MECHANISMS MEDIATING POSTPRANDIAL BLOOD-PRESSURE REDUCTION IN YOUNG AND ELDERLY SUBJECTS

The objective of this study was to clarify potential differences in ho rmonal, neurogenic and hemodynamic mechanisms mediating postprandial b lood pressure (BP) reduction. In 12 age- and body mass index-matched y oung normotensive (NT) subjects, 21 elderly NT, 17 young hypertensive (EH) patients, acid 32 elderly EH we measured BP, blood glucose, plasm a insulin (IRI), and norepinephrine (NE) levels before and every 30 mi n for 3 h after a 75 g oral glucose solution ingestion. Cardiac output (CO) and total systemic resistance (TSR) were also measured before an d 1 h after oral glucose ingestion. Postprandial BP reduction, defined as 10% or more decline in mean BP was recognized in 3/12 (25%) young NT, 9/21 (43%) elderly NT, 5/17 (29%) young EH, and 20/32 (63%) elderl y EH. The most consistent finding was that the IRI response to glucose was high in all subjects with postprandial BP reduction regardless of age or level of BP, although changes in blood glucose levels showed n o major differences, The NE level was low in young and elderly NT with postprandial BP reduction, but in EH the level was not different. Inc reases in CO in elderly subjects with postprandial BP reduction was si gnificantly less than that in subjects without postprandial BP reducti on. In addition, the decrease in TSR in young subjects with postprandi al BP reduction was significantly greater than that in subjects withou t postprandial BP reduction, while the decrease in elderly subjects wa s not different between the subjects with and without postprandial BP reduction. In conclusion, postprandial BP reduction in elderly EH appe ars to be associated with hyperinsulinemia independent of age and BP s tatus. The vasodilator effects of insulin may contribute to postprandi al BP reduction. A second conclusion is that impairment of sympathetic nervous system responses to insulin may also contribute to altered po stprandial hemodynamic responses especially in EH, suggesting multiple mechanisms in origin of postprandial BP reduction.