Jun-ichi Shiraishi

Comparisons of insulin related parameters in commercial-type chicks: Evidence for insulin resistance in broiler chicks

The aim of this study is to elucidate whether insulin acts differentially within the central nervous system (CNS) of two types of commercial chicks to control ingestive behavior. Male layer and broiler chicks (4-day-old) were intracerebroventricularly (ICV) injected with saline or insulin under satiated and starved conditions. Feed intake was measured at 30, 60 and 120 min after treatment. Secondly, blood and hypothalamus were collected from both chick types under ad libitum feeding and fasting for 24 h. Plasma insulin concentration was measured by time-resolved fluoro-immunoassay. Hypothalamic insulin receptor mRNA expression levels were measured by quantitative RT-PCR. The ICV injection of insulin significantly inhibited feed consumption in layer chicks when compared with saline (P<0.05), but not broiler chicks (P>0.1). Plasma insulin concentration of both chick types significantly decreased following 24 h of fasting, while insulin concentrations in the broiler chicks were significantly higher compared to the layers fed under ad libitum conditions. Hypothalamic insulin receptor mRNA expression levels were significantly lower (P<0.05) in broiler chicks than in layer ones under ad libitum feeding. Feed deprivation significantly decreased insulin receptor mRNA levels in layer chicks (P<0.01), but not in broiler chicks (P>0.1). Moreover, plasma insulin concentrations correlated negatively with hypothalamic insulin receptor protein expression in the two types of chicks fed ad libitum (P<0.05). These results suggest that insulin resistance exists in the CNS of broiler chicks, possibly due to persistent hyperinsulinemia, which results in a down-regulation of CNS insulin receptor expression compared to that in layer chicks.

The number of taste buds is related to bitter taste sensitivity in layer and broiler chickens

The relationship between taste sensitivity and the number of taste buds using a bitter tastant, quinine hydrochloride, was investigated in White Leghorn, Rhode Island Red, and broiler chickens. The White Leghorn and Rhode Island Red strains were able to perceive 2.0 mmol/L quinine hydrochloride, but the taste sensitivity of Rhode Island Red chickens was higher than that of White Leghorn chickens. Broiler chickens perceived 0.5 mmol/L quinine hydrochloride. The number of taste buds in the White Leghorn strain was the lowest, then the Rhode Island Red strain, with the number of taste buds highest in the broiler chickens. The number of taste buds was well correlated with bitter taste sensitivity. Therefore, we suggest that the number of taste buds is a vital factor in the perception of bitter taste and may be useful in selecting appropriate feeds for chickens.

Localization of hypothalamic insulin receptor in neonatal chicks: Evidence for insulinergic system control of feeding behavior

Feeding behavior is managed by various neuropeptides and/or neurotransmitters within the central nervous system in vertebrates. It is proposed that central insulin acts as the negative-feedback regulator of appetite via the central melanocortin system in neonatal chicks. The present study investigated the localization of insulin receptors in the chick hypothalamus using immunohistochemistry. Immunostaining revealed hypothalamic neuron expressing insulin receptors in the paraventricular nucleus, ventromedial hypothalamus, lateral hypothalamus and infundibular nucleus, the avian equivalent of the mammalian arcuate nucleus. Additionally, double-staining immunohistochemistry in the infundibular nucleus revealed the presence of insulin receptors in both α-melanocyto stimulating hormone and neuropeptide Y neurons. Immunohistological analysis indicates that the insulinergic system in the chick hypothalamus contributes to feeding behavior and this system regulates both anorexigenic and orexigenic neuropeptides. Furthermore, the mechanisms of central insulin induced-feeding behavior contributes to the regulation of the melanocortin system in the chick infundibular nucleus.

Effects of N-terminal fragments of β-endorphin on feeding in chicks

It is known that N-terminal fragments of beta-endorphin have biological activities, such as an antagonism effect of beta-endorphin (1-31) on the secretion of hormones or thermoregulation in mammals. We studied the effects of the N-terminal fragments on feeding behavior in male broiler chicks. Intracerebroventricular administration of beta-endorphin (1-27) (0.4nmol) stimulated feeding behavior compared with saline control during the 60-min experimental period. beta-Endorphin (1-17) (2.0nmol) also increased food intake at 30min postinjection. Co-injection of either beta-endorphin (1-27) or (1-17) was effective in reducing full-length beta-endorphin-induced feeding in chicks. These data suggest that the N-terminal fragments of beta-endorphin act as a partial agonist, and may regulate the activity of the central opioidergic system in chicks.

Effect of nociceptin/orphanin FQ on feeding behavior and hypothalamic neuropeptide expression in layer-type chicks

Nociceptin/orphanin FQ (N/OFQ) was identified in 1995 as the endogenous ligand for the orphan G(i)/G(o)-coupled opioid receptor-like 1 receptor (NOP(1)). Exogenous N/OFQ increases food intake in mammals, but its effect and mode of action in chicks are not fully known. We report herein that N/OFQ (5.0 nmol) has a stimulatory effect on food intake in layer-type chicks over a 2-h period after intracerebroventricular (icv) injection. Thirty minutes after central injection of N/OFQ (5.0 nmol) the concentration of agouti-related protein (AGRP) mRNA in the diencephalon increased, while cocaine- and amphetamine-regulated transcript (CART) mRNA decreased. However, concentrations of neuropeptide Y, proopiomelanocortin and glutamate decarboxylase mRNAs, and of catecholamines and excitatory amino acids were not affected. Simultaneous administration of alpha-melanocyte stimulating hormone (alpha-MSH: 1.0 pmol), a competitor of AGRP, completely blocked the orexigenic effect of N/OFQ (5.0 nmol). These data suggest that N/OFQ functions in layer chicks as an orexigenic peptide in the central nervous system, and that the AGRP and the CART neurons may mediate this function, as in mammals.

μ-Opioid receptor agonist diminishes POMC gene expression and anorexia by central insulin in neonatal chicks

Pro-opiomelanocortin (POMC) neurons in the hypothalamus are direct targets of peripheral satiety signals, such as leptin and insulin in mammals. The stimulation of these signals activates hypothalamic POMC neurons and elevates POMC-derived melanocortin peptides that inhibit food intake in mammals. On the other hand, it has been recognized that beta-endorphin, a post-translational processing of POMC, acts in an autoreceptor manner to the micro-opioid receptor (MOR) on POMC neurons, diminishing POMC neuronal activity in mammals. Recently, we found that central insulin functions as an anorexic peptide in chicks. Thus, the present study was done to elucidate whether beta-endorphin affects the activation of POMC neurons by insulin in neonatal chicks. Consequently, quantitative real-time PCR analysis shows that intracerebroventricular (ICV) injection of insulin with beta-endorphin significantly decreases brain POMC mRNA expression when compared with insulin alone. In addition, co-injection of MOR agonist (beta-endorphin or [d-Ala2, N-MePhe4, Gly5-ol]-enkephalin (DAMGO)) significantly attenuates insulin-induced hypophagia in chicks. These data suggest that beta-endorphin regulates the activity of the central melanocortin system, and its activation may provide an inhibitory feedback mechanism in the brain of neonatal chicks.

A genetically female brain is required for a regular reproductive cycle in chicken brain chimeras

Sexual differentiation leads to structural and behavioural differences between males and females. Here we investigate the intrinsic sex identity of the brain by constructing chicken chimeras in which the brain primordium is switched between male and female identities before gonadal development. We find that the female chimeras with male brains display delayed sexual maturation and irregular oviposition cycles, although their behaviour, plasma concentrations of sex steroids and luteinizing hormone levels are normal. The male chimeras with female brains show phenotypes similar to typical cocks. In the perinatal period, oestrogen concentrations in the genetically male brain are higher than those in the genetically female brain. Our study demonstrates that male brain cells retain male sex identity and do not differentiate into female cells to drive the normal oestrous cycle, even when situated in the female hormonal milieu. This is clear evidence for a sex-specific feature that develops independent of gonadal steroids.

Effects of Dietary Methionine or Arginine Levels on the Urinary Creatinine Excretion in Broiler Chicks

Two experiments were conducted to evaluate the usefulness of urinary creatinine levels as a criterion for the estimation of protein and amino acid requirements in poultry. Here we studied the effects of dietary precursor levels of creatinine, methionine and arginine, on urinary creatinine excretion in experiments. Both experiments used 15 Chunky broilers chicks that were 8 days old. The chicks were assigned to three dietary groups, with five chicks each, and were fed an experimental diet for 7 days. The experimental diets mainly consisted of corn and soybean meal, and contained deficient, adequate, or excessive methionine and arginine levels in experiments 1 and 2, respectively. Excreta were collected for the last 3 days of the feeding trial, and chicks were terminated by dislocation of the neck at the end of the feeding trial to collect their livers. Creatinine concentration in the excreta and hepatic l-arginine-glycine amidinotransferase (AGAT) activities were determined. Urinary creatinine levels increased with increasing both dietary methionine and arginine levels from deficient to adequate recommended by Japanese feeding standard (P<0.05), and then remained constant in experiments 1 and 2, respectively. The hepatic AGAT activity decreased when both dietary creatinine precursors levels were increased from deficient to adequate levels (p<0.05), and then remained constant. These results suggested that creatinine excretion was changed with both increasing dietary methionine and arginine, dose-dependently.

Effect of centrally administered methionine or related compounds on feeding behavior in chicks.

Abstract Bungo, T. and Shiraishi, J. 2010. Effect of centrally administered methionine or related compounds on feeding behavior in chicks. J. Appl. Anim. Res., 38: 197–200. The effects of intracerebroventricular (ICV) injection of methionine (150–600 mg), and the related compounds, taurine (125–500 mg) or S-adenosyl-L-methionine (1–100 mg) were investigated using neonatal chicks. L-Methionine (600 mg) and D-methionine (300 and 600 mg) significantly increased food consumption at 30 min post injection. Taurine, one of the metabolites of methionine, failed to accelerate feeding behavior in chicks. In addition, S-adenosyl-L-methionine (100 mg), which is synthesized from methionine, tended to depress food intake in ad libitum chicks. These findings indicate the involvement of methionine as a chemical mediator in the regulation of food intake in chicks.