Sterol Regulatory Element-binding Transcription Factor Research Articles

Effect of diets low in fish oil and supplemented with chlorogenic acid on fatty acid composition and lipid metabolism in Atlantic salmon (Salmo salarL.)

This study aimed to test the use of chlorogenic acid (CGA), a natural antioxidant, which might act improving the retention of eicosapentaenoic (EPA) and docosahexaenoic (DHA) fatty acids. Fish were fed one of three experimental diets. A diet with 160 g kg−1 fish oil (FO) and 80 g kg−1 vegetable oil (VO) was used as a positive control with high n-3 long-chain polyunsaturated fatty acids (LC)-PUFA, a diet containing 40 g kg−1 FO and 200 g kg−1 VO was used as a negative control for low n-3 LC-PUFA and 1 g kg−1 CGA was added to the negative control diet to test the impact of CGA on n-3 LC-PUFA synthesis. The expression of genes involved in PUFA synthesis was upregulated in the liver of fish fed the low n-3 LC-PUFA diets. This might be due to the activation of sterol regulatory element-binding transcription factor 1 (SREBP1) and liver X receptor. Moreover, malondialdehyde concentration tended to decrease, and accumulation of dietary EPA in the liver in relation to diet was observed in fish fed the low n-3 LC-PUFA diets. However, the concentration of EPA and DHA was higher in fish fed the positive control diet. The inclusion of 1 g kg−1 CGA did not exert any additional effect on lipid peroxidation, EPA and DHA concentrations or LC-PUFA metabolism.

Association between SCAP and SREBF1 gene polymorphisms and metabolic syndrome in schizophrenia patients treated with atypical antipsychotics

Objectives: The use of atypical antipsychotics (AAPs) in the treatment of schizophrenia has been relevant because of the high prevalence of metabolic syndrome (MetS). The sterol-regulatory element-binding protein (SREBP) pathway may contribute to the underlying pathophysiology of AAP-induced metabolic adverse effects. We explored the association between the variants of the sterol-regulatory element-binding transcription factor-1 (SREBF1) gene and the SREBP cleavage-activation protein (SCAP) gene with AAP-induced MetS in a genetic case–control study. Methods: Eleven single nucleotide polymorphisms (SNPs) of SREBF1 and five of SCAP were genotyped in a Han Chinese population in Beijing, China: a sample of 722 schizophrenia patients on monotherapy with AAPs (clozapine, olanzapine or risperidone). Metabolic parameters were collected and evaluated for MetS criteria. Results: The rs11654081 T-allele of the SREBF1 gene was significantly associated with an increased risk for MetS after correction (P = 0.019, odds ratio, OR =2.56, 95% confidence interval, CI: 1.4 4–4.54). The rs11654081-TT genotype appeared more frequently in MetS than in non-MetS after correction (P = 0.026, OR =2.37, 95% CI: 1.3 6–4.12). SCAP polymorphisms with drug-induced MetS were negative in this study. Conclusions: The genetic polymorphisms of SREBF1 could play a role in the mechanism for interindividual variation of AAP-induced MetS.

Central Injection of Neuropeptide Y Affects Dietary Macronutrient Composition‐Mediated Changes in Broiler Adipose Tissue mRNA Abundance

Neuropeptide Y (NPY) is a potent orexigenic (hunger increasing) factor that also promotes adipose tissue development in birds and mammals. The purpose of this study was to investigate how dietary macronutrient composition and exogenous NPY affect expression of lipid metabolism‐associated factors in different anatomical adipose (fat) depots of chickens. Chicks were fed one of three isocaloric diets (3,000 kcal metabolizable energy (ME)/kg) and isonitrogenous (22% crude protein; CP) corn and soybean meal‐based diets after hatch: high carbohydrate (HC; control), high fat (HF; 30% of ME from soybean oil) or high protein (HP; 27% CP) post hatch. On day 4 post hatch, 0.2 nmol of NPY or vehicle was injected intra cerebroventricularly (into left lateral ventricle) and abdominal and subcutaneous fat were collected at 1‐hour post injection. Total RNA was isolated, reverse transcribed and real‐time PCR performed to quantify expression of genes associated with adipogenesis: Krüppel‐like factor 7 (KLF7), GATA‐binding protein 2 (GATA 2), CCAAT/enhancer‐binding protein alpha (CEBPα), CEBPβ, peroxisome proliferator‐activated receptor gamma (PPARγ), sterol regulatory element‐binding transcription factor 1 (SREBP‐1), and fatty acid binding protein 4 (FABP4). The statistical model (within fat depot) included the main effects of diet and NPY treatment, and the two‐way interaction. There was an effect of diet (P < 0.05) for all of the genes measured in abdominal and subcutaneous fat, except for CEBPβ in subcutaneous fat. Chicks fed the HC diet expressed more (P < 0.0001) KLF7, CEBPα, CEBPβ, PPARγ, SREBP‐1, and FABP4 in abdominal fat than chicks fed the HF or HP diet. There were interactions of diet and NPY treatment on PPARγ (P = 0.04) and FABP4 (P = 0.03) mRNA in abdominal fat, and CEBPα (P = 0.01), PPARγ (P = 0.001), SREBP‐1 (P = 0.001) and FABP4 (P = 0.001) mRNA in subcutaneous fat. Pairwise comparison tests revealed that CEBPα (P < 0.003), PPARγ (P = 0.007), SREBP‐1 (P = 0.008) and FABP4 (P = 0.001) mRNA showed a more pronounced increase in subcutaneous fat of the HF than HC and HP fed chicks after NPY injection. PPARγ (P = 0.01), SREBP‐1 (P = 0.01) and FABP4 (P = 0.04) also showed a more accentuated decrease in subcutaneous fat of HC than HF and HP fed chicks after NPY injection. PPARγ (P = 0.003) and FABP4 (P = 0.003) in abdominal fat increased more in expression in HF than HC and HP fed chicks after NPY injection. These data demonstrate that consumption of diets differing in fat content affect adipose tissue physiology, with differences in gene expression of some adipogenesis‐associated factors during the first week post‐hatch; in general mRNA was greater in chicks fed HC than the HF or HP diet, with similar effects observed in different anatomical fat depots. Injection of NPY affected expression of these factors in an adipose depot‐dependent manner. These results may have implications for understanding how early‐life nutrition and appetite‐regulatory neuropeptides affect development of different adipose tissue depots in birds.Support or Funding InformationFunding for this work was provided in part, by the Virginia Agricultural Experiment Station and the Hatch Program of the National Institute of Food and Agriculture, U.S. Department of Agriculture, and by a John Lee Pratt Undergraduate Research Scholarship awarded to CW.

The Effects of Dietary Macronutrient Composition on Lipid Metabolism‐Associated Factor Gene Expression in the Adipose Tissue of Chickens are Influenced by 3 Hours of Fasting

Our objective was to determine how dietary macronutrient composition and fasting affect chick adipose tissue physiology during the early post‐hatch period. Broiler chicks were fed one of three isocaloric (3,000 kcal metabolizable energy (ME)/kg) and isonitrogenous (22% crude protein; CP) corn and soybean meal‐based diets after hatch: high carbohydrate (HC; control), high fat (HF; 30% of ME from soybean oil) or high protein (HP; 27% CP). At 4 days post hatch, chicks were fasted for 3 hours, and clavicular, gizzard and subcutaneous adipose depots were collected from fasted and fed chicks (n=10 per group). Total RNA was isolated, reverse transcribed and real‐time PCR performed to quantify 1‐acylglycerol‐3‐phosphate O‐acyltransferase 9 (AGPAT9), fatty acid binding protein 4 (FABP4), CCAAT/enhancer‐binding protein alpha (CEBPα), CEBPβ, peroxisome proliferator‐activated receptor gamma (PPARγ), monoglyceride lipase (MGLL), and sterol regulatory element‐binding transcription factor 1 (SREBP‐1) mRNA. The statistical model (within fat depot) included the main effects of diet and fasting, and the interaction. Means were separated within diet. There was greater CEBPα, PPARγ, and SREBP‐1, and less CEBPβ mRNA in clavicular, gizzard and subcutaneous fat in fasted than fed chicks (P < 0.05). In clavicular (P = 0.002) and subcutaneous (P = 0.01) fat, FABP4 expression was lower in chicks fed HP than HF or HC. In clavicular (P = 0.003) and gizzard (P = 0.009) fat, CEPBβ mRNA was greater in HF and HC than HP‐fed chicks. MGLL mRNA was greater (P = 0.007) in clavicular fat of HF than HP‐fed chicks. There were interactions of diet and fasting on PPARγ (P = 0.04) and SREBP‐1 (P = 0.008) in clavicular, PPARγ (P = 0.04) in gizzard, and CEBPα (P = 0.007) in subcutaneous fat. Post‐hoc testing revealed that CEBPα in subcutaneous (P < 0.003) and PPARg mRNA in gizzard (P < 0.03) fat showed a more pronounced decrease in expression during fasting in HC and HF than HP‐fed chicks. In clavicular fat, expression of AGPAT9 (P = 0.001), PPARg (P < 0.0001), and SREBP‐1 (P < 0.0001) mRNA decreased after 3 hours of fasting only in chicks that consumed the HC diet; expression was not affected by food withdrawal in chicks that consumed HF or HP. These data demonstrate that consumption of diets differing in fat and protein content affect gene expression of some lipid metabolism‐associated factors during the first week post‐hatch; in general mRNA was greater in chicks fed HC and HF than the HP diet, with similar effects observed in different anatomical fat depots. Fasting also influenced expression of these factors, in an adipose depot‐dependent manner. These results may have implications for understanding how early‐life nutrition affects development of different adipose tissue depots in birds.Support or Funding InformationFunding for this work was provided in part, by the Virginia Agricultural Experiment Station and the Hatch Program of the National Institute of Food and Agriculture, U.S. Department of Agriculture, and by a John Lee Pratt Fellowship awarded to Guoqing Wang.

Lipids and Cholesterol‐Lowering Activity of Red Cabbage Microgreens

Cardiovascular disease (CVD) is the leading cause of death in the United States and diet‐induced hypercholesterolemia is a major risk factor. Population, as well as experimental evidence, support that the consumption of a variety of vegetables can lower the risk of CVD through modulation of hypercholesterolemia. Microgreens are tiny edible greensharvested from vegetables and herbs at 7–14 days after germination, and are reported to possess a higher density of nutrients when compared to their mature counterparts. However, little is known about the health promoting efficacies of microgreens in terms of their effect on lipid and cholesterol levels. The present study used a rodent diet‐induced obesity model to address this question. C57B/6NCr mice (n=62, male, five week) were randomly assigned to six groups: 1) low fat diet (with 10% calories from fat); 2) high fat diet (with 45% calories from fat); 3) low fat diet+1.95%red cabbage microgreens; 4) low fat diet+1.95% mature red cabbage; 5) high fat diet+1.95% red cabbage microgreens; 6)high fat diet+1.95% mature red cabbage. The animals were on their respective diets for eight weeks. We found supplementing microgreens attenuated high fat diet induced weight gain after 8 weeks (17%). Moreover, we found microgreens significantly lowered circulating LDL levels (34%), hepatic triglycerides (23%)and cholesterol ester (65.5%) levels in animals fed a high fat diet. The effects of microgreens on hepatic triglycerides and cholesterol ester appeared to coincide with inhibition in triglycerides synthesis enzymes diacylglycerol O‐acyltransferase 1 (DGAT1), glycerol‐3‐phosphate acyltransferase (GPAM), cholesterolester synthesis enzymes acetyl‐CoA acetyltransferase 3 (ACAT3) and lecithin‐cholesterol acyltransferase (LCAT). However, no changes in expression in the genes related to cholesterol metabolism including sterol regulatory element binding transcription factor 2 (SREBP2), 3‐hydroxy‐3‐methylglutaryl‐CoA reductase (HMGCR), acyl‐CoA oxidase (ACOX), cytochrome P450, family 7, subfamily A, polypeptide 1 (CYP7A1) were observed. In summary, our data support dietary consumption of red cabbage microgreens modulates cholesterol metabolism, weight gain, and may protect against hypercholesterolemia and CVD.Support or Funding InformationThomas T. Y. Wang Address:Room 132, 10300Baltimore Ave, Bldg. 307‐C, BARC‐EAST, Beltsville, MD, 20705Phone number: 301‐504‐8459 Fax:301‐504‐9062Email address: tom.wang@ars.usda.gov

Sex-Related Differences of Lipid Metabolism Induced by Triptolide: The Possible Role of the LXRα/SREBP-1 Signaling Pathway.

Triptolide, a diterpenoid isolated from the plant Tripterygium wilfordii Hook. f., exerts a unique bioactive spectrum of anti-inflammatory and anticancer activities. However, triptolide’s clinical applications are limited due to its severe toxicities. Fatty liver toxicity occurs in response to triptolide, and this toxic response significantly differs between males and females. This report investigated the pathogenesis underlying the sex-related differences in the dyslipidosis induced by triptolide in rats. Wistar rats were administered 0, 150, 300, or 450 μg triptolide/kg/day by gavage for 28 days. Ultrastructural examination revealed that more lipid droplets were present in female triptolide-treated rats than in male triptolide-treated rats. Furthermore, liver triglyceride, total bile acid and free fatty acid levels were significantly increased in female rats in the 300 and 450 μg/kg dose groups. The expression of liver X receptor α (LXRα) and its target genes, cholesterol 7α-hydroxylase (CYP7A1) and Sterol regulatory element-binding transcription factor 1(SREBP-1), increased following triptolide treatment in both male and female rats; however, the female rats were more sensitive to triptolide than the male rats. In addition, the expression of acetyl-CoA carboxylase 1(ACC1), a target gene of SREBP-1, increased in the female rats treated with 450 μg triptolide/kg/day, and ACC1 expression contributed to the sex-related differences in the triptolide-induced dysfunction of lipid metabolism. Our results demonstrate that the sex-related differences in LXR/SREBP-1-mediated regulation of gene expression in rats are responsible for the sex-related differences in lipid metabolism induced by triptolide, which likely underlie the sex-related differences in triptolide hepatotoxicity. This study will be important for predicting sex-related effects on the pharmacokinetics and toxicity of triptolide and for improving its safety.

Arginine Methylation of SREBP1a via PRMT5 Promotes De Novo Lipogenesis and Tumor Growth.

Dysregulation of the sterol regulatory element-binding transcription factors sterol regulatory element-binding protein (SREBP) and SREBF activates de novo lipogenesis to high levels in cancer cells, a critical event in driving malignant growth. In this study, we identified an important posttranslational mechanism by which SREBP1a is regulated during metabolic reprogramming in cancer cells. Mass spectrometry revealed protein arginine methyltransferase 5 (PRMT5) as a binding partner of SREBP1a that symmetrically dimethylated it on R321, thereby promoting transcriptional activity. Furthermore, PRMT5-induced methylation prevented phosphorylation of SREBP1a on S430 by GSK3β, leading to its disassociation from Fbw7 (FBXW7) and its evasion from degradation through the ubiquitin-proteasome pathway. Consequently, methylation-stabilized SREBP1a increased de novo lipogenesis and accelerated the growth of cancer cells in vivo and in vitro. Clinically, R321 symmetric dimethylation status was associated with malignant progression of human hepatocellular carcinoma, where it served as an independent risk factor of poor prognosis. By showing how PRMT5-induced methylation of SREBP1a triggers hyperactivation of lipid biosynthesis, a key event in tumorigenesis, our findings suggest a new generalized strategy to selectively attack tumor metabolism.

Irisin Inhibits Hepatic Cholesterol Synthesis via AMPK-SREBP2 Signaling

Irisin, a myokine released during exercise, promotes browning of subcutaneous adipose tissue and regulates energy homeostasis. Although exercise constantly reduces blood cholesterol, whether irisin is involved in the regulation of cholesterol remains largely unknown. In the present study, subcutaneous infusion of irisin for 2weeks induced a reduction in plasma and hepatic cholesterol in high fat diet-induced obese (DIO) mice. These alterations were associated with an activation of 5′ AMP-activated protein kinase (AMPK) and inhibition of sterol regulatory element-binding transcription factor 2 (SREBP2) transcription and nuclear translocation. In primary hepatocytes from either lean or DIO mice, irisin significantly decreased cholesterol content via sequential activation of AMPK and inhibition of SREBP2. Suppression of AMPK by compound C or AMPKα1 siRNA blocked irisin-induced alterations in cholesterol contents and SREBP2. In conclusion, irisin could suppress hepatic cholesterol production via a mechanism dependent of AMPK and SREBP2 signaling. These findings suggest that irisin is a promising therapeutic target for treatment of hypercholesterolemia.

Cannabinoid receptor signaling regulates liver development and metabolism.

Endocannabinoid (EC) signaling mediates psychotropic effects and regulates appetite. By contrast, potential roles in organ development and embryonic energy consumption remain unknown. Here, we demonstrate that genetic or chemical inhibition of cannabinoid receptor (Cnr) activity disrupts liver development and metabolic function in zebrafish (Danio rerio), impacting hepatic differentiation, but not endodermal specification: loss of cannabinoid receptor 1 (cnr1) and cnr2 activity leads to smaller livers with fewer hepatocytes, reduced liver-specific gene expression and proliferation. Functional assays reveal abnormal biliary anatomy and lipid handling. Adult cnr2 mutants are susceptible to hepatic steatosis. Metabolomic analysis reveals reduced methionine content in Cnr mutants. Methionine supplementation rescues developmental and metabolic defects in Cnr mutant livers, suggesting a causal relationship between EC signaling, methionine deficiency and impaired liver development. The effect of Cnr on methionine metabolism is regulated by sterol regulatory element-binding transcription factors (Srebfs), as their overexpression rescues Cnr mutant liver phenotypes in a methionine-dependent manner. Our work describes a novel developmental role for EC signaling, whereby Cnr-mediated regulation of Srebfs and methionine metabolism impacts liver development and function.

Thyroid hormone responsive (THRSP) promotes the synthesis of medium-chain fatty acids in goat mammary epithelial cells

In nonruminants, thyroid hormone responsive (THRSP) is a crucial protein for cellular de novo lipogenesis. However, the role of THRSP in regulating the synthesis of milk fatty acid composition in goat mammary gland remains unknown. In the present study, we compared gene expression of THRSP among different goat tissues. Results revealed that THRSP had the highest expression in subcutaneous fat, and expression was higher during lactation compared with the dry period. Overexpression of THRSP upregulated the expression of fatty acid synthase (FASN), stearoyl-coenzyme A desaturase 1 (SCD1), diacylglycerol acyltransferase 2 (DGAT2), and glycerol-3-phosphate acyltransferase (GPAM) in goat mammary epithelial cells. In contrast, overexpression of THRSP led to downregulation of thrombospondin receptor (CD36) and had no effect on the expression of acetyl-coenzyme A carboxylase α (ACACA) and sterol regulatory element binding transcription factor1 (SREBF1). In addition, overexpressing THRSP in vitro resulted in a significant increase in triacylglycerol (TAG) concentration and the concentrations of C12:0 and C14:0. Taken together, these results highlight an important role of THRSP in regulating lipogenesis in goat mammary epithelial cells.

Wild ginseng cambial meristematic cells ameliorate hepatic steatosis and mitochondrial dysfunction in high-fat diet-fed mice.

The aim of this study was to determine the protective mechanisms of wild ginseng cambial meristematic cells (CMCs) on non-alcoholic fatty liver disease in high-fat diet (HFD)-fed mice. Male C57BL/6 mice received either normal-fat diet or HFD for 10 weeks along with wild ginseng CMCs (75, 150 and 300 mg/kg) or vehicle (0.5% carboxyl methyl cellulose) by oral administration once a day. Triglyceride and total cholesterol contents were measured in liver and serum samples. Parameters for hepatic lipid metabolism and mitochondria biogenesis were assessed. Treatment with wild ginseng CMCs markedly attenuated body weight, serum and hepatic lipid contents, and serum aminotransferase activity. While wild ginseng CMCs attenuated the increases in sterol regulatory element-binding transcription factor 1 (SREBP-1) and carbohydrate-responsive element-binding protein (ChREBP) expression, it enhanced the increases in carnitine palmitoyltransferase 1A (CPT1A) and peroxisome proliferator-activated receptor alpha (PPAR-α) expression. HFD decreased glutamate dehydrogenase activity and glutathione content, and increased lipid peroxidation, which were all attenuated by wild ginseng CMCs. Furthermore, wild ginseng CMCs enhanced mitochondrial biogenesis-related factors, including peroxisome proliferator-activated receptor-γ co activator 1α (PGC1α), nuclear respiratory factor 1 (NRF1) and mitochondrial transcription factor A (TFAM). Wild ginseng CMCs protect against HFD-induced liver injury, which prevents lipid accumulation and mitochondrial oxidative stress, and enhances mitochondrial biogenesis.

Association Study Between Metabolic Syndrome and rs8066560 Polymorphism in the Promoter Region of Sterol Regulatory Element-binding Transcription Factor 1 Gene in Iranian Children and Adolescents.

Background:Metabolic syndrome (MetS) is a prevalent disorder in pediatric age groups, described by a combination of genetic and environmental factors. Sterol regulatory element-binding transcription factor 1 (SREBF-1) induces the expression of a family of genes involved in fatty acid synthesis. Moreover, dysregulation of miR-33b, which is located within the intron 17 of the SREBF-1 gene, disrupts fatty acid oxidation and insulin signaling, thus leading to MetS. The aim of the present study was to investigate the association between SREBF-1 rs8066560 polymorphism and MetS in Iranian children and adolescents.Methods:This study includes 100 MetS and 100 normal individuals aged 9–19 years. Anthropological and biochemical indexes were measured. The -1099G > A polymorphism was genotyped by TaqMan real-time polymerase chain reaction.Results:Significant differences were observed in anthropometric measurements and lipid profiles between MetS and normal children. There were no differences in the genotype frequencies or allele distribution for -1099G > A polymorphism between MetS and control groups. High-density lipoprotein cholesterol levels were significantly higher in the MetS GG group than in the A allele carrier group. The genotype AA controls had significantly increased cholesterol and low-density lipoprotein cholesterol levels than AG genotypes. By logistic regression using different genetic models, no significant association was observed between SREBF-1 rs8066560 polymorphism and the risk of MetS.Conclusions:We conclude that the -1099G > A variant on SREBF-1 gene associated with serum lipid profiles, however, it may not be a major risk factor for the MetS in Iranian children and adolescents.

Expression of genes involved in adipogenesis and lipid metabolism in subcutaneous adipose tissue and longissimus muscle in low-marbled Pirenaica beef cattle

The ability to accumulate intramuscular fat (IMF) is a highly variable characteristic in beef cattle. In breeds with a low tendency to accumulate IMF, this can lead to compromised meat quality because of the contribution of fat to such organoleptic attributes as juiciness and taste. This study considered adiposity and gene expression of some of the main markers involved in adipogenesis and lipid metabolism in the subcutaneous (SC) adipose tissue (AT) and the longissimus thoracis muscle (LM) and investigated differences in adipogenic regulation between the tissues during growth and fattening under different conditions. Pirenaica beef cattle were chosen for the study due to the breed’s low tendency to accumulate IMF and the breed’s regional importance. The young Pirenaica bulls used (n=16) were allocated to four groups and slaughtered at 6, 12 and 18 months. From 12 months onwards the bulls slaughtered at 18 months were fed diets having different energy densities. Backfat thickness increased from 6 to 12 months (P<0.05) but then was unchanged, while other fattening parameters such as percentage chemical fat and marbling did not vary. The adipose cell size distribution displayed a bimodal distribution for SC adipocytes and a unimodal distribution for IMF cells, suggestive of tissue-specific hyperplasia. Gene expression of peroxisome proliferator-activated receptor γ (PPARG), CCAAT/enhancer-binding protein α (CEBPA), sterol regulatory element-binding transcription factor 1 (SREBF1), wingless-type MMTV integration site family 10B (WNT10B), fatty acid-binding protein 4 (FABP4), acetyl Co-A carboxylase α, lipoprotein lipase and fatty acid synthase (FASN) were determined by real-time quantitative PCR. Expression did not differ between the experimental groups within the tissues but did differ between the tissues: PPARG, FABP4 and FASN were upregulated in the SC AT, while CEBPA, WNT10B and SREBF1 were upregulated in the LM. Although age and diet energy density did not have a significant effect on increasing the amount of IMF, these factors could have influenced adipocyte development in this tissue differently than in the SC AT. This was evidenced by the different size distributions of the cells in the two tissues, and the differing expression patterns of certain markers in the SC AT and the LM, which may indicate a differential role of PPARG and WNT10B in triggering adipocyte proliferation and fat accumulation capacity.

Identification and characterization of SREBF2 expression and its association with chicken carcass traits.

The sterol regulatory element-binding transcription factor 2 gene (SREBF2) plays an important role in regulating lipid homeostasis. To reveal the genetic factors that underlie carcass fat deposition in chickens, we cloned the coding DNA sequence of chicken SREBF2, investigated SREBF2 mRNA expression levels in various tissues, detected single nucleotide polymorphisms (SNPs) in the exon regions of the gene, and conducted association analyses between single markers/haplotypes and carcass traits. The entire 2859-bp cDNA sequence of chicken SREBF2 that encoded 952 amino acids was obtained and characterized. SREBF2 mRNA was highly expressed in the uropygial gland, followed by the liver, breast muscle, and leg muscle. Ten SNPs were detected, and four (g.49363077T>A, g.49357503C>T, g.49355533G>A, and g.49354641G>A) were novel. When analyzing the associations between the single mutations and carcass traits, significant differences were found in three SNPs and g.49357915G>A was highly significantly associated with most carcass traits, except for abdominal fat weight and sebum thickness. In addition, haplotype combinations that were constructed using the SREBF2 SNPs were associated with breast muscle weight. Chickens with the combined genotype H21H21 had the highest live weight, carcass weight, eviscerated weight, and semi-eviscerated weight values. To the best of our knowledge, this is the first study conducted on chicken SREBF2 polymorphisms, which are predictive of the genetics that underlie the economic performance of chickens.

Retinoic acid receptor β2 agonists restore glycaemic control in diabetes and reduce steatosis.

To investigate the effects of specific retinoic acid receptor (RAR) agonists in diabetes and fatty liver disease. Synthetic agonists for RARβ2 were administered to wild-type (wt) mice in a model of high-fat-diet (HFD)-induced type 2 diabetes (T2D) and to ob/ob and db/db mice (genetic models of obesity-associated T2D). We show that administration of synthetic agonists for RARβ2 to either wt mice in a model of HFD-induced T2D or to ob/ob and db/db mice reduces hyperglycaemia, peripheral insulin resistance and body weight. Furthermore, RARβ2 agonists dramatically reduce steatosis, lipid peroxidation and oxidative stress in the liver, pancreas and kidneys of obese, diabetic mice. RARβ2 agonists also lower levels of mRNAs involved in lipogenesis, such as sterol regulatory element-binding transcription factor 1 (SREBP1) and fatty acid synthase, and increase mRNAs that mediate mitochondrial fatty acid β-oxidation, such as CPT1α, in these organs. RARβ2 agonists lower triglyceride levels in these organs, and in muscle. Collectively, our data show that orally active, rapid-acting, high-affinity pharmacological agonists for RARβ2 improve the diabetic phenotype while reducing lipid levels in key insulin target tissues. We suggest that RARβ2 agonists should be useful drugs for T2D therapy and for treatment of hepatic steatosis.

Up-regulation of liver Pcsk9 gene expression as a possible cause of hypercholesterolemia in experimental chronic renal failure.

Dyslipidemia commonly present in patients with chronic kidney disease (CKD) has been recently linked to increased proprotein convertase subtilisin/kexin type 9 (PCSK9) serum concentration. We tested a hypothesis that increased liver PCSK9 biosynthesis could be partially responsible for the elevated circulating PCSK9 level, and subsequently contribute to hypercholesterolemia observed in subjects with CKD. Rat model of chronic renal failure (CRF) was used in the study. Animals underwent a 5/6 nephrectomy or a sham operation. Liver expression of Pcsk9, sterol regulatory element-binding transcription factor 2 (Srebf-2), and β-actin were quantified by real-time RT-PCR. Liver protein levels of PCSK9, LDL-receptor (LDL-R), and SREBF-2 were analyzed using Western blotting. Serum PCSK9 concentration was estimated by immunoassay. Rats with an experimental CRF as compared to pair-fed and control ones were characterized by: (a) an up-regulation of liver Pcsk9 and Srebf-2 genes expression with parallel increase of serum PCSK9 concentration; (b) a decrease in liver LDL-R protein level, and (c) an increase of serum total and LDL-cholesterol concentrations. We also found significant correlations between serum creatinine and liver PCSK9 mRNA levels (r = 0.88, p < 0.001) and between serum creatinine and circulating PCSK9 levels (r = 0.73, p < 0.001). The results suggest that a rat model of CRF is associated with an increased liver Pcsk9 gene expression. The coordinated up-regulation of Pcsk9 and Srebf-2 genes expression suggests that SREBF-2 may play a key role in regulation of Pcsk9 gene expression, circulating PCSK9 level, and hypercholesterolemia in experimental CRF.

Optimized Rapeseed Oils Rich in Endogenous Micronutrients Protect High Fat Diet Fed Rats from Hepatic Lipid Accumulation and Oxidative Stress.

Micronutrients in rapeseed exert a potential benefit to hepatoprotection, but most of them are lost during the conventional refining processing. Thus some processing technologies have been optimized to improve micronutrient retention in oil. The aim of this study is to assess whether optimized rapeseed oils (OROs) have positive effects on hepatic lipid accumulation and oxidative stress induced by a high-fat diet. Methods: Rats received experiment diets containing 20% fat and refined rapeseed oil or OROs obtained with various processing technologies as lipid source. After 10 weeks of treatment, liver was assayed for lipid accumulation and oxidative stress. Results: All OROs reduced hepatic triglyceride contents. Microwave pretreatment-cold pressing oil (MPCPO) which had the highest micronutrients contents also reduced hepatic cholesterol level. MPCPO significantly decreased hepatic sterol regulatory element-binding transcription factor 1 (SREBP1) but increased peroxisome proliferator activated receptor α (PPARα) expressions, and as a result, MPCPO significantly suppressed acetyl CoA carboxylase and induced carnitine palmitoyl transferase-1 and acyl CoA oxidase expression. Hepatic catalase (CAT) and glutathione peroxidase (GPx) activities as well as reduced glutathione (GSH) contents remarkably increased and lipid peroxidation levels decreased in parallel with the increase of micronutrients. Conclusion: OROs had the ability to reduce excessive hepatic fat accumulation and oxidative stress, which indicated that OROs might contribute to ameliorating nonalcoholic fatty liver induced by high-fat diet.

Genome-wide RNAi analysis reveals that simultaneous inhibition of specific mevalonate pathway genes potentiates tumor cell death.

The mevalonate (MVA) pathway is often dysregulated or overexpressed in many cancers suggesting tumor dependency on this classic metabolic pathway. Statins, which target the rate-limiting enzyme of this pathway, 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR), are promising agents currently being evaluated in clinical trials for anti-cancer efficacy. To uncover novel targets that potentiate statin-induced apoptosis when knocked down, we carried out a pooled genome-wide short hairpin RNA (shRNA) screen. Genes of the MVA pathway were amongst the top-scoring targets, including sterol regulatory element binding transcription factor 2 (SREBP2), 3-hydroxy-3-methylglutaryl-coenzyme A synthase 1 (HMGCS1) and geranylgeranyl diphosphate synthase 1 (GGPS1). Each gene was independently validated and shown to significantly sensitize A549 cells to statin-induced apoptosis when knocked down. SREBP2 knockdown in lung and breast cancer cells completely abrogated the fluvastatin-induced upregulation of sterol-responsive genes HMGCR and HMGCS1. Knockdown of SREBP2 alone did not affect three-dimensional growth of lung and breast cancer cells, yet in combination with fluvastatin cell growth was disrupted. Taken together, these results show that directly targeting multiple levels of the MVA pathway, including blocking the sterol-feedback loop initiated by statin treatment, is an effective and targetable anti-tumor strategy.

ZnO Nanoparticles Upregulates Adipocyte Differentiation in 3T3-L1 Cells.

The present study was aimed to investigate the effect of zinc oxide (ZnO) nanoparticles on 3T3-L1 cell differentiation, by quantitating peroxisome proliferators-activated receptor γ (PPARγ), CCAAT/enhancer binding protein α (C/EBPα), fatty acid binding protein 4 (FABP4), sterol regulatory element-binding transcription factor 1 (SREBP1), and serine-threonine kinase cyclin-dependent kinase 4 (cdk4), which are critical for adipogenesis. 3T3-L1 preadipocyte cells were cultured and differentiated with the standard differentiation medium. Sulforhodamine B (SRB) assay determined 3T3-L1 cell viability. ZnO nanoparticles increased the lipid accumulation in differentiated adipocytes as evidenced by Oil Red O staining. The quantitative PCR (qPCR) analysis showed that the PPARγ, FABP4, C/EBPα, and SREBP1 messenger RNA (mRNA) expression was significantly increased in the ZnO nanoparticle-treated 3T3-L1 adipocytes. Western blot analysis showed increased PPARγ, FABP4, C/EBPα, and SREBP1 protein expression compared to their respective controls. Also, the immunofluorescence study showed the increased cdk4 and PPARγ expression in the nanoparticle-treated cells. Taking all these data together, it is concluded that ZnO nanoparticles may be a potent substance to alter 3T3-L1 preadipocyte differentiation and adipogenesis.

Liraglutide reduces oxidized LDL-induced oxidative stress and fatty degeneration in Raw 264.7 cells involving the AMPK/SREBP1 pathway.

BackgoundRecent studies have suggested a potential role for liraglutide in the prevention and stabilization of atherosclerotic vascular disease. However, the molecular mechanisms underlying the effect of liraglutide on atherosclerosis have not been well elucidated. The purpose of this study was to examine whether liraglutide protects against oxidative stress and fatty degeneration via modulation of AMP-activated protein kinase (AMPK)/sterol regulatory element binding transcription factor 1 (SREBP1) signaling pathway in foam cells.MethodsMouse macrophages Raw264.7 cells were exposed to oxidized low density lipoprotein (oxLDL) to induce the formation of foam cells. The cells were incubated with oxLDL (50 µg/mL), liraglutide (0.1, 0.5, 1 and 2 nmol/L) or exendin-3 (9-39) (1, 10 and 100 nmol/L) alone, or in combination. Oil Red O staining was used to detect intracellular lipid droplets. The levels of TG and cholesterol were measured using the commercial kits. Oxidative stress was determined by measuring intracellular reactive oxygen species (ROS), malondialdehyde (MDA) and superoxide dismutase 1 (SOD). Western blot analysis was used to examine the expression of AMPKα1, SREBP1, phosphorylated AMPKα1, phosphorylated SREBP1, glucagon-like peptide-1 (GLP-1) and GLP-1 receptor (GLP-1R).ResultsOil Red O staining showed that the cytoplasmic lipid droplet accumulation was visibly decreased in foam cells by treatment with liraglutide. The TG and cholesterol content in the liraglutide-treated foam cells was significantly decreased. In addition, foam cells manifested an impaired oxidative stress following liraglutide treatment, as evidenced by increased SOD, and decreased ROS and MDA. However, these effects of liraglutide on foam cells were attenuated by the use of GLP-1R antagonist exendin-3 (9-39). Furthermore, we found that the expression level of AMPKα1 and phosphorylated AMPKα1 was significantly increased while the expression level of SREBP1 and phosphorylated SREBP1 was significantly decreased in foam cells following treatment with liraglutide.ConclusionsThis study for the first time demonstrated that the effect of liraglutide on reducing oxidative stress and fatty degeneration in oxLDL-induced Raw264.7 cells is accompanied by the alteration of AMPK/SREBP1 pathway. This study provided a potential molecular mechanism for the effect of liraglutide on reducing oxidative stress and fatty degeneration.