Biology subjects

Burnett, L. A.

Publications and source records attributed to Burnett, L. A..

6 recordsLinked to original sources

bioRxiv2026

Alkamines reveal a hidden layer of steroid and drug metabolism

Biomedical research overlooks most genes in favor of a well-studied minority, yet whether analogous blind spots exist in metabolomics remains unknown. We show that reductive amination, forming secondary amines from aldehydes or ketones and amines, generates a previously hidden class of metabolites we term alkamines. Multiplexed synthesis of 8,475 alkamines combined with MS/MS searches across 1.7 billion spectra identified 1,626 candidates across multiple species and organs. Of these, 56 were confirmed in biological samples, including 27 steroid- and 12 drug-derived alkamines matching prescription patterns. Notably, 77% of synthesized alkamines are absent from PubChem. This combinatorial logic likely explains why alkamines have evaded detection and suggests drug metabolism frameworks substantially underestimate drug-derived metabolite diversity. Reductive amination is an overlooked route modifying steroids, bile acids, and xenobiotics.

biochemistry↗

bioRxiv2026

Pan-Metabolomics Repository Mapping of the Carnitine Landscape

Carnitines are a structurally diverse class of metabolites formed by conjugation of L-carnitine with fatty acids, amino acids, xenobiotics, and microbial metabolites. They play roles in transport, mitochondrial and peroxisomal metabolism, detoxification, and systemic signaling, yet their chemical diversity remains incompletely defined. We applied a pan-repository data mining strategy of LC-MS/MS data across GNPS/MassIVE, MetaboLights, and Metabolomics Workbench using MassQL diagnostic fragment ion filtering to systematically extract acylcarnitine spectra. This yielded a library of 34,222 unique MS/MS spectra representing 2,857 atomic compositions, corresponding to 3,872,050 detections. These datasets provide an MS/MS library for annotation, discovery, and contextualization of acylcarnitines, enabling identification of previously unknown carnitines, such as dihydroferulic acid conjugated carnitines and supporting future exploration of this metabolite class across host metabolism, diet, microbial activity, pharmacological exposures, and metabolic dysregulation.

bioinformatics↗

bioRxiv2026

Navigating the conjugated metabolome

Lifes chemical diversity far exceeds current biochemical maps. While metabolomics has catalogued tens of thousands of small molecules, conjugated metabolites, formed when two or more molecular entities are covalently fused through amidation, esterification, or related chemistries, remain underexplored. These molecules can act as microbial signals, detoxification intermediates, or endogenous regulators. Here, we mined 1.32 billion MS/MS spectra across public metabolomics repositories using reverse spectral searching coupled with delta-mass inference to map conjugation events. We generated structural hypotheses for 24,227,439 MS/MS clusters. From these, we inferred 217,291 substructure pairs with dual spectral support and 3,412,720 candidate conjugates with single-match support. Predictions span host-microbe co-metabolites, diet-derived conjugates, and drug-derived species, including drug-ethanolamine and creatinine conjugates with altered bioactivities. We also uncover a family of steroid-phosphoethanolamine conjugates. Fifty-five conjugates were matched by MS/MS of synthetic standards for this work, with 27 additionally supported by retention time matching in biological samples. Guidance on how to leverage this resource is also provided. Together, these results deliver a pan-repository map of potential conjugation chemistry, establish a resource for structural discovery and MS/MS annotation, and offer a scalable framework to explore the scope and diversity of the conjugated metabolome.

bioinformatics↗

bioRxiv2025

Environmental and Maternal Imprints on Infant Gut Metabolic Programming

Early life is a critical period for immune and metabolic programming, but developmental patterns remain underexplored in populations from low- and middle-income countries. Here, we profiled the microbiome and metabolome of 55 Bangladeshi mother-infant dyads over the first six months of life. Importantly, we observed an increase in microbially-derived bile amidates and N-acyl lipids with age in conjunction with reads matching the bile salt hydrolase/transferase (bsh) gene. While microbial source tracking confirmed maternal fecal seeding, a substantial environmental contribution was also highlighted. Differences in infant fecal metabolic profiles were associated with delivery mode, maternal milk composition, household assets, and household-level water treatment. C-section delivery and untreated drinking water were linked to transient metabolic differences, including increases in bile amidates, N-acyl lipids, and other host-microbe co-metabolic products, including acylcarnitines. Multi-omics analysis revealed specific microbial-metabolite relationships, highlighting how early environmental and maternal living circumstances shape metabolic gut programming through the microbiome.

microbiology↗

bioRxiv2025

Markers of mitochondrial function and oxidative metabolism in female skeletal muscle do not display intrinsic circadian regulation

Mitochondria are key regulators of metabolism and ATP supply in skeletal muscle, while circadian rhythms influence many physiological processes. However, whether mitochondrial function is intrinsically regulated in a circadian manner in mouse skeletal muscle is inadequately understood. Accordingly, we measured post-absorptive transcript abundance of markers of mitochondrial biogenesis, dynamics, and metabolism (extensor digitorum longus [EDL], soleus, gastrocnemius), protein abundance of electron transport chain complexes (EDL and soleus), enzymatic activity of SDH (tibialis anterior and plantaris), and maximum uncoupled respiration (tibialis anterior) in different skeletal muscles from female C57BL/6NJ mice at four zeitgeber times (ZT), ZT 1, 7, 13, and 19. Our findings demonstrate that markers of mitochondrial function and oxidative metabolism do not display intrinsic time-of-day regulation at the gene, protein, enzymatic, or functional level. The core-clock genes Bmal1 and Dbp exhibited intrinsic circadian rhythmicity in skeletal muscle (i.e., EDL, soleus, gastrocnemius) and circadian amplitude varied by muscle type. These findings demonstrate that female mouse skeletal muscle does not display circadian regulation of markers of mitochondrial function or oxidative metabolism over 24 hours.

physiology↗

bioRxiv2021

Mechanisms governing protective pregnancy-induced adaptions of the pelvic floor muscles in the rat pre-clinical model

BackgroundThe intrinsic properties of pelvic soft tissues in women who do and do not sustain birth injuries are likely divergent, however little is known about this. Rat pelvic floor muscles undergo protective pregnancy-induced structural adaptations, sarcomerogenesis and increase in intramuscular collagen content, that protect against birth injury. ObjectivesWe aimed to test the following hypotheses: 1) increased mechanical load of gravid uterus drives antepartum adaptations; 2) load-induced changes are sufficient to protect pelvic muscles from birth injury. Study DesignIndependent effects of load uncoupled from hormonal milieu of pregnancy were tested in 3- to 4-month-old Sprague-Dawley rats randomly divided into four groups, N=5- 10/group: (1) load-/pregnancy hormones- (controls); (2) load+/pregnancy hormones-; (3) reduced load/pregnancy hormones+; (4) load+/pregnancy hormones+. Mechanical load simulating a gravid uterus was simulated by weighing uterine horns with beads similar to fetal rat size and weight. Reduced load was achieved by unilateral pregnancy after unilateral uterine horn ligation. To assess acute and chronic phases required for sarcomerogenesis, rats were sacrificed at 4 hours or 21 days post bead loading. Coccygeus, iliocaudalis, pubocaudalis and non-pelvic tibialis anterior were harvested for myofiber and sarcomere length measurements. Intramuscular collagen content was assessed using hydroxyproline assay. Additional 20 load+/pregnancy hormones- rats underwent vaginal distention to determine whether load-induced changes are sufficient to protect from mechanical muscle injury in response to parturition-associated strains of various magnitude. Data, compared using two-way repeated measures analysis of variance/pairwise comparisons, are presented as mean {+/-} standard error of mean. ResultsAcute increase in load resulted in significant pelvic floor muscle stretch, accompanied by acute increase in sarcomere length compared to non-loaded control muscles (coccygeus: 2.69{+/-}0.03 vs 2.30{+/-}0.06 {micro}m, P<0.001; pubocaudalis: 2.71{+/-}0.04 vs 2.25{+/-}0.03 {micro}m, P<0.0001; iliocaudalis: 2.80{+/-}0.06 vs 2.35{+/-}0.04 {micro}m, P<0.0001). After 21 days of sustained load, sarcomeres returned to operational length in all pelvic muscles (P>0.05). However, the myofibers remained significantly longer in load+/pregnancy hormones- compared to load- /pregnancy hormones- in coccygeus (13.33{+/-}0.94 vs 9.97{+/-}0.26 mm, P<0.0001) and pubocaudalis (21.20{+/-}0.52 vs 19.52{+/-}0.34 mm, P<0.04) and not different from load+/pregnancy hormones+ (12.82{+/-}0.30 and 22.53{+/-}0.32mm, respectively, P>0.1), indicating that sustained load induced sarcomerogenesis in these muscles. Intramuscular collagen content in load+/pregnancy hormones- group was significantly greater relative to controls in coccygeus (6.55{+/-}0.85 vs 3.11{+/-}0.47{micro}g/mg, P<0.001) and pubocaudalis (5.93{+/-}0.79 vs 3.46{+/-}0.52 {micro}g/mg, P<0.05) and not different from load+/pregnancy hormones+ (7.45{+/-}0.65 and 6.05{+/-}0.62 {micro}g/mg, respectively, P>0.5). Iliocaudalis required both mechanical and endocrine cues for sarcomerogenesis. Tibialis anterior was not affected by mechanical or endocrine alterations. Despite equivalent extent of adaptations, load-induced changes were only partially protective against sarcomere hyperelongation. ConclusionsLoad induces plasticity of the intrinsic pelvic floor muscle components that renders protection against mechanical birth injury. The protective effect, which varies between individual muscles and strain magnitudes, is further augmented by the presence of pregnancy hormones. Maximizing impact of mechanical load on pelvic floor muscles during pregnancy, such as with specialized pelvic floor muscle stretching regimens, is a potentially actionable target for augmenting pregnancy-induced adaptations to decrease birth injury in women who may otherwise have incomplete antepartum muscle adaptations. AJOG at a GlanceO_LIWhy was the study conducted? O_LITo determine the role of mechanical load, uncoupled from the hormonal milieu of pregnancy, in driving protective pregnancy-induced adaptations previously discovered in the rat pelvic floor muscles. C_LI C_LIO_LIWhat are the key findings? O_LIMechanical load, in the absence of pregnancy hormones, induces sarcomerogenesis and extracellular matrix remodeling in rat pelvic floor muscles. C_LIO_LILoad-induced adaptations are partially protective against mechanical pelvic floor muscle injury consequent to parturition-associated strains. C_LI C_LIO_LIWhat does this study add to what is already known? O_LIThe effect of sustained increased mechanical load, uncoupled from the hormonal milieu of pregnancy, on pelvic floor muscle plasticity has not been previously studied. C_LIO_LIModulating pelvic floor muscles stretch antepartum, such as with specialized pelvic floor physical therapy regimens, could be a promising approach for augmentation of protective muscle adaptations in women. C_LI C_LI

physiology↗