Ascorbic Acid Supplementation Improves Skeletal Muscle Growth in Pacu (Piaractus mesopotamicus) Juveniles: In Vivo and In Vitro Studies

Physiological and morphological impact of physical activity and nutritional interventions to offset disuse-induced skeletal muscle atrophy

Skeletal muscle tissue acts as a functional unit for physical movements, energy metabolism, thermogenesis, and metabolic homeostasis. In this literature review, the underlying mechanisms of skeletal muscle atrophy and the prevention strategies, including vigorous training and nutritional modifications are focused. Furthermore, the comparative analysis of multiple interventions is briefly explained. Ageing is an inevitable process often associated with cognitive impairment and physical decline due to muscular atrophy. Skeletal muscle atrophy is characterized by low muscle mass due to multiple underlying factors, i.e., genetic predisposition, ageing, inflammation, and trauma. The structural alterations include myofiber shrinkage, changes in myosin isoforms, decrease in myofiber diameter, and total protein loss. Furthermore, there is an imbalance in protein anabolic and catabolic reactions. This may be due to changes in multiple signal transduction pathways of protein degradation (i.e., caspase, calpain, ubiquitin protein degradation system, autophagy) and protein anabolism via the mTOR pathway. Consequently, certain pathophysiological factors associated with health disparities may reduce mobility and functional capacity to perform ADLs. To tackle this issue, novel strategies linked to physical movement, and dietary intake must be incorporated in life. Exercise poses multiple health benefits, including improved muscle mass and mobility. Diet diversification [particularly protein-rich meals] and the "whole food" approach (based on non-protein nutrients) may enhance intramuscular anabolic signaling and tissue remodeling. However, there is a pressing need to fund large-scale evidence-based trials based on modern machine learning techniques (AI-driven nutrition). Additionally, entrepreneurial platforms for commercialization of consumer-friendly food products must be initiated in future.

Proteome of amino acids or IGF1-stimulated pacu muscle cells offers molecular insights and suggests FN1B and EIF3C as candidate markers of fish muscle growth

Study of fish skeletal muscle is essential to understand physiological or metabolic processes, and to develop programs searching for increased muscle mass and meat production. Amino acids (AA) and IGF1 stimulate processes that lead to muscle growth, but their signaling pathways and molecular regulation need further clarification in fish. We obtained the proteome of pacu (Piaractus mesopotamicus) cultured muscle cells treated with AA or IGF1, which induced the differential abundance of 67 and 53 proteins, respectively. Enrichment analyses showed that AA modulated histone methylation, cell differentiation, and metabolism, while IGF1 modulated ATP production and protein synthesis. In addition, we identified molecular networks with candidate markers that commonly regulate fish muscle cells: FN1B and EIF3C, respectively up- and down-regulated by both treatments. FN1B was related to cell proliferation, protein synthesis, and muscle repair, while EIF3C connected with negative regulators of muscle growth. Their gene expression was evaluated in pacu and Nile tilapia (Oreochromis niloticus) after nutrient manipulation, with fn1b increased during refeeding and eif3c increased during fasting in both species. Our work helps clarify the molecular regulation by AA or IGF1 and suggests that FN1B and EIF3C could be potential stimulatory and inhibitory biomarkers of fish muscle growth.

Mechanism of vitamin C alleviating the immunotoxicity of 17α-methyltestosterone in Carassius auratus

BACKGROUND

In recent years, the use of endocrine-disrupting chemicals (EDCs) has become increasingly common, leading to severe environmental pollution and harm to aquatic organisms. 17α-Methyltestosterone (MT) is a synthetic androgen that can cause immunotoxicity in aquaculture, affecting fish health. To address this issue, this study aimed to investigate the effect of Vitamin C (VC) on MT-induced immunotoxicity and determine the optimal VC supplementation.

RESULTS

Carassius auratus was exposed to 50 ng/L MT and treated with 25, 50, and 150 mg/kg VC for 7, 14, and 21 d. Morphological indicators, histological characteristics, hepatic antioxidant capacity, and immune-related gene expression were analyzed. Additionally, RNA-seq was performed on the liver tissues of the control, MT, and MT + 25 mg/kg VC groups after 21 d. Results showed that, MT treatment significantly increased liver malondialdehyde content and inhibited immune-related gene expression (TNF-α, IL-8, INF-γ, IL-10, Caspase-9, and IGF-I), causing oxidative stress and immunotoxicity, leading to hepatic steatosis. However, supplementation with 25-50 mg/kg VC effectively alleviated the MT-induced damage to the hepatic structure and immune system. RNA-seq revealed significant enrichment of differentially expressed genes in multiple signaling pathways, including the mTOR, MAPK, and Wnt pathways.

CONCLUSIONS

In summary, 25-50 mg/kg VC alleviated inhibitory effect of MT on immune-related genes in C. auratus liver, reducing MT-induced tissue damage. VC not only alleviated inflammation, oxidative stress, and immunotoxicity induced by MT through the regulation of the mTOR, MAPK, and Wnt signaling pathways, but also indirectly enhanced cellular antioxidant defense mechanisms by regulating the NRF2 pathway. This provides a theoretical basis for VC application in aquaculture, improving fish health and increasing efficiency.

Dietary nanocomposite of vitamin C and vitamin E enhanced the performance of Nile tilapia

Nowadays, nanomaterials enter high numbers of daily used products and drug manufacture. A nanocomposite of vitamins C (VC) and vitamin E (VE) with chitosan as a vehicle and protector was used in a comparative eight-week feeding study, Nile tilapia weighing 31.2 ± 0.36 g distributed in seven groups and fed (G1) basal diet, (G2) bulk VC, (G3) VC- nanoparticles (NPs), (G4) bulk VE, (G5) VE-NPs, bulk VCE (G6), and (G7) VC plus VE (VCE)-NPs, respectively. The Nile tilapia-fed nanocomposite vitamins had significantly higher growth performance compared to the control; VCE-NPs had the superiority among tested supplementations where total weight gain (63.6 g), daily weight gain (1.13 g), relative growth rate (206.1%) with lower feed conversion rate (1.6) and insignificant feed intake (101.5 g). Overall, the level of liver enzymes was significantly decreased in fish serum after eight-week nanocomposite supplementation, and dietary VCE-NPs caused a significant reduction of serum AST (18.45 IU/L) and ALT (14.77 IU/L) compared to the control 25.5 IU/L and 17.6 IU/L, respectively. Fish fed dietary VCE-NPs, VC-NPs, and VE-NPs had significant enhancement of RBCs 4.2 × 106/μL, 3.8 × 106/μL, and 3.55 × 106/μL; WBCs 46.15 × 103, 42.9 × 103, and 44 × 103/μL, respectively, Also TP was significantly higher 6.38 g/dL in VCE-NPs group compared to the control and the other treatments. Over all, the dietary nanocomposite vitamins boost the innate immunity of the experimental Nile tilapia, the oxidative burst activity (OBA), phagocytic activity (PA), phagocytic index (PI), and serum antibacterial (SAA) were significantly increased compared to those received bulk vitamins and the control. The activity of antioxidant biomarkers in fish serum including glutathione peroxidase (GPx), catalase (CAT), superoxide dismutase (SOD), total antioxidant capacity (TAC), glutathione reductase (GR), and myeloperoxidase (MPO) showed a rise in the serum of Nile tilapia received nano- and bulk-form of VC and VCE compared to the control and both forms of VE. Furthermore, the level of malondialdehyde (MDA), reduced glutathione (GSH), and oxidized glutathione (GSSG) were significantly increased in the fish serum following the trend of antioxidants enzymes. In conclusion, a dietary nanocomposite of vitamin C and vitamin E enhanced Nile tilapia's growth performance and feed utilization. It could also improve health status and immune response. The values of antioxidant biomarkers indicated that the nanocomposite could help the fish body scavenge the generated reactive oxidative species (ROS).

Selenium deficiency-induced high concentration of reactive oxygen species restricts hypertrophic growth of skeletal muscle in juvenile zebrafish by suppressing TORC1-mediated protein synthesis

Se deficiency causes impaired growth of fish skeletal muscle due to the retarded hypertrophy of muscle fibres. However, the inner mechanisms remain unclear. According to our previous researches, we infer this phenomenon is associated with Se deficiency-induced high concentration of reactive oxygen species (ROS), which could suppress the target of rapamycin complex 1 (TORC1) pathway-mediated protein synthesis by inhibiting protein kinase B (Akt), an upstream protein of TORC1. To test this hypothesis, juvenile zebrafish (45 d post-fertilisation) were fed a basal Se-adequate diet or a basal Se-deficient diet or them supplemented with an antioxidant (DL-α-tocopherol acetate, designed as VE) or a TOR activator (MHY1485) for 30 d. Zebrafish fed Se-deficient diets exhibited a clear Se-deficient status in skeletal muscle, which was not influenced by dietary VE and MHY1485. Se deficiency significantly elevated ROS concentrations, inhibited Akt activity and TORC1 pathway, suppressed protein synthesis in skeletal muscle, and impaired hypertrophy of skeletal muscle fibres. However, these negative effects of Se deficiency were partly (except that on ROS concentration) alleviated by dietary MHY1485 and completely alleviated by dietary VE. These data strongly support our speculation that Se deficiency-induced high concentration of ROS exerts a clear inhibiting effect on TORC1 pathway-mediated protein synthesis by regulating Akt activity, thereby restricting the hypertrophy of skeletal muscle fibres in fish. Our findings provide a mechanistic explanation for Se deficiency-caused retardation of fish skeletal muscle growth, contributing to a better understanding of the nutritional necessity and regulatory mechanisms of Se in fish muscle physiology.

Review: Understanding fish muscle biology in the indeterminate growth species pacu (Piaractus mesopotamicus)

The muscle phenotype of fish is regulated by numerous factors that, although widely explored, still need to be fully understood. In this context, several studies aimed to unravel how internal and external stimuli affect the muscle growth of these vertebrates. The pacu (Piaractus mesopotamicus) is a species of indeterminate muscular growth that quickly reaches high body weight. For this reason, it adds great importance to the productive sector, along with other round fish. In this context, we aimed to compile studies on fish biology and skeletal muscle growth, focusing on studies by our research group that used pacu as an experimental model along with other species. Based on these studies, new muscle phenotype regulators were identified and explored in vivo, in vitro, and in silico studies, which strongly contribute to advances in understanding muscle growth mechanisms with future applications in the productive sector.

Influences of l-ascorbic acid on cytotoxic, biochemical, and genotoxic damages caused by copper II oxide nanoparticles in the rainbow trout gonad cells-2

In parallel with the raising use of copper oxide nanoparticles (CuO NPs) in various industrial and commercial practices, scientific reports on their release to the environment and toxicity are increasing. The toxicity of CuO NPs is mostly based on their oxidative stress. Therefore, it is necessary to investigate the efficacy of well-known therapeutic agents as antioxidants against CuO NPs damage. This study aimed to investigate the mechanism of this damage and to display whether l-ascorbic acid could preserve against the cell toxicities induced by CuO NPs in the rainbow trout gonad cells-2 (RTG-2). While CuO NPs treatment significantly diminished cell viability, the l-ascorbic acid supplement reversed this. l-ascorbic acid treatment reversed the changes in expressions of sod1, sod2, gpx1a, and gpx4b genes while playing a supportive role in the changes in the expression of the cat gene induced by CuO NPs treatment. Moreover, CuO NPs treatment caused an upregulation in the expressions of growth-related genes (gh1, igf1, and igf2) and l-ascorbic acid treatment further increased these effects. CuO NPs treatment significantly up-regulated the expression of the gapdh gene (glycolytic enzyme gene) compared to the control group, and l-ascorbic acid treatment significantly down-regulated the expression of the gapdh gene compared to CuO NPs treatment. The genotoxicity test demonstrated that l-ascorbic acid treatment increased the genotoxic effect caused by CuO NPs by acting as a co-mutagen. Based on the findings, l-ascorbic acid has the potential to be sometimes inhibitory and sometimes supportive of cellular mechanisms caused by CuO NPs.

Identification of Novel Genes Associated with Fish Skeletal Muscle Adaptation during Fasting and Refeeding Based on a Meta-Analysis

The regulation of the fish phenotype and muscle growth is influenced by fasting and refeeding periods, which occur in nature and are commonly applied in fish farming. However, the regulators associated with the muscle responses to these manipulations of food availability have not been fully characterized. We aimed to identify novel genes associated with fish skeletal muscle adaptation during fasting and refeeding based on a meta-analysis. Genes related to translational and proliferative machinery were investigated in pacus (Piaractus mesopotamicus) subjected to fasting (four and fifteen days) and refeeding (six hours, three and fifteen days). Our results showed that different fasting and refeeding periods modulate the expression of the genes mtor, rps27a, eef1a2, and cdkn1a. These alterations can indicate the possible protection of the muscle phenotype, in addition to adaptive responses that prioritize energy and substrate savings over cell division, a process regulated by ccnd1. Our study reveals the potential of meta-analysis for the identification of muscle growth regulators and provides new information on muscle responses to fasting and refeeding in fish that are of economic importance to aquaculture.

Amino Acids and IGF1 Regulation of Fish Muscle Growth Revealed by Transcriptome and microRNAome Integrative Analyses of Pacu (Piaractus mesopotamicus) Myotubes

Amino acids (AA) and IGF1 have been demonstrated to play essential roles in protein synthesis and fish muscle growth. The myoblast cell culture is useful for studying muscle regulation, and omics data have contributed enormously to understanding its molecular biology. However, to our knowledge, no study has performed the large-scale sequencing of fish-cultured muscle cells stimulated with pro-growth signals. In this work, we obtained the transcriptome and microRNAome of pacu (Piaractus mesopotamicus)-cultured myotubes treated with AA or IGF1. We identified 1228 and 534 genes differentially expressed by AA and IGF1. An enrichment analysis showed that AA treatment induced chromosomal changes, mitosis, and muscle differentiation, while IGF1 modulated IGF/PI3K signaling, metabolic alteration, and matrix structure. In addition, potential molecular markers were similarly modulated by both treatments. Muscle-miRNAs (miR-1, -133, -206 and -499) were up-regulated, especially in AA samples, and we identified molecular networks with omics integration. Two pairs of genes and miRNAs demonstrated a high-level relationship, and involvement in myogenesis and muscle growth: marcksb and miR-29b in AA, and mmp14b and miR-338-5p in IGF1. Our work helps to elucidate fish muscle physiology and metabolism, highlights potential molecular markers, and creates a perspective for improvements in aquaculture and in in vitro meat production.

Degree of piRNA sharing and Piwi gene expression in the skeletal muscle of Piaractus mesopotamicus (pacu), Colossoma macropomum (tambaqui), and the hybrid tambacu

PiRNAs are a class of small noncoding RNAs that, in their mature form, bind to Piwi proteins to repress transposable element activity. Besides their role in gametogenesis and genome integrity, recent evidence indicates their action in non-germinative tissues. We performed a global analysis of piRNA and Piwi gene expression in the skeletal muscle of juveniles pacu (Piaractus mesopotamicus), tambaqui (Colossoma macropomum), and the hybrid tambacu to evaluate the degree of piRNA sharing among these three genotypes. Total RNA was sequenced and analyzed using specific parameters of piRNAs by bioinformatics tools. piRNA and Piwi gene expression was analyzed by RT-qPCR. We detected 24 piRNA clusters common to the three genotypes, with eight shared between pacu and tambacu, three between pacu and tambaqui, and five between tambaqui and tambacu; seven, five, and four clusters were unique to pacu, tambacu, and tambaqui, respectively. Genomic localization and fold change values showed two clusters and 100 piRNAs shared among the three genotypes. The gene expression of four piRNAs was evaluated to validate our bioinformatics results. piRNAs from cluster 17 were higher in tambacu than pacu and piRNAs from cluster 18 were more highly expressed in tambacu than tambaqui and pacu. In addition, the expression of Piwis 1 and 2 was higher in tambacu and tambaqui than pacu. Our results open an important window to investigate whether these small noncoding RNAs benefit the hybrid in terms of faster growth and offer a new perspective on the function of piRNAs and Piwis in fish skeletal muscle.

An insight on the impact of teleost whole genome duplication on the regulation of the molecular networks controlling skeletal muscle growth

Fish muscle growth is a complex process regulated by multiple pathways, resulting on the net accumulation of proteins and the activation of myogenic progenitor cells. Around 350–320 million years ago, teleost fish went through a specific whole genome duplication (WGD) that expanded the existent gene repertoire. Duplicated genes can be retained by different molecular mechanisms such as subfunctionalization, neofunctionalization or redundancy, each one with different functional implications. While the great majority of ohnolog genes have been identified in the teleost genomes, the effect of gene duplication in the fish physiology is still not well characterized. In the present study we studied the effect of WGD on the transcription of the duplicated components controlling muscle growth. We compared the expression of lineage-specific ohnologs related to myogenesis and protein balance in the fast-skeletal muscle of pacus (Piaractus mesopotamicus—Ostariophysi) and Nile tilapias (Oreochromis niloticus—Acanthopterygii) fasted for 4 days and refed for 3 days. We studied the expression of 20 ohnologs and found that in the great majority of cases, duplicated genes had similar expression profiles in response to fasting and refeeding, indicating that their functions during growth have been conserved during the period after the WGD. Our results suggest that redundancy might play a more important role in the retention of ohnologs of regulatory pathways than initially thought. Also, comparison to non-duplicated orthologs showed that it might not be uncommon for the duplicated genes to gain or loss new regulatory elements simultaneously. Overall, several of duplicated ohnologs have similar transcription profiles in response to pro-growth signals suggesting that evolution tends to conserve ohnolog regulation during muscle development and that in the majority of ohnologs related to muscle growth their functions might be very similar.