Acetyl-CoA from inflammation-induced fatty acids oxidation promotes hepatic malate-aspartate shuttle activity and glycolysis

The relationship and clinical significance of lactylation modification in digestive system tumors

Lactylation, an emerging post-translational modification, plays a pivotal role in the initiation and progression of digestive system tumors. This study presents a comprehensive review of lactylation in digestive system tumors, underscoring its critical involvement in tumor development and progression. By focusing on metabolic reprogramming, modulation of the tumor microenvironment, and the molecular mechanisms regulating tumor progression, the potential of targeting lactylation as a therapeutic strategy is highlighted. The research reveals that lactylation participates in gene expression regulation and cell signaling by affecting the post-translational states of histones and non-histone proteins, thereby influencing metabolic pathways and immune evasion mechanisms in tumor cells. Furthermore, this study assesses the feasibility of lactylation as a therapeutic target, providing insights for clinical treatment of gastrointestinal cancers. Future research should concentrate on elucidating the mechanisms of lactylation, developing efficient lactylation inhibitors, and validating their therapeutic efficacy in clinical trials, which could transform current cancer treatment and immunotherapy approaches. In summary, this review emphasizes the crucial role of lactylation in tumorigenesis and progression through a detailed analysis of its molecular mechanisms and clinical significance.

Physiology of malate dehydrogenase and how dysregulation leads to disease

Malate dehydrogenase (MDH) is pivotal in mammalian tissue metabolism, participating in various pathways beyond its classical roles and highlighting its adaptability to cellular demands. This enzyme is involved in maintaining redox balance, lipid synthesis, and glutamine metabolism and supports rapidly proliferating cells' energetic and biosynthetic needs. The involvement of MDH in glutamine metabolism underlines its significance in cell physiology. In contrast, its contribution to lipid metabolism highlights its role in essential biosynthetic processes necessary for cell maintenance and proliferation. The enzyme's regulatory mechanisms, such as post-translational modifications, underscore its complexity and importance in metabolic regulation, positioning MDH as a potential target in metabolic dysregulation. Furthermore, the association of MDH with various pathologies, including cancer and neurological disorders, suggests its involvement in disease progression. The overexpression of MDH isoforms MDH1 and MDH2 in cancers like breast, prostate, and pancreatic ductal adenocarcinoma, alongside structural modifications, implies their critical role in the metabolic adaptation of tumor cells. Additionally, mutations in MDH2 linked to pheochromocytomas, paragangliomas, and other metabolic diseases emphasize MDH's role in metabolic homeostasis. This review spotlights MDH's potential as a biomarker and therapeutic target, advocating for further research into its multifunctional roles and regulatory mechanisms in health and disease.

Fibroblast growth factor 21 enhances learning and memory performance in mice by regulating hippocampal L-lactate homeostasis

Fibroblast growth factor 21 (FGF21) is one endogenous metabolic molecule that functions as a regulator in glucose and lipid homeostasis. However, the effect of FGF21 on L-lactate homeostasis and its mechanism remains unclear until now. Forty-five Six-week-old male C57BL/6 mice were divided into three groups: control, L-lactate, and FGF21 (1.5 mg/kg) groups. At the end of the treatment, nuclear magnetic resonance-based metabolomics, and key proteins related to L-lactate homeostasis were determined respectively to evaluate the efficacy of FGF21 and its mechanisms. The results showed that, compared to the vehicle group, the L-lactate-treated mice displayed learning and memory performance impairments, as well as reduced hippocampal ATP and NADH levels, but increased oxidative stress, mitochondrial dysfunction, and apoptosis, which suggesting inhibited L-lactate-pyruvate conversion in the brain. Conversely, FGF21 treatment ameliorated the L-lactate accumulation state, accompanied by restoration of the learning and memory defects, indicating enhanced L-lactate uptake and utilization in hippocampal neurons. We demonstrated that maintaining constant L-lactate-pyruvate flux is essential for preserving neuronal bioenergetic and redox levels. FGF21 contributed to preparing the brain for situations of high availability of L-lactate, thus preventing neuronal vulnerability in metabolic reprogramming.

Palmitic Acid Exerts Anti-Tumorigenic Activities by Modulating Cellular Stress and Lipid Droplet Formation in Endometrial Cancer

Epidemiological and clinical evidence have extensively documented the role of obesity in the development of endometrial cancer. However, the effect of fatty acids on cell growth in endometrial cancer has not been widely studied. Here, we reported that palmitic acid significantly inhibited cell proliferation of endometrial cancer cells and primary cultures of endometrial cancer and reduced tumor growth in a transgenic mouse model of endometrial cancer, in parallel with increased cellular stress and apoptosis and decreased cellular adhesion and invasion. Inhibition of cellular stress by N-acetyl-L-cysteine effectively reversed the effects of palmitic acid on cell proliferation, apoptosis, and invasive capacity in endometrial cancer cells. Palmitic acid increased the intracellular formation of lipid droplets in a time- and dose-dependent manner. Depletion of lipid droplets by blocking DGAT1 and DGAT2 effectively increased the ability of palmitic acid to inhibit cell proliferation and induce cleaved caspase 3 activity. Collectively, this study provides new insight into the effect of palmitic acid on cell proliferation and invasion and the formation of lipid droplets that may have potential clinical relevance in the treatment of obesity-driven endometrial cancer.

Discovery of a New Anti-Inflammatory Agent from Anemoside B4 Derivatives and Its Therapeutic Effect on Colitis by Targeting Pyruvate Carboxylase

Anemoside B4 (AB4), a triterpenoidal saponin from Pulsatilla chinensis, shows significant anti-inflammatory activity, and may be used for treating inflammatory bowel disease (IBD). Nevertheless, its application is limited due to its high molecular weight and pronounced water solubility. To discover new effective agents for treating IBD, we synthesized 28 AB4 derivatives and evaluated their cytotoxic and anti-inflammatory activities in vitro. Among them, A3-6 exhibited significantly superior anti-inflammatory activity compared to AB4. It showed a significant improvement in the symptoms of DSS-induced colitis in mice, with a notably lower oral effective dose compared to AB4. Furthermore, we discovered that A3-6 bound with pyruvate carboxylase (PC), then inhibited PC activity, reprogramming macrophage function, and alleviated colitis. These findings indicate that A3-6 is a promising therapeutic candidate for colitis, and PC may be a potential new target for treating colitis.

Cyperus peptide SFRWQ inhibits oxidation and inflammation in RAW264.7 cell model

Oxidative stress can induce many diseases. Antioxidant peptides from food sources have the advantages of good safety, high activity, and good absorbability. In this study, a pentapeptide (SFRWQ; SER-PHE-ARG-TRP-GLN) was identified in a protein hydrolysate of Cyperus (Cyperus esculentus L.). Enzyme-linked immunosorbent assay (ELISA), real-time quantitative (qPCR), immunofluorescence and other techniques were used to evaluate the anti-inflammatory and antioxidant effects of SFRWQ. SFRWQ was found to have 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical-scavenging ability, help increase superoxide dismutase (SOD) and catalase (CAT) levels in RAW264.7 cells, reduce reactive oxygen species (ROS) levels, and decrease tumor necrosis factor alpha (TNF-α) and interleukin-6 (IL-6) gene expression and secretion. The binding score of SFRWQ to recombinant Kelch-like ECH-associated protein 1 (Keap1) was greater than that of TX6. These findings suggest that SFRWQ activates the Keap1-Nrf2 cellular antioxidant signaling pathway. According to metabolomics studies, SFRWQ increased glutathione (GSH), glutathione disulfide (GSSG), and γ-glutamylcysteine levels and decreased the levels of Prostaglandin D2 (PGD2), Prostaglandin E2 (PGE2), and Prostaglandin H2 (PGH2), which are involved in arachidonic acid metabolism, to protect cells from LPS-induced damage. By elucidating the mechanism of action of SFRWQ, we provide a reference for the development of dietary antioxidant peptides.

Acetyl-CoA metabolism as a therapeutic target for cancer

Acetyl-coenzyme A (acetyl-CoA), an essential metabolite, not only takes part in numerous intracellular metabolic processes, powers the tricarboxylic acid cycle, serves as a key hub for the biosynthesis of fatty acids and isoprenoids, but also serves as a signaling substrate for acetylation reactions in post-translational modification of proteins, which is crucial for the epigenetic inheritance of cells. Acetyl-CoA links lipid metabolism with histone acetylation to create a more intricate regulatory system that affects the growth, aggressiveness, and drug resistance of malignancies such as glioblastoma, breast cancer, and hepatocellular carcinoma. These fascinating advances in the knowledge of acetyl-CoA metabolism during carcinogenesis and normal physiology have raised interest regarding its modulation in malignancies. In this review, we provide an overview of the regulation and cancer relevance of main metabolic pathways in which acetyl-CoA participates. We also summarize the role of acetyl-CoA in the metabolic reprogramming and stress regulation of cancer cells, as well as medical application of inhibitors targeting its dysregulation in therapeutic intervention of cancers.

A novel metabolism-related gene signature in patients with hepatocellular carcinoma

Hepatocellular carcinoma (HCC) remains a global challenge as it is the sixth most common neoplasm worldwide and the third leading cause of cancer-related death. A key feature of HCC is abnormal metabolism, which promotes cancer cell proliferation, survival, invasion, and metastasis. However, the significance of metabolism-related genes (MRGs) in HCC remains to be elucidated. Here, we aim to establish a novel metabolism-related prognostic signature for the prediction of patient outcomes and to investigate the value of MRG expression in the prognostic prediction of HCC. In our research, a Metabolism-Related Risk Score (MRRS) model was constructed using 14 MRGs (DLAT, SEPHS1, ACADS, UCK2, GOT2, ADH4, LDHA, ME1, TXNRD1, B4GALT2, AK2, PTDSS2, CSAD, and AMD1). The Kaplan-Meier curve confirmed that the MRRS has a high accuracy in predicting the prognosis of HCC patients (p < 0.001). According to the MRRS model, the area under the curve (AUC) values for predicting the prognosis of patients with hepatocellular carcinoma at 1, 3, and 5 years reached 0.829, 0.760, and 0.739, respectively. Functional analyses revealed that signaling pathways associated with the cell cycle were largely enriched by differential genes between high and low-risk groups. In addition, dendritic cells (DCs) (p < 0.001), CD4+ T cells (p < 0.01), CD8+ T cells (p < 0.001), B cells (p < 0.001), neutrophils (p < 0.001), macrophages (p < 0.001) had a higher proportion of infiltrates in high-risk populations. Low GOT2 expression is associated with poor prognosis in patients with hepatocellular carcinoma. Knockdown of GOT2 significantly increased the migration capacity of the Huh7 and MHCC97H hepatocellular carcinoma lines. Our research reveals that GOT2 is negatively related to the survival of patients with hepatocellular carcinoma and GOT2 may contribute to tumor progression by inhibiting the ability of tumor cells to migrate.

Ketone Bodies in Diabetes Mellitus: Friend or Foe?

In glucose-deprived conditions, ketone bodies are produced by the liver mitochondria, through the catabolism of fatty acids, and are used peripherally, as an alternative energy source. Ketones are produced in the body under normal conditions, including during pregnancy and the neonatal period, when following a ketogenic diet (KD), fasting, or exercising. Additionally, ketone synthesis is also augmented under pathological conditions, including cases of diabetic ketoacidosis (DKA), alcoholism, and several metabolic disorders. Nonetheless, diet is the main regulator of total body ketone concentrations. The KDs are mimicking the fasting state, altering the default metabolism towards the use of ketones as the primary fuel source. Recently, KD has gained recognition as a medical nutrition therapy for a plethora of metabolic conditions, including obesity and diabetes mellitus (DM). The present review aims to discuss the role of ketones, KDs, ketonemia, and ketonuria in DM, presenting all the available new evidence in a comprehensive manner.

Low expression of GOT2 promotes tumor progress and predicts poor prognosis in hepatocellular carcinoma

Background: To explore the biological function and the underlying mechanisms of GOT2 in hepatocellular carcinoma (HCC). Materials & methods: The expression level and prognostic value of GOT2 were examined using International Cancer Genome Consortium and International Cancer Proteogenome Consortium databases. The cell counting kit-8 method, clone formation, Transwell® assays and western blotting were used to evaluate the effects of GOT2 on the biological function and autophagy of HCC cells. Results: The expression of GOT2 was downregulated in HCC tissues and correlated with poor prognosis of HCC patients. Knockdown of GOT2 promoted proliferation, migration and invasion of HCC cells and promoted cells' proliferation by inducing autophagy. Conclusion: GOT2 plays a tumor-inhibitory role in HCC and may be a potential therapeutic target for HCC.

Spotlight on GOT2 in Cancer Metabolism

GOT2 is at the nexus of several critical metabolic pathways in homeostatic cellular and dysregulated cancer metabolism. Despite this, recent work has emphasized the remarkable plasticity of cancer cells to employ compensatory pathways when GOT2 is inhibited. Here, we review the metabolic roles of GOT2, highlighting findings in both normal and cancer cells. We emphasize how cancer cells repurpose cell intrinsic metabolism and their flexibility when GOT2 is inhibited. We close by using this framework to discuss key considerations for future investigations into cancer metabolism.

Poly-pathways metabolomics for high-yielding cordycepin of Cordyceps militaris

Cordycepin is an important quality control marker in Cordyceps militaris. This study aimed to explain the metabolic mechanisms for high-yielding cordycepin of C. militaris. In this study, high-yielding strains of cordycepin were obtained by ultraviolet mutagenesis, and the polysaccharide and protein contents were also changed. In high-yielding strains, the protein content significantly increased, whereas the polysaccharide content decreased. Simultaneously, metabolic differences for high- and low-yielding cordycepin strains were detected by metabolomics. Metabolomics results showed that the relative content of most metabolites decreased in high-yielding cordycepin strains. Various metabolic pathways have been altered in high-yielding cordycepin strains, such as the citric acid cycle, purine metabolism, and pyrimidine metabolism, leading to an increase in cordycepin content. In addition, changes in metabolic poly-pathways related to polysaccharide and protein synthesis, such as galactose metabolism and amino acid metabolism, promoted an increase in cordycepin content. This study analyzes the high yield of cordycepin in C. militaris at the metabolic level and provides a theoretical basis for further increasing cordycepin content.

Saturation of the mitochondrial NADH shuttles drives aerobic glycolysis in proliferating cells

Proliferating cells exhibit a metabolic phenotype known as "aerobic glycolysis," which is characterized by an elevated rate of glucose fermentation to lactate irrespective of oxygen availability. Although several theories have been proposed, a rationalization for why proliferating cells seemingly waste glucose carbon by excreting it as lactate remains elusive. Using the NCI-60 cell lines, we determined that lactate excretion is strongly correlated with the activity of mitochondrial NADH shuttles, but not proliferation. Quantifying the fluxes of the malate-aspartate shuttle (MAS), the glycerol 3-phosphate shuttle (G3PS), and lactate dehydrogenase under various conditions demonstrated that proliferating cells primarily transform glucose to lactate when glycolysis outpaces the mitochondrial NADH shuttles. Increasing mitochondrial NADH shuttle fluxes decreased glucose fermentation but did not reduce the proliferation rate. Our results reveal that glucose fermentation, a hallmark of cancer, is a secondary consequence of MAS and G3PS saturation rather than a unique metabolic driver of cellular proliferation.

Lactate metabolism in human health and disease

The current understanding of lactate extends from its origins as a byproduct of glycolysis to its role in tumor metabolism, as identified by studies on the Warburg effect. The lactate shuttle hypothesis suggests that lactate plays an important role as a bridging signaling molecule that coordinates signaling among different cells, organs and tissues. Lactylation is a posttranslational modification initially reported by Professor Yingming Zhao’s research group in 2019. Subsequent studies confirmed that lactylation is a vital component of lactate function and is involved in tumor proliferation, neural excitation, inflammation and other biological processes. An indispensable substance for various physiological cellular functions, lactate plays a regulatory role in different aspects of energy metabolism and signal transduction. Therefore, a comprehensive review and summary of lactate is presented to clarify the role of lactate in disease and to provide a reference and direction for future research. This review offers a systematic overview of lactate homeostasis and its roles in physiological and pathological processes, as well as a comprehensive overview of the effects of lactylation in various diseases, particularly inflammation and cancer.

Cadmium exposure decreases fasting blood glucose levels and exacerbates type-2 diabetes in a mouse model

PURPOSE

Although the effects of cadmium (Cd) on the development of diabetes have been extensively investigated, the relationship between Cd exposure and the severity of established diabetes is unclear. Herein, we investigate the effects of long-term exposure to Cd in a streptozotocin-induced mouse model of type-2 diabetes mellitus (T2DM) and the underlying mechanism.

METHODS

C57BL/6 Mice were divided into the following four groups: (1) control group; (2) Cd-exposed group; (3) diabetic group; (4) Cd-exposed diabetic group. Cd exposure was established by the administration of 155 ppm CdCl₂ in drinking water. After 25 weeks of treatment, serum fasting glucose and insulin were measured. Meanwhile, the liver and pancreas specimens were sectioned and stained with Hematoxylin and eosin. Gluconeogenesis, glycolysis, lactate concentration, and fibrosis in liver were evaluated.

RESULTS

Clinical signs attributable to diabetes were more apparent in Cd-exposed diabetic mice, while no effects of Cd exposure were found on non-diabetic mice. Cd exposure significantly decreased fasting blood glucose (FBG) levels in diabetic group. We further demonstrated that the glycolysis related hepatic enzymes, pyruvate kinase M2 (PKM-2) and lactic dehydrogenase A (LDHA) were both increased, while the gluconeogenesis related hepatic enzymes, phosphoenolpyruvate-1 (PCK-1) and glucose-6-phosphatase (G6Pase) were both decreased in Cd exposed diabetic mice, indicating that Cd increased glycolysis and inhibited gluconeogenesis in diabetic model. Moreover, lactate accumulation was noted accompanied by the increased inflammation and fibrosis in the livers of diabetic mice following Cd exposure.

CONCLUSIONS

Cd exposure disturbed glucose metabolism and exacerbated diabetes, providing a biological relevance that DM patients are at greater risk when exposed to Cd.

TMAO-Activated Hepatocyte-Derived Exosomes Are Widely Distributed in Mice with Different Patterns and Promote Vascular Inflammation

Background

Trimethylamine-N-oxide (TMAO) has been shown to be an important player in cardiovascular disease (CVD) by promoting vascular inflammation and endothelial dysfunction. We recently found that exosomes (Exos) released from TMAO-activated hepatocytes (TMAO-Exos) could significantly induce inflammation and endothelial dysfunction. However, understandings of how are the Exos secreted by hepatocytes, where are they distributed in vivo, and what effects will they have on vascular inflammation remain limited. The present study aimed to explore the hub genes involved in the production of TMAO-Exos and their distributions in vivo and effects on inflammation.

Methods

The transcriptome profiles of primary rat hepatocytes stimulated with TMAO were obtained from the GSE135856 dataset in the Gene Expression Omnibus repository, and the hub genes associated with Exos were screened and verified by qPCR. Next, Exos derived from TMAO-treated hepatocytes were isolated using differential centrifugation and given intravenously to mice. After 24 h, the distributions of DiI-labelled Exos were visualized with a fluorescence microscope, and the levels of proinflammatory genes in the aorta were detected by qPCR.

Results

Phgdh, Mdh2, Echs1, Rap2a, Gpd1l, and Slc3a2 were identified as hub genes that may be involved in the production of TMAO-Exos. And TMAO-Exos were found to be efficiently taken up by cardiomyocytes, hepatocytes, and endothelial cells in the aorta and gastrocnemius muscle. Furthermore, TMAO-Exos, but not control-Exos, could significantly promote the mRNA expressions of Tnf, Icam1, Sele, and Cox-2 in the aorta.

Conclusions

We provided clues about how TMAO may stimulate hepatocytes to produce Exos and further offered evidence that Exos secreted by TMAO-treated hepatocytes could be widely distributed in vivo and promote vascular inflammation.

Metabolic Consequences of IgE- and Non-IgE-Mediated Mast Cell Degranulation

Mast cells are important effector cells in the immune system and undergo activation (i.e., degranulation) by two major mechanisms: IgE-mediated and non-IgE-mediated mechanisms. Although IgE-mediated degranulation is well researched, the cellular mechanisms of non-IgE-mediated mast cell activation are poorly understood despite the potential to induce similar pathophysiological effects. To better understand non-IgE mast cell degranulation, we characterized and compared cellular metabolic shifts across several mechanisms of degranulation (allergen-induced [IgE-mediated], 20 nm of silver nanoparticle-mediated [non-IgE], and compound 48/80-mediated [non-IgE]) in murine bone marrow-derived mast cells. All treatments differentially impacted mitochondrial activity and glucose uptake, suggesting diverging metabolic pathways between IgE- and non-IgE-mediated degranulation. Non-IgE treatments depleted mast cells' glycolytic reserve, and compound 48/80 further inhibited the ability to maximize mitochondrial respiration. This cellular reprogramming may be indicative of a stress response with non-IgE treatments. Neither of these outcomes occurred with IgE-mediated degranulation, hinting at a separate programmed response. Fuel flexibility between the three primary mitochondrial nutrient sources was also eliminated in activated cells and this was most significant in non-IgE-mediated degranulation. Lastly, metabolomics analysis of bone marrow-derived mast cells following degranulation was used to compare general metabolite profiles related to energetic pathways. IgE-mediated degranulation upregulated metabolite concentrations for the TCA cycle and glycolysis compared with other treatments. In conclusion, mast cell metabolism varies significantly between IgE- and non-IgE-mediated degranulation suggesting novel cell regulatory mechanisms are potentially driving unexplored pathways of mast cell degranulation.

Garcinol promotes hepatic gluconeogenesis by inhibiting P300/CBP-associated factor in late-pregnant sows

Disorder of hepatic glucose metabolism is the characteristic of late-pregnant sows. The purpose of our study was to look into the mechanism of garcinol on the improvement of hepatic gluconeogenic enzyme in late-pregnant sows. Thirty second- and third-parity sows (Duroc × Yorkshire × Landrace, n 10/diet) were fed a basal diet (control) or that diet supplemented with 100 mg/kg (Low Gar) or 500 mg/kg (High Gar) garcinol from day 90 of gestation to the end of farrowing. The livers were processed to measure enzymatic activity. Hepatocytes from pregnant sows were transfected with P300/CBP-associating factor (PCAF) small interfering RNA (siRNA) or treated with garcinol. Dietary garcinol had no effect on average daily feed intake, body weight (BW), backfat and BW gain of late-pregnant sows. Garcinol promoted plasma glucose levels in pregnant sows and newborn piglets. Garcinol up-regulated hepatic gluconeogenic enzyme expression and decreased PCAF activity. Garcinol had no effect on the expression of PPAR-γ co-activator 1α (PGC-1α) and Forkhead box O1 (FOXO1) but significantly increased their activity and decreased their acetylation in late-pregnant sows. Transfection of PCAF siRNA to hepatocytes of pregnant sows increased PGC-1α and FOXO1 activities. Furthermore, in hepatocytes of pregnant sows, garcinol treatment also up-regulated the activities of PGC-1α and FOXO1 and inhibited the acetylation of PGC-1α and FOXO1. Garcinol improves hepatic gluconeogenic enzyme expression in late-pregnant sows, and this may be due to the mechanism of down-regulating the acetylation of PGC-1α and FOXO1 induced by PCAF in isolated hepatocytes.

Development of an Aerobic Glycolysis Index for Predicting the Sorafenib Sensitivity and Prognosis of Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is a deadly tumor with high heterogeneity. Aerobic glycolysis is a common indicator of tumor growth and plays a key role in tumorigenesis. Heterogeneity in distinct metabolic pathways can be used to stratify HCC into clinically relevant subgroups, but these have not yet been well-established. In this study, we constructed a model called aerobic glycolysis index (AGI) as a marker of aerobic glycolysis using genomic data of hepatocellular carcinoma from The Cancer Genome Atlas (TCGA) project. Our results showed that this parameter inferred enhanced aerobic glycolysis activity in tumor tissues. Furthermore, high AGI is associated with poor tumor differentiation and advanced stages and could predict poor prognosis including reduced overall survival and disease-free survival. More importantly, the AGI could accurately predict tumor sensitivity to Sorafenib therapy. Therefore, the AGI may be a promising biomarker that can accurately stratify patients and improve their treatment efficacy.

Blocking mitochondrial pyruvate import in brown adipocytes induces energy wasting via lipid cycling

Combined fatty acid esterification and lipolysis, termed lipid cycling, is an ATP‐consuming process that contributes to energy expenditure. Therefore, interventions that stimulate energy expenditure through lipid cycling are of great interest. Here we find that pharmacological and genetic inhibition of the mitochondrial pyruvate carrier (MPC) in brown adipocytes activates lipid cycling and energy expenditure, even in the absence of adrenergic stimulation. We show that the resulting increase in ATP demand elevates mitochondrial respiration coupled to ATP synthesis and fueled by lipid oxidation. We identify that glutamine consumption and the Malate‐Aspartate Shuttle are required for the increase in Energy Expenditure induced by MPC inhibition in Brown Adipocytes (MAShEEBA). We thus demonstrate that energy expenditure through enhanced lipid cycling can be activated in brown adipocytes by decreasing mitochondrial pyruvate availability. We present a new mechanism to increase energy expenditure and fat oxidation in brown adipocytes, which does not require adrenergic stimulation of mitochondrial uncoupling.

Effects of inflammatory and anti-inflammatory environments on the macrophage mitochondrial function

Mitochondrial response to inflammation is crucial in the metabolic adaptation to infection. This study aimed to explore the mitochondrial response under inflammatory and anti-inflammatory environments, with a focus on the tricarboxylic acid (TCA) cycle. Expression levels of key TCA cycle enzymes and the autophagy-related protein light chain 3b (LC3b) were determined in raw 264.7 cells treated with lipopolysaccharide (LPS) and metformin (Met). Additionally, reactive oxygen species (ROS) levels and mitochondrial membrane potential were assessed using flow cytometry. Moreover, 8-week-old C57BL/6J mice were intraperitoneally injected with LPS and Met to assess the mitochondrial response in vivo. Upon LPS stimulation, the expression of key TCA enzymes, including citrate synthase, α-ketoglutarate dehydrogenase, and isocitrate dehydrogenase 2, and the mitochondrial membrane potential decreased, whereas the levels of LC3b and ROS increased. However, treatment with Met inhibited the reduction of LPS-induced enzyme levels as well as the elevation of LC3b and ROS levels. In conclusion, the mitochondrial TCA cycle is affected by the inflammatory environment, and the LPS-induced effects can be reversed by Met treatment.

The malate-aspartate shuttle (Borst cycle): How it started and developed into a major metabolic pathway

This article presents a personal and critical review of the history of the malate–aspartate shuttle (MAS), starting in 1962 and ending in 2020. The MAS was initially proposed as a route for the oxidation of cytosolic NADH by the mitochondria in Ehrlich ascites cell tumor lacking other routes, and to explain the need for a mitochondrial aspartate aminotransferase (glutamate oxaloacetate transaminase 2 [GOT2]). The MAS was soon adopted in the field as a major pathway for NADH oxidation in mammalian tissues, such as liver and heart, even though the energetics of the MAS remained a mystery. Only in the 1970s, LaNoue and coworkers discovered that the efflux of aspartate from mitochondria, an essential step in the MAS, is dependent on the proton‐motive force generated by the respiratory chain: for every aspartate effluxed, mitochondria take up one glutamate and one proton. This makes the MAS in practice uni‐directional toward oxidation of cytosolic NADH, and explains why the free NADH/NAD ratio is much higher in the mitochondria than in the cytosol. The MAS is still a very active field of research. Most recently, the focus has been on the role of the MAS in tumors, on cells with defects in mitochondria and on inborn errors in the MAS. The year 2019 saw the discovery of two new inborn errors in the MAS, deficiencies in malate dehydrogenase 1 and in aspartate transaminase 2 (GOT2). This illustrates the vitality of ongoing MAS research.

Peculiarities of Platelet Metabolism in Patients with Acute Coronary Syndrome with Anxiety-Depressive Disorders and Informativity of Enzymes in the Forecast of Development of Cardiovascular Complications

Anxiety–depressive disorders (ADD) are a risk factor of cardiovascular mortality in patients with coronary artery disease (CAD). Acute coronary syndrome (ACS) is the main clinical manifestation of a progressing CAD. Metabolic processes disorder in platelets can be one of the causes of cardiovascular complications in patients with ACS and concomitant ADD. We studied platelets metabolism and prognostic informativity of NAD(P)-dependent dehydrogenases of platelets in ACS patients with ADD in terms of forecasting cardiovascular complications development over a year of observation. The levels of NAD- and NADP-dependent dehydrogenases of platelets were determined by means of a bioluminescent method during the first 24 h after admission to hospital and in dynamics in 10 days. Among 315 examined patients, ADD was found in 161 (51.1%). ACS patients with concomitant ADD had both cytoplasmic and mitochondrial processes impairment in platelets that consisted in a decrease of energy metabolism intensity, inhibition of anaerobic glycolysis reactions and lipid catabolism. After 12 months of follow-up, 41 (25.5%) cardiovascular complications were detected in the group of ACS patients with ADD and 20 (13.0%) in the group of ACS patients without ADD. According to the results of the analysis of the neural network based on NAD(P)-dependent dehydrogenases of platelets activity in ACS patients with ADD, indicators were obtained that are informative for predicting the development of recurrent cardiovascular complications.

Big Data-Based Identification of Multi-Gene Prognostic Signatures in Liver Cancer

Simultaneous identification of multiple single genes and multi-gene prognostic signatures with higher efficacy in liver cancer has rarely been reported. Here, 1,173 genes potentially related to the liver cancer prognosis were mined with Coremine, and the gene expression and survival data in 370 samples for overall survival (OS) and 319 samples for disease-free survival (DFS) were retrieved from The Cancer Genome Atlas. Numerous survival analyses results revealed that 39 genes and 28 genes significantly associated with DFS and OS in liver cancer, including 18 and 12 novel genes that have not been systematically reported in relation to the liver cancer prognosis, respectively. Next, totally 9,139 three-gene combinations (including 816 constructed by 18 novel genes) for predicting DFS and 3,276 three-gene combinations (including 220 constructed by 12 novel genes) for predicting OS were constructed based on the above genes, and the top 15 of these four parts three-gene combinations were selected and shown. Moreover, a huge difference between high and low expression group of these three-gene combination was detected, with median survival difference of DFS up to 65.01 months, and of OS up to 83.57 months. The high or low expression group of these three-gene combinations can predict the longest prognosis of DFS and OS is 71.91 months and 102.66 months, and the shortest is 6.24 months and 13.96 months. Quantitative real-time polymerase chain reaction and immunohistochemistry reconfirmed that three genes F2, GOT2, and TRPV1 contained in one of the above combinations, are significantly dysregulated in liver cancer tissues, low expression of F2, GOT2, and TRPV1 is associated with poor prognosis in liver cancer. Overall, we discovered a few novel single genes and multi-gene combinations biomarkers that are closely related to the long-term prognosis of liver cancer, and they can be potential therapeutic targets for liver cancer.

Potential biomarkers in septic shock besides lactate

IMPACT STATEMENT

Elevated lactate has been commonly considered as a biomarker and a useful prognostic tool for resuscitation in septic shock, facilitating physician more rapid intervention and treatment. However, it can be initiated by hypoxia, but persistent hyperlactatemia may not represent persistent hypoxia only. In the article, it is the first time to review potential biomarkers in septic shock from the point of view of energy metabolism including intermediates of TCA cycle, MAS, the NAD⁺/NADH ratio, NAD⁺, NADH, malate, and MDH. And the combination of lactate and MDH is also proposed in septic shock for the first time, as MDH in cytoplasm and mitochondria participates in both MAS and TCA cycle for ATP generation. Its feasibility in clinic has been analyzed at the end, although related research is still limited. It is reasonable the combination of lactate and MDH will be more comprehensive to reflex hypoxia in septic shock.

Acetylation of Phenylalanine Hydroxylase and Tryptophan 2,3-Dioxygenase Alters Hepatic Aromatic Amino Acid Metabolism in Weaned Piglets

Weaning significantly alters hepatic aromatic amino acid (AAA) metabolism and physiological functions. However, less is known about the regulating mechanism of hepatic AAA metabolism after weaning. A total of 200 21-day-old piglets (Duroc × Landrace) were assigned randomly to the control group and the weaning group. In this study, weaning significantly decreased the concentration of phenylalanine, tryptophan, and tyrosine in piglet livers (p < 0.05). Additionally, through the detection of liver AAA metabolites and metabolic enzyme activity, it was observed that hepatic tryptophan catabolism was enhanced, while that of phenylalanine was weakened (p < 0.05). Intriguingly, acetyl-proteome profiling of liver from weaned piglets showed that weaning exacerbated the acetylation of phenylalanine hydroxylase (PAH) and the deacetylation of tryptophan 2,3-dioxygenase (TDO). Analysis of PAH and TDO acetylation in Chang liver cells showed that acetylation decreased the PAH activity, while deacetylation increased the TDO activity (p < 0.05). Furthermore, metabolites of AAAs and the acetylation statuses of PAH and TDO in primary hepatocytes from weaned piglets were consistent with the results in vivo. These findings indicated that weaning altered the PAH and TDO activity by affecting the acetylation state of the enzyme in piglets’’ livers. Lysine acetylation may be a potential regulatory mechanism for AAA metabolism in response to weaning.

Dietary Garcinol Attenuates Hepatic Pyruvate and Triglyceride Accumulation by Inhibiting P300/CBP-Associated Factor in Mid-to-Late Pregnant Rats

BACKGROUND

Increased hepatic glycolysis and lipogenesis are characteristic of pregnancy.

OBJECTIVES

The present study aimed to investigate the mechanism of garcinol on the amelioration of hepatic pyruvate and triglyceride (TG) accumulation in mid-to-late pregnant rats.

METHODS

Forty Sprague-Dawley pregnant rats (aged 9 wk, n = 10/diet) were fed a basal diet (control) or that diet plus garcinol at 100 ppm (Low Gar), 300 ppm (Mid Gar), or 500 ppm (High Gar) for 14 d. The livers were processed for Western blotting analyses and measuring enzymatic activity and pyruvate and TG concentrations. Hepatocytes from other pregnant Sprague Dawley rats were transfected with P300/CBP associating factor (PCAF) short interfering (si)RNAs; hepatocytes from nonpregnant Sprague-Dawley rats with overexpression of PCAF were treated with garcinol (5 μM). The activity and acetylation of upstream stimulatory factor (USF-1) and glycolytic enzymes were analyzed.

RESULTS

Dietary garcinol significantly decreased (P < 0.05) concentrations of hepatic and plasma TG (27.1-45.8%) and total cholesterol (25.3-49.5%), plasma free fatty acids (24.4-37.8%), and hepatic pyruvate (31.5-43.5%) and lactate (33.4-65.7%) in mid-to-late pregnant rats. Garcinol promoted (P < 0.05) antioxidant capacity in the liver and plasma by 27.4-32.1%. Garcinol downregulated (P < 0.05) lipid synthesis-related enzyme expression by 30.6-85.3% and decreased (P < 0.05) glycolytic enzyme activities by 22.5-74.6% and PCAF activity by 18.6-55.4%. Transfection of PCAF siRNAs to hepatocytes of pregnant rats decreased USF-1 and glycolytic enzyme activities by PCAF; garcinol treatment downregulated (P < 0.05) the acetylation and activities of USF-1 and glycolytic enzymes by 35.6-83.7%.

CONCLUSIONS

Garcinol attenuates hepatic pyruvate and TG accumulation in the liver of mid-to-late pregnant rats, which may be due to downregulating the acetylation of USF-1 and the glycolytic enzymes induced by PCAF in isolated hepatocytes.

Energy Expenditure and Protein Requirements Following Burn Injury

Severe burn injuries have long been known to have a profound effect on metabolic equilibrium that can persist after resolution of the cutaneous injuries. Following burn injury, metabolism is a dynamic state resulting in the need for frequent interval reassessment over the course of the care continuum. The acute phase of injury transitions to chronic alterations in macronutrient utilization characterized by futile energy cycling and disproportionate catabolism of skeletal muscle. Protein supplementation appears to be preferentially distributed to the burn wound rather than the skeletal muscle pool. Accurate assessment of caloric and protein requirements is extremely difficult in these patients but is an essential step in efforts to attenuate functional impairment. Indirect calorimetry should be utilized to determine caloric requirements, but trophic feeding strategies are preferred in the initial resuscitative phase to prevent overfeeding while maintaining enteric and immune function. Controversy persists regarding optimal protein targets, and weight-based estimates remain the norm. Exogenous protein and caloric provision performed in isolation is insufficient to optimize outcomes and should be incorporated within a multidisciplinary approach to include muscle loading and pharmaceutical adjuncts.