Neuromuscular and Muscle Metabolic Functions in MELAS Before and After Resistance Training: A Case Study

Abstract

Mitochondrial encephalomyopathy, lactic acidosis, and recurrent stroke-like episodes syndrome (MELAS) is a rare degenerative disease. Recent studies have shown that resistant training (RT) can ameliorate muscular force in mitochondrial diseases. However, the effects of RT in MELAS are unknown. The aim of this case report was to investigate the effects of RT on skeletal muscle and mitochondrial function in a 21-years old patient with MELAS. RT included 12 weeks of RT at 85% of 1 repetition maximum. Body composition (DXA), in vivo mitochondrial respiration capacity (mVO₂) utilizing Near-infrared spectroscopy on the right plantar-flexor muscles, maximal voluntary torque (MVC), electrically evoked resting twitch (EET) and maximal voluntary activation (VMA) of the right leg extensors (LE) muscles were measured with the interpolated twitch technique. The participant with MELAS exhibited a marked increase in body mass (1.4 kg) and thigh muscle mass (0.3 kg). After the training period MVC (+5.5 Nm), EET (+2.1 N⋅m) and VMA (+13.1%) were ameliorated. Data of mVO₂ revealed negligible changes in the end-exercise mVO₂ (0.02 mM min^-1), Δ mVO₂ (0.09 mM min^-1), while there was a marked amelioration in the kinetics of mVO₂ (τ mVO₂; Δ70.2 s). This is the first report of RT-induced ameliorations on skeletal muscle and mitochondrial function in MELAS. This case study suggests a preserved plasticity in the skeletal muscle of a patient with MELAS. RT appears to be an effective method to increase skeletal muscle function, and this effect is mediated by both neuromuscular and mitochondrial adaptations.

Keywords: MELAS; exercise; muscle respiratory capacity; neuromuscular function; resistance training.

FIGURE 1

Maximal voluntary contraction (MVC) and electrical evoked resting twitch (EET) characteristics. (A) Presents example tracings of the superimposed twitch technique utilized to determine muscle voluntary activation in leg extensors (LE) in a patient with mitochondrial encephalomyopathy, lactic acidosis, and recurrent stroke-like episodes syndrome (MELAS). The superimposed twitches (arrows) were imposed at the highest volitional steady-state torque. Representative examples of EET torque-time curves from LE are illustrated in (B). MELAS_PRE and MELAS_POST represents force-tracing in a patient with MELAS before and after 12 weeks of resistance training. Dashed line represent an example tracing of MVC (A) and EET (B) of a healthy control (CTRL).

FIGURE 2

In vivo mitochondrial respiration capacity. Panels (A,B) presents examples of the oxidative capacity measured by NIRS in the plantar flexor of a healthy 21-year-old male (CTRL) and a patient with MELAS before (MELAS_PRE) and after (MELAS_POST) 12 weeks of resistance training. The mVO₂ recovery data are fit to an exponential (continuous lines) to estimate the recovery k. The time constant (τ) is the reciprocal of the rate constant k (τ = 1/k).