Original Article | Published:

Epicatechin potentiation of glucose-stimulated insulin secretion in INS-1 cells is not dependent on its antioxidant activity

Acta Pharmacologica Sinica volume 39, pages 893902 (2018) | Download Citation

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Abstract

Epicatechin (EC) is a monomeric flavan-3-ol. We have previously demonstrated that glucose-intolerant rats fed flavan-3-ols exhibit improved pancreatic islet function corresponding with an increase in circulating EC-derived metabolites. Thus, we speculate that EC may act as a cellular signaling molecule in vivo to modulate insulin secretion. In this study we further examined the effects of different concentrations of EC on H2O2 or hyperglycemia-induced ROS production, as well as on saturated fatty acid (SFA)-impaired glucose-stimulated insulin secretion (GSIS) in INS-1 cell line in vitro. We showed that EC at a high concentration (30 μmol/L), but not a low concentration (0.3 μmol/L), significantly decreased H2O2 or hyperglycemia-induced ROS production in INS-1 cells. However, EC (0.3 μmol/L) significantly enhanced SFA-impaired GSIS in INS-1 cells. Addition of KN-93, a CaMKII inhibitor, blocked the effect of EC on insulin secretion and decreased CaMKII phosphorylation. Addition of GW1100, a GPR40 antagonist, significantly attenuated EC-enhanced GSIS, but only marginally affected CaMKII phosphorylation. These results demonstrate that EC at a physiological concentration promotes GSIS in SFA-impaired β-cells via activation of the CaMKII pathway and is consistent with its function as a GPR40 ligand. The findings support a role for EC as a cellular signaling molecule in vivo and further delineate the signaling pathways of EC in β-cells.

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References

  1. 1.

    , . Flavan-3-ols: nature, occurrence and biological activity. Mol Nutr Food Res 2008; 52: 79–104.

  2. 2.

    . Flavan-3-Ols and Proanthocyanidins. In: Nollet LML, and Toldrá F, editors. Handbook of analysis of active compounds in functional foods. CRC Press; 2012. p317–48.

  3. 3.

    , , , , . Transport of proanthocyanidin dimer, trimer, and polymer across monolayers of human intestinal epithelial Caco-2 cells. Antioxid Redox Signal 2001; 3: 957–67.

  4. 4.

    , , . Human studies on the absorption, distribution, metabolism, and excretion of tea polyphenols. Am J Clin Nutr 2013; 98: 1619S–1630S.

  5. 5.

    , , , , , . Green tea flavan-3-ols: colonic degradation and urinary excretion of catabolites by humans. J Agric Food Chem 2010; 58: 1296–304.

  6. 6.

    , , , , , , et al. The absorption, metabolism and excretion of flavan-3-ols and procyanidins following the ingestion of a grape seed extract by rats. Br J Nutr 2005; 94: 170–81.

  7. 7.

    , , , . Bioavailability of polyphenon E flavan-3-ols in humans with an ileostomy. J Nutr 2008; 138: 1535S–1542S.

  8. 8.

    , . , , , . Distribution of procyanidins and their metabolites in rat plasma and tissues after an acute intake of hazelnut extract. Food Funct 2011; 2: 562–8.

  9. 9.

    , , , , , , et al. Uptake and metabolism of epicatechin and its access to the brain after oral ingestion. Free Radic Biol Med 2002; 33: 1693–702.

  10. 10.

    , , . The gastrointestinal tract: a major site of antioxidant action? Free Radic Res 2000; 33: 819–30.

  11. 11.

    , , , , , , et al. Brain-targeted proanthocyanidin metabolites for Alzheimer's disease treatment. J Neurosci 2012; 32: 5144–50.

  12. 12.

    , , , , , . Modifications in nitric oxide and superoxide anion metabolism induced by fructose overload in rat heart are prevented by (−)-epicatechin. Food Funct 2016; 7: 1876–83.

  13. 13.

    , , , , . Cocoa flavonoid epicatechin protects pancreatic beta cell viability and function against oxidative stress. Mol Nutr Food Res 2014; 58: 447–56.

  14. 14.

    , , , . (-)-Epicatechin activation of endothelial cell endothelial nitric oxide synthase, nitric oxide, and related signaling pathways. Hypertension 2010; 55: 1398–405.

  15. 15.

    , , , , . Cell membrane mediated (-)-epicatechin effects on upstream endothelial cell signaling: Evidence for a surface receptor. Bioorg Med Chem Lett 2014; 24: 2749–52.

  16. 16.

    , , , , , , et al. The effects of (−)-epicatechin on endothelial cells involve the G protein-coupled estrogen receptor (GPER). Pharmacol Res 2015; 100: 309–20.

  17. 17.

    , , , . The anthocyanin delphinidin 3-rutinoside stimulates glucagon-like peptide-1 secretion in murine GLUTag cell line via the Ca2+/calmodulin-dependent kinase II pathway. PLoS One 2015; 10: e0126157.

  18. 18.

    , , , . Standardized biosynthesis of flavan-3-ols with effects on pancreatic beta-cell insulin secretion. Appl Microbiol Biotechnol 2007; 77: 797–807.

  19. 19.

    , . Effects of epicatechin on rat islets of Langerhans. Diabetes 1984; 33: 291–6.

  20. 20.

    , . , , , , et al. Protective effects of epicatechin against the toxic effects of streptozotocin on rat pancreatic islets: in vivo and in vitro. Pancreas 2003; 26: 292–9.

  21. 21.

    , , , , , . Inhibition of pancreatic β-cell Ca2+/calmodulin-dependent protein kinase ii reduces glucose-stimulated calcium influx and insulin secretion, impairing glucose tolerance. J Biol Chem 2014; 289: 12435–45.

  22. 22.

    , , , , , , et al. Hydrolysis enhances bioavailability of proanthocyanidin-derived metabolites and improves β-cell function in glucose intolerant rats. J Nutr Biochem 2015; 26: 850–9.

  23. 23.

    . Hydrogen peroxide alters mitochondrial activation and insulin secretion in pancreatic beta cells. J Biol Chem 1999; 274: 27905–13.

  24. 24.

    , , , , , , et al. Chronic palmitate exposure inhibits insulin secretion by dissociation of Ca2+ channels from secretory granules. Cell Metab 2009; 10: 455–65.

  25. 25.

    . CaM kinase II: a protein kinase with extraordinary talents germane to insulin exocytosis. Diabetes 1999; 48: 675–84.

  26. 26.

    , , , , , . Antidiabetic effect of Pycnogenol French maritime pine bark extract in patients with diabetes type II. Life Sci 2004; 75: 2505–13.

  27. 27.

    , , , , . Cinnamon improves glucose and lipids of people with type 2 diabetes. Diabetes Care 2003; 26: 3215–8.

  28. 28.

    , , , , , , et al. Grape seed proanthocyanidins ameliorate pancreatic beta-cell dysfunction and death in low-dose streptozotocin- and high-carbohydrate/high-fat diet-induced diabetic rats partially by regulating endoplasmic reticulum stress. Nutr Metab (Lond) 2013; 10: 51.

  29. 29.

    , , , , , , et al. Cocoa-rich diet attenuates beta cell mass loss and function in young Zucker diabetic fatty rats by preventing oxidative stress and beta cell apoptosis. Mol Nutr Food Res 2015; 59: 820–4.

  30. 30.

    , , . Flavonoids: antioxidants or signalling molecules? Free Radic Biol Med 2004; 36: 838–49.

  31. 31.

    . Role of fatty acids in the pathogenesis of insulin resistance and NIDDM. Diabetes 1997; 46: 3–10.

  32. 32.

    , . Free fatty acids in obesity and type 2 diabetes: defining their role in the development of insulin resistance and beta-cell dysfunction. Eur J Clin Invest 2002; 32 Suppl 3: 14–23.

  33. 33.

    , , , , , . Acute and chronic effects of different concentrations of free fatty acids on the insulin secreting function of islets. Diabetes Metab 2002; 28: 3S7–S12; discussion 3S108–S112.

  34. 34.

    , , , , , , et al. Saturated fatty acids synergize with elevated glucose to cause pancreatic beta-cell death. Endocrinology 2003; 144: 4154–63.

  35. 35.

    , . The multifunctional calcium/calmodulin-dependent protein kinase: from form to function. Annu Rev Physiol 1995; 57: 417–45.

  36. 36.

    , , , , , , et al. Group VIA phospholipase A2 forms a signaling complex with the calcium/calmodulin-dependent protein kinase IIbeta expressed in pancreatic islet beta-cells. J Biol Chem 2005; 280: 6840–9.

  37. 37.

    , , , , , , et al. Presence and possible involvement of Ca2+/calmodulin-dependent protein kinases in insulin release from the rat pancreatic beta cell. Biochem Biophys Res Commun 1993; 191: 255–61.

  38. 38.

    , , , , , , et al. Regulation of insulin secretion by overexpression of Ca2+/calmodulin-dependent protein kinase II in insulinoma MIN6 cells. Endocrinology 2000; 141: 2350–60.

  39. 39.

    , , , , . Correlation of the activation of Ca2+/calmodulin-dependent protein kinase II with the initiation of insulin secretion from perifused pancreatic islets. Endocrinology 1997; 138: 2359–64.

  40. 40.

    , , , . Chronic effects of palmitate overload on nutrient-induced insulin secretion and autocrine signalling in pancreatic MIN6 beta cells. PLoS One 2011; 6: e25975.

  41. 41.

    , , , , , , et al. Signaling diversity of PKA achieved via a Ca2+-cAMP-PKA oscillatory circuit. Nat Chem Biol 2011; 7: 34–40.

  42. 42.

    , , , , , , et al. β-cell-specific protein kinase A activation enhances the efficiency of glucose control by increasing acute-phase insulin secretion. Diabetes 2013; 62: 1527–36.

  43. 43.

    , , . The role of protein phosphatase-1 in the modulation of synaptic and structural plasticity. FEBS Lett 2004; 567: 121–8.

  44. 44.

    , , , , , , et al. Gating of CaMKII by cAMP-regulated protein phosphatase activity during LTP. Science 1998; 280: 1940–2.

  45. 45.

    , , . The molecular basis of CaMKII function in synaptic and behavioural memory. Nat Rev Neurosci 2002; 3: 175–90.

  46. 46.

    , , , , . Calcium/calmodulin-dependent kinase IV controls glucose-induced Irs2 expression in mouse beta cells via activation of cAMP response element-binding protein. Diabetologia 2011; 54: 1109–20.

  47. 47.

    , . Low antioxidant enzyme gene expression in pancreatic islets compared with various other mouse tissues. Free Radic Biol Med 1996; 20: 463–6.

  48. 48.

    , , , , , , et al. Reactive oxygen species as a signal in glucose-stimulated insulin secretion. Diabetes 2007; 56: 1783–91.

  49. 49.

    , , . , , . Transient oxidative stress damages mitochondrial machinery inducing persistent β-cell dysfunction. J Biol Chem 2009; 284: 23602–12.

  50. 50.

    , , , , , , et al. (-)Epicatechin stimulates ERK-dependent cyclic AMP response element activity and up-regulates GluR2 in cortical neurons. J Neurochem 2007; 101: 1596–606.

  51. 51.

    . , , , , . Cocoa and cocoa flavanol epicatechin improve hepatic lipid metabolism in in vivo and in vitro models. Role of PKCζ. J Funct Foods 2015; 17: 761–73.

  52. 52.

    . Banting lecture 2001: dysregulation of fatty acid metabolism in the etiology of type 2 diabetes. Diabetes 2002; 51: 7–18.

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Acknowledgements

This work was supported by an operating grant from Alberta Innovates BioSolutions and the Alberta Pulse Growers Commission. Neither funder placed any restrictions on publication of the present study. K YANG received stipend support from China Scholarship Council.

The authors would like to thank Ms A CLOSE, Mr K SUZUKI, and Mr K TAO for technical support.

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Affiliations

  1. Department of Agricultural, Food and Nutritional Science, University of Alberta Edmonton, Alberta, T6G 2E1 Canada

    • Kaiyuan Yang
    •  & Catherine B Chan
  2. Department of Physiology, University of Alberta, Edmonton, Alberta T6G 2P5, Canada

    • Catherine B Chan

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Correspondence to Catherine B Chan.

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DOI

https://doi.org/10.1038/aps.2017.174