Variation in human gut microbiota impacts tamoxifen pharmacokinetics.

Tamoxifen is the most prescribed drug used to prevent breast cancer recurrence, but patients show variable responses to tamoxifen. Such differential inter-individual response has a significant socioeconomic impact as one in eight women will develop breast cancer and nearly half a million people in the United States are treated with tamoxifen annually. Tamoxifen is orally delivered and must be activated by metabolizing enzymes in the liver; however, clinical studies show that neither genotype nor hepatic metabolic enzymes are sufficient to predict why some patients have sub-therapeutic levels of the drug.

Tryptophan metabolism is a physiological integrator regulating circadian rhythms.

Objective: The circadian clock aligns physiology with the 24-hour rotation of Earth. Light and food are the main environmental cues (zeitgebers) regulating circadian rhythms in mammals. Yet, little is known about the interaction between specific dietary components and light in coordinating circadian homeostasis.