Breastfeeding's legacy may protect against diabetes
Study of 18 women shows effects of insulin levels and sensitivity

Date:
August 25, 2020
Source:
UT Southwestern Medical Center
Summary:
Breastfeeding secures delivery of sugar and fat for milk production
by changing the insulin sensitivity of organs that supply or demand
these nutrients, a new study suggests. The findings could explain
how different tissues cooperate to start and maintain lactation
and offer strategies to help improve breastfeeding success for
mothers who have insufficient milk production.



FULL STORY ========================================================================== Breastfeeding secures delivery of sugar and fat for milk production by
changing the insulin sensitivity of organs that supply or demand these nutrients, a new study led by UT Southwestern scientists suggests. The findings, published in this month's print issue of Diabetes, could
explain how different tissues cooperate to start and maintain lactation
and offer strategies to help improve breastfeeding success for mothers
who have insufficient milk production.


========================================================================== Epidemiologic studies suggest that breastfeeding protects women from
developing Type 2 diabetes, even decades after their children have been
weaned. But how this benefit arises has been unclear, explains Maria
A. Ramos-Roman, M.D., an associate professor of internal medicine in
the division of endocrinology at UT Southwestern.

One hypothesis is that breastfeeding changes how the body uses
insulin, the hormone that allows cells to take in glucose from the
bloodstream. (Glucose is a type of sugar that powers cells.) Detailed
metabolic studies have shown that although pregnancy reduces the body's sensitivity to insulin, lactation may restore insulin sensitivity to a pre-pregnancy state. But it is unclear how this process happens and how it affects highly insulin-sensitive organs, such as the liver or fat tissue.

To learn more, Ramos-Roman and her colleagues recruited 18 women who
had recently given birth. Twelve of these women were either exclusively breastfeeding or giving their babies less than 6 ounces of formula per
day. The remaining six were exclusively formula feeding.

At five weeks postpartum, each of these women came to UT Southwestern for
a detailed medical exam to make sure they were healthy and could safely participate in other parts of the study. One week later, the volunteers returned for a second visit in which they underwent a hyperinsulinemic- euglycemic clamp, a test that quantifies insulin sensitivity. Although
the test measures insulin sensitivity for the body overall, these women
also received stable isotopes during the test -- tracers that helped
measure insulin sensitivity specifically for organs of interest, such
as the liver, or fat. At a third visit by eight weeks postpartum, the
study participants underwent a type of imaging called magnetic resonance spectroscopy that measured the amount of fat in their livers.

The researchers found that all of the women had low blood insulin concentrations characteristic of the postpartum period, regardless of how
they were feeding their new babies. However, even at these low insulin
levels, after a 12-hour fast, the lactating mothers produced 2.6-fold
more glucose and released 2.3-fold more fatty acids from storage in their
fat tissue -- a process known as lipolysis -- than that of the formula
feeders. Both glucose production and lipolysis were suppressed in both
groups when the researchers mimicked a "fed state" by delivering insulin through the clamp. But suppression of lipolysis was heightened by higher
levels of prolactin -- the hormone that stimulates milk production --
in the lactating mothers, accompanied by lower levels of fatty acids in
the blood and lower amounts of fat in their livers.

These results suggest that breastfeeding appears to increase
insulin sensitivity in highly insulin-sensitive organs, Ramos-Roman
explains. After a 12-hour fast, the liver and fat tissues of
lactating mothers release more sugar and fat into the bloodstream
than formula-feeding mothers; however, after food intake or under the conditions of a hyperinsulinemic-euglycemic clamp, lactating mothers
respond to small increases in insulin levels by holding on to more
stored fat than formula-feeding mothers. Both conditions maximize the
nutrients available for making milk in breastfeeding women, providing
a steady stream from either stored resources or food intake.

These changes in insulin levels and sensitivity might also provide
the legacy benefit observed in epidemiologic studies in women who have breastfed, offering a buffer against insulin resistance even decades
later, Ramos-Roman says.

(These previous studies showed an association between intensity or
duration of breastfeeding and a lower incidence of Type 2 diabetes
in the mothers.) In addition, she adds, better understanding of this
process could help researchers find new ways to help encourage it in
mothers who would like to breastfeed but are having problems with low
milk supply -- finding ways to stimulate insulin-sensitive tissues to
supply more nutrients into or demand less nutrients from the bloodstream
could boost milk production.

"Lactation is millions of years old, but we still have a long way to go
before we understand all there is to learn," Ramos-Roman says. "If we
know better how it happens in the body, we can help improve the health
of women and children." Other researchers who contributed to this study include Beverley Adams-Huet of UTSW; Majid M. Syed-Abdul and Elizabeth
J. Parks of the University of Missouri School of Medicine; and Brian
M. Casey, previously of UTSW and now at the University of Alabama.

This study was supported by funds from the American Diabetes Association
(1-14- TS-33) and the National Institutes of Health (R03 DK097463).


========================================================================== Story Source: Materials provided by UT_Southwestern_Medical_Center. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Maria A. Ramos-Roman, Majid M. Syed-Abdul, Beverley Adams-Huet,
Brian M.

Casey, Elizabeth J. Parks. Lactation Versus Formula Feeding:
Insulin, Glucose, and Fatty Acid Metabolism During the Postpartum
Period.

Diabetes, 2020; 69 (8): 1624 DOI: 10.2337/db19-1226 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/08/200825110800.htm

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