Fatostatin reverses progesterone resistance by inhibiting the SREBP1-NF-κB pathway in endometrial carcinoma.

Progesterone resistance can significantly restrict the efficacy of conservative treatment for patients with endometrial cancer who wish to preserve their fertility or those who suffer from advanced and recurrent cancer. SREBP1 is known to be involved in the occurrence and progression of endometrial cancer, although the precise mechanism involved remains unclear. In the present study, we carried out microarray analysis in progesterone-sensitive and progesterone-resistant cell lines and demonstrated that SREBP1 is related to progesterone resistance. Furthermore, we verified that SREBP1 is over-expressed in both drug-resistant tissues and cells. Functional studies further demonstrated that the inhibition of SREBP1 restored the sensitivity of endometrial cancer to progesterone both in vitro and in vivo, and that the over-expression of SREBP1 promoted resistance to progesterone. With regards to the mechanism involved, we found that SREBP1 promoted the proliferation of endometrial cancer cells and inhibited their apoptosis by activating the NF-κB pathway. To solve the problem of clinical application, we found that Fatostatin, an inhibitor of SREBP1, could increase the sensitivity of endometrial cancer to progesterone and reverse progesterone resistance by inhibiting SREBP1 both in vitro and in vivo. Our results highlight the important role of SREBP1 in progesterone resistance and suggest that the use of Fatostatin to target SREBP1 may represent a new method to solve progesterone resistance in patients with endometrial cancer.

Effects of dietary carbohydrate sources on lipid metabolism and SUMOylation modification in the liver tissues of yellow catfish.

Dysregulation in hepatic lipid synthesis by excess dietary carbohydrate intake is often relevant with the occurrence of fatty liver; therefore, the thorough understanding of the regulation of lipid deposition and metabolism seems crucial to search for potential regulatory targets. In the present study, we examined TAG accumulation, lipid metabolism-related gene expression, the enzyme activities of lipogenesis-related enzymes, the protein levels of transcription factors or genes involving lipogenesis in the livers of yellow catfish fed five dietary carbohydrate sources, such as glucose, maize starch, sucrose, potato starch and dextrin, respectively. Generally speaking, compared with other carbohydrate sources, dietary glucose promoted TAG accumulation, up-regulated lipogenic enzyme activities and gene expressions, and down-regulated mRNA expression of genes involved in lipolysis and small ubiquitin-related modifier (SUMO) modification pathways. Further studies found that sterol regulatory element binding protein 1 (SREBP1), a key transcriptional factor relevant to lipogenic regulation, was modified by SUMO1. Mutational analyses found two important sites for SUMOylation modification (K254R and K264R) in SREBP1. Mutant SREBP lacking lysine 264 up-regulated the transactivation capacity on an SREBP-responsive promoter. Glucose reduced the SUMOylation level of SREBP1 and promoted the protein expression of SREBP1 and its target gene stearoyl-CoA desaturase 1 (SCD1), indicating that SUMOylation of SREBP1 mediated glucose-induced hepatic lipid metabolism. Our study elucidated the molecular mechanism of dietary glucose increasing hepatic lipid deposition and found that the SREBP-dependent transactivation was regulated by SUMO1 modification, which served as a new target for the transcriptional programmes governing lipid metabolism.

Molecular Study on the Potential Protective Effects of Bee Venom against Fructose-Induced Nonalcoholic Steatohepatitis in Rats.

BACKGROUND: There is a causative relation between the increased hepatic steatohepatitis prevalence and sweeteners intake, fructose in particular. Despite an increasing understanding of the mechanisms of nonalcoholic steatohepatitis (NASH) pathogenesis, there are no drugs approved for it. OBJECTIVES: Evaluate the effect of bee venom (BV) treatment on the fructose-induced NASH in rats and demonstrate its possible molecular mechanisms. METHODS: NASH was induced in rats by 10% fructose in drinking water for 8 weeks. BV was administered (0.1 mg/kg, i.p.) 3 times per week during the last 2 weeks of the experiment. Sera were used for the determination of lipids, cholesterol, glucose, insulin, and liver enzymes. Hepatic gene expressions of farnesoid X receptor (FXR)α and the liver X receptor (LXR) were determined. Hepatic sterol regulatory element-binding protein (SREBP)1/2, oxidative stress, and inflammation parameters were measured. Liver parts were used for histopathological examination. Small intestine was removed for the determination of tight junction proteins. RESULTS: Fructose caused overt histological damage in the liver, and this was associated with parallel changes in all parameters measured. BV effectively prevented these changes, presumably through amelioration of hepatic SREBP1/2, LXR, and FXRα expression as well as intestinal tight junction proteins. CONCLUSION: These findings support the therapeutic usefulness of BV, a remedy with a favorable safety profile, in the prevention of fructose-induced NASH.

Baicalein reduces hepatic fat accumulation by activating AMPK in oleic acid-induced HepG2 cells and high-fat diet-induced non-insulin-resistant mice.

Nonalcoholic fatty liver disease (NAFLD) has become the most common liver disease worldwide; thus, a dietary supplement that can restrict hepatic fat accumulation is needed. Baicalein, a major component of Scutellaria baicalensis, is used as a dietary supplement in Eastern and Western cultures and can reduce hepatic fat accumulation. However, the detailed mechanism by which baicalein exerts this effect has yet to be elucidated in vivo and in vitro. In this study, we characterized the hepatic fat-lowering activity of baicalein and found that baicalein reduced hepatic fat accumulation by activating AMPK and suppressing SREBP1 cleavage, thus consequently inhibiting the transcriptional activity of SREBP1 and the synthesis of hepatic fat in oleic acid-induced HepG2 cells and high-fat diet-induced non-insulin-resistant mice. Moreover, baicalein improved NAFLD by decreasing TC, increasing HDLC, decreasing LDLC, affecting antioxidant activity, and exerting other effects. Therefore, the mechanism of baicalein with regard to NAFLD prevention and treatment might involve effects on multiple targets and pathways. Our study supports the use of baicalein as a dietary supplement due to its ability to reduce hepatic fat accumulation and to ameliorate NAFLD-related biochemical abnormalities.

Therapeutic effects of dimethyldiguanide combined with clomifene citrate in the treatment of polycystic ovary syndrome.

OBJECTIVE: In view of the high incidence of polycystic ovary syndrome (PCOS) and the unsatisfactory therapeutic effects of dimethyldiguanide or clomifene citrate alone, our study aimed to investigate the therapeutic effects of dimethyldiguanide combined with clomifene citrate in the treatment of PCOS. METHODS: A total of 79 patients with POCS and 35 healthy females were included, and endometrial biopsies were obtained. The sterol regulatory element-binding protein-1 (SREBP1) expression in endometrial tissues was detected by qRT-PCR. POC patients were randomly divided into group A (n=40) and group B (n=39). Patients in group A were treated with dimethyldiguanide combined with clomifene citrate, while patients in group B were treated with clomifene citrate alone. The number of mature follicles and cervical mucus score, follicular development rate and single follicle ovulation rate, cycle pregnancy rate, early miscarriage rate, ovulation rate, endometrial thickness, positive rate of three lines sign, follicle stimulating hormone level and luteinizing hormone level were compared between the two groups. RESULTS: The expression level of SREBP1 was higher in PCOS patients than that in the healthy control. SREBP1 expression was inhibited after treatment, while the inhibitory effects of combined treatment were stronger than those of clomifene citrate alone. Compared with clomifene citrate alone, the combined treatment improved cervical mucus score, follicle development rate, single follicle ovulation rate, endometrial thickness, positive rate of three lines sign, and follicle-stimulating hormone level. CONCLUSION: The therapeutic effect of combined treatment is better than clomifene citrate alone in the treatment of PCOS.

[Comparison of effects of oleic acid and palmitic acid on lipid deposition and mTOR / S6K1 / SREBP-1c pathway in HepG2 cells].

Objective: To explore the effects of oleic acid and palmitic acid on lipid deposition and mTOR/S6K1/SREBP-1c pathways in HepG2 cells. Methods: The model of steatosis was established with induction of oleic acid and palmitic acid and was intervened by rapamycin. The changes in lipid droplets were observed after staining the cells with oil Red O. Intracellular triglyceride (TG) contents in cells were measured by TG kit. mTOR, S6K1, and SREBP-1c mRNA expression levels were detected using QRT-PCR. Western blot was used to determine protein expression levels of mTOR, S6K1 and SREBP-1c. Results: Both fatty acids increased lipid droplets in HepG2 cells. Fatty degeneration with elevated TG occurred with significant changes in oleic acid group lipids. Rapamycin alleviated lipid deposition caused by oleic acid and palmitic acid and inhibited their induction of increased expression of mTOR, S6K1, and SREBP-1c. QRT-PCR and Western blot results showed that mRNA and protein expressions of mTOR, S6K1, and SREBP-1c in oleic acid and palmitic acid group were significantly higher than the control group (P < 0.05). The increase was more pronounced in the palmitic acid group (P < 0.05); however, after rapamycin intervention, the expression of mRNA and protein in the three groups were significantly lower (P < 0.05), and the change in palmitic acid group was more pronounced (P < 0.05). Conclusion: Oleic acid and palmitic acid can induce lipid deposition in HepG2 cells and increase expression of every component of mTOR/S6K1/SREBP-1c pathway; however, Oleic acid-induced lipid deposition is more pronounced, and the mTOR, S6K1, and SREBP-1c pathway change is more obvious in palmitic acid. Rapamycin has high potent inhibitory effect on palmitic acid-induced lipid deposition. These results specify that lipid synthesis involved in the mTOR/S6K1/SREBP-1c pathways are mainly associated to palmitic acid in HepG2 cells, whereas other signaling pathway may mediate oleic acid-induced lipid synthesis.

Ethanol extracts of Aster yomena (Kitam.) Honda inhibit adipogenesis through the activation of the AMPK signaling pathway in 3T3-L1 preadipocytes.

The leaves of Aster yomena (Kitam.) Honda have long been used as a traditional herb for treating disorders including coughs, asthma, and insect bites. According to recent studies, A. yomena leaf extracts have several pharmacological properties, including anti-inflammatory, antioxidant, and anti-asthmatic activities. However, little information is available regarding their anti-obesity effect. In this study, we investigated the inhibitory effect of the ethanol extracts of A. yomena leaves (EEAY) on adipocyte differentiation and adipogenesis using 3T3-L1 preadipocytes. When 3T3-L1 preadipocytes were treated with various concentrations of EEAY (ranging from non-toxic), the number of lipid droplets, lipid content, and triglyceride production, the typical characteristics of adipocytes, were suppressed in a concentration-dependent manner. During this process, EEAY significantly reduced the expression of adipogenic transcription factors, including peroxisome proliferator-activated receptor-γ, CCAAT/enhancer-binding protein α and ß, and sterol regulatory element-binding protein-1c. In addition, EEAY was also found to potently inhibit the expression of adipocyte-specific genes, including adipocyte fatty acid-binding protein and leptin. In particular, EEAY treatment effectively enhanced the activation of the AMP-activated protein kinase (AMPK) signaling pathway; however, the co-treatment with compound C, an inhibitor of AMPK, significantly restored the EEAY-induced inhibition of pro-adipogenic transcription factors and adipocyte-specific genes. These results indicate that EEAY may exert an anti-obesity effect by controlling the AMPK signaling pathway, suggesting that the leaf extract of A. yomena may be a potential anti-obesity agent.

Silybin counteracts lipid excess and oxidative stress in cultured steatotic hepatic cells.

AIM: To investigate in vitro the therapeutic effect and mechanisms of silybin in a cellular model of hepatic steatosis. METHODS: Rat hepatoma FaO cells were loaded with lipids by exposure to 0.75 mmol/L oleate/palmitate for 3 h to mimic liver steatosis. Then, the steatotic cells were incubated for 24 h with different concentrations (25 to 100 µmol/L) of silybin as phytosome complex with vitamin E. The effects of silybin on lipid accumulation and metabolism, and on indices of oxidative stress were evaluated by absorption and fluorescence microscopy, quantitative real-time PCR, Western blot, spectrophotometric and fluorimetric assays. RESULTS: Lipid-loading resulted in intracellular triglyceride (TG) accumulation inside lipid droplets, whose number and size increased. TG accumulation was mediated by increased levels of peroxisome proliferator-activated receptors (PPARs) and sterol regulatory element-binding protein-1c (SREBP-1c). The lipid imbalance was associated with higher production of reactive oxygen species (ROS) resulting in increased lipid peroxidation, stimulation of catalase activity and activation of nuclear factor kappa-B (NF-κB). Incubation of steatotic cells with silybin 50 µmol/L significantly reduced TG accumulation likely by promoting lipid catabolism and by inhibiting lipogenic pathways, as suggested by the changes in carnitine palmitoyltransferase 1 (CPT-1), PPAR and SREBP-1c levels. The reduction in fat accumulation exerted by silybin in the steatotic cells was associated with the improvement of the oxidative imbalance caused by lipid excess as demonstrated by the reduction in ROS content, lipid peroxidation, catalase activity and NF-κB activation. CONCLUSION: We demonstrated the direct anti-steatotic and anti-oxidant effects of silybin in steatotic cells, thus elucidating at a cellular level the encouraging results demonstrated in clinical and animal studies.

The Flavone Luteolin Inhibits Liver X Receptor Activation.

Luteolin is a dietary flavonoid with medicinal properties including antioxidant, antimicrobial, anticancer, antiallergic, and anti-inflammatory. However, the effect of luteolin on liver X receptors (LXRs), oxysterol sensors that regulate cholesterol homeostasis, lipogenesis, and inflammation, has yet to be studied. To unveil the potential of luteolin as an LXRα/ß modulator, we investigated by real-time RT-PCR the expression of LXR-target genes, namely, sterol regulatory element binding protein 1c (SREBP-1c) in hepatocytes and ATP-binding cassette transporter (ABC)A1 in macrophages. The lipid content of hepatocytes was evaluated by Oil Red staining. The results demonstrated, for the first time, that luteolin abrogated the LXRα/ß agonist-induced LXRα/ß transcriptional activity and, consequently, inhibited SREBP-1c expression, lipid accumulation, and ABCA1 expression. Therefore, luteolin could abrogate hypertriglyceridemia associated with LXR activation, thus presenting putative therapeutic effects in diseases associated with deregulated lipid metabolism, such as hepatic steatosis, cardiovascular diseases, and diabetes.

Effects of dietary phosphate on glucose and lipid metabolism.

Recent epidemiological and animal studies have suggested that excess intake of phosphate (Pi) is a risk factor for the progression of chronic kidney disease and its cardiovascular complications. However, little is known about the impact of dietary high Pi intake on the development of metabolic disorders such as obesity and type 2 diabetes. In this study, we investigated the effects of dietary Pi on glucose and lipid metabolism in healthy rats. Male 8-wk-old Sprague-Dawley rats were divided into three groups and given experimental diets containing varying amounts of Pi, i.e., 0.2 [low Pi(LP)], 0.6 [control Pi(CP)], and 1.2% [high Pi(HP)]. After 4 wk, the HP group showed lower visceral fat accumulation compared with other groups, accompanied by a low respiratory exchange ratio (V̇CO2/V̇O2) without alteration of locomotive activity. The HP group had lower levels of plasma insulin and nonesterified fatty acids. In addition, the HP group also showed suppressed expression of hepatic lipogenic genes, including sterol regulatory element-binding protein-1c, fatty acid synthase, and acetyl-CoA carboxylase, whereas there was no difference in hepatic fat oxidation among the groups. On the other hand, uncoupling protein (UCP) 1 and peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) expression were significantly increased in the brown adipose tissue (BAT) of the HP group. Our data demonstrated that a high-Pi diet can negatively regulate lipid synthesis in the liver and increase mRNA expression related to lipid oxidation and UCP1 in BAT, thereby preventing visceral fat accumulation. Thus, dietary Pi is a novel metabolic regulator.

Dietary umbelliferone attenuates alcohol-induced fatty liver via regulation of PPARα and SREBP-1c in rats.

This study investigated the effects of umbelliferone (UF) on alcoholic fatty liver and its underlying mechanism. Rats were fed a Lieber-DeCarli liquid diet with 36% of calories as alcohol with or without UF (0.05 g/L) for 8 weeks. Pair-fed rats received an isocaloric carbohydrate liquid diet. UF significantly reduced the severity of alcohol-induced body weight loss, hepatic lipid accumulation and droplet formation, and dyslipidemia. UF decreased plasma AST, ALT, and γGTP activity. UF significantly reduced hepatic cytochrome P450 2E1 activities and increased alcohol dehydrogenase and aldehyde dehydrogenase 2 activities compared to the alcohol control group, which resulted in a lower plasma acetaldehyde level in the rats that received UF. Chronic alcohol exposure inhibited hepatic AMPK activation compared to the pair-fed rats, which was reversed by UF supplementation. UF also significantly suppressed the lipogenic gene expression (SREBP-1c, SREBP-2, FAS, CIDEA, and PPARγ) and elevated the fatty acid oxidation gene expression (PPARα, Acsl1, CPT, Acox, and Acaa1a) compared to the alcohol control group, which could lead to inhibition of FAS activity and stimulation of CPT and fatty acid ß-oxidation activities in the liver of chronic alcohol-fed rats. These results indicated that UF attenuated alcoholic steatosis through down-regulation of SREBP-1c-mediated lipogenesis and up-regulation of PPARα-mediated fatty acid oxidation. Therefore, UF may provide a promising natural therapeutic strategy against alcoholic fatty liver.

Glycogen synthase kinase-3ß inhibition ameliorates cardiac parasympathetic dysfunction in type 1 diabetic Akita mice.

Decreased heart rate variability (HRV) is a major risk factor for sudden death and cardiovascular disease. We previously demonstrated that parasympathetic dysfunction in the heart of the Akita type 1 diabetic mouse was due to a decrease in the level of the sterol response element-binding protein (SREBP-1). Here we demonstrate that hyperactivity of glycogen synthase kinase-3ß (GSK3ß) in the atrium of the Akita mouse results in decreased SREBP-1, attenuation of parasympathetic modulation of heart rate, measured as a decrease in the high-frequency (HF) fraction of HRV in the presence of propranolol, and a decrease in expression of the G-protein coupled inward rectifying K(+) (GIRK4) subunit of the acetylcholine (ACh)-activated inward-rectifying K(+) channel (IKACh), the ion channel that mediates the heart rate response to parasympathetic stimulation. Treatment of atrial myocytes with the GSK3ß inhibitor Kenpaullone increased levels of SREBP-1 and expression of GIRK4 and IKACh, whereas a dominant-active GSK3ß mutant decreased SREBP-1 and GIRK4 expression. In Akita mice treated with GSK3ß inhibitors Li(+) and/or CHIR-99021, Li(+) increased IKACh, and Li(+) and CHIR-99021 both partially reversed the decrease in HF fraction while increasing GIRK4 and SREBP-1 expression. These data support the conclusion that increased GSK3ß activity in the type 1 diabetic heart plays a critical role in parasympathetic dysfunction through an effect on SREBP-1, supporting GSK3ß as a new therapeutic target for diabetic autonomic neuropathy.

Role for sterol regulatory element binding protein-1c activation in mediating skeletal muscle insulin resistance via repression of rat insulin receptor substrate-1 transcription.

AIMS/HYPOTHESIS: Sterol regulatory element binding protein-1c (SREBP-1c) is a master regulator of fatty acid synthase and controls lipogenesis. IRS-1 is the key insulin signalling mediator in skeletal muscle. In the present study, we investigated the role of SREBP-1c in the regulation of IRS-1 in skeletal muscle cells. METHODS: L6 muscle cells were treated with palmitic acid (PA) or metformin. Adenovirus vectors expressing Srebp-1c (also known as Srebf1) and small interfering RNA (siRNA) against Srebp-1c were transfected into the L6 cells. Protein-DNA interactions were assessed by luciferase reporter analysis, electrophoretic mobility shift assay and chromatin immunoprecipitation assay. RESULTS: We found that both gene and protein expression of SREBP-1c was increased in contrast to IRS-1 expression in PA-treated L6 cells. SREBP-1c overproduction decreased Irs-1 mRNA and IRS-1 protein expression in a dose-dependent manner, and suppressed the resultant insulin signalling, whereas SERBP-1c knockdown by Serbp-1c siRNA blocked the downregulation of IRS-1 induced by PA. Protein-DNA interaction studies demonstrated that SREBP-1c was able to bind to the rat Irs-1 promoter region, thereby repressing its gene transcription. Of particular importance, we found that metformin treatment downregulated Srebp-1c promoter activity, decreased the specific binding of SREBP-1c to Irs-1 promoter and upregulated Irs-1 promoter activity in PA-cultured L6 cells. CONCLUSIONS/INTERPRETATION: Our data indicate for the first time that SREBP-1c activation participates in skeletal muscle insulin resistance through a direct effect of suppressing Irs-1 transcription. These findings imply that SREBP-1c could serve as an attractive therapeutic target for insulin resistance.

Phthalate is associated with insulin resistance in adipose tissue of male rat: role of antioxidant vitamins.

Diethyl hexyl phthalate (DEHP) is a plasticizer, commonly used in a variety of products, including lubricants, perfumes, hairsprays and cosmetics, construction materials, wood finishers, adhesives, floorings and paints. DEHP is an endocrine disruptor and it has a continuum of influence on various organ systems in human beings and experimental animals. However, specific effects of DEHP on insulin signaling in adipose tissue are not known. Adult male albino rats of Wistar strain were divided into four groups. Control, DEHP treated (dissolved in olive oil at a dose of 10, and 100 mg/kg body weight, respectively, once daily through gastric intubations for 30 days) and DEHP + vitamin E (50 mg/kg body weight) and C (100 mg/kg body weight) dissolved in olive oil and distilled water, respectively, once daily through gastric intubations for 30 days. After the completion of treatment, adipose tissue was dissected out to assess various parameters. DEHP treatment escalated H(2)O(2) and hydroxyl radical levels as well as lipid peroxidation in the adipose tissue. DEHP impaired the expression of insulin signaling molecules and their phosphorelay pathways leading to diminish plasma membrane GLUT4 level and thus decreased glucose uptake and oxidation. Blood glucose level was elevated as a result of these changes. Supplementation of vitamins (C & E) prevented the DEHP-induced changes. It is concluded that DEHP-induced ROS and lipid peroxidation disrupts the insulin signal transduction in adipose tissue and favors glucose intolerance. Antioxidant vitamins have a protective role against the adverse effect of DEHP.

Beneficial effects of mangiferin on hyperlipidemia in high-fat-fed hamsters.

SCOPE: Mangiferin, a natural polyphenol, has been shown to have hypolipidemic effect in rat and mouse. However, the mechanism of action is not well understood. This study was conducted to determine the effect and mechanism of action of mangiferin on hyperlipidemia induced in hamsters by a high-fat diet. METHODS AND RESULTS: Forty male hamsters were randomly assigned to normal control, high-fat control, and high fat with mangiferin (50 and 150 mg/kg BW) groups. Mangiferin treatment significantly decreased final body weight, liver weight and visceral fat-pad weight, serum triglyceride (TG) and total free fatty acid (FFA) concentrations, hepatic TG levels and hepatic and muscle total FFA contents. Mangiferin upregulated mRNA expression of peroxisome proliferator-activated receptor-α (PPAR-α), fatty acid translocase (CD36) and carnitine palmitoyltransferase 1 (CPT-1), but downregulated mRNA expression of sterol regulatory element-binding protein 1c (SREBP-1c), acetyl CoA carboxylase (ACC), acyl-CoA:diacylglycerol acyltransferase 2 (DGAT-2) and microsomal triglyceride transfer protein (MTP) in liver. Mangiferin also stimulated mRNA expression of PPAR-α, CD36, CPT-1 and lipoprotein lipase (LPL) in muscle. CONCLUSIONS: The results suggest that mangiferin may ameliorate hypertriglyceridemia partly by modulating the expression levels of genes involved in lipid oxidation and lipogenesis.

Resveratrol inhibits cell differentiation in 3T3-L1 adipocytes via activation of AMPK.

Resveratrol (Res) is a natural polyphenolic compound with anti-inflammatory and antioxidant properties. Also, Res can inhibit lipogenesis and adipocyte differentiation. However, the underlying mechanisms of Res's functions remain largely unknown. AMP-activated protein kinase (AMPK) is a key player in adipocyte differentiation. Therefore, the purpose of our study was to determine the role played by AMPK in the Res-mediated regulation of adipocyte differentiation. Incubation of 3T3-L1 cells with Res confirmed that Res inhibited adipocyte differentiation. The phosphorylation of AMPKα was increased by Res in a dose-dependent manner, while total AMPKα levels were unchanged, and peroxisome proliferator-activated receptor γ (PPARγ), CCAAT-enhancer-binding protein α (C/EBPα), and sterol regulatory element-binding protein 1c (SREBP-1c) levels were decreased. Interestingly, pretreatment with AMPKα siRNA and Res promoted adipocyte differentiation, while the decrease of p-AMPKα increased PPARγ, C/EBPα, and SREBP-1c protein expression. Our study shows that Res is capable of inhibiting lipogenesis and differentiation of 3T3-L1 adipocytes via activation of AMPK, suggesting its potential therapeutic application in the treatment or prevention of obesity.

Short-term inhibition of SREBP-1c expression reverses diet-induced non-alcoholic fatty liver disease in mice.

OBJECTIVE: The present study investigates the level of Sterol-regulatory element-binding proteins (SREBP-1c) and related proteins in obese mice (DIO) treated with SREBP-1c antisense oligonucleotide (ASO) to observe a reversal of steatosis. MATERIALS AND METHODS: Swiss mice were fed on chow containing 61 kJ% saturated fat for 8 weeks to develop obesity. After this period, one group of animals was used to assess the molecular effects of SREBP-1c antisense oligonucleotide treatment by immunoblot analysis in a dose-response curve (0; 1.0; 2.0; 3.0; 4.0 nmol/day). After the dose (3.0 nmol/day) was determined, another group was treated for 14 days. After a period of 24 h following the last injection mice were killed and plasma and hepatic tissue were obtained to evaluate plasma triglycerides and total liver fat. Western blot was performed to evaluate SREBP-1c, FAS, SCD-1, PPARγ and CPT1 expression and AMPK[Thr172] and ACC[Ser79] phosphorylation. Livers were stained using the hematoxylin and eosin method for histological analysis. RESULTS: Body weight, epididymal fat and glucose levels were not affected by one daily dose of ASO. However, total plasma triglycerides and total liver fat were significantly reduced. Also, this treatment inhibited SREBP-1c and reduced protein levels of a series of proteins involved in lipogenesis, including ACC, FAS and SCD-1. Moreover, mice treated with ASO presented a significant reduction in macroscopic and microscopic features of hepatic steatosis. CONCLUSION: Our results demonstrate that the inhibition of SREBP-1c decreased the expression of lipogenic enzymes, reducing the accumulation of triglycerides and, finally, reversing hepatic steatosis in mice.

Effects of retinoic acid and hydrogen peroxide on sterol regulatory element-binding protein-1a activation during adipogenic differentiation of 3T3-L1 cells.

Both retinoic acid (RA) and oxidative stress (H2O2) increased transcription and cleavage of membrane-bound sterol regulatory element-binding protein (SREBP)-1, leading to enhanced transcription of fatty acid synthase (FAS) in hepatoma cells. On the other hand, RA and H2O2 decreased and increased lipogenesis in adipocytes, respectively, although roles of SREBP-1 activation in these effects remain to be elucidated. To elucidate its involvement, we examined the activation of SREBP-la, expression of FAS genes and lipid accumulation in 3T3-L1 cells in the presence of RA and/or H2O2. RA (1 microM) treatment suppressed expression of SREBP-1a and FAS genes and lipid accumulation. H2O2 (2 microM) treatment induced increased cleavage of SREBP-1a, without affecting amounts of SREBP-1a mRNA and precursor protein, and enhanced expression of FAS gene and lipid accumulation. Increased cleavage of SREBP-1a by H2O2 was also observed even in the presence of RA. These results suggest that H2O2, enhances a cleavage of SREBP-1a precursor protein, which independently occurs with the RA suppression of SREBP-1a gene expression, and that RA itself has no role in the SREBP-1a activation in adipocytes.

Anti-diabetic effects of lemon balm ( Melissa officinalis) essential oil on glucose- and lipid-regulating enzymes in type 2 diabetic mice.

The antioxidant activity of lemon balm (Melissa officinalis) essential oil (LBEO) on 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals and its hypoglycaemic effect in db/db mice were investigated. LBEO scavenged 97 % of DPPH radicals at a 270-fold dilution. Mice administered LBEO (0.015 mg/d) for 6 weeks showed significantly reduced blood glucose (65 %; P < 0.05) and TAG concentrations, improved glucose tolerance, as assessed by an oral glucose tolerance test, and significantly higher serum insulin levels, compared with the control group. The hypoglycaemic mechanism of LBEO was further explored via gene and protein expression analyses using RT-PCR and Western blotting, respectively. Among all glucose metabolism-related genes studied, hepatic glucokinase and GLUT4, as well as adipocyte GLUT4, PPAR-gamma, PPAR-alpha and SREBP-1c expression, were significantly up-regulated, whereas glucose-6-phosphatase and phosphoenolpyruvate carboxykinase expression was down-regulated in the livers of the LBEO group. The results further suggest that LBEO administered at low concentrations is an efficient hypoglycaemic agent, probably due to enhanced glucose uptake and metabolism in the liver and adipose tissue and the inhibition of gluconeogenesis in the liver.