Assessment of high-sensitivity C-reactive protein levels as diagnostic discriminator of maturity-onset diabetes of the young due to HNF1A mutations

An alternative approach using hs-CRP levels and age of onset in diagnostics of HNF1A-MODY

AIMS

The aim is to identify people with HNF1A-MODY among individuals in diabetic cohort solely based on low hs-CRP serum level and early diabetes onset.

METHODS

In 3537 participants, we analyzed the hs-CRP levels. We analyzed the HNF1A gene in 50 participants (1.4% of the cohort) with type 1 or type 2 diabetes who had hs-CRP ≤0.25 mg/L and were diagnosed with diabetes mellitus (DM) at the age of 8-40 years. We functionally characterized two identified missense variants.

RESULTS

Three participants had a rare variant in the HNF1A gene, two of which we classified as likely pathogenic: c.1369_1384dup (p.Val462Aspfs*92) and c.737T>G (p.Val246Gly), and one as likely benign: c.1573A>T (p.Thr525Ser). Our functional studies revealed that p.Val246Gly decreased HNF1α transactivation activity to ~59% and the DNA binding ability to ~16% of the wild-type, while p.Thr525Ser variant showed no effect on transactivation activity, DNA binding, nor nuclear localization. Based on the two identified HNF1A-MODY patients among 3537 people with diabetes, we estimate 0.057% as the minimal HNF1A-MODY prevalence in Slovakia. A positive predictive value of hs-CRP ≤0.25 mg/L for finding HNF1A-MODY individuals was 4.0% (95% CI 0.7%, 13.5%).

CONCLUSIONS

Hs-CRP value and age of DM onset could be an alternative approach to current diagnostic criteria with a potential to increase the diagnostic rate of HNF1A-MODY.

The use of precision diagnostics for monogenic diabetes: a systematic review and expert opinion

BACKGROUND

Monogenic diabetes presents opportunities for precision medicine but is underdiagnosed. This review systematically assessed the evidence for (1) clinical criteria and (2) methods for genetic testing for monogenic diabetes, summarized resources for (3) considering a gene or (4) variant as causal for monogenic diabetes, provided expert recommendations for (5) reporting of results; and reviewed (6) next steps after monogenic diabetes diagnosis and (7) challenges in precision medicine field.

METHODS

Pubmed and Embase databases were searched (1990-2022) using inclusion/exclusion criteria for studies that sequenced one or more monogenic diabetes genes in at least 100 probands (Question 1), evaluated a non-obsolete genetic testing method to diagnose monogenic diabetes (Question 2). The risk of bias was assessed using the revised QUADAS-2 tool. Existing guidelines were summarized for questions 3-5, and review of studies for questions 6-7, supplemented by expert recommendations. Results were summarized in tables and informed recommendations for clinical practice.

RESULTS

There are 100, 32, 36, and 14 studies included for questions 1, 2, 6, and 7 respectively. On this basis, four recommendations for who to test and five on how to test for monogenic diabetes are provided. Existing guidelines for variant curation and gene-disease validity curation are summarized. Reporting by gene names is recommended as an alternative to the term MODY. Key steps after making a genetic diagnosis and major gaps in our current knowledge are highlighted.

CONCLUSIONS

We provide a synthesis of current evidence and expert opinion on how to use precision diagnostics to identify individuals with monogenic diabetes.

De novo HNF1A mutation of young maturity-onset diabetes 3 of a young girl-Case report

Young maturity-onset diabetes of the young type3(MODY3) as a special type of diabetes, the probability of diagnosis is low. This article reports on a case and reviews the relevant knowledge of the disease. We report an 11-year-and-11-month-old girl whose grandmother died from diabetic complications while the rest of the families were non-diabetes. The proband was initially treated with insulin and metformin but the threatment proved inefficient. After an exome-targeted capture sequencing test, she was diagnosed with mature-onset diabetes of young type 3 (MODY3), and sulfonylureas make sense. The key to mody treatment is a correct and timely diagnosis, which contributes to helping patients overcome the problems of MODY3, especially for blood sugar control.

Fruit and Vegetable Consumption Interacts With HNF1A Variants on the C-Reactive Protein

Epidemiological studies have demonstrated the inverse association between the intake of fruits and vegetables and inflammation. However, the mechanisms by which inflammation-related genes interact with fruit and vegetable intake and the role of these combinations in inflammation remain unclear. Therefore, we assessed the effect of interactions between fruit and vegetable intake and the hepatic nuclear factor 1 alpha (HNF1A) genetic variants on the C-reactive protein (CRP) levels. Baseline data from the Ansan and Ansung Cohort Study of the Korean Genome and Epidemiology Study (KoGES) were used. A total of 7,634 participants (3,700 men and 3,934 women) were included in the analyses. Fruit and vegetable intake was assessed using semi-quantitative food frequency questionnaire data. Genotyping information for HNF1A was extracted from the Affymetrix Genome-Wide Human SNP array 5.0. Inflammation was determined after overnight fasting by measuring CRP levels using automated analyzers. Multivariable logistic regression was used to estimate the adjusted odds ratio (AOR) with a 95% confidence interval (CI). In the fully adjusted model, men and women with the GG genotype of HNF1A rs2393791 and high fruit intake had lower odds of elevated CRP levels compared to those with the AA genotype and low fruit intake (AOR 0.50, 95% CI 0.38–0.67; AOR 0.73, 95% CI 0.55–0.97, respectively). Men and women with the rs2393791 GG genotype and high vegetable intake had lower odds of having elevated CRP levels compared to those with the AA genotype and low fruit intake (AOR 0.57, 95% CI 0.43–0.75; AOR 0.65, 95% CI 0.49–0.86, respectively). Men and women with the GG genotype and high total fruit and vegetable intake had lower odds of having elevated CRP levels. These findings indicate that fruit and vegetable intake interacts with HNF1A genetic polymorphisms, consequently influencing the inflammation levels.

HNF1A Mutations and Beta Cell Dysfunction in Diabetes

Understanding the genetic factors of diabetes is essential for addressing the global increase in type 2 diabetes. HNF1A mutations cause a monogenic form of diabetes called maturity-onset diabetes of the young (MODY), and HNF1A single-nucleotide polymorphisms are associated with the development of type 2 diabetes. Numerous studies have been conducted, mainly using genetically modified mice, to explore the molecular basis for the development of diabetes caused by HNF1A mutations, and to reveal the roles of HNF1A in multiple organs, including insulin secretion from pancreatic beta cells, lipid metabolism and protein synthesis in the liver, and urinary glucose reabsorption in the kidneys. Recent studies using human stem cells that mimic MODY have provided new insights into beta cell dysfunction. In this article, we discuss the involvement of HNF1A in beta cell dysfunction by reviewing previous studies using genetically modified mice and recent findings in human stem cell-derived beta cells.

Maturity Onset Diabetes of the Young-New Approaches for Disease Modelling

Maturity-onset diabetes of the young (MODY) is a genetically heterogeneous group of monogenic endocrine disorders that is characterised by autosomal dominant inheritance and pancreatic β-cell dysfunction. These patients are commonly misdiagnosed with type 1 or type 2 diabetes, as the clinical symptoms largely overlap. Even though several biomarkers have been tested none of which could be used as single clinical discriminator. The correct diagnosis for individuals with MODY is of utmost importance, as the applied treatment depends on the gene mutation or is subtype-specific. Moreover, in patients with HNF1A-MODY, additional clinical monitoring can be included due to the high incidence of vascular complications observed in these patients. Finally, stratification of MODY patients will enable better and newer treatment options for MODY patients, once the disease pathology for each patient group is better understood. In the current review the clinical characteristics and the known disease-related abnormalities of the most common MODY subtypes are discussed, together with the up-to-date applied diagnostic criteria and treatment options. Additionally, the usage of pluripotent stem cells together with CRISPR/Cas9 gene editing for disease modelling with the possibility to reveal new pathophysiological mechanisms in MODY is discussed.

Monogenic diabetes: a gateway to precision medicine in diabetes

Monogenic diabetes refers to diabetes mellitus (DM) caused by a mutation in a single gene and accounts for approximately 1%-5% of diabetes. Correct diagnosis is clinically critical for certain types of monogenic diabetes, since the appropriate treatment is determined by the etiology of the disease (e.g., oral sulfonylurea treatment of HNF1A/HNF4A-diabetes vs. insulin injections in type 1 diabetes). However, achieving a correct diagnosis requires genetic testing, and the overlapping of the clinical features of monogenic diabetes with those of type 1 and type 2 diabetes has frequently led to misdiagnosis. Improvements in sequencing technology are increasing opportunities to diagnose monogenic diabetes, but challenges remain. In this Review, we describe the types of monogenic diabetes, including common and uncommon types of maturity-onset diabetes of the young, multiple causes of neonatal DM, and syndromic diabetes such as Wolfram syndrome and lipodystrophy. We also review methods of prioritizing patients undergoing genetic testing, and highlight existing challenges facing sequence data interpretation that can be addressed by forming collaborations of expertise and by pooling cases.

MODY patients exhibit shorter telomere length than non-diabetic subjects

BACKGROUND

Given the increasing evidence supporting the association between telomere shortening and diabetes, the aim of the present work was to establish whether MODY patients suffer a reduction in telomere lenght (TL) due to oxidative stress produced by chronic hyperglycemia, despite not presenting insulin resistance or inflammation.

METHODS

We analysed clinical and biochemical parameters in 35 MODY2 and 12 MODY3 patients compared with 48 control subjects. The absolute telomere length (aTL) of peripheral blood leukocytes was measured using the quantitative polymerase chain reaction (qPCR).

RESULTS

A significant negative correlation was observed between aTL and age in the whole population, among MODY patients and in each subtype studied, MODY2 and MODY3, which allowed us to validate the method. We found, for the first time, that MODY patients have shorter aTL with respect to non-diabetic controls (6.49 ± 3.31 kbp vs 11.13 ± 7.82 kbp, p = .006). However, no differences were found between MODY2 and MODY3. In addition, aTL showed a negative correlation with duration of the disease and fasting plasma glucose (FPG) levels in MODY patients in general and also with HbA1c in MODY2 patients in particular.

CONCLUSIONS

Both MODY2 and MODY3 types present telomere shortening, which, at least partly, responds to HbA1c and FPG levels. These findings suggest comparable mechanisms underlying the attrition of TL. Taken together, our results on aTL in MODY patients may provide a parameter relatively easy and inexpensive to quantify in order to measure the impact of high glucose levels and potentially carry out antidiabetic treatment with stricter targets.

Searching Far and Genome-Wide: The Relevance of Association Studies in Amyotrophic Lateral Sclerosis

Genome-wide association studies (GWAS) and rare variant association studies (RVAS) are applied across many areas of complex disease to analyze variation in whole genomes of thousands of unrelated patients. These approaches are able to identify variants and/or biological pathways which are associated with disease status and, in contrast to traditional linkage studies or candidate gene approaches, do so without requiring multigenerational affected families, prior hypotheses, or known genes of interest. However, the novel associations identified by these methods typically have lower effect sizes than those found in classical family studies. In the motor neuron disease amyotrophic lateral sclerosis (ALS), GWAS, and RVAS have been used to identify multiple disease-associated genes but have not yet resulted in novel therapeutic interventions. There is significant urgency within the ALS community to identify additional genetic markers of disease to uncover novel biological mechanisms, stratify genetic subgroups of disease, and drive drug development. Given the widespread and increasing application of genetic association studies of complex disease, it is important to recognize the strengths and limitations of these approaches. Here, we review ALS gene discovery via GWAS and RVAS.

Incidence of HNF1A and GCK MODY Variants in a South African Population

BACKGROUND AND AIM

Maturity-onset diabetes of the young (MODY) is the result of single gene variants. To date, fourteen different MODY subtypes have been described. Variants in genes coding for glucokinase (GCK, MODY2) and hepatic nuclear factor 1 alpha (HNF1A, MODY3) are most frequently encountered. MODY patients are often misdiagnosed with type 1 or type 2 diabetes, resulting in incorrect treatment protocols. At the time of reporting, no data are available on MODY prevalence in populations from Africa. Our study aimed to investigate and report on the incidence of MODY-related variants, specifically HNF1A variants, in a population from the Western Cape.

METHODS

Study participants were recruited (1643 in total, 407 males, 1236 females) and underwent anthropometric tests. Thereafter, blood was collected, and real-time PCR was used to screen for specific variants in HNF1A and GCK genes.

RESULTS

Ninety-seven individuals (5.9%) were identified with a specific HNF1A gene polymorphism (rs1169288) and twelve (0.9%) with a GCK polymorphism (rs4607517).

CONCLUSION

In total, 6.6% of the study population expressed MODY variants. To our knowledge, we are the first to report on MODY incidence in Africa. This research provides the basis for MODY incidence studies in South Africa, as well as data on non-Caucasian populations.

Clinical implications of the glucokinase impaired function - GCK MODY today

Heterozygous inactivating mutations of the glucokinase (GCK) gene are causing GCK-MODY, one of the most common forms of the Maturity Onset Diabetes of the Young (MODY). GCK-MODY is characterized by fasting hyperglycemia without apparent worsening with aging and low risk for chronic vascular complications. Despite the mild clinical course, GCK-MODY could be misdiagnosed as type 1 or type 2 diabetes. In the diagnostic process, the clinical suspicion is often based on the clinical diagnostic criteria for GCK-MODY and should be confirmed by DNA analysis. However, there are several issues in the clinical and also in genetic part that could complicate the diagnostic process. Most of the people with GCK-MODY do not require any pharmacotherapy. The exception are pregnant women with a fetus which did not inherit GCK mutation from the mother. Such a child has accelerated growth, and has increased risk for diabetic foetopathy. In this situation the mother should be treated with substitutional doses of insulin. Therefore, distinguishing GCK-MODY from gestational diabetes in pregnancy is very important. For this purpose, special clinical diagnostic criteria for clinical identification of GCK-MODY in pregnancy are used. This review updates information on GCK-MODY and discusses several currently not solved problems in the clinical diagnostic process, genetics, and treatment of this type of monogenic diabetes.

Update on Monogenic Diabetes in Korea

Monogenic diabetes, including maturity-onset diabetes of the young, neonatal diabetes, and other rare forms of diabetes, results from a single gene mutation. It has been estimated to represent around 1% to 6% of all diabetes. With the advances in genome sequencing technology, it is possible to diagnose more monogenic diabetes cases than ever before. In Korea, 11 studies have identified several monogenic diabetes cases, using Sanger sequencing and whole exome sequencing since 2001. The recent largest study, using targeted exome panel sequencing, found a molecular diagnosis rate of 21.1% for monogenic diabetes in clinically suspected patients. Mutations in glucokinase (GCK), hepatocyte nuclear factor 1α (HNF1A), and HNF4A were most commonly found. Genetic diagnosis of monogenic diabetes is important as it determines the therapeutic approach required for patients and helps to identify affected family members. However, there are still many challenges, which include a lack of simple clinical criterion for selecting patients for genetic testing, difficulties in interpreting the genetic test results, and high costs for genetic testing. In this review, we will discuss the latest updates on monogenic diabetes in Korea, and suggest an algorithm to screen patients for genetic testing. The genetic tests and non-genetic markers for accurate diagnosis of monogenic diabetes will be also reviewed.

Homozygous Hypomorphic HNF1A Alleles Are a Novel Cause of Young-Onset Diabetes and Result in Sulfonylurea-Sensitive Diabetes

OBJECTIVE

Heterozygous loss-of-function mutations in HNF1A cause maturity-onset diabetes of the young (MODY). Affected individuals can be treated with low-dose sulfonylureas. Individuals with homozygous HNF1A mutations causing MODY have not been reported.

RESEARCH DESIGN AND METHODS

We phenotyped a kindred with young-onset diabetes and performed molecular genetic testing, a mixed meal tolerance test, a sulfonylurea challenge, and in vitro assays to assess variant protein function.

RESULTS

A homozygous HNF1A variant (p.A251T) was identified in three insulin-treated family members diagnosed with diabetes before 20 years of age. Those with the homozygous variant had low hs-CRP levels (0.2-0.8 mg/L), and those tested demonstrated sensitivity to sulfonylurea given at a low dose, completely transitioning off insulin. In silico modeling predicted a variant of unknown significance; however, in vitro studies supported a modest reduction in transactivation potential (79% of that for the wild type; P < 0.05) in the absence of endogenous HNF1A.

CONCLUSIONS

Homozygous hypomorphic HNF1A variants are a cause of HNF1A-MODY. We thus expand the allelic spectrum of variants in dominant genes causing diabetes.

New clinical screening strategy to distinguish HNF1A variant-induced diabetes from young early-onset type 2 diabetes in a Chinese population

OBJECTIVE

Maturity-onset diabetes of the young caused by hepatocyte nuclear factor-1 alpha (HNF1A) variants (HNF1A-MODY) is a common form of monogenetic diabetes. Although patients with HNF1A-MODY might specifically benefit from sulfonylurea treatment, available methods for screening this specific type of diabetes are not cost-effective. This study was designed to establish an optimized clinical strategy based on multiple biomarkers to distinguish patients with HNF1A-MODY from clinically diagnosed early-onset type 2 diabetes (EOD) for genetic testing in a Chinese population.

RESEARCH DESIGN AND METHODS

A case-control study including 125 non-related young patients with EOD and 15 probands with HNF1A-MODY (cohort 1) was conducted to evaluate reported biomarkers for HNF1A-MODY. A cut-off for the fasting insulin (Fins) level, the 97.5 percentile of 150 healthy subjects with normal components of metabolic syndrome (cohort 2), was used to filter out individuals with obvious insulin resistance (Fins <102 pmol/L). An optimized clinical screening strategy (HNF1A-CSS) was established, and its effectiveness was assessed in another group of 410 young patients with EOD (cohort 3).

RESULTS

In cohort 1, body mass index (BMI), serum high-density lipoprotein cholesterol (HDL-c) and high-sensitivity C reactive protein (hs-CRP) levels were confirmed to be useful for the differential diagnosis of HNF1A-MODY. In cohort 3, eight probands with HNF1A-MODY were identified. In cohort 3 and young relatives with HNF1A-MODY, meeting three of four criteria (BMI <28 kg/m², hs-CRP <0.75 mg/L, Fins <102 pmol/L and HDL-c >1.12 mmol/L), the sensitivity and specificity of HNF1A-CSS were 100% and 69.3%, respectively. In the pooled analysis of all young patients, HNF1A-CSS displayed 90.5% sensitivity and 73.6% specificity for identifying patients with HNF1A-MODY among those with clinically diagnosed EOD.

CONCLUSION

Our HNF1A-CSS is useful for distinguishing patients with HNF1A-MODY from patients with EOD in a young Chinese population.

Novel insights into genetics and clinics of the HNF1A-MODY

MODY (Maturity Onset Diabetes of the Young) is a type of diabetes resulting from a pathogenic effect of gene mutations. Up to date, 13 MODY genes are known. Gene HNF1A is one of the most common causes of MODY diabetes (HNF1A-MODY; MODY3). This gene is polymorphic and more than 1200 pathogenic and non-pathogenic HNF1A variants were described in its UTRs, exons and introns. For HNF1A-MODY, not just gene but also phenotype heterogeneity is typical. Although there are some clinical instructions, HNF1A-MODY patients often do not meet every diagnostic criteria or they are still misdiagnosed as type 1 and type 2 diabetics. There is a constant effort to find suitable biomarkers to help with in distinguishing of MODY3 from Type 1 Diabetes (T1D) and Type 2 Diabetes (T2D). DNA sequencing is still necessary for unambiguous confirmation of clinical suspicion of MODY. NGS (Next Generation Sequencing) methods brought discoveries of multiple new gene variants and new instructions for their pathogenicity classification were required. The most actual problem is classification of variants with uncertain significance (VUS) which is a stumbling-block for clinical interpretation. Since MODY is a hereditary disease, DNA analysis of family members is helpful or even crucial. This review is updated summary about HNF1A-MODY genetics, pathophysiology, clinics functional studies and variant classification.

Update on clinical screening of maturity-onset diabetes of the young (MODY)

BACKGROUND

Maturity-onset diabetes of the young (MODY) is the most common type of monogenic diabetes, being characterized by beta-cell disfunction, early onset, and autosomal dominant inheritance. Despite the rapid evolution of molecular diagnosis methods, many MODY cases are misdiagnosed as type 1 or type 2 diabetes. High costs of genetic testing and limited knowledge of MODY as a relevant clinical entity are some of the obstacles that hinder correct MODY diagnosis and treatment. We present a broad review of clinical syndromes related to most common MODY subtypes, emphasizing the role of biomarkers that can help improving the accuracy of clinical selection of candidates for molecular diagnosis.

MAIN BODY

To date, MODY-related mutations have been reported in at least 14 different genes. Mutations in glucokinase (GCK), hepatocyte nuclear factor-1 homeobox A (HNF1A), and hepatocyte nuclear factor-4 homeobox A (HNF4A) are the most common causes of MODY. Accurate etiological diagnosis can be challenging. Many biomarkers such as apolipoprotein-M (ApoM), aminoaciduria, complement components, and glycosuria have been tested, but have not translated into helpful diagnostic tools. High-sensitivity C-reactive protein (hs-CRP) levels are lower in HNF1A-MODY and have been tested in some studies to discriminate HNF1A-MODY from other types of diabetes, although more data are needed. Overall, presence of pancreatic residual function and absence of islet autoimmunity seem the most promising clinical instruments to select patients for further investigation.

CONCLUSIONS

The selection of diabetic patients for genetic testing is an ongoing challenge. Metabolic profiling, diabetes onset age, pancreatic antibodies, and C-peptide seem to be useful tools to better select patients for genetic testing. Further studies are needed to define cut-off values in different populations.

Response to multiple glucose-lowering agents in a sib-pair with a novel HNF1α (MODY3) variant

Maturity-onset diabetes of the young (MODY) is a genetically and clinically heterogeneous group of disorders characterised by early onset, lean, non-autoimmunity mediated, non-insulin-dependent diabetes often with autosomal-dominant inheritance and specific pharmaco-genetic response. We describe two siblings with HNF1A-MODY (MODY3) due to a novel germline variant p.(His126Asp) which segregates with diabetes in the family. However, contrary to anticipated therapeutic response, blood glucose in this sib-pair did not respond to sulphonylureas (both low and high dose), dipeptidyl peptidase-4 inhibitors (DPP-4 inhibitors), and glucagon-like peptide-1 receptor agonists (GLP-1RA), also known as incretin mimetics. The unexpected limited pharmaco-therapeutic response could potentially be unique to this specific variant and/or progressive pancreatic β-cell failure associated with long-standing disease duration, higher BMI and glucose-toxicity. Therefore, we report a novel-variant MODY3 sib-pair with atypical pharmaco-therapeutic response i.e. resistant to multiple anti-diabetes agents namely sulphonylurea, DPP-4 inhibitors and GLP-1RA treatment.

Benefits and limitations of genome-wide association studies

Genome-wide association studies (GWAS) involve testing genetic variants across the genomes of many individuals to identify genotype-phenotype associations. GWAS have revolutionized the field of complex disease genetics over the past decade, providing numerous compelling associations for human complex traits and diseases. Despite clear successes in identifying novel disease susceptibility genes and biological pathways and in translating these findings into clinical care, GWAS have not been without controversy. Prominent criticisms include concerns that GWAS will eventually implicate the entire genome in disease predisposition and that most association signals reflect variants and genes with no direct biological relevance to disease. In this Review, we comprehensively assess the benefits and limitations of GWAS in human populations and discuss the relevance of performing more GWAS.

Maturity-onset diabetes of the young: From a molecular basis perspective toward the clinical phenotype and proper management

Maturity-onset diabetes of the young (MODY) comprises a heterogeneous group of monogenic disorders characterized by primary defect in pancreatic β-cell function, early onset and autosomal dominant inheritance, accounting for about 1-5% of all diabetes diagnoses. Mutations in 14 genes are responsible for the majority of all MODY cases described so far. The clinical phenotype relies on genetic defects, with important implications in the optimal treatment and prognosis definition. MODY's early diagnosis remains a challenge, since this group of inherited disorders comprises a large clinical spectrum and it usually overlaps with other types of diabetes, requiring a high index of suspicion even if the definitive statement demands a molecular genetic study. Recent advances on the genetic determinants and pathophysiology of MODY have allowed a better understanding of its underlying molecular mechanisms, providing a proper genetic counseling and early diagnosis. These new management insights will make possible to set up new therapeutic strategies, with drugs able to prevent, correct or at least delay the decline of pancreatic β-cell function, thus affording for a more personalized treatment and, ultimately, for a better patient care.

Using Clinical Indices to Distinguish MODY2 (GCK Mutation) and MODY3 (HNF1A Mutation) from Type 1 Diabetes in a Young Chinese Population

INTRODUCTION

Accurate diagnosis of maturity-onset diabetes of the young (MODY) is required in order to select appropriate treatment options and to assess prognosis. The aim of this study was to explore potential clinical indicators that could be used to differentiate MODY2, MODY3, and type 1 diabetes (T1D) in young subjects.

METHODS

Twelve patients with MODY3 and 29 patients with MODY2 were characterized and compared to 26 patients with T1D. These three groups were matched for age and gender. Clinical profiles of the 67 patients were collected. Receiver operating characteristic (ROC) curves were used to identify the optimal cutoff values of clinical indicators.

RESULTS

Compared to patients with T1D, subjects with MODY3 had higher fasting C-peptide levels (1.34 ± 1.51 vs. 0.29 ± 0.22 ng/mL; P  < 0.001) and lower high-sensitivity C-reactive protein (hsCRP) levels (0.18 ± 0.15 vs. 1.22 ± 1.49 mg/L, P  = 0.004); patients with MODY2 had lower hsCRP (0.37 ± 0.39 vs. 1.22 ± 1.49 mg/L; P  = 0.003), total cholesterol (4.12 ± 0.68 vs. 4.61 ± 0.81 mmol/L, P  = 0.034), and low-density lipoprotein cholesterol (LDL-C) (2.24 ± 0.68 vs. 2.67 ± 0.79 ng/L, P  = 0.002) levels and higher fasting C-peptide levels (0.96 ± 0.42 vs. 0.29 ± 0.22 ng/mL, P  = 0.002). The ROC-derived hsCRP values for discriminating MODY2 from T1D, MODY3 from T1D, and MODY3 from MODY2 were 0.675, 0.833, and 0.763, respectively. The ROC-derived fasting C-peptide levels for discriminating MODY2 from T1D and MODY3 from T1D were 0.951 and 0.975, respectively. The ROC-derived total cholesterol and LDL-C values for discriminating MODY2 from T1D were 0.670 and 0.662, respectively; the ROC-derived triglyceride value for discriminating MODY3 from MODY2 was 0.756. Additionally, a combination of indicators permitted better discrimination of MODY subtypes than any single parameter.

CONCLUSION

Our findings suggest that fasting C-peptide, hsCRP, and lipid levels permit good discrimination among MODY2, MODY3, and T1D. These clinical indicators could be used as markers of MODY2 and MODY3 in young patients with diabetes.

Pediatric Monogenic Diabetes: A Unique Challenge and Opportunity

Monogenic diabetes affects approximately 120,000 people in the United States but continues to be misdiagnosed. Within the pediatric population, 1% to 3% of diabetes is monogenic, and early diagnosis and genetically targeted management of congenital diabetes and maturity onset diabetes of the young (MODY) can have a tremendous impact on future health outcomes and quality of life. In some of the more common monogenic diabetes types, patients can switch from insulin therapy to sulfonylureas or even discontinue glucose-lowering therapy with stable glycemic control. Advancements in the field have identified tools and resources to aid in distinguishing patients likely to have monogenic diabetes from the more common forms of type 1 and type 2 diabetes. However, genetic testing with accurate interpretation of results is necessary to confirm a diagnosis and direct treatment selection and disease management. This article discusses challenges and opportunities in monogenic diabetes in the pediatric population. [Pediatr Ann. 2019;48(8):e319-e325.].

Maturity-onset diabetes of the young (MODY): current perspectives on diagnosis and treatment

Maturity-onset diabetes of the young (MODY) is characterized by autosomal dominant inheritance, onset before 25 years of age, absence of β-cell autoimmunity, and sustained pancreatic β-cell function. To date, mutations have been identified in at least 14 different genes, including six genes encoding proteins that, respectively, correspond to MODY subtypes 1-6: hepatocyte nuclear factor (HNF) 4α (HNF4α), glucokinase (GCK), HNF1α (HNF1 α), pancreatic and duodenal homeobox 1 (PDX1), HNF1β (HNF1 β), and neurogenic differentiation 1 (NEUROD1). Diagnostic tools based on currently available genetic tests can facilitate the correct diagnosis and appropriate treatment of patients with MODY. Candidates for genetic testing include nonobese subjects with hyperglycemia, no evidence of β-cell autoimmunity, sustained β-cell function, and a strong family history of similar-type diabetes among first-degree relatives. Moreover, identification of the MODY subtype is important, given the subtype-related differences in the age of onset, clinical course and progression, type of hyperglycemia, and response to treatment. This review discusses the current perspectives on the diagnosis and treatment of MODY, particularly with regard to the six major subtypes (MODY 1-6).

Altered N-glycosylation profiles as potential biomarkers and drug targets in diabetes

N-glycosylation is a ubiquitous protein modification, and N-glycosylation profiles are emerging as both biomarkers and functional effectors in various types of diabetes. Genome-wide association studies identified glycosyltransferase genes as candidate causal genes for type 1 and type 2 diabetes. Studies focused on N-glycosylation changes in type 2 diabetes demonstrated that patients can be distinguished from healthy controls based on N-glycome composition. In addition, individuals at an increased risk of future disease development could be identified based on N-glycome profiles. Moreover, accumulating evidence indicates that N-glycans have a major role in preventing the impairment of glucose-stimulated insulin secretion by maintaining the glucose transporter in proper orientation, indicating that interindividual variation in protein N-glycosylation might be a novel risk factor contributing to diabetes development. Defective N-glycosylation of T cells has been implicated in type 1 diabetes pathogenesis. Furthermore, studies of N-glycan alterations have successfully been used to identify individuals with rare types of diabetes (such as the HNF1A-MODY), and also to evaluate functional significance of novel diabetes-associated mutations. In conclusion, both N-glycans and glycosyltransferases emerge as potential therapeutic targets in diabetes.

A decision algorithm to identify patients with high probability of monogenic diabetes due to HNF1A mutations

PURPOSE

To investigate the utility of biomarkers of maturity-onset diabetes of the young (MODY), high-sensitivity C-reactive protein (hsCRP), and 1,5-anhydroglucitol (1,5-AG) in conjunction with other clinical and laboratory features to improve diagnostic accuracy and provide a diagnostic algorithm for HNF1A MODY.

METHODS

We examined 77 patients with HNF1A MODY, 88 with GCK MODY mutations, 99 with type 1 diabetes, and 92 with type 2 diabetes. In addition to 1,5-AG and hsCRP, we considered body mass index (BMI), fasting glucose, and fasting serum C-peptide as potential biomarkers. Logistic regression and receiver operating characteristic curves were used in marker evaluation.

RESULTS

Concentration of hsCRP was lowest in HNF1A MODY (0.51 mg/l) and highest in type 2 diabetes (1.33 mg/l). The level of 1,5-AG was lowest in type 1 diabetes and HNF1A MODY, 3.8 and 4.7 μg/ml, respectively, and highest (11.2 μg/ml) in GCK MODY. In the diagnostic algorithm, we first excluded patients with type 1 diabetes based on low C-peptide (C-statistic 0.98) before using high BMI and C-peptide to identify type 2 diabetes patients (C-statistic 0.92). Finally, 1,5-AG and hsCRP in conjunction yielded a C-statistic of 0.86 in discriminating HNF1A from GCK MODY. We correctly classified 92.9% of patients with type 1 diabetes, 84.8% with type 2 diabetes, 64.9% HNF1A MODY, and 52.3% GCK MODY patients.

CONCLUSIONS

Plasma 1,5-AG and serum hsCRP do not discriminate sufficiently HNF1A MODY from common diabetes types, but could be potentially useful in prioritizing Sanger sequencing of HNF1A gene.

Screening of HNF1A and HNF4A mutation and clinical phenotype analysis in a large cohort of Chinese patients with maturity-onset diabetes of the young

AIMS

The study aimed to screen the HNF1A and HNF4A mutation in a large Chinese cohort of high clinical suspicion of maturity-onset diabetes of the young (MODY) patients and characterize the clinical features of those patients. The performance of hsCRP as a biomarker to differentiate MODY3 from early onset T2DM was also evaluated.

METHODS

A total of 74 patients with a strong clinical suspicion of MODY from 59 families and 33 newly diagnosed early-onset T2DM were included. HNF1A and HNF4A mutations were analyzed by Sanger sequencing. ROC curves were used to identify the optimal cutoff of hsCRP.

RESULTS

One novel (c.864_865insG) and six recurrent HNF1A mutations (R203H, R263H, P379T, L422P, P519L and c.873delC) in 17 patients from 8 families (13.6%), as well as one novel HNF4A (R331H) mutation were identified. Nonspecific clinical presentations were observed in MODYX compared to MODY3 patients. MODY3 subjects exhibited with younger, lower BMI, TG, fasting and postprandial C-peptide, higher HDL than T2DM. Particularly, we confirmed serum hsCRP was lower in MODY3 than T2DM. ROC curve showed a good discrimination with an AUC of 0.852 and identified a cutoff hsCRP of 0.79 (75% sensitivity and 83% specificity). Good glycemic control was observed in all identified patients after switching to glimepiride therapy.

CONCLUSIONS

The prevalence of HNF1A mutation was relatively lower in Mainland China and HNF4A mutation was rare. Serum hsCRP concentrations performed well in discriminating MODY3 from T2DM. Molecular diagnosis of MODY3/1 did transform management in clinical practice and facilitated the glycemic control.

Monogenic Forms of Diabetes Mellitus

In addition to the common types of diabetes mellitus, two major monogenic diabetes forms exist. Maturity-onset diabetes of the young (MODY) represents a heterogenous group of monogenic, autosomal dominant diseases. MODY accounts for 1-2% of all diabetes cases, and it is not just underdiagnosed but often misdiagnosed to type 1 or type 2 diabetes. More than a dozen MODY genes have been identified to date, and their molecular classification is of great importance in the correct treatment decision and in the judgment of the prognosis. The most prevalent subtypes are HNF1A, GCK, and HNF4A. Genetic testing for MODY has changed recently due to the technological advancements, as contrary to the sequential testing performed in the past, nowadays all MODY genes can be tested simultaneously by next-generation sequencing. The other major group of monogenic diabetes is neonatal diabetes mellitus which can be transient or permanent, and often the diabetes is a part of a syndrome. It is a severe monogenic disease appearing in the first 6 months of life. The hyperglycemia usually requires insulin. There are two forms, permanent neonatal diabetes mellitus (PNDM) and transient neonatal diabetes mellitus (TNDM). In TNDM, the diabetes usually reverts within several months but might relapse later in life. The incidence of NDM is 1:100,000-1:400,000 live births, and PNDM accounts for half of the cases. Most commonly, neonatal diabetes is caused by mutations in KCNJ11 and ABCC8 genes encoding the ATP-dependent potassium channel of the β cell. Neonatal diabetes has experienced a quick and successful transition into the clinical practice since the discovery of the molecular background. In case of both genetic diabetes groups, recent guidelines recommend genetic testing.

Traditional clinical criteria outperform high-sensitivity C-reactive protein for the screening of hepatic nuclear factor 1 alpha maturity-onset diabetes of the young among young Asians with diabetes

BACKGROUND

Young adults with diabetes in Asia represent a heterogeneous group. Using traditional clinical criteria to preselect individuals for testing for maturity-onset diabetes of the young (MODY) may exclude a large proportion from testing. High-sensitivity C-reactive protein (hs-CRP) has shown promise as a biomarker to differentiate hepatic nuclear factor 1 alpha (HNF1A)-MODY from type 2 diabetes. We aimed to compare the use of hs-CRP as a biomarker versus traditional criteria, to guide testing for HNF1A-MODY among a cohort of young adults with diabetes in Singapore.

METHODS

A total of 252 adults (age of onset ⩽45 years) and 20 children with diabetes were recruited. Using traditional criteria (family history of diabetes and onset of diabetes ⩽25 years) and an hs-CRP cut off of ⩽0.5 mg/l, 125 and 37 adults, respectively, were identified for HNF1A gene testing. All children underwent HNF1A gene testing.

RESULTS

Five adults (5/143, 3.5%) with HNF1A-MODY were identified. There were no HNF1A gene mutations among the children. Traditional criteria correctly identified all five HNF1A-MODY individuals (5/125, 4%), while applying an hs-CRP level of ⩽0.5 mg/l selected just 1 of these 5 for HNF1A gene testing (1/37, 2.7%). None of those with a positive GAD antibody or undetectable C-peptide level had HNF1A-MODY.

CONCLUSION

The use of hs-CRP to guide screening for HNF1A-MODY among Asian young adults with diabetes did not improve the diagnostic yield. Applying a combination of age of onset of diabetes under 25 years and a family history of diabetes alone could guide targeted HNF1A-MODY screening in Asians, with an expected yield of 4% diagnosed with HNF1A-MODY among those screened.

Can Biomarkers Help Target Maturity-Onset Diabetes of the Young Genetic Testing in Antibody-Negative Diabetes?

BACKGROUND

Maturity-onset diabetes of the young (MODY) is an antibody-negative, autosomal dominant form of diabetes. With the increasing prevalence of diabetes and the expense of MODY testing, markers to identify those who need further genetic testing would be beneficial. We investigated whether HLA genotypes, random C-peptide, and/or high-sensitivity C-reactive protein (hsCRP) levels could be helpful biomarkers for identifying MODY in antibody-negative diabetes.

METHODS

Subjects (N = 97) with diabetes onset ≤age 25, measurable C-peptide (≥0.1 ng/mL), and negative for all four diabetes autoantibodies were enrolled at a large academic center and tested for MODY 1-5 through Athena Diagnostics. A total of 22 subjects had a positive or very likely pathogenic mutation for MODY.

RESULTS

Random C-peptide levels were significantly different between MODY-positive and MODY-negative subjects (0.16 nmol/L vs. 0.02 nmol/L; P = 0.02). After adjusting for age and diabetes duration, hsCRP levels were significantly lower in MODY-positive subjects (0.37 mg/L vs. 0.87 mg/L; P = 0.02). Random C-peptide level ≥0.15 nmol/L obtained at ≥6 months after diagnosis had 83% sensitivity for diagnosis of MODY with a negative predictive value of 96%. Receiver operating characteristic curves showed that area under the curve for random C-peptide (0.75) was significantly better than hsCRP (0.54), high-risk HLA DR3/4-DQB1*0302 (0.59), and high-risk HLA/random C-peptide combined (0.54; P = 0.03).

CONCLUSIONS

Random C-peptide obtained at ≥6 months after diagnosis can be a useful biomarker to identify antibody-negative individuals who need further genetic testing for MODY, whereas hsCRP and HLA do not appear to improve this antibody/C-peptide-based approach.

Hepatocyte nuclear factors as possible C-reactive protein transcriptional inducer in the liver and white adipose tissue of rats with experimental chronic renal failure

Inflammation related to chronic kidney disease (CKD) is an important clinical problem. We recently determined that hepatocyte nuclear factor 1α (HNF1α) was upregulated in the livers of chronic renal failure (CRF) rats—experimental model of CKD. Considering that the promoter region of gene encoding C-reactive protein (CRP) contains binding sites for HNF1α and that the loss-of-function mutation in the Hnfs1α leads to significant reduction in circulating CRP levels, we hypothesized that HNF1α can activate the Crp in CRF rats. Here, we found coordinated upregulation of genes encoding CRP, interleukin-6 (IL-6), HNF1α, and HNF4α in the livers and white adipose tissue (WAT) of CRF rats, as compared to the pair-fed and control animals. This was accompanied by elevated serum levels of CRP and IL-6. CRP and HNFs’ mRNA levels correlated positively with CRP and HNFs’ protein levels in the liver and WAT. Similar upregulation of the Crp, Il-6, and Hnfs in the liver and WAT and increased serum CRP and IL-6 concentrations were found in lipopolysaccharide (LPS)-induced systemic inflammation in rats. Moreover, silencing HNF1α in HepG2 cells by small interfering RNA led to decrease in CRP mRNA levels. Our results suggests that (a) HNFs act in concert with IL-6 in the upregulation of CRP production by the liver and WAT, leading to an increase in circulating CRP concentration in CRF rats and (b) CRF-related inflammation plays an important role in the upregulation of genes that encode HNFs and CRP in the liver and WAT of CRF rats.

Successful maintenance on sulphonylurea therapy and low diabetes complication rates in a HNF1A-MODY cohort

AIMS

HNF1A gene mutations are the most common cause of maturity-onset diabetes of the young (MODY) in the UK. Persons with HNF1A-MODY display sensitivity to sulphonylurea therapy; however, the long-term efficacy is not established. There is limited literature as to the prevalence of micro- and macrovascular complications in this unique cohort. The aim of this study was to determine the natural progression and clinical management of HNF1A-MODY diabetes in a dedicated MODY clinic.

METHODS

Sixty patients with HNF1A-MODY and a cohort of 60 BMI-, age-, ethnicity- and diabetes duration-matched patients with Type 1 diabetes mellitus participated in the study. All patients were phenotyped in detail. Clinical follow-up of the HNF1A-MODY cohort occurred on a bi-annual basis.

RESULTS

Following a genetic diagnosis of MODY, the majority of the cohort treated with sulphonylurea therapy remained insulin independent at 84-month follow-up (80%). The HbA1c in the HNF1A-MODY group treated with sulphonylurea therapy alone improved significantly over the study period [from 49 (44-63) mmol/mol, 6.6 (6.2-7.9)% to 41 (31-50) mmol/mol, 5.9 (5-6.7)%; P = 0.003]. The rate of retinopathy was significantly lower than that noted in the Type 1 diabetes mellitus group (13.6 vs. 50%; P = 0.0001).There was also a lower rate of microalbuminuria and cardiovascular disease in the HNF1A-MODY group compared with the Type 1 diabetes mellitus group.

CONCLUSIONS

This study demonstrates that the majority of patients with HNF1A-MODY can be maintained successfully on sulphonylurea therapy with good glycaemic control. We note a significantly lower rate of micro- and macrovascular complications than reported previously. The use of appropriate therapy at early stages of the disorder may decrease the incidence of complications.

Increased Oxidative Stress and Inflammation Independent of Body Adiposity in Diabetic and Nondiabetic Controls in falciparum Malaria

Information on the extent to which oxidative stress and inflammation occur in the presence of falciparum malaria and type 2 diabetes mellitus in the same individual is limited. This study sought to investigate the extent of inflammation and oxidative stress in adult uncomplicated malaria by measuring fasting levels of lipid peroxides, C-reactive protein (CRP), and total antioxidant power (TAP) before and during falciparum malaria, in 100 respondents with type 2 diabetes and 100 age-matched controls in the Cape Coast metropolis of Ghana. Also, body adiposity index, body mass index, and waist-to-hip ratio were computed. Before and during falciparum malaria, diabetes patients exhibited higher (P < 0.05) levels of CRP and peroxides than controls but TAP and BAI were comparable (P > 0.05) between the two groups. Baseline CRP correlated positively (r = 0.341, P = 0.002) with peroxide only in the diabetic group. During malaria, TAP level in both study groups declined (P < 0.05) by 80% of their baseline levels. CRP correlated negatively (r = −0.352, P = 0.011) with TAP in the control but not the diabetic group. Uncomplicated falciparum malaria elevated inflammation and peroxidation but decreased antioxidant power independent of adiposity. This finding may have implication on cardiovascular health.

When is it MODY? Challenges in the Interpretation of Sequence Variants in MODY Genes

The genomics revolution has raised more questions than it has provided answers. Big data from large population-scale resequencing studies are increasingly deconstructing classic notions of Mendelian disease genetics, which support a simplistic correlation between mutational severity and phenotypic outcome. The boundaries are being blurred as the body of evidence showing monogenic disease-causing alleles in healthy genomes, and in the genomes of individu-als with increased common complex disease risk, continues to grow. In this review, we focus on the newly emerging challenges which pertain to the interpretation of sequence variants in genes implicated in the pathogenesis of maturity-onset diabetes of the young (MODY), a presumed mono-genic form of diabetes characterized by Mendelian inheritance. These challenges highlight the complexities surrounding the assignments of pathogenicity, in particular to rare protein-alerting variants, and bring to the forefront some profound clinical diagnostic implications. As MODY is both genetically and clinically heterogeneous, an accurate molecular diagnosis and cautious extrapolation of sequence data are critical to effective disease management and treatment. The biological and translational value of sequence information can only be attained by adopting a multitude of confirmatory analyses, which interrogate variant implication in disease from every possible angle. Indeed, studies which have effectively detected rare damaging variants in known MODY genes in normoglycemic individuals question the existence of a sin-gle gene mutation scenario: does monogenic diabetes exist when the genetic culprits of MODY have been systematical-ly identified in individuals without MODY?

Hepatocyte Nuclear Factor 1A Is a Cell-Intrinsic Transcription Factor Required for B Cell Differentiation and Development in Mice

The hepatocyte NF (HNF) family of transcription factors regulates the complex gene networks involved in lipid, carbohydrate, and protein metabolism. In humans, HNF1A mutations cause maturity onset of diabetes in the young type 3, whereas murine HNF6 participates in fetal liver B lymphopoiesis. In this study, we have identified a crucial role for the prototypical member of the family HNF1A in adult bone marrow B lymphopoiesis. HNF1A(-/-) mice exhibited a clear reduction in total blood and splenic B cells and a further pronounced one in transitional B cells. In HNF1A(-/-) bone marrow, all B cell progenitors-from pre-pro-/early pro-B cells to immature B cells-were dramatically reduced and their proliferation rate suppressed. IL-7 administration in vivo failed to boost B cell development in HNF1A(-/-) mice, whereas IL-7 stimulation of HNF1A(-/-) B cell progenitors in vitro revealed a marked impairment in STAT5 phosphorylation. The B cell differentiation potential of HNF1A(-/-) common lymphoid progenitors was severely impaired in vitro, and the expression of the B lymphopoiesis-promoting transcription factors E2A, EBF1, Pax5, and Bach2 was reduced in B cell progenitors in vivo. HNF1A(-/-) bone marrow chimera featured a dramatic defect in B lymphopoiesis recapitulating that of global HNF1A deficiency. The HNF1A(-/-) lymphopoiesis defect was confined to B cells as T lymphopoiesis was unaffected, and bone marrow common lymphoid progenitors and hematopoietic stem cells were even increased. Our data demonstrate that HNF1A is an important cell-intrinsic transcription factor in adult B lymphopoiesis and suggest the IL-7R/STAT5 module to be causally involved in mediating its function.

Undiagnosed MODY: Time for Action

Maturity-onset diabetes of the young (MODY) is a monogenic form of diabetes that accounts for at least 1 % of all cases of diabetes mellitus. MODY classically presents as non-insulin-requiring diabetes in lean individuals typically younger than 25 with evidence of autosomal dominant inheritance, but these criteria do not capture all cases and can also overlap with other diabetes types. Genetic diagnosis of MODY is important for selecting the right treatment, yet ~95 % of MODY cases in the USA are misdiagnosed. MODY prevalence and characteristics have been well-studied in some populations, such as the UK and Norway, while other ethnicities, like African and Latino, need much more study. Emerging next-generation sequencing methods are making more widespread study and clinical diagnosis increasingly feasible; at the same time, they are detecting other mutations in the same genes of unknown clinical significance. This review will cover the current epidemiological studies of MODY and barriers and opportunities for moving toward a goal of access to an appropriate diagnosis for all affected individuals.

Maturity-Onset Diabetes of the Young: What Do Clinicians Need to Know?

Maturity-onset diabetes of the young (MODY) is a monogenic form of diabetes that is characterized by an early onset, autosomal dominant mode of inheritance and a primary defect in pancreatic β-cell function. MODY represents less than 2% of all diabetes cases and is commonly misdiagnosed as type 1 or type 2 diabetes mellitus. At least 13 MODY subtypes with distinct genetic etiologies have been identified to date. A correct genetic diagnosis is important as it often leads to personalized treatment for those with diabetes and enables predictive genetic testing for their asymptomatic relatives. Next-generation sequencing may provide an efficient method for screening mutations in this form of diabetes as well as identifying new MODY genes. In this review, I discuss a current update on MODY in the literatures and cover the studies that have been performed in Korea.

Monogenic diabetes and pregnancy

Monogenic diabetes is frequently mistakenly diagnosed as either type 1 or type 2 diabetes, yet accounts for approximately 1-2% of diabetes. Identifying monogenic forms of diabetes has practical implications for specific therapy, screening of family members and genetic counselling. The most common forms of monogenic diabetes are due to glucokinase (GCK), hepatocyte nuclear factor (HNF)-1A and HNF-4A, HNF-1B, m.3243A>G gene defects. Practical aspects of their recognition, diagnosis and management are outlined, particularly as they relate to pregnancy. This knowledge is important for all physicians managing diabetes in pregnancy, given this is a time when previously unrecognised monogenic diabetes may be uncovered with careful attention to atypical features of diabetes misclassified as type 1, type 2, or gestational diabetes.

High-sensitivity C-reactive protein does not improve the differential diagnosis of HNF1A-MODY and familial young-onset type 2 diabetes: A grey zone analysis

AIM

Low plasma levels of high-sensitivity C-reactive protein (hs-CRP) have been suggested to differentiate hepatocyte nuclear factor 1 alpha-maturity-onset diabetes of the young (HNF1A-MODY) from type 2 diabetes (T2D). Yet, differential diagnosis of HNF1A-MODY and familial young-onset type 2 diabetes (F-YT2D) remains a difficult challenge. Thus, this study assessed the added value of hs-CRP to distinguish between the two conditions.

METHODS

This prospective multicentre study included 143 HNF1A-MODY patients, 310 patients with a clinical history suggestive of HNF1A-MODY, but not confirmed genetically (F-YT2D), and 215 patients with T2D. The ability of models, including clinical characteristics and hs-CRP to predict HNF1A-MODY was analyzed, using the area of the receiver operating characteristic (AUROC) curve, and a grey zone approach was used to evaluate these models in clinical practice.

RESULTS

Median hs-CRP values were lower in HNF1A-MODY (0.25mg/L) than in F-YT2D (1.14mg/L) and T2D (1.70mg/L) patients. Clinical parameters were sufficient to differentiate HNF1A-MODY from classical T2D (AUROC: 0.99). AUROC analyses to distinguish HNF1A-MODY from F-YT2D were 0.82 for clinical features and 0.87 after including hs-CRP. For the grey zone analysis, the lower boundary was set to miss<1.5% of true positives in non-tested subjects, while the upper boundary was set to perform 50% of genetic tests in individuals with no HNF1A mutation. On comparing HNF1A-MODY with F-YT2D, 65% of patients were classified in between these categories - in the zone of diagnostic uncertainty - even after adding hs-CRP to clinical parameters.

CONCLUSION

hs-CRP does not improve the differential diagnosis of HNF1A-MODY and F-YT2D.

Low serum level of high-sensitivity C-reactive protein in a Japanese patient with maturity-onset diabetes of the young type 3 (MODY3)

High-sensitivity C-reactive protein (hs-CRP) levels in European populations are lower in patients with maturity-onset diabetes of the young type 3 (MODY3) than in those with type 2 diabetes. hs-CRP levels have been suggested to be useful for discriminating MODY3 from type 2 diabetes. As hs-CRP levels are influenced by various factors including race and body mass index, it is worthwhile to examine whether hs-CRP can serve as a biomarker for MODY3 in Japanese. Here we describe the case of a Japanese MODY3 patient with a nonsense mutation in the HNF1A gene. Two measurements showed consistently lower hs-CRP levels (<0.05 and 0.09 mg/L) than in Japanese patients with type 1 and type 2 diabetes. Hepatic expression of Crp messenger ribonucleic acid was significantly decreased in Hnf1a knockout mice. The hs-CRP level might be a useful biomarker for MODY3 in both Japanese and European populations.

Many faces of monogenic diabetes

Monogenic diabetes represents a heterogeneous group of disorders resulting from defects in single genes. Defects are categorized primarily into two groups: disruption of β-cell function or a reduction in the number of β-cells. A complex network of transcription factors control pancreas formation, and a dysfunction of regulators high in the hierarchy leads to pancreatic agenesis. Dysfunction among factors further downstream might cause organ hypoplasia, absence of islets of Langerhans or a reduction in the number of β-cells. Many transcription factors have pleiotropic effects, explaining the association of diabetes with other congenital malformations, including cerebellar agenesis and pituitary agenesis. Monogenic diabetes variants are classified conventionally according to age of onset, with neonatal diabetes occurring before the age of 6 months and maturity onset diabetes of the young (MODY) manifesting before the age of 25 years. Recently, certain familial genetic defects were shown to manifest as neonatal diabetes, MODY or even adult onset diabetes. Patients with neonatal diabetes require a thorough genetic work-up in any case, and because extensive phenotypic overlap exists between monogenic, type 2, and type 1 diabetes, genetic analysis will also help improve diagnosis in these cases. Next generation sequencing will facilitate rapid screening, leading to the discovery of digenic and oligogenic diabetes variants, and helping to improve our understanding of the genetics underlying other types of diabetes. An accurate diagnosis remains important, because it might lead to a change in the treatment of affected subjects and influence long-term complications.

Mutations in PCBD1 cause hypomagnesemia and renal magnesium wasting

Mutations in PCBD1 are causative for transient neonatal hyperphenylalaninemia and primapterinuria (HPABH4D). Until now, HPABH4D has been regarded as a transient and benign neonatal syndrome without complications in adulthood. In our study of three adult patients with homozygous mutations in the PCBD1 gene, two patients were diagnosed with hypomagnesemia and renal Mg(2+) loss, and two patients developed diabetes with characteristics of maturity onset diabetes of the young (MODY), regardless of serum Mg(2+) levels. Our results suggest that these clinical findings are related to the function of PCBD1 as a dimerization cofactor for the transcription factor HNF1B. Mutations in the HNF1B gene have been shown to cause renal malformations, hypomagnesemia, and MODY. Gene expression studies combined with immunohistochemical analysis in the kidney showed that Pcbd1 is expressed in the distal convoluted tubule (DCT), where Pcbd1 transcript levels are upregulated by a low Mg(2+)-containing diet. Overexpression in a human kidney cell line showed that wild-type PCBD1 binds HNF1B to costimulate the FXYD2 promoter, the activity of which is instrumental in Mg(2+) reabsorption in the DCT. Of seven PCBD1 mutations previously reported in HPABH4D patients, five mutations caused proteolytic instability, leading to reduced FXYD2 promoter activity. Furthermore, cytosolic localization of PCBD1 increased when coexpressed with HNF1B mutants. Overall, our findings establish PCBD1 as a coactivator of the HNF1B-mediated transcription necessary for fine tuning FXYD2 transcription in the DCT and suggest that patients with HPABH4D should be monitored for previously unrecognized late complications, such as hypomagnesemia and MODY diabetes.

Cystatin C is not a good candidate biomarker for HNF1A-MODY

Cystatin C is a marker of glomerular filtration rate (GFR). Its level is influenced, among the others, by CRP whose concentration is decreased in HNF1A-MODY. We hypothesized that cystatin C level might be altered in HNF1A-MODY. We aimed to evaluate cystatin C in HNF1A-MODY both as a diagnostic marker and as a method of assessing GFR. We initially examined 51 HNF1A-MODY patients, 56 subjects with type 1 diabetes (T1DM), 39 with type 2 diabetes (T2DM) and 43 non-diabetic individuals (ND) from Poland. Subjects from two UK centres were used as replication panels: including 215 HNF1A-MODY, 203 T2DM, 39 HNF4A-MODY, 170 GCK-MODY, 17 HNF1B-MODY and 58 T1DM patients. The data were analysed with additive models, adjusting for gender, age, BMI and estimated GFR (creatinine). In the Polish subjects, adjusted cystatin C level in HNF1A-MODY was lower compared with T1DM, T2DM and ND (p < 0.05). Additionally, cystatin C-based GFR was higher than that calculated from creatinine level (p < 0.0001) in HNF1A-MODY, while the two GFR estimates were similar or cystatin C-based lower in the other groups. In the UK subjects, there were no differences in cystatin C between HNF1A-MODY and the other diabetic subgroups, except HNF1B-MODY. In UK HNF1A-MODY, cystatin C-based GFR estimate was higher than the creatinine-based one (p < 0.0001). Concluding, we could not confirm our hypothesis (supported by the Polish results) that cystatin C level is altered by HNF1A mutations; thus, it cannot be used as a biomarker for HNF1A-MODY. In HNF1A-MODY, the cystatin C-based GFR estimate is higher than the creatinine-based one.

Prevalence, characteristics and clinical diagnosis of maturity onset diabetes of the young due to mutations in HNF1A, HNF4A, and glucokinase: results from the SEARCH for Diabetes in Youth

AIMS

Our study aims were to determine the frequency of MODY mutations (HNF1A, HNF4A, glucokinase) in a diverse population of youth with diabetes and to assess how well clinical features identify youth with maturity-onset diabetes of the young (MODY).

METHODS

The SEARCH for Diabetes in Youth study is a US multicenter, population-based study of youth with diabetes diagnosed at age younger than 20 years. We sequenced genomic DNA for mutations in the HNF1A, HNF4A, and glucokinase genes in 586 participants enrolled in SEARCH between 2001 and 2006. Selection criteria included diabetes autoantibody negativity and fasting C-peptide levels of 0.8 ng/mL or greater.

RESULTS

We identified a mutation in one of three MODY genes in 47 participants, or 8.0% of the tested sample, for a prevalence of at least 1.2% in the pediatric diabetes population. Of these, only 3 had a clinical diagnosis of MODY, and the majority was treated with insulin. Compared with the MODY-negative group, MODY-positive participants had lower FCP levels (2.2 ± 1.4 vs 3.2 ± 2.1 ng/mL, P < .01) and fewer type 2 diabetes-like metabolic features. Parental history of diabetes did not significantly differ between the 2 groups.

CONCLUSIONS/INTERPRETATION

In this systematic study of MODY in a large pediatric US diabetes cohort, unselected by referral pattern or family history, MODY was usually misdiagnosed and incorrectly treated with insulin. Although many type 2 diabetes-like metabolic features were less common in the mutation-positive group, no single characteristic identified all patients with mutations. Clinicians should be alert to the possibility of MODY diagnosis, particularly in antibody-negative youth with diabetes.

Monogenic diabetes: a diagnostic algorithm for clinicians

Monogenic forms of beta cell diabetes account for approximately 1%-2% of all cases of diabetes, yet remain underdiagnosed. Overlapping clinical features with common forms of diabetes, make diagnosis challenging. A genetic diagnosis of monogenic diabetes in many cases alters therapy, affects prognosis, enables genetic counseling, and has implications for cascade screening of extended family members. We describe those types of monogenic beta cell diabetes which are recognisable by distinct clinical features and have implications for altered management; the cost effectiveness of making a genetic diagnosis in this setting; the use of complementary diagnostic tests to increase the yield among the vast majority of patients who will have commoner types of diabetes which are summarised in a clinical algorithm; and the vital role of cascade genetic testing to enhance case finding.

Circulating CD36 is reduced in HNF1A-MODY carriers

INTRODUCTION

Premature atherosclerosis is a significant cause of morbidity and mortality in type 2 diabetes mellitus. Maturity onset diabetes of the young (MODY) accounts for approximately 2% of all diabetes, with mutations in the transcription factor; hepatocyte nuclear factor 1 alpha (HNF1A) accounting for the majority of MODY cases. There is somewhat limited data available on the prevalence of macrovascular disease in HNF1A-MODY carriers with diabetes. Marked insulin resistance and the associated dyslipidaemia are not clinical features of HNF1A-MODY carriers. The scavenger protein CD36 has been shown to play a substantial role in the pathogenesis of atherosclerosis, largely through its interaction with oxidised LDL. Higher levels of monocyte CD36 and plasma CD36(sCD36) are seen to cluster with insulin resistance and diabetes. The aim of this study was to determine levels of sCD36 in participants with HNF1A-MODY diabetes and to compare them with unaffected normoglycaemic family members and participants with type 2 diabetes mellitus.

METHODS

We recruited 37 participants with HNF1A-MODY diabetes and compared levels of sCD36 with BMI-matched participants with type 2 diabetes mellitus and normoglycaemic HNF1A-MODY negative family controls. Levels of sCD36 were correlated with phenotypic and biochemical parameters.

RESULTS

HNF1A-MODY participants were lean, normotensive, with higher HDL and lower triglyceride levels when compared to controls and participants with type 2 diabetes mellitus. sCD36 was also significantly lower in HNF1A-MODY participants when compared to both the normoglycaemic family controls and to lean participants with type 2 diabetes mellitus.

CONCLUSION

In conclusion, sCD36 is significantly lower in lean participants with HNF1A-MODY diabetes when compared to weight-matched normoglycaemic familial HNF1A-MODY negative controls and to lean participants with type 2 diabetes mellitus. Lower levels of this pro-atherogenic marker may result from the higher HDL component in the lipid profile of HNF1A-MODY participants.

Maturity onset diabetes of the young: identification and diagnosis

Maturity-onset diabetes of the young (MODY) is a monogenic disorder that results in a familial, young-onset non-insulin dependent form of diabetes, typically presenting in lean young adults before 25 years. Approximately 1% of diabetes has a monogenic cause but this is frequently misdiagnosed as Type 1 or Type 2 diabetes. A correct genetic diagnosis is important as it often leads to improved treatment for those affected with diabetes and enables predictive genetic testing for their asymptomatic relatives. An early diagnosis together with appropriate treatment is essential for reducing the risk of diabetic complications in later life. Mutations in the GCK and HNF1A/4 A genes account for up to 80% of all MODY cases. Mutations in the GCK gene cause a mild, asymptomatic and non-progressive fasting hyperglycaemia from birth usually requiring no treatment. In contrast, mutations in the genes encoding the transcription factors HNF1A and HNF4A cause a progressive insulin secretory defect and hyperglycaemia that can lead to vascular complications. The diabetes in these patients is usually well controlled with sulphonylurea tablets although insulin treatment may be required in later life. In this review, we outline the key clinical and laboratory characteristics of the common and rarer causes of MODY with the aim of raising awareness of this condition amongst health-care scientists.