Biology subjects

Castoldi, A.

Publications and source records attributed to Castoldi, A..

7 recordsLinked to original sources

bioRxiv2023

Beneficial metabolic effects of PAHSAs depend on the gut microbiota in diet-induced obese mice

Dietary lipids play an essential role in regulating the function of the gut microbiota and gastrointestinal tract, and these luminal interactions contribute to mediating host metabolism. PAHSAs are a class of lipids with anti-diabetic and anti-inflammatory properties, but whether the gut microbiota contributes to their beneficial effects on host metabolism is unknown. Here, we report that treating high fat diet (HFD)-fed germ-free mice with PAHSAs does not improve insulin sensitivity. However, transfer of feces from PAHSA-treated, but not Vehicle-treated, chow-fed mice increases insulin-sensitivity in HFD-fed germ free mice. Thus, the gut microbiota is necessary for and can transmit the insulin-sensitizing effects of PAHSAs in HFD-fed germ-free mice. Functional analyses of the cecal metagenome and lipidome of PAHSA-treated mice identified multiple lipid species that associate with the gut commensal Bacteroides thetaiotaomicron (Bt) and with insulin sensitivity resulting from PAHSA treatment. Bt supplementation in HFD-fed female mice prevented weight gain, reduced adiposity, improved glucose tolerance, fortified the colonic mucus barrier and reduced systemic inflammation versus chow-fed controls, effects that were not observed in HFD-fed male mice. Furthermore, ovariectomy partially reversed the beneficial Bt effects on host metabolism, indicating a role for sex hormones in mediating probiotic effects. Altogether, these studies highlight the fact that lipids can modulate the gut microbiota resulting in improvement in host metabolism and that PAHSA-induced changes in the microbiota result in at least some of their insulin-sensitizing effects in female mice.

physiology↗

bioRxiv2023

Lack of mTORC2 signaling in CD11c+ myeloid cells inhibits their migration and ameliorates experimental colitis

Mammalian target of rapamycin (mTOR) pathway plays a key role in determining immune cells function through modulation of their metabolic status. By specific deletion of Rictor in tissue-resident CD11c+ myeloid cells (CD11cRic{Delta}/{Delta}), this study investigated the role of mTOR complex 2 (mTORC2) signaling in dendritic cells (DCs) function in mice. We showed that upon DSS-induced colitis, lack of mTORC2 signaling CD11c+ cells diminish colonic inflammation, abrogates dendritic cell (DC) migration to the mesenteric lymph nodes (MLN), thereby diminishing the infiltration of T helper (Th) 17 cells in the lamina propria (LP). These findings corroborate with abrogation of cytoskeleton organization and decreased activation of Rac1 and Cdc42 GTPases observed in CD11c+-mTORC2-deficient cells. Meta-analysis on colonic samples from ulcerative colitis (UC) patients revealed increased gene expression of pro-inflammatory cytokines which coincided with augmented expression of mTOR pathway, positive correlation between the DC marker ITGAX, and IL-6, the expression of RICTOR, and CDC42. Together, this work proposes that targeting mTORC2 on DCs offers a key to hamper inflammatory responses and this way, ameliorates the progression and severity of intestinal inflammatory diseases.

immunology↗

bioRxiv2022

HIGHLY PHAGOCYTIC LIPID-ASSOCIATED MACROPHAGES (LAMs) ARE INCREASED IN COLONIC LAMINA PROPRIA IN OBESITY

Little is known about the effects of high fat diet (HFD)-induced obesity on resident colonic lamina propria (LP) macrophages (LPMs) function and metabolism. Here, we report that obesity and diabetes resulted in increased macrophage infiltration in the colon. These macrophages exhibited the residency phenotype CX3CR1hiMHCIIhi, and were CD4-TIM4-. During HFD, resident colonic LPM exhibited a lipid metabolism gene expression signature that overlapped that used to define lipid associated macrophages (LAMs). Via single cell RNA sequencing, we identified a sub-cluster of macrophages, increased in HDF, that were responsible for the LAM signature. Compared to other macrophages in the colon, these cells were characterized by elevated glycolysis, phagocytosis and efferocytosis signatures. CX3CR1hiMHCIIhi colonic resident LPMs had fewer lipid droplets (LD) and decreased triacylglycerol (TAG) content compared to equivalent cells in lean mice, and exhibited increased phagocytic capacity, suggesting that HFD induces adaptive responses in LPMs to limit bacterial translocation.

immunology↗

bioRxiv2022

In macrophages fatty acid oxidation spares glutamate for use in diverse metabolic pathways required for alternative activation

Fatty acid oxidation (FAO) is upregulated in IL-4-stimulated (alternatively activated) macrophages (M(IL-4)). We examined the effect of loss of function of the enzyme Cpt1a, which facilitates the entry of long chain fatty acids (FA) into mitochondria for FAO, on alternative activation. Expression of M(IL-4) markers ARG1, CD301 and RELM, was impaired in tamoxifen-treated ERT2Cre x Cpt1afl/fl macrophages and in macrophages expressing shRNA targeting Cpt1a (Cpt1a-shRNA). In contrast, VaviCre x Cpt1afl/fl and LysmCre x Cpt1afl/fl M(IL-4) responded normally to IL-4. Reduced alternative activation due to Cpt1a loss of function was linked to decreased cellular pools of -ketoglutarate, glutamate, and glutathione, diminished commitment of glucose carbon to serine/glycine synthesis, and decreased expression of genes in the Nrf2-oxidative stress response pathway. Consistent with this, reactive oxygen species were increased. Restoration of glutathione pools with N-acetyl cysteine normalized oxidative stress and allowed alternative activation in the face of Cpt1a-deficiency, pointing to a role for FAO in the control of ROS and as being important for alternative activation. In VaviCre x Cpt1afl/fl M(IL-4), glutamine uptake was increased, compensating for the loss of FAO to meet necessary metabolic demands, to allow alternative activation. The data indicate that macrophages are able to regulate glutamine metabolism to compensate for chronic disruption of FAO to meet metabolic needs.

immunology↗

bioRxiv2022

Resident T cells orchestrate adipose tissue remodeling in a site peripheral to infection

Infection with helminth parasites can affect adiposity, but underlying mechanisms that regulate this process are unclear. We found that fat content of mesenteric adipose tissue (mAT) declined in mice during infection with gut-restricted parasitic worms. This was associated with the accumulation of metabolically activated, immunostimulatory cytokine- and extracellular matrix-secreting multipotent stromal cells, which had potential to differentiate into preadipocytes. Concomitantly, mAT became infiltrated with Th2 lymphocytes that took up long-term residence and responded to signals from stromal cells by producing stromal cell-stimulating cytokines, including Amphiregulin. Signals delivered by Amphiregulin to stromal cells were required for immunity to infection. Our findings reveal intricate intercellular communication between Th2 cells and adipocyte progenitors and link immunity to intestinal infection to T cell-dependent effects on the adipocyte lineage.

immunology↗

bioRxiv2021

Predictive framework of macrophage activation

Macrophages populate every organ during homeostasis and disease, displaying features of tissue imprinting and heterogeneous activation. The disjointed picture of macrophage biology that emerged from these observations are a barrier for integration across models or with in vitro macrophage activation paradigms. We set out to contextualize macrophage heterogeneity across mouse tissues and inflammatory conditions, specifically aiming to define a common framework of macrophage activation. We built a predictive model with which we mapped the activation of macrophages across 12 tissues and 25 biological conditions, finding a striking commonality and finite number of transcriptional profiles, which we modelled as defined stages along four conserved activation paths. We verified this model with adoptive cell transfer experiments and identified transient RELM[a] expression as a feature of macrophage tissue engraftment. We propose that this integrative approach of macrophage classification allows the establishment of a common predictive framework of macrophage activation in inflammation and homeostasis. One Sentence SummaryWe propose an integrative approach of macrophage classification that allows the establishment of a common framework of macrophage activation in inflammation and homeostasis.

immunology↗

bioRxiv2020

Triacylglycerol synthesis enhances macrophage inflammatory function

Macrophages are integral to most tissues. Foam cells, macrophages with lipid droplets (LDs) which are stores of triacylglycerols (TGs) and cholesterol esters (CEs), are found in various disease states1. LDs can act as energy stores since TG lipolysis releases fatty acids (FAs) for mitochondrial oxidation (FAO), a process that relies on long-chain FA conversion into acylcarnitines by the enzyme Cpt1a2. However, in macrophages, proinflammatory signals result in diminished FAO and increased TG synthesis with LD development3,4. We explored the significance of LDs in cells that do not utilize FAO. We show that macrophages stimulated with lipopolysaccharide (LPS) plus interferon-{gamma} (IFN{gamma}) accumulate TGs in LDs, and long-chain acylcarnitines. In these cells, inhibition of TG synthesis results in diminished LD development, and increased long chain acylcarnitine levels, suggesting that FA fate is balanced between TG and acylcarnitine synthesis. Nevertheless, TG-synthesis is required for inflammatory macrophage function, since its inhibition negatively affects production of proinflammatory IL-1{beta}, IL-6 and PGE2, and phagocytic capacity, and protects against LPS-induced shock in vivo. Failure to make PGE2 is critical for this phenotype, since exogenous PGE2 reverses the anti-inflammatory effects of TG-synthesis inhibition. These findings place LDs in a position of central functional importance in inflammatory macrophages.

immunology↗