Effect of Liangfang Wenjing Decoction on expression of key glycolytic enzymes in uterus and ovaries of rats with coagulating cold and blood stasis syndrome / 中国中药杂志

This study aimed to investigate the relationship between coagulating cold and blood stasis syndrome and glycolysis, and observe the intervention effect of Liangfang Wenjing Decoction(LFWJD) on the expression of key glycolytic enzymes in the uterus and ovaries of rats with coagulating cold and blood stasis. The rat model of coagulating cold and blood stasis syndrome was established by ice-water bath. After modeling, the quantitative scoring of symptoms were performed, and according to the scoring results, the rats were randomly divided into a model group and LFWJD low-, medium-and high-dose groups(4.7, 9.4, 18.8 g·kg~(-1)·d~(-1)), with 10 in each group. Another 10 rats were selected as the blank group. After 4 weeks of continuous administration by gavage, the quantitative scoring of symptoms was repeated. Laser speckle flowgraphy was used to detect the changes of microcirculation in the ears and uterus of rats in each group. Hematoxylin-eosin(HE) staining was used to observe the pathological morphology of uterus and ovaries of rats in each group. The mRNA and protein expressions of pyruvate dehydrogenase kinase 1(PDK1), hexokinase 2(HK2) and lactate dehydrogenase A(LDHA) in the uterus and ovaries of rats were examined by real-time quantitative polymerase chain reaction(RT-qPCR) and Western blot, respectively. The rats in the model group showed signs of coagulating cold and blood stasis syndrome, such as curl-up, less movement, thickened veins under the tongue, and reduced blood perfusion in the microcirculation of the ears and uterus, and HE staining revealed a thinning of the endometrium with disorganized arrangement of epithelial cells and a decrease in the number of ovarian follicles. Compared with the model group, the treatment groups had alleviated coagulating cold and blood stasis, which was manifested as red tongue, reduced nail swelling, no blood stasis at the tail end as well as increased blood perfusion of the microcirculation in the ears and uterus(P<0.05 or P<0.01). Among the groups, the LFWJD medium-and high-dose groups had the most significant improvement in coagulating cold and blood stasis, with neatly arranged columnar epithelial cells in uterus, and the number of ovarian follicles was higher than that in the model group, especially mature follicles. The mRNA and protein expressions of PDK1, HK2, LDHA in uterus and ovaries were up-regulated in the model group(P<0.05 or P<0.01), while down-regulated in LFWJD medium-and high-dose groups(P<0.05 or P<0.01). The LFWJD low-dose group presented a decrease in the mRNA expressions of PDK1, HK2 and LDHA in uterus and ovaries as well as in the protein expressions of HK2 and LDHA in uterus and HK2 and PDK1 in ovaries(P<0.05 or P<0.01). The therapeutic mechanism of LFWJD against coagulating cold and blood stasis syndrome is related to the down-regulation of key glycolytic enzymes PDK1, HK2 and LDHA, and the inhibition of glycolytic activities in uterus and ovaries.

Baicalin inhibits PDK1 to mediate glucose metabolism reprogramming and intervene rheumatoid arthritis synovial inflammation / 药学学报

This study started from the effect of baicalin (BC), the main active component of the labiaceae plant Scutellaria baicalensis, on collagen-induced arthritis (CIA) in rats, to explore the mechanism of glucose metabolism reprogramming in fibroblast like synoviocytes (FLSs), a key effector cell of synovial inflammation in rheumatoid arthritis (RA). First of all, CIA rats and tumor necrosis factor-α (TNF-α)-induced RASFs in vitro and in vivo models were established, the arthritis index (AI) score and histopathological changes of CIA rats after BC administration were observed, and the levels of inflammatory factors in serum and cell supernatant were quantified by ELISA, immunocytochemistry and Western blot were used to detect the expression of G-protein-coupled receptor 81 (GPR81) and pyruvate dehydrogenase kinase 1 (PDK1) proteins. In addition, the kit was used to measure the levels of key products and enzyme activities in glucose metabolism reprogramming. The results showed that BC (50, 100 and 200 mg·kg-1) could alleviate the symptoms of arthritis in CIA rats in a dose-dependent manner, inhibit synovial hyperplasia, alleviate the infiltration of inflammatory cells, down-regulate the levels of pro-inflammatory factors TNF-α and interleukin (IL)-1β, and up-regulate the levels of anti-inflammatory factor IL-10 in CIA rats. At the same time, the secretion levels of lactate, pyruvate, acetyl-CoA, citrate and the activity of lactate dehydrogenase B (LDH-B) were decreased, and the expressions of GRP81 and PDK1 were down-regulated, suggesting that BC mediated the reprogramming process of glucose metabolism. However, when GPR81 inhibitor 3-OBA inhibited lactate uptake, the activity of LDH-B was significantly increased, suggesting that BC inhibited the expression of PDK1, a key enzyme in the reprogramming metabolism from glycolysis to oxidative phosphorylation. All animal experiments in this study were conducted in accordance with the ethical standards of the Laboratory Animal Care Center of Anhui University of Chinese Medicine (approval number: AHUCM-rats-2021049). These studies revealed that baicalin mediated metabolic reprogramming of RASFs from glycolysis to oxidative phosphorylation by inhibiting PDK1 protein expression, and alleviated joint inflammation in CIA rats.

AAZ2 induces mitochondrial-dependent apoptosis by targeting PDK1 in gastric cancer / 浙江大学学报（英文版）（B辑：生物医学和生物技术）

Drastic surges in intracellular reactive oxygen species (ROS) induce cell apoptosis, while most chemotherapy drugs lead to the accumulation of ROS. Here, we constructed an organic compound, arsenical N-‍(4-(1,3,2-dithiarsinan-2-yl)phenyl)acrylamide (AAZ2), which could prompt the ROS to trigger mitochondrial-dependent apoptosis in gastric cancer (GC). Mechanistically, by targeting pyruvate dehydrogenase kinase 1 (PDK1), AAZ2 caused metabolism alteration and the imbalance of redox homeostasis, followed by the inhibition of phosphoinositide-3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) pathway and leading to the activation of B-cell lymphoma 2 (Bcl2)/Bcl2-associated X (Bax)/caspase-9 (Cas9)/Cas3 cascades. Importantly, our in vivo data demonstrated that AAZ2 could inhibit the growth of GC xenograft. Overall, our data suggested that AAZ2 could contribute to metabolic abnormalities, leading to mitochondrial-dependent apoptosis by targeting PDK1 in GC.

Research progress on pyruvate dehydrogenase kinase inhibitors / 药学学报

Tumor cells can metabolize glucose through glycolysis to intermediates for biomacromolecule synthesis by inhibiting the activity of the pyruvate dehydrogenase complex (PDC) in mitochondria. In this process, pyruvate dehydrogenase kinases (PDKs) play a key role. The inhibition of the activity of PDKs can effectively block this metabolic pathway, activate mitochondrial oxidative metabolism, and induce tumor cell apoptosis. PDK inhibitors have become a research hotspot in medicinal chemistry, and novel structures targeting classical binding sites have been synthesized. In this paper, recent research progress on PDK inhibitors is reviewed to provide information on these latest entities and to explore their clinical applicability.

Pyruvate dehydrogenase activity and pyruvate dehydrogenase kinase 4 expression in skeletal muscle of end-stage renal disease patients / 上海交通大学学报（医学版）

Objective·To explore the changes of pyruvate dehydrogenase (PDH) activity and pyruvate dehydrogenase kinase 4 (PDK4) expression in the end-stage renal disease (ESRD) patients' skeletal muscles. Methods·Skeletal muscle samples were collected from non-chronic kidney disease (non-CKD) patients and ESRD patients. PDH activity was detected by ELISA assay. Real-time qPCR was performed to examine gene transcription levels of PDK1-PDK4 and PDH subunits.Western blotting analysis was used to detect protein expression levels of PDK1 and PDK4. Results·There were no demographic differences between two groups of patients. Plasma creatinine and urea nitrogen were significantly elevated in ESRD group (both P<0.05), while estimated glomerular filtration rate, hemoglobin and plasma albumin in ESRD group were significantly lower than those in non-CKD group (all P<0.05).Skeletal muscle PDH activity in ESRD group was markedly lower than that in non-CKD group(P=0.014).There were no differences in PDK1-PDK4 and PDH subunits mRNA transcription levels between ESRD and non-CKD group.PDK4 protein expression was significantly higher than that in non-CKD group (P=0.000). Conclusion·The decreased PDH activity in ESRD patients' skeletal muscle may be related to up-regulation of PDK4.

Pyruvate dehydrogenase activity and pyruvate dehydrogenase kinase 4 expression in skeletal muscle of end-stage renal disease patients / 上海交通大学学报（医学版）

Objective: To explore the changes of pyruvate dehydrogenase (PDH) activity and pyruvate dehydrogenase kinase 4 (PDK4) expression in the end-stage renal disease (ESRD) patients' skeletal muscles. Methods: Skeletal muscle samples were collected from non-chronic kidney disease (non-CKD) patients and ESRD patients. PDH activity was detected by ELISA assay. Real-time qPCR was performed to examine gene transcription levels of PDK1-PDK4 and PDH subunits. Western blotting analysis was used to detect protein expression levels of PDK1 and PDK4. Results: There were no demographic differences between two groups of patients. Plasma creatinine and urea nitrogen were significantly elevated in ESRD group (both P<0.05), while estimated glomerular filtration rate, hemoglobin and plasma albumin in ESRD group were significantly lower than those in non-CKD group (all P<0.05). Skeletal muscle PDH activity in ESRD group was markedly lower than that in non-CKD group (P=0.014). There were no differences in PDK1-PDK4 and PDH subunits mRNA transcription levels between ESRD and non-CKD group. PDK4 protein expression was significantly higher than that in non-CKD group (P=0.000). Conclusion: The decreased PDH activity in ESRD patients' skeletal muscle may be related to up-regulation of PDK4.

Mechanism of HIF-1α-PDK1 signaling system involved in glucose metabolism and drug resistance in acute monocytic leukemia / 上海交通大学学报（医学版）

Objective • To investigate the mechanism of HIF-1α-PDK1 signaling system mediated glucose metabolism and drug resistance in acute monocytic leukemia cells. Methods • The expression of pyruvate dehydrogenase kinase 1 (PDK1) mRNA in U937, U937/DNR and acute monocytic leukemia cells was detected by quantitative polymerase chain reaction (qPCR). siRNA HIF-1α plasmid was constructed and transferred to U937 and U937/ DNR cells for 24 h by gene silencing. Cell proliferation inhibition was examined by MTT assay. The level of PDK1 mRNA was detected by qPCR, and the expression of PDK1 and multi-drug resistance gene 1 (MDR1) proteins was detected by Western blotting. Cell membrane potential was measured by flow cytometry using JC-1. Lactic acid level in the culture fluid was determined by blood gas analyzer. Dichloroacetate (DCA) and daunorubicin (DNR) were added to treat U937/DNR and acute monocytic leukemia cells for 24 h, MTT was used to calculate cell proliferation inhibition and Western blotting was used to estimate the expression of PDK1 and MDR1 proteins. Results • PDK1 mRNA was highly expressed in U937, U937/DNR and acute monocytic leukemia cells. Silencing hypoxia-inducible factor-1α (HIF-1α) significantly inhibited the proliferation activity, PDK1 and MDR1 expression and lactic acid production in U937 and U937/DNR cells. DCA could reverse the resistance to DNR in U937/DNR and relapsed acute monocytic leukemia cells. Conclusion • HIF-1α-PDK1 signaling system may regulate glucose metabolism and participate in the drug resistance of acute monocytic leukemia.

PDK2 promotes chondrogenic differentiation of mesenchymal stem cells by upregulation of Sox6 and activation of JNK/MAPK/ERK pathway

This study was undertaken to clarify the role and mechanism of pyruvate dehydrogenase kinase isoform 2 (PDK2) in chondrogenic differentiation of mesenchymal stem cells (MSCs). MSCs were isolated from femurs and tibias of Sprague-Dawley rats, weighing 300-400 g (5 females and 5 males). Overexpression and knockdown of PDK2 were transfected into MSCs and then cell viability, adhesion and migration were assessed. Additionally, the roles of aberrant PDK2 in chondrogenesis markers SRY-related high mobility group-box 6 (Sox6), type ΙΙ procollagen gene (COL2A1), cartilage oligomeric matrix protein (COMP), aggrecan (AGC1), type ΙX procollagen gene (COL9A2) and collagen type 1 alpha 1 (COL1A1) were measured by quantitative reverse-transcription polymerase chain reaction (qRT-PCR). The expressions of c-Jun N-terminal kinase (JNK), p38 mitogen-activated protein kinase (MAPK) and extracellular regulated protein kinase (ERK) were measured. Overexpressing PDK2 promoted cell viability, adhesion and inhibited cell migration in MSCs (all P<0.05). qRT-PCR assay showed a potent increase in the mRNA expressions of all chondrogenesis markers in response to overexpressing PDK2 (P<0.01 or P<0.05). PDK2 overexpression also induced a significant accumulation in mRNA and protein expressions of JNK, p38MAPK and ERK in MSCs compared to the control (P<0.01 or P<0.05). Meanwhile, silencing PDK2 exerted the opposite effects on MSCs. This study shows a preliminary positive role and potential mechanisms of PDK2 in chondrogenic differentiation of MSCs. It lays the theoretical groundwork for uncovering the functions of PDK2 and provides a promising basis for repairing cartilage lesions in osteoarthritis.

Mechanisms of Vascular Calcification: The Pivotal Role of Pyruvate Dehydrogenase Kinase 4

Vascular calcification, abnormal mineralization of the vessel wall, is frequently associated with aging, atherosclerosis, diabetes mellitus, and chronic kidney disease. Vascular calcification is a key risk factor for many adverse clinical outcomes, including ischemic cardiac events and subsequent cardiovascular mortality. Vascular calcification was long considered to be a passive degenerative process, but it is now recognized as an active and highly regulated process similar to bone formation. However, despite numerous studies on the pathogenesis of vascular calcification, the mechanisms driving this process remain poorly understood. Pyruvate dehydrogenase kinases (PDKs) play an important role in the regulation of cellular metabolism and mitochondrial function. Recent studies show that PDK4 is an attractive therapeutic target for the treatment of various metabolic diseases. In this review, we summarize our current knowledge regarding the mechanisms of vascular calcification and describe the role of PDK4 in the osteogenic differentiation of vascular smooth muscle cells and development of vascular calcification. Further studies aimed at understanding the molecular mechanisms of vascular calcification will be critical for the development of novel therapeutic strategies.

Pyruvate Dehydrogenase Kinases: Therapeutic Targets for Diabetes and Cancers

Impaired glucose homeostasis is one of the risk factors for causing metabolic diseases including obesity, type 2 diabetes, and cancers. In glucose metabolism, pyruvate dehydrogenase complex (PDC) mediates a major regulatory step, an irreversible reaction of oxidative decarboxylation of pyruvate to acetyl-CoA. Tight control of PDC is critical because it plays a key role in glucose disposal. PDC activity is tightly regulated using phosphorylation by pyruvate dehydrogenase kinases (PDK1 to 4) and pyruvate dehydrogenase phosphatases (PDP1 and 2). PDKs and PDPs exhibit unique tissue expression patterns, kinetic properties, and sensitivities to regulatory molecules. During the last decades, the up-regulation of PDKs has been observed in the tissues of patients and mammals with metabolic diseases, which suggests that the inhibition of these kinases may have beneficial effects for treating metabolic diseases. This review summarizes the recent advances in the role of specific PDK isoenzymes on the induction of metabolic diseases and describes the effects of PDK inhibition on the prevention of metabolic diseases using pharmacological inhibitors. Based on these reports, PDK isoenzymes are strong therapeutic targets for preventing and treating metabolic diseases.

Effects of prior muscle glycogen depletion level on metabolic response during endurance exercise / 体力科学

Recent studies indicate that exercise with a low muscle glycogen state enhances exercise-induced metabolic adaptation. However, it is unclear whether metabolic adaptation is involved with muscle glycogen depletion level. In this study, we investigated the effects of prior muscle glycogen depletion level on metabolic response during acute continuous exercise. Seven men completed two experimental trials consisting of two exercise sessions per day. During the first session, participants performed either intermittent exercise (IE) at VO₂max (the IE-CE trial) or continuous exercise (CE) at lactate threshold (the CE-CE trial). During the second session, participants performed 60 minutes of CE at lactate threshold. During this second session, fatty acid oxidation (FAO) was calculated. To determine muscle glycogen content and PGC-1α and PDK-4 mRNA abundance, muscle biopsies were taken at rest after the first session and 2 hours after the second session. After the first session, muscle glycogen content was significantly lower in the IE-CE trial (38.1±5.0 mmol/kg w.w.) than in the CE-CE trial (56.7±10.2 mmol/kg w.w.), <i>P</i><0.05. FAO was higher in the IE-CE trial than the CE-CE trial at baseline and 15 minutes after the second session (both <i>P</i><0.05). PGC-1α mRNA abundance increased after exercise (IE-CE, 5.9±2.5; CE-CE, 2.6±1.3-fold; <i>P</i><0.1). PDK-4 mRNA abundance increased significantly after exercise (IE-CE, 22.2±8.8; CE-CE, 31.5±10.6-fold; <i>P</i><0.05). PGC-1α and PDK-4 mRNA were not significantly different between the trials. In conclusion, continuous exercise with a slightly muscle glycogen-depleted state induced similar level of PGC-1α and PDK-4 mRNA expression, but attenuated FAO, compared to exercise with a moderate muscle glycogen-depleted state.

Pyruvate Dehydrogenase Kinase as a Potential Therapeutic Target for Malignant Gliomas

Metabolic aberrations in the form of altered flux through key metabolic pathways are the major hallmarks of several life-threatening malignancies including malignant gliomas. These adaptations play an important role in the enhancement of the survival and proliferation of gliomas at the expense of the surrounding normal/healthy tissues. Recent studies in the field of neurooncology have directly targeted the altered metabolic pathways of malignant tumor cells for the development of anti-cancer drugs. Aerobic glycolysis due to elevated production of lactate from pyruvate regardless of oxygen availability is a common metabolic alteration in most malignancies. Aerobic glycolysis offers survival advantages in addition to generating substrates such as fatty acids, amino acids and nucleotides required for the rapid proliferation of cells. This review outlines the role of pyruvate dehydrogenase kinase (PDK) in gliomas as an inhibitor of pyruvate dehydrogenase that catalyzes the oxidative decarboxylation of pyruvate. An in-depth investigation on the key metabolic enzyme PDK may provide a novel therapeutic approach for the treatment of malignant gliomas.

Transcriptional Regulation of Pyruvate Dehydrogenase Kinase

The pyruvate dehydrogenase complex (PDC) activity is crucial to maintains blood glucose and ATP levels, which largely depends on the phosphorylation status by pyruvate dehydrogenase kinase (PDK) isoenzymes. Although it has been reported that PDC is phosphorylated and inactivated by PDK2 and PDK4 in metabolically active tissues including liver, skeletal muscle, heart, and kidney during starvation and diabetes, the precise mechanisms by which expression of PDK2 and PDK4 are transcriptionally regulated still remains unclear. Insulin represses the expression of PDK2 and PDK4 via phosphorylation of FOXO through PI3K/Akt signaling pathway. Several nuclear hormone receptors activated due to fasting or increased fat supply, including peroxisome proliferator-activated receptors, glucocorticoid receptors, estrogen-related receptors, and thyroid hormone receptors, also participate in the up-regulation of PDK2 and PDK4; however, the endogenous ligands that bind those nuclear receptors have not been identified. It has been recently suggested that growth hormone, adiponectin, epinephrine, and rosiglitazone also control the expression of PDK4 in tissue-specific manners. In this review, we discuss several factors involved in the expressional regulation of PDK2 and PDK4, and introduce current studies aimed at providing a better understanding of the molecular mechanisms that underlie the development of metabolic diseases such as diabetes.

Role of Pyruvate Dehydrogenase Kinase 4 in Regulation of Blood Glucose Levels / 당뇨병

In the well-fed state a relatively high activity of the pyruvate dehydrogenase complex (PDC) reduces blood glucose levels by directing the carbon of pyruvate into the citric acid cycle. In the fasted state a relatively low activity of the PDC helps maintain blood glucose levels by conserving pyruvate and other three carbon compounds for gluconeogenesis. The relative activities of the pyruvate dehydrogenase kinases (PDKs) and the opposing pyruvate dehydrogenase phosphatases determine the activity of PDC in the fed and fasted states. Up regulation of PDK4 is largely responsible for inactivation of PDC in the fasted state. PDK4 knockout mice have lower fasting blood glucose levels than wild type mice, proving that up regulation of PDK4 is important for normal glucose homeostasis. In type 2 diabetes, up regulation of PDK4 also inactivates PDC, which promotes gluconeogenesis and thereby contributes to the hyperglycemia characteristic of this disease. When fed a high fat diet, wild type mice develop fasting hyperglycemia but PDK4 knockout mice remain euglycemic, proving that up regulation of PDK4 contributes to hyperglycemia in diabetes. These finding suggest PDK4 inhibitors might prove useful in the treatment of type 2 diabetes.