L-lactic acidosis: pathophysiology, classification, and causes; emphasis on biochemical and metabolic basis

Circadian Regulation of the Lactate Metabolic Kinetics in Mice Using the [1H-13C]-NMR Technique

Lactate is not only the energy substrate of neural cells, but also an important signal molecule in brain. In modern societies, disturbed circadian rhythms pose a global challenge. Therefore, exploring the influence of circadian period on lactate and its metabolic kinetics is essential for the advancement of neuroscientific research. In the present study, the different groups of mice (L: 8:00 a.m.; D: 20:00 p.m.; SD: 20:00 p.m. with 12 h acute sleep deprivation) were infused with [3-13C] lactate through the lateral tail vein for a duration of 2 min. After 30-min lactate metabolism, the animals were euthanized and the tissues of brain and liver were obtained and extracted, and then, the [1H-13C] NMR technology was employed to investigate the kinetic information of lactate metabolism in different brain regions and liver to detect the enrichment of various metabolic kinetic information. Results revealed the fluctuating lactate concentrations in the brain throughout the day, with lower levels during light periods and higher levels during dark periods. Most metabolites displayed strong sensitivity to circadian rhythm, exhibiting significant day-night variations. Conversely, only a few metabolites showed changes after acute sleep deprivation, primarily in the temporal brain region. Interestingly, in contrast to brain lactate metabolism, liver lactate metabolism exhibited a significant increase following acute sleep deprivation. This study explored the kinetics of lactate metabolism, hinted at potential clinical implications for disorders involving circadian rhythm disturbances, and providing a new research basis for clinical exploration of brain and liver lactate metabolism.

The missing hydrogen ion, part-2: Where the evidence leads to

The purpose of this manuscript was to present the evidence for why cells do not produce metabolic acids. In addition, evidence that opposes common viewpoints and arguments used to support the cellular production of lactic acid (HLa) or liver keto-acids have been provided. Organic chemistry reveals that many molecules involved in cellular energy catabolism contain functional groups classified as acids. The two main acidic functional groups of these molecules susceptible to ∼H+ release are the carboxyl and phosphoryl structures, though the biochemistry and organic chemistry of molecules having these structures reveal they are produced in a non-acidic ionic (negatively charged) structure, thereby preventing pH dependent ∼H+ release. Added evidence from the industrial production of HLa further reveals that lactate (La-) is produced followed by an acidification step that converts La- to HLa due to pH dependent ∼H+ association. Interestingly, there is a plentiful list of other molecules that are classified as acids and compared to HLa have similar values for their H+ dissociation constant (pKd). For many metabolic conditions, the cumulative turnover of these molecules is far higher than for La-. The collective evidence documents the non-empirical basis for the construct of the cellular production of HLa, or any other metabolic acid.

Novel COVID-19 biomarkers identified through multi-omics data analysis: N-acetyl-4-O-acetylneuraminic acid, N-acetyl-L-alanine, N-acetyltriptophan, palmitoylcarnitine, and glycerol 1-myristate

This study aims to apply machine learning models to identify new biomarkers associated with the early diagnosis and prognosis of SARS-CoV-2 infection.Plasma and serum samples from COVID-19 patients (mild, moderate, and severe), patients with other pneumonia (but with negative COVID-19 RT-PCR), and healthy volunteers (control) from hospitals in four different countries (China, Spain, France, and Italy) were analyzed by GC-MS, LC-MS, and NMR. Machine learning models (PCA and PLS-DA) were developed to predict the diagnosis and prognosis of COVID-19 and identify biomarkers associated with these outcomes.A total of 1410 patient samples were analyzed. The PLS-DA model presented a diagnostic and prognostic accuracy of around 95% of all analyzed data. A total of 23 biomarkers (e.g., spermidine, taurine, L-aspartic, L-glutamic, L-phenylalanine and xanthine, ornithine, and ribothimidine) have been identified as being associated with the diagnosis and prognosis of COVID-19. Additionally, we also identified for the first time five new biomarkers (N-Acetyl-4-O-acetylneuraminic acid, N-Acetyl-L-Alanine, N-Acetyltriptophan, palmitoylcarnitine, and glycerol 1-myristate) that are also associated with the severity and diagnosis of COVID-19. These five new biomarkers were elevated in severe COVID-19 patients compared to patients with mild disease or healthy volunteers.The PLS-DA model was able to predict the diagnosis and prognosis of COVID-19 around 95%. Additionally, our investigation pinpointed five novel potential biomarkers linked to the diagnosis and prognosis of COVID-19: N-Acetyl-4-O-acetylneuraminic acid, N-Acetyl-L-Alanine, N-Acetyltriptophan, palmitoylcarnitine, and glycerol 1-myristate. These biomarkers exhibited heightened levels in severe COVID-19 patients compared to those with mild COVID-19 or healthy volunteers.

Advancements in wearable technology for monitoring lactate levels using lactate oxidase enzyme and free enzyme as analytical approaches: A review

Lactate is a metabolite that holds significant importance in human healthcare, biotechnology, and the food industry. The need for lactate monitoring has led to the development of various devices for measuring lactate concentration. Traditional laboratory methods, which involve extracting blood samples through invasive techniques such as needles, are costly, time-consuming, and require in-person sampling. To overcome these limitations, new technologies for lactate monitoring have emerged. Wearable biosensors are a promising approach that offers non-invasiveness, low cost, and short response times. They can be easily attached to the skin and provide continuous monitoring. In this review, we evaluate different types of wearable biosensors for lactate monitoring using lactate oxidase enzyme as biological recognition element and free enzyme systems.

Hybrid interpenetrating network of polyester coronary stent with tunable biodegradation and mechanical properties

Poly(l-lactide) (PLLA) is an important candidate raw material of the next-generation biodegradable stent for percutaneous coronary intervention, yet how to make a polyester stent with sufficient mechanical strength and relatively fast biodegradation gets to be a dilemma. Herein, we put forward a hybrid interpenetrating network (H-IPN) strategy to resolve this dilemma. As such, we synthesize a multi-functional biodegradable macromer of star-like poly(d,l-lactide-co-ɛ-caprolactone) with six acrylate end groups, and photoinitiate it, after mixing with linear PLLA homopolymer, to trigger the free radical polymerization. The resultant crosslinked polymer blend is different from the classic semi-interpenetrating network, and partial chemical crosslinking occurs between the linear polymer and the macromer network. Combined with the tube blow molding and the postprocessing laser cutting, we fabricate a semi-crosslinked-polyester biodegradable coronary stent composed of H-IPN, which includes a physical network of polyester spherulites and a chemical crosslinking network of copolyester macromers and a part of homopolymers. Compared with the currently main-stream PLLA stent in research, this H-IPN stent realizes a higher and more appropriate biodegradation rate while maintaining sufficient radial strength. A series of polymer chemistry, polymer physics, polymer processing, and in vitro and in vivo biological assessments of medical devices have been made to examine the H-IPN material. The interventional implanting of the H-IPN stent into aorta abdominalis of rabbits and the follow-ups to 12 months have confirmed the safety and effectiveness.

Immobilization of Enzyme Electrochemical Biosensors and Their Application to Food Bioprocess Monitoring

Electrochemical biosensors based on immobilized enzymes are among the most popular and commercially successful biosensors. The literature in this field suggests that modification of electrodes with nanomaterials is an excellent method for enzyme immobilization, which can greatly improve the stability and sensitivity of the sensor. However, the poor stability, weak reproducibility, and limited lifetime of the enzyme itself still limit the requirements for the development of enzyme electrochemical biosensors for food production process monitoring. Therefore, constructing sensing technologies based on enzyme electrochemical biosensors remains a great challenge. This article outlines the construction principles of four generations of enzyme electrochemical biosensors and discusses the applications of single-enzyme systems, multi-enzyme systems, and nano-enzyme systems developed based on these principles. The article further describes methods to improve enzyme immobilization by combining different types of nanomaterials such as metals and their oxides, graphene-related materials, metal-organic frameworks, carbon nanotubes, and conducting polymers. In addition, the article highlights the challenges and future trends of enzyme electrochemical biosensors, providing theoretical support and future perspectives for further research and development of high-performance enzyme chemical biosensors.

Relationship between the postoperative lactate dynamic levels, the acute gastrointestinal injury and the prognosis among patients who undergo surgical treatment for acute type A aortic dissection

Introduction

This study aimed to determine the relationship between the postoperative lactate dynamic levels, the postoperative acute gastrointestinal injury (AGI), and the prognosis among the patients who underwent surgical treatment for an acute Stanford type-A aortic dissection (aTAAD).

Methods

A total of 271 aTAAD patients were recruited and monitored. Of the 271 aTAAD patients, 29.2% developed an AGI and were designated as the AGI group (n = 79); the other patients (n = 192) were designated as the non-AGI group. According to the 2-year follow up, the aTAAD patients were also divided into the alive and death subgroups for further analysis.

Results

Binary logistic regression analysis revealed that the postoperative 4-h lactate (P4L) level, time-to-return to the normal blood lactate level (TRNL), postoperative 16-h lactate (P16L) level, and neutrophil granulocyte (NEU) count had a good predictive value for an AGI after aTAAD. The 8-week and 2-year mortality rates were higher in the AGI group than the non-AGI group (P < 0.05). Basic data and clinical characteristics were significantly different between the alive and death groups (P < 0.05). A higher AGI rate and mortality occurred in the P4L level ≥10.15 mmol/L subgroup, TRNL ≥21-h subgroup, P16L level ≥2.95 mmol/L subgroup, NEU count ≥10.9 × 10⁹/L subgroup, PaO₂ < 77.7 mmHg subgroup, WBC count ≥9.58 × 10⁹/L subgroup, and the operative time ≥427 min subgroup than the corresponding comparison subgroups (P < 0.05). The postoperative 0-h lactate (P0L) level, TRNL, postoperative 24-h lactate (P24L) level, D-dimer level, fibrinogen degradation products (FDP) level, duration of mechanical ventilation, and length of hospitalization were independent factors influencing the 30-day mortality rate in patients who underwent surgery for an aTAAD (P < 0.05). Cox regression multivariate analysis after univariate analysis of all-cause mortality showed the TRNL, postoperative 12-h lactate (P12L) level, P16L level, P24L level, D-dimer level, FDP level, and length of hospitalization were independently associated with the 2-year mortality rate in patients who underwent surgery for an aTAAD (P < 0.05).

Conclusion

The postoperative lactate changes and TRNL effectively predicted postoperative AGI and the mortality rate in patients with who underwent surgery for an aTAAD. The TRNL and P24L level were independent risk factors for the 30-day and 2-year mortality rates in patients who underwent surgery for an aTAAD.

Pediatric Malaria with Respiratory Distress: Prognostic Significance of Point-of-Care Lactate

Respiratory distress (RD) in pediatric malaria portends a grave prognosis. Lactic acidosis is a biomarker of severe disease. We investigated whether lactate, measured at admission using a handheld device among children hospitalized with malaria and RD, was predictive of subsequent mortality. We performed a pooled analysis of Ugandan children under five years of age hospitalized with malaria and RD from three past studies. In total, 1324 children with malaria and RD (median age 1.4 years, 46% female) from 21 health facilities were included. Median lactate level at admission was 4.6 mmol/L (IQR 2.6–8.5) and 586 patients (44%) had hyperlactatemia (lactate > 5 mmol/L). The mortality was 84/1324 (6.3%). In a mixed-effects Cox proportional hazard model adjusting for age, sex, clinical severity score (fixed effects), study, and site (random effects), hyperlactatemia was associated with a 3-fold increased hazard of death (aHR 3.0, 95%CI 1.8–5.3, p < 0.0001). Delayed capillary refill time (τ = 0.14, p < 0.0001), hypotension (τ = −0.10, p = 0.00049), anemia (τ = −0.25, p < 0.0001), low tissue oxygen delivery (τ = −0.19, p < 0.0001), high parasite density (τ = 0.10, p < 0.0001), and acute kidney injury (p = 0.00047) were associated with higher lactate levels. In children with malaria and RD, bedside lactate may be a useful triage tool, predictive of mortality.

Early passive orthostatic training prevents diaphragm atrophy and dysfunction in intensive care unit patients on mechanical ventilation: A retrospective case‒control study

BACKGROUND

Intensive care unit (ICU) patients on mechanical ventilation (MV), who are always bedridden, easily develop diaphragm atrophy and dysfunction. However, few studies have assessed diaphragmatic thickness and functional changes after early passive orthostatic training.

OBJECTIVES

This is the first study to investigate the efficacy of early passive orthostatic training in preventing diaphragm atrophy and dysfunction in ICU patients on MV.

METHODS

In this randomized retrospective case‒control study, 81 ICU patients on MV for 8 days or longer were enrolled. Forty-four patients received early passive orthostatic training initiated within 72 h of MV initiation (training group), and 37 patients did not receive training (no-training group). The protocol was performed for seven days, once a day for 30 min. The primary outcomes were diaphragmatic thickness and diaphragm contractile fraction (TFdi). The ventilatory parameters were secondary outcomes.

RESULTS

This study included 81 (45 male) ICU patients on MV [(mean ± SD) age = (60.63 ± 7.88) years]. The training group had a larger diaphragmatic thickness at end-expiration (Tdi_,ee) and a smaller magnitude of decrease in Tdi_,ee and TFdi (p = 0.001, 0.029, and <0.001, respectively) than the no-training group after 7 days of training. The mean arterial pressure, fraction of inspired oxygen, and white blood cell levels were decreased in the training group compared with the no-training group (p = 0.003, 0.001, and 0.026, respectively), but lactic acid levels decreased slightly in the training group with no significant difference (p = 0.708).

CONCLUSIONS

Early passive orthostatic training is suitable to ameliorate diaphragm atrophy and dysfunction in ICU patients on MV.

Oral pyruvate prevents high-intensity interval exercise-induced metabolic acidosis in rats by promoting lactate dehydrogenase reaction

Introduction

There is no denying the clinical benefits of exogenous pyruvate in the treatment of pathological metabolic acidosis. However, whether it can prevent exercise physiological metabolic acidosis, delay the occurrence of exercise fatigue, and improve the beneficial effects of exercise and its internal mechanism remain unclear.

Methods

We randomly divided 24 male SD rats into 3 groups: one group was a control without exercise (CC, n = 8), and the other two groups were supplemented with 616 mg/kg/day pyruvate (EP, n = 8) or distilled water of equal volume (EC, n = 8). These groups completed acute high-intensity interval exercise (HIIE) after 7 days of supplementation. The acid metabolism variables were measured immediately after exercise including blood pH (pH_e), base excess (BE), HCO₃ ^-, blood lactic acid and skeletal muscle pH (pH_i). The redox state was determined by measuring the oxidized coenzyme I/reduced coenzyme I (nicotinamide adenine dinucleotide [NAD⁺]/reduced NAD⁺ [NADH]) ratio and lactate/pyruvate (L/P) ratio. In addition, the activities of lactate dehydrogenase A (LDHA), hexokinase (HK), phosphofructokinase (PFK) and pyruvate kinase (PK) were determined by ELISA.

Results

Pyruvate supplementation significantly reversed the decrease of pHe, BE, HCO₃ ^- and pH_i values after HIIE (p < 0.001), while significantly increased the activities of LDHA (p = 0.048), HK (p = 0.006), and PFK (p = 0.047). Compared with the CC, the NAD+/NADH (p = 0.008) ratio and the activities of LDHA (p = 0.002), HK (p < 0.001), PFK (p < 0.001), and PK (p = 0.006) were significantly improved in EP group.

Discussion

This study provides compelling evidence that oral pyruvate attenuates HIIE-induced intracellular and extracellular acidification, possibly due to increased activity of LDHA, which promotes the absorption of H⁺ in the LDH reaction. The beneficial effects of improving the redox state and glycolysis rate were also shown. Our results suggest that pyruvate can be used as an oral nutritional supplement to buffer HIIE induced metabolic acidosis.

Lactic Acidosis Related to Pharmacotherapy and Human Diseases

Lactic acidosis represents one of the most common conditions that can compromise the health of intensive care unit (ICU) patients, increasing the mortality of patients with high levels of Lactate who do not receive a proper treatment within the first 6 h of hospitalization. There are two enantiomers of lactic acid: L-lactic acid (when the concentration increases, it can lead to a state of severe acidemia risking cardiovascular collapse, causing an increase in mortality in ICU patients) and D lactic acid (produced in the human organism by microbiota and its production increases during some pathological status). Generally, increased levels of serum lactic acid could be due to numerous factors, including hypoxia (caused for example by septic/cardiogenic/hypovolemic or obstructive shock), specific pathologies (e.g., liver disease), use of some drugs (e.g., metformin), presence of toxins, and trauma. Since the underlying cause could be fatal for the ICU patient, it is important to understand the root of this clinical status with a view to correct it and prevent the risk of a poor clinical outcome. Prevention and early treatment are the keys to control the negative clinical consequences. The aim of this review is to revise the scientific literature for further confirmation about the importance of early identification of acidotic statuses and to underline how an early diagnosis can prevent the worst clinical outcome, especially for ICU patients who are more fragile compared to the general population.

The Lactate and the Lactate Dehydrogenase in Inflammatory Diseases and Major Risk Factors in COVID-19 Patients

Lactate dehydrogenase (LDH) is a terminating enzyme in the metabolic pathway of anaerobic glycolysis with end product of lactate from glucose. The lactate formation is crucial in the metabolism of glucose when oxygen is in inadequate supply. Lactate can also be formed and utilised by different cell types under fully aerobic conditions. Blood LDH is the marker enzyme, which predicts mortality in many conditions such as ARDS, serious COVID-19 and cancer patients. Lactate plays a critical role in normal physiology of humans including an energy source, a signaling molecule and a pH regulator. Depending on the pH, lactate exists as the protonated acidic form (lactic acid) at low pH or as sodium salt (sodium lactate) at basic pH. Lactate can affect the immune system and act as a signaling molecule, which can provide a “danger” signal for life. Several reports provide evidence that the serum lactate represents a chemical marker of severity of disease similar to LDH under inflammatory conditions. Since the mortality rate is much higher among COVID-19 patients, associated with high serum LDH, this article is aimed to review the LDH as a therapeutic target and lactate as potential marker for monitoring treatment response of inflammatory diseases. Finally, the review summarises various LDH inhibitors, which offer potential applications as therapeutic agents for inflammatory diseases, associated with high blood LDH. Both blood LDH and blood lactate are suggested as risk factors for the mortality of patients in serious inflammatory diseases.

Untargeted Metabolomics Sensitively Differentiates Gut Bacterial Species in Single Culture and Co-Culture Systems

Gut microbiome plays a vital role in human health, and its characteristic has been widely identified through next-generation sequencing techniques. Although with great genomic insights into gut microbiome, its functional information is not clearly elaborated through metagenomic techniques. On the other hand, it is suggested that fecal metabolome can be used as a functional readout of the microbiome composition; therefore, we designed a proof-of-concept study to first characterize the metabolome of different gut microbes and then investigate the relationship between bacterial metabolomes and their compositions in co-culture systems. We selected eight representative bacteria species from Bifidobacterium (2), Bacteroides (1), Lactobacillus (4), and Akkermansia (1) genera as our model microbes. Liquid chromatography coupled mass spectrometry-based untargeted metabolomics was utilized to explore the microbial metabolome of bacteria single cultures and co-culture systems. Through spectral comparisons, our results showed that untargeted metabolomics could capture the similarity and differences in metabolic profiles from eight representative gut bacteria. Also, untargeted metabolomics could sensitively differentiate gut bacterial species based on our statistical analyses. For example, citrulline and histamine levels were significantly different among four Lactobacillus species. In addition, in the co-culture systems with different bacteria population ratios, gut bacterial metabolomes can be used to quantitatively reflect bacterial population in a mixed culture. For instance, the relative abundance of 2-hydroxybutyric acid changed proportionately with the changed population ratio of Lactobacillus reuteri in the co-culture system. In summary, we proposed a workflow that could demonstrate the capability of untargeted metabolomics in differentiating gut bacterial species and detecting their characteristic metabolites proportionally to the microbial population in co-culture systems.

Hyperlactataemia and acid-base disturbances in normotensive patients with acute heart failure

AIMS

Acute heart failure (AHF) may be associated with low-tissue perfusion and/or hypoxaemia leading to increased lactate levels and acid-base perturbations. Few data are available on the clinical significance of elevated lactate levels and primary acid-base disorders in the setting of AHF.

METHODS AND RESULTS

Arterial blood gas was obtained at admission in 4012 normotensive (systolic blood pressure ≥ 90 mmHg) patients with AHF. The association between lactate levels and acid-base status and in-hospital mortality was determined using multivariable logistic regression. Hyperlactataemia (>2 mmol/L) was present in 38.0% of patients and was strongly associated with markers of sympathetic activation, such as hyperglycaemia. Hyperlactataemia was present in 31.0%, 43.7%, and 42.0% of patients with normal pH, acidosis, and alkalosis, respectively. In-hospital mortality occurred in 16.4% and 11.1% of patients with and without hyperlactataemia [adjusted odds ratio (OR) 1.49; 95% confidence interval (CI) 1.22-1.82, P < 0.0001]. Compared with normal pH, the OR for in-hospital mortality was 2.48 (95% CI 1.95-3.16, P < 0.0001) in patients with acidosis and 1.77 (95% CI 1.32-2.26, P < 0.0001) in patients with alkalosis. The risk for in-hospital mortality was high with acidosis (18.1%) or alkalosis (10.4%) even with normal lactate. The most common primary acid-base disturbances included metabolic acidosis, respiratory acidosis, and metabolic alkalosis with respiratory acidosis having the highest risk for in-hospital mortality.

CONCLUSION

Hyperlactataemia was common in patients without hypotension and was associated with increased risk for in-hospital mortality. Hyperlactataemia is not associated with any specific acid-base disorder. Acute heart failure patients also present with diverse acid-base disorders portending increased in-hospital mortality.

Lactylation: a Passing Fad or the Future of Posttranslational Modification

Lactate is a glycolytic product and a significant energy source. Moreover, it regulates gene transcription via lactylation of histones and non-histone proteins, i.e., a novel posttranslational modification. This review summarizes recent advances related to lactylation in lactate metabolism and diseases. Notably, lactylation plays a vital role in cancer, inflammation, and regeneration; however, the specific mechanism remains unclear. Histone lactylation regulates oncogenic processes by targeting gene transcription and inflammation via macrophage activation. Eventually, we identified research gaps and recommended several primary directions for further studies.

CD38 in the age of COVID-19: a medical perspective

This medical review addresses the hypothesis that CD38/NADase is at the center of a functional axis (i.e., intracellular Ca2+ mobilization/IFNγ response/reactive oxygen species burst) driven by severe acute respiratory syndrome coronavirus 2 infection, as already verified in respiratory syncytial virus pathology and CD38 activity in other cellular settings. Key features of the hypothesis are that 1) the substrates of CD38 (e.g., NAD+ and NADP+) are depleted by viral-induced metabolic changes; 2) the products of the enzymatic activity of CD38 [e.g., cyclic adenosine diphosphate-ribose (ADPR)/ADPR/nicotinic acid adenine dinucleotide phosphate] and related enzymes [e.g., poly(ADP-ribose)polymerase, Sirtuins, and ADP-ribosyl hydrolase] are involved in the anti‐viral and proinflammatory response that favors the onset of lung immunopathology (e.g., cytokine storm and organ fibrosis); and 3) the pathological changes induced by this kinetic mechanism may be reduced by distinct modulators of the CD38/NAD+ axis (e.g., CD38 blockers, NAD+ suppliers, among others). This view is supported by arrays of associative basic and applied research data that are herein discussed and integrated with conclusions reported by others in the field of inflammatory, immune, tumor, and viral diseases.

Diagnosis and prediction of COVID-19 severity: can biochemical tests and machine learning be used as prognostic indicators?

OBJECTIVE

This study aimed to implement and evaluate machine learning based-models to predict COVID-19' diagnosis and disease severity.

METHODS

COVID-19 test samples (positive or negative results) from patients who attended a single hospital were evaluated. Patients diagnosed with COVID-19 were categorised according to the severity of the disease. Data were submitted to exploratory analysis (principal component analysis, PCA) to detect outlier samples, recognise patterns, and identify important variables. Based on patients' laboratory tests results, machine learning models were implemented to predict disease positivity and severity. Artificial neural networks (ANN), decision trees (DT), partial least squares discriminant analysis (PLS-DA), and K nearest neighbour algorithm (KNN) models were used. The four models were validated based on the accuracy (area under the ROC curve).

RESULTS

The first subset of data had 5,643 patient samples (5,086 negatives and 557 positives for COVID-19). The second subset included 557 COVID-19 positive patients. The ANN, DT, PLS-DA, and KNN models allowed the classification of negative and positive samples with >84% accuracy. It was also possible to classify patients with severe and non-severe disease with an accuracy >86%. The following were associated with the prediction of COVID-19 diagnosis and severity: hyperferritinaemia, hypocalcaemia, pulmonary hypoxia, hypoxemia, metabolic and respiratory acidosis, low urinary pH, and high levels of lactate dehydrogenase.

CONCLUSION

Our analysis shows that all the models could assist in the diagnosis and prediction of COVID-19 severity.

Investigation of Flexible Arrayed Lactate Biosensor Based on Copper Doped Zinc Oxide Films Modified by Iron-Platinum Nanoparticles

Potentiometric biosensors based on flexible arrayed silver paste electrode and copper-doped zinc oxide sensing film modified by iron-platinum nanoparticles (FePt NPs) are designed and manufactured to detect lactate in human. The sensing film is made of copper-doped zinc oxide (CZO) by a radio frequency (RF) sputtering system, and then modified by iron-platinum nanoparticles (FePt NPs). The surface morphology of copper-doped zinc oxide (CZO) is analyzed by scanning electron microscope (SEM). FePt NPs are analyzed by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The average sensitivity, response time, and interference effect of the lactate biosensors are analyzed by voltage-time (V-T) measurement system. The electrochemical impedance is analyzed by electrochemical impedance spectroscopy (EIS). The average sensitivity and linearity over the concentration range 0.2-5 mM are 25.32 mV/mM and 0.977 mV/mM, respectively. The response time of the lactate biosensor is 16 s, with excellent selectivity.

Regulation of RNA editing by intracellular acidification

The hydrolytic deamination of adenosine-to-inosine (A-to-I) by RNA editing is a widespread post-transcriptional modification catalyzed by the adenosine deaminase acting on RNA (ADAR) family of proteins. ADAR-mediated RNA editing modulates cellular pathways involved in innate immunity, RNA splicing, RNA interference, and protein recoding, and has been investigated as a strategy for therapeutic intervention of genetic disorders. Despite advances in basic and translational research, the mechanisms regulating RNA editing are poorly understood. Though several trans-acting regulators of editing have been shown to modulate ADAR protein expression, previous studies have not identified factors that modulate ADAR catalytic activity. Here, we show that RNA editing increases upon intracellular acidification, and that these effects are predominantly explained by both enhanced ADAR base-flipping and deamination rate at acidic pH. We also show that the extent of RNA editing increases with the reduction in pH associated with conditions of cellular hypoxia.

CD38 in the age of COVID-19: a medical perspective

This medical review addresses the hypothesis that CD38/NADase is at the center of a functional axis (i.e., intracellular Ca²⁺ mobilization/IFNγ response/reactive oxygen species burst) driven by severe acute respiratory syndrome coronavirus 2 infection, as already verified in respiratory syncytial virus pathology and CD38 activity in other cellular settings. Key features of the hypothesis are that 1) the substrates of CD38 (e.g., NAD⁺ and NADP⁺) are depleted by viral-induced metabolic changes; 2) the products of the enzymatic activity of CD38 [e.g., cyclic adenosine diphosphate-ribose (ADPR)/ADPR/nicotinic acid adenine dinucleotide phosphate] and related enzymes [e.g., poly(ADP-ribose)polymerase, Sirtuins, and ADP-ribosyl hydrolase] are involved in the anti‐viral and proinflammatory response that favors the onset of lung immunopathology (e.g., cytokine storm and organ fibrosis); and 3) the pathological changes induced by this kinetic mechanism may be reduced by distinct modulators of the CD38/NAD⁺ axis (e.g., CD38 blockers, NAD⁺ suppliers, among others). This view is supported by arrays of associative basic and applied research data that are herein discussed and integrated with conclusions reported by others in the field of inflammatory, immune, tumor, and viral diseases.

Terms, Definitions, Nomenclature, and Routes of Fluid Administration

Fluid therapy is administered to veterinary patients in order to improve hemodynamics, replace deficits, and maintain hydration. The gradual expansion of medical knowledge and research in this field has led to a proliferation of terms related to fluid products, fluid delivery and body fluid distribution. Consistency in the use of terminology enables precise and effective communication in clinical and research settings. This article provides an alphabetical glossary of important terms and common definitions in the human and veterinary literature. It also summarizes the common routes of fluid administration in small and large animal species.

Etiology of lactic acidosis in malaria

Lactic acidosis and hyperlactatemia are common metabolic disturbances in patients with severe malaria. Lactic acidosis causes physiological adverse effects, which can aggravate the outcome of malaria. Despite its clear association with mortality in malaria patients, the etiology of lactic acidosis is not completely understood. In this review, the possible contributors to lactic acidosis and hyperlactatemia in patients with malaria are discussed. Both increased lactate production and impaired lactate clearance may play a role in the pathogenesis of lactic acidosis. The increased lactate production is caused by several factors, including the metabolism of intraerythrocytic Plasmodium parasites, aerobic glycolysis by activated immune cells, and an increase in anaerobic glycolysis in hypoxic cells and tissues as a consequence of parasite sequestration and anemia. Impaired hepatic and renal lactate clearance, caused by underlying liver and kidney disease, might further aggravate hyperlactatemia. Multiple factors thus participate in the etiology of lactic acidosis in malaria, and further investigations are required to fully understand their relative contributions and the consequences of this major metabolic disturbance.

Combination of Antimicrobial Starters for Feed Fermentation: Influence on Piglet Feces Microbiota and Health and Growth Performance, Including Mycotoxin Biotransformation in vivo

The aim of this study was to apply a combination of the microbial starters Lactobacillus uvarum LUHS245, Lactobacillus casei LUHS210, Pediococcus acidilactici LUHS29, and Pediococcus pentosaceus LUHS183 for feed fermentation and to evaluate the influence of fermentation on feed acidity and microbiological characteristics, as well as on the piglet feces microbiota, health, and growth performance. Additionally, mycotoxin biotransformation was analyzed, including masked mycotoxins, in feed and piglet feces samples. The 36-day experiment was conducted using 25-day-old Large White/Norwegian Landrace (LW/NL) piglets with an initial body weight of 6.9–7.0 kg, which were randomly distributed into two groups (in each 100 piglets): control group, fed with basal diet (based on barley, wheat, potato protein, soybean protein concentrate, and whey powder), and treated group, fed with fermented feed at 500 g kg⁻¹ of total feed. Compared to a commercially available lactic acid bacteria (LAB) combination, the novel LAB mixture effectively reduced feed pH (on average pH 3.65), produced a 2-fold higher content of L(+) lactic acid, increased viable LAB count [on average 8.8 log₁₀ colony-forming units (CFU) g⁻¹], and led to stable feed fermentation during the entire test period (36 days). Fecal microbiota analysis showed an increased number of probiotic bacteria in the treated group, particularly Lactobacillus, when compared with the control group at the end of experiment. This finding indicates that fermented feed can modify microbial profile change in the gut of pigs. In treated piglets' blood (at day 61), the serum high-density lipoprotein (HDL) cholesterol and triglycerides (TG) were significantly higher, but the levels of T4, glucose, K, alkaline phosphatase (AP), and urea were significantly decreased (p ≤ 0.05) compared with the control group. Mycotoxin analysis showed that alternariol monomethyl ether (AME) and altenuene were found in 61-day-old control piglets' feces and in fermented feed samples. However, AME was not found in treated piglets' feces. Feed fermentation with the novel LAB combination is a promising means to modulate piglets' microbiota, which is essential to improve nutrient absorption, growth performance, and health parameters. The new LAB composition suggests a novel dietary strategy to positively manipulate fermented feed chemicals and bio-safety and the piglet gut microbial ecology to reduce antimicrobials use in pig production and increase local feed stock uses and economical effectiveness of the process.

Etiology and Management of Acute Metabolic Acidosis: An Update

BACKGROUND

The etiology of acute metabolic acidosis (aMA) is heterogeneous, and the consequences are potentially life-threatening. The aim of this article was to summarize the causes and management of aMA from a clinician's perspective.

SUMMARY

We performed a systematic search on PubMed, applying the following search terms: "acute metabolic acidosis," "lactic acidosis," "metformin" AND "acidosis," "unbalanced solutions" AND "acidosis," "bicarbonate" AND "acidosis" AND "outcome," "acute metabolic acidosis" AND "management," and "acute metabolic acidosis" AND "renal replacement therapy (RRT)/dialysis." The literature search did not consider diabetic ketoacidosis at all. Lactic acidosis evolves from various conditions, either with or without systemic hypoxia. The incidence of metformin-associated aMA is actually quite low. Unbalanced electrolyte preparations can induce hyperchloremic aMA. The latter potentially worsens kidney-related outcome parameters. Nevertheless, prospective and controlled data are missing at the moment. Recently, bicarbonate has been shown to improve clinically relevant endpoints in the critically ill, even if higher pH values (>7.3) are targeted. New therapeutics for aMA control are under development, since bicarbonate treatment can induce serious side effects. Key Messages: aMA is a frequent and potentially life-threatening complication of various conditions. Lactic acidosis might occur even in the absence of systemic hypoxia. The incidence of metformin-associated aMA is comparably low. Unbalanced electrolyte solutions induce hyperchloremic aMA, which most likely worsens the renal prognosis of critically ill patients. Bicarbonate, although potentially deleterious due to increased carbon dioxide production with subsequent intracellular acidosis, improves kidney-related endpoints in the critically ill.

HSPA12A unstabilizes CD147 to inhibit lactate export and migration in human renal cell carcinoma

Background: Metastasis accounts for 90% of cancer-associated mortality in patients with renal cell carcinoma (RCC). However, the clinical management of RCC metastasis is challenging. Lactate export is known to play an important role in cancer cell migration. This study investigated the role of heat shock protein A12A (HSPA12A) in RCC migration. Methods: HSPA12A expression was examined in 82 pairs of matched RCC tumors and corresponding normal kidney tissues from patients by immunoblotting and immunofluorescence analyses. The proliferation of RCC cells was analyzed using MTT and EdU incorporation assays. The migration of RCC cells was evaluated by wound healing and Transwell migration assays. Extracellular acidification was examined using Seahorse technology. Protein stability was determined following treatment with protein synthesis inhibitor cycloheximide and proteasome inhibitor MG132. Mass spectrometry, immunoprecipitation, and immunoblotting were employed to examine protein-protein interactions. Results: RCC tumors from patients showed downregulation of HSPA12A, which was associated with advanced tumor node metastasis stage. Intriguingly, overexpression of HSPA12A in RCC cells inhibited migration, whereas HSPA12A knockdown had the opposite effect. Lactate export, glycolysis rate, and CD147 protein abundance were also inhibited by HSPA12A overexpression but promoted by HSPA12A knockdown. An interaction of HSPA12A with HRD1 ubiquitin E3 ligase was detected in RCC cells. Further studies demonstrated that CD147 ubiquitination and proteasomal degradation were promoted by HSPA12A overexpression whereas inhibited by HSPA12A knockdown. Notably, the HSPA12A overexpression-induced inhibition of lactate export and migration were abolished by CD147 overexpression. Conclusion: Human RCC shows downregulation of HSPA12A. Overexpression of HSPA12A in RCC cells unstabilizes CD147 through increasing its ubiquitin-proteasome degradation, thereby inhibits lactate export and glycolysis, and ultimately suppresses RCC cell migration. Our results demonstrate that overexpression of HSPA12A might represent a viable strategy for managing RCC metastasis.

Predictors of Increased Lactate in Neonatal Cardiac Surgery: The Impact of Cardiopulmonary Bypass

OBJECTIVE

Hyperlactatemia develops intraoperatively during cardiac surgery and is associated with postoperative mortality. This study aimed to determine the factors that lead to an increase in lactate during cardiopulmonary bypass (CPB) in neonates undergoing cardiac surgery.

DESIGN

Retrospective study from July 2015 to December 2018.

SETTING

Academic tertiary children's hospital.

PARTICIPANTS

The study comprised 376 neonates.

INTERVENTIONS

No interventions were performed.

MEASUREMENTS AND MAIN RESULTS

Lactate measurements at prebypass, upon initiation of CPB and before coming off CPB, last in the operating room, and first in the cardiac intensive care unit were collected. The changes in lactate levels were compared using the nonparametric Wilcoxon signed rank test for paired data. Univariate and multivariate median regression models of the change during CPB were determined. The cohort characteristics were male (60%), median age 5 days (range 1-30), and weight 3.2 kg (range 1.5-4.7). Most patients had a STAT score of 4 (45%) or 5 (23%). Significant increases in lactate were observed from pre-CPB to start of CPB (p < 0.001) and from start to end of CPB (p < 0.001). In the multivariate regression analysis, duration of circulatory arrest (coefficient = 1.216; 95% confidence interval [CI] 0.754-1.678; p < 0.001), duration of mean arterial pressure < 25 mmHg (coefficient = 0.423; 95% CI 0.196-to- 0.651; p < 0.001), and duration of mean arterial pressure between 35 and 39 mmHg (coefficient = -0.246; 95% CI -0.397 to -0.095; p = 0.001) were identified as significant independent predictors of the lactate change per 30- minutes duration.

CONCLUSION

These results emphasized the importance of blood pressure management during CPB and the importance of the duration of circulatory arrest.

A fatal case of COVID-19 due to metabolic acidosis following dysregulate inflammatory response (cytokine storm)

The ongoing outbreak of COVID-19 has been expanding worldwide. As of 17 April 2020, the death toll stands at a sobering 147,027 and over two million cases, this has been straining the health care systems all over. Respiratory failure has been cited as the major cause of death but here we present a case about a patient who instead succumbed to severe metabolic acidosis with multiple organ failure.