The redox state of the plastoquinone (PQ) pool is connected to thylakoid lipid saturation in a marine diatom.

The redox state of the plastoquinone (PQ) pool is a known sensor for retrograde signaling. In this paper, we asked, "does the redox state of the PQ pool modulate the saturation state of thylakoid lipids?" Data from fatty acid composition and mRNA transcript abundance analyses suggest a strong connection between these two aspects in a model marine diatom. Fatty acid profiles of Phaeodactylum tricornutum exhibited specific changes when the redox state of the PQ pool was modulated by light and two chemical inhibitors [3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) or 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone (DBMIB)]. Data from liquid chromatography with tandem mass spectrometry (LC-MS/MS) indicated a ca. 7-20% decrease in the saturation state of all four conserved thylakoid lipids in response to an oxidized PQ pool. The redox signals generated from an oxidized PQ pool in plastids also increased the mRNA transcript abundance of nuclear-encoded C16 fatty acid desaturases (FADs), with peak upregulation on a timescale of 6 to 12 h. The connection between the redox state of the PQ pool and thylakoid lipid saturation suggests a heretofore unrecognized retrograde signaling pathway that couples photosynthetic electron transport and the physical state of thylakoid membrane lipids.

Disturbance of Fatty Acid Desaturation Mediated by FADS2 in Mesenteric Adipocytes Contributes to Chronic Inflammation of Crohn's Disease.

BACKGROUND AND AIMS: The aim of this study was to investigate the metabolic profile of mesenteric adipocytes and the correlations between key metabolic changes and local inflammation in the context of Crohn's disease [CD]. METHODS: Metabolic dysfunction was shown to be regulated by fatty acid desaturase-2 [FADS2], through metabolomics and functional analyses of mesenteric adipose tissue biopsies and primary mesenteric adipocytes isolated from surgical specimens collected from CD patients and control subjects. FADS2 was overexpressed in vitro and in vivo using a lentiviral vector and an adeno-associated virus [AAV], respectively. The interaction between mesenteric adipocytes and inflammation responses was evaluated by establishing a cell coculture system and a FADS2-AAV treated animal model; 3T3-L1 cells were used to elucidate the mechanism underlying FADS2 deregulation. RESULTS: We observed significant changes in the levels of metabolites involved in the multi-step synthesis of long-chain polyunsaturated fatty acids [PUFAs]. Gas chromatography analysis revealed impaired desaturation fluxes towards the n-6 and n-3 pathways, which are associated with reduced FADS2 activity in human mesentery tissue. Decreased FADS2 expression at both mRNA and protein levels was confirmed in surgical specimens. The restoration of FADS2 expression, which allows for the endogenous conversion of n-3 fatty acids into proresolving lipid mediators, resulted in a significant reduction in pro-inflammatory macrophage infiltration and attenuated expression of inflammatory cytokines or adipokines. CONCLUSIONS: These findings indicate that impaired fatty acid desaturation and lipid mediator imbalance within mesenteric adipose tissue contributes to chronic inflammation in CD. The therapeutic role of FADS2 may lead to improved CD treatment.

Reduced intestinal FADS1 gene expression and plasma omega-3 fatty acids following Roux-en-Y gastric bypass.

BACKGROUND & AIMS: Roux-en-Y gastric bypass (RYGB) limits food ingestion and may alter the intestinal expression of genes involved in the endogenous synthesis of polyunsaturated fatty acids (PUFAs). These changes may decrease the systemic availability of bioactive PUFAs after RYGB. To study the impact of RYGB on the dietary ingestion and plasma concentration of PUFAs and on the intestinal expression of genes involved in their endogenous biosynthesis in severely obese women with type 2 diabetes. METHODS: Before, and 3 and 12 months after RYGB, obese women (n = 20) self-reported a seven-day dietary record, answered a food frequency query and provided plasma samples for alpha-linolenic (ALA), eicosapentaenoic (EPA), docosahexaenoic (DHA) and arachidonic (ARA) acid assessment by gas chromatography. Intestinal biopsies (duodenum, jejunum and ileum) were collected through double-balloon endoscopy before and 3 months after RYGB for gene expression analysis by microarray (Human GeneChip 1.0 ST array) and RT-qPCR validation. RESULTS: Compared to the preoperative period, patients had decreased intakes of PUFAs, fish and soybean oil (p < 0.05) and lower plasma concentrations of ALA and EPA (p < 0.001) 3 and 12 months after RYGB. FADS1 gene expression was lower in duodenum (RT-qPCR fold change = -1.620, p < 0.05) and jejunum (RT-qPCR fold change = -1.549, p < 0.05) 3 months following RYGB, compared to before surgery. CONCLUSION: RYGB decreased PUFA ingestion, plasma ALA and EPA levels, and intestinal expression of FADS1 gene. The latter encodes a key enzyme involved in endogenous biosynthesis of PUFAs. These data suggest that supplementation of omega-3 PUFAs may be required for obese patients undergoing RYGB. Clinical Trial Registry number and website: www.clinicaltrials.gov - NCT01251016; Plataforma Brasil - 19339913.0.0000.0068.

Overexpression of OLE1 enhances stress tolerance and constitutively activates the MAPK HOG pathway in Saccharomyces cerevisiae.

OLE1 of Saccharomyces cerevisiae encodes the sole and essential Δ-9 desaturase catalyzing the conversion of saturated to unsaturated fatty acids. Upon ectopic overexpression of OLE1 in S. cerevisiae, significant increases in the membrane oleic acid content were observed. OLE1-overexpressing strains displayed enhanced tolerance to various stresses, better proton efflux, lower membrane permeability, and lessened internal hydrogen peroxide content. The OLE1-mediated enhanced stress tolerance was considerably diminished upon deletion of HOG1, which encodes the mitogen-activated protein kinase (MAPK) Hog1 of the high osmolarity glycerol (HOG) pathway. Furthermore, OLE1 overexpression constitutively activated Hog1, which remained in the cytoplasm. Hog1 activation was accomplished through the MAPK kinase kinase (MAPKKK) Ssk2, but not Ste11 and Ssk22, the other MAPKKKs of the HOG pathway. Despite its cytoplasmic location, activated Hog1 was able to activate the expression of its canonical targets, including CTT1, HSP12, and STL1, and further, the cAMP and stress response elements present in the promoter. OLE1 overexpression neither caused nor relieved endoplasmic reticulum stress. Individually or in combination, the physiological and molecular changes caused by OLE1 overexpression may contribute to enhanced tolerance to various types of stress. Biotechnol. Bioeng. 2017;114: 620-631. © 2016 Wiley Periodicals, Inc.

Detection of Acyl-CoA Derivatized with Butylamide for in vitro Fatty Acid Desaturase Assay.

Membrane-bound fatty acid desaturases acting on acyl-CoA contribute to the biosynthesis of unsaturated fatty acids, such as arachidonic acid and docosahexaenoic acid in higher organisms. We propose a simplified method for measuring the desaturase activity that combines the in vitro reaction by desaturase-expressing yeast cell homogenate and the detection of acyl-CoA product as butylamide derivatives by gas chromatography. To set up the in vitro reaction, we traced the in vivo activity of rat liver ∆6 fatty acid desaturase (D6d) expressed in the yeast, Saccharomyces cerevisiae, and determined the time taken for the D6d activity to reach its maximum level. The cell homogenate of yeast expressing the maximum D6d activity was made to react in vitro with linoleoyl-CoA to generate the D6d product, γlinolenoyl-CoA. This product was successfully detected as a peak corresponding to γ-linolenoyl butylamide on gas chromatography. This procedure, with low background expression, using non-labeled acyl-CoA as substrate, will contribute toward developing a simple in vitro desaturase assay. It will also help in elucidating the functions of membrane-bound fatty acid desaturases with various substrate specificities and regioselectivities.

Distribution of cold adaptation proteins in microbial mats in Lake Joyce, Antarctica: Analysis of metagenomic data by using two bioinformatics tools.

In this study, we report the distribution and abundance of cold-adaptation proteins in microbial mat communities in the perennially ice-covered Lake Joyce, located in the McMurdo Dry Valleys, Antarctica. We have used MG-RAST and R code bioinformatics tools on Illumina HiSeq2000 shotgun metagenomic data and compared the filtering efficacy of these two methods on cold-adaptation proteins. Overall, the abundance of cold-shock DEAD-box protein A (CSDA), antifreeze proteins (AFPs), fatty acid desaturase (FAD), trehalose synthase (TS), and cold-shock family of proteins (CSPs) were present in all mat samples at high, moderate, or low levels, whereas the ice nucleation protein (INP) was present only in the ice and bulbous mat samples at insignificant levels. Considering the near homogeneous temperature profile of Lake Joyce (0.08-0.29 °C), the distribution and abundance of these proteins across various mat samples predictively correlated with known functional attributes necessary for microbial communities to thrive in this ecosystem. The comparison of the MG-RAST and the R code methods showed dissimilar occurrences of the cold-adaptation protein sequences, though with insignificant ANOSIM (R = 0.357; p-value = 0.012), ADONIS (R(2) = 0.274; p-value = 0.03) and STAMP (p-values = 0.521-0.984) statistical analyses. Furthermore, filtering targeted sequences using the R code accounted for taxonomic groups by avoiding sequence redundancies, whereas the MG-RAST provided total counts resulting in a higher sequence output. The results from this study revealed for the first time the distribution of cold-adaptation proteins in six different types of microbial mats in Lake Joyce, while suggesting a simpler and more manageable user-defined method of R code, as compared to a web-based MG-RAST pipeline.

Protein restriction in the rat negatively impacts long-chain polyunsaturated fatty acid composition and mammary gland development at the end of gestation.

BACKGROUND AND AIMS: Maternal nutrition during gestation is critical for mammary gland cell proliferation and differentiation and development of optimal delta-6 (Δ6D) and delta-5 (Δ5D) desaturase and elongase 2 and 5 (Elovl 2 and 5) activity for synthesis of the long chain polyunsaturated fatty acids (LC-PUFAs), arachidonic (AA), eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids, important for normal fetal and neonatal brain development. We hypothesized that maternal low protein diet (LPD) impairs mammary gland preparation for lactation and PUFA synthesis. The aim of the study was to evaluate consequences of maternal LPD on mammary gland structure and development and expression of enzymes responsible for LC-PUFA production. METHODS: Pregnant rats were assigned to control or protein restricted, isocaloric diet (R). At 19 days gestation, mammary gland tissue was removed for histological analysis and lipid, AA, EPA and DHA determination by gas chromatography. Gene transcription was quantified by RT-PCR and protein by Western blot. RESULTS: In R mothers, mammary gland lobuloalveolar development was decreased and showed fat cell infiltration. Δ6D, Δ5D, and Elovl 5 mRNA were lower in R, whereas protein levels measured by Western blot were unchanged. This is the first report that detects mammary gland desaturase and elongase protein. Although Elovl 2 mRNA was not detectable by RT-PCR, Elovl 2 protein was not different between groups. AA and DHA were lower and EPA undetectable in the mammary gland of R mothers. CONCLUSIONS: Maternal LPD decreased late gestation mammary gland lobuloalveolar development and LC-PUFAs. Protein restriction negatively impacts maternal mammary gland development prior to lactation.

Imaging heterogeneity of membrane and storage lipids in transgenic Camelina sativa seeds with altered fatty acid profiles.

Engineering compositional changes in oilseeds is typically accomplished by introducing new enzymatic step(s) and/or by blocking or enhancing an existing enzymatic step(s) in a seed-specific manner. However, in practice, the amounts of lipid species that accumulate in seeds are often different from what one would predict from enzyme expression levels, and these incongruences may be rooted in an incomplete understanding of the regulation of seed lipid metabolism at the cellular/tissue level. Here we show by mass spectrometry imaging approaches that triacylglycerols and their phospholipid precursors are distributed differently within cotyledons and the hypocotyl/radicle axis in embryos of the oilseed crop Camelina sativa, indicating tissue-specific heterogeneity in triacylglycerol metabolism. Phosphatidylcholines and triacylglycerols enriched in linoleic acid (C18:2) were preferentially localized to the axis tissues, whereas lipid classes enriched in gadoleic acid (C20:1) were preferentially localized to the cotyledons. Manipulation of seed lipid compositions by heterologous over-expression of an acyl-acyl carrier protein thioesterase, or by suppression of fatty acid desaturases and elongases, resulted in new overall seed storage lipid compositions with altered patterns of distribution of phospholipid and triacylglycerol in transgenic embryos. Our results reveal previously unknown differences in acyl lipid distribution in Camelina embryos, and suggest that this spatial heterogeneity may or may not be able to be changed effectively in transgenic seeds depending upon the targeted enzyme(s)/pathway(s). Further, these studies point to the importance of resolving the location of metabolites in addition to their quantities within plant tissues.

Effect of different levels of supplied cobalt on the fatty acid composition of bovine milk.

In previous studies, administration of high amounts of Co decreased the proportion of MUFA in bovine milk. The present study was conducted to examine the amount of Co needed to obtain this effect. High-yielding dairy cows (n 4), equipped with ruminal cannulas, were used in a 4 × 4 Latin square design study. The basal diet consisted of concentrate mixture (9 kg/d) without added Co and grass silage (ad libitum). The following four levels of Co were administrated as cobalt acetate dissolved in distilled water: no Co (treatment 1, T1); 4·0 mg Co/d (T2); 380 mg Co/d (T3); 5300 mg Co/d (T4). Each period lasted for 18 d, including 11 d of treatment. During the treatment periods, the solutions were continuously infused into the rumen. Milk yield and milk concentration of fat, fatty acids (FA), protein, lactose, Co, Zn, Fe and Cu were determined. Blood plasma was analysed with respect to FA, Co, Zn, Fe and Cu. Feed intake and total tract digestibility of feed components were also determined. There was a linear effect of increasing the level of Co on milk FA composition. The effects of Co on FA composition in blood were insignificant compared with the effects on milk. In milk fat, the concentration of cis-9-18 : 1 was reduced by as much as 38 % on T4 compared with T1. Feed intake and milk yield were negatively affected by increasing the Co level.

Chemical and physical characteristics of lamb meat related to crossbreeding of Romanov ewes with Suffolk and Charollais sires.

The aim was to evaluate the effects of crossbreeding Romanov (RO) ewes with Suffolk (SF) and Charollais (CH) sires on the chemicophysical characteristics and FA profile of the Quadriceps femoris muscle (QFM) in lambs fattened under organic conditions. The experimental animals were male lamb twins of two different crossbreds; CH 50 RO 50 and SF 50 RO 50. Lambs were slaughtered at an average live weight of 31kg. CH 50 RO 50 displayed higher contents of dry matter and intramuscular fat of the QFM. A lower pH value of CH 50 RO 50 was reflected in an increase of WHC. Meat of SF 50 RO 50 lambs had more lightness (L*) and yellowness (b*). The CH 50 RO 50 genotype showed a significantly higher proportion of C18:3n-3cis and n-3 PUFA than the SF 50 RO 50 genotype. The genotype also affected the Δ(9)-desaturase (16) index.

Redberry juniper as a roughage source in lamb feedlot rations: wool and carcass characteristics, meat fatty acid profiles, and sensory panel traits.

Effects of replacing cottonseed hulls with juniper leaves on end products were investigated in lambs. Lambs were individually fed diets containing cottonseed hulls (CSH), half of the CSH replaced by juniper (CSHJ), or all the CSH replaced by juniper (JUN). Lambs grew the same amount of wool when measured as greasy fleece (P>0.19), clean fleece (P>0.46), and clean wool production per unit of BW (P>0.54). Average fiber diameter quadratically decreased (P=0.04) and became more uniform (P<0.04) as percentage of juniper increased in the diet. Carcass characteristics were not affected (P>0.16) by diet. Myristic, palmitoleic, and arachidic acids, cis-9, trans-11 CLA, and the ∆9 desaturase index linearly increased (P<0.09) and stearic acid linearly decreased (P=0.05) as percentage of juniper increased in the diet. Off-flavor linearly increased (P=0.02) as juniper increased in the diet.

A real-time PCR genotyping assay to detect FAD2A SNPs in peanuts (Arachis hypogaea L)

The high oleic (C18:1) phenotype in peanuts has been previously demonstrated to result from a homozygous recessive genotype (ol1ol1ol2ol2) in two homeologous fatty acid desaturase genes (FAD2A and FAD2B) with two key SNPs. These mutant SNPs, specifically G448A in FAD2A and 442insA in FAD2B, significantly limit the normal function of the desaturase enzyme activity which converts oleic acid into linoleic acid by the addition of a second double bond in the hydrocarbon chain. Previously, a genotyping assay was developed to detect wild type and mutant alleles in FAD2B. A real-time PCR assay has now been developed to detect wild type and mutant alleles (G448A) in FAD2A using either seed or leaf tissue. This assay was demonstrated to be applicable for the detection of homozygous and heterozygous samples. The FAD2A genotyping assay was validated by employing gas chromatography (GC) to determine total fatty acid composition and by genotyping peanut lines that have been well characterized. Overall, development of rapid assays such as real-time PCR which can identify key genotypes associated with important agronomic traits such as oleic acid, will improve breeding efficiency by targeting desirable genotypes at early stages of development.

The fatty acid desaturase 3 gene encodes for different FADS3 protein isoforms in mammalian tissues.

In 2000, Marquardt et al. (A. Marquardt, H. Stöhr, K. White, and B. H. F. Weber. 2000. cDNA cloning, genomic structure, and chromosomal localization of three members of the human fatty acid desaturase family. Genomics. 66: 176-183.) described the genomic structure of the fatty acid desaturase (FADS) cluster in humans. This cluster includes the FADS1 and FADS2 genes encoding, respectively, for the Delta 5- and Delta 6-desaturases involved in polyunsaturated fatty acid biosynthesis. A third gene, named FADS3, has recently been identified but no functional role has yet been attributed to the putative FADS3 protein. In this study, we investigated the FADS3 occurrence in rat tissues by using two specific polyclonal antibodies directed against the N-terminal and C-terminal ends of rat FADS3. Our results showed three potential protein isoforms of FADS3 (75 kDa, 51 kDa, and 37 kDa) present in a tissue-dependent manner. The occurrence of these FADS3 isoforms did not depend on the mRNA level determined by real-time PCR. In parallel, mouse tissues were also tested and showed the same three FADS3 isoforms but with a different tissue distribution. Finally, we reported the existence of FADS3 in human cells and tissues but different new isoforms were identified. To conclude, we showed in this study that FADS3 does exist under multiple protein isoforms depending on the mammalian tissues. These results will help further investigations to determine the physiological function of FADS3.

Regulation of fatty acid synthesis and Delta9-desaturation in senescence of human fibroblasts.

AIMS: Normal human cells in culture progressively lose their capacity for replication, ending in an irreversible arrested state known as replicative senescence. Senescence has been functionally associated to the process of organismal ageing and is also considered a major tumor-suppressing mechanism. Although a great deal of knowledge has uncovered many of the molecular aspects of senescence, little is known about the regulation of lipid synthesis, particularly the biosynthesis and Delta9-desaturation of fatty acids, during the senescence process. MAIN METHODS: By using immunoblotting and metabolic radiolabeling, we determined the senescence-associated changes in major lipogenic pathways. KEY FINDINGS: The levels of fatty acid synthase and stearoyl-CoA desaturase-1 and, consequently, the formation of monounsaturated fatty acids, were notably decreased in senescent cells when compared to proliferating (young) fibroblasts. Moreover, we detected a reduction in the de novo synthesis of phospholipids with a concomitant increase in the formation of cholesterol in senescent cells compared to young fibroblasts. Finally, it was found that exogenous fatty acids were preferentially incorporated into the triacylglycerol pool of senescent cells. SIGNIFICANCE: This set of observations is the first demonstration of a profound modification in lipid metabolism, particularly fatty acid biosynthesis and desaturation, caused by the senescence process and contributes to the increasing body of evidence linking de novo lipogenesis with cellular proliferation.

Fatty acid composition in postmortem brains of people who completed suicide.

OBJECTIVE: Cholesterol levels have been reported to be lower in suicidal patients, and alterations in blood levels of polyunsaturated fatty acids have been found in people with depression. Given that the evidence for the link between lipid metabolism and psychopathology thus far has almost exclusively hinged on alterations of these variables in blood, this study aimed to address whether similar alterations in fatty acids would be evident in the brains of people who complete suicide. METHODS: Using gas chromatography, we measured 49 different fatty acids in the orbitofrontal cortex and the ventral prefrontal cortex of people who had completed suicide with (n = 16) and without (n = 23) major depression and in control subjects (n = 19) with no current psychopathology and whose cause of death was sudden. RESULTS: Comparisons of fatty acids between the 3 groups did not reveal significant differences. CONCLUSION: Further research is required to better understand the link between fatty acids in the peripheral circulation and those in the central nervous system before determining whether fatty acids play a mediating role in suicidal behaviour.

Methodology for the in vivo measurement of the delta9-desaturation of myristic, palmitic, and stearic acids in lactating dairy cattle.

There is limited methodology available to quantitatively assess the activity of the Delta9-desaturase enzyme in vivo without chemically inhibiting the enzyme or using radioactively labeled substrates. The objective of these experiments was to develop methodology to determine the incorporation and desaturation of 13C-labeled fatty acids into milk lipids. In a preliminary experiment, 3.7 g [1-13C]myristic acid ([1-13C]14:0), 19.5 g [1-13C]palmitic acid ([1-13C]16:0), 20.0 g [1-13C]stearic acid ([1-13C]18:0) were combined and infused into the duodenum of a cow over 24 h. In a following experiment, 5.0 g [1-13C]14:0, 40.0 g [1-13C]16:0, and 50.0 g [1-13C]18:0 were infused into the abomasums of separate cows as a bolus over 20 min or continuously over 24 h. Milk fat was extracted using chloroform:methanol. Fatty acids were methylated, and fatty acid methyl esters (FAME) were converted to dimethyl disulfide derivatives (DMDS). The FAME and DMDS were analyzed by gas chromatography mass spectrometry. In the preliminary experiment, 13C enrichment in 14:0 but not 16:0 or 18:0 was observed. When dosage amounts were increased in the following experiment, peak enrichments from the bolus infusion were observed at 8 h. Enrichments for continuous infusion peaked at 16 h for 14:0 and 18:0, and at 24 h for 16:0. The Delta9-desaturase products of these fatty acids were estimated to be 90% of cis-9 14:1, 50% of cis-9 16:1, and 59% of cis-9 18:1. This study demonstrates that 13C-labeled fatty acids may be utilized in vivo to measure the activity of the Delta9-desaturase enzyme.

Biochemical characterization of enoyl reductase involved in Type II fatty acid synthesis in the intestinal coccidium Eimeria tenella (Phylum Apicomplexa).

An enoyl reductase (EtENR) closely related to those of green algae and involved in Type II fatty acid synthesis was characterized and localized to the apicoplast in the coccidium Eimeria tenella. Biochemical analysis using native EtENR protein extracted from parasites confirmed its function as an enoyl reductase using NADH as a cofactor. However, the recombinant form (rEtENR) expressed in bacteria was only able to oxidize NADH, but unable to transfer the electron to enoyl-CoA, possibly due to the inappropriate folding of rEtENR expressed in bacteria. The functions of both native and recombinant EtENR could be inhibited by triclosan (IC(50)=1.45 microM), suggesting that this enzyme may be explored as a drug target against coccidiosis.

Effects of varying doses of supplemental conjugated linoleic acid on production and energetic variables during the transition period.

Supplementing a high dose of dietary conjugated linoleic acid (CLA) inhibits milk fat synthesis in dairy cows immediately postpartum. During negative net energy balance (EBAL), it appears that moderate CLA-induced milk fat depression causes a positive response in milk yield; however, as milk fat depression becomes more severe, the milk yield response diminishes. Multiparous Holstein cows (n = 31) were randomly assigned to 1 of 3 treatments beginning 9 +/- 6 d before expected calving and ceased at 40 d in milk (DIM): 1) 578 g/d of a rumen-inert (RI) palm fatty acid distillate (control), 2) 600 g/d of RI-CLA for the entire trial period (CLA-1), and 3) 600 g/d of RI-CLA until 10 DIM followed by 200 g/d for the remainder of the trial (CLA-2). Each dose provided equal amounts of fatty acids by replacing and balancing each treatment with a RI palm fatty acid distillate. Doses provided a total of 522 g of fatty acids/ d and 0, 174, or 58 (depending upon DIM) g of CLA (mixed isomers)/d. To improve palatability, doses were mixed with 600 g/d of dried molasses; one-half of the supplement was fed at 0800 h, and the remainder at 1900 h. Individual milk yield, dry matter intake, and body weight were recorded daily and milk composition determined every other day. There was no overall CLA effect on either the content or yield of milk protein or lactose. Both CLA treatments decreased overall milk fat content (26.0 and 18.3%) and yield (22.5 and 17.3%) with CLA-induced milk fat depression becoming significant by d 8. The CLA-induced milk fat depression increased in magnitude with progressing DIM until reaching a plateau on d 18 for CLA-1 (43%) and on d 14 for CLA-2 (33%), although neither milk fat trans-10, cis-12 CLA content (1.8 mg/g) nor its transfer efficiency (6.3%) changed over time. Treatments had no effect on overall dry matter intake or milk yield, but there was a treatment x time interaction for milk production, as cows fed either CLA treatment had increased milk yield after the second week of lactation. Cows fed either CLA treatment had a significant improvement in overall EBAL (-5.1 vs. -1.8 Mcal/d), a decrease in nonesterified fatty acid levels (12%), and an increase in glucose levels (11%). A dietary supplement containing trans-10, cis-12 CLA markedly improves EBAL and bioenergetic variables and increases milk yield in the total mixed ration-fed transitioning dairy cow.

Influence of grass-based diets on milk fatty acid composition and milk lipolytic system in Tarentaise and Montbeliarde cow breeds.

Two experiments were conducted to evaluate the effects of nature of forage on fatty acid composition and lipolytic system in cow milk to increase the nutritional quality of dairy products. Each experiment was divided into a 4-wk preexperimental and 6- or 8-wk experimental period. During the 2 preexperimental periods, 56 midlactating Montbéliarde or Tarentaise cows received a diet based on corn silage. Subsequently, in Experiment 1,40 cows were allocated into 5 groups (4 Montbéliarde and 4 Tarentaise cows per group) and assigned to dietary treatments: corn silage (87% of dry matter intake), grass silage (86%), ryegrass hay (90%), mountain natural grassland hay (87%), or a diet rich in concentrate (CONC, 65/35% concentrate/hay). In Experiment 2, 16 cows divided into 2 groups were fed during 3 or 6 wk mountain natural pasture (100%) or mountain natural grassland hay (87%). Principal component analysis was applied to describe the relationships among dairy performances, milk fatty acids (FA), and lipolytic system. The milk 18:0, cis-9-18:1, trans-11-18:1, and cis-9, trans-11-18:2 percentages were closely associated with 3-wk mountain natural pasture diet, whereas short- and medium-chain (mostly saturated) FA were associated with the CONC diet. Tarentaise milk fat contained a lower proportion (-3 to 4 g/100 g) of 16:0 and higher proportions of stearic acid and fewer markedly polyunsaturated FA than Montbéliarde milk fat. Milk lipolysis was lowest for CONC and corn silage groups. Milk from Tarentaise cows presented lower initial free FA and postmilking lipolysis. Diets given to cows, especially young grass, modified the milk content of FA with a putative nutritional effect on human health.

Identification of mutation sites on delta5 desaturase genes from Mortierella alpina 1S-4 mutants.

The mutation sites on delta5 desaturase genes in delta5 desaturase-defective mutants derived from arachidonic acid-producing Mortierella alpina 1S-4 were identified. The mutations resulted in an amino acid replacement (G189E or W301Stop) and uncorrected transcription caused by recognition of an AG-terminal newly created on C207A gene mutation, resulting in low or no delta5 desaturase activity in these mutants.