Background: The host-parasite relationship is based on subtle interplay between parasite survival strategies and host defense mechanisms. It is well known that helminth infection, which afflicts more than one billion people globally, correlates with a decreased prevalence of obesity. Dissecting the underlying mechanisms can provide new targets for treating obesity from the host-parasite interaction perspective. Methods: C57BL/6 mice received a normal or high-fat diet (HFD) with or without Sjp40 (one main component of schistosome-derived soluble egg antigens) treatment. Both the loss and gain-of-function experiments by the inhibitor suppression and lentivirus treatment of miR-802 were utilized to elucidate the role of miR-802/AMPK axis in host lipid metabolism. Hepatocyte lipogenesis assay and metabolic parameters were assessed both in vivo and in vitro . The potential interactions among Sjp40, CD36, miR-802, Prkab1, and AMPK were clarified by pull-down, miRNA expression microarray, quantitative RT-PCR, dual-luciferase reporter assay, and western blotting analysis. Results: We showed a link between decreased miR-802 and impaired lipid metabolism in Schistosoma japonicum infected mice. The decreased miR-802 promotes murine Prkab1 or human Prkaa1 expression, respectively, which increases levels of phosphorylated AMPK, resulting in a decrease in hepatic lipogenesis. Also, injection with schistosome-derived soluble egg antigens (SEA) attenuated metabolism. We demonstrated that Sjp40 as a main component of SEA interacted with CD36 on hepatocytes to inhibit miR-802, resulting in the activation of AMPK pathway and subsequent attenuation of lipogenesis. Collectively: Our study reveals the significant role of miR-802/AMPK axis in hepatic lipid metabolism and identifies the therapeutic potential of Sjp40 in treating obesity-related fatty liver.

Background Hepatic granuloma formation and fibrosis as the consequence of tissue entrapped eggs produced by female schistosomes characterize the pathology of Schistosoma japonicum infection. It has been proposed that fucoidan, a sulfated polysaccharide existing naturally in brown seaweed Fucus vesiculosus, plays a diversified role to perform immunomodulatory activities. However, whether fucoidan functions in the host hepatic pathology is unknown and identifying the potential mechanism that is responsible for hepatic improvement is still necessary. Methods We evaluated the hepatic pathology from S. japonicum-infected mice after treatment with fucoidan. qRT-PCR and immunofluorescence were used to detect the pro- or anti-inflammatory factors and the phosphorylated p65 in the livers. In addition, flow cytometry was also performed to investigate the T cell subsets in the S. japonicum-infected mice after treatment with fucoidan, and functional molecules relatively specific to Treg cells were detected in vitro. Furthermore, macrophages were treated with fucoidan in vitro and to detect the inflammatory cytokines. Results Treatment with fucoidan significantly reduced the hepatic granuloma size and fibrosis response during S. japonicum infection. The attenuated phospho-p65 protein levels and the mRNA levels of pro-inflammatory cytokines (IL-6, IL-12 and TNF-α) were observed in the livers from fucoidan-treated S. japonicum-infected mice; however, the mRNA levels of anti-inflammatory cytokines (IL-4 and IL-13) were increased. In addition, the infiltration of Treg cells was significantly enhanced both in the livers and spleens from fucoidan-treated S. japonicum-infected mice. Consistent with this, the mRNA levels of IL-10 and TGF-β were dramatically increased in the livers from S. japonicum-infected mice after fucoidan treatment. Furthermore, in vitro stimulated splenocytes with fucoidan resulted in increasing Treg cells in splenocytes as well as the functional expression of CC chemokine receptor type 4 (CCR4) and CXC chemokine receptor type 5 (CXCR5) in Treg cells. Additionally, fucoidan promoted the mRNA levels of IL-4 and IL-13 in macrophages. Conclusions These findings suggest an important role of natural fucoidan in reducing hepatic pathology in the progress of S. japonicum infection with a stronger Treg response, which may reveal a new potential therapeutic strategy for hepatic disease caused by parasitic chronic infection.

Previous studies have indicated that indolepropionic acid (IPA), derived from dietary tryptophan via gut microbiota conversion, is negatively correlated with type 2 diabetes mellitus and systemic low-grade inflammation. However, the effects of IPA administration on obesity, as well as the underlying mechanisms, remain unclear. In the present study, we observed that obesity leads to a dramatic reduction in IPA levels in both the serum and colonic mucosa, and IPA supplementation exerted beneficial effects on weight, as well as on glucose and lipid metabolism disorders. In adipose tissue, IPA treatment had no direct effect on adipocyte differentiation, but it significantly ameliorated adipose inflammation, thus preventing adipocyte enlargement. Moreover, IPA administration promoted gut integrity, increased the expression of tight junction proteins, and downregulated colonic inflammation; these effects were demonstrated to have a poor relationship with gut microbiota composition. Mechanistically, IPA significantly promoted the expansion of the tuft cell lineage in the gut and increased the secretion of interleukin-25 both in vivo and ex vivo, which contributes to the integrity of the gut barrier. This may partly depend on the free fatty acid receptor 3 pathway in tuft cells. Overall, our results demonstrate that IPA supplementation prevents the development of highfat diet-induced obesity and metabolic disorders by restoring tuft cellinterleukin-25-mediated colonic barrier integrity; hence, IPA could be a potential agent for treatment of obesity.

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The immune systems, which mainly consist of T cells, B cells and NK cells, are responsible for the maintaining of host homeostasis, adaptive immune responses providing protection against disease and specially infectious disease. 1 In particular, CD4 + T cells different subsets were essential for immune responses during host defence against pathogen infection and inflammatory diseases, 2-7 mainly including Th1, Th2, Th17 and Treg cells. The signals promoting differentiation of naive CD4 + T cells into a particular T helper cell subset are provided by distinct cytokines through activating antigen-presenting cells (APCs). P21-activated kinases 1 (PAK1), which was highly expressed in antigen-presenting cells (APCs), 8,9 contained conserved six serine-threonine kinases and involved in cellular apoptosis, proliferation and migration. 10-12 PAK1 has been reported to play a vital role in variety of disorders such as cancer, Alzheimer's disease, diabetes, and neurofibromatosis. 13 Recent studies have implicated that PAK1 was overexpressed in the inflammation-related disease and promoted cell activation pathways expression involved in