Biology subjects

Garcia-Ocana, A.

Publications and source records attributed to Garcia-Ocana, A..

16 recordsLinked to original sources

bioRxiv2026

Development of CYP8B1-specific inhibitors for metabolic diseases

Changes in bile acids (BAs) balance lead to various metabolic diseases, yet current treatment options targeting these changes remain severely limited. CYP8B1 (cytochrome P450, family 8, subfamily B, polypeptide 1) is a liver-exclusive enzyme that controls the synthesis of 12-hydroxylated (12-OH) BAs. Inhibiting CYP8B1 is an attractive therapeutic strategy for attenuating 12-OH BA levels, remodeling the gut microbiota and thereby ameliorating metabolic diseases. CYP8B1-specific inhibitors are currently lacking due to structural similarities between the active site of CYP8B1 and other CYPs, and the lack of suitable high-throughput screening (HTS) assays. Herein, we developed a highly sensitive, and specific enzyme-coupled fluorescence assay to detect CYP8B1 activity, making it ideal for HTS. Employing this assay, structure-based drug design by protein X-ray crystallography, structure-activity relationship (SAR) analyses, and in vitro and in vivo validation, we developed novel CYP8B1-specific small molecule inhibitors. The lead candidate alters BA composition, favorably remodels the gut microbiota, and corrects metabolic disease in a metabolic dysfunction-associated steatotic liver disease (MASLD) mouse model. These findings reveal that pharmacologically inhibiting CYP8B1 is able to reshape the BA and gut microbiota profiles and effectively ameliorates metabolic diseases. Overall, CYP8B1-specific inhibitors represent a first-in-class promising, safe and effective therapeutic strategy against metabolic disorders.

pharmacology and toxicology↗

bioRxiv2026

Harmine Plus Exendin-4 Enhances Remission of Recent-Onset Type 1 Diabetes Following Anti-CD3 Therapy

Type 1 diabetes (T1D) results from autoimmune destruction of pancreatic {beta}-cells. While anti-CD3 therapy can delay disease progression and preserve residual {beta}-cell function, disease reversal will likely require both immune modulation and {beta}-cell regeneration. We found that the combination of harmine and exendin-4 (H+E) reduced inflammation-induced human {beta}-cell apoptosis, suppressed cytokine signaling and immunogenicity pathways, and improved {beta}-cell function. Although H+E alone did not reverse diabetes in NOD mice, low-dose anti-CD3 followed by H+E normalized blood glucose, increased insulin levels, improved glucose tolerance, expanded {beta}-cell mass, and enhanced diabetes remission. These effects were associated with reduced pro-inflammatory T-cell responses, increased regulatory T cells, and greater expression of exhaustion-related T-cell markers, without broad lymphocyte depletion. Similar immunomodulatory effects were observed in activated human PBMCs. Transcriptomic analyses identified the lncRNA SNHG6 as a key mediator of H+E action; SNHG6 protected {beta}-cells from cytokine-induced stress, apoptosis, and immunogenicity. Together, these findings demonstrate that H+E promotes {beta}-cell recovery and resilience while reducing {beta}-cell immunogenicity, enabling remission of recent-onset T1D when combined with anti-CD3 therapy. SNHG6 emerges as a novel regulator of {beta}-cell protection during inflammation.

cell biology↗

bioRxiv2025

Harmine Selectively Drives Human Beta Cell Differentiation and Function Via Protein Kinase A Pathways

Harmine and other small molecule inhibitors of the kinase DYRK1A induce human beta cells to replicate and regenerate in vitro and in vivo, and are effective at reversing diabetes in animal models. In addition to its beta cell proliferative and regenerative effects, harmine also induces expression of transcription factors and other genes involved in beta cell differentiation and function, exemplified by PDX1, MAFA, NKX6.1, GLP1R, PCSK1 and many others. Harmine also rapidly enhances glucose-stimulated insulin secretion in vitro and in vivo, reversing diabetes within days in diabetic mice transplanted with a marginal mass of human islets. We had assumed that this pro-differentiation or pro-function effect was a common feature of all DYRK1A inhibitors, and was mediated by DYRK1A inhibition. Thus, DYRK1A is a primary target (we refer to it as Target 1) for harmine. Here, to our surprise, we report that the pro-differentiation effect is not a generalized action for all small molecule DYRK1A inhibitors and does not result from DYRK1A interference or genetic silencing. Instead, the prodifferentiation effect is restricted to a small select subset of DYRK1A inhibitors (harmine, 2-2c and 5-IT). Remarkably, the pro-differentiation effect results from the unique ability of these drugs to activate protein kinase A (PKA), a dual mechanism that distinguishes this class from other DYRK1A inhibitors. The beneficial effects of harmine on PKA appear to be indirect, driven by an as yet unidentified, Target 2 in the PKA pathway. These findings make it clear that all DYRK1A inhibitors are not interchangeable, and that those that drive both proliferation and differentiation/function will likely be preferable in human clinical therapeutic settings. They also provide a novel target or roadmap for enhancing human beta cell differentiation in Type 1 and Type 2 diabetes. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=140 SRC="FIGDIR/small/692818v1_ufig1.gif" ALT="Figure 1"> View larger version (23K): org.highwire.dtl.DTLVardef@bd015corg.highwire.dtl.DTLVardef@a46f9borg.highwire.dtl.DTLVardef@19b4f65org.highwire.dtl.DTLVardef@179aa28_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2025

Nutrient excess remodels islet autonomic innervation via pancreatic schwann cells

Nutrient excess results in short- and long-term adaptations in the structure and function of metabolic organs, such as pancreatic islets. Pancreatic innervation contributes to islet architecture and function in many species, including humans, but little is known about its adaptation to over-nutrition. Here, we use 3D imaging to show that short-term high fat diet rapidly remodels islet sympathetic innervation while long-term high fat diet results in islet-specific cholinergic neuropathy. Using highly targeted, organ- and circuit-specific approaches, we demonstrate that remodeling of pancreatic innervation contributes to impaired glycemic control with short- and long-term nutrient excess. Counteracting the nutrient-induced changes in sympathetic and parasympathetic inputs to the pancreas using neuromodulation and repurposed FDA-approved approaches, we can significantly improve glycemic control even with long-term high fat diet. Finally, we identify islet Schwann cells as a source of the neurotrophic factor, S100b, contributing to rapid sympathetic hyperinnervation with short-term overnutrition. Our findings reveal novel adaptations in islet innervation contributing to nutrition-mediated metabolic dysfunction that can be ameliorated by targeting pancreatic neural circuits.

physiology↗

bioRxiv2024

Acute inhibition of iron-sulfur cluster biosynthesis disrupts metabolic flexibility in mice

Iron-sulfur clusters (ISCs) are cell-essential cofactors present in [~]60 proteins including subunits of OXPHOS complexes I-III, DNA polymerases, and iron-sensing proteins. Dysfunctions in ISC biosynthesis are associated with anemias, neurodegenerative disorders, and metabolic diseases. To assess consequences of acute ISC inhibition in a whole body setting, we developed a mouse model in which key ISC biosynthetic enzyme NFS1 can be acutely and reversibly suppressed. Contrary to in vitro ISC inhibition and pharmacological OXPHOS suppression, global NFS1 inhibition rapidly enhances lipid utilization and decreases adiposity without affecting caloric intake and physical activity. ISC proteins decrease, including key proteins involved in OXPHOS (SDHB), lipoic acid synthesis (LIAS), and insulin mRNA processing (CDKAL1), causing acute metabolic inflexibility. Age-related metabolic changes decelerate loss of adiposity substantially prolonged survival of mice with NFS1 inhibition. Thus, the observation that ISC metabolism impacts organismal fuel choice will aid in understanding the mechanisms underlying ISC diseases with increased risk for diabetes. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/608291v1_ufig1.gif" ALT="Figure 1"> View larger version (46K): org.highwire.dtl.DTLVardef@863cbaorg.highwire.dtl.DTLVardef@fce90borg.highwire.dtl.DTLVardef@27df04org.highwire.dtl.DTLVardef@1a2a9bf_HPS_FORMAT_FIGEXP M_FIG C_FIG Highlights- Acute ISC inhibition leads to rapid loss of adiposity in mice - Multi-metabolic pathway disruption upon ISC deficiency blocks energy storage - Nfs1 inhibition induces glucose dyshomeostasis due to ISC deficiency in {beta}-cells - Energy distress caused by inhibition of ISC synthesis is attenuated in aged mice

physiology↗

bioRxiv2024

Select DYRK1A Inhibitors Enhance Both Proliferation and Differentiation in Human Pancreatic Beta Cells

The small molecule DYRK1A inhibitor, harmine, induces human beta cell proliferation, expands beta cell mass, enhances expression of beta cell phenotypic genes, and improves human beta cell function in vitro and in vivo. It is unknown whether the "pro-differentiation effect" is a DYRK1A inhibitor class-wide effect. Here we compare multiple commonly studied DYRK1A inhibitors. Harmine, 2-2c and 5-IT increase expression of PDX1, MAFA, NKX6.1, SLC2A2, PCSK1, MAFB, SIX2, SLC2A2, SLC30A8, ENTPD3 in normal and T2D human islets. Unexpectedly, GNF4877, CC-401, INDY, CC-401 and Leucettine fail to induce expression of these essential beta cell molecules. Remarkably, the pro-differentiation effect is independent of DYRK1A inhibition: although silencing DYRK1A induces human beta cell proliferation, it has no effect on differentiation; conversely, harmine treatment enhances beta cell differentiation in DYRK1A-silenced islets. A careful screen of multiple DYRK1A inhibitor kinase candidate targets was unable to identify pro-differentiation pathways. Overall, harmine, 2-2c and 5-IT are unique among DYRK1A inhibitors in their ability to enhance both beta cell proliferation and differentiation. While beta cell proliferation is mediated by DYRK1A inhibition, the pro-differentiation effects of harmine, 2-2c and 5-IT are distinct, and unexplained in mechanistic terms. These considerations have important implications for DYRK1A inhibitor pharmaceutical development.

molecular biology↗

bioRxiv2024

LGR4 is essential for maintaining beta-cell homeostasis through suppression of RANK

Pancreatic {beta}-cell stress contributes to diabetes progression. This study demonstrates that Leucine-rich repeat-containing G-protein-coupled-receptor-4 (LGR4) is critical for maintaining {beta}-cell health and is modulated by stressors. In vitro, Lgr4 knockdown decreases proliferation and survival in rodent {beta}-cells, while overexpression protects against cytokine-induced cell death in rodent and human {beta}-cells. Mechanistically, LGR4 suppresses Receptor Activator of Nuclear Factor Kappa B (NF{kappa}B) (RANK) and its subsequent activation of NF{kappa}B to protect {beta}-cells. {beta}-cell-specific Lgr4-conditional knockout (cko) mice exhibit normal glucose homeostasis but increased {beta}-cell death in both sexes and decreased proliferation only in females. Male Lgr4cko mice under stress display reduced {beta}-cell proliferation and a further increase in {beta}-cell death. Upon aging, both male and female Lgr4cko mice display impaired {beta}-cell homeostasis, however, only female mice are glucose intolerant with decreased plasma insulin. We show that LGR4 is required for maintaining {beta}-cell health under basal and stress-induced conditions, through suppression of RANK. TeaserLGR4 receptor is critical for maintaining {beta}-cell health under basal and stressed conditions, through suppression of RANK.

physiology↗

bioRxiv2023

Human Pancreatic α-Cell Heterogeneity and Trajectory Inference Analysis Using Integrated Single Cell- and Single Nucleus-RNA Sequencing Platforms

Prior studies have shown that pancreatic -cells can transdifferentiate into {beta}-cells, and that {beta}-cells de-differentiate and are prone to acquire an -cell phenotype in type 2 diabetes (T2D). However, the specific human -cell and {beta}-cell subtypes that are involved in -to-{beta}-cell and {beta}-to--cell transitions are unknown. Here, we have integrated single cell RNA sequencing (scRNA-seq) and single nucleus RNA-seq (snRNA-seq) of isolated human islets and human islet grafts and provide additional insight into -{beta} cell fate switching. Using this approach, we make seven novel observations. 1) There are five different GCG-expressing human -cell subclusters [1, 2, -{beta}-transition 1 (AB-Tr1), -{beta}-transition 2 (AB-Tr2), and -{beta} (AB) cluster] with different transcriptome profiles in human islets from non-diabetic donors. 2) The AB subcluster displays multihormonal gene expression, inferred mostly from snRNA-seq data suggesting identification by pre-mRNA expression. 3) The 1, 2, AB-Tr1, and AB-Tr2 subclusters are enriched in genes specific for -cell function while AB cells are enriched in genes related to pancreatic progenitor and {beta}-cell pathways; 4) Trajectory inference analysis of extracted - and {beta}-cell clusters and RNA velocity/PAGA analysis suggests a bifurcate transition potential for AB towards both - and {beta}-cells. 5) Gene commonality analysis identifies ZNF385D, TRPM3, CASR, MEG3 and HDAC9 as signature for trajectories moving towards {beta}-cells and SMOC1, PLCE1, PAPPA2, ZNF331, ALDH1A1, SLC30A8, BTG2, TM4SF4, NR4A1 and PSCK2 as signature for trajectories moving towards -cells. 6) Remarkably, in contrast to the events in vitro, the AB subcluster is not identified in vivo in human islet grafts and trajectory inference analysis suggests only unidirectional transition from -to-{beta}-cells in vivo. 7) Analysis of scRNA-seq datasets from adult human T2D donor islets reveals a clear unidirectional transition from {beta}-to--cells compatible with dedifferentiation or conversion into -cells. Collectively, these studies show that snRNA-seq and scRNA-seq can be leveraged to identify transitions in the transcriptional status among human islet endocrine cell subpopulations in vitro, in vivo, in non-diabetes and in T2D. They reveal the potential gene signatures for common trajectories involved in interconversion between - and {beta}-cells and highlight the utility and power of studying single nuclear transcriptomes of human islets in vivo. Most importantly, they illustrate the importance of studying human islets in their natural in vivo setting.

cell biology↗

bioRxiv2023

Single Cell RNA-Seq Analysis of Regenerative Drug-Treated Human Pancreatic Islets Identifies A Cycling Alpha Cell Population As Key Beta Cell Progenitors

Diabetes ultimately results from an inadequate number of functional, insulin-producing human beta cells. Although current attempts to replenish the remaining beta cell pool in people with diabetes are encouraging, scalability and cost limit access for the millions of people with diabetes. The small molecule DYRK1A inhibitor class of beta cell regenerative drugs, either alone or in combination with GLP1 receptor agonists or TGF{beta} superfamily inhibitors, are capable of inducing beta cell replication in vitro and increasing beta cell mass in vivo. Despite these advances, the precise mechanisms of action of DYRK1A inhibitors remain incompletely understood. To address the mechanisms more deeply, we performed single cell RNA sequencing on human pancreatic islets treated with a DYRK1A inhibitor, either alone, or in combination with a GLP1 receptor agonist or a TGF{beta} superfamily inhibitor. We identify a cluster of Cycling Alpha Cells as the cells most responsive to DYRK1A inhibition. Velocity and pseudotime lineage trajectory analyses suggest that Cycling Alpha Cells serve as the primary target cell type for of DYRK1A inhibitors, and may serve as precursor cells that transdifferentiate into functional human beta cells in response to the DYRK1A inhibition. In addition to providing a novel mechanism of action for DYRK1A inhibitors, our findings suggest that efforts to target regenerative drugs to human beta cells may be mis-directed: the proper target may be Cycling Alpha Cells.

cell biology↗

bioRxiv2023

NRF2 Dysregulation in Mice Leads to Inadequate Beta-Cell Mass Expansion during Pregnancy and Gestational Diabetes

The late stages of the mammalian pregnancy are accompanied with increased insulin resistance due to the increased glucose demand of the growing fetus. Therefore, as a compensatory response to maintain the maternal normal blood glucose levels, maternal beta-cell mass expands leading to increased insulin release. Defects in beta-cell adaptive expansion during pregnancy can lead to gestational diabetes mellitus (GDM). Although the exact mechanisms that promote GDM are poorly understood, GDM strongly associates with impaired beta-cell proliferation and with increased levels of reactive oxygen species (ROS). Here, we show that NRF2 levels are upregulated in mouse beta-cells at gestation day 15 (GD15) concomitant with increased beta-cell proliferation. Importantly, mice with tamoxifen-induced beta-cell-specific NRF2 deletion display inhibition of beta-cell proliferation, increased beta-cell oxidative stress and elevated levels of beta-cell death at GD15. This results in attenuated beta-cell mass expansion and disturbed glucose homeostasis towards the end of pregnancy. Collectively, these results highlight the importance of NRF2-oxidative stress regulation in beta-cell mass adaptation to pregnancy and suggest NRF2 as a potential therapeutic target for treating GDM.

molecular biology↗

bioRxiv2023

Magnetogenetic cell activation using endogenous ferritin

The ability to precisely control the activity of defined cell populations enables studies of their physiological roles and may provide therapeutic applications. While prior studies have shown that magnetic activation of ferritin-tagged ion channels allows cell-specific modulation of cellular activity, the large size of the constructs made the use of adeno-associated virus, AAV, the vector of choice for gene therapy, impractical. In addition, simple means for generating magnetic fields of sufficient strength have been lacking. Toward these ends, we first generated a novel anti-ferritin nanobody that when fused to transient receptor potential cation channel subfamily V member 1, TRPV1, enables direct binding of the channel to endogenous ferritin in mouse and human cells. This smaller construct can be delivered in a single AAV and we validated that it robustly enables magnetically induced cell activation in vitro. In parallel, we developed a simple benchtop electromagnet capable of gating the nanobody-tagged channel in vivo. Finally, we showed that delivering these new constructs by AAV to pancreatic beta cells in combination with the benchtop magnetic field delivery stimulates glucose-stimulated insulin release to improve glucose tolerance in mice in vivo. Together, the novel anti-ferritin nanobody, nanobody-TRPV1 construct and new hardware advance the utility of magnetogenetics in animals and potentially humans.

bioengineering↗

bioRxiv2022

Single Nucleus RNA Sequencing of Human Pancreatic Islets In Vitro and In Vivo Identifies New Gene Sets and Three β-Cell Subpopulations with Different Transcriptional Profile

Single-cell RNA sequencing (scRNA-seq) has provided valuable insights into human islet cell types and their corresponding stable gene expression profiles. However, this approach requires cell dissociation that complicates its utility in vivo and provides limited information on the active transcriptional status of islet cells. On the other hand, single-nucleus RNA sequencing (snRNA-seq) does not require cell dissociation and affords enhanced information from intronic sequences that can be leveraged to identify actively transcribing genes in islet cell populations. Here, we first sought to compare scRNA-seq and snRNA-seq analysis of human islets in vitro using exon reads or combined exon and intron reads, respectively. Datasets reveal similar human islet cell clusters using both approaches. In the snRNA-seq data, however, the top differentially expressed genes in human islet endocrine cells are not the canonical genes but a new set of non-canonical gene markers including ZNF385D, TRPM3, LRFN2, PLUT ({beta} cells), PTPRT, FAP, PDK4, LOXL4 ( cells), LRFN5, ADARB2, ERBB4, KCNT2 ({delta} cells) and CACNA2D3, THSD7A, CNTNAP5, RBFOX3 ({gamma} cells). Notably, these markers also accurately define endocrine cell populations in human islet grafts in vivo. Further, by integrating the information from nuclear and cytoplasmic transcriptomes, we identify three {beta}-cell sub-clusters: an active INS mRNA transcribing cluster ({beta}1), an intermediate INS mRNA-transcribing cluster ({beta}2), and a mature INS mRNA rich cluster ({beta}3). These display distinct gene expression patterns representing different biological dynamic states both in vitro and in vivo. Interestingly, the INS mRNA rich cluster ({beta}3) becomes the predominant sub-cluster in vivo. In summary, snRNA-seq analysis of human islet cells is a previously unrecognized tool that can be accurately employed for improved identification of human islet cell types and their transcriptional status in vivo.

cell biology↗

bioRxiv2021

Nrf2 Regulates β-cell Mass by Suppressing Cell Death and Promoting Proliferation

Finding therapies that can protect and expand functional {beta}-cell mass is a major goal of diabetes research. Here we generated {beta}-cell-specific conditional knockout and gain-of-function mouse models and used human islet transplant experiments to examine how manipulating Nrf2 levels affects {beta}-cell survival, proliferation and mass. Depletion of Nrf2 in {beta}-cells resulted in decreased glucose-stimulated {beta}-cell proliferation ex vivo and decreased adaptive {beta}-cell proliferation and {beta}-cell mass expansion after a high fat diet in vivo. Nrf2 protects {beta}-cells from apoptosis after a high fat diet. Nrf2 loss-of-function decreases Pdx1 abundance and insulin content. Activating Nrf2 in a {beta}-cell-specific manner increases {beta}-cell proliferation and {beta}-cell mass. Human islets transplanted under the kidney capsule of immunocompromised mice and treated systemically with CDDO-Me, an Nrf2 activator, display increased {beta}-cell proliferation. Thus, Nrf2 regulates {beta}-cell mass and is an exciting therapeutic target for expanding {beta}-cell mass in diabetes.

physiology↗

bioRxiv2020

The Harmine and Exendin-4 Combination Markedly Expands Human Beta Cell Mass In Vivo: Quantification and Visualization By iDISCO+ 3D Imaging

463 million people globally suffer from diabetes. The majority are deficient in insulin-producing pancreatic beta cells, although beta cells remain in most people with diabetes. Unfortunately, although many diabetes drugs exist, none is able to increase adult human beta cell numbers. Recently, small molecules that inhibit the kinase, DYRK1A, have been suggested to induce human beta cell replication in vitro and in vivo as assessed using proliferation markers, and this is enhanced by drugs that stimulate the GLP1 receptor (GLP1R) on beta cells. DYRK1A inhibitors also enhance human beta cell differentiation and function. However, it is unknown whether any drug can actually increase human beta cell mass in vivo, reflecting: 1) the intrinsic resistance of human beta cells to regeneration; and, 2) the current technical inability to accurately assess human beta cell mass in vivo. Here, we demonstrate for the first time that combining a DYRK1A inhibitor with a GLP1R agonist increases actual human beta cell numbers and overall mass in vivo by 400-700% in diabetic and non-diabetic mice over three months. We further describe a novel application of tissue-clearing and 3D imaging for quantification of human beta cell mass. These findings should be transformative for diabetes treatment.

cell biology↗

bioRxiv2020

A common human variant of GIPR improves systemic glucose homeostasis in a sexual dimorphic manner

Glucose-dependent insulinotropic polypeptide (GIP) has a role in controlling postprandial metabolic tone. In humans, a GIP receptor (GIPR) variant (Q354, rs1800437) is associated with a lower body mass index (BMI) and increased risk for Type 2 Diabetes. To isolate the contribution of GIPR in metabolic control, we generated a mouse model of the GIPR-Q354 variant (GIPR-Q350 mice). Female GIPR-Q350 mice are leaner than littermate controls, and male GIPR-Q350 mice are resistant to diet-induced obesity, in line with the association of the variant with reduced BMI in humans. GIPR-Q350 mice of both sexes are more glucose tolerant and exhibit an increased sensitivity to GIP. Postprandial GIP levels are reduced in GIPR-Q350 mice, revealing feedback regulation that balances the increased sensitivity of GIP target tissues to secretion of GIP from intestinal endocrine cells. The increased GIP sensitivity is recapitulated ex vivo during glucose stimulated insulin secretion assays in islets. Generation of cAMP in islets downstream of GIPR activation is not affected by the Q354 substitution. However, post-activation traffic of GIPR-Q354 variant in {beta}-cells is altered, characterized by enhanced intracellular dwell time and increased localization to the Trans-Golgi Network (TGN). Consequently, our data link altered intracellular traffic of the GIPR-Q354 variant with GIP control of metabolism. We propose that this change in spatiotemporal signaling underlies the physiologic effects of GIPR-Q350/4 and GIPR-E350/4 in mice and humans. These findings contribute to a more complete understanding of the impact of GIPR-Q354 variant on glucose homeostasis that could perhaps be leveraged to enhance pharmacologic targeting of GIPR for the treatment of metabolic disease.

physiology↗

bioRxiv2019

Human pseudoislet system enables detection of differences in G-protein-coupled-receptor signaling pathways between α and β cells

G-protein-coupled-receptors (GPCRs) modulate insulin secretion from {beta} cells and glucagon secretion from cells. Here, we developed an integrated approach to study the function of primary human islet cells using genetically modified pseudoislets that resemble native islets across multiple parameters. We studied the Gi and Gq GPCR pathways by expressing the designer receptors exclusively activated by designer drugs (DREADDs) hM4Di or hM3Dq. Activation of Gi signaling reduced insulin and glucagon secretion, while activation of Gq signaling stimulated glucagon secretion but had both stimulatory and inhibitory effects on insulin secretion. Further, we developed a microperifusion system that allowed synchronous acquisition of GCaMP6f biosensor signal and hormone secretory profiles and showed that the dual effects for Gq signaling occur through changes in intracellular Ca2+. By combining pseudoislets with a microfluidic system, we co-registered intracellular signaling dynamics and hormone secretion and demonstrated differences in GPCR signaling pathways between human {beta} and cells.

cell biology↗