[Determination of organic acids and anions in exhaled breath by condensation collection-ion chromatography].

A non-invasive condensation collection-ion chromatography method was established for the determination of organic acids and anions including lactic acid, formic acid, acetic acid, pyruvic acid, chloride, nitrate, nitrite, and sulfate in the exhaled breath of humans. The breath exhaled was condensed and collected using a home-made exhaled breath condensation equipment. This equipment included a disposable mouthpiece as a blow-off port, one-way valve and flow meter, cold trap, disposable condensate collection tube placed in the cold trap, and gas outlet. A standard sampling procedure was used. Before collection, the collection temperature and sampling volume were set on the instrument control panel, and sampling was started when the cold-trap temperature dropped to the set value, while maintaining the balance. Subjects were required to gargle with pure water before sampling. During the sampling process, the subjects were required to inhale deeply until the lungs were full of gas and then exhale evenly through the air outlet. When the set volume was collected, the instrument made a prompt sound; then, the collection was immediately ended, the expiration time was recorded, and the average collection flow was calculated according to the expiration time and sampling volume. After collection, the disposable condensation collection tube was immediately taken out, sealed, and stored in the refrigerator at -20 ℃ away from light, and immediately used for further testing. The organic acids and anions in exhaled breath condensation (EBC) were filtered through a 0.22 µm membrane filter before injection and detected by ion chromatography with conductivity detection. Factors such as collection temperature and collection flow rate during condensation collection were optimized. The optimal cooling temperature was set at -15 ℃, and the optimal exhaled breath flow rate was set at 15 L/min. The mobile phase consisted of a mixture of sodium carbonate (1.5 mmol/L) and sodium bicarbonate (3 mmol/L). The flow rate was 0.8 mL/min, and the injection volume was 100 µL. An IC-SA3 column (250 mm×4.0 mm) was used, and the temperature was set at 45 ℃. An ICDS-40A electrodialysis suppressor was used, and the current was set at 150 mA. The linear ranges of the eight organic acids and anions were 0.1-10.0 mg/L; their correlation coefficients (r) were ≥0.9993. The limits of detection (LODs) for the eight organic acids and anions were 0.0017-0.0150 mg/L based on a signal-to-noise ratio of 3, and the limits of quantification (LOQs) were 0.0057-0.0500 mg/L based on a signal-to-noise ratio of 10. The intra-day precisions were 5.06%-6.33% (n=5), and the inter-day precisions were 5.37%-7.50% (n=5). This method was used to detect organic acids and anions in the exhaled breath of five healthy subjects. The contents of organic acids and anions in the exhaled breath were calculated. The content of lactic acid was relatively high, at 1.13-42.3 ng/L, and the contents of other seven organic acids and anions were 0.18-11.0 ng/L. During a 10 km-long run, the majority of organic acids and anions in the exhaled breath of five subjects first increased and then decreased. However, due to abnormal metabolism, the content changes of lactic acid, acetic acid, pyruvic acid and chloride in one subject were obviously different from others during exercise, showing a continuous rise. This method has the advantages of involving a simple sampling process and exhibiting good precision, few side effects, and no obvious discomfort or risk to the subjects. This study provides experimental ideas and a theoretical basis for future research on human metabolites.

Pyrene-Appended Boronic Acids on Graphene Foam Electrodes Provide Quantum Capacitance-Based Molecular Sensors for Lactate.

Molecular recognition and sensing can be coupled to interfacial capacitance changes on graphene foam surfaces linked to double layer effects and coupled to enhanced quantum capacitance. 3D graphene foam film electrodes (Gii-Sens; thickness approximately 40 µm; roughness factor approximately 100) immersed in aqueous buffer media exhibit an order of magnitude jump in electrochemical capacitance upon adsorption of a charged molecular receptor based on pyrene-appended boronic acids (here, 4-borono-1-(pyren-2-ylmethyl)pyridin-1-ium bromide, or abbreviated T1). This pyrene-appended pyridinium boronic acid receptor is employed here as a molecular receptor for lactate. In the presence of lactate and at pH 4.0 (after pH optimization), the electrochemical capacitance (determined by impedance spectroscopy) doubles again. Lactic acid binding is expressed with a Hillian binding constant (Klactate = 75 mol-1 dm3 and α = 0.8 in aqueous buffer, Klactate = 460 mol-1 dm3 and α = 0.8 in artificial sweat, and Klactate = 340 mol-1 dm3 and α = 0.65 in human serum). The result is a selective molecular probe response for lactic acid with LoD = 1.3, 1.4, and 1.8 mM in aqueous buffer media (pH 4.0), in artificial sweat (adjusted to pH 4.7), and in human serum (pH adjusted to 4.0), respectively. The role of the pyrene-appended boronic acid is discussed based on the double layer structure and quantum capacitance changes. In the future, this new type of molecular capacitance sensor could provide selective enzyme-free analysis without analyte consumption for a wider range of analytes and complex environments.

Reduced graphene oxide-functionalized polymer microneedle for continuous and wide-range monitoring of lactate in interstitial fluid.

Despite substantial developments in minimally invasive lactate monitoring microneedle electrodes, most such electrode developments have focused on either sensitivity or invasiveness while ignoring a wide range of detection, which is the most important factor in measuring the normal range of lactate in interstitial fluid (ISF). Herein, we present a polymer-based planar microneedle electrode fabrication using microelectromechanical and femtosecond laser technology for the continuous monitoring of lactate in ISF. The microneedle is functionalized with two-dimensional reduced graphene oxide (rGO) and electrochemically synthesized platinum nanoparticles (PtNPs). A particular quantity of Nafion (1.25 wt%) is applied on top of the lactate enzyme to create a diffusion-controlled membrane. Due to the combined effects of the planar structure of the microneedle, rGO, and membrane, the biosensor exhibited excellent linearity up to 10 mM lactate with a limit of detection of 2.04 µM, high sensitivity of 43.96 µA mM-1cm-2, a reaction time of 8 s and outstanding stability, selectivity, and repeatability. The feasibility of the microneedle is evaluated by using it to measure lactate concentrations in artificial ISF and human serum. The results demonstrate that the microneedle described here has great potential for use in real-time lactate monitoring for use in sports medicine and treatment.

Influence of lactic acid fermentation on the phenolic profile, antioxidant activities, and volatile compounds of black chokeberry (Aronia melanocarpa) juice.

Lactic acid fermentation is an effective method for improving the quality of black chokeberry. This study aimed to investigate the influence of lactic acid bacteria on the phenolic profile, antioxidant activities, and volatiles of black chokeberry juice. Initially, 107  cfu/mL of Lactiplantibacillus plantarum, Lactobacillus acidophilus, and Lacticaseibacillus rhamnosus were inoculated into pasteurized black chokeberry juice and fermented for 48 h at 37°C. All these strains enhanced the total phenolic and total flavonoid contents, with La. acidophilus showing the highest total phenolic (1683.64 mg/L) and total flavonoid (659.27 mg/L) contents. Phenolic acids, flavonoids, and anthocyanins were identified using ultrahigh-performance liquid chromatography-tandem mass spectrometry. The prevalent phenolic acid, flavonoid, and anthocyanin in the lactic-acid-fermented black chokeberry juice were cinnamic acid, rutin, and cyanidin-3-O-rutinoside, respectively. Furthermore, following fermentation, the DPPH and ABTS scavenging capacity, as well as the reducing power capacity, increased from 59.98% to 92.70%, 83.06% to 94.95%, and 1.24 to 1.82, respectively. Pearson's correlation analysis revealed that the transformation of phenolic acids, flavonoids, and anthocyanins probably contributed to enhancing antioxidant activities and color conversation in black chokeberry juice. A total of 40 volatiles were detected in the fermented black chokeberry juice by gas chromatography-ion mobility spectrometry. The off-flavor odors, such as 1-penten-3-one and propanal in the black chokeberry juice, were weakened after fermentation. The content of 2-pentanone significantly increased in all fermented juice, imparting an ethereal flavor. Hence, lactic acid fermentation can effectively enhance black chokeberry products' flavor and prebiotic value, offering valuable insights into their production. PRACTICAL APPLICATION: The application of lactic acid bacteria in black chokeberry juice not only enhances its flavor but also improves its health benefits. This study has expanded the range of black chokeberry products and offers a new perspective for the development of the black chokeberry industry.

Silica nanoparticles containing nano-silver and chlorhexidine respond to pH to suppress biofilm acids and modulate biofilms toward a non-cariogenic composition.

OBJECTIVES: Dental caries is caused by acids from biofilms. pH-sensitive nanoparticle carriers could achieve improved targeted effectiveness. The objectives of this study were to develop novel mesoporous silica nanoparticles carrying nanosilver and chlorhexidine (nMS-nAg-Chx), and investigate the inhibition of biofilms as well as the modulation of biofilm to suppress acidogenic and promote benign species for the first time. METHODS: nMS-nAg was synthesized via a modified sol-gel method. Carboxylate group functionalized nMS-nAg (COOH-nMS-nAg) was prepared and Chx was added via electrostatic interaction. Minimal inhibitory concentration (MIC), inhibition zone, and growth curves were evaluated. Streptococcus mutans (S. mutans), Streptococcus gordonii (S. gordonii), and Streptococcus sanguinis (S. sanguinis) formed multispecies biofilms. Metabolic activity, biofilm lactic acid, exopolysaccharides (EPS), and TaqMan real-time polymerase chain reaction (RT-PCR) were tested. Biofilm structures and biomass were observed by scanning electron microscopy (SEM) and live/dead bacteria staining. RESULTS: nMS-nAg-Chx possessed pH-responsive properties, where Chx release increased at lower pH. nMS-nAg-Chx showed good biocompatibility. nMS-nAg-Chx exhibited a strong antibacterial function, reducing biofilm metabolic activity and lactic acid as compared to control (p < 0.05, n = 6). Moreso, biofilm biomass was dramatically suppressed in nMS-nAg-Chx groups. In control group, there was an increasing trend of S. mutans proportion in the multispecies biofilm, with S. mutans reaching 89.1% at 72 h. In sharp contrast, in nMS-nAg-Chx group of 25 µg/mL, the ratio of S. mutans dropped to 43.7% and the proportion of S. gordonii and S. sanguinis increased from 19.8% and 10.9 to 69.8% and 56.3%, correspondingly. CONCLUSION: pH-sensitive nMS-nAg-Chx had potent antibacterial effects and modulated biofilm toward a non-cariogenic tendency, decreasing the cariogenic species nearly halved and increasing the benign species approximately twofold. nMS-nAg-Chx is promising for applications in mouth rinse and endodontic irrigants, and as fillers in resins to prevent caries.

Enhancing Kokumi Sensation and Reducing Bitterness in Acid-Hydrolyzed Vegetable Proteins through Lactate and Thermal Processing.

Previous studies have demonstrated that thermal processing in the presence of lactate and amino acids can produce taste-active N-lactoyl amino acids. This study aimed to investigate the impact of lactate and thermal processing on the sensory characteristics of acid-hydrolyzed vegetable proteins (aHVP). The results showed that the processed aHVP exhibited enhanced kokumi, a milder umami taste, and reduced bitterness on treatment with 1% lactate at 110 °C for 3 h or 3% lactate at 120 °C for 2 h compared to the unprocessed samples. Partial or orthogonal least-squares discriminant analysis and variable importance in projection (VIP) analyses revealed the significant contributions of N-,l-Lac-l-hydrophobic AAs [-Met, -Ile, -Leu, -Val, and -Phe (VIP > 1.2)] to the observed differences between the processed and unprocessed samples. Electronic tongue analysis confirmed the sensory findings and indicated a decrease in the aftertaste of bitterness in the processed samples. Furthermore, the study identified the sensory characteristics of N-l-Lac-l-Met, -Ile, and -Leu, highlighting their potential to enhance salty, umami, and kokumi perception in simulated broth. Furthermore, the study incorporated the addition of bitter amino acids (Val, Ile, Leu, Tyr, Phe, Lys, His, and Arg) and the aforementioned N-l-Lac-l-AAs to aHVP, providing further evidence for their contributions to bitterness and aftertaste-B as well as the kokumi differences, respectively. This study provides valuable insights into the sensory effects of lactate and thermal processing on aHVP, facilitating the development of improved taste-enhancing strategies.

Paper-based chiral biosensors using enzyme encapsulation in hydrogel network for point-of-care detection of lactate enantiomers.

Chiral analysis is of pivotal importance in a variety of fields due to the different biological activities and functions of enantiomers. Here, we develop a simple paper-based chiral biosensor that can perform sample-to-answer simultaneous analysis of lactate enantiomers in human serum samples. By modification of alginate hydrogel with "egg-box" three-dimensional network structure on a glass microfiber paper, reagents of enantiomer-selective enzymatic reactions are efficiently encapsulated forming the sensing regions for chiral analysis. Dual enzyme catalytic system (lactate dehydrogenase and glutamic pyruvic transaminase) is utilized to enhance the response of the biosensor. A smartphone with color analysis software is used to collect and analyze the fluorescence signal from the product nicotinamide adenine dinucleotide. The results show that the sensor has excellent selectivity toward lactate enantiomers with low limit-of-detection of (30.0 ± 0.7) µM for L-lactate and (3.0 ± 0.2) µM for D-lactate, and wide linear detection range of 0.1-3.0mM and 0.01-0.5 mM for L-lactate and D-lactate respectively. The proposed method is successfully applied to the simultaneous detection of L-/D-lactate concentrations in human serum with satisfactory accuracy. Our study provides a robust approach for developing chiral biosensors, which would have promising application prospect in point-of-care testing (POCT) analysis of various biological and food samples.

Influence of lactic acid fermentation on the microbiological parameters, biogenic amines, and volatile compounds of bovine colostrum.

In this study we hypothesized that the relations between the bovine colostrum (BC) microbiota, biogenic amine (BA) as well as volatile compound (VC) profiles can lead to new deeper insights concerning the BC changes during the biological preservation. To implement such an aim, BC samples were collected from 5 farms located in Lithuania and fermented with Lactiplantibacillus plantarum and Lacticaseibacillus paracasei strains. Nonfermented and fermented BC were subjected to microbiological [lactic acid bacteria (LAB), Escherichia coli, and total bacteria (TBC), total Enterobacteriaceae (TEC) and total mold and yeast (M-Y) viable counts] and physicochemical (pH, color coordinates, BA content and VC profile) parameters evaluation, and the relationship between the tested parameters were also further analyzed. In comparison pH and dry matter (DM) of nonfermented samples, significant differences were not found, and pH of BC was, on average, 6.30, and DM, on average, 27.5%. The pH of fermented samples decreased, on average, until 4.40 in Lp. plantarum fermented group, and, on average, until 4.37 in Lc. paracasei fermented group. Comparing color characteristics among nonfermented BC groups, significant differences between lightness (L*) and yellowness (b*) were not detected, however, the origin (i.e., agricultural company), LAB strain used for fermentation and the interaction between these factors were statistically significant on BC redness (a*) coordinate. The microbial contamination among all the tested BC groups was similar. However, different LAB strains used for BC fermentation showed different effects toward the microbial contamination reduction, and specifically Lc. paracasei was more effective than Lp. plantarum strain. Predominant BA in BC were putrescine and cadaverine. The main VC in nonfermented and fermented BC were decane, 2-ethyl-1-hexanol, dodecane, 1,3-di-tert-butylbenzene, 3,6-dimethyldecane and tetradecane. Moreover, this study showed worrying trends with respect to the frozen colostrum storage, because most of the dominant VC in BC were contaminants from the packaging material. Additionally, significant correlations between separate VC and microbial contamination were obtained. Finally, these experimental results showed that the separate VC in BC can be an important marker for biological as well as chemical contamination of BC. Also, it should be pointed out that despite the fermentation with LAB is usually described as a safe and natural process with many advantages, control of BA in the end product is necessary.

Machine learning assisted and smartphone integrated homogeneous electrochemiluminescence biosensor platform for sample to answer detection of various human metabolites.

The sensitive and accurate detection of glucose and lactate is essential for early diagnosis and effective management of diabetes complications. Herein, a 3D Printed ECL imaging system integrated with a Smartphone has been demonstrated to advance the traditional ECL to make a portable, affordable, and turnkey point-of-care solution to detect various human metabolites. A universal cross-platform application was introduced for analyzing ECL emitted signals to automate the whole detection process for real-time monitoring and rapid diagnostics. The developed ECL system was successfully applied and validated for detecting glucose and lactate using a single-electrode ECL biosensing platform. For glucose and lactate detection, the device showed a linear range from 0.1 mM to 1 mM and 0.1 mM-4 mM with a detection limit (LoD) of 0.04 mM and 0.1 mM, and a quantification limit (LoQ) of 0.142 mM and 0.342 mM, respectively. The developed method was evaluated for device stability, accuracy, interference, and real sample analysis. Furthermore, to assist in selecting the accurate and economic ECL sensing platform, SE-ECL devices fabricated via different fabrication approaches such as Laser-Induced Graphene, Screen Printing, and 3D Printing are studied for the conductivity of electrode and its significance on ECL signal. It was observed that emitted ECL signal is independent of the electrical conductivity for the same concentration of analytes. The findings suggested that the developed miniaturized point-of-care ECL platform would be a comprehensive and integrated solution for detecting other human metabolites and have the potential to be used in clinical applications.

Detection of lactate in human sweat via surface-modified, screen-printed carbon electrodes.

Real-time and continuous monitoring of lactate levels in sweat has been used as an indicator of physiological information to evaluate exercise outcomes and sports performance. We developed an optimal enzyme-based biosensor to detect the concentrations of lactate in different fluids (i.e., a buffer solution and human sweat). The surface of the screen-printed carbon electrode (SPCE) was first treated with oxygen plasma and then surface-modified by lactate dehydrogenase (LDH). The optimal sensing surface of the LDH-modified SPCE was identified by Fourier transform infrared spectroscopy and electron spectroscopy for chemical analysis. After connecting the LDH-modified SPCE to a benchtop E4980A precision LCR meter, our results showed that the measured response was dependent on the lactate concentration. The recorded data exhibited a broad dynamic range of 0.1-100 mM (R2 = 0.95) and a limit of detection of 0.1 mM, which was unachievable without the incorporation of redox species. A state-of-the-art electrochemical impedance spectroscopy (EIS) chip was developed to integrate the LDH-modified SPCE for a portable bioelectronic platform in the detection of lactate in human sweat. We believe the optimal sensing surface can improve the sensitivity of lactate sensing in a portable bioelectronic EIS platform for early diagnosis or real-time monitoring during different physical activities.

Lactate in exhaled breath condensate and its correlation to cancer: challenges, promises and a call for data.

Owing to its connection to cancer metabolism, lactate is a compound that has been a focus of interest in field of cancer biochemistry for more than a century. Exhaled breath volatile organic compounds (VOCs) and condensate analyses can identify and monitor volatile and non-VOCs, respectively, present in exhaled breath to gain information about the health state of an individual. This work aims to take into account the possible use of breath lactate measurements in tumor diagnosis and treatment control, to discuss technical barriers to measurement, and to evaluate directions for the future improvement of this technique. The use of exhaled breath condensate (EBC) lactic acid levels in disorders other than cancer is also discussed in brief. Whilst the use of EBC for the detection of lactate in exhaled breath is a promising tool that could be used to monitor and screen for cancer, the reliability and sensitivity of detection are uncertain, and hence its value in clinical practice is still limited. Currently, lactate present in plasma and EBC can only be used as a biomarker for advanced cancer, and therefore it presently has limited differential diagnostic importance and is rather of prognostic value.

HiSorb sorptive extraction for determining salivary short chain fatty acids and hydroxy acids in heart failure patients.

Variations in salivary short-chain fatty acids and hydroxy acids (e.g., lactic acid, and 3-hydroxybutyric acid) levels have been suggested to reflect the dysbiosis of human gut microbiota, which represents an additional factor involved in the onset of heart failure (HF) disease. The physical-chemical properties of these metabolites combined with the complex composition of biological matrices mean that sample pre-treatment procedures are almost unavoidable. This work describes a reliable, simple, and organic solvent free protocol for determining short-chain fatty acids and hydroxy acids in stimulated saliva samples collected from heart failure, obese, and hypertensive patients. The procedure is based on in-situ pentafluorobenzyl bromide (PFB-Br) derivatization and HiSorb sorptive extraction coupled to thermal desorption and gas chromatography-tandem mass spectrometry. The HiSorb extraction device is completely compatible with aqueous matrices, thus saving on time and materials associated with organic solvent-extraction methods. A Central Composite Face-Centred experimental design was used for the optimization of the molar ratio between PFB-Br and target analytes, the derivatization temperature, and the reaction time which were 100, 60 °C, and 180 min, respectively. Detection limits in the range 0.1-100 µM were reached using a small amount of saliva (20 µL). The use of sodium acetate-1-13C as an internal standard improved the intra- and inter-day precision of the method which ranged from 10 to 23%. The optimized protocol was successfully applied for what we believe is the first time to evaluate the salivary levels of short chain fatty acids and hydroxy acids in saliva samples of four groups of patients: i) patients admitted to hospital with acute HF symptoms, ii) patients with chronic HF symptoms, iii) patients without HF symptoms but with obesity, and iv) patients without HF symptoms but with hypertension. The first group of patients showed significantly higher levels of salivary acetic acid and lactic acid at hospital admission as well as the lowest values of hexanoic acid and heptanoic acid. Moreover, the significant high levels of acetic acid, propionic acid, and butyric acid observed in HF respect to the other patients suggest the potential link between oral bacteria and gut dysbiosis.

Flavocytochrome b2-Mediated Electroactive Nanoparticles for Developing Amperometric L-Lactate Biosensors.

L-Lactate is an indicator of food quality, so its monitoring is essential. Enzymes of L-Lactate metabolism are promising tools for this aim. We describe here some highly sensitive biosensors for L-Lactate determination which were developed using flavocytochrome b2 (Fcb2) as a bio-recognition element, and electroactive nanoparticles (NPs) for enzyme immobilization. The enzyme was isolated from cells of the thermotolerant yeast Ogataea polymorpha. The possibility of direct electron transfer from the reduced form of Fcb2 to graphite electrodes has been confirmed, and the amplification of the electrochemical communication between the immobilized Fcb2 and the electrode surface was demonstrated to be achieved using redox nanomediators, both bound and freely diffusing. The fabricated biosensors exhibited high sensitivity (up to 1436 A·M-1·m-2), fast responses, and low limits of detection. One of the most effective biosensors, which contained co-immobilized Fcb2 and the hexacyanoferrate of gold, having a sensitivity of 253 A·M-1·m-2 without freely diffusing redox mediators, was used for L-Lactate analysis in samples of yogurts. A high correlation was observed between the values of analyte content determined using the biosensor and referenced enzymatic-chemical photometric methods. The developed biosensors based on Fcb2-mediated electroactive nanoparticles can be promising for applications in laboratories of food control.

Can dietary fermented total mixed ration additives biological and chemical improve digestibility, performance, and rumen fermentation in ruminants?

The quantity and quality of animal feed are important factors for efficient and profitable animal farming. Feed ingredients and supplementation with high-density energy and nitrogen would be potentially useful on the farm. The new approach to feeding has shifted from animal-based diets to more readily fermentable feedstuffs in ruminants to meet the increased production of high-yielding animals. These methods encourage the use of fermented total mixed ration (FTMR). An advantage of feeding FTMR as opposed to total mixed ration (TMR) is the opportunity for a development alternative to efficiently handle ruminant diets. FTMR is a method to promote progressive nutrient utilization, extend the preservation of feed by preventing spoilage, and reduce anti-nutritive substances in feeds. Ruminal protein and starch degradability were increased due to proteolysis during storage by ruminants fed ensiled rations. The results found that FTMR can reduce the pH level and increase the lactic acid content of ensiled materials, which results in better quality feed and longer storage times. In addition, it can increase dry matter intake, growth rate, and milk production when compared with TMR. It was shown that the use of FTMR diet was effective for animal production. However, FTMR was rapidly spoiled when exposed to air or feed-out, particularly in hot and humid climates, resulting in a decrease in lactic acid concentration, an increase in pH, and the loss of nutrients. Thus, the appropriate method for enhancing the quality of FTMR should be considered.

Can salivary lactate be used as an anaerobic biomarker?

Background: Salivary lactate has been suggested as a non-invasive anaerobic biomarker in sports medicine for decades, yet has not been widely applied until now. This study aimed to explore possible issues related to its application and suggest directions for future method improvement. Methods: A liquid chromatography-mass spectrometry (LC-MS) method for the determination of salivary lactate was developed, validated and applied on saliva samples collected from a group of professional sprinters (n = 20). The samples were collected via chewing a cotton ball for one minute and centrifuging it afterwards. The evaluation included variation with mouth rinse times, consistency at different sampling times, change after treadmill or cycle ergometer trainings, and association with blood lactate. Sample sizes were calculated prior to the study. One-way analysis of variance (ANOVA), intra-class correlation coefficients (ICC) and relative standard deviation (RSD) were used to evaluate data variances. Pearson correlation was applied to show correlation between salivary and blood lactate. Effect sizes and power were calculated following ANOVA and correlation analyses. Results: The RSD of the LC-MS method was 19.70%. Salivary lactate concentration was affected by mouth rinse times before sampling (ANOVA p = 0.025, η 2 = 0.40, 1 - ß = 0.99, ICC = 0.23, mean RSD of four sampling = 55.30%), and stabilized after mouth rinsing for three times. The concentrations at resting state across three weeks were consistent at group level (ANOVA p = 0.57, η 2 = 0.03, 1 - ß = 0.20), but varied greatly individually (ICC = 0.22, mean RSD = 56.16%). Salivary lactate level significantly increased after treadmill and cycle ergometer trainings (ANOVA p = 0.0002, η 2 = 0.46, 1 - ß = 0.9999 and ANOVA p = 0.0019, η 2 = 0.40, 1 - ß = 0.9993, respectively), and displayed positive correlation with blood lactate concentration (r = 0.61, p = 0.0004, 1 - ß = 0.9596). Significant difference between male and female participants was observed in none of the tests conducted in this study. Discussion: Salivary lactate was found to be a potential anaerobic biomarker. However, reproducible methods for sample collection and analysis, as well as more knowledge on the secretion mechanism and pattern of salivary lactate are required to make it a practical anaerobic biomarker.

J-Difference editing (MEGA) of lactate in the human brain at 3T.

PURPOSE: The need to detect and quantify brain lactate accurately by MRS has stimulated the development of editing sequences based on J coupling effects. In J-difference editing of lactate, threonine can be co-edited and it contaminates lactate estimates due to the spectral proximity of the coupling partners of their methyl protons. We therefore implemented narrow-band editing 180° pulses (E180) in MEGA-PRESS acquisitions to resolve separately the 1.3-ppm resonances of lactate and threonine. METHODS: Two 45.3-ms rectangular E180 pulses, which had negligible effects 0.15-ppm away from the carrier frequency, were implemented in a MEGA-PRESS sequence with TE 139 ms. Three acquisitions were designed to selectively edit lactate and threonine, in which the E180 pulses were tuned to 4.1 ppm, 4.25 ppm, and a frequency far off resonance. Editing performance was validated with numerical analyses and acquisitions from phantoms. The narrow-band E180 MEGA and another MEGA-PRESS sequence with broad-band E180 pulses were evaluated in six healthy subjects. RESULTS: The 45.3-ms E180 MEGA offered a difference-edited lactate signal with lower intensity and reduced contamination from threonine compared to the broad-band E180 MEGA. The 45.3 ms E180 pulse had MEGA editing effects over a frequency range larger than seen in the singlet-resonance inversion profile. Lactate and threonine in healthy brain were both estimated to be 0.4 ± 0.1 mM, with reference to N-acetylaspartate at 12 mM. CONCLUSION: Narrow-band E180 MEGA editing minimizes threonine contamination of lactate spectra and may improve the ability to detect modest changes in lactate levels.

Exhaled breath condensate identifies metabolic dysregulation in patients with radiation-induced lung injury.

Radiation-induced lung injury (RILI) is a consequence of therapeutic thoracic irradiation (TR) for many cancers, and there are no FDA-approved curative strategies. Studies report that 80% of patients who undergo TR will have CT-detectable interstitial lung abnormalities, and strategies to limit the risk of RILI may make radiotherapy less effective at treating cancer. Our lab and others have reported that lung tissue from patients with idiopathic pulmonary fibrosis (IPF) exhibits metabolic defects including increased glycolysis and lactate production. In this pilot study, we hypothesized that patients with radiation-induced lung damage will exhibit distinct changes in lung metabolism that may be associated with the incidence of fibrosis. Using liquid chromatography/tandem mass spectrometry to identify metabolic compounds, we analyzed exhaled breath condensate (EBC) in subjects with CT-confirmed lung lesions after TR for lung cancer, compared with healthy subjects, smokers, and cancer patients who had not yet received TR. The lung metabolomic profile of the irradiated group was significantly different from the three nonirradiated control groups, highlighted by increased levels of lactate. Pathway enrichment analysis revealed that EBC from the case patients exhibited concurrent alterations in lipid, amino acid, and carbohydrate energy metabolism associated with the energy-producing tricarboxylic acid (TCA) cycle. Radiation-induced glycolysis and diversion of lactate to the extracellular space suggests that pyruvate, a precursor metabolite, converts to lactate rather than acetyl-CoA, which contributes to the TCA cycle. This TCA cycle deficiency may be compensated by these alternate energy sources to meet the metabolic demands of chronic wound repair. Using an "omics" approach to probe lung disease in a noninvasive manner could inform future mechanistic investigations and the development of novel therapeutic targets.NEW & NOTEWORTHY We report that exhaled breath condensate (EBC) identifies cellular metabolic dysregulation in patients with radiation-induced lung injury. In this pilot study, untargeted metabolomics revealed a striking metabolic signature in EBC from patients with radiation-induced lung fibrosis compared to patients with lung cancer, at-risk smokers, and healthy volunteers. Patients with radiation-induced fibrosis exhibit specific changes in tricarboxylic acid (TCA) cycle energy metabolism that may be required to support the increased energy demands of fibroproliferation.

Maternal and umbilical cord blood lactate for predicting perinatal death: a secondary analysis of data from a randomized controlled trial.

BACKGROUND: In high resource settings, lactate and pH levels measured from fetal scalp and umbilical cord blood are widely used as predictors of perinatal mortality. However, the same is not true in low resource settings, where much of perinatal mortality occurs. The scalability of this practice has been hindered by difficulty in collecting fetal scalp and umbilical blood sample. Little is known about the use of alternatives such as maternal blood, which is easier and safer to obtain. Therefore, we aimed to compare maternal and umbilical cord blood lactate levels for predicting perinatal deaths. METHODS: This was secondary analysis of data from a randomized controlled trial assessing the effect of sodium bicarbonate on maternal and perinatal outcomes among women with obstructed labour at Mbale regional referral hospital in Eastern Uganda. Lactate concentration in maternal capillary, myometrial, umbilical venous and arterial blood was measured at the bedside using a lactate Pro 2 device (Akray, Japan Shiga) upon diagnosis of obstructed labour. We constructed Receiver Operating Characteristic curves to compare the predictive ability of maternal and umbilical cord lactate and the optimal cutoffs calculated basing on the maximal Youden and Liu indices. RESULTS: Perinatal mortality risk was: 102.2 deaths per 1,000 live births: 95% CI (78.1-130.6). The areas under the ROC curves were 0.86 for umbilical arterial lactate, 0.71 for umbilical venous lactate, and 0.65 for myometrial lactate, 0.59 for maternal lactate baseline, and 0.65 at1hr after administration of bicarbonate. The optimal cutoffs for predicting perinatal death were 15 0.85 mmol/L for umbilical arterial lactate, 10.15mmol/L for umbilical venous lactate, 8.75mmol/L for myometrial lactate, and 3.95mmol/L for maternal lactate at recruitment and 7.35mmol/L after 1 h. CONCLUSION: Maternal lactate was a poor predictor of perinatal death, but umbilical artery lactate has a high predictive value. There is need for future studies on the utility of amniotic fluid in predicting intrapartum perinatal deaths.

A molecularly imprinted electrochemical microneedle sensor for multiplexed metabolites detection in human sweat.

This article demonstrates an array of inexpensive molecularly imprinted microneedle platforms for the multiplexed electrochemical detection of pH, epinephrine, dopamine, and lactate biomarkers in human sweat. The multiplexed sensors were fabricated via layer-by-layer (LbL) assembly on a polydimethylsiloxane (PDMS) microneedle platform coated with a conductive PDMS/carbon nanotube (CNT)/cellulose nanocrystal (CNC) composite (PDMS/CNT/CNC@PDMS). The pH sensor was comprised of a pH-responsive polyaniline (PANI)/CNT/CNC/silver nanoparticle (AgNP) composite layer. The epinephrine, dopamine, and lactate sensors consisted of an additional epinephrine, dopamine, or lactate-imprinted PANI-co-3-aminophenylboronic acid (PBA)/gold nanoparticle (AuNP) layer atop the PANI/CNT/CNC/AgNP composite layer. Each sensor rapidly (∼2 min) and selectively responded to their target analytes, with excellent precision between scans. The limits of detection (LOD) for the epinephrine, dopamine, and lactate sensors were 0.0007 ± 0.0002 µM, 2.11 ± 0.05 nM, and 0.07 ± 0.07 mM, respectively. The pH sensor accurately responded to a pH range of 4.25-10. The applicability of the sensor platforms were successfully verified through quantification of pH, epinephrine, dopamine, and lactate in a human sweat sample, showing promise for use as a wearable, point of need (PON) sensor for sweat analytics.

Yeast diversity during the spontaneous fermentation of wine with only the microbiota on grapes cultivated in Japan.

Making wine via spontaneous fermentation without sulfur dioxide and commercial yeast (spontaneous winemaking) is increasing in recent year, but there is scant research regarding microbial communities present in Japan during spontaneous winemaking using culture-independent molecular methods. We analyzed fungal communities and populations during laboratory-scale spontaneous winemaking using sterilized labware to avoid winery-resident microbes. In the spontaneous fermentation of four grape varieties (Pinot Noir, Riesling, Koshu, and Koshusanjaku) grown in the same Japanese vineyard, our analysis of yeast and other fungal species by next-generation sequencing based on the ITS1 region demonstrated that Saccharomyces cerevisiae was eventually dominant in seven of 12 fermentation batches (three replications for each grape variety), whereas non-Saccharomyces species (e.g., Schizosaccharomyces japonicus, Lachancea dasiensis, and Hanseniaspora valbyensis) became dominant in four batches at the end of fermentation. In another batch, lactic acid bacteria (LAB) became dominant and the fermentation remained incomplete. Diverse microbes were involved in the spontaneous fermentation (particularly in Koshusanjaku), indicating that residual sugar remained and lactic and acetic acid largely increased. Compared to the control wine made with SO2 and commercial yeast, the concentration of lactic acid was 47-fold higher in the must dominated by L. dasiensis, and the concentrations of acetic acid and lactic acid were 10-fold and 20-fold higher in the must dominated by LAB, respectively. Even when indigenous S. cerevisiae became dominant, the finished wines obtained high sensory-analysis scores for complexity but low scores for varietal typicality, indicating the risk of fermentation with unselected wild yeast on the grapes grown in Japan.