**Improvement of Psoriasis by Alteration of the Gut Environment by Oral Administration of Fucoidan from** *Cladosiphon Okamuranus*

**Masanobu Takahashi 1, Kento Takahashi 1, Sunao Abe 2, Kosuke Yamada 1, Manami Suzuki 1, Mai Masahisa 1, Mari Endo 1, Keiko Abe 3,4, Ryo Inoue 5 and Hiroko Hoshi 1,\***


Received: 1 February 2020; Accepted: 5 March 2020; Published: 10 March 2020

**Abstract:** Psoriasis is a chronic autoimmune inflammatory disease for which there is no cure; it results in skin lesions and has a strong negative impact on patients' quality of life. Fucoidan from *Cladosiphon okamuranus* is a dietary seaweed fiber with immunostimulatory e ffects. The present study reports that the administration of fucoidan provided symptomatic relief of facial itching and altered the gu<sup>t</sup> environment in the TNF receptor-associated factor 3-interacting protein 2 (*Traf3ip2*) mutant mice (*m-Traf3ip2* mice); the *Traf3ip2* mutation was responsible for psoriasis in the mouse model used in this study. A fucoidan diet ameliorated symptoms of psoriasis and decreased facial scratching. In fecal microbiota analysis, the fucoidan diet drastically altered the presence of major intestinal opportunistic microbiota. At the same time, the fucoidan diet increased mucin volume in ileum and feces, and IgA contents in cecum. These results sugges<sup>t</sup> that dietary fucoidan may play a significant role in the prevention of dysfunctional immune diseases by improving the intestinal environment and increasing the production of substances that protect the immune system.

**Keywords:** fucoidan; psoriasis; *Traf3ip2*; microbiota; mucin; IgA
