The gut microbiome contains trillions of microbes that produce chemicals, often referred to as metabolites, that support the health of the host. Gut microbial metabolites have been shown in recent studies to help support antioxidative status, the inflammatory response, gastrointestinal (GI) health, and signaling pathways related to lipid and blood sugar balance. A review by Wu and colleagues explored recent literature for the potential biochemical link between gut microbial metabolites and their supportive role in metabolic health. 

Short-chain fatty acids (SCFAs), for example, are microbial metabolites that are produced by microbes including some Bifidobacterium and Lactobacillus species. Butyric, propionic, and acetic acids are the most prevalent SCFAs and have been shown in research to help support many physiological processes in the body. These metabolites are also known as postbiotics. Recent evidence indicates that certain gut microbial metabolites such as SCFAs may help promote healthy lipid and blood sugar metabolism.

SCFAs support lipid metabolism by helping regulate fatty acid oxidation and its related cell signaling. They have also been shown to help decrease the expression of certain pro-inflammatory cytokines including nuclear factor-κB. The inflammatory process is thought to be involved in the etiology of many chronic illnesses related to metabolic dysfunction/dysregulation. 

The gut microbiome also transforms the essential amino acid, tryptophan, into metabolites that may help support healthy blood sugar metabolism. Tryptophan’s derivatives — indole-3 propionic acid, indole-3 lactate, and indole-3 acetaldehyde — have been shown in animal studies to help support the inflammatory response, cell differentiation, and healthy blood glucose balance.

Bile acids are originally synthesized in the liver and, through a complex biochemical pathway, are converted into secondary bile acids in the gut microbiome. They may regulate certain aspects of the inflammatory response and blood sugar sensitivity. Two bile acid receptors, farnesoid X receptor and Takeda G-protein coupled receptor 5 have been associated with glucose homeostasis and energy metabolism. An animal study involving fecal microbial transplantation from individuals with type 2 diabetes mellitus indicated that disruptions in blood glucose homeostasis occurred through the modulation of bile acid metabolism. However, the biochemistry of blood glucose metabolism is nuanced and multifactorial; more research is needed. 

Many clinical studies have investigated the link between blood sugar balance and gut microbial composition. A recently published clinical study associated the incidence of hyperglycemia with duodenal mucosal integrity, dysbiosis, and a systemic proinflammatory state. However, due to a small sample size (n=54) and other factors, larger human trials need to be conducted before clinical conclusions can be made. 

Metabolites produced in the gut microbiome may help support cell signaling, host-microbe crosstalk, and processes related to lipid and blood sugar metabolism. Prebiotic and probiotic-rich foods may help promote healthy gut microbial composition and microbial metabolite production. Supplementation directly with postbiotics, such as butyric acid, may also play a supportive role in metabolic and GI health.

By Dr. C. Ambrose, ND, MAT