Biology subjects

Karall, D.

Publications and source records attributed to Karall, D..

3 recordsLinked to original sources

bioRxiv2026

Naloxone as mitochondrial phenotype rescuer in a 3D bioprinted LCHADD/VLCADD model

For patients diagnosed with long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency (LCHADD) or very-long-chain acyl-CoA dehydrogenase deficiency (VLCADD), fasting episodes or high-energy demands remain life threatening. Due to the low incidence, clinical trials for novel LCHADD/VLCADD therapies are limited, and current mouse models recapitulate human symptoms only partially. Here, we report the use of mitochondrial morphology and 3D bioprinted, vascularized tissue models to establish a robust testing platform for dietary-based and experimental treatment approaches. Using this platform, we demonstrated that mitochondrial morphology is strictly regulated by NOX2-driven ROS formation. Treatment of LCHADD/VLCADD-derived fibroblasts with the NOX2-inhibitor naloxone led to the reassembly of mitochondrial structures controlled by DNM1L/MFN2. Using RNA transcriptomics, we identified a pro-fibrotic phenotype in LCHADD and VLCADD patient cells, which impaired vessel formation in fully 3D bioprinted human tissue equivalents. Metabolic supplementation with dietary approaches, which are used in standard therapy, partially improved vascularization. Naloxone induced the strongest improvement, restoring vessel length and network complexity to those of healthy controls, suggesting increased oxidative stress as main driver. Interestingly, naloxone had no effect on healthy fibroblasts, underscoring its safety. Taken together, these findings suggest the opioid antagonist naloxone as a potential rescue medication during LCHADD/VLCADD-driven metabolic crises.

molecular biology↗

bioRxiv2025

Biochemical signatures from dried blood spots in untargeted metabolics are influenced by matrix effects

Dried blood spots (DBS) represent a convenient clinical sample material, offering low infection risk, easy transport, and long-term metabolite stability. However, applying samples such as whole blood, serum or plasma onto filter paper introduces an additional matrix, potentially affecting metabolite extraction. Here, we compare metabolite recovery from liquid samples and their filter paper analogue using both targeted (acylcarnitines, amino acids) and untargeted metabolomics. Significant matrix effects were observed for some compounds, especially for dicarboxylic acylcarnitines (C3DC-C6DC) and specific amino acids (cystine, cystathionine). We did not identify specific metabolite characteristics that may predicted altered recovery. In a cohort of 229 authentic DBS samples -- including patients diagnosed with inherited metabolic disorders, obesity or under a ketogenic diet -- untargeted profiling combined with random-forest machine learning led to an effective stratification. Notably, C4DC, despite strong matrix effects, was ranked in the top ten variables of this random-forest model. With adequate validation, DBS can be safely used for diagnostic purposes despite possible matrix effects, but care must be taken in the comparison of values obtained when different sample materials are used.

biochemistry↗

bioRxiv2024

TXNIP mediates LAT1/SLC7A5 endocytosis to reduce amino acid uptake in cells entering quiescence

Entry and exit from cellular quiescence require dynamic adjustments in nutrient acquisition, yet the mechanisms by which quiescent cells downregulate amino acid (AA) transport remain poorly understood. Here, we demonstrate that cells entering quiescence select plasma membrane-resident AA transporters for endocytosis and lysosomal degradation, to match AA uptake with reduced translation. We identify the -arrestin TXNIP as a key regulator of AA uptake during quiescence, since it mediates the endocytosis of the SLC7A5-SLC3A2 (LAT1-4F2hc) transporter complex in response to reduced AKT signaling. Mechanistically, TXNIP interacts with HECT-type ubiquitin ligases to facilitate transporter ubiquitination. Loss of TXNIP disrupts this regulation, resulting in dysregulated AA uptake, sustained mTORC1 signaling, and accelerated quiescence exit. A novel TXNIP loss-of-function mutation in a patient with severe metabolic disease further supports its role in nutrient homeostasis and human health. These findings highlight TXNIPs role in controlling SLC7A5-SLC3A2 mediated AA acquisition with implications for quiescence biology and disease.

cell biology↗