Aortic carboxypeptidase–like protein, a WNT ligand, exacerbates nonalcoholic steatohepatitis
Toshiaki Teratani, Kengo Tomita, Takahiro Suzuki, Hirotaka Furuhashi, Rie Irie, Makoto Nishikawa, Junji Yamamoto, Toshifumi Hibi, Soichiro Miura, Tohru Minamino, Yuichi Oike, Ryota Hokari, Takanori Kanai
Toshiaki Teratani, Kengo Tomita, Takahiro Suzuki, Hirotaka Furuhashi, Rie Irie, Makoto Nishikawa, Junji Yamamoto, Toshifumi Hibi, Soichiro Miura, Tohru Minamino, Yuichi Oike, Ryota Hokari, Takanori Kanai
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Research Article Cell biology Hepatology

Aortic carboxypeptidase–like protein, a WNT ligand, exacerbates nonalcoholic steatohepatitis

Abstract

Incidence of nonalcoholic steatohepatitis (NASH), which is considered a hepatic manifestation of metabolic syndrome, has been increasing worldwide with the rise in obesity; however, its pathological mechanism is poorly understood. Here, we demonstrate that the hepatic expression of aortic carboxypeptidase–like protein (ACLP), a glycosylated, secreted protein, increases in NASH in humans and mice. Furthermore, we elucidate that ACLP is a ligand, unrelated to WNT proteins, that activates the canonical WNT pathway and exacerbates NASH pathology. In the liver, ACLP is specifically expressed in hepatic stellate cells (HSCs). As fatty liver disease progresses, ACLP expression is enhanced via activation of STAT3 signaling by obesity-related factors in serum. ACLP specifically binds to frizzled-8 and low-density lipoprotein–related receptor 6 to form a ternary complex that activates canonical WNT signaling. Consequently, ACLP activates HSCs by inhibiting PPARγ signals. HSC-specific ACLP deficiency inhibits fibrosis progression in NASH by inhibiting canonical WNT signaling in HSCs. The present study elucidates the role of canonical WNT pathway activation by ACLP in NASH pathology, indicating that NASH can be treated by targeting ACLP-induced canonical WNT pathway activation in HSCs.

Authors

Toshiaki Teratani, Kengo Tomita, Takahiro Suzuki, Hirotaka Furuhashi, Rie Irie, Makoto Nishikawa, Junji Yamamoto, Toshifumi Hibi, Soichiro Miura, Tohru Minamino, Yuichi Oike, Ryota Hokari, Takanori Kanai

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Figure 8

Obesity-related factors in serum enhance ACLP production in HSCs via activation of STAT3 signaling in murine NAFLD.

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Obesity-related factors in serum enhance ACLP production in HSCs via act...
(A, D–F) Eight-week-old male Aclpfl/fl and AclpHSC-KO mice were fed an HFC diet for 4 weeks (n = 5/group) or 24 weeks (n = 7/group) to prepare a murine model of NAFLD or were fed a control diet for 24 weeks (n = 6/group). (A) Serum levels of FFA, leptin, and IL-6. **P < 0.01 vs. Aclpfl/fl mice fed a control diet. (B) Quantification of hepatic Aclp mRNA in 8-week-old WT mice 4 hours after treatment with intralipid (n = 7/group), leptin (n = 7/group), IL-6 (n = 7/group), or PBS (n = 5/group). *P < 0.05; **P < 0.01 vs. control mice treated with PBS. (C) Quantification of Aclp mRNA in primary cultured murine HSCs treated with various combinations of palmitate (200 μM), leptin (100 ng/ml), and IL-6 (100 ng/ml) for 6 hours (n = 5–7/group). **P < 0.01 vs. control HSCs treated with PBS. (D–F) Liver sections from control and NAFLD model Aclpfl/fl mice were used. (D) (Upper panel) Representative images of immunofluorescence double-staining for p-STAT3 (red) and GFAP (green). Scale bars: 100 μm. Single-channel images are shown in Supplemental Figure 20. (Lower panel) Quantification of pSTAT3/GFAP double-positive cells. The nuclei were stained with DAPI (blue). p-STAT3/nucleus costained sites are shown in purple. **P < 0.01 vs. Aclpfl/fl mice fed a control diet. (E) (Upper panel) Representative immunofluorescence double-staining images of p-STAT3 (red) and ACLP (green). Scale bars: 100 μm. Single-channel images are shown in Supplemental Figure 21. (Lower panel) Quantification of pSTAT3/ACLP double-positive cells. The nuclei were stained with DAPI (blue). p-STAT3/nucleus costained sites are shown in purple. **P < 0.01 vs. Aclpfl/fl mice fed a control diet. (F) Correlation between p-STAT3/GFAP double-positive and ACLP-positive cells. P values obtained via 1-way ANOVA with Tukey’s post hoc test (A, C, D, and E), unpaired Student’s t tests (B), and Pearson’s correlation analysis (F). Data are shown as SEM.