Comparison of different methylation methods for the analysis of conjugated linoleic acid isomers by silver ion HPLC in beef lipids

Effect of including oilseed grains in bovine diets on fatty acid profile, lipid stability, and sensory aspects of burgers

The aim of this study was to evaluate the effect of including different oilseed grains in the diets of cattle on the qualitative and sensory characteristics and fatty acid profile of burger over a storage period of up to 120 days. The soybean diet increased 30% of ether extract in burgers when compared to the control diet. The inclusion of oilseeds in the bovine diet did not change the n-6/n-3 and hypocholesterolemic/hypercholesterolemic ratio, as well as the cholesterol levels in the burgers. The smallest flavor and aroma note scores were attributed to burgers produced with meat of bovine fed with cottonseed (4.35 and 4.67, respectively). The sunflower diet resulted in smaller lipid oxidation (1.03 mg/kg). The storage period increased lipid oxidation (0.43 and 1.97 mg/kg of malonaldehyde at 0 and 120 days, respectively). The inclusion of oilseeds in the diet of cattle does not change the ratios of fatty acids in burgers, which are important to human health. It is recommended to use soybean and sunflower grains in cattle diets to improve the sensory quality of burgers. A 30-day storage period is recommended to maintain the flavor and juiciness of beef burgers.

Tissue and Circulating Fatty Acids as Biomarkers to Evaluate Long-Term Fat Intake Are Tissue and Sex Dependent in CD-1 Mice

BACKGROUND

There is currently no consensus on which tissues are optimal for assessing specific diet-derived fatty acids (FAs) as biomarkers for long-term dietary studies.

OBJECTIVES

This study measured the content of unique diet-derived FAs from dairy, echium, and fish in tissues (adipose, muscle, liver, erythrocyte membranes, and plasma phospholipids, cholesterol esters, triglycerides, and free fatty acids) after long-term feeding in CD-1 mice.

METHODS

Beginning at weaning, mice (n = 10-11/sex/diet) were fed 1 of 4 diets (40% kcal/total energy) that only differed in FA composition: control fat blend (CON), reflecting the FA profile of the average US American diet, or CON supplemented with 30% of fish oil (FO), dairy fat (DF), or echium oil (EO). After 13 mo, tissues were collected to determine FAs via gas-liquid chromatography. Tissue FAs were analyzed via 2-factor ANOVA, and relationships between FA intake and tissue content were assessed with Spearman correlations.

RESULTS

As anticipated, 20:5n-3 (ω-3) tissue content was ≤32-fold greater in FO- compared with CON-fed mice (P < 0.05). In addition, 20:5n-3 intake strongly correlated with its content in all tissues (ρ = 0.67-0.76; P < 0.05). Echium oil intake also influenced tissue FA content in mice as expected. For example, 18:3n-6 was ≤25-fold greater in adipose, muscle, and liver tissues of EO-fed compared with CON-fed mice (P < 0.05). Tissue content of FAs typically considered biomarkers of dairy fat intake (15:0, 16:1 t9, and 17:0) was often not greater in mice fed DF than other diet groups, although 18:2 c9, t11 content was ≤6-fold greater in tissues from DF-fed compared with CON-fed mice (P < 0.05). The content of dairy-derived FAs in blood fractions of females was up to 2-fold greater compared with males, whereas docosapentaenoic acid content was up to 1-fold greater in all blood fractions and in liver tissue of males compared with females (P < 0.05). In adipose, muscle, and liver tissue, the content of γ-linolenic acid and stearidonic acid was less than 1-fold greater in females than in males (P < 0.05).

CONCLUSIONS

Our study indicates that the distribution of dietary FAs is tissue and sex dependent in aged CD-1 mice. Research using FA biomarkers should assess a combination of FA biomarkers to accurately validate patterns of FA intake and source.

The dietary c9,t11-conjugated linoleic acid enriched from butter reduces breast cancer progression in vivo

The c9,t11-conjugated linoleic acid (CLA), which is the minor polyunsaturated fatty acid (PUFA) naturally present in butter, has gained attention due to its important preventive effect against breast cancer in vitro. In this paper, the enrichment of c9,t11-CLA from butter was optimized and the preventive effect of dietary c9,t11-CLA against breast cancer in vivo was investigated. Results showed that the concentration of c9,t11-CLA increased more than 10 times via a one-step urea complexation. Furthermore, the dietary c9,t11-CLA showed obvious preventive effect against breast cancer in decreasing the tumor weight and volume, and reducing the tumor incidence up to 50%. In addition, the expression of progesterone receptor and Ki-67 decreased significantly with the treatment of c9,t11-CLA. In conclusion, the dietary c9,t11-CLA enriched from butter showed a preventive effect against breast cancer in vivo via the inhibition of the hormonal receptor and cell proliferation. PRACTICAL APPLICATIONS: This paper provided new insight into the preparation of specific c9,t11-CLA isomer. It can be enriched from butter in large-scale with low-cost by urea complexation. Meanwhile, the enriched dietary c9,t11-CLA can be further processed into cancer prevention functional foods.

Relationship between the fatty acid profile of hair and energy availability of lactating primiparous cows

We hypothesised that a relationship would exist between hair fatty acids, especially C12:0, C14:0 and C16:0, and parameters of energy metabolism such as energy intake, energy mobilisation, and energy requirement for maintenance and milk performance. For this study, 11 primiparous German Holstein cows were available from which hair samples at weeks 6 and 8 of lactation were analysed. The average body weight of these animals was 558 ± 27 kg at calving and milk yield at 100-days in milk was 3,537 ± 529 kg. Feed intake and milk yield were measured daily. Body weight and back fat thickness were measured at calving and in weeks 2, 4, and 8 of lactation. Energy balance and energy utilisation were calculated until week 6 of lactation. Spearman's correlation coefficients were found to be significantly positive for the relationship between the percentage of C12:0 and C14:0 fatty acids in the hair in lactation week 8 and energy intake in weeks 5 and 6 (0.62 < r < 0.65, P < 0.05). If the animals are grouped according to their energy utilisation between weeks 1 and 6 into two groups higher (n = 6) or lower (n = 5) than the median, animals of the high energy utilising group had a higher energy intake. These animals had also higher percentages of the C12:0 fatty acid in their hair fat (week 6: 4.9% vs. 3.1%, P < 0.05; week 8: 4.3% vs. 2.9%, P = 0.05). Our hypothesis is supported, and this study justifies further investigation of the content of medium-chain fatty acids in hair samples as biomarkers for the metabolic status of a cow during early lactation.

Influence of Nrf2 activators on subcellular skeletal muscle protein and DNA synthesis rates after 6 weeks of milk protein feeding in older adults

In older adults, chronic oxidative and inflammatory stresses are associated with an impaired increase in skeletal muscle protein synthesis after acute anabolic stimuli. Conjugated linoleic acid (CLA) and Protandim have been shown to activate nuclear factor erythroid-derived 2-like 2 (Nrf2), a transcription factor for the antioxidant response element and anti-inflammatory pathways. This study tested the hypothesis that compared to a placebo control (CON), CLA and Protandim would increase skeletal muscle subcellular protein (myofibrillar, mitochondrial, cytoplasmic) and DNA synthesis in older adults after 6 weeks of milk protein feeding. CLA decreased oxidative stress and skeletal muscle oxidative damage with a trend to increase messenger RNA (mRNA) expression of a Nrf2 target, NAD(P)H dehydrogenase quinone 1 (NQO1). However, CLA did not influence other Nrf2 targets (heme oxygenase-1 (HO-1), glutathione peroxidase 1 (Gpx1)) or protein or DNA synthesis. Conversely, Protandim increased HO-1 protein content but not the mRNA expression of downstream Nrf2 targets, oxidative stress, or skeletal muscle oxidative damage. Rates of myofibrillar protein synthesis were maintained despite lower mitochondrial and cytoplasmic protein syntheses after Protandim versus CON. Similarly, DNA synthesis was non-significantly lower after Protandim compared to CON. After Protandim, the ratio of protein to DNA synthesis tended to be greater in the myofibrillar fraction and maintained in the mitochondrial and cytoplasmic fractions, emphasizing the importance of measuring both protein and DNA synthesis to gain insight into proteostasis. Overall, these data suggest that Protandim may enhance proteostatic mechanisms of skeletal muscle contractile proteins after 6 weeks of milk protein feeding in older adults.

Supplementation of essential fatty acids to Holstein calves during late uterine life and first month of life alters hepatic fatty acid profile and gene expression

Linoleic acid is an essential dietary fatty acid (FA). However, how the supplementation of linoleic acid during uterine and early life may modify the FA profile and transcriptome regulation of the liver, and performance of preweaned dairy calves is unknown. Our objective was to evaluate the effect of supplementation of essential FA to Holstein calves during late uterine and early life on their hepatic FA profile and global gene expression at 30 d of age. During the last 8 wk of pregnancy, Holstein cattle (n=96) were fed either no fat supplement (control), a saturated FA supplement enriched with C18:0, or an unsaturated FA supplement enriched with linoleic acid. Male calves (n=40) born from these dams were fed a milk replacer (MR) with either low (LLA) or high linoleic acid (HLA) concentration as the sole feedstuff during the first 30 d. Liver biopsy was performed at 30 d of age, and microarray analysis was performed on 18 liver samples. Total concentration of FA in liver were greater in calves fed LLA compared with those fed HLA MR (8.2 vs. 7.1%), but plasma concentrations of total FA did not differ due to MR diets. The FA profiles of plasma and liver of calves were affected differently by the prepartum diets. Specifically, the FA profile in liver was affected moderately by the feeding of fat prepartum, but the profiles did not differ due to the type of FA fed prepartum. The type of MR fed during the first 30 d of life had major effects on both plasma and liver FA profiles, resembling the type of fat fed. Plasma and liver of calves fed LLA MR had greater percentage of medium-chain FA (C12:0 and C14:0), whereas plasma and liver from calves fed HLA MR had greater percentages of linoleic and α-linolenic acids. Dams fed fat or a specific type of FA modified the expression of some genes in liver of calves, particularly those genes involved in biological functions and pathways related to upregulation of lipid metabolism and downregulation of inflammatory responses. Feeding HLA instead of LLA MR modified the expression of hepatic genes, including genes predicted to decrease infections and to increase lipid utilization and protein synthesis. Research evaluating the effect of FA supplementation during uterine and neonatal life on the future productivity of the neonate is warranted.

Silver-Ion Solid Phase Extraction Separation of Classical, Aromatic, Oxidized, and Heteroatomic Naphthenic Acids from Oil Sands Process-Affected Water

The separation of classical, aromatic, oxidized, and heteroatomic (sulfur-containing) naphthenic acid (NA) species from unprocessed and ozone-treated oil sands process-affected water (OSPW) was performed using silver-ion (Ag-ion) solid phase extraction (SPE) without the requirement of pre-methylation for NAs. OSPW samples before SPE and SPE fractions were characterized using ultra performance liquid chromatography ion mobility time-of-flight mass spectrometry (UPLC-IM-TOFMS) to corroborate the separation of distinct NA species. The mass spectrum identification applied a mass tolerance of ±1.5 mDa due to the mass errors of NAs were measured within this range, allowing the identification of O2S-NAs from O2-NAs. Moreover, separated NA species facilitated the tandem mass spectrometry (MS/MS) characterization of NA compounds due to the removal of matrix and a simplified composition. MS/MS results showed that classical, aromatic, oxidized, and sulfur-containing NA compounds were eluted into individual SPE fractions. Overall results indicated that the separation of NA species using Ag-ion SPE is a valuable method for extracting individual NA species that are of great interest for environmental toxicology and wastewater treatment research, to conduct species-specific studies. Furthermore, the separated NA species on the milligram level could be widely used as the standard materials for environmental monitoring of NAs from various contamination sites.

A high-performance direct transmethylation method for total fatty acids assessment in biological and foodstuff samples

Isolation is the main bottleneck in the analysis of fatty acids in biological samples and foods. In the last few decades some methods described direct derivatization procedures bypassing these steps. They involve the utilization of methanolic HCL or BF3 as catalysts, but several evidences from previous works suggest these reagents are unstable, lead to the formation of artifacts and alter the distribution of specific compounds as hydroxy fatty acids or CLA. However, the main issue is that they are excellent esterification reagents but poor in transterification, being not suitable for the analysis of all lipid classes and leading to erroneous composition quantitations. The present research work is a comprehensive comparison of six general methylation protocols using base, acid or base/acid catalysts plus a proposed method in the analysis of total fatty acids in lipid standards mixtures, foodstuff and biological samples. The addition of aprotic solvents to the reaction mixture to avoid alterations was also tested. Results confirmed that procedures solely involving acid catalyst resulted in incomplete derivatizations and alteration of the fatty acid profile, partially corrected by addition of the aprotic solvent. The proposed method combining sodium methoxyde and sulfuric acid showed absence of alteration of the FAME profile and the best values for response factors (short chain fatty acids to PUFA), accuracy in the determination of total cholesterol and derivatization performance, thus showing a high reliability in the determination of the total fatty acid composition in biological samples and foods.

Comparison of two derivatization methods for the analysis of fatty acids and trans fatty acids in bakery products using gas chromatography

Two different procedures for the methylation of fatty acids (FAs) and trans fatty acids (TFAs) in food fats were compared using gas chromatography (GC-FID). The base-catalyzed followed by an acid-catalyzed method (KOCH3/HCl) and the base-catalyzed followed by (trimethylsilyl)diazomethane (TMS-DM) method were used to prepare FA methyl esters (FAMEs) from lipids extracted from food products. In general, both methods were suitable for the determination of cis/trans FAs. The correlation coefficients (r) between the methods were relatively small (ranging from 0.86 to 0.99) and had a high level of agreement for the most abundant FAs. The significant differences (P = 0.05) can be observed for unsaturated FAs (UFAs), specifically for TFAs. The results from the KOCH3/HCl method showed the lowest recovery values (%R) and higher variation (from 84% to 112%), especially for UFAs. The TMS-DM method had higher R values, less variation (from 90% to 106%), and more balance between variation and %RSD values in intraday and interday measurements (less than 4% and 6%, resp.) than the KOCH3/HCl method, except for C12:0, C14:0, and C18:0. Nevertheless, the KOCH3/HCl method required shorter time and was less expensive than the TMS-DM method which is more convenient for an accurate and thorough analysis of rich cis/trans UFA samples.

Method for screening of bacterial strains biosynthesizing specific conjugated linoleic acid isomers

A simple and accurate method for screening of bacterial strains with the ability to convert free linoleic acid into specific conjugated linoleic acid (CLA) isomers has been developed by combining the ultraviolet spectral scan and capillary electrophoresis analysis. The ultraviolet spectral scan was carried out for preliminary screening of bacterial strains with the capacity to biosynthesize CLA, and the absorption peak at 228-235 nm was used for assessing the possible production of CLA by bacteria. The capillary electrophoresis analysis was used as the follow-up confirmation to definitively conclude CLA production and the composition of CLA isomers. Linoleic acid at the concentration of 25 μg/mL, which showed little inhibitory effect on the growth of bacteria, was used for initial screening of CLA-producing strains. The strains with the ability to produce specific CLA isomers can be selected quickly from a large number of bacteria by this high-throughput method.

Production of conjugated linoleic acid and conjugated linolenic acid isomers by Bifidobacterium species

Conjugated linoleic acid (CLA) and conjugated linolenic acid (CLNA) isomers have attracted great interest because of their potential health benefits. Formation of CLA and CLNA takes place in the rumen during biohydrogenation. Several studies have indicated that certain types of intestinal bacteria, including bifidobacteria, are able to convert linoleic acid (LA) to CLA. The role of intestinal bacteria in the formation of CLNA isomers is largely unknown. In the present study, a screening of 36 different Bifidobacterium strains for their ability to produce CLA and CLNA from free LA and alpha-linolenic acid (LNA), respectively, was performed. The strains were grown in MRS broth, to which LA or LNA (0.5 mg ml(-1)) were added after 7 h of bacterial growth. Cultures were further incubated at 37 degrees C for 72 h. Six strains (four Bifidobacterium breve strains, a Bifidobacterium bifidum strain and a Bifidobacterium pseudolongum strain) were able to produce different CLA and CLNA isomers. Conversion percentages varied from 19.5% to 53.5% for CLA production and from 55.6% to 78.4% for CLNA production among these strains. The CLA isomers produced were further identified with Ag(+)-HPLC. LA was mainly converted to t9t11-CLA and c9t11-CLA. The main CLNA isomers were identified with GC-MS as c9t11c15-CLNA and t9t11c15-CLNA.

2-Propanol in the mobile phase reduces the time of analysis of CLA isomers by silver ion-HPLC

Individual isomers of octadecadienoic acid (C18:2) with conjugated double bonds (conjugated linoleic acids; CLA) exert different biological activities. Their distribution in food and tissues differs. Therefore, the separation of the various positional and geometric isomers is important. The time of analysis using silver ion-high performance liquid chromatography can extend up to 90 min. The aim of this study was to reduce this time. The time of analysis reduced from ca. 90 min onto 45 to 35 min, respectively, by the addition of 0.05% or 0.1% (v/v) 2-propanol to the mobile phase [acetonitrile (0.1%; v/v) and diethyl ether (0.5%; v/v) in n-hexane]. There was no effect on resolution of the 17 individual CLA isomers of the CLA mixture. Regarding the lowest coefficient of variation and an adequate baseline separation the use of 0.05% 2-propanol in the mobile phase is recommended, without any disadvantages and adverse effects on the service life of columns. In conclusion, adding 0.05% or 0.1% 2-propanol to the mobile phase shortens the time of analysis of CLA isomers, saves solvents and reduces costs.

Isomerisation of cis-9 trans-11 conjugated linoleic acid (CLA) to trans-9 trans-11 CLA during acidic methylation can be avoided by a rapid base catalysed methylation of milk fat

This study investigated the evolution of trans-9 trans-11 conjugated linoleic acid (CLA) from cis-9 trans-11 CLA during methylation and its avoidance through a rapid base methylation of milk fat. The study examined three conditions shown to result in loss of cis-9 trans-11 CLA during methylation namely: temperature, methylation time, water contamination in old reagents and acidic conditions. Three techniques currently used for the conversion of milk fat into fatty acid methyl esters for analysis of CLA content by gas liquid chromatography and a fourth procedure designed to eliminate acidic conditions and to limit methylation temperature and time were used. The four methods were: (i) acidic methylation (AM); (ii) acidic and basic bimethylation with fresh reagents (FBM); (iii) acidic and basic bimethylation with pre-prepared reagents (PBM) and (iv) basic methylation (BM). Each regime was carried out on six milk samples over two periods and methylated 1 ml freeze-dried milk (n=12 per regime). Total CLA was not different across methylation regimes (0·30 mg/ml). Isomer cis-9 trans-11 was higher (P<0·01) with BM than the other regimes and lowest with AM: 21·2, 17·8, 18·8 and 14·7 mg/100 ml for BM, FBM, PBM and AM, respectively. The inverse relationship was shown for trans-9 trans-11 with higher (P<0·001) amounts with AM than the other regimes and lowest with BM: 0·57, 2·55, 2·36 and 3·69 mg/100 ml for BM, FBM, PBM and AM, respectively. The trans-10 cis-12 isomer was also shown to alter with methylation procedure being higher (P<0·001) with AM than the other regimes: 0·43, 0·47, 0·29 and 1·20 mg/100 ml for BM, FBM, PBM and AM, respectively. Validation with known CLA free fatty acid and triacylglycerol standards confirmed that AM resulted in conversion of cis-9 trans-11 to trans-9 trans-11, and also elevated trans-10 cis-12 whilst BM of triacylglycerol CLA did not isomerise cis-9 trans-11 and was comparable to FBM.