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

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.

Caffeic acid does not protect human pancreatic β cells against stearic acid‐induced ER stress and apoptosis

“…Caffeic acid (CA) was reported to be protective in several cell types against various proapoptotic stimuli, including fatty acids. [14][15][16][17][18][19] Therefore, this study aimed to test whether it is also beneficial against saturated stearic acid (SA)-induced apoptosis of human pancreatic β cells NES2Y and 1.1B4. Firstly, we have tested the effect of CA alone since these data are also missing and in order to help select concentrations suitable for further experiments, that is, coapplication of CA with SA.…”

“…Our results (Figure 2) are inconsistent with those reported for hepatocytes where CA exhibits a protective effect against saturated fatty acids. [18,19] What we can exclude as a possible explanation for this dissimilarity is the duration of the treatment, as well as the concentrations of CA employed.…”

“…used 0.3 mM palmitate). [ 19 ] However, we tested the effect of CA also against 0.5 mM SA‐induced ER stress and apoptosis. We gained identical negative outcomes as with the 1 mM concentration (unpublished data).…”

“…In the previously mentioned papers the authors tested this only in hepatocytes. [ 18,19 ] Therefore, the objective of this study was to expand upon these previous findings, that is, to examine the impact of CA on the ability of saturated stearic acid to induce apoptosis in the human pancreatic β‐cell lines NES2Y and 1.1B4.…”

“…This natural polyphenolic compound was found to protect various cell types against several proapoptotic stimuli, [14][15][16][17] including FAs. [18,19] However, the potential protective effect of CA against FA-induced apoptosis in pancreatic β cells was not ascertained yet.…”