RESUMO
AIMS: Pancreatic beta-cell lipo-dysfunction decreases insulin secretion and predisposes to the development of type 2 diabetes. Through targeted Pex11ß knockdown and peroxisome depletion, our aim was to investigate the specific contribution of peroxisomes to palmitate mediated pancreatic beta-cell dysfunction. METHODS: MIN6 cells were transfected with probes targeted against Pex11ß, a regulator of peroxisome abundance, or with scrambled control probes. Peroxisome abundance was measured by PMP-70 protein expression. 48â¯h post transfection, cells were incubated with 250⯵M palmitate or BSA control for a further 48â¯h before measurement of glucose stimulated insulin secretion and of reactive oxygen species. RESULTS: Pex11ß 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 25â¯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/µg protein; Palmitate vs BSA P<0.001), but by just 37% in the Pex11ß knockdown cells. Comparing responses in the presence of palmitate, insulin secretion at 25â¯mM glucose was significantly greater in the Pex11ß knockdown cells compared with the scrambled controls (4.04±0.46 vs 2.54±0.25â¯ng/h/µg protein; p<0.05). Reactive oxygen species generation with palmitate was lower in the Pex11ß knockdown cells compared with the scrambled controls (P<0.001). CONCLUSION: Pex11ß 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 in palmitate mediated beta-cell dysfunction.