背景:肌肉减少性肥胖的特征是脂肪量过多和肌肉量/功能减少。DNAJA3,一种线粒体共伴侣蛋白,在骨骼肌发育中起着至关重要的作用。GMI,免疫调节蛋白,通过DNAJA3激活促进肌源性分化。这项研究旨在阐明肌肉Dnaja3单倍体功能不全对线粒体功能障碍和脂质代谢失调的生理作用,并评估GMI在体外和体内挽救肌少症性肥胖的功效。
方法:我们产生了在骨骼肌中特异性具有Dnaja3杂合性(HSA-Dna3f/+)的小鼠品系。体重,身体成分,并检查WT和HSA-Dnaja3f/+小鼠的运动活性。从WT和HSA-Dnaja3f/+小鼠分离的骨骼肌和原代成肌细胞,在年轻或年老时,被用来研究分子机制,线粒体呼吸和ROS水平,线粒体蛋白质组,和血清学分析,分别。评估GMI的疗效,短期和长期GMI治疗均腹膜内给予HSA-Dna3f/+年轻(4周龄)或成年(3月龄)小鼠,持续时间为1或6个月,分别。
结果:肌肉Dnaja3杂合性导致运动活动受损(P<0.05),肌肉横截面积减小(P<0.0001),以及骨骼肌脂肪生成(ACC2)和促炎症(STAT3)的上调(P<0.05)。来自HSA-Dnaja3f/+小鼠的原代成肌细胞显示线粒体呼吸受损(P<0.01)和线粒体ROS水平失衡。对来自原代成肌细胞的纯化线粒体进行系统蛋白质组学分析以显示线粒体功能和脂肪酸代谢的异常(P<0.0001)。在13至14个月的年龄,HSA-Dna3f/+小鼠体内脂肪量增加(P<0.001),无脂肪质量降低(P<0.01),糖耐量和胰岛素耐量受损(P<0.01)。短期GMI治疗可改善运动活性(P<0.01),下调STAT3蛋白水平(P<0.05),ACC2和线粒体呼吸复合物Ⅲ(UQCRC2)(P<0.01)经由过程DNAJA3激活。长期GMI治疗改善了脂肪量积累,葡萄糖不耐受,骨骼肌和全身性炎症(AST)(P<0.05),同时增强eWAT的产热作用(UCP1)(P<0.01)。GMI治疗促进肌生成,增加耗氧量,并通过体外DNAJA3激活(P<0.05)改善了STAT3(P<0.01)。
结论:肌Dnaja3单倍体功能不全调节线粒体功能和脂质代谢异常,然后导致肌少症性肥胖。GMI是通过DNAJA3激活治疗少肌症性肥胖的治疗方案。
BACKGROUND: Sarcopenic obesity is characterized by excess fat mass and diminished muscular mass/function. DNAJA3, a mitochondrial co-chaperone protein, plays a crucial role in skeletal muscle development. GMI, an immunomodulatory protein, promotes myogenic differentiation through DNAJA3 activation. This study aims to elucidate the physiological effects of muscular Dnaja3 haploinsufficiency on mitochondrial dysfunction and dysregulated lipid metabolism and to assess the efficacy of GMI in rescuing sarcopenic obesity both in vitro and in vivo.
METHODS: We generated mouse strain with Dnaja3 heterozygosity (HSA-Dnaja3f/+) specifically in skeletal muscle. The body weight, body composition, and locomotor activity of WT and HSA-Dnaja3f/+ mice were examined. The isolated skeletal muscles and primary myoblasts from the WT and HSA-Dnaja3f/+ mice, at young or old age, were utilized to study the molecular mechanisms, mitochondrial respiration and ROS level, mitochondrial proteomes, and serological analyses, respectively. To evaluate the therapeutic efficacy of GMI, both short-term and long-term GMI treatment were administrated intraperitoneally to the HSA-Dnaja3f/+ young (4 weeks old) or adult (3 months old) mice for a duration of either 1 or 6 months, respectively.
RESULTS: Muscular Dnaja3 heterozygosity resulted in impaired locomotor activity (P < 0.05), reduced muscular cross-sectional area (P < 0.0001), and up-regulation of lipogenesis (ACC2) and pro-inflammation (STAT3) in skeletal muscles (P < 0.05). Primary myoblasts from the HSA-Dnaja3f/+ mice displayed impaired mitochondrial respiration (P < 0.01) and imbalanced mitochondrial ROS levels. A systemic proteomic analysis of the purified mitochondria from the primary myoblasts was conducted to show the abnormalities in mitochondrial function and fatty acid metabolism (P < 0.0001). At age of 13 to 14 months, the HSA-Dnaja3f/+ mice displayed increased body fat mass (P < 0.001), reduced fat-free mass (P < 0.01), and impaired glucose and insulin tolerance (P < 0.01). The short-term GMI treatment improved locomotor activity (P < 0.01) and down-regulated the protein levels of STAT3 (P < 0.05), ACC2, and mitochondrial respiratory complex III (UQCRC2) (P < 0.01) via DNAJA3 activation. The long-term GMI treatment ameliorated fat mass accumulation, glucose intolerance, and systemic inflammation (AST) (P < 0.05) in skeletal muscle, while enhancing thermogenesis (UCP1) (P < 0.01) in eWAT. GMI treatment promoted myogenesis, enhanced oxygen consumption, and ameliorated STAT3 (P < 0.01) through DNAJA3 activation (P < 0.05) in vitro.
CONCLUSIONS: Muscular Dnaja3 haploinsufficiency dysregulates mitochondrial function and lipid metabolism then leads to sarcopenic obesity. GMI emerges as a therapeutic regimen for sarcopenic obesity treatment through DNAJA3 activation.