Stearoyl-coenzyme A Desaturase Research Articles

MicroRNA-192* impairs adipocyte triglyceride storage

We investigated the expression of miR-192* (miR-192-3p) in the visceral adipose tissue (VAT) of obese subjects and its function in cultured human adipocytes. This miRNA is a 3′ arm derived from the same pre-miRNA as miR-192 (miR-192-5p) implicated in type 2 diabetes, liver disease and cancers, and is predicted to target key genes in lipid metabolism. In morbidly obese subjects undergoing bariatric surgery preceded by a very low calorie diet, miR-192* in VAT correlated negatively (r=−0.387; p=0.046) with serum triglyceride (TG) and positively with high-density lipoprotein (HDL) concentration (r=0.396; p=0.041). In a less obese patient cohort, the miRNA correlated negatively with the body mass index (r=−0.537; p=0.026). To characterize the function of miR-192*, we overexpressed it in cultured adipocytes and analyzed the expression of adipogenic differentiation markers as well as cellular TG content. Reduced TG and expression of the adipocyte marker proteins aP2 (adipocyte protein 2) and perilipin 1 were observed. The function of miR-192* was further investigated by transcriptomic profiling of adipocytes expressing this miRNA, revealing impacts on key lipogenic genes. A number of the mRNA alterations were validated by qPCR. Western analysis confirmed a marked reduction of the lipogenic enzyme SCD (stearoyl coenzyme A desaturase-1), the fatty aldehyde dehydrogenase ALDH3A2 (aldehyde dehydrogenase 3 family member A2) and the high-density lipoprotein receptor SCARB1 (scavenger receptor B, type I). SCD and ALDH3A2 were demonstrated to be direct targets of miR-192*. To conclude, the present data identify miR-192* as a novel controller of adipocyte differentiation and lipid homeostasis.

Dietary conjugated linoleic acids increase intramuscular fat deposition and decrease subcutaneous fat deposition in Yellow Breed × Simmental cattle.

This study was conducted to estimate the effect of dietary conjugated linoleic acids (CLA) on intramuscular and subcutaneous fat deposition in Yellow Breed × Simmental cattle. The experiment was conducted for 60 days. The results showed that the average backfat thickness, (testicles + kidney + pelvic) fat percentage and subcutaneous fat percentage in dietary CLA were significantly lower than in the control group, while intramuscular the fat percentage was significantly higher. Compared to the control group, the Longissimus muscle enzyme activities of lipoprotein lipase (LPL), fatty acid synthase (FAS) and acetyl-coenzyme A carboxylase (ACC) in dietary CLA and the subcutaneous fat enzyme activities of LPL, hormone-sensitive lipase (HSL) and carnitine palmitoyltransferase-1 (CPT-1) were significantly increased. Similarly, compared to the control group, the Longissimus muscle sterol regulatory element binding protein 1 (SREBP-1), FAS, stearoyl-coenzyme A desaturase (SCD), ACC, peroxisome proliferator-activated receptor γ (PPARγ), heart fatty-acid binding protein (H-FABP) and LPL gene expression in dietary CLA were significant increased, as were the subcutaneous fat of PPARγ, H-FABP, LPL, CPT-1 and HSL in dietary CLA. These results indicated that dietary CLA increases IMF deposition mainly by the up-regulation of lipogenic gene expression, while decreasing subcutaneous fat deposition mainly by the up-regulation of lipolytic gene expression.

Relationship of Circulating Fatty Acid Profile to Metabolic Disorders Associated with Insulin Resistance

Relationship of Circulating Fatty Acid Profile to Metabolic Disorders Associated with Insulin Resistance

Anti-adipogenic activity of a new cyclic diarylheptanoid isolated from Alnus japonica on 3T3-L1 cells via modulation of PPARγ, C/EBPα and SREBP1c signaling

Total methanolic extract of Alnus japonica fruits exhibited significant anti-adipogenic activities in 3T3-L1 cells. A new cyclic diarylheptanoid (1) along with ten known compounds (2-11) were isolated by activity-guided fractionation. Compound 1, determined to be 4-hydroxy-alnus-3,5-dione, showed the most potent anti-adipogenic effect. Compound 1 significantly down-regulated expression of peroxisome proliferator-activated receptor γ (PPARγ), CCAAT/enhancer binding protein α (C/EBPα), and sterol regulatory element binding protein 1 (SREBP1c) in 3T3-L1 cells, as determined by quantitative real-time PCR and Western blot analysis. Furthermore, compound 1 suppressed mRNA expression of C/EBPβ and C/EBPδ during the early stage of adipogenesis as well as stearoyl coenzyme A desaturase 1 (SCD-1) and fatty acid synthase (FAS), target genes of SREBP1c. Upon investigating the mechanism of natural products, we propose that cyclic diarylheptanoid (1), the most potent constituent of A. japonica, can be a potent therapeutic agent against obesity through anti-adipogenesis via down-regulation of PPARγ, C/EBPα, and SREBP1c signaling.

The role of stearoyl-coenzyme A desaturase 1 in clear cell renal cell carcinoma.

This study aimed to investigate the correlations of stearoyl-coenzyme A desaturase 1 (SCD-1) with clear cell renal cell carcinoma (ccRCC) severity and PI3K-AKT-mTOR signaling pathway. From 2004 to 2006, tumor tissue and normal pericarcinomatous tissue from ccRCC samples were collected from ccRCC patients at Renji Hospital of Shanghai Jiaotong University. The expression of SCD-1 in the collected ccRCC samples and four cell lines (A498, 769-P, 786-O, and CAKI) was detected by Western blot. The correlation between SCD-1 expression and ccRCC severity was also analyzed by immunohistochemistry. Stable 786-O and 769-P ccRCC cells expressing SCD-1 short hairpin RNA (shRNA) were constructed, and the expression of proteins in the PI3K-AKT-mTOR signaling pathway was also detected. Finally, the inhibitory effect of PI3K-AKT-mTOR inhibitors (PI103, MK2206, rapamycin, AZD8055, and RAD001) on ccRCC cells stably expressing SCD-1 shRNA was also measured. Higher SCD-1 expression level was observed in ccRCC tissues compared with normal tissues. SCD-1 expression level was the highest in 786-O. SCD-1 expression was positively correlated with the tumor-node-metastasis (TNM) stage, grade of tumor cells, and lymphatic metastasis. There were no changes in the expression of AKT, ERK, PI3K, and PDK1. Significant differences were observed in the expression of p-AKT (at the Ser473 and Thr308 site), p-ERK, and two mTOR downstream molecules (4E-BP1 and p-P70S6K1) in cells stably expressing SCD-1 shRNA. PI103 and AZD8055 could enhance the inhibitory effect of SCD-1 interference on proliferation and migration of 786-O and 769-P cells. AZD8055 is recommended for the combined ccRCC treatment with shRNA interference.

Regulation of Stearoyl Coenzyme A Desaturase 1 Gene Promoter in Bovine Mammary Cells

Stearoyl-Coenzyme A desaturase 1 (SCD1) belongs to the fatty acid family of desaturases. In lactating ruminants, the SCD1 protein is highly expressed in the mammary gland and is relevant for the fatty acid composition of milk and dairy products. Bovine mammary epithelial cells (BME-UV1), cultured in vitro, have been proposed as a model to reproduce the biology of the mammary gland. The present study was designed to investigate the responsiveness of bovine SCD1 promoter to serum, insulin, oleic acid, and NFY transcription factor in BME-UV1 cells. A luciferase-based reporter assay was used to monitor the transcriptional activity of the SCD1 promoter region in BME-UV1 cells treated or not with insulin and/or oleic acid. The level of endogenous SCD1 mRNA was evaluated by Real time PCR. Insulin (20 ng/mL) induced a 2.0 to 2.5-fold increase of SCD1 promoter activity. Additionally, the effect of insulin was inhibited by oleic acid, serum components, and NFY enforced expression. Serum and NFY showed no synergistic or additive effect on SCD1 promoter activity suggesting that they repress SCD1 transcription through the same responsive element.

Effects of different roughage sources and feeding levels on adipogenesis of ovine adipocytes.

The objective of the present study was to conduct an adipogenic evaluation of different roughage sources and feeding levels during ruminant adipocyte differentiation in vitro. Six wether sheep were divided into a timothy hay feeding group (TFG, n = 3) and an Italian ryegrass straw feeding group (IFG, n = 3). The sheep were fed high-roughage (HR), medium roughage (MR) and low-roughage (LR) diets in a one-way layout design each over a 6-day period. Sheep serum samples collected on the last day of each dietary treatment were added to an adipogenic induction medium for differentiation of preadipocytes derived from sheep subcutaneous adipose tissue. The cytoplasmic lipid accumulations in the TFG serum-treated preadipocytes were significantly higher than those of the IFG-serum treated preadipocytes on day 12. Messenger RNA expression of CCAAT/enhancer-binding protein (C/EBP)-α, C/EBP-β, C/EBP-δ, fatty-acid-binding protein (aP2) and stearoyl-coenzyme A desaturase (SCD) were regulated by each serum treatment. This study shows that different roughage source diets and roughage-to-concentrate ratio diets can regulate adipocyte differentiation via ruminant blood composition.

Crystal structure of human stearoyl-coenzyme A desaturase in complex with substrate.

Stearoyl-coenzyme A desaturase-1 (SCD1) has an important role in lipid metabolism, and SCD1 inhibitors are potential therapeutic agents for the treatment of metabolic diseases and cancers. Here we report the 3.25-Å crystal structure of human SCD1 in complex with its substrate, stearoyl-coenzyme A, which defines the new SCD1 dimetal catalytic center and reveals the determinants of substrate binding to provide insights into the catalytic mechanism of desaturation of the stearoyl moiety. The structure also provides a mechanism for localization of SCD1 in the endoplasmic reticulum: human SCD1 folds around a tight hydrophobic core formed from four long α-helices that presumably function as an anchor spanning the endoplasmic reticulum membrane. Furthermore, our results provide a framework for the rational design of pharmacological inhibitors targeting the SCD1 enzyme.

Reductions in milk Δ9-desaturation ratios to oral dosing of cobalt-acetate are accompanied by the downregulation of SCD1 in lactating ewes

Oral administration of cobalt has been proven to alter milk fatty acid (FA) composition consistent with an inhibition of mammary stearoyl-coenzyme A desaturase (SCD) activity in ruminants, but the mechanisms explaining its mode of action remain uncertain. In this study, Co (as Co-acetate) was dosed to lactating ewes with the aims of examining mammary gene expression during Co-induced changes in milk FA composition, and estimating the endogenous synthesis of SCD products in milk of sheep fed an 18:3n-3-enriched diet. Twelve Assaf ewes fed a diet supplemented with 2% linseed oil were allocated to 2 experimental groups and received an oral drench supplying either 0 (control) or 9mg of Co/kg of body weight per day. Treatments were administered in 3 equal doses at 8-h intervals for 6 d. No effects of Co administration on animal performance were observed. The changes in milk FA (namely, reductions in most cis-9-containing FA) were consistent with an inhibition of SCD in the absence of detectable effects on the relative importance of mammary de novo synthesis and FA uptake. The high proportion of endogenous cis-9 trans-11 18:2 observed in this study (89%) would agree with a greater supply of trans-11 18:1 of ruminal origin in ewes fed linseed oil, compared with previous estimates in sheep fed a diet without lipid supplementation. Differences between studies could also be related to diet-induced changes in SCD activity. Altogether, both mechanisms would support that basal diet composition is a major determinant of the relative contribution of Δ9-desaturation to milk FA profile. Similarly, the consumption of a diet rich in 18:3n-3might also explain the low proportion of milk cis-9 18:1 estimated to derive from Δ9-desaturation (29%). The administration of Co to ewes fed linseed oil allowed to discriminate minor 18:3 isomers in milk, such as cis-9 trans-12 cis-15 18:3, as SCD products. Finally, Co dosing lowered the mRNA abundance of SCD1 in the mammary secretory tissue (33%), whereas no changes were detected in the SCD5 isoform or in the studied transcription factors (SREBF1, PPARG, SP1, and EGR2). These results suggest that the mode of action of Co in dairy ewes would be at least partly mediated by the downregulation of SCD1.

Association between erythrocyte membrane fatty acids and biomarkers of dyslipidemia in the EPIC-Potsdam study

Blood proportions of fatty acids (FAs) and FA-ratios reflecting desaturase activity are associated with the risk of chronic diseases like type 2 diabetes mellitus or cardiovascular diseases. Biomarkers of dyslipidemia are considered as potential mediators of this association. We evaluated associations of erythrocyte membrane proportions of individual disease-related polyunsaturated fatty acids (PUFAs), trans-FAs, dairy-derived saturated FAs (SFAs) (15:0, 17:0) and FA-ratios with biomarkers of dyslipidemia (high-density lipoprotein (HDL)-cholesterol, low-density lipoprotein (LDL)-cholesterol, non-HDL-cholesterol, triglycerides). We conducted a cross-sectional analysis of a subsample (n=1759) of the European Prospective Investigation into Cancer and Nutrition (EPIC)-Potsdam study. Associations of individual FAs and FA-ratios with plasma biomarkers of dyslipidemia were evaluated by linear multivariable regression. Most notably, FA-ratios reflecting activity of Δ6-desaturase (D6D) and stearoyl-coenzyme A-desaturase (SCD) were positively associated with triglyceride and LDL-cholesterol concentrations (adjusted means (95% confidence interval (CI)) of triglycerides (mg/dl) across D6D tertiles: men--102 (94.7-110), 111 (104-120), 144 (134-156) and women--73.5 (70.0-77.2), 82.9 (79.0-86.9), 94.2 (89.7-98.9)); across SCD tertiles: men--99.0 (91.8-107), 115 (107-124), 144 (134-156) and women--72.4 (69.0-76.0), 81.5 (77.8-85.5), 97.2 (92.6-102)), whereas inverse associations with triglycerides were observed for the estimated Δ5-desaturase (D5D) activity (adjusted means (95% CI) of triglycerides (mg/dl) across D5D tertiles: men--128 (119-138), 121 (113-131), 106 (97.9-114) and women--92.0 (87.6-96.6), 82.8 (78.9-86.9), 75.3 (71.6-79.1), P-values for trend at least 0.0006). Furthermore, we observed generally weaker and less consistent associations of dairy-derived SFAs (mainly 17:0) with triglycerides and HDL-cholesterol. Individual PUFAs and trans-FAs were, if at all, only weakly associated with dyslipidemia markers. Our findings suggest that triglyceride and LDL-cholesterol concentrations may be mediators that link intake and metabolism of FAs to metabolic risk.

Effects of lipopolysaccharide on the stearoyl-coenzyme A desaturase mRNA level in bovine primary hepatic cells

This study aimed to compare the effects of lipopolysaccharide (LPS) on stearoyl-coenzyme A desaturase (SCD) gene expression in mouse primary hepatic cells. To obtain sufficient total RNA, primary hepatic cells were plated on 6-cm diameter-type collagen 1-coated dishes (1 x 106 cells per dish). The test was divided into 6 groups with 6 replications per group. The 6 groups were treated with the following volumes of LPS (0.1 mg/mL): 0, 1, 1.5, 2, 4, and 8 μL. The cells were cultured for 24 h, and the total RNA was extracted from samples. Reverse transcription polymerase chain reaction was used to analyze SCD mRNA levels. With increasing LPS amounts, the SCD mRNA expression first decreased and then increased slightly; the expression was the lowest in the 2-μL LPS condition. The SCD mRNA levels from the 4- and 8-μL LPS conditions were slightly higher than that from the 2-μL LPS condition, but the difference was not significant (P > 0.05). The SCD mRNA level from the 2-μL LPS condition was obviously lower than that from the 0-, 1-, and 1.5-μL LPS condition, and the differences were significant (P < 0.05), and the SCD mRNA levels from the 0-, 1-, and 1.5-μL LPS conditions were not significantly different (P > 0.05). The SCD mRNA levels from the 4- and 8-μL LPS conditions were obviously lower than those from the 0- and 1-μL LPS conditions, and the differences were significant (P < 0.05).

Opportunities and Challenges in Developing Stearoyl-Coenzyme A Desaturase-1 Inhibitors as Novel Therapeutics for Human Disease

This review provides an overview of stearoyl-coenzyme A desaturase-1 (SCD1) as a novel therapeutic target for metabolic disorders and other indications. Target validation is reviewed, and limitations due to incomplete knowledge of the relevant biological systems are described. Assay development, particularly for high throughput screening, and characterization of SCD1 inhibition are summarized. The progress and evolution in medicinal chemistry are discussed, specifically focusing on key attributes of the most advanced SCD1 inhibitors described in the primary literature and in patent applications. This work culminated in numerous companies identifying potent selective inhibitors, some of which progressed to early clinical development. The status of current SCD1 drug discovery programs is reviewed. Challenges are discussed, and potential new directions are indicated.

Oral administration of cobalt acetate alters milk fatty acid composition, consistent with an inhibition of stearoyl-coenzyme A desaturase in lactating ewes

Previous investigations have shown that cobalt (Co) modifies milk fat composition in cattle, consistent with an inhibition of stearoyl-coenzyme A desaturase (SCD) activity, but it remains unclear whether other ruminant species are also affected. The present study examined the effects of oral administration of Co acetate on intake, rumen function, and milk production and fatty acid (FA) composition in sheep. Twenty lactating Assaf ewes were allocated into 1 of 4 groups and used in a continuous randomized block design that involved a 15-d adaptation, a 6-d treatment, and a 10-d posttreatment period. During the treatment period, animals received an oral drench supplying 0 (control), 3 (Co3), 6 (Co6), and 9 (Co9) mg of Co/kg of BW per day, administered in 3 equal doses at 8-h intervals. Cobalt acetate had no influence on intake or milk fat and protein concentrations, whereas treatments Co6 and Co9 tended to lower milk yield. Results on rumen parameters showed no effects on rumen fermentation, FA composition, or bacterial community structure. Administration of Co acetate decreased milk concentrations of FA containing a cis-9 double bond and SCD product:substrate ratios, consistent with an inhibition of SCD activity in the ovine mammary gland. Temporal changes in milk fat composition indicated that the effects of treatments were evident within 3d of dosing, with further changes being apparent after 6d and reverting to pretreatment values by d 6 after administration. Effect on milk FA composition did not differ substantially in response to incremental doses of Co acetate. On average, Co decreased milk cis-9 10:1/10:0, cis-9 12:1/12:0, cis-9 14:1/14:0, cis-9 16:1/16:0, cis-9 17:1/17:0, cis-9 18:1/18:0, and cis-9,trans-11 18:2/trans-11 18:1 concentration ratios by 30, 32, 38, 33, 21, 24, and 25%, respectively. Changes in milk fat cis-9 10:1, cis-9 12:1, and cis-9 14:1 concentrations to Co treatment indicated that 51% of cis-9 18:1 and cis-9,trans-11 18:2 secreted in milk originated from Δ9-desaturation. In conclusion, results demonstrated the potential of oral Co administration for the estimation of endogenous synthesis of FA containing a cis-9 double bond in the mammary gland of lactating ruminants. Indirect comparisons suggest that the effects of Co differ between sheep and cattle.

Effect of high versus low doses of fat and vitamin A dietary supplementation on fatty acid composition of phospholipids in mice

Dietary fat and vitamin A provide important precursors for potent bioactive ligands of nuclear hormone receptors, which regulate various enzymes involved in lipid homeostasis, metabolism and inflammation. We determined the effects of dietary fat and dietary vitamin A on hepatic expression of two fatty acid metabolizing enzymes, elongase 6 (ELOVL6) and stearoyl-coenzyme A desaturase 1 (SCD1) and the concentration of saturated fatty acids (SAFA) and monounsaturated fatty acid (MUFA) of phospholipids in serum and liver. Mice (n=6) were fed 4weeks with diets containing 2, 5 and 25% of fat or vitamin A (0, 2,500 and 326,500 RE/kg as retinyl palmitate). MUFAs and SAFAs were measured using GC and ESI-MS/MS. Hepatic expression of metabolizing enzymes was determined using QRT-PCR. ELOVL6 was significantly down-regulated in response to a high-fat diet (p<0.001) and significantly up-regulated in response to low-fat diet (p<0.05). SCD1 expression was significantly lower in high- versus low-fat diet (p<0.05). The vitamin A content in the diet did not influence the hepatic expression of both enzymes. In plasma, the amounts of MUFAs bound to phospholipids significantly decreased in response to a high-fat diet and increased after a low-fat diet. This tendency was also observed in the liver for various phospholipids sub-classes. In summary, this study shows that fat content in the diet has a stronger impact than the content of vitamin A on hepatic gene expression of SCD1 and ELOVL6 and thereby on MUFA and SAFA concentrations in liver and plasma.

Critical role of SCD1 in autophagy regulation via lipogenesis and lipid rafts-coupled AKT-FOXO1 signaling pathway

SCD1 (stearoyl-coenzyme A desaturase 1) is an endoplasmic reticulum-bound enzyme that catalyzes the formation of the first double bond at the cis-Δ9 position of saturated fatty acids (SFA) to form monounsaturated fatty acids (MUFA). Increasing evidence indicates that autophagy plays an important role in regulating lipid metabolism, while little is known about whether key enzymes of lipogenesis like SCD1 can regulate autophagy. In this study, we examined the role of SCD1 in autophagy using the tsc2−/− mouse embryonic fibroblasts (MEFs) possessing constitutively active MTORC1 as a cellular model. We found that mRNA and protein levels of SCD1 are significantly elevated in the tsc2−/− MEFs compared with Tsc2+/+ MEFs, resulting in significant increases in levels of various lipid classes. Furthermore, inhibition of SCD1 activity by either a chemical inhibitor or genetic knockdown resulted in an increase of autophagic flux only in the tsc2−/− MEFs. Induction of autophagy was independent of MTOR as MTORC1 activity was not suppressed by SCD1 inhibition. Loss of phosphorylation on AKT Ser473 was observed upon SCD1 inhibition and such AKT inactivation was due to disruption of lipid raft formation, without affecting the formation and activity of MTORC2. Increased nuclear translocation of FOXO1 was observed following AKT inactivation, leading to increased transcription of genes involved in the autophagic process. The tsc2−/− MEFs were also more susceptible to apoptosis induced by SCD1 inhibition and blockage of autophagy sensitized the cell death response. These results revealed a novel function of SCD1 on regulation of autophagy via lipogenesis and the lipid rafts-AKT-FOXO1 pathway.

Identifying Novel SNPs and Allelic Sequences of the Stearoyl-CoA Desaturase Gene (SCD) in Fat-Tailed and Thin-Tailed Sheep Breeds

Stearoyl-coenzyme A-desaturase (SCD) is a candidate gene for genetic variation in the fatty acid composition of meat and milk. The SCD enzyme catalyzes a D9-cis desaturation of a number of fatty acyl-CoA substrates with a preference for C16:0 and C18:0, which are converted to C16:1 and C18:1, respectively (Enoch et al. 1976). SCD is also a key enzyme in endogenous production of the cis-9, trans-11 isomer of conjugated linoleic acid (CLA) (Bauman et al. 1999). In sheep, two single nucleotide polymorphisms (SNPs), located in intron 4 (Miari et al. 2009) and intron 2 (GarciaFernandez et al. 2010), displayed significant association with CLA/VA variability and milk fat percentage, respectively. The objective of this study was to determine the existence of polymorphisms in the SCD gene in 458 lambs belonging to three traditional fat-tailed, medium fat-tailed, and thin-tailed Iranian sheep breeds.

Peroxisome proliferator-activated receptor-γ stimulates the synthesis of monounsaturated fatty acids in dairy goat mammary epithelial cells via the control of stearoyl-coenzyme A desaturase

In rodents, peroxisome proliferator-activated receptor-γ (PPARG) plays a crucial role in fatty acid (FA) metabolism through regulation of gene expression, including stearoyl-coenzyme A desaturase (SCD), which is the rate-limiting enzyme for the biosynthesis of monounsaturated FA. However, whether or how PPARG regulates the activity of mammary SCD in ruminants is unknown. This study explored the potential role of PPARG isoforms in regulating SCD mRNA expression in lactating goat mammary epithelial cells (GMEC). Using quantitative real-time PCR, we observed a positive correlation between PPARG and SCD expression in the goat mammary gland at peak lactation. Overexpression of both PPARG1 and PPARG2 in GMEC increased markedly the expression of SCD, the concentration of 16:1 and 18:1, and the desaturation indices of 16:1 and 18:1. The PPARG ligand rosiglitazone further increased SCD expression and desaturation indices in GMEC, overexpressing PPARG1 and PPARG2. Incubation with rosiglitazone alone increased the expression of SCD, but did not alter the concentration of 16- to 18-carbon FA or their desaturation indices. The results provide evidence that PPARG regulates the expression and activity of SCD in GMEC. As such, PPARG may contribute to regulation of SCD and monounsaturated FA synthesis during lactation.

Expression of key lipid metabolism genes in adipose tissue is not altered by once-daily milking during a feed restriction of grazing dairy cows

The objective of this study was to investigate the effect of reduced milking frequency, at 2 feeding levels, on gene expression in adipose tissue of grazing dairy cows during early lactation. Multiparous Holstein-Friesian and Holstein-Friesian × Jersey cows (n=120) were grazed on pasture and milked twice daily (2×) from calving to 34±6d in milk (mean ± standard deviation). Cows were then allocated to 1 of 4 treatments in a 2×2 factorial arrangement. Treatments consisted of 2 milking frequencies (2× or once daily; 1×) and 2 feeding levels for 3wk: adequately fed (AF), consuming 14.3kg of dry matter/cow per day, or underfed (UF), consuming 8.3kg of dry matter/cow per day. After the treatment period, all cows were fed to target grazing residuals ≥1,600kg of DM/cow per day and milked 2× for 20wk. Adipose tissue was collected from 12 cows per treatment by subcutaneous biopsy at −1, 3, and 5wk relative to treatment start, RNA was extracted, and transcript abundance of genes involved in lipid metabolism was quantified using a linear mixed model. At the end of the 3-wk treatment period, transcript abundance of genes involved in fatty acid (FA) uptake into adipose tissue (LPL), FA synthesis [FA synthase (FASN) and stearoyl-coenzyme A desaturase (SCD)], FA oxidation [acyl-coenzyme A synthetase long-chain family member 1 (ACSL1) and carnitine palmitoyltransferase 2 (CPT2)], glyceroneogenesis [glycerol-3-phosphate dehydrogenase 1 (GPD1) and pyruvate carboxylase (PC)], and triacylglyceride synthesis [diacylglycerol O-acyltransferase 2 (DGAT2)] were greater in AF1× cows compared with all other treatments. However, when cows were underfed, no effects of milking frequency were observed on transcript abundance of genes involved in adipose lipid metabolism. Despite increases in plasma NEFA concentrations in UF cows, no effects of underfeeding were observed on the transcription of lipolytic genes. At 5wk, after cows were returned to 2× milking and standard feed allowance, transcript abundances of genes involved in FA synthesis [acetyl-coenzyme A carboxylase α (ACACA) and SCD)] were increased in cows previously UF. Expression of ACSL1 was decreased in UF1× cows relative to UF2× cows and CPT2 expression was greater in AF1× cows compared with AF2× cows. In conclusion, after 3wk of reduced milking frequency during a feed restriction, transcription of genes involved in lipid metabolism in adipose tissue were not altered, possibly due to the reduced milk production in these animals. However, 3wk of 1× milking in AF cows increased transcription of genes involved in FA synthesis, oxidation, and triacylglyceride synthesis.

Salicortin-Derivatives from Salix pseudo-lasiogyne Twigs Inhibit Adipogenesis in 3T3-L1 Cells via Modulation of C/EBPα and SREBP1c Dependent Pathway

Obesity is reported to be associated with excessive growth of adipocyte mass tissue as a result of increases in the number and size of adipocytes differentiated from preadipocytes. To search for anti-adipogenic phytochemicals, we screened for inhibitory activities of various plant sources on adipocyte differentiation in 3T3-L1 preadipocytes. Among the sources, a methanolic extract of Salix pseudo-lasiogyne twigs (Salicaceae) reduced lipid accumulation in a concentration-dependent manner. During our search for anti-adipogenic constituents from S. pseudo-lasiogyne, five salicortin derivatives isolated from an EtOAc fraction of this plant and bearing 1-hydroxy-6-oxo-2-cyclohexene-carboxylate moieties, namely 2′,6′-O-acetylsalicortin (1), 2′-O-acetylsalicortin (2), 3′-O-acetylsalicortin (3), 6′-O-acetylsalicortin (4), and salicortin (5), were found to significantly inhibit adipocyte differentiation in 3T3-L1 cells. In particular, 2′,6′-O-acetylsalicortin (1) had the most potent inhibitory activity on adipocyte differentiation, with an IC50 value of 11.6 μM, and it significantly down-regulated the expressions of CCAAT/enhancer binding protein α (C/EBPα) and sterol regulatory element binding protein 1 (SREBP1c). Furthermore, 2′,6′-O-acetylsalicortin (1) suppressed mRNA expression levels of C/EBPβ during the early stage of adipocyte differentiation and stearoyl coenzyme A desaturase 1 (SCD-1), acetyl-CoA carboxylase (ACC), and fatty acid synthase (FAS) expression, target genes of SREBP1c. In the present study, we demonstrate that the anti-adipogenesis mechanism of 2′,6′-O-acetylsalicortin (1) may be mediated via down-regulation of C/EBPα and SREBP1c dependent pathways. Through their anti-adipogenic activity, salicortin derivatives may be potential novel therapeutic agents against obesity.

Overexpression of stearoyl-coenzyme A desaturase 1 in macrophages promotes reverse cholesterol transport

Stearoyl-coenzyme A desaturase 1 (SCD1) is the rate-limiting enzyme in the synthesis of monounsaturated fatty acids. However, the impact of SCD1 on atherosclerosis remains unclear. The aim of this study was to determine whether SCD1 affects macrophage reverse cholesterol transport (RCT) in mice. Compared to the control, adenoviral-mediated SCD1 overexpression in RAW264.7 macrophages increased cholesterol efflux to HDL, but not to apoA-I, without clear changes in ABCA1, ABCG1 and SR-BI expressions. While knockdown of ABCG1 and SR-BI did not affect the SCD1-induced cholesterol efflux to HDL, SCD1-overexpressing macrophages promoted the formation of both normal- and large-sized HDL in media, accompanying increased apolipoprotein A-I levels in HDL fractions. Transformation to larger particles of HDL was independently confirmed by nuclear magnetic resonance-based lipoprotein analysis. Interestingly, media transfer assays revealed that HDL generated by SCD1 had enhanced cholesterol efflux potential, indicating that SCD1 transformed HDL to a more anti-atherogenic phenotype. To study macrophage RCT in vivo, 3H-cholesterol-labeled RAW264.7 cells overexpressing SCD1 or the control were intraperitoneally injected into mice. Supporting the in vitro data, injection of SCD1-macrophages resulted in significant increases in 3H-tracer in plasma, liver, and feces compared to the control. Moreover, there was a shift towards larger particles in the 3H-tracer distribution of HDL fractions obtained from the mice.In conclusion, macrophage-specific SCD1 overexpression promotes overall RCT through increased cholesterol efflux to HDL, suggesting that macrophage SCD1 achieves an anti-atherogenic effect by enhancing RCT.