Pancreatic α-cells are functionally heterogeneous and sex-dependently regulated by neighboring endocrine cells.

Glucose and paracrine regulation on α-cells, particularly with respect to sex differences, remains unclear. Hence, we imaged islets of GluCre:GCaMP6f mice in pancreatic slices, additionally loaded with a red Ca²⁺ dye, to precisely interrogate Ca²⁺ dynamics in α-cells and the adjacent β- and δ-cells. During a glucose ramp (1.

Binding kinetics, bias, receptor internalization and effects on insulin secretion in vitro and in vivo of a novel GLP-1R/GIPR dual agonist, HISHS-2001.

Aims: The use of incretin analogues has emerged as an effective approach to achieve both enhanced insulin secretion and weight loss in Type 2 diabetes (T2D) patients. Agonists which bind and stimulate multiple receptors have shown particular promise. However, off-target effects remain a complication of using these agents, and modified versions with optimised pharmacological profiles and/or biased signalling are sought.

LONP1 regulation of mitochondrial protein folding provides insight into beta cell failure in type 2 diabetes.

Protein misfolding is a contributor to the development of type 2 diabetes (T2D), but the specific role of impaired proteostasis is unclear. Here we show a robust accumulation of misfolded proteins in the mitochondria of human pancreatic islets from patients with T2D and elucidate its impact on β cell viability through the mitochondrial matrix protease LONP1. Quantitative proteomics studies of protein aggregates reveal that islets from donors with T2D have a signature resembling mitochondrial rather than endoplasmic reticulum protein misfolding.

Effects of SGLT2 ablation or inhibition on corticosterone secretion in high-fat-fed mice: exploring a nexus with cytokine levels.

Aims/hypothesis: Despite recent therapeutic advances, achieving optimal glycaemic control remains a challenge in managing type 2 diabetes. Sodium-glucose cotransporter 2 (SGLT2) inhibitors have emerged as effective treatments by promoting urinary glucose excretion. However, the full scope of their mechanisms extends beyond glycaemic control.

Serine palmitoyltransferase-mediated de novo sphingolipid biosynthesis is required for normal insulin production and glucose tolerance.

Aims/hypothesis: The importance for normal insulin secretion of ceramide synthesis is unclear. ceramide synthesis requires serine palmitoyl transferase, SPT2, encoded by .

Methods: We generated β-cell-selective null mice by crossing animals with alleles to mice expressing recombinase from the locus.

Exploration of individual beta cell function over time effects of hyperglycemia and glucagon-like peptide-1 receptor (GLP1R) agonism.

The coordinated function of beta cells within the pancreatic islet is required for the normal regulation of insulin secretion and is partly controlled by specialized "leader" and highly connected "hub" beta-cell subpopulations. Whether cells within these subpopulations are functionally stable remains unclear. Here, we establish an approach to monitor Ca dynamics within individual beta cells over time, after engraftment into the anterior eye chamber, where continuous blood perfusion and near normal innervation pertain.

ER calcium stores contribute to glucose-induced Ca waves and intercellular connectivity in mouse pancreatic islets.

Defective insulin secretion is a hallmark of diabetes mellitus. Glucose-induced Ca oscillations are critical for the stimulation of insulin secretion, though the mechanisms through which these propagate across the islet are poorly understood. Here, we use beta cell-targeted GCaMP6f to explore the role of endoplasmic reticulum (ER) Ca mobilization in response to submaximal (11mM) and hyperglycemic (25mM) glucose concentrations.

Binding Kinetics, Bias, Receptor Internalization and Effects on Insulin Secretion and of a Novel GLP-1R/GIPR Dual Agonist, HISHS-2001.

The use of incretin analogues has emerged in recent years as an effective approach to achieve both enhanced insulin secretion and weight loss in type 2 diabetes (T2D) patients. Agonists which bind and stimulate multiple receptors have shown particular promise. However, off target effects, including nausea and diarrhoea, remain a complication of using these agents, and modified versions with optimized pharmacological profiles and/or biased signaling at the cognate receptors are increasingly sought.

Roles for the long non-coding RNA / in pancreatic beta cell function.

Long non-coding RNAs (lncRNAs) are emerging as crucial regulators of beta cell function. Here, we show that an lncRNA-transcribed antisense to Pax6, annotated as Pax6os1/PAX6-AS1, was upregulated by high glucose concentrations in human as well as murine beta cell lines and islets. Elevated expression was also observed in islets from mice on a high-fat diet and patients with type 2 diabetes.

Severe neonatal hypotonia due to variant affecting function of ZnT5 zinc transporter.

The tightly-regulated spatial and temporal distribution of zinc ion concentrations within cellular compartments is controlled by two groups of Zn transporters: the 14-member ZIP/SLC39 family, facilitating Zn influx into the cytoplasm from the extracellular space or intracellular organelles; and the 10-member ZnT/SLC30 family, mobilizing Zn in the opposite direction. Genetic aberrations in most zinc transporters cause human syndromes. Notably, previous studies demonstrated osteopenia and male-specific cardiac death in mice lacking the ZnT5/ zinc transporter, and suggested association of two homozygous frameshift variants with perinatal mortality in humans, due to hydrops fetalis and hypertrophic cardiomyopathy.

Investigating the pathogenicity of the recessive p.A251T variant in monogenic diabetes using iPSC-derived beta-like cells.

Monogenic diabetes, formerly called Maturity-Onset Diabetes of the Young (MODY), involves single-gene mutations, typically with dominant inheritance, and has been associated with variants in 14 genes. Among these, mutations are the most common, and their diagnosis allows the use of alternative therapies, including sulfonylureas. In an earlier study, we described a variant displaying recessive transmission, p.

Sex-dependent additive effects of dorzagliatin and incretin on insulin secretion in a novel mouse model of -MODY.

Glucokinase (GK) catalyses the key regulatory step in glucose-stimulated insulin secretion. Correspondingly, hetero- and homozygous mutations in human cause maturity-onset diabetes of the young (GCK-MODY) and permanent neonatal diabetes (PNDM), respectively. To explore the possible utility of glucokinase activators (GKA) and of glucagon-like receptor-1 (GLP-1) agonists in these diseases, we have developed a novel hypomorphic allele in mice encoding an aberrantly spliced mRNA deleted for exons 2 and 3.

Exercise activates AMPK in mouse and human pancreatic islets to decrease senescence.

Beta (β)-cell senescence contributes to type 2 diabetes mellitus (T2DM). While exercise is vital for T2DM management and significantly affects cellular ageing markers, its effect on β-cell senescence remains unexplored. Here, we show that short-term endurance exercise training (treadmill running, 1 h per day for 10 days) in two male and female mouse models of insulin resistance decreases β-cell senescence.

Liver kinase B1 (LKB1) regulates the epigenetic landscape of mouse pancreatic beta cells.

Liver kinase B1 (LKB1/STK11) is an important regulator of pancreatic β-cell identity and function. Elimination of Lkb1 from the β-cell results in improved glucose-stimulated insulin secretion and is accompanied by profound changes in gene expression, including the upregulation of several neuronal genes. The mechanisms through which LKB1 controls gene expression are, at present, poorly understood.

Exploring pancreatic beta-cell subgroups and their connectivity.

Functional pancreatic islet beta cells are essential to ensure glucose homeostasis across species from zebrafish to humans. These cells show significant heterogeneity, and emerging studies have revealed that connectivity across a hierarchical network is required for normal insulin release. Here, we discuss current thinking and areas of debate around intra-islet connectivity, cellular hierarchies and potential "controlling" beta-cell populations.

Engineered mini-G proteins block the internalization of cognate GPCRs and disrupt downstream intracellular signaling.

Mini-G proteins are engineered, thermostable variants of Gα subunits designed to stabilize G protein-coupled receptors (GPCRs) in their active conformations. Because of their small size and ease of use, they are popular tools for assessing GPCR behaviors in cells, both as reporters of receptor coupling to Gα subtypes and for cellular assays to quantify compartmentalized signaling at various subcellular locations. Here, we report that overexpression of mini-G proteins with their cognate GPCRs disrupted GPCR endocytic trafficking and associated intracellular signaling.

Optogenetic β cell interrogation in vivo reveals a functional hierarchy directing the Ca response to glucose supported by vitamin B6.

Coordination of cellular activity through Ca enables β cells to secrete precise quantities of insulin. To explore how the Ca response is orchestrated in space and time, we implement optogenetic systems to probe the role of individual β cells in the glucose response. By targeted β cell activation/inactivation in zebrafish, we reveal a hierarchy of cells, each with a different level of influence over islet-wide Ca dynamics.

Liver kinase B1 (LKB1) regulates the epigenetic landscape of mouse pancreatic beta cells.

Liver kinase B1 (LKB1/STK11) is an important regulator of pancreatic β-cell identity and function. Elimination of from the β-cell results in improved glucose-stimulated insulin secretion and is accompanied by profound changes in gene expression, including the upregulation of several neuronal genes. The mechanisms through which LKB1 controls gene expression are, at present, poorly understood.

Glucose Regulation of β-Cell KATP Channels: Is a New Model Needed?

The canonical model of glucose-induced increase in insulin secretion involves the metabolism of glucose via glycolysis and the citrate cycle, resulting in increased ATP synthesis by the respiratory chain and the closure of ATP-sensitive K+ (KATP) channels. The resulting plasma membrane depolarization, followed by Ca2+ influx through L-type Ca2+ channels, then induces insulin granule fusion. Merrins and colleagues have recently proposed an alternative model whereby KATP channels are controlled by pyruvate kinase, using glycolytic and mitochondrial phosphoenolpyruvate (PEP) to generate microdomains of high ATP/ADP immediately adjacent to KATP channels.

Effects of SGLT2 Ablation or Inhibition on Corticosterone Secretion in High-Fat-Fed Mice: Exploring a Nexus with Cytokine Levels.

Despite recent therapeutic advances, achieving optimal glycaemic control remains a challenge in managing Type 2 Diabetes (T2D). Sodium-glucose co-transporter type 2 (SGLT2) inhibitors have emerged as effective treatments by promoting urinary glucose excretion. However, the full scope of their mechanisms extends beyond glycaemic control.

Multiple genetic variants at the SLC30A8 locus affect local super-enhancer activity and influence pancreatic β-cell survival and function.

Variants at the SLC30A8 locus are associated with type 2 diabetes (T2D) risk. The lead variant, rs13266634, encodes an amino acid change, Arg325Trp (R325W), at the C-terminus of the secretory granule-enriched zinc transporter, ZnT8. Although this protein-coding variant was previously thought to be the sole driver of T2D risk at this locus, recent studies have provided evidence for lowered expression of SLC30A8 mRNA in protective allele carriers.

Proinflammatory cytokines suppress nonsense-mediated RNA decay to impair regulated transcript isoform processing in pancreatic β cells.

Introduction: Proinflammatory cytokines are implicated in pancreatic ß cell failure in type 1 and type 2 diabetes and are known to stimulate alternative RNA splicing and the expression of nonsense-mediated RNA decay (NMD) components. Here, we investigate whether cytokines regulate NMD activity and identify transcript isoforms targeted in ß cells.

Methods: A luciferase-based NMD reporter transiently expressed in rat INS1(832/13), human-derived EndoC-ßH3, or dispersed human islet cells is used to examine the effect of proinflammatory cytokines (Cyt) on NMD activity.