A team from Lund University in Sweden has found that certain amino acids in the blood are connected to conditions like obesity, cardiovascular disease, and type 2 diabetes, as well as the composition of the gut microbiome.

Previous studies have shown that people with these diseases have varying occurrences of different metabolites—small molecules or metabolic residues—in the bloodstream.

In the new study, the researchers sought to identify the metabolites in the blood that can be linked to obesity—including high body mass index—and investigated whether the obesity-related metabolites affect the composition of the bacterial flora in stool samples.

After analyzing blood plasma and stool samples in 674 volunteers, the researchers found 19 different metabolites that could be linked to the person’s body mass index (BMI).

The researchers also found that glutamate and BCAA (branched-chain and aromatic amino acids) had the strongest connection to obesity.

To achieve these findings, targeted profiling was performed on 48 plasma metabolites from patients in the study using targeted liquid chromatography-mass spectrometry. 

The researchers found that the obesity-related metabolites were linked to four different intestinal bacteria—Bautia, Dorea and Ruminococcus in the Lachnospiracae family and SHA98.

“The differences in BMI were largely explained by the differences in the levels of glutamate and BCAA,” Margo Orho-Melander, a professor of genetic epidemiology at Lund University, said in a statement. “This indicates that the metabolites and gut bacteria interact, rather than being independent of each other.”

The researchers found that the strongest risk factor for obesity is glutamate, which has been linked to obesity in previous studies. BCAA has also been used to predict the future onset of type 2 diabetes and cardiovascular disease.

“This means that future studies should focus more on how the composition of gut bacteria can be modified to reduce the risk of obesity and associated metabolic diseases and cardiovascular disease,” Orho-Melander said. “To get there, we first need to understand what a healthy normal gut flora looks like, and what factors impact the bacterial composition.

“This requires large population studies, like the Malmö Offspring Study, as well as intervention studies.”   

Most of the previous research on gut bacteria is based on animal studies, which cannot be directly applied to humans. Also, a healthy gut flora for one person might not necessarily be good for everyone else.

The study was published in The Journal of Clinical Endocrinology & Metabolism.