Effect of high-fat diet on isometric, concentric and eccentric contractile performance of skeletal muscle isolated from female CD-1 mice

Abstract

Despite evidence inferring muscle and contractile mode-specific effects of high-fat diet (HFD), no study has yet considered the impact of HFD directly on eccentric muscle function. The present work uniquely examined the effect of 20-week HFD on the isometric, concentric and eccentric muscle function of isolated mouse soleus (SOL) and extensor digitorum longus (EDL) muscles. CD-1 female mice were randomly split into a control (n = 16) or HFD (n = 17) group and for 20 weeks consumed standard lab chow or HFD. Following this period, SOL and EDL muscles were isolated and assessments of maximal isometric force and concentric work loop (WL) power were performed. Each muscle was then subjected to either multiple concentric or eccentric WL activations. Post-fatigue recovery, as an indicator of incurred damage, was measured via assessment of concentric WL power. In the EDL, absolute concentric power and concentric power normalised to muscle mass were reduced in the HFD group (P < 0.038). HFD resulted in faster concentric fatigue and reduced eccentric activity-induced muscle damage (P < 0.05). For the SOL, maximal isometric force was increased, and maximal eccentric power normalised to muscle mass and concentric fatigue were reduced in the HFD group (P < 0.05). HFD effects on eccentric muscle function are muscle-specific and have little relationship with changes in isometric or concentric function. HFD has the potential to negatively affect the intrinsic concentric and eccentric power-producing capacity of skeletal muscle, but a lack of a within-muscle uniform response indicates disparate mechanisms of action which require further investigation.

Keywords: isolated skeletal muscle; muscle lengthening; obesity; work‐loop.

FIGURE 1

Typical concentric (a, c) and eccentric (b, d) work loop shapes for isolated mouse EDL (a, b) and SOL (c, d) muscle optimised for maximal work at 10 and 5 Hz cycle frequency, 240 and 140 Hz stimulation frequency and 5% strain amplitude, respectively. Initiation of all work loops starts at L ₀ as indicated by the arrow in (a). Concentric work loops proceed in an anti‐clockwise direction and eccentric work loops in a clockwise direction, as indicated by grey arrows in each panel. The bold continuous line in each loop represents the stimulation duration (50 and 65 ms for the EDL and SOL, respectively, for concentric work loops; 55 and 72 ms for the EDL and SOL, respectively, for eccentric work loops).

FIGURE 2

The effect of 20 weeks of a HFD on maximal isometric force and stress of mouse soleus (a, b) and EDL muscle (c, d). Data presented as means ± SD; n = 16–17 in each group. *Significant difference between groups.

FIGURE 3

The effect of 20 weeks of a HFD on maximal absolute concentric and eccentric work loop power output of mouse soleus (a, b) and EDL muscle (c, d). Data presented as means ± SD; n = 16–17 for concentric, n = 8 for eccentric. *Significant difference between groups.

FIGURE 4

The effect of 20 weeks of a HFD on normalised maximal work loop power output of mouse soleus (a, b) and EDL muscle (c, d). Data presented as means ± SD; n = 16–17 for concentric, n = 8 for eccentric. *Significant difference between groups.

FIGURE 5

The effect of 20 weeks of a HFD on concentric (Con) and eccentric (Ecc) rate of fatigue, cumulative work and concentric recovery of maximally stimulate mouse SOL (a–c) and EDL muscle (d–f). Data presented as means ± SD; n = 8–9 in each group. *Significant difference between groups.

FIGURE 6

Statistical parametric mapping t‐test result for concentric (Con) and eccentric (Ecc) rate of fatigue and cumulative work for SOL (a–d) and EDL (e–h) muscle.