From the Journals

Insulin may be toxic to the placenta in early pregnancy



Insulin may be toxic to the placenta during early pregnancy, causing DNA damage, decreased cell survival, and apoptosis, but the toxic effects appear to be prevented with metformin, according to findings from an experimental in vitro study published in Fertility and Sterility.

Insulin syringes are shown. iStock/ThinkStock

“Collectively these results demonstrate that insulin itself may be directly toxic to the early human placenta but that metformin can prevent these deleterious effects,” wrote Mario Vega, MD, of Columbia University Fertility Center, New York, and his colleagues. “If confirmed in animal and human studies, this would indicate that screening and treatment for insulin resistance should focus on hyperinsulinemia.”

Dr. Vega and his colleagues cultivated trophoblast cells from three healthy women scheduled for manual vacuum aspiration during the first trimester of pregnancy to study the effects of insulin exposure alone, while trophoblast cells were cultured from a different set of women for the insulin and metformin follow-up experiments. The researchers tested each experiment against a control group of cultivated lung fibroblast cells. Insulin was measured in doses of 0.2 nmol, 1 nmol, and 5 nmol, while metformin was measured at 10 micromol. The primary outcome measures examined were gamma-H2AX for DNA damage, cell proliferation assay for cell survival, and cleaved caspase-3 for apoptosis.

Within 48 hours, the cultures showed DNA damage and induction of apoptosis when exposed to 1 nmol of insulin, but researchers said pretreatment with metformin prevented these effects. Exposing cells to metformin after insulin reduced but did not eliminate the effects of insulin.

The researchers noted the study is limited because the effects of insulin and metformin have not been examined in vivo, and it is not known at what level insulin causes damage. In addition, they suggested downregulation of genes in trophoblasts caused by insulin could cause apoptosis and DNA damage to trophoblast cells.

“Although studies performed on kidney and colon cells suggest that one possible mechanism of action for insulin-mediated genotoxicity is through AKT activation of mitochondria and subsequent reactive oxygen species production, the exact mechanism is poorly understood,” Dr. Vega and colleagues said. “Future studies will be necessary to determine variability among subjects, as well as mechanisms of action through which insulin exerts its cytotoxicity and genotoxicity.”

This study was funded by a grant from the National Institutes of Health Human Placenta Project. The authors reported no relevant financial disclosures.

SOURCE: Vega M et al. Fertil Steril. 2019. doi: 10.1016/j.fertnstert.2018.11.032.

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