Induction of creatininase activity in chronic renal failure: timing of creatinine degradation and effect of antibiotics

Diagnostic utility of selected faecal biochemical parameters in the determination of acute diarrhoea and associated defecation stooling characteristics in dogs: An observational study

Diarrhoea, which is a clinical manifestation of various illnesses, is frequently observed in dogs. Regrettably, many dog owners find it difficult to provide comprehensive case histories, primarily because of limited interaction with their canine companions. This study aimed to evaluate the potential of faecal biochemical analytes in detecting and characterizing acute diarrhoea in dogs. Sixty-two domestic dogs were selected using the proportionate stratified sample technique. A structured questionnaire was used to collect demographic and clinical data. Faecal stool specimens from the dogs were obtained using the colon flush technique. The specimens were taken through biochemical analysis to determine urea, creatinine, total bilirubin, total cholesterol, triglycerides, gamma-glutamyl transferase and uric acid levels. Results showed a significant association between the diarrhoea status of the participants and their age, weight, breed, body size, source of last diet, period of inappetence, and other gastrointestinal signs (p < 0.050, respectively). Dogs that had not eaten in at least three days were five times more likely (p < 0.05) to have diarrhoea. Furthermore, miniature breeds were about six times more likely to develop diarrhoea (p < 0.05). Of the seven selected biochemical parameters, total faecal cholesterol was the most predictive index in diagnosing acute diarrhoea in dogs, with a likelihood ratio of 6.5, and it was the most accurate in predicting defecation stooling frequency and texture. In summary, in situations of inadequate case histories, measuring total faecal cholesterol could assist veterinarians in detecting diarrhoea and predicting its faecal stooling texture and frequency in dogs.

Huaju Xiaoji Formula Regulates ERS-lncMGC/miRNA to Enhance the Renal Function of Hypertensive Diabetic Mice with Nephropathy

Background

Better therapeutic drugs are required for treating hypertensive diabetic nephropathy. In our previous study, the Huaju Xiaoji (HJXJ) formula promoted the renal function of patients with diabetes and hypertensive nephropathy. In this study, we investigated the therapeutic effect and regulation mechanism of HJXJ in hypertensive diabetic mice with nephropathy.

Methods

We constructed a mouse hypertensive diabetic nephropathy (HDN) model by treating mice with streptozotocin (STZ) and nomega-nitro-L-arginine methyl ester (LNAME). We also constructed a human glomerular mesangial cell (HGMC) model that was induced by high doses of sugar (30 mmol/mL) and TGFβ1 (5 ng/mL). Pathological changes were evaluated by hematoxylin and eosin (H&E) staining, periodic acid Schiff (PAS) staining, and Masson staining. The fibrosis-related molecules (TGFβ1, fibronectin, laminin, COL I, COL IV, α-SMA, and p-smad2/3) were detected by enzyme-linked immunosorbent assay (ELISA). The mRNA levels and protein expression of endoplasmic reticulum stress, fibrosis molecules, and their downstream molecules were assessed using qPCR and Western blotting assays.

Results

Administering HJXJ promoted the renal function of HDN mice. HJXJ reduced the expression of ER stress makers (CHOP and GRP78) and lncMGC, miR379, miR494, miR495, miR377, CUGBP2, CPEB4, EDEM3, and ATF3 in HDN mice and model HGMCs. The positive control drugs (dapagliflozin and valsartan) also showed similar effects after treatment with HJXJ. Additionally, in model HGMCs, the overexpression of CHOP or lncMGC decreased the effects of HJXJ-M on the level of fibrosis molecules and downstream target molecules.

Conclusion

In this study, we showed that the HJXJ formula may regulate ERS-lncMGC/miRNA to enhance renal function in hypertensive diabetic mice with nephropathy. This study may act as a reference for further investigating whether combining HJXJ with other drugs can enhance its therapeutic effect. The findings of this study might provide new insights into the clinical treatment of hypertensive diabetic nephropathy with HJXJ.

Diagnostic value and utility of commonly used biomarkers of cardiac and renal function in cardiorenal syndromes: a narrative review

Cardiorenal syndrome (CRS), first defined in 2004 as a consequence of the interactions between the kidneys and other circulatory departments leading to acute heart failure, has since been recognized as a complex clinical entity that is hard to define, diagnose and classify. The framework for the classification of CRS according to pathophysiologic background was laid out in 2008, dividing CRS into five distinct phenotypes. However, determining the timing of individual organ injuries and making a diagnosis of either renal or cardiac failure remains an elusive task. In clinical practice, the diagnosis and phenotyping of CRS is mostly based on using laboratory biomarkers in order to directly or indirectly estimate the degree of end-organ functional decline. Therefore, a well-educated clinician should be aware of the effects that the reduction of renal and cardiac function has on the diagnostic and predictive value and properties of the most commonly used biomarkers (e.g. troponins, N-terminal pro-brain natriuretic peptide, serum creatinine etc). They should also be acquainted, on a basic level, with emerging biomarkers that are specific to either the degree of glomerular integrity (cystatin C) or tubular injury (neutrophil gelatinase-associated lipocalin). This narrative review aims to provide a scoping overview of the different roles that biomarkers play in both the diagnosis of CRS and the prognosis of the disease in patients who have been diagnosed with it, along with highlighting the most important pitfalls in their interpretation in the context of impaired renal and/or cardiac function.

A spurious elevation of serum creatinine level in a patient with Crohn's disease without histologic kidney damage: a case report and review of the literature

Patients with inflammatory bowel disease (IBD) are prone to develop kidney injury. Renal involvement in IBD patients is usually diagnosed by the measurement of serum creatinine and the estimation of the glomerular filtration rate. We describe a patient with IBD who presented with large fluctuations in his serum creatinine level (~3.0-fold) without significant histologic abnormalities and with a normal cystatin C level. This appears to be related to a high-protein diet and intermittent fasting. Even though the impact of a high-protein diet on mild elevations of the serum creatinine level has been described, large fluctuations in serum creatinine from diet alone, as seen in this case, have never been reported, raising the question about the potential contribution of inflamed bowel on gut absorption or metabolism of creatinine. This case highlights the importance of a detailed history, including the dietary habits, when encountering a patient with increased serum creatinine level, and careful interpretation of serum creatinine in a patient with a creatinine high-protein diet or underlying IBD.

Measurement and estimation of glomerular filtration rate in children with neurogenic bladder: A prospective study

OBJECTIVE

To evaluate the performance of different equations used to estimate glomerular filtration rate (GFR) in children with neurogenic bladder (NB).

METHODS

The GFR measured with the technetium-99m-diethylenetriaminepentaacetic acid (^99mTc-DTPA) dual-plasma sample clearance method was defined as the true GFR (tGFR). The Chronic Kidney Disease in Children (CKiD) equation for serum creatinine (Scr) and/or cystatin C (Cys C) was used for GFR calculation. Estimated GFR (eGFR) using CKiD_Scr, CKiD_{Cys C}, and CKiD_{Scr+Cys C} equations was compared with tGFR in children with NB RESULTS: In total, 458 children with NB were prospectively enrolled in this study. The mean tGFR was 73.84±18.54 ml/min/1.73 m², mean eGFR_Scr was 77.94±18.38 ml/min/1.73 m², mean eGFR_{Cys C} was 74.20± 17.64 ml/min/1.73 m², and mean eGFR_{Scr+Cys C} was 75.70±18.07 ml/min/1.73 m². The correlation between the Scr-based equation and ^99mTc-DTPA clearance method was low (r=0.648). The Cys C-based equations exhibited the strongest correlations: CKiD_{Cys C} (r=0.891) and CKiD_{Scr+Cys C} (r=0.879). The overall prevalence of chronic kidney disease (CKD) was 20.7%, 19.7%, 17.5%, and 12.4% according to tGFR, eGFR_{Cys C}, eGFR_{Cys C+Scr} and eGFR_Scr, respectively. The area under the curve (AUC) for the Receiver operating characteristic (ROC) curve of the CKiD_{Cys C} equation was the highest (AUC_CKiDcys= 0.956).

CONCLUSIONS

The Cys C-based CKiD equation was the most accurate for estimating GFR compared with ^99mTc-DTPA clearance method in children with NB. The CKiD_Scr equation overestimated the GFR. The CKiD_{Cys C} equation can be used to detect initial stages of CKD in children with NB.

Gut Microbiota as a Source of Uremic Toxins

Uremic retention solutes are the compounds that accumulate in the blood when kidney excretory function is impaired. Some of these compounds are toxic at high concentrations and are usually known as “uremic toxins”. The cumulative detrimental effect of uremic toxins results in numerous health problems and eventually mortality during acute or chronic uremia, especially in end-stage renal disease. More than 100 different solutes increase during uremia; however, the exact origin for most of them is still debatable. There are three main sources for such compounds: exogenous ones are consumed with food, whereas endogenous ones are produced by the host metabolism or by symbiotic microbiota metabolism. In this article, we identify uremic retention solutes presumably of gut microbiota origin. We used database analysis to obtain data on the enzymatic reactions in bacteria and human organisms that potentially yield uremic retention solutes and hence to determine what toxins could be synthesized in bacteria residing in the human gut. We selected biochemical pathways resulting in uremic retention solutes synthesis related to specific bacterial strains and revealed links between toxin concentration in uremia and the proportion of different bacteria species which can synthesize the toxin. The detected bacterial species essential for the synthesis of uremic retention solutes were then verified using the Human Microbiome Project database. Moreover, we defined the relative abundance of human toxin-generating enzymes as well as the possibility of the synthesis of a particular toxin by the human metabolism. Our study presents a novel bioinformatics approach for the elucidation of the origin of both uremic retention solutes and uremic toxins and for searching for the most likely human microbiome producers of toxins that can be targeted and used for the therapy of adverse consequences of uremia.

Microbiota-Related Metabolites and the Risk of Type 2 Diabetes

OBJECTIVE

Recent studies have highlighted the significance of the microbiome in human health and disease. Changes in the metabolites produced by microbiota have been implicated in several diseases. Our objective was to identify microbiome metabolites that are associated with type 2 diabetes.

RESEARCH DESIGN AND METHODS

Our study included 5,181 participants from the cross-sectional Metabolic Syndrome in Men (METSIM) study that included Finnish men (age 57 ± 7 years, BMI 26.5 ± 3.5 kg/m²) having metabolomics data available. Metabolomics analysis was performed based on fasting plasma samples. On the basis of an oral glucose tolerance test, Matsuda ISI and disposition index values were calculated as markers of insulin sensitivity and insulin secretion. A total of 4,851 participants had a 7.4-year follow-up visit, and 522 participants developed type 2 diabetes.

RESULTS

Creatine, 1-palmitoleoylglycerol (16:1), urate, 2-hydroxybutyrate/2-hydroxyisobutyrate, xanthine, xanthurenate, kynurenate, 3-(4-hydroxyphenyl)lactate, 1-oleoylglycerol (18:1), 1-myristoylglycerol (14:0), dimethylglycine, and 2-hydroxyhippurate (salicylurate) were significantly associated with an increased risk of type 2 diabetes. These metabolites were associated with decreased insulin secretion or insulin sensitivity or both. Among the metabolites that were associated with a decreased risk of type 2 diabetes, 1-linoleoylglycerophosphocholine (18:2) significantly reduced the risk of type 2 diabetes.

CONCLUSIONS

Several novel and previously reported microbial metabolites related to the gut microbiota were associated with an increased risk of incident type 2 diabetes, and they were also associated with decreased insulin secretion and insulin sensitivity. Microbial metabolites are important biomarkers for the risk of type 2 diabetes.

Creatinine: From physiology to clinical application

Estimating static kidney function accurately and detecting changes in kidney function in a timely fashion are challenging but critically important tasks. Serum creatinine is the most widely used functional biomarker of the kidney. However, its use is associated with substantial shortcomings. Understanding these shortcomings is critical in allowing accurate interpretation of creatinine values and translating them into changes in kidney function. In this review, the pathways involved in creatinine generation and metabolism as well as the techniques involved in measuring creatinine concentrations are discussed. This allows for the discussion of the value and pitfalls in using creatinine as a marker of kidney function. In addition, information regarding alternative functional biomarkers of the kidney is provided.

Management of Presumed Acute Kidney Injury during Hypertensive Therapy: Stay Calm and Carry on?

BACKGROUND

Recent studies have demonstrated that intensive blood pressure control is associated with improved cardiovascular outcomes. Acute kidney injury (AKI), however, was more common in the intensive treatment group prompting concern in the nephrology community.

SUMMARY

Clinical trials on hypertension control have traditionally defined AKI by changes in serum creatinine. However, serum creatinine has several inherent limitations as a marker of kidney injury, with various factors influencing its production, secretion, and elimination. Urinary biomarkers of kidney injury and repair have the potential to provide insight on the presence and phenotype of kidney injury. In both the Systolic Blood Pressure Intervention Trial and the Action to Control Cardiovascular Risk in Diabetes study, urinary biomarkers have suggested that the increased risk of AKI associated with intensive treatment was due to hemodynamic changes rather than structural kidney injury. As such, clinicians who encounter rises in serum creatinine during intensification of hypertension therapy should "stay calm and carry on." Alternative explanations for serum creatinine elevation should be considered and addressed if appropriate. When the rise in serum creatinine is limited, particularly if albuminuria is stable or improving, intensive blood pressure control should be continued for its potential long-term benefits. Key Messages: Increases in serum creatinine during intensification of blood pressure control may not necessarily reflect kidney injury. Clinicians should evaluate for other contributing factors before stopping therapy. Urinary biomarkers may address limitations of serum creatinine as a marker of kidney injury.

A Systems-Level View of Renal Metabolomics

The measurement of select circulating metabolites such as creatinine, glucose, and cholesterol are integral to clinical medicine, with implications for diagnosis, prognosis, and treatment. Metabolomics studies in nephrology research seek to build on this paradigm, with the goal to identify novel markers and causal participants in the pathogenesis of kidney disease and its complications. This article reviews three themes pertinent to this goal. Each is rooted in long-established principles of human physiology, with recent updates enabled by metabolomics and other tools. First, the kidney has a broad and heterogeneous impact on circulating metabolites, with progressive loss of kidney function resulting in a multitude of small molecule alterations. Second, an increasing number of circulating metabolites have been shown to possess functional roles, in some cases acting as ligands for specific G-protein-coupled receptors. Third, circulating metabolites traffic through varied, and sometimes complex, interorgan circuits. Taken together, these themes emphasize the importance of viewing renal metabolomics at the systems level, recognizing the diverse origins and physiologic effects of blood metabolites. However, how to synthesize these themes and how to establish clinical relevance remain uncertain and will require further investigation.

Metabonomic strategy for the detection of metabolic effects of probiotics combined with prebiotic supplementation in weaned rats

The purpose of this study is to investigate the effects of probiotics combined with prebiotics (PP) supplementation on weaned rat metabolism. A metabonomic strategy employing ¹H-NMR spectroscopy and multivariate data analysis was used to examine weaned rat biological responses to PP supplementation. Male Sprague-Dawley rats (post-natal day 21, PD 21) received probiotics (Lactobacillus acidophilus NCFM (L-NCFM) and Bifidobacterium lactis Bi-07 (B-LBi07), 1 : 1, 1.0 × 10¹¹ cfu kg⁻¹) and prebiotics (Lycium barbarum polysaccharides (LBP), Poria cocos polysaccharides (PCPs) and Lentinan, 1 : 1 : 1, 24 g kg⁻¹) via intragastric administration for 28 consecutive days. Urine and feces were collected for analysis. Significant topographical metabolic variations were present in urine and feces. Urinary metabolites upregulated by PP treatment included alanine, N-acetylglycine, glutamine, dimethylamine, phosphorylcholine, ethylene glycol, mannitol, phenylacetylglycine and glycoate, which were related to alanine, aspartate and glutamate metabolism, and choline metabolism. Feces-derived metabolites, including caproate, valerate, butyrate, propionate, lactate, acetate, succinate, methanol, threonine and methionine, were significantly increased, which were related to short-chain fatty acid (SCFA) metabolism and TCA cycle metabolism. These results indicate that dietary PP supplementation can regulate common systemic metabolic processes, including energy metabolism, amino acid metabolism, lipid metabolism, nucleic acid metabolism, and gut microbiota-related metabolism. This study also illuminates the vital role of PP supplementation in regulating the metabolism of weaned rats.

Dietary probiotic supplementation is beneficial to the growth of weaned rats by regulating the metabolism.

Measurement and Estimation of Glomerular Filtration Rate in Children

Rapid, accurate, and precise measures of kidney function are essential for daily management of patients. While plasma and urinary clearances provide the greatest accuracy for assessing glomerular filtration rate (GFR), these are often impractical particularly for the care of children. Serum creatinine, the most commonly used endogenous marker, is simple, convenient, and practical but less accurate because of the influence of non-GFR determinants such as muscle mass, which increases with age in children. GFR estimating equations have been developed for adults and children to improve the accuracy of endogenous biomarkers, such as creatinine and cystatin C, by accounting for some of the non-GFR determinants, thus enhancing the practitioner's ability to assess GFR. In the steady state, when height is used as a surrogate for growth, there is a strong correlation between height/S_Cr and GFR. Current national guidelines recommend routine reporting of the estimated GFR alongside the serum creatinine value for adults using the Chronic Kidney Disease Epidemiology Collaboration creatinine-based formula and the updated Schwartz "bedside" formula (CKiD 2009) for children.

Cystatin C-Based Evaluation of Kidney Function of HIV-Infected Children in Benin City, Southern Nigeria

Background. Human immunodeficiency virus (HIV) is now a confirmed risk factor for kidney disease with an increased burden in persons of African descent. Method. We measured the serum cystatin C levels of 205 ART-naive, HIV-infected children by an ELISA technique and compared them with the levels of apparently healthy children. Result. The mean ± SD serum cystatin C level of children with HIV infection was 1.01 ± 0.44 mg/L, significantly higher than the mean value in the control group, that is, 0.72 ± 0.20 mg/L (P = 0.000). The mean ± SD cystatin C-based estimated GFR of children with HIV infection was 102.7 ± 31.0 mL/min/1.73 m², significantly lower than 126.9 ± 28.5 mL/min/1.73 m² in the control group, (P = 0.014). A significantly higher proportion of HIV-infected children compared to controls had eGFR < 90 mL/min/1.73 m² (21.5% versus 5.4%; P = 0.00). The prevalence of chronic kidney disease (CKD) among the HIV-infected children was 10.7%. The cystatin C-based eGFR of the HIV-infected children ≥5 years old correlated positively with their CD4 count (r = 0.23;  P = 0.022). Conclusion. There is a high prevalence of CKD among HIV-infected children, requiring regular monitoring of their kidney function using a cystatin C-based method.

Earlier recognition of nephrotoxicity using novel biomarkers of acute kidney injury

CONTEXT

A broad range of drugs and chemicals are capable of evoking acute kidney injury, which is conventionally determined by rising serum creatinine concentrations. However there are important limitations to this approach, and there has been interest in alternative biomarkers that might provide a more sensitive and rapid means of detecting acute kidney injury. Most of the available clinical data have thus far been ascertained in patients requiring critical care or with acute sepsis. However, if a sensitive indicator of acute kidney injury were developed, then this could provide a significantly improved means of detecting the effects of acute drug or toxin exposure.

OBJECTIVE

To review the available data concerning potential biomarkers of acute kidney injury and to assess their relative strengths and weaknesses in comparison to existing methods based on serum creatinine concentrations. A large number of possible biomarkers have been proposed. Evidence for individual biomarkers is reviewed with a particular emphasis on those with potential application in clinical toxicology. Where available, comparative data are presented.

METHODS

There were 236 papers identified using Medline, Embase, and Google Scholar databases, of which 52 were considered directly relevant. CREATININE: Creatinine is subject to glomerular filtration and, to a lesser extent tubular secretion. Serum concentrations are an insensitive marker of acute kidney injury, and the speed of an increase from baseline depends on the magnitude of the acute injury and pre-existing kidney functional reserve. A wide range of inter-individual concentrations means that single time-point determinations are difficult to interpret, and acute kidney injury may not manifest as a detectable increase in serum creatinine concentrations until at least 24-48 h after the primary insult. KIDNEY ENZYMES: Enzymes are often localised to specific anatomical locations, and acute injury may cause a detectable increase in urinary activity due to up-regulated activity or leakage due to cell membrane disruption. Key examples include gamma-glutamyl transpeptidase (GGT), glutathione-S-transferase (GST), and N-acetyl-glucosaminidase (NAG), which are found predominantly in the proximal tubule and urinary enzyme activity increases after acute exposure to heavy metals and other nephrotoxins. NEUTROPHIL GELATINASE-ASSOCIATED LIPOCALIN: Neutrophil gelatinase-associated lipocalin (NGAL) is expressed by renal tubular epithelium, and a rise in urinary concentrations may provide an indicator of acute renal injury caused by any one of a broad range of provoking factors that is detectable before a rise in serum creatinine concentrations. CYSTATIN C: Serum and urinary cystatin C concentrations are closely related to kidney function and, for example, in acute tubular necrosis allow better prediction of the need for renal replacement therapy than serum creatinine concentrations. KIDNEY INJURY MOLECULE 1: Kidney injury molecule 1 (KIM-1) is expressed in the proximal tubule in the setting of acute ischaemia. For example, urinary KIM-1 concentrations becomes detectable within 24 h of acute tubular necrosis. Urinary KIM-1 expression may be detected after exposure to a variety of nephrotoxic agents, even when serum creatinine concentrations do not increase, and this has been accepted by regulatory authorities as a sensitive biomarker of acute kidney injury during early drug development.

CONCLUSIONS

Novel biomarkers appear capable of offering a more sensitive means of detecting acute kidney injury than existing approaches. Certain of these allow discrimination between the various mechanisms and anatomical site of acute injury. Ultimately, clinical assessment might incorporate a panel of different biomarkers, each informing on the integrated aspects of glomerular, tubular and interstitial function. Presence of biomarkers may in some cases detect mild or transient renal dysfunction that is presently undetected, and the clinical relevance needs further exploration. Whilst many potentially useful biomarkers have been proposed, comparatively few clinical data exist to support their validity in routine practice. Further prospective clinical studies are required to examine the validity of biomarkers after acute drug or toxin exposure, and to establish whether they might offer improved clinical outcomes in the setting of clinical toxicology.

New biomarkers of acute kidney injury and the cardio-renal syndrome

Changes in renal function are one of the most common manifestations of severe illness. There is a clinical need to intervene early with proven treatments in patients with potentially deleterious changes in renal function. Unfortunately progress has been hindered by poor definitions of renal dysfunction and a lack of early biomarkers of renal injury. In recent years, the definitional problem has been addressed with the establishment of a new well-defined diagnostic entity, acute kidney injury (AKI), which encompasses the wide spectrum of kidney dysfunction, together with clearer definition and sub-classification of the cardio-renal syndromes. From the laboratory have emerged new biomarkers which allow early detection of AKI, including neutrophil gelatinase-associated lipocalin (NGAL) and cystatin C. This review describes the new concepts of AKI and the cardio-renal syndromes as well as novel biomarkers which allow early detection of AKI. Panels of AKI biomarker tests are likely to revolutionise the diagnosis and management of critically ill patients in the coming years. Earlier diagnosis and intervention should significantly reduce the morbidity and mortality associated with acute kidney damage.

Variation in antibiotic-induced microbial recolonization impacts on the host metabolic phenotypes of rats

The interaction between the gut microbiota and their mammalian host is known to have far-reaching consequences with respect to metabolism and health. We investigated the effects of eight days of oral antibiotic exposure (penicillin and streptomycin sulfate) on gut microbial composition and host metabolic phenotype in male Han-Wistar rats (n = 6) compared to matched controls. Early recolonization was assessed in a third group exposed to antibiotics for four days followed by four days recovery (n = 6). Fluorescence in situ hybridization analysis of the intestinal contents collected at eight days showed a significant reduction in all bacterial groups measured (control, 10(10.7) cells/g feces; antibiotic-treated, 10(8.4)). Bacterial suppression reduced the excretion of mammalian-microbial urinary cometabolites including hippurate, phenylpropionic acid, phenylacetylglycine and indoxyl-sulfate whereas taurine, glycine, citrate, 2-oxoglutarate, and fumarate excretion was elevated. While total bacterial counts remained notably lower in the recolonized animals (10(9.1) cells/g faeces) compared to the controls, two cage-dependent subgroups emerged with Lactobacillus/Enterococcus probe counts dominant in one subgroup. This dichotomous profile manifested in the metabolic phenotypes with subgroup differences in tricarboxylic acid cycle metabolites and indoxyl-sulfate excretion. Fecal short chain fatty acids were diminished in all treated animals. Antibiotic treatment induced a profound effect on the microbiome structure, which was reflected in the metabotype. Moreover, the recolonization process was sensitive to the microenvironment, which may impact on understanding downstream consequences of antibiotic consumption in human populations.

Crystal structure and molecular modeling study of N-carbamoylsarcosine amidase Ta0454 from Thermoplasma acidophilum

A crystal structure of the putative N-carbamoylsarcosine amidase (CSHase) Ta0454 from Thermoplasma acidophilum was solved by single-wavelength anomalous diffraction and refined at a resolution of 2.35A. CSHases are involved in the degradation of creatinine. Ta0454 shares a similar fold and a highly conserved C-D-K catalytic triad (Cys123, Asp9, and Lys90) with the structures of three cysteine hydrolases (PDB codes 1NBA, 1IM5, and 2H0R). Molecular dynamics (MD) simulations of Ta0454/N-carbamoylsarcosine and Ta0454/pyrazinamide complexes were performed to determine the structural basis of the substrate binding pattern for each ligand. Based on the MD-simulated trajectories, the MM/PBSA method predicts binding free energies of -24.5 and -17.1 kcal/mol for the two systems, respectively. The predicted binding free energies suggest that Ta0454 is selective for N-carbamoylsarcosine over pyrazinamide, and zinc ions play an important role in the favorable substrate bound states.

Measurement of renal function in pre-ESRD patients

The measurement of renal function in pre-dialysis patients is important in order to determine the appropriate time to begin renal replacement therapy, to forecast the start, and to compare, in groups of patients, the efficiency of different treatments that limit renal disease progression. The most reliable methods, such as inulin clearance or measurement by radioisotopes, are too awkward for the usual clinical follow-up of patients. Although much simpler and almost as reliable, the use of iohexol radiologic contrast does not allow the frequent monitoring of the patient either. The determinations of the plasmatic creatinine and its clearance or the estimate of the glomerular filtration rate by means of equations derived from the creatinine are the methods most often used in order to measure renal function, although not without problems in pre-dialysis. In order to try to overcome such problems, more precise equations and procedures, including the measurement of averaged urea-creatinine clearance or creatinine clearance with cimetidine, have been designed that better estimate the glomerular filtration rate. However, none of these methods is totally reliable in pre-dialysis. A new endogen marker, cystatin C, has advantages over creatinine, though more studies are needed in pre-dialysis in order to ascertain its use. The initial proposal of the National Kidney Foundation's Kidney Disease Outcome Quality Initiative (DOQI) guidelines to use weekly Kt/V and nutritional parameters to determine the time for starting renal replacement therapy has widened the prospects of the debate on the measurement of renal function in pre-dialysis, but further work is required to define their role in pre-dialysis patients' follow-up.

Inactivation of peroxynitrite in multiple sclerosis patients after oral administration of inosine may suggest possible approaches to therapy of the disease

Peroxynitrite has been implicated in the pathogenesis of multiple sclerosis (MS) and its animal model experimental allergic encephalomyelitis (EAE). Previously, we have shown that administration of uric acid (UA), a peroxynitrite scavenger, is therapeutic in EAE We have also shown that MS patients have lower levels of serum uric acid than healthy individuals or those with other neurological diseases. The aim of this investigation was therefore to raise serum UA levels in MS patients. Oral administration of UA failed to increase low serum UA levels, evidently due to its degradation by gastrointestinal bacteria. However, serum UA could be raised and maintained at elevated levels for a year and more without reported side-effects by oral administration of its precursor inosine. Three of 11 patients given inosine showed some evidence of clinical improvement and there was no sign of disease progression in the remaining patients. Gadolinium-enhanced lesions, observed in two patients before receiving inosine, could not be detected after either 10 or IS months inosine treatment These data provide evidence that serum UA levels can be readily manipulated and that the benefit of higher levels to individuals with MS should be studied further in greater number of patients.

Creatine and creatinine metabolism

The goal of this review is to present a comprehensive survey of the many intriguing facets of creatine (Cr) and creatinine metabolism, encompassing the pathways and regulation of Cr biosynthesis and degradation, species and tissue distribution of the enzymes and metabolites involved, and of the inherent implications for physiology and human pathology. Very recently, a series of new discoveries have been made that are bound to have distinguished implications for bioenergetics, physiology, human pathology, and clinical diagnosis and that suggest that deregulation of the creatine kinase (CK) system is associated with a variety of diseases. Disturbances of the CK system have been observed in muscle, brain, cardiac, and renal diseases as well as in cancer. On the other hand, Cr and Cr analogs such as cyclocreatine were found to have antitumor, antiviral, and antidiabetic effects and to protect tissues from hypoxic, ischemic, neurodegenerative, or muscle damage. Oral Cr ingestion is used in sports as an ergogenic aid, and some data suggest that Cr and creatinine may be precursors of food mutagens and uremic toxins. These findings are discussed in depth, the interrelationships are outlined, and all is put into a broader context to provide a more detailed understanding of the biological functions of Cr and of the CK system.

Rise in serum albumin and creatinine in the first half year on hemodialysis

Rise in serum albumin and creatinine in the first half year on hemodialysis.

BACKGROUND

Serum albumin and creatinine have been reported to rise in new hemodialysis patients; however, these trends have not been quantitated in a stable cohort, and their determinants and prognostic value are unknown.

METHODS

This study examined the changes in monthly values of serum albumin and creatinine over the first half year of hemodialysis in 115 patients who survived to the start of the sixth month. After verifying that the trends were approximately linear, we calculated the rates of rise (slope) of six predialysis values of serum albumin (months 1 through 6) and of creatinine (months 2 through 7) and examined their associations with age, diabetes, race, baseline 24-hour urine protein and creatinine excretion, and survival during the latter half of the first year.

RESULTS

Serum albumin rose by 13% over months 1 through 6 [0.08 +/- 0.12 (SD) g/dl/month, P < 10-9 vs. zero slope]. Patients who survived the entire year had higher mean values for both serum albumin (month 1, P < 0.003; months 3 through 6, P < 10-3) and rate of rise of albumin (0.09 +/- 0.11 g/dl/month vs. 0.01 +/- 0.13 g/dl/month, P < 0.005) than patients who died during months 6 through 12, but the slope was not an independent predictor of survival after adjusting for serum albumin concentration. Baseline proteinuria correlated inversely with serum albumin measured at the first and second months (P < 0.005) and directly with the albumin slope (r = 0.49, P < 10-5). Serum creatinine rose by 12% between months 2 through 7 (0.12 +/- 0.47 mg/dl/month, P < 0.02). Survivors had a significantly higher mean baseline creatinine excretion (P < 0. 03) and serum creatinine (month 2, P < 0.03; months 3 through 7, P < 0.01) but only a marginally higher rate of rise of serum creatinine (0.16 +/- 0.47 mg/dl/month vs. -0.07 +/- 0.48 mg/dl/month, P < 0.06) than patients who died during the second half of the year. Baseline urinary creatinine excretion correlated directly with serum creatinine at month 2 (P < 0.01) and more strongly at months 3 through 7 (P < 10-3), as well as correlating with the creatinine slope (r = 0.26, P < 0.03).

CONCLUSIONS

Serum albumin and creatinine rose by 12 to 13% during the first half year of hemodialysis in a stable cohort. The slope of serum albumin versus time predicted survival, but it was not as predictive as the absolute albumin concentration. The pattern of correlations of baseline urinary protein and creatinine excretion with the respective monthly serum values of albumin and creatinine and their slopes is consistent with the hypothesis that as residual renal function declines, progressive retention of protein and creatinine contributes to the respective rises in serum albumin and creatinine.