Fatty Acid Precursors Research Articles

Microbial Communities and Associated Enzyme Activities in Alpine Wetlands with Increasing Altitude on the Tibetan Plateau

Microbial communities, enzyme activities and soil physiochemical characteristics were investigated in alpine wetlands with altitude changes in the Nyainqentanglha Mountains on the Tibetan plateau. The results showed that with an increasing altitude gradient, soil physicochemical properties such as total organic carbon (TOC), total nitrogen (TN), water-soluble organic carbon (WSOC), water-soluble organic nitrogen (WSON) and pH decreased coincident with a decrease in mean annual temperature (MAT). Bacteria biomass, fungal biomass and actinobacterial biomass all decreased with an increase in altitude gradient. The ratio of Gram-positive bacteria to Gram-negative bacteria and the ratio of cyclopropyl to precursor fatty acids all indicate that the level of environmental harshness intensified with an increase in altitude. We also found that soil enzyme activities such as phenol oxidase, peroxidase, L-asparaginase, protease, urease and alkaline phosphatase all consistently decreased with an increase in altitude gradient. Additionally, the activities of peroxidase, protease and alkaline phosphatase declined, mainly due to a reduction in enzyme activities with temperature rather than the reduction of associated microbial biomass. Statistical analysis showed that both microbial biomass and enzyme activities were significantly influenced by mean annual temperature, suggesting that temperature is a key factor that affects microbial communities and soil enzyme activities in alpine wetlands on the Tibetan Plateau and indicating that climate warming may significantly impact these areas.

Milk fatty acid and protein profiles of late-lactation dairy cows as affected by time of allocation of a fresh strip of ryegrass-based pasture

Abstract Eighty late-lactation dairy cows were used to examine the effects of allocating a new strip of a perennial ryegrass-based sward in the morning (AM) or in the afternoon (PM) on milk fatty acid (FA) and protein profiles. Milk total polyunsaturated FA (PUFA) were greater from cows on AM herbage, whereas total saturated and monounsaturated FA (MUFA) were similar. Time of allocation only affected the milk protein α-casein, which was greater in milk from cows on PM herbage, in turn affecting the casein:whey ratio. Under the current conditions, timing of allocation altered the herbage nutrient supply to cows; a greater concentration of precursor FA in AM herbage resulted in a greater concentration of beneficial FA in milk compared with cows on PM herbage. Quantifying the composition of FA in herbage could potentially aid in the design of grazing strategies to increase precursors of beneficial FA in dairy products. Keywords: fatty acids, milk proteins, herbage composition, time of allocation

Calcium treatments promote the aroma volatiles emission of pear (Pyrus ussuriensis ‘Nanguoli’) fruit during post-harvest ripening process

Aroma is an important factor affecting pear fruit quality. This study was undertaken to assess whether pre-harvest calcium sprays (15 d before harvest, applications at 4%, w/v, 120 d after full bloom) could improve aroma of Pyrus ussuriensis ‘Nanguoli’ pear fruit at harvest and post-harvest, and analyse the mechanism of metabolic regulation.Most compounds contributing to overall flavor in ripe ‘Nanguoli’ fruit at harvest and post-harvest were enhanced in response to pre-harvest calcium applications. Ester, especially acetyl ester, content was enhanced by calcium treatment; however, contents of alcohols, aldehydes and hydrocarbons were little affected. These effects were consistent with higher pyruvate decarboxylase and alcohol dehydrogenase activities in treated fruit, suggesting that calcium treatment increased supply of alcohols and acyl CoAs for ester biosynthesis. We also found that activities of β-glucosidases (involved in the emission of bound volatile compounds) were improved and the contents of bound volatiles were reduced by calcium treatment. At the same time, relative contents of linoleic and linolenic acids were improved by calcium treatment, expression of genes encoding fatty acid desaturase involved in the biosynthesis of unsaturated fatty acid precursors (linoleic and linolenic acids) for volatile aroma were improved. Calcium treatment increased content of volatile aromatic substances, both because calcium promoted the decomposition of bound aroma substances to free aromatic forms, and also promoted the synthesis of volatile aromatic substances in pear fruit.

Effects of arachidonic acid supplementation in maturation diet on female reproductive performance and larval quality of giant river prawn (Macrobrachium rosenbergii).

The giant river prawn (Macrobrachium rosenbergii) is one of the most farmed freshwater crustaceans in the world. Its global production has been stalling in the past decade due to the inconsistent quality of broodstock and hatchery-produced seeds. A better understanding of the role of nutrition in maturation diets will help overcome some of the production challenges. Arachidonic acid (20:4 n-6, ARA) is a fatty acid precursor of signaling molecules important for crustacean reproduction, prostaglandins E and F of the series II (PGE2 and PGF2α), and is often lacking in maturation diets of shrimp and prawns. We examined the effects of ARA in a combination of different fish oil (FO) and soybean oil (SO) blends on females’ reproductive performance and larval quality. Adult females (15.22 ± 0.13 g and 11.12 ± 0.09 cm) were fed six isonitrogenous and isolipidic diets containing one of two different base compositions (A or B), supplemented with one of three levels of Mortierella alpine-derived ARA (containing 40% active ARA): 0, 1 or 2% by ingredient weight. The two base diets differed in the percentages of (FO and SO with diet A containing 2% SO and 2% FO and diet B containing 2.5% SO and 1.5% FO, resulting in differences in proportional contents of dietary linoleic acid (18:2n-6, LOA) and docosahexaenoic acid (22:6n-3, DHA)). After the eight-week experiment, prawns fed diet B with 1 and 2% ARA supplement (B1 and B2) exhibited the highest gonadosomatic index (GSI), hepatosomatic index (HSI), egg clutch weight, fecundity, hatching rate, number of larvae, and reproductive effort compared to those fed other diets (p ≤ 0.05). Larvae from these two dietary treatments also had higher tolerance to low salinity (2 ppt). The maturation period was not significantly different among most treatments (p ≥ 0.05). ARA supplementation, regardless of the base diet, significantly improved GSI, HSI, egg clutch weight and fecundity. However, the diets with an enhanced ARA and LOA (B1 and B2) resulted in the best reproductive performance, egg hatchability and larval tolerance to low salinity. These dietary treatments also allow for effective accumulation of ARA and an n-3 lcPUFA, DHA in eggs and larvae.

Biochemical precursor effects on the fatty acid production in cell suspension cultures of Theobroma cacao L.

Cocoa butter (CB) is composed of 96% palmitic, stearic, oleic, linoleic and linolenic fatty acids that are responsible for the hardness, texture and fusion properties of chocolate. Through in vitro plant cell culture it is possible to modify CB lipid profiles and to study the fatty acid biosynthesis pathway on a subcellular level, evaluating fundamental aspects to enhance in vitro fatty acid production in a specific and controlled way. In this research, culture media was supplemented with acetate, biotin, pyruvate, bicarbonate and glycerol at three different concentrations and the effects on the biomass production (g/L), cell viability, and fatty acids profile and production was evaluated in in vitro cell suspensions culture. It was found that biotin stimulated fatty acid synthesis without altering cell viability and cell growth. It was also evident a change in the lipid profile of cell suspensions, increasing middle and long chain fatty acids proportion, which are unusual to those reported in seeds; thus implying that it is possible to modify lipid profiles according to the treatment used. According to the results of sucrose gradients and enzyme assays performed, it is proposed that cacao cells probably use the pentose phosphate pathway, mitochondria being the key organelle in the carbon flux for the synthesis of reductant power and fatty acid precursors.

A fast and direct liquid chromatography‐mass spectrometry method to detect and quantify polyunsaturated aldehydes and polar oxylipins in diatoms

AbstractPolyunsaturated aldehydes (PUAs) are a group of microalgal metabolites that have attracted a lot of attention due to their biological activity. Determination of PUAs has become an important routine procedure in plankton and biofilm investigations, especially those that deal with chemically mediated interactions. Here we introduce a fast and direct derivatization free method that allows quantifying PUAs in the nanomolar range, sufficient to undertake the analysis from cultures and field samples. The sample preparation requires one simple filtration step and the initiation of PUA formation by cell disruption. After centrifugation the samples are ready for measurement without any further handling. Within one chromatographic run this method additionally allows us to monitor the formation of the polar oxylipins arising from the cleavage of precursor fatty acids. The robust method is based on analyte separation and detection using ultra high performance liquid chromatography‐atmospheric pressure chemical ionization mass spectrometry (UHPLC‐APCI MS) and enables high throughput investigations by employing an analysis time of only 5 min. Our protocol thus provides an alternative and extension to existing PUA determinations based on gas chromatography‐mass spectrometry (GC‐MS) with shorter run times and without any chemical derivatization. It also enables researchers with widely available LC‐MS analytical platforms to monitor PUAs. Additionally, non‐volatile oxylipins such as ω‐oxo‐acids and related compounds can be elucidated and monitored.

Effect of a 2-y dietary and physical activity intervention on plasma fatty acid composition and estimated desaturase and elongase activities in children: the Physical Activity and Nutrition in Children Study

Background: Evidence on the effects of lifestyle interventions on plasma fatty acid composition in children is limited.Objective: We investigated the effects of a dietary and physical activity intervention on plasma fatty acid composition of cholesteryl esters (CEs) and phospholipids and estimated desaturase and elongase activities in children.Design: We conducted a 2-y controlled dietary and physical activity intervention based on Finnish nutrition and physical activity recommendations in a population sample of 506 children aged 6–8 y. We assessed plasma fatty acid composition by gas chromatography and estimated desaturase and elongase activities as the ratio of product fatty acids to precursor fatty acids. We analyzed data by using linear mixed models adjusted for age and sex.Results: The proportion of total polyunsaturated fatty acids (PUFAs) in CEs tended to increase in the intervention group compared with the control group (P = 0.007 for group × time interaction). The proportion of total PUFAs in phospholipids (P = 0.019 for group × time interaction) and the proportion of linoleic acid in CEs (P = 0.038 for group × time interaction) decreased in the control group. The proportion of α-linolenic acid in CEs (P < 0.001 for group × time interaction) increased and in phospholipids (P = 0.015 for group × time interaction) tended to increase in the intervention group. The proportion of stearic acid in CEs decreased in the intervention group (P = 0.001 for group × time interaction). The proportion of oleic acid in CEs (P = 0.002 for group × time interaction) increased and in phospholipids (P = 0.023 for group × time interaction) tended to increase in the control group. Estimated elongase activity in CEs decreased in the control group (P = 0.050 for group × time interaction). Intervention had no effect on estimated desaturase activities.Conclusions: Dietary and physical activity intervention had a beneficial effect on plasma fatty acid composition in children by preventing the decrease in the proportion of total PUFAs and linoleic acid and by increasing the proportion of α-linolenic acid. This study was registered at clinicaltrials.gov as NCT01803776.

The role of two branched-chain amino acid transporters in Staphylococcus aureus growth, membrane fatty acid composition and virulence.

The branched-chain amino acids (BCAAs) are vital to both growth and virulence of the human pathogen Staphylococcus aureus. In addition to supporting protein synthesis, the BCAAs serve as precursors for branched-chain fatty acids (BCFAs), which are predominant membrane fatty acids, and, in association with the global regulatory protein CodY, the BCAAs are key co-regulators of virulence factors. Despite these critical functions, S. aureus represses Leu and Val synthesis, instead preferring to acquire them from the extracellular milieu. We previously identified BrnQ1 as a BCAA transporter, yet a brnQ1 mutant remained capable of BCAA acquisition. Here, we describe BcaP as an additional BCAA transporter, and determine that it plays a secondary role to BrnQ1 during S. aureus growth in a chemically defined medium. Furthermore, membrane fatty acid composition analysis revealed that BrnQ1, and not BcaP, is required for transporting Leu and Val to be used for iso-BCFA synthesis. Despite a predominant role for BrnQ1 in vitro, both BrnQ1 and BcaP are required for S. aureus fitness in vivo in a hematogenous spread infection model and a nasal colonisation model. These data demonstrate the importance of BrnQ1 and BcaP for growth, environmental adaptation and virulence of S. aureus.

Systemic availability and metabolism of colonic-derived short-chain fatty acids in healthy subjects: a stable isotope study.

The short-chain fatty acids (SCFAs) are bacterial metabolites produced during the colonic fermentation of undigested carbohydrates, such as dietary fibre and prebiotics, and can mediate the interaction between the diet, the microbiota and the host. We quantified the fraction of colonic administered SCFAs that could be recovered in the systemic circulation, the fraction that was excreted via the breath and urine, and the fraction that was used as a precursor for glucose, cholesterol and fatty acids. This information is essential for understanding the molecular mechanisms by which SCFAs beneficially affect physiological functions such as glucose and lipid metabolism and immune function. The short-chain fatty acids (SCFAs), acetate, propionate and butyrate, are bacterial metabolites that mediate the interaction between the diet, the microbiota and the host. In the present study, the systemic availability of SCFAs and their incorporation into biologically relevant molecules was quantified. Known amounts of 13 C-labelled acetate, propionate and butyrate were introduced in the colon of 12 healthy subjects using colon delivery capsules and plasma levels of 13 C-SCFAs 13 C-glucose, 13 C-cholesterol and 13 C-fatty acids were measured. The butyrate-producing capacity of the intestinal microbiota was also quantified. Systemic availability of colonic-administered acetate, propionate and butyrate was 36%, 9% and 2%, respectively. Conversion of acetate into butyrate (24%) was the most prevalent interconversion by the colonic microbiota and was not related to the butyrate-producing capacity in the faecal samples. Less than 1% of administered acetate was incorporated into cholesterol and <15% in fatty acids. On average, 6% of colonic propionate was incorporated into glucose. The SCFAs were mainly excreted via the lungs after oxidation to 13 CO2 , whereas less than 0.05% of the SCFAs were excreted into urine. These results will allow future evaluation and quantification of SCFA production from 13 C-labelled fibres in the human colon by measurement of 13 C-labelled SCFA concentrations in blood.

Absolute Configuration and Body Part Distribution of the Alkaloid 6-epi-Monanchorin from the Marine Polychaete Chaetopterus variopedatus

As a result of the first study on secondary metabolites from the cosmopolitan bioluminescent marine tube polychaete Chaetopterus variopedatus, a new bicyclic guanidine alkaloid, 6-epi-monanchorin (1), along with the previously known monanchorin (2) were isolated. The structure of 1 was elucidated by spectroscopic and chemical methods, including a cleavage of the C₁-0₇ bond to obtain a secondary alcohol (3), which was used to determine the absolute configurations by Mosher's method. It was found that 1 and 2 were mainly accumulated in a secreted mucus special organ of the worm (food net), where green and blue-green microalgae were detected. A biosynthetic pathway to 6-epi-monanchorin and monanchorin from dietary polyeic fatty acid precursors was proposed.

One-night sleep deprivation induces changes in the DNA methylation and serum activity indices of stearoyl-CoA desaturase in young healthy men.

BackgroundSleep deprivation has been associated with obesity among adults, and accumulating data suggests that stearoyl-CoA desaturase 1 (SCD1) expression has a relevant impact on fatty acid (FA) composition of lipid pools and obesity. The aim of this study was to investigate the effect of one-night total sleep deprivation (TSD) on DNA methylation in the 5’-prime region of SCD1, and whether detected changes in DNA methylation are associated with SCD activity indices (product to precursor FA ratios; 16:1n-7/16:0 and 18:1n-9/18:0) derived from serum phospholipids (PL).MethodsSixteen young, normal-weight, healthy men completed two study sessions, one with one-night TSD and one with one-night normal sleep (NS). Sleep quality and length was assessed by polysomnography, and consisted of electroencephalography, electrooculography, and electromyography. Fasting whole blood samples were collected on the subsequent morning for analysis of DNA methylation and FAs in serum PL. Linear regression analyses were performed to assess the association between changes in DNA methylation and SCD activity indices.ResultsThree CpG sites close to the transcription start site (TSS) of SCD1 (cg00954566, cg24503796, cg14089512) were significantly differentially methylated in dependency of sleep duration (−log10P-value > 1.3). Both SCD-16 and SCD-18 activity indices were significantly elevated (P < 0.05) following one-night TSD, and significantly associated with DNA methylation changes of the three mentioned probes in the 5’ region of SCD1.ConclusionOur results suggest a relevant link between TSD, hepatic SCD1 expression and de-novo fatty acid synthesis via epigenetically driven regulatory mechanisms.

Abstract 1043: Targeting ASCT2-mediated glutamine uptake and metabolism in breast cancer

Abstract Although a nonessential amino acid in normal cell growth, the demand for glutamine is dramatically increased throughout malignant transformation to provide catabolic substrates for ATP production and anabolic substrates for macromolecule biosynthesis. To maintain glutamine availability for these metabolic processes, cancer cells overexpress cell surface transporters that function to exchange amino acids across the plasma membrane. One such transporter is ASCT2 (alanine, serine, cysteine-preferring transporter 2; SLC1A5), a sodium-dependent symporter that mediates uptake of small, neutral amino acids, including glutamine. Blocking ASCT2 to prevent glutamine uptake and glutaminolysis has been shown to successfully prevent tumor cell proliferation in melanoma, non-small cell lung cancer, prostate cancer and acute myeloid leukaemia. We recently showed that in breast cancer, although ASCT2 is highly expressed in most tumor subtypes, only aggressive triple-negative (TN) breast cancer cells require ASCT2-mediated uptake of glutamine to sustain cell growth in vitro and in vivo. Gene expression analysis of xenograft-derived tumor tissue and TN patient samples suggested coordinate regulation of ASCT2 and other glutamine metabolism-related genes, such as glutaminase (GLS) and glutamate-ammonia ligase (GLUL), with global activation of glutaminolytic energy production pathways in these tumors. The metabolism-regulating transcription factors, MYC and ATF4, were significantly correlated with these genes, suggesting a dynamic MYC and ATF4-driven transcriptional program in TN breast cancer. We therefore hypothesized that highly proliferative TN breast cancers that are sensitive to ASCT2 inhibition may have unique metabolic signatures that could be additionally exploited for therapeutic purposes. We developed a targeted metabolomics approach that combined labelled substrate tracing, liquid chromatography coupled tandem-mass spectrometry (LC-MS/MS) and gas chromatography mass spectrometry (GC-MS) to analyze intracellular levels of key tricarboxylic acid (TCA) cycle intermediates, glycolytic metabolites, fatty acid precursors, and amino acids in human breast cancer cell lines. These analyses revealed distinct metabolic effects when ASCT2 transporter function was blocked in vitro by pharmacological inhibitors or inducible shRNA knockdown, in combination with CB-839, a GLS inhibitor in Phase I clinical trials. To confirm the clinical utility of these findings, we also determined mRNA and protein expression of glutamine metabolism-related genes in tissue microarrays of TN patient samples. These data suggest a reliance on glutamine availability in TN breast cancers and reinforce the link between increased glutamine metabolism and clinically aggressive breast cancers, thus highlighting the therapeutic potential of targeting the ASCT2 glutamine uptake and metabolism pathway in these patients. Citation Format: Michelle van Geldermalsen, Qian Wang, Jeff Holst. Targeting ASCT2-mediated glutamine uptake and metabolism in breast cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1043.

Regulatory divergence of homeologous Atlantic salmon elovl5 genes following the salmonid-specific whole-genome duplication

Fatty acyl elongase 5 (elovl5) is a critical enzyme in the vertebrate biosynthetic pathway which produces the physiologically essential long-chain polyunsaturated fatty acids (LC-PUFA), docosahexenoic acid (DHA), and eicosapentenoic acid (EPA) from 18 carbon fatty acids precursors. In contrast to most other vertebrates, Atlantic salmon possess two copies of elovl5 (elovl5a and elovl5b) as a result of a whole-genome duplication (WGD) which occurred at the base of the salmonid lineage. WGDs have had a major influence on vertebrate evolution, providing extra genetic material, enabling neofunctionalization to accelerate adaptation and speciation. However, little is known about the mechanisms by which such duplicated homeologous genes diverge. Here we show that homeologous Atlantic salmon elovl5a and elovl5b genes have been asymmetrically colonised by transposon-like elements. Identical locations and identities of insertions are also present in the rainbow trout duplicate elovl5 genes, but not in the nearest extant representative preduplicated teleost, the northern pike. Both elovl5 salmon duplicates possessed conserved regulatory elements that promoted Srebp1- and Srebp2-dependent transcription, and differences in the magnitude of Srebp response between promoters could be attributed to a tandem duplication of SRE and NF-Y cofactor binding sites in elovl5b. Furthermore, an insertion in the promoter region of elovl5a confers responsiveness to Lxr/Rxr transcriptional activation. Our results indicate that most, but not all, transposon mobilisation into elovl5 genes occurred after the split from the common ancestor of pike and salmon, but before more recent salmonid speciations, and that divergence of elovl5 regulatory regions have enabled neofuntionalization by promoting differential expression of these homeologous genes.

Broad substrate specificity of phosphotransbutyrylase from Listeria monocytogenes: A potential participant in an alternative pathway for provision of acyl CoA precursors for fatty acid biosynthesis

Listeria monocytogenes, the causative organism of the serious food-borne disease listeriosis, has a membrane abundant in branched-chain fatty acids (BCFAs). BCFAs are normally biosynthesized from branched-chain amino acids via the activity of branched chain α-keto acid dehydrogenase (Bkd), and disruption of this pathway results in reduced BCFA content in the membrane. Short branched-chain carboxylic acids (BCCAs) added as media supplements result in incorporation of BCFAs arising from the supplemented BCCAs in the membrane of L. monocytogenes bkd mutant MOR401. High concentrations of the supplements also effect similar changes in the membrane of the wild type organism with intact bkd. Such carboxylic acids clearly act as fatty acid precursors, and there must be an alternative pathway resulting in the formation of their CoA thioester derivatives. Candidates for this are the enzymes phosphotransbutyrylase (Ptb) and butyrate kinase (Buk), the products of the first two genes of the bkd operon. Ptb from L. monocytogenes exhibited broad substrate specificity, a strong preference for branched-chain substrates, a lack of activity with acetyl CoA and hexanoyl CoA, and strict chain length preference (C3–C5). Ptb catalysis involved ternary complex formation. Additionally, Ptb could utilize unnatural branched-chain substrates such as 2-ethylbutyryl CoA, albeit with lower efficiency, consistent with a potential involvement of this enzyme in the conversion of the carboxylic acid additives into CoA primers for BCFA biosynthesis.

Alternative splicing generates novel Fads3 transcript in mice.

Fads3 is the third member of the fatty acid desaturase gene cluster; with at least eight evolutionarily conserved alternative transcripts (AT), having no clearly established function as are known for FADS2 and FADS1. Here we present identification of a novel Fads3 transcript in mice (Fads3AT9), characterize Fads3AT9 expression in mouse tissues and evaluate correlations with metabolite profiles. Total RNA obtained from mouse tissues is reverse-transcribed into cDNA and used as template for PCR reactions. Tissue fatty acids were extracted and quantified by gas chromatography. Sequencing analysis revealed complete absence of exon 2 resulting in an open reading frame of 1239bp, encoding a putative protein of 412 aa with loss of 37 aa compared to classical Fads3 (Fads3CS). FADS3AT9 retains all the conserved regions characteristic of front end desaturase (cytochrome b5 domain and three histidine repeats). Both Fads3CS and Fads3AT9 are ubiquitously expressed in 11 mouse tissues. Fads3AT9 abundance was greater than Fads3CS in pancreas, liver, spleen, brown adipose tissue and thymus. Fads3CS expression is low in pancreas while Fads3AT9 is over ten-fold greater abundance. The eicosanoid precursor fatty acid 20:4n-6, the immediate desaturation product of the Fads1 coded Δ5-desaturase, was highest in pancreas where Fads3CS is low. Changes in expression patterns and fatty acid profiles suggest that Fads3AT9 may play a role in the regulation and/or biosynthesis of long chain polyunsaturated fatty acids from precursors.

Amino Acid Change in an Orchid Desaturase Enables Mimicry of the Pollinator’s Sex Pheromone

Mimicry illustrates the power of selection to produce phenotypic convergence in biology [1]. Astriking example is the imitation of female insectsby plants that are pollinated by sexual deception of males of the same insect species [2-4]. This involves mimicry of visual, tactile, andchemical signals of females [2-7], especially their sex pheromones [8-11]. The Mediterranean orchid Ophrys exaltata employs chemical mimicry of cuticular hydrocarbons, particularly the 7-alkenes, in an insect sex pheromone to attract andelicit mating behavior in its pollinators, males of the cellophane bee Colletes cunicularius [11-13]. A difference in alkene double-bond positions is responsible for reproductive isolation between O.exaltata and closely related species, such as O.sphegodes [13-16]. We show that these7-alkenes are likely determined by the action of the stearoyl-acyl-carrier-protein desaturase (SAD) homolog SAD5. After gene duplication, changes in subcellular localization relative to the ancestral housekeeping desaturase may have allowed proto-SAD5's reaction products to undergo further biosynthesis to both 7- and 9-alkenes. Such ancestral coproduction of two alkene classes may have led to pollinator-mediated deleterious pleiotropy. Despite possible evolutionary intermediates with reduced activity, amino acid changes at the bottom of the substrate-binding cavity have conferred enzyme specificity for 7-alkene biosynthesis by preventingthe binding of longer-chained fatty acid (FA) precursors by the enzyme. This change in desaturase function enabled theorchid to perfect its chemical mimicry of pollinator sex pheromones by escape from deleterious pleiotropy, supporting a role of pleiotropy in determining the possible trajectories of adaptive evolution.

Squalene modulates fatty acid metabolism: Enhanced EPA/DHA in obese/diabetic mice (KK‐Ay) model

Biosynthesis of long‐chain n‐3 fatty acids from precursors is limited. In vivo effect of squalene (SQ) on the metabolic fate of n‐3 fatty acid precursors in obese/diabetic KK‐Ay rodent model was evaluated in our work. Soybean oil, being rich in ALA (18:3 n‐3; a known precursor of EPA/DHA), was chosen as the n‐3 fatty acid precursor rich source. A high‐fat diet (20%) containing 7% soybean oil (SO) was fed to obesity/diabetes‐prone male KK‐Ay mice (control). In the case of diets fed to test groups, soybean oil was replaced with 5% SO and 2% SQ. Hepatic DHA levels increased (four fold) in SQ fed group over control (p &lt; 0.05). Gene and protein expressions of Δ5 and Δ6 desaturases, key enzymes involved in the fatty acid metabolism, further supported the results. Also, SQ exhibited a hypotriglyceridemic and hypoglycemic effect. The results clearly indicated the effect of SQ in modulating the n‐3 fatty acid metabolism, including EPA/DHA synthesis in the presence of n‐3 fatty acid precursor. This is the first report of enhancement of in vivo DHA/EPA by SQ and in turn, modulating the physiological fatty acid profile.Practical applications: Squalene (SQ) is an important marine biofunctional material that is found in some terrestrial sources as well. Squalene, being a cholesterol precursor, forms an interesting subject of research for its effect in vivo. SQ significantly enhanced proportions of EPA and/or DHA when their n‐3 fatty acid precursors were available in the diet. The study further establishes the usefulness of SQ in functional food formulations. The work provides an important basis for further evaluation of the role of SQ in normal and disease conditions.KK‐Ay mice were fed high fat/sucrose diet to induce obesity/diabetes. Fat source in control diet was lard and soybean oil while experimental group diet contained 2% squalene + 13% lard + 5% soybean oil. Feeding squalene for 4 weeks modulated fatty acid metabolism with increased docosahexaenoic acid (DHA) and decrease in triglycerides (TG), compared to control. The enhanced DHA in the fatty acid profile was supported by upregulated mRNA expression of Δ5‐desaturase enzyme and protein expression of Δ5 and Δ6 desaturases (FADS1 and FADS2). Additionally, squalene had a hypoglycemic effect in the mice.

Kinetics of Forming Aldehydes in Frying Oils and Their Distribution in French Fries Revealed by LC-MS-Based Chemometrics.

In this study, the kinetics of aldehyde formation in heated frying oils was characterized by 2-hydrazinoquinoline derivatization, liquid chromatography-mass spectrometry (LC-MS) analysis, principal component analysis (PCA), and hierarchical cluster analysis (HCA). The aldehydes contributing to time-dependent separation of heated soybean oil (HSO) in a PCA model were grouped by the HCA into three clusters (A1, A2, and B) on the basis of their kinetics and fatty acid precursors. The increases of 4-hydroxynonenal (4-HNE) and the A2-to-B ratio in HSO were well-correlated with the duration of thermal stress. Chemometric and quantitative analysis of three frying oils (soybean, corn, and canola oils) and French fry extracts further supported the associations between aldehyde profiles and fatty acid precursors and also revealed that the concentrations of pentanal, hexanal, acrolein, and the A2-to-B ratio in French fry extracts were more comparable to their values in the frying oils than other unsaturated aldehydes. All of these results suggest the roles of specific aldehydes or aldehyde clusters as novel markers of the lipid oxidation status for frying oils or fried foods.

The Entner-Doudoroff pathway is an overlooked glycolytic route in cyanobacteria and plants.

Glucose degradation pathways are central for energy and carbon metabolism throughout all domains of life. They provide ATP, NAD(P)H, and biosynthetic precursors for amino acids, nucleotides, and fatty acids. It is general knowledge that cyanobacteria and plants oxidize carbohydrates via glycolysis [the Embden-Meyerhof-Parnas (EMP) pathway] and the oxidative pentose phosphate (OPP) pathway. However, we found that both possess a third, previously overlooked pathway of glucose breakdown: the Entner-Doudoroff (ED) pathway. Its key enzyme, 2-keto-3-deoxygluconate-6-phosphate (KDPG) aldolase, is widespread in cyanobacteria, moss, fern, algae, and plants and is even more common among cyanobacteria than phosphofructokinase (PFK), the key enzyme of the EMP pathway. Active KDPG aldolases from the cyanobacterium Synechocystis and the plant barley (Hordeum vulgare) were biochemically characterized in vitro. KDPG, a metabolite unique to the ED pathway, was detected in both in vivo, indicating an active ED pathway. Phylogenetic analyses revealed that photosynthetic eukaryotes acquired KDPG aldolase from the cyanobacterial ancestors of plastids via endosymbiotic gene transfer. Several Synechocystis mutants in which key enzymes of all three glucose degradation pathways were knocked out indicate that the ED pathway is physiologically significant, especially under mixotrophic conditions (light and glucose) and under autotrophic conditions in a day/night cycle, which is probably the most common condition encountered in nature. The ED pathway has lower protein costs and ATP yields than the EMP pathway, in line with the observation that oxygenic photosynthesizers are nutrient-limited, rather than ATP-limited. Furthermore, the ED pathway does not generate futile cycles in organisms that fix CO2 via the Calvin-Benson cycle.

Is there A Role for Alpha-Linolenic Acid in the Fetal Programming of Health?

The role of ω3 alpha linolenic acid (ALA) in the maternal diet during pregnancy and lactation, and its effect on the prevention of disease and programming of health in offspring, is largely unknown. Compared to ALA, ω3 docosahexaenoic (DHA) and eicosapentaenoic (EPA) acids have been more widely researched due to their direct implication in fetal neural development. In this literature search we found that ALA, the essential ω3 fatty acid and metabolic precursor of DHA and EPA has been, paradoxically, almost unexplored. In light of new and evolving findings, this review proposes that ALA may have an intrinsic role, beyond the role as metabolic parent of DHA and EPA, during fetal development as a regulator of gene programming for the prevention of metabolic disease and promotion of health in offspring.