Different Phenolic Extracts of Oil Palm Fruits and Caffeic Acid Prevent Palmitic Acid-Induced Lipotoxicity in HepG2 Cells via Improving Mitochondrial Function

Xiaojing Liu,Jiexin Zhou,Shengbao Cai,Ou Wang

doi:10.1155/2020/8827707

Abstract

Oil palm (Elaeis guineensis Jacq.) fruits are rich in antioxidative phenolic compounds, which exert various health improving effects. This study aimed to comparatively study the protective effects of different phenolic fractions from the fruits treated with or without ultrahigh pressure (UHP) and their most abundant phenolic substance, caffeic acid, against the palmitic acid-induced lipotoxicity in HepG2 cells and to clarify the potential mechanisms. Results showed that the TG accumulation, intracellular reactive oxygen species content, cell apoptosis, and mitochondrial membrane potential depolarization were relieved by the administration of those phenolic fractions and caffeic acid. The protection of insoluble-bound (IB) phenolic fraction was the best, and UHP treatment significantly enhanced its protective effect on lipotoxicity. The lipotoxicity preventive effect may be achieved by alleviating intracellular oxidative stress, downregulating the expression of P-P38, COX-2, and iNOS to relieve inflammation, and downregulating Bax and cytochrome C and upregulating Bcl-2 to suppress the mitochondrial-mediated apoptosis. Therefore, the oil palm fruits phenolic fractions, especially the IB phenolic fraction, might be utilized as dietary antioxidants to relieve the adverse effects of a high-fat diet on the body, and UHP treatment is a potential method to increase this bioactivity.

Highlights

High-fat diet consumption is very common in modern society, which could lead to high level-free fatty acid (FFA) in the body circulation system and excessive fat deposition in organs [1]
When hepatocytes ingest a large amount of FFA, on the one hand, the FFA is stored as triglycerides in hepatocytes, resulting in hepatic steatosis [6]; on the other hand, the FFA is oxidized, leading to many reactive oxygen species (ROS) production and thereby damaging hepatocytes; and these will lead to the occurrence of fatty liver or/and steatohepatitis [6, 7]
We reported that oil palm fruit (OPF) was rich in phenolic compounds, especially caffeic acid, and exhibited good antioxidant activity in vitro; we found that ultrahigh pressure (UHP) treatment increased the phenolic compounds bioaccessibility and the antioxidant of OPF [19]. erefore, we hypothesized that OPF and its main phenolic compound, caffeic acid, might effectively prevent FFA-induced lipotoxicity and OPF treated by UHP may have a better effect, which has not been investigated

Summary

Introduction

High-fat diet consumption is very common in modern society, which could lead to high level-free fatty acid (FFA) in the body circulation system and excessive fat deposition in organs [1]. Ese results indicated that the inhibitory effect of IB fraction on cell apoptosis was upgraded after UHP treatment, which is probably due to its higher phenolic content [19] and the better antioxidant ability (Figure 2).

Results

Conclusion