A, Study protocol of streptozotocin (STZ)-induced diabetes and assessment of cardiac function. B, Blood glucose levels were highly elevated, whereas cardiac ejection fraction was preserved in STZ. Wilcoxon matched-pairs signed rank test. C, Morphological parameters in either vehicle-treated or STZ-treated CaMKIIδ-WT, S280A and MMVV mice. One-way ANOVA, followed by Dunnett’s multiple comparisons test. D, Preserved systolic heart function in STZ. E, Diastolic heart function (enlarged left atria, reduced E/A, increased E/e’) in 4-week diabetes. One-way ANOVA, followed by Dunnett’s multiple comparisons test. F, Incidence of premature ventricular complexes (PVCs) following isoproterenol+caffeine stress test was increased in diabetic WT animals, whereas CaMKIIδ-cKO was protective. Mann-Whitney test. G, Increased ryanodine receptor (RyR) S2814 phosphorylation and phospholampban (PLB) O-GlcNAcylation in STZ. Two technical replicates (blots) were performed for each protein sample. Mann-Whitney test. The number of biological replicates (n) is shown.