Development of a pharmacologically improved peptide agonist of the leptin receptor

Abstract

Leptin, a hormone produced by adipose tissue, regulates energy balance in the hypothalamus and is involved in fertility, immune response and carcinogenesis. The existence of disorders related to leptin deficit and leptin overabundance calls for the development of drugs activating or inhibiting the leptin receptor (ObR). We synthesized four proposed receptor-binding leptin fragments (sites I, IIa and IIb, III), their reportedly antagonist analogs, and a peptide chimera composed of the two discontinuous site II arms. To assess the pharmacological utility of leptin fragments, we studied the peptides' ability to stimulate the growth of ObR-positive and ObR-negative cells. The combined site II construct and site III derivatives selectively reversed leptin-induced growth of ObR-positive cells at mid-nanomolar concentrations. However, these peptides appeared to be partial agonists/antagonists as they activated cell growth in the absence of exogenous leptin. A designer site III analog, featuring non-natural amino acids at terminal positions to decrease proteolysis and a blood-brain barrier (BBB) penetration-enhancing carbohydrate moiety, proved to be full agonist to ObR, i.e., stimulated proliferation of different ObR-positive but not ObR-negative cells in the presence or absence of leptin. This glycopeptide bound to isolated ObR on solid-phase assays and activated ERK-1/2 signaling in ObR-positive MCF-7 cells at 100-500 nM concentrations. The glycopeptide was stable in mouse serum, readily crossed endothelial/astrocyte cell layers in a cellular BBB model, and was distributed into the brain of Balb/c mice after intraperitoneal administration. These characteristics suggest a potential pharmaceutical utility of the designer site III glycopeptide in leptin-deficient diseases.

Immunomodulatory effects of anti-microbial peptides

“…When one of the two activities is detected in any given assay, it likely depends upon the fine-tuned environment of the actual measures. The switch between receptor agonist and antagonist activities is a wellknown phenomenon in peptide pharmacology [108] and can occur in minor sequence-specific changes and assay design [109]. Based on all available reports, while for activating the innate immune system and preventing deleterious effects on infections, both activities should be positively viewed, it is unlikely that HDP will end up in the treatment arsenal against rheumatoid arthritis or other inflammatory diseases, as single experiments would suggest.…”

20 YEARS OF LEPTIN: Insights into signaling assemblies of the leptin receptor

“…Peptides corresponding to Aa 3-34 (helix A) and 70-95 (helix B) of human leptin have antagonistic properties in vitro and in vivo (Gonzalez & Leavis 2003). Similarly, a modified peptide corresponding to the binding site III was shown to have antagonistic effects (Otvos et al 2008).…”

Neuroprotective and anti-ageing role of leptin

“…In reference to this, an area of pharmacological interest is the treatment of rheumatoid arthritis, where antagonists of Lep receptor probably could be of therapeutic use (Otvos et al 2008(Otvos et al , 2011.…”