Leader β-cells coordinate Ca2+ dynamics across pancreatic islets in vivo

Salem, Victoria; Silva, Luis Delgadillo; Suba, Kinga; Georgiadou, Eleni; Gharavy, S. Neda Mousavy; Akhtar, Nadeem; Martin-Alonso, Aldara; Gaboriau, David; Rothery, Stephen; Stylianides, Theodoros; Carrat, Gaëlle; Pullen, Timothy J.; Singh, Sumeet Pal; Hodson, David J.; Leclerc, Isabelle; Shapiro, A. M. James; Marchetti, Piero; Briant, Linford J.B.; Distaso, Walter; Ninov, Nikolay; Rutter, Guy A.

doi:10.1038/s42255-019-0075-2

Cited by 138 publications

(234 citation statements)

References 60 publications

Supporting

Mentioning

204

Contrasting

Unclassified

Order By: Relevance

“…First, we assessed this response in vivo; we isolated islets from Gcg Cre+ mice crossed with a Cre-dependent GCaMP3 reporter mouse (from hereon, Gcg-GCaMP3 mice) and implanted them in the anterior chamber of the eye ( Fig. 4e-h; see Salem et al (2019)).…”

Section: Avp Evokes Hyperglycaemia and Hyperglucagonaemiamentioning

confidence: 99%

Arginine-vasopressin mediates counter-regulatory glucagon release and is diminished in type 1 diabetes

Kim

Knudsen

Madara

et al. 2020

Preprint

Self Cite

View full text Add to dashboard Cite

Hypoglycaemia is a major barrier to the treatment of diabetes. Accordingly, it is important that we understand the mechanisms regulating the circulating levels of glucagon -the body's principle blood glucose-elevating hormone which is secreted from alpha-cells of the pancreatic islets. In isolated islets, varying glucose over the range of concentrations that occur physiologically between the fed and fuel-deprived states (from 8 to 4 mM) has no significant effect on glucagon secretion and yet associates with dramatic changes in plasma glucagon in vivo. The identity of the systemic factor that stimulates glucagon secretion in vivo remains unknown. Here, we show that arginine-vasopressin (AVP), secreted from the posterior pituitary, stimulates glucagon secretion. Glucagon-secreting alpha-cells express high levels of the vasopressin 1b receptor (V1bR). Activation of AVP neurons in vivo increased circulating AVP, stimulated glucagon release and evoked hyperglycaemia; effects blocked by pharmacological antagonism of either the glucagon receptor or vasopressin 1b receptor. AVP also mediates the stimulatory effects of dehydration and hypoglycaemia produced by exogenous insulin and 2-deoxy-D-glucose on glucagon secretion. We show that the A1/C1 neurons of the medulla oblongata, which are known to be activated by hypoglycaemia, drive AVP neuron activation in response to insulin-induced hypoglycaemia.Hypoglycaemia also increases circulating levels of copeptin (derived from the same pre-pro hormone as AVP) levels in humans and this hormone stimulates glucagon secretion from isolated human islets. In patients with type 1 diabetes, hypoglycaemia failed to increase both plasma copeptin and glucagon. These findings provide a new mechanism for the central regulation of glucagon secretion in both health and disease.

show abstract

Section: Avp Evokes Hyperglycaemia and Hyperglucagonaemiamentioning

confidence: 99%

Arginine-vasopressin mediates counter-regulatory glucagon release and is diminished in type 1 diabetes

Kim

Knudsen

Madara

et al. 2020

Preprint

Self Cite

View full text Add to dashboard Cite

show abstract

“…This was also not associated with a loss of hierarchical behaviour and the loss of clearly identifiable "hub" cells following Monte Carlo simulation. Thus, we demonstrate that mitochondrial ultra-structure is important for normal beta-beta cell connections which are, in turn, essential for coordinated Ca 2+ influx into beta cells and ultimately, efficient and oscillatory insulin secretion [39].…”

Section: Deletion Of Mfn1/2 Ensured Near-complete Elimination Of Thementioning

confidence: 77%

“…Pearson-R correlations. Significantly correlated beta cell pairs were measured on islets incubated with Cal-520 as described previously [39,40]. Correlation coefficient (R) and heatmaps were generated using an in-house MATLAB script (available upon request).…”

Section: Connectivity Analysismentioning

confidence: 99%

“…Monte Carlo-based signal binarisation and data shuffling for identification of highly connected cells Data were analysed using approaches similar to those previously described [39,40] with modifications as below. Ca 2+ signals were denoised by subjecting the signal the Huang-Hilbert type (HHT) empirical mode decomposition (EMD).…”

Section: Connectivity Analysismentioning

confidence: 99%

“…5B, D; 0.88 vs 0.77 for WT vs KO, respectively), indicating that mitofusins affect the strength of connection rather than the number of coordinated beta cell pairs. We also explored beta cell connectivity using data binarisation and network theory to determine whether a hierarchy existed in the degree to which individual beta cells were coupled across the islet [39,40]. Clear adherence to a power law distribution of connected beta cells was apparent in both islet groups in the elevated glucose condition (~10% of "hub" cells hosted >20% of all connections to other beta cells; R 2 =0.21 for WT and R 2 =0.45 for KO islets) (Supp.…”

Section: Deletion Of Mfn1/2 Alters Mitochondrial Morphology In Beta Cmentioning

confidence: 99%

See 2 more Smart Citations

Mitofusins Mfn1 and Mfn2 are required to preserve glucose-but not incretin- stimulated beta cell connectivity and insulin secretion

Georgiadou

Muralidharan

Martínez

et al. 2020

Preprint

Self Cite

View full text Add to dashboard Cite

Background and aims: Mitochondria are highly dynamic organelles, fundamental to cellular energy homeostasis. Mitochondrial metabolism of glucose is essential for the initiation of insulin release from pancreatic beta cells. Whether mitochondrial ultrastructure, and the proteins controlling fission and fusion, are important for glucose recognition are unclear. Mitochondrial fusion is supported by proteins including mitofusin 1 (MFN1), mitofusin 2 (MFN2) and optic atrophy (OPA1), and fission by dynamin-related protein 1 (DRP1). Here, we generated mice with beta cell-selective, adult-restricted deletion of Mfn1 and Mfn2 (bMfn1/2-KO), and explored the impact on insulin secretion and glucose homeostasis in vivo and in vitro. Materials and methods: C57BL/6J mice bearing Mfn1 and Mfn2 alleles with loxP sites, were crossed to animals carrying an inducible Cre recombinase at the Pdx1 locus (Pdx CreERT ). Isolated islets were used for live beta cell fluorescence imaging of cytosolic (Cal-520) or mitochondrial (Pericam) free Ca 2+ concentration and membrane potential (TMRE). Mitochondrial network characteristics were quantified using super resolution fluorescence and transmission electron microscopy. Beta cellbeta cell connectivity was assessed using the Pearson (R) analysis and Monte Carlo simulation in intact mouse islets. Intravital imaging was performed in mice injected with an adeno-associated virus to express the cytosolic Ca 2+ sensor GCaMP6s selectively in beta cells and TMRM to visualise mitochondria using multiphoton microscopy. Results: bMfn1/2-KO mice displayed higher fasting glycaemia than control littermates at 14 weeks (8.6 vs 6.4 mmol/L, p>0.05) and a >five-fold decrease in plasma insulin post-intraperitoneal glucose injection (5-15 min, p<0.0001). Mitochondrial length, and glucose-induced Ca 2+ accumulation, mitochondrial hyperpolarisation and beta cell connectivity were all significantly reduced in bMfn1/2-KO mouse islets. Examined by intravital imaging of the exteriorised pancreas, antiparallel changes in cytosolic Ca 2+ and mitochondrial membrane potential, observed in control animals in vivo, were suppressed after Mfn1/2 deletion. 3 Conclusion: Mitochondrial fusion and fission cycles are essential in the beta cell to maintain normal mitochondrial bioenergetics and glucose sensing both in vitro and in the living mouse. Such cycles may be disrupted in some forms of diabetes to impair mitochondrial function and, consequently, insulin secretion. R Pearson correlation coefficient TMRE Tetramethylrhodamine ethyl ester TMRM Tetramethylrhodamine methyl ester WT Wild-type

show abstract

Microscopic modulation and analysis of islets of Langerhans in living zebrafish larvae

et al. 2022

View full text Add to dashboard Cite

Microscopic analysis of molecules and physiology in living cells and systems is a powerful tool in life sciences. While in vivo subcellular microscopic analysis of healthy and diseased human organs remains impossible, zebrafish larvae allow studying pathophysiology of many organs using in vivo microscopy. Here, we review the potential of the larval zebrafish pancreas in the context of islets of Langerhans and Type 1 diabetes. We highlight the match of zebrafish larvae with the expanding toolbox of fluorescent probes that monitor cell identity, fate and/or physiology in real time. Moreover, fast and efficient modulation and localization of fluorescence at a subcellular level, through fluorescence microscopy, including confocal and light sheet (single plane illumination) microscopes tailored to in vivo larval research, is addressed. These developments make the zebrafish larvae an extremely powerful research tool for translational research. We foresee that living larval zebrafish models will replace many cell line‐based studies in understanding the contribution of molecules, organelles and cells to organ pathophysiology in whole organisms.

show abstract

Leader β-cells coordinate Ca2+ dynamics across pancreatic islets in vivo

Cited by 138 publications

References 60 publications

Arginine-vasopressin mediates counter-regulatory glucagon release and is diminished in type 1 diabetes

Arginine-vasopressin mediates counter-regulatory glucagon release and is diminished in type 1 diabetes

Mitofusins Mfn1 and Mfn2 are required to preserve glucose-but not incretin- stimulated beta cell connectivity and insulin secretion

Microscopic modulation and analysis of islets of Langerhans in living zebrafish larvae

Contact Info

Product

Resources

About