Type 2 Diabetes More Common in Patients With Psoriatic Arthritis, Study Finds

Patients with psoriatic arthritis (PsA) face an elevated risk of type 2 diabetes (T2D) compared to the general population, according to a new review of studies from around the world.

Investigators from the University of Verona, in Italy, say it’s unclear exactly what mechanism links the two conditions, though they note that patients with PsA tend to face higher rates of several metabolic disorders. The investigators also argue that treatments for PsA might have impacts on the risk or severity of T2D.

Writing in the journal Rheumatology and Therapy, corresponding author Giacomo Dal Bello, MD, and colleagues say the overall prevalence of T2D is between 2.4% and 14.8% of the general population, depending on certain risk factors. To find out the prevalence among patients with PsA, they consulted English-language studies conducted between January 1989 and September 2019 that covered questions including the prevalence of TD2 in PsA, the pathogenic mechanisms linking the 2 conditions, and the effects systemic therapies for PsA might have on insulin sensitivity.

The review found the prevalence of T2D ranged from 6.1% to 20.2% among patients with PsA. Women with severe forms of PsA were found to be at the highest overall risk, the data showed. The review also indicated that North Americans with PsA were statistically more likely to have T2D compared to people in other regions. In addition to North America, the studies included in the review covered populations in Hong Kong, Israel, Spain, and the United Kingdom. Dal Bello and colleagues said the geographic difference could be related to higher rates of obesity and unhealthy lifestyles in North America.

When it comes to the reason for the linkage between the 2 conditions, investigators cite a number of possibilities.

“Elevated serum levels of adipokines, including TNF-α, which inhibits the autophosphorylation of the insulin receptor and suppresses the expression of glucose transporter 4, favor insulin resistance and could partially explain the association between PsA and diabetes mellitus,” Dal Bello and colleagues wrote.

The investigators also note that adiponectin and omentin are decreased in patients with PsA. Both have insulin-sensitizing and anti-atherogenic properties.

Another possibility is that treatments for PsA are impacting patients in ways that make them more likely to become diabetic. For instance, some treatments for PsA affect glucose homeostasis.

“Systemic corticosteroids are known to impair insulin resistance, whereas apremilast (phosphodiesterase type 4 inhibitor) and TNF-α inhibitors could exert neutral effect or reduce the insulin-resistance,” the authors wrote.

Dal Bello and colleagues also suggest that IL-17 or IL-23 inhibitors might bear some of the responsibility for the links between PsA and T2D. However, they say research into those links has so far been relatively sparse.

For clinicians treating patients with PsA, Dal Bello and his co-authors note that T2D is a risk factor for microvascular and macrovascular complications.

“It is possible that some new therapies, including apremilast and anti-TNF-α, could improve diabetes mellitus based on their mechanism of action, but currently few clinical data are available,” they said. “Considering glucose homeostasis, methotrexate could be safely used for PsA but it should be prescribed with caution for diabetic patients because it is associated with an increased risk of liver toxicity.”

Reference:

Dal Bello, G, Gisondi, P, Idolazzi, L, et al. Psoriatic arthritis and diabetes mellitus: A narrative review [published online April 18, 2020]. Rheumatol Ther. doi:10.1007/s40744-020-00206-7.