Regulation Of Fatty Acid Synthesis Research Articles

A novel role for an ECF sigma factor in fatty acid biosynthesis and membrane fluidity in Pseudomonas aeruginosa.

Extracytoplasmic function (ECF) sigma factors are members of cell-surface signaling systems, abundant in the opportunistic pathogen Pseudomonas aeruginosa. Twenty genes coding for ECF sigma factors are present in P. aeruginosa sequenced genomes, most of them being part of TonB systems related to iron uptake. In this work, poorly characterized sigma factors were overexpressed in strain PA14, in an attempt to understand their role in the bacterium´s physiology. Cultures overexpressing SigX displayed a biphasic growth curve, reaching stationary phase earlier than the control strain, followed by subsequent growth resumption. During the first stationary phase, most cells swell and die, but the remaining cells return to the wild type morphology and proceed to a second exponential growth. This is not due to compensatory mutations, since cells recovered from late time points and diluted into fresh medium repeated this behavior. Swollen cells have a more fluid membrane and contain higher amounts of shorter chain fatty acids. A proteomic analysis was performed to identify differentially expressed proteins due to overexpression of sigX, revealing the induction of several fatty acid synthesis (FAS) enzymes. Using qRT-PCR, we showed that at least one isoform from each of the FAS pathway enzymes were upregulated at the mRNA level in the SigX overexpressing strain thus pointing to a role for this ECF sigma factor in the FAS regulation in P. aeruginosa.

Spot14/Mig12 heterocomplex sequesters polymerization and restrains catalytic function of human acetyl‐CoA carboxylase 2

Acetyl-CoA carboxylase 2 (ACC2) is an isoform of ACC functioning as a negative regulator of fatty acid β-oxidation. Spot14, a thyroid hormone responsive protein, and Mig12, a Spot14 paralog, have recently been identified as regulators of fatty acid synthesis targeting ACC1, a distinctive subtype of ACC. Here, we examined whether Spot14/Mig12 modulates ACC2. Nanoscale protein topography mapped putative protein–protein interactions between purified human Spot14/Mig12 and ACC2, validated by functional assays. Human ACC2 displayed consistent enzymatic activity, and homogeneous particle distribution was probed by atomic force microscopy. Citrate-induced polymerization and enzymatic activity of ACC2 were restrained by the addition of the recombinant Spot14/Mig12 heterocomplex but only partially by the oligo-heterocomplex, demonstrating that the heterocomplex is a designated metabolic inhibitor of human ACC2. Moreover, Spot14/Mig12 demonstrated a sequestering role preventing an initial ACC2 nucleation step during filamentous polymer formation. Thus, the Spot14/Mig12 heterocomplex controls human ACC2 polymerization and catalytic function, emerging as a previously unrecognized molecular regulator in catalytic lipid metabolism. © 2013 The Authors. Journal of Molecular Recognition published by John Wiley & Sons, Ltd.

Acetylation Stabilizes ATP-Citrate Lyase to Promote Lipid Biosynthesis and Tumor Growth

Increased fatty acid synthesis is required to meet the demand for membrane expansion of rapidly growing cells. ATP-citrate lyase (ACLY) is upregulated or activated in several types of cancer, and inhibition of ACLY arrests proliferation of cancer cells. Here we show that ACLY is acetylated at lysine residues 540, 546, and 554 (3K). Acetylation at these three lysine residues is stimulated by P300/calcium-binding protein (CBP)-associated factor (PCAF) acetyltransferase under high glucose and increases ACLY stability by blocking its ubiquitylation and degradation. Conversely, the protein deacetylase sirtuin 2 (SIRT2) deacetylates and destabilizes ACLY. Substitution of 3K abolishes ACLY ubiquitylation and promotes de novo lipid synthesis, cell proliferation, and tumor growth. Importantly, 3K acetylation of ACLY is increased in human lung cancers. Our study reveals a crosstalk between acetylation and ubiquitylation by competing for the same lysine residues in the regulation of fatty acid synthesis and cell growth in response to glucose.

Differential Regulation of Gene Expression by LXRs in Response to Macrophage Cholesterol Loading

The ability of cells to precisely control gene expression in response to intracellular and extracellular signals plays an important role in both normal physiology and in pathological settings. For instance, the accumulation of excess cholesterol by macrophages initiates a genetic response mediated by the liver X receptors (LXRs)-α (NR1H3) and LXRβ (NR1H2), which facilitates the transport of cholesterol out of cells to high-density lipoprotein particles. Studies using synthetic LXR agonists have also demonstrated that macrophage LXR activation simultaneously induces a second network of genes that promotes fatty acid and triglyceride synthesis that may support the detoxification of excess free cholesterol by storage in the ester form. We now show that treatment of human THP-1 macrophages with endogenous or synthetic LXR ligands stimulates both transcriptional and posttranscriptional pathways that result in the selective recruitment of the LXRα subtype to LXR-regulated promoters. Interestingly, when human or mouse macrophages are loaded with cholesterol under conditions that mimic the development of atherogenic macrophage foam cells, a selective LXR response is generated that induces genes mediating cholesterol transport but does not coordinately regulate genes involved in fatty acid synthesis. The gene-selective response to cholesterol loading occurs, even in the presence of LXRα binding to the promoter of the gene encoding the sterol regulatory element-binding protein-1c, the master transcriptional regulator of fatty acid synthesis. The ability of promoter bound LXRα to recruit RNA polymerase to the sterol regulatory element-binding protein-1c promoter, however, appears to be ligand selective.

A proof of principle clinical trial to determine whether conjugated linoleic acid modulates the lipogenic pathway in human breast cancer tissue

Conjugated linoleic acid (CLA) is widely used as a "nutraceutical" for weight loss. CLA has anticancer effects in preclinical models, and we demonstrated in vitro that this can be attributed to the suppression of fatty acid (FA) synthesis. We tested the hypothesis that administration of CLA to breast cancer patients would inhibit expression of markers related to FA synthesis in tumor tissue, and that this would suppress tumor proliferation. Women with Stage I-III breast cancer were enrolled into an open label study and treated with CLA (1:1 mix of 9c,11t- and 10t,12c-CLA isomers, 7.5 g/d) for ≥ 10 days before surgery. Fasting plasma CLA concentrations measured pre- and post-CLA administration, and pre/post CLA tumor samples were examined by immunohistochemistry for Spot 14 (S14), a regulator of FA synthesis, FA synthase (FASN), an enzyme of FA synthesis, and lipoprotein lipase (LPL), the enzyme that allows FA uptake. Tumors were also analyzed for expression of Ki-67 and cleaved caspase 3. 24 women completed study treatment, and 23 tumors were evaluable for the primary endpoint. The median duration of CLA therapy was 12 days, and no significant toxicity was observed. S14 expression scores decreased (p = 0.003) after CLA administration. No significant change in FASN or LPL expression was observed. Ki-67 scores declined (p = 0.029), while cleaved caspase 3 staining was unaffected. Decrements in S14 or Ki-67 did not correlate with fasting plasma CLA concentrations at surgery. Breast tumor tissue expression of S14, but not FASN or LPL, was decreased after a short course of treatment with 7.5 g/day CLA. This was accompanied by reductions in the proliferation index. CLA consumption was well-tolerated and safe at this dose for up to 20 days. Overall, CLA may be a prototype compound to target fatty acid synthesis in breast cancers with a "lipogenic phenotype".

High stearoyl-CoA desaturase 1 expression is associated with shorter survival in breast cancer patients

Stearoyl-CoA desaturase 1 (SCD1) is an essential regulator of fatty acid synthesis. We have previously shown that overexpression of SCD1 increases the growth of breast cancer cell lines. The purpose of this study was to determine the relationship between SCD1 expression level and clinical-pathologic characteristics and survival of patients with breast cancer. Fine-needle aspirates were collected from the primary tumors of 250 patients with stage I-III breast cancer. Demographic and clinical characteristics including patient age, ethnicity, and menopausal status and tumor clinical stage, grade, and subtype were reviewed. SCD1 expression was analyzed using reverse-phase protein arrays. Samples were divided into high or low SCD1 expression levels based on a cut-off determined from martingale residual plots and regression tree analysis. SCD1 levels were significantly higher in tumors from patients >50-years old compared to patients ≤50-years old and were lower in triple-negative (estrogen/progesterone receptor-negative and human epidermal growth factor receptor-2-negative) breast cancers than other tumor subtypes. After adjusting for patient age, tumor subtype, tumor grade, and clinical stage, we found that patients with primary breast cancers expressing high SCD1 levels had significantly shorter relapse-free survival (RFS) (P = 0.0140) and overall survival (OS) (P = 0.039) in multivariable analysis. We conclude that SCD1 expression varies by breast cancer subtype and that high levels of SCD1 expression are associated with significantly shorter RFS and OS in multivariable analysis. Future studies are needed to define the role of SCD1 in the malignant phenotype of breast cancer and to evaluate the potential for SCD1 as a therapeutic target.

The SNPs in the ACACA gene are effective on fatty acid composition in holstein milk

Fatty acid composition is an important economic trait for both dairy and beef cattle and controlled by genetic factors. Candidate genes controlling fatty acid composition may be found in fat synthesis and metabolism pathways. Acetyl-CoA carboxylase is the flux-determining enzyme in the regulation of fatty acid synthesis in animal tissues. One of two isozymes of this enzyme, acetyl-CoA carboxylase-α (ACACA), catalyses the first committed step of fatty acid synthesis in mammalian cytosol, leading to the biosynthesis of long-chain fatty acids. In the current study, the sequence comparison of the coding sequence (CDS) and two promoter regions (PIA and PIII) in bovine ACACA gene was performed between Japanese Black and Holstein cattle to detect nucleotide polymorphisms influencing fatty acid composition in milk and beef. Five single nucleotide polymorphisms (SNPs) were identified in the CDS region, 28 SNPs in the PIA region and three SNPs in the PIII region. Association study revealed that CCT/CCT type of PIII_#1, #2/PIA_#26 indicated a higher percentage of C14:0 in the milk of the Holstein cattle than CCT/GTC type (p = 0.050) and that a difference of the percentage of C16:0 was observed between CCT/CCT and GTC/GTC type (p = 0.023). CDS_#2 T/T type indicated a higher percentage of C18:0 than T/C type (p = 0.008). In addition, the Japanese Black cattle with CC/GT type of PIII_#1, #2 showed a higher percentage of C18:2 in the meat than those with GT/GT type (p = 0.025). Since PIII is the promoter specific to mammary gland during lactation, the altered expression of the ACACA gene owing to the SNPs in the PIII region may influence the fatty acid composition in the milk.

Malonyl-CoA: the regulator of fatty acid synthesis and oxidation

In the catabolic state with no food intake, the liver generates ketones by breaking down fatty acids. During the nocturnal fast or longer starvation periods, this protects the brain, which cannot oxidize fatty acids. In 1977, we published a study in the JCI noting the surprising realization that malonyl-CoA, the substrate of fatty acid synthesis, was also an inhibitor of fatty acid oxidation. Subsequent experiments have borne out this finding and furthered our understanding of molecular metabolism.

Goat liver X receptor α, molecular cloning, functional characterization and regulating fatty acid synthesis in epithelial cells of goat mammary glands

The liver X receptor α (LXRα) is a nuclear receptor of the transcription factor and is known to play a crucial role in lipid metabolism processes such as bile acid and fatty acid synthesis in humans and rodents. However, very little information is available on the role of LXRα in the regulation of fatty acid synthesis in the goat mammary gland. In this investigation, a cDNA was isolated from the mammary gland of Xinong Saanen dairy goats and designated as goat LXRα. RT-PCR and RACE gave rise to the full-length cDNA of LXRα, which was comprised of 1654bp and characterized by an ORF of 1344bp and 5′- and 3′-UTR regions of 150 and 160bp, respectively. The deduced amino acid sequence encodes 477 amino acids with a predicted molecular weight (MW) of 50.4kDa and a theoretical isoelectric point (pI) of 6.3. Additionally, homology search and sequence multi-alignment indicated that the putative goat LXRα amino acid sequence is very similar to those of cattle, mice, rats, swine, and humans. Bioinformatic predictions demonstrated that the LXRα protein is located in the nucleus, containing characteristic signatures of a nuclear receptor with DNA-binding domain (DBD) and ligand-binding domain (LBD). Real-time quantitative PCR suggested that LXRα was predominantly expressed in the small intestine, liver, spleen and mammary gland. Treatment of goat mammary gland epithelial cells (GMEC) with different concentrations (i.e., 0.01, 0.1, 1μM) of T0901317, a synthetic agonist of LXRα, resulted in elevated sterol regulatory element binding protein 1 (SREBP1) and fatty acid synthase (FASN) mRNA levels in response to LXRα activation. The association between different T0901317 concentrations and fatty acid composition in GMEC also was examined using gas chromatography (GC). The results showed that activation of LXRα significantly increased GMEC C18:1 and C18:2 contents, but did not affect levels of saturated fatty acids (SFA). These discoveries are consistent with the notion that LXRα plays a key role in controlling lipogenesis and regulating synthesis of unsaturated fatty acids (UFA) in the mammary gland of goats, which may prove useful in regulation of milk fat production.

Abstract 682: Increased stearoyl-CoA desaturase 1 expression is associated with shorter survival in breast cancer patients

Abstract Stearoyl-CoA desaturase 1 (SCD1) is an essential regulator of fatty acid synthesis that affects cell membrane composition and may play a role in cancer cell metabolism. We have previously shown that SCD1 expression is increased by mTOR signaling and that SCD1 increases breast cancer cell growth in vitro. The purpose of this study was to determine protein levels of SCD1 in breast cancer and to determine whether there is an association between SCD1 levels and survival. Fine needle aspirates were collected from the primary breast cancers of 253 patients with Stage I-III breast cancer and protein lysates were prepared. SCD1 expression was analyzed using reverse phase proteomic array. Patient demographic and clinical characteristics including age, ethnicity, menopausal status, clinical stage, tumor grade, and tumor subtype were reviewed. Samples were divided into high or low SCD1 levels based on a cut-off determined from martingale residual plots and regression tree analysis. SCD1 levels were significantly higher in older patients and lower in triple negative (estrogen, progesterone, and HER2 negative) cancers, After adjusting for tumor subtype, tumor grade, age, and clinical stage, patients who had high SCD1 levels had significantly shorter relapse-free survival (RFS) (p=0.013) and overall survival (OS) (p=0.038). SCD1 level varies by breast cancer subtype and predicts significantly shorter RFS and OS. Future studies are needed to define the role of SCD1 in breast cancer and evaluate its potential as a therapeutic target. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 682. doi:1538-7445.AM2012-682

Kr-pok increases FASN expression by modulating the DNA binding of SREBP-1c and Sp1 at the proximal promoter

Kr-pok (kidney cancer-related POZ domain and Krüppel-like protein) is a new proto-oncogenic POZ-domain transcription factor. Fatty acid synthase gene (FASN) encodes one of the key enzymes in fatty acids synthesis and is the only enzyme that synthesizes fatty acids in cancer cells. Sp1 and SREBP-1c are the two major transcription activators of FASN. We investigated whether Kr-pok modulates transcription of the FASN. FASN expression is significantly decreased in Kr-pok knockout murine embryonic fibroblasts. Coimmunoprecipitation, GST fusion protein pull-down, and immunocytochemistry assays show that the zinc-finger domain of Kr-pok interacts directly with the bZIP DNA binding domain of SREBP-1. Electrophoretic mobility shift assay, oligonucleotide pull-down, and chromatin immunoprecipitation assays showed that Kr-pok changes the transcription factor binding dynamics of Sp1 and SREBP-1c to the SRE/E-box elements of the proximal promoter. We found that Kr-pok expression increased during 3T3-L1 preadipocyte differentiation and that FASN expression is decreased by the knockdown of Kr-pok. Kr-pok facilitates the SREBP-1c-mediated preadipocyte differentiation and/or fatty acid synthesis. Kr-pok may act as an important regulator of fatty acid synthesis and may induce rapid cancer cell proliferation by increasing palmitate synthesis.

TOFA (5-tetradecyl-oxy-2-furoic acid) reduces fatty acid synthesis, inhibits expression of AR, neuropilin-1 and Mcl-1 and kills prostate cancer cells independent of p53 status

A key player in prostate cancer development and progression is the androgen receptor (AR). Tumor-associated lipogenesis can protect cancer cells from carcinogenic- and therapeutic-associated treatments. Increased synthesis of fatty acids and cholesterol is regulated by androgens through induction of several genes in androgen-responsive cancer cells. Acetyl-CoA-carboxylase-α (ACCA) is a key enzyme in the regulation of fatty acids synthesis. Here we show that AR binds in vivo to intron regions of human ACCA gene. We also show that the level of ACCA protein in LNCaP depends on AR expression and that DHT treatment increases ACCA expression and fatty acid synthesis. Inhibition of ACCA by TOFA (5-tetradecyl-oxy-2-furoic acid) decreases fatty acid synthesis and induces caspase activation and cell death in most PCa cell lines. Our data suggest that TOFA can kill cells via the mitochondrial pathway since we found cytochrome c release after TOFA treatment in androgen sensitive cell lines. The results also imply that the pro-apoptotic effect of TOFA may be mediated via a decrease of neuropilin-1(NRP1) and Mcl-1expression. We have previously reported that Mcl-1 is under AR regulation and plays an important role in resistance to drug-induced apoptosis in prostate cancer cells, and NRP1 is known to regulate Mcl-1 expression. Here, we show for the first time that NRP1 expression is under AR control. Taken together, our data suggest that TOFA is a potent cell death inducing agent in prostate cancer cells.

Activation of liver X receptor (LXR) enhances de novo fatty acid synthesis in bovine mammary epithelial cells

Liver X receptor (LXR) is a nuclear receptor and a known regulator of lipid synthesis in rodents; however, the role of LXR in the regulation of fatty acid synthesis in bovine mammary epithelial cells has not yet been defined. The objective of the study was to evaluate the effect of LXR activation on the de novo synthesis of fatty acids in bovine mammary epithelial cells (BME-UV). Bovine mammary epithelial cells were treated with T0901317 (T09), an LXR agonist. Treatment of BME-UV with T09 increased the transcription of ATP-binding cassette transporter-G1, an LXR target gene, without modifying LXRα mRNA abundance. Acute and chronic treatment of BME-UV with T09 dramatically increased de novo fatty acid synthesis. Activation of LXR resulted in the upregulation of transcription, translation, and proteolytic cleavage of sterol regulatory element-binding protein-1 (SREBP1), a lipogenic transcription factor expressed in the bovine mammary gland. Additionally, the mRNA abundance of fatty acid synthase, an LXR and SREBP1 target gene, increased in response to LXR activation. Our data indicate that SREBP1 is regulated by LXR activation in BME-UV. Controlling LXR activation may prove useful in regulating milk fat production in lactating dairy cows.

Sterol regulatory element binding protein and dietary lipid regulation of fatty acid synthesis in the mammary epithelium

The lactating mammary gland synthesizes large amounts of triglyceride from fatty acids derived from the blood and from de novo lipogenesis. The latter is significantly increased at parturition and decreased when additional dietary fatty acids become available. To begin to understand the molecular regulation of de novo lipogenesis, we tested the hypothesis that the transcription factor sterol regulatory element binding factor (SREBF)-1c is a primary regulator of this system. Expression of Srebf1c mRNA and six of its known target genes increased ≥2.5-fold at parturition. However, Srebf1c-null mice showed only minor deficiencies in lipid synthesis during lactation, possibly due to compensation by Srebf1a expression. To abrogate the function of both isoforms of Srebf1, we bred mice to obtain a mammary epithelial cell-specific deletion of SREBF cleavage-activating protein (SCAP), the SREBF escort protein. These dams showed a significant lactation deficiency, and expression of mRNA for fatty acid synthase (Fasn), insulin-induced gene 1 (Insig1), mitochondrial citrate transporter (Slc25a1), and stearoyl-CoA desaturase 2 (Scd2) was reduced threefold or more; however, the mRNA levels of acetyl-CoA carboxylase-1α (Acaca) and ATP citrate lyase (Acly) were unchanged. Furthermore, a 46% fat diet significantly decreased de novo fatty acid synthesis and reduced the protein levels of ACACA, ACLY, and FASN significantly, with no change in their mRNA levels. These data lead us to conclude that two modes of regulation exist to control fatty acid synthesis in the mammary gland of the lactating mouse: the well-known SREBF1 system and a novel mechanism that acts at the posttranscriptional level in the presence of SCAP deletion and high-fat feeding to alter enzyme protein.

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.

Induced polymerization of mammalian acetyl-CoA carboxylase by MIG12 provides a tertiary level of regulation of fatty acid synthesis

Acetyl-CoA carboxylase (ACC), the first committed enzyme in fatty acid (FA) synthesis, is regulated by phosphorylation/dephosphorylation, transcription, and an unusual mechanism of protein polymerization. Polymerization of ACC increases enzymatic activity and is induced in vitro by supraphysiological concentrations of citrate (> 5 mM). Here, we show that MIG12, a 22 kDa cytosolic protein of previously unknown function, binds to ACC and lowers the threshold for citrate activation into the physiological range (< 1 mM). In vitro, recombinant MIG12 induced polymerization of ACC (as determined by nondenaturing gels, FPLC, and electron microscopy) and increased ACC activity by > 50-fold in the presence of 1 mM citrate. In vivo, overexpression of MIG12 in liver induced ACC polymerization, increased FA synthesis, and produced triglyceride accumulation and fatty liver. Thus, in addition to its regulation by phosphorylation and transcription, ACC is regulated at a tertiary level by MIG12, which facilitates ACC polymerization and enhances enzymatic activity.

Candidate gene markers involved in San Daniele ham quality

San Daniele dry-cured hams (also known as prosciutto) are produced in the Northeastern region of Italy. This high value product requires high quality fresh meat to avoid processing problems. The Sterol Regulatory Element Binding Protein-1 (SREBF1) is a transcription factor involved in the regulation of fatty acid synthesis in muscle and adipose tissues. The SREBF1 gene, its regulating genes SCAP and MBTPS1, and one of its target genes, SCD, were investigated for associations with several meat quality traits of San Daniele hams. Significant associations of some gene markers were found with carcass weight, lean percentage, backfat thickness, ham green weight, ham fat cover thickness, shear force (WBSF), salting losses and instrumental colour of both lean and fat. These findings provide initial evidences that SNPs in SREBF1, SCAP, MBTPS1 and SCD are associated with San Daniele ham quality and may be considered as markers for selective breeding programs.

Genetic variants of the FADS1 FADS2 gene cluster as related to essential fatty acid metabolism

The delta-5 and delta-6 desaturases have long been known to be important enzymes in the endogenous formation of long-chain polyunsaturated fatty acids (LC-PUFAs). Cloning of the coding sequences and chromosomal localization of the desaturase encoding genes fatty acid desaturase 1 and 2 (FADS1 and FADS2) opened the way for analyses of genetic factors as regulators of desaturase activity and LC-PUFA homeostasis. The present review summarizes the recent association studies on FADS genotypes and LC-PUFA levels and suggests ideas how FADS genotypes can be integrated in future research. An initial candidate gene study reported highly significant associations between FADS gene cluster polymorphisms and fatty acid levels in serum phospholipids with an extraordinary high genetically explained variance for arachidonic acid levels of 28.5%. Carriers of the minor alleles had enhanced levels of desaturase substrates and decreased levels of desaturase products, suggesting a decline in desaturase expression or activity because of the polymorphisms. These results were replicated in several association studies additionally showing an effect in different human tissues as well as in a recent genome-wide association study on LC-PUFA levels. The validated strong association between FADS genotypes and fatty acid levels in diverse human tissues shows that FADS gene cluster polymorphisms are, in addition to nutritional regulation of fatty acid synthesis, a very important regulator of LC-PUFA synthesis.

SREBP pathway genes as candidate markers in country ham production

Country hams are dry-cured products from the Southeastern region of the USA. This high value product requires quality fresh meat to avoid later processing problems. The marker SREBF1 is a transcription factor involved in the regulation of fatty acid synthesis and anti-oxidative enzyme transcription. The SREBF1 gene and its regulators, SCAP and MBTPS1, were investigated for associations with several meat quality traits in country hams. After single nucleotide polymorphism (SNP) identification, PCR-RFLP tests were designed for one polymorphism in each of the three investigated genes. Meat quality and physical traits were collected on 299 fresh hams. Significant associations were found with ham yield (MBTPS1, P<0.05 and SREBF1×MBTPS1, P<0.05) and ham circumference (MBTPS1, P<0.05 and SREBF1×MBTPS1, P<0.01), Hunter A colour score on fresh meat (SREBF1, P<0.05), Hunter B colour score on cured meat (MBTPS1, P<0.05 and SREBF1×MBTPS1, P<0.01), moisture (SCAP×MBTPS1, P<0.05) and salt percentage (SREBF1×SCAP, P<0.05). Our findings provide initial evidence that SNPs in SREBF1, SCAP and MBTPS1 are associated with some country ham quality traits. Breeders could use these gene tests to improve their animals, which would in turn improve country ham processing and other desired production goals.

Activation of AMP-activated protein kinase (AMPK) inhibits fatty acid synthesis in bovine mammary epithelial cells

Activation of AMP-activated protein kinase (AMPK), a heterotrimeric energy-sensing protein, decreases lipid synthesis in liver tissue of various species; however, little is known about the role of AMPK in the regulation of fatty acid synthesis in bovine mammary epithelial cells. Here we report the presence of AMPK mRNA in MAC-T bovine mammary epithelial cells and mammary gland. Treatment of MAC-T with an AMPK activator dramatically decreased de novo fatty acid synthesis by inactivating acetyl-CoA carboxylase-α. Activation of AMPK also modified the mRNA expression of several lipogenic genes including fatty acid synthase, glycerol-3-phosphate acyltransferase, and fatty acid binding protein-3. Additionally, decreases in energy availability or rises in intracellular Ca 2+ most likely activated AMPK in MAC-T. These data suggest the presence of LKB1 and Ca 2+/calmodulin-dependent kinase kinase, two known AMPK kinases, in MAC-T. Identifying AMPK as a molecular target capable of modifying energy substrate utilization may result in the development of new technologies that increase milk production or modify milk composition during periods of increased energy demand.