Characterization of Drugs Absorbance by Normal Gut Microbes

Abstract

The gut microbiome has evolved as a new organ of the body. Trillions of microbes reside in the gut in symbiotic fashion and play a key role in overall body health. The gut microbiome presents targets to alter the pharmacokinetics of orally administered drugs in the gut to manipulate clinical response. More recently, an in vitro study endorsed the idea that membrane transporters in microbes take up the orally administered drugs. Studies regarding structural homology show similarities between the membrane transport proteins of gut epithelial cells and the gut microbiome. The presence of such transport mechanisms in the normal flora of the gut of the host may compete for drug substrates with the host itself for its absorbance. Therefore, I hypothesized that orally administered drugs (that is, paracetamol, sulpiride, salicylic acid, phenobarbital, caffeine and propranolol) may interact with the gut microbiome and could be taken up by the microbes during their transit through small intestine. The interaction between the drugs and the microbiome may alter the normal microbiome after long term exposure to the drugs. Currently, no report confirms the absorbance of drugs by the gut microbiome in an in vivo animal model though a few in vitro reports endorse the idea. Similarly, very little data revealed changes in the microbiome after long term exposure to drugs. In vivo trials with each of the six drugs were conducted in normal healthy adult male rats (n=36) divided into the control group (without treatment) and five treatment groups, each group having six rats. The drugs were administered orally in single doses/kg body weight to treatment groups. Sampling was done at post-drug administration intestinal transit times of 2, 3, 4, 5 and 6 hours. Digesta was isolated from the small intestine and filtered to get a microbial mass. The microbial mass was used to extract microbial lysate to seek drug absorbance by the gut microbiome and for extraction of genomic DNA (gDNA) to determine gut microbiome ecology. The drug absorbance by the microbiome was determined by analysis of the microbial lysate by ultra violet reverse phase high performance liquid chromatography (reverse phase HPLC-UV) with a C18 column under isocratic conditions. Extracted gDNA from normal and drug-treated microbial samples were analyzed by quantitative PCR and high-throughput 16S rRNA gene sequencing, respectively. Firmicutes (96%) were among the most abundant resident normal flora of the small intestine. xxvii Maximum drug absorbance by the whole microbiome and maximum drug absorbance per milligram of microbial mass were significantly higher (P≤0.05) at 4, 4, 2, 2, 4 and 3 hours postdrug administration of paracetamol, phenobarbital, caffeine, salicylic acid, sulpiride and propranolol, respectively, as compared to all other groups. Maximum drug administered/dose recovery from paracetamol-, phenobarbital-, caffeine-, salicylic acid-, sulpiride- and propranololtreated groups was 13.16±0.55%, 5.73±0.19%, 31.60±2.33%, 1.70±0.16%, 3.91±0.25% and 72.6±3.79% at 4, 4, 2, 2, 4 and 3 hours post-drug administration, respectively, as compared to all other groups. Propranolol and caffeine are excellent, paracetamol is good, while phenobarbital, salicylic acid and sulpiride are poor substrates for the gut microbiome. Drug absorbance by the gut microbiome was observed at varied transit times and was reduced as a function of time due to competitive absorption between the gut microbiome and gut epithelial cells of the host. Maximum transit times of paracetamol, phenobarbital, caffeine, salicylic acid, sulpiride and propranolol were 5, 5, 5, 2, 4 and 3 hours post-drug administration, respectively. Results of the current study confirm the hypothesis of homology between membrane transporters of the gut microbiome and intestinal epithelium. Orally administered drugs can be absorbed by the gut microbiome competitively during transit in the small intestine and different drugs exhibit varied transit times. Long term exposure of such drugs increased Escherichia coli counts significantly (P≤0.05), while Lactobacillus counts decreased significantly (P≤0.05) in the gut microbiome. The gut microbiome is a drugable target with possibility to manipulate its composition.