Type 2 diabetic cardiomyopathy features Ca²⁺ signaling abnormalities, notably an altered mitochondrial Ca²⁺ handling. We here aimed to study if it might be due to a dysregulation of either the whole Ca²⁺ homeostasis, the reticulum–mitochondrial Ca²⁺ coupling, and/or the mitochondrial Ca²⁺ entry through the uniporter. Following a 16-week high-fat high-sucrose diet (HFHSD), mice developed cardiac insulin resistance, fibrosis, hypertrophy, lipid accumulation, and diastolic dysfunction when compared to standard diet. Ultrastructural and proteomic analyses of cardiac reticulum–mitochondria interface revealed tighter interactions not compatible with Ca²⁺ transport in HFHSD cardiomyocytes. Intramyocardial adenoviral injections of Ca²⁺ sensors were performed to measure Ca²⁺ fluxes in freshly isolated adult cardiomyocytes and to analyze the direct effects of in vivo type 2 diabetes on cardiomyocyte function. HFHSD resulted in a decreased IP3R–VDAC interaction and a reduced IP3-stimulated Ca²⁺ transfer to mitochondria, with no changes in reticular Ca²⁺ level, cytosolic Ca²⁺ transients, and mitochondrial Ca²⁺ uniporter function. Disruption of organelle Ca²⁺ exchange was associated with decreased mitochondrial bioenergetics and reduced cell contraction, which was rescued by an adenovirus-mediated expression of a reticulum-mitochondria linker. An 8-week diet reversal was able to restore cardiac insulin signaling, Ca²⁺ transfer, and cardiac function in HFHSD mice. Therefore, our study demonstrates that the reticulum–mitochondria Ca²⁺ miscoupling may play an early and reversible role in the development of diabetic cardiomyopathy by disrupting primarily the mitochondrial bioenergetics. A diet reversal, by counteracting the MAM-induced mitochondrial Ca²⁺ dysfunction, might contribute to restore normal cardiac function and prevent the exacerbation of diabetic cardiomyopathy.

2 型糖尿病心肌病以 Ca ²⁺信号异常为特征，特别是线粒体 Ca ²⁺处理的改变。我们在这里旨在研究这是否可能是由于整个 Ca ²⁺稳态、网状-线粒体 Ca ²⁺偶联和/或线粒体 Ca ²⁺通过单向转运蛋白进入的失调所致。在 16 周的高脂肪高蔗糖饮食 (HFHSD) 后，与标准饮食相比，小鼠出现了心脏胰岛素抵抗、纤维化、肥大、脂质积累和舒张功能障碍。心脏网-线粒体界面的超微结构和蛋白质组学分析显示与 Ca ²⁺不相容的更紧密的相互作用HFHSD 心肌细胞中的转运。进行了 Ca ²⁺传感器的心肌内腺病毒注射以测量新鲜分离的成体心肌细胞中的Ca ²⁺通量并分析体内 2 型糖尿病对心肌细胞功能的直接影响。HFHSD 导致 IP3R-VDAC 相互作用减少，IP3 刺激的 Ca ²⁺向线粒体的转移减少，网状 Ca ²⁺水平、细胞溶质 Ca ²⁺瞬变和线粒体 Ca ²⁺单向转运蛋白功能没有变化。细胞器 Ca ^{2+ 的}破坏交换与线粒体生物能学减少和细胞收缩减少有关，这可以通过腺病毒介导的网状线粒体接头表达来挽救。8 周的饮食逆转能够恢复HFHSD 小鼠的心脏胰岛素信号传导、Ca ²⁺转移和心脏功能。因此，我们的研究表明，网状体-线粒体 Ca ²⁺错配可能通过主要破坏线粒体生物能学在糖尿病心肌病的发展中发挥早期和可逆的作用。通过抵消 MAM 诱导的线粒体 Ca ²⁺功能障碍，饮食逆转可能有助于恢复正常的心脏功能并防止糖尿病心肌病的恶化。