Biology subjects

Frost, G.

Publications and source records attributed to Frost, G..

12 recordsLinked to original sources

bioRxiv2026

Multi-Omic Dissection of Autism Reveals Dominant Effects of Family, Sex, and Host-Microbe Metabolic Interactions

Autism spectrum disorder (ASD) has been associated with gut microbiome and metabolic alterations, but reported biomarkers are inconsistent and often inadequately account for family and shared environment. We analysed 620 children, including 334 with ASD and 286 neurotypical siblings, with a median age of 6.0 years (IQR 4.0-8.0). Faecal and urine samples were collected monthly up to eight times. After quality control, 869 microbiome, 754 faecal metabolome and 787 urine metabolome samples were analysed using 16S rRNA sequencing, NMR and LC-MS metabolomics. Mixed models accounted for family, repeated sampling and biological sex. Family membership explained 46.1% of variation across microbiome and metabolome profiles, compared with 8.0% attributable to ASD. After family adjustment, ASD explained only 0.1% to 0.3% of microbiome beta diversity. No stable taxonomic biomarkers were identified, and microbial classification was poor (AUROC <0.75). Urinary metabolomics identified elevated 5-hydroxy-L-tryptophan and altered phenylalanine metabolism. Structural equation modelling found no direct associations between selected taxa and metabolites. These findings argue against a universal ASD microbiome and indicate that family context contributes more strongly than diagnosis to microbial and metabolic variation.

microbiology↗

bioRxiv2026

Postprandial profiling of the duodenal microbiome reveals the impact of food structure and association with luminal metabolite and gut hormone responses

The human duodenum harbours a complex, dynamic microbial community that is challenging to study due to inaccessibility, particularly postprandially when nutrient-rich chyme and fluctuating metabolites create unique microbial niches. We used naso-duodenal intubation to longitudinally sample duodenal luminal contents following pea-based meals of differing food structure, alongside parallel blood collection. Shotgun metagenomic sequencing, comprehensive metabolomic profiling and gut hormone measurements were combined to explore microbe-metabolite-hormone interactions. Food structure significantly affected postprandial bacterial composition, with saccharolytic oral taxa increasing after meals with intact structure. Alpha diversity was influenced by structure type (P = 0.025), with whole pea seeds promoting greater diversity than pea flour. Network analysis revealed complex interactions between the duodenal microbiome, luminal metabolites and gut hormones, with most microbial associations linked to glucose-dependent insulinotropic polypeptide (GIP) rather than glucagon-like peptide-1 (GLP-1). Metabolic profiling showed meal-dependent changes in amino acid metabolism, including shifts in D/L amino acid ratios over time consistent with microbial metabolism. The duodenal microbiome showed close phylogenetic relationships with the oral microbiome, with composition influenced by food structuring and swallowing. These findings reveal dynamic microbe-metabolite interplay in the human duodenum during digestion and its relationship to gut hormone responses.

microbiology↗

bioRxiv2026

A fluorescent reporter system for scalable and live detection of PYY production from enteroendocrine cells with single-event resolution

Peptide YY (PYY) comprises the secretory repertoire of enteroendocrine L-cells alongside glucagon-like peptide-1 (GLP-1), and positively modulates postprandial satiety, digestion mechanics, and regeneration of the intestinal epithelium. Whereas immortalised GLP-1-secreting human L-cell models support pre-clinical drug discovery, comparable human lines that robustly secrete PYY are lacking, hindering mechanistic studies of its release. We present a biosensor for scalable detection of PYY production and secretion from human enteroendocrine cells in vitro. Guided by in silico structural prediction, we engineer a superecliptic phluorin (SEP)-tagged PYY, SEP-PYY, that engages native hormone processing machinery and is responsive to canonical nutrient stimuli when expressed in a human enteroendocrine cell line, NCI-H716. SEP-PYY production and secretion can be measured by optimised flow cytometry and spectrofluorometric plate readouts respectively, methods with superior time- and cost-efficacy to current hormone detection methods. Leveraging the pH sensitivity of SEP, we use this reporter system in detection of single-event hormone exocytosis by total internal reflection microscopy. Finally, we demonstrate the application of our system in screening ligands of metabolite-sensing G-protein coupled receptors that drive SEP-PYY secretion, and supporting discovery of druggable pathways in metabolic disease.

cell biology↗

bioRxiv2026

Nvj3 regulates Dga1-mediated triacylglycerol synthesis and lipid droplet formation at ER contact sites

Lipid droplet (LD) biogenesis is essential for lipid homeostasis during nutrient stress, yet how lipid intermediates are spatially organized to support efficient triacylglycerol (TAG) synthesis remains unclear. Here, we identify Nvj3 as a nutrient-responsive regulator that links diacylglycerol (DAG) availability to TAG synthesis and LD formation at the endoplasmic reticulum (ER). Nvj3 is induced by glucose depletion and recruited to LD-associated ER domains. Loss of Nvj3 causes neutral lipid accumulation under steady state conditions but delays TAG synthesis under acute inducible metabolic transitions. Using controlled TAG induction systems, we show that Nvj3 is required to couple Dga1-dependent TAG synthesis to LD formation. In the absence of Nvj3, TAG accumulates but remains inefficiently packaged into LDs. Consistent with this defect, nvj3{Delta} cells exhibit altered phospholipid remodeling and mislocalization of DAG away from ER domains during starvation. Together, these findings establish Nvj3 as an organizer of lipid availability during metabolic stress and suggest that spatial control of DAG is a key determinant of LD biogenesis. SummaryThis study identifies Nvj3 as a spatial organizer of Dga1-dependent lipid droplet formation. Nvj3 promotes proper diacylglycerol positioning, and enables efficient triacylglycerol synthesis during metabolic stress. We propose that Nvj3 regulates lipid flux through spatial compartmentalization of diacylglycerol at membrane contact site-associated ER domains.

cell biology↗

bioRxiv2025

D- and L-Lactate enhance intestinal barrier function via activation of an apical HCAR1/Giα pathway in a human colonic epithelial cell model

The stereoisomers of lactate, L- and D- are not only metabolic substrates but also signalling molecules, capable of activating and signalling through its G protein-coupled receptor, Hydroxycarboxylic acid receptor 1 (HCAR1). These stereoisomers are both produced by the gut microbiota at millimolar concentrations creating a physiological environment for lactate-sensing unique to the gut yet, poorly understood. Here we identify a role for D-/L-lactate on intestinal barrier function. A human colonic epithelial cell model, Caco2, activated Gi signalling in response to both L- and D-lactate, although L-lactate exhibited a more potent and rapid Gi signal profile. When differentiated, apically but not basally treated D-/L-lactate enhanced tight junctions and reduced cell permeability, consistent with the apical localization of HCAR1. This improved barrier function occurred in a Gi-dependent manner. In addition, apical lactate rescued the reduced intestinal barrier function induced by lipopolysaccharides. This work highlights the potential for D-/L-lactate supplementation in improving gut health. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=113 SRC="FIGDIR/small/685091v1_ufig1.gif" ALT="Figure 1"> View larger version (29K): org.highwire.dtl.DTLVardef@28fa82org.highwire.dtl.DTLVardef@56a75borg.highwire.dtl.DTLVardef@10578c6org.highwire.dtl.DTLVardef@3c3cd2_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗

bioRxiv2025

A selective and augmentable FFAR2 signal circuitry programs a butyrate-induced cellular identity of enteroendocrine L-cells

Activation of free fatty acid receptor 2 (FFAR2) on enteroendocrine L-cells mediates secretion of glucagon-like peptide 1 (GLP-1) and peptide YY (PYY), key regulators of central appetite control with therapeutic relevance to obesity. Here, we show that butyrate, a metabolite derived from fermentation of dietary fibre and an FFAR2 agonist, stimulates a PYY-biased profile in a human L-cell model at the transcriptional, morphological and secretory level via an FFAR2-Gi axis that does not require dynamin-dependent receptor internalization. We observe that butyrate modulates active Notch cascades within a Hes1-GFP mouse organoid model, which are antagonistic to secretory differentiation, and identify butyrate-dependent regulation of late-stage human enteroendocrine maturation markers, NeuroD1 and Pax6. Butyrate-mediated upregulation of Pyy and Pax6 is enhanced by the FFAR2-selective Gi biased allosteric agonist AZ-1729. Our study reveals functions of spatiotemporally-regulated butyrate-activated FFAR2 signalling mechanisms that could be pharmacologically amplified to fine-tune L-cell populations in the human colon. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=160 HEIGHT=200 SRC="FIGDIR/small/659710v1_ufig1.gif" ALT="Figure 1"> View larger version (27K): org.highwire.dtl.DTLVardef@14b9620org.highwire.dtl.DTLVardef@16d4c10org.highwire.dtl.DTLVardef@9cb031org.highwire.dtl.DTLVardef@f3a0e1_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗

bioRxiv2024

Modelling the gut microbiota of children with malnutrition: in vitro models reveal differences in fermentability of widely consumed carbohydrates

There is increasing evidence in children suffering from Severe Acute Malnutrition (SAM) that there is disruption of the gut microbiome and low gut microbiota diversity, which may be contributing factors to poor outcomes during nutritional treatment and recovery. The gut microbiome of children with SAM has been demonstrated to have a lower production of beneficial short chain fatty acids, which may contribute to impaired gut barrier function. Recently, several microbiota-directed therapies have been tested in clinical trials in children with SAM. Among them we hypothesized that feeds containing fermentable carbohydrates from various sources (legumes, chicory, milk oligosaccharides) would be fermented to produce beneficial microbial metabolites by the microbiota of children with SAM. In this study we used an in vitro model system inoculated with stool from children with SAM to investigate the fermentability of four substrates; inulin (a chicory-derived fructan), two milk powders (one supplemented with a human milk oligosaccharide) and a chickpea enriched feed. We demonstrated that while the milk powders and chickpea feed were fermented to produce short chain fatty acids, inulin was only fermented to a very limited degree. Through 16S rRNA sequencing we demonstrated that the samples inoculated with inulin had low microbial diversity and linked this to the limited ability to metabolise inulin. Through revealing the fermentability of different complementary feeds, the findings of this study will be of use for the design of future therapeutic feeds for treatment of SAM. ImportanceMalnutrition is a major contributor to childhood mortality globally and is a major public health problem primarily affecting Lower- and Middle-Income Countries. Despite the development of nutritional recovery therapies, for those with the severe and complicated form of malnutrition (SAM), mortality and relapse rates remain high. Emerging evidence suggests a role for the gut microbiome in these poor outcomes, which is known to be significantly altered in children in SAM, compared to healthy age matched controls. To aid in recovery from SAM, nutritional interventions should be designed to support the gut microbiome, using a range of ingredients targeted for colonic fermentation. It is important to understand the fermentation capacity of the gut microbiome of children with SAM, to design future nutritional interventions. In this work, we demonstrate that inulin, a widely used chicory-derived prebiotic, is not a suitable fermentation substrate for the gut microbiome of SAM children, while legume-based formulations and milk oligosaccharides result in increased production of beneficial metabolites.

microbiology↗

bioRxiv2023

Augmented gut hormone response to feeding in older adults exhibiting low appetite.

Age-related changes in gut hormones may play a role in anorexia of ageing. The aim of this study was to determine concentrations of ghrelin, PYY, and GLP-1 in older adults exhibiting an anorexia of ageing phenotype. Thirteen older adults with healthy appetite (OA-HA; 8f, 75{+/-}7 years, 26.0{+/-}3.2 kg{middle dot}m-2), fifteen older adults with low appetite (OA-LA; 10f, 72{+/-}7 years, 23.6{+/-}3.1 kg{middle dot}m-2), and twelve young adults (YA; 6f, 22{+/-}2 years, 24.4{+/-}2.0 kg{middle dot}m-2) completed the study. Healthy appetite and low appetite were determined based on BMI, habitual energy intake, self-reported appetite, and laboratory-assessed ad libitum lunch intake. Participants provided a fasted measure of subjective appetite and blood sample (0 minutes) before consuming a standardised breakfast (450 kcal). Appetite was measured every 30 minutes for 240 minutes and blood was sampled at 30, 60, 90, 120, 180 and 240 minutes. At 240 minutes, an ad libitum lunch meal was consumed. Relative energy intake at lunch (expressed as percentage of estimated total energy requirement) was lower for OA-LA (19.8{+/-}7.7%) compared with YA (41.5{+/-}9.2%, p<0.001) and OA-HA (37.3{+/-}10.0%, p<0.001). Ghrelin suppression was greater for OA-LA than YA at 90 minutes (-512{+/-}477 pg{middle dot}mL-1 vs. 174{+/-}182 pg{middle dot}mL-1, p=0.045) and 180 minutes (-502{+/-}147 pg{middle dot}mL-1 vs. -208{+/-}202 pg{middle dot}mL-1, p=0.049), and lower than OA-HA at 60 minutes (-447{+/-}447 pg{middle dot}mL-1 vs. -125{+/-}169 pg{middle dot}mL-1, p=0.039). GLP-1 concentration was higher for OA-LA compared with YA at 180 minutes (5.00{+/-}4.71 pM vs. 1.07{+/-}2.83 pM, p=0.040). Net AUC for PYY response to feeding was greater for OA-LA compared with OA-HA (p=0.052). No differences were seen in subjective appetite. These observations in older adults exhibiting an anorexia of ageing phenotype suggest augmented anorexigenic responses of gut hormones to feeding may be causal mechanisms of anorexia of ageing.

physiology↗

bioRxiv2020

AD-linked R47H-TREM2 mutation induces disease-enhancing proinflammatory microglial states in mice and humans

The hemizygous R47H variant of TREM2, a microglia-specific gene in the brain, increases risk for late-onset Alzheimers disease (AD). In this study, we identified a subpopulation of microglia with disease-enhancing proinflammatory signatures associated with the R47H mutation in human AD brains and tauopathy mouse brains. Using transcriptomic analysis at the single-nuclei level from AD patients with the R47H or the common variant (CV)-TREM2 with matched sex, pathology and APOE status, we found that the R47H mutation was associated with cell type- and sex-specific transcriptional changes in human AD brains, with microglia exhibiting the most robust alterations. Further characterization revealed that R47H-associated microglial subpopulations had enhanced inflammatory signatures including hyperactivation of Akt, one of the signaling pathways downstream of TREM2. In a newly-generated tauopathy knock-in mouse model expressing one allele of human TREM2 (hTREM2) with either the R47H mutation or CV, R47H induced and exacerbated tau-mediated spatial memory deficits in female mice. Single-cell transcriptomic analysis of microglia from these mice also revealed transcriptomic changes induced by R47H that had significant overlaps with R47H microglia in human AD brains, including robust increases in proinflammatory cytokines, activation of Syk-Akt-signaling, and elevation of a subset of disease-associated microglial signatures. Strikingly, pharmacological Akt inhibition largely reversed the enhanced inflammatory signatures induced by R47H in primary microglia treated with tau fibrils. By unraveling the disease-enhancing properties of the R47H mutation in mouse and human, our findings shed light on an immune-linked AD subtype and provide new directions for modulating microglial immune responses to treat AD.

neuroscience↗

bioRxiv2020

Short chain fatty acids enhance expression and activity of the umami taste receptor in enteroendocrine cells via a Gαi/o pathway

The short chain fatty acids (SCFAs) acetate, butyrate and propionate, are produced by the fermentation of non-digestible carbohydrates by the gut microbiota. SCFAs are of interest because they regulate appetite, adiposity, metabolism, glycemic control and immunity. SCFAs act at two distinct G protein-coupled receptors (GPCRs), FFAR2 and FFAR3. These are expressed in intestinal enteroendocrine cells (EECs), where they mediate SCFA-driven anorectic gut hormone release. EECs also express other GPCRs that act as nutrient sensors, in a manner that is plastic and adaptable to the environment. SCFAs may elicit some of their health-promoting effects by altering levels of GPCRs in EECs, thus, enhancing gut sensitivity to dietary molecules. Here, we identified that exposure of the murine EEC STC-1 cell-line to a concentration of SCFAs found in the colon, specifically enhances mRNA levels of the umami taste receptors TASR1 and TASR3, without altering levels of the SCFA GPCRs, FFAR2 and FFAR3. Interestingly, treatment of EECs with propionate or butyrate, but not acetate, increased levels of umami receptor transcripts. This phenomenon was reversed by inhibiting Gi/o signaling with pertussis toxin, suggesting that SCFAs act through FFAR2/3 to alter gene expression. Surprisingly, neither a FFAR3-nor a FFAR2-selective synthetic ligand could increase TASR1/TASR3 mRNA levels. We assessed the functional impact of increases in TASR1/TASR3 expression using unique pharmacological properties of the umami taste receptor; namely, the potentiation of signaling by inosine monophosphate. We found that the umami taste receptor induced inosine-1-phosphate and calcium signaling in response to L-alanine and L-monosodium glutamate, and that butyrate pretreatment significantly enhanced such signaling. Our study reveals that SCFAs may contribute to EEC adaptation and alter EEC sensitivity to bioactive nutrients.

cell biology↗

bioRxiv2020

Endosomal free fatty acid receptor 2 signaling is essential for propionate-induced anorectic gut hormone release

The ability of propionate, a short chain fatty acid produced from the fermentation of non-digestible carbohydrates in the colon, to stimulate the release of anorectic gut hormones, such as glucagon like peptide-1 (GLP-1), is an attractive approach to enhance appetite regulation, weight management and glycaemic control. Propionate induces GLP-1 release via its G protein-coupled receptor (GPCR), free fatty acid receptor 2 (FFA2); a GPCR that activates Gi and Gq/11 pathways. However, how pleiotropic GPCR signaling mechanisms in the gut regulates appetite is poorly understood. Here, we identify propionate-mediated G protein signaling is spatially directed within the cell via the targeting of FFA2 to very early endosomes. Furthermore, propionate activates an endosomal Gi/p38 signaling pathway, which is essential for propionate-induced GLP-1 release in enteroendocrine cells and colonic crypts. Our study reveals that intestinal metabolites can engage membrane trafficking pathways and endosomal signaling platforms to orchestrate complex GPCR pathways within the gut.

cell biology↗

bioRxiv2018

Discovery of biomarkers for glycaemic deterioration before and after the onset of type 2 diabetes: an overview of the data from the epidemiological studies within the IMI DIRECT Consortium

Abstract/SummaryO_ST_ABSBackground and aimsC_ST_ABSUnderstanding the aetiology, clinical presentation and prognosis of type 2 diabetes (T2D) and optimizing its treatment might be facilitated by biomarkers that help predict a persons susceptibility to the risk factors that cause diabetes or its complications, or response to treatment. The IMI DIRECT (Diabetes Research on Patient Stratification) Study is a European Union (EU) Innovative Medicines Initiative (IMI) project that seeks to test these hypotheses in two recently established epidemiological cohorts. Here, we describe the characteristics of these cohorts at baseline and at the first main follow-up examination (18-months).\n\nMaterials and methodsFrom a sampling-frame of 24,682 European-ancestry adults in whom detailed health information was available, participants at varying risk of glycaemic deterioration were identified using a risk prediction algorithm and enrolled into a prospective cohort study (n=2127) undertaken at four study centres across Europe (Cohort 1: prediabetes). We also recruited people from clinical registries with recently diagnosed T2D (n=789) into a second cohort study (Cohort 2: diabetes). The two cohorts were studied in parallel with matched protocols. Endogenous insulin secretion and insulin sensitivity were modelled from frequently sampled 75g oral glucose tolerance (OGTT) in Cohort 1 and with mixed-meal tolerance tests (MMTT) in Cohort 2. Additional metabolic biochemistry was determined using blood samples taken when fasted and during the tolerance tests. Body composition was assessed using MRI and lifestyle measures through self-report and objective methods.\n\nResultsUsing ADA-2011 glycaemic categories, 33% (n=693) of Cohort 1 (prediabetes) had normal glucose regulation (NGR), and 67% (n=1419) had impaired glucose regulation (IGR). 76% of the cohort was male, age=62(6.2) years; BMI=27.9(4.0) kg/m2; fasting glucose=5.7(0.6) mmol/l; 2-hr glucose=5.9(1.6) mmol/l [mean(SD)]. At follow-up, 18.6(1.4) months after baseline, fasting glucose=5.8(0.6) mmol/l; 2-hr OGTT glucose=6.1(1.7) mmol/l [mean(SD)]. In Cohort 2 (diabetes): 65% (n=508) were lifestyle treated (LS) and 35% (n=271) were lifestyle + metformin treated (LS+MET). 58% of the cohort was male, age=62(8.1) years; BMI=30.5(5.0) kg/m2; fasting glucose=7.2(1.4)mmol/l; 2-hr glucose=8.6(2.8) mmol/l [mean(SD)]. At follow-up, 18.2(0.6) months after baseline, fasting glucose=7.8(1.8) mmol/l; 2-hr MMTT glucose=9.5(3.3) mmol/l [mean(SD)].\n\nConclusionThe epidemiological IMI DIRECT cohorts are the most intensely characterised prospective studies of glycaemic deterioration to date. Data from these cohorts help illustrate the heterogeneous characteristics of people at risk of or with T2D, highlighting the rationale for biomarker stratification of the disease - the primary objective of the IMI DIRECT consortium.\n\nAbbreviations

epidemiology↗