Effects of Fermented Extracts of Wuniuzao Dark Loose Tea on Hepatic Sterol Regulatory Element-Binding Protein Pathway and Gut Microbiota Disorder in Obese Mice.

BACKGROUND: Artificially fermented dark loose tea is a type of novel dark tea prepared via fermentation by Eurotium cristatum. The effects of artificially fermented dark loose tea on lipid metabolism are still unclear. OBJECTIVES: This study aimed to explore if artificially fermented dark loose tea has the same effects as naturally fermented dark loose tea in regulating hepatic lipid metabolism. METHODS: Thirty-six 8-wk-old male C57BL/6 mice were randomly divided into 6 treatment groups, including normal control (NC), high-fat diet (HFD), positive control (PC), Wuniuzao dark raw tea (WDT), Wuniuzao naturally fermented dark loose tea (NFLT), and Wuniuzao artificially fermented dark loose tea (AFLT) groups. The HFD, PC, WDT, NFLT, and AFLT groups were fed a HFD. The PC group was supplemented with atorvastatin (10 mg/kg). The WDT group was supplemented with WDT (300 mg/kg), the NFLT group with NFLT (300 mg/kg), and the AFLT group with AFLT (300 mg/kg). RESULTS: The study compared the effect of WDT, NFLT, and AFLT on liver steatosis and gut microbiota disorder in obese mice. All 3 tea extracts reduced body weight, glucose tolerance, and serum lipid concentrations. Via sterol-regulatory element binding protein (SREBP)-mediated lipid metabolism, all 3 tea extracts alleviated hepatic steatosis in mice with obesity. Furthermore, NFLT and AFLT intervened in the abundance of Firmicutes, Bacteroidetes, Clostridia, Muribaculaceae, and Lachnospiraceae. CONCLUSION: In mice with obesity induced by a HFD, WDT, NFLT, and AFLT may improve hepatic steatosis through an SREBP-mediated lipid metabolism. Moreover, NFLT and AFLT improved the composition of gut microbiota.

Isoquercitrin from Apocynum venetum L. produces an anti-obesity effect on obese mice by targeting C-1-tetrahydrofolate synthase, carbonyl reductase, and glutathione S-transferase P and modification of the AMPK/SREBP-1c/FAS/CD36 signaling pathway in mice in vivo.

In the present study, mice with high-fat-diet-induced obesity were used in investigating the anti-obesity effects of an aqueous extract and isoquercitrin from Apocynum venetum L. The aqueous extract and the signal molecule isoquercitrin significantly reduced the body weight gain, food intake, water consumption, and fasting blood glucose, plasma triglyceride and total cholesterol levels of the obese mice. Furthermore, the mechanism of action of isoquercitrin was explored through RT-PCR analyses and uptake experiments of adenosine 5'-monophosphate-activated protein kinase (AMPK) and sterol regulatory-element binding protein (SREBP-1c) inhibitors and glucose. The indexes of SREBP-1c, fatty acid synthase (FAS), stearoyl-CoA desaturase-1 (SCD), and cluster of differentiation 36 (CD36) in obese mice significantly increased but returned to normal levels after the administration of isoquercitrin. Meanwhile, the anti-obesity effect of isoquercitrin was diminished by the inhibitors of AMPK and SREBP-1c. In addition, intestinal glucose uptake in normal mice was significantly inhibited after the oral administration of isoquercitrin. Moreover, 2D gel electrophoresis based proteome-wide cellular thermal shift assay (CETSA) showed that the potential target proteins of isoquercitrin were C-1-tetrahydrofolate synthase, carbonyl reductase, and glutathione S-transferase P. These results suggested that isoquercitrin produces an anti-obesity effect by targeting the above-mentioned proteins and regulating the AMPK/SREBP-1c signaling pathway and potentially prevents obesity and obesity-related metabolic disorders.

The effect of simvastatin on gene expression of low-density lipoprotein receptor, sterol regulatory element-binding proteins, stearoyl-CoA desaturase 1 mRNA in rat hepatic tissues.

The study aimed to assess the effect of simvastatin on gene expression of LDLR, SREBPs, and SCD1 in rat hepatic tissues fed with high-fat diets (HFD) and its association with some biochemical parameters. Thirty-two male Wister albino rats were divided into four equal groups (three test and one control groups). The biochemical parameters were determined by using spectrophotometer techniques and the Elisa method. Low-density lipoprotein receptor, sterol regulatory element-binding proteins, stearoyl-CoA desaturase1, Beta-actin were analysed by real-time quantitative polymerase chain reaction (RT-PCR) method. At the end of study, the livers of the rats were separated and changes of hepatic tissue were determined. LDLR, SREBP2, and SCD1 expression increased significantly when compared G1 versus G4 and G2 versus G4. The expression of LDLR, SREBP2, and SCD1 also increased significantly when compared G2 versus G3, G1versus G3 and G1 versus G3 and G2 versus G3. The serum level of cholesterol, triglyceride, glucose, LDL, and HDL increased significantly when compared G1 versus G3. LDL showed significantly decreased when compared G1 versus G2. Cholesterol, glucose and HDL and triglyceride levels were increased significantly when compared G1 versus G4 and G2. Treatment of rats with HFD and simvastatin 20 mg/kg, triglyceride and LDL were almost the same as a control group and LDLR expression increased 98% in liver tissue. Gene expressions may be up-regulated in liver tissue and they showed different effects on biochemical parameters.

[Effects of chrysophanol on expression of SREBPs and lipid metabolism in Huh-7 cells].

Rhubarb is a traditional Chinese medicines which possess laxative, lipid-lowering, and weight-loss activities, but the active compounds of lipid-lowering and underlying molecular mechanisms are not yet clear. This study aims to explore the effects of chrysophanol on the mRNA expressions of sterol regulatory element-binding proteins (SREBPs) and lipid metabolism in human liver carcinoma Huh-7 cells, which is one of the active compounds obtained from Rhubarb. A reporter gene assay was used to test the transcription of SREBP. The intracellular triglyceride and total cholesterol contents were measured by using commercially available test kits. The SREBPs target genes expressions were measured by Quantitative Real-Time PCR. Cell viability was evaluated by Cell Counting Kit-8. As the results shown, chrysophanol (40 µmol · L(-1), 16 h) could notably inhibited human SRE promoter activity in a dose-dependent manner and decrease intracellular cholesterol and triglyceride levels. Furthermore, the mRNA expressions of SREBPs target genes were significantly downregulated by chrysophanol treatment. However there are no significant differences on cell viability when compared with the control group. These results suggested that chrysophanol might improve lipid metabolism through suppressing the mRNA expressions of SREBPs target genes to attenuate intracellular lipid accumulation.

Cholesterol supply and SREBPs modulate transcription of the Niemann-Pick C-1 gene in steroidogenic tissues.

We tested whether sterol-regulatory element binding proteins (SREBPs) mediate sterol-regulated transactivation of the Niemann-Pick C-1 (NPC-1) gene. Loading granulosa cells with 22- or 25-hydroxycholesterol decreased NPC-1 mRNA, whereas culturing in cholesterol-depleted medium or inhibition of cholesterol biosynthesis increased NPC-1 promoter activity and NPC-1 mRNA abundance. Cotransfection of SREBP1a, SREBP1c, and SREBP2 and the NPC-1 promoter-luciferase reporter into granulosa cell lines increased the transcriptional activity of porcine, human, and mouse NPC-1 promoters. Deletion analysis of the 5' flanking region of the pig NPC-1 gene demonstrated significant promoter activity between fragments -934 and -636 bp upstream from the transcription initiation site. Sequence analysis revealed three sterol-regulatory elements (SREs) clustered between -558 and -650 bp. Each site, along with E-box sequences, bound recombinant SREBP in electromobility shift assays. Mutation of all three sites attenuated the SREBP induction of promoter activity. Chromatin immunoprecipitation (ChIP) assays revealed that cholesterol depletion enriched the association of both SREBP and acetylated histone H3 with the NPC-1 promoter fragment containing the three SREs. ChIP analysis confirmed that SREBP's association with SRE and the E-box was enriched in cells cultured in cholesterol-depleted medium. We conclude that NPC-1 is sterol-regulated, achieved by SREBP acting via SRE and the E-box sequences.

Inhibition of betaine-homocysteine S-methyltransferase causes hyperhomocysteinemia in mice.

Inhibitors and methyl donor substrates for betaine-homocysteine S-methyltransferase (BHMT) were used to study the role of this enzyme in the regulation of plasma total homocysteine (tHcy). Mice were administered an i.p. injection of S-(delta-carboxybutyl)-dl-homocysteine (CBHcy; 1 mg), a specific and potent inhibitor of BHMT, and tHcy and hepatic BHMT protein and activity levels were monitored over a 24-h period. Compared with saline-injected control mice, at 2 h postinjection, the CBHcy-treated mice had 87% lower BHMT activity and a 2.7-fold increase (11.1 vs. 3.0 micromol/L) in tHcy, effects that lasted nearly 8 h but returned to normal by 24 h. The level of BHMT protein remained constant over the 24-h period. After 6 CBHcy (1 mg) injections (one every 12 h), the mice had 7-fold higher tHcy, a 65% reduction in the liver S-adenosylmethionine:S-adenosylhomocysteine ratio, and a marked upregulation of BHMT protein expression. At 2 h after injection of the sulfoxide derivative of CBHcy (10 mg) into mice, there was a modest reduction in BHMT activity and a 90% increase in tHcy. When given an injection of Met (3 mg) or Met plus CBHcy (1 mg), post-Met load tHcy levels were 2.2-fold higher (128 vs. 40 micromol/L) at 2 h postinjection in the mice given CBHcy. Like betaine, dimethylsulfoniopropionate was an effective tHcy-lowering agent when given with a Met load. These studies are the first to show that transient inhibition of BHMT in vivo causes transient hyperhomocysteinemia, and that dimethylsulfoniopropionate can reduce a post-Met load rise in tHcy.