Methodology for the In Vivo Measurement of the Δ9-Desaturation of Myristic, Palmitic, and Stearic Acids in Lactating Dairy Cattle

Effects of increasing dietary inclusion of high oleic acid soybeans on milk production of high-producing dairy cows

Recent research has highlighted the importance of dietary fatty acid profile of fatty acid supplements on production responses of high-producing dairy cows. Conventional soybeans contain ∼15% oleic acid and ∼50% linoleic acid whereas high oleic acid soybeans (HOSB) contain ∼70% oleic acid and ∼7% linoleic acid. We determined the effect of increasing dietary inclusion of roasted and ground HOSB on production responses of high-producing dairy cows. Twenty-four multiparous Holstein cows (50.7 ± 4.45 kg/d of milk; 122 ± 57 DIM) were randomly assigned to treatment sequences in a replicated 4 × 4 Latin square design with 21-d periods. Treatments were increasing doses of HOSB at 0, 8, 16, and 24% DM. The HOSB replaced conventional soybean meal and hulls to maintain similar diet nutrient composition (% DM) of 27.4 - 29.4% (NDF), 20.6% forage NDF, 27.5% starch, and 15.9 - 16.5% CP. Total fatty acid content of treatments was 1.65, 3.11, 4.52, and 5.97% DM, respectively. Pre-planned polynomial orthogonal contrasts included the linear, quadratic, and cubic effects of increasing HOSB. Increasing dietary inclusion of HOSB linearly decreased DMI and milk urea nitrogen and increased yields of milk, 3.5% fat corrected milk, energy corrected milk, and milk fat, and quadratically increased milk protein. The increased response to milk fat was due to an increase in preformed milk fatty acids. Due to the increase in milk component yields and decrease in DMI, there was an increase in feed efficiency. Increasing HOSB inclusion linearly decreased plasma BUN concentration and tended to decrease plasma insulin. Increasing HOSB had no effect on BW change or BCS change. In summary, increasing dietary inclusion of HOSB up to 24% DM increased production responses of high-producing dairy cows and did not affect body reserves.

The Effect of Bioactive Aliment Compounds and Micronutrients on Non-Alcoholic Fatty Liver Disease

In the current review, we focused on identifying aliment compounds and micronutrients, as well as addressed promising bioactive nutrients that may interfere with NAFLD advance and ultimately affect this disease progress. In this regard, we targeted: 1. Potential bioactive nutrients that may interfere with NAFLD, specifically dark chocolate, cocoa butter, and peanut butter which may be involved in decreasing cholesterol concentrations. 2. The role of sweeteners used in coffee and other frequent beverages; in this sense, stevia has proven to be adequate for improving carbohydrate metabolism, liver steatosis, and liver fibrosis. 3. Additional compounds were shown to exert a beneficial action on NAFLD, namely glutathione, soy lecithin, silymarin, Aquamin, and cannabinoids which were shown to lower the serum concentration of triglycerides. 4. The effects of micronutrients, especially vitamins, on NAFLD. Even if most studies demonstrate the beneficial role of vitamins in this pathology, there are exceptions. 5. We provide information regarding the modulation of the activity of some enzymes related to NAFLD and their effect on this disease. We conclude that NAFLD can be prevented or improved by different factors through their involvement in the signaling, genetic, and biochemical pathways that underlie NAFLD. Therefore, exposing this vast knowledge to the public is particularly important.

Metabolic response of dolphins to short-term fasting reveals physiological changes that differ from the traditional fasting model

Bottlenose dolphins (Tursiops truncatus) typically feed on prey that are high in lipid and protein content and nearly devoid of carbohydrate, a dietary feature shared with other marine mammals. However, unlike fasted-adapted marine mammals that predictably incorporate fasting into their life history, dolphins feed intermittently throughout the day and are not believed to be fasting-adapted. To assess whether the physiological response to fasting in the dolphin shares features with or distinguishes them from those of fasting-adapted marine mammals, the plasma metabolomes of eight bottlenose dolphins were compared between post-absorptive and 24-h fasted states. Increases in most identified free fatty acids and lipid metabolites and reductions in most amino acids and their metabolites were consistent with the upregulation of lipolysis and lipid oxidation and the downregulation of protein catabolism and synthesis. Consistent with a previously hypothesized diabetic-like fasting state, fasting was associated with elevated glucose and patterns of certain metabolites (e.g. citrate, cis-aconitate, myristoleic acid) indicative of lipid synthesis and glucose cycling to protect endogenous glucose from oxidative disposal. Pathway analysis predicted an upregulation of cytokines, decreased cell growth and increased apoptosis including apoptosis of insulin-secreting β-cells. Metabolomic conditional mutual information networks were estimated for the post-absorptive and fasted states and 'topological modules' were estimated for each using the eigenvector approach to modularity network division. A dynamic network marker indicative of a physiological shift toward a negative energy state was subsequently identified that has the potential conservation application of assessing energy state balance in at-risk wild dolphins.

Determination of Fatty Acids Profile in Original Brown Cows Dairy Products and Relationship with Alpine Pasture Farming System

This study aimed to evaluate the relationships between fatty acids and the pattern that most contributes to discriminate between two farming systems, in which the main difference was the practice, or not, of alpine summer-grazing. Milk and cheese were sampled every month in two farms of Original Brown cows identical under geographical location and management during no grazing season point of view in the 2018 season. Fatty acids concentrations were determined by gas chromatography. The principal component analysis extracted three components (PCs). Mammary gland de novo synthetized fatty acids (C14:0, C14:1 n9, and C16:0) and saturated and monosaturated C18 fatty acids (C18:0, C18:1 n9c) were inversely associated in the PC1; PC2 included polyunsaturated C18 fatty acids (C18:2 n6c, C18:3 n3) and C15:0 while conjugated linoleic acid (CLA n9c, n11t) and fatty acids containing 20 or more carbon atoms (C21:0, C20:5 n3) were associated in the PC3. The processes of rumen fermentation and de novo synthesis in mammary gland that are, in turn, influenced by diet, could explain the relationships between fatty acids within each PC. The discriminant analyses showed that the PC2 included the fatty acids profile that best discriminated between the two farming systems, followed by PC3 and, lastly, PC1. This model, if validated, could be an important tool to the dairy industry.

Sterculic Acid: The Mechanisms of Action beyond Stearoyl-CoA Desaturase Inhibition and Therapeutic Opportunities in Human Diseases

In many tissues, stearoyl-CoA desaturase 1 (SCD1) catalyzes the biosynthesis of monounsaturated fatty acids (MUFAS), (i.e., palmitoleate and oleate) from their saturated fatty acid (SFA) precursors (i.e., palmitate and stearate), influencing cellular membrane physiology and signaling, leading to broad effects on human physiology. In addition to its predominant role in lipid metabolism and body weight control, SCD1 has emerged recently as a potential new target for the treatment for various diseases, such as nonalcoholic steatohepatitis, Alzheimer’s disease, cancer, and skin disorders. Sterculic acid (SA) is a cyclopropene fatty acid originally found in the seeds of the plant Sterculia foetida with numerous biological activities. On the one hand, its ability to inhibit stearoyl-CoA desaturase (SCD) allows its use as a coadjuvant of several pathologies where this enzyme has been associated. On the other hand, additional effects independently of its SCD inhibitory properties, involve anti-inflammatory and protective roles in retinal diseases such as age-related macular degeneration (AMD). This review aims to summarize the mechanisms by which SA exerts its actions and to highlight the emerging areas where this natural compound may be of help for the development of new therapies for human diseases.

Endogenous synthesis of milk oleic acid in dairy ewes: In vivo measurement using 13C-labeled stearic acid

The use of stable isotopes is a reliable and risk-free alternative to radioactive tracers for directly examining in vivo fatty acid (FA) metabolism. However, very limited information is available in ruminants, and none is available in sheep. Therefore, we conducted an experiment in dairy ewes to determine, for the first time in this species, the uptake, Δ⁹-desaturation, and secretion of ¹³C-labeled stearic acid (SA) into milk with the aim of measuring in vivo endogenous synthesis of milk oleic acid (OA) and stearoyl-CoA desaturase activity. Six lactating Assaf ewes fed a total mixed ration (forage:concentrate ratio = 30:70) received an intravenous injection of 2 g of ¹³C-labeled SA. At -24, -15, 0, 4, 8, 12, 16, 20, 24, 36, 48, 60, and 72 h postinjection (p.i.), milk yield was recorded and milk samples were collected to examine fat concentration and FA composition, including compound-specific isotope analysis of SA and OA by gas chromatography-combustion isotope ratio mass spectrometry. Over the p.i. period, the SA proportion ranged from 7.6 to 8.3% of total FA, with a maximum ¹³C enrichment of 1.9%, whereas OA was more abundant (14.3-15.4% of total FA) and had lower ¹³C enrichments (up to 0.69%). On average, 15% of the isotopic tracer was transferred to milk within 72 h p.i., and 47 to 50% of the SA taken up by the mammary gland would have been desaturated to OA. The proportion of oleic acid being synthesized endogenously was estimated to represent between 48 and 57% of the amount secreted in milk. Further research under different dietary conditions is recommended.

A post-GWAS confirming the SCD gene associated with milk medium- and long-chain unsaturated fatty acids in Chinese Holstein population

The stearoyl-CoA desaturase (delta-9-desaturase) gene encodes a key enzyme in the cellular biosynthesis of monounsaturated fatty acids. In our initial genome-wide association study (GWAS) of Chinese Holstein cows, 19 SNPs fell in a 1.8-Mb region (20.3-22.1 Mb) on chromosome 26 underlying the SCD gene and were highly significantly associated with C14:1 or C14 index. The aims of this study were to verify whether the SCD gene has significant genetic effects on milk fatty acid composition in dairy cattle. By resequencing the entire coding region of the bovine SCD gene, a total of six variations were identified, including three coding variations (g.10153G>A, g.10213T>C and g.10329C>T) and three intronic variations (g.6926A>G, g.8646G>A and g.16158G>C). The SNP in exon 3, g.10329C>T, was predicted to result in an amino acid replacement from alanine (GCG) to valine (GTG) in the SCD protein. An association study for 16 milk fatty acids using 346 Chinese Holstein cows with accurate phenotypes and genotypes was performed using the mixed animal model with the proc mixed procedure in sas 9.2. All six detected SNPs were revealed to be associated with six medium- and long-chain unsaturated fatty acids (P = 0.0457 to P < 0.0001), specifically for C14:1 and C14 index (P = 0.0005 to P < 0.0001). Subsequently, strong linkage disequilibrium (D' = 0.88-1.00) was observed among all six SNPs in SCD and the five SNPs (rs41623887, rs109923480, rs42090224, rs42092174 and rs42091426) within the 1.8-Mb region identified in our previous GWAS, indicating that the significant association of the SCD gene with milk fatty acid content traits reduced the observed significant 1.8-Mb chromosome region in GWAS. Haplotype-based analysis revealed significant associations of the haplotypes encompassing the six SCD SNPs and one SNP (rs109923480) in a GWAS with C14:1, C14 index, C16:1 and C16 index (P = 0.0011 to P < 0.0001). In summary, our findings provide replicate evidence for our previous GWAS and demonstrate that variants in the SCD gene are significantly associated with milk fatty acid composition in dairy cattle, which provides clear evidence for an increased understanding of milk fatty acid synthesis and enhances opportunities to improve milk-fat composition in dairy cattle.

Relationship between stearoyl-CoA desaturase 1 gene expression, relative protein abundance, and its fatty acid products in bovine tissues

Stearoyl-CoA desaturase 1 (SCD1) greatly contributes to the unsaturated fatty acids present in milk and meat of cattle. The SCD1 enzyme introduces a double bond into certain saturated fatty acyl-CoAs producing monounsaturated fatty acids (MUFA). The SCD1 enzyme also has been shown to be active in the bovine mammary gland converting t11 18:1 (vaccenic acid) to c9 t11 conjugated linoleic acid (CLA). The objective of this study was to determine any association between the gene expression of SCD1 and occurrence of its products (c9 14:1, c9 16:1, c9 18:1, and c9 t11 18:2) in various bovine tissues. Tissue samples were obtained from lactating Holstein cows (n=28) at slaughter, frozen in liquid nitrogen and stored at -80 °C. Total RNA was extracted and converted to complementary DNA for quantitative real time polymerase chain reaction (PCR) analysis of the SCD1 gene. Extracted lipid was converted to fatty acid methyl esters and analysed by GC. Tissues varied in expression of SCD1 gene with mammary, cardiac, intestinal adipose, and skeletal muscle expressing greater copy number as compared with lung, large intestine, small intestine and liver (371, 369, 328, 286, 257, 145, 73, and 21 copies/ng RNA, respectively). Tissues with high mRNA expression of SCD1 contained greater SCD1 protein whereas detection of SCD1 protein in tissues with low SCD1 mRNA expression was very faint or absent. Across tissues, the desaturase indices for c9 18:1 (r=0.24) and sum of SCD products (r=0.20) were positively correlated with SCD1 gene expression (P<0.01 for both). Within each tissue, the relationship between SCD1 gene expression and the desaturase indices varied. No correlation was detected between SCD1 expression and desaturase indices in the liver, large and small intestines, lung, cardiac or skeletal muscles. Positive correlations, however, were detected between SCD1 expression and the desaturase indices in intestinal adipose tissue (P<0.02 for all) except 14:1, whereas only c9 18:1, c9 t11 18:2 and sum of all desaturase indices were positively correlated with SCD1 expression in mammary tissue (P < or = 0.03). Overall, the relationship between SCD1 gene expression and occurrence of its products seems to be tissue specific.

Application of stable isotopes to investigate the metabolism of fatty acids, glycerophospholipid and sphingolipid species

Nature provides an enormous diversity of lipid molecules that originate from various pathways. To gain insight into the metabolism and dynamics of lipid species, the application of stable isotope-labeled tracers combined with mass spectrometric analysis represents a perfect tool. This review provides an overview of strategies to track fatty acid, glycerophospholipid, and sphingolipid metabolism. In particular, the selection of stable isotope-labeled precursors and their mass spectrometric analysis is discussed. Furthermore, examples of metabolic studies that were performed in cell culture, animal and clinical experiments are presented.

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

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

Effects of trans fatty acids on markers of inflammation in bovine mammary epithelial cells

Trans fatty acids (tFA) contribute to inflammation. The objective was to investigate the effects of tFA on mRNA expression of proinflammatory markers in cultured bovine mammary epithelial cells (MAC-T cell line). Bovine mammary epithelial cells were grown in Dulbecco's Modified Eagle Medium containing 10% fetal bovine serum. Cells were then subcultured in a medium lacking fetal bovine serum, to which incremental concentrations (up to 90 μM) of elaidic acid (trans-9 C18:1) or linoleidic acid (trans-9, trans-12 C18:2) were added. Bovine serum albumin (fatty acid-free) solutions were added and cells were collected at specific time points over 48 h. Then, RNA was extracted and converted to complementary DNA for quantitative real-time PCR analysis of proinflammatory gene expression. Presence of elaidic acid caused increases in mRNA expression of interleukin (IL)-1β (3.4-fold; dose-independently over a 6-h period) and intercellular adhesion molecule (ICAM)-1 (up to 1.4-fold) relative to that for cells treated with no tFA, whereas expression of IL-6 and IL-8 was reduced 0.75- and 0.85-fold, respectively. Presence of linoleidic acid reduced mRNA expression of IL-6 and IL-8 relative to that for control (0.95- and 0.87-fold, respectively). Trans mono- and dienoic fatty acids upregulated mRNA expression of IL-1β and ICAM-1, whereas expression of IL-6 and IL-8 was downregulated in MAC-T cells. Because these genes are ultimately involved in inflammation, elaidic or linoleidic acid, either directly fed or formed in the rumen during biohydrogenation, may alter the risk for mastitis in vivo.

Regulation of mammalian desaturases by myristic acid: N-terminal myristoylation and other modulations

Myristic acid, the 14-carbon saturated fatty acid (C14:0), usually accounts for small amounts (0.5%-1% weight of total fatty acids) in animal tissues. Since it is a relatively rare molecule in the cells, the specific properties and functional roles of myristic acid have not been fully studied and described. Like other dietary saturated fatty acids (palmitic acid, lauric acid), this fatty acid is usually associated with negative consequences for human health. Indeed, in industrialized countries, its excessive consumption correlates with an increase in plasma cholesterol and mortality due to cardiovascular diseases. Nevertheless, one feature of myristoyl-CoA is its ability to be covalently linked to the N-terminal glycine residue of eukaryotic and viral proteins. This reaction is called N-terminal myristoylation. Through the myristoylation of hundreds of substrate proteins, myristic acid can activate many physiological pathways. This review deals with these potentially activated pathways. It focuses on the following emerging findings on the biological ability of myristic acid to regulate the activity of mammalian desaturases: (i) recent findings have described it as a regulator of the Δ4-desaturation of dihydroceramide to ceramide; (ii) studies have demonstrated that it is an activator of the Δ6-desaturation of polyunsaturated fatty acids; and (iii) myristic acid itself is a substrate of some fatty acid desaturases. This article discusses several topics, such as the myristoylation of the dihydroceramide Δ4-desaturase, the myristoylation of the NADH-cytochrome b5 reductase which is part of the whole desaturase complex, and other putative mechanisms.

Genetic variability of milk fatty acids

The milk fatty acid (FA) profile is far from the optimal fat composition in regards to human health. The natural sources of variation, such as feeding or genetics, could be used to increase the concentrations of unsaturated fatty acids. The impact of feeding is well described. However, genetic effects on the milk FA composition begin to be extensively studied. This paper summarizes the available information about the genetic variability of FAs. The greatest breed differences in FA composition are observed between Holstein and Jersey milk. Milk fat of the latter breed contains higher concentrations of saturated FAs, especially short-chain FAs. The variation of the delta-9 desaturase activity estimated from specific FA ratios could explain partly these breed differences. The choice of a specific breed seems to be a possibility to improve the nutritional quality of milk fat. Generally, the proportions of FAs in milk are more heritable than the proportions of these same FAs in fat. Heritability estimates range from 0.00 to 0.54. The presence of some single nucleotide polymorphisms could explain partly the observed individual genetic variability. The polymorphisms detected on SCD1 and DGAT1 genes influence the milk FA composition. The SCD1 V allele increases the unsaturation of C16 and C18. The DGAT1 A allele is related to the unsaturation of C18. So, a combination of the molecular and quantitative approaches should be used to develop tools helping farmers in the selection of their animals to improve the nutritional quality of the produced milk fat.

Ruminal infusions of cobalt-EDTA reduce mammary delta9-desaturase index and alter milk fatty acid composition in lactating cows

Ruminal administration of a triple indigestible marker system comprised of cobalt EDTA (CoEDTA), ytterbium acetate (YbAc), and chromium-mordanted straw (CrS) decreases product:substrate ratios for Delta9-desaturase in bovine milk fat. This experiment was designed to identify the marker(s) responsible and develop an alternative system for simultaneous determination of nutrient flow in the gastro-intestinal tract and milk fatty acid composition. Five lactating dairy cows were used in a 5 x 5 Latin square with 21-d periods to evaluate the effects of YbAc, CoEDTA, and CrS independently or as part of a triple marker system (TMS), and CrEDTA as an alternative to CoEDTA on milk fat composition. Markers were administered in the rumen over a 7-d interval and samples of milk were collected on d -1, 3, 7, and 11. Both TMS and CoEDTA alone reduced the concentrations of milk fatty acids containing a cis-9 double bond, whereas YbAc, CrS, and CrEDTA had no effect. Reductions in product:substrate ratios for Delta9-desaturase were time dependent and evident within 3 d of administration. Ruminal infusion of CoEDTA for 7 d induced mean decreases in milk cis-9 14:1/14:0, cis-9 16:1/16:0, cis-9 18:1/18:0, and cis-9, trans-11 conjugated linoleic acid/trans-11 18:1 concentration ratios of 47.7, 26.7, 40.3, and 42.6%, respectively. In conclusion, ruminal infusion of CoEDTA alters milk fatty acid composition and appears to inhibit Delta9-desaturase activity in the bovine mammary gland. Results indicate that a TMS based on CrEDTA, YbAc, and indigestible neutral detergent fiber can be used for estimating nutrient flow without altering milk fat composition in lactating cows.