Association between continuous glucose monitoring-derived glycemic control indices and urinary biomarkers of diabetic kidney disease: Hyogo Diabetes Hypoglycemia Cognition Complications study

AIMS

Glomerular damage and proximal tubular damage play an important role in the pathogenesis of diabetic kidney disease. This study aimed to investigate the relationship between the urinary markers of proximal tubular injury, including urinary liver-type fatty acid-binding protein-to-creatinine ratio (uL-FABP/Cr) and urinary N-acetyl-β-D-glucosaminidase-to-creatinine ratio (uNAG/Cr), and glycemic control status.

METHODS

This cross-sectional study included 245 and 39 patients with type 2 diabetes mellitus (T2DM) and non-T2DM (NDM), respectively. The participants of this study were fitted with retrospective CGM, and glycemic control indices, such as time in range (TIR) and glycemia risk index (GRI), were calculated.

RESULTS

The results were presented as medians (interquartile ranges). The uL-FABP/Cr was significantly higher in the microalbuminuria than in the normo-albuminuria group [4.2 (2.7-7.1) and 2.2 (1.4-3.4) μg/gCr, respectively, P < 0.001], while the uNAG/Cr in the normo-albuminuria group [6.3 (4.5-10.1) U/gCr] was significantly higher than that in the NDM group [5.3 (3.8-6.3) U/gCr, P = 0.048] but significantly lower than that in the microalbuminuria group [9.2 (6.4-11.1) U/gCr, P = 0.004]. The multivariate logistic regression analysis indicated that CGM-derived TIR was significantly associated with the urinary albumin-to-creatinine ratio [uAlb/Cr, odds ratio (OR) 0.985, 95% confidence interval (CI) 0.971-0.998, P = 0.029] and uNAG/Cr (OR 0.973, 95% CI 0.957-0.989, P = 0.001) independent of renal function. GRI was similarly associated with uAlb/Cr and uNAG/Cr.

CONCLUSION

The findings of this study indicated that uNAG/Cr was elevated before albuminuria development and was associated with CGM-derived TIR and GRI.

Association between nonalbumin proteinuria and renal tubular damage of N-acetyl-β-d-glucosaminidase and its clinical relevance in patients with type 2 diabetes without albuminuria

AIM

Although albuminuria and urinary N-acetyl-β-d-glucosaminidase (uNAG) are known as progression markers of diabetic kidney disease, there is limited information regarding the association between urinary nonalbumin proteinuria (NAP) and uNAG and the clinical relevance thereof in patients without albuminuria.

METHODS

This cross-sectional study included samples from 244 consecutive patients with type 2 diabetes mellitus (T2D) without albuminuria. Proteinuria and albuminuria were defined according to protein-to-creatinine ratio (uPCR) and albumin-to-creatinine ratio (uACR), respectively. NAP was indirectly calculated by the difference between uPCR and uACR.

RESULTS

NAP and uNAG excretion were significantly correlated (r = 0.525, P < 0.001). Individuals whose NAP levels were in the highest tertile had a longer duration of diabetes, uncontrolled hyperglycemia, and impaired insulin stimulation (all P < 0.05), although more patients in the highest NAP tertile were prescribed insulin and sulfonylurea. Multiple linear regression analyses revealed associations among uNAG, diabetes duration, and waist circumference.

CONCLUSIONS

T2D patients without albuminuria excrete proteinuria and that presence of the protein in urine is associated with uNAG. NAP was positively correlated with T2D duration and waist circumference, but negatively correlated with body mass index. Lean, but centrally obese, T2D patients in late diabetes experience more tubular damage, regardless of the presence of albuminuria.