title: Eccentric contractions decrease glucose transporter transcription rate, mRNA, and protein in skeletal muscle.
abstract: We have recently shown that eccentric contractions (ECs; forced lengthening of active muscle) elicit a delayed decrease in glucose transporter (GLUT-4) protein content in rat skeletal muscle and a decrease in subsequent contraction-stimulated glucose transport. Here, we investigate whether this decrease in total GLUT-4 protein after prior ECs is due to changes in GLUT-4 gene transcription rate and GLUT-4 mRNA level. Furthermore, the effect of prior ECs on sarcolemmal GLUT-4 protein content in plasma membrane (PM) vesicles isolated from contraction-stimulated muscle was determined. Rat gastrocnemius muscle was electrically stimulated for ECs, and the contralateral muscle served, as unstimulated control (UC). Two days later, the total GLUT-4 protein content was decreased by 50% (P < 0.05) and 32% (P < 0.05) in the white and red gastrocnemius muscle, respectively. Furthermore, the GLUT-4 mRNA concentration was decreased by 41% (P < 0.05) in both the white and red gastrocnemius muscle. Moreover, the GLUT-4 transcription rate, determined by nuclear run-on analysis, was decreased by 75% (P < 0.05) in mixed EC gastrocnemius muscle compared with UC muscle. PM vesicles were isolated from EC and UC muscle after 15 min of isometric contractions. The PM GLUT-4 protein content was reduced by 51% (P < 0.05) in EC muscle compared with UC muscle. In conclusion, 2 days after ECs, the GLUT-4 transcription rate, GLUT-4 mRNA, and GLUT-4 protein content were decreased in rat skeletal muscle. Moreover, the PM GLUT-4 protein content in contraction-stimulated muscle was decreased. We suggest that eccentric muscle contractions decrease muscle GLUT-4 transcription rate, resulting in a lower GLUT-4 protein content, which in turn decreases the number of GLUT-4 transporters translocated to the sarcolemma, ultimately leading to decreased contraction-induced muscle glucose transport.
authors.affiliation: Copenhagen Muscle Research Centre, August Krogh Institute, Copenhagen, Denmark.
authors.forename: S
authors.initials: S
authors.lastname: Kristiansen
authors.forename: J
authors.initials: J
authors.lastname: Jones
authors.forename: A
authors.initials: A
authors.lastname: Handberg
authors.forename: G L
authors.initials: GL
authors.lastname: Dohm
authors.forename: E A
authors.initials: EA
authors.lastname: Richter
mesh_terms: D000818:Animals; D004558:Electric Stimulation; D051275:Glucose Transporter Type 4; D009004:Monosaccharide Transport Proteins / Q000235:genetics* / Q000378:metabolism* / Q000502:physiology; D009119:Muscle Contraction; D009124:Muscle Proteins; D018482:Muscle, Skeletal / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D014158:Transcription, Genetic
chemical_list: D051275:Glucose Transporter Type 4; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; D012333:RNA, Messenger; C495694:Slc2a4 protein, rat