Urinary interleukin-9 in youth with type 1 diabetes mellitus

Aims Interleukin-9 (IL-9) attenuates podocyte injury in experimental kidney disease, but its role in diabetic nephropathy is unknown. We sought to relate urinary IL-9 levels to the release of podocyte-derived extracellular vesicles (EVs) in youth with type 1 diabetes. We related urinary IL-9 levels to clinical variables and studied interactions between urinary IL-9, vascular endothelial growth factor (VEGF), tumor necrosis factor alpha (TNFα) and interleukin-6 (IL-6) on urinary albumin/creatinine ratio (ACR) a functional measure of podocyte injury. Methods We performed an analysis of urine samples and clinical data from a cohort of youth with type 1 diabetes ( n = 53). Cytokines were measured using a Luminex platform (Eve Technologies), and nanoscale flow cytometry was employed to quantify urinary podocyte-derived EVs. All urinary measures were normalized to urinary creatinine. Results Mean age was 14.7 ± 1.6 years, and the mean time from diagnosis was 6.7 ± 2.9 years. Mean HbA1c was 70.3 ± 13.9 mmol/mol, mean ACR was 1.3 ± 1.9 mg/mmol, and mean eGFR was 140.3 ± 32.6 ml/min/1.73 m 2 . IL-9 was inversely related to podocyte EVs ( r = − 0.56, p = 0.003). IL-9 was also inversely related to blood glucose, HbA1C and eGFR ( r = − 0.44, p = 0.002; r = − 0.41, p = 0.003; r = − 0.49, p < 0.001, respectively) and positively correlated with systolic BP ( r = 0.30, p = 0.04). There was a significant interaction between IL-9, EVs and ACR ( p = 0.0143), and the relationship between IL-9 and ACR depended on VEGF ( p = 0.0083), TNFα ( p = 0.0231) and IL-6 levels ( p = 0.0178). Conclusions IL-9 is associated with podocyte injury in early type 1 diabetes, and there are complex interactions between urinary IL-9, inflammatory cytokines and ACR.