Biology subjects

Lefebvre, C.

Publications and source records attributed to Lefebvre, C..

10 recordsLinked to original sources

bioRxiv2026

Stress limits the beneficial effects of glutamine in male ob/ob mice

IntroductionObesity is a major health issue associated with metabolic and psychological comorbidities, as well as an increased prevalence of disorders of gut-brain interaction (DGBI). Obesity and DGBI share common mechanisms such as inflammation, gut barrier dysfunction, and alterations of gut microbiota, which are all known to be regulated by stress. Glutamine (Gln), which is essential to maintain intestinal integrity and immune response, may counteract these alterations. This study aimed to evaluate the effects of oral Gln supplementation on stress-induced response in obese mice. MethodsSeven-week-old male leptin-deficient ob/ob mice were assigned to four groups: control, chronic restraint stress (CRS), Gln-supplemented, or both CRS and Gln-supplemented. Gln was administered in drinking water for two weeks, and CRS was performed during the final 4 days. Metabolic parameters, intestinal permeability, inflammatory markers, gene and protein expression, and gut microbiota composition were assessed. ResultsStress increased plasma corticosterone levels but had a limited effect on metabolic parameters. In obese mice without stress, Gln supplementation reduced body weight gain, improved body composition and reduced inflammation in the visceral adipose tissue. These effects were lost under stress conditions, with an increase in fasting glycaemia. Stress reduced occludin protein levels, while Gln exerted context-dependent effects, decreasing gene expression of Tjp3, Cldn15 and Ccl2 in unstressed mice but increasing gene expression of multiple tight junction (Tjp2, Tjp3, Cldn12, Cgn, F11r, Marveld2) and inflammatory markers (Tlr2, Myd88, Irf3) under stress. Interestingly, in unstressed obese mice, Gln altered the composition of the gut microbiota, with changes in key bacterial taxa (Thermodesulfobacteriota and Clostridiaceae). This was associated with decreased levels of cecal short-chain fatty acids and increased levels of branched-chain fatty acids. ConclusionIn conclusion, Gln improves metabolic and adipose inflammatory parameters in genetically obese mice. However, these benefits are no longer observed when mice are under stress conditions. Since, Gln has been found to increase fasting glycaemia and colonic inflammation, in association with alterations of gut microbiota.

pathology↗

bioRxiv2026

PDZD-8 interacts with LGG-2/LC3 to promote autolysosome formation

LGG-2/LC3 and LGG-1/GABARAP are members of the Atg8 ubiquitin-like protein family, playing central roles in autophagy. Through a yeast two-hybrid screen, we identified the endoplasmic reticulum protein PDZD-8 as a novel interactor of the C. elegans autophagy protein LGG-2/LC3. We demonstrate that PDZD-8 binds specifically to LGG-2 and not LGG-1 via a canonical LC3-interacting region (LIR) and colocalizes with LGG-2-positive autophagosomes in vivo. Loss of PDZD-8 leads to a transient accumulation of enlarged LGG-2-positive autophagosomes that remain closely associated with lysosomes. Genetic disruption of core autophagy genes suppresses the pdzd-8 mutant phenotype, indicating that this phenotype is dependent on autophagy. Moreover, loss of rab-7, which blocks autophagosome-lysosome fusion, also suppresses the pdzd-8 phenotype, suggesting that the RAB-7-dependent fusion step is epistatic to PDZD-8 and that PDZD-8 acts downstream of autophagosome-lysosome maturation. Microscopy approaches (TEM, CLEM, and FIB-SEM) reveal an accumulation of fused autophagosome-lysosome structures, pointing to a transient block in autophagic flux in pdzd-8 mutants. Furthermore, PDZD-8 lacking either the SMP lipid-transfer domain or the LIR motif phenocopies the pdzd-8 null mutant, underscoring the importance of both domains. Our findings support a model in which PDZD-8, in conjunction with LGG-2/LC3, mediates ER-autophagosome/autolysosome contacts that are critical for subsequent autolysosome completion. Significance StatementAutophagy is a conserved cellular degradation pathway essential for maintaining homeostasis and responding to stress. Although the molecular machinery driving autophagosome formation and fusion with lysosomes is relatively well-characterized, the contribution of membrane contact sites to autophagic flux remains poorly understood. Here, we identify PDZD-8, an endoplasmic reticulum (ER) protein, as a novel interactor of the Caenorhabditis elegans LC3/Atg8 homolog LGG-2. We show that PDZD-8 regulates the completion of autolysosome maturation by bridging ER-autophagosome/autolysosome contacts. Loss of PDZD-8 results in the accumulation of enlarged autophagosomes adjacent to lysosomes and a transient block in autophagic flux, a phenotype that depends on the RAB-7-mediated tethering step. These findings reveal a previously unrecognized role for PDZD-8 in coordinating ER-autophagosome/autolysosome dynamics during autophagy.

cell biology↗

bioRxiv2025

Glutamine alters the response to stress in mice with diet-induced obesity in a sex-dependent manner.

RationalePatients with class III obesity often suffer from irritable bowel syndrome (IBS) while obesity and IBS share common pathophysiological mechanisms such as altered intestinal barrier function and gut microbiota dysbiosis. Oral glutamine (Gln) supplementation previously showed beneficial effects on gut barrier function in a sex-dependent manner and reduced abdominal pain in IBS patients. Thus, we assessed the sex-dependent response to an oral Gln supplementation in mice with diet-induced obesity and subjected to a chronic restraint stress to mimic IBS. MethodsMale (M) and female (F) C57BL/6 mice received a high fat diet (HFD; 60% kcal from fat) during 14 weeks (W14) and were subjected or not to a restraint stress (S) for the 4 last days. From W12, mice received or not Gln in drinking water (2g/kg/day; n=12/group). Plasma corticosterone, body composition, glucose tolerance (OGTT), intestinal permeability, inflammatory markers in colonic and white adipose tissues, cecal microbiota and short-chain fatty acid (SCFA) composition have been assessed. Within each sex, groups were compared by Kruskal-Wallis test or a 1-way ANOVA test. ResultsIn M-HFD mice, chronic restraint stress was associated with a better glucose tolerance (-15,46% AUC) and a reduced fasting glycemia that was not observed in F-HFD mice. Gln partially prevented body weight loss, reduced plasma resistin, plasma corticosterone and colonic permeability in female stressed obese mice. In male stressed obese mice, Gln limited lean mass loss, reduced colonic permeability and Ccl2 mRNA level in the subcutaneous adipose tissue. Chronic restraint stress and Gln modified cecal microbiota in both sexes but cecal SCFA composition only in male mice. In particular, stress induced an increased abundance of Pseudomonadota in male mice that was partially restored after Gln supplementation. In addition, cecal total SCFA were reduced in Gln-supplemented stressed HFD male mice compared to unstressed HFD mice. In female HFD mice, stress associated to Gln supplementation increased the abundance of Thermodesulfobacteriota and reduced colonic expression of Cxcr3 mRNA. ConclusionsChronic restraint stress has beneficial effects on glycemia control in male HFD mice without additive effects of Gln supplementation. By contrast, Gln reduces stress-induced corticosterone level and body weight loss only in females. These data, as well as the differential impact of Gln on intestinal permeability and gut microbiota according to the sex, deserves further investigations to decipher the underlying mechanisms.

pathology↗

bioRxiv2025

Transcriptomic analysis of chronic chikungunya in the Reunionese CHIKGene cohort uncovers a shift in gene expression more than 10 years after infection

AimIn 2005-2006, a chikungunya epidemic of unprecedented magnitude hit Reunion Island, which raised a public health concern through the substantial proportions of long-lasting manifestations. To understand the pathophysiology underlying chronic chikungunya (CC), we designed the CHIKGene cohort study and collected blood samples from 133 subjects diagnosed with CC and from 86 control individuals that had recovered within 3 months, 12-to-15 years after exposure. MethodsWe conducted bulk RNAseq analysis on peripheral blood mononuclear cells to find differentially expressed genes (DEGs), gene set enrichment analysis (GSEA) and gene ontologies to uncover top-level enriched terms associated with DEGs, and weighted gene correlation network analysis (WGCNA) to elucidate underlying cellular processes. ResultsAmong 1549 DEGs, gene expression analysis identified 10 top genes including NR4A2 and TRIM58 (upregulated in CC), IGHG3 and IGHV3-49 (downregulated in CC) linked to immune regulation, OSBP2 (upregulated in CC) and SEMA6B (downregulated in CC) linked to neuronal homeostasis and axon guidance, respectively. GSEA and WGCNA unveiled cellular processes such as "Metabolism of RNA" and "Cell Cycle". ConclusionsThis study uncovers a shift in gene expression of CC subjects. IGHG3 and IGHV3-49 gene shut-offs spotlight the importance of neutralizing antibodies against chikungunya virus in the progression to chronic disease. Human diseases associations highlight connections to rheumatoid arthritis, nervous and cardiac systems. GSEA and WGCNA bounce the hypotheses of a persistent viral reservoir or an increased susceptibility to RNA viral pathogens with new onset infections. Together, our findings might offer potential targets for therapeutic options aimed at alleviating chronic chikungunya.

bioinformatics↗

bioRxiv2024

Sex-dependent effects of a glutamine supplementation on metabolic disorders, intestinal barrier function and gut microbiota in mice with diet-induced obesity.

RationaleObesity is often associated with sex-dependent metabolic complications, in which altered intestinal barrier function and gut microbiota contribute. Glutamine (Gln) supplementation previously showed beneficial effects on gut barrier function and glycemic control. We thus aimed to characterize in mice the sex-dependent effects of a Gln supplementation during high fat diet induced obesity. MethodsMale and female C57BL/6 mice received a standard (SD) or high fat diet (HFD; 60% kcal from fat) during 14 weeks (W14). From W12, mice received or not Gln in drinking water (2g/kg/day; n=12/group). Body composition, glucose tolerance, insulin sensitivity, intestinal permeability, colonic expression of 44 genes encoding factors involved in inflammatory response and gut barrier function, cecal microbiota and inflammatory/endocrine adipose response have been assessed. Data were analyzed using t-test or Mann-Whitney test (HFD effect), and two-way ANOVA (HFD x Gln) followed by Bonferroni post-tests. ResultsIn both male and female mice, Gln supplementation failed to improve body weight and body composition. However, Gln reduced glucose intolerance in HFD males (AUC reduced by 14.57%, p<0.05) that was associated to a partial restoration of plasma resistin and insulin and to a trend for a limitation of adipose inflammatory response. In males, Gln did not affect gut microbiota composition and colonic response. To the opposite, in females fed HFD, Gln supplementation led to gut microbiota changes (increase of Bacteroidota and Pseudomonadota phyla; increase of Muribaculaceae and Tannerellaceae families), increased colonic inflammatory markers (TNF, IL-1{beta}, TLR4, Myd88, Irf3) that were associated to increased inflammatory response in subcutaneous adipose tissue and increased HOMA-IR. ConclusionsHigh fat diet mice exhibit sex-dependent response to glutamine supplementation with protective effects in males and harmful effects in females. The role of gut microbiota should be deeply deciphered in further investigations.

pathology↗

bioRxiv2024

Sex-dependent effects of a high-fat diet on the hypothalamic response in mouse

Sex differences in rodent models of diet-induced obesity are still poorly documented, particularly regarding how central mechanisms vary between sexes in response to an obesogenic diet. Here, we wanted to determine whether obesity phenotype and hypothalamic response differed between male and female C57Bl/6J mice when exposed to a high-fat diet (HFD). Mice were exposed either a free 60% HFD or standard diet first for both a long-(14 weeks) and shorter-periods of time (3, 7, 14 and 28 days). Analysis of the expression profile of key neuronal, glial and inflammatory hypothalamic markers was performed using RT-qPCR. In addition, astrocytic and microglial morphology was examined in the arcuate nucleus. Monitoring of body weight and composition revealed that body weight and fat mass gain appeared earlier and was more pronounced in male mice. After 14 weeks of HFD exposure, normalized increase of body weight reached similar levels between male and female mice. Overall, both sexes under HFD displayed a decrease of orexigenic neuropeptides expression and an increase in POMC gene expression was observed only in female mice. In addition, changes in the expression of hypothalamic inflammatory markers were relatively modest. We also reported that the glial cell markers expression and morphology were affected by HFD in a sex- and time dependent manner, suggesting a more pronounced glial cell activation in female mice. Taken together, these data show that male and female mice responded differently to HFD exposure, both on short- and long-term and suggest that a strong inflammatory hypothalamic profile is not systematically present in DIO models. Nevertheless, in addition to these present data, the underlying mechanisms should be deciphered in further investigations.

neuroscience↗

bioRxiv2024

Reticulon dependent ER-phagy mediates adaptation to heat stress in Caenorhabditis elegans

The selective degradation of ER by autophagy, named ER-phagy, promotes the recovery of ER homeostasis after a stress. Depending on the ER stress, different types of ER-phagy involve various selective autophagy receptors. In this study, we report a macroER-phagy induced by the fragmentation of tubular ER in response to acute heat stress. We identified a novel ER-phagy receptor encoded by the reticulon long isoform RET-1d. RET-1d is mainly expressed in the nervous system and the epidermis and colocalize with the ubiquitin-like autophagy protein LGG-1/GABARAP during heat stress induced autophagy. Two LIR motifs in the long intrinsically disordered region of RET-1d mediate its interaction with LGG-1 protein. The specific depletion of RET-1d isoform resulted in a delay in autophagosome biogenesis and a decrease in the capacity of animals to adapt to heat stress. Our data revealed a RET-1d dependent ER-phagy mechanism that takes place in neurons and epidermis and participates to the adaptation of C. elegans to heat stress.

cell biology↗

bioRxiv2023

Critical contribution of mitochondria in the development of cardiomyopathy linked to desmin mutation

Beyond the observed alterations in cellular structure and mitochondria, the cellular mechanisms linking genetic mutations to the development of heart failure in patients affected by desmin defects remain unclear due, in part, to the lack of relevant human cardiomyocyte models. We investigated the role of mitochondria using cardiomyocytes derived from human induced pluripotent stem cells carrying the heterozygous DESE439K desmin mutation, that were either isolated from a patient or generated by gene editing. To increase physiological relevance, cells were either cultured on an anisotropic surface to obtain elongated and aligned cardiomyocytes, or as spheroids to create a micro- tissue. When applicable, results were confirmed with heart biopsies from the family harboring DESE439K mutation. We show that mutant cardiomyocytes reproduce critical defects in mitochondrial architecture, respiratory capacity and metabolic activity as observed in patients heart tissue. To challenge the pathological mechanism, normal mitochondria were transferred inside the mutant cardiomyocytes. This treatment restored mitochondrial and contractile functions. This work demonstrates the crucial role of mitochondrial abnormalities in the pathophysiology of desmin-related cardiomyopathy, and opens-up new potential therapeutic perspectives.

pathology↗

bioRxiv2021

LGG-1/GABARAP lipidation is dispensable for autophagy and development in C .elegans

The ubiquitin-like proteins Atg8/LC3/GABARAP are required for multiple steps of autophagy such as initiation, cargo recognition and engulfment, vesicle closure and degradation. Most of LC3/GABARAP functions are considered dependent on their post-translational modifications and addressing to membranes through a conjugation to a lipid, the phosphatidylethanolamine. Contrarily to mammals, C. elegans possesses single homologs of LC3 and GABARAP families, named LGG-2 and LGG-1. Using site directed mutagenesis, we inhibited the conjugation of LGG-1 to the autophagosomal membrane and generated mutants that express only cytosolic forms, either the precursor or the cleaved protein. LGG-1 is an essential gene for autophagy and development in C. elegans, but we discovered that its functions could be fully achieved independently of its localization to the membrane. This study reveals an essential role for the cleaved form of LGG-1 in autophagy but also in an autophagy independent embryonic function. Our data question the use of the lipidated GABARAP/LC3 as the main marker of autophagic flux and highlight the high plasticity of autophagy.

cell biology↗

bioRxiv2016

Gene expression patterns associated with neurological disease in HIV infection

To provide new insight into the pathogenesis of neurocognitive impairments (NCI) in HIV infection, we used the Gene Set Enrichment Analysis (GSEA) algorithm to analyze pathway dysregulations in gene expression profiles of HIV-infected patients with or without NCI and HIV encephalitis (HIVE). While HIVE was characterized by widespread inflammation and tissue damage, gene expression evidence of induction of interferon (IFN), cytokines and tissue injury was apparent in all brain regions studied before the emergence of NCI. Various degrees of white matter changes were present in all HIV-infected subjects and were the primary manifestation in patients with NCI in the absence of HIVE. The latter showed a distinct pattern of immune activation with induction of chemokines, cytokines, {beta}-defensins, and limited IFN induction.\n\nAltogether results indicate that significant neuroinflammation and neuronal suffering precede NCI. Patients with NCI without HIVE showed a predominantly white matter dysfunction with a distinct pattern of immune activation.

neuroscience↗