Original Contribution
Reactive oxygen species are produced at low glucose and contribute to the activation of AMPK in insulin-secreting cells

https://doi.org/10.1016/j.freeradbiomed.2011.10.437Get rights and content
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Abstract

Excess reactive oxygen species (ROS) production is thought to play a key role in the loss of pancreatic β-cell number and/or function, in response to high glucose and/or fatty acids. However, contradictory findings have been reported showing that in pancreatic β cells or insulin-secreting cell lines, ROS are produced under conditions of either high or low glucose. Superoxide production was measured in attached INS1E cells as a function of glucose concentration, by following in real time the oxidation of dihydroethidine. Minimal values of superoxide production were measured at glucose concentrations of 5–20 mM, whereas superoxide generation was maximal at 0–1 mM glucose. Superoxide generation started rapidly (15–30 min) after exposure to low glucose and was suppressed by its addition within minutes. Superoxide was totally suppressed by rotenone, but not myxothiazol, suggesting a role for complex I in this process. Indirect evidence for mitochondrial ROS generation was also provided by a decrease in aconitase activity. Activation of AMPK, a cellular metabolic sensor, and its downstream target ACC by low glucose concentration was largely inhibited by addition of MnTBAP, a MnSOD and catalase mimetic that also totally suppressed superoxide production. Taken together, the data show that low glucose activates AMPK in a superoxide-dependent, AMP-independent way.

Highlights

► Low but not high glucose generated superoxide in the pancreatic beta cell line INS1. ► The effect of low glucose was rapid and reversible. ► Low glucose-induced superoxide production localized at complex 1. ► Low glucose also induced AMPK activation. ► AMPK activation was ROS-dependent and AMP, LKB1 and CaMKK independent.

Keywords

Superoxide
Mitochondria
Complex I
Aconitase
INS1E cells
AMPK
ACC
Free radicals

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