Urinary tubular biomarkers in short-term type 2 diabetes mellitus patients: a cross-sectional study

The purpose of this study was to investigate the prevalence of tubular damage in short-term (less than five years) type 2 diabetes mellitus (T2DM) patients and to explore the correlation between tubular markers and their relationship with renal indices at different stages of diabetic nephropathy. A group of 101 short-term T2DM patients and 28 control subjects were recruited. Tubular markers, such as neutrophil gelatinase-associated lipocalin (NGAL), N-acetyl-β-D: -glucosaminidase (NAG), and kidney injury molecule 1 (KIM-1), as well as urinary albumin excretion were measured in voided urine. Glomerular filtration rate (GFR) was estimated via Macisaac's formula. The patients were further categorized into three groups, namely, the normoalbuminuria, microalbuminuria, and macroalbuminuria groups, according to their urine albumin/creatinine ratio (UACR). Urinary tubular markers were compared and their correlations with renal indices [UACR and estimated GFR (eGFR)] were analyzed among the different diabetic groups. Compared with the control group, Urinary NGAL [median (IQR)][83.6(41.4-138.7) μg/gcr vs. 32.9(26.1-64.5) μg/gcr], NAG [13.5(8.7-17.9) U/gcr vs. 7.6(6.5-13.0) U/gcr] and KIM-1 [120.0(98.4-139.9) ng/gcr vs. 103.1(86.8-106.2) ng/gcr] in the T2DM were all markedly increased. For all patients, urinary NGAL had stronger positive correlations with UACR than NAG (R = 0.556 vs. 0.305, both P < 0.05). In addition, only urinary NGAL showed a negative correlation with eGFR (R = -0.215, P < 0.05). Urinary KIM-1, however, showed no significant difference among the three T2DM groups and did not correlate with either UACR or eGFR. As UACR increased from the normoalbuminuria to the last macroalbuminuria group, all of the markers increased. However, only the concentrations of NGAL were statistically different among the three diabetic groups. The correlation between the tubular markers and their relationships with the renal indices differed markedly among the three T2DM groups. In conclusion, these results suggest that tubular damage is common in short-term T2DM patients. Urinary NGAL may be a promising early marker for monitoring renal impairment in short-term T2DM patients.