Dipeptidylpeptidase (DPP)-4 inhibitor therapy increases circulating levels of anti-inflammatory soluble frizzle receptor protein (sFRP)-5 which is decreased in severe COVID-19 disease

Background and Aim Obesity and type 2 diabetes (T2D) show an increased risk for a severe COVID-19 disease. Treatment with DPP4 inhibitor (DPP4i) results in reduced mortality and better clinical outcome. Here, we aimed to identify potential mechanisms for the observed DPP4i effect in COVID-19.

Methods We compared T2D subjects with (cases) and without (controls) DPP4i treatment (N=69), as well as patients hospitalised for severe COVID-19 and healthy controls (N=34) with regard to serum concentrations of soluble frizzle receptor protein 5 (sFRP5) using univariate statistics. Furthermore, we isolated pre-adipocytes, mature adipocytes and macrophages from adipose tissue biopsies (N=100) and performed western-blotting for sFRP5 and Wnt5a expression.

Results In T2D patients, we identified a significant increase of the anti-inflammatory adipokine sFRP5 in relation to DPP4 inhibition. sFRP5 is a specific antagonist to Wnt5a, a glycopeptide secreted by adipose tissue macrophages acting pro-inflammatory in various diseases. We therefore examined sFRP5 levels in patients hospitalised for severe COVID-19 and found significant lower levels compared to healthy controls. Since sFRP5 might consequently be a molecular link for the beneficial effects of DPP4i in COVID-19, we further aimed to identify the exact source of sFRP5 in adipose tissue on cellular level. Results from western-blotting in adipose tissues showed a sFRP5 expression specifically in mature adipocytes of subcutaneous and omental adipose tissue.

Conclusion In summary, our data suggest that DPP4i increase serum levels of anti-inflammatory sFRP5 which might be beneficial in COVID-19, reflecting a state of sFRP5 deficiency.

Conflict of Interest

No conflicts of interest to declare

Publication History

Article published online:
26 May 2022