Exercise reverses preamyloid oligomer and prolongs survival in αB-crystallin-based desmin-related cardiomyopathy

The R120G mutation in the small heat shock-like protein αB-crystallin (CryAB^R120G) causes desmin-related myopathy (DRM), which is characterized by the formation of desmin- and CryAB-containing aggregates within muscle fibers. Mice with cardiac-specific overexpression of CryAB ^R120G develop cardiomyopathy at 3 months and die at 6-7 months from heart failure (HF). Previous studies showed that overexpression of CryAB ^R120G results in accumulation of preamyloid oligomer (PAO). PAO is considered to be the cytotoxic entity in many of the protein misfolding-based neurodegenerative diseases. On the basis of data from mouse models of neurodegenerative diseases showing that exercise or environmental enrichment reduces the amyloid oligomer level and improves cognitive ability, we hypothesized that CryAB^R120G-induced DRM would also respond favorably to prolonged voluntary exercise, reducing HF symptoms and rescuing the mice from premature death. Six months of voluntary exercise in CryAB^R120G animals resulted in 100% survival at a time when all unexercised mice had died. After 22 weeks of exercise, PAO levels were decreased by 47% compared with the unexercised CryAB^R120G control mice (P = 0.00001). Although CryAB^R120G expression led to decreased levels of the metallomembrane endopeptidase neprilysin, normal levels were maintained in the exercised CryAB^R120G mice, and in vitro loss-of-function and gain-of-function experiments using adenovirus-infected cardiomyocytes confirmed the importance of neprilysin in ameliorating PAO accumulation. The data demonstrate that voluntary exercise slows the progression to HF in the CryAB^R120G DRM model and that PAO accumulation is mediated, at least in part, by decreased neprilysin activity.