Markku J. Savolainen

Genome-wide association study identifies multiple loci influencing human serum metabolite levels

Nuclear magnetic resonance assays allow for measurement of a wide range of metabolic phenotypes. We report here the results of a GWAS on 8,330 Finnish individuals genotyped and imputed at 7.7 million SNPs for a range of 216 serum metabolic phenotypes assessed by NMR of serum samples. We identified significant associations (P < 2.31 × 10−10) at 31 loci, including 11 for which there have not been previous reports of associations to a metabolic trait or disorder. Analyses of Finnish twin pairs suggested that the metabolic measures reported here show higher heritability than comparable conventional metabolic phenotypes. In accordance with our expectations, SNPs at the 31 loci associated with individual metabolites account for a greater proportion of the genetic component of trait variance (up to 40%) than is typically observed for conventional serum metabolic phenotypes. The identification of such associations may provide substantial insight into cardiometabolic disorders.

Cholesteryl ester transfer protein TaqIB variant, high-density lipoprotein cholesterol levels, cardiovascular risk, and efficacy of pravastatin treatment : individual patient meta-analysis of 13,677 subjects

Background—Several studies have reported that the cholesteryl ester transfer protein (CETP) TaqIB gene polymorphism is associated with HDL cholesterol (HDL-C) levels and the risk of coronary artery disease (CAD), but the results are inconsistent. In addition, an interaction has been implicated between this genetic variant and pravastatin treatment, but this has not been confirmed. Methods and Results—A meta-analysis was performed on individual patient data from 7 large, population-based studies (each >500 individuals) and 3 randomized, placebo-controlled, pravastatin trials. Linear and logistic regression models were used to assess the relation between TaqIB genotype and HDL-C levels and CAD risk. After adjustment for study, age, sex, smoking, body mass index (BMI), diabetes, LDL-C, use of alcohol, and prevalence of CAD, TaqIB genotype exhibited a highly significant association with HDL-C levels, such that B2B2 individuals had 0.11 mmol/L (0.10 to 0.12, P<0.0001) higher HDL-C levels than did B1B1 individuals. Second, after adjustment for study, sex, age, smoking, BMI, diabetes, systolic blood pressure, LDL-C, and use of alcohol, TaqIB genotype was significantly associated with the risk of CAD (odds ratio=0.78 [0.66 to 0.93]) in B2B2 individuals compared with B1B1 individuals (P for linearity=0.008). Additional adjustment for HDL-C levels rendered a loss of statistical significance (P=0.4). Last, no pharmacogenetic interaction between TaqIB genotype and pravastatin treatment could be demonstrated. Conclusions—The CETP TaqIB variant is firmly associated with HDL-C plasma levels and as a result, with the risk of CAD. Importantly, this CETP variant does not influence the response to pravastatin therapy.

The Apolipoprotein ε4 Allele Determines Prognosis and the Effect on Prognosis of Simvastatin in Survivors of Myocardial Infarction A Substudy of the Scandinavian Simvastatin Survival Study

BACKGROUND Carriers of the epsilon4 allele of the apolipoprotein E gene are at a higher risk of coronary heart disease than individuals with other genotypes. We examined whether the risk of death or a major coronary event in survivors of myocardial infarction depended on apolipoprotein E genotype and whether the benefits of treatment with simvastatin differed between genotypes. METHODS AND RESULTS Cox proportional hazards models were used to analyze 5.5 years of follow-up data from 966 Danish and Finnish myocardial infarction survivors enrolled in the Scandinavian Simvastatin Survival Study. A total of 16% of the 166 epsilon4 carriers in the placebo group died compared with 9% of the 312 patients without the allele, which corresponds to a mortality risk ratio of 1.8 (95% confidence interval, 1.1 to 3.1). The risk ratio was unaffected by considerations of sex, age, concurrent angina, diabetes, smoking, and serum lipids in multivariate analyses. Simvastatin treatment reduced the mortality risk to 0.33 (95% confidence interval, 0.16 to 0.69) in epsilon4 carriers and to 0.66 (95% confidence interval, 0. 35 to 1.24) in other patients (P=0.23 for treatment by genotype interaction). Apolipoprotein E genotype did not predict the risk of a major coronary event. Baseline serum levels of lipoprotein(a) also predicted mortality risk and could be combined with epsilon4-carrier status to define 3 groups of patients with different prognoses and benefits from treatment. CONCLUSIONS Myocardial infarction survivors with the epsilon4 allele have a nearly 2-fold increased risk of dying compared with other patients, and the excess mortality can be abolished by treatment with simvastatin.

Prevalence of the metabolic syndrome in drug-treated hypertensive patients and control subjects

Objectives. To determine the prevalence of the metabolic abnormalities associated with hypertension and to define the predictors of the metabolic syndrome by different definitions in random population‐based samples.

Metabonomic, transcriptomic, and genomic variation of a population cohort

Comprehensive characterization of human tissues promises novel insights into the biological architecture of human diseases and traits. We assessed metabonomic, transcriptomic, and genomic variation for a large population‐based cohort from the capital region of Finland. Network analyses identified a set of highly correlated genes, the lipid–leukocyte (LL) module, as having a prominent role in over 80 serum metabolites (of 134 measures quantified), including lipoprotein subclasses, lipids, and amino acids. Concurrent association with immune response markers suggested the LL module as a possible link between inflammation, metabolism, and adiposity. Further, genomic variation was used to generate a directed network and infer LL modules largely reactive nature to metabolites. Finally, gene co‐expression in circulating leukocytes was shown to be dependent on serum metabolite concentrations, providing evidence for the hypothesis that the coherence of molecular networks themselves is conditional on environmental factors. These findings show the importance and opportunity of systematic molecular investigation of human population samples. To facilitate and encourage this investigation, the metabonomic, transcriptomic, and genomic data used in this study have been made available as a resource for the research community.

Metabolic Signatures of Insulin Resistance in 7,098 Young Adults

Metabolite associations with insulin resistance were studied in 7,098 young Finns (age 31 ± 3 years; 52% women) to elucidate underlying metabolic pathways. Insulin resistance was assessed by the homeostasis model (HOMA-IR) and circulating metabolites quantified by high-throughput nuclear magnetic resonance spectroscopy in two population-based cohorts. Associations were analyzed using regression models adjusted for age, waist, and standard lipids. Branched-chain and aromatic amino acids, gluconeogenesis intermediates, ketone bodies, and fatty acid composition and saturation were associated with HOMA-IR (P < 0.0005 for 20 metabolite measures). Leu, Ile, Val, and Tyr displayed sex- and obesity-dependent interactions, with associations being significant for women only if they were abdominally obese. Origins of fasting metabolite levels were studied with dietary and physical activity data. Here, protein energy intake was associated with Val, Phe, Tyr, and Gln but not insulin resistance index. We further tested if 12 genetic variants regulating the metabolites also contributed to insulin resistance. The genetic determinants of metabolite levels were not associated with HOMA-IR, with the exception of a variant in GCKR associated with 12 metabolites, including amino acids (P < 0.0005). Nonetheless, metabolic signatures extending beyond obesity and lipid abnormalities reflected the degree of insulin resistance evidenced in young, normoglycemic adults with sex-specific fingerprints.

Relation of polymorphisms in the cholesteryl ester transfer protein gene to transfer protein activity and plasma lipoprotein levels in alcohol drinkers

We investigated the interaction between genetic and environmental factors in the regulation of plasma HDL cholesterol concentration by determining TaqI and EcoN I restriction fragment length polymorphisms at the cholesteryl ester transfer protein (CETP) gene locus in 93 male alcohol drinkers and 82 control men. The highest plasma CETP activity and the lowest HDL cholesterol concentration were in the control subjects who were homozygous for the presence of the TaqI B restriction site (genotype 1-1). The lowest CETP activity and the highest HDL cholesterol among the control subjects were in those with genotype 2-2. These associations were, however, evident only in the non-smokers (P = 0.03 for CETP activity and P = 0.05 for HDL cholesterol). The non-smoking control subjects with genotype 1-1 had 19% higher CETP activity and 16% lower HDL cholesterol than those with genotype 2-2 (mean +/- S.D., 113 +/- 25 nmol/h/ml and 1.16 +/- 0.30 mmol/l vs. 95 +/- 16 nmol/h/ml and 1.38 +/- 0.34 mmol/l, respectively), and CETP activity and HDL cholesterol were negatively correlated (r = -0.280, P = 0.03, n = 59). The alcohol drinkers had 30% lower CETP activity (P < 0.001) and 48% higher HDL cholesterol (P < 0.001) than the controls. CETP activity was not affected by the TaqI B genotype in the alcohol drinkers. The lowest HDL cholesterol was in subjects with genotype 1-1 (1.68 +/- 0.60 mmol/l), but those with genotype 2-2 had lower HDL cholesterol than those with genotype 1-2 (1.78 +/- 0.59 and 1.93 +/- 0.66 mmol/l, respectively). The data of the alcohol drinkers fitted better with the quadratic regression model than with the linear one, suggesting a trend towards a curved relationship between the TaqI B genotype and HDL cholesterol in both the non-smoking and smoking alcohol drinkers. Total, LDL or VLDL cholesterol, total or VLDL triglycerides did not differ between the TaqI B genotypes either in the alcohol drinkers or the controls. Lipid and lipoprotein levels and CETP activities were likewise similar in the TaqI A and EcoN I polymorphisms. Our data indicate that CETP TaqI B polymorphism is related to plasma CETP activity and HDL cholesterol concentration in non-smoking men, but these associations are affected by smoking and alcohol drinking.

Biochemical markers of alcoholism.

Abstract Alcohol and alcohol-related diseases have become a major cause of death in Western countries. The most sensitive and specific of the commonly used biomarkers of alcohol intake are carbohydrate-deficient transferrin (CDT), and the combination of γ-glutamyltransferase (GGT) and CDT. Other widely used laboratory markers are GGT, mean corpuscular volume of erythrocytes and the ratio of aspartate aminotransferase to alanine aminotransferase. Blood ethanol levels reveal recent alcohol use. However, more specific and sensitive biomarkers to improve the detection of excessive alcohol use at an early stage are needed. New biomarkers, not yet used in routine clinical work, include phosphatidylethanol, fatty acid ethyl esters, ethyl glucuronide, sialic acid, and acetaldehyde adducts. Clin Chem Lab Med 2007;45:953–61.

Cholesteryl ester transfer protein gene effect on CETP activity and plasma high-density lipoprotein in European populations

Variation at the cholesteryl ester transfer protein (CETP) gene locus has been implicated in determining the levels and activity of CETP, apoAI and high‐density lipoprotein (HDL) plasma concentration and the risk of developing coronary artery disease.

Apolipoprotein E and B polymorphisms - longevity factors assessed in nonagenarians☆

To test if the prevalence of genetic risk factors for coronary heart disease (CHD) is low in individuals who have reached an extremely old age, the allele frequencies of apolipoprotein E (apo E) and B (apo B) polymorphisms and plasma lipoprotein(a) levels were investigated in nonagenarians and in younger control groups. The frequency of the epsilon 4 allele of apo E was significantly lower in the nonagenarians than in the middle-aged and young adults (P < 0.05). Also, the frequency of EcoRI allele R- of apo B was low in the nonagenarians, whereas the allele frequency for the XbaI polymorphism of apo B and plasma lipoprotein(a) concentrations did not differ between the nonagenarians and the younger groups. These findings strongly suggest that the presence of these potential genetic risk factors for CHD, namely the epsilon 4 allele of apo E and the R- allele of apo B, decreases the probability of an individual reaching an extremely old age.