ABSTRACT
AIM:Atherosclerotic calcification is highly linked with plaque instability and cardiovascular events .Adenosine monophosphate-activated protein kinase ( AMPK) has been involved in the pathogenesis of various cardiovascular disease .The contributions of AMPKαsubunits to the development of atherosclerotic calcification in vivo remained unknown .We hypothesized that AMPKαsubunits may play a role in the development of atherosclerotic calcification .METHODS: Atherosclerotic calcification was generated by 24-week fed of western diet in ApoE-/-background mice .Calcification was evaluated in aortic roots and innominate arteries of ApoE-/-mice or in mice with dual deficiencies of ApoE and AMPKαsubunits globally ( AMPKα1 and AMPKα2 ) , or vascular smooth muscle cell ( VSMC)-specific or macrophage-specific knockout of AMPKα1 with atherosclerotic calcification pone diet . The mechanism of AMPKα1 in regulating Runx2 was further explored in human aortic VSMC .RESULTS: Ablation of AMPKα1 but not AMPKα2 in ApoE-/-background promoted atherosclerotic calcification with increased Runt -related transcription factor ( Runx2 ) expression in VSMC compared with ApoE-/-mice.Conversely, chronic administration of metformin, which activated AMPK, markedly reduced ath-erosclerotic calcification and Runx2 expression in ApoE-/-mice but had less effects in ApoE-/-/AMPKα1 -/-mice.Furthermore, VSMC-but not macrophage-specific deficiency of AMPKα1 in ApoE-/-background promoted atherosclerotic calcification in vivo com-pared with the controls .AMPKα1 silencing in human aortic VSMC prevented Runx 2 from proteasome degradation to trigger osteoblastic differentiation of VSMC .Conversely , activation of AMPK led to Runx 2 instability by inducing its small ubiquitin-like modifier modifi-cation (SUMOylation).Protein inhibitor of activated STAT-1 (PIAS1), the SUMO E3-ligase of Runx2, was directly phosphorylated by AMPKα1 at serine 510, to enhance its SUMO E3-ligase activity.Ablation of PIAS1 serine 510 phosphorylation inhibited metformin-in-duced Runx2 SUMOylation, and subsequently prevented the effect of metformin on reducing oxLDL-triggered Runx2 expression in hu-man aortic VSMC.CONCLUSION:Deficiency of AMPKα1 in VSMC increases Runx2 expression and promotes atherosclerotic calcifi-cation in vivo.AMPKα1 phosphorylates PIAS1 to enhance Runx2 SUMOyalation and subsequent degradation .
ABSTRACT
This study examined the effect of insulin on the expression of very low density lipoprotein receptor (VLDLR) subtypes of SGC7901 cells and discussed its biological implication. In vitro, moderately or poorly-differentiated human gastric adenocarcinoma cell line SGC7901 was incubated with insulin for different lengths of time, and then the expression of protein and RNA level in VLDLR subtypes were detected by Western blotting and real-time PCR, respectively. The results showed that, at certain time interval, insulin could down-regulate expression of type I VLDLR and up-regulate the expression of type II VLDLR in SGC7901 cells, at both protein and RNA level. We are led to conclude that insulin serves as a regulator in maintaining the balance between glucose and lipid metabolism in vivo, possibly through its effect on the differential expression of VLDLR subtypes.