Gut microbiome study reveals depths of racial health disparities

the intestine microbiota – the myriad of microorganisms, viruses and fungi living in your digestive tract – is the new frontier in understanding and protecting human health. But a new study suggests it could also reveal new insights into health disparities and how to treat them.

What’s up – In an article published Wednesday in PLOS ONE, researchers reveal how health disparities between black and white women in the United States play out in the gut microbiome. The researchers found clear differences in the gut bacteria populations of the women. The finding adds to the evidence that environmental factors help create and perpetuate racially unequal health outcomes.

Over the past 15 years, scientists have sought to map the human microbiome, all of the hundreds of thousands of microorganisms living in the digestive tract. Studies show that the microbiome is linked to obesity and diabetes, as well as non-metabolic conditions, like cancer and neurodegenerative diseases.

“What’s so fascinating about the microbiome is that it differs so much within each individual, and that’s determined by their outside environmental factors.” the study’s lead author, Candice A. Price, says Reverse.

“It can include things like their diet, their air quality, their psychological stress. The microbiome is kind of like a snapshot of the biological effect of these environmental factors,” she adds.

Why is it important – Marked differences in the gut microbiome between two groups of people may indicate marked differences in their environment.

Black women in the United States have higher rates of metabolic health problems than white women. According to the Centers for Disease Control, 45.1% of black women are classified as obese, compared to 24.5% of non-Hispanic white women, and 12.7% are diagnosed with diabetes, compared to 7.5% of non-white women. hispanics.

As with any racial disparity in health, unraveling the reasons for these health differences requires investigating how inequality and systematic racism intersect and manifest themselves on the human body.

Black communities in the United States generally have less access to healthy food, live with poorer air quality, and live under greater social stress, all of which play a role in health, according to Price.

“All of these social determinants of health, as we call them, are really related to these health disparities, but we don’t quite understand how,” she says.

The gut microbiome offers a new area for therapeutics and medicine. But for these treatments to work effectively for everyone, researchers need to study the gut microbiomes of many different groups.

Air quality, which negatively affects urban areas, such as Los Angeles (pictured), is a known factor linked to racial health disparities in the USStefan Ebersberger/EyeEm/EyeEm/Getty Images

How they did — In the study, which included 94 black women and 74 white women, researchers found that while the black participants’ microbiomes were similar to each other and the white participants’ microbiomes were similar to each other, the two groups were markedly different from each other. .

That there was a difference is an important finding in itself, says Price; it shows how a set of environmental factors affect black women compared to white women.

“The microbiome is kind of like a snapshot of the biological effect of these environmental factors.”

For example, black women had a higher abundance of actinobacteria, which is a phylum of bacteria associated with inflammation.

“Many studies show that inflammation is higher in black women than in white women,” Price notes.

Started in 1985, the study recruited 2,379 girls, aged 9 and 10, in hopes of tracking the development of obesity and cardiovascular disease and assessing risk factors. Half of the girls were black and the other half white. The study is ongoing.

For the new gut microbiome study, the researchers sought out volunteers from this population willing to submit stool samples. They found that body mass and fasting insulin were significantly higher in black women. Almost half of black women were insulin resistant, compared to 30% of white women. These factors alone could explain the differences in microbiome, so they adjusted the analyzes to take this into account.

And after – Price has no plans for new microbiome studies, but she says the possibilities are vast. The gut microbiome could be measured in an intervention study, trying to show the benefits of a dietary approach. There are also nasal and vaginal microbiomes that could reveal findings on health inequalities.

The study also attempted to take into account insulin sensitivity and resistance. Insulin sensitivity refers to how the body reacts to insulin. High insulin sensitivity is a sign of good metabolic health, while low insulin sensitivity, known as insulin resistance, can be a precursor to diabetes. Among women with high insulin sensitivity, black women had two or four times the amount of certain types of bacteria, but the significance of that – other than demonstrating again that both groups face environments of different health – is not yet known.

What these differences mean for metabolic health — and why they exist — will take more research to untangle. Scientific investigation of the microbiome is relatively new, and the gut still holds many secrets.

Summary: The prevalence of overweight and obesity is highest among black women in the United States, contributing to a disproportionate prevalence of type 2 diabetes compared to white women. Insulin resistance, independent of body mass index, tends to be higher in black women than in white women, but the mechanisms explaining these differences are not fully understood. The intestinal microbiota is implicated in the pathophysiology of obesity, insulin resistance and cardiometabolic diseases. Only two studies examined racial differences in black and white women, but neither characterized the gut microbiome in terms of insulin sensitivity by race and gender. Our aim was to determine whether gut microbiome profiles differ between black and white women and, if so, to determine whether these racial differences persisted when controlling for insulin sensitivity status. In a pilot cross-sectional analysis, we measured the relative abundance of bacteria in fecal samples collected from a subset of 168 black (n=94) and white (n=74) women from the National Growth and Health Study (NGHS ). We performed analyzes by self-identified race and by race plus insulin sensitivity status (eg, insulin sensitive versus insulin resistant, as determined by HOMA-IR). A greater proportion of black women were classified as IR (50%) compared to white women (30%). Alpha diversity did not differ by race or by race and insulin sensitivity status. Family-level beta diversity was significantly different by race (p = 0.033) and by the combination of race and insulin sensitivity (p = 0.038). Black women, regardless of insulin sensitivity, had a greater relative abundance of the Actinobacteria phylum (p=0.003), compared to white women. There was an interaction between race and insulin sensitivity for verrucomicrobial (p = 0.008), where among those with insulin resistance, black women had four times higher abundance than white women. At the family level, we observed significant interactions between race and insulin sensitivity for Lachnospiraceae (p = 0.007) and Clostridiales Family XIII (p = 0.01). Our results suggest that the gut microbiome, particularly the low beta diversity and larger actinobacteria, one of the most abundant species, may play an important role in driving black women’s cardiometabolic health disparities, indicating an influence of social and environmental factors on the gut microbiome.

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