DOCTORAL THESIS. Normal weight women accumulate fat in existing adipocytes (fat cells) during pregnancy, whereas those with obesity form new adipocytes. A PhD thesis at Sahlgrenska Academy has shown that the morphology of adipose tissue is associated with insulin resistance in pregnant women and may reveal the risk of developing type 2 diabetes.
Previous studies have found that obesity increases the risk of gestational diabetes, which makes it more likely that type 2 diabetes will develop later in life.
A PhD thesis at Sahlgrenska Academy, University of Gothenburg, studied changes to adipose tissue during pregnancy by carefully analyzing biopsies during both the first and third trimesters.
“We compared adipose tissue of 22 normal weight women to that of 11 women with obesity,” says Dr. Henrik Svensson at Sahlgrenska Academy. “The adipocytes of normal weight women accumulated fat during pregnancy. The average size of the adipocytes of women with obesity became smaller, suggesting that new cells had been formed.”
The second observation was confirmed when only women with increase BMI were included.
Formation of new adipocytes during pregnancy might serve as a protective mechanism, given that large adipocytes are associated with inflammation, insulin resistance (a precursor of diabetes) and development of type 2 diabetes. Although the women with obesity throughout pregnancy exhibited more pronounced insulin resistance, none of them developed gestational diabetes.
“BMI and the percentage of very large adipocytes in the third trimester were the factors that best explained insulin resistance,” Dr. Svensson says. “Our findings indicate that adipose tissue, along with the placenta as discovered earlier, may regulate maternal insulin resistance.”
Reduce the risk
The results also suggest that women with overweight or obesity reduce the risk of gestational diabetes if they lose weight before they become pregnant and/or limit weight gain both before and after pregnancy.
The thesis also studied 39 women who had been diagnosed with gestational diabetes six years earlier. Women who had developed preliminary stages of diabetes had higher BMI and more abdominal fat than those with normal glucose tolerance. They also had larger adipocytes and more indications of inflammation of adipose tissue.
“Women who have had gestational diabetes before, particularly those who are prone to accumulation of abdominal fat, need to keep their weight down as much as possible in order to prevent type 2 diabetes from developing,” Dr. Svensson says.
Associated with type 2 diabetes
High BMI, abdominal obesity and large adipocytes were the factors most closely associated with a preliminary stage of type 2 diabetes.
“The findings make it clear that monitoring women with gestational diabetes after childbirth, as well as supporting them in maintaining or losing weight, is vital to preventing or delaying the onset of type 2 diabetes,” Dr. Svensson says.
The impact of changes to adipose tissue during pregnancy on weight after childbirth is not known but will be explored in future studies.
Dr. Svensson defended “Human adipose tissue morphology and function – relation to insulin sensitivity and glucose tolerance with focus on pregnancy and women with previous gestational diabetes mellitus” on November 5.
