Age-dependent transition from islet insulin hypersecretion to hyposecretion in mice with the long QT-syndrome loss-of-function mutation Kcnq1-A340V

Anniek F Lubberding,Thomas Jespersen,Jens J Holst,Morten Lundh,Brice Emanuelli,Signe S Torekov,Mathilde S Søndergaard,Emil Z Skovhøj,Thomas Svava Nielsen,Thomas Mandrup-Poulsen,Geke A Boer,Jørgen K Kanters,Morten B Thomsen,Jakob B Hansen,Jonas T Treebak,Jinyi Zhang,Maria Villadsen

doi:10.1038/s41598-021-90452-8

Anniek F Lubberding, Thomas Jespersen + Show 15 more

Open Access

https://doi.org/10.1038/s41598-021-90452-8

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Abstract

Loss-of-function (LoF) mutations in KCNQ1, encoding the voltage-gated K+ channel Kv7.1, lead to long QT syndrome 1 (LQT1). LQT1 patients also present with post-prandial hyperinsulinemia and hypoglycaemia. In contrast, KCNQ1 polymorphisms are associated with diabetes, and LQTS patients have a higher prevalence of diabetes. We developed a mouse model with a LoF Kcnq1 mutation using CRISPR-Cas9 and hypothesized that this mouse model would display QT prolongation, increased glucose-stimulated insulin secretion and allow for interrogation of Kv7.1 function in islets. Mice were characterized by electrocardiography and oral glucose tolerance tests. Ex vivo, islet glucose-induced insulin release was measured, and beta-cell area quantified by immunohistochemistry. Homozygous mice had QT prolongation. Ex vivo, glucose-stimulated insulin release was increased in islets from homozygous mice at 12–14 weeks, while beta-cell area was reduced. Non-fasting blood glucose levels were decreased at this age. In follow-up studies 8–10 weeks later, beta-cell area was similar in all groups, while glucose-stimulated insulin secretion was now reduced in islets from hetero- and homozygous mice. Non-fasting blood glucose levels had normalized. These data suggest that Kv7.1 dysfunction is involved in a transition from hyper- to hyposecretion of insulin, potentially explaining the association with both hypoglycemia and hyperglycemia in LQT1 patients.

Highlights

Abbreviations analysis of variance (ANOVA) Analysis of variance areas under the curve (AUC) Area under the curve cyclin-dependent kinase inhibitor 1C (Cdkn1c) Cyclin-dependent kinase inhibitor 1C clustered regularly interspaced short palindromic repeats (CRISPR) Clustered regularly interspaced short palindromic repeats ECG Electrocardiogram endoplasmic reticulum (ER) Endoplasmic reticulum genome-wide association studies (GWAS) Genome-wide association study HET Heterozygous mouse HOM Homozygous mouse HOMA-IR Homeostasis model assessment-estimated insulin resistance
A study in human pancreatic beta-cells showed that some of these susceptibility variants near KNCQ1 were accompanied by either reduced depolarization-induced insulin secretion or impaired insulin granule d ocking[22]. It is unknown whether these variants influence K v7.1 channel function; a recent Danish retrospective cohort study showed that long-QT syndrome (LQTS) patients have a higher prevalence of diabetes, suggesting reduced K + currents could be involved[23]
RR intervals were comparable between genotypes at baseline and after isoprenaline administration (Fig. 1A), as were PR interval (Fig. 1B; P = 0.058) and QRS duration (Fig. 1C; P = 0.96) At baseline, the QT interval was prolonged in homozygous (HOM) mice compared to wildtype (WT; P = 0.03) with a QT interval of 58 ± 2, 60 ± 2 and 65 ± 4 ms in WT, heterozygous (HET) and HOM, respectively (Fig. 1D)

Summary

Introduction

Abbreviations ANOVA Analysis of variance AUC Area under the curve Cdkn1c Cyclin-dependent kinase inhibitor 1C CRISPR Clustered regularly interspaced short palindromic repeats ECG Electrocardiogram ER Endoplasmic reticulum GWAS Genome-wide association study HET Heterozygous mouse HOM Homozygous mouse HOMA-IR Homeostasis model assessment-estimated insulin resistance. Similar findings were made in patients with LoF mutations in KCNH2, encoding Kv11.1 (hERG), the second most common cause of LQTS12 This may be hazardous, since glucose ingestion, as well as hypoglycaemia, prolongs the QT interval in healthy individuals[12,13,14] and LQTS p atients[12,14], which could potentially lead to cardiac a rrhythmias[15]. Kcnq[1] homozygous knockout (KO) mice showed increased insulin sensitivity revealed by lower blood glucose and insulin levels during fasting[27] These observations emphasize that studies to provide a unifying model of the precise role of Kv7.1 in pancreatic beta-cell function and glucose homeostasis are in demand

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