1
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Colangeli L, Escobar Marcillo DI, Simonelli V, Iorio E, Rinaldi T, Sbraccia P, Fortini P, Guglielmi V. The Crosstalk between Gut Microbiota and White Adipose Tissue Mitochondria in Obesity. Nutrients 2023; 15:nu15071723. [PMID: 37049562 PMCID: PMC10097238 DOI: 10.3390/nu15071723] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Revised: 03/19/2023] [Accepted: 03/28/2023] [Indexed: 04/03/2023] Open
Abstract
Adipose tissue (AT) dysregulation is a key process in the pathophysiology of obesity and its cardiometabolic complications, but even if a growing body of evidence has been collected over recent decades, the underlying molecular basis of adiposopathy remains to be fully understood. In this context, mitochondria, the intracellular organelles that orchestrate energy production and undergo highly dynamic adaptive changes in response to changing environments, have emerged as crucial regulators of both white (WAT) and brown adipose tissue (BAT) metabolism and function. Given that the gut microbiota and its metabolites are able to regulate host metabolism, adipogenesis, WAT inflammation, and thermogenesis, we hypothesize that their frequently observed dysregulation in obesity could affect AT metabolism by exerting direct and indirect effects on AT mitochondria. By collecting and revising the current evidence on the connections between gut microbiota and AT mitochondria in obesity, we gained insights into the molecular biology of their hitherto largely unexplored crosstalk, tracing how gut microbiota may regulate AT mitochondrial function.
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2
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Stacpoole PW, McCall CE. The pyruvate dehydrogenase complex: Life's essential, vulnerable and druggable energy homeostat. Mitochondrion 2023; 70:59-102. [PMID: 36863425 DOI: 10.1016/j.mito.2023.02.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2022] [Revised: 01/30/2023] [Accepted: 02/13/2023] [Indexed: 03/04/2023]
Abstract
Found in all organisms, pyruvate dehydrogenase complexes (PDC) are the keystones of prokaryotic and eukaryotic energy metabolism. In eukaryotic organisms these multi-component megacomplexes provide a crucial mechanistic link between cytoplasmic glycolysis and the mitochondrial tricarboxylic acid (TCA) cycle. As a consequence, PDCs also influence the metabolism of branched chain amino acids, lipids and, ultimately, oxidative phosphorylation (OXPHOS). PDC activity is an essential determinant of the metabolic and bioenergetic flexibility of metazoan organisms in adapting to changes in development, nutrient availability and various stresses that challenge maintenance of homeostasis. This canonical role of the PDC has been extensively probed over the past decades by multidisciplinary investigations into its causal association with diverse physiological and pathological conditions, the latter making the PDC an increasingly viable therapeutic target. Here we review the biology of the remarkable PDC and its emerging importance in the pathobiology and treatment of diverse congenital and acquired disorders of metabolic integration.
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Affiliation(s)
- Peter W Stacpoole
- Department of Medicine (Division of Endocrinology, Metabolism and Diabetes), and Department of Biochemistry and Molecular Biology, University of Florida, College of Medicine, Gainesville, FL, United States.
| | - Charles E McCall
- Department of Internal Medicine and Translational Sciences, and Department of Microbiology and Immunology, Wake Forest University School of Medicine, Winston-Salem, NC, United States
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3
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Xu H, Wang W, Nie Z, Miao X, Li Y. Delayed First Feeding Chronically Impairs Larval Fish Growth Performance, Hepatic Lipid Metabolism, and Visceral Lipid Deposition at the Mouth-Opening Stage. MARINE BIOTECHNOLOGY (NEW YORK, N.Y.) 2023; 25:140-149. [PMID: 36510098 DOI: 10.1007/s10126-022-10187-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Accepted: 11/23/2022] [Indexed: 06/17/2023]
Abstract
During the mouth-opening stage, fish larvae are susceptible to delayed first feeding (DFF). In this study, we explored the effects of DFF for two days on later growth and energy metabolism in larval fish. Results showed that DFF chronically impaired larval growth performance, thereby reducing the efficiency of feed utilization by larvae. In DFF larvae, the mRNA levels of growth inhibitors (i.e., igfbp1a and igfbp1b) were significantly upregulated and consistently maintained at high expression levels, which may be an important attribution of larval growth retardation. Concomitantly, DFF retarded the growth of adipose tissue and reduced lipid deposition in larval viscera, suggesting lipid metabolism is disordered in DFF larvae and generates inefficient lipid reserves. In the liver, we observed that DFF resulted in a significant accumulation of neutral lipids, and this phenotype did not disappear rapidly after DFF larvae received exogenous nutrition. As to the transcript analyses, we found that the expression of genes related to hepatic lipid synthesis (e.g., srebf1, srebf2, dgat1a, dgat1b, fasn, and scdb) in DFF larvae was consistently upregulated, while the expression of genes involved in lipid transport (e.g., apoa2, apoa4b.1, and apoa4b.3) was downregulated. Therefore, it appears that the inefficient lipid reserves in DFF larvae are associated with their hepatic lipid transport dysfunction. Taken together, our findings contribute to understanding the impairments to fish larvae caused by delayed first feeding during the mouth-opening stage and to aiding larval management in the aquaculture industry.
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Affiliation(s)
- Hao Xu
- Fisheries and Aquaculture Biotechnology Laboratory, College of Fisheries, Southwest University, Chongqing, 400715, China
- Integrative Science Center of Germplasm Creation in Western China (CHONGQING) Science City, Chongqing, 401329, China
- Key Laboratory of Freshwater Fish Reproduction and Development (Ministry of Education), Key Laboratory of Aquatic Science of Chongqing, Southwest University, Chongqing, 400715, China
| | - Wenbo Wang
- Fisheries and Aquaculture Biotechnology Laboratory, College of Fisheries, Southwest University, Chongqing, 400715, China
| | - Zhentao Nie
- Fisheries and Aquaculture Biotechnology Laboratory, College of Fisheries, Southwest University, Chongqing, 400715, China
| | - Xiaomin Miao
- Fisheries and Aquaculture Biotechnology Laboratory, College of Fisheries, Southwest University, Chongqing, 400715, China
| | - Yun Li
- Fisheries and Aquaculture Biotechnology Laboratory, College of Fisheries, Southwest University, Chongqing, 400715, China.
- Integrative Science Center of Germplasm Creation in Western China (CHONGQING) Science City, Chongqing, 401329, China.
- Key Laboratory of Freshwater Fish Reproduction and Development (Ministry of Education), Key Laboratory of Aquatic Science of Chongqing, Southwest University, Chongqing, 400715, China.
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4
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Saed CT, Tabatabaei Dakhili SA, Ussher JR. Pyruvate Dehydrogenase as a Therapeutic Target for Nonalcoholic Fatty Liver Disease. ACS Pharmacol Transl Sci 2021; 4:582-588. [PMID: 33860188 DOI: 10.1021/acsptsci.0c00208] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2020] [Indexed: 12/19/2022]
Abstract
Excess caloric intake combined with a sedentary lifestyle in the general population has greatly increased the prevalence of obesity and nonalcoholic fatty liver disease (NAFLD), which is defined as the accumulation of excess fat in the liver in the absence of alcohol abuse or other attributable causes such as infection with hepatitis C. Furthermore, NAFLD increases the risk for insulin resistance, type 2 diabetes (T2D), and cardiovascular disease, while currently having no approved therapy to counteract its pathology. Thus, increasing efforts to understand the mechanisms responsible for NAFLD have been pursued in preclinical studies, in the hopes of developing novel therapies that can prevent the progression of insulin resistance and/or T2D. The pathology of NAFLD is multifactorial, with proposed mechanisms including inflammation, oxidative stress, and mitochondrial dysfunction to name a few. The latter remains a subject of ongoing debate, but may be attributed to impaired hepatic fatty acid oxidation, thereby increasing the accumulation of triacylglycerol within hepatocytes. More recent studies have also demonstrated that the mitochondrial dysfunction in NAFLD may also encompass impairments in glucose oxidation, despite oxidative energy production having minimal contribution to overall glucose/pyruvate metabolism in the liver. Accordingly, strategies to reverse this defect in glucose oxidation can ameliorate hepatic steatosis and improve glucose homeostasis. We will review herein the evidence supporting impaired hepatic glucose oxidation as a mechanism of NAFLD, while discussing the validity of pyruvate dehydrogenase (PDH), the rate-limiting enzyme of glucose oxidation, as a potential target for NAFLD. In addition, we will discuss potential mechanisms of action by which increased hepatic PDH activity and subsequent glucose oxidation can reverse the pathology of obesity-induced NAFLD, as well as opportunities to target this pathway with clinical agents.
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Affiliation(s)
- Christina T Saed
- Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Alberta T6G 2E1, Canada.,Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta T6G 2E1, Canada.,Cardiovascular Research Centre, University of Alberta, Edmonton, Alberta T6G 2E1, Canada
| | - Seyed Amirhossein Tabatabaei Dakhili
- Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Alberta T6G 2E1, Canada.,Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta T6G 2E1, Canada.,Cardiovascular Research Centre, University of Alberta, Edmonton, Alberta T6G 2E1, Canada
| | - John R Ussher
- Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Alberta T6G 2E1, Canada.,Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta T6G 2E1, Canada.,Cardiovascular Research Centre, University of Alberta, Edmonton, Alberta T6G 2E1, Canada
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5
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Patel MS, Mahmood S, Jung J, Rideout TC. Reprogramming of aerobic glycolysis in non-transformed mouse liver with pyruvate dehydrogenase complex deficiency. Physiol Rep 2021; 9:e14684. [PMID: 33400855 PMCID: PMC7785054 DOI: 10.14814/phy2.14684] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2020] [Revised: 11/26/2020] [Accepted: 11/27/2020] [Indexed: 12/19/2022] Open
Abstract
The Pyruvate Dehydrogenase Complex (PDC), a key enzyme in glucose metabolism, catalyzes an irreversible oxidative decarboxylation reaction of pyruvate to acetyl‐CoA, linking the cytosolic glycolytic pathway to mitochondrial tricarboxylic acid cycle and oxidative phosphorylation. Earlier we reported a down‐regulation of several key hepatic lipogenic enzymes and their upstream regulators in liver‐specific PDC‐deficient mouse (L‐PDCKO model by deleting the Pdha1 gene). In this study we investigated gene expression profiles of key glycolytic enzymes and other proteins that respond to various metabolic stresses in liver from L‐PDCKO mice. Transcripts of several, such as hexokinase 2, phosphoglycerate kinase 1, pyruvate kinase muscle‐type 2, and lactate dehydrogenase B as well as those for the nonglycolysis‐related proteins, CD‐36, C/EBP homologous protein, and peroxisome proliferator‐activated receptor γ, were up‐regulated in L‐PDCKO liver whereas hypoxia‐induced factor‐1α, pyruvate dehydrogenase kinase 1 and Sirtuin 1 transcripts were down‐regulated. The protein levels of pyruvate kinase muscle‐type 2 and lactate dehydrogenase B were increased whereas that of lactate dehydrogenase A was decreased in PDC‐deficient mouse liver. Analysis of endoplasmic reticulum and oxidative stress indicators suggests that the L‐PDCKO liver showed evidence of the former but not the latter. These findings indicate that (i) liver‐specific PDC deficiency is sufficient to induce “aerobic glycolysis characteristic” in mouse liver, and (ii) the mechanism(s) responsible for these changes appears distinct from that which induces the Warburg effect in some cancer cells.
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Affiliation(s)
- Mulchand S Patel
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY, USA
| | - Saleh Mahmood
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY, USA
| | - Jiwon Jung
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY, USA
| | - Todd C Rideout
- Department of Exercise and Nutrition Sciences, School of Public Health and Health Professions, University at Buffalo, Buffalo, NY, USA
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6
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Strong A. Revisiting Old Friends: Sortilin-1, Low-Density Lipoprotein Receptor, and Prorenin Receptor as Modulators of Lipoprotein and Energy Metabolism. Circ Res 2019; 122:652-654. [PMID: 29496794 DOI: 10.1161/circresaha.118.312656] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Affiliation(s)
- Alanna Strong
- From the Division of Human Genetics, Children's Hospital of Philadelphia, PA.
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7
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Svensson K, Dent JR, Tahvilian S, Martins VF, Sathe A, Ochala J, Patel MS, Schenk S. Defining the contribution of skeletal muscle pyruvate dehydrogenase α1 to exercise performance and insulin action. Am J Physiol Endocrinol Metab 2018; 315:E1034-E1045. [PMID: 30153068 PMCID: PMC6293170 DOI: 10.1152/ajpendo.00241.2018] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The pyruvate dehydrogenase complex (PDC) converts pyruvate to acetyl-CoA and is an important control point for carbohydrate (CHO) oxidation. However, the importance of the PDC and CHO oxidation to muscle metabolism and exercise performance, particularly during prolonged or high-intensity exercise, has not been fully defined especially in mature skeletal muscle. To this end, we determined whether skeletal muscle-specific loss of pyruvate dehydrogenase alpha 1 ( Pdha1), which is a critical subunit of the PDC, impacts resting energy metabolism, exercise performance, or metabolic adaptation to high-fat diet (HFD) feeding. For this, we generated a tamoxifen (TMX)-inducible Pdha1 knockout (PDHmKO) mouse, in which PDC activity is temporally and specifically ablated in adult skeletal muscle. We assessed energy expenditure, ex vivo muscle contractile performance, and endurance exercise capacity in PDHmKO mice and wild-type (WT) littermates. Additionally, we studied glucose homeostasis and insulin sensitivity in muscle after 12 wk of HFD feeding. TMX administration largely ablated PDHα in skeletal muscle of adult PDHmKO mice but did not impact energy expenditure, muscle contractile function, or low-intensity exercise performance. Additionally, there were no differences in muscle insulin sensitivity or body composition in PDHmKO mice fed a control or HFD, as compared with WT mice. However, exercise capacity during high-intensity exercise was severely impaired in PDHmKO mice, in parallel with a large increase in plasma lactate concentration. In conclusion, although skeletal muscle PDC is not a major contributor to resting energy expenditure or long-duration, low-intensity exercise performance, it is necessary for optimal performance during high-intensity exercise.
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Affiliation(s)
- Kristoffer Svensson
- Department of Orthopaedic Surgery, University of California San Diego , La Jolla, California
| | - Jessica R Dent
- Department of Orthopaedic Surgery, University of California San Diego , La Jolla, California
| | - Shahriar Tahvilian
- Department of Orthopaedic Surgery, University of California San Diego , La Jolla, California
| | - Vitor F Martins
- Department of Orthopaedic Surgery, University of California San Diego , La Jolla, California
| | - Abha Sathe
- Department of Orthopaedic Surgery, University of California San Diego , La Jolla, California
| | - Julien Ochala
- School of Basic and Medical Biosciences, Faculty of Life Sciences & Medicine, King's College London , London , United Kingdom
| | - Mulchand S Patel
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo , Buffalo, New York
| | - Simon Schenk
- Department of Orthopaedic Surgery, University of California San Diego , La Jolla, California
- Biomedical Sciences Graduate Program, University of California San Diego , La Jolla, California
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8
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Protein Expression Profile of Twenty-Week-Old Diabetic db/db and Non-Diabetic Mice Livers: A Proteomic and Bioinformatic Analysis. Biomolecules 2018; 8:biom8020035. [PMID: 29857581 PMCID: PMC6023011 DOI: 10.3390/biom8020035] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Revised: 05/27/2018] [Accepted: 05/29/2018] [Indexed: 02/08/2023] Open
Abstract
Type 2 diabetes mellitus is characterized by insulin resistance in the liver. Insulin is not only involved in carbohydrate metabolism, it also regulates protein synthesis. This work describes the expression of proteins in the liver of a diabetic mouse and identifies the metabolic pathways involved. Twenty-week-old diabetic db/db mice were hepatectomized, after which proteins were separated by 2D-Polyacrylamide Gel Electrophoresis (2D-PAGE). Spots varying in intensity were analyzed using mass spectrometry, and biological function was assigned by the Database for Annotation, Visualization and Integrated Discovery (DAVID) software. A differential expression of 26 proteins was identified; among these were arginase-1, pyruvate carboxylase, peroxiredoxin-1, regucalcin, and sorbitol dehydrogenase. Bioinformatics analysis indicated that many of these proteins are mitochondrial and participate in metabolic pathways, such as the citrate cycle, the fructose and mannose metabolism, and glycolysis or gluconeogenesis. In addition, these proteins are related to oxidation⁻reduction reactions and molecular function of vitamin binding and amino acid metabolism. In conclusion, the proteomic profile of the liver of diabetic mouse db/db exhibited mainly alterations in the metabolism of carbohydrates and nitrogen. These differences illustrate the heterogeneity of diabetes in its different stages and under different conditions and highlights the need to improve treatments for this disease.
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9
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Jackson LE, Kulkarni S, Wang H, Lu J, Dolezal JM, Bharathi SS, Ranganathan S, Patel MS, Deshpande R, Alencastro F, Wendell SG, Goetzman ES, Duncan AW, Prochownik EV. Genetic Dissociation of Glycolysis and the TCA Cycle Affects Neither Normal nor Neoplastic Proliferation. Cancer Res 2017; 77:5795-5807. [PMID: 28883002 DOI: 10.1158/0008-5472.can-17-1325] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2017] [Revised: 07/19/2017] [Accepted: 09/01/2017] [Indexed: 12/25/2022]
Abstract
Rapidly proliferating cells increase glycolysis at the expense of oxidative phosphorylation (oxphos) to generate sufficient levels of glycolytic intermediates for use as anabolic substrates. The pyruvate dehydrogenase complex (PDC) is a critical mitochondrial enzyme that catalyzes pyruvate's conversion to acetyl coenzyme A (AcCoA), thereby connecting these two pathways in response to complex energetic, enzymatic, and metabolic cues. Here we utilized a mouse model of hepatocyte-specific PDC inactivation to determine the need for this metabolic link during normal hepatocyte regeneration and malignant transformation. In PDC "knockout" (KO) animals, the long-term regenerative potential of hepatocytes was unimpaired, and growth of aggressive experimental hepatoblastomas was only modestly slowed in the face of 80%-90% reductions in AcCoA and significant alterations in the levels of key tricarboxylic acid (TCA) cycle intermediates and amino acids. Overall, oxphos activity in KO livers and hepatoblastoma was comparable with that of control counterparts, with evidence that metabolic substrate abnormalities were compensated for by increased mitochondrial mass. These findings demonstrate that the biochemical link between glycolysis and the TCA cycle can be completely severed without affecting normal or neoplastic proliferation, even under the most demanding circumstances. Cancer Res; 77(21); 5795-807. ©2017 AACR.
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Affiliation(s)
- Laura E Jackson
- Division of Neonatology, Department of Pediatrics, Children's Hospital of Pittsburgh of The University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania
| | - Sucheta Kulkarni
- Division of Hematology/Oncology, Department of Pediatrics, Children's Hospital of Pittsburgh of The University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania
| | - Huabo Wang
- Division of Hematology/Oncology, Department of Pediatrics, Children's Hospital of Pittsburgh of The University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania
| | - Jie Lu
- Division of Hematology/Oncology, Department of Pediatrics, Children's Hospital of Pittsburgh of The University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania
| | - James M Dolezal
- Division of Hematology/Oncology, Department of Pediatrics, Children's Hospital of Pittsburgh of The University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania
| | - Sivakama S Bharathi
- Division of Medical Genetics, Department of Pediatrics, Children's Hospital of Pittsburgh of The University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania
| | - Sarangarajan Ranganathan
- Department of Pathology, Children's Hospital of Pittsburgh of The University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania
| | - Mulchand S Patel
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, The State University of New York, Buffalo, New York
| | - Rahul Deshpande
- Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Frances Alencastro
- Department of Pathology, The McGowan Institute for Regenerative Medicine and The Pittsburgh Liver Research Center, The University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania
| | - Stacy G Wendell
- Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Eric S Goetzman
- Division of Medical Genetics, Department of Pediatrics, Children's Hospital of Pittsburgh of The University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania
| | - Andrew W Duncan
- Department of Pathology, The McGowan Institute for Regenerative Medicine and The Pittsburgh Liver Research Center, The University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania
| | - Edward V Prochownik
- Division of Hematology/Oncology, Department of Pediatrics, Children's Hospital of Pittsburgh of The University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania. .,Department of Microbiology and Molecular Genetics, The University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania.,The University of Pittsburgh Cancer Institute, Pittsburgh, Pennsylvania
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10
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Mahmood S, Birkaya B, Rideout TC, Patel MS. Lack of mitochondria-generated acetyl-CoA by pyruvate dehydrogenase complex downregulates gene expression in the hepatic de novo lipogenic pathway. Am J Physiol Endocrinol Metab 2016; 311:E117-27. [PMID: 27166281 PMCID: PMC4967143 DOI: 10.1152/ajpendo.00064.2016] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/19/2016] [Accepted: 05/03/2016] [Indexed: 12/20/2022]
Abstract
During the absorptive state, the liver stores excess glucose as glycogen and synthesizes fatty acids for triglyceride synthesis for export as very low density lipoproteins. For de novo synthesis of fatty acids from glucose, the mitochondrial pyruvate dehydrogenase complex (PDC) is the gatekeeper for the generation of acetyl-CoA from glucose-derived pyruvate. Here, we tested the hypothesis that limiting the supply of PDC-generated acetyl-CoA from glucose would have an impact on expression of key genes in the lipogenic pathway. In the present study, although the postnatal growth of liver-specific PDC-deficient (L-PDCKO) male mice was largely unaltered, the mice developed hyperinsulinemia with lower blood glucose levels in the fed state. Serum and liver lipid triglyceride and cholesterol levels remained unaltered in L-PDCKO mice. Expression of several key genes (ACL, ACC1) in the lipogenic pathway and their upstream regulators (LXR, SREBP1, ChREBP) as well as several genes in glucose metabolism (Pklr, G6pd2, Pck1) and fatty acid oxidation (FAT, Cpt1a) was downregulated in livers from L-PDCKO mice. Interestingly, there was concomitant upregulation of lipogenic genes in adipose tissue from L-PDCKO mice. Although, the total hepatic acetyl-CoA content remained unaltered in L-PDCKO mice, modified acetylation profiles of proteins in the nuclear compartment suggested an important role for PDC-generated acetyl-CoA in gene expression in de novo fatty acid synthesis in the liver. This finding has important implications for the regulation of hepatic lipid synthesis in pathological states.
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Affiliation(s)
- Saleh Mahmood
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, and
| | - Barbara Birkaya
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, and
| | - Todd C Rideout
- Department of Exercise and Nutrition Sciences, School of Public Health and Health Professions, University at Buffalo, Buffalo, New York
| | - Mulchand S Patel
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, and
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11
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Scheja L, Heeren J. Metabolic interplay between white, beige, brown adipocytes and the liver. J Hepatol 2016; 64:1176-1186. [PMID: 26829204 DOI: 10.1016/j.jhep.2016.01.025] [Citation(s) in RCA: 112] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/06/2015] [Revised: 01/11/2016] [Accepted: 01/25/2016] [Indexed: 02/07/2023]
Abstract
In mammalian evolution, three types of adipocytes have developed, white, brown and beige adipocytes. White adipocytes are the major constituents of white adipose tissue (WAT), the predominant store for energy-dense triglycerides in the body that are released as fatty acids during catabolic conditions. The less abundant brown adipocytes, the defining parenchymal cells of brown adipose tissue (BAT), internalize triglycerides that are stored intracellularly in multilocular lipid droplets. Beige adipocytes (also known as brite or inducible brown adipocytes) are functionally very similar to brown adipocytes and emerge in specific WAT depots in response to various stimuli including sustained cold exposure. The activation of brown and beige adipocytes (together referred to as thermogenic adipocytes) causes both the hydrolysis of stored triglycerides as well as the uptake of lipids and glucose from the circulation. Together, these fuels are combusted for heat production to maintain body temperature in mammals including adult humans. Given that heating by brown and beige adipocytes is a very-well controlled and energy-demanding process which entails pronounced shifts in energy fluxes, it is not surprising that an intensive interplay exists between the various adipocyte types and parenchymal liver cells, and that this influences systemic metabolic fluxes and endocrine networks. In this review we will emphasize the role of hepatic factors that regulate the metabolic activity of white and thermogenic adipocytes. In addition, we will discuss the relevance of lipids and hormones that are secreted by white, brown and beige adipocytes regulating liver metabolism in order to maintain systemic energy metabolism in health and disease.
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Affiliation(s)
- Ludger Scheja
- Department of Biochemistry and Molecular Cell Biology, University Medical Center Hamburg-Eppendorf, Martinistr. 52, 20246 Hamburg, Germany
| | - Joerg Heeren
- Department of Biochemistry and Molecular Cell Biology, University Medical Center Hamburg-Eppendorf, Martinistr. 52, 20246 Hamburg, Germany.
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12
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Parray HA, Yun JW. Proteomic Identification of Target Proteins of Thiodigalactoside in White Adipose Tissue from Diet-Induced Obese Rats. Int J Mol Sci 2015; 16:14441-63. [PMID: 26121299 PMCID: PMC4519851 DOI: 10.3390/ijms160714441] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2015] [Revised: 06/15/2015] [Accepted: 06/18/2015] [Indexed: 12/11/2022] Open
Abstract
Previously, galectin-1 (GAL1) was found to be up-regulated in obesity-prone subjects, suggesting that use of a GAL1 inhibitor could be a novel therapeutic approach for treatment of obesity. We evaluated thiodigalactoside (TDG) as a potent inhibitor of GAL1 and identified target proteins of TDG by performing comparative proteome analysis of white adipose tissue (WAT) from control and TDG-treated rats fed a high fat diet (HFD) using two dimensional gel electrophoresis (2-DE) combined with MALDI-TOF-MS. Thirty-two spots from a total of 356 matched spots showed differential expression between control and TDG-treated rats, as identified by peptide mass fingerprinting. These proteins were categorized into groups such as carbohydrate metabolism, tricarboxylic acid (TCA) cycle, signal transduction, cytoskeletal, and mitochondrial proteins based on functional analysis using Protein Annotation Through Evolutionary Relationship (PANTHER) and Database for Annotation, Visualization, Integrated Discovery (DAVID) classification. One of the most striking findings of this study was significant changes in Carbonic anhydrase 3 (CA3), Voltage-dependent anion channel 1 (VDAC1), phosphatidylethanolamine-binding protein 1 (PEBP1), annexin A2 (ANXA2) and lactate dehydrogenase A chain (LDHA) protein levels between WAT from control and TDG-treated groups. In addition, we confirmed increased expression of thermogenic proteins as well as reduced expression of lipogenic proteins in response to TDG treatment. These results suggest that TDG may effectively prevent obesity, and TDG-responsive proteins can be used as novel target proteins for obesity treatment.
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Affiliation(s)
- Hilal Ahmad Parray
- Department of Biotechnology, Daegu University, Kyungsan, Kyungbuk 712-714, Korea.
| | - Jong Won Yun
- Department of Biotechnology, Daegu University, Kyungsan, Kyungbuk 712-714, Korea.
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13
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Bakshi MV, Azimzadeh O, Barjaktarovic Z, Kempf SJ, Merl-Pham J, Hauck SM, Buratovic S, Eriksson P, Atkinson MJ, Tapio S. Total Body Exposure to Low-Dose Ionizing Radiation Induces Long-Term Alterations to the Liver Proteome of Neonatally Exposed Mice. J Proteome Res 2014; 14:366-73. [DOI: 10.1021/pr500890n] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
| | | | | | | | | | | | - Sonja Buratovic
- Department
of Environmental Toxicology, Uppsala University, 75236 Uppsala, Sweden
| | - Per Eriksson
- Department
of Environmental Toxicology, Uppsala University, 75236 Uppsala, Sweden
| | - Michael J. Atkinson
- Chair
of Radiation Biology, Technical University of Munich, 81675 Munich, Germany
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14
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Abstract
Insulin resistance is a major risk factor for type 2 diabetes. AMP-activated protein kinase (AMPK) is a drug target in the improvement of insulin sensitivity. Several insulin-sensitizing medicines are able to activate AMPK through inhibition of mitochondrial functions. These drugs, such as metformin and STZ, inhibit ATP synthesis in mitochondria to raise AMP/ATP ratio in the process of AMPK activation. However, chemicals that activate AMPK directly or by activating its upstream kinases have not been approved for treatment of type 2 diabetes in humans. In an early study, we reported that berberine inhibited oxygen consumption in mitochondria, and increased AMP/ATP ratio in cells. The observation suggests an indirect mechanism for AMPK activation by berberine. Berberine stimulates glycolysis for ATP production that offsets the cell toxicity after mitochondria inhibition. The study suggests that mitochondrial inhibition is an approach for AMPK activation. In this review article, literature is critically reviewed to interpret the role of mitochondria function in the mechanism of insulin resistance, which supports that mitochondria inhibitors represent a new class of AMPK activator. The inhibitors are promising candidates for insulin sensitizers. This review provides a guideline in search for small molecule AMPK activators in the drug discovery for type 2 diabetes.
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Grassian AR, Metallo CM, Coloff JL, Stephanopoulos G, Brugge JS. Erk regulation of pyruvate dehydrogenase flux through PDK4 modulates cell proliferation. Genes Dev 2011; 25:1716-33. [PMID: 21852536 DOI: 10.1101/gad.16771811] [Citation(s) in RCA: 143] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Loss of extracellular matrix (ECM) attachment leads to metabolic impairments that limit cellular energy production. Characterization of the metabolic alterations induced by ECM detachment revealed a dramatic decrease in uptake of glucose, glutamine, and pyruvate, and a consequent decrease in flux through glycolysis, the pentose phosphate pathway, and the tricarboxylic acid (TCA) cycle. However, flux through pyruvate dehydrogenase (PDH) is disproportionally decreased, concomitant with increased expression of the PDH inhibitory kinase, PDH kinase 4 (PDK4), and increased carbon secretion. Overexpression of ErbB2 maintains PDH flux by suppressing PDK4 expression in an Erk-dependent manner, and Erk signaling also regulates PDH flux in ECM-attached cells. Additionally, epidermal growth factor (EGF), a potent inducer of Erk, positively regulates PDH flux through decreased PDK4 expression. Furthermore, overexpression of PDK4 in ECM-detached cells suppresses the ErbB2-mediated rescue of ATP levels, and in attached cells, PDK4 overexpression decreases PDH flux, de novo lipogenesis, and cell proliferation. Mining of microarray data from human tumor data sets revealed that PDK4 mRNA is commonly down-regulated in tumors compared with their tissues of origin. These results identify a novel mechanism by which ECM attachment, growth factors, and oncogenes modulate the metabolic fate of glucose by controlling PDK4 expression and PDH flux to influence proliferation.
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Affiliation(s)
- Alexandra R Grassian
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA
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