Intake of Oolong Tea Polyphenols Exhibit Increase in Circadian Rhythm Gene Expression, Repair of Intestinal Microbiota, and Cognitive Function

 Almost all living organisms possess an internal biological clock, known as the circadian clock, that has circadian rhythms responsible for regulating important processes such as eating and sleepiness. The master circadian clock that coordinates the circadian rhythms in different tissues is located in the superchiasmatic nucleus (SCN) of the hypothalamus. Circadian rhythm disruptions can increase risk for developing sleep disturbance, obesity, gastrointestinal disease, etc.

            In the chapter titled, “Circadian Desynchrony and Health” in Atlas of Clinical Sleep Medicine, Dr. Fred W. Turek and Dr. Keith C. Summa discussed various diseases that are associated with circadian disruption. One of the diseases that Dr. Turek focused on was gastrointestinal disease. In the discussion, Dr. Turek first explained the effect of circadian disruption on gut microbiota. Gut microbiota are the microorganisms that reside in animals’ gastrointestinal tracts. Dr. Turek described that circadian disruption can lead to changes in the composition or structure of the gut microbiota. In addition, Dr. Turek also stated that changes to the gut microbiota are associated with metabolic dysfunction. In regard to an increased risk of developing gastrointestinal disease, he also explained that those with Crohn’s disease and inflammatory bowel disease also experience circadian disruption.

            In the research article, The modulatory effect of oolong tea polyphenols on intestinal flora and hypothalamus gene expression in a circadian rhythm disturbance mouse model, researchers investigated the effect of oolong tea polyphenol (OTP) intake on circadian rhythm gene expression, cognitive function, and structure of intestinal flora on mice that exhibited circadian rhythm disturbance. Tea polyphenols are shown to help improve memory impairments that were caused by circadian rhythm disorders. Epigallocatechin gallate (EGCG) is an ingredient in tea polyphenols that helps modulate the composition of intestinal flora. EGCG is abundant in oolong tea. It also produces positive regulation of circadian rhythm genes in the liver. In the study, one group of mice ingested OTP and the feces of this group was then transplanted into another group of mice. In addition, there were also groups of mice that did not ingest OTP. Maze tests like the Morris water maze test and a Y-maze were used to assess the cognitive function of the groups of mice. Single-cell RNA sequencing (scRNA-seq) was also used to analyze the development of various cell types and gene expression.

            From the study, the researchers found that the escape latency from the Morris water maze was faster in groups of mice with OTP compared to groups without OTP. Escape latency refers to the time it takes for the mouse to identify the platform and escape the water maze. In addition, researchers also found that there was an upregulation in the production of various cell types including astrocytes, oligodendrocytes, and microglia. Mice with OTP also exhibited higher gene expression of circadian rhythms genes like Clock. The researchers also concluded that OTP intake can slow weight gain in mice with circadian rhythm disturbances. Lastly, they also found that OTP can help restore or repair the structure of gut microbiota and induce production of metabolites.

            Circadian rhythms are essential to the normal function of organisms. Disturbances in circadian rhythms can increase the risk 4for developing cardiovascular disease, gastrointestinal disease, cancer, etc. Using the findings of Dr. Turek and Yan et al. on the effects of circadian rhythm disorders on the gastrointestinal tract (GI), more can be investigated on how circadian rhythm disorders disrupt the normal function of the GI and how substances like OTPs can improve health-related problems associated with circadian rhythm disorders.

 

References

Kryger, M. H., (2010). Circadian Desynchrony and Health. In F. W. Turek & K. C. Summa (Eds.), Atlas of Clinical Sleep and Medicine (pp. 168-174).

 

Yan, R., Ho, C., Liu, Y., Zhan, S., Wu, Z., & Zhang, X. (2024). The modulatory effect of oolong tea polyphenols on intestinal flora and hypothalamus gene expression in a circadian rhythm disturbance mouse model. Food Science and Human Wellness. 13, 748-764. https://doi.org/10.26599/FSHW.2022.9250064.