Nitric Oxide Mitigates Atorvastatin-Induced Muscle Dysfunction And Alterations in Mice

Giuseppe D’Antona1, Anna Mascaro1, Daniela Miglietta2, Ennio Ongini2, Roberto Bottinelli1. 1Department of Physiology, Human Physiology Unit and Interuniversity Institute of Myology, Pavia University, Pavia, Italy, 2Nicox Research Institute, Bresso, Milan, Italy

Statin-related myopathy is an important cause of statin intolerance and discontinuation of treatment. It is recognized that nitric oxide (NO) has a key role in regulating muscle function, such as myocyte differentiation, mitochondrial biogenesis and regulation of blood flow in the exercising muscle. Herein, we have compared the effects of NCX 6560, a dual acting molecule combining atorvastatin activity and NO donation, with atorvastatin on skeletal muscle function and structure in C57/Bl6 mice.

Mice (n = 15/group 4 months of age) were treated with either atorvastatin (40 mg/kg/day) or an equimolar dose of NCX 6560 (48 mg/kg/day) for 2 months. Incorporation of the drug into the diet led to similar plasma levels of atorvastatin and its active metabolites (2-OH-atorva and 4-OH-atorva). Skeletal muscle function was evaluated in vivo by exhaustion treadmill test (at 10, 30, 45 and 60 days), and ex vivo by measuring absolute (Po) and specific (Po/CSA) tension in isolated tibialis muscle preparations. Citrate synthase activity (CS) was measured as a marker of mitochondrial function in the gastrocnemius, diaphragm and heart.

After 10 days,the mice treated with atorvastatin showed a large deterioration of time to exhaustion which was stable until the end of treatment (p<0.001 vs vehicle at all time points), whereas those treated with NCX 6560 maintained a fully preserved in vivo muscle function (p<0.05 vs atorva at all time points). Atorvastatin caused a significant reduction of Po (12±5 vs 23±9 g vehicle, p<0.05) and Po/CSA (0.17±0.05 vs 0.3±0.05 g/µL vehicle, p<0.05) in the tibialis muscle, whereas NCX 6560 preserved muscle functional activity (Po: 25±11 g; Po/CSA: 0.33±0.15 g/µL).

The muscle dysfunction induced by atorvastatin was associated with a 6-fold increase of serum creatine kinase (CK) (322±92 vs 82±21 U/L vehicle, p<0.001) and Evans blue positive fibers in the tibialis and diaphragm. Moreover, atorvastatin induced muscle fiber atrophy in both the tibialis (1724±739 vs vehicle: 2182±666 µm2) and gastrocnemius (1645±486 vs 1871±440 µm2 vehicle). On the contrary, NCX 6560 prevented serum CK increase (175±51 U/L) and did not induce fiber atrophy (tibialis: 2197±665, gastrocnemius: 2288±743 µm2), thus preserving muscle structure. Finally, atorvastatin induced a significant reduction of CS in the gastrocnemius (14±3 vs 35±6 mmol/min/mg vehicle, p<0.001) diaphragm (40±4 vs 48±5 vehicle, p<0.05) and the heart (43±2 vs 56±7 vehicle, p<0.05), suggesting an impairment of mitochondrial function. Conversely, NCX 6560 prevented a CS decrease partly in the gastrocnemius (28±2) and completely in the diaphragm (54±2) and heart (51±2).

This study shows that a 2-month treatment with atorvastatin induces deterioration of muscle function, accompanied by an increase of serum CK, muscle fiber atrophy and a compromised CS activity, whereas NCX 6560 does not induce deleterious effects on muscle function and structure. In conclusion, these data suggest a significant prevention of statin myopathy by NO donation and thus, this investigational NCX 6560 could represent a safe alternative to those patients who are unable to tolerate statin therapy.