Effects of IL-33 on 3T3-L1 cells and obese mice models induced by a high-fat diet

•The content of IL-33 is different in various adipose tissues in obese mice fed a HFD diet.•The exogenous IL-33 reduces lipid accumulation in 3 T3-L1 cells and adipose tissue of obese mice.•The exogenous IL-33 alleviates type 1 inflammation and improves glucose and lipid metabolism in HFD-induced mice. Obesity is a syndrome that attributes to many factors such as genetics, diet, lifestyle and environment, which includes an imbalance of immune regulation. IL-33, as a new member of the IL-1 family, is classically associated with type 2 immune responses. Here, IL-33 was investigated for its ability to optimize lipid aggregation and ameliorate the inflammatory response in obesity. In vitro experimental results showed that, compared with the induction group, the treatment with 30 ng/mL IL-33 displayed a reduction in the number of lipid droplets. The expression levels of AceCS1 and PPARγ also decreased in the 30 ng/mL IL-33 group compared to the induction group. For confirmation in vivo, three groups of C57BL/6 mice were treated for 14 weeks: mice in control were fed with a normal diet; mice in the HFD and IL-33 groups were fed with a high-fat diet (HFD) and with sterile PBS or recombinant IL-33, respectively. Liver, muscle, spleen and four types of adipose tissue, as well as serum, were collected for further testing. Our data demonstrated that after 4-week treatment with recombinant IL-33, metabolic parameters in mice were improved significantly (visceral fat weight, glucose and insulin tolerance, liver steatosis, expression of lipid synthesis index and inflammatory response). Moreover, IL-33 treatment regulated the original distribution of IL-33 among different tissues. Hence, IL-33 modulated lipid metabolism and inflammatory response in obesity, which would be a novel therapeutic target for obesity and related metabolic diseases.