1 5334 148 QUADRICEPS MUSCLE WEAKNESS AND ATROPHY ARE ASSOCIATED WITH A DIFFERENTIAL EPIGENETIC PROFILE IN ADVANCED COPD. EPIGENETIC MECHANISMS REGULATE MUSCLE MASS AND FUNCTION IN MODELS OF MUSCLE DYSFUNCTION AND ATROPHY. WE ASSESSED WHETHER QUADRICEPS MUSCLE WEAKNESS AND ATROPHY ARE ASSOCIATED WITH A DIFFERENTIAL EXPRESSION PROFILE OF EPIGENETIC EVENTS IN PATIENTS WITH ADVANCED COPD (CHRONIC OBSTRUCTIVE PULMONARY DISEASE). IN VASTUS LATERALIS (VL) OF SEDENTARY SEVERE COPD PATIENTS (N=41), WHO WERE FURTHER SUBDIVIDED INTO THOSE WITH (N=25) AND WITHOUT (N=16) MUSCLE WEAKNESS AND HEALTHY CONTROLS (N=19), EXPRESSION OF MUSCLE-ENRICHED MIRNAS, HISTONE ACETYLTRANSFERASES (HATS) AND DEACETYLASES (HDACS), GROWTH AND ATROPHY SIGNALLING MARKERS, TOTAL PROTEIN AND HISTONE ACETYLATION, TRANSCRIPTION FACTORS, SMALL UBIQUITIN-RELATED MODIFIER (SUMO) LIGASES AND MUSCLE STRUCTURE WERE EXPLORED. ALL SUBJECTS WERE CLINICALLY EVALUATED. COMPARED WITH CONTROLS, IN VL OF ALL COPD TOGETHER AND IN MUSCLE-WEAKNESS PATIENTS, EXPRESSION OF MIR-1, MIR-206 AND MIR-27A, LEVELS OF LYSINE-ACETYLATED PROTEINS AND HISTONES AND ACETYLATED HISTONE 3 WERE INCREASED, WHEREAS EXPRESSION OF HDAC3, HDAC4, SIRTUIN-1 (SIRT-1), IGF-1 (INSULIN-LIKE GROWTH FACTOR-1) WERE DECREASED, AKT (V-AKT MURINE THYMOMA VIRAL ONCOGENE HOMOLOGUE 1) EXPRESSION DID NOT DIFFER, FOLLISTATIN EXPRESSION WAS GREATER, WHEREAS MYOSTATIN EXPRESSION WAS LOWER, SERUM REPONSE FACTOR (SRF) EXPRESSION WAS INCREASED AND FIBRE SIZE OF FAST-TWITCH FIBRES WAS SIGNIFICANTLY REDUCED. IN VL OF SEVERE COPD PATIENTS WITH MUSCLE WEAKNESS AND ATROPHY, EPIGENETIC EVENTS REGULATE MUSCLE DIFFERENTIATION RATHER THAN PROLIFERATION AND MUSCLE GROWTH AND ATROPHY SIGNALLING, PROBABLY AS FEEDBACK MECHANISMS TO PREVENT THOSE MUSCLES FROM UNDERGOING FURTHER ATROPHY. LYSINE-HYPERACETYLATION OF HISTONES MAY DRIVE ENHANCED PROTEIN CATABOLISM IN THOSE MUSCLES. THESE FINDINGS MAY HELP DESIGN NOVEL THERAPEUTIC STRATEGIES (ENHANCERS OF MIRNAS PROMOTING MYOGENESIS AND ACETYLATION INHIBITORS) TO SELECTIVELY TARGET MUSCLE WEAKNESS AND ATROPHY IN SEVERE COPD. 2015 2 1633 71 DO EPIGENETIC EVENTS TAKE PLACE IN THE VASTUS LATERALIS OF PATIENTS WITH MILD CHRONIC OBSTRUCTIVE PULMONARY DISEASE? MUSCLE DYSFUNCTION IS A MAJOR COMORBIDITY IN CHRONIC OBSTRUCTIVE PULMONARY DISEASE (COPD). SEVERAL BIOLOGICAL MECHANISMS INCLUDING EPIGENETIC EVENTS REGULATE MUSCLE MASS AND FUNCTION IN MODELS OF MUSCLE ATROPHY. INVESTIGATIONS CONDUCTED SO FAR HAVE FOCUSED ON THE ELUCIDATION OF BIOLOGICAL MECHANISMS INVOLVED IN MUSCLE DYSFUNCTION IN ADVANCED COPD. WE ASSESSED WHETHER THE EPIGENETIC PROFILE MAY BE ALTERED IN THE VASTUS LATERALIS OF PATIENTS WITH MILD COPD, NORMAL BODY COMPOSITION, AND MILDLY IMPAIRED MUSCLE FUNCTION AND EXERCISE CAPACITY. IN VASTUS LATERALIS (VL) OF MILD COPD PATIENTS WITH WELL-PRESERVED BODY COMPOSITION AND IN HEALTHY AGE-MATCHED CONTROLS, EXPRESSION OF DNA METHYLATION, MUSCLE-ENRICHED MICRORNAS, HISTONE ACETYLTRANSFERASES (HTAS) AND DEACETYLASES (HDACS), PROTEIN ACETYLATION, SMALL UBIQUITIN-RELATED MODIFIER (SUMO) LIGASES, AND MUSCLE STRUCTURE WERE EXPLORED. ALL SUBJECTS WERE CLINICALLY EVALUATED. COMPARED TO HEALTHY CONTROLS, IN THE VL OF MILD COPD PATIENTS, MUSCLE FUNCTION AND EXERCISE CAPACITY WERE MODERATELY REDUCED, DNA METHYLATION LEVELS DID NOT DIFFER, MIR-1 EXPRESSION LEVELS WERE INCREASED AND POSITIVELY CORRELATED WITH BOTH FORCED EXPIRATORY VOLUME IN ONE SECOND (FEV1) AND QUADRICEPS FORCE, HDAC4 PROTEIN LEVELS WERE INCREASED, AND MUSCLE FIBER TYPES AND SIZES WERE NOT DIFFERENT. MODERATE SKELETAL MUSCLE DYSFUNCTION IS A RELEVANT FEATURE IN PATIENTS WITH MILD COPD AND PRESERVED BODY COMPOSITION. SEVERAL EPIGENETIC EVENTS ARE DIFFERENTIALLY EXPRESSED IN THE LIMB MUSCLES OF THESE PATIENTS, PROBABLY AS AN ATTEMPT TO COUNTERBALANCE THE UNDERLYING MECHANISMS THAT ALTER MUSCLE FUNCTION AND MASS. THE STUDY OF PATIENTS AT EARLY STAGES OF THEIR DISEASE IS OF INTEREST AS THEY ARE A TARGET FOR TIMELY THERAPEUTIC INTERVENTIONS THAT MAY SLOW DOWN THE COURSE OF THE DISEASE AND PREVENT THE DELETERIOUS EFFECTS OF MAJOR COMORBIDITIES. 2014 3 3639 43 INCREASED EXPRESSION OF H19/MIR-675 IS ASSOCIATED WITH A LOW FAT-FREE MASS INDEX IN PATIENTS WITH COPD. BACKGROUND: LOSS OF MUSCLE MASS AND STRENGTH IS A SIGNIFICANT COMORBIDITY IN PATIENTS WITH CHRONIC OBSTRUCTIVE PULMONARY DISEASE (COPD) THAT LIMITS THEIR QUALITY OF LIFE AND HAS PROGNOSTIC IMPLICATIONS BUT DOES NOT AFFECT EVERYONE EQUALLY. TO IDENTIFY MECHANISMS THAT MAY CONTRIBUTE TO THE SUSCEPTIBILITY TO A LOW MUSCLE MASS, WE INVESTIGATED MICRORNA (MIRNA) EXPRESSION, METHYLATION STATUS, AND REGENERATION IN QUADRICEPS MUSCLE FROM COPD PATIENTS AND THE EFFECT OF MIRNAS ON MYOBLAST PROLIFERATION IN VITRO. THE RELATIONSHIPS OF MIRNA EXPRESSION WITH MUSCLE MASS AND STRENGTH WAS ALSO DETERMINED IN A GROUP OF HEALTHY OLDER MEN. METHODS: WE IDENTIFIED MIRNAS ASSOCIATED WITH A LOW FAT-FREE MASS (FFM) PHENOTYPE IN A SMALL GROUP OF PATIENTS WITH COPD USING A PCR SCREEN OF 750 MIRNAS. THE EXPRESSION OF TWO DIFFERENTIALLY EXPRESSED MIRNAS (MIR-675 AND MIR-519A) WAS DETERMINED IN AN EXPANDED GROUP OF COPD PATIENTS AND THEIR ASSOCIATIONS WITH FFM AND STRENGTH IDENTIFIED. THE ASSOCIATION OF THESE MIRNAS WITH FFM AND STRENGTH WAS ALSO EXPLORED IN A GROUP OF HEALTHY COMMUNITY-DWELLING OLDER MEN. AS THE EXPRESSION OF THE MIRNAS ASSOCIATED WITH FFM COULD BE REGULATED BY METHYLATION, THE RELATIVE METHYLATION OF THE H19 ICR WAS DETERMINED. FURTHERMORE, THE PROPORTION OF MYOFIBRES WITH CENTRALIZED NUCLEI, AS A MARKER OF MUSCLE REGENERATION, IN THE MUSCLE OF COPD PATIENTS WAS IDENTIFIED BY IMMUNOFLUORESCENCE. RESULTS: IMPRINTED MIRNAS (MIR-675 AND FROM A CLUSTER, C19MC WHICH INCLUDES MIR-519A) WERE DIFFERENTIALLY EXPRESSED IN THE QUADRICEPS OF PATIENTS WITH A LOW FAT-FREE MASS INDEX (FFMI) COMPARED TO THOSE WITH A NORMAL FFMI. IN LARGER COHORTS, MIR-675 AND ITS HOST GENE (H19) WERE HIGHER IN PATIENTS WITH A LOW FFMI AND STRENGTH. THE ASSOCIATION OF MIR-519A EXPRESSION WITH FFMI WAS PRESENT IN MALE PATIENTS WITH SEVERE COPD. SIMILAR ASSOCIATIONS OF MIR EXPRESSION WITH LEAN MASS AND STRENGTH WERE NOT OBSERVED IN HEALTHY COMMUNITY DWELLING OLDER MEN PARTICIPATING IN THE HERTFORDSHIRE SARCOPENIA STUDY. RELATIVE METHYLATION OF THE H19 ICR WAS REDUCED IN COPD PATIENTS WITH MUSCLE WEAKNESS BUT WAS NOT ASSOCIATED WITH FFM. IN VITRO, MIR-675 INHIBITED MYOBLAST PROLIFERATION AND PATIENTS WITH A LOW FFMI HAD FEWER CENTRALIZED NUCLEI SUGGESTING MIR-675 REPRESSES REGENERATION. CONCLUSIONS: THE DATA SUGGEST THAT INCREASED EXPRESSION OF MIR-675/H19 AND ALTERED METHYLATION OF THE H19 IMPRINTING CONTROL REGION ARE ASSOCIATED WITH A LOW FFMI IN PATIENTS WITH COPD BUT NOT IN HEALTHY COMMUNITY DWELLING OLDER MEN SUGGESTING THAT EPIGENETIC CONTROL OF THIS LOCI MAY CONTRIBUTE TO A SUSCEPTIBILITY TO A LOW FFMI. 2016 4 2904 20 GENE BODY METHYLATION FACILITATES THE TRANSCRIPTION OF CTSG VIA ANTISENSE LNCRNA AL136018.1 IN DERMATOMYOSITIC MYOIDEUM. DERMATOMYOSITIS (DM) IS CHARACTERIZED AS A CHRONIC AUTOIMMUNE DISORDER WITH MULTIPLE ORGAN INVOLVEMENT. OUR PREVIOUS STUDY HAS REVEALED THAT CATHEPSIN G (CTSG) HIGHLY EXPRESSED IN DERMATOMYOSITIC IN VIVO IS REGULATED BY DNMT3A THROUGH DNA METHYLATION OF 5'-C-PHOSPHATE-G-3' LOCI AT EXONS AND INTRONS. HOWEVER, THE MECHANISM OF GENE BODY METHYLATION ON REGULATING CTSG TRANSCRIPTION REMAINS UNKNOWN. IN THIS STUDY, WE STUDIED QUADRICEPS FEMORIS TISSUES OF SIX DM PATIENTS, AND OBSERVED THAT ANTISENSE LONG NONCODING RNA AL136018.1 CONTIGUOUS TO CTSG WAS HIGHLY EXPRESSED IN SKELETAL MUSCLE TISSUES OF DM AND POSITIVELY CORRELATED WITH THE TRANSCRIPTION LEVEL AND DNA METHYLATION LEVEL IN GENE BODY OF CTSG IN VIVO. MOREOVER, WE OBSERVED THAT THE LONGER TRANSCRIPT OF AL136018.1 (AL136018.1-201) COULD BIND TO THIRD AND FOURTH EXONS AND THIRD INTRON OF CTSG VIA THE 3'-END. FINALLY, AL136018.1-201 COULD RECRUIT DNMT3A TOWARDS GENE BODY VIA 5'-TERMINAL FOR ADDING DNA METHYLATION AND FACILITATING TRANSCRIPTION OF CTSG. TAKEN TOGETHER, OUR DATA UNCOVERED A NOVEL EPIGENETIC MECHANISM BEHIND THE GENE BODY METHYLATION FOR TRANSCRIPTIONAL REGULATION OF CTSG IN DM. 2021 5 5542 29 ROLE OF DNA METHYLATION ON HUMAN CTSG IN DERMATOMYOSITIC MYOIDEUM. DERMATOMYOSITIS (DM) IS A MULTIFACTORIAL CHRONIC AUTOIMMUNE DISORDER WITH CHARACTERISTIC SKIN AND MUSCLE PATHOLOGICAL CHANGES AND INVOLVEMENT OF OTHER ORGAN SYSTEMS. CATHEPSIN G (CTSG) CONTRIBUTES TO THE RISK OF DEVELOPING DM, WHICH IS LIKELY TO BE ASSOCIATED WITH INFLAMMATORY CYTOKINES. DIFFERENTIAL DNA METHYLATION ON CTSG HAS BEEN DETERMINED TO BE IMPLICATED IN DM IN VIVO. HOWEVER, THE UNDERLYING MECHANISM OF THIS EPIGENETIC REGULATION ON CTST IN DM IS POORLY EXPLORED. IN THIS STUDY, WE INVESTIGATED DNA METHYLATION SIGNATURE ON CTSG AT SINGLE-NUCLEOTIDE RESOLUTION IN QUADRICEPS FEMORIS OF SIX DM PATIENTS AND PARACANCEROUS MUSCLES OF THREE PATIENTS WITH RHABDOMYOSARCOMA ON INNER THIGH USING PYROSEQUENCING AND OBSERVED THAT THE OVERALL DNA METHYLATION LEVEL OF CTSG WAS INCREASED IN DM COMPARED WITH CONTROL, IN WHICH CPG LOCI AT THIRD AND FOURTH EXONS BUT NOT PROMOTER CONTRIBUTED TO THE SIGNIFICANT HYPERMETHYLATION. FURTHERMORE, WE OBSERVED THAT TRANSCRIPTION AND DNA METHYLATION OF CTSG WERE BOTH DECLINED IN DNMT3A KNOCKDOWN COMPARED WITH DNMT1 AND DNMT3B KNOCKDOWN IN HUMAN SKELETAL MUSCLE SJCRH30 AND A-204 CELL LINES EXPOSED TO TUMOR NECROSIS FACTOR-ALPHA. FURTHERMORE, BORTEZOMIB (NF-KAPPAB INHIBITOR) AND BREVILIN A (JAK/STAT INHIBITOR) WERE EMPLOYED TO TREAT SJCRH30 AND A-204 CELLS, RESPECTIVELY, AND WE OBSERVED THAT CTSG WAS HYPOMETHYLATED AND SILENCED AFTER BORTEZOMIB TREATMENT COMPARED WITH UNTREATMENT AND BREVILIN A. FINALLY, CHROMATIN IMMUNOPRECIPITATION-QUANTITATIVE POLYMERASE CHAIN REACTION INDICATED THAT DNMT3A COULD BIND TO THE CODING REGIONS OF CTSG AND THE INTERACTION WAS DEPENDENT ON NF-KAPPAB ACTIVITY. TAKEN TOGETHER, OUR RESULTS DETERMINED A NOVEL REGULATORY MECHANISM OF DNA METHYLATION ON CTSG IN DM. 2020 6 2170 69 EPIGENETIC MECHANISMS IN RESPIRATORY MUSCLE DYSFUNCTION OF PATIENTS WITH CHRONIC OBSTRUCTIVE PULMONARY DISEASE. EPIGENETIC EVENTS ARE DIFFERENTIALLY EXPRESSED IN THE LUNGS AND AIRWAYS OF PATIENTS WITH CHRONIC OBSTRUCTIVE PULMONARY DISEASE (COPD). MOREOVER, EPIGENETIC MECHANISMS ARE INVOLVED IN THE SKELETAL (PERIPHERAL) MUSCLE DYSFUNCTION OF COPD PATIENTS. WHETHER EPIGENETIC EVENTS MAY ALSO REGULATE RESPIRATORY MUSCLE DYSFUNCTION IN COPD REMAINS UNKNOWN. WE HYPOTHESIZED THAT EPIGENETIC MECHANISMS WOULD BE DIFFERENTIALLY EXPRESSED IN THE MAIN INSPIRATORY MUSCLE (DIAPHRAGM) OF PATIENTS WITH COPD OF A WIDE RANGE OF DISEASE SEVERITY COMPARED TO HEALTHY CONTROLS. IN DIAPHRAGM MUSCLE SPECIMENS (THORACOTOMY DUE TO LUNG LOCALIZED NEOPLASMS) OF SEDENTARY PATIENTS WITH MILD-TO-MODERATE AND SEVERE COPD, WITH PRESERVED BODY COMPOSITION, AND SEDENTARY HEALTHY CONTROLS, EXPRESSION OF MUSCLE-ENRICHED MICRORNAS, HISTONE ACETYLTRANSFERASES (HATS) AND DEACETYLASES (HDACS), TOTAL DNA METHYLATION AND PROTEIN ACETYLATION, SMALL UBIQUITIN-RELATED MODIFIER (SUMO) LIGASES, MUSCLE-SPECIFIC TRANSCRIPTION FACTORS, AND MUSCLE STRUCTURE WERE EXPLORED. ALL SUBJECTS WERE ALSO CLINICALLY EVALUATED: LUNG AND MUSCLE FUNCTIONS AND EXERCISE CAPACITY. COMPARED TO HEALTHY CONTROLS, PATIENTS EXHIBITED MODERATE AIRFLOW LIMITATION AND DIFFUSION CAPACITY, AND REDUCED EXERCISE TOLERANCE AND TRANSDIAPHRAGMATIC STRENGTH. MOREOVER, IN THE DIAPHRAGM OF THE COPD PATIENTS, MUSCLE-SPECIFIC MICRORNA EXPRESSION WAS DOWNREGULATED, WHILE HDAC4 AND MYOCYTE ENHANCER FACTOR (MEF)2C PROTEIN LEVELS WERE HIGHER, AND DNA METHYLATION LEVELS, MUSCLE FIBER TYPES AND SIZES DID NOT DIFFER BETWEEN PATIENTS AND CONTROLS. IN THE MAIN RESPIRATORY MUSCLE OF COPD PATIENTS WITH A WIDE RANGE OF DISEASE SEVERITY AND NORMAL BODY COMPOSITION, MUSCLE-SPECIFIC MICRORNAS WERE DOWNREGULATED, WHILE HDAC4 AND MEF2C LEVELS WERE UPREGULATED. IT IS LIKELY THAT THESE EPIGENETIC EVENTS ACT AS BIOLOGICAL ADAPTIVE MECHANISMS TO BETTER OVERCOME THE CONTINUOUS INSPIRATORY LOADS OF THE RESPIRATORY SYSTEM IN COPD. THESE FINDINGS MAY OFFER NOVEL THERAPEUTIC STRATEGIES TO SPECIFICALLY TARGET RESPIRATORY MUSCLE DYSFUNCTION IN PATIENTS WITH COPD. 2014 7 4359 39 MIR-422A SUPPRESSES SMAD4 PROTEIN EXPRESSION AND PROMOTES RESISTANCE TO MUSCLE LOSS. BACKGROUND: LOSS OF MUSCLE MASS AND STRENGTH ARE IMPORTANT SEQUELAE OF CHRONIC DISEASE, BUT THE RESPONSE OF INDIVIDUALS IS REMARKABLY VARIABLE, SUGGESTING IMPORTANT GENETIC AND EPIGENETIC MODULATORS OF MUSCLE HOMEOSTASIS. SUCH FACTORS ARE LIKELY TO MODIFY THE ACTIVITY OF PATHWAYS THAT REGULATE WASTING, BUT TO DATE, FEW SUCH FACTORS HAVE BEEN IDENTIFIED. METHODS: THE EFFECT OF MIR-422A ON SMAD4 EXPRESSION AND TRANSFORMING GROWTH FACTOR (TGF)-BETA SIGNALLING WERE DETERMINED BY WESTERN BLOTTING AND LUCIFERASE ASSAY. MIRNA EXPRESSION WAS DETERMINED BY QPCR IN PLASMA AND MUSCLE BIOPSY SAMPLES FROM A CROSS-SECTIONAL STUDY OF PATIENTS WITH CHRONIC OBSTRUCTIVE PULMONARY DISEASE (COPD) AND A LONGITUDINAL STUDY OF PATIENTS UNDERGOING AORTIC SURGERY, WHO WERE SUBSEQUENTLY ADMITTED TO THE INTENSIVE CARE UNIT (ICU). RESULTS: MIR-422A WAS IDENTIFIED, BY A SCREEN, AS A MICRORNA THAT WAS PRESENT IN THE PLASMA OF PATIENTS WITH COPD AND NEGATIVELY ASSOCIATED WITH MUSCLE STRENGTH AS WELL AS BEING READILY DETECTABLE IN THE MUSCLE OF PATIENTS. IN VITRO, MIR-422A SUPPRESSED SMAD4 EXPRESSION AND INHIBITED TGF-BETA AND BONE MORPHOGENETIC PROTEIN-DEPENDENT LUCIFERASE ACTIVITY IN MUSCLE CELLS. IN MALE PATIENTS WITH COPD AND THOSE UNDERGOING AORTIC SURGERY AND ON THE ICU, A MODEL OF ICU-ASSOCIATED MUSCLE WEAKNESS, QUADRICEPS EXPRESSION OF MIR-422A WAS POSITIVELY ASSOCIATED WITH MUSCLE STRENGTH (MAXIMAL VOLUNTARY CONTRACTION R = 0.59, P < 0.001 AND R = 0.51, P = 0.004, FOR COPD AND AORTIC SURGERY, RESPECTIVELY). FURTHERMORE, PRE-SURGERY LEVELS OF MIR-422A WERE INVERSELY ASSOCIATED WITH THE AMOUNT OF MUSCLE THAT WOULD BE LOST IN THE FIRST POST-OPERATIVE WEEK (R = -0.57, P < 0.001). CONCLUSIONS: THESE DATA SUGGEST THAT DIFFERENCES IN MIR-422A EXPRESSION CONTRIBUTE TO THE SUSCEPTIBILITY TO MUSCLE WASTING ASSOCIATED WITH CHRONIC AND ACUTE DISEASE AND THAT AT LEAST PART OF THIS ACTIVITY MAY BE MEDIATED BY REDUCED TGF-BETA SIGNALLING IN SKELETAL MUSCLE. 2018 8 4577 33 MYOSTATIN: BASIC BIOLOGY TO CLINICAL APPLICATION. MYOSTATIN IS A MEMBER OF THE TRANSFORMING GROWTH FACTOR (TGF)-BETA SUPERFAMILY. IT IS EXPRESSED BY ANIMAL AND HUMAN SKELETAL MUSCLE CELLS WHERE IT LIMITS MUSCLE GROWTH AND PROMOTES PROTEIN BREAKDOWN. ITS EFFECTS ARE INFLUENCED BY COMPLEX MECHANISMS INCLUDING TRANSCRIPTIONAL AND EPIGENETIC REGULATION AND MODULATION BY EXTRACELLULAR BINDING PROTEINS. DUE TO ITS ACTIONS IN PROMOTING MUSCLE ATROPHY AND CACHEXIA, MYOSTATIN HAS BEEN INVESTIGATED AS A PROMISING THERAPEUTIC TARGET TO COUNTERACT MUSCLE MASS LOSS IN EXPERIMENTAL MODELS AND PATIENTS AFFECTED BY DIFFERENT MUSCLE-WASTING CONDITIONS. MOREOVER, GROWING EVIDENCE INDICATES THAT MYOSTATIN, BEYOND TO REGULATE SKELETAL MUSCLE GROWTH, MAY HAVE A ROLE IN MANY PHYSIOLOGIC AND PATHOLOGIC PROCESSES, SUCH AS OBESITY, INSULIN RESISTANCE, CARDIOVASCULAR AND CHRONIC KIDNEY DISEASE. IN THIS CHAPTER, WE REVIEW MYOSTATIN BIOLOGY, INCLUDING INTRACELLULAR AND EXTRACELLULAR REGULATORY PATHWAYS, AND THE ROLE OF MYOSTATIN IN MODULATING PHYSIOLOGIC PROCESSES, SUCH AS MUSCLE GROWTH AND AGING. MOREOVER, WE DISCUSS THE MOST RELEVANT EXPERIMENTAL AND CLINICAL EVIDENCE SUPPORTING THE EXTRA-MUSCLE EFFECTS OF MYOSTATIN. FINALLY, WE CONSIDER THE MAIN STRATEGIES DEVELOPED AND TESTED TO INHIBIT MYOSTATIN IN CLINICAL TRIALS AND DISCUSS THE LIMITS AND FUTURE PERSPECTIVES OF THE RESEARCH ON MYOSTATIN. 2022 9 4410 36 MOLECULAR AND BIOLOGICAL PATHWAYS OF SKELETAL MUSCLE DYSFUNCTION IN CHRONIC OBSTRUCTIVE PULMONARY DISEASE. CHRONIC OBSTRUCTIVE PULMONARY DISEASE (COPD) WILL BE A MAJOR LEADING CAUSE OF DEATH WORLDWIDE IN THE NEAR FUTURE. WEAKNESS AND ATROPHY OF THE QUADRICEPS ARE ASSOCIATED WITH A SIGNIFICANTLY POORER PROGNOSIS AND INCREASED MORTALITY IN COPD. DESPITE THAT SKELETAL MUSCLE DYSFUNCTION MAY AFFECT BOTH RESPIRATORY AND LIMB MUSCLE GROUPS IN COPD, THE LATTER ARE FREQUENTLY MORE SEVERELY AFFECTED. THEREFORE, MUSCLE DYSFUNCTION IN COPD IS A COMMON SYSTEMIC MANIFESTATION THAT SHOULD BE EVALUATED ON ROUTINE BASIS IN CLINICAL SETTINGS. IN THE PRESENT REVIEW, SEVERAL ASPECTS OF COPD MUSCLE DYSFUNCTION ARE BEING REVIEWED, WITH SPECIAL EMPHASIS ON THE UNDERLYING BIOLOGICAL MECHANISMS. FIGURES ON THE PREVALENCE OF COPD MUSCLE DYSFUNCTION AND THE MOST RELEVANT ETIOLOGIC CONTRIBUTORS ARE ALSO PROVIDED. DESPITE THAT ONGOING RESEARCH WILL SHED LIGHT INTO THE CONTRIBUTION OF ADDITIONAL MECHANISMS TO COPD MUSCLE DYSFUNCTION, CURRENT KNOWLEDGE POINTS TOWARD THE INVOLVEMENT OF A WIDE SPECTRUM OF CELLULAR AND MOLECULAR EVENTS THAT ARE DIFFERENTIALLY EXPRESSED IN RESPIRATORY AND LIMB MUSCLES. SUCH MECHANISMS ARE THOROUGHLY DESCRIBED IN THE ARTICLE. THE CONTRIBUTION OF EPIGENETIC EVENTS ON COPD MUSCLE DYSFUNCTION IS ALSO REVIEWED. WE CONCLUDE THAT IN VIEW OF THE LATEST DISCOVERIES, FROM NOW, ON NEW AVENUES OF RESEARCH SHOULD BE DESIGNED TO SPECIFICALLY TARGET CELLULAR MECHANISMS AND PATHWAYS THAT IMPAIR MUSCLE MASS AND FUNCTION IN COPD USING PHARMACOLOGICAL STRATEGIES AND/OR EXERCISE TRAINING MODALITIES. 2016 10 2505 37 EPIGENETICS AND MUSCLE DYSFUNCTION IN CHRONIC OBSTRUCTIVE PULMONARY DISEASE. CHRONIC OBSTRUCTIVE PULMONARY DISEASE (COPD) IS A COMMON, PREVENTABLE, AND TREATABLE DISEASE AND A MAJOR LEADING CAUSE OF MORBIDITY AND MORTALITY WORLDWIDE. IN COPD, COMORBIDITIES, ACUTE EXACERBATIONS, AND SYSTEMIC MANIFESTATIONS NEGATIVELY INFLUENCE DISEASE SEVERITY AND PROGRESSION REGARDLESS OF THE RESPIRATORY CONDITION. SKELETAL MUSCLE DYSFUNCTION, WHICH IS ONE OF THE COMMONEST SYSTEMIC MANIFESTATIONS IN PATIENTS WITH COPD, HAS A TREMENDOUS IMPACT ON THEIR EXERCISE CAPACITY AND QUALITY OF LIFE. SEVERAL PATHOPHYSIOLOGICAL AND MOLECULAR UNDERLYING MECHANISMS INCLUDING EPIGENETICS (THE PROCESS WHEREBY GENE EXPRESSION IS REGULATED BY HERITABLE MECHANISMS THAT DO NOT AFFECT DNA SEQUENCE) HAVE BEEN SHOWN TO PARTICIPATE IN THE ETIOLOGY OF COPD MUSCLE DYSFUNCTION. THE EPIGENETIC MODIFICATIONS IDENTIFIED SO FAR IN CELLS INCLUDE DNA METHYLATION, HISTONE ACETYLATION AND METHYLATION, AND NONCODING RNAS SUCH AS MICRORNAS. HEREIN, WE FIRST REVIEW THE ROLE OF EPIGENETIC MECHANISMS IN MUSCLE DEVELOPMENT AND ADAPTATION TO ENVIRONMENTAL FACTORS IN SEVERAL MODELS. MOREOVER, THE EPIGENETIC EVENTS REPORTED SO FAR TO BE POTENTIALLY INVOLVED IN MUSCLE DYSFUNCTION AND MASS LOSS OF PATIENTS WITH COPD ARE ALSO DISCUSSED. FURTHERMORE, THE DIFFERENT EXPRESSION PROFILE OF SEVERAL MUSCLE-ENRICHED MICRORNAS IN THE DIAPHRAGM AND VASTUS LATERALIS MUSCLES OF PATIENTS WITH COPD ARE ALSO REVIEWED FROM RESULTS RECENTLY OBTAINED IN OUR GROUP. THE ROLE OF PROTEIN HYPERACETYLATION IN ENHANCED MUSCLE PROTEIN CATABOLISM OF LIMB MUSCLES IS ALSO DISCUSSED. FUTURE RESEARCH SHOULD FOCUS ON THE FULL ELUCIDATION OF THE TRIGGERS OF EPIGENETIC MECHANISMS AND THEIR SPECIFIC DOWNSTREAM BIOLOGICAL PATHWAYS IN COPD MUSCLE DYSFUNCTION AND WASTING. 2015 11 4543 31 MUSCLE DYSFUNCTION IN CHRONIC OBSTRUCTIVE PULMONARY DISEASE: UPDATE ON CAUSES AND BIOLOGICAL FINDINGS. RESPIRATORY AND/OR LIMB MUSCLE DYSFUNCTION, WHICH ARE FREQUENTLY OBSERVED IN CHRONIC OBSTRUCTIVE PULMONARY DISEASE (COPD) PATIENTS, CONTRIBUTE TO THEIR DISEASE PROGNOSIS IRRESPECTIVE OF THE LUNG FUNCTION. MUSCLE DYSFUNCTION IS CAUSED BY THE INTERACTION OF LOCAL AND SYSTEMIC FACTORS. THE KEY DELETERIOUS ETIOLOGIC FACTORS ARE PULMONARY HYPERINFLATION FOR THE RESPIRATORY MUSCLES AND DECONDITIONING SECONDARY TO REDUCED PHYSICAL ACTIVITY FOR LIMB MUSCLES. NONETHELESS, CIGARETTE SMOKE, SYSTEMIC INFLAMMATION, NUTRITIONAL ABNORMALITIES, EXERCISE, EXACERBATIONS, ANABOLIC INSUFFICIENCY, DRUGS AND COMORBIDITIES ALSO SEEM TO PLAY A RELEVANT ROLE. ALL THESE FACTORS MODIFY THE PHENOTYPE OF THE MUSCLES, THROUGH THE INDUCTION OF SEVERAL BIOLOGICAL PHENOMENA IN PATIENTS WITH COPD. WHILE RESPIRATORY MUSCLES IMPROVE THEIR AEROBIC PHENOTYPE (PERCENTAGE OF OXIDATIVE FIBERS, CAPILLARIZATION, MITOCHONDRIAL DENSITY, ENZYME ACTIVITY IN THE AEROBIC PATHWAYS, ETC.), LIMB MUSCLES EXHIBIT THE OPPOSITE PHENOTYPE. IN ADDITION, BOTH MUSCLE GROUPS SHOW OXIDATIVE STRESS, SIGNS OF DAMAGE AND EPIGENETIC CHANGES. HOWEVER, FIBER ATROPHY, INCREASED NUMBER OF INFLAMMATORY CELLS, ALTERED REGENERATIVE CAPACITY; SIGNS OF APOPTOSIS AND AUTOPHAGY, AND AN IMBALANCE BETWEEN PROTEIN SYNTHESIS AND BREAKDOWN ARE RATHER CHARACTERISTIC FEATURES OF THE LIMB MUSCLES, MOSTLY IN PATIENTS WITH REDUCED BODY WEIGHT. DESPITE THAT SIGNIFICANT PROGRESS HAS BEEN ACHIEVED IN THE LAST DECADES, FULL ELUCIDATION OF THE SPECIFIC ROLES OF THE TARGET BIOLOGICAL MECHANISMS INVOLVED IN COPD MUSCLE DYSFUNCTION IS STILL REQUIRED. SUCH AN ACHIEVEMENT WILL BE CRUCIAL TO ADEQUATELY TACKLE WITH THIS RELEVANT CLINICAL PROBLEM OF COPD PATIENTS IN THE NEAR-FUTURE. 2015 12 2348 35 EPIGENETIC REGULATION OF MUSCLE PHENOTYPE AND ADAPTATION: A POTENTIAL ROLE IN COPD MUSCLE DYSFUNCTION. QUADRICEPS MUSCLE DYSFUNCTION OCCURS IN ONE-THIRD OF PATIENTS WITH CHRONIC OBSTRUCTIVE PULMONARY DISEASE (COPD) IN VERY EARLY STAGES OF THEIR CONDITION, EVEN PRIOR TO THE DEVELOPMENT OF AIRWAY OBSTRUCTION. AMONG SEVERAL FACTORS, DECONDITIONING AND MUSCLE MASS LOSS ARE THE MOST RELEVANT CONTRIBUTING FACTORS LEADING TO THIS DYSFUNCTION. MOREOVER, EPIGENETICS, DEFINED AS THE PROCESS WHEREBY GENE EXPRESSION IS REGULATED BY HERITABLE MECHANISMS THAT DO NOT AFFECT DNA SEQUENCE, COULD BE INVOLVED IN THE SUSCEPTIBILITY TO MUSCLE DYSFUNCTION, PATHOGENESIS, AND PROGRESSION. HEREIN, WE REVIEW THE ROLE OF EPIGENETIC MECHANISMS IN MUSCLE DEVELOPMENT AND ADAPTATION TO ENVIRONMENTAL FACTORS SUCH AS IMMOBILIZATION AND EXERCISE, AND THEIR IMPLICATIONS IN THE PATHOPHYSIOLOGY AND SUSCEPTIBILITY TO MUSCLE DYSFUNCTION IN COPD. THE EPIGENETIC MODIFICATIONS IDENTIFIED SO FAR INCLUDE DNA METHYLATION, HISTONE ACETYLATION AND METHYLATION, AND NON-CODING RNAS SUCH AS MICRORNAS (MIRNAS). IN THE PRESENT REVIEW, WE DESCRIBE THE SPECIFIC CONTRIBUTION OF EPIGENETIC MECHANISMS TO THE REGULATION OF EMBRYONIC MYOGENESIS, MUSCLE STRUCTURE AND METABOLISM, IMMOBILIZATION, AND EXERCISE, AND IN MUSCLES OF COPD PATIENTS. EVENTS RELATED TO MUSCLE DEVELOPMENT AND REGENERATION AND THE RESPONSE TO EXERCISE AND IMMOBILIZATION ARE TIGHTLY REGULATED BY EPIGENETIC MECHANISMS. THESE ENVIRONMENTAL FACTORS PLAY A KEY ROLE IN THE OUTCOME OF MUSCLE MASS AND FUNCTION AS WELL AS IN THE SUSCEPTIBILITY TO MUSCLE DYSFUNCTION IN COPD. FUTURE RESEARCH REMAINS TO BE DONE TO SHED LIGHT ON THE SPECIFIC TARGET PATHWAYS OF MIRNA FUNCTION AND OTHER EPIGENETIC MECHANISMS IN THE SUSCEPTIBILITY, PATHOGENESIS, AND PROGRESSION OF COPD MUSCLE DYSFUNCTION. 2013 13 4899 33 OXIDATIVE STRESS MEDIATES THE APOPTOSIS AND EPIGENETIC MODIFICATION OF THE BCL-2 PROMOTER VIA DNMT1 IN A CIGARETTE SMOKE-INDUCED EMPHYSEMA MODEL. BACKGROUND: EMPHYSEMA IS A CRUCIAL PATHOLOGICAL CHARACTERISTIC OF CHRONIC OBSTRUCTIVE PULMONARY DISEASE (COPD). OXIDATIVE STRESS, APOPTOSIS AND EPIGENETIC MECHANISMS CONTRIBUTE TO THE PATHOGENESIS OF EMPHYSEMA. HOWEVER, AN ATTEMPT TO ACCURATELY IDENTIFY WHETHER THESE MECHANISMS INTERACT WITH EACH OTHER AND HOW THEY ARE TRIGGERED HAS NEVER BEEN CONDUCTED. METHOD: THE TOTAL REACTIVE OXYGEN SPECIES (ROS) LEVEL, PULMONARY APOPTOSIS AND B-CELL LYMPHOMA/LEUKEMIA-2 (BCL-2) EXPRESSION, AN APOPTOSIS REGULATOR, WERE DETECTED IN SAMPLES FROM COPD PATIENTS. BISULFITE SEQUENCING PCR (BSP) WAS CONDUCTED TO OBSERVE THE ALTERATIONS IN THE METHYLATION OF THE BCL-2 PROMOTER IN SPECIMENS. THE DYSREGULATION OF DNA METHYLTRANSFERASE ENZYME 1 (DNMT1), A VITAL DNA METHYLTRANSFERASE ENZYME, IN THE LUNGS OF PATIENTS WAS CONFIRMED THROUGH WESTERN BLOTTING. TO FIND OUT INTERACTIONS BETWEEN OXIDATIVE STRESS AND DNA METHYLATION IN EMPHYSEMA, MOUSE MODELS WERE BUILT WITH ANTIOXIDANT TREATMENT AND DNMT1 SILENCING, AND WERE EXAMINED WITH THE PULMONARY APOPTOSIS, BCL-2 AND DNMT1 LEVELS, AND EPIGENETIC ALTERATIONS OF BCL-2. RESULTS: HIGHER ROS LEVELS AND PULMONARY APOPTOSIS WERE OBSERVED IN COPD PATIENTS THAN IN HEALTHY CONTROLS. DOWNREGULATED BCL-2 EXPRESSION WITH INCREASED PROMOTER METHYLATION AND DNMT1 PROTEIN EXPRESSION WAS FOUND IN COPD PATIENTS. ANTIOXIDANT TREATMENT REDUCED THE LEVEL OF ROS, DNMT1 PROTEIN AND EMPHYSEMATOUS PROGRESSION IN THE SMOKING MODELS. FOLLOWING DNMT1 BLOCKADE, SMOKING MODELS SHOWED IMPROVED LUNG FUNCTION, PULMONARY APOPTOSIS, EMPHYSEMATOUS PROGRESSION, AND INCREASED BCL-2 PROTEIN LEVEL WITH LESS PROMOTER METHYLATION THAN EMPHYSEMA MICE. CONCLUSION: CIGARETTE-INDUCED OXIDATIVE STRESS MEDIATES PULMONARY APOPTOSIS AND HYPERMETHYLATION OF THE BCL-2 PROMOTER IN EMPHYSEMA MODELS THROUGH DNMT1. 2020 14 3447 34 HYPERMETHYLATION OF MITOCHONDRIAL TRANSCRIPTION FACTOR A INDUCED BY CIGARETTE SMOKE IS ASSOCIATED WITH CHRONIC OBSTRUCTIVE PULMONARY DISEASE. PURPOSE OF THE STUDY: CIGARETTE SMOKING IS A LEADING ENVIRONMENTAL CONTRIBUTOR TO CHRONIC OBSTRUCTIVE PULMONARY DISEASE (COPD), BUT ITS EPIGENETIC REGULATION OF MTTFA GENE REMAINS ELUSIVE. THIS STUDY AIMS TO EXPLORE THE RELATIONSHIP OF DNA METHYLATION OF MTTFA AND CIGARETTE SMOKING IN COPD. MATERIALS AND METHODS: WE ANALYZED DNA METHYLATION ON MTTFA PROMOTERS IN CLINICAL SAMPLES FROM COPD PATIENTS AND SUBJECTS WITH NORMAL PULMONARY FUNCTION. EXPRESSION OF MTTFA MRNA IN THE CLINICAL SAMPLES AND MTTFA MRNA AND PROTEIN IN HUMAN UMBILICAL VEIN ENDOTHELIAL CELLS(HUVECS) TREATED WITH CIGARETTE SMOKE EXTRACT (CSE) WAS EVALUATED. MTTFA MRNA AND PROTEIN LEVELS WERE MEASURED TO DETERMINE EFFECTS OF DEMETHYLATION AGENTS ON CSE-TREATED HUVECS. RESULTS: THE DNA METHYLATION LEVEL OF THE MTTFA PROMOTER WAS SIGNIFICANTLY INCREASED IN COPD GROUP. EXPRESSION OF MTTFA MRNA WAS DOWNREGULATED IN THE LUNGS AS A CONSEQUENCE OF HYPERMETHYLATION OF MTTFA PROMOTER. EXPRESSION OF MTTFA MRNA AND PROTEIN WAS DOWNREGULATED IN CSE-TREATED HUVECS AS A CONSEQUENCE OF HYPERMETHYLATION OF THE MTTFA PROMOTER. MTTFA EXPRESSION IN CSE-TREATED HUVECS WAS RESTORED BY THE METHYLATION INHIBITOR, 5-AZA-2'-DEOXYCYTIDINE(AZA). CONCLUSIONS: CIGARETTE SMOKE-INDUCED HYPERMETHYLATION OF THE MTTFA PROMOTER IS RELATED TO THE INITIATION AND PROGRESSION OF COPD. OUR FINDING MAY PROVIDE A NEW STRATEGY FOR THE INTERVENTION OF COPD BY DEVELOPING DEMETHYLATION AGENTS TARGETING MTTFA HYPERMETHYLATION. 2019 15 1550 31 DNA METHYLATION IS ASSOCIATED WITH AIRFLOW OBSTRUCTION IN PATIENTS LIVING WITH HIV. INTRODUCTION: PEOPLE LIVING WITH HIV (PLWH) SUFFER FROM AGE-RELATED COMORBIDITIES SUCH AS COPD. THE PROCESSES RESPONSIBLE FOR REDUCED LUNG FUNCTION IN PLWH ARE LARGELY UNKNOWN. WE PERFORMED AN EPIGENOME-WIDE ASSOCIATION STUDY TO INVESTIGATE WHETHER BLOOD DNA METHYLATION IS ASSOCIATED WITH IMPAIRED LUNG FUNCTION IN PLWH. METHODS: USING BLOOD DNA METHYLATION PROFILES FROM 161 PLWH, WE TESTED THE EFFECT OF METHYLATION ON FEV(1), FEV(1)/FVC RATIO AND FEV(1) DECLINE OVER A MEDIAN OF 5 YEARS. WE EVALUATED THE GLOBAL METHYLATION OF PLWH WITH AIRFLOW OBSTRUCTION BY TESTING THE DIFFERENTIAL METHYLATION OF TRANSPOSABLE ELEMENTS ALU AND LINE-1, A WELL-DESCRIBED MARKER OF EPIGENETIC AGEING. RESULTS: AIRFLOW OBSTRUCTION AS DEFINED BY A FEV(1)/FVC<0.70 WAS ASSOCIATED WITH 1393 DIFFERENTIALLY METHYLATED POSITIONS (DMPS), WHILE 4676 WERE ASSOCIATED WITH AIRFLOW OBSTRUCTION BASED ON THE FEV(1)/FVC 0.05). EPIGENETIC AGING WAS ASSOCIATED WITH GREATER EMOTIONAL STABILITY (R = -0.461, P = 0.027), CONSCIENTIOUSNESS (R = -0.549, P = 0.007), AND LOWER EXTRAVERSION (R = 0.414, P = 0.049) BUT NOT DEPRESSION OR AFFECT (P'S > 0.05). EPIGENETIC AGING WAS ALSO ASSOCIATED WITH LOWER EPISODIC (R = -0.698, P = 0.001) AND WORKING MEMORY (R = -0.760, P < 0.001). OUR FINDINGS SUGGEST THAT CHRONIC PAIN IS ASSOCIATED WITH ACCELERATED EPIGENETIC AGING IN HEALTHY, COMMUNITY-DWELLING OLDER INDIVIDUALS, AND FUTURE STUDIES WITH LARGER SAMPLES ARE NEEDED TO CONFIRM OUR FINDINGS. AN AGING BIOMARKER SUCH AS THE EPIGENETIC CLOCK MAY HELP IDENTIFY PEOPLE WITH CHRONIC PAIN AT GREATER RISK OF FUNCTIONAL DECLINE AND POORER HEALTH OUTCOMES. 2019 19 5679 43 SHORT- AND LONG-TERM HINDLIMB IMMOBILIZATION AND RELOADING: PROFILE OF EPIGENETIC EVENTS IN GASTROCNEMIUS. SKELETAL MUSCLE DYSFUNCTION AND ATROPHY ARE CHARACTERISTIC FEATURES ACCOMPANYING CHRONIC CONDITIONS. EPIGENETIC EVENTS REGULATE MUSCLE MASS AND FUNCTION MAINTENANCE. WE HYPOTHESIZED THAT THE PATTERN OF EPIGENETIC EVENTS (MUSCLE-ENRICHED MICRORNAS AND HISTONE ACETYLATION) AND ACETYLATION OF TRANSCRIPTION FACTORS KNOWN TO SIGNAL MUSCLE WASTING MAY DIFFER BETWEEN EARLY- AND LATE-TIME POINTS IN SKELETAL MUSCLES OF MICE EXPOSED TO HINDLIMB IMMOBILIZATION (I) AND RECOVERY FOLLOWING I. BODY AND MUSCLE WEIGHTS, GRIP STRENGTH, MUSCLE-ENRICHED MICRORNAS, HISTONE DEACETYLASES (HDACS), ACETYLATION OF PROTEINS, HISTONES, AND TRANSCRIPTION FACTORS (TF), MYOGENIC TF FACTORS, AND MUSCLE PHENOTYPE WERE ASSESSED IN GASTROCNEMIUS OF MICE EXPOSED TO PERIODS (1, 2, 3, 7, 15, AND 30 DAYS, I GROUPS) OF HINDLIMB IMMOBILIZATION, AND IN THOSE EXPOSED TO RELOADING FOR DIFFERENT PERIODS OF TIME (1, 3, 7, 15, AND 30 DAYS, R GROUPS) FOLLOWING 7-DAY IMMOBILIZATION. COMPARED TO NON-IMMOBILIZED CONTROLS, MUSCLE WEIGHT, LIMB STRENGTH, MICRORNAS, ESPECIALLY MIR-486, SIRT1 LEVELS, AND SLOW- AND FAST-TWITCH CROSS-SECTIONAL AREAS WERE DECREASED IN MICE OF I GROUPS, WHEREAS PAX7 AND ACETYLATED FOXO1 AND FOXO3 LEVELS WERE INCREASED. MUSCLE RELOADING FOLLOWING SPLINT REMOVAL IMPROVED MUSCLE MASS LOSS, STRENGTH, AND FIBER ATROPHY, BY INCREASING MICRORNAS, PARTICULARLY MIR-486, AND SIRT1 CONTENT, WHILE DECREASING ACETYLATED FOXO1 AND FOXO3 LEVELS. IN THIS MOUSE MODEL OF DISUSE MUSCLE ATROPHY, MUSCLE-ENRICHED MICRORNAS, ESPECIALLY MIR-486, THROUGH PAX7 REGULATION DELAYED MUSCLE CELL DIFFERENTIATION FOLLOWING UNLOADING OF GASTROCNEMIUS MUSCLE. ACETYLATION OF FOXO1 AND 3 SEEMED TO DRIVE MUSCLE MASS LOSS AND ATROPHY, WHILE DEACETYLATION OF THESE FACTORS THROUGH SIRT1 WOULD ENABLE THE MUSCLE FIBERS TO REGENERATE. J. CELL. PHYSIOL. 232: 1415-1427, 2017. (C) 2016 WILEY PERIODICALS, INC. 2017 20 4047 30 MAIN PATHOGENIC MECHANISMS AND RECENT ADVANCES IN COPD PERIPHERAL SKELETAL MUSCLE WASTING. CHRONIC OBSTRUCTIVE PULMONARY DISEASE (COPD) IS A WORLDWIDE PREVALENT RESPIRATORY DISEASE MAINLY CAUSED BY TOBACCO SMOKE EXPOSURE. COPD IS NOW CONSIDERED AS A SYSTEMIC DISEASE WITH SEVERAL COMORBIDITIES. AMONG THEM, SKELETAL MUSCLE DYSFUNCTION AFFECTS AROUND 20% OF COPD PATIENTS AND IS ASSOCIATED WITH HIGHER MORBIDITY AND MORTALITY. ALTHOUGH THE HISTOLOGICAL ALTERATIONS ARE WELL CHARACTERIZED, INCLUDING MYOFIBER ATROPHY, A DECREASED PROPORTION OF SLOW-TWITCH MYOFIBERS, AND A DECREASED CAPILLARIZATION AND OXIDATIVE PHOSPHORYLATION CAPACITY, THE MOLECULAR BASIS FOR MUSCLE ATROPHY IS COMPLEX AND REMAINS PARTLY UNKNOWN. MAJOR DIFFICULTIES LIE IN PATIENT HETEROGENEITY, ACCESSING PATIENTS' SAMPLES, AND COMPLEX MULTIFACTORIAL PROCESS INCLUDING EXTRINSIC MECHANISMS, SUCH AS TOBACCO SMOKE OR DISUSE, AND INTRINSIC MECHANISMS, SUCH AS OXIDATIVE STRESS, HYPOXIA, OR SYSTEMIC INFLAMMATION. MUSCLE WASTING IS ALSO A HIGHLY DYNAMIC PROCESS WHOSE INVESTIGATION IS HAMPERED BY THE DIFFERENTIAL PROTEIN REGULATION ACCORDING TO THE STAGE OF ATROPHY. IN THIS REVIEW, WE REPORT AND DISCUSS RECENT DATA REGARDING THE MOLECULAR ALTERATIONS IN COPD LEADING TO IMPAIRED MUSCLE MASS, INCLUDING INFLAMMATION, HYPOXIA AND HYPERCAPNIA, MITOCHONDRIAL DYSFUNCTION, DIVERSE METABOLIC CHANGES SUCH AS OXIDATIVE AND NITROSATIVE STRESS AND GENETIC AND EPIGENETIC MODIFICATIONS, ALL LEADING TO AN IMPAIRED ANABOLIC/CATABOLIC BALANCE IN THE MYOCYTE. WE RECAPITULATE DATA CONCERNING SKELETAL MUSCLE DYSFUNCTION OBTAINED IN THE DIFFERENT RODENT MODELS OF COPD. FINALLY, WE PROPOSE SEVERAL PATHWAYS THAT SHOULD BE INVESTIGATED IN COPD SKELETAL MUSCLE DYSFUNCTION IN THE FUTURE. 2023