Metformin, resveratrol, and exendin-4 inhibit high phosphate-induced vascular calcification via AMPK-RANKL signaling.

Vascular calcification increases the risk of developing cardiovascular disease, and it is closely associated with metabolic disorders such as diabetes mellitus and non-alcoholic fatty liver disease. We investigated whether the activators of AMP-activated protein kinase (AMPK), metformin, resveratrol, and exendin-4, improved inorganic phosphate (Pi)-induced vascular calcification in rat vascular smooth muscle cells (VSMCs) and whether these effects were via AMPK. Pi increased calcium deposition in a dose-dependent manner, and metformin, resveratrol, and exendin-4 significantly decreased calcium deposition in the Pi-treated VSMCs. Moreover, metformin and exendin-4 increased the expression of a SMC marker gene, α-smooth muscle actin, and Ampk and reduced the receptor activator of nuclear factor kappa-Β ligand (Rankl)/osteoprotegerin ratio. Metformin, resveratrol, and exendin-4 reduced the expression of osteoblast differentiation-associated factors, such as runt-related transcription factor 2, bone morphogenic protein-2, p-small mothers against decapentaplegic 1/5/8, and Rankl. Inhibition of AMPK by siRNA adversely affected the anti-calcification effects of metformin, resveratrol, and exendin-4 and reversed the reduction of the expression of Rankl by metformin and exendin-4 in the Pi-treated VSMCs. These data suggest that metformin, resveratrol, and exendin-4 ameliorate Pi-induced vascular calcification by inhibiting osteoblast differentiation of VSMCs, which is mediated by AMPK.