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Côté, Julie Anne

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Julie Anne
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Université Laval. École de nutrition
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Voici les éléments 1 - 9 sur 9
  • Publication
    Accès libre
    Characterization and visualization of the liposecretion process taking place during ceiling culture of human mature adipocytes
    (Wistar Institute of Anatomy and Biology, 2019-07-15) Marette, André.; Gauthier, Marie-Frédérique; Bellmann, Kerstin; Ostinelli, Giada; Côté, Julie Anne; Brochu, Dannick; Tchernof, André; Julien, François; Lebel, Stéfane
    Objective To investigate and further characterize the process of mature adipocyte dedifferentiation. Our hypothesis was that dedifferentiation does not involve mitosis but rather a phenomenon of liposecretion. Methods Mature adipocytes were isolated by collagenase digestion of human adipose tissue samples. Ceiling cultures were established using our six-well plate model. Cells were treated with cytosine β-d-arabinofuranoside (AraC) or vincristine (VCR), two agents blocking cell division, and were compared with vehicle. Liposecretion events were visualized by time-lapse microscopy, with and without AraC in adipocytes transducted with a baculovirus. Microscopic analyses were performed after labeling phosphorylated histone 3 and cyclin B1 in ceiling cultures. Results Treatment with AraC almost entirely prevented the formation of fibroblasts up to 12 days of ceiling culture. Similar results were obtained with VCR. The antimitotic effectiveness of the treatment was confirmed in fibroblast cultures from the adipose tissue stromal-vascular fraction by proliferation assays and colony-forming unit experiments. Using time-lapse microscopy, we visualized liposecretion events in which a large lipid droplet was rapidly secreted from isolated mature adipocytes. The same phenomenon was observed with AraC. This was observed in conjunction with histone 3 phosphorylation and cyclin B1 segregation to the nucleus. Conclusion Our results support the notion that dedifferentiation involves rapid secretion of the lipid droplet by the adipocytes with concomitant generation of fibroblast-like cells that subsequently proliferate to generate the dedifferentiated adipocyte population during ceiling culture. The presence of mitotic markers suggests that this process involves cell cycle progression, although cell division does not occur.
  • Publication
    Accès libre
    Circulating steroid levels as correlates of adipose tissue phenotype in premenopausal women
    (De Gruyter, 2018-05-11) Marchand, Geneviève B.; Carreau, Anne-Marie; Laforest, Sofia; Cianflone, Katherine M.; Côté, Julie Anne; Daris, Marleen; Tchernof, André; Prehn, Cornelia; Adamski, Jerzy
    Background: Obesity-related alterations in the circulating steroid hormone profile remain equivocal in women. Our objective was to identify circulating steroid levels that relate to increased adiposity and altered adipose phenotype in premenopausal women. Materials and methods: In a sample of 42 premenopausal women (age 46±3 years; BMI 27.1±4.2 kg/m2 ), 19 plasma steroids were quantified by ESI-LC-MS/MS. Body composition and fat distribution were assessed by dual-energy X-ray absorptiometry and computed tomography, respectively. Markers of adipose tissue function including adipocyte size distributions, radiological attenuation, and macrophage infiltration were also analyzed in surgically obtained visceral and subcutaneous fat samples. Results: Many negative correlations were observed between adiposity measurements such as BMI, body fat percentage or total abdominal adipose tissue area and plasma levels of androstenedione (r=-0.33 to -0.39, p≤0.04), androsterone (r=-0.30 to -0.38, p≤0.05) and plasma levels of steroid precursor pregnenolone (r=-0.36 to -0.46, p≤0.02). Visceral adipocyte hypertrophy was observed in patients with low pregnenolone concentrations (p<0.05). Visceral adipose tissue radiologic attenuation, a potential marker of adipocyte size, was also positively correlated with pregnenolone levels (r=0.33, p<0.05). Low levels of pregnenolone were related to increased number of macrophages infiltrating visceral and subcutaneous adipose tissue (p<0.05). Conclusion: Plasma levels of androgens and their precursors are lower in women with increased adiposity and visceral adipocyte hypertrophy. Low circulating pregnenolone concentration may represent a marker of adipose tissue dysfunction.
  • Publication
    Accès libre
    Nouveaux aspects de la biologie adipocytaire
    (2017) Côté, Julie Anne; Tchernof, André
    Le tissu adipeux a longtemps été considéré comme un tissu inerte servant uniquement à la mise en réserve et à la libération des acides gras, mais nous savons maintenant qu’il possède une fonction endocrine et inflammatoire, impliquant ainsi ce tissu dans la pathophysiologie de l’obésité. En ce sens, beaucoup d’efforts sont déployés afin de minimiser son expansion, favoriser sa mobilisation ou encore améliorer l’homéostasie de ses fonctions. Notre compréhension de la nature biologique et physiologique du tissu adipeux a grandement évolué au cours des dernières décennies. De nouveaux concepts ont récemment émergé sur le tissu adipeux, notamment en ce qui concerne : 1) sa densité; et 2) sa plasticité. Dans la présente thèse, nous avons abordé ces deux concepts. L’objectif général des travaux était de caractériser les phénomènes entourant la densité et la plasticité du tissu adipeux. Afin de rencontrer cet objectif, nous avons développé une approche méthodologique nous permettant de mesurer l’accumulation des graisses et la densité radiologique du tissu adipeux, aussi appelée l’atténuation radiologique (la capacité du tissu adipeux à bloquer les rayons X) au niveau abdominal par tomographie axiale dans une cohorte de plus de 240 femmes. Nous avons démontré que l’atténuation radiologique des tissus adipeux sous-cutané et viscéral est significativement et négativement corrélée avec la taille adipocytaire dans le dépôt correspondant. De plus, nos résultats ont révélé que les femmes caractérisées par une hypertrophie des adipocytes viscéraux ont un profil lipidique altéré comparativement aux femmes ayant de plus petits adipocytes. Ces différences sont atténuées après un ajustement statistique pour la surface de tissu adipeux et éliminées après un ajustement statistique pour la surface et l’atténuation des tissus adipeux. Nous avons donc démontré que l’atténuation radiologique des tissus adipeux est un marqueur de la taille adipocytaire. Par le fait même, la taille adipocytaire est un intégrateur de la qualité et de la quantité du tissu adipeux. Nous avons étudié la plasticité des cellules de la fraction stroma-vasculaire et des adipocytes du tissu adipeux. D’abord, nous avons utilisé la cytométrie en flux pour caractériser le phénotype des précurseurs adipocytaires de la fraction stroma-vasculaire. Nous avons démontré qu’une souspopulation de précurseurs adipocytaires natifs CD45- CD31- CD34+ expriment le marqueur de surface CD38. Nous avons observé une expression plus élevée des gènes associés à l’adipogénèse dans les précurseurs CD38+ comparativement aux précurseurs CD38-. Nous avons également démontré que le développement de l’obésité par le biais d’une diète riche en gras est associé à une augmentation du nombre de précurseurs adipocytaires CD38+, particulièrement dans le dépôt intraabdominal. Nos travaux suggèrent donc que le CD38 est un marqueur d’engagement vers la ifférenciation adipocytaire. Par ailleurs, nous avons étudié un exemple de la plasticité des adipocytes matures, soit la dédifférenciation. Nous avons utilisé des puces à ADN pour examiner les changements d’expression génique au cours du processus de dédifférenciation. Nous avons observé une diminution de l’expression des gènes associés aux fonctions de l’adipocyte mature et une augmentation de l’expression des gènes associés à la reprogrammation cellulaire, au cycle cellulaire et à la matrice extracellulaire. Par ailleurs, nous avons développé un modèle de culture cellulaire nous permettant de dédifférencier les adipocytes matures et de moduler certains aspects du processus de dédifférenciation. Cela nous a permis de démontrer un rôle pour le sentier métabolique du Transforming growth factor-β dans la modulation de l’expression des différents types de collagène au cours du processus de dédifférenciation des adipocytes matures. Finalement, nous avons effectué des expériences d’immunofluorescence et de microscopie en temps réel afin de caractériser le processus de dédifférenciation des adipocytes matures. Nous avons démontré que la dédifférenciation est complètement inhibée par l’ajout d’agents bloquant la division cellulaire. Nous avons observé la présence d’adipocytes binucléiques au cours du processus de dédifférenciation, ainsi que des marqueurs de mitose. En conclusion, nos travaux ont permis de caractériser deux nouveaux aspects du tissu adipeux qui reflètent des processus biologiques précis qui ont leurs racines dans le cycle de vie de l’adipocyte, dont l’expansion hypertrophique, la prolifération et la différenciation cellulaire, ainsi que la dédifférenciation des adipocytes matures. Ces travaux proposent des avancées significatives dans notre compréhension de la nature dynamique de ce tissu.
  • Publication
    Accès libre
    Temporal changes in gene expression profile during mature adipocyte dedifferentiation
    (Hindawi Publishing Corporation, 2017-03-19) Guénard, Frédéric; Biron, Simon; Lapointe, Marc; Vohl, Marie-Claude; Côté, Julie Anne; Lessard, Julie.; Tchernof, André
    Objective. To characterize changes in gene expression profile during human mature adipocyte dedifferentiation in ceiling culture. Methods. Subcutaneous (SC) and omental (OM) adipose tissue samples were obtained from 4 participants paired for age and BMI. Isolated adipocytes were dedifferentiated in ceiling culture. Gene expression analysis at days 0, 4, 7, and 12 of the cultures was performed using Affymetrix Human Gene 2.0 STvi arrays. Hierarchical clustering according to similarity of expression changes was used to identify overrepresented functions. Results. Four clusters gathered genes with similar expression between day 4 to day 7 but decreasing expression from day 7 to day 12. Most of these genes coded for proteins involved in adipocyte functions (LIPE, PLIN1, DGAT2, PNPLA2, ADIPOQ, CEBPA, LPL, FABP4, SCD, INSR, and LEP). Expression of several genes coding for proteins implicated in cellular proliferation and growth or cell cycle increased significantly from day 7 to day 12 (WNT5A, KITLG, and FGF5). Genes coding for extracellular matrix proteins were differentially expressed between days 0, 4, 7, and 12 (COL1A1, COL1A2, and COL6A3, MMP1, and TGFB1). Conclusion. Dedifferentiation is associated with downregulation of transcripts encoding proteins involved in mature adipocyte functions and upregulation of genes involved in matrix remodeling, cellular development, and cell cycle.
  • Publication
    Accès libre
    Generation of human adipose stem cells through dedifferentiation of mature adipocytes in ceiling cultures
    (Verlag nicht ermittelbar, 2015-03-07) Lapointe, Marc; Biertho, Laurent; Nadeau, Mélanie; Côté, Julie Anne; Pelletier, Mélissa; Marceau, Simon; Lessard, Julie.; Tchernof, André
    Mature adipocytes have been recently shown to reverse their phenotype into fibroblast-like cells in vitro through a technique called ceiling culture. Mature adipocytes can also be isolated from fresh adipose tissue for depot-specific characterization of their function and metabolic properties. Here, we describe a well-established protocol to isolate mature adipocytes from adipose tissues using collagenase digestion, and subsequent steps to perform ceiling cultures. Briefly, adipose tissues are incubated in a Krebs-Ringer-Henseleit buffer containing collagenase to disrupt tissue matrix. Floating mature adipocytes are collected on the top surface of the buffer. Mature cells are plated in a T25-flask completely filled with media and incubated up-side down for a week. An alternative 6-well plate culture approach allows the characterization of adipocytes undergoing dedifferentiation. Adipocyte morphology drastically changes over time of culture. Immunofluorescence can be easily performed on slides cultivated in 6-well plate as demonstrated 65 by FABP4 immunofluorescence staining. FABP4 protein is present in mature adipocytes but down-regulated through dedifferentiation of fat cells. Mature adipocyte dedifferentiation may represent a new avenue for cell therapy and tissue engineering.
  • Publication
    Accès libre
    Activité de la diacylglycérol acyltransférase des tissus adipeux : un marqueur de dysfonction métabolique?
    (2013) Côté, Julie Anne; Tchernof, André
    Chez l’humain, l’acyl-CoA : diacylglycérol acyltransférase (DGAT), une enzyme transmembranaire localisée au niveau du réticulum endoplasmique, joue un rôle important dans la synthèse des triglycérides puisqu’elle catalyse l’étape ultime de la synthèse de ces molécules lipidiques. Cette enzyme pourrait être impliquée dans la pathogénèse de l’obésité et dans le développement des complications métaboliques qui lui sont associées. Nous avons étudié les différences régionales dans l’activité de la DGAT dans des échantillons adipeux de femmes minces à obèses. Nous avons démontré que l’obésité abdominale n’est pas associée à des altérations dans l’activité de la DGAT lorsque cette dernière est exprimée par µg protéine ou par 1000 cellules. Par ailleur, un taux de synthèse défectueux des triglycérides était associé à un enrichissement en triglycérides des lipoprotéines sanguines, ainsi qu’à une plus grande adiposité lorsque l’activité de la DGAT était exprimée par mg lipide.
  • Publication
    Accès libre
    Temporal changes in gene expression profile during mature adipocyte dedifferentiation
    (Hindawi Publishing Corporation, 2017-03-19) Guénard, Frédéric; Biron, Simon; Lapointe, Marc; Vohl, Marie-Claude; Côté, Julie Anne; Lessard, Julie.; Tchernof, André
    Objective. To characterize changes in gene expression profile during human mature adipocyte dedifferentiation in ceiling culture. Methods. Subcutaneous (SC) and omental (OM) adipose tissue samples were obtained from 4 participants paired for age and BMI. Isolated adipocytes were dedifferentiated in ceiling culture. Gene expression analysis at days 0, 4, 7, and 12 of the cultures was performed using Affymetrix Human Gene 2.0 STvi arrays. Hierarchical clustering according to similarity of expression changes was used to identify overrepresented functions. Results. Four clusters gathered genes with similar expression between day 4 to day 7 but decreasing expression from day 7 to day 12. Most of these genes coded for proteins involved in adipocyte functions (LIPE, PLIN1, DGAT2, PNPLA2, ADIPOQ, CEBPA, LPL, FABP4, SCD, INSR, and LEP). Expression of several genes coding for proteins implicated in cellular proliferation and growth or cell cycle increased significantly from day 7 to day 12 (WNT5A, KITLG, and FGF5). Genes coding for extracellular matrix proteins were differentially expressed between days 0, 4, 7, and 12 (COL1A1, COL1A2, and COL6A3, MMP1, and TGFB1). Conclusion. Dedifferentiation is associated with downregulation of transcripts encoding proteins involved in mature adipocyte functions and upregulation of genes involved in matrix remodeling, cellular development, and cell cycle.
  • Publication
    Accès libre
    Computed tomography-measured adipose tissue attenuation and area both predict adipocyte size and cardiometabolic risk in women
    (Landes Bioscience, 2016-04-06) Nadeau, Mélanie; Nazare, Julie-Anne; Leboeuf, Mathieu; Côté, Julie Anne; Després, Jean-Pierre; Blackburn, Line; Tchernof, André
    Objective: To assess the ability of CT-derived measurements including adipose tissue attenuation and area to predict fat cell hypertrophy and related cardiometabolic risk. Methods: Abdominal adipose tissue areas and radiologic attenuation were assessed using 4 CT images in 241 women (age: 47 years, BMI: 26.5 kg/m2). Fat cell weight was measured in paired VAT and SAT samples. Fasting plasma lipids, glucose and insulin levels were measured. Results: Adipose tissue attenuation was negatively correlated with SAT (r=-0.46) and VAT (r=-0.67) fat cell weight in the corresponding depot (p<0.0001 for both). Women with visceral adipocyte hypertrophy had higher total-, VLDL-, LDL- and HDL-triglyceride and apoB levels as well as a higher cholesterol/HDL-cholesterol ratio, fasting glucose and insulin levels compared to women with smaller visceral adipocytes. Adjustment for VAT area minimized these differences while subsequent adjustment for attenuation eliminated all differences, with the exception of fasting glycaemia. In SAT, adjustment for VAT area and attenuation eliminated all adipocyte hypertrophy-related alterations except for fasting hyperglycaemia. Conclusion: CT-derived adipose tissue attenuation and area both contribute to explain variation in the cardiometabolic risk profile associated with the same biological parameter: visceral fat cell hypertrophy.
  • Publication
    Accès libre
    Role of the TGF-β pathway in dedifferentiation of human mature adipocytes
    (Elsevier, 2017-05-30) Lessard, Julie; Lescelleur, Odette; Marceau, Simon; Côté, Julie Anne; Pelletier, Mélissa; Fradette, Julie; Tchernof, André
    Dedifferentiation of adipocytes contributes to the generation of a proliferative cell population that could be useful in cellular therapy or tissue engineering. Adipocytes can dedifferentiate into precursor cells to acquire a fibroblast-like phenotype using ceiling culture, in which the buoyancy of fat cells is exploited to allow them to adhere to the inner surface of a container. Ceiling culture is usually performed in flasks, which limits the ability to test various culture conditions. Using a new six-well plate ceiling culture approach, we examined the relevance of TGF-β signaling during dedifferentiation. Adipose tissue samples from patients undergoing bariatric surgery were digested with collagenase, and cell suspensions were used for ceiling cultures. Using the six-well plate approach, cells were treated with SB431542 (an inhibitor of TGF-β receptor ALK5) or human TGF-β1 during dedifferentiation. Gene expression was measured in these cultures and in whole adipose tissue, the stromal–vascular fraction (SVF), mature adipocytes, and dedifferentiated fat (DFAT) cells. TGF-β1 and collagen type I alpha 1 (COL1A1) gene expression was significantly higher in DFAT cells compared to whole adipose tissue samples and SVF cells. TGF-β1, COL1A1, and COL6A3 gene expression was significantly higher at day 12 of dedifferentiation compared to day 0. In the six-well plate model, treatment with TGF-β1 or SB431542, respectively, stimulated and inhibited the TGF-β pathway as shown by increased TGF-β1, TGF-β2, COL1A1, and COL6A3 gene expression and decreased expression of TGF-β1, COL1A1, COL1A2, and COL6A3, respectively. Treatment of DFAT cells with TGF-β1 increased the phosphorylation level of SMAD 2 and SMAD 3. Thus, a new six-well plate model for ceiling culture allowed us to demonstrate a role for TGF-β in modulating collagen gene expression during dedifferentiation of mature adipocytes.