Synergistic effect of CART (cocaine- and amphetamine-regulated transcript) peptide and cholecystokinin on food intake regulation in lean mice

<p>Abstract</p> <p>Background</p> <p>CART (cocaine- and amphetamine-regulated transcript) peptide and cholecystokinin (CCK) are neuromodulators involved in feeding behavior. This study is based on previously found synergistic effect of leptin and CCK on food intake and our hypothesis on a co-operation of the CART peptide and CCK in food intake regulation and Fos activation in their common targets, the nucleus tractus solitarii of the brainstem (NTS), the paraventricular nucleus (PVN), and the dorsomedial nucleus (DMH) of the hypothalamus.</p> <p>Results</p> <p>In fasted C57BL/6 mice, the anorexigenic effect of CART(61-102) in the doses of 0.1 or 0.5 μg/mouse was significantly enhanced by low doses of CCK-8 of 0.4 or 4 μg/kg, while 1 mg/kg dose of CCK-A receptor antagonist devazepide blocked the effect of CART(61-102) on food intake. After simultaneous administration of 0.1 μg/mouse CART(61-102) and of 4 μg/kg of CCK-8, the number of Fos-positive neurons in NTS, PVN, and DMH was significantly higher than after administration of each particular peptide. Besides, CART(61-102) and CCK-8 showed an additive effect on inhibition of the locomotor activity of mice in an open field test.</p> <p>Conclusion</p> <p>The synergistic and long-lasting effect of the CART peptide and CCK on food intake and their additive effect on Fos immunoreactivity in their common targets suggest a co-operative action of CART peptide and CCK which could be related to synergistic effect of leptin on CCK satiety.</p

An analogue of the Prolactin Releasing Peptide reduces obesity and promotes adult neurogenesis

Hypothalamic Adult Neurogenesis (hAN) has been implicated in regulating energy homeostasis. Adult-generated neurons and adult Neural Stem Cells (aNSCs) in the hypothalamus control food intake and body weight. Conversely, diet-induced obesity (DIO) by high fat diets (HFD) exerts adverse influence on hAN. However, the effects of anti-obesity compounds on hAN are not known. To address this, we administered a lipidized analogue of an anti-obesity neuropeptide, Prolactin Releasing Peptide (PrRP), so-called LiPR, to mice. In the HFD context, LiPR rescued the survival of adult-born hypothalamic neurons and increased the number of aNSCs by reducing their activation. LiPR also rescued the reduction of immature hippocampal neurons and modulated calcium dynamics in iPSC-derived human neurons. In addition, some of these neurogenic effects were exerted by another anti-obesity compound, Liraglutide. These results show for the first time that anti-obesity neuropeptides influence adult neurogenesis and suggest that the neurogenic process can serve as a target of anti-obesity pharmacotherapy

Lipidization as a tool toward peptide therapeutics

AbstractPeptides, as potential therapeutics continue to gain importance in the search for active substances for the treatment of numerous human diseases, some of which are, to this day, incurable. As potential therapeutic drugs, peptides have many favorable chemical and pharmacological properties, starting with their great diversity, through their high affinity for binding to all sort of natural receptors, and ending with the various pathways of their breakdown, which produces nothing but amino acids that are nontoxic to the body. Despite these and other advantages, however, they also have their pitfalls. One of these disadvantages is the very low stability of natural peptides. They have a short half-life and tend to be cleared from the organism very quickly. Their instability in the gastrointestinal tract, makes it impossible to administer peptidic drugs orally. To achieve the best pharmacologic effect, it is desirable to look for ways of modifying peptides that enable the use of these substances as pharmaceuticals. There are many ways to modify peptides. Herein we summarize the approaches that are currently in use, including lipidization, PEGylation, glycosylation and others, focusing on lipidization. We describe how individual types of lipidization are achieved and describe their advantages and drawbacks. Peptide modifications are performed with the goal of reaching a longer half-life, reducing immunogenicity and improving bioavailability. In the case of neuropeptides, lipidization aids their activity in the central nervous system after the peripheral administration. At the end of our review, we summarize all lipidized peptide-based drugs that are currently on the market

Structural and functional study of the GlnB22-insulin mutant responsible for maturity-onset diabetes of the young.

The insulin gene mutation c.137G>A (R46Q), which changes an arginine at the B22 position of the mature hormone to glutamine, causes the monogenic diabetes variant maturity-onset diabetes of the young (MODY). In MODY patients, this mutation is heterozygous, and both mutant and wild-type (WT) human insulin are produced simultaneously. However, the patients often depend on administration of exogenous insulin. In this study, we chemically synthesized the MODY mutant [GlnB22]-insulin and characterized its biological and structural properties. The chemical synthesis of this insulin analogue revealed that its folding ability is severely impaired. In vitro and in vivo tests showed that its binding affinity and biological activity are reduced (both approximately 20% that of human insulin). Comparison of the solution structure of [GlnB22]-insulin with the solution structure of native human insulin revealed that the most significant structural effect of the mutation is distortion of the B20-B23 β-turn, leading to liberation of the B chain C-terminus from the protein core. The distortion of the B20-B23 β-turn is caused by the extended conformational freedom of the GlnB22 side chain, which is no longer anchored in a hydrogen bonding network like the native ArgB22. The partially disordered [GlnB22]-insulin structure appears to be one reason for the reduced binding potency of this mutant and may also be responsible for its low folding efficiency in vivo. The altered orientation and flexibility of the B20-B23 β-turn may interfere with the formation of disulfide bonds in proinsulin bearing the R46Q (GlnB22) mutation. This may also have a negative effect on the WT proinsulin simultaneously biosynthesized in β-cells and therefore play a major role in the development of MODY in patients producing [GlnB22]-insulin

Palmitoylation of Prolactin-Releasing Peptide Increased Affinity for and Activation of the GPR10, NPFF-R2 and NPFF-R1 Receptors: In Vitro Study

The anorexigenic neuropeptide prolactin-releasing peptide (PrRP) is involved in the regulation of food intake and energy expenditure. Lipidization of PrRP stabilizes the peptide, facilitates central effect after peripheral administration and increases its affinity for its receptor, GPR10, and for the neuropeptide FF (NPFF) receptor NPFF-R2. The two most potent palmitoylated analogs with anorectic effects in mice, palm11-PrRP31 and palm-PrRP31, were studied in vitro to determine their agonist/antagonist properties and mechanism of action on GPR10, NPFF-R2 and other potential off-target receptors related to energy homeostasis. Palmitoylation of both PrRP31 analogs increased the binding properties of PrRP31 to anorexigenic receptors GPR10 and NPFF-R2 and resulted in a high affinity for another NPFF receptor, NPFF-R1. Moreover, in CHO-K1 cells expressing GPR10, NPFF-R2 or NPFF-R1, palm11-PrRP and palm-PrRP significantly increased the phosphorylation of extracellular signal-regulated kinase (ERK), protein kinase B (Akt) and cAMP-responsive element-binding protein (CREB). Palm11-PrRP31, unlike palm-PrRP31, did not activate either c-Jun N-terminal kinase (JNK), p38, c-Jun, c-Fos or CREB pathways in cells expressing NPFF-1R. Palm-PrRP31 also has higher binding affinities for off-target receptors, namely, the ghrelin, opioid (KOR, MOR, DOR and OPR-L1) and neuropeptide Y (Y1, Y2 and Y5) receptors. Palm11-PrRP31 exhibited fewer off-target activities; therefore, it has a higher potential to be used as an anti-obesity drug with anorectic effects