Mitophagy Mitigates Mitochondrial Fatty Acid -oxidation Deficient Cardiomyopathy

Cardiomyocytes rely on mitochondrial fatty acid -oxidation (FAO) for ATP production in the healthy heart but can exhibit marked metabolic flexibility in response to diverse physiological circumstances. Mutations or deficiencies in FAO enzymes can lead to a spectrum of symptoms, ranging from muscle weakness to severe cardiomyopathy, and, in some instances, culminate in neonatal/infantile mortality. It is generally believed that under FAO deficit, mitochondria encounter stress, potentially triggering the initiation of mitophagy, a process crucial for maintaining mitochondrial quality. We explored the link between FAO deficiency and mitophagy utilizing FAO-deficient mice generated through cardiomyocyte-specific deletion of the Carnitine Palmitoyltransferase 2 (CPT2). Intriguingly, our findings contradicted the prevailing hypothesis, revealing an unexpected decline in mitophagy in FAO-deficient hearts. Employing an integrated approach involving quantitative proteomics, metabolomics, and transcriptomics assays, we identified suppressed a PINK1/Parkin signaling pathway in CPT2-deficient heart tissues. Our study demonstrated that the loss of cardiac FAO impairs the PINK1 pathway by modulating the mitochondrial rhomboid protease PARL (presenilin-associated rhomboid-like protein). Furthermore, inhibiting USP30, a mitochondrial deubiquitinating enzyme antagonizing PINK1/Parkin function, restored cardiac mitophagy, thereby alleviating FAO-associated cardiac dysfunction. Notably, the deletion of USP30 conferred a significant survival advantage to FAO-deficient animals, doubling the median survival and substantially improving the maximum survival rate. The study unveiled a novel connection between FAO and PINK1-dependent mitophagy, presenting a potential therapeutic avenue for addressing FAO-deficient cardiomyopathies. To gain insights into the mitophagic regulation underlying impaired FAO in the heart, we generated FAO-deficient mice with cardiomyocyte-specific deletion of the Carnitine Palmitoyltransferase 2 (CPT2) and USP30H-KO mice (Myh6-Cre/USP30fl/fl) lacking cardiac USP30 To study the loss of USP30 in the context of CPT2 deletion we also generated CPT2/USP30H-KO mice We then conducted RNASeq from the total RNA was isolated from mouse cardiac samples of each genotypes and performed a comprehensive transcriptomic analysis健康心脏中的心肌细胞依赖线粒体脂肪酸β-氧化（fatty acid β-oxidation, FAO）生成三磷酸腺苷（ATP），但在多种生理状态下可展现出显著的代谢灵活性。脂肪酸β-氧化酶的突变或缺陷可引发一系列病症，从轻症肌肉无力到重症心肌病，部分病例甚至会导致新生儿或婴儿期死亡。学界普遍认为，在脂肪酸β-氧化缺陷状态下，线粒体会遭遇应激，进而可能触发线粒体自噬（mitophagy）的启动——这一过程对维持线粒体质量至关重要。我们通过构建心肌细胞特异性敲除肉碱棕榈酰转移酶2（Carnitine Palmitoyltransferase 2, CPT2）的脂肪酸β-氧化缺陷小鼠模型，探究了脂肪酸β-氧化缺陷与线粒体自噬之间的关联。有趣的是，我们的研究结果与主流假说相悖，发现脂肪酸β-氧化缺陷的心脏组织中线粒体自噬出现了意料之外的下降。通过整合定量蛋白质组学、代谢组学与转录组学分析手段，我们在CPT2缺陷的心脏组织中发现PINK1/Parkin信号通路受到抑制。本研究证实，心肌细胞脂肪酸β-氧化的缺失会通过调控线粒体菱形蛋白酶PARL（早老素相关菱形样蛋白, presenilin-associated rhomboid-like protein）损伤PINK1通路。此外，抑制拮抗PINK1/Parkin功能的线粒体去泛素化酶USP30，可恢复心脏线粒体自噬，从而缓解脂肪酸β-氧化相关的心脏功能障碍。值得注意的是，敲除USP30能为脂肪酸β-氧化缺陷的动物带来显著的生存优势，将中位生存期延长一倍，并大幅提高最高生存率。本研究揭示了脂肪酸β-氧化与PINK1依赖型线粒体自噬之间的全新关联，为治疗脂肪酸β-氧化缺陷相关心肌病提供了潜在的治疗途径。为深入探究心脏脂肪酸β-氧化受损时的线粒体自噬调控机制，我们构建了心肌细胞特异性敲除CPT2的脂肪酸β-氧化缺陷小鼠，以及心脏特异性敲除USP30的USP30H-KO小鼠（Myh6-Cre/USP30fl/fl）。为研究CPT2敲除背景下USP30的缺失效应，我们还构建了CPT2/USP30H-KO双敲除小鼠。随后，我们从各基因型小鼠的心脏样本中提取总RNA进行RNA测序，并开展了全面的转录组学分析。