[D-TRP32]neuropeptide Y: a competitive antagonist of NPY in rat hypothalamus.
Neuropeptide Y (NPY) is a potent orexigenic peptide. Structure-activity studies have revealed that nearly the entire sequence of NPY is required to elicit feeding responses. Therefore, in order to develop antagonistic peptides for NPY-induced feeding, we synthesized full-length analogs of NPY, substituting D-Trp in the C-terminal receptor binding region, and screened their activity in rat hypothalamus. Although [D-Trp36]NPY and [D-Trp34]NPY inhibited isoproterenol-stimulated hypothalamic membrane adenylate cyclase activity, [D-Trp32]NPY exhibited no intrinsic activity. Furthermore, [D-Trp32]NPY inhibited [125I]NPY binding to rat hypothalamic membranes with a potency comparable to that of NPY. The presence of 30 and 300 nM concentrations of [D-Trp32]NPY shifted the inhibitory dose-response curve of NPY on isoproterenol-stimulated hypothalamic membrane adenylate cyclase activity parallel to the right with comparable KB values. Moreover, in vivo experiments in rats revealed that [D-Trp32]NPY (10 micrograms) significantly attenuated the 1-h feeding response induced by NPY (1 microgram). Several other substitutions at position 32 including 2-D-Nal resulted in agonist activity, suggesting that there are strict structural requirements to induce the antagonistic property in NPY. These findings confirm that [D-Trp32]NPY is a competitive antagonist of NPY in both in vitro and in vivo systems. Analogs based on [D-Trp32]NPY may have potential clinical application, since NPY has been implicated in the pathophysiology of a number of feeding disorders including obesity, anorexia, and bulimia.
Balasubramaniam
A
A
Department of Surgery, University of Cincinnati Medical Center, Ohio 45267-0558.
Sheriff
S
S
Johnson
M E
ME
Prabhakaran
M
M
Huang
Y
Y
Fischer
J E
JE
Chance
W T
WT
D000067956:Adenylyl Cyclase Inhibitors; D000262:Adenylyl Cyclases / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D004305:Dose-Response Relationship, Drug; D004435:Eating / Q000187:drug effects; D007031:Hypothalamus / Q000187:drug effects* / Q000201:enzymology; D008968:Molecular Conformation; D008969:Molecular Sequence Data; D009478:Neuropeptide Y / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors* / Q000138:chemical synthesis / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013237:Stereoisomerism
D000067956:Adenylyl Cyclase Inhibitors; D009478:Neuropeptide Y; C086545:neuropeptide Y, Trp(32)-; D000262:Adenylyl Cyclases