Reference intervals for insulin-like growth factor-1 (igf-i) from birth to senescence: results from a multicenter study using a new automated chemiluminescence IGF-I immunoassay conforming to recent international recommendations.

CONTEXT: Measurement of IGF-I is a cornerstone in diagnosis and monitoring of GH-related diseases, but considerable discrepancies exist between analytical methods. A recent consensus conference defined criteria for validation of IGF-I assays and for establishment of normative data. OBJECTIVES: Our objectives were development and validation of a novel automated IGF-I immunoassay (iSYS; Immunodiagnostic Systems) according to international guidelines and establishment of method-specific age- and sex-adjusted reference intervals and analysis of their robustness. SETTING AND PARTICIPANTS: We conducted a multicenter study with samples from 12 cohorts from the United States, Canada, and Europe including 15 014 subjects (6697 males and 8317 females, 0-94 years of age). MAIN OUTCOME MEASURES: We measured concentrations of IGF-I as determined by the IDS iSYS IGF-I assay. RESULTS: A new IGF-I assay calibrated against the recommended standard (02/254) and insensitive to the 6 high-affinity IGF binding proteins was developed and rigorously validated. Age- and sex-adjusted reference intervals derived from a uniquely large cohort reflect the age-related pattern of IGF-I secretion: a decline immediately after birth followed by an increase until a pubertal peak (at 15 years of age). Later in life, values decrease continuously. The impact of gender is small, although across the lifespan, women have lower mean IGF-I concentrations. Geographical region, sampling setting (community or hospital based), and rigor of exclusion criteria in our large cohort did not affect the reference intervals. CONCLUSIONS: Using large cohorts of well-characterized subjects from different centers allowed construction of robust reference ranges for a new automated IGF-I assay. The strict adherence to recent consensus criteria for IGF-I assays might facilitate clinical application of the results.

Metabolite profiling reveals new insights into the regulation of serum urate in humans.

Serum urate, the final breakdown product of purine metabolism, is causally involved in the pathogenesis of gout, and implicated in cardiovascular disease and type 2 diabetes. Serum urate levels highly differ between men and women; however the underlying biological processes in its regulation are still not completely understood and are assumed to result from a complex interplay between genetic, environmental and lifestyle factors. In order to describe the metabolic vicinity of serum urate, we analyzed 355 metabolites in 1,764 individuals of the population-based KORA F4 study and constructed a metabolite network around serum urate using Gaussian Graphical Modeling in a hypothesis-free approach. We subsequently investigated the effect of sex and urate lowering medication on all 38 metabolites assigned to the network. Within the resulting network three main clusters could be detected around urate, including the well-known pathway of purine metabolism, as well as several dipeptides, a group of essential amino acids, and a group of steroids. Of the 38 assigned metabolites, 25 showed strong differences between sexes. Association with uricostatic medication intake was not only confined to purine metabolism but seen for seven metabolites within the network. Our findings highlight pathways that are important in the regulation of serum urate and suggest that dipeptides, amino acids, and steroid hormones are playing a role in its regulation. The findings might have an impact on the development of specific targets in the treatment and prevention of hyperuricemia.

Discovery and fine mapping of serum protein loci through transethnic meta-analysis.

Many disorders are associated with altered serum protein concentrations, including malnutrition, cancer, and cardiovascular, kidney, and inflammatory diseases. Although these protein concentrations are highly heritable, relatively little is known about their underlying genetic determinants. Through transethnic meta-analysis of European-ancestry and Japanese genome-wide association studies, we identified six loci at genome-wide significance (p < 5 × 10(-8)) for serum albumin (HPN-SCN1B, GCKR-FNDC4, SERPINF2-WDR81, TNFRSF11A-ZCCHC2, FRMD5-WDR76, and RPS11-FCGRT, in up to 53,190 European-ancestry and 9,380 Japanese individuals) and three loci for total protein (TNFRS13B, 6q21.3, and ELL2, in up to 25,539 European-ancestry and 10,168 Japanese individuals). We observed little evidence of heterogeneity in allelic effects at these loci between groups of European and Japanese ancestry but obtained substantial improvements in the resolution of fine mapping of potential causal variants by leveraging transethnic differences in the distribution of linkage disequilibrium. We demonstrated a functional role for the most strongly associated serum albumin locus, HPN, for which Hpn knockout mice manifest low plasma albumin concentrations. Other loci associated with serum albumin harbor genes related to ribosome function, protein translation, and proteasomal degradation, whereas those associated with serum total protein include genes related to immune function. Our results highlight the advantages of transethnic meta-analysis for the discovery and fine mapping of complex trait loci and have provided initial insights into the underlying genetic architecture of serum protein concentrations and their association with human disease.

Meta-analysis of two genome-wide association studies identifies four genetic loci associated with thyroid function.

Thyroid hormones play key roles in cellular growth, development and metabolism. Although there is a strong genetic influence on thyroid hormone levels, the genes involved are widely unknown. The levels of circulating thyroid hormones are tightly regulated by thyrotropin (TSH), which also represents the most important diagnostic marker for thyroid function. Therefore, in order to identify genetic loci associated with TSH levels, we performed a discovery meta-analysis of two genome-wide association studies including two cohorts from Germany, KORA (n = 1287) and SHIP (n = 2449), resulting in a total sample size of 3736. Four genetic loci at 5q13.3, 1p36, 16q23 and 4q31 were associated with serum TSH levels. The lead single-nucleotide polymorphisms of these four loci were located within PDE8B encoding phosphodiesterase 8B, upstream of CAPZB that encodes the ß-subunit of the barbed-end F-actin-binding protein, in a former 'gene desert' that was recently demonstrated to encode a functional gene (LOC440389) associated with thyroid volume, and upstream of NR3C2 encoding the mineralocorticoid receptor. The latter association for the first time suggests the modulation of thyroid function by mineral corticoids. All four loci were replicated in three additional cohorts: the HUNT study from Norway (n = 1487) and the two German studies CARLA (CARLA, n = 1357) and SHIP-TREND (n = 883). Together, these four quantitative trait loci accounted for ∼3.3% of the variance in TSH serum levels. These results contribute to our understanding of genetic factors and physiological mechanisms mediating thyroid function.

Large-scale association analysis identifies 13 new susceptibility loci for coronary artery disease.

We performed a meta-analysis of 14 genome-wide association studies of coronary artery disease (CAD) comprising 22,233 individuals with CAD (cases) and 64,762 controls of European descent followed by genotyping of top association signals in 56,682 additional individuals. This analysis identified 13 loci newly associated with CAD at P < 5 × 10⁻8 and confirmed the association of 10 of 12 previously reported CAD loci. The 13 new loci showed risk allele frequencies ranging from 0.13 to 0.91 and were associated with a 6% to 17% increase in the risk of CAD per allele. Notably, only three of the new loci showed significant association with traditional CAD risk factors and the majority lie in gene regions not previously implicated in the pathogenesis of CAD. Finally, five of the new CAD risk loci appear to have pleiotropic effects, showing strong association with various other human diseases or traits.

Genome-wide association study identifies a new locus for coronary artery disease on chromosome 10p11.23.

AIMS: Recent genome-wide association (GWA) studies identified 10 chromosomal loci for coronary artery disease (CAD) or myocardial infarction (MI). However, these loci explain only a small proportion of the genetic variability of these pertinent diseases. We sought to identify additional CAD/MI loci by applying a three-stage approach. METHODS AND RESULTS: We genotyped n = 1157 MI cases and n = 1748 controls from a population-based study population [German MI Family Study (GerMIFS) III (KORA)] with genome-wide SNP arrays. At this first stage, n = 462 SNPs showed association with MI at P<1 × 10(-3) in two-sided logistic regression. In a second stage, 415 of these SNPs were evaluated in silico in two independent GWA samples, the GerMIFS I (875 cases/1644 controls) and GerMIFS II (1222 cases/1298 controls). Nine SNPs, representing three regions, displayed consistent replication in this in silico analysis (P<0.05 for each GWA sample): five SNPs at 9p21.3, a well-known CAD/MI locus, two SNPs at 10p11.21, and two SNPs at 2p24.3. Wet-lab replication, i.e. the third stage, of SNP rs3739998 (representing the novel locus at 10p11.21, p.S1002T in the KIAA1462 gene) in additional 5790 cases and 5302 controls confirmed the association (P=9.54 × 10(-4)), but not for the 2p24.3 locus. The combined P-value across all stages for SNP rs3739998 is P=1.27 × 10(-11) [odds ratio (OR) = 1.15 (1.11-1.20)]. CONCLUSION: Analysis of a GWA study followed by in silico and wet-lab replication steps identified the KIAA1462 gene, encoding a yet uncharacterized protein, on chromosome 10p11.23 with genome-wide significant association for CAD/MI. Further studies are needed to characterize the functional role of this locus in the aetiology of these diseases.

Genetic variation at chromosome 1p13.3 affects sortilin mRNA expression, cellular LDL-uptake and serum LDL levels which translates to the risk of coronary artery disease.

BACKGROUND: A single nucleotide polymorphism (SNP) rs599839 located at chromosome 1p13.3 has previously been associated with risk of coronary artery disease (CAD) and with serum levels of low-density lipoprotein cholesterol (LDL-C). A functional link explaining the association of SNP rs599839 with LDL-C levels and CAD risk has not yet been elucidated. METHODS: We analyzed the association of rs599839 with LDL-C in 6605 individuals across a wide age spectrum and with CAD in four case-control studies comprising 4287 cases and 7572 controls. Genome-wide expression array data was used to assess the association of SNP rs599839 with gene expression at chromosome 1p13. Finally, we overexpressed sortilin in transfected cells to study LDL-uptake in vitro. RESULTS: Each copy of the G-allele of rs599839 associated with a decrease of serum LDL-C by 0.14 mmol/L (90% confidence interval (CI) 0.09-0.17 mmol/L, p=2.6 x 10(-11)). Moreover, each copy of the G-allele associated with a 9% decrease of CAD risk (90% CI 4-14%) in the presently studied four case-control samples and with a 13% decrease (90% CI 10-17%, p=2.18 x 10(-9)) in a pooled meta-analysis including recent genome-wide association studies on CAD. The same allele was associated with higher mRNA-expression levels of the multiligand receptor sortilin (log transformed mRNA AA vs. GG=8.31 vs. 8.55; p=0.01). Overexpression of SORT1 cDNA resulted in a significant increase in LDL-particle uptake (+23%, p=0.01). CONCLUSIONS: Rs599839 associates with decreased LDL-C and a lower risk of CAD. Effects appear to be mediated by increased sortilin expression and subsequently enhanced LDL-uptake into cells.

Meta-analysis of 28,141 individuals identifies common variants within five new loci that influence uric acid concentrations.

Elevated serum uric acid levels cause gout and are a risk factor for cardiovascular disease and diabetes. To investigate the polygenetic basis of serum uric acid levels, we conducted a meta-analysis of genome-wide association scans from 14 studies totalling 28,141 participants of European descent, resulting in identification of 954 SNPs distributed across nine loci that exceeded the threshold of genome-wide significance, five of which are novel. Overall, the common variants associated with serum uric acid levels fall in the following nine regions: SLC2A9 (p = 5.2x10(-201)), ABCG2 (p = 3.1x10(-26)), SLC17A1 (p = 3.0x10(-14)), SLC22A11 (p = 6.7x10(-14)), SLC22A12 (p = 2.0x10(-9)), SLC16A9 (p = 1.1x10(-8)), GCKR (p = 1.4x10(-9)), LRRC16A (p = 8.5x10(-9)), and near PDZK1 (p = 2.7x10(-9)). Identified variants were analyzed for gender differences. We found that the minor allele for rs734553 in SLC2A9 has greater influence in lowering uric acid levels in women and the minor allele of rs2231142 in ABCG2 elevates uric acid levels more strongly in men compared to women. To further characterize the identified variants, we analyzed their association with a panel of metabolites. rs12356193 within SLC16A9 was associated with DL-carnitine (p = 4.0x10(-26)) and propionyl-L-carnitine (p = 5.0x10(-8)) concentrations, which in turn were associated with serum UA levels (p = 1.4x10(-57) and p = 8.1x10(-54), respectively), forming a triangle between SNP, metabolites, and UA levels. Taken together, these associations highlight additional pathways that are important in the regulation of serum uric acid levels and point toward novel potential targets for pharmacological intervention to prevent or treat hyperuricemia. In addition, these findings strongly support the hypothesis that transport proteins are key in regulating serum uric acid levels.

Genome-wide association scan meta-analysis identifies three Loci influencing adiposity and fat distribution.

To identify genetic loci influencing central obesity and fat distribution, we performed a meta-analysis of 16 genome-wide association studies (GWAS, N = 38,580) informative for adult waist circumference (WC) and waist-hip ratio (WHR). We selected 26 SNPs for follow-up, for which the evidence of association with measures of central adiposity (WC and/or WHR) was strong and disproportionate to that for overall adiposity or height. Follow-up studies in a maximum of 70,689 individuals identified two loci strongly associated with measures of central adiposity; these map near TFAP2B (WC, P = 1.9x10(-11)) and MSRA (WC, P = 8.9x10(-9)). A third locus, near LYPLAL1, was associated with WHR in women only (P = 2.6x10(-8)). The variants near TFAP2B appear to influence central adiposity through an effect on overall obesity/fat-mass, whereas LYPLAL1 displays a strong female-only association with fat distribution. By focusing on anthropometric measures of central obesity and fat distribution, we have identified three loci implicated in the regulation of human adiposity.

Lifelong reduction of LDL-cholesterol related to a common variant in the LDL-receptor gene decreases the risk of coronary artery disease--a Mendelian Randomisation study.

BACKGROUND: Rare mutations of the low-density lipoprotein receptor gene (LDLR) cause familial hypercholesterolemia, which increases the risk for coronary artery disease (CAD). Less is known about the implications of common genetic variation in the LDLR gene regarding the variability of cholesterol levels and risk of CAD. METHODS: Imputed genotype data at the LDLR locus on 1 644 individuals of a population-based sample were explored for association with LDL-C level. Replication of association with LDL-C level was sought for the most significant single nucleotide polymorphism (SNP) within the LDLR gene in three European samples comprising 6 642 adults and 533 children. Association of this SNP with CAD was examined in six case-control studies involving more than 15 000 individuals. FINDINGS: Each copy of the minor T allele of SNP rs2228671 within LDLR (frequency 11%) was related to a decrease of LDL-C levels by 0.19 mmol/L (95% confidence interval (CI) [0.13-0.24] mmol/L, p = 1.5x10(-10)). This association with LDL-C was uniformly found in children, men, and women of all samples studied. In parallel, the T allele of rs2228671 was associated with a significantly lower risk of CAD (Odds Ratio per copy of the T allele: 0.82, 95% CI [0.76-0.89], p = 2.1x10(-7)). Adjustment for LDL-C levels by logistic regression or Mendelian Randomisation models abolished the significant association between rs2228671 with CAD completely, indicating a functional link between the genetic variant at the LDLR gene locus, change in LDL-C and risk of CAD. CONCLUSION: A common variant at the LDLR gene locus affects LDL-C levels and, thereby, the risk for CAD.

Association between PPARalpha gene polymorphisms and myocardial infarction.

PPARalpha (peroxisome-proliferator-activated receptor alpha) regulates the expression of genes that are involved in lipid metabolism, tissue homoeostasis and inflammation. Consistent rodent and human studies suggest a link between PPARalpha function and cardiovascular disease, qualifying PPARalpha [PPARA in HUGO (Human Genome Organisation) gene nomenclature] as a candidate gene for coronary artery disease. In the present study, we comprehensively evaluated common genetic variations within the PPARalpha gene and assessed their association with myocardial infarction. First, we characterized the linkage disequilibrium within the PPARalpha gene in an initial case-control sample of 806 individuals from the Regensburg Myocardial Infarction Family Study using a panel of densely spaced SNPs (single nucleotide polymorphisms) across the gene. Single SNP analysis showed significant association with the disease phenotype [OR (odds ratio)=0.74, P=0.012, 95% CI (confidence interval)=0.61-0.94 for rs135551]. Moreover, we identified a protective three-marker haplotype with an association trend for myocardial infarction (OR=0.76, P=0.067, 95% CI=0.56-1.02). Subsequently, we were able to confirm the single SNP and haplotype association results in an independent second case-control cohort with 667 cases from the Regensburg Myocardial Infarction Family Study and 862 control individuals from the WHO (World Health Organization) MONICA (Monitoring of Trends and Determinants in Cardiovascular Disease) Augsburg project (OR=0.87, P=0.046, 95% CI=0.72-0.99 for rs135551 and OR=0.80, P=0.034, 95% CI=0.65-0.98 for the three-marker haplotype respectively). From these cross-sectional association results, we provide evidence that common variations in the PPARalpha gene may influence the risk of myocardial infarction in a European population.

Genetic variants within the LPIN1 gene, encoding lipin, are influencing phenotypes of the metabolic syndrome in humans.

OBJECTIVE: Lipin, a novel molecular protein expressed by adipocytes, has marked effects on adipose tissue mass, insulin sensitivity, and glucose homeostasis. Thus, we hypothesized that genetic variants within LPIN1 are associated with traits of the metabolic syndrome. RESEARCH DESIGN AND METHODS: A total of 15 single nucleotide polymorphisms (SNPs) covering the LPIN1 gene region were genotyped in an age- and sex-stratified sample of the general population (Monitoring Trends and Determinants on Cardiovascular Diseases Study Augsburg; DNA and phenotypes of 1,416 Caucasians). Ten SNPs were also genotyped for replication in an independent sample of 1,030 subjects recruited throughout Germany. The metabolic syndrome was defined via the sum of its core components and, additionally, by a factor score derived from factor analysis. Permutation-based methods were used to test the association between genetic LPIN1 variants and metabolic traits for empirical significance. RESULTS: Linkage disequilibrium (LD) analysis revealed three LD blocks encompassing LPIN1. We identified three associated three-marker haplotypes: one common haplotype (26.8% frequency) increases the risk for the metabolic syndrome (odds ratio 1.6 [95% CI 1.2-2.2]), while the other two, being less common (5.7 and 4.0%), are strongly associated with lower blood pressure levels (systolic blood pressure 127 +/- 18 vs. 135 +/- 20 mmHg; P = 0.0001), a lower BMI (24.6 +/- 3.6 vs. 26.9 +/- 4.1 kg/m(2); P = 3.7 x 10(-7)) and waist circumference (82 +/- 12 vs. 90 +/- 12 cm; P = 3.2 x 10(-8)), lower A1C levels (5.1 +/- 0.7 vs. 5.3 +/- 0.9%; P = 0.0002), as well as a lower metabolic syndrome factor score (-0.67 +/- 1.00 vs. 0.04 +/- 1.24; P = 1.4 x 10(-7)). Furthermore, the frequencies of arterial hypertension (23.7 vs. 46.4%; P = 0.00001), obesity (12.9 vs. 30.8%; P = 0.0003), diabetes (2.2 vs. 8.2%; P = 0.041), and the presence of three or more metabolic syndrome components (3.3 vs. 13.7%; P = 0.002) were significantly lower than in subjects not carrying one of these protective haplotypes. Strong associations were also observed in the replication sample using the same haplotypes but with effects in the opposite direction. CONCLUSIONS These data suggest that allelic variants of the LPIN1 gene have significant effects in human metabolic traits and thus implicate lipin in the pathophysiology of the metabolic syndrome.

Epistatic interaction between haplotypes of the ghrelin ligand and receptor genes influence susceptibility to myocardial infarction and coronary artery disease.

Data from both experimental models and humans provide evidence that ghrelin and its receptor, the growth hormone secretagogue receptor (ghrelin receptor, GHSR), possess a variety of cardiovascular effects. Thus, we hypothesized that genetic variants within the ghrelin system (ligand ghrelin and its receptor GHSR) are associated with susceptibility to myocardial infarction (MI) and coronary artery disease (CAD). Seven single nucleotide polymorphisms (SNPs) covering the GHSR region as well as eight SNPs across the ghrelin gene (GHRL) region were genotyped in index MI patients (864 Caucasians, 'index MI cases') from the German MI family study and in matched controls without evidence of CAD (864 Caucasians, 'controls', MONICA Augsburg). In addition, siblings of these MI patients with documented severe CAD (826 'affected sibs') were matched likewise with controls (n = 826 Caucasian 'controls') and used for verification. The effect of interactions between genetic variants of both genes of the ghrelin system was explored by conditional classification tree models. We found association of several GHSR SNPs with MI [best SNP odds ratio (OR) 1.7 (1.2-2.5); P = 0.002] using a recessive model. Moreover, we identified a common GHSR haplotype which significantly increases the risk for MI [multivariate adjusted OR for homozygous carriers 1.6 (1.1-2.5) and CAD OR 1.6 (1.1-2.5)]. In contrast, no relationship between genetic variants and the disease could be revealed for GHRL. However, the increase in MI/CAD frequency related to the susceptible GHSR haplotype was abolished when it coincided with a common GHRL haplotype. Multivariate adjustments as well as permutation-based methods conveyed the same results. These data are the first to demonstrate an association of SNPs and haplotypes within important genes of the ghrelin system and the susceptibility to MI, whereas association with MI/CAD could be identified for genetic variants across GHSR, no relationship could be revealed for GHRL itself. However, we found an effect of GHRL dependent upon the presence of a common, MI and CAD susceptible haplotype of GHSR. Thus, our data suggest that specific haplotypes of the ghrelin ligand and its receptor act epistatically to affect susceptibility or tolerance to MI and/or CAD.

Association of a functional polymorphism in the CYP4A11 gene with systolic blood pressure in survivors of myocardial infarction.

OBJECTIVE: Survivors of myocardial infarction (MI) are known to have a high prevalence of arterial hypertension which, at the same time, imposes a major risk to such patients. Genetic variants of the arachidonic acid monooxygenase CYP4A11 may result in decreased synthesis of 20-hydroxyeicostatetraenoic acid (20-HETE), experimental hypertension and elevated blood pressure levels in humans. The present study aimed to investigate the impact of the functionally relevant T8590C polymorphism of this gene on blood pressure and the prevalence of hypertension in MI patients. METHODS: Survivors of MI from the MONICA Augsburg MI registry (n = 560) were studied after a mean of 5.6 years after the acute event. Participants were examined by standardized anthropometric and echocardiographic measurements, as well as genotyping for CYP4A11 T8590C allele status. RESULTS: Genotype frequencies in MI patients (TT = 71.8%, CT = 26.2%, CC = 2.0%) did not differ from those in population-based controls (n = 1363; TT = 75.4%, CT = 22.5% and CC = 2.1%, P = 0.22). MI survivors with the CC genotype displayed higher systolic blood pressure levels (CC: 143.4 +/- 4.9 mmHg versus CT: 134.5 +/- 1.3 mmHg and TT: 131.1 +/- 0.8 mmHg; P = 0.02) and a non-significant trend towards higher diastolic blood pressure levels (CC: 88.4 +/- 3.0 mmHg versus CT: 84.9 +/- 0.8 mmHg and TT: 83.9 +/- 0.5 mmHg; P = 0.17) in multivariate models. Accordingly, the C allele was related to elevated odds ratios for hypertension in a recessive [4.14; 95% confidence interval (CI) = 1.07-15.96, P = 0.04] and in a dominant model (1.50; 95% CI = 1.03-2.20, P = 0.04), respectively. No blood pressure-independent association of the T8590C polymorphism with echocardiographic parameters of left ventricular function and/or geometry was found. CONCLUSION: The data obtained in the present study strengthen the evidence of an association of the CYP4A11 T8590C polymorphism with blood pressure levels and hypertension prevalence. Particularly, the risk of arterial hypertension is substantially higher in MI patients homozygous for the CC allele. By contrast, no evidence was obtained for an association between this genotype and MI.

Association of low-grade urinary albumin excretion with left ventricular hypertrophy in the general population: the MONICA/KORA Augsburg Echocardiographic Substudy.

BACKGROUND: Even mild renal dysfunction is a predictor of cardiovascular morbidity. We investigated whether sub-threshold microalbuminuria or mildly decreased estimated glomerular filtration rate (eGFR) are related to left ventricular hypertrophy (LVH) in the general population. METHODS: Urinary albumin-to-creatinine ratio (UACR) served to determine albuminuria, eGFR was estimated using modification of diet in renal disease (MDRD) formula, and LV geometry was assessed echocardiographically in the third MONItoring of trends and determinants in CArdiovascular disease/Cooperative Health Research in the Augsburg Area (MONICA/KORA) Augsburg survey (n = 1187). RESULTS: The prevalence of LVH increased in parallel with UACR. Compared with the first tertile of this normal population, the age, systolic blood pressure (SBP), body mass index, gender and diabetes adjusted odds ratio (OR) for LVH was elevated already in the second (4.32-8.75 mg/g in men; 4.60-9.48 mg/g in women; OR: 2.10, P = 0.001) as well as in the third UACR-tertile (> or =8.76 mg/g in men; > or =9.49 mg/g in women; OR: 1.63, P = 0.035). Likewise, adjusted SBP increased with UACR-tertiles [129 vs 132 (P = 0.036) and 137 mmHg (P < 0.001) in the first, second and third tertile, respectively], whereas diastolic blood pressure was significantly elevated only in the third UACR-tertile [79 vs 80 and 81 mmHg (P = 0.002) in the tertiles, respectively]. In contrast, tertiles of eGFR or mildly impaired eGFR (<90 ml/min/1.73 m(2)) were not associated with the prevalence of LVH in multivariate models. CONCLUSIONS: At the general population level, even low-grade albuminuria is associated with LVH. Thus, the conventional UACR-threshold of microalbuminuria (30 mg/g) may be too conservative given that end organ damage such as LVH is observed with increased frequency at much lower levels.

Association of the Ghrelin receptor gene region with left ventricular hypertrophy in the general population: results of the MONICA/KORA Augsburg Echocardiographic Substudy.

Growth hormone (GH) can influence left ventricular myocardial growth, structure, and function. The GH secretagogue receptor (GHSR, ghrelin receptor) is known to be involved in GH release and is expressed in the myocardium. We hypothesized that genetic variants within the GHSR are associated with parameters of left ventricular mass (LVM) and geometry. Ten single-nucleotide polymorphisms (SNPs) covering the gene region were genotyped in 1230 members of the general population (Monitoring Trends and Determinants on Cardiovascular Diseases Augsburg Echocardiographic Substudy). Linkage disequilibrium analysis revealed a linkage disequilibrium block consisting of 5 SNPs forming 2 common haplotypes. One haplotype was found significantly more often in subjects without left ventricular hypertrophy ([LVH] 69% versus 59%; permutated P=0.0015), whereas the second haplotype was significantly more frequent in individuals with LVH (32% versus 26%; P=0.019). Homozygous subjects presented with an increase of risk with respect to all heart size parameters. A significantly increasing frequency of the risk haplotype could be observed from the lowest (20.9%) to the highest quintile (31.0%) of gender-specific LVM distributions (P=0.0096). We found association of the minor alleles of individual single nucleotide polymorphisms contributing to the haplotypes with higher LVM indices, septal wall thickness, and different LVH criteria consistent in men and women in matched cases and controls (LVM, women: 144.8+/-30.9 [noncarrier] versus 171.3+/-36.0 [homozygous], P=0.001; men: 186.7+/-42.4 versus 236.3+/-64.5, P=0.002). These data suggest that common variants in the GHSR region are associated with parameters of LVM and geometry independent of blood pressure and body mass in the general population and, thus, may be involved in the pathogenesis of LVH.

Association of the T8590C polymorphism of CYP4A11 with hypertension in the MONICA Augsburg echocardiographic substudy.

Genetic variants of the arachidonic acid monooxygenase CYP4A11 result in decreased synthesis of 20-hydroxyeicostatetraenoic acid and experimental hypertension. Moreover, in humans, the T8590C polymorphism of CYP4A11 displayed association with arterial hypertension. The aim of the present study was to further investigate this association in a large population-based sample. Therefore, the participants of the echocardiographic substudy of the third MONICA (MONitoring trends and determinants In CArdiovascular disease) survey (n=1397) were studied by standardized anthropometric, echocardiographic, and biochemical measurements as well as genotyping for CYP4A11 T8590C allele status. Individuals with the CC genotype have higher systolic (CC 141.4+/-3.17 mm Hg versus CT 134.2+/-0.97 mm Hg and TT 134.3+/-0.53 mm Hg; P=0.03) and diastolic blood pressure levels (CC 85.4+/-2.06 mm Hg versus CT 80.3+/-0.63 mm Hg and TT 80.7+/-0.34 mm Hg; P=0.02). Accordingly, the odds ratio (adjusted for age, body mass index, and gender) of the CC genotype versus the CT and TT genotypes for hypertension was 3.31 (95% confidence interval [CI]), 1.38 to 7.96; P=0.016) in the entire study population, with similar trends in men (4.30 [95% CI, 1.08 to 17.15]) and women (2.93 [95% CI, 0.88 to 9.84]). Consistent with the renal effects of the gene, no blood pressure-independent association between the T8590C polymorphism and echocardiographic parameters of left ventricular function and geometry was found. In conclusion, our data strengthen the association between the T8590C polymorphism of CYP4A11 and hypertension and suggest a recessive mode of inheritance. In contrast, we found no blood pressure-independent modulatory effect of CYP4A11 T8590C on cardiac size, structure, and function.

Genetic linkage and association of the growth hormone secretagogue receptor (ghrelin receptor) gene in human obesity.

The growth hormone secretagogue receptor (GHSR) (ghrelin receptor) plays an important role in the regulation of food intake and energy homeostasis. The GHSR gene lies on human chromosome 3q26 within a quantitative trait locus strongly linked to multiple phenotypes related to obesity and the metabolic syndrome. Because the biological function and location of the GHSR gene make it an excellent candidate gene, we tested the relation between common single nucleotide polymorphisms (SNPs) in the GHSR gene and human obesity. We performed a comprehensive analysis of SNPs, linkage disequilibrium (LD), and haplotype structure across the entire GHSR gene region (99.3 kb) in 178 pedigrees with multiple obese members (DNA of 1,095 Caucasians) and in an independent sample of the general population (MONICA Augsburg left ventricular hypertrophy substudy; DNA of 1,418 Caucasians). The LD analysis revealed a disequilibrium block consisting of five SNPs, consistent in both study cohorts. We found linkage among all five SNPs, their haplotypes, and BMI. Further, we found suggestive evidence for transmission disequilibrium for the minor SNP alleles (P < 0.05) and the two most common haplotypes with the obesity affection status ("susceptible" P = 0.025, "nonsusceptible" P = 0.045) in the family cohort using the family-based association test program. Replication of these findings in the general population resulted in stronger evidence for an association of the SNPs (best P = 0.00001) and haplotypes with the disease ("susceptible" P = 0.002, "nonsusceptible" P = 0.002). To our knowledge, these data are the first to demonstrate linkage and association of SNPs and haplotypes within the GHSR gene region and human obesity. This linkage, together with significant transmission disequilibrium in families and replication of this association in an independent population, provides evidence that common SNPs and haplotypes within the GHSR region are involved in the pathogenesis of human obesity.

No association of interleukin-6 gene polymorphism (-174 G/C) with myocardial infarction or traditional cardiovascular risk factors.

BACKGROUND: Recently, a polymorphism at position -174 (G>C) of the interleukin-6 (IL-6) promoter was found to be associated with an increased prevalence of myocardial infarction (MI). The aim of the present study was to further investigate the association of the IL-6 -174 G/C allele status with specific end organ damage, i.e. myocardial infarction in large population-based samples. METHODS: Individuals from two Bavarian samples of MI patients (total n=1322) and the population-based Augsburg MONICA survey (1023 unselected controls) were studied by questionnaire, physical examination, echocardiographical assessment and biochemical analyses. The -174 G/C polymorphism was genotyped using a newly established PCR-RFLP. IL-6 levels were measured in a subset of 574 MI patients. RESULTS: In the population-based sample, the IL-6 genotype was neither associated with traditional cardiovascular risk factors (systolic and diastolic blood pressure, total cholesterol, HDL and LDL cholesterol, body mass index, diabetes mellitus) nor with cardiac structural or functional parameters (left ventricular mass index, ejection fraction, diastolic inflow pattern). Moreover, the genotype distribution of the -174 G/C polymorphism was not different in MI patients (GG: 34.1%; GC: 47.4%; CC: 18.5%) and population-based controls (GG: 32.4%; GC: 48.8%; CC: 18.9%) (p=0.67). IL-6 levels were neither related to the -174 G/C polymorphism (p=0.29) nor to ACE-inhibitor treatment (2.16 with vs. 2.09 pg/ml without ACE-inhibitor, p=0.27). However, patients receiving statins displayed significantly lower IL-6 levels (1.83 vs. 2.32 pg/ml in the group without statins, p<0.0001). CONCLUSIONS: This extensive investigation failed to obtain evidence that the IL-6 -174 G/C promoter polymorphism affects traditional cardiovascular risk factors or the prevalence of myocardial infarction in a Caucasian sample.