Appetite Suppression and Interleukin 17 Receptor Signaling Activation of Colonic Mycobiota Dysbiosis Induced by High Temperature and High Humidity Conditions.

Yinrui Guo,Xiangxiang Zhu,Jian Wang,Diling Chen,Hongya Guo,Yuanfei Fu,Lingyan Qiu,Haiting Zhang

doi:10.3389/fcimb.2021.657807

Abstract

It is known that the microbiome affects human physiology, emotion, disease, growth, and development. Most humans exhibit reduced appetites under high temperature and high humidity (HTHH) conditions, and HTHH environments favor fungal growth. Therefore, we hypothesized that the colonic mycobiota may affect the host’s appetite under HTHH conditions. Changes in humidity are also associated with autoimmune diseases. In the current study mice were fed in an HTHH environment (32°C ± 2°C, relative humidity 95%) maintained via an artificial climate box for 8 hours per day for 21 days. Food intake, the colonic fungal microbiome, the feces metabolome, and appetite regulators were monitored. Components of the interleukin 17 pathway were also examined. In the experimental groups food intake and body weight were reduced, and the colonic mycobiota and fecal metabolome were substantially altered compared to control groups maintained at 25°C ± 2°C and relative humidity 65%. The appetite-related proteins LEPT and POMC were upregulated in the hypothalamus (p < 0.05), and NYP gene expression was downregulated (p < 0.05). The expression levels of PYY and O-linked β-N-acetylglucosamine were altered in colonic tissues (p < 0.05), and interleukin 17 expression was upregulated in the colon. There was a strong correlation between colonic fungus and sugar metabolism. In fimo some metabolites of cholesterol, tromethamine, and cadaverine were significantly increased. There was significant elevation of the characteristic fungi Solicoccozyma aeria, and associated appetite suppression and interleukin 17 receptor signaling activation in some susceptible hosts, and disturbance of gut bacteria and fungi. The results indicate that the gut mycobiota plays an important role in the hypothalamus endocrine system with respect to appetite regulation via the gut-brain axis, and also plays an indispensable role in the stability of the gut microbiome and immunity. The mechanisms involved in these associations require extensive further studies.

Highlights

Our understanding of when and how abruptly this climate-driven disruption of biodiversity will occur is limited because biodiversity forecasts typically focus on individual snapshots of the future
Histograms of species distribution indicate that high temperature and high humidity (HTHH) conditions altered the colonic mycobiota extensively
IL-17 expression was upregulated in the colon, indicating that in mice appetite and immunity were altered under HTHH conditions

Summary

Introduction

Our understanding of when and how abruptly this climate-driven disruption of biodiversity will occur is limited because biodiversity forecasts typically focus on individual snapshots of the future. It is certain that biodiversity is threatened by climate change. Climate change can have adverse effects on biodiversity, by shifting species distributions (Barnosky et al, 2012; Wernberg et al, 2016; Provost et al, 2017), increasing extinction rates (Hultman et al, 2015), altering breeding times (Miller et al, 2018; Lv et al, 2020), and changing plant growth periods (Piao et al, 2019). An increasing number of reports indicate that climate change effects the microbial diversity in soil, forests, and oceans (Sen and Samanta, 2015; Ladau et al, 2018; Malard and Pearce, 2018; Praeg et al, 2019). Studies on gut microflora have generally focused on the characteristics of bacteria, and ignored the potential effects of fungi on metabolic health

Methods

Results

Conclusion