Hepatocellular EVs Regulate Lipid Metabolism via SIRT1/SREBP-1c/PGC-1α Signaling in Primary Calf Hepatocytes.

Abstract

SIRT1-SREBP-1c/PGC-1α signaling is involved in the production of non-esterified fatty acids (NEFAs) and liver lipid metabolism disorders in ketotic calf. The molecules contained in extracellular vesicles (EVs) regulate intercellular communication, and research on calf hepatocytes-derived EVs has become a hot spot. We hypothesized that EVs in cell culture supernatants could affect lipid metabolism in hepatocyte models via SIRT1/SREBP-1c/PGC-1α signaling. Non-ketosis (NK, 0 mM NEFA) and clinical ketosis calf models (CK, 2.4 mM NEFAs) were established in vitro cultured calf hepatocytes and EVs were extracted from their supernatants as NK-derived EVs and CK-derived EVs, respectively. In vitro hepatocyte models, comprising a normal culture group (normal) and the group treated with NEFAs at 2.4 mM (2.4 NEFA), were treated with NK and CK-derived EVs. In addition, we transfected an SIRT1-overexpressing adenovirus into calf hepatocytes and determined the expression of key genes, enzymes, and proteins involved in the SIRT1/SREBP-1c/PGC-1α pathway. The results showed that the NK-derived EVs inhibited the expression of the SREBP-1c gene and protein and increased the expression of the SIRT1 and PGC-1α genes and proteins (<i>p</i> < 0.05). In contrast, CK-derived EVs induced lipid metabolism disorders in the normal hepatocyte group and aggravated NEFA-induced lipid metabolism imbalances in hepatocytes (<i>p</i> < 0.05). Moreover, overexpression of SIRT1 confirmed that EVs exert vital functions in hepatocyte lipid metabolism via SIRT1/SREBP-1c/PGC-1α signaling to regulate hepatocyte lipid metabolism. In summary, NK-derived EVs alleviated liver lipid metabolism disorders caused by NEFAs via modulation of SIRT1/SREBP-1c/PGC-1α signaling, while CK-derived EVs had the opposite effect. NK-derived EVs upregulated lipid oxidation-related genes and downregulated lipid synthesis-related genes, suggesting that NK-derived EVs could be used as biological extracts to alleviate lipid metabolism disorders in ketotic calf.