The effect of lecithin supplementation on plasma choline concentrations during a marathon

BACKGROUND: Previous studies have shown that plasma and urinary free choline concentrations decrease significantly during a marathon, and that these decreases may be associated with decreased performance. OBJECTIVE: In a pilot study, we sought to determine whether lecithin supplementation prior to a marathon would maintain plasma free and urinary choline concentrations and improve performance versus placebo. METHODS: 12 accomplished marathon runners, males (7) and females (5), 21 to 50 years of age were randomized to receive lecithin (4 capsules BID; PhosChol 900) or placebo beginning one day prior to the 2000 Houston-Methodist Health Care Marathon. The lecithin supplement provided approximately 1.1 g of choline on a daily basis (2.2 g total). Runners estimated finish time based on recent performance and training. Fasting, pre- and post-marathon plasma and a five-hour urine collection were analyzed for free choline and plasma for phospholipid-bound choline. Pre-race predicted, as well as the actual finish time, were recorded. RESULTS: All subjects completed the marathon. Plasma free choline decreased significantly in the placebo group and increased significantly in the lecithin group (9.6 +/- 3.6 to 7.0 +/- 3.6 nmol/mL vs. 8.0 +/- 1.2 to 11.7 +/- 3.6 nmol/mL, p = 0.001 for the delta between groups). No significant changes in plasma phospholipid-bound choline concentration were observed. There was a non-significant decrease in urine free choline in both groups. Actual finish time was 256.3 +/- 46.3 minutes for the lecithin group vs. 240.8 +/- 62.0 for the placebo group and the actual:predicted time was 1.03 +/- 0.06 (lecithin) and 1.07 +/- 0.08 (placebo), p = 0.36. CONCLUSION: Short-term lecithin supplementation prior to a marathon maintains normal plasma free choline concentration during the race, but failed to improve performance.     

Oral vitamin B12 supplementation reduces plasma total homocysteine concentration in women in India

People in India have a high prevalence of low vitamin B12 status and high plasma total homocysteine (tHcy) concentrations. In a proof of principle trial, we studied the effect of oral vitamin B12 (500 microg) and/or 100 g cooked green leafy vegetables (GLV) every alternate day in a 2x2 factorial design over a 6-week period. Forty-two non-pregnant vegetarian women (age 20-50 years) were randomly allocated to four study groups. Clinical measurements were made at the beginning and at the end of the study, and blood samples were collected before, and 2 and 6 weeks after commencement of intervention. Forty women completed the trial. Twenty-six women had low vitamin B12 status (<150 pmol/L) and 24 had hyperhomocysteinemia (>15 micromol/L). GLV supplementation did not alter plasma folate or tHcy. Vitamin B12 supplementation increased plasma vitamin B12 concentration (125 to 215 pmol/L, p <0.05) and reduced tHcy concentration (18.0 to 13.0 micromol/L, p <0.05) within first 2 weeks, both of which remained stable for the next 4 weeks. Plasma vitamin B12 and tHcy concentrations did not change in those who did not receive vitamin B12, and there was no change in plasma folate concentration in any of the groups. Blood haemoglobin concentration increased marginally within first two weeks in those women who received vitamin B12 (by 3 g/L, p <0.05) and the number of women with macrocytosis decreased from 2 to zero. There was no change in vibration sensory threshold during the period of the study. High-dose per oral vitamin B12 supplementation significantly reduced plasma tHcy within 2 weeks but did not achieve normal plasma tHcy concentration even after 6 weeks. People in India have a high prevalence of low vitamin B12 status and high plasma total homocysteine (tHcy) concentrations.     

Amino acid losses during hemodialysis with polyacrylonitrile membranes: effect of intradialytic amino acid supplementation on plasma amino acid concentrations and nutritional variables in nondiabetic patients

BACKGROUND: Malnutrition is highly prevalent in hemodialysis patients. Amino acid (AA) losses during the dialysis procedure may be a contributing factor. OBJECTIVES: The objectives of this study were 1) to prospectively evaluate AA losses and their effect on plasma AA concentrations during dialysis with polyacrylonitrile at baseline and after administration of AAs by intradialysis and 2) to investigate the effects of intradialytic AA supplementation on nutritional status. DESIGN: Seventeen stable patients without diabetes who were receiving hemodialysis were studied. In the first phase, AA losses were evaluated over 2 wk in 10 patients randomly assigned to receive AA supplementation. AA losses were analyzed during the first week without supplementation and during the second week with AA administration. In the second phase, the patients' nutritional status was investigated after 3 mo of AA supplementation and was compared with those in 7 patients not receiving AAs. RESULTS: Mean +/- SD) AA losses during a 4-h dialysis session were 12 +/- 2 g; there was a significant decrease in plasma AA concentrations (386 +/- 298 micromol/L for essential and 902 +/- 735 micromol/L for nonessential AAs). After administration of AAs, the losses increased to 28 +/- 4 g. However, this procedure produced a positive net balance of AAs (10.6 +/- 5.6 g for total AAs), preventing a reduction in plasma concentrations. After 3 mo of AA administration, there was a significant increase in protein catabolic rate and serum albumin and transferrin. This improvement occurred without any change in the dialysis dose, ruling out the possibility that an increase in dialysis efficiency played a role. CONCLUSIONS: Intradialysis adequately provides AA supplements, prevents reductions in plasma AA concentrations, and favorably affects the nutritional status of patients receiving hemodialysis.     

Tomato paste supplementation improves endothelial dynamics and reduces plasma total oxidative status in healthy subjects

Consumption of tomato products is linked to beneficial outcomes through antioxidant and anti-inflammatory mechanisms. The aim of this study was to determine whether a 14-day period of tomato paste supplementation would improve endothelial function. Nineteen volunteers (mean age, 39 ± 13 years; 8 men/11 women) were studied in a randomized (exposure sequence), single-blind (operator), crossover design. The study consisted of a supplementation arm (70 g tomato paste containing 33.3 mg of lycopene) and a control arm, during which no tomato paste was added to their regular diet. Volunteers maintained their regular diet during study arms. Two-week washout periods preceded each arm. Flow-mediated dilatation (FMD) measured by brachial artery ultrasonography was used as an estimate of endothelial function at day 1 (acute response) and day 15 (midterm response). Plasma lipid peroxides were measured with a photometric enzyme-linked immunosorbent assay as an index of total oxidative status. Tomato supplementation led to an overall FMD increase compared with the control period (P = .047 for repeated-measures 3 × 2 analysis of variance). At day 1, FMD was not significantly increased (P = .329). By day 15, tomato supplementation resulted in an increase in FMD by 3.3% ± 1.4%, whereas at the control arm, FMD declined by −0.5% ± 0.6% (P = .03); magnitudes of change are absolute FMD values. Total oxidative status decreased at the end of the supplementation period compared with baseline values (P = .038). Daily tomato paste consumption exerts a beneficial midterm but not short-term effect on endothelial function. Further studies are warranted to explore the effects of tomato paste on endothelial dilation in different age groups and comorbidities.     

Fish-oil supplementation reduces stimulation of plasma glucose fluxes during exercise in untrained males

The present study examined the effects of a 3-week fish-oil supplementation (6 g/d) on the rate of plasma glucose disappearance (Rd glucose), hepatic glucose production (HGP), carbohydrate oxidation and lipid oxidation during exercise. Six untrained males (23+/-1 years; 67.6+/-2.7 kg) performed two 90 min cycling exercise sessions at 60 % of maximal O2 output separated by 20 d. During the 20 d before the first test, they ingested 6 g olive oil/d, then 6 g fish oil/d during the 20 d before the second test. Plasma glucose fluxes and lipolysis were traced using 6,6-[(2)H2]glucose and 1,1,2,3,3-[(2)H5]glycerol respectively. Substrates oxidation was obtained from indirect calorimetry. At rest HGP and the Rd glucose were similar after olive oil and fish oil (1.83 (SE 0.05) v. 1.67 (SE 0.11) mg/kg per min). During exercise, fish oil reduced the stimulation of both the Rd glucose (5.06 (SE 0.23) v. 6.37 (SE 0.12) mg/kg per min; P<0.05) and HGP (4.88 (SE 0.24) v. 5.91 (SE 0.21) mg/kg per min; P<0.05). Fish oil also reduced glucose metabolic clearance rate (6.93 (SE 0.29) v. 8.30 (SE 0.57) ml/min). Carbohydrate oxidation tended to be less stimulated by exercise after fish oil than after olive oil (12.09 (SE 0.60) v. 13.86 (se 1.11) mg/kg per min; NS). Lipid oxidation tended to be more stimulated by exercise after fish oil (7.34 (SE 0.45) v. 6.85 (SE 0.17) mg/kg per min; NS). Glycaemia, lactataemia, insulinaemia and glucagonaemia were similarly affected by exercise after fish oil and olive oil. Lipolysis at rest was similar after fish oil and olive oil (2.92 (SE 0.42) v. 2.94 (SE 0.28) micromol/kg per min) and similarly stimulated by exercise (6.42 (SE 0.75) v. 6.77 (SE 0.72) micromol/kg per min). It is concluded that fish oil reduced the Rd glucose by 26 % by reducing glucose metabolic clearance rate, possibly by facilitating fat oxidation, and reduced HGP by 21%, possibly by a feedback mechanism.     

The effect of probiotics on respiratory infections and gastrointestinal symptoms during training in marathon runners

Heavy exercise is associated with an increased risk of upper respiratory tract infections. Strenuous exercise also causes gastrointestinal (GI) symptoms. In previous studies probiotics have reduced respiratory tract infections and GI symptoms in general populations including children, adults, and the elderly. These questions have not been studied in athletes before. The purpose of this study was to investigate the effect of probiotics on the number of healthy days, respiratory infections, and GI-symptom episodes in marathon runners in the summer. Marathon runners (N = 141) were recruited for a randomized, double-blind intervention study during which they received Lactobacillus rhamnosus GG (LGG) or placebo for a 3-mo training period. At the end of the training period the subjects took part in a marathon race, after which they were followed up for 2 wk. The mean number of healthy days was 79.0 in the LGG group and 73.4 in the placebo group (P = 0.82). There were no differences in the number of respiratory infections or GI-symptom episodes. The duration of GI-symptom episodes in the LGG group was 2.9 vs. 4.3 d in the placebo group during the training period (P = 0.35) and 1.0 vs. 2.3 d, respectively, during the 2 wk after the marathon (P = 0.046). LGG had no effect on the incidence of respiratory infections or GI-symptom episodes in marathon runners, but it seemed to shorten the duration of GI-symptom episodes.     

Biotin deficiency during total parenteral nutrition: its clinical manifestation and plasma nonesterified fatty acid level

We report a case of biotin deficiency developed in a 25-yr-old man with Crohn's disease who had been on total parenteral nutrition for more than 9 months. His cutaneous, ophthalmic, and neurologic manifestations were characteristic of this disease entity described in literature. In particular, the appearance of his face deserves to be called "biotin deficiency facies." After administration of biotin the low plasma nonesterified fatty acid level promptly returned to normal. This phenomenon may prove to serve as a convenient means for the purpose of detecting biotin deficiency.     

Effect of parenteral glutamine supplementation on plasma amino acid concentrations in extremely low-birth-weight infants

BACKGROUND: Glutamine is one of the most abundant amino acids in both plasma and human milk and may be conditionally essential in premature infants. However, glutamine is not provided by standard intravenous amino acid solutions. OBJECTIVE: We assessed the effect of parenteral glutamine supplementation on plasma amino acid concentrations in extremely low-birth-weight infants receiving parenteral nutrition (PN). DESIGN: A total of 141 infants with birth weights of 401-1000 g were randomly assigned to receive a standard intravenous amino acid solution that did not contain glutamine or an isonitrogenous amino acid solution with 20% of the total amino acids as glutamine. Blood samples were obtained just before initiation of study PN and again after the infants had received study PN (mean intake: 2.3 +/- 1.0 g amino acids x kg(-1) x d(-1)) for approximately 10 d. RESULTS: Infants randomly assigned to receive glutamine had mean plasma glutamine concentrations that increased significantly and were approximately 30% higher than those in the control group in response to PN (425 +/- 182 and 332 +/- 148 micromol/L for the glutamine and control groups, respectively). There was no significant difference between the 2 groups in the relative change in plasma glutamate concentration between the baseline and PN samples. In both groups, there were significant decreases in plasma phenylalanine and tyrosine between the baseline and PN samples; the decrease in tyrosine was greater in the group that received glutamine. CONCLUSIONS: In extremely low-birth-weight infants, parenteral glutamine supplementation can increase plasma glutamine concentrations without apparent biochemical risk. Currently available amino acid solutions are likely to be suboptimal in their supply of phenylalanine, tyrosine, or both for these infants.     

Bolus arginine supplementation affects neither muscle blood flow nor muscle protein synthesis in young men at rest or after resistance exercise

The aim of this study was to investigate the ergogenic potential of arginine on NO synthesis, muscle blood flow, and skeletal muscle protein synthesis (MPS). Eight healthy young men (22.1 ± 2.6 y, 1.79 ± 0.06 m, 76.6 ± 6.2 kg; mean ± SD) participated in 2 trials where they performed a bout of unilateral leg resistance exercise and ingested a drink containing either 10 g essential amino acids with 10 g l-arginine (ARG) or an isonitrogenous control (CON). Femoral artery blood flow of both the nonexercised and exercised leg was measured continuously using pulsed-wave Doppler ultrasound, while rates of mixed and myofibrillar MPS were determined using a primed continuous infusion of L-[ring-(13)C(6)] or L-[ring-(2)H(5)]phenylalanine. The plasma arginine concentration increased 300% during the ARG trial but not during the CON trial (P < 0.001). Plasma nitrate, nitrite, and endothelin-1, all markers of NO synthesis, did not change during either the ARG or CON trial. Plasma growth hormone increased to a greater degree after exercise in the ARG trial than CON trial (P < 0.05). Femoral artery blood flow increased 270% above basal in the exercised leg (P < 0.001) but not in the nonexercised leg, with no differences between the ARG and CON trials. Mixed and myofibrillar MPS were both greater in the exercised leg compared with the nonexercised leg (P < 0.001), but did not differ between the ARG and CON treatments. We conclude that an oral bolus (10 g) of arginine does not increase NO synthesis or muscle blood flow. Furthermore, arginine does not enhance mixed or myofibrillar MPS either at rest or after resistance exercise beyond that achieved by feeding alone.     

Urinary amino acid excretion and plasma amino acid concentration in dogs fed crystalline amino acid diets

Plasma amino acid concentrations and urinary amino acid excretion were exanined in Pointer puppies fed a crystalline amino acid diet. Amino acids accounted for only a small percentage (1.7%) of total urinary nitrogen (N). In addition, amino acid excretion accounted for a low percentage (<1%) of amino acid intake. A complete urinary amino acid profile is presented. Free amino acid concentrations in plasma were examined at 0, 45, 90, 150, 210 and 300 minutes after feeding. Both the amount of time required for an ingested amino acid to reach its highest plasma concentration and the length of time plasma amino acid concentration remained elevated depended upon the amino acid in question. These data provide useful information for determining the optimal postprandial time for bleeding dogs fed a purified diet.     

High plasma citrulline and arginine levels ensured by sustained-release citrulline supplementation in rats

ObjectiveDietary-supplemented arginine has been shown to have positive effects on cardiovascular disease, but several drawbacks exist and could potentially be avoided by using L-citrulline, since it is recycled to L-arginine. However, citrulline is very rapidly metabolized. We therefore developed a sustained-release form of citrulline and evaluated its metabolic behavior in rats.MethodsMale Sprague Dawley rats were divided into three groups: receiving “empty microcapsule” (control group), 1 g/kg/d immediate-release citrulline (IR citrulline group), or 1 g/kg/d sustained-release citrulline (SR citrulline group). Citrulline was given each day at 9 a.m. after blood samples for 9 d, and on day 10, blood samples were drawn every 4 h to study the decrease in plasma amino acid concentrations.ResultsSR citrulline led to a sustained increase in citrullinemia and argininemia compared to IR citrulline, and on day 6 argininemia was significantly (P < 0.01) higher with SR compared to IR citrulline. Moreover, argininemia was significantly higher in the SR citrulline group than in controls throughout the study and SR citrulline maintained high argininemia and citrullinemia, at least over 12 h.ConclusionThis experimental study provides a strong rationale for using this new formulation for atherosclerosis treatment.     

Chronic binge ethanol-mediated acidemia reduces availability of glutamine and related amino acids in maternal plasma of pregnant sheep

Heavy drinking during pregnancy can result in fetal alcohol syndrome (FAS), of which, fetal and postnatal growth retardation and central nervous system deficits are cardinal features. Although a number of mechanisms have been proposed, none fully account for these deficiencies. We have previously reported that maternal ethanol exposure (1.75 g/kg) results in transient acidemia in the mother and fetus. Alterations in pH are known to regulate glutamine homeostasis. Therefore, we hypothesized that chronic binge ethanol-mediated acidosis reduces glutamine concentrations in maternal plasma that result in decreases in the circulating levels of amino acids related to glutamine metabolism. Pregnant ewes were divided into three groups: ethanol (1.75 g/kg), saline control, and acidemia (inspired fractional carbon dioxide [CO₂] was manipulated to mimic the maternal arterial pH pattern created by ethanol). The experiment was conducted on three consecutive days followed by four days without treatment beginning on gestational day (GD) 109, continuing to GD 132. Plasma samples were analyzed for nutrients and metabolites using HPLC and spectrophotometric methods.Maternal plasma concentrations of glutamate increased (58%), whereas glutamine, citrulline, and arginine decreased (between 14 and 53%) in response to an acute challenge after the chronic exposure in ethanol-treated ewes. No differences in these amino acid concentrations were noted between the ethanol and acidemic group subjects. Maternal plasma lactate levels increased by ∼100% in response to ethanol, whereas glucose and urea levels did not change in any group. We conclude that maternal chronic binge ethanol consumption results in acidosis-mediated reductions in circulating levels of glutamine and related amino acids that could be responsible for neuronal deficits, altered fetal growth, development, and programming. We also speculate that the consequent increase in fetal glutamate during critical periods of brain development may contribute to the pathogenesis of FAS.     

Amino acid metabolism during total parenteral nutrition in healthy volunteers: evaluation of a new amino acid solution

The aim of this study was to determine the metabolism and the tolerance of a new amino acid (AA) solution administered under conditions mimicking cyclical parenteral nutrition (PN) in humans. Eight healthy volunteers received peripheral PN for 10 h providing 10.5 mg N x kg(-1) x h(-1) and 2.0 kcal x kg(-1) x h(-1) (glucose-to-lipids ratio: 70/30%). For adaptation, a non-protein energy intake was increased progressively for 90 min; thereafter, AA infusion was started and maintained at a constant rate for 10 h. Plasma and urine concentrations of all the AAs were measured before, during and after the PN. For each given AA, the relation between plasma variations at the steady-state and infusion rate, plasma clearance (Cl), renal clearance (Clr), re-absorption rate (Reab) and, retention rate (Reten) were determined. The nitrogen balance (DeltaN) was calculated during the PN period. The results are presented as means+/-sem. All plasma AA concentrations decreased during the starting period of non-protein energy intake. The plasma AA concentrations reached a steady-state within 3 h upon AA infusion, except for glycine and lysine (6 h). At the steady state, the plasma concentrations of the infused AAs were closely correlated to their infusion rate (y= -18.3+1.5x, r(2)=0.92). The plasma glutamine concentration was maintained during the PN, which indicates that the solution might stimulate the de novo synthesis of this AA. When the PN was stopped, plasma levels of the AAs decreased, most of them returning to their basal levels, or significantly below for lysine (P<0.05), alanine (P<0.05), proline (P<0.01) and glutamine (P<0.05). No volunteer showed any adverse effect during the infusion period. DeltaN was: 0.8+/-0.5 gN/10 h. Metabolic characteristics for essential AAs were: Cl<0.5 l min(-1), Clr <1.5 ml x min(-1) Reab >or= 99%, Reten >or=99% and for non-essential AAs: Cl <0.6 l x min(-1) except aspartate (2.8+/-0.3 l x min(-1)), Clr < 3 ml x min(-1) except glycine (6.8+/-0.7), aspartate (8.2+/-3.5) and histidine (8.8+/-1.3); Reab >or= 98% except glycine (95+/-1), aspartate (94+/-2) and histidine (94+/-1), Reten >or=97% except histidine (94+/-1), glycine (95+/-3). These results indicate that in healthy subjects, the amounts of AAs provided by the new solution were well balanced for an intravenous administration, and so were well utilized without excessive urinary excretion. The present study provides useful metabolic parameters for a further evaluation in disease.     

Effects of addition of arginine, cystine, and glycine to the bovine milk-simulated amino acid mixture on the level of plasma and liver cholesterol in rats

The effects of the addition of varying levels of arginine (Arg), cystine (Cys), and glycine (Gly) to the bovine milk-simulated amino acid mixture on the levels of plasma and liver cholesterol were investigated in rats. The diets containing a high amount of Cys lowered significantly the level of plasma cholesterol as the amount of Cys in diets increased. The serum high density lipoprotein (HDL)-cholesterol level and fecal excretion of acidic steroids were higher in rats fed the Cys diets than in those fed the Arg and Gly diets. No differences, however, was observed in the content of liver cholesterol. Liver triglyceride contents elevated significantly on feeding the Arg and Cys diets. Furthermore, liver phospholipid contents elevated significantly on feeding the Arg diet but lowered on feeding the Cys diet. Therefore, these results indicated that the feeding of a high amount of Cys lowers the plasma cholesterol levels as the result of the enhanced conversion of cholesterol to bile acids.     

Changes in muscle and plasma amino acid metabolism in severe malnutrition--the influence of total parenteral nutrition

The concentrations of free amino acids in muscle and plasma were determined in nine female patients with severe anorexia nervosa before and after 3 to 5 weeks of total parenteral nutrition (TPN). The patients had lost 25 to 42% of their pre-morbid weight. During TPN their weight gain was around 2.5 kg/week. Initially total non-essential amino acids (NEAA) in muscle were decreased 30% compared to controls. The major part of this depletion was due to a 40% reduction in glutamine. After TPN the level of glutamine normalized. Alanine, being normal before TPN, decreased after TPN. Proline and several other non-essential amino acids in muscle were decreased before and after TPN. Total essential amino acids (EAA) in muscle were initially normal and were not significantly affected by TPN. Total NEAA in plasma were decreased at admission and normalized after TPN. Total EAA in plasma, however, were normal both before and after TPN. This study demonstrates that severely malnourished patients with anorexia nervosa have changes in amino acid patterns in both muscle and plasma. These changes were largely, though not completely, reversed after 3 to 5 weeks of TPN.