Clinical and molecular characterization of neonatal diabetes and monogenic syndromic diabetes in Asian Indian children

Case report: A 10-year prognosis of neonatal diabetes caused by a novel INS gene mutation

Background

Neonatal diabetes mellitus (NDM) is a rare form of diabetes. We analyzed a novel insulin gene (INS) mutation of a Chinese permanent neonatal diabetes mellitus (PNDM) patient to explore the clinical and genetic characteristics and put forward some opinions on treatment and its long-term management.

Case description

A proband was recruited who was diagnosed with permanent neonatal diabetes on his first day after birth. His clinical and follow-up data were collected for 10 years. All of the family members were given an oral glucose tolerance test. Whole exome sequencing was performed on the proband, and the genomic DNA of family members was used for verification by first-generation Sanger sequencing technology. The pathogenic variant was screened according to the American College of Medical Genetics and Genomics classification guidelines and the clinical phenotype of the patient.

Diagnostic assessment

The proband was diagnosed on the first day after birth, presenting with low birth weight, progressive hyperglycemia, and insulin deficiency. His parents and grandfathers were confirmed to have normal blood sugar levels. A novel homozygous mutation of c.1T>C in the INS gene was detected in the proband, located in the initiation codon. The heterozygous mutations were found in four family members, including his mother, father, and grandfathers. With regular insulin injections, long-term regular follow-up, close monitoring of blood glucose, balanced exercise and diet, and psychological and mutual family support, the blood glucose level was well controlled; there were no acute or chronic complications during this decade. The patient's growth and nervous system development are now no different to those of the same age.

Conclusion

A favorable prognosis is presented for a permanent neonatal diabetes mellitus (PNDM) patient with a novel mutation in the INS gene in China. The present findings indicate that the genetic diagnosis, early use of insulin, close monitoring of blood glucose, and psychological and mutual family support for patients with INS mutation are necessary for their favorable long-term prognosis.

Case Report: Fanconi-Bickel Syndrome in a Chinese Girl With Diabetes and Severe Hypokalemia

Fanconi-Bickel syndrome (FBS) is a rare autosomal recessive carbohydrate metabolism disorder. The main symptoms of FBS are hepatomegaly, nephropathy, postprandial hyperglycemia, fasting hypoglycemia, and growth retardation. Hypokalemia is a rare clinical feature in patients with FBS. In this study, we present a neonate suffering from FBS. She presented with hypokalemia, dysglycaemia, glycosuria, hepatomegaly, abnormality of liver function, and brain MRI. Trio whole-exome sequencing (WES) and Sanger sequencing were performed to identify the causal gene variants. A compound heterozygous mutation (NM_000340.2; p. Trp420*) of SLC2A2 was identified. Here, we report a patient with FBS in a consanguineous family with diabetes, severe hypokalemia, and other typical FBS symptoms. Patients with common clinical features may be difficult to diagnose just by phenotypes in the early stage of life, but WES could be an important tool. We also discuss the use of insulin in patients with FBS and highlight the importance of a continuous glucose monitoring system (CGMS), not only in diagnosis but also to avoid hypoglycemic events.

Neonatal Diabetes Mellitus: Novel Mutations

OBJECTIVE

To describe the spectrum of neonatal diabetes mellitus (NDM), document new mutations, and review published Indian literature on the etiology of NDM.

METHODS

Retrospective analysis of the clinical and genetic profile of 12 NDM patients.

RESULTS

Eight patients presented with NDM before the age of 6 mo. Three other patients, including 2 siblings presented in later part of infancy. An additional patient was diagnosed at age 5 y with the same etiology as her infant sibling. Four patients had transient diabetes [TNDM:1 each with a mutation in KCNJ11 and INS gene, 2 with ABCC8 mutation], 7 had permanent diabetes [PNDM: 2 siblings with complete glucokinase deficiency, 2 siblings with thiamine responsive megaloblastic anemia (TRMA), 1 with Immune dysregulation, Polyendocrinopathy, Enteropathy, X-linked (IPEX) syndrome and 2 with Wolcott Rallison syndrome, (WRS)]. Four patients had 5 novel mutations. Genetic etiology could not be established in 1 patient with features of insulin resistance. Poorly controlled blood glucose in the TRMA patient led to hyperglycemia-induced hemichorea-hemiballismus, a rare manifestation in children.

CONCLUSIONS

The authors describe 5 novel mutations, in the EIF2AK3, ABCC8, and GCK genes, a homozygous mutation at the ABCC8 locus presenting as TNDM, an obscure phenotype of the GCK gene mutation, and hyperglycemia-induced hemichorea-hemiballismus in a patient with TRMA. In India, PNDM is most commonly due to WRS similar to Middle Eastern countries with high consanguinity rates.

Demographic and clinical profile of youth onset diabetes patients in India-Results from the baseline data of a clinic based registry of people with diabetes in India with young age at onset-[YDR-02]

BACKGROUND

We here report the demographic and clinical profile of the patients enrolled in the Indian Council of Medical Research funded Registry of people with diabetes in India with young age at onset (YDR) from 1 January 2000 to 31 July 2011.

METHODS

The YDR registry recruits all diabetes cases (newly diagnosed or treated) reporting on or after 1 January 2000 with age of diagnosis ≤25 years, and residing within the assigned geographical area of the reporting centres. A baseline proforma was used to obtain information on demographic and clinical details at registration.

RESULTS

The registry has enrolled 5546 patients (49.5% male; 50.5% female) with youth onset diabetes from 205 reporting centres linked to 8 regional collaborating centres (RCC) across India. T1DM (63.9%; n = 3545) and T2DM (25.3%; n = 1401) were the commonest variants of youth onset diabetes, though their relative proportion varied across RCCs. The mean (SD) age at diagnosis for T1DM was 12.9 (6.5) years, while that for T2DM was 21.7 (3.7) years. Nearly half the T1DM patients were registered within 6 months of the onset of disease. Most cases of T2DM (47.3%) were registered after 3 years from their date of diagnosis. 56.1% of patients had at least one episode of hospitalization at registration.

CONCLUSION

The observations from YDR registry indicate the need to establish a surveillance system in India to monitor diabetes in youth, not only to understand its complex etiology and natural history but also due to its detrimental socio economic impact.

Genotype-phenotype correlation of KATP channel gene defects causing permanent neonatal diabetes in Indian patients

BACKGROUND

There are very few reports pertaining to Indian patients with neonatal diabetes mellitus (NDM). Activating or gain of function mutations of K_ATP channel genes namely KCNJ11 and ABCC8 are most predominant cause of permanent neonatal diabetes mellitus (PNDM).

OBJECTIVES

To identify the genotype-phenotype correlation of K_ATP channel gene defects in a large series of (n = 181) Indian PNDM patients.

METHODS

Direct sequencing of all exons of KCNJ11 and ABCC8 genes in all 181 patients with PNDM were performed. Clinical and biochemical data were collected.

RESULTS

We have identified the molecular basis of K_ATP -NDM in 39 out of 181 patients (22%). Of these, 20 had KCNJ11 mutations and 19 had ABCC8 mutations, thus comprising 51% of KCNJ11 and 49% of ABCC8. There were four novel mutations (D1128Tfs*16, Y1287C, S1422T, and H1537R) in ABCC8 gene. Three patients with KCNJ11 mutations had developmental delay with DEND syndrome. In patients with ABCC8 mutations developmental delay was seen in seven out of 19 (36.8%). Of this, three patients (15.7%) had DEND phenotype and four (21%) had iDEND. Of the 39 patients, 33 (84%) patients were shifted to sulfonylurea therapy (glibenclamide). Of this, 19(57.5%) patients harbored KCNJ11 mutations and 14(42.1%) ABCC8 mutations.

CONCLUSIONS

This is the first largest study in NDM patients in India demonstrating the importance of K_ATP channel gene mutation screening in PNDM and efficacy of glibenclamide for Indian patients with K_ATP -PNDM. The success rate of transfer is more in patients with KCNJ11 mutations compared with those with ABCC8 mutations.

Clinical and Genetic Characteristics of ABCC8 Nonneonatal Diabetes Mellitus: A Systematic Review

OBJECTIVES

Diabetes mellitus (DM) is a major chronic metabolic disease in the world, and the prevalence has been increasing rapidly in recent years. The channel of K_ATP plays an important role in the regulation of insulin secretion. The variants in ABCC8 gene encoding the SUR1 subunit of K_ATP could cause a variety of phenotypes, including neonatal diabetes mellitus (ABCC8-NDM) and ABCC8-induced nonneonatal diabetes mellitus (ABCC8-NNDM). Since the features of ABCC8-NNDM have not been elucidated, this study is aimed at concluding the genetic features and clinical characteristics.

METHODS

We comprehensively reviewed the literature associated with ABCC8-NNDM in the following databases: MEDLINE, PubMed, and Web of Science to investigate the features of ABCC8-NNDM.

RESULTS

Based on a comprehensive literature search, we found that 87 probands with ABCC8-NNDM carried 71 ABCC8 genetic variant alleles, 24% of whom carried inactivating variants, 24% carried activating variants, and the remaining 52% carried activating or inactivating variants. Nine of these variants were confirmed to be activating or inactivating through functional studies, while four variants (p.R370S, p.E1506K, p.R1418H, and p.R1420H) were confirmed to be inactivating. The phenotypes of ABCC8-NNDM were variable and could also present with early hyperinsulinemia followed by reduced insulin secretion, progressing to diabetes later. They had a relatively high risk of microvascular complications and low prevalence of nervous disease, which is different from ABCC8-NDM.

CONCLUSIONS

Genetic testing is essential for proper diagnosis and appropriate treatment for patients with ABCC8-NNDM. And further studies are required to determine the complex mechanism of the variants of ABCC8-NNDM.

Fanconi-Bickel Syndrome: A Review of the Mechanisms That Lead to Dysglycaemia

Accumulation of glycogen in the kidney and liver is the main feature of Fanconi-Bickel Syndrome (FBS), a rare disorder of carbohydrate metabolism inherited in an autosomal recessive manner due to SLC2A2 gene mutations. Missense, nonsense, frame-shift (fs), in-frame indels, splice site, and compound heterozygous variants have all been identified in SLC2A2 gene of FBS cases. Approximately 144 FBS cases with 70 different SLC2A2 gene variants have been reported so far. SLC2A2 encodes for glucose transporter 2 (GLUT2) a low affinity facilitative transporter of glucose mainly expressed in tissues playing important roles in glucose homeostasis, such as renal tubular cells, enterocytes, pancreatic β-cells, hepatocytes and discrete regions of the brain. Dysfunctional mutations and decreased GLUT2 expression leads to dysglycaemia (fasting hypoglycemia, postprandial hyperglycemia, glucose intolerance, and rarely diabetes mellitus), hepatomegaly, galactose intolerance, rickets, and poor growth. The molecular mechanisms of dysglycaemia in FBS are still not clearly understood. In this review, we discuss the physiological roles of GLUT2 and the pathophysiology of mutants, highlight all of the previously reported SLC2A2 mutations associated with dysglycaemia, and review the potential molecular mechanisms leading to dysglycaemia and diabetes mellitus in FBS patients.

New insights into KATP channel gene mutations and neonatal diabetes mellitus

The ATP-sensitive potassium channel (K_ATP channel) couples blood levels of glucose to insulin secretion from pancreatic β-cells. K_ATP channel closure triggers a cascade of events that results in insulin release. Metabolically generated changes in the intracellular concentrations of adenosine nucleotides are integral to this regulation, with ATP and ADP closing the channel and MgATP and MgADP increasing channel activity. Activating mutations in the genes encoding either of the two types of K_ATP channel subunit (Kir6.2 and SUR1) result in neonatal diabetes mellitus, whereas loss-of-function mutations cause hyperinsulinaemic hypoglycaemia of infancy. Sulfonylurea and glinide drugs, which bind to SUR1, close the channel through a pathway independent of ATP and are now the primary therapy for neonatal diabetes mellitus caused by mutations in the genes encoding K_ATP channel subunits. Insight into the molecular details of drug and nucleotide regulation of channel activity has been illuminated by cryo-electron microscopy structures that reveal the atomic-level organization of the K_ATP channel complex. Here we review how these structures aid our understanding of how the various mutations in the genes encoding Kir6.2 (KCNJ11) and SUR1 (ABCC8) lead to a reduction in ATP inhibition and thereby neonatal diabetes mellitus. We also provide an update on known mutations and sulfonylurea therapy in neonatal diabetes mellitus.

Congenital Generalized Lipoatrophy (Berardinelli-Seip Syndrome) Type 1: Description of Novel AGPAT2 Homozygous Variants Showing the Highly Heterogeneous Presentation of the Disease

Berardinelli-Seip congenital lipoatrophy (BSCL) is characterized by near total fat atrophy, associated with the progressive development of metabolic complications. BSCL type 1 (BSCL1) is caused by mutations in AGPAT2, encoding 1-acylglycerol-3phosphate-O-acyltransferase β (recently renamed lysophosphatidic acid acyltransferase beta), which catalyzes the transformation of lysophosphatidic acid in phosphatidic acid, the precursor of glycerophospholipids and triglycerides. BSCL1 is an autosomal recessive disease due to AGPAT2 pathogenic variants leading to a depletion of triglycerides inside the adipose organ, and to a defective signaling of key elements involved in proper adipogenesis. We herein investigated the characteristics of two AGPAT2 variants in Caucasian Italian patients with Berardinelli-Seip congenital lipoatrophy. The first patient exhibited a novel homozygous nonsense c.430 C > T AGPAT2 mutation (p.Gln144^*) predicting the synthesis of a truncated enzyme of approximately half of the proper size. The second patient harbored a homozygous AGPAT2 missense variant (p.Arg159Cys), never described previously in BSCL1 patients: the segregation of the disease with the mutation in the pedigree of the family and the in silico analysis are compatible with a causative role of the p.Arg159Cys variant. We remark that BSCL1 can be clinically very heterogeneous at presentation and that the associated complications, occurring in the natural history of the disease, reduce life-expectancy. We point to the necessity for medical treatments capable of reducing the risk of cardiovascular death. In BSCL1 patients, the assessment of cardiovascular disease with conventional diagnostic means maybe particularly challenging.

Functional characterization of activating mutations in the sulfonylurea receptor 1 (ABCC8) causing neonatal diabetes mellitus in Asian Indian children

BACKGROUND

Gain-of-function of ATP-sensitive K⁺ (K_ATP ) channels because of mutations in the genes encoding SUR1 (ABCC8) or Kir6.2 (KCNJ11) is a major cause of neonatal diabetes mellitus (NDM). Our aim is to determine molecular defects in K_ATP channels caused by ABCC8 mutations in Asian Indian children with NDM by in vitro functional studies.

METHODS

Wild-type (WT; NM_000352.4) or mutant sulfonylurea receptor 1 (SUR1) and Kir6.2 were co-expressed in COSm6 cells. Biogenesis efficiency and surface expression of mutant channels were assessed by immunoblotting and immunostaining. The response of mutant channels to cytoplasmic ATP and ADP was assessed by inside-out patch-clamp recordings. The response of mutant channels to known K_ATP inhibitors in intact cells were determined by ⁸⁶ Rb efflux assays.

RESULTS

Five SUR1 missense mutations, D212Y, P254S, R653Q, R992C, and Q1224H, were studied and showed increased activity in MgATP/MgADP. Two of the mutants, D212Y and P254S, also showed reduced response to ATP^4- inhibition, as well as markedly reduced surface expression. Moreover, all five mutants were inhibited by the K_ATP channel inhibitors glibenclamide and carbamazepine.

CONCLUSIONS

The study shows the mechanisms by which five SUR1 mutations identified in Asian Indian NDM patients affect K_ATP channel function to cause the disease. The reduced ATP^4- sensitivity caused by the D212Y and P254S mutations in the L0 of SUR1 provides novel insight into the role of L0 in channel inhibition by ATP. The results also explain why sulfonylurea therapy is effective in two patients and inform how it should be effective for the other three patients.

Precision Diabetes Is Slowly Becoming a Reality

The concept of precision medicine is becoming increasingly popular. The use of big data, genomics and other "omics" like metabolomics, proteomics and transcriptomics could make the dream of personalised medicine become a reality in the near future. As far as polygenic forms of diabetes like type 2 and type 1 diabetes are concerned, interesting leads are emerging, but precision diabetes is still in its infancy. However, with regard to monogenic forms of diabetes like maturity-onset diabetes of the young and neonatal diabetes mellitus, rapid strides have been made and precision diabetes has already become part of the clinical tools used at advanced diabetes centres. In patients with some monogenic form of diabetes, if the appropriate gene defects are identified, insulin injections can be stopped and be replaced by oral sulphonylurea drugs. In the coming years, rapid advances can be expected in the field of precision diabetes, thereby making the control of diabetes more effective and hopefully leading to prevention of its complications and improvement of the quality of life of people afflicted with diabetes.

Childhood diabetes in India

This review describes the epidemiology of childhood diabetes in India. It focuses on the incidence and prevalence of type 1 diabetes and its complications and comorbid conditions. The review also covers data related to type 2 diabetes, glucose intolerance, and monogenic diabetes from India. A brief discussion regarding unique contributions from India to the world literature is included. The topics discussed include use of camel milk as adjuvant therapy in type 1 diabetes, relevance of the A1/A2 hypothesis, and comprehensive clinico-etiopathological classification of type 1 diabetes.

Sulfonylurea for the treatment of neonatal diabetes owing to KATP-channel mutations: a systematic review and meta-analysis

The effect of sulfonylurea for the treatment of neonatal diabetes (NDM) is remain uncertain. We conducted this systematic review and meta-analysis to investigate the effect of sulfonylurea for NDM and to provide the latest and most convincing evidence for developing clinical practice guidelines of NDM. A literature review was performed to identify all published studies reporting the sulfonylurea on the treatment of neonatal diabetes. The search included the following databases: PUBMED, EMBASE and the Cochrane Library. The primary outcome was the success rates of treatment, change of glycosylated hemoglobin (HbA1c) and C-peptide. Data results were pooled by using MetaAnalyst with a random-effects model. Ten studies (6 cohort studies and 4 cross-sectional studies) involving 285 participants were included in the analysis. The pooled estimated success rate by the random-effects model was 90.1%(95% CI: 85.1%-93.5%). HbA1c had a significantly lower compared with before treatment. The pooled estimate of MD was -2.289, and the 95% CI was -2.790 to -1.789 (P < 0.001). The subgroup analysis showed a similar result for cohort studies and in cross-sectional studies. The common mild side effect is gastrointestinal reaction. The present meta-analysis suggested that sulfonylurea had a positive effect for treatment NDM due to K_ATP channel mutations. In addition, sulfonylurea also displayed sound safety except the mild gastrointestinal reaction. However, the findings rely chiefly on data from observational studies. Further well-conducted trials are required to assess sulfonylurea for NDM.

Fanconi syndrome and neonatal diabetes: phenotypic heterogeneity in patients with GLUT2 defects

Fanconi-Bickel syndrome, caused by mutations in SLC2A2 encoding the glucose transporter 2 (GLUT2), is characterized by generalized proximal renal tubular dysfunction manifesting in late infancy. We describe phenotypic heterogeneity of Fanconi-Bickel syndrome in three siblings, including early and atypical presentation with transient neonatal diabetes mellitus in one. The second-born of a non-consanguineous couple, evaluated for polyuria and growth retardation, had rickets, hepatomegaly and proximal tubular dysfunction from 4 to 6  months of age. A male sibling, who expired at 4 months, also had hepatomegaly and growth retardation. The third sibling had polyuria, glucosuria and mild proteinuria on day 3 of life. Hyperglycemia was detected 2 weeks later, which required therapy with insulin for 3 months. Mild metabolic acidosis was present at 2 weeks; hypercalciuria, phosphaturia and aminoaciduria were seen at 6 months. Sanger sequencing showed a homozygous missense mutation in SLC2A2 (exon 7, c.952G > A), causing glycine to arginine substitution; both parents were heterozygous carriers. Patients with SLC2A2 mutations may present either with isolated neonatal diabetes or with hepatomegaly and the renal Fanconi syndrome. Fanconi-Bickel syndrome shows phenotypic heterogeneity and may manifest early with subtle or atypical features, mandating a high index of suspicion.

Molecular and clinical features of KATP -channel neonatal diabetes mellitus in Japan

BACKGROUND

There are few reports pertaining to Asian patients with neonatal diabetes mellitus (NDM) caused by activating mutations in the ATP-sensitive potassium channel genes (KATP-NDM).

OBJECTIVES

To elucidate the characteristics of Japanese patients with KATP-NDM.

METHODS

By the amplification and direct sequencing of all exons and exon-intron boundaries of the KCNJ11 and ABCC8 genes, 25 patients with KATP-NDM were identified from a total of 70 patients with NDM. Clinical data were collected from the medical charts.

RESULTS

Sixteen patients had mutations in KCNJ11 and nine in ABCC8. Eight novel mutations were identified; two in KCNJ11 (V64M, R201G) and six in ABCC8 (R216C, G832C, F1176L, A1263V, I196N, T229N). Interestingly, V64M caused DEND (developmental delay, epilepsy, neonatal diabetes) syndrome in our patient, while mutation of the same residue (V64G) had been reported to cause congenital hyperinsulinism. Mutations in ABCC8 were associated with TNDM (4/9) or isolated PNDM (5/9), whereas those in KCNJ11 were associated with more severe phenotypes, including DEND (3/16), iDEND (intermediate DEND, 4/16), or isolated PNDM (6/16). Switching from insulin to glibenclamide monotherapy was successful in 87.5% of the patients. Neurological improvement was observed in two patients, one with DEND (T293N) and one with iDEND (R50P) syndrome. Three others with iDEND mutations (R201C, G53D, and V59M) remained neurologically normal at 5, 1, and 4 years of age, respectively, with early introduction of sulfonylurea.

CONCLUSION

Overall, clinical presentation of KATP-NDM in Japanese patients was similar to those of other populations. Early introduction of sulfonylurea appeared beneficial in ameliorating neurological symptoms.

A successful transition to sulfonylurea treatment in male infant with neonatal diabetes caused by the novel abcc8 gene mutation and three years follow-up

Neonatal diabetes mellitus is a rare monogenic disease with incidence of 1/90,000 newborns. A case of two months aged male infant with life threatening diabetic ketoacidosis is presented with novel ABCC8 gene mutation (p.F577L), successful transition from insulin to sulfonylurea and follow-up of three years.

An infant with diabetes mellitus: Is it always T1DM?

Here we describe a 2^1/2month old infant with neonatal diabetes mellitus (NDM) who was initially misdiagnosed to have T1DM and initiated on insulin. He was found to have a novel heterozygous mutation Arg992Cys in ABCC 8 gene and successfully switched to oral anti-diabetic drug.

Permanent neonatal diabetes misdiagnosed as type 1 diabetes in a 28-year-old female: a life-changing diagnosis

Many patients with monogenic diabetes are missed or misclassified. Herein, we report a 28-year-old Indian female who developed diabetes at the age of 3 months. An audit of our type 1 diabetes database led to her genetic testing. A KCNJ11 mutation was identified and she was successfully switched to sulphonylurea.

EIF2AK3 mutations in South Indian children with permanent neonatal diabetes mellitus associated with Wolcott-Rallison syndrome

OBJECTIVE

This study describes the clinical and genetic evaluation of permanent neonatal diabetes due to Wolcott-Rallison syndrome (WRS) in south Indian consanguineous families. We aimed to evaluate the genetic basis of the disease in eight children with WRS from five South Indian families.

PATIENTS AND METHODS

We studied eight children who presented with permanent neonatal diabetes from five South Indian families. Follow up clinical evaluation revealed features (like liver disease, skeletal dysplasia, and thyroid dysfunction) suggestive of WRS. All the coding exons along with splice sites of KCNJ11, ABCC8, INS, GCK and EIF2AK3 genes were sequenced in all the probands.

RESULTS

Two novel homozygous mutations (Trp658Ser, c.3150+1G>T) and one known homozygous mutation (Arg1065*, c.3193C>T) in EIF2AK3 gene were identified in children with WRS. Mutation Arg1065*was identified in four children.

CONCLUSIONS

Our results in these families show that the mutations in homozygous state are likely to be causative. We suggest the screening for EIF2AK3 gene mutations as WRS is now recognized as the most frequent cause of neonatal diabetes in children with consanguineous parents. As the mode of inheritance is recessive, screening for genetic mutations becomes important to aid in risk prediction and clinical management.