High-dose atorvastatin therapy progressively decreases skeletal muscle mitochondrial respiratory capacity in humans

Abstract

BACKGROUNDWhile the benefits of statin therapy on atherosclerotic cardiovascular disease are clear, patients often experience mild to moderate skeletal myopathic symptoms, the mechanism for which is unknown. This study investigated the potential effect of high-dose atorvastatin therapy on skeletal muscle mitochondrial function and whole-body aerobic capacity in humans.METHODSEight overweight (BMI, 31.9 ± 2.0) but otherwise healthy sedentary adults (4 females, 4 males) were studied before (day 0) and 14, 28, and 56 days after initiating atorvastatin (80 mg/d) therapy.RESULTSMaximal ADP-stimulated respiration, measured in permeabilized fiber bundles from muscle biopsies taken at each time point, declined gradually over the course of atorvastatin treatment, resulting in > 30% loss of skeletal muscle mitochondrial oxidative phosphorylation capacity by day 56. Indices of in vivo muscle oxidative capacity (via near-infrared spectroscopy) decreased by 23% to 45%. In whole muscle homogenates from day 0 biopsies, atorvastatin inhibited complex III activity at midmicromolar concentrations, whereas complex IV activity was inhibited at low nanomolar concentrations.CONCLUSIONThese findings demonstrate that high-dose atorvastatin treatment elicits a striking progressive decline in skeletal muscle mitochondrial respiratory capacity, highlighting the need for longer-term dose-response studies in different patient populations to thoroughly define the effect of statin therapy on skeletal muscle health.FUNDINGNIH R01 AR071263.

Keywords: Bioenergetics; Mitochondria; Muscle biology; Skeletal muscle.

Figure 1. Short-term statin therapy decreases skeletal muscle mitochondrial function in vivo and aerobic capacity.

(A) Whole-body aerobic capacity (VO₂ max) before and after 56 days of statin therapy. (B) Relative individual changes (%) in VO₂ max after statin therapy. (C) Insulin sensitivity measured by IVGTT. (D) Postexercise recovery kinetics of muscle oxygen consumption measured by near infrared spectroscopy (mVO₂) before (pre) and after (post) 56 days of statin therapy. (E and F) Following a single exponential fitting, the calculated rate constants (directly related to mitochondrial capacity) (E) and time constants (inversely related to mitochondrial capacity) (F) are shown. Data are mean ± SEM (n = 8 for all panels). Data analyzed by paired t tests. *P < 0.05 was considered significant.

Figure 2. Short-term statin therapy progressively decreases skeletal muscle mitochondrial respiratory capacity.

Permeabilized myofibers were prepared from skeletal muscle biopsies of the vastus lateralis,and mitochondrial function was measured by high-resolution respirometry prior to and after days 14, 28, and 56 of high-dose (80 mg/d) atorvastatin therapy. (A) ADP titration in the presence of 5 mM glutamate and 2 mM malate. (B) Glutamate titration in the presence of 2 mM malate and 4 mM ADP. (C) Succinate titration in the presence of 4 mM ADP and 10 μM rotenone. All protocols ended with a final addition of cytochrome c (+C) to check for mitochondrial integrity. (D–F) Maximal ADP-stimulated respiration from corresponding graphs in A–C. (G) Citrate synthase activity measured in whole muscle homogenates as an index of mitochondrial content. (H) Representative trace of mitochondrial H₂O₂ emission from permeabilized fiber bundles in response to sequential additions of 2 mM glutamate + 1 mM malate, 25 μM palmitoyl–L-carnitine, 10 mM succinate, and 10 mM glycerol-3-phosphate. (I) Mitochondrial H₂O₂ emitting rates (JH₂O₂) calculated from H. (J) Mitochondrial calcium retention capacity measured in permeabilized myofibers using fluorophore Calcium Green in the presence of 10 mM glutamate, 2 mM malate, and 0.2 mM ADP. Respiration was clamped with 5 mM 2-deoxyglucose and 2 U/mL hexokinase. Data are presented as mean ± SEM (n = 6–8 in A and B; n = 8 in C–F, G, and I; n = 7–8 in J). Data analyzed by repeated-measures 1-way ANOVA or mixed-effects analysis with Dunnett’s multiple-comparison test. *P < 0.05 was considered significant.

Figure 3. Acute statin exposure inhibits the activity of mitochondrial complex IV at low nanomolar concentrations in human skeletal muscle.

Specific activities of mitochondrial ETS complexes were assessed spectrophotometrically from skeletal muscle lysates obtained from human participants in the presence of varying concentrations of atorvastatin. (A, C, E, and G) Representative traces. (B, D, F, and H) Quantification of complex I–IV specific activities, expressed as percent relative to DMSO treatment. Data are presented as mean ± SEM (n = 6 in A–F; n = 4–6 in G and H). Data analyzed by 1-way ANOVA with Sidak’s multiple-comparison test. *P < 0.05, **P < 0.01.