Stable Isotope-Labeled Lipidomics to Unravel the Heterogeneous Development Lipotoxicity

Abstract

Non-alcoholic fatty liver disease (NAFLD) as a global health problem has clinical manifestations ranging from simple non-alcoholic fatty liver (NAFL) to non-alcoholic steatohepatitis (NASH), cirrhosis, and cancer. The role of different types of fatty acids in driving the early progression of NAFL to NASH is not understood. Lipid overload causing lipotoxicity and inflammation has been considered as an essential pathogenic factor. To correlate the lipid profiles with cellular lipotoxicity, we utilized palmitic acid (C16:0)- and especially unprecedented palmitoleic acid (C16:1)-induced lipid overload HepG2 cell models coupled with lipidomic technology involving labeling with stable isotopes. C16:0 induced inflammation and cell death, whereas C16:1 induced significant lipid droplet accumulation. Moreover, inhibition of de novo sphingolipid synthesis by myriocin (Myr) aggravated C16:0 induced lipoapoptosis. Lipid profiles are different in C16:0 and C16:1-treated cells. Stable isotope-labeled lipidomics elucidates the roles of specific fatty acids that affect lipid metabolism and cause lipotoxicity or lipid droplet formation. It indicates that not only saturation or monounsaturation of fatty acids plays a role in hepatic lipotoxicity but also Myr inhibition exasperates lipoapoptosis through ceramide in-direct pathway. Using the techniques presented in this study, we can potentially investigate the mechanism of lipid metabolism and the heterogeneous development of NAFLD.

The Expectation and Reality of the HepG2 Core Metabolic Profile

“…Seven papers of accumulated datasets studied the effects of sugars [ 63 , 64 ], acids [ 65 , 66 ], and other “neutral” compounds [ 67 , 68 , 69 ]. One work was devoted to the impact of gamma-irradiation [ 70 ] on the HepG2 cell line.…”

Lipidome remodeling activities of DPA-EA in palmitic acid-stimulated HepG2 cells and the in vivo anti-obesity effect of the DPA-EA and DHA-EA mixture prepared from algae oil

“…The present work also demonstrated that Pal administration caused lipid accumulation in HepG2 cells, with a significant elevation of lipid droplets. Besides, several lipidomics studies have noted that Pal can influence the overall lipid metabolism ( Shih et al, 2018 ; Cabezas et al, 2022 ). For example, Pal insult could affect lipid metabolites such as PE, PS, PC, and glycerophosphocholine (GPC) ( Cabezas et al, 2022 ).…”

“…For example, Pal insult could affect lipid metabolites such as PE, PS, PC, and glycerophosphocholine (GPC) ( Cabezas et al, 2022 ). The stable isotope-labeled lipidomics on Pal-stimulated HepG2 cells revealed that Pal significantly altered the levels of many lipids ( e.g., PL, Cer, GL, et al ), which were involved in biosynthetic pathways of DG, TG, PI, dihydroceramide (dHCer), Cer, SM, PC, PE, LPA, and LPE ( Shih et al, 2018 ). Our lipidomics study also showed Pal-induced a significantly dysregulated lipid profile in HepG2 cells.…”

Lipid Metabolism Reprograming as a Target for Cancer

“…Lipotoxicity induced cell death may be another reason. Lipotoxicity is the best studied in liver diseases [99], but it also occurs in cancer cells. For example, saturation or monounsaturation of fatty acids induced apoptotic cell death in liver cancer cells [100].…”