Recognition and Management of Individuals With Hyperglycemia Because of a Heterozygous Glucokinase Mutation

Understanding childhood diabetes mellitus: new pathophysiological aspects

Diabetes mellitus (DM) is not a single disease, but several pathophysiological conditions where synthesis, release, and/or action of insulin are disturbed. A progressive autoimmune/autoinflammatory destruction of islet cells is still considered the main pathophysiological event in the development of T1DM, but there is evidence that T1DM itself is a heterogeneous disease. More than 50 gene regions are closely associated with T1DM and a variety of epigenetic factors and metabolic patterns have been characterized, which may play a role in the development of T1DM. The pathogenesis and genetics of type 2 DM (T2DM) are distinct from T1DM. Genes associated with T2DM are distinct from those in T1DM. Characteristic metabolic patterns, different from those in T1DM were reported in T2DM, and some children with T2DM also express islet-antibodies. Huge progress has been made in the characterization of other specific types of DM, which had been considered very rare before. The molecular clarification of maturity-onset diabetes of the young (MODY) has greatly improved our understanding of the pathophysiology of DM. There are genetic overlaps between T2DM and monogenetic DM. Neonatal DM has been shown to be monogenetic in most cases, and genetic elucidation leads to more precise and individualized therapies. Cystic fibrosis related DM (CFRDM) should be considered a genuine part of cystic fibrosis, and not a complication, since pancreatic fibrosis does not sufficiently explain the pathophysiology of CFRDM. Disturbances of cystic fibrosis transmembrane conductance regulator (CFTR) as well as autoimmunity are involved in the pathogenesis of CFRDM.

Precision medicine in diabetes: an opportunity for clinical translation

Metabolic disorders present a public health challenge of staggering proportions. In diabetes, there is an urgent need to better understand disease heterogeneity, clinical trajectories, and related comorbidities. A pressing and timely question is whether we are ready for precision medicine in diabetes. Some biological insights that have emerged during the last decade have already been used to direct clinical decision making, especially in monogenic forms of diabetes. However, much work is necessary to integrate high-dimensional explorations into complex disease architectures, less penetrant biological alterations, and broader phenotypes, such as type 2 diabetes. In addition, for precision medicine to take hold in diabetes, reproducibility, interpretability, and actionability remain key guiding objectives. In this review, we examine how mounting data sets generated during the last decade to understand biological variability are now inspiring new venues to clarify diabetes nosology and ultimately translate findings into more effective prevention and treatment strategies.

Use of oral antidiabetic drugs in the treatment of maturity-onset diabetes of the young: A mini review

MODY (maturity-onset diabetes of the young) is a genetically linked group of clinically heterogeneous subtypes of diabetes. Roughly 5% of people with diabetes mellitus diagnosed prior to age 45 have MODY diabetes. Most of them have been erroneously diagnosed as patients with either type 1 or type 2 diabetes and, as a result, have been improperly treated. Genetic identification of MODY diabetes and its subtypes allows proper treatment and enables clinicians to switch many patients to oral antidiabetic agents, mainly sulphonylureas. However, some new classes of oral antidiabetic drugs have also been tested and found to be effective in MODY patients. We have searched for research articles and case reports written in full-text English or with an English abstract, using the following keywords: MODY and oral antidiabetic* in the databases Cochrane Library, PubMed, and Science Direct. Therapeutic options using currently standardized oral antidiabetic drugs (mainly sulphonylureas), as well as more experimental treatment with other classes of oral antidiabetic drugs in different types of MODY, are discussed, with special focus on the therapy of the most common MODY subtypes, including specific conditions such as pregnancy. This review article summarizes the currently available information about oral antidiabetic treatment of patients with MODY diabetes.

Functional Implications of HMG-CoA Reductase Inhibition on Glucose Metabolism

HMG-CoA reductase inhibitors, i.e. statins, are effective in reducing cardiovascular disease events but also in cardiac-related and overall mortality. Statins are in general well-tolerated, but currently the concerns are raised if statins may increase the risk of new-onset diabetes mellitus (NOD). In this review, the possible effects of statins on organs/tissues being involved in glucose metabolism, i.e. liver, pancreas, adipose tissue, and muscles, had been discussed. The net outcome seems to be inconsistent and often contradictory, which may be largely affected by in vitro experimental settings or/and in vivo animal conditions. The majority of studies point out statin-induced changes of regulations of isoprenoid metabolites and cell-associated cholesterol contents as predisposing factors related to the statin-induced NOD. On the other hand, it should be considered that dysfunctions of isoprenoid pathway and mitochondrial ATP production and the cholesterol homeostasis are already developed under (pre)diabetic and hypercholesterolemic conditions. In order to connect the basic findings with the clinical manifestation more clearly, further research efforts are needed.

Spectrum of mutations in monogenic diabetes genes identified from high-throughput DNA sequencing of 6888 individuals

BACKGROUND

Diagnosis of monogenic as well as atypical forms of diabetes mellitus has important clinical implications for their specific diagnosis, prognosis, and targeted treatment. Single gene mutations that affect beta-cell function represent 1-2% of all cases of diabetes. However, phenotypic heterogeneity and lack of family history of diabetes can limit the diagnosis of monogenic forms of diabetes. Next-generation sequencing technologies provide an excellent opportunity to screen large numbers of individuals with a diagnosis of diabetes for mutations in disease-associated genes.

METHODS

We utilized a targeted sequencing approach using the Illumina HiSeq to perform a case-control sequencing study of 22 monogenic diabetes genes in 4016 individuals with type 2 diabetes (including 1346 individuals diagnosed before the age of 40 years) and 2872 controls. We analyzed protein-coding variants identified from the sequence data and compared the frequencies of pathogenic variants (protein-truncating variants and missense variants) between the cases and controls.

RESULTS

A total of 40 individuals with diabetes (1.8% of early onset sub-group and 0.6% of adult onset sub-group) were carriers of known pathogenic missense variants in the GCK, HNF1A, HNF4A, ABCC8, and INS genes. In addition, heterozygous protein truncating mutations were detected in the GCK, HNF1A, and HNF1B genes in seven individuals with diabetes. Rare missense mutations in the GCK gene were significantly over-represented in individuals with diabetes (0.5% carrier frequency) compared to controls (0.035%). One individual with early onset diabetes was homozygous for a rare pathogenic missense variant in the WFS1 gene but did not have the additional phenotypes associated with Wolfram syndrome.

CONCLUSION

Targeted sequencing of genes linked with monogenic diabetes can identify disease-relevant mutations in individuals diagnosed with type 2 diabetes not suspected of having monogenic forms of the disease. Our data suggests that GCK-MODY frequently masquerades as classical type 2 diabetes. The results confirm that MODY is under-diagnosed, particularly in individuals presenting with early onset diabetes and clinically labeled as type 2 diabetes; thus, sequencing of all monogenic diabetes genes should be routinely considered in such individuals. Genetic information can provide a specific diagnosis, inform disease prognosis and may help to better stratify treatment plans.

More than kin, less than kind: one family and the many faces of diabetes in youth

Identification of the correct etiology of diabetes brings important implications for clinical management. In this report, we describe a case of a 4-year old asymptomatic girl with diabetes since age 2, along with several individuals in her family with different etiologies for hyperglycemia identified in youth. Genetic analyses were made by Sanger sequencing, laboratory measurements included HbA1c, lipid profile, fasting C-peptide, pancreatic auto-antibodies (glutamic acid decarboxylase [GAD], Islet Antigen 2 [IA-2], and anti-insulin). We found a Gly178Ala substitution in exon 5 of GCK gene in three individuals co-segregating with diabetes, and type 1 diabetes was identified in two other individuals based on clinical and laboratory data. One individual with previous gestational diabetes and other with prediabetes were also described. We discuss difficulties in defining etiology of hyperglycemia in youth in clinical practice, especially monogenic forms of diabetes, in spite of the availability of several genetic, laboratory, and clinical tools.

Nutrient sensing in pancreatic islets: lessons from congenital hyperinsulinism and monogenic diabetes

Pancreatic beta cells sense changes in nutrients during the cycles of fasting and feeding and release insulin accordingly to maintain glucose homeostasis. Abnormal beta cell nutrient sensing resulting from gene mutations leads to hypoglycemia or diabetes. Glucokinase (GCK) plays a key role in beta cell glucose sensing. As one form of congenital hyperinsulinism (CHI), activating mutations of GCK result in a decreased threshold for glucose-stimulated insulin secretion and hypoglycemia. In contrast, inactivating mutations of GCK result in diabetes, including a mild form (MODY2) and a severe form (permanent neonatal diabetes mellitus (PNDM)). Mutations of beta cell ion channels involved in insulin secretion regulation also alter glucose sensing. Activating or inactivating mutations of ATP-dependent potassium (K_ATP ) channel genes result in severe but completely opposite clinical phenotypes, including PNDM and CHI. Mutations of the other ion channels, including voltage-gated potassium channels (K_v 7.1) and voltage-gated calcium channels, also lead to abnormal glucose sensing and CHI. Furthermore, amino acids can stimulate insulin secretion in a glucose-independent manner in some forms of CHI, including activating mutations of the glutamate dehydrogenase gene, HDAH deficiency, and inactivating mutations of K_ATP channel genes. These genetic defects have provided insight into a better understanding of the complicated nature of beta cell fuel-sensing mechanisms.

A single dose of dapagliflozin, an SGLT-2 inhibitor, induces higher glycosuria in GCK- and HNF1A-MODY than in type 2 diabetes mellitus

AIMS

SGLT2 inhibitors are a new class of oral hypoglycemic agents used in type 2 diabetes (T2DM). Their effectiveness in maturity onset diabetes of the young (MODY) is unknown. We aimed to assess the response to a single dose of 10 mg dapagliflozin in patients with Hepatocyte Nuclear Factor 1 Alpha (HNF1A)-MODY, Glucokinase (GCK)-MODY, and type 2 diabetes.

METHODS

We examined 14 HNF1A-MODY, 19 GCK-MODY, and 12 type 2 diabetes patients. All studied individuals received a single morning dose of 10 mg of dapagliflozin added to their current therapy of diabetes. To assess the response to dapagliflozin we analyzed change in urinary glucose to creatinine ratio and serum 1,5-Anhydroglucitol (1,5-AG) level.

RESULTS

There were only four patients with positive urine glucose before dapagliflozin administration (one with HNF1A-MODY, two with GCK-MODY, and one with T2DM), whereas after SGLT-2 inhibitor use, glycosuria occurred in all studied participants. Considerable changes in mean glucose to creatinine ratio after dapagliflozin administration were observed in all three groups (20.51 ± 12.08, 23.19 ± 8.10, and 9.84 ± 6.68 mmol/mmol for HNF1A-MODY, GCK-MODY, and T2DM, respectively, p < 0.001 for all comparisons). Post-hoc analysis revealed significant differences in mean glucose to creatinine ratio change between type 2 diabetes and each monogenic diabetes in response to dapagliflozin (p = 0.02, p = 0.003 for HNF1-A and GCK MODY, respectively), but not between the two MODY forms (p = 0.7231). Significant change in serum 1,5-AG was noticed only in T2DM and it was -6.57 ± 7.34 mg/ml (p = 0.04).

CONCLUSIONS

A single dose of dapagliflozin, an SGLT-2 inhibitor, induces higher glycosuria in GCK- and HNF1A-MODY than in T2DM. Whether flozins are a valid therapeutic option in these forms of MODY requires long-term clinical studies.

Identification of Maturity-Onset Diabetes of the Young Caused by Glucokinase Mutations Detected Using Whole-Exome Sequencing

Glucokinase maturity-onset diabetes of the young (GCK-MODY) represents a distinct subgroup of MODY that does not require hyperglycemia-lowering treatment and has very few diabetes-related complications. Three patients from two families who presented with clinical signs of GCK-MODY were evaluated. Whole-exome sequencing was performed and the effects of the identified mutations were assessed using bioinformatics tools, such as PolyPhen-2, SIFT, and in silico modeling. We identified two mutations: p.Leu30Pro and p.Ser383Leu. In silico analyses predicted that these mutations result in structural conformational changes, protein destabilization, and thermal instability. Our findings may inform future GCK-MODY diagnosis; furthermore, the two mutations detected in two Korean families with GCK-MODY improve our understanding of the genetic basis of the disease.

Preliminary screening of mutations in the glucokinase gene of Chinese patients with gestational diabetes

Aims/Introduction

Mutations in the glucokinase gene (GCK) are a pathogenetic cause of maturity‐onset diabetes of the young. Studies have found that female patients with GCK maturity‐onset diabetes of the young often present with gestational diabetes during pregnancy. Our aim was to preliminarily assess the prevalence of mutations in the glucokinase gene in Chinese women with gestational diabetes.

Materials and Methods

Chinese gestational diabetes patients who underwent a 100‐g oral glucose tolerance test in Peking Union Medical College Hospital from July 2005 to May 2008 were retrospectively analyzed. Participants were selected for direct sequencing of the GCK gene if they met the following criteria: (i) fasting plasma glucose between 5.5 and 10.0 mmol/L; and (ii) a small increment (<4.6 mmol/L) during a 2‐h oral glucose tolerance test.

Results

Of the 501 participants with gestational diabetes, there were 38 participants who met the criteria for GCK analysis. In the 29 participants whose deoxyribonucleic acid samples were available, two mutations in coding regions were detected, c.626 C>T (p.T209M, NP_000153.1) mutation in exon 6 and c.824 G>A (p.R275H, NP_000153.1; rs767565869) mutation in exon 7. According to our results, the minimum prevalence of GCK mutations in Chinese women with gestational diabetes was estimated to be 0.4%, and the minimum prevalence of GCK maturity‐onset diabetes of the young in the Chinese population might be one in 2,000.

Conclusions

Our screening criteria allowed for the identification of glucokinase‐deficient patients who were diagnosed with gestational diabetes, and these mutations in the GCK gene were not common in Chinese women with gestational diabetes.

Precision diabetes: learning from monogenic diabetes

The precision medicine approach of tailoring treatment to the individual characteristics of each patient or subgroup has been a great success in monogenic diabetes subtypes, MODY and neonatal diabetes. This review examines what has led to the success of a precision medicine approach in monogenic diabetes (precision diabetes) and outlines possible implications for type 2 diabetes. For monogenic diabetes, the molecular genetics can define discrete aetiological subtypes that have profound implications on diabetes treatment and can predict future development of associated clinical features, allowing early preventative or supportive treatment. In contrast, type 2 diabetes has overlapping polygenic susceptibility and underlying aetiologies, making it difficult to define discrete clinical subtypes with a dramatic implication for treatment. The implementation of precision medicine in neonatal diabetes was simple and rapid as it was based on single clinical criteria (diagnosed <6 months of age). In contrast, in MODY it was more complex and slow because of the lack of single criteria to identify patients, but it was greatly assisted by the development of a diagnostic probability calculator and associated smartphone app. Experience in monogenic diabetes suggests that successful adoption of a precision diabetes approach in type 2 diabetes will require simple, quick, easily accessible stratification that is based on a combination of routine clinical data, rather than relying on newer technologies. Analysing existing clinical data from routine clinical practice and trials may provide early success for precision medicine in type 2 diabetes.

Natural selection? The evolution of diagnostic criteria for gestational diabetes

Gestational diabetes is a common pregnancy disorder which is generally managed with diet, exercise, metformin or insulin treatment and which usually resolves after delivery of the infant. Identifying and treating gestational diabetes improves maternal and fetal outcomes and allows for health promotion to reduce the mother's risk of type 2 diabetes in later life. However, there remains considerable controversy about the optimal method of identification and diagnosis of women with gestational diabetes. The NICE-2015 diagnostic criteria (75 g oral glucose tolerance test (OGTT) 0 h ≥5.6 mmol/L; 2 h ≥7.8 mmol/L) are based upon cost-effectiveness estimates using observational data, while the WHO-2013 criteria (75 g OGTT 0 h ≥5.1 mmol/L; 1 h ≥10.0 mmol/L; 2 h ≥8.5 mmol/L) identify women and infants at risk of adverse outcomes according to prospective data. There is also considerable controversy about testing for gestational diabetes using universal or risk factor-based screening, and when and how testing should be performed. The aim of this review is to provide a summary of the clinical biochemistry aspects to these debates and to highlight the importance of appropriate identification of gestational diabetes and subsequent type 2 diabetes in this population.

The Genetic Architecture of Diabetes in Pregnancy: Implications for Clinical Practice

The genetic architecture of diabetes mellitus in general and in pregnancy is complex, owing to the multiple types of diabetes that comprise both complex/polygenic forms and monogenic (largely caused by a mutation in a single gene) forms such as maturity-onset diabetes of the young (MODY). Type 1 diabetes (T1D) and type 2 diabetes (T2D) have complex genetic etiologies, with over 40 and 90 genes/loci, respectively, implicated that interact with environmental/lifestyle factors. The genetic etiology of gestational diabetes mellitus has largely been found to overlap that of T2D. Genetic testing for complex forms of diabetes is not currently useful clinically, but genetic testing for monogenic forms, particularly MODY, has important utility for determining treatment, managing risk in family members, and pregnancy management. In particular, diagnosing MODY2, caused by GCK mutations, indicates that insulin should not be used, including during pregnancy, with the possible exception of an unaffected pregnancy during the third trimester to prevent macrosomia. A relatively simple method for identifying women with MODY2 has been piloted. MODY1, caused by HNF4A mutations, can paradoxically cause neonatal hyperinsulinemic hypoglycemia and macrosomia, indicating that detecting these cases is also clinically important. Diagnosing all MODY types provides opportunities for diagnosing other family members.

A description of clinician reported diagnosis of type 2 diabetes and other non-type 1 diabetes included in a large international multicentered pediatric diabetes registry (SWEET)

BACKGROUND

Although type 1 diabetes (T1D) remains the most frequent form of diabetes in individuals aged less than 20 years at onset, other forms of diabetes are being increasingly recognized.

OBJECTIVES

To describe the population of children with other forms of diabetes (non-type 1) included in the multinational SWEET (Better control in Pediatric and Adolescent diabeteS: Working to crEate CEnTers of Reference) database for children with diabetes.

METHODS

Cases entered in the SWEET database are identified by their physician as T1D, type 2 diabetes (T2D) and other types of diabetes according to the ISPAD classification. Etiologic subgroups are provided for other types of diabetes. Descriptive analyses were tabulated for age at onset, gender, daily insulin doses, and hemoglobin A1c (A1C) for each type and subtype of diabetes and when possible, values were compared.

RESULTS

Of the 27 104 patients included in this report, 95.5% have T1D, 1.3% T2D, and 3.2% other forms of diabetes. The two most frequent etiologies for other forms of diabetes were maturity onset diabetes of the young (MODY) (n = 351) and cystic fibrosis-related diabetes (CFRD) (n = 193). The cause was unknown or unreported in 10% of other forms of diabetes. Compared with T1D, children with T2D and CFRD were diagnosed at an older age, took less insulin and had lower A1C (all P < .0001).

CONCLUSION

In centers included in SWEET, forms of diabetes other than type 1 remain rare and at times difficult to characterize. Sharing clinical information and outcome between SWEET centers on those rare forms of diabetes has the potential to improve management and outcome.

Common and rare forms of diabetes mellitus: towards a continuum of diabetes subtypes

Insights into the genetic basis of type 2 diabetes mellitus (T2DM) have been difficult to discern, despite substantial research. More is known about rare forms of diabetes mellitus, several of which share clinical and genetic features with the common form of T2DM. In this Review, we discuss the extent to which the study of rare and low-frequency mutations in large populations has begun to bridge the gap between rare and common forms of diabetes mellitus. We hypothesize that the perceived division between these diseases might be due, in part, to the historical ascertainment bias of genetic studies, rather than a clear distinction between disease pathophysiologies. We also discuss possible implications of a new model for the genetic basis of diabetes mellitus subtypes, where the boundary between subtypes becomes blurred.