Decreased AMPK/SIRT1/PDK4 induced by androgen excess inhibits human endometrial stromal cell decidualization in PCOS.

Polycystic ovary syndrome (PCOS) is a complex common endocrine disorder affecting women of reproductive age. Ovulatory dysfunction is recognized as a primary infertile factor, however, even when ovulation is medically induced and restored, PCOS patients continue to experience reduced cumulative pregnancy rates and a higher spontaneous miscarriage rate. Hyperandrogenism, a hallmark feature of PCOS, affects ovarian folliculogenesis, endometrial receptivity, and the establishment and maintenance of pregnancy. Decidualization denotes the transformation that the stromal compart of the endometrium must undergo to accommodate pregnancy, driven by the rising progesterone levels and local cAMP production. However, studies on the impact of hyperandrogenism on decidualization are limited. In this study, we observed that primary endometrial stromal cells from women with PCOS exhibit abnormal responses to progesterone during in vitro decidualization. A high concentration of testosterone inhibits human endometrial stromal cells (HESCs) decidualization. RNA-Seq analysis demonstrated that pyruvate dehydrogenase kinase 4 (PDK4) expression was significantly lower in the endometrium of PCOS patients with hyperandrogenism compared to those without hyperandrogenism. We also characterized that the expression of PDK4 is elevated in the endometrium stroma at the mid-secretory phase. Artificial decidualization could enhance PDK4 expression, while downregulation of PDK4 leads to abnormal decidualization both in vivo and in vitro. Mechanistically, testosterone excess inhibits IGFBP1 and PRL expression, followed by phosphorylating of AMPK that stimulates PDK4 expression. Based on co-immunoprecipitation analysis, we observed an interaction between SIRT1 and PDK4, promoting glycolysis to facilitate decidualization. Restrain of AR activation resumes the AMPK/SIRT1/PDK4 pathway suppressed by testosterone excess, indicating that testosterone primarily acts on decidualization through AR stimulation. Androgen excess in the endometrium inhibits decidualization by disrupting the AMPK/SIRT1/PDK4 signaling pathway. These data demonstrate the critical roles of endometrial PDK4 in regulating decidualization and provide valuable information for understanding the underlying mechanism during decidualization.

Inhibition of the ubiquitin-proteasome system reduces the abundance of pyruvate dehydrogenase kinase 1 in cultured myotubes.

Pyruvate dehydrogenase kinase (PDK), which phosphorylates the pyruvate dehydrogenase complex, regulates glucose metabolism in skeletal muscle. PDK1, an isozyme whose expression is controlled by hypoxia-inducible factor-1α (HIF-1α), is thought to play a role in muscle adaptation to hypoxia. While transcriptional upregulation of PDK1 by HIF-1α is well characterised, mechanisms controlling proteolysis of PDK1 in skeletal muscle have not been thoroughly investigated. Proteasome inhibitor MG132 paradoxically reduced the abundance of PDK1 in human cancer cells and rat L6 myotubes, suggesting that MG132 might direct PDK1 towards autophagic degradation. The objectives of our current study were to determine (1) whether MG132 suppresses PDK1 levels in primary human myotubes, (2) whether chloroquine, an inhibitor of autophagy, prevents MG132-induced suppression of PDK1 in L6 myotubes, and (3) whether PYR-41, an inhibitor of ubiquitination, suppresses PDK1 in L6 myotubes. Using qPCR and/or immunoblotting, we found that despite markedly upregulating HIF-1α protein, MG132 did not alter the PDK1 expression in cultured primary human myotubes, while it suppressed both PDK1 mRNA and protein in L6 myotubes. The PDK1 levels in L6 myotubes were suppressed also during co-treatment with chloroquine and MG132. PYR-41 markedly increased the abundance of HIF-1α in primary human and L6 myotubes, while reducing the abundance of PDK1. In L6 myotubes treated with PYR-41, chloroquine increased the abundance of the epidermal growth factor receptor, but did not prevent the suppression of PDK1. Collectively, our results suggest that cultured myotubes degrade PDK1 via a pathway that cannot be inhibited by MG132, PYR-41, and/or chloroquine.

PDK3 drives colorectal carcinogenesis and immune evasion and is a therapeutic target for boosting immunotherapy.

Pyruvate Dehydrogenase Kinase 3 (PDK3) has emerged as a significant player in various cancer types, yet its specific impact on cancers including colon cancer remains ambiguous. Through pan-cancer analysis using TCGA data, we found that the expression of PDK3 and the composition of the immune microenvironment for different tumors were highly heterogeneous across tumors. PDK3 is highly expressed in colorectal cancer and may promote tumor proliferation by activating PI3K-AKT signaling. In addition, we found that PDK3 was able to inhibit tumor antigen presentation signals to suppress immune killing. High PDK3 expression predicts less CD8+ T cell infiltration and effector function. Moreover, inhibition of PDK3 expression bolstered CD8+ T cell-mediated cytotoxicity CD8+ T cell infiltration and activation in vivo. Notably, PDK3 was found to facilitate STAT1 activation and elevate programmed death-ligand 1 (PD-L1) expression in colon cancer cells. Importantly, PDK3 inhibition combination with PD-1 blockade significantly activates the infiltrated CD8+ T cells to suppress tumor growth and improves the survival benefit in several murine tumor models. In summary, these findings underscore PDK3's role in fueling colon cancer growth by orchestrating PI3K-AKT signaling and PD-L1 expression and dampening CD8+ T cell function.

Design and synthesis of novel fluorene derivatives as inhibitors of pyruvate dehydrogenase kinase.

Activation of pyruvate dehydrogenase (PDH) by inhibition of pyruvate dehydrogenase kinase (PDHK) has the potential for the treatment of diabetes mellitus and its complications, caused by the malfunction of the glycolytic system and glucose oxidation. In this paper, we describe the identification of novel PDHK inhibitors with a fluorene structure. High-throughput screening using our in-house library provided compound 6 as a weak inhibitor that occupied the allosteric lipoyl group binding site in PDHK2. Structure-based drug design (SBDD) while addressing physicochemical properties succeeded in boosting inhibitory activity approximately 700-fold. Thus obtained compound 32 showed favorable pharmacokinetics profiles supported by high membrane permeability and metabolic stability, and exhibited activation of PDH in rat livers and a glucose lowering effect in Zucker fatty rats.

Dichloroacetate for Cancer Treatment: Some Facts and Many Doubts.

Rarely has a chemical elicited as much controversy as dichloroacetate (DCA). DCA was initially considered a dangerous toxic industrial waste product, then a potential treatment for lactic acidosis. However, the main controversies started in 2008 when DCA was found to have anti-cancer effects on experimental animals. These publications showed contradictory results in vivo and in vitro such that a thorough consideration of this compound's in cancer is merited. Despite 50 years of experimentation, DCA's future in therapeutics is uncertain. Without adequate clinical trials and health authorities' approval, DCA has been introduced in off-label cancer treatments in alternative medicine clinics in Canada, Germany, and other European countries. The lack of well-planned clinical trials and its use by people without medical training has discouraged consideration by the scientific community. There are few thorough clinical studies of DCA, and many publications are individual case reports. Case reports of DCA's benefits against cancer have been increasing recently. Furthermore, it has been shown that DCA synergizes with conventional treatments and other repurposable drugs. Beyond the classic DCA target, pyruvate dehydrogenase kinase, new target molecules have also been recently discovered. These findings have renewed interest in DCA. This paper explores whether existing evidence justifies further research on DCA for cancer treatment and it explores the role DCA may play in it.

Baicalin attenuates neuronal damage associated with SDH activation and PDK2-PDH axis dysfunction in early reperfusion.

BACKGROUND: Energy deficiency and oxidative stress are interconnected during ischemia/reperfusion (I/R) and serve as potential targets for the treatment of cerebral ischemic stroke. Baicalin is a neuroprotective antioxidant, but the underlying mechanisms are not fully revealed. PURPOSE: This study explored whether and how baicalin rescued neurons against ischemia/reperfusion (I/R) attack by focusing on the regulation of neuronal pyruvate dehydrogenase kinase 2 (PDK2)-pyruvate dehydrogenase (PDH) axis implicated with succinate dehydrogenase (SDH)-mediated oxidative stress. STUDY DESIGN: The effect of the tested drug was explored in vitro and in vivo with the model of oxygen-glucose deprivation/reoxygenation (OGD/R) and middle cerebral artery occlusion/reperfusion (MCAO/R), respectively. METHODS: Neuronal damage was evaluated according to cell viability, infarct area, and Nissl staining. Protein levels were measured by western blotting and immunofluorescence. Gene expression was investigated by RT-qPCR. Mitochondrial status was also estimated by fluorescence probe labeling. RESULTS: SDH activation-induced excessive production of reactive oxygen species (ROS) changed the protein expression of Lon protease 1 (LonP1) and hypoxia-inducible factor-1ɑ (HIF-1ɑ) in the early stage of I/R, leading to an upregulation of PDK2 and a decrease in PDH activity in neurons and cerebral cortices. Treatment with baicalin prevented these alterations and ameliorated neuronal ATP production and survival. CONCLUSION: Baicalin improves the function of the neuronal PDK2-PDH axis via suppression of SDH-mediated oxidative stress, revealing a new signaling pathway as a promising target under I/R conditions and the potential role of baicalin in the treatment of acute ischemic stroke.

Genetic Ablation of Pyruvate Dehydrogenase Kinase Isoform 4 Gene Enhances Recovery from Hyperoxic Lung Injury: Insights into Antioxidant and Inflammatory Mechanisms.

BACKGROUND: Pyruvate dehydrogenase kinase isoform 4 (PDK4) plays a pivotal role in the regulation of cellular proliferation and apoptosis. The objective of this study was to examine whether the genetic depletion of the PDK4 gene attenuates hyperoxia-induced lung injury in neonatal mice. METHODS: Neonatal PDK4-/- mice and wild-type (WT) mice were exposed to oxygen concentrations of 21% (normoxia) and 95% (hyperoxia) for the first 4 days of life. Pulmonary histological assessments were performed, and the mRNA levels of lung PDK4, monocyte chemoattractant protein (MCP)-1 and interleukin (IL)-6 were assessed. The levels of inflammatory cytokines in lung tissue were quantified. RESULTS: Following convalescence from neonatal hyperoxia, PDK4-/- mice exhibited improved lung alveolarization. Notably, PDK4-/- mice displayed significantly elevated MCP-1 protein levels in pulmonary tissues following 4 days of hyperoxic exposure, whereas WT mice showed increased IL-6 protein levels under similar conditions. Furthermore, neonatal PDK4-/- mice subjected to hyperoxia demonstrated markedly higher MCP-1 mRNA expression at 4 days of age compared to WT mice, while IL-6 mRNA expression remained unaffected in PDK4-/- mice. CONCLUSIONS: Newborn PDK4-/- mice exhibited notable recovery from hyperoxia-induced lung injury, suggesting the potential protective role of PDK4 depletion in mitigating lung damage.

lncRNA NORAD alleviates dysfunction of renal proximal tubular epithelial cells during the sepsis-associated acute kidney injury by modulating the miR-155-5p-PDK1 axis.

The sepsis-associated acute kidney injury (Sa-AKI) is closely related to high mortality rates worldwide. Injury to the renal proximal tubular epithelial cells (RPTECs), caused by pathological conditions, is a major cause of acute kidney injury (AKI). The lncRNA NORAD has been reported to be positively associated with kidney cancers. However, the biological roles and underlying mechanisms of NORAD in RPTECs during AKI are still unclear. In this study, we found that NORAD was significantly downregulated in RPTECs from AKI tissues. Overexpression of NORAD alleviated RPTECs injury induced by lipopolysaccharide (LPS). Additionally, glucose metabolism was significantly impaired during AKI, and LPS treatment inhibited glucose metabolism in RPTECs. We demonstrated that NORAD rescued the LPS-induced inhibition of glucose metabolism in RPTECs. Furthermore, miRNA-155-5p was significantly upregulated in RPTECs from AKI. Through bioinformatics analysis, RNA pull-down, RNA IP, and luciferase assays, we showed that NORAD directly associated with miR-155-5p to downregulate its expression. Moreover, overexpression of miR-155-5p inhibited glucose metabolism by directly targeting the 3'UTR of the glucose metabolism enzyme, pyruvate dehydrogenase kinase 1 (PDK1). Finally, rescue experiments validated that NORAD's protective effect on RPTECs injury was mediated through modulation of the miR-155-5p-PDK1-glucose metabolism pathway. In summary, these results reveal that lncRNA NORAD can alleviate RPTECs dysfunction by targeting the miR-155-5p-PDK1 axis, suggesting that NORAD has the potential to contribute to the development of therapeutic approaches against Sa-AKI.

Mitochondrial-related genes PDK2, CHDH, and ALDH5A1 served as a diagnostic signature and correlated with immune cell infiltration in ulcerative colitis.

We conducted an investigation to determine the potential of mitochondrial-related genes as diagnostic biomarkers in ulcerative colitis (UC), while also examining their association with immune cell infiltration. To achieve this, we acquired four datasets pertaining to UC, which included gene expression arrays and clinical data, from the GEO database. Subsequently, we selected three signature genes (PDK2, CHDH, and ALDH5A1) to construct a diagnostic model for UC. The nomogram and ROC curves exhibited exceptional diagnostic efficacy. Following this, quantitative real-time polymerase chain reaction and western blotting assays validated the decreased mRNA and protein expression of PDK2, CHDH, and ALDH5A1 in the model of UC cells and dextran sulfate sodium salt (DSS)-induced mice colitis tissues, aligning with the findings in the risk model. This investigation suggested a negative correlation between the expression of ALDH5A1, CHDH, and PDK2 and the infiltration of M1 macrophages. Then, immunofluorescence analysis confirmed the augmented expression of CD86 in the tissue of mice subjected to DSS, while a diminished expression of ALDH5A1, CHDH, and PDK2 was observed. Consequently, it can be inferred that targeting mitochondria-associated genes, namely PDK2, CHDH, and ALDH5A1, holds potential as a viable strategy for prognostic prediction and the implementation of immune therapy for UC.

Recent advances in pyruvate dehydrogenase kinase inhibitors: Structures, inhibitory mechanisms and biological activities.

Metabolism is reprogrammed in a variety of cancer cells to ensure their rapid proliferation. Cancer cells prefer to utilize glycolysis to produce energy as well as to provide large amounts of precursors for their division. In this process, cancer cells inhibit the activity of pyruvate dehydrogenase complex (PDC) by upregulating the expression of pyruvate dehydrogenase kinases (PDKs). Inhibiting the activity of PDKs in cancer cells can effectively block this metabolic transition in cancer cells, while also activating mitochondrial oxidative metabolism and promoting apoptosis of cancer cells. To this day, the study of PDKs inhibitors has become one of the research hotspots in the field of medicinal chemistry. Novel structures targeting PDKs are constantly being discovered, and some inhibitors have entered the clinical research stage. Here, we reviewed the research progress of PDKs inhibitors in recent years and classified them according to the PDKs binding sites they acted on, aiming to summarize the structural characteristics of inhibitors acting on different binding sites and explore their clinical application value. Finally, the shortcomings of some PDKs inhibitors and the further development direction of PDKs inhibitors are discussed.

Reducing Oxidative Stress and Inflammation by Pyruvate Dehydrogenase Kinase 4 Inhibition Is Important in Prevention of Renal Ischemia-Reperfusion Injury in Diabetic Mice.

BACKGRUOUND: Reactive oxygen species (ROS) and inflammation are reported to have a fundamental role in the pathogenesis of ischemia-reperfusion (IR) injury, a leading cause of acute kidney injury. The present study investigated the role of pyruvate dehydrogenase kinase 4 (PDK4) in ROS production and inflammation following IR injury. METHODS: We used a streptozotocin-induced diabetic C57BL6/J mouse model, which was subjected to IR by clamping both renal pedicles. Cellular apoptosis and inflammatory markers were evaluated in NRK-52E cells and mouse primary tubular cells after hypoxia and reoxygenation using a hypoxia work station. RESULTS: Following IR injury in diabetic mice, the expression of PDK4, rather than the other PDK isoforms, was induced with a marked increase in pyruvate dehydrogenase E1α (PDHE1α) phosphorylation. This was accompanied by a pronounced ROS activation, as well as tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), interleukin-1ß (IL-1ß), and monocyte chemoattractant protein-1 (MCP-1) production. Notably, sodium dichloroacetate (DCA) attenuated renal IR injury-induced apoptosis which can be attributed to reducing PDK4 expression and PDHE1α phosphorylation levels. DCA or shPdk4 treatment reduced oxidative stress and decreased TNF-α, IL-6, IL-1ß, and MCP-1 production after IR or hypoxia-reoxygenation injury. CONCLUSION: PDK4 inhibition alleviated renal injury with decreased ROS production and inflammation, supporting a critical role for PDK4 in IR mediated damage. This result indicates another potential target for reno-protection during IR injury; accordingly, the role of PDK4 inhibition needs to be comprehensively elucidated in terms of mitochondrial function during renal IR injury.

Glutaminase potentiates the glycolysis in esophageal squamous cell carcinoma by interacting with PDK1.

Increasing evidence has demonstrated that glutaminase (GLS) as a key mitochondrial enzyme plays a pivotal role in glutaminolysis, which widely participates in glutamine metabolism serving as main energy sources and building blocks for tumor growth. However, the roles and molecular mechanisms of GLS in esophageal squamous cell carcinoma (ESCC) remains unknown. Here, we found that GLS was highly expressed in ESCC tissues and cells. GLS inhibitor CB-839 significantly suppressed cell proliferation, colony formation, migration and invasion of ESCC cells, whereas GLS overexpression displayed the opposite effects. In addition, CB-839 markedly suppressed glucose consumption and lactate production, coupled with the downregulation of glycolysis-related proteins HK2, PFKM, PKM2 and LDHA, whereas GLS overexpression exhibited the adverse results. In vivo animal experiment revealed that CB-839 dramatically suppressed tumor growth, whereas GLS overexpression promoted tumor growth in ESCC cells xenografted nude mice. Mechanistically, GLS was localized in mitochondria of ESCC cells, which interacted with PDK1 protein. CB-839 attenuated the interaction of GLS and PDK1 in ESCC cells by suppressing PDK1 expression, which further evoked the downregulation of p-PDHA1 (s293), however, GLS overexpression markedly enhanced the level of p-PDHA1 (s293). These findings suggest that interaction of GLS with PDK1 accelerates the glycolysis of ESCC cells by inactivating PDH enzyme, and thus targeting GLS may be a novel therapeutic approach for ESCC patients.

Lactate accumulation induced by Akt2-PDK1 signaling promotes pulmonary fibrosis.

Idiopathic pulmonary fibrosis (IPF) is a chronic progressive disease with an abnormal accumulation of fibrotic tissue in the lung parenchyma and elevated glycolysis level in associated cells without effective therapy options. Lactate accumulation in pulmonary fibrotic tissue is a significant factor aggravating IPF development, but the main mechanism regulating glycolysis needs further investigation. In this study, lung fibrosis model was induced by bleomycin (BLM) intratracheally in female C57BL/6 mice. The changes of lactate level and fibrotic markers were detected. For in vitro studies, cell lines of alveolar epithelial cell and lung fibroblast cell were stimulated with TGF-ß1 and BLM respectively, to detect changes in their fibrotic properties. The function of lactate accumulation on facilitating fibrosis was verified. We demonstrated that BLM-induced pulmonary fibrosis is accompanied by lactate accumulation owing to glycolysis upregulation. Significantly high PDK1 expression in lung fibrotic tissue promotes glycolysis. Moreover, PDK1 stimulated trans-differentiation of lung fibroblasts and epithelial-mesenchymal transition (EMT) of alveolar epithelial cells. Furthermore, phosphorylated Akt2 activated PDK1 to cause pulmonary fibrosis and inhibitors of Akt2 and PDK1 could suppress fibrotic process. This study is the first to consider PDK1 facilitated lactate accumulation through glycolysis as a vital factor in pulmonary fibrosis and could be initiated by Akt2. We concluded that the pro-fibrotic properties of PDK1 are associated with Akt2 phosphorylation and thus provide new potential therapeutic targets for pulmonary fibrosis.

Circadian modulation of glucose utilization via CRY1-mediated repression of Pdk1 expression.

Life adapts to daily environmental changes through circadian rhythms, exhibiting spontaneous oscillations of biological processes. These daily functional oscillations must match the metabolic requirements responding to the time of the day. We focus on the molecular mechanism of how the circadian clock regulates glucose, the primary resource for energy production and other biosynthetic pathways. The complex regulation of the circadian rhythm includes many proteins that control this process at the transcriptional and translational levels and by protein-protein interactions. We have investigated the action of one of these proteins, cryptochrome (CRY), whose elevated mRNA and protein levels repress the function of an activator in the transcription-translation feedback loop, and this activator causes elevated Cry1 mRNA. We used a genome-edited cell line model to investigate downstream genes affected explicitly by the repressor CRY. We found that CRY can repress glycolytic genes, particularly that of the gatekeeper, pyruvate dehydrogenase kinase 1 (Pdk1), decreasing lactate accumulation and glucose utilization. CRY1-mediated decrease of Pdk1 expression can also be observed in a breast cancer cell line MDA-MB-231, whose glycolysis is associated with Pdk1 expression. We also found that exogenous expression of CRY1 in the MDA-MB-231 decreases glucose usage and growth rate. Furthermore, reduced CRY1 levels and the increased phosphorylation of PDK1 substrate were observed when cells were grown in suspension compared to cells grown in adhesion. Our data supports a model that the transcription-translation feedback loop can regulate the glucose metabolic pathway through Pdk1 gene expression according to the time of the day.

Targeting the pyruvate dehydrogenase complex/pyruvate dehydrogenase kinase (PDC/PDK) axis to discover potent PDK inhibitors through structure-based virtual screening and pharmacological evaluation.

Proliferating cancer cells are characterized by the Warburg effect, a metabolic alteration in which ATP is generated from cytoplasmic glycolysis instead of oxidative phosphorylation. The pyruvate dehydrogenase complex/pyruvate dehydrogenase kinase (PDC/PDK) axis plays a crucial role in this effect and has been identified as a potential target for anticancer drug development. Herein, we present the discovery and pharmacological evaluation of potent PDK inhibitors targeting the PDK/PDC axis. We successfully identified 6 compounds from a small molecule library through a structure-based virtual screening campaign and evaluated their enzymatic inhibitory potencies for PDK1-4. Our results indicated that compound 1 exhibited submicromolar inhibitory activities against PDK1-3 (IC50 = 109.3, 135.8, and 458.7 nM, respectively), but is insensitive to PDK4 (IC50 = 8.67 µM). Furthermore, compound 1 inhibited the proliferation of A549 cells with an EC50 value of 10.7 µM. In addition, compound 1 induced cell apoptosis, arrested the cell cycle at the S phase, and reduced cell invasion and migration, while showing low in vivo toxicity at a high dose. Based on these observations, it can be concluded that compound 1 is a promising anti-PDK1-3 lead that merits further investigation.

Stimulating cardiac glucose oxidation lessens the severity of heart failure in aged female mice.

Heart failure is a prevalent disease worldwide. While it is well accepted that heart failure involves changes in myocardial energetics, what alterations that occur in fatty acid oxidation and glucose oxidation in the failing heart remains controversial. The goal of the study are to define the energy metabolic profile in heart failure induced by obesity and hypertension in aged female mice, and to attempt to lessen the severity of heart failure by stimulating myocardial glucose oxidation. 13-Month-old C57BL/6 female mice were subjected to 10 weeks of a 60% high-fat diet (HFD) with 0.5 g/L of Nω-nitro-L-arginine methyl ester (L-NAME) administered via drinking water to induce obesity and hypertension. Isolated working hearts were perfused with radiolabeled energy substrates to directly measure rates of myocardial glucose oxidation and fatty acid oxidation. Additionally, a series of mice subjected to the obesity and hypertension protocol were treated with a pyruvate dehydrogenase kinase inhibitor (PDKi) to stimulate cardiac glucose oxidation. Aged female mice subjected to the obesity and hypertension protocol had increased body weight, glucose intolerance, elevated blood pressure, cardiac hypertrophy, systolic dysfunction, and decreased survival. While fatty acid oxidation rates were not altered in the failing hearts, insulin-stimulated glucose oxidation rates were markedly impaired. PDKi treatment increased cardiac glucose oxidation in heart failure mice, which was accompanied with improved systolic function and decreased cardiac hypertrophy. The primary energy metabolic change in heart failure induced by obesity and hypertension in aged female mice is a dramatic decrease in glucose oxidation. Stimulating glucose oxidation can lessen the severity of heart failure and exert overall functional benefits.

Protection against Aß-induced neuronal damage by KU-32: PDHK1 inhibition as important target.

A feature of most neurodegenerative diseases is the presence of "mis-folded proteins" that form aggregates, suggesting suboptimal activity of neuronal molecular chaperones. Heat shock protein 90 (Hsp90) is the master regulator of cell responses to "proteotoxic" stresses. Some Hsp90 modulators activate cascades leading to upregulation of additional chaperones. Novobiocin is a modulator at the C-terminal ATP-binding site of Hsp90. Of several novobiocin analogs synthesized and tested for protection against amyloid beta (Aß)-induced neuronal death, "KU-32" was the most potent in protecting primary neurons, but did not increase expression of other chaperones believed to help clear misfolded proteins. However, KU-32 reversed Aß-induced superoxide formation, activated Complex I of the electron transfer chain in mitochondria, and blocked the Aß-induced inhibition of Complex I in neuroblastoma cells. A mechanism for these effects of KU-32 on mitochondrial metabolism appeared to be the inhibition of pyruvate dehydrogenase kinase (PDHK), both in isolated brain mitochondria and in SH-SY5Y cells. PDHK inhibition by the classic enzyme inhibitor, dichloroacetate, led to neuroprotection from Aß25-35-induced cell injury similarly to KU-32. Inhibition of PDHK in neurons would lead to activation of the PDH complex, increased acetyl-CoA generation, stimulation of the tricarboxylic acid cycle and Complex I in the electron transfer chain, and enhanced oxidative phosphorylation. A focus of future studies may be on the potential value of PDHK as a target in AD therapy.

CcpA-Knockout Staphylococcus aureus Induces Abnormal Metabolic Phenotype via the Activation of Hepatic STAT5/PDK4 Signaling in Diabetic Mice.

Catabolite control protein A (CcpA), an important global regulatory protein, is extensively found in S. aureus. Many studies have reported that CcpA plays a pivotal role in regulating the tricarboxylic acid cycle and pathogenicity. Moreover, the CcpA-knockout Staphylococcus aureus (S. aureus) in diabetic mice, compared with the wild-type, showed a reduced colonization rate in the tissues and organs and decreased inflammatory factor expression. However, the effect of CcpA-knockout S. aureus on the host's energy metabolism in a high-glucose environment and its mechanism of action remain unclear. S. aureus, a common and major human pathogen, is increasingly found in patients with obesity and diabetes, as recent clinical data reveal. To address this issue, we generated CcpA-knockout S. aureus strains with different genetic backgrounds to conduct in-depth investigations. In vitro experiments with high-glucose-treated cells and an in vivo model study with type 1 diabetic mice were used to evaluate the unknown effect of CcpA-knockout strains on both the glucose and lipid metabolism phenotypes of the host. We found that the strains caused an abnormal metabolic phenotype in type 1 diabetic mice, particularly in reducing random and fasting blood glucose and increasing triglyceride and fatty acid contents in the serum. In a high-glucose environment, CcpA-knockout S. aureus may activate the hepatic STAT5/PDK4 pathway and affect pyruvate utilization. An abnormal metabolic phenotype was thus observed in diabetic mice. Our findings provide a better understanding of the molecular mechanism of glucose and lipid metabolism disorders in diabetic patients infected with S. aureus.

Scutellarin Rescued Mitochondrial Damage through Ameliorating Mitochondrial Glucose Oxidation via the Pdk-Pdc Axis.

Mitochondrial bioenergetic deficits and their resulting glucose hypometabolism are the key pathophysiological modulators that promote neurodegeneration. However, there are no specific potential molecules that have been identified to treat neurological diseases by regulating energy metabolism and repairing mitochondrial damage. Pyruvate dehydrogenase (PDH) complex (PDC), which can be phosphorylated by pyruvate dehydrogenase kinase (PDK), is the gate-keeping enzyme for mitochondrial glucose oxidation. In this study, a small-molecule scutellarin (SG) is discovered that can significantly alleviate the neuropathological changes in hippocampal CA1 of cerebral hypoperfusion model rats, rescued the morphological changes of abnormal mitochondria, and restored mitochondrial homeostasis. Mitochondrial proteomics, energy metabolism monitoring, and 13 C-metabolic flux analysis targeted SG activity on PDK2, thus regulating PDK-PDC-mediated glycolytic metabolism to TCA cycle during mitochondrial OXPHOS damage. The knockdown of PDK2 in the SK-N-SH cells validated that SG could rescue mitochondrial damage via the PDK-PDC axis, promote the MMP level and reduce the mitochondria-dependent apoptosis. Collectively, this study explored the novel therapeutic approach: the PDK-PDC axis for neurological injury and cognitive impairment and uncovered the effect of SG on mitochondrial protection via the PDK-PDC axis and mitochondrial glucose oxidation. The findings indicate that active components ameliorating mitochondrial bioenergetic deficits could be of significant value for neurological disease therapy.

Exploring diet-induced promoter hypomethylation and PDK4 overexpression: implications for type 2 diabetes mellitus.

BACKGROUND: Type 2 diabetes mellitus (T2DM) is a metabolic disorder characterized by limited metabolic flexibility in the body. Such limitation implicates the pyruvate dehydrogenase kinase 4 (PDK4) gene Poor nutrition, frequently observed among Southeast Asians usually involves excessive intakes of carbohydrates and monosodium glutamate (MSG), that have been frequently linked to an increased risk of T2DM. METHODS: The 14-week study aimed to assess the effects of high-carbohydrate (HC), high-MSG (HMSG), and a combination of high-carbohydrate and high-MSG (HCHMSG) diets on the development of T2DM using male mice. To assess the effects, the male mice were divided into four groups: control (C), HC, HMSG, and HCHMSG for 14 weeks. RESULTS: After 14 weeks, both the HC and HCHMSG groups showed signs of T2DM (168.83 ± 32.33; 156.42 ± 32.46). The blood samples from the HMSG, HC, and HCHMSG groups (57.67 ± 2.882; 49.22 ± 7.36; 48.9 ± 6.43) as well as skeletal muscle samples from the HMSG, HC, and HCHMSG groups (57.78 ± 8.54; 42.13 ± 7.25; 37.57 ± 10.42) exhibited a gradual hypomethylation. The HC groups particularly displayed significant PDK4 gene expression in skeletal muscle. A progressive overexpression of the PDK4 gene was observed as well in the HMSG, HCHMSG, and HC groups (2.03 ± 3.097; 3.21 ± 2.94; 5.86 ± 2.54). CONCLUSIONS: These findings suggest that T2DM can be induced by high-carbohydrate and high-MSG diets. However, the sole consumption of high MSG did not lead to the development of T2DM. Further research should focus on conducting long-term studies to fully comprehend the impact of a high MSG diet on individuals with pre-existing T2DM.