Sterol Regulatory Element-binding Protein-1 Gene Research Articles

Expression levels of genes involved in lipogenesis and cholesterol synthesis in adenomyosis

Abstract Objectives Adenomyosis is a benign uterine disease that occurs with the invasion of the endometrial gland and stoma into the myometrium. The etiology and molecular pathology of adenomyosis are not yet fully understood. Tissue samples of patients diagnosed with adenomyosis and healthy endometrial tissues were investigated for the lipogenesis and cholesterol synthesis pathways. It was aimed to determine the difference between adenomyosis and healthy endometrial tissues in terms of lipid metabolism and to investigate the mechanism of adenomyosis in this context. Methods Formalin-fixed paraffin-embedded archival tissues were used in the current retrospective study. A total of 76 patient samples and 3 groups were used. Group 1: adenomyotic tissue (n=28), Group 2: eutopic endometrial tissue (n=30), and Control Group (n=18). In these groups, Sterol regulatory element binding protein 1 (SREBP1) molecule, fatty acid synthase (FASN), acetyl-CoA carboxylase (ACACA), ATP-citrate lyase (ACLY), HMG-CoA reductase (HMGCR), and HMG-CoA synthase (HMGCS) markers were evaluated by using RT-PCR method. Results Statistically significant differences (p<0.05) were found between the groups regarding expression levels of HMGCR, HMGCS, ACLY, ACACA, and SREBP1. HMGCR, HMGCS, ACLY, and SREBP1 gene expression levels between Group 1 and Group 2 and HMGCS, ACACA, ACLY, and SREBP1 gene expression levels between Group 1 and Control Group were determined as statistically different. A significant difference was detected only in HMGCR gene expression levels between Group 2 and the Control Group. Conclusions These results show that genes involved in lipid metabolism may be associated with the molecular pathogenesis of adenomyosis.

The 84-bp Indel Polymorphism of The Sterol Regulatory Element-Binding Protein 1 (SREBP1) Gene in Several Cattle Breeds in Indonesia

Sterol regulatory element-binding protein 1 (SREBP1) gene is a gene that encodes SREBP1, a family of transcription factors that have a key role in lipid homeostasis as well as fatty acid metabolisms. The present study aimed to detect the 84-bp indel polymorphism in the intron 5 of the SREBP1 gene (84-bp indel) in several cattle breeds in Indonesia. A total of 740 cattle of six breeds (Limousin, Simmental, Holstein-Friesian, Bali, Sumbawa, and Pasundan) from two National Artificial Insemination Centers (NAICs) and smallholder farmers were used in this study. The detection of 84-bp indel polymorphism was performed using the polymerase chain reaction (PCR) method and visualized through a gel agarose electrophoresis system. The study showed that the L allele (insertion-type) was common and is fixed in Holstein-Friesian, Bali, and Sumbawa cattle (1.00). Meanwhile, the S allele (deletion-type) was found in Limousin, Simmental, and Pasundan cattle with a frequency of 0.24, 0.16, and 0.01, respectively. The presence of the S allele in Pasundan cattle was only found in the form of the heterozygous LS genotype (0.03). In conclusion, the 84-bp indel of the SREBP1 gene was found to be polymorphic in Limousin, Simmental, and Pasundan cattle, but monomorphic in Holstein-Friesian, Bali, and Sumbawa cattle.

As3MT via consuming SAM is involved in arsenic-induced nonalcoholic fatty liver disease by blocking m6A-mediated miR-142-5p maturation

Arsenic, a common environmental hazard, is a risk factor for nonalcoholic fatty liver disease (NAFLD). However, the mechanism remains unclear. Here, we found that chronic exposure to environmental-related doses of arsenic disturbed fatty acid and methionine metabolism in mice, caused liver steatosis, increased arsenic (3) methyltransferase (As3MT), sterol regulatory element binding protein 1 (SREBP1) and lipogenic gene levels, and decreased N6-methyladenosine (m6A) and S-adenosylmethionine (SAM) levels. Mechanistically, arsenic blocks m6A-mediated miR-142-5p maturation by consuming SAM via As3MT. miR-142-5p was involved in arsenic-induced cellular lipid accumulation by targeting SREBP1. SAM supplementation or As3MT deficiency blocked arsenic-induced lipid accumulation by promoting the maturation of miR-142-5p. Moreover, in mice, folic acid (FA) and vitamin B12 (VB12) supplementation blocked arsenic-induced lipid accumulation by restoring SAM levels. Arsenic-exposed heterozygous As3MT mice showed low liver lipid accumulation. Our study demonstrates that SAM consumption caused by arsenic, through As3MT, blocks m6A-mediated miR-142-5p maturation, thereby elevating the levels of SREBP1 and lipogenic genes, leading to NAFLD, which provides a new mechanism and biological insights into the therapy of NAFLD induced by environmental factors.

Silymarin diminishes oleic acid-induced lipid accumulation in HepG2 cells by modulating the expression of endoplasmic reticulum stress markers

Background and objectivesNon-alcoholic fatty liver disease (NAFLD) is a common metabolic disorder which presents with the accumulation of triglycerides in hepatocytes due to imbalances in the uptake, synthesis, export, and oxidation of fatty acids. Silymarin is a flavonolignan derived from milk thistle, a herbal medicine that has been used for centuries to treat liver disease. In this study, the effect of silymarin on genes involved in lipogenesis and endoplasmic reticulum (ER) stress was investigated in the cellular NAFLD model. Materials and methodsHepG2 cells were treated with 0.5 mM oleic acid (OA) in the presence or absence of silymarin for 24 h, and subsequently, lipid accumulation was assessed by staining the cells with Oil red O as well as the measurement of intracellular triglyceride (TG) content with an enzymatic method. Real-time reverse transcription polymerase chain reaction (RT-PCR) was used to measure the expression of sterol regulatory element-binding protein-1 (SREBP-1), fatty acid synthase (FAS), Sirtuin 1 (SIRT1), TRB3, and ATF4. ResultsLipid accumulation was increased in OA-treated hepatocytes, an effect that was attenuated by silymarin. The expression of FAS, SREBP-1, TRB3, and ATF4 was significantly increased in OA-treated HepG2 cells, while the expression of SIRT1 was decreased. Treatment with silymarin could successfully diminish SREBP-1, FAS, TRB3, and ATF4 gene expression while augmenting the expression of SIRT1. ConclusionsSilymarin not only efficiently reduces lipogenesis but also decreases ER stress, which is a critical parameter in lipogenesis. Therefore, silymarin might be considered an effective supplementary option in the treatment of liver steatosis.

The evaluation for CpG island methylation of FASN and SREBP promoter in Mongolian gerbils NAFLD model

IntroductionThe methylation of CpG island in promoter and its nearby area is one of the most important way to inhibit gene expression. The aim of this study was to examine the potential relationship between the CpG island methylation for fatty acid synthase (FASN) and sterol regulatory element-binding protein 1 (SREBP-1).Material and methodsTen newborn pups of gerbils as NB group, 10 adult gerbils with normal diet as control group, 10 adults with high-fat diet as NAFLD group, and 10 8-month-old as aged group. Blood and liver samples were collected for serum lipid detection and histopathology. A pyrosequencing technique was employed to determine the methylation rate. Then, the transcription and expression level for FASN and SREBP-1 were verified.ResultsSerum chelosterol and triglyceride was significantly increased in NAFLD and aged group (vs. control, P<0.05). The gerbils in NAFLD and aged group also showed obvious hepatic steatosis confirmed by histological examination. Control group had the highest methylation rate for FASN and SREBP-1, which were reduced in NAFLD and aged group. Except for NB group, both the transcription and expression levels of SREBP-1 and FASN genes were presented control group> Aged group > NAFLD group. Genes of SREBP and FASN showed a trend of hypomethylation in the NAFLD gerbil model.ConclusionsThe expression of SREBP gene tended to decrease, while the expression of FASN gene tended to increase with the age and disease development. FASN and SREBP-1 methylation might be a new method to evaluate NAFLD animal model and an available target for genetic marker screening.

Biological Behavior and Lipid Metabolism of Colon Cancer Cells are Regulated by a Combination of Sterol Regulatory Element-Binding Protein 1 and ATP Citrate Lyase.

PurposeTo research the effects of ATP citrate lyase (ACLY) and Sterol-regulatory element binding protein 1 (SREBP1) on the biology and lipid metabolism of colorectal cancer cells.MethodsColorectal cancer cells Caco-2 and Lovo were transfected with ACLY or SREBP1 gene knockdown lentiviruses. Four groups were set: ACLY knockdown, SREBP1 knockdown group, empty vector-transfected (negative control), and untreated cells (blank control). Cell proliferation was measured using CCK-8, colony formation, and EdU labeling assays. Apoptosis was detected using Annexin V-APC/7- AAD and JC-1 assay. Transwell migration and wound healing assays analyzed cell migration and invasion. A triglyceride test kit and oil red O stain assessed cell lipid production. Key factors related to lipid metabolism were detected.ResultsACLY and SREBP1 promoted cell proliferation at 48 and 120 h, but there was no significant difference in Caco-2 cells at 24 h, at which point the effect of SREBP1 was more important. ACLY’s effect on cell proliferation was more obvious at 120 h. Colony formation assays in Caco-2 showed similar results to the CCK-8 assay at 120 h, but ACLY knockdown had no effect in Lovo cells. EDU assays showed that ACLY or SREBP1 facilitated DNA reproduction in the two cell lines, in which SREBP1 was more significant. Knockdown of the two genes showed significant differences in Lovo cells. However, ALCY knockdown promoted apoptosis to a greater extent than SREBP1 knockdown in Caco-2 cells. In addition, ACLY and SREBP1 enhanced migration, invasion, and lipid production in both cell lines. Knockdown of ACLY or SREBP1 reduced lipid metabolism pathway gene expression in the two cell lines.ConclusionKnockdown of ACLY and SREBP1 genes inhibit the proliferation, migration, and invasion of colorectal cancer cells, while promoting their apoptosis. Our results identified potential new targets to treat colorectal cancer via lipid synthesis modulation in cancer cells.

Effect of acetate, β-hydroxybutyrate and their interaction on lipogenic gene expression, triglyceride contents and lipid droplet formation in dairy cow mammary epithelial cells

The purpose of this study was to assess the effects of acetate and β-hydroxybutyrate alone or in combination on lipogenic genes and their associated regulatory proteins in dairy cow mammary epithelial cells (DCMEC) using quantitative reverse transcription polymerase chain reaction (qRT-PCR), western blotting, lipid droplet staining and a triglyceride content detection kit, to determine whether SCFA are related to milk fat synthesis regulation in DCMEC. Our experiment shows that addition of different concentrations of acetate, β-hydroxybutyrate and their combinations to DCMEC increase in relative mRNA abundance of lipogenic genes and key transcription factors suggest an increase in lipogenic capacity, which is supported by an increased in cytosolic triglyceride content. Similarly, the protein expression level of acetyl-coenzyme A carboxylase (ACACA), fatty acid synthase (FASN) and sterol-coenzyme desaturase-1 (SCD1) genes and the transcription factor sterol regulatory element-binding protein-1 (SREBP1) were found to be increased by addition of acetate, β-hydroxybutyrate and their combinations. The expression pattern of fat-related genes and proteins showed similar trends in almost all treatments, suggesting that common transcription factor are regulating these genes. These results show that acetate and β-hydroxybutyrate regulate fat synthesis, further confirming that SCFAs work by targeting genes to activate the SREBP1 and insulin-induced gene 1 protein (INSIG1) signalling pathways in DCMEC.

Isolation, characterization, and SREBP1 functional analysis of mammary epithelial cell in buffalo.

Compared to cow milk, buffalo milk contains more protein, fat, and vitamin. Buffalo milk is an ideal food in human life. Sterol regulatory element-binding protein 1 (SREBP1), an important transcription factor, regulates the expression and activity of enzyme and protein involved in milk fat synthesis to influence on the synthesis and secretion of triglyceride in mammary epithelial cells. In the present study, we successfully isolated buffalo mammary epithelial cell by using enzymatic digestion, and then described the growth characteristics and expression characteristics of mammary epithelial cells. Moreover, we cloned the SREBP1 gene from total RNA isolated from milk fat globule and analyzed the function of the SREBP1 gene. After infected with shRNA-SREBP1 lentiviral particle and treated with fatty acid, the expression trend of ACACA, FABP3, FAS, SCD, ERK1, ERK2, PPARy, and Insigl genes was consistent with the expression trend of SREBP1 gene. These results suggested that SREBP1 gene is a central transcription factor in regulating milk fat synthesis and SREBP1 gene may act on ERK1/ERK2 signaling pathway to regulate the expression of PPARy gene. The current study will provide a theoretical basis for further reveal the molecular mechanism of milk fat synthesis in buffalo mammary epithelial cells. PRACTICAL APPLICATIONS: This study aim to separate and analysis characterization of mammary epithelial cell in buffalo. Compared to cow milk, buffalo milk contains more protein, fat, and vitamin. Buffalo milk is an ideal food in human life. This study will provide a theoretical basis for further research on the molecular mechanism of milk fat synthesis in buffalo mammary epithelial cells.

Role of SREBP2 gene polymorphism on knee osteoarthritis in the South Indian Hyderabad Population: A hospital based study with G595C variant

IntroductionOsteoarthritis (OA) is a multifactorial disease with genetic factors playing a crucial role, and it has been associated with a family history of obesity. G595C polymorphism in the sterol regulatory element-binding protein 2 (SREBP2) gene has demonstrated an association with knee osteoarthritis (KOA) patients. However, this polymorphism has been never explored in an Indian population. Hence, the current study aimed to examine whether G595C (rs2228314) polymorphism in SREBP2 gene was associated with KOA susceptibility in the South Indian Hyderabad population. MethodsG595C polymorphism was genotyped with 200 KOA cases and 200 healthy controls using polymerase chain reaction-restriction fragment length polymorphism analysis. ResultsA significant association was observed between age, body mass index (BMI), and family histories in KOA cases and controls (p < 0.05). The current allele (C vs G; OR-2.8 [95%CI = 2.1–3.7]; p < 0.0001) and genotype analysis confirms the significant association with (GC + CC vs GG; OR-3.5 [95%CI = 2.3–5.3]; p < 0.0001 & GC vs GG + CC; OR-1.7 [95%CI = 1.0–2.9]; p = 0.02) KOA vs. control subjects. On stratification analysis, genotype CC and C allele were associated with KOA. Gender association failed to demonstrate positive genotype frequencies (p > 0.05). Multifactor-dimensionality reduction (MDR) analysis showed a positive association with BMI and G595C genotypes (p < 0.05); 51% of the homozygous variant CC genotypes were present in obesity subjects. ConclusionIn conclusion, our findings suggest that G595C polymorphism in SREBP2 gene is associated with KOA in the South Indian Hyderabad population and presents scope for further investigation of the gene's function in KOA.

Inhibition of Stearoyl-CoA Desaturase-1 Activity Suppressed SREBP Signaling in Colon Cancer Cells and Their Spheroid Growth

Unsaturated fatty acids are critical in promoting colon tumorigenesis and its stemness. Stearoyl-CoA desaturase-1 (SCD1) is a rate-limiting lipid desaturase associated with colon cancer cell proliferation and metastasis control. This study aims to evaluate the effects of SCD1 inhibition on colon cancer spheroid growth in a three-dimensional cell culture system. An analysis of clinical data showed that increased SCD1 gene expression in colon tumors was negatively correlated with the prognosis. A chemical inhibitor of SCD1, CAY10566, inhibited the growth of colon cancer cells in both monolayer and sphere cultures. In addition, oleic acid administration—a monounsaturated fatty acid generated by the action of SCD1—prevented the suppression of sphere formation by CAY10566. RNA-sequencing data from 382 colon tumor patient samples obtained from the Cancer Genome Atlas database showed that 806 genes were SCD1-associated genes in human colon cancer. Correlation analysis identified the master regulator of lipid homeostasis sterol regulatory element-binding protein 2 (SREBP2) as a prominent transcription factor, whose expression was positively correlated with SCD1 in human colon cancer. SCD1 knockdown using siRNA in colon cancer samples, suppressed SREBP2 gene expression, providing direct evidence that SREBP signaling is under the control of SCD1 in these cells. Pathway analysis in the Ingenuity Pathways Analysis platform showed that SCD1 expression positively correlated with genes involved in multiple pathways, including lipid synthesis and incorporation, cell proliferation, and tissue tumorigenesis. Further network analysis revealed a central role for Myc in the network hierarchy of the SCD1-correlated genes. These findings suggested that SCD1 inhibition would be an effective strategy for suppressing colon cancer spheroid growth, partly through downregulating SREBP-mediated lipid and cholesterol metabolism and Myc signaling.

Association of SREBP2 gene polymorphisms with the risk of osteonecrosis of the femoral head relates to gene expression and lipid metabolism disorders.

Although lipid metabolism disorders have been recognized as a primary factor of osteonecrosis of the femoral head (ONFH), the molecular pathogenesis remains unclear. Sterol regulatory element‑binding protein 2 (SREBP2) specifically regulates cholesterol and fatty acid metabolism to maintain lipid homeostasis. To explore the roles of the SREBP2 gene in the development of ONFH, the authors analyzed the gene polymorphism and gene expression of three tag single nucleotide polymorphisms of the SREBP2 gene, the serum lipids levels, and their associations with ONFH development in 182 ONFH patients and 179 healthy controls. The results demonstrated that the stageIV proportions of ONFH patients carrying the rs2267439CT or CC genotype were significantly higher and lower than the stageIII proportions of ONFH patients (P=0.039), respectively. The serum triglyceride, low‑density lipoprotein (LDL)‑c levels, and LDL‑C/high‑density lipoprotein (HDL)‑C ratio in the ONFH group were significantly increased compared to those in the control group (P=0.01, P=0.005, P=0.0001) while the HDL‑C level of ONFH group was remarkably lower than that of the control group (P=0.0001). Association analysis further revealed that the LDL‑c levels of the rs226744 GG and AG genotype carriers were statistically higher than that of the AA genotype carriers (P=0.039, P=0.05). These results demonstrated that the gene polymorphism of SREBP2 not only significantly associated with the clinical phenotypes of ONFH but also closely related to lipid metabolism disorder. The results indicated that SREBP2 gene polymorphism and function may play key roles in the development of ONFH.

Effects of different levels of protein supplementary diet on gene expressions related to intramuscular deposition in early‐weaned yaks

This study was conducted to estimate different levels of protein supplementary diet on gene expressions related to intramuscular deposition in early-weaned yaks. Results showed that supplementary dietary protein significantly increased final weight, average daily gain (ADG), intramuscular fat (IMF), serum free fatty acid (FFA), total triglycerides, total cholesterol (Ch), low-density lipoprotein cholesterol (LDL) and high-density lipoprotein cholesterol (HDL) content. There was a quadratic response of ADG, IMF, FFA, Ch, HDL and LDL to dietary crude protein (CP) level. Lipoprotein lipase (LPL), fatty acid synthase (FAS) and acetyl-CoA carboxylase (ACC) enzyme activities were significantly increased by supplementary dietary CP, while hormone-sensitive lipase (HSL) and carnitine palmitoyltransferase-1 (CPT-1) activities were significantly decreased. LPL, ACC and FAS enzyme activities showed quadratic increase as dietary CP increased. Peroxisome proliferator-activated receptor γ (PPARγ), LPL, FAS, sterol regulatory element binding protein 1 (SREBP-1), ACC, stearoyl-CoA desaturase (SCD) and heart fatty-acid binding protein (H-FABP) gene expression were significantly increased by supplementary dietary CP, while HSL and CPT-1 gene expression were significantly decreased. PPARγ, LPL, SREBP-1, ACC and H-FABP gene expression showed quadratic increase as dietary CP increased. These results indicated that supplementary dietary protein increased IMF accumulation mainly to increased intramuscular lipogenic gene expression and decreased lipolytic gene expression.

Effect of a Synthetic Liver X Receptor Agonist TO901317 on Cholesterol Concentration in Goose Primary Hepatocytes

In this study, we investigated the role of liver X receptor (LXR) in regulating cholesterol concentration in goose primary hepatocytes. Intracellular and extracellular cholesterol concentration, mRNA expression levels of genes related to phosphatidylinositol 3-kinase (PI3K) pathway, sterol regulatory element-binding protein 2 (SREBP-2), and 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR) were measured in primary goose hepatocytes. We found that the intracellular cholesterol concentration showed an uptrend manner when the TO901317 concentration was under 1 μmol/L; compared with 1 μmol/L TO901317, 10 μmol/L TO901317 had an inhibiting effect (P<0.05). The regulation mode of SREBP-2 and HMGR gene expression is similar with that of intracellular cholesterol concentration. These data suggested that LXR activation may stimulate the cholesterol biosynthesis by activating expression of SREBP-2 and HMGR. Interestingly, the mRNA levels of genes related with PI3K pathway increased in the presence of TO901317, which suggested that LXR activation could promote PI3K signalling activity.

Association of rs8066560 variant in the sterol regulatory element-binding protein 1 (SREBP-1) and miR-33b genes with hyperglycemia and insulin resistance.

This study aims to evaluate the association of miR-33b/SREBP-1 rs8066560 with hyperglycemia and insulin resistance in Iranian children and adolescents. This case-control study comprised 200 participants with 9-19 years of age, consisting of 100 MetS and 100 healthy controls. Anthropometric and biochemical parameters were measured, and the polymorphism was genotyped by TaqMan real-time PCR method. Logistic regression analysis of genotype distribution of rs8066560 did not show a significant association with MetS neither in boys (OR, 1.745; 95% CI, 0.695-4.382; p=0.236) nor in girls (OR, 1.075; 95% CI, 0.420-2.752; p=0.880). Participants with GG/AG genotypes had significant higher LDL-C levels than those with the AA genotype. No statistically significant difference was documented in fasting blood glucose and insulin levels between the three rs8066560 genotypes. We found that rs8066560 variant on SREBP-1 and miR-33b genes is associated with LDL-C levels; however, it may not be an important determinant for the MetS, hyperglycemia, and insulin resistance in children and adolescents.

Retinol binding protein 4 and fatty liver: A direct link?

Retinol-binding protein 4 (RBP4) is a 21-kDa protein that facilitates the transport of retinol through the circulation to peripheral tissues. The principal source of RBP4 in the body is the liver. Hepatocytes are the primary producers of RBP4; they use the protein to contribute to total-body retinol homeostasis by complexing it with dietary retinol and secreting the retinol-RBP4 holoprotein into the circulation.1 Although hepatocytes are clearly a dominant source of RBP4, cells from other tissues also synthesize the protein. An important secondary source is the adipocyte. Under lean conditions, adipocytes express about one-fifth as much RBP4 mRNA as a hepatocyte;2 in obesity, this expression increases substantially.3

Polymorphisms in genes in the SREBP1 signalling pathway and SCD are associated with milk fatty acid composition in Holstein cattle

Genes in the sterol regulatory element-binding protein-1 (SREBP1) pathway play a central role in regulation of milk fat synthesis, especially the de-novo synthesis of saturated fatty acids. SCD, a SREBP-responsive gene, is the key enzyme in the synthesis of monounsaturated fatty acids in the mammary gland. In the present study, we discovered SNP in candidate genes associated with this signalling pathway and SCD to identify genetic markers that can be used for genetic and metabolically directed selection in cattle. We resequenced six candidate genes in the SREBP1 pathway (SREBP1, SCAP, INSIG1, INSIG2, MBTPS1, MBTPS2) and two genes for SCD (SCD1 and SCD5) and discovered 47 Tag SNP that were used in a marker-trait association study. Milk and blood samples were collected from Holstein cows in their 1st or 2nd parity at 100-150 days of lactation. Individual fatty acids from C4 to C20, saturated fatty acid (SFA) content, monounsaturated fatty acid content, polyunsaturated fatty acid content and desaturase indexes were measured and used to perform the asociation analysis. Polymorphisms in the SCD5 and INSIG2 genes were the most representative markers associated with SFA/unsaturated fatty acid (UFA) ratio in milk. The analysis of desaturation activity determined that markers in the SCD1 and SCD5 genes showed the most significant effects. DGAT1 K232A marker was included in the study to examine the effect of this marker on the variation of milk fatty acids in our Holstein population. The percentage of variance explained by DGAT1 in the analysis was only 6% of SFA/UFA ratio. Milk fat depression was observed in one of the dairy herds and in this particular dairy one SNP in the SREBP1 gene (rs41912290) accounted for 40% of the phenotypic variance. Our results provide detailed SNP information for key genes in the SREBP1 signalling pathway and SCD that can be used to change milk fat composition by marker-assisted breeding to meet consumer demands regarding human health, as well as furthering understanding of technological aspects of cows' milk.

Effects of bovine fatty acid synthase, stearoyl-coenzyme A desaturase, sterol regulatory element-binding protein 1, and growth hormone gene polymorphisms on fatty acid composition and carcass traits in Japanese Black cattle1

The quality of fat is an important factor in defining the quality of meat. Fat quality is determined by the composition of fatty acids. Among lipid metabolism-related genes, including fatty acid synthesis genes, several genetic variations have been reported in the bovine fatty acid synthase (FASN), stearoyl-CoA desaturase (SCD), sterol regulatory element-binding protein 1 (SREBP1), and GH genes. In the present study, we evaluated the single and epistatic effects of 5 genetic variations (4 SNP and 1 insertion/deletion) in 4 genes (FASN, SCD, SREBP1, and GH) on the fatty acid composition of the longissimus thoracis muscle and carcass and meat quality traits in 480 commercial Japanese Black cattle. Significant single effects of FASN, SCD, and GH(L127V) polymorphisms on the fatty acid composition of the longissimus thoracis muscle were detected. The A293V polymorphism of SCD had the largest effect on myristic acid (C14:0, P < 0.001), myristoleic acid (C14:1, P < 0.001), stearic acid (C18:0, P < 0.001), oleic acid (C18:1, P < 0.001), and MUFA (P < 0.001). Polymorphisms in the FASN, SCD, and SREBP1 genes showed no effect on any meat yield trait. There were no significant epistatic effects on fatty acid composition among pairs of the 3 genes (FASN, SCD, and SREBP1) involved in fatty acid synthesis. No epistatic interactions (P > 0.1) were detected between FASN and SCD for any carcass trait. When the genotypes of 3 markers (FASN, SCD, and GH(L127V)) were substituted from the lesser effect allele to the greater effect allele, the proportion of C18:1 increased by 4.46%. More than 20% of the genetic variance in the C18:1 level could be accounted for by these 3 genetic markers. The present results revealed that polymorphisms in 2 fatty acid synthesis genes (FASN and SCD) independently influenced fatty acid composition in the longissimus thoracis muscle. These results suggest that SNP in the FASN and SCD genes are useful markers for the improvement of fatty acid composition in commercial Japanese Black cattle.

Chronic social defeat stress disrupts regulation of lipid synthesis

Several psychiatric disorders increase the risk of cardiovascular disease, including posttraumatic stress disorder and major depression. While the precise mechanism for this association has not yet been established, it has been shown that certain disorders promote an unfavorable lipid profile. To study the interaction of stress and lipid dysregulation, we utilized chronic social defeat stress (CSDS), a mouse model of chronic stress with features of posttraumatic stress disorder and major depression. Following exposure to CSDS, mice were given access to either regular chow or a Western-style diet high in fat and cholesterol (HFD). The combination of social stress and HFD resulted in significant perturbations in lipid regulation, including two key features of the metabolic syndrome: increased plasma levels of non-HDL cholesterol and intrahepatic accumulation of triglycerides. These effects were accompanied by a number of changes in the expression of hepatic genes involved in lipid regulation. Transcriptional activity of LXR, SREBP1c, and ChREBP were significantly affected by exposure to HFD and CSDS. We present CSDS as a model of social stress induced lipid dysregulation and propose that social stress alters lipid metabolism by increasing transcriptional activity of genes involved in lipid synthesis.

The polymorphisms of stearoyl-CoA desaturase (SCD1) and sterol regulatory element binding protein-1 (SREBP-1) genes and their association with the fatty acid profile of muscle and subcutaneous fat in Fleckvieh bulls

The previously reported genetic polymorphisms of the stearoyl-CoA desaturase (SCD1) and sterol regulatory element binding protein-1 (SREBP-1) genes were investigated in Fleckvieh bulls using the PCR-RFLP and AS-PCR methods, respectively. The genomic DNA was obtained from a total of 370 bulls. The frequencies of alleles A and V of the single nucleotide polymorphism in exon 5 of the SCD1 gene (SNP 878C>T) were 0.555 and 0.445, respectively. In the 84-bp Ins/Del polymorphism in intron 5 of the SREBP-1 gene, the frequency of the L allele (insertion) was markedly higher (0.920) than that of the S allele (deletion; 0.080). Fatty acid profile was determined in a total of 367 samples of muscle fat (MSF) and 150 samples of subcutaneous fat (SCF). The AA genotype of SCD1 polymorphism showed a lower content of C18:0 (P<0.01) and higher contents of C14:1 cis-9 (P<0.001) and C18:1 cis-9 (P<0.05) in MSF compared to the VV genotype. As a result, the bulls with genotypes AA or AV had lower SFA (P<0.01), higher MUFA (P<0.05) and higher MUFA/SFA (P<0.01) than VV animals. The results obtained for SCF were similar. The SREBP-1 polymorphism was associated with a higher content of C14:1 cis-9 (P<0.01) in the LS compared to LL genotype in SCF. The results of this study demonstrated the existence of the polymorphisms in the SCD1 and SREBP-1 genes in the population of Fleckvieh cattle and their associations with the concentrations of several MSF and SCF fatty acids.

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.