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

TL;DR

This study shows that EVs from healthy calf liver cells can help reduce fat metabolism issues in sick calves by regulating specific signaling pathways.

Contribution

The study demonstrates the role of hepatocellular EVs in modulating lipid metabolism via SIRT1/SREBP−1c/PGC−1α signaling in calf hepatocytes.

Findings

NK-derived EVs inhibited SREBP−1c and increased SIRT1 and PGC−1α expression, improving lipid metabolism.

CK-derived EVs worsened lipid metabolism in normal and NEFA-treated hepatocytes.

SIRT1 overexpression confirmed the pathway's role in EV-mediated lipid regulation.

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 (p < 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 (p < 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.

Figures