Modulation by dietary restriction in gene expression related to insulin-like growth factor-1 in rat muscle.
Physiological adaptations induced by dietary restriction might include the modulation of the insulin-like growth factor 1 (IGF-1) axis. We investigated the effects of dietary restriction on aging-dependent changes in plasma level of IGF-1 and gene expression levels of type-1 IGF receptor (IGFR), insulin receptor substrate-1 (IRS-1), and IGF-1 in the diaphragm and quadriceps femoris muscle (QFM) of male F344 rats. The animals were fed ad libitum throughout life (AL), or provided with 70% of diet of AL rats from 6 weeks of age (DR). The plasma IGF-1 and steady-state levels of the genes were quantified by radioimmunoassay and the reverse transcription-polymerase chain reaction method, respectively. Immunohistochemical analysis in tissue sections was also performed for IGFR. Our results showed that dietary restriction: 1) decreased the plasma level of IGF-1; 2) increased the steady-state level of IGFR-mRNA at 6 and 16 months of age. and the peptide level at 6 months; 3) maintained IGF-1- and IRS-1-mRNA at a level similar to that in AL rats; and 4) delayed or inhibited an aging-dependent increase in IGFR-mRNA in the muscles. The present results suggest that dietary restriction could modulate IGF-1 signaling by augmenting local tissue response to IGF-1 and by maintaining the local production of the peptide, even though plasma IGF-1 is reduced.
Tomita
M
M
Department of Pathology, Nagasaki University School of Medicine, Japan.
Shimokawa
I
I
Higami
Y
Y
Yanagihara-Outa
K
K
Kawahara
T
T
Tanaka
K
K
Ikeda
T
T
Shindo
H
H
D000375:Aging / Q000502:physiology*; D000818:Animals; D003964:Diaphragm / Q000737:chemistry / Q000502:physiology*; D002149:Energy Intake / Q000502:physiology*; D015870:Gene Expression / Q000502:physiology; D007334:Insulin-Like Growth Factor I / Q000235:genetics* / Q000378:metabolism; D008297:Male; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D011916:Rats, Inbred F344; D017526:Receptor, IGF Type 1 / Q000032:analysis
D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I; D017526:Receptor, IGF Type 1