Chemical sympathectomy further increases muscle protein degradation of acutely diabetic rats.
The present work investigated the role of the sympathetic nervous system (SNS) in the control of protein degradation in skeletal muscles from rats with streptozotocin (STZ)-induced diabetes. Diabetes (1, 3, and 5 days after STZ) induced a significant increase in the norepinephrine content of soleus and EDL muscles, but it did not affect plasma catecholamine levels. Chemical sympathectomy induced by guanethidine (100 mg/kg body weight, for 1 or 2 days) reduced muscle norepinephrine content to negligible levels (less than 5%), decreased plasma epinephrine concentration, and further increased the high rate of protein degradation in muscles from acutely diabetic rats. The rise in the rate of proteolysis (nmol.mg wet wt(-1).2h(-1)) in soleus from 1-day diabetic sympathectomized rats was associated with increased activities of lysosomal (0.127 +/- 0.008 vs. 0.086 +/- 0.013 in diabetic control) and ubiquitin (Ub)-proteasome-dependent proteolytic pathways (0.154 +/- 0.007 vs. 0.121 +/- 0.006 in diabetic control). Increases in Ca2+-dependent (0.180 +/- 0.007 vs. 0.121 +/- 0.011 in diabetic control) and Ub-proteasome-dependent proteolytic systems (0.092 +/- 0.003 vs. 0.060 +/- 0.002 in diabetic control) were observed in EDL from 1-day diabetic sympathectomized rats. The lower phosphorylation levels of AKT and Foxo3a in EDL muscles from 3-day diabetic rats were further decreased by sympathectomy. The data suggest that the SNS exerts acute inhibitory control of skeletal muscle proteolysis during the early stages of diabetes in rats, probably involving the AKT/Foxo signaling pathway.
Baviera
Amanda Martins
AM
Department of Biochemistry & Immunology, School of Medicine, University of São Paulo, Ribeirão Preto, SP, Brazil.
Zanon
Neusa Maria
NM
Navegantes
Luiz Carlos C
LC
Migliorini
Renato Hélios
RH
Kettelhut
Isis C
IC
D000818:Animals; D001786:Blood Glucose / Q000187:drug effects; D001835:Body Weight / Q000187:drug effects / Q000502:physiology; D002118:Calcium / Q000378:metabolism; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism* / Q000473:pathology; D004195:Disease Models, Animal; D004837:Epinephrine / Q000097:blood; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors / Q000378:metabolism; D006145:Guanethidine / Q000633:toxicity; D008247:Lysosomes / Q000378:metabolism; D008297:Male; D009124:Muscle Proteins / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism*; D009638:Norepinephrine / Q000378:metabolism; D051058:Oncogene Protein v-akt / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013563:Sympathectomy, Chemical; D013997:Time Factors; D025801:Ubiquitin / Q000378:metabolism
D001786:Blood Glucose; C499515:FOXO3 protein, rat; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors; D009124:Muscle Proteins; D025801:Ubiquitin; D051058:Oncogene Protein v-akt; D046988:Proteasome Endopeptidase Complex; D002118:Calcium; D009638:Norepinephrine; D004837:Epinephrine; D006145:Guanethidine