Myasthenia gravis genome-wide association study implicates AGRN as a risk locus.

BACKGROUND: Myasthenia gravis (MG) is a rare autoimmune disorder affecting the neuromuscular junction (NMJ). Here, we investigate the genetic architecture of MG via a genome-wide association study (GWAS) of the largest MG data set analysed to date. METHODS: We performed GWAS meta-analysis integrating three different data sets (total of 1401 cases and 3508 controls). We carried out human leucocyte antigen (HLA) fine-mapping, gene-based and tissue enrichment analyses and investigated genetic correlation with 13 other autoimmune disorders as well as pleiotropy across MG and correlated disorders. RESULTS: We confirmed the previously reported MG association with TNFRSF11A (rs4369774; p=1.09×10-13, OR=1.4). Furthermore, gene-based analysis revealed AGRN as a novel MG susceptibility gene. HLA fine-mapping pointed to two independent MG loci: HLA-DRB1 and HLA-B. MG onset-specific analysis reveals differences in the genetic architecture of early-onset MG (EOMG) versus late-onset MG (LOMG). Furthermore, we find MG to be genetically correlated with type 1 diabetes (T1D), rheumatoid arthritis (RA), late-onset vitiligo and autoimmune thyroid disease (ATD). Cross-disorder meta-analysis reveals multiple risk loci that appear pleiotropic across MG and correlated disorders. DISCUSSION: Our gene-based analysis identifies AGRN as a novel MG susceptibility gene, implicating for the first time a locus encoding a protein (agrin) that is directly relevant to NMJ activation. Mutations in AGRN have been found to underlie congenital myasthenic syndrome. Our results are also consistent with previous studies highlighting the role of HLA and TNFRSF11A in MG aetiology and the different risk genes in EOMG versus LOMG. Finally, we uncover the genetic correlation of MG with T1D, RA, ATD and late-onset vitiligo, pointing to shared underlying genetic mechanisms.

Clinical and Genetic Predictors of Glycemic Control and Weight Loss Response to Liraglutide in Patients with Type 2 Diabetes.

Background: Evidence suggests a heterogeneous response to therapy with glucagon-like peptide-1 receptor agonists (GLP-1 RAs) in patients with type 2 diabetes mellitus (T2DM). The aim of this study is to identify the genetic and clinical factors that relate to glycemic control and weight loss response to liraglutide among patients with T2DM. Methods: The medical records of 116 adults with T2DM (51% female, mean body mass index 35.4 ± 6.4 kg/m2), who had been on treatment with liraglutide for at least 6 months and were genotyped for CTRB1/2 rs7202877 (T > G) polymorphism, were evaluated. Clinical and laboratory parameters were measured at baseline, 3, and 6 months after initiating liraglutide treatment. The good glycemic response was defined as one of the following: (i) achievement of glycated hemoglobin (HbA1c) < 7% (ii) reduction of the baseline HbA1c by ≥1%, and (iii) maintenance of HbA1c < 7% that a patient already had before switching to liraglutide. Weight loss responders were defined as subjects who lost ≥3% of their baseline weight. Results: Minor allele frequency was 16%. Individuals were classified as glycemic control and weight loss responders (81 (70%) and 77 (66%), respectively). Carriers of the rs7202877 polymorphic allele had similar responses to liraglutide treatment in terms of glycemic control (odds ratio (OR): 1.25, 95% confidence interval (CI): 0.4, 3.8, p = 0.69) and weight loss (OR: 1.12, 95% CI: 0.4, 3.2, p = 0.84). In the multivariable analysis, higher baseline HbA1c (adjusted OR: 1.45, 95% CI: 1.05, 2.1, p = 0.04) and lower baseline weight (adjusted OR: 0.97, 95% CI: 0.94, 0.99, p = 0.01) were associated with better glycemic response to liraglutide, while higher baseline weight was associated with worse weight response (adjusted OR: 0.97, 95% CI: 0.95, 0.99, p = 0.02). Conclusions: Specific patient features can predict glycemic and weight loss response to liraglutide in individuals with T2DM.

Oxidative Stress Genes in Diabetes Mellitus Type 2: Association with Diabetic Kidney Disease.

Diabetic type 2 patients compared to nondiabetic patients exhibit an increased risk of developing diabetic kidney disease (DKD), the leading cause of end-stage renal disease. Hyperglycemia, hypertension, oxidative stress (OS), and genetic background are some of the mechanisms and pathways implicated in DKD pathogenesis. However, data on OS pathway susceptibility genes show limited success and conflicting or inconclusive results. Our study is aimed at exploring OS pathway genes and variants which could be associated with DKD. We recruited 121 diabetes mellitus type 2 (DM2) patients with DKD (cases) and 220 DM2, non-DKD patients (control) of Greek origin and performed a case-control association study using genome-wide association data. PLINK and EIGENSOFT were used to analyze the data. Our results indicate 43 single nucleotide polymorphisms with their 21 corresponding genes on the OS pathway possibly contributing or protecting from DKD: SPP1, TPO, TTN, SGO2, NOS3, PDLIM1, CLU, CCS, GPX4, TXNRD2, EPHX2, MTL5, EPX, GPX3, ALOX12, IPCEF1, GSTA, OXR1, GPX6, AOX1, and PRNP. Therefore, a genetic OS background might underlie the complex pathogenesis of DKD in DM2 patients.

Variants in clock genes could be associated with lower risk of type 2 diabetes in an elderly Greek population.

OBJECTIVES: Recent evidence has linked circadian rhythm dysregulation to an increased risk of metabolic disorders. This study explores a potential association between variation in genes regulating the endogenous circadian timing system (clock genes) and the risk of type 2 diabetes (T2D) in a sample of Greek elderly people. STUDY DESIGN: Variants within and upstream or downstream of PPARA, PPARD, CLOCK/TMEM165, PER1, PER2 and PER3 genes were genotyped in 716 individuals with T2D (A) and 569 normoglycemic controls (B), and allele frequencies were compared between the groups in a case control study design. MAIN OUTCOME MEASURES: Samples were genotyped on Illumina Human PsychArray. Permutation test analysis was implemented to determine statistical significance. To avoid the possibility of subjects with prediabetes being included in the control group, people with HbA1c <5.7% and fasting glucose <100 mg/dl comprised group C (n = 393), for whom a separate analysis was performed (secondary analysis). RESULTS: A protective role against T2D was identified for 14 variants in the PPARA gene. The rs7291444, rs36125344, rs6008384 in PKDREJ, located upstream of PPARA, and rs2859389 in UTS2, located upstream of PER3, demonstrated a protective role against T2D in both analyses. In contrast, rs6744132, located between HES6 and PER2, was positively correlated with T2D risk. Only in the secondary analysis, rs2278637 in VAMP2, located downstream of PER1, and rs11943456 in CLOCK/TMEM165 were found to confer protection against T2D. In a recessive model analysis of all groups, PPARD variants exhibited a protective role against disease. CONCLUSIONS: Our findings suggest a possible implication of clock genes in T2D susceptibility. Further studies are needed to clarify the mechanisms that connect circadian rhythm dysfunction and T2D pathogenesis.

Increased parathyroid hormone is associated with higher fasting glucose in individuals with normocalcemic primary hyperparathyroidism and prediabetes: A pilot study.

AIMS: This pilot study aimed to evaluate differences in glycemic parameters between patients with prediabetes and normocalcemic primary hyperparathyroidism (NPHPT) and controls with prediabetes and normal parathyroid hormone (PTH) and calcium concentrations. METHODS: 20 patients with NPHPT and prediabetes and 42 age-, gender-, and body mass index-matched controls with prediabetes were included. Glycemic parameters [fasting glucose (fGlu), glycosylated hemoglobin (HbA1c), fasting insulin (fIns)] were evaluated. Homeostasis Model Assessment was used for estimating insulin secretion (HOMA-B) and resistance (HOMA-IR). Participants underwent a 75-g oral glucose tolerance test. RESULTS: HbA1c (5.9 ± 0.0 vs 5.9 ± 0.0%, p = 0.44), HOMA-IR (3.7 ± 1.2 vs 2.9 ± 0.2, p = 0.48), HOMA-B (117.8 ± 31.8 vs 146.9 ± 22.0%, p = 0.14), fIns (14.0 ± 4.3 vs 12.2 ± 1.1 µIU/ml, p = 0.53) and 2-hour post-load glucose concentrations (157.2 ± 2.2 vs 152.2 ± 2.0 mg/dl, p = 0.07), were nondifferent in the two groups. Higher fGlu levels were evident in the NPHPT, compared to the control group (105.6 ± 2.8 vs 98.2 ± 1.8 mg/dl, p = 0.01). fGlu demonstrated a positive correlation with PTH concentrations (rho = 0.374, p = 0.005). CONCLUSIONS: Individuals with NPHPT and prediabetes present an unfavorable glycemic profile compared to age-matched people with prediabetes, suggesting a direct adverse effect of elevated PTH on glucose homeostasis.

Genetic variation in CARD8, a gene coding for an NLRP3 inflammasome-associated protein, alters the genetic risk for diabetic nephropathy in the context of type 2 diabetes mellitus.

BACKGROUND: Approximately one third of type 2 diabetes mellitus (T2DM) cases present with diabetic nephropathy (DN), the leading cause of end-stage renal disease. Inflammation plays an important role in T2DM disease and DN pathogenesis. NLRP3 inflammasomes are complexes that regulate interleukin-1B (IL-1B) and IL-18 secretion, both involved in inflammatory responses. Activation of NLRP3 is associated with DN onset and progression. Here, we explore whether DN is associated with variants in genes encoding key members of the NLRP3 inflammasome pathway. METHODS: Using genome-wide association data, we performed a pilot case-control association study, between 101 DN-T2DM and 185 non-DN-T2DM cases from the Hellenic population across six NLRP3 inflammasome pathway genes. RESULTS: Three common CARD8 variants confer decreased risk for DN, namely rs11665831 (OR = 0.62, p = 0.016), rs11083925 (OR = 0.65, p = 0.021), and rs2043211 (OR = 0.66, p = 0.026), independent of sex or co-inheritance with an IL-1B variant. CONCLUSION: CARD8 acts as an NLRP3, NF-κB and caspase-1 inhibitor; perhaps, alterations in the cross-talk between CARD8, NF-κB, and NLRP3, which could affect the pro-inflammatory environment in T2DM, render diabetic carriers of certain common CARD8 variants potentially less likely to develop T2DM-related pro-inflammatory responses followed by DN. These preliminary, yet novel, observations will require validation in larger cohorts from several ethnic groups.

Association between CUBN gene variants, type 2 diabetes and vitamin D concentrations in an elderly Greek population.

Accumulating evidence suggests a potential implication of vitamin D biological network in the pathogenesis of diabetes mellitus. The megalin-cubilin endocytotic system constitutes a key transport structure, with a modulating role in vitamin D metabolism. We aimed to assess the contribution of variants in the CUBN gene to the genetic risk of Type 2 Diabetes Mellitus (T2DM). 95 polymorphisms within CUBN were genotyped in 716 patients with T2DM and 542 controls of Greek origin. Samples were analyzed on Illumina Human PsychArray. Permutation test analysis was implemented to determine statistical significance. Twenty-five-hydroxy-vitamin-D [25(OH)D)] levels were measured in a sub-group of participants (n = 276). Permutation analysis associated rs11254375_G/T (pemp = 0.00049, OR = 1.482), rs6602175_G/T (pemp = 0.016, OR = 0.822), rs1801224_G/T (pemp = 0.025, OR = 0.830), rs4366393_A/G (pemp = 0.028, OR = 0.829) and rs7071576_A/G (pemp = 0.04, OR = 1.219) with T2DM. Mean 25(OH)D concentrations were significantly lower in patients with T2DM compared to controls (16.70 ±â€¯6.69 ng/ml vs 18.51 ±â€¯6.71 ng/ml, p < 0.001), although both groups were vitamin D deficient. In a further quantitative analysis, rs41301097 was strongly associated with higher 25(OH)D concentrations (p = 5.233e-6, beta = 15.95). Our results indicate a potential role of CUBN gene in T2DM genetic susceptibility in the Greek population. These findings may also denote an indirect effect of vitamin D metabolism dysregulation on the pathogenesis of T2DM. Further studies are required to replicate our findings and clarify the complex underlying mechanisms.

The combined effect of vitamin D and parathyroid hormone concentrations on glucose homeostasis in older patients with prediabetes: A cross-sectional study.

BACKGROUND: The combined effect of vitamin D and parathyroid hormone on glucose homeostasis has not been adequately investigated. The aim of this study was to examine the role of parathyroid hormone/vitamin D axis on glucose homeostasis in elderly persons with prediabetes. METHODS: Patients with prediabetes ( n = 144) and healthy age-matched controls ( n = 81) were included in this cross-sectional study. Study parameters included anthropometric characteristics, morning fasting glucose (fasting plasma glucose), insulin (fasting plasma insulin), parathyroid hormone, 25-hydroxyvitamin D, homeostasis model assessment of insulin resistance and homeostasis model assessment of ß-cell function. Both groups were stratified into subgroups according to vitamin D status and tertiles of parathyroid hormone. RESULTS: Both groups were comparable in terms of body mass index, 25-hydroxyvitamin D and parathyroid hormone status. In the prediabetes group, fasting plasma glucose differed significantly across parathyroid hormone tertiles, increasing from the first to the third tertile ( p = 0.011). There were higher fasting plasma glucose values in participants with vitamin D deficiency/parathyroid hormone third tertile compared to all other groups ( p = 0.031, 0.027 and 0.039, respectively). CONCLUSION: Parathyroid hormone status is associated with impaired glucose homeostasis; hypovitaminosis D combined with high parathyroid hormone concentrations are associated with glycaemic dysregulation in elderly patients with prediabetes.

Assessment of association between lipoxygenase genes variants in elderly Greek population and type 2 diabetes mellitus.

BACKGROUND: Inflammation plays a pivotal role in the pathogenesis of diabetes and its complications. Arachidonic acid lipoxygenases have been intensively studied in their role in inflammation in metabolic pathways. Thus, we aimed to explore variants of lipoxygenase genes (arachidonate lipoxygenase genes) in a diabetes adult population using a case-control study design. METHODS: Study population consisted of 1285 elderly participants, 716 of whom had type 2 diabetes mellitus. The control group consisted of non-diabetes individuals with no history of diabetes history and with a glycated haemoglobin <6.5% (<48 mmol/mol)] and fasting plasma glucose levels <126 mg/dL. Blood samples were genotyped on Illumina Infinium PsychArray. Variants of ALOX5, ALOX5AP, ALOX12, ALOX15 were selected. All statistical analyses were undertaken within PLINK and SPSS packages utilising permutation analysis tests. RESULTS: Our findings showed an association of rs9669952 (odds ratio = 0.738, p = 0.013) and rs1132340 (odds ratio = 0.652, p = 0.008) in ALOX5AP and rs11239524 in ALOX5 gene with disease (odds ratio = 0.808, p = 0.038). Rs9315029 which is located near arachidonate ALOX5AP also associated with type 2 diabetes mellitus ( p = 0.025). No variant of ALOX12 and ALOX15 genes associated with disease. CONCLUSION: These results indicate a potential protective role of ALOX5AP and 5-arachidonate lipoxygenase gene in diabetes pathogenesis, indicating further the importance of the relationship between diabetes and inflammation. Larger population studies are required to replicate our findings.

Association analysis of FTO gene polymorphisms with obesity in Greek adults.

Nowadays, obesity is the greatest scourge worldwide, particularly for the developed countries and is a huge burden for the public health. Over the past decade, GWAS have revealed a number of genes associated with obesity. The fat mass and obesity associated (FTO) gene was the first one associated with obesity in a significant number of populations and recent meta-analysis studies confirm this association. FTO is a N-methyladenosine demethylase and in addition to the genetic association, its biological role in the regulation of body weight has been documented. Due to lack of replication regarding FTO association with obesity in the Greek adult population, we analyzed three SNPs, i.e. rs9939609, rs9930506 and rs3751812 in a cohort of 203 adults, comprising of 95 obese, 58 overweight and 50 control individuals. Analysis has shown a significant association for FTO (rs9930506; A/G) 'G' allele with obesity and a difference by 3.2 BMI units between the two homozygotes (AA versus GG). This association, which was detected for the first time in this population, suggests that FTO rs9930506 is a predisposition marker to obesity in the Greek adults, but the results should be taken cautiously due to the limitation of the relatively small sample size of the subjects.

Thyroid Autoimmunity in the Context of Type 2 Diabetes Mellitus: Implications for Vitamin D.

Vitamin D deficiency has been associated with both type 2 diabetes mellitus (T2DM) and autoimmune disorders. The association of vitamin D with T2DM and thyroid autoimmunity (TAI) has not been investigated. Thus, we aimed to explore the putative association between T2DM and thyroid autoimmunity (TAI) focusing on the role of 25-hydroxy-vitamin D (25(OH)D). Study population included 264 T2DM patients and 234 controls. To explore the potential association between 25(OH)D and thyroid autoimmunity while controlling for potential confounders-namely, age, gender, body mass index, and presence of T2DM-multivariate logistic regression analyses were undertaken. Patients with T2DM were younger (P < 0.001) and had significantly lower 25(OH)D levels (P < 0.001) and higher anti-TPO titers (P = 0.005). Multivariable logistic regression analyses suggested that T2DM and 25(OH)D levels were significantly associated with the presence of thyroid autoimmunity. In an elderly population of diabetic patients and controls with a high prevalence of vitamin D deficiency/insufficiency, a patient with T2DM was found to be 2.5 times more likely to have thyroid autoimmunity compared to a nondiabetic individual and the higher the serum 25(OH)D levels were, the higher this chance was.

Response of biochemical markers of bone turnover to oral glucose load in diseases that affect bone metabolism.

OBJECTIVE: Postprandial suppression of bone resorption is considered one of the main contributors in the circadian rhythm of bone turnover markers. The aim of this study was to investigate this physiological response of bone tissue in diseases that affect bone metabolism. PATIENTS AND METHODS: In this study, 118 patients (45 hypothyroid, 40 hyperthyroid, and 33 ß-thalassemic patients) and 78 healthy individuals matched for age and body mass index were included. An oral glucose test (75 g glucose) was performed after overnight fasting. Serum levels of procollagen type-I N-terminal propeptide (P1NP), ß-C-terminal telopeptide of type I collagen (ß-CTX), and osteocalcin were assayed at 0, 60, and 120 min. RESULTS: Baseline values of bone turnover markers were significantly elevated in hyperthyroid and ß-thalassemic patients but not in hypothyroid patients compared with the control group. After oral glucose, the levels of ß-CTX but not P1NP or osteocalcin were significantly suppressed in all groups (mean change from baseline is 46.9% for ß-CTX, 7.9% for P1NP, and 8% for osteocalcin). The percentage change from baseline for ß-CTX was significantly augmented in hypothyroidism (52 vs 42%, P=0.009). CONCLUSION: The preservation or even augmentation of postprandial suppression of bone resorption in diseases that affect bone metabolism through distinct pathogenetic mechanisms suggests the importance of this physiological response to nutrients for the general homeostasis and functional integrity of the skeleton.