Non-alcoholic fatty liver disease (NAFLD) is strongly associated with obesity, but the molecular mechanisms of liver steatosis and its progression to non-alcoholic steatohepatitis and fibrosis are incompletely understood. Immune reactivity plays an important role in the pathogenesis of NAFLD. The IL-33/ST2 axis has a protective role in adiposity and atherosclerosis, but its role in obesity-associated metabolic disorders requires further clarification. To investigate the unresolved role of IL-33/ST2 signalling in NAFLD, we used ST2-deficient (ST2-/-) and wild type (WT) BALB/c mice maintained on a high-fat diet (HFD) for 24 weeks. HFD-fed ST2-/- mice exhibited increased weight gain, visceral adipose tissue weight and triglyceridaemia and decreased liver weight compared with diet-matched WT mice. Compared with WT mice on an HFD, ST2 deletion significantly reduced hepatic steatosis, liver inflammation and fibrosis and downregulated the expression of genes related to lipid metabolism in the liver. The frequency of innate immune cells in the liver, including CD68+ macrophages and CD11c+ dendritic cells, was lower in HFD-fed ST2-/- mice, accompanied by lower TNFα serum levels compared with diet-matched WT mice. Less collagen deposition in the livers of ST2-/- mice on an HFD was associated with lower numbers of profibrotic CD11b+Ly6clow monocytes and CD4+IL-17+ T cells in the liver, lower hepatic gene expression of procollagen, IL-33 and IL-13, and lower serum levels of IL-33 and IL-13 compared with diet-matched WT mice.
Our findings suggest that the IL-33/ST2 axis may have a complex role in obesity-associated metabolic disorders. Although it is protective in HFD-induced adiposity, the IL-33/ST2 pathway promotes hepatic steatosis, inflammation and fibrosis.
If the inline PDF is not rendering correctly, you can download the PDF file here.
1. Cohen JC Horton JD Hobbs HH. Human fatty liver disease: old questions and new insights. Science. 2011;332(6037):1519-23.
2. Henao-Mejia J Elinav E Jin C Hao L Mehal WZ Strowig T et al. Inflammasome-mediated dysbiosis regulates progression of NAFLD and obesity. Nature. 2012;482(7384):179-85.
3. Choi S Diehl AM. Role of inflammation in nonalcoholic steatohepatitis. Current opinion in gastroenterology. 2005;21(6):702-7.
4. Mouralidarane A Soeda J Visconti-Pugmire C Samuelsson AM Pombo J Maragkoudaki X et al. Maternal obesity programs offspring nonalcoholic fatty liver disease by innate immune dysfunction in mice. Hepatology. 2013;58(1):128-38.
5. Li Z Soloski MJ Diehl AM. Dietary factors alter hepatic innate immune system in mice with nonalcoholic fatty liver disease. Hepatology. 2005;42(4):880-5.
6. Grarup N Sandholt CH Hansen T Pedersen O. Genetic susceptibility to type 2 diabetes and obesity: from genome-wide association studies to rare variants and beyond. Diabetologia. 2014;57(8):1528-41.
7. Lin YC Chang PF Chang MH Ni YH. Genetic variants in GCKR and PNPLA3 confer susceptibility to nonalcoholic fatty liver disease in obese individuals. Am J Clin Nutr. 2014;99(4):869-74.
8. Postic C Girard J. Contribution of de novo fatty acid synthesis to hepatic steatosis and insulin resistance: lessons from genetically engineered mice. J Clin Invest. 2008;118(3):829-38.
9. Ferre P Foufelle F. Hepatic steatosis: a role for de novo lipogenesis and the transcription factor SREBP-1c. Diabetes obesity & metabolism. 2010;12 Suppl 2:83-92.
10. Negrin KA Roth Flach RJ DiStefano MT Matevossian A Friedline RH Jung D et al. IL-1 signaling in obesity-induced hepatic lipogenesis and steatosis. PLoS One. 2014;9(9):e107265.
11. Milovanovic M Volarevic V Radosavljevic G Jovanovic I Pejnovic N Arsenijevic N et al. IL-33/ST2 axis in inflammation and immunopathology. Immunol Res. 2012;52(1-2):89-99.
12. Miller AM Asquith DL Hueber AJ Anderson LA Holmes WM McKenzie AN et al. Interleukin-33 induces protective effects in adipose tissue inflammation during obesity in mice. Circ Res. 2010;107(5):650-8.
13. Marvie P Lisbonne M L'Helgoualc'h A Rauch M Turlin B Preisser L et al. Interleukin-33 overexpression is associated with liver fibrosis in mice and humans. J Cell Mol Med. 2010;14(6b):1726-39.
14. McHedlidze T Waldner M Zopf S Walker J Rankin AL Schuchmann M et al. Interleukin-33-dependent innate lymphoid cells mediate hepatic fibrosis. Immunity. 2013;39(2):357-71.
15. Townsend MJ Fallon PG Matthews DJ Jolin HE McKenzie AN. T1/ST2-deficient mice demonstrate the importance of T1/ST2 in developing primary T helper cell type 2 responses. J Exp Med. 2000;191(6):1069-76.
16. Junqueira LC Bignolas G Brentani RR. Picrosirius staining plus polarization microscopy a specific method for collagen detection in tissue sections. Histochem J. 1979;11(4):447-55.
17. Hadi AM Mouchaers KT Schalij I Grunberg K Meijer GA Vonk-Noordegraaf A et al. Rapid quantification of myocardial fibrosis: A new macro-based automated analysis. Anal Cell Pathol (Amst). 2010;33(5):257-69.
18. Deutsch MJ Schriever SC Roscher AA Ensenauer R. Digital image analysis approach for lipid droplet size quantitation of Oil Red O-stained cultured cells. Anal Biochem. 2014;445:87-9.
19. Juluri R Vuppalanchi R Olson J Unalp A Van Natta ML Cummings OW et al. Generalizability of the non-alcoholic steatohepatitis Clinical Research Network histologic scoring system for nonalcoholic fatty liver disease. J Clin Gastroenterol. 2011;45(1):55-8.
20. Volarevic V Mitrovic M Milovanovic M Zelen I Nikolic I Mitrovic S et al. Protective role of IL-33/ST2 axis in Con A-induced hepatitis. J Hepatol. 2012;56(1):26-33.
21. Foster B Prussin C Liu F Whitmire JK Whitton JL. Detection of intracellular cytokines by flow cytometry. Curr Protoc Immunol. 2007;Chapter 6:Unit 6.24.
22. Livak KJ Schmittgen TD. Analysis of relative gene expression data using real-time quantitative PCR and the 2(-Delta Delta C(T)) Method. Methods. 2001;25(4):402-8.
23. Montgomery MK Hallahan NL Brown SH Liu M Mitchell TW Cooney GJ et al. Mouse strain-dependent variation in obesity and glucose homeostasis in response to high-fat feeding. Diabetologia. 2013;56(5):1129-39.
24. Pantic JM Pejnovic NN Radosavljevic GD Jovanovic I.P Djukic ALJ Arsenijevic NN Lukic ML. Lack of ST2 enhances high - fat diet -induced visceral adiposity and inflammation in BALB/c mice [Delecija gena za ST2 promoviše gojaznost i inflamaciju u visceralnom adipoznom tkivu BALB/c miševa na dijeti sa visokim sadržajem masti]. Serb J Exp Clin Res 2013; 14(4): 155 -160.
25. Donnelly KL Smith CI Schwarzenberg SJ Jessurun J Boldt MD Parks EJ. Sources of fatty acids stored in liver and secreted via lipoproteins in patients with nonalcoholic fatty liver disease. J Clin Invest. 2005;115(5):1343-51.
26. Langin D. Adipose tissue lipolysis as a metabolic pathway to define pharmacological strategies against obesity and the metabolic syndrome. Pharmacol Res. 2006;53(6):482-91.
27. McKenna LA Jordan F Brown EA Huda SS Mackay VA Miller AM et al. The role of interleukin-33 and its receptor ST2 in human pregnancy. Archives of Disease in Childhood - Fetal and Neonatal Edition. 2011;96(Suppl 1):Fa98.
28. Su X Abumrad NA. Cellular fatty acid uptake: a pathway under construction. Trends Endocrinol Metab. 2009;20(2):72-7.
29. Grefhorst A Parks EJ. Reduced insulin-mediated inhibition of VLDL secretion upon pharmacological activation of the liver X receptor in mice. J Lipid Res. 2009;50(7):1374-83.
30. Beaven SW Matveyenko A Wroblewski K Chao L Wilpitz D Hsu TW et al. Reciprocal regulation of hepatic and adipose lipogenesis by liver X receptors in obesity and insulin resistance. Cell metabolism. 2013;18(1):106-17.
31. Moran-Salvador E Lopez-Parra M Garcia-Alonso V Titos E Martinez-Clemente M Gonzalez-Periz A et al. Role for PPARgamma in obesity-induced hepatic steatosis as determined by hepatocyte- and macrophage-specific conditional knockouts. FASEB J. 2011;25(8):2538-50.
32. Tang Y Bian Z Zhao L Liu Y Liang S Wang Q et al. Interleukin-17 exacerbates hepatic steatosis and inflammation in non-alcoholic fatty liver disease. Clin Exp Immunol. 2011;166(2):281-90.
33. Tan Z Qian X Jiang R Liu Q Wang Y Chen C et al. IL-17A plays a critical role in the pathogenesis of liver fibrosis through hepatic stellate cell activation. J Immunol. 2013;191(4):1835-44.
34. Lin SL Castano AP Nowlin BT Lupher ML Jr. Duffield JS. Bone marrow Ly6Chigh monocytes are selectively recruited to injured kidney and differentiate into functionally distinct populations. J Immunol. 2009;183(10):6733-43.
35. Karlmark KR Weiskirchen R Zimmermann HW Gassler N Ginhoux F Weber C et al. Hepatic recruitment of the inflammatory Gr1+ monocyte subset upon liver injury promotes hepatic fibrosis. Hepatology. 2009;50(1):261-74.
36. Tacke F. Functional role of intrahepatic monocyte subsets for the progression of liver inflammation and liver fibrosis in vivo. Fibrogenesis & tissue repair. 2012;5(Suppl 1 Proceedings of Fibroproliferative disorders: from biochemical analysis to targeted therapies-Petro E Petrides and David Brenner):S27.