Abstract
BACKGROUND Berberine (BBR), a natural alkaloid isolated from Coptis chinensis, has frequently been reported as an antidiabetic reagent, partly due to its lipid-lowering activity. Evidence suggests that BBR ameliorates palmitate-induced lipid deposition and apoptosis in renal tubular epithelial cells (TECs), which tracks in tandem with the enhancement of peroxisome proliferator-activated receptor alpha (PPAR-alpha). The study aim was to investigate the roles of BBR in renal lipotoxicity in vitro, and investigate whether PPAR-alpha was the underlying mechanism. MATERIAL AND METHODS Human TECs (HK-2 cells) were injured with palmitic acid (PA), and then treated with BBR, BBR+PPAR-alpha inhibitor (GW6471), and PA+PPAR-alpha agonist (fenofibrate). Endoplasmic reticulum (ER) stress was assessed by measuring the expression of prospective evaluation of radial keratotomy (PERK), C/EBP-homologous protein (CHOP), and 78 kDa glucose-regulated protein (GRP78). Lipid metabolism was assessed by determining lipid anabolism-associated genes, including fatty acid synthase (FAS), acetyl-CoA carboxylase (ACC), and lipoprotein lipase (LPL), as well as lipid catabolism-associated gene, including carnitine palmitoyl transferase 1 (CPT1). Inflammatory response of HK-2 cells was evaluated by measuring interleukin (IL)-6 and tumor necrosis factor (TNF)-alpha. Cell apoptosis and protein levels of cleaved-caspase-3 were evaluated. RESULTS PA downregulated PPAR-alpha and induced server lipotoxicity in HK-2 cells by ER stress, increasing lipid deposition, and elevating inflammatory response of HK-2 cells accompanied with inducting cell apoptosis and cleaved-caspase-3, which were obviously reversed by additional treatment of BBR or PPAR-alpha agonist. However, the protective effect of BBR in PA-induced lipotoxicity in HK-2 cells was significantly ameliorated by PPAR-alpha inhibitor. CONCLUSIONS BBR attenuated PA-induced lipotoxicity via the PPAR-alpha pathway.