Acevedo Luz M, Raya Ana I, Ríos Rafael, Aguilera-Tejero Escolástico, Rivero José-Luis L
Laboratorio de Biopatología Muscular, Departamento de Anatomía y Anatomía Patológica Comparadas, Universidad de Córdoba, Córdoba, Spain.
Departamento de Ciencias Biomédicas, Universidad Central de Venezuela, Maracay, Venezuela.
J Appl Physiol (1985). 2017 Jul 1;123(1):249-259. doi: 10.1152/japplphysiol.00282.2017. Epub 2017 May 18.
A clear picture of skeletal muscle adaptations to obesity and related comorbidities remains elusive. This study describes fiber-type characteristics (size, proportions, and oxidative enzyme activity) in two typical hindlimb muscles with opposite structure and function in an animal model of genetic obesity. Lesser fiber diameter, fiber-type composition, and histochemical succinic dehydrogenase activity (an oxidative marker) of muscle fiber types were assessed in slow (soleus)- and fast (tibialis cranialis)-twitch muscles of obese Zucker rats and compared with age (16 wk)- and sex (females)-matched lean Zucker rats ( = 16/group). Muscle mass and lesser fiber diameter were lower in both muscle types of obese compared with lean animals even though body weights were increased in the obese cohort. A faster fiber-type phenotype also occurred in slow- and fast-twitch muscles of obese rats compared with lean rats. These adaptations were accompanied by a significant increment in histochemical succinic dehydrogenase activity of slow-twitch fibers in the soleus muscle and fast-twitch fiber types in the tibialis cranialis muscle. Obesity significantly increased plasma levels of proinflammatory cytokines but did not significantly affect protein levels of peroxisome proliferator-activated receptors PPARγ or PGC1α in either muscle. These data demonstrate that, in female Zucker rats, obesity induces a reduction of muscle mass in which skeletal muscles show a diminished fiber size and a faster and more oxidative phenotype. It was noteworthy that this discrepancy in muscle's contractile and metabolic features was of comparable nature and extent in muscles with different fiber-type composition and antagonist functions. This study demonstrates a discrepancy between morphological (reduced muscle mass), contractile (shift toward a faster phenotype), and metabolic (increased mitochondrial oxidative enzyme activity) characteristics in skeletal muscles of female Zucker fatty rats. It is noteworthy that this inconsistency was comparable (in nature and extent) in muscles with different structure and function.
骨骼肌对肥胖及相关合并症的适应性变化仍不明确。本研究描述了在遗传性肥胖动物模型中，两种结构和功能相反的典型后肢肌肉的纤维类型特征（大小、比例和氧化酶活性）。评估了肥胖Zucker大鼠慢肌（比目鱼肌）和快肌（胫骨前肌）中肌纤维类型的较小纤维直径、纤维类型组成和组织化学琥珀酸脱氢酶活性（一种氧化标记物），并与年龄（16周）和性别（雌性）匹配的瘦Zucker大鼠（每组n = 16）进行比较。与瘦动物相比，肥胖动物的两种肌肉类型的肌肉质量和较小纤维直径均较低，尽管肥胖组的体重增加。与瘦大鼠相比，肥胖大鼠的慢肌和快肌中也出现了更快的纤维类型表型。这些适应性变化伴随着比目鱼肌慢肌纤维和胫骨前肌快肌纤维类型的组织化学琥珀酸脱氢酶活性显著增加。肥胖显著增加了促炎细胞因子的血浆水平，但对两种肌肉中过氧化物酶体增殖物激活受体PPARγ或PGC1α的蛋白水平均无显著影响。这些数据表明，在雌性Zucker大鼠中，肥胖导致肌肉质量减少，其中骨骼肌的纤维尺寸减小，表型更快且氧化程度更高。值得注意的是，在具有不同纤维类型组成和拮抗功能的肌肉中，肌肉收缩和代谢特征的这种差异在性质和程度上具有可比性。本研究表明，雌性Zucker肥胖大鼠骨骼肌的形态学（肌肉质量减少）、收缩性（向更快表型转变）和代谢（线粒体氧化酶活性增加）特征之间存在差异。值得注意的是，这种不一致在具有不同结构和功能的肌肉中（在性质和程度上）具有可比性。
