Fetal osteocalcin levels are related to placental 11 beta-hydroxysteroid dehydrogenase activity in humans

Inhibition of 11β-hydroxysteroid dehydrogenase 2 by the fungicides itraconazole and posaconazole

Impaired 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2)-dependent cortisol inactivation can lead to electrolyte dysbalance, hypertension and cardiometabolic disease. Furthermore, placental 11β-HSD2 essentially protects the fetus from high maternal glucocorticoid levels, and its impaired function has been associated with altered fetal growth and a higher risk for cardio-metabolic diseases in later life. Despite its important role, 11β-HSD2 is not included in current off-target screening approaches. To identify potential 11β-HSD inhibitors among approved drugs, a pharmacophore model was used for virtual screening, followed by biological assessment of selected hits. This led to the identification of several azole fungicides as 11β-HSD inhibitors, showing a significant structure-activity relationship between azole scaffold size, 11β-HSD enzyme selectivity and inhibitory potency. A hydrophobic linker connecting the azole ring to the other, more polar end of the molecule was observed to be favorable for 11β-HSD2 inhibition and selectivity over 11β-HSD1. The most potent 11β-HSD2 inhibition, using cell lysates expressing recombinant human 11β-HSD2, was obtained for itraconazole (IC₅₀ 139±14nM), its active metabolite hydroxyitraconazole (IC₅₀ 223±31nM) and posaconazole (IC₅₀ 460±98nM). Interestingly, experiments with mouse and rat kidney homogenates showed considerably lower inhibitory activity of these compounds towards 11β-HSD2, indicating important species-specific differences. Thus, 11β-HSD2 inhibition by these compounds is likely to be overlooked in preclinical rodent studies. Inhibition of placental 11β-HSD2 by these compounds, in addition to the known inhibition of cytochrome P450 enzymes and P-glycoprotein efflux transport, might contribute to elevated local cortisol levels, thereby affecting fetal programming.

Adverse maternal exposures, methylation of glucocorticoid-related genes and perinatal outcomes: a systematic review

Aim: Maternal environmental exposures affect perinatal outcomes through epigenetic placental changes. We examine the literature addressing associations between adverse maternal exposures, perinatal outcomes and methylation of key genes regulating placental cortisol metabolism. Methods: We searched three databases for studies that examined NR3C1 and HSD11β1/HSD11 β 2 methylation with maternal exposures or perinatal outcomes. Nineteen studies remained after screening. We followed Cochrane's PRISMA reporting guidelines (2009). Results: NR3C1 and HSD11 β methylation were associated with adverse infant neurobehavior, stress response, blood pressure and physical development. In utero exposure to maternal stress, nutrition, preeclampsia, smoking and diabetes were associated with altered NR3C1 and HSD11 β methylation. Conclusion: NR3C1 and HSD11 β methylation are useful biomarkers of specific environmental stressors associated with important perinatal outcomes that determine pediatric and adult disease risk.

Glucocorticoids as mediators of developmental programming effects

Epidemiological evidence suggests that exposure to an adverse environment in early life is associated with an increased risk of cardio-metabolic and behavioral disorders in adulthood, a phenomenon termed 'early life programming'. One major hypothesis for early life programming is fetal glucocorticoid overexposure. In animal studies, prenatal glucocorticoid excess as a consequence of maternal stress or through exogenous administration to the mother or fetus is associated with programming effects on cardiovascular and metabolic systems and on the brain. These effects can be transmitted to subsequent generations. Studies in humans provide some evidence that prenatal glucocorticoid exposure may exert similar programming effects on glucose/insulin homeostasis, blood pressure and neurodevelopment. The mechanisms by which glucocorticoids mediate these effects are unclear but may include a role for epigenetic modifications. This review discusses the evidence for glucocorticoid programming in animal models and in humans.

Maternal supplementation with dietary arachidonic and docosahexaenoic acids during lactation elevates bone mass in weanling rat and guinea pig offspring even if born small sized

Whether post-natal long chain polyunsaturated fatty acids (LCPUFA) elevates bone mineral content (BMC) of small and normal neonates was studied using pregnant rats and guinea pigs fed a control (C) diet or low protein (LP) diet to induce small neonates followed by C or LCPUFA diets during lactation. Measurements (days 3 and 21 post-partum) included BMC and density (BMD) plus bone metabolism. In rats LP reduced birth weight but at day 21 elevated weight and whole body BMC; LCPUFA enhanced spine BMC, tibia BMC and BMD and whole body BMD. In guinea pig pups, at days 3 and 21, LP reduced weight, whole body and regional BMC and BMD whereas LCPUFA reduced day 3 osteocalcin and elevated day 21 spine BMD. LCPUFA minimized loss of whole body BMC in dams and elevated osteocalcin in sows. LCPUFA during lactation enhances bone in normal and small neonates without compromising maternal bone.

Glucocorticoids, prenatal stress and the programming of disease

An adverse foetal environment is associated with increased risk of cardiovascular, metabolic, neuroendocrine and psychological disorders in adulthood. Exposure to stress and its glucocorticoid hormone mediators may underpin this association. In humans and in animal models, prenatal stress, excess exogenous glucocorticoids or inhibition of 11β-hydroxysteroid dehydrogenase type 2 (HSD2; the placental barrier to maternal glucocorticoids) reduces birth weight and causes hyperglycemia, hypertension, increased HPA axis reactivity, and increased anxiety-related behaviour. Molecular mechanisms that underlie the 'developmental programming' effects of excess glucocorticoids/prenatal stress include epigenetic changes in target gene promoters. In the case of the intracellular glucocorticoid receptor (GR), this alters tissue-specific GR expression levels, which has persistent and profound effects on glucocorticoid signalling in certain tissues (e.g. brain, liver, and adipose). Crucially, changes in gene expression persist long after the initial challenge, predisposing the individual to disease in later life. Intriguingly, the effects of a challenged pregnancy appear to be transmitted possibly to one or two subsequent generations, suggesting that these epigenetic effects persist.

Association between umbilical cord glucocorticoids and blood pressure at age 3 years

BACKGROUND

Animal data show that decreased activity of placental 11-beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2), which potently inactivates glucocorticoids (e.g. cortisol) to inert forms (cortisone), allows increased access of maternal glucocorticoids to the fetus and 'programs' hypertension. Data in humans are limited. We examined in humans the association between venous umbilical cord blood glucocorticoids, a potential marker for placental 11beta-HSD2 enzyme activity, and blood pressure at age 3 years.

METHODS

Among 286 newborns in Project Viva, a prospective pre-birth cohort study based in eastern Massachusetts, we measured cortisol (F) and cortisone (E) in venous cord blood and used the ratio of F/E as a marker for placental 11beta-HSD2 activity. We measured blood pressure (BP) when the offspring reached age 3 years. Using mixed effects regression models to control for BP measurement conditions, maternal and child characteristics, we examined the association between the F/E ratio and child BP.

RESULTS

At age 3 years, each unit increase in the F/E ratio was associated with a 1.6 mm Hg increase in systolic BP (95% CI 0.0 to 3.1). The F/E ratio was not associated with diastolic blood pressure or birth weight for gestational age z-score.

CONCLUSION

A higher F/E ratio in umbilical venous cord blood, likely reflecting reduced placental 11beta-HSD2 activity, was associated with higher systolic blood pressure at age 3 years. Our data suggest that increased fetal exposure to active maternal glucocorticoids may program later systolic blood pressure.

Epigenetic mechanisms of perinatal programming of hypothalamic-pituitary-adrenal function and health

Environmental effects on the materno-foetal interaction determine birth outcomes that predict health over the lifespan. Thus, maternal undernutrition or stress associate with low birth weight, leading to an increased risk of metabolic and cardiovascular illness in the offspring. We argue that these effects are, in part, mediated by direct and indirect effects on the hypothalamic-pituitary-adrenal (HPA) axis such that (i) the effect of maternal adversity on foetal growth is mediated by adrenal glucocorticoids and (ii) environmental adversity alters maternal physiology and behaviour, which then programs HPA activity in the offspring.

Glucocorticoid "Programming" and PTSD Risk

Epidemiological data have linked an adverse fetal environment with increased risks of cardiovascular, metabolic, neuroendocrine, and psychiatric disorders in adulthood. Prenatal stress and/or glucocorticoid excess might underlie this link. In animal models, prenatal stress, glucocorticoid exposure or inhibition/knockout of 11 beta-hydroxysteroid dehydrogenase type 2 (11 beta-HSD-2), the feto-placental barrier to maternal glucocorticoids, reduces birth weight and causes permanent hypertension, hyperglycemia, increased hypothalamic-pituitary-adrenal (HPA) axis activity and behavior resembling of anxiety. In humans, 11 beta-HSD-2 gene mutations cause low birth weight and placental 11 beta-HSD-2 activity correlates directly with birth weight and inversely with infant blood pressure. Low birth weight babies have higher plasma cortisol levels throughout adult life, indicating HPA programming. In human pregnancy, severe maternal stress affects the offspring HPA axis and associates with neuropsychiatric disorders. Posttraumatic stress disorder (PTSD) appears to be a variable in the effects. Intriguingly, some of these effects appear to be 'inherited' into a further generation, itself unexposed to exogenous glucocorticoids at any point in the lifespan from fertilization, implying epigenetic marks persist into subsequent generation(s). Overall, the data suggest that prenatal exposure to excess glucocorticoids programs peripheral and CNS functions in adult life, predisposing to some pathologies, perhaps protecting from others, and these may be transmitted perhaps to one or two subsequent generations.

Glucocorticoid programming

Epidemiological evidence suggests that an adverse fetal environment permanently programs physiology, leading to increased risks of cardiovascular, metabolic, and neuroendocrine disorders in adulthood. Prenatal glucocorticoid excess or stress might link fetal maturation and adult pathophysiology. In a variety of animal models, prenatal glucocorticoid exposure or inhibition of 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2), the fetoplacental "barrier" to maternal glucocorticoids, reduces birth weight and causes permanent hypertension, hyperglycemia, and increased hypothalamic-pituitary-adrenal axis (HPA) activity and behavior resembling anxiety. In humans, 11beta-HSD2 gene mutations cause low birth weight and reduced placental 11beta-HSD2 activity associated with intrauterine growth retardation. Low birth weight babies have higher plasma cortisol levels throughout adult life, indicating HPA programming. The molecular mechanisms may reflect permanent changes in the expression of specific transcription factors; key is the glucocorticoid receptor itself. Differential programming of the glucocorticoid receptor in different tissues reflects effects upon one or more of the multiple tissue-specific alternate first exons/promoters of the glucocorticoid receptor gene. Overall, the data suggest that either pharmacological or physiological exposure to excess glucocorticoids prenatally programs pathologies in adult life.

Glucocorticoid programming of the fetus; adult phenotypes and molecular mechanisms

It has been long recognised that the glucocorticoid administration to pregnant mammals (including humans) reduces offspring birth weight. Epidemiologically, low weight or thinness at birth is associated with an increased risk of cardiovascular and metabolic disorders in adult life. So, does fetal exposure to glucocorticoids produce such 'programming' of adult disorders? Here data are reviewed which show, in rodents and other model species, that antenatal exposure to glucocorticoids reduces offspring birth weight and produces permanent hypertension, hyperglycaemia, hyperinsulinaemia, altered behaviour and neuroendocrine responses throughout the lifespan. This occurs with exogenous (dexamethasone) or endogenous glucocorticoids, the latter achieved by inhibiting 11 beta-hydroxysteroid dehydrogenase type 2, the feto-placental enzymic barrier to maternal glucocorticoids. Processes underlying fetal programming include determination of the 'set point' of the hypothalamic-pituitary-adrenal axis and of tissue glucocorticoid receptor expression. Detailed molecular mechanisms are being dissected. Analogous stress axis hyperreactivity occurs in lower birth weight humans and may be an early manifestation and indicate approaches to manipulation or prevention of the phenotype.

Glucocorticoid programming of pituitary-adrenal function: mechanisms and physiological consequences

Increasing epidemiological evidence supports the notion that adverse events in fetal life permanently alter the structure and physiology of the adult offspring, a phenomenon dubbed 'fetal programming'. In particular, low weight or thinness at birth in humans is associated with an increased risk of cardiovascular and metabolic disorders as well as neuroendocrine dysfunction in adult life. Glucocorticoid administration during pregnancy is well-documented to both reduce offspring birth weight and alter the maturation of organs (hence their use to accelerate fetal lung maturation in premature labour). Here data are reviewed which show, in rodents and other models, that antenatal exposure to endogenous or exogenous glucocorticoids reduces offspring birth weight and produces permanent hypertension, hyperglycaemia, hyperinsulinaemia, altered behaviour and neuroendocrine responses throughout the lifespan. Processes underlying fetal programming include determination of the 'set point' of the hypothalamic-pituitary-adrenal (HPA) axis and of tissue glucocorticoid receptor (GR) expression. Similar HPA axis hyperreactivity occurs in lower birth weight humans and may be an early manifestation of the 'low birth weight' phenotype.

Treatment with interferon-alpha (IFN alpha) of hepatitis C patients induces lower serum dipeptidyl peptidase IV activity, which is related to IFN alpha-induced depressive and anxiety symptoms and immune activation

We have shown that treatment with interleukin-2 (IL-2) or interferon-alpha (IFN alpha) may induce depressive symptoms and activation of the cytokine network and that IL-2 treatment may diminish serum dipeptidyl pepdidase IV (DPP IV) activity. DPP IV (EC 3.4.14.5) is a membrane bound serine protease which catalyzes the cleavage of some cytokines and neuroactive peptides which modulate T cell activity. The aims of the present study were to examine the effects of IFN alpha-based immunotherapy on serum DPP IV activity in relation to induction of the inflammatory response system. In 18 patients with chronic active hepatitis C, we determined the Montgomery and Asberg Rating Scale (MADRS), the Hamilton Anxiety Rating Scale (HAM-A), serum DPP IV activity, the kynurenine/tryptophan (K/T) quotient, which is an indicator of cytokine (in particular IFN)-induced catabolism of tryptophan, and serum interleukin-8 (IL-8) before starting therapy and 2, 4, 16 and 24 weeks after immunotherapy with IFN alpha. IFN alpha-immunotherapy significantly suppressed serum DPP IV 2--4 weeks and 16--24 weeks after starting IFN alpha-based immunotherapy. The reduction in serum DPP IV activity was more pronounced 16--24 weeks after starting immunotherapy than after 2--4 weeks. The IFN alpha-induced suppression of serum DPP IV activity was significantly correlated to IFN alpha-induced increases in the MADRS and HAM-A and increases in the K/T quotient and serum IL-8. In conclusion, long-term immunotherapy with IFN alpha suppresses serum DPP IV activity and the immunotherapy-induced changes in DPP IV are related to increases in severity of depression, anxiety and activation of the inflammatory response system.

11 beta-hydroxysteroid dehydrogenase (11 beta-HSD-II) activity in human placenta: its relationship to placental weight and birth weight and its possible role in hypertension

It has been assumed that low birth weight and high placenta weight were key factors for predicting hypertension in human adulthood. A deficiency in placental 11 beta-HSD-II enzyme activity was supposed to be the underlying cause. To possibly establish 11 beta-HSD-II as a leading factor, we determined 11 beta-HSD-II activities in 133 healthy pregnancies, 21 proteinuric pregnancies complicated by pregnancy-induced hypertension (PIH), 26 non proteinuric PIH pregnancies and 15 pregnancies complicated by fetal growth restriction (32nd-41st gestational week). We could not identify differences in 11 beta-HSD-II activity between pregnancies with the rare combination of small babies with big placentas and others (p = 0.59; Kruskal-Wallis test). And although there was no correlation between 11 beta-HSD-II activity and birth weight, in the control gestational age correlated with 11 beta-HSD-II activity (r = 0.22; p < 0.05; Spearman). 11 beta-HSD-II activity in the proteinuric PIH group was significantly higher than in the controls (11.7 pmol/min/mg prot.; range 10-13.2 vs. 7.9; range 7.0-9.1; p < 0.05). The lowest, but not significant, enzyme activities were in the IUGR group (5.8 pmol/min/mg prot.; range 4.0-9.2). In this group, analysis of variance detected a correlation between enzyme activity and placental weight. In conclusion, we could not confirm that placental 11 beta-HSD-II deficiencies act as an indicator for the risk of adult hypertension in small fetuses with large placentas. However, in growth restriction 11 beta-HSD-II activity might play a role. To clarify the influence in this group, further research is needed. Increased 11 beta-HSD-II activities with gestational age in the control may serve to sustain fetal adrenal steroid genesis and to prepare the fetus for autonomic life.

Glucocorticoids, 11beta-hydroxysteroid dehydrogenase, and fetal programming

Epidemiological studies in many distinct human populations have associated low weight or thinness at birth with a substantially increased risk of cardiovascular and metabolic disorders, including hypertension and insulin resistance/type 2 diabetes, in adult life. The concept of fetal "programming" has been advanced to explain this phenomenon. Prenatal glucocorticoid therapy reduces birthweight, and steroids are known to exert long-term organizational effects during specific "windows" of development. Therefore, we hypothesized that fetal overexposure to endogenous glucocorticoids might underpin the link between early life events and later disease. In rats, birthweight is reduced following prenatal exposure to the synthetic glucocorticoid dexamethasone, which readily crosses the placenta, or to carbenoxolone, which inhibits 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2), the physiological feto-placental "barrier" to endogenous glucocorticoids. Although the offspring regain the weight deficit by weaning, as adults they exhibit permanent hypertension, hyperglycemia, and increased hypothalamic-pituitary-adrenal axis activity. Moreover, physiological variations in placental 11beta-HSD2 activity near term correlate directly with fetal weight. In humans, 11beta-HSD2 gene mutations produce a low birthweight, and some studies show reduced placental 11beta-HSD2 activity in association with intrauterine growth retardation. Moreover, low birthweight babies have higher plasma cortisol levels throughout adult life, indicating that hypothalamic-pituitary-adrenal axis programming also occurs in humans. The molecular mechanisms of glucocorticoid programming are beginning to be unraveled and involve permanent and tissue-specific changes in the expression of key genes, notably of the glucocorticoid receptor itself. Thus, glucocorticoid programming may explain, in part, the association between fetal events and subsequent disorders in adult life.

Lack of effect of nicotine or ethanol on the activity of 11beta-hydroxysteroid dehydrogenase type 2

Low birth weight in combination with a large placenta predicts human hypertension. The pathophysiological link remains unclear, but glucocorticoid excess impairs fetal growth and leads to offspring hypertension. A key controller of fetal glucocorticoid exposure and local tissue availability is 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2). The activity of placental 11beta-HSD2 correlates with fetal growth in animals and humans. Ethanol abuse and smoking are known to retard fetal growth which may relate to altered glucocorticoid action or dynamics. This study has examined whether nicotine or ethanol modulate glucocorticoid action in the placenta or fetus by inhibiting 11beta-HSD2, using clonal cell cultures, freshly isolated dually perfused intact human placentas and placentas from in vivo treated rats. No significant effect on the activity of 11beta-HSD2 by pathophysiologically relevant nicotine or ethanol concentrations was observed. The mechanism of action of nicotine and ethanol relevant to reduced fetal growth requires further study.

Glucocorticoids, feto-placental 11 beta-hydroxysteroid dehydrogenase type 2, and the early life origins of adult disease

Increasing human epidemiological data suggest that events that subtly retard intrauterine growth may determine common disorders, such as hypertension and non-insulin-dependent diabetes, in adult life. The underlying mechanisms are unknown. However, excessive fetal exposure to glucocorticoids retards growth and "programs" adult hypertension in rats. 11 beta-Hydroxysteroid dehydrogenase type 2 (11 beta-HSD2) catalyzes the rapid inactivation of cortisol and corticosterone to inert 11 keto-products. Normally, 11 beta-HSD2 in the placenta and some fetal tissues is thought to protect the fetus from excess maternal glucocorticoids. In both rats and humans there is considerable natural variation in placental 11 beta-HSD2, and enzyme activity correlates with birth weight. Moreover, inhibition of feto-placental 11 beta-HSD2 in the rat reduces birth weight and produces hypertensive and hyperglycaemic adult offspring, many months after prenatal treatment; effects are dependent upon intact maternal adrenals, suggesting a direct action on the fetus or placenta. Maternal protein restriction during pregnancy also produces hypertensive offspring and selectively attenuates placental 11 beta-HSD2 activity. These data suggest that feto-placental 11 beta-HSD2, by regulating fetal exposure to maternal glucocorticoids, crucially determines fetal growth and the programming of later disorders. Deficiency of the barrier to maternal glucocorticoids may represent a common pathway between the maternal environment and feto-placental programming of later disease. These data may, at least in part, explain the human observations linking early life events to the risk of subsequent disease.

Point mutations abolish 11 beta-hydroxysteroid dehydrogenase type II activity in three families with the congenital syndrome of apparent mineralocorticoid excess

The 11 beta-hydroxysteroid dehydrogenase type II enzyme (11 beta HSD2) converts cortisol into mineralocorticoid receptor inactive cortisone, thus preventing occupation of the non-selective mineralocorticoid receptor by glucocorticoids in the kidney. Mutations generating inactive enzymes have been described in the HSD11B2 gene in the congenital syndrome of apparent mineralocorticoid excess (AME), although proof of mutant protein synthesis was not provided. In the present study we have examined the metabolism of cortisol in mammalian cells transfected with plasmids expressing the wild type and mutant enzymes from three additional families of patients with mutations in the HSD11B2 gene. These studies revealed that the mutants were enzymatically inactive in intact mammalian cells expressing significant levels of both full length and truncated proteins. This is the first study to definitively show that point mutations in the HSD11B2 gene abolish 11 beta HSD2 enzymatic activity in the syndrome of AME.

11 beta-Hydroxysteroid dehydrogenases: key enzymes in determining tissue-specific glucocorticoid effects

Recent studies have demonstrated that the interconversion of active and inactive glucocorticoids plays a key role in determining the specificity of the mineralocorticoid receptor and controlling local tissue glucocorticoid receptor activation. Two distinct isoforms of the enzyme 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD) have been identified. 11 beta-HSD1 is NADPH-dependent and at its major site of action (the liver) is a reductase, converting cortisone to cortisol (11-dehydrocorticosterone to corticosterone in the rat). 11 beta-HSD2 is NAD-dependent, is present in tissues such as the kidney and placenta, and converts cortisol to cortisone (corticosterone to 11-dehydrocorticosterone in the rat). Congenital or acquired deficiency of 11 beta-HSD2 produces the syndrome of apparent mineralocorticoid excess (SAME) in which cortisol gains access to the unprotected nonspecific mineralocorticoid receptor. The congenital deficiency is associated with mutations in the gene encoding the kidney isoform of 11 beta-HSD2; the acquired form results from inhibition of the enzyme by licorice, carbenoxolone, ACTH-dependent steroids in the ectopic ACTH syndrome, and possibly circulating inhibitors of the enzyme. This paper focuses on recent evidence, which suggest that low levels of placental 11 beta-HSD2 result in increased exposure of the fetus to maternal glucocorticoid and low birth weight. In animal studies using the rat we have shown that birth weight is correlated positively and placental weight negatively with the level of placental 11 beta-HSD. Thus animals with low birth weight and large placentae were those likely to be exposed to the highest level of maternal glucocorticoid. In man a similar relationship was found with birth weight being significantly correlated either with placental 11 beta-HSD activity or with the extent of cortisol inactivation by isolated perfused placental cotyledons. Administration of dexamethasone (which is poorly metabolized by placental 11 beta-HSD2) to pregnant rats resulted in decreased birth weight and the development of hypertension in the pups when adult. The same results were obtained when pregnant rats were given carbenoxolone, an inhibitor of placental 11 beta-HSD2. Low protein diet during pregnancy in the rat resulted in low birth weight of the pups, increased placental weight but decreased placental 11 beta-HSD activity, and adult hypertension. Thus increased glucocorticoid exposure of the fetus secondary to a failure of the normal inactivation of maternal glucocorticoid by the placental may be an important mechanism linking changes in the in utero environment and common adult diseases.

Placental 11 beta-hydroxysteroid dehydrogenase and the programming of hypertension

Excessive foetal exposure to glucocorticoids retards growth and "programmes" adult hypertension in rats. Placental 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD), which catalyses the conversion of corticosterone and cortisol to inert 11 keto-products, normally protects the foetus from excess maternal glucocorticoids. In both rats and humans there is considerable natural variation in placental 11 beta-HSD, and enzyme activity correlates with birth weight. Moreover, inhibition of placental 11 beta-HSD in the rat reduces birth weight and produces hypertensive adult offspring, many months after prenatal treatment with enzyme inhibitors; these effects are dependent upon maternal adrenal products. These data suggest that placental 11 beta-HSD, by regulating foetal exposure to maternal glucocorticoids, crucially determines foeto-placental growth and the programming of hypertension. Maternal protein restriction during pregnancy also produces hypertensive offspring and selectively attenuates placental 11 beta-HSD activity. Thus, deficiency of the placental barrier to maternal glucocorticoids may represent a common pathway between the maternal environment and foeto-placental programming of later disease. These data may, at least in part, explain the human epidemiological observations linking early life events to the risk of subsequent hypertension. The recent characterization, purification and cDNA cloning of a distinct human placental 11 beta-HSD (type 2) will aid the further study of these intriguing findings.