Geographic differences in allele frequencies of susceptibility SNPs for cardiovascular disease

Assessment of causal relationships between omega-3 and omega-6 polyunsaturated fatty acids in autoimmune rheumatic diseases: a brief research report from a Mendelian randomization study

Background

Currently, the association between the consumption of polyunsaturated fatty acids (PUFAs) and the susceptibility to autoimmune rheumatic diseases (ARDs) remains conflict and lacks substantial evidence in various clinical studies. To address this issue, we employed Mendelian randomization (MR) to establish causal links between six types of PUFAs and their connection to the risk of ARDs.

Methods

We retrieved summary-level data on six types of PUFAs, and five different types of ARDs from publicly accessible GWAS statistics. Causal relationships were determined using a two-sample MR analysis, with the IVW approach serving as the primary analysis method. To ensure the reliability of our research findings, we used four complementary approaches and conducted multivariable MR analysis (MVMR). Additionally, we investigated reverse causality through a reverse MR analysis.

Results

Our results indicate that a heightened genetic predisposition for elevated levels of EPA (ORIVW: 0.924, 95% CI: 0.666-1.283, P IVW = 0.025) was linked to a decreased susceptibility to psoriatic arthritis (PsA). Importantly, the genetically predicted higher levels of EPA remain significantly associated with an reduced risk of PsA, even after adjusting for multiple testing using the FDR method (P IVW-FDR-corrected = 0.033) and multivariable MR analysis (P MV-IVW < 0.05), indicating that EPA may be considered as the risk-protecting PUFAs for PsA. Additionally, high levels of LA showed a positive causal relationship with a higher risk of PsA (ORIVW: 1.248, 95% CI: 1.013-1.538, P IVW = 0.037). It is interesting to note, however, that the effects of these associations were weakened in our MVMR analyses, which incorporated adjustment for lipid profiles (P MV-IVW > 0.05) and multiple testing using the FDR method (P IVW-FDR-corrected = 0.062). Moreover, effects of total omega-3 PUFAs, DHA, EPA, and LA on PsA, were massively driven by SNP effects in the FADS gene region. Furthermore, no causal association was identified between the concentrations of other circulating PUFAs and the risk of other ARDs. Further analysis revealed no significant horizontal pleiotropy and heterogeneity or reverse causality.

Conclusion

Our comprehensive MR analysis indicated that EPA is a key omega-3 PUFA that may protect against PsA but not other ARDs. The FADS2 gene appears to play a central role in mediating the effects of omega-3 PUFAs on PsA risk. These findings suggest that EPA supplementation may be a promising strategy for preventing PsA onset. Further well-powered epidemiological studies and clinical trials are warranted to explore the potential mechanisms underlying the protective effects of EPA in PsA.

Population-based meta-analysis and gene-set enrichment identifies FXR/RXR pathway as common to fatty liver disease and serum lipids

Nonalcoholic fatty liver disease (NAFLD) is prevalent worldwide. NAFLD is associated with elevated serum triglycerides (TG), low-density lipoprotein cholesterol (LDL), and reduced high-density lipoprotein cholesterol (HDL). Both NAFLD and blood lipid levels are genetically influenced and may share a common genetic etiology. We used genome-wide association studies (GWAS)-ranked genes and gene-set enrichment analysis to identify pathways that affect serum lipids and NAFLD. We identified credible genes in these pathways and characterized missense variants in these for effects on serum traits. We used MAGENTA to identify 58 enriched pathways from publicly available TG, LDL, and HDL GWAS (n = 99,000). Three of these pathways were also enriched for associations with European-ancestry NAFLD GWAS (n = 7176). One pathway, farnesoid X receptor (FXR)/retinoid X receptor (RXR) activation, was replicated for association in an African-ancestry NAFLD GWAS (n = 3214) and plays a role in serum lipids and NAFLD. Credible genes (proteins) in FXR/RXR activation include those associated with cholesterol/bile/bilirubin transport/absorption (ABCC2 (MRP2) [ATP binding cassette subfamily C member (multidrug resistance-associated protein 2)], ABCG5, ABCG8 [ATP-binding cassette (ABC) transporters G5 and G8], APOB (APOB) [apolipoprotein B], FABP6 (ILBP) [fatty acid binding protein 6 (ileal lipid-binding protein)], MTTP (MTP) [microsomal triglyceride transfer protein], SLC4A2 (AE2) [solute carrier family 4 member 2 (anion exchange protein 2)]), nuclear hormone-mediated control of metabolism (NR0B2 (SHP) [nuclear receptor subfamily 0 group B member 2 (small heterodimer partner)], NR1H4 (FXR) [nuclear receptor subfamily 1 group H member 4 (FXR)], PPARA (PPAR) [peroxisome proliferator activated receptor alpha], FOXO1 (FOXO1A) [forkhead box O1]), or other pathways (FETUB (FETUB) [fetuin B]). Missense variants in ABCC2 (MRP2), ABCG5 (ABCG5), ABCG8 (ABCG8), APOB (APOB), MTTP (MTP), NR0B2 (SHP), NR1H4 (FXR), and PPARA (PPAR) that associate with serum LDL levels also associate with serum liver function tests in UK Biobank. Conclusion: Genetic variants in NR1H4 (FXR) that protect against liver steatosis increase serum LDL cholesterol while variants in other members of the family have congruent effects on these traits. Human genetic pathway enrichment analysis can help guide therapeutic development by identifying effective targets for NAFLD/serum lipid manipulation while minimizing side effects. In addition, missense variants could be used in companion diagnostics to determine their influence on drug effectiveness.

Transcription factor 7-like 2 single nucleotide polymorphisms rs290487 and rs290481 are associated with dyslipidemia in the Balinese population

Background

Dyslipidemia is one of the major risks for the development of cardiovascular diseases which has been the leading cause of death in developing countries. Previously, common polymorphisms of the transcription factor 7-like 2 (TCF7L2) gene have been associated with altered lipid profiles. In this study, we investigated the associations of TCF7L2 SNPs, rs290487 and rs290481, with dyslipidemia and altered lipid profile in the Balinese.

Methods

A total of 565 subjects from four locations in the Bali Province, Indonesia, were recruited. Serum lipid concentrations (triglycerides (TG), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), total cholesterol (TC)) were measured using standard protocol. SNP genotyping was done using the amplification refractory system mutation polymerase chain reaction (ARMS-PCR) method.

Results

We found the shifted major/minor allele frequencies of both SNPs (0.56 for rs290487 T allele, 0.53 for rs290481 T allele) in the Balinese, as compared to dbSNP. The rs290487 and rs290481 C alleles were significantly associated with dyslipidemia, particularly high TC and high LDL-C. These associations were independent of age, sex, population, obesity, diabetes mellitus, and high TyG index as a proxy for insulin resistance. The haplotype CC also showed similar association with these traits. Our findings indicate that TCF7L2 polymorphisms are associated with dyslipidemia and altered lipid profile in the Balinese.

Integrating SNPs-based genetic risk factor with blood epigenomic response of differentially arsenic-exposed rural subjects reveals disease-associated signaling pathways

Arsenic (As) contamination in groundwater is responsible for numerous adverse health outcomes among millions of people. Epigenetic alterations are among the most widely studied mechanisms of As toxicity. To understand how As exposure alters gene expression through epigenetic modifications, a systematic genome-wide study was designed to address the impact of multiple important single nucleotide polymorphisms (SNPs) related to As exposure on the methylome of drinking water As-exposed rural subjects from Pakistan. Urinary As levels were used to stratify subjects into low, medium and high exposure groups. Genome-wide DNA methylation was investigated using MeDIP in combination with NimbleGen 2.1 M Deluxe Promotor arrays. Transcriptome levels were measured using Agilent 8 × 60 K expression arrays. Genotyping of selected SNPs (As3MT, DNMT1a, ERCC2, EGFR and MTHFR) was measured and an integrated genetic risk factor for each respondent was calculated by assigning a specific value to the measured genotypes based on known risk allele numbers. To select a representative model related to As exposure we compared 9 linear mixed models comprising of model 1 (including the genetic risk factor), model 2 (without the genetic risk factor) and models with individual SNPs incorporated into the methylome data. Pathway analysis was performed using ConsensusPathDB. Model 1 comprising the integrated genetic risk factor disclosed biochemical pathways including muscle contraction, cardio-vascular diseases, ATR signaling, GPCR signaling, methionine metabolism and chromatin modification in association with hypo- and hyper-methylated gene targets. A unique pathway (direct P53 effector) was found associated with the individual DNMT1a polymorphism due to hyper-methylation of CSE1L and TRRAP. Most importantly, we provide here the first evidence of As-associated DNA methylation in relation with gene expression of ATR, ATF7IP, TPM3, UBE2J2. We report the first evidence that integrating SNPs data with methylome data generates a more representative epigenome profile and discloses a better insight in disease risks of As-exposed individuals.

Polygenic risk for coronary artery disease in the Scottish and English population

Background

Epidemiological studies have repeatedly observed a markedly higher risk for coronary artery disease (CAD) in Scotland as compared to England. Up to now, it is unclear whether environmental or genetic factors might explain this phenomenon.

Methods

Using UK Biobank (UKB) data, we assessed CAD risk, based on the Framingham risk score (FRS) and common genetic variants, to explore the respective contribution to CAD prevalence in Scotland (n = 31,963) and England (n = 317,889). We calculated FRS based on sex, age, body mass index (BMI), total cholesterol (TC), high density lipoprotein cholesterol (HDL-C), systolic blood pressure (SBP), antihypertensive medication, smoking status, and diabetes. We determined the allele frequency of published genome-wide significant risk CAD alleles and a weighted genetic risk score (wGRS) for quantifying genetic CAD risk.

Results

Prevalence of CAD was 16% higher in Scotland as compared to England (8.98% vs. 7.68%, P < 0.001). However, the FRS only predicted a marginally higher CAD risk (less than 1%) in Scotland (12.5 ± 10.5 vs.12.6 ± 10.6, P = 0.03). Likewise, the overall number of genome-wide significant variants affecting CAD risk (157.6 ± 7.7 and 157.5 ± 7.7; P = 0.12) and a wGRS for CAD (2.49 ± 0.25 in both populations, P = 0.14) were remarkably similar in the English and Scottish population. Interestingly, we observed substantial differences in the allele frequencies of individual risk variants. Of the previously described 163 genome-wide significant variants studied here, 35 variants had higher frequencies in Scotland, whereas 37 had higher frequencies in England (P < 0.001 each).

Conclusions

Neither the traditional risk factors included in the FRS nor a genetic risk score (GRS) based on established common risk alleles explained the higher CAD prevalence in Scotland. However, we observed marked differences in the distribution of individual risk alleles, which emphasizes that even geographically and ethnically closely related populations may display relevant differences in the genetic architecture of a common disease.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12872-021-02398-4.

Molecular analysis of HLA Class I and Class II genes in five different South Indian linguistic groups

South Indians are a heterogeneous population who speak different languages and differ in their life style and physical appearance. Major population movements, social structure and caste endogamy have influenced the genetic structure of Indian populations. The human leukocyte antigen (HLA) system of populations is highly informative because of the high level of polymorphisms. Knowledge of allele and haplotype frequencies of the HLA system is important in the search for unrelated bone marrow donors. We investigated the distribution of HLA A, B, C, DRB1 and DQB1 loci in five linguistic groups from South India. HLA-A*01:01:01~B*57:01:01:01~C*06:02:01~DRB1*07:01:01~DQB1*03:03:02 was the common haplotype with highest frequency in all the five populations studied. A few relevant haplotypes were identified as most common haplotypes in each linguistic group. Comparison of HLA-A, -B and -DRB1 allele distribution in these five linguistic groups with the other Asian population showed that the South Indian populations were closely related to Sri Lankan populations. A large South Indian donor registry might serve as good source of donors for patients from Sri Lanka and vice versa.

Influence of SH2B3, MTHFD1L, GGCX, and ITGB3 Gene Polymorphisms on theVariability on Warfarin Dosage Requirements and Susceptibility to CVD in the Jordanian Population

The purpose of this study was to investigate the effects of the SH2B3, MTHFD1L, GGCX, and ITGB3 gene variants on the efficacy of warfarin treatment and its effects on the risk of cardiovascular disorders in Jordanian patients. The selected genes and their polymorphisms are involved in many Genome-Wide Association Study (GWAS) associated with cardiovascular disease and the variability of warfarin therapy. The current study conducted a genetic association and pharmacogenetics study in (212) Jordanian cardiovascular patients treated with warfarin and (213) healthy controls. DNA extraction and the Mass ARRAY™ system were used to genotype ten selected polymorphisms within four genes (SH2B3, MTHFD1L, GGCX, and ITGB3). This study confirmed a genetic association of MTHFD1L rs6922269 Single Nucleotide Polymorphism (SNP) with warfarin sensitivity during the initial and stabilization phases of treatment. Moreover, this SNP showed significant differences in the initial and maintenance doses of warfarin. This study also found an association between the genetic haplotypes (AGC and GAT) within the SH2B3 gene and responsiveness to warfarin. However, possession of an MTHFD1L rs491552 variant allele was found to affect the outcome measure of the international normalized ratio (INR) during the stabilization phase of warfarin treatment. In contrast, there was no association between all selected SNPs and susceptibility to cardiovascular disorders. This study extends the current understanding of the high variability of the warfarin response, including variability in dose requirements and susceptibility to cardiovascular disease in the Jordanian-Arab population. Other studies on a larger sample and in different ethnic groups could help to better understand the pharmacogenetics of warfarin and its application in personalized medicine.

Comparison and Analysis of Epidemiologic Characteristics of Stroke in Sichuan Province, China

Previous studies have shown that there is a geographic variation in the prevalence of stroke, with a lower prevalence of stroke in Sichuan province. And a stroke transition was found during the period of economic development as well. However, as the center of Southwest China, with a greatly developed economy, whether the geographic variation remained with lower burden of stroke in Sichuan province is unknown. Therefore, in this study, we analyzed the secular stroke status in Sichuan province to help explore the potential reasons for geographic disparity. From a cross-sectional study conducted based on eight national disease surveillance points (DSPs) in Sichuan province in 2013, the epidemiologic data of stroke were collected. Data of risk factors were obtained from a cross-sectional study based on 12 national DSPs in Sichuan province in 2013. The results showed that the age-standardized prevalence, incidence, and mortality of stroke in Sichuan province were 338.6/100,000 people [95% confidence interval (CI), 267.8–409.4], 147.1/100,000 person-years (95% CI = 100.6–193.6), and 72.4/100,000 person-years (95% CI = 40.0–104.8), respectively, which were significantly lower than those determined from the contemporary data of China in 2013. The analysis of the risk factors showed that the weights of contribution of the potential risk factors to stroke were in consistency with those published reports from other areas. In conclusion, the disparity of lower stroke burden in Sichuan than the average China remained, although with the great developments in Sichuan province over all those decades. In addition to traditional modifiable factors, we suggest that unknown or intrinsic differences such as genetic factors might play an important role in geographic disparity, which should be investigated in future studies.

Differences in the frequency of genetic variants associated with iron imbalance among global populations

Iron deficiency anaemia is a major health problem affecting approximately 1.2 billion people worldwide. Young children, women of reproductive age and pregnant women living in sub-Saharan Africa are the most vulnerable. It is estimated that iron deficiency accounts for half of anaemia cases. Apart from nutritional deficiency, infection, inflammation and genetic factors are the major drivers of anaemia. However, the role of genetic risk factors has not been thoroughly investigated. This is particularly relevant in African populations, as they carry high genetic diversity and have a high prevalence of anaemia. Multiple genetic variations in iron regulatory genes have been linked to impaired iron status. Here we conducted a literature review to identify genetic variants associated with iron imbalance among global populations. We compare their allele frequencies and risk scores and we investigated population-specific selection among populations of varying geographic origin using data from the Keneba Biobank representing individuals in rural Gambia and the 1000 Genomes Project. We identified a significant lack of data on the genetic determinants of iron status in sub-Saharan Africa. Most of the studies on genetic determinants of iron status have been conducted in Europeans. Also, we identified population differences in allele frequencies in candidate putative genetic risk factors. Given the disproportionately high genetic diversity in African populations coupled with their high prevalence of iron deficiency, there is need to investigate the genetic influences of low iron status in Sub-Saharan Africa. The resulting insights may inform the future implementation of iron intervention strategies.

Targeted Sequencing Study to Uncover Shared Genetic Susceptibility Between Peripheral Artery Disease and Coronary Heart Disease-Brief Report

Objective- It is unclear to what extent genetic susceptibility variants are shared between peripheral artery disease (PAD) and coronary heart disease (CHD), both manifestations of atherosclerotic vascular disease. We investigated whether common and low-frequency/rare variants in loci associated with CHD are also associated with PAD. Approach and Results- Targeted sequencing of 41 genomic regions associated with CHD in genome-wide association studies was performed in 1749 PAD cases (65±11 years, 61% men) and 1855 controls (60±11 years, 56% men) of European ancestry. PAD cases had a resting/postexercise ankle-brachial index ≤0.9, or history of lower extremity revascularization; controls had no history of PAD. We tested the association of common (defined as minor allele frequency ≥5%) variants with PAD assuming an additive genetic model with adjustment for age and sex. To identify low-frequency/rare variants (minor allele frequency <5%) associated with PAD, we conducted gene-level analyses using sequence kernel association test and permutation test. After Bonferroni correction, we found common variants in SH2B3, ABO, and ZEB2 to be associated with PAD ( P<4.5×10^-5). At the gene level, the strongest associations were for LPL and SH2B3. Conclusions- Targeted sequencing of 41 genomic regions associated with CHD revealed several common variants/genes to be associated with PAD, highlighting the basis of shared genetic susceptibility between CHD and PAD.

Transcriptome responses in blood reveal distinct biological pathways associated with arsenic exposure through drinking water in rural settings of Punjab, Pakistan

BACKGROUND

Groundwater Arsenic (As) contamination is a global public health concern responsible for various health implications and a neglected area of environmental health research in Pakistan. Because of interindividual differences in genetic predisposition, As-related health issues may not be equally distributed among the As-exposed population. However, till date, no studies have been conducted including multiple SNPs involved in As metabolism and disease risk using a linear mixed effect model approach to analyze peripheral blood transcriptomics results.

OBJECTIVES

In order to detect early responses on the gene expression level and to evaluate the impact of selected SNPs inferring disease risks associated with As exposure, we designed a systematic study to investigate blood transcriptomics profiles of 57 differentially exposed rural subjects living in drinking water As-contaminated settings of Lahore and Kasur districts in Punjab Province in southeast Pakistan. Exposure among the subjects was correlated with individual transcriptome responses applying urinary As profiles as the main biomarker for risk stratification.

METHODS

We performed whole genome gene expression analysis in blood of subjects using microarrays. Linear effect mixed models were applied for evaluating the combined impact of SNPs hypothetically increasing the risk for As exposure-induced health effects (GSTM1, GSTT1, As3MT, DNMT1, MTHFR, ERCC2 and EGFR).

RESULTS

Our findings confirmed important signaling, growth factor, cancer and other disease related pathways known to be associated with increased As exposure levels. In addition, upon implementing our integrative SNPs-based genetic risk factor, pathways associated with an increased risk of NAFLD and diabetes appeared significantly enhanced by down-regulation of genes NDUFV3, IKBKB, IL6R, ADIPOR1, PPARA, OGT and FOXO1.

CONCLUSION

We report the first comprehensive study applying state-of-the-art bioinformatics approaches to address multiple SNP-based inter-individual variability in adverse molecular responses among subjects exposed to drinking water As contamination in Pakistan thereby providing strong evidence of various gene expression targets associated with development of known As-related diseases.

REVIEW: Current understanding of the pathogenesis of Fuchs' endothelial corneal dystrophy

Fuchs' endothelial corneal dystrophy (FECD) is the most prominent reason for corneal-endothelial transplantations across the globe. The disease pathophysiology manifests through a combination of various genetic and non-heritable factors. This review provides a comprehensive list of known genetic players that cause FECD, and discusses the prominent pathological features that participate in disease progression, such as channel dysfunction, abnormal extracellular matrix deposition, RNA toxicity, oxidative stress, and apoptosis. Although current practices to correct visual acuity involve surgical intervention, this review also discusses the scope of various non-surgical therapeutics to remedy FECD.

Type 2 diabetes mellitus: distribution of genetic markers in Kazakh population

Background

Ethnic differences exist in the frequencies of genetic variations that contribute to the risk of common disease. This study aimed to analyse the distribution of several genes, previously associated with susceptibility to type 2 diabetes and obesity-related phenotypes, in a Kazakh population.

Methods

A total of 966 individuals belonging to the Kazakh ethnicity were recruited from an outpatient clinic. We genotyped 41 common single nucleotide polymorphisms (SNPs) previously associated with type 2 diabetes in other ethnic groups and 31 of these were in Hardy–Weinberg equilibrium. The obtained allele frequencies were further compared to publicly available data from other ethnic populations. Allele frequencies for other (compared) populations were pooled from the haplotype map (HapMap) database. Principal component analysis (PCA), cluster analysis, and multidimensional scaling (MDS) were used for the analysis of genetic relationship between the populations.

Results

Comparative analysis of allele frequencies of the studied SNPs showed significant differentiation among the studied populations. The Kazakh population was grouped with Asian populations according to the cluster analysis and with the Caucasian populations according to PCA. According to MDS, results of the current study show that the Kazakh population holds an intermediate position between Caucasian and Asian populations.

Conclusion

A high percentage of population differentiation was observed between Kazakh and world populations. The Kazakh population was clustered with Caucasian populations, and this result may indicate a significant Caucasian component in the Kazakh gene pool.

Blood Eosinophil Count and Metabolic, Cardiac and Pulmonary Outcomes: A Mendelian Randomization Study

Blood eosinophil count is associated with a variety of common complex outcomes in epidemiological observation. The aim of this study was to explore the causal association between determined blood eosinophil count and 20 common complex outcomes (10 metabolic, 6 cardiac, and 4 pulmonary). Through Mendelian randomization, we investigated genetic evidence for the genetically determined eosinophil in association with each outcomes using individual-level LifeLines cohort data (n = 13,301), where a weighted eosinophil genetic risk score comprising five eosinophil associated variants was created. We further examined the associations of the genetically determined eosinophil with those outcomes using summary statistics obtained from genome-wide association study consortia (6 consortia and 14 outcomes). Blood eosinophil count, by a 1-SD genetically increased, was not statistically associated with common complex outcomes in the LifeLines. Using the summary statistics, we showed that a higher genetically determined eosinophil count had a significant association with lower odds of obesity (odds ratio (OR) 0.81, 95% confidence interval (CI) [0.74, 0.89]) but not with the other traits and diseases. To conclude, an elevated eosinophil count is unlikely to be causally associated to higher risk of metabolic, cardiac, and pulmonary outcomes. Further studies with a stronger genetic risk score for eosinophil count may support these results.

Genetic loci associated with coronary artery disease harbor evidence of selection and antagonistic pleiotropy

Traditional genome-wide scans for positive selection have mainly uncovered selective sweeps associated with monogenic traits. While selection on quantitative traits is much more common, very few signals have been detected because of their polygenic nature. We searched for positive selection signals underlying coronary artery disease (CAD) in worldwide populations, using novel approaches to quantify relationships between polygenic selection signals and CAD genetic risk. We identified new candidate adaptive loci that appear to have been directly modified by disease pressures given their significant associations with CAD genetic risk. These candidates were all uniquely and consistently associated with many different male and female reproductive traits suggesting selection may have also targeted these because of their direct effects on fitness. We found that CAD loci are significantly enriched for lifetime reproductive success relative to the rest of the human genome, with evidence that the relationship between CAD and lifetime reproductive success is antagonistic. This supports the presence of antagonistic-pleiotropic tradeoffs on CAD loci and provides a novel explanation for the maintenance and high prevalence of CAD in modern humans. Lastly, we found that positive selection more often targeted CAD gene regulatory variants using HapMap3 lymphoblastoid cell lines, which further highlights the unique biological significance of candidate adaptive loci underlying CAD. Our study provides a novel approach for detecting selection on polygenic traits and evidence that modern human genomes have evolved in response to CAD-induced selection pressures and other early-life traits sharing pleiotropic links with CAD.

Polymorphisms associated with a tropical climate and root crop diet induce susceptibility to metabolic and cardiovascular diseases in Solomon Islands

The people of the Solomon Islands represent an Austronesian (AN)-speaking population's adaptation to a humid tropical environment and subsistence of tuberous crops. Genome-wide association studies (GWASs) of other populations (e.g. the Human Genome Diversity Project [HGDP]) have suggested the existence of genotypes adaptive to ecoregion, diet, and subsistence, and that those genotypes are also associated with metabolic and cardiovascular diseases. Recently, the incidence of non-communicable diseases has been increasing in the Solomon Islands. In the present study, we explored the association of genotypes adaptive to a tropical environment and tuberous crop diet with metabolic and cardiovascular conditions in rural and urban AN-speaking Melanesian and Micronesian populations of the Solomon Islands. A total of 561 participants were genotyped for single nucleotide polymorphisms (SNPs) potentially associated with a tropical environment (rs174570 and rs2237892) and a tuberous crop diet (rs162036, rs185819, and rs2722425). The results showed that the allele frequencies of the Solomon Islands populations adopted patterns similar to those in populations from other hot, tropical areas with a tuberous crop diet in previous studies. Furthermore, rs162036, rs185819, rs2237892, and rs2722425 were all strongly associated with one or more metabolic and cardiovascular conditions. The derived allele of rs2722425 (i.e. rs2722425-G) was significantly associated with an elevated LDL level (P = 0.000264) even after the significance level was adjusted for multiple testing (i.e., α = 0.0005). Our results suggest that the inhabitants of the Solomon Islands exhibit the effects of the tropical environment and tuberous crop diet on their allele frequencies, and that their susceptibility to metabolic and cardiovascular diseases is therefore considered to be associated with their environment and diet.

Basigin rs8259 Polymorphism Confers Decreased Risk of Chronic Heart Failure in a Chinese Population

Left ventricular remodeling is an essential risk factor contributing to the pathogenesis of chronic heart failure (CHF). Basigin (BSG) promotes cardiovascular inflammation and myocardial remodeling processes by induction of extracellular matrix metalloproteinases and inflammatory cytokines. BSG rs8259 polymorphism was associated with BSG expression and risk of acute coronary syndrome. Therefore, we investigated whether rs8259 polymorphism contributes to risk and prognosis of CHF in Chinese patients. In total 922 adult patients with CHF and 1107 matched healthy controls were enrolled. BSG rs8259 polymorphism was genotyped using PCR-restriction fragment length polymorphism. Whole blood BSG mRNA expression data from Genotype-Tissue Expression project was accessed. Evaluation of follow-up data was performed in only 15.2% (140) of the patients with CHF. BSG rs8259 TT genotype was associated with a decreased risk of CHF (OR = 0.83, 95% CI = 0.72–0.96, p = 0.010), especially in patients with hypertension (OR = 0.80, 95% CI = 0.68–0.95, p = 0.011) and coronary heart disease (OR = 0.81, 95% CI = 0.69–0.96, p = 0.013) after adjustment for multiple cardiovascular risk factors. Rs8259 T allele was associated with decreased BSG mRNA in whole blood from 338 healthy normal donors (p = 1.31 × 10⁻⁶). However, rs8259 polymorphism failed to exhibit an association with cardiovascular mortality (p = 0.283). BSG rs8259 polymorphism may contribute to decreased risk of CHF in a Chinese Han population.

Population Structure of UK Biobank and Ancient Eurasians Reveals Adaptation at Genes Influencing Blood Pressure

Analyzing genetic differences between closely related populations can be a powerful way to detect recent adaptation. The very large sample size of the UK Biobank is ideal for using population differentiation to detect selection and enables an analysis of the UK population structure at fine resolution. In this study, analyses of 113,851 UK Biobank samples showed that population structure in the UK is dominated by five principal components (PCs) spanning six clusters: Northern Ireland, Scotland, northern England, southern England, and two Welsh clusters. Analyses of ancient Eurasians revealed that populations in the northern UK have higher levels of Steppe ancestry and that UK population structure cannot be explained as a simple mixture of Celts and Saxons. A scan for unusual population differentiation along the top PCs identified a genome-wide-significant signal of selection at the coding variant rs601338 in FUT2 (p = 9.16 × 10-9). In addition, by combining evidence of unusual differentiation within the UK with evidence from ancient Eurasians, we identified genome-wide-significant (p = 5 × 10-8) signals of recent selection at two additional loci: CYP1A2-CSK and F12. We detected strong associations between diastolic blood pressure in the UK Biobank and both the variants with selection signals at CYP1A2-CSK (p = 1.10 × 10-19) and the variants with ancient Eurasian selection signals at the ATXN2-SH2B3 locus (p = 8.00 × 10-33), implicating recent adaptation related to blood pressure.

Evidence of Polygenic Adaptation in the Systems Genetics of Anthropometric Traits

Many signals of natural selection have been identified in the human genome. However, except for some single-locus mechanisms, most molecular processes generating these adaptation signals are still unknown. We developed an approach that integrates datasets related to genome-wide association studies (GWAS) with information about systems biology and genetic signatures of natural selection to identify evidence of polygenic adaptation. Specifically, we focused on five anthropometric measurements: body mass index (BMI), height, waist-to-hip ratio adjusted for BMI (WHR), and waist circumference adjusted for BMI (WC), and sex differences for WHR and WC. We performed an enrichment analysis for signals of natural selection in protein interaction networks associated with anthropometric traits in European populations. The adaptation signals-enriched gene networks associated highlighted epistatic interactions in the context of polygenic selection for the investigated traits. These polygenic mechanisms indicated intriguing selective mechanisms related to the anthropometric traits: adult locomotory behavior for BMI, infection resistance for height, interplay between lipid transport and immune systems for WHR, and female-specific polygenic adaptation for WHR and WC. In conclusion, we observed evidence of polygenic adaptation in the context of systems genetics of anthropometric traits that indicates polygenic mechanisms related to the natural selection in European populations.

Population structure from NOS genes correlates with geographical differences in coronary incidence across Europe

OBJECTIVES

The population analysis of cardiovascular risk and non-risk genetic variation can help to identify adaptive or random demographic processes that shaped coronary incidence variation across geography.

MATERIAL AND METHODS

In this study, 114 single nucleotide polymorphisms and 17 tandem repeat polymorphisms from Nitric Oxide Synthases (NOS) regions were analyzed in 1686 individuals from 35 populations from Europe, North Africa, and the Middle East. NOS genes encode for key enzymes on nitric oxide availability, which is involved in several cardiovascular processes. These genetic variations were used to test for selection and to infer the population structure of NOS regions. Moreover, we tested whether the variation in the incidence of coronary events and in the levels of classical risk factors in 11 of these European populations could be explained by the population structure estimates.

RESULTS

Our results supported, first, the absence of clear signs of selection for NOS genetic variants associated with cardiovascular diseases, and second, the presence of a continuous genetic pattern of variation across European and North African populations without a Mediterranean barrier for gene flow. Finally, population structure estimates from NOS regions are closely correlated with coronary event rates and classical risk parameters (explaining 39-98%) among European populations.

CONCLUSION

Our results reinforce the hypothesis that genetic bases of cardiovascular diseases and associated complex phenotypes could be geographically shaped by random demographic processes.

The Impact of Evolutionary Driving Forces on Human Complex Diseases: A Population Genetics Approach

Investigating the molecular evolution of human genome has paved the way to understand genetic adaptation of humans to the environmental changes and corresponding complex diseases. In this review, we discussed the historical origin of genetic diversity among human populations, the evolutionary driving forces that can affect genetic diversity among populations, and the effects of human movement into new environments and gene flow on population genetic diversity. Furthermore, we presented the role of natural selection on genetic diversity and complex diseases. Then we reviewed the disadvantageous consequences of historical selection events in modern time and their relation to the development of complex diseases. In addition, we discussed the effect of consanguinity on the incidence of complex diseases in human populations. Finally, we presented the latest information about the role of ancient genes acquired from interbreeding with ancient hominids in the development of complex diseases.

Potential Signals of Natural Selection in the Top Risk Loci for Coronary Artery Disease: 9p21 and 10q11

BACKGROUND

Coronary artery disease (CAD) is a complex disease and the leading cause of death in the world. Populations of different ancestry do not always share the same risk markers. Natural selective processes may be the cause of some of the population differences detected for specific risk mutations.

OBJECTIVE

In this study, 384 single nucleotide polymorphisms (SNPs) located in four genomic regions associated with CAD (1p13, 1q41, 9p21 and 10q11) are analysed in a set of 19 populations from Europe, Middle East and North Africa and also in Asian and African samples from the 1000 Genomes Project. The aim of this survey is to explore for the first time whether the genetic variability in these genomic regions is better explained by demography or by natural selection.

RESULTS

The results indicate significant differences in the structure of genetic variation and in the LD patterns among populations that probably explain the population disparities found in markers of susceptibility to CAD.

CONCLUSIONS

The results are consistent with potential signature of positive selection in the 9p21 region and of balancing selection in the 9p21 and 10q11. Specifically, in Europe three CAD risk markers in the 9p21 region (rs9632884, rs1537371 and rs1333042) show consistent signals of positive selection. The results of this study are consistent with a potential selective role of CAD in the configuration of genetic diversity in current human populations.

The genetic basis of peripheral arterial disease: current knowledge, challenges, and future directions

Several risk factors for atherosclerotic peripheral arterial disease (PAD), such as dyslipidemia, diabetes mellitus, and hypertension, are heritable. However, predisposition to PAD may be influenced by genetic variants acting independently of these risk factors. Identification of such genetic variants will provide insights into underlying pathophysiologic mechanisms and facilitate the development of novel diagnostic and therapeutic approaches. In contrast to coronary heart disease, relatively few genetic variants that influence susceptibility to PAD have been discovered. This may be, in part, because of greater clinical and genetic heterogeneity in PAD. In this review, we (1) provide an update on the current state of knowledge about the genetic basis of PAD, including results of family studies and candidate gene, linkage as well as genome-wide association studies; (2) highlight the challenges in investigating the genetic basis of PAD and possible strategies to overcome these challenges; and (3) discuss the potential of genome sequencing, RNA sequencing, differential gene expression, epigenetic profiling, and systems biology in increasing our understanding of the molecular genetics of PAD.

L-Arginine and SDMA Serum Concentrations Are Associated with Subclinical Atherosclerosis in the Study of Health in Pomerania (SHIP)

Objective

Even though ˪-arginine (ARG) derivatives can predict cardiovascular mortality, their role as atherosclerotic biomarkers is unclear. We tested the hypothesis if asymmetric dimethylarginine (ADMA), symmetric dimethylarginine (SDMA) and the sum of both (DMA) are positively, while ARG and ARG/ADMA ratio are inversely associated with carotid intima-media thickness (cIMT) and atherosclerotic plaque in the carotid artery.

Approach and Results

Cross-sectional data of 1999 subjects (age: 45–81 years; 48.2% ♀) from the population-based Study of Health in Pomerania (SHIP-0) was used. Analysis of variance and logistic regression models were calculated and all adjusted models were corrected for sex, age, smoking status, waist-to-hip ratio and estimated glomerular filtration rate. Increased cIMT (>75^th age-sex specific percentile) was found in 517 subjects (25.7%), while atherosclerotic plaque was detected in 1413 subjects (70.4%). SDMA tertiles were significantly positively associated with larger cIMT among subjects with high SDMA levels [>66^th: 0.82 (95%-CI 0.80; 0.85) mm]. High SDMA levels were related to a higher odds ratio (OR) of increased cIMT [OR 1.39 (95%-CI 1.08; 1.79)]. Furthermore, ARG was positively associated with atherosclerotic plaques [OR 1.41 (95%-CI 1.07; 1.85)]. No relation was found for ADMA and atherosclerosis.

Conclusions

In conclusion, the hypothesis of a positive association between SDMA with an increased cIMT was confirmed. Unexpectedly, ARG was positively related to atherosclerotic plaque. In view of these inconsistent findings, the impact of ARG derivatives as atherosclerotic biomarkers deserves further research.

Genetic link of type 1 diabetes susceptibility loci with rheumatoid arthritis in Pakistani patients

Rheumatoid arthritis (RA) and type 1 diabetes (T1D) are two autoimmune disorders that have been reported to co-occur in the same subjects or in different subjects from the same family. This suggests the sharing of disease susceptibility loci between RA and T1D. This study was aimed to find out such susceptibility loci that are common in both T1D and RA in Pakistani population. A total of 366 Pakistanis comprising related and unrelated RA cases and controls were recruited. Blood samples were collected from all patients followed by DNA isolation. Thirty-one single-nucleotide polymorphisms (SNPs) previously reported to be associated with T1D were genotyped in RA cases and controls using TaqMan SNP genotyping assays. Data was analyzed using FamCC software. We have identified seven SNP associations that survived multiple testing corrections using false discovery rate: SKAP2/rs7804356 (p = 2.47E-04), GLIS3/rs7020673 (p = 2.86E-04), GSDMB/rs2290400 (p = 23.48E-04), BACH2/rs11755527 (p = 9.16E-04), C6orf173/ rs9388489 (p = 3.11E-03), PRKCQ/DKFZp667F0711/ rs947474 (p = 4.53E-03), and DLK1/ rs941576 (p = 9.51E-03). Our results support the presence of overlapping loci between RA and T1D in Pakistani patients.

The ATXN2-SH2B3 locus is associated with peripheral arterial disease: an electronic medical record-based genome-wide association study

OBJECTIVES

In contrast to coronary heart disease (CHD), genetic variants that influence susceptibility to peripheral arterial disease (PAD) remain largely unknown.

BACKGROUND

We performed a two-stage genomic association study leveraging an electronic medical record (EMR) linked-biorepository to identify genetic variants that mediate susceptibility to PAD.

METHODS

PAD was defined as a resting/post-exercise ankle-brachial index (ABI) ≤0.9 or ≥1.4 and/or history of lower extremity revascularization. Controls were patients without history of PAD. In Stage I we performed a genome-wide association analysis adjusting for age and sex, of 537, 872 SNPs in 1641 PAD cases (66 ± 11 years, 64% men) and 1604 control subjects (61 ± 7 year, 60% men) of European ancestry. In Stage II we genotyped the top 48 SNPs that were associated with PAD in Stage I, in a replication cohort of 740 PAD cases (70 ± 11 year, 63% men) and 1051 controls (70 ± 12 year, 61% men).

RESULTS

The SNP rs653178 in the ATXN2-SH2B3 locus was significantly associated with PAD in the discovery cohort (OR = 1.23; P = 5.59 × 10(-5)), in the replication cohort (OR = 1.22; 8.9 × 10(-4)) and in the combined cohort (OR = 1.22; P = 6.46 × 10(-7)). In the combined cohort this SNP remained associated with PAD after additional adjustment for cardiovascular risk factors including smoking (OR = 1.22; P = 2.15 × 10(-6)) and after excluding patients with ABI > 1.4 (OR = 1.24; P = 3.98 × 10(-7)). The SNP is in near-complete linkage disequilibrium (LD) (r (2) = 0.99) with a missense SNP (rs3184504) in SH2B3, a gene encoding an adapter protein that plays a key role in immune and inflammatory response pathways and vascular homeostasis. The SNP has pleiotropic effects and has been previously associated with multiple phenotypes including myocardial infarction.

CONCLUSIONS

Our findings suggest that the ATXN2-SH2B3 locus influences susceptibility to PAD.

Signatures of natural selection on genetic variants affecting complex human traits

It has recently been hypothesized that polygenic adaptation, resulting in modest allele frequency changes at many loci, could be a major mechanism behind the adaptation of complex phenotypes in human populations. Here we leverage the large number of variants that have been identified through genome-wide association (GWA) studies to comprehensively study signatures of natural selection on genetic variants associated with complex traits. Using population differentiation based methods, such as FST and phylogenetic branch length analyses, we systematically examined nearly 1300 SNPs associated with 38 complex phenotypes. Instead of detecting selection signatures at individual variants, we aimed to identify combined evidence of natural selection by aggregating signals across many trait associated SNPs. Our results have revealed some general features of polygenic selection on complex traits associated variants. First, natural selection acting on standing variants associated with complex traits is a common phenomenon. Second, characteristics of selection for different polygenic traits vary both temporarily and geographically. Third, some studied traits (e.g. height and urate level) could have been the primary targets of selection, as indicated by the significant correlation between the effect sizes and the estimated strength of selection in the trait associated variants; however, for most traits, the allele frequency changes in trait associated variants might have been driven by the selection on other correlated phenotypes. Fourth, the changes in allele frequencies as a result of selection can be highly stochastic, such that, polygenic adaptation may accelerate differentiation in allele frequencies among populations, but generally does not produce predictable directional changes. Fifth, multiple mechanisms (pleiotropy, hitchhiking, etc) may act together to govern the changes in allele frequencies of genetic variants associated with complex traits.

Genetic epidemiology of type 2 diabetes and cardiovascular diseases in Africa

The burdens of type 2 diabetes (T2D) and cardiovascular diseases (CVD) are increasing in Africa. T2D and CVD are the result of the complex interaction between inherited characteristics, lifestyle, and environmental factors. The epidemic of obesity is largely behind the exploding global incidence of T2D. However, not all obese individuals develop diabetes and positive family history is a powerful risk factor for diabetes and CVD. Recent implementations of high throughput genotyping and sequencing approaches have advanced our understanding of the genetic basis of diabetes and CVD by identifying several genomic loci that were not previously linked to the pathobiology of these diseases. However, African populations have not been adequately represented in these global genomic efforts. Here, we summarize the state of knowledge of the genetic epidemiology of T2D and CVD in Africa and highlight new genomic initiatives that promise to inform disease etiology, public health and clinical medicine in Africa.

Human leukocyte antigen alleles, genotypes and haplotypes frequencies in renal transplant donors and recipients from West Central India

BACKGROUND:

Human leukocyte antigen (HLA) is comprised of a highly polymorphic set of genes which determines the histocompatibility of organ transplantation. The present study was undertaken to identify HLA class I and class II allele, genotype and haplotype frequencies in renal transplant recipients and donors from West Central India.

MATERIALS AND METHODS:

HLA typing was carried out using Polymerase Chain Reaction-Sequence Specific Primer in 552 live related and unrelated renal transplant recipients and donors.

RESULTS:

The most frequent HLA class I and class II alleles and their frequencies in recipients were HLA-AFNx0101 (0.1685) and AFNx0102 (0.1649), HLA-BFNx0135 (0.1322), and HLA-DR beta 1 (DRB 1)FNx0115 (0.2192), whereas in donors, these were HLA-AFNx0102 (0.1848) and AFNx0101 (0.1667), HLA-BFNx0135 (0.1359), and HLA-DRB1FNx0115 (0.2409). The two-locus haplotype statistical analysis revealed HLA-AFNx0102-B61 as the most common haplotype with the frequency of 0.0487 and 0.0510 in recipients and donors, respectively. Further, among the three locus haplotypes HLA-AFNx0133-BFNx0144-DRB1FNx0107 and HLA-AFNx0102-BFNx0161-DRB1FNx0115 were the most common haplotypes with frequencies 0.0362 and 0.0326, respectively in recipients and 0.0236 and 0.0323, respectively in donors. Genotype frequency revealed a high prevalence of genotype HLA-AFNx0102/AFNx0124 in recipients (0.058) compared to donors (0.0109) whereas low prevalence of HLA-AFNx0101/AFNx0102 in recipients (0.0435) than in donors (0.0797). The phylogenetic and principal component analysis of HLA allele and haplotype frequency distribution revealed genetic similarities of various ethnic groups. Further, case control analysis provides preliminary evidence of association of HLA-A genotype (P < 0.05) with renal failure.

CONCLUSION:

This study will be helpful in suitable donor search besides providing valuable information for population genetics and HLA disease association analysis.

Polymorphisms in Fatty Acid Desaturase (FADS) Gene Cluster: Effects on Glycemic Controls Following an Omega-3 Polyunsaturated Fatty Acids (PUFA) Supplementation

Changes in desaturase activity are associated with insulin sensitivity and may be associated with type 2 diabetes mellitus (T2DM). Polymorphisms (SNPs) in the fatty acid desaturase (FADS) gene cluster have been associated with the homeostasis model assessment of insulin sensitivity (HOMA-IS) and serum fatty acid composition. Objective: To investigate whether common genetic variations in the FADS gene cluster influence fasting glucose (FG) and fasting insulin (FI) responses following a 6-week n-3 polyunsaturated fatty acids (PUFA) supplementation. Methods: 210 subjects completed a 2-week run-in period followed by a 6-week supplementation with 5 g/d of fish oil (providing 1.9 g–2.2 g of EPA + 1.1 g of DHA). Genotyping of 18 SNPs of the FADS gene cluster covering 90% of all common genetic variations (minor allele frequency ≥ 0.03) was performed. Results: Carriers of the minor allele for rs482548 (FADS2) had increased plasma FG levels after the n-3 PUFA supplementation in a model adjusted for FG levels at baseline, age, sex, and BMI. A significant genotype*supplementation interaction effect on FG levels was observed for rs482548 (p = 0.008). For FI levels, a genotype effect was observed with one SNP (rs174456). For HOMA-IS, several genotype*supplementation interaction effects were observed for rs7394871, rs174602, rs174570, rs7482316 and rs482548 (p = 0.03, p = 0.01, p = 0.03, p = 0.05 and p = 0.07; respectively). Conclusion: Results suggest that SNPs in the FADS gene cluster may modulate plasma FG, FI and HOMA-IS levels in response to n-3 PUFA supplementation.

Coronary artery disease in Bangladesh: a review

Coronary artery disease (CAD) is an increasingly important medical and public health problem, and is the leading cause of mortality in Bangladesh. Like other South Asians, Bangladeshis are unduly prone to develop CAD, which is often premature in onset, follows a rapidly progressive course and angiographically more severe. The underlying pathophysiology is poorly understood. Genetic predisposition, high prevalence of metabolic syndrome and conventional risk factors play important role. Lifestyle related factors, including poor dietary habits, excess saturated and trans fat, high salt intake, and low-level physical activity may be important as well. Some novel risk factors, including hypovitaminosis D, arsenic contamination in water and food-stuff, particulate matter air pollution may play unique role. At the advent of the new millennium, we know little about our real situation. Large scale epidemiological, genetic and clinical researches are needed to explore the different aspects of CAD in Bangladesh.

The effect of copy number variation in the phase II detoxification genes UGT2B17 and UGT2B28 on colorectal cancer risk

BACKGROUND

Genetic polymorphisms in combination with the Western-style diet, physical inactivity, smoking, excessive alcohol consumption, and obesity have been hypothesized to affect colorectal cancer (CRC) risk. Metabolizers of environmental carcinogenic and endogenous compounds affecting CRC risk include the phase II detoxification UDP-glucuronosyltransferase (UGT) enzymes UGT2B17 and UGT2B28, which are 2 of the most commonly deleted genes in the genome.

METHODS

To study the effect of UGT2B17 and UGT2B28 copy number variation (CNV) on CRC risk, 665 Caucasian CRC cases and 621 Caucasian controls were genotyped who had completed extensive demographics and lifestyle questionnaires.

RESULTS

A significant association between the UGT2B17 deletion genotype (0/0) and decreased CRC risk was found when the entire population was analyzed (P = .044). Stratification by sex yielded a decreased risk (P = .020) in men with the UGT2B17 deletion (0/0), but no association was observed in women (P = .724). A significant association between UGT2B17 (0/0) and decreased risk for rectal (P = .0065) but not colon cancer was found. No significant association was found between UGT2B28 CNV and CRC risk.

CONCLUSIONS

The UGT2B17 deletion genotype (0/0) was associated with a decreased CRC risk in a Caucasian population. After sex stratification, the association was observed in men but not in women, which is consistent with previous findings that men have higher UGT2B17 expression and activity than women. Because UGT2B17 metabolizes certain nonsteroidal anti-inflammatory drugs and flavonoids with antioxidative properties, individuals with a gene deletion may have higher levels of these protective dietary components.

DRD4 gene and obsessive compulsive disorder: do symptom dimensions have specific genetic correlates?

INTRODUCTION

The dopamine D4 receptor (DRD4) is a promising candidate gene in obsessive compulsive disorder (OCD). A 48-bp variable number of tandem repeats (VNTR) sequence in exon 3 has been studied previously, and alleles containing 2-11 repeats (2R-11R) have been identified. We investigated the association of DRD4 VNTR polymorphism with OCD and its relationship with various clinical parameters (age of onset, gender, family history, co-morbidity, factor-analyzed symptom dimensions and insight).

METHODOLOGY

One hundred and seventy three South Indian OCD patients (DSM-IV) recruited from a specialty OCD clinic were evaluated using the Yale-Brown obsessive compulsive scale (YBOCS), YBOCS item-11 for insight, Mini International Neuropsychiatric Interview (MINI) plus, tic disorder subsection of the MINI-KID and Clinical Global Impression scale. 201 healthy controls were evaluated using MINI plus. All subjects were genotyped for the DRD4 VNTR polymorphism.

RESULTS

Genotype frequencies did not deviate significantly from the Hardy-Weinberg equilibrium. Case-control association analysis revealed that the 7R allele frequency was significantly greater in OCD patients than controls. This difference was restricted to the women subsample when performing the gender sub-analysis. Among other clinical variables examined, factor 3 (symmetry) was associated with presence of 2R allele. Linear regression analysis confirmed the association of symmetry dimension with the 2R allele (Beta=0.23, t=2.96, p=0.004, CI=0.19-0.95).

CONCLUSIONS

Our data provides further evidence that DRD4 VNTR polymorphism is associated with OCD. Furthermore, the presence of the 2R allele was significantly associated with the symmetry dimension. This dimension may represent a more homogeneous subtype of OCD with a genetic etiology.

Adaptive genetic variation and population differences

Since the expansion of modern humans (Homo sapiens) from Africa to the rest of the world between 50,000 and 100,000 years ago, the human genome has been shaped not only by demographic history but also by adaptation to local environments, including regional climate, landscape, food sources, culture, and pathogens. Genetic differences among populations interact with environmental factors, such as diet and lifestyle, leading to differences in nutrient metabolism, which translate into differences in susceptibility to a variety of diseases. Individuals from different populations sharing the same environments can exhibit differences in disease risk, as do individuals from the same population living in various regions of the globe. Therefore, it is important to understand how adaptive genetic variations interact with environments to influence health. This knowledge will provide a broad foundation for designing experiments and approaches in nutrigenomics research and strengthening the knowledge base for dietary recommendations for disease prevention. The objectives of this chapter are to (1) understand the methodology employed in examining adaptive genetic variation across populations, (2) establish the importance of adaptive genetic variation to human health, and (3) discuss the implications for nutrigenomics research and disease prevention.