title: Insulin-releasing and cytotoxic properties of the frog skin peptide, tigerinin-1R: a structure-activity study.
abstract: The frog skin host-defense peptide tigerinin-1R (RVCSAIPLPICH.NH2) is insulinotropic both in vitro and in vivo. This study investigates the effects on insulin release and cytotoxicity of changes in cationicity and hydrophobicity produced by selected substitutions of amino acids by l-arginine, l-lysine and l-tryptophan. The [A5W], [L8W] and [I10W] analogs produced a significant (P<0.01) increase in the rate of insulin release from BRIN-BD11 rat clonal β cells at concentration of 0.01 nM compared with 0.1 nM for tigerinin-1R. The increase in the rate of insulin release produced by a 3 μM concentration of the [S4R], [H12K], and [I10W] analogs from both BRIN-BD11 cells and mouse islets was significantly greater (P<0.05) than that produced by tigerinin-1R. No peptide stimulated the release of lactate dehydrogenase at concentrations up to 3 μM indicating that plasma membrane integrity had been preserved. [A5W] tigerinin-1R was the only analog tested that showed cytotoxic activity against human erythrocytes (LC50=265 ± 16 μM) and inhibited growth of Escherichia coli (MIC=500 μM) and Staphylococcus aureus (MIC=250 μM). The circular dichroism spectra of tigerinin-1R and [A5W] tigerinin-1R indicate that the peptides adopt a mixture of β-sheet, random coil and reverse β-turn conformations in 50% trifluoroethanol/water and methanol/water. Administration of [S4R] tigerinin-1R (75 nmol/kg body weight) to high-fat fed mice with insulin resistance significantly (P<0.05) enhanced insulin release and improved glucose tolerance over a 60 min period following an intraperitoneal glucose load. The study supports the claim that tigerinin-1R shows potential for development into novel therapeutic agents for treatment of type 2 diabetes mellitus.
authors: School of Biomedical Sciences, University of Ulster, Cromore Road, Coleraine, Northern Ireland BT52 1SA, United Kingdom.
authors: Dinesh
authors: D
authors: Srinivasan
authors: School of Biomedical Sciences, University of Ulster, Cromore Road, Coleraine, Northern Ireland BT52 1SA, United Kingdom.
authors: Opeolu O
authors: OO
authors: Ojo
authors: School of Biomedical Sciences, University of Ulster, Cromore Road, Coleraine, Northern Ireland BT52 1SA, United Kingdom.
authors: Yasser H A
authors: YH
authors: Abdel-Wahab
authors: School of Biomedical Sciences, University of Ulster, Cromore Road, Coleraine, Northern Ireland BT52 1SA, United Kingdom.
authors: Peter R
authors: PR
authors: Flatt
authors: Normandie Université, COBRA, UMR 6014, IRIB et FR 3038; Université de Rouen; INSA de Rouen; CNRS, IRCOF, 76821 Mont-Saint-Aignan Cedex, France.
authors: Laure
authors: L
authors: Guilhaudis
authors: Department of Biochemistry, College of Medicine and Health Sciences, United Arab Emirates University, 17666 Al-Ain, United Arab Emirates. Electronic address: jmconlon@uaeu.ac.ae.
authors: J Michael
authors: JM
authors: Conlon
mesh_terms: D029845:Amphibian Proteins / Q000737:chemistry / Q000494:pharmacology*; D000818:Animals; D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000494:pharmacology*; D020013:Calcium Signaling / Q000187:drug effects; D002460:Cell Line; D004926:Escherichia coli / Q000187:drug effects; D018149:Glucose Intolerance / Q000188:drug therapy; D006801:Humans; D054795:Incretins / Q000737:chemistry / Q000494:pharmacology*; D007328:Insulin / Q000378:metabolism*; D007333:Insulin Resistance; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects; D008810:Mice, Inbred C57BL; D008826:Microbial Sensitivity Tests; D051381:Rats; D013211:Staphylococcus aureus / Q000187:drug effects; D013329:Structure-Activity Relationship
chemical_list: D029845:Amphibian Proteins; D000900:Anti-Bacterial Agents; D054795:Incretins; D007328:Insulin; C000593416:tigerinin-1R peptide, Hoplobatrachus rugulosus
keywords: Cytotoxicity, Type 2 diabetes mellitus; Frog skin peptide; Incretin; Tigerinin