Biology subjects

Marette, A.

Publications and source records attributed to Marette, A..

5 recordsLinked to original sources

bioRxiv2026

Discovery of a hydrolysis operon in Lachnospiraceae provides a genetic basis to understanding castalagin metabolism by the human microbiome in a clinical study.

Gut microbes metabolize the ellagitannin castalagin to ellagic acid and urolithins, a process associated with health effects for the host. Despite the use of the castalagin-rich camu camu extracts in clinical trials, the genes and taxa responsible for castalagin hydrolysis remain elusive. We used multi-omics to discover a castalagin associated hydrolase (cah) operon sparsely distributed in Lachnospiraceae. Analysis of fecal samples from a camu camu supplementation clinical trial demonstrates functional redundancy with prevalence of cah and other ellagic acid metabolism genes in different taxa explaining the prevalence of metabolites. Employing genome mining strategies, we discovered and validated ellagitannin metabolism genes in uncharacterized and uncultured species. We further identified flavogallonic acid as a prevalent metabolite of castalagin in human fecal samples. Collectively, this work provides a genetic basis for castalagin metabolism to urolithins and flavogallonic acid end-metabolites and sets the stage to study the role of metabolism in clinical trials.

microbiology↗

bioRxiv2026

Dietary protein source dictates the impact of obesogenic diets on hepatic steatosis and insulin resistance via carnitine-dependent regulation of acetyl-CoA carboxylase

Nutritional strategies to mitigate obesity and type 2 diabetes (T2D) have largely focused on dietary fat and carbohydrate composition, with less attention given to protein sources. While total dietary protein intake is recognized as an important modulator of energy balance and glucose metabolism, it remains unclear how the composition of dietary proteins can influence energy metabolism and body weight gain. Here, we investigated the metabolic effects of three distinct protein sources from meat (pork), dairy (casein) and plant (soy) on either a low-fat low sucrose (LFLS) or a high-fat high sucrose (HFHS) diet. While protein sources failed to influence metabolic homeostasis on LFLS, mice kept on the HFHS diet were distinctly impacted by the dietary protein sources. Pork and to a lesser extent soy protein feeding exacerbated obesity, glucose intolerance, and hepatic insulin resistance. Remarkably, livers of mice fed pork or soy protein on the HFHS diet were characterized by extensive microvesicular steatosis compared to the predominant macrovesicular steatosis in HFHS fed mice fed casein protein. Liver transcriptomic and metabolomic signatures in pork and soy protein fed mice were consistent with increased mitochondrial beta-oxidation. Intake of pork and soy proteins in HFHS fed mice lead to a striking reduction in hepatic acetyl CoA carboxylase 2 (ACC2) protein levels relative to casein fed HFHS mice. Pork and soy feeding raised carnitine exposure in the post-prandial period and we determined that exposure of hepatocytes to carnitine provokes downregulation of ACC2 and hepatic insulin resistance in the presence of palmitate:oleate and fructose. Collectively, these findings identify a novel mechanism by which dietary proteins modulate obesity and associated metabolic disturbances through a carnitine-mediated regulation of ACC2 protein and mitochondrial lipid handling in liver. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=140 SRC="FIGDIR/small/732886v1_ufig1.gif" ALT="Figure 1"> View larger version (55K): org.highwire.dtl.DTLVardef@1cc5b9corg.highwire.dtl.DTLVardef@1929e43org.highwire.dtl.DTLVardef@d453faorg.highwire.dtl.DTLVardef@1d56149_HPS_FORMAT_FIGEXP M_FIG C_FIG

physiology↗

bioRxiv2026

Respiratory microbiota as a health biomarker in blue, fin and humpback whales: Pilot study in the Gulf of St-Lawrence (Quebec, Canada)

1.Amplicon-based profiling of airway microbiota is increasingly used to assess respiratory health in mammals, yet baseline data for free-ranging baleen whales remain scarce. We characterised the exhaled-breath ("blow") microbiota of rorqual whales in the Gulf of St. Lawrence (Canada) and examined associations with individual health indicators. Blow samples were collected opportunistically from six whales (two blue, two fin and two humpback), with seawater and air controls. The V4 region of the 16S rRNA gene was sequenced on an Illumina MiSeq platform and processed in R (v4.5) using the DADA2 pipeline for quality filtering, denoising and amplicon sequence variant (ASV) inference. Alpha diversity varied among individuals (Shannon = 2.72 - 4.33) and beta-diversity analyses revealed a significant effect of environment (whale blow vs. seawater) on community composition (PERMANOVA: R2 = 0.140, F = 1.31, p = 0.030). The relative abundance of pathobionts (22.8-48.8%) was negatively correlated with alpha diversity (Spearman {rho} = -0.88 to -0.94, p < 0.05), while higher diversity correlated positively with good skin condition ({rho} = 0.84, p = 0.03). These findings provide the first baseline description of rorqual respiratory microbiota in the Gulf of St. Lawrence and support blow microbiome metrics as non-invasive health biomarkers.

microbiology↗

bioRxiv2022

Experimental Diets Dictate the Metabolic Benefits of Lactobacillus Strains in Obesity

BackgroundGrowing evidence supports the use of probiotics to prevent or mitigate obesity-related dysmetabolism and non-alcoholic fatty liver disease (NAFLD). However, frequent reports of responders versus non-responders to probiotic treatment warrant a better understanding of key modifiers of host-microbe interactions. The influence of host diet on probiotic efficacy, in particular against metabolic diseases, remains elusive. MethodWe fed C57BL6/J mice a low fat reference diet or one of two energy-matched high fat and high sucrose diets for 12 weeks; a classical high fat diet (HFD) and a customized fast food-mimicking diet (FFMD). During the studies, mice fed either obesogenic diet were gavaged daily with one of two probiotic lactic acid bacteria (LAB) strains previously classified as Lactobaccillus, namely Limosilactobacillus reuteri (L. reuteri) or Lacticaseibacillus paracasei subsp. paracasei (L. paracasei), or vehicle. ResultsThe tested probiotics exhibited a reproducible efficacy but dichotomous response according to the obesogenic diets used. Indeed, L. paracasei prevented weight gain, improved insulin sensitivity, and protected against NAFLD development in mice fed HFD, but not FFMD. Conversely, L. reuteri improved glucoregulatory capacity, reduced NAFLD development, and increased distal gut bile acid levels associated with changes in predicted functions of the gut microbiota exclusively in the context of FFMD-feeding. ConclusionWe found that the probiotic efficacy of two LAB strains is highly dependent on experimental obesogenic diets. These findings highlight the need to carefully consider the confounding impact of diet in order to improve both the reproducibility of preclinical probiotic studies and their clinical research translatability. Graphical abstract O_FIG_DISPLAY_L [Figure 1] M_FIG_DISPLAY C_FIG_DISPLAY

microbiology↗

bioRxiv2019

Lysates of Methylococcus capsulatus Bath induce a lean-like microbiota, intestinal FoxP3+RORγt+IL-17+ Tregs and improve metabolism

Interactions between host and gut microbial communities may be modulated by diets and play pivotal roles in securing immunological homeostasis and health. Here we show that intake of feed based on whole-cell lysates of the non-commensal bacterium Methylococcus capsulatus Bath (McB) as protein source reversed high fat high sucrose-induced changes in the gut microbiota to a state resembling that of lean, low fat diet-fed mice, both under mild thermal stress (T22{degrees}C) and at thermoneutrality (T30{degrees}C). McB feeding selectively upregulated triple positive (Foxp3+ROR{gamma}t+IL-17+) regulatory T cells in the small intestine and colon, and enhanced mucus production and glycosylation status suggesting improved gut health. Mice receiving McB lysates further exhibited improved glucose regulation, reduced body and liver fat along with diminished hepatic immune infiltration. Collectively, these data points towards profound whole-body effects elicited by the McB lysate suggesting that it may serve as a potent modulator of immunometabolic homeostasis.

immunology↗