Lactic Acid: No Longer an Inert and End-Product of Glycolysis

Effects of lactate ions on the cardiorespiratory system in rainbow trout (Oncorhynchus mykiss)

Lactate ions are involved in several physiological processes, including a direct stimulation of the carotid body, causing increased ventilation in mammals. A similar mechanism eliciting ventilatory stimulation in other vertebrate classes has been demonstrated, but it remains to be thoroughly investigated. Here, we investigated the effects of lactate ions on the cardiorespiratory system in swimming rainbow trout by manipulating the blood lactate concentration. Lactate elicited a vigorous, dose-dependent elevation of ventilation and bradycardia at physiologically relevant concentrations at constant pH. After this initial confirmation, we examined the chiral specificity of the response and found that only l-lactate induced these effects. By removal of the afferent inputs from the first gill arch, the response was greatly attenuated, and a comparison of the responses to injections up- and downstream of the gills collectively demonstrated that the lactate response was initiated by branchial cells. Injection of specific receptor antagonists revealed that a blockade of serotonergic receptors, which are involved in the hypoxic ventilatory response, significantly reduced the lactate response. Finally, we identified two putative lactate receptors based on sequence homology and found that both were expressed at substantially higher levels in the gills. We propose that lactate ions modulate ventilation by stimulating branchial oxygen-sensing cells, thus eliciting a cardiorespiratory response through receptors likely to have originated early in vertebrate evolution.

Resveratrol Delivery from Porous Poly(lactide- co-glycolide) Scaffolds Promotes an Anti-Inflammatory Environment within Visceral Adipose Tissue

As biomaterial therapies emerge to address adipose tissue dysfunction that underlies metabolic disease, the immune response to these systems must be established. As a potential therapy, we are investigating resveratrol delivery from porous poly(lactide- co-glycolide) scaffolds designed to integrate with adipose tissue. Resveratrol was selected for its ability to protect mice and primates from high fat diet and broad anti-inflammatory properties. Herein, we report fabrication of scaffolds with high resveratrol loading that are stable and active for up to one year. In vitro release profiles indicate that drug release is biphasic with a burst release over 3 days followed by a plateau. Surprisingly, we find that PLG scaffolds implanted into adipose tissue of mice promote an anti-inflammatory environment characterized by high arginase-1 and low TNF-α and IL-6 compared to naïve unmanipulated fat. Resveratrol delivery from the scaffold augments this anti-inflammatory environment by decreasing monocyte and lymphocyte numbers at the implant site and increasing expression of IL-10 and IL-13, cytokines that promote healthy adipose tissue. In terms of therapeutic applications, implant of scaffolds designed to release resveratrol into the visceral fat decreases MCP-1 expression in mice fed a high fat diet, a molecule that drives both local and systemic inflammation during obesity. Taken together, resveratrol delivery to adipose tissue using poly(lactide- co-glycolide) scaffolds is a promising therapeutic strategy for the treatment of adipose tissue inflammation that drives metabolic disease.

Metabolomics Research Reveals the Mechanism of Action of Astragalus Polysaccharide in Rats with Digestive System Disorders

With the diversity of modern dietary lifestyles, digestive system disorders (DSD) have become a frequently occurring disease in recent years. Astragalus polysaccharide (APS) is a homogeneous polysaccharide extracted from Astragalus, which might ameliorate the digestive and absorptive functions. However, the treatment mechanisms remain unclear. In this study, rats with DSD were fed a high-fat⁻low-protein diet and subjected to weight-bearing swimming until exhaustion. When body weight and autonomous activities of the rats decreased, they were administered APS. After two weeks, serum metabolomics analysis based on LC-MS was performed to validate the therapeutic effect of APS and explore its mechanism. APS pharmacodynamics was determined in this study, and serum metabolomics analysis discovered and identified 16 significant, differentially produced metabolites involved in energy, amino acid, and lipid metabolism, including citric acid, lactic acid, alanine, phosphatidylcholine, phenylalanine. After treatment with APS, the levels of the above small-molecule metabolites were reversed. Our results show the efficacy of APS in DSD treatment through the regulation of perturbed metabolic pathways related to energy, amino acid, and lipid metabolism.

Zinc finger E-box-binding homeobox 1 mediates aerobic glycolysis via suppression of sirtuin 3 in pancreatic cancer

AIM

To uncover the roles of tumor-promoting gene ZEB1 in aerobic glycolysis regulation and shed light on the underlying molecular mechanism.

METHODS

Endogenous zinc finger E-box binding homeobox-1 (ZEB1) was silenced using a lentivirus-mediated method, and the impact of ZEB1 and methyl-CpG binding domain protein 1 (MBD1) on aerobic glycolysis was measured using seahorse cellular flux analyzers, reactive oxygen species quantification, and mitochondrial membrane potential measurement. The interaction between ZEB1 and MBD1 was assessed by co-immunoprecipitation and immunofluorescence assays. The impact of ZEB1 and MBD1 interaction on sirtuin 3 (SIRT3) expression was confirmed by quantitative polymerase chain reaction, western blotting, and dual-luciferase and chromatin-immunoprecipitation assays.

RESULTS

ZEB1 was a positive regulator of aerobic glycolysis in pancreatic cancer. ZEB1 transcriptionally silenced expression of SIRT3, a mitochondrial-localized tumor suppressor, through interaction with MBD1.

CONCLUSION

ZEB1 silenced SIRT3 expression via interaction with MBD1 to promote aerobic glycolysis in pancreatic cancer.

PLGA: From a classic drug carrier to a novel therapeutic activity contributor

Poly(lactic-co-glycolic acid) (PLGA) is well known for its biocompatibility and minimal toxicity. It is one of the most promising biodegradable polymeric drug delivery systems able to get endorsement from regulatory bodies to enter market. For many decades, PLGA has been functioning as an excipient, which by definition is pharmaceutically inert at a given dose of formulation. Lactate (one of the hydrolysis products of PLGA) has a key role in biochemical pathways and could improve physiological activities in certain illnesses by exerting therapeutic effects such as angiogenesis and promotion of healing. These activities, however, depend on the released amounts and metabolic clearance of lactate and route of formulation delivery. In the current commentary, along with several key notes on the lactate interactions, we would like to inform the PLGA research community that lactate (resulting from local delivery of physiologically significant amount of PLGA) may positively or negatively affect therapeutic efficacy of certain drugs. Hence, the excipient role of PLGA may be investigated for its potential pharmacological contributions in some biomedical applications.

CDK2 positively regulates aerobic glycolysis by suppressing SIRT5 in gastric cancer

Although significant progress has been made in the diagnosis and treatment of gastric cancer, the overall survival rate of the disease remains unchanged at approximately 20%‐25%. Thus, there is an urgent need for a better understanding of the molecular biology aspects of the disease in the hope of discovering novel diagnosis and treatment strategies. Recent years have witnessed decisive roles of aberrant cancer cell metabolism in the maintenance of malignant hallmarks of cancers, and cancer cell metabolism has been regarded as a novel target for the treatment of cancer. CDK2, a cell cycle‐dependent kinase that usually regulates cell cycle progression and the DNA damage response, is reported to be upregulated in many cancers. However, little is known about its role in cancer cell metabolism. In the present study, we showed that silencing CDK2 inhibited the aerobic glycolytic capacity of gastric cancer cell lines. Mechanism explorations showed that silencing CDK2 increased expression of the SIRT5 tumor suppressor. In addition, the physiological roles of SIRT5 in the regulation of proliferation and glycolysis were studied in gastric cancer cells. Taken together, the present study uncovered novel roles of the CDK2/SIRT5 axis in gastric cancer and suggests future studies concerning gastric cancer cell metabolism.

Fatty and hydroxycarboxylic acid receptors: The missing link of immune response and metabolism in cattle

Fatty and hydroxycarboxylic acids are one of the main intermediates of energy metabolism in ruminants and critical in the milk production of cattle. High production demands on a dairy farm can induce nutritional imbalances and metabolism disorders, which have been widely associated with the onset of sterile inflammatory processes and increased susceptibility to infections. The literature suggests that short-chain fatty acids (SCFA), long-chain fatty acids (LCFA) and hydroxycarboxylic acids are relevant modulators of the host innate inflammatory response. For instance, increased SCFA and lactate levels are associated with subacute ruminal acidosis (SARA) and the activation of pro-inflammatory processes mediated by diverse leukocyte and vascular endothelial cells. As such, free LCFA and the ketone body β-hydroxybutyrate are significantly increased in the plasma 1-2 weeks postpartum, coinciding with the time period in which cows are more susceptible to acquiring infectious diseases that the host innate immune system should actively oppose. Today, many of these pro-inflammatory responses can be related to the activation of specific G protein-coupled receptors, including GPR41/FFA3 and GPR43/FFA2 for SCFA; GPR40/FFA1 and GPR120/FFA4 for LCFA, GPR109A/HCA2 for ketone body β-hydroxybutyrate, and GPR81/HCA₁ for lactate, all expressed in different bovine tissues. The activation of these receptors modulates the release of intracellular granules [e.g., metalloproteinase-9 (MMP-9) and lactoferrin], radical oxygen species (ROS) production, chemotaxis, and the production of relevant pro-inflammatory mediators. The article aimed to review the role of natural ligands and receptors and the resulting impact on the host innate immune reaction of cattle and, further, to address the most recent evidence supporting a potential connection to metabolic disorders.