Green microfluidic liquid-phase microextraction of polar and non-polar acids from urine.

In this work, hippuric acid (log P = 0.5), anthranilic acid (log P = 1.3), ketoprofen (log P = 3.6), and naproxen (log P = 3.0) were simultaneously extracted by a green microfluidic device based on the principles of liquid-phase microextraction (LPME). Different deep eutectic solvents (DESs) were investigated as supported liquid membrane (SLM), and a mixture of camphor and menthol as eutectic solvents in the molar ratio 1:1 was found to be highly efficient for the simultaneous extraction of non-polar and polar acidic drugs. LPME was conducted for 6 min per sample. Urine sample was delivered to the system at 1 µL min-1, and target analytes were extracted exhaustively (75-100% recovery) across the DES SLM, and into pure aqueous phosphate buffer pH 11.0 delivered as acceptor at 1 µL min-1. The acceptor was analyzed with liquid chromatography-UV detection. Interestingly, the DES enabled extraction of both the polar and non-polar model analytes at the same time; all chemicals were green and non-hazardous, and the chemical waste was less than 1 mg per sample.

Biochemical phenotype and its relationship to treatment in 16 individuals with PCCB c.1606A > G (p.Asn536Asp) variant propionic acidemia.

Propionic acidemia (PA) is caused by inherited deficiency of mitochondrial propionyl-CoA carboxylase (PCC) and results in significant neurodevelopmental and cardiac morbidity. However, relationships among therapeutic intervention, biochemical markers, and disease progression are poorly understood. Sixteen individuals homozygous for PCCB c.1606A > G (p.Asn536Asp) variant PA participated in a two-week suspension of therapy. Standard metabolic markers (plasma amino acids, blood spot methylcitrate, plasma/urine acylcarnitines, urine organic acids) were obtained before and after stopping treatment. These same markers were obtained in sixteen unaffected siblings. Echocardiography and electrocardiography were obtained from all subjects. We characterized the baseline biochemical phenotype of untreated PCCB c.1606A > G homozygotes and impact of treatment on PCC deficiency biomarkers. Therapeutic regimens varied widely. Suspension of therapy did not significantly alter branched chain amino acid levels, their alpha-ketoacid derivatives, or urine ketones. Carnitine supplementation significantly increased urine propionylcarnitine and its ratio to total carnitine. Methylcitrate blood spot and urine levels did not correlate with other biochemical measures or cardiac outcomes. Treatment of PCCB c.1606A > G homozygotes with protein restriction, prescription formula, and/or various dietary supplements has a limited effect on core biomarkers of PCC deficiency. These patients require further longitudinal study with standardized approaches to better understand the relationship between biomarkers and disease burden.

[Recommendations for urinary organic acids analysis]. / Recommandations concernant l'analyse des acides organiques urinaires.

Biochemical diagnosis of hereditary metabolic diseases requires the detection and simultaneous identification of a large number of compounds, hence the interest in metabolic profiles. Organic acid chromatography allows the identification of several hundred compounds and the quantification of the main molecules of interest. As part of the accreditation process for medical biology examinations according to standard NF EN ISO 15189, the group from the French society for inborn errors of metabolism (SFEIM) recommends an approach to accredit organic acid chromatography. Validation parameters and recommendations are discussed in this specific framework.

Rapid Quantification of Urinary Organic Acids by HPLC Mass Spectrometry to Assess Nutritional Individuality in Chinese Children.

A urinary organic acids profile can be utilized as an effective screening tool for analyzing abnormality of nutrient metabolism. By using these metabolic markers in conjunction with one another, it helps in understanding how individual nutrient metabolism is executed and to determine where there may be imbalances in the metabolic cycle. In this study, we developed a rapid quantification method of 20 urinary organic acids by HPLC-mass spectrometry. A pre-analytical process of organic acid extraction from a urine sample is crucial in this methodology. The process was accomplished by liquid-liquid extraction followed by strong anion exchange. Compared with previous methods, this method greatly reduces the analysis time and allows for the simultaneous quantification of 20 organic acids within 10 min for the first time. This methodology enabled us to analyze urine samples collected from 34 Chinese children. The abnormalities of some urinary organic acids were found in this group, which revealed evidence of functional inadequacy of specific nutrients. The preliminary data in this study confirmed the suitability of the method for rapid and accurate quantification of the target organic acids in urine samples.

In-situ synthesis of flower like Co3O4 nanorod arrays on anodized aluminum substrate templated from layered double hydroxide as a nanosorbent for thin film microextraction of acidic drugs followed by HPLC-UV quantitation.

The present study is the first report of in-situ growth and application of nanorods-flower like Co3O4 nanosorbent coated on the anodized aluminum substrate for thin film microextraction (TFME) approach. The flower like Co3O4 was successfully fabricated by conversion of Co-Al layered double hydroxide (LDH) precursor to Co3O4 using the simple calcinations process. The cheap and available aluminum foil was electrochemically anodized and used as a porous substrate. Response surface methodology (RSM) was explored for optimization step. Different acidic drugs, including: paracetamol, ibuprofen, aspirin and diclofenac were extracted from biological fluids in order to investigate the capability of the prepared sorbent. The extracted analytes were then analyzed using high performance liquid chromatography-ultraviolet detection (HPLC-UV). Under the optimized conditions, the limits of detection were between 0.2 and 1.7 µg L-1 in different selected matrices. The obtained limits of quantification were also calculated to be between 0.8 and 5.1 µg L-1 in the selected matrices. In addition the enrichment factors were also in the range of 105-169. Batch-to-batch reproducibility at 100 µg L-1 concentration level was also evaluated to be lower than 5.2% (n = 3). Finally, the method was successfully used for analysis of these compounds in the biological fluids.

Influence of Sex on Urinary Organic Acids: A Cross-Sectional Study in Children.

The characterization of urinary metabolome, which provides a fingerprint for each individual, is an important step to reach personalized medicine. It is influenced by exogenous and endogenous factors; among them, we investigated sex influences on 72 organic acids measured through GC-MS analysis in the urine of 291 children (152 males; 139 females) aging 1-36 months and stratified in four groups of age. Among the 72 urinary metabolites, in all age groups, 4-hydroxy-butirate and homogentisate are found only in males, whereas 3-hydroxy-dodecanoate, methylcitrate, and phenylacetate are found only in females. Sex differences are still present after age stratification being more numerous during the first 6 months of life. The most relevant sex differences involve the mitochondria homeostasis. In females, citrate cycle, glyoxylate and dicarboxylate metabolism, alanine, aspartate, glutamate, and butanoate metabolism had the highest impact. In males, urinary organic acids were involved in phenylalanine metabolism, citrate cycle, alanine, aspartate and glutamate metabolism, butanoate metabolism, and glyoxylate and dicarboxylate metabolism. In addition, age specifically affected metabolic pathways, the phenylalanine metabolism pathway being affected by age only in males. Relevantly, the age-influenced ranking of metabolic pathways varied in the two sexes. In conclusion, sex deeply influences both quantitatively and qualitatively urinary organic acids levels, the effect of sex being age dependent. Importantly, the sex effects depend on the single organic acid; thus, in some cases the urinary organic acid reference values should be stratified according the sex and age.

Increased body fatness adversely relates to 24-hour urine pH during childhood and adolescence: evidence of an adipo-renal axis.

BACKGROUND: Reduced net acid excretion (NAE) capacity indicates a decrease in renal function. This reduction manifests as a disproportionally low 24-h urine pH in relation to the sum of actually excreted ammonium and titratable acidity by the kidney. OBJECTIVE: The aim of this study was to test the hypothesis that higher body fatness is one determinant of kidney function impairment with a lowered urine pH even at a young age. METHODS: NAE, pH, urea, and creatinine were measured in 24-h urine samples from 524 healthy children and adolescents (aged 6-17 y) participating in the DOrtmund Nutritional and Anthropometric Longitudinally Designed (DONALD) Study. Body fatness was assessed anthropometrically by body mass index-standard deviation score (BMI-SDS), fat mass index (FMI), body fat % (BF%), and waist circumference (WC). Multivariable linear and mixed linear regressions were used to examine cross-sectionally (n = 524 urine samples; age groups: 6-8, 9-11, 12-14, 15-17 y) and longitudinally (n = 1999 urine samples) the associations of body fatness with 24-h urine pH as the outcome variable, respectively. RESULTS: After adjusting for the kidneys' total net acid load (24-h urinary NAE) and further relevant covariates, FMI showed significant inverse relations with urinary pH in all 4 age groups, and BMI-SDS, BF%, and WC each in 3 out of these 4 groups (P ≤ 0.02). Longitudinal results substantiated these interindividual relations and further showed intraindividual increases in body fatness to be paralleled by urine pH decreases (P ≤ 0.0002). CONCLUSIONS: Independent of underlying acid load, an early increase in body fatness is associated with increased free proton excretion, and thus with a decline in the kidney's acid excretion function, which could potentiate the risk of renal nephrolithiasis.

Urinary organic acids as biomarkers in the assessment of pulmonary function in children with asthma.

Childhood asthma prevalence continues to rise despite advancements in prevention and medical management strategies. The purpose of this study was to investigate correlations between urinary organic acids and pulmonary diagnostic tests, asthma control in Greek asthmatic children. We hypothesized that urinary organic acids are positively associated with poor pulmonary function in children with asthma. Seventy-two children, 5 to 12 years old with asthma were recruited from a pediatric asthma clinic in Athens, Greece. Pulmonary function was assessed using spirometry and exhaled nitric oxide analysis. Asthma control was measured qualitatively using the Asthma Control Questionnaire. Targeted metabolomic analysis of 34 urinary organic acids in children was conducted by gas chromatography-mass spectrometry. A statistically significant difference between girls and boys was found for asthma control score (P = .02), lactic acid (P = .03), but not for any other organic acids (P > .05). Statistically significant correlations were found between lactic acid and Forced Expiratory Volume in 1 second (FEV1) (P = .02), Forced Vital Capacity (FVC) (P = .03); 4- hydroxyphenylacetic acid and FEV1 (P = .01), FVC (P = .01); 5-hydroxyindoleacetic acid and FEV1/FVC (P = .03), eNO (P = .05); glycolic acid with Peak Expiratory Flow (PEF) (P = .03); and malic acid with asthma control (P = .02). In conclusion, metabolomics was used to determine correlations between urinary organic acids and conventional pulmonary diagnostic tests in Greek asthmatic children. Metabolomics could be a promising approach for asthma research and in detection of novel biomarkers for asthma monitoring and therapeutic targets for childhood asthma. This study contributes towards a better understanding of the biochemical pathways involved in asthma.

Insufficiency of urinary acid excretion of overweight or obese patients with chronic kidney disease and its involvement with renal tubular injury.

AIM: Metabolic acidosis occurs due to insufficient urinary ammonium excretion as chronic kidney disease (CKD) advances. Because obese subjects tend to have excessive consumption of protein and sodium chloride, they are prone to chronic acid loading and may therefore be predisposed to acid-induced kidney injury. We investigated the involvement of obesity in ammoniagenesis within damaged kidneys. METHODS: In the clinical study, urinary ammonium excretion was compared between 13 normal-weight and 15 overweight/obese CKD outpatients whose creatinine clearance was higher than 25 mL/min. For animal experiments, NH4 Cl was loaded to KKAy/TaJcl (KKAy), a metabolic syndrome model, and control BALB/c mice for 20 weeks. Kidney injury was evaluated through histological analysis and the expression of proinflammatory markers. RESULTS: Urinary ammonium excretion was lower in overweight/obese patients than in normal-weight patients, while intakes of protein and sodium chloride were higher in overweight/obese patients, implying that subclinical metabolic acidosis occurs in overweight/obese patients. The increase in urinary ammonium excretion induced by NH4 Cl loading was attenuated in KKAy mice after 16 weeks, whereas the increase was maintained in BALB/c mice throughout the study period. Histological study and real-time polymerase chain reaction analysis showed proximal tubular injury and enhanced expression levels of neutrophil gelatinase-associated lipocalin (NGAL) protein and messenger RNA, respectively, in KKAy mice but not in BALB/c mice. Finally, urinary NGAL concentration was higher in overweight/obese patients than in normal-weight patients in the early stage of CKD. CONCLUSION: Obesity could facilitate the induction of subclinical metabolic acidosis and acid accumulation in the kidney, which may potentially exacerbate kidney injury in CKD patients.

Sodium bicarbonate loading limits tubular cast formation independent of glomerular injury and proteinuria in Dahl salt-sensitive rats.

Sodium bicarbonate (NaHCO3) slows the decline in kidney function in patients with chronic kidney disease (CKD), yet the mechanisms mediating this effect remain unclear. The Dahl salt-sensitive (SS) rat develops hypertension and progressive renal injury when fed a high salt diet; however, the effect of alkali loading on kidney injury has never been investigated in this model. We hypothesized that NaHCO3 protects from the development of renal injury in Dahl salt-sensitive rats via luminal alkalization which limits the formation of tubular casts, which are a prominent pathological feature in this model. To examine this hypothesis, we determined blood pressure and renal injury responses in Dahl SS rats drinking vehicle (0.1 M NaCl) or NaHCO3 (0.1 M) solutions as well as in Dahl SS rats lacking the voltage-gated proton channel (Hv1). We found that oral NaHCO3 reduced tubular NH4+ production, tubular cast formation, and interstitial fibrosis in rats fed a high salt diet for 2 weeks. This effect was independent of changes in blood pressure, glomerular injury, or proteinuria and did not associate with changes in renal inflammatory status. We found that null mutation of Hv1 also limited cast formation in Dahl SS rats independent of proteinuria or glomerular injury. As Hv1 is localized to the luminal membrane of TAL, our data suggest that alkalization of the luminal fluid within this segment limits cast formation in this model. Reduced cast formation, secondary to luminal alkalization within TAL segments may mediate some of the protective effects of alkali loading observed in CKD patients.

Acidosis and acute kidney injury in severe malaria.

BACKGROUND: In severe falciparum malaria metabolic acidosis and acute kidney injury (AKI) are independent predictors of a fatal outcome in all age groups. The relationship between plasma acids, urine acids and renal function was investigated in adult patients with acute falciparum malaria. METHODS: Plasma and urinary acids which previously showed increased concentrations in proportion to disease severity in patients with severe falciparum malaria were quantified. Patients with uncomplicated malaria, sepsis and healthy volunteers served as comparator groups. Multiple regression and multivariate analysis were used to assess the relationship between organic acid concentrations and clinical syndromes, in particular AKI. RESULTS: Patients with severe malaria (n = 90), uncomplicated malaria (n = 94), non-malaria sepsis (n = 19), and healthy volunteers (n = 61) were included. Univariate analysis showed that both plasma and creatinine-adjusted urine concentrations of p-hydroxyphenyllactic acid (pHPLA) were higher in severe malaria patients with AKI (p < 0.001). Multiple regression analysis, including plasma or creatinine-adjusted urinary acids, and PfHRP2 as parasite biomass marker as independent variables, showed that pHPLA was independently associated with plasma creatinine (ß = 0.827) and urine creatinine (ß = 0.226). Principal component analysis, including four plasma acids and seven urinary acids separated a group of patients with AKI, which was mainly driven by pHPLA concentrations. CONCLUSIONS: Both plasma and urine concentrations of pHPLA closely correlate with AKI in patients with severe falciparum malaria. Further studies will need to assess the potential nephrotoxic properties of pHPLA.

Insulin-resistance in glycogen storage disease type Ia: linking carbohydrates and mitochondria?

BACKGROUND: Glycogen storage disease type I (GSDI) is an inborn error of carbohydrate metabolism caused by mutations of either the G6PC gene (GSDIa) or the SLC37A4 gene (GSDIb). GSDIa patients are at higher risk of developing insulin-resistance (IR). Mitochondrial dysfunction has been implicated in the development of IR. Mitochondrial dysfunction can demonstrate abnormalities in plama acylcarnitines (ACs) and urine organic acids (UOA). The aim of the study was to investigate the presence of mitochondrial impairment in GSDI patients and its possible connection with IR. METHODS: Fourteen GSDIa, seven GSDIb patients, 28 and 14 age and sex-matched controls, were enrolled. Plasma ACs, UOA, and surrogate markers of IR (HOMA-IR, QUICKI, ISI, VAI) were measured. RESULTS: GSDIa patients showed higher short-chain ACs and long-chain ACs levels and increased urinary excretion of lactate, pyruvate, 2-ketoglutarate, 3-methylglutaconate, adipate, suberate, aconitate, ethylmalonate, fumarate, malate, sebacate, 4-octenedioate, 3OH-suberate, and 3-methylglutarate than controls (p < 0.05). GSDIb patients showed higher C0 and C4 levels and increased urinary excretion of lactate, 3-methylglutarate and suberate than controls (p < 0.05). In GSDIa patients C18 levels correlated with insulin serum levels, HOMA-IR, QUICKI, and ISI; long-chain ACs levels correlated with cholesterol, triglycerides, ALT serum levels, and VAI. DISCUSSION: Increased plasma ACs and abnormal UOA profile suggest mitochondrial impairment in GSDIa. Correlation data suggest a possible connection between mitochondrial impairment and IR. We hypothesized that mitochondrial overload might generate by-products potentially affecting the insulin signaling pathway, leading to IR. On the basis of the available data, the possible pathomechanism for IR in GSDIa is proposed.

Identifying the localization and exploring a functional role for Gprc5c in the kidney.

The investigation of orphan GPCRs (GPRs) has the potential to uncover novel insights into whole animal physiology. In this study, our goal was to determine the renal localization of Gprc5c, a receptor that we previously reported to be highly expressed in murine whole kidney, and to examine physiologic parameters in Gprc5c knockout (KO) mice to gain insight into function. Gprc5c localized to the apical membrane of renal proximal tubules (PTs) in mice, rats, and humans. With the comparison of Gprc5c wild-type (WT) and KO mice, we found that Gprc5c KO mice have altered acid-base homeostasis. Specifically, Gprc5c KO mice have lower blood pH and higher urine pH compared with WT mice, with a reduced level of titratable acids in their urine. In an in vitro GPCR internalization assay, we observed that Gprc5c internalization (an index of activation) was triggered by alkaline extracellular pH. Furthermore, with the use of an in vitro BCECF assay, we observed that Gprc5c increases Na+/H+ exchanger 3 (NHE3) activity at alkaline pH. We also find that the NHE3 activity is reduced in Gprc5c KO mice by 2 photon imaging in seminaphthorhodafluors (SNARF)-4F-loaded kidney sections. NHE3 is a primary contributor to apical transport of H+ in the renal PT. Together, these data imply that Gprc5c modulates the renal contribution to systemic pH homeostasis, at least in part, by taking part in the regulation of NHE3.-Rajkumar, P., Cha, B., Yin, J., Arend, L. J., Paunescu, T. G., Hirabayashi, Y., Donowitz, M., Pluznick, J. L. Identifying the localization and exploring a functional role for Gprc5c in the kidney.

Application of metabolomics: Focus on the quantification of organic acids in healthy adults.

Metabolomics, a 'budding' discipline, may accurately reflect a specific phenotype which is sensitive to genetic and epigenetic interactions. This rapidly evolving field in science has been proposed as a tool for the evaluation of the effects of epigenetic factors, such as nutrition, environment, drug and lifestyle on phenotype. Urine, being sterile, is easy to obtain and as it contains metabolized or non­metabolized products, is a favored study material in the field of metabolomics. Urine organic acids (OAs) reflect the activity of main metabolic pathways and have been used to assess health status, nutritional status, vitamin deficiencies and response to xenobiotics. To date, a limited number of studies have been performed which actually define reference OA values in a healthy population and as reference range for epigenetic influences, and not as a reference to congenital metabolic diseases. The aim of the present study was thus the determination of reference values (RVs) for urine OA in a healthy adult population. Targeted metabolomics analysis of 22 OAs in the urine of 122 healthy adults by gas chromatography­mass spectrometry, was conducted. Percentile distributions of the OA concentrations in urine, as a base for determining the RVs in the respective population sample, were used. No significant differences were detected between female and male individuals. These findings can facilitate the more sensitive determination of OAs in pathological conditions. Therefore, the findings of this study may contribute or add to the information already available on urine metabolite databases, and may thus promote the use of targeted metabolomics for the evaluation of OAs in a clinical setting and for pathophysiological evaluation. However, further studies with well­defined patients groups exhibiting specific symptoms or diseases are warranted in order to discern between normal and pathological values.

Food groups associated with measured net acid excretion in community-dwelling older adults.

BACKGROUND/OBJECTIVES: Acid-producing diets have been associated with adverse health conditions. Dietary acid load can be estimated from dietary intake data, but the available methods require a full dietary assessment. We sought to identify a simpler means to estimate 24-h urinary net acid excretion (NAE), a robust measure of net endogenous acid production, using self-reported intakes of fruits, vegetables (acid-neutralizing foods), grain and/or protein (acid-producing foods) acquired by two different methods in community-dwelling older adults. Identifying food groups associated with NAE by using a method not requiring a full diet assessment could have a broad clinical application. SUBJECTS/METHODS: Fruit, vegetable, protein and grain servings/day were estimated with a widely used food frequency questionnaire (study A, n=162, 63±8 years). Differences in their intakes across NAE categories (<5, ⩾5 to <15, ⩾15 to <50, ⩾50 milliequivalents (mEq)/day) were analyzed using analysis of variance. The findings were verified in a second study, which estimated dietary intakes, using a more detailed record-assisted 24-h recall (study B, n=232, 67±6 years). RESULTS: Fruit intake was significantly associated with NAE in both studies. In study A, fruit intake was 9% lower with each categorical NAE increase (unstandardized beta=-0.21, P=0.01) and 7% lower with each categorical NAE increase in study B (unstandardized beta=-0.18; P=0.02). Grain intake was positively associated with NAE in study B only (unstandardized beta=+0.14; P=0.01). Vegetable and protein intake were not associated with NAE in either study. CONCLUSIONS: The inverse association between fruit intake and NAE suggests low self-reported fruit intake may be an indicator of acid-producing diets in older adults.

A cohort study of pyridoxine-dependent epilepsy and high prevalence of splice site IVS11+1G>A mutation in Chinese patients.

PURPOSE: Pyridoxine-dependent epilepsy (PDE) is a rare autosomal recessive disorder caused by mutations of the ALDH7A1 gene. We aimed to analyze the relations between the clinical diagnosis and treatment of PDE and ALDH7A1 gene mutations in Chinese PDE patients. METHODS: The clinical manifestations, diagnosis and treatment were observed in a cohort of PDE patients with early onset of seizure. Video-electroencephalogram (VEEG) and magnetic resonance imaging (MRI) were performed. The mutation of ALDH7A1 gene was analyzed. RESULTS: Of eight patients, six were males and two were females. Age of seizure onset ranged from 1 to 100 days and 75% patients presented with seizures in the neonatal period. All patients showed different degrees of developmental delay. EEGs showed focal or multifocal discharges, or were normal. Molecular analysis revealed 10 ALDH7A1 mutations, including 2 splice site mutations. Five patients had mutation at IVS11+1G>A site, six patients had missense mutations, one with nonsense mutation and another patient had 9-bp genomic deletion mutation. Among them, two mutations were first time reported. CONCLUSIONS: Seizure onset was in neonatal or early infantile period in our PDE patients. Early recognition and diagnosis of the disease is necessary for early intervention and improve cognitive development in the later life. In this study, on the molecular level, we also identified the splice site mutation IVS11+1G>A as a high prevalence mutation site with a frequency of 31.25% (5 of 16 alleles) in Chinese PDE patients.

Potassium Bicarbonate Supplementation Lowers Bone Turnover and Calcium Excretion in Older Men and Women: A Randomized Dose-Finding Trial.

The acid load accompanying modern diets may have adverse effects on bone and muscle metabolism. Treatment with alkaline salts of potassium can neutralize the acid load, but the optimal amount of alkali is not established. Our objective was to determine the effectiveness of two doses of potassium bicarbonate (KHCO3 ) compared with placebo on biochemical markers of bone turnover, and calcium and nitrogen (N) excretion. In this double-blind, randomized, placebo-controlled study, 244 men and women age 50 years and older were randomized to placebo or 1 mmol/kg or 1.5 mmol/kg of KHCO3 daily for 3 months; 233 completed the study. The primary outcomes were changes in 24-hour urinary N-telopeptide (NTX) and N; changes in these measures were compared across the treatment groups. Exploratory outcomes included 24-hour urinary calcium excretion, serum amino-terminal propeptide of type I procollagen (P1NP), and muscle strength and function assessments. The median administered doses in the low-dose and high-dose groups were 81 mmol/day and 122 mmol/day, respectively. When compared with placebo, urinary NTX declined significantly in the low-dose group (p = 0.012, after adjustment for baseline NTX, gender, and change in urine creatinine) and serum P1NP declined significantly in the low-dose group (p = 0.004, adjusted for baseline P1NP and gender). Urinary calcium declined significantly in both KHCO3 groups versus placebo (p < 0.001, adjusted for baseline urinary calcium, gender, and changes in urine creatinine and calcium intake). There was no significant effect of either dose of KHCO3 on urinary N excretion or on the physical strength and function measures. KHCO3 has favorable effects on bone turnover and calcium excretion and the lower dose appears to be the more effective dose. Long-term trials to assess the effect of alkali on bone mass and fracture risk are needed.

Detection of iso-α-acids to confirm beer consumption in postmortem specimens.

Iso-α-acids (IAAs) can be used as markers for the consumption of beer. Postmortem specimens from a range of coronial cases were analyzed for IAAs in order to determine the prevalence of beer consumption and any correlation to blood alcohol concentrations (BAC). A total of 130 cases were included in this study including those where beer was mentioned in the case circumstances, cases where beer was not mentioned specifically but alcohol was detected, and cases where neither beer was mentioned nor a positive BAC was present. Available blood, serum, vitreous humour and urine specimens were analyzed. Of the 50 cases where beer was mentioned, 86% had one or more IAAs detected. In cases that only had a positive BAC (n = 60), 57% of these cases also showed the presence of these beer markers. IAAs were detected in specimens obtained from traumatized, burnt, and decomposed cases with a mention of beer consumption or where BAC was positive in blood. No IAAs were detected in cases where BAC was negative. There was little or no correlation between blood IAA concentrations and BAC. This study demonstrates the possible detection of IAAs as a marker for beer consumption.

GC-MS analysis of organic acids in human urine in clinical settings: a study of derivatization and other analytical parameters.

In the current paper the analytical conditions for the determination of ten free organic acids by GC-MS are studied with the aim to establish a method for organic acid profiling in human urine to be used as a tool for the detection of metabolic or other health disorders. Studies included the GC-MS method development, the derivatization (trimethylsilylation) reaction conditions, the stability of the standard solutions during storage in the freezer, and the stability of the formed trimethylsilyl derivatives. Best results were obtained at a derivatization temperature of 50°C, and a reaction time of 30 min. Standard solutions were stable for 22 days, derivatized samples were stable at least for 30 h when stored at -24°C. GC-MS analysis achieved sensitive determination of the organic acids under study with limits of detection ranging from 0.03 mmol/mol creatinine for glutaric acid, to 0.34 mmol/mol creatinine for glycolic acid. Within-day and day-to-day assay imprecision was found satisfactory with relative standard deviations being below 10%. The developed method was successfully applied to the quantitative analysis of free organic acids in urine samples obtained from hospitalized children. Creatinine-corrected excretion rates of all analyzed organic acids were within reference intervals.