Dual effects of fructose on ChREBP and FoxO1/3α are responsible for AldoB up-regulation and vascular remodelling

Abstract

Increased production of methylglyoxal (MG) in vascular tissues is one of the causative factors for vascular remodelling in different subtypes of metabolic syndrome, including hypertension and insulin resistance. Fructose-induced up-regulation of aldolase B (AldoB) contributes to increased vascular MG production but the underlying mechanisms are unclear. Serum levels of MG and fructose were determined in diabetic patients with hypertension. MG level had significant positive correlations with blood pressure and fructose level respectively. C57BL/6 mice were fed with control or fructose-enriched diet for 3 months and ultrasonographic and histologic analyses were performed to evaluate arterial structural changes. Fructose-fed mice exhibited hypertension and high levels of serum MG with normal glucose level. Fructose intake increased blood vessel wall thickness and vascular smooth muscle cell (VSMC) proliferation. Western blotting and real-time PCR analysis revealed that AldoB level was significantly increased in both the aorta of fructose-fed mice and the fructose-treated VSMCs, whereas aldolase A (AldoA) expression was not changed. The knockdown of AldoB expression prevented fructose-induced MG overproduction and VSMC proliferation. Moreover, fructose significantly increased carbohydrate-responsive element-binding protein (ChREBP), phosphorylated FoxO1/3α and Akt1 levels. Fructose induced translocation of ChREBP from the cytosol to nucleus and activated AldoB gene expression, which was inhibited by the knockdown of ChREBP. Meanwhile, fructose caused FoxO1/3α shuttling from the nucleus to cytosol and inhibited its binding to AldoB promoter region. Fructose-induced AldoB up-regulation was suppressed by Akt1 inhibitor but enhanced by FoxO1/3α siRNA. Collectively, fructose activates ChREBP and inactivates FoxO1/3α pathways to up-regulate AldoB expression and MG production, leading to vascular remodelling.