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DOI: 10.1055/s-0033-1336678
A new human adipocyte model derived from a PTEN-deficient lipoma
Aims: We aimed to characterise a new human adipocyte model termed LipPD1 derived from a lipoma of a patient with PTEN-Hamartoma-Tumor Syndrome and asked whether the deficiency of PTEN had an impact on adipocyte function and signaling pathways.
Methods: Adipose differentiation of LipPD1 cells was determined by lipid staining and cell counting. Lipolysis rates were determined by glycerol release after stimulation with isoproterenol and insulin-stimulated glucose uptake was quantified by measuring 14C-labelled-2-deoxyglucose uptake. Phosphoinositide-3-kinase (PI3K) activity was determined by fluorescence redistribution after photobleaching (FRAP)/TIRF (total internal reflection fluorescence) analysis. SGBS preadipocytes were used for comparison.
Results: A proportion of 55.1 ± 4.2% of LipPD1 cells was able to undergo in vitro adipose differentiation after 29 population doublings. The adipocyte markers PPARy, FASN, adiponectin and aP2 were expressed in LipPD1 cells during differentiation to a similar extend as in SGBS. Functional analysis revealed no significant differences between LipPD1 and SGBS in 2-deoxyglucose uptake after insulin stimulation and lipolysis after isoproterenol stimulation. PTEN mRNA and protein levels were significantly decreased in LipPD1 compared with SGBS preadipocytes (p < 0.01 for mRNA, p < 0.001 for protein). A fluorescent biomarker reflecting PI3K activity by redistribution to the plasma membrane was found membrane-associated at a higher amount in LipPD1 (33.4 ± 2.7%) compared to SGBS preadipocytes (20.9 ± 2.3%). A constitutive activation of the kinase AKT was found by detecting increased phosphorylation of AKT in LipPD1 cells, which was further enhanced after stimulation with IGF-I.
Conclusion: LipPD1 cells are a suitable model to investigate molecular mechanisms of adiposity. The activation of the PI3K/AKT signaling pathway in LipPD1 cells is increased compared to SGBS cells, however no impact on adipocyte function was observed in our study.