Max-Delbrück-Center for Molecular Medicine in the Helmholtz Association (MDC), Berlin, Germany.
DZHK (German Centre for Cardiovascular Research), partner site Berlin, Berlin, Germany.
J Cachexia Sarcopenia Muscle. 2021 Oct;12(5):1249-1265. doi: 10.1002/jcsm.12749. Epub 2021 Jul 1.
Aging is associated with a progressive reduction in cellular function leading to poor health and loss of physical performance. Mitochondrial dysfunction is one of the hallmarks of aging; hence, interventions targeting mitochondrial dysfunction have the potential to provide preventive and therapeutic benefits to elderly individuals. Meta-analyses of age-related gene expression profiles showed that the expression of Ahnak1, a protein regulating several signal-transduction pathways including metabolic homeostasis, is increased with age, which is associated with low VO and poor muscle fitness. However, the role of Ahnak1 in the aging process remained unknown. Here, we investigated the age-related role of Ahnak1 in murine exercise capacity, mitochondrial function, and contractile function of cardiac and skeletal muscles.
We employed 15- to 16-month-old female and male Ahnak1-knockout (Ahnak1-KO) and wild-type (WT) mice and performed morphometric, biochemical, and bioenergetics assays to evaluate the effects of Ahnak1 on exercise capacity and mitochondrial morphology and function in cardiomyocytes and tibialis anterior (TA) muscle. A human left ventricular (LV) cardiomyocyte cell line (AC16) was used to investigate the direct role of Ahnak1 in cardiomyocytes.
We found that the level of Ahnak1 protein is significantly up-regulated with age in the murine LV (1.9-fold) and TA (1.8-fold) tissues. The suppression of Ahnak1 was associated with improved exercise tolerance, as all aged adult Ahnak1-KO mice (100%) successfully completed the running programme, whereas approximately 31% male and 8% female WT mice could maintain the required running speed and distance. Transmission electron microscopic studies showed that LV and TA tissue specimens of aged adult Ahnak1-KO of both sexes have significantly more enlarged/elongated mitochondria and less small mitochondria compared with WT littermates (P < 0.01 and P < 0.001, respectively) at basal level. Further, we observed a shift in mitochondrial fission/fusion balance towards fusion in cardiomyocytes and TA muscle from aged adult Ahnak1-KO mice. The maximal and reserve respiratory capacities were significantly higher in cardiomyocytes from aged adult Ahnak1-KO mice compared with the WT counterparts (P < 0.05 and P < 0.01, respectively). Cardiomyocyte contractility and fatigue resistance of TA muscles were significantly increased in Ahnak1-KO mice of both sexes, compared with the WT groups. In vitro studies using AC16 cells have confirmed that the alteration of mitochondrial function is indeed a direct effect of Ahnak1. Finally, we presented Ahnak1 as a novel cardiac mitochondrial membrane-associated protein.
Our data suggest that Ahnak1 is involved in age-related cardiac and skeletal muscle dysfunction and could therefore serve as a promising therapeutical target.
衰老与细胞功能的逐渐下降有关，导致健康状况不佳和身体机能丧失。线粒体功能障碍是衰老的标志之一；因此，针对线粒体功能障碍的干预措施有可能为老年人提供预防和治疗益处。与年龄相关的基因表达谱的荟萃分析表明，调节包括代谢稳态在内的几种信号转导途径的蛋白质 Ahnak1 的表达随着年龄的增长而增加，这与低 VO 和肌肉健康状况不佳有关。然而，Ahnak1 在衰老过程中的作用仍不清楚。在这里，我们研究了 Ahnak1 在小鼠运动能力、线粒体功能和心脏和骨骼肌收缩功能方面的与年龄相关的作用。
我们使用 15-16 个月大的雌性和雄性 Ahnak1 敲除（Ahnak1-KO）和野生型（WT）小鼠，并进行形态计量学、生化和生物能量学测定，以评估 Ahnak1 对运动能力以及心肌和胫骨前肌（TA）中线粒体形态和功能的影响。我们使用人类左心室（LV）心肌细胞系（AC16）来研究 Ahnak1 在心肌细胞中的直接作用。
我们发现，Ahnak1 蛋白的水平在小鼠 LV（1.9 倍）和 TA（1.8 倍）组织中随年龄显著上调。Ahnak1 的抑制与运动耐受力的改善有关，因为所有年龄较大的成年 Ahnak1-KO 小鼠（100%）都成功完成了跑步计划，而大约 31%的雄性和 8%的雌性 WT 小鼠能够保持所需的跑步速度和距离。透射电子显微镜研究表明，与 WT 同窝仔相比，LV 和 TA 组织标本的两性年龄较大的成年 Ahnak1-KO 具有明显更大/更长的线粒体和更少的小线粒体（分别为 P < 0.01 和 P < 0.001）在基础水平。此外，我们观察到心肌细胞和 TA 肌肉中线粒体分裂/融合平衡向融合方向转变。与 WT 对照相比，年龄较大的成年 Ahnak1-KO 小鼠的心肌细胞的最大和储备呼吸能力显著更高（分别为 P < 0.05 和 P < 0.01）。两性 Ahnak1-KO 小鼠的 TA 肌肉的心肌收缩力和抗疲劳能力均显著增加。体外研究使用 AC16 细胞证实，线粒体功能的改变确实是 Ahnak1 的直接作用。最后，我们将 Ahnak1 作为一种新型的心脏线粒体膜相关蛋白。
我们的数据表明，Ahnak1 参与与年龄相关的心脏和骨骼肌功能障碍，因此可能成为有前途的治疗靶点。
