Intracerebroventricular injection taurine changes free amino acid concentrations in the brain and plasma in chicks.

Brain amino acid metabolism has been reported to regulate body temperature, feeding behavior and stress response. Central injection of taurine induced hypothermic and anorexigenic effects in chicks. However, it is still unknown how the amino acid metabolism is influenced by the central injection of taurine. Therefore, the objective of this study was to investigate the changes in brain and plasma free amino acids following central injection of taurine. Five-day-old male Julia layer chicks (n = 10) were subjected to intracerebroventricular (ICV) injection with saline or taurine (5 µmol/10 µL). Central taurine increased tryptophan concentrations in the diencephalon, and decreased tyrosine in the diencephalon, brainstem, cerebellum, telencephalon and plasma at 30 min post-injection. Taurine was increased in all the brain parts after ICV taurine. Although histidine and cystathionine concentrations were increased in the diencephalon and brainstem, several amino acids such as isoleucine, arginine, methionine, phenylalanine, glutamic acid, asparagine, proline, and alanine were reduced following central injection of taurine. All amino acid concentrations were decreased in the plasma after ICV taurine. In conclusion, central taurine quickly changes free amino acid concentrations in the brain and plasma, which may have a role in thermoregulation, food intake and stress response in chicks.

Prostaglandin E2-induced anorexia involves hypothalamic brain-derived neurotrophic factor and ghrelin in chicks.

Central administration of prostaglandin E2 (PGE2) is associated with potent anorexia in rodents and chicks, although hypothalamic mechanisms are not fully understood. The objective of the present study was to identify hypothalamic nuclei and appetite-related factors that are involved in this anorexigenic effect, using chickens as a model. Intracerebroventricular injection of 2.5, 5, and 10 nmol of PGE2 suppressed food and water intake in broiler chicks in a dose-dependent manner. c-Fos immunoreactivity was increased in the paraventricular nucleus (PVN) at 60 min post injection of 5 nmol of PGE2. Under the same treatment condition, hypothalamic expression of melanocortin receptor 3 and ghrelin mRNAs increased, whereas neuropeptide Y receptor sub-type 5 and tropomyosin receptor kinase B (TrkB) mRNAs decreased in PGE2-treated chicks. In the PVN, chicks injected with PGE2 had more brain-derived neurotrophic factor (BDNF), ghrelin, and c-Fos mRNA but less corticotrophin-releasing factor receptor 1 (CRFR1), CRFR2, and TrkB mRNA expression. In conclusion, PGE2 injection resulted in decreased food and water intake that likely involves BDNF and ghrelin originating in the PVN. Because the anorexigenic effect is so potent and hypothalamic mechanisms are similar in chickens and rodents, a greater understanding of the role of PGE2 in acute appetite regulation may have implications for treating eating and metabolic disorders in humans.

Migratory state and patterns of steroid hormone regulation in the pectoralis muscle of a nomadic migrant, the pine siskin (Spinus pinus).

The endocrine system is known to mediate responses to environmental change and transitions between different life stages (e.g., a non-breeding to a breeding life stage). Previous works from the field of environmental endocrinology have primarily focused on changes in circulating hormones, but a comprehensive understanding of endocrine signaling pathways requires studying changes in additional endocrine components (e.g., receptor densities) in a diversity of contexts and life stages. Migratory birds, for instance, can exhibit dramatic changes in their physiology and behavior, and both sex steroids as well as glucocorticoids are proposed mediators of the transition into a migratory state. However, the role of changes in endocrine signaling components within integral target tissues, such as flight muscles, in modulating the transition into a migratory state remains poorly understood. Here, we examined changes in gene expression levels of and correlational patterns (i.e., integration) between 8 endocrine signaling components associated with either glucocorticoids or sex steroid signaling in the pectoralis muscles of a nomadic migratory bird, the pine siskin (Spinus pinus). The pectoralis muscle is essential to migratory flight and undergoes conspicuous changes in preparation for migration, including hypertrophy. We focus on endocrine receptors and enzymes (e.g., 5α-reductase) that modulate the signaling capacity of circulating hormones within target tissues and may influence either catabolic or anabolic functioning within the pectoralis. Endocrine signaling components were compared between captive birds sampled prior to the expression of vernal migratory preparation and during the expression of a vernal migratory state. While birds exhibited differences in the size and color of the flight muscle and behavioral shifts indicative of a migratory state (i.e., zugunruhe), none of the measured endocrine components differed before and after the transition into the migratory state. Patterns of integration amongst all genes did, however, differ between the two life stages, suggesting the contrasting demands of different life stages may shape entire endocrine signaling networks within target tissues rather than individual components. Our work aligns with previous endocrine studies on pine siskins and, viewed together, suggest additional studies are needed to understand the endocrine system's role in mediating the development and progression of the vernal migratory state in this species. Further, the patterns observed in pine siskins, a nomadic migrant, differ from previous studies on obligate migrants and suggest that different mechanisms or interactions between endocrine signaling components may mediate the migratory transition in nomadic migrants.

Hypothalamic-pituitary-adrenal axis regulation and organization in urban and rural song sparrows.

Urban habitats present animals with persistent disturbances and acute stressors not present in rural habitats or present at significantly lower levels. Differences in the glucocorticoid stress response could underlie colonization of these novel habitats. Despite urban habitats characterization as more stressful, previous comparisons of urban and rural birds have failed to find consistent differences in baseline and stress induced glucocorticoid levels. Another aspect of glucocorticoid regulation that could underlie an animal's ability to inhabit novel habitats, but has yet to be well examined, is more efficient termination of the glucocorticoid stress response which would allow birds in urban habitats to recover more quickly after a disturbance. The glucocorticoid stress response is terminated by negative feedback achieved primarily through their binding of receptors in the hippocampus and hypothalamus and subsequent decreased synthesis and release from the adrenals. We investigated if male song sparrows (Melospiza melodia) in urban habitats show more efficient termination of the glucocorticoid stress response than their rural counterparts using two approaches. First, we measured glucocorticoid receptor, mineralocorticoid receptor and 11ß-HSD2 (an enzyme that inactivates corticosterone) mRNA expression in negative feedback targets of the brain (the hippocampus and hypothalamus) as a proxy measure of sensitivity to negative feedback. Second, we measured plasma corticosterone levels after standardized restraint and again following a challenge with the synthetic glucocorticoid, dexamethasone, as a means of assessing how quickly birds decreased glucocorticoid synthesis and release. Though there were no differences in the hypothalamus of urban and rural song sparrows, urban birds had lower glucocorticoid receptor and 11ß-HSD2 mRNA expression in the hippocampus. Further, urban and rural birds had similar reductions in corticosterone following the dexamethasone challenge, suggesting that they do not differ in how quickly they decrease glucocorticoid synthesis and release. Thus, urban and rural song sparrows display similar termination of the glucocorticoid stress response even though urban birds have decreased hippocampal glucocorticoid receptor and 11ß-HSD2 abundance.

The anorexigenic effect of neuropeptide AF in Japanese quail, Coturnix japonica, is associated with activation of the melanocortin system.

Neuropeptide AF (NPAF) decreases food and water intake in birds and food intake in mammals. In this study, the objective was to determine the effects of centrally administered NPAF on food and water intake, hypothalamic c-Fos immunoreactivity and hypothalamic mRNA abundance of appetite-regulating factors in Japanese quail (Coturnix japonica). Seven days post hatch, 6 h fasted quail were intracerebroventricularly (ICV) injected with 0 (vehicle), 4, 8, or 16 nmol of NPAF and food and water intake were measured at 30 min intervals for 180 min. In Experiment 1, chicks which received 4, 8, and 16 nmol ICV NPAF had reduced food intake for 120, 60 and 180 min following injection, respectively, and reduced water intake during the entire 180 min observation. In Experiment 2, there was increased c-Fos immunoreactivity in the paraventricular nucleus, the ventromedial nucleus of the hypothalamus, and the dorsomedial hypothalamic nucleus in NPAF-injected quail. In Experiment 3, ICV NPAF was associated with decreased corticotropin-releasing factor mRNA, and an increase in hypothalamic proopiomelanocortin and melanocortin receptor 4 mRNA. These results demonstrate that central NPAF suppresses food and water intake in quail, effects that are likely mediated via the melanocortin system in the hypothalamus.

Ferulic acid, a phytochemical with transient anorexigenic effects in birds.

Ferulic acid (FA) is a phenolic acid found within the plant cell wall that has physiological benefits as an antioxidant. Although metabolic benefits of FA supplementation are described, lacking are reports of effects on appetite regulation. Thus, our objective was to determine if FA affects food or water intake, using chicks as a model. At 4 days post-hatch, broiler chicks were intraperitoneally injected with 0 (vehicle), 12.5, 25, or 50 mg/kg of FA. Chicks treated with 50 mg/kg of FA consumed 70% less food than controls at 30 min post-injection, and the effect dissipated thereafter. Water intake was not affected at any time. In a behavior analysis, FA-treated chicks defecated fewer times than vehicle-injected chicks, while other behaviors were not affected. There was an increase in c-Fos immunoreactivity within the hypothalamic arcuate nucleus (ARC) of FA-treated chicks, and no differences were detected in other nuclei. mRNA abundance was measured in the whole hypothalamus and the ARC. There was decreased hypothalamic galanin, ghrelin, melanocortin receptor 3, and pro-opiomelanocortin (POMC) mRNA in FA-treated chicks. Within the ARC, there was an increase in c-Fos mRNA and a decrease in POMC mRNA in response to FA. It is likely that the mechanism responsible for mediating FA's transient effects on food intake originates within the ARC, possibly involving POMC. A greater understanding of the short-term, mild appetite-suppressive effects of FA may have applications to treating eating disorders and modulating food intake in animal models of obesity.

Central GABAA receptor mediates taurine-induced hypothermia and possibly reduces food intake in thermo-neutral chicks and regulates plasma metabolites in heat-exposed chicks.

The aim of this study was to examine the central action of taurine on body temperature and food intake in neonatal chicks under control thermoneutral temperature (CT) and high ambient temperature (HT). Intracerebroventricular injection of taurine caused dose-dependent hypothermia and reduced food intake under CT. The mRNA expression of the GABAA receptors, GABAAR-α1 and GABAAR-γ, but not that of GABABR, significantly decreased in the diencephalon after central injection of taurine. Subsequently, we found that picrotoxin, a GABAAR antagonist, attenuated taurine-induced hypothermia. Central taurine significantly decreased the brain concentrations of 3-methoxy-4-hydroxyphenylglycol, a major metabolite of norepinephrine; however, the concentrations of serotonin, dopamine, and the epinephrine metabolites, 3,4-hydroxyindoleacetic acid and homovanillic acid, were unchanged. Although hypothermia was not observed under HT after central injection of taurine, plasma glucose and uric acid levels were higher, and plasma sodium and calcium levels were lower, than those in chicks under CT. In conclusion, brain taurine may play a role in regulating body temperature and food intake in chicks through GABAAR. The changes in plasma metabolites under heat stress suggest that brain taurine may play an important role in maintaining homeostasis in chicks.

Reduced food intake during exposure to high ambient temperatures is associated with molecular changes in the nucleus of the hippocampal commissure and the paraventricular and arcuate hypothalamic nuclei.

Exposure to high ambient temperatures (HAT) is associated with increased mortality, weight loss, immunosuppression, and metabolic malfunction in birds, all of which are likely downstream effects of reduced food intake. While the mechanisms mediating the physiological responses to HAT are documented, the neural mechanisms mediating behavioral responses are poorly understood. The aim of the present study was thus to investigate the hypothalamic mechanisms mediating heat-induced anorexia in four-day old broiler chicks. In Experiment 1, chicks exposed to HAT reduced food intake for the duration of exposure compared to controls in a thermoneutral environment (TN). In Experiment 2, HAT chicks that were administered an intracerebroventricular (ICV) injection of neuropeptide Y (NPY) increased food intake for 60 min post-injection, while TN chicks that received NPY increased food intake for 180 min post-injection. In Experiment 3, chicks in both the TN and HAT groups that received ICV injections of corticotropin-releasing factor (CRF) reduced food intake for up to 180 min post-injection. In Experiment 4, chicks that were exposed to HAT and received an ICV injection of astressin ate the same as controls in the TN group. In Experiment 5, chicks exposed to HAT that received an ICV injection of α-melanocyte stimulating hormone reduced food intake at both a high and low dose, with the low dose not reducing food intake in TN chicks. In Experiment 6, there was increased c-Fos expression in the hypothalamic paraventricular nucleus (PVN), lateral hypothalamic area (LHA), and the nucleus of the hippocampal commissure (NHpC). In Experiment 7, exposure to HAT was associated with decreased CRF mRNA in the NHpC, increased CRF mRNA in the PVN, and decreased NPY mRNA in the arcuate nucleus (ARC). In sum, these results demonstrate that exposure to HAT causes a reduction in food intake that is likely mediated via downregulation of NPY via the CRF system.

The hypothalamic mechanism of neuropeptide S-induced satiety in Japanese quail (Coturnix japonica) involves the paraventricular nucleus and corticotropin-releasing factor.

Neuropeptide S (NPS), a 20-amino acid neuropeptide, is produced in the brain and is associated with appetite suppression.Our group was the first to report this anorexigenic effect in birds using chicken as a model, although a hypothalamic molecular mechanism remains to be elucidated. Thus, we designed the present study using Japanese quail(Coturnix japonica).In Experiment 1, quail intracerebroventricularly injected with NPS reduced both food and water intake. In Experiment 2, food-restricted quail injected with NPS displayed a reduction in water intake.In Experiment 3, NPS-injected quail reduced their feeding and exploratory pecks.In Experiment 4, we quantified the number of cells expressing the early intermediate gene product c-Fos (as a marker of neuronal activation) in appetite associated hypothalamic nuclei and found that immunoreactivity was increased in the paraventricular nucleus (PVN). In Experiment 5, we utilized real-time PCR to screen for neuropeptide changes within the PVN of NPS-injected quail. Mesotocin and corticotropin-releasing factor (CRF) mRNAs increased in response to NPS injection. In Experiment 6, co-injection of astressin, a CRF receptor antagonist, was sufficient to block the food intake-suppressive effects of NPS, but in Experiment 7, co-injection of an oxytocin receptor antagonist was not sufficient to block the food intake-suppressive effects of NPS. Collectively, results support that NPS induces an anorexigenic response in Japanese quail that is mediated within the PVN and is associated with CRF.

Short communication: Short-term fasting and refeeding induced changes in subcutaneous adipose tissue physiology in 7-day old Japanese quail.

Adipose tissue development is influenced by a variety of factors, including nutrition and genetic background. Among avian species, the most is known in chickens and it is unclear if other less-artificially-selected birds are similar during the first week post-hatch. The aim of this study was thus to determine effects of fasting and refeeding on adipose tissue physiology in Japanese quail (Coturnix japonica). On day 7 post-hatch, quail were randomly assigned to fed (control), 6 h of fasting (fasted), or 6 h of fasting followed by 1 h of refeeding (refed) groups. Blood samples were collected for plasma non-esterified fatty acid (NEFA) determination and subcutaneous adipose tissues were harvested for gene expression analyses. Plasma NEFAs were elevated in the fasted state and restored to baseline within 1 h of refeeding, whereas the expression of monoglyceride lipase in subcutaneous adipose tissue was not affected by feeding status. CCAAT/enhancer binding protein α mRNA was decreased by fasting and this change persisted through refeeding, whereas neuropeptide Y receptor 5 mRNA was decreased in refed compared to fasted birds. Our results suggest that fasting promotes lipolysis and gene expression changes in young quail with some of these changes restored to original levels within only 1 h of refeeding. Thus, in quail, adipose tissue physiology is dynamic and influenced by short-term changes in nutritional status during the early post-hatch period.

Oxyntomodulin induces satiety and activates the arcuate nucleus of the hypothalamus in Japanese quail.

Oxyntomodulin (OXM) is a proglucagon-derived peptide that suppresses hunger in humans. There are some differences in its food intake-inhibitory effects among species. The central mechanisms are unclear and it is unknown if OXM is more efficacious in a gallinaceous species that has not undergone as much selection for growth as the chicken. The objective was thus to determine the effects of OXM on food and water intake and hypothalamic physiology in Japanese quail. At 7 days post-hatch, 6-h-fasted quail were injected intracerebroventricularly (ICV) or intraperitoneally (IP) with 0.32, 0.65, or 1.3 nmol of OXM. All doses decreased food intake for 180 min post-ICV injection. On a cumulative basis, water intake was not affected until 120 min, with the lowest and highest doses decreasing water intake after ICV injection. The two highest doses were anorexigenic when administered via the IP route, whereas all doses were anti-dipsogenic starting at 30 min post-injection. In hypothalamic samples collected at 1-h post-ICV injection, there was an increase in c-Fos immunoreactivity, an indicator of recent neuronal activation, in the arcuate nucleus (ARC) and dorsomedial nucleus (DMN) of the hypothalamus in OXM-injected individuals. Results suggest that quail are more sensitive than chickens to the satiety-inducing effects of OXM. The central mechanism is likely mediated through a pathway in the ARC that is conserved among species, and through activation of the DMN, an effect that is unique to quail. Such knowledge is critical for facilitating the development of novel, side effect-free anti-eating strategies to promote weight-loss in obesity.

Changes in adipose tissue physiology during the first two weeks posthatch in chicks from lines selected for low or high body weight.

Chickens from lines selected for low (LWS) or high (HWS) body weight (BW) differ in appetite and adiposity. Mechanisms associated with the predisposition to becoming obese are unclear. The objective of the experiment was to evaluate developmental changes in depot-specific adipose tissue during the first 2 wk posthatch. Subcutaneous (SQ), clavicular (CL), and abdominal (AB) depots were collected at hatch (DOH) and days 4 (D4) and 14 (D14) posthatch for histological and mRNA measurements. LWS chicks had decreased SQ fat mass on a BW basis with reduced adipocyte size from DOH to D4 and increased BW and fat mass with unchanged adipocyte size from D4 to D14. HWS chicks increased in BW from DOH to D14 and increased in fat mass in all three depots with enlarged adipocytes in the AB depot from D4 to D14. Meanwhile, CCAAT/enhancer-binding protein-α, neuropeptide Y, peroxisome proliferator-activated receptor-γ, and acyl-CoA dehydrogenase mRNAs differed among depots between lines at different ages. Plasma nonesterified fatty acids were greater in LWS than HWS at D4 and D14. From DOH to D4, LWS chicks mobilized SQ fat and replenished the reservoir through hyperplasia, whereas HWS chicks were dependent on hyperplasia and hypertrophy to maintain adipocyte size and depot mass. From D4 to D14, adipose tissue catabolism and adipogenesis slowed. Whereas LWS fat depots and adipocyte sizes remained stable, HWS chicks rapidly accumulated fat in CL and AB depots. Chicks predisposed to be anorexic or obese have different fat development patterns during the first 2 wk posthatch.

Hypothalamic mechanism of corticotropin-releasing factor's anorexigenic effect in Japanese quail (Coturnix japonica).

Central administration of corticotropin-releasing factor (CRF), a 41-amino acid peptide, is associated with anorexigenic effects across various species, with particularly potent reductions in food intake in rodents and chickens (Gallus gallus domesticus), a species for which the most is known. The purpose of the current study was to determine the hypothalamic mechanism of CRF-induced anorexigenic effects in 7 day-old Japanese quail (Coturnix japonica), a less-intensely-selected gallinaceous relative to the chicken that can provide more evolutionary perspective. After intracerebroventricular (ICV) injection of 2, 22, or 222 pmol of CRF, a dose-dependent decrease in food intake was observed that lasted for 3 and 24 h for the 22 and 222 pmol doses, respectively. The 2 pmol dose had no effect on food or water intake. The numbers of c-Fos immunoreactive cells were increased in the paraventricular nucleus (PVN) and lateral hypothalamic area (LHA) at 1 h post-injection in quail injected with 22 pmol of CRF. The hypothalamic mRNA abundance of proopiomelanocortin, melanocortin receptor subtype 4, CRF, and CRF receptor sub-type 2 was increased at 1 h in quail treated with 22 pmol of CRF. Behavior analyses demonstrated that CRF injection reduced feeding pecks and jumps and increased the time spent standing. In conclusion, results demonstrate that the anorexigenic effects of CRF in Japanese quail are likely influenced by the interaction between CRF and melanocortin systems and that injection of CRF results in species-specific behavioral changes.

Hypothalamic mechanisms associated with neuropeptide K-induced anorexia in Japanese quail (Coturnix japonica).

Central administration of neuropeptide K (NPK), a 36-amino acid peptide, is associated with anorexigenic effects in rodents and chickens. The mechanisms underlying the potent anorexigenic effects of NPK are still poorly understood. Thus, the aim of the present study was to identify the hypothalamic nuclei and neuropeptides that mediate anorexic effects of NPK in 7 day-old Japanese quail (Coturnix japonica). After a 6 h fast, intracerebroventricular (ICV) injection of NPK decreased food and water intake for 180 min post-injection. Quail injected with NPK had more c-Fos immunoreactive cells in the arcuate nucleus (ARC), lateral hypothalamus, and paraventricular nucleus (PVN) compared to the birds that were injected with the vehicle. In the ARC of NPK-injected quail, there was decreased neuropeptide Y (NPY), NPY receptor sub-type 1, and agouti-related peptide mRNA, and increased CART, POMC, and neurokinin receptor 1 mRNA. NPK-injected quail expressed greater amounts of corticotropin-releasing factor (CRF), CRF receptor sub-type 2, melanocortin receptors 3 and 4, and urocortin 3 mRNA in the PVN. In conclusion, results provide insights into understanding NPK-induced changes in hypothalamic physiology and feeding behavior, and suggest that the anorexigenic effects of NPK involve the ARC and PVN, with increased CRF and melanocortin and reduced NPY signaling.

Short communication: Adipogenic, metabolic, and apoptotic marker mRNA in cellular fractions of adipose tissue from chickens predisposed to be anorexic or obese.

The body weight-selected lines of chickens are a model for understanding factors that predispose an individual to anorexia or obesity. The high body weight-selected (HWS) individuals are compulsive eaters that become obese whereas the low body weight-selected (LWS) are relatively lean and hypophagic. The objective of this study was to measure gene expression of various preadipocyte, proliferation, metabolic, and apoptotic markers in the stromal-vascular fraction and adipocytes from LWS and HWS adipose tissue. Although preadipocyte and proliferation markers were more highly expressed in the stromal-vascular fraction of LWS than HWS chicks, greater expression of granzyme-A and the presence of more annexin V-positive cells suggests that apoptosis may limit the adipogenic potential of adipocyte precursor cells and represent a novel mechanism that regulates the expansion of adipose tissue. Results provide insights on cellular mechanisms associated with adipose tissue development in the lean and obese state.

Fasting and refeeding induce differential changes in hypothalamic mRNA abundance of appetite-associated factors in 7 day-old Japanese quail, Coturnix japonica.

There is little information regarding effects of fasting on feeding behavior and hypothalamic physiology in young Japanese quail. The aim was thus to measure food intake and hypothalamic mRNA in response to fasting and refeeding. Five d-old quail ate little during the dark cycle. Food intake was greatest during the first 2 h of the light cycle. Six day-old quail fasted for 6 h ate the most during the first 15 min of refeeding. In 7 d-old quail, 3 h of fasting up-regulated hypothalamic neuropeptide Y (NPY), NPY receptor sub-type 2 (NPYR2), agouti-related peptide (AgRP), orexin receptor 2 (ORXR2), melanocortin receptors 3 and 4 (MC3R and MC4R, respectively), and neuropeptide S (NPS) and decreased corticotropin-releasing factor receptor sub-type 1 (CRFR1) mRNA. Quail fasted for 3 h and refed for 1 h had greater NPY, AgRP, POMC, and MC3R but less CRFR1 mRNA than fed quail. Quail fasted for 6 h expressed more NPY, NPYR1, NPYR2, and MC3R and less ORXR2, prolactin releasing peptide (PrRP), cocaine- and amphetamine-regulated transcript (CART), and calcitonin (CAL) mRNA than fed quail. Quail fasted for 6 h and refed for 1 h expressed more NPY, NPYR1, NPYR2, AgRP, MC3R, MC4R, and NPS and less galanin, ORXR2, PrRP, CART, and CAL mRNA than fed birds. Hence, fasting induced changes in hypothalamic mRNA, with the largest changes occurring in genes associated with NPY and melanocortin signaling. Most genes remained elevated or downregulated after refeeding, suggesting that there was a time lag for transcription to respond to compensatory feeding.

Anorexigenic effects of mesotocin in chicks are genetic background-dependent and are associated with changes in the paraventricular nucleus and lateral hypothalamus.

Mesotocin (MT) decreases food intake and induces hyperthermia in chicks although hypothalamic mechanisms are unknown. The purpose of this study was thus to investigate effects of receptor antagonists and MT on feeding behavior and hypothalamic physiology. Intracerebroventricular injection of 2.5 nmol into broiler chicks was associated with decreased food intake for 180 min and water intake from 60 to 180 min. Cloacal temperatures were elevated in chicks injected with 0.156 and 0.625 nmol at 30 and 60 min, and up to 180 min in those injected with 2.5 nmol. MT also increased temperatures and decreased food and water intake in chicks from lines selected for low (LWS) or high (HWS) body weight with a higher dose threshold but longer food intake response in HWS chicks. An oxytocin receptor antagonist prevented MT-mediated changes in food intake but not water intake or temperature. Yohimbine, an α2-adrenergic receptor antagonist, did not affect food intake, temperature, or MT-mediated effects. MT increased c-Fos immunoreactivity in the paraventricular nucleus (PVN) and lateral hypothalamus (LH). Hypothalamic agouti-related peptide, corticotropin-releasing factor receptor sub-type 1, and melanocortin receptor 3 mRNAs increased in response to MT. There was increased MT mRNA in the LH and L-aromatic amino acid decarboxylase mRNA in the PVN of MT-injected chicks. In conclusion, MT induced anorexia and hyperthermia and reduced water intake. MT was associated with activation of the PVN and LH and differences in the mRNA abundance of some appetite-associated factors, thus implicating these nuclei and several signaling pathways in the effects observed.

Dietary macronutrient composition and central neuropeptide Y injection affect dietary preference and hypothalamic gene expression in chicks.

OBJECTIVE: The objective of this study was to determine the influence of dietary macronutrient composition on central NPY's orexigenic effect in chicks. METHODS: Day-of-hatch chicks were fed one of three diets (3000 kcal ME/kg) ad libitum from hatch: high carbohydrate (HC), high fat (HF; 30% ME derived from soybean oil), and high protein (HP; 25 vs. 22% CP). In Experiment 1, chicks received intracerebroventricular injections of 0 (vehicle), 0.2, or 2.0 nmol NPY on day 4 and food intake was recorded for 6 hours. In Experiment 2, chicks were given all three diets before and after injection. In Experiment 3, hypothalamus was collected at 1-hour post-injection for gene expression analysis. RESULTS: The HC diet-fed chicks responded with a greater increase, while the chicks fed the HF diet had a lower threshold response in food intake to NPY. Neuropeptide Y dose-dependently increased food intake in chicks fed the HC and HP diets. Chicks administered 0.2 nmol NPY preferred the HC and HP diets over the HF diet. Relative quantities of hypothalamic NPYR1 and MC4R mRNA were reduced by NPY in chicks that consumed the HP and HC diets, respectively. DISCUSSION: Consumption of the HC diet was associated with the most robust NPY-induced increase in food intake. Injection of NPY accentuated differences among dietary groups in hypothalamic gene expression of several appetite-associated factors, results suggesting that the NPY/agouti-related peptide and melanocortin pathways are associated with some of the diet- and NPY-induced differences observed in this study.

Dietary macronutrient composition affects hypothalamic appetite regulation in chicks.

OBJECTIVE: The objective was to determine the effects of high-protein and high-fat diets, and fasting and refeeding, on appetite regulation in chicks. METHODS: Day of hatch chicks were fed one of four diets: basal, high protein (25% crude protein), and 15 and 30% high fat (15 and 30% metabolizable energy derived from soybean oil, respectively), and assigned to one of three treatments at 4 days: (1) access to feed, (2) 3 hours of fasting, or (3) fasting followed by 1 hour of refeeding. The hypothalamus was collected, total RNA isolated, and mRNA abundance measured. RESULTS: Food intake was reduced in chicks fed the high-protein and high-fat diets. Agouti-related peptide, neuropeptide Y (NPY), NPY receptors 1, 2, and 5, melanocortin receptors 3 and 4 (MC3R and 4R, respectively), mesotocin, corticotropin-releasing factor (CRF), and CRF receptor sub-type 2 (CRFR2) mRNAs were greatest in chicks that consumed the basal diet. Refeeding was associated with increased MC3R mRNA in the high-protein diet group. CRFR2 mRNA was increased by fasting and refeeding in chicks that consumed the high-protein diet. DISCUSSION: Food intake and hypothalamic gene expression of some important appetite-associated factors were reduced in chicks fed the high-protein or high-fat diets. Fasting and refeeding accentuated several differences and results suggest that the CRF and melanocortin pathways are involved.

Responses to peripheral neuropeptide Y in avian adipose tissue are diet, depot, and time specific.

The goal of this research was to determine the effect of dietary macronutrient composition on peripheral neuropeptide Y (NPY)-induced changes in adipose tissue dynamics in chicks. Chicks were fed one of three isocaloric diets from the day of hatch: high carbohydrate (HC), high fat (HF), or high protein (HP). On day 4 post-hatch, 0 (vehicle), 60, or 120 µg/kg BW of NPY was injected intraperitoneally, and subcutaneous, clavicular and abdominal adipose tissue samples were collected at 1 and 3 h post-injection. The effect of NPY was most pronounced in chicks fed the HF or HP diet. In the subcutaneous fat at 1 h post-injection, 60 µg/kg BW of NPY was associated with an increase in NPY receptor 2 (NPYR2) mRNA in chicks fed the HP diet and a decrease in 1-acylglycerol-3-phosphate O-acyltransferase 2 (AGPAT2) mRNA in chicks fed the HC diet. In response to 120 µg/kg BW of NPY, there was greater AGPAT2 mRNA in the clavicular fat of chicks that consumed the HP diet and less CCAAT/enhancer-binding protein alpha in the abdominal fat of chicks that were provided the HF diet. There were no gene expression changes in the abdominal fat at 3 h post-injection, whereas there were decreases in AGPAT2, adipose triglyceride lipase, fatty acid binding protein 4 and NPY mRNA in the clavicular fat of chicks fed the HP diet. Results demonstrate that diet affects exogenous NPY-dependent physiological effects in a time- and depot-dependent manner in chick adipose tissue.