Browsing by Author "Zhen-Yu, Du"

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    Environmental concentrations of antibiotics impair zebrafish gut health.
    (Elsevier, 2018-01-04) Li, Zhou; Samwel Mchele Limbu; Fang, Qiao; Zhen-Yu, Du; Meiling, Zhang
    Antibiotics have been widely used in human and veterinary medicine to both treat and prevent disease. Due to their high water solubility and low bioavailability, many antibiotic residues have been found in aquatic environments. Fish are an indispensable link between the environmental pollution and human health. However, the chronic effects of environmental concentrations of antibiotics in fish have not been thoroughly investigated. Sulfamethoxazole (SMX) and oxytetracycline (OTC) are frequently detected in aquatic environments. In this study, zebrafish were exposed to SMX (260 ng/L) and OTC (420 ng/L) for a six-week period. Results indicated that exposure to antibiotics did not influence weight gain of fish but increased the metabolic rate and caused higher mortality when treated fish were challenged with Aeromonas hydrophila. Furthermore, exposure to antibiotics in water resulted in a significant decrease in intestinal goblet cell numbers, alkaline phosphatase (AKP), acid phosphatase (ACP) activities, and the anti-oxidant response while there was a significant increase in expression of inflammatory factors. Antibiotic exposure also disturbed the intestinal microbiota in the OTC-exposed group. Our results indicated that environmental antibiotic concentrations can impair the gut health of zebrafish. The potential health risk of antibiotic residues in water should be evaluated in the future.
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    IGF-1 induces SOCS-2 but not SOCS-1 and SOCS-3 transcription in juvenile Nile tilapia (Oreochromis niloticus).
    (The Company of Biologists Limited, 2018-04-12) Cai-Zhi, Liu; Yuan, Luo; Samwel Mchele Limbu; Li-Qiao, Chen; Zhen-Yu, Du
    Insulin-like growth factor-1 (IGF-1) plays a crucial role in regulating growth in vertebrates while suppressors of cytokine signaling (SOCS) act as feedback inhibitors of the GH/IGF-1 axis. Although SOCS-2 binds IGF-1 receptor and inhibits IGF-1-induced STAT3 activation, presently there is no clear evidence whether IGF-1 could induce SOCS genes expression. The current study aimed to determine whether IGF-1 could induce the transcription of SOCS in juvenile Nile tilapia (Oreochromis niloticus). We show that there is a common positive relationship between the mRNA expression of IGF-I and SOCS-2 under different nutritional statuses and stimulants, but not the expression of SOCS-1 and SOCS-3 mRNA. Furthermore, rhIGF-1 treatment and transcriptional activity assay confirmed the hypothesis that IGF-1 could induce SOCS-2 expression, while has no effect or even decreased the expression of SOCS-1 and SOCS-3. Overall, we obtained evidence that the transcription of SOCS-2, but not SOCS-1 or SOCS-3 could be induced by IGF signaling, suggesting the SOCS-2 serves as a feedback suppressor of IGF-1 axis in juvenile Nile tilapia.
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    Influence of Long-Term Feeding Antibiotics on the Gut Health of Zebrafish
    (Zebrafish, 2018-08-01) Li, Zhou; Samwel Mchele Limbu; Fang, Qiao; Zhen-Yu, Du; Meiling, Zhang
    The use of antibiotics for anti-infection and growth promotion has caused the overuse of antibiotics in aquaculture. However, the benefit or risk of the long-term use of antibiotics on fish growth or health has not been fully addressed. In the present study, zebrafish were fed with sulfamethoxazole (SMX) or oxytetracycline (OTC) at the therapeutic concentrations (100 and 80 mg/kg body weight per day, respectively) for 6 weeks to mimic the long-term use of antibiotics. The digestive enzyme activities were higher in both antibiotic treatments, and higher oxygen consumption rate was found in OTC treated group. As a result, SMX increased the weight gain of zebrafish, and OTC treatment did not show significant prompting effect on growth. The mortality was higher in SMX or OTC treated group on 2nd–4th day after exposure to Aeromonas hydrophila. Lower alkaline phosphatase (AKP) and acid phosphatase (ACP) activities were found in OTC treated group, while higher malondialdehyde (MDA) content was found in the intestine of both SMX and OTC treated zebrafish. Furthermore, feeding OTC decreased the intestinal microbial richness. This study revealed that long-term use of legal aquaculture concentrations of antibiotics caused systemic adverse effects on fish gut health; stringent policy for use of antibiotics in fish is urgent.
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    Inhibited fatty acid β-oxidation impairs stress resistance ability in Nile tilapia (Oreochromis niloticus)., 68: 500-508.
    (Elsevier, 2017-07-31) Han, Pan; Ling-Yu, Li; Jia-Min, Li; Wei-Li, Wang; Samwel Mchele Limbu; Pascal, Degrace; Dong-Liang, Li; Zhen-Yu, Du
    Energy metabolism plays important roles in stress resistance and immunity in mammals, however, such functions have not been established in fish. In the present study, Nile tilapia (Oreochromis niloticus) was fed with mildronate, an inhibitor of mitochondrial fatty acid (FA) β-oxidation, for six weeks subsequently challenged with Aeromonas hydrophila and ammonia nitrogen exposure. Mildronate treatment reduced significantly l-carnitine concentration and mitochondrial FA β-oxidation efficiency, while it increased lipid accumulation in liver. The fish with inhibited hepatic FA catabolism had lower survival rate when exposed to Aeromonas hydrophila and ammonia nitrogen. Moreover, fish fed mildronate supplemented diet had lower immune enzymes activities and anti-inflammatory cytokine genes expressions, but had higher pro-inflammatory cytokine genes expressions. However, the oxidative stress-related biochemical indexes were not significantly affected by mildronate treatment. Taken together, inhibited mitochondrial FA β-oxidation impaired stress resistance ability in Nile tilapia mainly through inhibiting immune functions and triggering inflammation. This is the first study showing the regulatory effects of lipid catabolism on stress resistance and immune functions in fish.
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    Lipophagy is essential for lipid metabolism in fish.
    (Elsevier, 2018-05-30) Jing, Wang; Si-Lan, Han; Ling-Yu, Li; Dong-Liang, Li; Samwel Mchele Limbu; Dong-Liang, Li; Mei-Ling, Zhang; Zhen-Yu, Du
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    The metabolic regulation of dietary L-carnitine in aquaculture nutrition: present status and future research strategies.
    (Wiley, 2018-09-26) Ling-Yu, Li; Samwel Mchele Limbu; Qiang, Ma; Li‐Qiao, Chen; Mei‐Ling, Zhang; Zhen-Yu, Du
    L‐carnitine is a multi‐functional nutrient which plays a leading role in fatty acid metabolism in mammals and other eukaryotes. Its main physiological function is to promote fatty acid β‐oxidation to produce energy, which reduces body fat content and improves body weight without affecting moisture content in whole body and muscle. In recent years, its dietary supplementation in aquaculture nutrition has been studied in different cultured species. It has been proved that L‐carnitine can improve growth and increase lipid utilization rate in some aquatic animals. However, such beneficial effects of dietary L‐carnitine are limited or absent in other species. The reasons for the conflicting results obtained on L‐carnitine functions in aquatic animals need to be elucidated. This review explores comprehensively the different physiological functions of L‐carnitine in various aquatic animals. In the end, research strategies are provided to elucidate the existing conflicts on dietary L‐carnitine application in aquaculture nutrition in order to promote its utilization in aquatic feed industry.
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    The presence or absence of intestinal microbiota affects lipid deposition and related genes expression in zebrafish (Danio rerio).
    (Frontiers Media SA, 2018-05-29) Yi, Sheng; Hui, Ren; Samwel Mchele Limbu; Yuhong, Sun; Fang, Qiao; Wanying, Zhai; Zhen-Yu, Du; Meiling, Zhang
    Understanding how intestinal microbiota alters energy homeostasis and lipid metabolism is a critical process in energy balance and health. However, the exact role of intestinal microbiota in the regulation of lipid metabolism in fish remains unclear. Here, we used two zebrafish models (germ-free and antibiotics-treated zebrafish) to identify the role of intestinal microbiota in lipid metabolism. Conventional and germ-free zebrafish larvae were fed with egg yolk. Transmission electron microscopy was used to detect the presence of lipid droplets in the intestinal epithelium. The results showed that, microbiota increased lipid accumulation in the intestinal epithelium. The mRNA sequencing technology was used to assess genes expression level. We found majority of the differentially expressed genes were related to lipid metabolism. Due to the limitation of germ-free zebrafish larvae, antibiotics-treated zebrafish were also used to identify the relationship between the gut microbiota and the host lipid metabolism. Oil-red staining showed antibiotics-treated zebrafish had less intestinal lipid accumulation than control group. The mRNA expression of genes related to lipid metabolism in liver and intestine was also quantified by using real-time PCR. The results indicated that apoa4, hsl, cox15, slc2a1a, and lss were more related to intestinal bacteria in fish, while the influence of intestinal microbiota on the activity of fabp6, acsl5, cd36, and gpat2 was different between the liver and intestine. This study identified several genes regulated by intestinal microbiota. Furthermore, the advantages and disadvantages of each model have been discussed. This study provides valuable information for exploring host-microbiota interactions in zebrafish in future.
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    Tracking pollutants in dietary fish oil: from ocean to table.
    (Elsevier, 2018-05-16) Sheng-Xiang, Sun; Xue-Ming, Hua; Yun-Yun, Deng; Yun-Ni, Zhang; Jia-Min, Li; Zhao, Wu; Samwel Mchele Limbu; Da-Sheng, Lu; Hao-Wen, Yin; Guo-Quan, Wang; Rune, Waagbø; Frøyland, Livar; Mei-Ling, Zhang; Zhen-Yu, Du
    Dietary fish oil used in aquafeed transfers marine pollutants to farmed fish. However, the entire transfer route of marine pollutants in dietary fish oil from ocean to table fish has not been tracked quantitatively. To track the entire transfer route of marine pollutants from wild fish to farmed fish through dietary fish oil and evaluate the related human health risks, we obtained crude and refined fish oils originating from the same batch of wild ocean anchovy and prepared fish oil-containing purified aquafeeds to feed omnivorous lean Nile tilapia and carnivorous fatty yellow catfish for eight weeks. The potential human health risk of consumption of these fish was evaluated. Marine persistent organic pollutants (POPs) were concentrated in fish oil, but were largely removed by the refining process, particularly dioxins and polychlorinated biphenyls (PCBs). The differences in the POP concentrations between crude and refined fish oils were retained in the fillets of the farmed fish. Fillets fat content and fish growth were positively and negatively correlated to the final POPs deposition in fillets, respectively. The retention rates of marine POPs in the final fillets through fish oil-contained aquafeeds were 1.3%–5.2%, and were correlated with the POPs concentrations in feeds and fillets, feed utilization and carcass ratios. The dietary crude fish oil-contained aquafeeds are a higher hazard ratio to consumers. Prohibiting the use of crude fish oil in aquafeed and improving growth and feed efficiency in farmed fish are promising strategies to reduce health risks originating from marine POPs.