title: Circulating dipeptidyl peptidase-4 activity is associated with diabetic retinopathy in type 1 diabetic patients.
abstract: OBJECTIVE
  Diabetic retinopathy (DR) is the most frequent complication among patients with type 1 diabetes mellitus (T1DM). Dipeptidyl peptidase-4 (DPP4) is a protease with elevated activity in patients with T1DM. Several studies indicate that DPP4 inhibitors might have beneficial effect on nonproliferative retinopathy (NPR) development as well as on its progression to proliferative retinopathy (PR). We aimed to explore the relationship between serum DPP4 activity and DR in patients with T1DM.
  
  
  METHODS
  This cross-sectional study recruited 44 patients with T1DM. The DPP4 activity was measured by colorimetric assay in a microplate reader. Photodocumented retinopathy status was made according to the EURODIAB protocol.
  
  
  RESULTS
  A total of 28 (63.6%) patients were men, mean age 45.36 years, diabetes duration 23.71 years, glycated hemoglobin A1c (HbA1c) 7.4%. Patients were stratified into 2 groups according to retinopathy prevalence. Group 1 comprised 14 (31.85%) patients with DR absence while the second group consisted of 30 (68.15%) patients with both PR and NPR. Group 1 had lower fasting serum DPP4 activity (25.85 vs 33.84 U/L, p&lt;0.001) when compared to the second group. In the binary logistic regression model adjusted for age, sex, diabetes duration, and HbA1c level, DPP4 activity was associated with DR prevalence (odds ratio 1.887 [1.073-3.321]).
  
  
  CONCLUSIONS
  Serum DPP4 activity may be independently associated with both DR types in patients with T1DM. Further study is warranted to elucidate whether there is an association between DPP4 activity and DR severity and/or progression.
authors.affiliation: Vuk Vrhovac Clinic for Diabetes, Endocrinology and Metabolic Diseases, University Hospital Merkur, Medical School, University of Zagreb, Zagreb - Croatia.
authors.forename: Kristina
authors.initials: K
authors.lastname: Blaslov
authors.forename: Tomislav
authors.initials: T
authors.lastname: Bulum
authors.forename: Lea
authors.initials: L
authors.lastname: Duvnjak
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D003124:Colorimetry; D003430:Cross-Sectional Studies; D003922:Diabetes Mellitus, Type 1 / Q000201:enzymology*; D003930:Diabetic Retinopathy / Q000201:enzymology*; D018819:Dipeptidyl Peptidase 4 / Q000097:blood*; D005260:Female; D006442:Glycated Hemoglobin / Q000378:metabolism; D006801:Humans; D008297:Male; D008875:Middle Aged; D012307:Risk Factors
chemical_list: D001786:Blood Glucose; D018819:Dipeptidyl Peptidase 4; D006442:Glycated Hemoglobin; C042807:DPP4 protein, human