Diabetic cardiac fibrosis increases ventricular stiffness and facilitates the occurrence of diastolic dysfunction. Our previous studies have shown that berberine, a natural alkaloid, attenuates cardiac ischemia-reperfusion injury in diabetic rats. The aim of present study was to investigate the effects of long-term berberine treatment on cardiac remodeling in diabetic rats and the underlying mechanisms. Diabetic rats induced by low-dose streptozotocin injection combined with 8 wk of high-fat diet displayed significant cardiac matrix collagen deposition and dysfunction, whereas berberine administration (200 mg·kg-1·day-1, gavage 4 wk) significantly ameliorated cardiac fibrosis and dysfunction and reduced cardiac IGF-1 receptor (IGF-1R) expression in diabetic rats. Interestingly, IGF-1R expression was upregulated in cardiac fibroblasts isolated from diabetic hearts or cultured in high-glucose conditions (30 mM). High glucose treatment or IGF-1R overexpression increased matrix metalloproteinase (MMP)-2/MMP-9 expression, α-smooth muscle actin (α-SMA), and collagen type I expression in cardiac fibroblasts. In contrast, berberine treatment significantly inhibited IGF-1R expression and exerted an antifibrotic effect in high glucose-cultured cardiac fibroblasts, as manifested by decreased MMP-2/MMP-9, α-SMA, and collagen type I expression, whereas IGF-1R siRNA plus berberine treatment did not further enhance this antifibrotic effect compared with berberine treatment alone. Taken together, long-term berberine treatment ameliorates cardiac fibrosis and dysfunction by downregulating IGF-1R expression in cardiac fibroblasts and subsequently reducing MMP-2/MMP-9, α-SMA, and collagen type I expression in diabetic hearts. The findings suggest the therapeutic potential of berberine for diabetic cardiomyopathy associated with cardiac fibrosis. NEW & NOTEWORTHY Berberine downregulated IGF-1 receptor expression and matrix metalloproteinase-2/matrix metalloproteinase-9 levels in cardiac fibroblasts and thus inhibited fibroblast differentiation and collagen overproduction in diabetic hearts, suggesting a novel mechanism for antifibrotic cardioprotection of berberine in type 2 diabetes.
Keywords: berberine; cardiac fibrosis; diabetic cardiomyopathy; insulin-like growth factor-1 receptor; matrix metalloproteinases.