Maturity-onset diabetes of the young (MODY): a new challenge for pediatric diabetologists.

The differential diagnosis of hyperglycemia in childhood and adolescence has to take into consideration early-onset non-insulin-dependent diabetes, defined as maturity onset diabetes of the young (MODY). To date, mutations in genes of five proteins have been shown to cause MODY: glucokinase (MODY2), hepatic nuclear factor-1 alpha (HNF-1 alpha) (MODY3), hepatic nuclear factor-4 alpha (HNF-4 alpha) (MODY1), insulin promoter factor 1 (IPF-1) (MODY4) and hepatic nuclear factor-1 beta (HNF-1 beta) (MODY5), but other MODY genes still await elucidation. Clinical and metabolic heterogeneity of these subtypes of type 2 diabetes need to be defined, as deficiency of each factor has its own phenotype. Pediatric diabetologists should be aware of the increasing importance of MODY as a possible cause of hyperglycemia in children and adolescents. This will allow for the early diagnosis of these metabolic conditions and for the appropriate follow-up and treatment.     

Molecular and biochemical analysis of the MODY syndromes

Maturity onset diabetes of the young (MODY) is characterized by youth-onset diabetes that is inherited in an autosomal dominant (monogenic) pattern. Classic MODY accounts for less than 5% of cases of childhood diabetes in Caucasians, presents prior to age 25 years, is nonketotic, and may not require insulin treatment. A variant form of MODY that lacks a clearly defined genetic basis occurs in African Americans [atypical diabetes mellitus (ADM)] clinically presents more acutely and is initially insulin requiring. To date, five molecular causes of classic MODY have been identified: hepatocyte nuclear factor-4α (HNF-4α; MODY1), glucokinase (MODY2), hepatocyte nuclear factor-1α (HNF-1α; MODY3), insulin promoter factor-1 (IPF-1, MODY4), and hepatocyte nuclear factor-1β (HNF-1β; MODY5). MODY is studied as a model of beta cell hypofunction and modest insulinopenia. Clinical recognition of ADM is important for patient management to avoid confusion with type 1 diabetes mellitus.     

Mutational analysis of melanocortin-4 receptor, agouti-related protein, and alpha-melanocyte-stimulating hormone genes in severely obese children

OBJECTIVE: To search for mutations in melanocortin pathway elements, that is, the melanocortin-4 receptor (MC4R ), agouti-related protein (AGRP ), and (alpha-melanocyte-stimulating hormone (alpha MSH ) genes in children with severe obesity. STUDY DESIGN: Direct sequencing of the MC4R encoding sequence and single-strand polymorphism conformation analysis of AGRP and alpha MSH genes were performed in 63 severely obese children. Polymerase chain reaction (PCR) assays of restriction fragment length polymorphism were used to assess the frequency of each newly discovered mutation in 283 non-obese control subjects. RESULTS: Four dominantly inherited, heterozygous, missense MC4R mutations (Val50Met, Ser58Cys, Ile102Ser, and Ile170Val) were identified in 4 unrelated children and none of the control subjects. Expression of the obese phenotype was variable in mutation-positive family members. Clinical and laboratory features were similar in the obese children with and without an MC4R mutation. Two polymorphisms were detected in the AGRP -encoding sequence (a silent mutation in exon 1 and Ala67Thr in exon 2), with similar frequencies in the obese and control groups. No mutations were found in the alpha MSH gene. CONCLUSIONS: MC4R mutations may be a non-negligible cause of severe obesity in children with variable expression and penetrance. Mutations in AGRP and alpha MSH genes were not among the causes of obesity in our population.     

Aetiological heterogeneity of asymptomatic hyperglycaemia in children and adolescents

Introduction Randomly estimated fasting hyperglycaemia in an asymptomatic individual may represent the first sign of pancreatic β-cell dysfunction. Objective We aimed at specifying the genetic aetiology of asymptomatic hyperglycaemia in a cohort of children and adolescents.Subjects and methods We analysed the aetiological diagnosis in 82 non-obese paediatric subjects (38 males) aged 0.2-18.5 years (median: 13.1) who were referred for elucidation of a randomly found blood glucose level above 5.5 mmol/l. In addition to fasting glycaemia and circulating levels of insulin and C-peptide, the subjects were tested by an oral glucose tolerance test and an intravenous glucose tolerance test and screened for mutations in the genes encoding glucokinase (GCK), HNF-1α (TCF1), Kir6.2 (KCNJ11) (if aged <2 years) and HNF-4α (HNF4A) (those with a positive family history of diabetes). Results and discussion We identified 35 carriers of GCK mutations causing MODY2, two carriers of TCF1 mutations causing MODY3, one carrier of a HNF4A mutation causing MODY1 and one carrier of a KCNJ11 mutation causing permanent neonatal diabetes mellitus. Of the remaining patients, 11 progressed to type 1 diabetes mellitus (T1DM) and 9 had impaired glucose tolerance or diabetes mellitus of unknown origin. In 23 subjects, an impairment of blood glucose levels was not confirmed. We conclude that 39 of 82 paediatric patients (48%) with randomly found fasting hyperglycaemia suffered from single gene defect conditions, MODY2 being the most prevalent. An additional 11 patients (13%) progressed to overt T1DM. The aetiological diagnosis in asymptomatic hyperglycaemic children and adolescents is a clue to introducing an early and effective therapy or, in MODY2, to preventing any future extensive re-investigations.     

A novel MC4R mutation associated with childhood-onset obesity: A case report

The melanocortin-4-receptor gene (MC4R) is a key regulator of energy homeostasis, food intake and body weight. MC4R gene mutations are associated with early-onset severe obesity. Most patients are heterozygotes, with some reports of homozygotes and compound heterozygotes. The authors report a case involving an eight-year-old girl with progressive weight gain from infancy, body mass index 44 kg/m² (>97th percentile), hyperphagia, hyperinsulinemia and increased linear growth. There was no phenotype of morbid obesity in the parents or sibling. Coding regions and intron-exon boundaries of the genes encoding leptin, leptin receptor, pro-opiomelanocortin and MC4R were analyzed. Two heterozygous coding mutations in the MCR4 gene (S94N and C293R) were detected, of which the second has not been previously reported. The mutations were on opposite chromosomes, confirming compound heterozygosity. The molecular findings and clinical features associated with this novel MC4R mutation are described. The authors emphasize that rare mutations can be found in some patients with severe childhood-onset obesity.     

Leptin and the genetics of obesity

The discovery of the Ob gene and its product, leptin, is a good example of the contribution made by molecular biology to the understanding of mechanisms initially hypothesized from classic physiological studies. Leptin is produced in adipose tissue and acts on the central nervous system to regulate multiple neuroendocrine secretions. In three rare cases of human morbid obesity, the discovery of mutations in the leptin and leptin receptor genes shows that leptin plays a crucial role in the control of weight and several endocrine functions (particularly reproduction). These studies also illustrate the limits of genetics in the investigation of monogenic forms of animal obesity, and the difficulties of linking molecular findings to the pathophysiology of complex diseases, such as human common obesity. Previous searches for mutations in the leptin and leptin receptor genes indicated that these are probably not major genes for common forms of human obesity. This review focuses on the recent molecular findings that have indicated a putative role for the leptin axis in human obesity.     

Leptin and the genetics of obesity

Clément K. Leptin and the genetics of obesity. Acta Pædiatr 1999; Suppl 428: 51–7. Stockholm. ISSN 0803–5326
The discovery of the Ob gene and its product, leptin, is a good example of the contribution made by molecular biology to the understanding of mechanisms initially hypothesized from classic physiological studies. Leptin is produced in adipose tissue and acts on the central nervous system to regulate multiple neuroendocrine secretions. In three rare cases of human morbid obesity, the discovery of mutations in the leptin and leptin receptor genes shows that leptin plays a crucial role in the control of weight and several endocrine functions (particularly reproduction). These studies also illustrate the limits of genetics in the investigation of monogenic forms of animal obesity, and the difficulties of linking molecular findings to the pathophysiology of complex diseases, such as human common obesity. Previous searches for mutations in the leptin and leptin receptor genes indicated that these are probably not major genes for common forms of human obesity. This review focuses on the recent molecular findings that have indicated a putative role for the leptin axis in human obesity. □ Adipose tissue, genetics, leptin, leptin receptor, obesity     

Comprehensive molecular analysis of Japanese patients with pediatric-onset MODY-type diabetes mellitus

Yorifuji T, Fujimaru R, Hosokawa Y, Tamagawa N, Shiozaki M, Aizu K, Jinno K, Maruo Y, Nagasaka H, Tajima T, Kobayashi K, Urakami T. Comprehensive molecular analysis of Japanese patients with pediatric‐onset MODY‐type diabetes mellitus. Background: In Asians, mutations in the known maturity‐onset diabetes of the young (MODY) genes have been identified in only <15% of patients. These results were obtained mostly through studies on adult patients. Objective: To investigate the molecular basis of Japanese patients with pediatric‐onset MODY‐type diabetes. Subjects: Eighty Japanese patients with pediatric‐onset MODY‐type diabetes. Methods: Mitochondrial 3243A>G mutation was first tested by the polymerase chain reaction restriction fragment length polymorphism analysis for maternally inherited families. Then, all coding exons and exon–intron boundaries of the HNF1A, HNF1B, GCK, and HNF4A genes were amplified from genomic DNA and directly sequenced. Multiplex ligation‐dependent probe amplification analysis was also performed to detect whole‐exon deletions. Results: After excluding one patient with a mitochondrial 3243A>G, mutations were identified in 38 (48.1%) patients; 18 had GCK mutations, 11 had HNF1A mutations, 3 had HNF4A mutations, and 6 had HNF1B mutations. In patients aged <8 yr, mutations were detected mostly in GCK at a higher frequency (63.6%). In patients >9 yr of age, mutations were identified less frequently (45.1%), with HNF1A mutations being the most frequent. A large fraction of mutation‐negative patients showed elevated homeostasis model assessment (HOMA) insulin‐resistance and normal HOMA‐β indices. Most of the HNF1B mutations were large deletions, and, interestingly, renal cysts were undetectable in two patients with whole‐gene deletion of HNF1B. Conclusion: In Japanese patients with pediatric‐onset MODY‐type diabetes, mutations in known genes were identified at a much higher frequency than previously reported for adult Asians. A fraction of mutation‐negative patients presented with insulin‐resistance and normal insulin‐secretory capacities resembling early‐onset type 2 diabetes.     

Diagnosis of MODY in the offspring of parents with insulin-dependent and non-insulin-dependent diabetes mellitus

Maturity Onset Diabetes of the Young (MODY) is an autosomal dominant monogenic form of type 2 diabetes mellitus (DM) representing 5% of youth-onset DM in the Caucasian population. In young adults the disease can be present as either non-insulin dependent or insulin-dependent DM. The diagnosis of this genetic disorder in children and adolescents is rare because of the mild glucose metabolism disorder at this time. We performed a metabolic, autoimmune and genetic study in 40 offspring of young parents affected by insulin-dependent DM (Group A) and in 35 offspring of young parents affected by early-onset non-insulin-dependent DM (Group B). Two children of Group A (5%) were found to be affected by fasting hyperglycemia and carry a GCK gene mutation that in one case was present also in the diabetic father. Eighteen offspring of Group B (51%) were positive for GCK or HNF-1alpha gene mutations present in the affected parents. All but two of these young patients had impaired fasting glucose (IFG) or impaired glucose tolerance (IGT). Eleven of them were younger than 16 years. We conclude that screening for DM in youth should be extended to MODY in young families with both non-insulin-dependent and insulin-dependent DM. The sensitivity of the metabolic tests will precede the genetic diagnosis.     

Autosomal inheritance of diabetes in two families characterized by obesity and a novel H241Q mutation in NEUROD1

Background:  The aim of the study was to search for mutations in the NEUROD1 and IPF-1 genes in patients with clinical characteristics of maturity-onset diabetes of the young (MODY) but with no mutations in the HNF-4A (MODY1), GCK (MODY2) and TCF1 (MODY3) genes.
Methods:  We studied 30 unrelated Czech probands with a clinical diagnosis of MODY (median age at testing, 18 yr; median age at the recognition of hyperglycaemia, 16 yr). The promoter, exons and exon/intron boundaries of the NEUROD1 and IPF-1 genes were examined by polymerase chain reaction–denaturing high performance liquid chromatography and direct sequencing.
Results:  While no mutations were found in the IPF-1 gene, a novel H241Q substitution of NEUROD1 gene was identified in two unrelated families. In the first proband, the H241Q mutation led to early diagnosed (20 yr) hyperglycaemia followed by development of diabetic microvascular complications by the age of 32 yr. The second proband suffered from slowly progressing hyperglycaemia detected at the age of 30 yr. Affected members of both families were obese. The overall prevalence of the variant among the general population was 4 of 13 568 chromosomes.
Conclusions:  We report a novel disease-associated variant in NEUROD1 identified among a set of MODYX families. The variant seems to precipitate type-2-like diabetes in excessively obese individuals.     

Childhood obesity complicating the differential diagnosis of maturity-onset diabetes of the young and type 2 diabetes

OBJECTIVE: To describe a proband with features of type 2 diabetes who was found to have concomitant maturity-onset diabetes of the young (MODY) and the consequent multigeneration genetic analysis. DESIGN: Familial genetic analysis. SETTING: Tertiary university medical center. PARTICIPANTS: The proband was a 13.5-yr-old boy with marked non-ketotic hyperglycemia, obesity, systolic hypertension, and insulin resistance. His mother, maternal aunt, grandmother, and great grandmother had diabetes; his father was obese and had early ischemic heart disease. INTERVENTIONS: Clinical examination, laboratory work-up, and DNA study. Outcome measures: Mutation in hepatocyte nuclear factor-1alpha gene, the most common cause of MODY. Results: The proband showed elevated C-peptide level and was negative for beta-cell antibodies. On genetic analysis for MODY, the 291fsinsC mutation was identified in all affected family members. A younger sister who was obese but had no signs of impaired glucose tolerance was also tested on the basis of these findings and was found to have the same mutation. CONCLUSIONS: The patient, who presented with apparent type 2 diabetes, had concomitant MODY 3, inherited from his mother's side, and some features of type 2 diabetes secondary to marked obesity. This combination probably caused an earlier and more severe presentation of the disease and had significant implications for medical management. A search for MODY mutations should be considered in patients with a history of diabetes in three generations of one side of the family, even those in whom the clinical picture resembles type 2 diabetes.     

Adipositas

Twin, adoption, and family studies point to the relevance of genetic factors in body weight regulation. Relatively uniform heritability estimates in the magnitude of 0.6-0.7 have been obtained in twin studies; some family studies have come up with similarly high estimates. In molecular genetic terms the clinically most relevant finding pertains to mutations in the melanocortin-4 receptor gene (MC4R). Approximately 2.5% of extremely obese German children and adolescents harbor such mutations. This type of obesity is inherited in an autosomal dominant fashion. Adult mutation carriers are 15–30 kg heavier than their family members with the wild-type genotype. Hence, functionally relevant MC4R mutations exert a major effect on body weight. Recently, single polygenes have been identified; the respective alleles have a minor effect on body weight.     

Onset of type 1 diabetes mellitus in two patients with maturity onset diabetes of the young

The association between maturity onset diabetes of the young (MODY) and type 1 diabetes mellitus (T1DM) has been rarely described. We report two patients affected by MODY who developed T1DM. Case 1: a 4-yr-old girl referred for glycosuria presented hemoglobin A1c (HbA1c) of 6.6%. Islet cell antibodies (ICA) and anti-glutamic acid decarboxylase (GADA) were initially negative. As her father, uncle and grandmother showed mild hyperglycemia, they were screened for MODY 2. A novel mutation in glucokinase gene was found in the family. Few months later, her glycemic control worsened consistently and she required insulin treatment. A high titer of GADA and ICA was then detected. Six years afterwards insulin requirement is 0.8 U/kg and HbA1c 6.7%. Case 2: a 15-yr-old boy treated for growth hormone deficiency was found with a blood glucose level of 106 mg/dL. HbA1c was 7.2%, ICA and GADA were negative. Family history was positive for autoimmune diseases and type 2 diabetes mellitus. The patient was investigated for MODY 2 and MODY 3, and a mutation of hepatocyte nuclear factor-1 alpha gene was found. The same mutation was found in the mother who had never been referred for hyperglycemia. After 1 yr, due to an unjustified worsening of the metabolic control, autoimmunity was again investigated and a mild positivity was found. He then required insulin therapy and after 5 yr current HbA1c was 8.2%. The diagnosis of MODY does not exclude the risk of developing T1DM. Therefore autoimmunity should be investigated when ordinary treatments fail and metabolic control unexpectedly worsens.     

A novel INS mutation in a family with maturity‐onset diabetes of the young: Variable insulin secretion and putative mechanisms

Insulin gene (INS) mutations cause a rare form of maturity‐onset diabetes of the young (MODY), a heterogeneous group of autosomal dominant diabetes with at least 14 confirmed causative genes. Here, we describe a family with MODY due to a novel INS mutation, detected using massively parallel sequencing (MPS). The proband presented aged 11 years with mild diabetic ketoacidosis. She was negative for IA2 and GAD antibodies. She had a strong family history of diabetes affecting both her two siblings and her mother, none of whom had ketosis but who were considered to have type 1 diabetes and managed on insulin, and her maternal grandfather, who was managed for decades on sulfonylureas. Of note, her younger sister had insulin deficiency but an elevated fasting proinsulin:insulin ratio of 76% (ref 5%‐30%). Sanger sequencing of HNF4A, HNF1A, and HNF1B in the proband was negative. Targeted MPS using a custom‐designed amplicon panel sequenced on an Illumina MiSeq detected a heterozygous INS mutation c.277G>A (p.Glu93Lys). Sanger sequencing confirmed the variant segregated with diabetes within the family. Structural analysis of this variant suggested disruption of a critical hydrogen bond between insulin and the insulin receptor; however, the clinical picture in some individuals also suggested abnormal insulin processing and insulin deficiency. This family has a novel INS mutation and demonstrated variable insulin deficiency. MPS represents an efficient method of MODY diagnosis in families with rarer gene mutations.