Type I diabetes affects skeletal muscle glutamine uptake in a fiber-specific manner.
Skeletal muscle serves as the body's major glutamine repository, and releases glutamine at enhanced rates during diabetes, but whether all muscles are equally affected is unknown. System N(m) activity mediates most trans-sarcolemmal glutamine movement, and although two System N (SN) isoforms have been identified (SN1/sodium-coupled neutral amino acid transporter or System N and A transporters [SNAT]-3; and SN2/SNAT5), their expression in skeletal muscle remains controversial. Here, the impact of Type I diabetes on glutamine uptake and System N transporter expression were examined in fast- and slow-twitch skeletal muscle from spontaneously diabetic (BB/Wor-DP) rats. Net glutamine uptake in fast-twitch fibers was decreased 75%-95%, but enhanced more than 2-fold in slow-twitch muscle from diabetic animals relative to nondiabetic controls. Both SNAT3 and SNAT5 mRNA were expressed in both muscle fiber types and their abundance was unaffected by diabetes. This represents the first report of differential fiber-specific effects of diabetes on skeletal muscle glutamine transport and the co-expression of distinct System N transporters in skeletal muscle.
Onan
Marie C
MC
Department of Biology, Saint Louis University, St. Louis, MO 63103-2010, USA.
Fisher
Jonathan S
JS
Ju
Jeong-Sun
JS
Fuchs
Bryan C
BC
Bode
Barrie P
BP
D026921:Amino Acid Transport Systems, Neutral / Q000235:genetics; D000818:Animals; D001483:Base Sequence; D018076:DNA, Complementary; D003922:Diabetes Mellitus, Type 1 / Q000378:metabolism*; D005973:Glutamine / Q000378:metabolism*; D008969:Molecular Sequence Data; D018485:Muscle Fibers, Skeletal / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D012689:Sequence Homology, Nucleic Acid
D026921:Amino Acid Transport Systems, Neutral; D018076:DNA, Complementary; D012333:RNA, Messenger; C424137:SLC38A5 protein, human; C403222:system N protein 1; D005973:Glutamine