Utilization of milk fatty acids by the suckling Iberian piglets

A total of 16 pure-bred Iberian (IB) sows, all of them suckling six piglets, were used, eight of them in each of the two consecutive trials (1 and 2). Daily milk yield and composition were determined weekly over a 34-day lactation period. Within each litter, one piglet at birth and four piglets on day 35 of life were slaughtered. Milk intake per piglet tended to be greater in trial 2 (832 v. 893 g/day; P=0.066), but piglets grew at 168±3.3 g/day, irrespective of the trial. In the IB sow milk, the linoleic (LA) : linolenic (LNA) acid ratio averaged 14.6 and 15.2 in trial 1 and trial 2, respectively. A fivefold increase in piglet body fat content was observed over lactation (P<0.001). Most of this fat (81.4%) was present in the carcass. After 34 days of lactation, whole-body relative content of palmitic, palmitoleic, stearic and oleic acids were very close to those in the milk consumed, suggesting direct deposition. Daily deposition of LA derivatives and of LNA and its derivatives was found to be extremely low (<0.02 g, on average). Moreover, some of the arachidonic acid (ARA) in tissues of the IB piglet at birth disappeared throughout the lactating period. An overall fractional deposition for total fatty acids (FA) was 0.409. Fractional oxidation (disappearance) rates were 0.939 and 0.926 for n-6 and n-3 polyunsaturated FA. The overall rate of disappearance for the major non-essential FA (myristic, palmitic, palmitoleic, stearic and oleic acids), estimated as 1−the overall fractional deposition rate, was 0.546. It is concluded that the high degree of FA unsaturation, high oxidation rate of LA and LNA, and poor synthesis of ARA from LA and of docosahexaenoic acid from LNA found in the suckling piglet might increase the energy cost of whole-body fat accretion, a contributor to the observed low efficiency of use of milk energy for growth.     

Polyunsaturated fatty acids in maternal plasma and in breast milk

In order to explain processes underlying the transfer of fatty acids from the maternal compartment into human milk, the lipid content and the fatty acid composition of maternal plasma and milk have been analyzed in breastfeeding mothers at 1 day and 3 months of lactation.The rise in milk lipids occurring during the study period was concomitant with a fall in plasma total fat content, mainly due to the decrease of triglycerides. Significant correlations between plasma and milk fatty acids at the two time points were observed only for linoleic (LA, 18:2 n-6) and (alpha;-linolenic acid (alpha LNA, 18:3 n-3), while for arachidonic (AA, 20:4 n-6) and docosahexaenoic acid (DHA, 22:6 n-3) correlations were found only at one day and 3 months, respectively.These data suggest that levels of the n-6 and n-3 18C polyunsaturated fatty acids in milk are closely dependent on their concentrations in maternal plasma, in turn related with the dietary intake, while the accumulation of AA and DHA in milk is the result of a sequence of transfer and metabolic processes.     

Natural milk fatty acids affect survival and invasiveness of Listeria monocytogenes

The effects of 12 fatty acids, naturally occurring in milk from several mammalian species, on the survival and invasion ability of Listeria monocytogenes , a food-borne pathogen, were determined. The survival was tested in the presence of 200 μg ml⁻¹ fatty acids suspended in brain hearth infusion broth or in storage conditioning solution (NaCl 1%) of Mozzarella cheese, an Italian soft unripened cheese, at pH 7·0 or 5·0. Lauric (C12:0), linoleic (C18:2) and linolenic (C18:3) acids exerted the strongest bactericidal activity. The invasive efficiency of L. monocytogenes , determined in the Caco-2 enterocyte-like cell line, was strongly decreased in the presence of the fatty acids tested (from about 20 to 500-fold). This research suggests that naturally occurring fatty acids of milk, supplemented in milk derivatives, could affect both bacterial growth and invasiveness and consequently, could serve as barriers towards L. monocytogenes infection.     

Interaction of fatty acids with beta-lactoglobulin and albumin from ruminant milk

beta-Lactoglobulin isolated from milk of cow, sheep, and goat had about 0.5 mol of fatty acids bound per mol of monomer protein. Fatty acids, mainly palmitic and oleic acids, were the major components (about 75% of total lipids). Albumin isolated from the same samples had about 4.5 mol of fatty acids bound per mol of protein. These two proteins were the only whey proteins able to bind labeled fatty acids in vitro. Interaction of beta-lactoglobulin and albumin with insolubilized fatty acids showed some differences, suggesting different structures of the respective fatty acid binding sites.     

Nutritional status and intermediate chain-length fatty acids influence the conservation of essential fatty acids in the milk of northern Nigerian women

The milk of 89 women in northern Nigeria was analyzed for the fatty acid composition of the total milk lipids, and assessed for the effect nutritional status has on the conservation of essential and non-essential fatty acids when the proportions of C(10)-C(14)fatty acids are increased. The women were stratified on the basis of their body mass index, and calculations were made to estimate the effects of a 3.3-fold increase in the proportion of C(10)-C(14)fatty acids on the proportion of alpha-linolenic acid, docosahexaenoic acid, linoleic acid and arachidonic in total milk lipids. In the well-nourished group (group III, body mass index >23 kg/m(2)), the critical n-3 and n-6 fatty acids were not conserved, while in poorly nourished women (group I, body mass index <19 kg/m(2)), marked conservation of alpha-linolenic acid, docosahexaenoic acid, arachidonic acid, and palmitic acid was seen. Poor nutritional status of the mother appears to promote selective retention of critical essential and non-essential fatty acids in the milk lipid fraction.     

Rat mammary-gland acetyl-coenzyme A carboxylase. Interaction with milk fatty acids

1. Highly purified rat mammary-gland acetyl-CoA carboxylase was inhibited by milk obtained from rats 12h after their young were weaned. 2. All the inhibitory activity was found in the particulate fraction (R(105)) obtained on centrifuging the milk. It could be extracted from milk fraction R(105) with acetone and identified as a complex mixture of non-esterified fatty acids, present in high concentration (nearly 10mm) in the milk. 3. Inhibition of acetyl-CoA carboxylase was observed at low concentrations (0.2-20mum) of several of these fatty acids when fresh fully active enzyme was used. Enzyme that had been partly inactivated by aging, or by storing in the absence of citrate, was stimulated by low concentrations but inhibited by high concentrations of fatty acids. 4. Various experiments suggested that fatty acids produce irreversible inactivation of acetyl-CoA carboxylase. 5. The effects of palmitoyl-CoA on mammary-gland acetyl-CoA carboxylase were found to resemble those of fatty acids, except that palmitoyl-CoA was effective at lower concentration. 6. The effect of milk fraction R(105) was tested on six other enzymes previously shown to decline to various extents after weaning. Although several of these enzymes were affected by unfractionated milk fraction R(105), none was significantly inhibited by the acetone extract or by low concentrations of lauric acid. 7. The findings are consistent, both qualitatively and quantitatively, with a regulatory mechanism whereby milk fatty acids shut off fatty acid synthesis in the mammary gland after weaning by inhibiting acetyl-CoA carboxylase.     

Genetic modification of essential fatty acids biosynthesis in Hansenula polymorpha

The Delta(6)-desaturase gene isoform II involved in the formation of gamma-linolenic acid (GLA) was identified from Mucor rouxii. To study the possibility of alteration of the synthetic pathway of essential fatty acids in the methylotrophic yeast, Hansenula polymorpha, the cloned gene of M. rouxii under the control of the methanol oxidase (MOX) promoter of H. polymorpha, was used for genetic modification of this yeast. Changes in flux through the n-3 and n-6 pathways in the transgenic yeast were observed. The proportion of GLA varied dramatically depending on the growth temperature and media composition. This can be explained by the effects of either substrate availability or enzymatic activity. In addition to the potential application for manipulating the fatty acid profile, this study provides an attractive model system of H. polymorpha for investigating the deviation of fatty acid metabolism in eukaryotes.     

Specific distribution of short-chain fatty acids in molecular distillates of bovine milk fat

Triglycerides with a total of 34-44 acyl carbon atoms have previously been shown to account for nearly 50% of bovine milk fat. About 80% of this material was isolated by molecular distillation and a representative fraction of these glycerides was subjected to a stereospecific analysis. Of the 29 moles % of C(4)-C(8) fatty acids present in the analyzed fraction, at least 95% were specifically attached to the glycerol molecule in the position corresponding to carbon 3 of sn-glycerol 3-(dihydrogen phosphate) (L-alpha-glycerophosphate). The distribution of the other fatty acids (C(10) or greater) did not show such marked specificity for either the 1- or the 2-position. The data support the hypothesis that the short-chain fatty acids are esterified with long-chain diglycerides, or are substituted in glycerophosphatide intermediates, during the final step in the biosynthesis of milk fat triglycerides.     

Transfer of fatty acids from female seal blubber via milk to pup blubber

Fatty acids were determined by gas chromatography followed by principal component analysis (PCA) and soft independent modelling of class analogy (SIMCA) in the blubber of 18 female grey seals, Halichoerus grypus, in their milk and in the blubber of their 1-week-old nursing pups. Large individual differences were observed in both blubber and milk content of fatty acids. The fatty acid composition of the milk was systematically different from the composition in maternal blubber, with higher relative amounts of the saturated acids, the monounsaturated with 20 carbon atoms and the n3 polyunsaturated, except 18:3n3. The composition of the fatty acids in the blubber of the pups was different from that of the milk. The same fatty acids that were enriched in the milk were depleted in the blubber of the pups. Therefore the fatty acid composition in the blubber of the pups was similar to that in the adults, although not identical. The results from this investigation imply that the composition of the fatty acids in the blubber of female seals and in the blubber of their pups cannot be determined directly by analysis of fatty acid composition of milk. Accepted: 16 February 2000     

Impact of maternal dietary n-3 and n-6 fatty acids on milk medium-chain fatty acids and the implications for neonatal liver metabolism

Levels of n-6, n-3, and medium-chain fatty acids (MCFA) in milk are highly variable. Higher carbohydrate intakes are associated with increased mammary gland MCFA synthesis, but the role of unsaturated fatty acids for milk MCFA secretion is unclear. This study addressed whether n-6 and n-3 fatty acids, which are known to inhibit hepatic fatty acid synthesis, influence MCFA in rat and human milk and the implications of varying MCFA, n-6, and n-3 fatty acids in rat milk for metabolic regulation in the neonatal liver. Rats were fed a low-fat diet or one of six higher-fat diets, varying in 16:0, 18:1n-9, 18:2n-6, 18:3n-3, and long-chain (LC) n-3 fatty acids. Higher maternal dietary 18:2n-6 or 18:3n-3 did not influence milk MCFA, but lower maternal plasma triglycerides, due to either a low-fat or a high-fat high-LC n-3 diet led to higher milk MCFA. MCFA levels were inversely associated with 18:1n-9, 18:2n-6, and 18:3n-3 in human milk, likely reflecting the association between dietary total fat and unsaturated fatty acids. High LC n-3 fatty acid in rat milk was associated with lower hepatic Pklr, Acly, Fasn, and Scd1 and higher Hmgcs2 in the milk-fed rat neonate, with no effect of milk 18:1n-9, 18:2n-6, or MCFA. These studies show that the dietary fatty acid composition does not impact MCFA secretion in milk, but the fatty acid composition of milk, particularly the LC n-3 fatty acid, is relevant to hepatic metabolic regulation in the milk-fed neonate.     

Genetic loci associated with circulating levels of very long-chain saturated fatty acids

Very long-chain saturated fatty acids (VLSFAs) are saturated fatty acids with 20 or more carbons. In contrast to the more abundant saturated fatty acids, such as palmitic acid, there is growing evidence that circulating VLSFAs may have beneficial biological properties. Whether genetic factors influence circulating levels of VLSFAs is not known. We investigated the association of common genetic variation with plasma phospholipid/erythrocyte levels of three VLSFAs by performing genome-wide association studies in seven population-based cohorts comprising 10,129 subjects of European ancestry. We observed associations of circulating VLSFA concentrations with common variants in two genes, serine palmitoyl-transferase long-chain base subunit 3 (SPTLC3), a gene involved in the rate-limiting step of de novo sphingolipid synthesis, and ceramide synthase 4 (CERS4). The SPTLC3 variant at rs680379 was associated with higher arachidic acid (20:0 , P = 5.81 × 10⁻¹³). The CERS4 variant at rs2100944 was associated with higher levels of 20:0 (P = 2.65 × 10⁻⁴⁰) and in analyses that adjusted for 20:0, with lower levels of behenic acid (P = 4.22 × 10⁻²⁶) and lignoceric acid (P = 3.20 × 10⁻²¹). These novel associations suggest an inter-relationship of circulating VLSFAs and sphingolipid synthesis.     

Exploring causal networks of bovine milk fatty acids in a multivariate mixed model context

Background

Knowledge regarding causal relationships among traits is important to understand complex biological systems. Structural equation models (SEM) can be used to quantify the causal relations between traits, which allow prediction of outcomes to interventions applied to such a network. Such models are fitted conditionally on a causal structure among traits, represented by a directed acyclic graph and an Inductive Causation (IC) algorithm can be used to search for causal structures. The aim of this study was to explore the space of causal structures involving bovine milk fatty acids and to select a network supported by data as the structure of a SEM.

Results

The IC algorithm adapted to mixed models settings was applied to study 14 correlated bovine milk fatty acids, resulting in an undirected network. The undirected pathway from C4:0 to C12:0 resembled the de novo synthesis pathway of short and medium chain saturated fatty acids. By using prior knowledge, directions were assigned to that part of the network and the resulting structure was used to fit a SEM that led to structural coefficients ranging from 0.85 to 1.05. The deviance information criterion indicated that the SEM was more plausible than the multi-trait model.

Conclusions

The IC algorithm output pointed towards causal relations between the studied traits. This changed the focus from marginal associations between traits to direct relationships, thus towards relationships that may result in changes when external interventions are applied. The causal structure can give more insight into underlying mechanisms and the SEM can predict conditional changes due to such interventions.     

Diurnal variation of milk fatty acids in early-lactation Holstein cows with and without hyperketonemia

Estimates of milk constituents by Fourier-transform mid-infrared (FTIR) analysis have been shown to be a useful tool in monitoring energy deficit in early-lactation dairy cows. Our objectives were to describe the diurnal variation in milk fatty acids (FAs) and estimate the association of hyperketonemia with concentrations and diurnal patterns of FTIR estimates of milk FA. Blood samples were collected via jugular catheters bihourly for 5 d from multiparous Holstein cows (n = 28) enrolled between 3 and 9 days in milk. Milk samples were collected thrice daily at 0600, 1400, and 2200 h for d 2, 3, and 4 of the study period. Cows were retrospectively classified as hyperketonemic (HYK; n = 13) or non-HYK (n = 15) based on blood beta-hydroxybutyrate (bBHB) concentrations analyzed during the study period. Cows were classified as HYK if bBHB was ≥ 1.2 mmol/l for ≥ 50% (22/44) of bihourly timepoints; cows were classified as non-HYK if bBHB was ≥ 1.2 mmol/l for < 50% of bihourly timepoints. The HYK cows had bBHB ≥ 1.2 mmol/l for 31.4 ± 6.8 timepoints while the non-HYK cows had bBHB ≥ 1.2 mmol/l for 8.0 ± 3.9 timepoints. We used generalized linear mixed models to analyze concentrations of milk FA over time and differences between HYK groups. The relative percentage of de novo, mixed, and preformed FAs all followed diurnal patterns, however only the yield of preformed FA diurnally cycled, reaching a nadir at 0600 h and peaking at 1400 h. The yield per milking of preformed FA was also greater in the HYK cows than in the non-HYK cows. Oleic acid in milk followed a similar diurnal pattern to the yield of preformed FA, likely driving the cyclical nature of preformed FA. Finally, stearic acid was greater in HYK cows. Our results suggest that FTIR estimates of milk FA offer the potential to provide insight on the energy status of early-lactation cows, and when interested in understanding the absolute concentrations and yields of milk FA, diurnal variation should be considered.     

Intraspecies variability of cellular fatty acids among soil and intestinal strains of Desulfovibrio desulfuricans.

A comparison of cellular fatty acid profiles of Desulfovibrio desulfuricans DSM 642 and 14 wild strains of this species, isolated from two completely different environments, soil and the human intestine, was carried out. All the D. desulfuricans strains grown on lactate and sulfate indicated the presence of considerable amounts of i-C15:0, i-C17:1 and C16:0. Although differences in the quantities of individual fatty acids present in each strain were clear in the group of soil strains (similarity, 67.6%), in contrast to almost identical fatty acid patterns (similarity, near 100%) in the intestinal strains, the results were variable within the limits acceptable for species demonstration. The higher similarity of the fatty acid profiles of intestinal strains may be a result of the similarity of biocenoses in the human digestive tract. The coefficients of variability of i-C17:1 and i-C15:0 (the major branched-chain fatty acids), as well as clustering of the investigated strains compared with strains described in the literature after plotting percentages of i-C17:1 fatty acid against i-C15:0 fatty acid, confirmed a certain heterogeneity of cellular fatty acid profiles within the group of soil strains, in contrast to almost ideal homogeneity within the group of intestinal isolates. Intestinal strains contained a higher ratio of saturated to unsaturated fatty acids (2.2 +/- 0.14) than did soil strains (1.6 +/- 0.2; in one case, 2.7). We propose that intestinal D. desulfovibrio bacteria should be assumed to be a highly homogeneous group and should be represented by the strain D. desulfuricans subsp. intestinus in collections of microbial cultures.