Serum Albumin Modifies the Effect of Peripheral Blood Monocytes on Severity of Diabetic Nephropathy in an Adult Population.

Background: Our aim in this study was to characterize clinical associations between peripheral blood immune populations and diabetic kidney disease (DKD) in patients with type 2 diabetes mellitus.

Methods: We queried hospital records from an outpatient diabetes primary care clinic between 2018 and 2019 for clinical and laboratory data, including complete blood counts with differentials, serum albumin and globulin, glycated hemoglobin (A1C) and urine albumin-to-creatinine ratio. One hundred ninety-eight patients had complete cross-sectional data with temporally proximate complete blood counts and urine albumin-to-creatinine ratios. After univariable correlation assessment, we used a forward multivariable linear regression model to test the hypothesis that higher numbers of circulating innate immune populations would be associated with DKD, while accounting for known demographic, clinical and laboratory risk factors. We defined DKD as an albumin-to-creatinine ratio of >3 mg/mmol or an estimated glomerular filtration rate (eGFR) of <60 mL/min/1.73 m from the Chronic Kidney Disease Epidemiology Collaboration.

Results: Adjusted analyses demonstrated significant (p<0.01) associations between higher urine albumin-to-creatinine ratio and peripheral circulating monocytes, independent of other established significant risk factors, including blood pressure, A1C, age and sex. We also identified serum albumin as a potentially important modifying factor of albuminuric kidney disease, which interacts with monocytes in more advanced disease. In contrast, the variable most strongly predictive of eGFR was age.

Conclusions: Circulating monocytes and serum albumin are significantly associated with albuminuria, but not eGFR in DKD. These results support the potential role of the innate immune system in diabetic microvascular end-organ damage and urinary protein loss, and may be readily translatable clinical markers to incorporate into risk-assessment models for prognostication in diabetes.