Urinary lysosomal enzyme excretion after renal allotransplantation

Sugar industry sponsorship of germ-free rodent studies linking sucrose to hyperlipidemia and cancer: An historical analysis of internal documents

In 1965, the Sugar Research Foundation (SRF) secretly funded a review in the New England Journal of Medicine that discounted evidence linking sucrose consumption to blood lipid levels and hence coronary heart disease (CHD). SRF subsequently funded animal research to evaluate sucrose's CHD risks. The objective of this study was to examine the planning, funding, and internal evaluation of an SRF-funded research project titled "Project 259: Dietary Carbohydrate and Blood Lipids in Germ-Free Rats," led by Dr. W.F.R. Pover at the University of Birmingham, Birmingham, United Kingdom, between 1967 and 1971. A narrative case study method was used to assess SRF Project 259 from 1967 to 1971 based on sugar industry internal documents. Project 259 found a statistically significant decrease in serum triglycerides in germ-free rats fed a high sugar diet compared to conventional rats fed a basic PRM diet (a pelleted diet containing cereal meals, soybean meals, whitefish meal, and dried yeast, fortified with a balanced vitamin supplement and trace element mixture). The results suggested to SRF that gut microbiota have a causal role in carbohydrate-induced hypertriglyceridemia. A study comparing conventional rats fed a high-sugar diet to those fed a high-starch diet suggested that sucrose consumption might be associated with elevated levels of beta-glucuronidase, an enzyme previously associated with bladder cancer in humans. SRF terminated Project 259 without publishing the results. The sugar industry did not disclose evidence of harm from animal studies that would have (1) strengthened the case that the CHD risk of sucrose is greater than starch and (2) caused sucrose to be scrutinized as a potential carcinogen. The influence of the gut microbiota in the differential effects of sucrose and starch on blood lipids, as well as the influence of carbohydrate quality on beta-glucuronidase and cancer activity, deserve further scrutiny.

Determination of urinary and serum beta-glucuronidase and alkaline phosphatase in various renal disease and kidney rejection transplanted patients

Beta-glucuronidase (beta-Glu) and alkaline phosphatase (ALP) were evaluated in serum and urine in 50 subjects classified into five equal groups. Group I was control healthy subjects, while groups II, III, IV, and V were patients with nephritic syndrome, pyelonephritis, kidney rejection, and end-stage renal disease, respectively. Urinary beta-Glu was significantly elevated in all four groups; while serum enzyme showed no change. On the other hand, serum ALP showed a significant elevation in all abnormal groups. Accordingly, urinary beta-Glu and serum ALP could be used as diagnostic markers for various renal diseases.

Diagnostic value of urinary enzyme determination in renal transplantation

The measurement of enzyme activity in urine provides a sensitive assessment for renal tubular cell damage. The present study was undertaken to evaluate the clinical value of the determination of tubular brush-border-associated enzymes, alkaline phosphatase (AP), gamma-glutamyl transferase (GGT), leucine aminopeptidase (LAP), and dipeptidyl peptidase IV (DPP), of patients with normal graft function (NOR, n = 20), with acute tubular necrosis (ATN, n = 11), with an acute rejection episode (ARE, n = 17) after transplantation, and of healthy persons (n = 20). The second urine of the morning was collected daily during the patients' stay in hospital. The enzyme activities were measured at 25 degrees C and were expressed as U/mmol creatinine. The enzymuria in NOR is higher than in healthy controls, but is still in the normal range. By 5 days after transplantation the initial increased excretion declines as the graft function improves. Elevated enzymuria (DPP 0.69 +/- 0.56, AP 3.06 +/- 3.24, GGT 4.16 +/- 4.13, and LAP 1.39 +/- 1.27) was observed during the rejection episodes. Two days before clinical diagnosis of rejection, the release of DPP-IV and GGT increases to double, and the AP and LAP increases to 3 times the value on the fourth day before rejection. Successful treatment of rejection coincided with a quick return by the third day of the rejection period to the previous enzyme distribution. In ATN no decrease of enzymuria occurs and the excretion is much higher than in ARE. Our method with the every day monitoring of kidney graft function offers the possibility for the early diagnosis of acute rejection.

Urinary excretion of N-acetyl-beta-glucosaminidase and beta-galactosidase by patients with epilepsy

In an effort to detect active renal tubular dysfunction in 74 epileptic patients being treated with antiepileptic drugs (AEDs), we measured the urinary activity of two lysosomal enzymes, N-acetyl-beta-glucosaminidase (NAG) and beta-galactosidase (beta-gal). The heterogeneity of the types of seizures and therapeutic regimens permitted us to examine the potential differences in AED effects. We also examined the chronological changes in the urinary excretion rates of NAG and beta-gal in 132 healthy controls, aged 3 months to 37 years. Increased NAG excretion rates (defined as > or = 2 S.D. compared with age-matched controls) were found in 36.5% of the patients. Valproic acid was highly associated with this increase, and in combination with potassium bromide caused the highest levels of NAG excretion. Among the patients taking carbamazepine, only 11.1% exhibited high levels of NAG in urine. Children under 1 year of age showed higher levels of NAG excretion than older patients. In spite of the abnormally high urinary excretion of NAG, we could not detect any signs of renal dysfunction by urinalysis and measurement of blood urea nitrogen and serum electrolytes. We cannot exclude the possibility that the increased levels of urinary NAG in epileptic patients might be due to renal tubular enzyme induction by AEDs.

Enzyme immunoassay of urinary beta-hexosaminidase isoenzymes in patients with renal transplants

beta-Hexosaminidase (NAG) and percent of NAG B were studied in twenty patients following renal transplantation. Median urinary NAG for twenty reference individuals was 0.26 U/mmol creatinine and NAG B was 24%. Urinary NAG decreased rapidly from a median of 3.7 U/mmol on the third day, to 1.2 U/mmol on the 15th day after transplantation in the patients with no major complications. The percentage of NAG B did not change significantly during this period and did not differ from the reference population. Rejection and cyclosporine toxicity were diagnosed on 17 occasions. Urinary NAG rose more than twofold in 15 of these episodes. The percentage of NAG B was slightly increased in 6 of these. Six months after discharge 17 of the renal transplants functioned well. They exhibited a marked decrease (almost normalized) of urinary NAG with no change in the percentage of NAG B.

Differential quantitation of urinary beta-glucuronidase of human and bacterial origins

A method for the differential quantitation of urinary beta-glucuronidases of human and bacterial origins is presented. The activity of human enzyme at pH 6.5 was 36 per cent of its peak activity at pH 5.0 while the activity of bacterial enzyme at pH 5.0 was 20 per cent of its peak activity at pH 6.5. By simultaneous determination of the activity in a mixture of the enzymes of these two sources at both pH 5.0 and 6.5 and by simple mathematic proportion the individual activity of human and bacterial enzymes could be determined separately. This provides a quick method for differential diagnosis between bacterial and non-bacterial disease of the urinary system.

Urinary N-acetyl-beta-D-glucosaminidase and aminopeptidase N in the diagnosis of graft rejection after live donor renal transplantation

An evaluation of the usefulness of urinary N-acetyl-beta-D-glucosaminidase (NAG) and aminopeptidase N (AAP) measurements in the diagnosis and prediction of acute and chronic renal allograft rejection was made. Enzyme activities were measured in 2,745 morning spot urine samples from 53 consecutive live donor renal allograft recipients up to 180 days after transplantation. Reference ranges of urinary enzyme activities in 14 recipients with normal graft function were higher than those established in a carefully selected group of healthy controls. 89 and 91% of 76 clinically diagnosed acute rejection episodes (ARE) in the remaining 39 graft recipients were accompanied by sharp increase over baseline of NAG and AAP respectively. All rejection episodes occurring in the early period after transplantation were characterised by high enzymuria. AAP was more sensitive than NAG as the magnitude of its increase over baseline was more, while NAG was more specific with less number of false positive elevations. Both enzymes were found to be equally good prognostic indices of graft loss and chronic graft deterioration. Regular monitoring of urinary NAG and AAP activities throughout the post transplant period would thus be valuable in (a) diagnosis and prediction of ARE in the early as well as late post operative period and (b) prediction of eventual graft outcome.

Early monitoring of human renal transplantations by N-acetyl-beta-D-glucosaminidase isoenzyme activities in urines

Monitoring of variations in N-acetyl-beta-D-glucosaminidase (NAG) urinary activity, following renal transplantation, has been proposed for the early diagnosis of rejection episodes. In this study, the measurement of urinary NAG-B activity was conducted as a complement to total NAG (A + B) measurement, which is normally used alone. Selective measurement of NAG-B activity is carried out after fixation of NAG-A on ion exchanger in test tubes. Results of NAG (A + B) activity confirm that the assay of urinary NAG is a useful indicator of rejection, but a positive correlation between NAG-B and NAG (A + B) activities was observed during the various complications which can occur after transplantation. The specific measurement of this isoenzyme does not, therefore, seem to provide additional information in the early monitoring of human renal transplantations. Apart from rejection episodes, other factors are likely to produce marked NAG-B excretion, e.g. gentamicin therapy.

Distribution of N-acetyl-beta-D-glucosaminidase isoenzymes along the rabbit nephron

Total N-acetyl-beta-D-glucosaminidase (NAG) activity has been measured in microdissected glomeruli (G) and tubular segments [proximal convoluted tubule (PCT), pars recta (PR), medullary thick ascending limb (MAL), and cortical collecting tubule (CCT)] of the rabbit kidney, by a fluorimetric method using synthetic substrate. Selective activity of the isoenzyme NAG B was also determined. Isoenzyme profiles of NAG were obtained by electrofocusing on each segment. Characterization of the isoenzymes was performed by chromatofocusing and thermosensitivity experiments on PCT. Total NAG activity, mainly composed of NAG A, was low in glomeruli and two and one-half to four times higher in PCT than in other segments, in which comparable activities were found. NAG B was detectable all along the nephron. It represented a very small fraction of total NAG, except in PCT where it was more abundant (20 to 30%). Electrofocusing revealed the presence of a minor form (NAG I) all along the nephron. Chromatofocusing and thermosensitivity studies indicated that NAG I could represent imperfectly solubilized NAG A rather than a well defined entity. From these results, it could be suggested that the reported increase in urinary excretion of NAG B after renal injury may reflect the intensity of proximal tubular lesions.

Comparison of urinary N-acetyl-beta-D-glucosaminidase and urinary fibrin degradation products for diagnosis of rejection after renal transplantation

A comparison was made of two established tests to see which was the better indicator of rejection after renal transplantation. Daily urine samples were assayed for excretion of N-acetyl-beta-D-glucosaminidase (NAG) and fibrin degradation products (FDP). Twenty-five rejection episodes were studied in 19 patients. Both indicators tended to move in parallel. NAG was more often elevated in rejection, namely in 96% of rejection episodes as against 76% for FDP, FDP had the advantage of fewer false positive results and when it correctly indicated rejection its increase above the baseline was relatively greater than for NAG, NAG and FDP can both provide early warning of rejection. NAG is preferred for its ease of assay. Assays are performed daily and are of practical value in clinical management. The results of assays must be interpreted in conjunction with all relevant information.