Fat depot-related differences in gene expression, adiponectin secretion, and insulin action and signalling in human adipocytes differentiated in vitro from precursor stromal cells |
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Authors: | S Perrini L Laviola A Cignarelli M Melchiorre F De Stefano C Caccioppoli A Natalicchio M R Orlando G Garruti M De Fazio G Catalano V Memeo R Giorgino F Giorgino |
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Institution: | (1) Department of Emergency and Organ Transplantation, Section of Internal Medicine, Endocrinology and Metabolic Diseases, University of Bari School of Medicine, Bari, Italy;(2) Department of Emergency and Organ Transplantation, Section of General Surgery, University of Bari School of Medicine, Bari, Italy;(3) Department of Emergency and Organ Transplantation, Section of Internal Medicine, Endocrinology and Metabolic Diseases, University of Bari, Piazza Giulio Cesare, 11, I-70124 Bari, Italy |
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Abstract: | Aim/hypothesis The distinct metabolic properties of visceral and subcutaneous adipocytes may be due to inherent characteristics of the cells
that are resident in each fat depot. To test this hypothesis, human adipocytes were differentiated in vitro from precursor
stromal cells obtained from visceral and subcutaneous fat depots and analysed for genetic, biochemical and metabolic endpoints.
Methods Stromal cells were isolated from adipose tissue depots of nondiabetic individuals. mRNA levels of adipocyte-specific proteins
were determined by real-time RT-PCR. Insulin signalling was evaluated by immunoblotting with specific antibodies. Glucose
transport was measured by a 2-deoxy-glucose uptake assay. Adiponectin secretion in the adipocyte-conditioned medium was determined
by a specific RIA.
Results With cell differentiation, mRNA levels of PPARG, C/EBPα (also known as CEBPA), AP2 (also known as GTF3A), GLUT4 (also known as SLC2A4) were markedly upregulated, whereas GLUT1 (also known as SLC2A1) mRNA did not change. However, expression of C/EBPα, AP2 and adiponectin was higher in subcutaneous than in visceral adipocytes. By contrast, adiponectin was secreted at threefold
higher rates by visceral than by subcutaneous adipocytes while visceral adipocytes also showed two- to threefold higher insulin-stimulated
glucose uptake. Insulin-induced phosphorylation of the insulin receptor, IRS proteins, Akt and extracellular signal-regulated
kinase-1/2 was more rapid and tended to decrease at earlier time-points in visceral than in subcutaneous adipocytes.
Conclusions/interpretation Subcutaneous and visceral adipocytes, also when differentiated in vitro from precursor stromal cells, retain differences in
gene expression, adiponectin secretion, and insulin action and signalling. Thus, the precursor cells that reside in the visceral
and subcutaneous fat depots may already possess inherent and specific metabolic characteristics that will be expressed upon
completion of the differentiation programme.
Electronic supplementary material The online versin of this article (doi:) contains supplementary material, which is available to authorised users. |
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Keywords: | Adiponectin Akt Erk Extracellular signal-regulated kinase Glucose uptake Insulin signalling Subcutaneous fat Visceral fat |
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