Hypothalamic mechanisms associated with corticotropin-releasing factor-induced anorexia in chicks

AgRP/NPY and POMC neurons in the arcuate nucleus and their potential role in treatment of obesity

Obesity is a major health crisis affecting over a third of the global population. This multifactorial disease is regulated via interoceptive neural circuits in the brain, whose alteration results in excessive body weight. Certain central neuronal populations in the brain are recognised as crucial nodes in energy homeostasis; in particular, the hypothalamic arcuate nucleus (ARC) region contains two peptide microcircuits that control energy balance with antagonistic functions: agouti-related peptide/neuropeptide-Y (AgRP/NPY) signals hunger and stimulates food intake; and pro-opiomelanocortin (POMC) signals satiety and reduces food intake. These neuronal peptides levels react to energy status and integrate signals from peripheral ghrelin, leptin, and insulin to regulate feeding and energy expenditure. To manage obesity comprehensively, it is crucial to understand cellular and molecular mechanisms of information processing in ARC neurons, since these regulate energy homeostasis. Importantly, a specific strategy focusing on ARC circuits needs to be devised to assist in treating obese patients and maintaining weight loss with minimal or no side effects. The aim of this review is to elucidate the recent developments in the study of AgRP-, NPY- and POMC-producing neurons, specific to their role in controlling metabolism. The impact of ghrelin, leptin, and insulin signalling via action of these neurons is also surveyed, since they also impact energy balance through this route. Lastly, we present key proteins, targeted genes, compounds, drugs, and therapies that actively work via these neurons and could potentially be used as therapeutic targets for treating obesity conditions.

DNA methylation-modifiers reduced food intake in juvenile chickens (Gallus gallus) and Japanese quail (Coturnix japonica)

S-Adenosylmethionine (SAM) is the major endogenous methyl donor for methyltransferase reactions, while 5-Azacytidine (AZA) is a synthetic drug inhibiting DNA methyltransferase activity. Both molecules can thus influence DNA methylation patterns in an organism and thereby affect gene expression and ultimately behavior in the long-term. Whether or not effects on behavior are exerted on a shorter time scale is unclear. The goal of this study was to explore the direct effects of SAM and AZA on appetite regulation, using broiler chicken and Japanese quail as the animal models. Fed or 180 min-fasted broilers (at day 4 post-hatch) or 360 min-fasted quail (at day 7 post-hatch) were intracerebroventricularly injected with SAM or AZA and food intake was measured for 360 min. For broilers, there was no effect of AZA, at any dose, on food intake in either fed or fasted chicks at any time point. In contrast, 1 and 10 µg doses of SAM reduced food intake in fed chicks at 60 min post-injection. In fasted chicks, although there were no differences for the first 30 min post-injection, SAM suppressed food intake during the second 30-min period. For quail, however, AZA (25 µg dose) decreased food intake at 60 and 150-360 min post-injection in fasted birds. A reduction in food intake was also observed at 120- and 360-min post-injection in fed quail in response to 5 and 25 µg doses of AZA, respectively. SAM had no effect when quail were fasted, whereas 1 µg dose of SAM suppressed food consumption in fed quail during the third 30-min period. Thus, when administered directly into the central nervous system, SAM may act as a transient appetite suppressant in both broilers and quail, whereas the direct inhibitory effect of AZA on food consumption depends on species and nutritional states.

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.

Microglia exosomal miRNA-137 attenuates ischemic brain injury through targeting Notch1

Microglia are the resident immune cells in the central nervous system and play an essential role in brain homeostasis and neuroprotection in brain diseases. Exosomes are crucial in intercellular communication by transporting bioactive miRNAs. Thus, this study aimed to investigate the function of microglial exosome in the presence of ischemic injury and related mechanism. Oxygen-glucose deprivation (OGD)-treated neurons and transient middle cerebral artery occlusion (TMCAO)-treated mice were applied in this study. Western blotting, RT-PCR, RNA-seq, luciferase reporter assay, transmission electron microscope, nanoparticle tracking analysis, immunohistochemistry, TUNEL and LDH assays, and behavioral assay were applied in mechanistic and functional studies. The results demonstrated that exosomes derived from microglia in M2 phenotype (BV2-Exo) were internalized by neurons and attenuated neuronal apoptosis in response to ischemic injury in vitro and in vivo. BV2-Exo also decreased infarct volume and behavioral deficits in ischemic mice. Exosomal miRNA-137 was upregulated in BV2-Exo and participated in the partial neuroprotective effect of BV2-Exo. Furthermore, Notch1 was a directly targeting gene of exosomal miRNA-137. In conclusion, these results suggest that BV2-Exo alleviates ischemia-reperfusion brain injury through transporting exosomal miRNA-137. This study provides novel insight into microglial exosomes-based therapies for the treatment of ischemic brain injury.

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.

Prolactin-releasing peptide increases food intake and affects hypothalamic physiology in Japanese quail (Coturnix japonica)

Prolactin-releasing peptide (PrRP) increases food intake in birds, whereas it is a potent satiety factor in rodents and fish. The aim of this study was to determine the effects of central injection of PrRP on feeding behaviors and hypothalamic physiology in juvenile Japanese quail (Coturnix japonica). Intracerebroventricular injection of 1,692 pmol of PrRP increased food intake for the first 90 min after injection but did not affect water intake. Quail treated with PrRP displayed more food and drink pecks, less time standing but more perching, and decreased defecations. Prolactin-releasing peptide-injected quail had increased c-Fos immunoreactivity in the dorsomedial nucleus (DMN) and arcuate nucleus (ARC) of the hypothalamus. Hypothalamic neuropeptide Y receptor subtypes 2 and 5 and melanocortin receptor 4 mRNAs were greater in PrRP- than vehicle-injected quail. In the DMN, there was less corticotropin-releasing factor (CRF) mRNA and in the ARC, more CRF mRNA in PrRP- than vehicle-injected chicks. Thus, PrRP increases food intake in quail, which is associated with changes in hypothalamic CRF and neuropeptide Y receptor gene expression and c-Fos-immunolabeled cells in the ARC and DMN.