LRP1 Receptor Controls Adipogenesis and Is Up-Regulated In Human and Mouse Obese Adipose Tissue

The cell surface low-density lipoprotein receptor-related protein 1, LRP1, plays a major role in lipid metabolism. The question that remains open concerns the function of LRP1 in adipogenesis. Here, we show that LRP1 is highly expressed in murine preadipocytes as well as in primary culture of human adipocytes. Moreover, LRP1 remains abundantly synthesised during mouse and human adipocyte differentiation. We demonstrate that LRP1 silencing in 3T3F442A murine preadipocytes significantly inhibits the expression of PPARγ, HSL and aP2 adipocyte differentiation markers after adipogenesis induction, and leads to lipid-depleted cells. We further show that the absence of lipids in LRP1-silenced preadipocytes is not caused by lipolysis induction. In addition, we provide the first evidences that LRP1 is significantly up-regulated in obese C57BI6/J mouse adipocytes and obese human adipose tissues. Interestingly, silencing of LRP1 in fully-differentiated adipocytes also reduces cellular lipid level and is associated with an increase of basal lipolysis. However, the ability of mature adipocytes to induce lipolysis is independent of LRP1 expression. Altogether, our findings highlight the dual role of LRP1 in the control of adipogenesis and lipid homeostasis, and suggest that LRP1 may be an important therapeutic target in obesity

Positive Regulation of DNA Double Strand Break Repair Activity during Differentiation of Long Life Span Cells: The Example of Adipogenesis

Little information is available on the ability of terminally differentiated cells to efficiently repair DNA double strand breaks (DSBs), and one might reasonably speculate that efficient DNA repair of these threatening DNA lesions, is needed in cells of long life span with no or limited regeneration from precursor. Few tissues are available besides neurons that allow the study of DNA DSBs repair activity in very long-lived cells. Adipocytes represent a suitable model since it is generally admitted that there is a very slow turnover of adipocytes in adult. Using both Pulse Field Gel Electrophoresis (PFGE) and the disappearance of the phosphorylated form of the histone variant H2AX, we demonstrated that the ability to repair DSBs is increased during adipocyte differentiation using the murine pre-adipocyte cell line, 3T3F442A. In mammalian cells, DSBs are mainly repaired by the non-homologous end-joining pathway (NHEJ) that relies on the DNA dependent protein kinase (DNA-PK) activity. During the first 24 h following the commitment into adipogenesis, we show an increase in the expression and activity of the catalytic sub-unit of the DNA-PK complex, DNA-PKcs. The increased in DNA DSBs repair activity observed in adipocytes was due to the increase in DNA-PK activity as shown by the use of DNA-PK inhibitor or sub-clones of 3T3F442A deficient in DNA-PKcs using long term RNA interference. Interestingly, the up-regulation of DNA-PK does not regulate the differentiation program itself. Finally, similar positive regulation of DNA-PKcs expression and activity was observed during differentiation of primary culture of pre-adipocytes isolated from human sub-cutaneous adipose tissue

Place des adipocytes dans la réponse tissulaire aux radiations ionisantes

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

LDV peptidomimetics equipped with biotinylated spacer-arms: synthesis and biological evaluation on CCRF-CEM cell line.

The tripeptide Leu-Asp-Val (LDV) is known to bind α(4)β(1) integrin in leukemia cells. Here we have synthesized a LDV peptidomimetic equipped with a biotin-conjugated spacer-arm. Compound 9 acts as an inhibitor of the α(4)β(1) integrin in an adhesion assay using fluorescently labeled, α(4)β(1) integrin-expressing leukemia CCRF-CEM cells. Furthermore, when bound to neutravidin-coated plates, compound 9 could capture CCRF-CEM cells. Such biotin-conjugated LDV peptidomimetic may thus represent a novel tool for biotechnological applications using avidin interaction for leukapheresis or leukemia cell targeting

Diaryl urea LDV peptidomimetics as α 4β 1 integrin antagonists: Synthesis, adhesion inhibition and toxicity evaluation on CCRF-CEM cell line

The α 4β 1 (VLA-4) integrin plays an important role in the leukocytes migration to sites of inflammation and has been validated as a therapeutic target for treating inflammatory diseases. Two families of regioisomeric peptidomimetics based on the Leu-Asp-Val (LDV) motif recognized by the α 4β 1 integrin were synthesized. Their activity was evaluated through cell adhesion and cell detachment assays using the CCRF-CEM cell line (Human T cells lymphoblast-like). Among the 20 antagonists tested, 17 appeared to be a good inhibitor of the adhesion of CCRF-CEM to fibronectin with an IC 50 value of 24 μM, comparable to the reference LDV peptide derivative 2. The toxicity of the peptidomimetics was also controlled. © 2012 The Royal Society of Chemistry

Cancer-associated adipocytes promotes breast tumor radioresistance.

International audienceMature adipocytes are excellent candidates to influence tumor behavior through heterotypic signaling processes since these cells produce hormones, growth factors, cytokines and other molecules, a heterogeneous group of molecules named adipokines. Using a 2D coculture system, we demonstrate that breast tumor cells previously co-cultivated with mature adipocytes exhibit radioresistance and an earlier and higher increase in the effector kinase Chk1, a phenotype that was associated with decreased cell death as compared to tumor cells grown alone. Interestingly, the adipocytes-induced tumor changes taking place during the coculture time preceding the exposure to IR were sufficient to confer the radioresistant effect. Notorious among the changes brought by adipocytes was the significant increase of IL-6 expression in tumor cells, whose activity may well account for the observed tumor cell protection from IR toxicity. Indeed, our data confirmed the protective role of this cytokine as tumor cells incubated after irradiation with recombinant IL-6 exhibit an increased in Chk1 phosphorylation and a radioresistant phenotype, thus far recapitulating the effects observed in the presence of adipocytes. Our current study sheds light on a new role of tumor-surrounding adipocytes in fostering a radioresistant phenotype in breast tumors, a finding that might have important clinical implications in obese patients that frequently exhibit aggressive diseases

Adipocyte differentiation is associated with an early increase in DNA-PKcs expression.

<p>(A) Expression of DNA repair proteins (DNA-PKcs, Ku70, Ku80, XRCC4, Rad51 and ATM) or adipocyte differentiation marker (HSL) was analyzed by Western Blots in exponentially growing 3T3F442A fibroblast cells (Ex), in 3T3F442A fibroblast cells grown to confluence (Co) or after the indicated time of culture in adipogenic differentiation medium (B) Similar experiments were performed in exponentially growing pre-adipocytes (Ex), in pre-adipocytes grown to confluence (Co) or during the first two days of culture in adipogenic medium) (C) Expression of DNA-PKcs protein in a murine fibroblast cell line (Balb-C) grown to confluence in the presence or not of insulin in comparison to exponentially growing cells.</p

Expression of DNA-PKcs is enhanced during adipogenesis of human pre-adipocytes isolated from sub-cutaneous adipose tissue.

<p>Cells isolated from the stromal vascular fraction of collagenase digested subcutaneous tissue were grown for the indicated times in adipogenic medium as described in the <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0003345#s2" target="_blank">Material and Methods</a> section. (A) Photographs of the cultured cells and (B) Western blots experiments using indicated antibodies. NS, non specific band that show equal loading between the different samples.</p