Metformin and resveratrol inhibit Drp1-mediated mitochondrial fission and prevent ER stress-associated NLRP3 inflammasome activation in the adipose tissue of diabetic mice

This study was designed to investigate the hypothesis that metformin and resveratrol exhibited the same effect on inhibition of NLRP3 inflammasome activation with regulation of AMPK in adipose tissue exposed to high glucose. To induce adipose tissue dysfunction, we treated epididymal adipose tissue of mice or differentiated 3T3-L1 adipocytes with high glucose (33 mM) for 24 h. Meanwhile, mice were injected with streptozotocin STZ to induce diabetes and followed by oral administration of metformin (200 mg/kg), resveratrol (50 mg/kg) or ER stress inhibitor TUDCA (50 mg/kg) for 7 days. The effects of metformin and resveratrol on ROS production, mitochondrial fission, ER stress, TXNIP/NLRP3 inflammasome activation, inflammation and apoptosis were observed. Metformin and resveratrol inhibited ROS-associated mitochondrial fission by upregulating Drp1 phosphorylation (Ser 637) in an AMPK-dependent manner, and then suppressed ER stress indicated by dephosphorylation of IRE1α and eIF2α in the adipose tissue. As a result from suppressing TXNIP/NLRP3 inflammasome activation, metformin and resveratrol inhibited inflammation and reduced cell apoptosis in adipose tissue or adipocytes exposed to high glucose. Metformin and resveratrol protected mitochondrial integrity by inhibiting Drp1 activity and prevented NLRP3 inflammasome activation by suppressing ER stress, and thereby protected adipose function from high glucose insult.