Apelin-13 drives VSMC proliferation and atherosclerosis through REEP5-dependent disruption of ER-mitochondria...

Atherosclerosis is characterized by pathological vascular smooth muscle cell (VSMC) proliferation and metabolic dysregulation, yet the underlying mechanisms remain incompletely understood. Here, we identified receptor expression enhancer protein 5 (REEP5) as a potential regulator of VSMC proliferation in atherosclerosis by analyzing single-cell RNA sequencing datasets from human atherosclerotic coronary arteries and aortic tissues. REEP5 expression was markedly reduced in proliferative SMCs. In human aortic VSMCs, apelin-13 downregulated REEP5 in a time- and concentration-dependent manner. The REEP5 downregulation was associated with disrupted endoplasmic reticulum architecture, increased endoplasmic reticulum vacuolization, and impaired mitochondria-associated membrane coupling. Moreover, apelin-13 elevated mitochondrial reactive oxygen species, reduced mitochondrial membrane potential, and decreased mitochondrial Ca²⁺ levels, indicating mitochondrial dysfunction. Functionally, apelin-13 promoted a metabolic shift toward glycolysis, as evidenced by increased glucose consumption, lactate production, glycolytic enzyme expression and activity, and extracellular acidification rate, together with reduced oxidative phosphorylation and decreased oxygen consumption rate in vitro. REEP5 overexpression largely reversed these alterations and inhibited apelin-13-induced VSMC proliferation. Inhibition of glycolysis similarly attenuated the pro-proliferative effect of apelin-13. In ApoE^-/- mice, REEP5 overexpression alleviated apelin-13-induced exacerbation of atherosclerosis, reduced lesion burden, ameliorated dyslipidemia, and reduced glycolytic marker expression in plaques. Collectively, these findings suggested that apelin-13 may promote VSMC proliferation and atherosclerotic progression, at least in part, by downregulating REEP5 and disrupting mitochondria-associated membrane coupling, thereby contributing to a glycolytic metabolic shift in VSMCs. Targeting the REEP5/mitochondria-associated membrane coupling axis may be a potential therapeutic target for atherosclerosis.