Role of GLP-1 in the Hypoglycemic Effects of Wild Bitter Gourd

الملخص EN

This study aimed to examine the role of GLP-1 in the hypoglycemic activity of wild bitter gourd (Momordica charantia L., BG).

In vitro, the GLP-1 secretion in STC-1, a murine enteroendocrine cell line, was dose dependently stimulated by water extract (WE), its fractions (WEL, >3 kD and WES, <3 kD), and a bitter compounds-rich fraction of BG.

These stimulations were partially inhibited by probenecid, a bitter taste receptor inhibitor, and by U-73122, a phospholipase Cβ2 inhibitor.

These results suggested that the stimulation might involve, at least in part, certain bitter taste receptors and/or PLCβ2-signaling pathway.

Two cucurbitane triterpenoids isolated from BG, 19-nor-cucurbita-5(10),6,8,22-(E),24-pentaen-3β-ol, and 5β,19-epoxycucurbita-6,24-diene-3β,23ξ-diol (karavilagenine E,) showed relative high efficacy in the stimulation.

In vivo, mice fed BG diet showed higher insulinogenic index in an oral glucose tolerance test.

A single oral dose of WE or WES pretreatment significantly improved intraperitoneal glucose tolerance.

A single oral dose of WES significantly decreased glucose and increased insulin and GLP-1 in serum after 30 min.

This acute hypoglycemic effect of WES was abolished by pretreatment with exendin-9, a GLP-1 receptor antagonist.

Our data provide evidence that BG stimulates GLP-1 secretion which contributes, at least in part, to the antidiabetic activity of BG through an incretin effect.