Endogenous ACTH, not only alpha-melanocyte-stimulating hormone, reduces food intake mediated by hypothalamic mechanisms

The effects of neuropeptide W on food consumption and feeding behavior in neonatal meat-type chicks: Role of CRF1/CRF2 and NPY1 receptors

In several studies, the regulatory role of the neuropeptide W (NPW) system in food intake has been demonstrated. Considering the lack of avian studies in this field, the current research was conducted to evaluate the effects of intracerebroventricular (ICV) infusion of NPW and its interferences with corticotropin, melanocortin, and neuropeptide Y (NPY) receptors on meal consumption and feeding behaviors of broilers. In the first experiment, birds were injected with NPW (0.75, 1.5, and 3 nmol) in addition to saline. In the second experiment, saline, CRF1 receptor antagonist (NBI35965, 30 μg), NPW (3 nmol), and simultaneous injections of NBI35965 and NPW were performed. Experiments 3-8 were identical to experiment 2, except that CRF2 receptor antagonist (K41498, 30 μg), MC3/MC4 receptor antagonist (SHU9119, 0.5 nmol), MC4 receptor antagonist (HS024, 0.5 nmol), NPY1 receptor antagonist (BMS193885, 1.25 nmol), NPY2 receptor antagonist (CYM9484, 1.25 nmol), and NPY5 receptor (antagonist L-152,804, 1.25 nmol) were administrated instead of NBI35965. After that, cumulative feed intake and feeding behavior were monitored for 2 h and 30 min after injections, respectively. Following the infusion of NPW (1.5 and 3 nmol), there was a significant stimulation of meal consumption in chickens (P < 0.05). Concomitant injection of NBI35965 and K41498 with NPW enhanced the appetite-increasing effect of NPW (P < 0.05); while BMS193885 suppressed this effect of NPW (P < 0.05). Injection of SHU9119, HS024, CYM9484, and L-152804 with NPW at the same time, had no significant effect on NPW-induced hyperphagia (P > 0.05). NPW also significantly decreased the standing period and the number of jumps, steps, and exploratory pecks, and led to an increase in sitting period and feeding pecks (P < 0.05). Based on the observations, it seems that NPW-induced hyperphagia could be mediated through CRF1, CRF2, and NPY1 receptors in neonatal broilers.

Identification and characterization of hypothalamic circular RNAs associated with bovine residual feed intake

Residual feed intake (RFI) is crucial economic indicator used for calculating the feed efficiency of growing beef cattle. circRNA plays an important biological role in gene transcriptional regulation, but little is known about its potential functional regulation underlying RFI phenotypic variation. As the core center of regulation of animal feeding, the hypothalamus is closely associated with RFI. Therefore, the present study aimed to identify the key genes and functional pathways contributing to variance in cattle RFI phenotypes using RNA sequencing from hypothalamic tissue samples, in order to gain insight into the potential regulatory role of circRNAs in bovine RFI phenotypic variation. Differentially expressed genes were detected by RNA sequencing for beef cattle in the high and low RFI groups, followed by GO, KEGG enrichment, and circRNA-miRNA co-expression network analysis. A total of 257 circRNAs were differentially expressed between the two groups, with 128 significantly upregulated and 129 significantly downregulated genes in H group compared to L group. Among them, 9 unique circRNAs were present in group L and 4 unique circRNAs were present in group H. GO and KEGG enrichment analysis of the source genes of the differentially expressed circRNAs revealed that they were mainly involved in metabolic processes, such as cellular metabolic processes, cellular macromolecular metabolic processes, and regulatory pathways related to nutrient metabolism, including protein and amino acid metabolism, as well as vitamin metabolism and pancreatic secretion associated with the animal feeding behavior. The circRNAs detected in this study were mostly novel, and have not been investigated directly to be associated with the RFI phenotype. Interestingly, most miRNAs of differentially expressed circRNAs predicted based on the circRNA-miRNA co-expression network analysis by using top 50 differentially expressed circRNAs and 13 unique circRNAs, have been reported to be related to animal RFIs, implying that circRNAs in bovine hypothalamic tissue may regulate phenotypic variation in RFI through miRNAs. The study results illustrate the complex biological functions of the hypothalamus in regulating feed efficiency and showing the potential role of circRNAs in the feeding behavior regulation of livestock, which would contributing to expanding the understanding of circRNA.

Endogenous NUCB2/Nesfatin-1 Regulates Energy Homeostasis Under Physiological Conditions in Male Rats

Nesfatin-1 is the proteolytic cleavage product of Nucleobindin 2, which is expressed both in a number of brain nuclei (e. g., the paraventricular nucleus of the hypothalamus) and peripheral tissues. While Nucleobindin 2 acts as a calcium binding protein, nesfatin-1 was shown to affect energy homeostasis upon central nervous administration by decreasing food intake and increasing thermogenesis. In turn, Nucleobindin 2 mRNA expression is downregulated in starvation and upregulated in the satiated state. Still, knowledge about the physiological role of endogenous Nucleobindin 2/nesfatin-1 in the control of energy homeostasis is limited and since its receptor has not yet been identified, rendering pharmacological blockade impossible. To overcome this obstacle, we tested and successfully established an antibody-based experimental model to antagonize the action of nesfatin-1. This model was then employed to investigate the physiological role of endogenous Nucleobindin 2/nesfatin-1. To this end, we applied nesfatin-1 antibody into the paraventricular nucleus of satiated rats to antagonize the presumably high endogenous Nucleobindin 2/nesfatin-1 levels in this feeding condition. In these animals, nesfatin-1 antibody administration led to a significant decrease in thermogenesis, demonstrating the important role of endogenous Nucleobindin 2/nesfatin-1in the regulation of energy expenditure. Additionally, food and water intake were significantly increased, confirming and complementing previous findings. Moreover, neuropeptide Y was identified as a major downstream target of endogenous Nucleobindin 2/nesfatin-1.

Cosyntropin Attenuates Neuroinflammation in a Mouse Model of Traumatic Brain Injury

Aim: Traumatic brain injury (TBI) is a leading cause of mortality/morbidity and is associated with chronic neuroinflammation. Melanocortin receptor agonists including adrenocorticotropic hormone (ACTH) ameliorate inflammation and provide a novel therapeutic approach. We examined the effect of long-acting cosyntropin (CoSyn), a synthetic ACTH analog, on the early inflammatory response and functional outcome following experimental TBI.

Methods: The controlled cortical impact model was used to induce TBI in mice. Mice were assigned to injury and treatment protocols resulting in four experimental groups including sham + saline, sham + CoSyn, TBI + saline, and TBI + CoSyn. Treatment was administered subcutaneously 3 h post-injury and daily injections were given for up to 7 days post-injury. The early inflammatory response was evaluated at 3 days post-injury through the evaluation of cytokine expression (IL1β and TNFα) and immune cell response. Quantification of immune cell response included cell counts of microglia/macrophages (Iba1+ cells) and neutrophils (MPO+ cells) in the cortex and hippocampus. Behavioral testing (n = 10–14 animals/group) included open field (OF) and novel object recognition (NOR) during the first week following injury and Morris water maze (MWM) at 10–15 days post-injury.

Results: Immune cell quantification showed decreased accumulation of Iba1+ cells in the perilesional cortex and CA1 region of the hippocampus for CoSyn-treated TBI animals compared to saline-treated. Reduced numbers of MPO+ cells were also found in the perilesional cortex and hippocampus in CoSyn treated TBI mice compared to their saline-treated counterparts. Furthermore, CoSyn treatment reduced IL1β expression in the cortex of TBI mice. Behavioral testing showed a treatment effect of CoSyn for NOR with CoSyn increasing the discrimination ratio in both TBI and Sham groups, indicating increased memory performance. CoSyn also decreased latency to find platform during the early training period of the MWM when comparing CoSyn to saline-treated TBI mice suggesting moderate improvements in spatial memory following CoSyn treatment.

Conclusion: Reduced microglia/macrophage accumulation and neutrophil infiltration in conjunction with moderate improvements in spatial learning in our CoSyn treated TBI mice suggests a beneficial anti-inflammatory effect of CoSyn following TBI.

Neurohormonal Regulation of Appetite and its Relationship with Stress: A Mini Literature Review

Stress has long been known to affect eating behaviors in humans. Stress-induced hyperphagia is considered a potential cause for the development of obesity. Given the high prevalence of obesity and its association with other cardiovascular and metabolic disorders, the subject of stress-induced eating has become even more important. We reviewed data from past studies to further elucidate the relationship between stress, appetite regulation and eating patterns in humans. Even though it is difficult to say with certainty that a person exposed to stress will undereat or overeat, but certain assumptions can be made. Generally, acute stress results in decreased eating whereas chronic stress results in increased eating. Glucocorticoids, the effector molecules of the stress response, increase the tendency to consume high-calorie, palatable foods. Further studies that can link the biological markers of stress-response with the hormones and neurotransmitters of appetite regulation can broaden our understanding of the subject. These studies can provide a groundwork for the development of effective anti-obesity strategies.

Development of obesity can be prevented in rats by chronic icv infusions of AngII but less by Ang(1-7)

Considering that obesity is one of the leading risks for death worldwide, it should be noted that a brain-related mechanism is involved in AngII-induced and AT₁-receptor-dependent weight loss. It is moreover established that activation of the Ang(1-7)/ACE2/Mas axis reduces weight, but it remains unclear whether this Ang(1-7) effect is also mediated via a brain-related mechanism. Additionally to Sprague Dawley (SD) rats, we used TGR(ASrAOGEN) selectively lacking brain angiotensinogen, the precursor to AngII, as we speculated that effects are more pronounced in a model with low brain RAS activity. Rats were fed with high-calorie cafeteria diet. We investigated weight regulation, food behavior, and energy balance in response to chronic icv.-infusions of AngII (200 ng•h^-1), or Ang(1-7) (200/600 ng•h^-1) or artificial cerebrospinal fluid. High- but not low-dose Ang(1-7) slightly decreased weight gain and energy intake in SD rats. AngII showed an anti-obese efficacy in SD rats by decreasing energy intake and increasing energy expenditure and also improved glucose control. TGR(ASrAOGEN) were protected from developing obesity. However, Ang(1-7) did not reveal any effects in TGR(ASrAOGEN) and those of AngII were minor compared to SD rats. Our results emphasize that brain AngII is a key contributor for regulating energy homeostasis and weight in obesity by serving as a negative brain-related feedback signal to alleviate weight gain. Brain-related anti-obese potency of Ang(1-7) is lower than AngII but must be further investigated by using other transgenic models as TGR(ASrAOGEN) proved to be less valuable for answering this question.

Systemic N-terminal fragments of adrenocorticotropin reduce inflammation- and stress-induced anhedonia in rats

Emerging evidence implicates impaired self-regulation of the hypothalamic-pituitary-adrenal (HPA) axis and inflammation as important and closely related components of the pathophysiology of major depression. Antidepressants show anti-inflammatory effects and are suggested to enhance glucocorticoid feedback inhibition of the HPA axis. HPA axis activity is also negatively self-regulated by the adrenocorticotropic hormone (ACTH), a potent anti-inflammatory peptide activating five subtypes of melanocortin receptors (MCRs). There are indications that ACTH-mediated feedback can be activated by noncorticotropic N-terminal ACTH fragments such as a potent anti-inflammatory MC1/3/4/5R agonist α-melanocyte-stimulating hormone (α-MSH), corresponding to ACTH(1-13), and a MC3/5R agonist ACTH(4-10). We investigated whether intraperitoneal administration of rats with these peptides affects anhedonia, which is a core symptom of depression. Inflammation-related anhedonia was induced by a single intraperitoneal administration of a low dose (0.025mg/kg) of lipopolysaccharide (LPS). Stress-related anhedonia was induced by the chronic unpredictable stress (CUS) procedure. The sucrose preference test was used to detect anhedonia. We found that ACTH(4-10) pretreatment decreased LPS-induced increase in serum corticosterone and tumor necrosis factor (TNF)-α, and a MC3/4R antagonist SHU9119 blocked this effect. Both α-MSH and ACTH(4-10) alleviated LPS-induced anhedonia. In the CUS model, these peptides reduced anhedonia and normalized body weight gain. The data indicate that systemic α-MSH and ACTH(4-10) produce an antidepressant-like effect on anhedonia induced by stress or inflammation, the stimuli that trigger the release of ACTH and α-MSH into the bloodstream. The results suggest a counterbalancing role of circulating melanocortins in depression and point to a new approach for antidepressant treatment.

PC1/3 Deficiency Impacts Pro-opiomelanocortin Processing in Human Embryonic Stem Cell-Derived Hypothalamic Neurons

We recently developed a technique for generating hypothalamic neurons from human pluripotent stem cells. Here, as proof of principle, we examine the use of these cells in modeling of a monogenic form of severe obesity: PCSK1 deficiency. The cognate enzyme, PC1/3, processes many prohormones in neuroendocrine and other tissues. We generated PCSK1 (PC1/3)-deficient human embryonic stem cell (hESC) lines using both short hairpin RNA and CRISPR-Cas9, and investigated pro-opiomelanocortin (POMC) processing using hESC-differentiated hypothalamic neurons. The increased levels of unprocessed POMC and the decreased ratios (relative to POMC) of processed POMC-derived peptides in both PCSK1 knockdown and knockout hESC-derived neurons phenocopied POMC processing reported in PC1/3-null mice and PC1/3-deficient patients. PC1/3 deficiency was associated with increased expression of melanocortin receptors and PRCP (prolylcarboxypeptidase, a catabolic enzyme for α-melanocyte stimulating hormone (αMSH)), and reduced adrenocorticotropic hormone secretion. We conclude that the obesity accompanying PCSK1 deficiency may not be primarily due to αMSH deficiency.

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Stem cell-derived hypothalamic neurons are used to study human obesity

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shRNA and CRISPR-Cas9 were used to generate models of PCSK1 deficiency

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PC1/3 deficiency impaired POMC processing in arcuate-like neurons

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Adaptive changes occurred in “downstream” POMC processing enzymes

Regulation of Agouti-Related Protein and Pro-Opiomelanocortin Gene Expression in the Avian Arcuate Nucleus

The arcuate nucleus is generally conserved across vertebrate taxa in its neuroanatomy and neuropeptide expression. Gene expression of agouti-related protein (AGRP), neuropeptide Y (NPY), pro-opiomelanocortin (POMC), and cocaine- and amphetamine-regulated transcript (CART) has been established in the arcuate nucleus of several bird species and co-localization demonstrated for AGRP and NPY. The proteins encoded by these genes exert comparable effects on food intake in birds after central administration to those seen in other vertebrates, with AGRP and NPY being orexigenic and CART and α-melanocyte-stimulating hormone anorexigenic. We have focused on the measurement of arcuate nucleus AGRP and POMC expression in several avian models in relation to the regulation of energy balance, incubation, stress, and growth. AGRP mRNA and POMC mRNA are, respectively, up- and downregulated after energy deprivation and restriction. This suggests that coordinated changes in the activity of AGRP and POMC neurons help to drive the homeostatic response to replace depleted energy stores in birds as in other vertebrates. While AGRP and POMC expression are generally positively and negatively correlated with food intake, respectively, we review here situations in some avian models in which AGRP gene expression is dissociated from the level of food intake and may have an influence on growth independent of changes in appetite. This suggests the possibility that the central melanocortin system exerts more pleiotropic functions in birds. While the neuroanatomical arrangement of AGRP and POMC neurons and the sensitivity of their activity to nutritional state appear generally conserved with other vertebrates, detailed knowledge is lacking of the key nutritional feedback signals acting on the avian arcuate nucleus and there appear to be significant differences between birds and mammals. In particular, recently identified avian leptin genes show differences between bird species in their tissue expression patterns and appear less closely linked in their expression to nutritional state. It is presently uncertain how the regulation of the central melanocortin system in birds is brought about in the situation of the apparently reduced importance of leptin and ghrelin compared to mammals.

Pharmacological induction of skin pigmentation unveils the neuroendocrine circuit regulated by light

Light-regulated skin colour change is an important physiological process in invertebrates and lower vertebrates, and includes daily circadian variation and camouflage (i.e. background adaptation). The photoactivation of melanopsin-expressing retinal ganglion cells (mRGCs) in the eye initiates an uncharacterized neuroendocrine circuit that regulates melanin dispersion/aggregation through the secretion of alpha-melanocyte-stimulating hormone (α-MSH). We developed experimental models of normal or enucleated Xenopus embryos, as well as in situ cultures of skin of isolated dorsal head and tails, to analyse pharmacological induction of skin pigmentation and α-MSH synthesis. Both processes are triggered by a melanopsin inhibitor, AA92593, as well as chloride channel modulators. The AA9253 effect is eye-dependent, while functional data in vivo point to GABAA receptors expressed on pituitary melanotrope cells as the chloride channel blocker target. Based on the pharmacological data, we suggest a neuroendocrine circuit linking mRGCs with α-MSH secretion, which is used normally during background adaptation.

Nesfatin-1 increases energy expenditure and reduces food intake in rats

OBJECTIVE

Energy homeostasis results from a balance of food intake and energy expenditure, accomplished by the interaction of peripheral and central nervous signals. The recently discovered adipokine nesfatin-1 is involved in the central control of food intake, but whether it also participates in the regulation of thermogenesis is unknown.

METHODS

Nesfatin-1 was administered intracerebroventricularly to freely moving, male Wistar rats and direct calorimetry was performed to assess its effects on thermogenesis. Furthermore, food intake was measured and hypothalamic and N. tractus solitarius (NTS) neuropeptide expression was determined by quantitative real-time polymerace chain reaction. Leptin, which is involved in both the regulation of food intake and thermogenesis, was used as positive control.

RESULTS

For the first time it was shown that central nervous administration of nesfatin-1 profoundly increases thermogenesis in rats to a similar extent as leptin and the role of both peptides in the control of food intake was confirmed. Nesfatin-1 significantly downregulated neuropeptide Y (NPY) mRNA expression in both hypothalamus and NTS.

CONCLUSIONS

The results strongly support the prominent role of nesfatin-1 for both energy expenditure and food intake and NPY neurons appear to be involved in this effect.

Food-intake regulation during stress by the hypothalamo-pituitary-adrenal axis

The prevalence of obesity is increasing worldwide with serious consequences such as diabetes mellitus type 2 and cardiovascular diseases. Emotional stress is considered to be one of the main reasons of obesity development in humans. However, there are some contradictory results, which should be addressed. First of all stress induces anorexia, but not overeating in laboratory animals. Glucocorticoids, the effector molecules of the hypothalamo-pituitary-adrenocortical (HPA) axis stimulate and stress inhibits food intake. It is also not clear if stress is diabetogenic or an antidiabetogenic factor. The review will discusses these issues and the involvement of the whole HPA axis and its separate molecules (glucocorticoids, adrenocorticotropin, corticotropin-releasing hormone) in food intake regulation under stress.

Intranasal leptin reduces appetite and induces weight loss in rats with diet-induced obesity (DIO)

Resistance to brain-mediated effects of leptin is a characteristic feature of obesity, resulting from alterations in leptin receptor signaling in hypothalamic neurons and/or transport across the blood-brain-barrier. We have shown previously, that the latter can be circumvented by intranasal (i.n.) application of leptin in lean rats. This prompted us to test i.n. leptin in animals with diet-induced obesity (DIO) as a basis for future human administration. DIO was induced in male Wistar rats by feeding a cafeteria diet for 25 or 32 wk, respectively. Consecutively, these DIO animals (seven to eight per treatment) and standard diet rats (lean) (14-15 per treatment, matched for age and diet duration) were treated with 0.1, 0.2 mg/kg leptin, or control solution i.n. daily for 4 wk before onset of dark period. Energy intake and body weight were measured daily; blood glucose, serum insulin, and leptin were measured before and after treatment. Expression of hypothalamic neuropeptides was assessed by quantitative real-time PCR. We demonstrate, for the first time, that i.n. leptin reduces appetite and induces weight loss in DIO to the same extent as in lean rats. Our findings are supported accordingly by an altered expression pattern of anorexigenic and orexigenic neuropeptides in the hypothalamus, e.g. proopiomelanocortin, cocaine and amphetamine-related transcript, neuropeptide Y, agouti-related protein. It now appears clear that i.n. leptin is effectively acting in obese animals in the same fashion as in their lean counterparts. These findings now clearly warrant studies in humans and may open new perspectives in the treatment of obesity.

Expanding neurotransmitters in the hypothalamic neurocircuitry for energy balance regulation

The current epidemic of obesity and its associated metabolic syndromes impose unprecedented challenges to our society. Despite intensive research on obesity pathogenesis, an effective therapeutic strategy to treat and cure obesity is still lacking. Exciting studies in last decades have established the importance of the leptin neural pathway in the hypothalamus in the regulation of body weight homeostasis. Important hypothalamic neuropeptides have been identified as critical neurotransmitters from leptin-sensitive neurons to mediate leptin action. Recent research advance has significantly expanded the list of neurotransmitters involved in body weight-regulating neural pathways, including fast-acting neurotransmitters, gamma-aminobutyric acid (GABA) and glutamate. Given the limited knowledge on the leptin neural pathway for body weight homeostasis, understanding the function of neurotransmitters released from key neurons for energy balance regulation is essential for delineating leptin neural pathway and eventually for designing effective therapeutic drugs against the obesity epidemic.

Adipocyte-brain: crosstalk

The initial discovery of leptin, an appetite-suppressing hormone originating from fat tissue, substantially supported the idea that fat-borne factors act on the brain to regulate food intake and energy expenditure. Since then, a growing number of cytokines have been found to be released from adipose tissue, thus acting in an endocrine manner. These adipocytokines include not only, e.g., adiponectin, apelin, resistin, and visfatin, but also inflammatory cytokines and steroid hormones such as estrogens and glucocorticoids. They are secreted from their adipose depots and differ in terms of release stimuli, downstream signaling, and their action on the brain. Clearly, adipocytokines play a prominent role in the central control of body weight, and the deregulation of this circuit may lead to the development of obesity and related disorders. In this chapter, we will focus on crosstalk mechanisms and the deregulation of adipocytokines at the expression level and/or sites of central action that eventually will lead to the development and perpetuation of obesity and diabetes.