A liquid chromatographic/tandem mass spectroscopic method for quantification of the cyclic peptide melanotan-II. Plasma and brain tissue concentrations following administration in mice

LC-HRMS characterization of the skin pigmentation and sexual enhancers melanotan II and bremelanotide sold on the black market of performance and image enhancing drugs

The spread of performance and image enhancing drugs (PIEDs) often requires forensic toxicology laboratories to identify unknown compounds without reference standards. We characterized the PIEDs melanotan II and bremelanotide, not legally marketed, in eight unknown samples confiscated by police together with anabolic steroids, hormone modulators, sexual enhancers and stimulants, intended for the black market of bodybuilders, using liquid chromatography-high resolution/high accuracy Orbitrap mass spectrometry (LC-HRMS). The characterization was carried out by the accurate mass measurements of MH⁺ ionic species, the study of their isotopic patterns and the associated relative isotopic abundance (RIA) values, as well as the accurate mass measurements of collision-induced product ions obtained in fragmentation experiments. LC-HRMS confirmed itself as a powerful analytical tool to elucidate the elemental composition and structural characteristics of unknown compounds.

Biphasic effect of melanocortin agonists on metabolic rate and body temperature

The melanocortin system regulates metabolic homeostasis and inflammation. Melanocortin agonists have contradictorily been reported to both increase and decrease metabolic rate and body temperature. We find two distinct physiologic responses occurring at similar doses. Intraperitoneal administration of the nonselective melanocortin agonist MTII causes a melanocortin-4 receptor (Mc4r)-mediated hypermetabolism/hyperthermia. This is preceded by a profound, transient hypometabolism/hypothermia that is preserved in mice lacking any one of Mc1r, Mc3r, Mc4r, or Mc5r. Three other melanocortin agonists also caused hypothermia, which is actively achieved via seeking a cool environment, vasodilation, and inhibition of brown adipose tissue thermogenesis. These results suggest that the hypometabolic/hypothermic effect of MTII is not due to a failure of thermoregulation. The hypometabolism/hypothermia was prevented by dopamine antagonists, and MTII selectively activated arcuate nucleus dopaminergic neurons, suggesting that these neurons may contribute to the hypometabolism/hypothermia. We propose that the hypometabolism/hypothermia is a regulated response, potentially beneficial during extreme physiologic stress.

Transarterial embolization with sorafenib in animal livers: a pharmacokinetics study

PURPOSE

To assess the safety and feasibility of the targeted delivery of the antiangiogenic drug sorafenib to the liver using transarterial chemoembolization methodology as a novel approach to hepatocellular carcinoma (HCC) therapy.

MATERIALS AND METHODS

Seven healthy New Zealand white rabbits were used in the study. After placement of a catheter in the common hepatic artery, six rabbits were treated with chemoembolization of sorafenib in iodized oil (Lipiodol) (sorafenib dose 0.1 mg/kg), and one rabbit received Lipiodol only. Liquid chromatography tandem mass spectrometry was used to measure the concentration of sorafenib in the peripheral blood and liver tissue 24 hours and 72 hours after treatment. Histochemical staining of the liver sections and biochemical measurements were performed.

RESULTS

The administration of sorafenib in Lipiodol emulsions by transarterial chemoembolization resulted in sorafenib concentrations of 794 ng/g ± 240 and 64 ng/g ± 15 in the liver tissue 24 hours and 72 hours after treatment. The average liver-to-serum ratios 24 hours and 72 hours after treatment were approximately 14 and 22. The histochemical staining of the liver tissue sections and aspartate aminotransferase, alanine aminotransferase, γ-glutamyltransferase and total bilirubin concentrations indicated no significant liver damage.

CONCLUSIONS

Transarterial chemoembolization with sorafenib in Lipiodol is an effective methodology for the localized delivery of this drug to the liver and has possible practical implications in therapeutic interventions for the treatment of hepatocellular carcinoma.

Ghrelin Agonist JMV 1843 Increases Food Intake, Body Weight and Expression of Orexigenic Neuropeptides in Mice

Ghrelin and agonists of its receptor GHS-R1a are potential substances for the treatment of cachexia. In the present study, we investigated the acute and long term effects of the GHS R1a agonist JMV 1843 (H Aib-DTrp-D-gTrp-CHO) on food intake, body weight and metabolic parameters in lean C57BL/6 male mice. Additionally, we examined stability of JMV 1843 in mouse blood serum. A single subcutaneous injection of JMV 1843 (0.01-10 mg/kg) increased food intake in fed mice in a dose-dependent manner, up to 5-times relative to the saline-treated group (ED50=1.94 mg/kg at 250 min). JMV 1843 was stable in mouse serum in vitro for 24 h, but was mostly eliminated from mouse blood after 2 h in vivo. Ten days of treatment with JMV 1843 (subcutaneous administration, 10 or 20 mg/kg/day) significantly increased food intake, body weight and mRNA expression of the orexigenic neuropeptide Y and agouti-related peptide in the medial basal hypothalamus and decreased the expression of uncoupling protein 1 in brown adipose tissue. Our data suggest that JMV 1843 could have possible future uses in the treatment of cachexia.

Evaluation of protein quantification using standard peptides containing single conservative amino acid replacements

Structural analogs are evaluated as peptide internal standards for protein quantification with liquid chromatography-multiple reaction monitoring mass spectrometry (LC-MRM); specifically, single conservative amino acid replacements (SCAR) are performed to create tagged standards that differ by the addition or subtraction of a single methylene group in one amino acid side chain. Because the performance of stable isotope-labeled standards (SIS) has been shown to be superior to structural analogs, differences in both development and quantitative performance between assays based on SIS and SCAR peptides are explored. To establish an assay using the structural analogs, analysis of endogenous, SCAR and SIS peptides was performed to examine their ion signal, fragmentation patterns and response in LC-MRM. Performance of SCAR and SIS peptides was compared for quantification of epidermal growth factor receptor from lung cancer cell lysates and immunoglobulin M in the serum of multiple myeloma patients.

Genetic dissection of the functions of the melanocortin-3 receptor, a seven-transmembrane G-protein-coupled receptor, suggests roles for central and peripheral receptors in energy homeostasis

The melanocortin-3 receptor (MC3R) gene is pleiotropic, influencing body composition, natriuresis, immune function, and entrainment of circadian rhythms to nutrient intake. MC3Rs are expressed in hypothalamic and limbic regions of the brain and in peripheral tissues. To investigate the roles of central MC3Rs, we inserted a "lox-stop-lox" (LoxTB) 5' of the translation initiation codon of the mouse Mc3r gene and reactivated transcription using neuron-specific Cre transgenic mice. As predicted based on earlier observations of Mc3r knock-out mice, Mc3r(TB/TB) mice displayed reduced lean mass, increased fat mass, and accelerated diet-induced obesity. Surprisingly, rescuing Mc3r expression in the nervous system using the Nestin-Cre transgene only partially rescued obesity in chow-fed conditions and had no impact on the accelerated diet-induced obesity phenotype. The ventromedial hypothalamus (VMH), a critical node in the neural networks regulating feeding-related behaviors and metabolic homeostasis, exhibits dense Mc3r expression relative to other brain regions. To target VMH MC3R expression, we used the steroidogenic factor-1 Cre transgenic mouse. Although restoring VMH MC3R signaling also had a modest impact on obesity, marked improvements in metabolic homeostasis were observed. VMH MC3R signaling was not sufficient to rescue the lean mass phenotype or the regulation of behaviors anticipating food anticipation. These results suggest that actions of MC3Rs impacting on energy homeostasis involve both central and peripheral sites of action. The impact of central MC3Rs on behavior and metabolism involves divergent pathways; VMH MC3R signaling improves metabolic homeostasis but does not significantly impact on the expression of behaviors anticipating nutrient availability.

The Peptidic GHS-R antagonist [D-Lys(3)]GHRP-6 markedly improves adiposity and related metabolic abnormalities in a mouse model of postmenopausal obesity

It was demonstrated that estrogen deficiency and consuming high fat (HF) diet enhanced orexigenic activity of ghrelin. Therefore, we hypothesized that antagonizing of ghrelin action would attenuate food intake and body weight in mice obese both from ovariectomy (OVX) and feeding a HF diet. Ghrelin receptor antagonist [D-Lys(3)]GHRP-6 after seven days of subcutaneous treatment markedly decreased food intake in OVX mice fed both HF and standard diets; furthermore, it reduced body weight and blood glucose, insulin and leptin, and increased β-hydroxybutyrate level and uncoupling-protein-1 mRNA in brown adipose tissue. Pair-feeding revealed that effect of [D-Lys(3)]GHRP-6 was primary anorexigenic. Estrogen supplementation reduced anorexigenic effects of [D-Lys(3)]GHRP-6. OVX [D-Lys(3)]GHRP-6 treatment in mice on HF diet resulted in markedly increased circulating level and liver expression of a major metabolic regulator, fibroblast growth factor 21. Our data suggest that ghrelin antagonists could be especially beneficial in individuals with common obesity combined with estrogen deficiency.

Assessment of voluntary ethanol consumption and the effects of a melanocortin (MC) receptor agonist on ethanol intake in mutant C57BL/6J mice lacking the MC-4 receptor

BACKGROUND

The melanocortin (MC) system is composed of peptides that are cleaved from the polypeptide precursor proopiomelanocortin (POMC). Recent evidence shows that chronic exposure to ethanol significantly blunts central MC peptide immunoreactivity and MC receptor (MCR) agonists protect against high ethanol intake characteristic of C57BL/6J mice. Here, we assessed the role of the MC-4 receptor (MC4R) in voluntary ethanol intake and in modulating the effects of the nonselective MCR agonist melanotan-II (MTII) on ethanol consumption.

METHODS

To assess the role of the MC4R, MC4R knockout (Mc4r(-/-) ) and littermate wild-type (Mc4r(+/+) ) mice on a C57BL/6J background were used. Voluntary ethanol (3, 5, 8, 10, 15, and 20%, v/v) and water intake were assessed using standard two-bottle procedures. In separate experiments, Mc4r(-/-) and Mc4r(+/+) mice were given intracerebroventricular (i.c.v.) infusion of MTII (0, 0.5, or 1.0 μg/1 μl) or intraperitoneal (i.p.) injection of MTII (0 or 5 mg/kg/5 ml). The effects of MTII (0 or 0.5 μg/1 μl, i.c.v.) on 10% sucrose and 0.15% saccharin intake were assessed in C57BL/6J mice.

RESULTS

Mc4r(-/-) mice showed normal consumption of ethanol over all concentrations tested. I.c.v. infusion of MTII significantly reduced ethanol drinking in Mc4r(+/+) mice, but failed to influence ethanol intake in Mc4r(-/-) mice. When administered in an i.p. injection, MTII significantly reduced ethanol drinking in both Mc4r(-/-) and Mc4r(+/+) mice. MTII attenuated consumption of caloric (ethanol, sucrose, and food) and noncaloric (saccharin) reinforcers.

CONCLUSIONS

When given centrally, the MCR agonist MTII reduced ethanol drinking by signaling through the MC4R. On the other hand, MTII-induced reduction of ethanol drinking did not require the MC4R when administered peripherally. Together, the present observations show that the MC4R is necessary for the central actions of MCR agonists on ethanol drinking and that MTII blunts the consumption natural reinforcers, regardless of caloric content, in addition to ethanol.