Mendelian randomization as applied to coronary heart disease, including recent advances incorporating new technology

Mendelian randomization in pharmacogenomics: The unforeseen potentials

Mendelian randomization (MR) is an epidemiological method that uses genetic variants to proxy an exposure predicting its causal association with an outcome. It occupies a valuable niche between observational studies and randomized trials. MR applications expanded lately, facilitated by the availability of big data, to include disease risk causation prediction, supporting evidence of prior observational data, identifying new drug targets, and drug repurposing. Concurrently, the last decade witnessed the growth of pharmacogenomics (PGx) research as a cornerstone in precision medicine. PGx research, conducted at discovery and implementation levels, resulted in validated PGx biomarkers and tests. Despite many clinically relevant PGx associations that could be translated into clinical applications, worldwide implementation is lagging far behind. The current review examines the intersection zones between MR and PGx research. MR can provide supporting evidence that allows generalizing PGx findings supporting its implementation. Interchangeability, PGx research can fuel MR studies with libraries of genetic variants of validated biological relevance. Furthermore, PGx and MR exhibit a synergistic relationship in drug discovery that can accelerate identifying new targets and repurposing old drugs. Interdisciplinary research applied by PGx researchers, epidemiologists with MR experience, and data scientists' collaborations can unlock unforeseen opportunities in accelerating precision medicine acquisition.

East Asian variant aldehyde dehydrogenase type 2 genotype exacerbates ischemia/reperfusion injury with ST-elevation myocardial infarction in men: possible sex differences

Mitochondrial aldehyde dehydrogenase 2 (ALDH2) detoxifies toxic aldehydes generated during ischemia/reperfusion (I/R) injury in ST-elevation myocardial infarction (STEMI). The deficient variant ALDH2 genotype (ALDH2*2) is prevalent among East Asians. Whether ALDH2*2 exacerbates I/R injury of in patients with STEMI is not known. The study subjects comprised 218 Japanese patients with STEMI (158 men and 60 women, mean age 67.9 ± 11.9) who underwent successful percutaneous coronary intervention. Of these, 120 (55.0%) were the carriers of variant ALDH2*2 and 98 (45.0%) those of wild ALDH2*1/*1 on genotyping. There were no differences in clinical characteristics between the ALDH2*2 and ALDH2*1/*1 group except lower alcohol habit (14.2% vs 46.3%, P < 0.001) in the ALDH2*2 group. The peak plasma levels of creatine phosphokinase myocardial binding (CKMB), a marker of myocardial injury, however, were significantly higher in the patients with ALDH2*2 than in those with ALDH2*1/*1 [a median 275.0 (175.8-407.5) vs 177.5 (126.9-344.3) U/L, P = 0.001] among men but not among women (P = 0.811). There was a significant interaction between men (male sex) and ALDH2*2 for I/R injury (χ2 = 4.425, P = 0.040). The variant ALDH2*2 was associated with more severe I/R injury than the wild ALDH2*1/*1 in STEMI patients in men with possible sex differences.

In-depth Mendelian randomization analysis of causal factors for coronary artery disease

Selecting a set of valid genetic variants is critical for Mendelian randomization (MR) to correctly infer risk factors causing a disease. We here developed a method for selecting genetic variants as valid instrumental variables for inferring risk factors causing coronary artery disease (CAD). Using this method, we selected two sets of single-nucleotide-polymorphism (SNP) genetic variants (SNP338 and SNP363) associated with each of the three potential risk factors for CAD including low density lipoprotein cholesterol (LDL-c), high density lipoprotein cholesterol (HDL-c) and triglycerides (TG) from two independent GWAS datasets. We performed in-depth multivariate MR (MVMR) analyses and the results from both datasets consistently showed that LDL-c was strongly associated with increased risk for CAD (β = 0.396,OR = 1.486 per 1 SD (equivalent to 38 mg/dL), 95CI = (1.38, 1.59) in SNP338; and β = 0.424, OR = 1.528 per 1 SD, 95%CI = (1.42, 1.65) in SNP363); HDL-c was strongly associated with reduced risk for CAD (β = −0.315, OR = 0.729 per 1 SD (equivalent to 16 mg/dL), 95CI = (0.68, 0.78) in SNP338; and β = −0.319, OR = 0.726 per 1 SD, 95%CI = (0.66, 0.80), in SNP363). In case of TG, when using the full datasets, an increased risk for CAD (β = 0.184, OR = 1.2 per 1 SD (equivalent to 89 mg/dL), 95%CI = (1.12, 1.28) in SNPP338; and β = 0.207, OR = 1.222 per 1 SD, 95%CI = (1.10, 1.36) in SNP363) was observed, while using partial datasets that contain shared and unique SNPs showed that TG is not a risk factor for CAD. From these results, it can be inferred that TG itself is not a causal risk factor for CAD, but it’s shown as a risk factor due to pleiotropic effects associated with LDL-c and HDL-c SNPs. Large-scale simulation experiments without pleiotropic effects also corroborated these results.

East Asians Variant Mitochondrial Aldehyde Dehydrogenase 2 Genotype Exacerbates Nitrate Tolerance in Patients With Coronary Spastic Angina

BACKGROUND

Aldehyde dehydrogenase 2 (ALDH2) plays a central role in the biotransformation of glyceryl trinitrate (GTN) or nitroglycerin, which is widely used for the treatment of coronary artery disease (CAD). The deficient variant ALDH2 genotype (ALDH2*2) is prevalent among East Asians. This study examined whether there are differences in nitroglycerine-mediated dilation (NMD) and flow-mediated dilation (FMD) response between wildALDH2*1/*1and variantALDH2*2patients with CAD.Methods and Results:The study subjects comprised 55 coronary spastic angina (CSA) patients, confirmed by coronary angiography and intracoronary injection of acetylcholine (42 men and 13 women, mean age 68.0±9.0 years). They underwent NMD and FMD tests in the morning before and after continuous transdermal GTN administration for 48 h. NMD was lower at baseline inALDH2*2than in theALDH2*1/*1group (P=0.0499) and decreased significantly in both groups (P<0.0001 and P<0.0001, respectively) after GTN, with significantly lower levels in theALDH2*2group (P=0.0002). FMD decreased significantly in bothALDH2*1/*1andALDH2*2groups (P<0.0001and P=0.0002, respectively) after continuous GTN administration, with no significant differences between the 2 groups both before and after GTN.

CONCLUSIONS

Continuous administration of GTN produced endothelial dysfunction as well as nitrate tolerance in bothALDH2*1/1andALDH2*2patients with CSA.ALDH2*2attenuated GTN response and exacerbated GTN tolerance, but not endothelial dysfunction, as compared toALDH2*1/*1in patients with CSA.

Association of East Asian Variant Aldehyde Dehydrogenase 2 Genotype (ALDH2*2*) with Coronary Spasm and Acute Myocardial Infarction

Coronary spasm plays an important role in the pathogenesis of ischemic heart disease, including angina pectoris, acute myocardial infarction (AMI), silent myocardial ischemia, and sudden death. The prevalence of coronary spasm is higher among East Asians probably due to genetic as well as environmental factors. ALDH2 eliminates toxic aldehydes including 4-hydroxy-2-nonenal (4-HNE) derived from lipid peroxidation and acrolein in tobacco smoking as well as ethanol-derived acetaldehyde and thereby protects tissues and cells from oxidative damage. Deficient variant ALDH2*2 genotype is prevalent among East Asians and is a significant risk factor for both coronary spasm and AMI through accumulation of toxic aldehydes, thereby contributing to oxidative stress, endothelial damage, vasoconstriction, and thrombosis. Toxic aldehydes are thus identified as risk factors to be targeted for the treatment of coronary spasm and AMI.

Are toll-like receptors potential drug targets for atherosclerosis? Evidence from genetic studies to date

Low-density lipoprotein cholesterol lowering, most notably via statin therapy, has successfully reduced the burden of coronary artery disease (CAD) in recent decades. However, the residual risk remaining even after aggressive lipid lowering has renewed interest in alternative targets. Anti-inflammatory drugs are thought to have much potential in this context, but side effects associated with long-term use of conventional anti-inflammatories, such as NSAIDs and glucocorticoids, preclude their use as preventive agents for CAD. Evidence from epidemiological studies and murine models of atherosclerosis suggests that toll-like receptors (TLRs) may have utility as targets for more focused anti-inflammatories, but it remains unclear if this pathway is causally related to CAD in man. Here, we review recent insight into this question gained from genetic studies of cardiovascular risk and innate immune function, focussing on the potential of Mendelian randomisation approaches based on intracellular-signalling pathways to identify and prioritise targets for drug development.

Association of lactase persistence genotype with milk consumption, obesity and blood pressure: a Mendelian randomization study in the 1982 Pelotas (Brazil) Birth Cohort, with a systematic review and meta-analysis

Background: Milk intake has been associated with lower blood pressure (BP) in observational studies, and randomized controlled trials suggested that milk-derived tripeptides have BP-lowering effects. Milk intake has also been associated with body mass index (BMI). Nevertheless, it is unclear whether increasing milk consumption would reduce BP in the general population.

Methods: We investigated the association of milk intake with obesity and BP using genetically-defined lactase persistence (LP) based on the rs4988235 polymorphism in a Mendelian randomization design in the 1982 Pelotas (Southern Brazil) Birth Cohort. These results were combined with published reports identified through a systematic review using meta-analysis.

Results: In the 1982 Pelotas Birth Cohort, milk intake was 42 [95% confidence interval (CI): 18; 67) ml/day higher in LP individuals. In conventional observational analysis, each 1-dl/day increase in milk intake was associated with −0.26 (95% CI: −0.33; −0.19) kg/m² in BMI and −0.31 (95% CI: −0.46; −0.16) and -0.35 (95% CI: −0.46; −0.23) mmHg in systolic and diastolic BP, respectively. These results were not corroborated when analysing LP status, but confidence intervals were large. In random effects meta-analysis, LP individuals presented higher BMI [0.17 (95% CI: 0.07; 0.27) kg/m²] and higher odds of overweight-obesity [1.09 (95% CI: 1.02; 1.17)]. There were no reliable associations for BP.

Conclusions: Our study supports that LP is positively associated with obesity, suggesting that the negative association of milk intake with obesity is likely due to limitations of conventional observational studies. Our findings also do not support that increased milk intake leads to lower BP.

Variant Aldehyde Dehydrogenase 2 (ALDH2*2) Is a Risk Factor for Coronary Spasm and ST-Segment Elevation Myocardial Infarction

BACKGROUND

Mitochondrial aldehyde dehydrogenase 2 (ALDH2) plays a key role in removing toxic aldehydes. Deficient variant ALDH2*2 genotype is prevalent in up to 40% of the East Asians and reported to be associated with acute myocardial infarction (AMI). To elucidate the mechanisms underlying the association of ALDH2*2 with AMI, we compared the clinical features of AMI patients with ALDH2*2 to those with wild-type ALDH2*1/*1.

METHODS AND RESULTS

The study subjects consisted of 202 Japanese patients with acute ST-segment elevation myocardial infarction (STEMI) (156 men and 46 women; mean age, 67.3±12.0) who underwent primary percutaneous coronary intervention (PCI). In 85 patients, provocation test for coronary spasm was also done 6 month post-PCI. ALDH2 genotyping was performed by direct application of the TaqMan polymerase chain system. Of the 202 patients, 103 (51.0%) were carriers of ALDH2*2 and 99 (49.0%) those of ALDH2*1/*1. There were no differences in clinical features between ALDH2*2 and ALDH2*1/*1 carrier groups except higher frequencies of coronary spasm and alcohol flush syndrome (AFS) (88.6% vs 56.1%; P=0.001 and 94.3% vs 17.6%; P<0.001), less-frequent alcohol habit (14.6% vs 51.5%; P<0.001), and higher peak plasma creatine phophokinase levels (2224 vs 1617 mg/dL; P=0.002) in the ALDH2*2 than the ALDH2*1/*1 carrier group.

CONCLUSIONS

ALDH2*2 is prevalent (51.0%) among Japanese STEMI patients, and those with ALDH2*2 had higher frequencies of coronary spasm and AFS and more-severe myocardial injury compared to those with ALDH2*1/*1.

Association of Lipid-Related Genetic Variants with the Incidence of Atrial Fibrillation: The AFGen Consortium

BACKGROUND

Several studies have shown associations between blood lipid levels and the risk of atrial fibrillation (AF). To test the potential effect of blood lipids with AF risk, we assessed whether previously developed lipid gene scores, used as instrumental variables, are associated with the incidence of AF in 7 large cohorts.

METHODS

We analyzed 64,901 individuals of European ancestry without previous AF at baseline and with lipid gene scores. Lipid-specific gene scores, based on loci significantly associated with lipid levels, were calculated. Additionally, non-pleiotropic gene scores for high-density lipoprotein cholesterol (HDLc) and low-density lipoprotein cholesterol (LDLc) were calculated using SNPs that were only associated with the specific lipid fraction. Cox models were used to estimate the hazard ratio (HR) and 95% confidence intervals (CI) of AF per 1-standard deviation (SD) increase of each lipid gene score.

RESULTS

During a mean follow-up of 12.0 years, 5434 (8.4%) incident AF cases were identified. After meta-analysis, the HDLc, LDLc, total cholesterol, and triglyceride gene scores were not associated with incidence of AF. Multivariable-adjusted HR (95% CI) were 1.01 (0.98-1.03); 0.98 (0.96-1.01); 0.98 (0.95-1.02); 0.99 (0.97-1.02), respectively. Similarly, non-pleiotropic HDLc and LDLc gene scores showed no association with incident AF: HR (95% CI) = 1.00 (0.97-1.03); 1.01 (0.99-1.04).

CONCLUSIONS

In this large cohort study of individuals of European ancestry, gene scores for lipid fractions were not associated with incident AF.

Exploring causal associations of alcohol with cardiovascular and metabolic risk factors in a Chinese population using Mendelian randomization analysis

Observational studies suggest that moderate alcohol consumption may be protective for cardiovascular disease, but results may be biased by confounding and reverse causality. Mendelian randomization, which uses genetic variants as proxies for exposures, can minimise these biases and therefore strengthen causal inference. Using a genetic variant in the ALDH2 gene associated with alcohol consumption, rs671, we performed a Mendelian randomization analysis in 1,712 diabetes cases and 2,076 controls from Nantong, China. Analyses were performed using linear and logistic regression, stratified by sex and diabetes status. The A allele of rs671 was strongly associated with reduced odds of being an alcohol drinker in all groups, but prevalence of alcohol consumption amongst females was very low. The A allele was associated with reduced systolic and diastolic blood pressure and decreased total and HDL cholesterol in males. The A allele was also associated with decreased triglyceride levels, but only robustly in diabetic males. There was no strong evidence for associations between rs671 and any outcomes in females. Our results suggest that associations of alcohol consumption with blood pressure and HDL-cholesterol are causal. Alcohol also appeared to have adverse effects on triglyceride levels, although this may be restricted to diabetics.

Circulating cholesteryl ester transfer protein and coronary heart disease: mendelian randomization meta-analysis

BACKGROUND

The cholesteryl ester transfer protein (CETP) plays a central role in reverse cholesterol transport. Currently, it remains unresolved whether circulating CETP is causally associated with coronary heart disease (CHD). We aimed to investigate this causal association using CETP gene rs708272 polymorphism as an instrument in a Mendelian randomization meta-analysis.

METHODS AND RESULTS

We searched PubMed and EMBASE before May 2014. Data and study quality were assessed in duplicate. Thirty-four articles (17 813 CHD patients and 22 203 controls) were qualified. Overall analyses revealed a significant association of rs708272-B1 allele with a reduced CHD risk compared with B2 allele under allelic (odds ratio and 95% confidence interval: 0.87 and 0.82-0.92; P<0.001), homozygous genotypic (0.74 and 0.66-0.83; P<0.001), and dominant (0.87 and 0.80-0.94; P<0.001) models. Carriers of rs708272-B1B1 genotype (weighted mean difference and 95% confidence interval: -0.21 and -0.41 to 0.00 μg/dL; P=0.052) or B1 allele (-0.15 and -0.30 to 0.00 μg/dL; P=0.056) had a marginally lower circulating CETP level compared with B2B2 genotype carriers. In Mendelian randomization analysis, there was a 25% (odds ratio and 95% confidence interval: 0.75 and 0.19-0.91) and a 17% (0.83 and 0.41-0.96) significantly reduced risk of CHD by a reduction of 0.2 μg/mL in circulating CETP for the comparison of B1B1 genotype and B1 allele with B2B2 genotype, respectively. There were low probabilities of publication bias.

CONCLUSIONS

Our findings demonstrate that the long-term genetically reduced circulating CETP might be causally associated with the low risk of CHD.

Genetic and environmental influences on the prospective correlation between systemic inflammation and coronary heart disease death in male twins

OBJECTIVE

Because of lack of evidence, we aimed to examine to what degree low-grade systemic inflammation and coronary heart disease (CHD) death shared common genetic and environmental substrates.

APPROACH AND RESULTS

From the 41-year prospective National Heart, Lung, and Blood Institute Twin Study, we included 950 middle-aged male twins at baseline (1969-1973). Low-grade systemic inflammation was measured with plasma levels of interleukin-6 (IL-6) and C-reactive protein. Univariate and bivariate structural equation models were used, adjusted for a risk score for CHD death. The score-adjusted heritability was 19% for IL-6, 27% for C-reactive protein, and 22% for CHD death. The positive phenotypic correlation of IL-6 with CHD death (radjusted=0.27; 95% confidence interval [CI], 0.08-0.43) was driven by additive genetic factors (contribution [relative contribution], 0.30 [111%]) but attenuated by unique environment (-0.03 [-11%]). The genetic correlation between IL-6 and CHD death was 0.74 (95% CI, 0.21-1.00), whereas the unique environmental correlation was -0.05 (95% CI, -0.35 to 0.25). The proportion of genetic variance for CHD death shared with that for IL-6 was 74%. The phenotypic correlation of C-reactive protein with CHD death (radjusted=0.10; 95% CI, -0.02 to 0.22) was explained by additive genetic factors (0.20 [149%]) but was attenuated by the unique environment (-0.09 [-49%]). The genetic correlation of C-reactive protein with CHD death was 0.63 (95% CI, -0.07 to 1.00), whereas the unique environmental correlation was -0.07 (95% CI, -0.29 to 0.17).

CONCLUSIONS

Low-grade systemic inflammation, measured by IL-6, and long-term CHD death share moderate genetic substrates that augment both traits.

Common variants associated with plasma triglycerides and risk for coronary artery disease

Triglycerides are transported in plasma by specific triglyceride-rich lipoproteins; in epidemiologic studies, increased triglyceride levels correlate with higher risk for coronary artery disease (CAD). However, it is unclear whether this association reflects causal processes. We used 185 common variants recently mapped for plasma lipids (P<5×10⁻⁸ for each) to examine the role of triglycerides on risk for CAD. First, we highlight loci associated with both low-density lipoprotein cholesterol (LDL-C) and triglycerides, and show that the direction and magnitude of both are factors in determining CAD risk. Second, we consider loci with only a strong magnitude of association with triglycerides and show that these loci are also associated with CAD. Finally, in a model accounting for effects on LDL-C and/or high-density lipoprotein cholesterol, a polymorphism's strength of effect on triglycerides is correlated with the magnitude of its effect on CAD risk. These results suggest that triglyceride-rich lipoproteins causally influence risk for CAD.

Lactase non-persistence as a determinant of milk avoidance and calcium intake in children and adolescents

This study examines if lactase non-persistent (LNP) children and adolescents differ from those who are lactase persistent (LP) as regards milk avoidance and Ca intake. We also studied potential differences in anthropometric features related to obesity, and examined if milk avoidance is associated with lactase-persistence status. Additionally, we aimed to determine if heterozygous subjects showed an intermediary phenotype as regards Ca intake. Furthermore, we tested if LP and LNP influence vitamin D intake. The European Youth Heart Study is an ongoing international, multi-centre cohort study primarily designed to address CVD risk factors. Children (n 298, mean age 9·6 years) and adolescents (n 386, mean age 15·6 years) belonging to the Swedish part of the European Youth Heart Study were genotyped for the LCT-13910 C > T polymorphism. Mendelian randomisation was used. Milk avoidance was significantly more common in LNP adolescents (OR 3·2; 95% CI 1·5, 7·3). LP subjects had higher milk consumption (P < 0·001). Accordingly, energy consumption derived from milk and Ca intake was lower in LNP (P < 0·05 and P < 0·001, respectively). Heterozygous subjects did not show an intermediary phenotype concerning milk consumption. LP or LNP status did not affect vitamin D intake or anthropometric variables. LNP in children and adolescents is associated with reduced intake of milk and some milk-product-related nutritional components, in particular Ca. This reduced intake did not affect the studied anthropometric variables, indicators of body fat or estimated vitamin D intake. However, independently of genotype, age and sex, daily vitamin D intake was below the recommended intakes. Milk avoidance among adolescents but not children was associated with LNP.

First-line allogeneic hematopoietic stem cell transplantation of HLA-matched sibling donors compared with first-line ciclosporin and/or antithymocyte or antilymphocyte globulin for acquired severe aplastic anemia

BACKGROUND

Acquired severe aplastic anemia is a rare and potentially fatal disease, which is characterized by hypocellular bone marrow and pancytopenia. The major signs and symptoms are severe infections, bleeding, and exhaustion. First-line allogeneic hematopoietic stem cell transplantation (HSCT) of a human leukocyte antigen (HLA)-matched sibling donor (MSD) is a treatment for newly diagnosed patients with severe aplastic anemia. First-line treatment with ciclosporin and/or antithymocyte or antilymphocyte globulin (as first-line immunosuppressive therapy) is an alternative to MSD-HSCT and is indicated for patients where no MSD is found.

OBJECTIVES

To evaluate the effectiveness and adverse events of first-line allogeneic hematopoietic stem cell transplantation of HLA-matched sibling donors compared to first-line immunosuppressive therapy including ciclosporin and/or antithymocyte or antilymphocyte globulin in patients with acquired severe aplastic anemia.

SEARCH METHODS

We searched the electronic databases MEDLINE (Ovid), EMBASE (Ovid), and The Cochrane Library CENTRAL (Wiley) for published articles from 1946 to 22 April 2013. Further searches included trial registries, reference lists of recent reviews, and author contacts.

SELECTION CRITERIA

The following prospective study designs were eligible for inclusion: randomized controlled trials (RCTs) and non-randomized controlled trials if the allocation of patients to treatment groups was consistent with 'Mendelian randomization'. We included participants with newly diagnosed severe aplastic anemia who received MSD-HSCT or immunosuppressive therapy without prior HSCT or immunosuppressive therapy, and with a minimum of five participants per treatment group. We did not apply limits on publication year or languages.

DATA COLLECTION AND ANALYSIS

Two review authors abstracted the data on study and patient characteristics and assessed the risk of bias independently. We resolved differences by discussion or by appeal to a third review author. The primary outcome was overall mortality. Secondary outcomes were treatment-related mortality, graft failure, no response to first-line immunosuppressive therapy, graft-versus-host-disease (GVHD), relapse after initial successful treatment, secondary clonal and malignant disease, health-related quality of life, and performance score.

MAIN RESULTS

We identified three trials that met the inclusion criteria. None of these trials was a RCT. 302 participants are included in this review. The three included studies were prospectively conducted and had features consistent with the principle of 'Mendelian randomization' as defined in the present review. All studies had a high risk of bias due to the study design. All studies were conducted more than 10 years ago and may not be applicable to the standard of care of today. Primary and secondary outcome data showed no statistically significant difference between treatment groups. We present results for first-line allogeneic hematopoietic stem cell transplantation of an HLA-matched sibling donor, which we denote as the MSD-HSCT group, versus first-line treatment with ciclosporin and/or antithymocyte or antilymphocyte globulin, which we denote as the immunosuppressive therapy group in the following section.The pooled hazard ratio for overall mortality for the MSD-HSCT group versus the immunosuppressive therapy group was 0.95 (95% confidence interval 0.43 to 2.12, P = 0.90, low quality evidence). Therefore, overall mortality was not statistically significantly different between the groups. Treatment-related mortality ranged from 20% to 42% for the MSD-HSCT group and was not reported for the immunosuppressive therapy group (very low quality evidence). The authors reported graft failure from 3% to 16% for the MSD-HSCT group and GVHD from 26% to 51% (both endpoints not applicable for the immunosuppressive therapy group, very low quality evidence). The authors did not report any data on response and relapse for the MSD-HSCT group. For the immunosuppressive therapy group, the studies reported no response from 15% (not time point stated) to 64% (three months) and relapse in one of eight responders after immunosuppressive therapy at 5.5 years (very low quality evidence). The authors reported secondary clonal disease or malignancies for the MSD-HSCT group versus the immunosuppressive therapy group in 1 of 34 versus 0 of 22 patients in one study and in 0 of 28 versus 4 of 86 patients in the other study (low quality evidence). None of the included studies addressed health-related quality of life. The percentage of the evaluated patients with a Karnofsky performance status score in the range of 71% to 100% was 92% in the MSD-HSCT group and 46% in the immunosuppressive therapy group.

AUTHORS' CONCLUSIONS

There are insufficient and biased data that do not allow any conclusions to be made about the comparative effectiveness of first-line allogeneic hematopoietic stem cell transplantation of an HLA-matched sibling donor and first-line treatment with ciclosporin and/or antithymocyte or antilymphocyte globulin (as first-line immunosuppressive therapy). We are unable to make firm recommendations regarding the choice of intervention for treatment of acquired severe aplastic anemia.

Mendelian randomization analysis of the effect of maternal homocysteine during pregnancy, as represented by maternal MTHFR C677T genotype, on birth weight

Background

We used Mendelian randomization analysis to investigate the causal relationship between maternal homocysteine level, as represented by maternal methylenetetrahydrofolate reductase (MTHFR) C677T genotype, with the birth weight of offspring.

Methods

We recruited women at 24 to 28 weeks’ gestation who visited Ewha Womans University Hospital for prenatal care during the period from August 2001 to December 2003. A total of 473 newborns with a gestational age of at least 37 weeks were analyzed in this study. We excluded twin births and children of women with a history of gestational diabetes, gestational hypertension, or chronic renal disease. The association of maternal homocysteine concentration with the birth weight of infants was analyzed using 2-stage regression.

Results

MTHFR C677T genotype showed a dose–response association with homocysteine concentration for each additional T allele (P_trend < 0.01). Birth weight decreased from 120 to 130 grams as maternal homocysteine level increased, while controlling for confounding factors; however, the association was of marginal significance (P = 0.06).

Conclusions

Our results suggest an adverse relationship between maternal homocysteine level and birth weight. A reduction in homocysteine levels might positively affect birth outcomes.

Testing the utility of an integrated analysis of copy number and transcriptomics datasets for inferring gene regulatory relationships

Correlation patterns between matched copy number variation and gene expression data in cancer samples enable the inference of causal gene regulatory relationships by exploiting the natural randomization of such systems. The aim of this study was to test and verify experimentally the accuracy of a causal inference approach based on genomic randomization using esophageal cancer samples. Two candidates with strong regulatory effects emerging from our analysis are components of growth factor receptors, and implicated in cancer development, namely ERBB2 and FGFR2. We tested experimentally two ERBB2 and three FGFR2 regulated interactions predicted by the statistical analysis, all of which were confirmed. We also applied the method in a meta-analysis of 10 cancer datasets and tested 15 of the predicted regulatory interactions experimentally. Three additional predicted ERBB2 regulated interactions were confirmed, as well as interactions regulated by ARPC1A and FANCG. Overall, two thirds of experimentally tested predictions were confirmed.

Causal Relevance of Blood Lipid Fractions in the Development of Carotid Atherosclerosis

Background—

Carotid intima–media thickness (CIMT), a subclinical measure of atherosclerosis, is associated with risk of coronary heart disease events. Statins reduce progression of CIMT and coronary heart disease risk in proportion to the reduction in low-density lipoprotein cholesterol. However, interventions targeting triglycerides (TGs) or high-density lipoprotein cholesterol (HDL-C) have produced inconsistent effects on CIMT and coronary heart disease risk, making it uncertain whether such agents are ineffective for coronary heart disease prevention or whether CIMT is an inadequate marker of HDL-C or TG-mediated effects. We aimed to determine the causal association among the 3 major blood lipid fractions and common CIMT using mendelian randomization analysis.

Methods and Results—

Genetic scores specific for low-density lipoprotein cholesterol, HDL-C, and TGs were derived based on single nucleotide polymorphisms from a gene-centric array in ≈5000 individuals (Cardiochip scores) and from a genome-wide association meta-analysis in >100 000 individuals (Global Lipids Genetic Consortium scores). These were used as instruments in a mendelian randomization analysis in 2 prospective cohort studies. A genetically predicted 1 mmol/L higher low-density lipoprotein cholesterol concentration was associated with a higher common CIMT by 0.03 mm (95% confidence interval, 0.01–0.04) and 0.04 mm (95% confidence interval, 0.02–0.06) based on the Cardiochip and Global Lipids Genetic Consortium scores, respectively. HDL-C and TGs were not causally associated with CIMT.

Conclusions—

Our findings confirm a causal relationship between low-density lipoprotein cholesterol and CIMT but not with HDL-C and TGs. At present, the suitability of CIMT as a surrogate marker in trials of cardiovascular therapies targeting HDL-C and TGs is questionable and requires further study.

Association of the European lactase persistence variant (LCT-13910 C>T polymorphism) with obesity in the Canary Islands

Background

European lactose tolerance genotype (LCT -13910 C>T, rs4988234) has been positively associated to body mass indexes (BMI) in a meta-analysis of 31,720 individuals of northern and central European descent. A strong association of lactase persistence (LP) with BMI and obesity has also been traced in a Spanish Mediterranean population. The aim of this study was to analyze a potential association of LP compared to lactase non-persistence (LNP) with BMI in inhabitants of the Canary Islands of Spain using Mendelian randomization.

Methods

A representative, randomly sampled population of adults belonging to the Canary Islands Nutrition Survey (ENCA) in Spain, aged 18–75 years (n = 551), was genotyped for the LCT – 13910 C>T polymorphism. Milk consumption was assessed by a validated questionnaire. Anthropometric variables were directly measured. WHO classification of BMI was used.

Results

LP individuals were significantly more obese than LNP subjects (χ² = 10.59; p<0.005). LP showed in a multivariate linear regression analysis showed a positive association of LP with BMI compared to LNP, (β = 0.96; 95% CI: 0.08–1.85, p = 0.033). In a multinomial logistic regression analysis normal range weight LP subjects showed an odds ratio for obesity of 2.41; 95%CI 1.39–418, (p = 0.002) compared to LNP.

Conclusions

The T-13910 of the allele LCT-13910 C>T polymorphism is positively associated with BMI. LP increases significantly the risk to develop obesity in the studied population. The LCT-13910 C>T polymorphism stands proxy for the lifetime exposure pattern, milk intake, that may increase susceptibility to obesity and to obesity related pathologies.

Developing the 2011 Integrated Pediatric Guidelines for Cardiovascular Risk Reduction

This article reviews aspects of development of the recently released "Integrated Guidelines for Cardiovascular Health and Risk Reduction in Children and Adolescents" for pediatric care providers that remain in the area of human judgment. Discussed will be the context in which the guidelines were developed, the formal evidence review process, a consideration of how quality grades were established, key social/ethical issues that the panel confronted, and a critique of the final work with recommendations for future guideline development. Lessons learned are that both a formal evidence review process is essential to developing a credible document, and human judgment is critical to producing a meaningful result. Guideline development is a dynamic process that must be continuously self-critical as new evidence is acquired and sociopolitical and environmental contexts evolve.

Promises and challenges of pharmacogenetics: an overview of study design, methodological and statistical issues

Pharmacogenetics is the study of inherited variation in drug response. The goal of pharmacogenetics is to develop novel ways of maximizing drug efficacy and minimizing toxicity for individual patients. Personalized medicine has the potential to allow for a patient's genetic information to predict optimal dosage for a drug with a narrow therapeutic index, to select the most appropriate pharmacological agent for a given patient and to develop cost-effective treatments. Although there is supporting evidence in favour of pharmacogenetics, its adoption in clinical practice has been slow because of sometimes conflicting findings among studies. This failure to replicate findings may result from a lack of high-quality pharmacogenetic studies, as well as unresolved methodological and statistical issues. The objective of this review is to discuss the benefits of incorporating pharmacogenetics into clinical practice. We will also address outstanding methodological and statistical issues that may lead to heterogeneity among reported pharmacogenetic studies and how they may be addressed.

C-reactive protein is a bystander of cardiovascular disease

A large number of studies have evaluated the association of hs-C-reactive protein with atherosclerosis and coronary heart disease (CHD) in mechanistic, genetic, population-based studies, as well as clinical trials. This paper reviews the collective evidence to determine if hs-C-reactive protein is part of the causal pathway of atherosclerosis and CHD or whether it is a bystander.