Jun Qiang

Changes in the fatty acid composition and regulation of antioxidant enzymes and physiology of juvenile genetically improved farmed tilapia Oreochromis niloticus (L.), subjected to short-term low temperature stress

We evaluated the effect of cold shock on the fatty acid composition, antioxidant enzymes, and physiological responses of genetically improved farmed tilapia (GIFT). Experimental GIFT tilapia, a warm-water teleost, were initially acclimated at 28°C and then transferred directly to 13°C. Stress responses were monitored for 120h. There was a significant change in all parameters in response to the cold stressor (P<0.05). Serum cortisol levels increased from 336.93ng/ml to a peak of 1165.31ng/ml 24h after the initial cold shock, and declined rapidly thereafter. Serum glucose and cholesterol levels were significantly lower in the low temperature group than the control group at 120h (P<0.05). Acute low temperature stress enhanced superoxide dismutase, glutathione peroxidase, catalase, and glutathione levels in the liver of GIFT tilapia. The GIFT tilapia were able to selectively metabolize fatty acids for energy needs during the early period of exposure to low-temperature stress. During this time, they primarily used saturated fatty acids for energy. However as the duration of the stressor and loss of muscle fat increased, the fish began to metabolize long-chain polyunsaturated fatty acids. Increased malondialdehyde was produced by oxidation of these fatty acids leading to oxidative damage. Our results provide insight into the changes in fatty acid metabolism physiology that allow GIFT tilapia juveniles to adapt to short-term cold stress.

Temperature modulates hepatic carbohydrate metabolic enzyme activity and gene expression in juvenile GIFT tilapia (Oreochromis niloticus) fed a carbohydrate-enriched diet.

The effects of rearing temperature on hepatic glucokinase (GK), glucose-6-phosphatase (G6Pase) and Glucose-6-phosphate dehydrogenase (G6PD) activity and gene expression were studied in GIFT (genetically improved farmed tilapia) tilapia fed a high carbohydrate diet containing 28% crude protein, 5% crude lipid and 40% wheat starch. Triplicate groups of fish (11.28 g initial body weight) were fed the diet for 45 days at 22 °C, 28 °C or 34 °C. At the end of the trial, final body weight of juvenile at 28 °C (59.12 g) was higher than that of the fish reared at 22 °C (27.13 g) and 34 °C (43.17 g). Feed intake, feed efficiency and protein efficiency ratio were also better at 28 °C. Liver glycogen levels were higher at 28 °C, while plasma glucose levels were higher in the 22 °C group. Significant (P<0.05) effects of water temperature on enzymes activities and gene expression were observed. Hepatic GK activity and mRNA level were higher at 28 °C than at 34 °C. Higher G6Pase and G6PD activity and gene expression were observed at 22 °C. Overall, the data show that juveniles reared at 28 °C exhibited enhanced liver glycolytic capacity. In contrast, hepatic gluconeogenesis and lipogenesis were increased by low temperature (22 °C).

miR-29a modulates SCD expression and is regulated in response to a saturated fatty acid diet in juvenile genetically improved farmed tilapia (Oreochromis niloticus)

ABSTRACT MicroRNAs (miRNAs) are small non-coding RNAs that regulate target gene expression by binding to the 3′ untranslated region (3′ UTR) of the target mRNA. MiRNAs regulate a large variety of genes, including those involved in liver biology and disease. Here, we report for the first time that miR-29a post-transcriptionally regulates stearoyl-CoA desaturase (SCD) by binding to its 3′ UTR in genetically improved farmed tilapia (GIFT), Oreochromis niloticus, as shown by a 3′ UTR luciferase reporter assay. miR-29a antagomir treatment in vivo resulted in significant upregulation of SCD expression. We found that miR-29a expression was negatively correlated with SCD expression in GIFT liver. Inhibition of miR-29a led to a significant increase in SCD expression on day 60 induced by a saturated fatty acid diet, thereby increasing conversion of 16:0 and 18:0 to 16:1 and 18:1, respectively, and activating serum insulin, which would favor glucose and lipid uptake by the liver. These results indicate that miR-29a regulates SCD levels by binding to its 3′ UTR, and this interaction affects saturated fatty acid stress induction and insulin and lipid accumulation in serum. Our results suggest that miR-29a is critical in regulating lipid metabolism homeostasis in GIFT liver, and this might provide a basis for understanding the biological processes and therapeutic intervention encountered in fatty liver. Summary: miR-29a targets SCD 3′ UTR directly. Inhibition of miR-29a could mediate conversion of C16:0 and C18:0 to C16:1 and C18:1, respectively, and activate serum insulin and glucose uptake in GIFT by increasing SCD.

The expression profiles of miRNA–mRNA of early response in genetically improved farmed tilapia ( Oreochromis niloticus ) liver by acute heat stress

Genetically improved farmed tilapia (GIFT, Oreochromis niloticus) are commercially important fish that are cultured in China. GIFT are highly susceptible to diseases when exposed to high temperatures in summer. Better understanding the GIFT regulatory response to heat stress will not only help in determining the relationship between heat stress signalling pathways and adaption mechanisms, but will also contribute to breeding new high-temperature tolerant strains of GIFT. In this study, we built control (28 °C) and heat-treated (37.5 °C) groups, and extracted RNA from the liver tissues for high-throughput next-generation sequencing to study the miRNA and mRNA expression profiles. We identified 28 differentially expressed (DE) miRNAs and 744 DE mRNAs between the control and heat-treated groups and annotated them using the KEGG database. A total of 38 target genes were predicted for 21 of the DE miRNAs, including 64 negative miRNA–mRNA interactions. We verified 15 DE miRNA–mRNA pairs and 16 other DE mRNAs by quantitative real-time PCR. Important regulatory pathways involved in the early response of GIFT to heat stress included organism system, metabolism, and diseases. Our findings will facilitate the understanding of regulatory pathways affected by acute heat stress, which will help to better prevent heat damage to GIFT.

Sex-Reversal Effect of Dietary Aloe vera (Liliaceae) on Genetically Improved Farmed Nile Tilapia Fry

AbstractWe evaluated the hypothesis that administering dietary Aloe vera to sexually undifferentiated fry of genetically improved farmed Nile Tilapia Oreochromis niloticus for 30 d would affect their sex ratio. Five experimental treatments were designed, including a control and 100% A. vera powder incorporated into the feed at 0.5, 1.0, 2.0, and 4.0%. After 30 d of feeding, the experimental diets were replaced with a commercial diet, which was administered to the fish for another 42 d to attain the size at which sex determination was possible. Based on logistic regression analysis, an increase in the A. vera inclusion level from 1.0% to 4.0% resulted in a significantly greater percentage of males compared to the control and the 0.5% A. vera inclusion level, with the 4.0% A. vera group presenting potent masculinization effects (67.62% male). However, the survival percentage among fish that received 4.0% A. vera was significantly lower than survival in the other groups. The present results indicate that A. ...