Down-regulation of MyoD gene expression in rat diaphragm muscle with heart failure

Diaphragm myopathy has been described in patients with heart failure (HF), with alterations in myosin heavy chains (MHC) expression. The pathways that regulate MHC expression during HF have not been described, and myogenic regulatory factors (MRFs) may be involved. The purpose of this investigation was to determine MRF mRNA expression levels in the diaphragm. Diaphragm muscle from both HF and control Wistar rats was studied when overt HF had developed, 22 days after monocrotaline administration. MyoD, myogenin and MRF4 gene expression were determined by RT-PCR and MHC isoforms by polyacrylamide gel electrophoresis. Heart failure animals presented decreased MHC IIa/IIx protein isoform and MyoD gene expression, without altering MHC I, IIb, myogenin and MRF4. Our results show that in HF, MyoD is selectively down-regulated, which might be associated with alterations in MHC IIa/IIx content. These changes are likely to contribute to the diaphragm myopathy caused by HF.

Inflammation and apoptosis induced by mastoparan Polybia-MPII on skeletal muscle

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Metabolic responses to acute physical exercise in young rats recovered from fetal protein malnutrition with a fructose-rich diet

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Carcass characteristics of broilers at 42 days receiving diets with phytase in different energy and crude protein levels

Objetivou-se, com este trabalho, estudar as características de carcaça e qualidade da carne do peito depois da inclusão de fitase em dietas para frangos de corte, com diferentes níveis de energia metabolizável aparente corrigida para nitrogênio (EMAn) e proteína bruta (PB) reduzida, suplementadas com aminoácidos essenciais seguindo o conceito de proteína ideal. Foram utilizados 1.500 frangos machos Cobb dos 22 aos 42 dias de idade com peso inicial de 833 ± 7 g e final de 2741 ± 48 g distribuídos em delineamento inteiramente casualizado em esquema fatorial 3x3+1 (três níveis de EMAn - 2950, 3100 e 3250 kcal/kg - e três de PB - 14, 16 e 18% - e um tratamento adicional - controle, sem fitase, com 3100 kcal/kg EMAn, 19,2% de PB e 0,4% de fósforo disponível) em seis repetições com 25 aves cada. Ao final do experimento, duas aves de cada parcela foram sacrificadas para a mensuração do rendimento de carcaça e de cortes e determinação da composição química da carne do peito. Os níveis de energia e proteína em rações com fitase influenciaram (P<0,05) os rendimentos de carcaça, peito e gordura abdominal a porcentagem de umidade, proteína e lipídios no músculo pectoralis major das aves, sendo os níveis de 3100 kcal EMAn/kg e 18% de PB os que proporcionaram maiores rendimentos de carcaça e de peito e menor deposição de gordura abdominal, mas em maior teor de lipídios na carne do peito. Conclui-se que a manipulação da energia em rações com reduzido teor de proteína e suplementadas com aminoácidos e fitase influencia o rendimento de cortes e a qualidade da carne do peito de frangos aos 42 dias.

Hydrolyzed alpha-lactalbumin as a source of protein to the exercising

This work describes the effect of feeding enzymatically hydrolyzed a-lactalbumin on blood sugar, albumin and fatty acids, muscular and hepatic glycogen of rats subjected to physical exercise. Three normoenergetic/normoproteic diets, containing either casein (C), alpha-lactalbumin (L) or alpha-lactalbumin hydrolyzate (H) were fed to thirty male Wistar rats for five weeks. During this period, half of the rats swam for 1 hr daily (T category) while the other half remained sedentary (S category). At the end of training, all rats were required to swim to exhaustion. The results showed that those rats of the T-category consuming diet H reached exhaustion with significantly higher concentrations of serum glucose ([H] 56.0 and [L] 32.3 mg/100ml), serum albumin ([H] 3.8 and [L] 2.1 mg/dl) and muscle glycogen ([H] 2.1 and [L] 0.6 mg/g), while no differences were observed between diets regarding the time of arrival to exhaustion. Results from diets C and L differed minimally. It was concluded that feeding the hydrolyzed protein may result in nutritional advantage to the exercising rat. (C) 1998 Elsevier B.V.

CONCERTED ACTION OF THE HIGH-AFFINITY CALCIUM-BINDING SITES IN SKELETAL-MUSCLE TROPONIN-C

Mutants of each of the four divalent cation binding sites of chicken skeletal muscle troponin C (TnC) were constructed using site directed mutagenesis to convert Asp to Ala at the first coordinating position in each site. With a view to evaluating the importance of site-site interactions both within and between the N- and C-terminal domains, in this study the mutants are examined for their ability to associate with other components of the troponin-tropomyosin regulatory complex and to regulate thin filaments. The functional effects of each mutation in reconstitution assays are largely confined to the domain in which it occurs, where the unmutated site is unable to compensate for the defect, Thus the mutants of sites I and II bind to the regulatory complex but are impaired in ability to regulate tension and actomyosin ATPase activity, whereas the mutants of sites III and IV regulate activity but are unable to remain bound to thin filaments unless Ca2+ is present. When all four sites are intact, free Mg2+ causes a 50-60-fold increase in TnC's affinity for the other components of the regulatory complex, allowing it to attach firmly to thin filaments. Calcium can replace Mg2+ at a concentration ratio of 1:5000, and at this ratio the Ca2 . TnC complex is more tightly bound to the filaments than the Mg2 . TnC form, In the C-terminal mutants, higher concentrations of Ca2+ (above tension threshold) are required to effect this transformation than in the recombinant wild-type protein, suggesting that the mutants reveal an attachment mediated by Ca2+ in the N-domain sites.

Chemical composition and tenderness of longissimus dorsi muscle from non- castrated Murrah buffaloes slaughtered at different weights

Buffalo meat production has been arising interest breeder and emerges as alternative to consumer, more and more demanding of the quality products. Thus, this research was conducted to study the chemical composition and tenderness of Longissimus dorsi muscle from 10 non-castrated Murrah buffaloes slaughtered at different weights. The research was carried in feedlot of School of Veterinary Medicine and Animal Science of the São Paulo State University, Botucatu, São Paulo, Brazil. Animals were divided in two groups, received diet ad libitum and slaughtered when reached 450 and 500 kg of live weight. The experiment design was completely randomized, with five repetitions to each treatment. Meat sample from Longissimus dorsi muscle, taken between 12(th) and 13(th) ribs, were carried analysis of moisture, crude protein, fat, ash, Longissimus muscle area (LMA), fat thickness (FT), marbling, calorie and tenderness. It did not have significant difference between the groups. Average values at of 76.0; 20.7; 2.1 and 1.2 of moisture, crude protein, fat and ash respectively, were obtained. Calorie, tenderness, LMA, FT and marbling were obtained at average values of 132 kca1/100g; 3.94 kgf; 34.2 cm(2); 5.9 mm and 2 points, respectively. Values obtained for tenderness are similar in the literature and has been proving that buffalo meat is tender (< 5kgf). Positive correlation was observed between the protein percentage and the shear force of the meat. The buffalo meat is excellent alternative source of red protein of high biological value to feeding of Brazilian consumers.

Effects of soy protein and resistance exercise on body composition and blood lipids in postmenopausal women

Objective: To assess the effect of soy protein and progressive resistance training on body composition and lipids in postmenopausal women.Design: In a controlled trial, 46 postmenopausal women were randomized to one of four groups: 25 g of soy protein (SP, n = 10), 25 g of soy protein plus resistance exercise (SPE, n = 14), 25 g of maltodextrine (placebo) (PL, n = 11), or placebo plus resistance exercise (PLE, n = 11). Progressive resistance training was held three times a week for 16 weeks and included 8 exercises (3 series of 8-12 repetitions). At baseline and after 16 weeks, body mass index, waist circumference (WC), body fat, muscle mass and serum lipid levels were measured. To confirm isoflavone absorption, urinary concentrations were determined. The t-test of Student and ANOVA were used in the statistical analysis.Results: Subjects were classified as overweight and showed android fat distribution: Urinary isoflavone excretion indicated compliance to soy protein treatment. After 16 weeks of intervention, both SPE and PLE groups showed a significant increase of 1.3 kg in muscle mass and reduction in WC of -1.4 and -2.1 cm, respectively (p < 0.05). Significant decreases in the mean values of total cholesterol and LDL (-29.0 and -24.0 mg/dL, p < 0.001 and p < 0.006, respectively) were observed in the users of soy protein alone (SP).Conclusions: Soy protein supplementation did not influence the indicators of body composition. However, it exerted possible favorable effects on lipid profile in postmenopausal women. The increase in muscle mass and reduction in abdominal fat were correlated with resistance training. (c) 2006 Elsevier B.V.. All rights reserved.

Effects of dietary macronutrient content on energy metabolism and uncoupling protein mRNA expression in broiler chickens

The objective of the present study was to investigate the effects of dietary macronutrient ratio on energy metabolism and on skeletal muscle mRNA expression of avian uncoupling protein (UCP), thought to be implicated in thermogenesis in birds. Broiler chickens from 2 to 6 weeks of age received one of three isoenergetic diets containing different macronutrient ratios (low-lipid (LL) 30 v. 77 g lipid/kg-, low-protein (LP) 125 v. 197 g crude protein (N X 6.25)/kg; low-carbohydrate (LC) 440 v. 520 g carbohydrate/kg). LP chickens were characterised by significantly lower body weights and food intakes compared with LL and LC chickens (-47 and -38% respectively) but similar heat production/kg metabolic body weight, as measured by indirect calorimetry, in the three groups. However, heat production/g food ingested was higher in animals receiving the LP diet (+41%, P<0.05). These chickens also deposited 57% less energy as protein (P<0.05) and 33% more as fat. No significant differences in energy and N balances were detected between LL and LC chickens. The diets with the higher fat contents (i.e. The LP and LC diets) induced slightly but significantly higher relative expressions of avian UCP mRNA in gastrocnemius muscle, measured by reverse transcription-polymerase chain reaction, than the LL diet (88 and 90 v. 78% glyceraldehyde-3-phosphate dehydrogenase respectively, P<0.05). Our present results are consistent with the recent view that UCP homologues could be involved in the regulation of lipid utilisation as fuel substrate and provide evidence that the macronutrient content of the diet regulates energy metabolism and especially protein and fat deposition.

Expression of heat shock protein in broiler embryo tissues after acute cold or heat stress

This study evaluated the expression of heat shock protein 70 kD (hsp70) in broiler chicken embryos subjected to cold (Experiment 1) or high incubation temperature (Experiment 11). In each experiment, fertile eggs were distributed in three incubators kept at 37.8degreesC. At day 13 (D13), D16, and D19 of incubation, the embryos were subjected to acute cold (32degreesC) or heat (40degreesC) for 4-6 hr. Immediately after cold or heat exposure, samples from the liver, heart, breast muscle, brain, and lungs of 40 embryos were taken per age and treatment (control or stressed embryos), A tissue pool from 10 embryos was used as 1 replication. The levels of hsp70 in each tissue sample was quantified by Western blot analysis. The data were analyzed in a 3 x 2 factorial arrangement of treatments with four replications. hsp70 was detected in all embryo tissues, and the brain contained 2- to 5-times more hsp70 protein compared to the other tissues in either cold or heat stressed embryos. hsp70 increases were observed in the heart and breast muscle of cold stressed embryos at D16 and D19, respectively. Heat stressed embryos showed an increase of hsp70 in the heart at D13 and D19, and in the lung at D19 of incubation. Younger embryos had higher hsp70 synthesis than older embryos, irrespective of the type of thermal stressor. The results indicate that the expression of hsp70 in broiler chicken embryos is affected by cold and heat distress, and is tissue- and age-dependent. (C) 2004 Wiley-Liss, Inc.

GNN is a self-glucosylating protein involved in the initiation step of glycogen biosynthesis in Neurospora crassa

The initiation of glycogen synthesis requires the protein glycogenin, which incorporates glucose residues through a self-glucosylation reaction, and then acts as substrate for chain elongation by glycogen synthase and branching enzyme. Numerous sequences of glycogenin-like proteins are available in the databases but the enzymes from mammalian skeletal muscle and from Saccharomyces cerevisiae are the best characterized. We report the isolation of a cDNA from the fungus Neurospora crassa, which encodes a protein, GNN, which has properties characteristic of glycogenin. The protein is one of the largest glycogenins but shares several conserved domains common to other family members. Recombinant GNN produced in Escherichia coli was able to incorporate glucose in a self-glucosylation reaction, to trans-glucosylate exogenous substrates, and to act as substrate for chain elongation by glycogen synthase. Recombinant protein was sensitive to C-terminal proteolysis, leading to stable species of around 31 kDa, which maintained all functional properties. The role of GNN as an initiator of glycogen metabolism was confirmed by its ability to complement the glycogen deficiency of a S. cerevisiae strain (glg1 glg2) lacking glycogenin and unable to accumulate glycogen. Disruption of the gnn gene of N. crassa by repeat induced point mutation (RIP) resulted in a strain that was unable to synthesize glycogen, even though the glycogen synthase activity was unchanged. Northern blot analysis showed that the gnn gene was induced during vegetative growth and was repressed upon carbon starvation. (C) 2004 Elsevier B.V. All rights reserved.

Role of endothelial cell apoptosis in regulation of skeletal muscle angiogenesis during high and low salt intake

Angiogenesis, under normal conditions, is a tightly regulated balance between pro- and antiangiogenic factors. The goal of this study was to investigate the mechanisms involved in the control of the skeletal muscle angiogenic response induced by electrical stimulation during the suppression of plasma renin activity (PRA) with a high-salt diet. Rats fed 0.4% or 4% salt diets were exposed to electrical stimulation for 7 days. The tibialis anterior ( TA) muscles from stimulated and unstimulated hindlimbs were removed and prepared for gene expression analysis, CD31-terminal deoxynucleotide transferase-mediated dUTP nick-end labeling ( TUNEL) double-staining assay, and Bcl-2 and Bax protein expression by Western blot. Rats fed a low-salt diet showed a dramatic angiogenesis response in the stimulated limb compared with the unstimulated limb. This angiogenesis response was significantly attenuated when rats were placed on a high-salt diet. Microarray analysis showed that in the stimulated limb of rats fed a low-salt diet many genes related to angiogenesis were upregulated. In contrast, in rats fed a high-salt diet most of the genes upregulated in the stimulated limb function in apoptosis and cell cycle arrest. Endothelial cell apoptosis, as analyzed by CD31-TUNEL staining, increased by fourfold in the stimulated limb compared with the unstimulated limb. There was also a 48% decrease in the Bcl-2-to-Bax ratio in stimulated compared with unstimulated limbs of rats fed a high-salt diet, confirming severe apoptosis. This study suggests that the increase in endothelial cell apoptosis in TA muscle might contribute to the attenuation of angiogenesis response observed in rats fed a high-salt diet.

EFFECTS OF INTRAUTERINE AND POSTNATAL PROTEIN-CALORIE MALNUTRITION ON METABOLIC ADAPTATIONS TO EXERCISE IN YOUNG-RATS

The effect of intrauterine and postnatal protein-calorie malnutrition on the biochemical ability to perform exercise was investigated in young male rats. Malnourished rats were obtained by feeding dams a low-protein (6%) casein-based diet prepared in the laboratory during pregnancy and lactation. Control rats received an isocaloric diet containing 25% protein. The low-protein diet contained additional starch and glucose. At 45 days of age, malnourished rats showed lower body weight, serum protein, albumin and glucose levels, hematocrit values and heart glycogen content but higher circulating free fatty acids and gastrocnemius muscle glycogen than control rats. In response to exercise (50 min of swimming), control rats displayed lower heart, gastrocnemius and liver glycogen levels whereas malnourished rats showed low glycogen levels only in the gastrocnemius muscle. Both control and malnourished rats showed high serum glucose and free fatty acid levels after exercise. In conclusion, protein-calorie malnutrition improved muscle glycogen storage but this substrate was broken down to a greater extent in response to exercise. Malnourished rats were able to perform exercise maintaining high blood glucose levels, as observed in control rats, perhaps as a consequence of the elevated availability of circulating free fatty acids.

A Preliminary and Qualitative Metallomics Study of Mercury in the Muscle of Fish from Amazonas, Brazil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)