Moderate caloric restriction increases type 1 IGF receptors and protein synthesis in aging rats

• Published in: Mechanisms of ageing and development Vol. 71; no. 1; pp. 59 - 71
• Main Authors: D'Costa, Anselm P., Lenham, John E., Ingram, Rhonda L., Sonntag, William E.
• Format: Journal Article
• Language: English
• Published: Shannon Elsevier Ireland Ltd 01.10.1993; Elsevier Science
• Subjects: Aging; Aging - metabolism; Animals; Biological and medical sciences; Carrier Proteins - blood; Carrier Proteins - genetics; Development. Metamorphosis. Moult. Ageing; Energy Intake - physiology; Fundamental and applied biological sciences. Psychology; Insulin-Like Growth Factor Binding Protein 1; Insulin-Like Growth Factor I - genetics; Liver - metabolism; Male; Moderate caloric restriction; Plasma IGF-1; Protein Biosynthesis; Protein synthesis; Rats; Rats, Inbred BN; RNA, Messenger - metabolism; Somatomedins - genetics; Somatomedins - metabolism; Type 1 IGF receptors; Vertebrates: anatomy and physiology, studies on body, several organs or systems; Plasma IGF-1; Type 1 IGF receptors; Aging; Protein synthesis; Moderate caloric restriction; Proteins; Calorie; Vertebrata; Senescence; Mammalia; Deficient diet; Rat; Somatomedin C; Rodentia; Biosynthesis; Age; Biological receptor
• ISSN: 0047-6374; 1872-6216
• DOI: 10.1016/0047-6374(93)90035-P

Insulin-like growht factor-1 (IGF-1) is an anabolic hormone that mediates the actions of growth hormone (GH) and is found at lower concentrations in aged animals. These decreases in GH and IGF-1 appear to have important physiological consequences for aging, since protein synthesis decreases with age, and administration of GH and/or IGF-1 has been shown to increase protein synthesis. The present study was designed to determine (a) the relationship between the age-related changes in rates of tissue protein synthesis and plasma IGF-1 concentrations, (b) type 1 IGF receptor density in tissues and (c) whether long-term moderate caloric restriction, which is known to increase life-span, affects these relationships. Male Brown Norway rats were fed ad libitum or caloric-restricted (60% ad libitum) from 14 weeks of age and sacrificed at different ages. In ad libitum fed animals there were age-related decreases in plasma IGF-1 concentrations (14%) and in the rates of protein synthesis of the heart (36%) and liver (38%). Type 1 IGF receptor density remained constant in all tissues with age. The caloric-restricted animals exhibited plasma IGF-1 concentrations 33 to 42% lower than the ad libitum fed animals. However, rates of protein synthesis increased by 70 and 30% in heart and diaphragm, and this increase was associated with 60 to 100% increases in type 1 IGF receptor densities when compared with ad libitum fed animals. These data suggest that alterations in tissue type 1 IGF receptors as well as availability of IGF-1 may be important factors in understanding the regulation of protein synthesis by IGF-1 during aging or under conditions of long-term caloric restriction.