Identification of Circulating Microbial DNA and Its Correlation in Patients with Diabetic Kidney Disease

Background: In recent years, substantial studies have been accumulated to indicate the important role of gut microbiota in diabetic kidney disease (DKD). The abnormal changes of bacterial-derived products could imply specific injuries or play beneficial or harmful roles in DKD progression. Our previous study reported a “leaky gut” was induced in mice with DKD, leading to intestine-derived Klebsiella oxytoca translocation to circulation and kidneys then promoting DKD progression. However, the presence of K. oxytoca was not investigated in DKD patients. Therefore, the present study examines the K. oxytoca levels in circulation and their association with clinical characteristics in patients with DKD. Methods: We enrolled a total of 16 healthy participants, 17 patients with DKD, 5 patients with DKD needing hemodialysis (HD), and 7 patients with CKD without diabetes, who were admitted to Kanazawa University Hospital in 2021. Bacterial-derived DNA (16S rDNA and a specific K. oxytoca gene) in the blood was detected using droplet digital PCR, then investigated the relationship with clinical characteristics. Results: The K. oxytoca gene was detected in all patient groups with rates of 64.7% in patients with DKD without HD, 60% in DKD with HD group, and 42.9% in the non-DKD CKD group, but only 1/11 (6.25%) in healthy participants. Patients with DKD (with or without HD) exhibited trends of higher levels of K. oxytoca copies and K. oxytoca / 16S rDNA ratio compared to patients with non-DKD CKD. Interestingly, blood K. oxytoca copies and K.oxytoca/ 16S rDNA ratio have been identified to have a positive correlation with blood creatinine (r=0.7007 and 0.6492) or BUN levels (r=0.582 and 0.5619) in DKD patients. Considering eGFR, negative correlations were observed with both K. oxytoca copies and the K.oxytoca/16S rDNA ratio, with correlation coefficients of -0.4509 and -0.4664, respectively. Moreover, there was a correlation between K. oxytoca gene copies and higher neutrophil percentages (r=0.4816), along with a lower lymphocyte frequency (r=-0.5558), and elevated neutrophil-to-lymphocyte ratio (r=0.4998). Conclusion: The presence of the K. oxytoca gene in the circulation could serve as a biomarker reflecting reduced renal function and chronic inflammation in DKD patients. Funding: Government Support – Non-U.S.