Muscle-type specific intramyocellular and hepatic lipid metabolism during starvation in wistar rats.
The physiological dynamics of intramyocellular lipids (IMCLs) in different muscle types and of hepatocellular lipids (HepCLs) are still uncertain. The dynamics of IMCLs in the soleus, tibialis anterior, and extensor digitorum longus (EDL) muscles and HepCL during fed, 12- to 72-h starved, and refed conditions were measured in vivo by (1)H-magnetic resonance spectroscopy (MRS) in Wistar rats. Despite significant elevations of free fatty acids (FFAs) during starvation, HepCLs and IMCLs in soleus remained constant. In tibialis anterior and EDL, however, IMCLs increased significantly by 170 and 450% after 72 h of starvation, respectively. After refeeding, elevated IMCLs dropped immediately in both muscles. Total muscle long-chain acyl-CoAs (LCACoAs) remained constant during the study period. Hepatic palmitoleoyl-CoA (C16:1) decreased significantly during starvation while total hepatic LCACoAs increased significantly. Consistent with constant values for FFAs, HepCLs, IMCLs, and muscle LCACoAs from 12-72 h of starvation, insulin sensitivity did not change. We conclude that during starvation-induced adipocytic lipolysis, oxidative muscles dispose elevated FFAs by oxidation, while nonoxidative ones neutralize FFAs by reesterification. Both mechanisms might prevent impairment of insulin signaling by maintaining low levels of LCACoAs. Hepatic palmitoleoyl-CoA might have a special role in lipid metabolism due to its unique dynamic profile during starvation.
Aventis Pharma Deutschland, Frankfurt, Germany.
Claudia
C
Neumann-Haefelin
Anja
A
Beha
Johanna
J
Kuhlmann
Ulrich
U
Belz
Martin
M
Gerl
Manfred
M
Quint
Gabriele
G
Biemer-Daub
Mark
M
Broenstrup
Marion
M
Stein
Elke
E
Kleinschmidt
Hans-Ludwig
HL
Schaefer
Dieter
D
Schmoll
Werner
W
Kramer
Hans-Paul
HP
Juretschke
Andreas W
AW
Herling
D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D015309:Glucose Clamp Technique; D050356:Lipid Metabolism; D008099:Liver / Q000378:metabolism*; D008112:Liver Glycogen / Q000378:metabolism*; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism*; D009928:Organ Specificity; D051381:Rats; D017208:Rats, Wistar; D013217:Starvation / Q000378:metabolism*; D013997:Time Factors; D014280:Triglycerides / Q000378:metabolism
D001786:Blood Glucose; D008112:Liver Glycogen; D014280:Triglycerides