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Study: The Impact of Diet on Psoriasis Inflammation

The traditional Western diet alters the gut microbiome, which may influence psoriatic inflammation.

It may be possible to manage or mitigate the inflammation that contributes to psoriatic disease, in part, through dietary modifications, according to recent research published in the Journal of Investigative Dermatology. [1]

According to researchers a Western diet rich in fat and sugar appears to result in an imbalance in the gut microbiome, which also enhances susceptibility to interleukin (IL)-23-mediated inflammation common in psoriatic disease.

“We can clearly link changes in the gut microbiome to the diet,” says Samuel T. Hwang, M.D., Ph.D., professor and chair of dermatology, University of California Davis School of Medicine, Sacramento, Calif. “And when provided a trigger for psoriasis, there are more changes in the gut.”

In previous work, Dr. Hwang and colleagues have shown that a Western diet can result in clinically and molecularly significant signs of skin inflammation in mice in as little as 4 weeks, suggesting that diet may influence inflammatory signaling in the skin.[2] Other studies have linked the gut microbiome with the development of inflammatory and immune-mediated conditions like inflammatory bowel disease, type 1 diabetes, cardiovascular disease, and cancer. [3] Data from these studies suggest the balance of microorganisms in the gut may play a role in shaping inflammation like that which may lead to psoriasis and related comorbidities such as psoriatic arthritis, the researchers note, as research has indicated the gut microbiome is altered in patients with psoriasis. [4]

Additionally, it is now commonly understood that diet directly influences the balance of microorganisms in the gut [5] The Western diet, characterized by high-fat and sugar-laden foods, has been associated with changes in physiology and overall health that can lead to weight gain and metabolic disturbances that result in systemic inflammation and altered immune function. [6] And, while obesity itself is a notable risk factor for psoriasis, Dr. Hwang says this recent study indicates that the detrimental effects of diet may influence psoriatic inflammation before you get to that obese state.

“What's new about our work is that we're showing that the diet itself can increase your susceptibility to psoriatic inflammation, both in the joints and in the skin,” Dr. Hwang says.

Using a mouse model, Dr. Hwang, in collaboration with University of California Davis School of Medicine colleagues Satya Dandekar, Ph.D., Department of Medical Microbiology and Immunology, and Yu-Jui Yvonne Wan, Ph.D., Department of Medical Pathology and Laboratory Medicine, and others, examined the effects of diet on intestinal dysbiosis for evidence of impact on skin and joint inflammation. 

First, the researchers looked at the impact of the Western diet on susceptibility to IL-23-mediated skin inflammation. The researchers fed mice either a chow or standard diet, or a Western diet for 6 weeks, at which time the mice were injected with either IL-23 minicircle (MC) DNA to induce systemic IL-23 overexpression or control green florescent protein (GFP) MC DNA. After another 4 weeks, the mice injected with IL-23 MC DNA showed a significant elevation of serum IL-23. Additionally, they developed skin changes consisting of erythema and scaling. However, the mice fed the chow diet had much milder changes while the mice injected with the GFP MC DNA showed no changes.

“Short-term Western diet intake appears sufficient to enhance susceptibility to IL-23‒mediated psoriasis-like skin inflammation,” the authors wrote.

In characterizing the immunological features observed in the mice injected with the IL-23 MC DNA, the authors noted that mice fed the Western diet appeared to have worse skin inflammation. What this means, Dr. Hwang explains is that while a Western diet alone may result in changes that can lead to psoriatic inflammation, if you have other factors that might trigger psoriasis, a Western diet can make it worse.

The researchers also discovered the Western diet appeared to predispose mice to IL-23‒mediated joint inflammation.

A critical finding of their study was establishing the gut microbiome as a pathogenic link between diet and psoriatic inflammation. The researchers observed significant differences in bacterial abundance between groups. Mice fed the Western diet had a lower microbial diversity than the chow-fed mice, including a loss of beneficial bacteria, and the changes in microbial diversity were exacerbated in the group injected with IL-23 MC DNA.

Are the changes reversible? This was the final question Dr. Hwang and colleagues examined. They fed a group of mice a Western diet for 6 weeks and then injected them with IL-23 MC DNA to initiate psoriatic-like disease. These mice were then divided into two groups: one which continued the Western diet and one which switched to the chow diet. After 4 weeks, the mice that switched to the chow diet showed less scaling, reduced ear thickness, as well as other molecular changes such as diminished epidermal thickness and cellular infiltrates than those which maintained the Western diet. In addition, the researchers observed a beneficial change in gut microbiota composition in the mice switched to the chow diet.

“We know that psoriasis is a systemic disease,” Dr. Hwang says. “But I think we're now understanding that environmental contributions such as diet can make a difference — and sometimes a pretty striking difference.”

Psoriasis results from predisposing genetic factors and the influence of external triggers, so while you cannot change your genetics, you can modify your diet, Dr. Hwang says. And possibly, by implementing changes at the first sign of psoriatic skin inflammation, it may be possible to reduce the risk of joint disease, he adds. Further, by combining weight loss, which often involves dietary changes or caloric restriction, with other treatments, we may get a better outcome.

He says he now advises patients that this is a lifestyle change, but it does not have to be onerous. Modifying a Western diet to something like a Mediterranean diet does not mean you are just eating lettuce every day, he says. There are different ways to modify the balance of one’s diet to get a beneficial effect and this work suggests that’s possible, he adds.  Working with an experienced dietician or certified nutritionist as part of your collaborative care team can be beneficial.

I hope that gives patients hope, Dr. Hwang says. Even for those with other pro-inflammatory stimuli or other triggers that are not easily changed. If you can change your diet, it may be enough to mitigate these other factors enough that it lessens disease severity, he says.

Dr. Hwang says his team continues to explore the possible connection with the gut microbiome and its impact on psoriatic disease as they examine the particular roles of bacterial species and the role of bacterial metabolites in skin inflammation.

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References

References

1. Shi Z, Wu X, Santos Rocha C, et al. Short-term western diet intake promotes il-23‒mediated skin and joint inflammation accompanied by changes to the gut microbiota in mice. Journal of Investigative Dermatology. 2021;141(7):1780-1791

2. Shi Z, Wu X, Yu S, et al. Short-term exposure to a western diet induces psoriasiform dermatitis by promoting accumulation of il-17a–producing γδ t cells. Journal of Investigative Dermatology. 2020;140(9):1815-1823.

3. Tlaskalová-Hogenová H, Štěpánková R, Kozáková H, et al. The role of gut microbiota (Commensal bacteria) and the mucosal barrier in the pathogenesis of inflammatory and autoimmune diseases and cancer: contribution of germ-free and gnotobiotic animal models of human diseases. Cell Mol Immunol. 2011;8(2):110-120.

4. Tan L, Zhao S, Zhu W, et al. The Akkermansia muciniphila is a gut microbiota signature in psoriasis. Exp Dermatol. 2018;27(2):144-149.

5. Singh RK, Chang H-W, Yan D, et al. Influence of diet on the gut microbiome and implications for human health. J Transl Med. 2017;15(1):73.

6. Christ A, Lauterbach M, Latz E. Western diet and the immune system: an inflammatory connection. Immunity. 2019;51(5):794-811.

 

Author

Heather Onorati

Title

Freelance writer

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