Proopiomelanocortin Peptides Research Articles

THU128 Transcription Factor ETV5 In POMC Neurons Regulate Energy And Glucose Homeostasis

Abstract Disclosure: S. Gahlot: None. A. Caron: None. S. Lee: None. J.K. Elmquist: None. Pro-opiomelanocortin (POMC) neurons in the arcuate nucleus of the hypothalamus (ARH) are critical for the regulation of energy balance and glucose homeostasis. Pomc gene transcription is regulated by the Erythrocyte Transformation Specific (ETS)-domain transcription factors, including Etv1, Etv2, Etv4, and Etv5. Large-scale genome-wide association studies have identified ETV5 genetic variants linked with human obesity and body mass index. Histological studies in adult mouse pituitaries also show the co-localization of ETV5 with POMC and POMC-derived peptides: adrenocorticotropic hormone (ACTH) and alpha-melanocyte stimulating hormone (α-MSH). Furthermore, whole-body Etv5 knockout mice are lean, severely glucose intolerant and hypoinsulinaemic. While these findings suggest a potential role for Etv5 in the control of energy and glucose balance, the role of Etv5 remains unknown. This study aims to determine whether ETV5 binds to the Pomc promoter to alter its expression and regulate energy balance and glucose homeostasis. To assess whether ETV5 binds to the Pomc promoter, we performed chromatin immunoprecipitation with quantitative real-time PCR (ChIP-qPCR) in C57BL/6J mice. ChIP-qPCR determined that Etv5 directly binds to the Pomc promoter. We further performed luciferase reporter assay in mouse neuroblastoma N2a cell lysates to measure the Pomc promoter activity after Etv5 knockdown or overexpression. Luciferase assay revealed that Etv5 knockdown increased, while Etv5 overexpression reduced the Pomc promoter activity in N2a cells. Also, Etv5 overexpression blocked the leptin-induced POMC activation. Further, to determine the role of Etv5 in POMC neurons to regulate energy balance and glucose homeostasis, we used the Cre/loxP system to selectively delete Etv5 from POMC neurons both prenatally and postnatally. Mice were fed either a standard chow or a 60% high-fat diet (HFD), followed by serial body weight, food intake, body composition, metabolic assessment, glucose tolerance and insulin tolerance test measurements. We found that mice with a prenatal deletion of Etv5 in POMC neurons had reduced body weight, reduced lean mass, and were protected from HFD-induced insulin resistance. Similarly, postnatal deletion of Etv5 in POMC neurons resulted in reduced body weight, lean mass and fat mass, and increased insulin sensitivity and energy expenditure in mice of 8 weeks age. We also performed electrophysiological recordings in hypothalamic slices from these mice to assess POMC neuron excitability. We found that loss of Etv5 increased the activity and electrical excitability of POMC neurons. These findings highlight a previously unrecognized role of Etv5 in POMC neurons in the regulation of energy balance and glucose homeostasis. These results also point to the potential therapeutic applications for Etv5 against obesity. Presentation: Thursday, June 15, 2023

Hyperpigmentation on the dorsal tongue

•A 73-year-old man had hyperpigmentation on the dorsum of the tongue.•His-symptoms were consistent with addison's disease from metastatic adrenal tumors.•Hyperpigmentation in addison's disease can occur anywhere due to various stimuli.•Hyperpigmentation could indicate susceptibility to acute adrenal insufficiency. A 73-year-old man diagnosed with brain metastasis from non-small cell lung carcinoma, not otherwise specified (NSCLC-NOS), was hospitalized for 1 week due to anorexia. A computed tomography revealed a 16.5 mm irregular-shaped nodule in the right lung apex, lymphadenopathy of the mediastinum, mesentery, and peri-aorta, and bilateral adrenal enlargement (46.3 and 48.7 mm in diameter). About 1 week before admission, his systolic blood pressure, which was approximately 110 mmHg suddenly dropped to approximately 80 mmHg. Simultaneously, his fasting blood glucose, also decreased to approximately 100 mg/dL from 200 mg/dL with a fever of 38 °C; he had poorly controlled type 2 diabetes. Since he had an electrolyte disorder with hyponatremia of 131 mEq/L and a slightly high serum potassium level of 5.7 mEq/L, he was referred to our department. A physical examination revealed hyperpigmentation on the dorsum of his tongue, which he reported had been present for 3 months prior to admission (Fig. 1A). What is the diagnosis? The symptoms are consistent with Addison's disease due to metastatic bilateral adrenal tumors. His-early-morning fasting blood cortisol (9.98 µg/dL) was inappropriately low against a markedly high adrenocorticotropic hormone (ACTH) level (145 pg/mL). His-dehydroepiandrosterone-sulfate level (11 µg/dL) was disproportionately low. Additionally, his plasma aldosterone concentration was <4.0 pg/mL, which is inappropriately low against the active renin concentration of 14.26 pg/mL, suggesting that his bilateral adrenal metastases impaired adrenal steroidogenesis in all layers of the adrenal cortex. The comparatively lower blood glucose, hypotension, and hyperkalemia are compatible with fever-induced acute adrenal insufficiency, which requires hydrocortisone and fludrocortisone replacement. One month following treatment initiation, the tongue discoloration disappeared (Fig. 1B). The coupling of pro-opiomelanocortin (POMC) peptides, α–melanocyte-stimulating hormone, and ACTH with the melanocortin-1 receptor stimulates melanogenesis [[1]Buscà R. Ballotti R. Cyclic AMP a key messenger in the regulation of skin pigmentation.Pigment Cell Res. 2000; 13: 60-69https://doi.org/10.1034/j.1600-0749.2000.130203.xCrossref PubMed Scopus (664) Google Scholar,[2]Wolf Horrell E.M. Boulanger M.C. D'Orazio J.A Melanocortin 1 receptor: structure, function, and regulation.Front Genet. 2016; 7: 95https://doi.org/10.3389/fgene.2016.00095Crossref PubMed Scopus (136) Google Scholar]. In Addison's disease, decreased negative feedback to the hypothalamus and pituitary due to reduced adrenal cortisol secretion increases POMC peptides, causing hyperpigmentation, which tends to occur in areas exposed to ultraviolet, chronic friction, and pressure [[3]Dunlop D. Eighty-six cases of Addison's disease.Br Med J. 1963; 2: 887-891https://doi.org/10.1136/bmj.2.5362.887Crossref PubMed Scopus (153) Google Scholar]. Furthermore, the pigmentation generally occurs on the side of the tongue touching the teeth. The patient had consistently brushed his tongue with a toothbrush and believed the friction might have caused hyperpigmentation; thus, when hyperpigmentation is observed in high-risk patients, they should be informed that they are susceptible to acute adrenal insufficiency when under intense stress, such as fever or trauma.

Proopiomelanocortin projections to the nucleus accumbens modulate acquisition and maintenance of operant palatable pellet administration in mice

Obesity is a crisis in the United States, producing many co-morbid diseases that can drastically decrease quality of life. While diet is a major focus for therapeutic intervention, the need to understand underlying appetitive neurocircuitry persists. Proopiomelanocortin (POMC) peptides are well-known for their anorexigenic activity, but also mediate reward and learning. The nucleus accumbens (NAcc) is best known for its role in reward-based learning, but the contribution of POMC projections to NAcc on feeding are controversial since the two major POMC-derived peptides (β-endorphin and α-MSH) have opposite effects on food intake. Our objective was to determine the effect of stimulating POMC projections in the NAcc on acquisition and maintenance of operant self-administration of a palatable food. Adult POMCCre mice were microinjected into the NAcc with a Cre-dependent retrograde adeno-associated viral vector expressing Gq Designer Receptors Exclusively Activated by Designer Drugs (DREADDs). Mice were trained to self-administer palatable 20-mg pellets in daily operant sessions. Acquisition of self-administration (fixed ratio 30) and baseline self-administration were measured in daily sessions, with mice receiving injections of either JHU37152 (DREADD agonist) or saline (i.p.) 15 min prior to the sessions. POMC neuron stimulation (JHU injection) before training sessions produced a significant increase in rate of acquisition and accuracy compared to the saline treated group, with no significant effect on rewards earned. Removal of POMC neuron stimulation before sessions initially reduced consumption with a gradual increase in responding for reinforcer over 3 days of saline injections. Reinstatement of POMC neuron stimulation (JHU) before the session resulted in a significant decrease in responding and rewards earned. These results suggest a complex role of POMC peptides within the NAcc that increase reward learning for a novel palatable food while decreasing consumption of the reinforcer following experience with it.

Identification and characterization of a receptor for N-terminal pro-opiomelanocortin peptide

Identification and characterization of a receptor for N-terminal pro-opiomelanocortin peptide

TRPV1-Mediated Sensing of Sodium and Osmotic Pressure in POMC Neurons in the Arcuate Nucleus of the Hypothalamus.

The central melanocortin system conducted by anorexigenic pro-opiomelanocortin (POMC) neurons and orexigenic agouti-related peptide (AgRP) neurons in the arcuate nucleus of the hypothalamus (ARC) not only regulates feeding behavior but also blood pressure. Excessive salt intake raises the Na+ concentration ([Na+]) in the cerebrospinal fluid (CSF) and worsens hypertension. The blood–brain barrier is immature in the ARC. Therefore, both AgRP and POMC neurons in the ARC have easy access to the electrolytes in the blood and can sense changes in their concentrations. However, the sensitivity of AgRP and POMC neurons to Na+ remains unclear. This study aimed to explore how the changes in the extracellular Na+ concentration ([Na+]) influence these neurons by measuring the cytosolic Ca2+ concentration ([Ca2+]i) in the single neurons isolated from the ARC that were subsequently immunocytochemically identified as AgRP or POMC neurons. Both AgRP and POMC neurons responded to increases in both [Na+] and osmolarity in C57BL/6 mice. In contrast, in transient receptor potential vanilloid 1 (TRPV1) knockout (KO) mice, POMC neurons failed to respond to increases in both [Na+] and osmolarity, while they responded to high glucose and angiotensin II levels with increases in [Ca2+]i. Moreover, in KO mice fed a high-salt diet, the expression of POMC was lower than that in wild-type mice. These results demonstrate that changes in [Na+] and osmolarity are sensed by the ARC POMC neurons via the TRPV1-dependent mechanism.

Appetite Control With Ageing

The anorexia of ageing, a reduction in food intake with increased age, is associated with negative health outcomes such as sarcopenia frailty, cachexia morbidity and mortality. Pharmacological agents such as appetite stimulants have been a major focus to combat the anorexia of ageing; however, these medications are linked to various adverse side effects. Therefore, understanding the physiological causes of reduced appetite may lead to the creation of innovative intervention strategies in the ageing population. Current research has identified the pro-opiomelanocortin (POMC) and Agouti-related peptide (AgRP) neuronal subsets of the arcuate nucleus (ARC) as the centre of appetite regulation. This review investigates the current understanding of appetite regulation and subsequent dysregulation with age, and the age-associated changes in the anorectic (appetite-suppression) and orexigenic (appetite-stimulating) pathways, thereby implicating the POMC and AgRP neurons. It primarily investigates the physiological changes underlying appetite reduction with ageing to orient future interventions to combat the anorexia of ageing.

Sex differences and the lack of effects of chemogenetic manipulation of pro-opiomelanocortin (POMC) neurons on alcohol consumption in male and female mice

The endogenous opioid system has been implicated in the rewarding and reinforcing effects of alcohol. Pro-opiomelanocortin (POMC) neurons located within the arcuate nucleus of the hypothalamus (ArcN) secrete multiple peptides associated with alcohol consumption, including β-endorphin (β-END), α-melanocyte stimulating hormone (α-MSH), and adrenocorticotropic hormone (ACTH). In this study, we utilized chemogenetics to bidirectionally modulate ArcN POMC neurons to determine their role in alcohol and saccharin consumption and regional levels of POMC-derived peptides. Male and female POMC-cre mice were infused with viral vectors designed for cre-dependent expression of either excitatory and inhibitory DREADDs or a control vector into the ArcN. Following recovery, animals were allowed to consume alcohol or saccharin using the drinking-in-the-dark (DID) paradigm of binge-like intake for 4 consecutive days. Prior to the final test session, animals were injected with clozapine-N-oxide (2.5 mg/kg, i.p.) for DREADD activation. Following the last DID session, animals were euthanized and the ArcN, VTA, amygdala and NAc were dissected and assessed for POMC peptide expression utilizing western blotting. We found that female mice consumed more alcohol than males during DID sessions 2–4, and that chemogenetic activation had no effect on alcohol or saccharin consumption in either sex. We found that β-END expression within the ArcN positively correlated with alcohol consumption. Given the molecular and functional heterogeneity of ArcN POMC neurons, future studies are needed to assess the effects of modulation of specific subpopulations of these neurons within the ArcN on consumption of rewarding substances such as alcohol and saccharin.

Inhibition of POMC neurons in mice undergoing activity-based anorexia selectively blunts food anticipatory activity without affecting body weight or food intake.

Anorexia nervosa (AN) is a debilitating eating disorder characterized by severely restricted eating and significant body weight loss. In addition, many individuals also report engaging in excessive exercise. Previous research using the activity-based anorexia (ABA) model has implicated the hypothalamic proopiomelanocortin (POMC) system. Using the ABA model, Pomc mRNA has been shown to be transiently elevated in both male and female rodents undergoing ABA. In addition, the POMC peptide β-endorphin appears to contribute to food anticipatory activity (FAA), a characteristic of ABA, as both deletion and antagonism of the µ opioid receptor (MOR) that β-endorphin targets, results in decreased FAA. The role of β-endorphin in reduced food intake in ABA is unknown and POMC neurons release multiple transmitters in addition to β-endorphin. In the current study, we set out to determine whether targeted inhibition of POMC neurons themselves rather than their peptide products would lessen the severity of ABA. Inhibition of POMC neurons during ABA via chemogenetic Designer Receptors Exclusively Activated by Designer Drugs (DREADD) technology resulted in reduced FAA in both male and female mice with no significant changes in body weight or food intake. The selective reduction in FAA persisted even in the face of concurrent chemogenetic inhibition of additional cell types in the hypothalamic arcuate nucleus. The results suggest that POMC neurons could be contributing preferentially to excessive exercise habits in patients with AN. Furthermore, the results also suggest that metabolic control during ABA appears to take place via a POMC neuron-independent mechanism.

Should I Lay or Should I Grow: Photoperiodic Versus Metabolic Cues in Chickens.

While photoperiod has been generally accepted as the primary if not the exclusive cue to stimulate reproduction in photoperiodic breeders such as the laying hen, current knowledge suggests that metabolism, and/or body composition can also play an influential role to control the hypothalamic-pituitary gonadal (HPG)-axis. This review thus intends to first describe how photoperiodic and metabolic cues can impact the HPG axis, then explore and propose potential common pathways and mechanisms through which both cues could be integrated. Photostimulation refers to a perceived increase in day-length resulting in the stimulation of the HPG. While photoreceptors are present in the retina of the eye and the pineal gland, it is the deep brain photoreceptors (DBPs) located in the hypothalamus that have been identified as the potential mediators of photostimulation, including melanopsin (OPN4), neuropsin (OPN5), and vertebrate-ancient opsin (VA-Opsin). Here, we present the current state of knowledge surrounding these DBPs, along with their individual and relative importance and, their possible downstream mechanisms of action to initiate the activation of the HPG axis. On the metabolic side, specific attention is placed on the hypothalamic integration of appetite control with the stimulatory (Gonadotropin Releasing Hormone; GnRH) and inhibitory (Gonadotropin Inhibitory Hormone; GnIH) neuropeptides involved in the control of the HPG axis. Specifically, the impact of orexigenic peptides agouti-related peptide (AgRP), and neuropeptide Y (NPY), as well as the anorexigenic peptides pro-opiomelanocortin (POMC), and cocaine-and amphetamine regulated transcript (CART) is reviewed. Furthermore, beyond hypothalamic control, several metabolic factors involved in the control of body weight and composition are also presented as possible modulators of reproduction at all three levels of the HPG axis. These include peroxisome proliferator-activated receptor gamma (PPAR-γ) for its impact in liver metabolism during the switch from growth to reproduction, adiponectin as a potential modulator of ovarian development and follicular maturation, as well as growth hormone (GH), and leptin (LEP).

Transcription factor Creb3l1 regulates the synthesis of prohormone convertase enzyme PC1/3 in endocrine cells.

Transcription factor cAMP responsive element‐binding protein 3 like 1 (Creb3l1) is a non‐classical endoplasmic reticulum stress molecule that is emerging as an important component for cellular homeostasis, particularly within cell types with high peptide secretory capabilities. We have previously shown that Creb3l1 serves an important role in body fluid homeostasis through its transcriptional control of the gene coding for antidiuretic hormone arginine vasopressin in the neuropeptide‐rich magnocellular neurones of the supraoptic nucleus. In response to osmotic stimuli such as dehydration, vasopressin magnocellular neurones undergo remarkable transcriptome changes, including increased Creb3l1 expression, to ensure that the supply of vasopressin meets demand. To determine where else Creb3l1 fits into the secretory cell supply chain, we performed RNA‐sequencing of Creb3l1 knockdown anterior pituitary mouse corticotroph cell line AtT20. The target chosen for further investigation was Pcsk1, which encodes proprotein convertase enzyme 1 (PC1/3). PC1/3 is crucial for processing of neuropeptides and peptide hormones such as pro‐opiomelanocortin (POMC), proinsulin, proglucagon, vasopressin and oxytocin. Viral manipulations in supraoptic nuclei by over‐expression of Creb3l1 increased Pcsk1, whereas Creb3l1 knockdown decreased Pcsk1 expression. In vitro promoter activity and binding studies showed that Creb3l1 was a transcription factor of the Pcsk1 gene binding directly to a G‐box motif in the promoter. In the dehydrated rat anterior pituitary, Creb3l1 and Pcsk1 expression decreased in parallel compared to control, supporting our findings from manipulations in AtT20 cells and the supraoptic nucleus. No relationship was observed between Creb3l1 and Pcsk1 expression in the neurointermediate lobe of the pituitary, indicating a different mechanism of PC1/3 synthesis by these POMC‐synthesising cells. Therefore, Creb3l1, by regulating the expression of Pcsk1, does not control the processing of POMC peptides in the intermediate lobe.

Intermittent Hypoxia Up-Regulates Gene Expressions of Peptide YY (PYY), Glucagon-like Peptide-1 (GLP-1), and Neurotensin (NTS) in Enteroendocrine Cells.

The patients with sleep apnea syndrome are exposed to intermittent hypoxia (IH) during sleep. We previously demonstrated the IH-induced up-regulation of the mRNA levels of anorexigenic peptides proopiomelanocortin (POMC), and cocaine- and amphetamine-regulated transcript (CART) in human neuronal cells. Appetite is regulated not only by the central nervous system but also by the peptides from gastrointestinal tract. Here, we investigated the effects of IH on the gene expression(s) of appetite-inhibiting gut hormones. Human enteroendocrine Caco-2 and mouse STC-1 cells were exposed to IH [64 cycles of 5 min hypoxia (1% O2) and 10 min normoxia (21% O2)] or normoxia for 24 h. Real-time RT-PCR revealed that IH significantly increased the mRNA levels of peptide YY (PYY), glucagon-like peptide-1 (GLP-1), and neurotensin (NTS) in Caco-2 and STC-1 cells. ELISA showed that the concentrations of PYY, GLP-1, and NTS in the culture medium were significantly increased by IH. The mRNA levels of PYY, GLP-1, and NTS were significantly up-regulated even in normoxia by Trichostatin A (TSA) and were significantly decreased even in IH by 5-azacytidine (5AZC), suggesting that IH increases PYY, GLP-1, and NTS mRNAs via alterations in the chromatin structure in enteroendocrine cells. IH might have an anorexigenic influence on the enteric nervous system.

Steroid receptor coactivator-1 modulates the function of Pomc neurons and energy homeostasis

Hypothalamic neurons expressing the anorectic peptide Pro-opiomelanocortin (Pomc) regulate food intake and body weight. Here, we show that Steroid Receptor Coactivator-1 (SRC-1) interacts with a target of leptin receptor activation, phosphorylated STAT3, to potentiate Pomc transcription. Deletion of SRC-1 in Pomc neurons in mice attenuates their depolarization by leptin, decreases Pomc expression and increases food intake leading to high-fat diet-induced obesity. In humans, fifteen rare heterozygous variants in SRC-1 found in severely obese individuals impair leptin-mediated Pomc reporter activity in cells, whilst four variants found in non-obese controls do not. In a knock-in mouse model of a loss of function human variant (SRC-1L1376P), leptin-induced depolarization of Pomc neurons and Pomc expression are significantly reduced, and food intake and body weight are increased. In summary, we demonstrate that SRC-1 modulates the function of hypothalamic Pomc neurons, and suggest that targeting SRC-1 may represent a useful therapeutic strategy for weight loss.

Effects of Naltrexone on Energy Balance and Hypothalamic Melanocortin Peptides in Male Mice Fed a High-Fat Diet.

The hypothalamic melanocortin system composed of proopiomelanocortin (POMC) and agouti-related protein (AgRP) neurons plays a key role in maintaining energy homeostasis. The POMC-derived peptides, α-MSH and β-EP, have distinct roles in this process. α-MSH inhibits food intake, whereas β-EP, an endogenous opioid, can inhibit POMC neurons and stimulate food intake. A mouse model was used to examine the effects of opioid antagonism with naltrexone (NTX) on Pomc and Agrp gene expression and POMC peptide processing in the hypothalamus in conjunction with changes in energy balance. There were clear stimulatory effects of NTX on hypothalamic Pomc in mice receiving low- and high-fat diets, yet only transient decreases in food intake and body weight gain were noted. The effects on Pomc expression were accompanied by an increase in POMC prohormone levels and a decrease in levels of the processed peptides α-MSH and β-EP. Arcuate expression of the POMC processing enzymes Pcsk1, Pcsk2, and Cpe was not altered by NTX, but expression of Prcp, an enzyme that inactivates α-MSH, increased after NTX exposure. NTX exposure also stimulated hypothalamic Agrp expression, but the effects of NTX on energy balance were not enhanced in Agrp-null mice. Despite clear stimulatory effects of NTX on Pomc expression in the hypothalamus, only modest transient decreases in food intake and body weight were seen. Effects of NTX on POMC processing, and possibly α-MSH inactivation, as well as stimulatory effects on AgRP neurons could mitigate the effects of NTX on energy balance.

POMC: The Physiological Power of Hormone Processing.

Pro-opiomelanocortin (POMC) is the archetypal polypeptide precursor of hormones and neuropeptides. In this review, we examine the variability in the individual peptides produced in different tissues and the impact of the simultaneous presence of their precursors or fragments. We also discuss the problems inherent in accurately measuring which of the precursors and their derived peptides are present in biological samples. We address how not being able to measure all the combinations of precursors and fragments quantitatively has affected our understanding of the pathophysiology associated with POMC processing. To understand how different ratios of peptides arise, we describe the role of the pro-hormone convertases (PCs) and their tissue specificities and consider the cellular processing pathways which enable regulated secretion of different peptides that play crucial roles in integrating a range of vital physiological functions. In the pituitary, correct processing of POMC peptides is essential to maintain the hypothalamic-pituitary-adrenal axis, and this processing can be disrupted in POMC-expressing tumors. In hypothalamic neurons expressing POMC, abnormalities in processing critically impact on the regulation of appetite, energy homeostasis, and body composition. More work is needed to understand whether expression of the POMC gene in a tissue equates to release of bioactive peptides. We suggest that this comprehensive view of POMC processing, with a focus on gaining a better understanding of the combination of peptides produced and their relative bioactivity, is a necessity for all involved in studying this fascinating physiological regulatory phenomenon.

The Serine Protease Activity of Corin Is Required for Normal Pigment Type Switching

The Serine Protease Activity of Corin Is Required for Normal Pigment Type Switching

Various transgenic mouse lines to study proopiomelanocortin cells in the brain stem label disparate populations of GABAergic and glutamatergic neurons.

Products of the proopiomelanocortin (POMC) prohormone regulate aspects of analgesia, reward, and energy balance; thus, the neurons that produce POMC in the hypothalamus have received considerable attention. However, there are also cells in the nucleus of the solitary tract (NTS) that transcribe Pomc, although low levels of Pomc mRNA and relative lack of POMC peptide products in the adult mouse NTS have hindered the study of these cells. Therefore, studies of NTS POMC cells have largely relied on transgenic mouse lines. Here, we set out to determine the amino acid (AA) transmitter phenotype of NTS POMC neurons by using Pomc-Gfp transgenic mice to identify POMC cells. We found that cells expressing the green fluorescent protein (GFP) represent a mix of GABAergic and glutamatergic cells as indicated by Gad2 and vesicular Glut2 ( vGlut2) mRNA expression, respectively. We then examined the AA phenotype of POMC cells labeled by a Pomc-Cre transgene and found that these are also a mix of GABAergic and glutamatergic cells. However, the NTS cells labeled by the Gfp- and Cre-containing transgenes represented distinct populations of cells in three different Pomc-Cre mouse lines. Consistent with previous work, we were unable to reliably detect Pomc mRNA in the NTS despite clear expression in the hypothalamus. Thus, it was not possible to determine which transgenic tool most accurately identifies NTS cells that may express Pomc or release POMC peptides, although the results indicate the transgenic tools for study of these NTS neurons can label disparate populations of cells with varied AA phenotypes.

Immune-Neuroendocrine Interactions: Evolution, Ecology, and Susceptibility to Illness.

The integration between immune and neuroendocrine systems is crucial for maintaining homeostasis from invertebrates to humans. In the first, the phagocytic cell, i.e., the immunocyte, is the main actor, while in the latter, the principle player is the lymphocyte. Immunocytes are characterized by the presence of pro-opiomelanocortin (POMC) peptides, CRH, and other molecules that display a significant similarity to their mammalian counterparts regarding their functions, as both are mainly involved in fundamental functions such as immune (chemotaxis, phagocytosis, cytotoxicity, etc.) and neuroendocrine (stress) responses. Furthermore, the immune-neuroendocrine system provides vital answers to ecological and immunological demands in terms of economy and efficiency. Finally, susceptibility to disease emerges as the result of a continuous dynamic interaction between the world within and the world outside. New fields such as ecological immunology study the susceptibility to pathogens in an evolutionary perspective while the field of neuro-endocrine-immunology studies the susceptibility from a more immediate perspective.

Effects of Opioid Antagonism on Cerebrospinal Fluid Melanocortin Peptides and Cortisol Levels in Humans.

Context:Hypothalamic proopiomelanocortin (POMC) is processed to α-melanocyte-stimulating hormone, which interacts with the melanocortin antagonist agouti-related protein (AgRP), to regulate energy balance. The POMC-derived opioid peptide β-endorphin (β-EP) also affects feeding behavior via interactions with brain µ-opioid receptors (MORs), including autoinhibitory interactions with MOR expressed by POMC neurons. The opioid antagonist naltrexone (NTX) stimulates POMC neurons in rodents and decreases food intake.Objective and Design:The effect of NTX on brain POMC in humans was assessed by measuring POMC peptide concentrations in lumbar cerebrospinal fluid (CSF). AgRP and cortisol levels were also measured because both are inhibited by opioids. In a double-blinded crossover study, 14 healthy subjects were given NTX (50 mg daily) or placebo for either 2 or 7 days.Results:CSF β-EP levels increased after 2 and 7 days of NTX treatment; CSF POMC levels did not change, but the β-EP-to-POMC ratio increased. CSF AgRP levels did not change, but plasma AgRP levels tended to increase after NTX (P = 0.06). Cortisol increased in plasma and CSF after NTX treatment; these changes correlated positively with changes in AgRP levels.Conclusion:Opioid antagonism stimulates POMC peptide release into CSF in humans. The increase in the CSF β-EP-to-POMC ratio could indicate selective release of processed peptides or an effect on POMC processing. Furthermore, AgRP and cortisol stimulation by NTX may mitigate POMC-induced decrease in food intake. It remains to be determined if biomarkers in CSF and plasma could be used to predict responses to pharmacotherapy targeting the melanocortin system.

Lorcaserin improves glycemic control via a melanocortin neurocircuit

ObjectiveThe increasing prevalence of type 2 diabetes (T2D) and associated morbidity and mortality emphasizes the need for a more complete understanding of the mechanisms mediating glucose homeostasis to accelerate the identification of new medications. Recent reports indicate that the obesity medication lorcaserin, a 5-hydroxytryptamine (5-HT, serotonin) 2C receptor (5-HT2CR) agonist, improves glycemic control in association with weight loss in obese patients with T2D. Here we evaluate whether lorcaserin has an effect on glycemia without body weight loss and how this effect is achieved. MethodsMurine models of common and genetic T2D were utilized to probe the direct effect of lorcaserin on glycemic control. ResultsLorcaserin dose-dependently improves glycemic control in mouse models of T2D in the absence of reductions in food intake or body weight. Examining the mechanism of this effect, we reveal a necessary and sufficient neurochemical mediator of lorcaserin's glucoregulatory effects, brain pro-opiomelanocortin (POMC) peptides. To clarify further lorcaserin's therapeutic brain circuit, we examined the receptor target of POMC peptides. We demonstrate that lorcaserin requires functional melanocortin4 receptors on cholinergic preganglionic neurons (MC4RChAT) to exert its effects on glucose homeostasis. In contrast, MC4RChAT signaling did not impact lorcaserin's effects on feeding, indicating a divergence in the neurocircuitry underpinning lorcaserin's therapeutic glycemic and anorectic effects. Hyperinsulinemic-euglycemic clamp studies reveal that lorcaserin reduces hepatic glucose production, increases glucose disposal and improves insulin sensitivity. ConclusionsThese data suggest that lorcaserin's action within the brain represents a mechanistically novel treatment for T2D: findings of significance to a prevalent global disease.

Effects of Chronic ACTH Excess on Human Adrenal Cortex

Chronic ACTH excess leads to chronic cortisol excess, without escape phenomenon, resulting in Cushing’s syndrome. Excess adrenal androgens also occur: in females, they will overcompensate the gonadotrophic loss, inducing high testosterone; in males, they will not compensate it, inducing low testosterone. Chronic ACTH excess leads to chronic adrenal mineralocorticoid excess and low aldosterone levels: after an acute rise, aldosterone plasma levels resume low values after a few days when ACTH is prolonged. Two other mineralocorticoids in man, cortisol and 11 deoxycorticosterone (DOC), at the zona fasciculata, will not escape the long-term effect of chronic ACTH excess and their secretion rates will remain elevated in parallel. Over all, the concomitant rise in cortisol and 11 DOC will more than compensate the loss of aldosterone, and eventually create a state of chronic mineralocorticoid excess, best evidenced by the accompanying suppression of the renin plasma levels, a further contribution to the suppression of aldosterone secretion. Prolonged in vivo stimulation with ACTH leads to an increase in total adrenal protein and RNA synthesis. Cell proliferation is indicated by an increase in total DNA the resulting adrenocortical hyperplasia participates in the amplified response of the chronically stimulated gland, and the weight of each gland can be greatly increased. The growth-stimulatory effect of ACTH in vivo most likely proceeds through the activation of a local and complex network of autocrine growth factors and their own receptors; a number of compounds, including non-ACTH proopiomelanocortin peptides such as γ3-MSH, have been shown to exert some adrenocortical growth effect.