Betina H. Thuesen

Cohort Profile: The Health2006 cohort, Research Centre for Prevention and Health

Research Centre for Prevention and Health, Copenhagen University Hospital Glostrup, The Capital Region of Denmark, Denmark, National Allergy Research Centre, Department of Dermato-Allergology, Copenhagen University Hospital Gentofte, Denmark, Danish Research Centre for Chemical Sensitivities, Gentofte University Hospital, University of Copenhagen, Copenhagen, Denmark, Hagedorn Research Institute and Steno Diabetes Centre, Gentofte, Denmark, The Novo Nordisk Foundation Centre for Basic Metabolic Research, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark, Faculty of Health Sciences, University of Southern Denmark, Odense, Denmark and Faculty of Health Sciences, University of Aarhus, Aarhus, Denmark

The Association Between IGF-I and Insulin Resistance A general population study in Danish adults

OBJECTIVE IGF-I has an almost 50% amino acid sequence homology with insulin and elicits nearly the same hypoglycemic response. Studies showed that low and high IGF-I levels are related to impaired glucose tolerance and to a higher risk of type 2 diabetes. The aim of the current study was to evaluate the association between IGF-I level and insulin resistance in a Danish general population. RESEARCH DESIGN AND METHODS Included were 3,354 adults, aged 19–72 years, from the cross-sectional Health2006 study. The homeostasis model assessment of insulin resistance (HOMA-IR) was used as the index to estimate insulin resistance. Serum IGF-I levels were determined by an immunoassay and grouped into quintiles (Q1–Q5). Linear or multinomial logistic regression analyses were performed. RESULTS In the study population, 520 subjects (15.5%) had increased HOMA-IR values above 2.5. After adjustment for age, sex, physical activity, and waist-to-height ratio, a U-shaped association between IGF-I and HOMA-IR was found. Low IGF-I (Q1: odds ratio [OR] 1.65 [95% CI 1.16–2.34], P < 0.01) as well as high IGF-I (Q5: 1.96 [1.38–2.79], P < 0.01) levels were related to a higher odds of increased HOMA-IR values compared with subjects with intermediate (Q3) IGF-I levels. These associations remained statistically significant after the exclusion of subjects with type 2 diabetes and by using the updated computer HOMA2-IR model. CONCLUSIONS Low- and high-normal IGF-I levels are both related to insulin resistance. The biological mechanism of this complex phenomenon has to be elucidated in more detail for future risk stratification.

Serum 25(OH)D and Type 2 Diabetes Association in a General Population: A prospective study

OBJECTIVE This study aimed to examine vitamin D status as a determinant for development of type 2 diabetes and deterioration of glucose homeostasis. RESEARCH DESIGN AND METHODS A random sample of the general population of Copenhagen, Denmark, was taken as part of the Inter99 study. Included were 6,405 men and women aged 30–65 years at baseline (1999–2001), with 4,296 participating in the follow-up examination 5 years later (2004–2006). Vitamin D was determined at baseline as serum 25-hydroxyvitamin D [25(OH)D]. Diabetes was defined based on an oral glucose tolerance test and a glycosylated hemoglobin (HbA1c) test. Secondary outcomes included continuous markers of glucose homeostasis. RESULTS The risk of incident diabetes associated with a 10 nmol/L increase in 25(OH)D was odds ratio (OR) 0.91 (95% CI 0.84–0.97) in crude analyses. The association became statistically nonsignificant after adjustment for confounders, with an OR per 10 nmol/L of 0.94 (0.86–1.03). Low 25(OH)D status was significantly associated with unfavorable longitudinal changes in continuous markers of glucose homeostasis after adjustment for confounders. Fasting and 2-h glucose and insulin as well as the degree of insulin resistance increased significantly more during follow-up among those with low 25(OH)D levels compared with those with higher levels. CONCLUSIONS Low 25(OH)D status was not significantly associated with incident diabetes after adjustment for confounders. However, it was significantly associated with unfavorable longitudinal changes in continuous markers of glucose homeostasis, indicating that low vitamin D status could be related to deterioration of glucose homeostasis.

Vitamin D Status and Changes in Cardiovascular Risk Factors: A Prospective Study of a General Population

Objectives: A low vitamin D level has been associated with increased cardiovascular disease risk but possible mechanisms remain unclear. We investigated the association between vitamin D levels and 5-year changes in blood pressure, lipid profile and incidence of the metabolic syndrome, hypertension and hypercholesterolemia. Methods: A random sample of 6,784 individuals aged 30–60 years from a general population was investigated in the Inter99 study in 1999–2001. Vitamin D (serum 25-hydroxyvitamin D) was measured at baseline by high-performance liquid chromatography, and 4,330 individuals participated at the 5-year follow-up and were included in the present study. Results: The median baseline vitamin D concentration was 48.0 nmol/l. In multivariable linear regression analyses, a 10 nmol/l higher baseline level of vitamin D was associated with a decrease in triglycerides and very low density lipoprotein cholesterol by 0.52 (p = 0.03) and 0.66% (p = 0.005), respectively. In multivariable logistic regression analyses, the odds ratios per 10 nmol/l higher baseline vitamin D level were 0.95 (p < 0.05) and 0.94 (p = 0.01) for the development of the metabolic syndrome and hypercholesterolemia, respectively. There was no association between vitamin D and blood pressure. Conclusions: An optimal vitamin D status may influence cardiovascular health by changing the lipid profile in a favorable direction and decreasing the incidence of the metabolic syndrome.

Lifestyle and genetic determinants of folate and vitamin B12 levels in a general adult population

Danish legislation regarding food fortification has been very restrictive resulting in few fortified food items on the Danish market. Folate and vitamin B12 deficiency is thought to be common due to inadequate intakes but little is known about the actual prevalence of low serum folate and vitamin B12 in the general population. The aim of the present study was to evaluate the folate and vitamin B12 status of Danish adults and to investigate associations between vitamin status and distinct lifestyle and genetic factors. The study included a random sample of 6784 individuals aged 30-60 years. Information on lifestyle factors was obtained by questionnaires and blood samples were analysed for serum folate and vitamin B12 concentrations and several genetic polymorphisms. The overall prevalence of low serum folate ( < 6.8 nmol/l) was 31.4 %. Low serum folate was more common among men than women and the prevalence was lower with increasing age. Low serum folate was associated with smoking, low alcohol intake, high coffee intake, unhealthy diet, and the TT genotype of the methylenetetrahydrofolate reductase (MTHFR)-C677T polymorphism. The overall prevalence of low serum vitamin B12 ( < 148 pmol/l) was 4.7 %. Low serum vitamin B12 was significantly associated with female sex, high coffee intake, low folate status, and the TT genotype of the MTHFR-C677T polymorphism. In conclusion, low serum folate was present in almost a third of the adult population in the present study and was associated with several lifestyle factors whereas low serum concentrations of vitamin B12 were less common and only found to be associated with a few lifestyle factors.

Prospective Population-Based Study of the Association between Serum 25-Hydroxyvitamin-D Levels and the Incidence of Specific Types of Cancer

Background: Observational studies have suggested an inverse association between vitamin D status and cancer. We investigated the prospective associations between vitamin D status and the total and specific type of cancer in three cohorts from the general Danish population. Methods: A total of 12,204 individuals 18 to 71 years old were included. The level of 25-hydroxyvitamin D was measured at baseline, and information about cancer was obtained from the Danish Cancer Registry. Results: During the 11.3-year median follow-up time, there were 1,248 incident cancers. HRs [95% confidence intervals (CI)] per 10 nmol/L higher baseline vitamin D level were: for all cancers (HR = 1.02; 95% CI, 0.99–1.04), all cancers excluding non-melanoma skin cancer, NMSC (HR = 1.00; 95% CI, 0.97–1.03), head and neck cancer (HR = 0.97; 95% CI, 0.84–1.12), colorectal cancer (HR = 0.95; 95% CI, 0.88–1.02), cancer of bronchus and lung (HR = 0.98; 95% CI, 0.91–1.05), breast cancer (HR = 1.02; 95% CI, 0.96–1.09), cancer of the uterus (HR = 1.10; 95% CI, 0.95–1.27), prostate cancer (HR = 1.00; 95% CI, 0.93–1.08), cancer of the urinary organs (HR = 1.01; 95% CI, 0.90–1.14), NMSC (HR = 1.06; 95% CI, 1.02–1.10), and malignant melanoma (HR = 1.06; 95% CI, 0.95–1.17). Conclusions: Apart from a significantly higher risk for NMSC with higher vitamin D status, we found no statistically significant associations between vitamin D status and total or specific cancers. Impact: Our results do not indicate that there is an impact of vitamin D on total cancer incidence. Cancer Epidemiol Biomarkers Prev; 23(7); 1220–9. ©2014 AACR.

Genetic Architecture of Vitamin B 12 and Folate Levels Uncovered Applying Deeply Sequenced Large Datasets

Genome-wide association studies have mainly relied on common HapMap sequence variations. Recently, sequencing approaches have allowed analysis of low frequency and rare variants in conjunction with common variants, thereby improving the search for functional variants and thus the understanding of the underlying biology of human traits and diseases. Here, we used a large Icelandic whole genome sequence dataset combined with Danish exome sequence data to gain insight into the genetic architecture of serum levels of vitamin B12 (B12) and folate. Up to 22.9 million sequence variants were analyzed in combined samples of 45,576 and 37,341 individuals with serum B12 and folate measurements, respectively. We found six novel loci associating with serum B12 (CD320, TCN2, ABCD4, MMAA, MMACHC) or folate levels (FOLR3) and confirmed seven loci for these traits (TCN1, FUT6, FUT2, CUBN, CLYBL, MUT, MTHFR). Conditional analyses established that four loci contain additional independent signals. Interestingly, 13 of the 18 identified variants were coding and 11 of the 13 target genes have known functions related to B12 and folate pathways. Contrary to epidemiological studies we did not find consistent association of the variants with cardiovascular diseases, cancers or Alzheimers disease although some variants demonstrated pleiotropic effects. Although to some degree impeded by low statistical power for some of these conditions, these data suggest that sequence variants that contribute to the population diversity in serum B12 or folate levels do not modify the risk of developing these conditions. Yet, the study demonstrates the value of combining whole genome and exome sequencing approaches to ascertain the genetic and molecular architectures underlying quantitative trait associations.

Standardizing serum 25-hydroxyvitamin D data from four Nordic population samples using the Vitamin D Standardization Program protocols: Shedding new light on vitamin D status in Nordic individuals

Abstract Knowledge about the distributions of serum 25-hydroxyvitamin D (25(OH)D) concentrations in representative population samples is critical for the quantification of vitamin D deficiency as well as for setting dietary reference values and food-based strategies for its prevention. Such data for the European Union are of variable quality making it difficult to estimate the prevalence of vitamin D deficiency across member states. As a consequence of the widespread, method-related differences in measurements of serum 25(OH)D concentrations, the Vitamin D Standardization Program (VDSP) developed protocols for standardizing existing serum 25(OH)D data from national surveys around the world. The objective of the present work was to apply the VDSP protocols to existing serum 25(OH)D data from a Danish, a Norwegian, and a Finnish population-based health survey and from a Danish randomized controlled trial. A specifically-selected subset (n 100–150) of bio-banked serum samples from each of the studies were reanalyzed for 25(OH)D by LC-MS/MS and a calibration equation developed between old and new 25(OH)D data, and this equation was applied to the entire data-sets from each study. Compared to estimates based on the original serum 25(OH)D data, the percentage vitamin D deficiency (< 30 nmol/L) decreased by 21.5% in the Danish health survey but by only 1.4% in the Norwegian health survey; but was relatively unchanged (0% and 0.2%) in the Finish survey or Danish RCT, respectively, following VDSP standardization. In conclusion, standardization of serum 25(OH)D concentrations is absolutely necessary in order to compare serum 25(OH)D concentrations across different study populations, which is needed to quantify and prevent vitamin D deficiency.Knowledge about the distributions of serum 25-hydroxyvitamin D (25(OH)D) concentrations in representative population samples is critical for the quantification of vitamin D deficiency as well as for setting dietary reference values and food-based strategies for its prevention. Such data for the European Union are of variable quality making it difficult to estimate the prevalence of vitamin D deficiency across member states. As a consequence of the widespread, method-related differences in measurements of serum 25(OH)D concentrations, the Vitamin D Standardization Program (VDSP) developed protocols for standardizing existing serum 25(OH)D data from national surveys around the world. The objective of the present work was to apply the VDSP protocols to existing serum 25(OH)D data from a Danish, a Norwegian, and a Finnish population-based health survey and from a Danish randomized controlled trial. A specifically-selected subset (n 100-150) of bio-banked serum samples from each of the studies were reanalyzed for 25(OH)D by LC-MS/MS and a calibration equation developed between old and new 25(OH)D data, and this equation was applied to the entire data-sets from each study. Compared to estimates based on the original serum 25(OH)D data, the percentage vitamin D deficiency (< 30 nmol/L) decreased by 21.5% in the Danish health survey but by only 1.4% in the Norwegian health survey; but was relatively unchanged (0% and 0.2%) in the Finish survey or Danish RCT, respectively, following VDSP standardization. In conclusion, standardization of serum 25(OH)D concentrations is absolutely necessary in order to compare serum 25(OH)D concentrations across different study populations, which is needed to quantify and prevent vitamin D deficiency.

Vitamin D status and cause-specific mortality: a general population study.

Background Vitamin D deficiency is associated with an increased risk of all-cause mortality in observational studies. The specific causes of death underlying this association lack clarity. We investigated the association between vitamin D status and cause-specific mortality. Methods We included a total of 9,146 individuals from the two population-based studies, Monica10 and Inter99, conducted in 1993–94 and 1999–2001, respectively. Vitamin D status was assessed as serum 25-hydroxyvitamin D. Information on causes of death was obtained from The Danish Register of Causes of Death until 31 December 2009. There were a total of 832 deaths (median follow-up 10.3 years). Results Multivariable Cox regression analyses with age as underlying time axis and vitamin D quartiles showed significant associations between vitamin D status and death caused by diseases of the respiratory system, the digestive system, and endocrine, nutritional and metabolic diseases with hazard ratios (HRs) 0.26 (ptrend = 0.0042), 0.28 (ptrend = 0.0040), and 0.21 (ptrend = 0.035), respectively, for the fourth vitamin D quartile compared to the first. We found non-significantly lower HRs for death caused by mental and behavioural diseases and diseases of the nervous system, but no association between vitamin D status and death caused by neoplasms or diseases of the circulatory system. Conclusion The associations of vitamin D status and cause-specific mortality suggest that we also look elsewhere (than to cardiovascular disease and cancer) to explain the inverse association between vitamin D status and mortality.

Vitamin D Status, Filaggrin Genotype, and Cardiovascular Risk Factors: A Mendelian Randomization Approach

Background Vitamin D deficiency is associated with increased cardiovascular disease risk in observational studies. Whether these associations are causal is not clear. Loss-of-function mutations in the filaggrin gene result in up to 10% higher serum vitamin D concentrations, supposedly due to a decreased UV-protection of the keratinocytes. We used a Mendelian randomization approach to estimate the causal effect of vitamin D status on serum lipids, blood pressure, body mass index, waist circumference, and the metabolic syndrome. Methods Three population based studies were included, Monica10 (2,656 individuals aged 40–71 years), Inter99 (6,784 individuals aged 30–60 years), and Health2006 (3,471 individuals aged 18–69 years) conducted in 1993–94, 1999–2001, and 2006–2008, respectively. Participants were genotyped for the two most common filaggrin gene mutations in European descendants R501X and 2282del4, in all three studies and further for the R2447X mutation in the Inter99 and Health2006 studies. Filaggrin genotype was used as instrumental variable for vitamin D status. Baseline measurements of serum 25-hydroxyvitamin D were performed in all three studies. Results Instrumental variable analyses showed a 23.8% (95% confidence interval, CI 3.0, 48.6) higher HDL cholesterol level and a 30.5% (95% CI: 0.8, 51.3) lower serum level of triglycerides per doubling of vitamin D. These associations were, however, not statistically significant when applying the Bonferroni adjusted significance level. The remaining lipids showed non-significant changes in a favorable direction. Doubling of vitamin D gave a non-significantly lower odds ratio = 0.26 (95% CI: 0.06, 1.17) of the metabolic syndrome. There were no statistically significant causal effects of vitamin D status on blood pressure, body mass index, or waist circumference. Conclusion Our results support a causal effect of higher vitamin D status on a more favorable lipid profile, although more studies in other populations are needed to confirm our results.