Association Between Glycemic Control and Complications With Concentration of Urinary Exfoliated Proximal Tubule Kidney Cells in People With Diabetes Mellitus

Background: Emerging evidence suggests cell exfoliation could be operating under the control of cell metabolism. It is unclear if there are associations between the concentration of exfoliated kidney proximal tubule cells (PTCs) in urine with glycemic control and complications. Our study is aimed at exploring this. Methods: Urine samples were collected from 122 adult study participants and stored at -80°C. Exfoliated PTCs were extracted from thawed urine using a validated specific immunomagnetic separation method based on anti-CD13 and anti-SGLT-2 antibodies. The number of PTCs was assessed using brightfield microscopy. Study participants were grouped into those with no diabetes mellitus (DM) and those with DM. Individuals with DM were further subgrouped into those with and without retinopathy. Adjusted Poisson regression analysis was conducted for the DM cohort, investigating associations between demographic, clinical, and biochemical parameters with mean urinary exfoliated PTCs. Results: The adjusted Poisson regression analysis noted sex to have a significant association with mean number of urinary exfoliated PTCs, with a lower incidence rate in males compared to females (incidence rate ratio (IRR) 0.56, 95% CI 0.35-0.89, p = 0.014). Each 1% increase in glycated haemoglobin (HbA1c) was associated with an increase of 1.03 times in mean exfoliated PTCs (IRR 1.03, 95% CI 1.01-1.04, p = 0.007), and DM patients with retinopathy had an increase of 1.68 times in mean exfoliated PTCs compared to those without retinopathy (IRR 1.68, 95% CI 1.07-2.62, p = 0.024). No significant associations were observed with albuminuria or estimated glomerular filtration rate (eGFR). Conclusions: Our results indicate increased shedding of PTCs into the urinary tract in patients with poorer glycemic control, particularly those with diabetic retinopathy and in females.