BMAL1 modulates ROS generation and insulin secretion in pancreatic beta-cells: An effect possibly mediated via NOX2

Author(s)

de Jesus, Daniel Simoes ; Bargi-Souza, Paula ; Cruzat, Vinicius ; Yechoor, Vijay ; Carpinelli, Angelo Rafael ; Peliciari-Garcia, Rodrigo Antonio

• Document type: Journal article
• Source: Molecular and Cellular Endocrinology; v. 555, p. 8-pg., 2022-09-15.

Abstract

The pancreatic beta cells circadian clock plays a relevant role in glucose metabolism. NADPH oxidase (NOX) family is responsible for producing reactive oxygen species (ROS), such as superoxide anion and hydrogen peroxide, using NADPH as an electron donor. In pancreatic beta-cells, NOX-derived ROS inhibits basal and glucose-stimulated insulin secretion. Thus, we hypothesized that the absence of BMAL1, a core circadian clock component, could trigger an increase of NOX2-derived ROS in pancreatic beta cells, inhibiting insulin secretion under basal and stimulated glucose conditions. To test such hypothesis, Bmal1 knockdown (KD) was performed in cultured clonal beta-cell line (INS-1E) and knocked out in isolated pancreatic islets, using a tissue-specific beta-cells Bmal1 knockout (KO) mice. The insulin secretion was assessed in the presence of NOX inhibitors. The Bmal1 KD within INS-1E cells elicited a rise of intracellular ROS content under both glucose stimuli (2.8 mM and 16.7 mM), associated with an increase in Nox2 expression. Additionally, alterations of glutathione levels, CuZnSOD and catalase ac-tivities, reduction of ATP/ADP ratio, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and aconitase ac-tivities, followed by glucokinase and Slc2a2 (Glut2) expression were also observed in INS-1E beta-cells, reflecting in a diminished insulin secretion pattern. The isolated islets from beta-cell Bmal1(-/-) mice have shown a similar cellular response, where an increased NOX2-derived ROS content and a reduced basal-and glucose-stimulated insulin secretion were observed. Therefore, together with NOX inhibition (Apocynin), polyethene-glycol linked to superoxide dismutase (PEG-SOD), phorbol myristate acetate (PMA), and diethyldithiocarbamate (DDC) data, our findings suggest a possible BMAL1-mediated NOX2-derived ROS generation in pancreatic beta cells, leading to the modulation of both basal-and glucose-stimulated insulin secretion. (AU)

• FAPESP's process: 13/08769-1 - The role of NAD(P)H oxidase in the physiological and pathological molecular mechanisms of insulin secreting cells
• Grantee: Angelo Rafael Carpinelli
• Support Opportunities: Research Projects - Thematic Grants