2‐Arachidonoyl glycerol potently induces cholecystokinin secretion in murine enteroendocrine STC‐1 cells via cannabinoid receptor CB1

Abstract

Cholecystokinin (CCK) is a peptide hormone secreted from enteroendocrine cells and regulates the exocrine pancreas, gastric motility, and appetite. Dietary triacylglycerols are hydrolyzed to fatty acids (FA) and 2‐monoacylglycerols (2‐MAG) in the small intestine. Although it is well known that FA stimulate CCK secretion, whether 2‐MAG have the CCK‐releasing activity remains unclear. We examined the CCK‐releasing activity of four commercially available 2‐MAG in a murine CCK‐producing cell line, STC‐1, and the molecular mechanism underlying 2‐MAG‐induced CCK secretion. CCK released from the cells was measured using ELISA. Among four 2‐MAG (2‐palmitoyl, 2‐oleoyl, 2‐linoleoyl, and 2‐arachidonoyl monoacylglycerols) examined, 2‐arachidonoyl glycerol (2‐AG) potently stimulated CCK secretion in a dose‐dependent manner. Structurally related compounds, such as 2‐arachidonoyl glycerol ether and 1‐arachidonoyl glycerol, did not stimulate CCK secretion. Both arachidonic acid and 2‐AG stimulated CCK secretion at 100 μM, but only 2‐AG did at 50 μM. 2‐AG‐induced CCK secretion but not arachidonic acid‐induced CCK secretion was attenuated by treatment with a cannabinoid receptor 1 (CB1) antagonist. These results indicate that a specific 2‐MAG, 2‐AG, directly stimulates CCK secretion via CB1.

2‐Arachidonoyl glycerol suppresses gastric emptying via the cannabinoid receptor 1‐cholecystokinin signaling pathway in mice

“…Treatment with a CCK‐A receptor antagonist, devazepide, reversed the gastric inhibitory effect of oral 2‐AG (Figure 2), suggesting the involvement of CCK signaling. Our previous finding (Ochiai et al, 2021) that 2‐AG promoted CCK secretion in the CCK‐producing cell line, STC‐1 supports that orally given 2‐AG acts on CCK‐producing enteroendocrine cells, namely, I cells, to promote CCK secretion.…”

“…Oral administration of 2‐AG (25 mg/kg) significantly reduced acetaminophen levels at 15 min, similar to 20:4n‐6 (25 mg/kg; Figure 1); however, the time at which the acetaminophen concentration peaked tended to differ between 2‐AG (15 min) and 20:4n‐6 (30 min). In our previous recent study using the murine enteroendocrine cell line, STC‐1 (Ochiai et al, 2021), 2‐AG was shown to stimulate CCK secretion via CB1, whereas 20:4n‐6 stimulated CCK secretion via G protein‐coupled receptor 120 (GRP120). Although further studies are warranted to elucidate the mechanism underlying the effect of 20:4n‐6 in vivo, the present results (Figure 1) suggest that 20:4n‐6‐rich TAG could effectively exert inhibitory effects on gastric emptying.…”

“…Furthermore, CB1 expression has been confirmed in murine CCK‐producing cells (Argueta et al, 2019; Sykaras et al, 2012). We recently demonstrated that 2‐AG potently stimulates CCK secretion via CB1 expressed in the CCK‐producing cell line, STC‐1 (Ochiai et al, 2021). Therefore, 2‐AG might stimulate CCK secretion by acting on CB1 expressed in CCK‐producing enteroendocrine cells, thereby suppressing gastric emptying.…”

“…We have recently demonstrated that one of 2‐MAG and endocannabinoids, 2‐arachidonoyl glycerol (2‐AG), potently stimulates cholecystokinin (CCK) secretion via CB1 in the murine enteroendocrine cell line, STC‐1 (Ochiai et al, 2021). CCK, a gastrointestinal hormone produced by enteroendocrine “I cells” located in the upper small intestine (Dockray, 2012; Rehfeld, 2000), plays a major role in suppressing gastric emptying (Liddle et al, 1986).…”

The Microbiome and Gut Endocannabinoid System in the Regulation of Stress Responses and Metabolism

“…Indeed, eCB signaling in the small intestine has been implicated in the suppression of meal-induced CCK release in obesity ( Argueta et al, 2019 ). Furthermore, 2-AG directly stimulates CCK secretion in murine enteroendocrine STC-1 cells ( Ochiai et al, 2021 ). Therefore, eCBs can directly control the nutrient-induced release of CCK.…”