Background: Non-alcoholic fatty liver disease (NAFLD) is the most common hepatic chronic disease worldwide. NAFLD is characterized by an abnormal triglyceride (TG) accumulation (steatosis) in the liver, that may lead to hepatic inflammation (1). DGAT2 is a key enzyme that catalyzes the final step of TG synthesis and whose expression is elevated in NAFLD (2). FABP4 is a transporter of intracellular lipids and its levels are related with inflammation, characterized by a high expression of proinflammatory cytokines such as TNF-α, IL-6 and IL-1β. Palmitic acid (PA, C16:0) and oleic acid (OA; C18:1) are two of the most abundant fatty acids that participate in the formation of TGs in hepatic cells in vivo and in vitro (3). Lampaya medicinalis Phil. (Verbenaceae) is a small bush that grows in the “Puna atacameña” in the North of Chile. The infusion from leaves and aerial parts of the plant has been used by local ethnic groups to treat and cure inflammatory diseases (4). The aim of this study was to assess in vitro the effect of the hydroalcoholic extract of Lampaya medicinalis (HEL) against OA/PA-induced steatosis and proinflammatory marker expression in HepG2 hepatocytes.
Methods: HEL (0.01, 0.1, 1, 10 μg/mL) cytotoxicity potential (48 h) was evaluated by Trypan blue exclusion. Cells were exposed for 48 h to 1 mM OA/PA (2:1) in the presence or not of 0.01 or 10 μg/mL HEL. Intracellular TGs were assessed with Oil Red O staining and quantified with Nile Red reagent by fluorimetry. mRNA expression of DGAT2, TNF-α, IL-6 and IL-1β was evaluated by qRT-PCR. FABP4 content was assessed by Western blot. The levels of TNF-α and IL-6 in the culture media were analysed by ELISA.
Results: HEL was not cytotoxic at any concentration assessed (n=4; p>0.05). The increased content of TG induced by OA/PA was reduced in the presence of HEL (n=7; p<0.05), showing a strong consistency with Oil Red O staining. The increase in the protein content of FABP4 as well as the increment in mRNA expression of DGAT2, TNF-α, IL-6 and IL-1β induced by OA/PA were lower in cells co-exposed to HEL (n=6-9; p<0.05). The incubation with HEL+OA/PA reduced proinflammatory cytokine levels in culture media compared to cells exposed to OA/PA alone (n=6-7; p<0.05).
Conclusion: HEL reduces the OA/PA-induced increase in intracellular TG, DGAT2 and proinflammatory cytokine expression and FABP4 content, as well as the levels of secreted proinflammatory cytokines in HepG2 cells. These findings suggest a protective role for HEL against OA/PA-induced steatosis and inflammation, and therefore that Lampaya medicinalis may represent a promising therapeutic tool for pathologies such as NAFLD.
References: (1) Gluchowski L, et al. Nat Rev Gastroenterol Hepatol. 2017;14(6):343-355. (2) Perry, et al. Nature. 2014;510(7503):84-91. (3) Cunningham P, et al. J Nutr. 2009;139(4):636–639. (4) Morales G, et al. Biol Res. 2014;47:6.