Red Muscle Research Articles

Study Proportions and Chemical Composition of red and white muscles of Tilapia Zillii and Acanthopagrus latus

The present study deals with two types of teleost; Tilapia zillii (Cichlidae), and Acanthopagrus latus (Sparidae), to study some aspects with relation to the fish activity such as the proportion of red and white muscle fibers, and estimation of the chemical content (protein, lipid, moisture, ash) in different regions of fish studied. The results showed that the red muscles less than the white muscles in (R1, R2) in studied fish, The red muscles ranged between (5.01–10.5%) and (4.67–9.64%) in T. zillii and A. latus respectively, while the proportion of white muscles were ranged between (94.98–88.49%) and (95.32–90.35%) in T. zillii and A. latus respectively beside to increasing of red muscles towards of the posterior region (caudal peduncle), therefore these fish are put in the intermediate activity. The results which related to chemical content in muscles including (protein, lipid, moisture, ash) in (R1, R2) from fish body, showed that the proportion of protein were ranged (17.97–19.05%) and (16.89–17.46%) in T. zillii and A. latus respectively, while the proportion of lipid were ranged between (1.54–2.08%) and (3.08–3.13%) in fish studied, therefore T. zillii put in non-lipid fishes or flesh fishes, while A. latus put in intermediate lipid fishes.

Estimation of the gill respiratory surface area and some features of the red muscle fibers in two teleost species

The current study is a comparative analysis of the Gill Respiratory Surface Area (GRSA) and some features of the red muscle fibers including the proportions and diameters of the red muscle fibers in three body regions in two teleosts species; torpedo scad, Megalspis cordyla (L.) which belongs to the carangid and the red belly tilapia, Cotodon zillii (Gervaias, 1848) which belongs to cichlids. Fifty fishes (25 fishes for each species) were used in the current investigation. They range in length from 100 to 300 mm and their weight ranged between 66 and 305 gm. The results show that the M. cordyla have GRSA ranged between 78 and 100 mm2/gm whereas it ranged between 56 and 146 mm²/gm in C. zillii. The fish weight was the influential factor on the values of the relative GRSA (mm²/gm) while the total length of gill filaments was the influential factor on the values of the total GRSA (mm²) of the studied fishes which showed significant differences (p<0.05) between the studied species. The difference in the proportions of the red muscle fibers among the three body regions of both species showed a significant difference (P<0.05) between the total length of the fish and the proportions of the red muscle fibers which ranged between 8.16 and 12.80 % in M. cordyla whereas it was between 5.42 and 9.24 % in C. zillii. Also the results presented an increase in the proportions of the red muscle fibers towards the posterior region (R3) which were 8.80-12.80 % in M. cordyla while they were 6.24-9.24 % in C. zillii. The results revealed that the approximate diameters of the red muscle fibers varied between 13.70 and 47.85 μm in M. cordyla while they ranged between 17.10 and 44.50 μm in C .zillii but were not statistically significant differences (P>0.05) between the two species.

Recombinant Bovine Growth Hormone-Induced Metabolic Remodelling Enhances Growth of Gilthead Sea-Bream (Sparus aurata): Insights from Stable Isotopes Composition and Proteomics.

Growth hormone and insulin-like growth factors (GH/IGF axis) regulate somatic growth in mammals and fish, although their action on metabolism is not fully understood in the latter. An intraperitoneal injection of extended-release recombinant bovine growth hormone (rbGH, Posilac®) was used in gilthead sea bream fingerlings and juveniles to analyse the metabolic response of liver and red and white muscles by enzymatic, isotopic and proteomic analyses. GH-induced lipolysis and glycogenolysis were reflected in liver composition, and metabolic and redox enzymes reported higher lipid use and lower protein oxidation. In white and red muscle reserves, rBGH increased glycogen while reducing lipid. The isotopic analysis of muscles showed a decrease in the recycling of proteins and a greater recycling of lipids and glycogen in the rBGH groups, which favoured a protein sparing effect. The protein synthesis capacity (RNA/protein) of white muscle increased, while cytochrome-c-oxidase (COX) protein expression decreased in rBGH group. Proteomic analysis of white muscle revealed only downregulation of 8 proteins, related to carbohydrate metabolic processes. The global results corroborated that GH acted by saving dietary proteins for muscle growth mainly by promoting the use of lipids as energy in the muscles of the gilthead sea bream. There was a fuel switch from carbohydrates to lipids with compensatory changes in antioxidant pathways that overall resulted in enhanced somatic growth.

Measurement of fish freshness: Flow cytometry analysis of isolated muscle mitochondria

Mitochondria are real sensors of the physiological status of tissues. After the death of an animal, they maintain physiological activity for several days. This activity is highly dependent on the availability of nutrients in the tissue. In this study, flow cytometry was used to measure the membrane potential of mitochondria isolated from European seabass (Dicentrarchus labrax) red muscle stored in ice for seven days in order to characterize fish freshness. Two probes, TMRM and Rhodamine 123, were used to measure mitochondrial potential. During the first few days (D0 to D3), isolated mitochondria maintained high potential, and then lost their potential (from D3 to D5), but were always re-polarizable after addition of substrates (glutamate, malate and succinate). From D7, the mitochondria were more strongly depolarized and were difficult to repolarize by the substrates. Using flow cytometry, we demonstrated that mitochondria were an excellent marker to confirm seabass freshness.

Genome-wide DNA methylation profiles provide insight into epigenetic regulation of red and white muscle development in Chinese perch Siniperca chuatsi.

Fish skeletal muscles are composed of spatially well-separated fiber types, namely, red and white muscles with different physiological functions and metabolism. To compare the DNA methylation profiles of the two types of muscle tissues and identify potential candidate genes for the muscle growth and development under epigenetic regulation, genome-wide DNA methylation of the red and white muscle in Chinese perch Siniperca chuatsi were comparatively analyzed using bisulfate sequencing methods. An average of 0.9 billion 150-bp paired-end reads were obtained, of which 86% were uniquely mapped to the genome. Methylation mostly occurred at CG sites at a ratio of 94.43% in the red muscle and 93.16% in the white muscle. The mean methylation levels at C-sites were 5.95% in red muscle and 5.83% in white muscle, whereas the mean methylation levels of CG, CHG, and CHH were 73.23%, 0.62%, and 0.67% in red muscle, and 71.01%, 0.62%, and 0.67% in white muscle, respectively. A total of 4192 differentially methylated genes (DMGs) were identified significantly enriched in cell signaling pathways related to skeletal muscle differentiation and growth. Various muscle-related genes, including myosin gene isoforms and regulatory factors, are differentially methylated in the promoter region between the red and white muscles. Further analysis of the transcriptional expression of these genes showed that the muscle regulatory factors (myf5, myog, pax3, pax7, and twitst2) and myosin genes (myh10, myh16, myo18a, myo7a, myo9a, and myl3) were differentially expressed between the two kinds of muscles, consistent with the DNA methylation analysis results. ELISA assays confirmed that the level of 5mC in red muscle was significantly higher than in white muscle (P<0.05). The RT-qPCR assays revealed that the expression levels of the three DNA methylation transferase (dnmt) subtypes, dnmt1, dnmt3ab, and dnmt3bb1, were significantly higher in red muscle than in white muscle. The higher DNA methylation levels in the red muscle may result from higher DNA methylation transferase expression in the red muscles. Thus, this study might provide a theoretical foundation to better understand epigenetic regulation in the growth and development of red and white muscles in animals, at least in Chinese perch fish.

Mitochondria are responsible for reactive oxygen species damage in fish muscle

Ever since the Great Oxygenation Event approximately 2.4 billion years ago, when cyanobacteria flooded the atmosphere with oxygen, life has been in a Faustian pact with the colourless gas. Oxygen reacts with glucose in cells to produce the energy that powers life through a chain of events that culminates within the mitochondria. However, these reactions with the life-giving gas also produce a plethora of toxic by-products, known as reactive oxygen species, which can in turn damage DNA, proteins and lipids in cells. The question was whether the mitochondrial powerhouses are the main source of harmful oxygen toxins, or whether they are generated by other sources in the cell. ‘People have assumed that mitochondria are the main culprits in reactive oxygen species production, but Yufeng Zhang and Hoi Shan Wong challenged this notion in a Commentary in Journal of Experimental Biology in 2021’, says Stephen Kinsey from the University of North Carolina Wilmington, USA.Fortunately, Kinsey and graduate student Julie Neurohr (University of North Carolina Wilmington) knew of a unique tissue that could help to answer the question: fish muscle. ‘Fish red and white muscle is easily delineated and metabolically distinct’, says Kinsey, explaining that red muscle is packed with mitochondria and consumes large quantities of oxygen, while the larger white muscles are largely devoid of mitochondria and depend instead on anaerobic metabolism. By comparing the amount of damage caused by reactive oxygen species in the two tissues – and how both forms of muscle deal with the collateral damage – Kinsey and Neurohr might be able to begin unravelling whether mitochondria are the key culprits in the oxidative damage sustained by fish muscle.After fishing for pinfish (Lagodon rhomboides) in the Intracoastal Waterway at Wrightsville Beach, USA, Kinsey, Neurohr and Erik Paulson (University of North Carolina Wilmington) used an electron microscope to scrutinise both forms of muscle, revealing that the red muscle was packed with 7 times more mitochondria (comprising 6.9% of the muscle volume) than the white muscle (0.89% muscle volume). And when Neurohr checked the amount of damage caused by reactive oxygen species to DNA, proteins and lipids in both forms of muscle, the red muscle came out on top, suffering the most damage in all three categories, despite having higher levels of the reactive oxygen species neutralising proteins – superoxide dismutase and catalase – for protection. The red muscle with larger quantities of mitochondria seemed to be at most risk from the damage caused by reactive oxygen species produced by the cell's powerhouses.So, how do vulnerable red muscle cells deal with the increased risk of tissue damage caused by oxygen? Knowing that cells resort to two different forms of disposal – an engulfing system to clear up larger clusters of damaged proteins and a more targeted strategy, the ubiquitin–proteasome system, to dispose of individual unravelling proteins – the team checked for evidence of both and found that the red muscle was best prepared for mopping up individual damaged proteins. In contrast, the white muscle allows damaged proteins to form larger clumps before engulfing them.And, when Neurohr checked how quickly both forms of muscle produced new proteins, the red muscle was working at almost double the rate of the white muscle to replace the damaged proteins. ‘Together, these results suggest that higher mitochondrial content, which imparts the capacity for endurance in muscle, is associated with greater oxidative damage and cellular maintenance’, says Kinsey.

A higher mitochondrial content is associated with greater oxidative damage, oxidative defenses, protein synthesis and ATP turnover in resting skeletal muscle.

An unavoidable consequence of aerobic metabolism is the production of reactive oxygen species (ROS). Mitochondria have historically been considered the primary source of ROS; however, recent literature has highlighted the uncertainty in primary ROS production sites and it is unclear how variation in mitochondrial density influences ROS-induced damage and protein turnover. Fish skeletal muscle is composed of distinct, highly aerobic red muscle and anaerobic white muscle, offering an excellent model system in which to evaluate the relationship of tissue aerobic capacity and ROS-induced damage under baseline conditions. The present study used a suite of indices to better understand potential consequences of aerobic tissue capacity in red and white muscle of the pinfish, Lagodon rhomboides. Red muscle had a 7-fold greater mitochondrial volume density than white muscle, and more oxidative damage despite also having higher activity of the antioxidant enzymes superoxide dismutase and catalase. The dominant protein degradation system appears to be tissue dependent. Lysosomal degradation markers and autophagosome volume density were greater in white muscle, while ubiquitin expression and 20S proteasome activity were significantly greater in red muscle. However, ubiquitin ligase expression was significantly higher in white muscle. Red muscle had a more than 2-fold greater rate of translation and total ATP turnover than white muscle, results that may be due in part to the higher mitochondrial density and the associated increase in oxidative damage. Together, these results support the concept that an elevated aerobic capacity is associated with greater oxidative damage and higher costs of protein turnover.

Red and white muscle proportions and enzyme activities in mesopelagic sharks.

In the last decade, there has been an increase in the study of the ecology of deep-sea organisms. One way to understand an organism's ecology is the study of its metabolism. According to literature, deep-sea sharks possess a lower anaerobic enzyme activity than their shallow-water counterparts, but no difference has been observed regarding their aerobic enzyme activities. These studies have suggested deep-sea sharks should be slow and listless swimmers. However, other studies based on video observations have revealed differences in cruise swimming speed between different species. The present study examined muscles of squaliform sharks, including both luminous and non-luminous species. We combined measurements of the relative amounts of red and white muscle with assays of enzymes that are used as markers for aerobic (citrate synthase, malate dehydrogenase) and anaerobic (lactate dehydrogenase) metabolism, searching for a relationship with cruising speeds. Non-luminous deep-sea species displayed lower aerobic enzyme activities but similar anaerobic enzyme activities than the benthic shallow-water counterpart (Squalus acanthias). Conversely, luminous Etmopteridae species were found to have similar aerobic enzyme activities to S. acanthias but displayed lower anaerobic enzyme activities. Analyses revealed that red muscle proportion and aerobic enzyme activities were positively related to the cruise swimming speed. In contrast, Dalatias licha, which swims at the slowest cruise swimming speed ever recorded, presented a very low aerobic metabolic phenotype (lower aerobic marker enzymes and less red muscle). Finally, the values obtained for white muscle proportion and anaerobic metabolic phenotype suggested a high burst capacity for D. licha and non-luminous sharks.

Carcass Yields and Physical-Chemical Meat Quality Characteristics of Namibian Red Hartebeest (Alcelaphus buselaphus) as Influenced by Sex and Muscle.

This study determined the carcass yields of red hartebeest from Namibia and compared the physical-chemical meat quality characteristics of six different muscles (biceps femoris, infraspinatus, longissimus thoracis et lumborum, semimembranosus, semitendinosus, and supraspinatus) for both males and females. Red hartebeest males were heavier (133.92 kg) than females (114.20 kg) but the average dressing percentage did not differ between the two sexes. Muscles from females had a lower mean shear force value of 3.59 kg/1.27 cm ø, compared to males (4.23 kg/1.27 cm ø). The most tender muscle was the infraspinatus of the female treatment group, while the semimembranosus of the male treatment group was the least tender muscle. Drip loss, cooking loss and L* (lightness) values were not affected by sex. The largest hue angle was observed in the semitendinosus muscle of the female treatment group (28.94°), and it was thus the lightest red muscle. The highest chroma values (17.3) were observed in the semimembranosus muscle. Muscle protein content averaged 20.5% over all treatment combinations, and the mean intra-muscular fat content for both male and female muscles was low (2.4%). The shoulder muscles, infraspinatus and supraspinatus, of the females had the highest fat content (2.7%). The results indicate that red hartebeest meat should be market according to specific muscles and that sex of the animals need not be considered during marketing.

Chromosome-Scale Genome Assembly and Transcriptome Assembly of Kawakawa Euthynnus affinis; A Tuna-Like Species.

Kawakawa Euthynnus affinis, also known as eastern little tuna or mackerel tuna, is a species of tuna (Thunnini tribe, subgroup Pelagiaria clade) (Sanciangco et al., 2016). Tuna includes 15 species: eight of genus Thunnus (true tuna) and seven “tuna-like” of four genera: Allothunnus, Auxis, Euthynnus, and Katsuwonus. E. affinis is widely distributed throughout the tropical and subtropical waters of the continental shelf areas of the Indo-Pacific region (Collette, 2001). The fish reaches a length of 45–60 cm and matures at approximately 3 years of age. It inhabits almost exclusively the upper layers of the ocean (Bernal et al., 2017) and feeds mainly on small pelagic fish (Griffiths et al., 2009). E. affinis makes up a substantial proportion of the commercial and artisanal fishery in many countries of the Indo-Pacific region. The meat of E. affinis is of high quality (Mukundan et al., 1979) with a comparatively high level of docosahexaenoic acid (Saito et al., 1999), but deteriorates rapidly if not properly handled (Mukundan et al., 1979). E. affinis exhibits the swimming mechanics of true tunas (Donley and Dickson, 2000) but has no swim bladder and differs from true tunas in red muscle distribution, allometry, and vascular anatomy (Bernal et al., 2017). The ability to maintain an elevated temperature in eye, brain, and red muscle has been suggested for the genus Euthynnus (Dickson et al., 2000), but reports specific to E. affinis are lacking. Compared to true tunas, E. affinis has received scant attention from researchers, and little is known about its biology and physiology. This is likely to change, as E. affinis has recently become of interest in marine aquaculture. E. affinis is the second tuna species whose full-life cycle culture in captivity has been developed so far, including spawning, egg collection, incubation, larval rearing, and grow-out to marketable size (Yazawa et al., 2015, 2016). Aquaculture in general is currently facing significant challenges to increasing production while maintaining sustainability (Bridson et al., 2020). Genetic improvement, via selective breeding and genetic engineering, is a major focus of research and can yield rapid benefits to efficient production in fish farming (Lu and Luo, 2020). To these ends, a high-quality species genome assembly is critical. Despite recent advances in sequencing technologies and genomics that, in addition to basic fish science (Lien et al., 2016; Hughes et al., 2018; Yuan et al., 2018; Du et al., 2020), have applications to aquaculture practices (Lu and Luo, 2020) and fisheries (Benestan, 2020), genomic information of tuna species is limited. To date, the genomes of only three tuna species are available in the public repositories, none of which are assembled to chromosome level. This situation exists within the entire Pelagiaria clade that, along with tuna, includes the economically important mackerel (Scombrini tribe) and bonito (Sardini tribe). Here, we report the chromosome-level genome assembly of kawakawa E. affinis (NCBI:txid8227). To our knowledge, this is the first available chromosome-level assembly within the Pelagiaria clade. The reported genome assembly is accompanied by transcriptome assembly, genetic linkage map, annotation of transposons, repetitive elements, and 23,059 genes. The dataset provides a solid genome resource not only for further study of E. affinis basic biology and genome-scale selective breeding but also for enhancing both basic and applied research within the Pelagiaria clade.

NMR-based metabolic profiling and discrimination of wild tropical tunas by species, size category, geographic origin, and on-board storage condition

Tunas are among the most traded and valued fish species, and good traceability of tuna products in the world market is needed to protect both consumers and tuna stocks. To that purpose, high-resolution proton nuclear magnetic resonance (1H NMR) spectroscopy combined with multivariate data analysis was used to investigate the molecular components of the aqueous extract of white and red muscles in three species of wild tropical tuna species, namely yellowfin tuna (Thunnus albacares), skipjack tuna (Katsuwonus pelamis) and bigeye tuna (T. obesus). Principal component analysis (PCA) and partial least squares-discriminant analysis (PLS-DA) applied to the processed 1H NMR spectra showed significant separation according to the species and size category (i.e., small tunas < 80 cm fork length vs large tunas > 80 cm fork length), the storage conditions on-board the purse-seine vessels (i.e., brine- vs deep-freezing), and the geographical origin (i.e., where the tuna was caught: Mozambique Channel vs western-central Indian Ocean). The major groups of metabolites responsible for differentiation in PLS-DA score plots were the dipeptides (anserine, carnosine) and organic acids (lactate, creatine/phosphocreatine) in the white muscle, and the free amino acids, essential nutrients (choline and its derivatives, phosphatidylethanolamine), dipeptides and organic acids in the red muscle. Our results showed that NMR-based metabolomics is a powerful tool to efficiently discriminate specific profiles among wild tuna species, raw muscle tissues, fish storage conditions and tuna geographical origin.

Molecular identification of glucose transporter 4: The responsiveness to starvation, glucose, insulin and glucagon on glucose transporter 4 in common carp (Cyprinus carpio L.).

Glucose transporter 4 (GLUT4) is comprehensively investigated in mammals, while the comparative research of GLUT4 in common carp is deficient. To investigate the function of GLUT4, carp glut4 was first isolated. The open reading frame of carp glut4 was 1518 bp in length, encoding 505 amino acids. A high-sequence homology was identified in carp and teleost, and the phylogenetic tree displayed that the carp GLUT4 was clustered with the teleost. A high level of glut4 mRNA was analysed in fat, red muscle and white muscle. After fasting treatment, glut4 mRNA expression was increased significantly in muscle. In the oral glucose tolerance test experiment, glut4 mRNA was also significantly elevated in muscle, gut and fat. Furthermore, intraperitoneal injection of insulin resulted in the upregulation of glut4 gene expression significantly in white muscle, gut and fat. On the contrary, the glut4 mRNA level in the white muscle, gut and fat was markedly downregulated after glucagon injection. These results suggest that GLUT4 might play important roles in food intake and could be regulated by nutrient condition, insulin and glucagon in common carp. Our study is the first to report on GLUT4 in common carp. These data provide a basis for further study on fish GLUT4.

Coming up for air

Coming up for air

Characterization of Carcass Color Differences Between Hens (Small Birds) and Meat-Type Male Pheasants (Large Birds)

The underlying changes in hen carcass color upon freezing were compared with the color of meat-type male pheasants upon freezing. Chemical and physical assessments of these two pheasant types (n=5) and the effects of different chilling methods on hen carcasses (n=10) were evaluated. The results showed that hen carcasses exhibited more red pigmentation (myoglobin, hemoglobin), as well as significantly higher pH values and redness, than the carcasses from meat-type pheasants. The moisture content was higher in hens than in meat-type pheasants, especially in the skin. The intermediate fiber (IIA) type was the only type found in the pectoralis major muscle, regardless of pheasant type. Chilling method significantly changed the color attributes of the hen carcass. Immersion chilling decreased skin redness (less pigmentation and Commission Internationale de l ́Eclairage [CIE] a*); the breast meat was less red than that from the chilling-in-a-bag condition. The skin had substantially higher levels of red pigmentation than the breast muscles, irrespective of the pheasant type and chilling method (P &amp;lt; 0.05). Our findings suggest that the more intense red appearance may be related to a combination of greater residual hemoglobin levels and higher pH within the skin. The greater moisture content of the skin may have facilitated the development of greater transparency to the darker, more red breast muscle.

Histological and biochemical evaluation of skeletal muscle in the two salmonid species Coregonus maraena and Oncorhynchus mykiss.

The growth of fishes and their metabolism is highly variable in fish species and is an indicator for fish fitness. Therefore, somatic growth, as a main biological process, is ecologically and economically significant. The growth differences of two closely related salmonids, rainbow trout (Oncorhynchus mykiss) and maraena whitefsh (Coregonus maraena), have not been adequately studied as a comparative study and are therefore insufficiently understood. For this reason, our aim was to examine muscle growth in more detail and provide a first complex insight into the growth and muscle metabolism of these two fish species at slaughter size. In addition to skeletal muscle composition (including nuclear counting and staining of stem and progenitor cells), biochemical characteristics, and enzyme activity (creatine kinase, lactate dehydrogenase, isocitrate dehydrogenase) of rainbow trout and maraena whitefish were determined. Our results indicate that red muscle contains cells with a smaller diameter compared to white muscle and those fibres had more stem and progenitor cells as a proportion of total nuclei. Interestingly, numerous interspecies differences were identified; in rainbow trout muscle RNA content, intermediate fibres and fibre diameter and in whitefish red muscle cross-sectional area, creatine kinase activity were higher compared to the other species at slaughter weight. The proportional reduction in red muscle area, accompanied by an increase in DNA content and a lower activity of creatine kinase, exhibited a higher degree of hypertrophic growth in rainbow trout compared to maraena whitefish, which makes this species particularly successful as an aquaculture species.

Exercise-induced angiogenesis is dependent on metabolically primed ATF3/4+ endothelial cells

SummaryExercise is a powerful driver of physiological angiogenesis during adulthood, but the mechanisms of exercise-induced vascular expansion are poorly understood. We explored endothelial heterogeneity in skeletal muscle and identified two capillary muscle endothelial cell (mEC) populations that are characterized by differential expression of ATF3/4. Spatial mapping showed that ATF3/4+ mECs are enriched in red oxidative muscle areas while ATF3/4low ECs lie adjacent to white glycolytic fibers. In vitro and in vivo experiments revealed that red ATF3/4+ mECs are more angiogenic when compared with white ATF3/4low mECs. Mechanistically, ATF3/4 in mECs control genes involved in amino acid uptake and metabolism and metabolically prime red (ATF3/4+) mECs for angiogenesis. As a consequence, supplementation of non-essential amino acids and overexpression of ATF4 increased proliferation of white mECs. Finally, deleting Atf4 in ECs impaired exercise-induced angiogenesis. Our findings illustrate that spatial metabolic angiodiversity determines the angiogenic potential of muscle ECs.

Temperature effects on the contractile performance and efficiency of oxidative muscle from a eurythermal versus a stenothermal salmonid.

ABSTRACTWe compared the thermal sensitivity of oxidative muscle function between the eurythermal Atlantic salmon (Salmo salar) and the more stenothermal Arctic char (Salvelinus alpinus; which prefers cooler waters). Power output was measured in red skeletal muscle strips and myocardial trabeculae, and efficiency (net work/energy consumed) was measured for trabeculae, from cold (6°C) and warm (15°C) acclimated fish at temperatures from 2 to 26°C. The mass-specific net power produced by char red muscle was greater than in salmon, by 2-to 5-fold depending on test temperature. Net power first increased, then decreased, when the red muscle of 6°C-acclimated char was exposed to increasing temperature. Acclimation to 15°C significantly impaired mass-specific power in char (by ∼40–50%) from 2 to 15°C, but lessened its relative decrease between 15 and 26°C. In contrast, maximal net power increased, and then plateaued, with increasing temperature in salmon from both acclimation groups. Increasing test temperature resulted in a ∼3- to 5-fold increase in maximal net power produced by ventricular trabeculae in all groups, and this effect was not influenced by acclimation temperature. Nonetheless, lengthening power was higher in trabeculae from warm-acclimated char, and char trabeculae could not contract as fast as those from salmon. Finally, the efficiency of myocardial net work was approximately 2-fold greater in 15°C-acclimated salmon than char (∼15 versus 7%), and highest at 20°C in salmon. This study provides several mechanistic explanations as to their inter-specific difference in upper thermal tolerance, and potentially why southern char populations are being negatively impacted by climate change.

Alanine alters the carbohydrate metabolism of rainbow trout: glucose flux and cell signaling.

In rainbow trout, dietary carbohydrates are poorly metabolized compared with other macronutrients. One prevalent hypothesis suggests that high dietary amino acid levels could contribute to the poor utilization of carbohydrates in trout. In mammals, alanine is considered an important gluconeogenic precursor, but has recently been found to stimulate AMP-activated protein kinase (AMPK) to reduce glucose levels. In trout, the effect of alanine on glucose flux is unknown. The goal of this study was to determine the effects of 4 h exogenous alanine infusion on glucose metabolism in rainbow trout. Glucose flux, and the rate of glucose appearance (Ra) and disposal (Rd) were measured in vivo. Key glycolytic and gluconeogenic enzyme expression and activity, and cell signaling molecules relevant to glucose metabolism were assessed in the liver and muscle. The results show that alanine inhibits glucose Ra (from 13.2±2.5 to 7.3±1.6 μmolkg-1 min-1) and Rd (from 13.2±2.5 to 7.4±1.5 μmolkg-1 min-1) and the slight mismatch between Ra and Rd caused a reduction in glycemia, similar to the effects of insulin in trout. The reduction in glucose Rd can be partially explained by a reduction in glut4b expression in red muscle. In contrast to mammals, trout alanine-dependent glucose-lowering effects did not involve hepatic AMPK activation, suggesting a different mechanistic basis. Interestingly, protein kinase B (AKT) activation increased only in muscle, similar to effects observed in insulin-infused trout. We speculate that alanine-dependent effects were probably mediated through stimulation of insulin secretion, which could indirectly promote alanine oxidation to provide the needed energy.

A 1-Month Ketogenic Diet Increased Mitochondrial Mass in Red Gastrocnemius Muscle, but Not in the Brain or Liver of Middle-Aged Mice.

Alterations in markers of mitochondrial content with ketogenic diets (KD) have been reported in tissues of rodents, but morphological quantification of mitochondrial mass using transmission electron microscopy (TEM), the gold standard for mitochondrial quantification, is needed to further validate these findings and look at specific regions of interest within a tissue. In this study, red gastrocnemius muscle, the prefrontal cortex, the hippocampus, and the liver left lobe were used to investigate the impact of a 1-month KD on mitochondrial content in healthy middle-aged mice. The results showed that in red gastrocnemius muscle, the fractional area of both subsarcolemmal (SSM) and intermyofibrillar (IMM) mitochondria was increased, and this was driven by an increase in the number of mitochondria. Mitochondrial fractional area or number was not altered in the liver, prefrontal cortex, or hippocampus following 1 month of a KD. These results demonstrate tissue-specific changes in mitochondrial mass with a short-term KD and highlight the need to study different muscle groups or tissue regions with TEM to thoroughly determine the effects of a KD on mitochondrial mass.

Health-Promoting Properties of the Wild-Harvested Meat of Roe Deer (Capreolus capreolus L.) and Red Deer (Cervus elaphus L.)

Simple SummaryDue to its chemical composition, roe and red deer meat can be a valuable component of a well-balanced diet for the modern consumer; however, the raw material from the carcasses of animals living in the wild can show differences in nutritional value. The present study provides an analysis of the content of basic nutrients (protein, fat, crude ash), Fe, Cd and Pb and fatty acid profile based on which the health-promoting value of wild-harvested roe deer and red deer meat was evaluated. Sixty carcasses were selected for chemical analysis; 30 of roe deer (15 does and 15 bucks) and 30 of red deer (15 hinds and 15 stags). The study leads to the conclusion that the evaluated meat of roe deer and red deer had high dietary value as it contained a high protein and low fat content and had an advantageous fatty acids composition. The noted content of cadmium and lead in the haunch of roe and red deer was significantly lower than permissible standard values, which corroborates that the meat is healthy and safe for consumers.The present studies aimed to analyse and assess the health-promoting properties of the musculus semimembranosus (MS) of roe and red deer harvested in the wild. The experimental materials comprising the carcasses of roe deer (15 does and 15 bucks) and red deer (15 hinds and 15 stags) were selected for analysis based on the following criteria: age of animals at harvest—3–4 years; time that passed from the harvest of animals to carcass cutting—48–54 h. After chilling the carcasses for 24 h at +2 °C, the haunches were cut from the carcasses and transported to the laboratory in isothermal ice-packed containers. Samples of the musculus semimembranosus were analysed to determine the chemical composition (proximate components, energy value, Fe, Pb, Cd, fatty acids). More (p ≤ 0.05) dry matter and total protein and less (p ≤ 0.05) crude fat was found in the musculus semimembranosus of roe deer in comparison to red deer. No significant influence of the animal’s sex was observed in the content of the evaluated nutrients, apart from crude fat content, which was increased in the haunch of females from both species. The energy content in the muscle of roe deer was 10% higher than the energy value of MS in red deer (p ≤ 0.05). The content of iron was significantly (p ≤ 0.05) higher (6.64 mg/kg) in the meat of red deer compared to the meat of roe deer (31.68 mg/kg). Roe deer haunch contained more lead but less cadmium than red deer haunch. Irrespective of sex, the lipid fraction of red deer muscle contained more saturated fatty acids (SFA). Intramuscular fat (IMF) in roe deer meat contained a higher percentage of polyunsaturated fatty acids (PUFA). The atherogenicity (AI) and thrombogenicity (TI) index values were significantly lower in roe deer haunch, and the hypocholesterolaemic-to-hypercholesterolaemic fatty acids ratio (HH) was lower (p ≤ 0.05) in red deer meat. To sum up, the evaluated roe deer and red deer haunch featured high dietary value as it contained a high protein and low fat content and had an advantageous fatty acids composition. As regards the content of cadmium and lead, roe deer and red deer haunch can be considered safe for consumers.