Key points• Statin myopathy impairs phosphatidylinositol 3-kinase/Akt signalling and activates forkhead box protein O (FOXO) transcription factors in vivo in rodent skeletal muscle. This is associated with upregulation of downstream gene targets known to increase proteasomal and lysosomal-mediated protein breakdown, oxidative stress and inflammation, and inhibit muscle carbohydrate (CHO) oxidation.• We hypothesised that forcibly increasing muscle CHO oxidation in vivo, using the pyruvate dehydrogenase complex activator, dichloroacetate (DCA), would blunt statin-mediated increases in mRNA expression of these FOXO gene targets, thereby reducing statin myopathy.• Chronic administration of DCA with simvastatin dampened statin-mediated increases in muscle atrophy F-box (MAFbx), cathepsin-L and pyruvate dehydrogenase kinase-4 mRNA in a dose-dependent manner, which was corroborated by protein activity and expression measurements, and blunted statin myopathy.• These results provide convincing evidence that pharmacologically increasing muscle CHO oxidation reduces simvastatin-induced myopathy by dampening the upregulation of genes known to increase proteasomal and lysosomal protein breakdown and inhibit CHO oxidation.Abstract We previously reported that statin myopathy is associated with impaired carbohydrate (CHO) oxidation in fast-twitch rodent skeletal muscle, which we hypothesised occurred as a result of forkhead box protein O1 (FOXO1) mediated upregulation of pyruvate dehydrogenase kinase-4 (PDK4) gene transcription. Upregulation of FOXO gene targets known to regulate proteasomal and lysosomal muscle protein breakdown was also evident. We hypothesised that increasing CHO oxidation in vivo, using the pyruvate dehydrogenase complex (PDC) activator, dichloroacetate (DCA), would blunt activation of FOXO gene targets and reduce statin myopathy. Female Wistar Hanover rats were dosed daily for 12 days (oral gavage) with either vehicle (control, 0.5% w/v hydroxypropyl-methylcellulose 0.1% w/v polysorbate-80; n = 9), 88 mg kg −1 day −1 simvastatin (n = 8), 88 mg kg −1 day −1 simvastatin + 30 mg kg −1 day −1 DCA (n = 9) or 88 mg kg −1 day −1 simvastatin + 40 mg kg −1 day −1 DCA (n = 9). Compared with control, simvastatin reduced body mass gain and food intake, increased muscle fibre necrosis, plasma creatine kinase levels, muscle PDK4, muscle atrophy F-box (MAFbx) and cathepsin-L mRNA expression, increased PDK4 protein expression, and proteasome and cathepsin-L activity, and reduced muscle PDC activity. Simvastatin with DCA maintained body mass gain and food intake, abrogated the myopathy, decreased muscle PDK4 mRNA and protein, MAFbx and cathepsin-L mRNA, increased activity of PDC and reduced proteasome activity compared with simvastatin. PDC activation abolished statin myopathy in rodent skeletal muscle, which occurred at least in part via inhibition of FOXO-mediated transcription of genes regulating muscle CHO utilisation and protein breakdown.

Two novel hypolipidaemi c agents, both members of the aminopyrimidin e series, with a mode of action of inhibition of oxidosqualen e cyclase (OSC), were administered orally to dogs and mice for 14 and 28 days. Both compounds produced a similar spectrum of pathologic changes. In dogs, the agents produced equatorial single cell necrosis and cataract in the lens (also observed clinically); atrophy, ulceration, and in ammation of the cornea; hyperkeratosis , acanthosis, hair papillary atrophy, and in ammation of the skin; and epithelial degeneration and sperm granuloma in the epididymides . One female dog showed signs of liver toxicity. In mice, severe cataract formation was seen with both compounds, and liver toxicity was produced by one of the compounds . The severity and speed of onset of the cataract formation were very marked. The changes seen were dissimilar to those reported with the most commonly used class of hypolipidaemi c agents in the clinic, the hydroxymethy l glutaryl coenzyme A (HMGCoA) reductase inhibitors but were reminiscent of those reported for the hypolipidaemi c agent Triparanol, which was predictive of toxicity seen in man.

Image analysis is now routinely employed as a tool in toxicologic pathology to help quantitate end points of efficacy and safety. It is regarded as a proficient and a sensitive technique to generate numerical data that can be easily interrogated for statistical evaluation. Traditional semiquantitative pathology scoring on the other hand is sometimes regarded as less accurate due to the limitations of the scoring systems employed and the day-to-day variations often noted between pathologists. We therefore decided to generate an optimized histochemical staining and image analysis protocol to compare the accuracy of semiquantitative scoring with computerized image analysis. In order to achieve this, we describe a standardized protocol for staining and image analysis that eliminates or minimizes as many sources of error as possible. The results of this experiment demonstrate that despite consistent variations in scoring between two independent pathologists, correlation with image analysis data of 0.91 to 0.95 (Spearman's Rho test) was achieved. These data indicate that either image analysis or traditional semiquantitative scoring can generate accurate data. As a result of this, it appears that it is equally safe to employ either method dependent upon the complexity and the practicality of the task at hand provided that the experimental conditions are rigorously optimized and rigidly adhered to.

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