Defective lipid metabolism is associated with increased risk of various chronic diseases, such as obesity, cardiovascular diseases, and diabetes. Resveratrol (RSV), a natural polyphenol, has been shown the potential of ameliorating disregulations of lipid metabolism. The objective of this study was to investigate the effects of feed intake and RSV on lipid metabolism in zebrafish (Danio rerio). The adult males were randomly allocated to 6 groups: control (Con, 8 mg cysts/fish/day), control with 20 μmol/L RSV (Con+RSV), calorie restriction (CR, 5 mg cysts/fish/day), calorie restriction with RSV (CR+RSV), overfeed (OF, 60 mg cysts/fish/day), and overfeed with RSV (OF+RSV) groups. The treatment period was 8 weeks. Results showed that CR reduced body length, body weight, and condition factor of zebrafish. CR reduced levels of plasma triglyceride (TG) and induced protein expression of phosphorylated AMP-activated protein kinase-α (pAMPKα), silent information regulator 2 homolog 1 (Sirt1), and peroxisome proliferator activated receptor gamma coactivator-1α (PGC1α). RSV attenuated CR-induced pAMPKα/AMPKαincreases. RSV increased levels of Sirt1 protein in the OF zebrafish, and decreased OF-induced increase in peroxisome proliferator-activated receptor-γ (PPARγ) protein level. Additionally, RSV down-regulated caveolin-1 and up-regulated microtubule-associated protein 1 light chain 3 -II (LC3-II) protein levels in OF zebrafish. In conclusion, these results suggest that 1) CR reduces plasma TG level through activation of the AMPKα-Sirt1- PGC1α pathway; 2) under different dietary stress conditions RSV might regulate AMPK phosphorylation bi-directionally; 3) RSV might regulate lipid metabolism through the AMPKα-Sirt1-PPARγ pathway in OF zebrafish.

Edited by Xiao-Fan WangUnderstanding the mechanism of how liver ductal cells (cholangiocytes) differentiate into hepatocytes would permit liver-regenerative medicine. Emerging liver ductal organoids provide an ex vivo system to investigate cholangiocyte-to-hepatocyte differentiation. However, as current gene manipulation methods require organoid dissociation into single cells and have only low efficiency, it is difficult to dissect specific gene functions in these organoids. Here we developed the adeno-associated virus (AAV) vector AAV-DJ as a powerful tool to transduce mouse and human liver ductal organoids. Via AAV-DJmediated up-or down-regulation of target genes, we successfully manipulated cholangiocyte-to-hepatocyte differentiation. We induced differentiation by overexpressing the hepatocytespecifying regulator hepatocyte nuclear factor 4␣ (HNF4␣) and blocked differentiation by stimulating Notch signaling or interfering with Smad signaling. Further screening for transcriptional factors critical for cholangiocyte-to-hepatocyte differentiation identified HOP homeobox (HOPX), T-box 15 (TBX15), and transcription factor CP2-like 1 (TFCP2L1) as master regulators. We conclude that this highly efficient and convenient gene manipulation system we developed could facilitate investigation into genes involved in cell lineage transitions and enable application of engineered organoids in regenerative medicine.

Liver regeneration after injury requires fine‐tune regulation of connective tissue growth factor (Ctgf). It also involves dynamic expression of hepatocyte nuclear factor (Hnf)4α, Yes‐associated protein (Yap), and transforming growth factor (Tgf)‐β. The upstream inducers of Ctgf, such as Yap, etc, are well‐known. However, the negative regulator of Ctgf remains unclear. Here, we investigated the Hnf4α regulation of Ctgf post‐various types of liver injury. Both wild‐type animals and animals contained siRNA‐mediated Hnf4α knockdown and Cre‐mediated Ctgf conditional deletion were used. We observed that Ctgf induction was associated with Hnf4α decline, nuclear Yap accumulation, and Tgf‐β upregulation during early stage of liver regeneration. The Ctgf promoter contained an Hnf4α binding sequence that overlapped with the cis‐regulatory element for Yap and Tgf‐β. Ctgf loss attenuated inflammation, hepatocyte proliferation, and collagen synthesis, whereas Hnf4α knockdown enhanced Ctgf induction and liver fibrogenesis. These findings provided a new mechanism about fine‐tuned regulation of Ctgf through Hnf4α antagonism of Yap and Tgf‐β activities to balance regenerative and fibrotic signals.