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Wang XH, Price SR. Organ Crosstalk Contributes to Muscle Wasting in Chronic Kidney Disease. Semin Nephrol 2023; 43:151409. [PMID: 37611335 DOI: 10.1016/j.semnephrol.2023.151409] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/25/2023]
Abstract
Muscle wasting (ie, atrophy) is a serious consequence of chronic kidney disease (CKD) that reduces muscle strength and function. It reduces the quality of life for CKD patients and increases the risks of comorbidities and mortality. Current treatment strategies to prevent or reverse skeletal muscle loss are limited owing to the broad and systemic nature of the initiating signals and the multifaceted catabolic mechanisms that accelerate muscle protein degradation and impair protein synthesis and repair pathways. Recent evidence has shown how organs such as muscle, adipose, and kidney communicate with each other through interorgan exchange of proteins and RNAs during CKD. This crosstalk changes cell functions in the recipient organs and represents an added dimension in the complex processes that are responsible for muscle atrophy in CKD. This complexity creates challenges for the development of effective therapies to ameliorate muscle wasting and weakness in patients with CKD.
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Affiliation(s)
- Xiaonan H Wang
- Renal Division, Department of Medicine, Emory University, Atlanta, GA
| | - S Russ Price
- Department of Biochemistry and Molecular Biology, Brody School of Medicine, East Carolina University, Greenville, NC; Department of Internal Medicine, Brody School of Medicine, East Carolina University, Greenville, NC.
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2
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Kim B, Sasaki A, Murphy K, Matthews SG. DNA methylation signatures in human neonatal blood following maternal antenatal corticosteroid treatment. Transl Psychiatry 2022; 12:132. [PMID: 35354798 PMCID: PMC8967826 DOI: 10.1038/s41398-022-01902-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Revised: 03/01/2022] [Accepted: 03/15/2022] [Indexed: 11/09/2022] Open
Abstract
Antenatal corticosteroids (ACS) are used to treat women at risk of preterm birth to improve neonatal survival. Though affected children may be at long-term risk of neurobehavioural disorders, the driving mechanisms remain unknown. Animal studies have shown that ACS exposure can lead to overlapping changes in DNA methylation between the blood and the brain, identifying gene pathways for neurodevelopment, which highlights the potential to examine peripheral blood as a surrogate for inaccessible human brain tissue. We hypothesized that differential methylation will be identified in blood of term-born neonates following ACS. Mother-infant dyads that received ACS were retrospectively identified through the Ontario Birth Study at Sinai Health Complex and matched to untreated controls for maternal age, BMI, parity and foetal sex (n = 14/group). Genome-wide methylation differences were examined at single-nucleotide resolution in DNA extracted from dried bloodspot cards using reduced representative bisulfite sequencing approaches. 505 differentially methylated CpG sites (DMCs) were identified, wherein 231 were hypermethylated and 274 were hypomethylated. These sites were annotated to 219 genes, of which USP48, SH3PXD2A, NTM, CAMK2N2, MAP6D1 were five of the top ten genes with known neurological function. Collectively, the set of hypermethylated genes were enriched for pathways of transcription regulation, while pathways of proteasome activity were enriched among the set of hypomethylated genes. This study is the first to identify DNA methylation changes in human neonatal blood following ACS. Understanding the epigenetic changes that occur in response to ACS will support future investigations to delineate the effects of prenatal glucocorticoid exposure on human development.
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Affiliation(s)
- Bona Kim
- Department of Physiology, University of Toronto, Toronto, ON, Canada. .,Lunenfeld-Tanenbaum Research Institute, Sinai Health System, Toronto, ON, Canada.
| | - Aya Sasaki
- grid.17063.330000 0001 2157 2938Department of Physiology, University of Toronto, Toronto, ON Canada ,grid.250674.20000 0004 0626 6184Lunenfeld-Tanenbaum Research Institute, Sinai Health System, Toronto, ON Canada
| | - Kellie Murphy
- grid.17063.330000 0001 2157 2938Department of Obstetrics & Gynecology, University of Toronto, Toronto, ON Canada
| | - Stephen G. Matthews
- grid.17063.330000 0001 2157 2938Department of Physiology, University of Toronto, Toronto, ON Canada ,grid.250674.20000 0004 0626 6184Lunenfeld-Tanenbaum Research Institute, Sinai Health System, Toronto, ON Canada ,grid.17063.330000 0001 2157 2938Department of Obstetrics & Gynecology, University of Toronto, Toronto, ON Canada
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3
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Wang XH, Mitch WE, Price SR. Pathophysiological mechanisms leading to muscle loss in chronic kidney disease. Nat Rev Nephrol 2022; 18:138-152. [PMID: 34750550 DOI: 10.1038/s41581-021-00498-0] [Citation(s) in RCA: 60] [Impact Index Per Article: 30.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/01/2021] [Indexed: 12/16/2022]
Abstract
Loss of muscle proteins is a deleterious consequence of chronic kidney disease (CKD) that causes a decrease in muscle strength and function, and can lead to a reduction in quality of life and increased risk of morbidity and mortality. The effectiveness of current treatment strategies in preventing or reversing muscle protein losses is limited. The limitations largely stem from the systemic nature of diseases such as CKD, which stimulate skeletal muscle protein degradation pathways while simultaneously activating mechanisms that impair muscle protein synthesis and repair. Stimuli that initiate muscle protein loss include metabolic acidosis, insulin and IGF1 resistance, changes in hormones, cytokines, inflammatory processes and decreased appetite. A growing body of evidence suggests that signalling molecules secreted from muscle can enter the circulation and subsequently interact with recipient organs, including the kidneys, while conversely, pathological events in the kidney can adversely influence protein metabolism in skeletal muscle, demonstrating the existence of crosstalk between kidney and muscle. Together, these signals, whether direct or indirect, induce changes in the levels of regulatory and effector proteins via alterations in mRNAs, microRNAs and chromatin epigenetic responses. Advances in our understanding of the signals and processes that mediate muscle loss in CKD and other muscle wasting conditions will support the future development of therapeutic strategies to reduce muscle loss.
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Affiliation(s)
- Xiaonan H Wang
- Renal Division, Department of Medicine, Emory University, Atlanta, GA, USA
| | - William E Mitch
- Nephrology Division, Department of Medicine, Baylor College of Medicine, Houston, TX, USA
| | - S Russ Price
- Department of Biochemistry and Molecular Biology, Brody School of Medicine, East Carolina University, Greenville, NC, USA. .,Department of Internal Medicine, Brody School of Medicine, East Carolina University, Greenville, NC, USA.
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4
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Zhang L, Chen Q, Chen Z, Wang Y, Gamboa JL, Ikizler TA, Garibotto G, Mitch WE. Mechanisms Regulating Muscle Protein Synthesis in CKD. J Am Soc Nephrol 2020; 31:2573-2587. [PMID: 32764136 DOI: 10.1681/asn.2019121277] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Accepted: 06/21/2020] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND CKD induces loss of muscle proteins partly by suppressing muscle protein synthesis. Muscles of mice with CKD have increased expression of nucleolar protein 66 (NO66), as do muscle biopsy specimens from patients with CKD or those undergoing hemodialysis. Inflammation stimulates NO66 expression and changes in NF-κB mediate the response. METHODS Subtotal nephrectomy created a mouse model of CKD with BUN >80 mg/dl. Crossing NO66flox/flox with MCK-Cre mice bred muscle-specific NO66 (MCK-NO66) knockout mice. Experiments assessed the effect of removing NO66. RESULTS Muscle-specific NO66 knockout in mice blocks CKD-induced loss of muscle mass and improves protein synthesis. NO66 suppression of ribosomal biogenesis via demethylase activity is the mechanism behind these responses. In muscle cells, expression of NO66, but not of demethylase-dead mutant NO66, decreased H3K4me3 and H3K36me3 and suppressed pre-rRNA expression. Knocking out NO66 increased the enrichment of H3K4me3 and H3K36me3 on ribosomal DNA. In primary muscle cells and in muscles of mice without NO66, ribosomal RNA, pre-rRNA, and protein synthesis all increased. CONCLUSIONS CKD suppresses muscle protein synthesis via epigenetic mechanisms that NO66 mediates. Blocking NO66 could suggest strategies that counter CKD-induced abnormal muscle protein catabolism.
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Affiliation(s)
- Liping Zhang
- Nephrology Division, Department of Medicine, Baylor College of Medicine, Houston, Texas
| | - Qin Chen
- Department of Epigenetics and Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Zihong Chen
- Nephrology Division, Department of Medicine, Baylor College of Medicine, Houston, Texas
| | - Ying Wang
- Nephrology Division, Department of Medicine, Baylor College of Medicine, Houston, Texas
| | - Jorge L Gamboa
- Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Talat Alp Ikizler
- Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Giacomo Garibotto
- Nephrology Division, Department of Internal Medicine, Genoa University, Scientific Hospitalization and Treatment Institute Policlinico San Martino Hospital, Genoa, Italy
| | - William E Mitch
- Nephrology Division, Department of Medicine, Baylor College of Medicine, Houston, Texas
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5
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Watson EL, Baker LA, Wilkinson TJ, Gould DW, Graham‐Brown MP, Major RW, Ashford RU, Philp A, Smith AC. Reductions in skeletal muscle mitochondrial mass are not restored following exercise training in patients with chronic kidney disease. FASEB J 2019; 34:1755-1767. [DOI: 10.1096/fj.201901936rr] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Revised: 11/07/2019] [Accepted: 11/08/2019] [Indexed: 12/17/2022]
Affiliation(s)
- Emma L. Watson
- Department of Cardiovascular Sciences University of Leicester Leicester UK
| | - Luke A. Baker
- Department of Health Sciences University of Leicester Leicester UK
| | | | - Douglas W. Gould
- Department of Cardiovascular Sciences University of Leicester Leicester UK
- Intensive Care National Audit and Research Centre London UK
| | - Matthew P.M. Graham‐Brown
- Department of Cardiovascular Sciences University of Leicester Leicester UK
- John Walls Renal Unit University Hospitals of Leicester NHS Trust Leicester UK
- National Centre for Sport and Exercise Medicine School of Sport, Exercise and Health Sciences Loughborough University Loughborough UK
| | - Rupert W. Major
- Department of Health Sciences University of Leicester Leicester UK
- John Walls Renal Unit University Hospitals of Leicester NHS Trust Leicester UK
| | - Robert U. Ashford
- Leicester Orthopaedics University Hospitals of Leicester Leicester UK
- Leicester Cancer Research Centre University of Leicester Leicester UK
| | - Andrew Philp
- Garvan Institute of Medical Research Darlinghurst NSW Australia
- UNSW Medicine UNSW Sydney Sydney NSW Australia
| | - Alice C. Smith
- Department of Health Sciences University of Leicester Leicester UK
- John Walls Renal Unit University Hospitals of Leicester NHS Trust Leicester UK
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Gandhimathi K, Karthi S, Manimaran P, Varalakshmi P, Ashokkumar B. Riboflavin transporter-2 (rft-2) of Caenorhabditis elegans: Adaptive and developmental regulation. J Biosci 2016; 40:257-68. [PMID: 25963255 DOI: 10.1007/s12038-015-9512-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Riboflavin transporters (rft-1 and rft-2), orthologous to human riboflavin transporter-3 (hRVFT-3), are identified and characterized in Caenorhabditis elegans. However, studies pertaining to functional contribution of rft-2 in maintaining body homeostatic riboflavin levels and its regulation are very limited. In this study, the expression pattern of rft-2 at different life stages of C. elegans was studied through real-time PCR, and found to be consistent from larval to adult stages that demonstrate its involvement in maintaining the body homeostatic riboflavin levels at whole animal level all through its life. A possible regulation of rft-2 expression at mRNA levels at whole animal was studied after adaptation to low and high concentrations of riboflavin. Abundance of rft-2 transcript was upregulated in riboflavin-deficient conditions (10 nM), while it was downregulated with riboflavin-supplemented conditions (2 mM) as compared with control (10 meu M). Further, the 5'-regulatory region of the rft-2 gene was cloned, and transgenic nematodes expressing transcriptional rft-2 promoter::GFP fusion constructs were generated. The expression of rft-2 was found to be adaptively regulated in vivo when transgenic worms were maintained under different extracellular riboflavin levels, which was also mediated partly via changes in the rft-2 levels that directs towards the possible involvement of transcriptional regulatory events.
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Affiliation(s)
- Krishnan Gandhimathi
- Department of Genetic Engineering, School of Biotechnology, Madurai Kamaraj University, Madurai 625 021, India
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7
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Implications of a pre-exercise alkalosis-mediated attenuation of HSP72 on its response to a subsequent bout of exercise. Amino Acids 2015; 48:499-504. [PMID: 26433893 DOI: 10.1007/s00726-015-2103-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Accepted: 09/22/2015] [Indexed: 10/23/2022]
Abstract
The aim of this study was to investigate if a pre-exercise alkalosis-mediated attenuation of HSP72 had any effect on the response of the same stress protein after a subsequent exercise. Seven physically active males [25.0 ± 6.5 years, 182.1 ± 6.0 cm, 74.0 ± 8.3 kg, peak aerobic power (PPO) 316 ± 46 W] performed a repeated sprint exercise (EXB1) following a dose of 0.3 g kg(-1) body mass of sodium bicarbonate (BICARB), or a placebo of 0.045 g kg(-1) body mass of sodium chloride (PLAC). Participants then completed a 90-min intermittent cycling protocol (EXB2). Monocyte expressed HSP72 was significantly attenuated after EXB1 in BICARB compared to PLAC, however, there was no difference in the HSP72 response to the subsequent EXB2 between conditions. Furthermore there was no difference between conditions for measures of oxidative stress (protein carbonyl and HSP32). These findings confirm the sensitivity of the HSP72 response to exercise-induced changes in acid-base status in vivo, but suggest that the attenuated response has little effect upon subsequent stress in the same day.
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8
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Hochberg I, Harvey I, Tran QT, Stephenson EJ, Barkan AL, Saltiel AR, Chandler WF, Bridges D. Gene expression changes in subcutaneous adipose tissue due to Cushing's disease. J Mol Endocrinol 2015; 55:81-94. [PMID: 26150553 PMCID: PMC4543687 DOI: 10.1530/jme-15-0119] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 07/06/2015] [Indexed: 01/15/2023]
Abstract
Glucocorticoids have major effects on adipose tissue metabolism. To study tissue mRNA expression changes induced by chronic elevated endogenous glucocorticoids, we performed RNA sequencing on the subcutaneous adipose tissue from patients with Cushing's disease (n=5) compared to patients with nonfunctioning pituitary adenomas (n=11). We found a higher expression of transcripts involved in several metabolic pathways, including lipogenesis, proteolysis and glucose oxidation as well as a decreased expression of transcripts involved in inflammation and protein synthesis. To further study this in a model system, we subjected mice to dexamethasone treatment for 12 weeks and analyzed their inguinal (subcutaneous) fat pads, which led to similar findings. Additionally, mice treated with dexamethasone showed drastic decreases in lean body mass as well as increased fat mass, further supporting the human transcriptomic data. These data provide insight to transcriptional changes that may be responsible for the comorbidities associated with chronic elevations of glucocorticoids.
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Affiliation(s)
- Irit Hochberg
- Institute of EndocrinologyDiabetes and Metabolism, Rambam Health Care Campus, Haifa, IsraelLife Science InstituteUniversity of Michigan, Ann Arbor, MI, USAPhysiologyUTHSC, Memphis, TN, USAPreventive MedicineUTHSC, Memphis, TN, USAInternal MedicineUniversity of Michigan, Ann Arbor, MI USANeurosurgeryUniversity of Michigan, Ann Arbor, MI USAPediatricsUTHSC, Memphis, TN, USA Institute of EndocrinologyDiabetes and Metabolism, Rambam Health Care Campus, Haifa, IsraelLife Science InstituteUniversity of Michigan, Ann Arbor, MI, USAPhysiologyUTHSC, Memphis, TN, USAPreventive MedicineUTHSC, Memphis, TN, USAInternal MedicineUniversity of Michigan, Ann Arbor, MI USANeurosurgeryUniversity of Michigan, Ann Arbor, MI USAPediatricsUTHSC, Memphis, TN, USA
| | - Innocence Harvey
- Institute of EndocrinologyDiabetes and Metabolism, Rambam Health Care Campus, Haifa, IsraelLife Science InstituteUniversity of Michigan, Ann Arbor, MI, USAPhysiologyUTHSC, Memphis, TN, USAPreventive MedicineUTHSC, Memphis, TN, USAInternal MedicineUniversity of Michigan, Ann Arbor, MI USANeurosurgeryUniversity of Michigan, Ann Arbor, MI USAPediatricsUTHSC, Memphis, TN, USA
| | - Quynh T Tran
- Institute of EndocrinologyDiabetes and Metabolism, Rambam Health Care Campus, Haifa, IsraelLife Science InstituteUniversity of Michigan, Ann Arbor, MI, USAPhysiologyUTHSC, Memphis, TN, USAPreventive MedicineUTHSC, Memphis, TN, USAInternal MedicineUniversity of Michigan, Ann Arbor, MI USANeurosurgeryUniversity of Michigan, Ann Arbor, MI USAPediatricsUTHSC, Memphis, TN, USA
| | - Erin J Stephenson
- Institute of EndocrinologyDiabetes and Metabolism, Rambam Health Care Campus, Haifa, IsraelLife Science InstituteUniversity of Michigan, Ann Arbor, MI, USAPhysiologyUTHSC, Memphis, TN, USAPreventive MedicineUTHSC, Memphis, TN, USAInternal MedicineUniversity of Michigan, Ann Arbor, MI USANeurosurgeryUniversity of Michigan, Ann Arbor, MI USAPediatricsUTHSC, Memphis, TN, USA
| | - Ariel L Barkan
- Institute of EndocrinologyDiabetes and Metabolism, Rambam Health Care Campus, Haifa, IsraelLife Science InstituteUniversity of Michigan, Ann Arbor, MI, USAPhysiologyUTHSC, Memphis, TN, USAPreventive MedicineUTHSC, Memphis, TN, USAInternal MedicineUniversity of Michigan, Ann Arbor, MI USANeurosurgeryUniversity of Michigan, Ann Arbor, MI USAPediatricsUTHSC, Memphis, TN, USA
| | - Alan R Saltiel
- Institute of EndocrinologyDiabetes and Metabolism, Rambam Health Care Campus, Haifa, IsraelLife Science InstituteUniversity of Michigan, Ann Arbor, MI, USAPhysiologyUTHSC, Memphis, TN, USAPreventive MedicineUTHSC, Memphis, TN, USAInternal MedicineUniversity of Michigan, Ann Arbor, MI USANeurosurgeryUniversity of Michigan, Ann Arbor, MI USAPediatricsUTHSC, Memphis, TN, USA
| | - William F Chandler
- Institute of EndocrinologyDiabetes and Metabolism, Rambam Health Care Campus, Haifa, IsraelLife Science InstituteUniversity of Michigan, Ann Arbor, MI, USAPhysiologyUTHSC, Memphis, TN, USAPreventive MedicineUTHSC, Memphis, TN, USAInternal MedicineUniversity of Michigan, Ann Arbor, MI USANeurosurgeryUniversity of Michigan, Ann Arbor, MI USAPediatricsUTHSC, Memphis, TN, USA
| | - Dave Bridges
- Institute of EndocrinologyDiabetes and Metabolism, Rambam Health Care Campus, Haifa, IsraelLife Science InstituteUniversity of Michigan, Ann Arbor, MI, USAPhysiologyUTHSC, Memphis, TN, USAPreventive MedicineUTHSC, Memphis, TN, USAInternal MedicineUniversity of Michigan, Ann Arbor, MI USANeurosurgeryUniversity of Michigan, Ann Arbor, MI USAPediatricsUTHSC, Memphis, TN, USA Institute of EndocrinologyDiabetes and Metabolism, Rambam Health Care Campus, Haifa, IsraelLife Science InstituteUniversity of Michigan, Ann Arbor, MI, USAPhysiologyUTHSC, Memphis, TN, USAPreventive MedicineUTHSC, Memphis, TN, USAInternal MedicineUniversity of Michigan, Ann Arbor, MI USANeurosurgeryUniversity of Michigan, Ann Arbor, MI USAPediatricsUTHSC, Memphis, TN, USA Institute of EndocrinologyDiabetes and Metabolism, Rambam Health Care Campus, Haifa, IsraelLife Science InstituteUniversity of Michigan, Ann Arbor, MI, USAPhysiologyUTHSC, Memphis, TN, USAPreventive MedicineUTHSC, Memphis, TN, USAInternal MedicineUniversity of Michigan, Ann Arbor, MI USANeurosurgeryUniversity of Michigan, Ann Arbor, MI USAPediatricsUTHSC, Memphis, TN, USA
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9
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Sala D, Zorzano A. Differential control of muscle mass in type 1 and type 2 diabetes mellitus. Cell Mol Life Sci 2015; 72:3803-17. [PMID: 26091746 PMCID: PMC11113699 DOI: 10.1007/s00018-015-1954-7] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2015] [Revised: 06/04/2015] [Accepted: 06/08/2015] [Indexed: 12/25/2022]
Abstract
Diabetes mellitus--whether driven by insulin deficiency or insulin resistance--causes major alterations in muscle metabolism. These alterations have an impact on nutrient handling, including the metabolism of glucose, lipids, and amino acids, and also on muscle mass and strength. However, the ways in which the distinct forms of diabetes affect muscle mass differ greatly. The most common forms of diabetes mellitus are type 1 and type 2. Thus, whereas type 1 diabetic subjects without insulin treatment display a dramatic loss of muscle, most type 2 diabetic subjects show no changes or even an increase in muscle mass. However, the most commonly used rodent models of type 2 diabetes are characterized by muscle atrophy and do not mimic the features of the disease in humans in terms of muscle mass. In this review, we analyze the processes that are differentially regulated under these forms of diabetes and propose regulatory mechanisms to explain them.
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Affiliation(s)
- David Sala
- Development, Aging and Regeneration Program (DARe), Sanford-Burnham Medical Research Institute, 10901 North Torrey Pines Rd, La Jolla, CA, 92037, USA
| | - Antonio Zorzano
- Institute for Research in Biomedicine (IRB Barcelona), C/Baldiri Reixac 10, 08028, Barcelona, Spain.
- Departament de Bioquímica i Biologia Molecular, Facultat de Biologia, Universitat de Barcelona, Av. Diagonal 645, 08028, Barcelona, Spain.
- CIBER de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Instituto de Salud Carlos III, Madrid, Spain.
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10
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Nakashima K, Ishida A, Ijiri D, Ohtsuka A. Effect of dexamethasone on the expression of atrogin-1/MAFbx in chick skeletal muscle. Anim Sci J 2015; 87:405-10. [DOI: 10.1111/asj.12437] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2014] [Revised: 03/09/2015] [Accepted: 03/13/2015] [Indexed: 11/30/2022]
Affiliation(s)
- Kazuki Nakashima
- Animal Physiology and Nutrition Division; NARO Institute of Livestock and Grassland Science; Tsukuba Japan
| | - Aiko Ishida
- Animal Physiology and Nutrition Division; NARO Institute of Livestock and Grassland Science; Tsukuba Japan
| | - Daichi Ijiri
- Department of Biochemical Science and Technology, Faculty of Agriculture; Kagoshima University; Kagoshima Japan
| | - Akira Ohtsuka
- Department of Biochemical Science and Technology, Faculty of Agriculture; Kagoshima University; Kagoshima Japan
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11
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Stenvinkel P, Carrero JJ, von Walden F, Ikizler TA, Nader GA. Muscle wasting in end-stage renal disease promulgates premature death: established, emerging and potential novel treatment strategies. Nephrol Dial Transplant 2015; 31:1070-7. [PMID: 25910496 DOI: 10.1093/ndt/gfv122] [Citation(s) in RCA: 125] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Accepted: 03/27/2015] [Indexed: 12/15/2022] Open
Abstract
Muscle wasting (or sarcopenia) is a common feature of the uremic phenotype and predisposes this vulnerable patient population to increased risk of comorbid complications, poor quality of life, frailty and premature death. The old age of dialysis patients is in addition a likely contributor to loss of muscle mass. As recent evidence suggests that assessment of muscle strength (i.e. function) is a better predictor of outcome and comorbidities than muscle mass, this opens new screening, assessment and therapeutic opportunities. Among established treatment strategies, the benefit of resistance exercise and endurance training are increasingly recognized among nephrologists as being effective and should be promoted in sedentary chronic kidney disease patients. Testosterone and growth hormone replacement appear as the most promising among emerging treatments strategies for muscle wasting. As treatment of muscle wasting is difficult and seldom successful in this often old, frail, sedentary and exercise-hesitant patient group, novel treatment strategies are urgently needed. In this review, we summarize recent studies on stimulation of mitochondrial biogenesis, myogenic stem (satellite) cells and manipulation of transforming growth factor family members, all of which hold promise for more effective therapies to target muscle mass loss and function in the future.
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Affiliation(s)
- Peter Stenvinkel
- Department of Renal Medicine, CLINTEC, Karolinska Institutet, Stockholm, Sweden
| | - Juan Jesus Carrero
- Department of Renal Medicine, CLINTEC, Karolinska Institutet, Stockholm, Sweden
| | - Ferdinand von Walden
- Department of Women's and Children's Health, Karolinska Institutet, Stockholm, Sweden
| | - T Alp Ikizler
- Division of Nephrology, Vanderbilt University Medical Center, Nashville, USA
| | - Gustavo A Nader
- Department of Kinesiology, The Pennsylvania State University, University Park, USA
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12
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Circulating 20S proteasome is independently associated with abdominal muscle mass in hemodialysis patients. PLoS One 2015; 10:e0121352. [PMID: 25803510 PMCID: PMC4372611 DOI: 10.1371/journal.pone.0121352] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2014] [Accepted: 01/30/2015] [Indexed: 11/29/2022] Open
Abstract
Protein-energy wasting is highly prevalent in hemodialysis patients, and it contributes to patient morbidity and mortality. The ubiquitin-proteasome system is the major pathway for intracellular protein degradation and it is involved in the regulation of basic cellular processes. However, the role of this system in the determination of nutritional status is largely unknown. To examine a relationship between protein-energy wasting and the ubiquitin-proteasome system, a cross-sectional study of 76 hemodialysis patients was performed. Plasma concentrations of 20S proteasome were studied to evaluate its association with muscle and fat mass, which were investigated by abdominal muscle and fat areas measured using computed tomography and by creatinine production estimated using the creatinine kinetic model. Plasma 20S proteasome concentrations significantly and negatively correlated with abdominal muscle areas and creatinine production (rho = -0.263, P < 0.05 and rho = -0.241, P < 0.05, respectively), but not abdominal subcutaneous and visceral fat areas. Multiple regression analyses showed that 20S proteasome was a significant independent predictor of abdominal muscle area (P < 0.05). In conclusion, plasma 20S proteasome concentrations were independently associated with abdominal muscle mass in hemodialysis patients. Our findings indicate a relationship between circulating 20S proteasomes and muscle metabolism in these patients.
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Abstract
In patients with chronic kidney disease (CKD), loss of cellular proteins increases the risks of morbidity and mortality. Persistence of muscle protein catabolism in CKD results in striking losses of muscle proteins as whole-body protein turnover is great; even small but persistent imbalances between protein synthesis and degradation cause substantial protein loss. No reliable methods to prevent CKD-induced muscle wasting currently exist, but mechanisms that control cellular protein turnover have been identified, suggesting that therapeutic strategies will be developed to suppress or block protein loss. Catabolic pathways that cause protein wasting include activation of the ubiquitin-proteasome system (UPS), caspase-3, lysosomes and myostatin (a negative regulator of skeletal muscle growth). These pathways can be initiated by complications associated with CKD, such as metabolic acidosis, defective insulin signalling, inflammation, increased angiotensin II levels, abnormal appetite regulation and impaired microRNA responses. Inflammation stimulates cellular signalling pathways that activate myostatin, which accelerates UPS-mediated catabolism. Blocking this pathway can prevent loss of muscle proteins. Myostatin inhibition could yield new therapeutic directions for blocking muscle protein wasting in CKD or disorders associated with its complications.
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Affiliation(s)
- Xiaonan H Wang
- Renal Division, Department of Medicine, Emory University, 1639 Pierce Drive, WMB 338, Atlanta, GA 30322, USA
| | - William E Mitch
- Nephrology Division, Department of Medicine, Baylor College of Medicine, One Baylor Plaza, ABBR R705, Houston, TX 77030, USA
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Molina PE, Bagby GJ, Nelson S. Biomedical consequences of alcohol use disorders in the HIV-infected host. Curr HIV Res 2014; 12:265-75. [PMID: 25053365 PMCID: PMC4222574 DOI: 10.2174/1570162x12666140721121849] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2013] [Revised: 04/08/2014] [Accepted: 04/08/2014] [Indexed: 02/06/2023]
Abstract
Alcohol abuse is the most common and costly form of drug abuse in the United States. It is well known that alcohol abuse contributes to risky behaviors associated with greater incidence of human immunodeficiency virus (HIV) infections. As HIV has become a more chronic disease since the introduction of antiretroviral therapy, it is expected that alcohol use disorders will have an adverse effect on the health of HIV-infected patients. The biomedical consequences of acute and chronic alcohol abuse are multisystemic. Based on what is currently known of the comorbid and pathophysiological conditions resulting from HIV infection in people with alcohol use disorders, chronic alcohol abuse appears to alter the virus infectivity, the immune response of the host, and the progression of disease and tissue injury, with specific impact on disease progression. The combined insult of alcohol abuse and HIV affects organ systems, including the central nervous system, the immune system, the liver, heart, and lungs, and the musculoskeletal system. Here we outline the major pathological consequences of alcohol abuse in the HIV-infected individual, emphasizing its impact on immunomodulation, erosion of lean body mass associated with AIDS wasting, and lipodystrophy. We conclude that interventions focused on reducing or avoiding alcohol abuse are likely to be important in decreasing morbidity and improving outcomes in people living with HIV/AIDS.
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Affiliation(s)
| | | | - Steve Nelson
- LSUHSC Physiology, 1901 Perdido St., New Orleans, LA 70112, USA.
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15
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Muscle wasting in hemodialysis patients: new therapeutic strategies for resolving an old problem. ScientificWorldJournal 2013; 2013:643954. [PMID: 24382946 PMCID: PMC3870868 DOI: 10.1155/2013/643954] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2013] [Accepted: 10/28/2013] [Indexed: 01/01/2023] Open
Abstract
Muscle wasting has long been recognized as a major clinical problem in hemodialysis (HD) patients. In addition to its impact on quality of life, muscle wasting has been proven to be associated with increased mortality rates. Identification of the molecular mechanisms underlying muscle wasting in HD patients provides opportunities to resolve this clinical problem. Several signaling pathways and humeral factors have been reported to be involved in the pathogenic mechanisms of muscle wasting in HD patients, including ubiquitin-proteasome system, caspase-3, insulin/insulin-like growth factor-1 (IGF-1) signaling, endogenous glucocorticoids, metabolic acidosis, inflammation, and sex hormones. Targeting the aforementioned crucial signaling and molecules to suppress protein degradation and augment muscle strength has been extensively investigated in HD patients. In addition to exercise training, administration of megestrol acetate has been proven to be effective in improving anorexia and muscle wasting in HD patients. Correction of metabolic acidosis through sodium bicarbonate supplements can decrease muscle protein degradation and hormone therapy with nandrolone decanoate has been reported to increase muscle mass. Although thiazolidinedione has been shown to improve insulin sensitivity, its role in the treatment of muscle wasting remains unclear. This review paper focuses on the molecular pathways and potential new therapeutic approaches to muscle wasting in HD patients.
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16
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Interferon-γ causes cardiac myocyte atrophy via selective degradation of myosin heavy chain in a model of chronic myocarditis. THE AMERICAN JOURNAL OF PATHOLOGY 2012; 181:2038-46. [PMID: 23058369 DOI: 10.1016/j.ajpath.2012.08.040] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2012] [Revised: 08/09/2012] [Accepted: 08/30/2012] [Indexed: 11/23/2022]
Abstract
Interferon-γ (IFN-γ), a proinflammatory cytokine, has been implicated in the pathogenesis of a number of forms of heart disease including myocarditis and congestive heart failure. In fact, overexpression of IFN-γ in mice causes dilated cardiomyopathy. However, the direct effects of IFN-γ on cardiac myocytes and the mechanism by which it causes cardiac dysfunction have not been described. Here, we present the molecular pathology of IFN-γ exposure and its effect on myofibrillar proteins in isolated neonatal rat ventricular myocytes. Treatment with IFN-γ caused cardiac myocyte atrophy attributable to a specific decrease in myosin heavy chain protein. This selective degradation of myosin heavy chain was not accompanied by a decrease in total protein synthesis or by an increase in total protein degradation. IFN-γ increased both proteasome and immunoproteasome activity in cardiac myocytes and their inhibition blocked myosin heavy chain loss and myocyte atrophy, whereas inhibition of the lysosome or autophagosome did not. Collectively, these results provide a mechanism by which IFN-γ causes cardiac pathology in the setting of chronic inflammatory diseases.
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17
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Significance of the adrenal and sympathetic response to burn injury. TOTAL BURN CARE 2012. [DOI: 10.1016/b978-1-4377-2786-9.00024-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
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18
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Rodela TM, Esbaugh AJ, McDonald MD, Gilmour KM, Walsh PJ. Evidence for transcriptional regulation of the urea transporter in the gill of the Gulf toadfish, Opsanus beta. Comp Biochem Physiol B Biochem Mol Biol 2011; 160:72-80. [PMID: 21740977 DOI: 10.1016/j.cbpb.2011.06.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2011] [Revised: 06/24/2011] [Accepted: 06/24/2011] [Indexed: 02/01/2023]
Abstract
Ureotelic Gulf toadfish (Opsanus beta) do not excrete urea continuously; instead, urea is accumulated internally until a branchial urea transport mechanism is activated to facilitate the excretion of urea in distinct pulses. This unusual pulsatile urea excretion pattern is regulated, in part, by permissive declines in circulating cortisol concentrations. The current study examined toadfish urea transporter (tUT) and glucocorticoid receptor (GR) transcript levels in toadfish gill following chronic (days) and acute (hours) changes in corticosteroid activity. Experimentally lowering circulating cortisol did not significantly alter tUT mRNA abundance but increased GR mRNA. On an acute timescale, a 6.2-fold upregulation of tUT mRNA occurred 12 to 18 h following a urea pulse event with no change in GR mRNA. In silico analysis of an isolated 1.2 kb fragment, upstream promoter region of the tUT gene, revealed 6 putative glucocorticoid response element (GRE) half sites. In vivo reporter assays of the tUT promoter fragment demonstrated relative luciferase activity was enhanced 3.4- and 9.8-fold following exposure to moderate (via a 48 h crowding stress) and high (via infusion for 48 h) cortisol. We conclude that a GRE-mediated upregulation of mRNA may be required to maintain tUT activity by offsetting post-transcriptional and/or post-translational changes that may be associated with chronically elevated plasma cortisol.
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Affiliation(s)
- Tamara M Rodela
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada.
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19
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Protein and Amino Acid Supplementation Does Not Alter Proteolytic Gene Expression following Immobilization. J Nutr Metab 2011; 2011:539690. [PMID: 21845220 PMCID: PMC3153915 DOI: 10.1155/2011/539690] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2010] [Revised: 01/28/2011] [Accepted: 06/13/2011] [Indexed: 01/23/2023] Open
Abstract
Objective. To determine if supplementation of protein and amino acids (PAA) decreases skeletal muscle expression of atrophy-related genes, muscle mass, and strength during immobilization in humans. Methods. Twenty males wore a lower-limb immobilization boot for 28 days and consumed either a PAA supplement (28 g protein) or carbohydrate placebo (28 g maltodextrose), while consuming their normal daily diet. Testing sessions included dietary analysis, lower-leg girth and body composition measurements, strength testing, and gastrocnemius muscle biopsies. Muscle was analyzed for mRNA expression of markers in the ubiquitin and calpain systems, myostatin, TNF-α, and NF-κB. Results. All genes of interest increased over time (P < .05), but there was no difference between groups. Lower-leg girth decreased over time (P = 0.02); however, there were no significant changes in body composition or strength. Conclusion. Short-term lower-limb disuse, despite the absence of significant muscle atrophy, is associated with increases in skeletal muscle gene expression of several proteolysis-related genes. These changes do not appear to be altered by oral PAA supplementation.
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20
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Baehr LM, Furlow JD, Bodine SC. Muscle sparing in muscle RING finger 1 null mice: response to synthetic glucocorticoids. J Physiol 2011; 589:4759-76. [PMID: 21807613 DOI: 10.1113/jphysiol.2011.212845] [Citation(s) in RCA: 154] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Skeletal muscle atrophy occurs under a variety of conditions and can result from alterations in both protein synthesis and protein degradation. The muscle-specific E3 ubiquitin ligases, MuRF1 and MAFbx, are excellent markers of muscle atrophy and increase under divergent atrophy-inducing conditions such as denervation and glucocorticoid treatment. While deletion of MuRF1 or MAFbx has been reported to spare muscle mass following 14 days of denervation, their role in other atrophy-inducing conditions is unclear. The goal of this study was to determine whether deletion of MuRF1 or MAFbx attenuates muscle atrophy after 2 weeks of treatment with the synthetic glucocorticoid dexamethasone (DEX). The response of the triceps surae (TS) and tibialis anterior (TA) muscles to 14 days of DEX treatment (3 mg kg(-1) day(-1)) was examined in 4 month-old male and female wild type (WT) and MuRF1 or MAFbx knock out (KO) mice. Following 14 days of DEX treatment, muscle wet weight was significantly decreased in the TS and TA of WT mice. Comparison of WT and KO mice following DEX treatment revealed significant sparing of mass in both sexes of the MuRF1 KO mice, but no muscle sparing in MAFbx KO mice. Further analysis of the MuRF1 KO mice showed significant sparing of fibre cross-sectional area and tension output in the gastrocnemius (GA) after DEX treatment. Muscle sparing in the MuRF1 KO mice was related to maintenance of protein synthesis, with no observed increases in protein degradation in either WT or MuRF1 KO mice. These results demonstrate that MuRF1 and MAFbx do not function similarly under all atrophy models, and that the primary role of MuRF1 may extend beyond controlling protein degradation via the ubiquitin proteasome system.
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Affiliation(s)
- Leslie M Baehr
- Department of Neurobiology, Physiology, and Behavior, University of California-Davis, One Shields Avenue, Davis, CA 95616, USA
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21
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Wing SS, Lecker SH, Jagoe RT. Proteolysis in illness-associated skeletal muscle atrophy: from pathways to networks. Crit Rev Clin Lab Sci 2011; 48:49-70. [PMID: 21699435 DOI: 10.3109/10408363.2011.586171] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Improvements in health in the past decades have resulted in increased numbers of the elderly in both developed and developing regions of the world. Advances in therapy have also increased the prevalence of patients with chronic and degenerative diseases. Muscle wasting, a feature of most chronic diseases, is prominent in the elderly and contributes to both morbidity and mortality. A major research goal has been to identify the proteolytic system(s) that is responsible for the degradation of proteins that occurs in muscle atrophy. Findings over the past 20 years have clearly confirmed an important role of the ubiquitin proteasome system in mediating muscle proteolysis, particularly that of myofibrillar proteins. However, recent observations have provided evidence that autophagy, calpains and caspases also contribute to the turnover of muscle proteins in catabolic states, and furthermore, that these diverse proteolytic systems interact with each other at various levels. Importantly, a number of intracellular signaling pathways such as the IGF1/AKT, myostatin/Smad, PGC1, cytokine/NFκB, and AMPK pathways are now known to interact and can regulate some of these proteolytic systems in a coordinated manner. A number of loss of function studies have identified promising therapeutic approaches to the prevention and treatment of wasting. However, additional biomarkers and other approaches to improve early identification of patients who would benefit from such treatment need to be developed. The current data suggests a network of interacting proteolytic and signaling pathways in muscle. Future studies are needed to improve understanding of the nature and control of these interactions and how they work to preserve muscle function under various states of growth and atrophy.
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Affiliation(s)
- Simon S Wing
- Departments of Medicine, McGill University and McGill University Health Centre Research Institute, Montreal, Quebec, Canada.
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22
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Price SR, Gooch JL, Donaldson SK, Roberts-Wilson TK. Muscle atrophy in chronic kidney disease results from abnormalities in insulin signaling. J Ren Nutr 2011; 20:S24-8. [PMID: 20797566 DOI: 10.1053/j.jrn.2010.05.007] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Muscle atrophy is a significant consequence of chronic kidney disease that increases a patient's risk of mortality and decreases their quality of life. The loss of lean body mass results, in part, from an increase in the rate of muscle protein degradation. In this review, the proteolytic systems that are activated during chronic kidney disease and the key insulin signaling pathways that regulate the protein degradative processes are described.
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Affiliation(s)
- S Russ Price
- Renal Division, School of Medicine, Emory University, Atlanta, Georgia 30322, USA.
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23
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Kraut JA, Madias NE. Consequences and therapy of the metabolic acidosis of chronic kidney disease. Pediatr Nephrol 2011; 26:19-28. [PMID: 20526632 PMCID: PMC2991191 DOI: 10.1007/s00467-010-1564-4] [Citation(s) in RCA: 105] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/26/2010] [Revised: 04/22/2010] [Accepted: 05/04/2010] [Indexed: 01/18/2023]
Abstract
Metabolic acidosis is common in patients with chronic kidney disease (CKD), particularly once the glomerular filtration rate (GFR) falls below 25 ml/min/1.73 m(2). It is usually mild to moderate in magnitude with the serum bicarbonate concentration ([HCO(3)(-)]) ranging from 12 to 23 mEq/l. Even so, it can have substantial adverse effects, including development or exacerbation of bone disease, growth retardation in children, increased muscle degradation with muscle wasting, reduced albumin synthesis with a predisposition to hypoalbuminemia, resistance to the effects of insulin with impaired glucose tolerance, acceleration of the progression of CKD, stimulation of inflammation, and augmentation of β(2)-microglobulin production. Also, its presence is associated with increased mortality. The administration of base to patients prior to or after initiation of dialysis leads to improvement in many of these adverse effects. The present recommendation by the National Kidney Foundation Kidney Disease Outcomes Quality Initiative (NKF KDOQI) is to raise serum [HCO(3)(-)] to ≥ 22 mEq/l, whereas Caring for Australians with Renal Impairment (CARI) recommends raising serum [HCO(3)(-)] to >22 mEq/l. Base administration can potentially contribute to volume overload and exacerbation of hypertension as well as to metastatic calcium precipitation in tissues. However, sodium retention is less when given as sodium bicarbonate and sodium chloride intake is concomitantly restricted. Results from various studies suggest that enhanced metastatic calcification is unlikely with the pH values achieved during conservative base administration, but the clinician should be careful not to raise serum [HCO(3)(-)] to values outside the normal range.
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Affiliation(s)
- Jeffrey A. Kraut
- Medical and Research Services, VHAGLA Healthcare System, UCLA Membrane Biology Laboratory, Los Angeles, CA USA ,Division of Nephrology, VHAGLA Healthcare System, Los Angeles, USA ,David Geffen School of Medicine, Los Angeles, CA USA
| | - Nicolaos E. Madias
- Division of Nephrology, Department of Medicine, St. Elizabeth’s Medical Center, 736 Cambridge St., Boston, MA 02135 USA ,Department of Medicine, Tufts University School of Medicine, Boston, MA USA
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24
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Zheng B, Ohkawa S, Li H, Roberts-Wilson TK, Price SR. FOXO3a mediates signaling crosstalk that coordinates ubiquitin and atrogin-1/MAFbx expression during glucocorticoid-induced skeletal muscle atrophy. FASEB J 2010; 24:2660-9. [PMID: 20371624 DOI: 10.1096/fj.09-151480] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Muscle atrophy is a consequence of chronic diseases (e.g., diabetes) and glucocorticoid-induced insulin resistance that results from enhanced activity of the ubiquitin-proteasome pathway. The PI3K/Akt pathway inhibits the FOXO-mediated transcription of the muscle-specific E3 ligase atrogin-1/MAFbx (AT-1), whereas the MEK/ERK pathway increases Sp1 activity and ubiquitin (UbC) expression. The observations raise a question about how the transcription of these atrogenes is synchronized in atrophic muscle. We tested a signaling model in which FOXO3a mediates crosstalk between the PI3K/Akt and MEK/ERK pathways to coordinate AT-1 and UbC expression. In rat L6 myotubes, dexamethasone (> or = 24 h) reduced insulin receptor substrate (IRS)-1 protein and PI3K/Akt signaling and increased AT-1 mRNA. IRS-2 protein, MEK/ERK signaling, Sp1 phosphorylation, and UbC transcription were simultaneously increased. Knockdown of IRS-1 using small interfering RNA or adenovirus-mediated expression of constitutively activated FOXO3a increased IRS-2 protein, MEK/ERK signaling, and UbC expression. Changes in PI3K/Akt and MEK/ERK signaling were recapitulated in rat muscles undergoing atrophy due to streptozotocin-induced insulin deficiency and concurrently elevated glucocorticoid production. IRS-1 and Akt phosphorylation were decreased, whereas MEK/ERK signaling and expression of IRS-2, UbC and AT-1 were increased. We conclude that FOXO3a mediates a reciprocal communication between the IRS-1/PI3K/Akt and IRS-2/MEK/ERK pathways that coordinates AT-1 and ubiquitin expression during muscle atrophy.
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Affiliation(s)
- Bin Zheng
- Renal Division, Emory University School of Medicine, Atlanta, GA 30322, USA
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25
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Eaton DC, Malik B, Bao HF, Yu L, Jain L. Regulation of epithelial sodium channel trafficking by ubiquitination. PROCEEDINGS OF THE AMERICAN THORACIC SOCIETY 2010; 7:54-64. [PMID: 20160149 PMCID: PMC3137150 DOI: 10.1513/pats.200909-096js] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2009] [Accepted: 11/02/2009] [Indexed: 01/13/2023]
Abstract
Amiloride-sensitive epithelial sodium (Na(+)) channels (ENaC) play a crucial role in Na(+) transport and fluid reabsorption in the kidney, lung, and colon. The magnitude of ENaC-mediated Na(+) transport in epithelial cells depends on the average open probability of the channels and the number of channels on the apical surface of epithelial cells. The number of channels in the apical membrane, in turn, depends upon a balance between the rate of ENaC insertion and the rate of removal from the apical membrane. ENaC is made up of three homologous subunits, alpha, beta, and gamma. The C-terminal domain of all three subunits is intracellular and contains a proline rich motif (PPxY). Mutations or deletion of this PPxY motif in the beta and gamma subunits prevent the binding of one isoform of a specific ubiquitin ligase, neural precursor cell expressed developmentally down-regulated protein (Nedd4-2) to the channel in vitro and in transfected cell systems, thereby impeding ubiquitin conjugation of the channel subunits. Ubiquitin conjugation would seem to imply that ENaC turnover is determined by the ubiquitin-proteasome system, but when MDCK cells are transfected with ENaC, ubiquitin conjugation apparently leads to lysosomal degradation. However, in untransfected epithelial cells (A6) expressing endogenous ENaC, ENaC appears to be degraded by the ubiquitin-proteasome system. Nonetheless, in both transfected and untransfected cells, the rate of ENaC degradation is apparently controlled by the rate of Nedd4-2-mediated ENaC ubiquitination. Controlling the rate of degradation is apparently important enough to have multiple, redundant pathways to control Nedd4-2 and ENaC ubiquitination.
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Affiliation(s)
- Douglas C Eaton
- Department of Physiology, Whitehead Biomedical Research Building, 615 Micheal Street, Suite 601, Atlanta, GA 30322, USA.
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26
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Lecker SH. Given the Science on Malnutrition, How Does the Clinician Respond? Practical Lessons for and Application to the Dialysis Patient. Clin J Am Soc Nephrol 2009; 4 Suppl 1:S64-70. [DOI: 10.2215/cjn.02650409] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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27
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Frassetto LA, Hsu CY. Metabolic Acidosis and Progression of Chronic Kidney Disease. J Am Soc Nephrol 2009; 20:1869-70. [DOI: 10.1681/asn.2009070710] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
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28
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Chiu YW, Kopple JD, Mehrotra R. Correction of Metabolic Acidosis to Ameliorate Wasting in Chronic Kidney Disease: Goals and Strategies. Semin Nephrol 2009; 29:67-74. [DOI: 10.1016/j.semnephrol.2008.10.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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29
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Critical illness myopathy: sepsis-mediated failure of the peripheral nervous system. Eur J Anaesthesiol 2008; 42:73-82. [PMID: 18289421 DOI: 10.1017/s0265021507003262] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
With better survival of critically ill patients, 'de novo' arising neuromuscular complications like critical illness myopathy or polyneuropathy have been increasingly observed. Prolonged hospitalization not only imposes risks like pneumonia or thrombosis on patients but also represents a real budget threat to modern intensive-care medicine. Clinical symptoms like muscle weakness and weaning failure are common to critical illness myopathy and critical illness polyneuropathy and do not allow for distinction. Specific therapies are not yet available, and the quest for the pathomechanisms has proved more complicated than anticipated. Especially for critical illness myopathy, multiple sites of disturbances to the excitation-contraction coupling cascade are possible causes of muscle weakness. The present review summarizes the epidemiological, clinical and diagnostic features of critical illness myopathy and then focuses on current concepts of the presumed pathomechanisms of critical illness myopathy. Sepsis was shown to be a major cause of critical illness myopathy and special emphasis will be placed on how sepsis and inflammatory mediators influence (i) the membrane excitability at the level of voltage-gated ion channels and (ii) the intracellular protein signalling that results in selective loss of myosin protein content and muscle wasting. For (i), critical illness myopathy represents a new type of acquired channelopathy affecting the inactivation properties of Na+ channels. For (ii), both protein proteolysis and protein build up at the transcriptional level seem to be involved. Findings from different studies are put into a common context to propose a model for cytokine-mediated failure of muscle in severe sepsis. This can open a series of new possible trials to test specific therapeutic strategies in the future.
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30
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Rajan V, Mitch WE. Ubiquitin, proteasomes and proteolytic mechanisms activated by kidney disease. Biochim Biophys Acta Mol Basis Dis 2008; 1782:795-9. [PMID: 18723090 DOI: 10.1016/j.bbadis.2008.07.007] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2008] [Revised: 07/27/2008] [Accepted: 07/30/2008] [Indexed: 01/08/2023]
Abstract
The ubiquitin-proteasome system (UPS) includes 3 enzymes that conjugate ubiquitin to intracellular proteins that are then recognized and degraded in the proteasome. The process participates in the regulation of cell metabolism. In the kidney, the UPS regulates the turnover of transporters and signaling proteins and its activity is down regulated in acidosis-induced proximal tubular cell hypertrophy. In chronic kidney disease (CKD), muscle wasting occurs because complications of CKD including acidosis, insulin resistance, inflammation, and increased angiotensin II levels stimulate the UPS to degrade muscle proteins. This response also includes caspase-3 and calpains which act to cleave muscle proteins to provide substrates for the UPS. For example, caspase-3 degrades actomyosin, leaving a 14 kDa fragment of actin in muscle. The 14 kDa actin fragment is increased in muscle of patient with kidney disease, burn injury and surgery. In addition, acidosis, insulin resistance, inflammation and angiotensin II stimulate glucocorticoid production. Glucocorticoids are also required for the muscle wasting that occurs in CKD. Thus, the UPS is involved in regulating kidney function and participates in highly organized responses that degrade muscle protein in response to loss of kidney function.
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Affiliation(s)
- Vik Rajan
- Nephrology Division, M/S: BCM 285 Baylor College of Medicine, One Baylor Plaza, Alkek N-520 Houston, TX 77030, USA
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31
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Rajan VR, Mitch WE. Muscle wasting in chronic kidney disease: the role of the ubiquitin proteasome system and its clinical impact. Pediatr Nephrol 2008; 23:527-35. [PMID: 17987322 PMCID: PMC2259254 DOI: 10.1007/s00467-007-0594-z] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/07/2007] [Revised: 06/13/2007] [Accepted: 06/14/2007] [Indexed: 02/06/2023]
Abstract
Muscle wasting in chronic kidney disease (CKD) and other catabolic diseases (e.g. sepsis, diabetes, cancer) can occur despite adequate nutritional intake. It is now known that complications of these various disorders, including acidosis, insulin resistance, inflammation, and increased glucocorticoid and angiotensin II production, all activate the ubiquitin-proteasome system (UPS) to degrade muscle proteins. The initial step in this process is activation of caspase-3 to cleave the myofibril into its components (actin, myosin, troponin, and tropomyosin). Caspase-3 is required because the UPS minimally degrades the myofibril but rapidly degrades its component proteins. Caspase-3 activity is easily detected because it leaves a characteristic 14kD actin fragment in muscle samples. Preliminary evidence from several experimental models of catabolic diseases, as well as from studies in patients, indicates that this fragment could be a useful biomarker because it correlates well with the degree of muscle degradation in dialysis patients and in other catabolic conditions.
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Affiliation(s)
- Vik R. Rajan
- Nephrology Division M/S: BCM 285, Baylor College of Medicine, One Baylor, Plaza, Alkek N-520, Houston, TX 77030 USA
| | - William E. Mitch
- Nephrology Division M/S: BCM 285, Baylor College of Medicine, One Baylor, Plaza, Alkek N-520, Houston, TX 77030 USA
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32
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Menconi M, Fareed M, O'Neal P, Poylin V, Wei W, Hasselgren PO. Role of glucocorticoids in the molecular regulation of muscle wasting. Crit Care Med 2007; 35:S602-8. [PMID: 17713416 DOI: 10.1097/01.ccm.0000279194.11328.77] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
OBJECTIVE To review glucocorticoid-regulated molecular mechanisms of muscle wasting. DESIGN Review of recent literature describing the role of glucocorticoids in the regulation of proteolytic mechanisms, transcription factors, and nuclear cofactors in skeletal muscle during various catabolic conditions. MAIN RESULTS Catabolic doses of glucocorticoids induce muscle atrophy both in vivo and in vitro by stimulating protein breakdown and inhibiting protein synthesis. Signaling pathways that regulate muscle protein synthesis at the translational level are inhibited by glucocorticoids. Glucocorticoids increase the expression and activity of the ubiquitin-proteasome pathway, a major proteolytic mechanism of muscle atrophy. The expression and activity of muscle wasting-related transcription factors, including C/EBPbeta and delta and Forkhead box O 1, 3, and 4, as well as the nuclear cofactor p300, are up-regulated by glucocorticoid excess. CONCLUSIONS Muscle wasting in various catabolic conditions is, at least in part, regulated by glucocorticoids. The role of glucocorticoids in muscle wasting is complex and reflects regulation at the molecular level of multiple mechanisms influencing both synthesis and degradation of muscle proteins.
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Affiliation(s)
- Michael Menconi
- Department of Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
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33
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Hirschberg R, Maroni BJ. Protein and Energy Metabolism in Acute Renal Failure. Semin Dial 2007. [DOI: 10.1111/j.1525-139x.1997.tb00859.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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De Blaauw I, Deutz NE, Von Meyenfeldt MF. Metabolic changes in cancer cachexia--first of two parts. Clin Nutr 2007; 16:169-76. [PMID: 16844595 DOI: 10.1016/s0261-5614(97)80002-7] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/1997] [Accepted: 06/17/1997] [Indexed: 11/24/2022]
Affiliation(s)
- I De Blaauw
- Department of Surgery, Fac II, Maastricht University, Maastricht, The Netherlands
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Marinovic AC, Zheng B, Mitch WE, Price SR. Tissue-specific regulation of ubiquitin (UbC) transcription by glucocorticoids: in vivo and in vitro analyses. Am J Physiol Renal Physiol 2007; 292:F660-6. [PMID: 16954342 DOI: 10.1152/ajprenal.00178.2006] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In uremia, muscle wasting involves increased glucocorticoid production and activation of the ubiquitin-proteasome proteolytic pathway, including increased expression of ubiquitin. Previously, we reported that glucocorticoids stimulate ubiquitin transcription by a mechanism involving Sp1 in L6 muscle cells (Marinovic AC, Zheng B, Mitch WE, Price SR. J Biol Chem 277: 16673–16681, 2002). This finding was surprising because Sp1 is a general transcriptional activator. To better understand the mechanism of glucocorticoid-induced ubiquitin ( UbC) gene transcription, we examined whether this response occurs in many organs or uniquely in skeletal muscle. Glucocorticoid-responsive cells of different organs were transfected with a human UbC promoter-luciferase reporter plasmid; dexamethasone stimulated UbC reporter activity 220% ( P < 0.05) in L6 skeletal muscle cells but not in HepG2 hepatocytes, NRK kidney cells, CaCo-2 colon cells, or H9c2 cardiomyocytes. Transactivation of the Sp1-responsive SV40 viral promoter was also increased in muscle but not in other nonmuscle cells. The muscle-specific nature of the UbC response was confirmed in vivo in rats with insulin deficiency, a condition associated with high glucocorticoid production: UbC mRNA was elevated in skeletal muscle but not in liver, kidney, intestine, or heart. Electrophoretic mobility shift assays and in vivo genomic footprinting demonstrated that insulin deficiency increased Sp1 binding to GC-rich elements in the UbC promoter. Thus glucocorticoids increase UbC transcription by a mechanism involving Sp1 that is unique to muscle.
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Jones SB, Muthu K, Shankar R, Gamelli RL. Significance of the adrenal and sympathetic response to burn injury. TOTAL BURN CARE 2007:343-360. [DOI: 10.1016/b978-1-4160-3274-8.50028-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
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Mitch WE. Proteolytic mechanisms, not malnutrition, cause loss of muscle mass in kidney failure. J Ren Nutr 2006; 16:208-11. [PMID: 16825021 DOI: 10.1053/j.jrn.2006.04.014] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Hypoalbuminemia and muscle atrophy are frequently found in patients with chronic kidney disease (CKD) and patients being treated by dialysis. These abnormalities are usually attributed to malnutrition, meaning that they are caused by an inadequate diet. However, the evidence indicates that malnutrition is rarely the mechanism causing loss of protein stores. Instead, low values of serum albumin are closely related to the presence of inflammation and loss of muscle mass is attributable to activation of specific proteases. In uremic rodents and patients, the initial step in the loss of muscle protein is an activation of caspase-3. This cleaves the complex structure of muscle, and its action can be detected by the presence of a characteristic 14-kDa actin fragment in the insoluble fraction of muscle. The second step in uremia-induced loss of muscle protein is an activation of the ubiquitin-proteasome system, which rapidly degrades proteins released by caspase-3 cleavage of muscle proteins. Activation of both caspase-3 and the ubiquitin-proteasome system occur when there is suppression of the cellular signaling pathway activated by insulin/insulinlike growth factor 1, the phosphatidylinositol 3-kinase/Akt pathway. A potential therapeutic target for preventing loss of muscle protein is to stimulate activity of this signaling pathway.
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Affiliation(s)
- William E Mitch
- Nephrology Division, Baylor College of Medicine, Houston, TX 77030, USA.
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Yang H, Wei W, Menconi M, Hasselgren PO. Dexamethasone-induced protein degradation in cultured myotubes is p300/HAT dependent. Am J Physiol Regul Integr Comp Physiol 2006; 292:R337-4. [PMID: 16973938 DOI: 10.1152/ajpregu.00230.2006] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Muscle proteolysis during sepsis and other catabolic conditions is, at least in part, regulated by glucocorticoids. Dexamethasone-treated myotubes are a commonly used in vitro model of muscle wasting. We reported recently that treatment of cultured L6 myotubes with dexamethasone resulted in increased gene and protein expression of the nuclear cofactor p300 but it is not known whether glucocorticoids upregulate p300 histone acetyl transferase (HAT) activity in muscle and whether p300/HAT activity regulates glucocorticoid-induced muscle proteolysis. Here, we found that treatment of cultured L6 myotubes with dexamethasone resulted in increased nuclear p300/HAT activity. Treatment of myotubes with p300 siRNA or transfection of muscle cells with a plasmid expressing p300 that was mutated in its HAT activity domain blocked the dexamethasone-induced increase in protein degradation, supporting a role of p300/HAT in glucocorticoid-induced muscle proteolysis. In addition to increased HAT activity, treatment of the myotubes with dexamethasone resulted in reduced nuclear expression and activity of histone deacetylases (HDACs) 3 and 6. When myotubes were treated with the HDAC inhibitor trichostatin A, protein degradation increased to the same degree as in dexamethasone-treated myotubes. The results suggest that glucocorticoids increase HAT and decrease HDAC activities in muscle, changes that both favor hyperacetylation. The results also provide evidence that dexamethasone-induced protein degradation in cultured myotubes is, at least in part, regulated by p300/HAT activity.
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Affiliation(s)
- Hongmei Yang
- Department of Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA
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Wang X, Hu Z, Hu J, Du J, Mitch WE. Insulin resistance accelerates muscle protein degradation: Activation of the ubiquitin-proteasome pathway by defects in muscle cell signaling. Endocrinology 2006; 147:4160-8. [PMID: 16777975 DOI: 10.1210/en.2006-0251] [Citation(s) in RCA: 418] [Impact Index Per Article: 23.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Conditions such as acidosis, uremia, and sepsis are characterized by insulin resistance and muscle wasting, but whether the insulin resistance associated with these disorders contributes to muscle atrophy is unclear. We examined this question in db/db mice with increased blood glucose despite high levels of plasma insulin. Compared with control littermate mice, the weights of different muscles in db/db mice and the cross-sectional areas of muscles were smaller. In muscle of db/db mice, protein degradation and activities of the major proteolytic systems, caspase-3 and the proteasome, were increased. We examined signals that could activate muscle proteolysis and found low values of both phosphatidylinositol 3 kinase (PI3K) activity and phosphorylated Akt that were related to phosphorylation of serine 307 of insulin receptor substrate-1. To assess how changes in circulating insulin and glucose affect muscle protein, we treated db/db mice with rosiglitazone. Rosiglitazone improved indices of insulin resistance and abnormalities in PI3K/Akt signaling and decreased activities of caspase-3 and the proteasome in muscle leading to suppression of proteolysis. Underlying mechanisms of proteolysis include increased glucocorticoid production, decreased circulating adiponectin, and phosphorylation of the forkhead transcription factor associated with increased expression of the E3 ubiquitin-conjugating enzymes atrogin-1/MAFbx and MuRF1. These abnormalities were also corrected by rosiglitazone. Thus, insulin resistance causes muscle wasting by mechanisms that involve suppression of PI3K/Akt signaling leading to activation of caspase-3 and the ubiquitin-proteasome proteolytic pathway causing muscle protein degradation.
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Affiliation(s)
- Xiaonan Wang
- Renal Division, WMB 338, Emory University School of Medicine, M/S 1930/001/1AG, 1639 Pierce Drive, Atlanta, Georgia 30322, USA.
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40
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Löfberg E, Gutierrez A, Anderstam B, Wernerman J, Bergström J, Price SR, Mitch WE, Alvestrand A. Effect of bicarbonate on muscle protein in patients receiving hemodialysis. Am J Kidney Dis 2006; 48:419-29. [PMID: 16931215 DOI: 10.1053/j.ajkd.2006.05.029] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2005] [Accepted: 05/03/2006] [Indexed: 11/11/2022]
Abstract
BACKGROUND Metabolic acidosis stimulates whole-body net protein breakdown in healthy adults and patients with kidney failure, but few studies investigated how acidosis affects protein metabolism in individual tissues, such as skeletal muscle. METHODS We evaluated the effect of metabolic acidosis on protein turnover in skeletal muscle, assessed by means of phenylalanine kinetics and free amino acid concentrations in plasma and muscle. Long-term hemodialysis patients (n = 16) were divided into 2 groups in an open crossover study design. In group A, we administered bicarbonate supplements and increased blood standard bicarbonate levels from 17.8 +/- 0.03 to 27.1 +/- 1.2 mEq/L (17.8 +/- 0.03 to 27.1 +/- 1.2 mmol/L). In group B, we decreased bicarbonate supplements, which caused a decrease in standard bicarbonate levels from 26.6 +/- 0.7 to 18.6 +/- 0.3 mEq/L (26.6 +/- 0.7 to 18.6 +/- 0.3 mmol/L). RESULTS Net phenylalanine efflux from leg tissues (muscle) was significantly less when acid-base balance was corrected compared with acidosis (10.8 +/- 1.5 versus 18.6 +/- 3.8 nmol/min/100 g tissue; P = 0.014), as was the rate of phenylalanine appearance (28.3 +/- 3.0 versus 38.4 +/- 5.9 nmol/min/100 g tissue; P = 0.016); the rate of phenylalanine disposal was unchanged. Cortisol and C-reactive protein levels in blood were unchanged after correction of acidosis, as were levels of messenger RNAs encoding components of the ubiquitin-proteasome pathway in muscle biopsy specimens. CONCLUSION Our findings indicate that acidosis increases protein breakdown in skeletal muscle, but additional studies are needed to identify the pathways stimulated to degrade muscle protein in response to acidosis.
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Affiliation(s)
- Erland Löfberg
- Department of Clinical Science, Intervention, and Technology, Division of Renal Medicine, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden
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Urso ML, Scrimgeour AG, Chen YW, Thompson PD, Clarkson PM. Analysis of human skeletal muscle after 48 h immobilization reveals alterations in mRNA and protein for extracellular matrix components. J Appl Physiol (1985) 2006; 101:1136-48. [PMID: 16763108 DOI: 10.1152/japplphysiol.00180.2006] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
We examined the effects of 48 h of knee immobilization on alterations in mRNA and protein in human skeletal muscle. We hypothesized that 48 h of immobilization would increase gene expression and respective protein products for ubiquitin-proteasome pathway (UPP) components. Also, we used microarray analysis to identify novel pathways. Biopsies were taken from the vastus muscle of five men (20.4 +/- 0.5 yr) before and after 48-h immobilization. Global changes in gene expression were analyzed by use of Affymetrix GeneChips. Candidate genes were confirmed via quantitative RT-PCR. Western blotting (WB) was used to quantify protein products of candidate genes and to assess Akt pathway activation. Immunohistochemistry was used to localize proteins found to be altered when assessed via WB. The greatest percentage of genes showing altered expression with the GeneChip included genes involved in the UPP, metallothionein function, and extracellular matrix (ECM) integrity. Quantitative RT-PCR analysis confirmed increases in mRNA for UPP components [USP-6, small ubiquitin-related modifier (SUMO-1)] and the metallothioneins (MT2A, MT1F, MT1H, MT1X) and decreases in mRNA content for matrix metalloproteinases (MMP-28, TIMP-1) and ECM structural components [collagen III (COLIII) and IV (COLIV)]. Only phosphorylated Akt (Ser473, Thr308), COLIII and COLIV protein levels were significantly different postimmobilization (25, 10, 88, and 28% decrease, respectively). Immunohistochemistry confirmed WB showing decreased staining for collagens postimmobilization. Our results suggest that 48 h of immobilization increases mRNA content for components of the UPP and metallothionein function while decreasing mRNA and protein for ECM components as well as decreased phosphorylation of Akt.
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Affiliation(s)
- Maria L Urso
- Department of Exercise Science, 110 Totman Bldg., University of Massachusetts, Amherst, 01003, USA.
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42
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Malik B, Price SR, Mitch WE, Yue Q, Eaton DC. Regulation of epithelial sodium channels by the ubiquitin-proteasome proteolytic pathway. Am J Physiol Renal Physiol 2006; 290:F1285-94. [PMID: 16682484 DOI: 10.1152/ajprenal.00432.2005] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Amiloride-sensitive epithelial Na+channels (ENaC) play a crucial role in Na+transport and fluid reabsorption in the kidney, lung, and colon. The magnitude of ENaC-mediated Na+transport in epithelial cells depends on the average open probability of the channels and the number of channels on the apical surface of epithelial cells. The number of channels in the apical membrane, in turn, depends on a balance between the rate of ENaC insertion and the rate of removal from the apical membrane. ENaC is made up of three homologous subunits: α, β, and γ. The COOH-terminal domain of all three subunits is intracellular and contains a proline-rich motif (PPxY). Mutations or deletion of this PPxY motif in the β- and γ-subunits prevent the binding of one isoform of a specific ubiquitin ligase, neural precursor cell-expressed, developmentally downregulated protein (Nedd4–2), to the channel in vitro and in transfected cell systems, thereby impeding ubiquitin conjugation of the channel subunits. Ubiquitin conjugation would seem to imply that ENaC turnover is determined by the ubiquitin-proteasome system, but when Madin-Darby canine kidney cells are transfected with ENaC, ubiquitin conjugation apparently leads to lysosomal degradation. However, in untransfected renal cells (A6) expressing endogenous ENaC, ENaC is indeed degraded by the ubiquitin-proteasome system. Nonetheless, in both transfected and untransfected cells, the rate of ENaC degradation is apparently controlled by Nedd4–2 activity. In this review, we discuss the role of the ubiquitin conjugation and the alternative degradative pathways (lysosomal or proteasomal) in regulating the rate of ENaC turnover in untransfected renal cells and compare this regulation to that of transfected cell systems.
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Affiliation(s)
- B Malik
- Dept. of Physiology, Emory University, Atlanta, GA 30322, USA
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43
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Lecker SH, Goldberg AL, Mitch WE. Protein degradation by the ubiquitin-proteasome pathway in normal and disease states. J Am Soc Nephrol 2006; 17:1807-19. [PMID: 16738015 DOI: 10.1681/asn.2006010083] [Citation(s) in RCA: 874] [Impact Index Per Article: 48.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Affiliation(s)
- Stewart H Lecker
- Nephrology Division, Beth Isreal Deaconess, Harvard Medical School, Boston, Massachusetts, USA
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44
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Cano NJM, Fouque D, Leverve XM. Application of branched-chain amino acids in human pathological states: renal failure. J Nutr 2006; 136:299S-307S. [PMID: 16365103 DOI: 10.1093/jn/136.1.299s] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
During renal failure, abnormalities of BCAA and branched-chain keto acid (BCKA) metabolism are due to both the lack of renal contribution to amino acid metabolism and the impact of renal failure and acidosis on whole-body nitrogen metabolism. Abnormal BCAA and BCKA metabolism result in BCAA depletion as reflected by low plasma BCAAs and cellular valine. BCAA metabolic disturbances can alter tissue activities, particularly brain function, and nutritional status. In dialysis patients, BCAA oral supplementation can induce an improvement of appetite and nutritional status. During chronic renal failure, the aims of nutritional interventions are to minimize uremic toxicity, avoid malnutrition and delay progression of kidney disease. BCAA and BCKA supplements have been proposed to decrease further protein intake while maintaining satisfactory nutritional status. In this setting, BCAAs or BCKAs have not been administrated solely but in association with other essential AA or keto analogs. Therefore, the proper effects of BCAAs and/or BCKAs have not been studied separately. Protein restriction together with keto acids and/or essential AAs has been reported to improve insulin sensitivity and hyperparathyroidism and to be compatible with a preservation of nutritional status. Nonetheless, a careful monitoring of protein-calorie intake and nutritional status is needed. A recent meta-analysis concluded that reducing protein intake in patients with chronic renal failure reduces the occurrence of renal death by approximately 40% as compared with larger or unrestricted protein intake. The additional effect of essential amino acids and keto acids on retardation of progression of renal failure has not been demonstrated.
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Affiliation(s)
- Noël J M Cano
- INSERM-E0221, Université Joseph Fourier, Grenoble, France.
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45
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Du J, Hu Z, Mitch WE. Cellular signals activating muscle proteolysis in chronic kidney disease: A two-stage process. Int J Biochem Cell Biol 2005; 37:2147-55. [PMID: 15982920 DOI: 10.1016/j.biocel.2005.03.012] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2004] [Revised: 03/08/2005] [Accepted: 03/22/2005] [Indexed: 11/27/2022]
Abstract
Muscle atrophy is a prominent feature of catabolic conditions and in animal models of these conditions there is accelerated muscle proteolysis that is dependent on the ubiquitin-proteasome system. However, ubiquitin system cannot degrade actomyosin or myofibrils even though it rapidly degrades actin or myosin. We identified caspase-3 as the initial and potentially rate-limiting proteolytic step that cleaves actomyosin/myofibrils. In rodent models of catabolic conditions, we find that caspase-3 is activated to cleave muscle proteins and actomyosin to fragments that are rapidly degraded by the ubiquitin system. This initial proteolytic step in muscle can be recognized because it leaves a footprint of a characteristic 14-kDa actin band. Stimulation of caspase-3 activity depends on activation of phosphatidylinositol 3-kinase. When we suppressed this enzyme in muscle cells, protein breakdown increased as did the expression of caspase-3. In addition, there was increased expression of E3-ubiquitin-conjugating enzymes that are involved in muscle proteolysis, atrogin-1/MAFbx and MuRF1. Thus, when phosphatidylinositol 3-kinase activity is low in muscle cells or rat muscle, both caspase-3 and the ubiquitin-proteasome system are stimulated to degrade protein. Additional investigations will be needed to define the cell signaling processes that activate muscle proteolysis in uremia and catabolic conditions.
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Affiliation(s)
- Jie Du
- Nephrology Division, Baylor College of Medicine, One Baylor Plaza-BCM 285, Houston, TX 77030, USA
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Kansara V, Pal D, Jain R, Mitra AK. Identification and functional characterization of riboflavin transporter in human-derived retinoblastoma cell line (Y-79): mechanisms of cellular uptake and translocation. J Ocul Pharmacol Ther 2005; 21:275-87. [PMID: 16117691 DOI: 10.1089/jop.2005.21.275] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Drug delivery to the retina is a challenging task owing to its complex physiology and presence of the blood-retinal barrier (BRB), which regulates the permeation of substances from blood into the retina. Transporter-targeted drug delivery has become a clinically significant drug-delivery approach for enhancing the bioavailability of various drugs. Different nutrient transporters have been reported to be expressed on the retina. Riboflavin (vitamin B2), an essential nutritional vitamin for the development and maintenance of the surface structures and functions of epithelial cells of the ocular tissues, must be acquired from retinal or choroidal blood supply. The uptake mechanism, cellular translocation, and major regulatory pathways of riboflavin uptake into retina are poorly understood. Therefore, the aim of this study was to investigate the presence of a riboflavin transporter and delineate uptake and intracellular trafficking of riboflavin in the human-derived retinoblastoma cell line (Y-79), a model for neural retina. Uptake characteristics of [3H]riboflavin in Y-79 cells were found to be (1) linear with time over 10 min of incubation; (2) temperature- and energy-dependent; (3) sodium, chloride-, and pH-independent; (4) concentration dependence with an apparent K(m) of 19.21 +/- 0.37 nM and V(max) of 6.98 +/- 0.30 pmol/min/mg protein; (5) inhibited by the structural analogs (lumiflavin and lumichrome) but not by the structurally unrelated vitamins; and (6) uptake of [3H]riboflavin was trans-stimulated by the intracellular riboflavin. Neither protein kinase C- nor protein tyrosine kinase-mediated pathways were involved in regulating riboflavin uptake. However, protein kinase A pathway activators (IBMX and forskolin) and inhibitors (H-89) and Ca2+/calmodulin pathways appeared to play important roles in the regulation of riboflavin uptake in Y-79 cells through significant reduction in V(max) (39%) and significant increase in K(m) (112%) of the uptake process. These studies demonstrated, for the first time, the existence of a specialized carrier-mediated system for riboflavin uptake in human-derived retinoblastoma cells. The system appears to be regulated by protein kinase A and Ca2+/calmodulin pathways. Being a high-affinity low-capacity transport system, the presence of this transporter on the retina may be suitable for the design of transporter-targeted prodrugs to achieve enhanced permeability for highly potent, but poorly bioavailable, compounds where a small increase in the bioavailability could result in a significant increase in therapeutic response.
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Affiliation(s)
- Viral Kansara
- Division of Pharmaceutical Sciences, School of Pharmacy, University of Missouri Kansas City, Kansas City, MO 64112-2499, USA
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47
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Bailey JL. Metabolic acidosis: An unrecognized cause of morbidity in the patient with chronic kidney disease. Kidney Int 2005. [DOI: 10.1016/s0085-2538(15)51228-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Abstract
Metabolic acidosis is noted in the majority of patients with chronic kidney disease (CKD) when glomerular filtration rate (GFR) decreases to less than 20% to 25% of normal, although as many as 20% of individuals can have acid-base parameters close to or within the normal range. Acidosis generally is mild to moderate in degree, with plasma bicarbonate concentrations ranging from 12 to 22 mEq/L (mmol/L), and it is rare to see values less than 12 mEq/L (mmol/L) in the absence of an increased acid load. Degree of acidosis approximately correlates with severity of renal failure and usually is more severe at a lower GFR. The metabolic acidosis can be of the high-anion-gap variety, although anion gap can be normal or only moderately increased even with stage 4 to 5 CKD. Several adverse consequences have been associated with metabolic acidosis, including muscle wasting, bone disease, impaired growth, abnormalities in growth hormone and thyroid hormone secretion, impaired insulin sensitivity, progression of renal failure, and exacerbation of beta 2 -microglobulin accumulation. Administration of base aimed at normalization of plasma bicarbonate concentration might be associated with certain complications, such as volume overload, exacerbation of hypertension, and facilitation of vascular calcifications. Whether normalization of plasma bicarbonate concentrations in all patients is desirable therefore requires additional study. In the present review, we describe clinical and laboratory characteristics of metabolic acidosis, discuss potential adverse effects, and address benefits and complications of therapy.
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Affiliation(s)
- Jeffrey A Kraut
- Division of Nephrology, Veterans Affairs Greater Los Angeles Health Care System, Los Angeles, CA 90073, USA.
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49
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Kalantar-Zadeh K, Mehrotra R, Fouque D, Kopple JD. Metabolic acidosis and malnutrition-inflammation complex syndrome in chronic renal failure. Semin Dial 2005; 17:455-65. [PMID: 15660576 DOI: 10.1111/j.0894-0959.2004.17606.x] [Citation(s) in RCA: 134] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Metabolic acidosis, a common condition in patients with renal failure, may be linked to protein-energy malnutrition (PEM) and inflammation, together also known as malnutrition-inflammation complex syndrome (MICS). Methods of serum bicarbonate measurement may misrepresent the true bicarbonate level, since the total serum carbon dioxide measurement usually overestimates the serum bicarbonate concentration. Moreover, the air transportation of blood samples to distant laboratories may lead to erroneous readings. In patients with chronic kidney disease (CKD) or end-stage renal disease (ESRD), a significant number of endocrine, musculoskeletal, and metabolic abnormalities are believed to result from acidemia. Metabolic acidosis may be related to PEM and MICS due to an increased protein catabolism, decreased protein synthesis, endocrine abnormalities including insulin resistance, decreased serum leptin level, and inflammation among individuals with renal failure. Evidence suggests that the catabolic effects of metabolic acidosis may result from an increased activity of the adenosine triphosphate (ATP)-dependent ubiquitin-proteasome and branched-chain keto acid dehydrogenase. In contrast to the metabolic studies, many epidemiologic studies in maintenance dialysis patients have indicated a paradoxically inverse association between mildly decreased serum bicarbonate and improved markers of protein-energy nutritional state. Hence metabolic acidosis may be considered as yet another element of the reverse epidemiology in ESRD patients. Interventional studies have yielded inconsistent results in CKD and ESRD patients, although in peritoneal dialysis patients, mitigating acidemia appears to more consistently improve nutritional status and reduce hospitalizations. Large-scale, prospective randomized interventional studies are needed to ascertain the potential benefits of correcting acidemia in malnourished and/or inflamed CKD and maintenance hemodialysis patients. Until then, all attempts should be made to adhere to the National Kidney Foundation Kidney Disease and Dialysis Outcome Quality Initiative guidelines to maintain a serum bicarbonate level in ESRD patients of at least 22 mEq/L.
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Affiliation(s)
- Kamyar Kalantar-Zadeh
- Division of Nephrology and Hypertension, Harbor-UCLA Medical Center, 1124 West Carson Street, Torrance, CA 90502, USA.
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50
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Ahuja TS, Mitch WE. The evidence against malnutrition as a prominent problem for chronic dialysis patients. Semin Dial 2005; 17:427-31. [PMID: 15660572 DOI: 10.1111/j.0894-0959.2004.17602.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
A large number of dialysis patients have been classified as being malnourished because of anthropometric measurements and laboratory values that are similar to those in patients with protein-energy malnutrition. Malnutrition implies that abnormalities can be reversed with better nutrition. However, this approach of providing more nutrients in the diet has been unsuccessful in reversing these changes, suggesting that a diagnosis of malnutrition is generally a misdiagnosis for dialysis patients In this review we discuss mechanisms that cause a loss of protein stores, muscle mass, albumin, and other plasma proteins in dialysis patients. We also review the shortcomings of techniques that are used to measure the nutritional status of these patients.
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Affiliation(s)
- Tejinder S Ahuja
- Department of Medicine, Division of Nephrology, University of Texas Medical Branch, 301 University Boulevard, Galveston, TX 77555-0562, USA.
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