👤 Arvind Shakya

The association and mechanisms between biotin and dementia remain unclear. We investigated the association through a population and animal study. UK Biobank data were used to evaluate the association of biotin with incident dementia and brain structural alteration. To validate our findings, we established a biotin-deficient mouse model, and performed behavioural tests, immunofluorescence, RT-qPCR, Western blotting, and molecular docking. In humans, higher biotin intake was significantly associated with reduced risks of all-cause dementia (moderate: 0.83 [0.74-0.94]; high: 0.78 [0.68-0.89]), Alzheimer's disease (AD, moderate: 0.74 [0.61-0.89]; high: 0.79 [0.64-0.98]), and delayed-onset dementia (DOD, moderate: 0.810 [0.715-0.918]; high: 0.776 [0.672-0.896]), but not vascular dementia (VD) and early-onset dementia (EOD). Neuroimaging results revealed a "pseudo-atrophy" pattern-reduced cortical volume with increased tissue intensity-resembling structural remodelling rather than neurodegeneration. In mice, biotin deficiency triggered region-specific alteration of APP, PSEN1, and APOE in the hippocampus and prefrontal cortex. It was accompanied by elevated Aβ42 levels and an increased Aβ42/40 ratio. Molecular docking suggested that biotin physically interacts with the catalytic pocket of PSEN1 and the receptor-binding domain of APOE. Dietary biotin is associated with a lower risk of dementia, especially AD, potentially by inhibiting amyloidogenic processing and modulating APOE-mediated clearance. The observed neuroimaging and molecular patterns suggest that maintaining adequate biotin intake is a viable strategy for dementia prevention. This work was supported by the National Natural Science Foundation of China (No. 82273619). Show less

Glioblastoma (GBM) displays marked cellular and metabolic heterogeneity that varies among cellular microenvironments within a tumor. Metabolic targeting has long been advocated as a therapy against many tumors including GBM, but how lipid metabolism is altered to suit different microenvironmental conditions and whether cancer stem cells (CSCs) have altered lipid metabolism are outstanding questions in the field. We interrogated gene expression in separate microenvironments of GBM organoid models that mimic the transition between nutrient-rich and nutrient-poor pseudopalisading/perinecrotic tumor zones using spatial-capture RNA-sequencing. We revealed a striking difference in lipid processing gene expression and total lipid content between diverse cell populations from the same patient, with lipid enrichment in hypoxic organoid cores and also in perinecrotic and pseudopalisading regions of primary patient tumors. This was accompanied by regionally restricted upregulation of hypoxia-inducible lipid droplet-associated (HILPDA) gene expression in organoid cores and pseudopalisading regions of clinical GBM specimens, but not lower-grade brain tumors. CSCs have low lipid droplet accumulation compared to non-CSCs in organoid models and xenograft tumors, and prospectively sorted lipid-low GBM cells are functionally enriched for stem cell activity. Targeted lipidomic analysis of multiple patient-derived models revealed a significant shift in lipid metabolism between GBM CSCs and non-CSCs, suggesting that lipid levels may not be simply a product of the microenvironment but also may be a reflection of cellular state. CSCs had decreased levels of major classes of neutral lipids compared to non-CSCs, but had significantly increased polyunsaturated fatty acid production due to high fatty acid desaturase (FADS1/2) expression which was essential to maintain CSC viability and self-renewal. Our data demonstrate spatially and hierarchically distinct lipid metabolism phenotypes occur clinically in the majority of patients, can be recapitulated in laboratory models, and may represent therapeutic targets for GBM. Show less

The mechanisms whereby the crucial pluripotency transcription factor Oct4 regulates target gene expression are incompletely understood. Using an assay system based on partially differentiated embryonic stem cells, we show that Oct4 opposes the accumulation of local H3K9me2 and subsequent Dnmt3a-mediated DNA methylation. Upon binding DNA, Oct4 recruits the histone lysine demethylase Jmjd1c. Chromatin immunoprecipitation (ChIP) time course experiments identify a stepwise Oct4 mechanism involving Jmjd1c recruitment and H3K9me2 demethylation, transient FACT (facilitates chromatin transactions) complex recruitment, and nucleosome depletion. Genome-wide and targeted ChIP confirms binding of newly synthesized Oct4, together with Jmjd1c and FACT, to the Pou5f1 enhancer and a small number of other Oct4 targets, including the Nanog promoter. Histone demethylation is required for both FACT recruitment and H3 depletion. Jmjd1c is required to induce endogenous Oct4 expression and fully reprogram fibroblasts to pluripotency, indicating that the assay system identifies functional Oct4 cofactors. These findings indicate that Oct4 sequentially recruits activities that catalyze histone demethylation and depletion. Show less