Mean arterial blood pressure and serum levels of the molar ratio of insulin-like growth factor-1 to its binding protein-3 in healthy centenarians

Objective Healthy centenarians have a greater molar ratio of plasma insulin -like growth factor-1 to insulin-like growth factor binding protein-3 than that of aged subjects. We investigated the question of whether differences in mean arterial pressure and in this plasma ratio were related in healthy centenarians. Subjects and methods We studied 52 subjects in total, 30 aged subjects (70- 99 years) and 22 healthy centenarians (>100 years) to determine differences in mean arterial pressure, endothelial function and intracellular cation l evels. Results In the healthy centenarians, the molar ratio of fasting plasma insu lin-like growth factor-1 to its binding protein-3 was significantly correla ted with mean arterial pressure (r = -0.66, P < 0.001). Baseline (19.3 +/- 1.5 versus 27.6 +/- 2.2 pmol/l, P < 0.05) and L-arginine-stimulated percent age increases in the plasma total nitrate : nitrite ratio (67 +/- 3.4 versu s 48 +/- 4.5%, P < 0.03) were greater in the healthy centenarians than in t he aged subjects. An L-arginine bolus elicited an increase in forearm blood flow which was correlated with the percentage increase in the plasma total nitrate : nitrite ratio (r = 0.79, P < 0.001) and with the fasting erythro cyte magnesium concentration (r = 0.80, P < 0.001) in healthy centenarians. Both correlations remained significant (P < 0.01) after adjustment for sex , body mass index and the waist : hip ratio. Moreover, the fasting plasma m olar ratio of insulin-like growth factor-1 to its binding protein-3 was cor related with the percentage increase in forearm blood flow (r = 0.59, P < 0 .005) and with the percentage increase in the plasma total nitrate : nitrit e ratio (r = 0.54, P < 0.009) in healthy centenarians. The centenarians had higher baseline total erythrocyte magnesium and lower calcium concentratio ns than the aged subjects. The addition of insulin growth factor-1 to the i ncubation medium increased the total intracellular erythrocyte magnesium co ntent and decreased the calcium content in both groups of subjects. Neverth eless, the percentage increase in total erythrocyte magnesium (33 +/- 3.8 v ersus 12 +/- 3.4%, P < 0.03) and decline in intracellular calcium (17 +/- 2 .8 versus 8 +/- 3.1%, P < 0.02) concentrations were greater in the healthy centenarians than the aged subjects. Conclusion In healthy centenarians, insulin-like growth factor-1 may preser ve endothelial function and modulate the intracellular cation content, thus contributing to a lower mean arterial pressure than that in aged subjects. J Hypertens 1999, 17:67-73 (C) Lippincott Williams & Wilkins.