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

• Published in: Archives of oral biology Vol. 49; no. 10; pp. 777 - 782
• Main Authors: Saito, T, Fukui, K, Akutsu, S, Nakagawa, Y, Ishibashi, K, Nagata, J, Shuler, C.F, Yamane, A
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01-10-2004
• Subjects: Animals; Dentistry; Diet consistency; Food; IGF; IGFBP; IGFR; Insulin-Like Growth Factor Binding Proteins - analysis; Insulin-Like Growth Factor I - analysis; Insulin-Like Growth Factor II - analysis; Male; Masseter; Masseter Muscle - growth & development; Masseter Muscle - metabolism; Myosin Heavy Chains - analysis; Nerve Fibers - metabolism; Rats; Rats, Wistar; Receptor, IGF Type 1 - analysis; Receptor, IGF Type 2 - analysis; Receptors, Somatomedin - analysis; Reverse Transcriptase Polymerase Chain Reaction - methods; RNA, Messenger - analysis; Somatomedins - analysis; Weaning; IGFBP; IGFR; Masseter; IGF; Diet consistency
• ISSN: 0003-9969; 1879-1506
• DOI: 10.1016/j.archoralbio.2004.02.014

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.