Incident microalbuminuria and complement factor mannan-binding lectin-associated protein 19 in people with newly diagnosed type 1 diabetes

Background: Evidence links the lectin pathway of complement activation to diabetic kidney disease. Upon carbohydrate-recognition by pattern-recognition molecules, eg, mannan-binding lectin (MBL), the MBL-associated serine protease (MASP-2) is activated and initiates the complement cascade. The MASP2 gene encodes MASP-2 and the alternative splice product MBL-associated protein 19 (MAp19). Both MAp19 and MASP-2 circulate in complex with MBL. We tested the hypothesis that MAp19 and MASP-2 concentrations predict the risk of incident microalbuminuria. Methods: Baseline MAp19 and MASP-2 were measured in 270 persons with newly diagnosed type 1 diabetes tracked for incidence of persistent microalbuminuria in a prospective observational 18-year-follow-up study. Results: Seventy-five participants (28%) developed microalbuminuria during follow-up. MBL-associated protein 19 concentrations were higher in participants that later progressed to microalbuminuria as compared with those with persistent normoalbuminuria (268 ng/mL [95% CI, 243-293] vs 236 ng/mL [95% CI, 223-250], P =.02). Participants with MAp19 concentration within the highest quartile of the cohort had an increased risk of microalbuminuria as compared with participants with MAp19 concentration within the combined lower 3 quartiles in unadjusted Cox analysis, hazard ratio 1.86 ([95% CI, 1.17-2.96], P =.009). This remained significant in adjusted models, eg, adjusting for age, sex, HbA_1c, systolic blood pressure, urinary albumin excretion, smoking, serum creatinine, and serum cholesterol. MBL-associated serine protease concentration was not associated with incidence of microalbuminuria. Conclusions: In conclusion, the results show an association between baseline MAp19 concentration and the incidence of microalbuminuria in an 18-year-follow-up study on persons with newly diagnosed type 1 diabetes.