Comprehensive review on lactate metabolism in human health

Effects of High-Intensity Interval Training Protocols on Blood Lactate Levels and Cognition in Healthy Adults: Systematic Review and Meta-Regression

BACKGROUND

Some health benefits from high-intensity interval training (HIIT) are facilitated by peripheral blood lactate levels. However, the lactate response from HIIT is variable and dependent on protocol parameters.

OBJECTIVES

We aimed to determine the HIIT protocol parameters that elicited peak lactate levels, and how these levels are associated with post-HIIT cognitive performance.

STUDY DESIGN

We conducted a systematic review with meta-regression.

METHODS

MEDLINE, Embase, CENTRAL, SPORTDiscus, and CINAHL + were searched from database inception to 8 April, 2022. Peer-reviewed primary research in healthy adults that determined lactate (mmol/L) and cognitive performance after one HIIT session was included. Mixed-effects meta-regressions determined the protocol parameters that elicited peak lactate levels, and linear regressions modelled the relationship between lactate levels and cognitive performance.

RESULTS

Study entries (n = 226) involving 2560 participants (mean age 24.1 ± 4.7 years) were included in the meta-regression. A low total work-interval volume (~ 5 min), recovery intervals that are about five times longer than work intervals, and a medium session volume (~ 15 min), elicited peak lactate levels, even when controlling for intensity, fitness (peak oxygen consumption) and blood measurement methods. Lactate levels immediately post-HIIT explained 14-17% of variance in Stroop interference condition at 30 min post-HIIT.

CONCLUSIONS

A HIIT protocol that uses the above parameters (e.g., 8 × 30-s maximal intensity with 90-s recovery) can elicit peak lactate, a molecule that is known to benefit the central nervous system and be involved in exercise training adaptations. This review reports the state of the science in regard to the lactate response following HIIT, which is relevant to those in the sports medicine field designing HIIT training programs.

TRIAL REGISTRY

Clinical Trial Registration: PROSPERO (CRD42020204400).

Altered Distribution of Unesterified Cholesterol among Lipoprotein Subfractions of Patients with Diabetes Mellitus Type 2

Biomarkers are important tools to improve the early detection of patients at high risk for developing diabetes as well as the stratification of diabetic patients towards risks of complications. In addition to clinical variables, we analyzed 155 metabolic parameters in plasma samples of 51 healthy volunteers and 66 patients with diabetes using nuclear magnetic resonance (NMR) spectrometry. Upon elastic net analysis with lasso regression, we confirmed the independent associations of diabetes with branched-chain amino acids and lactate (both positive) as well as linoleic acid in plasma and HDL diameter (both inverse). In addition, we found the presence of diabetes independently associated with lower concentrations of free cholesterol in plasma but higher concentrations of free cholesterol in small HDL. Compared to plasmas of non-diabetic controls, plasmas of diabetic subjects contained lower absolute and relative concentrations of free cholesterol in all LDL and HDL subclasses except small HDL but higher absolute and relative concentrations of free cholesterol in all VLDL subclasses (except very small VLDL). These disbalances may reflect disturbances in the transfer of free cholesterol from VLDL to HDL during lipolysis and in the transfer of cell-derived cholesterol from small HDL via larger HDL to LDL.

Prediction of the Postoperative Outcome in Liver Resection Using Perioperative Serum Lactate Levels

Background: The aim of our study was to analyze perioperative lactate levels and their predictive value for postoperative mortality and morbidity after liver resection. Methods: The clinicopathological characteristics and outcomes of 152 patients who underwent liver resection for benign and malign diagnoses were analyzed retrospectively. Lactate concentrations at three different time points, (1) before liver resection (LAC-PRE), (2) after liver resection on day 0 (LAC-POST), and (3) on day one after the operation (LAC-POD1) were assessed regarding the prognostic value in predicting postoperative complications and mortality according to the Clavien–Dindo (CD) classification. Results: The rates of postoperative complications (CD ≥ IIIb) and mortality rates were 19.7% (N = 30) and 4.6% (N = 7), respectively. The LAC-PRE levels showed no correlation with the postoperative outcome. The ROC curve analysis showed that LCT-POST and LCT-POD1 values were moderately strong in predicting postoperative morbidity (0.681 and 0.768, respectively) and had strong predictive accuracies regarding postoperative mortality (0.800 and 0.838, respectively). The multivariate analysis revealed LAC-POST as a significant predictor of postoperative complications (CD ≥ IIIb: OR 9.28; 95% CI: 2.88–29.9; p < 0.001) and mortality (OR 11.69; 95% CI: 1.76–77.7; p = 0.011). Conclusion: Early postoperative lactate levels are a useful and easily practicable predictor of postoperative morbidity and mortality in patients after liver resection.

Compared with Milk Protein, a Wheat and Pea Protein Blend Reduces High-Fat, High-Sucrose Induced Metabolic Dysregulations while Similarly Supporting Tissue Protein Anabolism in Rats

BACKGROUND

Plant proteins (PPs) have been associated with better cardiovascular health than animal proteins (APs) in epidemiological studies. However, the underlying metabolic mechanisms remain mostly unknown.

OBJECTIVES

Using a combination of cutting-edge isotopic methods, we aimed to better characterize the differences in protein and energy metabolisms induced by dietary protein sources (PP compared with AP) in a prudent or western dietary context.

METHODS

Male Wistar rats (n = 44, 8 wk old) were fed for 4.5 mo with isoproteic diets differing in their protein isolate sources, either AP (100% milk) or PP (50%:50% pea: wheat) and being normal (NFS) or high (HFS) in sucrose (6% or 15% kcal) and saturated fat (7% or 20% kcal), respectively. We measured body weight and composition, hepatic enzyme activities and lipid content, and plasma metabolites. In the intestine, liver, adipose tissues, and skeletal muscles, we concomitantly assessed the extent of amino acid (AA) trafficking using a ¹⁵N natural abundance method, the rates of macronutrient routing to dispensable AA using a ¹³C natural abundance method, and the metabolic fluxes of protein synthesis (PS) and de novo lipogenesis using a ²H labeling method. Data were analyzed using ANOVA and Mixed models.

RESULTS

At the whole-body level, PP limited HFS-induced insulin resistance (-27% in HOMA-IR between HFS groups, P < 0.05). In the liver, PP induced lower lipid content (-17%, P < 0.01) and de novo lipogenesis (-24%, P < 0.05). In the different tissues studied, PP induced higher AA transamination accompanied by higher routings of dietary carbohydrates and lipids toward dispensable AA synthesis by glycolysis and β-oxidation, resulting in similar tissue PS and protein mass.

CONCLUSIONS

In growing rats, compared with AP, a balanced blend of PP similarly supports protein anabolism while better limiting whole-body and tissue metabolic dysregulations through mechanisms related to their less optimal AA profile for direct channeling to PS.

Addressing Cognitive Biases in Interpreting an Elevated Lactate in a Patient with Type 1 Diabetes and Thiamine Deficiency

We present the case of a young woman admitted for diabetic ketoacidosis with persistent, asymptomatic lactic acid (LA) elevation during the evolving COVID-19 pandemic. Cognitive biases in interpreting an elevated LA in this patient's care resulted in an extensive infectious workup instead of the low-cost and potentially diagnostic provision of empiric thiamine. We discuss clinical patterns and etiologies of LA elevation and the role of thiamine deficiency. We also address cognitive biases potentially affecting the interpretation of elevated lactate levels and provide guidance for clinicians to determine appropriate patients for empiric thiamine administration.

Hypoxia enhances IPF mesenchymal progenitor cell fibrogenicity via the lactate/GPR81/HIF1α pathway

Hypoxia is a sentinel feature of idiopathic pulmonary fibrosis (IPF). The IPF microenvironment contains high lactate levels, and hypoxia enhances cellular lactate production. Lactate, acting through the GPR81 lactate receptor, serves as a signal molecule regulating cellular processes. We previously identified intrinsically fibrogenic mesenchymal progenitor cells (MPCs) that drive fibrosis in the lungs of patients with IPF. However, whether hypoxia enhances IPF MPC fibrogenicity is unclear. We hypothesized that hypoxia increases IPF MPC fibrogenicity via lactate and its cognate receptor GPR81. Here we show that hypoxia promotes IPF MPC self-renewal. The mechanism involves hypoxia-mediated enhancement of LDHA function and lactate production and release. Hypoxia also increases HIF1α levels, and this increase in turn augments the expression of GPR81. Exogenous lactate operating through GPR81 promotes IPF MPC self-renewal. IHC analysis of IPF lung tissue demonstrates IPF MPCs expressing GPR81 and hypoxic markers on the periphery of the fibroblastic focus. We show that hypoxia enhances IPF MPC fibrogenicity in vivo. We demonstrate that knockdown of GPR81 inhibits hypoxia-induced IPF MPC self-renewal in vitro and attenuates hypoxia-induced IPF MPC fibrogenicity in vivo. Our data demonstrate that hypoxia creates a feed-forward loop that augments IPF MPC fibrogenicity via the lactate/GPR81/HIF1α pathway.

Lactate: a pearl dropped in the ocean-an overlooked signal molecule in physiology and pathology

Lactate, once recognized as a wasty product from anaerobic glycolysis, is proved to be a pivotal signal molecule. Lactate accumulation occurs in diverse physiological and pathological settings due to the imbalance between lactate production and clearance. Under the condition with drastic changes in local microenvironment, such as tumorigenesis, inflammation, and microbial infection, the glycolysis turns to be active in surrounding cells leading to increased lactate release. Meanwhile, lactate can be utilized by these cells as an energy substrate and acts as a signal molecule to regulate cell functions through receptor-dependent or independent pathways. In this review, we tended to tease out the contribution of lactate in tumor progression and immunomodulation. And we also discussed the accessory role of lactate, beyond as the energy source only, in the growth of invading pathogens.

Acute effects of moderate vs. vigorous endurance exercise on urinary metabolites in healthy, young, physically active men-A multi-platform metabolomics approach

Introduction: Endurance exercise alters whole-body as well as skeletal muscle metabolism and physiology, leading to improvements in performance and health. However, biological mechanisms underlying the body's adaptations to different endurance exercise protocols are not entirely understood. Methods: We applied a multi-platform metabolomics approach to identify urinary metabolites and associated metabolic pathways that distinguish the acute metabolic response to two endurance exercise interventions at distinct intensities. In our randomized crossover study, 16 healthy, young, and physically active men performed 30 min of continuous moderate exercise (CME) and continuous vigorous exercise (CVE). Urine was collected during three post-exercise sampling phases (U01/U02/U03: until 45/105/195 min post-exercise), providing detailed temporal information on the response of the urinary metabolome to CME and CVE. Also, fasting spot urine samples were collected pre-exercise (U00) and on the following day (U04). While untargeted two-dimensional gas chromatography-mass spectrometry (GC×GC-MS) led to the detection of 608 spectral features, 44 metabolites were identified and quantified by targeted nuclear magnetic resonance (NMR) spectroscopy or liquid chromatography-mass spectrometry (LC-MS). Results: 104 urinary metabolites showed at least one significant difference for selected comparisons of sampling time points within or between exercise trials as well as a relevant median fold change >1.5 or <0. 6 ¯ (NMR, LC-MS) or >2.0 or <0.5 (GC×GC-MS), being classified as either exercise-responsive or intensity-dependent. Our findings indicate that CVE induced more profound alterations in the urinary metabolome than CME, especially at U01, returning to baseline within 24 h after U00. Most differences between exercise trials are likely to reflect higher energy requirements during CVE, as demonstrated by greater shifts in metabolites related to glycolysis (e.g., lactate, pyruvate), tricarboxylic acid cycle (e.g., cis-aconitate, malate), purine nucleotide breakdown (e.g., hypoxanthine), and amino acid mobilization (e.g., alanine) or degradation (e.g., 4-hydroxyphenylacetate). Discussion: To conclude, this study provided first evidence of specific urinary metabolites as potential metabolic markers of endurance exercise intensity. Future studies are needed to validate our results and to examine whether acute metabolite changes in urine might also be partly reflective of mechanisms underlying the health- or performance-enhancing effects of endurance exercise, particularly if performed at high intensities.

Role of Impaired Glycolysis in Perturbations of Amino Acid Metabolism in Diabetes Mellitus

The most frequent alterations in plasma amino acid concentrations in type 1 and type 2 diabetes are decreased L-serine and increased branched-chain amino acid (BCAA; valine, leucine, and isoleucine) levels. The likely cause of L-serine deficiency is decreased synthesis of 3-phosphoglycerate, the main endogenous precursor of L-serine, due to impaired glycolysis. The BCAA levels increase due to decreased supply of pyruvate and oxaloacetate from glycolysis, enhanced supply of NADH + H⁺ from beta-oxidation, and subsequent decrease in the flux through the citric acid cycle in muscles. These alterations decrease the supply of α-ketoglutarate for BCAA transamination and the activity of branched-chain keto acid dehydrogenase, the rate-limiting enzyme in BCAA catabolism. L-serine deficiency contributes to decreased synthesis of phospholipids and increased synthesis of deoxysphinganines, which play a role in diabetic neuropathy, impaired homocysteine disposal, and glycine deficiency. Enhanced BCAA levels contribute to increased levels of aromatic amino acids (phenylalanine, tyrosine, and tryptophan), insulin resistance, and accumulation of various metabolites, whose influence on diabetes progression is not clear. It is concluded that amino acid concentrations should be monitored in patients with diabetes, and systematic investigation is needed to examine the effects of L-serine and glycine supplementation on diabetes progression when these amino acids are decreased.

Immune Metabolism in TH2 Responses: New Opportunities to Improve Allergy Treatment - Disease-Specific Findings (Part 1)

PURPOSE OF REVIEW

Recent high-level publications have shown an intricate connection between immune effector function and the metabolic state of the respective cells. In the last years, studies have begun analyzing the metabolic changes associated with allergies. As the first part of a two-article series, this review will briefly summarize the basics of immune metabolism and then focus on the recently published studies on metabolic changes observed in allergic patients.

RECENT FINDINGS

In the last 3 years, immune-metabolic research in allergology had a clear focus on asthma with some studies also reporting findings in food allergy and atopic dermatitis. Current results suggest asthma to be associated with a shift in cellular metabolism towards increased aerobic glycolysis (Warburg metabolism), while also displaying substantial changes in fatty acid- and amino acid metabolism (depending on investigated patient collective, asthma phenotype, and disease severity). Understanding immune-metabolic changes in allergies will allow us to (I) better understand allergic disease pathology and (II) modulate immune-metabolic pathways to improve allergy treatment.

Understanding the Contribution of Lactate Metabolism in Cancer Progress: A Perspective from Isomers

Lactate mediates multiple cell-intrinsic effects in cancer metabolism in terms of development, maintenance, and metastasis and is often correlated with poor prognosis. Its functions are undertaken as an energy source for neighboring carcinoma cells and serve as a lactormone for oncogenic signaling pathways. Indeed, two isomers of lactate are produced in the Warburg effect: L-lactate and D-lactate. L-lactate is the main end-production of glycolytic fermentation which catalyzes glucose, and tiny D-lactate is fabricated through the glyoxalase system. Their production inevitably affects cancer development and therapy. Here, we systematically review the mechanisms of lactate isomers production, and highlight emerging evidence of the carcinogenic biological effects of lactate and its isomers in cancer. Accordingly, therapy that targets lactate and its metabolism is a promising approach for anticancer treatment.

A Selective Fluorescent l-Lactate Biosensor Based on an l-Lactate-Specific Transcription Regulator and Förster Resonance Energy Transfer

Selective detection of l-lactate levels in foods, clinical, and bacterial fermentation samples has drawn intensive attention. Many fluorescent biosensors based on non-stereoselective recognition elements have been developed for lactate detection. Herein, the allosteric transcription factor STLldR from Salmonella enterica serovar Typhimurium LT2 was identified to be stereo-selectively respond to l-lactate. Then, STLldR was combined with Förster resonance energy transfer (FRET) to construct a fluorescent l-lactate biosensor FILLac. FILLac was further optimized by truncating the N- and C-terminal amino acids of STLldR between cyan and yellow fluorescent proteins. The optimized biosensor FILLac_10N0C exhibited a maximum emission ratio change (ΔR_max) of 33.47 ± 1.91%, an apparent dissociation constant (K_d) of 6.33 ± 0.79 μM, and a limit of detection of 0.68 μM. FILLac_10N0C was applied in 96-well microplates to detect l-lactate in bacterial fermentation samples and commercial foods such as Jiaosu and yogurt. The quantitation results of FILLac_10N0C exhibited good agreement with that of a commercial l-lactate biosensor SBA-40D bioanalyzer. Thus, the biosensor FILLac_10N0C compatible with high-throughput detection may be a potential choice for quantitation of l-lactate in different biological samples.

Environmental oxygen affects ex vivo growth and proliferation of mesenchymal progenitors by modulating mitogen-activated protein kinase and mammalian target of rapamycin signaling

BACKGROUND AIMS

Stem and progenitor cells of hematopoietic and mesenchymal lineages reside in the bone marrow under low oxygen (O₂) saturation. O₂ levels used in ex vivo expansion of multipotent mesenchymal stromal cells (MSCs) affect proliferation, metabolism and differentiation.

METHODS

Using cell-based assays and transcriptome and proteome data, the authors compared MSC cultures simultaneously grown under a conventional 19.95% O₂ atmosphere or at 5% O₂.

RESULTS

In 5% O₂, MSCs showed better proliferation and higher self-renewal ability, most probably sustained by enhanced signaling activity of mitogen-activated protein kinase and mammalian target of rapamycin pathways. Non-oxidative glycolysis-based energy metabolism supported growth and proliferation in 5% O₂ cultures, whereas MSCs grown under 19.95% O₂ also utilized oxidative phosphorylation. Cytoprotection mechanisms used by cells under 5% O₂ differed from 19.95% O₂  suggesting differences in the triggers of cell stress between these two O₂  conditions.

CONCLUSIONS

Based on the potential benefits for the growth and metabolism of MSCs, the authors propose the use of 5% O₂ for MSC culture.

Colonocyte-derived lactate promotes E. coli fitness in the context of inflammation-associated gut microbiota dysbiosis

BACKGROUND

Intestinal inflammation disrupts the microbiota composition leading to an expansion of Enterobacteriaceae family members (dysbiosis). Associated with this shift in microbiota composition is a profound change in the metabolic landscape of the intestine. It is unclear how changes in metabolite availability during gut inflammation impact microbial and host physiology.

RESULTS

We investigated microbial and host lactate metabolism in murine models of infectious and non-infectious colitis. During inflammation-associated dysbiosis, lactate levels in the gut lumen increased. The disease-associated spike in lactate availability was significantly reduced in mice lacking the lactate dehydrogenase A subunit in intestinal epithelial cells. Commensal E. coli and pathogenic Salmonella, representative Enterobacteriaceae family members, utilized lactate via the respiratory L-lactate dehydrogenase LldD to increase fitness. Furthermore, mice lacking the lactate dehydrogenase A subunit in intestinal epithelial cells exhibited lower levels of inflammation in a model of non-infectious colitis.

CONCLUSIONS

The release of lactate by intestinal epithelial cells during gut inflammation impacts the metabolism of gut-associated microbial communities. These findings suggest that during intestinal inflammation and dysbiosis, changes in metabolite availability can perpetuate colitis-associated disturbances of microbiota composition. Video Abstract.

Rap1b-loss increases neutrophil lactate dehydrogenase activity to enhance neutrophil migration and acute inflammation in vivo

Introduction

Neutrophils are critical for host immune defense; yet, aberrant neutrophil tissue infiltration triggers tissue damage. Neutrophils are heterogeneous functionally, and adopt 'normal' or 'pathogenic' effector function responses. Understanding neutrophil heterogeneity could provide specificity in targeting inflammation. We previously identified a signaling pathway that suppresses neutrophilmediated inflammation via integrin-mediated Rap1b signaling pathway.

Methods

Here, we used Rap1-deficient neutrophils and proteomics to identify pathways that specifically control pathogenic neutrophil effector function.

Results

We show neutrophil acidity is normally prevented by Rap1b during normal immune response with loss of Rap1b resulting in increased neutrophil acidity via enhanced Ldha activity and abnormal neutrophil behavior. Acidity drives the formation of abnormal invasive-like protrusions in neutrophils, causing a shift to transcellular migration through endothelial cells. Acidity increases neutrophil extracellular matrix degradation activity and increases vascular leakage in vivo. Pathogenic inflammatory condition of ischemia/reperfusion injury is associated with increased neutrophil transcellular migration and vascular leakage. Reducing acidity with lactate dehydrogenase inhibition in vivo limits tissue infiltration of pathogenic neutrophils but less so of normal neutrophils, and reduces vascular leakage.

Discussion

Acidic milieu renders neutrophils more dependent on Ldha activity such that their effector functions are more readily inhibited by small molecule inhibitor of Ldha activity, which offers a therapeutic window for antilactate dehydrogenase treatment in specific targeting of pathogenic neutrophils in vivo.

Associations of Metabolic Syndrome and Abdominal Obesity with Anion Gap Metabolic Acidosis among US Adults

BACKGROUND

Obesity is a recently identified risk factor for metabolic acidosis and anion gap elevations in the absence of CKD. Metabolic acidosis is a treatable condition with substantial adverse effects on human health. Additional investigations are needed to characterize at-risk populations and explore potential mechanisms. We hypothesized metabolic syndrome (MetS) and waist circumference (WC) would be closely associated with this pathology.

METHODS

Adult participants from NHANES 1999-2018 meeting study criteria were compiled as main (n=31,163) and fasting (n=12,860) cohorts. Regression models adjusted for dietary acid, eGFR, and other factors examined associations of WC and MetS features with anion gap metabolic acidosis and its components (serum bicarbonate ≤23 mEq/L and anion gap >95th percentile).

RESULTS

Greater WC and MetS features were associated with progressively lower bicarbonate, higher anion gap, and greater odds ratios (OR) of metabolic acidosis (MA) and anion gap metabolic acidosis (AGMA). Compared with the reference, participants with the highest WC had ORs for MA and AGMA of 2.26; 95% CI, 1.96 to 2.62 and 2.89; 95% CI, 1.97 to 4.21; those with three and four versus zero MetS features had ORs for AGMA of 2.52; 95% CI, 1.95 to 2.94 and 3.05; 95% CI, 2.16 to 3.82. Associations of body mass index with outcomes were attenuated or absent after adjustment for WC or MetS. Findings were preserved after excluding eGFR <90 ml/min per 1.73 m² and albuminuria. A lower MA cutoff (<22 mEq/L) raised the estimate of association between MetS and MA (OR for three and four vs zero features: 3.56; 95% CI, 2.53 to 5.02 and 5.44; 95% CI, 3.66 to 8.08).

CONCLUSIONS

Metabolic diseases are characterized by metabolic acidosis and anion gap elevations. Metabolic dysfunction may predispose patients without CKD to systemic acidosis from endogenous sources. Comprehensive acid-base analyses may be informative in patients with metabolic diseases.

Radiosynthesis, Preclinical, and Clinical Positron Emission Tomography Studies of Carbon-11 Labeled Endogenous and Natural Exogenous Compounds

The presence of positron emission tomography (PET) centers at most major hospitals worldwide, along with the improvement of PET scanner sensitivity and the introduction of total body PET systems, has increased the interest in the PET tracer development using the short-lived radionuclides carbon-11. In the last few decades, methodological improvements and fully automated modules have allowed the development of carbon-11 tracers for clinical use. Radiolabeling natural compounds with carbon-11 by substituting one of the backbone carbons with the radionuclide has provided important information on the biochemistry of the authentic compounds and increased the understanding of their in vivo behavior in healthy and diseased states. The number of endogenous and natural compounds essential for human life is staggering, ranging from simple alcohols to vitamins and peptides. This review collates all the carbon-11 radiolabeled endogenous and natural exogenous compounds synthesised to date, including essential information on their radiochemistry methodologies and preclinical and clinical studies in healthy subjects.

Different Impacts of Heat-Killed and Viable Lactiplantibacillus plantarum TWK10 on Exercise Performance, Fatigue, Body Composition, and Gut Microbiota in Humans

Lactiplantibacillus plantarum TWK10, a probiotic strain, has been demonstrated to improve exercise performance, regulate body composition, and ameliorate age-related declines. Here, we performed a comparative analysis of viable and heat-killed TWK10 in the regulation of exercise performance, body composition, and gut microbiota in humans. Healthy adults (n = 53) were randomly divided into three groups: Control, TWK10 (viable TWK10, 3 × 1011 colony forming units/day), and TWK10-hk (heat-killed TWK10, 3 × 1011 cells/day) groups. After six-week administration, both the TWK10 and TWK10-hk groups had significantly improved exercise performance and fatigue-associated features and reduced exercise-induced inflammation, compared with controls. Viable TWK10 significantly promoted improved body composition, by increasing muscle mass proportion and reducing fat mass. Gut microbiota analysis demonstrated significantly increasing trends in the relative abundances of Akkermansiaceae and Prevotellaceae in subjects receiving viable TWK10. Predictive metagenomic profiling revealed that heat-killed TWK10 administration significantly enhanced the signaling pathways involved in amino acid metabolisms, while glutathione metabolism, and ubiquinone and other terpenoid-quinone biosynthesis pathways were enriched by viable TWK10. In conclusion, viable and heat-killed TWK10 had similar effects in improving exercise performance and attenuating exercise-induced inflammatory responses as probiotics and postbiotics, respectively. Viable TWK10 was also highly effective in regulating body composition. The differences in efficacy between viable and heat-killed TWK10 may be due to differential impacts in shaping gut microbiota.

Cancer-testis antigen lactate dehydrogenase C4 as a novel biomarker of male infertility and cancer

A unique lactate dehydrogenase (LDH) isoenzyme designated as lactate dehydrogenase C4 (LDH-C4) is found in mammalian mature testis and spermatozoa. Thus far, LDH-C4 has been well studied with regard to its gene and amino acid sequences, structure, biological properties, and peptide synthesis. Accumulating evidence has shown that LDH-C4 is closely related to spermatic energy metabolism and plays a critical role in sperm motility, capacitation, and fertilization. Defects in the catalytic activity of LDH-C4 are key to pathophysiological abnormalities underlying infertility. LDH-C4 was originally thought to be present only in mature testis and spermatozoa; however, recent studies have implicated LDH-C4 as a cancer-testis antigen (CTA), owing to its aberrant transcription in a broad spectrum of human neoplasms. This review highlights the recent findings on LDH-C4 with particular emphasis on its role in male infertility and tumors.

Low levels of serum LDH are associated with depression and suicide attempts

BACKGROUND

A huge body of evidence has signaled a correlation between adult depression and energy metabolism. The key links are the energy supply and substrates for brain energy metabolism and the crucial signaling molecule lactate. Nevertheless, the association between lactate metabolism and depression remains elusive.

OBJECTIVE

The primary objective of this study was to explore the difference in serum LDH levels between patients with major depressive disorder (MDD) and the normal population and to determine whether LDH can be employed as a predictor of suicide attempt (SA) in MDD patients.

METHODS

Serum LDH levels were measured in 232 patients with MDD and 110 healthy controls. Depressive symptoms were assessed using the 24-item Hamilton Depression Scale (HAMD-24). The data were collected and analyzed with SPSS 22.0.

RESULTS

The serum LDH level of the control group was (196.50 ± 34.40) U/L, while that of the MDD group was (177.94 ± 25.89) U/L (P < 0.001). Notably, the LDH level [(169.96 ± 25.31) U/L] in the SA group was significantly lower than that in the control and non-SA groups [(181.25 ± 25.47) U/L] (P < 0.01); There was no significant correlation with HAMD-24 score (P > 0.05). Collectively, this study demonstrated that a decrease in serum LDH levels is an independent risk factor for SA in MDD patients.

CONCLUSION

Our results imply that a decrease in LDH levels may be associated with MDD and suicidal behaviors. Early identification of suicide risk and evaluation of the prognosis of depression is critical.

Targeting lactate-related cell cycle activities for cancer therapy

Lactate has long been considered as a metabolic by-product of aerobic glycolysis for cancer. However, more and more studies have shown that lactate can regulate cancer progression via multiple mechanisms such as cell cycle regulation, immune suppression, energy metabolism and so on. A recent discovery of lactylation attracted a lot of attention and is already a hot topic in the cancer field. In this review, we summarized the latest functions of lactate and its underlying mechanisms in cancer. We also included our analysis of protein lactylation in different rat organs and compared them with other published lactylation data. The unresolved challenges in this field were discussed, and the potential application of these new discoveries of lactate-related cell cycle activities for cancer target therapy was speculated.

Integrative Analysis of the Nasal Microbiota and Serum Metabolites in Bovines with Respiratory Disease by 16S rRNA Sequencing and Gas Chromatography/Mass Selective Detector-Based Metabolomics

Bovine respiratory disease (BRD) continues to pose a serious threat to the cattle industry, resulting in substantial economic losses. As a multifactorial disease, pathogen infection and respiratory microbial imbalance are important causative factors in the occurrence and development of BRD. Integrative analyses of 16S rRNA sequencing and metabolomics allow comprehensive identification of the changes in microbiota and metabolism associated with BRD, making it possible to determine which pathogens are responsible for the disease and to develop new therapeutic strategies. In our study, 16S rRNA sequencing and metagenomic analysis were used to describe and compare the composition and diversity of nasal microbes in healthy cattle and cattle with BRD from different farms in Yinchuan, Ningxia, China. We found a significant difference in nasal microbial diversity between diseased and healthy bovines; notably, the relative abundance of Mycoplasma bovis and Pasteurella increased. This indicated that the composition of the microbial community had changed in diseased bovines compared with healthy ones. The data also strongly suggested that the reduced relative abundance of probiotics, including Pasteurellales and Lactobacillales, in diseased samples contributes to the susceptibility to bovine respiratory disease. Furthermore, serum metabolomic analysis showed altered concentrations of metabolites in BRD and that a significant decrease in lactic acid and sarcosine may impair the ability of bovines to generate energy and an immune response to pathogenic bacteria. Based on the correlation analysis between microbial diversity and the metabolome, lactic acid (2TMS) was positively correlated with Gammaproteobacteria and Bacilli and negatively correlated with Mollicutes. In summary, microbial communities and serum metabolites in BRD were characterized by integrative analysis. This study provides a reference for monitoring biomarkers of BRD, which will be critical for the prevention and treatment of BRD in the future.

Effect of syringic acid on steroid and gonadotropic hormones, hematological indices, sperm characteristics and morphologies, and markers of tissue damage in methyl cellosolve-administered rats

Methyl cellosolve (MTC) is an established gonadotoxic and hematotoxic compound that is commonly and universally utilized in herbicide, liquid soap, stain, dye, paint, and brake fluid manufacturing industries as a solvent. Due to its wide range usage, this study therefore investigated the effect of syringic acid (SYAC) on hematological indices, sperm characteristics and morphologies, and markers of tissue damage in MTC administered male Wistar rats. Thirty (30) rats divided into six groups were used. Rats in group 1 served as control, those in group 2 were administered MTC for 30 consecutive days, those in groups 3, 4, and 5 were treated with 25, 50, and 75 mg/kg body weight of SYAC respectively also for 30 consecutive days immediately after each day MTC administrations, while rats in group 6 received 75 mg/kg body weight of SYAC only throughout. Compared with control, administrations of MTC resulted in a significant decrease in spermatozoa count, number of normal and live spermatozoa, Hb count, MCH, MCHC, serum TC, and LH, while number of abnormal spermatozoa, RBC and WBC counts, activities of serum AST, ALT, GGT, LDH, and ADH were significantly increased. Treatments with 25 mg/kg of SYAC significantly reduced the RBC and WBC counts, serum activities of AST, ALT, GGT, and increased TC concentration. Treatments with 50 mg/kg SYAC significantly lowered the number of abnormal spermatozoa, RBC count, activities of serum ALT, AST, LDH, ADH, and increased the number of normal spermatozoa, MCV, MCH, and MCHC, while 75 mg/kg of SYAC significantly decreased the serum activities of AST, ALT, GGT, LDH, ADH, and increased serum TC concentration. Findings from this study have revealed the hepatoprotective effect of SYAC at all doses investigated but did not confer spermatoprotection and hematoprotection against MTC-induced toxicities, and looking at the 3 doses investigated, 50 mg/kg of SYAC yielded the best effect.

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MTC significantly decreased live sperm, sperm count, MCH, MCHC, and Hb counts.

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MTC significantly increased number of abnormal sperm, RBC and WBC counts.

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MTC significantly increased serum activities of AST, ALT, GGT, LDH, and ADH.

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SYAC significantly decreased RBC and WBC counts, AST, ALT, GGT, LDH, and ADH.

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SYAC significantly increased number of normal sperm, MCV, MCH, and MCHC counts.

Metformin-Associated Lactic Acidosis in a Diabetic Patient with Normal Kidney Function and Occult Cirrhosis

Background

Lactic acidosis is a well-known complication of metformin accumulation in diabetic patients with kidney failure. However, it is not usual to raise the diagnosis of metformin-associated lactic acidosis when patients have normal kidney function. The causes of metformin-induced high lactate include the accumulation of normal doses of metformin in chronic kidney disease, an overdose of this drug without kidney failure, or an increase in lactate production due to the inhibition of liver gluconeogenesis. Case Presentation. We report the case of a 61-year-old diabetic man who was brought to the emergency room in a comatose state. His family reported abdominal pain with diarrhea in the last two days. He was found to have severe lactic acidosis with normal serum creatinine. He was on a regular dose of metformin, and his family denied any other medical history or any alcohol abuse. He showed no signs of infection, his liver enzymes were slightly elevated, and he had severe anemia. His hemodynamics deteriorated quickly within hours, and an abdominal computed tomography scan revealed no abnormalities. He underwent a laparotomy that ruled out mesenteric ischemia and revealed an abnormal liver. The liver biopsy later confirmed the diagnosis of cirrhosis.

Conclusions

We discuss here the probable causes of severe lactic acidosis and the role of metformin in exacerbating this acid-base disturbance in cirrhotic patients. Future research is needed to determine whether these patients might benefit from dialysis.

Black Ginger (Kaempferia parviflora) Extract Enhances Endurance Capacity by Improving Energy Metabolism and Substrate Utilization in Mice

Black ginger (Kaempferia parviflora) extract (KPE), extracted from KP, a member of the ginger family that grows in Thailand, has a good promotion effect on cellular energy metabolism and therefore has been used to enhance exercise performance and treatment of obesity in previous studies. However, the effect of single-dose administration of KPE on endurance capacity has not been thoroughly studied, and whether the positive effect of KPE on cellular energy metabolism can have a positive effect on exercise capacity in a single dose is unknown. In the present study, we used a mouse model to study the effects of acute KPE administration 1 h before exercise on endurance capacity and the underlying mechanisms. The purpose of our study was to determine whether a single administration of KPE could affect endurance performance in mice and whether the effect was produced through a pro-cellular energy metabolic pathway. We found that a single administration of KPE (62.5 mg/kg·bodyweight) can significantly prolong the exercise time to exhaustion. By measuring the mRNA expression of Hk2, Slc2a4 (Glut4), Mct1, Ldh, Cd36, Cpt1β, Cpt2, Lpl, Pnpla2 (Atgl), Aco, Acadm (Mcad), Hadh, Acacb (Acc2), Mlycd (Mcd), Pparg, Ppargc1a (Pgc-1α), Tfam, Gp, Gs, Pfkm, Pck1 (Pepck), G6pc (G6pase), Cs, and Pfkl in skeletal muscle and liver, we found that acute high-concentration KPE administration significantly changed the soleus muscle gene expression levels (p < 0.05) related to lipid, lactate, and glycogen metabolism and mitochondrial function. In gastrocnemius muscle and liver, glycogen metabolism-related gene expression is significantly changed by a single-dose administration of KPE. These results suggest that KPE has the potential to improve endurance capacity by enhancing energy metabolism and substrate utilization in muscles and liver.

Protein Conformational Space at the Edge of Allostery: Turning a Non-allosteric Malate Dehydrogenase into an "Allosterized" Enzyme using Evolution Guided Punctual Mutations

We unveil the intimate relationship between protein dynamics and allostery by following the trajectories of model proteins in their conformational and sequence spaces. Starting from a nonallosteric hyperthermophilic malate dehydrogenase, we have tracked the role of protein dynamics in the evolution of the allosteric capacity. Based on a large phylogenetic analysis of the malate (MalDH) and lactate dehydrogenase (LDH) superfamily, we identified two amino acid positions that could have had a major role for the emergence of allostery in LDHs, which we targeted for investigation by site-directed mutagenesis. Wild-type MalDH and the single and double mutants were tested with respect to their substrate recognition profiles. The double mutant displayed a sigmoid-shaped profile typical of homotropic activation in LDH. By using molecular dynamics simulations, we showed that the mutations induce a drastic change in the protein sampling of its conformational landscape, making transiently T-like (inactive) conformers, typical of allosteric LDHs, accessible. Our data fit well with the seminal key concept linking protein dynamics and evolvability. We showed that the selection of a new phenotype can be achieved by a few key dynamics-enhancing mutations causing the enrichment of low-populated conformational substates.

Assessment of cellular responses in three-dimensional cell cultures through chemical exchange saturation transfer and 1 H MRS

Metabolic responses to physiological changes have been detected using chemical exchange saturation transfer (CEST) imaging in clinical settings. Similarly to other MRI techniques, the CEST technique was based originally on phantoms from buffer solutions and was then further developed through animal experiments. However, CEST imaging can capture certain dynamics of metabolism that solution phantoms cannot model. Cell culture phantoms can fill the gap between buffer phantoms and animal models. In this study, we used ¹ H NMR and CEST in a B₀ field of 9.4 T to investigate HEK293T cells from two-dimensional (2D) cultures, three-dimensional (3D) cultures, and 3D cultures seeded with cell spheroids. Two CEST dips were observed: the magnitude of the amine dip at 2.8 ppm increased during the incubation period, whereas the hydroxyl dip at 1.2 ppm remained approximately the same or modestly increased. We also observed a CEST dip at 2.8 ppm from the 2D culture responding dramatically to doxorubicin treatment. By cross-validating with pH values and the concentrations of amine and hydroxyl protons extracted through ¹ H NMR, we observed that they did not correspond to an increase in the amine pool. We believe that the denaturation or degradation of proteins from the fetal bovine serum increased the size of the amine pool. Although 3D culture conditions can be further improved, our study suggests that 3D cultures have the potential to bridge studies of solution phantoms and those on animals.

UHPLC-MS/MS-Based Metabolomics and Clinical Phenotypes Analysis Reveal Broad-Scale Perturbations in Early Pregnancy Related to Gestational Diabetes Mellitus

Gestational diabetes mellitus (GDM) is the most common metabolic disturbance during pregnancy, with adverse effects on both mother and fetus. The establishment of early diagnosis and risk assessment model is of great significance for preventing and reducing adverse outcomes of GDM. In this study, the broad-scale perturbations related to GDM were explored through the integration analysis of metabolic and clinical phenotypes. Maternal serum samples from the first trimester were collected for targeted metabolomics analysis by using ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). Statistical analysis was conducted based on the levels of the 184 metabolites and 76 clinical indicators from GDM women ( $n$  =60) and matched healthy controls ( $n$  =90). Metabolomics analysis revealed the down-regulation of fatty acid oxidation in the first trimester of GDM women, which was supposed to be related to the low serum level of dehydroepiandrosterone.While the significantly altered clinical phenotypes were mainly related to the increased risk of cardiovascular disease, abnormal iron metabolism, and inflammation. A phenotype panel established from the significantly changed serum indicators can be used for the early prediction of GDM, with the area under the receiver-operating characteristic curve (ROC) 0.83. High serum uric acid and C-reaction protein levels were risk factors for GDM independent of body mass indexes, with ORs 4.76 (95% CI: 2.08-10.90) and 3.10 (95% CI: 1.38-6.96), respectively. Predictive phenotype panel of GDM, together with the risk factors of GDM, will provide novel perspectives for the early clinical warning and diagnosis of GDM.

Liraglutide reduces oxidative stress and improves energy metabolism in methylglyoxal-induced SH-SY5Y cells

Diabetes mellitus can result in severe complications, such as neurodegenerative diseases including cognitive impairment and dementia. The glucagon-like peptide-1 (GLP-1) receptor agonist, liraglutide, is a novel antidiabetic drug with neuroprotective effects against neurodegenerative diseases. In this study, we explored the protective effect of liraglutide on SH-SY5Y cells exposed to methylglyoxal (MG), a byproduct of glucose metabolism that plays a key role in the development of diabetic encephalopathy. We found that liraglutide reduced the MG-induced oxidative stress, increased the activity of superoxide dismutase (SOD) and expression levels of P22phox, Gp91phox, and Xdh genes, and reduced reactive oxygen species (ROS) content. Metabolomics analysis based on ¹H nuclear magnetic resonance showed that liraglutide induced alterations in metabolites involved in energy metabolism，including promotion of gluconeogenesis. Moreover, we found that liraglutide promoted oxidative phosphorylation and inhibited glycolysis in SH-SY5Y cells. This study revealed that liraglutide improved diabetes-related neuropathy damage by reducing the level of oxidative stress and maintaining the balance of energy metabolism, thus offering new insights into the potential mechanism of liraglutide in neuronal protection.

Influence of acetate- vs. lactate-containing fluid bolus therapy on acid-base status, electrolytes, and plasma lactate in dogs

Objective

Acetate- and lactate-containing fluids influence the acid-base and electrolyte status. This prospective, randomized, clinical study compared two balanced crystalloid solutions regarding their influence on acid-base status, electrolytes, and lactate values, when given to dogs as a resuscitation bolus of 30 mL/kg.

Material and methods

One hundred client-owned dogs presenting to the emergency service with signs of fluid deficits were randomly assigned to receive an intravenous bolus of 30 mL/kg of either a lactate- (LAC), or an acetate-containing solution (ACET). Before and after the bolus, vital parameters were assessed, and a venous blood gas analysis was performed.

Results

Both solutions performed equally well in decreasing the heart rate (ACET: −10 ± 27 bpm, LAC: −12 ± 30 bpm; p = 0.737). The acetate-containing solution caused a significant decrease in plasma lactate levels (p = 0.016), anion gap (p &lt; 0.001), and potassium (p &lt; 0.001), and a significant increase in chloride (p &lt; 0.001), and ionized calcium (p = 0.014). The lactate-containing solution caused a significant decrease in anion gap (p &lt; 0.001), sodium (p = 0.016), and potassium (p = 0.001), and a significant increase in chloride (p &lt; 0.001). ACET causes a stronger decrease in plasma lactate (p = 0.015), sodium (p = 0.039), potassium (p = 0.006), and an increase in chloride (p &lt; 0.001), and ionized calcium (p = 0.016) compared to LAC.

Conclusion

Both solutions caused mild changes in electrolyte concentrations and had minor influence on acid-base status when used for bolus therapy in dogs with fluid deficits. Further studies are needed to evaluate their influence on acid-base status, lactate, and electrolytes when used in larger volumes and for a longer time span.

Activation of GPR81 Aggravates Remote Organ Injury During Hepatic Ischemia-Reperfusion Injury

Hepatic ischemia-reperfusion injury (HIRI) is a serious situation with high morbidity and mortality, which is usually accompanied with hyperlactatemia due to impaired lactate clearance in liver. G-protein-coupled receptor 81 (GPR81) has recently been identified as the bioactive receptor of lactate. GPR81 is profoundly involved in the modulation of metabolism and inflammation, but its significance in HIRI remains unclear. The present study investigated the potential roles of GPR81 in HIRI by using the GPR81 agonist 3-chloro-5-hydroxybenzoic acid (CHBA). The results indicated that treatment with CHBA had no obvious effects on HIRI-induced histologic abnormalities and elevation of serum aspartate aminotransferase, alanine aminotransferase. However, CHBA significantly upregulated the serum level of tumor necrosis factor alpha and interleukin-6 in mice with HIRI. Administration of CHBA also exacerbated HIRI-induced histologic lesions in lung, increased the level of myeloperoxidase in lung tissue and the protein concentration in bronchoalveolar lavage fluid. In addition, the serum levels of brain natriuretic peptide and creatinine also increased in CHBA-treated mice. The results indicate that activation of GPR81 might aggravate HIRI-induced remote organ injury and result in serious outcomes.

L-lactate as an indicator for cellular metabolic status: An easy and cost-effective colorimetric L-lactate assay

Background

In recent times, the study of metabolic pathways has become inevitable and predominant for a variety of research fields as cancer biology and immunology. L-lactate as a product of anaerobic glycolysis has shown to be an important indicator of the cellular metabolic status and can be associated with diverse cellular effects. For this reason, L-lactate assay kits are of high demand when metabolic effects need to be considered. Nevertheless, commercially available kits are not affordable if multiple samples must be evaluated.

Principal finding

In this work, we develop an easy and cost-effective colorimetric assay for quantification of L-lactate suitable for cells with low or high L-lactate production based on LDH activity and suitable for 96 well-plate format. Using different metabolic regulators, we demonstrate the capacity of the assay to detect and quantify L-lactate from the supernatant of HeLa cancer cell line. Furthermore, we validate the assay against a commercially available kit by demonstrating no significant difference between both assays. Finally, we show that the assay is capable of quantifying L-lactate in primary cells such as hPBMCs that were stimulated with toll-like receptor ligands and treated with different metabolic regulators.

Conclusion

We herein present an easy custom assay that is suitable for cells with low and high L-lactate production at very low cost compared to commercially available kits. These advantages of the custom assay can simplify the research in the field of metabolism and related fields.

Hyperlactatemia associated with elective tumor craniotomy: Protocol for an observational study of pathophysiology and clinical implications

Hyperlactatemia occurs frequently after brain tumor surgery. Existing studies are scarce and predominantly retrospective, reporting inconsistent associations to new neurological deficits and prolonged hospital stay. Here we describe a protocol for a prospective observational study of hyperlactatemia during and after elective tumor craniotomy and the association with postoperative outcome, as well as selected pathophysiological aspects, and possible risk factors. We will include 450 brain tumor patients scheduled for elective craniotomy. Arterial blood samples for lactate and glucose measurement will be withdrawn hourly during surgery and until six hours postoperatively. To further explore the association of hyperlactatemia with perioperative insulin resistance, additional blood sampling measuring markers of insulin resistance will be done in 100 patients. Furthermore, in a subgroup of 20 patients, blood from a jugular bulb catheter will be drawn simultaneously with blood from the radial artery to measure the arterial to jugular venous concentration difference of lactate, in order to study the direction of cerebrovascular lactate flux. Functional clinical outcome will be determined by the modified Rankin Scale, length of stay and mortality at 30 days, 6 months, 1 year and 5 years. Clinical outcome will be compared between patients with and without hyperlactatemia. Multivariate logistic regression will be used to identify risk factors for hyperlactatemia. A statistical analysis plan will be publicized to support transparency and reproducibility. Results will be published in a peer-reviewed journal and presented at international conferences.

Lactate Metabolism-Associated lncRNA Pairs: A Prognostic Signature to Reveal the Immunological Landscape and Mediate Therapeutic Response in Patients With Colon Adenocarcinoma

Background

Lactate metabolism is critically involved in the tumor microenvironment (TME), as well as cancer progression. It is important to note, however, that lactate metabolism-related long non-coding RNAs (laRlncRNAs) remain incredibly understudied in colon adenocarcinoma (COAD).

Methods

A gene expression profile was obtained from the Cancer Genome Atlas (TCGA) database to identify laRlncRNA expression in COAD patients. A risk signature with prognostic value was identified from TCGA and Gene Expression Omnibus (GEO) cohort based on laRlncRNA pairs by the least absolute shrinkage and selection operator (LASSO) and Cox regression analyses. Quantitative real-time polymerase chain reaction (qRT-PCR) and functional experiments were carried out to verify the expression of laRlncRNAs in COAD. The relationship of laRlncRNA pairs with immune landscape as well as the sensitivity of different therapies was explored.

Results

In total, 2378 laRlncRNAs were identified, 1,120 pairs of which were studied to determine their prognostic validity, followed by a risk signature established based on the screened 5 laRlncRNA pairs. The laRlncRNA pairs-based signature provided a better overall survival (OS) prediction than other published signatures and functioned as a prognostic marker for COAD patients. According to the calculated optimal cut-off point, patients were divided into high- and low-risk groups. The OS of COAD patients in the high-risk group were significantly shorter than that of those in the low-risk group (P=4.252e-14 in the TCGA cohort and P=2.865-02 in the GEO cohort). Furthermore, it remained an effective predictor of survival in strata of gender, age, TNM stage, and its significance persisted after univariate and multivariate Cox regressions. Additionally, the risk signature was significantly correlated with immune cells infiltration, tumor mutation burden (TMB), microsatellite instability (MSI) as well as immunotherapeutic efficacy and chemotherapy sensitivity. Finally, one of the laRlncRNA, LINC01315, promotes proliferation and migration capacities of colon cancer cells.

Conclusion

The newly identified laRlncRNAs pairs-based signature exhibits potential effects in predicting prognosis, deciphering patients’ immune landscape, and mediating sensitivity to immunotherapy and chemotherapy. Findings in our study may provide evidence for the role of laRlncRNAs pairs as novel prognostic biomarkers and potentially individualized therapy targets for COAD patients.

Tumor Microenvironment: Lactic Acid Promotes Tumor Development

Lactic acid is a "metabolic waste" product of glycolysis that is produced in the body. However, the role of lactic acid in the development of human malignancies has gained increasing interest lately as a multifunctional small molecule chemical. There is evidence that tumor cells may create a large amount of lactic acid through glycolysis even when they have abundant oxygen. Tumor tissues have a higher quantity of lactic acid than normal tissues. Lactic acid is required for tumor development. Lactate is an immunomodulatory chemical that affects both innate and adaptive immune cells' effector functions. In immune cells, the lactate signaling pathway may potentially serve as a link between metabolism and immunity. Lactate homeostasis is significantly disrupted in the TME. Lactate accumulation results in acidosis, angiogenesis, immunosuppression, and tumor cell proliferation and survival, all of which are deleterious to health. Thus, augmenting anticancer immune responses by lactate metabolism inhibition may modify lactate levels in the tumor microenvironment. This review will evaluate the role of lactic acid in tumor formation, metastasis, prognosis, treatment, and histone modification. Our findings will be of considerable interest to readers, particularly those engaged in the therapeutic treatment of cancer patients. Treatments targeting the inhibition of lactate synthesis and blocking the source of lactate have emerged as a potential new therapeutic option for oncology patients. Additionally, lactic acid levels in the plasma may serve as biomarkers for disease stage and may be beneficial for evaluating therapy effectiveness in individuals with tumors.

Different dietary starch patterns in low-protein diets: effect on nitrogen efficiency, nutrient metabolism, and intestinal flora in growing pigs

Background

Protein releases amino acids faster than starch releases glucose in digestive tract of pigs fed low-protein (LP) diets. Poor synchronization of dietary glucose and amino acids supply leads to compromised nitrogen efficiency. Dietary starch patterns modulation may improve this situation.

Methods

Growing barrows (29.7 ± 2.0 kg) were randomly allotted into 5 dietary treatments with LP diets consisting of different purified starches. Treatments included: waxy corn starch (W LP), corn starch + waxy corn starch (C + W LP), corn starch (C LP), pea starch + waxy corn starch (P + W LP) and pea starch (P LP). In the experiment, growth performance, protein deposition, nutrient metabolism, and fecal microbial community of pigs were investigated. In vitro starch digestion was used for predicting the in vivo glucose response.

Results

Dietary starch in vitro glucose release profile was determined by starch source and the ratio of amylopectin and amylose. C + W LP treatment showed decreased total nitrogen excretion and plasma citrulline concentration and improved plasma leptin concentration among treatments (P < 0.05). Besides, the highest nitrogen apparent biological value, whole-body protein deposition and growth performance and lowest urinary nitrogen excretion were also observed in C + W LP treatment. Compared with the other groups, C + W LP and C LP showed increased plasma pyruvate, IGF-1, and lipase concentrations (P < 0.05). The W LP group presented dramatically increased plasma alanine and urea nitrogen concentration and decreased aldolase and leptin concentrations (P < 0.05). Dietary starch patterns did not make an impact on bacterial richness and diversity, but changed the taxonomic and functional structures of the microbial communities. Microbial protein fermentation product (isobutyrate and isovalerate) presented increased in P LP treatments compared with the other treatments (P < 0.05).

Conclusions

Dietary starch patterns modulation can regulate dietary glucose release profile, nutrient metabolism, protein turnover, and fecal microbial fermentation in pigs. The optimal dietary glucose release profile effectively strengthened whole-body protein deposition and improve nitrogen efficiency and growth performance in growing pigs fed LP diets.

Chemoresistant Cancer Cell Lines Are Characterized by Migratory, Amino Acid Metabolism, Protein Catabolism and IFN1 Signalling Perturbations

Simple Summary

While chemoresistance remains a major barrier to improving the outcomes for patients with ovarian cancer, the molecular features, and associated biological functions, which underpin chemoresistance in ovarian cancer remain poorly understood. In this study we aimed to provide insight into the proteins and metabolites, and their associated biological pathways, which play a role in conferring chemoresistance to ovarian cancer. Through mass spectrometry analysis comparing the proteome and metabolome of chemosensitive vs chemoresistant ovarian cancer cell lines we revealed numerous perturbations in signalling and metabolic pathways in chemoresistant cells. Further comparison to primary cells taken from patients with chemoresistant or chemosensitive disease identified a shared dysregulation in cytokine and type 1 interferon signalling. Our research sets the foundation for a deeper understanding of the proteomic and metabolomic features of chemoresistance and identifies type 1 interferon signalling as a common feature of chemoresistance.

Abstract

Chemoresistance remains the major barrier to effective ovarian cancer treatment. The molecular features and associated biological functions of this phenotype remain poorly understood. We developed carboplatin-resistant cell line models using OVCAR5 and CaOV3 cell lines with the aim of identifying chemoresistance-specific molecular features. Chemotaxis and CAM invasion assays revealed enhanced migratory and invasive potential in OVCAR5-resistant, compared to parental cell lines. Mass spectrometry analysis was used to analyse the metabolome and proteome of these cell lines, and was able to separate these populations based on their molecular features. It revealed signalling and metabolic perturbations in the chemoresistant cell lines. A comparison with the proteome of patient-derived primary ovarian cancer cells grown in culture showed a shared dysregulation of cytokine and type 1 interferon signalling, potentially revealing a common molecular feature of chemoresistance. A comprehensive analysis of a larger patient cohort, including advanced in vitro and in vivo models, promises to assist with better understanding the molecular mechanisms of chemoresistance and the associated enhancement of migration and invasion.

Acetate-mediated-obestatin modulation attenuates adipose-hepatic dysmetabolism in high fat diet-induced obese rat model

PURPOSE

Approximately 650 million of world adult population is affected by obesity, which is characterized by adipose and hepatic metabolic dysfunction. Short chain fatty acids (SCFAs) have been linked to improved metabolic profile. However, the effect of SCFAs, particularly acetate on adipose-hepatic dysfunction is unclear. Therefore, the present study investigated the role of acetate on adipose-hepatic metabolic dysfunction and the possible involvement of obestatin in high fat diet-induced obese Wistar rats.

METHODS

Adult male Wistar rats (160-190 g) were allotted into groups (n = 6/group): Control, acetate-treated, obese and obese + acetate-treated groups received vehicle (distilled water), sodium acetate (200 mg/kg), 40% HFD and 40% HFD plus sodium acetate respectively. The administration lasted for 12 weeks.

RESULTS

HFD caused increased body weight gain and visceral adiposity, insulin resistance, hyperinsulinemia and increased pancreatic-β cell function and plasma/hepatic triglyceride and total cholesterol as well as decreased adipose triglyceride and total cholesterol, increased plasma, adipose, and hepatic malondialdehyde, TNF-α, uric acid, lactate production and plasma/adipose but not gamma-glutamyl transferase and decreased plasma, adipose, and hepatic nitric oxide, glucose-6-phosphate dehydrogenase (G6PD), glutathione (GSH) and obestatin concentration compared to the control group. Notwithstanding, treatment with acetate attenuated the alterations.

CONCLUSIONS

The results demonstrate that high fat diet-induced obesity is characterized with adipose and hepatic lipid dysmetabolism, which is associated with obestatin suppression. Findings also suggest that acetate provide protection against adipose and hepatic metabolic perturbations by restoring obestatin as well as G6PD/GSH-dependent antioxidant system.

Metabolomic, proteomic and lactylated proteomic analyses indicate lactate plays important roles in maintaining energy and C:N homeostasis in Phaeodactylum tricornutum

Background

Phaeodactylum tricornutum accumulates lipids while the growth also increases under high CO₂, shedding light on its potential application in the reduction of CO₂ emissions and at the same time acquiring biodiesel raw materials. However, the sensing and transducing of high C:N signals and the related response mechanism(s) remained unknown.

Results

In this study, a multiple omics analysis was performed with P. tricornutum under low nitrogen (LN) and high CO₂ (HC) conditions. The results indicated that 2-oxoglutarate was significantly increased under both LN and HC. Meanwhile, proteins involved in carbon concentration mechanism decreased, indicated that 2-oxoglutarate might regulate C:N balance through suppressing carbon fixation. Lactate, which acts in energy metabolism, signal transduction and ‘LactoylLys’ modification on proteins, was the most upregulated metabolite under both LN and HC conditions. Meanwhile, proteins involved in carbon, nitrogen and energy metabolisms were significantly regulated. Western blotting analysis suggested that non-histone L-lactylation modification was enhanced under LN and HC. Moreover, lactylated proteins were enriched in photosynthesis, central carbon metabolism, nitrogen metabolism, fatty acid synthesis and oxidative phosphorylation.

Conclusion

It is suggested that lactate might play important roles in energy homeostatic maintenance and C:N balance regulation in P. tricornutum through protein lactylation modification.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13068-022-02152-8.

Impact of body fat, body water content, and skeletal muscle mass index on peak salivary lactate levels after squat jump exercise in healthy non-athlete adult males

BACKGROUND

In the rehabilitation and sports science fields, comprehensive assessment of the response to exercise is important for accurately prescribing exercise programs. Lactate is an important energy substrate that is frequently measured in clinical practice because it provides information on aerobic capacity. Salivary lactate, which can be measured non-invasively, has recently been focused on as an alternative to blood lactate. This study aimed to determine the combined effects of body fat, body water content, and skeletal muscle mass index on peak salivary lactate levels.

METHODS

Thirty-seven non-athletic males performed a squat jump exercise. Their salivary lactate levels were measured before, immediately after, and every 5 min after the exercise using a simplified device. We also assessed body composition. A linear multiple regression analysis was performed with peak salivary lactate levels as the dependent variable and body fat ratio, body water content, and the skeletal muscle mass index as independent variables.

RESULTS

The participants' body fat ratio (positive effect; p = 0.001) and body water content (negative effect; p = 0.035) significantly affected peak salivary lactate levels. Skeletal muscle mass index tended to positively influence salivary lactate levels (p = 0.099), albeit not significantly. The adjusted R-squared value of the model was 0.312 (p = 0.001).

CONCLUSIONS

The combined effect of body fat, body water content, and skeletal muscle mass index on peak salivary lactate levels was 31.2%. Better nutritional guidance may be effective in promoting weight loss and increasing body water content to improve aerobic capacity in the rehabilitation setting.

Sepsis Management for the Nephrologist

The definition of sepsis has evolved significantly over the past three decades. Today, sepsis is defined as a dysregulated host immune response to microbial invasion leading to end organ dysfunction. Septic shock is characterized by hypotension requiring vasopressors after adequate fluid resuscitation with elevated lactate. Early recognition and intervention remain hallmarks for sepsis management. We addressed the current literature and assimilated thought regarding optimum initial resuscitation of the patient with sepsis. A nuanced understanding of the physiology of lactate is provided in our review. Physiologic and practical knowledge of steroid and vasopressor therapy for sepsis is crucial and addressed. As blood purification may interest the nephrologist treating sepsis, we have also added a brief discussion of its status.

The Effects of Alcohol Drinking on Oral Microbiota in the Chinese Population

The dysbiosis of oral microbiota is linked to numerous diseases and is associated with personal lifestyles, such as alcohol drinking. However, there is inadequate data to study the effect of alcohol drinking on oral microbiota from the Chinese population. Here, we profiled the oral microbiota of 150 healthy subjects in the Chinese population by 16S rRNA gene sequencing. The results showed that drinkers had significantly higher alpha diversity than non-drinkers. A significant difference in overall microbiota composition was observed between non-drinkers and drinkers. Additionally, using DESeq analysis, we found genus Prevotella and Moryella, and species Prevotella melaninogenica and Prevotella tannerae were significantly enriched in drinkers; meanwhile, the genus Lautropia, Haemophilus and Porphyromonas, and species Haemophilus parainfluenzae were significantly depleted in drinkers. PICRUSt analysis showed that significantly different genera were mainly related to metabolism pathways. The oxygen-independent pathways, including galactose, fructose and mannose metabolism pathways, were enriched in drinkers and positively associated with genera enriched in drinkers; while the pyruvate metabolism pathway, an aerobic metabolism pathway, was decreased in drinkers and negatively associated with genera enriched in drinkers. Our results suggested that alcohol drinking may affect health by altering oral microbial composition and potentially affecting microbial functional pathways. These findings may have implications for better understanding the potential role those oral bacteria play in alcohol-related diseases.

Metabolic Pathway of Cardiospecific Troponins: From Fundamental Aspects to Diagnostic Role (Comprehensive Review)

Many molecules of the human body perform key regulatory functions and are widely used as targets for the development of therapeutic drugs or as specific diagnostic markers. These molecules undergo a significant metabolic pathway, during which they are influenced by a number of factors (biological characteristics, hormones, enzymes, etc.) that can affect molecular metabolism and, as a consequence, the serum concentration or activity of these molecules. Among the most important molecules in the field of cardiology are the molecules of cardiospecific troponins (Tns), which regulate the processes of myocardial contraction/relaxation and are used as markers for the early diagnosis of ischemic necrosis of cardiomyocytes (CMC) in myocardial infarction (MI). The diagnostic value and diagnostic capabilities of cardiospecific Tns have changed significantly after the advent of new (highly sensitive (HS)) detection methods. Thus, early diagnostic algorithms of MI were approved for clinical practice, thanks to which the possibility of rapid diagnosis and determination of optimal tactics for managing patients with MI was opened. Relatively recently, promising directions have also been opened for the use of cardiospecific Tns as prognostic markers both at the early stages of the development of cardiovascular diseases (CVD) (arterial hypertension (AH), heart failure (HF), coronary heart disease (CHD), etc.), and in non-ischemic extra-cardiac pathologies that can negatively affect CMC (for example, sepsis, chronic kidney disease (CKD), chronic obstructive pulmonary disease (COPD), etc.). Recent studies have also shown that cardiospecific Tns are present not only in blood serum, but also in other biological fluids (urine, oral fluid, pericardial fluid, amniotic fluid). Thus, cardiospecific Tns have additional diagnostic capabilities. However, the fundamental aspects of the metabolic pathway of cardiospecific Tns are definitively unknown, in particular, specific mechanisms of release of Tns from CMC in non-ischemic extra-cardiac pathologies, mechanisms of circulation and elimination of Tns from the human body, mechanisms of transport of Tns to other biological fluids and factors that may affect these processes have not been established. In this comprehensive manuscript, all stages of the metabolic pathway are consistently and in detail considered, starting from release from CMC and ending with excretion (removal) from the human body. In addition, the possible diagnostic role of individual stages and mechanisms, influencing factors is analyzed and directions for further research in this area are noted.

Acute Response to One Bout of Dynamic Standing Exercise on Blood Glucose and Blood Lactate Among Children and Adolescents With Cerebral Palsy Who are Nonambulant

PURPOSE

To investigate the acute exercise effects of dynamic standing exercise on blood glucose and blood lactate among children and adolescents with cerebral palsy who are nonambulant.

METHODS

Twenty-four participants with cerebral palsy who are nonambulant performed 30 minutes of dynamic standing exercise using a motorized device enabling assisted passive movements in an upright weight-bearing position. Capillary blood samples were taken from the fingertip for measurement of blood glucose and blood lactate at rest and at the end of exercise.

RESULTS

At rest, the participants had hyperlactatemia that was unaffected after exercise, presented as median and interquartile range at rest 1.8 (1.3:2.7) mmol/L, and after exercise 2.0 (1.1:2.5) mmol/L. Children and adolescents with Gross Motor Function Classification System, level V, had higher lactate levels at rest (2.5 [1.8:2.9] vs 1.4 [1.0:2.0]; P = .030) and after exercise (2.3 [2.0:2.6] vs 1.2 [0.9:2.2]; P = .032) compared with children and adolescents with Gross Motor Function Classification System, level IV, respectively. A statistically significant larger decrease in blood lactate levels after exercise was observed in children and adolescents with higher resting blood lactate levels (ρ = .56; P = .004). There were no statistically significant changes in blood glucose.

CONCLUSIONS

Forty percentage of the participants had mild hyperlactatemia at rest and participants with the highest blood lactate levels at rest had the greatest decrease in blood lactate levels after one bout of exercise. Children and adolescents who were classified with the highest level of the Gross Motor Function Classification Scale had higher blood lactate levels. More studies are needed on how to prevent chronically high resting levels of lactate with exercise in children with cerebral palsy who are nonambulant.

Lactate Is Answerable for Brain Function and Treating Brain Diseases: Energy Substrates and Signal Molecule

Research to date has provided novel insights into lactate's positive role in multiple brain functions and several brain diseases. Although notable controversies and discrepancies remain, the neurobiological role and the metabolic mechanisms of brain lactate have now been described. A theoretical framework on the relevance between lactate and brain function and brain diseases is presented. This review begins with the source and route of lactate formation in the brain and food; goes on to uncover the regulatory effect of lactate on brain function; and progresses to gathering the application and concentration variation of lactate in several brain diseases (diabetic encephalopathy, Alzheimer's disease, stroke, traumatic brain injury, and epilepsy) treatment. Finally, the dual role of lactate in the brain is discussed. This review highlights the biological effect of lactate, especially L-lactate, in brain function and disease studies and amplifies our understanding of past research.

The novel pretreatment immune prognostic index discriminates survival outcomes in locally advanced non-operative esophageal squamous cell carcinoma patients treated with definitive chemoradiotherapy: a 6-year retrospective study

•

dNLR and LDH were correlated with OS and PFS in locally advanced ESCC patients received dCRT.

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The EIPI, a novel inflammatory-based and immune-related prognostic score, was an independent prognostic indicator in locally advanced ESCC.

•

The risk stratification of EIPI can help set individualized treatment strategies and intensities for different subgroups of ESCC patients.

Objective

We aimed to construct risk stratification to help set individualized treatment strategies and intensities for different subgroups of patients.

Methods

The Esophagus Immune Prognostic Index (EIPI) scores were constructed according to the levels of derived neutrophil-to-lymphocyte ratio (dNLR) and lactate dehydrogenase (LDH) before treatment, and the patients were divided into low-, medium-, and high-risk groups. Finally, restricted cubic splines (RCS) were used to explore the relationship between dNLR, LDH, and survival outcomes.

Results

The median follow-up period of overall survival (OS) and progression-free survival (PFS) were 25.2 and 17.6 months, respectively. Multivariate Cox regression analysis showed dNLR were the independent prognostic factors that were associated with OS and PFS. The 3-year OS and PFS rates in the low-, medium-, and high-risk groups were 44.4% and 38.2%, 26.1% and 23.6%, and 10.5% and 5.3%, respectively. Patients who received chemotherapy had better OS and PFS than those who did not receive chemotherapy in low-risk and medium/high-risk groups (all p < 0.05). Besides, the results also revealed significant differences for patients with clinical T, N, and TNM stage groups of the OS and PFS in different risk groups. Finally, RCS analysis indicated a nonlinear relationship between the dNLR, LDH, and survival for esophageal squamous cell carcinoma (ESCC) patients. The death hazard ratios of dNLR and LDH sharply increased at 1.97 and 191, respectively.

Conclusions

In summary, the EIPI, a novel inflammatory-based and immune-related prognostic score, is an independent prognostic indicator in locally advanced ESCC patients undergoing definitive chemoradiotherapy (dCRT).

High-intensity interval resistance training (HIIRT) improves liver gluconeogenesis from lactate in Swiss mice

High-intensity physical exercise favors anaerobic glycolysis and increases lactatemia. Lactate is converted back to glucose in the liver, so that the lactate threshold, an indicator of physical performance, must be related to the gluconeogenic capacity of the liver. This research assessed the effect of a high-intensity interval resistance training (HIIRT) on liver gluconeogenesis from lactate. Swiss mice were trained (groups T) on vertical ladder with overload of 90% of their maximal load. Control animals remained untrained (groups C0 and C8). In situ liver perfusion with lactate and adrenaline was performed in rested mice after 6 hours of food deprivation. There were larger outputs of glucose (T6, 71.90%; T8, 54.53%) and pyruvate (T8, 129.28%) (representative values for 4 mM lactate) in the groups trained for 6 or 8 weeks (T6 and T8), and of glucose in the presence of adrenaline in group T8 (280%). The content of PEPCK, an important regulatory enzyme of the gluconeogenic pathway, was 69.13% higher in group T8 than in the age-matched untrained animals (C8). HIIRT augmented liver gluconeogenesis from lactate and this might improve the lactate threshold. Novelty: The liver metabolizes lactate from muscle into glucose. Physical training may enhance the gluconeogenic capacity of the liver. As lactate clearance by the liver improves, lactate threshold is displaced to higher exercise intensities.

Non-invasive Lactate Monitoring System Using Wearable Chipless Microwave Sensors with Enhanced Sensitivity and Zero Power Consumption

AbstractMonitoring lactate levels is an established method for determining hyperlactatemia in critically ill patients and assessing aerobic fitness. It is a widely used gold-standard technique in both professional and serious amateur sports. Non-invasive real-time lactate monitoring offers significant advantages over the current technology of finger-prick blood sampling. Possible candidate technology for developing non-invasive real-time lactate monitoring should be highly sensitive, flexible, and capable of real-time monitoring of lactate levels in interstitial fluid or within specific working muscle groups depending on the type of sport. Herein we describe a planar, flexible, passive, chipless tag resonator that is electromagnetically coupled to a reader placed in proximity to the lactate sensor tag. The tag resonator is a thin metallic tracing that can be taped on the skin. The resonance frequency of the tag fluctuates proportionately with changing lactate concentrations in a solution mimicking human interstitial fluid with very high sensitivity. The spectrum of the tag is reflected in the spectrum of the reader, which is a planar microwave resonator designed at a different frequency. The reader could be embedded in a cellphone or an application-specific wearable device for data communication and processing. The tag can accurately and reproducibly measure lactate concentrations in the range of 1 to 10 mM, which is in the physiological range of lactate observed at rest and during intense physical activity. Furthermore, the chrematistics of this technology will allow monitoring of lactate in specific working muscle groups.