Natural Compound Celastrol, Through NF-κB Inhibition, Up-regulates MiR-223to Restore Palmitic Acid-impaired Glucose-lowering Ability In Hepatocyte

Background and Purpose: Palmitic acid (PA) at high concentrations impairscellular glucose tolerance, a problem causing many metabolic disorders. To finda realistic way to counteract PA-caused deterioration, we investigate the effectsand underlying mechanisms of the natural compound celastrol on PA-impaired glucosetolerance in human hepatocyte HepG2.Experimental Approach: Glucose-lowering ability and relevant proteins, aswell as insulin resistance-related microRNAs (miR), were compared in PA-treatedHepG2receiving subsequent celastrol treatment (or not). Glucose-lowering ability,PA, and celastrol’s action were also compared in cells with differentlymanipulated miR-223.Key Results: Incubation with PA at250μM (or higher) for2d impairedHepG2’s insulin-driven or basal ability to lower extracellular glucose, and causedmultiple molecular alterations related to impaired glucose tolerance, includingdown-regulation of Glut-1, Glut-4, and IRS-1, hyperphosphorylation of Ser307onIRS-1, and up-regulation of TNF-α, IL-1β, and IL-6. Subsequent celastrol treatment(600nM for6h) reversed all PA-caused alterations. Celastrol’s glucose tolerancerestoration was due to NF-κB activation inhibition, an action which re-raisedPA-caused miR-223declines. MiR-223’s important role was demonstrated as knockingdown miR-223mimicked PA’s action and abolished celastrol’s effects, whileover-expression mimicked celastrol’s action, ameliorating PA deterioration. Conclusions and Implications: Our work confirmed that celastrol throughinhibiting NF-κB thus re-raising miR-223could counteract PA’s action indeteriorating glucose-lowering ability; the safety for such application ofcelastrol in clinical is also deduced in Discussion.