Abstract
Pancreatic islets are complex micro-organs consisting of at least three different cell types: glucagon-secreting alpha, insulin-producing beta and somatostatin-releasing delta cells1. Somatostatin is a powerful paracrine inhibitor of insulin and glucagon secretion2. In diabetes, increased somatostatinergic signalling leads to defective counter-regulatory glucagon secretion3. This increases the risk of severe hypoglycaemia, a dangerous complication of insulin therapy4. The regulation of somatostatin secretion involves both intrinsic and paracrine mechanisms5 but their relative contributions and whether they interact remain unclear. Here we show that dapagliflozin-sensitive glucose- and insulin-dependent sodium uptake stimulates somatostatin secretion by elevating the cytoplasmic Na+ concentration (intracellular [Na+]; [Na+]i) and promoting intracellular Ca2+-induced Ca2+ release. This mechanism also becomes activated when [Na+]i is elevated following the inhibition of the plasmalemmal Na+-K+ pump by reductions of the extracellular K+ concentration emulating those produced by exogenous insulin in vivo6. Islets from some donors with type-2 diabetes hypersecrete somatostatin, leading to suppression of glucagon secretion that can be alleviated by a somatostatin receptor antagonist. Our data highlight the role of Na+ as an intracellular second messenger, illustrate the significance of the intra-islet paracrine network and provide a mechanistic framework for pharmacological correction of the hormone secretion defects associated with diabetes that selectively target the delta cells.
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Data availability
The data that support the findings of this study are available from the corresponding authors upon request.
References
Dolensek, J., Rupnik, M. S. & Stozer, A. Structural similarities and differences between the human and the mouse pancreas. Islets 7, e1024405 (2015).
Hauge-Evans, A. C. et al. Somatostatin secreted by islet δ-cells fulfills multiple roles as a paracrine regulator of islet function. Diabetes 58, 403–411 (2009).
Yue, J. T. et al. Somatostatin receptor type 2 antagonism improves glucagon and corticosterone counterregulatory responses to hypoglycemia in streptozotocin-induced diabetic rats. Diabetes 61, 197–207 (2012).
Cryer, P. E. Mechanisms of hypoglycemia-associated autonomic failure and its component syndromes in diabetes. Diabetes 54, 3592–3601 (2005).
Rorsman, P. & Huising, M. O. The somatostatin-secreting pancreatic δ-cell in health and disease. Nat. Rev. Endocrinol. 14, 404–414 (2018).
Caduff, A. et al. Dynamics of blood electrolytes in repeated hyper- and/or hypoglycaemic events in patients with type 1 diabetes. Diabetologia 54, 2678–2689 (2011).
Adriaenssens, A. E. et al. Transcriptomic profiling of pancreatic alpha, beta and delta cell populations identifies delta cells as a principal target for ghrelin in mouse islets. Diabetologia 59, 2156–2165 (2016).
Zhang, Q. et al. R-type Ca(2+)-channel-evoked CICR regulates glucose-induced somatostatin secretion. Nat. Cell Biol. 9, 453–460 (2007).
Trube, G., Rorsman, P. & Ohno-Shosaku, T. Opposite effects of tolbutamide and diazoxide on the ATP-dependent K+ channel in mouse pancreatic beta-cells. Pflugers Arch. 407, 493–499 (1986).
Vergari, E. et al. Insulin inhibits glucagon release by SGLT2-induced stimulation of somatostatin secretion. Nat. Commun. 10, 139 (2019).
van der Meulen, T. et al. Urocortin3 mediates somatostatin-dependent negative feedback control of insulin secretion. Nat. Med. 21, 769–776 (2015).
Zhang, Q. et al. Role of KATP channels in glucose-regulated glucagon secretion and impaired counterregulation in type 2 diabetes. Cell Metab. 18, 871–882 (2013).
Briant, L. J. B. et al. δ-cells and β-cells are electrically coupled and regulate ɑ-cell activity via somatostatin. J. Physiol. 596, 197–215 (2018).
Wright, E. M., Loo, D. D. & Hirayama, B. A. Biology of human sodium glucose transporters. Physiol. Rev. 91, 733–794 (2011).
Henquin, J. C. & Meissner, H. P. The electrogenic sodium-potassium pump of mouse pancreatic B-cells. J. Physiol. 332, 529–552 (1982).
Unwin, R. J., Luft, F. C. & Shirley, D. G. Pathophysiology and management of hypokalemia: a clinical perspective. Nat. Rev. Nephrol. 7, 75–84 (2011).
Denwood, G. et al. Glucose stimulates somatostatin secretion in pancreatic delta-cells by cAMP-dependent intracellular Ca(2+) release. J. Gen. Physiol. 151, 1094–1115 (2019).
Rosengren, A. H. et al. Reduced insulin exocytosis in human pancreatic β-cells with gene variants linked to type 2 diabetes. Diabetes 61, 1726–1733 (2012).
Knudsen, J. G. et al. Dysregulation of glucagon secretion by hyperglycemia-induced sodium-dependent reduction of ATP production. Cell Metab. 29, 430–442 e434 (2019).
Abdel-Halim, S. M., Guenifi, A., Efendic, S. & Ostenson, C. G. Both somatostatin and insulin responses to glucose are impaired in the perfused pancreas of the spontaneously noninsulin-dependent diabetic GK (Goto-Kakizaki) rats. Acta Physiol. Scand. 148, 219–226 (1993).
Hermansen, K. Characterisation of the abnormal pancreatic D and A cell function in streptozotocin diabetic dogs: studies with D-glyceraldehyde, dihydroxyacetone, D-mannoheptulose, D-glucose, and L-arginine. Diabetologia 21, 489–494 (1981).
Ghezzi, C., Loo, D. D. F. & Wright, E. M. Physiology of renal glucose handling via SGLT1, SGLT2 and GLUT2. Diabetologia 61, 2087–2097 (2018).
Kuhre, R. E. et al. No direct effect of SGLT2 activity on glucagon secretion. Diabetologia 62, 1011–1023 (2019).
Ghezzi, C. & Wright, E. M. Regulation of the human Na+-dependent glucose cotransporter hSGLT2. Am. J. Physiol. Cell Physiol. 303, C348–C354 (2012).
Bonner, C. et al. Inhibition of the glucose transporter SGLT2 with dapagliflozin in pancreatic alpha cells triggers glucagon secretion. Nat. Med. 21, 512–517 (2015).
Ferrannini, E. et al. Metabolic response to sodium-glucose cotransporter 2 inhibition in type 2 diabetic patients. J. Clin. Invest. 124, 499–508 (2014).
Hawley, S. A. et al. The Na+/glucose cotransporter inhibitor canagliflozin activates AMPK by inhibiting mitochondrial function and increasing cellular AMP levels. Diabetes 65, 2784–2794 (2016).
Hermansen, K., Lindskog, S. & Ahren, B. Stimulation of somatostatin secretion by 3-O-methylglucose in the perfused dog pancreas. Int. J. Pancreatol. 20, 103–107 (1996).
Rorsman, P., Ammala, C., Berggren, P. O., Bokvist, K. & Larsson, O. Cytoplasmic calcium transients due to single action-potentials and voltage-clamp depolarizations in mouse pancreatic B-cells. EMBO J. 11, 2877–2884 (1992).
Palty, R. et al. NCLX is an essential component of mitochondrial Na+/Ca2+ exchange. Proc. Natl Acad. Sci. USA 107, 436–441 (2010).
Chera, S. et al. Diabetes recovery by age-dependent conversion of pancreatic δ-cells into insulin producers. Nature 514, 503–507 (2014).
Adam, J. et al. Fumarate hydratase deletion in pancreatic β cells leads to progressive diabetes. Cell Rep. 20, 3135–3148 (2017).
Schmittgen, T. D. & Livak, K. J. Analyzing real-time PCR data by the comparative C(T) method. Nat. Protoc. 3, 1101–1108 (2008).
Briant, L. J. B. et al. CPT1a-dependent long-chain fatty acid oxidation contributes to maintaining glucagon secretion from pancreatic islets. Cell Rep. 23, 3300–3311 (2018).
Acknowledgements
Studies in the laboratories of P.R. were supported by a Wellcome Trust Senior Investigator Award (095531/Z/11/Z), the Leona M. and Harry B. Helmsley Charitable Trust, the Swedish Research Council and the Knut and Alice Wallenberg’s Stiftelse. L.J.B.B. is supported by a Sir Henry Wellcome Postdoctoral Fellowship (grant no. 201325/Z/16/Z) and a JRF from Trinity College, Oxford. E.V. was supported by the OXION Wellcome Training Programme. Q.Z. and R.R. were supported by RD Lawrence fellowships (Diabetes UK) and A.H. by a Diabetes UK studentship. Q.Z. is also supported by the EFSD. C.R. and T.H. are supported by a Novo Nordisk–University of Oxford postdoctoral fellowship. I.W.A. was supported by the Novo Nordisk Foundation (grant no. NNF19OC0056601), the Swedish Research Council (grant nos. 2017-00792 and 2013-7107), the Swedish Diabetes Foundation (grant no. DIA2018-358) and the IngaBritt and Arne Lundberg Research Foundation (grant no. 2016-0045). L.E. and A.S. are supported by the Swedish Research Council (project grant no. SFO-EXODIAB) and the Swedish Foundation for Strategic Research (LUDC-IRC). A.S. was also supported by the Forget Foundation and the Mats Paulsson Foundation. Work in the Reimann/Gribble laboratory is supported by the Wellcome Trust (grant nos. 106262/Z/14/Z and 106263/Z/14/Z) and the UK Medical Research Council (grant no. MRC_MC_UU_12012/3).
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E.V., L.J.B.B. and P.R. designed experiments. E.V., A.A., A.B., M.V.C., G.D., T.G.H., C.G., A.H., F.R., R.R., N.J.G.R., A.S., I.S., A.I.T., Q.Z., J.N.W., L.E., J.A. and I.W.A. performed research and analysed data. P.R. and L.J.B.B. wrote the paper. All co-authors read and approved the final version of the manuscript.
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Extended data
Extended Data Fig. 1 Effect of tolbutamide, glucose and Ca2+ channel blockers on intracellular Ca2+ oscillations in delta cells.
a-d, Effect of tolbutamide (a), diazoxide (b), isradipine (c) and SNX482 (d) on [Ca2+]i in delta cells in islet exposed to 1 (a) or 20 mM glucose (b-d). Compounds were added as indicated by horizontal lines.
Extended Data Fig. 2 Dependence of glucose-induced somatostatin release on intracellular Ca2+ stores and plasmalemmal Ca2+ channels.
a, Somatostatin secretion at 1 or 20 mM glucose and at 20 mM glucose plus 10µM thapsigargin, Data represent 4 experiments per conditions using islets from 3 mice. Statistical significances were determined by one-way ANOVA followed by Tukey’s post hoc. **p<0.005 vs 1 mM glucose; †p<0.05 vs. 20 mM glucose. b, As in (a) but testing the effects of the R-type Ca2+ channel blocker SNX-482 and L-type Ca2+ channel blocker isradipine. ***p<0.001 vs 1 mM glucose; ††p<0.005 and †p<0.05 vs 20 mM glucose. Experiments (n=4, 5 or 6) from 3 mice. c-d, Representative recordings of [Ca2+]i at 20 mM glucose alone (c) or 20 mM glucose plus thapsigargin (d) as indicated. e, Effects of thapsigargin on the frequency of [Ca2+]i oscillations recorded at 20 mM glucose in experiments of the type displayed in (c-d). Data are derived from n=68 cells in 3 different islets isolated from 3 different mice. Statistical significances were evaluated by one-way ANOVA followed by Tukey’s post hoc. *p<0.05 vs 20 mM glucose alone. All data are represented as mean ± SEM.
Extended Data Fig. 3 Dependence of dapagliflozin-induced somatostatin secretion on cAMP.
a-b, Somatostatin secretion from (a) mouse and (b) human islets at 4 mM glucose in the presence and absence of forskolin and dapagliflozin as indicated. Data are based on 4 experiments from 8 mice and n=4 experiments from 4 human donors run in at least quadruplicate (n>16). Statistical significances were determined by one-way ANOVA followed by Tukey’s post hoc. Data have been normalized to somatostatin secretion at 4 mM glucose. *p<0.05; ***p<0.001; ns=not significant (p=0.78). c-d, Insulin (c) and somatostatin secretion (d) at 1 and 20 mM glucose in the absence and presence of the insulin receptor antagonist S961 as indicated. Data are based on n=10 experiments using islets from 4 mice. Statistical significances were determined by one-way ANOVA followed by Tukey’s post hoc. Data have been normalized to secretion at 1 mM glucose. ***p<0.001 vs 1 mM glucose; ††p<0.01 vs 20mM glucose. All data are represented as mean ± SEM.
Extended Data Fig. 4 Somatostatin secretion in the presence of glucose, dapagliflozin and CYN154806.
a, Glucagon secretion in the presence of 1 mM glucose, dapagliflozin and CYN154806 as indicated (n=6, n=9 experiments/3 mice). Glucagon secretion has been normalized to responses at 1 mM glucose. b, Somatostatin secretion in the presence of glucose, dapagliflozin and CYN154806 as indicated (n=6, n=9 experiments/3 mice). Secretion has been normalized to responses at 1 mM glucose. Statistical significances were determined by one-way ANOVA followed by Tukey’s post hoc. ***p<0.001 vs 1 mM glucose; †††p<0.001 vs 20mM; ‡‡p<0.01 20 mM glucose, dapagliflozin and CYN154806 vs 20 mM glucose and CYN154806 alone. c, Effects of dapagliflozin on delta-cell electrical activity recorded from delta cells in intact islets exposed to 20 mM glucose. In 2 out of 4 cells, dapagliflozin repolarized the δ-cell and suppressed electrical activity whereas it was without effect in the remaining 2 cells (islets from 4 different mice). d, Failure of 19 mM αMDG to evoke electrical activity in delta cells exposed to 1 mM glucose. Measurements are representative of 7 different cells in islets from 4 different mice. e, Sodium Green fluorescence (heatmap) measured in 40 different delta cells from 4 different mice simultaneously. Each line represents an individual cell (cell number indicated for the first 7 cells to the left). Note that αMDG has an effect in ~40% of the cells. All data are represented as mean ± SEM.
Extended Data Fig. 5 Cell-to-cell variabiltiy in delta-cell response to dapagliflozin.
a-b, Changes in [Ca2+]i in delta cells exposed to 20mM glucose upon addition of dapagliflozin (12.5µM, highlighted by red rectangles) where the SGLT2 inhibitor either inhibits (a) or was without effect (b). 31 cells from 3 islets from 3 mice; dapagliflozin reduced Ca2+ oscillation frequency in 17/31 cells, and did not change Ca2+ oscillation frequency in the remaining 14/31 cells.
Extended Data Fig. 6 The effect of dapagliflozin on insulin-induced changes in intracellular Na+.
a, The effects of dapagliflozin (1 µM) on the insulin-dependent potentiation of αMDG-induced increase in [Na+]i. All experiments measured in 1 mM glucose in the presence of 19 mM αMDG. Solid line represents representative insulin-responsive δ-cell. The dashed line represents an insulin-nonresponsive δ-cell. Data in b are mean values ± S.E.M. in of 88 dispersed delta cells from 2 mice. Similar results were seen for a lower concentration of dapagliflozin (1 nM, see Fig. 3e,f). 1-way RM ANOVA with Tukey’s adjustment; *p<0.05 vs. no insulin or dapagliflozin, #p<0.05 vs. 100 nM insulin. All data are represented as mean ± SEM.
Extended Data Fig. 7 Delta-cell response to the ionophore monensin and alterations to extracellular potassium.
a, Histograms summarizing frequency of [Ca2+]i oscillations at 1 mM glucose alone, following the addition of monensin and in the presence of monensin and a cocktail of isradipine (2.5 µM), SNX482 (100 nM) and diazoxide (100 µM) n= 53 cells from 3 islets/2 mice **p<0.005, one-way ANOVA followed by Tukey’s post hoc for indicated comparisons. b, Membrane potential recordings from a δ-cell at 1 mM glucose in the absence and presence of monensin. Representative of 4 cells (n=3 mice). c, Effects of decreasing [K+]o from the normal 3.6 mM to 1.7 mM. Note that the delta cell is hyperpolarized at 1 mM glucose and not electrically active. Reducing [K+]o leads to further hyperpolarization. d, Relationship between [K+]o and membrane δ-cell potential. This relationship indicates that the membrane potential in delta cells exposed to 1 mM glucose is principally (but not exclusively) determined by the K+ permeability. All data are represented as mean ± SEM.
Extended Data Fig. 8 Glucagon content and alpha-cell electrical activity in islets from human donors with and without T2DM.
a, Average islet somatostatin content from non-diabetic and T2DM organ donors (n=17 non-diabetic (ND) and n=6 T2DM donors. b, Average islet glucagon content from non-diabetic and T2DM organ donors (n=41 non-diabetic and n=12 T2DM donors). Unpaired 2-sided t-test; ***P<0.001 vs. ND. In a-b, data for each donor was treated as one experiment. c, Membrane potential recording at 1, 6 and 20 mM glucose (indicated above membrane potential trace) from an α-cell identified by its low cell capacitance (2 pF) showing spontaneous action potential firing at 1 mM glucose. Representative of a total of 5 α-cell from 4 non-diabetic donors (3 cells were identified as alpha cells by immunocytochemistry). d, As in (c) but measurements were made from an α-cell (identified by immunocytochemistry) in an islet from a donor with type 2 diabetes. Note that action potential firing is frequently interrupted by transient hyperpolarizations (arrows) and that these are almost abolished in the presence of CYN154806. Similar data were obtained from another 3 alpha cells (identified by low cell capacitance and spontaneous action potential firing) from the same donor. Data represented as mean ± SEM.
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Vergari, E., Denwood, G., Salehi, A. et al. Somatostatin secretion by Na+-dependent Ca2+-induced Ca2+ release in pancreatic delta cells. Nat Metab 2, 32–40 (2020). https://doi.org/10.1038/s42255-019-0158-0
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DOI: https://doi.org/10.1038/s42255-019-0158-0
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