Prolonged activation of human islet cannabinoid receptors in vitro induces adaptation but not dysfunction.
BACKGROUND
Although in vivo studies have implicated endocannabinoids in metabolic dysfunction, little is known about direct, chronic activation of the endocannabinoid system (ECS) in human islets. Therefore, this study investigated the effects of prolonged exposure to cannabinoid agonists on human islet gene expression and function.


METHODS
Human islets were maintained for 2 and 5 days in the absence or presence of CB1r (ACEA) or CB2r (JWH015) agonists. Gene expression was quantified by RT-PCR, hormone levels by radioimmunoassay and apoptosis by caspase activities.


RESULTS
Human islets express an ECS, with mRNAs encoding the biosynthetic and degrading enzymes NAPE-PLD, FAAH and MAGL being considerably more abundant than DAGLα, an enzyme involved in 2-AG synthesis, or CB1 and CB2 receptor mRNAs. Prolonged activation of CB1r and CB2r altered expression of mRNAs encoding ECS components, but did not have major effects on islet hormone secretion. JWH015 enhanced insulin and glucagon content at 2 days, but had no effect after 5 days. Treatment with ACEA or JWH015 for up to 5 days did not have marked effects on islet viability, as assessed by morphology and caspase activities.


CONCLUSIONS
Maintenance of human islets for up to 5 days in the presence of CB1 and CB2 receptor agonists causes modifications in ECS element gene expression, but does not have any major impact on islet function or viability.


CONCLUSIONS
These data suggest that the metabolic dysfunction associated with over-activation of the ECS in obesity and diabetes in humans is unlikely to be secondary to impaired islet function.
Diabetes Research Group, Division of Diabetes and Nutritional Sciences, King's College London, UK; Universidad Nacional Autonoma de Mexico, FES Iztacala, Mexico.
Alonso
A
Vilches-Flores
Diabetes Research Group, Division of Diabetes and Nutritional Sciences, King's College London, UK.
Zara
Z
Franklin
Diabetes Research Group, Division of Diabetes and Nutritional Sciences, King's College London, UK; Department of Life Sciences, University of Roehampton, London, UK.
Astrid C
AC
Hauge-Evans
Diabetes Research Group, Division of Diabetes and Nutritional Sciences, King's College London, UK.
Bo
B
Liu
Diabetes Research Group, Division of Diabetes and Nutritional Sciences, King's College London, UK.
Guo C
GC
Huang
Diabetes Research Group, Division of Diabetes and Nutritional Sciences, King's College London, UK.
Pratik
P
Choudhary
Diabetes Research Group, Division of Diabetes and Nutritional Sciences, King's College London, UK.
Peter M
PM
Jones
Diabetes Research Group, Division of Diabetes and Nutritional Sciences, King's College London, UK.
Shanta J
SJ
Persaud
2-AG, 2-arachidonoyl glycerol; ACEA, N-(2-Chloroethyl)-5Z,8Z,11Z,14Z-eiscosatetraenamide; AEA, anandamide; Apoptosis; CB1r, cannabinoid receptor type 1; CB2r, cannabinoid receptor type 2; DAGL, diacylglycerol lipase; ECS, endocannabinoid system; Endocannabinoid system; FAAH, fatty acid amide hydrolase; Gene expression; Glucagon; Human islets; Insulin; JWH015, (2-methyl-1propyl-1H-indol-3-yl)-1-napthalenylmethanone; MAGL, monoacylglycerol lipase; NAPE-PLD, N-acyl-phosphatidyl ethanolamide-hydrolysing phospholipase D; PPG, preproglucagon; PPI, preproinsulin