Melanocyte Stimulating Research Articles

Hydrophilic bioconjugatable trans-AB-porphyrins and peptide conjugates

Porphyrins bearing a single bioconjugatable group and a single water-solubilization motif in a trans-AB-architecture (with no other substituents) provide a compact design of value for studies in diverse disciplines. Established synthetic methods have been employed to prepare four new free base porphyrins and one Mn ( III ) chelate. The hydrophilic motif includes 4-N-methylpyridinium, 2,4,6-tris(carboxymethoxy)phenyl, 2,6-bis(phosphonomethoxy)phenyl, and carboxy; the bioconjugatable unit includes carboxy, maleimido, and N-hydroxysuccinimido (NHS) ester. Bioconjugation experiments with a protected porphyrin-diphosphate or unprotected porphyrin-diphosphonate were examined in organic solution or water, respectively. Both approaches were employed to conjugate to the ε-amino group of Lys11 in AcKPV- NH 2, a tripeptide fragment [ Ac -α-MSH(11-13)- NH 2] of melanocyte stimulating hormone, yielding porphyrin-peptide conjugates.

Modulation of γ2-MSH hepatoprotection by antisense peptides and melanocortin subtype 3 and 4 receptor antagonists.

Melanocortins, i.e., melanocyte stimulating hormones (MSH) are peptides with strong antiinflammatory effects. The most investigated aspects of γ2-MSH are related to cardiovascular effects and natriuresis, with limited research available about its anti-inflammatory and cytoprotective effects. The aims of this study were: 1) to examine the effects of γ2-MSH and its derivative [D-Trp(8)]-γ2-MSH on the acetaminophen model of liver damage in CBA mice; 2) to evaluate the modulation of γ2-MSH hepatoprotection by melanocortin subtypes 3 and 4 receptor antagonists SHU 9119 and HS 024; 3) to define the importance of central MSH pharmacophore region (HFRW) by using antisense peptides LVKAT and VKAT. In this study, specific antagonists and antisense peptides were used to target central pharmacophore region of γ2-MSH and [D-Trp(8)]-γ2-MSH, enabling the evaluation of hepatoprotection from the standpoint of the receptor and pharmacophore blockade. The criteria for monitoring the effects of the hormones on the liver damage were alanine transaminase, aspartate transaminase activities (U/L), and pathohistological scoring of liver necrosis (scale 0-5). γ2-MSH (0.24 mg/kg) indicated hepatoprotective effects in comparison to control (p < 0.001). In contrast, [D-Trp(8)]-γ2-MSH did not show any hepatoprotective effects. Application of antagonists SHU 9119 and HS 024, and antisense peptides LVKAT and VKAT, also did not show any hepatoprotective effects. In fact, when combined with γ2-MSH, it annulled its hepatoprotective effect. The results provide evidence for hepatoprotective and antiinflammatory effects of the γ2-MSH in the liver.

Abba Kastin: The melanocyte stimulating hormone story and the future of the proteophathies

From a personal viewpoint, Abba was always a congenial colleague and a good friend. I recall the hours of unraveling complex, confusing, and many times contradictory data sets with him and the excitement we both felt as what had been puzzling began to make sense. Most of all, I feel privileged to have Abba as a long and valued friend.

Hormonal regulation of colour change in eyes of a cryptic fish.

ABSTRACTColour change of the skin in lower vertebrates such as fish has been a subject of great scientific and public interest. However, colour change also takes place in eyes of fish and while an increasing amount of data indicates its importance in behaviour, very little is known about its regulation. Here, we report that both eye and skin coloration change in response to white to black background adaptation in live sand goby Pomatoschistus minutes, a bentic marine fish. Through in vitro experiments, we show that noradrenaline and melanocyte concentrating hormone (MCH) treatments cause aggregation of pigment organelles in the eye chromatophores. Daylight had no aggregating effect. Combining forskolin to elevate intracellular cyclic adenosine monophosphate (cAMP) with MCH resulted in complete pigment dispersal and darkening of the eyes, whereas combining prolactin, adrenocorticotrophic hormone (ACTH) or melanocyte stimulating hormone (α-MSH) with MCH resulted in more yellow and red eyes. ACTH and MSH also induced dispersal in the melanophores, resulting in overall darker eyes.By comparing analysis of eyes, skin and peritoneum, we conclude that the regulation pattern is similar between these different tissues in this species which is relevant for the cryptic life strategy of this species. With the exception of ACTH which resulted in most prominent melanophore pigment dispersal in the eyes, all other treatments provided similar results between tissue types. To our knowledge, this is the first study that has directly analysed hormonal regulation of physiological colour change in eyes of fish.

The effect of ghrelin and estradiol on mean concentration of thyroid hormones.

Background:Ghrelin is a novel peptide hormone that has GH releasing activity and also other endocrine and metabolic functions. It can also increase food intake and decrease T3 and T4 concentrations. Several parameters of hypothalamic-pituitary-thyroid (HPT) axis function are modulated by 17β-estradiol (E2).Objectives:The purpose of this study was to investigate the effect of interactions between ghrelin and estradiol (injected via ICV route) on plasma T3 and T4 concentrations in female rats.Materials and Methods:Eighteen Wistar female rats (bodyweight, 200-250 g) were randomly divided into three groups. Group 1 received estradiol, Group 2 received ghrelin and Group 3 received ghrelin and estradiol. Plasma samples were used to assess T3 and T4 concentration by RIA.Results:The results indicated that ghrelin significantly decreased thyroid hormone concentrations, whereas estradiol increased these concentrations. The simultaneous injection of ghrelin and estradiol significantly decreased the inhibitory effect of ghrelin on thyroid hormone concentrations (P < 0.05).Conclusions:According to the results of this study, both ghrelin and estradiol affect the concentration of thyroid hormone but in opposite directions. This difference might be due to different underlying hormonal mechanisms such as HPA and/or HPT axis melanocyte stimulating hormone (MSH) systems could be suggested.

Synthesis and bioactivity of MSH4 oligomers prepared by an A2 + B2 strategy

Oligomers incorporating the tetrapeptide MSH4, the minimum active sequence of melanocyte stimulating hormone, were synthesized by an A2+B2 strategy involving microwave-assisted copper-catalyzed azide-alkyne cycloaddition. A2 contained an MSH4 core while B2 contained a (Pro-Gly)3 spacer. Soluble mixtures containing compounds with up to eight MSH4 units were obtained from oligomerizations at high monomer concentrations. The avidities of several oligomeric mixtures were evaluated by means of a competitive binding assay using HEK293 cells engineered to overexpress the melanocortin 4 receptor. When based on total MSH4 concentrations, avidities were only minimally enhanced compared with a monovalent control. The lack of variation in the effect of ligands on probe binding is consistent with high off rates for MSH4 in both monovalent and oligomeric constructs relative to that of the competing probe.

Effects of risperidone treatment on the expression of hypothalamic neuropeptide in appetite regulation in Wistar rats

Although the use of atypical antipsychotic drugs has been successful in the treatment of schizophrenia, they can cause some complications in the long-term use, including weight gain. Patients using these drugs tend to disrupt treatment primarily due to side effects. The atypical antipsychotic mechanism of action regulates a number of highly disrupted neurotransmitter pathways in the brains of psychotic patients but may also cause impairment of neurohormonal pathways in different brain areas. In this study, we investigated the circulating levels of hypothalamic neurohormones, which are related to appetite regulation; neuropeptide Y (NPY); alpha melanocyte stimulating hormone (α-MSH); cocaine and amphetamine regulated transcript (CART); agouti-related peptide (AgRP); and leptin in male Wistar rats, which were treated with risperidone, a serotonin antagonist, for four weeks. Alterations in the mRNA expression levels of these candidate genes in the hypothalamus were also analyzed. We hypothesized that risperidone treatment might alter both hypothalamic and circulating levels of neuropeptides through serotonergic antagonism, resulting in weight gain. Gene expression studies revealed that the mRNA expression levels of proopiomelanocortin (POMC), AgRP, and NPY decreased as well as their plasma levels, except for NPY. Unexpectedly, CART mRNA levels increased when their plasma levels decreased. Because POMC neurons express the serotonin receptor (5HT2C), the serotonergic antagonism of risperidone on POMC neurons may cause an increase in appetite and thus increase food consumption even in a short-term trial in rats.

Tyrosinase 및 TRP-2의 발현 억제를 통한 황칠나무 잎 추출물의 Melanin 생성 저해 효과

황칠나무는 한국의 남부 해안 및 제주도 등에서 자생하는 식물이다. 본 연구에서는 황칠나무 잎 추출물의 미백 활성의 원인을 규명하고자 연구를 수행하였다. <TEX>${\alpha}$</TEX>-MSH로 자극된 B16 melanoma 세포에 대한 추출물의 멜라닌 생합성 저해 활성을 측정하였다. 추출물은 25 및 <TEX>$50{\mu}g/mL$</TEX> 농도에서 유의적으로 멜라닌 함량을 감소시켰으며, 세포 내의 tyrosinase 활성뿐만 아니라 tyrosinase와 TRP-2의 단백질 발현도 상당히 저해하였다. 결과적으로, 황칠나무 잎 추출물은 세포 내의 tyrosinase활성과 멜라닌 생합성에 직접적으로 관련된 효소의 발현을 저해함으로써 미백효과를 나타내었다. 본 연구 결과는 황칠나무 잎 추출물이 새로운 미백 화장품의 원료로써 이용 가능함을 시사한다. Dendropanax morbifera (D. morbifera) grows in the southern coastal areas and on Jeju Island in Korea. In this study, D. morbifera leaf extract was investigated to determine the mechanism of its whitening effect. The inhibitory activities of the extract on melanogenesis were tested in B16 melanoma cells treated with the <TEX>${\alpha}$</TEX>-melanocyte stimulating hormone (<TEX>${\alpha}$</TEX>-MSH). D. morbifera leaf extracts remarkably decreased the melanin content at 25 and <TEX>$50{\mu}g/mL$</TEX>. The extracts significantly inhibited the intracellular tyrosinase activity and protein expression of tyrosinase and tyrosinase related protein-2 (TRP-2). In conclusion, D. morbifera leaf extracts would show a whitening effect by inhibiting intracellular tyrosinase activities and the expression of enzymes directly involved in the melanin biosynthesis. The results indicate that fractions of D. morbifera leaf extracts show potential for application as a whitening agent in the new whitening cosmetics.

Synthesis and evaluation of bivalent ligands for binding to the human melanocortin-4 receptor

Membrane proteins, especially G-protein coupled receptors (GPCRs), are interesting and important theragnostic targets since many of them serve in intracellular signaling critical for all aspects of health and disease. The potential utility of designed bivalent ligands as targeting agents for cancer diagnosis and/or therapy can be evaluated by determining their binding to the corresponding receptors. As proof of concept, GPCR cell surface proteins are shown to be targeted specifically using multivalent ligands. We designed, synthesized, and tested a series of bivalent ligands targeting the over-expressed human melanocortin 4 receptor (hMC4R) in human embryonic kidney (HEK) 293 cells. Based on our data suggesting an optimal linker length of 25±10Å inferred from the bivalent melanocyte stimulating hormone (MSH) agonist, the truncated heptapeptide, referred to as MSH(7): Ac-Ser-Nle-Glu-His-D-Phe-Arg-Trp-NH2 was used to construct a set of bivalent ligands incorporating a hMC4R antagonist, SHU9119: Ac-Nle-c[Asp-His-2′-D-Nal-Arg-Trp-Lys]-NH2 and another set of bivalent ligands containing the SHU9119 antagonist pharmacophore on both side of the optimized linkers. These two binding motifs within the bivalent constructs were conjoined by semi-rigid (Pro-Gly)3 units with or without the flexible poly(ethylene glycol) (PEGO) moieties. Lanthanide-based competitive binding assays showed bivalent ligands binds to the hMC4R with up to 240-fold higher affinity than the corresponding linked monovalent ligands.

An Essential Role for the K+-dependent Na+/Ca2+-exchanger, NCKX4, in Melanocortin-4-receptor-dependent Satiety

K(+)-dependent Na(+)/Ca(2+)-exchangers are broadly expressed in various tissues, and particularly enriched in neurons of the brain. The distinct physiological roles for the different members of this Ca(2+) transporter family are, however, not well described. Here we show that gene-targeted mice lacking the K(+)-dependent Na(+)/Ca(2+)-exchanger, NCKX4 (gene slc24a4 or Nckx4), display a remarkable anorexia with severe hypophagia and weight loss. Feeding and satiety are coordinated centrally by melanocortin-4 receptors (MC4R) in neurons of the hypothalamic paraventricular nucleus (PVN). The hypophagic response of Nckx4 knock-out mice is accompanied by hyperactivation of neurons in the PVN, evidenced by high levels of c-Fos expression. The activation of PVN neurons in both fasted Nckx4 knock-out and glucose-injected wild-type animals is blocked by Ca(2+) removal and MC4R antagonists. In cultured hypothalamic neurons, melanocyte stimulating hormone induces an MC4R-dependent and sustained Ca(2+) signal, which requires phospholipase C activity and plasma membrane Ca(2+) entry. The Ca(2+) signal is enhanced in hypothalamic neurons from Nckx4 knock-out animals, and is depressed in cells in which NCKX4 is overexpressed. Finally, MC4R-dependent oxytocin expression in the PVN, a key essential step in satiety, is prevented by blocking phospholipase C activation or Ca(2+) entry. These findings highlight an essential, and to our knowledge previously unknown, role for Ca(2+) signaling in the MC4R pathway that leads to satiety, and a novel non-redundant role for NCKX4-mediated Ca(2+) extrusion in controlling MC4R signaling and feeding behavior. Together, these findings highlight a novel pathway that potentially could be exploited to develop much needed new therapeutics to tackle eating disorders and obesity.

The role of neuropeptides in the control of regional immunity

Neuropeptides (NPs) and neurotransmitters are a heterogeneous group of soluble factors that make connections within the neuroendocrine and immune systems. NPs, including substance P (SP), vasoactive intestinal peptide (VIP), α melanocyte–stimulating hormone (α-MSH), and calcitonin gene–related peptide (CGRP), released by nerves that innervate the skin, can modulate the action of innate and adaptive skin immunity as well as the skin cells functions. Their role in several inflammatory skin diseases, such as atopic dermatitis, psoriasis, and vitiligo, and in the isotopic response has been reported.Further progress in understanding the various processes that modulate the interactions of the nervous and the skin immune system is essential to develop effective treatment for inflammatory skin conditions with neurogenic components and for understanding signs and symptoms in the isotopic response and, in general, in the control of global and regional immunity.

Decreased serotonin transporter immunoreactivity in the human hypothalamic infundibular nucleus of overweight subjects.

Context: That serotonin plays a role in the regulation of feeding behavior and energy metabolism has been known for a long time. Serotonin transporters (SERT) play a crucial role in serotonin signaling by regulating its availability in the synaptic cleft. The neuroanatomy underlying serotonergic signaling in humans is largely unknown, and until now, SERT immunoreactivity in relation to body weight has not been investigated.Objective: To clarify the distribution of SERT immunoreactivity throughout the human hypothalamus and to compare SERT immunoreactivity in the infundibular nucleus (IFN), the human equivalent of the arcuate nucleus, in lean and overweight subjects.Design: First, we investigated the distribution of serotonin transporters (SERT) over the rostro-caudal axis of six post-mortem hypothalami by means of immunohistochemistry. Second, we estimated SERT immunoreactivity in the IFN of lean and overweight subjects. Lastly, double-labeling of SERT with Neuropeptide Y (NPY) and melanocortin cell populations was performed to further identify cells showing basket-like SERT staining.Results: SERT-immunoreactivity was ubiquitously expressed in fibers throughout the hypothalamus and was the strongest in the IFN. Immunoreactivity in the IFN was lower in overweight subjects (p = 0.036). Basket-like staining in the IFN was highly suggestive of synaptic innervation. A very small minority of cells showed SERT double labeling with NPY, agouti-related protein and α–melanocyte stimulating hormone.Conclusions: SERT is ubiquitously expressed in the human hypothalamus. Strong SERT immunoreactivity, was observed in the IFN a region important for appetite regulation, in combination with lower SERT immunoreactivity in the IFN of overweight and obese subjects, may point toward a role for hypothalamic SERT in human obesity.

The melanogenesis alteration effects of Achillea millefolium L. essential oil and linalyl acetate: involvement of oxidative stress and the JNK and ERK signaling pathways in melanoma cells.

The mitogen-activated protein kinase (MAPK) family, including extracellular signal-regulated kinase (ERK)1/2, c-Jun N-terminal kinase (JNK)1/2 and p38 MAPK, is known to be activated by ultraviolet (UV) radiation in melanocytes to regulate melanin production. Reactive oxygen species (ROS) play important roles in the pathway of ERK and JNK activation. It has been established that the essential oil of Achillea millefolium L. (AM-EO) has activities that suppress the oxidative stress and inflammatory responses. Thus, we analyzed the effects of AM-EO on melanogenesis in melanocyte stimulating hormone (α-MSH) treated melanoma cells. The results demonstrated that AM-EO suppresses melanin production by decreasing tyrosinase activity through the regulation of the JNK and ERK signaling pathways. This effect might be associated with the AM-EO activity leading to the suppression of ROS, and linalyl acetate is its major functional component. Therefore, we propose that AM-EO has the potential to treat hyperpigmentation in the future.

Multivalent cell specific therapeutics for treatment of metabolic disorders (1108.1)

Metabolic Homeostasis is mediated via multi‐organ endocrine signaling. Because many systems are involved, therapeutics often have wide‐ranging side‐effects. We have shown therapeutic specificity can be achieved with agents that simultaneously bind two different receptors that, as a combination, are relatively unique to a given cell type. Bivalent ligands, that target cells within the homeostatic axis, were produced; melanocyte stimulating hormone linked to CCK (MSH/CCK), and Glucagon Like Peptide 1 (GLP‐1) linked to Glibenclamide (Glb, SUR1 antagonist). Binding analyses, assessed with cells expressing the complementary receptor pair, indicate an apparent Kd of ~5 nM for MSH/CCK, ~10nM for GLP‐1/Glb. Constants for the individual domains within the bivalent constructs were 30 nM or greater, and neither ligand bound with high affinity to cells expressing only one of the complementary receptors, indicating that high affinity binding requires both receptors. Once bound, the ligand/ receptor complex is rapidly endocytosed. Both ligands maintain signaling capacity, though the magnitude, sensitivity of 2nd messenger and physiological effects, differ from the constituent monomers. Uniquely, GLP‐1/Glb was found to potentiate insulin secretion at stimulatory glucose concentrations, but inhibit, rather than activate, at non‐stimulatory glucose. Thus, these bivalent ligands exhibit enhanced affinity, cell type specificity and maintain functional efficacy, and thereby hold promise as cell specific therapeutic agents.Grant Funding Source: Supported by: Juvenile Diabetes Research Foundation, National Institutes of Health, NCI, CA123547

αMSH blunts endotoxin-induced MuRF1 and atrogin-1 upregulation in skeletal muscle by modulating NF-κB and Akt/FoxO1 pathway.

Alpha melanocyte stimulating hormone (αMSH) has been shown to have anti-inflammatory and anticachectic actions. We hypothesized that αMSH administration could attenuate the effect of lipopolysaccharide (LPS) on the skeletal muscle through modifications in IGF-Akt-FoxO1 pathway, or/and in serum corticosterone. Adult male Wistar rats were injected with LPS and/or αMSH. αMSH administration reduced LPS-induced increase in liver TNFα and serum nitrites as well as NF-κB activation in skeletal muscle. In contrast, αMSH was not able to prevent the stimulatory effect of LPS on serum concentration of ACTH and corticosterone. LPS decreased serum levels of IGF-I and IGFBP3 and their expression in the liver (P < 0.01). However IGFBP3 expression in the gastrocnemius was increased by LPS. Treatment with αMSH prevented the effects of LPS on IGFBP3 but not on IGF-I. In the gastrocnemius αMSH blocked LPS-induced decrease in pAkt as well as the increase in pNF-κB(p65), FoxO1, atrogin-1, and MuRF1 levels. These results suggest that αMSH blunts skeletal muscle response to endotoxin by downregulating atrogenes and FoxO1 at least in part by controlling NF-κB activation and Akt signalling, but not through modifications in the secretion of corticosterone or IGF-I.

Recent advances in melasma

Melasma is one of the most common pigmentary disorders worldwide with a still unresolved pathogenesis and treatment continues to be challenging. Increased sun exposure and genetic factors are considered the two most important etiological factors. Estrogens, progesterones and increased melanocyte stimulating hormone are also involved. Melasma treatment can be very frustrating as many modalities can turn out to be ineffective. Dermal and mixed variants are quite resistant to therapy. Most patients seek medical help much after the onset of the condition, making treatment even more difficult. Sunscreens and topical depigmenting agents remain mainstay of therapy. Chemical peels and light sources are beneficial as adjuncts. There have been numerous advances in the understanding and management of melasma. This review attempts to look at these newer vistas in melasma. Literature search for the review was done from PubMed, the Cochrane Library, MEDLINE and Embase using the key word melisma, melasma pathogenesis and melasma treatment.

톳 분획물이 B16F10 흑색종 세포에서의 멜라닌합성에 미치는 영향 연구

본 연구에서는 톳 분획물의 미백효과 및 그에 따른 생화학적 기전의 해석을 위하여 톳 분획물이 <TEX>${\alpha}$</TEX>-MSH에 의해 인위적으로 유발된 melanogenesis 과정에 있어서 어떠한 영향을 미치는 지를 조사하였고, 이때 MITF, TRP1, TRP2, tyrosinase 등과 같은 melanin 생성에 관여하는 유전자들의 발현에 어떠한 변화가 유발되었는지를 조사하였다. 톳 분획물 처리가 B16F10 mouse melanoma cell의 멜라닌의 생성량과 tyrosinase의 활성에 미치는 영향을 확인한 결과, butanol fraction (BFHF) 처리군과 water fraction (WFHF) 처리군을 제외한 ethyl extract (EEHF) 처리군, dichlorimethane fraction (CFHF ) 처리군, ethyl acetate fraction (EAFHF) 처리군 모두 농도의존적으로 멜라닌 생성량과 tyrosinase 활성이 억제되었으며, MITF, TRP1, TRP2, tyrosinase의 발현이 단백질 수준에서 감소하였음을 확인하였다. 그 중 특히 EEHF 처리군과 CFHF 처리군은 50 <TEX>${\mu}g/ml$</TEX>의 농도에서 멜라닌 생성량을 40.5%, 33.2% 감소시켰으며, tyrosinase 활성도 50 <TEX>${\mu}g/ml$</TEX>의 농도에서 각각 53.3%, 54.1% 감소시켰다. 또한 EEHF, CFHF, EAFHF 처리군에서 MITF, TRP1, TRP2, tyrosinase의 발현이 농도 의존적으로 감소하였음을 확인하였다. 이상의 결과를 살펴볼 때 톳 분획물 중 특히 EEHF 처리군과 CFHF 처리군이 B16F10 mouse melanoma cell에서 melanin 생성에 관여하는 유전자인 MITF, TRP1, TRP2, tyrosinase 발현을 억제하므로 향후 미백 기능성 소재로서의 활용이 가능할 것이라고 사료된다. The objective of this study was to evaluate the anti-melanogenic effects of Hizikia fusiforme (HF) fractions in <TEX>${\alpha}$</TEX>-melanocyte stimulating hormone-induced B16F10 mouse melanoma cells. Ethanol extractions of Hizikia fusiforme (EEHF) were subjected to fraction by using dichloromethane (CFHF), ethyl acetate (EAFHF), butanol (BFHF), and water (WFHF). EEHF, CFHF, and EAFHF inhibited tyrosinase activity and melanin synthesis in B16F10 mouse melanoma cells in a dose-dependent manner. The melanin contents were inhibited by 40.5% and 33.2% in response to treatment with 50 <TEX>${\mu}g/ml$</TEX> of EEHF and CFHF, respectively. In addition, tyrosinase activities showed a 53.3% and 54.1% reduction in treatment with 50 <TEX>${\mu}g/ml$</TEX> of EEHF and CFHF. Western blotting analysis showed that EEHF, CFHF, and EAFHF inhibited tyrosinase, TRP-1, TRP-2, and MITF expression in a dose-dependent manner. In conclusion, these findings indicate that ethanol and dichloromethane fractions of Hizikia fusiforme, which inhibit melanin synthesis and tyrosinase activity, are effective skin-whitening agents.

Lentivirus‐Mediated α‐Melanocyte‐Stimulating Hormone Overexpression in the Hypothalamus Decreases Diet Induced Obesity in Mice

Melanocyte stimulating hormone (MSH) derived from the pro-hormone pro-opiomelanocortin (POMC) has potent effects on metabolism and feeding that lead to reduced body weight in the long-term. To determine the individual roles of POMC derived peptides and their sites of action, we created a method for the delivery of single MSH peptides using lentiviral vectors and studied the long-term anti-obesity effects of hypothalamic α-MSH overexpression in mice. An α-MSH lentivirus (LVi-α-MSH-EGFP) vector carrying the N'-terminal part of POMC and the α-MSH sequence was generated and shown to produce bioactive peptide in an in vitro melanin synthesis assay. Stereotaxis was used to deliver the LVi-α-MSH-EGFP or control LVi-EGFP vector to the arcuate nucleus (ARC) of the hypothalamus of male C57Bl/6N mice fed on a high-fat diet. The effects of 6-week-treatment on body weight, food intake, glucose tolerance and organ weights were determined. Additionally, a 14-day pairfeeding study was conducted to assess whether the weight decreasing effect of the LVi-α-MSH-EGFP treatment is dependent on decreased food intake. The 6-week LVi-α-MSH-EGFP treatment reduced weight gain (8.4 ± 0.4 g versus 12.3 ± 0.6 g; P < 0.05), which was statistically significant starting from 1 week after the injections. The weight of mesenteric fat was decreased and glucose tolerance was improved compared to LVi-EGFP treated mice. Food intake was decreased during the first week in the LVi-α-MSH-EGFP treated mice but subsequently increased to the level of LVi-EGFP treated mice. The LVi-EGFP injected control mice gained more weight even when pairfed to the level of food intake by LVi-α-MSH-EGFP treated mice. We demonstrate that gene transfer of α-MSH, a single peptide product of POMC, into the ARC of the hypothalamus, reduces obesity and improves glucose tolerance, and that factors other than decreased food intake also influence the weight decreasing effects of α-MSH overexpression in the ARC. Furthermore, viral MSH vectors delivered stereotaxically provide a novel tool for further exploration of chronic site-specific effects of POMC peptides.

Complex structural and regulatory evolution of the pro-opiomelanocortin gene family

The melanocortin system is a neuroendocrine machinery that has been associated with phenotypic diversification in a number of vertebrate lineages. Central to the highly pleiotropic melanocortin system is the pro-opiomelanocortin (pomc) gene family, a family of pre-prohormones that each give rise to melanocyte stimulating hormone (MSH), adrenocorticotropic releasing hormone (ACTH), β-lipotropin hormone, and β-endorphin. Here we examine the structure, tissue expression profile, and pattern of cis transcriptional regulation of the three pomc paralogs (α1, α2, and β) in the model cichlid fish Astatotilapia burtoni and other cichlids, teleosts, and mammals. We found that the hormone-encoding regions of pomc α1, pomc α2 and pomc β are highly conserved, with a few notable exceptions. Surprisingly, the pomc β gene of cichlids and pomacentrids (damselfish) encodes a novel melanocortin peptide, ε-MSH, as a result of a tandem duplication of the segment encoding ACTH. All three genes are expressed in the brain and peripheral tissues, but pomc α1 and α2 show a more spatially restricted expression profile than pomc β. In addition, the promoters of each pomc gene have diverged in nucleotide sequence, which may have facilitated the diverse tissue-specific expression profiles of these paralogs across species. Increased understanding of the mechanisms regulating pomc gene expression will be invaluable to the study of pomc in the context of phenotypic evolution.

Changes in plasma melanocyte stimulating hormone, ACTH, prolactin, GH, LH, FSH, and thyroid stimulating hormone in response to injection of sulpiride, thyrotropin releasing hormone, or vehicle in insulin sensitive and insensitive mares

Six insulin-sensitive and 6 insulin-insensitive mares were used in a replicated 3 by 3 Latin square design to determine the pituitary hormonal responses (compared with vehicle) to sulpiride and thyrotropin-releasing hormone (TRH), 2 compounds commonly used to diagnose pituitary pars intermedia dysfunction (PPID) in horses. Mares were classified as insulin sensitive or insensitive by their previous glucose responses to direct injection of human recombinant insulin. Treatment days were February 25, 2012, and March 10 and 24, 2012. Treatments were sulpiride (racemic mixture, 0.01 mg/kg BW), TRH (0.002 mg/kg BW), and vehicle (saline, 0.01 mL/kg BW) administered intravenously. Blood samples were collected via jugular catheters at −10, 0, 5, 10, 20, 30, 45, 60, 90, and 120 min relative to treatment injection. Plasma ACTH concentrations were variable and were not affected by treatment or insulin sensitivity category. Plasma melanocyte-stimulating hormone (MSH) concentrations responded (P < 0.01) to both sulpiride and TRH injection and were greater (P < 0.05) in insulin-insensitive mares than in sensitive mares. Plasma prolactin concentrations responded (P < 0.01) to both sulpiride and TRH injection, and the response was greater (P < 0.05) for sulpiride; no effect of insulin sensitivity was observed. Plasma thyroid-stimulating hormone (TSH) concentrations responded (P < 0.01) to TRH injection only and were higher (P < 0.05) in insulin-sensitive mares in almost all time periods. Plasma LH and FSH concentrations varied with time (P < 0.05), particularly in the first week of the experiment, but were not affected by treatment or insulin sensitivity category. Plasma GH concentrations were affected (P < 0.05) only by day of treatment. The greater MSH responses to sulpiride and TRH in insulin-insensitive mares were similar to, but not as exaggerated as, those observed by others for PPID horses. In addition, the reduced TSH concentrations in insulin-insensitive mares are consistent with our previous observation of elevated plasma triiodothyronine concentrations in hyperleptinemic horses (later shown to be insulin insensitive as well).