Defining the genetic control of human blood plasma N-glycome using genome-wide association study.

Glycosylation is a common post-translational modification of proteins. Glycosylation is associated with a number of human diseases. Defining genetic factors altering glycosylation may provide a basis for novel approaches to diagnostic and pharmaceutical applications. Here we report a genome-wide association study of the human blood plasma N-glycome composition in up to 3811 people measured by Ultra Performance Liquid Chromatography (UPLC) technology. Starting with the 36 original traits measured by UPLC, we computed an additional 77 derived traits leading to a total of 113 glycan traits. We studied associations between these traits and genetic polymorphisms located on human autosomes. We discovered and replicated 12 loci. This allowed us to demonstrate an overlap in genetic control between total plasma protein and IgG glycosylation. The majority of revealed loci contained genes that encode enzymes directly involved in glycosylation (FUT3/FUT6, FUT8, B3GAT1, ST6GAL1, B4GALT1, ST3GAL4, MGAT3 and MGAT5) and a known regulator of plasma protein fucosylation (HNF1A). However, we also found loci that could possibly reflect other more complex aspects of glycosylation process. Functional genomic annotation suggested the role of several genes including DERL3, CHCHD10, TMEM121, IGH and IKZF1. The hypotheses we generated may serve as a starting point for further functional studies in this research area.

Plasma Fucosylated Glycans and C-Reactive Protein as Biomarkers of HNF1A-MODY in Young Adult-Onset Nonautoimmune Diabetes.

OBJECTIVE: Maturity-onset diabetes of the young (MODY) due to variants in HNF1A is the most common type of monogenic diabetes. Frequent misdiagnosis results in missed opportunity to use sulfonylureas as first-line treatment. A nongenetic biomarker could improve selection of subjects for genetic testing and increase diagnosis rates. We previously reported that plasma levels of antennary fucosylated N-glycans and high-sensitivity C-reactive protein (hs-CRP) are reduced in individuals with HNF1A-MODY. In this study, we examined the potential use of N-glycans and hs-CRP in discriminating individuals with damaging HNF1A alleles from those without HNF1A variants in an unselected population of young adults with nonautoimmune diabetes. RESEARCH DESIGN AND METHODS: We analyzed the plasma N-glycan profile, measured hs-CRP, and sequenced HNF1A in 989 individuals with diabetes diagnosed when younger than age 45, persistent endogenous insulin production, and absence of pancreatic autoimmunity. Systematic assessment of rare HNF1A variants was performed. RESULTS: We identified 29 individuals harboring 25 rare HNF1A alleles, of which 3 were novel, and 12 (in 16 probands) were considered pathogenic. Antennary fucosylated N-glycans and hs-CRP were able to differentiate subjects with damaging HNF1A alleles from those without rare HNF1A alleles. Glycan GP30 had a receiver operating characteristic curve area under the curve (AUC) of 0.90 (88% sensitivity, 80% specificity, cutoff 0.70%), whereas hs-CRP had an AUC of 0.83 (88% sensitivity, 69% specificity, cutoff 0.81 mg/L). CONCLUSIONS: Half of rare HNF1A sequence variants do not cause MODY. N-glycan profile and hs-CRP could both be used as tools, alone or as adjuncts to existing pathways, for identifying individuals at high risk of carrying a damaging HNF1A allele.

A molecular case-control study of association of HNF1A gene polymorphisms (rs2259816 and rs7310409) with risk of coronary artery disease in Iranian patients.

BACKGROUND: Coronary artery disease (CAD) is the one of the most common heart diseases, being the main factor of mortality and morbidity worldwide. CAD has been known as a multifactorial disease and its progression depends on genetic and environmental factors. Numerous studies have shown evidence for association between 12q24.3 locus and CAD. OBJECTIVES: In the present study, the association of two HNF1A polymorphisms, rs2259816 and rs7310409, located on 12q24.3 locus with CAD was investigated in Iranian patients. METHODS: Whole genomic DNA was isolated from peripheral blood obtained from 411 Iranian volunteer. Then, the polymorphisms rs2259816 and rs7310409 located on 12q24.3 locus were genotyped using TaqMan Probe Real Time PCR. Statistical analysis was performed by SPSS software, version 19. RESULTS: rs2259816 (p-value = 0.006) and rs7310409 (p-value = 0.001) showed statistically significant association with CAD risk. Our results indicated that there was a significant correlation between rs2259816 and blood triglyceride. However, no correlation was found between rs2259816, rs7310409 and other CAD risk factors.

Apolipoprotein M.

Apolipoprotein M (ApoM) is a novel apolipoprotein that was discovered in 1999 and is bound primarily to high-density lipoproteins (HDLs) in the plasma. Multiple factors may influence its expression at both the post-transcriptional and the transcriptional levels both in vivo and ex vivo as follows: hepatocyte nuclear factor-1α, 4α (HNF-1α, 4α), liver receptor homolog-1 (LRH-1), forkhead box A2 (Foxa2) and platelet activating factor (PAF) upregulate its expression; liver X receptor (LXR), retinoid X receptor (RXR), farnesoid X receptor (FXR), small heterodimer partner (SHP) and the majority of cytokines downregulate its expression. However, mechanisms underlying these processes remain unknown. Structurally, there exists a characterized hydrophobic binding pocket within the apoM protein, which enables it to bind functional lipids such as Sphingosine-1-Phosphate (S1P). Functionally, it facilitates the formation of preß-HDL and enhances an avalanche of atheroprotective effects exerted by HDL. Moreover, in patients with diabetes, the levels of plasma apoM may decrease, whereas the augmentation of apoM decreases plasma glucose levels and magnifies the secretion of insulin. This article offers a panorama of the progress made in the research regarding the characteristics of apoM, particularly the regulation of its expression and its functions.

Monogenic diabetes: old and new approaches to diagnosis.

Up to 5% of young adults diagnosed with diabetes have a monogenic aetiology, the most common of which is maturity-onset diabetes of the young (MODY). A definitive molecular diagnosis is important, as this affects treatment, prognosis and family screening. Currently, however, rates of diagnosis are low due to a combination of lack of awareness of the benefits of making the diagnosis and the challenges of differentiating patients with MODY from those with common forms of diabetes. This article aims to introduce general physicians to the characteristics of monogenic diabetes and the clinical features that can be used to diagnose patients. Recently, genomewide association studies have resulted in the identification of C-reactive protein and glycan profile as specific biomarkers for the most common MODY subtype due to HNF1A mutations, and the potential translation of these findings are discussed.

Japanese boy with maturity-onset diabetes of the young type 3 who developed diabetes at 19 months old.

Maturity-onset diabetes of the young type 3 (MODY3) is caused by hepatocyte nuclear factor 1α gene mutation and is clinically characterized by young onset and insufficient insulin secretion. We report a 19-month-old Japanese boy with a family history of young-onset diabetes who was initially diagnosed with type 1 diabetes. Mutational analysis of the hepatocyte nuclear factor 1α gene revealed a novel heterozygous frameshift mutation (c.593delA p.Lys198fs) resulting in a truncated protein in the patient and his father. The patient was diagnosed as having MODY3 and was successfully treated with insulin glargine. We could not determine the genetic or environmental factors to explain the difference in the age of disease onset within the same family. This is the youngest case of a MODY3 child presenting with overt diabetes. Our experience suggests that clinicians should always consider the possible diagnosis of MODY3 in a diabetic child with a family history of young-onset diabetes and should perform molecular investigations.

Low abundance plasma proteins in labour.

Every year, millions of births worldwide are complicated by prematurity or difficult post-term deliveries, resulting in a high incidence of perinatal mortality and morbidity. Our poor understanding of human parturition is a key reason for our inability to improve the management of preterm and post-term birth. In this study, we used proteomic techniques to look into protein changes in placental blood plasma obtained from women before or after spontaneous or induced labour, with vaginal or caesarean section deliveries. Our aim was to understand the basic mechanisms of human parturition regardless of whether the signals that trigger labour are of maternal and/or fetal origin. We found proteins from 33 genes with significantly altered expression profiles in relation to mode of labour and delivery. Most changes in labour occurred in proteins associated with 'immune and defence responses'. Although the signal transduction and regulation of these pathways varied among modes of delivery, hepatocyte nuclear factor 1 homeobox A emerged as a shared protein in the mechanism of labour. Moreover, several apolipoproteins such as apolipoprotein A-IV and APOE were found to change with labour, and these changes were also confirmed in maternal plasma. This study has identified significant protein changes in placental intervillous plasma with labour and has revealed several pathways related to human parturition.

Lipoprotein composition in HNF1A-MODY: differentiating between HNF1A-MODY and type 2 diabetes.

INTRODUCTION: The young-onset diabetes seen in HNF1A-MODY is often misdiagnosed as Type 2 diabetes. Type 2 diabetes, unlike HNF1A-MODY, is associated with insulin resistance and a characteristic dyslipidaemia. We aimed to compare the lipid profiles in HNF1A-MODY, Type 2 diabetes and control subjects and to determine if lipids can be used to aid the differential diagnosis of diabetes sub-type. METHODS: 1) 14 subjects in each group (HNF1A-MODY, Type 2 diabetes and controls) were matched for gender and BMI. Fasting lipid profiles and HDL lipid constituents were compared in the 3 groups. 2) HDL-cholesterol was assessed in a further 267 patients with HNF1A-MODY and 297 patients with a diagnosis of Type 2 diabetes to determine its discriminative value. RESULTS: 1) In HNF1A-MODY subjects, plasma-triglycerides were lower (1.36 vs. 1.93 mmol/l, p = 0.07) and plasma-HDL-cholesterol was higher than in subjects with Type 2 diabetes (1.47 vs. 1.15 mmol/l, p = 0.0008), but was similar to controls. Furthermore, in the isolated HDL; HDL-phospholipid and HDL-cholesterol ester content were higher in HNF1A-MODY, than in Type 2 diabetes (1.59 vs. 1.33 mmol/L, p = 0.04 and 1.10 vs. 0.83 mmol/L, p = 0.019, respectively), but were similar to controls (1.59 vs. 1.45 mmol/L, p = 0.35 and 1.10 vs. 1.21 mmol/L, p = 0.19, respectively). 2) A plasma-HDL-cholesterol > 1.12 mmol/L was 75% sensitive and 64% specific (ROC AUC = 0.76) at discriminating HNF1A-MODY from Type 2 diabetes. CONCLUSION: The plasma-lipid profiles of HNF1A-MODY and the lipid constituents of HDL are similar to non-diabetic controls. However, HDL-cholesterol was higher in HNF1A-MODY than in Type 2 diabetes and could be used as a biomarker to aid in the identification of patients with HNF1A-MODY.

Oligonucleotide chip for the diagnosis of HNF-1 alpha mutations.

Mutations in HNF-1 alpha cause maturity-onset diabetes of the young (MODY) type 3, which is the most prevalent MODY subtype in most countries. In the present study, we investigated an oligonucleotide microchip for the detection of the known HNF-1 alpha mutations. We first optimized the coupling chemistries for covalent immobilization of allele-specific oligonucleotides on aldehyde (CHO)- and thiocyanate (NCS)-activated glass slides and compared their hybridization efficiencies. CHO-glass was found to provide a more favorable environment for hybridization than NCS-glass, whereas the binding capacity of NCS-glass for amine-activated oligonucleotide was much greater than with CHO-glass. We also investigated the effects of the length of the capture probes on the hybridized signals. To determine the presence of HNF-1 alpha mutations in a human sample, we prepared an oligonucleotide chip from selected mutation sites of exon2 from HNF-1 alpha. Cy3-labeled RNA target probes were obtained by in vitro transcription of promoter-tagged PCR products from a wild-type blood sample and subsequent fragmentation. Hybridization of the chip with the RNA target probes successfully identified all of the genotypes for the tested sites. This work demonstrates that oligonucleotide chip-based analysis is a good candidate for routine clinical testing for HNF-1 alpha mutations.