CFTR potentiator therapy ameliorates impaired insulin secretion in CF patients with a gating mutation

JCF-01257; No of Pages 3

Journal of Cystic Fibrosis xx (2015) xxx – xxx www.elsevier.com/locate/jcf

Short Communication

CFTR potentiator therapy ameliorates impaired insulin secretion in CF patients with a gating mutation☆ Reuven Tsabari a , Hila Iron Elyashar a , Malena Cohen Cymberknowh a , Oded Breuer a , Shoshana Armoni a , Galit Livnat c , Eitan Kerem a , David Haim Zangen b,⁎ b

a Division of Pediatric Pulmonology and CF center, Jerusalem 91240, Israel Division of Pediatric Endocrinology, Hadassah Hebrew University Medical Center, Jerusalem 91240, Israel c Israel CF center, Carmel Medical Center, Haifa, Israel

Received 15 August 2015; Available online xxxxrevised 12 October 2015; accepted 19 October 2015

Abstract Objective: To investigate the effect of treatment with ivacaftor on insulin secretion in patients with cystic fibrosis (CF) (ΔF508\S549R) having CFRD/impaired insulin secretion. Methods: A standard OGTT was performed before and after 16 weeks of treatment with ivacaftor in 2 sibling patients with CF carrying the S549R gating mutation. The area under the curve (AUC) for glucose and insulin was calculated using the trapezoidal estimation. Results: Before treatment, the OGTT of case 1 showed indeterminate glycemia; the OGTT of case 2 indicated CFRD. After ivacaftor treatment the OGTT demonstrated improved insulin secretion pattern mainly by increased first phase early insulin secretion, resulting in reduction of the AUC of glucose in both cases. Conclusions: The treatment with ivacaftor in patients with CF carrying gating mutation can ameliorate impaired insulin secretion. Further studies and larger cohorts are needed to evaluate the impact of ivacaftor on insulin secretion in patients with CF carrying gating or other mutations. © 2015 European Cystic Fibrosis Society. Published by Elsevier B.V. All rights reserved. Keywords: Cystic fibrosis; CFRD; Impaired OGTT; CFTR potentiator; Ivacaftor; Gating mutation

1. Introduction The prevalence of decreased insulin secretory capacity in patients with cystic fibrosis (CF) increases with age. Mild Abbreviations: ATP, adenosine triphosphate; BMI, body mass index; CF, cystic fibrosis; CFRD, cystic fibrosis-related diabetes; CFTR, cystic fibrosis transmembrane conductance regulator; FEV1, forced expiratory volume in 1 second; IGT, indeterminate glucose tolerance test; OGTT, oral glucose tolerance test ☆ This case study has not been published or presented previously. ⁎ Corresponding author at: Division of Pediatric Endocrinology and Diabetes, Hadassah Hebrew University Medical Center, Jerusalem 91240, Israel. Tel.: +972 25844430; fax: + 972 25845028. E-mail address: [email protected] (D.H. Zangen). ☆ This case study has not been published or presented previously.

postprandial hyperglycemia, resulting from delayed first phase insulin secretion, subsequently deteriorates into impaired glucose tolerance and cystic fibrosis related diabetes (CFRD) with or without fasting hyperglycemia [1]. To date, 15–20% of adolescents and about half of the adult patients with CF have CFRD [2]. Given the improved treatment, prognosis and longevity of life in CF, it is expected that most patients with CF will develop CFRD during the course of the disease. CF gating mutations are characterized by a defect in the flux of chloride through the CFTR. Ivacaftor, a medication that potentiates the chloride flux by activating the CFTR protein without ATP [3], has recently become available for the treatment of patients with CF carrying gating mutations [4]. Although CFTR protein is expressed in pancreatic β cells, its exact role in insulin secretion has not been carefully

http://dx.doi.org/10.1016/j.jcf.2015.10.012 1569-1993/© 2015 European Cystic Fibrosis Society. Published by Elsevier B.V. All rights reserved. Please cite this article as: Tsabari R, et al, CFTR potentiator therapy ameliorates impaired insulin secretion in CF patients with a gating mutation, J Cyst Fibros (2015), http://dx.doi.org/10.1016/j.jcf.2015.10.012

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characterized. Several recent studies have focused on the correlation between CFTR function and β cells insulin secretion capacity. The inhibition or knockdown of CFTR in β cells resulted in reduced glucose-induced electrical activities and insulin secretion [5,6]. Given that ivacaftor induces potentiation of mutated CFTR protein in the lungs, we evaluated the possible effect of ivacaftor on CFRD in CF patients carrying class III mutations. We present two patients with CFRD/impaired insulin secretion in which ivacaftor therapy for 16 weeks improved insulin secretion and resolved CFRD or indeterminate glycemia (INDET). 2. Clinical cases and methods 2.1. Case 1 A 24 year old male with pancreatic insufficient CF (ΔF508\S549R) was diagnosed at 1.5 years of age. His clinical course included chronic bronchiectatic lung disease. At age 24 y he had FEV1 of 75% predicted and a body mass index (BMI) of 21.5. He was diagnosed with indeterminate glycemia at 22 y of age. He has not required either oral hypoglycemic medications or insulin treatment. 2.2. Case 2 A 22 year old sister of case 1 was diagnosed with CF at birth (ΔF508\S549R). Her clinical course included chronic bronchiectatic lung disease and at 22 y of age she had FEV1 of 57% predicted, a BMI of 21 and pancreatic insufficiency. At the age of 19 y, she was diagnosed with impaired glucose tolerance test which deteriorated to CFRD at the age of 21 y. Insulin administration was recommended but deferred due to patient refusal. 2.3. Methods A standard OGTT was performed before and following 16 weeks of ivacaftor treatment. A 50% glucose solution at a dose of 1.75 g/kg body weight (maximum 75 g) was administered orally. Plasma glucose levels were assessed in venous blood samples at baseline and at 30, 60, 90 and 120 min using a YSI 2700 glucose analyzer (Yellow Springs Instruments, Yellow Springs, OH). Concomitant insulin levels were measured by radioimmunoassay (Linco Research, St. Charles, MO). The area under the curve (AUC) for glucose and insulin was calculated using the trapezoidal estimation. The study was approved by the Institutional Review Board of the Hadassah-Hebrew University Medical Center and written informed consent was obtained from the study participants. 3. Results Glucose and insulin levels during the OGTT of case 1 are shown in Fig. 1A. The OGTT pre-ivacaftor demonstrating indeterminate glycemia with a glucose level of 208 mg/dl at the

60 min time point normalized after ivacaftor treatment. The insulin secretion profile also was modified after treatment. While the first phase response was relatively low pretreatment and reached only 102 pmol/l at the 30 min time point, after 16 weeks of ivacaftor treatment, plasma insulin level at this time point increased to 140 pmol/l. While insulin secretion during ivacaftor therapy was approximately 40% higher by the 30 minute point in patient 1, it was lower during the rest of the OGTT. Despite lower 60–120 min insulin levels, the AUC of glucose levels after ivacaftor treatment decreased by 12.35%, highlighting the importance of early insulin secretion in maintaining oral glucose tolerance. Reactive hypoglycemia was present at the end of the OGTT following ivacaftor treatment (as previously reported) indicating the need to monitor glucose levels for hypoglycemia at the end of OGTT or following significant carbohydrate ingestion. The glucose and insulin levels during the OGTTs of case 2 are shown in Fig. 1B. The OGTT pre-ivacaftor treatment demonstrated CFRD with fasting hyperglycemia. Glucose level at time 0 was 130 mg/dl (0 min) and at 120 min the glucose level was 214 mg/dl, meeting the criteria of CFRD. After 16 weeks of ivacaftor treatment, the glucose level of 257 at 60 min did place the patient in the category of (only) indeterminate glycemia, but both fasting and the 120 glucose levels were lower and within the normal range. When comparing OGTT testing done before and after ivacaftor treatment, the AUC for insulin increased by 77% and the AUC for glucose decreased by 16%. 4. Discussion In this report we show an improvement of glucose metabolism in two patients with CF carrying gating mutations following 16 weeks of ivacaftor treatment. In one subject, the initiation of ivacaftor treatment was associated with a change from CFRD to indeterminate glycemia and in the other, ivacaftor was associated with improvement from indeterminate glycemia to normal glucose tolerance . Analyzing insulin levels during the OGTT we found that the increased insulin levels (reflecting higher secretion capacity) in the first 30–60 min of the OGTT may be the mechanism for this clinical observation. Further support for our observation is based on an additional case at another CF center where a 13.5 y girl with CF (W1282X/S549R) and BMI of 24.4 was diagnosed with CFRD based on blood glucose level of 206 mg/dl at 120 min during OGTT. After 10 weeks of treatment with ivacaftor there was a resolution of the CFRD resulting in a normal OGTT. Unfortunately, insulin measurements where not reported. A recent pilot study on CF patients with another gating mutation (G551D) demonstrated that one month treatment of ivacaftor may have generally improved the total insulin secretion capacity of their pancreatic beta cells [7]. When analyzing the data in the 2 patients from this study that had overt CFRD, ivacaftor treatment actually lowered the total insulin levels (during the OGTT or IVGTT) whereas glucose levels during the OGTT were not decreased in both patients. In our 2 patients, the total AUC of insulin was not increased but the 30–60 min insulin level is better post-ivacaftor in both

Please cite this article as: Tsabari R, et al, CFTR potentiator therapy ameliorates impaired insulin secretion in CF patients with a gating mutation, J Cyst Fibros (2015), http://dx.doi.org/10.1016/j.jcf.2015.10.012

R. Tsabari et al. / Journal of Cystic Fibrosis xx (2015) xxx–xxx

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Fig. 1. Oral glucose tolerance test results in Case 1(A) and Case 2(B).

patients resulting in an overall lower and better glucose response during the OGTT. This difference may be due to the longer exposure (3 months) to ivacaftor in our study, and is similar to the findings in another patient reported recently [8]. Alternatively, it might be that the defective first phase insulin secretion may be responsible for abnormal glucose metabolism in CF. Improving this specific parameter in the S549R mutation may account for the improvement of the OGTT which may slow down the pathophysiologic cascade leading to overt CFRD. Two very recent intracellular mechanistic studies focused on the role of CFTR in pancreatic beta cells (5–6). CFTR was found to be expressed in insulin secreting cells while its inhibition resulted in decreased glucose induced insulin secretion possibly due to reduction in membrane chloride current (5), which is essential for the promotion of exocytosis of intracellular insulin granules (6). Our observation that ivacaftor primarily improves the early phase of insulin secretion goes along with these findings as improving CFTR function may enable the immediate exocytosis of intracellular insulin granules in response to hyperglycemia. The insulin secretion in response to ivacaftor enables early phase insulin action and early normalization or improvement of the OGTT in patients with CFRD In conclusion, we describe the beneficial effect of 4 month ivacaftor treatment on the pathologic OGTT of 2 patients with CF carrying the S549R gating mutation. This beneficial effect may be partially due to the increased earlier insulin secretion capacity. Further data and statistical analysis are needed to confirm the causal relationship in our observation. Larger cohorts and studies on the clinical importance of CFTR in beta

cell function are indicated in order to evaluate the efficacy of new medications in treating different stages of aberrant glucose metabolism in CF. Acknowledgments The authors thank Peloton Advantage, Parsippany, NJ, for editorial assistance and formatting this manuscript for submission. References [1] O'Riordan SMP, et al. Management of cystic fibrosis-related diabetes in children and adolescents. Pediatr Diabetes 2009;10(Suppl. 1):43–50 (Part I). [2] Moran A, et al. Cystic fibrosis-related diabetes: current trends in prevalence, incidence, and mortality. Diabetes Care 2009;32(9):1626–31. [3] Eckford PDW, et al. (CFTR) potentiator VX-770 (ivacaftor) opens the defective channel gate of mutant CFTR in a phosphorylation-dependent but ATP-independent manner *, 770; 2012. [4] De Boeck K, et al. Efficacy and safety of ivacaftor in patients with cystic fibrosis and a non-G551D gating mutation. J Cyst Fibros 2014;13(6): 674–80. [5] Guo JH, et al. Glucose-induced electrical activities and insulin secretion in pancreatic islet β-cells are modulated by CFTR. Nat Commun 2014;5:4420. [6] Edlund A, et al. CFTR and Anoctamin 1 (ANO1) contribute to cAMP amplified exocytosis and insulin secretion in human and murine pancreatic beta-cells. BMC Med 2014;12:87. [7] Bellin M, Laguna T. Insulin secretion improves in cystic fibrosis following ivacaftor correction of CFTR: a small pilot study. Pediatr Diabetes 2013; 14(6):417–21. [8] Jr DH, et al. Resolution of cystic fibrosis-related diabetes with ivacaftor therapy. Am J Respir Crit Care Med 2014;190(5):590–1.

Please cite this article as: Tsabari R, et al, CFTR potentiator therapy ameliorates impaired insulin secretion in CF patients with a gating mutation, J Cyst Fibros (2015), http://dx.doi.org/10.1016/j.jcf.2015.10.012