Hypolipidemic Effect of Rice Bran Oil Extract Tocotrienol in High-Fat Diet-Induced Hyperlipidemia Zebrafish (Danio Rerio) Induced by High-Fat Diet.

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.

Anti-inflammatory and antioxidant properties of rice bran oil extract in copper sulfate-induced inflammation in zebrafish (Danio rerio).

Tocotrienols have strong antioxidant properties; however, tocotrienol has not been investigated in detail in aquatic products. In this study, the anti-inflammatory and antioxidant activities of the tocotrienol-rich fraction from rice bran oil and its potential mechanism were verified in a zebrafish CuSO4 inflammation model. The in vitro antioxidant activity was evaluated using the 2,2-Diphenyl-1-picrylhydrazyl (DPPH) stable radical method. The copper chelating activity was determined using the pyrocatechol violet method. Intracellular reactive oxygen species in zebrafish were detected using a fluorescent ROS probe. Transgenic Tg (lyz: DsRed2) zebrafish were used for neutrophil transmigration assays. The mRNA expression levels of antioxidant and pro-inflammatory factor genes were measured using quantitative real-time reverse transcription PCR. In the concentration range tested, 100 µg/mL TRF had the highest copper chelating activity (10%). TRF showed DPPH-free radical scavenging ability, which was 53% at 100 µg/mL TRF. TRF effectively repressed ROS generation and inhibited neutrophil migration to the inflamed site. Moreover, TRF upregulated the expression of antioxidant genes sod and gpx4b, inhibited the expression of pro-inflammatory factors tnfa and il8, and suppressed CuSO4-induced inflammation. In conclusion, TRF has significant anti-inflammatory and antioxidant properties, which supports the use of TRF as an aquatic feed additive to improve the anti-inflammatory and antioxidant capacity of aquatic products.