SLC6A8 creatine transporter deficiency can be detected by plasma creatine and creatinine concentrations.

Creatine transporter deficiency has been described with normal or uninformative levels of creatine and creatinine in plasma, while urine has been the preferred specimen type for biochemical diagnosis. We report a cohort of untreated patients with creatine transporter deficiency and abnormal plasma creatine panel results, characterized mainly by markedly decreased plasma creatinine. We conclude that plasma should be considered a viable specimen type for the biochemical diagnosis of this disorder, and abnormal results should be followed up with further confirmatory testing.

Creatine homeostasis and the kidney: comparison between kidney transplant recipients and healthy controls.

Creatine is a natural nitrogenous organic acid that is integral to energy metabolism and crucial for proper cell functioning. The kidneys are involved in the first step of creatine production. With kidney transplantation being the gold-standard treatment for end-stage kidney disease, kidney transplant recipients (KTR) may be at risk of impaired creatine synthesis. We aimed to compare creatine homeostasis between KTR and controls. Plasma and urine concentrations of arginine, glycine, guanidinoacetate, creatine and creatinine were measured in 553 KTR and 168 healthy controls. Creatine intake was assessed using food frequency questionnaires. Iothalamate-measured GFR data were available in subsets of 157 KTR and 167 controls. KTR and controls had comparable body weight, height and creatine intake (all P > 0.05). However, the total creatine pool was 14% lower in KTR as compared to controls (651 ± 178 vs. 753 ± 239 mmol, P < 0.001). The endogenous creatine synthesis rate was 22% lower in KTR as compared to controls (7.8 ± 3.0 vs. 10.0 ± 4.1 mmol per day, P < 0.001). Despite lower GFR, the plasma guanidinoacetate and creatine concentrations were 21% and 41% lower in KTR as compared to controls (both P < 0.001). Urinary excretion of guanidinoacetate and creatine were 66% and 59% lower in KTR as compared to controls (both P < 0.001). In KTR, but not in controls, a higher measured GFR was associated with a higher endogenous creatine synthesis rate (std. beta: 0.21, 95% CI: 0.08; 0.33; P = 0.002), as well as a higher total creatine pool (std. beta: 0.22, 95% CI: 0.11; 0.33; P < 0.001). These associations were fully mediated (93% and 95%; P < 0.001) by urinary guanidinoacetate excretion which is consistent with production of the creatine precursor guanidinoacetate as rate-limiting factor. Our findings highlight that KTR have a disturbed creatine homeostasis as compared to controls. Given the direct relationship of measured GFR with endogenous creatine synthesis rate and the total creatine pool, creatine supplementation might be beneficial in KTR with low kidney function.Trial registration ID: NCT02811835.Trial registration URL: https://clinicaltrials.gov/ct2/show/NCT02811835 .

Evaluation of Residual Kidney Function during Once-Weekly Incremental Hemodialysis.

BACKGROUND: The initial once-weekly administration of incremental hemodialysis to patients with residual kidney function (RKF) has recently attracted considerable interest. METHODS: The aim of our study was to assess the performance of a series of different methods in measuring serum urea nitrogen and serum Cr (sCr) RKF in patients on once-weekly hemodialysis (1WHD). Evaluations were carried out by means of 24-h predialysis urine collection (Kr-24H) or 6-day inter-dialysis collection (Kr-IDI) and estimation of glomerular filtration rate based on (KrSUN + KrsCr)/2 for the purpose of identifying a simple reference calculation to be used in assessing RKF in patients on 1WHD dialysis. Ninety-five urine samples were collected from 12 1WHD patients. A solute solver urea and Cr kinetic modeling program was used to calculate residual urea and Cr clearances. Mann-Whitney U test, Pearson's correlation coefficient (R), and linear determination coefficient (R2) were used for statistical analysis. RESULTS: 1WHD patients displayed a mean KrSUN-IDI of 4.5 ± 1.2 mL/min, while KrSUN-24H corresponded to 4.1 ± 0.9 mL/min, mean KrsCr-IDI to 9.1 ± 4.0 mL/min, and KrsCr 24H to 8.9 ± 4.2 mL/min, with a high regression between IDI and 24-h clearances (for IDI had R2 = 0.9149 and for 24H had R2 = 0.9595). A good correlation was also observed between KrSUN-24H and (KrSUN + KrsCR/2) (R2 = 0.7466, p < 0.01. DISCUSSION: Urine collection over a 24-h predialysis period yielded similar results for both KrSUN and KrsCr compared to collection over a longer interdialytic interval (KrSUN + KrsCr)/2 could be applied to reliably assess RKF in patients on 1WHD. CONCLUSION: The parameters evaluated are suitable for use as a routine daily method indicating the commencement and continued use of the 1WHD Incremental Program.

GC-MS Studies on Derivatization of Creatinine and Creatine by BSTFA and Their Measurement in Human Urine.

In consideration of its relatively constant urinary excretion rate, creatinine (2-amino-1-methyl-5H-imidazol-4-one, MW 113.1) in urine is a useful endogenous biochemical parameter to correct the urinary excretion rate of numerous endogenous and exogenous substances. Reliable measurement of creatinine by gas chromatography (GC)-based methods requires derivatization of its amine and keto groups. Creatinine exists in equilibrium with its open form creatine (methylguanidoacetic acid, MW 131.1), which has a guanidine and a carboxylic group. Trimethylsilylation and trifluoroacetylation of creatinine and creatine are the oldest reported derivatization methods for their GC-mass spectrometry (MS) analysis in human serum using flame- or electron-ionization. We performed GC-MS studies on the derivatization of creatinine (d0-creatinine), [methylo-2H3]creatinine (d3-creatinine, internal standard) and creatine (d0-creatine) with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) using standard derivatization conditions (60 min, 60 °C), yet in the absence of any base. Reaction products were characterized both in the negative-ion chemical ionization (NICI) and in the positive-ion chemical ionization (PICI) mode. Creatinine and creatine reacted with BSTFA to form several derivatives. Their early eluting N,N,O-tris(trimethylsilyl) derivatives (8.9 min) were found to be useful for the precise and accurate measurement of the sum of creatinine and creatine in human urine (10 µL, up to 20 mM) by selected-ion monitoring (SIM) of m/z 271 (d0-creatinine/d0-creatine) and m/z 274 (d3-creatinine) in the NICI mode. In the PICI mode, SIM of m/z 256, m/z 259, m/z 272 and m/z 275 was performed. BSTFA derivatization of d0-creatine from a freshly prepared solution in distilled water resulted in formation of two lMate-eluting derivatives (14.08 min, 14.72 min), presumably creatinyl-creatinine, with the creatininyl residue existing in its enol form (14.08 min) and keto form (14.72 min). Our results suggest that BSTFA derivatization does not allow specific analysis of creatine and creatinine by GC-MS. Preliminary analyses suggest that pentafluoropropionic anhydride (PFPA) is also not useful for the measurement of creatinine in the presence of creatine. Both BSTFA and PFPA facilitate the conversion of creatine to creatinine. Specific measurement of creatinine in urine is possible by using pentafluorobenzyl bromide in aqueous acetone.

s-Ethyl cysteine, an amino acid derivative, attenuated cisplatin induced nephrotoxicity.

Renal protection from s-ethyl cysteine (SEC) against cisplatin (CP)-induced inflammatory and oxidative injury was examined. Mice were divided into five groups: normal group, 0.25% SEC group, CP group, 0.125% SEC + CP group, 0.25% SEC + CP group. After 2 weeks supplementation, mice of CP and SEC + CP groups received CP treatment. H&E stain showed that CP caused infiltration of inflammatory cells and necrosis of tubular cells. SEC pre-treatments attenuated CP-induced inflammatory injury and degeneration. SEC pre-treatments limited CP-stimulated release of interleukin (IL)-1beta, IL-6, tumor necrosis factor-alpha and prostaglandin E2 in kidney. CP raised the renal activity and mRNA expression of cyclooxygenase-2 and nuclear factor kappa B. SEC pre-treatments reversed these alterations. CP increased the production of reactive oxygen species and nitric oxide, and lowered glutathione content, glutathione peroxidase and glutathione reductase activities in kidney. SEC pre-treatments reversed these changes. CP up-regulated renal inducible nitric oxide synthase (iNOS) mRNA expression, and down-regulated nuclear factor E2-related factor (Nrf)-2 and heme oxygenase (HO)-1 mRNA expression. SEC pre-treatments suppressed iNOS mRNA expression; and enhanced renal Nrf2 and HO-1 mRNA expression. These novel findings suggest that dietary SEC via exerting its multiple bio-functions could be considered as a protective agent for kidney against CP.

Iodine deficiency in pregnant women in Sweden: a national cross-sectional study.

PURPOSE: Voluntary salt iodization at 50 mg/kg salt ensures adequate iodine nutrition in Swedish school-aged children, but iodine status in pregnant women is uncertain. METHODS: We conducted a cross-sectional national study of 743 pregnant women, at median gestational age of 23 weeks (IQR 9, 38), recruited from maternal health care centers. We measured: urinary iodine concentration (UIC) and urinary creatinine concentration in spot urine samples; thyroglobulin (Tg), thyroid-stimulating hormone (TSH), and total thyroxine (tT4) on dried blood spots (DBS); and thyreoperoxidase antibodies in serum samples. Data on dietary supplement use were obtained, and women were classified as supplement users (consuming multivitamins containing ≥ 150 µg iodine/day) and non-supplement users (no supplements or < 150 µg iodine/day from supplements). RESULTS: Overall median UIC [bootstrapped 95% confidence interval (CI)] was 101 µg/L (95, 108; n = 737): 149 µg/L (132, 164) in supplement users (n = 253) and 85 µg/L (79, 92) in non-supplement users (n = 440) (p < 0.001). Overall geometric mean DBS-Tg (95% CI) was 22.1 µg/L (20.8, 23.5; n = 675) and the prevalence of elevated DBS-Tg was 19%. DBS-Tg was lower in supplement users (n = 229) than in non-supplement users (n = 405) (19.1 vs 24.4 µg/L, p < 0.001). DBS-TSH, DBS-tT4, and S-TPOab positivity did not differ between the two groups. CONCLUSIONS: Pregnant women in Sweden have inadequate iodine nutrition. Women not taking iodine supplements containing ≥ 150 µg iodine/day are affected by mild iodine deficiency and are at higher risk for increased thyroid activity, while maintaining euthyroidism. Iodine intake should be improved in women both before and after conception by promotion of iodized salt instead of non-iodized salt. We urge regular monitoring of iodine status in the general Swedish population, as well as in risk groups.

Evaluation of Proteinuria Using Urine Protein : Creatine Ratio in Treatment with Molecular Targeted Agents for Advanced Renal Cell Carcinoma.

The usefulness of the urine protein : creatine ratio (UPCR) in management of molecular targeted therapy and immunotherapy has not been studied, although urine protein dipstick testing (uPr) is widely used in the clinical setting. The aim of this study was to investigate the usefulness of UPCR as compared to uPr in patients undergoing molecular targeted therapy for advanced renal cell carcinoma (RCC). A total of 25 patients (median age 68 years) with advanced RCC were included. Sunitinib, pazopanib, axitinib, sorefenib, everolimus, and nivolumab were administered to 15, 9, 16, 3, 7, and 13 patients, respectively, with duplication. Proteinuria was managed according to the grade determined by UPCR. Data at every treatment visit were retrospectively collected and uPr and UPCR were compared. The overall incidences of any grade of proteinuria associated with sunitinib, pazopanib, axitinib, sorafenib and everolimus were 86.7, 88.9, 93.8, 100, and 85.7%, respectively. There were discordances between the uPr-based grade and UPCR-based grade. UPCR did not meet the criteria of Grade 3 in 70.6, 100, 83.3, and 83.3% at visits in cases with uPr 3+ for sunitinib, pazopanib, sorafenib, and everolimus, respectively. In axitinib treatment, UPCR did not meet the criteria for withholding in 46.2% of the cases of uPr 2+ and more. Our study suggests that UPCR may be useful tool in management of adverse events associated with tyrosine kinase inhibitors, everolimus and can provide patients with optimal opportunities for receiving treatment.

Detecting creatine excreted in the urine of swimming athletes by means of Raman spectroscopy.

High-level sport requires analysis of athletes' metabolic conditions in order to improve the training. Raman spectroscopy can be used to assess urinary composition advantageously when compared to conventional methods of urinalysis. In this work, Raman spectroscopy has been employed to detect creatine in urine of professional swimmers before and after training compared to sedentaries. It has been collected urine samples from five swimmers before and immediately after 150 min of swimming and submitted to Raman spectroscopy (830 nm excitation, 350 mW laser power, 20 s integration time) and compared to the urine from a control group (14 sedentary subjects). The Raman spectra of urine from four swimmers after training showed peaks related to creatine at 829, 915, 1049, and 1397 cm-1, besides peaks referred to urea, creatinine, ketone bodies, and phosphate. A spectral model estimated the concentration of creatine to be from 0.26 to 0.72 g/dL in the urine of these athletes. The presence of this metabolic biomarker in the urine of some swimmers suggests a metabolic profile influenced by the diet, supplementation, individual metabolism, and the self-response to the training. Raman spectroscopy allows a rapid and reliable detection of creatine excreted in the urine of swimming athletes, which may be used to adjust the nutrition/supplementation of each individual as well as the individual response and energy consumption depending on the type and duration of the training.

Albuminuria Testing by Race and Ethnicity among Patients with Hypertension with and without Diabetes.

BACKGROUND: Detection of chronic kidney disease (CKD) with urine albumin-to-creatinine ratio (UACR) among patients with hypertension (HTN) provides an opportunity for early treatment, potentially mitigating risk of CKD progression and cardiovascular complications. Differences in UACR testing patterns among racial/ethnic populations at risk for CKD could contribute to known disparities in CKD complications. METHODS: We examined the prevalence of UACR testing among low-income adult primary care patients with HTN, defined by a new administrative code for HTN or 2 clinic blood pressures >140/90 mm Hg between January 1, 2014, and January 1, 2017, in one public health-care delivery system with a high prevalence of end-stage kidney disease among race/ethnic minorities. Logistic regression was used to identify odds of UACR testing within 1 year of a HTN diagnosis, overall, and by racial/ethnic subgroup, adjusted for demographic factors, estimated glomerular filtration rate, and HTN severity. Models were also stratified by diabetes status. RESULTS: The cohort (n = 16,414) was racially/ethnically diverse (16% White, 21% Black, 34% Asian, 19% Hispanic, and 10% other) and 51% female. Only 35% of patients had UACR testing within 1 year of a HTN diagnosis. Among individuals without diabetes, odds of UACR testing were higher among Asians, Blacks, and Other subgroups compared to Whites (adjusted OR [aOR] 1.19; 95% CI 1.00-1.42 for Blacks; aOR 1.33; 1.13-1.56 for Asians; aOR 1.30; 1.04-1.60 for Other) but were not significantly different between Hispanics and Whites (aOR 1.17; 0.97-1.39). Among individuals with diabetes, only Asians had higher odds of UACR testing compared to Whites (aOR 1.35; 1.12-1.63). CONCLUSIONS: Prevalence of UACR testing among low-income patients with HTN is low in one public health-care delivery system, with higher odds of UACR testing among racial/ethnic minority subgroups compared to Whites without diabetes and similar odds among those with diabetes. If generalizable, less albuminuria testing may not explain higher prevalence of kidney failure in racial/ethnic minorities.

Ultra-Performance Liquid Chromatography-High-Resolution Mass Spectrometry and Direct Infusion-High-Resolution Mass Spectrometry for Combined Exploratory and Targeted Metabolic Profiling of Human Urine.

The application of metabolic phenotyping to epidemiological studies involving thousands of biofluid samples presents a challenge for the selection of analytical platforms that meet the requirements of high-throughput precision analysis and cost-effectiveness. Here direct infusion-nanoelectrospray (DI-nESI) was compared with an ultra-performance liquid chromatography (UPLC)-high-resolution mass spectrometry (HRMS) method for metabolic profiling of an exemplary set of 132 human urine samples from a large epidemiological cohort. Both methods were developed and optimized to allow the simultaneous collection of high-resolution urinary metabolic profiles and quantitative data for a selected panel of 35 metabolites. The total run time for measuring the sample set in both polarities by UPLC-HRMS was 5 days compared with 9 h by DI-nESI-HRMS. To compare the classification ability of the two MS methods, we performed exploratory analysis of the full-scan HRMS profiles to detect sex-related differences in biochemical composition. Although metabolite identification is less specific in DI-nESI-HRMS, the significant features responsible for discrimination between sexes were mostly the same in both MS-based platforms. Using the quantitative data, we showed that 10 metabolites have strong correlation (Pearson's r > 0.9 and Passing-Bablok regression slope of 0.8-1.3) and good agreement assessed by Bland-Altman plots between UPLC-HRMS and DI-nESI-HRMS and thus can be measured using a cheaper and less sample- and time-consuming method. A further twenty metabolites showed acceptable correlation between the two methods with only five metabolites showing weak correlation (Pearson's  r < 0.4) and poor agreement due to the overestimation of the results by DI-nESI-HRMS.

Diabetic Nephropathy Can Be Treated with Calcium Dobesilate by Alleviating the Chronic Inflammatory State and Improving Endothelial Cell Function.

BACKGROUND/AIMS: Diabetic kidney disease (DKD) is a leading cause of end-stage renal disease. However, no effective treatments for this disease are available. Calcium dobesilate (CaD) is widely used to treat diabetic retinopathy. DKD and retinopathy often co-exist and have similar mechanisms of pathogenesis. The aim of the present study was to elucidate the safety and efficacy of CaD in the treatment of DKD. METHODS: In the prospective randomised controlled study, 100 DKD from Type 2 diabetes mellitus (DM) patients with a urinary albumin/ creatinine ratio (ACR) ≥30 mg/g and urinary protein level between 150 mg/24 h and 2 g/24 h with GFR> 90ml/min were enrolled. The patients were randomly divided into the treatment group (500 mg of CaD, administered orally, 3 times per day) and the control group. DKD patients were treated for 3 months. In the case control study, DM patients without proteinuria and healthy individuals were also enrolled. Clinical data and related biochemical parameters were collected. Endothelial function markers (VEGF, ET-1, eNOS, NO) and inflammatory markers (MCP-1, ICAM, PTX3) were detected by ELISA. RESULTS: In the prospective randomised controlled study, the 24 h urinary albumin and 24 h urinary protein levels significantly decreased after three months of treatment with CaD in the patients with DKD, but the cystatin C-based glomerular filtration rate (GFR) remained unchanged. In addition, the levels of inflammatory markers (PTX3, MCP-1, hsCRP, ICAM) and endothelial dysfunction markers (VEGF, ET-1) were significantly reduced compared to pre-treatment levels, NO was signifcantly increased post treatment. In the case control study, we found that PTX3, MCP-1, ICAM, VEGF and ET-1 levels were positively correlated with urinary albumin in DKD patients, while the NO level was negatively correlated. Logistic regression analysis showed that PTX3, NO and HbAlc were influential factors in DKD. After patients with DKD were treated with CaD for three months, the 24 h urinary albumin and 24 h urinary protein levels significantly decreased, but the cystatin C-based glomerular filtration rate (GFR) remained unchanged. In addition, the levels of inflammatory markers (PTX3, MCP-1, hsCRP, ICAM) and endothelial dysfunction markers (VEGF, NO, ET-1) were significantly reduced compared to pre-treatment levels. CONCLUSION: CaD can be safely and effectively used to treatdiabetic nephropathy.

A novel SLC6A8 mutation associated with intellectual disabilities in a Chinese family exhibiting creatine transporter deficiency: case report.

BACKGROUND: X-linked creatine transporter deficiency (OMIM#300036,CRTR-D) is characterized by cerebral creatine deficiency, intellectual disabilities, severe speech impairment, seizures and behavioral problems. Mutations in the creatine transporter gene SLC6A8, a member of the solute-carrier family 6 mapped to Xq28, have been reported to cause the creatine transporter deficiency. CASE PRESENTATION: The proband presented at 5 yrs. 1 month of age with delays in intellectual and development, seizures and behavioral problems. A novel missense mutation, c.1181C > A (p.Thr394Lys), in the SLC6A8 gene (NM_005629.3) was detected via targeted exome sequencing, and then validated by Sanger sequencing. Multiple in silico variant effect analysis methods, including SIFT, PolyPhen2, PROVEAN, and Mutation Taster predicted that this variant was likely damaging or diseasing-causing. This hemizygous variation was also identified in the affected brother with the same clinical condition and inherited from the heterozygous carrier mother. The diagnosis was suggested by increased urinary creatine/creatinine (Cr:Crn) ratio and markedly reduced creatine content peak by brain proton magnetic resonance spectroscopy (MRS). The proband's mother became pregnant with a 3rd sibling, in whom the Sanger sequencing result of c.1181C > A was negative. CONCLUSION: The novel mutation c.1181C > A in the SLC6A8 gene reported in a Chinese family has expanded the mutation spectrum of CRTR-D. The combination of powerful new technologies such as targeted exome sequencing with thorough systematic clinical evaluation of patients will improve the diagnostic yield, and assist in genetic counselling and prenatal diagnosis for suspected genetic disorders.

Circulating and Urinary miR-210 and miR-16 Increase during Cardiac Surgery Using Cardiopulmonary Bypass - A Pilot Study.

A pilot study to measure and compare blood and urine microRNAs miR-210 and miR-16 in patients undergoing cardiac surgery with cardiopulmonary bypass (CPB) and off-pump coronary artery bypass grafting surgery. Frequent serial blood and urine samples were taken from patients undergoing cardiac surgery with CPB (n = 10) and undergoing off-pump cardiac surgery (n = 5) before, during, and after surgery. Circulating miR-210 and miR-16 levels were determined by relative quantification real-time polymerase chain reaction. Levels of plasma-free haemoglobin (fHb), troponin-T, creatine kinase, and creatinine were measured. Perioperative serum miR-210 and miR-16 were elevated significantly compared to preoperative levels in patients undergoing cardiac surgery with CPB (CPB vs. Pre Op and Rewarm vs. Pre Op; p < .05 for both). There were increases of greater than 200% in miR-210 levels during rewarming and immediately postoperatively and a 3,000% increase in miR-16 levels immediately postoperatively in urine normalized to urinary creatinine concentration. Serum levels of miR-16 were relatively constant during off-pump surgery. miR-210 levels increased significantly in off-pump patients perioperatively (p < .05 Octopus on vs. Pre Op); however, the release was less marked when compared to cardiac surgery with CPB. A significant association was observed between both miR-16 and miR-210 and plasma fHb when CPB was used (r = -.549, p < .0001 and r = -.463, p < .0001 respectively). Serum and urine concentrations of hypoxically regulated miR-210 and hemolysis-associated miR-16 increased in cardiac surgery using CPB compared to off-pump surgery. These molecules may have utility in indicating severity of cardiac, red cell, and renal injury during cardiac surgery.

Laboratory diagnosis of creatine deficiency syndromes: a technical standard and guideline of the American College of Medical Genetics and Genomics.

Disclaimer: These ACMG Standards and Guidelines are intended as an educational resource for clinical laboratory geneticists to help them provide quality clinical laboratory genetic services. Adherence to these standards and guidelines is voluntary and does not necessarily assure a successful medical outcome. These Standards and Guidelines should not be considered inclusive of all proper procedures and tests or exclusive of others that are reasonably directed to obtaining the same results. In determining the propriety of any specific procedure or test, clinical laboratory geneticists should apply their professional judgment to the specific circumstances presented by the patient or specimen. Clinical laboratory geneticists are encouraged to document in the patient's record the rationale for the use of a particular procedure or test, whether or not it is in conformance with these Standards and Guidelines. They also are advised to take notice of the date any particular guideline was adopted, and to consider other relevant medical and scientific information that becomes available after that date. It also would be prudent to consider whether intellectual property interests may restrict the performance of certain tests and other procedures.Cerebral creatine deficiency syndromes are neurometabolic conditions characterized by intellectual disability, seizures, speech delay, and behavioral abnormalities. Several laboratory methods are available for preliminary and confirmatory diagnosis of these conditions, including measurement of creatine and related metabolites in biofluids using liquid chromatography-tandem mass spectrometry or gas chromatography-mass spectrometry, enzyme activity assays in cultured cells, and DNA sequence analysis. These guidelines are intended to standardize these procedures to help optimize the diagnosis of creatine deficiency syndromes. While biochemical methods are emphasized, considerations for confirmatory molecular testing are also discussed, along with variables that influence test results and interpretation.Genet Med 19 2, 256-263.

A fully validated bioanalytical method using an UHPLC-MS/MS system for quantification of DNA and RNA oxidative stress biomarkers.

A new, rapid and effective ultra-high-performance liquid chromatography method with mass spectrometry detection is described for the separation and quantification of 8-hydroxy-2-deoxyguanosine, 8-hydroxyguanosine and creatinine in human urine. The present study uses an isotope-labelled internal standard ([15N]5-8-hydroxy-2-deoxyguanosine), a BIO core-shell stationary phase and an isocratic elution of methanol and water. Sample preparation of human urine was performed by solid-phase extraction (SPE) on Oasis HLB cartridges with methanol/water 50:50 (v/v) elution. Extraction recoveries ranged from 98.1% to 109.2%. Biological extracts showed high short-term stability. Several aspects of this procedure make it suitable for both clinical and research purposes: a short elution time of less than 3.2 min, an intra-day precision of 2.5-8.9%, an inter-day precision of 3.4-8.7% and low limits of quantification (27.7 nM for 8-hydroxyguanosine, 6.0 nM for 8-hydroxy-2-deoxyguanosine). Finally, simultaneous analysis of DNA and RNA oxidative stress biomarkers is a useful tool for monitoring disease progression in neurodegenerative disorders and cancer. Graphical abstract UHPLC-MS/MS analysis of DNA and RNA oxidative stress biomarkers.

Association Between Plasma Homocysteine and Microalbuminuria in Untreated Patients with Essential Hypertension: a Case-Control Study.

BACKGROUND/AIMS: Kidney function is critical for homocysteine (Hcy) clearance, and plasma Hcy levels are frequently increased in patients with renal failure. Microalbuminuria (MAU) is an important marker of early renal damage caused by hypertension. At present, there is insufficient evidence on the relationship between Hcy and microalbuminuria. METHODS: This is a 1: 2 matched, hospital-based case-control study. At initial visit, out of 1535 outpatients with no prior history of medication, 450 qualified subjects were selected based on inclusion and exclusion criteria. The concentration of Hcy in the serum was evaluated using a cyclic enzyme method. MAU was defined by a urine albumin/creatinine ratio (UACR) between 30 µg/mg and 300 µg/mg. RESULTS: A total of 450 patients were included in this study (150 in the MAU group and 300 in the non-MAU group). The MAU group had higher mean systolic blood pressure (SBP), mean diastolic blood pressure (DBP), heart rate (HR) and plasma Hcy levels than did the non-MAU group. The area under the receiver operating characteristics (ROC) curves was 0.772 (95% CI: 0.724-0.819, P < 0.001) with a cut-off value of 15.0, and the sensitivity and specificity of Hcy in predicting the MAU status in hypertensive patients were 49.3% and 92.3%, respectively. Multiple logistic regression modelling suggested that patients with a higher Hcy level (> 15 µmol/L) were more likely to have MAU (95% CI: 5.650-16.543, P < 0.001). The other predictive factor for MAU was 24-h mean SBP (95% CI: 0.941-0.993, P = 0.015). CONCLUSION: This matched case-control study indicates that Hcy may increase the susceptibility of essential hypertensive subjects to MAU.

Using urinary parameters to estimate seasonal variation in the physical condition of female white-faced capuchin monkeys (Cebus capucinus imitator).

OBJECTIVES: The physical condition of females depends on access to resources, which vary over space and time. Assessing variation in physical condition can help identify factors affecting reproductive success, but noninvasive measurement is difficult in wild animals. Creatinine concentration relative to the specific gravity (i.e., density) of urine has promise for noninvasively quantifying the relative muscle mass (RMM) of wild primates. We verified the relationship between these urinary parameters for wild white-faced capuchin monkeys, and assessed temporal changes in the RMM of females across groups and between periods of high and low resource abundance. MATERIALS AND METHODS: We collected urine from 25 adult females in three groups across varying seasons at Sector Santa Rosa, Costa Rica. We measured the specific gravity and creatinine concentration of 692 samples and the effect of specific gravity on creatinine concentration. We used the residuals of this relationship to measure effects of group and season using mixed-effects models. RESULTS: Specific gravity significantly predicted creatinine concentration. Season, group membership and the interaction between these variables were significant predictors of residual creatinine variation. Specifically, RMM was higher during months with high fruit energy density, lower in one social group, and less variable among females in the smallest group. DISCUSSION: Our findings suggest that specific gravity and creatinine may be used as urinary parameters to make inferences about the RMM of capuchins. Using this technique, we infer that females experienced changes in muscle mass according to variation in resource energy availability and social group variation.

Congolese children with sickle cell trait may exhibit glomerular hyperfiltration: A case control study.

BACKGROUND: The prevalence of sickle cell trait is extremely high in sub-Saharan Africa. Recent studies have reported the impact of sickle cell carriers on renal function. However, data on renal abnormalities in children with sickle cell trait in this part of the world are unknown. In this report, we assess the glomerular function of children with sickle cell trait (SCT). METHODS: A case control study was conducted to assess the glomerular function in 43 Congolese children with sickle cell trait (Hb-AS) matched for age to 65 children with sickle cell anemia in steady state (Hb-SS) and 67 normal controls (Hb-AA). RESULTS: There was a significant difference in the blood pressure levels between the Hb-AS group vs Hb-SS group (P<.05). The estimated glomerular filtration rate (eGFR) corrected for body surface area was increased in Hb-AS group compared to Hb-AA group, but there was no significant difference between the two groups (P=.48). At the same time, the eGFR was decreased, but no significantly so, in the Hb-AS group compared to the Hb-SS group (P=.19). The proportion of children with Hb-AS (16.3%) who had hyperfiltration was higher compared to the proportion (6.1%) found in the Hb-AA group, but lower compared to the proportion found in the Hb-SS group (30%). However, in both situations, the difference was not statistically significant. No case of proteinuria was detected in children with Hb-AS. CONCLUSION: It appears that at least one of six children with SCT had hyperfiltration. The findings could form a basis for further studies on this renal physiology among SCT individuals in Africa.

Association between nephrinuria, podocyturia, and proteinuria in women with pre-eclampsia.

AIM: Podocyte depletion in the kidney is associated with end-stage kidney disease (ESKD). Pre-eclampsia (PE) increases the risk of ESKD in later life. This study was performed to determine whether nephrinuria (soluble nephrin in the urine) is correlated with proteinuria and/or podocyturia (podocytes in the urine) in PE women. METHODS: Eighty-three urine samples, consisting of 45 and 38 samples from 27 normotensive and nine PE women, respectively, underwent simultaneous determination of nephrin, protein, and creatinine concentrations in the urine supernatant and quantitative analysis of podocyte-specific protein mRNA expression. This included podocin (Pod-mRNA) and nephrin (Nep-mRNA), using real-time polymerase chain reaction in the pelleted urine. Nephrinuria and proteinuria were corrected by creatinine concentration. Pod- and Nep-mRNA expression levels were corrected by GAPDH. RESULTS: Nephrinuria, proteinuria, Pod-mRNA expression, and Nep-mRNA expression all increased with advancing gestation in PE women, while not in normotensive women. The nephrinuria was strongly correlated with proteinuria (R = 0.901, P <  0.001), Pod-mRNA expression level (R = 0.824, P < 0.001), and Nep-mRNA expression level (R  =  0.724, P <  0.001) in urine samples from PE women, while the nephrinuria was significantly correlated with proteinuria alone (R  =  0.419, P <  0.005) in urine samples from normotensive women. CONCLUSION: Nephrinuria reflected well the degrees of proteinuria and podocyturia in PE women. This suggested that increased nephrinuria/proteinuria was associated with podocyte loss in the kidneys of PE women.

Guanidinoacetate methyltransferase (GAMT) deficiency: a rare but treatable epilepsy.

Epilepsy commonly presents in childhood as part of a syndrome, and some such children may reach adult services without an underlying syndromic diagnosis. For adult neurologists taking over their care, it is often unclear how hard to search for an underlying diagnosis. The diagnostic yield may be small and such a diagnosis may not change management. Young adults with learning difficulties are also challenging to investigate, as they may not tolerate standard epilepsy tests.We present such a case in which simple tests identified a unifying diagnosis. With the new diagnosis came a new treatment that had a significant impact on seizures and quality of life.