Research Centre for Physical Activity, Sport and Exercise Science, Coventry University, Coventry, UK.
Faculty of Life Sciences, University of Bradford, Bradford, UK.
Exp Physiol. 2024 Feb;109(2):283-301. doi: 10.1113/EP091493. Epub 2023 Nov 20.
Evidence suggests vitamin D (VD) supplementation can reduce accumulation of adipose tissue and inflammation and promote myogenesis in obese individuals, and thus could mitigate obesity-induced reductions in skeletal muscle (SkM) contractility. However, this is yet to be directly investigated. This study, using the work-loop technique, examined effects of VD (cholecalciferol) supplementation on isolated SkM contractility. Female mice (n = 37) consumed standard low-fat diet (SLD) or high-fat diet (HFD), with or without VD (20,000 IU/kg ) for 12 weeks. Soleus and EDL (n = 8-10 per muscle per group) were isolated and absolute and normalized (to muscle size and body mass) isometric force and power output (PO) were measured, and fatigue resistance determined. Absolute and normalized isometric force and PO of soleus were unaffected by diet (P > 0.087). However, PO normalized to body mass was reduced in HFD groups (P < 0.001). Isometric force of extensor digitorum longus (EDL) was unaffected by diet (P > 0.588). HFD reduced EDL isometric stress (P = 0.048) and absolute and normalized PO (P < 0.031), but there was no effect of VD (P > 0.493). Cumulative work during fatiguing contractions was lower in HFD groups (P < 0.043), but rate of fatigue was unaffected (P > 0.060). This study uniquely demonstrated that high-dose VD had limited effects on SkM contractility and did not offset demonstrated adverse effects of HFD. However, small and moderate effect sizes suggest improvement in EDL muscle performance and animal morphology in HFD VD groups. Given effect sizes observed, coupled with proposed inverted U-shaped dose-effect curve, future investigations are needed to determine dose/duration specific responses to VD, which may culminate in improved function of HFD SkM.
有证据表明，维生素 D（VD）补充剂可以减少脂肪组织的积累和炎症，并促进肥胖个体的肌肉生成，从而减轻肥胖引起的骨骼肌（SkM）收缩力下降。然而，这尚未得到直接研究。本研究使用工作循环技术，研究了 VD（胆钙化醇）补充对分离的 SkM 收缩性的影响。雌性小鼠（n = 37）分别食用标准低脂饮食（SLD）或高脂饮食（HFD），同时或不补充 VD（20,000 IU/kg）12 周。分离比目鱼肌和 EDL（每组肌肉 n = 8-10），测量等长力和功率输出（PO）的绝对值和归一化值（肌肉大小和体重），并确定疲劳抵抗力。饮食对比目鱼肌的绝对和归一化等长力和 PO 没有影响（P > 0.087）。然而，HFD 组 PO 归一化至体重降低（P < 0.001）。伸趾长肌（EDL）的等长力不受饮食影响（P > 0.588）。HFD 降低 EDL 等张应力（P = 0.048）和绝对及归一化 PO（P < 0.031），但 VD 无影响（P > 0.493）。疲劳收缩过程中的累积工作量在 HFD 组较低（P < 0.043），但疲劳速度不受影响（P > 0.060）。本研究独特地表明，高剂量 VD 对 SkM 收缩性的影响有限，并且不能抵消 HFD 的不良影响。然而，小和中等效应量表明 HFD VD 组 EDL 肌肉性能和动物形态的改善。考虑到观察到的效应量，再加上提出的倒 U 形剂量-效应曲线，未来需要进行研究以确定 VD 的剂量/持续时间特异性反应，这可能导致 HFD SkM 功能的改善。
