Even-chain Fatty Acids Research Articles

Supplementing branched-chain volatile fatty acids in dual-flow cultures varying in dietary forage and corn oil concentrations. II: Biohydrogenation and incorporation into bacterial lipids

To maintain membrane homeostasis, ruminal bacteria synthesize branched-chain fatty acids (BCFA) or their derivatives (vinyl ethers) that are recovered during methylation procedures as branched-chain aldehydes (BCALD). Many strains of cellulolytic bacteria require 1 or more branched-chain volatile fatty acid (BCVFA). Therefore, the objective of this study was to investigate BCVFA incorporation into bacterial lipids under different dietary conditions. The study was an incomplete block design with 8 continuous culture fermenters used in 4 periods with treatments (n = 4) arranged as a 2 × 2 × 2 factorial. The factors were high (HF) or low forage (LF, 67 or 33% forage, 33:67 alfalfa:orchardgrass), without or with supplemental corn oil (CO; 3% dry matter, 1.5% linoleic fatty acid), and without or with 2.15 mmol/d (5 mg/d 13C each of isovalerate, isobutyrate, and 2-methylbutyrate). After methylation of bacterial pellets collected from each fermenter's effluent, fatty acids and fatty aldehydes were separated before analysis by gas chromatography and isotope ratio mass spectrometry. Supplementation of BCVFA did not influence biohydrogenation extent. Label was only recovered in branched-chain lipids. Lower forage inclusion decreased BCFA in bacterial fatty acid profile from 9.45% with HF to 7.06% with LF and decreased BCALD in bacterial aldehyde profile from 55.4% with HF to 51.4% with LF. Supplemental CO tended to decrease iso even-chain BCFA and decreased iso even-chain BCALD in their bacterial lipid profiles. The main 18:1 isomer was cis-9 18:1, which increased (P < 0.01) by 25% from CO (data not shown). Dose recovery in bacterial lipids was 43.3% lower with LF than HF. Supplemental CO decreased recovery in the HF diet but increased recovery with LF (diet × CO interaction). Recovery from anteiso odd-chain BCFA and BCALD was the greatest; therefore, 2-methylbutyrate was the BCVFA primer most used for branched-chain lipid synthesis. Recovery in iso odd-chain fatty acids (isovalerate as primer) was greater than label recovery in iso even-chain fatty acids (isobutyrate as primer). Fatty aldehydes were less than 6% of total bacterial lipids, but 26.0% of 13C recovered in lipids were recovered in BCALD because greater than 50% of aldehydes were branched-chain. Because BCFA and BCALD are important in the function and growth of bacteria, especially cellulolytics, BCVFA supplementation can support the rumen microbial consortium, increasing fiber degradation and efficiency of microbial protein synthesis.

The Differences of Nutrient Components in Edible and Feeding Coix Seed at Different Developmental Stages Based on a Combined Analysis of Metabolomics.

Coix lachryma-jobi L. is an excellent plant resource that has a concomitant function for medicine, foodstuff and forage in China. At present, the commonly used cultivar for both medicine and foodstuff is Xiaobaike, and the cultivar for foraging is Daheishan. However, differences in the internal composition of plants lead to the expression of different phenotypic traits. In order to comprehensively elucidate the differences in nutrient composition changes in Coix seeds, a non-targeted metabolomics method based on ultra-performance liquid chromatography quadrupole time-of-flight mass spectrometry (LC-Q-TOF-MS) was used to analyze the metabolic changes in Coix seeds at different developmental stages. An edible Coix relative (Xiaobaike) and a feeding Coix relative (Daheishan) were selected as the research subjects. In the metabolome analysis of Coix seed, 314 metabolites were identified and detected, among which organic acids, carbohydrates, lipids, nucleotides and flavonoids were the main components. As an important standard for evaluating the quality of Coix seed, seven lipids were detected, among which fatty acids included not only even-chain fatty acids, but also odd-chain fatty acids, which was the first time detecting a variety of odd-chain fatty acids in Coix seed. The analysis of the compound contents in edible and feeding-type Coix lachryma-jobi L. and the lipid content at the mature stage showed that, among them, arachidic acid, behenic acid, heptadecanoic acid, heneicosanoic acid and pristanic acid may be the key compounds affecting the lipid content. In addition, in the whole process of semen coicis maturation, edible and feeding Coix show similar trends, and changes in the third period show clear compounds in the opposite situation, suggesting that edible and feeding Coix not only guarantee the relative stability of species but also provide raw materials for genetic breeding. This study provides valuable information on the formation of the edible and medicinal qualities of Coix.

13C-Metabolic flux analysis of 3T3-L1 adipocytes illuminates its core metabolism under hypoxia

Hypoxia has been identified as a major factor in the pathogenesis of adipose tissue inflammation, which is a hallmark of obesity and obesity-linked type 2 diabetes mellitus. In this study, we have investigated the impact of hypoxia (1% oxygen) on the physiology and metabolism of 3T3-L1 adipocytes, a widely used cell culture model of adipose. Specifically, we applied parallel labeling experiments, isotopomer spectral analysis, and 13C-metabolic flux analysis to quantify the impact of hypoxia on adipogenesis, de novo lipogenesis and metabolic flux reprogramming in adipocytes. We found that 3T3-L1 cells can successfully differentiate into lipid-accumulating adipocytes under hypoxia, although the production of lipids was reduced by about 40%. Quantitative flux analysis demonstrated that short-term (1 day) and long-term (7 days) exposure to hypoxia resulted in similar reprogramming of cellular metabolism. Overall, we found that hypoxia: 1) reduced redox and energy generation by more than 2-fold and altered the patterns of metabolic pathway contributions to production and consumption of energy and redox cofactors; 2) redirected glucose metabolism from pentose phosphate pathway and citric acid cycle to lactate production; 3) rewired glutamine metabolism, from net glutamine production to net glutamine catabolism; 4) suppressed branched chain amino acid consumption; and 5) reduced biosynthesis of odd-chain fatty acids and mono-unsaturated fatty acids, while synthesis of saturated even-chain fatty acids was not affected. Together, these results highlight the profound impact of extracellular microenvironment on adipocyte metabolic activity and function.

Microbial production of odd-chain fatty acids.

Odd-chain fatty acids (OcFAs) and their derivatives have attracted much attention due to their beneficial physiological effects and their potential to be alternatives to advanced fuels. However, cells naturally produce even-chain fatty acids (EcFAs) with negligible OcFAs. In the process of biosynthesis of fatty acids (FAs), the acetyl-CoA serves as the starter unit for EcFAs, and propionyl-CoA works as the starter unit for OcFAs. The lack of sufficient propionyl-CoA, the precursor, is usually regarded as the main restriction for large-scale bioproduction of OcFAs. In recent years, synthetic biology strategies have been used to modify several microorganisms to produce more propionyl-CoA that would enable an efficient biosynthesis of OcFAs. This review discusses several reported and potential metabolic pathways for propionyl-CoA biosynthesis, followed by advances in engineering several cell factories for OcFAs production. Finally, trends and challenges of synthetic biology driven OcFAs production are discussed.

Safety evaluation of odd-chain fatty acid algal oil

In the food industry, most fatty acid-rich oils are primarily composed of saturated even-chain fatty acids. However, saturated odd-chain fatty acids are potentially a beneficial alternative to other saturated fatty acid-containing oils. In this communication, we examine the safety of odd-chain fatty acid (OCFA) algal oil, a microalgal-sourced oil composed primarily of the saturated odd-chain fatty acids pentadecanoic acid and heptadecanoic acid. OCFA algal oil was assessed for toxicity in a 14-day palatability study and comprehensive 13-week dietary study at inclusion levels of 5%, 10%, and 15% in the diet, utilizing a DHA-rich algal oil as a comparator control. No adverse effects attributed to the consumption of OCFA algal oil were observed in either study. Therefore, we report a No Observable Adverse Effect Level (NOAEL) of 150,000 ppm (15% in the diet), equivalent to an OCFA algal oil intake of 7553.9 and 8387.7 mg/kg bw/day for male and female rats, respectively. The genotoxic potential of OCFA algal oil was also examined in an in vitro bacterial reverse mutation assay and in vivo mammalian bone marrow chromosome aberration test. OCFA algal oil was non-mutagenic in Salmonella typhimurium and Escherichia coli test strains and did not exhibit clastogenicity in vivo.

Conditions stimulating neutral detergent fiber degradation by dosing branched-chain volatile fatty acids. III: Relation with solid passage rate and pH on prokaryotic fatty acid profile and community in continuous culture

Our objectives were to evaluate potential interactions in culture conditions that influence how exogenously dosed branched-chain VFA (BCVFA) would be recovered as elongated fatty acids (FA) or would affect bacterial populations. A 2 × 2 × 2 factorial arrangement of treatments evaluated 3 factors: (1) without versus with BCVFA (0 vs. 2 mmol/d each of isobutyrate, isovalerate, and 2-methylbutyrate; each dose was partially substituted with 13C-enriched tracers before and during the collection period); (2) high versus low pH (ranging diurnally from 6.3 to 6.8 vs. 5.7 to 6.2); and (3) low versus high particulate-phase passage rate (kp; 2.5 vs. 5.0%/h) in continuous cultures administered a 50:50 forage:concentrate diet twice daily. Samples of effluent were collected and composited before harvesting bacteria from which FA and DNA were extracted. Profiles and enrichments of FA in bacteria were evaluated by gas chromatography and isotope-ratio mass spectrometry. The 13C enrichment in bacterial FA was calculated as percentage recovery of dosed 13C-labeled BCVFA. Dosing BCVFA increased the even-chain iso-FA, preventing the reduced concentration at higher kp and potentially as a physiological response to decreased pH. However, decreasing pH decreased recovery of 13C in these even-chain FA, suggesting greater reliance on isobutyrate produced from degradation of dietary valine. The iso-FA were decreased, whereas anteiso-FA and 16:0 increased with decreasing pH. Thus, 2-methylbutyrate still appeared to be important as a precursor for anteiso-FA to counter the increased rigidity of bacterial membranes that had more saturated straight-chain FA when pH decreased. Provision of BCVFA stimulated the relative sequence abundance of Fibrobacter and Treponema, both of which require isobutyrate and 2-methylbutyrate. Numerous bacterial community members were shifted by low pH, including increased Prevotella and genera within the phylum Proteobacteria, at the expense of members within phylum Firmicutes. Because of relatively few interactions with pH and kp, supplementation of BCVFA can stimulate neutral detergent fiber degradability via key fibrolytic bacteria across a range of conditions. Decreasing pH shifted bacterial populations and their FA composition, suggesting that further research is needed to distinguish pH from dietary changes.

Triheptanoin for the treatment of brain energy deficit: A 14‐year experience

Triheptanoin is an odd-chain triglyceride with anaplerotic properties-that is, replenishing the pool of metabolic intermediates in the Krebs cycle. Unlike even-chain fatty acids metabolized to acetyl-CoA only, triheptanoin can indeed provide both acetyl-CoA and propionyl-CoA, two key carbon sources for the Krebs cycle. Triheptanoin was initially used in patients with long-chain fatty acid oxidation disorders. The first demonstration of the possible benefit of triheptanoin for brain energy deficit came from a patient with pyruvate carboxylase deficiency, a severe metabolic disease that affects anaplerosis in the brain. In an open-label study, triheptanoin was then shown to decrease nonepileptic paroxysmal manifestations by 90% in patients with glucose transporter 1 deficiency syndrome, a disease that affects glucose transport into the brain. 31 P magnetic resonance spectroscopy studies also indicated that triheptanoin was able to correct bioenergetics in the brain of patients with Huntington disease, a neurodegenerative disease associated with brain energy deficit. Altogether, these studies indicate that triheptanoin can be a treatment for brain energy deficit related to altered anaplerosis and/or glucose metabolism. © 2017 Wiley Periodicals, Inc.

Feasibility of discriminating powdery mildew-affected grape berries at harvest using mid-infrared attenuated total reflection spectroscopy and fatty acid profiling

Background and Aims Powdery mildew (Erysiphe necator) reduces the quality of winegrapes, and objective methods for assessment are required. Mid-infrared spectroscopy and fatty acid analysis were investigated for rapid diagnosis of affected berries. Methods and Results Colonisation by E. necator reduced berry diameter and mass and increased the surface area : volume ratio. Mid-infrared spectra (1800–1185 cm−1) contained information on E. necator and compounds related to infection, but spectral similarity of visually healthy and partly infected berries confounded differentiation between these groups. Fatty acids in E. necator and berries were identified and quantified by gas chromatography. Six saturated even-chain fatty acids were prevalent in E. necator, arachidic acid being most abundant. Following stepwise linear discriminant analysis, four saturated fatty acids distinguished 97% of healthy berries and assigned approximately 75% of partly and fully infected berries to their original groups. Arachidic acid concentration, which changed amongst healthy, partly and fully infected berries (P = 0.001), correctly classified 90% of healthy berries. Conclusions Analysis of fatty acids allowed discrimination of healthy and infected berries whereas mid-infrared spectroscopy proved less informative. Arachidic acid concentration increased with disease severity. Significance of the Study Fatty acid analysis offers a new approach for objective measurement of powdery mildew. Arachidic acid is proposed as a biomarker for powdery mildew on grapes.

Glyoxylate detoxification is an essential function of malate synthase required for carbon assimilation in Mycobacterium tuberculosis

The glyoxylate shunt is a metabolic pathway of bacteria, fungi, and plants used to assimilate even-chain fatty acids (FAs) and has been implicated in persistence of Mycobacterium tuberculosis (Mtb). Recent work, however, showed that the first enzyme of the glyoxylate shunt, isocitrate lyase (ICL), may mediate survival of Mtb during the acute and chronic phases of infection in mice through physiologic functions apart from fatty acid metabolism. Here, we report that malate synthase (MS), the second enzyme of the glyoxylate shunt, is essential for in vitro growth and survival of Mtb on even-chain fatty acids, in part, for a previously unrecognized activity: mitigating the toxicity of glyoxylate excess arising from metabolism of even-chain fatty acids. Metabolomic profiling revealed that MS-deficient Mtb cultured on fatty acids accumulated high levels of the ICL aldehyde endproduct, glyoxylate, and increased levels of acetyl phosphate, acetoacetyl coenzyme A (acetoacetyl-CoA), butyryl CoA, acetoacetate, and β-hydroxybutyrate. These changes were indicative of a glyoxylate-induced state of oxaloacetate deficiency, acetate overload, and ketoacidosis. Reduction of intrabacterial glyoxylate levels using a chemical inhibitor of ICL restored growth of MS-deficient Mtb, despite inhibiting entry of carbon into the glyoxylate shunt. In vivo depletion of MS resulted in sterilization of Mtb in both the acute and chronic phases of mouse infection. This work thus identifies glyoxylate detoxification as an essential physiologic function of Mtb malate synthase and advances its validation as a target for drug development.

Catabolism of Branched Chain Amino Acids Contributes Significantly to Synthesis of Odd-Chain and Even-Chain Fatty Acids in 3T3-L1 Adipocytes.

The branched chain amino acids (BCAA) valine, leucine and isoleucine have been implicated in a number of diseases including obesity, insulin resistance, and type 2 diabetes mellitus, although the mechanisms are still poorly understood. Adipose tissue plays an important role in BCAA homeostasis by actively metabolizing circulating BCAA. In this work, we have investigated the link between BCAA catabolism and fatty acid synthesis in 3T3-L1 adipocytes using parallel 13C-labeling experiments, mass spectrometry and model-based isotopomer data analysis. Specifically, we performed parallel labeling experiments with four fully 13C-labeled tracers, [U-13C]valine, [U-13C]leucine, [U-13C]isoleucine and [U-13C]glutamine. We measured mass isotopomer distributions of fatty acids and intracellular metabolites by GC-MS and analyzed the data using the isotopomer spectral analysis (ISA) framework. We demonstrate that 3T3-L1 adipocytes accumulate significant amounts of even chain length (C14:0, C16:0 and C18:0) and odd chain length (C15:0 and C17:0) fatty acids under standard cell culture conditions. Using a novel GC-MS method, we demonstrate that propionyl-CoA acts as the primer on fatty acid synthase for the production of odd chain fatty acids. BCAA contributed significantly to the production of all fatty acids. Leucine and isoleucine contributed at least 25% to lipogenic acetyl-CoA pool, and valine and isoleucine contributed 100% to lipogenic propionyl-CoA pool. Our results further suggest that low activity of methylmalonyl-CoA mutase and mass action kinetics of propionyl-CoA on fatty acid synthase result in high rates of odd chain fatty acid synthesis in 3T3-L1 cells. Overall, this work provides important new insights into the connection between BCAA catabolism and fatty acid synthesis in adipocytes and underscores the high capacity of adipocytes for metabolizing BCAA.

Against the stream: relevance of gluconeogenesis from fatty acids for natives of the arctic regions

Background. The question whether even-chain fatty acids can be converted into glucose has a long-standing tradition in biochemistry. Since the glyoxylate shunt is absent from mammals, the question has been considered to be solved. It is of particular relevance for understanding the metabolic state of natives of the arctic regions due to the very high fat content of their traditional diet only containing negligible amounts of carbohydrates.Methods & Results. Using an in silico approach, we discovered several hitherto unknown routes in human metabolism that allow the conversion of even-chain fatty acids into carbohydrates in humans. These pathways proceed via ketogenesis over the intermediate of acetone and produce the gluconeogenic precursor pyruvate. While these pathways can make a contribution to glucose production during times of limited carbohydrate supply, we found that their capacity might be limited due to a high demand in reducing equivalents in acetone degradation. Considering the traditional diet of natives of the arctic regions, the detected pathways are not only important in order to improve carbohydrate supply, but moreover reduce the amount of protein that needs to be used for gluconeogenesis.Conclusion. In summary, our study sheds new light on our understanding of the metabolic state of natives from the arctic regions on their traditional diet. Moreover, they provide an avenue for new analyses that can reveal how humans have adapted metabolically to a practically carbohydrate-free diet.

Can sugars be produced from fatty acids? A test case for pathway analysis tools

In recent years, several methods have been proposed for determining metabolic pathways in an automated way based on network topology. The aim of this work is to analyse these methods by tackling a concrete example relevant in biochemistry. It concerns the question whether even-chain fatty acids, being the most important constituents of lipids, can be converted into sugars at steady state. It was proved five decades ago that this conversion using the Krebs cycle is impossible unless the enzymes of the glyoxylate shunt (or alternative bypasses) are present in the system. Using this example, we can compare the various methods in pathway analysis. Elementary modes analysis (EMA) of a set of enzymes corresponding to the Krebs cycle, glycolysis and gluconeogenesis supports the scientific evidence showing that there is no pathway capable of converting acetyl-CoA to glucose at steady state. This conversion is possible after the addition of isocitrate lyase and malate synthase (forming the glyoxylate shunt) to the system. Dealing with the same example, we compare EMA with two tools based on graph theory available online, PathFinding and Pathway Hunter Tool. These automated network generating tools do not succeed in predicting the conversions known from experiment. They sometimes generate unbalanced paths and reveal problems identifying side metabolites that are not responsible for the carbon net flux. This shows that, for metabolic pathway analysis, it is important to consider the topology (including bimolecular reactions) and stoichiometry of metabolic systems, as is done in EMA.

Can sugars be produced from fatty acids? A test case for pathway analysis tools

In recent years, several methods have been proposed for determining metabolic pathways in an automated way based on network topology. The aim of this work is to analyse these methods by tackling a concrete example relevant in biochemistry. It concerns the question whether even-chain fatty acids, being the most important constituents of lipids, can be converted into sugars at steady state. It was proved five decades ago that this conversion using the Krebs cycle is impossible unless the enzymes of the glyoxylate shunt (or alternative bypasses) are present in the system. Using this example, we can compare the various methods in pathway analysis. Elementary modes analysis (EMA) of a set of enzymes corresponding to the Krebs cycle, glycolysis and gluconeogenesis supports the scientific evidence showing that there is no pathway capable of converting acetyl-CoA to glucose at steady state. This conversion is possible after the addition of isocitrate lyase and malate synthase (forming the glyoxylate shunt) to the system. Dealing with the same example, we compare EMA with two tools based on graph theory available online, PathFinding and Pathway Hunter Tool. These automated network generating tools do not succeed in predicting the conversions known from experiment. They sometimes generate unbalanced paths and reveal problems identifying side metabolites that are not responsible for the carbon net flux. This shows that, for metabolic pathway analysis, it is important to consider the topology (including bimolecular reactions) and stoichiometry of metabolic systems, as is done in EMA. Supplementary data are available at Bioinformatics online.

Highly Active Antiretroviral Therapy Does Not Affect Mitochondrial β-Oxidation of Fatty Acids: An in Vitro Study in Fibroblasts

Preeclampsia is a multifactorial pregnancy-specific disease. In some cases, severe preeclampsia and related disorders of acute fatty liver of pregnancy and hemolysis, elevated liver enzymes, low platelets syndrome are associated with inherited defects in mitochondrial beta-oxidation of fatty acids, especially a deficiency of long-chain 3-hydroxyacyl coenzyme A dehydrogenase (LCHAD). Recently, an unexplained increase in the incidence of preeclampsia has been documented in human immunodeficiency virus (HIV)-infected pregnant women on treatment with highly active antiretroviral therapy (HAART). We performed this study to determine if antiretroviral drugs affect mitochondrial beta-oxidation fatty acids in vitro. Two normal and 1 heterozygous LCHAD-deficient cell lines were exposed to up to 5 times the therapeutic concentrations of the following antiretroviral drugs: nevirapine, didanosine, lamivudine, and a combination of nelfinavir, zidovudine, and lamivudine. One homozygous LCHAD-deficient cell line served as the positive control. After exposure of the fibroblasts to these drugs for periods ranging from 2 to 10 days, accumulations of even-chain 3-hydroxy fatty acids (3-OH-C6 to 3-OH-C18) in the culture media were measured by stable-isotope dilution gas chromatography/mass spectrometry. Compared to the respective unexposed fibroblasts, there was no significant build-up of 3-hydroxy fatty acids in the culture media of normal or heterozygous LCHAD-deficient fibroblasts exposed to antiretroviral drugs. Our results show that the commonly used antiretroviral drugs do not adversely affect fatty acid oxidation in fibroblasts. Therefore, an altered fatty acid oxidation may not be the mechanism for the reported increased risk of preeclampsia in HIV-infected pregnant women on HAART.

Conjugated linolenic acid (CLnA), conjugated linoleic acid (CLA) and other biohydrogenation intermediates in plasma and milk fat of cows fed raw or extruded linseed

Thirty lactating dairy cows were used in a 3 × 3 Latin-square design to investigate the effects of a raw or extruded blend of linseed and wheat bran (70:30) on plasma and milk fatty-acids (FA). Linseed diets, containing 16.6% linseed blend on a dry-matter basis, decreased milk yield and protein percentage. They decreased the proportions of FA with less than 18 carbons in plasma and milk and resulted in cis-9, cis-12, cis-15 18:3 proportions that were more than three and four times higher in plasma and milk, respectively, whereas cis-9, cis-12 18:2 proportions were decreased by 10–15%. The cis-9, trans-11, cis-15 18:3 isomer of conjugated linolenic acid was not detected in the milk of control cows, but was over 0.15% of total FA in the milk fat of linseed-supplemented cows. Similarly, linseed increased plasma and milk proportions of all biohydrogenation (BH) intermediates in plasma and milk, including the main isomer of conjugated linoleic acid cis-9, trans-11 18:2, except trans-4 18:1 and cis-11, trans-15 18:2 in plasma lipids. In milk fat, compared with raw linseed, extruded linseed further reduced 6:0–16:0 even-chain FA, did not significantly affect the proportions of 18:0, cis-9 18:1 and cis-9, cis-12 18:2, tended to increase cis-9, cis-12, cis-15 18:3, and resulted in an additional increase in the proportions of most BH intermediates. It was concluded that linseed addition can improve the proportion of conjugated linoleic and linolenic acids, and that extrusion further increases the proportions of intermediates of ruminal BH in milk fat.

Effects of odd-numbered medium-chain fatty acids on the accumulation of long-chain 3-hydroxy-fatty acids in long-chain L-3-hydroxyacyl CoA dehydrogenase and mitochondrial trifunctional protein deficient skin fibroblasts

The treatment for patients with genetic disorders of mitochondrial long-chain fatty acid β-oxidation is directed toward providing sufficient sources of energy for normal growth and development, and at the same time preventing the adverse effects that precipitate or result from metabolic decompensation. Standard of care treatment has focused on preventing the mobilization of lipids that result from fasting and providing medium-chain triglycerides (MCT) in the diet in order to bypass the long-chain metabolic block. MCTs that are currently available as commercial preparations are in the form of even-chain fatty acids that are predominately a mixture of octanoate and decanoate. Recently, the use of odd-chain fatty acids has been proposed as an alternative treatment. We have shown previously that the even-numbered medium-chain fatty acids (MCFAs) that are found in MCT preparations can reduce the accumulation of potentially toxic long-chain metabolites of fatty acid oxidation (FAO). In the current study, we undertook to determine if the same is true of odd-numbered MCFAs. We found that provision of odd-chain species does decrease the build-up of long-chain FAO intermediates in our in vitro skin fibroblast model, but to a lesser extent than even-numbered MCFAs.

Nitrogen Supplementation of Corn Silages. 2. Assessing Rumen Function Using Fatty Acid Profiles of Bovine Milk

The effects of N supplementation strategies on milk fatty acid profiles of dairy cows and their use as a noninvasive technique to diagnose rumen function, and to guide protein feeding decisions on-farm were evaluated in three experiments. Each experiment was designed according to three 3 x 3 Latin squares with 9 Holstein cows receiving total mixed rations based on corn silage. Experiment 1 was designed to study effects of diets with different ratios of effective rumen-degradable protein (ERDP; g) to fermentable metabolizable energy (FME; j) providing, respectively, a large deficiency, a slight deficiency, and a slight excess in relation to the target level of 11 g of ERDP/MJ FME for lactating cows. Experiment 2 evaluated effects of different proportions of quickly and slowly rumen-degradable protein achieved by replacing soybean meal with urea in the concentrates (0, 0.5, and 1% urea for U0, U5, and U10, respectively). Experiment 3 investigated effects of synchronizing the availability of FME and ERDP in rumen by offering the protein-rich concentrate once or twice per day before the meal (corn silage, ryegrass hay, and energy-rich concentrate), or included in the total mixed ration. Milk fatty acid profiles were significantly affected by dietary N and carbohydrate supply. Principal component factor analysis provided a reasonable description of the data, clearly discriminating between fatty acids that are synthesized by different metabolic pathways. Several sources/pathways were distinguished: de novo synthesis in the mammary gland (short- and medium-chain fatty acids), delta9-desaturase activity (monoenoic fatty acids), direct absorption from the blood stream (long-chain fatty acids), and de novo synthesis by the rumen microbial populations (odd-chain fatty acids). Discriminant canonical analysis showed that milk odd-chain fatty acids had a higher ability to discriminate between diets than even-chain fatty acids. The anteiso C15:0 increased in line with increasing sugar supply, and C17:0 appears to be a marker of protein deficiency. Additionally, iso C17:0 and anteiso C17:0 were associated with the NDF and CP contents of diets. The results suggests that milk odd-chain fatty acids have the potential to be used as a noninvasive technique to assess rumen function in terms of microbial populations, substrates and interactions.

Volatile ketone formation in bacteria: release of 3-oxopentanoate by soil pseudomonads during growth on heptanoate.

During enrichments to search for soil bacteria that form the volatile ketones, acetone and butanone, we isolated pure cultures of Pseudomonas aureofaciens, P. fluorescens, and P. putida that excrete the beta-keto-acid, 3-oxopentanoate (3-OPA), when grown on heptanoic acid as carbon source. Analysis of 3-OPA used enzymatic decarboxylation by acetoacetate decarboxylase to yield butanone, which was detected by headspace gas chromatography. The formation of 3-OPA was strongly dependent on heptanoic acid concentration, the level of oxygen, and the state of growth, and was not seen with even-chain or other odd-chain fatty acids. Uptake of 3-OPA during stationary phase of growth is probably related to polyhydroxyalkanoate (PHA) formation in these isolates. A model for formation and release of 3-OPA is proposed.

Effects of propionate on rat hepatocyte metabolism

The aim of the present study was to investigate the effects of propionate or even-chain fatty acids (butyrate, octanoate, and oleate) on glucogenic or ketogenic substrate metabolism as well as ureagenesis. Therefore, rat hepatocytes were incubated in complex media containing near-physiological concentrations of glucose, lactate, alanine, and glutamine. On hepatocytes from fed rats, propionate impaired lactate metabolism, whose threshold for net utilization was shifted from 2.5 mM to more than 4 mM, whereas even-chain fatty acids presented the opposite effect. Furthermore, propionate, in contrast to even-chain fatty acids, effectively lowered lactate utilization in hepatocytes from starved rats. Determination of the cellular concentration of glycolysis effectors (citrate, fructose 2,6-bisphosphate, and xylulose 5-phosphate) indicates that this pathway might be accelerated by propionate and depressed by even-chain fatty acids. Cellular pyruvate was markedly increased by propionate and depressed by even-chain fatty acids. Thus, the sparing effect of propionate on lactate seems mainly a consequence of sustaining high pyruvate concentrations in hepatocytes. Ammonia increased lactate utilization, and propionate partially thwarted the effect of ammonia on lactate flux. Propionate did not influence alanine utilization, but favored the production of alanine in an amino acid-free medium. Ketogenesis, very active in hepatocytes from starved rats, was significantly decreased in the presence of propionate, whatever the fatty acid precursor (butyrate, octanoate, or oleate) together with β-hydroxybutyrate/acetoacetate ratio. Because propionate did not affect oleate utilization, it could switch fatty acids from ketogenesis to other pathways like reesterification. Finally, propionate exerts important effects on cellular metabolism, and it helps to reduce the catabolism of some substrates such as lactate or oleate.

Exceptional lipids and fatty acids in the pteropod Clione limacina (Gastropoda) from both polar oceans

Abstract The gymnosomatous and thecosomatous pteropods, Clione limacina and its only prey Limacina helicina and L. retroversa , from Arctic and Antarctic waters as well as particulate matter have been investigated with respect to their lipid compositions. The close trophic relationships between phytoplankton– Limacina – Clione were partially reflected by the fatty acid compositions due to high amounts of 16:1( n −7), which indicate the ingestion of diatoms in L. helicina . However, the outstanding feature of this food chain concerns the extraordinary lipid and fatty acid compositions of C. limacina . Up to 40.6% of its total lipid consisted of 1- O -alkyldiacylglycerol ethers, a very unusual depot lipid in the zooplankton. The other major storage lipid were triacylglycerols, which occurred in similar amounts. In addition, the various lipid classes of C. limacina exhibited unique fatty acid compositions, due to high percentages of odd-chain length components, up to one third of total fatty acids. The dominant odd-chain fatty acid was 17:1( n −8) reaching 18%, followed by 15:0 and 17:0, with 17:1( n −8) enriched in the diacylglycerol ethers. Major even-chain fatty acids were 16:0, 16:1( n −7), 20:5( n −3) and 22:6( n −3). In L. helicina neither diacylglycerol ethers nor odd-chain fatty acids could be detected, indicating that these atypical lipids are not ingested with the prey by C. limacina . De novo biosynthesis of these compounds is therefore suggested. The synthesis of odd-chain fatty acids is initiated with propionate. This precursor may originate from dimethyl- β -propiothetin (DMPT), which has been described to be accumulated by L. helicina via phytoplankton uptake. Hence, C. limacina not only represents an exceptional member of the polar zooplankton due to its extreme trophic specialisation, it has also developed exceptional lipid biochemical adaptations in the Arctic and Antarctic ocean.