Effect And Mechanism Of Itaconate On Metaflammation In Obesity By Regulating Macrophage Inflammation

Objective: Metaflammation plays a key role in the process of metabolic complications caused by obesity.Inflammatory activation of macrophages is a key link in metaflammation.Itaconate has recently been found to have a strong immunomodulatory effect on macrophages,showing good therapeutic potential in a variety of inflammatory diseases.The aim of this work was to investigate the function of itaconate in metaflammation.Methods: 1.Wild type(WT)and IRG1-/-mice were fed high fat diet to induce obesity model,to study the effects of itaconate deficiency on metaflammation of obesity.The experimental groups were: WT+normal diet group,IRG1-/-+normal diet group,WT+high fat diet group,IRG1-/-+high fat diet group.Detecting the glucose and lipid metabolism,and the levels of circulating,adipose tissue,liver and bone marrow-derived macrophage(BMDM)inflammation.2.Palmitic acid(PA)was used to induce macrophage inflammatory response,and the molecular mechanism of itaconate derivative 4-OI regulating macrophage inflammation was explored in vitro.3.To explore the feasibility of 4-OI therapy to improve metaflammation in obesity by exogenous supplement of itaconate derivative 4-OI.The experimental groups were:normal diet group,high fat diet group,and high fat diet+4-OI treatment group.Detecting the glucose and lipid metabolism,and the levels of circulating,liver,adipose tissue and BMDM inflammation.Results: 1.IRG1-/-mice were more sensitive to high fat diet induced obesity,with significantly increased body weight,liver weight and adipose tissue content.IRG1-/-mice had more serious glucose and lipid metabolism disorder during obesity.The levels of inflammatory cytokines IL-1β,IL-18 in circulation,liver and adipose tissue of IRG1-/-mice were significantly increased.In IRG1-/-mice liver and adipose tissue,there was a considerably higher level of NLRP3 inflammasome activation.IRG1-/-BMDM showed a stronger inflammatory response under LPS induction in vitro.2.In RAW 264.7 macrophages,itaconate derivative 4-OI inhibited PA-induced levels of IL-1β,IL-18 and NLRP3 inflammasome.4-OI inhibited PA-induced macrophage ROS production.Meanwhile,ROS inhibitor NAC could also significantly inhibit ROS production in macrophages,showing a similar inhibitory effect on NLRP3 inflammasome as 4-OI.4-OI could activate Nrf2,and Nrf2 inhibitor ML385 reversed the inhibitory effect of 4-OI on ROS production and NLRP3 inflammasome.3.4-OI treatment resulted in weight loss and improved the impaired glucose and lipid metabolism in obese mice.4-OI treatment decreased the levels of circulating,liver and adipose tissue inflammatory cytokines.In liver and adipose tissue,4-OI treatment increased Nrf2 protein and inhibited the NLRP3 inflammasome.4-OI treatment inhibited LPS-induced BMDM inflammatory response in obese mice.Conclusions: 1.In the high fat diet induced obesity model,compared with WT mice,IRG1-/-mice gained more weight,had more severe disorders of glucose and lipid metabolism,increased levels of circulatory,adipose tissue,liver and BMDM inflammation,and increased activation of NLRP3 inflammasome.These results suggest that itaconate deficiency may promote the development of metaflammation in obesity.2.Itaconate derivative 4-OI inhibited ROS production by activating Nrf2,and then blocked the activation of NLRP3 inflammasome,thus alleviating PA-induced macrophage inflammatory response.3.In obese mice,4-OI treatment inhibited NLRP3 inflammasome activation in liver,adipose tissue and BMDM,reduced the inflammation induced by obesity,and improved the disorder of glucose and lipid metabolism,which is expected to become a new strategy to intervene in metaflammation.