Biology subjects

Distaso, W.

Publications and source records attributed to Distaso, W..

4 recordsLinked to original sources

bioRxiv2022

Intra-islet glucagon signalling regulates pulsatile insulin secretion and glucose homeostasis

BackgroundType 2 diabetes (T2D) is characterised by the loss of pulsatile insulin secretion. We studied mice with {beta}-cell specific loss of the glucagon receptor (Gcgr fl/fl X Ins-1Cre), to investigate the role of intra-islet glucagon receptor signalling on pan-islet calcium oscillations and insulin pulsatility. MethodsFrequently sampled intravenous glucose tolerance tests were conducted on Gcgr {beta}-cell-/- and littermate controls. Crossing with GCaMP6f (STOP flox) animals further allowed for {beta}-cell specific expression of a fluorescent calcium indicator. These islets were functionally imaged in vitro and in vivo. Wild-type mice were transplanted with islets expressing GCaMP6f in {beta}-cells into the anterior eye chamber and placed on a high fat diet. Part of the cohort received a glucagon analogue (GCG-analogue) for 40 days and the control group were fed to achieve weight matching. Calcium imaging was performed regularly during the development of hyperglycaemia and in response to GCG-analogue treatment. ResultsGcgr {beta}-cell-/- mice exhibited impaired glucose tolerance following intraperitoneal glucose challenge (control 12.7mmol/L {+/-}0.6 vs. Gcgr {beta}-cell-/- 15.4mmol/L {+/-}0.0 at 15 min, p=0.002); fasting glycaemia was not different to controls. In vitro, Gcgr {beta}-cell-/- islets showed profound loss of synchronised calcium waves in response to glucose which was only partially rescued in vivo. First-phase insulin pulsatility on peripheral blood sampling (n=5) was significantly disordered in Gcgr {beta}-cell-/- mice (burst mass Gcgr {beta}-cell-/- 0.30 {+/-}0.03 versus 0.84 {+/-}0.23 for controls p=0.04). Diet induced obesity and hyperglycaemia resulted in a loss of co-ordinated [Ca2+]I waves in transplanted islets. This was reversed with GCG-analogue treatment, independently of weight-loss (n=8). ConclusionThese data provide novel evidence for the role of intra-islet GCGR signalling in sustaining synchronised calcium oscillations and support a possible therapeutic role for glucagonergic agents to restore the insulin pulsatility lost in T2D.

physiology↗

bioRxiv2020

The Vagus Nerve Mediates the Physiological but not Pharmacological Effects of PYY3-36 on Food Intake

Peptide YY (PYY3-36) is a post-prandially released gut hormone with potent appetite-reducing activity mediated by the neuropeptide Y (NPY) Y2 receptor (Y2R). However, the neuronal pathways by which PYY3-36 acts to supress appetite are unclear. Determining how the PYY3-36 system physiologically regulates food intake may help exploit its therapeutic potential. Here we demonstrate that germline and post-natal targeted knockdown of the Y2R in the afferent vagus nerve inhibits the anorectic effects of physiologically-released PYY3-36, but not peripherally-administered higher doses. Post-natal knockdown of the Y2R results in a transient body weight phenotype that is compensated for in the germline model. Loss of vagal Y2R signalling also alters meal patterning and accelerates gastric emptying. These results may facilitate the design of PYY-based anti-obesity agents. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=98 SRC="FIGDIR/small/241851v1_ufig1.gif" ALT="Figure 1"> View larger version (25K): org.highwire.dtl.DTLVardef@bef424org.highwire.dtl.DTLVardef@8e7d68org.highwire.dtl.DTLVardef@cb6757org.highwire.dtl.DTLVardef@1edb059_HPS_FORMAT_FIGEXP M_FIG C_FIG

physiology↗

bioRxiv2020

The type 2 diabetes gene product STARD10 is a phosphoinositide binding protein that controls insulin secretory granule biogenesis

ObjectiveRisk alleles for type 2 diabetes at the STARD10 locus are associated with lowered STARD10 expression in the {beta}-cell, impaired glucose-induced insulin secretion and decreased circulating proinsulin:insulin ratios. Although likely to serve as a mediator of intracellular lipid transfer, the identity of the transported lipids, and thus the pathways through which STARD10 regulates {beta}-cell function, are not understood. The aim of this study was to identify the lipids transported and affected by STARD10 in the {beta}-cell and its effect on proinsulin processing and insulin granule biogenesis and maturation. MethodsWe used isolated islets from mice deleted selectively in the {beta}-cell for Stard10 ({beta}StarD10KO) and performed electron microscopy, pulse-chase, RNA sequencing and lipidomic analyses. Proteomic analysis of STARD10 binding partners was executed in INS1 (832/13) cell line. X-ray crystallography followed by molecular docking and lipid overlay assay were performed on purified STARD10 protein. Results{beta}StarD10KO islets had a sharply altered dense core granule appearance, with a dramatic increase in the number of "rod-like" dense cores. Correspondingly, basal secretion of proinsulin was increased. Amongst the differentially expressed genes in {beta}StarD10KO islets, expression of the phosphoinositide binding proteins Pirt and Synaptotagmin 1 were decreased while lipidomic analysis demonstrated changes in phosphatidyl inositol levels. The inositol lipid kinase PIP4K2C was also identified as a STARD10 binding partner. STARD10 bound to inositides phosphorylated at the 3 position and solution of the crystal structure of STARD10 to 2.3 [A] resolution revealed a binding pocket capable of accommodating polyphosphoinositides. ConclusionOur data indicate that STARD10 binds to, and may transport, phosphatidylinositides, influencing membrane lipid composition, insulin granule biosynthesis and insulin processing.

cell biology↗

bioRxiv2019

β-cell dedifferentiation is associated with epithelial-mesenchymal transition triggered by miR-7-mediated repression of mSwi/Snf complex

{beta}-cell dedifferentiation has been revealed as a pathological mechanism underlying pancreatic dysfunction in diabetes. However, little is known on the genetic and epigenetic changes linked with the dedifferentiation of {beta}-cells. We now report that {beta}-cell dedifferentiation is associated with epithelial to mesenchymal transition (EMT) triggered by miR-7-mediated repression of Smarca4/Brg1 expression, a catalytic subunit of the mSwi/Snf chromatin remodeling complexes essential for {beta}-cell transcription factors ({beta}-TFs) activity. miR-7-mediated repression of Brg1 expression in diabetes causes an overall compaction of chromatin structure preventing {beta}-TFs from accessing and transactivating genes maintaining the functional and epithelial identity of {beta}-cells. Concomitantly, loss of {beta}-cell identity impairs the ability of {beta}-TFs Pdx1, Nkx6-1, Neurod1 to repress non-{beta}-cell genes enriched selectively in mesenchymal cells leading to EMT, change in islet microenvironment, and fibrosis. Remarkably, anti-EMT agents normalized glucose tolerance of diabetic mice, thus revealing mesenchymal reprogramming of {beta}-cells as a novel therapeutic target in diabetes. This study sheds light on the genetic signature of dedifferentiated {beta}-cells and highlights how loss of mSwi/Snf activity in diabetes initiating a step-wise remodeling of epigenetic landscapes of {beta}-cells leading to the induction of an EMT process reminiscent of a response to tissue injury.

genomics↗