Original Research
Obstetrics
Metformin as a prevention and treatment for preeclampsia: effects on soluble fms-like tyrosine kinase 1 and soluble endoglin secretion and endothelial dysfunction

https://doi.org/10.1016/j.ajog.2015.12.019Get rights and content

Background

Preeclampsia is associated with placental ischemia/hypoxia and secretion of soluble fms-like tyrosine kinase 1 and soluble endoglin into the maternal circulation. This causes widespread endothelial dysfunction that manifests clinically as hypertension and multisystem organ injury. Recently, small molecule inhibitors of hypoxic inducible factor 1α have been found to reduce soluble fms-like tyrosine kinase 1 and soluble endoglin secretion. However, their safety profile in pregnancy is unknown. Metformin is safe in pregnancy and is also reported to inhibit hypoxic inducible factor 1α by reducing mitochondrial electron transport chain activity.

Objective

The purposes of this study were to determine (1) the effects of metformin on placental soluble fms-like tyrosine kinase 1 and soluble endoglin secretion, (2) to investigate whether the effects of metformin on soluble fms-like tyrosine kinase 1 and soluble endoglin secretion are regulated through the mitochondrial electron transport chain, and (3) to examine its effects on endothelial dysfunction, maternal blood vessel vasodilation, and angiogenesis.

Study Design

We performed functional (in vitro and ex vivo) experiments using primary human tissues to examine the effects of metformin on soluble fms-like tyrosine kinase 1 and soluble endoglin secretion from placenta, endothelial cells, and placental villous explants. We used succinate, mitochondrial complex II substrate, to examine whether the effects of metformin on soluble fms-like tyrosine kinase 1 and soluble endoglin secretion were mediated through the mitochondria. We also isolated mitochondria from preterm preeclamptic placentas and gestationally matched control subjects and measured mitochondrial electron transport chain activity using kinetic spectrophotometric assays.

Endothelial cells or whole maternal vessels were incubated with metformin to determine whether it rescued endothelial dysfunction induced by either tumor necrosis factor-α (to endothelial cells) or placenta villous explant–conditioned media (to whole vessels). Finally, we examined the effects of metformin on angiogenesis on maternal omental vessel explants.

Results

Metformin reduced soluble fms-like tyrosine kinase 1 and soluble endoglin secretion from primary endothelial cells, villous cytotrophoblast cells, and preterm preeclamptic placental villous explants. The reduction in soluble fms-like tyrosine kinase 1 and soluble endoglin secretion was rescued by coadministration of succinate, which suggests that the effects of metformin on soluble fms-like tyrosine kinase 1 and soluble endoglin were likely to be regulated at the level of the mitochondria. In addition, the mitochondrial electron transport chain inhibitors rotenone and antimycin reduced soluble fms-like tyrosine kinase 1 secretion, which further suggests that soluble fms-like tyrosine kinase 1 secretion is regulated through the mitochondria. Mitochondrial electron transport chain activity in preterm preeclamptic placentas was increased compared with gestation-matched control subjects.

Metformin improved features of endothelial dysfunction relevant to preeclampsia. It reduced endothelial cell messenger RNA expression of vascular cell adhesion molecule 1 that was induced by tumor necrosis factor–α (vascular cell adhesion molecule 1 is an inflammatory adhesion molecule up-regulated with endothelial dysfunction and is increased in preeclampsia). Placental conditioned media impaired bradykinin-induced vasodilation; this effect was reversed by metformin. Metformin also improved whole blood vessel angiogenesis impaired by fms-like tyrosine kinase 1.

Conclusion

Metformin reduced soluble fms-like tyrosine kinase 1 and soluble endoglin secretion from primary human tissues, possibly by inhibiting the mitochondrial electron transport chain. The activity of the mitochondrial electron transport chain was increased in preterm preeclamptic placenta. Metformin reduced endothelial dysfunction, enhanced vasodilation in omental arteries, and induced angiogenesis. Metformin has potential to prevent or treat preeclampsia.

Section snippets

Objective

This study had 3 objectives: (1) to assess the effects of metformin on sFlt-1 and sENG secretion from primary placental and endothelial cells/tissues and to investigate whether these effects are mediated through mitochondrial electron transport chain inhibition; (2) to assess whether mitochondrial electron transport chain activity positively regulates sFlt-1 secretion and if preterm preeclamptic placenta have increased mitochondrial electron transport chain activity; and (3) to assess whether

Patient population

We performed functional experiments in which we administered metformin to human tissues and assessed its effects on sFlt-1 and sENG secretion, mitochondrial electron transport chain function, and endothelial dysfunction. To perform our experiments, we examined tissues from placenta and blood vessels.

We collected several types of placental tissues. We isolated human umbilical vein endothelial cells (HUVECs)63 and primary villous cytotrophoblast cells64 from the placenta and umbilical cord that

Metformin reduces sFlt-1 secretion from primary endothelial cells and placental tissues

We assessed the effects of metformin on sFlt-1 secretion from endothelial and placental tissues because they are its main tissue source. Administering metformin dose-dependently reduced sFlt-1 secretion from endothelial cells (HUVECs; Figure 1, A) and primary cells that were isolated from placenta (villous cytotrophoblast cells; Figure 1, B). At the highest doses, metformin reduced endothelial and placental cell secretion by 53% and 63%, respectively. Metformin also reduced sFlt-1 secretion

Primary findings of the study

Metformin reduces sFlt-1 and sENG secretion from primary human tissues, possibly by inhibiting the mitochondrial electron transport chain. Second, mitochondrial electron transport chain activity positivity regulates sFlt-1 secretion, and mitochondrial electron transport chain activity is increased in preterm preeclamptic placenta. By using assays to replicate the endothelial and vascular dysfunction that may be occurring in preeclampsia, we found that metformin reduces endothelial dysfunction,

Acknowledgments

We thank the research midwives, Gabrielle Pell, Genevieve Christophers, Rachel Murdoch, and Debra Jinks, and the patients at Mercy Hospital for Women for participating in this research.

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    Supported by The National Health and Medical Research Council of Australia (NHMRC; #1048707, #1046484, #1101871) and an Arthur Wilson RANZCOG scholarship; by an Australian Postgraduate Award and an AVANT scholarship (F.B); by a CR Roper Research Fellowship (N.J.R.); the NHMRC provided salary support (#1050765 [S.T.]; #1062418 [T.K.L.]; #628549 [S.S.]). The funders had no role in study design, data collection, analysis, decision to publish or the preparation of the manuscript.

    The authors report no conflict of interest.

    Cite this article as: Brownfoot FC, Hastie R, Hannan NJ, et al. Metformin as a prevention and treatment for preeclampsia: effects on soluble fms-like tyrosine kinase 1 and soluble endoglin secretion and endothelial dysfunction. Am J Obstet Gynecol 2016;214:356.e1-15.

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    These authors have contributed equally to this article.

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