Calcium release channel RyR2 regulates insulin release and glucose homeostasis
Gaetano Santulli, … , Alain Lacampagne, Andrew R. Marks
Gaetano Santulli, … , Alain Lacampagne, Andrew R. Marks
Published April 6, 2015
Citation Information: J Clin Invest. 2015;125(5):1968-1978. https://doi.org/10.1172/JCI79273.
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Research Article Cardiology Metabolism

Calcium release channel RyR2 regulates insulin release and glucose homeostasis

Abstract

The type 2 ryanodine receptor (RyR2) is a Ca2+ release channel on the endoplasmic reticulum (ER) of several types of cells, including cardiomyocytes and pancreatic β cells. In cardiomyocytes, RyR2-dependent Ca2+ release is critical for excitation-contraction coupling; however, a functional role for RyR2 in β cell insulin secretion and diabetes mellitus remains controversial. Here, we took advantage of rare RyR2 mutations that were identified in patients with a genetic form of exercise-induced sudden death (catecholaminergic polymorphic ventricular tachycardia [CPVT]). As these mutations result in a “leaky” RyR2 channel, we exploited them to assess RyR2 channel function in β cell dynamics. We discovered that CPVT patients with mutant leaky RyR2 present with glucose intolerance, which was heretofore unappreciated. In mice, transgenic expression of CPVT-associated RyR2 resulted in impaired glucose homeostasis, and an in-depth evaluation of pancreatic islets and β cells from these animals revealed intracellular Ca2+ leak via oxidized and nitrosylated RyR2 channels, activated ER stress response, mitochondrial dysfunction, and decreased fuel-stimulated insulin release. Additionally, we verified the effects of the pharmacological inhibition of intracellular Ca2+ leak in CPVT-associated RyR2-expressing mice, in human islets from diabetic patients, and in an established murine model of type 2 diabetes mellitus. Taken together, our data indicate that RyR2 channels play a crucial role in the regulation of insulin secretion and glucose homeostasis.

Authors

Gaetano Santulli, Gennaro Pagano, Celestino Sardu, Wenjun Xie, Steven Reiken, Salvatore Luca D’Ascia, Michele Cannone, Nicola Marziliano, Bruno Trimarco, Theresa A. Guise, Alain Lacampagne, Andrew R. Marks

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Figure 1

Humans and mice with leaky RyR2 channels exhibit glucose intolerance.

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Humans and mice with leaky RyR2 channels exhibit glucose intolerance. OG...
OGTT in healthy subjects (see Supplemental Table 1 for patient characteristics) and patients with CPVT due to RYR2 mutations (see Supplemental Table 2 for RYR2 mutations in CPVT patients) with determination of blood glucose (A) and serum insulin levels (B). *P < 0.05 compared with healthy subjects, 2-tailed Student’s t test. (C) Representative immunoblots of pancreatic islets from CPVT mice chronically (50 mg/kg/d, 4 weeks) treated with S107. 2,4 DNPH, 2,4-dinitrophenylhydrazone; Cys-NO, nitrosylation. (D–F) Quantification of data shown in C (from triplicate experiments). (G and H) Resting cytosolic [Ca2+]cyt is elevated in pancreatic β cells from CPVT mice (pancreatic β cell Ca2+ imaged using acetoxy-methyl-ester fura-2, fura-2 AM). (G) ER Ca2+ stores measured using caffeine to release the RyR2 Ca2+ pool are markedly depleted in pancreatic β cells from CPVT mice (H); acute (10 μM, 4 hours) S107 treatment restores ER Ca2+ by inhibiting RyR2-mediated leak. (I and J) Blood glucose levels following i.p. glucose challenge in WT, RyR2-R2474S, and RyR2-N2386I mice chronically treated with S107. Insulin concentration measured in sera from WT, RyR2-R2474S (K), and RyR2-N2386I (L) mice, following i.p. glucose challenge, with and without chronic S107. (M) Plasma glucagon in fed and fasted (6 hours) conditions. (N) Blood glucose levels measured following i.p. insulin injection. Insets in I–L represent AUC. Data are expressed as mean ± SEM. n = 9–12/group. *P < 0.05 compared with WT, ANOVA, Tukey-Kramer post hoc correction. Additional details are given in Methods.