John Beilby

Novel loci affecting iron homeostasis and their effects in individuals at risk for hemochromatosis (vol 5, 4926, 2014)

Corrigendum: Novel loci affecting iron homeostasis and their effects in individuals at risk for hemochromatosis

Sequence variants affecting eosinophil numbers associate with asthma and myocardial infarction

Eosinophils are pleiotropic multifunctional leukocytes involved in initiation and propagation of inflammatory responses and thus have important roles in the pathogenesis of inflammatory diseases. Here we describe a genome-wide association scan for sequence variants affecting eosinophil counts in blood of 9,392 Icelanders. The most significant SNPs were studied further in 12,118 Europeans and 5,212 East Asians. SNPs at 2q12 (rs1420101), 2q13 (rs12619285), 3q21 (rs4857855), 5q31 (rs4143832) and 12q24 (rs3184504) reached genome-wide significance (P = 5.3 × 10−14, 5.4 × 10−10, 8.6 × 10−17, 1.2 × 10−10 and 6.5 × 10−19, respectively). A SNP at IL1RL1 associated with asthma (P = 5.5 × 10−12) in a collection of ten different populations (7,996 cases and 44,890 controls). SNPs at WDR36, IL33 and MYB that showed suggestive association with eosinophil counts were also associated with atopic asthma (P = 4.2 × 10−6, 2.2 × 10−5 and 2.4 × 10−4, respectively). We also found that a nonsynonymous SNP at 12q24, in SH2B3, associated significantly (P = 8.6 × 10−8) with myocardial infarction in six different populations (6,650 cases and 40,621 controls).

Identification of IL6R and chromosome 11q13.5 as risk loci for asthma

BACKGROUND We aimed to identify novel genetic variants affecting asthma risk, since these might provide novel insights into molecular mechanisms underlying the disease. METHODS We did a genome-wide association study (GWAS) in 2669 physician-diagnosed asthmatics and 4528 controls from Australia. Seven loci were prioritised for replication after combining our results with those from the GABRIEL consortium (n=26,475), and these were tested in an additional 25,358 independent samples from four in-silico cohorts. Quantitative multi-marker scores of genetic load were constructed on the basis of results from the GABRIEL study and tested for association with asthma in our Australian GWAS dataset. FINDINGS Two loci were confirmed to associate with asthma risk in the replication cohorts and reached genome-wide significance in the combined analysis of all available studies (n=57,800): rs4129267 (OR 1·09, combined p=2·4×10(-8)) in the interleukin-6 receptor (IL6R) gene and rs7130588 (OR 1·09, p=1·8×10(-8)) on chromosome 11q13.5 near the leucine-rich repeat containing 32 gene (LRRC32, also known as GARP). The 11q13.5 locus was significantly associated with atopic status among asthmatics (OR 1·33, p=7×10(-4)), suggesting that it is a risk factor for allergic but not non-allergic asthma. Multi-marker association results are consistent with a highly polygenic contribution to asthma risk, including loci with weak effects that might be shared with other immune-related diseases, such as NDFIP1, HLA-B, LPP, and BACH2. INTERPRETATION The IL6R association further supports the hypothesis that cytokine signalling dysregulation affects asthma risk, and raises the possibility that an IL6R antagonist (tocilizumab) may be effective to treat the disease, perhaps in a genotype-dependent manner. Results for the 11q13.5 locus suggest that it directly increases the risk of allergic sensitisation which, in turn, increases the risk of subsequent development of asthma. Larger or more functionally focused studies are needed to characterise the many loci with modest effects that remain to be identified for asthma. FUNDING National Health and Medical Research Council of Australia. A full list of funding sources is provided in the webappendix.

Hyperhomocysteinemia but Not the C677T Mutation of Methylenetetrahydrofolate Reductase Is an Independent Risk Determinant of Carotid Wall Thickening The Perth Carotid Ultrasound Disease Assessment Study (CUDAS)

BACKGROUND Hyperhomocysteinemia has been identified as a potential risk factor for atherosclerosis. This study examined whether a modest elevation of plasma total homocysteine (tHcy) was an independent risk factor for increased carotid artery intimal-medial wall thickness (IMT) and focal plaque formation in a large, randomly selected community population. We also examined whether vitamin cofactors and the C677T genetic mutation of the methylenetetrahydrofolate reductase (MTHFR) enzyme were major contributors to elevated plasma tHcy and carotid vascular disease. METHODS AND RESULTS In 1111 subjects (558 men, 553 women) 52+/-13 years old (mean+/-SD; range, 27 to 77 years) recruited from a random electoral roll survey, we measured fasting tHcy and performed bilateral carotid B-mode ultrasound. For the total population, mean tHcy was 12.1+/-4.0 micromol/L. Plasma tHcy levels were correlated with IMT (Spearman rank rs=0.31, P=0.0001). After adjustment for age, sex, and other conventional risk factors, subjects in the highest versus the lowest quartile of tHcy had an odds ratio of 2.60 (95% CI, 1.51 to 4.45) for increased IMT and 1.76 (95% CI, 1.10 to 2.82) for plaque. Serum and dietary folate levels and the C677T mutation in MTHFR were independent determinants of tHcy (all P=0.0001). The mutant homozygotes (10% of the population) had higher mean tHcy than heterozygotes or those without the mutation (14.2 versus 12.3 versus 11.6 micromol/L, respectively, P=0.0001). The inverse association of folate levels with tHcy was steeper in the mutant homozygotes. Despite this, the C677T MTHFR mutation was not independently predictive of increased carotid IMT or plaque formation. CONCLUSIONS Mild hyperhomocysteinemia is an independent risk factor for increased carotid artery wall thickness and plaque formation in a general population. Lower levels of dietary folate intake and the C677T mutation in MTHFR are important causes of mild hyperhomocysteinemia and may therefore contribute to vascular disease in the community.

Elevated Interleukin-18 Levels Are Associated With the Metabolic Syndrome Independent of Obesity and Insulin Resistance

Objective—Activated innate immunity is thought to be involved in the pathogenesis of metabolic syndrome and type 2 diabetes. Interleukin-18 (IL-18) is a pleiotropic proinflammatory cytokine with important regulatory functions in the innate immune response. We sought to determine whether an elevated IL-18 concentration was a risk predictor for metabolic syndrome in a community population independent of obesity and hyperinsulinemia. Methods and Results—A representative general population, aged 27 to 77 years, without clinical diabetes was studied for clinical and biochemical risk factors for metabolic syndrome. Serum IL-18 concentration measured in 955 subjects correlated with metabolic syndrome traits including body mass index (BMI), waist circumference, triglyceride, high-density lipoprotein (inversely), and fasting glucose and insulin levels (all P<0.001). Mean IL-18 levels rose progressively with the increasing number of metabolic risk factors (ANOVA P<0.001). After adjusting for age, gender, BMI, and insulin levels, increasing IL-18 tertiles were associated with an odds ratio for metabolic syndrome of 1.0, 1.42, and 2.28, respectively (P trend=0.007). The graded risk relation was even stronger in nonobese subjects and not attenuated when adjusted for C-reactive protein and IL-6 levels. Conclusion—Our findings support the hypothesis that activation of IL-18 is involved in the pathogenesis of the metabolic syndrome.

Monocyte Count, But Not C-Reactive Protein or Interleukin-6, Is an Independent Risk Marker for Subclinical Carotid Atherosclerosis

Background and Purpose— Systemic inflammatory markers have been shown to predict future cardiovascular events, but whether they are associated with early atherosclerosis is uncertain. We investigated the relationship of inflammatory markers interleukin-6 (IL-6), high-sensitive C-reactive protein (hs-CRP), fibrinogen, monocyte count, and white cell count (WCC) with subclinical carotid atherosclerosis in a healthy community population. Methods— B-mode carotid ultrasound was performed on 1111 randomly selected male and female subjects aged 27 to 77 years. Serum IL-6, hs-CRP, plasma fibrinogen, monocyte count, and WCC were measured on all subjects, along with conventional cardiovascular risk factors. Results— Multivariate analysis showed that IL-6 (P <0.0001), fibrinogen (P =0.007), and monocyte count (P =0.001) were associated with carotid plaque formation in the whole population. Monocyte count remained associated independently with carotid plaque formation when adjusted further for conventional risk factors (odds ratio per SD increase in monocyte count 1.4; 95% CI, 1.13 to 1.73; P =0.002). IL-6 (P <0.0001), fibrinogen (P <0.0001), and monocyte count (P =0.04) were also associated with carotid intima-medial thickness (IMT) in the whole population. However, when adjusted further for conventional risk factors, none remained independently predictive of carotid IMT. Further analysis showed an age–monocyte interaction (P =0.03), with monocyte count being an independent predictor of carotid IMT in the older age group only (>53 years; P =0.003). Conclusion— In a healthy community population, monocyte count is a better independent predictor of common carotid IMT and plaque formation than IL-6, hs-CRP, fibrinogen, and WCC. Monocyte count may represent an inexpensive, easy-to-measure risk marker for subclinical carotid atherosclerosis.

Effect of water immersion methods on post-exercise recovery from simulated team sport exercise

This study aimed to compare the efficacy of hot/cold contrast water immersion (CWI), cold-water immersion (COLD) and no recovery treatment (control) as post-exercise recovery methods following exhaustive simulated team sports exercise. Repeated sprint ability, strength, muscle soreness and inflammatory markers were measured across the 48-h post-exercise period. Eleven male team-sport athletes completed three 3-day testing trials, each separated by 2 weeks. On day 1, baseline measures of performance (10 m x 20 m sprints and isometric strength of quadriceps, hamstrings and hip flexors) were recorded. Participants then performed 80 min of simulated team sports exercise followed by a 20-m shuttle run test to exhaustion. Upon completion of the exercise, and 24h later, participants performed one of the post-exercise recovery procedures for 15 min. At 48 h post-exercise, the performance tests were repeated. Blood samples and muscle soreness ratings were taken before and immediately after post-exercise, and at 24h and 48 h post-exercise. In comparison to the control and CWI treatments, COLD resulted in significantly lower (p<0.05) muscle soreness ratings, as well as in reduced decrements to isometric leg extension and flexion strength in the 48-h post-exercise period. COLD also facilitated a more rapid return to baseline repeated sprint performances. The only benefit of CWI over control was a significant reduction in muscle soreness 24h post-exercise. This study demonstrated that COLD following exhaustive simulated team sports exercise offers greater recovery benefits than CWI or control treatments.

Age-Related Changes in Thyroid Function: A Longitudinal Study of a Community-Based Cohort

CONTEXT In cross-sectional studies, serum TSH concentrations increase with age. This has not been examined longitudinally, and it is uncertain whether the TSH increase reflects healthy aging or occult thyroid failure. METHODS We measured serum TSH, free T(4), thyroid peroxidase, and thyroglobulin antibodies in 1100 participants in the 1981 and 1994 Busselton Health Surveys and derived a reference group of 908 individuals without thyroid disease or thyroid antibodies. We examined changes in thyroid function longitudinally and, in 781 participants, explored associations with the CAPZB polymorphism rs10917469. RESULTS At 13 yr follow-up, mean serum TSH increased from 1.49 to 1.81 mU/liter, a change in mean TSH (ΔTSH) of 0.32 mU/liter [95% confidence interval (CI) 0.27, 0.38, P < 0.001], whereas mean free T(4) concentration was unchanged (16.6 vs. 16.6 pmol/liter, P = 0.7). The TSH increase was most marked in the elderly, such that gender-adjusted ΔTSH increased by 0.08 mU/liter (95% CI 0.04, 0.11) for each decade of baseline age. People with higher baseline TSH values had proportionally smaller increases in TSH, with each additional 1.0 mU/liter of baseline TSH associated with a 0.13 mU/liter decrease (age and gender adjusted) in ΔTSH (95% CI 0.09, 0.16). The ΔTSH did not differ significantly by CAPZB genotype. CONCLUSIONS Aging is associated with increased serum TSH concentrations, with no change in free T(4) concentrations. The largest TSH increase is in people with the lowest TSH at baseline. This suggests that the TSH increase arises from age-related alteration in the TSH set point or reduced TSH bioactivity rather than occult thyroid disease.

Circulating adiponectin levels associate with inflammatory markers, insulin resistance and metabolic syndrome independent of obesity

Background:Adiponectin is an abundantly expressed adipocyte-specific protein, whose level is decreased in obesity, and which appears to be a key participant in developing inflammation, insulin resistance and metabolic syndrome (MetS). We examined whether the relationship between adiponectin and inflammatory markers, insulin resistance and MetS was independent of obesity.Methods and results:The study was performed in 1094 men and women, aged 27–77 years, from a representative community population. We measured serum inflammatory markers, homoeostasis model assessment of insulin resistance (HOMA-IR) and prevalent MetS using National Cholesterol Education Program ATPIII criteria. Sex- and age-adjusted plasma adiponectin concentration was inversely correlated with body mass index (BMI), waist–hip ratio, diastolic blood pressure, triglycerides, glucose and fasting insulin, and positively correlated with HDL cholesterol (all P<0.005). Log plasma adiponectin was a significant negative correlate of the levels of C-reactive protein, interleukin-6, interleukin-18, fibrinogen and white cell count independent of level of obesity. Log plasma adiponectin was also an inverse associate of log HOMA-IR (P<0.001) independent of obesity. Subjects in the top compared to bottom sex-specific plasma adiponectin quartile had a multivariate-adjusted odds ratio (OR) of 0.21 (95% CI, 0.11–0.42; P<0.001) for prevalent MetS, and the association was independent of age, sex, BMI, log insulin and log intereukin-18 levels.Conclusion:Our findings suggest that higher circulating adiponectin levels may mitigate against adipose-related inflammation, insulin resistance and MetS as much in lean as obese persons. At any rate circulating adiponectin level is a strong risk marker for MetS, which is independent of measures of adiposity, insulin resistance and inflammatory markers.

Reduced serum total osteocalcin is associated with metabolic syndrome in older men via waist circumference, hyperglycemia, and triglyceride levels

OBJECTIVE Bone-derived undercarboxylated osteocalcin regulates insulin secretion and sensitivity in mice, and reduced serum total osteocalcin (TOC) is associated with diabetes in humans. However, the relationship between TOC levels and other cardiovascular risk factors is uncertain. We sought to determine whether serum TOC is associated with metabolic syndrome and its components in older men. DESIGN Cross-sectional analysis from a population-based cohort of men aged >or=70 years. METHODS Early morning sera were assayed for TOC. Insulin resistance was estimated using a homeostatic model (HOMA2-IR). Metabolic syndrome was defined according to NCEP-ATPIII criteria. RESULTS TOC was assayed in 4047 men. Men who were not fasting and reported having bone fractures, Pagets disease, or bisphosphonate, glucocorticoid, or warfarin use were excluded, leaving 2765 men with metabolic syndrome present in 797 (28.8%). TOC was inversely associated with waist circumference, glucose, and triglyceride levels and HOMA2-IR (all P<0.001), and was lower in men with metabolic syndrome (mean+/-S.E.M.: 20.1+/-0.4 vs 21.4+/-0.2 microg/l, P=0.002). In multivariate analysis, men with TOC of 13.25-16.55 and <13.25 microg/l had 1.5- to 2-fold increased risk of metabolic syndrome compared with men with levels >or=30 microg/l. TOC remained associated with metabolic syndrome after adjustment for individual components, but not after adjusting for both waist circumference and glucose. CONCLUSIONS Increased waist circumference, reduced TOC, elevated glucose, and triglyceride levels are inter-related in aging men. Osteocalcin may lie in the causal pathway between central adiposity and insulin resistance. Further research is required to evaluate whether interventions which raise osteocalcin levels might decrease cardiovascular risk.