scd knockout activates β-oxidation of fatty acids via accumulating stearic acid (18:0) and induces anorexia in zebrafish

Effects of the plastic additive 2,4-di-tert-butylphenol on intestinal microbiota of zebrafish

Plastic additives such as the antioxidant 2,4-di-tert-butylphenol (2,4-DTBP) have been widely detected in aquatic environments, over a wide range of concentrations reaching 300 μg/L in surface water, potentially threatening the health of aquatic organisms and ecosystems. However, knowledge of the specific effects of 2,4-DTBP on aquatic vertebrates is still limited. In this study, adult zebrafish were exposed to different concentrations of 2,4-DTBP (0, 0.01, 0.1 and 1.0 mg/L) for 21 days in the laboratory. The amplicon sequencing results indicated that the diversity and composition of the zebrafish gut microbiota were significantly changed by 2,4-DTBP, with a shift in the dominant flora to more pathogenic genera. Exposure to 2,4-DTBP at 0.1 and 1.0 mg/L significantly increased the body weight and length of zebrafish, suggesting a biological stress response. Structural assembly defects were also observed in the intestinal tissues of zebrafish exposed to 2,4-DTBP, including autolysis of intestinal villi, adhesions and epithelial detachment of intestinal villi, as well as inflammation. The transcriptional expression of some genes showed that 2,4-DTBP adversely affected protein digestion and absorption, glucose metabolism and lipid metabolism. These results are consistent with the PICRUSt2 functional prediction analysis of intestinal microbiota of zebrafish exposed to 2,4-DTBP. This study improves our understanding of the effects of 2,4-DTBP on the health of aquatic vertebrates and ecosystems.

The knockout of cytoglobin 1 in zebrafish (Danio rerio) alters lipid metabolism, iron homeostasis and oxidative stress response

Cytoglobin (Cygb) is an evolutionary ancient heme protein with yet unclear physiological function(s). Mammalian Cygb is ubiquitously expressed in all tissues and is proposed to be involved in reactive oxygen species (ROS) detoxification, nitric oxide (NO) metabolism and lipid-based signaling processes. Loss-of-function studies in mouse associate Cygb with apoptosis, inflammation, fibrosis, cardiovascular dysfunction or oncogenesis. In zebrafish (Danio rerio), two cygb genes exist, cytoglobin 1 (cygb1) and cytoglobin 2 (cygb2). Both have different coordination states and distinct expression sites within zebrafish tissues. The biological roles of the cygb paralogs are largely uncharacterized. We used a CRISPR/Cas9 genome editing approach and generated a knockout of the penta-coordinated cygb1 for in vivo analysis. Adult male cygb1 knockouts develop phenotypic abnormalities, including weight loss. To identify the molecular mechanisms underlying the occurrence of these phenotypes and differentiate between function and effect of the knockout we compared the transcriptomes of cygb1 knockout at different ages to age-matched wild-type zebrafish. We found that immune regulatory and cell cycle regulatory transcripts (e.g. tp53) were up-regulated in the cygb1 knockout liver. Additionally, the expression of transcripts involved in lipid metabolism and transport, the antioxidative defense and iron homeostasis was affected in the cygb1 knockout. Cygb1 may function as an anti-inflammatory and cytoprotective factor in zebrafish liver, and may be involved in lipid-, iron-, and ROS-dependent signaling.