colorectal cancer risk. However, when the study by Bae et al. was removed from the analysis, there was some evidence to indicate a higher T-allele frequency in Asian colorectal cancer patients (OR = 1.30, 95% CI: 1.02-1.67, P = 0.03). Neither ABCB1 rs2032582 nor ABCB1 rs3789243 indicated an association with colorectal cancer risk. An increased frequency only of the wild-type combined allele (rs2032582G/rs1045642C) was found in Caucasian patients (OR = 1.22, 95% CI: 1.03-1.44, P = 0.02). There is some evidence to indicate an association between ABCB1 rs1045642T and colorectal cancer risk in Asians. Compared with the ABCB1 gene SNPs rs1045642, rs2032582 or rs3789243 alone, combined haplotypes of several SNPs might be a better marker to determine the genetic influence on the susceptibility to colorectal cancer among Caucasians.

Correlation between single nucleotide polymorphisms in CYP4F2 and warfarin dosing in chinese valve replacement patients

BackgroundIndividuals with implanted mechanical valve prostheses require lifelong anticoagulation therapy with warfarin. The narrow therapeutic index of warfarin makes it difficult to dose and maintain proper anticoagulation. A number of single nucleotide polymorphisms (SNPs) affecting vitamin K or warfarin metabolism have been shown to affect warfarin dosing. Our aim was to study the effect of the CYP4F2 rs2108622-1347 (C > T) variant on warfarin dosing in Chinese patients.MethodsWe studied 352 patients after heart valve replacement surgery. Warfarin dosing for patients was adjusted to achieve 1.8 ≤ INR ≤ 2.5. We determined the presence of SNPs in CYP4F2 in these patients and investigated their association with warfarin dosing.ResultsWe found the frequency of the CYP4F2 rs2108622 C allele was 79.5% and T-allele frequency was 20.5%. The warfarin dose requirement for CC individuals was significantly lower than that for CT or TT individuals (P < 0.05). TT-homozygous individuals required a 0.56 mg/day higher dose of warfarin than their CC counterparts.ConclusionsThis study demonstrates that CYP4F2 rs2108622 significantly affects the warfarin dose requirement to achieve adequate anticoagulant activity in Chinese individuals. Genotyping of this SNP may allow clinicians to determine the initiation dose for patients following valve-replacement surgery in China.

Genetic thromobophilia in pregnancy: a case–control study among North Indian women

In the present study, an attempt is made to understand the role of genetic thrombophilias i.e. MTHFR C677T and FVL in the causation of various pregnancy complications like pregnancy induced hypertension (PIH), recurrent abortions, intra-uterine growth retardation (IUGR) and intra-uterine death on the whole and also individually along with the comparative assessment of pathophysiological basis of various pregnancy complications via the genetic proximities. One thousand and eleven (1,011) women of reproductive age group were recruited in the present study comprising various complications and controls. Recruitment criteria for all the pregnancy complications and controls was made and followed strictly. MTHFR C677T and FVL mutation detection was done in all the subjects. Vegetarianism was found to be significant risk factors for all the pregnancy complications and also when assessed individually. With respect to MTHFR C677T polymorphism, higher frequency of 677T allele was found among controls as compared to cases. 677T allele was found to pose decreased risk for various pregnancy complications on the whole and also individually. On adjusting the diet, regression analysis revealed no risk of mutant allele (T) for various pregnancy complications. FVL homozygous mutants were found to be absent among controls. In conclusion, the present study depicts dietary pattern as one of the most important factors in demonstrating the role of MTHFR C677T in various pregnancy complications and is indicative of a relatively deleterious effect of double dose of FVL in the presently studied population. Additionally, these polymorphisms play an important role in the orchestration of PIH to IUGR and vice versa.

Increased T-Allele Frequency of 677 C&gt;T Polymorphism in the Methylenetetrahydrofolate Reductase Gene in Differentiated Thyroid Carcinoma

Epigenetic alterations in the global DNA methylation status may be associated with an increased risk of some cancer types in humans. The methylenetetrahydrofolate reductase (MTHFR) gene is involved in folic acid metabolism and plays an essential role in inherited DNA methylation profiles. The common 677 C>T and 1298 A>C polymorphisms in the MTHFR gene cause the production of a thermolabile enzyme with reduced function and, eventually, genomic DNA hypomethylation. The current preliminary study was designed to determine the association between germ-line polymorphism in the MTHFR gene and differentiated thyroid carcinoma (DTC). In the current case-control study of 60 thyroid carcinomas (TC); 45 papillary TC, 9 follicular TC, and 6 DTC of an uncertain malignant potential were examined. Genomic DNA was extracted from peripheral blood with EDTA, genotyped by a multiplex real-time polymerase chain reaction. An elevated 2.33-fold risk was observed for DTC in individuals with the 677TT genotype when compared with the control group (odds ratio [OR]: 1.92, 95% confidence interval [CI]: 1.03-3.58). Current DTC patients showed similar results as a control group for the 1298 A>C allele. No significant risk was detected for the homozygous 1298CC genotype (CC vs. AA or AC) (OR: 1.30, 95% CI: 0.73-2.29). The current results are supportive of the hypothesis that the homozygous MTHFR 677TT genotype increases the risk factor of developing thyroid cancer, and further large-scale studies are needed to validate this association.

Genetic study of phenylthiocarbamide (PTC) taste perception among six human populations of Jammu and Kashmir (India)

BackgroundThe ability to taste phenylthiocarbamide (PTC), a bitter chemical has long been known to be a bimodal autosomal trait inherited in a simple Mendelian recessive pattern which is being widely used for both genetic and anthropological studies. The frequency of taster and non-taster allele is found to vary in different populations. The present paper deals with the distribution of PTC tasting ability as a marker to study the genetic structure among Muslim populations of Jammu; as no detailed information is available. AimTo investigate the prevalence and gene frequencies of PTC taste sensitivity among male and females. Subjects and methodsWe have undertaken a survey of gene frequencies of PTC taste ability for six different endogamous groups including tribal population. PTC serial dilution method was used to assess the PTC taster and non-taster phenotypes. Hardy–Weinberg method was used to determine allele frequencies. ResultsGujjar and Bakarwal population showed highest PTC threshold while Syed had the least. The phenotypic frequency for PTC taste ability varies within six populations; Syed were observed with highest taster frequency while Gujjar and Bakarwal had lowest taster frequency. The taster frequency of six different populations showed that the percentage of taster frequency was more frequent than that of the non-tasters. Also, females (χ2=4.563, df=5, p=0.471) had more PTC tasters than males (χ2=5.254, df=5, p=0.385), being statistically significant. The allelic frequencies in Gujjar and Bakarwal for non-taster (t) males and females were 55.86 and 54.55, respectively. In Syed population, t-allele frequencies for males and females were 45.75 and 37.79, respectively, while the other four populations showed intermediate t-allele frequencies. The heterozygosity showed little variation among all of the six populations.

Association of the C677T Polymorphism in the Human Methylenetetrahydrofolate Reductase (MTHFR) Gene with the Genetic Predisposition for Type 2 Diabetes Mellitus in a Moroccan Population

Type 2 diabetes mellitus (T2DM) is a major public health problem around the world. The C677T and A1298C polymorphisms of the methylenetetrahydrofolate reductase (MTHFR) gene have been reported to be associated with T2DM and its complications. This study aimed to investigate this association in the Moroccan population. A case-control study was performed among 282 Moroccan diabetic patients and 232 healthy controls. The MTHFR C677T and A1298C polymorphisms were genotyped by polymerase chain reaction, followed by enzymatic digestion with HinfI and MboII enzymes, respectively. There was a significant association between C677T polymorphism and T2DM in both additive and dominant models. In addition, the 677T allele frequency differed significantly between the diabetic and control groups (26.06% vs. 33.20%, respectively). However, no significant association was found between A1298C polymorphism and T2DM. The frequencies of combined genotypes 677CC/1298AA and 677CT/1298AC differed significantly between the diabetic and control groups (32.62% vs. 20.61% and 9.57% vs. 17.55%, respectively). These results show an evident association between the MTHFR C677T polymorphism and T2DM in Moroccan patients but no significant association with the MTHFR A1298C polymorphism.

Effects of lecithin: Cholesterol acyltransferase genotypes, enzyme levels, and activity on high-density lipoprotein levels

Lecithin:cholesterol acyltransferase (LCAT) is one of the key enzymes controlling cholesterol homeostasis and plays a primary role in high-density lipoprotein cholesterol (HDL-C) maturation. The aim of our study was to evaluate the effects of LCAT gene polymorphisms 511C/T (exon4), 4886C/T (rs5923), and 608C/T (rs5922) on LCAT enzyme level, activity, and HDL-C levels. The study population was selected from consecutive subjects with low (<35 mg/dL) and high HDL-C levels (>65 mg/dL) seen in our lipid clinic. LCAT polymorphisms were analyzed with a restriction fragment length polymorphism assay. LCAT activity and levels were measured by colorimetric enzymatic and enzyme-linked immunoassay methods, respectively. The 4886C/T polymorphism was the most commonly observed variant of LCAT gene. T-allele frequencies in subjects with low (n = 50) and high (n = 50) HDL-C were 0.54 and 0.37, respectively (P = .019). TT genotype was more common among low HDL-C group (30% vs 14%, P = .05). The effects of LCAT enzyme appeared to depend on the HDL-C level. In subjects with low HDL-C, LCAT enzyme levels correlated positively with body mass index (P < .001, r = 0.544), HDL-C (P = .006, r = 0.404), triglycerides (P = .001, r = 0.487), total cholesterol (P < .001, r = 0.541), and low-density lipoprotein-cholesterol (P = .001, r = 0.477) levels. LCAT activity correlated positively with fasting glucose levels (P = .008, r = 0.390). LCAT genotype, enzyme level, and activity modulate HDL-C metabolism, particularly among subjects with low HDL-C levels.

Genotype association of C(-735)T polymorphism of the MMP-2 gene with the risk of carotid atherosclerosis-vulnerable plaque in the Han Chinese population

The aim of the current study was to explore the possible association of the polymorphism of C(-735)T in MMP-2 with the vulnerable plaque risk in ultrasound-confirmed carotid atherosclerosis cases. Serum MMP-2 levels were measured to investigate the relationship between the MMP-2 level and the genetic variability. The MMP-2 polymorphism was detected by PCR-RFLP in the 243 cases with stable plaque and 221 cases with vulnerable plaque. Serum MMP-2 levels were measured with ELISA. The results showed that MMP-2 was significantly higher in the cases with vulnerable plaque than in the cases with stable plaque. A statistical difference was found between the genotype distributions in the vulnerable plaque cases and that in the stable cases. T-allele frequency was also found to be over-represented in the stable plaque cases than in the vulnerable plaque cases, which might partially explain the observed difference in the serum MMP-2 levels in the different plaque cases. The current results also suggested that MMP-2 was a risk factor in the cases with vulnerable plaques, whereas TT genotype and T allele might be protective factors in the cases with vulnerable plaques.

677TT Genotype Is Associated with Elevated Risk of Methotrexate (MTX) Toxicity in Juvenile Idiopathic Arthritis: Treatment Outcome, Erythrocyte Concentrations of MTX and Folates, and MTHFR Polymorphisms

To investigate whether methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C polymorphisms and erythrocyte concentration of methotrexate (EMTX) could serve as predictors of methotrexate (MTX) efficacy and toxicity in patients with juvenile idiopathic arthritis (JIA). Genetic analyses and EMTX and folate assessment were performed in 69 patients with JIA aged 2.5-19.6 years (30 male) treated with MTX using a dose-escalation protocol and classified as full responders (disease inactivity; n = 51) or nonresponders (< 30% improvement in pediatric American College of Rheumatology-30 criteria while receiving ≥ 15 mg/m(2)/week parenteral MTX for at least 3 months; n = 18). Nonresponders were treated with the higher median MTX dose (17.2 vs 12.6 mg/m(2)/week; p < 0.0001) and accumulated more EMTX (217 vs 106 nmol/l; p < 0.02) and erythrocyte folates (763 vs 592 nmol/l; p = 0.052) than responders. Analysis of MTHFR allele and genotype frequencies in relation to response failed to detect association. The frequency of any adverse effect was 29.4% in responders and 33.3% in nonresponders (p = 0.77). The frequency of 677T allele was elevated in patients with adverse effects (52.4% vs 20.9%; OR 3.88, 95% CI 1.8-8.6, p < 0.002). The probability of any adverse effect was significantly higher in patients with 677TT compared to the 677CC genotype (OR 55.5, 95% CI 2.9-1080, p < 0.001). MTHFR genotyping may have a predictive value for the risk of MTX-associated toxicity in patients with JIA. Despite the lack of therapeutic effect, nonresponders accumulated adequate concentrations of EMTX.

Photoperiod at conception predicts C677T‐MTHFR genotype: A novel gene‐environment interaction

Data is presented, which suggest that the day length a woman experiences during the periconceptional period predicts the C677T-MTHFR genotype of her child. Logistic regression analysis involving 375 neonates born in the same geographical location within a three year period demonstrated that photoperiod (minutes) at conception predicts both genotype (P = 0.0139) and mutant allele carriage (P = 0.0161); the trend clearly showing that the 677T-MTHFR allele frequency increases as photoperiod increases. We propose a number of explanations, including a hypothesis in which a long photoperiod around conception decreases maternal systemic folate because of UVA induced dermal oxidative degradation of 5-methyl-H(4)folate, leading to a lower cellular 5,10-methylene-H(4)folate status. In this scenario, 5,10-methylene-H(4)folate would be more efficiently used for dTMP and DNA synthesis by 677T-MTHFR embryos than wildtype embryos giving the 677T-MTHFR embryos increased viability, and hence increasing mutant T-allele frequency. Alternate hypotheses include: increased seasonal availability of folate rich foods that genetically buffer any negative effect of 677T-MTHFR in embryos; seasonal oxidative stress lowering embryo-toxic homocysteine; an undefined hormonal effect of photoperiod on the neuroendocrine axis, which mediates genotype/embryo selection. The effect of photoperiod on genotype seems clear, but the speculative molecular mechanism underpinning the effect needs careful examination.

The allele frequencies of three polymorphisms in genes involved in homocysteine metabolism in a group of unrelated healthy Singaporeans.

The cystathionine β-synthase (CBS) 844ins68 polymorphism, methionine synthase (MS) A2756G SNP, and 5,10-methylenetetrahydrofolate reductase (MTHFR) C677T SNP are associated with homocysteine (Hcy) level in humans. Elevated Hcy level is considered a risk factor for atherosclerotic diseases among Asian populations. Therefore, the three polymorphisms may vary the risk for developing such diseases in Singaporeans. In this study, the three polymorphisms were determined in a group of unrelated healthy Singaporeans (273 Chinese, 127 Indians, and 156 Malays). Regarding allele frequencies, Indians had the highest frequencies of the CBS insertion allele (2.0%) and the MS 2756G allele (26.4%), while Chinese had the highest MTHFR 677T allele frequency (27.5%). In addition, the MTHFR 677T allele was found significantly lower in Chinese males than in their female counterparts. As the CBS insertion allele was suggested to be associated with lower Hcy level, whereas the MS 2756G allele and the MTHFR T/T genotype were related to higher Hcy level, the MS A/G or G/G genotype and the MTHFR T/T genotype were considered double genetic risk factors for elevated Hcy level. The frequency of such double genetic risk was 0.7% (4 subjects) in the total population consisting of 3 Chinese (1.1%) and 1 Malays (0.6%). No MTHFR T/T genotype was found in Indians. Such results suggested that Chinese could have higher Hcy levels than Malays while the situation for Indians was complicated. Since human Hcy levels are also affected by environmental factors, further studies are required to better evaluate the association between these three polymorphisms and Hcy levels and/or disease susceptibilities in Singaporeans.

Endothelial Nitric Oxide Synthase (eNOS) Gene Polymorphism in Early Term Chronic Allograft Nephropathy

Chronic allograft nephropathy (CAN) is a complex phenomenon caused by underlying kidney disease with superimposed enviromental and genetic factors. CAN development begins with progressive renal microvascular injury. Endothelial cells play key roles in the regulation of vascular tone, permeability, and remodeling. A reduction in basal nitric oxide (NO) release as a result of genetic variation in endothelial NO synthase (eNOS) function may predispose to hypertension, thrombosis, vasospasm, and atherosclerosis, all contributing to the development of CAN. We analyzed the G894T mutation at exon 7 of the eNOS gene in relationship to CAN among 81 children with renal transplantations. The 20 patients who developed CAN underwent renal biopsies for histological confirmation. Proteinuria and hypertension were observed in CAN. We selected 173 healthy reference subjects. The G894T polymorphism of the eNOS gene was determined by PCR–restriction fragment-length polymorphism analysis. The group included 33 male and 48 female subjects who received 32 living-related grafts and 49 from deceased donors (DD) donors. Donor age (y) was 32.7 ± 13.7 and the HLA A,B,DR mismatch number of the cadaveric cases was 3.5 ± 0.79. The distribution of the genotypes were ENOS GG/GT/TT 48%, 33%, 19%, respectively. G-alleles frequency was 64.8%; T-allele frequency was 35.2%. ENOS G894T gene polymorphism did not seem to influence long-term renal allograft outcome. Recipient ENOS G894T gene polymorphism did not alter the risk of chronic allograft failure. Even if NO synthesis and bioactivity are influenced by this polymorphism, many vasoactive factors may have roles to suppress the advantageous effects of NO.

Polymorphisms of serotonin receptor 2A and 2C genes and COMT in relation to obesity and type 2 diabetes.

BackgroundCandidate genes of psychological importance include 5HT2A, 5HT2C, and COMT, implicated in the serotonin, noradrenaline and dopamine pathways, which also may be involved in regulation of energy balance. We investigated the associations of single nucleotide polymorphisms (SNPs) of these genes with obesity and metabolic traits.Methodology/Principal FindingsIn a population of 166 200 young men examined at the draft boards, obese men (n = 726, BMI≥31.0 kg/m2) and a randomly selected group (n = 831) were re-examined at two surveys at mean ages 46 and 49 years (S-46, S-49). Anthropometric, physiological and biochemical measures were available. Logistic regression analyses were used to assess age-adjusted odds ratios. No significant associations were observed of 5HT2A rs6311, 5HT2C rs3813929 and COMT rs4680 with obesity, except that COMT rs4680 GG-genotype was associated with fat-BMI (OR = 1.08, CI = 1.01–1.16). The SNPs were associated with a number of physiological variables; most importantly 5HT2C rs3813929 T-allele was associated with glucose (OR = 4.56, CI = 1.13–18.4) and acute insulin response (OR = 0.65, CI = 0.44–0.94) in S-49. COMT rs4680 GG-genotype was associated with glucose (OR = 1.04, CI = 1.00–1.09). Except for an association between 5HT2A rs6311 and total-cholesterol at both surveys, significant in S-46 (OR = 2.66, CI = 1.11–6.40), no significant associations were observed for the other phenotypes. Significant associations were obtained when combined genotype of 5HT2C rs3813929 and COMT rs4680 were examined in relation to BMI (OR = 1.12, CI = 1.03–1.21), fat-BMI (OR = 1.22, CI = 1.08–1.38), waist (OR = 1.13, CI = 1.04–1.22), and cholesterol (OR = 5.60, CI = 0.99–31.4). Analyses of impaired glucose tolerance (IGT) and type 2 diabetes (T2D) revealed, a 12.3% increased frequency of 5HT2C rs3813929 T-allele and an 11.6% increased frequency of COMT rs4680 GG-genotype in individuals with IGT or T2D (χ2, p = 0.05 and p = 0.06, respectively). Examination of the combined genotypes of 5HT2C and COMT showed a 34.0% increased frequency of IGT or T2D (χ2, p = 0.01).ConclusionsThe findings lend further support to the involvement of serotonin, noradrenaline and dopamine pathways on obesity and glucose homeostasis, in particular when combined genotype associations are explored.