Effect of exercise intensities on free fatty acid uptake in whole-body organs measured with (123)I-BMIPP-SPECT.
Our purpose was to evaluate the effects of exercise intensities on free fatty acid (FFA) uptake in skeletal muscles, myocardium and liver among humans using (123)I-labeled 15-(p-iodophenyl)-3-(R,S)-methyl-pentadecanoic acid ((123)I-BMIPP) and single photon emission computed tomography technique (SPECT). Six untrained male subjects were studied after 35 min of ergometer bicycle exercise at 40, 70 and 80% maximal aerobic power (VO(2max)) One subject was studied as resting control. SPECT scan was done 40 min after (123)I-BMIPP injection. Mean fractional uptake (FU) in quadriceps femoris muscle (QF) were 0.029 +/- 0.001, 0.029 +/- 0.002 and 0.025 +/- 0.002% at 40, 70 and 80% VO(2max), respectively. FU of QF at 40 and 70% VO(2max) were significantly higher than those of 80% VO(2max). Mean FU into myocardium were 0.048 +/- 0.002, 0.052 +/- 0.004 and 0.050 +/- 0.003% and those in liver were 0.033 +/- 0.002, 0.032 +/- 0.002 and 0.034 +/- 0.003% at each loads, respectively. Any significant changes were not suggestive in liver and myocardium after exercise. Mean FU (the mean values of all exercise intensity) at exercise is 2.86, 0.96 and 0.71 times higher than those at rest in QF, myocardium and liver. These results suggest: (1) in skeletal muscles, energy requirements at above lactate threshold at high exercise intensity predominantly depend upon other intramuscular energy substrates, (2) there is possibility of energy compensation by other substrates in myocardium at higher exercise intensity, (3) FFA uptake in liver might decrease after exercise; however, the influence of exercise intensities is not suggested.
Kitada
Koji
K
Department of Medicine and Science in Sports and Exercise, Graduate School of Medicine, Tohoku University, Sendai 980-8576, Japan.
Kubota
Kazuo
K
Nagatomi
Ryoichi
R
Itoh
Masatoshi
M
Tashiro
Manabu
M
Fukuda
Hiroshi
H
Masud
Mehedi
M
Fujimoto
Toshihiko
T
D004734:Energy Metabolism; D015444:Exercise / Q000502:physiology*; D005227:Fatty Acids / Q000008:administration & dosage / Q000493:pharmacokinetics*; D005230:Fatty Acids, Nonesterified / Q000378:metabolism*; D006321:Heart / Q000000981:diagnostic imaging; D006801:Humans; D007275:Injections, Intravenous; D007457:Iodine Radioisotopes; D007462:Iodobenzenes / Q000008:administration & dosage / Q000493:pharmacokinetics*; D008099:Liver / Q000000981:diagnostic imaging / Q000378:metabolism*; D008297:Male; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism*; D010101:Oxygen Consumption; D015899:Tomography, Emission-Computed, Single-Photon; D055815:Young Adult
D005227:Fatty Acids; D005230:Fatty Acids, Nonesterified; D007457:Iodine Radioisotopes; D007462:Iodobenzenes; C049338:iodofiltic acid