Exp Clin Endocrinol Diabetes 2015; 123 - P14_02
DOI: 10.1055/s-0035-1547775

Increased PI3K/AKT/MTOR signaling in PTEN-deficient compared to normal human preadipocytes is not present in adipocytes

A Garten 1, F Kässner 1, N Händel 2, A Tannert 3, T Sauer 1, W Kiess 4, A Koerner 5
  • 1Universität Leipzig; Klinik und Poliklinik für Kinder- und Jugendmedizin; Zentrum für Pädiatrische Forschung Leipzig
  • 2Univ.-Kinderklinik Leipzig
  • 3Universität Leipzig; Rudolf-Boehm-Institut für Pharmakologie and Toxikologie
  • 4University of Leipzig; Hospital for Children & Adolescents; Hospital for Children & Adolescents
  • 5Universitätskinderklinik Leipzig; Zentrum für Pädiatrische Forschung; Zentrum für Pädiatrische Forschung Leipzig

Aims: Patients with PTEN Hamartoma Tumor Syndrome (PHTS) frequently develop lipomatosis with health problems related to unrestricted lipoma growth. We analysed AKT/mTOR signaling in cells derived from lipomas of patients with PHTS and aimed to find differently regulated signaling molecules compared to normal preadipocytes and adipocytes.

Methods: Phosphoinositide-3-kinase (PI3K) activity was determined by fluorescence redistribution after photobleaching/total internal reflection fluorescence analysis. PTEN expression, AKT- and 4E-binding protein(4E-BP)-1-phosphorylation was determined by Western Blot. SGBS cells were used as controls. Lipoma and normal adipose tissue was obtained with informed consent from patients undergoing surgery. Size of adipocytes was measured using Keyence-Hybrid Cell Count).

Results: PTEN expression in lipoma-derived preadipocytes was significantly decreased compared to SGBS control preadipocytes (p < 0.01 for mRNA, p < 0.001 for protein), while SGBS preadipocytes expressed PTEN protein in amounts comparable to primary preadipocytes. Basal PI3-kinase activity and AKT phosphorylation were found to be significantly increased in lipoma-derived preadipocytes (1.6-fold, p < 0.05 and 3.2-fold, p < 0.05, respectively) compared to control preadipocytes. Additionally, a trend towards increased phosphorylation of the mTOR target 4E-BP-1 in lipoma-derived preadipocytes was measured. Since mTOR is a regulator of cell growth, size of adipocytes in lipoma tissue from patients with PHTS was measured. PHTS adipocytes were found to be significantly larger than adipocytes in normal adipose tissue of matched controls (p < 0.05). However, the signaling differences found in preadipocytes were not detected in adipocytes allthough PTEN protein and mRNA expression did not change significantly during adipocyte differentiation.

Conclusion: Decreased PTEN expression was found to influence the PI3K/AKT/mTOR signaling pathway in lipoma-derived preadipocytes, but not in adipocytes.