Gut microbiota, one of the determinants of pharmacokinetics, has long been underestimated. It is now generally accepted that the gut microbiota plays an important role in drug metabolism during enterohepatic circulation either before drug absorption or through various microbial enzymatic reactions in the gut. In addition, some drugs are metabolized by the intestinal microbiota to specific metabolites that cannot be formed in the liver. More importantly, metabolizing drugs through the gut microbiota prior to absorption can alter the systemic bioavailability of certain drugs. Therefore, understanding intestinal flora-mediated drug metabolism is critical to interpreting changes in drug pharmacokinetics. Here, we summarize the effects of gut microbiota on drug pharmacokinetics, and propose that the influence of intestinal flora on pharmacokinetics should be organically related to the therapeutic effects and side effects of drugs. More importantly, we could rationally perform the strategy of intestinal microflora-mediated metabolism to design drugs.

Nifedipine is completely absorbed by the gastrointestinal tract and its pharmacokinetics and metabolism may be influenced by microorganisms. If gut microbes are involved in the metabolism of nifedipine, plateau hypoxia may regulate the bioavailability and the therapeutic effect of nifedipine by altering the metabolic activity of the gut microbiota. We herein demonstrated for the first time that gut flora is involved in the metabolism of nifedipine by in vitro experiments. In addition, based on the results of 16S rRNA analysis of feces in rats after acute plateau, we first confirmed that the plateau environment could cause changes in the number and composition of intestinal microbes. More importantly, these changes in flora could lead to a slower metabolic activity of nifedipine in the body after an acute plateau, resulting in increased bioavailability and therapeutic efficacy of nifedipine. Our research will provide basis and new ideas for changes in the fecal flora of human acutely entering the plateau, and contribute to rational drug use of nifedipine.

There are more than 1000 species of microbes reside in the human gut, umbering∼10¹⁴ microbes. As the invisible organ of human beings, gut microbiota can usually participate in drug metabolism by producing specific enzymes, such as reductase and hydrolytic enzyme, thus affecting the efficacy, toxicity, and bioavailability of drugs. At least 30 commercially available drugs have been shown to be substrates of gut microbes-derived enzymes, and an increasing number of drugs may have the potential to contact with the distal gut with the help of improved release systems or poor solubility/permeability, more drugs are expected to be found to be metabolized through the gut flora. By collecting examples of intestinal flora participating in the metabolism of synthetic drugs and traditional Chinese medicine components, this article provides a comprehensive reference for future researchers to study drug metabolism by intestinal flora. Noticeably, the composition and quantity of intestinal flora varies among individuals, and can be affected by some drug administration (such as antibiotics) or environmental changes (acute plateau hypoxia). This seems to suggest that intestinal flora could have the potential to be a new drug target to affect the efficacy of drugs which can be metabolized by Intestinal flora. Accordingly, understanding the impact of intestinal flora on drug metabolism and clarifying the drug transformation process is of great significance for guiding rational clinical use, individualized use, toxicological evaluation, and promoting drug discovery and development.

Although extensive studies have focused on the development of acute mountain sickness (AMS), the exact mechanisms of AMS are still obscure. In this study, we used isobaric tags for relative and absolute quantitation (iTRAQ) proteomic analysis to identify novel AMS−associated biomarkers in human plasma. After 9 hours of hypobaric hypoxia the abundance of proteins related to tricarboxylic acid (TCA) cycle, glycolysis, ribosome, and proteasome were significantly reduced in AMS resistant (AMS−) group, but not in AMS susceptible (AMS+) group. This suggested that AMS− individuals could reduce oxygen consumption via repressing TCA cycle and glycolysis, and reduce energy consumption through decreasing protein degradation and synthesis compared to AMS+ individuals after acute hypoxic exposure. The inflammatory response might be decreased resulting from the repressed TCA cycle. We propose that the ability for oxygen consumption reduction may play an important role in the development of AMS. Our present plasma proteomic study in plateau of the Han Chinese volunteers gives new data to address the development of AMS and potential AMS correlative biomarkers.

Ginseng polysaccharide (GP) is one of the most abundant components in Panax ginseng. However, the absorption pathways and mechanisms of GPs have not been investigated systematically due to the challenges of their detection. The fluorescein isothiocyanate derivative (FITC) was employed to label GP and ginseng acidic polysaccharide (GAP) to obtain target samples. HPLC-MS/MS assay was used to determine the pharmacokinetics of GP and GAP in rats. The Caco-2 cell model was used to investigate the uptake and transport mechanisms of GP and GAP in rats. Our results demonstrated that the absorption of GAP was more than that of GP in rats after gavage administration, while there was no significant difference between both after intravenous administration. In addition, we found that GAP and GP were more distributed in the kidney, liver and genitalia, suggesting that GAP and GP are highly targeted to the liver, kidney and genitalia. Importantly, we explored the uptake mechanism of GAP and GP. GAP and GP are endocytosed into the cell via lattice proteins or niche proteins. Both are transported lysosomally mediated to the endoplasmic reticulum (ER) and then enter the nucleus through the ER, thus completing the process of intracellular uptake and transportation. Our results confirm that the uptake of GPs by small intestinal epithelial cells is primarily mediated via lattice proteins and the cytosolic cellar. The discovery of important pharmacokinetic properties and the uncovering of the absorption mechanism provide a research rationale for the research of GP formulation and clinical promotion.