Simvastatin effects on skeletal muscle: relation to decreased mitochondrial function and glucose intolerance

Abstract

Objectives: Glucose tolerance and skeletal muscle coenzyme Q(10) (Q(10)) content, mitochondrial density, and mitochondrial oxidative phosphorylation (OXPHOS) capacity were measured in simvastatin-treated patients (n = 10) and in well-matched control subjects (n = 9).

Background: A prevalent side effect of statin therapy is muscle pain, and yet the basic mechanism behind it remains unknown. We hypothesize that a statin-induced reduction in muscle Q(10) may attenuate mitochondrial OXPHOS capacity, which may be an underlying mechanism.

Methods: Plasma glucose and insulin concentrations were measured during an oral glucose tolerance test. Mitochondrial OXPHOS capacity was measured in permeabilized muscle fibers by high-resolution respirometry in a cross-sectional design. Mitochondrial content (estimated by citrate synthase [CS] activity, cardiolipin content, and voltage-dependent anion channel [VDAC] content) as well as Q(10) content was determined.

Results: Simvastatin-treated patients had an impaired glucose tolerance and displayed a decreased insulin sensitivity index. Regarding mitochondrial studies, Q(10) content was reduced (p = 0.05), whereas mitochondrial content was similar between the groups. OXPHOS capacity was comparable between groups when complex I- and complex II-linked substrates were used alone, but when complex I + II-linked substrates were used (eliciting convergent electron input into the Q intersection [maximal ex vivo OXPHOS capacity]), a decreased (p < 0.01) capacity was observed in the patients compared with the control subjects.

Conclusions: These simvastatin-treated patients were glucose intolerant. A decreased Q(10) content was accompanied by a decreased maximal OXPHOS capacity in the simvastatin-treated patients. It is plausible that this finding partly explains the muscle pain and exercise intolerance that many patients experience with their statin treatment.