Dissociation of bone mineral density from age-related decreases in insulin-like growth factor-I and its binding proteins in the male rat

• Published in: Journal of gerontology (Kirkwood) Vol. 49; no. 5; p. B224
• Main Authors: Benedict, M R, Adiyaman, S, Ayers, D C, Thomas, F D, Calore, J D, Dhar, V, Richman, R A
• Format: Journal Article
• Language: English
• Published: United States 01.09.1994
• Subjects: Aging - metabolism; Animals; Bone and Bones - metabolism; Bone Density - physiology; Bone Diseases, Metabolic - etiology; Bone Diseases, Metabolic - metabolism; Carrier Proteins - blood; Carrier Proteins - metabolism; Insulin-Like Growth Factor I - metabolism; Male; Rats; Rats, Inbred F344; Specific Pathogen-Free Organisms
• ISSN: 0022-1422
• DOI: 10.1093/geronj/49.5.B224

We evaluated the possibility that age-related decreases in circulating and/or bone-associated insulin-like growth factor-I (IGF-I) and its binding proteins (BPs) were associated with the development of osteopenia in 8-, 16-, and 24-month-old specific pathogen-free Brown Norway/Fischer 344 male rats. We measured bone mineral densities (BMD) of femurs by dual-energy x-ray absorptiometry. IGFs and IGFBPs were extracted from bone and separated by molecular exclusion HPLC before quantitation by specific radioligand assays. BMD did not change significantly between 8 and 24 months of age. IGF-I levels decreased by about 30% between 8 and 24 months in both serum and bone. Similarly, both circulating and bone-derived IGFBPs also declined (30% and 60%, respectively) with age. Thus, maintenance of femoral BMD throughout most of the adult rat life span was dissociated from the age-related decline in circulating and bone-associated IGF-I and IGFBPs.