Effects of Delaying Post-hatch Feeding on the Plasma Metabolites of Broiler Chickens Revealed by Targeted and Untargeted Metabolomics.

Exogenous nutrients are essential for body and skeletal muscle growth in newly hatched chicks, and delaying post-hatch feeding negatively affects body growth, meat yield, and meat quality. The aim of this study was to investigate the effects of delayed post-hatch feeding on the metabolic profiles of broiler chickens using a combination of targeted and untargeted metabolomics. Newly hatched chicks had either immediate free access to feed (freely fed chicks) or no access to feed from 0 to 2 days of age (delayed-fed chicks); both groups were subsequently provided feed ad libitum until 13 days of age. Untargeted metabolomic analysis was performed using gas chromatography-mass spectrometry, whereas targeted metabolomic analysis of amino acids was performed using high-performance liquid chromatography with ortho-phthalaldehyde derivatization. Delayed feeding increased the plasma levels of sucrose, maltose, serotonin, lactitol, gentiobiose, xylitol, threonic acid, and asparagine, and decreased the plasma levels of creatinine, aspartic acid, and glutamic acid. In addition, the digestibility of the nitrogen-free extract (starch and sugar) and the cecal butyric acid concentration increased in chicks subjected to delayed feeding. In contrast, delayed feeding did not affect muscle protein degradation or digestibility in chicks. Taken together, our results indicate that delaying feeding until 48 h post-hatch alters multiple metabolic pathways, which are accompanied by changes in intestinal carbohydrate digestion and cecal butyric acid content in broiler chickens.

Regulation of autophagy in chick myotube cultures: Effect of uncoupling mitochondrial oxidative phosphorylation.

Abstracts: Skeletal muscles have a high demand for ATP, which is met largely through mitochondria oxidative phosphorylation. Autophagy is essential for the maintenance of skeletal muscle mass under catabolic conditions. This study investigated the effect of uncoupling mitochondrial oxidative phosphorylation on autophagy in chicken skeletal muscle. Chick myotubes were incubated with the mitochondrial uncoupler carbonyl cyanide m-chlorophenyl hydrazone (CCCP) at 25 µM for 3h. CCCP prevented the phosphorylation of p70 ribosomal S6 kinase 1 (Thr389), S6 ribosomal protein (Ser240/244), and eukaryotic translation initiation factor 4E-binding protein 1 (Thr37/46), which are the measures of the mechanistic target of rapamycin complex 1 (mTORC1) activity. CCCP significantly increased cytoplasmic and mitochondrial LC3-II content, which act as indices of index for autophagosome formation and mitophagy, respectively, but did not influence the expression of autophagy-related genes LC3B, GABARAPL1, and ATG12. Finally, surface sensing of translation method revealed that protein synthesis, a highly energy consuming process, was significantly decreased upon CCCP treatment. These results indicate that the uncoupling of mitochondrial oxidative phosphorylation stimulates autophagy and inhibits protein synthesis through mTORC1 signaling in chick myotube cultures.

Effects of low-protein diet and feed restriction on mRNA expression of cationic amino acid transporters in porcine skeletal muscles.

We investigated the effects of a low-protein diet and feed restriction on the mRNA expression of cationic amino acid transporters (CATs) in the longissimus dorsi (LD), rhomboideus (RH), and biceps femoris (BF) muscles of pigs. Eighteen piglets were divided into three groups: a control (CP21%), low-protein diet (LP, CP16%), and feed-restricted diet (FR, CP21%, 76% feed intake of control pigs) groups. The expression levels of CAT-1 in the LD and BF muscles of LP pigs were higher than that of control pigs, whereas that of FR pigs showed no difference. The CAT-2A expression levels in the RH muscle of FR pigs were higher than that of control pigs. The free lysine concentrations in all muscles of LP and FR pigs were lower than that of control pigs. To examine the factors that affect CATs mRNA expression, we evaluated the effects of lysine, arginine, insulin-like growth factor-I, and dexamethasone on the expression of CATs in C2C12 myotubes. CAT-1 expression levels increased in lysine and/or arginine deprivation. We show that CAT-1 and CAT-2A expression levels in skeletal muscles differ in response to dietary treatments and CAT-1 expression in skeletal muscles appears to increase in response to low free lysine concentrations.

AMP-activated Protein Kinase Activation Suppresses Protein Synthesis and mTORC1 Signaling in Chick Myotube Cultures.

Protein synthesis in skeletal muscle is considered one of the most energy-consuming cellular processes. AMP-activated protein kinase (AMPK) is a metabolic master switch that regulates glucose and lipid metabolism, and it is implicated in protein synthesis control in skeletal muscles. The mechanistic target of rapamycin complex 1 (mTORC1) is a central regulator of protein metabolism in cells. However, the effect of AMPK activation on protein synthesis and mTORC1 signaling in chicken skeletal muscle remains unclear. Therefore, in this study, we aimed to investigate the effect of 5-aminoimidazole-4-carboxamide-1-ß-D-ribofuranoside (AICAR), an AMPK activator, on protein synthesis and mTORC1 signaling in chick myotube cultures. The incubation of chick myotubes with AICAR (1 mM) for 3 h led to a significant increase in AMPK (Thr172) phosphorylation. Nonetheless, protein synthesis, measured using the surface sensing of translation method, was significantly decreased by AICAR. In addition, the phosphorylation of p70 ribosomal S6 kinase 1 (S6K1, Thr389), S6 ribosomal protein (Ser240/244), and eukaryotic translation initiation factor 4E-binding protein 1 (4E-BP1, Thr37/46) was significantly reduced by AICAR. These results suggest that AMPK activation suppresses protein synthesis and mTORC1 signaling (through the phosphorylation of S6K1, S6 ribosomal protein, and 4E-BP1) in chick myotubes.

Suppression of FoxO1 mRNA by ß2 -adrenoceptor-cAMP signaling through miR-374b-5p and miR-7a-1-3p in C2C12 myotubes.

ß2 -Adrenoceptor (ß2 -AR) signaling decreases the transcriptional activity of forkhead box O (FoxO), but the underlying mechanisms remain incompletely understood. Here, we investigated how ß2 -AR signaling regulates the protein abundance of FoxO and its transcriptional activity in skeletal muscle. We observed that stimulation of ß2 -AR with its selective agonist, clenbuterol, rapidly decreased FoxO1 mRNA expression, and this was accompanied by a decrease in either FoxO1 protein level or FoxO transcriptional activity. We subsequently observed that miR-374b-5p and miR-7a-1-3p were rapidly upregulated in response to ß2 -AR stimulation. Transfection with mimics of either miRNA successfully decreased FoxO1 mRNA. Moreover, because ß2 -AR stimulation increased cAMP concentration, pretreatment with an adenylyl cyclase inhibitor canceled out these effects of ß2 -AR stimulation. These results suggest that ß2 -AR stimulation results in rapid upregulation of miR-374b-5p and miR-7a-1-3p in myotubes, which in turn results in a decrease in FoxO1 mRNA expression via the ß2 -AR-cAMP signaling pathway.

A fatal case of diffuse alveolar hemorrhage complicated by rheumatoid arthritis.

We describe a fatal case of diffuse alveolar hemorrhage (DAH) complicated by rheumatoid arthritis (RA). A female patient was diagnosed with RA two months earlier and was treated with prednisolone and tacrolimus due to abnormalities in chest images. The patient was admitted to Hamanomachi Hospital for exertional dyspnea and was treated for exacerbation of chronic heart failure. Even after treatment for heart failure, exertional dyspnea remained. Chest CT imaging revealed contractile, patchy consolidations and ground-glass opacities (GGO) with a peribronchial distribution, suggesting an organizing pneumonia (OP) pattern. She was then treated with an additional 25 mg/day of prednisolone following a clinical diagnosis of OP. When the prednisolone dose was tapered, chest imaging showed worsening infiltration. A bronchoscopy was conducted, and bronchoalveolar lavage fluid was sanguineous, indicating DAH. Given that additional workup for the other etiology of DAH was negative, DAH was thought to be related to RA. Intensive treatment, including pulse dose methylprednisolone, failed to halt progression of respiratory failure, leading to a fatal outcome. The clinical presentation proved challenging due to its rarity. DAH might be a differential diagnosis in RA patients with consolidations and GGO in chest CT images. We review past cases of RA-associated DAH and assess potential treatment choices for future cases.

Three cases of sequential treatment with nintedanib following pulsed-dose corticosteroids for acute exacerbation of interstitial lung diseases.

We describe three cases of acute exacerbation of interstitial lung diseases (ILDs) in which patients were treated with pulsed-doses of corticosteroids followed by nintedanib and maintenance doses of corticosteroids. All cases responded well to pulsed-dose corticosteroids. However, in conventional practice, corticosteroids can complicate adverse events, including opportunistic infections, diabetes, and osteoporosis. One of the cases reported here involved dermatomyositis-associated ILD with anti-EJ antibodies. Considering possible side effects of corticosteroids and the frequent recurrence of ILDs associated with anti-EJ antibodies, we decided to use nintedanib as a sequential treatment for acute exacerbation of ILDs. Nintedanib has just been approved for treatment of progressive fibrosing ILD, but to date, few reports of acute exacerbation of ILDs treated with nintedanib have been published. This case series may contribute to a more thorough discussion regarding the use and timing of nintedanib in treating acute exacerbation of ILDs.

Insulin Stimulation of Protein Synthesis and mTOR Signaling in Chick Myotube Cultures.

Insulin stimulates protein synthesis in skeletal muscles. Protein synthesis is controlled by the mechanistic target of rapamycin (mTOR) signaling in skeletal muscles. This study was conducted to investigate the effect of insulin on protein synthesis and mTOR signaling in chick myotube cultures. Chick myotubes were incubated with insulin (1 µg/ml) for 1 h. Protein synthesis, measured using the surface sensing of translation method, was significantly increased by insulin. The phosphorylation of AKT (Thr308 and Ser473), p70 ribosomal S6 kinase 1 (S6K1, Thr389), S6 ribosomal protein (Ser235/236), and eukaryotic translation initiation factor 4E-binding protein 1 (4E-BP1, Thr37/46) was also significantly increased by insulin. These results suggest that insulin stimulates protein synthesis via mTOR signaling (phosphorylation of AKT, S6K1, S6 ribosomal protein, and 4E-BP1) in chick myotube cultures.

Effects of delaying post-hatch feeding on lipid peroxidation and antioxidant enzyme mRNA expression in the pectoralis major muscle of newly hatched chicks.

Excessive lipid peroxidation negatively affects the physiological response and meat quality of chickens. Delaying post-hatch feeding was previously found to increase lipid peroxidation in the skeletal muscle of finishing broiler chickens. The aims of this study were to investigate the effects of delayed post-hatch feeding on lipid peroxidation and the mRNA expressions of antioxidant enzymes in the pectoralis major muscle of broiler chicks during the post-hatching period. Newly hatched chicks either had immediate free access to feed (freely-fed chicks) or had no access to feed from 0 to 2 days old (delayed-fed chicks), after which both groups were fed ad libitum until 4 or 13 days old. The lipid peroxidation level was higher in the delayed-fed than freely-fed chicks at 2, 4, and 13 days old. At 2 days old, the mRNA expressions of Cu/Zn-SOD, Mn-SOD, and GPX7 were lower in the delayed-fed than freely-fed chicks, while catalase mRNA levels did not differ. Furthermore, at 4 and 13 days old, lower mRNA expressions of Cu/Zn-SOD and Mn-SOD were observed in the delayed-fed than freely-fed chicks. These results suggest that delaying post-hatch feeding reduces the mRNA levels of Cu/Zn-SOD and Mn-SOD, consequently affecting muscle lipid peroxidation in chicks during subsequent growth.

Regulation of Autophagy in Chick Skeletal Muscle: Effect of mTOR Inhibition.

Autophagy in the skeletal muscle increases under catabolic conditions resulting in muscle atrophy. This study investigated the effect of inhibition of mechanistic target of rapamycin (mTOR) on autophagy in chick skeletal muscle. We examined the effects of Torin1, an mTOR inhibitor, on autophagy. Chick myotubes were incubated with Torin1 (100 nM) for 3 h. It was observed that Torin1 inhibited the phosphorylation of AKT (Ser473), p70 ribosomal S6 kinase 1 (S6K1, Thr389), S6 ribosomal protein (Ser235/236), and eukaryotic translation initiation factor 4E-binding protein 1 (4E-BP1, Thr37/46), which are used for measurement of mTOR activity. Torin1 significantly (P< 0.01) increased the LC3-II/LC3-I ratio, an index for autophagosome formation, while it did not influence the expression of autophagy-related genes (LC3B, GABARAPL1, and ATG12). In addition, Torin1 increased atrogin-1/MAFbx (a muscle-specific ubiquitin ligase) mRNA expression. Fasting for 24 h inhibited the phosphorylation of AKT (Ser473), S6K1 (Ther389), S6 ribosomal protein (Ser235/236), and 4E-BP1 (Thr37/46) in chick skeletal muscle and significantly (P<0.01) increased the LC3-II/LC3-I ratio. Fasting also increased GABARAPL1 and atrogin-1/MAFbx mRNA expression but not LC3B or ATG12 mRNA expression. These results indicate that mTOR signaling regulates autophagy and the ubiquitin-proteasome proteolytic pathway in chick skeletal muscle.

Insulin acutely increases glucose transporter 1 on plasma membranes and glucose uptake in an AKT-dependent manner in chicken adipocytes.

Avian glucose transporters (GLUT) responsible for insulin-responsive glucose uptake into adipocytes remain poorly characterized. We aimed to identify the insulin-responsive GLUT using primary culture of chicken adipocytes. Acute stimulation with 1 µM insulin for 20 min increased 2-deoxyglucose uptake, AKT protein phosphorylation, and GLUT1 protein levels on the plasma membrane of the chicken adipocytes, whereas pretreatment with 10 µM triciribine, an AKT inhibitor, canceled these effects. Furthermore, the insulin stimulation did not affect GLUT12 protein levels on the plasma membrane of the chicken adipocytes. Our results suggest that GLUT1 is an insulin-responsive GLUT in chicken adipocytes.

The ß2-adrenergic receptor is involved in differences in the protein degradation level of the pectoral muscle between fast- and slow-growing chicks during the neonatal period.

The aim of this study was to investigate whether ß2-AR mRNA expression is involved in either atrogin-1/MAFbx mRNA expression or protein degradation in chicken skeletal muscle by comparing fast- and slow-growing chicks during the neonatal period. Based on their body weight gain from 1 to 5 days of age, 5-day-old chicks (Gallus gallus domestics) were divided into a slow-growing and a fast-growing group, the mean weight gains of which were 6.3 ±â€¯1.3 g/day and 11.3 ±â€¯0.9 g/day, respectively. The ratio of pectoral muscle weight to total body weight was higher in the fast-growing group of chicks than in the slow-growing group. In addition, the plasma 3-methylhistidine concentration, an index of protein degradation in skeletal muscle, was significantly lower in the fast-growing than in the slow-growing chicks. The mRNA expression of ß2-AR, which we previously found is involved in decreasing muscle protein degradation by suppression atrogin-1/MAFbx mRNA expression, was significantly higher in the pectoral muscle of the fast-growing group compared with that of the slow-growing group. Concordantly, lower mRNA expression of atrogin-1/MAFbx was observed in the pectoral muscle of the fast-growing chicks. However, in the sartorius muscle, which is a muscle in the thigh, the ratio of the muscle weight to total body weight was not significantly different between the two groups of chicks at 5 days of age. In addition, there was no significant difference in the mRNA expressions of ß2-AR and atrogin-1/MAFbx in the sartorius muscle between these two groups. These results suggest that ß2-AR expression levels might be physiologically significant in the control of protein degradation in the pectoral muscle of neonatal chicks.

Regulation of Autophagy in Chick Myotubes: Effects of Insulin, Insulin-Like Growth Factor-I, and Amino Acids.

Autophagy, an intracellular bulk protein degradation system in skeletal muscle, is increased under catabolic conditions resulting in muscle atrophy. This study aimed to investigate the effects of insulin, insulin-like growth factor (IGF)-I, and amino acids on autophagy (LC3-II content and expression of autophagy-related genes) in chick myotubes. Chick myotubes were incubated with insulin (1 µg/ml), IGF-I (100 ng/ml), and amino acids for 3 h. The LC3-II content, an index of autophagosome formation, and mRNA expression of LC3B and GABARAPL1 were significantly decreased by insulin. The LC3-II content, but not mRNA expression of autophagy-related genes, was also significantly decreased by IGF-I. The LC3-II content and LC3B mRNA level were also significantly decreased by amino acids. The mRNA expression of atrogin-1/MAFbx, a muscle-specific ubiquitin ligase, was also significantly decreased by insulin, IGF-I, and amino acids in chick myotubes. These results indicated that insulin, IGF-I, and amino acids regulate autophagy as well as the ubiquitin-proteasome proteolytic pathway in chick myotubes.

Expression of cationic amino acid transporters in pig skeletal muscles during postnatal development.

The cationic amino acid transporter (CAT) protein family transports lysine and arginine in cellular amino acid pools. We hypothesized that CAT expression changes in pig skeletal muscles during rapid pig postnatal development. We aimed to investigate the tissue distribution and changes in the ontogenic expression of CATs in pig skeletal muscles during postnatal development. Six piglets at 1, 12, 26, 45, and 75 days old were selected from six litters, and their longissimus dorsi (LD), biceps femoris (BF), and rhomboideus (RH) muscles, and their stomach, duodenum, jejunum, ileum, colon, liver, kidney, heart, and cerebrum were collected. CAT-1 was expressed in all the 12 tissues investigated. CAT-2 (CAT-2A isoform) expression was highest in the skeletal muscle and liver and lowest in the jejunum, ileum, kidney, and heart. CAT-3 was expressed mainly in the colon and detected in the jejunum, ileum, and cerebrum. The CAT-1 expression was higher in the skeletal muscle of day 1 pigs than in that of older pigs (P < 0.05). The CAT-2 mRNA level was lowest at day 1, but increased with postnatal development (P < 0.05). There was no significant change in CAT-1 expression among the LD, BF, and RH during postnatal development (P > 0.05); however, there was a change in CAT-2 expression. The CAT-2 expression was highest in the LD of 12-, 26-, 45-, and 75-day-old pigs, followed by the BF and RH (P < 0.05). These results suggest that CAT-1 and CAT-2 play different roles in pig skeletal muscles during postnatal development.

Loading and removal of PAHs, fragrance compounds, triclosan and toxicity by composting process from sewage sludge.

Although the production of compost from sewage sludge is well established in developed countries, the use of sludge-based compost may represent a source of pollutants. The present study assessed the levels of potentially harmful compounds in compost as well as their rates of decrease during composting. The concentrations of 16 polycyclic aromatic hydrocarbons (PAHs), three fragrance compounds (OTNE, HHCB and AHTN) and triclosan were determined in the initial sewage sludge and in compost over the span of 1year. Simultaneously, the toxicity to luminescent bacteria (Aliivibrio fischeri) and aryl hydrocarbon receptor reactivity of organic solvent extracts of sludge and compost samples were assessed. Higher PAH, fragrance compounds, and triclosan concentrations were found in sewage sludge from urban areas compared with rural regions, and the urban sludge was also more toxic than the rural sludge. The high pollutant concentrations in urban sludge raised the concentrations of these compounds in the raw materials for composting and in the resulting composts. The organic matter was decomposed by 65% during the composting process, and the measured toxic substances were decreased by a similar amount, with the exception of triclosan, which decreased by only 35%. The toxicity to A. fischeri decreased to a greater extent (90%) than did the organic matter, while the aryl hydrocarbon receptor reactivity decreased by only 35%. This lower decrease coincided with that of the aryl hydrocarbon receptor-reactive PAHs (37%).

ß1- and ß2-adrenergic receptor stimulation differ in their effects on PGC-1α and atrogin-1/MAFbx gene expression in chick skeletal muscle.

Adrenaline changes expression of the genes encoding peroxisome proliferator-activated receptor-gamma coactivator-1 alpha (PGC-1α), which is known as a regulator of muscle size, and atrogin-1/muscle atrophy F-box (MAFbx), which is a muscle-specific ubiquitin ligase. However, the subtype of ß-adrenergic receptor (ß-AR) involved in regulating these genes in skeletal muscle is not yet well defined. In this study, the effects of intraperitoneal injection of adrenaline and three ß1-3-AR selective agonists on chick skeletal muscle metabolism were examined, to evaluate the functions of ß-AR subtypes. Adrenaline decreased atrogin-1/MAFbx mRNA levels accompanied by an increase in PGC-1α mRNA and protein levels. However, among the three selective agonists, only the ß1-AR agonist, dobutamine, increased PGC-1α mRNA and protein levels, while the ß2-AR agonist, clenbuterol, suppressed atrogin-1/MAFbx mRNA levels. In addition, preinjection of the ß1-AR antagonist, acebutolol, and the ß2-AR antagonist, butoxamine, inhibited the adrenaline-induced increase in PGC-1α mRNA levels and the decrease in atrogin-1/MAFbx mRNA levels, respectively. Compared with adrenaline administration, the ß3-AR agonist, BRL37344, decreased PGC-1α mRNA levels and increased atrogin-1/MAFbx mRNA levels. These results suggest that, in chick skeletal muscle, PGC-1α is induced via the ß1-AR, while atrogin-1/MAFbx is suppressed via the ß2-AR.

Effects of first exogenous nutrients on the mRNA levels of atrogin-1/MAFbx and GLUT1 in the skeletal muscles of newly hatched chicks.

The aim of this study was to examine the effects of first exogenous nutrients on the mRNA levels of muscle atrophy F-box (atrogin-1/MAFbx) and glucose transporters (GLUTs) in the skeletal muscles of newly hatched chicks with no feed experience. In experiment 1, newly hatched chicks had free access to feed or were fasted for the first 24h. The chicks having free access to feed for the first 24h increased their body weight and had decreased atrogin-1/MAFbx mRNA levels in their sartorius and pectoralis major muscles compared with the fasted chicks. In experiment 2, newly hatched chicks received a single feed via intubation into the crop. Three hours after intubation, levels of atrogin-1/MAFbx mRNA in the sartorius muscle were decreased whereas the plasma insulin concentration and phosphorylated AKT levels in the sartorius muscle were increased. In addition, the mRNA levels of GLUT1 and GLUT8 were increased in the sartorius muscle after the intubation. However, in the pectoralis major muscle, AKT phosphorylation and levels of atrogin-1/MAFbx, GLUT1 and GLUT8 mRNA were not affected 3h after intubation. The first exogenous nutrients increased the level of phosphorylated AKT in the sartorius muscle of newly hatched chicks, possibly because of the decrease in atrogin-1/MAFbx mRNA levels. Furthermore, the sartorius muscle in newly hatched chicks appeared to be more susceptible to the first feed compared with the pectoralis major muscle.

Effects of Insulin-Like Growth Factor-I on the Expression of Atrogin-1/MAFbx in Chick Myotube Cultures.

The expression of atrogin-1/MAFbx, a muscle-specific E3 ubiquitin ligase, is increased in catabolic conditions that result in muscle atrophy. The expression of atrogin-1/MAFbx mRNA is also decreased by the insulin-like growth factor-I (IGF-I) in mammalian skeletal muscle cell cultures. This study investigated the effect of IGF-I on the expression of atrogin-1/MAFbx in chicken skeletal muscle cell cultures. Chick myotubes were incubated with IGF-I for 1, 6, or 24 h. Protein content was increased by IGF-I (100 ng/ml) and incubated for 24 h in chick myotubes. The expression of atrogin-1/MAFbx mRNA decreased in the presence of IGF-I (1, 10, and 100 ng/ml) for 6 h in chick myotubes. The expression of the m-calpain large subunit and cathepsin B mRNA was not decreased by IGF-I. Phosphorylation of Akt and FOXO1 increased in the presence of IGF-I (100 ng/ml) for 1 h in chick myotubes. These results indicate that IGF-I suppresses atrogin-1/MAFbx mRNA expression by phosphorylation of Akt and FOXO1, resulting in an increase in muscle growth in chick myotube cultures.

Clenbuterol changes phosphorylated FOXO1 localization and decreases protein degradation in the sartorius muscle of neonatal chicks.

To investigate the intracellular signaling mechanisms by which clenbuterol reduces muscle protein degradation, we examined the phosphorylation level and intracellular localization of FOXO1 in the sartorius muscle of neonatal chicks. One-day-old chicks were given a single intraperitoneal injection of clenbuterol (0.1 mg/kg body weight). Three hours after injection, AKT protein was phosphorylated in the sartorius muscle by clenbuterol injection. Coincidentally, clenbuterol increased cytosolic level of phosphorylated FOXO1 protein, while it decreased nuclear level of FOXO1 protein in the sartorius muscle. Furthermore, clenbuterol decreased the expression of mRNAs for muscle-specific ubiquitin ligases (atrogin-1/MAFbx and MuRF1) in the sartorius muscle accompanied by decreased plasma 3-methylhistidine concentration, an index of muscle protein degradation, at 3 h after injection. These results suggested that, in the sartorius muscle of the chicks, clenbuterol changed the intracellular localization of phosphorylated FOXO1, and consequently decreased protein degradation via suppressing the expression of genes encoding muscle-specific ubiquitin ligases.

Gene expression pattern of glucose transporters in the skeletal muscles of newly hatched chicks.

The gene expression pattern of the glucose transporters (GLUT1, GLUT3, GLUT8, and GLUT12) among pectoralis major and minor, biceps femoris, and sartorius muscles from newly hatched chicks was examined. GLUT1 mRNA level was higher in pectoralis major muscle than in the other muscles. Phosphorylated AKT level was also high in the same muscle, suggesting a relationship between AKT and GLUT1 expression.