Pharmacological characterization of lipidized analogs of prolactin-releasing peptide with a modified C- terminal aromatic ring.

Prolactin-releasing peptide (PrRP) is an anorexigenic neuropeptide expressed in the brain where it regulates food intake and energy expenditure. The C-terminal Arg-Phe-NH2 of PrRP is crucial for its biological activity. In our previous study, we showed that PrRP analogs myristoylated or palmitoylated at the N- terminus seem to cross the blood-brain barrier and lower food intake following peripheral administration. In this study, myristoylated and palmitoylated PrRP31 analogs with a modified C-terminal Phe were designed and tested. Lipidized analogs containing Phe(31) replaced by aromatic non-coded amino acids or tyrosine revealed high binding affinity to rat pituitary RC-4B/C cells with endogenous PrRP and neuropeptide FF 2 receptors and to CHO-K1 cells overexpressing either PrRP or neuropeptide FF 2 receptors. The analogs also showed strong agonistic properties at the GPR10 receptor using the beta-lactamase reporter gene assay. Moreover, lipidized PrRP analogs, especially those that were palmitoylated, demonstrated strong and long-lasting anorexigenic effects in fasted mice after subcutaneous administration. The most efficient PrRP31 analogs with PheCl2(31), either palmitoylated or myristoylated at the N-terminus, are promising candidates for the study of food disorders, possibly for anti-obesity treatment. Despite the therapeutic potential in targeting central GPR10, the endogenous ligand PrRP cannot cross the blood-brain barrier. Understanding biological activity and transport of novel structural analogs of PrRP with a potential central anorexigenic effect is of key therapeutic significance.

Novel lipidized analogs of prolactin-releasing peptide have prolonged half-lives and exert anti-obesity effects after peripheral administration.

OBJECTIVES: Obesity is a frequent metabolic disorder but an effective therapy is still scarce. Anorexigenic neuropeptides produced and acting in the brain have the potential to decrease food intake and ameliorate obesity but are ineffective after peripheral application. We have designed lipidized analogs of prolactin-releasing peptide (PrRP), which is involved in energy balance regulation as demonstrated by obesity phenotypes of both PrRP- and PrRP-receptor-knockout mice. RESULTS: Lipidized PrRP analogs showed binding affinity and signaling in PrRP receptor-expressing cells similar to natural PrRP. Moreover, these analogs showed high binding affinity also to anorexigenic neuropeptide FF-2 receptor. Peripheral administration of myristoylated and palmitoylated PrRP analogs to fasted mice induced strong and long-lasting anorexigenic effects and neuronal activation in the brain areas involved in food intake regulation. Two-week-long subcutaneous administration of palmitoylated PrRP31 and myristoylated PrRP20 lowered food intake, body weight and improved metabolic parameters, and attenuated lipogenesis in mice with diet-induced obesity. CONCLUSIONS: Our data suggest that the lipidization of PrRP enhances stability and mediates its effect in central nervous system. Strong anorexigenic and body-weight-reducing effects make lipidized PrRP an attractive candidate for anti-obesity treatment.

Changes in FGF21 serum concentrations and liver mRNA expression in an experimental model of complete lipodystrophy and insulin-resistant diabetes.

Patients with obesity and type 2 diabetes often display high levels of the anti-diabetic factor fibroblast growth factor-21 (FGF21), suggesting that the overproduction of FGF21 may result from increased adiposity in an attempt by white adipose tissue (WAT) to counteract insulin resistance. However, the production of FGF21 diabetes in the absence of WAT has not been examined. In this study, we investigated the effects of lipodystrophy in A-ZIP F-1 mice on FGF21 production in relation to diabetes. A-ZIP F-1 mice displayed high FGF21 plasma levels resulting from enhanced FGF21 mRNA expression in the liver. Concomitant enhancement of FGF21 receptor (FGFR1) and glucose transporter 1 (GLUT-1) mRNA expression was observed in the muscles of A-ZIP F-1 mice. Furthermore, the activation of hypothalamic NPY and AgRP mRNA expression positively correlated with plasma levels of FGF21 but not active ghrelin. Our study demonstrates that an increased FGF21 plasma level in lipodystrophic A-ZIP F-1 mice results mainly from up-regulated liver production but does not suffice to overcome the lipodystrophy-induced severe type 2-diabetes and insulin resistance in the liver linked to the augmented liver fat deposition.

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 (ED(50)=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.

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 ß-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.