Search

The microbial communities of the oral cavity are important elements of oral and systemic health. With emerging evidence highlighting the heritability of oral bacterial microbiota, this study aimed to identify host genome variants that influence oral microbial traits. Using data from 16S rRNA gene amplicon sequencing, we performed genome-wide association studies with univariate and multivariate traits of the salivary microbiota from 610 unrelated adults from the Danish ADDITION-PRO cohort. We identified six single nucleotide polymorphisms (SNPs) in human genomes that showed associations with abundance of bacterial taxa at different taxonomical tiers (P < 5 × 10–8). Notably, SNP rs17793860 surpassed our study-wide significance threshold (P < 1.19 × 10–9). Additionally, rs4530093 was linked to bacterial beta diversity (P < 5 × 10–8). Out of these seven SNPs identified, six exerted effects on metabolic traits, including glycated hemoglobin A1c, triglyceride and high-density lipoprotein cholesterol levels, the risk of type 2 diabetes and stroke. Our findings highlight the impact of specific host SNPs on the composition and diversity of the oral bacterial community. Importantly, our results indicate an intricate interplay between host genetics, the oral microbiota, and metabolic health. We emphasize the need for integrative approaches considering genetic, microbial, and metabolic factors. [ABSTRACT FROM AUTHOR]

Latent autoimmune diabetes in adults (LADA) is a heterogeneous disease characterized by autoantibodies against insulin producing pancreatic beta cells and initial lack of need for insulin treatment. The aim of the present study was to investigate if individuals with LADA have an altered gut microbiota relative to non-diabetic control subjects, individuals with type 1 diabetes (T1D), and individuals with type 2 diabetes (T2D). Bacterial community profiling was performed with primers targeting the variable region 4 of the 16S rRNA gene and sequenced. Amplicon sequence variants (ASVs) were generated with DADA2 and annotated to the SILVA database. The gut virome was sequenced, using a viral particle enrichment and metagenomics approach, assembled, and quantified to describe the composition of the viral community. Comparison of the bacterial alpha- and beta-diversity measures revealed that the gut bacteriome of individuals with LADA resembled that of individuals with T2D. Yet, specific genera were found to differ in abundance in individuals with LADA compared with T1D and T2D, indicating that LADA has unique taxonomical features. The virome composition reflected the stability of the most dominant order Caudovirales and the families Siphoviridae, Podoviridae, and Inoviridae, and the dominant family Microviridae. Further studies are needed to confirm these findings. [ABSTRACT FROM AUTHOR]

Background: Previous observational studies have indicated a protective effect of drinking milk on asthma and allergy. In Mendelian Randomization, one or more genetic variants are used as unbiased markers of exposure to examine causal effects. We examined the causal effect of milk intake on hay fever, asthma, forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) by using the lactase rs4988235 genotype associated with milk intake. Methods: We performed a Mendelian Randomization study including 363,961 participants from the UK Biobank. Results: Observational analyses showed that self-reported milk-drinkers vs. non-milk drinkers had an increased risk of hay fever: odds ratio (OR) = 1.36 (95% CI 1.32, 1.40, p < 0.001), asthma: OR = 1.33 (95% CI 1.38, 1.29, p < 0.001), yet a higher FEV1: β = 0.022 (SE = 0.004, p < 0.001) and FVC: β = 0.026 (SE = 0.005, p < 0.001). In contrast, genetically determined milk-drinking vs. not drinking milk was associated with a lower risk of hay fever: OR = 0.791 (95% CI 0.636, 0.982, p = 0.033), and asthma: OR = 0.587 (95% CI 0.442, 0.779, p = 0.001), and lower FEV1: β = − 0.154 (standard error, SE = 0.034, p < 0.001) liter, and FVC: β = − 0.223 (SE = 0.034, p < 0.001) liter in univariable MR analyses. These results were supported by multivariable Mendelian randomization analyses although not statistically significant. Conclusions: As opposed to observational results, genetic association findings indicate that drinking milk has a protective effect on hay fever and asthma but may also have a negative effect on lung function. The results should be confirmed in other studies before any recommendations can be made. [ABSTRACT FROM AUTHOR]

Aims/hypothesis: The common muscle-specific TBC1D4 p.Arg684Ter loss-of-function variant defines a subtype of non-autoimmune diabetes in Arctic populations. Homozygous carriers are characterised by elevated postprandial glucose and insulin levels. Because 3.8% of the Greenlandic population are homozygous carriers, it is important to explore possibilities for precision medicine. We aimed to investigate whether physical activity attenuates the effect of this variant on 2 h plasma glucose levels after an oral glucose load. Methods: In a Greenlandic population cohort (n = 2655), 2 h plasma glucose levels were obtained after an OGTT, physical activity was estimated as physical activity energy expenditure and TBC1D4 genotype was determined. We performed TBC1D4–physical activity interaction analysis, applying a linear mixed model to correct for genetic admixture and relatedness. Results: Physical activity was inversely associated with 2 h plasma glucose levels (β[main effect of physical activity] −0.0033 [mmol/l] / [kJ kg−1 day−1], p = 6.5 × 10−5), and significantly more so among homozygous carriers of the TBC1D4 risk variant compared with heterozygous carriers and non-carriers (β[interaction] −0.015 [mmol/l] / [kJ kg−1 day−1], p = 0.0085). The estimated effect size suggests that 1 h of vigorous physical activity per day (compared with resting) reduces 2 h plasma glucose levels by an additional ~0.7 mmol/l in homozygous carriers of the risk variant. Conclusions/interpretation: Physical activity improves glucose homeostasis particularly in homozygous TBC1D4 risk variant carriers via a skeletal muscle TBC1 domain family member 4-independent pathway. This provides a rationale to implement physical activity as lifestyle precision medicine in Arctic populations. Data repository: The Greenlandic Cardio-Metabochip data for the Inuit Health in Transition study has been deposited at the European Genome-phenome Archive (https://www.ebi.ac.uk/ega/dacs/EGAC00001000736) under accession EGAD00010001428. [ABSTRACT FROM AUTHOR]

Knowledge about in vivo effects of human circulating C-6 hydroxylated bile acids (BAs), also called muricholic acids, is sparse. It is unsettled if the gut microbiome might contribute to their biosynthesis. Here, we measured a range of serum BAs and related them to markers of human metabolic health and the gut microbiome. We examined 283 non-obese and obese Danish adults from the MetaHit study. Fasting concentrations of serum BAs were quantified using ultra-performance liquid chromatography-tandem mass-spectrometry. The gut microbiome was characterized with shotgun metagenomic sequencing and genome-scale metabolic modeling. We find that tauro- and glycohyocholic acid correlated inversely with body mass index (P = 4.1e-03, P = 1.9e-05, respectively), waist circumference (P = 0.017, P = 1.1e-04, respectively), body fat percentage (P = 2.5e-03, P = 2.3e-06, respectively), insulin resistance (P = 0.051, P = 4.6e-4, respectively), fasting concentrations of triglycerides (P = 0.06, P = 9.2e-4, respectively) and leptin (P = 0.067, P = 9.2e-4). Tauro- and glycohyocholic acids, and tauro-a-muricholic acid were directly linked with a distinct gut microbial community primarily composed of Clostridia species (P = 0.037, P = 0.013, P = 0.027, respectively). We conclude that serum conjugated C-6-hydroxylated BAs associate with measures of human metabolic health and gut communities of Clostridia species. The findings merit preclinical interventions and human feasibility studies to explore the therapeutic potential of these BAs in obesity and type 2 diabetes. [ABSTRACT FROM AUTHOR]

Asthma with severe exacerbation is the most common cause of hospitalization among young children. We aim to increase the understanding of this clinically important disease entity through a genome-wide association study. The discovery analysis comprises 2866 children experiencing severe asthma exacerbation between ages 2 and 6 years, and 65,415 non-asthmatic controls, and we replicate findings in 918 children from the Copenhagen Prospective Studies on Asthma in Childhood (COPSAC) birth cohorts. We identify rs281379 near FUT2/MAMSTR on chromosome 19 as a novel risk locus (OR = 1.18 (95% CI = 1.11–1.25), Pdiscovery = 2.6 × 10−9) as well as a biologically plausible interaction between functional variants in FUT2 and ABO. We further discover and replicate a potential causal mechanism behind this interaction related to S. pneumoniae respiratory illnesses. These results suggest a novel mechanism of early childhood asthma and demonstrates the importance of phenotype-specificity for discovery of asthma genes and epistasis. Genetic variants discovered through genome-wide association studies for asthma together account for a small portion of the heritability. Here, the authors identify a possible epistatic relationship between coding variants in FUT2 and ABO, especially pronounced in severe and early onset asthma. [ABSTRACT FROM AUTHOR]

Aims/hypothesis: Abnormal gut microbiota and blood metabolome profiles have been reported both in children and adults with uncomplicated type 1 diabetes as well as in adults with type 1 diabetes and advanced stages of diabetic nephropathy. In this study we aimed to investigate the gut microbiota and a panel of targeted plasma metabolites in individuals with type 1 diabetes of long duration without and with different levels of albuminuria. Methods: In a cross-sectional study we included 161 individuals with type 1 diabetes and 50 healthy control individuals. Individuals with type 1 diabetes were categorised into three groups according to historically measured albuminuria: (1) normoalbuminuria (<3.39 mg/mmol); (2) microalbuminuria (3.39–33.79 mg/mmol); and (3) macroalbuminuria (≥33.90 mg/mmol). From faecal samples, the gut microbiota composition at genus level was characterised by 16S rRNA gene amplicon sequencing and in plasma a targeted profile of 31 metabolites was analysed with ultra HPLC coupled to MS/MS. Results: Study participants were aged 60 ± 11 years (mean ± SD) and 42% were women. The individuals with type 1 diabetes had had diabetes for a mean of 42 ± 15 years and had an eGFR of 75 ± 25 ml min−1 (1.73 m)−2. Measures of the gut microbial beta diversity differed significantly between healthy controls and individuals with type 1 diabetes, either with micro- or macroalbuminuria. Taxonomic analyses showed that 79 of 324 genera differed in relative abundance between individuals with type 1 diabetes and healthy controls and ten genera differed significantly among the three albuminuria groups with type 1 diabetes. For the measured plasma metabolites, 11 of 31 metabolites differed significantly between individuals with type 1 diabetes and healthy controls. When individuals with type 1 diabetes were stratified by the level of albuminuria, individuals with macroalbuminuria had higher plasma concentrations of indoxyl sulphate and l-citrulline than those with normo- or microalbuminuria and higher plasma levels of homocitrulline and l-kynurenine compared with individuals with normoalbuminuria. Whereas plasma concentrations of tryptophan were lower in individuals with macroalbuminuria compared with those with normoalbuminuria. Conclusions/interpretation: We demonstrate that individuals with type 1 diabetes of long duration are characterised by aberrant profiles of gut microbiota and plasma metabolites. Moreover, individuals with type 1 diabetes with initial stages of diabetic nephropathy show different gut microbiota and plasma metabolite profiles depending on the level of albuminuria. [ABSTRACT FROM AUTHOR]

Aims/hypothesis: We aimed to investigate whether the impact of obesity and unfavourable lifestyle on type 2 diabetes risk is accentuated by genetic predisposition. Methods: We examined the joint association of genetic predisposition, obesity and unfavourable lifestyle with incident type 2 diabetes using a case-cohort study nested within the Diet, Cancer and Health cohort in Denmark. The study sample included 4729 individuals who developed type 2 diabetes during a median 14.7 years of follow-up, and a randomly selected cohort sample of 5402 individuals. Genetic predisposition was quantified using a genetic risk score (GRS) comprising 193 known type 2 diabetes-associated loci (excluding known BMI loci) and stratified into low (quintile 1), intermediate and high (quintile 5) genetic risk groups. Lifestyle was assessed by a lifestyle score composed of smoking, alcohol consumption, physical activity and diet. We used Prentice-weighted Cox proportional-hazards models to test the associations of the GRS, obesity and lifestyle score with incident type 2 diabetes, as well as the interactions of the GRS with obesity and unfavourable lifestyle in relation to incident type 2 diabetes. Results: Obesity (BMI ≥ 30 kg/m2) and unfavourable lifestyle were associated with higher risk for incident type 2 diabetes regardless of genetic predisposition (p > 0.05 for GRS–obesity and GRS–lifestyle interaction). The effect of obesity on type 2 diabetes risk (HR 5.81 [95% CI 5.16, 6.55]) was high, whereas the effects of high genetic risk (HR 2.00 [95% CI 1.76, 2.27]) and unfavourable lifestyle (HR 1.18 [95% CI 1.06, 1.30]) were relatively modest. Even among individuals with low GRS and favourable lifestyle, obesity was associated with a >8-fold risk of type 2 diabetes compared with normal-weight individuals in the same GRS and lifestyle stratum. Conclusions/interpretation: Having normal body weight is crucial in the prevention of type 2 diabetes, regardless of genetic predisposition. [ABSTRACT FROM AUTHOR]

Obesity and type 2 diabetes (T2D) are metabolic disorders influenced by lifestyle and genetic factors that are characterized by insulin resistance in skeletal muscle, a prominent site of glucose disposal. Numerous genetic variants have been associated with obesity and T2D, of which the majority are located in non-coding DNA regions. This suggests that most variants mediate their effect by altering the activity of gene-regulatory elements, including enhancers. Here, we map skeletal muscle genomic enhancer elements that are dynamically regulated after exposure to the free fatty acid palmitate or the inflammatory cytokine TNFα. By overlapping enhancer positions with the location of disease-associated genetic variants, and resolving long-range chromatin interactions between enhancers and gene promoters, we identify target genes involved in metabolic dysfunction in skeletal muscle. The majority of these genes also associate with altered whole-body metabolic phenotypes in the murine BXD genetic reference population. Thus, our combined genomic investigations identified genes that are involved in skeletal muscle metabolism. Obesity and type 2 diabetes (T2D) are metabolic disorders characterized by insulin resistance in skeletal muscle. Here, the authors map skeletal muscle enhancer elements dynamically regulated after exposure to free fatty acid palmitate or inflammatory cytokine TNFα and identify target genes involved in metabolic dysfunction in skeletal muscle. [ABSTRACT FROM AUTHOR]

Aims/hypothesis: Epidemiological studies have shown that diabetes is a well-established independent but modifiable risk factor for stroke. The aim of this post hoc analysis of data from the Steno-2 Study was to examine whether multiple risk factor intervention reduced the risk for stroke in individuals with type 2 diabetes and microalbuminuria. Methods: In the Steno-2 Study, 160 individuals with type 2 diabetes and microalbuminuria were randomised to intensified or conventional multiple risk factor intervention, targeting classical cardiovascular disease risk factors for a mean of 7.8 years, and then followed for a total mean of 21.2 years. The primary endpoint in this post hoc analysis was time to first stroke event. Results: During follow-up, 30 participants experienced a total of 39 strokes. Individuals randomised to conventional therapy were more likely to experience a stroke than those in the intensive-therapy group, with 29 total strokes occurring in 21 participants (26%) in the conventional-therapy group vs a total of ten strokes in nine participants (11%) in the intensive-therapy group (HR 0.31 [95% CI 0.14, 0.69]; p = 0.004). Also, the number of recurrent strokes was significantly reduced with intensive therapy. Conclusions/interpretation: Intensified multiple risk factor intervention in patients with type 2 diabetes and microalbuminuria reduces the risk for strokes as well as the number of recurrent cerebrovascular events. Trial registration: ClinicalTrials.gov NCT00320008. [ABSTRACT FROM AUTHOR]

Background: The weight loss after bariatric surgery shows considerable individual variation. Twin studies of response to dietary interventions and studies of bariatric surgery patients suggest that genetic differences may play a role. This study aimed to examine the effect of three genetic risk scores on the inter-individual variation in excess body mass index loss (EBMIL) after Roux-en-Y gastric bypass. Furthermore, we searched among known adiposity-related single nucleotide polymorphisms (SNPs) for genetic determinants of the inter-individual variation in EBMIL. Methods: Patients with morbid obesity underwent Roux-en-Y gastric bypass and were genotyped (n = 577). Two genetic risk scores for weight loss after bariatric surgery and a genetic risk score for body mass index were calculated. Associations between the genetic risk scores and EBMIL were evaluated. Lasso regression was performed on 126 SNPs known to be associated with adiposity. Results: The average EBMIL was 76.9% (range 21.7–149.2%). EBMIL was 81.1% (SD 20.6) and 73.9% (SD 21.7) in the high and low tertile groups of a genetic risk score for weight loss. Patients with a low genetic risk score for body mass index (in the lowest 5% percentile) had an EBMIL of 68.8% (SD 20.6, p = 0.018). Thirteen adiposity-related SNPs were identified to associate with EBMIL through lasso regression. Discussion: A genetic risk score was associated with EBMIL after bariatric surgery, but may not yet be applicable to clinical practice. Patients genetically predisposed to low body mass index had lower weight loss after bariatric surgery. [ABSTRACT FROM AUTHOR]

Aims/hypothesis: Individuals with type 2 diabetes have an altered bacterial composition of their gut microbiota compared with non-diabetic individuals. However, these alterations may be confounded by medication, notably the blood-glucose-lowering biguanide, metformin. We undertook a clinical trial in healthy and previously drug-free men with the primary aim of investigating metformin-induced compositional changes in the non-diabetic state. A secondary aim was to examine whether the pre-treatment gut microbiota was related to gastrointestinal adverse effects during metformin treatment. Methods: Twenty-seven healthy young Danish men were included in an 18-week one-armed crossover trial consisting of a pre-intervention period, an intervention period and a post-intervention period, each period lasting 6 weeks. Inclusion criteria were men of age 18–35 years, BMI between 18.5 kg/m2 and 27.5 kg/m2, HbA1c < 39 mmol/mol (5.7%) and plasma creatinine within the normal range. No prescribed medication, including antibiotics, for 2 months prior to recruitment were allowed and no previous gastrointestinal surgery, discounting appendectomy or chronic illness requiring medical treatment. During the intervention the participants were given metformin up to 1 g twice daily. Participants were examined five times in the fasting state with blood sampling and recording of gastrointestinal symptoms. Examinations took place at Frederiksberg Hospital, Denmark before and after the pre-intervention period, halfway through and immediately after the end of intervention and after the wash-out period. Faecal samples were collected at nine evenly distributed time points, and bacterial DNA was extracted and subjected to 16S rRNA gene amplicon sequencing in order to evaluate gut microbiota composition. Subjective gastrointestinal symptoms were reported at each visit. Results: Data from participants who completed visit 1 (n=23) are included in analyses. For the primary outcome the relative abundance of 11 bacterial genera significantly changed during the intervention but returned to baseline levels after treatment cessation. In line with previous reports, we observed a reduced abundance of Intestinibacter spp. and Clostridium spp., as well as an increased abundance of Escherichia/Shigella spp. and Bilophila wadsworthia. The relative abundance at baseline of 12 bacterial genera predicted self-reported gastrointestinal adverse effects. Conclusions/interpretation: Intake of metformin changes the gut microbiota composition in normoglycaemic young men. The microbiota changes induced by metformin extend and validate previous reports in individuals with type 2 diabetes. Secondary analyses suggest that pre-treatment gut microbiota composition may be a determinant for development of gastrointestinal adverse effects following metformin intake. These results require further investigation and replication in larger prospective studies. Trial registration: Clinicaltrialsregister.eu 2015-000199-86 and ClinicalTrials.gov NCT02546050 Funding: This project was funded by Danish Diabetes Association and The Novo Nordisk Foundation [ABSTRACT FROM AUTHOR]

Aims/hypothesis: Long-term follow-up of the Steno-2 study demonstrated that intensified multifactorial intervention increased median lifespan by 7.9 years and delayed incident cardiovascular disease by a median of 8.1 years compared with conventional multifactorial intervention during 21.2 years of follow-up. In this post hoc analysis of data from the Steno-2 study, we aimed to study the difference in direct medical costs associated with conventional vs intensified treatment.Methods: In 1993, 160 Danish individuals with type 2 diabetes and microalbuminuria were randomised to conventional or intensified multifactorial target-driven intervention for 7.8 years. Information on direct healthcare costs was retrieved from health registries, and the costs in the two groups of participants were compared by bootstrap t test analysis.Results: Over 21.2 years of follow-up, there was no difference in total direct medical costs between the intensified treatment group, €12,126,900, and the conventional treatment group, €11,181,700 (p = 0.48). The mean cost per person-year during 1996-2014 was significantly lower in the intensified treatment group (€8725 in the intensive group and €10,091 in the conventional group, p = 0.045). The main driver of this difference was reduced costs associated with inpatient admissions related to cardiovascular disease (p = 0.0024).Conclusions/interpretation: Over a follow-up period of 21.2 years, we found no difference in total costs and reduced cost per person-year associated with intensified multifactorial treatment for 7.8 years compared with conventional multifactorial treatment. Considering the substantial gain in life-years and health benefits achieved with intensified treatment, we conclude that intensified multifaceted intervention in high-risk individuals with type 2 diabetes seems to be highly feasible when balancing healthcare costs and treatment benefits in a Danish healthcare setting. [ABSTRACT FROM AUTHOR]

Aims/hypothesis: In a recent study using a standard additive genetic model, we identified a TBC1D4 loss-of-function variant with a large recessive impact on risk of type 2 diabetes in Greenlanders. The aim of the current study was to identify additional genetic variation underlying type 2 diabetes using a recessive genetic model, thereby increasing the power to detect variants with recessive effects.Methods: We investigated three cohorts of Greenlanders (B99, n = 1401; IHIT, n = 3115; and BBH, n = 547), which were genotyped using Illumina MetaboChip. Of the 4674 genotyped individuals passing quality control, 4648 had phenotype data available, and type 2 diabetes association analyses were performed for 317 individuals with type 2 diabetes and 2631 participants with normal glucose tolerance. Statistical association analyses were performed using a linear mixed model.Results: Using a recessive genetic model, we identified two novel loci associated with type 2 diabetes in Greenlanders, namely rs870992 in ITGA1 on chromosome 5 (OR 2.79, p = 1.8 × 10−8), and rs16993330 upstream of LARGE1 on chromosome 22 (OR 3.52, p = 1.3 × 10−7). The LARGE1 variant did not reach the conventional threshold for genome-wide significance (p < 5 × 10−8) but did withstand a study-wide Bonferroni-corrected significance threshold. Both variants were common in Greenlanders, with minor allele frequencies of 23% and 16%, respectively, and were estimated to have large recessive effects on risk of type 2 diabetes in Greenlanders, compared with additively inherited variants previously observed in European populations.Conclusions/interpretation: We demonstrate the value of using a recessive genetic model in a historically small and isolated population to identify genetic risk variants. Our findings give new insights into the genetic architecture of type 2 diabetes, and further support the existence of high-effect genetic risk factors of potential clinical relevance, particularly in isolated populations.Data availability: The Greenlandic MetaboChip-genotype data are available at European Genome-Phenome Archive (EGA; https://ega-archive.org/) under the accession EGAS00001002641. [ABSTRACT FROM AUTHOR]

Aims/hypothesis: In type 2 diabetes mellitus, heart failure is a frequent, potentially fatal and often forgotten complication. Glucose-lowering agents and adjuvant therapies modify the risk of heart failure. We recently reported that 7.8 years of intensified compared with conventional multifactorial intervention in individuals with type 2 diabetes and microalbuminuria in the Steno-2 study reduced the risk of cardiovascular disease and prolonged life over 21.2 years of follow-up. In this post hoc analysis, we examine the impact of intensified multifactorial intervention on the risk of hospitalisation for heart failure.Methods: One hundred and sixty individuals were randomised to conventional or intensified multifactorial intervention, using sealed envelopes. The trial was conducted using the Prospective, Randomised, Open, Blinded Endpoints (PROBE) design. After 7.8 years, all individuals were offered intensified therapy and the study continued as an observational follow-up study for an additional 13.4 years. Heart-failure hospitalisations were adjudicated from patient records by an external expert committee blinded for treatment allocation. Event rates were compared using a Cox regression model adjusted for age and sex.Results: Eighty patients were assigned to each treatment group. Ten patients undergoing intensive therapy vs 24 undergoing conventional therapy were hospitalised for heart failure during follow-up. The HR (95% CI) was 0.30 (0.14, 0.64), p = 0.002 in the intensive-therapy group compared with the conventional-therapy group. Including death in the endpoint did not lead to an alternate overall outcome; HR 0.51 (0.34, 0.76), p = 0.001. In a pooled cohort analysis, an increase in plasma N-terminal pro-B-type natriuretic peptide (NT-proBNP) during the first two years of the trial was associated with incident heart failure.Conclusions/interpretation: Intensified, multifactorial intervention for 7.8 years in type 2 diabetic individuals with microalbuminuria reduced the risk of hospitalisation for heart failure by 70% during a total of 21.2 years of observation.Trial registration:: ClinicalTrials.gov NCT00320008. [ABSTRACT FROM AUTHOR]

Aims/hypothesis: A genetic risk score (GRS) consisting of 53 insulin resistance variants (GRS53) was recently demonstrated to associate with insulin resistance in adults. We speculated that the GRS53 might already associate with insulin resistance during childhood, and we therefore aimed to investigate this in populations of Danish children and adolescents. Furthermore, we aimed to address whether the GRS associates with components of the metabolic syndrome and altered body composition in children and adolescents.Methods: We examined a total of 689 children and adolescents who were overweight or obese and 675 children and adolescents from a population-based study. Anthropometric data, dual-energy x-ray absorptiometry scans, BP, fasting plasma glucose, fasting serum insulin and fasting plasma lipid measurements were obtained, and HOMA-IR was calculated. The GRS53 was examined for association with metabolic traits in children by linear regressions using an additive genetic model.Results: In overweight/obese children and adolescents, the GRS53 associated with higher HOMA-IR (β = 0.109 ± 0.050 (SE); p = 2.73 × 10−2), fasting plasma glucose (β = 0.010 ± 0.005 mmol/l; p = 2.51 × 10−2) and systolic BP SD score (β = 0.026 ± 0.012; p = 3.32 × 10−2) as well as lower HDL-cholesterol (β = −0.008 ± 0.003 mmol/l; p = 1.23 × 10−3), total fat-mass percentage (β = −0.143 ± 0.054%; p = 9.15 × 10−3) and fat-mass percentage in the legs (β = −0.197 ± 0.055%; p = 4.09 × 10−4). In the population-based sample of children, the GRS53 only associated with lower HDL-cholesterol concentrations (β = −0.007 ± 0.003 mmol/l; p = 1.79 × 10−2).Conclusions/interpretation: An adult-based GRS comprising 53 insulin resistance susceptibility SNPs associates with insulin resistance, markers of the metabolic syndrome and altered fat distribution in a sample of Danish children and adolescents who were overweight or obese. [ABSTRACT FROM AUTHOR]

Background/objectives: A vegan diet has been associated with increased bone fracture risk, but the physiology linking nutritional exposure to bone metabolism has only been partially elucidated. This study investigated whether a vegan diet is associated with increased bone turnover and altered calcium homeostasis due to insufficient intake of calcium and vitamin D.Subjects/methods: Fractionated and total 25-hydroxyvitamin D (25(OH)-D), parathyroid hormone (PTH), calcium, and four bone turnover markers (osteocalcin, N-terminal propeptide of type I procollagen (PINP), bone-specific alkaline phosphatase (BAP), and C-terminal telopeptide of type I collagen (CTX)) were measured in serum from 78 vegans and 77 omnivores.Results: When adjusting for seasonality and constitutional covariates (age, sex, and body fat percentage) vegans had higher concentrations of PINP (32 [95% CI: 7, 64]%, P = 0.01) and BAP (58 [95% CI: 27, 97]%, P < 0.001) compared to omnivores, whereas CTX (30 [95% CI: -1, 72]%, P = 0.06) and osteocalcin (21.8 [95% CI: -9.3, 63.7]%, P = 0.2) concentrations did not differ between the two groups. Vegans had higher serum PTH concentration (38 [95% CI: 19, 60]%; P < 0.001) and lower 25(OH)-D serum concentration (-33 [95% CI: -45, -19]%; P < 0.001), but similar serum calcium concentration (-1 [95% CI: -3, 1]%, P = 0.18 compared to omnivores.Conclusions: Vegans have higher levels of circulating bone turnover markers compared to omnivores, which may in the long-term lead to poorer bone health. Differences in dietary habits including intake of vitamin D and calcium may, at least partly, explain the observed differences. [ABSTRACT FROM AUTHOR]

Aims/hypothesis: The secretion of glucagon is controlled by blood glucose and inappropriate secretion of glucagon contributes to hyperglycaemia in diabetes. Besides its role in glucose regulation, glucagon regulates amino acid metabolism in hepatocytes by increasing ureagenesis. Disruption of this mechanism causes hyperaminoacidaemia, which in turn increases glucagon secretion. We hypothesised that hepatic insulin resistance (secondary to hepatic steatosis) via defective glucagon signalling/glucagon resistance would lead to impaired ureagenesis and, hence, increased plasma concentrations of glucagonotropic amino acids and, subsequently, glucagon.Methods: To examine the association between glucagon and amino acids, and to explore whether this relationship was modified by hepatic insulin resistance, we studied a well-characterised cohort of 1408 individuals with normal and impaired glucose regulation. In this cohort, we have previously reported insulin resistance to be accompanied by increased plasma concentrations of glucagon. We now measure plasma levels of amino acids in the same cohort. HOMA-IR was calculated as a marker of hepatic insulin resistance.Results: Fasting levels of glucagonotropic amino acids and glucagon were significantly and inversely associated in linear regression models (persisting after adjustment for age, sex and BMI). Increasing levels of hepatic, but not peripheral insulin resistance (p > 0.166) attenuated the association between glucagon and circulating levels of alanine, glutamine and tyrosine, and was significantly associated with hyperaminoacidaemia and hyperglucagonaemia. A doubling of the calculated glucagon–alanine index was significantly associated with a 30% increase in hepatic insulin resistance, a 7% increase in plasma alanine aminotransferase levels, and a 14% increase in plasma γ-glutamyltransferase levels.Conclusions/interpretation: This cross-sectional study supports the existence of a liver–alpha cell axis in humans: glucagon regulates plasma levels of amino acids, which in turn feedback to regulate the secretion of glucagon. With hepatic insulin resistance, reflecting hepatic steatosis, the feedback cycle is disrupted, leading to hyperaminoacidaemia and hyperglucagonaemia. The glucagon–alanine index is suggested as a relevant marker for hepatic glucagon signalling. [ABSTRACT FROM AUTHOR]

Background/objectives: Studies of the effect of vitamin B12 and folate on the risk of asthma and hay fever have shown inconsistent results that may be biased by reverse causation and confounding. We used a Mendelian randomization approach to examine a potential causal effect of vitamin B12 and folate on hay fever, asthma, and selected biomarkers of allergy by using 11 vitamin B12-associated single-nucleotide polymorphisms (SNPs) and 2 folate-associated SNPs as unconfounded markers.Subjects/methods: We included 162,736 participants from 9 population-based studies including the UK Biobank. Results were combined in instrumental variable and meta-analyses and effects expressed as odds ratios (ORs) or estimates with 95% confidence interval (CI).Results: Using genetic proxies for B12 and folate, instrumental variable analyses did not show evidence for associations between serum B12 and hay fever: OR = 1.02 (95% CI: 0.98, 1.05), asthma: OR = 0.99 (95% CI: 0.95, 1.04), allergic sensitization: OR = 1.02 (95% CI: 0.74, 1.40), or change in serum IgE: 10.0% (95% CI: -9.6%, 29.6%) per 100 pg/ml B12. Similarly, there was no evidence for association between serum folate and hay fever: OR = 0.74 (95% CI: 0.45, 1.21), asthma: OR = 0.80 (95% CI: 0.43, 1.49), or allergic sensitization: OR = 1.92 (95% CI: 0.11, 33.45), but there was a statistically significant association with change in serum IgE: 2.0% (95% CI: 0.43%, 3.58%) per 0.1 ng/ml serum folate.Conclusions: Our results did not support the hypothesis that levels of vitamin B12 and folate are causally related to hay fever, asthma, or biomarkers of allergy, but we found evidence of a positive association between serum folate and serum total IgE. [ABSTRACT FROM AUTHOR]

Purpose: Low birth weight (BW) and low ponderal index (PI) are associated with increased risk of type 2 diabetes mellitus. This study has two purposes: first to investigate the influence of PI on the risk of gestational diabetes mellitus (GDM); second, to study the association between glucose metabolism and BW in women with previous GDM.Methods: GDM cohort: 185 women with GDM in 1978-1996, attending a follow-up study in 2000-2002. Control cohort: 1137 women from a population-based diabetes screening study (Inter99) in a neighbouring county in 1999-2001. BW and birth length were collected from the original midwifery records. BW and PI were stratified into tertiles for analysis.Results: PI in the lower tertiles was associated with an increased risk of GDM [odds ratio 1.59 (95% confidence interval 1.07-2.36, p = 0.021)]. Among women with previous GDM, the area under the curve (AUC) for plasma levels of glucose and insulin during an OGTT was highest for the lower tertiles of BW (for AUCglucose p = 0.048, for AUCinsulin p = 0.047 adjusted for age and BMI).Conclusions: Lower PI is associated with increased risk of GDM. In women with previous GDM, lower BW is associated with a more severe impairment of glucose metabolism one to two decades after the pregnancy complicated by GDM. [ABSTRACT FROM AUTHOR]

Aims/hypothesis: Fasting plasma levels of branched-chain amino acids (BCAAs) are associated with insulin resistance, but it remains unclear whether there is a causal relation between the two. We aimed to disentangle the causal relations by performing a Mendelian randomisation study using genetic variants associated with circulating BCAA levels and insulin resistance as instrumental variables. Methods: We measured circulating BCAA levels in blood plasma by NMR spectroscopy in 1,321 individuals from the ADDITION-PRO cohort. We complemented our analyses by using previously published genome-wide association study (GWAS) results from the Meta-Analyses of Glucose and Insulin-related traits Consortium (MAGIC) ( n = 46,186) and from a GWAS of serum BCAA levels ( n = 24,925). We used a genetic risk score (GRS), calculated using ten established fasting serum insulin associated variants, as an instrumental variable for insulin resistance. A GRS of three variants increasing circulating BCAA levels was used as an instrumental variable for circulating BCAA levels. Results: Fasting plasma BCAA levels were associated with higher HOMA-IR in ADDITION-PRO (β 0.137 [95% CI 0.08, 0.19] p = 6 × 10). However, the GRS for circulating BCAA levels was not associated with fasting insulin levels or HOMA-IR in ADDITION-PRO (β −0.011 [95% CI −0.053, 0.032] p = 0.6 and β −0.011 [95% CI −0.054, 0.031] p = 0.6, respectively) or in GWAS results for HOMA-IR from MAGIC (β for valine-increasing GRS −0.012 [95% CI −0.069, 0.045] p = 0.7). By contrast, the insulin-resistance-increasing GRS was significantly associated with increased BCAA levels in ADDITION-PRO (β 0.027 [95% CI 0.005, 0.048] p = 0.01) and in GWAS results for serum BCAA levels (β 1.22 [95% CI 0.71, 1.73] p = 4 × 10, β 0.96 [95% CI 0.45, 1.47] p = 3 × 10, and β 0.67 [95% CI 0.16, 1.18] p = 0.01 for isoleucine, leucine and valine levels, respectively) and instrumental variable analyses in ADDITION-PRO indicated that HOMA-IR is causally related to higher circulating fasting BCAA levels (β 0.73 [95% CI 0.26, 1.19] p = 0.002). Conclusions/interpretation: Our results suggest that higher BCAA levels do not have a causal effect on insulin resistance while increased insulin resistance drives higher circulating fasting BCAA levels. [ABSTRACT FROM AUTHOR]

We aimed to examine heterogeneity in glucose response curves during an oral glucose tolerance test with multiple measurements and to compare cardiometabolic risk profiles between identified glucose response curve groups. We analyzed data from 1,267 individuals without diabetes from five studies in Denmark, the Netherlands and the USA. Each study included between 5 and 11 measurements at different time points during a 2-h oral glucose tolerance test, resulting in 9,602 plasma glucose measurements. Latent class trajectories with a cubic specification for time were fitted to identify different patterns of plasma glucose change during the oral glucose tolerance test. Cardiometabolic risk factor profiles were compared between the identified groups. Using latent class trajectory analysis, five glucose response curves were identified. Despite similar fasting and 2-h values, glucose peaks and peak times varied greatly between groups, ranging from 7-12 mmol/L, and 35-70 min. The group with the lowest and earliest plasma glucose peak had the lowest estimated cardiovascular risk, while the group with the most delayed plasma glucose peak and the highest 2-h value had the highest estimated risk. One group, with normal fasting and 2-h values, exhibited an unusual profile, with the highest glucose peak and the highest proportion of smokers and men. The heterogeneity in glucose response curves and the distinct cardiometabolic risk profiles may reflect different underlying physiologies. Our results warrant more detailed studies to identify the source of the heterogeneity across the different phenotypes and whether these differences play a role in the development of type 2 diabetes and cardiovascular disease. [ABSTRACT FROM AUTHOR]

Lower serum vitamin B12 levels have been related to adverse metabolic health profiles, including adiposity. We used a Mendelian randomization design to test whether this relation might be causal. We included two Danish population-based studies (n = 9311). Linear regression was used to test for associations between (1) serum vitamin B12 levels and body mass index (BMI), (2) genetic variants and serum vitamin B12 levels, and (3) genetic variants and BMI. The effect of a genetically determined decrease in serum vitamin B12 on BMI was estimated by instrumental variable regression. Decreased serum vitamin B12 associated with increased BMI ( P < 1 × 10). A genetic risk score based on eight vitamin B12 associated variants associated strongly with serum vitamin B12 ( P < 2 × 10), but not with BMI ( P = 0.91). Instrumental variable regression showed that a 20% decrease in serum vitamin B12 was associated with a 0.09 kg/m (95% CI 0.05; 0.13) increase in BMI ( P = 3 × 10), whereas a genetically induced 20% decrease in serum vitamin B12 had no effect on BMI [−0.03 (95% CI −0.22; 0.16) kg/m] (P = 0.74). Nevertheless, the strongest serum vitamin B12 variant, FUT2 rs602662, which was excluded from the B12 genetic risk score due to potential pleiotropic effects, showed a per allele effect of 0.15 kg/m (95% CI 0.01; 0.32) on BMI ( P = 0.03). This association was accentuated including two German cohorts (n = 5050), with a combined effect of 0.19 kg/m (95% CI 0.08; 0.30) ( P = 4 × 10). We found no support for a causal role of decreased serum vitamin B12 levels in obesity. However, our study suggests that FUT2, through its regulation of the cross-talk between gut microbes and the human host, might explain a part of the observational association between serum vitamin B12 and BMI. [ABSTRACT FROM AUTHOR]

Aims/hypothesis: The aim of this work was to study the potential long-term impact of a 7.8 years intensified, multifactorial intervention in patients with type 2 diabetes mellitus and microalbuminuria in terms of gained years of life and years free from incident cardiovascular disease. Methods: The original intervention (mean treatment duration 7.8 years) involved 160 patients with type 2 diabetes and microalbuminuria who were randomly assigned (using sealed envelopes) to receive either conventional therapy or intensified, multifactorial treatment including both behavioural and pharmacological approaches. After 7.8 years the study continued as an observational follow-up with all patients receiving treatment as for the original intensive-therapy group. The primary endpoint of this follow-up 21.2 years after intervention start was difference in median survival time between the original treatment groups with and without incident cardiovascular disease. Non-fatal endpoints and causes of death were adjudicated by an external endpoint committee blinded for treatment allocation. Results: Thirty-eight intensive-therapy patients vs 55 conventional-therapy patients died during follow-up (HR 0.55 [95% CI 0.36, 0.83], p = 0.005). The patients in the intensive-therapy group survived for a median of 7.9 years longer than the conventional-therapy group patients. Median time before first cardiovascular event after randomisation was 8.1 years longer in the intensive-therapy group ( p = 0.001). The hazard for all microvascular complications was decreased in the intensive-therapy group in the range 0.52 to 0.67, except for peripheral neuropathy (HR 1.12). Conclusions/interpretation: At 21.2 years of follow-up of 7.8 years of intensified, multifactorial, target-driven treatment of type 2 diabetes with microalbuminuria, we demonstrate a median of 7.9 years of gain of life. The increase in lifespan is matched by time free from incident cardiovascular disease. Trial registration:: ClinicalTrials.gov registration no. NCT00320008. Funding:: The study was funded by an unrestricted grant from Novo Nordisk A/S. [ABSTRACT FROM AUTHOR]

Aims/hypothesis: We examined the extent to which surrogate measures of insulin release have shared genetic causes. Methods: Genetic and phenotypic correlations were calculated in a family cohort ( n = 315) in which beta cell indices were estimated based on fasting and oral glucose-stimulated plasma glucose, serum C-peptide and serum insulin levels. Furthermore, we genotyped a large population-based cohort ( n = 6,269) for common genetic variants known to associate with type 2 diabetes, fasting plasma glucose levels or fasting serum insulin levels to examine their association with various indices. Results: We found a notable difference between the phenotypic and genetic correlations for the traits, emphasising that the phenotypic correlation is an insufficient measure of the magnitude of shared genetic impact. In addition, we found that corrected insulin response, insulinogenic index and incAUC for insulin after an oral glucose challenge shared the majority of their genetic backgrounds, with genetic correlations of 0.80-0.99. The BIGTT index for acute insulin response differed slightly more from the latter with genetic correlations of 0.78-0.87. The HOMA for beta cell function was genetically closely related to fasting insulin with a genetic correlation of 0.85. The effects of 82 selected susceptibility single nucleotide polymorphisms on these insulin secretion indices supported our interpretation of the data and added insight into the biological differences between the examined traits. Conclusions/interpretation: The level of shared genetic background varies between surrogate measures of insulin release, and this should be considered when designing a genetic association study to best obtain information on various mechanisms of insulin release. [ABSTRACT FROM AUTHOR]

Aims/hypothesis: Elevated serum ferritin levels are associated with an increased risk of type 2 diabetes, but the nature of this association remains elusive. The aim of this study was to test the hypothesis that an elevated fasting serum ferritin level is associated with an increased risk of type 2 diabetes due to its association with impaired beta cell function and decreased insulin sensitivity. Methods: We investigated 6,392 individuals from the Danish general population. Surrogate measures of beta cell function and insulin sensitivity were calculated for approximately 6,100 individuals based on OGTT examinations. Results: The ORs for type 2 diabetes were 4.2 (95% CI 2.4, 7.2) for the highest vs the lowest quintile of serum ferritin, and 17 (95% CI 8.9, 33) for serum ferritin levels ≥97.5th percentile vs <20th percentile. Elevated serum ferritin levels were associated with elevated plasma glucose levels at 0, 30 and 120 min ( p < 0.001), elevated serum insulin levels at 0 and 120 min ( p = 0.02 and p < 0.001), decreased beta cell function estimated as the insulinogenic index and corrected insulin response ( p < 0.001), and decreased insulin sensitivity estimated by the Matsuda index of insulin sensitivity and HOMA-IR ( p < 0.001). Whereas the association with impaired beta cell function was present in both men and women, the association with decreased insulin sensitivity was observed among men and older women but not among younger women. Conclusions/interpretation: Elevated fasting serum ferritin levels are associated with surrogate measures of both impaired beta cell function and decreased insulin sensitivity. Menopause seems to modify the association with insulin sensitivity. [ABSTRACT FROM AUTHOR]

Purpose: Meta-analyses have suggested an effect of MTHFR C677T genotype (rs1801133), a proxy for blood total homocysteine, on cardiovascular disease (CVD) in populations with low population dietary folate. The aim was to examine the association and effect modification by serum folate and vitamin B12 levels between MTHFR and CVD-related outcomes in a general population with no mandatory folic acid fortification policy. Methods: The study population included 13,748 adults retrieved from pooling of four population-based studies conducted in Denmark. MTHFR genotype, serum folate (measured in approximately 9,356 individuals), and serum vitamin B12 (9,215 individuals), hypertension, and dyslipidemia were measured at baseline, and participants were followed for a mean of 10.5-11.7 years in central registries for diagnoses of stroke (623 incidents), ischaemic heart disease (IHD) (835 incidents), and all-cause mortality (1,272 incidents). Results: The MTHFR genotype (TT vs. CC/CT) was not associated with hypertension [OR (95 % CI) 1.09 (0.95-1.25)], dyslipidemia [OR (95 % CI) 0.97 (0.84-1.11)], stroke [HR (95 % CI) 0.92 (0.69-1.23)], and all-cause mortality [HR (95 % CI) 0.94 (0.77-1.14)], either overall, or in participants with low serum folate or B12 status ( P values for interactions 0.15-0.94). Individuals with the MTHFR TT genotype had a higher risk of IHD (HR (95 % CI) 1.38 (1.11-1.71)), but this association was not modified by folate status ( P value for interaction 0.45). Conclusions: Our results do not support a causal relationship between homocysteine and CVD. However, we cannot exclude a direct causal effect of MTHFR C677T genotype on IHD. [ABSTRACT FROM AUTHOR]

The Greenlandic population, a small and historically isolated founder population comprising about 57,000 inhabitants, has experienced a dramatic increase in type 2 diabetes (T2D) prevalence during the past 25 years. Motivated by this, we performed association mapping of T2D-related quantitative traits in up to 2,575 Greenlandic individuals without known diabetes. Using array-based genotyping and exome sequencing, we discovered a nonsense p.Arg684Ter variant (in which arginine is replaced by a termination codon) in the gene TBC1D4 with an allele frequency of 17%. Here we show that homozygous carriers of this variant have markedly higher concentrations of plasma glucose (β = 3.8 mmol l−1, P = 2.5 × 10−35) and serum insulin (β = 165 pmol l−1, P = 1.5 × 10−20) 2 hours after an oral glucose load compared with individuals with other genotypes (both non-carriers and heterozygous carriers). Furthermore, homozygous carriers have marginally lower concentrations of fasting plasma glucose (β = −0.18 mmol l−1, P = 1.1 × 10−6) and fasting serum insulin (β = −8.3 pmol l−1, P = 0.0014), and their T2D risk is markedly increased (odds ratio (OR) = 10.3, P = 1.6 × 10−24). Heterozygous carriers have a moderately higher plasma glucose concentration 2 hours after an oral glucose load than non-carriers (β = 0.43 mmol l−1, P = 5.3 × 10−5). Analyses of skeletal muscle biopsies showed lower messenger RNA and protein levels of the long isoform of TBC1D4, and lower muscle protein levels of the glucose transporter GLUT4, with increasing number of p.Arg684Ter alleles. These findings are concomitant with a severely decreased insulin-stimulated glucose uptake in muscle, leading to postprandial hyperglycaemia, impaired glucose tolerance and T2D. The observed effect sizes are several times larger than any previous findings in large-scale genome-wide association studies of these traits and constitute further proof of the value of conducting genetic association studies outside the traditional setting of large homogeneous populations. [ABSTRACT FROM AUTHOR]

In this paper, we mine full mtDNA sequences from an exome capture data set of 2000 Danes, showing that it is possible to get high-quality full-genome sequences of the mitochondrion from this resource. The sample includes 1000 individuals with type 2 diabetes and 1000 controls. We characterise the variation found in the mtDNA sequence in Danes and relate the variation to diabetes risk as well as to several blood phenotypes of the controls but find no significant associations. We report 2025 polymorphisms, of which 393 have not been reported previously. These 393 mutations are both very rare and estimated to be caused by very recent mutations but individuals with type 2 diabetes do not possess more of these variants. Population genetics analysis using Bayesian skyline plot shows a recent history of rapid population growth in the Danish population in accordance with the fact that >40% of variable sites are observed as singletons. [ABSTRACT FROM AUTHOR]

During the past 7 years, genome-wide association studies have shed light on the contribution of common genomic variants to the genetic architecture of type 2 diabetes, obesity and related intermediate phenotypes. The discoveries have firmly established more than 175 genomic loci associated with these phenotypes. Despite the tight correlation between type 2 diabetes and obesity, these conditions do not appear to share a common genetic background, since they have few genetic risk loci in common. The recent genetic discoveries do however highlight specific details of the interplay between the pathogenesis of type 2 diabetes, insulin resistance and obesity. The focus is currently shifting towards investigations of data from targeted array-based genotyping and exome and genome sequencing to study the individual and combined effect of low-frequency and rare variants in metabolic disease. Here we review recent progress as regards the concepts, methodologies and derived outcomes of studies of the genetics of type 2 diabetes and obesity, and discuss avenues to be investigated in the future within this research field. [ABSTRACT FROM AUTHOR]

Aims/hypothesis: The aim of this study was to estimate the heritability of quantitative measures of glucose regulation obtained from a tolbutamide-modified frequently sampled IVGTT (t-FSIGT) and to correlate the heritability of the glucose-stimulated beta cell response to the tolbutamide-induced beta cell response. In addition, single nucleotide polymorphisms (SNPs) having an exclusive effect on either glucose- or tolbutamide-stimulated insulin release were identified. Methods: Two hundred and eighty-four non-diabetic family members of patients with type 2 diabetes underwent a t-FSIGT with intravenous injection of glucose at t = 0 min and tolbutamide at t = 20 min. Measurements of plasma glucose, serum insulin and serum C-peptide were taken at 33 time points from fasting to 180 min. Insulin secretion rate, acute insulin response (AIR), disposition index (D) after glucose and disposition index after tolbutamide (D), insulin sensitivity (S), glucose effectiveness (S) and beta cell responsiveness to glucose were calculated. A polygenic variance component model was used to estimate heritability, genetic correlations and associations. Results: We found high heritabilities for acute insulin secretion subsequent to glucose stimulation (AIR h ± SE: 0.88 ± 0.14), but these were slightly lower after tolbutamide (AIR h ± SE: 0.69 ± 0.14). We also estimated the heritabilities for S ( h ± SE: 0.26 ± 0.12), S ( h ± SE: 0.47 ± 0.13), D ( h ± SE: 0.56 ± 0.14), D ( h ± SE: 0.49 ± 0.14) and beta cell responsiveness to glucose ( h ± SE: 0.66 ± 0.12). Additionally, strong genetic correlations were found between measures of beta cell response after glucose and tolbutamide stimulation, with correlation coefficients ranging from 0.77 to 0.88. Furthermore, we identified five SNPs with an exclusive effect on either glucose-stimulated (rs5215, rs1111875, rs11920090) or tolbutamide-stimulated (rs10946398, rs864745) insulin secretion. Conclusions/interpretation: Our data demonstrate that both glucose- and tolbutamide-induced insulin secretions are highly heritable traits, which are largely under the control of the same genes. [ABSTRACT FROM AUTHOR]

To quantify known and unknown microorganisms at species-level resolution using shotgun sequencing data, we developed a method that establishes metagenomic operational taxonomic units (mOTUs) based on single-copy phylogenetic marker genes. Applied to 252 human fecal samples, the method revealed that on average 43% of the species abundance and 58% of the richness cannot be captured by current reference genome-based methods. An implementation of the method is available at http://www.bork.embl.de/software/mOTU/. [ABSTRACT FROM AUTHOR]

The genetic architecture of common traits, including the number, frequency, and effect sizes of inherited variants that contribute to individual risk, has been long debated. Genome-wide association studies have identified scores of common variants associated with type 2 diabetes, but in aggregate, these explain only a fraction of the heritability of this disease. Here, to test the hypothesis that lower-frequency variants explain much of the remainder, the GoT2D and T2D-GENES consortia performed whole-genome sequencing in 2,657 European individuals with and without diabetes, and exome sequencing in 12,940 individuals from five ancestry groups. To increase statistical power, we expanded the sample size via genotyping and imputation in a further 111,548 subjects. Variants associated with type 2 diabetes after sequencing were overwhelmingly common and most fell within regions previously identified by genome-wide association studies. Comprehensive enumeration of sequence variation is necessary to identify functional alleles that provide important clues to disease pathophysiology, but large-scale sequencing does not support the idea that lower-frequency variants have a major role in predisposition to type 2 diabetes.

GLP-1 is an insulinotropic hormone that synergistically with glucose gives rise to an increased insulin response. Its secretion is increased following a meal and it is thus of interest to describe the secretion of this hormone following an oral glucose tolerance test (OGTT). The aim of this study was to build a mechanism-based population model that describes the time course of total GLP-1 and provides indices for capability of secretion in each subject. The goal was thus to model the secretion of GLP-1, and not its effect on insulin production. Single 75 g doses of glucose were administered orally to a mixed group of subjects ranging from healthy volunteers to patients with type 2 diabetes (T2D). Glucose, insulin, and total GLP-1 concentrations were measured. Prior population data analysis on measurements of glucose and insulin were performed in order to estimate the glucose absorption rate. The individual estimates of absorption rate constants were used in the model for GLP-1 secretion. Estimation of parameters was performed using the FOCE method with interaction implemented in NONMEM VI. The final transit/indirect-response model obtained for GLP-1 production following an OGTT included two stimulation components (fast, slow) for the zero-order production rate. The fast stimulation was estimated to be faster than the glucose absorption rate, supporting the presence of a proximal-distal loop for fast secretion from l-cells. The fast component ( st = 8.64·10 [mg]) was estimated to peak around 25 min after glucose ingestion, whereas the slower component ( st = 26.2·10 [mg]) was estimated to peak around 100 min. Elimination of total GLP-1 was characterised by a first-order loss. The individual values of the early phase GLP-1 secretion parameter ( st) were correlated ( r = 0.52) with the AUC(0-60 min.) for GLP-1. A mechanistic population model was successfully developed to describe total GLP-1 concentrations over time observed after an OGTT. The model provides indices related to different mechanisms of subject abilities to secrete GLP-1. The model provides a good basis to study influence of different demographic factors on these components, presented mainly by indices of the fast- and slow phases of GLP-1 response. [ABSTRACT FROM AUTHOR]

We have previously shown that heterozygous single-base deletions in the carboxyl-ester lipase ( CEL) gene cause exocrine and endocrine pancreatic dysfunction in two multigenerational families. These deletions were found in the first and fourth repeats of a variable number of tandem repeats (VNTR), which has proven challenging to sequence due to high GC-content and considerable length variation. We have therefore developed a screening method consisting of a multiplex PCR followed by fragment analysis. The method detected putative disease-causing insertions and deletions in the proximal repeats of the VNTR, and determined the VNTR-length of each allele. When blindly testing 56 members of the two families with known single-base deletions in the CEL VNTR, the method correctly assessed the mutation carriers. Screening of 241 probands from suspected maturity-onset diabetes of the young (MODY) families negative for mutations in known MODY genes (95 individuals from Denmark and 146 individuals from UK) revealed no deletions in the proximal repeats of the CEL VNTR. However, we found one Danish patient with a short, novel CEL allele containing only three VNTR repeats (normal range 7–23 in healthy controls). This allele co-segregated with diabetes or impaired glucose tolerance in the patient’s family as six of seven mutation carriers were affected. We also identified individuals who had three copies of a complete CEL VNTR. In conclusion, the CEL gene is highly polymorphic, but mutations in CEL are likely to be a rare cause of monogenic diabetes. [ABSTRACT FROM AUTHOR]

Mitochondria play an important role in many processes, like glucose metabolism, fatty acid oxidation and ATP synthesis. In this study, we aimed to identify association of common polymorphisms in nuclear-encoded genes involved in mitochondrial protein synthesis and biogenesis with type II diabetes mellitus (T2DM) using a two-stage design. In the first stage, we analyzed 62 tagging single nucleotide polymorphisms (SNPs) in the Hoorn study (n=999 participants) covering all common variation in 13 biological candidate genes. These 13 candidate genes were selected from four clusters regarded essential for correct mitochondrial protein synthesis and biogenesis: aminoacyl tRNA synthetases, translation initiation factors, tRNA modifying enzymes and mitochondrial DNA transcription and replication. SNPs showing evidence for association with T2DM were measured in second stage genotyping (n=10164 participants). After a meta-analysis, only one SNP in SIRT4 (rs2522138) remained significant (P=0.01). Extending the second stage with samples from the Danish Steno Study (n=1220 participants) resulted in a common odds ratio (OR) of 0.92 (0.85–1.00), P=0.06. Moreover, in a large meta-analysis of three genome-wide association studies, this SNP was also not associated with T2DM (P=0.72). In conclusion, we did not find evidence for association of common variants in 13 nuclear-encoded mitochondrial proteins with T2DM.European Journal of Human Genetics (2009) 17, 1056–1062; doi:10.1038/ejhg.2009.4; published online 11 February 2009 [ABSTRACT FROM AUTHOR]

The mechanistic link between the FTO locus and risk of obesity has remained elusive. However, a new study presents compelling evidence suggesting that the browning of white adipocytes into beige adipocytes (together with regulation of thermogenesis), might be an important and potentially modifiable pathway for development of obesity therapeutics. [ABSTRACT FROM AUTHOR]

Using a large-scale genotyping analysis of gene-based single nucleotide polymorphisms (SNPs) in Japanese type 2 diabetic patients, we have identified a gene encoding neurocalcin δ ( NCALD) as a candidate for a susceptibility gene to diabetic nephropathy; the landmark SNP was found in the 3′ UTR of NCALD (rs1131863: exon 4 +1340 A vs. G, P = 0.00004, odds ratio = 1.59, 95% CI 1.27–1.98). We also discovered two other SNPs in exon 4 of this gene (+999 T/A, +1307 A/G) that showed absolute linkage disequilibrium to the landmark SNP. Subsequent in vitro functional analysis revealed that synthetic mRNA corresponding to the disease susceptible haplotype (exon 4 +1340 G, +1307 G, +999 A) was degraded faster than mRNA corresponding to the major haplotype (exon 4 +1340 A, +1307 A, +999 T), and allelic mRNA expression of the disease susceptibility allele was significantly lower than that of the major allele in normal kidney tissues. In an experiment using a short interfering RNA targeting NCALD, we found that silencing of the NCALD led to a considerable enhancement of cell migration, accompanied by a significant reduction in E-cadherin expression, and by an elevation of α smooth muscle actin expression in cultured renal proximal tubular epithelial cells. We also identified the association of the landmark SNP with the progression of diabetic nephropathy in a 8-year prospective study (A vs. G, P = 0.03, odds ratio = 1.91, 95% CI 1.07–3.42). These results suggest that the NCALD gene is a likely candidate for conferring susceptibility to diabetic nephropathy. [ABSTRACT FROM AUTHOR]

Food intake and weight gain are influenced by endocannabinoids whose actions are regulated by the fatty acid amide hydrolase (FAAH) enzyme. The homozygous Thr/Thr genotype of the functional Pro129Thr variant (rs324420) in the gene encoding FAAH was recently reported to associate with overweight and obesity in white and black populations. We investigated the Pro129Thr variant in relation to overweight and obesity in a relatively large population-based study sample of Danish whites ( n = 5,801). In case-control studies of obesity, a borderline association with the major Pro allele was identified; however, after correction for multiple testing, no association was found. Furthermore, a possible association between the major Pro allele and obesity was not supported by studies of obesity-related quantitative traits. In conclusion, in a large study sample, we were unable to find robust evidence of an association of the Pro129Thr FAAH variant with overweight, obesity, and any related quantitative traits among the examined whites. [ABSTRACT FROM AUTHOR]

The development of obesity is influenced by both genetic and environmental risk factors. Whereas changes in the environment appear to be responsible for the increasing prevalence of obesity, genetic factors interacting with environmental factors would contribute to explain obesity onset and severity. To explore epidemiologic genotype-by-nutrient interactions in obesity. A total of 42 polymorphisms of 26 candidate genes for obesity were genotyped in 549 adult obese women recruited from eight European centres in a case-only study. The nutritional variables assessed in this study were the dietary fibre intake (grams per day), the ratio of dietary polyunsaturated fat to saturated fat (P:S ratio) and the percentage of energy derived from fat in the diet as calculated from a weighed three-day food record (%E). Under the assumption of genotype-nutrient independence in the population, the odds ratio calculated in a sample of obese women would indicate the existence of genotype-by-nutrient interactions, measured as deviations from the multiplicative effects of the genetic and the nutrient factors separately. No new but confirmaty evidences for genotype-by-nutrient interactions in obesity were detected in this case-only study. The test of interaction between fibre intake and the −514 C > T polymorphism of the hepatic lipase gene ( LIPC) yielded P-values of 0.01 across different statistical models. Likewise, the −11377G > C polymorphism of the adiponectin gene ( ADIPOQ) and the −681 C > G polymorphism of the PPARG3 gene might interact with the percentage of energy derived from fat in the diet for the development of obesity ( P-values in the range of 0.01–0.05 across different statistical models). The P-values were not adjusted for multiple testing, so these results should be considered with caution. Although the use of obese-only samples is theoretically a useful approach to detect interactions, few genotype-by-nutrient interactions have been suggested in obese European women after the analysis of candidate polymorphisms and the selected nutrient variables. The most remarkable multiplicative interaction found in this study refers to the combination of the hepatic lipase gene polymorphism −514 C > T and fibre intake. [ABSTRACT FROM AUTHOR]

CDK4 is involved in the regulation of body weight, pancreatic ß-cell proliferation, insulin responsiveness, and diabetes pathogenesis. CDK4 activity is inhibited by CDKN1C, which is regulated by insulin. In addition, CDKN1C plays an important role in ß-cell proliferation and is involved in the pathogenesis of the Beckwith-Wiedemann syndrome, a disorder characterized by neonatal hyperinsulinaemic hypoglycaemia and pre- and post-natal overgrowth. The aim of this study was to investigate if variations in the proximal promoter and the coding region of the CDKN1C and CDK4 genes are associated with type 2 diabetes or changes in related quantitative phenotypes among glucose-tolerant subjects. Mutation analyses of the two genes in 62 type 2 diabetic patients resulted in the discovery of seven variants of CDKN1C and two variants of CDK4. In a case-control study comprising 717 type 2 diabetic patients and 518 glucose-tolerant subjects the most frequent variants did not show any difference in allele frequencies between the type 2 diabetic patients and the control subjects. However, in two genotype-quantitative trait correlation studies involving 206 glucose-tolerant offspring of type 2 diabetic patients and 359 young, healthy subjects the CDKN1C del171APVA variant associated with increased birth weight ( P=0.05 and P=0.05). Furthermore, the same variant tended to be associated with decreased basal glucose oxidation among 16 genotypically discordant dizygotic twins ( P=0.03). In a genotype-quantitative trait study involving 500 middle-aged glucose-tolerant subjects the CDK4 IVS2-31G?A variant was associated with an increased waist circumference ( P=0.03) and waist-to-hip ratio ( P=0.02) and altered fasting plasma glucose ( P=0.03). However, these later findings could not be replicated in additional studies. In conclusion, variants in CDKN1C may contribute to the inter-individual variation in birth weight. [ABSTRACT FROM AUTHOR]

Obesity and inactivity are major risk factors of feline diabetes mellitus (FDM) and human type II diabetes mellitus (T2DM). In recent years, changes in the gut microbiota have been suggested as a contributing factor to T2DM. Whether the gut microbiota (GM) composition plays a role in FDM remains unknown. The aim of the current study was firstly a cross-sectional comparison of the GM of diabetic cats, to that of lean, and of obese/overweight non-diabetic cats of a similar age. Specifically, fecal samples from 82 privately-owned cats from Denmark and Switzerland were sequenced using 16S rRNA gene amplicon metabarcoding. Secondly dietary intervention data was generated, by obtaining additional samples from a subset of cats after placing them on a high-protein diet for four weeks. The GM diversity of diabetic cats was lower than that of lean cats in the cross-sectional study, and lower compared to lean and to overweight/obese cats after diet intervention. Diabetic cats also exhibited fewer Anaerotruncus, Dialister, and unknown Ruminococcaceae than lean cats. Serum fructosamine levels correlated negatively with Prevotellaceae abundance and positively with Enterobacteriaceae abundance. In summary the intestinal microbiota of diabetic cats was characterized by decreased GM diversity and loss of butyrate producing bacterial genera. [ABSTRACT FROM AUTHOR]

BACKGROUND Type 2 diabetes mellitus is a progressive disease, which requires intensification of treatment regimens over time in order to maintain target glucose levels. OBJECTIVE To compare rosiglitazone, metformin and glyburide monotherapies for the treatment of type 2 diabetes mellitus. DESIGN AND INTERVENTION A Diabetes Outcome Progression Trial (ADOPT) was an international, multicenter, randomized, double-blind, head-to-head study of patients with newly diagnosed type 2 diabetes mellitus. Eligible patients were aged 30-75 years, with a fasting plasma glucose (FPG) level 7-10 mmol/I, and no previous pharmacotherapy for type 2 diabetes mellitus. Patients with congestive heart failure, uncontrolled hypertension, angina, renal impairment, or liver disease were excluded. Patients were randomly allocated to receive one of three monotherapies: 4 mg rosigiitazone daily, 500 mg metformin daily, or 2.5 mg glyburide daily. Doses were adjusted to maintain an FPG level <7.8 mmol/l. OUTCOME MEASURES The primary outcome measure was the interval from baseline to treatment failure (defined as an FPG level >10 mmol/I). Secondary outcome measures included HbA1c levels, insulin sensitivity, β-cell function, weight, and adverse events. RESULTS The study enrolled 1,456 patients in the rosiglitazone group, 1,454 in the metformin group and 1,441 in the glyburide group. Median treatment duration was 3.3 years in the glyburide group and 4.0 years in the rosiglitazone and metformin groups. The study completion rates for rosiglitazone, metformin and glyburide were 63%, 62% and 56%, respectively. The 5-year Kaplan-Meier cumulative incidence of treatment failure was 15% with rosiglitazone, 21% with metformin and 34% with glyburide. The risk of treatment failure was reduced by 32% and 63% when rosiglitazone was compared with metformin and glyburide, respectively. Progression to an FPG level >7.8mmol/I occurred in 15.4% of patients treated with rosiglitazone, 24.4% of patients treated with metformin and 33.3% of patients treated with glyburide. Annual rates of increase in the FPG levels were 0.04 mmol/I (rosiglitazone), 0.15mmol/I (metformin) and 0.31mmol/I (glyburide). Annual rates of increase in the HbA1c levels were 0.07% (rosiglitazone), 0.14% (metformin) and 0.24% (glyburide). At study end, 40% of patients in the rosiglitazone group had HbAlc levels <7%, compared with 36% and 26% of patients in the metformin and glyburide groups, respectively. Insulin sensitivity improved in the rosiglitazone and metformin groups, but not in the glyburide group. β-Cell function declined by 2.0% (rosiglitazone), 3.1% (metformin) and 6.1% (glyburide). Treatment with rosiglitazone was more frequently associated with weight gain, congestive heart failure, edema, high LDL cholesterol levels, and non-vertebral fractures than treatment with metformin or glyburide. Metformin treatment had the highest rate of gastrointestinal events, whereas glyburide treatment had the highest rate of hypoglycemia but the lowest risk of cardiovascular events. CONCLUSION Although rosigiitazone was the most effective monotherapy in this study, cost and adverse events could limit its use as an initial treatment for type 2 diabetes mellitus. [ABSTRACT FROM AUTHOR]