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How a low-protein diet predisposes offspring to adulthood hypertension

Date:
July 25, 2012
Source:
Society for the Study of Reproduction
Summary:
The children of mothers on a low-protein diet are more likely to develop hypertension as adults, but why? New research finds that the high maternal testosterone levels associated with a low-protein diet in rats are caused by reduced activity of a testosterone inactivator, thereby allowing more testosterone to reach the fetus and increase the offspring's susceptibility to adulthood hypertension.

Testosterone in the maternal plasma is transported into placental zones, where part of the testosterone is inactivated by HSD17B2. The rest of the testosterone escapes the inactivation due to the reduced expression of Hsd17b2. Thus, excess testosterone goes into fetal circulation, affecting fetal growth and development and presumably predisposing the development of hypertension in offspring.
Credit: Image concept by C. Yallampalli; Drawing by Alan Sheffield; oCurtesy of Society for the Study of Reproduction

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.

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 Hsd17b2 expression 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.


Story Source:

The above story is based on materials provided by Society for the Study of Reproduction. Note: Materials may be edited for content and length.


Journal Reference:

  1. Haijun Gao, Uma Yallampalli and Chandra Yallampalli. Gestational Protein Restriction Reduces Expression of Hsd17b2 in Rat Placental Labyrinth. Biology of Reproduction, 2012 DOI: 10.1095/biolreprod.112.100479

Cite This Page:

Society for the Study of Reproduction. "How a low-protein diet predisposes offspring to adulthood hypertension." ScienceDaily. ScienceDaily, 25 July 2012. <www.sciencedaily.com/releases/2012/07/120725162444.htm>.
Society for the Study of Reproduction. (2012, July 25). How a low-protein diet predisposes offspring to adulthood hypertension. ScienceDaily. Retrieved July 23, 2014 from www.sciencedaily.com/releases/2012/07/120725162444.htm
Society for the Study of Reproduction. "How a low-protein diet predisposes offspring to adulthood hypertension." ScienceDaily. www.sciencedaily.com/releases/2012/07/120725162444.htm (accessed July 23, 2014).

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