University of Florida, Institute on Aging, Department of Aging and Geriatric Research, Gainesville, FL, USA; Northwestern University Feinberg School of Medicine, Department of Preventive Medicine, Chicago, IL, USA.
Northwestern University Feinberg School of Medicine, Department of Preventive Medicine, Chicago, IL, USA; Northwestern University Feinberg School of Medicine, Department of Medicine, Chicago, IL, USA.
Free Radic Biol Med. 2020 Nov 20;160:680-689. doi: 10.1016/j.freeradbiomed.2020.09.004. Epub 2020 Sep 8.
Peripheral artery disease (PAD) is associated with mitochondrial dysfunction in calf skeletal muscle and a greater abundance of mitochondrial DNA (mtDNA) heteroplasmy. However, it is unknown whether calf skeletal muscle mtDNA of PAD participants harbors a greater abundance of mitochondrial DNA 4977-bp common deletion (mtDNA), strand breaks and oxidative damage (i.e., oxidized purines) compared to non-PAD participants and whether these mtDNA abnormalities are associated with poor walking performance in participants with PAD.
Calf muscle biopsies were obtained from 50 PAD participants (ankle-brachial index (ABI) < 0.95) and 25 non-PAD participants (ABI = 0.99-1.40) matched by age, sex, and race. The abundance of mtDNA copy number, mtDNA deletion, strand breaks, and oxidized purines in selected mtDNA regions coding for electron transport chain (ETC) constituents and the non-coding D-Loop region was determined in calf muscle. All participants completed measurement of 6-min walk and usual and fast-paced 4-m walking velocity test.
Participants with PAD (mean age = 65.4 years, SD = 6.9; 14 (28%) women, 38 (76%) black) and without PAD (mean age = 65.2 years, SD = 6.7; 7 (28%) women, 16 (64%) black) did not differ in the abundance of calf muscle mtDNA deletion, mtDNA strand breaks, and oxidized purines. Though, a greater abundance of mtDNA strand breaks within ND4/5 genes was significantly associated with poorer 6-min walk distance, lower usual-paced 4-m walking velocity, and lower fast-paced 4-m walking velocity in non-PAD participants. Significant associations were also found in the density of strand break damage (i.e., damage per mtDNA copy) within ND1/2, ND4/5 and COII/ATPase 6/8 region with 6-min walk distance, usual-paced 4-m walking velocity and fast-paced 4-m walking velocity in non-PAD participants. Significant interactions were found between PAD presence vs. absence and density of strand break damage within ND1/2, ND4/5, COII/ATPase 6/8 regions for the associations with 6-min walk distance, usual-paced 4-m walking velocity, fast-paced 4-m walking velocity. Conversely, of the three walking performance measures only the usual-paced 4-m walking velocity showed a significant, although modest, negative association with the abundance of oxidized purines in the D-Loop (P = 0.031) and ND4/5 (P = 0.033) regions in the calf skeletal muscle of people with PAD.
Overall, these data suggest that the abundance of calf muscle mtDNA strand breaks and mtDNA common deletion are not associated with walking performance in people with PAD and may not be directly involved in the pathophysiology of PAD. Conversely, strand breaks in specific mtDNA regions may contribute to poor walking performance in people without PAD. Further study is needed to confirm whether usual-paced 4-m walking velocity is associated significantly with a greater abundance of oxidized purines in the D-loop, a "mutational hotspot" for oxidative damage, and why this association may differ from the association with 6-min walk distance and fast-paced 4-m walking velocity.
周围动脉疾病（PAD）与小腿骨骼肌中线粒体功能障碍和更大的线粒体 DNA（mtDNA）异质性相关。然而，尚不清楚 PAD 参与者的小腿骨骼肌 mtDNA 是否比非 PAD 参与者具有更大的线粒体 DNA 4977-bp 常见缺失（mtDNA）、链断裂和氧化损伤（即氧化嘌呤），以及这些 mtDNA 异常是否与 PAD 参与者的行走能力较差有关。
从 50 名 PAD 参与者（踝臂指数（ABI）<0.95）和 25 名非 PAD 参与者（ABI=0.99-1.40）中获得小腿肌肉活检，这些参与者按年龄、性别和种族进行匹配。在选定的编码电子传递链（ETC）成分和非编码 D 环区的 mtDNA 区域中，确定了 mtDNA 拷贝数、mtDNA 缺失、链断裂和氧化嘌呤的丰度。所有参与者均完成了 6 分钟步行和常规及快速 4 米步行速度测试。
PAD 参与者（平均年龄 65.4 岁，标准差 6.9；14 名（28%）女性，38 名（76%）黑人）和无 PAD 参与者（平均年龄 65.2 岁，标准差 6.7；7 名（28%）女性，16 名（64%）黑人）在小腿肌肉 mtDNA 缺失、mtDNA 链断裂和氧化嘌呤的丰度上没有差异。然而，ND4/5 基因内更大的 mtDNA 链断裂与非 PAD 参与者的 6 分钟步行距离较短、常规步伐 4 米步行速度较低和快速步伐 4 米步行速度较低显著相关。在非 PAD 参与者中，还发现了 ND1/2、ND4/5 和 COII/ATPase 6/8 区域内的链断裂损伤密度（即每 mtDNA 拷贝的损伤）与 6 分钟步行距离、常规步伐 4 米步行速度和快速步伐 4 米步行速度之间存在显著相关性。在 PAD 存在与否与 ND1/2、ND4/5、COII/ATPase 6/8 区域内的链断裂损伤密度之间的相关性中发现了显著的相互作用，用于与 6 分钟步行距离、常规步伐 4 米步行速度和快速步伐 4 米步行速度相关。相反，在三种步行表现测量中，只有常规步伐 4 米步行速度与 PAD 参与者小腿骨骼肌 D 环（P=0.031）和 ND4/5（P=0.033）区域 mtDNA 氧化嘌呤的丰度呈显著负相关，尽管相关性较弱。
总体而言，这些数据表明，小腿骨骼肌 mtDNA 链断裂和 mtDNA 常见缺失的丰度与 PAD 患者的步行表现无关，并且可能与 PAD 的病理生理学无关。相反，特定 mtDNA 区域的链断裂可能会导致非 PAD 患者的步行表现不佳。需要进一步研究以确认常规步伐 4 米步行速度是否与 D 环中更大的氧化嘌呤丰度（氧化损伤的“突变热点”）显著相关，以及为什么这种关联与 6 分钟步行距离和快速步伐 4 米步行速度的关联不同。
