Noninvasive prenatal diagnosis of Mendelian disorders for consanguineous couples by relative genotype dosage.

Noninvasive prenatal diagnosis relies on the presence in maternal blood of circulating cell-free fetal DNA released by apoptotic trophoblast cells. Widely used for aneuploidy screening, it can also be applied to monogenic diseases (NIPD-M) in case of known parental mutations. Due to the confounding effect of maternal DNA, detection of maternal or biparental mutations requires relative haplotype dosage (RHDO), a method relying on the presence of SNPs that are heterozygous in one parent and homozygous in the other. Unavoidably, there is a risk of test failure by lack of such informative SNPs, an event particularly likely for consanguineous couples who often share common haplotypes in regions of identity-by-descent. Here we present a novel approach, relative genotype dosage (RGDO) that bypasses this predicament by directly assessing fetal genotype with SNPs that are heterozygous in both parents (frequent in regions of identity-by-descent). We show that RGDO is as sensitive as RHDO and that it performs well over a large range of fetal fractions and DNA amounts, thereby opening NIPD-M to most consanguineous couples. We also report examples of couples, consanguineous or not, where combining RGDO and RHDO allowed a diagnosis that would not have been possible with only one approach.

Atypical diabetes with spontaneous remission associated with systemic lupus erythematosus in an adolescent girl of African ancestry, a case report.

BACKGROUND: New-onset diabetes in youth encompasses type 1 diabetes, type 2 diabetes, monogenic diabetes, and rarer subtypes like Type B insulin resistance syndrome and ketosis-prone atypical diabetes in African populations. Some cases defy classification, posing management challenges. Here, we present a case of a unique, reversible diabetes subtype. CASE PRESENTATION: We describe an adolescent African girl recently diagnosed with systemic lupus erythematosus. At age 15, she presented with ketoacidosis, HbA1c of 108.7 mmol/mol (12.1%), and positive anti-insulin antibodies. Initially diagnosed with type 1 diabetes, insulin was prescribed. Due to the presence of obesity and signs of insulin resistance, we added metformin. Concurrently, she received treatment for lupus with hydroxychloroquine, mycophenolate mofetil, and prednisone. After discharge, she stopped insulin due to cultural beliefs. Five months later, her glycemia and HbA1c normalized (37 mmol/mol or 5.5%) without insulin, despite corticosteroid therapy and weight gain. Autoantibodies normalized, and lupus activity decreased. Genetic testing for monogenic diabetes was negative, and the type 1 genetic risk score was exceptionally low. CONCLUSIONS: We present a complex, reversible diabetes subtype. Features suggest an autoimmune origin, possibly influenced by overlapping HLA risk haplotypes with lupus. Lupus treatment or immunomodulation may have impacted diabetes remission. Ancestry-tailored genetic risk scores are currently designed to improve diagnostic accuracy.

[Monogenic diabetes : a pioneer in precision medicine management]. / Diabète monogénique : pionnier dans la prise en charge par la médecine de précision.

Diabetes mellitus in children is subdivided into several categories depending on the underlying pathological mechanism. Type 1 diabetes is due to the autoimmune destruction of pancreatic beta-cells, type 2 diabetes to progressive impairment in insulin secretion or insulin sensitivity, and monogenic diabetes due to genetic abnormalities, impairing insulin secretion. In monogenic diabetes, genetic defects result in pancreatic or beta-cell defects (abnormal function or destruction), resulting in neonatal or MODY (Maturity-Onset Diabetes of the Young) diabetes, depending on the age of onset. The identification of monogenic diabetes is crucial as it allows the initiation of targeted and personalized treatment.

Le diabète sucré de l'enfant est subdivisé en plusieurs catégories en fonction du mécanisme pathologique sous-jacent : de type 1 par destruction autoimmune des cellules bêta du pancréas, de type 2 par perte progressive d'une sécrétion adéquate ou de sensibilité à l'insuline et monogénique par anomalie génétique perturbant la sécrétion d'insuline. Dans ce dernier, les anomalies génétiques entraînent des défauts du développement du pancréas ou de la cellule bêta (anomalie de fonction ou destruction), menant à un diabète néonatal ou un diabète MODY (Maturity-Onset Diabetes of the Young) en fonction de l'âge d'apparition. L'identification du diabète monogénique est primordiale puisqu'elle permet l'instauration d'un traitement ciblé et personnalisé.

[Obesity in infancy: new precision treatment]. / Obésité infantile : nouveautés thérapeutiques ciblées.

Obesity is a chronical disease, which leads to multiple short- and long-term complications. 4% of Swiss children and adolescents are obese. A prompt diagnosis and multicomponent lifestyle intervention is mandatory to avoid persistence of the disease into adulthood. Growth and BMI charts are still the essential tools to diagnose and define the etiology of obesity. A precocious and severe obesity, accompanied by hyperphagia, will raise the suspicion of monogenic obesity. The precise molecular diagnosis enables in some patients the use of a specific treatment. Leptine in case of LEP gene defects, or setmelanotide when the affected gene is part of the MC4R signaling pathway (LEPR, POMC, PCSK1).

L'obésité est une maladie chronique, associée à de multiples complications à court et à long termes, présente chez 4 % des enfants et adolescents en Suisse. Un dépistage et une intervention multidisciplinaire précoces sont essentiels pour éviter la persistance de la maladie à l'âge adulte. Les courbes de croissance et de l'IMC sont les outils indispensables pour repérer la maladie et orienter l'étiologie. Ainsi, une obésité d'apparition précoce, de caractère sévère et accompagnée d'une hyperphagie oriente le clinicien vers le diagnostic d'obésité monogénique. Un diagnostic moléculaire précis permet de connaître le gène défectueux et offre, dans certains cas, un traitement ciblé très efficace pour le patient : la leptine en cas de mutation du gène LEP, ou le setmélanotide dans les défauts de la voie de signalisation du MC4R (LEPR, POMC, PCSK1).

Pancreatic beta-cell function dynamics in youth with GCK, HNF1A, and KCNJ11 genes mutations during mixed meal tolerance test.

OBJECTIVE: The aims were (1) to assess beta-cell function in GCK diabetes patients over 2-year period; (2) to evaluate the dynamics of beta-cell function in HNF1A and KCNJ11 patients after treatment optimization; using mixed meal tolerance test (MMTT) as a gold standard for non-invasive beta-cell function assessment. RESEARCH DESIGN AND METHODS: Twenty-two GCK diabetes patients, 22 healthy subjects, 4 patients with HNF1A and 2 with KCNJ11 were recruited. Firstly, beta-cell function was compared between GCK patients versus controls; the dynamics of beta-cell function were assessed in GCK patients with two MMTTs in 2-year period. Secondly, the change of beta-cell function was evaluated in HNF1A and KCNJ11 patients after successful treatment optimization in 2-year period. RESULTS: GCK diabetes patients had lower area under the curve (AUC) of C-peptide (CP), average CP and peak CP compared to controls. Also, higher levels of fasting, average, peak and AUC of glycemia during MMTT were found in GCK patients compared to healthy controls. No significant changes in either CP or glycemia dynamics were observed in GCK diabetes group comparing 1st and 2nd MMTTs. Patients with HNF1A and KCNJ11 diabetes had significantly improved diabetes control 2 years after the treatment was optimized (HbA1c 7.1% vs. 5.9% [54 mmol/mol vs. 41 mmol/mol], respectively, p = 0.028). Higher peak CP and lower HbA1c were found during 2nd MMTT in patients with targeted treatment compared to the 1st MMTT before the treatment change. CONCLUSION: In short-term perspective, GCK diabetes group revealed no deterioration of beta-cell function. Individualized treatment in monogenic diabetes showed improved beta-cell function.

[MODY type diabetes: an often-misunderstood entity]. / Diabète de type MODY : une entité souvent méconnue.

MODY diabetes, for Maturity Onset Diabetes of the Young, is a form of monogenic diabetes characterized by a typical onset before the age of 25 years, the lack of autoimmunity against the b cells of the pancreas, a preserved ß cells function and an autosomal dominant mode of inheritance. This type of diabetes constitutes 2 to 5% of all cases of diabetes but remains often undiagnosed. Nearly 15 MODY subtypes have been identified to date. The 3 most common subtypes are caused by mutations in the genes encoding glucokinase, HNF1a and HNF4a, and account for approximately 80% of all MODY cases. Carrying out a genetic test can thus make it possible to make the diagnosis of MODY diabetes and to set up an appropriate treatment. In this article we will discuss these 3 main MODY sub-type, although there are other forms, which may be characterized by associated specific organ damage.

Le diabète Maturity Onset Diabetes of the Young (MODY) est une forme de diabète monogénique se caractérisant par une apparition typique avant l'âge de 25 ans, l'absence d'autoimmunité contre les cellules ß du pancréas, une fonction préservée des cellules ß et un mode de transmission autosomique dominant. Ce type de diabète constitue 2 à 5 % de tous les cas de diabètes, mais reste souvent non diagnostiqué. Près de 15 sous-types sont, à ce jour, identifiés. Les 3 les plus fréquents sont causés par des mutations des gènes codant pour la glucokinase, HNF1α et HNF4α, qui représentent environ 80 % des cas de MODY. La réalisation d'un test génétique peut ainsi permettre de poser le diagnostic de MODY et mettre en place un traitement approprié. Dans cet article nous discutons de ces 3 sous-types principaux de MODY, bien qu'il existe d'autres formes plus rares pouvant se caractériser par des atteintes d'organes spécifiques associées.

Exome sequencing identifies a de novo FOXA2 variant in a patient with syndromic diabetes.

OBJECTIVE: When diabetes is associated with congenital malformations, without autoimmune antibodies, a genetic cause is suspected. Here, we aimed to identify a defective gene that led to diabetes. RESEARCH DESIGN AND METHODS: We performed an exome analysis of an index case and his healthy parents. RESULTS: The child presented with childhood-onset diabetes, congenital hypopituitarism, cardiac malformation, and anal atresia. A DNA analysis revealed a heterozygous de novo pathogenic variant in the developmental transcription factor, forkhead box A2 (FOXA2). The mutation resided in the DNA-binding domain, which is highly conserved among species. Tridimensional molecular dynamics simulation modeling predicted an altered interaction between the mutated protein and DNA. CONCLUSIONS: A defect in the FOXA2 DNA-binding domain was associated with childhood-onset diabetes and multiple congenital anomalies, which reflected the pleiotropic nature of the gene. This report extends the recently described phenotype of neonatal hypoglycemia to later-onset diabetes. We suggest to include FOXA2 analysis for neonatal hypoglycemia and to implement a long-term follow-up, particularly for the risk of diabetes.

Ketosis After Cardiopulmonary Bypass in Children Is Associated With an Inadequate Balance Between Oxygen Transport and Consumption.

OBJECTIVES: Hyperglycemia after cardiac surgery and cardiopulmonary bypass in children has been associated with worse outcome; however, causality has never been proven. Furthermore, the benefit of tight glycemic control is inconsistent. The purpose of this study was to describe the metabolic constellation of children before, during, and after cardiopulmonary bypass, in order to identify a subset of patients that might benefit from insulin treatment. DESIGN: Prospective observational study, in which insulin treatment was initiated when postoperative blood glucose levels were more than 12 mmol/L (216 mg/dL). SETTING: Tertiary PICU. PATIENTS: Ninety-six patients 6 months to 16 years old undergoing cardiac surgery with cardiopulmonary bypass. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Metabolic tests were performed before anesthesia, at the end of cardiopulmonary bypass, at PICU admission, and 4 and 12 hours after PICU admission, as well as 4 hours after initiation of insulin treatment. Ketosis was present in 17.9% patients at the end of cardiopulmonary bypass and in 31.2% at PICU admission. Young age was an independent risk factor for this condition. Ketosis at PICU admission was an independent risk factor for an increased difference between arterial and venous oxygen saturation. Four hours after admission (p = 0.05). Insulin corrected ketosis within 4 hours. CONCLUSIONS: In this study, we found a high prevalence of ketosis at PICU admission, especially in young children. This was independently associated with an imbalance between oxygen transport and consumption and was corrected by insulin. These results set the basis for future randomized controlled trials, to test whether this subgroup of patients might benefit from increased glucose intake and insulin during surgery to avoid ketosis, as improving oxygen transport and consumption might improve patient outcome.

Diabetes and immune thrombocytopenic purpura: a new association with good response to anti-CD20 therapy.

Type 1 diabetes (T1D) is rarely a component of primary immune dysregulation disorders. We report two cases in which T1D was associated with thrombocytopenia. The first patient, a 13-year-old boy, presented with immune thrombocytopenia (ITP), thyroiditis, and, 3 wk later, T1D. Because of severe thrombocytopenia resistant to immunoglobulins, high-dose steroids, and cyclosporine treatment, anti-cluster of differentiation (CD20) therapy was introduced, with consequent normalization of thrombocytes and weaning off of steroids. Three and 5 months after anti-CD20 therapy, levothyroxin and insulin therapy, respectively, were stopped. Ten months after stopping insulin treatment, normal C-peptide and hemoglobin A1c (HbA1c) levels and markedly reduced anti-glutamic acid decarboxylase (GAD) antibodies were measured. A second anti-CD20 trial for relapse of ITP was initiated 2 yr after the first trial. Anti-GAD antibody levels decreased again, but HbA1c stayed elevated and glucose monitoring showed elevated postprandial glycemia, demanding insulin therapy. To our knowledge, this is the first case in which insulin treatment could be interrupted for 28 months after anti-CD20 treatment. In patient two, thrombocytopenia followed a diagnosis of T1D 6 yr previously. Treatment with anti-CD20 led to normalization of thrombocytes, but no effect on T1D was observed. Concerning the origin of the boys' conditions, several primary immune dysregulation disorders were considered. Thrombocytopenia associated with T1D is unusual and could represent a new entity. The diabetes manifestation in patient one was probably triggered by corticosteroid treatment; regardless, anti-CD20 therapy appeared to be efficacious early in the course of T1D, but not long after the initial diagnosis of T1D, as shown for patient two.

Concomitant alpha7 and beta2 nicotinic AChR subunit deficiency leads to impaired energy homeostasis and increased physical activity in mice.

Nicotinic acetylcholine receptors (nAChRs) are pentameric ligand-gated cation channels well characterized in neuronal signal transmission. Moreover, recent studies have revealed nAChR expression in nonneuronal cell types throughout the body, including tissues involved in metabolism. In the present study, we screen gene expression of nAChR subunits in pancreatic islets and adipose tissues. Mice pancreatic islets present predominant expression of α7 and ß2 nAChR subunits but at a lower level than in central structures. Characterization of glucose and energy homeostasis in α7ß2nAChR(-/-) mice revealed no major defect in insulin secretion and sensitivity but decreased glycemia apparently unrelated to gluconeogenesis or glycogenolysis. α7ß2nAChR(-/-) mice presented an increase in lean and bone body mass and a decrease in fat storage with normal body weight. These observations were associated with elevated spontaneous physical activity in α7ß2nAChR(-/-) mice, mainly due to elevation in fine vertical (rearing) activity while their horizontal (ambulatory) activity remained unchanged. In contrast to α7nAChR(-/-) mice presenting glucose intolerance and insulin resistance associated to excessive inflammation of adipose tissue, the present metabolic phenotyping of α7ß2nAChR(-/-) mice revealed a metabolic improvement possibly linked to the increase in spontaneous physical activity related to central ß2nAChR deficiency.

Enhancing fetal outcomes in GCK-MODY pregnancies: a precision medicine approach via non-invasive prenatal GCK mutation detection.

Background: Mutations in the GCK gene cause Maturity Onset Diabetes of the Young (GCK-MODY) by impairing glucose-sensing in pancreatic beta cells. During pregnancy, managing this type of diabetes varies based on fetal genotype. Fetuses carrying a GCK mutation can derive benefit from moderate maternal hyperglycemia, stimulating insulin secretion in fetal islets, whereas this may cause macrosomia in wild-type fetuses. Modulating maternal glycemia can thus be viewed as a form of personalized prenatal therapy, highly beneficial but not justifying the risk of invasive testing. We therefore developed a monogenic non-invasive prenatal diagnostic (NIPD-M) test to reliably detect the transmission of a known maternal GCK mutation to the fetus. Methods: A small amount of fetal circulating cell-free DNA is present in maternal plasma but cannot be distinguished from maternal cell-free DNA. Determining transmission of a maternal mutation to the fetus thus implies sequencing adjacent polymorphisms to determine the balance of maternal haplotypes, the transmitted haplotype being over-represented in maternal plasma. Results: Here we present a series of such tests in which fetal genotype was successfully determined and show that it can be used to guide therapeutic decisions during pregnancy and improve the outcome for the offspring. We discuss several potential hurdles inherent to the technique, and strategies to overcome these. Conclusion: Our NIPD-M test allows reliable determination of the presence of a maternal GCK mutation in the fetus, thereby allowing personalized in utero therapy by modulating maternal glycemia, without incurring the risk of miscarriage inherent to invasive testing.

Atypical familial diabetes associated with a novel NEUROD1 nonsense variant.

OBJECTIVES: We aimed to identify the origin of atypical diabetes in a family with four generations of diabetes from South Asia. The family members showed different clinical phenotypes. Members of generation one to three were presumed to have type 2 diabetes and generation four to have type 1 diabetes. CASE PRESENTATION: We performed a genetic analysis of the family using targeted high throughput sequencing. CONCLUSIONS: We identified a novel nonsense variant in the neurogenic differentiation 1 (NEUROD1) gene, co-segregating with diabetes. The variant was located in the DNA-binding domain, altering a protein residue that was very well conserved among different species.

Precision medicine in diabetes: A non-invasive prenatal diagnostic test for the determination of fetal glucokinase mutations.

Hyperglycemia caused by mutations in the glucokinase gene, GCK, is the most common form of monogenic diabetes. Prenatal diagnosis is important, as it impacts on treatment. This study reports a monogenic non-invasive prenatal diagnostic (NIPD-M) test on cell-free DNA in maternal plasma using the relative haplotype dosage. In three pregnancies of two families with known maternal GCK mutations, the fetal genotype was determined unambiguously already at 12 weeks of gestation. In summary, proof is provided of the feasibility for NIPD-M in GCK diabetes.

Co-segregation analysis and functional trial in vivo of candidate genes for monogenic diabetes.

INTRODUCTION: The aim of this study was to perform familial co-segregation analysis and functional trial in vivo during mixed meal tolerance test (MMTT) of novel variants in diabetes candidate genes. RESEARCH DESIGN AND METHODS: It is a continuation of the project "Genetic diabetes in Lithuania" with the cohort of 1209 patients with diabetes. Prior screening for autoimmune markers confirmed type 1 diabetes (T1D) diagnosis in 88.1% (n=1065) of patients, and targeted next-generation sequencing identified 3.5% (n=42) pathogenic variants in MODY genes. Subsequently, 102 patients were classified as having diabetes of unknown etiology. 12/102 were found to have novel variants in potential diabetes genes (RFX2, RREB1, SLC5A1 (3 patients with variants in this gene), GCKR, MC4R, CASP10, TMPRSS6, HGFAC, DACH1, ZBED3). Co-segregation analysis and MMTT were carried out in order to study beta-cell function in subjects with specific variants. RESULTS: MMTT analysis showed that probands with variants in MC4R, CASP10, TMPRSS6, HGFAC, and SLC5A1 (c.1415T>C) had sufficient residual beta-cell function with stimulated C-peptide (CP) >200 pmol/L. Seven individuals with variants in RFX2, RREB1, GCKR, DACH1, ZBED3 and SLC5A1 (c.1415T>C, and c.932A>T) presented with complete beta-cell failure. No statistical differences were found between patients with sufficient CP production and those with complete beta-cell failure when comparing age at the onset and duration of diabetes. Nineteen family members were included in co-segregation analysis; no diabetes cases were reported among them. Only in patient with the variant c.1894G>A in RFX2 gene, none of the family members were affected by proband's variant. CONCLUSIONS: Functional beta-cell study in vivo allowed to select five most probable genes for monogenic diabetes. Familial co-segregation analysis showed that novel variant in RFX2 gene could be a possible cause of diabetes. Future functional analysis in vitro is necessary to support or rule out the genetic background as a cause of diabetes.