title: Prolonged Exposure of Primary Human Muscle Cells to Plasma Fatty Acids Associated with Obese Phenotype Induces Persistent Suppression of Muscle Mitochondrial ATP Synthase β Subunit.
abstract: Our previous studies show reduced abundance of the β-subunit of mitochondrial H+-ATP synthase (β-F1-ATPase) in skeletal muscle of obese individuals. The β-F1-ATPase forms the catalytic core of the ATP synthase, and it is critical for ATP production in muscle. The mechanism(s) impairing β-F1-ATPase metabolism in obesity, however, are not completely understood. First, we studied total muscle protein synthesis and the translation efficiency of β-F1-ATPase in obese (BMI, 36±1 kg/m2) and lean (BMI, 22±1 kg/m2) subjects. Both total protein synthesis (0.044±0.006 vs 0.066±0.006%·h-1) and translation efficiency of β-F1-ATPase (0.0031±0.0007 vs 0.0073±0.0004) were lower in muscle from the obese subjects when compared to the lean controls (P<0.05). We then evaluated these same responses in a primary cell culture model, and tested the specific hypothesis that circulating non-esterified fatty acids (NEFA) in obesity play a role in the responses observed in humans. The findings on total protein synthesis and translation efficiency of β-F1-ATPase in primary myotubes cultured from a lean subject, and after exposure to NEFA extracted from serum of an obese subject, were similar to those obtained in humans. Among candidate microRNAs (i.e., non-coding RNAs regulating gene expression), we identified miR-127-5p in preventing the production of β-F1-ATPase. Muscle expression of miR-127-5p negatively correlated with β-F1-ATPase protein translation efficiency in humans (r = - 0.6744; P<0.01), and could be modeled in vitro by prolonged exposure of primary myotubes derived from the lean subject to NEFA extracted from the obese subject. On the other hand, locked nucleic acid inhibitor synthesized to target miR-127-5p significantly increased β-F1-ATPase translation efficiency in myotubes (0.6±0.1 vs 1.3±0.3, in control vs exposure to 50 nM inhibitor; P<0.05). Our experiments implicate circulating NEFA in obesity in suppressing muscle protein metabolism, and establish impaired β-F1-ATPase translation as an important consequence of obesity.
authors.affiliation: Center for Metabolic and Vascular Biology, Arizona State University and Mayo Clinic in Arizona, Scottsdale, Arizona, United States of America.|School of Life Sciences, Arizona State University, Tempe, Arizona, United States of America.
authors.forename: Lee
authors.initials: L
authors.lastname: Tran
authors.affiliation: Center for Metabolic and Vascular Biology, Arizona State University and Mayo Clinic in Arizona, Scottsdale, Arizona, United States of America.|School of Life Sciences, Arizona State University, Tempe, Arizona, United States of America.
authors.forename: Paul D
authors.initials: PD
authors.lastname: Hanavan
authors.affiliation: Center for Metabolic and Vascular Biology, Arizona State University and Mayo Clinic in Arizona, Scottsdale, Arizona, United States of America.|School of Life Sciences, Arizona State University, Tempe, Arizona, United States of America.
authors.forename: Latoya E
authors.initials: LE
authors.lastname: Campbell
authors.affiliation: Department of Medicine, Mayo Clinic, Scottsdale, Arizona, United States of America.
authors.forename: Elena
authors.initials: E
authors.lastname: De Filippis
authors.affiliation: Center for Metabolic and Vascular Biology, Arizona State University and Mayo Clinic in Arizona, Scottsdale, Arizona, United States of America.|School of Life Sciences, Arizona State University, Tempe, Arizona, United States of America.
authors.forename: Douglas F
authors.initials: DF
authors.lastname: Lake
authors.affiliation: Center for Metabolic and Vascular Biology, Arizona State University and Mayo Clinic in Arizona, Scottsdale, Arizona, United States of America.|College of Health Solutions, Arizona State University, Phoenix, Arizona, United States of America.
authors.forename: Dawn K
authors.initials: DK
authors.lastname: Coletta
authors.affiliation: Department of Medicine, Mayo Clinic, Scottsdale, Arizona, United States of America.
authors.forename: Lori R
authors.initials: LR
authors.lastname: Roust
authors.affiliation: Center for Metabolic and Vascular Biology, Arizona State University and Mayo Clinic in Arizona, Scottsdale, Arizona, United States of America.|College of Health Solutions, Arizona State University, Phoenix, Arizona, United States of America.|Department of Medicine, Mayo Clinic, Scottsdale, Arizona, United States of America.
authors.forename: Lawrence J
authors.initials: LJ
authors.lastname: Mandarino
authors.affiliation: Department of Physiology, Midwestern University, Glendale, Arizona, United States of America.
authors.forename: Chad C
authors.initials: CC
authors.lastname: Carroll
authors.affiliation: Center for Metabolic and Vascular Biology, Arizona State University and Mayo Clinic in Arizona, Scottsdale, Arizona, United States of America.|School of Life Sciences, Arizona State University, Tempe, Arizona, United States of America.
authors.forename: Christos S
authors.initials: CS
authors.lastname: Katsanos
mesh_terms: D000328:Adult; D002478:Cells, Cultured; D004041:Dietary Fats / Q000008:administration & dosage; D044127:Epigenesis, Genetic; D005230:Fatty Acids, Nonesterified / Q000097:blood / Q000378:metabolism*; D005260:Female; D006801:Humans; D008297:Male; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism; D008931:Mitochondria, Muscle / Q000201:enzymology; D025261:Mitochondrial Proton-Translocating ATPases / Q000235:genetics / Q000378:metabolism*; D024510:Muscle Development / Q000235:genetics; D018485:Muscle Fibers, Skeletal / Q000201:enzymology / Q000378:metabolism*; D009124:Muscle Proteins / Q000096:biosynthesis / Q000235:genetics; D017570:MyoD Protein / Q000235:genetics; D018008:Myogenin / Q000235:genetics; D009765:Obesity / Q000097:blood / Q000235:genetics / Q000378:metabolism*; D013851:Thinness / Q000097:blood / Q000235:genetics / Q000378:metabolism
chemical_list: C506526:ATP5F1B protein, human; D004041:Dietary Fats; D005230:Fatty Acids, Nonesterified; C547276:MIRN127 microRNA, human; D035683:MicroRNAs; D009124:Muscle Proteins; D017570:MyoD Protein; C057363:MyoD1 myogenic differentiation protein; D018008:Myogenin; D025261:Mitochondrial Proton-Translocating ATPases