Gut microbial β-glucuronidases reactivate estrogens as components of the estrobolome that reactivate estrogens

Abstract

Edited by Wolfgang Peti Gut microbial ␤-glucuronidase (GUS) enzymes have been suggested to be involved in the estrobolome, the collection of microbial reactions involving estrogens. Furthermore, bacterial GUS enzymes within the gastrointestinal tract have been postulated to be a contributing factor in hormone-driven cancers. However, to date, there has been no experimental evidence to support these hypotheses. Here we provide the first in vitro analysis of the ability of 35 human gut microbial GUS enzymes to reactivate two distinct estrogen glucuronides, estrone-3-glucuronide and estradiol-17-glucuronide, to estrone and estradiol, respectively. We show that certain members within the Loop 1, mini-Loop 1, and FMN-binding classes of gut microbial GUS enzymes can reactivate estrogens from their inactive glucuronides. We provide molecular details of key interactions that facilitate these catalytic processes and present the structures of two novel human gut microbial GUS enzymes related to the estrobolome. Further, we demonstrate that estrogen reactivation by Loop 1 bacterial GUS enzymes can be inhibited both in purified enzymes and in fecal preparations of mixed murine fecal microbiota. Finally, however, despite these in vitro and ex vivo data, we show that a Loop 1 GUS-specific inhibitor is not capable of reducing the development of tumors in the PyMT mouse model of breast cancer. These findings validate that gut microbial GUS enzymes participate in the estrobolome but also suggest that the estrobolome is a multidimensional set of processes ongoing within the mammalian gastrointestinal tract that likely involves many enzymes, including several distinct types of GUS proteins.

Fecal bacteria and metabolite responses to dietary lysozyme in a sow model from late gestation until lactation

“…Microbiota remodeling during the perinatal period may be a positive process enabling the mother to support their own health, as well as that of their offspring. Gut microbiota play a key role in the metabolism of nutrients, immune function, gut hormone secretion and provide protection from pathogens [2][3][4][5] . At the same time, microbial flora is regulated by nutrients as well as the immunological and metabolic statuses of the host.…”

Predicting drug-metagenome interactions: Variation in the microbial β-glucuronidase level in the human gut metagenomes

“…For example, many opioids (including morphine [ 62 , 63 ], codeine [ 62 , 63 ], hydromorphone [ 64 , 65 ], nalmefene [ 66 ], ketobemidone [ 67 ], and buprenorphine [ 68 ]) are reported to be glucuronidated in the liver and reactivated by β-glucuronidases. Estrogens are also known to form conjugates with glucuronides and could be reactivated by β-glucuronidase as well [ 69 – 73 ]. NSAIDs such as naproxen is metabolized by glucuronidation and is reactivated in the gut by microbial β-glucuronidases [ 74 ].…”

“…buprenorphine [68]) are reported to be glucuronidated in the liver and reactivated by β-glucuronidases. Estrogens are also known to form conjugates with glucuronides and could be reactivated by β-glucuronidase as well [69][70][71][72][73]. NSAIDs such as naproxen is metabolized by glucuronidation and is reactivated in the gut by microbial β-glucuronidases [74].…”

Indoxylsulfate, a Metabolite of the Microbiome, Has Cytostatic Effects in Breast Cancer via Activation of AHR and PXR Receptors and Induction of Oxidative Stress

“…In that sense, IS behaves similar to other cytostatic metabolites [ 16 , 17 , 25 , 32 , 39 , 40 , 41 , 42 , 43 , 45 , 46 ]. Of note, in addition to the loss of cytostatic properties, the breast cancer oncobiome has an increased capacity for reactive estrogens and increase estrogen enterohepatic circulation [ 1 , 93 ]. Consequently, parent estrogens, estrone and estradiol, boost cell proliferation, and their catechol-quinone metabolites cause oxidative DNA damage and mutagenesis [ 94 ].…”