Lawal Tokunbor A, Riekhof Willa, Groom Linda, Varma Pooja, Chrismer Irene C, Kokkinis Angela, Grunseich Christopher, Witherspoon Jessica W, Razaqyar Muslima S, Sinaii Ninet, Meilleur Katherine G, Xiang Lichen, Buzkova Jana, Euro Liliya, Mohassel Payam, Dirksen Robert T, Todd Joshua J
Skeletal Myopathies Unit, Translational Biobehavioral and Health Disparities Branch, NIH Clinical Center, National Institutes of Health, Bethesda, MD, USA.
National Institute of Nursing Research, National Institutes of Health, Bethesda, MD, USA.
Skelet Muscle. 2025 Aug 22;15(1):22. doi: 10.1186/s13395-025-00390-6.
Pathogenic variants in RYR1 cause a spectrum of rare congenital myopathies associated with intracellular calcium dysregulation. Glutathione redox imbalance has been reported in several Ryr1 disease model systems and clinical studies. NAD and NADP are essential cofactors in cellular metabolism and redox homeostasis. NAD deficiency has been associated with skeletal muscle bioenergetic deficits in mitochondrial myopathy and sarcopenia.
Using a new colorimetric assay and large control dataset (n = 299), we assessed redox balance (glutathione, NAD, and NADP) in whole blood from 28 RYR1-RM affected individuals (NCT02362425). Analyses were expanded to human skeletal muscle (n = 4), primary myotube cultures (n = 5), and whole blood and skeletal muscle specimens from Ryr1 Y524S mice. The in vitro effects of nicotinamide riboside (NR) on cellular NAD content and mitochondrial respirometry were also tested.
At baseline, a majority of affected individuals exhibited systemic NAD deficiency (19/28 [68%] < 21 µM) and increased NADPH concentrations (22/26 [85%] > 1.6 µM). When compared to controls, decreased NAD/NADH and NADP/NADPH ratios were observed in 9/28 and 23/26 individuals, respectively. In patient-derived myotube cultures (n = 5), NR appeared to increase cellular NAD concentrations in a dose and time-dependent manner at 72-h only and favorably modified maximal respiration and ATP production. Average whole blood GSH/GSSG ratio was comparable between groups, and redox imbalance was not observed in Ryr1 Y524S specimens.
NAD and NADP dyshomeostasis was identified in a subset of RYR1-RM affected individuals. Further experiments are warranted to confirm if NAD repletion could be an attractive therapeutic approach given the favorable outcomes reported in other neuromuscular disorders.
RYR1基因的致病性变异会导致一系列与细胞内钙调节异常相关的罕见先天性肌病。在多个Ryr1疾病模型系统和临床研究中均报道了谷胱甘肽氧化还原失衡。NAD和NADP是细胞代谢和氧化还原稳态中必不可少的辅助因子。NAD缺乏与线粒体肌病和肌肉减少症中的骨骼肌生物能量缺陷有关。
我们使用一种新的比色测定法和大型对照数据集（n = 299），评估了28名RYR1-RM患者（NCT02362425）全血中的氧化还原平衡（谷胱甘肽、NAD和NADP）。分析扩展至人类骨骼肌（n = 4）、原代肌管培养物（n = 5）以及Ryr1 Y524S小鼠的全血和骨骼肌标本。还测试了烟酰胺核糖（NR）对细胞NAD含量和线粒体呼吸测定的体外影响。
在基线时，大多数患者表现出全身性NAD缺乏（19/28 [68%] < 21 μM）和NADPH浓度升高（22/26 [85%] > 1.6 μM）。与对照组相比，分别在9/28和23/26的个体中观察到NAD/NADH和NADP/NADPH比值降低。在患者来源的肌管培养物（n = 5）中，NR似乎仅在72小时时以剂量和时间依赖性方式增加细胞NAD浓度，并有利地改善了最大呼吸和ATP产生。各组之间全血GSH/GSSG比值平均相当，且在Ryr1 Y524S标本中未观察到氧化还原失衡。
在一部分RYR1-RM患者中发现了NAD和NADP稳态失衡。鉴于在其他神经肌肉疾病中报道的良好结果，有必要进行进一步实验以确认补充NAD是否可能是一种有吸引力的治疗方法。
