Impairments in pyridoxine-dependent sulphur amino acid metabolism are highly sensitive to the degree of vitamin B6 deficiency and repletion in the pig

Methionine and cysteine oxidation are regulated in a dose dependent manner by dietary Cys intake in neonatal piglets receiving enteral nutrition

Methionine (Met) is an indispensable amino acid (AA) in piglets. Met can synthesize cysteine (Cys), and Cys has the ability to reduce the Met requirement by 40% in piglets. However, whether this sparing effect on Met is facilitated by downregulation of Cys synthesis has not been shown. This study investigated the effects of graded levels of Cys on Met and Cys oxidation, and on plasma AA concentrations. Piglets (n = 32) received a complete elemental diet via gastric catheters prior to being randomly assigned to one of the eight dietary Cys levels (0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.40, 0.50 g kg-1d-1) with an adequate Met concentration (0.25g kg-1d-1). Constant infusion of L-[1-14C]-Met and L-[1-14C]-Cys were performed for 6 h on d 6 and d 8 to determine Met and Cys oxidation, respectively. Met oxidation decreased as Cys intake increased (P<0.05). At higher Cys intakes (0.15 to 0.5g kg-1d-1), Met oxidation decreased (P<0.05) at a slower rate. Cys oxidation was similar (P>0.05) among dietary Cys intakes; however, a significant polynomial relationship was observed between Cys oxidation and intake (P<0.05, R2 = 0.12). Plasma Met concentrations increased (P<0.05) linearly with increasing levels of dietary Cys, while plasma Cys concentrations changed (P<0.05) in a cubic manner and the highest concentrations occurred at the highest intake levels. Increasing dietary levels of Cys resulted in a reduction in Met oxidation until the requirement for the total sulfur AA was met, indicating the sparing capacity by Cys of Met occurs through inhibition of the transsulfuration pathway in neonatal piglets.

Flaxseed Increases Animal Lifespan and Reduces Ovarian Cancer Severity by Toxically Augmenting One-Carbon Metabolism

We used an LC-MS/MS metabolomics approach to investigate one-carbon metabolism in the plasma of flaxseed-fed White Leghorn laying hens (aged 3.5 years). In our study, dietary flaxseed (via the activity of a vitamin B6 antagonist known as "1-amino d-proline") induced at least 15-fold elevated plasma cystathionine. Surprisingly, plasma homocysteine (Hcy) was stable in flaxseed-fed hens despite such highly elevated cystathionine. To explain stable Hcy, our data suggest accelerated Hcy remethylation via BHMT and MS-B12. Also supporting accelerated Hcy remethylation, we observed elevated S-adenosylmethionine (SAM), an elevated SAM:SAH ratio, and elevated methylthioadenosine (MTA), in flaxseed-fed hens. These results suggest that flaxseed increases SAM biosynthesis and possibly increases polyamine biosynthesis. The following endpoint phenotypes were observed in hens consuming flaxseed: decreased physiological aging, increased empirical lifespan, 9-14% reduced body mass, and improved liver function. Overall, we suggest that flaxseed can protect women from ovarian tumor metastasis by decreasing omental adiposity. We also propose that flaxseed protects cancer patients from cancer-associated cachexia by enhancing liver function.

Actinobacillus utilizes a binding protein-dependent ABC transporter to acquire the active form of vitamin B6

Bacteria require high-efficiency uptake systems to survive and proliferate in nutrient-limiting environments, such as those found in host organisms. ABC transporters in the bacterial plasma membrane provide a mechanism for transport of many substrates. In this study, we examine an operon containing a periplasmic binding protein in Actinobacillus for its potential role in nutrient acquisition. The electron density map of 1.76 Å resolution obtained from the crystal structure of the periplasmic binding protein was best fit with a molecular model containing a pyridoxal-5'-phosphate (P5P/pyridoxal phosphate/the active form of vitamin B6) ligand within the protein's binding site. The identity of the P5P bound to this periplasmic binding protein was verified by isothermal titration calorimetry, microscale thermophoresis, and mass spectrometry, leading us to name the protein P5PA and the operon P5PAB. To illustrate the functional utility of this uptake system, we introduced the P5PAB operon from Actinobacillus pleuropneumoniae into an Escherichia coli K-12 strain that was devoid of a key enzyme required for P5P synthesis. The growth of this strain at low levels of P5P supports the functional role of this operon in P5P uptake. This is the first report of a dedicated P5P bacterial uptake system, but through bioinformatics, we discovered homologs mainly within pathogenic representatives of the Pasteurellaceae family, suggesting that this operon exists more widely outside the Actinobacillus genus.

Cyst(e)ine fortification in low crude protein diet improves growth performance of broilers by modulating serum metabolite profile

This study was aimed to explore the metabolomical mechanisms for the potentially ameliorative effect of cyst(e)ine (Cys) fortification on growth performance of broilers fed low crude protein (CP) diet. A total of 432 1-d-old broilers were randomly divided into 6 groups, each of which received one of the following diets: normal-CP diet (positive control, PC), low-CP diet (negative control, NC), NC diet fortified with 0.05%, 0.1%, 0.15% or 0.2% of Cys. Samples were collected on d 42. Results showed that increasing Cys fortification quadratically elevated (P < 0.05) the accumulative growth performance and leg muscle yield of broilers fed NC diet, with 0.1% being the optimal dose. Thus, samples from PC, NC and NC plus 0.1% Cys (NCC) groups were selected for further analysis. Both dietary CP reduction and fortification of 0.1% Cys in NC diet caused complex changes (P < 0.05) in serum amino acids and some other metabolites primarily involved in lipid metabolism. Multiple lipogenesis-related pathways were regulated (P < 0.05) following Cys fortification in NC diet, which could at least partially interpret the benefit of Cys fortification in NC diet on broiler performance. In conclusion, fortifying low-CP diet with 0.1% Cys promoted the growth performance of broilers probably through modulating serum metabolite profile.

The combination of nutraceuticals and functional feeds as additives modulates gut microbiota and blood markers associated with immune response and health in weanling piglets

This study aimed to evaluate the effects of a combination of feed additives with complementary functional properties on the intestinal microbiota, homocysteine, and vitamins E and B status as well as systemic immune response of weanling piglets. At weaning, 32 litters were assigned to one of the following dietary treatments (DT): 1) conventional diet (CTRL); 2) CTRL diet supplemented with antibiotics (ATB); 3) a cocktail of feed additives containing cranberry extract, encapsulated carvacrol, yeast-derived products, and extra vitamins A, D, E, and B complex (CKTL); or 4) CKTL diet with bovine colostrum in replacement of plasma proteins (CKTL + COL). Within each litter, the piglets with lowest and highest birth weights (LBW and HBW, respectively) and two piglets of medium birth weight (MBW) were identified. The MBW piglets were euthanized at 42 d of age in order to characterize the ileal and colonic microbiota. Blood samples were also collected at weaning and at 42 d of age from LBW and HBW piglets to measure insulin-like growth factor-1 (IGF-1), cysteine, homocysteine, and vitamins E, B₆, and B₁₂, and to characterize the leukocyte populations. At 42 d of age, cytokine production by stimulated peripheral blood mononuclear cells was also measured. In a second experiment, piglets were reared under commercial conditions to evaluate the effects of the DT on the growth performance. At the indicator species analysis, the highest indicator value (IV) for Succinivibrio dextrinosolvens was found in the CKTL group, whereas the highest IV for Lactobacillus reuteri and Faecalibacterium prausnitzii was evidenced in the CKTL + COL group (P < 0.05). Compared with the other DT, CTRL piglets had higher concentrations of homocysteine, whereas the CKTL and CKTL + COL supplementations increased the concentrations of vitamins E and B₁₂ (P < 0.05). DT had no effect on IGF-1 concentration and on blood leukocytes populations; however, compared with HBW piglets, LBW animals had lower values of IGF-1, whereas the percentages of γδ T lymphocytes and T helper were decreased and increased, respectively (P < 0.05). CKTL + COL also improved the growth performance of piglets reared under commercial conditions (P < 0.05). This study highlights the impact of birth weight on piglet systemic immune defenses and the potential of weaning diet supplemented with feed additives and bovine colostrum to modulate the homocysteine metabolism and the intestinal microbiota.

Substitution of Dietary Sulfur Amino Acids by DL-2-hydroxy-4-Methylthiobutyric Acid Increases Remethylation and Decreases Transsulfuration in Weaned Piglets

BACKGROUND

DL-2-hydroxy-4-methylthiobutyric acid (DL-HMTBA), an L-methionine (L-Met) hydroxyl analogue, has been suggested to be a dietary L-Met source. How dietary DL-HMTBA compared with L-Met affects whole-body L-Met kinetics in growing individuals is unknown.

OBJECTIVES

We determined to what extent DL-HMTBA supplementation of an L-Met-deficient diet affects whole-body L-Met and L-cysteine (L-Cys) kinetics, protein synthesis (PS), and the L-Met incorporation rate in liver protein (L-MetInc) compared with L-Met and DL-Met supplementation in a piglet model.

METHODS

Forty-five, 28-d-old weaned piglets (male, German Landrace) were allocated to 4 dietary groups: L-Met-deficient diet [Control: 69% of recommended L-Met plus L-Cys supply; 0.22% standardized ileal digestible (SID) L-Met; 0.27% SID L-Cys; n = 12] and Control diet supplemented equimolarly to 100% of recommended intake with either L-Met (n = 12; LMET), DL-Met (n = 11; DLMET), or DL-HMTBA (n = 10; DLHMTBA). At 47 d of age, the piglets were infused with L-[1-13C; methyl-2H3]-Met and [3,3-2H2]-Cys to determine the kinetics and PS rates. Plasma amino acid (AA) concentrations, hepatic mRNA abundances of L-Met cycle and transsulfuration (TS) enzymes, and L-MetInc were measured.

RESULTS

During feed deprivation, L-Met kinetics did not differ between groups, and were ≤3 times higher in the fed state (P < 0.01). Remethylation (RM) was 31% and 45% higher in DLHMTBA than in DLMET and Control pigs, respectively, and the RM:transmethylation (TM) ratio was 50% higher in DLHMTBA than in LMET (P < 0.05). Furthermore, TS and the TS:TM ratio were 32% lower in DLHMTBA than in LMET (P < 0.05). L-MetInc was 42% lower in DLMET and DLHMTBA than in L-Met-deficient Control pigs, whereas plasma AA and hepatic mRNA abundances were similar among DL-HMTBA-, L-Met-, and DL-Met-supplemented pigs.

CONCLUSIONS

In piglets, DL-HMTBA compared with L-Met and DL-Met supplementation increases RM and reduces the TS rate to conserve L-Met, but all 3 Met isomers support growth at a comparable rate.

A Vitamin B-6 Antagonist from Flaxseed Perturbs Amino Acid Metabolism in Moderately Vitamin B-6-Deficient Male Rats

BACKGROUND

Pyridoxal 5'-phosphate (PLP) plays a crucial role as a cofactor in amino acid metabolism. There is a prevalence of moderate vitamin B-6 deficiency in the population that may be exacerbated through the ingestion of 1-amino d-proline (1ADP), a vitamin B-6 antagonist found in flaxseed.

OBJECTIVE

Given prior evidence of the impact of synthetic 1ADP on indexes of pyridoxine metabolism, the current study was designed to investigate the effects of 1ADP derived from flaxseed on amino acid metabolism in moderately vitamin B-6-deficient rats.

METHODS

Male weanling rats (n = 8/treatment) consumed a semipurified diet containing either 7 mg pyridoxine hydrochloride/kg diet [optimum vitamin B-6 (OB)] or 0.7 mg pyridoxine hydrochloride/kg diet [moderately vitamin B-6 deficient (MB)], each with 0 or 10 mg vitamin B-6 antagonist/kg diet, in either a synthetic form (1ADP) or as a flaxseed extract (FE), for 5 wk. At the end of the experiment, plasma vitamin B-6 and amino acid concentrations and the activities of hepatic PLP-dependent enzymes were analyzed.

RESULTS

Compared with the MB control group, plasma PLP concentrations were 26% and 69% lower, respectively, in the MB+FE and MB+1ADP rats (P ≤ 0.001). In the MB+FE group, the plasma cystathionine concentration was 100% greater and the plasma α-aminobutyric acid and glutamic acid concentrations were 59% and 30% lower, respectively, than in the MB control group. Both synthetic 1ADP and FE significantly (P < 0.001) inhibited the in vitro hepatic activities of 2 PLP-dependent enzymes, cystathionine β-synthase (up to 44%) and cystathionine γ-lyase (up to 60%), irrespective of vitamin B-6 concentrations. Because of vitamin B-6 antagonist exposure, observed perturbations in plasma biomarkers and hepatic enzyme activities were not evident or of lesser magnitude in rats consuming adequate vitamin B-6.

CONCLUSION

The current data from a rat model provide evidence that a vitamin B-6 antagonist now prevalent in the human food supply may pose challenges to individuals of moderate vitamin B-6 status.

Oral supplementations of betaine, choline, creatine and vitamin B6 and their influence on the development of homocysteinaemia in neonatal piglets

Homocysteine (Hcy) is an intermediary sulphur amino acid recognised for pro-oxidative properties in several species which may weaken immune competence in piglets. In this species, there is an acute 10-fold increase of concentrations of plasma Hcy (pHcy) during the first 2 weeks of life. The present experiment aimed to determine if pHcy in piglets can be regulated by oral supplementations of betaine as a methyl group supplier, creatine for reducing the demand for methyl groups, choline with both previous functions and vitamin B₆ as enzymic co-factor for Hcy catabolism. A total of seventeen sows (second parity) were fed gestation and lactation diets supplemented with folic acid (10 mg/kg) and vitamin B₁₂ (150 µg/kg). Eight piglets in each litter received daily one of the eight following oral treatments (mg/kg body weight): (1) control (saline); (2) betaine (50); (3) choline (70); (4) creatine (300); (5) pyridoxine (0·2); (6) treatments 2 and 5; (7) treatments 3 and 4; and (8) treatments 2, 3, 4 and 5. According to age, pHcy increased sharply from 2·48 µm at birth to 17·96 µm at 21 d of age (P < 0·01). Concentrations of pHcy tended to be lower (P = 0·09) in treated than in control piglets but the highest and sole pairwise significant decrease (23 %) was observed between treatments 1 and 8 (P = 0·03). Growth from birth to 21 d of age was not influenced by treatments (P > 0·70). Therefore, it appears possible to reduce pHcy concentrations in suckling piglets but a combination of all chosen nutrients is required.

Investigation of vitamin B₆ inadequacy, induced by exposure to the anti-B₆ factor 1-amino D-proline, on plasma lipophilic metabolites of rats: a metabolomics approach

PURPOSE

Vitamin B6 status in the body is affected by several factors including dietary supply of the antivitamin B6 factor, 1-amino D-proline (1ADP), which is present in flaxseed. Owing to the prevalence of moderate B6 deficiency in the general population, a co-occurrence of 1ADP may lead to a further deterioration of B6 status. To this end, we applied a nontargeted metabolomics approach to identify potential plasma lipophilic biomarkers of deleterious effect of 1ADP on moderately vitamin B6-deficient rats using a high-performance liquid chromatography/quadrupole time-of-flight mass spectrometry.

METHODS

Twenty-four rats were fed with a semi-purified diet containing pyridoxine·HCl (PN·HCl) either 7 mg/kg diet (optimal B6) or 0.7 mg/kg diet (moderate B6). The rats were divided into four treatments (n = 6), and one treatment in each B6 diet group was also fed ad libitum with 10 mg/kg diet of synthetic 1ADP. After 5 weeks of study, plasma was collected from the rats and lipophilic metabolites were extracted using acetonitrile as a solvent for analysis.

RESULTS

Ten potential plasma lipophilic biomarkers were identified out of >2500 detected entities, which showed significant differences between the treatments. Plasma glycocholic acid, glycoursodeoxycholic acid, murocholic acid, N-docosahexaenoyl GABA, N-arachidonoyl GABA, lumula, nandrolone and orthothymotinic acid concentrations were significantly elevated, while plasma cystamine and 3-methyleneoxindole concentrations were significantly reduced as a result of either low B6 status or 1ADP or their interaction.

CONCLUSION

Changes in these metabolites revealed a potential defect in pathways linked with the biosynthesis and metabolism of bile acid components, N-acyl amino acids, analgesic androgens, anti-inflammatory and neuroprotective molecules. We also noted that the changes in these biomarkers can be alleviated by the application of adequate vitamin B6.

Oral exposure to the anti-pyridoxine compound 1-amino D-proline further perturbs homocysteine metabolism through the transsulfuration pathway in moderately vitamin B₆ deficient rats

Pyridoxal 5'-phosphate (PLP; a B₆ vitamer) serves as an important cofactor in a myriad of metabolic reactions, including the transsulfuration (TS) pathway, which converts homocysteine (Hcy) to cysteine. While overt vitamin B₆ deficiency is rare, moderate deficiency is common and may be exacerbated by anti-pyridoxine factors in the food supply. To this end, we developed a model of moderate B₆ deficiency and a study was conducted to examine the in vivo effect of 1-amino D-proline (1ADP), an anti-pyridoxine factor found in flaxseed, on indices of Hcy metabolism through the TS pathway in moderately B₆ deficient rats. Male weaning rats received a semi-purified diet containing either 7 mg/kg (control; CD) or 0.7 mg/kg (moderately deficient; MD) diet of pyridoxine·hydrochloride (PN∙HCl), each with 1 of 4 levels of 1ADP, viz. 0, 0.1, 1 and 10 mg/kg diet for 5 weeks. Perturbations in vitamin B₆ biomarkers were more pronounced in the MD group. Plasma PLP was significantly reduced, while plasma Hcy (8-fold) and cystathionine (11-fold) were increased in rats consuming the highest amount of 1ADP in the MD group. The activities of hepatic cystathionine β-synthase and cystathionine γ-lyase enzymes were significantly reduced in rats consuming the highest 1ADP compared to the lowest, for both levels of PN∙HCl. Dilation of hepatic central veins and sinusoids, mild steatosis and increased liver triglycerides were present in MD rats consuming the highest 1ADP level. The current data provide evidence that the consumption of an anti-pyridoxine factor linked to flaxseed may pose a risk for subjects who are moderate/severe vitamin B₆ deficient.

Effects of pyridoxine on growth performance and plasma aminotransferases and homocysteine of white pekin ducks

A dose-response experiment with seven supplemental pyridoxine levels (0, 0.66, 1.32, 1.98, 2.64, 3.30, and 3.96 mg/kg) was conducted to investigate the effects of pyridoxine on growth performance and plasma aminotransferases and homocysteine of White Pekin ducks and to estimate pyridoxine requirement for these birds. A total of 336 one-day-old male White Pekin ducks were divided to 7 experimental treatments and each treatment contained 8 replicate pens with 6 birds per pen. Ducks were reared in raised wire-floor pens from hatch to 28 d of age. At 28 d of age, the weight gain, feed intake, feed/gain, and the aspartate aminotransferase, alanine aminotransferase, and homocysteine in plasma of ducks from each pen were all measured. In our study, the pyridoxine deficiency of ducks was characterized by growth depression, decreasing plasma aspartate aminotransferase activity and increasing plasma homocysteine. The ducks fed vitamin B₆-deficient basal diets had the worst weight gain and feed/gain among all birds and this growth depression was alleviated (p<0.05) when pyridoxine was supplemented to basal diets. On the other hand, plasma aspartate aminotransferase and homocysteine may be the sensitive indicators for vitamin B₆ status of ducks. The ducks fed basal diets had much lower aspartate aminotransferase activity and higher homocysteine level in plasma compared with other birds fed pyridoxine-supplemented diets (p<0.05). According to quadratic regression, the supplemental pyridoxine requirements of Pekin ducks from hatch to 28 days of age was 2.44 mg/kg for feed/gain and 2.08 mg/kg for plasma aspartate aminotransferase and the corresponding total requirements of this vitamin for these two criteria were 4.37 and 4.01 mg/kg when the pyridoxine concentration of basal diets was included, respectively. All data suggested that pyridoxine deficiency could cause growth retardation in ducks and the deficiency of this vitamin could be indicated by decreasing plasma aspartate aminotransferase activity and increasing plasma homocysteine.