Purinergic P2X7 receptors regulate secretion of interleukin-1 receptor antagonist and beta cell function and survival.
OBJECTIVE
In obesity, beta cells activate compensatory mechanisms to adapt to the higher insulin demand. Interleukin-1 receptor antagonist (IL-1Ra) prevents obesity-induced hyperglycaemia and is a potent target for the treatment of diabetes, but the mechanisms of its secretion and regulation in obesity are unknown. In the present study, we hypothesise the regulation of IL-1Ra secretion by purinergic P2X(7) receptors in islets.


METHODS
Production and regulation of P2X(7) were studied in pancreatic sections from lean and obese diabetic patients, non-diabetic controls and in isolated islets. IL-1Ra, IL-1beta and insulin secretion, glucose tolerance and beta cell mass were studied in P2x7 (also known as P2Rx7)-knockout mice.


RESULTS
P2X(7) levels were elevated in beta cells of obese patients, but downregulated in patients with type 2 diabetes mellitus. Elevated glucose and non-esterified fatty acids rapidly activated P2X(7) and IL-1Ra secretion in human islets, and this was inhibited by P2X(7) blockade. In line with our results in vitro, P2x7-knockout mice had a lower capacity to secrete IL-1Ra. They exhibited severe and rapid hyperglycaemia, glucose intolerance and impaired beta cell function in response to a high-fat/high-sucrose diet, were unable to compensate by increasing their beta cell mass in response to the diet and showed increased beta cell apoptosis.


CONCLUSIONS
Our study shows a tight correlation of P2X(7) activation, IL-1Ra secretion and regulation of beta cell mass and function. The increase in P2X(7) production is one mechanism that may explain how beta cells compensate by adapting to the higher insulin demand. Disturbances within that system may result in the progression of diabetes.
Glas
R
R
Department of Medicine, Larry L. Hillblom Islet Research Center, UCLA, Los Angeles, CA, USA.
Sauter
N S
NS
Schulthess
F T
FT
Shu
L
L
Oberholzer
J
J
Maedler
K
K
D000818:Animals; D002470:Cell Survival; D003433:Crosses, Genetic; D048909:Diabetes Complications / Q000503:physiopathology; D005951:Glucose Tolerance Test; D006801:Humans; D050417:Insulin-Secreting Cells / Q000166:cytology / Q000473:pathology / Q000502:physiology*; D053590:Interleukin 1 Receptor Antagonist Protein / Q000378:metabolism*; D053583:Interleukin-1beta / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009765:Obesity / Q000150:complications / Q000503:physiopathology; D018048:Receptors, Purinergic P2 / Q000235:genetics / Q000502:physiology*; D058486:Receptors, Purinergic P2X7; D012016:Reference Values; D014404:Tubulin / Q000235:genetics
D053590:Interleukin 1 Receptor Antagonist Protein; D053583:Interleukin-1beta; C546468:P2RX7 protein, human; C546469:P2rx7 protein, mouse; D018048:Receptors, Purinergic P2; D058486:Receptors, Purinergic P2X7; D014404:Tubulin