Mika Kähönen

Cohort Profile: The Cardiovascular Risk in Young Finns Study

In Finland, coronary heart disease (CHD) incidence was very high in the 1960s and 1970s. In line with this high incidence, the Seven Countries Study showed that the level of serum cholesterol in Finns was also the highest among the investigated countries in the 1960s. Because several studies indicated that the atherosclerotic process starts early in life, and in accord with the World Health Organization Recommendation of 1978 which stated that studies assessing atherosclerosis precursors in children should be initiated, a program was launched in Finland in the late 1970s to study cardiovascular risk in the youth. The Cardiovascular Risk in Young Finns Study was designed as a collaborative effort between five university departments of medical schools (i.e. in Helsinki, Kuopio, Oulu, Tampere and Turku) and several other institutions in Finland. The aim was to study the levels of CHD risk factors and their determinants in children and adolescents of various ages in different parts of the country. Two pilot studies were carried out in 1978 (N1⁄4 264, age 8 years) and in 1979 (N1⁄4 634, aged 3, 12 and 17 years). The first main cross-sectional (baseline) study was performed in 1980. The baseline study included 3596 children and adolescents aged 3, 6, 9, 12, 15 and 18 years. Between 1980 and 1992, these cohorts were followed up at 3-year intervals. The latest examination of the Cardiovascular Risk in Young Finns Study was performed in 2001, when the participants were young adults, aged 24–39 years. At the time of writing, the 27-year (i.e. 27 years since the start of the study when the participants are aged 30–45 years) follow-up field studies are being conducted, and will be completed in the beginning of 2008.

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.

Risk Factors Identified in Childhood and Decreased Carotid Artery Elasticity in Adulthood The Cardiovascular Risk in Young Finns Study

Background—Exposure to risk factors in childhood may have long-term influences on vascular function. We examined the relationship between risk factors identified in childhood and arterial elasticity assessed in adulthood. Methods and Results—Carotid artery compliance (CAC), Young’s elastic modulus (YEM), and stiffness index (SI), 3 measures of large-artery elasticity, were assessed with noninvasive ultrasound in 2255 healthy white adults aged 24 to 39 years participating in a population-based cohort study and who had risk factor data available since childhood. In multivariate models, childhood obesity (skinfold thickness) predicted decreased CAC (P<0.001), increased YEM (P<0.01), and increased SI (P<0.01) in adulthood. Childhood blood pressure was inversely associated with CAC (P<0.001) and directly associated with YEM (P<0.001). The number of risk factors identified in childhood, which included high LDL cholesterol (at or above 80th percentile), elevated blood pressure, skinfold thickness, low HDL cholesterol (at or below 20th percentile), and smoking, was related inversely with CAC (P<0.001) and directly with YEM (P<0.001). These associations remained highly significant after adjustment for the number of risk factors identified in adulthood (P=0.005 for CAC and P<0.001 for YEM). Conclusions—Cardiovascular risk factors identified in childhood and adolescence predict decreased carotid artery elasticity in adulthood. These data suggest that risk factors operating in early life may have sustained deleterious effects on arterial elasticity.

miR-21, miR-210, miR-34a, and miR-146a/b are up-regulated in human atherosclerotic plaques in the Tampere Vascular Study

OBJECTIVE MicroRNAs are small non-coding RNAs that inversely regulate their target gene expression. The whole miRNA profile of human atherosclerotic plaques has not been studied previously. The aim of this study was to investigate the miRNA expression profile in human atherosclerotic plaques as compared to non-atherosclerotic left internal thoracic arteries (LITA), and to connect this expression to the processes in atherosclerosis. METHODS The miRNA expression profiles of six LITAs and 12 atherosclerotic plaques obtained from aortic, carotid, and femoral atherosclerotic arteries from Tampere Vascular Study were analyzed. The analyses were performed with Agilents miRNA Microarray. The expression levels of over 4-fold up-regulated miRNAs were verified with qRT-PCR from a larger population (n=50). Messenger RNA levels were analyzed with Illuminas Expression BeadChip to study miRNA target expression. RESULTS Ten miRNAs were found to be differently expressed in atherosclerotic plaques when compared to controls (p<0.05). The expression of miR-21, -34a, -146a, -146b-5p, and -210 was verified and found to be significantly up-regulated in atherosclerotic arteries versus LITAs (p<0.001, fold changes 4.61, 2.55, 2.87, 2.82, and 3.92, respectively). Several predicted targets of these miRNAs were down-regulated, and gene set enrichment analysis showed several pathways which could be differently expressed due to this miRNA profile. CONCLUSIONS The microRNA expression profile differs significantly between atherosclerotic plaques and control arteries. The most up-regulated miRNAs are involved in processes known to be connected to atherosclerosis. Interfering with the miRNA expression in the artery wall is a potential way to affect atherosclerotic plaque and cardiovascular disease development.

Tracking of Serum Lipid Levels, Blood Pressure, and Body Mass Index from Childhood to Adulthood: The Cardiovascular Risk in Young Finns Study.

OBJECTIVES To examine tracking and predictiveness of childhood lipid levels, blood pressure, and body mass index for risk profile in adulthood and the best age to measure the childhood risk factor levels. STUDY DESIGN Study subjects were participants of the longitudinal Cardiovascular Risk in Young Finns Study, started in 1980 (age 3, 6, 9, 12, 15, and 18 years). A total of 2204 subjects participated to the 27-year follow-up in 2007 (age, 30 to 45 years). RESULTS In both sex groups and in all age groups, childhood risk factors were significantly correlated with levels in adulthood. The correlation coefficients for cholesterol levels and body mass index were 0.43 to 0.56 (P < .0001), and for blood pressure and triglyceride levels, they were 0.21 to 0.32 (P < .0001). To recognize children with abnormal adult levels, the National Cholesterol Education Program and the National High Blood Pressure Education Program cutoff points for lipid and blood pressure values and international cutoff points for overweight and obesity were used. Age seemed to affect associations. The best sensitivity and specificity rates were observed in 12- to 18-year-old subjects. CONCLUSIONS Childhood blood pressure, serum lipid levels, and body mass index correlate strongly with values measured in middle age. These associations seemed to be stronger with increased age at measurements.

Influence of Age on Associations Between Childhood Risk Factors and Carotid Intima-Media Thickness in Adulthood The Cardiovascular Risk in Young Finns Study, the Childhood Determinants of Adult Health Study, the Bogalusa Heart Study, and the Muscatine Study for the International Childhood Cardiovascular Cohort (i3C) Consortium

Background— Atherosclerosis has its roots in childhood. Therefore, defining the age when childhood risk exposure begins to relate to adult atherosclerosis may have implications for pediatric cardiovascular disease prevention and provide insights about the early determinants of atherosclerosis development. The aim of this study was to investigate the influence of age on the associations between childhood risk factors and carotid artery intima-media thickness, a marker of subclinical atherosclerosis. Methods and Results— We used data for 4380 members of 4 prospective cohorts—Cardiovascular Risk in Young Finns Study (Finland), Childhood Determinants of Adult Health study (Australia), Bogalusa Heart Study (United States), and Muscatine Study (United States)—that have collected cardiovascular risk factor data from childhood (age 3 to 18 years) and performed intima-media thickness measurements in adulthood (age 20 to 45 years). The number of childhood risk factors (high [highest quintile] total cholesterol, triglycerides, blood pressure, and body mass index) was predictive of elevated intima-media thickness (highest decile) on the basis of risk factors measured at age 9 years (odds ratio [95% confidence interval] 1.37 [1.16 to 1.61], P =0.0003), 12 years (1.48 [1.28 to 1.72], P <0.0001), 15 years (1.56 [1.36 to 1.78], P <0.0001), and 18 years (1.57 [1.31 to 1.87], P <0.0001). The associations with risk factors measured at age 3 years (1.17 [0.80 to 1.71], P =0.42) and 6 years (1.20 [0.96 to 1.51], P =0.13) were weaker and nonsignificant. Conclusions— Our analyses from 4 longitudinal cohorts showed that the strength of the associations between childhood risk factors and carotid intima-media thickness is dependent on childhood age. On the basis of these data, risk factor measurements obtained at or after 9 years of age are predictive of subclinical atherosclerosis in adulthood. # Clinical Perspective {#article-title-31}

Branched-Chain and Aromatic Amino Acids Are Predictors of Insulin Resistance in Young Adults

OBJECTIVE Branched-chain and aromatic amino acids are associated with the risk for future type 2 diabetes; however, the underlying mechanisms remain elusive. We tested whether amino acids predict insulin resistance index in healthy young adults. RESEARCH DESIGN AND METHODS Circulating isoleucine, leucine, valine, phenylalanine, tyrosine, and six additional amino acids were quantified in 1,680 individuals from the population-based Cardiovascular Risk in Young Finns Study (baseline age 32 ± 5 years; 54% women). Insulin resistance was estimated by homeostasis model assessment (HOMA) at baseline and 6-year follow-up. Amino acid associations with HOMA of insulin resistance (HOMA-IR) and glucose were assessed using regression models adjusted for established risk factors. We further examined whether amino acid profiling could augment risk assessment of insulin resistance (defined as 6-year HOMA-IR >90th percentile) in early adulthood. RESULTS Isoleucine, leucine, valine, phenylalanine, and tyrosine were associated with HOMA-IR at baseline and for men at 6-year follow-up, while for women only leucine, valine, and phenylalanine predicted 6-year HOMA-IR (P < 0.05). None of the other amino acids were prospectively associated with HOMA-IR. The sum of branched-chain and aromatic amino acid concentrations was associated with 6-year insulin resistance for men (odds ratio 2.09 [95% CI 1.38–3.17]; P = 0.0005); however, including the amino acid score in prediction models did not improve risk discrimination. CONCLUSIONS Branched-chain and aromatic amino acids are markers of the development of insulin resistance in young, normoglycemic adults, with most pronounced associations for men. These findings suggest that the association of branched-chain and aromatic amino acids with the risk for future diabetes is at least partly mediated through insulin resistance.

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.

Pediatric Metabolic Syndrome Predicts Adulthood Metabolic Syndrome, Subclinical Atherosclerosis, and Type 2 Diabetes Mellitus but Is No Better Than Body Mass Index Alone The Bogalusa Heart Study and the Cardiovascular Risk in Young Finns Study

Background— The clinical utility of identifying pediatric metabolic syndrome (MetS) is controversial. This study sought to determine the status of pediatric MetS as a risk factor for adult subclinical atherosclerosis (carotid intima-media thickness [cIMT]) and type 2 diabetes mellitus (T2DM) and compare and contrast this prediction with its individual components. Methods and Results— Using data from the population-based, prospective, observational Bogalusa Heart and Cardiovascular Risk in Young Finns studies, we examined the utility of 4 categorical definitions of youth MetS and their components in predicting adult high cIMT and T2DM among 1781 participants aged 9 to 18 years at baseline (1984 to 1988) who were then examined 14 to 27 years later (2001–2007) when aged 24 to 41 years. Youth with MetS were at 2 to 3 times the risk of having high cIMT and T2DM as adults compared with those free of MetS at youth. Risk estimates with the use of high body mass index were similar to those of MetS phenotypes in predicting adult outcomes. Comparisons of area under the receiver operating characteristic curve and net reclassification index suggested that prediction of adult MetS, high cIMT, and T2DM in adulthood with the use of youth MetS was either equivalent or inferior to classification based on high body mass index or overweight and obesity. Conclusions— Youth with MetS are at increased risk of meaningful adult outcomes; however, the simplicity of screening for high BMI or overweight and obesity in the pediatric setting offers a simpler, equally accurate alternative to identifying youth at risk of developing adult MetS, high cIMT, or T2DM.

Genome-Wide Association Studies of Asthma in Population-Based Cohorts Confirm Known and Suggested Loci and Identify an Additional Association near HLA

Rationale Asthma has substantial morbidity and mortality and a strong genetic component, but identification of genetic risk factors is limited by availability of suitable studies. Objectives To test if population-based cohorts with self-reported physician-diagnosed asthma and genome-wide association (GWA) data could be used to validate known associations with asthma and identify novel associations. Methods The APCAT (Analysis in Population-based Cohorts of Asthma Traits) consortium consists of 1,716 individuals with asthma and 16,888 healthy controls from six European-descent population-based cohorts. We examined associations in APCAT of thirteen variants previously reported as genome-wide significant (P<5x10−8) and three variants reported as suggestive (P<5×10−7). We also searched for novel associations in APCAT (Stage 1) and followed-up the most promising variants in 4,035 asthmatics and 11,251 healthy controls (Stage 2). Finally, we conducted the first genome-wide screen for interactions with smoking or hay fever. Main Results We observed association in the same direction for all thirteen previously reported variants and nominally replicated ten of them. One variant that was previously suggestive, rs11071559 in RORA, now reaches genome-wide significance when combined with our data (P = 2.4×10−9). We also identified two genome-wide significant associations: rs13408661 near IL1RL1/IL18R1 (P Stage1+Stage2 = 1.1x10−9), which is correlated with a variant recently shown to be associated with asthma (rs3771180), and rs9268516 in the HLA region (P Stage1+Stage2 = 1.1x10−8), which appears to be independent of previously reported associations in this locus. Finally, we found no strong evidence for gene-environment interactions with smoking or hay fever status. Conclusions Population-based cohorts with simple asthma phenotypes represent a valuable and largely untapped resource for genetic studies of asthma.