Plasma Methionine Concentrations Research Articles

Comparison of the effects of taurine and methionine supplementation on the nitrogen metabolism of beef steers elucidated through plasma metabolome profiling

The objectives of the experiment were to compare the effects of rumen-protected taurine (RPT) and rumen-protected methionine (RPM) on the nitrogen (N) metabolism, plasma biochemical parameters, and metabolomics in beef steers and to clarify whether taurine plays similar roles as methionine (Met) in improving the regulation of N metabolism in beef steers. Six Simmental steers aged 12 months (liveweight 325 ± 7 kg) were used as experimental animals. The experimental treatments included a basal diet, the basal diet + 70.0 g/d RPT and the basal diet + 74.2 g/d RPM. The treatments were assigned in a replicated 3 × 3 Latin square design. Each experimental period included 15 d of adaptation and 5 d of sampling. The results showed that supplementing the diet with RPT or RPM did not affect the apparent nutrient digestibility (P > 0.05). Supplementing the diet with RPT or RPM increased the N retention (P < 0.05) and the N utilization efficiency (NUE) (P < 0.05) and decreased the urinary excretion of 3-Methylhistidine (P < 0.05) and the estimated skeletal protein degradation rate (P < 0.05). Supplementing the diet with RPT increased the plasma concentrations of taurine (P < 0.001), cysteine (P = 0.010), valine (P = 0.013) and total non-essential amino acids (NEAA) (P = 0.047) and tended to increase the plasma concentrations of essential amino acids (EAA) + NEAA (P = 0.087), but it did not affect the plasma concentrations of total EAA (P > 0.05). Supplementing the diet with RPM increased the plasma concentrations of methionine (P = 0.033), lysine (P = 0.047), cysteine (P = 0.007), leucine (P = 0.046), isoleucine (P = 0.046), valine (P = 0.034), total EAA (P = 0.028), total NEAA (P = 0.004) and EAA + NEAA (P = 0.004). The plasma metabolomics profiling revealed that supplementing the diet with RPT upregulated the plasma concentrations of taurine (P < 0.001), L-Cysteine (P = 0.004) and some amino acid (AA) analogues (P < 0.05) and RPM upregulated the plasma concentrations of Met (P = 0.021), L-Isoleucine (P = 0.036), L-Tryptophan (P = 0.006) and some AA analogues (P < 0.05). In conclusion, taurine has similar impacts to Met in improving the N retention and the NUE in beef steers. Taurine deficiency is one of the main reasons that the NUE of beef steers is low. Supplementation of the diet with taurine is beneficial to the N utilization in beef steers.

Dietary guanidinoacetic acid as arginine spare molecule for beef cows at late gestation: Effects on cow’s performance and metabolism, and offspring growth and development

We aimed to assess whether guanidinoacetic acid (GAA) affects the performance, metabolism, and placental vascularization of pregnant beef cows during late gestation as well as its impact on the offspring’s performance. Twenty-eight pregnant Brahman cows, averaging 532±15.1 kg and carrying male (n=15) and female (n=13) fetuses, were used. The basal diet consisted of 688 g/kg corn silage, 147 g/kg sugarcane bagasse, 47.7 g/kg corn, 89.6 g/kg soybean meal, 6.86 g/kg urea, and 21.2 g/kg mineral mixture (DM basis). Cows were fed the experimental diets from 180 to 270 days of gestation. The following treatments were evaluated: control (no addition of GAA) or addition of 0.2 % GAA to the total diet (DM basis). There was no effect (P≥0.37) of GAA on voluntary intake. Similarly, GAA addition did not affect (P≥0.54) cows performance variables, except for ribeye area (REA), which had a lower (P<0.01) variation compared to the initial REA in cows fed dietary GAA compared to the control group. Dietary GAA increased (P≤0.02) both serum nitric oxide and placental vascularization compared to cows fed the control diet. There was no effect (P≥0.43) of GAA on urine and serum creatine concentrations. In contrast, dietary GAA increased (P≤0.03) plasma concentration of arginine, ornithine, citrulline, and tyrosine compared to the control. Conversely, dietary GAA decreased (P<0.02) plasma methionine concentration. Dietary GAA increased AGAT activity (P<0.03) in the liver, with no differences observed (P>0.68) on GAMT activity. There was no effect (P≥0.15) of GAA on performance of the offspring. Addition of GAA in maternal diet did not affect skeletal muscle fiber number (P>0.09) and diameter (P>0.23) of the offspring. Guanidinoacetic acid decreases skeletal muscle mobilization and enhances placental vascularization of beef cows during late gestation. However, providing GAA seems to not affect the performance of the offspring.

Supplementing dietary betaine during late gestation increases plasma betaine and methionine concentrations in pregnant Merino ewes but not neonatal lambs

Supplementing dietary betaine during pregnancy has improved vigour and post-natal survival rates to day seven in twin lambs, potentially due to improvements in the circulating metabolite profile of these animals. This study determined whether maternal betaine supplementation during late gestation would increase circulating levels of betaine, creatinine and other amino acids in ewes and their newborn lambs, leading to subsequent improvements in lamb viability and growth. Twenty-five single-bearing Merino ewes received dietary betaine at either 0 (Control, CTL), 2 (Low Betaine, LB) or 4 g/day (High Betaine, HB) from day 125 of gestation (dG 125) until parturition (150.7 ± 0.6 days). Blood samples were collected from the ewes prior to feeding (0 h), and at 2, 4, 6, 8 and 24 h post-feeding on dG 125 and dG 140 prior to feeding and from the lamb within 2 h after birth. Lamb viability measures were taken at 2, 24 and 72 h and day 7 post-partum, marking (⁓30 days of age) and weaning (⁓104 days of age). Betaine supplementation at LB and HB increased plasma betaine levels at 6, 8 and 24 h post-feeding on dG 125 (P < 0.05) and tended to increase plasma betaine on dG 140 (P = 0.085). Plasma methionine levels increased at 2 and 4 h post-feeding on dG 125 relative to baseline levels (0 h) in LB ewes, yet remained unchanged in HB ewes. On dG 125, creatinine levels were higher in CTL ewes compared with betaine-supplemented ewes at 4 and 8 h post-feeding (both P < 0.05). While plasma betaine and methionine levels were unchanged in neonatal lambs, plasma concentrations of glutamine and lysine were higher (P < 0.05) in HB lambs compared to CTL and LB lambs. HB lambs tended to be heavier at marking (P = 0.057) and were heavier at weaning compared to CTL and LB lambs (P < 0.05). This study indicated that betaine supplementation increased plasma betaine and methionine levels in ewes, but not in neonatal lambs. Further research is warranted to determine whether higher levels of betaine supplementation increase neonatal concentrations.

Dynamics of blood Taurine concentration and its correlation with nutritional and physiological status during the fattening period of Japanese black cattle.

Taurine, biosynthesized from methionine or cysteine in the liver, plays a crucial regulatory role in bile acid conjugation, antioxidant effects, and glucose and cholesterol metabolism. This may influence the metabolic changes associated with fat accumulation in beef cattle. However, the physiological role of taurine in this species has not been fully elucidated. In this study, we explored the physiological role of taurine in Japanese Black steers (Bos taurus) in different phases during the fattening period. To examine the correlation among plasma taurine concentrations, various physiological parameters, and genes related to taurine synthesis in the liver, we used biopsied liver tissues, blood samples, and rumen fluids collected from 21 steers at three different stages, i.e., early (T1; 13 mo of age), middle (T2; 20 mo of age), and late (T3; 28 mo of age) phases. Additionally, to investigate the regulatory mechanisms underlying the expression profile of taurine synthesis genes, primary bovine hepatocytes obtained from 4-wk-old Holstein calves were treated with palmitate, oleate, acetate, propionate, or β-hydroxybutyrate (BHBA). Plasma taurine and cholesterol concentrations significantly (P < 0.001) increased in the T2 phase, which is potentially attributable to increased energy intake and assimilation induced by increased intake of concentrated feed. Cysteine-sulfinic acid decarboxylase (CSAD) expression significantly increased (P < 0.01) in T2 than in other phases. The expression levels of cysteine dioxygenase type 1 (CDO1) and cholesterol 7 alpha-hydroxylase (CYP7A1) were significantly higher (P < 0.05) in T2 than in T3; moreover, the CDO1/glutamate-cysteine ligase catalytic subunit (GCLC) ratio was higher (P < 0.05) in T2 than in T1. Plasma taurine concentrations were positively correlated with plasma methionine (r = 0.51; P < 0.05) and total cholesterol (r = 0.56; P < 0.05) concentrations at T2. Relative CDO1 mRNA expression was upregulated in cultured bovine hepatocytes treated with oleate and propionate, whereas it was downregulated upon acetate treatment. These findings indicate that the increase in plasma taurine concentrations in the T2 phase is associated with changes in lipid and methionine metabolism in Japanese Black steers.

Methionine supply during mid-gestation modulates the bovine placental mTOR pathway, nutrient transporters, and offspring birth weight in a sex-specific manner.

The mechanistic target of rapamycin (mTOR) predominantly regulates the expression and activity of placental nutrient transporters. The mTOR pathway can be activated by several nutrients, including the essential amino acid methionine. Additionally, previous research in nonruminant animals suggests that mTOR is influenced in a sexually dimorphic manner. In bovine, there is limited understanding of how maternal nutrition and offspring sexual dimorphism affect the placental transfer of nutrients. Thus, we investigated the effects of increasing the supply of dietary methionine to beef cattle heifers during mid-gestation on mTOR signaling, placental nutrient transporters, and fetal growth in male and female offspring. Forty purebred Angus heifers were used in a randomized complete block design experiment. From days 90 to 180 of gestation, heifers received a basal diet with no added methionine (CON, n = 20), or the basal diet plus 8.3g of rumen-protected methionine (MET, n = 20) per animal daily. All animals received a basal diet in the first and third trimesters of gestation. Cotyledonary tissue samples were collected at parturition and utilized to examine the mTOR pathway and nutrient transporters through protein and gene expression analysis. The offspring's body weight was measured at birth. Data were analyzed using a mixed model that included the fixed effect of treatment, offspring sex, their interactions, and the random effect of block. At day 170 of gestation, MET-supplemented heifers showed higher plasma concentrations of methionine and glutamate (P < 0.01) and lower glycine and proline levels (P ≤ 0.01) compared to the CON group. A treatment × sex interaction was observed for calf birth weight (P = 0.03). In heifers that delivered male calves, MET supplementation increased the birth weight of the calves (P < 0.01). However, the dietary treatments had no effect on the birth weight of female calves (P = 0.32). The increase in birth weight of male calves from MET-fed heifers resembles the upregulation of placental mTOR and phosphorylated mTOR (P ≤ 0.03), as well as the amino acid transporters SLC1A5, SLC7A5, SLC38A6, and SLC38A11, and the glucose transporters SLC2A1 and SLC2A8 (P ≤ 0.05). Our findings suggest that increasing the supply of methionine to beef heifers during mid-gestation can modulate placental nutrient transport and fetal growth in a sex-dependent manner and that these effects are mediated, at least in part, by the mTOR pathway.

Effects of faba bean, blue lupin and rapeseed meal supplementation on amino acid metabolism of dairy cows fed grass silage-based diets.

Information about the amino acid (AA) supply of locally produced protein supplements to dairy cow metabolism is needed to design sustainable diets for milk production. In this dairy cow experiment, grass silage and cereal-based diets supplemented with isonitrogenous amounts of rapeseed meal (RSM), faba beans (FB) and blue lupin seeds (BL) were compared with a control diet (CON) without protein supplementation. The diets were arranged as a 4×4 Latin Square using periods of 21days, and four rumen-cannulated Nordic Red dairy cows were used in the experiment. The intake of all AAs increased in response to protein supplementation and was for many individual AAs higher when RSM rather than the grain legumes FB and BL were fed. The total AA flow at the omasal canal was 3026, 3371, 3373 and 3045g/day for cows fed CON, RSM, FB and BL, respectively, but only RSM resulted in higher milk protein output. This may be explained by the higher provision of essential AA for milk protein synthesis when RSM was fed. The cows fed FB showed some positive features such as a tendency for greater omasal flow of branched-chain AA compared with BL. Overall, low plasma methionine and/or glucose concentrations in all treatments suggest that their supply was possibly limiting further production responses under the dietary conditions of the current study. It seems that the benefits of grain legume supplementation are limited when high-quality grass silage and cereal-based diets are used as the basal diet, but higher responses in amino acid supply and subsequent production responses can be expected when RSM is used.

СЕРОСОДЕРЖАЩИЕ АМИНОКИСЛОТЫ И РИСК РАЗВИТИЯ АРТЕРИАЛЬНОЙ ГИПЕРТЕНЗИИ У ДЕТЕЙ

Introduction. Currently, sulfur-containing amino acids are potential candidates as risk factors for cardiovascular disease. The purpose: to establish the role of sulfur-containing amino acids and their derivatives in the risk of developing arterial hypertension in children. Matherial and methods. 111 children aged 14 to 18 years were examined. All patients were divided into 3 groups: the 1st group (n=51) consisted of children with arterial hypertension, the 2nd group (n=30) – with high normal blood pressure, the 3rd group – 30 healthy children. The content of sulfur-containing amino acids and their derivatives in blood plasma was determined by high-performance liquid chromatography. Result. The concentration of sulfur-containing amino acids methionine, homocysteine, cysteine and cysteinylglycine in the blood plasma of children with arterial hypertension tend to increase in comparison with the group of healthy children. Pathological decrease in endothelium-dependent vasodilation accompanied by an increase in the concentration of methionine, homocysteine, cysteine, cysteinylglycine, glutathione in blood plasma and a decrease – taurine. A prognostic model has been developed based on the determination of the concentration of homocysteine and cysteinylglycine in the blood plasma of children. With a calculated value of p≥0,44, makes it possible to predict a high probability of arterial hypertension with a sensitivity of 90,2%, a specificity of 66,7% and a diagnostic efficiency of 82,1%. Conclusions. The concentration of sulfur-containing amino acids methionine, homocysteine, cysteine and cysteinylglycine in the blood plasma of children with arterial hypertension tend to increase in comparison with the group of healthy children.

In Vivo Methylation Capacity Is Not Impaired in Healthy Men during Short-Term Dietary Folate and Methyl Group Restriction

Ten healthy adult men were fed a diet low in folate and exogenous methyl groups to study the effects on in vivo methylation capability. The men were housed in a metabolic unit for the entire 108 d of the study. After a 9-d baseline period (Period 1), the men were fed a soy-product-amino acid defined diet for 45 d, which provided 25 µg/d of folate for 30 d (Period 2) and, with a folate supplement, 99 µg/d for 15 d (Period 3). During Period 2 and Period 3, the low methionine and choline diet was supplemented with methionine for half the subjects to vary the dietary methyl group intake. The periods were then repeated over the next 54 d (Periods 4–6), with a crossover of methionine intakes in Period 5 and Period 6. A 1-g oral dose of nicotinamide was given at the end of each period and methylated urine metabolites determined. Other measures related to in vivo methylation capability included urine creatinine, and plasma and urine carnitine. Even with moderate folate depletion, none of these measures was decreased by low methionine and choline intakes. Plasma methionine concentrations were unchanged throughout. Limiting exogenous methyl group intake by restricting dietary methionine and choline did not impair in vivo methylation capabilities for the variables tested, even at low folate intake.

Peptidomic Characterization and Amino Acid Availability after Intake of Casein vs. a Casein Hydrolysate in a Pig Model.

It is known that casein hydrolysis accelerates gastrointestinal transit in comparison to intact casein, although the effect of the protein hydrolysis on the composition of the digests is not fully understood. The aim of this work is to characterize, at the peptidome level, duodenal digests from pigs, as a model of human digestion, fed with micellar casein and a previously described casein hydrolysate. In addition, in parallel experiments, plasma amino acid levels were quantified. A slower transit of nitrogen to the duodenum was found when the animals received micellar casein. Duodenal digests from casein contained a wider range of peptide sizes and a higher number of peptides above five amino acids long in comparison with the digests from the hydrolysate. The peptide profile was markedly different, and although β-casomorphin-7 precursors were also found in hydrolysate samples, other opioid sequences were more abundant in the casein digests. Within the same substrate, the evolution of the peptide pattern at different time points showed minimal changes, suggesting that the protein degradation rate relies more on the gastrointestinal location than on digestion time. Higher plasma concentrations of methionine, valine, lysine and amino acid metabolites were found in animals fed with the hydrolysate at short times (<200 min). The duodenal peptide profiles were evaluated with discriminant analysis tools specific for peptidomics to identify sequence differences between both substrates that can be used for future human physiological and metabolic studies.

Differential expression of cystathionine beta synthase in adolescents with Down syndrome: impact on adiposity.

Obesity is more prevalent among people with Down Syndrome (DS) compared to general population. In this pilot study, we investigated the effect of cystathionine beta-synthase (CBS) overdosage on the regulation of transsulfuration pathway and the obesity phenotype in fifty adolescents (25 obese/overweight and 25 lean) with trisomy 21. The transcriptional levels of CBS in leukocytes and its translational levels in plasma were quantified using real time polymerase chain reaction and enzyme-linked immunosorbent assay respectively. Meanwhile, ultra performance liquid chromatography tandem mass spectrometry was used to determine the plasma concentrations of methionine, homocysteine, cystathionine and cysteine. Fasting plasma lipid profiles were assessed by colorimetric assays. The anthropometric measurements and indices of all subjects were recorded. Both DS groups had comparable levels of CBS transcripts (p = 0.2734). The plasma levels of the enzyme were significantly higher in the lean DS cases (p = 0.0174) compared to the obese/overweight participants. Total cholesterol, triglycerides, high-density lipoprotein, low-density lipoprotein, methionine, homocysteine, cystathionine and cysteine showed similar plasma levels in both groups. However, the plasma cysteine levels exceeded the normal range in all DS cases. We reported a statistically significant inverse association between CBS enzyme levels and weight (r= - 0.3498, p = 0.0128), hip circumference (r= - 0.3584, p = 0.0106), body mass index (r= - 0.3719, p = 0.0078) and body adiposity index (r= - 0.3183, p = 0.0243). Our data suggests that the high concentrations of CBS enzyme together with cysteine modulate the DS obesity presumably through increased hydrogen sulfide production which has recently showed anti-adiposity effects.

Effect of ensiled total mixed rations containing sake lees on digestion, nitrogen use, and plasma metabolite concentrations in sheep.

Sake lees are a byproduct of Japanese rice wine and used as ruminant feed with high protein and ethanol contents. This study aimed to explore the effects of ensiled total mixed ration (TMR) containing sake lees on rumen fermentation, digestion, nitrogen (N) use, and plasma metabolites in sheep. Four mature wethers were assigned to a 4 × 4 Latin square design with a factorial arrangement of ensiling treatment (non-ensiled or ensiled TMR) and types of sake lees (traditional or liquefied). Although dietary ethanol consumption was higher in sheep fed ensiled TMR, ruminal and plasma concentrations of methanol and ethanol increased after feeding in all dietary treatments, which was accompanied by the increased plasma concentrations of formate. The intake and digestion of dry matter and N were lower in sheep fed ensiled TMR than in those fed non-ensiled TMR. The plasma concentrations of most amino acids decreased in sheep fed ensiled TMR. Although plasma methionine, serine, and glycine concentrations were not altered by diet, homocysteine concentration was the highest in sheep fed ensiled TMR containing traditional sake lees. The negative impacts of ensiling treatment on N digestion and amino acid utilization should be considered for formulating ensiled TMR containing sake lees.

Longitudinal assessment of taurine and amino acid concentrations in dogs fed a green lentil diet.

A recent association between the inclusion of pulses in canine diets and taurine deficiency has become a prevalent issue in the pet food industry. Although dogs do not currently have a nutritional requirement for taurine, taurine deficiencies that do occur can result in serious health issues, such as dilated cardiomyopathy. The objective of this study was to determine the circulating concentrations of plasma and whole blood taurine, indispensable and dispensable amino acid concentrations in the plasma, and taurine and creatinine concentrations in the urine of adult dogs fed a green lentil diet. Twelve adult, intact, female beagles were randomly assigned to a diet containing 45% green lentils (GLD) or a poultry byproduct meal diet (CON) for 90 d. Fresh urine samples were collected every 30 d and analyzed for taurine and creatinine concentrations. A blood sample was also collected every 30 d and analyzed for amino acids including taurine. Animal procedures were approved by the University of Illinois Institutional Animal Care and Use Committee. All diets were formulated to meet or exceed the nutrient requirements for adult dogs at maintenance. The concentrations of taurine in the plasma and whole blood showed no differences (P > 0.05) between dietary treatments or across time points. Similarly, no differences (P > 0.05) in plasma methionine concentrations were observed between treatments or across time points. A treatment effect (P < 0.05) showed dogs fed GLD had higher total primary fecal bile acid excretion compared with dogs fed CON. The differential abundance of fecal microbial communities showed Firmicutes as the predominant phyla in dogs fed both GLD and CON, with Bacteroidaceae, Erysipelotrichaceae, and Lactobacillaceae as predominant families in dogs fed GLD. The α-diversity of dogs fed GLD (P < 0.05) was lower than in dogs fed CON. These data suggest that the inclusion of 45% green lentil in extruded diets does not lower whole blood and plasma taurine concentrations during a 90-d period and is appropriate for use in a complete and balanced formulation for dogs.

PSXIV-5 Methionine supply during mid-gestation affects offspring birth weight in a sex-dependent manner in beef cattle

Abstract In previous studies with dairy cattle, methionine supply during late-gestation enhanced cow feed intake and affected calf growth in utero and postnatally. Our objective was to investigate how methionine supply during mid-gestation, phase where the secondary myogenesis occurs, alters heifers’ plasma concentration of amino acids and offspring’ birth weight in beef cattle. Forty purebred Angus heifers were blocked by expected parturition day and blocks were balanced by sire, body weight, and body condition score. Heifers were randomly assigned to a basal diet with no added methionine (Control) or the basal diet plus a commercial source of rumen-protected methionine (Methionine). The methionine source was dosed to deliver 6 grams of metabolizable methionine daily. Heifers received the treatments from day 90 to 180 of gestation, and all heifers were pair-feed during early- and late-gestation. Heifers’ plasma samples were collected on day 180 of gestation. Data were analyzed using mixed models. The model for plasma samples included the fixed effect of treatment and the random effect of block, while the birth weight model included the fixed effect of treatment, sex, and its interaction and the random effect of block. Plasma concentrations of insulin, glucose, and urea were not affected by treatments (P ≥ 0.20). Dietary supply of methionine increased plasma concentration of methionine (P &amp;lt; 0.01), and decreased glycine and serine (P &amp;lt; 0.01). None of the other essential and non-essential amino acids were affected by treatments (P ≥ 0.12). Heifers supplemented with methionine had a greater plasma concentration of the antioxidant taurine than control heifers (P = 0.04). A treatment × sex interaction was observed for calf birth weight; methionine-fed heifers delivered heavier male calves than control-fed heifers (P = 0.03). No treatment or sex effect was observed for calf birth weight (P ≥ 0.18). Our preliminary results indicate that methionine supply during mid-gestation affects fetal growth in beef cattle in a sex-dependent manner.

Addition of dietary methionine but not dietary taurine or methyl donors/receivers to a grain-free diet increases postprandial homocysteine concentrations in adult dogs.

Grain-based ingredients are replaced in part by pulse ingredients in grain-free pet foods. Pulse ingredients are lower in methionine and cysteine, amino acid (AA) precursors to taurine synthesis in dogs. Although recent work has investigated plasma and whole blood taurine concentrations when feeding grain-free diets, supplementation of a grain-free diet with various nutrients involved in the biosynthesis of taurine has not been evaluated. This study aimed to investigate the effects of supplementing a complete grain-free dry dog food with either methionine (MET), taurine (TAU), or methyl donors (choline) and methyl receivers (creatine and carnitine; CCC) on postprandial AA concentrations. Eight healthy Beagle dogs were fed one of the three treatments or the control grain-free diet (CON) for 7 d in a 4 × 4 Latin square design. On day 7, cephalic catheters were placed and one fasted sample (0 min) and a series of nine post-meal blood samples were collected at 15, 30, 60, 90, 120, 180, 240, 300, and 360 min. Data were analyzed as repeated measures using the PROC GLIMMIX function in SAS (Version 9.4). Dogs fed MET had greater plasma and whole blood methionine concentrations from 30 to 360 min after a meal (P < 0.0001) and greater plasma homocysteine concentrations from 60 to 360 min after a meal (P < 0.0001) compared with dogs fed CON, TAU, and CCC. Dogs fed TAU had greater plasma taurine concentrations over time compared with dogs fed CON (P = 0.02) but were not different than dogs fed MET and CCC (P > 0.05). In addition, most AAs remained significantly elevated at 6 h post-meal compared with fasted samples across all treatments. Supplementation of creatine, carnitine, and choline in grain-free diets may play a role in sparing the methionine requirement without increasing homocysteine concentrations. Supplementing these nutrients could also aid in the treatment of disease that causes metabolic or oxidative stress, including cardiac disease in dogs, but future research is required.

Acute hypermethioninemia impairs redox homeostasis and acetylcholinesterase activity in the hippocampus, striatum, and cerebellum of young rats

Hypermethioninemia is characterized by high plasma concentrations of methionine (Met) and its metabolites, such as methionine sulfoxide (MetO), and neurological changes, such as cerebral edema and cognitive deficits. The aim of this study was to analyze the redox status and acetylcholinesterase (AChE) activity in the hippocampus, striatum, and cerebellum of young Wistar rats subjected to an acute hypermethioninemia protocol. The animals received, by subcutaneous injection, a single dose of Met (0.4g/kg), MetO (0.1g/kg), and Met+MetO, and 1 or 3hr after administration, the animals were euthanatized for brain structure obtaining. In the hippocampus, an increase in lipid peroxidation and glutathione peroxidase (GPx) activity was observed at 1hr in the MetO and Met+MetO groups, and a reduction in the superoxide dismutase activity was found in the Met+MetO group. Met and/or MetO induced a decrease in the thiol content and GPx activity and enhanced the lipid peroxidation at 3hr. In the striatum, a reduction in the thiol content and GPx activity, an increase in lipid peroxidation, and AChE activity were induced by Met and/or MetO at 1 or 3hr. Additionally, in the cerebellum, an increase in the AChE in the MetO and Met+MetO groups 1hr after administration was observed. These data help to better understand the pathophysiological mechanisms that underlie the neurological changes found in hypermethioninemia patients.

83 The acute effects of feeding a grain-free diet with or without methionine, taurine or methyl donor/acceptor supplementation on plasma and whole blood amino acid concentrations in dogs

Abstract Grain-free pet foods have been sold for over a decade and comprise more than 40% of dog and cat diets sold today. Grain-free diets replace grain ingredients with pulse ingredients, which are high in lysine but low in methionine and cysteine, the precursor amino acids to taurine synthesis in the dog. The objective of this study was to evaluate the postprandial response of plasma methionine and taurine and whole blood taurine concentrations of dogs fed a grain-free diet without supplementation (CON) or with methionine (MET), taurine (TAU) or creatine, carnitine and choline (CCC) supplementation. Eight Beagles were pair housed and fed one of the four experimental diets for seven days in a 4x4 Latin Square Design. On the morning of d 7, cephalic catheters were placed and one fasted sample (0 min) and nine post-meal blood samples (15, 30, 60, 90, 120, 180, 240, 300 and 360 min) were collected. Data were analyzed as repeated measures using the PROC GLIMMIX function in SAS (Version 9.4). Dogs supplemented with MET had significantly higher plasma methionine concentrations from 30 to 360 minutes post-meal compared to dogs on CON, TAU and CCC treatments (P &amp;lt; 0.05). However, no differences were observed in plasma methionine concentrations between CON, TAU and CCC treatments at any time point (P &amp;gt; 0.05). Plasma taurine concentrations were significantly higher across time points in all treatment groups compared to CON (P &amp;lt; 0.05). Whole blood taurine concentrations tended to be higher across time points in MET and TAU treatment groups compared to CCC (P = 0.0513). Overall, MET, TAU and CCC supplementation increased plasma taurine concentrations compared to CON, but only MET supplementation increased plasma methionine concentrations from 30 to 360 minutes post-meal.

Adenosine kinase deficiency: Three new cases and diagnostic value of hypermethioninemia

Adenosine kinase (ADK) deficiency is characterized by liver disease, dysmorphic features, epilepsy and developmental delay. This defect disrupts the adenosine/AMP futile cycle and interferes with the upstream methionine cycle. We report the clinical, histological and biochemical courses of three ADK children carrying two new mutations and presenting with neonatal cholestasis and neurological disorders. One of them died of liver failure whereas the other two recovered from their liver damage. As the phenotype was consistent with a mitochondrial disorder, we studied liver mitochondrial respiratory chain activities in two patients and revealed a combined defect of several complexes. In addition, we retrospectively analyzed methionine plasma concentration, a hallmark of ADK deficiency, in a cohort of children and showed that methionine level in patients with ADK deficiency was strongly increased compared with patients with other liver diseases. ADK deficiency is a cause of neonatal or early infantile liver disease that may mimic primary mitochondrial disorders. In this context, an elevation of methionine plasma levels over twice the upper limit should not be considered as a nonspecific finding. ADK deficiency induced-liver dysfunction is most often transient, but could be life-threatening.

Relative availability of metabolizable methionine from 2 ruminally protected sources of methionine fed to lactating dairy cattle

Our objective was to evaluate the lactational responses of dairy cows to methionine provided from 2 ruminally protected sources of methionine activity. Twenty-one Holstein dairy cows [11 primiparous (634 kg of body weight, 140 d in milk) and 10 second-parity (670 kg of body weight, 142 d in milk)] were assigned to a treatment sequence in 4 replicated 5 × 5 Latin squares plus 1 cow, with 14-d periods. Treatments were as follows: control; 7.5 or 15 g/d of a ruminally protected product of 2-hydoxy-4-methylthio-butyric acid (NTP-1401; Novus International Inc., St. Charles, MO); or 7.5 or 15 g/d of a ruminally protected dl-methionine product (Smartamine M; Adisseo, Alpharetta, GA). The diet was predicted to meet metabolizable protein and energy requirements. Diets contained 16.1% crude protein, and the control diet was predicted to be deficient in metabolizable methionine (1.85% of metabolizable protein) but sufficient in lysine (6.8% of metabolizable protein). Feed intake and milk yield were measured on d 11 to 14. Blood was collected on d 14. Dry matter intake, milk yield, energy-corrected milk, milk fat yield and percentage, and efficiencies of milk and energy-corrected milk yield were not affected by treatment. Milk protein percentage and milk protein yield increased linearly with supplementation, without differences between methionine sources or interactions between source and level. Linear regressions of milk protein percentage and milk protein yield against supplement amount within source led to slope ratios (NTP-1401:Smartamine M) of 95% for protein percentage and 84% for protein yield, with no differences between sources for increasing milk protein. Plasma methionine concentrations were increased linearly by methionine supplementation; the increase was greater for Smartamine M than for NTP-1401. Plasma d-methionine was increased only by Smartamine M. Plasma 2-hydoxy-4-methylthio-butyric acid was increased only by NTP-1401. Our data demonstrated that supplementation with these methionine sources can improve milk protein percentage and yield, and the 2 methionine sources did not differ in their effect on lactation performance or milk composition.

Effects of different carbohydrate sources on taurine status in healthy Beagle dogs.

This study evaluated the effects of a grain-based (GB) and grain-free (GF) diet on protein utilization and taurine status in healthy Beagle dogs. Two practical dog diets sufficient in crude protein, sulfur amino acids, and taurine content were formulated with the same ingredients with exception of the carbohydrate sources. The GB contained sorghum, millet, and spelt while potatoes, peas, and tapioca starch were used in the GF. A total of 12 Beagle dogs were used in a completely randomized design with six replicates per treatment. The study consisted of an adaptation period of 2 wk followed by an experimental period of 28 d in which GB and GF were fed to the dogs. At the end of the adaptation period and every 2 wk after it (day 0, day 14, day 28), markers of taurine metabolism were analyzed in whole blood (taurine), plasma (taurine, methionine, and cystine), urine (taurine:creatinine), and fresh fecal samples (primary and secondary bile acids). Fecal samples were collected during the last 6 d of experimental period for digestibly assessment using titanium dioxide as an external marker. Taurine markers and digestibility data were analyzed in a repeated measures model and one-way ANOVA, respectively, using PROC GLIMMIX in SAS (version 9.4). Apparent crude protein digestibility was not affected by treatment, but dogs fed GF diet had lower apparent organic matter digestibility compared with those fed GB (P < 0.05). Greater plasma taurine concentrations were observed at days 14 and 28 compared with day 0; wherein dogs fed GF exhibited greater increase compared to those fed GB (P < 0.05). Whole blood taurine concentrations, plasma methionine concentrations, and urinary taurine:creatinine were also greater at days 14 and 28 compared with day 0 (P < 0.05), but no effect of diet was observed. Total bile acid excretion was similar between GF and GB groups, but dogs fed GF excreted a higher proportion of primary bile acids compared with those fed GB (25.49% vs. 12.09% at day 28, respectively). In summary, overall taurine status was not affected by dietary treatments, however, our results suggest that the higher content of oligosaccharides and soluble fibers in the GF diet may alter the composition of the fecal bile acid pool.

Cystathionine beta synthase deficiency and brain edema associated with methionine excess under betaine supplementation: Four new cases and a review of the evidence

CBS deficient individuals undergoing betaine supplementation without sufficient dietary methionine restriction can develop severe hypermethioninemia and brain edema. Brain edema has also been observed in individuals with severe hypermethioninemia without concomitant betaine supplementation. We systematically evaluated reports from 11 published and 4 unpublished patients with CBS deficiency and from additional four cases of encephalopathy in association with elevated methionine. We conclude that, while betaine supplementation does greatly exacerbate methionine accumulation, the primary agent causing brain edema is methionine rather than betaine. Clinical signs of increased intracranial pressure have not been seen in patients with plasma methionine levels below 559 μmol/L but occurred in one patient whose levels did not knowingly exceed 972 μmol/L at the time of manifestation. While levels below 500 μmol/L can be deemed safe it appears that brain edema can develop with plasma methionine levels close to 1000 μmol/L. Patients with CBS deficiency on betaine supplementation need to be regularly monitored for concordance with their dietary plan and for plasma methionine concentrations. Recurrent methionine levels above 500 μmol/L should alert clinicians to check for clinical signs and symptoms of brain edema and review dietary methionine intake. Levels approaching 1000 μmol/L do increase the risk of complications and levels exceeding 1000 μmol/L, despite best dietetic efforts, should be acutely addressed by reducing the prescribed betaine dose.