Elevated plasma levels of alpha-melanocyte stimulating hormone (alpha-MSH) are correlated with insulin resistance in obese men

Obesity, bone marrow adiposity, and leukemia: Time to act

Obesity has taken the face of a pandemic with less direct concern among the general population and scientific community. However, obesity is considered a low-grade systemic inflammation that impacts multiple organs. Chronic inflammation is also associated with different solid and blood cancers. In addition, emerging evidence demonstrates that individuals with obesity are at higher risk of developing blood cancers and have poorer clinical outcomes than individuals in a normal weight range. The bone marrow is critical for hematopoiesis, lymphopoiesis, and myelopoiesis. Therefore, it is vital to understand the mechanisms by which obesity-associated changes in BM adiposity impact leukemia development. BM adipocytes are critical to maintain homeostasis via different means, including immune regulation. However, obesity increases BM adiposity and creates a pro-inflammatory environment to upregulate clonal hematopoiesis and a leukemia-supportive environment. Obesity further alters lymphopoiesis and myelopoiesis via different mechanisms, which dysregulate myeloid and lymphoid immune cell functions mentioned in the text under different sequentially discussed sections. The altered immune cell function during obesity alters hematological malignancies and leukemia susceptibility. Therefore, obesity-induced altered BM adiposity, immune cell generation, and function impact an individual's predisposition and severity of leukemia, which should be considered a critical factor in leukemia patients.

Serum Levels of Hormones Regulating Appetite in Patients with Fetal Alcohol Spectrum Disorders

Prenatal alcohol exposure is the cause of impaired growth and a wide range of developmental and behavioral disorders in the child. Improper eating patterns are commonly associated with fetal alcohol spectrum disorders (FASD) and may contribute to poor nutrition and growth restriction. To date, there have been only a few studies investigating the hormonal regulation of appetite in patients with FASD. We analyzed the levels of neuropeptide Y (NPY), Agouti signaling protein (ASP), alpha-melanocyte-stimulating hormone (α-MSH), and kisspeptin (KISS1) in 57 patients with FASD and 23 healthy controls. A comparison of the hormone levels studied was also performed in subgroups of fetal alcohol syndrome (FAS) and neurobehavioral disorder associated with prenatal alcohol exposure (ND PAE), as well as in males and females. We have found no differences in hormone levels tested between affected individuals and the controls and between FASD subgroups. In addition, sex had no effect on hormone levels. However, we identified some associations between hormone concentrations and parameters describing the clinical status of patients with FASD. Most of them concerned ASP, which has shown a positive correlation with age and hormones involved in appetite and metabolism, such as proopiomelanocortin (POMC) and adrenocorticotropic hormone (ACTH). We have also found a negative correlation of α-MSH with age, BMI percentile, and glycated hemoglobin (HbA1c). Furthermore, we found a weak negative correlation of NPY with HbA1c. Although FASD has been associated with impaired child growth and development, including nutrition and puberty onset, we did not identify differences in the levels of the hormones studied, which may suggest that prenatal alcohol exposure does not affect the levels of these metabolites.

MC1R signaling through the cAMP-CREB/ATF-1 and ERK-NFκB pathways accelerates G1/S transition promoting breast cancer progression

MC1R, a G-protein coupled receptor, triggers ultraviolet light-induced melanin synthesis and DNA repair in melanocytes and is implicated in the pathogenesis of melanoma. Although widely expressed in different tissue types, its function in non-cutaneous tissue is relatively unknown. Herein, we demonstrate that disruptive MC1R variants associated with melanomagenesis are less frequently found in patients with several cancers. Further exploration revealed that breast cancer tissue shows a significantly higher MC1R expression than normal breast tissue, and knocking down MC1R significantly reduced cell proliferation in vitro and in vivo. Mechanistically, MC1R signaling through the MC1R-cAMP-CREB/ATF-1 and MC1R-ERK-NFκB axes accelerated the G1-S transition in breast cancer cells. Our results revealed a new association between MC1R and breast cancer, which could be potentially targeted therapeutically. Moreover, our results suggest that MC1R-enhancing/activating therapies should be used cautiously, as they might be pro-tumorigenic in certain contexts.

Evaluating the association between the Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) diet, mental health, and cardio-metabolic risk factors among individuals with obesity

BACKGROUND

Several previous investigations have examined the brain-protective role of the Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) diet. However, more knowledge is needed about the MIND diet's other favorable impacts. The purpose of this study was to examine the relationship between the MIND diet, mental health, and metabolic markers in individuals with obesity.

METHODS

In this cross-sectional study, we included 339 individuals with obesity (BMI ≥ 30 kg/m²) aged 20-50 years. We utilized a semi-quantitative Food Frequency Questionnaire (FFQ), we assessed dietary intake, including 168 food items, and calculated the value of MIND. Metabolic syndrome (MetS) was defined according to the National Cholesterol Education Program Adult Treatment Panel III (NCEP-ATP III) guidelines. We assessed biochemical parameters using Enzymatic methods. Blood pressure and body composition were also determined.

RESULTS

Higher tertiles of the MIND diet score were associated with significantly higher energy intake, macronutrients, and brain-healthy food intakes (P < 0.001). Among the brain-unhealthy foods, only the intake of sweets and pastries was significantly lower in the highest versus lowest MIND tertiles. We also observed lower odds of stress (P < 0.05) and higher insulin sensitivity (P < 0.05) in the highest versus lowest MIND diet tertiles. We witnessed no significant changes in other parameters.

CONCLUSION

Lower stress levels and higher insulin sensitivity independent of some confounders like age, BMI, sex, and physical activity were associated with the highest tertile of MIND diet score.

Melanocortin-5 Receptor: Pharmacology and Its Regulation of Energy Metabolism

As the most recent melanocortin receptor (MCR) identified, melanocortin-5 receptor (MC5R) has unique tissue expression patterns, pharmacological properties, and physiological functions. Different from the other four MCR subtypes, MC5R is widely distributed in both the central nervous system and peripheral tissues and is associated with multiple functions. MC5R in sebaceous and preputial glands regulates lipid production and sexual behavior, respectively. MC5R expressed in immune cells is involved in immunomodulation. Among the five MCRs, MC5R is the predominant subtype expressed in skeletal muscle and white adipose tissue, tissues critical for energy metabolism. Activated MC5R triggers lipid mobilization in adipocytes and glucose uptake in skeletal muscle. Therefore, MC5R is a potential target for treating patients with obesity and diabetes mellitus. Melanocortin-2 receptor accessory proteins can modulate the cell surface expression, dimerization, and pharmacology of MC5R. This minireview summarizes the molecular and pharmacological properties of MC5R and highlights the progress made on MC5R in energy metabolism. We poInt. out knowledge gaps that need to be explored in the future.

Serum levels of hormones regulating appetite in patients with cystic fibrosis - a single-center, cross-sectional study

Cystic fibrosis (CF), which is the most common inherited genetically determined disease caused by a mutation in the gene for the CF transmembrane conductance regulator protein. Pulmonary failure is the leading cause of death in this population, while the dysregulation of endocrine system creates significant disorders, including malnutrition, underweight, and CF-related diabetes. Therefore, the objective of our study was to determine the following hormones in the serum of patients with CF: ghrelin, putative peptide YY (PYY), Agouti-signaling protein (ASP), and alpha-melanocyte-stimulating hormone (α-MSH). To our knowledge, serum levels of PYY, ASP, and α-MSH have not yet been assessed in CF. For this purpose, we measured hormone levels using enzyme-linked immunosorbent assays in 38 patients from the local CF care center, as well as 16 sex- and age-matched healthy controls. Moreover, we estimated the correlations between the tested hormones and the parameters of the patients' clinical status. In this study, we found sinificantly reduced serum levels of ghrelin and ASP in patients with CF (p<0.01). There was no difference in PYY and α-MSH levels between participants with CF and healthy subjects. Furthermore, there was no difference in hormone levels between females and males with CF. The type of gene mutation (homozygous or heterozygous for ΔF508) had no effect on hormone levels. Ghrelin was negatively correlated with age, body mass index, and C-reactive protein. PYY was negatively associated with the age of the patients. Hormone dysregulation in CF may contribute to decreased appetite, as well as many other disturbed processes. Therefore, ghrelin appears to play a key role in the regulation of energy management of CF. Future multicenter and multidisciplinary studies should focus on an unequivocal understanding of the role of these hormones in CF.

Association between Ag-RP, alpha-MSH and cardiovascular risk factors regarding adherence to diet quality index-international (DQI-I) among obese individuals

Introduction: Obesity is a strong promoter of cardiometabolic risk factors and is associated with several chronic comorbidities. Recently, the role of α-melanocyte stimulating hormone (α-MSH) and agouti related peptide (Ag-RP) in regulation of energy balance has attracted much attention. In current study, we evaluated the association between α-MSH and Ag-RP with cardiometabolic factors among obese individuals with different adherence to Diet Quality Index-International (DQI-I) values.

Methods: In this research, 188 obese adults aged between 20 and 50 years old and body mass index (BMI) between 30 and 40 kg/m² were recruited. Dietary intakes of participants and DQI-I calculation was performed using a semi-quantitative food frequency questionnaire (FFQ) with 132 food items. Serum glucose, lipids, insulin, and plasma α-MSH and Ag-RP levels were measured using ELISA kits. Homeostasis model assessment for insulin resistance index (HOMA-IR) and quantitative insulin sensitivity check index (QUICKI) were also calculated.

Results: Among those with the lowest adherence to DQI-I, Ag-RP was positively associated with systolic blood pressure (SBP) (P = 0.03) among males, which was associated with waist circumference (WC) (P = 0.01) and diastolic blood pressure (DBP) (P = 0.01). Moreover, among males with low and moderate adherence to DQI-I, α-MSH was positively associated with insulin (P = 0.04), weight (P = 0.03), WC (P < 0.01), SDP (P = 0.02) and DBP (P = 0.01). Also, Ag-RP showed a positive association with BMI values (R² = 0.03; P = 0.03).

Conclusion: According to our findings, in obese subjects with poor to moderate adherence to DQI-I, Ag-RP and α-MSH were in positive correlation with cardiometabolic risk factors. These findings further clarify the clinical importance of these parameters as prognostic factors of cardiometabolic abnormalities.

Alpha-Melanocyte-Stimulating Hormone is Elevated in Hypothalamic Obesity Associated with Childhood Craniopharyngioma

OBJECTIVE

The purpose of this study was to investigate the peripheral concentrations of leptin and neuropeptides taking part in the melanocortin pathway in hypothalamic obesity (HO) associated with craniopharyngioma (CP) and to find a peripheral marker for diagnosis.

METHODS

Thirty-one patients (52% girls; median age 16 years) with CP were enrolled in the study group. They were grouped as CP with obesity (CP^obesity , n = 17) and CP without obesity (CP^nonobesity , n = 14). Two control groups without CP consisted of 27 children with obesity (OC) (55% girls; median age 13.8 years) and 25 children without obesity (normal control [NC]) (72% girls; median age 14.5 years). Obesity was defined as BMI percentile ≥ 95%. Fasting serum concentrations of leptin, brain-derived neurotrophic factor (BDNF), and alpha-melanocyte-stimulating hormone (α-MSH) were measured in the groups.

RESULTS

Leptin and BDNF concentrations were correlated with BMI SD score (SDS) in controls (OC + NC) and CP. However, there was no correlation between α-MSH and BMI-SDS in CP or control groups. After adjusting for age, sex, and BMI-SDS, α-MSH was found to be significantly higher in CP^obesity than in other groups, whereas leptin and BDNF were comparable among the four groups.

CONCLUSIONS

Serum BDNF, just like leptin, increased with BMI, regardless of hypothalamic damage. On the contrary, α-MSH concentration was significantly high in HO, designating a potential biomarker for HO in CP.

L-Cell Expression of Melanocortin-4-Receptor Is Marginal in Most of the Small Intestine in Mice and Humans and Direct Stimulation of Small Intestinal Melanocortin-4-Receptors in Mice and Rats Does Not Affect GLP-1 Secretion

The molecular sensors underlying nutrient-stimulated GLP-1 secretion are currently being investigated. Peripheral administration of melanocortin-4 receptor (MC4R) agonists have been reported to increase GLP-1 plasma concentrations in mice and humans but it is unknown whether this effect results from a direct effect on the GLP-1 secreting L-cells in the intestine, from other effects in the intestine or from extra-intestinal effects. We investigated L-cell expression of MC4R in mouse and human L-cells by reanalyzing publicly available RNA sequencing databases (mouse and human) and by RT-qPCR (mouse), and assessed whether administration of MC4R agonists to a physiologically relevant gut model, isolated perfused mouse and rat small intestine, would stimulate GLP-1 secretion or potentiate glucose-stimulated secretion. L-cell MC4R expression was low in mouse duodenum and hardly detectable in the ileum and MC4R expression was hardly detectable in human L-cells. In isolated perfused mouse and rat intestine, neither intra-luminal nor intra-arterial administration of NDP-alpha-MSH, a potent MC4R agonist, had any effect on GLP-1 secretion (P ≥0.98, n = 5-6) from the upper or lower-half of the small intestine in mice or in the lower half in rats. Furthermore, HS014-an often used MC4R antagonist, which we found to be a partial agonist-did not affect the glucose-induced GLP-1 response in the rat, P = 0.62, n = 6). Studies on transfected COS7-cells confirmed bioactivity of the used compounds and that concentrations employed were well within in the effective range. Our combined data therefore suggest that MC4R-activated GLP-1 secretion in rodents either exclusively occurs in the colon or involves extra-intestinal signaling.

Exercise Attenuates Anabolic Steroids-Induced Anxiety via Hippocampal NPY and MC4 Receptor in Rats

The aim of our study was to evaluate the effects of chronic administration of nandrolone-decanoate (ND) or testosterone-enanthate (TE) in supraphysiological doses and a prolonged swimming protocol, alone and in combination with ND or TE, on anxiety-like behavior in rats. We investigated the immunohistochemical alterations of the hippocampal neuropeptide Y (NPY) and melanocortin 4 receptor (MC4R) neurons, as a possible underlying mechanism in a modulation of anxiety-like behavior in rats. Both applied anabolic androgenic steroids (AASs) induced anxiogenic effect accompanied with decreased serum and hippocampal NPY. The exercise-induced anxiolytic effect was associated with increased hippocampal NPY expression. ND and TE increased the number of MC4R, while the swimming protocol was followed by the reduction of MC4R in the CA1 region of the hippocampus. However, NPY/MC4R ratio in hippocampus was lowered by AASs and elevated by exercise in all hippocampal regions. An augmentation of this ratio strongly and positively correlated to increased time in open arms of elevated plus maze, in the context that indicates anxiolytic effect. Our findings support the conclusion that alterations in both hippocampal NPY and MC4R expression are involved in anxiety level changes in rats, while their quantitative relationship (NPY/MC4R ratio) is even more valuable in the estimation of anxiety regulation than individual alterations for both NPY and MC4R expression in the hippocampus.

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.

Integrated insights into the role of alpha-melanocyte stimulatory hormone in the control of food intake and glycaemia

Identifying peptide hormones with multipotent actions on both weight and glycaemia can have a significant impact on therapeutic options in the treatment of obesity and diabetes. This has been exemplified by recent advances involving pharmacological exploitation of glucagon-like peptide 1 biology. Herein, we summarise evidence supporting the potential candidacy in this light of alpha-melanocyte stimulatory hormone, an endogenous peptide hormone and a breakdown product of the neuropeptide pro-opiomelanocortin. We reference its well described central actions in the control of food intake and moreover highlight new data pointing to an important role for this peptide hormone in the periphery, in relation to glycaemic control.

Serum α-melanocyte-stimulating hormone may act as a protective biomarker for non-traumatic osteonecrosis of the femoral head

Background The α-melanocyte-stimulating hormone (α-MSH), an endogenous neuropeptide derived from proopiomelanocortin (POMC), has been identified to suppress inflammation and prevent osteoblast damage. Objective The present study was aimed to investigate the role of serum α-MSH in non-traumatic osteonecrosis of the femoral head (ONFH). Methods Seventy-nine patients diagnosed with non-traumatic ONFH and 79 sex- and age-matched healthy controls were enrolled in the study. Serum α-MSH concentrations were examined with a double antibody radioimmunoassay. The radiographic progression of ONFH was assessed by X-ray plain film according to the FICAT grading system. The symptomatic severity was evaluated by visual analogue scale scores, Harris hip scores and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores. The serum concentrations of protective marker adiponectin and bone necrosis inflammation factor IL-33 concentrations were also examined. The receiver operating characteristic (ROC) analysis curve was performed to explore the diagnostic value of α-MSH, adiponectin and IL-33 for radiographic progression. Results Serum α-MSH concentrations were significantly lower in ONFH patients than in healthy controls. The case group included 29 non-traumatic ONFH patients with FICAT grade I/II, 27 with grade III and 23 with grade IV. ONFH patients with grade I/II had significantly higher α-MSH concentrations in serum compared with those with FICAT grades III and IV. ONFH patients with FICAT grade III showed significantly elevated concentrations of α-MSH in serum compared with those with FICAT grade IV. Serum α-MSH concentrations were negatively associated with radiographic progression by FICAT grading system, and symptomatic severity defined by visual analogue scale scores, Harris hip scores and WOMAC scores. In addition, serum α-MSH concentrations were positively related to the expression of adiponectin and negatively associated with IL-33. ROC analysis curve demonstrated that α-MSH exhibited the equal value for the diagnosis of ONFH radiographic progression compared with IL-33. Conclusions Serum α-MSH may act as a protective biomarker for non-traumatic ONFH. Systematic application of α-MSH serving as an adjunctive therapy for treating non-traumatic ONFH deserves further investigation.

α-Melanocyte stimulating hormone promotes muscle glucose uptake via melanocortin 5 receptors

Objective

Central melanocortin pathways are well-established regulators of energy balance. However, scant data exist about the role of systemic melanocortin peptides. We set out to determine if peripheral α-melanocyte stimulating hormone (α-MSH) plays a role in glucose homeostasis and tested the hypothesis that the pituitary is able to sense a physiological increase in circulating glucose and responds by secreting α-MSH.

Methods

We established glucose-stimulated α-MSH secretion using humans, non-human primates, and mouse models. Continuous α-MSH infusions were performed during glucose tolerance tests and hyperinsulinemic-euglycemic clamps to evaluate the systemic effect of α-MSH in glucose regulation. Complementary ex vivo and in vitro techniques were employed to delineate the direct action of α-MSH via the melanocortin 5 receptor (MC5R)–PKA axis in skeletal muscles. Combined treatment of non-selective/selective phosphodiesterase inhibitor and α-MSH was adopted to restore glucose tolerance in obese mice.

Results

Here we demonstrate that pituitary secretion of α-MSH is increased by glucose. Peripheral α-MSH increases temperature in skeletal muscles, acts directly on soleus and gastrocnemius muscles to significantly increase glucose uptake, and enhances whole-body glucose clearance via the activation of muscle MC5R and protein kinase A. These actions are absent in obese mice, accompanied by a blunting of α-MSH-induced cAMP levels in skeletal muscles of obese mice. Both selective and non-selective phosphodiesterase inhibition restores α-MSH induced skeletal muscle glucose uptake and improves glucose disposal in obese mice.

Conclusion

These data describe a novel endocrine circuit that modulates glucose homeostasis by pituitary α-MSH, which increases muscle glucose uptake and thermogenesis through the activation of a MC5R-PKA-pathway, which is disrupted in obesity.

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Glucose stimulates α-MSH release from the pituitary.

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Systemic α-MSH drives glucose disposal and thermogenesis in skeletal muscles.

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α-MSH acts on MC5R expressed on skeletal muscles and activate cAMP-PKA pathway.

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The combined treatment of nonselective or selective PDE 4 inhibitor and α-MSH ameliorates glucose intolerance in obese mice.

Blood-brain barrier transport kinetics of the neuromedin peptides NMU, NMN, NMB and NT

The neuromedin peptides are peripherally and centrally produced, but until now, it is generally believed that they only function as locally acting compounds without any quantitative knowledge about their blood-brain barrier (BBB) passage. Here, we characterize the transport kinetics of four neuromedins (NMU, NMN, NMB and NT) across the BBB, as well as their metabolization profile, and evaluate if they can act as endocrine hormones. Using the in vivo mouse model, multiple time regression (MTR), capillary depletion (CD) and brain efflux studies were performed. Data was fitted using linear (NMU, NT and NMB) or biphasic modeling (NMU and NMN). Three of the four investigated peptides, i.e. NMU, NT and NMN, showed a significant influx into the brain with unidirectional influx rate constants of 1.31 and 0.75 μL/(g × min) for NMU and NT respectively and initial influx constants (K1) of 72.14 and 7.55 μL/(g × min) and net influx constants (K) of 1.28 and 1.36 × 10(-16) μL/(g×min) for NMU and NMN respectively. The influx of NMB was negligible. Only NMN and NT showed a significant efflux out of the brain with an efflux constant (kout) of 0.042 min(-1) and 0.053 min(-1) respectively. Our results indicate that locally produced neuromedin peptides and/or fragments can be transported through the whole body, including passing the BBB, and taken up by different organs/tissues, supporting the idea that the neuromedins could have a much bigger role in the regulation of biological processes than currently assumed.

Increased corticotropin-releasing hormone (CRH) expression in cutaneous lupus lesions

Objective

Corticotropin-releasing hormone (CRH) and pro-opiomelanocortin (POMC) axis activation leads to the production of hormones, such as adrenocorticotrophic hormone (ACTH) and the α-melanocyte stimulating hormone (α-MSH). Data regarding the role of these hormones in systemic lupus erythematosus (SLE) are scarce. In the present study we aim to evaluate the participation of this axis in the cutaneous involvement of SLE.

Methods

Seventeen SLE patients were clinically evaluated, and biopsies from affected and unaffected skin of these patients were compared with 17 healthy control individuals. Immunohistochemical analyses for CRH, ACTH, α-MSH, and MC-1R were performed, and the serum levels of α-MSH, IL-1, IL-1ra, IL-6, IL-10, IL-12p70, IL-17, TNF-α, and IFN-γ were measured.

Results

The affected skin of the SLE patients exhibited higher CRH expression in the deep dermis compared to the skin of the controls ( p = 0.024), whereas the tissue expression of ACTH, cortisol, α-MSH and its receptor MC-1R were comparable in SLE patients and controls. Higher serum levels of IFN-γ ( p = 0.041), TNF-α ( p = 0.001) and IL-6 ( p = 0.049) were observed in SLE patients compared with controls, while α-MSH levels were similar in both groups.

Conclusion

The novel finding of elevated CRH expression solely in the affected skin deep dermis supports the notion of a cutaneous local dysfunction of the CRH-POMC axis in the pathogenesis of cutaneous SLE lesions.

The modulatory role of alpha-melanocyte stimulating hormone administered spinally in the regulation of blood glucose level in d-glucose-fed and restraint stress mouse models

Alpha-melanocyte stimulating hormone (α-MSH) is known as a regulator of the blood glucose homeostasis and food intake. In the present study, the possible roles of α-MSH located in the spinal cord in the regulation of the blood glucose level were investigated in d-glucose-fed and immobilization stress (IMO) mouse models. We found in the present study that intrathecal (i.t.) injection with α-MSH alone did not affect the blood glucose level. However, i.t. administration with α-MSH reduced the blood glucose level in d-glucose-fed model. The plasma insulin level was increased in d-glucose-fed model and was further increased by α-MSH, whereas α-MSH did not affect plasma corticosterone level in d-glucose-fed model. In addition, i.t. administration with glucagon alone enhanced blood glucose level and, i.t. injection with glucagon also increased the blood glucose level in d-glucose-fed model. In contrasted to results observed in d-glucose-fed model, i.t. treatment with α-MSH caused enhancement of the blood glucose level in IMO model. The plasma insulin level was increased in IMO model. The increased plasma insulin level by IMO was reduced by i.t. treatment with α-MSH, whereas i.t. pretreatment with α-MSH did not affect plasma corticosterone level in IMO model. Taken together, although spinally located α-MSH itself does not alter the blood glucose level, our results suggest that the activation of α-MSH system located in the spinal cord play important modulatory roles for the reduction of the blood glucose level in d-glucose fed model whereas α-MSH is responsible for the up-regulation of the blood glucose level in IMO model. The enhancement of insulin release may be responsible for modulatory action of α-MSH in down-regulation of the blood glucose in d-glucose fed model whereas reduction of insulin release may be responsible for modulatory action of α-MSH in up-regulation of the blood glucose in IMO model.

The brain–adipose axis: A review of involvement of molecules

Many molecules are involved in the regulation of feeding behavior, and they and their receptors are located in the brain hypothalamus and adipocytes. On the basis of evidence suggesting an association between the brain and adipose tissue, we propose the concept of the brain-adipose axis. This model consists of (l) the expression of endogenous molecules and/or their receptors in the hypothalamus and peripheral adipose tissue, (2) the function of these molecules as appetite regulators in the brain, (3) their existence in the general circulation as secreted proteins and (4) the physiological affects of these molecules on fat cell size and number. These molecules can be divided into two anorexigenic and orexigenic classes. In adipose tissue, all orexigenic molecules possess adipogenic activity, and almost all anorexigenic molecules suppress fat cell proliferation. Although the manner, in which they present in the circulating blood connect the brain and peripheral adipocytes, remains to be well-organized, these observations suggest the positive feedback axis affecting molecules in the hypothalamus and adipose tissue. Analysis of the disturbance and dysregulation of this axis might promote the development of new anti-obesity drugs useful in treating the metabolic syndrome.

The investigation of leptin and hypothalamic neuropeptides role in first attack psychotic male patients: olanzapine monotherapy

The mechanism underlying the weight gain due to treatment with olanzapine and other second generation antipsychotics has not been fully understood. To examine olanzapine's weight gain effects, we accepted first attack psychotic patients with no medication (pre-treatment) (n=22) and the healthy control group (n=26) in this study. After patientś diagnosis, they were hospitalized and then treated for four weeks with olanzapine (post-treatment). We used case-control association design to test body mass index (BMI) and biochemical changes in each group. We also investigated peripheral leptin and neuropeptides/hormones namely, pro-opiomelanocortin (POMC), cocaine and amphetaime regulated transcript (CART), and neuropeptide Y (NPY) levels. These neuropeptides which are synthesized/secreted from arcuate nucleus of hypothalamus affect food intake and therefore, body weight. After 4 weeks of olanzapine treatment; BMI (body mass index), waist circumference, blood triglyceride, total cholesterol, and very low density lipoprotein (VLDL) levels were increased significantly in patients compared to their pre-treatment baseline. In pre-treatment, patients' NPY levels were significantly lower while α-MSH, the anorexigenic product of POMC levels were significantly higher vs. control. Both leptin and NPY levels were significantly increased in patients after the treatment but the NPY levels were also significantly lower in post-treatment vs. the control group. The CART levels did not change after the treatment. We may presume that the antagonist effect of olanzapine on the serotonin (5HT2CR and 5HT1BR) receptors of the arcuate hypothalamic neurons may be a basis for a deregulation of the neurohormones secretion.

Melanin and melanogenesis in adipose tissue: possible mechanisms for abating oxidative stress and inflammation?

Obesity has become a worldwide epidemic and can lead to multiple chronic diseases. Adipose tissue is increasingly thought to play an active role in obesity-related pathologies such as insulin resistance and non-alcoholic fatty liver disease. Obesity has been strongly associated with systemic inflammation and, to a lesser degree, with oxidative stress, although the causal relationships among these factors are unclear. A recent study demonstrating an expression of the components of the melanogenic pathway and the presence of melanin in visceral adipose has raised questions regarding the possible role of melanogenesis in adipose tissue. As this study also found larger amounts of melanin in the adipose tissue of obese patients relative to lean ones, we hypothesize that melanin, a pigment known for its antioxidant and anti-inflammatory properties, may scavenge reactive oxygen species and abate oxidative stress and inflammation in adipose tissue. This review considers the evidence to support such a hypothesis, and speculates on the role of melanin within adipocytes. Furthermore, we consider whether the α-melanocyte-stimulating hormone or its synthetic analogues could be used to stimulate melanin production in adipocytes, should the hypothesis be supported in future experiments.

The increase of alpha-melanocyte-stimulating hormone in the plasma of chronic fatigue syndrome patients

Background

Despite extensive research, no reliable biological marker for chronic fatigue syndrome (CFS) has yet been identified. However, hyperactivation of melanotrophs in the pituitary gland and increased levels of plasma alpha-melanocyte-stimulating hormone (α-MSH) have recently been detected in an animal model of chronic stress. Because CFS is considered to be caused partly by chronic stress events, increased α-MSH plasma levels may also occur in CFS patients. We therefore examined α-MSH levels in CFS patients.

Methods

Fifty-five CFS patients, who were previously diagnosed within 10 years of with the disease, were enrolled in this study. Thirty healthy volunteers were studied as controls. Fasting bloods samples were collected in the morning and evaluated for their plasma levels of α-MSH, adrenocorticotropic hormone (ACTH), serum cortisol and dehydroepiandrosterone sulfate (DHEA-S). Mean levels of α-MSH were compared between the CFS and control groups using Welch's t test.

Results

The mean plasma α-MSH concentration in the CFS group (17.9 ± 1.0 pg/mL) was significantly higher than that in healthy controls (14.5 ± 1.0 pg/mL, p = 0.02). However, there was a wide range of values in the CFS group. The factors correlated with the plasma α-MSH values were analyzed using Spearman's rank correlation. A negative correlation was found between the duration of the CFS and the plasma α-MSH values (p = 0.04, r_s = -0.28), but no correlations with ACTH, cortisol or DHEA-S levels were identified (p = 0.55, 0.26, 0.33, respectively). The CFS patients were divided into two groups: patients diagnosed for ≤ 5 years' duration, and those diagnosed for 5-10 years' duration. They were compared with the healthy controls using one-way ANOVA and Tukey-Kramer multiple comparison tests. The mean α-MSH concentration in the ≤ 5 years group was 20.8 ± 1.2 pg/mL, which was significantly higher than that in the healthy controls (p < 0.01). There was no significant difference between the 5-10 year group (15.6 ± 1.4 pg/mL) and the healthy controls.

Conclusions

CFS patients with a disease duration of ≤ 5 years had significantly higher levels of α-MSH in their peripheral blood. α-MSH could be a potent biological marker for the diagnosis of CFS, at least during the first 5 years after onset of the disease.

Changes of peripheral alpha-melanocyte-stimulating hormone in childhood obesity

Relationships of blood circulating melanocortins to childhood obesity are not well established. We evaluated serum alpha-melanocyte-stimulating hormone (alpha-MSH) in lean children and different study groups of childhood obesity. We examined serum alpha-MSH in 52 otherwise healthy children with childhood obesity (Ob; mean age, 11 years; 32 girls/20 boys), 27 normal-weight children of same age, 7 additional obese patients with reduced melanocortin-4 receptor function (MC4Rmut), and 22 patients with craniopharyngioma (CP). Fasting serum alpha-MSH and leptin were measured by radioimmunoassay. Serum alpha-MSH was also evaluated 1 hour after 500-kcal liquid meal (CP and Ob) and at the end of 1-year lifestyle intervention in 24 Ob patients. The alpha-MSH levels were similar in obese vs lean children but significantly lower in CP (P < .001) and significantly higher (P < .05) in MC4Rmut patients compared with Ob. One hour after liquid meal, alpha-MSH increased in patients with Ob but not with CP. After 1 year, alpha-MSH levels increased significantly in the successful weight reduction Ob subgroup despite unchanged cortisol levels. The alpha-MSH changes correlated to weight status changes (r = 0.67, P = .0003) but not to changes of cortisol, insulin, or homeostasis model assessment of insulin resistance index. Persistently low alpha-MSH levels in CP patients are suspected to be due to pituitary or hypothalamic damage. High peripheral levels in MC4Rmut carriers indicate up-regulation of alpha-MSH. Changes of weight status are associated with changes of peripheral alpha-MSH.

Weak functional coupling of the melanocortin-1 receptor expressed in human adipocytes

The melanocortin (MC) receptor type-1 (MC1-R) is the only one of the five MC receptor subtypes expressed in human adipose tissue explants, human mesenchymal stem cells (MSCs), and MSC-derived adipocytes. Following our recent expression studies (Obesity 2007, 15, 40-49), we now investigated the functional role of MC1-R in these tissues and cells to deduce the coupling state of MC1-R to intracellular output signals in human fat cells and tissue. Expression of MC1-R by undifferentiated and differentiated MSCs was quantified by real-time TaqMan PCR. Intracellular output signals (cAMP, lipolysis, secretion of IL-6, IL-10, and TNF-alpha), as well as effects on the metabolic rate and proliferation of human MSCs were analyzed by standard assays, exposing undifferentiated and differentiated MSCs and, in part, human adipose tissue explants to the potent MC1-R agonist, [Nle(4), D-Phe(7)]-alpha-MSH (NDP-MSH). This agonist induced a weak cAMP signal in MSC-derived adipocytes. However, it did not affect lipolysis in these cells or in adipose tissue explants, nor did it modulate cytokine release and mRNA expression of IL-6, IL-8, and TNF-alpha upon LPS stimulation. In undifferentiated MSCs, NDP-MSH did not alter the metabolic rate, but it showed a significant antiproliferative effect. Therefore, it appears that MC1-R-effector coupling in (differentiated) human adipocytes is too weak to induce a regulatory effect on lipolysis or inflammation; by contrast, MC1-R stimulation in undifferentiated MSCs induces an inhibitory signal on cell proliferation.

Plasma alpha-melanocyte-stimulating hormone: sex differences and correlations with obesity

Rodent experiments raise the possibility of a regulatory role of peripheral alpha-melanocyte-stimulating hormone (alpha-MSH) in obesity and metabolism, but human data on peripheral alpha-MSH levels remain fragmentary. Because of the possible relationship between alpha-MSH and obesity, we endeavored to test the hypothesis that higher levels of alpha-MSH in obese patients would correlate with leptin levels and with other markers of obesity. Sixty normal-weight to obese healthy men and women participated. Weight, measures of body composition, and diet diaries were obtained; fasting blood was analyzed for alpha-MSH, lipids, glucose, insulin, leptin, and adiponectin. To begin to understand the source of peripherally measured hormones, alpha-MSH was also measured in serum samples from 5 individuals with untreated Addison disease. Levels of alpha-MSH were higher in men vs women (10.1 +/- 4.3 vs 7.6 +/- 3.4 pmol/L, P = .019), and alpha-MSH levels were higher in patients with Addison disease vs controls (17.7 +/- 2.3 vs 8.7 +/- 0.52 pmol/L, P < .001). Measures of adiposity correlated with insulin and leptin in men and women, and with adiponectin in women. alpha-Melanocyte-stimulating hormone levels did not correlate significantly with any parameter of adiposity or diet composition. The elevated alpha-MSH levels in patients with untreated Addison disease suggest possible pituitary secretion of alpha-MSH to the periphery. The lack of correlation between peripheral alpha-MSH and parameters of adiposity suggests that endogenous plasma alpha-MSH levels are not a metric for body composition per se.

Hormonal regulation of the mouse adrenal melanocortinergic system

Adrenocortical cells of several species have been reported to express significant levels of Agouti-related protein (Agrp) as well as melanocortin 4-receptor (MC4-R). In this study, we used the mouse tumoral adrenal cell line ATC7- L that secretes corticosterone in basal conditions with a 2- fold increase in response to ACTH treatment. We reported that these cells expressed functional MC4-R. They also expressed Agrp mRNA and secreted immunoreactive Agrp in the culture medium. Long-term treatment of ATC7-L with (Nle4,D-Phe7)-alpha MSH (NDP-alpha MSH) or forskolin as well as Agrp strongly reduced MC4-R level by more than 30%. On the contrary, leptin treatment did not modify this level although it significantly reduced MC2-R level. These results could be correlated to some data obtained in vivo on adrenal glands removed from diet-induced obese mice exhibiting a hyperleptinemia, where the level of both MC2-R and MC4-R appeared to be reduced as Agrp mRNA expression level was increased compared to Control mice. All these data would suggest the existence of a link between the metabolic status and the activation of the adrenal melanocortinergic system.

Expression and localization of melanocortin-1 receptor in human adipose tissues of severely obese patients

OBJECTIVE

The melanocortin system is a key regulator in the hypothalamus of energy intake and expenditure. It is frequently linked with obesity and apparently modulates sympathetic outflow to white adipose tissues. The role of the melanocortins within adipose tissues, however, is not entirely clear. This study was aimed at determining the quantitative expression of the five melanocortin receptors (MC1-R to MC5-R) in subcutaneous and omental fat of obese patients and non-obese subjects.

RESEARCH METHODS AND PROCEDURES

Expression of MC1-R to MC5-R, proopiomelanocortin, agouti signaling protein, leptin, leptin receptor, and uncoupling protein-1 was investigated in human fat samples by quantitative reverse transcription-polymerase chain reaction. MC1-R expression was also studied in preadipocytes, adipocytes, and monocytic THP-1 cells and by immunohistochemical localization in adipose tissues.

RESULTS

Notable expression was found for MC1-R, whereas no mRNA for MC2-R and MC3-R was detected; MC4-R and MC5-R mRNA was occasionally detectable but at very low levels. MC1-R mRNA in subcutaneous fat was increased in obese patients as compared with controls; omental fat of both groups had slightly higher MC1-R expression than subcutaneous fat and did not differ between patient groups. Immunohistochemical analysis of the MC1-R in adipose tissue sections showed that MC1-R expression was higher in macrophages but also present in adipocytes.

DISCUSSION

The expression of MC1-R and the lack of MC2-R in human adipose tissues indicate that the melanocortins may regulate cell proliferation and/or inflammatory signals rather than lipolysis. Also, the increased expression of MC1-R in subcutaneous fat of obese subjects may reflect one aspect of the pathophysiology of obesity.

Overweight humans are resistant to the weight-reducing effects of melanocortin4-10

CONTEXT

By enhancing energy expenditure and suppressing appetite, melanocortin peptides derived from proopiomelanocortin play a primary role in the hypothalamic regulation of body weight. In a recent study in normal-weight adults, the 6-wk intranasal administration of the MSH/ACTH(4-10) core fragment of proopiomelanocortin resulted in a distinct reduction of body weight and body fat, accompanied by significant decreases in leptin and insulin plasma concentrations.

OBJECTIVE

The present study aimed to generalize this finding to overweight patients.

DESIGN, SUBJECTS, AND INTERVENTION

MSH/ACTH(4-10) (0.5 mg) and placebo were intranasally administered once in the morning and once in the evening over a period of 12 wk in 23 overweight men (body mass index, mean +/- sem: 29.72 +/- 0.43 kg/m(2)).

RESULTS

MSH/ACTH(4-10) did not induce any significant reduction in body weight, body fat, and plasma levels of insulin and leptin as compared with the effects of placebo. Melanocortin treatment was accompanied by reduced cortisol concentrations.

CONCLUSIONS

We conclude that contrasting with normal-weight humans, overweight subjects are not susceptible to the effects of melanocortin administration on hypothalamic weight regulatory systems. In overweight subjects, a decreased sensitivity to ACTH/MSH peptides may derive from alterations at the level of the melanocortin receptor or at subsequent steps in the processing of the body fat signal.

Correlation between plasma -melanocyte-stimulating hormone concentration and body mass index in healthy horses

OBJECTIVE

To evaluate the correlation between plasma alpha-melanocyte-stimulating hormone (alpha-MSH) concentration and body mass index (BMI) in healthy horses.

ANIMALS

82 healthy horses.

PROCEDURE

Plasma alpha-MSH concentration was determined by radioimmunoassay. At the time blood samples were collected, body condition scores (BCS) were determined and measurements of girth circumference, body length, and height were obtained. Weight was estimated by use of the following formula: estimated weight (kg) = [girth (cm)2 x length (cm)]/11,877. Body mass index was calculated as estimated weight (kg)/height (m)2.

RESULTS

A correlation was found between BMI and BCS (rs = 0.60 [95% confidence interval (CI), 0.44 to 0.731). A weak correlation was found between plasma alpha-MSH concentration and BMI (rs = 0.25 [95% CI, 0.03 to 0.45]) and BCS (rs = 0.26 [95% CI, 0.04 to 0.46]). A correlation was found between plasma alpha-MSH concentration and BMI in horses > or = 10 years old (rs = 0.49 [95% CI, 0.20 to 0.69]) but not in horses < 10 years old (rs = -0.04). Horses in the upper quartile of BMI had significantly greater plasma alpha-MSH concentration (median, 9.1 pmol/L; range, 2.0 to 95.3 pmol/L) than horses in the lowest quartile of BMI (median, 70 pmol/L; range, 3.6 to 15.7 pmol/L).

CONCLUSIONS AND CLINICAL RELEVANCE

A correlation exists between plasma alpha-MSH concentration and BMI in horses. Further study is required to determine whether melanocortin receptor defects underlie this correlation or, alternately, whether plasma alpha-MSH concentration is simply a correlate of adiposity.

Plasma concentrations of alpha-MSH, AgRP and leptin in lean and obese men and their relationship to differing states of energy balance perturbation

OBJECTIVE

A great deal of attention has focused on the central role of alpha melanocyte-stimulating hormone (alpha-MSH) and its antagonism at the melanocortin-4 receptor (MC4R) by agouti related protein (AgRP) in the regulation of energy balance. However, very little is known regarding the function of circulating AgRP and alpha-MSH in humans. We aimed to determine whether circulating alpha-MSH and AgRP are responsive to long-term perturbations in energy balance, in a manner consistent with their central putative functions.

DESIGN AND MEASUREMENTS

Circulating alpha-MSH, AgRP and leptin were measured in both lean (n = 11) and obese (n = 18) male volunteers, some of whom (lean n = 11, obese n = 12) were then allocated one of two weight-loss dietary strategies to achieve about 5% weight loss. This was achieved by either total starvation (for 4-6 days) for rapid weight loss or a very low calorie diet (VLCD, 2.6 MJ/day) (11-12 days) for less rapid weight loss, in both the lean and obese volunteers.

RESULTS

At baseline, prior to any weight loss both plasma alpha-MSH (15.8 +/- 1.2 vs. 5.8 +/- 1.0 pmol/l +/- SEM; P < 0.001) and AgRP (49.4 +/- 2.4 vs. 10.1 +/- 0.9 pg/ml +/- SEM; P < 0.001) were elevated in obese subjects compared with lean. In both cases this correlated closely with fat mass (P < 0.001), percentage body fat (P < 0.001) and leptin (P < 0.05). Plasma AgRP increased significantly during a 6-day fast in lean individuals (11.1 +/- 1.6 vs. 21.6 +/- 3.1 pg/ml +/- SEM; P < 0.05) but not in the VLCD subjects or in the obese, while alpha-MSH was not affected by any changes in energy balance in either the lean or the obese volunteers.

CONCLUSION

We show a difference in alpha-MSH and AgRP in lean and obese subjects that correlates closely with body fat at baseline. We demonstrate an increase in plasma AgRP during a 6-day fast in lean individuals that is coincident with a decrease in plasma leptin. This increase in AgRP was not due to weight loss per se as there was no change in AgRP as a result of the same weight loss in the VLCD intervention in lean individuals. The source of the increase in plasma AgRP and its physiological function in the periphery remains to be elucidated but we suggest that the dynamics of the change in plasma leptin may determine the elevation in fasting plasma AgRP in lean subjects.

Agouti-related protein antagonizes glucocorticoid production induced through melanocortin 4 receptor activation in bovine adrenal cells: a possible autocrine control

Agouti-related protein (Agrp), primarily expressed in the hypothalamus, is an endogenous antagonist of alphaMSH at the level of melanocortin 3 receptor (MC3-R) and MC4-R, but the adrenal gland represents the second major Agrp-expressing tissue. In adrenal fasciculata cells, the glucocorticoid secretion is under the control of ACTH, which binds specifically MC2-R, the only functional melanocortin receptor described in these cells to date. Nevertheless, using cultured bovine fasciculata adrenal cells, we report that Agrp has no antagonistic properties against ACTH at the level of MC2-R. In our studies, (Nle4, d-Phe7)-alphaMSH (NDP-alphaMSH) stimulated the production of cortisol in a dose-dependent manner, and these effects were abolished by Agrp or SHU9119, a synthetic antagonist of MC3-R and MC4-R. Using a more specific antagonist (JKC-363) and RT-PCR analysis, we can postulate that the effects of NDP-alphaMSH were mediated via MC4-R. These results are suggestive that adrenal glucocorticoid production could be regulated through MC4-R that may have some relevance in the physiology of adrenal cells. Moreover, Agrp might exert an autocrine control on adrenal cells because a protein with biological Agrp-like activity is secreted by these cells. This peptide could then modulate locally the functions of some peripheral tissues such as adrenals.

Generation of expression constructs that secrete bioactive alphaMSH and their use in the treatment of experimental autoimmune encephalomyelitis

alpha Melanocyte-stimulating hormone (alphaMSH) is a 13 amino acid peptide with potent anti-inflammatory effects. We created two DNA expression constructs (miniPOMC and pACTH1-17) that encode bioactive versions of the alphaMSH peptide, and tested these constructs for therapeutic effects in experimental autoimmune encephalomyelitis (EAE). Each construct contained the sequences for alphaMSH, as well as the sequences that are involved in the secretion and processing of the POMC gene with the assumption that these sequences would promote processing and release of the encoded alphaMSH peptide. The differences between the two constructs lie at the C-terminal end where amino acids necessary for amidation of alphaMSH were included in only the pACTH1-17 construct. These two constructs were tested in vitro in bioassays, and in vivo in a mouse model of EAE. The results show that although bioactive peptides are secreted from cells transfected with either construct, there appears to be a significant therapeutic effect only with the pACTH1-17 construct which contains the extra C-terminal amino acids. The data suggest that it is possible to engineer DNA expression vectors encoding small secreted peptides such as alphaMSH, and that similar type constructs may be useful as therapeutics for the treatment of inflammatory diseases.