Prdm4 induction by the small molecule butein promotes white adipose tissue browning.

Increasing the thermogenic activity of adipocytes holds promise as an approach to combating human obesity and related metabolic diseases. We identified induction of mouse PR domain containing 4 (Prdm4) by the small molecule butein as a means to induce expression of uncoupling protein 1 (Ucp1), increase energy expenditure, and stimulate the generation of thermogenic adipocytes. This study highlights a Prdm4-dependent pathway, modulated by small molecules, that stimulates browning of white adipose tissue.

Antiadipogenic and proosteogenic effects of luteolin, a major dietary flavone, are mediated by the induction of DnaJ (Hsp40) Homolog, Subfamily B, Member 1.

Luteolin (3,4,5,7-tetrahydroxyflavones), a major dietary flavone, regulates a variety of biological effects including cancer progression, insulin resistance and inflammation. However, its exact actions on adipogenesis and osteogenesis and the underlying molecular mechanisms are yet to be clarified. In this study, we show that luteolin suppresses lipid accumulation but increases osteoblast differentiation. In mechanism studies, luteolin increases the expression of the heat shock proteins (Hsp) 40 (Dnajb1) and Hsp90 (Hsp90b1), but not those of other heat shock proteins including Hsp20, Hsp27, Hsp47, Hsp70, Hsp72, and Hsp90, and another type of Hsp40 (Dnaja1). Silencing Dnajb1 by using small interfering RNAs (siRNAs), but not against Hsp90b1, recapitulates the effects of luteolin in adipocyte and osteoblast differentiation. Consistently, the forced expression of Dnajb1 decreases the lipid accumulation and stimulates alkaline phosphatase (ALPL) activity. The antiadipogenic and proosteogenic effects of luteolin are significantly blunted in Dnajb1-deficient cells, further suggesting that Dnajb1 is, at least in part, required for luteolin's dual actions in adipogenesis and osteogenesis. Together, our data implicate luteolin as an ingredient and Dnajb1 as a molecular target for the development of functional foods and drugs in metabolic and bone-related diseases.

Notch1 deficiency decreases hepatic lipid accumulation by induction of fatty acid oxidation.

Notch signaling pathways modulate various cellular processes, including cell proliferation, differentiation, adhesion, and communication. Recent studies have demonstrated that Notch1 signaling also regulates hepatic glucose production and lipid synthesis. However, the effect of Notch1 signaling on hepatic lipid oxidation has not yet been directly investigated. To define the function of Notch1 signaling in hepatic lipid metabolism, wild type mice and Notch1 deficient antisense transgenic (NAS) mice were fed a high-fat diet. High-fat diet -fed NAS mice exhibited a marked reduction in hepatic triacylglycerol accumulation compared with wild type obese mice. The improved fatty liver was associated with an increased expression of hepatic genes involved in fatty acid oxidation. However, lipogenic genes were not differentially expressed in the NAS liver, suggesting lipolytic-specific regulatory effects by Notch1 signaling. Expression of fatty acid oxidative genes and the rate of fatty acid oxidation were also increased by inhibition of Notch1 signaling in HepG2 cells. In addition, similar regulatory effects on lipid accumulation were observed in adipocytes. Taken together, these data show that inhibition of Notch1 signaling can regulate the expression of fatty acid oxidation genes and may provide therapeutic strategies in obesity-induced hepatic steatosis.

Sulfuretin induces osteoblast differentiation through activation of TGF-ß signaling.

The identification and examination of potential determinants controlling the progression of cell fate toward osteoblasts can be intriguing subjects. In this study, the effects of sulfuretin, a major compound isolated from Rhus verniciflua Stokes, on osteoblast differentiation were investigated. Treatments of sulfuretin induced alkaline phosphatase (ALP) activity in mesenchymal C3H10T1/2 cells and mineralization in preosteoblast MC3T3-E1 cells. Pro-osteogenic effects of sulfuretin were consistently observed in freshly isolated primary bone marrow cells. In mechanical studies, sulfuretin specifically induced expression of TGF-ß target genes, such as SMAD7 and PAI-1, but not other signaling pathway-related genes. Similar to the results of gene expression analysis, reporter assays further demonstrated TGF-ß-specific induction by sulfuretin. Furthermore, disruption of TGF-ß signaling using treatment with TGF-ß-specific inhibitor, SB-431542, and introduction of SMAD2/3 small interfering RNA impaired the effects of sulfuretin in inducing ALP activity and expression of ALP mRNA. Together, these data indicate that the pro-osteogenic effects of sulfuretin are mediated through activation of TGF-ß signaling, further supporting the potential of sulfuretin in the prevention of bone-related diseases such as bone fracture and osteoporosis.

miR-195a inhibits adipocyte differentiation by targeting the preadipogenic determinator Zfp423.

MicroRNAs (miRNAs) play essential roles in various cellular processes including proliferation and differentiation. In this study, we identified miRNA-195a (miR-195a) as a regulator of adipocyte differentiation. Differential expression of miR-195a in preadipocytes and adipocytes suggests its role in lipid accumulation and adipocyte differentiation. Forced expression of miR-195a mimics suppressed lipid accumulation and inhibited expression of adipocyte markers such as PPARγ and aP2 in 3T3-L1 and C3H10T1/2 cells. Conversely, downregulation of miR-195a by anti-miR-195a increased lipid accumulation and expression of adipocyte markers. Target prediction analysis suggested zinc finger protein 423 (Zfp423), a preadipogenic determinator, as a potential gene recognized by miR-195a. In line with this, mimicked expression of miR-195a reduced the expression of Zfp423, whereas anti-miR-195a increased its expression. Predicted targeting sequences in Zfp423 3'UTR, but not mutated sequences fused to luciferase, were regulated by miR-195a. Ectopic Zfp423 expression in 3T3-L1 cells increased lipid accumulation and expression of adipocyte markers, consistent with the observation that miR-195a targets Zfp423, resulting in suppressed adipocyte differentiation. In addition, miR-195a and Zfp423 were inversely correlated in obese fat tissues, raising the possibility of miRNA's role in obesity. Together, our data show that miR-195a is an anti-adipogenic regulator, which acts by targeting Zfp423, and further suggest the roles of miR-195a in obesity and metabolic diseases.