[Insulinotropic action of hippocampal cholinergic neurostimulating peptide mediated by activated type 3 muscarinic receptor in INS-1 cells].

Objective: [corrected] To characterize the insulinotropic action of hippocampal cholinergic neurostimulating peptide (HCNP) and analyze the role of type 3 muscarinic receptor (M(3)R) pathway in the action of HCNP.
Methods: INS-1 cells were incubated in routine RPMI 1640 medium (control group), RPMI 1640 supplemented with 50 pg/ml synthetic HCNP (HCNP group), or HCNP-containing medium with the addition of PMA 18 h prior to insulin release assay. The insulin levels in the medium was measured using radioimmunoassay following stimulation with different concentrations of glucose. Real-time quantitative PCR was used for detecting the gene expression of HCNP-pp, choline acetyltransferase (ChAT) and M(3)R in HCNP group and control group.
Results: After stimulation with different concentrations of glucose (5.6 and 16.7 mmol/L), HCNP group showed significantly higher insulin levels than the control and HCNP+ PMA groups. Compared with those in the control group, the mRNA levels of HCNP-pp, ChAT, and M(3)R were all lowered in HCNP group.
Conclusion: HCNP can promote insulin release in INS-1 cells by increasing ChAT activity and activating M(3)R, and this effect is inhibited by PMA.