The present research aimed to provide novel information regarding the antidiabetic mechanism of action of coffee silverskin extract (CSE) and its components chlorogenic acid (CGA) and caffeine (CF). Their effect on insulin secretion and biomarkers of oxidative stress in INS-1E cells in vitro cultured under physiological and stressed conditions were assessed. Under physiological conditions, CSE and pure CGA and CF did not affect cells´ oxidative status and viability. However, concentrations of CSE ≥ 1 μg/mL and CGA ≥ 5 μM significantly increased (p < 0.05) the enzymatic activity of glutathione peroxidase (GPx). Moreover, all concentrations of CSE (1–10 μg/mL) and the dose of 10 μM of CGA, significantly stimulated (p < 0.05) insulin secretion in cells cultured in media containing 4 and 10 mM of glucose. CSE (1 μg/mL) and CGA (10 μM) reinforced antioxidant defence and increased insulin secretion in response to glucose in beta cells stressed with streptozotocin (STZ). Since CGA concentration in CSE was of ≈ 0.1 nM it can be assumed that other antioxidants present in this particular extract may also contribute to the observed effect. In conclusion, here we provide evidence that CSE could be a new potential antidiabetic agent through its antioxidant actions and its ability to modulate insulin secretory function.

This work was supported by the grants SUSCOFFEE (AGL2014-57239-R), AGL2010-17579, AGL2014-58205-REDC from Programa Consolider-Ingenio and CIBERDEM from Spanish Ministry of Economy and Competitiveness (MINECO). B. Fernandez-Gomez is a fellow of the FPI predoctoral programme of MINECO (BES-2011-046827).

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