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The study, published today in the Journal of Investigative Dermatology, suggests that dietary ingredients, rather than obesity itself, may lead to dermatitis and the development of psoriasis. A common and chronic skin disease, psoriasis causes skin cells to form itchy and sometimes painful red peels and patches.
Diet and dermatitis
Previous studies have shown that obesity is a risk factor for psoriasis development or exacerbation. The Western diet, which is characterized by eating large amounts of saturated fat, sucrose and low fiber intake, has been associated with an increased prevalence of obesity in the world.
"In our study, we found that short-term exposure to the Western diet is capable of causing psoriasis before body weight is significantly increased," said Hwang, professor and head of dermatology at the University of California, Davis and lead author of the study.
For the UC Davis Health study, which used a mouse model, Hwang and his colleagues found that a diet high in fat and sugar (mimicking the Western diet in humans) was required to induce observed dermatitis. In just four weeks, mice on a Western diet significantly increased ear swelling and visible dermatitis compared to mice that fed on a controlled diet and those on a high-fat-only diet.
"An unhealthy diet not only affects your waistline, but also your skin immunity," said Zhenrui Shi, visiting assistant researcher in the Department of Dermatology at the University of California, Davis and lead author of the study.
Bile acids and dermatitis
The study details the mechanisms by which inflammation occurs after a Western diet. Bile acids have been identified as key signaling molecules in regulating skin immunity. Bile acids in the liver are produced from cholesterol and metabolism in the intestines is done by gut microbiota. They play an important role in absorbing dietary fat and cholesterol balance.
The study found that cholesterol, a drug used to lower cholesterol levels by linking to bile acids in the intestines, helps reduce the risk of dermatitis. The results indicate that bile acids mediate the development of psoriasis. Cholesterol association with bile acids in the intestines and subsequent release through feces allows for a reduction in dermatitis.
Further studies are needed to understand the mechanism behind diet-induced dermatitis and the interaction between metabolism, microbes and immunity.
This study was supported by the National Psoriasis Foundation Discovery Grant, the NIH/NIAMS R01 Grant (1R01AR063091-01A1) and the NCI/NIH Grant (U01-CA179582-03A1).
Other collaborators include Xuesong Wu, Mindy Huynh and Mimi Nguyen from the Department of Dermatology at UC Davis, Prasant Jena and Yui-Jui Yvonne Wan of Medical Pathology and Laboratory Medicine at UC Davis and Sebastian Yu of the Department of Dermatology at Kaohsiung Medical University.
The source of the story:
Materials provided by the University of California- Davis Health. Note: Content can be adjusted to style and length.
Zhenrui Shi, Xuesong Wu, Sebastian Yu, Mindy Huynh, Prasant Kumar Jena, Mimi Nguyen, Yu-Jui Yvonne Wan, Samuel T.Hwang. Short-term exposure to a Western diet leads to psoriatic dermatitis by promoting the accumulation of IL-17A-producing T cells. Journal of Dermatology Survey, 2020; DOI: 10.1016 / j.jid.2020.01.020
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