Metabolic Enzyme Activities Research Articles

Elucidation of the Mechanism of Rapid Growth Recovery in Rice Seedlings after Exposure to Low-Temperature Low-Light Stress: Analysis of Rice Root Transcriptome, Metabolome, and Physiology.

Late spring cold is a disastrous weather condition that often affects early rice seedlings in southern China, limiting the promotion of direct seeding cultivation. However, there are few reports on the effect of these events and on the growth recovery mechanism of rice root systems after rice seedlings are exposed to this stress. This study selected the strong-growth-recovery variety B116 (R310/R974, F17) and the slow-recovery variety B811 (Zhonghui 286) for direct seeding cultivation and exposed them to low temperature and low-light stress to simulate a late spring cold event in an artificial climate chamber. The treatment consisted of 4 days of exposure to a day/night temperature of 14/10 °C and a light intensity of 266 µmol m-2s-1 while the control group was kept at a day/night temperature of 27/25 °C and light intensity of 533 µmol m-2s-1. The results showed that 6 days after stress, the total length, surface area, and volume of B116 roots increased by 335.5%, 290.1%, and 298.5%, respectively, while those of B811 increased by 228.8%, 262.0%, and 289.1%, respectively. In B116, the increase in root fresh weight was 223.1%, and that in B811 was 165.6%, demonstrating rapid root recovery after stress and significant differences among genotypes. The content of H2O2 and MDA in the B116 roots decreased faster than that in the B811 roots after normal light intensity and temperature conditions were restored, and the activity of ROS metabolism enzymes was stronger in B116 roots than in B811 roots. The correlation analysis between the transcriptome and metabolome showed that endogenous signal transduction and starch and sucrose metabolism were the main metabolic pathways affecting the rapid growth of rice seedling roots after exposure to combined stress from low temperature and low light intensities. The levels of auxin and sucrose in the roots of the strong-recovery variety B116 were higher, and this variety's metabolism was downregulated significantly faster than that of B811. The auxin response factor and sucrose synthesis-related genes SPS1 and SUS4 were significantly upregulated. This study contributes to an understanding of the rapid growth recovery mechanism in rice after exposure to combined stress from low-temperature and low-light conditions.

How soon do metabolic alterations and oxidative distress precede the reduction of muscle mass and strength in Wistar rats in aging process?

Here we investigate metabolic changes, the antioxidant system and the accumulation of oxidative damage in muscles with different fiber types during the aging process in Wistar rats and try to map how sooner the changes occur. To do so, 30 male Wistar rats were submitted to behavioral evaluation to determine voluntary strength in the 11, 15, and 19 month old rats, measuring the energy metabolism, antioxidant system, oxidative damage and structure in the soleus and extensor digitorum longus muscles. We detected structural and metabolic changes in both muscles, especially in the EDL of 15 month old rats and in the soleus of 19 month old rats. In the 15 month old rats, there was a reduction in the cross-sectional area of the fibers, and a reduction in the proportion of type I fibers, accompanied by an increase in fiber density and the amount of type IIA fibers. This change in the fiber profile was followed by an increase in the activity of anaerobic metabolism enzymes, suggesting a reduction in the oxidative capacity of the muscle. In addition, there was an increase in the rate of lipid peroxidation, accompanied by a reduced antioxidant capacity. In the 19 month old rats, these disturbances got stronger. In summary, the present study demonstrated that before functional disturbances, there was an accumulation of oxidative damage and structural changes in the skeletal muscle beginning at 15 months old in the EDL and the soleus only in the biochemical parameters. Therefore, the metabolic alterations occurred at 15 months old and not before.

Metabolic Enzyme SLC27A5 Regulates PIP4K2A pre-mRNA Splicing as a Noncanonical Mechanism to Suppress Hepatocellular Carcinoma Metastasis.

Solute carrier family 27 member 5, a key enzyme in fatty acid transport and bile acid metabolism in the liver, is frequently expressed in low quantities in patients with hepatocellular carcinoma, resulting in poor prognosis. However, it is unclear whether SLC27A5 plays non-canonical functions and regulates HCC progression. Here, an unexpected non-canonical role of SLC27A5 is reported: regulating the alternative splicing of mRNA to inhibit the metastasis of HCC independently of its metabolic enzyme activity. Mechanistically, SLC27A5 interacts with IGF2BP3 to prevent its translocation into the nucleus, thereby inhibiting its binding to target mRNA and modulating PIP4K2A pre-mRNA splicing. Loss of SLC27A5 results in elevated levels of the PIP4K2A-S isoform, thus positively regulating phosphoinositide 3-kinase signaling via enhanced p85 stability in HCC. SLC27A5 restoration by AAV-Slc27a5 or IGF2BP3 RNA decoy oligonucleotides exerts an inhibitory effect on HCC metastasis with reduced expression of the PIP4K2A-S isoform. Therefore, PIP4K2A-S may be a novel target for treating HCC with SLC27A5 deficiency.

CA-g-CS/PLA film packaging improved storage stability through the MAPK signaling pathway of postharvest Agaricus bisporus

In this study, caffeic acid-graft-chitosan/polylactic acid (CA-g-CS/PLA) packaging was shown to be effective in enhancing the storage stability of postharvest Agaricus bisporus, and its regulatory pathway was further elucidated. Results showed that expression levels of essential genes in the mitogen-activated protein kinase (MAPK) signaling pathway such as Sho1, Ssk2, Pbs2, and Hog1 were upregulated in CA-g-CS/PLA packaging group. Furthermore, the accumulation of stress-resistant compounds was promoted by the packaging. Glycerol, γ-aminobutyric acid (GABA), proline, and glutamate were 2.6, 2, 1.4, and 2.3 times higher respectively than the PE group at the end of storage and their associated metabolic enzyme activities were promoted, similarly. Moreover, through correlation analysis, the pathway was shown to be related to the synthesis of stress-resistant compounds. These findings indicated that CA-g-CS/PLA packaging acted synergistically through both the synthesis of stress-resistant compounds and regulation of the MAPK signaling pathway to delay quality deterioration of postharvest A. bisporus.

Methyl jasmonate suppressed the pericarp browning in postharvest longan fruit by modulating membrane lipid and energy metabolisms

Methyl jasmonate (MeJA) is an important bioactive metabolite in fruits and vegetables that regulates various physiological processes. The effects of MeJA on pericarp browning in longan fruit and its underlying mechanism were investigated. Results showed that treatment with 100 μM MeJA substantially suppressed the development of pericarp browning in harvested longan fruit. Compared to untreated fruit, MeJA-treated fruit exhibited reduced cell membrane permeability during storage. Meanwhile, MeJA-treated fruit displayed lower levels of phosphatidic acid and higher content of phosphatidylcholine, phosphatidylinositol, phosphatidylglycerol, and phosphatidylethanolamine through suppressing the activities of key enzymes involved in membrane lipids metabolism, such as phospholipases, lipase and lipoxygenase. Furthermore, MeJA treatment enhances the energy status of the fruit, evidenced by elevated the levels of adenosine triphosphate and energy charge. This effect could be attributed to the enhanced activities of various energy metabolism enzymes. Overall, all results suggest that MeJA is a promising agent for inhibiting pericarp browning in longan fruit through modulation of membrane lipid and energy metabolisms.

Post-Emergence Water-Dispersal Application Provides Equal Herbicidal Activity against Echinochloa crus-galli and Rice Safety as Foliar Spraying of Penoxsulam

Penoxsulam is an acetolactate synthase (ALS)-inhibiting herbicide usually applied by post-emergence foliar spraying (PFS) for the control of Echinochloa crus-galli and numerous annual weeds in paddy fields. Herbicides applied by foliar spraying can have negative impacts on the environment, ecosystems, and human health. In this study, the response of E. crus-galli and rice to the PFS and post-emergence water-dispersal (PWD) applications of penoxsulam, and the differences in the detoxification displayed by them between the two treatment methods were compared. The results showed that the PWD application of penoxsulam provides a similar control efficacy against E. crus-galli as PFS at the 1-, 3-, and 5-leaf stages. Meanwhile, the PWD application had a higher safety for the rice. After being treated with 30 g a.i. ha−1 penoxsulam, residues were not detected in the rice treated by the PWD application method, whereas, with the PFS treatment, there was 59.0 µg/kg penoxsulam remaining. With the PFS application, there were many more residues of penoxsulam in the E. crus-galli than with the PWD method; the amount of residues was 32-fold higher 12 h after treatment. The in vitro enzyme activity assays revealed that the activities of ALS, glutathione-S-transferase (GST), and cytochrome P450 monooxygenases (P450) were increased in the PWD treatments, and were 1.5-, 1.3-, and 2.3-fold higher than with PFS 72 h after treatment. The real-time quantitative PCR (qRT-PCR) revealed that the GST1 and P450 genes, CYP81A14, CYP81A12, CYP81A18, and CYP81A21 were upregulated with the PWD application versus PFS in the E. crus-galli. In summary, these results demonstrate that the herbicidal activity was not affected by the upregulation of target and metabolic enzyme activities with the PWD application of penoxsulam. This research could contribute to application strategies reducing the risk of rice injury and environmental impacts by using water-dispersal formulations of penoxsulam.

Summer fades, deer change: Photoperiodic control of cellular seasonal acclimatization of skeletal muscle

We found major seasonal changes of polyunsaturated fatty acids (PUFAs) in muscular phospholipids (PL) in a large non-hibernating mammal, the red deer (Cervus elaphus). Dietary supply of essential linoleic acid (LA) and α-linolenic acid (ALA) had no, or only weak influence, respectively. We further found correlations of PL PUFA concentrations with the activity of key metabolic enzymes, independent of higher winter expression. Activity of the sarcoplasmic reticulum (SR) Ca++-ATPase increased with SR PL concentrations of n-6 PUFA, and of cytochrome c oxidase and citrate synthase, indicators of ATP-production, with concentrations of eicosapentaenoic acid in mitochondrial PL. All detected cyclic molecular changes were controlled by photoperiod and are likely of general relevance for mammals living in seasonal environments, including humans. During winter, these changes at the molecular level presumably compensate for Arrhenius effects in the colder peripheral body parts and thus enable a thrifty life at lower body temperature.

Activities of Energy Metabolism Enzymes in Atlantic Salmon Salmo salar L. Smolts and Parr Grown under Different Light Regimens.

Activities of enzymes of energy and carbohydrate metabolism in muscles and the liver were studied in Atlantic salmon Salmo salar L. smolts and parr grown under continuous or natural lighting and different feeding regimens in autumn followed by a short photoperiod in winter. Enzyme activities were found to differ between test and control salmon groups and between parr and smolts sampled at the end of the winter period. Smolts grown under continuous lighting and round-the-clock feeding differed from other groups by having higher cytochrome c oxidase (COX) activity and lower aldolase activity in muscles. Differences in aerobic metabolism in muscles between parr and smolts were found to be the same in all experimental groups, COX and aldolase activities being relatively higher in smolts. The pattern of changes in enzyme activities in the liver from parr to smolts differed between different experimental groups. Based on the results, the photoperiod was assumed to affect the activities of energy metabolism enzymes in salmon juveniles and may eventually affect the completion of smoltification.

Identification of distinct active pools of yeast serine palmitoyltransferase in sub-compartments of the ER.

Sphingolipids (SPs) are one of the three major lipid classes in eukaryotic cells and serve as structural components of the plasma membrane. The rate-limiting step in SP biosynthesis is catalyzed by the serine palmitoyltransferase (SPT). In budding yeast (Saccharomyces cerevisiae), SPT is negatively regulated by the two proteins, Orm1 and Orm2. Regulating SPT activity enables cells to adapt SP metabolism to changing environmental conditions. Therefore, the Orm proteins are phosphorylated by two signaling pathways originating from either the plasma membrane or the lysosome (or vacuole in yeast). Moreover, uptake of exogenous serine is necessary for the regulation of SP biosynthesis, which suggests the existence of differentially regulated SPT pools based on their intracellular localization. However, measuring lipid metabolic enzyme activity in different cellular sub-compartments has been challenging. Combining a nanobody recruitment approach with SP flux analysis, we show that the nuclear endoplasmic reticulum (ER)-localized SPT and the peripheral ER localized SPT pools are differentially active. Thus, our data add another layer to the complex network of SPT regulation. Moreover, combining lipid metabolic enzyme re-localization with flux analysis serves as versatile tool to measure lipid metabolism with subcellular resolution.

Liver metabolomics reveals potential mechanism of Jieduan-Niwan formula against acute-on-chronic liver failure (ACLF) by improving mitochondrial damage and TCA cycle

BackgroundAcute-on-chronic liver failure (ACLF) is a refractory disease with high mortality, which is characterized by a pathophysiological process of inflammation-related dysfunction of energy metabolism. Jieduan-Niwan formula (JDNWF) is a eutherapeutic Chinese medicine formula for ACLF. However, the intrinsic mechanism of its anti-ACLF effect still need to be studied systematically.PurposeThis study aimed to investigate the mechanism of JDNWF against ACLF based on altered substance metabolic profile in ACLF the expression levels of related molecules.Materials and methodsThe chemical characteristics of JDNWF were characterized using ultra performance liquid chromatography (UPLC) coupled with triple quadrupole mass spectrometry. Wistar rats subjected to a long-term CCL4 stimulation followed by a combination of an acute attack with LPS/D-GalN were used to establish the ACLF model. Liver metabolites were analyzed by LC–MS/MS and multivariate analysis. Liver function, coagulation function, histopathology, mitochondrial metabolic enzyme activity and mitochondrial damage markers were evaluated. The protein expression of mitochondrial quality control (MQC) was investigated by western blot.ResultsLiver function, coagulation function, inflammation, oxidative stress and mitochondrial enzyme activity were significantly improved by JDNWF. 108 metabolites are considered as biomarkers of JDNWF in treating ACLF, which were closely related to TCA cycle. It was further suggested that JDNWF alleviated mitochondrial damage and MQC may be potential mechanism of JDNWF improving mitochondrial function.ConclusionsMetabolomics revealed that TCA cycle was impaired in ACLF rats, and JDNWF had a regulatory effect on it. The potential mechanism may be improving the mitochondrial function through MQC pathway, thus restoring energy metabolism.

The gut-joint axis mediates the TNF-induced RA process and PBMT therapeutic effects through the metabolites of gut microbiota

ABSTRACT The gut-joint axis, one of the mechanisms that mediates the onset and progression of joint and related diseases through gut microbiota, and shows the potential as therapeutic target. A variety of drugs exert therapeutic effects on rheumatoid arthritis (RA) through the gut-joint axis. However, the anti-inflammatory and immunomodulatory effect of novel photobiomodulatory therapy (PBMT) on RA need further validation and the involvement of gut-joint axis in this process remains unknown. The present study demonstrated the beneficial effects of PBMT on RA, where we found the restoration of gut microbiota homeostasis, and the related key pathways and metabolites after PBMT. We also discovered that the therapeutic effects of PBMT on RA mainly through the gut-joint axis, in which the amino acid metabolites (Alanine and N-acetyl aspartate) play the key role and rely on the activity of metabolic enzymes in the target organs. Together, the results prove that the metabolites of amino acid from gut microbiota mediate the regulation effect on the gut-joint axis and the therapeutic effect on rheumatoid arthritis of PBMT.

In Vivo and in Vitro Regulatory Effect of Silibinin on Some Metabolic Enzyme Activities against Cobalt Induced Toxicity in Rats: A Biochemical Approach

In Vivo and in Vitro Regulatory Effect of Silibinin on Some Metabolic Enzyme Activities against Cobalt Induced Toxicity in Rats: A Biochemical Approach

Mitochondrial Functionality Is Regulated by Alkylphospholipids in Human Colon Cancer Cells.

Alkylphospholipids (APLs) have been studied as anticancer drugs that interfere with biological membranes without targeting DNA. Although their mechanism of action is not fully elucidated yet, it is known that they disrupt the intracellular trafficking of cholesterol and its metabolism. Here, we analyzed whether APLs could also interfere with mitochondrial function. For this purpose, we used HT29 colorectal cancer cells, derived from a primary tumor, and SW620 colorectal cancer cells, derived from a metastasis site. After treatment with the APLs miltefosine and perifosine, we analyzed various mitochondrial parameters, including mitochondrial mass, cardiolipin content, mitochondrial membrane potential, H2O2 production, the levels of oxidative phosphorylation (OXPHOS) complexes, metabolic enzymes activity, the oxygen consumption rate, and the levels of apoptosis and autophagy markers. APLs, especially perifosine, increased mitochondrial mass while OXPHOS complexes levels were decreased without affecting the total oxygen consumption rate. Additionally, we observed an increase in pyruvate dehydrogenase (PDH) and isocitrate dehydrogenase (IDH) levels and a decrease in lactate dehydrogenase (LDH) activity, suggesting a metabolic rewiring induced by perifosine. These alterations led to higher mitochondrial membrane potential, which was potentiated by decreased uncoupling protein 2 (UCP2) levels and increased reactive oxygen species (ROS) production. Consequently, perifosine induced an imbalance in mitochondrial function, resulting in higher ROS production that ultimately impacted cellular viability.

Hypoglycemic Effect of Betulin in Rats With Experimental Diabetes

Betulin is natural pentacyclic triterpenoids lupane-structure, which shows a wide range of biological activity, including possibly hypoglycemic effects. Diabetes mellitus is a metabolic disease, accompanied by chronic hyperglycemia caused by absolute or relative insulin deficiency. The main effective drug in the treatment of type 1 diabetes is insulin injections. In the case of type 2 diabetes, it is an adjuvant therapy. To purpose of this study was to show hypoglycemic action of betulin in a model of experimentally induced diabetes in rats. For the induction of diabetes, alloxan at a dose of 170 mg/kg, i.p. was used. The hypoglycemic effect of betulin was evaluated using doses of 50 and 100 mg/kg/day for 30 days. The activity of glucose metabolism enzymes: liver glycogen phosphorylase, hexokinase and liver and skeletal muscle phosphofructokinase in rats, glucose-6-phosphate dehydrogenase (DG-6-P) of the liver was also evaluated. Betulin in a dose-dependent manner normalized of glycemia, increased the basal insulin concentration in the blood serum, increased the activity of carbohydrate metabolizing enzymes and on the gene expression profile of enzymes involved in carbohydrate metabolism. Betulin also significant improved the morphology of the pancreas. In particular, there was an increase in the area of the islands, their diameter, an increase in the number of β cells in the composition of the islands. We conclude that betulin has hypoglycemic properties, improving glycemia and carbohydrate metabolizing enzymes and pancreatic morphology.

In vivo mutagenicity assessment of orally treated tert-butyl hydroperoxide in the liver and glandular stomach of MutaMouse

Backgroundtert-Butyl hydroperoxide (TBHP; CAS 75–91-2), a hydroperoxide, is mainly used as a polymerization initiator to produce polyethylene, polyvinyl chloride, and unsaturated polyester. It is a high-production chemical, widely used in industrial countries, including Japan. TBHP is also used as an additive for the manufacturing of food utensils, containers, and packaging (UCP). Therefore, there could be consumer exposure through oral intake of TBHP eluted from UCPs. TBHP was investigated in various in vitro and in vivo genotoxicity assays. In Ames tests, some positive results were reported with and/or without metabolic activation. As for the mouse lymphoma assay, the positive result was reported, regardless of the presence or absence of metabolic activation enzymes. The results of some chromosomal aberrations test and comet assay in vitro also demonstrated the genotoxic positive results. On the other hand, in in vivo tests, there are negative results in the bone marrow micronucleus test of TBHP-administered mice by single intravenous injection and the bone marrow chromosomal aberration test using rats exposed to TBHP for 5 days by inhalation. Also, about dominant lethal tests, the genotoxic positive results appeared. In contrast, there is little information about in vivo mutagenicity and no information about carcinogenicity by oral exposure.ResultsWe conducted in vivo gene mutation assay using MutaMice according to the OECD Guidelines for the Testing of Chemicals No. 488 to investigate in vivo mutagenicity of TBHP through oral exposure. After repeated dosing for 28 days, there were no significant differences in the mutant frequencies (MFs) of the liver and glandular stomach up to 300 mg/kg/day (close to the maximum tolerable dose (MTD)). The positive and negative controls produced the expected responses.ConclusionsThese findings show that orally administrated TBHP is not mutagenic in the mouse liver and glandular stomach under these experimental conditions.

Simultaneous aerobic nitrogen and phosphate removal capability of novel salt-tolerant strain, Pseudomonas mendocina A4: Characterization, mechanism and application potential

A salt-tolerant strain, Pseudomonas mendocina A4, was isolated from brackish-water ponds showing simultaneous heterotrophic nitrification-aerobic denitrification and phosphorus removal capability. The optimal conditions for nitrogen and phosphate removal of strain A4 were pH 7–8, carbon/nitrogen ratio 10, phosphorus/nitrogen ratio 0.2, temperature 30 °C, and salinity range of 0–5 % using sodium succinate as the carbon source. The nitrogen and phosphate removal efficiencies were 96–100 % and 88–96 % within 24 h, respectively. The nitrogen and phosphate removal processes were matched with the modified Gompertz model, and the underlying mechanisms were confirmed by the activities of key metabolic enzymes. Under 10 % salinity, the immobilization technology was employed to enhance the nitrogen and phosphate removal efficiencies of strain A4, achieving 87 % and 76 %, respectively. These findings highlight the potential application of strain A4 in both freshwater and marine culture wastewater treatment.

Harmonizing Biological and Chemical Strategies for Hazardous Chemical Detoxification: An Integrative Review

The management and mitigation of hazardous chemicals pose significant challenges to environmental and human health. This comprehensive review critically examines the efficacy of biological and chemical methods for the detoxification of hazardous chemicals. Hazardous chemicals, ranging from organic pollutants to heavy metals, often contaminate soil, water, and air, leading to adverse ecological and health impacts. Traditional chemical-based approaches have limitations, such as secondary pollutant generation and high operational costs. In contrast, biological methods harness the metabolic activities of microorganisms, plants, and enzymes to transform or degrade hazardous compounds. This review evaluates the performance of biological systems, including bioremediation, phytoremediation, and enzyme-based approaches, in detoxifying various classes of hazardous chemicals. Additionally, chemical methods, such as advanced oxidation processes, redox reactions, and adsorption, are scrutinized for their efficiency in chemical degradation and transformation. The comparative analysis considers factors like effectiveness, cost, environmental impact, and applicability to different chemical classes. Understanding the strengths and weaknesses of these detoxification approaches is essential for informed decision-making in environmental remediation and industrial processes. This review offers valuable insights into the selection of appropriate detoxification methods, based on the nature of the hazardous chemicals and the desired environmental and economic outcomes.

Novel triazole bridged quinoline-anthracene derivatives: synthesis, characterization, molecular docking, evaluation of electronic and enzyme inhibitory properties

Two novel quinoline-anthracene conjugates comprising styrylquinoline and anthracene moieties linked by triazole bridges were designed and synthesized in good yields. These molecules were determined for some metabolic enzymes activities. Results indicated that the synthetic molecules exhibited powerful inhibitory actions against all aims as compared to the control molecules. Ki values of novel compound QA-1 for hCA I, hCA II, AChE, and α-glycosidase enzymes were obtained of 20.18 ± 2.46 µM, 14.63 ± 1.14 µM, 71.48 ± 7.76 nM, 401.35 ± 36.84 nM, respectively. Both compounds showed promising candidate complexes for drug development with considerable in vitro different enzymes inhibitory activities. The binding conformations patterns and interaction of QA-1 and QA-2 compounds with α-glucosidase, acetycholinesterase, carbonic anhydrase-I and carbonic anhydrase-II enzymes were investigated through molecular docking profiles. The docking outputs are consistent with the Ki and IC50 values of novel compounds. Three dimensional geometries and electronic properties of the title compounds were obtained by the applicational computational approach at B3LYP/6–31++G(d,p) level of theory. Communicated by Ramaswamy H. Sarma

Use of black soldier fly (Hermetia illucens) larvae meal in diets for gilthead seabream juveniles: Effects on growth-related gene expression, intermediary metabolism, digestive enzymes, and gut microbiota modulation

A study was conducted to evaluate the effects of dietary inclusion of defatted Hermetia illucens larvae meal (HM) on the expression of growth-related genes, plasma metabolites, activity of intermediary metabolism enzymes, and gut microbiota modulation in gilthead seabream (Sparus aurata) juveniles. Four experimental diets were formulated (43% crude protein, 18% crude lipids) with increasing levels of defatted HM: 0 (HM0), 15 (HM15), 30 (HM30), and 45% (HM45) replacing fishmeal (included at 34% in the control diet) at 0, 22, 60, and 100%, respectively. Fish were fed these diets for 67 days. At the end of the trial, the expression of muscle growth hormone receptors (ghr1 and ghr2), insulin-like growth factors (igf1 and igf2), cathepsins (cts-a and cts-b), and myogenic determination factor 1 (myod1) were not affected, while a downregulation of myogenic determination factor 2 (myod2) and upregulation of myostatin (mstn) was observed with HM inclusion. Plasma metabolites profile was unaffected by diet composition, except for a linear decrease trend in total lipids. A linear increase of liver alanine aminotransferase (ALT) and glutamate dehydrogenase (GDH) activity and a linear decrease of glucose 6-phosphate dehydrogenase (G6PDH), malic enzyme (ME), and (FAS) activity were observed with HM inclusion. The activity of β-hydroxy acyl-CoA dehydrogenase (HOAD) followed a quadratic trend, being higher in fish fed with diet HM15 than in the control. Likewise, amylase, trypsin, and chymotrypsin activity were higher in the posterior intestine of fish fed with diet HM15. Digesta of fish fed the HM-containing diets showed an increase in the number of operational taxonomic units, microbial richness, and diversity. Conversely, a reduction in these indexes was observed in the mucosa. Among the identified bacteria, Firmicutes represented the predominant phyla. The inclusion of HM increased the abundance of Oceanobacillus, Lederbergia, Bacillus, and Corynebacterium in the digesta while Lactobacillus and Caldalkalibacillus abundance was reduced. Overall, total FM replacement with defatted HM had no major effects on plasma metabolites and muscle growth-related genes but induced a few differences in intermediary metabolism and digestive enzymes activity. HM inclusion improved gut digesta microbiota richness and diversity, promoting the growth of potential beneficial bacteria.

Growth Performance, Feed Utilisation, Digestive and Metabolic Enzyme Activity, and Liver Morphohistology in Hybrid Tilapia (Oreochromis mossambicus × Oreochromis niloticus) Juveniles Fed with the Inclusion of Chitosan in Their Diet

This study aimed to evaluate the growth performance, feed utilisation, digestive and metabolic enzyme activity, and liver histology in juveniles of hybrid red tilapia (Oreochromis mossambicus × Oreochromis niloticus) fed with the inclusion of chitosan in their diet. Six dietary chitosan levels (0 “control’’, 10, 20, 30, 40, and 50 g kg−1) were used to feed juvenile fish (initial weight 7.50 ± 0.20 g) that were cultured for eight weeks in 18 tanks at a density of 15 fish/tank. The growth performance presented significant differences (p ˂ 0.05) for weight gain, specific growth rate, feed conversion ratio, hepatosomatic index, and survival rate. The digestive and metabolic enzyme activities were significantly (p < 0.05) influenced by the levels of chitosan in the administered diet. Histologically, no damage was found in the liver; however, morphometrically, a significant difference (p < 0.05) was found in the hepatocyte area and sinusoid area. Vacuolisation of hepatocytes was found in treatments with 40 and 50 g kg−1 of chitosan in the diet. Treatments with doses of chitosan showed a better response (p < 0.05) compared to the control treatment in most of the different groups of variables analysed. The result of the principal component analysis suggests that a diet containing 40 g kg−1 of chitosan is optimal for tilapia growth performance.