Defects of KCJN11 gene, encoding Kir6.2 potassium channel subunit, is the most frequent cause of diabetes developing in children up to 6 months of age. Activated heterozygous missense mutation in the KCNJ11 gene disturbs the biosynthesis of insulin and cause diabetes which manifested during the first weeks of life. We performed the first molecular genetic study and made description of case of neonatal diabetes in Kazakhstan. The role of molecular genetic analysis of defects of beta-cell function in the differential diagnosis of diabetes in children during the first year of life was described.
Actuality: Neonatal diabetes is diagnosed within the first 6 months of life and affects approximately 1 in 100,000 live births. Two main subgroups are recognised in about equal proportions: permanent neonatal diabetes and transient neonatal diabetes. The latter remits in infancy/childhood but may recur later in life. Neonatal diabetes is a monogenic disorder with mutations in 20 different genes reported. Early genetic diagnosis is important, since some forms involve the ATP-sensitive potassium channel on the beta cell membrane and respond to treatment with sulfonylureas.
Research aim: the determination of role molecular genetic analysis in the diagnosis of neonatal diabetes.
Research source: Histories of illnesses of patients with the inherited diabetes mellitus.
There are more data testifying the genetic heterogeneity of diabetes mellitus (DM) in childhood. The molecular-genetic analysis's achievements are allowed to reveal the etiology of DM in the patients of the first 6 months of life [1]. For the children of this age-related group with autoimmune defeat of pancreas with development of type 1 diabetes can be related to innate genetic pathology of beta-cell function. The diabetes mellitus that educed in the first 6 months of life called neonatal diabetes. Neonatal diabetes is attributed to the group of monogenic forms of diabetes. It is caused by the mutation of one gene [2].
A neonatal diabetes is caused by the defects in β-cells of pancreas and associated with mutations which are activating of in the genes of КСNJ11, ABCC8 encoding the ATP-dependent potassium channels today [3-5].
ATP-sensitive potassium channels play a central role in glucose- stimulated insulin secretion from pancreatic beta cells: insulin secretion is initiated by closure of the channels and inhibited by their opening (Fig. 1). Potassium channel is an octameric complex of four pore-forming, inwardly rectifying potassium- channel subunits (Kir6.2) and four regulatory sulfonylureareceptor subunits (SUR1). Both Kir6.2 and SUR1 are required for correct metabolic regulation of the channel: ATP closes the channel by binding to Kir6.2, and magnesium nucleotides (Mg- ADP and Mg-ATP) stimulate channel activity by interacting with
SUR1. Sulfonylureas stimulate insulin secretion in type 2 diabetes by binding to SUR1 and closing potassium channels by an ATP-independent mechanism.
The gene of KCJN11 encodes the subunit Kir6.2 and gene ABCC8 - subunit of SUR1. The Kir6.2 and SUR1 are need to regulation of insulin secretion. While the KCNJ11 is causing the closure of ATP- sensitive potassium channels by activating mutations, it's leads to the development of neonatal diabetes. The pathogenesis of the disease is associated with a decrease in the output of potassium from the cells and hyperpolarization β-cells of membrane. Children with this mutation usually have diabetes before the age of 6 months, accompanied by ketoacidosis and the lack of C- peptide [4].
Here is a description of the own observation of the child which have type 1 diabetes and after a detailed examination - was changed to neonatal diabetes.
Child K.A, aged 2 years enrolled in our hospital DCCH "Aksai" with type 1 diabetes. This child age of 1 month entered infectious hospital with complaints of fever up to 38 degrees, thirst, polydipsia, polyuria, weight loss, dry skin, weakness. There was educed a hyperglycaemia 30 mmol/l, ketonuria at a receipt. There was diagnosed type 1 diabetes performed intravenous rehydration therapy and insulin therapy. The girl was transferred to CMCH №2 after 5 days where admission was noted lethargy, drowsiness. The examination revealed hypoglycemia 2.5 mmol / l, therefore carried out by intravenous infusion of 40% glucose. Hypodermic introduction of aktrapid was further conducted a child for to a 1 unit 5 times before every feeding with pectoral milk. Then a child was translated on the mode of frequent injections: 2 units of lantus before sleep and 1 unit of novorapid before eating.
The child was observed a tendency to hypoglycemia at the age of 4 months called the "honeymoon" because of that the insulin dose was reduced.
A child was hospitalized in the DCCH "Aksay" in age 1,5 years. Anthropometric data correspond to the age-related norm: a height are 80 cm, weight are 11 kg. Before entering permanent establishment a child got the intensifyed insulin therapy: 1 units of protaphane before sleep and 0,2 units of novorapid before 3 basic eating. There was a not symptom of deficit of insulin absented at an inspection: a skin and mucous membranes were well water-wets, there was not a deficit of mass of body, poliurias and polydesum. A child has got normoglycemia: 08.00- 5,9mmol / l after 2 hours -6,9mmol / l 13.00- 5,2mmol / l after 2 hours - 6,6mmol / l 18.00- 5,2mmol / l after 2 hours - 6.6 mmol / l 22.00 - 5.3 mmol / l 03.00-4,7 mmol / l.
The level of glycated hemoglobin (HbA1c) was low-near 3.75% (normal laboratory 4,2-5,7%).
The diagnosis of type 1 diabetes was rejected on the basis of age of onset of diabetes (1 month), low insulin requirements (less than 1 unit per day), low level of glycated hemoglobin (HbA1c 3.75%) show hidden hypoglycemia, low birth weight (2800 grams). Because of that for a child diagnosed transient neonatal diabetes and insulin child canceled.
Unfortunately molecular genetic analysis of monogenic forms of diabetes is not carried out in Kazakhstan. Therefore research of genes KCNJ11, INS, ABCC8, responsible was conducted in the laboratory of the University of Exeter genetic (UK). The child revealed heterozygous missense mutation in the gene KCNJ11, exon 1, c.685G> A, r.Glu229Lys (p.E229K), confirming the diagnosis of transient neonatal diabetes.
Description of 12 cases of this mutation was first p.E229 conducted by British scientists molecular laboratory of the University of Exeter (Flanaganetal, 2007) [3]. There are such a manifestation of diabetes is observed in individuals under the age of 0 to 16 weeks. Our patient's DM debuted at the age of 4 weeks.
Remission of the disease and normalization of glycemia observed up to 6 months - the average age of 35 weeks (2-208). In our case we decrease the dose of insulin was carried out at 16 weeks due to the increasing incidence of hypoglycemia although the complete cancelling of insulin was carried out. An information we need was about two-phase flow of diabetes in individuals with a mutation p.E229K. The authors said that relapse occurs in adolescence and early adulthood. Among those with a mutation can be p.E229K adult patients with diabetes and are not identified in the neonatal period. All of that was the reason for genetic research of parents of the child.
In a research of the mother aged 23 years old was found hyperglycemia 15 mmol / l. Note that maternal diabetes haven't got any symptoms. Molecular genetic analysis revealed a heterozygous missense in women similar mutation in the gene KCNJ11, exon 1, c.685G> A, r.Glu229Lys (p.E229K).
The molecular genetic research is proving that p.E229K mutation may be responsible not only for the appearance of transient
neonatal diabetes but also cause diabetes in other age groups which is often misdiagnosed as type 1 or type 2 diabetes. A molecular research should be carried out in patients with diabetes regardless of age of onset and duration of diabetes. In this clinical case a mutation was inherit from mother to child. There are 2 healthy children in the family.
From the works of British scientists it is known that patients with activating mutations in KCNJ11 observed good response to insulin secretion sulfonylureas. There are up to 90% of children with neonatal diabetes can be successfully transferred from insulin to sulfonylurea drugs [3-5]. Therefore, all children with diabetes manifestation of up to age of 6 months should be carried out genetic testing. When the child is stabilized on insulin therapy it may be an attempt to transfer to the tablet formulations of sulfonylureas.
The child's mother was appointed sulfonylurea hypoglycemic drugs. At this therapy was achieve normalization of carbohydrate metabolism. In the case of recurrence of diabetes of a child during adolescence or early adulthood it may be an attempt to treat it with oral sulfonylureas and not insulin.
In conclusion, important to say that the molecular genetic research of patients with diabetes mellitus is significantly. It is possible to:
- A differential diagnosis conduct between neonatal diabetes mellitus and autoimmune type 1 diabetes in young children
- Identify transient diabetes with onset in infancy
- Completely abolish insulin to child with transient diabetes
- Identify maternal diabetes, which is asymptomatic
- Assign to the mother tablet sulfonylurea to achieve normoglycemia.
- Provide medical and genetic counseling of families with monogenic diabetes.
It is necessary to introduce molecular genetic diagnosis of monogenic forms of diabetes in Kazakhstan. It must be carried out in patients with diabetes regardless of age of onset and disease duration.
The authors are grateful to the scientists molecular laboratory of the University of Exeter (UK) for free assistance in conducting genetic studies in families with hereditary diabetes.
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