Inhibition of fetal growth and survival by testosterone administration to pregnant sheep

Prenatal testosterone-induced fetal growth restriction is associated with down-regulation of rat placental amino acid transport

BACKGROUND

Exposure of pregnant mothers to elevated concentrations of circulating testosterone levels is associated with fetal growth restriction and delivery of small-for-gestational-age babies. We examined whether maternal testosterone crosses the placenta to directly suppress fetal growth or if it modifies placental function to reduce the capacity for transport of nutrients to the fetus.

METHODS

Pregnant rats were exposed to testosterone propionate (TP; 0.5 mg/kg) by daily subcutaneous injection from gestational days (GD) 15-19. Maternal and fetal testosterone levels, placental nutrient transport activity and expression of transporters and birth weight of pups and their anogenital distances were determined.

RESULTS

This dose of TP doubled maternal testosterone levels but had no effect on fetal testosterone levels. Maternal daily weight gain was significantly lower only on GD 19 in TP treated dams compared to controls. Placental weight and birth weight of pups were significantly reduced, but the anogenital distance of pups were unaffected by TP treatment. Maternal plasma amino acids concentrations were altered following testosterone exposure, with decreases in glutamine, glycine, tyrosine, serine, proline, and hydroxyproline and increases in asparagine, isoleucine, leucine, lysine, histidine and arginine. In the TP dams, placental system A amino acid transport activity was significantly reduced while placental glucose transport capacity was unaffected. Decreased expression of mRNA and protein levels of slc38a2/Snat2, an amino acid transporter, suggests that reduced transporter proteins may be responsible for the decrease in amino acid transport activity.

CONCLUSIONS

Taken together, these data suggest that increased maternal testosterone concentrations do not cross the placenta to directly suppress fetal growth but affects amino acid nutrient delivery to the fetus by downregulating specific amino acid transporter activity.

Maternal androgen levels during pregnancy are associated with early-life growth in Geoffroy's marmosets, Callithrix geoffroyi

Fetal development is a critical period of physical development, and factors in the intrauterine environment can cause lasting effects on the growth and development of offspring. There is little research evaluating organizational effects of early androgen exposure of endogenous maternal origins on the prenatal and postnatal growth of offspring. We evaluated the association between maternal androgen levels during gestation and pre- and postnatal growth of offspring. Maternal androgen levels in marmoset females were measured using enzyme immunoassays of urine samples acquired during 18 pregnancies. Somatic measurements of the resulting 25 viable offspring were taken on postnatal days (PND) 2, 30, 60, 120, 180, 240, and 300. Maternal androgen levels during the first trimester were negatively associated with weight, body length, and several girth measurements (i.e., torso, head, chest, and arm circumference) of offspring on PND 2. First trimester maternal androgen was also negatively associated with physical growth during early and late infancy but seemed to be positively associated with a rebound in juvenile growth. Exposure to maternal androgen during early gestation led to both a reduction in birth weight and postnatal catch-up for both males and females, equally. Fetal growth retardation and the reprogramming of metabolic tissues by exposure to prenatal androgen could be mediating factors of suppressed postnatal growth.

Prenatal testosterone excess programs reproductive and metabolic dysfunction in the female

Findings discussed in this review stress the importance of normal estrogen and androgen signaling at appropriate developmental time points in maintaining normal phenotypic expression, reproductive and metabolic function and document how inappropriate steroid signaling, at inopportune times can have undesirable outcomes. For example, inappropriate testosterone exposure during fetal life alters the developmental trajectory of the female culminating in a suite of disorders, which include intrauterine growth-retardation and postnatal catch up growth, phenotypic masculinization, reproductive neuroendocrine and ovarian disruptions leading to progressive loss of cyclicity and metabolic disruptions manifested as hyperinsulinemia.