Methodological considerations for identifying multiple plasma proteins associated with all-cause mortality in a population-based prospective cohort.

Novel methods to characterize the plasma proteome has made it possible to examine a wide range of proteins in large longitudinal cohort studies, but the complexity of the human proteome makes it difficult to identify robust protein-disease associations. Nevertheless, identification of individuals at high risk of early mortality is a central issue in clinical decision making and novel biomarkers may be useful to improve risk stratification. With adjustment for established risk factors, we examined the associations between 138 plasma proteins measured using two proximity extension assays and long-term risk of all-cause mortality in 3,918 participants of the population-based Malmö Diet and Cancer Study. To examine the reproducibility of protein-mortality associations we used a two-step random-split approach to simulate a discovery and replication cohort and conducted analyses using four different methods: Cox regression, stepwise Cox regression, Lasso-Cox regression, and random survival forest (RSF). In the total study population, we identified eight proteins that associated with all-cause mortality after adjustment for established risk factors and with Bonferroni correction for multiple testing. In the two-step analyses, the number of proteins selected for model inclusion in both random samples ranged from 6 to 21 depending on the method used. However, only three proteins were consistently included in both samples across all four methods (growth/differentiation factor-15 (GDF-15), N-terminal pro-B-type natriuretic peptide, and epididymal secretory protein E4). Using the total study population, the C-statistic for a model including established risk factors was 0.7222 and increased to 0.7284 with inclusion of the most predictive protein (GDF-15; P < 0.0001). All multiple protein models showed additional improvement in the C-statistic compared to the single protein model (all P < 0.0001). We identified several plasma proteins associated with increased risk of all-cause mortality independently of established risk factors. Further investigation into the putatively causal role of these proteins for longevity is needed. In addition, the examined methods for identifying multiple proteins showed tendencies for overfitting by including several putatively false positive findings. Thus, the reproducibility of findings using such approaches may be limited.

Meta-analysis uncovers genome-wide significant variants for rapid kidney function decline.

Rapid decline of glomerular filtration rate estimated from creatinine (eGFRcrea) is associated with severe clinical endpoints. In contrast to cross-sectionally assessed eGFRcrea, the genetic basis for rapid eGFRcrea decline is largely unknown. To help define this, we meta-analyzed 42 genome-wide association studies from the Chronic Kidney Diseases Genetics Consortium and United Kingdom Biobank to identify genetic loci for rapid eGFRcrea decline. Two definitions of eGFRcrea decline were used: 3 mL/min/1.73m2/year or more ("Rapid3"; encompassing 34,874 cases, 107,090 controls) and eGFRcrea decline 25% or more and eGFRcrea under 60 mL/min/1.73m2 at follow-up among those with eGFRcrea 60 mL/min/1.73m2 or more at baseline ("CKDi25"; encompassing 19,901 cases, 175,244 controls). Seven independent variants were identified across six loci for Rapid3 and/or CKDi25: consisting of five variants at four loci with genome-wide significance (near UMOD-PDILT (2), PRKAG2, WDR72, OR2S2) and two variants among 265 known eGFRcrea variants (near GATM, LARP4B). All these loci were novel for Rapid3 and/or CKDi25 and our bioinformatic follow-up prioritized variants and genes underneath these loci. The OR2S2 locus is novel for any eGFRcrea trait including interesting candidates. For the five genome-wide significant lead variants, we found supporting effects for annual change in blood urea nitrogen or cystatin-based eGFR, but not for GATM or LARP4B. Individuals at high compared to those at low genetic risk (8-14 vs. 0-5 adverse alleles) had a 1.20-fold increased risk of acute kidney injury (95% confidence interval 1.08-1.33). Thus, our identified loci for rapid kidney function decline may help prioritize therapeutic targets and identify mechanisms and individuals at risk for sustained deterioration of kidney function.

Glucose-dependent insulinotropic peptide and risk of cardiovascular events and mortality: a prospective study.

AIMS/HYPOTHESIS: Evidence that glucose-dependent insulinotropic peptide (GIP) and/or the GIP receptor (GIPR) are involved in cardiovascular biology is emerging. We hypothesised that GIP has untoward effects on cardiovascular biology, in contrast to glucagon-like peptide 1 (GLP-1), and therefore investigated the effects of GIP and GLP-1 concentrations on cardiovascular disease (CVD) and mortality risk. METHODS: GIP concentrations were successfully measured during OGTTs in two independent populations (Malmö Diet Cancer-Cardiovascular Cohort [MDC-CC] and Prevalence, Prediction and Prevention of Diabetes in Botnia [PPP-Botnia]) in a total of 8044 subjects. GLP-1 (n = 3625) was measured in MDC-CC. The incidence of CVD and mortality was assessed via national/regional registers or questionnaires. Further, a two-sample Mendelian randomisation (2SMR) analysis between the GIP pathway and outcomes (coronary artery disease [CAD] and myocardial infarction) was carried out using a GIP-associated genetic variant, rs1800437, as instrumental variable. An additional reverse 2SMR was performed with CAD as exposure variable and GIP as outcome variable, with the instrumental variables constructed from 114 known genetic risk variants for CAD. RESULTS: In meta-analyses, higher fasting levels of GIP were associated with risk of higher total mortality (HR[95% CI] = 1.22 [1.11, 1.35]; p = 4.5 × 10-5) and death from CVD (HR[95% CI] 1.30 [1.11, 1.52]; p = 0.001). In accordance, 2SMR analysis revealed that increasing GIP concentrations were associated with CAD and myocardial infarction, and an additional reverse 2SMR revealed no significant effect of CAD on GIP levels, thus confirming a possible effect solely of GIP on CAD. CONCLUSIONS/INTERPRETATION: In two prospective, community-based studies, elevated levels of GIP were associated with greater risk of all-cause and cardiovascular mortality within 5-9 years of follow-up, whereas GLP-1 levels were not associated with excess risk. Further studies are warranted to determine the cardiovascular effects of GIP per se.

Plasma kidney injury molecule-1 (p-KIM-1) levels and deterioration of kidney function over 16 years.

BACKGROUND: The kidney injury molecule-1 (KIM-1) has previously been associated with kidney function in rodents and humans. Yet its role as a predictive marker for future decline in kidney function has remained less clear. METHODS: At baseline (1991-1994), fasting plasma KIM-1 (p-KIM-1) was measured in 4739 participants of the population-based Malmö Diet and Cancer Study. Creatinine and cystatin C were used to calculate estimated glomerular filtration rate (eGFR) according to Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) Collaboration 2012 creatinine-cystatin C equation at baseline and follow-up examination (2007-2012). Incident CKD was defined as an eGFR <60 mL/min/1.73 m2 at follow-up. RESULTS: During a mean follow-up time of 16.6 years, high p-KIM-1 levels were associated with a greater decline in eGFR (quartile 1 -1.36 versus quartile 4 -1.54 mL/min/1.73 m2; P < 0.001). In multivariate analyses, the risk for incident CKD at the follow-up examination was higher among participants with baseline p-KIM-1 levels in the highest quartile {odds ratio [OR] 1.45 [95% confidence interval (CI) 1.10-1.92]} compared with those within the lowest quartile. The relative impact of baseline p-KIM-1 on incidence of CKD [OR 1.20 (95% CI 1.08-1.33) per 1 standard deviation (SD) increase in p-KIM-1] was comparable to those of age and systolic blood pressure (SBP) [OR 1.55 (95% CI 1.38-1.74) and OR 1.21 (95% CI 1.09-1.35) per 1 SD increase, respectively]. Adding p-KIM-1 to a conventional risk model resulted in significantly improved C-statistics (P = 0.04) and reclassified 9% of the individuals into the correct risk direction (continuous net reclassification improvement P = 0.02). Furthermore, the risk for hospitalization due to impaired renal function increased with increasing baseline p-KIM-1 [hazard ratio per 1 SD 1.43; (95% CI 1.18-1.74)] during a mean follow-up time of 19.2 years. CONCLUSION: Our results show that p-KIM-1 predicts the future decline of eGFR and risk of CKD in healthy middle-aged participants. Whether p-KIM-1 can be used to prioritize preventive action that needs to be further investigated.

Dimethylguanidino Valerate: A Lifestyle-Related Metabolite Associated With Future Coronary Artery Disease and Cardiovascular Mortality.

Background Identification of lifestyle modifiable metabolic pathways related to cardiometabolic disease risk is essential for improvement of primary prevention in susceptible individuals. It was recently shown that plasma dimethylguanidino valerate (DMGV) levels are associated with incident type 2 diabetes mellitus. Our aims were to investigate whether plasma DMGV is related to risk of future coronary artery disease and with cardiovascular mortality and to replicate the association with type 2 diabetes mellitus and pinpoint candidate lifestyle interventions susceptible to modulate DMGV levels. Methods and Results Plasma DMGV levels were measured using liquid chromatography-mass spectrometry in a total of 5768 participants from the MDC (Malmö Diet and Cancer Study-Cardiovascular Cohort), MPP (Malmö Preventive Project), and MOS (Malmö Offspring Study). Dietary intake assessment was performed in the MOS. Baseline levels of DMGV associated with incident coronary artery disease in both the MDC (hazard ratio=1.29; CI=1.16-1.43; P<0.001) and MPP (odds ratio=1.25; CI=1.08-1.44; P=2.4e-3). In the MDC, DMGV was associated with cardiovascular mortality and incident coronary artery disease, independently of traditional risk factors. Furthermore, the association between DMGV and incident type 2 diabetes mellitus was replicated in both the MDC (hazard ratio=1.83; CI=1.63-2.05; P<0.001) and MPP (odds ratio=1.65; CI=1.38-1.98; P<0.001). Intake of sugar-sweetened beverages was associated with increased levels of DMGV, whereas intake of vegetables and level of physical activity was associated with lower DMGV. Conclusions We discovered novel independent associations between plasma DMGV and incident coronary artery disease and cardiovascular mortality, while replicating the previously reported association with incident type 2 diabetes mellitus. Additionally, strong associations with sugar-sweetened beverages, vegetable intake, and physical activity suggest the potential to modify DMGV levels using lifestyle interventions.

Polygenetic risk for coronary artery disease increases hospitalization burden and mortality.

BACKGROUND: Coronary artery disease (CAD) is a leading cause of death worldwide and increasing cost for society. Genome wide association studies (GWAS) have identified common variants associated with CAD. Combining single nucleotide polymorphisms (SNPs) into a genetic risk score (GRS) can estimate an individual's genetic burden. OBJECTIVES: To investigate whether GRS for CAD can predict hospitalization and mortality. METHODS: 23,594 individuals without CAD at baseline and with full data for all covariates from the population based prospective study Malmö diet and cancer study were investigated. The association between hospitalizations was calculated by negative binomial regression and risk of mortality was calculated by Cox proportional hazards regression. The GRS was constructed from 50 SNPs. RESULTS: The study population was divided into quintiles according to the value of GRS. During the mean follow-up time of 17.8 years, 17,254 individuals were hospitalized at least once. Individuals in the highest quintile of GRS were hospitalized 10% more often than individuals in the lowest quintile (IRR: 1.10 [95% CI 1.04-1.16], p = 0.001), mainly for cardiovascular reasons (IRR: 1.31 [95% CI 1.20-1.43], p = 5.17 × 10-10). These individuals had highly increased risk of CVD mortality (HR: 1.44 [1.25-1.66], p = 6.56 × 10-7) but not the risk of mortality due to other causes. CONCLUSION: Our results suggest that genetic predisposition for CAD can predict hospitalization burden and mortality, especially due to cardiovascular causes, independently of traditional risk factors. As the risk conferred by the GRS is partially modifiable, our results may help to reduce societal costs, individual suffering and prolong life.

Subsequent Event Risk in Individuals With Established Coronary Heart Disease.

BACKGROUND: The Genetics of Subsequent Coronary Heart Disease (GENIUS-CHD) consortium was established to facilitate discovery and validation of genetic variants and biomarkers for risk of subsequent CHD events, in individuals with established CHD. METHODS: The consortium currently includes 57 studies from 18 countries, recruiting 185 614 participants with either acute coronary syndrome, stable CHD, or a mixture of both at baseline. All studies collected biological samples and followed-up study participants prospectively for subsequent events. RESULTS: Enrollment into the individual studies took place between 1985 to present day with a duration of follow-up ranging from 9 months to 15 years. Within each study, participants with CHD are predominantly of self-reported European descent (38%-100%), mostly male (44%-91%) with mean ages at recruitment ranging from 40 to 75 years. Initial feasibility analyses, using a federated analysis approach, yielded expected associations between age (hazard ratio, 1.15; 95% CI, 1.14-1.16) per 5-year increase, male sex (hazard ratio, 1.17; 95% CI, 1.13-1.21) and smoking (hazard ratio, 1.43; 95% CI, 1.35-1.51) with risk of subsequent CHD death or myocardial infarction and differing associations with other individual and composite cardiovascular endpoints. CONCLUSIONS: GENIUS-CHD is a global collaboration seeking to elucidate genetic and nongenetic determinants of subsequent event risk in individuals with established CHD, to improve residual risk prediction and identify novel drug targets for secondary prevention. Initial analyses demonstrate the feasibility and reliability of a federated analysis approach. The consortium now plans to initiate and test novel hypotheses as well as supporting replication and validation analyses for other investigators.

Commonly consumed beverages associate with different lifestyle and dietary intakes.

Sugar sweetened beverages (SSB), artificially sweetened beverages (ASB), juice, coffee and tea has been associated with risk of metabolic disease. High consumption of these beverages may be associated with certain characteristics of the overall diet that would be important to take into account when analysing beverage-disease associations. Here, we investigate five beverages and their association with lifestyle and diet in 25,112 individuals from the Malmö Diet and Cancer Cohort. We observed that high consumption of SSB was associated with lower intakes of foods perceived as healthy. However, high consumption of both tea and juice was associated with higher intakes of foods perceived as healthy. Further, high consumption of ASB was associated with higher intakes of low-fat products. High consumption of coffee was associated with higher intakes of meat and high-fat margarine, and lower intake of breakfast cereals. We observe five beverages to associate with different lifestyle and dietary patterns.

Polygenic Risk Score for Coronary Heart Disease Modifies the Elevated Risk by Cigarette Smoking for Disease Incidence.

BACKGROUND: Coronary heart disease (CHD) is a multifactorial disease with both genetic and environmental components. Smoking is the most important modifiable risk factor for CHD. Our aim was to test whether the increased CHD incidence by smoking is modified by genetic predisposition to CHD. METHODS AND RESULTS: Our study included 24 443 individuals from the MDCS (Malmö Diet and Cancer Study). A weighted polygenic risk score (PRS) was created by summing the number of risk alleles for 50 single-nucleotide polymorphisms associated with CHD. Individuals were classified as current, former, or never smokers. Interactions were primarily tested between smoking status and PRS and secondarily with individual single-nucleotide polymorphisms. Then, the predictive use of PRS for CHD incidence was tested among different smoking categories. During a median follow-up time of 19.4 years, 3217 incident CHD cases were recorded. The association between smoking and CHD was modified by the PRS (Pinteraction=0.005). The magnitude of increased incidence of CHD by smoking was highest among individuals in the lowest tertile of PRS (odds ratio, 1.42; 95% confidence interval, 1.29-1.56 per smoking risk category) compared with the highest tertile (odds ratio, 1.20; 95% confidence interval, 1.11-1.30 per smoking risk category). This interaction was stronger among men (Pinteraction=0.001) compared with women (Pinteraction=0.44). The PRS provided a significantly better net reclassification and discrimination on top of traditional risk factors among never smokers compared with current smokers (P<0.001). CONCLUSIONS: Genetic predisposition to CHD modifies the associated increased CHD risk by smoking. The PRS has a better predictive use among never smokers compared with smokers.

Dietary and genetic risk scores and incidence of type 2 diabetes.

BACKGROUND: Both lifestyle and genetic predisposition determine the development of type 2 diabetes (T2D), and studies have indicated interactions between specific dietary components and individual genetic variants. However, it is unclear whether the importance of overall dietary habits, including T2D-related food intakes, differs depending on genetic predisposition to T2D. We examined interaction between a genetic risk score for T2D, constructed from 48 single nucleotide polymorphisms identified in genome-wide association studies, and a diet risk score of four foods consistently associated with T2D in epidemiological studies (processed meat, sugar-sweetened beverages, whole grain and coffee). In total, 25,069 individuals aged 45-74 years with genotype information and without prevalent diabetes from the Malmö Diet and Cancer cohort (1991-1996) were included. Diet data were collected with a modified diet history method. RESULTS: During 17-year follow-up, 3588 incident T2D cases were identified. Both the diet risk score (HR in the highest risk category 1.40; 95% CI 1.26, 1.58; P trend = 6 × 10-10) and the genetic risk score (HR in the highest tertile of the genetic risk score 1.67; 95% CI 1.54, 1.81; P trend = 7 × 10-35) were associated with increased incidence of T2D. No significant interaction between the genetic risk score and the diet risk score (P = 0.83) or its food components was observed. The highest risk was seen among the 6% of the individuals with both high genetic and dietary risk scores (HR 2.49; 95% CI 2.06, 3.01). CONCLUSIONS: The findings thus show that both genetic heredity and dietary habits previously associated with T2D add to the risk of T2D, but they seem to act in an independent fashion, with the consequence that all individuals, whether at high or low genetic risk, would benefit from favourable food choices.

A genome-wide association study of IgM antibody against phosphorylcholine: shared genetics and phenotypic relationship to chronic lymphocytic leukemia.

Phosphorylcholine (PC) is an epitope on oxidized low-density lipoprotein (oxLDL), apoptotic cells and several pathogens like Streptococcus pneumoniae. Immunoglobulin M against PC (IgM anti-PC) has the ability to inhibit uptake of oxLDL by macrophages and increase clearance of apoptotic cells. From our genome-wide association studies (GWASs) in four European-ancestry cohorts, six single nucleotide polymorphisms (SNPs) in 11q24.1 were discovered (in 3002 individuals) and replicated (in 646 individuals) to be associated with serum level of IgM anti-PC (the leading SNP rs35923643-G, combined ß = 0.19, 95% confidence interval 0.13-0.24, P = 4.3 × 10-11). The haplotype tagged by rs35923643-G (or its proxy SNP rs735665-A) is also known as the top risk allele for chronic lymphocytic leukemia (CLL), and a main increasing allele for general IgM. By using summary GWAS results of IgM anti-PC and CLL in the polygenic risk score (PRS) analysis, PRS on the basis of IgM anti-PC risk alleles positively associated with CLL risk (explained 0.6% of CLL variance, P = 1.2 × 10-15). Functional prediction suggested that rs35923643-G might impede the binding of Runt-related transcription factor 3, a tumor suppressor playing a central role in the immune regulation of cancers. Contrary to the expectations from the shared genetics between IgM anti-PC and CLL, an inverse relationship at the phenotypic level was found in a nested case-control study (30 CLL cases with 90 age- and sex-matched controls), potentially reflecting reverse causation. The suggested function of the top variant as well as the phenotypic association between IgM anti-PC and CLL risk needs replication and motivates further studies.

N1-methylnicotinamide is a signalling molecule produced in skeletal muscle coordinating energy metabolism.

Obesity is a major health problem, and although caloric restriction and exercise are successful strategies to lose adipose tissue in obese individuals, a simultaneous decrease in skeletal muscle mass, negatively effects metabolism and muscle function. To deeper understand molecular events occurring in muscle during weight-loss, we measured the expressional change in human skeletal muscle following a combination of severe caloric restriction and exercise over 4 days in 15 Swedish men. Key metabolic genes were regulated after the intervention, indicating a shift from carbohydrate to fat metabolism. Nicotinamide N-methyltransferase (NNMT) was the most consistently upregulated gene following the energy-deficit exercise. Circulating levels of N1-methylnicotinamide (MNA), the product of NNMT activity, were doubled after the intervention. The fasting-fed state was an important determinant of plasma MNA levels, peaking at ~18 h of fasting and being lowest ~3 h after a meal. In culture, MNA was secreted by isolated human myotubes and stimulated lipolysis directly, with no effect on glucagon or insulin secretion. We propose that MNA is a novel myokine that enhances the utilization of energy stores in response to low muscle energy availability. Future research should focus on applying MNA as a biomarker to identify individuals with metabolic disturbances at an early stage.

Plasma Concentration of Caspase-8 Is Associated With Short Sleep Duration and the Risk of Incident Diabetes Mellitus.

Context: The biological mechanism for the association between sleep duration and incident diabetes mellitus (DM) is unclear. Sleep duration and caspase-8, a marker of apoptotic activity, have both been implicated in ß-cell function. Objective: To investigate the associations between sleep duration and plasma caspase-8 and incident DM, respectively. Design: Prospective cohort study. Setting: The Malmö Diet and Cancer (MDC) Study is a population-based, prospective study run in the city of Malmö, Sweden. Participants: A total of 4023 individuals from the MDC Study aged 45 to 68 years at baseline without a history of prevalent DM and with information on habitual sleep duration. Main Outcomes: Incident DM. Results: Mean follow-up time was 17.8 years. Sleep duration was the only behavioral variable significantly associated with plasma caspase-8. Plasma caspase-8 was significantly associated with incident DM per standard deviation of its transformed continuous form [hazard ratio (HR) = 1.24; 95% confidence interval (CI), 1.13 to 1.36] and when dichotomized into high (quartile 4) (HR = 1.44; 95% CI, 1.19 to 1.74) compared with low (quartiles 1 to 3) concentrations. Caspase-8 interacted with sleep duration; compared with individuals who had 7 to 8 hours of sleep and low plasma caspase-8, those with high plasma caspase-8 and sleep duration <6 hours (HR = 3.54; 95% CI, 2.12 to 5.90), 6 to 7 hours (HR = 1.81; 95% CI, 1.24 to 2.65), and 8 to 9 hours (HR = 1.54; 95% CI, 1.09 to 2.18) were at significantly increased risks of incident DM. Conclusions: Sleep duration is associated with plasma caspase-8. Caspase-8 independently predicts DM years before disease onset and modifies the effect of sleep duration on incident DM. Future studies should investigate if change of sleep duration modifies plasma concentrations of caspase-8.

SNPs related to vitamin D and breast cancer risk: a case-control study.

BACKGROUND: It has been suggested that vitamin D might protect from breast cancer, although studies on levels of vitamin D in association with breast cancer have been inconsistent. Genome-wide association studies (GWASs) have identified several single-nucleotide polymorphisms (SNPs) to be associated with vitamin D. The aim of this study was to investigate such vitamin D-SNP associations in relation to subsequent breast cancer risk. A first step included verification of these SNPs as determinants of vitamin D levels. METHODS: The Malmö Diet and Cancer Study included 17,035 women in a prospective cohort. Genotyping was performed and was successful in 4058 nonrelated women from this cohort in which 865 were diagnosed with breast cancer. Levels of vitamin D (25-hydroxyvitamin D) were available for 700 of the breast cancer cases and 643 of unaffected control subjects. SNPs previously associated with vitamin D in GWASs were identified. Logistic regression analyses yielding ORs with 95% CIs were performed to investigate selected SNPs in relation to low levels of vitamin D (below median) as well as to the risk of breast cancer. RESULTS: The majority of SNPs previously associated with levels of vitamin D showed a statistically significant association with circulating vitamin D levels. Heterozygotes of one SNP (rs12239582) were found to have a statistically significant association with a low risk of breast cancer (OR 0.82, 95% CI 0.68-0.99), and minor homozygotes of the same SNP were found to have a tendency towards a low risk of being in the group with low vitamin D levels (OR 0.72, 95% CI 0.52-1.00). Results from stratified analyses showed diverse associations with breast cancer risk for a few of the tested SNPs, depending on whether vitamin D level was high or low. CONCLUSIONS: SNPs associated with vitamin D may also be associated with the risk of breast cancer. Even if such a risk is small, the allele frequency of the SNP variants is high, and therefore the population attributable risk could be substantial. It is also possible that vitamin D levels may interact with genomic traits with regard to breast cancer risk.

Thyroid-associated genetic polymorphisms in relation to breast cancer risk in the Malmö Diet and Cancer Study.

Previous studies have suggested that thyroid function is associated with breast cancer risk, which could have an important clinical impact, as one in eight women will develop a thyroid disorder during her lifetime. However, the underlying pathomechanism behind the association is still unknown. We used the Malmö Diet and Cancer Study (a population-based prospective study consisting of 17,035 women) to examine 17 single nucleotide polymorphisms (SNPs) previously related to levels of free thyroxine (free T4) and thyroid peroxidase antibodies (TPO-Ab) as potential genetic risk factors for breast cancer. A baseline examination including free T4 and TPO-Ab levels was conducted at the time of inclusion. Genotyping was performed on 901 breast cancer patients and 3335 controls. Odds ratios (95% confidence intervals) for high free T4, TPO-Ab positivity, and breast cancer were calculated by logistic regression and adjusted for confounders. We identified one free T4-related SNP (rs2235544, D101 gene) that was significantly associated with both free T4 level and breast cancer risk. There was a suggested association between rs11675434 (TPO gene) and TPO-Ab level, and TPO-Ab-related rs11675434 (TPO), rs3094228 (HCP5), rs1033662 (no registered gene), and rs301806 (RERE) were associated with breast cancer risk. There was an indicated interaction between rs6485050 (no registered gene) and free T4 level in regards to breast cancer risk. This is the first study to suggest an association between thyroid-related SNPs and breast cancer risk. All SNPs have a biological plausibility of being associated with breast cancer risk, and may contribute to the genetic predisposition to breast cancer.

Incident diabetes mellitus may explain the association between sleep duration and incident coronary heart disease.

AIMS/HYPOTHESIS: Sleep duration is a risk factor for incident diabetes mellitus and CHD. The primary aim of the present study was to investigate, in sex-specific analyses, the role of incident diabetes as the possible biological mechanism for the reported association between short/long sleep duration and incident CHD. Considering that diabetes is a major risk factor for CHD, we hypothesised that any association with sleep duration would not hold for cases of incident CHD occurring before incident diabetes ('non-diabetes CHD') but would hold true for cases of incident CHD following incident diabetes ('diabetes-CHD'). METHODS: A total of 6966 men and 9378 women aged 45-73 years from the Malmö Diet Cancer Study, a population-based, prospective cohort, who had answered questions on habitual sleep duration and did not have a history of prevalent diabetes or CHD were included in the analyses. Incident cases of diabetes and CHD were identified using national registers. Sex-specific Cox proportional hazards regression models were stratified by BMI and adjusted for known covariates of diabetes and CHD. RESULTS: Mean follow-up times for incident diabetes (n = 1137/1016 [men/women]), incident CHD (n = 1170/578), non-diabetes CHD (n = 1016/501) and diabetes-CHD (n = 154/77) were 14.2-15.2 years for men, and 15.8-16.5 years for women. In men, short sleep duration (< 6 h) was associated with incident diabetes (HR 1.35, 95% CI 1.01, 1.80), CHD (HR 1.41, 95% CI 1.06, 1.89) and diabetes-CHD (HR 2.34, 95% CI 1.20, 4.55). Short sleep duration was not associated with incident non-diabetes CHD (HR 1.35, 95% CI 0.98, 1.87). Long sleep duration (≥ 9 h) was associated with incident diabetes (HR 1.37, 95% CI 1.03, 1.83), CHD (HR 1.33, 95% CI 1.01, 1.75) and diabetes-CHD (HR 2.10, 95% CI 1.11, 4.00). Long sleep duration was not associated with incident non-diabetes CHD (HR 1.33, 95% CI 0.98, 1.80). In women, short sleep duration was associated with incident diabetes (HR 1.53, 95% CI 1.16, 2.01), CHD (HR 1.46, 95% CI 1.03, 2.07) and diabetes-CHD (HR 2.88, 95% CI 1.37, 6.08). Short sleep duration was not associated with incident non-diabetes CHD (HR 1.29, 95% CI 0.86, 1.93). CONCLUSIONS/INTERPRETATION: The associations between sleep duration and incident CHD directly reflect the associations between sleep duration and incident diabetes. Incident diabetes may thus be the explanatory mechanism for the association between short and long sleep duration and incident CHD.

Genetic determinants of circulating GIP and GLP-1 concentrations.

The secretion of insulin and glucagon from the pancreas and the incretin hormones glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic peptide (GIP) from the gastrointestinal tract is essential for glucose homeostasis. Several novel treatment strategies for type 2 diabetes (T2D) mimic GLP-1 actions or inhibit incretin degradation (DPP4 inhibitors), but none is thus far aimed at increasing the secretion of endogenous incretins. In order to identify new potential therapeutic targets for treatment of T2D, we performed a meta-analysis of a GWAS and an exome-wide association study of circulating insulin, glucagon, GIP, and GLP-1 concentrations measured during an oral glucose tolerance test in up to 7,828 individuals. We identified 6 genome-wide significant functional loci associated with plasma incretin concentrations in or near the SLC5A1 (encoding SGLT1), GIPR, ABO, GLP2R, F13A1, and HOXD1 genes and studied the effect of these variants on mRNA expression in pancreatic islet and on metabolic phenotypes. Immunohistochemistry showed expression of GIPR, ABO, and HOXD1 in human enteroendocrine cells and expression of ABO in pancreatic islets, supporting a role in hormone secretion. This study thus provides candidate genes and insight into mechanisms by which secretion and breakdown of GIP and GLP-1 are regulated.

Utilization of genetic data can improve the prediction of type 2 diabetes incidence in a Swedish cohort.

The aim of this study was to measure the impact of genetic data in improving the prediction of type 2 diabetes (T2D) in the Malmö Diet and Cancer Study cohort. The current study was performed in 3,426 Swedish individuals and utilizes of a set of genetic and environmental risk data. We first validated our environmental risk model by comparing it to both the Finnish Diabetes Risk Score and the T2D risk model derived from the Framingham Offspring Study. The area under the curve (AUC) for our environmental model was 0.72 [95% CI, 0.69-0.74], which was significantly better than both the Finnish (0.64 [95% CI, 0.61-0.66], p-value < 1 x 10-4) and Framingham (0.69 [95% CI, 0.66-0.71], p-value = 0.0017) risk scores. We then verified that the genetic data has a statistically significant positive correlation with incidence of T2D in the studied population. We also verified that adding genetic data slightly but statistically increased the AUC of a model based only on environmental risk factors (RFs, AUC shift +1.0% from 0.72 to 0.73, p-value = 0.042). To study the dependence of the results on the environmental RFs, we divided the population into two equally sized risk groups based only on their environmental risk and repeated the same analysis within each subpopulation. While there is a statistically significant positive correlation between the genetic data and incidence of T2D in both environmental risk categories, the positive shift in the AUC remains statistically significant only in the category with the lower environmental risk. These results demonstrate that genetic data can be used to increase the accuracy of T2D prediction. Also, the data suggests that genetic data is more valuable in improving T2D prediction in populations with lower environmental risk. This suggests that the impact of genetic data depends on the environmental risk of the studied population and thus genetic association studies should be performed in light of the underlying environmental risk of the population.

Fasting levels of growth hormone are associated with carotid intima media thickness but are not affected by fluvastatin treatment.

BACKGROUND: Growth hormone (GH) has been linked to cardiovascular disease but the exact mechanism of this association is still unclear. We here test if the fasting levels of GH are cross-sectionally associated with carotid intima media thickness (IMT) and whether treatment with fluvastatin affects the fasting level of GH. METHODS: We examined the association between GH and IMT in 4425 individuals (aged 46-68 years) included in the baseline examination (1991-1994) of the Malmö Diet and Cancer cardiovascular cohort (MDC-CC). From that cohort we then studied 472 individuals (aged 50-70 years) who also participated (1994-1999) in the ß-Blocker Cholesterol-Lowering Asymptomatic Plaque Study (BCAPS), a randomized, double blind, placebo-controlled, single-center clinical trial. Using multivariate linear regression models we related the change in GH-levels at 12 months compared with baseline to treatment with 40 mg fluvastatin once daily. RESULTS: In MDC-CC fasting values of GH exhibited a positive cross-sectional relation to the IMT at the carotid bulb independent of traditional cardiovascular risk factors (p = 0.002). In a gender-stratified analysis the correlation were significant for males (p = 0.005), but not for females (p = 0.09). Treatment with fluvastatin was associated with a minor reduction in the fasting levels of hs-GH in males (p = 0.05) and a minor rise in the same levels among females (p = 0.05). CONCLUSIONS: We here demonstrate that higher fasting levels of GH are associated with thicker IMT in the carotid bulb in males. Treatment with fluvastatin for 12 months only had a minor, and probably not clinically relevant, effect on the fasting levels of hs-GH.