The serum and glucocorticoid-inducible kinase 1 (SGK1) is an inducible kinase the physiological function of which has been characterized primarily in the kidney. Here we show that SGK1 is expressed in white adipose tissue and that its levels are induced in the conversion of preadipocytes into fat cells. Adipocyte differentiation is significantly diminished via small interfering RNA inhibition of endogenous SGK1 expression, whereas ectopic expression of SGK1 in mesenchymal precursor cells promotes adipogenesis. The SGK1-mediated phenotypic effects on differentiation parallel changes in the mRNA levels for critical regulators and markers of adipogenesis, such as peroxisome proliferator-activated receptor gamma, CCAAT enhancer binding protein alpha, and fatty acid binding protein aP2. We demonstrate that SGK1 affects differentiation by direct phosphorylation of Foxo1, thereby changing its cellular localization from the nucleus to the cytosol. In addition we show that SGK1-/- cells are unable to relocalize Foxo1 to the cytosol in response to dexamethasone. Together these results show that SGK1 influences adipocyte differentiation by regulating Foxo1 phosphorylation and reveal a potentially important function for this kinase in the control of fat mass and function.

Zinc finger proteins constitute the largest family of transcription regulators in eukaryotes. These factors are involved in diverse processes in many tissues, including development and differentiation. We report here the characterization of the zinc finger protein ZNF638 as a novel regulator of adipogenesis. ZNF638 is induced early during adipocyte differentiation. Ectopic expression of ZNF638 increases adipogenesis in vitro, whereas its knockdown inhibits differentiation and decreases the expression of adipocyte-specific genes. ZNF638 physically interacts and transcriptionally cooperates with CCAAT/enhancer-binding protein (C/EBP) β and C/EBPδ. This interaction leads to the expression of peroxisome proliferator-activated receptor γ, which is the key regulator of adipocyte differentiation. In summary, ZNF638 is a novel and early regulator of adipogenesis that works as a transcription cofactor of C/EBPs.

Mammalian lipoxygenases (LOXs) are categorized with respect to their positional specificity of arachidonic acid oxygenation. Sitedirected mutagenesis identified sequence determinants for the positional specificity of these enzymes, and a critical amino acid for the stereoselectivity was recently discovered. To search for sequence determinants of murine (12R Lipoxygenases (LOXs)2 form a heterogeneous family of lipid peroxidizing enzymes that catalyze dioxygenation of free and/or esterified polyunsaturated fatty acids to their corresponding hydroperoxy derivatives (1). They are involved in the biosynthesis of eicosanoids (2) such as the pro-inflammatory leukotrienes (3) and anti-inflammatory lipoxins (4), but have also been implicated in cell maturation (5), cancer (6), psoriasis (7), atherogenesis (8), and osteoporosis (9).Mechanistically, the LOX reaction consists of four elementary reactions, the stereochemistry of which is tightly controlled (see Scheme 1): (i) stereoselective hydrogen abstraction from a bisallylic methylene, forming a carbon-centered fatty acid radical; (ii) [ϩ2] or [Ϫ2] rearrangement of the fatty acid radical; (iii) stereospecific insertion of molecular dioxygen, forming an oxygen-centered hydroperoxy radical; and (iv) reduction of the hydroperoxy fatty acid radical to the corresponding anion. Our current understanding of how mammalian LOXs control the stereochemistry of the oxygenation reaction is derived from the x-ray structure of rabbit reticulocyte 15-LOX (10), from extensive mutagenesis studies on various LOX isoforms (11-15), and from experiments with chemically modified fatty acid substrates (16,17). The substrate-binding cleft of the rabbit enzyme is a U-shaped pocket, the bottom of which is defined by a triad of amino acids (Phe 353 , Ile 418 , and Ile 593 ). A simple model for substrate alignment at the active site of this enzyme suggests that polyenoic fatty acids may slide into the substratebinding pocket with their methyl end ahead (12). Molecular modeling (10, 18) and site-directed mutagenesis (12) suggest that the volume of the active site might be important for the positional specificity. This space-related hypothesis was initially opposed by the orientation-based model, which suggests the possibility of an inverse head-to-tail substrate alignment (19,20). However, more recent experimental data suggest that both hypotheses appear to be valid (12,17).Most of the mechanistic studies performed out in the past on the structural basis for the positional specificity of LOXs have been carried out on classical S-LOX isoforms (see Ref. 12 for review), but little is known about the corresponding mechanisms of the more recently discovered R-lipoxygenating enzyme species (21-23). However, during the preparation of this manuscript, a study that also included two R-LOXs was published (24). Multiple amino acid sequence alignments of R-and S-LOXs suggest that the R-lipoxygenating enzymes contain a conserved Gly in the central part of their primary structure. Mutation of Gly 427 to Ala in (...

Phthalates, an endocrine disruptor group, cause oxidative stress (OS) in the placenta. However, no studies have reported OS-related miRNAs induced by phthalates. In the present study, we demonstrate that mono-(2-ethylhexyl) phthalate (MEHP) induces OS responsive miR-17-5p, miR-155-5p, and miR-126-3p in HTR8/SVneo in a dose- and time-dependent manner. Furthermore, MEHP altered the expression of phosphoinositide-3-kinase regulatory subunit 1α, phosphatase and tensin homolog, CDKN2A interacting protein, superoxide dismutase 2, and 3β-hydroxysterol-D24 reductase, which are involved in OS and predicted to be regulated by these miRNAs. Our results suggest that placental exposure to MEHP may result in aberrant miRNA expression leading to pregnancy complications.