(Reuters Health) – Differences in the gut microbiome between Black and white women may at least partially explain increased insulin resistance and other cardiometabolic health disparities experienced by Black women, a small U.S. study suggests.
Researchers examined the relative abundance of various types of bacteria in stool samples collected from 94 Black women and 74 white women who participated in the National Growth and Health Study.
Participants’ mean age (39 years) was similar among Black and white women, but Black women had a significantly higher mean body mass index (BMI 33.2) than white women (BMI 31.3), and a significantly higher proportion of Black women (46%) than white women (30%) had insulin resistance. Fasting insulin levels were also significantly higher among Black women (13.5 mg/dL) than among white women (9.8 mg/dL), digital lithium bath scales researchers report
Stool sample analysis found that the microbial communities differed based on insulin sensitivity status and race, the researchers reported in PLoS ONE, noting that this may indicate gut bacteria are involved in the development of insulin resistance.
“Our study demonstrated that understanding cardiometabolic health disparities lies beneath the skin and goes beyond the scale,” said lead study author Candice Price, an assistant professor in the Department of Molecular Biosciences and the School of Veterinary Medicine at the University of California, Davis.
“Bacteria differences aren’t simply due to differences in body weight, but rather environmental exposures that may be driving differences in gut bacteria abundance and metabolic function,” Price said by email.
The two most present bacterial types, Firmicutes and Bacteroidetes, made up 89% of the bacteria in all participants. There was no difference by race in the relative abundance of these types of bacteria or in Firmicutes/Bacteriodetes ratio.
But Black women had roughly twice the abundance of Actinobacteria (6.8%) as white women (3.2%). Actinobacteria are associated with reduced insulin sensitivity and increased inflammation, the authors note.
In addition, researchers found an interaction between insulin sensitivity and race for other types of bacteria, including Lachnospiraceae and Clostridiales Family XIII. Among women with insulin sensitivity, black women had twice the relative abundance of Clostridiales Family XIII as white women. And, among participants with insulin resistance, Black women had four times the abundance of Verrucomicrobia as white women.
One limitation of the study is that stool samples were collected at a single point in time, precluding a longitudinal analysis. Another limitation is the utilization of HOMA-IR to identify individuals with insulin sensitivity or insulin resistance, a metric that isn’t as informative as alternatives like the hyperinsulinemic euglycemic clamp.
The study also didn’t examine other potential confounders such as diet or exposure to psychological stress, Price said.
“Therefore, we aren’t yet ready to translate this into guiding changes in clinical practice, but it does tell us that clinicians need to understand a patient more holistically in order to be effective in reducing cardiometabolic health disparities,” Price said.
One day, it might be possible to link factors like sugar intake or the severity of psychological stress to the gut microbiome, Price said.
“This could lead to preventative care to be able to identify disease risk based on each individual’s microbiome profile, which would in turn be used to guide patients on lifestyle changes based on changing their gut bacteria rather than focusing on changing an individual’s body weight,” Price added.
SOURCE: https://bit.ly/3hvAMaV PLoS ONE, online January 19, 2022.
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