Aging is associated with decreased suppression of insulin-like growth factor binding protein-1 by insulin.
We determined whether aging influences circulating insulin-like growth factor-binding protein-1 (IGFBP-1) concentrations and, if so, whether this effect is explained by altered regulation of IGFBP-1 by insulin. Fasting levels of glucose, insulin, and IGFBP-1 were measured in 94 healthy volunteers, ages 24-93 yr. To determine the effect of aging on insulin-induced suppression of IGFBP-1, an oral glucose tolerance test (OGTT) was performed in 10 older (72-92 yr) and 10 younger (24-58 yr) nonobese subjects, matched for sex and body mass index. For all ages combined, the mean glucose level (+/- SE) averaged 4.9 +/- 0.1 mmol/L, and there was no significant change with aging. Fasting insulin and IGFBP-1 concentrations increased with advancing age (r = 0.37, P < 0.001 for age vs. insulin and r = 0.47, P < 0.001 for age vs. IGFBP-1). However, there was no correlation between insulin and IGFBP-1 concentrations. In multiple linear regression analysis, the age-related increase in IGFBP-1 was independent of body mass index. During the OGTT, the mean insulin concentration was significantly higher in the older group compared with the younger group (P < 0.001). Serum IGFBP-1 concentrations were higher in the fasting state as well as during the OGTT, and the mean percent decrease of IGFBP-1 below baseline was significantly smaller in the older compared to the younger subjects at 3 h (35 +/- 5% vs. 55 +/- 2%, P < 0.01). We conclude that aging is associated with decreased suppression of serum IGFBP-1 by insulin, as demonstrated by 1) lack of the inverse correlation between fasting insulin and IGFBP-1 seen in young adults; 2) concurrent elevation of fasting insulin and IGFBP-1 concentrations; and 3) a blunted decrease in serum IGFBP-1 during an OGTT.
Rutanen
E M
EM
Department of Obstetrics and Gynecology, Helsinki University Central Hospital, Finland.
Kärkkäinen
T
T
Stenman
U H
UH
Yki-Järvinen
H
H
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D002352:Carrier Proteins / Q000037:antagonists & inhibitors*; D005260:Female; D005951:Glucose Tolerance Test; D006801:Humans; D007328:Insulin / Q000494:pharmacology*; D018970:Insulin-Like Growth Factor Binding Protein 1; D008297:Male; D008875:Middle Aged; D009994:Osmolar Concentration; D013002:Somatomedins / Q000378:metabolism
D002352:Carrier Proteins; D007328:Insulin; D018970:Insulin-Like Growth Factor Binding Protein 1; D013002:Somatomedins