Abstract
Insulin resistance is a risk factor for coronary heart disease. The protection of
young women from coronary events is sharply reduced with menopause. To assess the
impact of menopause on glucose tolerance, insulin resistance, body weight gain, heart
size, and cardiac energy metabolism, we studied 28-week-old female SHR and Wistar-Kyoto
(WKY) rats, who were either ovariectomized (SHROVX and WKYOVX ) or sham-operated (SHRSHAM and WKYSHAM ). Animals underwent blood-pressure measurement and an oral glucose tolerance test
(OGTT). Hearts were weighed and assayed for metabolic enzyme activities. Female SHR were 33 % lighter and hypertensive (+ 36 mmHg), with 33 % larger hearts
(when corrected for body weight differences) compared to WKY. Although ovariectomized
animals of both strains were heavier overall than their sham-operated counterparts,
when heart weights were corrected for body weight, both OVX strains had lighter hearts
than both SHAM strains. Glucose and insulin responses during OGTT were similar between
the four groups; however, free fatty acid (FFA) responses were approximately 50 %
greater in SHR than WKY, although less in SHROVX than SHRSHAM . WKYOVX demonstrated 8 % lower ventricular hexokinase activity than WKYSHAM , which may reflect reduced cardiac glucose utilization. We also noted 16 % higher
citrate synthase activity in WKY hearts. In conclusion, the insulin resistance characteristic
of younger SHR is blunted in middle-aged female rats, although FFA responses remain
elevated. Ovariectomy did not alter in vivo glucose tolerance in this group; however, sex hormones may be important in maintaining
normal heart size and the potential for cardiac glucose metabolism.
Key words
Insulin Resistance - Hypertension - Cardiac Hypertrophy - Menopause
References
arthur.swislocki@med.va.gov
