Pex11 β knockdown decreases peroxisome abundance and reverses the inhibitory effect of palmitate on pancreatic beta-cell function.

Abstract

AimsReactive oxygen species generated by the peroxisomes and mitochondria contribute to lipotoxicity in pancreatic beta-cells. 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. MethodsMIN6 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. 48hrs post transfection, cells were incubated with or without 250M palmitate for a further 48hrs before measurement of reactive oxygen species, mitochondrial respiratory function, and glucose stimulated insulin secretion. ResultsPex11{beta} knockdown decreased target gene expression by more than 80% compared with the scrambled control (P<0.001), leading to decreased PMP-70 expression (p<0.01). Pex11{beta} knockdown decreased palmitate mediated generation of reactive oxygen species (P<0.001), but with no effect on mitochondrial respiratory function. At 25mM glucose, palmitate treatment decreased insulin secretion in the control cells (2.54{+/-}0.25 vs 7.07{+/-}0.83 [mean{+/-}SEM] ng/hr/g protein; P<0.001), with a similar pattern in the Pex11{beta} knockdown cells. However, in the presence of palmitate, insulin secretion was significantly higher in the Pex11{beta} knockdown versus control cells (4.04{+/-}0.46 vs 2.54{+/-}0.25 ng/hr/g protein; p<0.05). ConclusionPex11{beta} knockdown decreased peroxisome abundance, decreased palmitate mediated ROS generation, and reversed the inhibitory effect of palmitate on insulin secretion. These findings highlight a specific and independent role for peroxisomes in pancreatic beta-cell lipotoxicity.