Biology subjects

Evstafev, I.

Publications and source records attributed to Evstafev, I..

3 recordsLinked to original sources

bioRxiv2026

Measurement of a panel of 21 steroids in a quantitative assay in human plasma, adipose tissue, and fecal samples using ultra-high-performance liquid chromatography-tandem mass spectrometry

Comprehensive detection of steroids, beyond the limited panels typically analyzed in clinical chemistry laboratories, has become increasingly important given their pivotal roles in diverse biological processes. However, steroid quantification poses several analytical challenges, including differences in ionization efficiency and structural similarities across the entire steroid metabolic network. To address these challenges, we developed a targeted ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) assay to analyze 21 steroids using reverse-phase chromatography combined with rapid polarity switching. Mass spectrometry (MS) analysis was performed in scheduled multiple reaction monitoring (sMRM) mode. Depending on the steroid and matrix, the validated lower limits of quantitation (LLOQ) ranged from 12.0 pM to 1216 pM in plasma and 41.1 pM to 384 pM in fecal sample homogenates. In adipose tissue, it was from 0.01 pmol/g to 9 pmol/g. Measured steroid concentrations obtained from the commercial control samples (MassTrak Steroid Serum QC Set 1 and the MassCheck(R) Steroid Panel 1 Serum Control) showed close agreement with the reference values. As a proof of concept, the method was successfully applied to 469 plasma samples in several projects, 15 adipose tissue samples, and 332 fecal samples, demonstrating its applicability to large-scale studies. In conclusion, the method enables sensitive, derivatization-free quantification of an expanded steroid panel in plasma and complex biological matrices, including adipose tissue and fecal samples, representing a significant advancement in comprehensive steroid profiling. Graphical abstractFor Table of Contents Only O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=114 SRC="FIGDIR/small/737297v1_ufig1.gif" ALT="Figure 1"> View larger version (35K): org.highwire.dtl.DTLVardef@807582org.highwire.dtl.DTLVardef@1a2cbe9org.highwire.dtl.DTLVardef@f96f76org.highwire.dtl.DTLVardef@4b8c9_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗

bioRxiv2026

Feasibility of multimodal metabolic analysis for detecting early changes in acute neuroinflammation

Given the prevalence of metabolic perturbations in a variety of neurological and neurodegenerative diseases, understanding and monitoring brain metabolism is a key step in our advancement of therapies. The details of the citric acid cycle were established at the beginning of the last century but only recently have its metabolic intermediates been observed in vivo in the brain. In this study, we employed orthogonal analyses to investigate metabolic alterations in response to acute neuroinflammation in vivo, demonstrating a multi-technique approach that could be used for future studies. Hyperpolarized 13C-pyruvate spectroscopy revealed an early decline in pyruvate metabolism via pyruvate dehydrogenase (PDH), leading to reduced 13C-bicarbonate formation. This metabolic disruption occurred despite the absence of structural or perfusion changes on conventional MRI. Further analysis of polar metabolites in the ipsilateral hemisphere confirmed ongoing inflammatory processes. These findings highlight the potential of this dual technique approach to inform upon metabolic changes due to neuroinflammation. Combining methods to probe metabolism in invasive (metabolomics) and non-invasive (hyperpolarized MRI) manners, this represents a promising translational approach for real-time metabolic assessments in an area of the body, the brain, where studying processes such as metabolism has traditionally been challenging. This study has demonstrated the approach to monitor changes in metabolism in response to inflammation in the brain.

neuroscience↗

bioRxiv2025

Pharmacokinetics and efficacy of tank-water administered BRAF-inhibitor dabrafenib in a zebrafish model of BRAF-mutant melanoma

Zebrafish models are widely used to study the biology of BRAF-mutant melanoma. However, long-term treatment of adult fish with small molecule BRAF inhibitors is challenging, limiting the usefulness of this model to study treatment-induced effects in melanoma biology. In addition, pharmacokinetic studies on small molecule inhibitors in zebrafish that could inform rational dosing strategies, are largely lacking. Here, we have assessed the pharmacokinetics, metabolism and efficacy of continuous tank water -administered BRAF-inhibitor dabrafenib in adult zebrafish. Our results demonstrate that dabrafenib is quickly absorbed from the tank water, reaching efficacious plasma levels within one hour following treatment, but also shows fast elimination kinetics with a half-life of 1.6 hours. We could detect most of the human metabolites of dabrafenib in zebrafish, suggesting that dabrafenib metabolism in zebrafish follows a similar process as in humans. Continuous tank water -administered dabrafenib led to therapeutically relevant steady-state plasma levels that inhibited the BRAF-driven signaling and growth in zebrafish melanoma cells in vitro, and resulted in robust in vivo efficacy in a genetic zebrafish model of BRAF-mutant melanoma, with no apparent toxicity. Together, our results demonstrate that continuous tank water -administered dabrafenib provides a feasible, efficient, and well-tolerated dosing strategy to study treatment-related effects in zebrafish models of BRAF-mutant melanoma. We expect that tank water-administration may also facilitate the dosing of other small molecule inhibitors, especially those with short in vivo half-life in zebrafish. HighlightsO_LIPharmacokinetic analysis demonstrates fast absorption kinetics and short plasma half-life for tank water -administered dabrafenib in zebrafish C_LIO_LIDabrafenib is metabolized in zebrafish following a similar metabolic process as in humans C_LIO_LITank water -administered dabrafenib provides a feasible, efficient, and well-tolerated dosing strategy to study treatment-related effects in zebrafish models of BRAF-mutant melanoma C_LIO_LITank water-administration may facilitate dosing of small molecule inhibitors with short in vivo half-life in zebrafish C_LI

cancer biology↗