Growth-arrested 3T3-L1 preadipocytes rapidly express CCAAT/enhancer-binding protein-␤ (C/EBP␤) upon hormonal induction of differentiation. However, the DNA binding activity of C/EBP␤ is not activated until the cells synchronously reenter S phase during the mitotic clonal expansion (MCE) phase of differentiation. In this period, C/EBP␤ is sequentially phosphorylated by MAPK and glycogen synthase kinase-3␤, inducing C/EBP␤ DNA binding activity and transcription of its target genes. Because the DNA binding activity of C/EBP␤ is further enhanced by oxidation in vitro, we investigated how redox state affects C/EBP␤ DNA binding and MCE during adipogenesis. When 3T3-L1 cells were treated with H 2 O 2 and hormonal stimuli, differentiation was accelerated with increased expression of peroxisome proliferator-activated receptor ␥. Interestingly, cell cycle progression (S to G 2 /M phase) was markedly enhanced by H 2 O 2 , whereas antioxidants caused an S phase arrest during the MCE. H 2 O 2 treatment resulted in the early appearance of a punctate pattern observed by immunofluorescent staining of C/EBP␤, which is a hallmark for C/EBP␤ binding to regulatory elements, whereas a short antioxidant treatment rapidly dispersed the centromeric localization of C/EBP␤. Consistently, reactive oxygen species production was increased during 3T3-L1 differentiation. Our results indicate that redox-induced C/EBP␤ DNA binding activity, along with the dual phosphorylation of C/EBP␤, is required for the MCE and terminal differentiation of adipocytes.

Recently, hepatic peroxisome proliferator-activated receptor (PPAR)γ has been implicated in hepatic lipid accumulation. We found that the C3H mouse strain does not express PPARγ in the liver and, when subject to a high-fat diet, is resistant to hepatic steatosis, compared with C57BL/6 (B6) mice. Adenoviral PPARγ2 injection into B6 and C3H mice caused hepatic steatosis, and microarray analysis demonstrated that hepatic PPARγ2 expression is associated with genes involved in fatty acid transport and the triglyceride synthesis pathway. In particular, hepatic PPARγ2 expression significantly increased the expression of monoacylglycerol O-acyltransferase 1 (MGAT1). Promoter analysis by luciferase assay and electrophoretic mobility shift assay as well as chromatin immunoprecipitation assay revealed that PPARγ2 directly regulates the MGAT1 promoter activity. The MGAT1 overexpression in cultured hepatocytes enhanced triglyceride synthesis without an increase of PPARγ expression. Importantly, knockdown of MGAT1 in the liver significantly reduced hepatic steatosis in 12-wk-old high-fat-fed mice as well as ob/ob mice, accompanied by weight loss and improved glucose tolerance. These results suggest that the MGAT1 pathway induced by hepatic PPARγ is critically important in the development of hepatic steatosis during dietinduced obesity.nonalcoholic fatty liver disease | adenoviral expression | SREBP1c | ChREBP | TLR4

Acute intestinal ischemia is a medical emergency with a high mortality rate, attesting to the need for a better understanding of its pathogenesis and the development of effective therapies. The goal of this study was to delineate the relationships among intracellular and extracellular events in intestinal ischemia/reperfusion (I/R) injury, particularly the formation of reactive oxygen species (ROS), cell membrane instability associated with lipid peroxidation and the innate autoimmune response mediated by natural IgM and complement. A murine model of natural IgM-mediated intestinal I/R was used. Mice overexpressing anti-oxidant enzyme SOD1 were found to have significantly reduced intestinal tissue damage and complete blockage of IgM-mediated complement activation compared with WT controls. To determine if cell membrane instability was an event intermediate between ROS formation and natural IgM-mediated innate autoimmune response, the cell membrane stabilizer (trehalose) was administered to WT mice prior to the induction of intestinal ischemia. Treatment with trehalose significantly protected animals from I/R injury and inhibited IgM-mediated complement activation although it did not prevent membrane lipid peroxidation. These data indicate that in normal mice subjected to I/R injury, intracellular ROS formation is an event upstream of the lipid peroxidation which results in cell membrane instability. The membrane instability leads to an innate autoimmune response by natural IgM and complement. Trehalose, a nontoxic disaccharide tolerated well by animals and humans, has promise as a protective agent for patients with medical conditions related to acute intestinal ischemia.

PLR decreases the amplitude and delays the onset of the reflected aortic pressure wave. This decreases wasted LV pressure energy and workload.