Alzheimer's disease (AD) is characterized by progressive neurodegeneration leading to loss of cognitive abilities and ultimately to death. Postmortem investigations revealed decreased expression of cerebral insulin-like growth factor (IGF)-1 receptor (IGF-1R) and insulin receptor substrate (IRS) proteins in patients with AD. To elucidate the role of insulin/IGF-1 signaling in AD, we crossed mice expressing the Swedish mutation of amyloid precursor protein (APP(SW), Tg2576 mice) as a model for AD with mice deficient for either IRS-2, neuronal IGF-1R (nIGF-1R(-/-)), or neuronal insulin receptor (nIR(-/-)), and analyzed survival, glucose, and APP metabolism. In the present study, we show that IRS-2 deficiency in Tg2576 mice completely reverses premature mortality in Tg2576 females and delays beta-amyloid (Abeta) accumulation. Analysis of APP metabolism suggested that delayed Abeta accumulation resulted from decreased APP processing. To delineate the upstream signal responsible for IRS-2-mediated disease protection, we analyzed mice with nIGF-1R or nIR deficiency predominantly in the hippocampus. Interestingly, both male and female nIGF-1R(-/-)Tg2576 mice were protected from premature death in the presence of decreased Abeta accumulation specifically in the hippocampus formation. However, neuronal IR deletion had no influence on lethality of Tg2576 mice. Thus, impaired IGF-1/IRS-2 signaling prevents premature death and delays amyloid accumulation in a model of AD.

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Increasing adipocyte size as well as numbers is important in the development of obesity and type 2 diabetes, with adipocytes being generated from mesenchymal precursor cells. This process includes the determination of mesenchymal stem cells (MSC) into preadipocytes (PA) and the differentiation of PA into mature fat cells. Although the process of differentiation has been highly investigated, the determination in humans is poorly understood. In this study, we compared human MSC and human committed PA on a cellular and molecular level to gain further insights into the regulatory mechanisms in the determination process. Both cell types showed similar morphology and expression patterns of common mesenchymal and hematopoietic surface markers. However, although MSC were able to differentiate into adipocytes and osteocytes, PA were only able to undergo adipogenesis, indicating that PA lost their multipotency during determination. WNT-5a expression showed significantly higher levels in MSC compared with PA suggesting that WNT-5a down-regulation might be important in the determination process. Indeed, incubation of human MSC in medium containing neutralizing WNT-5a antibodies abolished their ability to undergo osteogenesis, although adipogenesis was still possible. An opposite effect was achieved using recombinant WNT-5a protein. On a molecular level, WNT-5a was found to promote c-Jun N-terminal kinase-dependent intracellular signaling in MSC. Activation of this noncanonical pathway resulted in the induction of osteopontin expression further indicating pro-osteogenic effects of WNT-5a. Our data suggest that WNT-5a is necessary to maintain osteogenic potential of MSC and that inhibition of WNT-5a signaling therefore plays a role in their determination into PA in humans.

Generation of new adipocytes plays a major role in the development of obesity. We previously have shown that transcriptional repressor factor that binds to IST (FBI)-1 exerts a dual effect in the process of adipogenesis by inhibiting proliferation and promoting differentiation of preadipocytes. The aim of the present study was to identify FBI-1 regulated molecular effectors that could account for these effects. Overexpressing FBI-1 in preadipocytes resulted in reduced expression of the cell cycle regulator cyclin A, which may explain FBI-1 induced inhibition of proliferation. Interestingly, FBI-1 repressed cyclin A promoter activity through an indirect mechanisms that did not involve direct binding of FBI-1 to the promoter sequence, but rather FBI-1 inhibition of transcriptional activator Sp1 binding to a regulatory element at -452 to -443. We also show that FBI-1 promotes terminal preadipocyte differentiation through a mechanism involving decreased levels of expression of the PPARgamma inhibitor E2F-4. FBI-1 significantly reduced E2F-4 promoter activity. Contrary to cyclin A, we found FBI-1-induced repression of E2F-4 is mediated by a direct mechanism via a FBI-1 regulatory element at -11 to -5. As function of transcriptional repressors normally depends on the presence of regulatory co-factors we also performed expression profiling of potential FBI-1 co-repressors throughout adipogenesis. In these experiments Sin3A and histon deacetylase (HDAC)-1 showed a similar expression pattern compared to FBI-1. Strikingly, co-immunoprecipitation studies revealed that FBI-1 binds Sin3A and HDAC-1 to form a repressor complex. Furthermore, by mutational analysis the amino terminal Poxvirus (POZ) domain of FBI-1 was found to be important for Sin3A and HDAC-1 binding. Taken together, FBI-1 is the first transcriptional repressor shown to act as a dual regulator in adipogenesis exerting repressor activities on target genes by both, direct and indirect mechanisms.

Insulin‐like growth factor (IGF)‐1 increases proliferation, inhibits apoptosis and promotes differentiation of oligodendrocytes and their precursor cells, indicating an important function for IGF‐1 receptor (IGF‐1R) signaling in myelin development. The insulin receptor substrates (IRS), IRS‐1 and ‐2 serve as intracellular IGF‐1R adaptor proteins and are expressed in neurons, oligodendrocytes and their precursors. To address the role of IRS‐2 in myelination, we analyzed myelination in IRS‐2 deficient (IRS‐2−/−) mice and age‐matched controls during postnatal development. Interestingly, expression of the most abundant myelin proteins, myelin basic protein and proteolipid protein was reduced in IRS‐2−/− brains at postnatal day 10 (P10) as compared to controls. myelin basic protein immunostaining in P10‐IRS‐2−/− mice revealed a reduced immunostaining, but an unchanged regional distribution pattern. In cerebral myelin isolates at P10 unaltered relative expression of different myelin proteins was found, indicating quantitatively reduced but not qualitatively altered myelination. Interestingly, up‐regulation of IRS‐1 expression and increased IGF‐1R signaling were observed in IRS‐2−/− mice at P10‐14, indicating a compensatory mechanism to overcome IRS‐2 deficiency. Adult IRS‐2−/− mice showed unaltered myelination and motor function. Furthermore, in neuronal/brain‐specific insulin receptor knockout mice myelination was unchanged. Thus, our experiments reveal that IGF‐1R/IRS‐2 mediated signals are critical for appropriate timing of myelination in vivo.

In brains from patients with Alzheimer's disease (AD), expression of insulin receptor (IR), insulin-like growth factor-1 receptor (IGF-1R), and insulin receptor substrate proteins is downregulated. A key step in the pathogenesis of AD is the accumulation of amyloid precursor protein (APP) cleavage products, β-amyloid (Aβ)

There are two principal cyclooxygenase isoforms referred to as COX-1 and COX-2. Recently, COX-3 has been identified. We have demonstrated the expression of COX-2 in platelets from patients after coronary artery bypass grafting (CABG). Careful biochemical analysis revealed that, when compared to recombinant COX-2, platelet COX-2 had a slightly higher electrophoretic mobility. Two COX-2 sequences (approximately 1.8 kb, approximately 1.7 kb) were cloned from platelet mRNA. The approximately 1.7 kb sequence, designated COX-2a, differed from the human COX-2 sequence only in a deletion from position +458 to +567. Similar to the human COX-3, there is a frame shift in the COX-2a sequence resulting in a TAA stop codon at position +490. Thus, the expression of a COX-2a protein corresponding to the 67 kDa COX-2 protein is not clear. However, the marked shifting from COX-2 to COX-2a in platelets from some patients after CABG is a striking finding.

Recent studies suggest that the perinatal period is a sensitive part in human development with respect to the pathogenesis of metabolic diseases in adulthood. Neonates, who are either small or large for gestational age (SGA or LGA) have a greater risk of developing obesity and insulin resistance in later life. The term "perinatal priming" is used to describe this phenomenon. Therefore, in the present study we first aimed to investigate if birth weight influences fetal adiponectin and RBP-4 metabolism. Umbilical cord blood was obtained form 40 neonates born on term+/-4 weeks and the adipokine concentrations in the serum were measured. In this analysis adiponectin but not RBP-4 levels showed a positive significant correlation to birth weight. Since maternal preconceptional obesity is associated with an increased birth weight and the risk for LGA neonates, we further aimed to investigate, if the maternal nutritional state influences fetal adiponectin and RBP-4. Therefore umbilical cord blood levels of the adipokines were correlated to maternal preconceptional BMI. In this analysis, neither adiponectin nor RBP-4 levels showed a significant correlation. Taken together, in the present study for the first time we directly compare fetal adiponectin and RBP-4 levels in respect to birth weight and maternal preconceptional BMI. Our data suggest that (1) adiponectin is more likely to have a role in perinatal priming of obesity and insulin resistance than RBP-4 and (2) that birth weight has a greater impact on fetal adipokine serum levels than maternal preconceptional obesity.