Stine E. Nielsen

Urinary Proteomics for Early Diagnosis in Diabetic Nephropathy

Diabetic nephropathy (DN) is a progressive kidney disease, a well-known complication of long-standing diabetes. DN is the most frequent reason for dialysis in many Western countries. Early detection may enable development of specific drugs and early initiation of therapy, thereby postponing/preventing the need for renal replacement therapy. We evaluated urinary proteome analysis as a tool for prediction of DN. Capillary electrophoresis–coupled mass spectrometry was used to profile the low–molecular weight proteome in urine. We examined urine samples from a longitudinal cohort of type 1 and 2 diabetic patients (n = 35) using a previously generated chronic kidney disease (CKD) biomarker classifier to assess peptides of collected urines for signs of DN. The application of this classifier to samples of normoalbuminuric subjects up to 5 years prior to development of macroalbuminuria enabled early detection of subsequent progression to macroalbuminuria (area under the curve [AUC] 0.93) compared with urinary albumin routinely used to determine the diagnosis (AUC 0.67). Statistical analysis of each urinary CKD biomarker depicted its regulation with respect to diagnosis of DN over time. Collagen fragments were prominent biomarkers 3–5 years before onset of macroalbuminuria. Before albumin excretion starts to increase, there is a decrease in collagen fragments. Urinary proteomics enables noninvasive assessment of DN risk at an early stage via determination of specific collagen fragments.

Neutrophil Gelatinase-Associated Lipocalin (NGAL) and Kidney Injury Molecule 1 (KIM1) in patients with diabetic nephropathy: a cross-sectional study and the effects of lisinopril.

Diabet. Med. 27, 1144–1150 (2010)

Urinary Liver-Type Fatty Acid-Binding Protein Predicts Progression to Nephropathy in Type 1 Diabetic Patients

OBJECTIVE Urinary liver-type fatty acid-binding protein (u-LFABP) is a marker of tubulointerstitial inflammation and has been shown to be increased in patients with type 1 diabetes and is further increased in patients who progress to micro- and macroalbuminuria. Our aim was to evaluate u-LFABP as a predictor of progression to micro- and macroalbuminuria in type 1 diabetes. RESEARCH DESIGN AND METHODS From an inception cohort of 277 patients, u-LFABP, adjusted for urinary creatinine (enzyme-linked immunosorbent assay), was measured in 24-h urine samples from 165 normoalbuminuric patients 9.6 ± 3.5 (mean ±SD) years after onset of type 1 diabetes. The outcome measured was development of persistent micro- or macroalbuminuria or death. RESULTS Patients were followed for a median of 18 (range 1–19) years; 39 progressed to microalbuminuria, 8 of those progressed further to macroalbuminuria, and 24 died. In a Cox regression model, baseline log u-LFABP levels predicted the development of microalbuminuria, adjusted for known risk factors (sex, age, A1C, systolic and diastolic blood pressure, albumin excretion rate, serum creatinine, and smoking) (hazard ratio [HR] 2.3 [95% CI 1.1–4.6]) and log u-LFABP predicted mortality (adjusted HR 3.0 [1.3–7.0]). u-LFABP (above versus below the median) predicted the development of macroalbuminuria (adjusted HR 2.6 [1.2–5.4]). As a continuous variable, u-LFABP tended to predict macroalbuminuria (HR 1.9, P = 0.2), but numbers were small. CONCLUSIONS High levels of the tubular inflammation marker u-LFABP predict the initiation and progression to diabetic nephropathy and all-cause mortality, independent of urinary albumin excretion rate and other established risk factors.

Tubular markers do not predict the decline in glomerular filtration rate in type 1 diabetic patients with overt nephropathy

Recent studies have shown that both glomerular and tubulointerstitial damage are important factors in the pathophysiology and progression of diabetic nephropathy. To examine whether markers of tubular damage are useful in monitoring the progression of disease, we measured urinary levels of neutrophil gelatinase-associated lipocalin (NGAL), liver-fatty acid-binding protein (LFABP), and kidney injury molecule-1 (KIM-1) in a 3-year intervention study of 63 type 1 diabetic patients with kidney disease. The baseline mean glomerular filtration rate (GFR) was 87 ml/min per 1.73 m(2) and urinary albumin excretion 1141 mg/24 h. Patients with the highest compared with the lowest quartile of urinary NGAL at baseline had higher urinary KIM-1 levels and a significant decrease in their GFR each year. Using linear regression analysis, we found that elevated urinary NGAL and KIM-1 concentrations were associated with a faster decline in GFR, but not after adjustment for known promoters of progression. Urinary LFABP was not related to decline in GFR. Losartan treatment (100 mg/day) reduced urinary KIM-1 by 43% over a 12-month period. Thus, urine biomarker measurements in patients with type 1 diabetic nephropathy did not provide additional prognostic information to that of known progression promoters.

Spironolactone diminishes urinary albumin excretion in patients with type 1 diabetes and microalbuminuria: a randomized placebo-controlled crossover study.

Diabet. Med. 29, e184–e190 (2012)

Tubular and glomerular injury in diabetes and the impact of ACE inhibition.

OBJECTIVE We studied tubular and glomerular damage in type 1 diabetic patients by measuring urinary–liver fatty acid binding protein (U-LFABP) and albuminuria. Subsequently, we evaluated the effect of ACE inhibition on U-LFABP in patients with diabetic nephropathy. RESEARCH DESIGN AND METHODS We studied Caucasians with type 1 diabetes: 58 with normoalbuminuria (urinary albumin <30 mg/24 h), 45 with persistent microalbuminuria (30–300 mg/24 h), and 45 with persistent macroalbuminuria (≥300 mg/24 h). A control group consisted of 57 healthy individuals. The groups were matched by sex and duration of diabetes. In addition, U-LFABP was measured in 48 type 1 diabetic patients with diabetic nephropathy in a randomized crossover trial consisting of 2 months of treatment with 20, 40, and 60 mg lisinopril once daily in random order. RESULTS In the cross-sectional study, levels of U-LFABP were significantly higher in normoalbuminuric patients versus those in the control group (median 2.6 [interquartile range 1.3–4.1] vs. 19 [0.8–3.0] μg/g creatinine, P = 0.02) and increased with increasing levels of albuminuria (microalbuminuric group 4.2 [1.8–8.3] μg/g creatinine and nephropathy group 71.2 [8.1–123.4], P < 0.05 for all comparisons). U-LFABP correlates with the urinary albumin-to-creatinine ratio (R2 = 0.54, P < 0.001). In the intervention study, all doses of lisinopril significantly reduced urinary albumin excretion rate and U-LFABP from baseline. The reductions in U-LFABP were 43, 46, and 40% with increasing doses of lisinopril (NS). CONCLUSIONS An early and progressive increase in tubulointerstitial damage as reflected by increased U-LFABP levels occurs in type 1 diabetic patients and is associated with albuminuria. Furthermore, ACE inhibition reduces the tubular and glomerular damage and dysfunction.

Tubular markers are associated with decline in kidney function in proteinuric type 2 diabetic patients.

UNLABELLED Our aim was to investigate u-NGAL, u-KIM1 and p-FGF23 and prediction of decline in kidney function in type 2 diabetic patients with proteinuria. METHODS We performed a follow-up study, follow-up median (range) 3.5 (1-5) years. At baseline u-NGAL, u-KIM1 and p-FGF23 (ELISA) was measured and patients were followed yearly with estimated(e)-GFR (MDRD) and u-albumin. RESULTS We included 177 patients (44 women), mean age (SD) 59 (9) years. eGFR 90 (24) ml/min/1.73 m(2) at baseline, u-albumin: median (interquartile range) 104 (39-238) mg/24 h. Patients with levels of u-KIM1 in the highest quartile had a greater decline in eGFR than patients with the lowest quartile 6.0 (5.4) versus 3.2 (5.5) ml/min/1.73 m(2) per year (p=0.02). u-NGAL in the highest versus lowest quartile eGFR decline: 5.1 (4.7) and 2.8 (7.1)ml/min/1.73 m(2) per year (p=0.07). Higher values of u-NGAL and u-KIM1 were associated with enhanced decline in eGFR (R=0.16 and R=0.19, p<0.05), however not after adjustment for progression promoters. p-FGF23 was not predictive of decline in eGFR. CONCLUSION Higher levels of markers of tubular damage are associated with a faster decline in eGFR. However, since this is not independent of known progression promoters, measurement of tubular markers does not give additional prognostic information.

Urinary Neutrophil Gelatinase-Associated Lipocalin and Progression of Diabetic Nephropathy in Type 1 Diabetic Patients in a Four-Year Follow-Up Study

Background: Neutrophil gelatinase-associated lipocalin (NGAL), a marker of renal tubular damage, predicts progression in non-diabetic chronic kidney. We evaluated urinary (u)-NGAL as a predictor of progression in diabetic nephropathy in type 1 diabetic (T1D) patients. Methods: As a substudy of a 4-year randomized, intervention study evaluating low-protein diet in T1D patients with diabetic nephropathy, 78 patients were studied with yearly measurements of u-NGAL (ELISA, BioPorto). Outcome: Decline in glomerular filtration rate (GFR) (51Cr-EDTA), and end-stage renal disease (ESRD) or death. Results: Mean age 40.7 (8.2) years and 50 men. 13 patients developed ESRD or died. Baseline GFR (mean, SD): 68 (31) ml/min/1.73 m2. Baseline u-NGAL [geometric mean (95% CI)] and GFR were 15.6 ng/24 h (11.8–20.7) and 68 (31) ml/min/1.73 m2. During follow-up, an increase in u-NGAL [geometric mean (95% CI)] of 15%/year (4–27) and a decline in GFR of 3.7 (3.0) ml/min/year were observed. Baseline u-NGAL was not associated with the decline in GFR. Elevated u-NGAL at baseline (log-transformed) predicted death and ESRD (HR 3.8, 95% CI 1.04–14.0), however not after adjustment for known progression promoters (HR 2.0, p = 0.6). Conclusion: Elevated u-NGAL was not related to decline in GFR during a 4-year follow-up. Elevated u-NGAL was associated with the development of ESRD and death, but not after adjustment.

The effect of RAAS blockade on markers of renal tubular damage in diabetic nephropathy: u-NGAL, u-KIM1 and u-LFABP

Abstract Aim. Blockade of the renin-angiotensin-aldosterone system (RAAS) affects both the glomerulus and tubules. We aimed to investigate the effect of irbesartan on the tubular markers: urinary (u) neutrophil gelatinase associated protein (NGAL), Kidney injury molecule 1 (KIM1) and liver-fatty acid-binding protein (LFABP). Methods. A substudy of a double-masked, randomized, cross-over study including 52 patients with type 2 diabetes, hypertension and microalbuminuria. After 2 months washout of all antihypertensive medication except bendroflumethiazid, patients were treated in random order with irbesartan 300, 600 and 900 mg for 2 months. End points. Urinary tubular markers at baseline and after each treatment period (ELISA), 24-h blood pressure, glomerular filtration rate (GFR, 51CrEDTA) and 24-h urine albumin excretion (UAER). Results. Fifty-two patients completed the study (41 male). Age (mean (SD)): 58(10) years and diabetes duration 13(8) years. Baseline GFR was 101(24) and UAER (geometric mean [95%CI]) 133 (103–172) mg/24 h. With increasing doses of irbesartan (300, 600, 900 mg) u-KIM1 was reduced with 15%, 10% and 15% (p = 0.07 between 300 mg vs. baseline and no difference between doses). Patients with high u-KIM1 at baseline (above median) had a 32% reduction in u-KIM1 during treatment (p = 0.01). No significant decline in U-NGAL compared to baseline. U-LFABP increased during treatment (p < 0.01). Conclusions. Irbesartan treatment reduced levels of the tubular marker u-KIM1 in patients with type 2 diabetes and microalbuminuria. u-NGAL changed insignificantly and u-LFABP increased. More studies with longer follow up are needed to determine the role of tubular markers in monitoring treatment effect and prediction of prognosis in diabetic nephropathy.

Levels of NT-proBNP, markers of low-grade inflammation, and endothelial dysfunction during spironolactone treatment in patients with diabetic kidney disease

Renin-angiotensin-aldosterone system (RAAS) blockade may reduce levels of biomarkers of chronic low-grade inflammation and endothelial dysfunction. We investigated the effect of spironolactone added to standard RAAS blockade on these biomarkers in an analysis of four original studies. Materials and methods: The studies were double-blind, randomised, placebo-controlled studies in 46 type 1 and 23 type 2 diabetic patients with micro- or macroalbuminuria treated with angiotensin-converting enzyme inhibitor (ACE inhibitor) or angiotensin receptor blocker (ARB), and randomised to additional treatment with spironolactone 25 mg and placebo daily for 60 days. Outcome measures: Changes in inflammatory (hsCRP, s-ICAM, TNFα, IL-6, IL-8, Serum amyloid A, IL1β), endothelial dysfunction (sE-selectin, s-ICAM1, s-VCAM1, VWF, p-selectin, s-thrombomodulin) and NT-proBNP after each treatment period. Results: During spironolactone treatment, u-albumin excretion rate was reduced from 605 (411–890) to 433 (295–636) mg/24 h, as previously reported. Markers of inflammation and endothelial dysfunction did not change; only changes in NT-proBNP (reduced by 14%, p=0.05) and serum amyloid A (reduced by 62%, p=0.10) were borderline significant. Discussions: Our results indicate that the renoprotective effect of spironolactone when added to RAAS blockade is not mediated through anti-inflammatory pathways since markers of inflammation and endothelial dysfunction are not affected during treatment.