Beta-2-microglobulin (B2M) expression in the urinary sediment correlates with clinical markers of kidney disease in patients with type 1 diabetes.

PURPOSE: After observing variation in the expression of the housekeeping gene B2M in cells of the urinary sediment during a study of candidate genes potentially involved in diabetic kidney disease (DKD), we hypothesized that B2M mRNA expression in the urinary sediment could reflect the presence of DKD. METHODS: qPCR was used to quantify B2M mRNA expression in cells of the urinary sediment of 51 type 1 diabetes (T1D) patients (61% women, 33.5 [27.0-39.7] years old, with diabetes duration of 21.0 [15.0-28.0] years and HbA1c of 8.2% [7.3-8.9]; median [interquartile interval]) sorted according to the diabetic nephropathy (DN) stages; 8 focal segmental glomerulosclerosis (FSGS) patients and 10 healthy controls. B2M mRNA expression was also evaluated in human embryonic kidney epithelium-like (HEK-293) cells exposed to 25mM glucose and to albumin in order to mimic, respectively, a diabetic and a proteinuric milieu. RESULTS: No differences were found in B2M mRNA expression among healthy controls, FSGS and T1D patients. Nonetheless B2M mRNA expression was higher in the group composed by T1D patients with incipient or overt DN combined with FSGS patients versus T1D patients without DN combined with healthy controls (P=0.0007). B2M mRNA expression was higher in T1D patients with incipient or overt DN versus without DN (P=0.03). B2M mRNA expression positively correlated with albuminuria in the overall T1D population (r=0.43; P=0.01) and negatively correlated with estimated glomerular filtration rate in male T1D patients (r=- 0.57; P=0.01). Increased B2M expression was observed in HEK-293 cells exposed to 25mM glucose and to albumin. CONCLUSIONS: Β2M mRNA expression in cells of the urinary sediment is higher in T1D patients with DKD and in patients with FSGS in comparison to healthy subjects, maybe reflecting a tubulointerstitial injury promoted by albumin. Given the proinflammatory nature of B2M, we suggest that this protein contributes to diabetic (and possibly, to non-diabetic) tubulopathy.

High-resolution gel electrophoresis and sodium dodecyl sulphate-agarose gel electrophoresis on urine samples for qualitative analysis of proteinuria in dogs.

The aims of the current study were to assess whether sodium dodecyl sulphate-agarose gel electrophoresis (SDS-AGE) and high-resolution electrophoresis (HRE) can identify dogs with a urinary protein-to-creatinine ratio (UPC ratio) >0.2 and whether HRE can provide preliminary information about the type of proteinuria, using SDS-AGE as a reference method. HRE and SDS-AGE were conducted on 87 urine samples classified according to the International Renal Interest Society as non-proteinuric (NP; UPC ratio: <0.20; 32/87), borderline proteinuric (BP; UPC ratio: 0.21-0.50; 15/87), or proteinuric (P; UPC ratio: >0.51; 40/87). SDS-AGE and HRE were positive in 14 out of 32 and 3 out of 32 NP samples and in 52 out of 55 and 40 out of 55 samples with a UPC ratio >0.20, respectively. The concordance between HRE or SDS and UPC ratio was comparable (κ = 0.59; κ = 0.55). However, specificity (90%) and positive likelihood ratio (7.76) were higher for HRE than for SDS-AGE (56% and 2.16) while sensitivity was lower (73% vs. 94%). The analysis of HRE results revealed that a percentage of albumin >41.4% and an albumin/α(1)-globulin ratio (alb/α(1) ratio) >1.46 can identify samples classified by SDS-AGE as affected by glomerular proteinuria while a percentage of α(1)-globulin >40.8% and an alb/α(1) ratio <0.84 can identify samples classified by SDS-AGE as affected by tubular proteinuria. In conclusion, both SDS-AGE and HRE could misclassify samples with a UPC ratio higher or lower than 0.20. Therefore, UPC ratio must always be determined before conducting these tests. The percentage of albumin and α(1)-globulin or the alb/α(1) ratio determined by HRE can provide preliminary information about the origin of proteinuria.

Renal parenchymal thickness and urinary protein levels in patients with ureteropelvic junction obstruction after nephrostomy placement.

OBJECTIVE: To assess recovery of renal parenchymal thickness and urinary protein levels in patients with severely hydronephrotic kidneys after nephrostomy placement. METHODS: Fourteen patients (median age 1 year, range 6 months-7 years) who underwent nephrostomy placement for unilateral ureteropelvic junction obstruction at our hospital between May 2007 and January 2009 were included in a retrospective analysis. All patients had severe hydronephrosis, with a median parenchymal thickness of 1.8 mm (range 1-2.5 mm). Kidney morphology was examined by ultrasound before the procedure and 1, 2, 3, 4, 6 and 8 weeks after. Urinary proteins (including albumin, immunoglobulin [IgG], alpha2-macroglobulin, alpha1-microglobulin, beta2-microglobulin [beta2-MG] and kappa chain) and creatinine levels were also tested during these follow-up visits. Fifteen healthy children were assessed for urinary protein levels as well and made up the control group. RESULTS: Parenchymal thickness increased within 4 weeks of nephrostomy placement. Kidney volumes were significantly decreased within 2 weeks. No further changes in morphology were detected after 4 weeks. Urinary alpha1-microglobulin and beta2-MG levels decreased to baseline within 1 and 4 weeks, respectively. Urinary albumin, IgG, alpha2-macroglobulin and kappa chain levels decreased gradually after nephrostomy, but did not return to baseline within 8 weeks. CONCLUSIONS: After nephrostomy placement, parenchymal thickness increases within 4 weeks, tubular function returns to normal earlier than glomerular function and glomerular membrane repair is inversely correlated with the severity of damage.

Species-specific chemosignals evoke delayed excitation of the vomeronasal amygdala in freely-moving female rats.

Male rat chemosignals attract females and influence their reproductive status. Through the accessory olfactory bulb and its projection target, the posteromedial cortical nucleus of the amygdala (PMCo), species-specific chemosignals detected by the vomeronasal organ (VNO) may reach the hypothalamus. To test this hypothesis in vivo, behavioural activation and neurotransmitter release in the PMCo were simultaneously monitored in freely moving female oestrus rats exposed to either rat or mouse urinary stimuli, or to odorants. Plasma levels of the luteinizing hormone were subsequently monitored. All stimuli induced an immediate behavioural activation, but only species-specific chemosignals led to a delayed behavioural activation. This biphasic behavioural activation was accompanied by a VNO-mediated release of the excitatory amino acids, aspartate and glutamate, in the PMCo. The late behavioural and neurochemical activation was followed by an increase in the levels of circulating luteinizing hormone. In conclusion, these data show that only species-specific chemosignals induce a delayed behavioural activation and excitatory activation of the PMCo, which is dependent on an intact VNO.

Dietary exposure to cadmium at close to the current provisional tolerable weekly intake does not affect renal function among female Japanese farmers.

Dietary cadmium (Cd) exposure and renal tubular function were investigated in 1381 female farmers from five districts in Japan (Japanese Multi-centered Environmental Toxicant Study project; JMETS). Dietary Cd exposure of the five populations was assessed from the individual Cd concentrations of the rice consumed by the study participants and the quantities of rice consumed daily. The populations showed a sequential difference in dietary Cd exposure, ranging from a level as low as that of the general Japanese population to one close to the current provisional tolerable weekly intake (PTWI). The levels of urinary Cd excretion, an indicator of Cd accumulation in the kidneys, increased along the same sequential pattern as dietary Cd exposure. However, no differences were observed among the populations in levels of urinary alpha 1-microglobulin and beta 2-microglobulin excretion, which are indicators of renal tubular function. These results indicate that the current PTWI is sufficient to prevent Cd-induced renal dysfunction among the general population.

Electrophoretic pattern of concentrated urine: comparison between 24-hour collection and random samples.

The electrophoretic pattern of concentrated urine samples can be used to identify the type of proteins leaking into the urine and has diagnostic and prognostic value, providing information about the location (glomerular or tubular) and degree of renal injury. This test usually requires a 24-hour urine collection, which can be inconvenient because of its heavy dependence on patient compliance and frequently is unreliable because of errors in collecting a complete 24-hour urine sample. In this study, we compared the electrophoretic pattern in 24-hour urine collections and random samples among patients with glomerular diseases and a wide range of proteinuria. Forty adult patients were evaluated; 24-hour urine collections and random urine samples were analyzed. Protein concentrations were determined using the sulfosalicylic acid method standardized with human serum. Electrophoresis was performed with concentrated urine samples (Ultrafree, PF/Millipore Corporation, Bedford, MA) using Beckman Paragon Electrophoresis System (agarose gels and blue staining; Beckman Instruments, Inc, Brea, CA). Densitometric scanning of electrophoretic pattern (Appraise Clinical Densitometer; Beckman Instruments, Inc) was performed, and the results were reported in percentages of each observed fraction. Our results revealed that despite the significant difference between protein concentration in 24-hour collections and in random samples, the pattern of protein excretion, in percentage basis, remains the same. There were no differences between the albumin, alpha(1)-globulin, alpha(2)-globulin, beta-globulin, and gamma-globulin fractions in both types of specimens. This study shows that, at least in glomerular proteinuria, the electrophoretic analysis of the urine can be performed accurately in random samples, avoiding the inconveniences and errors of a 24-hour urine collection.

Renal follow up of premature infants with and without perinatal indomethacin exposure.

AIMS: To evaluate early childhood renal growth, structure, and function in children born at less than 33 weeks gestation and to investigate possible independent effects of perinatal indomethacin exposure. METHODS: A total of 66 children born at less than 33 weeks gestation, 31 of them with perinatal indomethacin exposure (study group) and 35 without (control group), were examined at 2-4 years of age. Serum cystatin C and protein; plasma creatinine, sodium, and potassium; urine protein, calcium:creatinine ratios, and alpha(1) microglobulin; and glomerular filtration rate (GFR) were determined. Renal sonography examinations were performed. RESULTS: The mean serum cystatin C concentrations were slightly higher in the control group than in the study group. Mean values of serum protein, and plasma creatinine and sodium did not differ between the groups, neither did median plasma potassium concentrations and urine protein:creatinine and calcium:creatinine ratios. None had tubular proteinuria. Abnormal GFR (<89 ml/min/1.73 m(2)) was found in one case in each group and renal structural abnormalities in five in each group. In logistic regression analysis the duration of umbilical artery catheter (UAC) use and furosemide treatment emerged as the significant independent risk factors for renal structural abnormalities. Furosemide treatment and assisted ventilation remained the risk factors associated with renal abnormalities in general-that is, functional and/or structural abnormal findings. CONCLUSION: Perinatal indomethacin does not seem to affect long term renal growth, structure, or function in children born at less than 33 weeks gestation. Duration of UAC use, furosemide treatment, and assisted ventilation may be correlated with later renal structural and functional abnormalities.

Glutathione transferase alpha as a marker for tubular damage after trichloroethylene exposure.

To investigate possible persistent nephrotoxic effects of trichloroethylene (TRI), a retrospective study was carried out on 39 workers exposed to high levels of TRI from 1956 to 1975. Total protein levels in urine, as well as serum and urine creatinine and serum urea were unchanged in comparison with the control. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) was applied to differentiate between tubular and/or glomerular dysfunction. Urinary excretion of alpha-1-microglobulin and glutathione transferase (GST) alpha, as markers of proximal tubular damage, were correlated with the SDS-PAGE patterns of urinary proteins both in the TRI exposed and the control group. GST alpha was found in elevated concentrations in the urine of the TRI-exposed workers. No increase of urinary GST alpha was observed in the control group, even when alpha-1-microglobulin was elevated as a result of non-toxic damage. Both in the control and exposed groups, GST pi, a marker of distal tubular damage, was in the normal range. The results show that chronic exposure to high doses of TRI causes persistent changes to the proximal tubular system of the kidney and that GST alpha excretion into the urine is a marker well suited for quantitation of the extent of renal damage.

Composition of protein in urine from dogs with pyoderma.

The protein fractions in urine from proteinuric dogs with and without pyoderma were estimated. Fifteen dogs with pyoderma (five with superficial and 10 with deep pyoderma) were compared with 10 dogs with glomerulopathy and 27 dogs with diseases other than pyoderma or urinary tract problems. Agarose gel electrophoresis was used to fractionate the proteins. Three types of electrophoretogram were obtained with albuminuria, globulinuria and serum-like profiles. An albuminuria profile was found in eight of the 27 dogs with other diseases, in three of the five dogs with superficial pyoderma, in eight of the 10 dogs with deep pyoderma and in all 10 dogs with glomerulopathy. The albuminuria profile (mean [sem] albumin/globulin ratio 1.98 [0.10]) was also characterised by alpha 1b, alpha 2a and beta 2 globulin peaks in all 29 dogs with this profile, which was therefore thought to indicate that albuminuria (glomerular proteinuria) was a result of glomerular damage and inflammation because alpha 1b, alpha 2a, and beta 2 globulins are considered to be acute phase proteins. The serum-like profile (mean [sem] albumin/globulin ratio 0.72 [0.01]) was observed in 13 per cent of the proteinuric dogs examined and contained all the protein fractions normally detected by electrophoresis of serum. The profile was considered to be a variant from of the albuminuria profile, probably indicating advanced glomerular lesions and inflammation. The globulinuria profile (mean [sem] albumin/globulin ratio 0.33 [0.08]) was significantly different from the other two in that it was characterised by a low albumin peak and the presence of globulin fractions not clearly distinguishable from each other because of their confluency and absence of individual peaks. This profile could indicate severe glomerulotubular lesions and degradation of certain protein fractions. It could also be a result of increased secretion of tissue and other proteins by damaged tubules. It was concluded that glomerular damage leads to glomerular proteinuria characterised by high proportions of albumin together with alpha 1b, alpha 2a and beta 2 globulins in lower but significantly diagnostic proportions.

Urinary protein fractions in healthy subjects using cellulose acetate membrane electrophoresis followed by staining with acid violet 17.

We fractionated normal urinary proteins obtained from 40 healthy subjects using cellulose acetate membrane electrophoresis and stained them with Acid Violet 17. The electrophoretic patterns were classified into four groups. Each of groups I, II, III, IV had an albumin peak and 1, 2, 3, and 4 additional globulin peaks, respectively. Within-day variation study showed that the pattern was fundamentally specific to the individual, although some intermediate cases were observed. We were unable to determine which type was standard for normal subjects. However, the concentration of Tamm-Horsfall protein was speculated to be an important factor in determining the patterns. Group III showed significantly higher values than group I in urine albumin, total protein, and beta-N-acetyl-D-glucosaminidase and this group was believed to include subjects in the subclinical stage of a glomerular disease. All specimens belonging to group IV showed an obvious fraction of alpha 1 globulin which is often found in urine specimens of patients with renal diseases of tubular origin or other pathological conditions.

Quantitative determination of urinary marker proteins: a model to detect intrarenal bioeffects after extracorporeal lithotripsy.

To detect the source of relevant acute intrarenal side effects after extracorporeal piezoelectric lithotripsy and its impact on repeat treatment, urinary excretion of highly specific marker proteins was determined before (day-1) and after (days 0, 1, 4, 7, 14 and 21) treatment. Marker proteins included high molecular weight alpha-2-macroglobulin, immunoglobulin G, albumin, alpha-1-microglobulin as well as the enzyme N-acetyl-beta-glucosaminidase. Of 50 patients who underwent 4,000 shock waves to caliceal stones (group 1) 15 were identically retreated after 5 (group 2) or 15 (group 3) days, respectively, to determine the shortest safe interval to repeat extracorporeal piezoelectric lithotripsy. The course of lithotripsy damage was also evaluated in 15 pre-damaged kidneys (group 4). The alpha-2-macroglobulin enhancement found in all groups on day 0 (p less than 0.005 to p less than 0.05) documented intrarenal bleeding from ruptured vessels. Ratios of alpha-2-macroglobulin/albumin greater than 2.00 on days 0 and 1 exclude a glomerular source of gross hematuria (groups 1 to 4). There was only slight acute tubular damage after extracorporeal piezoelectric lithotripsy (N-acetyl-beta-glucosaminidase increase, p less than 0.05 for groups 1 to 4). Retreatment after 5 days did not enhance the amount of proteinuria compared to the same patients from group 1 (statistically significant at p less than 0.45 to p less than 0.10). Group 3 also showed a similar elevation of proteinuria as the identical patients pretreated 15 days previously. Thus, the data seem to suggest that early repeat sessions of extracorporeal piezoelectric lithotripsy are as safe as delayed retreatments. The course of proteinuria in group 4 did not suggest enhancement of extracorporeal piezoelectric lithotripsy damage in pre-injured kidneys. The urinary marker alpha-2-macroglobulin detects intrarenal vessel ruptures, which are responsible for intrarenal hematomas, as evidenced by animal and human histology. A model is offered to understand and detect the most important parenchymal bioeffects to minimize the risk of injury.

[Development and clinical evaluation of a new urinary protein test paper (URINE-TP)].

Because standard urinary protein test paper reacts more strongly to albumin than to globulin, we attempted to develop a test paper sensitive to globulin by applying chromatic analysis principles used in quantitative analysis of urinary protein. We developed a new urinary protein test paper (URINE-TP) containing a reagent of ACID VIOLET 17. It was found that URINE-TP reacts with the same strength to gamma-globulin as to albumin. This new test paper therefore allows accurate detection of Bence Jones protein, which was formerly detectable with standard test paper. There was a correlation between values for urinary protein obtained with URINE-TP and those obtained by quantitative analysis. As with standard test paper, URINE-TP indicates urinary protein values in the normal range by a lack of reaction, but on URINE-TP positive and negative results are more clearly distinguishable than on standard test paper. From these results, we conclude that URINE-TP enables detection of both gamma-globulin and albumin in the urine, and that is as sensitive as the analytical method in the screening of urinary proteins.

Dysproteinuria induced in rats by O,O,S-trimethyl phosphorothioate.

Administration of a single oral dose of 60 mg/kg O,O,S-trimethyl phosphorothioate (OOS-Me), a malathion impurity, resulted in a substantial increase in the amounts of amino acids along with a change in the nature of proteins excreted in the urine of treated rats. In contrast to control rats, a small increase in albumin and a small decrease in alpha 1-globulin were observed. However, alpha2-, beta- and gamma 1-globulin, which were not detected in the urine of control rats, were found in substantial amounts in the urine of OOS-Me-treated rats. These findings, coupled with observed increases in urinary glucose levels and consistent specific gravity readings of 1.01 even though treated rats were experiencing oliguria, provide evidence for OOS-Me-induced kidney tubule damage.

Isolation and characterization of post gamma globulin in mouse.

A protein of about 13,000 daltons was isolated from mouse CBA urine after inducing a tubular renal dysfunction. This protein was demonstrated similar to human Post Gamma globulin by electrophoresis, aminoacid content and immunochemical criteria.

Protein excretion patterns in cadmium-exposed individuals: high resolution electrophoresis.

High resolution electrophoresis was used to evaluate protein excretion patterns in six cadmium-exposed individuals with proteinuria, seven subjects with nonspecific nephropathies, and four normal unexposed subjects. The aim of the investigation was to determine (a) the type of excretion pattern (i.e., glomerular, tubular, or mixed) associated with cadmium exposure and (b) if the pattern in the cadmium-exposed individuals was distinctly different from subjects with nonspecific nephropathies. The electrophoretic results were consistent with the quantitative results for the cadmium-exposed workers. The results suggest that the pattern associated with cadmium exposure can be glomerular or mixed and that it is different (i.e., no gamma band) from nonspecific nephropathies.