Effect of hyperglycaemia on muscarinic M3 receptor expression and secretory sensitivity to cholinergic receptor activation in islets.

AC Hauge-Evans, C Reers, A Kerby, Z Franklin, S Amisten, AJ King, Z Hassan, A Vilches-Flores, Z Tippu, SJ Persaud, PM Jones

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11 Citations (Scopus)


Aims: Islets are innervated by parasympathetic nerves which release acetylcholine (ACh) to amplify glucose-induced insulin secretion, primarily via muscarinic M3 receptors (M3R). Here we investigate the consequence of chronic hyperglycaemia on islet M3R expression and secretory sensitivity of mouse islets to cholinergic receptor activation.

Methods: The impact of hyperglycaemia was studied in (i) islets isolated from ob/ob mice, (ii) alginate-encapsulated mouse islets transplanted intraperitoneally into streptozotocin-induced diabetic mice and (iii) mouse and human islets maintained in vitro at 5.5 or 16 mmol/l glucose. Blood glucose levels were assessed by a commercial glucose meter, insulin content by RIA and M3R expression by qPCR and immunohistochemistry.

Results: M3R mRNA expression was reduced in both ob/ob islets and islets maintained at 16 mmol/l glucose for 3 days (68 and 50% control, respectively). In all three models of hyperglycaemia the secretory sensitivity to the cholinergic receptor agonist, carbachol, was reduced by 60–70% compared to control islets. Treatment for 72 h with the irreversible PKC activator, PMA, or the PKC inhibitor, Gö6983, did not alter islet M3R mRNA expression nor did incubation with the PI3K-inhibitor, LY294002, although enhancement of glucose-induced insulin secretion by LY294002 was reduced in islets maintained at 16 mmol/l glucose, as was mRNA expression of the PI3K regulatory subunit, p85α.

Conclusions: Cholinergic regulation of insulin release is impaired in three experimental islet models of hyperglycaemia consistent with reduced expression of M3 receptors. Our data suggest that the receptor downregulation is a PKC- and PI3K-independent consequence of the hyperglycaemic environment, and they imply that M3 receptors could be potential targets in the treatment of type 2 diabetes.
Original languageEnglish
Pages (from-to)947-956
JournalDiabetes, Obesity & Metabolism
Issue number10
Publication statusPublished - Oct 2014

Bibliographical note

Acknowledgements: We are thankful to the relatives of organ donors for the pancreata used in our research and to Guo-Cai Huang and the King's College London Human Islet Isolation Unit (London, UK) for the provision of human islets. We gratefully acknowledge financial support from the National Centre for the Replacement, Refinement and Reduction of Animals in Research (NC3Rs), Diabetes UK [BDA: RD07/0003510] and the MRC Centenary Early Career Award (MR/J500380/1). A. H. E. and S. A. are Diabetes UK RD Lawrence Fellows [BDA: 10/0003980, 11/0004172].


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