Conversion of cholesterol to biologically active steroids is a multi-step enzymatic process. Along with some important enzymes, like cholesterol side-chain cleavage enzyme (P450scc) and 3β-hydroxysteroid dehydrogenase/isomerase (3β-HSD), several proteins play key role in steroidogenesis. The role of steroidogenic acute regulatory (StAR) protein is well established. A novel protein, BRE, found mainly in brain, adrenals and gonads, was highly expressed in hyperplastic rat adrenals with impaired steroidogenesis, suggesting its regulation by pituitary hormones. To further elucidate its role in steroidogenic tissues, mouse Leydig tumor cells (mLTC-1) were transfected with BRE antisense probes. Morphologically the BRE antisense cells exhibited large cytoplasmic lipid droplets and failed to shrink in response to human chorionic gonadotropin. Although cAMP production, along with StAR and P450scc mRNA expression, was unaffected in BRE antisense clones, progesterone and testosterone yields were significantly decreased, while pregnenolone was increased in response to human chorionic gonadotropin stimulation or in the presence of 22(R)OH-cholesterol. Furthermore, whereas exogenous progesterone was readily converted to testosterone, pregnenolone was not, suggesting impairment of pregnenolone-to-progesterone conversion, a step metabolized by 3β-HSD. That steroidogenesis was compromised at the 3β-HSD step was further confirmed by the reduced expression of 3β-HSD type I (3ß-HSDI) mRNA in BRE antisense cells compared with controls. Our results suggest that BRE influences steroidogenesis through its effects on 3β-HSD action, probably affecting its transcription.

Thyroid hormones (THs) are essential for normal fetal development, with even mild perturbation in maternal thyroid status in early pregnancy being associated with neurodevelopmental delay in children. Transplacental transfer of maternal THs is critical, with increasing evidence suggesting a role for 3,3′,5-tri-iodothyronine (T3) in development and function of the placenta itself, as well as in development of the central nervous and other organ systems. Intrauterine growth restriction (IUGR) is associated with fetal hypothyroxinaemia, a factor that may contribute to neurodevelopmental delay. The recent description of monocarboxylate transporter 8 (MCT8) as a powerful and specific TH membrane transporter, and the association of MCT8 mutations with profound neurodevelopmental delay, led us to explore MCT8 expression in placenta. We describe the expression of MCT8 in normal human placenta throughout gestation, and in normal third-trimester placenta compared with that associated with IUGR using quantitative reverse transcriptase PCR. MCT8 mRNA was detected in placenta from early first trimester, with a significant increase with advancing gestation (P=0.007). In the early third trimester, MCT8 mRNA was increased in IUGR placenta compared with normal samples matched for gestational age (P<0.05), but there was no difference between IUGR and normal placenta in the late third trimester. Western immunoblotting findings in IUGR and normal placentae were in accord with mRNA data. MCT8 immunostaining was demonstrated in villous cytotrophoblast and syncytiotrophoblast as well as extravillous trophoblast cells from the first trimester onwards with increasingly widespread immunoreactivity seen with advancing gestation. In conclusion, expression of MCT8 in placenta from early gestation is compatible with an important role in TH transport during fetal development and a specific role in placental development. Altered expression in placenta associated with IUGR may reflect a compensatory mechanism attempting to increase T3 uptake by trophoblast cells.