Biology subjects

Aresti, J.

Publications and source records attributed to Aresti, J..

2 recordsLinked to original sources

bioRxiv2020

pH-dependent spontaneous hydrolysis rather than gut bacterial metabolism reduces levels of the ADHD treatment, Methylphenidate

Methylphenidate is absorbed in the small intestine. The drug is known to have low bioavailability and a high interindividual variability in terms of response to the treatment. Gut microbiota has been shown to reduce the bioavailability of a wide variety of orally administered drugs. Here, we tested the ability of small intestinal bacteria to metabolize methylphenidate. In silico analysis identified several small intestinal bacteria to harbor homologues of the human carboxylesterase 1 enzyme responsible for the hydrolysis of methylphenidate in the liver. Despite our initial results hinting towards possible bacterial hydrolysis of the drug, up to 60% of methylphenidate was spontaneously hydrolyzed in the absence of bacteria and this hydrolysis was pH-dependent. Overall, the study shows that pH-dependent spontaneous hydrolysis rather than gut bacterial metabolism reduces levels of methylphenidate and suggest a role of the luminal pH in the bioavailability of the drug.View Full Text

microbiology↗

bioRxiv2017

The MYC antagonist MNT autoregulates its expression and supports proliferation in MAX deficient cells

MNT is a transcription factor of the MXD family. MNT-MAX dimers down-regulate genes by binding to E-box sequences, which can also be bound by MYC-MAX to activate transcription. MNT has been described as a modulator of MYC activity but little is known about MNT regulation and whether MNT has MAX-independent functions. Using a MAX deficient cell line and siRNA-mediated silencing of MAX, we show that in the absence of MAX, the total MNT levels are elevated and that MNT localizes both in the cytoplasm and the nucleus. In contrast, MNT is predominantly nuclear when MAX is expressed. MNT is required for optimal cell proliferation even in the absence of MAX, being the first report of a MAX-independent function of MNT. Interestingly, MNT forms homodimers and autoregulates its expression by repressing its own promoter. The tight MNT regulation and its activity in absence of MAX suggest its importance on cell homeostasis.

cancer biology↗