Objective: Non-alcoholic fatty liver disease (NAFLD) is strongly associated with hyperlipidemia, which is closely related to high levels of sugar and fat. β-sitosterol is a natural product with significant hypolipidemic and cholesterol-lowering effects. However, the underlying mechanism of its action on aquatic products is not completely understood. Methods: A high-fat diet (HFD)-induced NAFLD zebrafish model was successfully established, and the anti-hyperlipidemic effect and potential mechanism of β-sitosterol were studied using oil red O staining, filipin staining, and lipid metabolomics. Results: β-sitosterol significantly reduced the accumulation of triglyceride, glucose, and cholesterol in the zebrafish model. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis showed that differential lipid molecules in β-sitosterol mainly regulated the lipid metabolism and signal transduction function of the zebrafish model. β-sitosterol mainly affected steroid biosynthesis and steroid hormone biosynthesis in the zebrafish model. Compared with the HFD group, the addition of 500 mg/100 g of β-sitosterol significantly inhibited the expression of Ppar-γ and Rxr-α in the zebrafish model by at least 50% and 25%, respectively. Conclusions: β-sitosterol can reduce lipid accumulation in the zebrafish model of NAFLD by regulating lipid metabolism and signal transduction and inhibiting adipogenesis and lipid storage.

In recent years, the potent influence of tocotrienol (T3) on diminishing blood glucose and lipid concentrations in both Mus musculus (rats) and Homo sapiens (humans) has been established. However, the comprehensive exploration of tocotrienol’s hypolipidemic impact and the corresponding mechanisms in aquatic species remains inadequate. In this study, we established a zebrafish model of a type 2 diabetes mellitus (T2DM) model through high-fat diet administration to zebrafish. In the T2DM zebrafish, the thickness of ocular vascular walls significantly increased compared to the control group, which was mitigated after treatment with T3. Additionally, our findings demonstrate the regulatory effect of T3 on lipid metabolism, leading to the reduced synthesis and storage of adipose tissue in zebrafish. We validated the expression patterns of genes relevant to these processes using RT-qPCR. In the T2DM model, there was an almost two-fold upregulation in pparγ and cyp7a1 mRNA levels, coupled with a significant downregulation in cpt1a mRNA (p < 0.01) compared to the control group. The ELISA revealed that the protein expression levels of Pparγ and Rxrα exhibited a two-fold elevation in the T2DM group relative to the control. In the T3-treated group, Pparγ and Rxrα protein expression levels consistently exhibited a two-fold decrease compared to the model group. Lipid metabolomics showed that T3 could affect the metabolic pathways of zebrafish lipid regulation, including lipid synthesis and decomposition. We provided experimental evidence that T3 could mitigate lipid accumulation in our zebrafish T2DM model. Elucidating the lipid-lowering effects of T3 could help to minimize the detrimental impacts of overfeeding in aquaculture.

The microbial community structure in aquaculture water plays an important role in the intestinal microbial diversity of aquatic animals. The Chinese soft-shelled turtle (SST) (Trionyx sinensis) is an important aquaculture species of high economic value in the Asia-Pacific region. An intuitive understanding of the microbial diversity and abundances of SST aquaculture is crucial for comprehending these ecosystems. Herein, the evolutionary characteristics of the bacterial communities in the SST and its aquaculture water systems were investigated using Illumina MiSeq sequencing. This experiment sampled nine SSTs from a pond outside a greenhouse and was repeated three times. The sequencing results revealed significant differences in the microflora composition at the phylum and genus levels in both the intestine and aquaculture water of the SSTs in the greenhouse and pond aquaculture environments. A total of 1039 genera belonging to 65 phyla were identified. At the phylum level, the relative abundances of Chloroflexi (24%), Acidobacteria (5%), and Nitrospira (3%) were higher in the greenhouse water than in the pond water. The relative abundances of Bacteroidetes (35%), Actinobacteria (8%), and Cyanobacteria (4%) were higher in the pond water than in the greenhouse water. The intestinal microorganisms in the SSTs experienced significant changes after the SSTs were transferred from a greenhouse culture to a pond culture environment for 28 days. After the SSTs were cultured in the ponds, we observed decreases in the relative abundances of Actinobacteria (39% to 25%), Cyanobacteria (24% to 0.8%), Chlorobacteria (9% to 3%), and Firmicutes (5.5% to 0.8%. However, we observed increases in the relative abundances of Bacteroidetes (2% to 35%) and Acidobacteria (0.3% to 25%). These results showed that the bacterial diversity and richness compositions in the intestinal tract and aquaculture water were the same. However, the relative abundances of bacterial communities varied. The results of this study are of great significance in understanding how the environment affects SST cultures. These data may provide valuable instructions for Chinese soft-shelled turtle aquaculture management.