Transglutaminase 2 predicts parasitic worm-mediated protection against hepatic steatosis in obese mice

Abstract

Parasitic worm infection can mitigate high fat diet-induced chronic inflammation in obese mice by reducing hepatic fat accumulation and improving insulin sensitivity. However, the molecular alterations during infection-mediated regulation of hepatic steatotic events in obesity remain poorly understood. Here, we integrated proteomic and metabolomic analyses of infected obese mice, a functional deworming and interleukin-4c (IL-4c) treated animal model, and an obese patient cohort before and after bariatric surgery to uncover molecular targets/pathways indicative of the regulation of hepatic steatosis by gut Heligmosomoides polygyrus bakeri (H. p. bakeri) helminth infection. Proteomic analysis identified alterations in several molecules related to metabolism and showed elevated levels of transglutaminase 2 (TGM2) proportionate with an infection-regulated lipid load in diet-induced obese (DIO) mice. The role of TGM2 as a reliable predictor of hepatic steatosis was validated using deworming experiments which revealed a decrease in the liver tissue levels of Tgm2 following removal of H. p. bakeri. Further validation showing increase in Tgm2 levels in IL-4c treated mice confirmed its relevance as a general response indicator of type 2 immune response induced by helminth infection. Assessment of circulating TGM2 levels in matched obese patients before and after bariatric surgery revealed no change, indicating that differential expression of TGM2 is a unique functional response to regulation of hepatic steatosis by H. p. bakeri infection. Together, our data show that TGM2 is a unique predictive marker of improvement in hepatic lipid profile and provides additional evidence that parasitic worm infection protects against hepatic steatosis in DIO mice. These findings pave the way for novel therapeutic opportunities to resolve hepatic steatosis and prevent its progression to severe forms of metabolic dysfunction-associated steatotic liver disease, based on TGM2 coupled with mimetics of H. p. bakeri-derived products. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=138 SRC="FIGDIR/small/689654v1_ufig1.gif" ALT="Figure 1"> View larger version (36K): org.highwire.dtl.DTLVardef@1cae718org.highwire.dtl.DTLVardef@9ec0aorg.highwire.dtl.DTLVardef@1679b1corg.highwire.dtl.DTLVardef@f86bc9_HPS_FORMAT_FIGEXP M_FIG C_FIG