Long-Term Sulfonylurea Response in KCNJ11 Neonatal Diabetes

Neonatal diabetes mellitus is a rare, monogenic form of diabetes occurring during the first 6-9 months of life characterized by hyperglycemia requiring exogenous insulin therapy. The estimated incidence is 1 per 12000 newborns. Although homozygous or compound heterozygous mutations in the genes IPF1 or GCK were the first genetic causes of this disease to be identified, activating mutations in the KIR6.2 and sulfonylurea receptor 1 (SUR1) subunits of the pancreatic ATP-sensitive K+ channel, coded for by the genes KCNJ11 and ABCC8, have recently been identified as the major causes of both transient and permanent neonatal diabetes. In the normal pancreatic beta-cell, metabolism results in increased cellular ATP, which binds to KIR6.2. The potassium channel subsequently closes and hence depolarizes the membrane initiating insulin release via increased calcium entry. Conversely, increased cellular ADP acts on SUR1 to open the channel and prevent insulin release. Activating mutations in these channels reduces sensitivity to the inhibitory actions of ATP and increases sensitivity to the stimulatory actions of ADP. This causes the ATP-sensitive K+ channel to remain open, even in the presence of glucose, therefore preventing insulin release. Sulfonylureas act by an ATP-independent mechanism to close these channels even when mutations are present. Sulfonylureas result in insulin release and were therefore immediately considered and showed to be a potential treatment option in neonatal diabetes caused by mutations in these channels. The effective replacement of insulin treatment by high-dose sulfonylureas has been shown to be successful in 90% of patients with Kir6.2 mutations and 85% of patients with SUR1 mutations resulting in improved glycemic control.

This dramatic effect of sulfonylurea is now standard, world-wide treatment in neonatal diabetes due to a mutation in either KCNJ11 or ABCC8. There is, however, far no information on long-term use of sulfonylurea in patients with KCNJ11 or ABCC8 mutations. The investigators have therefore initiated an international, multicenter, prospective study aiming to include some 75 patients aged from 9 years with a genetic diagnosis of diabetes due to a KCNJ11 gene mutation identified by sequencing in Bergen, Norway; Exeter, U.K.; Paris, France or Rome, Italy. Most patients were referred based on membership in the International Society of Pediatric and Adolescent Diabetes. All of the patients attempted transfer from treatment with insulin to a sufficient dose of sulfonylureas. No other selection criteria were applied, and all patients were included when there was outcome data following the attempted transfer. The observation period was at least 9 years after commencing sulfonylureas in all patients. The study is conducted in accordance with the Declaration of Helsinki and informed consent has been obtained from all participating patients, with parental consent given on behalf of children.

Inclusion criteria

• Permanent diabetes due to a mutation in KCNJ11 (KIR6.2)
• Patients successfully transferred from insulin to sulfonylurea
• Transferred to sulfonylurea treatment before November 1, 2006 (ie 9 years off insulin)
• Willing and able to provide informed consent (parents if younger than 16 years of age)

Exclusion criteria

• Permanent diabetes not due to a mutation in KCNJ11 (KIR6.2)
• Patients not successfully transferred from insulin to sulfonylurea
• Transferred to sulfonylurea treatment after November 1, 2006 (ie less than 9 years off insulin)
• Not willing or able to provide informed consent (parents if younger than 16 years of age)