Two groups of juvenile gilthead sea bream were kept on two different swimming regimes (Exercise, E: 1.5 body length s(-1) or Control, C: voluntary activity) for 1 month. All fish were first adapted to an experimental diet low in protein and rich in digestible carbohydrates (37.2% protein, 40.4% carbohydrates, 12.5% lipid). The cellularity and capillarisation of white muscle from two selected areas (cranial (Cr), below the dorsal fin, and caudal (Ca), behind the anal fin) were compared. The body weight and specific growth rate (SGR) of group E rose significantly without an increment in feed intake, pointing to higher nutrient-use efficiency. The white muscle fibre cross-sectional area and the perimeter of cranial samples increased after sustained activity, evidencing that sustained exercise enhances hypertrophic muscle development. However, we cannot conclude or rule out the possibility of fibre recruitment because the experimental period was too short. In the control group, capillarisation, which is extremely low in gilthead sea bream white muscle, showed a significantly higher number of fibres with no surrounding capillaries (F0) in the cranial area than in the caudal area, unlike the exercise group. Sustained swimming improved muscle machinery even in tissue normally associated with short bouts of very rapid anaerobic activity. So, through its effect on the use of tissue reserves and nutrients, exercise contributes to improvements in fish growth what can contribute to reducing nitrogen losses.

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BackgroundThe adult skeletal muscle is a plastic tissue with a remarkable ability to adapt to different levels of activity by altering its excitability, its contractile and metabolic phenotype and its mass. We previously reported on the potential of adult zebrafish as a tractable experimental model for exercise physiology, established its optimal swimming speed and showed that swimming-induced contractile activity potentiated somatic growth. Given that the underlying exercise-induced transcriptional mechanisms regulating muscle mass in vertebrates are not fully understood, here we investigated the cellular and molecular adaptive mechanisms taking place in fast skeletal muscle of adult zebrafish in response to swimming.ResultsFish were trained at low swimming speed (0.1 m/s; non-exercised) or at their optimal swimming speed (0.4 m/s; exercised). A significant increase in fibre cross-sectional area (1.290 ± 88 vs. 1.665 ± 106 μm2) and vascularization (298 ± 23 vs. 458 ± 38 capillaries/mm2) was found in exercised over non-exercised fish. Gene expression profiling by microarray analysis evidenced the activation of a series of complex transcriptional networks of extracellular and intracellular signaling molecules and pathways involved in the regulation of muscle mass (e.g. IGF-1/PI3K/mTOR, BMP, MSTN), myogenesis and satellite cell activation (e.g. PAX3, FGF, Notch, Wnt, MEF2, Hh, EphrinB2) and angiogenesis (e.g. VEGF, HIF, Notch, EphrinB2, KLF2), some of which had not been previously associated with exercise-induced contractile activity.ConclusionsThe results from the present study show that exercise-induced contractile activity in adult zebrafish promotes a coordinated adaptive response in fast muscle that leads to increased muscle mass by hypertrophy and increased vascularization by angiogenesis. We propose that these phenotypic adaptations are the result of extensive transcriptional changes induced by exercise. Analysis of the transcriptional networks that are activated in response to exercise in the adult zebrafish fast muscle resulted in the identification of key signaling pathways and factors for the regulation of skeletal muscle mass, myogenesis and angiogenesis that have been remarkably conserved during evolution from fish to mammals. These results further support the validity of the adult zebrafish as an exercise model to decipher the complex molecular and cellular mechanisms governing skeletal muscle mass and function in vertebrates.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-15-1136) contains supplementary material, which is available to authorized users.

In recent years, the altitude acclimatization responses elicited by short-term intermittent exposure to hypoxia have been subject to renewed attention. The main goal of short-term intermittent hypobaric hypoxia exposure programs was originally to improve the aerobic capacity of athletes or to accelerate the altitude acclimatization response in alpinists, since such programs induce an increase in erythrocyte mass. Several model programs of intermittent exposure to hypoxia have presented efficiency with respect to this goal, without any of the inconveniences or negative consequences associated with permanent stays at moderate or high altitudes. Artificial intermittent exposure to normobaric hypoxia systems have seen a rapid rise in popularity among recreational and professional athletes, not only due to their unbeatable cost/efficiency ratio, but also because they help prevent common inconveniences associated with high-altitude stays such as social isolation, nutritional limitations, and other minor health and comfort-related annoyances. Today, intermittent exposure to hypobaric hypoxia is known to elicit other physiological response types in several organs and body systems. These responses range from alterations in the ventilatory pattern to modulation of the mitochondrial function. The central role played by hypoxia-inducible factor (HIF) in activating a signaling molecular cascade after hypoxia exposure is well known. Among these targets, several growth factors that upregulate the capillary bed by inducing angiogenesis and promoting oxidative metabolism merit special attention. Applying intermittent hypobaric hypoxia to promote the action of some molecules, such as angiogenic factors, could improve repair and recovery in many tissue types. This article uses a comprehensive approach to examine data obtained in recent years. We consider evidence collected from different tissues, including myocardial capillarization, skeletal muscle fiber types and fiber size changes induced by intermittent hypoxia exposure, and discuss the evidence that points to beneficial interventions in applied fields such as sport science. Short-term intermittent hypoxia may not only be useful for healthy people, but could also be considered a promising tool to be applied, with due caution, to some pathophysiological states.

Marine and freshwater algae and their products are in growing demand worldwide because of their nutritional and functional properties. Microalgae (unicellular algae) will constitute one of the major foods of the future for nutritional and environmental reasons. They are sources of high-quality protein and bioactive molecules with potential application in the modern epidemics of obesity and diabetes. They may also contribute decisively to sustainability through carbon dioxide fixation and minimization of agricultural land use. This paper reviews current knowledge of the effects of consuming edible microalgae on the metabolic alterations known as metabolic syndrome (MS). These microalgae include Chlorella, Spirulina (Arthrospira) and Tetraselmis as well as Isochrysis and Nannochloropsis as candidates for human consumption. Chlorella biomass has shown antioxidant, antidiabetic, immunomodulatory, antihypertensive, and antihyperlipidemic effects in humans and other mammals. The components of microalgae reviewed suggest that they may be effective against MS at two levels: in the early stages, to work against the development of insulin resistance (IR), and later, when pancreatic -cell function is already compromised. The active components at both stages are antioxidant scavengers and anti-inflammatory lipid mediators such as carotenoids and -3 PUFAs (eicosapentaenoic acid/docosahexaenoic acid; EPA/DHA), prebiotic polysaccharides, phenolics, antihypertensive peptides, several pigments such as phycobilins and phycocyanin, and some vitamins, such as folate. As a source of high-quality protein, including an array of bioactive molecules with potential activity against the modern epidemics of obesity and diabetes, microalgae are proposed as excellent foods for the future. Moreover, their incorporation into the human diet would decisively contribute to a more sustainable world because of their roles in carbon dioxide fixation and reducing the use of land for agricultural purposes.

Seven healthy young men were submitted twice to a hypoxia tolerance test at a simulated altitude (3000 m). Their first acute exposure was in a hypobaric chamber; and the second, in a hypoxic tent. Cardiorespiratory parameters and heart rate variability measurements were obtained under each hypoxic condition. A significant decrease of 6% to 8% compared to normal oxygen conditions was observed in arterial oxygen saturation (SpO 2 ) in both hypoxic conditions at rest; whereas exercise led to decreases of 10% in SpO 2 despite an increase of 27% in respiratory minute volume. The low frequency (LF) and high frequency (HF) components of heart rate variability significantly changed from normoxia (LF: 37.1, HF: 62.9, LF/HF: 1.27) to hypobaric hypoxia (HH) (LF: 49.1, HF: 50.6, LF/HF: 1.96). However, these changes were not observed under normobaric hypoxia. Thus, heart rate variability behaved differently in the two hypoxic conditions, supporting the hypothesis that normobaric hypoxia and hypobaric hypoxia are not equal stimuli to the cardiovascular and respiratory systems. A correlation was found between sympathetic and vagal modulations in normoxia and SpO 2 at exercise under hypobaric hypoxia (HH). Individuals with higher sympathetic modulation (LF%) in normoxia had higher SpO 2 at exercise under HH (r = 0.808, P < 0.05) and individuals with higher vagal modulation (HF%) in normoxia showed a trend to lower SpO 2 in exercise under HH (r = −0.636, P = 0.125). This opens up the possibility of using this correlation as a tool for predicting the individual capacity to altitude acclimatization. © 2011 Consell Català de l'Esport. Generalitat de Catalunya. Published by Elsevier España, S.L. All rights reserved. * Corresponding author. E-mail address: gviscor@ub.edu (G. Viscor). PALABRAS CLAVEVariabilidad de la frecuencia cardiaca; Prueba de tolerancia a hipoxia; Tienda hipóxica; Cámara hipobárica; Saturación arterial de oxígeno Parámetros cardiorrespiratorios durante ejercicio submáximo en hipoxia aguda hipobárica y normobáricaResumen Siete jóvenes sanos y en buena condición física realizaron dos pruebas de tolerancia a hipoxia a una altitud simulada de 3.000 m. La primera fue en cámara hipobárica, mientras que la segunda se efectuó en una tienda hipóxica. Se registraron varios parámetros cardiorrespiratorios y la variabilidad de la frecuencia cardiaca. En comparación con las condiciones de normoxia, se observó un decremento significativo del 6% al 8% en la saturación de oxígeno arterial (SpO 2 ) en reposo en ambas condiciones de hipoxia. El ejercicio desencadenó descensos de un 10% en SpO 2 pese a un incremento del 27% del volumen minuto ventilatorio. Tanto los componentes de baja (LF) como alta frecuencia (HF) de la variabilidad del ritmo cardiaco cambiaron significativamente en hipoxia hipobárica (LF: 49,1, HF: 50,6, LF/HF: 1,96) respecto a normoxia (LF: 37,1, HF: 62,9, LF/HF: 1,27). Estos cambios no se apreciaron en condiciones de hipoxia normobárica, lo cual apoya la hipótesis de que la hipoxia hipobárica y norm...

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Mitochondrial membrane lipid composition is a critical factor in non-alcoholic steatohepatitis (NASH). Exercise is the most prescribed therapeutic strategy against NASH and a potential modulator of lipid membrane. Thus, we aimed to analyze whether physical exercise exerted preventive (voluntary physical activity - VPA) and therapeutic (endurance training - ET) effect on NASH-induced mitochondrial membrane changes. Sprague-Dawley rats (n=36) were divided into standard-diet sedentary (SS, n=12), standard-diet VPA (SVPA, n=6), high-fat diet sedentary (HS, n=12) and high-fat diet VPA (HVPA, n=6). After 9 weeks of diet-specific feeding, half of SS and HS group were engaged in an ET program for 8 weeks/5 day/week/1h/day (SET, HET). Liver mitochondria were isolated for oxygen consumption and transmembrane-electric potential (ΔΨ) assays. Mitochondrial phospholipid classes and fatty acids were quantified through thin layer chromatography and gas chromatography, respectively, while cardiolipin (CL), phosphatidylcholine (PC) phosphatidylethanolamine (PE) and phosphatidylinositol (PI) molecular profile was determined by electrospray mass spectrometry. In parallel with histological signs of NASH, high-fat diet decreased PI, CL and PC/PE ratio, whereas PE and phosphatidic acid content increased in sedentary animals (HS vs. SS). Moreover, a decrease in linolelaidic, monounsaturated fatty acids content and an increase in saturated fatty acids (SFAS) were observed. Along with phospholipidomic alterations, HS animals showed a decrease in respiratory control ratio (RCR), ΔΨ and FCCP-induced uncoupling respiration (HS vs. SS). Both phospholipidomic (PC/PE, SFAS) and mitochondrial respiratory alterations were counteracted by exercise interventions. Exercise used as preventive (VPA) or therapeutic (ET) strategies preserved liver mitochondrial phospholipidomic profile and maintained mitochondrial function in a model of NASH.