Stearoyl-coenzyme A Desaturase Research Articles

Lipid content in hepatic and gonadal adipose tissue parallel aortic cholesterol accumulation in mice fed diets with different omega-6 PUFA to EPA plus DHA ratios

Diets with low omega (ω)-6 polyunsaturated fatty acids (PUFA) to eicosapentaenoic acid (EPA) plus docosahexaenoic acid (DHA) ratios have been shown to decrease aortic cholesterol accumulation and have been suggested to promote weight loss. The involvement of the liver and gonadal adipose tissue (GAT) in mediating these effects is not well understood. LDL receptor null mice were used to assess the effect of an atherogenic diet with different ω-6:EPA+DHA ratios on weight gain, hepatic and GAT lipid accumulation, and their relationship to atherosclerosis. Four groups of mice were fed a high saturated fat and cholesterol diet (HSF ω-6) alone, or with ω-6 PUFA to EPA+DHA ratios up to 1:1 for 32 weeks. Liver and GAT were collected for lipid and gene expression analysis. The fatty acid profile of liver and GAT reflected the diets. All diets resulted in similar weight gains. Compared to HSF ω-6 diet, the 1:1 ratio diet resulted in lower hepatic total cholesterol (TC) content. Aortic TC was positively correlated with hepatic and GAT TC and triglyceride. These differences were accompanied by significantly lower expression of CD36, ATP-transporter cassette A1, scavenger receptor B class 1, 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR), acetyl-CoA carboxylase alpha, acyl-CoA synthetase long-chain family member 5, and stearoyl-coenzyme A desaturase 1 (SCD1) in GAT, and HMGCR, SCD1 and cytochrome P450 7A1 in liver. Dietary ω-6:EPA+DHA ratios did not affect body weight, but lower ω-6:EPA+DHA ratio diets decreased liver lipid accumulation, which possibly contributed to the lower aortic cholesterol accumulation.

Down‐Regulation of Hepatic Stearoyl‐CoA Desaturase‐1 Expression by Fucoxanthin via Leptin Signaling in Diabetic/Obese KK‐Ay Mice

Stearoyl-coenzyme A desaturase-1 (SCD1) is a rate-limiting enzyme that catalyzes the biosynthesis of monounsaturated fatty acids from saturated fatty acids. Recently, SCD1 down-regulation has been implicated in the prevention of obesity, and the improvement of insulin and leptin sensitivity. In this study, we examined the effect of fucoxanthin, a marine carotenoid, on hepatic SCD1 in obese mouse models of hyperleptinemia KK-A(y) and leptin-deficiency ob/ob. In KK-A(y) mice, providing a diet containing 0.2 % fucoxanthin for 2 weeks markedly suppressed SCD1 mRNA and protein expressions in the liver. The fatty acid composition of liver lipids was also affected by an observed decrease in the ratio of oleic acid to stearic acid. Furthermore, serum leptin levels were significantly decreased in hyperleptinemia KK-A(y) mice after 2 weeks of fucoxanthin feeding. However, the suppressive effects of fucoxanthin on hepatic SCD1 and body weight gain were not observed in ob/ob mice. These results show that fucoxanthin down-regulates SCD1 expression and alters fatty acid composition of the liver via regulation of leptin signaling in hyperleptinemia KK-A(y) mice but not in leptin-deficient ob/ob mice.

Grain feeding coordinately alters expression patterns of transcription factor and metabolic genes in subcutaneous adipose tissue of crossbred heifers1,2

The ability to improve meat quality and production efficiency in cattle is limited by an inability to enhance marbling and simultaneously limit undesirable adipose tissue accretion. The objective of this study was to examine expression of regulatory genes in subcutaneous (SCF) adipose tissue of heifers in response to increasing days on feed (DOF) and finishing strategy. Crossbred heifers (n = 24) were allotted as follows: Group 1 = 0 d, Group 2 = 99 d on winter annual ryegrass (grass; Lolium multiflorum Lam.), Group 3 = 218 g on grass, Group 4 = 99 d on grass followed by 119 d on grain. Adipose tissue samples were collected at time of harvest and frozen. Carcass characteristics were measured 24 h postharvest. As expected, HCW (P < 0.0001), ribeye area (REA; P < 0.0002), backfat (BF; P < 0.0001), KPH (P < 0.0001), and marbling score (P < 0.0009) increased with DOF though frame score was not different (P < 0.95). Average daily gain decreased with DOF (P < 0.0001). Yield grade increased (P < 0.0014) but cook loss percentage decreased (P < 0.001) with DOF without changes in 24-h pH (P < 0.31). Interestingly, Warner-Bratzler shear force (WBS) was decreased with DOF (P < 0.0089). Meanwhile, BF (P < 0.01) and KPH (P < 0.05) were greater, whereas marbling values trended greater in grain versus grass-finished heifers. Neither ADG (P < 0.89), HCW (P < 0.26), frame score (P < 0.85), nor REA (P < 0.38) were different between these groups. Grain finishing increased yield grade (P < 0.001) but did not affect 24-h pH (P < 0.88), cook loss percentage (P < 0.98), or WBS (P < 0.44) compared with grass-finished heifers. The expression of PPARγ, bone morphogenic protein 2 (BMP2), and SMAD family member 1 (SMAD1) mRNA was upregulated in response to DOF and grain finishing, whereas sterol regulatory element binding protein 1c (SREBP-1c), sonic hedgehog (SHH), chicken ovalbumin protein transcription factor 1 (COUP-TF1), chicken ovalbumin protein transcription factor 2 (COUP-TF2), and preadipocyte factor-1 (PREF-1) mRNA was decreased in response to DOF and grain finishing. These changes were associated with increased expression of lipoprotein lipase (LPL), stearoyl-coenzyme A desaturase (SCD), and fatty acid synthase (FAS) mRNA. In summary, increasing DOF was associated with improved meat quality whereas gene expression studies suggest several novel genes are associated with subcutaneous adipose tissue development in growing and finishing cattle.

Plasma stearoyl‐CoA desaturase indices: Association with lifestyle, diet, and body composition

Stearoyl-coenzyme A desaturase-1 (SCD1) is a key enzyme in fatty acid and energy metabolism. Increased hepatic SCD1 activity is associated with obesity and obesity-related diseases. We examined the relations of two plasma SCD activity indices (16:1n-7/16:0, 18:1n-9/18:0) with body composition, and the association of lifestyle and dietary variables with the plasma SCD indices. This population-based, cross-sectional study of 2021 elderly (71-74 y) men and women from the Hordaland Health Study in Western Norway was conducted using a validated food frequency questionnaire, body composition measurements by dual-energy X-ray absorptiometry and determination of the plasma fatty acid profile. In multivariate regression analyses, plasma SCD indices were positively associated with BMI and body fat (P < 0.001 for both). From the 2.5th to 97.5th percentiles of plasma SCD-16 and SCD-18 indices, fat mass differed by about 8 kg and 5 kg, respectively. Intake of polyunsaturated fatty acids were negatively associated with SCD-16 (partial r = -0.30) and SCD-18 (partial r = -0.24) (P < 0.001 for both). Alcohol intake was positively associated with SCD-16 (partial r = 0.26) and SCD-18 (partial r = 0.16) (P < 0.001 for both), whereas coffee consumption and physical activity were inversely associated with SCD-16 (P = 0.026 and P = 0.006, respectively) and SCD-18 (P = 0.001 and P = 0.022, respectively). In this elderly population, plasma markers of SCD1 activity are associated with increased adiposity. Furthermore, modifiable dietary habits and lifestyle are associated with plasma SCD indices. These results suggest that SCD1 activity may be a promising target for weight control.

Change in subcutaneous adipose tissue metabolism and gene network expression during the transition period in dairy cows, including differences due to sire genetic merit

Adipose metabolism is an essential contributor to the efficiency of milk production, and metabolism is controlled by several mechanisms, including gene expression of critical proteins; therefore, the objective of this study was to determine how lactational state and the genetic merit of dairy cattle affects adipose tissue (AT) metabolism and mRNA expression of genes known to control metabolism. Animals of high (HGM) and low genetic merit (LGM) were fed to requirements, and weekly dry matter intake, milk production, blood glucose, and nonesterified fatty acids were measured. Subcutaneous AT biopsies were collected at −21, 7, 28 and 56 d in milk (DIM). The mRNA expression of genes coding for lipogenic enzymes [phosphoenolpyruvate carboxykinase 1 (soluble) (PCK1), fatty acid synthase (FASN), diacylglycerol O-acyltransferase 2 (DGAT2), and stearoyl-coenzyme A desaturase (SCD)], transcription regulators [peroxisome proliferator-activated receptor γ (PPARG), thyroid hormone responsive (THRSP), wingless-type MMTV integration site family, member 10B (WNT10B), sterol regulatory element binding transcription factor 1 (SREBF1), and adiponectin (ADIPOQ)], lipolytic enzymes [hormone-sensitive lipase (LIPE), patatin-like phospholipase domain containing 2 (PNPLA2), monoglyceride lipase (MGLL), adrenoceptor β-2 (ADRB2), adipose differentiation-related protein (ADFP), and α-β-hydrolase domain containing 5 (ABHD5)], and genes controlling the sensing of intracellular energy [phosphodiesterase 3A (PDE3A); PDE3B; protein kinase, AMP-activated, α-1 catalytic subunit (PRKAA1); PRKAA2; and growth hormone receptor (GHR)] was measured. Dry matter intake, blood glucose, and nonesterified fatty acid concentrations did not differ between genetic merit groups. Milk production was greater for HGM cows from 6 to 8 wk postpartum. As expected, the rates of lipogenesis decreased in early lactation, whereas stimulated lipolysis increased. At 7 DIM, lipogenesis in HGM cows increased as a function of substrate availability (0.5, 1, 2, 3, 4, or 8mM acetic acid), whereas the response in LGM cows was much less pronounced. However, the lipogenic response at 28 DIM reversed and rates were greater in tissue from LGM than HGM cows. Peak lipolytic response, regardless of DIM, was observed at the lowest dose of isoproterenol (10−8M), and −21d tissue had a greater lipolysis rate than tissue at 7, 28, and 56d. In HGM compared with LGM cows, stimulated lipolysis at 7 and 28 DIM was greater but peaked at 10−7M isoproterenol, suggesting differences in tissue responsiveness due to genetic merit. Regardless of genetic merit, the expression of lipogenic genes decreased markedly in early lactation, whereas those controlling lipolysis stayed similar or decreased slightly. Cows of HGM had lower expression of lipogenic genes after parturition and through 56 DIM. In contrast, the expression of most of the lipolytic enzymes, receptors and proteins was similar in all cows pre- and postpartum. These results confirm that gene transcription is a major control mechanism for AT lipogenesis during early lactation, but that control of lipolysis is likely primarily by posttranslational mechanisms.

Associations of acetyl-coenzyme A carboxylase α, stearoyl-coenzyme A desaturase, and lipoprotein lipase genes with dairy traits in Alpine goats

Milk yield and composition are of great economic importance for the dairy goat industry. The identification of genes associated with phenotypic differences for these traits could allow for the implementation of gene-assisted selection programs in goats. Associations between polymorphisms at 3 candidate genes and milk production traits in Alpine goats farmed in Italy were investigated in the present research. Considered genes were acetyl-coenzyme A carboxylase α (ACACA), the major regulatory enzyme of fatty acid biosynthesis; stearoyl-coenzyme A desaturase (SCD), involved in the biosynthesis of monounsaturated fatty acids in the mammary gland; and lipoprotein lipase (LPL), which plays a central role in plasma triglyceride metabolism. An approach somewhat similar to the granddaughter design for detecting quantitative trait loci in dairy cattle was followed. Effects of genotypes of a sample of 59 Alpine bucks on phenotypes of their 946 daughters raised in 75 flocks were investigated. Data comprised 13,331 daily records for milk yields (L/d), fat and protein yields (kg/d), and fat and protein contents (%) of 2,200 lactations. Population genetics parameters were calculated and associations between milk production traits and 10 single nucleotide polymorphisms (SNP) at the 3 genes were tested. Two markers at the ACACA, 1 for the SCD and 1 at the LPL locus, deviated significantly from the Hardy-Weinberg equilibrium, with an observed heterozygosity lower than expected. Flock, age of the goat, kidding season, and stage of lactation affected all traits considered, except fat percentage. Three SNP were found to be significantly associated with milk production traits. The SNP located on the ACACA gene showed an effect on milk yield, with daughters of TT bucks having an average test-day milk yield of about 0.3 to 0.25 L/d lower than the other 2 genotypes. The marker on the LPL locus was highly associated with milk yield, with the largest values for CC daughters (about 0.50L more than GG). The TGT deletion located on the untranslated region of the SCD gene showed significant effects on average milk and protein yields. The homozygote-deleted genotype had values about 0.5 L/d and 16 g/d lower for milk and protein daily yield, respectively, compared with the TGT/TGT genotype. Differences between genotypes were quite constant across most of the lactation. Associations found in the present study, which should be tested in a larger sample, especially for those markers that show rare genotypes, may offer useful indications for the genetic improvement of dairy traits in goats.

Expressed sequence tag analysis of the emu (Dromaius novaehollandiae) pituitary by 454 GS Junior pyrosequencing

Emus (Dromaius novaehollandiae) are farmed for their oil for pharmaceutical and cosmetic uses. This emu pituitary expressed sequence tag study was undertaken to identify novel transcripts in the emu pituitary to propel their identification and functional studies. By mapping reads derived from the Roche 454 GS Junior pyrosequencer to 8 reference species (human, mouse, chicken, zebra finch, fruit fly, turkey, round worm, and Carolina anole lizard) from the UniGene database, a total of 81,788 reads (53,312 mapped reads) were obtained and assembled with Reference Sequence (RefSeq). We annotated 6,676 potential emu genes by referencing 7 species (excluding lizard) and identified 1,232 potential genes common among 3 species (human, mouse, and chicken) with complete available reference genomes. Gene Ontology analysis revealed 376 Gene Ontology terms showing, with the highest counts, their involvements in biological processes, metabolism, and cellular components. These potential genes were detected to associate with 20 pathways including mitogen-activated protein kinase, insulin, neurotrophin signaling pathways, and carbohydrate digestion and absorption pathway. We also revealed a panel of tissue-specific genes including regulator of G-protein signaling protein (RGS), glucagon-like peptide receptor (GLPR), and growth hormone-inducible transmembrane protein (GHITM). Additionally, fatty acid binding protein (FABP), fatty acid desaturase (FAS), and stearoyl-coenzyme A desaturase (SCD), key enzyme genes in fat metabolism, were found to be also expressed in emu pituitary. This expressed sequence tag study represents the first step in functional characterization of emu pituitary gene expression and SNP identification for the improvement of fat production in the emu.

2 TRANSCRIPTOME ANALYSIS OF GRANULOSA CELLS FROM GROWING DOMINANT FOLLICLE REVEALS AGE-ASSOCIATED CHANGES AT THE TIME OF FOLLICLE SELECTION IN AGED BEEF CATTLE

Growing dominant follicles at the time of selection from aged (n = 3; 15 ± 1.5 years) and young (n = 3; 6 ± 1.1 years) Hereford cows were compared using bovine-specific microarrays containing 40 000 targets. The objective of the study was to determine age-associated changes in transcriptome of granulosa cells at the time of dominant follicle selection. Cows were given prostaglandin F2α to cause ovulation (Day 0) and granulosa cells from dominant follicles were collected on Day 3 either by ultrasound-guided follicle aspiration or after ovariectomy. The mRNA was extracted, analyzed for quality, converted into antisense RNA, amplified, labelled with red and green florescent dyes, and hybridized with microarrays. Feature intensities were measured using Array-Pro software (Media Cybernetics Inc., Rockville, MD), and differentially expressed genes were obtained using FlexArray 1.6. A total of 169 transcripts were differentially expressed with a fold change of ≥2 (P ≤ 0.05) in aged cows v. young cows. Ingenuity System Pathway (IPA; Ingenuity Systems Inc., Redwood City, CA) analysis of these transcripts revealed that granulosa cells of aged cows exhibit (1) reduced capability to regulate gonadotropins [↓follistatin (FST), ↓inhibin beta A (INHBA), ↓inhibin beta B (INHBB)] and reduced responsiveness to gonadotropin-induced changes in cytoskeleton [↑tropomyosin 2 (TPM2), ↑actin gamma 2 (ACTG2), ↓tubulin beta] and extracellular matrix [↓tumor necrosis factor alpha-induced protein 6 (TNFAIP6), ↓versican (VCAN)], (2) inefficiency in processing lipids [↓low-density lipoprotein receptor (LDLR), ↓stearoyl-coenzyme A desaturase (SCD), ↑cluster of differentiation 36 (CD36), ↓sterol-C4-methyl oxidase-like (SC4MOL)] and synthesizing steroids [↓cytochrome P450, family 19, subfamily A, polypeptide 1 (CYP19A1), ↓cytochrome P450, family 51, subfamily A, polypeptide 1 (CYP51A1)], (3) decreased proliferation [↓proliferating cell nuclear antigen (PCNA)] and control of cell cycle check points [↓checkpoint kinase 1 (CHEK1), ↓centromere-associated protein E (CENPE)] and have poor intercellular communication [↓gap junction protein alpha 1 (GJA1)], and (4) higher expression of oxidative stress responsive genes [↑vanin-1 (VNN1), ↑vanin-2 (VNN2), and ↑glutathione peroxidase 3 (GPX3)]. A total of 6 transcripts: CYP19A1 (aromatase; P ≤ 0.1), VNN1 (P ≤ 0.05), INHBA (P ≥ 0.1), PCNA (P ≤ 0.001), TPM2 (P ≤ 0.1), and GJA1 (P ≤ 0.05) were selected to validate the microarray results via quantitative real-time PCR. In conclusion, granulosa cells of growing dominant follicles exhibit age-related changes in the transcriptome at the time of selection relative to young cows; changes that may explain follicle-associated loss of oocyte competence in aged cows. Research was supported by the Natural Sciences and Engineering Research Council of Canada (Ottawa, ON, Canada).

Effect of taurine and N-acetylcysteine on methionine restriction-mediated adiposity resistance

ObjectivesMethionine-restricted (MR) rats, which are lean and insulin sensitive, have low serum total cysteine (tCys) and taurine and decreased hepatic expression and activity indices of stearoyl-coenzyme A desaturase-1 (SCD1). These effects are partly or completely reversed by cysteine supplementation. We investigated whether reversal of MR phenotypes can be achieved by other sulfur compounds, namely taurine or N-acetylcysteine (NAC). MethodsMR and control-fed (CF) rats were supplemented with taurine (0.5%) or NAC (0.5%) for 12weeks. Adiposity, serum sulfur amino acids (SAA), Scd1 gene expression in liver and white adipose tissue, and SCD1 activity indices (calculated from serum fatty acid profile) were monitored. ResultsTaurine supplementation of MR rats did not restore weight gain or hepatic Scd1 expression or indices to CF levels, but further decreased adiposity. Taurine supplementation of CF rats did not affect adiposity, but lowered triglyceridemia. NAC supplementation in MR rats raised tCys and partly or completely reversed MR effects on weight, fat %, Scd1 expression in liver and white adipose tissue, and estimated SCD1 activity. In CF rats, NAC decreased body fat % and lowered SCD1-18 activity index (P<0.001). Serum triglycerides and leptin were over 40% lower in CF+NAC relative to CF rats (P≤0.003 for both). In all groups, change in tCys correlated with change in SCD1-16 index (partial r=0.60, P<0.001) independent of other SAA. ConclusionThe results rule out taurine as a mediator of increased adiposity produced by cysteine in MR, and show that NAC, similar to L-cysteine, blocks anti-obesity effects of MR. Our data show that dietary SAA can influence adiposity in part through mechanisms that converge on SCD1 function. This may have implications for understanding and preventing human obesity.

Genetic correlation between composition of bovine milk fat in winter and summer, and DGAT1 and SCD1 by season interactions

Milk fat composition shows substantial seasonal variation, most of which is probably caused by differences in the feeding of dairy cows. The present study aimed to know whether milk fat composition in winter is genetically the same trait as milk fat composition in summer. For this purpose, we estimated heritabilities, genetic correlations, effects of acyl-coenzyme A:diacylglycerol acyltransferase 1 (DGAT1) K232A, and stearoyl-coenzyme A desaturase 1 (SCD1) A293V polymorphisms for milk fat composition in winter and summer, and tested for genotype by season interactions of DGAT1 K232A and SCD1 A293V polymorphisms. Milk samples were obtained from 2,001 first-lactation Dutch Holstein-Friesian cows, most with records in both winter and summer. Summer milk contained higher amounts of unsaturated fatty acids (FA) and lower amounts of saturated FA compared with winter milk. Heritability estimates were comparable between seasons: moderate to high for short- and medium-chain FA (0.33 to 0.74) and moderate for long-chain FA (0.19 to 0.43) in both seasons. Genetic correlations between winter and summer milk were high, indicating that milk fat composition in winter and in summer can largely be considered as genetically the same trait. Effects of DGAT1 K232A and SCD1 A293V polymorphisms were similar across seasons for most FA. Allele DGAT1 232A in winter as well as in summer milk samples was negatively associated with most FA with less than 18 carbons, saturated FA, saturated FA to unsaturated FA ratio, and C10 to C16 unsaturation indices, and was positively associated with C14:0, unsaturated C18, unsaturated FA, and C18 and conjugated linoleic acid unsaturation indices. Allele SCD1 293V in winter as well as in summer milk samples was negatively associated with C18:0, C10:1 to cis-9 C14:1, trans-11 C18:1, and C10 to C14 unsaturation indices, and positively associated with C8:0 to C14:0, cis-9 C16:1, and C16 to conjugated linoleic acid unsaturation indices. In addition, significant DGAT1 K232A by season interaction was found for some FA and SCD1 A293V by season interaction was only found for trans-11 C18:1. These interactions were due to scaling of genotype effects.

Genetic effects of stearoyl-coenzyme A desaturase (SCD) polymorphism on milk production traits in the Chinese dairy population

Stearoyl-CoA desaturase (SCD) is a multifunctional complex enzyme important in the cellular biosynthesis of fatty acids. The present study was to investigate the association of the SCD gene with milk production traits in dairy cattle. Two single nucleotide polymorphisms (SNPs) (g.6926A>G and g.8646A>G) in introns 3 and 4, and three SNPs (g.10153A>G, g.10213T>C and g.10329C>T) in exon 5 were identified with pooled DNA sequencing and genotyped using matrix-assisted laser desorption/ionization time of flight mass spectrometry assay in 752 Chinese Holstein cows. Polymorphism g.10329C>T was predicted to result in an amino acid replacement from alanine to valine in the SCD protein. With a mixed animal model, the significant associations of the five SNPs with 305-day milk, fat and protein yields and protein percentage were determined. We further demonstrated cows with heterozygous genotypes (A/G or C/T) had highest 305 day milk yield, fat yield, protein yield and lowest protein percentage. Heterozygous cows with genotype AG at the g.6926A>G locus showed the greatest milk yield (P < 0.0001), fat yield (P < 0.0001) and protein yield (P < 0.0001) among other heterozygous genotypes at any of the loci. Dominance effects of all identified SNPs on milk, fat and protein yields and protein percentage were significant. Moreover, significant allele substitution effects at g.6926A>G locus on milk yield and at g.10213T>C on protein yield were observed. Five-locus haplotypes and strong linkage disequilibrium (D' > 0.9) between the five SNPs were also observed. The results suggest that identified polymorphisms could be potential genetic markers to improve the production performance of Chinese Holstein.

Adipogenic gene expression and fatty acid composition in subcutaneous adipose tissue depots of Angus steers between 9 and 16 months of age1

We have demonstrated that among carcass adipose tissue depots, brisket subcutaneous adipose tissue contains the greatest concentration of MUFA and lowest concentration of SFA. Therefore, we hypothesized that brisket subcutaneous adipose tissue depots would exhibit greater adipogenic gene expression over time than other major subcutaneous adipose tissue depots. Four Angus steers, each at 9, 12, 14, and 16 mo of age, were harvested and fresh subcutaneous adipose tissue samples were collected from over the brisket, chuck, rib, loin, sirloin, round, flank, and plate. Relative gene expression for C/EBPβ, PPARγ, carnitine palmitoyltransferase-1 beta (CPT-1β), stearoyl-coenzyme A desaturase (SCD), AMP-activated protein kinase alpha (AMPKα), and G-coupled protein receptor 43 (GPR43) was analyzed by quantitative real-time PCR. Expression of C/EBPβ, PPARγ, and CPT-1β was greatest at 12 to 14 mo of age (all P < 0.0001) and declined to very low abundance by 16 mo of age in all depots. Expression of PPARγ and CPT-1β was greater (P < 0.03) in flank, rib, and sirloin subcutaneous adipose tissues than in brisket and round adipose tissues. The expression of the SCD gene did not differ among the 4 age groups (P = 0.95). The palmitoleic:stearic acid ratio (an estimate of SCD activity) was greater (P < 0.001) in the subcutaneous adipose tissues from brisket, plate, and round than in the loin, rib, and sirloin. Conversely, subcutaneous adipose tissue from the loin, rib, and sirloin had greater (P < 0.001) SCD gene expression than the brisket, plate, and round. In general, subcutaneous adipose tissues with the highest concentration of MUFA and least SFA consistently exhibited the least SCD gene expression and adipogenic gene expression. We conclude that MUFA in the brisket and other depots with large SCD indices were deposited before 9 mo of age, during a time when the subcutaneous adipocytes were highly differentiated.

TCF/Lef1-Mediated Control of Lipid Metabolism Regulates Skin Barrier Function

Defects in the function of the skin barrier are associated with a wide variety of skin diseases, many of which are not well characterized at the molecular level. Using Lef1 (lymphoid enhancer-binding factor 1) dominant-negative mutant mice, we demonstrate here that altered epidermal TCF (T cell factor)/Lef1 signaling results in severe impairment of the stratum corneum skin barrier and early postnatal death. Barrier defects were accompanied by major changes in lipid composition and ultrastructural abnormalities in assembly and extrusion of lipid lamellae of the interfollicular epidermis, as well as abnormal processing of profilaggrin. In contrast, tight-junction formation and stratified organization of the interfollicular epidermis was not obviously disturbed in Lef1 mutant mice. Molecular analysis revealed that TCF/Lef1 signaling regulates expression of lipid-modifying enzymes, such as Elovl3 and stearoyl coenzyme A desaturase 1 (SCD1), which are key regulators of barrier function. Promoter analysis and chromatin immunoprecipitation experiments indeed showed that SCD1 is a direct target of Lef1. Together, our data demonstrate that functional TCF/Lef1 signaling governs important aspects of epidermal differentiation and lipid metabolism, thereby regulating skin barrier function.

Jacaric Acid, a Linolenic Acid Isomer with a Conjugated Triene System, Reduces Stearoyl-CoA Desaturase Expression in Liver of Mice

Conjugated fatty acid is a collective term used for fatty acids with conjugated double bond systems. Seed oils from certain plants include conjugated linolenic acids, which have a conjugated triene system and are geometrical and positional isomers of α-linolenic acid. One of these isomers, jacaric acid (JA, 8c, 10t, 12c-18:3), has not been examined widely. Therefore, we investigated the absorption and metabolism of JA in normal animals (ICR mice). An oral dose of JA of 5 mg/day for 1 week had no effects on body weight, food intake and tissue weight of mice. JA was detected in the serum, kidney, liver, lung and epididymal white adipose tissue. Analysis of the fatty acid composition in liver and white adipose tissue showed a tendency to increase levels of saturated fatty acids (SFAs) such as palmitic acid (16:0) and stearic acid (18:0) and to decrease levels of monounsaturated fatty acids (MUFAs) such as palmitoleic acid (16:1) and oleic acid (18:1). Thus, JA treatment decreased the desaturation index (16:1/16:0, 18:1/18:0) in liver and white adipose tissue. This index is used as an indicator of the activity of stearoyl coenzyme A desaturase (SCD), an endoplasmic reticulum enzyme that catalyzes the biosynthesis of MUFAs from SFAs. The change in this index indicates that JA inhibited SCD activity in ICR mice, and further experiments showed that JA also decreased the expression level of SCD-1 mRNA. Inhibition of SCD activity may have anti-obesity and anti-diabetes effects, and therefore the findings in this study suggest that JA may be effective for preventing obesity and diabetes.

Muscle transcriptomic analyses in Angus cattle with divergent tenderness

Beef tenderness contributes significantly to variation of beef palatability, and is largely influenced by various genetic and environmental factors. To identify candidate genes and pathways related to beef tenderness, we analyzed the longissimus dorsi (LD) muscle of Angus cattle that had different degrees of tenderness, measured by Warner-Bratzler shear force (WBSF). Microarray and RT-PCR analyses identified 53 genes that were differentially expressed in LD samples categorized as either tough or tender, including myosin, heavy chain 3 skeletal muscle embryonic (MYH3), myosin heavy chain 8 skeletal muscle perinatal (MYH8), guanylate binding protein 5 (GBP5), fatty acid binding protein 4 (FABP4), Stearoyl-coenzyme A desaturase (SCD), Fatty acid synthase (FASN), ubiquitin-like with PHD and ring finger domains 1 (UHRF1). Most of these genes are involved in lipid metabolism and skeletal muscle contraction. Employing Gene ontology (GO) and Ingenuity Pathway Analysis (IPA), several GO terms and pathways were found to be related to hydrolase, peptidase and GTPase activity, lipid metabolism, small molecule biochemistry, molecular transport, and tissue development. Overall, this analysis provides insight into the metabolic relationships between muscle biology and beef quality.

Regulation of stearoyl-coenzyme A desaturase and fatty acid delta-6 desaturase-2 expression by linoleic acid and arachidonic acid in human sebocytes leads to enhancement of proinflammatory activity but does not affect lipogenesis

Treatment of SZ95 sebocytes with the essential fatty acid linoleic acid (LA) and the polyunsaturated fatty acid arachidonic acid (AA) leads to sebaceous lipogenesis. Animal data indicate that stearoyl-coenzyme A desaturase (SCD), a key enzyme in fatty acid biosynthesis, is involved in sebaceous lipogenesis and proinflammatory signalling in the sebaceous gland. On the other hand, fatty acid delta-6 desaturase-2 (FADS2) catalyses the conversion of LA to AA. To identify the effects of LA and AA on the expression of SCD and FADS2 and to detect its biological relevance. SZ95 sebocytes were treated with LA (10(-5) and 10(-4) mol L(-1) ), AA (10(-6) and 10(-5) mol L(-1) ) and the combination of LA (10(-4) mol L(-1) ) and testosterone (2 × 10(-8) mol L(-1) ), with or without addition of the SCD inhibitor FPCA (10(-8) and 10(-6) mol L(-1) ). Cytotoxicity was determined by the lactate dehydrogenase assay. SCD and FACS2 mRNA levels were assessed by semiquantitative reverse transcription-polymerase chain reaction and protein expression by Western blot analysis. SZ95 sebocyte lipid content and cell number were measured by the Nile red and the fluorescein diacetate microassays, respectively. Determination of interleukin (IL)-6 and IL-8 release was evaluated by enzyme-linked immunosorbent assay. LA treatment induced an increase of SCD and FADS2 at mRNA and protein levels in SZ95 sebocytes after 1·5 h. Treatment with AA led to an increase of SCD but to a decrease of FADS2 mRNA levels. LA/testosterone cotreatment stimulated lipogenesis in SZ95 sebocytes. A distinct proinflammatory pattern was registered: whereas LA strongly upregulated IL-6 secretion only, AA induced a mild level of IL-6 and IL-8 release from SZ95 sebocytes. Treatment with the SCD inhibitor FPCA reduced the LA/testosterone-upregulated SCD and FADS2 mRNA levels and resulted in an anti-inflammatory effect, but did not affect sebaceous lipogenesis. LA-induced sebaceous lipogenesis is likely to be an SCD-independent effect. Regulation of SCD and FADS2 expression by LA and AA leads to enhancement of proinflammatory activity but does not affect lipogenesis in human sebocytes.

Effect of Njangsa Oil Seeds (Ricinodendron heudelitii) on Expression of Stearoyl-coenzyme a Desaturase in Laying Hens

Pathogenesis of liver steatosis in laying hen remains poorly understood. However, it has been suggested that regulation of the expression of Stearoyl-Coenzyme A Desaturase-1 (SCD-1) may alter hepatic lipid metabolism and prevent liver steatosis in laying hens. SCD-1 is an integral membrane protein that catalyzes the biosynthesis of monounsaturated fatty acids required for the synthesis of triglycerides, cholesterol esters and phospholipids. This study was conducted to determine whether Njangsa Oil Seed (NOS) (Ricinodendron heudelotii) which is rich in polyunsaturated fatty acids, specifically omega-3 fatty acids can regulate the expression of SCD-1 gene and lower hepatic lipid accumulation in laying hens. The experiment was carried out with seventy-two white leghorn hens (24 months old) which were randomly assigned to three layer diet supplemented with 0%, 10% or 20% NOS for 6 weeks. The mRNA levels in SCD1 gene was quantified using forward and reverse primers specific to chicken SCD-1 in real-time reverse transcription-PCR (RT-PCR) technique with SYBER Green detection. Histological studies with liver tissues were performed with oil red stain and electron transmission microscope. Results indicate that NOS supplementation at 10% level tended to increase (p>0.05) SCD-1 mRNA expression in hens. Histological examination revealed micro-vesicular fat accumulation in the liver of hen fed NOS diets, indicating that supplementation of NOS in the diet may not prevent development of fatty liver. Results from this study suggest that NOS supplementation may regulate genes involve in lipid biosynthesis but may not prevent liver steatosis.

Effects of weight loss and exercise on insulin resistance, and intramyocellular triacylglycerol, diacylglycerol and ceramide.

Intramyocellular lipids, including diacylglycerol (DAG) and ceramides, have been linked to insulin resistance. This randomised repeated-measures study examined the effects of diet-induced weight loss (DIWL) and aerobic exercise (EX) on insulin sensitivity and intramyocellular triacylglycerol (IMTG), DAG and ceramide. Sixteen overweight to obese adults (BMI 30.6 ± 0.8; 67.2 ± 4.0 years of age) with either impaired fasting glucose, or impaired glucose tolerance completed one of two lifestyle interventions: DIWL (n = 8) or EX (n = 8). Insulin sensitivity was determined using hyperinsulinaemic-euglycaemic clamps. Intramyocellular lipids were measured in muscle biopsies using histochemistry and tandem mass spectrometry. Insulin sensitivity was improved with DIWL (20.6 ± 4.7%) and EX (19.2 ± 12.9%). Body weight and body fat were decreased by both interventions, with greater decreases in DIWL compared with EX. Muscle glycogen, IMTG content and oxidative capacity were all significantly (p < 0.05) decreased with DIWL and increased with EX. There were decreases in DAG with DIWL (-12.4 ± 14.6%) and EX (-40.9 ± 12.0%). Ceramide decreased with EX (-33.7 ± 11.2%), but not with DIWL. Dihydroceramide was decreased with both interventions. Sphingosine was decreased only with EX. Changes in total DAG, total ceramides and other sphingolipids did not correlate with changes in glucose disposal. Stearoyl-coenzyme A desaturase 1 (SCD1) content was decreased with DIWL (-19.5 ± 8.5%, p < 0.05), but increased with EX (19.6 ± 7.4%, p < 0.05). Diacylglycerol acyltransferase 1 (DGAT1) was unchanged with the interventions. Diet-induced weight loss and exercise training both improved insulin resistance and decreased DAG, while only exercise decreased ceramides, despite the interventions having different effects on IMTG. These alterations may be mediated through differential changes in skeletal muscle capacity for oxidation and triacylglycerol synthesis. ClinicalTrials.gov NCT00766298.

Adipose tissue palmitoleic acid and obesity in humans: does it behave as a lipokine?

Animal models have shown that adipose-derived palmitoleic acid may serve as a lipokine that contributes to resistance to diet-induced obesity. Studies in humans have evaluated only plasma palmitoleic acid concentrations, which reflect stearoyl-coenzyme A desaturase 1 (SCD1) activity in the liver and are associated with increased risk of obesity. These apparent opposite effects of palmitoleic acid deserve further research in humans. Because carbohydrate intake can increase hepatic SCD1 activity, it could be used as a stratifying variable to disentangle the effects of adipose tissue SCD1 compared with the effects of liver SCD1 activity on obesity. We examined whether the effects of adipose tissue palmitoleic acid and SCD1 activity were associated with decreased obesity prevalence and whether this association was modified by carbohydrate intake. Prevalence ratios (PRs) of obesity [body mass index (in kg/m²) > 30] were examined in a cross-sectional study in 1926 adults in Costa Rica. Two desaturation indexes (16:1/16:0 and 18:1/18:0) were used as surrogate measures of adipose tissue SCD1 activity. We observed a positive association between adipose tissue palmitoleic acid concentrations and obesity (PR for lowest compared with highest quintiles of palmitoleic acid: 2.27; 95% CI: 1.52, 3.38; P for trend < 0.0001). A significant association was also observed between obesity and adipose desaturation indexes. The association between adipose tissue palmitoleic acid concentrations and obesity was attenuated in persons with low carbohydrate intake. There is no direct evidence that adipose tissue palmitoleic acid behaves as a lipokine to reduce obesity occurrence in humans. However, the attenuation of the association by low carbohydrate intake warrants further research on adipose-derived palmitoleic acid and obesity risk.

Erythrocyte membrane phospholipid fatty acids, desaturase activity, and dietary fatty acids in relation to risk of type 2 diabetes in the European Prospective Investigation into Cancer and Nutrition (EPIC)–Potsdam Study

The long-term role of fatty acids (FAs) in the cause of diabetes remains largely unclear. We aimed to investigate erythrocyte membrane FAs, desaturase activity, and dietary FAs in relation to the incidence of type 2 diabetes. We applied a nested case-cohort design (n = 2724, including 673 incident diabetes cases) within the European Prospective Investigation into Cancer and Nutrition (EPIC)-Potsdam Study, which involves 27,548 middle-aged subjects. Thirty erythrocyte membrane FAs (percentage of total FAs) and FA intake (percentage of total fat) were measured at baseline, and physician-confirmed incident diabetes was assessed during a mean follow-up of 7.0 y. We evaluated Δ⁵ desaturase (D5D) and Δ⁶ desaturase (D6D) activity by using FA product-to-precursor ratios (traditional approach) and by investigating variants in FADS1 and FADS2 genes that encode these desaturases (Mendelian randomization approach). As a main finding, erythrocyte 16:1n-7 and 18:3n-6 and FA ratios, which reflect stearoyl coenzyme A desaturase (SCD) and D6D activity, were directly related to diabetes risk in multivariable-adjusted models [relative risks (95% CIs) comparing extreme quintiles: 16:1n-7, 2.11 (1.46, 3.05); 18:3n-6, 2.00 (1.38, 2.88); SCD, 2.61 (1.75, 3.89); and D6D, 2.46 (1.67, 3.63)], whereas the FA ratio that reflects D5D activity was inversely associated with risk [0.46 (0.31, 0.70)]. The Mendelian randomization approach corroborated the direct relation for D6D activity and tended to support the inverse relation for D5D activity. Proportions of dietary FAs showed only modest to low correlations with erythrocyte FAs and were not significantly associated with risk. The FA profile of erythrocyte membrane phospholipids and activity of desaturase enzymes are strongly linked to the incidence of type 2 diabetes.