Actions of PGLa-AM1 and its [A14K] and [A20K] analogues and their therapeutic potential as anti-diabetic agents

Abstract

PGLa-AM1 (GMASKAGSVLGKVAKVALKAAL.NH) was first identified in skin secretions of the frog Xenopus amieti (Pipidae) on the basis of its antimicrobial properties. PGLa-AM1 and its [A14K] and [A20K] analogues produced a concentration-dependent stimulation of insulin release from BRIN-BD11 rat clonal β-cells without cytotoxicity at concentrations up to 3 μM. In contrast, the [A3K] analogue was cytotoxic at concentrations ≥ 30 nM. The potency and maximum rate of insulin release produced by the [A14K] and [A20K] peptides were significantly greater than produced by PGLa-AM1. [A14K]PGLa-AM1 also stimulated insulin release from mouse islets at concentrations ≥ 1 nM and from the 1.1B4 human-derived pancreatic β-cell line at concentrations > 30 pM. PGLa-AM1 (1 μM) produced membrane depolarization in BRIN-BD11 cells with a small, but significant (P < 0.05), increase in intracellular Ca concentrations but the peptide had no direct effect on K channels. The [A14K] analogue (1 μM) produced a significant increase in cAMP concentration in BRIN-BD11 cells and down-regulation of the protein kinase A pathway by overnight incubation with forskolin completely abolished the insulin-releasing effects of the peptide. [A14K]PGLa-AM1 (1 μM) protected against cytokine-induced apoptosis (p < 0.001) in BRIN-BD11 cells and augmented (p < 0.001) proliferation of the cells to a similar extent as GLP-1. Intraperitoneal administration of the [A14K] and [A20K] analogues (75 nmol/kg body weight) to both lean mice and high fat-fed mice with insulin resistance improved glucose tolerance with a concomitant increase in insulin secretion. The data provide further support for the assertion that host defense peptides from frogs belonging to the Pipidae family show potential for development into agents for the treatment of patients with Type 2 diabetes.

Review of antimicrobial peptides with anti‐Helicobacter pylori activity

“…In addition to antibacterial effects, it has been shown that this peptide stimulates the secretion of glucagon‐like peptide 1 and thus stimulates the insulin production in BRIN‐BD11 rat clonal B cells. Consequently, this peptide has the potential to be developed into molecules for the treatment of patients with Type 2 diabetes …”

Cellular models for beta‐cell function and diabetes gene therapy

“…In our laboratory, we have recently exploited 1.1B4 cells to assess the effects of PYY, NPY and pancreatic polypeptide and demonstrated beneficial effects on beta‐cell function and survival, thus providing a basis for the potential use of these and related agents for the treatment and/or prevention of diabetes . Additionally, the cells have been used for human translational studies such as the in vitro evaluation of mechanisms of lipotoxicity and assessment of novel peptide analogues for potential use as antidiabetic agents …”

Assessment of the potential of temporin peptides from the frog Rana temporaria (Ranidae) as anti‐diabetic agents

“…BRIN‐BD11 rat clonal β‐cells and 1.1B4 human‐derived pancreatic β‐cells were cultured at 37°C in an atmosphere of 5% CO 2 and 95% air in RPMI‐1640 tissue culture medium containing 10% (v/v) fetal bovine serum, antibiotics (100 U/mL penicillin, 0.1 mg/mL streptomycin), and 11.1 mM glucose as previously described . Cells were seeded into 24‐multiwell plates and allowed to attach during overnight incubation at 37°C.…”

“…Cells were seeded into 24‐multiwell plates and allowed to attach during overnight incubation at 37°C. After incubation, the culture medium was removed and replaced with 1 mL Krebs‐Ringer bicarbonate (KRB) buffer, pH 7.4 containing 0.1% bovine serum albumin (BSA), supplemented with 1.1 mM glucose and pre‐incubated for 40 minutes at 37°C. Incubations with temporins (10 −12 ‐ 3 × 10 −6 M; n = 8) were carried out for 20 minutes at 37°C using KRB buffer supplemented with 5.6 mM glucose.…”

“…Preliminary data demonstrating that temporin peptides from Rana ornativentris and Lithobates virgatipes and from Lithobates catesbeianus stimulated the rate of release of insulin from BRIN‐BD11 glucose‐responsive rat clonal β‐cells at concentrations ≥100 nM without cyotoxicity suggested that these peptides may be developed into agents for the treatment of patients with Type 2 diabetes mellitus (T2DM). A more recent study has shown that the frog skin derived peptide PGLa‐AM1, as well as enhancing insulin secretion, will also promote β‐cell proliferation and protect against cytokine‐induced apoptosis . Little is known about structure‐activity relationships within the temporin family with regard to insulinotropic and proliferative activities.…”