Maturity-onset Diabetes Of The Young Families Research Articles

An Italian MODY family with proband and son carrying variants in GCK and HFN1A: is it a true case of digenic MODY?

Maturity Onset Diabetes of the Young (MODY) is a monogenic autosomal dominant disorder affecting 1-5 % of all patients with diabetes mellitus. In Caucasians, GCK and HNF1A mutations are the most common cause of MODY. Here, we report two family members carrying a genetic variant of both GCK and HNF1A gene and their nine year clinical follow-up. Our report urges physicians to be cautious when variants in two genes are found in a single patient and suggests that collaboration with MODY genetics experts is necessary for correct diagnosis and treatment.

Identification and precision therapy for three maturity-onset diabetes of the young (MODY) families caused by mutations in the HNF4A gene.

Heterozygous pathogenic variants in HNF4A gene cause maturity-onset diabetes of the young type 1 (MODY1). The mutation carriers for MODY1 have been reported to be relatively rare, in contrast to the most frequently reported forms of MODY2 and MODY3. Whole exome sequencing (WES) and Sanger sequencing were performed for genetic analysis of MODY pedigrees. Tertiary structures of the mutated proteins were predicted using PyMOL software. Three heterozygous missense mutations in the HNF4A gene, I159T, W179C, and D260N, were identified in the probands of three unrelated MODY families using WES, one of which (W179C) was novel. Cascade genetic screening revealed that the mutations co-segregated with hyperglycemic phenotypes in their families. The molecular diagnosis of MODY1 has partly transformed its management in clinical practice and improved glycemic control. The proband in family A successfully converted to sulfonylureas and achieved good glycemic control. Proband B responded well to metformin combined with diet therapy because of his higher body mass index (BMI). The proband in family C, with paternal-derived mutations, had markedly defective pancreatic β-cell function due to the superposition effect of T2DM susceptibility genes from the maternal grandfather, and he is currently treated with insulin. In silico analysis using PyMOL showed that the I159T and D260N mutations altered polar interactions with the surrounding residues, and W179C resulted in a smaller side chain. We identified three heterozygous missense mutations of HNF4A from Chinese MODY families. Structural alterations in these mutations may lead to defects in protein function, further contributing to the hyperglycemic phenotype of mutation carriers.

1550-P: A Gain-of-Function Maturity-Onset Diabetes of the Young (MODY)–Associated TALK1 Mutation Impairs Glucose Metabolism in Mice

A Leu substitution with Pro at position 114 (L114P) of TALK1 K+ channels has recently been identified in a MODY (maturity-onset-diabetes-of-the-young) family. Previous in vitro studies have shown this gain-of-function TALK1-L114P mutant may attenuate Ca2+ homeostasis and inhibit insulin secretion; nevertheless, how this mutant induces diabetes in vivo remains elusive. In this study, we have generated a transgenic mouse line that carries a TALK1-L114P mutation. About three-quarters of TALK1L/P and TALK1P/- mice died within ten days after birth due to hyperglycemia. Interestingly, those survival mice till adulthood exhibited diverse levels of glucose intolerance with islet morphology that is commonly observed in patients with type 2 diabetes. Electrophysiological recording further indicated that only a portion of the beta cells is glucose responsive, and high glucose challenge often yielded in low-frequency action potential bursting. According to our results, we hypothesized that despite the augment of membrane K+ conductance by the TALK1-L114P channel, high glucose might still be enough to depolarize beta cells and generate action potential bursting. This dampened beta cell excitation may result in a weakened Ca2+ influx and insufficient insulin secretion to cause glucose intolerance. In conclusion, this study has revealed a vital role of the TALK1 channel in regulating glucose homeostasis and a plausible diabetogenic mechanism of TALK1-L114P mutation. Disclosure W.Tsai: None. S.Yang: None. Funding National Science and Technology Council, Taiwan (111-2320-B-001-008-MY3)

Identification of Maturity-Onset-Diabetes of the Young (MODY) mutations in a country where diabetes is endemic

Genetic variants responsible for Maturity-Onset-Diabetes of the Young (MODY) in Kuwait were investigated. A newly established a National Referral Clinic, the Dasman Diabetes Institute (DDI-NRC), assessed forty-five members from 31 suspected MODY families by whole exome sequencing. Thirty-three of the 45 samples were independently sequenced at the DDI-NRI, Exeter University, UK (https://www.diabetesgenes.org/) using targeted 21-gene panel approach. Pathogenic mutations in GCK, HNF1A, HNF1B, HNF4A, and PDX1 confirmed MODY in 7 families, giving an overall positivity rate of 22.6% in this cohort. Novel variants were identified in three families in PDX1, HNF1B, and HNF1B. In this cohort, Multiplex Ligation-dependent Probe Amplification assay did not add any value to MODY variant detection rate in sequencing negative cases. In highly selected familial autoantibody negative diabetes, known MODY genes represent a minority and 77.3% of the familial cases have yet to have a causal variant described.

Recognition of maturity-onset diabetes of the young in China.

Aims/IntroductionGiven that mutations related to maturity‐onset diabetes of the young (MODY) are rarely found in Chinese populations, we aim to characterize the mutation spectrum of MODY pedigrees.Materials and MethodsMaturity‐onset diabetes of the young candidate gene‐ or exome‐targeted capture sequencing was carried out in 76 probands from unrelated families fulfilling the clinical diagnostic criteria for MODY. MAF <0.01 in the GnomAD or ExAC database was used to filter significant variants. Sanger sequencing was then carried out to validate findings. Function prediction by SIFT, PolyPhen‐2 and PROVEAN or CADD was carried out in missense mutations.ResultsA total of 32 mutations in six genes were identified in 31 families, accounting for 40.79% of the potential MODY families. The MODY subtype detection rate was 18.42% for GCK, 15.79% for HNF1A, 2.63% for HNF4A, and 1.32% for KLF11, PAX4 and NEUROG3. Seven nonsense/frameshift mutations and four missense mutations with damaging prediction were newly identified novel mutations. The clinical features of MODY2, MODY3/1 and MODYX are similar to previous reports. Clinical phenotype of NEUROG3 p.Arg55Glufs*23 is characterized by hyperglycemia and mild intermittent abdominal pain.ConclusionsThis study adds to the emerging pattern of MODY epidemiology that the proportion of MODY explained by known pathogenic genes is higher than that previously reported, and found NEUROG3 as a new causative gene for MODY.

1658-P: A Novel Mutation in Hepatocyte Nuclear Factor-1 Beta (HNF1B) in Maturity-Onset Diabetes of the Young 5 (MODY5)

Maturity-onset diabetes of the young (MODY) is a group of dominantly inherited non-autoimmune diabetes characterized by early onset. Delayed diagnosis or misdiagnosis as type 1 or 2 diabetes is common, but early and correct diagnosis of MODY is important because it significantly alters the management of both the patient and his or her relatives. MODY5 is caused by mutations in the HNF1B, associated with renal and pancreatic abnormalities. Recently, we had identified a novel pathogenic mutation in IVS3-1G&amp;gt;C of HNF1B, in a Japanese MODY family. A 30-year-old male presented to our office with a diagnosis of NIDDM at age 15; autoimmune antibodies were negative, glycemia was initially managed with basal-bolus insulin. Abdominal ultrasound showed bilateral hyperechogenic kidneys but unlike with the reported typical abnormalities in MODY5, only a few renal cysts were observed, and pancreas was intact. An initial diagnosis of early-onset type 2 diabetes was made. However, the case subsequently showed high probability of MODY, when he reported a strong family history of early-onset diabetes in his sister, his father and paternal grandmother. Genetic testing performed in him, his sister and his father revealed shared unreported gene mutation g.37731831C&amp;gt;G (GRCH38 Chr17) in the HNF1B gene suggesting a diagnosis of MODY5. The mutation locates in the splicing site which may result in the production of abnormal proteins or failure of protein synthesis. Our MODY5 case was unique in the point that despite the mild renal morphological abnormalities, the proband had renal dysfunction and microalbuminuria from the early stage of disease, evoking the importance of considering the possibility of monogenic diabetes even in scarce structural abnormalities but having atypical diabetes with strong family history. It also suggests the necessity of further investigation of the exact mechanism of the development of diabetes and the cause of abnormalities in the kidney by this certain mutation. Disclosure Y. Fujita: None. T. Hyo: Speaker’s Bureau; Self; ARKRAY, Kissei Pharmaceutical Co., Ltd., LifeScan, Inc., Medtronic, Novo Nordisk Inc. M. Matsubara: None. Y. Hamamoto: Research Support; Self; Sumitomo Dainippon Pharma Co., Ltd. Speaker’s Bureau; Self; Novo Nordisk Inc. D. Tanaka: None. Y. Seino: Research Support; Self; ARKRAY, Bayer Yakuhin, Ltd., Boehringer Ingelheim International GmbH, Eli Lilly Japan K.K., Merck Sharp &amp; Dohme Corp., Nippon Boehringer Ingelheim Co. Ltd., Novo Nordisk Inc., Ono Pharmaceutical Co., Ltd., Sumitomo Dainippon Pharma Co., Ltd., Taisho Pharmaceutical Co., Ltd., Takeda Pharmaceutical Company Limited, Terumo Medical Corporation. Speaker’s Bureau; Self; Becton, Dickinson and Company, Eli Lilly Japan K.K., Kao Corporation, Merck Sharp &amp; Dohme Corp., Nippon Boehringer Ingelheim Co. Ltd., Novo Nordisk Inc., Taisho Pharmaceutical Co., Ltd., Takeda Pharmaceutical Company Limited.

A Missense (c.T1424C:p.L475P) Mutation of ZYG11A Causes Maturity-Onset Diabetes of the Young

Maturity-onset diabetes of the young (MODY) is a monogenic form of diabetes inherited in an autosomal dominant mode. Approximately, 80% of Thai MODY families did not carry mutations of known MODY genes. This study aims, therefore, to identify an unknown causative gene of MODY in Thais. Exome sequencing was performed in DNA samples of two diabetic and one nondiabetic members of a MODY family with unknown genetic etiology. Only heterozygous non-synonymous variants with minor allele frequencies &amp;lt;0.01%, which were shared between the two diabetic but not existed in nondiabetic family members, were selected for segregation analysis. Among these, a missense mutation (NM_001004339, c.T1424C:p.L475P) in a gene encoding zyg-11 family member A (ZYG11A) showed complete segregation with diabetes in three generations. This mutation is not present in any database and not detected in nondiabetic controls (n = 400) as well as other MODY-X probands (n = 90). The amino acid residue L475 of ZYG11A is evolutionally conserved among many species. Several prediction software tools suggested a deleterious effect of the L475P mutation. ZYG11A acts as a target recruitment subunit of an E3 ubiquitin ligase complex, which plays an important role in degradation of cyclinB1- a regulatory protein involved in mitosis. Suppression of ZYG11A in 1.1B4 β-cell line by specific small interfering RNA (siRNA) significantly reduced cell proliferation (p = 0.001) while increased cyclinB1 protein levels (p = 0.001). Moreover, 1.1B4 cells overexpressing ZYG11A showed a significant increase in proliferation as compared to the control cells (p = 0.019) whereas this effect was not observed in the cells overexpressing the mutant ZYG11A (p = 0.659). Taken together, this finding demonstrates the crucial role of ZYG11A in β-cell cycle regulation. It also suggests heterozygous ZYG11A-L475P mutation as a cause of MODY in the Thai family studied. Disclosure C. Charoensuk: None. P. Jungtrakoon: None. W. Tangjittipokin: None. J. Sujjitjoon: None. N. Plengvidhya: None. P. Yenchitsomanus: None.

Quantitative Evaluation of Serum Proteins Uncovers a Protein Signature Related to Maturity-Onset Diabetes of the Young (MODY).

Maturity-onset diabetes of the young (MODY) is an inherited monogenic type of diabetes. Genetic mutations in MODY often cause nonsynonymous changes that directly lead to the functional distortion of proteins and the pathological consequences. Herein, we proposed that the inherited mutations found in a MODY family could cause a disturbance of protein abundance, specifically in serum. The serum samples were collected from a Uyghur MODY family through three generations, and the serum proteins after depletion treatment were examined by quantitative proteomics to characterize the MODY-related serum proteins followed by verification using target quantification of proteomics. A total of 32 serum proteins were preliminarily identified as the MODY-related. Further verification test toward the individual samples demonstrated the 12 candidates with the significantly different abundance in the MODY patients. A comparison of the 12 proteins among the sera of type 1 diabetes, type 2 diabetes, MODY, and healthy subjects was conducted and revealed a protein signature related with MODY composed of the serum proteins such as SERPINA7, APOC4, LPA, C6, and F5.

Clinical application of ACMG-AMP guidelines in HNF1A and GCK variants in a cohort of MODY families.

Maturity-onset diabetes of the young (MODY) is a form of monogenic diabetes with autosomal dominant inheritance. GCK -MODY and HNF1A -MODY are the prevalent subtypes. Currently, there is growing concern regarding the correct interpretation of molecular genetic findings. The American College of Medical Genetics and Genomics (ACMG) updated guidelines to interpret and classify molecular variants. This study aimed to determine the prevalence of MODY ( GCK / HNF1A ) in a large cohort of Brazilian families, to report variants related to phenotype, and to classify them according to ACMG guidelines. One hundred and nine probands were investigated, 45% with clinical suspicion of GCK -MODY and 55% with suspicion of HNF1A -MODY. Twenty-five different variants were identified in GCK gene (30 probands-61% of positivity), and 7 variants in HNF1A (10 probands-17% of positivity). Fourteen of them were novel (12- GCK /2- HNF1A ). ACMG guidelines were able to classify a large portion of variants as pathogenic (36%- GCK /86%- HNF1A ) and likely pathogenic (44%- GCK /14%- HNF1A ), with 16% (5/32) as uncertain significance. This allows us to determine the pathogenicity classification more efficiently, and also reinforces the suspected associations with the phenotype among novel variants.

Genetic diagnosis and treatment of a Chinese ketosis-prone MODY 3 family with depression

BackgroundTo analyze the gene mutation and mental disorder of a Chinese ketosis-prone diabetes (KPD) family, and to make a precise diagnosis and give a treatment for them.MethodsWe studied a Chinese family with a clinical diagnosis of maturity-onset diabetes of the young (MODY). The clinical data and the blood samples were collected. The promotor and coding regions inclusive intron exon boundaries of the HNF1A, HNF4A were detected by polymerase chain reaction (PCR) and direct sequencing. The missense mutation was also analyzed by bioinformatics. Genetic counseling was performed twice a month to relieve the mental disorder of the persons.ResultsThe missense mutation c.779 C>T (p.T260M) in exon4 of HNF1A gene was detected, and the symptom heterogenicity among persons in this family were found. All the members were retreated with Gliclazide and stopped to use other medicine, the blood glucose of them were well controlled. We also performed an active genetic counseling to them and the mental disorder of the proband’s sister was relieved.ConclusionsA missense mutation of HNF1A gene was first found in Chinese ketosis-prone MODY family with manifestations heterogenicity among the persons. Sulphonylureas medicine and genetic counseling are efficiency ways to treat MODY 3 and its’ mental disorder respectively.

A three-step programmed method for the identification of causative gene mutations of maturity onset diabetes of the young (MODY)

To establish a three-step programmed method to find gene mutations related to maturity onset diabetes of the young (MODY). Target region capture and next-generation sequencing (NGS) were performed using customized oligonucleotide probes designed to capture suspected genes for MODY in 11 probands with clinically diagnosed MODY. The suspected associations of certain genes with MODY were then confirmed by Sanger sequencing in the probands and their family members. Finally, to validate variants of one of the genes of interest (glucokinase, GCK) as pathogenic mutations, protein function editing by the variant genes was assessed. In the target region capture and NGS phase, a total of nine variants of seven genes (GCK, WFS1, SLC19A2, SH2B1, SERPINB4, RFX6, and GATA6) were identified in eight probands. Two heterozygous GCK mutations located on the same allele (p.Leu77Arg and p.Val101Met) were identified in a MODY family. Sanger sequencing was used to confirm the variants identified by NGS to be present in probands and their diabetic family members, but not in non-diabetic family members. Finally, enzyme kinetic and thermal stability analyses revealed that the p.Leu77Arg mutation or the p.Leu77Arg mutation in combination with the p.Val101Met mutation inactivates GCK function and stability, while mutation of p.Val101Met alone does not. The p.Leu77Arg but not p.Val101Met GCK mutation is therefore considered a pathogenic mutation associated with MODY. Genetic screening coupled with gene-editing protein function testing is an effective and reliable method by which causative gene mutations of MODY can be identified.

Studies of genetic variability of the hepatocyte nuclear factor-1α gene in an Indian maturity-onset diabetes of the young family.

Maturity-onset diabetes of the young (MODY), one of the specific types of diabetes mellitus, is a monogenetic disorder characterized by an autosomal dominant (AD) inheritance and β-cell dysfunction. To study an Indian family with clinical diagnosis of MODY and detect the genetic mutations in the aspect of molecular mechanism, seven blood samples were obtained from the diabetic patients of this pedigree and genomic DNA was extracted from peripheral leukocytes. The exon1, exon2 and exon4 of hepatocyte nuclear factor-1α (HNF-1α) gene were amplified by polymerase chain reaction. Then the products were sequenced and compared with standard sequences on gene bank. As a result, two mutations were detected in exon1. That was CTC → CTG (Leu → Leu) in codon17 and ATC → CTC (Ile → Leu) in codon27. I27L was speculated to have a close relationship with the glycometabolism and the pathogenesis of diabetes mellitus together with the putative novel mutation existed in this Indian pedigree. Meanwhile, one mutation of GGG → GGC (Gly → Gly) in codon288 of exon4 was detected in the proband. No mutations were found in exon2 but a G → T base substitution in the intron4 region among all seven samples was detected. It may have some potential effects on the onset of diabetes in this family, but we do not have any evidence right now. Although it requires further investigation on the function of mutations found in the intron region, our research may provide some clue for this issue and it deserves more attention.

Substantial proportion of MODY among multiplex families participating in a Type 1 diabetes prediction programme.

Patients with maturity-onset diabetes of the young (MODY) might be over-represented in families with histories of Type 1 diabetes. Our aim was to re-evaluate families participating in the Czech T1D Prediction Programme (PREDIA.CZ) with at least two members affected with diabetes to assess the proportion of MODY among these families and determine its most significant clinical predictors. Of the 557 families followed up by the PREDIA.CZ, 53 (9.5%) had two or more family members with diabetes. One proband with diabetes from these families was chosen for direct sequencing of the GCK, HNF1A, HNF4A and INS genes. Non-parametric tests and a linear logistic regression model were used to evaluate differences between MODY and non-MODY families. MODY was genetically diagnosed in 24 of the 53 families with multiple occurrences of diabetes (45%). Mutations were detected most frequently in GCK (58%), followed by HNF1A (38%) and INS (4%). MODY families were more likely to have a parent with diabetes and had a higher proportion of females with diabetes than non-MODY families. Higher age (P < 0.001), a lower level of HbA1c (P < 0.001) at clinical onset and at least two generations affected by diabetes were the variables most predictive for probands of MODY families already presenting with diabetes. A prediction programme for Type 1 diabetes would provide a useful new source of patients with MODY most likely to benefit from an accurate diagnosis. This identification has implications for patient treatment and disease prognosis.

A family with the Arg103Pro mutation in the NEUROD1 gene detected by next-generation sequencing – Clinical characteristics of mutation carriers

Until now only a few families with early onset autosomal diabetes due to the NEUROD1 gene mutations have been identified. Moreover, only some of them meet strict MODY (maturity-onset diabetes of the young) criteria. Next-generation sequencing (NGS) provides an opportunity to detect more pathogenic mutations in this gene.Here, we evaluated the segregation of the Arg103Pro mutation in the NEUROD1 gene in a pedigree in which it was detected, and described the clinical characteristics of the mutation carriers. MethodsWe included 156 diabetic probands of MODY families, among them 52 patients earlier tested for GCK-MODY and/or HNF1A-MODY by Sanger sequencing with negative results. Genetic testing was performed by targeted NGS sequencing using a panel of 28 monogenic diabetes genes. ResultsAs detected by NGS, one patient had the missense Arg103Pro (CGC/CCC) mutation in the gene NEUROD1 changing the amino-acid structure of the DNA binding domain of this transcription factor. We confirmed this sequence difference by Sanger sequencing. This family had previously been tested with negative results for HNF1A gene mutations. 17 additional members of this family were invited for further testing. We confirmed the presence of the mutation in 11 subjects. Seven adult mutation carriers (all but one) from three generations had been already diagnosed with diabetes. There were 3 individuals with the Arg103Pro mutation diagnosed before the age of 30 years in the family. The range of age of the four unaffected mutation carriers (3 minors and 1 adult) was 3–48 years. Interestingly, one mutation carrier had a history of transient neonatal hypoglycemia, of which the clinical course resembled episodes typical for HNF4A-MODY. ConclusionsWe report a family with autosomal dominant diabetes related to a new NEUROD1 mutation, one of very few meeting MODY criteria. The use of the NGS method will facilitate identification of more families with rare forms of MODY.

Identification of Candidate Gene Variants in Korean MODY Families by Whole-Exome Sequencing

Aims: To date, 13 genes causing maturity-onset diabetes of the young (MODY) have been identified. However, there is a big discrepancy in the genetic locus between Asian and Caucasian patients with MODY. Thus, we conducted whole-exome sequencing in Korean MODY families to identify causative gene variants. Methods: Six MODY probands and their family members were included. Variants in the dbSNP135 and TIARA databases for Koreans and the variants with minor allele frequencies >0.5% of the 1000 Genomes database were excluded. We selected only the functional variants (gain of stop codon, frameshifts and nonsynonymous single-nucleotide variants) and conducted a case-control comparison in the family members. The selected variants were scanned for the previously introduced gene set implicated in glucose metabolism. Results: Three variants c.620C>T:p.Thr207Ile in PTPRD, c.559C>G:p.Gln187Glu in SYT9, and c.1526T>G:p.Val509Gly in WFS1 were respectively identified in 3 families. We could not find any disease-causative alleles of known MODY 1-13 genes. Based on the predictive program, Thr207Ile in PTPRD was considered pathogenic. Conclusions: Whole-exome sequencing is a valuable method for the genetic diagnosis of MODY. Further evaluation is necessary about the role of PTPRD, SYT9 and WFS1 in normal insulin release from pancreatic beta cells.

Frameshift mutations in the insulin gene leading to prolonged molecule of insulin in two families with Maturity-Onset Diabetes of the Young

Mutations in the insulin (INS) gene rarely occur in patients with Maturity-Onset Diabetes of the Young (MODY). We aimed to describe in detail two MODY families with INS mutations.The INS gene was screened by direct sequencing. The probands and their affected relatives underwent a mixed-meal test. Mutation predictions were modeled using I-TASSER and were visualized by Swiss-PdbViewer. A novel heterozygous frameshift mutation p.Gln78fs in the INS gene was found in three generations of patients with clinically distinct diabetes. The single nucleotide deletion (c.233delA) is predicted to change and prolong amino acid sequence, resulting in aberrant proinsulin without native structures of C-peptide and A-chain. In the second family, the heterozygous mutation c.188-31G>A within the terminal intron was detected. The mother and her daughter were misdiagnosed as having type 1 diabetes since the ages of 6 and 2 years, respectively. This result is in contrast to the previously described carrier of the same mutation who was diagnosed with permanent neonatal diabetes. We identified a novel coding frameshift mutation and an intronic mutation in the INS gene leading to childhood-onset diabetes. INS mutations may result in various phenotypes, suggesting that additional mechanisms may be involved in the pathogenesis and clinical manifestation of diabetes.

Molecular genetic testing of patients with monogenic diabetes and hyperinsulinism.

Genetic sequencing has become a critical part of the diagnosis of certain forms of pancreatic beta cell dysfunction. Despite great advances in the speed and cost of DNA sequencing, determining the pathogenicity of variants remains a challenge, and requires sharing of sequence and phenotypic data between laboratories. We reviewed all diabetes and hyperinsulinism-associated molecular testing done at the Seattle Children's Molecular Genetics Laboratory from 2009 to 2013. 331 probands were referred to us for molecular genetic sequencing for Neonatal Diabetes (NDM), Maturity-Onset Diabetes of the Young (MODY), or Congenital Hyperinsulinism (CHI) during this period. Reportable variants were identified in 115 (35%) patients with 91 variants in one of 6 genes: HNF1A, GCK, HNF4A, ABCC8, KCNJ11, or INS. In addition to identifying 23 novel variants, we identified unusual mechanisms of inheritance, including mosaic and digenic MODY presentations. Re-analysis of all reported variants using more recently available databases led to a change in variant interpretation from the original report in 30% of cases. These results represent a resource for molecular testing of monogenic forms of diabetes and hyperinsulinism, providing a mutation spectrum for these disorders in a large North American cohort. In addition, they highlight the importance of periodic review of molecular testing results.

Serum metabonomic study of two Uyghur families with maturity-onset diabetes of the young

Objective To study the characteristics of serum metabolites in two Uyghur families with maturityonset diabetes of the young(MODY).Methods Two MODY families were composed of four generations of Uyghur with 52 members collected from Kashgar region,Xinjiang Uyghur Autonomous Region.The general information,blood glucose and lipid levels,and blood pressure were analyzed.Using 1H nuclear magnetic resonance (1H NMR )spectroscopy,serum metabolites were measured for each subject.After having conducted data pretreatment on the spectrogram,orthogonal partial least squares discriminant analysis ( OPLS-DA ) was used to interpret data.The subjects were divided into two groups according to blood glucose ( diabetes and non-diabetes ),blood pressure,body mass index ( BMI ) for comparing differences in the metabolites.The differences of serum metabolic components between two groups were determined using pearson correlation coefficients with significant difference detection and two-dimensional spectrum technology.Results lsoleucine and tyrosine levels in diabetes group were decreased significantly,while α-glucose and β-glucose levels were increased significantly compared with non-diabetes group( all P＜0.05 ).Citrate,phaseomannite,1 -methyl histidine,and tyrosine levels in hypertension group were all decreased significantly compared with normal blood pressure group( all P＜0.05 ).No significant metabonomic differences were observed between normal BMI group and high BMI group.Conclusions Metabonomic changes in diabetic patients from MODY families indicate that diabetic patients suffer from disordered tricarboxylic acid cycle ( TCA cycle )metabolism,with reduced glycolysis of glycogen in liver and muscle.There exist the metabolic disorder in TCA cycle and obstruction of fat metabolism in patients with hypertension from the MODY families. Key words: Maturity-onset diabetes of the young; Pedigree; Metabonomics; 1H nuclear magnetic resonance

Human Mutation within Per-Arnt-Sim (PAS) Domain-containing Protein Kinase (PASK) Causes Basal Insulin Hypersecretion

PAS kinase (PASK) is a glucose-regulated protein kinase involved in the control of pancreatic islet hormone release and insulin sensitivity. We aimed here to identify mutations in the PASK gene that may be associated with young-onset diabetes in humans. We screened 18 diabetic probands with unelucidated maturity-onset diabetes of the young (MODY). We identified two rare nonsynonymous mutations in the PASK gene (p.L1051V and p.G1117E), each of which was found in a single MODY family. Wild type or mutant PASKs were expressed in HEK 293 cells. Kinase activity of the affinity-purified proteins was assayed as autophosphorylation at amino acid Thr307 or against an Ugp1p-derived peptide. Whereas the PASK p.G1117E mutant displayed a ∼25% increase with respect to wild type PASK in the extent of autophosphorylation, and a ∼2-fold increase in kinase activity toward exogenous substrates, the activity of the p.L1051V mutant was unchanged. Amino acid Gly1117 is located in an α helical region opposing the active site of PASK and may elicit either: (a) a conformational change that increases catalytic efficiency or (b) a diminished inhibitory interaction with the PAS domain. Mouse islets were therefore infected with adenoviruses expressing wild type or mutant PASK and the regulation of insulin secretion was examined. PASK p.G1117E-infected islets displayed a 4-fold decrease in glucose-stimulated (16.7 versus 3 mM) insulin secretion, chiefly reflecting a 4.5-fold increase in insulin release at low glucose. In summary, we have characterized a rare mutation (p.G1117E) in the PASK gene from a young-onset diabetes family, which modulates glucose-stimulated insulin secretion.

Identification of HNF1A-MODY and HNF4A-MODY in Irish families: Phenotypic characteristics and therapeutic implications

Aim The prevalence of hepatocyte nuclear factor ( HNF)- 1A and HNF4A mutations, and the clinical implications following the genetic diagnosis of maturity-onset diabetes of the young (MODY) in the Irish population, remain unknown. The aim of this study was to establish the occurrence of HNF1A and HNF4A mutations in subjects classified clinically as MODY to identify novel mutations, and to determine the phenotypic features and response to therapy. Methods A total of 36 unrelated index cases with a clinical diagnosis of MODY were analyzed for HNF1A/HNF4A mutations. OGTT was performed to determine the degree of glucose tolerance and insulin secretory response. Also, 38 relatives underwent OGTT and were tested for the relevant known mutations. HNF1A-/HNF4A-MODY subjects were compared with nine HNF1A mutation-negative relatives and 20 type 2 diabetic (T2DM) patients. Results Seven different HNF1A mutations were identified in 11/36 (30.5%) index cases, two of which were novel (S352fsdelG and F426X), as well as two novel HNF4A mutations (M1? and R290C; 6%). Family screening revealed 20 subjects with HNF1A and seven with HNF4A mutations. Only 51.6% of HNF1A mutation carriers were diagnosed with diabetes by age 25 years; 11 of the mutation carriers were overweight and four were obese. Insulin secretory response to glucose was significantly lower in HNF1A-MODY subjects than in T2DM patients and HNF1A mutation-negative relatives ( P = 0.01). Therapeutic changes occurred in 48% of mutation carriers following genetic diagnosis. Conclusion There was an HNF1A-MODY pick-up rate of 30.5% and an HNF4A-MODY pick-up rate of 6% in Irish MODY families. Genetically confirmed MODY has significant therapeutic implications.