Skeletal Muscle Mitochondrial Capacity in Patients with Statin‐Associated Muscle Symptoms (SAMS)

Abstract

BackgroundMitochondrial dysfunction may be a key mechanism underlying SAMS. Near infrared spectroscopy (NIRS) is a non‐invasive technique of assessing tissue oxygenation and mitochondrial function and has never been evaluated as a diagnostic tool for SAMS.Methods and ResultsSAMS was confirmed using an 8‐week randomized, double‐blind crossover trial of simvastatin 20 mg / day and placebo separated by a 4‐week washout phase in 39 adults with self‐reported SAMS (Age: 65 ± 6 y; 25 female, 14 male). Tissue oxygenation was measured using NIRS during a handgrip exercise protocol at increasing intensities of maximal voluntary contraction (MVC) before and after statin or placebo treatment. Patients were considered to have SAMS only if they had muscle symptoms on simvastatin and not placebo. Similar to our previous trials, 17/39 (44%) patients were confirmed as having SAMS. There was a significant interaction (p < 0.01) between placebo vs. statin, pre‐ vs. post‐treatment, and SAMS/not SAMS. Tissue oxygenation for average (20‐40%) MVC was significantly lower with placebo when symptoms were present compared with when participants did not have symptoms on a statin (15.66% ± 28.21% vs. 2.35% ± 19.13%, respectively) (p = 0.02). Neither group changed tissue oxygenation with statin therapy (both p > 0.22; SAMS: 28.0 ± 17.6% vs. 22.6 ± 11.9%; No SAMS: 30.5 ± 18.8% vs. 31.0 ± 16.4%, respectively), but the decrease was numerically greater in SAMS patients. There were no significant differences in MVC change score based on symptoms however, patients with SAMS experienced more variable MVC change score responses compared with patients who did not have symptoms.ConclusionsThese results indicate that NIRS may be effective for differentiating patients with SAMS from those with non‐specific muscle pain, however this must be verified with a larger sample.