Insulin-like growth factor binding protein 5 (IGFBP5) is expressed in many cell types including osteoblasts and modulates IGF activities. IGFBP5 may affect osteoblasts and bone formation, in part by mechanisms independent of binding IGFs. The highly conserved IGFBP5 proximal promoter within 100 nucleotides of the start of transcription contains functional cis regulatory elements for C/EBP, Myb and AP-2. We report evidence for a functional Nuclear Factor I (NFI) cis element that mediates activation or repression of IGFBP5 transcription by the NFI gene family. All four NFI genes were expressed in human osteoblast cultures and osteosarcoma cell lines. Co-transfection with human IGFBP5 promoter luciferase reporter and murine Nfi expression vectors showed that Nfib was the most active in stimulating transcription. Nfix was less active and Nfia and Nfic were inhibitory. Knockdown of NFIB and NFIC expression using siRNA decreased and increased IGFBP5 expression, respectively. Analysis of IGFBP5 promoter deletion and mutation reporter constructs identified a functional NFI cis element. All four NFI proteins bound the NFI site in electrophoretic mobility shift experiments and NFI-B bound in Chromatin Immunoprecipitation assays. Results suggest that NFI proteins are important regulators of IGFBP5 expression in human osteoblasts and thus in modulating IGFBP5 functions in bone.

To date, therapies to prevent or treat Alzheimer's disease (AD) have largely focused on removing excess aggregation-prone amyloid peptide Aβ from the brain, an approach that has produced disappointing clinical outcomes. An alternative hypothesis proposes that Aβ production and aggregation is a symptom of a larger, systemic disease affecting the regulation of lipids, including cholesterol. In this scenario, lipid dysregulation would likely occur early in the disease process, making it an ideal target for predicting risk of mild cognitive impairment (MCI) to AD conversion. Here, we report that levels of filipin, a fluorescent polyene macrolide widely used as a diagnostic tool for diseases of lipid dysregulation, correlate with cellular damage caused by 27-hydroxycholesterol and with dementia status in human peripheral blood cells. These results provide strong preliminary data suggesting that filipin could be of use in the development of a quick and inexpensive method to measure the risk of AD conversion in patients with MCI, supplementing existing testing strategies that focus on the consequences of Aβ accumulation.