Hyperhomocysteinemia attenuates angiogenesis through reduction of HIF-1α and PGC-1α levels in muscle fibers during hindlimb ischemia

Hyperhomocysteinemia (HHcy) is associated with elderly frailty, skeletal muscle injury and malfunction, reduced vascular integrity and function, and mortality. Although HHcy has been implicated in the impairment of angiogenesis after hindlimb ischemia in murine models, the underlying mechanisms are still unclear. We hypothesized that HHcy compromises skeletal muscle perfusion, collateral formation, and arteriogenesis by diminishing postischemic vasculogenic responses in muscle fibers. To test this hypothesis, we created femoral artery ligation in wild-type and heterozygous cystathionine beta-synthase (CBS+/-) mice (a model for HHcy) and assessed tissue perfusion, collateral vessel formation, and skeletal muscle function using laser-Doppler perfusion imaging, barium angiography, and fatigue tests. In addition, we assessed postischemic levels of VEGF and levels of its muscle-specific regulators: hypoxia-inducible factor (HIF)-1 alpha and peroxisome proliferator-activated receptor-gamma coactivator (PGC)-1 alpha. The observations indicated dysregulation of VEGF, HIF-1 alpha, and PGC-1 alpha levels in ischemic skeletal muscles of CBS+/- mice. Concomitant with the reduced ischemic angiogenic responses, we also observed diminished leptin expression and attenuated Akt signaling in ischemic muscle fibers of CBS+/- mice. Moreover, there was enhanced atrogene, ubiquitin ligases that conjugate proteins for degradation during muscle atrophy, transcription, and reduced muscle function after ischemia in CBS+/- mice. These results suggest that HHcy adversely affects muscle-specific ischemic responses and contributes to muscle frailty.