Ameliorative Effect And Mechanisms Of Punicalagin On Non-alcoholic Fatty Liver Disease

Pomegranate is a widely grown fruit in China. It is popular among people because of its rich nutrition. Punicalagin is an important polyphenol in pomegranate, distributed in most parts of pomegranate. In recent years, the biological activities of punicalagin have been studied extensively by researchers around the world. The studies demonstrated that punicalagin has antioxidant, anti-inflammatory, anti-tumor and anti-bacterial activity. Non-alcoholic fatty liver disease(NAFLD) is a chronic metabolic disease, it has become a serious global public health issue, with people’s lifestyle changing. The epidemiology of NAFLD is tightly related with obesity, insulin resistance, inflammation, oxidative stress and other factors. This study determined the effects of punicalagin on NAFLD by in vitro experiments. We detected protein expression using Western Blot and tested some biochemical indexes, to explore the potential mechanism of punicalagin on NAFLD. The results are as follows:(1)The NAFLD steatosis cell model was well established after 0.25 mM sodium palmitate treatment. After 10 μg/mL punicalagin pretreatment, intracellular lipid droplets and TG, TC content reduced significantly. This result suggested that punicalagin alleviate the hepatic lipid accumulation in vitro.(2) The sodium palmitate inhibited insulin-stimulated tyrosine phosphorylation of IRS, serine phosphorylation of Akt, and glucose uptake activity, which represents the NAFLD steatosis cell model occurred insulin resistance. However, after 5 μg/mL and 10 μg/mL punicalagin pretreatment, levels of phosphorylated IRS and Akt increased. Insulin resistance improved by punicalagin, and this may be the potential mechanism of hepatic lipid accumulation reduction in vivo after punicalagin intervention.(3)Recent data indicated that AMP-activated protein kinase(AMPK) plays a key role in hepatic lipogenesis and fatty acid oxidation. The sodium palmitate reduced phosphorylated AMPK level and phosphorylated ACC level, which leads to AMPK activity inhibition and ACC activation. 5 μg/mL and 10 μg/mL punicalagin increased the threonine phosphorylation of AMPK and serine phosphorylation of ACC, which indicates that AMPK/ACC pathway could be stimulated by punicalagin. AMPK/ACC pathway activation may be another mechanism of hepatic lipid accumulation reduction by punicalagin.(4) Sodium palmitate stimulation can also induce liver inflammation and oxidative stress. Insulin resistance, lipid accumulation and NASH could be induced by these two factors. Punicalagin effectively suppressed ROS overproduction and restored mitochondrial membrane potential(Δψm). It could also suppress NF-κB、JNK、p38 phosphorylation. This result demonstrated that punicalagin have anti-inflammation and antioxidant activity in steatosis HepG2 cell, and gave evidence to amelioration effect of insulin resistance and lipid accumulation by punicalagin treatment.