Sex-specific and polygenic effects underlying resting heart rate and associated risk of cardiovascular disease.

AIMS: Resting heart rate (RHR) is associated with cardiovascular disease (CVD) and mortality. This study aimed to identify genetic loci associated with RHR, develop a genome-wide polygenic risk score (PRS) for RHR, and assess associations between the RHR PRS and CVD outcomes, to better understand the biological mechanisms linking RHR to disease. Sex-specific analyses were conducted to potentially elucidate different pathways between the sexes. METHODS: We performed a genome-wide meta-analysis of RHR (n=550,467) using two independent study populations, The Trøndelag Health Study (HUNT) and the UK Biobank (UKB), comprising 69,155 and 481,312 participants, respectively. We also developed a genome-wide PRS for RHR using UKB and tested for association between the PRS and 13 disease outcomes in HUNT. RESULTS: We identified 403, 253, and 167 independent single nucleotide polymorphisms (SNPs) significantly associated with RHR in the total population, women, and men, respectively. The sex-specified analyses indicated differences in the genetic contribution to RHR and revealed loci significantly associated with RHR in only one of the sexes. The SNPs were mapped to genes enriched in heart tissue and cardiac conduction pathways, as well as disease-pathways, including dilated cardiomyopathy. The PRS for RHR was associated with increased risk of hypertension and dilated cardiomyopathy, and decreased risk of atrial fibrillation. CONCLUSION: Our findings provide insight into the pleiotropic effects of the RHR variants, contributing towards an improved understanding of mechanisms linking RHR and disease. In addition, the sex-specific results might contribute to a more refined understanding of RHR as a risk factor for the different diseases.

We conducted a genome-wide meta-analysis on resting heart rate (RHR), created a polygenic risk score for RHR and examined the associations to cardiovascular disease outcomes. Sex-specific analyses indicated differences in the genetic contribution to RHR between men and women.High genetically predicted RHR was associated with increased risk of dilated cardiomyopathy and hypertension, and decreased risk of atrial fibrillation.

Insight into the relationship between resting heart rate and atrial fibrillation: a Mendelian randomization study.

AIMS: A low resting heart rate (RHR) implies a more efficient heart function and a lower risk of cardiovascular disease. However, observational studies have reported a U-shaped association between RHR and atrial fibrillation (AF). In contrast, Mendelian randomization (MR) studies have found an inverse causal association between RHR and AF. Hence, the causal nature of the relationship is not clear. The aim is to investigate the causal association and its shape between RHR on AF using linear and non-linear MR (NLMR). METHODS AND RESULTS: Linear and non-linear MR were performed on individual-level data in the Trøndelag Health Study (HUNT) and UK Biobank (UKB). HUNT consists of 69 155 individuals with 7,062 AF cases, while UKB provides data on 431 852 individuals with 20 452 AF cases. The linear MR found an inverse relationship between RHR and AF with an OR = 0.95 [95% confidence interval (CI): 0.93-0.98] and OR = 0.96 (95% CI: 0.95-0.97) per unit decrease in RHR in HUNT and UKB, respectively. The NLMR was supportive of an inverse linear relationship in both HUNT and UKB for RHR values <90 beats per minute (bpm). Several sensitivity analyses were also consistent. CONCLUSION: In contrast with the current observational knowledge of RHR and AF, an inverse causal association between RHR and AF was demonstrated in both linear and non-linear MR for RHR values up to 90 bpm. Further exploring the underlying mechanisms of the genetic instrument for RHR may shed light on whether pleiotropy is biasing this association.

Associations of polygenic inheritance of physical activity with aerobic fitness, cardiometabolic risk factors and diseases: the HUNT study.

Physical activity (PA), aerobic fitness, and cardiometabolic diseases (CMD) are highly heritable multifactorial phenotypes. Shared genetic factors may underlie the associations between higher levels of PA and better aerobic fitness and a lower risk for CMDs. We aimed to study how PA genotype associates with self-reported PA, aerobic fitness, cardiometabolic risk factors and diseases. PA genotype, which combined variation in over one million of gene variants, was composed using the SBayesR polygenic scoring methodology. First, we constructed a polygenic risk score for PA in the Trøndelag Health Study (N = 47,148) using UK Biobank single nucleotide polymorphism-specific weights (N = 400,124). The associations of the PA PRS and continuous variables were analysed using linear regression models and with CMD incidences using Cox proportional hazard models. The results showed that genotypes predisposing to higher amount of PA were associated with greater self-reported PA (Beta [B] = 0.282 MET-h/wk per SD of PRS for PA, 95% confidence interval [CI] = 0.211, 0.354) but not with aerobic fitness. These genotypes were also associated with healthier cardiometabolic profile (waist circumference [B = -0.003 cm, 95% CI = -0.004, -0.002], body mass index [B = -0.002 kg/m2, 95% CI = -0.004, -0.001], high-density lipoprotein cholesterol [B = 0.004 mmol/L, 95% CI = 0.002, 0.006]) and lower incidence of hypertensive diseases (Hazard Ratio [HR] = 0.97, 95% CI = 0.951, 0.990), stroke (HR = 0.94, 95% CI = 0.903, 0.978) and type 2 diabetes (HR = 0.94, 95 % CI = 0.902, 0.970). Observed associations were independent of self-reported PA. These results support earlier findings suggesting small pleiotropic effects between PA and CMDs and provide new evidence about associations of polygenic inheritance of PA and intermediate cardiometabolic risk factors.

Exploring shared genetics between maximal oxygen uptake and disease: the HUNT study.

Low cardiorespiratory fitness, measured as maximal oxygen uptake (V̇o2max), is associated with all-cause mortality and disease-specific morbidity and mortality and is estimated to have a large genetic component (∼60%). However, the underlying mechanisms explaining the associations are not known, and no association study has assessed shared genetics between directly measured V̇o2max and disease. We believe that identifying the mechanisms explaining how low V̇o2max is related to increased disease risk can contribute to prevention and therapy. We used a phenome-wide association study approach to test for shared genetics. A total of 64,479 participants from the Trøndelag Health Study (HUNT) were included. Genetic variants previously linked to V̇o2max were tested for association with diseases related to the cardiovascular system, diabetes, dementia, mental disorders, and cancer as well as clinical measurements and biomarkers from HUNT. In the total population, three single-nucleotide polymorphisms (SNPs) in and near the follicle-stimulating hormone receptor gene (FSHR) were found to be associated (false discovery rate < 0.05) with serum creatinine levels and one intronic SNP in the Rap-associating DIL domain gene (RADIL) with diabetes type 1 with neurological manifestations. In males, four intronic SNPs in the PBX/knotted homeobox 2 gene (PKNOX2) were found to be associated with endocarditis. None of the association tests in the female population reached overall statistical significance; the associations with the lowest P values included other cardiac conduction disorders, subdural hemorrhage, and myocarditis. The results might suggest shared genetics between V̇o2max and disease. However, further effort should be put into investigating the potential shared genetics between inborn V̇o2max and disease in larger cohorts to increase statistical power.NEW & NOTEWORTHY To our knowledge, this is the first genetic association study exploring how genes linked to cardiorespiratory fitness (CRF) relate to disease risk. By investigating shared genetics, we found indications that genetic variants linked to directly measured CRF also affect the level of blood creatinine, risk of diabetes, and endocarditis. Less certain findings showed that genetic variants of high CRF might cause lower body mass index, healthier HDL cholesterol, and lower resting heart rate.

Lipoprotein subfraction profiling in the search of new risk markers for myocardial infarction: The HUNT study.

BACKGROUND: Traditional biomarkers used to measure risk of myocardial infarction (MI) only explain a modest proportion of the incidence. Lipoprotein subfractions have the potential to improve risk prediction of MI. AIM: We aimed to identify lipoprotein subfractions that were associated with imminent MI risk. METHODS: We identified apparently healthy participants with a predicted low 10-year risk of MI from The Trøndelag Health Survey 3 (HUNT3) that developed MI within 5 years after inclusion (cases, n = 50) and 100 matched controls. Lipoprotein subfractions were analyzed in serum by nuclear magnetic resonance spectroscopy at time of inclusion in HUNT3. Lipoprotein subfractions were compared between cases and controls in the full population (N = 150), and in subgroups of males (n = 90) and females (n = 60). In addition, a sub analysis was performed in participants that experienced MI within two years and their matched controls (n = 56). RESULTS: None of the lipoprotein subfractions were significantly associated with future MI when adjusting for multiple testing (p<0.002). At nominal significance level (p<0.05), the concentration of apolipoprotein A1 in the smallest high-density lipoprotein (HDL) subfractions was higher in cases compared to controls. Further, in sub analyses based on sex, male cases had lower lipid concentration within the large HDL subfractions and higher lipid concentration within the small HDL subfractions compared to male controls (p<0.05). No differences were found in lipoprotein subfractions between female cases and controls. In sub analysis of individuals suffering from MI within two years, triglycerides in low-density lipoprotein were higher among cases (p<0.05). CONCLUSION: None of the investigated lipoprotein subfractions were associated with future MI after adjustment for multiple testing. However, our findings suggests that HDL subfractions may be of interest in relation to risk prediction for MI, especially in males. This need to be further investigated in future studies.

Associations between circulating microRNAs and lipid-rich coronary plaques measured with near-infrared spectroscopy.

Lipid-rich coronary atherosclerotic plaques often cause myocardial infarction (MI), and circulating biomarkers that reflect lipid content may predict risk of MI. We investigated the association between circulating microRNAs (miRs) are lipid-rich coronary plaques in 47 statin-treated patients (44 males) with stable coronary artery disease undergoing percutaneous coronary intervention. We assessed lipid content in non-culprit coronary artery lesions with near-infrared spectroscopy and selected the 4 mm segment with the highest measured lipid core burden index (maxLCBI4mm). Lipid-rich plaques were predefined as a lesion with maxLCBI4mm ≥ 324.7. We analyzed 177 circulating miRs with quantitative polymerase chain reaction in plasma samples. The associations between miRs and lipid-rich plaques were analyzed with elastic net. miR-133b was the miR most strongly associated with lipid-rich coronary plaques, with an estimated 18% increase in odds of lipid-rich plaques per unit increase in miR-133b. Assessing the uncertainty by bootstrapping, miR-133b was present in 82.6% of the resampled dataset. Inclusion of established cardiovascular risk factors did not attenuate the association. No evidence was found for an association between the other analyzed miRs and lipid-rich coronary plaques. Even though the evidence for an association was modest, miR-133b could be a potential biomarker of vulnerable coronary plaques and risk of future MI. However, the prognostic value and clinical relevance of miR-133b needs to be assessed in larger cohorts.

The association between circulating lipoprotein subfractions and lipid content in coronary atheromatous plaques assessed by near-infrared spectroscopy.

Background: Lipid content in coronary atheromatous plaques, measured by near-infrared spectroscopy (NIRS), can predict the risk of future coronary events. Biomarkers that reflect lipid content in coronary plaques may therefore improve coronary artery disease (CAD) risk assessment. Purpose: We aimed to investigate the association between circulating lipoprotein subfractions and lipid content in coronary atheromatous plaques in statin-treated patients with stable CAD undergoing percutaneous coronary intervention. Methods: 56 patients with stable CAD underwent three-vessel imaging with NIRS when feasible. The coronary artery segment with the highest lipid content, defined as the maximum lipid core burden index within any 4 mm length across the entire lesion (maxLCBI4mm), was defined as target segment. Lipoprotein subfractions and Lipoprotein a (Lp(a)) were analyzed in fasting serum samples by nuclear magnetic resonance spectroscopy and by standard in-hospital procedures, respectively. Penalized linear regression analyses were used to identify the best predictors of maxLCBI4mm. The uncertainty of the lasso estimates was assessed as the percentage presence of a variable in resampled datasets by bootstrapping. Results: Only modest evidence was found for an association between lipoprotein subfractions and maxLCBI4mm. The lipoprotein subfractions with strongest potential as predictors according to the percentage presence in resampled datasets were Lp(a) (78.1 % presence) and free cholesterol in the smallest high-density lipoprotein (HDL) subfractions (74.3 % presence). When including established cardiovascular disease (CVD) risk factors in the regression model, none of the lipoprotein subfractions were considered potential predictors of maxLCBI4mm. Conclusion: In this study, serum levels of Lp(a) and free cholesterol in the smallest HDL subfractions showed the strongest potential as predictors for lipid content in coronary atheromatous plaques. Although the evidence is modest, our study suggests that measurement of lipoprotein subfractions may provide additional information with respect to coronary plaque composition compared to traditional lipid measurements, but not in addition to established risk factors. Further and larger studies are needed to assess the potential of circulating lipoprotein subfractions as meaningful biomarkers both for lipid content in coronary atheromatous plaques and as CVD risk markers.

Small LDL subfractions are associated with coronary atherosclerosis despite no differences in conventional lipids.

Lipoprotein subfractions currently represent a new source of cardiovascular disease (CVD) risk markers that may provide more information than conventional lipid measures. We aimed to investigate whether lipoprotein subfractions are associated with coronary atherosclerosis in patients without prior known CVD. Fasting serum samples from 60 patients with suspected coronary artery disease (CAD) were collected before coronary angiography and analyzed by nuclear magnetic resonance (NMR) spectroscopy. The severity of coronary atherosclerosis was quantified by the Gensini score (≤20.5 = nonsignificant coronary atherosclerosis, 20.6-30.0 = intermediate coronary atherosclerosis, ≥30.1 = significant CAD). Differences in lipoprotein subfractions between the three Gensini groups were assessed by two-way ANOVA, adjusted for statin use. Despite no differences in conventional lipid measures between the three Gensini groups, patients with significant CAD had higher apolipoprotein-B/apolipoprotein-A1 ratio, 30% more small and dense low-density lipoprotein 5 (LDL-5) particles, and increased levels of cholesterol, triglycerides, and phospholipids within LDL-5 compared with patients with nonsignificant coronary atherosclerosis and intermediate coronary atherosclerosis (P ≤ 0.001). In addition, the low-density lipoprotein (LDL) cholesterol/high-density lipoprotein cholesterol ratio, and triglyceride levels of LDL 4 were significantly increased in patients with significant CAD compared with patients with nonsignificant coronary atherosclerosis. In conclusion, small and dense lipoprotein subfractions were associated with coronary atherosclerosis in patients without prior CVD. Additional studies are needed to explore whether lipoprotein subfractions may represent biomarkers offering a clinically meaningful improvement in the risk prediction of CAD.

COX7A2L genetic variants determine cardiorespiratory fitness in mice and human.

Mitochondrial respiratory complexes form superassembled structures called supercomplexes. COX7A2L is a supercomplex-specific assembly factor in mammals, although its implication for supercomplex formation and cellular metabolism remains controversial. Here we identify a role for COX7A2L for mitochondrial supercomplex formation in humans. By using human cis-expression quantitative trait loci data, we highlight genetic variants in the COX7A2L gene that affect its skeletal muscle expression specifically. The most significant cis-expression quantitative trait locus is a 10-bp insertion in the COX7A2L 3' untranslated region that increases messenger RNA stability and expression. Human myotubes harboring this insertion have more supercomplexes and increased respiration. Notably, increased COX7A2L expression in the muscle is associated with lower body fat and improved cardiorespiratory fitness in humans. Accordingly, specific reconstitution of Cox7a2l expression in C57BL/6J mice leads to higher maximal oxygen consumption, increased lean mass and increased energy expenditure. Furthermore, Cox7a2l expression in mice is induced specifically in the muscle upon exercise. These findings elucidate the genetic basis of mitochondrial supercomplex formation and function in humans and show that COX7A2L plays an important role in cardiorespiratory fitness, which could have broad therapeutic implications in reducing cardiovascular mortality.

Genome-Wide Association Study Identifies New Genetic Determinants of Cardiorespiratory Fitness: The Trøndelag Health Study.

PURPOSE: Low cardiorespiratory fitness (CRF) is a major risk factor for cardiovascular disease (CVD) and a stronger predictor of CVD morbidity and mortality than established risk factors. The genetic component of CRF, quantified as peak oxygen uptake (V̇O 2peak ), is estimated to be ~60%. Unfortunately, current studies on genetic markers for CRF have been limited by small sample sizes and using estimated CRF. To overcome these limitations, we performed a large-scale systematic screening for genetic variants associated with V̇O 2peak . METHODS: A genome-wide association study was performed with BOLT-LMM including directly measured V̇O 2peak from 4525 participants in the HUNT3 Fitness study and 14 million single-nucleotide polymorphisms (SNP). For validation, similar analyses were performed in the United Kingdom Biobank (UKB), where CRF was assessed through a submaximal bicycle test, including ~60,000 participants and ~60 million SNP. Functional mapping and annotation of the genome-wide association study results was conducted using FUMA. RESULTS: In HUNT, two genome-wide significant SNP associated with V̇O 2peak were identified in the total population, two in males, and 35 in females. Two SNP in the female population showed nominally significant association in the UKB. One of the replicated SNP is located in PIK3R5 , shown to be of importance for cardiac function and CVD. Bioinformatic analyses of the total and male population revealed candidate SNP in PPP3CA , previously associated with CRF. CONCLUSIONS: We identified 38 novel SNP associated with V̇O 2peak in HUNT. Two SNP were nominally replicated in UKB. Several interesting genes emerged from the functional analyses, among them one previously reported to be associated with CVD and another with CRF.

Atherogenic lipidomics profile in healthy individuals with low cardiorespiratory fitness: The HUNT3 fitness study.

BACKGROUND AND AIMS: Low cardiorespiratory fitness is a strong and independent risk factor for cardiovascular disease (CVD). Serum profiling of healthy individuals with large differences in cardiorespiratory fitness may therefore reveal early biomarkers of CVD development. Thus, we aimed to identify circulating lipoprotein subfractions differentially expressed between groups of individuals with large differences in cardiorespiratory fitness, measured as maximal oxygen uptake (VO2max). METHODS: Healthy subjects (40-59 years) were selected from the third wave of the Trøndelag health study (HUNT3) based on having an age-dependent high VO2max (47.1 ± 7.7 mL kg-1·min-1, n = 103) or low VO2max (31.4 ± 4.9 mL kg-1·min-1, n = 108). The individuals were matched on gender, age, physical activity level and fasting status. RESULTS: 99 lipoprotein subfractions were quantified in serum samples using nuclear magnetic resonance (NMR) lipidomics. Standard clinical analyses showed similar levels of total cholesterol, low-density lipoprotein (LDL)-cholesterol and high-density lipoprotein (HDL)-cholesterol between the groups, and slightly higher levels of triglycerides in participants with low VO2max. Thirteen lipoprotein subfractions were increased in the low VO2max group compared to the high VO2max group (p < 0.005), including mainly large very low-density lipoprotein (VLDL) subfractions. In addition, triglyceride levels in small-sized HDL and LDL particles were increased in participants with low VO2max. Correlation analyses between VO2max and lipoproteins subfractions displayed a negative correlation between VO2max and the levels of cholesterol and phospholipids in the small HDL particles. The lipoprotein profile of individuals with low VO2max is similar to the profile of insulin resistant individuals. CONCLUSIONS: Low VO2max was associated with enrichment of large VLDL particles, as well as an increased triglycerides content in the small and dense HDL and LDL particles. This unfavorable lipid profile is likely to be involved in the strong associations between VO2max and CVD.

Associations between circulating microRNAs and coronary plaque characteristics: potential impact from physical exercise.

microRNAs (miRs) are involved in different steps in the development of atherosclerosis and are proposed as promising biomarkers of coronary artery disease (CAD). We hypothesized that circulating levels of miRs were associated with coronary plaque components assessed by radiofrequency intravascular ultrasound (RF-IVUS) before and after aerobic exercise intervention. Thirty-one patients with CAD treated with percutaneous coronary intervention (PCI) previously included in a randomized trial with aerobic interval training (AIT) or moderate continuous training (MCT) as post-PCI intervention were included. Coronary plaque characteristics by grayscale and RF-IVUS and predefined circulating candidate miRs in plasma were analyzed at baseline and follow-up. Associations between miRs and coronary plaque composition, and the potential effect from exercise, were analyzed using linear regression. Circulating levels of miR-15a-5p, miR-30e-5p, miR-92a-3p, miR-199a-3p, miR-221-3p, and miR-222-3p were associated with baseline coronary necrotic core volume. Following exercise intervention, decreased levels of miR-15a-5p, miR-93-5p, and miR-451a, and increased levels of miR-146a-5p were associated with an observed regression of coronary plaque burden. A mirPath prediction tool identified that genes regulated by miR-15a-5p, miR-199a-3p, and miR-30e-5p were significantly overrepresented in pathways related to fatty acid biosynthesis and fatty acid metabolism. This exploratory study demonstrated six miRs associated with coronary necrotic core, a marker of plaque vulnerability. In addition, changes in four miRs were associated with a regression of coronary plaque burden following exercise intervention. These novel findings may identify potential future biomarkers of CAD and coronary plaque composition.

Genome wide association study of response to interval and continuous exercise training: the Predict-HIIT study.

BACKGROUND: Low cardiorespiratory fitness (V̇O2peak) is highly associated with chronic disease and mortality from all causes. Whilst exercise training is recommended in health guidelines to improve V̇O2peak, there is considerable inter-individual variability in the V̇O2peak response to the same dose of exercise. Understanding how genetic factors contribute to V̇O2peak training response may improve personalisation of exercise programs. The aim of this study was to identify genetic variants that are associated with the magnitude of V̇O2peak response following exercise training. METHODS: Participant change in objectively measured V̇O2peak from 18 different interventions was obtained from a multi-centre study (Predict-HIIT). A genome-wide association study was completed (n = 507), and a polygenic predictor score (PPS) was developed using alleles from single nucleotide polymorphisms (SNPs) significantly associated (P < 1 × 10-5) with the magnitude of V̇O2peak response. Findings were tested in an independent validation study (n = 39) and compared to previous research. RESULTS: No variants at the genome-wide significance level were found after adjusting for key covariates (baseline V̇O2peak, individual study, principal components which were significantly associated with the trait). A Quantile-Quantile plot indicates there was minor inflation in the study. Twelve novel loci showed a trend of association with V̇O2peak response that reached suggestive significance (P < 1 × 10-5). The strongest association was found near the membrane associated guanylate kinase, WW and PDZ domain containing 2 (MAGI2) gene (rs6959961, P = 2.61 × 10-7). A PPS created from the 12 lead SNPs was unable to predict V̇O2peak response in a tenfold cross validation, or in an independent (n = 39) validation study (P > 0.1). Significant correlations were found for beta coefficients of variants in the Predict-HIIT (P < 1 × 10-4) and the validation study (P < × 10-6), indicating that general effects of the loci exist, and that with a higher statistical power, more significant genetic associations may become apparent. CONCLUSIONS: Ongoing research and validation of current and previous findings is needed to determine if genetics does play a large role in V̇O2peak response variance, and whether genomic predictors for V̇O2peak response trainability can inform evidence-based clinical practice. Trial registration Australian New Zealand Clinical Trials Registry (ANZCTR), Trial Id: ACTRN12618000501246, Date Registered: 06/04/2018, http://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=374601&isReview=true .

Circulating MicroRNA-210 Concentrations in Patients with Acute Heart Failure: Data from the Akershus Cardiac Examination 2 Study.

BACKGROUND: MicroRNA (miR)-210 expression is induced by acute and chronic hypoxia and provides prognostic information in patients with aortic stenosis and acute coronary syndrome. We hypothesized that circulating miR-210 concentrations could provide diagnostic and prognostic information in patients with acute heart failure (HF). METHODS: We measured miR-210 concentrations in serum samples on admission from 314 patients hospitalized for acute dyspnea and 9 healthy control subjects. The diagnostic and prognostic properties of miR-210 were tested in patients after adjudication of all diagnoses and with median follow-up of 464 days. RESULTS: All patients and control subjects had miR-210 concentrations within the range of detection, and the analytical variation was low as the coefficient of variation of synthetic spike-in RNA was 4%. Circulating miR-210 concentrations were increased in patients with HF compared to healthy control subjects, but miR-210 concentrations did not separate patients with acute HF (n = 143) from patients with non-HF-related dyspnea (n = 171): the area under the curve was 0.50 (95% CI 0.43-0.57). Circulating miR-210 concentrations were associated with mortality (n = 114) after adjustment for clinical risk factors (hazard ratio 1.65 [95% CI 1.03-2.62] per unit miR-210 increase), but this association was attenuated and not significant after adjustment for established cardiac protein biomarkers. CONCLUSIONS: Circulating miR-210 concentrations are associated with mortality, but do not add to established protein biomarkers for diagnosis or prognosis in patients with acute dyspnea.

Identification of novel genetic variants associated with cardiorespiratory fitness.

INTRODUCTION: Low maximal oxygen uptake (VO2max) is a strong and independent risk factor for all-cause and cardiovascular disease (CVD) mortality. For other CVD risk factors, numerous genetic association studies have been performed, revealing promising risk markers and new therapeutic targets. However, large genomic association studies on VO2max are still lacking, despite the fact that VO2max has a large genetic component. METHODS: We performed a genetic association study on 123.545 single-nucleotide polymorphisms (SNPs) and directly measured VO2max in 3470 individuals (exploration cohort). Candidate SNPs from the exploration cohort were analyzed in a validation cohort of 718 individuals, in addition to 7 wild-card SNPs. Sub-analyses were performed for each gender. Validated SNPs were used to create a genetic score for VO2max. In silico analyses and genotype-phenotype databases were used to predict physiological function of the SNPs. RESULTS: In the exploration cohort, 41 SNPs were associated with VO2max (p < 5.0 ∗ 10-4). Six of the candidate SNPs were associated with VO2max also in the validation cohort, in addition to three wild-card SNPs (p < 0.05, in men, women or both). The cumulative number of high-VO2max-SNPs correlated negatively with CVD risk factors, e.g. waist-circumference, visceral fat, fat %, cholesterol levels and BMI. In silico analysis indicated that several of the VO2max-SNPs influence gene expression in adipose tissue, skeletal muscle and heart. CONCLUSION: We discovered and validated new SNPs associated with VO2max and proposed possible links between VO2max and CVD. Studies combining several large cohorts with directly measured VO2max are needed to identify more SNPs associated with this phenotype.

Circulating microRNAs as predictive biomarkers of myocardial infarction: Evidence from the HUNT study.

BACKGROUND AND AIMS: Several risk prediction models for coronary heart disease (CHD) are available today, however, they only explain a modest proportion of the incidence. Circulating microRNAs (miRs) have recently been associated with processes in CHD development, and may therefore represent new potential risk markers. The aim of the study was to assess the incremental value of adding circulating miRs to the Framingham Risk Score (FRS). METHODS: This is a case-control study with a 10-year observation period, with fatal and non-fatal myocardial infarction (MI) as endpoint. At baseline, ten candidate miRs were quantified by real-time polymerase chain reaction in serum samples from 195 healthy participants (60-79 years old). During the follow-up, 96 participants experienced either a fatal (n = 36) or a non-fatal MI (n = 60), whereas the controls (n = 99) remained healthy. By using best subset logistic regression, we identified the miRs that together with the FRS for hard CHD best predicted future MI. The model evaluation was performed by 10-fold cross-validation reporting area under curve (AUC) from the receiver operating characteristic curve (ROC). RESULTS: The best miR-based logistic regression risk-prediction model for MI consisted of a combination of miR-21-5p, miR-26a-5p, mir-29c-3p, miR-144-3p and miR-151a-5p. By adding these 5 miRs to the FRS, AUC increased from 0.66 to 0.80. In comparison, adding other important CHD risk factors (waist-hip ratio, triglycerides, glucose, creatinine) to the FRS only increased AUC from 0.66 to 0.68. CONCLUSIONS: Circulating levels of miRs can add value on top of traditional risk markers in predicting future MI in healthy individuals.

A Multi-Center Comparison of O2peak Trainability Between Interval Training and Moderate Intensity Continuous Training.

There is heterogeneity in the observed O2peak response to similar exercise training, and different exercise approaches produce variable degrees of exercise response (trainability). The aim of this study was to combine data from different laboratories to compare O2peak trainability between various volumes of interval training and Moderate Intensity Continuous Training (MICT). For interval training, volumes were classified by the duration of total interval time. High-volume High Intensity Interval Training (HIIT) included studies that had participants complete more than 15 min of high intensity efforts per session. Low-volume HIIT/Sprint Interval Training (SIT) included studies using less than 15 min of high intensity efforts per session. In total, 677 participants across 18 aerobic exercise training interventions from eight different universities in five countries were included in the analysis. Participants had completed 3 weeks or more of either high-volume HIIT (n = 299), low-volume HIIT/SIT (n = 116), or MICT (n = 262) and were predominately men (n = 495) with a mix of healthy, elderly and clinical populations. Each training intervention improved mean O2peak at the group level (P < 0.001). After adjusting for covariates, high-volume HIIT had a significantly greater (P < 0.05) absolute O2peak increase (0.29 L/min) compared to MICT (0.20 L/min) and low-volume HIIT/SIT (0.18 L/min). Adjusted relative O2peak increase was also significantly greater (P < 0.01) in high-volume HIIT (3.3 ml/kg/min) than MICT (2.4 ml/kg/min) and insignificantly greater (P = 0.09) than low-volume HIIT/SIT (2.5 mL/kg/min). Based on a high threshold for a likely response (technical error of measurement plus the minimal clinically important difference), high-volume HIIT had significantly more (P < 0.01) likely responders (31%) compared to low-volume HIIT/SIT (16%) and MICT (21%). Covariates such as age, sex, the individual study, population group, sessions per week, study duration and the average between pre and post O2peak explained only 17.3% of the variance in O2peak trainability. In conclusion, high-volume HIIT had more likely responders to improvements in O2peak compared to low-volume HIIT/SIT and MICT.

Impact of High-Intensity Interval Training on Disease Activity and Disease in Patients With Psoriatic Arthritis: A Randomized Controlled Trial.

OBJECTIVE: To evaluate the impact of high-intensity interval training (HIIT) on disease activity and disease perception in patients with psoriatic arthritis (PsA) and to evaluate whether a potential effect could be sustained for a longer period of time. METHODS: We randomly assigned 67 patients with PsA (43 women and 24 men) to an intervention group in which patients performed HIIT for 11 weeks or a control group of patients who were instructed not to change their physical exercise habits. Outcomes were assessed at 3 months and 9 months with the patient's global assessment (PGA), fatigue, and pain scores measured on a 100-mm visual analog scale (VAS), and the composite Disease Activity Score in 44 joints (DAS44) was calculated. We used linear mixed models to calculate the mean difference (95% confidence interval [95% CI]) between groups according to the intent-to-treat principle. RESULTS: At 3 months, there was no clear difference in the PGA score (-0.49 [95% CI -10.91, 9.94]), DAS44 (-0.08 [95% CI -0.36, 0.20]), or pain intensity (5.45 [95% CI -4.36, 15.26]) between the groups. However, patients in the intervention group reported less fatigue (-12.83 [95% CI -25.88, 0.23]) than those in the control group. There was no evidence of long-term effects of HIIT on outcomes measured at 9 months. CONCLUSION: HIIT showed no clear effects on disease activity markers in patients with PsA, but the intervention (exercise) group reported meaningfully less fatigue after the intervention period. The results of this study suggest that patients with PsA tolerate HIIT without deterioration of disease activity and with improvement in fatigue.

Effect of high-intensity interval training on cardiovascular disease risk factors and body composition in psoriatic arthritis: a randomised controlled trial.

BACKGROUND: Psoriatic arthritis (PsA) is associated with an accumulation of cardiovascular disease (CVD) risk factors. The aim of this study was to evaluate the effect of high-intensity interval training (HIIT) on CVD risk factors in patients with PsA. METHODS: We randomly assigned 61 patients with PsA (41 women and 20 men) to an intervention group performing HIIT for 11 weeks or a control group who were instructed to not change their physical exercise habits. Outcomes were assessed at 3 and 9 months with measures on maximal oxygen uptake (VO2max), fat percentage and Body Mass Index (BMI). We used linear mixed models to calculate mean difference with 95% CI between the groups according to the intention-to-treat principle. RESULTS: At 3 months, the HIIT group had a 3.72 mL/kg/min (95% CI 2.38 to 5.06) higher VO2max and a 1.28 (95% CI -2.51 to -0.05) lower truncal fat percentage than controls. There was also some evidence that the HIIT group had lower total fat percentage (-0.80; 95% CI -1.71 to 0.10) and slightly lower BMI (-0.31; 95% CI -0.78 to 0.17) than the control group. At 9 months, the HIIT group had still a higher VO2max (3.08; 95% CI 1.63 to 4.53) than the control group, whereas the difference in other factors were small. CONCLUSION: In patients with PsA, 3 months with HIIT was associated with a substantial increase in VO2max and a reduction in truncal fat percentage compared with controls. The beneficial effect on VO2max was also sustained through 9 months. TRIAL REGISTRATION NUMBER: NCT02995460.