KIM-1 AND NGAL AS BIOMARKERS OF NEPHROPATHY IN TYPE II DIABETES.

Background: clinically detectable diabetic nephropathy is based on albumin excretion and glomerular filtration rate that mainly reflects the glomerular damage. New biomarkers have arisen with the promise of detecting kidney damage prior to the currently used markers. Objectives: to assess the usefulness of the urinary neutrophil gelatinase-associated lipocalin and kidney injury molecule-1 for the early diagnosis of diabetic kidney disease in type2 diabetes mellitus and to estimate their relation to the degree of nephropathy in comparison to the level of albuminuria and other parameters. Design: cross sectional study. Setting: the internal medicine department - al-zahraa university hospital and endocrinology department - helwan university hospital from 2014 / 2015. Patients and methods: seventy diabetic patients were chosen and divided into 3 subgroups (normoalbuminuric, microalbuminuric and macroalbuminuric), compared to 19 healthy controls. For all participants, clinical examination, urine analysis, fasting and 2hours post prandial serum glucose, glycated hemoglobin a1c%, serum cholesterol, triglycerides, serum creatinine, urea, estimated glomerular filtration rate, urinary albumin to creatinine ratio, urinary kim-1 and ngal were done. Results: both urinary ngal and kim-1 correlated positively with urinary albumin, disease duration and hba1c. Ukim-1 correlated negatively with estimated glomerular filtration rate. The cutoff point to differentiate the normoalbuminuric group from control for ukim-1 was 88.5ng/l. The diagnostic sensitivity was 91.6%, diagnostic specificity was 84%. At the cutoff value 3.25 μg/l for ungal the diagnostic sensitivity was 100%, diagnostic specificity was 89.4%. Conclusion: ukim-1 and ungal are sensitive and specific markers for detection of diabetic nephropathy in patients with type2 diabetes mellitus. severity of glomerular damage. ( 2 ) Tubular injury with prolonged exposure to a variety of hemodynamic and metabolic factors may contribute in a primary way, rather than a secondary manner, to the development of DN. ( 3 ) A growing of evidence indicates that some tubular biomarkers have good predictability for early diagnosis of diabetic nephropathy, such as kidney injury molecule-1(KIM-1) and neutrophil gelatinase-associated lipocalin (NGAL). ( 4 ) Neutrophil gelatinase-associated lipocalin and urinary kidney injury molecule-1 are tubular damage markers that are reported as early detectors of acute kidney injury and they are investigated as early markers in chronic kidney disease patients. ( 5 ) Kidney injury molecule-1 is a transmembrane glycoprotein that not expressed in normal proximal tubule cells but is up regulated in the proximal tubule during various forms of acute kidney injury, and also expressed in chronic kidney diseases, which is mainly characterized by tubulointerstitial changes. ( 6 ) Urinary levels of KIM-1 were significantly higher in diabetic patients in comparison with non-diabetic subjects indicating the possible clinical utility of urinary KIM-1 as early complementary biomarker of DN. Neutrophil gelatinase-associated lipocalin is one of acute-phase proteins that belongs to a lipocalin family which is a family of proteins that is highly induced in inflammatory conditions, ischemia, and nephrotoxic injury of the kidneys. ( 7 ) Serum NGAL is filtered by the glomerulus then degraded in the proximal renal tubule after capture by the megalin complex, and a minimal amount is excreted in urine. Its low molecular size, protease resistance and early appearance independent of GFR make it a convenient biomarker of kidney injury. ( 8 ) Clinical and experimental studies of human biopsies with fibrotic damage or tubular necrosis revealed that, both uNGAL, uKIM-1 are good markers of active tubular damage and not tubular scarring. Therefore they are representative of the functioning tubular mass that can still 3 levels of to the level of protein in urine a rough for detection of normoalbuminurea, microalbuminurea and macralbuminurea for patients' classification then urinary protein level is determined by albumin/creatinine ratio using cobas c311 auto analyzer commercial kits supplied by Roche Diagnostics which automatically calculate the albumin/creatinine ratio in each urine sample. Quantitative determination of urinary albumin was done by immunoturbidimetric assay, using ALBT2, Tina-quant Albumin Gen2 kit supplied by Roche Diagnostics. Estimation of (KIM-1) and (NGAL) were done by using ELISA Kit Glory Diagnostics Estimated glomerular filtration rate (e-GFR) was calculated using Cockcroft-Gault GFR (11) if / Cr= serum Results were collected, tabulated, and statistically analyzed using statistical package SPSS version Two types of statistics were performed: Descriptive statistics - for example, mean ( X ) and SD - and analytic statistics. The ’t’ value was calculated and the probability (P) value then deduced. Mann-Whitney U -test (nonparametric test) is used for comparison between two groups not normally distributed having quantitative significantly higher compared to diabetic normoalbuminuric and control groups. These results are in accordance with the other studies which reported that hyperglycemia is the driving force for the development of DN. ( 12 ) Elevated HbA1c is associated with the development of microangiopathy because HbA1c has a special affinity for oxygen, causing tissue anoxia and microangiopathy. ( 17 ) We found an increased NGAL level in normoalbuminuric subgroup of diabetic patients compared to the control group and its urinary excretion had a statistically significant positive correlation with the degree of albuminuria in micro-macroalbuminuric patients. This finding was similar to what is observed by Zachwieja et al ( 18 ) after studying the level of serum and urine NGAL in children with normal-range albuminuria, they suggest that normal-range albuminuria could not exclude DN. Thus, the increased urinary NGAL levels may reflect the degree of subclinical tubular impairment, representing an earlier measurable marker of renal injury. ( 19 ) In contrast to Assalʼs ( 20 ) study who found a significant correlation between urine NGAL and serum creatinine, our study was in line with Zachwieja et al (18) showed no statistically significant correlation with serum creatinine and eGFR. This can be referred to that our study excluded severe renal impaired patients. Wu et al (21) reported markedly increased uNGAL in type2 diabetic patients from the normoalbuminuria to the macroalbuminuria and urinary NGAL showed strong positive correlations with urinary albumin creatinine ratio (ACR) and negative correlation with eGFR. In agreement with this study, Thrailkill et al ( 22 ) reported a significant positive correlation between uNGAL and duration of the disease. Other authors reported the absence of this correlation. ( 23 ) KIM-1 is not detected in normal kidneys but it is expressed in surviving renal proximal tubules after injury and can be quantified in the urine. So, uKIM-1 could be a sensitive marker for nephropathy. group microalbuminuric group. KIM-1 kidney injury in mechanisms that differ from albuminuria. KIM-1 increased risk of deterioration in function and incident chronic independent of albuminuria. Previous that expression of KIM-1correlated positively with interstitial damage, and serum creatinine, did not correlate with proteinuria. In a significant negative correlation between uKIM-1 eGFR. there is no significant statistical correlation serum creatinine. Urinary excretion of KIM-1 is not only related to the tubular production specific to tubular damage, confirmed by biopsies in both clinical and experimental studies. KIM-1 is a good of active tubular damage not tubular scarring.