Assay of D-lactate in urine of infants and children with reference values taking into account data below detection limit

Gut Microbiome Dysbiosis as a Potential Risk Factor for Idiopathic Toe-Walking in Children: A Review

Idiopathic toe walking (ITW) occurs in about 5% of children. Orthopedic treatment of ITW is complicated by the lack of a known etiology. Only half of the conservative and surgical methods of treatment give a stable positive result of normalizing gait. Available data indicate that the disease is heterogeneous and multifactorial. Recently, some children with ITW have been found to have genetic variants of mutations that can lead to the development of toe walking. At the same time, some children show sensorimotor impairment, but these studies are very limited. Sensorimotor dysfunction could potentially arise from an imbalanced production of neurotransmitters that play a crucial role in motor control. Using the data obtained in the studies of several pathologies manifested by the association of sensory-motor dysfunction and intestinal dysbiosis, we attempt to substantiate the notion that malfunction of neurotransmitter production is caused by the imbalance of gut microbiota metabolites as a result of dysbiosis. This review delves into the exciting possibility of a connection between variations in the microbiome and ITW. The purpose of this review is to establish a strong theoretical foundation and highlight the benefits of further exploring the possible connection between alterations in the microbiome and TW for further studies of ITW etiology.

Rapid review shows that probiotics and fermented infant formulas do not cause d-lactic acidosis in healthy children

AIM

Extensive ongoing research on probiotics and infant formulas raises a number of safety questions. One concern is the potential influence of d-lactic acid-containing preparations on the health of infants and children. The aim of this review was to summarise the available knowledge on the ingestion of d-lactic acid-producing bacteria, acidified infant formulas and fermented infant formulas as a potential cause of paediatric d-lactic acidosis.

METHODS

A Medline database search was performed in July 2017, with no restrictions on the language, article type or publication date. The 1715 search results were screened for clinical trials, review articles, case series and case reports of relevance to the topic.

RESULTS

We identified five randomised controlled trials from 2005 to 2017 covering 544 healthy infants and some case reports and experimental studies. No clinically relevant adverse effects of d-lactic acid-producing probiotics and fermented infant formulas were described in healthy children. However, a harmless, subclinical accumulation of d-lactate was theoretically possible. The only known cases of paediatric d-lactic acidosis occurred in patients with short bowel syndrome or, historically, in infants fed with acidified formulas.

CONCLUSION

Our main finding was that probiotics and fermented formulas did not cause d-lactic acidosis in healthy children.

Safety and tolerance of three probiotic strains in healthy infants: a multi-centre randomized, double-blind, placebo-controlled trial

Some strains of species belonging to the genera Bifidobacterium and Lactobacillus are used in order to maintain health. Although these organisms have a long record of safe use, it is important to assess their safety and tolerance in potentially vulnerable populations, such as infants. The objective of this study was to evaluate the safety and tolerance of three probiotic strains (Bifidobacterium longum subsp. infantis R0033, Bifidobacterium bifidum R0071 and Lactobacillus helveticus R0052) in healthy infants aged 3 to 12 months. A multi-centre randomized, double-blind, placebo-controlled intervention study with 221 healthy full-term infants was conducted. Infants received either a placebo or one of the 3 probiotic strains (3×109 cfu) daily during an 8 week intervention period. Growth (weight, height and head circumference), adverse events (AEs)/serious adverse events (SAEs), concentrations of D-lactic acid in urine samples, characteristics of the stools and use of medication were collected for safety evaluation. All 4 groups were homogeneous with respect to age, gender, feeding type, ethnicity, height, weight and head circumference at the start of the study. The results showed that changes in growth (weight, height and head circumference) were equivalent in all 4 groups. No SAEs were reported. Total number of AEs recorded was equivalent in all groups. Thus, the use of B. infantis R0033, L. helveticus R0052 and B. bifidum R0071 in infancy is safe, and well tolerated.

Normal growth of infants receiving an infant formula containing Lactobacillus reuteri, galacto-oligosaccharides, and fructo-oligosaccharide: a randomized controlled trial

BACKGROUND

The safety of an infant formula containing a new mixture of the prebiotics galacto-oligosaccharides (GOS) and fructo-oligosaccharide (FOS) and the probiotic Lactobacillus reuteri needs to be evaluated.

METHODS

Healthy term infants in Singapore were randomly assigned (using computer-generated allocation sequences) to receive exclusively an experimental infant formula containing L. reuteri, GOS (5.50 g/L), and FOS (0.36 g/L) or a control formula containing only L. reuteri from enrollment (7-14 days of age) to 4 months of age. The primary objective of this trial was to demonstrate that weight change between birth and 4 months of age in infants fed the experimental formula was not inferior to World Health Organization (WHO) Child Growth standards. The non-inferiority margin was -0.5 standard deviations (SD). The secondary objectives were to compare changes in anthropometric measurements (weight, length, body mass index, and head circumference), digestive tolerance, stool bacterial counts, urinary D- and L- lactate concentrations, and adverse events in the two formula groups.

RESULTS

The intention-to-treat (ITT) population included all randomized infants stratified by gender, (experimental group, N = 68 and control group, N = 72). The per-protocol (PP) population included 61 infants in the experimental and 62 infants in the control groups. The change in weight-for-age z-score between birth and 4 months was +0.93 (95% confidence interval [CI]: +0.63 to +1.23) SD in the experimental group and +0.92 (95% CI: +0.62 to +1.22) SD in the control group in the PP population, indicating non-inferior weight gain in both formulas groups compared with WHO standards. The ITT population had similar results. Liquid stools occurred more frequently in the experimental compared with the control group and median bifidobacteria, lactobacilli, and enterococci counts were higher in the experimental group (p < 0.05). Other secondary outcomes were not significantly different between groups.

CONCLUSIONS

Infant formula containing L. reuteri + GOS/FOS supports normal growth and is safe.

TRIAL REGISTRATION

ClinicalTrial.gov: NCT01010113.

A Randomized Double Blind Controlled Safety Trial Evaluating d-Lactic Acid Production in Healthy Infants Fed a Lactobacillus reuteri-containing Formula

BACKGROUND

d-Lactic acidosis in infants fed lactic acid bacteria-containing products is a concern.

METHODS

The primary objective of this non-inferiority trial was to compare urinary d-lactic acid concentrations during the first 28 days of life in infants fed formula containing Lactobacillus reuteri (1.2 × 10⁶ colony forming units (CFU)/ml) with those fed a control formula. The non-inferiority margin was set at a two-fold increase in d-lactic acid (0.7 mmol/mol creatinine, log-transformed). Healthy term infants in Greece were enrolled between birth and 72 hours of age, and block randomized to a probiotic (N = 44) or control (N = 44) group. They were exclusively fed their formulae until 28 days of age and followed up at 7, 14, 28, 112, and 168 ± 3 days. Anthropometric measurements were taken at each visit and tolerance recorded until 112 days. Urine was collected before study formula intake and at all visits up to 112 days and blood at 14 days.

RESULTS

d-Lactic acid concentration in the probiotic group was below the non-inferiority margin at 28 days: treatment effect −0.03 (95% confidence interval [CI]: [−0.48 to 0.41]) mmol/mol creatinine but was above the non-inferiority margin at 7 and 14 days—treatment effect 0.50 (95% CI: [0.05–0.96]) mmol/mol creatinine and 0.45 (95% CI: [0.00–0.90]) mmol/mol creatinine, respectively. Blood acid excess and pH, anthropometry, tolerance, and adverse events (AEs) were not significantly different between groups.

CONCLUSION

Intake of L. reuteri-containing formula was safe and did not cause an increase in d-lactic acid beyond two weeks.

Growth advantage of Streptococcus thermophilus over Lactobacillus bulgaricus in vitro and in the gastrointestinal tract of gnotobiotic rats

The yoghurt bacteria, Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus, are alleged to have beneficial effects on human health. The objective of this study was to characterise growth, biochemical activity and competitive behaviour of these two bacteria in vitro and in vivo. S. thermophilus LMD-9 and L. bulgaricus ATCC 11842 growth and lactate production were monitored in different media and in the gastrointestinal tract (GIT) of germ-free rats. In vitro, particularly in milk, S. thermophilus had a selective growth advantage over L. bulgaricus. The GIT of germ-free rats not supplemented with lactose was colonised by S. thermophilus but not by L. bulgaricus. Both bacteria were able to colonise the GIT of germ-free rats supplemented with 45 g/l lactose in their drinking water. However, if germ-free rats were inoculated with a mixture of the two bacteria and were supplemented with lactose, S. thermophilus rapidly and extensively colonised the GIT (1010 cfu/g faeces) at the expense of L. bulgaricus, which remained in most cases at levels <102 cfu/g faeces. S. thermophilus specifically produced L-lactate, while L. bulgaricus produced only D-lactate, both in vitro and in vivo. S. thermophilus showed competitive and growth advantage over L. bulgaricus in vitro as well as in vivo in the GIT of germ-free rats and, accordingly, L-lactate was the main lactate isomer produced.

L(+) and D(-) lactate are increased in plasma and urine samples of type 2 diabetes as measured by a simultaneous quantification of L(+) and D(-) lactate by reversed-phase liquid chromatography tandem mass spectrometry

BACKGROUND

Plasma and urinary levels of D-lactate have been linked to the presence of diabetes. Previously developed techniques have shown several limitations to further evaluate D-lactate as a biomarker for this condition.

METHODS

D- and L-lactate were quantified using ultraperformance liquid chromatography tandem mass spectrometry with labelled internal standard. Samples were derivatized with diacetyl-L-tartaric anhydride and separated on a C(18)-reversed phase column. D- and L-lactate were analysed in plasma and urine of controls, patients with inflammatory bowel disease (IBD), and patients with type 2 diabetes (T2DM).

RESULTS

Quantitative analysis of D- and L-lactate was achieved successfully. Calibration curves were linear (r(2) > 0.99) over the physiological and pathophysiological ranges. Recoveries for urine and plasma were between 96% and 113%. Inter- and intra-assay variations were between 2% and 9%. The limits of detection of D-lactate and L-lactate in plasma were 0.7 μmol/L and 0.2 μmol/L, respectively. The limits of detection of D-lactate and L-lactate in urine were 8.1 nmol/mmol creatinine and 4.4 nmol/mmol creatinine, respectively. Plasma and urinary levels of D- and L-lactate were increased in patients with IBD and T2DM as compared with controls.

CONCLUSION

The presented method proved to be suitable for the quantification of D- and L-lactate and opens the possibility to explore the use of D-lactate as a biomarker.

Sensitive determination of D-lactic acid and L-lactic acid in urine by high-performance liquid chromatography-tandem mass spectrometry

D-lactic acid in urine originates mainly from bacterial production in the intestinal tract. Increased D-lactate excretion as observed in patients affected by short bowel syndrome or necrotizing enterocolitis reflects D-lactic overproduction. Therefore, there is a need for a reliable and sensitive method able to detect D-lactic acid even at subclinical elevation levels. A new and highly sensitive method for the simultaneous determination of L- and D-lactic acid by a two-step procedure has been developed. This method is based on the concentration of lactic acid enantiomers from urine by supported liquid extraction followed by high-performance liquid chromatography-tandem mass spectrometry. The separation was achieved by the use of an Astec Chirobiotic™ R chiral column under isocratic conditions. The calibration curves were linear over the ranges of 2-400 and 0.5-100 µmol/L respectively for L- and D-lactic acid. The limit of detection of D-lactic acid was 0.125 µmol/L and its limit of quantification was 0.5 µmol/L. The overall accuracy and precision were well within 10% of the nominal values. The developed method is suitable for production of reference values in children and could be applied for accurate routine analysis.

Peritoneal and plasma D-lactate concentrations in horses with colic

OBJECTIVE

To evaluate the association between peritoneal fluid and plasma d-lactate concentration with variables used in the diagnosis and prognosis of horses with colic.

ANIMALS

Clinically healthy horses (n=6) and 90 horses with colic.

STUDY DESIGN

Prospective cross-sectional study.

METHODS

D-lactate concentration was determined in peritoneal fluid and plasma of all horses. Information on other blood and peritoneal fluid variables, signalment, results from the physical examination, outcome, need for surgery, lesion location, and type was retrieved from medical records.

RESULTS

Peritoneal D-lactate concentration was strongly correlated with plasma D-lactate concentration (r=0.71; P<.001). Peritoneal and plasma D-lactate concentrations were positively correlated with peritoneal (r=0.8; P<.001) and plasma L-lactate (r=0.33; P=.001) concentrations, respectively. Peritoneal D-lactate concentration was negatively correlated with survival to discharge (U=430.5; P<.001). Median peritoneal D-lactate concentration of horses with septic peritonitis (455.2 μmol/L) and horses with gastrointestinal rupture (599.5 μmol/L) were higher compared with horses with nonstrangulating obstructions (77.7 μmol/L). A cut-off concentration of peritoneal D-lactate of 116.6 μmol/L had a sensitivity of 0.813 and a specificity of 0.651 to differentiate between nonstrangulating and strangulating obstructions.

CONCLUSIONS

Peritoneal D-lactate concentration may be more useful for identifying horses with strangulating obstructions (high sensitivity, low probability of a false negative) than to ruling out strangulating obstruction (moderate specificity, high probability of a false positive).

Increased plasma d-lactic acid associated with impaired memory in rats

AIM

d-Lactic acidosis is associated with memory impairment in humans. Recent research indicates that d-lactic acid may inhibit the supply of energy from astrocytes to neurons involved with memory formation. However, little is known about the effects of increased hind-gut fermentation due to changes in diet on circulating lactic acid concentrations and memory.

METHOD

Thirty-six male Wistar rats were fed three dietary treatments: a commercial rat and mouse chow, a soluble carbohydrate based diet or a fermentable carbohydrate based diet. The parameters estimating memory were examined by employing the object recognition test. Physical parameters of fermentation including hind-gut and plasma lactic acid concentrations were examined after sacrifice, either 3 or 21h after feeding.

RESULTS

Increased fermentation in the hind-gut of rats, indicated by lower caecum pH, was associated with increased plasma l-lactic acid (r=-0.41, p=0.020) and d-lactic acid (r=-0.33, p=0.087). Memory, being able to discriminate between a familiar and a novel object during the object recognition test, was reduced with increasing plasma d-lactic acid (r=-0.51, p=0.021).

CONCLUSIONS

Memory impairment was associated with alterations in plasma d-lactic acid following the fermentation of carbohydrate in the hind-gut. Further work is still required to determine whether these effects are mediated centrally or via direct connections through the enteric nervous system.

Determination of lactic acid enantiomers in human urine by high-performance immunoaffinity LC-MS

In this study, a monoclonal anti-d-hydroxy acid antibody was used as chiral selector for chromatographic enantiomer separation and quantification of lactic acid contained in human urine samples. The immunoaffinity column was directly coupled to an electrospray ionization mass spectrometer for detection. Separations were performed at room temperature and under isocratic conditions using ammonium bicarbonate buffer (pH 7.8; 10 mM) as mobile phase. No elaborate sample preparation or analyte derivatization was required and individual runs were completed in less than 10 min.

An approach to the design of a particulate system for oral protein delivery. I. In vitro stability of various poly (alpha-hydroxy acids)-microspheres in simulated gastrointestinal fluids

The stability of various biodegradable polyester polymers with different molecular weights and lactic/glycolic acids ratios were evaluated in simulated gastrointestinal fluids as an approach to apply microparticles for oral protein delivery on the basis of particle uptake mechanism. A common w/o/w emulsion solvent evaporation technique using dichloromethane for dissolving the polymer and polyvinyl alcohol as the stabilizer was used for encapsulation. Microspheres were incubated at 37 degrees C in USP simulated fluids with a concentration of 20 mg mL(-1) and also in the literature, which suggested fed or fasted simulated intestinal fluids for different times up to 24 h, while shaking at 75 rpm. The stability assessment was done by detecting pH alterations of the media, enzymatic assay of L-lactic acid, performing differential scanning calorimetric studies and observing the size and morphology of particles. Results showed that the three polymers, namely Resomers R207, RG756 and RG505, could be suitable for the preparation of protein-loaded microspheres.

Analytical investigation: assay of D-lactate in diabetic plasma and urine

OBJECTIVE

In this study we developed a 96-micro plate enzymatic assay for D-lactate in plasma and urine.

METHODS

D-lactate was assayed enzymatically with a UV-spectrophotometer in plasma from 38 and in urine from 37 diabetics and from 42 non-diabetic controls.

RESULTS

The within-run coefficients of variations (CV) were 2.6% for plasma and 5.7% for urine. The between run CVs were 6.8% for plasma and 6.7% for urine. The mean recovery with standard deviation (S.D.) was 107.4+/-7.3% for plasma and 100.1%+/-6.7% for urine. The plasma D-lactate in diabetics were (mean+/-S.D.) 39.6+/-23.7 microM. We found significant difference between the urinary d-lactate in controls and diabetics (18.2+/-12.0 vs. 35.9+/-24.2 microM/mM creatinine, p<0.0001).

CONCLUSIONS

The assay proved reliable with acceptable precision and recovery. Results suggest that diabetics have elevated urinary and plasma D-lactate as compared to controls.

Reverse iontophoresis of L‐lactate: In vitro and in vivo studies

This work investigates the reverse iontophoretic extraction of lactate, a widely used marker of tissue distress in critically ill patients and of sports performance. In vitro experiments were performed to establish the relationship between subdermal lactate levels and lactate iontophoretic extraction fluxes. Subsequently, the iontophoretic extraction of lactate was performed in vivo in healthy volunteers. Lactate was quickly and easily extracted by iontophoresis both in vitro and in vivo. During a short initial phase, iontophoresis extracts the lactate present in the skin reservoir, providing information of relevance, perhaps, for dermatological and cosmetic applications. In a second step, lactate is extracted from the interstitial subdermal fluid allowing local lactate kinetics to be followed in a completely non-invasive way. The simultaneous in vivo extraction of chloride, and its possible role as an internal standard to calibrate lactate reverse iontophoretic fluxes, was also demonstrated. Despite these positive findings, however, considerably more research is necessary to eliminate potential artefacts and to facilitate interpretation of the data.

High performance liquid chromatography–tandem mass spectrometry (HPLC/MS/MS) assay for chiral separation of lactic acid enantiomers in urine using a teicoplanin based stationary phase

A novel method for the separation and simultaneous determination of urinary D- and L-lactic acid enantiomers by high performance liquid chromatography-tandem mass spectrometry (HPLC/MS/MS) is presented. The chiral separation was optimized on a Chirobiotic teicoplanin aglyocone (TAG) column. Most interestingly, the addition of water in small volume fraction to the polar organic mobile phase was found to significantly improve the chromatography. Calibration curves were linear (r2>0.9950) over the range 3-1000 mg/L for L-lactic acid and 0.5-160.8 mg/L for D-lactic acid. The limit of detection (LOD) (S/N=3) and limit of quantification (LOQ) (S/N=10) were determined experimentally (n=3) to be 0.2 and 0.5mg/L for L-lactic acid and 0.4 and 1.3 mg/L for D-lactic acid, respectively. The normal patient range of L-lactic acid was 1-20 microg/mg creatinine with an elevated value of 85 microg/mg creatinine. For D-lactic acid, the range of normal values were between 0 and 5 microg/mg creatinine with an elevated value of 40 microg/mg creatinine. Finally, the validated method allows for rapid analysis with a total run time of 7.5 min.

[D-lactic acidosis in an 11-year-old patient with short bowel syndrome]

The short bowel syndrome is the result of a congenital or acquired loss of a large part of the small intestine. The most frequent causes of surgical resection of the intestine in infants are arterial or venous thrombosis, intestinal volvulus, necrotizing enterocolitis, and Crohn's disease. Symptoms include nutrient and electrolyte malabsorption, steatorrhea and diarrhea, which can result in failure to thrive. The consequences of extensive small bowel resections consist of nutritional deficiencies, gastric acid hypersecretion, nephrolithiasis, cholelithiasis and lactic acidosis. Of these, D-lactic acidosis is an infrequent but important complication because of the symptoms that it can produce. D-lactic acid in the human organism is generated by intestinal bacteria, D-lactate ingestion, or endogenous production in the methyl glycoxylase pathway. Neurological symptoms such as somnolence, ataxia or altered behavior in a patient with short bowel syndrome should make us think of D-lactic acidosis caused by bacterial overgrowth. We present the case of an 11-year-old boy with short bowel syndrome secondary to multiple resections during the postnatal period who was admitted to hospital for episodes of confusion and altered behavior. The diagnosis was lactic acidosis. Outcome was favorable due to prompt instauration of treatment.

Application of optical isomer analysis by diastereomer derivatization GC/MS to determine the condition of patients with short bowel syndrome

To establish a method for separating the optical isomers of lactic acid, we modified the derivatization steps in our procedure for urinary mass-screening for inborn errors of metabolism. For chiral recognition, we chose O-trifluoroacetyl-(-)-menthylation derivatization instead of our previous method, trimethylsilyl derivatization, and the samples were then analyzed under GC/MS by capillary gas chromatography on a DB-5MS column. This method can be used to follow-up the condition of a patient with short bowel syndrome and to prevent onset and/or seizure. d-Lactic acid was also isolated from the urine of healthy controls as one of the main peaks in the chromatogram.

Optically Specific Detection of D- and L-Lactic Acids by a Flow-Injection Dual Biosensor System with On-line Microdialysis Sampling

A flow-injection dual biosensor system with microdialysis sampling is proposed for the simultaneous determination of D-lactic and L-lactic acids. The dialysate from the microdialysis tube is delivered to a sample loop of the six-way autoinjector and then automatically injected into the flow-injection line with a dual enzyme electrode arranged in perpendicular to the flow direction. The dual enzyme electrode is constructed by hybridizing a poly(1,2-diaminobenzene) film into two sensing parts which respond selectively to D-lactic and L-lactic acids, respectively, without any cross-reactivity. The proposed flow-injection analysis method can be successfully applied to the simultaneous determination of D,L-lactic acids in alcoholic beverages.

D-lactate in human and ruminant metabolism

D-lactate is normally present in the blood of mammals at nanomolar concentrations due to methylglyoxal metabolism; millimolar d-lactate concentrations can arise due to excess gastrointestinal microbial production. Grain overload in ruminants, short-bowel syndrome in humans, and diarrhea in calves can all result in profound D-lactic acidemia, with remarkably similar neurological manifestations. In the past, D-lactate was thought to be excreted mainly in the urine, and metabolized slowly by the enzyme d-alpha-hydroxy acid dehydrogenase. More recent studies reported that mammals have a relatively high capacity for D-lactate metabolism and identified a putative mammalian D-lactate dehydrogenase. A growing body of literature is also emerging describing subclinical elevation of D-lactate as an indicator of sepsis and trauma. This article describes advances in the understanding of D-lactate metabolism, D-lactic acidosis in ruminants and humans, and subclinical elevation of d-lactate.

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Organic Acids in the Second Morning Urine in a Healthy Swiss Paediatric Population

Organic acid analysis is used for the early detection/ exclusion and for the follow-up of inherited disorders of amino acid and organic acid metabolism. Urinary organic acid concentrations in 417 healthy Caucasian children (1 day to 17 years of age) were determined after liquid solid extraction, as their trimethylsilyl derivatives, by gas chromatography and mass spectrometry. Concentrations of most of the organic acids adjusted for creatinine tend to decrease with age. No differences were found between gender except for the Krebs cycle intermediates in the older age groups. In neonates, the immaturity of the neonatal kidney led to a much larger variation of organic acid levels when related to creatinine. The low number of subjects (n = 36-52) per age class resulted in large 95% confidence intervals of the percentiles used for decision. This must be taken into account when using the data for exclusion or diagnosis of disorders.

Identification of putative mammalian D-lactate dehydrogenase enzymes

Mammalian L-isomer dehydrogenases represent an expansive and well characterized class of metabolic enzymes. Surprisingly, little is known regarding their evolutionarily distinct counterparts, D-isomer dehydrogenases, since few mammalian D-isomer 2-hydroxy acid enzymes have been isolated. Here we present the identification and initial characterization of putative human and murine D-lactate dehydrogenases (DLD) that can interact with the muscle-specific cysteine-rich protein CRP3/MLP. Sequence analysis reveals that the human and mouse transcripts encode novel proteins that display strong similarities to the yeast D-lactate dehydrogenase proteins DLD1, AIP2, and YEL071W. Expression analysis of the mammalian proteins indicates widespread distribution with transcripts present in striated muscle tissues and a variety of other tissue types. Immunofluorescence subcellular localization of the mouse DLD protein indicates that it resides within mitochondria, a feature shared by many dehydrogenases. The identification of the human and mouse DLD clones provides new insight regarding the activity of D-isomer-specific enzymes in mammalian cells.