Camille Lefevre

Cancer cachexia is a debilitating disease characterized by muscle atrophy. Given the gut dysbiosis in cancer cachexia and the increasing evidence of a gut-muscle axis, we explored the potential beneficial effects of bacteria-dependent metabolites on myotube atrophy. Using both hypothesis-driven and hypothesis-free approaches, in-depth metabolomic analysis of blood samples from cachectic C26 tumor-bearing mice treated or not with antibiotics, as well as disease-free germ-free and conventionalized mice, identified 7 bacteria-dependent metabolites decreased under cachectic conditions. Such alterations were not mediated by reduced caloric intake. Among them, 2 metabolites, namely 2-phenylpropanoic acid (2PPA, also known as 2-phenylpropionic acid) and 3-(3,4-dihydroxyphenyl)propanoic acid (3,4OHPP, also known as 3,4-dihydroxyhydrocinnamic acid or dihydrocaffeic acid), demonstrated anti-atrophying effect, alone and in combination, on mouse C2C12 myotubes. Transcriptomics revealed that these 2 bacteria-dependent metabolites restored the amino acid homeostasis with an activation of ATF4 and the serine biosynthesis pathway. Pharmacological inhibition of the phosphoglycerate dehydrogenase (PHGDH), the rate-limiting enzyme of this pathway, prevented the anti-atrophying effects of 2PPA and 3,4OHPP, indicating a causal role for PHGDH in this effect. By identifying microbiota-dependent metabolites as potential therapeutic levers, the current work not only advances our understanding of microbiome-host crosstalk in disease but also opens avenues for innovative, targeted interventions to mitigate muscle atrophy. Abstract Figure: Graphical Bacteria-dependent metabolites that are decreased upon cancer cachexia in mice mitigate muscle atrophy in vitro.: 7 metabolites were identified as depleted in cachectic condition and microbiota-dependent, among which 2 of them, namely 2-phenylpropanoic acid (2PPA) and 3-(3,4-dihydroxyphenyl)propanoic acid (3,4OHPP), counteracted C2C12 myotube atrophy induced by dexamethasone. Created with BioRender.com.

Le tissu adipeux (TA) contribue à l’inflammation chronique associée aux complications de l’obésité (diabète, ). Au début de l’obésité, l’inflammation est de bas grade suggérant des mécanismes immunosuppresseurs, dont l’activité décroit avec l’obésité, accélérant la survenue des complications. Les cellules souches adipocytaires (CSA) participent au développement puis à l’homéostasie des dépôts de TA sous-cutanés (SAT) et viscéraux (VAT). Sous l’effet de stimuli inflammatoires, elles exercent in vitro des fonctions immunosuppressives, ces propriétés sont cependant perdues quand elles sont isolées de TA inflammatoires dans l’obésité avancée. Le rôle des CSA dans l’homéostasie immunitaire du TA est peu connu. Nous avons émis l’hypothèse que les CSA ont une fonction immunosuppressive active dès le début de l’obésité et que son altération participe à la survenue des complications de l’obésité. Pour aborder cette question, j’ai mis en œuvre deux protocoles d’obésité induite par la diète chez la souris C57Bl/6 et exploré les fonctions des CSA isolées des dépôts sous-cutanés (CSA-S) et viscéraux (CSA-V). Mes travaux confirment d’importantes différences à l’état sain, dans le potentiel de prolifération et de différenciation des CSA-S et -V. Nous montrons que ces différences correspondent à des métabolomes distincts avec une plus forte activité glycolytique des CSA-V, et mitochondriale des CSA-S. Grâce à ce modèle, nous avons pu étudier les propriétés immunosuppressives des CSA dans les phases précoces de l’obésité et dans les deux types de dépôts de TA. Une cinétique de 6, 10 et 14 semaines (s) de régime riche en gras (HF) nous a permis de couvrir plusieurs étapes de l’obésité, depuis l’intolérance au glucose dès 6 s, sans inflammation des TA, jusqu’à la résistance à l’insuline à 14 s de régime et l’inflammation du VAT mais pas du SAT. Mes résultats montrent que dès 6 s, les CSA-V en réponse au HF attirent les macrophages tout en inhibant leur polarisation M1 pro-inflammatoire. En parallèle, les CSA-S induites par le régime HF suppriment la prolifération des lymphocytes T activés et inhibent fortement leur migration. Cette étude montre (i) que les CSA des 2 dépôts sont activées par le régime HF indépendamment de l’inflammation et de la durée du régime, (ii) que les propriétés immunosuppressives induites concernent des cibles différentes selon les dépôts, (iii) qu’elles sont encore présentes au début de la résistance à l’insuline. L’analyse des TA fraichement isolés montre que la progression de l’obésité diminue la prolifération et la proportion des CSA. A ce stade de l’obésité précédant l’inflammation du SAT, le caractère souche des CSA in vitro n’est pas touché mais l’exposition à l’environnement obésogène empêche leur maintien dans les dépôts. Dans un second protocole, j’ai exploré l’impact de la surnutrition maternelle pendant l’allaitement sur les propriétés des CSA de la descendance adulte. Ce contexte prédispose la descendance au développement de maladies métaboliques. Nous voulions savoir si les CSA sont des cibles du régime maternel et conservent des altérations à long terme. J’ai isolé les CSA-S et -V de la descendance 6 s après le sevrage et exploré l’impact d’un régime HF post-sevrage. L’analyse par RNAseq montre que le régime maternel altère le transcriptome des CSA à l’âge adulte et induit une intolérance au glucose, même avec un régime standard post-sevrage. Trois catégories de gènes sont particulièrement affectées par les régimes HF : mortalité, stress métabolique, synthèse des protéines et ribosomes. D'autres ne sont affectées que par le régime de la mère. Pour les gènes associés à la mortalité, une accentuation du différentiel est observée lors du cumul des régimes HF maternel et post-sevrage. Nous montrons que les CSA sont altérées avant les complications de la descendance adulte. Les CSA peuvent donc être programmées par la surnutrition des mères et pourraient être des vecteurs des dysfonctionnements futurs du TA

Obesity is a risk factor for many diseases, such as type 2 diabetes and cardiovascular diseases. In line with the need for precision medicine, the search for biomarkers reporting the progression of obesity- and diet-associated disorders is urgent. We used NMR to determine the metabolomics profile of key organs (lung, liver, heart, skeletal muscle, kidney, and brain) and serum from male C57Bl/6J mice (5 weeks old) fed for 6, 10, and 14 weeks on a high-fat and high-sucrose diet (HFHSD) vs. a standard diet (STD). We determined metabolite concentrations in the organs at each time point, which allowed us to discriminate age- and diet-related effects as well as the interactions between both, highlighting the need to evaluate the influence of age as a confounding factor on metabolic signatures. Notably, the analysis revealed the influence of time on metabolite concentrations in the STD condition, probably reflecting the juvenile-to-adult transition. Variations impacted the liver and lung metabolites, revealing the strong influence of the HFHS diet on normal metabolism maturation during youth.

Background: The aryl hydrocarbon receptor (AHR) is expressed in the intestine and liver, where it has pleiotropic functions and target genes. This study aims to explore the potential implication of AHR in cancer cachexia, an inflammatory and metabolic syndrome contributing to cancer death. Specifically, we tested the hypothesis that targeting AHR can alleviate cachectic features, particularly through the gut–liver axis.Methods: AHR pathways were explored in multiple tissues from four experimental mouse models of cancer cachexia (C26, BaF3, MC38 and APC^Min/+) and from non‐cachectic mice (sham‐injected mice and non‐cachexia‐inducing [NC26] tumour‐bearing mice), as well as in liver biopsies from cancer patients. Cachectic mice were treated with an AHR agonist (6‐formylindolo(3,2‐b)carbazole [FICZ]) or an antibody neutralizing interleukin‐6 (IL‐6). Key mechanisms were validated in vitro on HepG2 cells.Results: AHR activation, reflected by the expression of Cyp1a1 and Cyp1a2, two major AHR target genes, was deeply reduced in all models (C26 and BaF3, P < 0.001; MC38 and APC^Min/+, P < 0.05) independently of anorexia. This reduction occurred early in the liver (P < 0.001; before the onset of cachexia), compared to the ileum and skeletal muscle (P < 0.01; pre‐cachexia stage), and was intrinsically related to cachexia (C26 vs. NC26, P < 0.001). We demonstrate a differential modulation of AHR activation in the liver (through the IL‐6/hypoxia‐inducing factor 1α pathway) compared to the ileum (attributed to the decreased levels of indolic AHR ligands, P < 0.001), and the muscle. In cachectic mice, FICZ treatment reduced hepatic inflammation: expression of cytokines (Ccl2, P = 0.005; Cxcl2, P = 0.018; Il1b, P = 0.088) with similar trends at the protein levels, expression of genes involved in the acute‐phase response (Apcs, P = 0.040; Saa1, P = 0.002; Saa2, P = 0.039; Alb, P = 0.003), macrophage activation (Cd68, P = 0.038) and extracellular matrix remodelling (Fga, P = 0.008; Pcolce, P = 0.025; Timp1, P = 0.003). We observed a decrease in blood glucose in cachectic mice (P < 0.0001), which was also improved by FICZ treatment (P = 0.026) through hepatic transcriptional promotion of a key marker of gluconeogenesis, namely, G6pc (C26 vs. C26 + FICZ, P = 0.029). Strikingly, these benefits on glycaemic disorders occurred independently of an amelioration of the gut barrier dysfunction. In cancer patients, the hepatic expression of G6pc was correlated to Cyp1a1 (Spearman's ρ = 0.52, P = 0.089) and Cyp1a2 (Spearman's ρ = 0.67, P = 0.020).Conclusions: With this set of studies, we demonstrate that impairment of AHR signalling contributes to hepatic inflammatory and metabolic disorders characterizing cancer cachexia, paving the way for innovative therapeutic strategies in this context.

Mesenchymal stem cells from healthy adipose tissue are adipocytes progenitors with immunosuppressive potential that are used for years in cell therapy. Whether adipose stem cells (ASC) may prevent inflammation in early obesity is not known. To address this question, we performed a kinetic study of high‐fat (HF) diet induced obesity in mice to follow the immune regulating functions of adipose stem cells (ASC) isolated from the subcutaneous (SAT) and the visceral adipose tissue (VAT). Our results show that, early in obesity and before inflammation was detected, HF diet durably and differently activated ASC from SAT and VAT. Subcutaneous ASC from HF‐fed mice strongly inhibited the proliferation of activated T lymphocytes, whereas visceral ASC selectively inhibited TNFα expression by macrophages and simultaneously released higher concentrations of IL6. These depot specific differences may contribute to the low‐grade inflammation that develops with obesity in VAT while inflammation in SAT is delayed. The mechanisms involved differ from those already described for naïve cells activation with inflammatory cytokines and probably engaged metabolic activation. These results evidence that adipose stem cells are metabolic sensors acquiring an obesity‐primed immunocompetent state in answer to depot‐specific intrinsic features with overnutrition, placing these cells ahead of inflammation in the local dialog with immune cells.

White adipose tissues are functionally heterogeneous and differently manage the excess of energy supply. While the expansion of subcutaneous adipose tissues (SAT) is protective in obesity, that of visceral adipose tissues (VAT) correlates with the emergence of metabolic diseases. Maintained in fat pads throughout life, adipose stem cells (ASC) are mesenchymal-like stem cells with adipogenesis and multipotent differentiation potential. ASC from distinct fat pads have long been reported to present distinct proliferation and differentiation potentials that are maintained in culture, yet the origins of these intrinsic differences are still unknown. Metabolism is central to stem cell fate decision in line with environmental changes. In this study, we performed high-resolution nuclear magnetic resonance (NMR) metabolomic analyses of ASC culture supernatants in order to characterize their metabolic phenotype in culture. We identified and quantified 29 ASC exometabolites and evaluated their consumption or secretion over 72 h of cell culture. Both ASC used glycolysis and mitochondrial metabolism, as evidenced by the high secretions of lactate and citrate, respectively, but V-ASC mostly used glycolysis. By varying the composition of the cell culture medium, we showed that glutaminolysis, rather than glycolysis, supported the secretion of pyruvate, alanine, and citrate, evidencing a peculiar metabolism in ASC cells. The comparison of the two types of ASC in glutamine-free culture conditions also revealed the role of glutaminolysis in the limitation of pyruvate routing towards the lactate synthesis, in S-ASC but not in V-ASC. Altogether, our results suggest a difference between depots in the capacity of ASC mitochondria to assimilate pyruvate, with probable consequences on their differentiation potential in pathways requiring an increased mitochondrial activity. These results highlight a pivotal role of metabolic mechanisms in the discrimination between ASC and provide new perspectives in the understanding of their functional differences.