Alpha cells secrete acetylcholine as a non-neuronal paracrine signal priming beta cell function in humans

Abstract

Acetylcholine is a neurotransmitter that has a major role in the function of the insulin-secreting pancreatic beta cell1,2. Parasympathetic innervation of the endocrine pancreas, the islets of Langerhans, has been shown to provide cholinergic input to the beta cell in several species1,3,4, but the role of autonomic innervation in human beta cell function is at present unclear. Here we show that, in contrast to the case in mouse islets, cholinergic innervation of human islets is sparse. Instead, we find that the alpha cells of human islets provide paracrine cholinergic input to surrounding endocrine cells. Human alpha cells express the vesicular acetylcholine transporter and release acetylcholine when stimulated with kainate or a lowering in glucose concentration. Acetylcholine secretion by alpha cells in turn sensitizes the beta cell response to increases in glucose concentration. Our results demonstrate that in human islets acetylcholine is a paracrine signal that primes the beta cell to respond optimally to subsequent increases in glucose concentration. Cholinergic signaling within islets represents a potential therapeutic target in diabetes5, highlighting the relevance of this advance to future drug development.

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Figure 1: Endocrine cells in human pancreatic islets express cholinergic markers.
Figure 2: Human alpha cells express vAChT and ChAT.
Figure 3: Isolated human islets secrete acetylcholine (ACh) in response to alpha cell–specific stimuli.
Figure 4: Endogenously released ACh amplifies glucose-induced insulin secretion in human islets.

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Acknowledgements

We thank A. Formoso for help with data analyses, K. Johnson for histological work and M. Correa-Medina for assistance with RT-PCR. This work was funded by the Diabetes Research Institute Foundation, US National Institutes of Health grants R56DK084321 (A.C.), R01DK084321 (A.C.), R01DC000374 (S.D.R.), R01DC007630 (S.D.R.), F32DK083226 (M.H.A.) and 5U01DK070460-07 (C.R.), the Juvenile Diabetes Research Foundation, the Swedish Research Council, the Novo Nordisk Foundation, the Swedish Diabetes Association, the Family Erling-Persson Foundation and the World Class University program through the National Research Foundation of Korea funded by the Ministry of Education, Science and Technology (R31-2008-000-10105-0). Human islets were made available through the Islet Cell Resource basic science islet distribution program, Islet Cell Resource Centers Consortium, Division of Clinical Research, National Center for Research Resources, US National Institutes of Health.

Author information

R.R.-D., M.C.J.-S., A.F. and J.M. performed hormone assay experiments and ELISAs; R.D. performed experiments with biosensor cells to detect acetylcholine secretion; R.R.-D. and M.C.J.-S. conducted Amplex assays to measure acetylcholine secretion; R.R.-D. and M.H.A. collected, analyzed and quantified immunohistochemical data, and R.R.-D. performed RT-PCR and western blotting. R.R.-D., R.D., M.H.A., C.R., S.D.R., P.-O.B. and A.C. designed the study, analyzed data and wrote the paper. R.R.-D. and R.D. contributed equally to the study. All authors discussed the results and commented on the manuscript.

Correspondence to Per-Olof Berggren or Alejandro Caicedo.

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Supplementary information

Supplementary Text and Figures

Supplementary Figures 1–3 (PDF 662 kb)

Supplementary Video 1

Three-dimensional rendering of the vAChT immunostaining pattern in a mouse islet. Nerve fibers immunostained for vAChT are visualized as they enter the core of the islet to innervate beta cells. Reconstruction based on 45 confocal images (z step = 0.3 µm) was performed using Volocity Visualization software. (AVI 89557 kb)

Supplementary Video 2

Three-dimensional rendering of the vAChT immunostaining pattern in a human islet. Strong immunostaining is present in cells expressing glucagon. Immunostained nerve fibers cannot be seen in the islet but are visible in the exocrine tissue. Reconstruction based on 45 confocal images (z step = 0.3 µm) was performed using Volocity Visualization software. (AVI 99452 kb)

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Rodriguez-Diaz, R., Dando, R., Jacques-Silva, M. et al. Alpha cells secrete acetylcholine as a non-neuronal paracrine signal priming beta cell function in humans. Nat Med 17, 888–892 (2011). https://doi.org/10.1038/nm.2371

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