Effects of a high-fat and high-carbohydrate diet on appetite regulation and central AMPK in the hypothalamus of blunt snout bream (Megalobrama amblycephala).

Adenosine monophosphate-activated protein kinase (AMPK) is a sensor of cellular energy changes and controls food intake. This study investigates the effect of a high-calorie diet (high fat diet [HFD], high carbohydrate diet [HCD] and high energy diet [HED]) on appetite and central AMPK in blunt snout bream. In the present study, fish (average initial weight 45.84 ± 0.07 g) were fed the control, HFD, HCD and HED in four replicates for 12 weeks. At the end of the feeding trial, the result showed that body mass index, specific growth rate, feed efficiency ratio and feed intake were not affected (p > 0.05) by dietary treatment. However, fish fed the HFD obtained a significantly higher (p < 0.05) lipid productive value, lipid gain and lipid intake than those fed the control diet, but no significant difference was attributed to others. Also, a significantly higher (p < 0.05) energy intake content was found in fish-fed HFD, HCD and HED than those given the control diet. Long-term HFD and HCD feeding significantly increased (p < 0.05) plasma glucose, glycated serum protein, advanced glycation end product, insulin and leptin content levels than the control group. Moreover, a significantly lower (p < 0.05) complex 1, 2 and 3 content was found in fish-fed HFD and HCD than in the control, but no differences (p > 0.05) were attributed to those in HED. Fish-fed HED significantly upregulated (p < 0.05) hypothalamic ampα 1 and ampα 2 expression, whereas the opposite trend was observed in the hypothalamic mammalian target of rapamycin than those in HFD and HCD compared to the control. However, hypothalamic neuropeptide y, peroxisome proliferator-activated receptor α (pparα), acetyl-coa oxidase and carnitine palmitoyltransferase 1 were significantly upregulated (p < 0.05) in the HCD group, while the opposite was seen in cholecystokinin expression compared to those in the control group. Our findings indicated that the central AMPK signal pathway and appetite were modulated according to the diet's energy level to regulate nutritional status and maintain energy homoeostasis in fish.

Metabolism, antioxidant and immunity in acute and chronic hypoxic stress and the improving effect of vitamin C in the channel catfish (Ictalurus punctatus).

Hypoxia is the most significant factor that threatens the health and even survival of freshwater and marine fish. Priority should be given to the investigation of hypoxia adaptation mechanisms and their subsequent modulation. Acute and chronic studies were designed for the current study. Acute hypoxia comprised of normoxia dissolved oxygen (DO) 7.0 ± 0.5 mg/mL (N0), low-oxygen 5.0 ± 0.5 mg/mL(L0), and hypoxia 1.0 ± 0.1 mg/mL (H0) and 300 mg/L Vc for hypoxia regulation (N300, L300, H300). Chronic hypoxia comprised of normoxia (DO 7.0 ± 0.5 mg/mL) with 50 mg/kg Vc in the diet (N50) and low oxygen (5.0 ± 0.5 mg/mL) with 50, 250, 500 mg/kg Vc in the diet (L50, L250, L500) to assess the effect of Vc in hypoxia. The growth, behavior, hematological parameters, metabolism, antioxidants, and related inflammatory factors of channel catfish were investigated, and it was found that channel catfish have a variety of adaptive mechanisms in response to acute and chronic hypoxia. Under acute 5 mg/mL DO, the body color lightened (P < 0.05) and reverted to normal with 300 mg/mL Vc. PLT was significantly elevated after 300 mg/L Vc (P < 0.05), indicating that Vc can effectively restore hemostasis following oxygen-induced tissue damage. Under acute hypoxia, the significantly increased of cortisol, blood glucose, the gene of pyruvate kinase (pk), and phosphofructokinase (pfk), together with the decreased expression of fructose1,6-bisphosphatase (fbp) and the reduction in myoglycogen, suggested that Vc might enhance the glycolytic ability of the channel catfish. And the enzyme activities of superoxide dismutase (SOD) and catalase (CAT) and the gene expression of sod rose significantly, showing that Vc might improve the antioxidant capacity of the channel catfish. The significant up-regulation of tumor necrosis factor-alpha (tnf-α), interleukin-1ß (il-1ß), and cd68 under acute hypoxia implies that hypoxia may generate inflammation in channel catfish, whereas the addition of Vc and down-regulation of these genes suggests that Vc suppresses inflammation under acute hypoxia. We found that the final weight, WGR, FCR, and FI of channel catfish were significantly reduced under chronic hypoxia, and that feeding 250 mg/kg of Vc in the diet was effective in alleviating the growth retardation caused by hypoxia. The significant increase in cortisol, blood glucose, myoglycogen, and the expression of tnf-α, il-1ß, and cd68 (P < 0.05) and the significant decrease in lactate (P < 0.05) under chronic hypoxia indicated that the channel catfish had gradually adapted to the survival threat posed by hypoxia and no longer relied on carbohydrates as their primary source of energy. While the addition of Vc did not appear to increase the energy supply of the fish under hypoxia in terms of glucose metabolism, but the significantly decreased expression of tnf-α, il-1ß, and cd68 (P < 0.05) also were found, indicating that chronic hypoxia, similar acute hypoxia, may increase inflammation in the channel catfish. This study indicates that under acute stress, channel catfish withstand stress by raising energy supply through glycolysis, and acute hypoxic stress significantly promotes inflammation in channel catfish, but Vc assists the channel catfish resist stress by raising glycolysis, antioxidant capacity, and decreasing the production of inflammatory markers. Under chronic hypoxia, the channel catfish no longer utilize carbohydrates as their primary energy source, and Vc may still effectively reduce inflammation in the channel catfish under hypoxia.

High-fat diet alters intestinal microbiota and induces endoplasmic reticulum stress via the activation of apoptosis and inflammation in blunt snout bream.

The primary organ for absorbing dietary fat is the gut. High dietary lipid intake negatively affects health and absorption by causing fat deposition in the intestine. This research explores the effect of a high-fat diet (HFD) on intestinal microbiota and its connections with endoplasmic reticulum stress and inflammation. 60 fish (average weight: 45.84 ± 0.07 g) were randomly fed a control diet (6% fat) and a high-fat diet (12 % fat) in four replicates for 12 weeks. From the result, hepatosomatic index (HSI), Visceralsomatic index (VSI), abdominal fat (ADF), Intestosomatic index (ISI), mesenteric fat (MFI), Triglycerides (TG), total cholesterol (TC), non-esterified fatty acid (NEFA) content were substantially greater on HFD compared to the control diet. Moreover, fish provided the HFD significantly obtained lower superoxide dismutase (SOD) and glutathione peroxidase (GPX) activities. In contrast, an opposite result was seen in malondialdehyde (MDA) content in comparison to the control. HFD significantly altered intestinal microbiota in blunt snout bream, characterized by an increased abundance of Aeromonas, Plesiomonas proteobacteria, and firmicutes with a reduced abundance of Cetobacterium and ZOR0006. The transcriptional levels of glucose-regulated protein 78 (grp78), inositol requiring enzyme 1 (ire1), spliced X box-binding protein 1 (xbp1), DnaJ heat shock protein family (Hsp40) member B9 (dnajb9), tumor necrosis factor alpha (tnf-α), nuclear factor-kappa B (nf-κb), monocyte chemoattractant protein-1 (mcp-1), and interleukin-6 (il-6) in the intestine were markedly upregulated in fish fed HFD than the control group. Also, the outcome was similar in bax, caspases-3, and caspases-9, ZO-1, Occludin-1, and Occludin-2 expressions. In conclusion, HFD could alter microbiota and facilitate chronic inflammatory signals via activating endoplasmic reticulum stress.

Oral bovine serum albumin administration alleviates inflammatory signals and improves antioxidant capacity and immune response under thioacetamide stress in blunt snout bream fed a high-calorie diet.

This investigation looks at the impact of oral bovine serum albumin (BSA) on antioxidants, immune responses, and inflammation signals in blunt snout bream fed a high-calorie diet. 480 fish (average weight: 45.84 ± 0.07 g) were randomly fed a control diet, a high-fat diet (HFD), a high carbohydrate diet (HCD), and a high-energy diet (HED) in six replicates for 12 weeks. After the feeding trial, fish were orally administered with 10% BSA for 10 h, then blood and liver samples from five fish were randomly obtained after 10 h to determine plasma inflammatory markers and inorganic components. Also, the leftover fish were injected with thioacetamide, blood and liver samples were simultaneously obtained at 12, 48, and 96 h, respectively, to determine antioxidant, immune, and inflammatory signals, with survival rates recorded at the same time interval. After 10 h, plasma inflammatory markers such as tumour necrosis factors (TNF-α), interleukin 6 (IL6), nitric oxide (NO), Monocyte chemoattractant protein-1(MCP-1), and cortisol were significantly improved in fish fed HCD and HED as compared to the control. After thioacetamide stress, plasma lysozyme (LYM), complement 3, myeloperoxidase (MPO), and alkaline phosphatase activities, as well as immunoglobulin M, levels all increased significantly (P < 0.05) with increasing time with maximum value attained at 96 h, but shows no difference among dietary treatment. Similar results were observed in liver superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPX) activities and malondialdehyde (MDA) content, but tended to reduce at 96 h. nf-kb, tnf-α, and mcp-1 tend to decrease with the minimum value attained at 48 h and gradually decrease with increasing time at 96 h. After 96 h of the thioacetamide (TAA) challenge, the survival rate of blunt snout bream fed with an HFD and HCD was significantly lower (P < 0.05) at 48, and 96 h before the administration of BSA. However, no differences were observed among dietary treatments after the BSA administration. Overall, this study indicated that oral dietary administration of BSA might greatly enhance the antioxidant capability and innate immunity and mitigates inflammation signals after TAA stress in blunt snout bream fed high energy diet.

Interactive effects of dietary leucine and isoleucine affect amino acid profile and metabolism through AKT/TOR signaling pathways in blunt snout bream (Megalobrama amblycephala).

The purpose of this research is to explore the interaction between dietary leucine and isoleucine levels on whole-body composition, plasma and liver biochemical indexes, amino acids deposition in the liver, and amino acid metabolism of blunt snout bream (Megalobrama amblycephala). The test fish (average weight: 56.00 ± 0.55 g) were fed one of six diets at random containing two leucine levels (1.70% and 2.50%) and three isoleucine levels (1.00%, 1.20%, and 1.40%) for 8 weeks. The results showed that the final weight and weight gain rate were the highest in the fish fed low-level leucine and high-level isoleucine diets (P > 0.05). Furthermore, the crude lipid content was significantly adjusted by diets with diverse levels of leucine and isoleucine (P < 0.05). In addition, interactive effects of these two branched-chain amino acids (BCAAs) were found on plasma total protein, blood ammonia, and blood urea nitrogen of test fish (P < 0.05). Additionally, the liver amino acid profiles were significantly influenced by the interactive effects of the two BCAAs (P < 0.05). Moreover, interactive effects of dietary leucine and isoleucine were significantly observed in the expressions of amino acid metabolism-related genes (P < 0.05). These findings suggested that dietary leucine and isoleucine had interaction. Meanwhile, the interaction between them was more conducive to the growth and quality improvement of blunt snout bream when the dietary leucine level was 1.70% and isoleucine level was 1.40%.

Dietary Leucine Supplementation Improves Muscle Fiber Growth and Development by Activating AMPK/Sirt1 Pathway in Blunt Snout Bream (Megalobrama amblycephala).

This research is aimed at evaluating the effects of leucine supplementation on muscle fibers growth and development of blunt snout bream through a feeding trial and a primary muscle cells treatment. An 8-week trial with diets containing 1.61% leucine (LL) or 2.15% leucine (HL) was conducted in blunt snout bream (mean initial weight = 56.56 ± 0.83 g). Results demonstrated that the specific gain rate and the condition factor of fish in the HL group were the highest. The essential amino acids content of fish fed HL diets was significantly higher than that fed LL diets. The texture (hardness, springiness, resilience, and chewiness), the small-sized fiber ratio, fibers density, and sarcomere lengths in fish all obtained the highest in the HL group. Additionally, the proteins expression related with the activation of the AMPK pathway (p-Ampk, Ampk, p-Ampk/Ampk, and Sirt1) and the expression of genes (myogenin (myog), myogenic regulatory factor 4 (mrf4) and myoblast determination protein (myod), and protein (Pax7) related to muscle fiber formation were significantly upregulated with increasing level of dietary leucine. In vitro, the muscle cells were treated with 0, 40 and 160 mg/L leucine for 24 h. The results showed that treated with 40 mg/L leucine significantly raised the protein expressions of BCKDHA, Ampk, p-Ampk, p-Ampk/Ampk, Sirt1, and Pax7 and the gene expressions of myog, mrf4, and myogenic factor 5 (myf5) in muscle cells. In summary, leucine supplementation promoted muscle fibers growth and development, which may be related to the activation of BCKDH and AMPK.