PXR is a target of (-)-epicatechin in skeletal muscle

Abstract

Epicatechin (EC) is a flavanol that has shown numerous biological effects such as: decrease risk of cardiovascular dysfunction, metabolism regulation, skeletal muscle (SkM) performance improvement and SkM cells differentiation induction, among others. The described EC acceptor/receptor molecules do not explain the EC's effect on SkM. We hypothesize that the pregnane X receptor (PXR) can fulfill those characteristics, based on structural similitude between EC and steroidal backbone and that PXR activation leads to similar effects as those induced by EC. In order to demonstrate our hypothesis, we: 1) analyzed the possible EC and mouse PXR interaction through in silico strategies, 2) developed an EC's affinity column to isolate PXR, 3) evaluated, in mouse myoblast (C2C12 cells) the inhibition of EC-induced PXR's nucleus translocation by ketoconazole, a specific blocker of PXR and 4) analyzed the effect of EC as an activator of mouse PXR, evaluating the expression modulation of cytochrome 3a11 (Cyp3a11) gen and myogenin protein. (-)-Epicatechin interacts and activates PXR, promoting this protein translocation to the nucleus, increasing the expression of Cyp3a11, and promoting C2C12 cell differentiation through increasing myogenin expression. These results can be the base of further studies to analyze the possible participation of PXR in the skeletal muscle effects shown by EC.

(-)-Epicatechin Is a Biased Ligand of Apelin Receptor

“…To isolate (-)-epicatechin-interacting proteins from skeletal muscle, we synthesized an affinity column according to a previously reported method [ 7 ]. For the isolation, a homogenate of C57BL/6 mice quadriceps was incubated overnight (4 °C) with the affinity chromatography column; noninteracting proteins were eliminated after several column washes (10×) with PBS (1×, pH = 7.4), and interacting proteins were detached with an acidic solution (MES, pH = 4.5).…”

“…Many of the reported EC-induced effects are associated with the activation of intermediaries of specific signaling pathways, such as the mitogen-activated protein kinases (MAPKs), Akt, and AMPK pathways, which may depend on transmembrane receptor activation. Recently, using molecular and functional approaches, we demonstrated that EC interacts with two receptors, the G protein-coupled estrogen receptor (GPER), a transmembrane receptor, [ 5 , 6 ], and the pregnane X receptor (PXR), a nuclear receptor [ 7 ]. EC-induced GPER activity induces vasodilation through increases in nitric oxide synthase activity [ 6 ].…”

“…It also induces mitochondrial biogenesis [ 5 ]. EC-induced PXR activity relates to the modulation of cytochromes CYP450 (Cyp3a11) and increases the expression of myogenin [ 7 ]. However, neither receptor stimuli seem to be associated with the EC-induced effects found in skeletal muscle.…”

Microbial Metabolites as Ligands to Xenobiotic Receptors: Chemical Mimicry as Potential Drugs of the Future

“…PXR may prognosticate for survival in patients undergoing liver transplantation (Amer, McColl et al 2019), perhaps via its effects on tacrolimus metabolism (Stifft, van Kuijk et al 2018). In addition, recent work has highlighted new roles for PXR as a factor promoting radio resistance in cancer (Niu, Cui et al 2022), drug sensitivity or resistance (Creusot, Gassiot et al 2020, Sári, Mikó et al 2020, Matheux, Gassiot et al 2021, Ozawa, Miura et al 2021, and promotes striated and smooth muscle metabolism and physiology (Swales, Moore et al 2012, Ortiz-Flores, Portilla-Martínez et al 2020. Our prior work demonstrated that gut microbe-produced indole metabolites of L-tryptophan (e.g., indole and indole propionic acid) are ligands of PXR (Venkatesh, Mukherjee et al 2014).…”

Mechanisms Modified by (−)-Epicatechin and Taxifolin Relevant for the Treatment of Hypertension and Viral Infection: Knowledge from Preclinical Studies

“…The same authors showed that further mechanisms of EC action in the vasculature involve modulation of potassium and calcium channels, which participate in the hyperpolarization and depolarization of vascular smooth muscle cells [ 68 ]. Recent studies of Ortiz-Flores et al have shown that EC interacts with and activates the pregnane X receptor [ 173 ]. There is a limited number of studies that investigated the vascular effects of TX.…”