Dietary Seleno-l-Methionine Causes Alterations in Neurotransmitters, Ultrastructure of the Brain, and Behaviors in Zebrafish (Danio rerio)

Abstract

Elevated concentrations of dietary selenium (Se) cause abnormalities and extirpation of fish inhabiting in Se-contaminated environments. However, its effect on fish behavior and the underlying mechanisms remain largely unknown. In this study, two-month-old zebrafish (Danio rerio) was fed seleno-l-methionine (Se-Met) at environmentally relevant concentrations (i.e., control (2.61), low (5.43), medium (12.16), and high (34.61) μg Se/g dry weight (dw), respectively, corresponding to the C, L, M, and H treatments) for 60 days. Targeted metabolomics, histopathological, and targeted transcriptional endpoints were compared to behavioral metrics to evaluate the effects of dietary exposure to Se-Met . The results showed that the levels of total Se and malondialdehyde in fish brains were increased in a dose-dependent pattern. Meanwhile, mitochondrial damages and decreased activities of the mitochondria respiratory chain complexes were observed in the neurons at the M and H treatments. In addition, dietary Se-Met affected neurotransmitters, metabolites, and transcripts of the genes associated with the dopamine, serotonin, gamma-aminobutyric acid, acetylcholine, and histamine signaling pathways in zebrafish brains at the H treatments. The total swimming distance and duration in the Novel Arm were lowered in fish from the H treatment. This study has demonstrated that dietary Se-Met affects the ultrastructure of the zebrafish brain, neurotransmitters, and associated fish behaviors and may help enhance adverse outcome pathways for neurotransmitter-behavior key events in zebrafish.

Dietary Seleno-l-methionine Alters the Microbial Communities and Causes Damage in the Gastrointestinal Tract of Japanese Medaka Oryzias latipes

“…40−42 It is likely that the fish with reduced growth might be more vulnerable to predation and could be extirpated from the Se-contaminated aquatic environments. 2 Though many studies 43,44 and our recent companion paper 32 have shown that Se at essential levels might be beneficial to fish growth, stimulated growth was not observed in the Se-Met treated Oryzias latipes in this study.…”

“…Similarly, decreased body weight, fork length, and condition factor have been observed in the Sacramento splittail ( Pogonichthys macrolepidotus ), rainbow trout ( Oncorhynchus mykiss ), and white sturgeon ( Acipenser transmontanus ) fed the Se-Met enriched diet for over 2 months, implying the deleterious effects of excess Se on fish growth. − It is likely that the fish with reduced growth might be more vulnerable to predation and could be extirpated from the Se-contaminated aquatic environments . Though many studies , and our recent companion paper have shown that Se at essential levels might be beneficial to fish growth, stimulated growth was not observed in the Se-Met treated Oryzias latipes in this study. Since the Japanese medaka used were adults, they might have passed the ages for fast growth which normally occurs in juvenile fish .…”

“…Dietborne and dissloved Se exposures at elevated concentrations often cause lipid peroxidation in various tissues of different fish, probably due to the increased intracellular ROS formation. 32,48,49 Meanwhile, aqueous Se-Met exposure also results in a decline of glutathione in the embryos of Oryzias latipes. 50 In addition, decreased ratio of GSH/GSSG has been seen in the cultured hepatocytes of Oncorhynchus mykiss treated with elevated Se-Met for 4 and 24 h. 51 All these results indicate that Se exposure can affect the antioxidant physiology in fish, probably due to the excess ROS.…”

“…Seleno- l -methionine (Se-Met, purity >98%) was purchased from Ryon Biological Technology Co., Ltd. (Shanghai, China). Nominal concentrations of dietary Se-Met (i.e., control (C), 3 (low: L), 10 (medium: M), and 30 (high: H) μg Se/g dry weight) were chosen based on the environmental relevance of these concentrations. , A stock was prepared and further diluted to 3, 10, and 30 μg Se/g (in 200 mL) using deionized distilled water. A total of 200 mL of each stock solution were mixed with 200 g of Otohime feed with 0.36 mm in grain size (Nissin Feed Products Co., Ltd., Japan) and freeze-dried in a freeze-dryer (Labconco, U.S.A.).…”

Selenium Speciation in the Sediments and the Oligochaete Lumbriculus Variegatus

“…Conclusive evidence for its toxicity at elevated concentrations to aquatic organisms has been obtained from the two heavily Se-contaminated aquatic ecosystems, i.e., the Belews Lake and Kesterson Reservoir, which have witnessed the extinction of a number of apex predatory species ( sh and birds) in the aquatic food chain (Hamilton, 2004;Lemly, 2004). Meanwhile, laboratory experiments have documented a variety of adverse effects of Se in different aquatic organisms, including teratogenicity (Wang et al, 2020), neurotoxicity (Li et al, 2021), oxidative stress (Janz et al, 2010), the composition of microbial community (Liu et al, 2022), etc.…”