Adipocyte Differentiation

Fat tissue was resected during gastric bypass surgery for management of obesity. All subjects had fasted at least 10 hours before surgery. Subjects with malignancies were excluded. No subjects were taking thiazolidinediones or steroids. None had fasting plasma glucose levels over 120 mg/ dl. One half to 10 g of abdominal subcutaneous (external to the fascia superficialis), mesenteric, and greater omental fat were obtained from each subject. The tissue was collected in Hanks balanced salt solution with bicarbonate, penicillin, and gentamicin. Fat tissue was minced and then digested in HBSS containing 1 mg/ml collagenase and 7.5% fetal bovine serum in a 37*C shaking water bath until fragments were no longer visible and the digest had a milky appearance. Digests were filtered and centrifuged at 800xG for 10 min. The digests were treated with an erythrocyte lysis buffer. Cells were plated in 1:1 Dulbeccos modified Eagles medium:Hams F12 that contained 10% fetal bovine serum and antibiotics at a density of 4 x 104 cells/cm2. After 18 hours cultures were trypsinized until 95% of cells were detached (leaving endothelial cells and macrophages behind) and re-plated. Macrophages were rare (less than 5 per 106 cells, as assessed by phase contrast microscopy) in the re-plated cultures, irrespective of fat depot origin. Plating medium was changed every 2 days until confluence. For differentiation, preadipocytes were treated for 30 days with plating medium (without serum) enriched with 100 nM dexamethasone, 500 nM human insulin, 200 pM triiodothyronine, 0.5 *M rosiglitazone, antibiotics, and 540 *M methylisobutylxanthine (removed after 2 days). Higher rosiglitazone and insulin concentrations did not further enhance differentiation. Medium was changed every 2 days. For the final 2 days, differentiation medium was removed and cells were cultured in plating medium without serum. Undifferentiated preadipocytes were maintained in plating medium until confluence, when serum was removed for 2 days. For telomerase-expressing clones, preadipocytes were isolated and when cells had undergone 7 population doublings, they were transduced with a retrovirus containing the plasmid, pBABE-hTERT-Hygro. This vector expresses the human telomerase reverse transcriptase component (hTERT) driven by the Moloney murine leukemia virus long terminal repeat promoter and a hygromycin resistance sequence driven by the SV40 promoter. The 3 abdominal subcutaneous and 3 omental stably transduced, hygromycin-resistant clones capable of achieving confluence fastest were selected from 38 subcutaneous and 42 omental clones. Telomerase activity in these clones was verified using a PCR-based telomere repeat amplification protocol. RNA was isolated from preadipocytes by the Trizol method. RNA samples were labeled using the standard one-cycle Affymetrix GeneChip Eukaryotic Target Labeling Assay for Expression Analysis. Samples were hybridized for 16 hours at 45 C and 60 rpm, washed and stained according to the standard Affymetrix Antibody Amplification for Eukaryotic Targets protocol, and scanned at 488 nm. Images were quantified and linearly scaled using Affymetrix GeneChip Operating Software 1.1 using default analysis settings.

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Tchkonia T, Lenburg M, Thomou T, Giorgadze N, Frampton G, Pirtskhalava T, Cartwright A, Cartwright M, Flanagan J, Karagiannides I, Gerry N, Forse RA, Tchoukalova Y, Jensen MD, Pothoulakis C, Kirkland JL