The effects of knee injury on skeletal muscle function, Na⁺ , K⁺ -ATPase content, and isoform abundance

Abstract

While training upregulates skeletal muscle Na+, K+-ATPase (NKA), the effects of knee injury and associated disuse on muscle NKA remain unknown. This was therefore investigated in six healthy young adults with a torn anterior cruciate ligament, (KI; four females, two males; age 25.0 ± 4.9 years; injury duration 15 ± 17 weeks; mean ± SD) and seven age- and BMI-matched asymptomatic controls (CON; five females, two males). Each participant underwent a vastus lateralis muscle biopsy, on both legs in KI and one leg in CON. Muscle was analyzed for muscle fiber type and cross-sectional area (CSA), NKA content ([3H]ouabain binding), and α1–3 and β1–2 isoform abundance. Participants also completed physical activity and knee function questionnaires (KI only); and underwent quadriceps peak isometric strength, thigh CSA and postural sway assessments in both injured and noninjured legs. NKA content was 20.1% lower in the knee-injured leg than the noninjured leg and 22.5% lower than CON. NKA α2 abundance was 63.0% lower in the knee-injured leg than the noninjured leg, with no differences in other NKA isoforms. Isometric strength and thigh CSA were 21.7% and 7.1% lower in the injured leg than the noninjured leg, respectively. In KI, postural sway did not differ between legs, but for two-legged standing was 43% higher than CON. Hence, muscle NKA content and α2 abundance were reduced in severe knee injury, which may contribute to impaired muscle function. Restoration of muscle NKA may be important in rehabilitation of muscle function after knee and other lower limb injury.

Distinct α2 Na,K-ATPase membrane pools are differently involved in early skeletal muscle remodeling during disuse

“…Although adaptations of Na,K-ATPase content and activity in response to increased physiological loading are well documented ( Yuan et al, 2007 ; Kristensen et al, 2008 ; Murphy et al, 2008 ; Juel, 2009 ; Nordsborg et al, 2010 ; Benziane et al, 2012 ; Clausen, 2013 ), the effects of physical inactivity induced by functional unloading and other conditions ( Leivseth et al, 1992 ; Krivoĭ et al, 2008 ; Boon et al, 2012 ; Kravtsova et al, 2015 ; Perry et al, 2015 ) are relatively few in numbers. The molecular mechanisms underlying the changes have not been investigated.…”

“…Other studies also suggest that the α2 Na,K-ATPase plays a special role in adaptations to skeletal muscle disuse. Chronic disuse resulting from spinal cord injury ( Boon et al, 2012 ) or knee injury ( Perry et al, 2015 ) significantly decreases the α2 Na,K-ATPase content in skeletal muscles. The disuse-induced decrease in Na,K-ATPase α2 electrogenic activity and steady membrane depolarization is expected to decrease muscle excitability and contractility.…”

Muscle fiber conduction velocity in the vastus lateralis and medialis muscles of soccer players after ACL reconstruction

“…20 Physiologically, the Na+-K+-ATP ase pump contributes to maintain and regulate the basal membrane excitability as well as the muscle contractility, strength, and endurance. 19,38,39 Moreover, since the proportion of Na+-K+-ATP ase pump is higher in type II compared to type I muscle fibers, 38 high MFCV values may reflect the increased spread of action potentials along the muscle fibers belonging to HTMUs. 20,38 Downregulation of the Na+-K+-ATP ase has been demonstrated in various adverse conditions.…”

Human skeletal muscle fiber type percentage and area after reduced muscle use: A systematic review and meta‐analysis

“…These correlation values were calculated from individual pre‐ and post‐reduced muscle activity data (n = 38) of three separate studies and was received from Prof. Jesper Løvind Andersen and Prof. Gerasimos Terzis. These datasets originated from previously published work 12,45 and in addition published individual data from the PhD‐thesis of Dr Ben D. Perry 46 . For subgroup‐analysis, the data were stratified according to type of intervention model received; (a) detraining after a period of exercise training (DE), (b) studies using unilateral leg unloading (LU) and (c) studies employing bed rest as intervention (BR).…”