Urinary excretion of N-acetyl-beta-D-glucosaminidase and its isoenzymes in cats with urinary disease

Renoprotective effects of docosahexaenoic acid in cats with early chronic kidney disease due to polycystic kidney disease: a pilot study

OBJECTIVES

Lipids containing n-3 fatty acids have been reported to have protective effects on renal function, with docosahexaenoic acid (DHA) expected to be particularly effective. However, no reports have demonstrated the renoprotective effects of DHA-enriched lipids in cats with chronic kidney disease (CKD). Therefore, the aim of this pilot study was to examine the renoprotective effects of DHA-enriched fish oil in cats.

METHODS

Five healthy cats and five cats with early non-azotaemic CKD due to autosomal dominant polycystic kidney disease (PKD) were orally administered DHA-enriched fish oil in liquid form (250 or 500 mg/kg body weight [BW] and 250 mg/kg BW of DHA, respectively) for 28 days. Inappropriately dilute urine and markedly increased urinary N-acetyl-d-glucosamine (NAG) index were detected in cats with PKD before DHA-enriched fish oil administration. Changes in the fatty acid composition ratio in the blood of all 10 cats were assessed after orally administering 250 mg/kg of DHA.

RESULTS

Post-administration, no adverse clinical effects were observed, and blood and urine tests were within the reference intervals in healthy cats. Cats with PKD showed significantly decreased serum symmetric dimethylarginine (SDMA), urine protein:creatinine ratio (UPC) and urinary NAG index at post-administration. Furthermore, oral administration of DHA-enriched fish oils significantly decreased the blood concentration ratio of arachidonic acid (AA) in cats with PKD post-administration. Furthermore, the concentration ratio of DHA in the blood significantly increased in both healthy cats and cats with PKD, and the DHA:AA ratio also increased.

CONCLUSIONS AND RELEVANCE

Oral administration of DHA-enriched fish oils for 28 days significantly decreased blood AA levels and significantly increased DHA concentration and DHA:AA ratios in cats with PKD, and improved the SDMA, UPC and urinary NAG index, suggesting its potential for renoprotective effects in cats with early non-azotaemic CKD due to PKD.

Effect of non-steroidal anti-inflammatory drugs on glomerular filtration rate and urinary N-acetyl-β-D-glucosaminidase activity in cats after dental surgery

OBJECTIVE

To compare the effects of meloxicam or carprofen on glomerular filtration rate (GFR), and to evaluate the effect of meloxicam on urinary N-acetyl-β-D-glucosaminidase (NAG) activity, of cats after dental surgery.

STUDY DESIGN

Randomized, blinded, controlled trial.

ANIMALS

A total of 24 mixed breed cats.

METHODS

Cats were randomly assigned to one of three groups (n = 8 per group): meloxicam (0.2 mg kg^-1); carprofen (4 mg kg^-1); or saline (2 mL). Acepromazine (0.04 mg kg^-1) and buprenorphine (0.02 mg kg^-1) were administered intramuscularly as preanaesthetic medication. Test drugs were injected subcutaneously at the time of preanaesthetic medication. Anaesthesia was induced with intravenous propofol and maintained with isoflurane in oxygen. Mean arterial blood pressure (MAP), respiratory rate (f_R), heart rate (HR) and haemoglobin oxygen saturation values (SpO₂) were recorded. All cats underwent ultrasonic dental scaling with polishing. Teeth extraction involved mucosal flap creation, removal of alveolar bone and flap closure. Plasma iohexol clearance (ICL), a measure of GFR, was estimated before and 24 hours after anaesthesia induction in all cats. Urinary NAG index was estimated in saline and meloxicam groups at the same time points as GFR. Between-group and -time point differences in GFR and NAG index were compared using mixed model analyses. Data are presented as mean ± standard deviation (p < 0.05).

RESULTS

There was no significant difference in plasma ICL rate (range: from 1.22 ± 0.05 to 1.27 ± 0.04 mL kg minute^-1) between groups or between time points. Urinary NAG index (range: from 1.0 ± 0.19 to 1.36 ± 0.29 Units gram^-1) was not significantly different between meloxicam and saline groups. MAP, HR, f_R and SpO₂ did not differ significantly between groups.

CONCLUSIONS AND CLINICAL RELEVANCE

Meloxicam and carprofen appeared to produce nonsignificant effects on GFR, and meloxicam did not affect the urinary NAG activity, of cats after dental surgery.

The impact of nandrolone decanoate abuse on experimental animal model: Hormonal and biochemical assessment

Nandrolone decanoate (ND) is one of the most commonly abused anabolic androgenic steroids compounds in the world owing to its ability to improve physical performance but its abuse is associated with several adverse effects. The current study was performed to evaluate the effect of recommended and overdose of nandrolone decanoate (ND) for short and long term on the alterations of biochemical markers related to kidney, liver, adrenal, thyroid gland functions and oxidant and antioxidant activities. Sixty male rats were randomly assigned into two major groups. The first was treated with ND for 6 weeks and the second was treated with same drug for 12 weeks. Each of these groups was further subdivided into three sub groups: 1-Control (untreated rats), 2- Rats intraperitoneally injected with ND 3 mg/kg weekly, 3- Rats intraperitoneally injected with ND 15 mg/kg weekly. Administration of high ND dose for either short or long term significantly elevated kidney function biomarkers, liver enzymes both in serum, cytosol and mitochondria, insignificantly increased thyroid function, significantly increased adrenal function while, decreased ACTH. Moreover, oxidative stress biomarkers were significantly upregulated associated with depression in antioxidants activities. Administration of high ND dose for either short or long term as well as the repeated use of recommended ND dose for long term proved to have harmful effects manifested in impairing the functions of kidneys, liver, thyroid and adrenal glands as well as oxidant antioxidant balance.

Equine urinary N-acetyl-β-D-glucosaminidase assay validation and correlation with other markers of kidney injury

Detection of equine acute kidney injury (AKI) is hindered by limited markers of early renal damage in horses. N-acetyl-β-D-glucosaminidase (NAG), a lysosomal enzyme in renal tubular epithelium released into urine during tubular insult, has shown promise for early identification of AKI in humans and other species. We validated an assay for NAG in equine urine and measured urinary NAG in 7 azotemic and 7 non-azotemic client-owned adult horses. The enzymatic NAG assay was validated using within- and between-run coefficients of variation (CVs), recovery following standard addition, and linearity of dilution. Intra- and inter-run CVs (21% and 3.2%, respectively), average recovery following standard addition (99-109%), and linearity under serial dilution (R² = 0.997) were satisfactory. Urine NAG index was significantly correlated with urinary fractional excretion of sodium (FE_Na; ρ = 0.76, p < 0.001) and plasma creatinine (ρ = 0.74, p = 0.001). Median urine NAG indices were higher in azotemic horses (p = 0.006), in horses with increased urinary FE_Na (p = 0.006), and in horses with increased urine gamma-glutamyl transferase index (p = 0.032). Urine NAG can be measured in horses and shows positive correlation with 2 current renal biomarkers. Additional work is needed to establish normal equine reference intervals and characterize the increase of urine NAG index in horses in relation to tubular injury.

Urine protein, urine protein to creatinine ratio and N-acetyl-β-D-glucosaminidase index in cats with idiopathic cystitis vs healthy control cats

Objectives The objective was to compare urine protein, urine protein to creatinine ratio (UPC) and N-acetyl-β-D-glucosaminidase (NAG) index between cats with idiopathic cystitis and clinically normal cats. Methods Urine and blood samples were collected from 19 clinically normal cats and 19 cats with idiopathic cystitis without azotaemia at the time of first presentation. Urine protein, urine creatinine and UPC were measured. Additionally, the urinary NAG concentration was measured using the colorimetric method, and the NAG index was calculated by dividing the urinary NAG concentration by the urine creatinine ratio. Results Urine protein concentration (mean ± SEM) was four times higher in cats with idiopathic cystitis (218.29 ± 58.95) than in clinically normal cats (56.13 ± 9.95) (P <0.05). The UPC (mean ± SEM) of cats with idiopathic cystitis (0.70 ± 0.19) was also five times higher than that of clinically normal cats (0.14 ± 0.02) (P <0.05). The mean ± SEM NAG index in cats with idiopathic cystitis (4.79 ± 1.53 U/g) was two times higher than that in clinically normal cats (2.14 ± 0.48 U/g). The log UPC was positively correlated with the log NAG index in cats with idiopathic cystitis at moderate levels (r2 = 0.512; P <0.05). Conclusions and relevance Cats with idiopathic cystitis had increased amounts of urine protein and an increased UPC. Further study is needed to address the role of urinary NAG and its relationship with glycosaminoglycan levels in cats with idiopathic cystitis.

Urinary biomarker N-acetyl-β-D-glucosaminidase can predict severity of renal damage in diabetic nephropathy

Background

Diabetic nephropathy is a clinical diagnosis where proteinuria is present in a patient with diabetes. Early intervention can significantly improve the prognosis. However, imprecision of the currently available biomarkers have impaired effective therapies in a timely manner. Urinary N-acetyl-β-D-glucosaminidase (NAG) is excreted in abnormally high amounts in many renal diseases. The aim of this study was to evaluate urinary NAG as an early biomarker in detection of diabetic nephropathy and whether it parallels the severity of kidney damage in different stages of diabetic nephropathy.

Methods

Fifty patients with type 2 DM were classified into 3 groups (normoalbuminurea, microalbuminurea and macroalbuminurea) and 10 healthy subjects served as a control group. Urinary NAG, albumin and creatinine were measured. Blood urea, serum creatinine, serum albumin, total proteins, serum cholesterol, alanine aminotransferase (ALT), aspartate aminotransferase (AST), fasting and postprandial blood glucose, HbA1c and creatinine clearance were measured for all subjects.

Results

All diabetic patients had a significantly higher level of urinary NAG compared to control. NAG value increased in parallel with the severity of renal involvement.

Conclusion

Urinary NAG expresses the degree of renal impairment in diabetic nephropathy.

Biomarkers in the assessment of acute and chronic kidney diseases in the dog and cat

In both human and veterinary medicine, diagnosing and staging renal disease can be difficult. Measurement of glomerular filtration rate is considered the gold standard for assessing renal function but methods for its assessment can be technically challenging and impractical. The main parameters used to diagnose acute and chronic kidney disease include circulating creatinine and urea concentrations, and urine-specific gravity. However, these parameters can be insensitive. Therefore, there is a need for better methods to diagnose and monitor patients with renal disease. The use of renal biomarkers is increasing in human and veterinary medicine for the diagnosis and monitoring of acute and chronic kidney diseases. An ideal biomarker would identify site and severity of injury, and correlate with renal function, among other qualities. This article will review the advantages and limitations of renal biomarkers that have been used in dogs and cats, as well as some markers used in humans that may be adapted for veterinary use. In the future, measuring a combination of biomarkers will likely be a useful approach in the diagnosis of kidney disorders.

Feline CKD: Pathophysiology and risk factors--what do we know?

PRACTICAL RELEVANCE

Chronic kidney disease (CKD) is one of the most frequently encountered disorders in cats, having increased in prevalence in recent decades. Although the underlying cause is rarely identified, the common final outcome of feline CKD is tubulointerstitial fibrosis. Knowledge of CKD pathophysiology is necessary for optimal individualised patient management, especially with regard to diagnosis and treatment of extrarenal complications.

PATIENT GROUP

CKD is most common in senior and geriatric cats, but should be considered in any feline patient with ureterolithiasis, hyperthyroidism, retrovirus infection, systemic hypertension, cardiovascular disease or urinary tract infection.

EVIDENCE BASE

Most of our knowledge of the pathogenesis of CKD is extrapolated from human nephrology and experimental animal studies. There is, therefore, a need for further studies in cats. The prevalence of clinical signs in feline CKD is well documented. Several concurrent diseases associated with CKD have also been reported in cats, especially in the geriatric population, but there is no or only limited published evidence demonstrating a cause-and-effect relationship between most of these conditions and CKD. Studies performed over the past 15 years have nevertheless allowed identification of major risk factors (proteinuria, plasma phosphate and plasma creatinine) influencing the progression of feline CKD.

CLINICAL CHALLENGES

Clinical signs occur in the late stages of renal disease, so populations at higher risk of CKD should be screened routinely. CKD-associated complications (systemic hypertension, secondary renal hyperparathyroidism, hypokalaemia, anaemia, metabolic acidosis) must not be overlooked as they may affect the progression of disease. Disease progression is itself unpredictable and renal function may remain stable for extended periods. Most cats with early CKD do not progress to end-stage CKD before they die.

AUDIENCE

General practitioners play a major role in screening feline patients at risk of development or progression of CKD.

Clinical approach to advanced renal function testing in dogs and cats

Serum creatinine concentration is insensitive for detecting kidney injury and does not assist in differentiation between glomerular versus tubular damage. Advanced renal function tests, including glomerular filtration rate testing, determining fractional excretion of electrolytes, and assay of urine biomarkers, may allow earlier detection of reduced renal function mass, differentiation of renal from non-renal causes of azotemia, and assist with localization of damage. This article reviews the principles, indications, and limitations of these tests and describes their use in sample clinical scenarios.

Evaluation of predictors of the development of azotemia in cats

BACKGROUND

Chronic kidney disease (CKD) is a common condition in geriatric cats. Diagnosis is based on the development of persistent azotemia with inadequate urine concentrating ability. Biomarkers are sought for early identification.

HYPOTHESIS

Clinical variables, urine concentrating ability, proteinuria, and N-acetyl-beta-D-glucosaminidase (NAG) index will be predictive of cats at risk of developing azotemia within 12 months.

ANIMALS

Client-owned nonazotemic geriatric (>or=9 years) cats.

METHODS

Prospective longitudinal cohort study monitoring a population of healthy nonazotemic geriatric cats every 6 months until development of azotemia, death, or the study end point (September 30, 2007). Multivariable logistic regression analysis was used to assess baseline clinical, biochemical, and urinalysis variables, urine protein to creatinine ratio (UP/C), urine albumin to creatinine (UA/C) ratio, and urinary NAG index as predictors of development of azotemia.

RESULTS

One hundred and eighteen cats were recruited with a median age of 13 years. Ninety-five cats (80.5%) had been followed or reached the study end point by 12 months of which 30.5% (29/95) developed azotemia. Age, systolic blood pressure, plasma creatinine concentration, urine specific gravity, UP/C, UA/C, and NAG index were significantly associated with development of azotemia in the univariable analysis (P<or=.05). However, in the multivariable analysis, only plasma creatinine concentration with either UP/C (Model 1) or UA/C (Model 2) remained significant.

CONCLUSIONS AND CLINICAL IMPORTANCE

This study demonstrates a high incidence of azotemia in a population of previously healthy geriatric cats. Proteinuria at presentation was significantly associated with development of azotemia although causal association cannot be inferred. Evaluation of NAG index offered no additional benefit.

N-acetyl-beta-D-glucosaminidase index as an early biomarker for chronic kidney disease in cats with hyperthyroidism

BACKGROUND

Hyperthyroid cats are at risk of developing azotemic chronic kidney disease (CKD) and diagnostic tools currently used to screen for CKD in hyperthyroid cats are either unreliable or impractical.

HYPOTHESIS

Urine N-acetyl-beta-D-glucosaminidase index (NAG(i)) is a good biomarker for azotemic CKD in hyperthyroid cats.

ANIMALS

Twenty-four newly diagnosed nonazotemic hyperthyroid cats and 10 healthy cats.

METHODS

All cats were evaluated for hyperthyroidism at baseline. Hyperthyroid cats were treated with methimazole and reevaluated once euthyroid. At the end of the study, cats were divided into 3 groups: healthy cats, nonazotemic, and azotemic euthyroid cats. Baseline group characteristics were compared to predict azotemic CKD. The influence of treatment on NAG(i) was evaluated.

RESULTS

Baseline NAG(i) was significantly different among groups (P= .004). Azotemic cats had a higher median value (13.12 U/g) when compared with healthy cats (1.38 U/g). With NAG(i) >2.76 U/g, negative and positive predictive values for development of azotemia were 77.7 and 50%, whereas the combination of a urine specific gravity (USG) <or=1.035 and T(4) >7.80 microg/dL enhanced predictive values to 88.9 and 83.3%, respectively. NAG(i) values decreased significantly over time in treated nonazotemic cats.

CONCLUSIONS AND CLINICAL RELEVANCE

Baseline NAG(i) did not differentiate azotemic from nonazotemic euthyroid cats. NAG(i) could be used to assess renal function during medical therapy allowing the clinician to adjust methimazole dosage accordingly. The combination of USG and T(4) could optimize identification of appropriate candidates for permanent treatment of hyperthyroidism.

Effects of Long-Term Oral Administration of Ketoprofen in Clinically Healthy Beagle Dogs

To investigate the adverse effects of long-term administration of ketoprofen in dogs, ketoprofen (1 mg/kg) was administered to five clinically healthy beagle dogs (ketoprofen group) and gelatin capsules (control group) were administered to four clinically healthy beagle dogs for 30 days. We monitored the dogs through periodic physical examination, blood analyses, endoscopic examinations, fecal occult blood tests, renal function tests, urinalysis, urinary enzyme indices and cuticle bleeding time analysis. The lesions in the stomach, especially in the pyloric antrum, and fecal occult blood progressively worsened in the ketoprofen group. However, the differences between the ketoprofen group and the control group were not statistically significant. One dog in the ketoprofen group temporarily exhibited a decrease in renal plasma flow and two dogs exhibited enzymuria. However, these changes did not persist and the other examinations showed no significant difference between premedication and postmedication in the ketoprofen group. Therefore, the adverse effects of long-term administration of ketoprofen observed in this study were not clinically important in healthy dogs. Nevertheless, further investigation of adverse renal effects from long-term administration of ketoprofen is necessary in the dogs with subclinical renal disease.