Cristian Guja

Robust associations of four new chromosome regions from genome-wide analyses of type 1 diabetes

The Wellcome Trust Case Control Consortium (WTCCC) primary genome-wide association (GWA) scan on seven diseases, including the multifactorial autoimmune disease type 1 diabetes (T1D), shows associations at P < 5 × 10−7 between T1D and six chromosome regions: 12q24, 12q13, 16p13, 18p11, 12p13 and 4q27. Here, we attempted to validate these and six other top findings in 4,000 individuals with T1D, 5,000 controls and 2,997 family trios independent of the WTCCC study. We confirmed unequivocally the associations of 12q24, 12q13, 16p13 and 18p11 (Pfollow-up ≤ 1.35 × 10−9; Poverall ≤ 1.15 × 10−14), leaving eight regions with small effects or false-positive associations. We also obtained evidence for chromosome 18q22 (Poverall = 1.38 × 10−8) from a GWA study of nonsynonymous SNPs. Several regions, including 18q22 and 18p11, showed association with autoimmune thyroid disease. This study increases the number of T1D loci with compelling evidence from six to at least ten.

A genome-wide association study of nonsynonymous SNPs identifies a type 1 diabetes locus in the interferon-induced helicase (IFIH1) region.

In this study we report convincing statistical support for a sixth type 1 diabetes (T1D) locus in the innate immunity viral RNA receptor gene region IFIH1 (also known as mda-5 or Helicard) on chromosome 2q24.3. We found the association in an interim analysis of a genome-wide nonsynonymous SNP (nsSNP) scan, and we validated it in a case-control collection and replicated it in an independent family collection. In 4,253 cases, 5,842 controls and 2,134 parent-child trio genotypes, the risk ratio for the minor allele of the nsSNP rs1990760 A → G (A946T) was 0.86 (95% confidence interval = 0.82–0.90) at P = 1.42 × 10−10.

Parameters for reliable results in genetic association studies in common disease

It is increasingly apparent that the identification of true genetic associations in common multifactorial disease will require studies comprising thousands rather than the hundreds of individuals employed to date. Using 2,873 families, we were unable to confirm a recently published association of the interleukin 12B gene in 422 type I diabetic families. These results emphasize the need for large datasets, small P values and independent replication if results are to be reliable.

Exenatide once weekly plus dapagliflozin once daily versus exenatide or dapagliflozin alone in patients with type 2 diabetes inadequately controlled with metformin monotherapy (DURATION-8): a 28 week, multicentre, double-blind, phase 3, randomised controlled trial

BACKGROUND Glucagon-like peptide-1 (GLP-1) receptor agonists and sodium-glucose co-transporter-2 (SGLT2) inhibitors reduce glycaemia and weight, and improve cardiovascular risk factors via different mechanisms. We aimed to compare the efficacy and safety of co-initiation of the GLP-1 receptor agonist exenatide and the SGLT2 inhibitor dapagliflozin with exenatide or dapagliflozin alone in patients with type 2 diabetes inadequately controlled by metformin. METHODS DURATION-8 was a 28 week, multicentre, double-blind, randomised, active-controlled phase 3 trial done at 109 sites in six countries. Adults (aged ≥18 years) with type 2 diabetes and inadequate glycaemic control (HbA1c 8-12% [64-108 mmol/mol]) despite stable metformin monotherapy (≥1500 mg/day) were randomly assigned (1:1:1), via an interactive voice and web-response system, to receive once-weekly exenatide 2 mg by subcutaneous injection plus once-daily dapagliflozin 10 mg oral tablets, exenatide with dapagliflozin-matched oral placebo, or dapagliflozin with exenatide-matched placebo injections. Randomisation was stratified by baseline HbA1c (<9·0% vs ≥9·0% [<75 mmol/mol vs ≥75 mmol/mol]). The primary endpoint was change in HbA1c from baseline to week 28. Secondary endpoints were the change from baseline in fasting plasma glucose at week 2 and week 28, and 2 h postprandial glucose at week 28; the proportion of patients with an HbA1c less than 7·0% (<53 mmol/mol) at week 28; change in weight at week 28; the proportion of patients with weight loss of 5% or more at week 28; and change in systolic blood pressure at week 28. Analyses were by intention to treat. This trial is registered with ClinicalTrials.gov, number NCT02229396. FINDINGS Between Sept 4, 2014, and Oct 15, 2015, we randomly assigned 695 patients to receive exenatide plus dapagliflozin (n=231), exenatide alone (n=231; n=1 untreated), or dapagliflozin alone (n=233). The intention-to-treat population comprised 685 participants (mean HbA1c 9·3% [SD 1·1]; 78 mmol/mol [12]), of whom 611 (88%) completed the study. After 28 weeks, the change in baseline HbA1c was -2·0% (95% CI -2·1 to -1·8) in the exenatide plus dapagliflozin group, -1·6% (-1·8 to -1·4) in the exenatide group, and -1·4% (-1·6 to -1·2) in the dapagliflozin group. Exenatide plus dapagliflozin significantly reduced HbA1c from baseline to week 28 compared with exenatide alone (-0·4% [95% CI -0·6 to -0·1]; p=0·004) or dapagliflozin alone (-0·6% [-0·8 to -0·3]; p<0·001). Exenatide plus dapagliflozin was significantly superior to either drug alone for all secondary efficacy endpoints, with greater reductions in fasting plasma and postprandial glucose, more patients with an HbA1c less than 7·0% (<53 mmol/mol), greater weight loss, a greater proportion of patients with weight loss of 5% or more, and greater reductions in systolic blood pressure (all p≤0·025). Adverse events were recorded in 131 (57%) of 231 patients in the exenatide plus dapagliflozin group, 124 (54%) of 230 patients in the exenatide group, and 121 (52%) of 233 patients in the dapagliflozin group. The most common adverse events (≥5% of patients in any group) were diarrhoea, injection-site nodules, nausea, and urinary tract infections. No episodes of major hypoglycaemia or minor hypoglycaemia were reported. INTERPRETATION Co-initiation of exenatide and dapagliflozin improved various glycaemic measures and cardiovascular risk factors in patients with type 2 diabetes inadequately controlled by metformin monotherapy. The dual treatment regimen was well tolerated, with the expected safety profile for this combination. Additional data from an ongoing study (eg, AWARD-10; NCT02597049) will further inform the use of these drug classes in combination. FUNDING AstraZeneca.

Assessing the validity of the association between the SUMO4 M55V variant and risk of type 1 diabetes

Assessing the validity of the association between the SUMO4 M55V variant and risk of type 1 diabetes

Cost-effective analysis of candidate genes using htSNPs: a staged approach

We have previously shown that the selection of haplotype tag single nucleotide polymorphisms (htSNPs) and their statistical analysis in a multi-locus transmission/disequilibrium test (TDT) results in a more cost-effective genotyping strategy in disease association studies of genes by minimising redundancy due to linkage disequilibrium between SNPs. Further savings can be achieved by the use of a two-stage genotyping strategy. This approach is illustrated here in conjunction with the multi-locus TDT in determining whether common alleles of the immune regulatory genes RANK and its ligand TRANCE (RANKL) are associated with type 1 diabetes (T1D). A saving of approximately 75% of potential genotyping reactions could be made with minimal loss of power. There was little evidence from our analysis for association between the TRANCE and RANK genes and T1D in the populations tested.

Association of intercellular adhesion molecule-1 gene with type 1 diabetes

Intercellular adhesion molecule-1 (ICAM-1) functions via its ligands, the leucocyte integrins, in adhesion of immune cells to endothelial cells and in T cell activation. The third immunoglobulin-like extracellular domain binds integrin Mac-1 and contains a common non-conservative aminoacid polymorphism, G241R. Phenotypically, ICAM-1 has been associated with type 1 diabetes, a T-cell-mediated autoimmune disease. We assessed two independent datasets, and noted that R241 was associated with lower risk of type 1 diabetes than is G241 (3695 families, relative risk 0.91, p=0.03; 446 families, 0.60, p=0.006). Our data indicate an aetiological role for ICAM-1 in type 1 diabetes, which needs to be confirmed in future genetic and functional experiments.

The study of CTLA-4 and vitamin D receptor polymorphisms in the Romanian type 1 diabetes population

Several studies suggested that part of the genetic susceptibility for Type 1 diabetes (TIDM) is encoded by some polymorphisms of CTLA‐4 gene (2q33) and of Vitamin D Receptor gene (VDR; 12q12‐14). Our aim was to assess their contribution to TIDM genetic susceptibility in the Romanian population. We typed CTLA‐4 49 A/G and VDR FokI (F/f), ApaI (A/a) and TaqI (T/t) polymorphisms by Sequence Specific Primer PCR (SSP‐PCR) in 204 Romanian diabetic families (756 individuals: 212 TIDM probands and 544 unaffected parents and siblings). We studied alleles transmission using the Transmission Disequilibrium Test (TDT). We found an increased transmission of CTLA‐4 49G allele to diabetics (54.8%, p=0.11). The transmission of F (56.1%, p=0.063), a (55.7%, p=0.061) and T (51.8%, p=0.37) alleles of VDR gene to diabetics was increased but did not reach statistical significance. In conclusion we found the same increased transmission of CTLA‐4 49 G allele to diabetics as previously reported. VDR FoqI F allele seems to be predisposing while TaqI T allele seems to be protective.

LOW FREQUENCY OF HLA DRB1*03 - DQB1*02 AND DQB1*0302 HAPLOTYPES IN ROMANIA IS CONSISTENT WITH THE COUNTRY'S LOW INCIDENCE OF TYPE I DIABETES

Abstract.Aims/hypothesis: Our study aimed to determine the association of HLA class II HLA-DQB1 alleles with Type I (insulin-dependent) diabetes mellitus and the frequencies of these alleles in the Romanian population, which has one of the lowest incidences of Type I diabetes in children aged 0–14 years in Europe at 3–4 cases per 100 000 person-years. Methods: We used the sequence specific primer-polymerase chain reaction (PCR-SSP) technique to type HLA-DQB1 alleles, the HLA-DRB1 alleles DRB1*03 and one single nucleotide polymorphism (SNP) in the insulin gene (INS). We studied 204 Type I diabetic Romanian families, 196 of which were simplex with 70.3 % of subjects diagnosed under 14 years of age. Data was analysed using a modified version of the Transmission Disequilibrium Test, the Transmission Disequilibrium Test itself, and the affected family-based control method. Results: We found, as expected, the strong positive DQB1*02-DRB1*03 and DQB1*0302, and negative DQB1*0602, HLA class II allele associations with Type I diabetes in these Romanian families. However, using the affected family-based control method, we found relatively low population frequencies of DQB1*02-DRB1*03 and DQB1*0302 alleles in Romania (15.8 %) compared with Sardinia (31.3 %), a high incidence European region (35 cases per 100 000 person-years in children aged 0–14 years). The INS locus had a strong effect in this data set with 80.5 % transmission of the susceptible INS allele from parents to affected siblings (relative risk = 4.1). Conclusion/interpretation: Part of the explanation for the low incidence of Type I diabetes in Romania could be the lower frequency of the DRB1*03 – DQB1*02 and DQB1*0302 susceptibility haplotypes in this country. [Diabetologia (2001) 44 [Suppl 3]: B 60–B 66]

Construction and analysis of tag single nucleotide polymorphism maps for six human-mouse orthologous candidate genes in type 1 diabetes

BackgroundOne strategy to help identify susceptibility genes for complex, multifactorial diseases is to map disease loci in a representative animal model of the disorder. The nonobese diabetic (NOD) mouse is a model for human type 1 diabetes. Linkage and congenic strain analyses have identified several NOD mouse Idd (insulin dependent diabetes) loci, which have been mapped to small chromosome intervals, for which the orthologous regions in the human genome can be identified. Here, we have conducted re-sequencing and association analysis of six orthologous genes identified in NOD Idd loci: NRAMP1/SLC11A1 (orthologous to Nramp1/Slc11a1 in Idd5.2), FRAP1 (orthologous to Frap1 in Idd9.2), 4-1BB/CD137/TNFRSF9 (orthologous to 4-1bb/Cd137/Tnrfrsf9 in Idd9.3), CD101/IGSF2 (orthologous to Cd101/Igsf2 in Idd10), B2M (orthologous to B2m in Idd13) and VAV3 (orthologous to Vav3 in Idd18).ResultsRe-sequencing of a total of 110 kb of DNA from 32 or 96 type 1 diabetes cases yielded 220 single nucleotide polymorphisms (SNPs). Sixty-five SNPs, including 54 informative tag SNPs, and a microsatellite were selected and genotyped in up to 1,632 type 1 diabetes families and 1,709 cases and 1,829 controls.ConclusionNone of the candidate regions showed evidence of association with type 1 diabetes (P values > 0.2), indicating that common variation in these key candidate genes does not play a major role in type 1 diabetes susceptibility in the European ancestry populations studied.