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Yan X, Zhao Z, Weaver J, Sun T, Yun JW, Roneker CA, Hu F, Doliba NM, McCormick CCW, Vatamaniuk MZ, Lei XG. Role and mechanism of REG2 depletion in insulin secretion augmented by glutathione peroxidase-1 overproduction. Redox Biol 2022; 56:102457. [PMID: 36063729 PMCID: PMC9463454 DOI: 10.1016/j.redox.2022.102457] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2022] [Revised: 08/15/2022] [Accepted: 08/24/2022] [Indexed: 11/23/2022] Open
Abstract
We previously reported a depletion of murine regenerating islet-derived protein 2 (REG2) in pancreatic islets of glutathione peroxidase-1 (Gpx1) overexpressing (OE) mice. The present study was to explore if and how the REG2 depletion contributed to an augmented glucose stimulated insulin secretion (GSIS) in OE islets. After we verified a consistent depletion (90%, p < 0.05) of REG2 mRNA, transcript, and protein in OE islets compared with wild-type (WT) controls, we treated cultured and perifused OE islets (70 islets/sample) with REG2 (1 μg/ml or ml · min) and observed 30-40% (p < 0.05) inhibitions of GSIS by REG2. Subsequently, we obtained evidences of co-immunoprecipitation, cell surface ligand binding, and co-immunofluorescence for a ligand-receptor binding between REG2 and transmembrane, L-type voltage-dependent Ca2+ channel (CaV1.2) in beta TC3 cells. Mutating the C-type lectin binding domain of REG2 or deglycosylating CaV1.2 removed the inhibition of REG2 on GSIS and(or) the putative binding between the two proteins. Treating cultured OE and perifused WT islets with REG2 (1 μg/ml or ml · min) decreased (p < 0.05) Ca2+ influx triggered by glucose or KCl. An intraperitoneal (ip) injection of REG2 (2 μg/g) to OE mice (6-month old, n = 10) decreased their plasma insulin concentration (46%, p < 0.05) and elevated their plasma glucose concentration (25%, p < 0.05) over a 60 min period after glucose challenge (ip, 1 g/kg). In conclusion, our study identifies REG2 as a novel regulator of Ca2+ influx and insulin secretion, and reveals a new cascade of GPX1/REG2/CaV1.2 to explain how REG2 depletion in OE islets could decrease its binding to CaV1.2, resulting in uninhibited Ca2+ influx and augmented GSIS. These findings create new links to bridge redox biology, tissue regeneration, and insulin secretion.
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Affiliation(s)
- Xi Yan
- Department of Animal Science, Cornell University, Ithaca, NY, 14853, USA
| | - Zeping Zhao
- Department of Animal Science, Cornell University, Ithaca, NY, 14853, USA
| | - Jeremy Weaver
- Department of Animal Science, Cornell University, Ithaca, NY, 14853, USA
| | - Tao Sun
- Department of Animal Science, Cornell University, Ithaca, NY, 14853, USA
| | - Jun-Won Yun
- Department of Animal Science, Cornell University, Ithaca, NY, 14853, USA; Laboratory of Veterinary Toxicology, College of Veterinary Medicine, Seoul National University, Seoul, 08826, Republic of Korea
| | - Carol A Roneker
- Department of Animal Science, Cornell University, Ithaca, NY, 14853, USA
| | - Fenghua Hu
- Department of Molecular Biology and Genetics, Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY, 14853, USA
| | - Nicolai M Doliba
- Institute of Diabetes, Obesity and Metabolism, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | | | - Marko Z Vatamaniuk
- Department of Animal Science, Cornell University, Ithaca, NY, 14853, USA.
| | - Xin Gen Lei
- Department of Animal Science, Cornell University, Ithaca, NY, 14853, USA.
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2
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Rafiei N, Moghadam MG, Au A, Regeenes R, Chidambaram S, Liang T, Wang Y, Yip CM, Gaisano H, Rocheleau JV. Design of a versatile microfluidic device for imaging precision-cut-tissue slices. Biofabrication 2022; 14. [PMID: 35793653 DOI: 10.1088/1758-5090/ac7eea] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Accepted: 07/06/2022] [Indexed: 11/12/2022]
Abstract
Precision-cut-tissues (PCTs), which preserve many aspects of a tissue's microenvironment, are typically imaged using conventional sample dishes and chambers. These can require large amounts of reagent and, when used for flow-through experiments, the shear forces applied on the tissues are often ill-defined. Their physical design also makes it difficult to image large volumes and repetitively image smaller regions of interest in the living slice. We report here on the design of a versatile microfluidic device capable of holding mouse or human pancreas PCTs for 3D fluorescence imaging using confocal and selective plane illumination microscopy (SPIM). Our design positions PCTs within a 5 × 5 mm × 140µm deep chamber fitted with 150µm tall channels to facilitate media exchange. Shear stress in the device is localized to small regions on the surface of the tissue and can be easily controlled. This design allows for media exchange at flowrates ∼10-fold lower than those required for conventional chambers. Finally, this design allows for imaging the same immunofluorescently labeled PCT with high resolution on a confocal and with large field of view on a SPIM, without adversely affecting image quality.
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Affiliation(s)
- Nafiseh Rafiei
- Advanced Diagnostics, Toronto General Hospital Research Institute, Toronto, ON, Canada
| | - Mohammadamir G Moghadam
- Advanced Diagnostics, Toronto General Hospital Research Institute, Toronto, ON, Canada.,Institute of Biomedical Engineering, University of Toronto, Toronto, ON, Canada
| | - Aaron Au
- Institute of Biomedical Engineering, University of Toronto, Toronto, ON, Canada.,Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, ON, Canada
| | - Romario Regeenes
- Advanced Diagnostics, Toronto General Hospital Research Institute, Toronto, ON, Canada.,Institute of Biomedical Engineering, University of Toronto, Toronto, ON, Canada
| | | | - Tao Liang
- Department of Medicine, University of Toronto, Toronto, ON, Canada
| | - Yufeng Wang
- Advanced Diagnostics, Toronto General Hospital Research Institute, Toronto, ON, Canada.,Institute of Biomedical Engineering, University of Toronto, Toronto, ON, Canada
| | - Christopher M Yip
- Institute of Biomedical Engineering, University of Toronto, Toronto, ON, Canada.,Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, ON, Canada.,Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, ON, Canada.,Department of Biochemistry, University of Toronto, Toronto, ON, Canada
| | - Herbert Gaisano
- Advanced Diagnostics, Toronto General Hospital Research Institute, Toronto, ON, Canada.,Department of Medicine, University of Toronto, Toronto, ON, Canada.,Department of Physiology, University of Toronto, Toronto, ON, Canada
| | - Jonathan V Rocheleau
- Advanced Diagnostics, Toronto General Hospital Research Institute, Toronto, ON, Canada.,Institute of Biomedical Engineering, University of Toronto, Toronto, ON, Canada.,Department of Medicine, University of Toronto, Toronto, ON, Canada.,Department of Physiology, University of Toronto, Toronto, ON, Canada
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3
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Slepchenko KG, Chen S, Counts GP, Corbin KL, Colvin RA, Nunemaker CS. Synchrotron fluorescence imaging of individual mouse beta-cells reveals changes in zinc, calcium, and iron in a model of low-grade inflammation. Metallomics 2021; 13:6353533. [PMID: 34402906 DOI: 10.1093/mtomcs/mfab051] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Accepted: 08/02/2021] [Indexed: 12/31/2022]
Abstract
Pancreatic beta-cells synthesize and secrete insulin maintaining an organism's energy homeostasis. In humans, beta-cell dysfunction and death contribute to the pathogenesis of type 2 diabetes (T2D). Although the causes of beta-cell dysfunction are complex, obesity-induced low-grade systemic inflammation plays a role. For example, obese individuals exhibiting increased levels of proinflammatory cytokines IL-6 and IL-1beta have a higher risk of beta-cell dysfunction and T2D. Interestingly, obesity-induced inflammation changes the expression of several cellular metal regulating genes, prompting this study to examine changes in the beta-cell metallome after exposure to proinflammatory-cytokines. Primary mouse beta-cells were exposed to a combination of IL-6 and IL-1beta for 48 hours, were chemically fixed and imaged by synchrotron X-ray fluorescent microscopy. Quantitative analysis showed a surprising 2.4-fold decrease in the mean total cellular content of zinc from 158 ± 57.7 femtograms (fg) to 65.7 ± 29.7 fg; calcium decreased from 216 ± 67.4 to 154.3 ± 68.7 fg (control vs. cytokines, respectively). The mean total cellular iron content slightly increased from 30.4 ± 12.2 to 47.2 ± 36.4 fg after cytokine treatment; a sub-population of cells (38%) exhibited larger increases of iron density. Changes in the subcellular distributions of zinc and calcium were observed after cytokine exposure. Beta-cells contained numerous iron puncta that accumulated still more iron after exposure to cytokines. These findings provide evidence that exposure to low levels of cytokines is sufficient to cause changes in the total cellular content and/or subcellular distribution of several metals known to be critical for normal beta-cell function.
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Affiliation(s)
- Kira G Slepchenko
- Department of Biological Sciences, Ohio University, Athens, Ohio, USA.,Molecular and Cellular Biology, Ohio University, Athens, Ohio, USA.,Department of Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University, Athens, Ohio, USA
| | - Si Chen
- Advanced Photon Source, Argonne National Laboratory, Lemont, Illinois, USA
| | - Grace P Counts
- Department of Biological Sciences, Ohio University, Athens, Ohio, USA
| | - Kathryn L Corbin
- Department of Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University, Athens, Ohio, USA
| | - Robert A Colvin
- Department of Biological Sciences, Ohio University, Athens, Ohio, USA.,Molecular and Cellular Biology, Ohio University, Athens, Ohio, USA
| | - Craig S Nunemaker
- Molecular and Cellular Biology, Ohio University, Athens, Ohio, USA.,Department of Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University, Athens, Ohio, USA
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4
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Corbin KL, West HL, Brodsky S, Whitticar NB, Koch WJ, Nunemaker CS. A Practical Guide to Rodent Islet Isolation and Assessment Revisited. Biol Proced Online 2021; 23:7. [PMID: 33641671 DOI: 10.1186/s12575-021-00143-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2020] [Accepted: 01/26/2021] [Indexed: 02/06/2023] Open
Abstract
Insufficient insulin secretion is a key component of both type 1 and type 2 diabetes. Since insulin is released by the islets of Langerhans, obtaining viable and functional islets is critical for research and transplantation. The effective and efficient isolation of these small islands of endocrine cells from the sea of exocrine tissue that is the rest of the pancreas is not necessarily simple or quick. Choosing and administering the digestive enzyme, separation of the islets from acinar tissue, and culture of islets are all things that must be considered. The purpose of this review is to provide a history of the development of islet isolation procedures and to serve as a practical guide to rodent islet research for newcomers to islet biology. We discuss key elements of mouse islet isolation including choosing collagenase, the digestion process, purification of islets using a density gradient, and islet culture conditions. In addition, this paper reviews techniques for assessing islet viability and function such as visual assessment, glucose-stimulated insulin secretion and intracellular calcium measurements. A detailed protocol is provided that describes a common method our laboratory uses to obtain viable and functional mouse islets for in vitro study. This review thus provides a strong foundation for successful procurement and purification of high-quality mouse islets for research purposes.
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5
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West HL, Corbin KL, D'Angelo CV, Donovan LM, Jahan I, Gu G, Nunemaker CS. Postnatal maturation of calcium signaling in islets of Langerhans from neonatal mice. Cell Calcium 2021; 94:102339. [PMID: 33422769 DOI: 10.1016/j.ceca.2020.102339] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2020] [Revised: 12/20/2020] [Accepted: 12/21/2020] [Indexed: 01/02/2023]
Abstract
Pancreatic islet cells develop mature physiological responses to glucose and other fuels postnatally. In this study, we used fluorescence imaging techniques to measure changes in intracellular calcium ([Ca2+]i) to compare islets isolated from mice on postnatal days 0, 4, and 12 with islets from adult CD-1 mice. In addition, we used publicly available RNA-sequencing data to compare expression levels of key genes in β-cell physiology with [Ca2+]i data across these ages. We show that islets isolated from mice on postnatal day 0 displayed elevated [Ca2+]i in basal glucose (≤4 mM) but lower [Ca2+]i responses to stimulation by 12-20 mM glucose compared to adult. Neonatal islets displayed more adult-like [Ca2+]i in basal glucose by day 4 but continued to show lower [Ca2+]i responses to 16 and 20 mM glucose stimulation up to at least day 12. A right shift in glucose sensing (EC50) correlated with lower fragment-per-kilobase-of-transcript-per-million-reads-mapped (FPKM) of Slc2a2 (glut2) and Actn3 and increased FPKM for Galk1 and Nupr1. Differences in [Ca2+]i responses to additional stimuli were also observed. Calcium levels in the endoplasmic reticulum were elevated on day 0 but became adult-like by day 4, which corresponded with reduced expression in Atp2a2 (SERCA2) and novel K+-channel Ktd17, increased expression of Pml, Wfs1, Thada, and Herpud1, and basal [Ca2+]i maturing to adult levels. Ion-channel activity also matured rapidly, but RNA sequencing data mining did not yield strong leads. In conclusion, the maturation of islet [Ca2+]i signaling is complex and multifaceted; several possible gene targets were identified that may participate in this process.
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Law NC, Marinelli I, Bertram R, Corbin KL, Schildmeyer C, Nunemaker CS. Chronic stimulation induces adaptive potassium channel activity that restores calcium oscillations in pancreatic islets in vitro. Am J Physiol Endocrinol Metab 2020; 318:E554-E563. [PMID: 32069073 PMCID: PMC7191410 DOI: 10.1152/ajpendo.00482.2019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Insulin pulsatility is important to hepatic response in regulating blood glucose. Growing evidence suggests that insulin-secreting pancreatic β-cells can adapt to chronic disruptions of pulsatility to rescue this physiologically important behavior. We determined the time scale for adaptation and examined potential ion channels underlying it. We induced the adaptation both by chronic application of the ATP-sensitive K+ [K(ATP)] channel blocker tolbutamide and by application of the depolarizing agent potassium chloride (KCl). Acute application of tolbutamide without pretreatment results in elevated Ca2+ as measured by fura-2AM and the loss of endogenous pulsatility. We show that after chronic exposure to tolbutamide (12-24 h), Ca2+ oscillations occur with subsequent acute tolbutamide application. The same experiment was conducted with potassium chloride (KCl) to directly depolarize the β-cells. Once again, following chronic exposure to the cell stimulator, the islets produced Ca2+ oscillations when subsequently exposed to tolbutamide. These experiments suggest that it is the chronic stimulation, and not tolbutamide desensitization, that is responsible for the adaptation that rescues oscillatory β-cell activity. This compensatory response also causes islet glucose sensitivity to shift rightward following chronic tolbutamide treatment. Mathematical modeling shows that a small increase in the number of K(ATP) channels in the membrane is one adaptation mechanism that is compatible with the data. To examine other compensatory mechanisms, pharmacological studies provide support that Kir2.1 and TEA-sensitive channels play some role. Overall, this investigation demonstrates β-cell adaptability to overstimulation, which is likely an important mechanism for maintaining glucose homeostasis in the face of chronic stimulation.
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Affiliation(s)
- Nathan C Law
- Department of Biomedical Sciences Heritage College of Osteopathic Medicine, Ohio University, Athens, Ohio
- Diabetes Institute, Heritage College of Osteopathic Medicine, Ohio University, Athens, Ohio
| | | | - Richard Bertram
- Department of Mathematics and Programs in Neuroscience and Molecular Biophysics, Florida State University, Tallahassee, Florida
| | - Kathryn L Corbin
- Department of Biomedical Sciences Heritage College of Osteopathic Medicine, Ohio University, Athens, Ohio
- Diabetes Institute, Heritage College of Osteopathic Medicine, Ohio University, Athens, Ohio
| | - Cara Schildmeyer
- Department of Biomedical Sciences Heritage College of Osteopathic Medicine, Ohio University, Athens, Ohio
- Diabetes Institute, Heritage College of Osteopathic Medicine, Ohio University, Athens, Ohio
| | - Craig S Nunemaker
- Department of Biomedical Sciences Heritage College of Osteopathic Medicine, Ohio University, Athens, Ohio
- Diabetes Institute, Heritage College of Osteopathic Medicine, Ohio University, Athens, Ohio
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7
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Scarl RT, Corbin KL, Vann NW, Smith HM, Satin LS, Sherman A, Nunemaker CS. Intact pancreatic islets and dispersed beta-cells both generate intracellular calcium oscillations but differ in their responsiveness to glucose. Cell Calcium 2019; 83:102081. [PMID: 31563790 DOI: 10.1016/j.ceca.2019.102081] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2019] [Revised: 09/12/2019] [Accepted: 09/14/2019] [Indexed: 01/19/2023]
Abstract
Pancreatic islets produce pulses of insulin and other hormones that maintain normal glucose homeostasis. These micro-organs possess exquisite glucose-sensing capabilities, allowing for precise changes in pulsatile insulin secretion in response to small changes in glucose. When communication among these cells is disrupted, precision glucose sensing falters. We measured intracellular calcium patterns in 6-mM-steps between 0 and 16 mM glucose, and also more finely in 2-mM-steps from 8 to 12 mM glucose, to compare glucose sensing systematically among intact islets and dispersed islet cells derived from the same mouse pancreas in vitro. The calcium activity of intact islets was uniformly low (quiescent) below 4 mM glucose and active above 8 mM glucose, whereas dispersed beta-cells displayed a broader activation range (2-to-10 mM). Intact islets exhibited calcium oscillations with 2-to-5-min periods, yet beta-cells exhibited longer 7-10 min periods. In every case, intact islets showed changes in activity with each 6-mM-glucose step, whereas dispersed islet cells displayed a continuum of calcium responses ranging from islet-like patterns to stable oscillations unaffected by changes in glucose concentration. These differences were also observed for 2-mM-glucose steps. Despite the diversity of dispersed beta-cell responses to glucose, the sum of all activity produced a glucose dose-response curve that was surprisingly similar to the curve for intact islets, arguing against the importance of "hub cells" for function. Beta-cells thus retain many of the features of islets, but some are more islet-like than others. Determining the molecular underpinnings of these variations could be valuable for future studies of stem-cell-derived beta-cell therapies.
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Affiliation(s)
- Rachel T Scarl
- Department of Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University, Athens, OH, United States
| | - Kathryn L Corbin
- Department of Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University, Athens, OH, United States; Diabetes Institute, Heritage College of Osteopathic Medicine, Ohio University, Athens, OH, United States
| | - Nicholas W Vann
- Department of Biomedical Engineering, University of Virginia, Charlottesville, VA, United States
| | - Hallie M Smith
- Department of Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University, Athens, OH, United States
| | - Leslie S Satin
- Brehm Diabetes Research Center, University of Michigan Medical School, Ann Arbor, MI, United States; Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI, United States
| | - Arthur Sherman
- Laboratory of Biological Modeling, NIDDK, NIH, Bethesda, MD, United States
| | - Craig S Nunemaker
- Department of Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University, Athens, OH, United States; Diabetes Institute, Heritage College of Osteopathic Medicine, Ohio University, Athens, OH, United States.
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8
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Jahan I, Corbin KL, Bogart AM, Whitticar NB, Waters CD, Schildmeyer C, Vann NW, West HL, Law NC, Wiseman JS, Nunemaker CS. Reducing Glucokinase Activity Restores Endogenous Pulsatility and Enhances Insulin Secretion in Islets From db/db Mice. Endocrinology 2018; 159:3747-3760. [PMID: 30239634 PMCID: PMC6202857 DOI: 10.1210/en.2018-00589] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/15/2018] [Accepted: 09/12/2018] [Indexed: 12/22/2022]
Abstract
An early sign of islet failure in type 2 diabetes (T2D) is the loss of normal patterns of pulsatile insulin release. Disruptions in pulsatility are associated with a left shift in glucose sensing that can cause excessive insulin release in low glucose (relative hyperinsulinemia, a hallmark of early T2D) and β-cell exhaustion, leading to inadequate insulin release during hyperglycemia. Our hypothesis was that reducing excessive glucokinase activity in diabetic islets would improve their function. Isolated mouse islets were exposed to glucose and varying concentrations of the glucokinase inhibitor d-mannoheptulose (MH) to examine changes in intracellular calcium ([Ca2+]i) and insulin secretion. Acutely exposing islets from control CD-1 mice to MH in high glucose (20 mM) dose dependently reduced the size of [Ca2+]i oscillations detected by fura-2 acetoxymethyl. Glucokinase activation in low glucose (3 mM) had the opposite effect. We then treated islets from male and female db/db mice (age, 4 to 8 weeks) and heterozygous controls overnight with 0 to 10 mM MH to determine that 1 mM MH produced optimal oscillations. We then used 1 mM MH overnight to measure [Ca2+]i and insulin simultaneously in db/db islets. MH restored oscillations and increased insulin secretion. Insulin secretion rates correlated with MH-induced increases in amplitude of [Ca2+]i oscillations (R2 = 0.57, P < 0.01, n = 10) but not with mean [Ca2+]i levels in islets (R2 = 0.05, not significant). Our findings show that correcting glucose sensing can restore proper pulsatility to diabetic islets and improved pulsatility correlates with enhanced insulin secretion.
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Affiliation(s)
- Ishrat Jahan
- Department of Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University, Athens, Ohio
- Diabetes Institute, Heritage College of Osteopathic Medicine, Ohio University, Athens, Ohio
| | - Kathryn L Corbin
- Department of Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University, Athens, Ohio
- Diabetes Institute, Heritage College of Osteopathic Medicine, Ohio University, Athens, Ohio
| | - Avery M Bogart
- Department of Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University, Athens, Ohio
- Honors Tutorial College, Ohio University, Athens, Ohio
| | - Nicholas B Whitticar
- Department of Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University, Athens, Ohio
| | - Christopher D Waters
- Department of Biomedical Engineering, University of Virginia, Charlottesville, Virginia
| | - Cara Schildmeyer
- Department of Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University, Athens, Ohio
- Honors Tutorial College, Ohio University, Athens, Ohio
| | - Nicholas W Vann
- Department of Biomedical Engineering, University of Virginia, Charlottesville, Virginia
| | - Hannah L West
- Department of Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University, Athens, Ohio
- Honors Tutorial College, Ohio University, Athens, Ohio
| | - Nathan C Law
- Department of Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University, Athens, Ohio
| | | | - Craig S Nunemaker
- Department of Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University, Athens, Ohio
- Diabetes Institute, Heritage College of Osteopathic Medicine, Ohio University, Athens, Ohio
- Correspondence: Craig S. Nunemaker, PhD, Department of Biomedical Sciences, 228 Irvine Hall, Ohio University Heritage College of Osteopathic Medicine, Athens, Ohio 45701. E-mail:
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9
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Roder P, Hille C. Local tissue manipulation via a force- and pressure-controlled AFM micropipette for analysis of cellular processes. Sci Rep 2018; 8:5892. [PMID: 29651136 PMCID: PMC5897369 DOI: 10.1038/s41598-018-24255-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2018] [Accepted: 03/28/2018] [Indexed: 11/08/2022] Open
Abstract
Local manipulation of complex tissues at the single-cell level is challenging and requires excellent sealing between the specimen and the micromanipulation device. Here, biological applications for a recently developed loading technique for a force- and pressure-controlled fluidic force microscope micropipette are described. This technique allows for the exact positioning and precise spatiotemporal control of liquid delivery. The feasibility of a local loading technique for tissue applications was investigated using two fluorescent dyes, with which local loading behaviour could be optically visualised. Thus, homogeneous intracellular distribution of CellTracker Red and accumulation of SYTO 9 Green within nuclei was realised in single cells of a tissue preparation. Subsequently, physiological micromanipulation experiments were performed. Salivary gland tissue was pre-incubated with the Ca2+-sensitive dye OGB-1. An intracellular Ca2+ rise was then initiated at the single-cell level by applying dopamine via micropipette. When pre-incubating tissue with the nitric oxide (NO)-sensitive dye DAF-FM, NO release and intercellular NO diffusion was observed after local application of the NO donor SNP. Finally, local micromanipulation of a well-defined area along irregularly shaped cell surfaces of complex biosystems was shown for the first time for the fluidic force microscope micropipette. Thus, this technique is a promising tool for the investigation of the spatiotemporal effects of locally applied substances in complex tissues.
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Affiliation(s)
- Phillip Roder
- Department of Physical Chemistry/Applied Laser Sensing in Complex Biosystems (ALS ComBi), Institute of Chemistry, University of Potsdam, Potsdam, Germany
| | - Carsten Hille
- Department of Physical Chemistry/Applied Laser Sensing in Complex Biosystems (ALS ComBi), Institute of Chemistry, University of Potsdam, Potsdam, Germany.
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10
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Gelin L, Li J, Corbin KL, Jahan I, Nunemaker CS. Metformin Inhibits Mouse Islet Insulin Secretion and Alters Intracellular Calcium in a Concentration-Dependent and Duration-Dependent Manner near the Circulating Range. J Diabetes Res 2018; 2018:9163052. [PMID: 29862303 PMCID: PMC5971297 DOI: 10.1155/2018/9163052] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Revised: 12/25/2017] [Accepted: 01/17/2018] [Indexed: 12/23/2022] Open
Abstract
Metformin is considered the first-line treatment for type 2 diabetes. While metformin primarily increases insulin sensitivity, evidence also suggests that metformin affects the activity of insulin-secreting pancreatic islets. This study was designed to systematically examine the direct effects of metformin by measuring insulin secretion and the kinetics of the calcium response to glucose stimulation in isolated mouse islets using varying concentrations (20 μM, 200 μM, and 1 mM) and durations (~1, 2, and 3 days) of metformin exposure. We observed both concentration- and duration-dependent inhibitory effects of metformin. Concentrations as little as 20 μM (nearing circulating therapeutic levels) were sufficient to reduce insulin secretion following 3-day treatment. Concentrations of 200 μM and 1 mM produced more pronounced effects more rapidly. With 1 mM metformin, islets showed severe impairments in calcium handling, inhibition of insulin secretion, and increased cell death. No stimulatory effects of metformin were observed for any experimental endpoint. We conclude that the direct effects of metformin on islets are inhibitory at near-physiological concentrations. Beneficial effects of metformin observed on islets under various stressors may occur by "resting" fatigued cellular processes. However, metformin may have unintended consequences on normally functioning islets within the circulating range that require further evaluation.
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Affiliation(s)
- Lindor Gelin
- Department of Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University, Athens, OH, USA
| | - Jiewen Li
- Department of Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University, Athens, OH, USA
| | - Kathryn L. Corbin
- Department of Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University, Athens, OH, USA
| | - Ishrat Jahan
- Department of Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University, Athens, OH, USA
| | - Craig S. Nunemaker
- Department of Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University, Athens, OH, USA
- Diabetes Institute, Heritage College of Osteopathic Medicine, Ohio University, Athens, OH, USA
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11
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Corbin KL, Waters CD, Shaffer BK, Verrilli GM, Nunemaker CS. Islet Hypersensitivity to Glucose Is Associated With Disrupted Oscillations and Increased Impact of Proinflammatory Cytokines in Islets From Diabetes-Prone Male Mice. Endocrinology 2016; 157:1826-38. [PMID: 26943366 PMCID: PMC4870867 DOI: 10.1210/en.2015-1879] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Pulsatile insulin release is the primary means of blood glucose regulation. The loss of pulsatility is thought to be an early marker and possible factor in developing type 2 diabetes. Another early adaptation in islet function to compensate for obesity is increased glucose sensitivity (left shift) associated with increased basal insulin release. We provide evidence that oscillatory disruptions may be linked with overcompensation (glucose hypersensitivity) in islets from diabetes-prone mice. We isolated islets from male 4- to 5-week-old (prediabetic) and 10- to 12-week-old (diabetic) leptin-receptor-deficient (db/db) mice and age-matched heterozygous controls. After an overnight incubation in media with 11 mM glucose, we measured islet intracellular calcium in 5, 8, 11, or 15 mM glucose. Islets from heterozygous 10- to 12-week-old mice were quiescent in 5 mM glucose and displayed oscillations with increasing amplitude and/or duration in 8, 11, and 15 mM glucose, respectively. Islets from diabetic 10- to 12-week-old mice, in contrast, showed robust oscillations in 5 mM glucose that declined with increasing glucose. Similar trends were observed at 4-5-weeks of age. A progressive left shift in maximal insulin release was also observed in islets as db/db mice aged. Reducing glucokinase activity with 1 mM D-mannoheptulose restored oscillations in 11 mM glucose. Finally, overnight low-dose cytokine exposure negatively impacted oscillations preferentially in high glucose in diabetic islets compared with heterozygous controls. Our findings suggest the following: 1) islets from frankly diabetic mice can produce oscillations, 2) elevated sensitivity to glucose prevents diabetic mouse islets from producing oscillations in normal postprandial (11-15 mM glucose) conditions, and 3) hypersensitivity to glucose may magnify stress effects from inflammation or other sources.
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Affiliation(s)
- Kathryn L Corbin
- Department of Biomedical Sciences (K.L.C., C.S.N.), Heritage College of Osteopathic Medicine, and Diabetes Institute (K.L.C., C.S.N.), Ohio University, Athens, Ohio 45701; and Departments of Medicine (C.D.W., B.K.S., G.M.V.) and Biomedical Engineering (C.D.W.), University of Virginia, Charlottesville, Virginia 22908
| | - Christopher D Waters
- Department of Biomedical Sciences (K.L.C., C.S.N.), Heritage College of Osteopathic Medicine, and Diabetes Institute (K.L.C., C.S.N.), Ohio University, Athens, Ohio 45701; and Departments of Medicine (C.D.W., B.K.S., G.M.V.) and Biomedical Engineering (C.D.W.), University of Virginia, Charlottesville, Virginia 22908
| | - Brett K Shaffer
- Department of Biomedical Sciences (K.L.C., C.S.N.), Heritage College of Osteopathic Medicine, and Diabetes Institute (K.L.C., C.S.N.), Ohio University, Athens, Ohio 45701; and Departments of Medicine (C.D.W., B.K.S., G.M.V.) and Biomedical Engineering (C.D.W.), University of Virginia, Charlottesville, Virginia 22908
| | - Gretchen M Verrilli
- Department of Biomedical Sciences (K.L.C., C.S.N.), Heritage College of Osteopathic Medicine, and Diabetes Institute (K.L.C., C.S.N.), Ohio University, Athens, Ohio 45701; and Departments of Medicine (C.D.W., B.K.S., G.M.V.) and Biomedical Engineering (C.D.W.), University of Virginia, Charlottesville, Virginia 22908
| | - Craig S Nunemaker
- Department of Biomedical Sciences (K.L.C., C.S.N.), Heritage College of Osteopathic Medicine, and Diabetes Institute (K.L.C., C.S.N.), Ohio University, Athens, Ohio 45701; and Departments of Medicine (C.D.W., B.K.S., G.M.V.) and Biomedical Engineering (C.D.W.), University of Virginia, Charlottesville, Virginia 22908
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Nunemaker CS. Considerations for Defining Cytokine Dose, Duration, and Milieu That Are Appropriate for Modeling Chronic Low-Grade Inflammation in Type 2 Diabetes. J Diabetes Res 2016; 2016:2846570. [PMID: 27843953 PMCID: PMC5097812 DOI: 10.1155/2016/2846570] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/22/2016] [Accepted: 09/25/2016] [Indexed: 02/07/2023] Open
Abstract
Proinflammatory cytokines have been implicated in the pathophysiology of both type 1 diabetes (T1D) and type 2 diabetes (T2D). T1D is an autoimmune disease involving the adaptive immune system responding to pancreatic beta-cells as antigen-presenting cells. This attracts immune cells that surround pancreatic islets (insulitis) and secrete cytokines, such as IL-1beta, IFN-gamma, and TNF-alpha, in close proximity to pancreatic beta-cells. In contrast, there is little evidence for such a focused autoimmune response in T2D. Instead, the innate immune system, which responds to cellular damage and pathogens, appears to play a key role. There are three major sources of proinflammatory cytokines that may impact islet/beta-cell function in T2D: (1) from islet cells, (2) from increased numbers of intraislet macrophages/immune cells, and (3) from increased circulating levels of proinflammatory cytokines due to obesity, presumably coming from inflamed adipose tissue. These differences between T1D and T2D are reflected by significant differences in the cytokine concentration, duration, and milieu. This review focuses on chronic versus acute cytokine action, cytokine concentrations, and cytokine milieu from the perspective of the pancreatic islet in T2D. We conclude that new cytokine models may be needed to reflect the pathophysiology of T2D more effectively than what are currently employed.
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Affiliation(s)
- Craig S. Nunemaker
- Diabetes Institute, Heritage College of Osteopathic Medicine, Ohio University, Athens, OH, USA
- Department of Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University, Athens, OH, USA
- *Craig S. Nunemaker:
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Sharma PR, Mackey AJ, Dejene EA, Ramadan JW, Langefeld CD, Palmer ND, Taylor KD, Wagenknecht LE, Watanabe RM, Rich SS, Nunemaker CS. An Islet-Targeted Genome-Wide Association Scan Identifies Novel Genes Implicated in Cytokine-Mediated Islet Stress in Type 2 Diabetes. Endocrinology 2015; 156:3147-56. [PMID: 26018251 PMCID: PMC4541617 DOI: 10.1210/en.2015-1203] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Genome-wide association studies in human type 2 diabetes (T2D) have renewed interest in the pancreatic islet as a contributor to T2D risk. Chronic low-grade inflammation resulting from obesity is a risk factor for T2D and a possible trigger of β-cell failure. In this study, microarray data were collected from mouse islets after overnight treatment with cytokines at concentrations consistent with the chronic low-grade inflammation in T2D. Genes with a cytokine-induced change of >2-fold were then examined for associations between single nucleotide polymorphisms and the acute insulin response to glucose (AIRg) using data from the Genetics Underlying Diabetes in Hispanics (GUARDIAN) Consortium. Significant evidence of association was found between AIRg and single nucleotide polymorphisms in Arap3 (5q31.3), F13a1 (6p25.3), Klhl6 (3q27.1), Nid1 (1q42.3), Pamr1 (11p13), Ripk2 (8q21.3), and Steap4 (7q21.12). To assess the potential relevance to islet function, mouse islets were exposed to conditions modeling low-grade inflammation, mitochondrial stress, endoplasmic reticulum (ER) stress, glucotoxicity, and lipotoxicity. RT-PCR revealed that one or more forms of stress significantly altered expression levels of all genes except Arap3. Thapsigargin-induced ER stress up-regulated both Pamr1 and Klhl6. Three genes confirmed microarray predictions of significant cytokine sensitivity: F13a1 was down-regulated 3.3-fold by cytokines, Ripk2 was up-regulated 1.5- to 3-fold by all stressors, and Steap4 was profoundly cytokine sensitive (167-fold up-regulation). Three genes were thus closely associated with low-grade inflammation in murine islets and also with a marker for islet function (AIRg) in a diabetes-prone human population. This islet-targeted genome-wide association scan identified several previously unrecognized candidate genes related to islet dysfunction during the development of T2D.
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Affiliation(s)
- Poonam R Sharma
- Department of Medicine (P.R.S., E.A.D., J.W.R., C.S.N.), Center for Public Health Genomics (A.J.M., S.S.R.), and Department of Chemistry (E.A.D.), University of Virginia, Charlottesville, Virginia 22904; Department of Biochemistry (N.D.P.), Center for Genomics and Personalized Medicine Research (N.D.P.), Center for Diabetes Research (N.D.P.), Center for Public Health Genomics (C.D.L., N.D.P., L.E.W.), Department of Biostatistical Sciences (C.D.L.), and Division of Public Health Sciences (L.E.W.), Wake Forest School of Medicine, Winston-Salem, North Carolina 27157; Department of Physiology and Biophysics (R.M.W.), Department of Preventive Medicine, and USC Diabetes and Obesity Research Institute (R.M.W.), Keck School of Medicine of University of Southern California, Los Angeles, California 90033; and Institute for Translational Genomics and Population Sciences (K.D.T.) and Department of Pediatrics (K.D.T.), Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California 90502
| | - Aaron J Mackey
- Department of Medicine (P.R.S., E.A.D., J.W.R., C.S.N.), Center for Public Health Genomics (A.J.M., S.S.R.), and Department of Chemistry (E.A.D.), University of Virginia, Charlottesville, Virginia 22904; Department of Biochemistry (N.D.P.), Center for Genomics and Personalized Medicine Research (N.D.P.), Center for Diabetes Research (N.D.P.), Center for Public Health Genomics (C.D.L., N.D.P., L.E.W.), Department of Biostatistical Sciences (C.D.L.), and Division of Public Health Sciences (L.E.W.), Wake Forest School of Medicine, Winston-Salem, North Carolina 27157; Department of Physiology and Biophysics (R.M.W.), Department of Preventive Medicine, and USC Diabetes and Obesity Research Institute (R.M.W.), Keck School of Medicine of University of Southern California, Los Angeles, California 90033; and Institute for Translational Genomics and Population Sciences (K.D.T.) and Department of Pediatrics (K.D.T.), Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California 90502
| | - Eden A Dejene
- Department of Medicine (P.R.S., E.A.D., J.W.R., C.S.N.), Center for Public Health Genomics (A.J.M., S.S.R.), and Department of Chemistry (E.A.D.), University of Virginia, Charlottesville, Virginia 22904; Department of Biochemistry (N.D.P.), Center for Genomics and Personalized Medicine Research (N.D.P.), Center for Diabetes Research (N.D.P.), Center for Public Health Genomics (C.D.L., N.D.P., L.E.W.), Department of Biostatistical Sciences (C.D.L.), and Division of Public Health Sciences (L.E.W.), Wake Forest School of Medicine, Winston-Salem, North Carolina 27157; Department of Physiology and Biophysics (R.M.W.), Department of Preventive Medicine, and USC Diabetes and Obesity Research Institute (R.M.W.), Keck School of Medicine of University of Southern California, Los Angeles, California 90033; and Institute for Translational Genomics and Population Sciences (K.D.T.) and Department of Pediatrics (K.D.T.), Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California 90502
| | - James W Ramadan
- Department of Medicine (P.R.S., E.A.D., J.W.R., C.S.N.), Center for Public Health Genomics (A.J.M., S.S.R.), and Department of Chemistry (E.A.D.), University of Virginia, Charlottesville, Virginia 22904; Department of Biochemistry (N.D.P.), Center for Genomics and Personalized Medicine Research (N.D.P.), Center for Diabetes Research (N.D.P.), Center for Public Health Genomics (C.D.L., N.D.P., L.E.W.), Department of Biostatistical Sciences (C.D.L.), and Division of Public Health Sciences (L.E.W.), Wake Forest School of Medicine, Winston-Salem, North Carolina 27157; Department of Physiology and Biophysics (R.M.W.), Department of Preventive Medicine, and USC Diabetes and Obesity Research Institute (R.M.W.), Keck School of Medicine of University of Southern California, Los Angeles, California 90033; and Institute for Translational Genomics and Population Sciences (K.D.T.) and Department of Pediatrics (K.D.T.), Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California 90502
| | - Carl D Langefeld
- Department of Medicine (P.R.S., E.A.D., J.W.R., C.S.N.), Center for Public Health Genomics (A.J.M., S.S.R.), and Department of Chemistry (E.A.D.), University of Virginia, Charlottesville, Virginia 22904; Department of Biochemistry (N.D.P.), Center for Genomics and Personalized Medicine Research (N.D.P.), Center for Diabetes Research (N.D.P.), Center for Public Health Genomics (C.D.L., N.D.P., L.E.W.), Department of Biostatistical Sciences (C.D.L.), and Division of Public Health Sciences (L.E.W.), Wake Forest School of Medicine, Winston-Salem, North Carolina 27157; Department of Physiology and Biophysics (R.M.W.), Department of Preventive Medicine, and USC Diabetes and Obesity Research Institute (R.M.W.), Keck School of Medicine of University of Southern California, Los Angeles, California 90033; and Institute for Translational Genomics and Population Sciences (K.D.T.) and Department of Pediatrics (K.D.T.), Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California 90502
| | - Nicholette D Palmer
- Department of Medicine (P.R.S., E.A.D., J.W.R., C.S.N.), Center for Public Health Genomics (A.J.M., S.S.R.), and Department of Chemistry (E.A.D.), University of Virginia, Charlottesville, Virginia 22904; Department of Biochemistry (N.D.P.), Center for Genomics and Personalized Medicine Research (N.D.P.), Center for Diabetes Research (N.D.P.), Center for Public Health Genomics (C.D.L., N.D.P., L.E.W.), Department of Biostatistical Sciences (C.D.L.), and Division of Public Health Sciences (L.E.W.), Wake Forest School of Medicine, Winston-Salem, North Carolina 27157; Department of Physiology and Biophysics (R.M.W.), Department of Preventive Medicine, and USC Diabetes and Obesity Research Institute (R.M.W.), Keck School of Medicine of University of Southern California, Los Angeles, California 90033; and Institute for Translational Genomics and Population Sciences (K.D.T.) and Department of Pediatrics (K.D.T.), Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California 90502
| | - Kent D Taylor
- Department of Medicine (P.R.S., E.A.D., J.W.R., C.S.N.), Center for Public Health Genomics (A.J.M., S.S.R.), and Department of Chemistry (E.A.D.), University of Virginia, Charlottesville, Virginia 22904; Department of Biochemistry (N.D.P.), Center for Genomics and Personalized Medicine Research (N.D.P.), Center for Diabetes Research (N.D.P.), Center for Public Health Genomics (C.D.L., N.D.P., L.E.W.), Department of Biostatistical Sciences (C.D.L.), and Division of Public Health Sciences (L.E.W.), Wake Forest School of Medicine, Winston-Salem, North Carolina 27157; Department of Physiology and Biophysics (R.M.W.), Department of Preventive Medicine, and USC Diabetes and Obesity Research Institute (R.M.W.), Keck School of Medicine of University of Southern California, Los Angeles, California 90033; and Institute for Translational Genomics and Population Sciences (K.D.T.) and Department of Pediatrics (K.D.T.), Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California 90502
| | - Lynne E Wagenknecht
- Department of Medicine (P.R.S., E.A.D., J.W.R., C.S.N.), Center for Public Health Genomics (A.J.M., S.S.R.), and Department of Chemistry (E.A.D.), University of Virginia, Charlottesville, Virginia 22904; Department of Biochemistry (N.D.P.), Center for Genomics and Personalized Medicine Research (N.D.P.), Center for Diabetes Research (N.D.P.), Center for Public Health Genomics (C.D.L., N.D.P., L.E.W.), Department of Biostatistical Sciences (C.D.L.), and Division of Public Health Sciences (L.E.W.), Wake Forest School of Medicine, Winston-Salem, North Carolina 27157; Department of Physiology and Biophysics (R.M.W.), Department of Preventive Medicine, and USC Diabetes and Obesity Research Institute (R.M.W.), Keck School of Medicine of University of Southern California, Los Angeles, California 90033; and Institute for Translational Genomics and Population Sciences (K.D.T.) and Department of Pediatrics (K.D.T.), Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California 90502
| | - Richard M Watanabe
- Department of Medicine (P.R.S., E.A.D., J.W.R., C.S.N.), Center for Public Health Genomics (A.J.M., S.S.R.), and Department of Chemistry (E.A.D.), University of Virginia, Charlottesville, Virginia 22904; Department of Biochemistry (N.D.P.), Center for Genomics and Personalized Medicine Research (N.D.P.), Center for Diabetes Research (N.D.P.), Center for Public Health Genomics (C.D.L., N.D.P., L.E.W.), Department of Biostatistical Sciences (C.D.L.), and Division of Public Health Sciences (L.E.W.), Wake Forest School of Medicine, Winston-Salem, North Carolina 27157; Department of Physiology and Biophysics (R.M.W.), Department of Preventive Medicine, and USC Diabetes and Obesity Research Institute (R.M.W.), Keck School of Medicine of University of Southern California, Los Angeles, California 90033; and Institute for Translational Genomics and Population Sciences (K.D.T.) and Department of Pediatrics (K.D.T.), Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California 90502
| | - Stephen S Rich
- Department of Medicine (P.R.S., E.A.D., J.W.R., C.S.N.), Center for Public Health Genomics (A.J.M., S.S.R.), and Department of Chemistry (E.A.D.), University of Virginia, Charlottesville, Virginia 22904; Department of Biochemistry (N.D.P.), Center for Genomics and Personalized Medicine Research (N.D.P.), Center for Diabetes Research (N.D.P.), Center for Public Health Genomics (C.D.L., N.D.P., L.E.W.), Department of Biostatistical Sciences (C.D.L.), and Division of Public Health Sciences (L.E.W.), Wake Forest School of Medicine, Winston-Salem, North Carolina 27157; Department of Physiology and Biophysics (R.M.W.), Department of Preventive Medicine, and USC Diabetes and Obesity Research Institute (R.M.W.), Keck School of Medicine of University of Southern California, Los Angeles, California 90033; and Institute for Translational Genomics and Population Sciences (K.D.T.) and Department of Pediatrics (K.D.T.), Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California 90502
| | - Craig S Nunemaker
- Department of Medicine (P.R.S., E.A.D., J.W.R., C.S.N.), Center for Public Health Genomics (A.J.M., S.S.R.), and Department of Chemistry (E.A.D.), University of Virginia, Charlottesville, Virginia 22904; Department of Biochemistry (N.D.P.), Center for Genomics and Personalized Medicine Research (N.D.P.), Center for Diabetes Research (N.D.P.), Center for Public Health Genomics (C.D.L., N.D.P., L.E.W.), Department of Biostatistical Sciences (C.D.L.), and Division of Public Health Sciences (L.E.W.), Wake Forest School of Medicine, Winston-Salem, North Carolina 27157; Department of Physiology and Biophysics (R.M.W.), Department of Preventive Medicine, and USC Diabetes and Obesity Research Institute (R.M.W.), Keck School of Medicine of University of Southern California, Los Angeles, California 90033; and Institute for Translational Genomics and Population Sciences (K.D.T.) and Department of Pediatrics (K.D.T.), Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, California 90502
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14
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Qureshi FM, Dejene EA, Corbin KL, Nunemaker CS. Stress-induced dissociations between intracellular calcium signaling and insulin secretion in pancreatic islets. Cell Calcium 2015; 57:366-375. [PMID: 25861744 DOI: 10.1016/j.ceca.2015.03.002] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2015] [Accepted: 03/09/2015] [Indexed: 12/22/2022]
Abstract
In healthy pancreatic islets, glucose-stimulated changes in intracellular calcium ([Ca(2+)]i) provide a reasonable reflection of the patterns and relative amounts of insulin secretion. We report that [Ca(2+)]i in islets under stress, however, dissociates with insulin release in different ways for different stressors. Islets were exposed for 48h to a variety of stressors: cytokines (low-grade inflammation), 28mM glucose (28G, glucotoxicity), free fatty acids (FFAs, lipotoxicity), thapsigargin (ER stress), or rotenone (mitochondrial stress). We then measured [Ca(2+)]i and insulin release in parallel studies. Islets exposed to all stressors except rotenone displayed significantly elevated [Ca(2+)]i in low glucose, however, increased insulin secretion was only observed for 28G due to increased nifedipine-sensitive calcium-channel flux. Following 3-11mM glucose stimulation, all stressors substantially reduced the peak glucose-stimulated [Ca(2+)]i response (first phase). Thapsigargin and cytokines also substantially impacted aspects of calcium influx and ER calcium handling. Stressors did not significantly impact insulin secretion in 11mM glucose for any stressor, although FFAs showed a borderline reduction, which contributed to a significant decrease in the stimulation index (11:3mM glucose) observed for FFAs and also for 28G. We also clamped [Ca(2+)]i using 30mM KCl+250μM diazoxide to test the amplifying pathway. Only rotenone-treated islets showed a robust increase in 3-11mM glucose-stimulated insulin secretion under clamped conditions, suggesting that low-level mitochondrial stress might activate the metabolic amplifying pathway. We conclude that different stressors dissociate [Ca(2+)]i from insulin secretion differently: ER stressors (thapsigargin, cytokines) primarily affect [Ca(2+)]i but not conventional insulin secretion and 'metabolic' stressors (FFAs, 28G, rotenone) impacted insulin secretion.
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Affiliation(s)
- Farhan M Qureshi
- Department of Medicine, University of Virginia, Charlottesville, VA.,Department of Chemistry, University of Virginia, Charlottesville, VA
| | - Eden A Dejene
- Department of Medicine, University of Virginia, Charlottesville, VA.,Department of Chemistry, University of Virginia, Charlottesville, VA
| | - Kathryn L Corbin
- Department of Medicine, University of Virginia, Charlottesville, VA
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Abstract
Proinflammatory cytokines are thought to play a significant role in the pathogenesis of type 2 diabetes (T2D) and are elevated in the circulation even before the onset of the disease. However, the full complement of cytokines involved in the development of T2D is not known. In this study, 32 serum cytokines were measured from diabetes-prone BKS.Cg-m+/+Lepr(db)/J (db/db) mice and heterozygous age-matched control mice at 5 weeks (non-diabetic/non-obese), 6-7 weeks (transitional-to-diabetes), or 11 weeks (hyperglycemic/obese) and then correlated with body weight, blood glucose, and fat content. Among these 32 cytokines, C-X-C motif ligand 1 (CXCL1) showed the greatest increase (+78%) in serum levels between db/db mice that were hyperglycemic (blood glucose: 519±23 mg/dl, n=6) and those that were non-hyperglycemic (193±13 mg/dl, n=8). Similarly, increased CXCL1 (+68%) and CXCL5 (+40%) were associated with increased obesity in db/db mice; note that these effects could not be entirely separated from age. We then examined whether islets could be a source of these chemokines. Exposure to cytokines mimicking low-grade systemic inflammation (10 pg/ml IL1β+20 pg/ml IL6) for 48 h upregulated islet CXCL1 expression by 53±3-fold and CXCL5 expression by 83±10-fold (n=4, P<0.001). Finally, overnight treatment with the combination of CXCL1 and CXCL5 at serum levels was sufficient to produce a significant decrease in the peak calcium response to glucose stimulation, suggesting reduced islet function. Our findings demonstrated that CXCL1 and CXCL5 i) are increased in the circulation with the onset of T2D, ii) are produced by islets under stress, and iii) synergistically affect islet function, suggesting that these chemokines participate in the pathogenesis of T2D.
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Affiliation(s)
- Craig S Nunemaker
- Division of Endocrinology and MetabolismDepartment of MedicineDepartment of Biomedical EngineeringDepartment of BiologyUniversity of Virginia, PO Box 801413, Charlottesville, Virginia 22908, USA
| | - H Grace Chung
- Division of Endocrinology and MetabolismDepartment of MedicineDepartment of Biomedical EngineeringDepartment of BiologyUniversity of Virginia, PO Box 801413, Charlottesville, Virginia 22908, USADivision of Endocrinology and MetabolismDepartment of MedicineDepartment of Biomedical EngineeringDepartment of BiologyUniversity of Virginia, PO Box 801413, Charlottesville, Virginia 22908, USA
| | - Gretchen M Verrilli
- Division of Endocrinology and MetabolismDepartment of MedicineDepartment of Biomedical EngineeringDepartment of BiologyUniversity of Virginia, PO Box 801413, Charlottesville, Virginia 22908, USADivision of Endocrinology and MetabolismDepartment of MedicineDepartment of Biomedical EngineeringDepartment of BiologyUniversity of Virginia, PO Box 801413, Charlottesville, Virginia 22908, USA
| | - Kathryn L Corbin
- Division of Endocrinology and MetabolismDepartment of MedicineDepartment of Biomedical EngineeringDepartment of BiologyUniversity of Virginia, PO Box 801413, Charlottesville, Virginia 22908, USA
| | - Aditi Upadhye
- Division of Endocrinology and MetabolismDepartment of MedicineDepartment of Biomedical EngineeringDepartment of BiologyUniversity of Virginia, PO Box 801413, Charlottesville, Virginia 22908, USA
| | - Poonam R Sharma
- Division of Endocrinology and MetabolismDepartment of MedicineDepartment of Biomedical EngineeringDepartment of BiologyUniversity of Virginia, PO Box 801413, Charlottesville, Virginia 22908, USA
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16
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O'Neill CM, Lu C, Corbin KL, Sharma PR, Dula SB, Carter JD, Ramadan JW, Xin W, Lee JK, Nunemaker CS. Circulating levels of IL-1B+IL-6 cause ER stress and dysfunction in islets from prediabetic male mice. Endocrinology 2013; 154:3077-88. [PMID: 23836031 PMCID: PMC3749476 DOI: 10.1210/en.2012-2138] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Elevated levels of circulating proinflammatory cytokines are associated with obesity and increased risk of type 2 diabetes, but the mechanism is unknown. We tested whether proinflammatory cytokines IL-1B+IL-6 at low picogram per milliliter concentrations (consistent with serum levels) could directly trigger pancreatic islet dysfunction. Overnight exposure to IL-1B+IL-6 in islets isolated from normal mice and humans disrupted glucose-stimulated intracellular calcium responses; cytokine-induced effects were more severe among islets from prediabetic db/db mice that otherwise showed no signs of dysfunction. IL-1B+IL-6 exposure reduced endoplasmic reticulum (ER) calcium storage, activated ER stress responses (Nos2, Bip, Atf4, and Ddit3 [CHOP]), impaired glucose-stimulated insulin secretion, and increased cell death only in islets from prediabetic db/db mice. Furthermore, we found increased serum levels of IL-1B and IL-6 in diabetes-prone mice at an age before hyperglycemia was exhibited, suggesting that low-grade systemic inflammation develops early in the disease process. In addition, we implanted normal outbred and inbred mice with subcutaneous osmotic mini-pumps containing IL-1B+IL-6 to mimic the serum increases found in prediabetic db/db mice. Both IL-1B and IL-6 were elevated in serum from cytokine-pump mice, but glucose tolerance and blood glucose levels did not differ from controls. However, when compared with controls, isolated islets from cytokine-pump mice showed deficiencies in calcium handling and insulin secretion that were similar to observations with islets exposed to cytokines in vitro. These findings provide proof of principle that low-grade systemic inflammation is present early in the development of type 2 diabetes and can trigger ER stress-mediated islet dysfunction that can lead to islet failure.
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Affiliation(s)
- Christina M O'Neill
- University of Virginia, Department of Medicine, Charlottesville, Virginia 22908, USA
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17
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Nandula SR, Dey P, Corbin KL, Nunemaker CS, Bagavant H, Deshmukh US. Salivary gland hypofunction induced by activation of innate immunity is dependent on type I interferon signaling. J Oral Pathol Med 2012; 42:66-72. [PMID: 22672212 DOI: 10.1111/j.1600-0714.2012.01181.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
BACKGROUND Activation of innate immunity through polyinosinic:polycytidylic acid [poly(I:C)] causes acute salivary gland hypofunction. As a major consequence of poly(I:C) treatment is type I interferon (IFN) production, this study was undertaken to investigate their role in salivary gland dysfunction. METHODS Different strains of mice deficient in either interferon alpha receptor (IFNAR1(-/-)) or IL-6(-/-), or IL-10(-/-), or EBI3(-/-) were treated with poly(I:C). Salivary gland function was determined by measuring pilocarpine-induced saliva volume. Gene expression levels were measured by real-time PCR. Ca(2+) mobilization studies were performed using ex-vivo acinar cells. RESULTS A single injection of poly(I:C) rapidly induced salivary gland hypofunction in wild-type B6 mice (41% drop in saliva volumes compared to PBS-treated mice). In contrast, the loss of function in poly(I:C)-treated IFNAR(-/-) mice was only 9.6%. Gene expression analysis showed reduced levels of Il-6, Il-10, and Il-27 in submandibular glands of poly(I:C)-treated IFNAR(-/-) mice. While salivary gland dysfunction in poly(I:C)-treated IL-10(-/-) and EBI3(-/-) mice was comparable to wild-type mice, the IL-6(-/-) mice were more resistant, with only a 21% drop in function. Pilocarpine-induced Ca(2+) flux was significantly suppressed in acinar cells obtained from poly(I:C)-treated wild-type mice. CONCLUSIONS Our data demonstrate that a combined action of type I IFNs and IL-6 contributes toward salivary gland hypofunction. This happens through interference with Ca(2+) mobilization within acinar cells. Thus, in acute viral infections and diseases like Sjögren's syndrome, elevated levels of type I IFNs and IL-6 can directly affect glandular function.
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Affiliation(s)
- Seshagiri-Rao Nandula
- Division of Nephrology, Center for Immunity Inflammation and Regenerative Medicine, University of Virginia, Charlottesville, VA 22908, USA
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Ramadan JW, Steiner SR, O'Neill CM, Nunemaker CS. The central role of calcium in the effects of cytokines on beta-cell function: implications for type 1 and type 2 diabetes. Cell Calcium 2011; 50:481-90. [PMID: 21944825 DOI: 10.1016/j.ceca.2011.08.005] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2011] [Revised: 07/20/2011] [Accepted: 08/16/2011] [Indexed: 12/29/2022]
Abstract
The appropriate regulation of intracellular calcium is a requirement for proper cell function and survival. This review focuses on the effects of proinflammatory cytokines on calcium regulation in the insulin-producing pancreatic beta-cell and how normal stimulus-secretion coupling, organelle function, and overall beta-cell viability are impacted. Proinflammatory cytokines are increasingly thought to contribute to beta-cell dysfunction not only in type 1 diabetes (T1D), but also in the progression of type 2 diabetes (T2D). Cytokine-induced disruptions in calcium handling result in reduced insulin release in response to glucose stimulation. Cytokines can alter intracellular calcium levels by depleting calcium from the endoplasmic reticulum (ER) and by increasing calcium influx from the extracellular space. Depleting ER calcium leads to protein misfolding and activation of the ER stress response. Disrupting intracellular calcium may also affect organelles, including the mitochondria and the nucleus. As a chronic condition, cytokine-induced calcium disruptions may lead to beta-cell death in T1D and T2D, although possible protective effects are also discussed. Calcium is thus central to both normal and pathological cell processes. Because the tight regulation of intracellular calcium is crucial to homeostasis, measuring the dynamics of calcium may serve as a good indicator of overall beta-cell function.
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Affiliation(s)
- James W Ramadan
- Department of Medicine, University of Virginia, Charlottesville, United States
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Reiner T, Thurber G, Gaglia J, Vinegoni C, Liew CW, Upadhyay R, Kohler RH, Li L, Kulkarni RN, Benoist C, Mathis D, Weissleder R. Accurate measurement of pancreatic islet beta-cell mass using a second-generation fluorescent exendin-4 analog. Proc Natl Acad Sci U S A 2011; 108:12815-20. [PMID: 21768367 DOI: 10.1073/pnas.1109859108] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The hallmark of type 1 diabetes is autoimmune destruction of the insulin-producing β-cells of the pancreatic islets. Autoimmune diabetes has been difficult to study or treat because it is not usually diagnosed until substantial β-cell loss has already occurred. Imaging agents that permit noninvasive visualization of changes in β-cell mass remain a high-priority goal. We report on the development and testing of a near-infrared fluorescent β-cell imaging agent. Based on the amino acid sequence of exendin-4, we created a neopeptide via introduction of an unnatural amino acid at the K(12) position, which could subsequently be conjugated to fluorophores via bioorthogonal copper-catalyzed click-chemistry. Cell assays confirmed that the resulting fluorescent probe (E4(×12)-VT750) had a high binding affinity (~3 nM). Its in vivo properties were evaluated using high-resolution intravital imaging, histology, whole-pancreas visualization, and endoscopic imaging. According to intravital microscopy, the probe rapidly bound to β-cells and, as demonstrated by confocal microscopy, it was internalized. Histology of the whole pancreas showed a close correspondence between fluorescence and insulin staining, and there was an excellent correlation between imaging signals and β-cell mass in mice treated with streptozotocin, a β-cell toxin. Individual islets could also be visualized by endoscopic imaging. In short, E4(×12)-VT750 showed strong and selective binding to glucose-like peptide-1 receptors and permitted accurate measurement of β-cell mass in both diabetic and nondiabetic mice. This near-infrared imaging probe, as well as future radioisotope-labeled versions of it, should prove to be important tools for monitoring diabetes, progression, and treatment in both experimental and clinical contexts.
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