Adiponectin is an adipocyte-specific secretory hormone that can increase insulin sensitivity and promote adipocyte differentiation. Administration of adiponectin to obese or diabetic mice reduces plasma glucose and free fatty acid levels. Green tea polyphenols possess many pharmacological activities such as antioxidant, anti-inflammatory, antiobesity, and antidiabetic activities. To investigate whether green tea polyphenols have an effect on the regulation of adiponectin, we measured expression and secretion levels of adiponectin protein after treatment of each green tea polyphenols in 3T3-L1 adipocytes. We found that (−)-catechin enhanced the expression and secretion of adiponectin protein in a dose- and time-dependent manner. Furthermore, treatment of (−)-catechin increased insulin-dependent glucose uptake in differentiated adipocytes and augmented the expression of adipogenic marker genes, including PPARγ, CEBPα, FAS, and SCD-1, when (−)-catechin was treated during adipocyte differentiation. In search of the molecular mechanism responsible for inducible effect of (−)-catechin on adiponectin expression, we found that (−)-catechin markedly suppresses the expression of Kruppel-like factor 7 (KLF7) protein, which has recently been reported to inhibit the expression of adiponectin and other adipogenesis related genes, including leptin, PPARγ, C/EBPα, and aP2 in adipocytes. KLF7 is a transcription factor in adipocyte and plays an important role in the pathogenesis of type 2 diabetes. Taken together, these data suggest that the upregulation of adiponectin protein by (−)-catechin may involve, at least in part, suppression of KLF7 in 3T3-L1 cells.

To develop an anti-obesity agent containing dietary components, we focused on the mechanisms that enhance both lipolysis and fatty acid oxidation. Caffeine and arginine (CA), a nonselective adenosine-receptor antagonist and an inducer of lipolytic hormone, respectively, were used to stimulate lipolysis. Soy isoflavones and L-carnitine (SL), stimulators of carnitine palmitoyl transferase 1A and a cofactor for beta-oxidation of fatty acids, respectively, were used to enhance fatty acid oxidation. Effects of a combination of CA and SL (CASL) on lipid metabolism were studied in vitro and in vivo. During 3T3-L1 differentiation, lipid accumulation was significantly lower in cells treated with CASL (50 micromol/L, 1 mmol/L, 1 micromol/L, and 1 mmol/L, respectively) compared with each alone. Lipolysis was also significantly greater in 3T3-L1 adipocytes treated with CASL (50 micromol/L, 1 mmol/L, 10 micromol/L and 0.5 mmol/L, respectively) compared with each alone. In addition, treatment with higher concentrations of CASL (2 mmol/L, 1 mmol/L, 10 micromol/L, and 1 mmol/L, respectively) significantly enhanced beta-oxidation in HepG2 cells. The effects of CASL-containing diets (250 mg, 6 g, 200 mg, and 1.5 g/kg diet, respectively) were studied in vivo. When KK mice were food deprived for 48 h and subsequently refed a fat-free diet for 72 h, hepatic triglyceride (TG) accumulation was significantly lower in mice fed CASL compared with the control mice. In addition, after obese KK mice were fed a low-fat diet for 2 wk, adipose tissue weights were significantly lower in those fed CASL, but not CA or SL alone, compared with the control mice. Plasma and liver TG levels were also lower in mice fed CASL than in the control mice. These results suggest that CASL is effective for controlling obesity.

Prp19p is an integral component of the heteromeric protein complex (the NineTeen complex) in the nucleus, and it is essential for the structural integrity of NineTeen complex and its subsequent activation of the spliceosome. We identified Prp19p, which has never been reported in relation to any function outside of the nucleus, as a member of proteins associated with lipid droplets. Down-regulation of Prp19p expression with RNA interference in 3T3-L1 cells repressed lipid droplet formation with the reduction in the level of expression of perilipin and S3-12. The levels of expression of SCD1 (stearoyl-CoA desaturase-1), DGAT-1 (acyl-CoA diacylglycerol acyltransferase-1), and glycerol-3-phosphate acyltransferase were also reduced in Prp19p down-regulated cells, and a significant decrease in triglycerides was observed. Unlike perilipin, which is one of the most extensively studied lipid droplet-associated proteins, Prp19p is not essential for cAMP-and hormone-sensitive lipasedependent lipolysis pathways, even though Prp19p is a component of the lipid droplet phospholipid monolayer, and downregulation of Prp19p represses fat accretion significantly. These results suggest that Prp19p or Prp19-interacting proteins during lipid droplet biogenesis in adipocytes may be considered as another class of potential targets for attacking obesity and obesity-related problems.Lipid droplets are subcellular organelles that function as major energy depots by storing neutral lipids, mainly triacylglycerols (1, 2). Therefore, the biogenesis of a lipid droplet is central to whole body energy homeostasis. In addition to their function as energy depots, lipid droplets appear to have important roles in lipid trafficking in adipocytes, cell signaling, and several important human diseases (3-7). It is thus important to understand the mechanism of deposition and mobilization of cellular neutral lipids. Although the mechanisms of lipid droplet biogenesis are still not entirely clear, it is expected that a set of proteins involved in lipid droplet biogenesis could comprise effective targets for the regulation of the whole body energy homeostasis. Lipid droplets are surrounded by a phospholipid monolayer into which many proteins are embedded (8). These surface proteins on adipocyte lipid droplets include structural proteins, such as PAT (perilripin/ADRP/TIP47) family proteins, S3-12, vimentin, and caveolin-1, and enzymes involved in many aspects of lipid metabolism, such as hormone-sensitive lipase (HSL)-, acyl-CoA synthetase-, lanosterol synthase-, CGI-58-, and NAD(P)-dependent steroid dehydrogenase-like protein and members of the Rab family of GTPases. Some of these lipid droplet-associated proteins are reported to play important roles in the functions of the lipid droplets (7, 9 -13).In this study, in order to explore proteins that are involved in lipid droplet biogenesis, we investigated the protein composition of lipid droplets isolated from cultured 3T3-L1 adipocytes, and we identified several more lipid droplet-associated proteins using ...

Ginsenosides, the major active ingredients of ginseng, show a variety of biomedical efficacies such as antiaging and antioxidation. Here, we investigate the protective activity of the ginsenoside F1, an enzymatically modified derivative of ginsenoside Rg1, against ultraviolet-B-induced damage in human HaCaT keratinocytes. Ginsenoside F1 significantly reduced ultraviolet-B-induced cell death and protected HaCaT cells from apoptosis caused by ultraviolet B irradiation. Furthermore, ginsenoside F1 prevented ultraviolet-B-induced cleavage of poly(ADP-ribose) polymerase in HaCaT cells. In search of the molecular mechanism responsible for the antiapoptotic effect of ginsenoside F1, we find that protection from ultraviolet-B-induced apoptosis is tightly correlated with ginsenoside-F1-mediated inhibition of ultraviolet-B-induced downregulation of Bcl-2 and Brn-3a expression.

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Genistein is one of the most abundant isoflavones in soy. The effects of genistein on cholesterol synthesis and fatty acid oxidation have been well documented, but the effect of genistein on fatty acid synthesis remains unclear. Thus, we investigated the effect of genistein on fatty acid synthase (FAS) expressions in HepG2 cells. In HepG2 cells treated with 10 micromol/L genistein, mRNA and protein expressions of FAS, as well as FAS activity, were significantly decreased. The promoter region of FAS contains binding sites for the transcription factor called sterol regulated element binding protein 1 (SREBP-1); SREBP-1 must be processed by site-1 (S1P) and site-2 proteases to be activated. We also investigated the effects of genistein on S1P, SREBP-1 expression, and subsequent SREBP-1 processing by S1P in HepG2 cells. Genistein reduced the expression of S1P and the processing of SREBP-1 but did not change the expression of SREBP-1 mRNA. SREBP-1 is also a transcription factor for lipogenic genes, such as stearoyl coenzyme-A desaturase1 (SCD1), glycerol-3-phosphate acyltransferase (GPAT), and acetyl-CoA carboxylase (ACC)1, and ACC2. Genistein also significantly inhibited the expression of these lipogenic genes. Thus, genistein treatment of HepG2 cells decreased the expression of lipogenic genes such as FAS, SCD1, GPAT, and ACC, which is, at least in part, mediated through the downregulation of S1P expression and subsequent SREBP-1 proteolytic cleavage.

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Genistein and daidzein can up-regulate CPT1A enzyme activity through up-regulation of CPT1A transcription. Co-treatment of L-carnitine and genistein additively increases CPT1A enzyme activity in HepG2 cells. A stable Huh7 cell line transfected with the CPT1A promoter luciferase reporter gene was established and characterized.