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Chen X, Daniels NA, Cottrill D, Cao Y, Wang X, Li Y, Shriwas P, Qian Y, Archer MW, Whitticar NB, Jahan I, Nunemaker CS, Guo A. Natural Compound α-PGG and Its Synthetic Derivative 6Cl-TGQ Alter Insulin Secretion: Evidence for Diminishing Glucose Uptake as a Mechanism. Diabetes Metab Syndr Obes 2021; 14:759-772. [PMID: 33658814 PMCID: PMC7917315 DOI: 10.2147/dmso.s284295] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/06/2020] [Accepted: 12/24/2020] [Indexed: 12/17/2022] Open
Abstract
PURPOSE Previously we showed that natural compound α-penta-galloyl-glucose (α-PGG) and its synthetic derivative 6-chloro-6-deoxy-1,2,3,4-tetra-O-galloyl-α-D-glucopyranose (6Cl-TGQ) act to improve insulin signaling in adipocytes by increasing glucose transport. In this study, we investigated the mechanism of actions of α-PGG and 6Cl-TGQ on insulin secretion. METHODS Mouse islets and/or INS-1832/13 beta-cells were used to test the effects of our compounds on glucose-stimulated insulin secretion (GSIS), intracellular calcium [Ca2+]i using fura-2AM, glucose transport activity via a radioactive glucose uptake assay, intracellular ATP/ADP, and extracellular acidification (ECAR) and mitochondrial oxygen consumption rates (OCAR) using Seahorse metabolic analysis. RESULTS Both compounds reduced GSIS in beta-cells without negatively affecting cell viability. The compounds primarily diminished glucose uptake into islets and beta-cells. Despite insulin-like effects in the peripheral tissues, these compounds do not act through the insulin receptor in islets. Further interrogation of the stimulus-secretion pathway showed that all the key metabolic factors involved in GSIS including ECAR, OCAR, ATP/ADP ratios, and [Ca2+]i of INS-1832/13 cells were diminished after the compound treatment. CONCLUSION The compounds suppress glucose uptake of the beta-cells, which consequently slows down the rates of glycolysis and ATP synthesis, leading to decrease in [Ca2+]i and GSIS. The difference between adipocytes and beta-cells in effects on glucose uptake is of great interest. Further structural and functional modifications could produce new compounds with optimized therapeutic potentials for different target cells. The higher potency of synthetic 6Cl-TGQ in enhancing insulin signaling in adipocytes but lower potency in reducing glucose uptake in beta-cells compared to α-PGG suggests the feasibility of such an approach.
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Affiliation(s)
- Xiaozhuo Chen
- The Diabetes Institute at Ohio University, Athens, OH, 45701, USA
- The Edison Biotechnology Institute, Athens, OH, 45701, USA
- Department of Biological Sciences, Athens, OH, 45701, USA
- Department of Biomedical Sciences, Athens, OH, 45701, USA
- Heritage College of Osteopathic Medicine, Athens, OH, 45701, USA
- Interdisciplinary Graduate Program in Molecular and Cellular Biology, Athens, OH, 45701, USA
- Department of Chemistry and Biochemistry, Athens, OH, 45701, USA
| | - Nigel A Daniels
- The Diabetes Institute at Ohio University, Athens, OH, 45701, USA
- Department of Biomedical Sciences, Athens, OH, 45701, USA
- Heritage College of Osteopathic Medicine, Athens, OH, 45701, USA
- Department of Specialty Medicine, Athens, OH, 45701, USA
| | - David Cottrill
- The Edison Biotechnology Institute, Athens, OH, 45701, USA
- Department of Biological Sciences, Athens, OH, 45701, USA
| | - Yanyang Cao
- The Edison Biotechnology Institute, Athens, OH, 45701, USA
- Department of Biological Sciences, Athens, OH, 45701, USA
| | - Xuan Wang
- The Edison Biotechnology Institute, Athens, OH, 45701, USA
- Department of Biological Sciences, Athens, OH, 45701, USA
| | - Yunsheng Li
- The Edison Biotechnology Institute, Athens, OH, 45701, USA
| | - Pratik Shriwas
- The Edison Biotechnology Institute, Athens, OH, 45701, USA
- Department of Biological Sciences, Athens, OH, 45701, USA
| | - Yanrong Qian
- The Edison Biotechnology Institute, Athens, OH, 45701, USA
| | - Michael W Archer
- The Diabetes Institute at Ohio University, Athens, OH, 45701, USA
- Department of Biomedical Sciences, Athens, OH, 45701, USA
| | - Nicholas B Whitticar
- Department of Biomedical Sciences, Athens, OH, 45701, USA
- Translational Biomedical Sciences Program, Ohio University, Athens, OH, 45701, USA
| | - Ishrat Jahan
- The Diabetes Institute at Ohio University, Athens, OH, 45701, USA
- Department of Biomedical Sciences, Athens, OH, 45701, USA
| | - Craig S Nunemaker
- The Diabetes Institute at Ohio University, Athens, OH, 45701, USA
- Department of Biological Sciences, Athens, OH, 45701, USA
- Department of Biomedical Sciences, Athens, OH, 45701, USA
- Heritage College of Osteopathic Medicine, Athens, OH, 45701, USA
- Craig S Nunemaker Department of Biomedical Sciences, 1 Ohio University, Athens, OH, 45701, USATel +1 740-593-2387Fax +1 740-593-4795 Email
| | - Aili Guo
- Department of Internal Medicine, Division of Endocrinology, Diabetes and Metabolism, University of California at Davis (UC Davis) School of Medicine, UC Davis Health Science, Sacramento, CA, 95817, USA
- Correspondence: Aili Guo Department of Internal Medicine, Division of Endocrinology, Diabetes and Metabolism, University of California at Davis (UC Davis) School of Medicine, UC Davis Health Science, PSSB, G400, 4150 V St., Sacramento, CA, 95817, USATel +1 916-734-3730Fax +1 916-734-2292 Email
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McKillop AM, Ng MT, Abdel-Wahab YHA, Flatt PR. Evidence for inhibitory autocrine effects of proinsulin C-peptide on pancreatic β-cell function and insulin secretion. Diabetes Obes Metab 2014; 16:937-46. [PMID: 24702738 DOI: 10.1111/dom.12300] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Revised: 02/28/2014] [Accepted: 03/31/2014] [Indexed: 12/21/2022]
Abstract
AIMS Autocrine and paracrine regulatory mechanisms ensure integrated secretion of islet hormones that respond efficiently to changes in metabolic need. As proinsulin C-peptide exerts various biological effects and binds to cell membranes including insulin-secreting β cells, its physiological role in insulin release was examined. METHODS Insulin releasing activity of human and rat C-peptides were studied in the clonal pancreatic cell line, BRIN-BD11, with findings substantiated using isolated islets and in vivo studies employing SWISS TO mice. RESULTS Acute exposure of clonal β cells to human C-peptide resulted in concentration-dependent inhibitory effects on insulin secretion at 5.6 mM (p < 0.05-p < 0.001) and 16.7 mM (p < 0.01-p < 0.001) glucose. At physiologically relevant intra-islet concentrations (10(-9) -10(-6) M), C-peptide suppressed the insulin-secretory responses to a range of secretagogues acting at different points in the β cell stimulus-secretion coupling pathway including alanine (p < 0.05), Ca(2+) (p < 0.001), arginine (p < 0.05), tolbutamide (p < 0.001), glucagon-like peptide 1 (GLP-1) (p < 0.001), isobutylmethylxanthine (IBMX) (p < 0.01) and KCl (p < 0.05). Similar results were obtained using isolated mouse pancreatic islets. Human C-peptide (3 × 10(-7) M, p < 0.001), somatostatin-14 (3 × 10(-7) M, p < 0.01) and diazoxide (300 µM, p < 0.001) reduced both alanine and glucose-stimulated insulin release by 43, 25 and 48%, respectively. The effects of human C-peptide were reproduced using rat C-peptide I and II. C-peptide also inhibited in vivo glucose-stimulated insulin release and impaired glucose tolerance in mice. CONCLUSIONS C-peptide is a biologically active endogenous peptide hormone that exerts inhibitory autocrine effects on pancreatic β-cell function. Mechanisms involving the activation of K(+) channels and a distal effect downstream of increased cytoplasmic Ca(2+) appear to be implicated in the inhibition of insulin secretion.
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Affiliation(s)
- A M McKillop
- SAAD Centre for Pharmacy & Diabetes, School of Biomedical Sciences, University of Ulster, Coleraine, UK
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