A new study examining the gene expression of gut microbes suggests that the heart-healthy benefits of walnuts may be related to beneficial changes in the mix of microbes found in our gut. The results could help identify other foods or supplements with similar nutritional benefits.
Researchers led by Kristina S. Petersen of Texas Tech University in the United States found that introduce nuts into the diet of a person can alter the mix of microbes in the gut – known as the microbiome – in ways that increase the body’s production of L-homoarginine amino acid. Homoarginine deficiency has been linked to an increased risk of cardiovascular disease.
“Research has shown that walnuts may have beneficial effects on the heart, such as lower cholesterol levels and blood pressure explains Mansi Chandra, a researcher at Juniata College in Huntingdon. This motivated us to study how walnuts benefited the gut microbiome and whether those effects led to potential benefits. Our findings represent a novel mechanism through which walnuts may reduce the risk of cardiovascular disease,” she highlights.
Last generation technology
The researchers used a method known as metatranscriptómica to study gene expression in gut microbes. This newly developed technology can be used to quantify gene expression levels and monitor how they change in response to various conditions, such as changes in diet.
“To our knowledge, this is the first study using metatranscriptomic analysis to study the impact of walnut consumption on gut microbiota gene expression,” Chandra said. “These exploratory analyzes contribute to our understanding of microbiome modulation.” walnut-related gut health, which could be very impactful in learning how gut health impacts our overall heart health.”
He metatranscriptomic analysis used samples acquired from a previously conducted controlled feeding study, in which 35 participants at high cardiovascular risk were placed on a two-week standard Western diet and then randomly assigned to one of three study diets. Study participants followed each diet for six weeks with a break in between.
The diets included one that incorporated whole nuts, another that included the same amount of omega-3 fatty acid alpha-linolenic acid, or ALAand polyunsaturated fatty acids than the walnut diet but without walnuts, and another that partially substituted another fatty acid known as oleic acid for the same amount of ALA found in walnuts but without consuming any walnuts.
The diets were designed to obtain information on how walnuts affected cardiovascular health due to their bioactive compounds and their ALA content, and whether ALA from walnuts is the best substitute for saturated fat in the diet compared to oleic acid.
Gastrointestinal tract bacteria
For the new work, the researchers used metatranscriptomics to analyze gene expression and gastrointestinal tract bacteria from fecal samples collected shortly before participants finished the break-in diet and each of the three study diets.
The analysis revealed higher levels of Gordonibacter bacteria in the intestine of participants on the walnut diet. This bacterium converts plant polyphenols ellagitannins and ellagic acid into metabolites that allow their absorption by the body.
The participants who ate the walnut diet also showed higher levels of expression of several genes involved in important metabolic and biosynthetic pathways, including those that increase the body’s production of the amino acid L-homoarginine.
Although more studies are needed to confirm these observations, the research could help inform nut-based dietary interventions. “Since many people are allergic to nutsthese findings also suggest that other substances may be beneficial to health,” says Chandra.
Next, the researchers want to apply metabolomic and proteomic analyzes to identify the end products of the genes that showed higher levels of expression, which would allow them to better understand the biological mechanisms involved.