Effect of lipid infusion on metabolism and force of rat skeletal muscles during intense contractions.
The hypothesis that during intense muscle contraction induced by electrical stimulation, long chain fatty acids (LCFA) might reduce mitochondrial ATP/ADP ratio, raising the contribution of glycolysis for ATP production was examined. The effect of a lipid infusion (Lipovenus emulsion) on UCP-3 mRNA level, lactate, glucose-6-phosphate (G-6P) and glycogen content was investigated in rat. Blood samples for determination of free fatty acids and lactate were collected at 0, 30 and 60 min during rest and at 0, 10 and 20 min during muscle contraction. The content of lactate, glycogen and G-6P was also determined in soleus (SO), red gastrocnemius (RG) and white gastrocnemius (WG) muscles collected immediately after muscle contraction period. In addition, the force level was determined during muscle contractions. The effect of Lipovenus emulsion on respiration of mitochondria isolated from rat skeletal muscle, and content of UCP-3 and lactate in cultured skeletal muscle cells was also determined. The in vivo experiments showed that Lipovenus induced a significant increase of UCP-3 mRNA levels. After Lipovenus infusion, lactate level was increased in RG muscle only, whereas the contents of glycogen and G-6P were decreased in both RG and WG muscles (P < 0.05). Lipovenus infusion failed to exert any effect on muscle force performance (P > 0.05). The in vitro experiments showed that Lipovenus infusion induced a significant increase in mitochondrial respiration, but had no effect on UCP-3 content. Lactate concentration was significantly increased in the culture medium of stimulated cells in the control and Lipovenus groups compared with the respective not-stimulated cells (P< 0.05). We concluded that as mitochondrial function becomes limited by the FFA-uncoupling effect, the ATP demand is mainly supplied by anaerobic glucose metabolism preventing an expected decrease in muscle contraction performance.
Silveira
Leonardor
L
Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of Sao Paulo, Botantã, Sao Paulo, Brazil.
Hirabara
Sandro M
SM
Alberici
Luciane C
LC
Lambertucci
Rafael H
RH
Peres
Carmem M
CM
Takahashi
Hilton K
HK
Pettri
Adhemar
A
Alba-Loureiro
Tatiana
T
Luchessi
Augusto D
AD
Cury-Boaventura
Maria F
MF
Vercesi
Anibal E
AE
Curi
Rui
R
D000818:Animals; D001483:Base Sequence; D002478:Cells, Cultured; D017931:DNA Primers / Q000235:genetics; D004558:Electric Stimulation; D005230:Fatty Acids, Nonesterified / Q000097:blood; D019298:Glucose-6-Phosphate / Q000378:metabolism; D007262:Infusions, Intravenous; D007473:Ion Channels / Q000235:genetics / Q000378:metabolism; D019344:Lactic Acid / Q000097:blood; D008055:Lipids / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D008931:Mitochondria, Muscle / Q000187:drug effects / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D018485:Muscle Fibers, Skeletal / Q000187:drug effects / Q000378:metabolism; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology*; D010101:Oxygen Consumption / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D000071246:Uncoupling Protein 2; D000071247:Uncoupling Protein 3
D017931:DNA Primers; D005230:Fatty Acids, Nonesterified; D007473:Ion Channels; D008055:Lipids; D024101:Mitochondrial Proteins; D012333:RNA, Messenger; C000604394:Ucp3 protein, rat; D000071246:Uncoupling Protein 2; D000071247:Uncoupling Protein 3; D019344:Lactic Acid; D019298:Glucose-6-Phosphate