Sunday, November 28, 2010

Gastric bypass and psoriasis????

Hossler EW, Maroon MS, & Mowad CM (2010). Gastric bypass surgery improves psoriasis. Journal of the American Academy of Dermatology PMID: 20655127

How could I not blog this article? What could possibly be the connection between gastric bypass and a skin disease?

The authors - dermatologists - describe two cases of significant long-lasting improvement in psoriasis after weight loss from gastric bypass surgery. They point out that obesity has been thought to be a risk factor for psoriasis, and that the risk increases with body mass index (BMI).

But why? The authors propose three possible mechanisms.

First, chronic low-grade inflammation is associated with both obesity and psoriasis, specifically through tumor necrosis factor (TNF)-alpha. Adipose (fat) tissue can secrete TNF-alpha in anyone, and the adipose tissue of obese individuals produces 2.5 times more TNF-alpha than that of people with a normal BMI. And, according to the authors, TNF-alpha plays a major role in the chronic inflammation found in the plaques of psoriasis. Weight loss can result in a decrease in production of TNF-alpha.

So, what is TNF-alpha? It's a cytokine involved in systemic inflammation. And a cytokine? It's a protein molecule secreted by the glial cells of the nervous system and by numerous cells of the immune system. They are used extensively in communication between cells. Dysregulation of cytokines may be involved in autoimmune diseases. Cytokines are also implicated in chronic inflammation. (And you thought the glial cells were just neuron wannabes!)

Second, the connection may be related to leptin. Leptin is a hormone that plays a key role in regulating satiety and metabolism. Obese people have excessive amounts of leptin circulating in their blood, and that's the problem. If it's circulating in the blood, it's not binding to its receptors and doing its job, that is, increasing the feeling of satiety. It has been hypothesized that obese individuals are resistant to leptin in a similar way that people with Type II diabetes are resistant to insulin.

Studies have also demonstrated that leptin levels are higher in people with psoriasis than in control groups. Further, leptin levels decrease after weight loss. Leptin increases the production of the type of T cells found in psoriasis, and stimulates the production of TNF-alpha.

Third, weight loss may alter bacteria on the skin. Obesity has been associated with an increased risk for bacterial and non-bacterial skin infections. The authors are hopeful that weight loss will become an effective treatment for psoriasis.

I'd like to learn more about inflammation. Cursory MedLine searches show that the word "inflammation" occurs in article titles suggesting a link with cardiovascular disease, cancer, some forms of non-Alzheimer's dementia, obesity, psoriasis, eczema, autoimmune disorders, depression, and schizophrenia. With a rap sheet this long, inflammation might be the new public health enemy #1.