The Science and Translation of Lactate Shuttle Theory

Microglia lactylation in relation to central nervous system diseases

The development of neurodegenerative diseases is closely related to the disruption of central nervous system homeostasis. Microglia, as innate immune cells, play important roles in the maintenance of central nervous system homeostasis, injury response, and neurodegenerative diseases. Lactate has been considered a metabolic waste product, but recent studies are revealing ever more of the physiological functions of lactate. Lactylation is an important pathway in lactate function and is involved in glycolysis-related functions, macrophage polarization, neuromodulation, and angiogenesis and has also been implicated in the development of various diseases. This review provides an overview of the lactate metabolic and homeostatic regulatory processes involved in microglia lactylation, histone versus non-histone lactylation, and therapeutic approaches targeting lactate. Finally, we summarize the current research on microglia lactylation in central nervous system diseases. A deeper understanding of the metabolic regulatory mechanisms of microglia lactylation will provide more options for the treatment of central nervous system diseases.

Probing the alterations in mice cecal content due to high-fat diet

The global prevalence of obesity more than doubled between 1990 and 2022. By 2022, 2.5 billion adults aged 18 and older were overweight, with over 890 million of them living with obesity. The urgent need for understanding the impact of high-fat diet, together with the demanding of analytical methods with low energy/chemicals consumption, can be fulfilled by rapid, high-throughput spectroscopic techniques. To understand the impact of high-fat diet on the metabolic signatures of mouse cecal contents, we characterized metabolite variations in two diet-groups (standard vs high-fat diet) using FTIR spectroscopy and multivariate analysis. Their cecal content showed distinct spectral features corresponding to high- and low-molecular-weight metabolites. Further quantification of 13 low-molecular-weight metabolites using liquid chromatography showed significant reduction in the production of short chain fatty acids and amino acids associated with high-fat diet samples. These findings demonstrated the potential of spectroscopy to follow changes in gut metabolites.

Metabolic regulation of preimplantation embryo development in vivo and in vitro: Molecular mechanisms and insights

Understanding of embryonic development has led to the clinical application of Assisted Reproductive technologies (ART), with the resulting birth of millions of children. Recent developments in metabolomics, proteomics, and transcriptomics have brought to light new insights into embryonic growth dynamics, with implications spanning reproductive medicine, stem cell research, and regenerative medicine. The review explores the key metabolic processes and molecular pathways active during preimplantation embryo development, including PI3K-Akt, mTOR, AMPK, Wnt/β-catenin, TGF-β, Notch and Jak-Stat signaling pathways. We focused on analyzing the differences occurring in vitro as opposed to in vivo development and we discussed significant physiological and clinical implications.

Peripheral to brain and hippocampus crosstalk induced by exercise mediates cognitive and structural hippocampal adaptations

Endurance exercise leads to robust increases in memory and learning. Several exercise adaptations occur to mediate these improvements, including in both the hippocampus and in peripheral organs. Organ crosstalk has been becoming increasingly more present in exercise biology, and studies have shown that peripheral organs can communicate to the hippocampus and mediate hippocampal changes. Both learning and memory as well as other hippocampal functional-related changes such as neurogenesis, cell proliferation, dendrite morphology and synaptic plasticity are controlled by these exercise responsive peripheral proteins. These peripheral factors, also called exerkines, are produced by several organs including skeletal muscle, liver, adipose tissue, kidneys, adrenal glands and circulatory cells. Previous reviews have explored some of these exerkines including muscle-derived irisin and cathepsin B (CTSB), but a full picture of peripheral to hippocampus crosstalk with novel exerkines such as selenoprotein 1 (SEPP1) and platelet factor 4 (PF4), or old overlooked ones such as lactate and insulin-like growth factor 1 (IGF-1) is still missing. We provide 29 different studies of 14 different exerkines that crosstalk with the hippocampus. Thus, the purpose of this review is to explore peripheral exerkines that have shown to exert hippocampal function following exercise, demonstrating their particular effects and molecular mechanisms in which they could be inducing adaptations.

How to Equalize High- and Low-Intensity Endurance Exercise Dose

PURPOSE

Without appropriate standardization of exercise doses, comparing high- (HI) and low-intensity (LI) training outcomes might become a matter of speculation. In athletic preparation, proper quantification ensures an optimized stress-to-recovery ratio. This review aims to compare HI and LI doses by estimating theoretically the conversion ratio, 1:x, between HI and LI: How many minutes, x, of LI are equivalent to 1 minute of HI using various quantification methods? A scrutinized analysis on how the dose increases in relation to duration and intensity was also made.

ANALYSIS

An estimation was conducted across 4 categories encompassing 10 different approaches: (1) "arbitrary" methods, (2) physiological and perceptual measurements during exercise, (3) postexercise measurements, and comparison to (4a) acute and (4b) chronic intensity-related maximum dose. The first 2 categories provide the most conservative estimation for the HI:LI ratio (1:1.5-1:10), and the third, slightly higher (1:4-1:11). The category (4a) provides the highest estimation (1:52+) and (4b) suggests 1:10 to 1:20. The exercise dose in the majority of the approaches increase linearly in relation to duration and exponentially in relation to intensity.

CONCLUSIONS

As dose estimations provide divergent evaluations of the HI:LI ratio, the choice of metric will have a large impact on the research designs, results, and interpretations. Therefore, researchers should familiarize themselves with the foundations and weaknesses of their metrics and justify their choice. Last, the linear relationship between duration and exercise dose is in many cases assumed rather than thoroughly tested, and its use should be subjected to closer scrutiny.

Lactate and lactylation in cardiovascular diseases: current progress and future perspectives

Cardiovascular diseases (CVDs) are often linked to structural and functional impairments, such as heart defects and circulatory dysfunction, leading to compromised peripheral perfusion and heightened morbidity risks. Metabolic remodeling, particularly in the context of cardiac fibrosis and inflammation, is increasingly recognized as a pivotal factor in the pathogenesis of CVDs. Metabolic syndromes further predispose individuals to these conditions, underscoring the need to elucidate the metabolic underpinnings of CVDs. Lactate, a byproduct of glycolysis, is now recognized as a key molecule that connects cellular metabolism with the regulation of cellular activity. The transport of lactate between different cells is essential for metabolic homeostasis and signal transduction. Disruptions to lactate dynamics are implicated in various CVDs. Furthermore, lactylation, a novel post-translational modification, has been identified in cardiac cells, where it influences protein function and gene expression, thereby playing a significant role in CVD pathogenesis. In this review, we summarized recent advancements in understanding the role of lactate and lactylation in CVDs, offering fresh insights that could guide future research directions and therapeutic interventions. The potential of lactate metabolism and lactylation as innovative therapeutic targets for CVD is a promising avenue for exploration.

Survival rates and factors associated with survival and laminitis of horses with acute diarrhoea admitted to referral institutions

BACKGROUND

Clinicopathological findings and their association with the outcome and development of laminitis in horses with acute diarrhoea has not been investigated in a multicentre study across different geographic regions.

OBJECTIVES

Describe and compare clinicopathologic findings of diarrhoeic horses between different geographic regions, survival rates and factors associated with non-survival and laminitis.

STUDY DESIGN

Multicentre retrospective case series.

METHODS

Information from horses with acute diarrhoea presenting to participating institutions between 2016 and 2020 was collected, and clinicopathological data were compared between surviving and non-surviving horses and horses that did and did not develop laminitis. Survival rates and seasonal and geographic differences were also investigated.

RESULTS

One thousand four hundred thirty-eight horses from 26 participating institutions from 4 continents were included; 76% survived to discharge with no differences identified between geographic regions. The survival proportion of horses with SIRS and creatinine concentrations > 159 μmol/L was 55% (154/279) compared with 81% (358/437) for those with SIRS and creatinine concentrations < 159 μmol/L (p < 0.001). The survival proportion of horses with SIRS that had an L-lactate concentration > 2.8 mmol/L was 59% (175/298) compared with 81% (240/296) in horses with SIRS and L-lactate concentration < 2.8 mmol/L (p < 0.001). The proportion of horses that developed laminitis was lower in Europe (4%, 19/479) compared with North America (8%, 52/619), Australia (8%, 12/138) and Latin America (11%, 16/146) (p < 0.05). More horses developed laminitis in the summer (46%, 39/85) compared with winter (18%, 15/85), spring (18%, 15/85) and fall (19%, 16/85) (p < 0.01). Horses with laminitis had greater odds of non-survival than those without laminitis (OR: 3.73, 95% CI: 2.47-5.65).

MAIN LIMITATIONS

Not all variables were available for all horses due to the retrospective nature.

CONCLUSIONS

Clinicopathological findings in horses with acute diarrhoea and their association with survival are similar across geographic regions. However, developing laminitis secondary to diarrhoea is less common in Europe. In addition, factors associated with non-survival were indicative of disease severity and subsequent cardiovascular compromise.

Regulation of glycolysis-derived L-lactate production in astrocytes rescues the memory deficits and Aβ burden in early Alzheimer's disease models

Aberrant energy metabolism in the brain is a common pathological feature in the preclinical Alzheimer's Disease (AD). Recent studies have reported the early elevations of glycolysis-involved enzymes in AD brain and cerebrospinal fluid according to a large-scale proteomic analysis. It's well-known that astrocytes exhibit strong glycolytic metabolic ability and play a key role in the regulation of brain homeostasis. However, its relationship with glycolytic changes and cognitive deficits in early AD patients is unclear. Here, we investigated the mechanisms by which astrocyte glycolysis is involved in early AD and its potential as a therapeutic target. Our results suggest that Aβ-activated microglia can induce glycolytic-enhanced astrocytes in vitro, and that these processes are dependent on the activation of the AKT-mTOR-HIF-1α pathway. In early AD models, the increase in L-lactate produced by enhanced glycolysis of astrocytes leads to spatial cognitive impairment by disrupting synaptic plasticity and accelerating Aβ aggregation. Furthermore, we find rapamycin, the mTOR inhibitor, can rescue the impaired spatial memory and Aβ burden by inhibiting the glycolysis-derived L-lactate in the early AD models. In conclusion, we highlight that astrocytic glycolysis plays a critical role in the early onset of AD and that the modulation of glycolysis-derived L-lactate by rapamycin provides a new strategy for the treatment of AD.

Predicting lymphoma prognosis using machine learning-based genes associated with lactylation

BACKGROUND

Lactylation, a newly discovered PTM involving lactic acid, is linked to solid tumor proliferation and metastasis. Lymphoma patients exhibit high lactic acid levels, yet lactylation's role in lymphoma is underexplored. This study aimed to identify lactylation-related genes in lymphoma using tumor databases and assess their predictive value in patient prognosis through cell experiments and clinical specimens.

METHODS

Using TCGA and GEO datasets, we analyzed the expression levels of lactylation-related genes in diffuse large B-cell lymphoma patients. We also evaluated the prognostic significance of lactylation gene risk scores, exploring their impact on drug sensitivity and tumor immune function. Key lactylation-affecting genes were identified and functionally validated through cell experiments and mouse in vivo experiments. Additionally, the relationship between lactylation and lymphoma prognosis was examined in clinical specimens.

RESULTS

We identified 70 genes linked to diffuse large B-cell lymphoma prognosis from the lactylation-related gene set. Using clinical data and a COX regression algorithm, we developed an optimized lactylation Riskscore model. This model significantly correlated with prognosis and showed differences in immune cell infiltration, particularly macrophages. High-risk patients showed resistance to chemotherapy drugs but responded well to immunotherapy. HNRNPH1, a lactylation-related gene, influenced patient prognosis, apoptosis, cell cycle distribution in lymphoma cells, and tumor volume in mice. In lymphoma specimens, lactylation levels correlated with Bcl-2, C-myc, and P53 levels.

CONCLUSIONS

Lactylation impacts diffuse large B-cell lymphoma prognosis, tumor immune function, and drug resistance. Our lactylation-based Riskscore model aids in patient stratification and treatment selection. HNRNPH1 regulates lactylation, thereby affecting patient prognosis.

SARS-CoV-2 uses Spike glycoprotein to control the host's anaerobic metabolism by inhibiting LDHB

The SARS-CoV-2 pandemic, responsible for approximately 7 million deaths worldwide, highlights the urgent need to understand the molecular mechanisms of the virus in order to prevent future outbreaks. The Spike glycoprotein of SARS-CoV-2, which is critical for viral entry through its interaction with ACE2 and other host cell receptors, has been a focus of study. This research goes beyond receptor recognition to explore Spike's influence on cellular metabolism. AP-MS interactome analysis revealed an interaction between the Spike S1 domain and lactate dehydrogenase B (LDHB), which was further confirmed by co-immunoprecipitation and immunofluorescence, indicating colocalisation in cells expressing the S1 domain. The study showed that Spike inhibits the catalytic activity of LDHB, leading to increased lactate levels in HEK-293T cells overexpressing the S1 subunit. The hypothesised mechanism is that Spike deprives LDHB of NAD+, facilitating a metabolic switch from aerobic to anaerobic energy production during infection. The Spike-NAD+ interacting region was characterised and mainly involves the W436 within the RDB domain. This novel hypothesis suggests that the Spike protein may play a broader role in altering host cell metabolism, thereby contributing to the pathophysiology of viral infection.

Hyperglycemia Suppresses Lactate Clearance During Exercise in Type 1 Diabetes

CONTEXT

Circulating lactate concentration is an important determinant of exercise tolerance.

OBJECTIVE

This work aimed to determine the role of hyperglycemia on lactate metabolism during exercise in individuals with type 1 diabetes (T1D).

METHODS

The protocol at the University of Virginia compared 7 T1D participants and 7 participants without diabetes (ND) at euglycemia (5.5 mM) or hyperglycemia (9.2 mM) in random order in T1D and at euglycemia in ND. Intervention included [1-13C] lactate infusion, exercise at 65% maximal oxygen uptake (VO2max), euglycemia, and hyperglycemia visits. The main outcome measure was lactate turnover before, during, and after 60 minutes of exercise at 65% VO2max.

RESULTS

A 2-compartment model with loss only from the peripheral compartment described lactate kinetics. Volume of distribution of the accessible compartment was similar between T1D and ND individuals (P = .76) and concordant with plasma volume (∼40 mL/kg). Circulating lactate concentrations were higher (P < .001) in T1D participants during exercise at hyperglycemia than euglycemia. Exercise-induced lactate appearance did not differ (P = .13) between hyperglycemia and euglycemia. However, lactate clearance (CL) was lower (P = .03) during hyperglycemia than euglycemia in T1D participants. There were no differences in any of the aforementioned parameters between T1D and ND participants during euglycemia.

CONCLUSION

Hyperglycemia modulates lactate metabolism during exercise by lowering CL, leading to higher circulating lactate concentrations in T1D individuals. This novel observation implies that exercise during hyperglycemia can lead to higher circulating lactate concentrations thus increasing the likelihood of reaching the lactate threshold sooner in T1D, and has high translational relevance both for providers and recreationally active people with T1D.

The impact of histone lactylation on the tumor microenvironment and metabolic pathways and its potential in cancer therapy

BACKGROUND

The complexity of cancer is intricately linked to its multifaceted biological processes, including the roles of the tumor microenvironment (TME) as well as genetic and metabolic regulation. Histone lactylation has recently emerged as a novel epigenetic modification mechanism that plays a pivotal role in regulating cancer initiation, proliferation, invasion, and metastasis.

OBJECTIVE

This review aims to elucidate the role of histone lactylation in modulating various aspects of tumor biology, including DNA repair mechanisms, glycolytic metabolic abnormalities, functions of non-tumor cells in the TME, and the promotion of tumor inflammatory responses and immune escape. Additionally, the review explores potential therapeutic strategies targeting histone lactylation.

METHODS

A comprehensive literature review was performed, analyzing recent findings on histone lactylation and its impact on cancer biology. This involved a systematic examination of studies focusing on biochemical pathways, cellular interactions, and clinical implications related to histone lactylation.

RESULTS

Histone lactylation was identified as a critical regulator of tumor cell DNA repair mechanisms and glycolytic metabolic abnormalities. It also significantly influences the functions of non-tumor cells within the TME, promoting tumor inflammatory responses and immune escape. Moreover, histone lactylation acts as a multifunctional biological signaling molecule impacting immune responses within the TME. Various cell types within the TME, including T cells and macrophages, were found to regulate tumor growth and immune escape mechanisms through lactylation.

CONCLUSION

Histone lactylation offers a novel perspective on tumor metabolism and its role in cancer development. It presents promising opportunities for the development of innovative cancer therapies. This review underscores the potential of histone lactylation as a therapeutic target, paving the way for new strategies in cancer treatment.

Lactate triggers KAT8-mediated LTBP1 lactylation at lysine 752 to promote skin rejuvenation by inducing collagen synthesis in fibroblasts

Decreased collagen synthesis by fibroblasts is a key aspect of skin aging. Poly-L-Lactic Acid (PLLA) is a bioabsorbable material that can release lactate continuously, stimulating endogenous collagen synthesis in the skin. Herein, this study aimed to investigate the impact of PLLA-released lactate on collagen production in fibroblasts for skin rejuvenation. Human fibroblasts were exposed to varying concentrations of PLLA in vitro, while PLLA was injected into the back skin of aged mice in vivo. Safety and efficacy of PLLA on collagen synthesis and skin rejuvenation were evaluated through Calcein-AM/PI staining, EdU proliferation assay, and analysis of collagen I and collagen III expression in fibroblasts using western blotting and immunofluorescence. To elucidate the underlying mechanisms, lactate contents in cell-free supernatant and cell lysates from PLLA-treated fibroblasts, as well as total lysine lactylation (Pan Kla) levels were measured. Additionally, we found that fibroblasts can uptake extracellular lactate released from PLLA through monocarboxylate transporter-1 (MCT1) to facilitate latent-transforming growth factor beta-binding protein 1 (LTBP1) lactylation at lysine 752 (K752) via a KAT8-dependent mechanism, then increases the protein levels of collagen I and collagen III in fibroblasts. Overall, this study highlights a valuable insight into lactylation modification of non-histone protein for skin rejuvenation.

Lactic acid: The culprit behind the immunosuppressive microenvironment in hepatocellular carcinoma

As a solid tumor with high glycolytic activity, hepatocellular carcinoma (HCC) produces excess lactic acid and increases extracellular acidity, thus forming a unique immunosuppressive microenvironment. L-lactate dehydrogenase (LDH) and monocarboxylate transporters (MCTs) play a very important role in glycolysis. LDH is the key enzyme for lactic acid (LA) production, and MCT is responsible for the cellular import and export of LA. The synergistic effect of the two promotes the formation of an extracellular acidic microenvironment. In the acidic microenvironment of HCC, LA can not only promote the proliferation, survival, transport and angiogenesis of tumor cells but also have a strong impact on immune cells, ultimately leading to an inhibitory immune microenvironment. This article reviews the role of LA in HCC, especially its effect on immune cells, summarizes the progress of LDH and MCT-related drugs, and highlights the potential of immunotherapy targeting lactate combined with HCC.

Resident immune responses to spinal cord injury: role of astrocytes and microglia

Spinal cord injury can be traumatic or non-traumatic in origin, with the latter rising in incidence and prevalence with the aging demographics of our society. Moreover, as the global population ages, individuals with co-existent degenerative spinal pathology comprise a growing number of traumatic spinal cord injury cases, especially involving the cervical spinal cord. This makes recovery and treatment approaches particularly challenging as age and comorbidities may limit regenerative capacity. For these reasons, it is critical to better understand the complex milieu of spinal cord injury lesion pathobiology and the ensuing inflammatory response. This review discusses microglia-specific purinergic and cytokine signaling pathways, as well as microglial modulation of synaptic stability and plasticity after injury. Further, we evaluate the role of astrocytes in neurotransmission and calcium signaling, as well as their border-forming response to neural lesions. Both the inflammatory and reparative roles of these cells have eluded our complete understanding and remain key therapeutic targets due to their extensive structural and functional roles in the nervous system. Recent advances have shed light on the roles of glia in neurotransmission and reparative injury responses that will change how interventions are directed. Understanding key processes and existing knowledge gaps will allow future research to effectively target these cells and harness their regenerative potential.

Acute performance fatigability following continuous versus intermittent cycling protocols is not proportional to total work done

Classical training theory postulates that performance fatigability following a training session should be proportional to the total work done (TWD); however, this notion has been questioned. This study investigated indices of performance and perceived fatigability after primary sessions of high-intensity interval training (HIIT) and constant work rate (CWR) cycling, each followed by a cycling time-to-task failure (TTF) bout. On separate days, 16 participants completed an incremental cycling test, and, in a randomized order, (i) a TTF trial at 80% of peak power output (PPO), (ii) an HIIT session, and (iii) a CWR session, both of which were immediately followed by a TTF trial at 80% PPO. Central and peripheral aspects of performance fatigability were measured using interpolated twitch technique, and perceptual measures were assessed prior to and following the HIIT and CWR trials, and again following the TTF trial. Despite TWD being less following HIIT (P = 0.029), subsequent TTF trial was an average of 125 s shorter following HIIT versus CWR (P < 0.001), and this was accompanied by greater impairments in voluntary and electrically evoked forces (P < 0.001), as well as exacerbated perceptual measures (P < 0.001); however, there were no differences in any fatigue measure following the TTF trial (P ≥ 0.149). There were strong correlations between the decline in TTF and indices of peripheral (r = 0.70) and perceived fatigability (r ≥ 0.80) measured at the end of HIIT and CWR. These results underscore the dissociation between TWD and performance fatigability and highlight the importance of peripheral components of fatigability in limiting endurance performance during high-intensity cycling exercise.

Lactate-induced metabolic remodeling and myofiber type transitions via activation of the Ca2+-NFATC1 signaling pathway

Lactate can serve as both an energy substrate and a signaling molecule, exerting diverse effects on skeletal muscle physiology. Due to the apparently positive effects, it would be interesting to consider it as a sports supplement. However, the mechanism behind these effects are yet to be comprehensively understood. In this study, we observed that lactate administration could improve the ability of antifatigue, and we further found that lactate upregulated the expression of myosin heavy chain (MYHC I) and MYHC IIa, while downregulating the expression of MYHC IIb. Besides, transcriptomics and metabolomics revealed significant changes in the metabolic profile of gastrocnemius muscle following lactate administration. Furthermore, lactate enhanced the activities of metabolic enzymes, including HK, LDHB, IDH, SDM, and MDH, and promoted the expression of lactate transport-related proteins MCT1 and CD147, thereby improving the transport and utilization of lactate in both vivo and vitro. More importantly, lactate administration increased cellular Ca2+ concentration and facilitated nuclear translocation of nuclear factor of activated T cells (NFATC1) in myotubes, whereas inhibition of NFATC1 significantly attenuated the effects of lactate treatment on NFATC1 nuclear translocation and MyHC expression. Our results elucidate the ability of lactate to induce metabolic remodeling in skeletal muscle and promote myofiber-type transitions by activating the Ca2+-NFATC1 signaling pathway. This study is useful in exploring the potential of lactate as a nutritional supplement for skeletal muscle adaptation and contributing to a mechanistic understanding of the central role of lactate in exercise physiology.

Metabolic profiling and combined therapeutic strategies unveil the cytotoxic potential of selenium-chrysin (SeChry) in NSCLC cells

Lung cancer ranks as the predominant cause of cancer-related mortalities on a global scale. Despite progress in therapeutic interventions, encompassing surgical procedures, radiation, chemotherapy, targeted therapies and immunotherapy, the overall prognosis remains unfavorable. Imbalances in redox equilibrium and disrupted redox signaling, common traits in tumors, play crucial roles in malignant progression and treatment resistance. Cancer cells, often characterized by persistent high levels of reactive oxygen species (ROS) resulting from genetic, metabolic, and microenvironmental alterations, counterbalance this by enhancing their antioxidant capacity. Cysteine availability emerges as a critical factor in chemoresistance, shaping the survival dynamics of non-small cell lung cancer (NSCLC) cells. Selenium-chrysin (SeChry) was disclosed as a modulator of cysteine intracellular availability. This study comprehensively characterizes the metabolism of SeChry and investigates its cytotoxic effects in NSCLC. SeChry treatment induces notable metabolic shifts, particularly in selenocompound metabolism, impacting crucial pathways such as glycolysis, gluconeogenesis, the tricarboxylic acid (TCA) cycle, and amino acid metabolism. Additionally, SeChry affects the levels of key metabolites such as acetate, lactate, glucose, and amino acids, contributing to disruptions in redox homeostasis and cellular biosynthesis. The combination of SeChry with other treatments, such as glycolysis inhibition and chemotherapy, results in greater efficacy. Furthermore, by exploiting NSCLC's capacity to consume lactate, the use of lactic acid-conjugated dendrimer nanoparticles for SeChry delivery is investigated, showing specificity to cancer cells expressing monocarboxylate transporters.

Metabolic flexibility and resting autonomic function in active menopausal women

PURPOSE

The present study aims to analyze the relationship between cardiac autonomic control at rest-i.e., baseline Heart Rate Variability (HRV)-and metabolic flexibility assessed by means of the FATox and CHOox oxidation rates at the intensities of maximum fat and carbohydrate oxidation (MFO and MCO, respectively).

METHODS

Twenty-four active over-60 women (66.8 ± 4.4 years) had their HRV assessed with 10 min recordings under resting conditions, and this was analyzed with Kubios Scientific software. After this, an incremental submaximal cycling test, starting at 30 watts, with increments of 10 watts every 3 min 15 s was performed. FATox and CHOox were calculated in the last 60 s at each step, using Frayn's equation. MFO and MCO were further obtained.

RESULTS

Nonlinear SampEn and 1-DFAα1 (Detrending Fluctuation Analysis score) at rest were both moderate and significantly (p < 0.05) related to FATox (r = 0.43, r = -0.40) and CHOox (r = -0.59, r = 0.41), as well as RER (r = -0.43, r = 0.43) at FATmax intensity. At the MCO intensity, no association was observed between HRV and oxidation rates. However, DFAα1 (r = -0.63, p < 0.05), the frequency ratio LF/HF (r = -0.63, p < 0.05), and the Poincaré ratio SD1/SD2 (r = 0.48, p < 0.05) were correlated with blood lactate concentration.

CONCLUSION

These results support the autonomic resources hypothesis, suggesting that better autonomic function at rest is related to enhanced metabolic flexibility in postmenopausal women. They also underpin a comprehensive analysis of cardiovascular-autonomic health with aging. The results imply that non-linear DFAα1 and SampEn are appropriate to analyze this association in health of the aging cardiovascular-autonomic system.

Lactate-carried Mitochondrial Energy Overflow

We addressed the question of mitochondrial lactate metabolism using genetically-encoded sensors. The organelle was found to contain a dynamic lactate pool that leads to dose- and time-dependent protein lactylation. In neurons, mitochondrial lactate reported blood lactate levels with high fidelity. The exchange of lactate across the inner mitochondrial membrane was found to be mediated by a high affinity H + -coupled transport system involving the mitochondrial pyruvate carrier MPC. Assessment of electron transport chain activity and determination of lactate flux showed that mitochondria are tonic lactate producers, a phenomenon driven by energization and stimulated by hypoxia. We conclude that an overflow mechanism caps the redox level of mitochondria, while saving energy in the form of lactate.

One Sentence Summary

Mitochondrial lactate production.

Altered neuronal lactate dehydrogenase A expression affects cognition in a sex- and age-dependent manner

The astrocyte-neuron lactate shuttle (ANLS) model posits that astrocyte-generated lactate is transported to neurons to fuel memory processes. However, neurons express high levels of lactate dehydrogenase A (LDHA), the rate-limiting enzyme of lactate production, suggesting a cognitive role for neuronally generated lactate. It was hypothesized that lactate metabolism in neurons is critical for learning and memory. Here transgenic mice were generated to conditionally induce or knockout (KO) the Ldha gene in CNS neurons of adult mice. High pattern separation memory was enhanced by neuronal Ldha induction in young females, and by neuronal Ldha KO in aged females. In older mice, Ldha induction caused cognitive deficits whereas Ldha KO caused cognitive improvements. Genotype-associated cognitive changes were often only observed in one sex or oppositely in males and females. Thus, neuronal-generated lactate has sex-specific cognitive effects, is largely indispensable at young age, and may be detrimental to learning and memory with aging.

The Multiple Roles of Lactate in the Skeletal Muscle

Believed for a long time to be merely a waste product of cell metabolism, lactate is now considered a molecule with several roles, having metabolic and signalling functions together with a new, recently discovered role as an epigenetic modulator. Lactate produced by the skeletal muscle during physical exercise is conducted to the liver, which uses the metabolite as a gluconeogenic precursor, thus generating the well-known "Cori cycle". Moreover, the presence of lactate in the mitochondria associated with the lactate oxidation complex has become increasingly clear over the years. The signalling role of lactate occurs through binding with the GPR81 receptor, which triggers the typical signalling cascade of the G-protein-coupled receptors. Recently, it has been demonstrated that lactate regulates chromatin state and gene transcription by binding to histones. This review aims to describe the different roles of lactate in skeletal muscle, in both healthy and pathological conditions, and to highlight how lactate can influence muscle regeneration by acting directly on satellite cells.

Lactate and Lactylation in Sepsis: A Comprehensive Review

Sepsis is a disorder of the immune response to infection or infectious factors with high morbidity and mortality in clinical settings. The lactylation of lysine residues, fueled by lactate, plays a pivotal role in its pathophysiology. In conducting a literature review on sepsis-related research, we employed a systematic approach to ensure comprehensiveness and accuracy. Initially, we conducted an extensive literature search through the PubMed database, utilizing a range of keywords including "sepsis", "lactate", "lactylation", and "epigenetic modification". The aim was to capture the most recent research related to the pathophysiological mechanisms of sepsis, metabolic disorders, and the role of lactylation. The results of the literature review revealed a close link between sepsis and metabolic dysfunction, particularly the pivotal role of lactylation in regulating immune responses and inflammatory processes. Lactate, not only an energy metabolic byproduct produced during glycolysis, affects the activity of various proteins, including those involved in immune regulation and cell signaling, through lactylation. In the context of sepsis, changes in the levels of lactylation may be closely associated with the severity and prognosis of the disease. In summary, lactylation, as an emerging type of epigenetic modification, provides a new perspective for the diagnosis and treatment of sepsis. Future research needs to further elucidate the exact mechanisms of lactylation in sepsis and explore its potential as a therapeutic target.

Regulation of macrophage activation by lactylation in lung disease

Lactylation is a process where lactate, a cellular metabolism byproduct, is added to proteins, altering their functions. In the realm of macrophage activation, lactylation impacts inflammatory response and immune regulation. Understanding the effects of lactylation on macrophage activation is vital in lung diseases, as abnormal activation and function are pivotal in conditions like pneumonia, pulmonary fibrosis, COPD, and lung cancer. This review explores the concept of lactylation, its regulation of macrophage activation, and recent research progress in lung diseases. It offers new insights into lung disease pathogenesis and potential therapeutic targets.

Relationship of peak capillary blood lactate accumulation and body composition in determining the mechanical energy equivalent of lactate during sprint cycling

AIM

A 15-s all-out sprint cycle test (i.e., νLamax-test) and the post-exercise change in capillary blood lactate concentration is an emerging diagnostic tool that is used to quantify the maximal glycolytic rate. The goal of this study was to determine the relation between 15 s-work, change in capillary blood lactate concentration (∆La) and body composition in a νLamax-test.

METHOD

Fifty cyclists performed a 15 s all-out sprint test on a Cyclus2 ergometer twice after a previous familiarization trial. Capillary blood was sampled before and every minute (for 8 min) after the sprint to determine ∆La. Body composition was determined employing InBody720 eight-electrode impedance analysis.

RESULT

Simple regression models of fat-free mass (FFM) and also the product of FFM and ∆La showed similar ability to predict 15 s-work (R2 = 0.79; 0.82). Multiple regression combining both predictors explains 93% of variance between individuals. No differences between males and females were found regarding 15 s-work relative to the product of fat-free mass and ∆La. Considering pairs of similar FFM, a change 1 mmol/l of ∆La is estimated to be equal to 12 J/kg in 15 s-work (R2 = 0.85).

DISCUSSION

Fifteen s-work is both closely related to FFM and also the product of ∆La and lactate-distribution space approximated by FFM. Differences in 15 s-work between males and females disappear when total lactate production is considered. Considering interindividual differences, the mechanical energy equivalent of blood lactate accumulation seems a robust parameter displaying a clear relationship between ∆La and 15 s-work relative to FFM.

Lactate transported by MCT1 plays an active role in promoting mitochondrial biogenesis and enhancing TCA flux in skeletal muscle

Once considered as a "metabolic waste," lactate is now recognized as a major fuel for tricarboxylic acid (TCA) cycle. Our metabolic flux analysis reveals that skeletal muscle mainly uses lactate to fuel TCA cycle. Lactate is transported through the cell membrane via monocarboxylate transporters (MCTs) in which MCT1 is highly expressed in the muscle. We analyzed how MCT1 affects muscle functions using mice with specific deletion of MCT1 in skeletal muscle. MCT1 deletion enhances running performance, increases oxidative fibers while decreasing glycolytic fibers, and enhances flux of glucose to TCA cycle. MCT1 deficiency increases the expression of mitochondrial proteins, augments cell respiration rate, and elevates mitochondrial activity in the muscle. Mechanistically, the protein level of PGC-1α, a master regulator of mitochondrial biogenesis, is elevated upon loss of MCT1 via increases in cellular NAD+ level and SIRT1 activity. Collectively, these results demonstrate that MCT1-mediated lactate shuttle plays a key role in regulating muscle functions by modulating mitochondrial biogenesis and TCA flux.

Lactylation: The emerging frontier in post-translational modification

Lactate, a metabolic byproduct, has gained recognition as a highly influential signaling molecule. Lactylation, an emerging form of post-translational modification derived from lactate, plays a crucial role in numerous cellular processes such as inflammation, embryonic development, tumor proliferation, and metabolism. However, the precise molecular mechanisms through which lactylation governs these biological functions in both physiological and pathological contexts remain elusive. Hence, it is imperative to provide a comprehensive overview of lactylation in order to elucidate its significance in biological processes and establish a foundation for forthcoming investigations. This review aims to succinctly outline the process of lactylation modification and the characterization of protein lactylation across diverse organisms. Additionally, A summary of the regulatory mechanisms of lactylation in cellular processes and specific diseases is presented. Finally, this review concludes by delineating existing research gaps in lactylation and proposing primary directions for future investigations.

The role of lactate-induced protein lactylation in gliomas: implications for preclinical research and the development of new treatments

The most prevalent primary brain tumors in adults are gliomas. In addition to insufficient therapeutic alternatives, gliomas are fatal mostly due to the rapid proliferation and continuous infiltration of tumor cells into the surrounding healthy brain tissue. According to a growing body of research, aerobic glycolysis, or the Warburg effect, promotes glioma development because gliomas are heterogeneous cancers that undergo metabolic reprogramming. Therefore, addressing the Warburg effect might be a useful therapeutic strategy for treating cancer. Lactate plays a critical role in reprogramming energy metabolism, allowing cells to rapidly access large amounts of energy. Lactate, a byproduct of glycolysis, is therefore present in rapidly proliferating cells and tumors. In addition to the protumorigenesis pathways of lactate synthesis, circulation, and consumption, lactate-induced lactylation has been identified in recent investigations. Lactate plays crucial roles in modulating immune processes, maintaining homeostasis, and promoting metabolic reprogramming in tumors, which are processes regulated by the lactate-induced lactylation of the lysine residues of histones. In this paper, we discuss the discovery and effects of lactylation, review the published studies on how protein lactylation influences cancer growth and further explore novel treatment approaches to achieve improved antitumor effects by targeting lactylation. These findings could lead to a new approach and guidance for improving the prognosis of patients with gliomas.

Protocol for deep mining the correlation between acute pancreatitis and ferroptosis using the MIMIC-III database and STATA software

The limitations associated with distinguishing serum Fe2+ and Fe3+ hinder the widespread application of ferroptosis, beyond laboratory settings. Here, we present a protocol for deep mining the correlation between acute pancreatitis and ferroptosis using the MIMIC-III database and STATA software. We describe steps for using Cox regression, decision curve analysis (DCA), and receiver operating characteristic (ROC) approaches to establish the relationship between them and determine the relevant factors. This protocol has potential application in establishing novel research models that integrate both fundamental and clinical methodologies. For complete details on the use and execution of this protocol, please refer to Yueling Deng et al.1.

Renshen Yangrong decoction for secondary malaise and fatigue: network pharmacology and Mendelian randomization study

Background

Renshen Yangrong decoction (RSYRD) has been shown therapeutic effects on secondary malaise and fatigue (SMF). However, to date, its bioactive ingredients and potential targets remain unclear.

Purpose

The purpose of this study is to assess the potential ingredients and targets of RSYRD on SMF through a comprehensive strategy integrating network pharmacology, Mendelian randomization as well as molecular docking verification.

Methods

Search for potential active ingredients and corresponding protein targets of RSYRD on TCMSP and BATMAN-TCM for network pharmacology analysis. Mendelian randomization (MR) was performed to find therapeutic targets for SMF. The eQTLGen Consortium (sample sizes: 31,684) provided data on cis-expression quantitative trait loci (cis-eQTL, exposure). The summary data on SMF (outcome) from genome-wide association studies (GWAS) were gathered from the MRC-IEU Consortium (sample sizes: 463,010). We built a target interaction network between the probable active ingredient targets of RSYRD and the therapeutic targets of SMF. We next used drug prediction and molecular docking to confirm the therapeutic value of the therapeutic targets.

Results

In RSYRD, network pharmacology investigations revealed 193 possible active compounds and 234 associated protein targets. The genetically predicted amounts of 176 proteins were related to SMF risk in the MR analysis. Thirty-seven overlapping targets for RSYRD in treating SMF, among which six (NOS3, GAA, IMPA1, P4HTM, RB1, and SLC16A1) were prioritized with the most convincing evidence. Finally, the 14 active ingredients of RSYRD were identified as potential drug molecules. The strong affinity between active components and putative protein targets was established by molecular docking.

Conclusion

This study revealed several active components and possible RSYRD protein targets for the therapy of SMF and provided novel insights into the feasibility of using Mendelian randomization for causal inference between Chinese medical formula and disease.

Critical Role of Mitochondrial Fatty Acid Metabolism in Normal Cell Function and Pathological Conditions

There is a "popular" belief that a fat-free diet is beneficial, supported by the scientific dogma indicating that high levels of fatty acids promote many pathological metabolic, cardiovascular, and neurodegenerative conditions. This dogma pressured scientists not to recognize the essential role of fatty acids in cellular metabolism and focus on the detrimental effects of fatty acids. In this work, we critically review several decades of studies and recent publications supporting the critical role of mitochondrial fatty acid metabolism in cellular homeostasis and many pathological conditions. Fatty acids are the primary fuel source and essential cell membrane building blocks from the origin of life. The essential cell membranes phospholipids were evolutionarily preserved from the earlier bacteria in human subjects. In the past century, the discovery of fatty acid metabolism was superseded by the epidemic growth of metabolic conditions and cardiovascular diseases. The association of fatty acids and pathological conditions is not due to their "harmful" effects but rather the result of impaired fatty acid metabolism and abnormal lifestyle. Mitochondrial dysfunction is linked to impaired metabolism and drives multiple pathological conditions. Despite metabolic flexibility, the loss of mitochondrial fatty acid oxidation cannot be fully compensated for by other sources of mitochondrial substrates, such as carbohydrates and amino acids, resulting in a pathogenic accumulation of long-chain fatty acids and a deficiency of medium-chain fatty acids. Despite popular belief, mitochondrial fatty acid oxidation is essential not only for energy-demanding organs such as the heart, skeletal muscle, and kidneys but also for metabolically "inactive" organs such as endothelial and epithelial cells. Recent studies indicate that the accumulation of long-chain fatty acids in specific organs and tissues support the impaired fatty acid oxidation in cell- and tissue-specific fashion. This work, therefore, provides a basis to challenge these established dogmas and articulate the need for a paradigm shift from the "pathogenic" role of fatty acids to the critical role of fatty acid oxidation. This is important to define the causative role of impaired mitochondrial fatty acid oxidation in specific pathological conditions and develop novel therapeutic approaches targeting mitochondrial fatty acid metabolism.

Review of the Predictive Value of Biomarkers in Sepsis Mortality

Sepsis is a leading cause of mortality among severely ill individuals, primarily due to its potential to induce fatal organ dysfunction. For clinicians, it is vital to have appropriate indicators, including the physiological status and personal experiences of patients with sepsis, to monitor the condition and assess prognosis. This approach aids in preventing the worsening of the illness and reduces mortality. Recent guidelines for sepsis focus on improving patient outcomes through early detection and timely treatment. Nonetheless, identifying severe cases and predicting their prognoses remain challenging. In recent years, there has been considerable interest in utilising the C-reactive protein (CRP)/albumin ratio (CAR) to evaluate the condition and forecast the prognosis of patients with sepsis. This research concentrates on the significance of CAR in the pathological process of sepsis, its association with prognosis, and the latest developments in employing procalcitonin, lactic acid, CRP, and other potential biomarkers. The CAR, with its predictive value for sepsis prognosis and mortality, is increasingly used as a clinical biochemical marker in diagnosing and monitoring patients with sepsis.

Can molecular hydrogen supplementation enhance physical performance in healthy adults? A systematic review and meta-analysis

Background

Physical exertion during exercise often leads to increased oxidative stress and inflammatory responses, significantly affecting physical performance. Current strategies to mitigate these effects are limited by their effectiveness and potential side effects. Molecular hydrogen (H₂) has gained attention for its antioxidant and anti-inflammatory properties. Studies have suggested that H2 supplementation contributes to antioxidant potential and anti-fatigue during exercise, but the variance in the observations and study protocols is presented across those studies.

Objective

This systematic review and meta-analysis aimed to comprehensively characterize the effects of H₂ supplementation on physical performance (i.e., endurance, muscular strength, and explosive power), providing knowledge that can inform strategies using H2 for enhancing physical performance.

Methods

We conducted a literature search of six databases (PubMed, Web of Science, Medline, Sport-Discus, Embase, and PsycINFO) according to the PRISMA guidelines. The data were extracted from the included studies and converted into the standardized mean difference (SMD). After that, we performed random-effects meta-analyses and used the I 2 statistic to evaluate heterogeneity. The Grading of Recommendations Assessment, Development, and Evaluation (GRADE) was used to assess the quality of the evidence obtained from this meta-analysis.

Results

In total, 27 publications consisting of 597 participants were included. The search finally included aerobic endurance, anaerobic endurance, muscular strength, lower limb explosive power, rating of perceived exertion (RPE), blood lactate (BLA), and average heart rate (HRavg) in the effect size (ES) synthesis. The ES of H2 on aerobic endurance, including V̇O2max (SMD = 0.09, p = 0.394; I 2 = 0%) and aerobic endurance exercise (SMD = 0.04, p = 0.687; I 2 = 0%), were not significant and trivial; the ES of H2 on 30 s maximal anaerobic endurance (SMD = 0.19, p = 0.239; I 2 = 0%) was not significant and trivial; the ES of H2 on muscular strength (SMD = 0.19, p = 0.265; I 2 = 0%) was not significant and trivial; but the ES of H2 on lower limb explosive power (SMD = 0.30, p = 0.018; I 2 = 0%) was significant and small. In addition, H2 reduces RPE (SMD = -0.37, p = 0.009; I 2 = 58.0%) and BLA (SMD = -0.37, p = 0.001; I 2 = 22.0%) during exercise, but not HRavg (SMD = -0.27, p = 0.094; I 2 = 0%).

Conclusion

These findings suggest that H2 supplementation is favorable in healthy adults to improve lower limb explosive power, alleviate fatigue, and boost BLA clearance, but may not be effectively improving aerobic and anaerobic endurance and muscular strength. Future studies with more rigorous designs are thus needed to examine and confirm the effects of H2 on these important functionalities in humans.

Systematic review registration

http://www.crd.york.ac.uk/PROSPERO.

Lactate and lactylation: Behind the development of tumors

There is growing evidence that lactate can have a wide range of biological impacts in addition to being a waste product of metabolism. Because of the Warburg effect, tumors generate lots of lactate, which create a tumor microenvironment (TME) with low nutrition, hypoxia, and low pH. As a result, the immunosuppressive network is established to gain immune escape potential and regulate tumor growth. Consequently, the tumor lactate pathway is emerging as a possible therapeutic target for tumor. Importantly, Zhao et al. first discovered histone lysine lactylation (Kla) in 2019, which links gene regulation to cell metabolism through dysmetabolic activity and epigenetic modifications, influencing TME and tumor development. Therefore, the aim of this paper is to explore the effects of lactate and lactylation on the TME and tumors, and provide theoretical basis for further research on potential therapeutic targets and biomarkers, with the view to providing new ideas and methods for tumor treatment and prognosis evaluation.

Association of ratios of visceral fat area/subcutaneous fat area and muscle area/standard body weight at T12 CT level with the prognosis of acute respiratory distress syndrome

Background

It is well-known that body composition metrics can influence the prognosis of various diseases. This study investigated how body composition metrics predict acute respiratory distress syndrome (ARDS) prognosis, focusing on the ratio of visceral fat area (VFA) to subcutaneous fat area (SFA), SFA to standard body weight (SBW), VFA to SBW, and muscle area (MA) to SBW. These metrics were assessed at the level of the twelfth thoracic vertebra (T12 computed tomography [CT] level) to determine their correlation with the outcomes of ARDS. The goal was to utilize these findings to refine and personalize treatment strategies for ARDS.

Methods

Patients with ARDS admitted to the intensive care units (ICUs) of three hospitals from January 2016 to July 2023 were enrolled in this study. Within 24 hours of ARDS onset, we obtained chest CT scans to measure subcutaneous fat, visceral fat, and muscle area at the T12 level. We then compared these ratios between survivors and non-survivors. Logistic regression was employed to identify prognostic risk factors. Receiver operating characteristic (ROC) curve analysis was utilized to determine the optimal cutoff for predictors of in-hospital mortality. Based on this cutoff, patients with ARDS were stratified. To reduce confounding factors, 1:1 propensity score matching (PSM) was applied. We conducted analyses of clinical feature and prognostic differences pre- and post-PSM between the stratified groups. Additionally, Kaplan-Meier survival curves were generated to compare the survival outcomes of these groups.

Results

Of 258 patients with ARDS, 150 survived and 108 did not. Non-survivors had a higher VFA/SFA ratio (P <0.001) and lower SFA/SBW and MA/SBW ratios (both P <0.001). Key risk factors were high VFA/SFA ratio (OR=2.081; P=0.008), age, acute physiology and chronic health evaluation (APACHE) II score, and lactate levels, while MA/SBW and albumin were protective. Patients with a VFA/SFA ratio ≥0.73 were associated with increased mortality, while those with an MA/SBW ratio >1.55 cm²/kg had lower mortality, both pre- and post-PSM (P=0.001 and P <0.001, respectively). Among 170 patients with pulmonary-origin ARDS, 87 survived and 83 did not. The non-survivor group showed a higher VFA/SFA ratio (P <0.001) and lower SFA/SBW and MA/SBW (P=0.003, P <0.001, respectively). Similar risk and protective factors were observed in this cohort. For VFA/SFA, a value above the cutoff of 1.01 predicted higher mortality, while an MA/SBW value below the cutoff of 1.48 cm²/kg was associated with increased mortality (both P <0.001 pre-/post-PSM).

Conclusions

Among all patients with ARDS, the VFA to SFA ratio, MA to SBW ratio at the T12 level, age, APACHE II score, and lactate levels emerged as independent risk factors for mortality.

Prehospital lactate-glucose interaction in acute life-threatening illnesses: metabolic response and short-term mortality

BACKGROUND AND IMPORTANCE

Lactate is an already recognized biomarker for short-term mortality. However, how glycemia and diabetes affect the predictive ability of lactate needs to be revealed.

OBJECTIVE

To determine how hypoglycemia, normoglycemia, and hyperglycemia modify the predictive ability of lactate for short-term mortality (3 days). The secondary objective was to evaluate the predictive ability of lactate in diabetic patients.

DESIGN, SETTINGS AND PARTICIPANTS

Prospective, observational study performed between 26 October 2018 and 31 December 2022. Multicenter, EMS-delivery, ambulance-based study, considering 38 basic life support units and 5 advanced life support units referring to four tertiary care hospitals (Spain). Eligible patients were adults recruited from among all phone requests for emergency assistance who were later evacuated to emergency departments.

OUTCOMES MEASURE AND ANALYSIS

The primary outcome was in-hospital mortality from any cause within the third day following EMS attendance. The main predictors considered were lactate, blood glucose levels and previous diabetes.

MAIN RESULTS

A total of 6341 participants fulfilled the inclusion criteria. 68 years (IQR: 51-80); 41.4% were female. The 3-day in-hospital mortality rate was 3.5%. The predictive capacity of lactate for 3-day mortality was only significantly different between normo-glycemia and hyperglycemia. The best predictive result was for normo-glycemia - AUC = 0.897 (95% CI: 0.881-0.913) - then hyperglycemia - AUC = 0.819 (95% CI: 0.770-0.868) and finally, hypoglycemia - AUC = 0.703 (95% CI: 0.422-0.983). The stratification according to diabetes presented no statistically significant difference, and the predictive results were AUC = 0.924 (95% CI: 0.892-0.956), AUC = 0.906 (95% CI: 0.884-0.928), and AUC = 0.872 (95% CI: 0.817-0.927) for nondiabetes, uncomplicated cases, and end-organ damage diabetes, respectively.

CONCLUSION

Our results demonstrated that glycemia, but not diabetes, alters the predictive ability of lactate. Therefore, hyperglycemia should be considered when interpreting lactate, since this could improve screening to detect cryptic shock conditions.

Diet xylo-oligosaccharide supplementation improves growth performance, immune function, and intestinal health of broilers

The effects of xylo-oligosaccharides (XOS) on broiler growth performance, immune function, and intestinal health were investigated. A total of 540 one-d-old Arbor Acres Plus broilers were randomly divided into 5 groups with 6 replicates per group and 18 chickens per replicate. Broilers in the control (CON) group received a corn-soybean meal based basal diet, those in the antibiotics (ANT) group received the basal diet plus 500 mg/kg oxytetracycline, and those in XOS groups received the basal diet plus 150, 300, or 450 mg/kg XOS. Compared with CON, the body weight at 42 d and average daily gain from 1 to 42 d were significantly increased in the 150, 450 mg/kg XOS-added and ANT groups (P = 0.018), and the relative expression of claudin-1 and ZO-1 mRNA in the ileum was significantly higher in the 300 and 450 mg/kg XOS-added groups (P < 0.001). The feed conversion ratios (P < 0.001) and abdominal fat rates (P = 0.012) of broilers from 1 to 42 d of age were significantly lower in all XOS-added groups than in the control group. Splenic index (P = 0.036) and bursa of Fabricius index (P = 0.009) were significantly better in the ANT group and each XOS-added group than in the control group. Compared to CON and ANT, serum IgA (P = 0.007) and IgG (P = 0.002) levels were significantly higher in the 300 mg/kg XOS-added group, and the relative abundance of short-chain fatty acid-producing genera (Alistipes) was also significantly higher (P < 0.001). Meanwhile, ileal villus height (P < 0.001) and ratio of villus height to crypt depth (V:C) (P = 0.001) were significantly increased in XOS-added broilers. In analysis of relationships between cecal microbes and the physical barrier of the gut, [Ruminococcus]_torques_group was positively correlated with mRNA expression of ileal ZO-1 and claudin-1 (P < 0.05), and Bacteroides was positively correlated with increased ileal villus height and V:C (P < 0.05). Overall, XOS addition to broiler diets improved growth performance, promoted intestinal health by enhancing intestinal barrier function and regulating cecal microbiota diversity, and had positive effects on immunity.

Molecular insights of exercise therapy in disease prevention and treatment

Despite substantial evidence emphasizing the pleiotropic benefits of exercise for the prevention and treatment of various diseases, the underlying biological mechanisms have not been fully elucidated. Several exercise benefits have been attributed to signaling molecules that are released in response to exercise by different tissues such as skeletal muscle, cardiac muscle, adipose, and liver tissue. These signaling molecules, which are collectively termed exerkines, form a heterogenous group of bioactive substances, mediating inter-organ crosstalk as well as structural and functional tissue adaption. Numerous scientific endeavors have focused on identifying and characterizing new biological mediators with such properties. Additionally, some investigations have focused on the molecular targets of exerkines and the cellular signaling cascades that trigger adaption processes. A detailed understanding of the tissue-specific downstream effects of exerkines is crucial to harness the health-related benefits mediated by exercise and improve targeted exercise programs in health and disease. Herein, we review the current in vivo evidence on exerkine-induced signal transduction across multiple target tissues and highlight the preventive and therapeutic value of exerkine signaling in various diseases. By emphasizing different aspects of exerkine research, we provide a comprehensive overview of (i) the molecular underpinnings of exerkine secretion, (ii) the receptor-dependent and receptor-independent signaling cascades mediating tissue adaption, and (iii) the clinical implications of these mechanisms in disease prevention and treatment.

Lactylation: the novel histone modification influence on gene expression, protein function, and disease

Lactic acid, traditionally considered as a metabolic waste product arising from glycolysis, has undergone a resurgence in scientific interest since the discovery of the Warburg effect in tumor cells. Numerous studies have proved that lactic acid could promote angiogenesis and impair the function of immune cells within tumor microenvironments. Nevertheless, the precise molecular mechanisms governing these biological functions remain inadequately understood. Recently, lactic acid has been found to induce a posttranslational modification, lactylation, that may offer insight into lactic acid's non-metabolic functions. Notably, the posttranslational modification of proteins by lactylation has emerged as a crucial mechanism by which lactate regulates cellular processes. This article provides an overview of the discovery of lactate acidification, outlines the potential "writers" and "erasers" responsible for protein lactylation, presents an overview of protein lactylation patterns across different organisms, and discusses the diverse physiological roles of lactylation. Besides, the article highlights the latest research progress concerning the regulatory functions of protein lactylation in pathological processes and underscores its scientific significance for future investigations.

Lactate facilitated mitochondrial fission-derived ROS to promote pulmonary fibrosis via ERK/DRP-1 signaling

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, fibrotic interstitial lung diseases, which mainly existed in middle-aged and elderly people. The accumulation of reactive oxygen species (ROS) is a common characteristic of IPF. Previous research also shown that lactate levels can be abnormally elevated in IPF patients. Emerging evidence suggested a relationship between lactate and ROS in IPF which needs further elucidation. In this article, we utilized a mouse model of BLM-induced pulmonary fibrosis to detect alterations in ROS levels and other indicators associated with fibrosis. Lactate could induce mitochondrial fragmentation by modulating expression and activity of DRP1 and ERK. Moreover, Increased ROS promoted P65 translocation into nucleus, leading to expression of lung fibrotic markers. Finally, Ulixertinib, Mdivi-1 and Mito-TEMPO, which were inhibitor activity of ERK, DRP1 and mtROS, respectively, could effectively prevented mitochondrial damage and production of ROS and eventually alleviate pulmonary fibrosis. Taken together, these findings suggested that lactate could promote lung fibrosis by increasing mitochondrial fission-derived ROS via ERK/DRP1 signaling, which may provide novel therapeutic solutions for IPF.

Emerging roles of lactate in acute and chronic inflammation

Traditionally, lactate has been considered a 'waste product' of cellular metabolism. Recent findings have shown that lactate is a substance that plays an indispensable role in various physiological cellular functions and contributes to energy metabolism and signal transduction during immune and inflammatory responses. The discovery of lactylation further revealed the role of lactate in regulating inflammatory processes. In this review, we comprehensively summarize the paradoxical characteristics of lactate metabolism in the inflammatory microenvironment and highlight the pivotal roles of lactate homeostasis, the lactate shuttle, and lactylation ('lactate clock') in acute and chronic inflammatory responses from a molecular perspective. We especially focused on lactate and lactate receptors with either proinflammatory or anti-inflammatory effects on complex molecular biological signalling pathways and investigated the dynamic changes in inflammatory immune cells in the lactate-related inflammatory microenvironment. Moreover, we reviewed progress on the use of lactate as a therapeutic target for regulating the inflammatory response, which may provide a new perspective for treating inflammation-related diseases.

Prognosis of patients with advanced bile tract carcinoma: assessment using the modified-Gustave Roussy Immune Score (mGRIm-s) as a clinico-immunological tool

BACKGROUND

The emergence of immune checkpoint inhibitors (ICIs) has enhanced survival outcomes for certain patients with advanced biliary tract carcinoma (BTC). Pinpointing those who would benefit most from immunotherapy remains elusive. We investigated the predictive value of the modified Gustave Roussy Immune Score (mGRIm-s) in BTC patients treated with ICIs.

METHODS

Data from 110 patients at Chinese People's Liberation Army General Hospital, spanning September 2015 to April 2021, were analyzed. The median follow-up duration was 38.7 months as of December 2023. Risk factors included low albumin, high lactate dehydrogenase, and an elevated neutrophil-lymphocyte ratio. Patients were stratified into low (patients with no risk factors) and high (patients with at least one risk factor) mGRIm-s groups based on these factors.

RESULTS

Survival outcomes post-immunotherapy favored the low mGRIm-s group, with significantly improved progression-free survival (PFS) and overall survival (OS) (8.50 months vs. 3.70 months and 21.60 months vs. 8.00 months). COX regression confirmed an elevated risk in the high mGRIm-s group. Subgroup analysis highlighted a notable survival advantage for low mGRIm-s patients receiving first-line immunotherapy.

CONCLUSIONS

This study underscores mGRIm-s's potential in predicting immunotherapy response in BTC, paving the way for more targeted approaches.

LPS-induced monocarboxylate transporter-1 inhibition facilitates lactate accumulation triggering epithelial-mesenchymal transformation and pulmonary fibrosis

The epithelial-mesenchymal transformation (EMT) process of alveolar epithelial cells is recognized as involved in the development of pulmonary fibrosis. Recent evidence has shown that lipopolysaccharide (LPS)-induced aerobic glycolysis of lung tissue and elevated lactate concentration are associated with the pathogenesis of sepsis-associated pulmonary fibrosis. However, it is uncertain whether LPS promotes the development of sepsis-associated pulmonary fibrosis by promoting lactate accumulation in lung tissue, thereby initiating EMT process. We hypothesized that monocarboxylate transporter-1 (MCT1), as the main protein for lactate transport, may be crucial in the pathogenic process of sepsis-associated pulmonary fibrosis. We found that high concentrations of lactate induced EMT while moderate concentrations did not. Besides, we demonstrated that MCT1 inhibition enhanced EMT process in MLE-12 cells, while MCT1 upregulation could reverse lactate-induced EMT. LPS could promote EMT in MLE-12 cells through MCT1 inhibition and lactate accumulation, while this could be alleviated by upregulating the expression of MCT1. In addition, the overexpression of MCT1 prevented LPS-induced EMT and pulmonary fibrosis in vivo. Altogether, this study revealed that LPS could inhibit the expression of MCT1 in mouse alveolar epithelial cells and cause lactate transport disorder, which leads to lactate accumulation, and ultimately promotes the process of EMT and lung fibrosis.

Evidence of 13 C-lactate oxidation in the human brain from hyperpolarized 13 C-MRI

PURPOSE

To test the hypothesis that lactate oxidation contributes to the  13 $$ {}^{13} $$ C-bicarbonate signal observed in the awake human brain using hyperpolarized  13 $$ {}^{13} $$ C MRI.

METHODS

Healthy human volunteers (N = 6) were scanned twice using hyperpolarized  13 $$ {}^{13} $$ C-MRI, with increased radiofrequency saturation of  13 $$ {}^{13} $$ C-lactate on one set of scans.  13 $$ {}^{13} $$ C-lactate,  13 $$ {}^{13} $$ C-bicarbonate, and  13 $$ {}^{13} $$ C-pyruvate signals for 132 brain regions across each set of scans were compared using a clustered Wilcoxon signed-rank test.

RESULTS

Increased  13 $$ {}^{13} $$ C-lactate radiofrequency saturation resulted in a significantly lower  13 $$ {}^{13} $$ C-bicarbonate signal (p = 0.04). These changes were observed across the majority of brain regions.

CONCLUSION

Radiofrequency saturation of  13 $$ {}^{13} $$ C-lactate leads to a decrease in  13 $$ {}^{13} $$ C-bicarbonate signal, demonstrating that the  13 $$ {}^{13} $$ C-lactate generated from the injected  13 $$ {}^{13} $$ C-pyruvate is being converted back to  13 $$ {}^{13} $$ C-pyruvate and oxidized throughout the human brain.

Comprehensive multiscale analysis of lactate metabolic dynamics in vitro and in vivo using highly responsive biosensors

As a key glycolytic metabolite, lactate has a central role in diverse physiological and pathological processes. However, comprehensive multiscale analysis of lactate metabolic dynamics in vitro and in vivo has remained an unsolved problem until now owing to the lack of a high-performance tool. We recently developed a series of genetically encoded fluorescent sensors for lactate, named FiLa, which illuminate lactate metabolism in cells, subcellular organelles, animals, and human serum and urine. In this protocol, we first describe the FiLa sensor-based strategies for real-time subcellular bioenergetic flux analysis by profiling the lactate metabolic response to different nutritional and pharmacological conditions, which provides a systematic-level view of cellular metabolic function at the subcellular scale for the first time. We also report detailed procedures for imaging lactate dynamics in live mice through a cell microcapsule system or recombinant adeno-associated virus and for the rapid and simple assay of lactate in human body fluids. This comprehensive multiscale metabolic analysis strategy may also be applied to other metabolite biosensors using various analytic platforms, further expanding its usability. The protocol is suited for users with expertise in biochemistry, molecular biology and cell biology. Typically, the preparation of FiLa-expressing cells or mice takes 2 days to 4 weeks, and live-cell and in vivo imaging can be performed within 1-2 hours. For the FiLa-based assay of body fluids, the whole measuring procedure generally takes ~1 min for one sample in a manual assay or ~3 min for 96 samples in an automatic microplate assay.

Lactate ameliorates palmitate-induced impairment of differentiative capacity in C2C12 cells through the activation of voltage-gated calcium channels

Palmitic acid (PA), a saturated fatty acid enriched in high-fat diet, has been implicated in the development of skeletal muscle regeneration dysfunction. This study aimed to examine the effects and mechanisms of lactate (Lac) treatment on PA-induced impairment of C2C12 cell differentiation capacity. Furthermore, the involvement of voltage-gated calcium channels in this context was examined. In this study, Lac could improve the PA-induced impairment of differentiative capacity in C2C12 cells by affecting Myf5, MyoD and MyoG. In addition, Lac increases the inward flow of Ca2+, and promotes the depolarization of the cell membrane potential, thereby activating voltage-gated calcium channels during C2C12 cell differentiation. The enchancement of Lac on myoblast differentiative capacity was abolished after the addition of efonidipine (voltage-gated calcium channel inhibitors). Therefore, voltage-gated calcium channels play an important role in improving PA-induced skeletal muscle regeneration disorders by exercising blood Lac. Our study showed that Lac could rescue the PA-induced impairment of differentiative capacity in C2C12 cells by affecting Myf5, MyoD and MyoG through the activation of voltage-gated calcium channels.

Reliability of power output, maximal rate of capillary blood lactate accumulation, and phosphagen contribution time following 15-s sprint cycling in amateur cyclists

Based on Mader's mathematical model, the rate of capillary blood lactate concentration (νLamax) following intense exercise is thought to reflect the maximal glycolytic rate. We aimed to investigate the reliability of important variables of Mader's model (i.e. power output, lactate accumulation, predominant phosphagen contribution time frames (tP Cr)) and resulting νLamax values derived during and after a 15-s cycling sprint. Fifty cyclists performed a 15-s all-out sprint test on a Cyclus2 ergometer three times. The first sprint test was considered a familiarization trial. Capillary blood was sampled before and every minute (for 8 min) after the sprint to determine νLamax. Test-retest analysis between T2 and T3 revealed excellent reliability for power output (Pmean and Ppeak; ICC = 0.99, 0.99), ∆La and νLamax with tPCr of 3.5 s (ICC = 0.91, 0.91). νLamax calculated with tPCr = tP peak (ICC = 0.87) and tP Cr = tPpeak-3.5% (ICC = 0.79) revealed good reliability. tPpeak and tPpeak-3.5% revealed only poor and moderate reliability (ICC = 0.41, 0.52). Power output and ∆La are reliable parameters in the context of this test. Depending on tPCr, reliability of νLamax varies considerably with tP Cr of 3.5 s showing excellent reliability. We recommend standardization of this type of testing especially tP Cr.

Deciphering mitochondrial dysfunction: Pathophysiological mechanisms in vascular cognitive impairment

Vascular cognitive impairment (VCI) encompasses a range of cognitive deficits arising from vascular pathology. The pathophysiological mechanisms underlying VCI remain incompletely understood; however, chronic cerebral hypoperfusion (CCH) is widely acknowledged as a principal pathological contributor. Mitochondria, crucial for cellular energy production and intracellular signaling, can lead to numerous neurological impairments when dysfunctional. Recent evidence indicates that mitochondrial dysfunction-marked by oxidative stress, disturbed calcium homeostasis, compromised mitophagy, and anomalies in mitochondrial dynamics-plays a pivotal role in VCI pathogenesis. This review offers a detailed examination of the latest insights into mitochondrial dysfunction within the VCI context, focusing on both the origins and consequences of compromised mitochondrial health. It aims to lay a robust scientific groundwork for guiding the development and refinement of mitochondrial-targeted interventions for VCI.

Histone lactylation in macrophages is predictive for gene expression changes during ischemia induced-muscle regeneration

OBJECTIVES

We have previously shown that lactate is an essential metabolite for macrophage polarisation during ischemia-induced muscle regeneration. Recent in vitro work has implicated histone lactylation, a direct derivative of lactate, in macrophage polarisation. Here, we explore the in vivo relevance of histone lactylation for macrophage polarisation after muscle injury.

METHODS

To evaluate macrophage dynamics during muscle regeneration, we subjected mice to ischemia-induced muscle damage by ligating the femoral artery. Muscle samples were harvested at 1, 2, 4, and 7 days post injury (dpi). CD45+CD11b+F4/80+CD64+ macrophages were isolated and processed for RNA sequencing, Western Blotting, and CUT&Tag-sequencing to investigate gene expression, histone lactylation levels, and histone lactylation genomic localisation and enrichment, respectively.

RESULTS

We show that, over time, macrophages in the injured muscle undergo extensive gene expression changes, which are similar in nature and in timing to those seen after other types of muscle-injuries. We find that the macrophage histone lactylome is modified between 2 and 4 dpi, which is a crucial window for macrophage polarisation. Absolute histone lactylation levels increase, and, although subtly, the genomic enrichment of H3K18la changes. Overall, we find that histone lactylation is important at both promoter and enhancer elements. Lastly, H3K18la genomic profile changes from 2 to 4 dpi were predictive for gene expression changes later in time, rather than being a reflection of prior gene expression changes.

CONCLUSIONS

Our results suggest that histone lactylation dynamics are functionally important for the function of macrophages during muscle regeneration.

Functional activation of pyruvate dehydrogenase in human brain using hyperpolarized [1-13 C]pyruvate

PURPOSE

Pyruvate, produced from either glucose, glycogen, or lactate, is the dominant precursor of cerebral oxidative metabolism. Pyruvate dehydrogenase (PDH) flux is a direct measure of cerebral mitochondrial function and metabolism. Detection of [13 C]bicarbonate in the brain from hyperpolarized [1-13 C]pyruvate using carbon-13 (13 C) MRI provides a unique opportunity for assessing PDH flux in vivo. This study is to assess changes in cerebral PDH flux in response to visual stimuli using in vivo 13 C MRS with hyperpolarized [1-13 C]pyruvate.

METHODS

From seven sedentary adults in good general health, time-resolved [13 C]bicarbonate production was measured in the brain using 90° flip angles with minimal perturbation of its precursors, [1-13 C]pyruvate and [1-13 C]lactate, to test the hypothesis that the appearance of [13 C]bicarbonate signals in the brain reflects the metabolic changes associated with neuronal activation. With a separate group of healthy participants (n = 3), the likelihood of the bolus-injected [1-13 C]pyruvate being converted to [1-13 C]lactate prior to decarboxylation was investigated by measuring [13 C]bicarbonate production with and without [1-13 C]lactate saturation.

RESULTS

In the course of visual stimulation, the measured [13 C]bicarbonate signal normalized to the total 13 C signal in the visual cortex increased by 17.1% ± 15.9% (p = 0.017), whereas no significant change was detected in [1-13 C]lactate. Proton BOLD fMRI confirmed the regional activation in the visual cortex with the stimuli. Lactate saturation decreased bicarbonate-to-pyruvate ratio by 44.4% ± 9.3% (p < 0.01).

CONCLUSION

We demonstrated the utility of 13 C MRS with hyperpolarized [1-13 C]pyruvate for assessing the activation of cerebral PDH flux via the detection of [13 C]bicarbonate production.