Identification of New Non-BBB Permeable Tryptophan Hydroxylase Inhibitors for Treating Obesity and Fatty Liver Disease.

Serotonin (5-hydroxytryptophan) is a hormone that regulates emotions in the central nervous system. However, serotonin in the peripheral system is associated with obesity and fatty liver disease. Because serotonin cannot cross the blood-brain barrier (BBB), we focused on identifying new tryptophan hydroxylase type I (TPH1) inhibitors that act only in peripheral tissues for treating obesity and fatty liver disease without affecting the central nervous system. Structural optimization inspired by para-chlorophenylalanine (pCPA) resulted in the identification of a series of oxyphenylalanine and heterocyclic phenylalanine derivatives as TPH1 inhibitors. Among these compounds, compound 18i with an IC50 value of 37 nM was the most active in vitro. Additionally, compound 18i showed good liver microsomal stability and did not significantly inhibit CYP and Herg. Furthermore, this TPH1 inhibitor was able to actively interact with the peripheral system without penetrating the BBB. Compound 18i and its prodrug reduced body weight gain in mammals and decreased in vivo fat accumulation.

Lack of contribution of nitric oxide synthase to cholinergic vasodilation in murine renal afferent arterioles.

We have previously reported significant increases in neuronal nitric oxide synthase (NOS) immunostaining in renal arterioles of angiotensin type 1A receptor (AT1A) knockout mice, and in arterioles and macula densa cells of AT1A/AT1B knockout mice. The contribution of nitric oxide derived from endothelial and macula densa cells in the maintenance of afferent arteriolar tone and acetylcholine-induced vasodilation was functionally determined in kidneys of wild-type, AT1A, and AT1A/AT1B knockout mice. Acetylcholine-induced changes in arteriolar diameters of in vitro blood-perfused juxtamedullary nephrons were measured during control conditions, in the presence of the nonspecific NOS inhibitor, Nω-nitro-l-arginine methyl ester (NLA), or the highly selective neuronal NOS inhibitor, N5-(1-imino-3-butenyl)-l-ornithine (VNIO). Acetylcholine (0.1 mM) produced a significant vasoconstriction in afferent arterioles of AT1A/AT1B mice (-10.9 ± 5.1%) and no changes in afferent arteriolar diameters of AT1A knockout mice. NLA (0.01-1 mM) or VNIO (0.01-1 µM) induced significant dose-dependent vasoconstrictions (-19.8 ± 4.0% 1 mM NLA; -7.8 ± 3.5% 1 µM VNIO) in afferent arterioles of kidneys of wild-type mice. VNIO had no effect on afferent arteriole diameters of AT1A knockout or AT1A/AT1B knockout mice, suggesting nonfunctional neuronal nitric oxide synthase. These data indicate that acetylcholine produces a significant renal afferent arteriole vasodilation independently of nitric oxide synthases in wild-type mice. AT1A receptors are essential for the manifestation of renal afferent arteriole responses to neuronal nitric oxide synthase-mediated nitric oxide release.

Pyruvate dehydrogenase kinase 4 deficiency attenuates cisplatin-induced acute kidney injury.

Clinical prescription of cisplatin, one of the most widely used chemotherapeutic agents, is limited by its side effects, particularly tubular injury-associated nephrotoxicity. Since details of the underlying mechanisms are not fully understood, we investigated the role of pyruvate dehydrogenase kinase (PDK) in cisplatin-induced acute kidney injury. Among the PDK isoforms, PDK4 mRNA and protein levels were markedly increased in the kidneys of mice treated with cisplatin, and c-Jun N-terminal kinase activation was involved in cisplatin-induced renal PDK4 expression. Treatment with the PDK inhibitor sodium dichloroacetate (DCA) or genetic knockout of PDK4 attenuated the signs of cisplatin-induced acute kidney injury, including apoptotic morphology of the kidney tubules along with numbers of TUNEL-positive cells, cleaved caspase-3, and renal tubular injury markers. Cisplatin-induced suppression of the mitochondrial membrane potential, oxygen consumption rate, expression of electron transport chain components, cytochrome c oxidase activity, and disruption of mitochondrial morphology were noticeably improved in the kidneys of DCA-treated or PDK4 knockout mice. Additionally, levels of the oxidative stress marker 4-hydroxynonenal and mitochondrial reactive oxygen species were attenuated, whereas superoxide dismutase 2 and catalase expression and glutathione synthetase and glutathione levels were recovered in DCA-treated or PDK4 knockout mice. Interestingly, lipid accumulation was considerably attenuated in DCA-treated or PDK4 knockout mice via recovered expression of peroxisome proliferator-activated receptor-α and coactivator PGC-1α, which was accompanied by recovery of mitochondrial biogenesis. Thus, PDK4 mediates cisplatin-induced acute kidney injury, suggesting that PDK4 might be a therapeutic target for attenuating cisplatin-induced acute kidney injury.

Gemigliptin ameliorates Western-diet-induced metabolic syndrome in mice.

Dipeptidyl peptidase 4 (DPP-4) inhibitors are widely used antihyperglycemic agents for type 2 diabetes mellitus. Recently, increasing attention has been focused on the pleiotropic actions of DPP-4 inhibitors. The aim of the present study was to examine whether gemigliptin, a recently developed DPP-4 inhibitor, could ameliorate features of metabolic syndrome. Mice were fed a Western diet (WD) for 12 weeks and were subsequently divided into 2 groups: mice fed a WD diet alone or mice fed a WD diet supplemented with gemigliptin for an additional 4 weeks. Gemigliptin treatment attenuated WD-induced body mass gain, hypercholesterolemia, adipocyte hypertrophy, and macrophage infiltration into adipose tissue, which were accompanied by an increased expression of uncoupling protein 1 in subcutaneous fat. These events contributed to improved insulin sensitivity, as assessed by the homeostasis model assessment of insulin resistance and intraperitoneal insulin tolerance test. Furthermore, gemigliptin reduced WD-induced hepatic triglyceride accumulation via inhibition of de novo lipogenesis and activation of fatty acid oxidation, which was accompanied by AMP-dependent protein kinase activation. Gemigliptin ameliorated WD-induced hepatic inflammation and fibrosis through suppression of oxidative stress. These results suggest that DPP-4 inhibitors may represent promising therapeutic agents for metabolic syndrome beyond their current role as antihyperglycemic agents.

Method and analysis of color changes of facial skin after applying skin makeup.

This study investigated facial skin color differences before and after makeup. Toward this goal, a photo gauge, devised with a pair of color checkers as a reference, collected face images. In addition, color calibration and a deep-learning method extracted the color values of representative areas of facial skin. The photo gauge photographed 516 Chinese females before and after applying makeup. Then, the collected images were calibrated by referencing skin color patches, and the lower cheek regions' pixel colors were extracted using open-source computer vision libraries. Following the visible color spectrum of humans, the color values were computed in L*, a*, and b* of CIE1976L*a*b*. The results showed that the facial colors of the Chinese females changed to become brighter, less reddish, and less yellowish after applying the makeup, resulting in a paler skin tone. During the experiment, subjects were given five varieties of liquid foundation to choose one sample that best fits their skin. However, we failed to find any noticeable relationship between the individual's facial skin color characteristics and the liquid foundation selected. In addition, 55 subjects were identified according to their makeup use frequency and skill, but their color changes did not differ from the other subjects. This study provided quantitative evidence of makeup trends in the Shanghai region in China, and the method proposes a novel approach toward remote skin color research.

Effect of Low-Dose Persistent Organic Pollutants on Mitochondrial Function: Human and in Vitro Evidence.

BACKGROUND: Chronic exposure to low-dose persistent organic pollutants (POPs) can induce mitochondrial dysfunction. This study evaluated the association between serum POP concentrations and oxygen consumption rate (OCR) as a marker of mitochondrial function in humans and in vitro cells. METHODS: Serum concentrations of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) were measured in 323 adults. The OCRs of platelets and peripheral blood mononuclear cells (PBMCs) were assessed in 20 mL of fresh blood using a Seahorse XF analyzer. Additionally, the in vitro effects of Arochlor-1254, ß-hexachlorocyclohexane, and p,p´-dichlorodiphenyltrichloroethane at concentrations of 0.1 pM to 100 nM were evaluated in human platelets, human PBMCs, and Jurkat T-cells. RESULTS: The association between serum POP concentrations and OCR differed depending on the cell type. As serum OCP concentrations increased, basal platelet OCR levels decreased significantly; according to the OCP quintiles of summary measure, they were 8.6, 9.6, 8.2, 8.0, and 7.1 pmol/min/µg (P trend=0.005). Notably, the basal PBMC OCR levels decreased remarkably as the serum PCB concentration increased. PBMC OCR levels were 46.5, 34.3, 29.1, 16.5, and 13.1 pmol/min/µg according to the PCB quintiles of summary measure (P trend <0.001), and this inverse association was consistently observed in all subgroups stratified by age, sex, obesity, type 2 diabetes mellitus, and hypertension, respectively. In vitro experimental studies have also demonstrated that chronic exposure to low-dose POPs could decrease OCR levels. CONCLUSION: The findings from human and in vitro studies suggest that chronic exposure to low-dose POPs can induce mitochondrial dysfunction by impairing oxidative phosphorylation.

Glomerular filtration rate determinations in conscious type II diabetic mice.

Diabetic nephropathy is a major cause of end-stage renal disease worldwide. The current studies were performed to determine the later stages of the progression of renal disease in type II diabetic mice (BKS; db/db). Methodology was developed for determining glomerular filtration rate (GFR) in conscious, chronically instrumented mice using continuous intravenous infusion of FITC-labeled inulin to achieve a steady-state plasma inulin concentration. Obese diabetic mice exhibited increased GFR compared with control mice. GFR averaged 0.313 ± 0.018 and 0.278 ± 0.007 ml/min in 18-wk-old obese diabetic (n = 11) and control (n = 13) mice, respectively (P < 0.05). In 28-wk-old obese diabetic (n = 10) and control (n = 15) mice, GFR averaged 0.348 ± 0.030 and 0.279 ± 0.009 ml/min, respectively (P < 0.05). GFR expressed per gram BW was significantly reduced in 18- and 28-wk-old obese diabetic compared with control mice (5.9 ± 0.3 vs. 9.0 ± 0.3; 6.6 ± 0.6 vs. 7.8 ± 0.3 µl·min(-1)·g body wt(-1)), respectively (P < 0.05). However, older nonobese type II diabetic mice had significantly reduced GFR (0.179 ± 0.023 ml/min; n = 6) and elevated urinary albumin excretion (811 ± 127 µg/day) compared with obese diabetic and control mice (514 ± 54, 171 ± 18 µg/day), which are consistent with the advanced stages of renal disease. These studies suggest that hyperfiltration contributes to the progression of renal disease in type II diabetic mice.

Drug evaluation based on phosphomimetic PDHA1 reveals the complexity of activity-related cell death in A549 non-small cell lung cancer cells.

Cancer cells predominantly generate energy via glycolysis, even in the presence of oxygen, to support abnormal cell proliferation. Suppression of PDHA1 by PDK1 prevents the conversion of cytoplasmic pyruvate into Acetyl-CoA. Several PDK inhibitors have been identified, but their clinical applications have not been successful for unclear reasons. In this study, endogenous PDHA1 in A549 cells was silenced by the CRISPR/Cas9 system, and PDHA1WT and PDHA13SD were transduced. Since PDHA13SD cannot be phosphorylated by PDKs, it was used to evaluate the specific activity of PDK inhibitors. This study highlights that PDHA1WT and PDHA13SD A549 cells can be used as a cell-based PDK inhibitor-distinction system to examine the relationship between PDH activity and cell death by established PDK inhibitors. Leelamine, huzhangoside A and otobaphenol induced PDH activity-dependent apoptosis, whereas AZD7545, VER-246608 and DCA effectively enhanced PDHA1 activity but little toxic to cancer cells. Furthermore, the activity of phosphomimetic PDHA1 revealed the complexity of its regulation, which requires further in-depth investigation. [BMB Reports 2021; 54(11): 563-568].

Pyruvate dehydrogenase kinase 1 and 2 deficiency reduces high-fat diet-induced hypertrophic obesity and inhibits the differentiation of preadipocytes into mature adipocytes.

Obesity is now recognized as a disease. This study revealed a novel role for pyruvate dehydrogenase kinase (PDK) in diet-induced hypertrophic obesity. Mice with global or adipose tissue-specific PDK2 deficiency were protected against diet-induced obesity. The weight of adipose tissues and the size of adipocytes were reduced. Adipocyte-specific PDK2 deficiency slightly increased insulin sensitivity in HFD-fed mice. In studies with 3T3-L1 preadipocytes, PDK2 and PDK1 expression was strongly increased during adipogenesis. Evidence was found for epigenetic induction of both PDK1 and PDK2. Gain- and loss-of-function studies with 3T3-L1 cells revealed a critical role for PDK1/2 in adipocyte differentiation and lipid accumulation. PDK1/2 induction during differentiation was also accompanied by increased expression of hypoxia-inducible factor-1α (HIF1α) and enhanced lactate production, both of which were absent in the context of PDK1/2 deficiency. Exogenous lactate supplementation increased the stability of HIF1α and promoted adipogenesis. PDK1/2 overexpression-mediated adipogenesis was abolished by HIF1α inhibition, suggesting a role for the PDK-lactate-HIF1α axis during adipogenesis. In human adipose tissue, the expression of PDK1/2 was positively correlated with that of the adipogenic marker PPARγ and inversely correlated with obesity. Similarly, PDK1/2 expression in mouse adipose tissue was decreased by chronic high-fat diet feeding. We conclude that PDK1 and 2 are novel regulators of adipogenesis that play critical roles in obesity.

Major role for ACE-independent intrarenal ANG II formation in type II diabetes.

Combination therapy of angiotensin-converting enzyme (ACE) inhibition and AT(1) receptor blockade has been shown to provide greater renoprotection than ACE inhibitor alone in human diabetic nephropathy, suggesting that ACE-independent pathways for ANG II formation are of major significance in disease progression. Studies were performed to determine the magnitude of intrarenal ACE-independent formation of ANG II in type II diabetes. Although renal cortical ACE protein activity [2.1 +/- 0.8 vs. 9.2 +/- 2.1 arbitrary fluorescence units (AFU) x mg(-1) x min(-1)] and intensity of immunohistochemical staining were significantly reduced and ACE2 protein activity (16.7 +/- 3.2 vs. 7.2 +/- 2.4 AFU x mg(-1) x min(-1)) and intensity elevated, kidney ANG I (113 +/- 24 vs. 110 +/- 45 fmol/g) and ANG II (1,017 +/- 165 vs. 788 +/- 99 fmol/g) levels were not different between diabetic and control mice. Afferent arteriole vasoconstriction due to conversion of ANG I to ANG II was similar in magnitude in kidneys of diabetic (-28 +/- 3% at 1 microM) and control (-23 +/- 3% at 1 microM) mice; a response completely inhibited by AT(1) receptor blockade. In control kidneys, afferent arteriole vasoconstriction produced by ANG I was significantly attenuated by ACE inhibition, but not by serine protease inhibition. In contrast, afferent arteriole vasoconstriction produced by intrarenal conversion of ANG I to ANG II was significantly attenuated by serine protease inhibition, but not by ACE inhibition in diabetic kidneys. In conclusion, there is a switch from ACE-dependent to serine protease-dependent ANG II formation in the type II diabetic kidney. Pharmacological targeting of these serine protease-dependent pathways may provide further protection from diabetic renal vascular disease.

Fursultiamine Alleviates Choroidal Neovascularization by Suppressing Inflammation and Metabolic Reprogramming.

Purpose: To assess the therapeutic effects of fursultiamine on choroidal neovascularization (CNV) through its modulation of inflammation and metabolic reprogramming in the retinal pigment epithelium (RPE). Methods: The anti-angiogenic effects of fursultiamine were assessed by measuring vascular leakage and CNV lesion size in the laser-induced CNV mouse model. Inflammatory responses were evaluated by quantitative polymerase chain reaction, western blot, and ELISA in both CNV eye tissues and in vitro cell cultures using ARPE-19 cells or primary human RPE (hRPE) cells under lipopolysaccharide (LPS) treatment or hypoxia. Mitochondrial respiration was assessed by measuring oxygen consumption in ARPE-19 cells treated with LPS with or without fursultiamine, and lactate production was measured in ARPE-19 cells subjected to hypoxia with or without fursultiamine. Results: In laser-induced CNV, fursultiamine significantly decreased vascular leakage and lesion size, as well as the numbers of both choroidal and retinal inflammatory cytokines, including IL-1ß, IL-6, IL-8, and TNF-α. In LPS-treated ARPE-19 cells, fursultiamine decreased proinflammatory cytokine secretion and nuclear factor kappa B phosphorylation. Furthermore, fursultiamine suppressed LPS-induced upregulation of IL-6, IL-8, and monocyte chemoattractant protein-1 in a dose-dependent and time-dependent manner in primary hRPE cells. Interestingly, fursultiamine significantly enhanced mitochondrial respiration in the LPS-treated ARPE-19 cells. Additionally, fursultiamine attenuated hypoxia-induced aberrations, including lactate production and inhibitory phosphorylation of pyruvate dehydrogenase. Furthermore, fursultiamine attenuated hypoxia-induced VEGF secretion and mitochondrial fission in primary hRPE cells that were replicated in ARPE-19 cells. Conclusions: Our findings show that fursultiamine is a viable putative therapeutic for neovascular age-related macular degeneration by modulating the inflammatory response and metabolic reprogramming by enhancing mitochondrial respiration in the RPE.

Progression of Multifaceted Immune Cells in Atherosclerotic Development.

Atherosclerosis is a major cause of morbidity and mortality due to cardiovascular diseases, such as coronary artery disease, stroke, and peripheral vascular disease, that are associated with thrombosis-induced organ infarction. In Westernized countries, the high prevalence of obesity-induced insulin resistance is predicted to be a major factor leading to atherosclerotic vascular disease. Both genetic and environmental factors interfere with immune responses in atherosclerosis development with chronic and non-resolving states. The most known autoimmune disease therapy is cytokine-targeted therapy, which targets tumor necrosis factor-α and interleukin (IL)-17 antagonists. Recently, a clinical trial with the anti-IL-1ß antibody (canakinumab) had shown that the anti-inflammatory effects in canakinumab-treated subjects play a critical role in reducing cardiovascular disease prevalence. Recent emerging data have suggested effective therapeutics involving anti-obesity and anti-diabetic agents, as well as statin and anti-platelet drugs, for atherothrombosis prevention. It is well-known that specialized immune differentiation and activation completely depends on metabolic reprogramming mediated by mitochondrial dynamics in distinct immune cells. Therefore, there is a strong mechanistic link between metabolism and immune function mediated by mitochondrial function. In this review, we describe that cellular metabolism in immune cells is strongly interconnected with systemic metabolism in terms of diverse phenotypes and activation.

Lifestyle of Patients with Alcoholic Liver Disease and Factors Leading to Hospital Readmission: A Prospective Observational Study.

The objective of this study was to clarify the lifestyle characteristics of patients with alcoholic liver disease (ALD) who were readmitted to the hospital, and to identify the background factors associated with these characteristics. This was a prospective observational study. Over a period of 3 months following hospital discharge, we conducted structured interviews to investigate the following five lifestyle characteristics based on our previous research: dietary intake, alcohol consumption or abstinence, psycho-emotional status, regularity of life habits, adherence to treatment. We also collected data on background factors from medical records and questionnaires. The analysis was performed using conceptual cluster matrices, with participants divided into two groups (at-home recovery and readmission). Lifestyle, health status, and background factors were compared between the two groups. Of the 34 patients with ALD recruited, 21 completed the one-month follow-up and were included in the analysis-14 patients were in the at-home recovery group and 7 in the readmission group. The at-home group's lifestyle was characterized by controlled alcohol consumption, but with maintenance of regular life and eating habits and adherence to treatment. In contrast, irregular eating habits (p=0.006) and the development of irregular life habits or the discontinuation of treatment very quickly after hospital discharge characterized the readmission group's lifestyle. Experiences of loss were a lifestyle-related background factor that was associated with readmission (p=0.017). Based on these findings, supporting patients with ALD in maintaining regular eating habits and taking experiences of loss into consideration would be important in avoiding readmission over the short-term.

Recent advances in the pathogenesis of microvascular complications in diabetes.

Millions of people worldwide have diabetes, which is diagnosed by fasting blood glucose levels exceeding 126 mg/dL. Regardless of the type of diabetes, prolonged hyperglycemia is damaging to several organs including eyes, kidneys, nerve, and/or heart. The damages are associated with a high risk of morbidity and mortality. Diabetes has been implicated in ischemia in the microvasculature of the target tissues, which occurs due to the insufficient perfusion of tissues. The resulting occlusion and pain affect the quality of life. Multiple therapeutic approaches have been proposed for a long time to overcome these vascular complications. Apart from systemically controlling high glucose levels, other therapeutic strategies are not well understood. In this review, we summarize the recent literature for biochemical/cellular targets that are being utilized for the treatment of diabetic microvascular diseases. These targets, which are closely associated with mitochondrial dysfunction, include the polyol and diacylglycerol-protein kinase C pathways, oxidative stress, non-enzymatic glycation and the formation of advanced glycation end products, and immune dysregulation/inflammation.

Identification of Novel Resorcinol Amide Derivatives as Potent and Specific Pyruvate Dehydrogenase Kinase (PDHK) Inhibitors.

Pyruvate dehydrogenase kinases (PDHKs) promote abnormal respiration in cancer cells. Studies with novel resorcinol amide derivatives based on VER-246608 (6) led to the identification of 19n and 19t containing five-membered heteroaromatic rings as unique structural features. These substances possess single-digit nanomolar activities against PDHKs. 19t exhibits higher potencies against PDHK1/2/4 than does 6 and inhibits only PDHKs among 366 kinases. Moreover, 19g, 19l, and 19s were found to be isotype-selective PDHK inhibitors. Molecular dynamics simulations provide a better understanding of how the heteroaromatic rings affect the activities of 19n and 19t on PDHK1/2/3/4. Moreover, 19n possesses a much higher antiproliferative activity against cancer cells than does 6. We demonstrated that the results of PDH assays better correlate with cellular activities than do those of PDHK kinase assays. Furthermore, 19n induces apoptosis of cancer cells via mitochondrial dysfunction, suppresses tumorigenesis, and displays a synergistic effect on satraplatin suppression of cancer cell proliferation.

Therapeutic effect of dichloroacetate against atherosclerosis via hepatic FGF21 induction mediated by acute AMPK activation.

Dyslipidemia-induced atherosclerosis, which has a risk of high morbidity and mortality, can be alleviated by metabolic activation associated with mitochondrial function. The effect of dichloroacetate (DCA), a general pyruvate dehydrogenase kinase (PDK) inhibitor, on in vivo energy expenditure in ApoE-/- mice fed a western diet (WD) has not yet been investigated. WD-fed ApoE-/- mice developed atherosclerotic plaques and hyperlipidemia along with obesity, which were significantly ameliorated by DCA administration. Increased oxygen consumption was associated with heat production in the DCA-treated group, with no change in food intake or physical activity compared with those of the control. These processes were correlated with the increased gene expression of Dio2 and Ucp-1, which represents brown adipose tissue (BAT) activation, in both WD-induced atherosclerosis and high-fat-induced obesity models. In addition, we found that DCA stimulated hepatic fibroblast growth factor 21 (Fgf21) mRNA expression, which might be important for lowering lipid levels and insulin sensitization via BAT activation, in a dose- and time-dependent manner associated with serum FGF21 levels. Interestingly, Fgf21 mRNA expression was mediated in an AMP-activated protein kinase (AMPK)-dependent manner within several minutes after DCA treatment independent of peroxisome proliferator-activated receptor alpha (PPARα). Taken together, the results suggest that enhanced glucose oxidation by DCA protects against atherosclerosis by inducing hepatic FGF21 expression and BAT activation, resulting in augmented energy expenditure for heat generation.

Discovery of Novel Pyruvate Dehydrogenase Kinase 4 Inhibitors for Potential Oral Treatment of Metabolic Diseases.

Pyruvate dehydrogenase kinase 4 (PDK4) activation is associated with metabolic diseases including hyperglycemia, insulin resistance, allergies, and cancer. Structural modifications of hit anthraquinone led to the identification of a new series of allosteric PDK4 inhibitors. Among this series, compound 8c showed promising in vitro activity with an IC50 value of 84 nM. Good metabolic stability, pharmacokinetic profiles, and possible metabolites were suggested. Compound 8c improved glucose tolerance in diet-induced obese mice and ameliorated allergic reactions in a passive cutaneous anaphylaxis mouse model. Additionally, compound 8c exhibited anticancer activity by controlling cell proliferation, transformation, and apoptosis. From the molecular docking studies, compound 8c displayed optimal fitting in the lipoamide binding site (allosteric) with a full fitness, providing a new scaffold for drug development toward PDK4 inhibitors.

Pyruvate Dehydrogenase Kinase Is a Metabolic Checkpoint for Polarization of Macrophages to the M1 Phenotype.

Metabolic reprogramming during macrophage polarization supports the effector functions of these cells in health and disease. Here, we demonstrate that pyruvate dehydrogenase kinase (PDK), which inhibits the pyruvate dehydrogenase-mediated conversion of cytosolic pyruvate to mitochondrial acetyl-CoA, functions as a metabolic checkpoint in M1 macrophages. Polarization was not prevented by PDK2 or PDK4 deletion but was fully prevented by the combined deletion of PDK2 and PDK4; this lack of polarization was correlated with improved mitochondrial respiration and rewiring of metabolic breaks that are characterized by increased glycolytic intermediates and reduced metabolites in the TCA cycle. Genetic deletion or pharmacological inhibition of PDK2/4 prevents polarization of macrophages to the M1 phenotype in response to inflammatory stimuli (lipopolysaccharide plus IFN-γ). Transplantation of PDK2/4-deficient bone marrow into irradiated wild-type mice to produce mice with PDK2/4-deficient myeloid cells prevented M1 polarization, reduced obesity-associated insulin resistance, and ameliorated adipose tissue inflammation. A novel, pharmacological PDK inhibitor, KPLH1130, improved high-fat diet-induced insulin resistance; this was correlated with a reduction in the levels of pro-inflammatory markers and improved mitochondrial function. These studies identify PDK2/4 as a metabolic checkpoint for M1 phenotype polarization of macrophages, which could potentially be exploited as a novel therapeutic target for obesity-associated metabolic disorders and other inflammatory conditions.

Augmented renal vascular nNOS and renin protein expression in angiotensin type 1 receptor null mice.

The present study was performed to determine the influence of absence of angiotensin type 1A (AT(1A)) and/or AT(1B) receptor feedback regulation of kidney neuronal nitric oxide synthase (nNOS) and renin protein expression. Kidneys were harvested from wild-type (WT), AT(1A)(-/-), AT(1B)(-/-), and AT(1A)(-/-)AT(1B)(-/-) mice and immunostained for nNOS and renin protein localization. AT(1A)(-/-) and AT(1A)(-/-)AT(1B)(-/-) kidneys demonstrated an increase in the percentage of glomeruli with nNOS-positive afferent and interlobular arterioles compared with WT mice. Density of vascular nNOS immunostaining was 20-fold higher in kidneys of AT(1A)(-/-) and AT(1A)(-/-)AT(1B)(-/-) compared with WT mice. Density of macula densa nNOS immunostaining was 7-fold higher in AT(1A)(-/-)AT(1B)(-/-) than in WT mice. Percent of glomeruli positive for juxtaglomerular (JG) cell renin was 3-fold higher, whereas the density of JG cell renin immunostaining was 15-fold higher in kidneys of AT(1A)(-/-) and AT(1A)(-/-)AT(1B)(-/-) compared with WT mice. Kidneys of AT(1A)(-/-) and AT(1A)(-/-)AT(1B)(-/-) mice displayed recruitment of renin protein expression along afferent and interlobular arterioles. Absence of AT(1) receptor signaling resulted in enhanced nNOS protein expression in both microvascular and tubular structures. Enhanced NO generation may contribute to the reduced renal vascular tone and blood pressure observed with blockade of the renin-angiotensin system.

Role of the Pyruvate Dehydrogenase Complex in Metabolic Remodeling: Differential Pyruvate Dehydrogenase Complex Functions in Metabolism.

Mitochondrial dysfunction is a hallmark of metabolic diseases such as obesity, type 2 diabetes mellitus, neurodegenerative diseases, and cancers. Dysfunction occurs in part because of altered regulation of the mitochondrial pyruvate dehydrogenase complex (PDC), which acts as a central metabolic node that mediates pyruvate oxidation after glycolysis and fuels the Krebs cycle to meet energy demands. Fine-tuning of PDC activity has been mainly attributed to post-translational modifications of its subunits, including the extensively studied phosphorylation and de-phosphorylation of the E1α subunit of pyruvate dehydrogenase (PDH), modulated by kinases (pyruvate dehydrogenase kinase [PDK] 1-4) and phosphatases (pyruvate dehydrogenase phosphatase [PDP] 1-2), respectively. In addition to phosphorylation, other covalent modifications, including acetylation and succinylation, and changes in metabolite levels via metabolic pathways linked to utilization of glucose, fatty acids, and amino acids, have been identified. In this review, we will summarize the roles of PDC in diverse tissues and how regulation of its activity is affected in various metabolic disorders.