The influence of work intensity on postexercise proteinuria

Fifteen men were studied during 100 m, 400 m and 3,000 m runs at maximal speed to determine total urinary protein and albumin excretion rates in relation to different distances of running. Venous blood lactate rose to 7.5 mmol.l-1 after the 100 m and 3,000 m events, while reaching 12 mmol.l-1 after the 400 m dash. Total urinary protein excretion increased to 330, 1640 and 565 micrograms.min-1 after the 100 m, 400 m and 3,000 m runs respectively, as compared with basal values (70 micrograms.min-1). In the meantime, albumin excretion increased respectively by 5, 25 and 18 fold of the resting values. The renal clearance of albumin increased to 0.84, 5.62 and 3.35 microliter.min-1 after the three runs, as compared with a mean value of 0.19 microliter.min-1 at rest. Exponential relationships (r = 0.85) were recorded between post-exercise venous lactate and albumin, and total protein excretion. The present work illustrates the major influence of the intensity of exercise (anaerobic glycolytic component), rather than its duration, on the excretion rate of urinary proteins.     

Transferrin and albumin excretion as a measure of glomerular function

Albumin and transferrin are relatively small protein molecules and highly negatively charged. Their levels in urine are a useful indicator of the integrity of membrane barriers of the kidney glomerular capillary wall. The present data shows that the excretion rates of albumin and transferrin and their kinetics of excretions are similar. Thus, their filtration mechanisms at the active site of the kidney membrane pores are similar. Total urinary protein/creatinine or albumin or transferrin/creatinine ratio were found to be linear and highly significant. Their measurement could indicate the degree of impaired glomerular permeability. Also, in the present study, a rapid biochemical method of measurement of the selectivity of proteinuria based on the transferrin/albumin ratios in random samples is reported. This method is particularly useful in the early stages of glomerular basement membrane damage.     

Wilm's Tumor-1 Protein Levels in Urinary Exosomes from Diabetic Patients with or without Proteinuria

Background

Podocyte injury is an early feature of diabetic nephropathy (DN). Recently, urinary exosomal Wilm''s tumor-1 protein (WT1), shed by renal epithelial cells, has been proposed as a novel biomarker for podocyte injury. However, its usefulness as biomarker for early diabetic nephropathy has not been verified yet. We investigated urinary exosomal WT1 in type-1 diabetic patients to confirm its role as a non-invasive biomarker for predicting early renal function decline.

Methods

The expression of WT1 protein in urinary exosomes from spot urine samples of type-1 diabetes mellitus patients (n = 48) and healthy controls (n = 25) were analyzed. Patients were divided based on their urinary albumin excretion, ACR (mg/g creatinine) into non- proteinuria group (ACR<30 mg/g, n = 30) and proteinuria group (ACR>30 mg/g, n = 18). Regression analysis was used to assess the association between urinary exosomal levels of WT1 with parameters for renal function. Receiver Operating Characteristic (ROC) curve analysis was used to determine the diagnostic performance of exosomal WT-1.

Results

WT1 protein was detected in 33 out of 48 diabetic patients and in only 1 healthy control. The levels of urinary exosomal WT1 protein is significantly higher (p = 0.001) in patients with proteinuria than in those without proteinuria. In addition, all the patients with proteinuria but only half of the patients without proteinuria were positive for exosomal WT1. We found that the level of exosomal WT1 were associated with a significant increase in urine protein-to-creatinine ratio, albumin-to-creatinine ratio, and serum creatinine as well as a decline in eGFR. Furthermore, patients exhibiting WT1-positive urinary exosomes had decreased renal function compared to WT1-negative patients. ROC analysis shows that WT-1 effectively predict GFR<60 ml. min-1/1.73 m².

Conclusion

The predominant presence of WT1 protein in urinary exosomes of diabetic patients and increase in its expression level with decline in renal function suggest that it could be useful as early non-invasive marker for diabetic nephropathy.     

Microtransferrinuria and microalbuminuria. I. In the diabetic human

We studied albumin, transferrin and total protein excretion in the urine of 110 diabetics visiting a family practice department. Of these patients 18.2% had an elevated total urinary protein above the reference range (greater than 200 mg/g creatinine). Of the remaining patients (normoproteinuria), 25.5% have elevated transferrin (greater than 0.9 mg/g creatinine) while 18.8% have elevated albumin (greater than 32 mg/g creatinine). The correlation coefficient between transferrin and albumin in urine when total urinary protein is normal was 0.77. Moderate exercise increased urinary transferrin in normal subjects 950%, while for albumin the increase was 440%. These data demonstrate the usefulness of microtransferrinuria, a potentially more sensitive indicator than microalbuminuria for diabetic nephropathy.     

Recovery from an activity-induced metabolic acidosis in the American alligator, Alligator mississippiensis

The metabolic acidosis resulting from an intense exercise bout is large in crocodilians. Here we studied recovery from this pH perturbation in the American alligator. Metabolic rate, minute ventilation, arterial pH and gases, and strong ion concentration were measured for 10 h after exhaustion to elucidate the mechanisms and time course of recovery. Exhaustion resulted in a significant increase in lactate, metabolic rate, and ventilation, and a decrease in arterial PCO2), pH and bicarbonate. By 15 min after exhaustion, oxygen consumption returned to rest though carbon dioxide excretion remained elevated for 30 min. Arterial PO2), [Na+], and [K+], increased following exhaustion and recovered by 30 min post-exercise. Minute ventilation, tidal volume, [Cl-], and respiratory exchange ratio returned to resting values by 1 h. The air convection requirement for oxygen was elevated between 15 and 60 min of recovery. Breathing frequency and pH returned to resting values by 2 h of recovery. Lactate levels remained elevated until 6 h post-exercise. Arterial PCO2) and [HCO3-] were depressed until 8 h post-exercise. Compensation during recovery of acid-base balance was achieved by altering ventilation: following the initial metabolic acidosis and titration of bicarbonate, a relative hyperventilation prevented a further decrease in pH.     

Protein creatinine index and Albustix in assessment of proteinuria.

The protein creatinine index in early morning and random urine specimens was compared with the 24 hour urinary excretion of protein in normal subjects and outpatients with abnormal proteinuria. A protein creatinine index (defined as (mg protein/1 divided by creatinine mmol/1) times 10) below 125 in a random specimen excluded abnormal proteinuria, whereas an index of more than 136 indicated the presence of pathological proteinuria. The index for random specimens provided a useful semiquantitative assessment of the 24 hour excretion of protein (mg protein/24 hours), but the index for early morning specimens was less reliable. Errors with Albustix were partly due to intra and inter observer variations in the interpretation of the colour formed when compared with the chart provided. It is proposed that the protein creatinine index on random urine samples should be used to supplement dipsticks in screening for proteinuria in cases where misclassification would be serious.     

Diurnal fluctuations of protein contents and the pH dependence of β<Subscript>2</Subscript>-microglobulin stability in urine

Diurnal fluctuations of protein excretion into urine and the effect of urinary pH on the urinary protein concentrations were studied in patients with various kidney diseases. The diurnal kinetics of γ-immunoglobulin, transferrin, albumin, α₁-microglobulin, γ-immunoglobulin light chains, and the retinol-binding protein proved to positively correlate with the diurnal fluctuations of proteinuria and to negatively correlate with urinary pH. Diurnal changes in urinary β₂-microglobulin content did not correlate with those of any other protein. Oral bicarbonate intake alkalinized the urine, increased the urinary β₂-microglobulin content, and led to a direct correlation between β₂-microglobulin excretion and excretion of other low-molecular proteins. Thus, proteinuria, single protein excretion, and urinary pH displayed diurnal rhythmicity in the patients; β₂-microglobulin was unstable in acid urine and its urinary level depended on the urinary pH.     

Urinary N tau-methylimidazole acetic acid excretion in respiratory disease

N tau-methylimidazole acetic acid (N tau-MIAA) is the principal urinary metabolite of histamine. The basal urinary excretion rate of N tau-MIAA was determined as 0.117 +/- 0.008 (SE) mg/h, with a renal clearance for N tau-MIAA of 273 +/- 27 ml/min implying active secretion. After subpharmacological infusion of histamine (50 ng.kg-1.min-1 over 2 h) in five volunteers that increased plasma histamine from 0.28 +/- 0.04 to 0.71 +/- 0.15 ng/ml, urinary excretion of N tau-MIAA over 8 h was increased by less than 17% compared with a control saline infusion. Urinary N tau-MIAA excretion in normal controls (273 +/- 14 micrograms/mmol creatinine) was similar to that observed in patients with severe acute asthma (253 +/- 22 micrograms/mmol), antigen-induced bronchoconstriction (269 +/- 21 micrograms/mmol), seasonal allergic rhinitis (304 +/- 31 micrograms/mmol), and clinically stable bronchiectasis (270 +/- 22 micrograms/mmol). In contrast, large increases in metabolite excretion (greater than 7,000 micrograms/mmol creatinine) were observed in a patient with systemic mastocytosis where very high plasma histamine levels were recorded (greater than 500 ng/ml) and marked systemic hemodynamic effects occurred. We conclude that urinary N tau-MIAA will only be increased in pathologies where sustained hyperhistaminemia occurs and that increased local histamine production in the lung or the upper airway does not cause a measurable change in the basal urinary excretion of this metabolite.     

An increase in the excretion of total protein and albumin by the human kidney during water diuresis

The rate of excretion of the total protein and albumin during an increase in diuresis after water loading was studied in healthy volunteers. In the control period, the excretion of protein (7.3–11.1 mg/2 h) and albumin (0.29–0.42 mg/2 h) was within of the physiological norm range. Water loading (20 ml/kg) caused water diuresis, urine formation rate increased by a factor of 15, and the reabsorption of solute-free water changed into its excretion. The increase in diuresis was accompanied by a statistically significant increase in the urinary protein and albumin excretion, as well as by an increase in the protein-to-creatinine ratio. After water loading, the excretion of total protein, as compared to the initial period, increased by a factor of 8.4, and of the albumin excretion, by a factor of 2.8, exceeding the generally accepted limits of the norm. The role of intraglomerule hemodynamics in the development of physiological proteinuria related to water diuresis is discussed.     

Urinary excretion of electrolytes during prolonged physical activity in normal man

Nine normal young male students were studied during 2 days of relative rest, during 2 days of physical training and again during the succeeding 2 days of relative rest. Twenty-four hour urine collections showed that sodium and potassium excretion were lower during the exercise days, while urinary aldosterone excretion was increased. No differences in the 24-h urinary excretion of creatinine, calcium, and magnesium were found between the resting and exercise days. Hemoglobin concentration, hematocrit and red cell counts were decreased at 14 h and 42 h after exercise; these findings together with the increased serum bilirubin concentration could result from hemolysis. Plasma renin activity, angiotensin II and aldosterone concentration were increased 14 h after exercise but returned to baseline 42 h after exercise. Our data shows that one should take into account previous exercise when interpreting results of certain of these tests.     

Effect of protein restriction in insulin dependent diabetics at risk of nephropathy.

Persistent proteinuria is strongly associated with increased mortality in insulin dependent diabetes, and risk of this condition can be predicted many years in advance by subclinical increases in albumin excretion rate (microalbuminuria). Eight normotensive insulin dependent diabetics with microalbuminuria who had overnight albumin excretion rates of between 15 and 200 micrograms/min underwent a three week randomised crossover study of their normal protein diet (median 92 (range 55-117) g/day) and a low protein diet (47 (38-57) g/day). Both diets were isoenergetic, and the low protein diet was supplemented with calcium and phosphate. Median overnight albumin excretion rate fell from 23.0 (15.0-170.1) micrograms/min during the normal diet to 15.4 (4.1-97.8) micrograms/min during the low protein diet. No consistent change was found in urinary excretion of beta 2 microglobulin during the two diets. The reduction in albumin excretion rate was accompanied by a significant fall in median glomerular filtration rate and fractional renal clearance of albumin. Kidney volume remained unchanged. There were no significant changes in glycaemic control or arterial blood pressure. In these few patients restriction of dietary protein had a beneficial effect on microalbuminuria, independent of changes in glucose concentrations and arterial blood pressure.     

Urinary fibrin-fibrinogen degradation products in nephrotic syndrome.

The urinary concentration of fibrin-fibrinogen degradation products (F.D.P.) was measured in 90 patients with proteinuria above 2 g/1 and correlated with proteinuria, differential protein clearances, serum urea and creatinine, and renal biopsy findings. There was a linear correlation (r equals 0-7; P less than 0-001) between the urinary F.D.P. excretion and the selectivity of the proteinuria such that patients with highly selective proteinuria excreted only small amounts of F.D.P. whereas those with non-selective proteinuria excreted much higher levels. There was a significant correlation between the urinary F.D.P. excretion and the urine:serum (U:S) ratio of IgG excretion but not with the U:S ratio or urinary excretion of albumin or transferrin. Sephadex G200 column chromatography of the concentrated urine in 26 cases showed that patients with highly selective proteinuria excreted predominantly F.D.P. of low molecular weight in the urine whereas those with non-selective proteinuria excreted mainly fibrinogen and products of high molecular weight. Hence the type and quantity of F.D.P. in the urine are determined primarily by the differential filtration of fibrinogen and the various degradation products from the plasma through the glomerular basement membrane, which in turn is determined by the "pore size" of the basement membrane. In clinical nephrology measurement of the urinary F.D.P. level provides a rapid and convenient means of estimating the differential protein clearance.     

Indirect estimation of the maximal aerobic power of a male and female population from Brussels aged 6 to 23 years. Comparison with a direct technic for measuring maximal oxygen consumption

Validation of the maximal multistage 20 m shuttle run test with 1 min steps has been compared with a stepwise load increase on a bicycle ergometer among 201 male and female subjects ranging from 14 to 30 years. A slight underestimation of VO2 max (5.2%) amounting to 2.71 ml . min-1 . kg-1 was observed for the multistage shuttle test as compared to the bicycle test (r = 0.72). The analysis of the biological values collected after exercise does not show major differences between the two tests (plasma lactate, urinary total protein and albumin, creatinine). The renal handling of plasma proteins appears to be equally disturbed under the influence of exhaustive exercise. Maximal aerobic power regularly increases with age in both sexes, being more pronounced however for boys (1.16 to 3.37 l . min-1) than for girls (1.17 to 2.43 l . min-1) from 6 to 20 years old. Boys nearly sustain 50 ml . min-1 . kg-1 throughout childhood. On the contrary, from 8 years on girls progressively reduce their VO2 max down to 37.1 ml . min-1 . kg-1 at the age of 19. The decrease is more pronounced during the 11-16 years period. The present results constitute tentative norms on 1,025 brussels male and female subjects ranging from 6 to 23 years.     

Detection of urinary podocytes and nephrin as markers for children with glomerular diseases

The purpose of this study was to detect the urinary podocytes and its related protein, nephrin, in the urine of the children with glomerular disease in order to analyze the relationship of the clinical testing with the significance of the glomerular disease. A total of 65 children with nephrotic syndrome were selected for this study. The podocytes and nephrin were detected in the urinary sediment by indirect immunofluorescence, enzyme-linked immunosorbent assay, and Western blotting. The urinary podocytes and nephrin positive rates were 53.8% and 50.8%, respectively, in the children with glomerular disease. The serum total protein and albumin decreased in the podocyte-positive children, while the urine total protein at 24 h, urinary albumin/creatinine ratio, blood urea nitrogen, and serum creatinine were significantly elevated as compared to those of the podocyte-negative patients. Furthermore, the results were the same in the patients with positive nephrin as compared to that of the patients with negative nephrin. The podocyte number and nephrin level were significantly higher in the lupus nephritis group as compared to those of the other groups. Likewise, the podocyte number and nephrin level dramatically increased in the focal segmental glomerulosclerosis group as compared to those of the mesangial proliferative glomerulonephritis and minimal change disease groups. In addition, the podocyte numbers and nephrin expression were significantly higher in severe proteinuria group as compared to those of the mild proteinuria group. The urinary nephrin expression was positively related to podocyte and urinary albumin/creatinine ratio. We concluded that the detection of the urinary podocytes and nephrin could be taken as markers for children with glomerular disease, reflecting the type of the disease. Therefore, this can be used as a noninvasive method to evaluate the severity of the kidney disease in children.     

Liquid chromatography-based determination of urinary free and total N(epsilon)-(carboxymethyl)lysine excretion in normal and diabetic subjects

We propose a specific, reproducible and sensitive HPLC method for the determination of N(epsilon)-(carboxymethyl)lysine (CML) excreted in urine. Total CML was measured in acid hydrolysates of urine samples, while free CML was measured in acetonitrile-deproteinised urine samples using a RP-HPLC method with ortho-phtaldialdehyde (OPA)-derivatisation and fluorescence detection suited for automation. We compared the CML excretion of 51 non-proteinuric patients with diabetes mellitus (DM) (age 57+/-14 years, HbA1c 8.0+/-1.8%) to 42 non-diabetic controls (C) (age 45+/-17 years). The urinary excretion of total CML in diabetic patients was increased by approximately 30% (DM: 0.58+/-0.21; C: 0.45+/-0.14 microM/mmol creatinine; P<0.001). While urinary excretion of free CML was not significantly different, excretion of bound CML was increased (DM: 0.36+/-0.17; C: 0.27+/-0.14; P<0.05) in diabetic patients. CML excretion was correlated with protein and albumin excretion, but did not correlate with HbA1c, duration of DM or diabetic complications such as neuropathy or retinopathy. Furthermore, no age-dependent change of total CML excretion was found, while free CML excretion was lower in younger subjects. The specific and sensitive determination of CML by RP-HPLC of its OPA-derivative is well suited for automation and better than that of less defined glycoxidation products (AGEs).     

Increased renal TXA2 synthesis in diabetes mellitus: simultaneous determination of urinary TXB2 and 2,3-dinor-TXB2

The present study was designed to determine urinary excretion of kallikrein(KAL)-kinin as well as prostaglandin (PG) E2, TXB2 and 2,3-dinor-TXB2, a major urinary metabolite of TXA2 synthesized in platelets, by specific RIAs in patients with diabetes mellitus (DM). KAL or kinin excretion in 26 type II DM did not differ from control values obtained in 18 age-matched healthy subjects (C), although DM with HbA1 greater than 11% excreted less KAL. Urinary PGE2 excretion (7.6 +/- 2.8 ng/mg creatinine, mean +/- SE) was significantly lower in DM compared to C (17.5 +/- 3.9, p less than 0.05), while DM excreted more TXB2 (0.57 +/- 0.09, p less than 0.01) and 2,3-dinor-TXB2 (0.56 +/- 0.12, N.S.) than C (0.19 +/- 0.02 or 0.33 +/- 0.01). DM with or without mild proteinuria demonstrated lower PGE2, but higher TXB2 and 2,3-dinor-TXB2 excretion. A positive correlation of TXB2/2,3-dinor-TXB2 with proteinuria was observed in this group. However, in DM with massive proteinuria over 500 micrograms/mg creatinine, TXB2 and 2,3-dinor-TXB2 excretion decreased to levels almost identical to C. As a whole, a ratio of TXB2 to PGE2 or 2,3-dinor-TXB2 in DM was significantly higher than in C. The results suggest that a relative preponderance of TXB2 to 2,3-dinor-TXB2 may indicate an augmented renal, in addition to platelet, TXA2 synthesis. An excessive vasoconstrictive and proaggregatory TXA2 renal synthesis, concomitant with a decrease in vasodilatory and antiaggregatory PGE2, may have profound effects on renal functions such as protein excretion in DM.     

Urinary albumin in space missions

Proteinuria was hypothesized for space mission but research data are missing. Urinary albumin, as index of proteinuria, was analyzed in frozen urine samples collected by astronauts during space missions onboard MIR station and on ground (control). Urinary albumin was measured by a double antibody radioimmunoassay. On average, 24h urinary albumin was 27.4% lower in space than on ground; the difference was statistically significant. Low urinary albumin excretion could be another effect of exposure to weightlessness (microgravity).     

Short term effect of captopril on microalbuminuria induced by exercise in normotensive diabetics.

OBJECTIVE--To investigate whether captopril has any effect on microalbuminuria induced by exercise in normotensive diabetic patients with early stage nephropathy. DESIGN--Randomised, double blind, crossover trial. SETTING--Outpatient department. PATIENTS--22 diabetics with stage II nephropathy (urinary albumin excretion rate less than 20 micrograms/min; 15 with type I diabetes and seven with type II), 32 patients with stage III nephropathy (urinary albumin excretion rate 20-200 micrograms/min; 14 with type I diabetes and 18 with type II), and 10 normal subjects. INTERVENTIONS--Four exercise tests on a cycle ergometer: the first two under basal conditions and the third and fourth after subjects had received captopril (two 25 mg doses in 24 hours) or placebo (two tablets in 24 hours). END POINT--Exercised until 90% of maximum heart rate achieved. MEASUREMENTS AND MAIN RESULTS--Mean urinary excretion one hour after the first two exercise tests was 21 micrograms/min in normal subjects, 101 micrograms/min in diabetic patients with stage II nephropathy, and 333 micrograms/min in those with stage III nephropathy. Similar results were obtained after placebo. After captopril the urinary excretion rate one hour after exercise was significantly decreased in diabetics with stage II (36 micrograms/min) and stage III (107 micrograms/min) disease compared with placebo but not in normal subjects. Systolic and diastolic pressures were similar in the three groups after placebo and captopril had been given. CONCLUSIONS--Captopril significantly reduces microalbuminuria induced by exercise in normotensive diabetics without affecting systemic blood pressure. Captopril may reduce renal intracapillary pressure.     

Decrease in Urinary Creatinine Excretion in Early Stage Chronic Kidney Disease

Background

Little is known about muscle mass loss in early stage chronic kidney disease (CKD). We used 24-hour urinary creatinine excretion rate to assess determinants of muscle mass and its evolution with kidney function decline. We also described the range of urinary creatinine concentration in this population.

Methods

We included 1072 men and 537 women with non-dialysis CKD stages 1 to 5, all of them with repeated measurements of glomerular filtration rate (mGFR) by ⁵¹Cr-EDTA renal clearance and several nutritional markers. In those with stage 1 to 4 at baseline, we used a mixed model to study factors associated with urinary creatinine excretion rate and its change over time.

Results

Baseline mean urinary creatinine excretion decreased from 15.3±3.1 to 12.1±3.3 mmol/24 h (0.20±0.03 to 0.15±0.04 mmol/kg/24 h) in men, with mGFR falling from ≥60 to <15 mL/min/1.73 m², and from 9.6±1.9 to 7.6±2.5 (0.16±0.03 to 0.12±0.03) in women. In addition to mGFR, an older age, diabetes, and lower levels of body mass index, proteinuria, and protein intake assessed by urinary urea were associated with lower mean urinary creatinine excretion at baseline. Mean annual decline in mGFR was 1.53±0.12 mL/min/1.73 m² per year and that of urinary creatinine excretion rate, 0.28±0.02 mmol/24 h per year. Patients with fast annual decline in mGFR of 5 mL/min/1.73 m² had a decrease in urinary creatinine excretion more than twice as big as in those with stable mGFR, independent of changes in urinary urea as well as of other determinants of low muscle mass.

Conclusions

Decrease in 24-hour urinary creatinine excretion rate may appear early in CKD patients, and is greater the more mGFR declines independent of lowering protein intake assessed by 24-hour urinary urea. Normalizing urine analytes for creatininuria may overestimate their concentration in patients with reduced kidney function and low muscle mass.     

Biochemical changes in a 100 km run: free amino acids, urea, and creatinine.

Free amino acids, urea, and creatinine were analyzed in venous blood and urine of 11 trained (28--81 years old) male subjects before, immediately after, and 1 day after a 100 km running competition. The urinary excretion per minute of all amino acids was lowered after the contest. The renal clearance of creatinine was reduced from 116 to 60 ml/min and the clearance of most amino acids was reduced to a similar extent. However, for the amino acids with a resting clearance under 1 ml/min (x), a high relative clearance ratio (y in % of x) was seen post-exercise: y = -92.3 (log10 x) +23.1, r = -0.83, showing that their high reabsorption capacity had been impaired. Serum concentrations of most free amino acids, including the branched-chain amino acids and alanine, were reduced to 35--85% of the pre-race values. The sulfur amino acids were elevated either at the end of (cystine, to 180%) or 24 h after (methionine, to 155%) the race. Urea production increased by 44% while creatinine production tended to decrease. The production of 3-methylhistidine remained unchanged. These findings are compatible with a stimulation of gluconegenesis at the expense of the amino acid pool without induction of muscle protein catabolism.