Background Emerging evidence suggests mitochondrial dysfunction may play a role in the fatigue experienced by individuals with post-COVID-19 condition (PCC), commonly called long COVID, which can be assessed using MR spectroscopy. Purpose To compare mitochondrial function between participants with fatigue-predominant PCC and healthy control participants using MR spectroscopy, and to investigate the relationship between MR spectroscopic parameters and fatigue using the 11-item Chalder fatigue questionnaire. Materials and Methods This prospective, observational, single-center study (June 2021 to January 2024) included participants with PCC who reported moderate to severe fatigue, with normal blood test and echocardiographic results, alongside control participants without fatigue symptoms. MR spectroscopy was performed using a 3-T MRI system, measuring hydrogen 1 (1H) and phosphorus 31 (31P) during exercise and recovery in the gastrocnemius muscle. General linear models were used to compare the phosphocreatine recovery rate time constant (hereafter, τPCr) and maximum oxidative flux, also known as mitochondrial capacity (hereafter, Qmax), between groups. Pearson correlations were used to assess the relationship between MR spectroscopic parameters and fatigue scores. Results A total of 41 participants with PCC (mean age, 44 years ± 9 [SD]; 23 male) (mean body mass index [BMI], 26 ± 4) and 29 healthy control participants (mean age, 34 years ± 11; 18 male) (mean BMI, 23 ± 3) were included in the study. Participants with PCC showed higher resting phosphocreatine levels (mean difference, 4.10 mmol/L; P = .03). Following plantar flexion exercise in situ (3-5 minutes), participants with PCC had a higher τPCr (92.5 seconds ± 35.3) compared with controls (51.9 seconds ± 31.9) (mean difference, 40.6; 95% CI: 24.3, 56.6; P ≤ .001), and Qmax was higher in the control group, with a mean difference of 0.16 mmol/L per second (95% CI: 0.07, 0.26; P = .008). There was no correlation between MR spectroscopic parameters and fatigue scores (r ≤ 0.25 and P ≥ .10 for all). Conclusion Participants with PCC showed differences in τPCr and Qmax compared with healthy controls, suggesting potential mitochondrial dysfunction. This finding did not correlate with fatigue scores. Published under a CC BY 4.0 license. Supplemental material is available for this article. See also the editorial by Parraga and Eddy in this issue.

中文翻译：

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1H 和 31P MR 光谱评估长期 COVID 中的肌肉线粒体功能障碍。


背景 新出现的证据表明，线粒体功能障碍可能在患有 COVID-19 后疾病 （PCC） 的个体所经历的疲劳中发挥作用，通常称为长期 COVID，这可以使用 MR 光谱进行评估。目的 使用 MR 光谱比较疲劳为主的 PCC 参与者和健康对照参与者的线粒体功能，并使用 11 项 Chalder 疲劳问卷研究 MR 光谱参数与疲劳之间的关系。材料和方法 这项前瞻性、观察性、单中心研究（2021 年 6 月至 2024 年 1 月）包括报告中度至重度疲劳、血液检查和超声心动图结果正常的 PCC 参与者，以及没有疲劳症状的对照参与者。使用 3-T MRI 系统进行 MR 光谱分析，测量腓肠肌运动和恢复过程中的氢 1 （1H） 和磷 31 （31P）。使用一般线性模型比较各组之间的磷酸肌酸恢复速率时间常数（以下简称 τPCr）和最大氧化通量，也称为线粒体容量（以下简称 Qmax）。Pearson 相关性用于评估 MR 光谱参数与疲劳评分之间的关系。结果 共有 41 名 PCC 参与者 （平均年龄 44 岁 ± 9 [SD];23 名男性）（平均体重指数 [BMI]，26 ± 4）和 29 名健康对照参与者 （平均年龄，34 岁± 11 岁;18 名男性）（平均 BMI，23 ± 3）被纳入研究。PCC 参与者显示较高的静息磷酸肌酸水平（平均差，4.10 mmol/L;P = .03）。在原位跖屈运动 （3-5 分钟） 后，与对照组 （51.9 秒± 31） 相比，PCC 参与者的 τPCr （92.5 秒± 35.3） 更高。9） （均数差，40.6;95% CI：24.3,56.6;P ≤ .001），对照组 Qmax 更高，平均差为 0.16 mmol/L /秒 （95% CI： 0.07， 0.26;P = .008）。MR 光谱参数与疲劳评分之间没有相关性 （r ≤ 0.25，P ≥ .10）。结论 与健康对照组相比，PCC 参与者的 τPCr 和 Qmax 存在差异，提示潜在的线粒体功能障碍。这一发现与疲劳评分无关。在 CC BY 4.0 许可证下发布。本文提供了补充材料。另请参阅本期 Parraga 和 Eddy 的社论。