Effects of diet consistency on the expression of insulin-like growth factors (IGFs), IGF receptors and IGF binding proteins during the development of rat masseter muscle soon after weaning.
A soft diet facilitates the development of faster-type fibres in rat masseter muscle in the 9 days after weaning compared with a hard diet. To determine whether insulin-like growth factors (IGFs), IGF receptors (IGFRs) and IGF binding proteins (IGFBPs) are involved in this fibre-type alteration, the expression of myosin heavy chain (MHC), IGF, IGFR and IGFBP mRNAs in the masseter muscle of rats fed a hard or soft diet for 9 days after weaning was analysed using competitive, reverse transcriptase-polymerase chain reaction. A soft diet decreased the expression of MHC IIa (slower type) by 70%, but increased the expression of MHC IIx (intermediate type) and IIb (faster type) by 80 and 582%, respectively, compared with a hard diet. These findings verified that a soft diet facilitates the development of faster-type fibres in rat masseter muscle compared with a hard diet. A soft diet induced reductions of 25-76% (P < 0.05-0.01) in the expression of IGF-I, IGF-II, IGFR2, IGFBP4 and IGFBP6 compared with a hard diet, but induced a 25% (P < 0.05) increase only in expression of IGFBP3. These findings suggest that the changes in expression of IGF-I, IGF-II, IGFR2, IGFBP3, IGFBP4 and IGFBP6 are associated with the fibre-type alteration of rat masseter muscle in response to diet consistency soon after weaning.
Second Department of Oral and Maxillofacial Surgery, Tsurumi University School of Dental Medicine, 2-1-3, Tsurumi-ku, Yokohama 230-8501, Japan.
T
T
Saito
K
K
Fukui
S
S
Akutsu
Y
Y
Nakagawa
K
K
Ishibashi
J
J
Nagata
C F
CF
Shuler
A
A
Yamane
D000818:Animals; D005502:Food; D018969:Insulin-Like Growth Factor Binding Proteins / Q000032:analysis*; D007334:Insulin-Like Growth Factor I / Q000032:analysis; D007335:Insulin-Like Growth Factor II / Q000032:analysis; D008297:Male; D008406:Masseter Muscle / Q000254:growth & development / Q000378:metabolism*; D018995:Myosin Heavy Chains / Q000032:analysis; D009412:Nerve Fibers / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D017526:Receptor, IGF Type 1 / Q000032:analysis; D017527:Receptor, IGF Type 2 / Q000032:analysis; D017451:Receptors, Somatomedin / Q000032:analysis*; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D013002:Somatomedins / Q000032:analysis*; D014886:Weaning
D018969:Insulin-Like Growth Factor Binding Proteins; D012333:RNA, Messenger; D017527:Receptor, IGF Type 2; D017451:Receptors, Somatomedin; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D017526:Receptor, IGF Type 1; D018995:Myosin Heavy Chains