Urinary excretions of lipocalin-type prostaglandin D synthase predict renal injury in type-2 diabetes: a cross-sectional and prospective multicentre study.

BACKGROUND: Urinary excretions of lipocalin-type prostaglandin D synthase/beta-trace (L-PGDS) probably reflect the increased permeability of injured glomerular capillary walls of the kidney. We tested the hypothesis in cross-sectional and prospective studies that urinary L-PGDS excretions predict renal injury in type-2 diabetes. METHODS: (1) In the cross-sectional studies, we evaluated whether urinary L-PGDS excretions were able to predict renal diseases in a pooled population including 793 healthy subjects and 200 patients with various forms of renal diseases. (2) We determined the cut-off point of urinary L-PGDS excretions to predict >or=30 mg/gCr albuminuria in 666 patients with type-2 diabetes. (3) In the prospective study, 121 type-2 diabetic patients with <30 mg/gCr albuminuria were followed for almost 2 years to examine whether urinary L-PGDS excretions predict the future status of renal injury in type-2 diabetes. RESULTS: (1) In the cross-sectional studies, receiver operating characteristic analysis revealed that urinary L-PGDS excretions better predicted the patients with kidney diseases than the other markers of renal injury. (2) It was also demonstrated that >or=4.2 mg/gCr urinary L-PGDS excretions better predicted >or=30 mg/gCr albuminuria in type-2 diabetic patients than other markers. (3) The prospective study revealed that in type-2 diabetic patients with <30 mg/ gCr albuminuria, the patients with >or=4.2 mg/gCr urinary L-PGDS excretions more likely exhibited the renal injury during the follow-up periods than those with <4.2 mg/gCr urinary L-PGDS excretions. CONCLUSIONS: Urinary L-PGDS excretions reflect the current increased permeability of injured glomerular capillary walls and better predict the future status of renal injury in type-2 diabetes with <30 mg/gCr albuminuria.

Urinary PGDS levels are associated with vascular injury in type 2 diabetes patients.

BACKGROUND: The presence of metabolic syndrome has been shown to be predictors of cardiovascular morbidity and mortality in patients with type 2 diabetes. In a cross-sectional clinical study, we investigated the association of metabolic syndrome with asymptomatic lacunar strokes and cardiovascular disease (CVD) and we compared its significance with urinary protein markers. METHODS: We studied Japanese type 2 diabetes patients (n=233, men=124, women=109). The diagnosis of metabolic syndrome was made according to WHO and International Diabetes Federation (IDF) criteria. Cardiovascular events were recorded and asymptomatic lacunar lesions were evaluated with magnetic resonance imaging (MRI). We also measured urinary levels of albumin, type IV collagen, beta2-microglobulin (beta2MG), N-acetyl-beta-d-glucosaminidase (NAG) and lipocalin-type prostaglandin D synthase (PGDS). RESULTS: The prevalence of metabolic syndrome is 31.3% (IDF) and 52% (WHO) in 233 patients and microalbuminuria was present in 62 subjects (26.6%). Metabolic syndrome (WHO) significantly associated with asymptomatic lacunar lesions (p=0.035, OR=2.854, CI 1.075-7.579), while metabolic syndrome (IDF) or urinary markers failed to associate with presence of asymptomatic lacunar lesions. The presence of metabolic syndrome or microalbuminuria did not show significant association with CVD; however, the elevation of beta2MG, NAG and PGDS showed significant association with CVD. By a logistic regression analysis using urinary proteins as independent variables, the presence of higher PGDS excretion independently associated with history of CVD (p=0.025, OR=3.847, CI 1.180-12.545). CONCLUSIONS: In type 2 diabetes patients, the elevation of urinary PGDS secretion closely associated with cardiovascular events and may be a supplemental or additional marker to the criteria of metabolic syndrome.

Lipocalin-type prostaglandin D synthase in urine in adriamycin-induced nephropathy of mice.

BACKGROUND/AIMS: Lipocalin-type prostaglandin D synthase (L-PGDS), an enzyme converting prostaglandin H(2) to prostaglandin D(2), occurs particularly in the cardiovascular system. Urinary L-PGDS excretion is increased in diabetes prior to overt proteinuria, suggesting that it is a predictor of renal injury. In this study, we tested the hypothesis that L-PGDS excretion reflects renal injury in primary glomerular diseases using Adriamycin-induced nephropathy in mice. METHODS: Twenty 6-week-old ICR female mice were intravenously given a dose of 25 mg Adriamycin/kg body weight through the tail vein. 24-hour urine was collected every day, and blood samples were obtained. RESULTS: The mice developed significant albuminuria from day 3 onward (p < 0.05), which was followed by overt proteinuria from day 4 (p < 0.05). Histological examination revealed focal mesangial expansion with partial tubular atrophy. Urinary L-PGDS excretion significantly increased from day 1 onward (p < 0.05), and apparently preceded the increase in urinary albumin excretions. Either serum L-PGDS or creatinine levels were not changed by administration of Adriamycin. However, serum creatinine levels were inversely correlated to urinary L-PGDS excretions (r = -0.88, p < 0.05). Immunohistochemistry showed that L-PGDS occurred in the tubules, but not in the glomeruli in Adriamycin mice and L-PGDS mRNA paralleled urinary L-PGDS excretion. CONCLUSION: Urinary L-PGDS excretion is increased in Adriamycin-induced nephropathy, and this precedes overt albuminuria.

Urinary excretions of lipocalin-type prostaglandin D2 synthase predict the development of proteinuria and renal injury in OLETF rats.

BACKGROUND: Otsuka Long-Evans Tokushima Fatty (OLETF) rats genetically develop diabetes which is associated with hypertension. In preliminary studies, urinary excretions of L-PGDS (lipocaline-type prostaglandin D synthase) increase before diabetic nephropathy obviously develops, and this may predict progression of renal injury following diabetes. In the present study, we attempted to define whether urinary excretions of L-PGDS behave as the predictor of development of diabetic nephropathy in OLETF rats. METHODS: We investigated alterations of urinary L-PGDS excretions during the establishment of diabetes and assessed the relationship between the L-PGDS excretions and renal function in OLETF rats. Furthermore, we treated OLETF rats with troglitazone and analysed the effects on L-PGDS metabolisms. Urinary L-PGDS was measured by immunoenzyme assay and the occurrence of L-PGDS and its mRNA in the kidney was assessed by immunohistochemistry and a PCR method. RESULTS: Urinary excretions of L-PGDS were significantly higher in OLETF rats than non-diabetic Long-Evans Tokushima Otsuka (LETO) rats. The excretions age-dependently increased in OLETF and this increase appeared to be due to increased glomerular permeability to L-PGDS. Messenger RNA and antigenicity of L-PGDS were demonstrated in renal tissue; however, the de novo synthesis of L-PGDS mRNA seemingly contributed to urinary L-PGDS excretions much less than glomerular filtration. Multiple regression analysis revealed that urinary L-PGDS was determined by urinary protein excretions, and not by high blood pressure per se. Conversely, urinary proteinuria in the established diabetic nephropathy was predicted by urinary L-PGDS excretions in the early stage of diabetes. CONCLUSIONS: Urinary excretions of L-PGDS are likely to reflect the underlying increase in glomerular permeability. This property may be useful to predict forthcoming glomerular damage following diabetes in OLETF rats.

Development and evaluation of a practical ELISA for human urinary lipocalin-type prostaglandin D synthase.

BACKGROUND: Urinary excretion of lipocalin-type prostaglandin D synthase (L-PGDS) is significantly increased in patients with chronic renal failure, but its diagnostic potential in less advanced stages of renal diseases remains to be elucidated. METHODS: Six mouse monoclonal antibodies (MAbs) were raised against recombinant human L-PGDS. We constructed a sandwich ELISA with two MAbs that recognized different epitopes with high affinities and assessed its assay performance and clinical utility with urine samples from healthy controls, diabetic patients, and patients with various renal diseases. RESULTS: Western blot analyses with NH(2)-terminus-truncated L-PGDS mapped the epitopes to Ala(23)-Val(28) (MAb-7F5 and -10A3), Ser(52)-Ala(73) (MAb-9A6), Tyr(107)-Val(120) (MAb-1B7 and -6F5), and Gly(140)-Pro(155) (MAb-6B9). A sandwich ELISA was constructed with MAb-1B7 and -7F5, the K(d) values of which were 3.6 and 3.9 nmol/L, respectively, for native L-PGDS. Recoveries were 91-111%, and intra- and interassay CVs were <6% and <9%, respectively. The ELISA showed parallelism of standard and urine samples and no significant interference by a variety of urinary constituents. Urinary L-PGDS excretion was significantly increased in patients with diabetic nephropathy, IgA nephropathy, and chronic glomerulonephritis even when serum creatinine was not increased. In patients with renal diseases, urinary L-PGDS was correlated with urinary albumin (r = 0.64; P <0.0001), N-acetyl-beta-D-glucosaminidase (r = 0.43; P <0.001), and serum creatinine (r = 0.66; P <0.0001). At a cutoff value of 284 mg/mol creatinine, the assay had sensitivities of 74% for diabetic nephropathy and 83% for chronic glomerulonephritis and a specificity of 93%. CONCLUSIONS: This ELISA system is suitable for measurement of urinary L-PGDS in a routine clinical assay and may be useful to detect less advanced stages of renal diseases.

Lipocalin-type prostaglandin d synthase in essential hypertension.

Lipocalin-type prostaglandin D synthase (L-PGDS) reportedly well predicts cardiovascular injuries in humans. However, little is known about the implications of L-PGDS in hypertension. In the present study, we investigated the alterations of serum and urinary L-PGDS in hypertensive patients with or without renal dysfunction. A total of 111 patients with hypertension (EHT; 65 with normoalbuminuria, 23 with microalbuminuria, 12 with macroalbuminuria, 11 with renal failure) and 102 normotensive, nomoalbuminuric subjects (NT) were studied. L-PGDS was measured by enzyme-linked immunosorbent assay, and L-PGDS in the kidney was localized using immunohistochemical methods. Blood pressure was higher in EHT groups than in the NT group (P<0.0001). There were no differences in age, gender, BMI, TC, TG, and HbA1c levels among the groups. Serum creatinine and urinary albumin levels were higher in the group with renal failure. Serum levels of L-PGDS were increased in EHT with normoalbuminuria, as compared with NT (0.88 +/- 0.05 versus 0.65 +/- 0.02 microg/mL; P<0.001). Serum levels of L-PGDS increased with the renal function worsened and positively correlated with serum creatinine, particularly in patients with renal impairments (r=0.76, P<0.0001). Similarly, the urinary L-PGDS excretions in EHT with normoalbuminuria were higher than that in NT (2.31 +/- 0.29 versus 1.16 +/- 0.14 mg/gCr, P<0.001), whereas there were no differences in urinary albumin excretion between the 2 groups. Moreover, urinary L-PGDS excretion increased dramatically with an increase in albuminuria or proteinuria. L-PGDS was stained in the tubules and the interstitium of the kidney in nephrosclerosis. In conclusion, patients with hypertension exhibited a higher level of L-PGDS in serum and urine, and this became increasingly obvious along with advance in renal dysfunction. These data suggest that L-PGDS metabolism is related to blood pressure and kidney injuries associated with hypertension.

Blood sugar control reverses the increase in urinary excretion of prostaglandin D synthase in diabetic patients.

BACKGROUND/AIMS: We investigated basal levels of serum and urinary lipocalin-type prostaglandin D synthase/beta-trace (L-PGDS) in type-2 diabetic patients and explored whether glycemic control affects L-PGDS status in another 55 diabetic inpatients with normoalbuminuria. METHODS: Fifty-five type-2 diabetic outpatients (HbA1c, 9.14 +/- 0.20%; creatinine (Cr), 85.1 +/- 2.4 micromol/l), and 55 age-matched healthy control subjects were recruited. Serum and urinary levels of L-PGDS were determined with respect to the stage of diabetic nephropathy. The L-PGDS was localized by immunohistochemistry. RESULTS: The urinary L-PGDS index increased in diabetic patients, compared with the controls (234.8 +/- 27.4 vs. 73.8 +/- 7.8 microg/mmol Cr, p < 0.001). Even in normoalbuminuric patients as well as in microalbuminuric patients, urinary L-PGDS indexes were higher than the controls (166.0 +/- 21.1, p < 0.0001 and 338.6 +/- 62.5 microg/mmol Cr, p < 0.0001, respectively), although the serum L-PGDS level was equal to that in the control subjects. Multiple regression analysis revealed that the urinary L-PGDS index was predicted solely by glucose levels and type-IV collagen index, whereas the serum L-PGDS was determined mainly by age and serum Cr. Glycemic control reduced the urinary L-PGDS index towards the normal range in diabetic patients with normoalbuminuria (172.3 +/- 6.6 vs. 118.1 +/- 2.6 (SE) microg/mmol Cr, p < 0.0001). Immunohistochemistry showed that L-PGDS was uniquely present in the renal tubules in diabetes while in nondiabetics, L-PGDS occurred solely in the peritubular interstitium, not in the tubular cells. CONCLUSION: Inadequate glycemic control is responsible for urinary L-PGDS excretion in the diabetic patients. Urinary L-PGDS is useful to predict subclinical renal injury associated with type-2 diabetes.