Department of Structural and Functional Biology, Institute of Biosciences, São Paulo State University (UNESP), Botucatu, São Paulo, Brazil.
Anesthesiology and Pain Medicine, Northwest Metabolomics Research Center, Mitochondria and Metabolism Center, University of Washington, Seattle, WA, USA.
Skelet Muscle. 2023 Sep 13;13(1):16. doi: 10.1186/s13395-023-00325-z.
Duchenne muscular dystrophy (DMD) is a severe form of muscular dystrophy without an effective treatment, caused by mutations in the DMD gene, leading to the absence of dystrophin. DMD results in muscle weakness, loss of ambulation, and death at an early age. Metabolomics studies in mdx mice, the most used model for DMD, reveal changes in metabolites associated with muscle degeneration and aging. In DMD, the tongue muscles exhibit unique behavior, initially showing partial protection against inflammation but later experiencing fibrosis and loss of muscle fibers. Certain metabolites and proteins, like TNF-α and TGF-β, are potential biomarkers for dystrophic muscle characterization.
To investigate disease progression and aging, we utilized young (1 month old) and old (21-25 months old) mdx and wild-type tongue muscles. Metabolite changes were analyzed using 1H nuclear magnetic resonance, while TNF-α and TGF-β were assessed using Western blotting to examine inflammation and fibrosis. Morphometric analysis was conducted to assess the extent of myofiber damage between groups.
The histological analysis of the mid-belly tongue showed no differences between groups. No differences were found between the concentrations of metabolites from wild-type or mdx whole tongues of the same age. The metabolites alanine, methionine, and 3-methylhistidine were higher, and taurine and glycerol were lower in young tongues in both wild type and mdx (p < 0.001). The metabolites glycine (p < 0.001) and glutamic acid (p = 0.0018) were different only in the mdx groups, being higher in young mdx mice. Acetic acid, phosphocreatine, isoleucine, succinic acid, creatine, and the proteins TNF-α and TGF-β had no difference in the analysis between groups (p > 0.05).
Surprisingly, histological, metabolite, and protein analysis reveal that the tongue of old mdx remains partially spared from the severe myonecrosis observed in other muscles. The metabolites alanine, methionine, 3-methylhistidine, taurine, and glycerol may be effective for specific assessments, although their use for disease progression monitoring should be cautious due to age-related changes in the tongue muscle. Acetic acid, phosphocreatine, isoleucine, succinate, creatine, TNF-α, and TGF-β do not vary with aging and remain constant in spared muscles, suggesting their potential as specific biomarkers for DMD progression independent of aging.
杜氏肌营养不良症（DMD）是一种严重的肌肉营养不良症，没有有效的治疗方法，由 DMD 基因突变引起，导致肌营养不良蛋白缺失。DMD 导致肌肉无力、丧失行动能力，并导致早逝。在 mdx 小鼠（DMD 最常用的模型）的代谢组学研究中，揭示了与肌肉退化和衰老相关的代谢物变化。在 DMD 中，舌肌表现出独特的行为，最初对炎症有一定的保护作用，但随后经历纤维化和肌肉纤维丧失。某些代谢物和蛋白质，如 TNF-α 和 TGF-β，是肌肉营养不良特征的潜在生物标志物。
为了研究疾病进展和衰老，我们利用年轻（1 个月大）和年老（21-25 个月大）的 mdx 和野生型舌肌。使用 1H 核磁共振分析代谢物变化，使用 Western 印迹分析 TNF-α 和 TGF-β，以检查炎症和纤维化。进行形态计量学分析以评估各组之间肌纤维损伤的程度。
中腹舌的组织学分析显示各组之间无差异。同年龄的野生型或 mdx 全舌的代谢物浓度无差异。年轻的野生型和 mdx 舌中，丙氨酸、蛋氨酸和 3-甲基组氨酸的浓度较高，牛磺酸和甘油的浓度较低（p<0.001）。只有 mdx 组的代谢物甘氨酸（p<0.001）和谷氨酸（p=0.0018）不同，年轻的 mdx 小鼠中这两种代谢物的浓度较高。在组间分析中，乙酸、磷酸肌酸、异亮氨酸、琥珀酸、肌酸和 TNF-α、TGF-β 蛋白无差异（p>0.05）。
令人惊讶的是，组织学、代谢物和蛋白质分析表明，老年 mdx 舌的肌肉坏死程度仍部分低于其他肌肉观察到的严重程度。尽管由于舌肌的年龄相关变化，使用这些代谢物进行疾病进展监测应谨慎，但丙氨酸、蛋氨酸、3-甲基组氨酸、牛磺酸和甘油可能对特定评估有效。乙酸、磷酸肌酸、异亮氨酸、琥珀酸、肌酸、TNF-α 和 TGF-β 不随年龄变化，在未受损肌肉中保持不变，这表明它们可能成为独立于年龄的 DMD 进展的特定生物标志物。
