Non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH) are frequently observed in patients with type 2 diabetes or obesity, and almost 9–20 % and 0–2.8 % of NASH progress to cirrhosis and hepatocellular carcinoma (HCC), respectively.1 Because they are deeply involved in worsening their quality of life and prognosis, it is important to clarify the mechanisms for the progress of liver diseases in those patients in order to prevent them. Recently, it was reported that the existence of diabetes worsens liver fibrosis.2 Therefore, the prevention of liver fibrosis, especially in diabetes patients, can be thought of as one of the important strategies in the treatment of co-existing liver diseases.

There is accumulating clinical evidence indicating that sodium-glucose co-transporter 2 (SGLT2) inhibitors, a class of anti-diabetes medicine, suppresses liver fibrosis in patients with type 2 diabetes and NAFLD.3,4 In addition, several studies have shown that some SGLT2 inhibitors alleviate hepatic steatosis or steatohepatitis in mouse and rat models for type 2 diabetes. Recently, we have also demonstrated that canagliflozin, an SGLT2 inhibitor, prevents the development of hepatocellular carcinoma in STAM mouse, a mouse model for NASH, HCC, and diabetes.5

Interleukin-33 (IL-33) is a cytokine that is one of the members of the IL-1 superfamily.6 The expressions of IL-33 and ST2, a receptor for IL-33, increase in the liver with the progression of liver fibrosis. IL-33 correlates with collagen expression and plays an important role in hepatic fibrosis at the mRNA and protein levels.7 IL-33 is extracellularly released from stressed hepatocytes, and binds to ST2 on various leukocytes, such as mastocytes, stomach, small intestine, and colon, where it produces Th2-type cytokines and plays both physiological and pathological functions. For example, it is involved in the defense mechanism against parasitic infection,8 allergic diseases such as asthma and sinusitis, collagen diseases such as rheumatoid arthritis, inflammatory bowel disease, and SLE, diabetes, Alzheimer's disease, and heart diseases.9 It has also been suggested that IL-33 plays an important role in the progression of NASH with fibrosis and the proliferation of HCC in a xenograft mouse model.10 And IL-33 knock out mice had been investigated previous study.11 However, whether the direct inhibition of IL-33 signaling prevents NAFLD from progressing to NASH and HCC has not been clarified.

Recently, a research group of Hashiguchi et al., one of the co-authors of this study, et al., generated a monoclonal antibody against IL33 receptor α (IL-33RAb) by using 2B4.11 cell hybridoma cells. Because their previous study demonstrated that the IL-33RAb decreased the expression of IL-5, a downstream effector molecule in IL-33 signaling, in lung tissues and kidney cell lines, this antibody was considered a neutralizing antibody in these tissues and cells.12 In this study, we also used IL-33RAb, similar to Hashiguchi et al. And We have demonstrated the mechanism by which SGLT2 inhibitor improves NAFLD and NASH model mouse. Our previous study revealed that SGLT2 inhibitor prevent pre-inflammatory cytokines via decreasing steatohepatitis in NAFLD on diabetic state. Therefore, we prepared a group as a positive control SGLT2 inhibitor how to differs from the improvement of NAFLD caused by anti-IL-33R Ab. Both IL-33RAb and Luseogliflozin, a SGLT2 inhibitor, were administered to a model mouse for NASH and HCC, and their effects were compared to investigate the mechanisms of how IL-33 is involved in the pathogenesis of NASH progression.