Upregulation of the thioredoxin-dependent redox system during differentiation of 3T3-L1 cells to adipocytes.

Hydrogen peroxide acts as a signaling molecule in early adipogenesis. In differentiating adipocytes, elevated hydrogen peroxide generation is balanced through induction of antioxidant enzymes such as catalase and peroxiredoxins. Thioredoxin reductases (TrxR) and glutathione peroxidases (GPx) are selenoenzymes that constitute part of the major thiol-dependent antioxidant systems in cells.

Cross-talk between NR4A orphan nuclear receptors and β-catenin signaling pathway in osteoblasts.

The canonical Wnt signaling pathway and its key mediator β-catenin are important regulators of osteoblast function. NR4A orphan nuclear receptors (Nurr1, NGFI-B, and Nor1) are expressed in osteoblasts and have been shown to regulate the expression of osteoblastic genes and osteoblastic differentiation. Recently, interplay between Nurr1 and the canonical Wnt signaling pathway was reported in 293F cells.

Transcriptional activity of estrogen-related receptor γ (ERRγ) is stimulated by the phytoestrogen equol.

Estrogen-related receptor γ (ERRγ) is an orphan nuclear receptor lacking identified natural ligands. The synthetic estrogen receptor ligands 4-hydroxytamoxifen and diethylstilbestrol have, however, been shown to bind to and abolish the constitutive transcriptional activity of ERRγ. Certain phytoestrogens were recently reported to act as agonists of the related ERRα.

ERRalpha regulates osteoblastic and adipogenic differentiation of mouse bone marrow mesenchymal stem cells.

The orphan nuclear receptor estrogen-related receptor-alpha (ERRalpha) has been reported to have both a positive and a negative regulatory role in osteoblastic and adipocytic differentiation. We have studied the role of ERRalpha in osteoblastic and adipogenic differentiation of mesenchymal stem cells. Bone marrow mesenchymal stem cells were isolated from ERRalpha deficient mice and their differentiation capacities were compared to that of the wild-type cells.

Cross-talk between the NR3B and NR4A families of orphan nuclear receptors.

Estrogen-related receptors (NR3B family) and Nurr1, NGFI-B, and Nor1 (NR4A family) are orphan nuclear receptors lacking identified natural ligands. The mechanisms regulating their transcriptional activities have remained elusive. We have previously observed that the members of NR3B and NR4A families are coexpressed in certain cell types such as osteoblasts and that the ability of Nurr1 to transactivate the osteopontin promoter is repressed by ERRs.