Utilization of methylmalonate for the synthesis of branched-chain fatty acids by preparations of chicken liver and sheep adipose tissue

Methylmalonic acid in aging and disease

Metabolic byproducts have conventionally been disregarded as waste products without functions. In this opinion article, we bring to light the multifaceted role of methylmalonic acid (MMA), a byproduct of the propionate metabolism pathway mostly commonly known as a clinical biomarker of vitamin B12 deficiency. MMA is normally present at low levels in the body, but increased levels can come from different sources, such as vitamin B12 deficiency, genetic mutations in enzymes related to the propionate pathway, the gut microbiota, and aggressive cancers. Here, we describe the diverse metabolic and signaling functions of MMA and discuss the consequences of increased MMA levels, such as during the aging process, for several age-related human pathologies.

Changes of Metabolites and Gene Expression under Different Feeding Systems Associated with Lipid Metabolism in Lamb Meat

The effects of the different feeding systems, graze feeding (GSF), time-limited graze feeding (GF), and stall-feeding (SF)) on the fatty acid content, metabolites, and genes expression of the longissimus dorsi (LD) in Tan lambs were investigated in the present study. Thirty-nine 4-month-old male Tan lambs with similar body weight (24.91 ± 1.74 kg) were selected and divided into the three feeding systems (n = 13) randomly. Lambs were slaughtered after 83 days of the feeding trails, and LD muscle samples were collected for further analysis. The results indicated that different feeding systems have no significant effect on short-chain fatty acids in Tan lambs (p > 0.05). However, the total saturated fatty acids (∑SFA) and monounsaturated fatty acids (∑MUFA) in the GSF and GF groups were lower than those in the SF group (p < 0.001). The total polyunsaturated fatty acids (∑PUFA) in the GSF group were higher than those in the GF and SF groups (p < 0.001). Moreover, in the comparison of both GF vs GSF groups and SF vs GSF groups, metabolomic analysis showed that metabolites such as cis-(6,9,12)-linolenic acid, arachidic acid, acetylcarnitine, and L-carnitine with lower concentration were significantly enriched in the biosynthesis of unsaturated fatty acid pathway (p < 0.05), but metabolites such as phosphorylcholine, glycerophosphocholine, cytidine 5'-diphosphocholine, and glycerol-3-phosphate with higher concentrations were enriched in the glycerophospholipid metabolism pathway. KEGG (Kyoto Encyclopedia of Genes and Genomes) analysis of the results indicated that in the comparison of the GSF group with the SF group, differentially expressed genes (DEGs) such as LIPC, ERFE, FABP3, PLA2R1, LDLR, and SLC10A6, were enriched in the steroid biosynthesis and cholesterol metabolism pathways. In addition, differential metabolites and genes showed a significant correlation with the content of ∑SFA, ∑MUFA, and ∑PUFA in lamb meat (p < 0.05). These findings demonstrated that the feeding system was an important factor in regulating fatty acid content by affecting lipid-metabolism-related metabolites and gene expression in muscle, and graze-feeding system provided lamb meat with higher ∑PUFA content than time-limited-grazing and stall-feeding systems.

Alteration of fatty acid profile of milk in Holstein cows fed Bacillus coagulans as probiotic: a field study

BACKGROUND

Probiotics may improve milk quality and the general health status of animals.

AIMS

The effects of dietary Bacillus coagulans PRM101 on milk components, milk fatty acids (FA), and some health indicators of dairy cows were investigated.

METHODS

The probiotic was added to the feed of 12 Holstein cows (2 g/cow: 2 × 1011 CFU/cow) for 63 days compared to a control group fed on the basal ration (n=11). Milk and blood samples were taken on days 0, 21, 42, and 63.

RESULTS

The yields of milk and energy corrected milk (ECM; computed from milk weight and its fat and protein content) decreased linearly and similarly (P=0.60) in both groups. The treatment cows, however, showed quadratic increases in the weights of milk (P=0.03) and ECM (P=0.04) at d42 of the study. Energy corrected milk (d42, P<0.05) and crude protein content of milk (d42, P<0.05; d63, P<0.1) were higher in the cows receiving the probiotic. The proportions of heptadecanoic (C17:0; P=0.002) and linoleic (C18:2; P=0.077) acids in milk fat (g/100 g fat) were higher in the treatment cows on d63. Milk total antioxidant capacity (TAC), malondialdehyde (MDA), and similarly, amyloid A (AA) and haptoglobin (Hp) of milk and blood were not affected. Total antioxidant capacity and MDA were negatively correlated in the control group (r=-0.669, P=0.005). Heptadecanoic acid correlated negatively with milk MDA (r=-0.611, P=0.035) and positively (r=0.591, P=0.043) with serum Hp in the treatment cows.

CONCLUSION

Dietary B. coagulans PRM101 may improve the proportions of C17:0 and C18:2 FA in milk. Some improvements in milk protein and the health status of the cows may also be anticipated.

NMR-metabolomics profiling of mammary gland secretory tissue and milk serum in two goat breeds with different levels of tolerance to seasonal weight loss

Goats are of special importance in the Mediterranean and tropical regions for producing a variety of dairy products. The scarcity of pastures during the dry season leads to seasonal weight loss (SWL), which affects milk production. In this work, we studied the effect of feed-restriction on two dairy goat breeds, with different tolerance levels to SWL: the Majorera breed (tolerant) and the Palmera breed (susceptible). Nuclear magnetic resonance (NMR) was used to compare the metabolome of an aqueous fraction of the mammary gland and milk serum from both breeds. Goats in mid-lactation were divided by breed, and each in two feed-regime groups: the control group and the restricted-fed group (to achieve 15-20% reduction of body weight at the end of the experiment). Milk and mammary gland samples were collected at the end of the experimental period (23rd day). (1)H NMR spectra were collected from the aqueous extract of the mammary gland biopsies and the milk serum. Profiling analysis has led to the identification of 46 metabolites in the aqueous extract of the mammary gland. Lactose, glutamate, glycine and lactate were found to be the most abundant. Analysis of milk serum allowed the identification of 50 metabolites, the most abundant being lactose, citrate and creatine. Significant differences were observed, in mammary gland biopsies and milk serum, between control and restricted-fed groups in both breeds, albeit with no differences between the breeds. Variations seem to be related to metabolism adaptation to the low-energy diet and are indicative of breed-specific microflora. Milk serum showed more metabolites varying between control and restricted groups, than the mammary gland. The Majorera breed also showed more variations than the Palmera breed in milk samples, which could be an indication of a prompt adaptation to SWL by the Majorera breed.

Characterization of the fatty acid composition of lamb commercially available in northern Spain: Emphasis on the trans-18:1 and CLA content and profile

A survey of commercially available lamb meat was performed in northern Spain in order to evaluate their fatty acid (FA) composition with emphasis on trans fatty acid (TFA) and conjugated linoleic acid (CLA) isomers. Samples were collected in spring (n=24) and winter (n=24) of 2013, and were obtained in about equal numbers from grocery stores and butcher-shops. Subcutaneous fat, known to be a sensitive indicator of TFA content in ruminants, was analyzed by GC-FID. In general, very few differences were observed between collection periods and type of stores because of the high variability within the groups that was believed to be associated with differences in genetics and feeding strategies. However, the 10t/11t ratio of all samples showed two clearly identifiable groups irrespective of the source: 1) when 10t/11t was >1, 10t-shifted samples; 2) when 10t/11t was ≤1, non-shifted samples where 11t-18:1 was the predominant isomer. These two groups were clearly identified and associated with distinct FAs using principal component analysis.

Fatty Acid Composition of Muscle, Adipose Tissue and Liver from Muskoxen (Ovibos moschatus) Living in West Greenland

Information about lipid content and fatty acid (FA) composition of muskoxen (Ovibos moschatos) edible tissues is very limited in comparison to other meat sources. Thus, this work aims to present the first in-depth characterization of the FA profile of meat, subcutaneous adipose tissue and liver of muskoxen living in West Greenland. Furthermore, we aim to evaluate the effect of sex in the FA composition of these edible tissues. Samples from muscle (Longissimus dorsi), subcutaneous adipose tissue and liver were collected from female and male muskoxen, which were delivered at the butchery in Kangerlussuaq (West Greenland) during the winter hunting season. The lipid content of muscle, adipose tissue and liver averaged 284, 846 and 173 mg/g of dry tissue, respectively. This large lipid contents confirms that in late winter, when forage availability is scarce, muskoxen from West Greenland still have high fat reserves, demonstrating that they are well adapted to seasonal feed restriction. A detailed characterization of FA and dimethylacetal composition of muskoxen muscle, subcutaneous adipose tissue and liver showed that there are little differences on FA composition between sexes. Nevertheless, the 18:1cis-9 was the most abundant FA in muscle and adipose tissue, reaching 43% of total FA in muscle. The high content of 18:1cis-9 suggests that it can be selectively stored in muskoxen tissues. Regarding the nutritional composition of muskoxen edible tissues, they are not a good source of polyunsaturated FA; however, they may contribute to a higher fat intake. Information about the FA composition of muskoxen meat and liver is scarce, so this work can contribute to the characterization of the nutritional fat properties of muskoxen edible tissues and can be also useful to update food composition databases.

Does the fat tailed Damara ovine breed have a distinct lipid metabolism leading to a high concentration of branched chain fatty acids in tissues?

Fat tailed sheep breeds are known for their adaptation to nutritional stress, among other harsh production conditions. Damara sheep, native to Southern Africa, have recently been exported to other areas of the world, particularly Australia, aiming to produce lamb in semi-arid regions. Damaras have a unique hanging fat tail, a fat depot able to be mobilized under nutritional stress. In this article we perform an in-depth characterization of the fatty acid profiles of the fat tail in underfed and control Damara rams. Profiles were very similar between experimental groups, with the exception of palmitic acid (16:0) that was lower (P = 0.014) in underfed animals. However, the most striking result was the very high proportions of non-terminal branched chain fatty acids found in the fat tail adipose tissue, as well as the gastrocnemius muscle of Damara rams. The muscle of Dorper and Merino rams used in the same experiment did not present non-terminal branched chain fatty acids, suggesting that Damara rams have a unique lipid metabolism. Herein, we interpret this trait relating it to a higher ability of Damara sheep to digest fibrous fodder and to putative differences in the propionate metabolism by comparison to other sheep breeds.

Effect of dietary saponins from Quillaja saponaria L. on fatty acid composition and cholesterol content in muscle Longissimus dorsi of lambs

The purpose of this study was to evaluate the effects of increasing levels of saponins from Quillaja saponaria on fatty acid (FA) composition and cholesterol content in muscle Longissimus dorsi of lambs. A total of 24 Barbarine lambs were assigned to four dietary treatments: control diet (C) consisting of oat hay ad libitum and 400 g of concentrate (80% barley, 17.5% soybean meal and 2.5% vitamin and mineral supplement); C diet plus 30 ppm of Q. saponaria L. (QS30); C diet plus 60 ppm of Quillaja (QS60); C diet plus 90 ppm of Quillaja (QS90). Saponin supplementation reduced the concentration of C14:1 cis-9 (P = 0.001) and of its desaturation index (P = 0.002). None of the FA intermediates of ruminal biohydrogenation (BH) was affected by Quillaja saponin supplementation (P > 0.05). The concentration of C20:4n-6 was higher in the meat of animals receiving 60 ppm of Quillaja than C and QS30 groups. Supplementing 60 ppm of Quillaja reduced the ratio between α-linolenic and linoleic acids compared with the C group (P = 0.023). We did not find any significant effect of Quillaja saponins on muscle cholesterol level. Further investigations are necessary to assess the metabolic fate of saponins in the rumen and to understand whether there is an effect of saponin on Δ9-desaturase enzyme activity, ruminal BH and cholesterol metabolism in ruminants. Supplementing up to 90 ppm of Quillaja saponins did not produce detrimental effects on the overall meat FA profile.

The effect of maternal linseed supplementation and/or lamb linseed supplementation on muscle and subcutaneous adipose tissue fatty acid composition of indoor lambs

Eighty eight lambs were used in a 2×2 factorial arrangement 1) to investigate the effect of maternal dietary linseed supplementation and/or lamb linseed supplemented concentrate on growth performance, carcass fat quality and fatty acid (FA) composition of muscle and dorsal adipose tissue of indoor lambs 2) to study the relationships between subcutaneous fat quality and FA composition. Feeding linseed to ewes increased C18:3 n-3 (ALA) proportion in milk and therefore the ALA supply to suckling lambs. However, ALA and n-3 polyunsaturated FA (n-3 PUFA) proportions in lamb tissues were not affected. Feeding linseed to lambs during the post-weaning period significantly increased the proportions of ALA and n-3 PUFA in tissues. Softer and more colored fat was associated with a decrease in even medium-chain saturated FA and increases in odd and methyl FA proportions but not with ALA proportion in subcutaneous adipose tissue.

Utilization of extruded linseed to modify fatty composition of intensively-reared lamb meat: effect of associated cereals (wheat vs. corn) and linoleic acid content of the diet

Sixty male lambs were used in two trials to study the efficiency of transfer and elongation of linolenic acid (ALA) in muscle and caudal adipose tissue and to assess factors affecting this process and related changes in fatty acid (FA) profile. In experiment 1, lambs were fed a control diet or extruded linseed (L) diet either with wheat (W, rapid starch) or corn (C, slow starch). In experiment 2, lambs were fed L with "normal" rapeseed, or high-oleic rapeseed, or soybean. In experiment 1, L increased ALA proportion and total n-3 PUFA in muscle and adipose tissue. In adipose tissue but not in muscle, LC lambs had higher proportion of ALA than LW lambs. In experiment 2, increasing linoleic acid (LA) intake increased LA proportion in muscle and adipose tissue but did not modify ALA proportion. Moreover, in muscle, it did not change the desaturation and elongation processes of ALA to long-chain n-3 PUFA.

Apparent recovery of duodenal odd- and branched-chain fatty acids in milk of dairy cows

This study compared flows of odd- and branched-chain fatty acids (OBCFA) at the duodenum with corresponding yields in milk. Four mid-lactation Holstein-Friesian dairy cows were offered 4 dietary treatments, based on different ratios of ryegrass silage and concentrates (80:20, 65:35, 50:50, and 35:65 on a dry matter basis), in a 4 x 4 Latin square design experiment with 4-wk periods. Samples of milk and duodenal digesta were collected during the final week of each period and analyzed for fatty acids. Biohydrogenation of linoleic and alpha-linolenic acids (C18:2 and C18:3) was extensive for all treatments, with a tendency to be lower for C18:3 with increased concentrate feeding. The proportion of duodenal flows of these fatty acids that appeared in milk declined with increasing concentrate feeding. There was little change in the yield of OBCFA in milk in response to increasing level of concentrate inclusion and no significant relationship with the yield of microbial protein at the duodenum. The efficiency of transfer of iso C15:0 and anteiso C15:0 from the duodenum to milk was similar to that for C18:3, with a reduced proportion transferred into milk at higher flows. Yields of C15:0, C17:0, and iso C17:0 in milk were higher than duodenal flows, confirming synthesis in animal tissues.

Novel function of lipids as a pheromone from the Harderian gland of golden hamster

Sexual diversity of ADG in Harderian gland of golden hamster was demonstrated on TLC. Female ADG contained iso- and anteiso-branched acyl and alkyl components, but male ADG contained only straight chain ones, which suggested the hormonal control of the expression of acyl-CoA dehydrogenases in the catabolism of BCAA. Acyl-CoA dehydrogenases were not expressed in the absence of testosterone, and then isovaleryl-CoA, 2-methylbutyryl-CoA, and isobutyryl-CoA accumulated, and acted as primers for the synthesis of iso- and anteiso-branched fatty acids. The incorporation of [U-(14)C] leucine into lipids was monitored by TLC. The cholesterol fraction was labeled in males but not in female, which means that cholesterol was not produced from BCAA in female gland due to the lack of expression of acyl-CoA dehydrogenases. We monitored the behavior of male hamsters toward female gland lipids, and found slightly greater attractiveness in female ones than that in male ones although the difference was not significant. Considering the lifestyle of golden hamster in nature, we propose a hypothesis that the lipids from the Harderian gland of golden hamster serve as a pheromone to declare their territory and to seek the mate with good congeniality.

Effects of dietaryn-3 polyunsaturated fatty acids, breed and dietary vitamin E on the fatty acids of lamb muscle, liver and adipose tissue

The effect of feedingn-3 PUFA on the fatty acid composition of muscle, adipose tissue and liver of lambs was investigated. Groups of eight ram lambs per breed, Suffolk×Lleyn (24kg live weight) and Scottish Blackface (18kg live weight), were each fed one of six diets containing one of three fat sources (50g fatty acids/kg DM; Megalac® (calcium soap of palm fatty acid distillate; Volac Ltd, Royston, Herts., UK) and formaldehyde-treated whole linseed (Trouw Nutrition UK, Northwich, Ches., UK) either alone or with fish oil (1:1, w/w) and either 100 or 500mg α-tocopheryl acetate/kg DM. Feed was offeredad libitumuntil slaughter at approximately half breed mature live weight. The type of dietary fat had no effect on intake, growth rate or feed conversion ratio. The 3·0-fold higher concentration of 18:3n-3 in the linseed compared with the Megalac® diet approximately doubled (P<0·001) the concentration in the neutral and polar lipid fractions of musculus semimembranosus and liver, and in adipose tissue it increased 2·5-fold. Feeding protected linseed also increased (P<0·001) concentrations of 20:5n-3 and 22:5n-3 in muscle polar lipids and both lipid fractions of liver. The linseed–fish oil raised the 20:5n-3 concentrations above those for the linseed diet and also increased 22:6n-3. Scottish Blackface lambs had lower concentrations of 18:3n-3 in all lipids compared with Suffolk x Lleyn lambs, but more 20:5n-3 in the polar lipids of muscle and liver. High levels of dietary vitamin E were associated with small decreases in the concentration of monounsaturated fatty acids and increases in PUFA. Linseed raised the PUFA:saturated fatty acid ratios in liver and adipose tissue but not in muscle, and improved then-6:n-3 fatty acid ratio, as did the linseed–fish oil. Different combinations of dietary fatty acids and better protection against rumen biohydrogenation are required to improve muscle PUFA:saturated fatty acids ratios.

Effects of dietary lipoic acid on plasma lipid,in vivoinsulin sensitivity, metabolic response to corticosterone andin vitrolipolysis in broiler chickens

The present study consisted of two experiments. The first experiment was conducted to determine the effects of lipoic acid (ALA; 200mg/kg) on plasma lipids and insulin sensitivity of whole-body tissue in broilers treated with or without corticosterone (5mg/kg). Chickens received these agents from 2 to 5 weeks of age in a 2×2 factorial arrangement. Thereafter, from 39 to 42d of age, insulin sensitivity was estimated using the euglycaemic and hyperinsulinaemic clamp technique. Experiment 2 examined whether ALA supplementation for 5 weeks (400mg/kg) would alter short-chain acyl-CoA concentration in the liver andin vitrolipolysis of an adipose tissue slice, in relation to noradrenaline (10μm) supplementation. In experiment 1, ALA had no effect on the corticosterone-induced negative growth performance. ALA lowered plasma glucose level (P<0·05) and, in contrast, increased triacylglycerol level (P<0·05). These responses to ALA had, however, no interrelationship with corticosterone. The rate of glucose uptake of whole-bodyP<0·05) but was not affected by noradrenaline supplementation. This study suggests that ALA stimulates the insulin sensitivity of tissues regardless of corticosterone-dependent metabolism and that the ALA-induced fatty acid metabolism of broilers differs between the liver and adipose tissue.

Effects of Dietary Protein and Starch on Intake, Milk Production, and Milk Fatty Acid Profiles of Dairy Cows Fed Corn Silage-Based Diets

Feed intake, milk production, and milk fatty acid profiles of dairy cows fed corn silage-based diets with different protein and starch concentrations were measured in a 3-period experiment in a changeover design using 12 Holstein cows. Each experimental period lasted for 3 wk. The diet fed as a total mixed ration consisted of 45% corn silage, 5% coarsely chopped wheat straw, and 50% concentrate, on a dry matter (DM) basis. The 4 treatments, formulated to be isoenergetic and to differ in concentrations of dietary crude protein (CP) and starch (DM basis), were as follows: low CP and low starch (LPLS; 14% CP and 15% starch), low CP and high starch (LPHS; 14% CP and 25% starch), high CP and low starch (HPLS; 16% CP and 15% starch), and high CP and high starch (HPHS; 16% CP and 25% starch). The LPLS treatment led to lower DM intake, milk yield, milk protein concentration, and milk lactose yield, probably due to a shortage of both rumen-degradable protein supply to rumen microbes and glucogenic nutrients to the animal. There were no differences between protein-rich diets and LPHS, suggesting that this diet satisfied the rumen-degradable protein requirements of rumen microbes and did not limit feed intake, and the increased supply of glucogenic nutrients spared AA so that the nutrient requirements of mid lactation dairy cows were met. Further increases in CP concentration increased plasma urea concentration and resulted in decreased efficiency of conversion of dietary N into milk N. Milk fatty acid profiles were affected by starch and protein supply, with starch having the largest effect. Additionally, increasing dietary starch concentration decreased the apparent transfer of dietary polyunsaturated fatty acids to milk, suggesting an increased channeling of fatty acids to adipose tissue. The results further suggest that C(15:0) and C(17:0) are synthesized de novo in animal tissues.

Ruminant fat volatiles as affected by diet. A review

Volatile compounds in meat have been widely studied for their favourable or undesirable effects on meat flavour, or for their potential use in tracing the animal feeding system. To date, the chemical mechanisms causing the appearance of volatile compounds in meat have been largely understood. Several variables are involved in the accumulation of volatiles in animal tissues and among them animal diet plays a key role. The purpose of the present review is to highlight the effects of different dietary regimes (concentrate, green grass and fat-enriched diets) on the appearance of fat volatile compounds in ruminant meat. Grain-based diets induce greater accumulations in meat of branched-chain fatty acids, some aldehydes, and lactones while meat fat from grazing animals contains high levels of phenols, terpenes, indoles and sulphur compounds. Fat-enriched diets exert their effect mainly on those volatiles which originate from polyunsaturated fatty acids. Cooking procedures have been considered for their contribution to fat volatiles in meat by reactions induced by high temperatures.

Softness and fatty acid composition of subcutaneous adipose tissue, and methylmalonic acid concentrations in the plasma of intensively reared lambs

The aim of the present work was to study the relationships between lamb growth performance, soft adipose tissue and fatty acid composition of subcutaneous adipose tissue of intensively reared lambs, and to determine if the occurrence of soft fat, and of odd numbered (Odd FA) and methyl-branched-chain fatty acids in subcutaneous adipose tissue was related to plasma concentrations of methylmalonic acid (MMA). For this purpose, a sensitive gas chromatography assay to measure low plasma concentrations of MMA was developed and validated. In all, 49 male lambs were reared from 23.6 to 41.0kg. They were fed ad libitum with hay and pelleted concentrates containing either cereals (80%, C) or sugar beet pulp (70%, BP). Plasma concentrations of MMA were measured 12 days before slaughter. Softness score and fatty acid compositions of caudal adipose tissue were determined after slaughter. At the end of the trial, 75% of the carcasses had soft adipose tissue. The occurrence of soft fat appears to be related to high metabolisable energy intake per kg body weight. Soft fat was characterised by a higher water content, a lower proportion of saturated even-numbered fatty acids and higher proportions of Odd FA and methyl-branched-chain fatty acids in caudal adipose tissue, compared to firm fat. Despite high proportions of Odd FA and branched-chain fatty acids in caudal adipose tissue, plasma concentrations of MMA were low (2.02+/-1.98&mgr;mol/l). No clear relationships between MMA concentrations and soft fat or the proportions of branched-chain fatty acids other than the Iso and Anteiso acids was observed. It was concluded that the present study does not support the hypothesis that the liver's capacity to metabolise MMA was exceeded.

Effect of dietary propionate on intake patterns and fatty acid composition of adipose tissues in lambs

The aim of the present trial was to study the effect of dietary propionate supplementation on growth performance, intake patterns and on the proportion of odd-numbered and methyl-branched chain fatty acids in internal or in subcutaneous adipose tissues. These fatty acids are responsible, in part, for abnormally soft subcutaneous adipose tissue. Eleven male lambs were fed ad libitum carbohydrate-rich diets based mainly on barley, supplemented (P diet) or not supplemented (C diet) with 5.6% DM of sodium propionate. During the trial, the intake patterns were recorded on three non-consecutive days over a 9h-period. The fatty acid compositions of four adipose tissue sites, two subcutaneous (dorsal, caudal) and two internal (omental, perirenal) were analysed. The ME intake (3.32+/-0.44Mcal per day) and average daily gain (316+/-64g per day) were not different (P>0.10) between the C and P treatments. The intake patterns of these lambs given ad libitum access to feed did not show any large meal even after the morning distribution of feed. No differences in intake patterns were observed between the two diets. The dietary propionate supplementation increased (P<0.05) the proportion of odd-numbered fatty acids (Odd FA) in both internal (increase of 0.7wt.% of total fatty acids) and subcutaneous adipose tissues (increase of 1.7% of total fatty acids). The effect of dietary propionate supplementation on branched-chain fatty acids was less conclusive although it tended to increase (P=0.09) the proportion of branched-chain fatty acids other than the iso and anteiso fatty acids (BCFAO) in dorsal adipose tissue. This experiment confirms the role of propionate as an important precursor of odd-numbered and methyl-branched chain fatty acids. Moreover, the dorsal adipose tissue seems to be the most sensitive adipose tissue to dietary increment in ruminal propionate content. A positive relationship between the mean ME intake rate measured over 8.5h and the proportions of Odd FA and BCFA in dorsal adipose tissue was shown. However, it does not appear to play a predominant role in the explanation of the individual variability in dorsal fatty acid composition.

Cobalt-vitamin B12 deficiency causes accumulation of odd-numbered, branched-chain fatty acids in the tissues of sheep

Nine 5-month-old lambs were randomly allocated to two groups and were fed on either a Co-deficient whole-barley diet (n5), or the same diet supplemented with Co (n4). The lambs were fed on their respective diets for 28 weeks. Plasma vitamin B12 concentrations fell below the lower limit of normality after 6 weeks, and plasma methylmalonic acid (MMA) concentrations rose above the upper limit of normality after 10 weeks. However, plasma MMA concentrations fell to near normal levels towards the end of the experiment suggesting that diagnosis of more severe Co deficiency based on determination of plasma MMA concentrations may be of limited value. Analysis of tissue samples collected at slaughter revealed a marked reduction in the vitamin B12 concentration and the activity of methylmalonyl-CoA mutase (EC5.4.99.2) in the tissues taken from the Co-deficient sheep, by comparison with the controls. Although tissue concentrations of MMA in the Co-deficient animals were not significantly different from those of the controls, we did detect increased concentrations of branched-chain fatty acids. This suggested that misincorporation of MMA, but not propionic acid, into fatty acids had occurred. The Co-deficient lambs did not develop any neurological signs, suggesting that accumulation of branched-chain fatty acids may not be involved in the development of neurological lesions.

Inhibition in vitro of lipogenic enzymes from bovine (Bos taurus) mammary tissue by methylmalonyl-coenzyme A and coenzyme A

Bovine mammary fatty acid synthetase was inhibited by approximately 50% by 40 microM methylmalonyl-CoA; this inhibition was competitive with respect to malonyl-CoA (apparent Ki = 11 microM). Similarly, 6.25 microM coenzyme A inhibited the synthetase by 35% and this inhibition was again competitive (apparent Ki = 1.7 microM). Apparent Km for malonyl-CoA was 29 microM. The short-chain dicarboxylic acids malonic, methylmalonic and ethylmalonic at high concentrations (160-320 microM) and ATP (5 mM) enhanced the synthetase activity by about 50% respectively; the activating effects of methylmalonic acid and ATP on the synthetase were additive. Methylmalonyl-CoA at 50 microM concentration inhibited the partially purified acetyl-CoA carboxylase uncompetitively by 10% and the propionyl-CoA carboxylase activity of the enzyme preparation competitively (apparent Ki = 21 microM) by 40%. Malonyl-CoA also inhibited the acetyl-CoA carboxylase activity competitively (apparent Ki = 7 microM) by 35% and the propionyl-CoA carboxylating activity of the preparation competitively (apparent Ki = 4 microM) by 82%. The possibility that methylmalonyl-CoA may be a causal factor in the aetiology of the low milk-fat syndrome in high yielding dairy cows is discussed.

Propionate for fatty acid synthesis by the mammary gland of the lactating goat

Isolated mammary glands of lactating goats were perfused with heparinized and oxygenated blood for 8 to 15 h. Adequate quantities of glucose, acetate, and amino acid were added to the perfusate. After addition of propionate to the perfusion blood, concentrations of odd-numbered and of monomethyl-substituted fatty acids other than those with iso and anteiso configuration increased in the milk fat. These acids seem to be synthesized de novo in the mammary gland. The increase of C17:0 concentration was weak and problematic. We suggest that propionate is acting as a precursor for monomethyl-substituted fatty acids by way of methylmalonyl-CoA. The activating effect of propionate administration upon milk fatty acid production was largest for odd-numbered followed by monomethyl-substituted fatty acids. No increase of iso acids was observed in milk fat in the propionate-infused glands whereas the increase of anteiso acids was extremely small. This agrees with the conception that iso and anteiso fatty acids are synthesized by rumen bacteria.

The effect of dietary methyl branched-chain fatty acids on aspects of hepatic lipid metabolism in the rat

1. Rats were fed to appetite on a stock laboratory diet or on diets consisting of the stock diet and in addition 50 or 200 g triolein/kg, 50 g palmitic acid/kg or 50 g/kg of a concentrate mixture of methyl branched-chain fatty acids (Me-BCFA) which had been prepared from sheep adipose triacylglycerols. 2. No differences could be detected in the delta 9-desaturase activity or fatty acid synthetase activity of liver preparations from rats which had been fed on either the stock diet, the 50 g palmitic acid/kg or the 50 and 200 g triolein/kg diet; the palmitic acid diet was therefore taken as the control diet in subsequent experiments. 3. Rats consuming the 50 g Me-BCFA/kg diet exhibited a marked reduction in the capacity of their liver microsomes for delta 9-desaturation when compared with animals receiving the control diet. The delta 6-desaturase activity also showed an inhibitory trend with the Me-BCFA diet. 4. Microsomal omega-oxidation of fatty acids, mitochondrial succinate oxidation and the activity of cytosolic fatty acid synthetase (FAS) were unaffected by the ingestion of the Me-BCFA mixture compared with the diet which included palmitic acid. 5. There were no differences in the plasma concentration of thyroxin, insulin and glucagon between animals fed on the diets containing palmitic acid or the Me-BCFA. 6. For a given concentration of fatty acids the Me-BCFA had a greater inhibitory effect when added to incubations of liver microsomes from rats fed on the standard diet than did the addition of palmitic acid. 7. The observations in vivo and in vitro strongly suggested that the Me-BCFA were having a specific inhibitory effect on the desaturation reaction.

Effects of cobalt deficiency in pregnant and post-parturient ewes and their lambs

1. Two groups of ewes were fed on a cobalt-deficient diet throughout pregnancy; one group (group A) was given the diet from the beginning of pregnancy, whilst the other (group B) received the diet for 16 weeks before mating. The ewes in group A continued to receive the diet for 12 weeks post-partum. 2. The vitamin B12 content of serum was estimated on three occasions before parturition and, for group A ewes, at 12 weeks post partum. Urinary concentration of methylmalonic acid was also determined at intervals before the lambs were born. 3. Serum values for vitamin B12 indicated that the ewes in both groups were depleted of the vitamin, though those in group B were more severely affected, as was evidenced by the high incidence of perinatal mortality among the lambs born to these ewes. Perinatal mortality appeared to be associated with abnormally-high values for urinary concentration of methylmalonic acid. 4. Analysis of liver lipids and adipose tissue triacylglycerols of some of the vitamin B12 -deprived lambs which died before, or within 1 d of, birth showed that, compared with the corresponding tissues of control lambs, these lipids contained unusually high proportions of odd-numbered fatty acids (mostly 15:0, 17:0 and 19:0). This observation is discussed in relation to the likelihood that, in vitamin B12-deprived lambs, propionate becomes available as a primer unit for fatty acid synthesis when the metabolism of its carboxylation product, methylmalonic acid, is impaired due to partial lack of a vitamin B12-containing enzyme system.

The use of clustering techniques in the elucidation or confirmation of metabolic pathways. Application to the branched-chain fatty acids present in the milk fat of lactating goats

The aim of this paper is 2-fold. (1) To propose the use of a group of mathematical techniques, called clustering, in the elucidation of complex metabolic relationships. (2) To apply clustering for the identification of related groups of saturated fatty acids having a common metabolic pathway for their biosynthesis in the milk fat of lactating goats. In this way, four groups of branched-chain fatty acids and two groups of straight-chain fatty acids are identified; the odd-numbered iso-, the even-numbered iso-, the anteiso-acids and the branched-chain fatty acids with methyl substitution in the chain, the odd-numbered straight-chain and the even-numbered straight-chain fatty acids. The long-chain fatty acids are not part of any group. The different metabolic pathways for their biosynthesis are discussed. From the results, it is concluded that clustering is indeed a potentially useful tool in the study of complex metabolic relationships.

Composition and variability of the branched-chain fatty acid fraction in the milk of goats and cows

Branched-chain fatty acids of the milk fat of goats were analyzed by high resolution gas chromatography-mass spectrometry. Iso-and anteiso-acids predominated, but a range of other monomethyl-branched components, mostly with methyl-substitution on carbons 4 and 6, was present. Analysis of the milk fat of cows revealed the presence of iso-and anteiso-fatty acid; other monomethyl-substituted fatty acids, as found in the milk fat of the goat, were virtually absent. Only a trace amount of 6-methylhexadecanoate was detected. The difference between goats and cows in the effectiveness with which these animals metabolize propionyl-CoA and methylmalonyl-CoA is discussed.

Methylmalonic acid in low-fat milk syndrome

The possible association between low-fat milk syndrome and methylmalonic acid accumulation in blood was investigated. Blood was sampled from the internal iliac artery of nine lactating dairy cows fed ad libitum roughage plus grain or high grain, restricted roughage diets. Daily milk fat percent and milk fat production were decreased 44% and 47% on the high grain, restricted roughage diet. No differences in blood methylmalonate concentrations could be detected in the cows fed the two diets. The effect of methylmalonate and its metabolic precursor, propionate, on mammary rates of fatty acid synthesis was determined with bovine mammary tissue slices. Neither of these metabolites affected acetate incorporation into fatty acids. Methylmalonate and propionate were incorporated into fatty acids at extremely low rates. Low-fat milk syndrome is not caused by accumulation of methylmalonic acid.

Mammary extraction of propionate in lactating cows

Four cows with exteriorized carotid arteries were in an intensive study of concentrations in plasma and mammary extraction of propionate. A restricted-roughage, high-grain diet produced higher arterial propionate concentrations and larger carotid-subcutaneous abdominal vein (arteriovenous) differences that the control diet. Concomitant changes in acetate, beta-hydroxybutyrate, and glucose in plasma and in fat and protein in milk were measured. Mammary arteriovenous difference in propionate was correlated negatively with milk fat percentage. However, since arterial propionate and beta-hydroxybutyrate also were correlated negatively, evidence of a direct inhibitory effect of propionate in mammary gland is equivocal.

Identification of methyl-branched fatty acids from the triacylglycerols of subcutaneous adipose tissue of lambs

A concentrate of branched chain fatty acids (as methyl esters) was prepared from the triacylglycerols of subcutaneous adipose tissue lipids of lambs receiving a carbohydrate-rich (cereal diet). This was accomplished by procedures which allowed the removal of unsaturated components by peroxidation and straight chain saturated components by urea-adduct formation. The concentrate was analyzed by high resolution gas chromatography in combination with mass spectrometry and was shown to consist of a complex mixture of saturated methyl-substituted fatty acids. Methyl substitution occurred on even-numbered carbon atoms (relative to the carboxyl group) and the chain lengths of the acids ranged from 10 to 18 carbon atoms. Acids with one methyl substituent in the fatty acyl chain were most abundant; di-, tri- and tetramethyl-substituted acids were also present. The biosynthesis of these methyl-substituted acids is discussed briefly.

Identification of branched chain fatty acids in baboon liver lipids

A total of 26 monomethyl branched saturated fatty acids was identified in baboon liver lipids; these included a novel anteiso component with an odd number of carbon atoms in the chain (13-methylpentadecanoic acid).