Your dietary choices impact your health and well-being in
countless ways, and one of them involves the microbes residing in your gut. As
our knowledge of the critical importance of this microbial environment grows,
one area researchers are currently exploring is the link between diet and
Perhaps the most pressing reason we need to better
understand this relationship is that insulin resistance can lead to type 2
diabetes. According to the World Health Organization, the global prevalence of
diabetes among people older than 18 years increased from 4.7 percent in 1980 to
8.5 percent in 2014.
This percentage does not include the many millions of people
with prediabetes, a large percentage of whom will go on to develop type 2
diabetes within a few years. It also does not highlight the serious,
associated with diabetes.
and insulin resistance: a new study
At the University of Toronto in Canada, a group of
researchers set out to learn about the impact of diet—specifically a high-fat
diet—on insulin resistance and the microbial environment in the gut. The study
involved both mouse models and analysis of fecal samples from humans.
The researchers pointed out that a link between the
microbial environment in the gut and the intestinal immune system is
immunoglobulin A (IgA). This immune-derived molecule is an antibody made by
immune cells called B cells.
Therefore, in the first arm of their study of diet and insulin resistance, the scientists explored the idea that IgA may be the missing link that explains how an inadequate diet can result in insulin resistance by changing the gut environment and immunity. To do so, they used obese mouse models, some of whom had no IgA. When the IgA-deficient mice consumed a high-fat diet, insulin resistance got worse.
The researchers took it one step further and collected
bacteria from the guts of the IgA-deficient mice and transplanted them into
mice who didn’t have bacteria in their gut. This second group of mice also
developed insulin resistance.
This finding suggests that normal IgA levels are helpful in
keeping gut bacteria levels up and thus help prevent insulin resistance. The
researchers also found that mice without IgA had higher leakage of harmful
bacteria from the gut into the rest of the body, or higher gut permeability.
In the second arm of the study, the researchers analyzed
fecal samples for IgA content from individuals both before and after they
underwent bariatric surgery. They discovered that IgA levels were higher after
surgery, indicating that the antibody was impacted by diet and linked to
According to Helen Luck, the study’s lead author, obesity is
associated with lower levels of a B cell in the gut that produces IgA, an
antibody that is “crucial to regulating the bacteria that live in our gut.” The
researchers’ findings suggest there’s a direct relationship between consuming a
high-fat diet and obesity, and having lower levels of IgA in the gut and the
development of insulin resistance.
Given these findings, future studies will likely explore how
to enhance levels of B cells that produce IgA, as this intervention may protect
against insulin resistance and, ultimately, type 2 diabetes. Co-author Dr.
Daniel Winer pointed out that “Going forward, this work could form the basis
for new gut immune biomarkers or therapies for obesity and its complications,
like insulin resistance and type 2 diabetes.” Other complications of obesity
include heart disease, fatty liver disease, certain cancers (e.g., breast,
colon, endometrial), stroke, gallbladder disease, sleep apnea, and arthritis,
The findings of this study suggest that a high-fat diet and
obesity are linked to insulin resistance and the integrity of the gut
environment. Since diet is a personal choice, everyone has the ability to help
prevent insulin resistance and maintain a healthy bacterial balance in their
gut by making conscious food choices involving whole foods and healthy fats
while also maintaining a healthy weight.
Luck H et al. Gut-associated IgA+ immune cells regulate
obesity-related insulin resistance. Nature Communications
2019 Aug; 10(3650)
Health Organization. Diabetes.
2018 Oct 30