In cirrhotic patients reduced muscle strength is unrelated to muscle capacity for ATP turnover suggesting a central limitation

Background and aims: We investigated whether in patients with liver cirrhosis reduced muscle strength is related to dysfunction of muscle mitochondria. Methods: The mitochondrial respiratory capacity of the tibial anterior muscle was evaluated in seven patients and eight healthy control subjects by ³¹P nuclear magnetic resonance spectroscopy (³¹PMRS) to express ATP turnover in vivo and by respirometry of permeabilized fibres from the same muscle to express the in vitro capacity for oxygen consumption. Results: Maximal voluntary contraction force for plantar extension was low in the patients (46% of the control value; P<0·05), but neither the capacity for mitochondrial ATP synthesis, V_max‐ATP (0·38 ± 0·26 vs. 0·50 ± 0·07 mM s^?1; P = 0·13) nor the in vitro VO_2max (0·52 ± 0·21 vs. 0·48 ± 0·21 μmol O₂ (min g wet wt.)^?1P = 0·25) were lowered correspondingly. Also, the activity of citrate synthesis and the respiratory chain complexes II and IV were similar in patients and controls. However during the contractions, the contribution to initial anaerobic ATP production from glycolysis relative to that from PCr was reduced in the patients (0·73 ± 0·22 vs. 0·99 ± 0·09; P<0·01). Conclusions: These results demonstrate that the markedly lower capacity for force generation in patients with liver cirrhosis is unrelated to their capacity for muscle ATP turnover, but the attenuated initial acceleration of anaerobic glycolysis suggests that these patients could be affected by a central limitation to force generation.