Browsing by Author "Zhang, Mei-Ling"

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    The comparisons in protective mechanisms and efficiencies among dietary α-lipoic acid, β-glucan and L-carnitine on Nile tilapia infected by Aeromonas hydrophila
    (Elsevier, 2018-12-13) Lu, Dong-Liang; Samwel Mchele Limbu; Hong-Bo, Lv; Ma, Qiang; Chen, Li-Qiao; Zhang, Mei-Ling; Du, Zhen-Yu
    Dietary α-lipoic acid (LA), β-glucan (Gluc) and l-carnitine (L-Ca) are commonly used additives to promote fish growth and stress resistance in aquaculture production. However their mechanisms and efficiencies in helping fish to resist diseases have not been compared before. In this study, we fed Nile tilapia (Oreochromis niloticus) with diets containing appropriate doses of LA, Gluc and L-Ca for five weeks and further intraperitoneally injected the fish with Aeromonas hydrophila. After dietary treatment, none of the additives affected the fish growth, but dietary Gluc and L-Ca reduced protein and lipid body contents in fish, respectively. After A. hydrophila challenge, all fish treated with the three dietary additives showed higher survival rate, but those fed on dietary L-Ca had lower survival than those fed on LA and Gluc diets, indicating high protection efficiency of LA and Gluc. The protective mechanisms of the three feed additives were quite different under A. hydrophila infection. Dietary LA induced higher total antioxidant capacity and higher mRNA expression of anti-oxidative genes than other additives in liver and also activated partly the immune function in serum and spleen. Gluc largely increased the immune function by activating the immunity enzymes in serum, inducing inflammation in liver and increasing the expression of immune genes in spleen and head kidney. Gluc also increased partly the antioxidant capacity in serum and liver and lipid catabolism in liver. L-Ca largely increased lipid catabolism in liver while it increased partly the antioxidant capacities in serum and liver. Taken together, these results indicate that, dietary LA, Gluc and L-Ca have various protective mechanisms and differ in their efficiencies on resisting A. hydrophila infection in Nile tilapia.
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    Fasting enhances cold resistance in fish through stimulation of lipid catabolism and autophagy
    (Wiley, 2019-01-07) Lu, Dong-Liang; Ma, Qiang; Ning, Li-Jun; Wang, Jing; Li, Ling-Yu; Li, Jia-Min; Han, Si-Lan; Sun, Sheng-Xiang; Samwel Mchele Limbu; Li, Dong-Liang; Qiao, Fang; Chen, Li-Qiao; Zhang, Mei-Ling; Du, Zhen-Yu
    In cold environments, most homeothermic animals increase their food intake to supply more energy to maintain body temperature, whereas most poikilothermic animals such as fishes decrease or even stop feeding under cold stress. However, the physiological value of fasting during cold resistance in poikilotherms has not been explained. Here, we show that moderate fasting largely enhanced cold resistance in fish. By using pharmacological (fenofibrate, mildronate, chloroquine and rapamycin) and nutritional approaches (fatty acids diets and amino acids diets) in wild‐type or specific gene knock‐out zebrafish models (carnitine palmitoyltransferase‐1b‐deficient strain, CPT1b−/−, or autophagy‐related protein 12‐deficient strain, ATG12−/−), we verified that fasting‐stimulated lipid catabolism and autophagy played essential roles in the improved cold resistance. Moreover, suppression of the mechanistic target of rapamycin (mTOR) pathway by using rapamycin mostly mimicked the beneficial effects of fasting in promoting cold resistance as either the physiological phenotype or transcriptomic pattern. However, these beneficial effects were largely reduced when the mTOR pathway was activated through high dietary leucine supplementation. We conclude that fasting helps fish to resist cold stress by modulating lipid catabolism and autophagy, which correlates with the mTOR signalling pathway. Therefore, fasting can act as a protective strategy of fish in resisting coldness.
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    High fat diet worsens the adverse effects of antibiotic on intestinal health in juvenile Nile tilapia (Oreochromis niloticus).
    (Elsevier, 2019-08-25) Samwel Mchele Limbu; Ma, Qiang; Zhang, Mei-Ling; Du, Zhen-Yu
    Antibiotics and high fat diets are commonly used independently in global aquaculture production for fish health management and to spare the use of costly protein as energy sources, respectively, causing relatively similar meta bolic effects and stresses. However, it is unknown whether dietary high fat worsens or attenuates the adverse effects caused by antibiotics in fish. We determined the ability of high fat diet to influence the adverse effects of oxytetra cycline on Nile tilapia, Oreochromis niloticus. Thirty Nile tilapia weighing 8.45 ± 0.15 g were fed on medium fat (MF; 70 g/kg) and high fat (HF; 120 g/kg) diets and the same fat levels supplemented with 2.00 g/kg diet of OTC (80 mg/kg body weight/day) hereafter, MFO and HFO for 65 days. The general growth performance, feed efficiency and intestinal health of fish were evaluated. The Nile tilapia fed on HFO diet had significantly lower growth rate, body protein content and feed efficiency compared to those fed on MFO diet. Dietary HFO affected the intestine histomorphology, which decreased dramatically the tight junction proteins of Nile tilapia and induced microbiota dysbiosis compared to MFO diet. The Nile tilapia fed on HFO diet had increased oxidative stress, which stimulated drug detoxification response, caused endoplasmic reticulum stress and apoptosis compared to those fed on MFO diet. The new findings from our study demonstrate that, the adverse effects of antibiotics in fish are different at me dium and high fat contents. Feeding fish with high fat diets with antibiotics worsen the adverse effects. This en lightens our understanding on the risks of antibiotics misuse and also suggests that antibiotics should be more strictly limited in aquaculture, in which high fat diets are currently widely used in fish production worldwide.