BSPED2010 Oral Communications Oral Communications 3 (3 abstracts)
In vitro recovery of functional KATP channels in congenital hyperinsulinism of infancy (CHI)
K E Cosgrove 1 , P D Powell 1 , C Bellanne-Chantelot 2 , S Ellard 3 , P Clayton 4 , K Hussain 5 , P de Lonlay 2 & M J Dunne 1
1University of Manchester, Manchester, UK; 2Hopital Necker Enfants Malades, Paris, France; 3Royal Devon and Exeter Foundation NHS Trust, Exeter, UK; 4Royal Manchester Children’s Hospital, Manchester, UK; 5Institute of Child Health, London, UK.
Congenital hyperinsulinism (CHI) is characterised by unregulated insulin secretion from pancreatic β-cells. The most severe forms are associated with defects in SUR1 and Kir6.2 (encoded by ABCC8 and KCNJ11), which form KATP channels in β-cells. Diazoxide therapy often fails in the treatment of CHI and may be due to reduced cell surface expression of KATP channels. We investigated methods to increase surface expression of KATP channels using conditions known to increase trafficking in recombinant expression systems. Tissue was isolated during pancreatectomy from 8 patients with CHI and from adult cadaver organ donors with permission. Isolated cells were maintained at 37oC or 25oC in the presence or absence of [1] PMA, forskolin and IBMX; [2] 4-phenylbutyrate; or [3] BPDZ154. Surface expression of functional KATP channels was assessed by patch-clamp electrophysiology. RT-PCR on RNA from CHI β-cells and mutation screening of DNA were used document the expression of KATP channel genes. In 5/8 patients, all of whom had ABCC8 mutations, no changes in KATP channel activity were observed under different cell culture conditions. However, in 3 patients, in vitro recovery of functional KATP channels occurred. Patient #1 demonstrated recovery of KATP channel function in vitro following incubation of cells at 25oC with/without 4-phenylbutyrate. KATP channels were recovered in Patient #2 β-cells following incubation with PMA, forskolin and IBMX, or BPDZ154. Patient #3 β-cells demonstrated KATP channel recovery following incubation with BPDZ154. All 3 patients had mutations in ABCC8 detected by DNA screening or by RT-PCR on pancreatic RNA. This study demonstrates that modified cell culture conditions enhance cell surface expression of KATP channels in CHI β-cells and suggests that chemical modification of SUR1 by agents such as 4-phenylbutyrate may have some clinical benefit in the future treatment of CHI.
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Endocrine Abstracts
ISSN 1470-3947 (print) | ISSN 1479-6848 (online)
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