eLife: Type 2 diabetes genes are associated with gestational diabetes

A study published in the journal eLife suggests that complex genes that contribute to a higher risk of developing type 2 diabetes may also increase the risk
of developing diabetes during pregnancy in women of South Asian descent.

This finding may lead to new ways to determine which women could benefit
from interventions to prevent gestational diabetes.

People of South Asian descent are at higher risk of developing type 2 diabetes
.
Women in this group are twice as likely to develop gestational diabetes during pregnancy as women of European descent
.
But why South Asians are at increased risk of both diseases is unclear
.

Amel Lamri, an associate researcher at McMaster University and the Population Health Institute (PHRI) in Ontario, Canada, said: "Only a few studies have looked at how genetic and environmental factors interact
in gestational diabetes in South Asian women.
" "No one has yet studied how genes associated with type 2 diabetes interact with environmental factors that contribute to gestational diabetes
in South Asian women.
"

To close this gap, Lamri and colleagues evaluated the relationship
between genes associated with type 2 diabetes, environmental factors, and gestational diabetes.
They examined whether genetic traits associated with type 2 diabetes risk were associated with gestational diabetes in 837 and 4,372 South Asian women who participated in the South Asian Birth Cohort (START) study and the Bradford (BiB) study
, respectively.

The team measures the genetic risk of type 2 diabetes using the polygenic risk score, which estimates an individual's genetic risk of developing a disease based on the number of risk
alleles an individual has.
The researchers found that women with higher polygenic risk scores for type 2 diabetes in South Asia also had a higher risk of gestational diabetes; Each increase in the score increases the risk of developing the disease by 45%.

When the scientists looked at the risk of gestational diabetes at the population level, they found that among South Asian women, the highest third of polygenic risk scores explained the 12.
5 percent risk
of this happening.
When they ranked type 2 diabetes family history and polygenic risk scores in the top third, this explained the 25 percent risk
of gestational diabetes.

"These results suggest that higher polygenic risk scores for type 2 diabetes and family history of diabetes are strongly and independently associated
with gestational diabetes among women of South Asian descent," Lamri explains.

The scientists also looked at whether environmental factors modulated these genetic risk factors
.
In both studies, most of the environmental factors they considered (probably with the exception of body mass index and diet quality) did not significantly alter the risk of
developing diabetes during pregnancy.
But the authors note that these studies may not be large enough to detect milder environmental effects, and that further research is needed to confirm the regulatory effects
they observe.

"Our findings support the idea that type 2 diabetes and gestational diabetes share a common genetic background," concludes senior author Sonia Anand, the Michael G.
DeGroote Chair in Population Health and a senior scientist
at the Institute for Disease Research, McMaster University, and Hamilton Health Sciences.
"If future studies confirm our results, this information may help determine which women benefit most
from interventions to prevent diabetes during pregnancy.
"