Regulatory Element Binding Protein Gene Research Articles

Effects of Curcumin on the Egg Quality and Hepatic Lipid Metabolism of Laying Hens.

Curcumin, the major active compound of turmeric, has shown potential benefits for poultry health and production in various studies. However, its specific role in enhancing the egg quality and liver health of laying hens, as well as its underlying mechanisms, have yet to be determined. Here, a total of 600 Su Qin No.1 Laying hens, aged 55 weeks and with similar laying rates, were randomly placed into five groups, with 10 replicates of 12 hens each. Curcumin doses of 0, 100, 200, 400, and 800 mg/kg were added to the basal diet to form the experimental groups. After an 8-week feeding period, no significant changes were observed in the production performance of laying hens due to curcumin supplementation. However, additional tests revealed that a 200 mg/kg curcumin supplementation improved albumen height, yolk color, Haugh unit, and eggshell thickness, while reducing the thin albumen's weight and proportion. This was accompanied by a significant down-regulation of the mRNA expression level of the Prolactin Receptor (Prlr) in the oviduct magnum. Furthermore, the number of hepatic lipid droplets and the hepatic triglyceride (TG) content, as well as malondialdehyde (MDA) levels were significantly reduced, indicating improved hepatic lipid metabolism and oxidative status. This was accompanied by a significant reduction in the expressions of sterol regulatory element binding protein-1 gene (Srebp-1), fatty acid synthase gene (Fasn), as well as fatty acid synthase (FASN), which are closely related to fatty acid synthesis in the liver. Overall, these findings suggest that curcumin supplementation at a dosage of 200 mg/kg could lead to significant improvements in egg quality and hepatic lipid metabolism.

The transcriptome analysis on urea response mechanism in the process of ergosterol synthesis by Cordyceps cicadae

Nitrogen source is required for the growth of Cordyceps cicadae and involved in the regulation of metabolite synthesis. In order to further investigate the regulatory effects of nitrogen sources on the ergosterol synthesis by C. cicadae. We first confirmed that urea could significantly increase the ergosterol synthesis. The transcriptome analysis showed that compared with biomass cultured in the control fermentation medium (CFM), 1340 differentially expressed genes (DEGs) were obtained by Gene Ontology (GO) annotation, and 312 DEGs were obtained by Kyoto Encyclopedia of Genes and Genomes (KEGG) annotation from the biomass cultured in CFM + CO(NH2)2. Urea up-regulated D-3-phosphoglycerate dehydrogenase gene transcription level and down-regulated enolase and L-serine/L-threonine ammonialyase gene transcription level, increased serine synthesis, allosterically activate pyruvate kinase, to promote the synthesis of pyruvate and CH3CO ~ SCOA, the primer of ergosterol; Urea increase the genes transcription related with ergosterol synthesis by up-regulating the steroid regulatory element binding protein gene transcription levels. The transcriptome results were provided by those of qRT-PCR. Collectively, our finding provided valuable insights into the regulatory effect of nitrogen source on the ergosterol synthesis by C. cicadae.

Effects of Phosphoethanolamine Supplementation on Mitochondrial Activity and Lipogenesis in a Caffeine Ingestion Caenorhabditis elegans Model.

Caffeine intake is strongly linked to lipid metabolism. We previously reported the age-dependent physiological effects of caffeine intake in a Caenorhabditis elegans model. Since nutritional status can actively influence metabolism and overall health, in this study, we evaluated the effect of caffeine intake on lipid metabolism in adult-stage C. elegans. We found that, in C. elegans, fat storage and the level of phosphoethanolamine (PE) were significantly reduced with caffeine intake. In addition, mitochondrial activity decreased and mitochondrial morphology was disrupted, and the expression of oxidative stress response genes, hsp-6, gst-4, and daf-16, was induced by caffeine intake. Furthermore, the level of an energy metabolism sensor, phospho-AMP-activated protein kinase, was increased, whereas the expression of the sterol regulatory element binding protein gene and its target stearoyl-CoA desaturase genes, fat-5, -6, and -7, was decreased with caffeine intake. These findings suggest that caffeine intake causes mitochondrial dysfunction and reduces lipogenesis. Interestingly, these changes induced by caffeine intake were partially alleviated by PE supplementation, suggesting that the reduction in mitochondrial activity and lipogenesis is in part because of the low PE level, and proper dietary supplementation can improve organelle integrity.

Sterol regulatory element binding protein-1 (SREBP1) gene expression is similarly increased in polycystic ovary syndrome and endometrial cancer.

Women with polycystic ovary syndrome have a three-fold higher risk of endometrial cancer. Insulin resistance and hyperlipidemia may be pertinent factors in the pathogenesis of both conditions. The aim of this study was to investigate endometrial sterol regulatory element binding protein-1 gene expression in polycystic ovary syndrome and endometrial cancer endometrium, and to correlate endometrial sterol regulatory element binding protein-1 gene expression with serum lipid profiles. A cross-sectional study was performed at Nottingham University Hospital, UK. A total of 102 women (polycystic ovary syndrome, endometrial cancer and controls; 34 participants in each group) were recruited. Clinical and biochemical assessments were performed before endometrial biopsies were obtained from all participants. Taqman real-time polymerase chain reaction for endometrial sterol regulatory element binding protein-1 gene and its systemic protein expression were analyzed. The body mass indices of women with polycystic ovary syndrome (29.28±2.91kg/m2 ) and controls (28.58±2.62kg/m2 ) were not significantly different. Women with endometrial cancer had a higher mean body mass index (32.22±5.70kg/m2 ). Sterol regulatory element binding protein-1 gene expression was significantly increased in polycystic ovary syndrome and endometrial cancer endometrium compared with controls (p<0.0001). Sterol regulatory element binding protein-1 gene expression was positively correlated with body mass index (r=0.017, p=0.921) and waist-hip ratio (r=0.023, p=0.544) in polycystic ovary syndrome, but this was not statistically significant. Similarly, statistically insignificant positive correlations were found between endometrial sterol regulatory element binding protein-1 gene expression and body mass index in endometrial cancer (r=0.643, p=0.06) and waist-hip ratio (r=0.096, p=0.073). Sterol regulatory element binding protein-1 gene expression was significantly positively correlated with triglyceride in both polycystic ovary syndrome and endometrial cancer (p=0.028 and p=0.027, respectively). Quantitative serum sterol regulatory element binding protein-1 gene correlated with endometrial gene expression (p<0.05). Sterol regulatory element binding protein-1 gene expression is significantly increased in the endometrium of women with polycystic ovary syndrome and women with endometrial cancer compared with controls and positively correlates with serum triglyceride in both polycystic ovary syndrome and endometrial cancer.

Genome-Wide Analysis of Hypoxia-Responsive Genes in the Rice Blast Fungus, Magnaporthe oryzae.

Rice blast fungus, Magnaporthe oryzae, is the most destructive pathogen in the rice-growing area. This fungus has a biotrophic phase early in infection and later switches to a necrotrophic lifestyle. During the biotrophic phase, the fungus competes with its host for nutrients and oxygen. Continuous uptake of oxygen is essential for successful establishment of blast disease of this pathogen. Here, we report transcriptional responses of the fungus to oxygen limitation. Transcriptome analysis using RNA-Seq identified that 1,047 genes were up-regulated in response to hypoxia. Those genes are involved in mycelial development, sterol biosynthesis, and metal ion transport based on hierarchical GO terms, and are well-conserved among three fungal species. In addition, null mutants of two hypoxia-responsive genes were generated and their roles in fungal development and pathogenicity tested. The mutant for the sterol regulatory element-binding protein gene, MoSRE1, exhibited increased sensitivity to a hypoxia-mimicking agent, increased conidiation, and delayed invasive growth within host cells, which is suggestive of important roles in fungal development. However, such defects did not cause any significant decrease in disease severity. The other null mutant, for the alcohol dehydrogenase gene MoADH1, showed no defect in the hypoxia-mimicking condition (using cobalt chloride) and fungal development. Taken together, this comprehensive transcriptional profiling in response to a hypoxic condition with experimental validations would provide new insights into fungal development and pathogenicity in plant pathogenic fungi.

Candidate gene marker associations with fatty acid profiles in heavy pigs

Heavy pigs are used in Italy to produce fresh meat, dry-cured ham, salami and lard. Fatty acid profile determines both the dietary and organoleptic qualities of these products. The objective was to study the polymorphisms of two genes that code for enzymes of the fatty acid metabolism, namely, Stearoyl-CoA desaturase (SCD) and Fatty acid desaturase 2 (FADS2). We also investigated the polymorphism of the Sterol regulatory element binding protein gene (SREBF1) as it regulates SCD and FADS2 transcription. Significant associations of SCD were found with the ratio of oleic to stearic acid; with the concentration (g/100g of fat) of stearic and oleic acids. The concentrations of arachidonic and linoleic acids and the ratio of dihomo-gamma-linolenic to linoleic acid were significantly associated with FADS2 polymorphisms. SREBF1 polymorphism was associated with oleic acid concentrations and the ratio of arachidonic to linoleic acids.Our findings suggest that the SCD, FADS2 and SREBF1 polymorphisms are associated with dietary quality of heavy pig meat products.

Short communication: Effects of β-lactoglobulin, stearoyl-coenzyme A desaturase 1, and sterol regulatory element binding protein gene allelic variants on milk production, composition, acidity, and coagulation properties of Brown Swiss cows

Associations of allelic variants of the β-lactoglobulin (LGB), stearoyl-coenzyme A desaturase 1 (SCD), and sterol regulatory element binding protein (SREBP-1) genes with milk production, composition (fat, protein, and casein content), acidity (pH and titratable acidity), and coagulation properties (rennet coagulation time and curd firmness) were investigated in Brown Swiss cows. In total, 294 animals (progeny of 15 sires) reared in 16 herds were milk-sampled once. The additive effects of LGB (rs109625649:C>T), SCD (ss469414220:C>T), and SREBP-1 (AB355704: g.101_185ins) polymorphisms on the aforementioned traits were analyzed through Bayesian linear models. The LGB genotype affected rennet coagulation time, with TT (or BB) alleles showing longer rennet coagulation time compared with CC (or AA) cows. The SCD gene allelic variants were found to be associated with protein and casein contents and curd firmness: CC animals had the lowest values for the aforementioned traits. An association was found between SREBP-1 alleles and fat content, with the highest values for cows carrying the 84-bp insertion (or L) allele. Results suggest a possible use of these loci in gene-assisted selection programs for the improvement of milk quality traits and coagulation properties in Brown Swiss cattle.

Membrane Localization of Protein-Tyrosine Phosphatase 1B is Essential for its Activation of Sterol Regulatory Element-Binding Protein-1 Gene Expression and Consequent Hypertriglyceridaemia

Protein-tyrosine phosphatase 1B (PTP1B) is a major regulator of insulin sensitivity. We have described a novel action of PTP1B in the induction of sterol regulatory element-binding protein-1 (SREBP-1) gene expression through activation of protein phosphatase 2A (PP2A). PTP1B is anchored to the endoplasmic reticulum membrane via its C-terminal tail. We have previously reported that membrane localization of PTP1B is essential for PP2A activation, which is crucial for enhancing SREBP-1 gene expression in in vitro experiments. In this study, we further investigated the physiological importance of membrane localization of PTP1B in vivo. We found that transient liver-specific overexpression of wild-type PTP1B (PTP1B-WT) using adenovirus-mediated gene transfer was associated with hypertriglyceridaemia and enhanced hepatic SREBP-1 gene expression in mice. However, overexpression of the C-terminal truncated PTP1B (PTP1BDeltaCT) failed to increase hepatic SREBP-1 expression or serum triglyceride levels, despite causing insulin resistance. Our results indicate that activation of PTP1B in the liver could induce hypertriglyceridaemia and that anchoring of PTP1B to the membrane is crucial for its action.

N-3 polyunsaturated fatty acid regulation of hepatic gene transcription

The liver plays a central role in whole body lipid metabolism and adapts rapidly to changes in dietary fat composition. This adaption involves changes in the expression of genes involved in glycolysis, de-novo lipogenesis, fatty acid elongation, desaturation and oxidation. This review brings together metabolic and molecular studies that help explain n-3 (omega-3) polyunsaturated fatty acid regulation of hepatic gene transcription. Dietary n-3 polyunsaturated fatty acid regulates hepatic gene expression by targeting three major transcriptional regulatory networks: peroxisome proliferator-activated receptor alpha, sterol regulatory element binding protein-1 and the carbohydrate regulatory element binding protein/Max-like factor X heterodimer. 22:6,n-3, the most prominent n-3 polyunsaturated fatty acid in tissues, is a weak activator of peroxisome proliferator-activated receptor alpha. Hepatic metabolism of 22:6,n-3, however, generates 20:5,n-3, a strong peroxisome proliferator-activated receptor alpha activator. In contrast to peroxisome proliferator-activated receptor alpha, 22:6,n-3 is the most potent fatty acid regulator of hepatic sterol regulatory element binding protein-1. 22:6,n-3 suppresses sterol regulatory element binding protein-1 gene expression while enhancing degradation of nuclear sterol regulatory element binding protein-1 through 26S proteasome and Erk1/2-dependent mechanisms. Both n-3 and n-6 polyunsaturated fatty acid suppress carbohydrate regulatory element binding protein and Max-like factor X nuclear abundance and interfere with glucose-regulated hepatic metabolism. These studies have revealed unique mechanisms by which specific polyunsaturated fatty acids control peroxisome proliferator activated receptor alpha, sterol regulatory element binding protein-1 and carbohydrate regulatory element binding protein/Max-like factor X function. As such, specific metabolic and signal transduction pathways contribute significantly to the fatty acid regulation of these transcription factors and their corresponding regulatory networks.

Membrane localization of protein-tyrosine phosphatase 1B is essential for its activation of sterol regulatory element-binding protein-1 gene expression

Sterol regulatory element-binding protein-1 (SREBP-1) is a key transcription factor in stimulating lipogenesis in the liver. Protein-tyrosine phosphatase 1B (PTP1B) induces SREBP-1 gene expression via protein phosphatase 2A (PP2A) activation. PTP1B is reported to be anchored on the endoplasmic reticulum (ER) via its C-terminal tail, and change in intracellular localization of PTP1B by C-terminal-truncation did not alter its inhibitory effects on insulin signaling. In this study, we investigated whether the change in intracellular localization of PTP1B could influence SREBP-1 gene expression. Overexpression of C-terminal truncated PTP1B (PTP1BΔCT) in rat Fao cells did not induce SREBP-1 gene expression. Furthermore, PTP1BΔCT failed to bind PP2A, resulting in impaired PP2A activation, whereas overexpression of wild-type PTP1B (PTP1BWT) associated with PP2A. Moreover, a membrane-targeted PTP1BΔCT activated PP2A with restored PP2A binding, despite the absence of its C-terminal region. Finally, overexpression of PTP1BΔCT into mouse primary cultured hepatocytes failed to enhance SREBP-1c mRNA, whereas membrane-targeted PTP1BΔCT led to enhanced SREBP-1c mRNA in hepatocytes as well as PTP1BWT. In conclusion, membrane localization of PTP1B is essential for PP2A activation, which is crucial for its enhancement of SREBP-1 gene expression.

A rare missense mutation in a type 2 diabetes patient decreases the transcriptional activity of human sterol regulatory element binding protein-1

Sterol regulatory element binding protein 1 (SREBP-1) transcription factors play a key role in energy homeostasis by regulating genes involved in both carbohydrate and lipid metabolism, and in adipocyte differentiation. The 5' end of the mRNA-encoding SREBP-1 exists in two forms, designated 1a and 1c. The divergence results from the use of two transcription start sites that produce two separate 5' exons, each of which is spliced to a common exon 2. Mutations in the sterol regulatory element binding protein gene (SREBF)-1 may contribute to insulin resistance states. However, the variants described to date do not affect the SREBP function. In this study, we investigated the functional consequences of a novel missense mutation common to both SREBP-1 isoforms identified in a Spanish type 2 diabetic patient (c.677C>T, SREBP-1a p.T226M; c.605C>T, SREBP-1c p.T202M). Using reporter gene analysis and electrophoretic mobility shift assays, we found that this variant impairs the transcriptional activity and reduces DNA binding ability despite its comparable protein stability to the wild-type SREBP-1. This decreased activity impairs the expression of known downstream targets, such as the LDL receptor and fatty acid synthase genes. Our findings suggest that the threonine residue and/or surrounding region play an important role in the SREBP-1 function.

SREBF-1 gene polymorphisms are associated with obesity and type 2 diabetes in French obese and diabetic cohorts.

Sterol regulatory element-binding protein (SREBP)-1 transcription factors play a central role in energy homeostasis by promoting glycolysis, lipogenesis, and adipogenesis. The sterol regulatory element-binding protein gene (SREBF)-1 is a good candidate gene for obesity and obesity-related metabolic traits such as type 2 diabetes and dyslipidemia. The SREBF-1 molecular screening of 40 unrelated obese patients by PCR/single-strand conformation polymorphism revealed 19 single nucleotide polymorphisms (SNPs). Six SNPs were genotyped for an association study in large French obese and nonobese cohorts. Case-control studies using two independent nonobese cohorts indicated that SNP17 (54G/C, exon 18c) is associated with morbid obesity (odds ratio 1.5, P = 0.006 and P = 0.02, respectively). SNP3 (-150G/A, exon 1a), SNP5 (-36delG, exon 1a), and SNP17 are found in high linkage disequilibrium (D' > 0.8). The haplotype including wild-type alleles of these SNPs (C/G/G/T/C/G, HAP2) is identified as a risk factor for morbid obesity (P = 0.003). In the obese group, SNP3, SNP5, and SNP17 are associated with male-specific hypertriglyceridemia (P = 0.07, P = 0.01, and P = 0.05, respectively). SNP17 is also associated with type 2 diabetes (P = 0.03) and increased prevalence of nephropathy (P = 0.028) in a diabetic cohort. Our results indicate a role of the SREBF-1 gene in genetic predisposition of metabolic diseases such as obesity, type 2 diabetes, and dyslipidemia.

Protein-tyrosine Phosphatase 1B as New Activator for Hepatic Lipogenesis via Sterol Regulatory Element-binding Protein-1 Gene Expression

Like hyperglycemia, postprandial (diet-induced) hypertriglyceridemia is thought to play crucial roles in the pathogenesis of insulin resistant/metabolic syndrome. Sterol regulatory element-binding protein-1 (SREBP-1) is a key transcription factor to induce postprandial hypertriglyceridemia. We found that insulin-resistant rats fed a diet high in fructose showed an increased proteintyrosine phosphatase 1B (PTP1B) content with strong expression of SREBP-1 mRNA in the liver. To clarify the association of PTP1B with SREBP-1 gene expression, we overexpressed PTP1B in rat hepatocytes, which led to increased mRNA content and promoter activity of SREBP-1a and -1c, resulting in the increased mRNA expression of fatty-acid synthase, one of the SREBP-1-responsive lipogenic genes. Because PTP1B overexpression increased phosphatase 2A (PP2A) activity, we inhibited PP2A activity by expression of its selective inhibitor, SV40 small T antigen and found that this normalized the PTP1B-enhanced SREBP-1a and -1c mRNA expressions through activation of the Sp1 site. These results indicate that PTP1B may regulate gene expression of SREBP-1 via enhancement of PP2A activity, thus mediating hepatic lipogenesis and postprandial hypertriglyceridemia. We demonstrate here a unique serial activation of the PTP1B-PP2A axis as a novel mechanism for the regulation of gene expression in the biosynthesis of triglyceride.

Hepatic expression of microsomal triglyceride transfer protein and in vivo secretion of triglyceride-rich lipoproteins are increased in obese diabetic mice.

Secondary hyperlipidemia is a major cardiovascular risk factor in individuals with type 2 diabetes. Increased hepatic production of apolipoprotein B (apoB)-containing lipoproteins contributes to the elevated plasma levels, but the mechanism is poorly understood. Recent results have established that microsomal triglyceride transfer protein (MTP) is rate limiting for the assembly and secretion of apoB-containing lipoproteins. To better understand the mechanism of type 2 diabetes-associated hyperlipidemia, we quantified hepatic MTP mRNA levels, hepatic microsomal triglyceride transfer activity, and in vivo triglyceride secretion from the liver in two diabetic mouse models. Obese diabetic (ob/ob) mice had 45% higher (P = 0.006) hepatic MTP mRNA levels, 54% higher (P < 0.0001) microsomal triglyceride transfer activity, and 70% higher (P < 0.0001) in vivo triglyceride secretion rates compared with ob/+ control mice. In contrast, in lean streptozotocin-treated diabetic mice, hepatic MTP mRNA levels were unchanged, whereas microsomal triglyceride transfer activity and in vivo triglyceride secretion rates were marginally decreased. These studies suggest that obesity-induced type 2 diabetes in mice confers increases in hepatic MTP expression and secretion of triglyceride-rich lipoproteins. High blood glucose and altered hepatic expression of sterol regulatory element binding protein genes play a minor role in this diabetic response.

Increased Expression of the Sterol Regulatory Element-binding Protein-1 Gene in Insulin Receptor Substrate-2−/−Mouse Liver

Insulin receptor substrate (IRS)-2(-/-) mice develop diabetes because of insulin resistance in the liver and failure to undergo beta-cell hyperplasia. Here we show by DNA chip microarray analysis that expression of the sterol regulatory element-binding protein (SREBP)-1 gene, a downstream target of insulin, was paradoxically increased in 16-week-old IRS-2(-/-) mouse liver, where insulin-mediated intracellular signaling events were substantially attenuated. The expression of SREBP-1 downstream genes, such as the spot 14, ATP citrate-lyase, and fatty acid synthase genes, was also increased. Increased liver triglyceride content in IRS-2(-/-) mice assures the physiological importance of SREBP-1 gene induction. IRS-2(-/-) mice showed leptin resistance; low dose leptin administration, enough to reduce food intake and body weight in wild-type mice, failed to do so in IRS-2(-/-) mice. Interestingly, high dose leptin administration reduced SREBP-1 expression in IRS-2(-/-) mouse liver. Thus, IRS-2 gene disruption results in leptin resistance, causing an SREBP-1 gene induction, obesity, fatty liver, and diabetes.