Rare and low-frequency coding variants alter human adult height

Height is a highly heritable, classic polygenic trait with approximately 700 common associated variants identified through genome-wide association studies so far. Here, we report 83 height-associated coding variants with lower minor-allele frequencies (in the range of 0.1-4.8%) and effects of up to 2 centimetres per allele (such as those in IHH, STC2, AR and CRISPLD2), greater than ten times the average effect of common variants. In functional follow-up studies, rare height-increasing alleles of STC2 (giving an increase of 1-2 centimetres per allele) compromised proteolytic inhibition of PAPP-A and increased cleavage of IGFBP-4 in vitro, resulting in higher bioavailability of insulin-like growth factors. These 83 height-associated variants overlap genes that are mutated in monogenic growth disorders and highlight new biological candidates (such as ADAMTS3, IL11RA and NOX4) and pathways (such as proteoglycan and glycosaminoglycan synthesis) involved in growth. Our results demonstrate that sufficiently large sample sizes can uncover rare and low-frequency variants of moderate-to-large effect associated with polygenic human phenotypes, and that these variants implicate relevant genes and pathways.

Bone mineral density and microarchitecture in patients with essential thrombocythemia and polycythemia vera

In this cross-sectional study of 45 patients with myeloproliferative neoplasms, we found no evidence of secondary osteoporosis.

INTRODUCTION

Patients with essential thrombocythemia (ET) and polycythaemia vera (PV) are at increased risk of fractures but the underlying mechanisms have not been settled. We conducted a study to assess bone mineral density, microarchitecture, estimated bone strength and global bone turnover in 45 patients with ET or PV.

METHODS

Patients were evaluated in a cross-sectional study with dual energy X-ray absorptiometry (DXA) at the hip and spine; high-resolution peripheral quantitative computed tomography (HR-pQCT) at the distal radius and distal tibia; and biochemical markers of bone turnover including pro-collagen type 1 N-terminal pro-peptide, osteocalcin, C-terminal cross-linking telopeptide of type 1 collagen and bone-specific alkaline phosphatase. Also, 45 healthy comparisons, matched on age, height and weight with each patient were included as control subjects.

RESULTS

Patients and comparisons had almost identical BMDs: 0.96 (IQR: 0.85-1.07) g/cm² and 0.96 g/cm² (IQR: 0.86-1.05 g/cm²), respectively. As well all microarchitecture and estimated bone strength measures were highly similar in the two groups. Levels of bone turnover markers were within reference values in patients.

CONCLUSION

These results reveal no evidence of secondary osteoporosis among patients with ET or PV. The mechanism behind the increased fracture risk in ET or PV patients remains unknown.

Numerous Brugada syndrome-associated genetic variants have no effect on J-point elevation, syncope susceptibility, malignant cardiac arrhythmia, and all-cause mortality

PURPOSE

We investigated whether Brugada syndrome (BrS)-associated variants identified in the general population have an effect on J-point elevation as well as whether carriers of BrS variants were more prone to experience syncope and malignant ventricular arrhythmia and had increased mortality compared with noncarriers.

METHODS

All BrS-associated variants were identified using the Human Gene Mutation Database (HGMD). Individuals were randomly selected from a general population study using whole-exome sequencing data (n = 870) and genotype array data (n = 6,161) and screened for BrS-associated variants. Electrocardiograms (ECG) were analyzed electronically, and data on syncope, ventricular arrhythmias, and mortality were obtained from administrative health-care registries.

RESULTS

In HGMD, 382 BrS-associated genetic variants were identified. Of these, 28 variants were identified in the study cohort. None of the carriers presented with type 1 BrS ECG pattern. Mean J-point elevation in V1 and V2 were within normal guideline limits for carriers and noncarriers. There was no difference in syncope susceptibility (carriers 8/624; noncarriers 98/5,562; P = 0.51), ventricular arrhythmia (carriers 4/620; noncarriers 9/5,524; P = 0.24), or overall mortality (hazard ratio 0.93, 95% CI 0.63-1.4).

CONCLUSIONS

Our data indicate that a significant number of BrS-associated variants are not the monogenic cause of BrS.Genet Med advance online publication 06 October 2016.

Plasma Alkylresorcinols Reflect Gluten Intake and Distinguish between Gluten-Rich and Gluten-Poor Diets in a Population at Risk of Metabolic Syndrome

BACKGROUND

Many patients with celiac disease experience difficulties in adherence to a gluten-free diet. Methods for testing compliance to a gluten-free diet are costly and cumbersome. Thus, a simple biomarker of gluten intake is needed in a clinical setting and will be useful for epidemiologic studies investigating wider effects of gluten intake.

OBJECTIVE

The aim was to evaluate plasma total alkylresorcinol concentrations as a measure of gluten intake.

METHODS

In this randomized, controlled, crossover intervention study in 52 Danish adults with features of the metabolic syndrome, we compared 8 wk of a gluten-rich and gluten-poor diet separated by a washout period of ≥6 wk. We measured fasting plasma concentrations of alkylresorcinols to determine if they reflected differences in gluten intake as a secondary outcome of the original study. In addition, we investigated in 118 Danish adults the cross-sectional association between self-reported gluten intake and plasma alkylresorcinols in the same and a similar study at baseline. We used mixed-model ANCOVA for examining treatment effects, a classification tree to determine compliance to the gluten-poor diet, and linear regression models for examining baseline correlation between plasma alkylresorcinol concentrations and gluten intake.

RESULTS

Plasma total alkylresorcinols decreased more during the gluten-poor period (geometric mean: -124.8 nmol/L; 95% CI: -156.5, -93.0 nmol/L) than in the gluten-rich period (geometric mean: -31.8 nmol/L; 95% CI: -63.1, -0.4 nmol/L) (P < 0.001). On the basis of the plasma alkylresorcinol profile, we built a classification tree to objectively determine compliance and found an overall participant misclassification error of 3.9%. In the cross-sectional study we found a 5.6% (95% CI: 2.4%, 8.9%) increase in plasma total alkylresorcinols per 1-g increase in reported gluten intake (P < 0.001).

CONCLUSION

We propose the use of plasma alkylresorcinols to monitor compliance to a gluten-free diet as well as to help investigations into the possible effects of gluten in the wider population. This trial was registered at www.clinicaltrials.gov as NCT017119913 and NCT01731366.

Genetic risk scores link body fat distribution with specific cardiometabolic profiles

OBJECTIVE

Forty-nine known single nucleotide polymorphisms (SNPs) associating with body mass index (BMI)-adjusted waist-hip-ratio (WHR) (WHRadjBMI) were recently suggested to cluster into three groups with different associations to cardiometabolic traits. Genetic risk scores of the clusters on the risk of incident diabetes and associations with detailed cardiometabolic phenotypes were tested.

METHODS

In a prospective study of 6,121 Inter99 individuals, the risk of incident diabetes using Cox proportional hazards regression was evaluated. Using linear regession, the associations between genetic risk scores and anthropometry and blood samples at fasting and during an oral glucose tolerance test were tested. Analyses were adjusted for age, sex, and BMI.

RESULTS

Cluster 1 associated with an increased risk of diabetes (HR = 1.05, P = 2.74 × 10(-) (4) ) and with a poor metabolic profile, including fasting serum triglyceride (β = 0.98% mmol/L, P = 3.33 × 10(-) (8) ) and Matsuda index (β = -0.74%, P = 1.29 × 10(-) (4) ). No similar associations for Clusters 2 and 3 were found. The three clusters showed different patterns of association with waist circumference, hip circumference, and height.

CONCLUSIONS

Our results suggest that the 49 WHRadjBMI-associated SNPs affect metabolic health differently depending on the cluster of SNPs. The clusters further associate differently with anthropometric measures.

Variant ASGR1 Associated with a Reduced Risk of Coronary Artery Disease

BACKGROUND

Several sequence variants are known to have effects on serum levels of non-high-density lipoprotein (HDL) cholesterol that alter the risk of coronary artery disease.

METHODS

We sequenced the genomes of 2636 Icelanders and found variants that we then imputed into the genomes of approximately 398,000 Icelanders. We tested for association between these imputed variants and non-HDL cholesterol levels in 119,146 samples. We then performed replication testing in two populations of European descent. We assessed the effects of an implicated loss-of-function variant on the risk of coronary artery disease in 42,524 case patients and 249,414 controls from five European ancestry populations. An augmented set of genomes was screened for additional loss-of-function variants in a target gene. We evaluated the effect of an implicated variant on protein stability.

RESULTS

We found a rare noncoding 12-base-pair (bp) deletion (del12) in intron 4 of ASGR1, which encodes a subunit of the asialoglycoprotein receptor, a lectin that plays a role in the homeostasis of circulating glycoproteins. The del12 mutation activates a cryptic splice site, leading to a frameshift mutation and a premature stop codon that renders a truncated protein prone to degradation. Heterozygous carriers of the mutation (1 in 120 persons in our study population) had a lower level of non-HDL cholesterol than noncarriers, a difference of 15.3 mg per deciliter (0.40 mmol per liter) (P=1.0×10(-16)), and a lower risk of coronary artery disease (by 34%; 95% confidence interval, 21 to 45; P=4.0×10(-6)). In a larger set of sequenced samples from Icelanders, we found another loss-of-function ASGR1 variant (p.W158X, carried by 1 in 1850 persons) that was also associated with lower levels of non-HDL cholesterol (P=1.8×10(-3)).

CONCLUSIONS

ASGR1 haploinsufficiency was associated with reduced levels of non-HDL cholesterol and a reduced risk of coronary artery disease. (Funded by the National Institutes of Health and others.).

Oxyntomodulin Identified as a Marker of Type 2 Diabetes and Gastric Bypass Surgery by Mass-spectrometry Based Profiling of Human Plasma

Low-abundance regulatory peptides, including metabolically important gut hormones, have shown promising therapeutic potential. Here, we present a streamlined mass spectrometry-based platform for identifying and characterizing low-abundance regulatory peptides in humans. We demonstrate the clinical applicability of this platform by studying a hitherto neglected glucose- and appetite-regulating gut hormone, namely, oxyntomodulin. Our results show that the secretion of oxyntomodulin in patients with type 2 diabetes is significantly impaired, and that its level is increased by more than 10-fold after gastric bypass surgery. Furthermore, we report that oxyntomodulin is co-distributed and co-secreted with the insulin-stimulating and appetite-regulating gut hormone glucagon-like peptide-1 (GLP-1), is inactivated by the same protease (dipeptidyl peptidase-4) as GLP-1 and acts through its receptor. Thus, oxyntomodulin may participate with GLP-1 in the regulation of glucose metabolism and appetite in humans. In conclusion, this mass spectrometry-based platform is a powerful resource for identifying and characterizing metabolically active low-abundance peptides.

Levels of the inflammation marker YKL-40 in young adults exposed to intrauterine hyperglycemia

Plasma levels of the inflammatory marker YKL-40 were investigated in 597 adult offspring born to women with and without diabetes during pregnancy. No association between fetal exposure to maternal hyperglycemia and levels of YKL-40 was found. However, female sex and increasing BMI in the offspring were associated to YKL-40.

Effects of biphasic, basal-bolus or basal insulin analogue treatments on carotid intima-media thickness in patients with type 2 diabetes mellitus: the randomised Copenhagen Insulin and Metformin Therapy (CIMT) trial

OBJECTIVE

To assess the effect of 3 insulin analogue regimens on change in carotid intima-media thickness (IMT) in patients with type 2 diabetes.

DESIGN AND SETTING

Investigator-initiated, randomised, placebo-controlled trial with a 2 × 3 factorial design, conducted at 8 hospitals in Denmark.

PARTICIPANTS AND INTERVENTIONS

Participants with type 2 diabetes (glycated haemoglobin (HbA1c) ≥ 7.5% (≥ 58 mmol/mol), body mass index >25 kg/m(2)) were, in addition to metformin versus placebo, randomised to 18 months open-label biphasic insulin aspart 1-3 times daily (n=137) versus insulin aspart 3 times daily in combination with insulin detemir once daily (n=138) versus insulin detemir alone once daily (n=137), aiming at HbA1c ≤ 7.0% (≤ 53 mmol/mol).

OUTCOMES

Primary outcome was change in mean carotid IMT (a marker of subclinical cardiovascular disease). HbA1c, insulin dose, weight, and hypoglycaemic and serious adverse events were other prespecified outcomes.

RESULTS

Carotid IMT change did not differ between groups (biphasic -0.009 mm (95% CI -0.022 to 0.004), aspart+detemir 0.000 mm (95% CI -0.013 to 0.013), detemir -0.012 mm (95% CI -0.025 to 0.000)). HbA1c was more reduced with biphasic (-1.0% (95% CI -1.2 to -0.8)) compared with the aspart+detemir (-0.4% (95% CI -0.6 to -0.3)) and detemir (-0.3% (95% CI -0.4 to -0.1)) groups (p<0.001). Weight gain was higher in the biphasic (3.3 kg (95% CI 2.7 to 4.0) and aspart+detemir (3.2 kg (95% CI 2.6 to 3.9)) compared with the detemir group (1.9 kg (95% CI 1.3 to 2.6)). Insulin dose was higher with detemir (1.6 IU/kg/day (95% CI 1.4 to 1.8)) compared with biphasic (1.0 IU/kg/day (95% CI 0.9 to 1.1)) and aspart+detemir (1.1 IU/kg/day (95% CI 1.0 to 1.3)) (p<0.001). Number of participants with severe hypoglycaemia and serious adverse events did not differ.

CONCLUSIONS

Carotid IMT change did not differ between 3 insulin regimens despite differences in HbA1c, weight gain and insulin doses. The trial only reached 46% of planned sample size and lack of power may therefore have affected our results.

TRIAL REGISTRATION NUMBER

NCT00657943.

Metformin versus placebo in combination with insulin analogues in patients with type 2 diabetes mellitus-the randomised, blinded Copenhagen Insulin and Metformin Therapy (CIMT) trial

OBJECTIVE

To assess the effect of metformin versus placebo both in combination with insulin analogue treatment on changes in carotid intima-media thickness (IMT) in patients with type 2 diabetes.

DESIGN AND SETTING

Investigator-initiated, randomised, placebo-controlled trial with a 2 × 3 factorial design conducted at eight hospitals in Denmark.

PARTICIPANTS AND INTERVENTIONS

412 participants with type 2 diabetes (glycated haemoglobin (HbA1c) ≥ 7.5% (≥ 58 mmol/mol); body mass index >25 kg/m2) were in addition to open-labelled insulin treatment randomly assigned 1:1 to 18 months blinded metformin (1 g twice daily) versus placebo, aiming at an HbA1c ≤ 7.0% (≤ 53 mmol/mol).

OUTCOMES

The primary outcome was change in the mean carotid IMT (a marker of subclinical cardiovascular disease). HbA1c, insulin dose, weight and hypoglycaemic and serious adverse events were other prespecified outcomes.

RESULTS

Change in the mean carotid IMT did not differ significantly between the groups (between-group difference 0.012 mm (95% CI -0.003 to 0.026), p=0.11). HbA1c was more reduced in the metformin group (between-group difference -0.42% (95% CI -0.62% to -0.23%), p<0.001)), despite the significantly lower insulin dose at end of trial in the metformin group (1.04 IU/kg (95% CI 0.94 to 1.15)) compared with placebo (1.36 IU/kg (95% CI 1.23 to 1.51), p<0.001). The metformin group gained less weight (between-group difference -2.6 kg (95% CI -3.3 to -1.8), p<0.001). The groups did not differ with regard to number of patients with severe or non-severe hypoglycaemic or other serious adverse events, but the metformin group had more non-severe hypoglycaemic episodes (4347 vs 3161, p<0.001).

CONCLUSIONS

Metformin in combination with insulin did not reduce carotid IMT despite larger reduction in HbA1c, less weight gain, and smaller insulin dose compared with placebo plus insulin. However, the trial only reached 46% of the planned sample size and lack of power may therefore have affected our results.

TRIAL REGISTRATION NUMBER

NCT00657943; Results.

Asthma Associates With Human Abdominal Aortic Aneurysm and Rupture

OBJECTIVE

Both asthma and abdominal aortic aneurysms (AAA) involve inflammation. It remains unknown whether these diseases interact.

APPROACH AND RESULTS

Databases analyzed included Danish National Registry of Patients, a population-based nationwide case-control study included all patients with ruptured AAA and age- and sex-matched AAA controls without rupture in Denmark from 1996 to 2012; Viborg vascular trial, subgroup study of participants from the population-based randomized Viborg vascular screening trial. Patients with asthma were categorized by hospital diagnosis, bronchodilator use, and the recorded use of other anti-asthma prescription medications. Logistic regression models were fitted to determine whether asthma associated with the risk of ruptured AAA in Danish National Registry of Patients and an independent risk of having an AAA at screening in the Viborg vascular trial. From the Danish National Registry of Patients study, asthma diagnosed <1 year or 6 months before the index date increased the risk of AAA rupture before (odds ratio [OR]=1.60-2.12) and after (OR=1.51-2.06) adjusting for AAA comorbidities. Use of bronchodilators elevated the risk of AAA rupture from ever use to within 90 days from the index date, before (OR=1.10-1.37) and after (OR=1.10-1.31) adjustment. Patients prescribed anti-asthma drugs also showed an increased risk of rupture before (OR=1.12-1.79) and after (OR=1.09-1.48) the same adjustment. In Viborg vascular trial, anti-asthmatic medication use associated with increased risk of AAA before (OR=1.45) or after adjustment for smoking (OR=1.45) or other risk factors (OR=1.46).

CONCLUSIONS

Recent active asthma increased risk of AAA and ruptured AAA. These findings document and furnish novel links between airway disease and AAA, 2 common diseases that share inflammatory aspects.

Genome-wide meta-analysis uncovers novel loci influencing circulating leptin levels

Leptin is an adipocyte-secreted hormone, the circulating levels of which correlate closely with overall adiposity. Although rare mutations in the leptin (LEP) gene are well known to cause leptin deficiency and severe obesity, no common loci regulating circulating leptin levels have been uncovered. Therefore, we performed a genome-wide association study (GWAS) of circulating leptin levels from 32,161 individuals and followed up loci reaching P<10(-6) in 19,979 additional individuals. We identify five loci robustly associated (P<5 × 10(-8)) with leptin levels in/near LEP, SLC32A1, GCKR, CCNL1 and FTO. Although the association of the FTO obesity locus with leptin levels is abolished by adjustment for BMI, associations of the four other loci are independent of adiposity. The GCKR locus was found associated with multiple metabolic traits in previous GWAS and the CCNL1 locus with birth weight. Knockdown experiments in mouse adipose tissue explants show convincing evidence for adipogenin, a regulator of adipocyte differentiation, as the novel causal gene in the SLC32A1 locus influencing leptin levels. Our findings provide novel insights into the regulation of leptin production by adipose tissue and open new avenues for examining the influence of variation in leptin levels on adiposity and metabolic health.

Severe hypoglycaemia during treatment with sulphonylureas in patients with type 2 diabetes in the Capital Region of Denmark

AIMS

Sulphonylureas (SU) are currently recommended as a well-established second line treatment in guidelines for type 2 diabetes (T2DM). In the Capital Region of Denmark 16,865 patients were given SU as part of their treatment of T2DM in 2010-2011. To what extent SU are associated with hospitalizations due to severe hypoglycaemic episodes, defined as episodes with a need for external assistance, was investigated. The prevalence and characteristics of these patients and potential risk factors were studied.

METHODS

ICD-10 diagnosis codes were used to identify patients hospitalized due to hypoglycaemia and T2DM for a period of 2 years (2010-2011). Inclusion criteria were T2DM, hospitalization due to hypoglycaemia and treatment with SU as monotherapy or in combination with other glucose-lowering drugs except insulin treatment.

RESULTS

We identified 161 patients fulfilling the inclusion criteria. Their mean age was 76 (53-97) years and 54% were males. Sixty percent of the patients had diabetic complications, including 19% with diabetic nephropathy. The major reason for severe hypoglycaemia was an unchanged dose of SU despite of a significant decline in food intake (45%). In 22% of the patients more than one reason was listed, most commonly a concomitant infection associated with decreased food intake and unchanged dose of SU.

CONCLUSION

The incidence of hospital admission-requiring severe hypoglycaemia in patients treated with SU was 0.48 episodes per 100 patient-years of SU-treated patients. It was mainly older patients with diminished food intake, excessive alcohol use or other medications, concomitant infection, and with diabetic complications.

Intake of macro- and micronutrients in Danish vegans

Background

Since information about macro- and micronutrient intake among vegans is limited we aimed to determine and evaluate their dietary and supplementary intake.

Methods

Seventy 18–61 years old Danish vegans completed a four-day weighed food record from which their daily intake of macro- and micronutrients was assessed and subsequently compared to an age-range-matched group of 1 257 omnivorous individuals from the general Danish population. Moreover, the vegan dietary and supplementary intake was compared to the 2012 Nordic Nutrition Recommendations (NNR).

Results

Dietary intake differed significantly between vegans and the general Danish population in all measured macro- and micronutrients (p < 0.05), except for energy intake among women and intake of carbohydrates among men. For vegans the intake of macro- and micronutrients (including supplements) did not reach the NNR for protein, vitamin D, iodine and selenium. Among vegan women vitamin A intake also failed to reach the recommendations. With reference to the NNR, the dietary content of added sugar, sodium and fatty acids, including the ratio of PUFA to SFA, was more favorable among vegans.

Conclusions

At the macronutrient level, the diet of Danish vegans is in better accordance with the NNR than the diet of the general Danish population. At the micronutrient level, considering both diet and supplements, the vegan diet falls short in certain nutrients, suggesting a need for greater attention toward ensuring recommended daily intake of specific vitamins and minerals.

Electronic supplementary material

The online version of this article (doi:10.1186/s12937-015-0103-3) contains supplementary material, which is available to authorized users.

A Splice Region Variant in LDLR Lowers Non-high Density Lipoprotein Cholesterol and Protects against Coronary Artery Disease

Through high coverage whole-genome sequencing and imputation of the identified variants into a large fraction of the Icelandic population, we found four independent signals in the low density lipoprotein receptor gene (LDLR) that associate with levels of non-high density lipoprotein cholesterol (non-HDL-C) and coronary artery disease (CAD). Two signals are novel with respect to association with non-HDL-C and are represented by non-coding low frequency variants (between 2–4% frequency), the splice region variant rs72658867-A in intron 14 and rs17248748-T in intron one. These two novel associations were replicated in three additional populations. Both variants lower non-HDL-C levels (rs72658867-A, non-HDL-C effect = -0.44 mmol/l, P_adj = 1.1 × 10⁻⁸⁰ and rs17248748-T, non-HDL-C effect = -0.13 mmol/l, P_adj = 1.3 × 10⁻¹²) and confer protection against CAD (rs72658867-A, OR = 0.76 and P_adj = 2.7 × 10⁻⁸ and rs17248748-T, OR = 0.92 and P_adj = 0.022). The LDLR splice region variant, rs72658867-A, located at position +5 in intron 14 (NM_000527:c.2140+5G>A), causes retention of intron 14 during transcription and is expected to produce a truncated LDL receptor lacking domains essential for function of the receptor. About half of the transcripts generated from chromosomes carrying rs72658867-A are characterized by this retention of the intron. The same variant also increases LDLR mRNA expression, however, the wild type transcripts do not exceed levels in non-carriers. This demonstrates that sequence variants that disrupt the LDL receptor can lower non-HDL-C and protect against CAD.

Cholesterol levels in the bloodstream, in particular elevated low-density lipoprotein cholesterol (LDL-C), are strong risk factors for cardiovascular disease, and LDL-C reduction reduces mortality in people at risk. One of the major determinants of plasma LDL-C levels is the low density lipoprotein receptor (LDLR) that acts as a scavenger for cholesterol rich lipoprotein particles. Mutations that disrupt the function of the LDLR or lead to reduction in the number of LDLR usually result in elevated LDL-C in blood. In the current study, we identified, through whole-genome sequencing and imputation into a large fraction of the Icelandic population, four LDLR gene variants that affect non-HDL-C levels (that includes cholesterol in LDL and other pro-atherogenic lipoproteins) and risk of coronary artery disease (CAD). Two variants are known and two are novel. One of them, a splice region variant in intron 14 (rs72658867-A), affects normal splicing and is predicted to generate a truncated LDLR, lacking domains essential for receptor function. Despite this, rs72658867-A lowers non-HDL-C substantially and protects against CAD in the general population, demonstrating that variants that disrupt the LDLR can result in lower cholesterol levels.

Associations of the Inflammatory Marker YKL-40 with Measures of Obesity and Dyslipidaemia in Individuals at High Risk of Type 2 Diabetes

Introduction

Circulating levels of the inflammatory marker YKL-40 are elevated in cardiovascular disease and obesity-related type 2 diabetes (T2D), and serum YKL-40 levels are related to elements of dyslipidaemia.

Objective

We aimed to investigate the associations between serum YKL-40 and obesity-related traits in a Danish sample of non-diabetic relatives to T2D patients and, furthermore, to estimate the heritability of YKL-40.

Research Design and Methods

324 non-diabetic individuals with family relation to a T2D patient were included in the study. The participants underwent oral- and intravenous glucose tolerance tests for estimation of glucose tolerance and surrogate measures of insulin sensitivity. Anthropometric measures were retrieved and biochemical measures of the plasma lipid profile and serum YKL-40 levels were obtained. Association-analyses between serum YKL-40 and obesity-related traits and estimates of the narrow sense heritability of YKL-40 were based on a polygenic variance component model.

Results

Fasting serum levels of YKL-40 were positively associated with waist-hip-ratio (p<0.001) and fasting plasma triglyceride levels (p<0.001). None of the insulin sensitivity indexes were significantly associated with YKL-40. According to the AE model, the familiality-estimate h² of YKL-40 was 0.45 (SE 0.13). When the ACE-model was applied, the heritability-estimate h² of YKL-40 did not reach statistical significance.

Conclusions

Our results suggest a role of serum YKL-40 in obesity-related low grade inflammation, but do not indicate that YKL-40 is directly involved in the development of T2D.

Impact of PTBP1 rs11085226 on glucose-stimulated insulin release in adult Danes

BACKGROUND

The variant rs11085226 (G) within the gene encoding polypyrimidine tract binding protein 1 (PTBP1) was reported to associate with reduced insulin release determined by an oral glucose tolerance test (OGTT) as well as an intravenous glucose tolerance test (IVGTT). The aim of the present study was to validate the association of the rs11085226 G-allele of PTBP1 with previously investigated OGTT- and IVGTT-derived diabetes-related metabolic quantitative phenotypes, to conduct exploratory analyses of additional measures of beta-cell function, and to further investigate a potential association with type 2 diabetes.

METHODS

PTBP1 rs11085226 was genotyped in 20,911 individuals of Danish Caucasian ethnicity ascertained from 9 study samples. Case control analysis was performed on 5,634 type 2 diabetic patients and 11,319 individuals having a normal fasting glucose level as well as 4,641 glucose tolerant controls, respectively. Quantitative trait analyses were performed in up to 13,605 individuals subjected to an OGTT or blood samples obtained after an overnight fast, as well as in 596 individuals subjected to an IVGTT.

RESULTS

Analyses of fasting and OGTT-derived quantitative traits did not show any significant associations with the PTBP1 rs11085226 variant. Meta-analysis of IVGTT-derived quantitative traits showed a nominally significant association between the variant and reduced beta-cell responsiveness to glucose (β = -0.1 mmol · kg(-1) · min(-1); 95% CI: -0.200.20 - -0.024; P = 0.01) assuming a dominant model of inheritance, but failed to replicate a previously reported association with area under the curve (AUC) for insulin. Case control analysis did not show an association of the PTBP1 rs11085226 variant with type 2 diabetes.

CONCLUSIONS

Despite failure to replicate the previously reported associations of PTBP1 rs11085226 with OGTT- and IVGTT-derived measures of beta-cell function, we did find a nominally significant association with reduced beta-cell responsiveness to glucose during an IVGTT, a trait not previously investigated, leaving the potential influence of this variant in PTBP1 on glucose stimulated insulin release open for further investigation. However, the present study does not support the hypothesis that the variant confers risk of type 2 diabetes.

The potential role of inhibitor of differentiation-3 in human adipose tissue remodeling and metabolic health

Metabolic health in obesity is known to differ among individuals, and the distribution of visceral (VAT) and subcutaneous adipose tissue (SAT) plays an important role in this regard. Adipose tissue expansion is dependent on new blood vessel formation in order to prevent hypoxia and inflammation in the tissue. Regulation of angiogenesis in SAT and VAT in response to diet is therefore crucial for the metabolic outcome in obesity. Knowledge about the underlying genetic mechanisms determining metabolic health in obesity is very limited. We aimed to review the literature of the inhibitor of differentiation-3 (ID3) gene in relation to adipose tissue and angiogenesis in humans in order to determine whether ID3 could be involved in the regulation of adipose tissue expansion and metabolic health in human obesity. We find evidence that ID3 is involved in regulatory mechanisms in adipose tissue and regulates angiogenesis in many tissues including adipose tissue. We discuss how this might influence obesity and metabolic health in obesity and further discuss some potential mechanisms by which ID3 might regulate visceral and subcutaneous adipose tissue expansion. The combined results from the reviewed literature suggest ID3 to play a potential role in the underlying regulatory mechanisms of metabolic health in human obesity. The literature is still sparse and further studies focusing on human ID3 in relation to the nature of obesity are warranted.

Discovery of biomarkers for glycaemic deterioration before and after the onset of type 2 diabetes: rationale and design of the epidemiological studies within the IMI DIRECT Consortium

AIMS/HYPOTHESIS

The DIRECT (Diabetes Research on Patient Stratification) Study is part of a European Union Framework 7 Innovative Medicines Initiative project, a joint undertaking between four industry and 21 academic partners throughout Europe. The Consortium aims to discover and validate biomarkers that: (1) predict the rate of glycaemic deterioration before and after type 2 diabetes onset; (2) predict the response to diabetes therapies; and (3) help stratify type 2 diabetes into clearly definable disease subclasses that can be treated more effectively than without stratification. This paper describes two new prospective cohort studies conducted as part of DIRECT.

METHODS

Prediabetic participants (target sample size 2,200-2,700) and patients with newly diagnosed type 2 diabetes (target sample size ~1,000) are undergoing detailed metabolic phenotyping at baseline and 18 months and 36 months later. Abdominal, pancreatic and liver fat is assessed using MRI. Insulin secretion and action are assessed using frequently sampled OGTTs in non-diabetic participants, and frequently sampled mixed-meal tolerance tests in patients with type 2 diabetes. Biosamples include venous blood, faeces, urine and nail clippings, which, among other biochemical analyses, will be characterised at genetic, transcriptomic, metabolomic, proteomic and metagenomic levels. Lifestyle is assessed using high-resolution triaxial accelerometry, 24 h diet record, and food habit questionnaires.

CONCLUSIONS/INTERPRETATION

DIRECT will yield an unprecedented array of biomaterials and data. This resource, available through managed access to scientists within and outside the Consortium, will facilitate the development of new treatments and therapeutic strategies for the prevention and management of type 2 diabetes.

Circulating sCD36 is associated with unhealthy fat distribution and elevated circulating triglycerides in morbidly obese individuals

Background:

The recently identified circulating sCD36 has been proposed to reflect tissue CD36 expression, and is upregulated in case of obesity, insulin resistance and hepatic steatosis. The aim of this study was to explore the effect of weight loss secondary to bariatric surgery in relation to sCD36 among morbidly obese individuals. Furthermore, we investigated the levels of sCD36 in relation to obesity-related metabolic complications, low-grade inflammation and fat distribution.

Methods:

Twenty morbidly obese individuals (body mass index (BMI) 43.0±5.4 kg m⁻²) with a referral to Roux-en-Y gastric bypass were included. Anthropometric measurements and fasting blood samples were collected at a preoperative baseline visit and 3 months after surgery. sCD36 was measured by an in-house assay, whereas insulin sensitivity and the hepatic fat accumulation were estimated by the homeostasis model assessment (HOMA-%S) and liver fat percentage (LF%), respectively.

Results:

Postoperatively, BMI was reduced by 20% to 34.3±5.2 kg m⁻² (P<0.001). sCD36 was reduced by 31% (P=0.001) and improvements were observed in the amount of fat mass (P<0.001), truncal fat mass (P<0.001), circulating triglycerides (P=0.001), HOMA-%S (P=0.007), LF% (P=0.001) and the inflammatory marker high-sensitive C-reactive protein (P=0.005). sCD36 correlated with triglycerides (ρ=0.523, P=0.001) and truncal fat mass (ρ=0.357, P=0.026), and triglycerides were found to be an independent predictor of sCD36. At baseline, participants with the metabolic syndrome had a higher LF% and higher levels of the inflammatory biomarker YKL-40 (P=0.003 and P=0.014) as well as a tendency towards higher levels of sCD36.

Conclusion:

sCD36 was reduced by weight loss and associated with an unhealthy fat accumulation and circulating triglycerides, which support the proposed role of sCD36 as a biochemical marker of obesity-related metabolic complications and risks.