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A recent hypothesis suggests that a high glycaemic load diet-associated increase of insulin-like growth factor-1 (IGF-1) and insulin may promote acne by reducing nuclear localization of the forkhead box-O1 (FoxO1) transcription factor via activation of the phosphoinositide-3-kinase (PI3K)/Akt pathway. Using SZ95 sebocytes as a model, we investigated the effect of the most important insulinotropic western dietary factors, IGF-1 and insulin on acne. SZ95 sebocytes were stimulated with different concentrations of IGF-1 and insulin (0.001, 0.01, 0.1 and 1 μM) for 15 to 120 min ± PI3K inhibitor LY294002 (50 μM). Cytoplasmic and nuclear protein expression of p-Akt and p-FoxO1 as well as FoxO transcriptional activity was analysed. In addition, the proliferation and differentiation of sebocytes and their TLR2/4 expression were determined. We found that high concentrations of IGF-1 and insulin differentially stimulate the PI3K/Akt/FoxO1 pathway by an early up-regulation of cytoplasmic p-Akt and delayed up-regulation of p-FoxO1 resulting in FoxO1 shift to the cytoplasm and the reduction of FoxO transcriptional activity, physiological serum concentration had no effect. IGF-1 at concentrations of 0.1 and 1 μM significantly reduced proliferation but increased differentiation of sebocytes to a greater extent than insulin (0.1 and 1 μM), but up-regulated TLR2/4 expression to comparable extent. These data provide the first in vitro evidence that FoxO1 principally might be involved in the regulation of growth-factor-stimulatory effects on sebaceous lipogenesis and inflammation in the pathological condition of acne. However, the in vivo significance under physiological conditions remains to be elucidated.

Objective: For more than 3 decades, isotretinoin [13-cis retinoic acid (13-cis RA)] is established as the most potent oral treatment for severe acne. However, the molecular mechanisms of isotretinoin action have not been fully elucidated. Recently, we showed that insulin and insulin-like growth factor 1 (IGF-1) increase differentiation and decrease proliferation of SZ95 sebocytes in vitro via activation of the phosphoinositide 3-kinase (PI3K)/Akt/forkhead box-O1 (FoxO1) pathway. Furthermore, this pathway is activated in patient acne biopsies in vivo. Using SZ95 sebocytes as an in vitro model, the aim of this study was to investigate the effect of isotretinoin on PI3K pathway activation. Methods: SZ95 sebocytes were treated under light protection with 0.1 μM isotretinoin in the presence or absence of 1.0 and 0.1 μM IGF-1 or insulin or 50 μM LY294002 inhibitor in a time- dependent manner. The expression of p-Akt and its downstream target p-FoxO1 was analyzed by Western blot. FoxO transcriptional activity was measured by dual luciferase assay. Nuclear and cytoplasmic mobilization of FoxO1, p-FoxO1, and p-Akt were also determined by immunofluorescence microscopy.Proliferation of sebocytes was measured by [3H]-thymidine incorporation and sebocyte differentiation by oil red O staining. Results: We show that isotretinoin activates the PI3K/Akt pathway and decreases the nuclear content of FoxO1 and its transcriptional activity in sebocytes in vitro and in sebaceous gland biopsies from an isotretinoin-treated acne patient. Isotretinoin reduces the proliferation of IGF-1- or insulin-stimulated sebocytes more effectively than IGF-1 and insulin alone. However, it normalizes the increased lipid accumulation in IGF-1- or insulin-stimulated sebocytes via a PI3K-independent pathway. Conclusion: Our data from the SZ95 sebocyte in vitro model suggest that the potent therapeutic effect of isotretinoin in acne is not mediated via the PI3K/Akt/FoxO1 pathway.

Hyper-glycemic food increases insulin-like growth factor 1 (IGF-1) and insulin signaling and regulates endocrine responses and thereby may modulate the course of acne. Inflammation and adaptive immune responses have a pivotal role in all stages of acne. Recent hypothesis suggests that hyperglycemic food reduces nuclear forkhead box-O1 (FoxO1) transcription factor and may eventually induces acne. The aim of our study was to investigate the role of IGF-1 and insulin on the phosphoinositide-3-kinase (PI3K)/Akt/FoxO1 pathway in human primary T cells and on the molecular functions of T cells in vitro. T cells were stimulated with 0.001 μM IGF-1 or 1 μM insulin +/− 20 μM PI3K inhibitor LY294002. T cells were also exposed to SZ95 sebocyte supernatants which were pre-stimulated with IGF-1 or insulin. We found that 0.001 µM IGF-1 and 1 µM insulin activate the PI3K pathway in T cells leading to up-regulation of p-Akt and p-FoxO1 at 15 and 30 minutes. Nuclear FoxO1 was decreased and FoxO transcriptional activity was reduced. 0.001 µM IGF-1 and 1 µM insulin increased T cell proliferation but have no significant effect on Toll-like receptor2/4 (TLR) expression. Interestingly, supernatants from IGF-1- or insulin-stimulated sebocytes activated the PI3K pathway in T cells but reduced T cell proliferation. Taken together, this study helps to support that high glycemic load diet may contribute to induce activation of the PI3K pathway and increase of proliferation in human primary T cells. Factors secreted by IGF-1- and insulin-stimulated sebocytes induce the PI3K pathway in T cells and reduce T cell proliferation, which probably can reflect a protective mechanism of the sebaceous gland basal cells.

Summary Background Various materials have been investigated as possible skin substitutes to repair skin defects such as burns. Because of its unique characteristics, acellular amniotic membrane seems to provide a good scaffold for cell cultures. Aim To investigate the proliferation of fibroblasts on an amniotic membrane scaffold, and the preparation of a temporary skin substitute using this method. Methods Neonatal foreskin tissue was harvested after circumcision and used for isolation of skin fibroblasts. The skin sample was refrigerated in cell-culture solution, and later treated with trypsin, minced, and incubated in the same solution at 37 °C with in an atmosphere of 95% O2/5% CO2. The confluent cultures were treated with trypsin, and fibroblasts were subcultured up to the 10th passage. Cells were tested for microbial contamination, presentation of major histocompatibility complex, and karyotype changes. Amniotic membrane was harvested after elective caesarean section from donors who had been screened for infection. The membrane was washed and then subjected to three freeze–thaw cycles, before having the cells removed. The fibroblasts were seeded onto the scaffold, and after 24 h, the prepared skin substitute was ready. This was examined under electron microscopy. Results The skin substitute showed excellent growth of fibroblasts on the amniotic membrane scaffold. Conclusions Fibroblasts had excellent adherence to and viability on the acellular amniotic membrane, which seems to provide an acceptable temporary skin substitute that can be used for wounds.