Hualiang Liang

Dietary arginine affects the insulin signaling pathway, glucose metabolism and lipogenesis in juvenile blunt snout bream Megalobrama amblycephala

This study evaluated the mechanisms governing insulin resistance, glucose metabolism and lipogenesis in juvenile fish fed with graded levels of dietary arginine. The results showed that, compared with the control group (0.87%), 2.31% dietary arginine level resulted in the upregulation of the relative gene expression of IRS-1, PI3K and Akt in the insulin signaling pathway, while 2.70% dietary arginine level led to inhibition of these genes. 1.62% dietary arginine level upregulated glycolysis by increasing GK mRNA level; 2.70% dietary arginine level upregulated gluconeogenesis and resulted in high plasma glucose content by increasing PEPCK and G6P mRNA level. Furthermore, 2.70% dietary arginine level significantly lowered GLUT2 and increased PK mRNA levels. 1.62% dietary arginine level significantly upregulated ACC, FAS and G6PDH mRNA levels in the fat synthesis pathway and resulted in high plasma TG content. These results indicate that 1.62% dietary arginine level improves glycolysis and fatty acid synthesis in juvenile blunt snout bream. However, 2.70% dietary arginine level results in high plasma glucose, which could lead to negative feedback of insulin resistance, including inhibition of IRS-1 mRNA levels and activation of gluconeogenesis-related gene expression. This mechanism seems to be different from mammals at the molecular level.

Comparative transcriptome analysis reveals the gene expression profiling in bighead carp (Aristichthys nobilis) in response to acute nitrite toxicity

Objective: Nitrite exposure induces growth inhibition, metabolic disturbance, oxidative stress, organic damage, and infection‐mediated mortality of aquatic organism. This study aimed to investigate the mechanism in responses to acute nitrite toxicity in bighead carp (Aristichthys nobilis, A. nobilis) by RNA‐seq analysis. Methods: Bighead carps were exposed to water with high nitrite content (48.63mg/L) for 72h, and fish livers and gills were separated for RNA‐seq analysis. De novo assembly was performed, and differentially expressed genes (DEGs) between control and nitrite‐exposed fishes were identified. Furthermore, enrichment analysis was performed for DEGs to annotate the molecular functions. Results: A total of 406,135 transcripts and 352,730 unigenes were tagged after de novo assembly. Accordingly, 4108 and 928 DEGs were respectively identified in gill and liver in responses to nitrite exposure. Most of these DEGs were up‐regulated DEGs. Enrichment analysis showed these DEGs were mainly associated with immune responses and nitrogen metabolism. Conclusions: We suggested that the nitrite toxicity‐induced DEGs were probably related to dysregulation of nitrogen metabolism and immune responses in A. nobilis, particularly in gill. HIGHLIGHTSNitrite exposure caused DEGs in bighead carp gill and liver.DEGs in gill and liver responded to nitrite stress were associated with immune response.Nitrite exposure‐induced pathomechanism associated with immune responses and infections.Gills of bighead carp are more susceptible to nitrite stress than liver.

Effects of dietary arginine on antioxidant status and immunity involved in AMPK-NO signaling pathway in juvenile blunt snout bream

ABSTRACT The present study assessed the effects of dietary arginine on antioxidant status and immunity involved in AMPK‐NO signaling pathway in juvenile blunt snout bream. Fish were fed six practical diets with graded arginine levels ranging from 0.87% to 2.70% for 8 weeks. The results showed that compared with the control group (0.87% dietary arginine level), significantly higher mRNA levels of adenosine monophosphate activated protein kinase (AMPK) and nitric oxide synthetase (NOS), activities of total nitric oxide synthetase (T‐NOS) and nitric oxide synthetase (iNOS), and plasma nitric oxide (NO) contents were observed in fish fed with 1.62%–2.70% dietary arginine levels. Significantly higher levels of NOS and iNOS were observed in fish fed with 1.62%–2.70% dietary arginine levels in enzyme‐linked immune sorbent assay. At dietary arginine levels of 1.22%–2.70%, the mRNA levels of iNOS were significantly improved. Dietary arginine also significantly influenced plasma interleukin 8 (IL‐8) and tumour necrosis factor‐&agr; (TNF‐&agr;) contents. Furthermore, dietary arginine significantly affected the activity and mRNA level of glutathione peroxidase (GPx), the mRNA levels of pro‐inflammatory factor including IL‐8 and TNF‐&agr; and plasma malondialdehyde (MDA) content. However, total superoxide dismutase (T‐SOD) activity, plasma complement component 3 (C3) content, plasma immunoglobulin M (IgM) content, plasma interleukin 1&bgr; (IL‐1&bgr;) content and the mRNA levels of copperzinc superoxide dismutase (Cu/Zn‐SOD), manganese superoxide dismutase (Mn‐SOD) and IL‐1&bgr; were not significantly affected by dietary arginine. After Aeromonas hydrophila challenge, the death rate was significantly lowered in fish fed with 1.62%–1.96% dietary arginine levels. Furthermore, the mRNA levels of AMPK, NOS and iNOS, plasma NO content and the activities of T‐NOS and iNOS showed an upward trend with increasing dietary arginine levels. Significantly higher levels of NOS and iNOS were observed in fish fed with 1.62%–2.70% dietary arginine levels in enzyme‐linked immune sorbent assay. At dietary arginine levels of 1.96%–2.31%, T‐SOD activities were significantly improved. Significantly higher GPx activities were observed in fish fed with 1.22%–2.70% dietary arginine levels. At dietary arginine levels of 1.22%–2.31%, the plasma TNF‐&agr; and IL‐8 contents were significantly decreased. Significantly lower plasma IL‐1&bgr; contents were observed in fish fed 1.62%–1.96% dietary arginine levels. Dietary arginine significantly influenced the mRNA levels of antioxidant and pro‐inflammatory genes including Cu/Zn‐SOD, Mn‐SOD, GPx, IL‐8, TNF‐&agr; and IL‐1&bgr;. Significantly higher plasma C3 contents and significantly lower plasma MDA contents were observed in fish fed with 1.62%–1.96% arginine levels. Furthermore, plasma IgM contents were significantly improved at dietary arginine levels of 1.62%–2.31%. However, high dietary arginine group (2.70%) significantly improved the mRNA levels of pro‐inflammatory genes including IL‐8, TNF‐&agr; and IL‐1&bgr; and plasma MDA, IL‐8, TNF‐&agr; and IL‐1&bgr; contents as compared with optimal dietary arginine levels (1.62% and 1.96%). The present results indicate that optimal arginine level (1.62% and 1.96%) could improve antioxidant capacity, immune response and weaken tissues inflammatory involved in arginine‐AMPK‐NO signaling pathway, while high arginine level resulted in excessive NO production, leading to increase oxidative stress damage and inflammatory response in juvenile blunt snout bream. HIGHLIGHTSDietary arginine supplementation could increase NO production in M. amblycephala.Optimal dietary arginine level (1.62%–1.96%) could improve antioxidant capacity by AMPK‐NO signaling pathway.Optimal dietary arginine level could improve immune response and weaken tissues inflammatory.High arginine level (2.70%) resulted in excessive NO production, which has a negative effect on M. amblycephala.

Regulation mechanism of oxidative stress induced by high glucose through PI3K/Akt/Nrf2 pathway in juvenile blunt snout bream (Megalobrama amblycephala)

ABSTRACT This study was conducted to investigate the effects of oral administration of a high concentration of glucose on the respiratory burst, antioxidant status, and hepatic gene expression of heme oxygenase‐1 (ho1) and PI3K/Akt/Nrf2‐related signaling molecules in juvenile blunt snout bream (Megalobrama amblycephala). Blunt snout bream juveniles with an initial body weight of 19.94 ± 0.58 g were orally fed with a high concentration of glucose (3 g/kg body weight). The results indicated that plasma glucose exhibited a biphasic response. Acute and persistent hyperglycemia due to the oral glucose administration significantly reduced (P < 0.05) the white blood cell count, red blood cell count, and hemoglobin content and caused oxidative stress (significantly increased alanine aminotransferase, aspartate transaminase, alkaline phosphatase, and glucose levels) and early apoptosis of hepatocytes in the fish. Hepatic superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase activities increased rapidly (P < 0.05) as protection from oxidative stress and were downregulated (P < 0.05) because of persistent hyperglycemia. Blood respiratory burst was significantly reduced (P < 0.05) because of hyperglycemia and showed a trend that was opposite to that of plasma glucose. Slight upregulation of nrf2 mRNA and antioxidants acts as a compensative protection mechanism, and the downregulated PI3K/Akt pathway blocked this function of Nrf2. In conclusion, the PI3K/Akt pathway and Nrf2 mediated the antioxidative mechanism independently in the blunt snout bream juveniles subjected to the oral administration of a high glucose concentration. HighlightsOral glucose administration affected blood respiratory burst in M. amblycephala.Oral glucose administration induced blood glucose fluctuation and oxidative stress.Upregulation of Nrf2 against oxidative stress injury due to hyperglycemia.Inhibition of PI3K, Akt, and HO‐1 induced inflammation due to hyperglycemia.

Publisher Correction: Dietary arginine affects the insulin signaling pathway, glucose metabolism and lipogenesis in juvenile blunt snout bream Megalobrama amblycephala

A correction to this article has been published and is linked from the HTML version of this paper. The error has been fixed in the paper.

Effects of dietary arginine on intestinal antioxidant status and immunity involved in Nrf2 and NF-κB signaling pathway in juvenile blunt snout bream, Megalobrama amblycephala

Abstract The present study assessed the effects of dietary arginine on intestinal antioxidant status and immunity involved in Nrf2 and NF‐&kgr;B signaling pathway in juvenile blunt snout bream. Fish were fed three practical diets with graded arginine levels (0.87%, 1.62% and 2.70%) for 8 weeks. Compared with the control group (0.87%), the counts of white blood cell (WBC), red blood cell (RBC) and hemoglobin (HGB) content were significantly improved at dietary arginine levels of 1.62% (P<0.05). Plasma albumin (ALB) levels and alkaline phosphatase (ALP) activities were significantly improved at dietary arginine levels of 1.62% and 2.70% (P < 0.05). Alanine transaminase (ALT) activity was decreased in fish fed with 1.62% dietary arginine level (P<0.05). Plasma glutathione peroxidase (GPx) activities, copper‐zinc superoxide dismutase (Cu/Zn‐SOD) activities, total antioxidant capacity (T‐AOC) activities and glutathione (GSH) levels were significantly increased at dietary arginine levels of 1.62% and 2.70% (P<0.05). Plasma total superoxide dismutase (T‐SOD) activities and catalase (CAT) activities were significantly improved in fish fed with 1.62% dietary arginine level. Significantly higher manganese superoxide dismutase (Mn‐SOD) activity was observed in fish fed with 1.62% dietary arginine level compared with 2.70% dietary arginine level (P<0.05). 1.62% and 2.70% dietary arginine levels significantly lowered malondialdehyde (MDA) levels. The relative expression of nuclear factor erythroid 2‐related factor 2 (Nrf2) was significantly increased in fish fed with 1.62% dietary arginine level, inversely, the relative expression of Kelch‐like ECH‐associated protein 1 (Keap1) showed a converse trend. 1.62% and 2.70% dietary arginine levels significantly improved the relative expressions of Cu/Zn‐SOD, GPx and CAT. Furthermore, 2.70% dietary arginine level significantly lowered the relative expression of Mn‐SOD compared with the control group and 1.62% dietary arginine levels. The relative expressions of Interleukin 1&bgr; (IL‐1&bgr;), tumour necrosis factor‐&agr; (TNF‐&agr;) and nuclear factor‐kappa B (NF‐&kgr;B) were lowered in fish fed with 1.62% dietary arginine level. 1.62% and 2.70% dietary arginine levels significantly improved the relative expressions of transforming growth factor‐&bgr; (TGF‐&bgr;). Hematocrit (HCT), aspartate aminotransferase (AST) activities, interleukin 8 (IL‐8) and interleukin 10 (IL‐10) expressions were not significantly affected by the graded dietary arginine levels. These results suggest that the optimal dietary arginine level plays an important role in enhancing antioxidant and immune status to maintain the intestinal health of juvenile blunt snout bream. HighlightsOptimal dietary arginine level (1.62%) could improve antioxidant capacity by Nrf2 signaling pathway.Optimal dietary arginine level (1.62%) could weaken inflammatory response by NF‐&kgr;B signaling pathway.Optimal dietary arginine (1.62%) plays an important role in enhancing intestinal health.

Dietary leucine modulates growth performance, Nrf2 antioxidant signaling pathway and immune response of juvenile blunt snout bream (Megalobrama amblycephala)

ABSTRACT The present study assessed the effects of dietary leucine on growth performance, antioxidant status and immunity in juvenile blunt snout bream. Fish were fed six practical diets of graded leucine levels ranging from 0.90% to 2.94% of dry basis for 8 weeks. Trail results showed that compared to control group (0.90%), 1.72% dietary leucine level significantly improved final weight (FW), weight gain rate (WG) and specific growth rate (SGR), and significantly lowered feed conversion ratio (FCR). Based on WG and SGR, the optimal dietary leucine level was obtained at 1.40% and 1.56%, respectively. Whole body crude lipid and protein contents were improved with increasing dietary leucine up to 2.14% and thereafter showed a downward trend, while whole body moisture content showed a converse trend. No significant change was found in whole body ash content. 1.72% dietary leucine level significantly improved the antioxidant capacity of fish by regulating the plasma superoxide dismutase (SOD) activity, glutathione peroxidase (GPx) activity, total antioxidant capacity (T‐AOC) activity, catalase (CAT) activity, aspartate aminotransferase (AST) activities and malondialdehyde (MDA) content, furthermore, 1.72% dietary leucine level also significantly improved the antioxidant genes expressions of associated with Nrf2 signaling pathway by regulating heme oxygenase‐1 (HO‐1), GPx, copperezinc superoxide dismutase (Cu/Zn‐SOD), manganese superoxide dismutase (Mn‐SOD), 2.14% dietary leucine levels also significantly improved glutathione transferase (GST) mRNA level. Dietary leucine levels significantly affected plasma immunity parameters such as the contents of plasma complement component 3 (C3), immunoglobulin M (IgM) and lowered the hepatopancreas genes expressions of pro‐inflammatory factor by regulating interleukin 1&bgr; (IL‐1&bgr;), interleukin 8 (IL‐8) and tumour necrosis factor‐&agr; (TNF‐&agr;) mRNA levels. The present study indicated that optimal dietary leucine level plays an important role in improving growth, enhancing antioxidant and immune status to maintain the health in juvenile blunt snout bream. HIGHLIGHTSThe dietary leucine requirement was estimated to be 1.40% and 1.56% of diet.Leucine levels affected lipid, protein and moisture contents of whole body in M. amblycephala.The optimal dietary leucine level could improve antioxidant capacity by Nrf2 signaling pathway.The optimal dietary leucine level could improve immune response.