Chronic insomnia and cardiometabolic disease: gut microbiota and bile acids involved?

Bile acids are currently a hot topic in research: in addition to helping the absorption of nutrients, they may play an important role in interactions between gut microbiota and host. Following their synthesis in the liver, bile acids are released into the gut and transformed by bacteria whose activity influences the composition of the gut microbiota. Reabsorbed by the colon, these “secondary” bile acids may then act as signaling molecules in various metabolic and immune processes.²

Sequencing, metabolomics, and statistics

Chinese researchers have put forward the idea that the gut microbiota and bile acids are involved in the still poorly understood relationship between chronic insomnia and cardiometabolic disease. Several recent discoveries have led them down this path. For example, the gut microbiota has its own circadian rhythms, different from that of the host and sensitive to insomnia. In mice, repeated sleep interruptions modify gut microbiota composition and the metabolism of bile acids. Lastly, gut microbiota dysbiosis and the dysregulation of bile acid metabolism both impair metabolic health.

To test their hypothesis, the researchers used two cohorts, a “discovery cohort” (sidenote: Discovery cohort The “discovery cohort” included 1,809 subjects from the prospective Guangzhou Nutrition and Health Study (GNHS) ) and a “validation cohort” (sidenote: Validation cohort The “validation cohort” included 6,122 participants from the cross-sectional Guangdong Gut Microbiome Project (GGMP), whose gut microbiota was sequenced by the researchers. ) . They collected detailed information on the subjects’ sleep and cardiometabolic parameters over a six-year period prior to the collection of the stool samples. Lastly, they analyzed the fecal bile acid metabolome of 954 subjects from the Guangzhou Nutrition and Health Study (GNHS) cohort.

Two bacterial genera and specific bile acids stand out

The researchers showed that chronic insomnia and cardiometabolic disorders were correlated with lower levels of two bacteria from the Ruminococcaceae family in both cohorts studied. By further analyzing the GNHS cohort, they also found that:

• Certain bile acids, such as isolithocholic acid (IsoLCA), murocholic acid (MCA), and norcholic acid (NorCA) mediated these associations. 
• Tea consumption (green, black, oolong, etc.) was associated with higher levels of Ruminococcaceae and lower levels of NorCA, as well as a decreased risk of insomnia.

Tea time to reduce the cardiometabolic risk of chronic insomnia?

The researchers believe that the gut microbiota-bile acid axis may be a potential intervention target for reducing the impact of chronic insomnia on cardiometabolic health. However, they remain cautious regarding tea: more research is needed to confirm that tea consumption has a beneficial effect on the bacteria in the microbiota linked to cardiometabolic health.