Changes Of Serum And Urine NGAL In Type 2 Diabetic Patients With Early Nephropathy Before And After Telmisartan Treatment

1. Backgrounds and aimsDiabetic nephropathy (DN) is one of serious microvascular complications which does great harm to diabetes patients. Unfortunately, now the laboratory indicatrixes mainly reflecting glomerulum injury are not sensitive enough to illustrate early change of renal function of patients with DN. Neutrophil gelatinase–associated lipocalin (NGAL) is a small secreted 25-kDa monomer of the lipocalin superfamily which has powerful function especially in the physiopathologic mechanism of kidney. As one of the most promising novel tubular tubular and inflammatory biomarker, NGAL has emerged in clinical and experimental diagnostic field of acute and chronic renal diseases in the last decade. Meanwhile, more and more attention is concentrated in the hot topic about NGAL and DN. However, the change of NGAL after interventional treatment is still controversial and the mechanism of NGAL in the occurrence and development of DN still merits further studies. In this study, We detected the levels of sNGAL ,uNGAL and other renal function parameters (CysC, hsCRP, BUN, sCr, eGFR and UACR)from a cohort of 72 type 2 diabetes patients with non-macroalbuminurie and 35 non-diabetic control subjects. Pearson /Spearman correlation test and Linear regression analysis were used to investigate the relationship between NGAL and other parameters while ROC curves were constructed to assessed the clinical value of NGAL in type 2 DN patients. Furthermore, a second prospective controlled trial that treated with telmisartan 80 mg per day for a random time lasting for 3 or 12 months can help to explore the main cause of NGAL change.2. MethodsIn a cross-sectional study, we evaluated the levels of sNGAL and uNGAL from a cohort of 72 type 2 diabetes patients with non-macroalbuminurie ( inculding 27 normo- and 45 microalbuminuric, divided according to urinary albumin /urinary creatinine rate (UACR)and 35 non-diabetic control subjects. Furthermore, 68 patients accomplished in a second prospective controlled trial, and 43 of them were treated with telmisartan 80 mg per day based on general diabetes treatment (including standard strategies for diabetes, hypertension, and hyperlipidemia ), for a random time lasting for 3 or 12 months. For doing the comparion, the other 25 patients only accepted general diabetes treatment for 12 months without telmisartan. Assays of sNGAL, uNGAL and renal parameters were repeated.uNGAL and sNGAL were quantified by enzyme-linked immunosorbent assay method (ELISA) both in the cross-sectional and interventional study. Radioimmunoassay was used to measure urinary albumin while Kinetic Jaffe’s method was used to assess urinary creatinine in sterile urine from early morning or random spot collections of urine. And the ratio of urinary albumin to urinary creatinine was obtained to divide groups. Meanwhile, different statistical methods were used to analyzed the correlations between NGAL and other clinical parameters.3. ResultsIn the cross-sectional study, results indicated that :(1) sNGAL in normoalbuminurics was higher than microalbuminurics and controls(both p<0.001). There was no statistical difference between the latter groups. uNGAL elevated with increasing albuminuria (all p<0.001). (2) eGFR elevated statistically in microalbuminurics compared with normoalbuminurics and controls (p<0.05 and p=0.000). (3) ROC curve anclysis suggested when using controls + diabetic normoalbuminuric patients as the status variables, an optimal sNGAL cutoff of 225.5ng/mL had a sensitivity of 38.7%, specificity of 81.5%, AUC of 0.96, surpassed than the other parameters above. uNGAL cutoff of 46.00ng/ml had the second highest AUC of 0.86, sensitivity of 74.1%, specificity of 88.6%. When using normo- + microalbuminuric diabetic patients as the status variables, uNGAL cutoff of 60.05 ng/ml had the highest AUC of 0.79, sensitivity of 95.6%, specificity of 66.7%.In the prospective interventional controlled trial, results indicated that :(1) sNGAL and uNGAL evidently decreased after telmisartan treatment in both two diabetes groups(both p<0.001),the decreasing amplitude of 12 months were much higher than 3 months. (2): The high eGFR levels reduced remarkably (p=0.000) after telmisartan therapy, and had no statistically different from baseline controls. (3): After one year general treatment without telmisartan in microalbuminurics, sNGAL also descended in both two diabetes groups (both p<0.05), but the decreasing amplitude was greatly lower than telmisartan treatment. In contrast, the changes of uNGAL had no statistical significance. (4): Dependablity analysis: There is a strong correlation between sNGAL and uNGAL, and both of them were closely correlated with other renal function parameters. The correlation differed in different period of DN and changed after interventional treament.4. Conclusion(1) sNGAL and uNGAL might be useful markers in screening DN. sNGAL>225.5 ng/ml and /or uNGAL >46.00ng/ml in T2DM course beyond 5 years may be an indicatro for DN. uNGAL might be more meaningful in assessing renal injury progression for its levels increasing with increasing albuminuria. (2) The contraction of sNGAL might be relating to the rise of eGFR in type 2 diabetic patients with microalbuminuric nephropathy. Telmisartan plays an important renoprotective role in improving glomerular filtration and tubular reabsorption. Therefore, high eGFR regressed to normal state while excretion of NGAL and albumin reduced correspondingly. (3) NGAL is cycling dynamically and has final complicated and changed expression in serum and urine. A series of comprehensive factors including glomerular filtration, tubular reabsorption, renal or extrarenal tissues secretion might determine sNGAL and uNGAL levels in distinct nephropathy periods.