Biology subjects

Chapman, J. E.

Publications and source records attributed to Chapman, J. E..

3 recordsLinked to original sources

bioRxiv2026

D-Methionine Improves Spatial Navigation and Attenuates Oxidative Stress and Amyloid Pathology in a Sex-Specific Manner

BackgroundOxidative stress and maladaptive neuroimmune activation contribute to cognitive decline in Alzheimers disease (AD) and represent therapeutic targets beyond amyloid-centered approaches. ObjectiveTo determine whether oral D-methionine (D-Met), a redox-active amino acid, reduces amyloid pathology and lipid peroxidation and confers disease-modifying benefits in AD mouse models. MethodsMale and female APP/PS1 and APPNL-F mice with advanced AD pathology received oral D-Met or vehicle. Behavioral assessments included locomotor activity and hippocampal-dependent spatial learning and memory. Amyloid burden, lipid peroxidation, peripheral metabolic and inflammatory markers, and hippocampal microglial phenotypes were evaluated using biochemical and histological analyses. ResultsD-Met did not alter locomotor or exploratory behavior but improved spatial memory recall in both sexes of APP/PS1 mice and in female APPNL-F mice. APPNL-F males exhibited improved learning during Morris water maze (MWM) acquisition. Amyloid pathology was modestly and region-specifically reduced, including decreased hippocampal plaque size in male APPNL-F mice, reduced cortical plaque size in female APP/PS1 mice, and lower soluble amyloid-{beta} (A{beta})42 in male APP/PS1 mice. Lipid peroxidation, assessed by malondialdehyde, was reduced only in female APPNL-F mice. D-Met induced pronounced sex-dependent peripheral effects, increasing adiposity and pro-inflammatory adipose signaling in males, while reducing perigonadal white adipose tissue (pgWAT) IL-6 expression in female APPNL-F mice. In the hippocampus, D-Met remodeled microglial signatures, with female APPNL-F mice showing reduced Iba1 and disease-associated microglial (DAM) markers and increased Axl expression. ConclusionShort-term D-Met acts as a metabolic and redox modulator with modest amyloid-lowering effects mediated by improved microglial function. Therapeutic efficacy is strongly sex- and model-dependent, with the greatest benefit observed in female APPNL-F mice.

neuroscience↗

bioRxiv2026

Multilayer Network Modelling of the Human Reading System

Reading is supported by rapid and flexible coordination of neural activity across distributed brain regions. We have previously shown that left fusiform gyrus (FusG) provides a bridge flexibly linking the visual form analysis required for reading with the language system. Here, we investigate the dynamic organisation of an extending reading network encompassing classical perisylvian language areas and FusG. We do so by applying multilayer network modelling to language fMRI data acquired through the Australian Epilepsy Project, using a paradigm that contrasts reading with visuospatial judgements. The dataset included 201 participants with left dominant language, both with and without seizure disorders. We hypothesised that the relative strength of dynamic inter-actions within this extended language network is associated with reading ability. Time resolved functional connectivity was estimated using a sliding window Pearsons correlation approach, and the resulting connectivity matrices were entered into a multilayer community detection algorithm to quantify spatiotemporal community structure within the reading network. We concentrate our analyses on allegiance, the probability that a pair of regions is assigned to the same community over time. Our results show that community structure within the reading network is characterised by a preference for within hemisphere assignment over cross hemisphere assignment, as well as higher nodal allegiance among left language regions compared with their right hemisphere homologues. As anticipated, within versus between network allegiance followed a similar gradient in both language and attention networks: lowest between left language and right attentional regions, intermediate between the left FusG and each respective network, and highest within-network (left language or right attention). Importantly, as hypothesised, reading ability was associated with FusG-inferior frontal gyrus (IFG) interactions: higher left FusG-left IFG allegiance correlated with better reading performance, whereas increased right FusG-left IFG allegiance correlated with poorer reading. These findings highlight hemispheric asymmetries in the dynamic organisation of the reading system and provide novel evidence linking individual differences in reading ability to network level dynamics. Our findings align with a developmental literature suggesting that as reading proficiency improves, there is a shift from bilateral to unilateral left occipitotemporal engagement.

neuroscience↗

bioRxiv2025

Surgical Removal of Visceral Adipose Tissue has Therapeutic Benefit in Male APPNL-F Mice

PurposeVisceral white adipose tissue (vWAT) accumulation causes systemic inflammation, insulin resistance, metabolic syndrome, and senescent cell accumulation that are risk factors for Alzheimers disease (AD). Visceral fat removal (VFR) improves metabolism and reduces pro-inflammatory cytokines. We hypothesized that VFR removal in AD mice would improve metabolism and cognition. MethodsMale and female APPNL-F mice underwent sham or vWAT surgical resection (periovarian or epididymal and perirenal) at 4 (pre-symptomatic) and 16 (symptomatic) months of age to understand interventional and therapeutic effects, respectively. At 18 months of age, glucose metabolism and novel object recognition (NOR) memory were assayed followed by assessment of body composition and tissue-specific markers of metabolism, cell senescence, inflammation, or amyloid accumulation. ResultsMale and female APPNL-F mice showed distinct VFR responses. In pre-symptomatic males, increased vWAT lipolysis and hepatic lipogenesis led to ectopic liver lipid accumulation, with reduced adiponectin and leptin, elevated visfatin, and impaired glucose metabolism. Symptomatic males showed reduced vWAT lipogenesis, enhanced hepatic lipolysis, glycolysis, and glycogenesis, lowering liver lipids and improving insulin sensitivity. Only symptomatic males improved NOR, linked to elevated hippocampal learning and memory markers. Female vWAT reaccumulation was due to increased lipogenesis and lower lipolysis. Pre-symptomatic females had lower hepatic lipogenesis, while glycolysis and glycogenesis declined with disease progression. Hippocampal senescence and inflammation were elevated early in the disease that persisted symptomatically. ConclusionsSex-specific differences in glucose and lipid metabolism and lipid accumulation underlie the divergent responses to VFR in APPNL-F mice, with symptomatic males showing the only beneficial outcomes in metabolism and cognition. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=140 SRC="FIGDIR/small/669175v2_ufig1.gif" ALT="Figure 1"> View larger version (64K): org.highwire.dtl.DTLVardef@6ec644org.highwire.dtl.DTLVardef@9ad821org.highwire.dtl.DTLVardef@1e37775org.highwire.dtl.DTLVardef@b7a558_HPS_FORMAT_FIGEXP M_FIG C_FIG Male and female APPNL-F mice exhibited distinct VFR responses to AD progression. In males, early disease stages were marked by vWAT lipolysis and hepatic lipid accumulation with metabolic dysfunction, while symptomatic stages showed a metabolic shift that improved insulin sensitivity and NOR performance. In contrast, females displayed progressive vWAT reaccumulation, reduced hepatic metabolism, and persistent hippocampal senescence and inflammation from early stages onward.

neuroscience↗