Acknowledgements

We thank all members of our laboratories in the University of Toyama and Toyama Prefectural Institute for Pharmaceutical Research for helpful discussions. The authors sincerely thank Toyama Prefecture for supporting our laboratory.

This work was supported by grants from Grant-in-Aid for Scientific Research from the Japan Society for the Promotion of Science (JSPS) (JSPS KAKENHI Grant Numbers JP16K19532 to Y. W., JP15K08527 to Y.N., JP24390119 to K.T., and JP15K07960 to H.H.), JST, PRESTO (Y.N.), Hokuriku Innovation Cluster for Health Science, MEXT Regional Innovation Cluster Program, Toyama/Ishikawa Region (K.T.), and Hokuriku Life Science Cluster, MEXT Regional Innovation Strategy Support Program (K.T.).

#### Conflict of interest statement

The authors declare no competing financial interests.

#### Abbreviations

3.2.2. Inhibitory effects of isoliquiritigenin on PRR-mediated adipose tissue fibrosis

128 Biological Activities and Action Mechanisms of Licorice Ingredients

These increases were significantly attenuated by ILG stimulation (Figure 1).

by ILG stimulation [51] (Figure 1).

activation of innate immune sensors.

4. Concluding remarks

obesity-associated diseases.

Acknowledgements

Toyama Prefecture for supporting our laboratory.

In addition to inflammation, fibrosis may have an important role in adipose tissue dysfunction [9]. Because TLR4 signaling in immune cells has a key role in the development of obesity- and endotoxin-mediated adipose tissue fibrosis [50], we examined whether ILG attenuated TLR4 stimulated expression of fibrosis-related genes in peritoneal macrophages and stromal vascular fraction (SVF) of obese eWAT. Lipid A stimulation increased the expression of fibrosisrelated genes, such as TGF-β and TIMP-1 (tissue inhibitor of metalloproteinase-1) in these cells.

Mincle stimulation is also crucial for fibrogenesis in SVF of obese adipose tissue [22]. The SVF from HFD-fed mice was stimulated with a Mincle ligand trehalose-6,6′-dimycolate (TDM), a mycobacterial cell wall glycolipid [22, 51]. TDM stimulation significantly increased TIMP-1 and PDGF-B mRNA expression in the SVF and these increases were significantly attenuated

Finally, we examined whether ILG improved HFD-induced adipose tissue fibrosis. Histological analysis revealed that HFD treatment induced extensive interstitial fibrosis in eWAT, which was markedly suppressed by ILG supplementation (0.5% w/w in HFD) [51]. HFD treatment increased collagen 1, TGF-β, TIMP-1, and PDGF-B mRNA expression in eWAT. These expressions were markedly decreased by ILG supplementation. These results highlight that ILG is a promising therapeutic candidate for HFD-induced adipose tissue fibrosis by suppressing the

It has now become clear that G. uralensis-derived components including ILG have a major impact in innate immunity to prevent adipose tissue inflammation and fibrosis. On the other hand, ILG also acts on adipocytes, and consequently suppresses inflammatory changes elicited by macrophage-derived mediators such as TNF-α [51], suggesting that ILG targets multiple cells that constitute adipose tissue. Moreover, activation of various innate immune sensors is affected by ILG stimulation, consequently suppressing adipose tissue inflammation and fibrosis. A better understanding of these mechanisms will be addressed in the near future. With these new findings, we will be enabled to design better therapeutic strategies based on innate immunity through the usage of ILG to combat

We thank all members of our laboratories in the University of Toyama and Toyama Prefectural Institute for Pharmaceutical Research for helpful discussions. The authors sincerely thank

