REductions in skeletal muscle oxidative capacity exist pre & post lung transplantation

Introduction: Lung Transplant (LTx) recipients have a reduced VO2 peak in the range of 50% predicted. Reductions in Type I fibre proportions (%) and oxidative enzyme activity (OX-E) have been demonstrated in vastus lateralis (VL) in severe GOAD. LTx may permit retraining by removing the ventilatory limitation to exercise. Aim: To determine whether reductions in VL Type I fibre % and OX-E are present in all forms of severe lung disease and if LTx leads to any further changes. Method: Subjects underwent VL biopsies immediately prior to and 3 months post LTx. Muscle was analysed for fibre type %, OX-E-[Citrate Synthase (CS), 3-hydroxyacyl dehydrogenase (HADH)], & glycolytic enzyme activity (GLY-E) - [Phosphorylase (Phos), Phosphofructokinase (PFK), and Hexokinase (HK)]. Subjects: 8 COAD, 5 Bronchiectasis, 3 Cystic Fibrosis, 1 Pulmonary Fibrosis and 1 Eisenmenger Syndrome. Results: (\j. ±SEM): Type I fibre % was reduced pre-LTx [30.8± 3.3%] compared to controls [55.3 ±3.0 %, p<0.05]; without further significant change post LTx [24.5 ±2.5 %]. N CS HADH PHOS PFK HK Controls 9 16.43±1.14 8.79±0.86 14.18±0.38 33.9112.86 2.47±0.29 Pre LTx 18 12.41 ±1.09* 4.71 ±0.37* 14.53±0.57 26.8±2.15 1.85±0.16' Post LTx 13 11.88±0.94 4.93±0.51 12.15±1.0* 25.5±2.53 2.12±0.29* [μ,mol/min/g wet weight muscle]; *p<M.05 vs controls; *p<.05 vs pre LTx. Conclusions: Reductions in Type I fibre % and oxidative enzymes are seen uniformly in all the severe lung diseases studied without significant improvement post LTx. Therefore the reduction in VÜ2 peak seen post LTx is at least partially due to abnormalities in skeletal muscle fibre type and oxidative capacity developed pre LTx .