Biology subjects

Rabhi, N.

Publications and source records attributed to Rabhi, N..

5 recordsLinked to original sources

bioRxiv2023

Adrenergic Reprogramming of Preexisting Adipogenic Trajectories Steer Naive Mural Cells Toward Beige Differentiation

In adult white adipose tissue, cold or {beta}3-adrenoceptor activation promotes the appearance of thermogenic beige adipocytes. Our comprehensive single-cell analysis revealed that these cells arise through the reprogramming of existing adipogenic trajectories, rather than from a single precursor. These trajectories predominantly arise from SM22-expressing vascular mural progenitor cells. Central in this transition is the activation of Adrb3 in mature adipocytes, leading to subsequent upregulation of Adrb1 in primed progenitors. Under thermoneutral conditions, synergistic activation of both Adrb3 and Adrb1 recapitulates the pattern of cold-induced SM22+ cell recruitment. Lipolysis-derived eicosanoids, specifically docosahexaenoic acid (DHA) and arachidonic acid (AA) prime these processes and in vitro, were sufficient to recapitulate progenitor cells priming. Collectively, our findings provide a robust model for cold-induced beige adipogenesis, emphasizing a profound relationship between mature adipocytes and mural cells during cold acclimation, and revealing the metabolic potential of this unique cellular reservoir.

cell biology↗

bioRxiv2021

A crosstalk between E2F1 and GLP-1 signaling pathways modulates insulin secretion

Compromised {beta}-cell function contributes to type 2 diabetes (T2D) development. The glucagon like peptide 1 (Glp-1) has emerged as a hormone with broad pharmacological potential toward T2D treatment, notably by improving {beta}-cell functions. Recent data have shown that the transcription factor E2f1, besides its role as a cell cycle regulator, is involved in glucose homeostasis by modulating {beta}-cell mass, function and identity. Here, we demonstrate a crosstalk between the E2F1, phosphorylation of retinoblastoma protein (pRb) and Glp-1 signaling pathways. We found that {beta}-cell specific E2f1 deficient mice (E2f1{beta}-/-) presented with impaired glucose homeostasis and decreased glucose stimulated-insulin secretion mediated by exendin 4 (i.e., GLP1R agonist), which were associated with decreased expression of Glp1r encoding Glp-1 receptor (GLP1R) in E2f1{beta}-/- pancreatic islets. Decreasing E2F1 transcriptional activity with an E2F inhibitor in islets from nondiabetic humans decreased GLP1R levels and blunted the incretin effect of exendin 4 on insulin secretion. Conversely, overexpressing E2f1 in pancreatic {beta} cells increased Glp1r expression associated with enhanced insulin secretion mediated by GLP1R agonist. Interestingly, kinome analysis of mouse islets demonstrated that an acute treatment with exendin 4 increased pRb phosphorylation and subsequent E2f1 transcriptional activity. This study suggests a molecular crosstalk between the E2F1/pRb and GLP1R signaling pathways that modulates insulin secretion and glucose homeostasis.

physiology↗

bioRxiv2020

Pancreatic β-cell specific loss of E2f1 impairs insulin secretion and β-cell identity through the epigenetic repression of non β-cell programs

The loss of pancreatic {beta}-cell identity emerges as an important feature of type 2 diabetes development, but the molecular mechanisms are still elusive. Here, we explore the cell-autonomous role of the cell cycle regulator and transcription factor E2F1 in the maintenance of {beta}-cell identity and insulin secretion. We show that the {beta}-cell-specific loss of E2f1 function in mice triggers glucose intolerance associated with defective insulin secretion, an altered -to-{beta}-cell ratio, a downregulation of many {beta}-cell genes and a concomitant increase of non-{beta}-cell markers. Mechanistically, the epigenomic profiling of non-beta cell upregulated gene promoters identified an enrichment of bivalent H3K4me3/H3K27me3 or H3K27me3 marks. Conversely, downregulated genes were enriched in active chromatin H3K4me3 and H3K27ac histone marks. We find that histone deacetylase inhibitors modulate E2F1 transcriptional and epigenomic signatures associated with these {beta}-cell dysfunctions. Finally, the pharmacological inhibition of E2F transcriptional activity in human islets also impairs insulin secretion and the expression of {beta}-cell identity genes. Our data suggest that E2F1 is critical for maintaining {beta}-cell identity through a sustained repression of non {beta}-cell transcriptional programs.

physiology↗

bioRxiv2020

Single cell atlas of beige remodeling of white adipose tissue reveals a myeloid to lymphoid shift during cold exposure compared to beta 3 adrenergic stimulation

White adipose tissue (WAT) is a dynamic tissue, which responds to environmental stimuli and dietary cues by changing its morphology and metabolic capacity. The ability of WAT to undergo a beige remodeling has become an appealing strategy to combat obesity and its related metabolic complications. Within the cell mixture that constitutes the stromal vascular fraction (SVF), WAT beiging is initiated through expansion and differentiation of adipocytes progenitor cells, however, the extent of the SVF cellular changes is still poorly understood. Additionally, direct beta 3 adrenergic receptor (Adrb3) stimulation has been extensively used to mimic physiological cold- induced beiging, yet it is still unknown whether Adrb3 activation induces the same WAT remodeling as cold exposure. Here, by using single cell RNA sequencing, we provide a comprehensive atlas of the cellular dynamics during beige remodeling within white adipose tissue. We reveal drastic changes both in the overall cellular composition and transcriptional states of individual cell subtypes between Adrb3- and cold-induced beiging. Moreover, we demonstrate that cold exposure induces a myeloid to lymphoid shift of the immune compartment compared to Adrb3 activation. Further analysis, showed that Adrb3 stimulation leads to activation of the interferon/Stat1 pathways favoring infiltration of myeloid immune cells, while repression of this pathway by cold promotes lymphoid immune cells recruitment. These findings provide new insight into the cellular dynamics during WAT beige remodeling and could ultimately lead to novel strategies to identify translationally-relevant drug targets to counteract obesity and T2D.

cell biology↗

bioRxiv2019

Triphenyl phosphate is a selective PPARγ modulator that does not induce brite adipogenesis in vitro and in vivo

Triphenyl phosphate (TPhP) is an environmental PPAR{gamma} ligand, and growing evidence suggests that it is a metabolic disruptor. We have shown previously that the structurally similar ligand, tributyltin, does not induce brite adipocyte gene expression. Here, using in vivo and in vitro models, we tested the hypothesis that TPhP is a selective PPAR{gamma} ligand, which fails to induce brite adipogenesis. C57BL/6J male mice were fed either a low or very high fat diet for 13 weeks. From weeks 7-13, mice were injected intraperitoneally, daily, with vehicle, rosiglitazone (Rosi), or TPhP (10 mg/kg). Compared to Rosi, TPhP did not induce expression of browning-related genes (e.g. Elovl3, Cidea, Acaa2, CoxIV) in mature adipocytes isolated from inguinal adipose. To determine if this resulted from an effect directly on the adipocytes, 3T3-L1 cells and primary human preadipocytes were differentiated into adipocytes in the presence of Rosi or TPhP. Rosi, but not TPhP, induced expression of brite adipocyte genes, mitochondrial biogenesis and cellular respiration. Further, Rosi and TPhP induced distinct proteomes and phosphoproteomes; Rosi enriched more regulatory pathways related to fatty acid oxidation and mitochondrial proteins. We assessed the role of phosphorylation of PPAR{gamma} in these differences in 3T3-L1 cells. Only Rosi protected PPAR{gamma} from phosphorylation at Ser273. TPhP gained the ability to stimulate brite adipocyte gene expression in the presence of the CDK5 inhibitor and in 3T3-L1 cells expressing alanine at position 273. We conclude that TPhP is a selective PPAR{gamma} modulator that fails to protect PPAR{gamma} from phosphorylation at ser273.

pharmacology and toxicology↗