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Pregnancy Timeline by SemestersFemale Reproductive SystemFertilizationThe Appearance of SomitesFirst TrimesterSecond TrimesterThird TrimesterFetal liver is producing blood cellsHead may position into pelvisBrain convolutions beginFull TermWhite fat begins to be madeWhite fat begins to be madeHead may position into pelvisImmune system beginningImmune system beginningPeriod of rapid brain growthBrain convolutions beginLungs begin to produce surfactantSensory brain waves begin to activateSensory brain waves begin to activateInner Ear Bones HardenBone marrow starts making blood cellsBone marrow starts making blood cellsBrown fat surrounds lymphatic systemFetal sexual organs visibleFinger and toe prints appearFinger and toe prints appearHeartbeat can be detectedHeartbeat can be detectedBasic Brain Structure in PlaceThe Appearance of SomitesFirst Detectable Brain WavesA Four Chambered HeartBeginning Cerebral HemispheresEnd of Embryonic PeriodEnd of Embryonic PeriodFirst Thin Layer of Skin AppearsThird TrimesterDevelopmental Timeline
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July 27, 2012--------News Archive Return to: News Alerts


In response to protein restriction, estosterone becomes elevated in maternal plasma,
and is transported into placental zones, where part of the testosterone is turned off by
HSD17B2. The rest escapes inactivation due to the reduced expression of HSD17B2.

Excess testosterone enters into fetal circulation, affecting fetal growth and
development and predisposing the development of hypertension in the baby.

Credit: Image concept: C. Yallampalli. Drawing: Alan Sheffield

WHO Child Growth Charts

       

Low-Protein Diet Predisposes Baby to Adult Hypertension

Studies have shown that the offspring of mothers on a low-protein diet are more likely to develop hypertension as adults

Now, Drs. Gao, Yallampalli, and Yallampalli of the University of Texas Medical Branch at Galveston report that in rats, the high maternal testosterone levels associated with a low-protein diet are caused by reduced activity of an enzyme that inactivates testosterone, allowing more testosterone to reach the fetus and increase the offspring's susceptibility to adulthood hypertension.


High maternal testosterone levels associated with
a low-protein diet are caused by reduced activity
of an enzyme that inactivates testosterone,
allowing more testosterone to reach the fetus
increasing the offspring's susceptibility
to adulthood hypertension.


Fetal programming is a term used to describe the impact of maternal stress on an unborn child's physical characteristics at birth, as well as its long-term health. The placenta is thought to be a major contributor to fetal programming due to its critical roles in hormone production and nutrient transport, as well as its susceptibility to environmental disruptions.


Recently, a study found that protein restriction
doubles the plasma testosterone levels in pregnant rats.
Elevated testosterone levels are associated with
pregnancy-related complications such as preeclampsia
and polycystic ovarian syndrome in humans,
and emerging evidence suggests that testosterone
may play a role in fetal programming of hypertension.


Gao et al. hypothesized that the increased testosterone levels were caused either by increased activity of an enzyme that produces testosterone or by decreased activity of an enzyme that reduces testosterone, specifically Hsd17b2, which converts testosterone to a less potent androgen, androstenedione.


The team found that Hsd17b2 expression in rats
was affected by protein restriction in two parts
of the placenta. It was increased in the junctional zone,
which is responsible for hormone production,
but was reduced in the labyrinth zone,
which is essential for nutrient transport from
mother to fetus and also acts as a protective barrier.


Based on this novel finding, Gao et al. propose that the reduction in Hsd17b2expression in the protective labyrinth zone may allow more testosterone to reach the fetus and play a role in fetal programming of hypertension.

The finding that Hsd17b2 was the only enzyme for testosterone production affected by gestational protein restriction suggests an important role for Hsd17b2 in regulating the testosterone levels at the maternal-fetal interface; further research is needed to determine its exact functions.

Biology of Reproduction, published by the Society for the Study of Reproduction, is a top-rated peer-reviewed research journal in the field of reproductive biology.

Gao H, Yallampalli U, Yallampalli C. Gestational protein restriction reduces expression of Hsd17b2 in rat placental labyrinth. Biol Reprod 2012; (in press). Published online ahead of print 18 July 2012; DOI 10.1095/biolreprod.112.100479.

Original article: http://www.eurekalert.org/pub_releases/2012-07/sfts-hal072012.php