Rabbits fed cholesterol-enriched diets exhibit pathological features of inclusion body myositis

Abstract

Sporadic inclusion body myositis (IBM) is the most common age-related muscle disease in humans; however, its etiology is unknown, there are few animal models for this disease, and effective treatments have not been identified. Similarities between pathological findings in Alzheimer's disease brain and IBM skeletal muscle include increased levels of amyloid precursor protein (APP) and amyloid β-protein (Aβ). Moreover, there have been suggestions that elevated levels of free cholesterol might participate in the pathogenesis of Alzheimer's disease and IBM due, in part, to its role in Aβ generation. Here, we tested the hypothesis that rabbits fed cholesterol-enriched diets might faithfully exhibit human-like IBM pathological features. In skeletal muscle of one-third of the female rabbits fed cholesterol-enriched diet but not control diet, we found features of IBM, including vacuolated muscle fibers, increased numbers of mononuclear inflammatory cells, increased intramuscular deposition of Aβ, hyperphosphorylated tau, and increased numbers of muscle fibers immunopositive for ubiquitin. The cholesterol-enriched diet increased mRNA and protein levels of APP, increased the protein levels of βAPP cleaving enzyme, and shifted APP processing in favor of Aβ production. Our study has demonstrated that increased ingestion of high levels of dietary cholesterol can result in pathological features that resemble IBM closely and thus may serve as an important new model with which to study this debilitating disorder.