Maturity-onset diabetes of the young with end-stage nephropathy: a new indication for simultaneous pancreas and kidney transplantation?

BACKGROUND AND CASE: Simultaneous pancreas and kidney transplantation (SPK) is applied almost exclusively in C-peptide-negative type 1 diabetic patients, although some data on SPK in type 2 diabetes have been published as well. Nothing is known about SPK in the autosomal diabetes form, maturity-onset diabetes of the young (MODY). SPK was performed in a 47-year old man who has MODY3 because of a Arg272His mutation in the hepatocyte nuclear factor-1alphagene. He developed overt diabetes mellitus at 19 years and end-stage diabetic nephropathy 26 years thereafter. Before SPK, the patient had measurable fasting serum C-peptide levels, but lacked beta-cell response to intravenous glucose and glucagon. He was treated with 34 IU of insulin per day. At 2 years post-transplantation, the patient remains normoglycemic and insulin independent. A hyperglycemic clamp test showed a normal beta-cell function. CONCLUSION: Identification of MODY3 among all C-peptide-positive patients with advanced diabetic nephropathy might help to select a specific group profiting from SPK.     

A novel -192c/g mutation in the proximal P2 promoter of the hepatocyte nuclear factor-4 alpha gene (HNF4A) associates with late-onset diabetes

Recently, it has been shown that mutations in the P2 promoter of the hepatocyte nuclear factor (HNF)-4 alpha gene (HNF4A) cause maturity-onset diabetes of the young (MODY), while single nucleotide polymorphisms in this locus are associated with type 2 diabetes. In this study, we examined 1,189 bp of the P2 promoter and the associated exon 1D of HNF4A for variations associated with diabetes in 114 patients with type 2 diabetes, 72 MODYX probands, and 85 women with previous gestational diabetes mellitus. A -192c/g mutation was found in five patients. We screened 1,587 diabetic subjects and 4,812 glucose-tolerant subjects for the -192c/g mutation and identified 5 diabetic and 1 glucose-tolerant mutation carriers (P=0.004). Examination of the families showed that carriers of the -192c/g mutation had a significantly impaired glucose-stimulated insulin release and lower levels of serum total cholesterol compared with matched control subjects. Furthermore, the mutation disrupted the binding of an unidentified sequence-specific DNA binding complex present in human islet extracts. Also, two novel linked polymorphisms in the P2 promoter at positions -1107g/t and -858c/t were identified. These variants were not significantly associated with type 2 diabetes or any pre-diabetic traits. In conclusion, a rare, novel mutation that disrupts a protein binding site in the pancreatic HNF4A promoter associates with late-onset diabetes.     

A hepatocyte nuclear factor-4 alpha gene (HNF4A) P2 promoter haplotype linked with late-onset diabetes: studies of HNF4A variants in the Norwegian MODY registry

Variants in hepatocyte nuclear factor (HNF)-4alpha cause maturity-onset diabetes of the young, type 1 (MODY1) and may also be risk factors for type 2 diabetes. We sequenced the HNF4A gene of 95 MODY3-negative probands from the Norwegian MODY Registry. We found three novel coding variants in exon 8 of HNF4A: G326R, T339I, and W340X. In intron 7, we noted a single nucleotide polymorphism in the binding site of a previously published primer pair, which in some cases caused allelic drop out when amplifying exon 8. We also detected two novel sequence variants of the P2 promoter region, of which P2 -192C>G showed linkage with diabetes in two families (maximal logarithm of odds score of 3.1 and 0.8, respectively). This variant and a surrounding haplotype restricted by 3.7 Mb was also found in two Danish MODY pedigrees. The age of onset was higher in the P2 -192C>G carriers (median 45 years) compared with that reported for other MODY1 individuals. We could not support a biological role of the P2 promoter variant by in vitro transfection assays. In conclusion, we have identified three novel HNF4A mutations and a 3.7-Mb haplotype, including the HNF4A P2 promoter, which was linked with diabetes.     

Spatial Environment Affects HNF4A Mutation-Specific Proteome Signatures and Cellular Morphology in hiPSC-Derived β-Like Cells

Studies of monogenic diabetes are particularly useful because we can gain insight into the molecular events of pancreatic β-cell failure. Maturity-onset diabetes of the young 1 (MODY1) is a form of monogenic diabetes caused by a mutation in the HNF4A gene. Human-induced pluripotent stem cells (hiPSCs) provide an excellent tool for disease modeling by subsequently directing differentiation toward desired pancreatic islet cells, but cellular phenotypes in terminally differentiated cells are notoriously difficult to detect. Re-creating a spatial (three-dimensional [3D]) environment may facilitate phenotype detection. We studied MODY1 by using hiPSC-derived pancreatic β-like patient and isogenic control cell lines in two different 3D contexts. Using size-adjusted cell aggregates and alginate capsules, we show that the 3D context is critical to facilitating the detection of mutation-specific phenotypes. In 3D cell aggregates, we identified irregular cell clusters and lower levels of structural proteins by proteome analysis, whereas in 3D alginate capsules, we identified altered levels of glycolytic proteins in the glucose sensing apparatus by proteome analysis. Our study provides novel knowledge on normal and abnormal function of HNF4A, paving the way for translational studies of new drug targets that can be used in precision diabetes medicine in MODY.     

Evaluation of Evidence for Pathogenicity Demonstrates That BLK,KLF11, and PAX4 Should Not Be Included in Diagnostic Testing for MODY

Maturity-onset diabetes of the young (MODY) is an autosomal dominant form of monogenic diabetes, reported to be caused by variants in 16 genes. Concern has been raised about whether variants in BLK (MODY11), KLF11 (MODY7), and PAX4 (MODY9) cause MODY. We examined variant-level genetic evidence (cosegregation with diabetes and frequency in population) for published putative pathogenic variants in these genes and used burden testing to test gene-level evidence in a MODY cohort (n = 1,227) compared with a control population (UK Biobank [n = 185,898]). For comparison we analyzed well-established causes of MODY, HNF1A, and HNF4A. The published variants in BLK, KLF11, and PAX4 showed poor cosegregation with diabetes (combined logarithm of the odds [LOD] scores ≤1.2), compared with HNF1A and HNF4A (LOD scores >9), and are all too common to cause MODY (minor allele frequency >4.95 × 10⁻⁵). Ultra-rare missense and protein-truncating variants (PTV) were not enriched in a MODY cohort compared with the UK Biobank population (PTV P > 0.05, missense P > 0.1 for all three genes) while HNF1A and HNF4A were enriched (P < 10⁻⁶). Findings of sensitivity analyses with different population cohorts supported our results. Variant and gene-level genetic evidence does not support BLK, KLF11, or PAX4 as a cause of MODY. They should not be included in MODY diagnostic genetic testing.     

Common variants in maturity-onset diabetes of the young genes contribute to risk of type 2 diabetes in Finns

Prior reports have suggested that variants in the genes for maturity-onset diabetes of the young (MODY) may confer susceptibility to type 2 diabetes, but results have been conflicting and coverage of the MODY genes has been incomplete. To complement our previous studies of HNF4A, we examined the other five known MODY genes for association with type 2 diabetes in Finnish individuals. For each of the five genes, we selected 1) nonredundant single nucleotide polymorphisms (SNPs) (r(2)< 0.8 with other SNPs) from the HapMap database or another linkage disequilibrium map, 2) SNPs with previously reported type 2 diabetes association, and 3) nonsynonymous coding SNPs. We tested 128 SNPs for association with type 2 diabetes in 786 index cases from type 2 diabetic families and 619 normal glucose-tolerant control subjects. We followed up 35 of the most significant SNPs by genotyping them on another 384 case subjects and 366 control subjects from Finland. We also supplemented our previous HNF4A results by genotyping 12 SNPs on additional Finnish samples. After correcting for testing multiple correlated SNPs within a gene, we find evidence of type 2 diabetes association with SNPs in five of the six known MODY genes: GCK, HNF1A, HNF1B, NEUROD1, and HNF4A. Our data suggest that common variants in several MODY genes play a modest role in type 2 diabetes susceptibility.     

Maturity onset diabetes of the young: clinical characteristics and outcome after kidney and pancreas transplantation in MODY3 and RCAD patients: a single center experience

The diabetes and renal phenotype of patients with maturity-onset diabetes of the young (MODY) on a transplantation waiting list is not known; neither is their outcome after pancreas (PT) and/or kidney transplantation (KT). Between 2002 and 2009, we screened 50 of 150 patients referred for kidney and pancreas transplantation to the Kremlin-Bicêtre center for HNF1B and HNF1A mutations if one or more of the following criteria was present (i) an atypical history of diabetes (ii) diabetes with at least one affected parent or two affected relatives, (iii) an absence of auto-antibodies at diagnosis (iv) a persistent secretion of fasting C peptide (v) a personal or a family history of renal cysts or dysplasia. Their phenotype and their outcome were analyzed. Four HNF1A (MODY3) and eight HNF1B mutations [renal cysts and diabetes (RCAD)] were identified. All MODY3 patients had diabetic nephropathy, but only 50% of RCAD patients. Four patients underwent a kidney and pancreas transplantation and two a kidney transplant alone. After 4.1 ± 1.1 years of follow-up, 83% of patients still have a functioning kidney and 75% a functioning pancreas. PT can be proposed with good results for MODY3 and RCAD patients.     

Mutations in HNF1A Result in Marked Alterations of Plasma Glycan Profile

A recent genome-wide association study identified hepatocyte nuclear factor 1-α (HNF1A) as a key regulator of fucosylation. We hypothesized that loss-of-function HNF1A mutations causal for maturity-onset diabetes of the young (MODY) would display altered fucosylation of N-linked glycans on plasma proteins and that glycan biomarkers could improve the efficiency of a diagnosis of HNF1A-MODY. In a pilot comparison of 33 subjects with HNF1A-MODY and 41 subjects with type 2 diabetes, 15 of 29 glycan measurements differed between the two groups. The DG9-glycan index, which is the ratio of fucosylated to nonfucosylated triantennary glycans, provided optimum discrimination in the pilot study and was examined further among additional subjects with HNF1A-MODY (n = 188), glucokinase (GCK)-MODY (n = 118), hepatocyte nuclear factor 4-α (HNF4A)-MODY (n = 40), type 1 diabetes (n = 98), type 2 diabetes (n = 167), and nondiabetic controls (n = 98). The DG9-glycan index was markedly lower in HNF1A-MODY than in controls or other diabetes subtypes, offered good discrimination between HNF1A-MODY and both type 1 and type 2 diabetes (C statistic ≥0.90), and enabled us to detect three previously undetected HNF1A mutations in patients with diabetes. In conclusion, glycan profiles are altered substantially in HNF1A-MODY, and the DG9-glycan index has potential clinical value as a diagnostic biomarker of HNF1A dysfunction.Genome-wide association studies are providing novel insights into the genetic architecture and biological basis of many diseases, but immediate translation into clinical practice has been limited. We recently performed a genome-wide association study of the human plasma N-glycome and found evidence of association involving common variants near the hepatocyte nuclear factor 1-α (HNF1A) gene; follow-up functional experiments established HNF1A as a master regulator of plasma protein fucosylation (1). Fucosylation, a specific type of glycosylation, comprises the addition of fucose residues to glycans. Here we evaluate the hypothesis that mutations causing a more severe deficit in HNF1A function (resulting in the monogenic subtype of diabetes known as HNF1A maturity-onset diabetes of the young [MODY; HNF1A-MODY]) are associated with marked alterations of plasma glycome composition, and we assess the value of glycan profiles as a diagnostic biomarker for HNF1A-MODY.Most human proteins are posttranslationally modified by the addition of complex oligosaccharide structures (glycans) (2). Despite the impact on protein structure and function, the clinical consequences of changes in the human glycome remain largely unexplored, primarily because reliable analytical techniques have been developed only recently (3). In recent studies, HNF1A was shown to promote both the de novo and salvage pathways for the synthesis of guanosine diphosphate–fucose (1) and to regulate fucosyltransferase VI (1,4). HNF1A thereby controls the outer-arm (antennary) fucosylation of proteins with N-linked glycans through effects on both the supply of activated precursors and the incorporation of fucose (1,4).Mutations disrupting HNF1A are responsible for the most common subtype of monogenic diabetes, HNF1A-MODY (5). Like other forms of MODY, HNF1A-MODY is characterized by autosomal dominant inheritance and pancreatic β-cell dysfunction. This typically leads to diabetes diagnosed in the second to fourth decade of life in the absence of β-cell autoimmunity and insulin resistance (5,6). In clinical practice, diagnostic differentiation between HNF1A-MODY and other causes of early-onset diabetes (including type 1 and type 2 diabetes and other forms of MODY) is complicated by the overlap of phenotypic features. In most countries only a minority of cases of HNF1A-MODY are referred for definitive molecular testing (i.e., HNF1A sequencing), and many patients with HNF1A-MODY are misdiagnosed with type 1 or type 2 diabetes (7). Failures or delays in accurate molecular diagnosis can have clinical repercussions because, unlike other forms of diabetes, the optimal treatment for HNF1A-MODY is low-dose sulfonylureas (8). Patients with undiagnosed HNF1A-MODY may spend many years receiving inappropriate treatment (including exogenous insulin) and experiencing suboptimal glycemic control (9).We aimed to test the hypothesis that inactivating mutations in HNF1A, such as those found in HNF1A-MODY, are associated with decreased antennary fucosylation of circulating proteins and to evaluate the clinical translational potential of measuring glycan profiles in diabetes.     

Genetic modifiers of the age at diagnosis of diabetes (MODY3) in carriers of hepatocyte nuclear factor-1alpha mutations map to chromosomes 5p15, 9q22, and 14q24

Mutations in hepatocyte nuclear factor (HNF)-1alpha (MODY3) account for the largest proportion of maturity-onset diabetes of the young (MODY) cases in the U.S. This form of diabetes is characterized by impaired insulin secretion in response to glucose, but wide variability exists in the severity of hyperglycemia and in the age at which it becomes clinically manifest. We have previously shown that the age at onset of diabetes in MODY3 families is influenced by familial factors (including modifying genes) and exposure to diabetes in utero. To identify genes influencing the onset of MODY3, we conducted a genome scan in 13 extended MODY families in which diabetes segregates with an HNF-1alpha mutation. Linkage with age at onset of diabetes was assessed by genetic variance component analysis using SOLAR. The locus with the strongest evidence of linkage was on chromosome 14q24 (D14S588; logarithm of odds [LOD] = 2.58, P = 0.0004). This location overlaps with IDDM11 and includes SEL1L, a negative regulator of the Notch pathway that may control islet development. Linkage evidence also supported loci on 5p15 (D5S817; LOD = 2.44, P = 0.0004) and 9q22 (D9S910; LOD = 2.02, P = 0.0018). The latter matches a region linked to 2-h insulin levels in Pima Indians. Less strong linkage evidence was observed at three other regions: chromosomes 3p24 (LOD = 1.44), 7q21 (1.20), and 16q23 (1.51). Our data are consistent with the existence of multiple loci that contribute to the expression of the MODY3 phenotype. Identification of these genes will offer new insights into the pathophysiology of MODY that may, in turn, increase our understanding of the cellular events underlying more common forms of diabetes.     

A genome-wide scan in families with maturity-onset diabetes of the young: evidence for further genetic heterogeneity

Maturity-onset diabetes of the young (MODY) is a heterogeneous single gene disorder characterized by non-insulin-dependent diabetes, an early onset and autosomal dominant inheritance. Mutations in six genes have been shown to cause MODY. Approximately 15-20% of families fitting MODY criteria do not have mutations in any of the known genes. These families provide a rich resource for the identification of new MODY genes. This will potentially enable further dissection of clinical heterogeneity and bring new insights into mechanisms of beta-cell dysfunction. To facilitate the identification of novel MODY loci, we combined the results from three genome-wide scans on a total of 23 families fitting MODY criteria. We used both a strict parametric model of inheritance with heterogeneity and a model-free analysis. We did not identify any single novel locus but provided putative evidence for linkage to chromosomes 6 (nonparametric linkage [NPL]score 2.12 at 71 cM) and 10 (NPL score 1.88 at 169-175 cM), and to chromosomes 3 (heterogeneity LOD [HLOD] score 1.27 at 124 cM) and 5 (HLOD score 1.22 at 175 cM) in 14 more strictly defined families. Our results provide evidence for further heterogeneity in MODY.     

Comprehensive genetic screening reveals wide spectrum of genetic variants in monogenic forms of diabetes among Pakistani population

BACKGROUNDMonogenic forms of diabetes (MFD) are single gene disorders. Their diagnosis is challenging, and symptoms overlap with type 1 and type 2 diabetes.AIMTo identify the genetic variants responsible for MFD in the Pakistani population and their frequencies.METHODSA total of 184 patients suspected of having MFD were enrolled. The inclusion criterion was diabetes with onset below 25 years of age. Brief demographic and clinical information were taken from the participants. The maturity-onset diabetes of the young (MODY) probability score was calculated, and glutamate decarboxylase ELISA was performed. Antibody negative patients and features resembling MODY were selected (n = 28) for exome sequencing to identify the pathogenic variants. RESULTSA total of eight missense novel or very low-frequency variants were identified in 7 patients. Three variants were found in genes for MODY, i.e. HNF1A (c.169C>A, p.Leu57Met), KLF11 (c.401G>C, p.Gly134Ala), and HNF1B (c.1058C>T, p.Ser353Leu). Five variants were found in genes other than the 14 known MODY genes, i.e. RFX6 (c.919G>A, p.Glu307Lys), WFS1 (c.478G>A, p.Glu160Lys) and WFS1 (c.517G>A, p.Glu173Lys), RFX6 (c.1212T>A, p.His404Gln) and ZBTB20 (c.1049G>A, p.Arg350His).CONCLUSIONThe study showed wide spectrum of genetic variants potentially causing MFD in the Pakistani population. The MODY genes prevalent in European population (GCK, HNF1A, and HNF4a) were not found to be common in our population. Identification of novel variants will further help to understand the role of different genes causing the pathogenicity in MODY patient and their proper management and diagnosis.     

Diagnosis, management, and prognosis of HNF1B nephropathy in adulthood

Mutations in HNF1B are responsible for a dominantly inherited disease with renal and nonrenal consequences, including maturity-onset diabetes of the young (MODY) type 5. While HNF1B nephropathy is typically responsible for bilateral renal cystic hypodysplasia in childhood, the adult phenotype is poorly described. To help define this we evaluated the clinical presentation, imaging findings, genetic changes, and disease progression in 27 adults from 20 families with HNF1B nephropathy. Whole-gene deletion was found in 11 families, point mutations in 9, and de novo mutations in half of the kindred tested. Renal involvement was extremely heterogeneous, with a tubulointerstitial profile at presentation and slowly progressive renal decline throughout adulthood as hallmarks of the disease. In 24 patients tested, there were cysts (≤5 per kidney) in 15, a solitary kidney in 5, hypokalemia in 11, and hypomagnesemia in 10 of 16 tested, all as characteristics pointing to HNF1B disease. Two patients presented with renal Fanconi syndrome and, overall, 4 progressed to end-stage renal failure. Extrarenal phenotypes consisted of diabetes mellitus in 13 of the 27 patients, including 11 with MODY, abnormal liver tests in 8 of 21, diverse genital tract abnormalities in 5 of 13 females, and infertility in 2 of 14 males. Thus, our findings provide data that are useful for recognition and diagnosis of HNF1B disease in adulthood and might help in renal management and genetic counseling.