Peroxisomes and pancreatic beta-cell lipo-dysfunction

Aims: Pancreatic beta-cell lipo-dysfunction decreases insulin secretion and predisposes to the development of type 2 diabetes. Through targeted Pex11 beta knockdown and peroxisome depletion, our aim was to investigate the specific contribution of peroxisomes to palmitate mediated pancreatic beta-cell dysfunction. Methods: MINE cells were transfected with probes targeted against Pex11 beta, a regulator of peroxisome abundance, or with scrambled control probes. Peroxisome abundance was measured by PMP-70 protein expression. 48 h post transfection, cells were incubated with 250 mu M palmitate or BSA control for a further 48 h before measurement of glucose stimulated insulin secretion and of reactive oxygen species. Results: Pex11 beta knockdown decreased target gene expression by >80% compared with the scrambled control (P<0.001). This led to decreased PMP-70 expression (p<0.01) and a 22% decrease in peroxisome number (p<0.05). At 25 mM glucose, palmitate treatment decreased insulin secretion by 64% in the scrambled control cells (2.54 +/- 0.25 vs 7.07 +/- 0.83 [mean +/- SEM] ng/h/mu g protein; Palmitate vs BSA P<0.001), but by just 37% in the Pex11 beta knockdown cells. Comparing responses in the presence of palmitate, insulin secretion at 25 mM glucose was significantly greater in the Pex11 beta knockdown cells compared with the scrambled controls (4.04 +/- 0.46 vs 2.54 +/- 0.25 ng/h/mu g protein; p<0.05). Reactive oxygen species generation with palmitate was lower in the Pex11 beta knockdown cells compared with the scrambled controls (P<0.001). Conclusion: Pex11 beta knockdown decreased peroxisome abundance, decreased palmitate mediated reactive oxygen species generation, and reversed the inhibitory effect of palmitate on insulin secretion. These findings reveal a distinct role of peroxisomes inpalmitate mediated beta-cell dysfunction. (C) 2020 Elsevier Inc. All rights reserved.