Muscle Of Rainbow Trout Research Articles

Effects of sexual maturation and feeding level on fatty acid metabolism gene expression in muscle, liver, and visceral adipose tissue of diploid and triploid rainbow trout, Oncorhynchus mykiss.

In many cultured fish species, such as salmonids, gonadal development occurs at the expense of stored energy and nutrients, including lipids. However, mechanisms regulating nutrient repartitioning during sexual maturation are not well understood. This study compared sexually maturing diploid (2N) and sterile triploid (3N) female rainbow trout to investigate effects of sexual maturation on expression of 35 genes involved in fatty acid metabolism, including genes within fatty acid synthesis, β-oxidation, and cofactors of the mTOR and PPAR signaling pathways, in liver, white muscle, and visceral adipose tissue. Diploid fish were fed at different rations (0.25% and 0.50% tank biomass, and satiation) to determine effects of ration on gene expression. Gene expression was affected by ration level only in white muscle; erk and acat2 had higher expression in fish fed higher rations. On the other hand, sexual maturation affected gene expression across all three tissue types. Data indicate 2N fish have higher expression of β-oxidation genes within white muscle and within visceral adipose tissue. These findings support enhanced fatty acid mobilization within these tissues during sexual maturation. Higher expression of fatty acid synthesis genes in 3N female liver is associated with higher expression of mTOR cofactors and pparγ, which reflects continued deposition of lipids in these fish. Furthermore, greater expression of genes involved in β-oxidation pathways across ration levels in 2N females suggests that sexual maturation and the associated maturation-related signals are stronger regulators of lipid metabolism-related genes rather the rations applied in the current study.

Oxidative stress biomarkers in different tissues of rainbow trout (Oncorhynchus mykiss) exposed to Disinfectant-CIP formulated with peracetic acid and hydrogen peroxide

Abstract The aim of study was to determine the effects of exposure to the product DEZYNFEKTANT-CIP (Eng. - Disinfectant-CIP), which is formulated with peracetic acid and hydrogen peroxide, on oxidative stress biomarkers (lipid peroxidation (LPO) levels and the carbonyl content of oxidatively modified proteins) and antioxidant defenses (superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), glutathione peroxidase (GPx), total antioxidant capacity) in muscle, gill, hepatic, and cardiac tissues of rainbow trout, Oncorhynchus mykiss (Walbaum). LPO and carbonyl contents changed with tissue type. Exposure to Disinfectant-CIP led to a significant decrease in LPO in muscle tissues and carbonyl content in muscle and gill tissues. The inhibition of SOD and CAT activity in muscle, hepatic, and cardiac tissues was observed probably because of increased oxidative stress during disinfection; however, hepatic and cardiac GPx activity increased in an attempt to counteract oxidative stress. We suggest that oxidative stress during the oxidation of peracetic acid and hydrogen peroxide could be counteracted by the antioxidant system in trout tissues. Correlative analysis between oxidative stress biomarkers and antioxidant defense confirms the pivotal role of SOD and CAT against CIP-induced oxidative stress

Occurrence of tetracyclines, sulfonamides, fluoroquinolones and florfenicol in farmed rainbow trout in Iran

This study was carried out to determine the occurrence of tetracyclines, sulfonamides, fluoroquinolones and florfenicol residues in rainbow trout muscle samples (n = 138) obtained from Iranian trout farms. Concentrations of the antibiotics were determined using competitive enzyme-linked immunosorbent assay method. At measurable levels, 63.1%, 16.7%, 19.6% and 40.6% of the samples contained the residues of tetracyclines, sulfonamides, fluoroquinolones and florfenicol, respectively. The detected range of concentrations for positive samples was 1.43–101.4 µg/kg for tetracyclines, 4.03–90.4 µg/kg for sulfonamides, 6.75–99.8 µg/kg for fluoroquinolones and 0.11–172.6 µg/kg for florfenicol. The residues of the antibiotics in trout samples did not exceed the maximum residue levels recommended by the Institute of Standards and Industrial Research of Iran. However, the high occurrence of tetracyclines and florfenicol in the samples is alarming and could be a potential hazard for public health. Further investigations should be performed to determine the residues of antibiotics in other farmed fish species in Iran.

Dietary methionine availability affects the main factors involved in muscle protein turnover in rainbow trout (Oncorhynchus mykiss).

Methionine is a limiting essential amino acid in most plant-based ingredients of fish feed. In the present study, we aimed to determine the effect of dietary methionine concentrations on several main factors involved in the regulation of mRNA translation and the two major proteolytic pathways (ubiquitin-proteasome and autophagy-lysosomal) in the white muscle of rainbow trout (Oncorhynchus mykiss). The fish were fed for 6 weeks one of the three isonitrogenous diets providing three different methionine concentrations (deficient (DEF), adequate (ADQ) and excess (EXC)). At the end of the experiment, the fish fed the DEF diet had a significantly lower body weight and feed efficiency compared with those fed the EXC and ADQ diets. This reduction in the growth of fish fed the DEF diet was accompanied by a decrease in the activation of the translation initiation factors ribosomal protein S6 and eIF2α. The levels of the main autophagy-related markers (LC3-II and beclin 1) as well as the expression of several autophagy genes (atg4b, atg12 l, Uvrag, SQSTM1, Mul1 and Bnip3) were higher in the white muscle of fish fed the DEF diet. Similarly, the mRNA levels of several proteasome-related genes (Fbx32, MuRF2, MuRF3, ZNF216 and Trim32) were significantly up-regulated by methionine limitation. Together, these results extend our understanding of mechanisms regulating the reduction of muscle growth induced by dietary methionine deficiency, providing valuable information on the biomarkers of the effects of low-fishmeal diets.

Lycopene improves activation of antioxidant system and Nrf2/HO-1 pathway of muscle in rainbow trout (Oncorhynchus mykiss) with different stocking densities

The purpose of this study was to describe the effect of lycopene on antioxidant status, heat shock protein 70 (Hsp70), nuclear factor (erythroid-derived 2)-like 2 (Nrf2) and heme-oxygenase 1(HO-1) levels in the muscle of rainbow trout (Oncorhynchus mykiss). The fish were kept at low (20 kg m3 − 1) or high (100 kg m3 − 1) stocking densities till the end of study and fed a basal diet or the basal diet supplemented with either 200 or 400 mg of lycopene kg− 1 of diet. The protein, lipid and ash contents in the muscle were not changed by the supplementation of lycopene in rainbow trout kept under high or low stocking densities. In response to increasing supplemental lycopene level, there were linear increases in lycopene levels, superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) activities (P < 0.001) and Nrf2 and HO-1 levels of muscle; linear decreases in muscle malondialdehyde (MDA) and Hsp70 levels (P < 0.001). In conclusion, lycopene supplementation to fish reduces the detrimental effects of oxidative stress and lipid peroxidation resulting from stocking densities via activating host defence system at cellular level.

Differential effects of temperature and glucose on glycogenolytic enzymes in tissues of rainbow trout ( Oncorhynchus mykiss )

The pathways and regulatory mechanisms of glycogenolysis remain relatively unexplored in non-mammalian vertebrates, especially poikilotherms. We studied the temperature sensitivity and inhibition of glycogenolytic enzymes in liver, ventricle, and white muscle of rainbow trout acclimated to 14 °C. Glycogen phosphorylase (GP) and acid α-glucosidase (GAA) activities were measured in homogenates of tissues at physiological temperatures (4, 14, and 24 °C), and in the presence of allosteric inhibitor, glucose. Higher GP versus GAA activity in all three tissues suggested a predominance of phosphorolytic glycogenolysis over the lysosomal glucosidic pathway. GP activities at 14 °C were ~2-fold higher in the ventricle and white muscle versus the liver and selectively increased by AMP in striated muscle. Conversely, the activities of GAA and lysosomal marker acid phosphatase were 8- to 10-fold higher in the liver compared with the ventricle and white muscle. Thermal sensitivity (Q10) was increased for GP in all tissues below 14 °C and decreased in striated muscle in the absence of AMP above 14 °C. GAA had lower Q10 values than GP below 14 °C, and, unlike GP, Q10s for GAA were not different between tissues or affected by temperature. Both GP (in the absence of AMP) and GAA were inhibited by glucose in a dose-dependent manner, with the lowest IC50 values observed in the white muscle (1.4 and 6.3 mM, respectively). In conclusion, despite comparatively low kinetic potential, lysosomal GAA might facilitate glycogenolysis at colder body temperatures in striated muscle and intracellular glucose could limit phosphorolytic and glucosidic glycogenolysis in multiple tissues of the rainbow trout.

Effect of Red Grape Pomace Extract on the Shelf Life of Refrigerated Rainbow Trout (Oncorhynchus mykiss) Minced Muscle

The use of naturally derived antioxidants to produce ready-to-cook fish-based foods is a growing trend. Grape pomace is a rich source of phenolic compounds with antioxidant and antimicrobial effects. The effects of red grape pomace (RGP) extracts on the shelf life of minced rainbow trout muscles were evaluated. Extracts were added to trout patties to give a final concentration of 0, 1, and 3%. RGP extracts were effective in delaying lipid oxidation and cadaverine formation in minced trout muscle after 6 days of refrigerated storage. It is concluded that RGP extract in minced trout muscle can enhance the quality and shelf life of this ready-to-cook fish-based food and simultaneously provide a functional food with natural antioxidants beneficial for consumers.

The effect of vacuum packaging on physicochemical changes in rainbow trout (Oncorhynchus mykiss) during cold storage

The aim of the study was to monitor changes in selected physical (awwater activity, pH values) and chemical (TVBN total volatile basic nitrogen, TMA-N trimethylamine nitrogen, FFA free fatty acids, PV peroxide values, TBA thiobarbituric acid value) properties in the shelf life of rainbow trout (Oncorhynchus mykiss) muscle. A total of 192 trout were examined. Control samples (96 samples) were simply packaged in contact with atmospheric oxygen, while experimental samples (96 samples) were packaged in a commercial vacuum (98%). All the samples were stored at 2 ± 2° C for 11 days. Analyses were performed on storage days 1, 2, 4, 7, 9, and 11. During the experiment, aw values increased in both types of packaging (in air: 0.982; vacuum-packaged: 0.989). At the end of storage, TVBN and TMA concentrations were at 28.88 ± 4.42 and 19.28 ± 3.00 g mg·100-1, respectively, in the muscle of vacuum-packaged trout; and at 30.52 ± 2.91 and 19.94 ± 2.05 mg·100 g-1, respectively, in fish in simple packaging. The FFA content in vacuum-packaged fish initially declined before increasing to 3.67 ± 2.37% of total fat as oleic acid later in the experiment. The pattern of PV changes was inconclusive, and significant changes (P &lt; 0.01) were observed in both types of packaging. On monitoring day 11, TBA values had ​​increased to 7.34 ± 3.10 mg·kg-1 in vacuum-packaged fish and to 26.03 ± 8.00 mg·kg-1 in fish in simple packaging. Free fatty acids are not a good indicator of spoilage because they are converted to hydroperoxides. Vacuum packaging effectively slowed down oxidative changes in rainbow trout muscle. The peroxide content is not a suitable indicator of shelf life as peroxides are decomposed to secondary products. Total volatile basic nitrogen and thiobarbituric acid value can be recommended as suitable indicators of freshness and shelf life.

Effect of modified atmosphere and vacuum packaging on selected chemical parameters of rainbow trout (Oncorhynchus mykiss) and carp (Cyprinus carpio) cuts freshness

The purpose of food packing in modified atmosphere is to extend its sustainability by preventing both biochemical processes and growth of spoilage bacteria. Gases or their mixtures which are mostly used in the modified atmosphere food packing technology are carbon-dioxide (CO2), oxygen (O2) and nitrogen (N2). The aim of our research was to examine the influence of packaging in modified atmosphere and vacuum on the total volatile basic nitrogen (TVB-N) content and pH in muscle of rainbow trout (Oncorhynchus mykiss) and common carp (Cyprinus carpio), as well as to determine the most suitable gas mixtures for packing of these freshwater species. Three sample groups of trout and carp cuts were investigated. The first two groups were packaged in modified atmosphere with different gas ratios: 60%CO2+40%N2 (I group) and 40%CO2+60%N2 (II group), whereas the samples from third, control group, (III group) were vacuum packaged. During trials samples were stored in refrigerator at +3?C. Determination of TVB-N and pH was performed on 1st, 7th and 14th day of storage. The obtained results indicate that the investigated mixtures of gases and vacuum as well had a significant influence on the values of TVB-N in trout and carp cuts samples. The lowest increase in TVB-N was established in trout and carp cuts samples from the group I, whereas the highest increase was established in samples from group III. Statistical significant difference (p &lt; 0,001) between the average values of TVB-N for trout (I group: 18,17 ? 0,93; II group: 20,90 ? 0,81 and III group: 36,18 ? 2,65 mg N/100 g ) and carp cuts (I group: 26,74 ? 1,48; II group: 30,02 ? 0,31 and III group: 35,10 ? 1,75 mg N/100 g) was established on 14th day. The lowest pH value was established in samples packaged in modified atmosphere with 60% CO2 +40% N2 (I group). On 14th day of testing the obtained value was 6,15 ? 0,09 for trout and 5,94 ? 1,11 for carp samples. Increase in pH value in trout samples packed in vacuum was established during the whole period of investigation (p &lt; 0,001), while in carp cuts samples packaged in vacuum the increase in pH value (p &lt; 0,05) was established up to 7th day of testing. Based on the obtained results it can be concluded that gas mixture consisting of 60% CO2 and 40% N2 was the most suitable for packaging of fresh trout and carp cuts in terms of selected chemical parameters, such as TVB-N and pH.

Determination of malachite green residues in farmed rainbow trout in Iran

This study was carried out to determine the residues of malachite green (MG) in rainbow trout muscle samples (n = 144) obtained from trout farms in Iran. A high-performance liquid chromatography method with visible detection at 618 nm has been developed to determine the sum of MG and leucomalachite green (LMG) in the muscle samples. This method is based on in situ oxidation of colorless LMG to chromic MG with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone. The method was validated according to the criteria described in Commission Decision 2002/657/EC. The recoveries for MG and LMG in spiked muscle samples were higher than 70%; and the relative standard deviations were lower than 9.9% for repeatability and 11.5% for within-laboratory reproducibility. The values of decision limit (CCα) and detection capability (CCβ) for MG were 0.16 μg/kg and 0.39 μg/kg, respectively, which are below the minimum required performance limit (MRPL) of 2 μg/kg for sum of MG and LMG. The residues of MG were detected in 48.6% of the rainbow trout muscle samples, ranging between 0.30 and 146.1 μg/kg. Most of the contaminated samples contained MG at the level of 2–10 μg/kg. The results indicated that application of MG in such a level in trout farms could be a potential hazard for public health. Further investigations should be carried out to determine the residues of MG in other farmed fish species in Iran.

Detection of free and covalently bound microcystins in different tissues (liver, intestines, gills, and muscles) of rainbow trout (Oncorhynchus mykiss) by liquid chromatography–tandem mass spectrometry: Method characterization

So far only a few publications have explored the development of extraction methods of cyanotoxin extracted from complex matrices. With regard to cyanobacterial microcystins (MCs), the data on the contamination of the flesh of aquatic organisms is hard to compare and very limited due to the lack of validated methods. In recent years, evidence that both free and bound fractions of toxin are found in these tissues has highlighted the need to develop effective methods of quantification. Several techniques do exist, but only the Lemieux oxidation has so far been used to investigate complex tissue matrices. In this study, protocols based on the Lemieux approach were adapted for the quantitative chemical analysis of free MC-LR and MMPB derived from bound toxin in the tissues of juvenile trout gavaged with MC-LR. Afterwards, the NF V03 110 guideline was used to characterize the protocols elaborated and evaluate their effectiveness.

The potential of soya oil industry products as oil alternatives in rainbow trout (Oncorhynchus mykiss) diet

This study investigated the effects of different soya oil products on growth, nutrient digestibility, and fatty acid composition of muscle in rainbow trout. The products’ ingredients were soap stock, fat powder, crude oil, and refined soya oil as a control. Four experimental diets were formulated by addition of 12 % of each of the four ingredients to a basal diet. Replacement of refined soya oil by the soya oil products did not influence growth performance until 8 weeks (P > 0.05). This replacement, however, reduced fat digestibility in rainbow trout (83.7 vs. 73.3–79.8 %; P < 0.05). Dietary inclusions of fat powder and crude oil led to larger values of protein digestibility than those of refined soya oil and soap stock (P < 0.05). The compositions of saturated and monounsaturated fatty acids of the muscle were similar, but linoleic acid concentration (LA, 18: 2n-6) increased in fish muscle fed refined soya oil compared to the other diets (37 vs. 30–31 %; P < 0.05). Arachidonic acid (ArA, 20: 4n-6) concentration was higher (P < 0.05) in fish fed both fat powder and soap stock than those fed the other diets. In conclusion, refined soya oil can be replaced by soya oil products in rainbow trout diet with no negative impacts on the growth. However, fish fed on diet containing refined soya oil had higher concentration of LA and lower density of ArA. It appears that rainbow trout is capable of digesting soya oil products though the digestibility rate reduced slightly with an increase in saturated fatty acid content.

Macronutrient Composition of the Diet Affects the Feeding-Mediated Down Regulation of Autophagy in Muscle of Rainbow Trout (O. mykiss)

Autophagy functions as an important catabolic mechanism by mediating the turnover of intracellular organelles and protein complexes through a lysosome dependent degradative pathway. Although the induction of autophagy by starvation has been extensively studied, we still know very little about how autophagy is regulated under normal nutritional conditions. The purpose of the present study was to characterize both in vivo and in vitro the response of the autophagy-lysosomal degradative pathway to nutrient (amino acids and carbohydrates) availability in the muscle of the carnivorous rainbow trout. We report that meal feeding is accompanied by a rapid activation of Akt, FoxO1 and the Target of Rapamycin (TOR) signaling pathways and a concomitant decrease of autophagosome formation. We also show that this effect occurs only when the proportion of dietary proteins increases at the expense of carbohydrates. Concurrently, our in vitro study on primary culture of trout muscle cells demonstrates an opposite effect of amino acids and glucose on the regulation of autophagy-lysosomal pathways. More specifically, the addition of amino acids in cell culture medium inhibited the formation of autophagosomes, whereas the addition of glucose had an opposite effect. The effect of amino acids was accompanied by an activation of TOR, considered as an important regulator of autophagosomal formation. However, the mechanisms involved in the effect of glucose were independent of Akt, TOR and AMPK and remain to be determined. Together, these results demonstrated the specific role of macronutrients as well as that of their interactions in the regulation of autophagy and highlight the interest to consider the macronutrient composition of the diets in the control of this degradative pathway.

Effects of dietary lipid levels on growth, feed utilization and mitochondrial function in low- and high-feed efficient families of rainbow trout (Oncorhynchus mykiss)

A 2×3 factorial study was conducted to investigate the effects of dietary lipid levels on growth, feed utilization and mitochondrial enzyme activities in juvenile all-female rainbow trout (Oncorhynchus mykiss). Practical diets with a fixed crude protein content of 42%, formulated to contain 10% (42/10), 20% (42/20) and 30% (42/30) dietary lipid, were fed to apparent satiety to triplicate groups of either low-feed efficient (low-FE, 105.67±3.04g initial average mass) or high-feed efficient (high-FE, 97.86±4.02g) families of fish, twice per day, for 108days. At the end of the experiment, the group of fish fed diets 42/20 and 42/30 showed higher growth and feed efficiency (FE), coupled with a lower daily feed consumption (FC), than fish fed 42/10 diet, although similar results were found with diets 42/10 and 42/30 for growth (P<0.05). With similar FC, the high-FE family showed higher growth, FE, protein efficiency ratio (PER) and protein productive value (PPV) than the low-FE family (P<0.05). Fish fed diets 42/20 and 42/30 had the highest PER and PPV (P<0.05). The lipid efficiency ratio was highest in fish from the high-FE family fed diet 42/10 (P<0.05). Fish fed diet 42/30 showed the highest visceral fat and viscerosomatic index (P<0.05). In the liver, the respiratory chain enzymatic activity was significantly affected by both diet and family for complexes I and IV, and by diet for complexes II, III and V (P<0.05). In the intestine, significant family×diet interaction effects were observed for complexes III and IV (P<0.05). There were both significant family and diet main effects on complexes I and II, whereas complex V was only affected by family (P<0.05). In the muscle, significant (P<0.05) diet×family interaction effects were observed for complexes II and IV activities; complex III activity was significantly affected by the diet, whereas complex V activity was affected by both the diet and the family main effects; the activity of complex I was not affected by the treatments (P>0.05). The overall results of this study established that feeding a 42% CP diet with a minimum of 20% dietary lipid leads to high growth, feed utilization on the one hand, and that these zootechnical parameters are coupled with high mitochondrial enzymatic function in the liver, the intestine and the muscle of rainbow trout. Also, as it was expected, the high-FE family showed higher response to treatments than the low-FE family.

Effects of sustained swimming on the red and white muscle transcriptome of rainbow trout (Oncorhynchus mykiss) fed a carbohydrate-rich diet

Training at sustainable swimming speeds can produce changes in fish skeletal muscle that are important for aquaculture due to their growth-potentiating effects. Such changes may be even more relevant when fish are fed diets containing an increasing proportion of carbohydrates as an energy source. We evaluated the effects of moderate-intensity sustained swimming on the transcriptomic response of red and white muscle in rainbow trout fed a carbohydrate-rich diet using microarray and qPCR. Analysis of the red and white muscle transcriptome in resting or swimming (1.3 body lengths/s) fish for 30days revealed significant changes in the expression of a large number of genes (395 and 597, respectively), with a total of 218 differentially expressed genes (DEGs) common for both muscles. A large number of the genes involved in glucose use and energy generation, contraction, development, synthesis and catabolism of proteins were up-regulated in red and white muscle. Additionally, DEGs in both muscles were involved in processes of defense response and apoptosis. Skeletal muscle contraction activates a transcriptional program required for the successful adaptation of both muscles to the changing demands imposed by swimming conditions. Future studies should further clarify the mechanisms involved in the adaptation of both tissues to exercise and assess possible benefits of such conditions for cultured fish.

Structure–activity relationship of non-coplanar polychlorinated biphenyls toward skeletal muscle ryanodine receptors in rainbow trout (Oncorhynchus mykiss)

Research addressing the health impacts of polychlorinated biphenyls (PCBs) has primarily focused on the effects of coplanar, or dioxin-like (DL), congeners, which is especially true for research assessing impacts in fish species. Ortho substituted non-coplanar, termed non-dioxin-like (NDL), PCBs have received less attention. In mammals, NDL PCBs enhance the activity of ryanodine receptors (RyR), calcium release channels necessary for engaging excitation–contraction (EC) coupling in striated muscle. We utilized in vitro receptor binding analysis to determine whether NDL PCB congeners detected in aquatic environments alter the activity of RyR isoform 1 (RyR1) found in the skeletal muscle of rainbow trout. Congeners 52, 95, 136, and149 were the most efficacious leading to an increase in receptor activity that was approximately 250% greater than that found under solvent control conditions. Other environmentally relevant congeners, namely PCB 153, 151 and 101, which all contain two or more chlorines in the ortho-position, enhanced receptor activity by greater than 160% of baseline. The mono-ortho congeners or the non-ortho PCB 77 had negligible impact on the RyR1. When combined, in binary or environmentally relevant mixtures, congeners shown to enhance receptor activity appeared to display additivity and when the active PCB 95 was present with the non-active congener PCB 77 the impact on receptor activity was reduced from 250% to 230%. The important role of the RyR and the demonstrated additive nature of NDL congeners toward altering channel function calls for further investigation into the ecological implications of altered RyR function in fish with high PCB burdens.

Root Effect Hemoglobin May Have Evolved to Enhance General Tissue Oxygen Delivery

The Root effect is a pH-dependent reduction in hemoglobin-O2 carrying capacity. Specific to ray-finned fishes, the Root effect has been ascribed specialized roles in retinal oxygenation and swimbladder inflation. We report that when rainbow trout are exposed to elevated water carbon dioxide (CO2), red muscle partial pressure of oxygen (PO2) increases by 65%--evidence that Root hemoglobins enhance general tissue O2 delivery during acidotic stress. Inhibiting carbonic anhydrase (CA) in the plasma abolished this effect. We argue that CA activity in muscle capillaries short-circuits red blood cell (RBC) pH regulation. This acidifies RBCs, unloads O2 from hemoglobin, and elevates tissue PO2, which could double O2 delivery with no change in perfusion. This previously undescribed mechanism to enhance O2 delivery during stress may represent the incipient function of Root hemoglobins in fishes.

Evolution of Mammalian Diving Capacity Traced by Myoglobin Net Surface Charge

Extended breath-hold endurance enables the exploitation of the aquatic niche by numerous mammalian lineages and is accomplished by elevated body oxygen stores and adaptations that promote their economical use. However, little is known regarding the molecular and evolutionary underpinnings of the high muscle myoglobin concentration phenotype of divers. We used ancestral sequence reconstruction to trace the evolution of this oxygen-storing protein across a 130-species mammalian phylogeny and reveal an adaptive molecular signature of elevated myoglobin net surface charge in diving species that is mechanistically linked with maximal myoglobin concentration. This observation provides insights into the tempo and routes to enhanced dive capacity evolution within the ancestors of each major mammalian aquatic lineage and infers amphibious ancestries of echidnas, moles, hyraxes, and elephants, offering a fresh perspective on the evolution of this iconic respiratory pigment.

Epistasis Among Adaptive Mutations in Deer Mouse Hemoglobin

Epistatic interactions between mutant sites in the same protein can exert a strong influence on pathways of molecular evolution. We performed protein engineering experiments that revealed pervasive epistasis among segregating amino acid variants that contribute to adaptive functional variation in deer mouse hemoglobin (Hb). Amino acid mutations increased or decreased Hb-O2 affinity depending on the allelic state of other sites. Structural analysis revealed that epistasis for Hb-O2 affinity and allosteric regulatory control is attributable to indirect interactions between structurally remote sites. The prevalence of sign epistasis for fitness-related biochemical phenotypes has important implications for the evolutionary dynamics of protein polymorphism in natural populations.

Tissue damage in organic rainbow trout muscle investigated by proteomics and bioinformatics

The response to tissue damage is a complex process, which involves the coordinated regulation of multiple proteins to ensure tissue repair. In order to investigate the effect of tissue damage in a lower vertebrate, samples were taken from rainbow trout (Oncorhynchus mykiss) at day 7 after damage and proteins were separated using 2DE. The experimental design included two groups of rainbow trout, which were fed organic feed either with or without astaxanthin. In total, 96 proteins were found to be affected by tissue damage, clearly demonstrating in this lower vertebrate the complexity and magnitude of the cellular response, in the context of a regenerative process. Using a bioinformatics approach, the main biological function of these proteins were assigned, showing the regulation of proteins involved in processes such as apoptosis, iron homeostasis, and regulation of muscular structure. Interestingly, it was established that exclusively within the astaxanthin feed group, three members of the annexin protein family (annexin IV, V, and VI) were regulated in response to tissue damage.