Estrogen stimulates fetal vascular endothelial growth factor expression and microvascularization.

We recently showed that the ratio of capillaries to myofibers in skeletal muscle, which accounts for 80% of insulin-directed glucose uptake and metabolism, was reduced in baboon fetuses in which estrogen was suppressed by maternal letrozole administration. Since vascular endothelial growth factor (VEGF) promotes angiogenesis, the present study determined the impact of estrogen deprivation on fetal skeletal muscle VEGF expression, capillary development, and long-term vascular and metabolic function in 4- to 8-year-old adult offspring. Maternal baboons were untreated or treated with letrozole or letrozole plus estradiol on days 100-164 of gestation (term = 184 days). Skeletal muscle VEGF protein expression was suppressed by 45% (P < 0.05) and correlated (P = 0.01) with a 47% reduction (P < 0.05) in the number of capillaries per myofiber area in fetuses of baboons in which serum estradiol levels were suppressed 95% (P < 0.01) by letrozole administration. The reduction in fetal skeletal muscle microvascularization was associated with a 52% decline (P = 0.02) in acetylcholine-induced brachial artery dilation and a 23% increase (P = 0.01) in mean arterial blood pressure in adult progeny of letrozole-treated baboons, which was restored to normal by letrozole plus estradiol. The present study indicates that estrogen upregulates skeletal muscle VEGF expression and systemic microvessel development within the fetus as an essential programming event critical for ontogenesis of systemic vascular function and insulin sensitivity/glucose homeostasis after birth in primate offspring.