High-Fat Diet and Vitamin D Effects on Contractile Performance of Isolated Mouse Soleus and EDL

Abstract

Abstract Evidence suggests vitamin D (VD) could mitigate adverse effects of obesity on skeletal muscle (SkM) function, however, this is yet to be directly investigated. Therefore, this study used the work-loop technique to examine effects of high dose dietary VD supplementation on contractile performance of isolated SkM. Female mice (N = 37) consumed standard (SLD) or high-fat diet (HFD), with or without VD (20,000 IU/kg− 1) for 12-weeks. Soleus and EDL (N = 8–10) were isolated and absolute and normalised (relative to muscle size and body mass) isometric force and power output (PO) were measured, and fatigue resistance determined. Absolute and normalised isometric force and PO of the soleus were unaffected by diet (P > 0.087). However, PO normalised to body mass was reduced in HFD groups (P < 0.001). Isometric force of the EDL was unaffected by diet (P > 0.588). HFD evoked reduced EDL isometric stress (P = 0.048) and absolute and normalised PO (P < 0.031), but there was no effect of VD (P > 0.493). Cumulative work during fatiguing contractions was lower in HFD treated SkM (P < 0.043), but the rate of fatigue was unaffected (P > 0.060). This study uniquely demonstrated that high dose dietary VD had limited effects on SkM contractile function and did not offset the demonstrated adverse effects of HFD. However, there was non-significant small and moderate effects suggesting improvement in EDL muscle performance and animal morphology in HFD VD groups. Given trends observed, coupled with the 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 treated SkM.