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. 2021 Apr 30;129(1):98–113. doi: 10.1161/CIRCRESAHA.120.318402

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© 2021 The Authors.

Circulation Research is published on behalf of the American Heart Association, Inc., by Wolters Kluwer Health, Inc. This is an open access article under the terms of the Creative Commons Attribution Non-Commercial-NoDerivs License, which permits use, distribution, and reproduction in any medium, provided that the original work is properly cited, the use is noncommercial, and no modifications or adaptations are made.

This article is made available via the PMC Open Access Subset for unrestricted re-use and analyses in any form or by any means with acknowledgement of the original source. These permissions are granted for the duration of the COVID-19 pandemic or until permissions are revoked in writing. Upon expiration of these permissions, PMC is granted a perpetual license to make this article available via PMC and Europe PMC, consistent with existing copyright protections.

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Figure 6. — Diabetes-induced diastolic sarcoplasmic reticulum (SR) Ca2+ leak is CaMKIIδ (Ca²⁺/calmodulin-dependent protein kinase II)-S280 O-GlcNAcylation-dependent. A, Experimental protocol and representative intracellular Ca²⁺ signals (as changes in Fluo-4 fluorescence) showing spontaneous Ca²⁺ waves in wild type (WT) following 4-week of streptozotocin (STZ)-induced diabetes. B, Diabetes slightly reduced the amplitude of the intracellular Ca²⁺ transient and prolonged the Ca²⁺ transient decay without significantly altering SR Ca²⁺ load (n[CaT]=total number of cells/animals, WT+vehicle/normal glucose=16/7, WT+vehicle/high-glucose=9/7, WT+STZ/normal glucose=20/6, WT+STZ/high-glucose=11/6, S280A+STZ/normal glucose=13/5, S280A+STZ/high-glucose=11/5, mutated Met281Val and Met282Val [MMVV]+STZ/normal glucose=13/5, MMVV+STZ/high-glucose=10/5; n[SR load]=total number of cells/animals, WT+Vehicle=12/6, WT+STZ=12/7, S280A+STZ=9/5, MMVV+STZ=10/5). Acute effect of high-glucose within the same genotype/treatment was tested using nested t test. Effect of STZ-induced diabetes (in normal glucose) vs WT+Vehicle was tested using nested 1-way ANOVA, followed by Dunnett multiple comparisons test. C, Ca²⁺ sparks were increased in diabetic WT and further increased by acute high-glucose treatment. D, The increase in Ca²⁺ spark rate was prevented in CaMKIIδ-S280A and was attenuated in the CaMKIIδ-MMVV (n=total number of cells/animals, WT+Vehicle=12/6, WT+STZ=10/6, S280A+STZ=9/5, MMVV+STZ=10/5). Nested t test. CaSpF indicates Ca²⁺ spark frequency.