Effects of Amino Acid Supplementation to a Low-Protein Diet on the Growth Performance and Protein Metabolism-related Factors in Broiler Chicks.

A low-protein (LP) diet may alleviate the environmental impact of chicken meat production by reducing nitrogen excretion and ammonia emissions. Thus, this study investigated the effect of a 15% reduced protein diet with or without amino acid (AA) supplementation on the growth performance of broiler chicks from 10 to 35 days of age and the underlying mechanism for loss of skeletal muscle mass. Thirty-six male broiler chicks were allocated to three experimental groups based on body weight: control, LP, and essential AA-supplemented LP (LP+AA).

Periodic and Local LED Light Switching Induces Broiler Locomotion.

Wooden breast myopathy and leg weakness are serious problems in the broiler chicken industry. The color and intensity of light in the chicken habitat affect behavior, including walking of chicks. The present study was conducted to determine whether periodic and local light switching induces locomotion and affects wooden breast myopathy and leg weakness in broiler chicks.

Effects of Dietary Brown Rice and Sake Lees on the Growth Performance and Color of Meat in Broiler Chicks.

In this study, we examined whether brown rice and sake lees (domestic feed ingredients) could replace corn and soybean meal (major imported feed ingredients) in broiler chick feed. In Experiment 1, 21-day-old broiler chicks were assigned to two groups and fed a corn-soybean- or a brown rice-soybean-based diet for three weeks (3 birds × 4 replicates/group). Dietary brown rice significantly improved body weight gain and feed conversion ratio.

Role of Hypothalamic Transforming Growth Factor- (TGF-)/Smad Signaling in Feeding Regulation in Chickens.

Previous studies in mammalian obesity models have suggested that central transforming growth factor- (TGF-) controls the gene expression of appetite-regulating neuropeptides and peripheral energy metabolism. In the present study, we investigated the possible involvement of central TGF-/Smad signaling in feeding regulation in chickens. Central administration of TGF-1 resulted in phosphorylation of Smad2 in the hypothalamus of chicks and suppressed feed intake without changing the gene expression of hypothalamic appetite-regulating neuropeptides (neuropeptide Y, agouti-related protein, proopiomelanocortin, and corticotropin-releasing factor).

Atrogin-1 knockdown inhibits the autophagy-lysosome system in mammalian and avian myotubes.

Atrogin-1 plays an important role in ubiquitin-proteasome proteolysis in vertebrate skeletal muscles. Recently, atrogin-1 has been shown to be involved in the autophagy-lysosome system, another proteolytic system, in the murine and fish hearts and skeletal muscles. With the aim to elucidate the effect of atrogin-1 on the autophagy-lysosome system in mammalian and avian skeletal muscles, this study has examined the effects of atrogin-1 knockdown on autophagy-lysosome-related proteins in C2C12 and chicken embryonic myotubes.

IGF-1 knockdown inhibits phosphorylation of Akt and ERK in chicken embryonic myotubes.

Objective: We examined whether auto/paracrine insulin-like growth factor-1 (IGF-1) contributes to the phosphorylation of Akt and ERK in chicken myotubes.

Methods: Chicken myotubes were treated with IGF-1 siRNA, and then total RNA and protein were harvested for real-time PCR and western blot analysis.

Results: Treatment with IGF-1 siRNA inhibited the phosphorylation of Akt and ERK, but not of ribosomal protein S6, in chicken myotubes.

Role of Corticosterone in Lipid Metabolism in Broiler Chick White Adipose Tissue.

Excessive accumulation of body fat in broiler chickens has become a serious problem in the poultry industry. However, the molecular mechanism of triglyceride accumulation in chicken white adipose tissue (WAT) has not been elucidated. In the present study, we investigated the physiological importance of the catabolic hormone corticosterone, the major glucocorticoid in chickens, in the regulation of chicken WAT lipid metabolism.

Comparison of the effects of intracerebroventricular administration of glucagon-like peptides 1 and 2 on hypothalamic appetite regulating factors and sleep-like behavior in chicks.

Glucagon-like peptide (GLP)-1 and GLP-2, proglucagon-derived brain-gut peptides, function as anorexigenic neuropeptides in mammals. We previously showed that central administration of GLP-1 and GLP-2 potently suppressed food intake in chicks. GLP-1 and GLP-2 specifically activate their receptors GLP-1 receptor (GLP1R) and GLP-2 receptor (GLP2R), respectively in chickens.

Enzymatically-Synthesized Glycogen Induces Cecal Glucagon-Like Peptide-1 Production and Suppresses Food Intake in Mice.

It is well known that dietary fiber stimulates the release of satiety hormones such as glucagon-like peptide-1 (GLP-1), which in turn suppresses appetite. In order to evaluate appetite regulating role of enzymatically synthesized glycogen (ESG, one of the resistant starch), we examined the effects of dietary supplementation of ESG on food intake and cecal proglucagon gene expression in normal and high fat diet-fed mice. Twenty four male ICR mice were weighed and assigned to four groups: normal diet group; normal diet containing 25% ESG group; high-fat diet (HFD) group; HFD containing 25% ESG group.

Central administration of insulin and refeeding lead to Akt and ERK phosphorylation in the chicken medulla.

The purpose of this study was to investigate whether medullary cellular signaling pathways contribute to feeding regulation in chickens. Fasting inhibited the phosphorylated protein and its rates of ERK but not Akt in the chicken medulla, while refeeding promoted Akt and ERK. Intraperitoneal administration of sulfate cholecystokinin 8 did not affect medullary Akt and ERK phosphorylation in chickens.

Effects of fasting and re-feeding on the expression of CCK, PYY, hypothalamic neuropeptides, and IGF-related genes in layer and broiler chicks.

Cholecystokinin (CCK) and peptide YY (PYY) have been investigated as gut hormones that send satiation signals to the brain in mammals. There is evidence that chicken PYY mRNA expression was the highest in the pancreas compared to other tissues. We recently suggested that insulin-like growth factor (IGF)-1 and its binding proteins (IGFBPs) may be involved in the appetite regulation system in chicks.

Central administration of insulin-like growth factor-2 suppresses food intake in chicks.

Insulin-like growth factor (IGF)-2 is a multifunctional hormone with structural and functional similarity to IGF-1 in mammals and chickens. We previously showed that intracerebroventricular administration of IGF-1 suppresses food intake in chicks. Also, central administration of IGF-2 suppresses food intake in rats.

Role of Insulin-like Growth Factor-1 in the Central Regulation of Feeding Behavior in Chicks.

Insulin-like growth factor-1 (IGF-1) is a key regulator of muscle development and metabolism in chickens. Recently, we have demonstrated that intracerebroventricular administration of IGF-1 significantly decreased food intake in broiler chicks. However, the molecular mechanisms underlying the IGF-1-induced anorexia and the anorexigenic effect of IGF-1 in different strains of commercial chicks have not been investigated.

Myostatin Increases Smad2 Phosphorylation and Atrogin-1 Expression in Chick Embryonic Myotubes.

Skeletal muscle mass is an important trait in poultry meat production. In mammals, myostatin, a negative regulator of skeletal muscle growth, activates Smad transcription factors and induces the expression of atrogin-1 by regulating the Akt/FOXO pathway. Although the amino acid sequence of chicken myostatin is known to be completely identical to its mammalian counterpart, previous studies in chicken skeletal muscles have implied that the physiological roles of chicken myostatin are different from those of mammals.

Differential regulation of protein synthesis by skeletal muscle type in chickens.

In mammalian skeletal muscles, protein synthesis rates vary according to fiber types. We herein demonstrated differences in the regulatory mechanism underlying the protein synthesis in the pectoralis major (a glycolytic twitch muscle), adductor superficialis (an oxidative twitch muscle), and adductor profound (a tonic muscle) muscles of 14-day-old chickens. Under ad libitum feeding conditions, protein synthesis is significantly higher in the adductor superficialis muscle than in the pectoralis major muscle, suggesting that protein synthesis is upregulated in oxidative muscles in chickens, similar to that in mammals.

Central administration of insulin and refeeding lead to the phosphorylation of AKT, but not FOXO1, in the hypothalamus of broiler chicks.

Several studies in rodents and layer chickens have demonstrated that insulin upregulates hypothalamic AKT-mediated signaling and expression of proopiomelanocortin (POMC, the precursor of alpha-melanocyte stimulating hormone, an anorexigenic peptide) and suppresses appetite in these animals. However, a previous study has also reported that insulin fails to suppress food intake in broiler chicks. In the present study, no significant differences were observed in hypothalamic AKT and forkhead box O1 (FOXO1) phosphorylation levels between broiler and layer chicks.

The Extract of Soybean Protein Increases Slow-Myosin Heavy Chain Expression in C2C12 Myotubes.

Skeletal muscle is composed of four types of fibers in mammals; oxidative slow-twitch type I, oxidative fast-twitch IIA, and glycolytic fast-twitch IIB and IIX/D. In this study using C2C12 myotubes, an extract of soybean protein significantly upregulated mRNA level of myosin heavy chain 7 (Myh7), the predominant isoform expressed in oxidative slow-twitch type I and downregulated mRNA levels of Myh4, the predominant isoform expressed in glycolytic fast-twitch IIB. Similarly, its hydrolysate prepared using digestive enzyme also significantly increased Myh7 expression.

Hypothalamic Akt-mediated signaling regulates food intake in chicks.

The central anorexigenic mechanism seems to be similar in mammals and chicks, because the appetite-suppressive action of a number of peptide hormones is similar in both species. Accumulating evidence in mammals has revealed that hypothalamic Akt-mediated signaling factors (for instance, mTOR and FOXO1) are significantly involved in the regulation of food intake. However, the role of hypothalamic Akt in feeding regulation is yet to be determined in chickens.

Effects of Enzymatically Synthesized Glycogen and Exercise on Abdominal Fat Accumulation in High-Fat Diet-Fed Mice.

The combination of diet and exercise is the first choice for the treatment of obesity and metabolic syndrome. We previously reported that enzymatically synthesized glycogen (ESG) suppresses abdominal fat accumulation in obese rats. However, the effect of the combination of ESG and exercise on abdominal fat accumulation has not yet been investigated.

Effects of Fasting and Refeeding on the mRNA levels of Insulin-like Growth Factor-binding Proteins in Chick Liver and Brain.

The physiological functions of insulin-like growth factor-binding proteins (IGFBPs) in mammals have been evaluated in several studies. However, the physiological roles of IGFBPs in chickens have not yet been elucidated. In this study, we examined the effects of short-term (6 h) fasting and refeeding on the mRNA levels of IGFBPs in chick liver and brain.

Fasting and Glucagon Stimulate Gene Expression of Pyruvate Dehydrogenase Kinase 4 in Chickens.

The excessive accumulation of body fat has become a serious problem in the broiler industry. However, the molecular mechanisms underlying the regulation of lipid metabolism-related genes in broiler chickens are not fully understood. In the present study, we investigated the role of glucagon on the expression of lipid metabolism-related genes in chicken white adipose tissue (WAT).

Central and peripheral administrations of insulin-like growth factor-1 suppress food intake in chicks.

A number of studies have been made on the physiological actions of insulin-like growth factor-1 (IGF-1) in mammals and birds. In mammals, the effects of central administration of IGF-1 on food intake have been examined. For example, intracerebroventricular administration of IGF-1 significantly decreased food intake in diabetic rats, but not in sheep and nondiabetic rats.

The IGF-1/Akt/S6 pathway and expressions of glycolytic myosin heavy chain isoforms are upregulated in chicken skeletal muscle during the first week after hatching.

Skeletal muscle mass is an important trait in the animal industry. We previously reported an age-dependent downregulation of the insulin-like growth factor 1 (IGF-1)/Akt/S6 pathway, major protein synthesis pathway, in chicken breast muscle after 1 week of age, despite a continuous increase of breast muscle weight. Myosin heavy chain (HC), a major protein in muscle fiber, has several isoforms depending on chicken skeletal muscle types.

Gut Hormones and Regulation of Food Intake in Birds.

Gut hormones act as appetite regulatory hormones in mammals. For example, the hunger hormone ghrelin, which is released from the stomach before food intake, stimulates appetite. In contrast, satiety hormones such as cholecystokinin, glucagon-like peptide-1, and peptide YY, which are released from the intestines after food intake, suppress appetite.

Effects of continuous white light and 12h white-12h blue light-cycles on the expression of clock genes in diencephalon, liver, and skeletal muscle in chicks.

The core circadian clock mechanism relies on a feedback loop comprised of clock genes, such as the brain and muscle Arnt-like 1 (Bmal1), chriptochrome 1 (Cry1), and period 3 (Per3). Exposure to the light-dark cycle synchronizes the master circadian clock in the brain, and which then synchronizes circadian clocks in peripheral tissues. Birds have long been used as a model for the investigation of circadian rhythm in human neurobiology.