Urinary Neutrophil Gelatinase-Associated Lipocalin Is Complementary to Albuminuria in Diagnosis of Early-Stage Diabetic Kidney Disease in Type 2 Diabetes

Early kidney damage in diabetic adolescents with increased blood pressure and glomerular hyperfiltration

BACKGROUND

The early impact of type 1 diabetes mellitus (DM1), increased blood pressure and glomerular hyperfiltration (GHF) on kidney damage in adolescents using two urinary markers of kidney injury - neutrophil gelatinase-associated lipocalin (uNGAL) and transferrin (uTransf) - was assessed.

METHODS

The study group consisted of 80 adolescents with DM1, of whom 42 were patients with increased blood pressure (IBP), and 38 were patients with normal blood pressure (NBP). Blood pressure was assessed by 24-hour ambulatory blood-pressure monitoring. All patients showed estimated glomerular-filtration rates (eGFRs) above 90 mL/min/1.73 m2. The control group consisted of 19 healthy, age and gender-matched adolescents.

RESULTS

All diabetic children showed a significant increase in uNGAL (P<0.001). This increase was not related to blood pressure. The uNGAL was elevated in all patients with normal albuminuria, normal eGFR and NBP. The concentration of uTransf was not increased in the entire studied group and was not related to blood pressure. Children with GHF had significantly higher levels of both uTransf (P=0.010) and uNGAL (P<0.001). In patients with GHF, blood pressure was normal. Patients with IBP showed a significantly higher value for triglycerides (r=0.247; P=0.032) and a longer duration of diabetes (r=0.264; P=0.019).

CONCLUSIONS

Diabetes is the leading risk factor for early kidney injury. However, increased blood pressure does not lead to kidney damage, at least in the early stage of DM1. The uNGAL is the early indicator of kidney injury and increases in patients with normal albuminuria, normal glomerular filtration and normal blood pressure. Glomerular hyperfiltration seems to be a marker of diabetic-kidney involvement.

Urinary NGAL Measured after the First Year Post Kidney Transplantation Predicts Changes in Glomerular Filtration over One-Year Follow-Up

Currently, serum creatinine and estimated glomerular filtration rate (eGFR) together with albuminuria or proteinuria are laboratory markers used in long-term monitoring of kidney transplant recipients. There is a need for more sensitive markers that could serve as early warning signs of graft dysfunction. Our aim was to assess the urinary concentrations of neutrophil gelatinase-associated lipocalin (NGAL) as a predictor of changes in kidney transplant function after the first year post-transplantation. We prospectively recruited 109 patients with functioning graft at least one year after the transplantation, with no acute conditions over the past three months, during their control visits in kidney transplant ambulatory. Urinary NGAL measured on recruitment was twice higher in patients with at least 10% decrease in eGFR over 1-year follow-up compared to those with stable or improving transplant function. Baseline NGAL significantly predicted the relative and absolute changes in eGFR and the mean eGFR during the follow-up independently of baseline eGFR and albuminuria. Moreover, baseline NGAL significantly predicted urinary tract infections during the follow-up, although the infections were not associated with decreasing eGFR. Additionally, we assessed urinary concentrations of matrix metalloproteinase 9-NGAL complex in a subgroup of 77 patients and found higher levels in patients who developed urinary tract infections during the follow-up but not in those with decreasing eGFR. High urinary NGAL in clinically stable kidney transplant recipients beyond the first year after transplantation may be interpreted as a warning and trigger the search for transient or chronic causes of graft dysfunction, or urinary tract infection.

Markers of Glomerular and Tubular Damage in the Early Stage of Kidney Disease in Type 2 Diabetic Patients

Diabetic kidney disease develops in half of genetically predisposed patients with type 2 diabetes (T2DM). Early diagnosis of kidney damage and nephroprotective treatment are the ways of preventing the disease progression. Our aim was to evaluate selected laboratory markers of glomerular and tubular damage in T2DM patients with early stages of chronic kidney disease (G1/G2, A1/A2) for their associations with A2 albuminuria and early decline in the estimated glomerular filtration rate (eGFR). Among 80 T2DM patients with median eGFR of 92.4 ml/min/1.73 m² and median urinary albumin to creatinine ratio (uACR) of 4.69 mg/g, 19 had uACR > 30 mg/g (A2). Higher serum cystatin C, serum and urine neutrophil gelatinase associated lipocalin (NGAL), urine kidney injury molecule 1 (KIM-1), detectable urine transferrin and IgG, and lower serum uromodulin significantly predicted A2 albuminuria, urine KIM-1/creatinine ratio, and IgG being the best predictors. Albuminuria, urine NGAL/creatinine, and IgG correlated with diabetes duration. Albuminuria, urine NGAL, transferrin, IgG, and uromodulin correlated with diabetes control. In a subgroup of 29 patients, retrospective data were available on changes in eGFR and uACR over one year. Decline in eGFR was observed in 17 patients and increase in uACR in 10 patients. Serum and urine NGAL correlated with eGFR changes. Higher urine NGAL, KIM-1/creatinine ratio, and detectable IgG were significantly associated with the increase in uACR. Widely available markers, serum cystatin C, urine IgG, transferrin, and NGAL, may help in early assessment of kidney disease in T2DM patients; however, large prospective studies are needed to confirm the conclusion.