Oral Amino Acid Research Articles

Use of amino acids as growth hormone-releasing agents by athletes

Specific amino acids, such as arginine, lysine and ornithine, can stimulate growth hormone (GH) release when infused intravenously or administered orally. Many individuals consume amino acids before strength training workouts, believing this practice accentuates the exercise-induced GH release, thereby promoting greater gains in muscle mass and strength. The GH response to amino acid administration has a high degree of interindividual variability and may be altered by training status, sex, age, and diet. Although parenteral administration consistently leads to increased circulating GH concentration, oral doses that are great enough to induce significant GH release are likely to cause stomach discomfort and diarrhea. During exercise, intensity is a major determinant of GH release. Although one study showed that arginine infusion can heighten the GH response to exercise, no studies found that pre-exercise oral amino acid supplementation augments GH release. Further, no appropriately conducted scientific studies found that oral supplementation with amino acids, which are capable of inducing GH release, before strength training increases muscle mass and strength to a greater extent than strength training alone. The use of specific amino acids to stimulate GH release by athletes is not recommended.

Successful treatment of hypoalbuminemic hemodialysis patients with a modified regimen of oral essential amino acids

Successful treatment of hypoalbuminemic hemodialysis patients with a modified regimen of oral essential amino acids

Amino acid challenge in patients with cirrhosis: a model for the assessment of treatments for hepatic encephalopathy

Background/Aims: To mimic episodic hepatic encephalopathy after gastrointestinal bleeding under controlled conditions, cirrhotic patients were challenged with an amino acid mixture of comparable composition to haemoglobin. Methods: Basal EEG, psychometric score (HE test), reaction times and venous blood ammonia were recorded. Following a 54 or 108 gm oral amino acid challenge, blood ammonia levels and EEG were recorded at 30-min intervals, and psychometric testing was repeated at 180 min. Ten controls (57±2) and 31 cirrhotics (52±2) of which 21 were Child's grade A or B and 10 grade C underwent the challenge. Nine had a transjugular intrahepatic porta-systemic shunt in situ. Results: Seventeen patients had abnormal baseline HE scores. Basal blood ammonia and reaction time A were significantly greater in patients (52±5 μmol/l and 478±20 ms, respectively) than controls (19±2 μmol/l and 372±14 ms) ( P<0.001 ). Following the challenge, in patients with advanced liver disease (Child's grade B and C) the slowing of reaction time A (+85±38 and +71±31 ms, respectively; P<0.03 ) and EEG (ratio of slow to fast wave activity +0.31±0.12 and +0.58±0.19; P<0.02 ) were significantly greater than in controls (−3.3±8 ms and 0.00±0.03, respectively). Patients with an abnormal basal HE score had the most pronounced changes (reaction time A +110±39 ms, P<0.01 , EEG +0.52±13, P<0.01 , respectively). The change in EEG ratio correlated with the dose of amino acid administered ( r=0.96 ; P<0.008 ). Conclusion: The amino acid challenge constitutes a reproducible human model of episodic, Type C hepatic encephalopathy unaffected by the complications usually encountered in clinical practice.

Effect of prolonged branched-chain amino acid supplementation on metabolic response to anaerobic exercise in standardbreds

Summary This study investigated the effect of prolonged BCAA supplementation on metabolic response to a 1600m run on treadmill in Standardbred trotters. Four trained Standardbreds were divided into two groups and assigned in a 2×2 Latin square design. Both groups were fed and exercised similarly: one group received an oral amino acids supplement (12 g leucine, 9 g isoleucine and 9 g valine) 30 minutes prior to exercise and immediately after, the other group received a placebo. The horses received the supplement 3 days per week for 5 weeks. In the last week horses performed an anaerobic exercise test on an inclined (3.5%) high-speed treadmill. The exercise consisted of a 15 minute warm-up phase immediately followed by a 1600 m run at maximal speed (heart rate > 200 beats/min). Blood samples were collected pre-exercise, after exercise and during recovery (10 min, 30 min, and 24 h), and analyzed for lactate, ammonia, total protein, urea, uric acid, creatinine, free fatty acids (FFA), creatine kinase (CK), lactate dehydrogenase (LDH), aspartate amino transferase (AST). Heart rate was continuously recorded during exercise and recovery. No statistical differences between the groups were observed for all the considered parameters. Nevertheless, BCAA supplementation resulted in a higher plasma ammonia and urea concentrations as reported in previous studies in humans and rats. These data suggest that a BCAA supplementation are not effective in enhancing performance in healthy and well-fed horses.

Oral amino acids stimulate muscle protein anabolism in the elderly despite higher first-pass splanchnic extraction

Muscle protein synthesis and breakdown and amino acid transport were measured in 7 healthy young (30 +/- 2 yr) and 8 healthy elderly (71 +/- 2 yr) volunteers in the postabsorptive state and during the oral administration of an amino acid mixture with L-[ring-(2)H(5)]phenylalanine infusion, femoral artery and vein catheterization, and muscle biopsies. Phenylalanine first-pass splanchnic extraction was measured by adding L-[ring-(13)C(6)]phenylalanine to the mixture. In the postabsorptive state, no differences in muscle amino acid kinetics were detected between young and elderly volunteers. Phenylalanine first-pass splanchnic extraction was significantly higher in the elderly (P < 0. 003) during ingestion of amino acids, but the delivery to the leg increased to the same extent in both groups. Phenylalanine transport into the muscle, muscle protein synthesis, and net balance increased significantly (P < 0.01) and similarly in both the young and the elderly. We conclude that, despite an increased splanchnic first-pass extraction, muscle protein anabolism can be stimulated by oral amino acids in the elderly as well as in the young.

Effects of oral branched-chain amino acids (BCAA) administration in the treatment of cancer anorexia

Effects of oral branched-chain amino acids (BCAA) administration in the treatment of cancer anorexia

Low-dose amino acid supplementation: no effects on serum human growth hormone and insulin in male weightlifters.

Using a double-blind, crossover protocol, we studied the possible effects of a 4-day combined L-arginine, L-ornithine, and L-lysine supplementation (each 2 g/day, divided into two daily doses) on 24-hr level of serum human growth hormone (hGH) and insulin in 11 competitive weightlifters, ages 19 to 35 yrs. Three similar daily hGH peaks, seemingly preceded by a decrease in serum insulin concentration, were found during both amino acid and placebo supplementation. Supplementation did not affect the physiological variation of serum hGH concentration (treatment and treatment x time interaction: p = 0.43-0.55). Analogously, serum insulin levels were not higher after amino acid supplementation. Therefore the ergogenic value of low-dose oral amino acid supplementation in increasing hGH or insulin secretion seems questionable.

Intravenous amino acids stimulate human gallbladder emptying and hormone release

Gallbladder stasis during prolonged total parenteral nutrition (TPN) has been documented. We have examined the effect of intravenous amino acid infusion on human gallbladder contraction and release of cholecystokinin (CCK). Five healthy adult volunteers were given amino acid infusions at different rates (65, 125, 240, and 600 mg.kg-1.h-1). The volume of the gallbladder was calculated by means of ultrasonographic measurements. Plasma samples were analyzed for CCK immunoreactivity. Gallbladder and hormone responses after intravenous amino acids were compared with responses after a fat meal, after a protein meal, and after ingestion of an oral amino acid mixture. We found that intravenous amino acids stimulated human gallbladder contraction in a dose-related manner. The mechanism of stimulation may be through the release of CCK although significant correlation was not demonstrated. The magnitude of response is similar to that seen after meal stimulation. To compare the delivery of amino acids during a standard meal and during each dose of intravenous amino acids, peripheral plasma levels of dietary amino acids were measured after a standard commercially prepared enteral supplement meal and after each dose of intravenous amino acids. Our lower doses of amino acid infused resulted in levels of circulating amino acid comparable to those after a meal. The induction of gallbladder contraction and release of CCK in human recipients of parenteral nutrition may be of value in some circumstances.

Amino acid tolerance in cirrhotic patients following oral protein and amino acid loads

Plasma amino acid and venous blood ammonia concentrations were measured in six patients with well-compensated cirrhosis and in six healthy volunteers, both in the fasting state and serially for 5 h following ingestion of 30 g mixed protein and 30 g amino acid mixture, administered on separate occasions. Mean fasting plasma concentrations of threonine, serine, proline, glycine, and of the three branched-chain amino acids, valine, isoleucine and leucine, were significantly reduced in the cirrhotic patients compared with the control subjects, while mean (+/- 1 s.d.) fasting venous blood ammonia concentrations were comparable 71.2 +/- 31.4 cf. 56.0 +/- 25.4 mumol/L. Following the oral protein and amino acid loads, increases were observed in plasma amino acid concentrations in the majority of subjects with a return to baseline values by the end of the study. Changes in the circulating concentrations of most amino acids were independent of their concentration in the oral protein and amino acid loads, and their relative distribution in the circulation varied over time. The increases in the concentrations of the three branched-chain amino acids did, however, reflect their concentrations in the two nitrogen loads and did remain constant, relative to one another, over time. There were wide intra- and inter-individual variations in plasma amino acid concentrations following protein and amino acid ingestion in both study groups, and in general no significant differences in responses were observed between them. Similarly, no significant inter-group differences were observed in the ammonia response to the two nitrogen loads. No fundamental differences exist in the ways in which patients with well-compensated cirrhosis handle oral protein or amino acid loads of the magnitude employed in the present study.

肝不全用経口アミノ酸製剤の服薬方法の検討

Oral amino acid preparations, enriched branched chain amino acids (BCAA) based on Fischer's theory have been used parenterally in hepatic failure with hepatic coma so far. Recently theoral powder form which was administered by dissolving in warm water was commercially developedand now widely used. But this preparation contains so much of bitter BCAA and haveto take it continuously over a long period that patients are suffering from the taste and largevolume of the solution prepared.We tried to test here to improve the taste of the preparation by mixing many soft drinks commercially available as the flavoring agents. As the results, bitterness of the preparation was effectively suppressed by especially tasting sour and sweet with soft drinks. Also use of tubes similar to straws for soft drinks was useful to take much volume of the solution without tasting bitter.

The effect of amino acid administration on skeletal muscle blood flow

A protein meal increases renal and splanchnic blood flow and this study was undertaken to assess the effect of amino acids on skeletal muscle blood flow. In one group of ten subjects oral water was compared with oral amino acids and in a second group intravenous saline was compared with intravenous amino acids. Oral water produced no change in muscle blood flow while oral amino acids produced a significant increase. Neither intravenous saline nor intravenous amino acids had any significant effect. It is postulated that the increase in tissue blood flow is in all instances due to glomerulopressin, a substance produced in the liver during amino acid metabolism.

A study of growth hormone release in man after oral administration of amino acids

A study was carried out in 15 male volunteers to evaluate qualitatively the secretion of growth factors following stimulation by oral amino acids. The results showed that oral administration of a combination of two amino acids (1200 mg 1-lysine plus 1200 mg 1-arginine) provoked a release of pituitary somatotropin and insulin. This phenomenon was reproducible and the growth hormone secreted in response to this stimulation had biological activity (as demonstrated by a radioreceptor assay and somatomedin induction). The effect appeared to be specific to the combination of the two amino acids; neither of the amino acids demonstrated appreciable stimulating activity when administered alone, even at the same doses.

Loss of Amino Acids during Hemodialysis: Effect of Oral Essential Amino Acid Supplementation

The aim of this study was to investigate the effect of amino acid (AA) supplementation on the loss and its time course of free AA, during hemodialysis. 2 uremic patients on regular hemodialysis received an increasing number of essential AA tablets during the dialysis. The loss and its time course of 6 essential and 7 nonessential free AA during dialysis was assayed in the dialysate. The loss per dialysis treatment of the administered essential AA increased almost proportionally with the doses of AA tablets. For the nonessential AA, no definite relationship between doses of AA tablets and losses was observed. At all levels of supplementation, methionine was retained best: 90% of the amount present in the tablets. Threonine showed the lowest retention: 15-55%.

Dietary Management of Chronic Renal Failure with Oral Amino Acids

6 patients in end-stage renal failure of varying aetiologies have been studied on low protein dietary regiments according to a P 6 formulation. All patients had part of their daily protein allowance substituted by an essential amino acid capsule also containing histidine and glutamic acid. All patients were maintained in nutritional balance as a result of the regiments prescribed. No toxic effects were noted and patient compliance was good. Our studies suggest the amino acid formulation given is safe and did not cause any fluctuations in patient plasma amino acid profiles. Our studies suggest an improved method of low protein dietary management for chronic renal failure patients together with a greater flexibility and wider range of prescribing possibilities. It is recommended that amino acid supplements according to the formula produced here constitute an improvement on currently prescribed Giovannetti regimens.

Determination of Intravenous Non-Protein Energy and Nitrogen Requirements in Growing Rats

Two experiments were conducted to estimate total non-protein energy and nitrogen requirements in growing healthy male Wistar rats nourished by parenteral nutrition. In experiment 1, non-protein energy varying from 30 to 70 kcal/day/rat were administered to animals receiving a constant dose of 80 mg nitrogen, plus vitamins and minerals. In experiment 2, nitrogen dosages varying from 0 to 280 mg N/day/rat with a constant dose of 60 kcal non-protein energy were studied. The formulation of the amino acid solution used in both experiments was based upon recommended oral amino acid requirements for growing rats. Dextrose served as the source of non-protein energy. Weight gain and nitrogen balance during a 6-day experimental period were used to determine requirements. Plasma free amino acids were also analyzed to evaluate the amino acid solution. Results indicate that under total parenteral nutrition conditions 578 to 621 mg/kg body weight3/4 nitrogen and 171 to 182 kcal/kg body weight3/4 non-protein energy are required to achieve growth of approximately 3 g/day. Inconsistent responses of plasma amino acid concentrations to the amounts infused were observed. It is suggested that the determined requirements can be applied as guidelines to research using the rat as an animal model in total parenteral nutrition.

Effect of fasting, glucose, amino acids and food intake on in vivo insulin release in the chicken.

Insulin release was studied in vivo in the chicken using the radioimmunoassay previously described (Simon, Freychet and Rosselin 1974). An orally administered glucose load (2 g/kg b.w.) stimulated insulin release and was rapidly metabolized. A prolonged fasting period (65 hr) increased both initial plasma glucose and initial plasma insulin levels and highly impaired the glucose tolerance. A fasting-impaired insulin release and/or a fasting tissue "insulin resistance" accounted for this fasting-impaired glucose tolerance. An orally administered amino acid mixture (1 g/kg b.w.) stimulated insulin release to a very low extent. The effect was however sufficient to decrease the plasma glucose level. In combination with glucose, the oral amino acid load potentiated the effect of a dose of glucose on insulin release and highly improved the glucose tolerance. This synergism was still observed with the intake of a mixed and balanced diet. Therefore, except for some characteristics observed in the chicken which are discussed, the insulin regulation and the pancreatic beta-cell function are qualitatively similar in the chicken and in mammals.

Oral Amino Acid Load Test of Protein Nutrition: Effect of Protein Quantity and Quality in the Rat

Oral Amino Acid Load Test of Protein Nutrition: Effect of Protein Quantity and Quality in the Rat

Loss of Insulin Response to Ingested Amino Acids After Jejunoileal Bypass Surgery for Morbid Obesity

Amino acid tolerance tests were performed before and after jejunoileal bypass surgery for morbid obesity to determine whether an enteric factor(s) originating in the bypassed jejunum and/or ileum potentiates the insulin response to oral nitrogen loading. Preoperatively a 30-gm. mixture of amino acids given orally evoked a larger peak insulin than an intravenous load yielding comparable plasma amino acid elevations (82 +/- 17 muU./ml versus 38 +/- 8 muU./ml., p less than 0.05). Four months after operation, basal insulin concentrations were 46 per cent (p less than 0.001) of preoperative values. After surgery the response to intravenous amino acids was preserved when expressed as percentage increase above basal. In contrast, the peak increment and the percentage increase in insulin secretion after 30-gm. oral amino acid loading was significantly blunted (p less than 0.005). A smaller amino acid load (16.5 gm.) was given preoperatively to duplicate the plasma amino acid elevations seen postoperatively with the 30-gm. mixture given by mouth. The insulin response postoperatively was still significantly lower (167 +/- 33 per cent versus 98 +/- 16 per cent, p less than 0.05). After various explanations for the diminished postoperative insulin release following oral amino acid ingestion are considered, the results are best explained by the loss of an enteric insulinotrophic factor(s) normally released by the bypassed portions of jejunum or ileum in response to ingested protein.

Effect of oral amino acid supplementation on liver disease after jejunoileal bypass for morbid obesity

Previous work in our laboratory and others suggests that protein malnutrition plays an important role in the pathogenesis of hepatic steatosis and dysfunction which characteristically appears after jejunoileal bypass for morbid obesity. Postoperative protein-calorie malnutrition is at least in part a consequence of diminished intestinal absorption of free amino acids. In an attempt to prevent liver disease, six morbidly obese patients were orally supplemented with essential amino acids for 4 months after surgery. Oral amino acid supplementation only partially influenced protein malnutrition and had no effect on deterioration of hepatic morphology and dysfunction. Although this mode of therapy appears to be ineffective in preventing postoperative liver abnormalities, other studies suggest that oral oligopeptide supplementation and parenteral administration of amino acids are beneficial. In addition to protein deificiency, other factors which may contribute to the development of liver disease are reviewed.

Diabetes mellitus in gonadal dysgenesis: studies of insulin and growth hormone secretion.

On the basis of results obtained from an oral glucose tolerance test, (OGTT), twenty patients with gonadal dysgenesis were classified as normal (N = 8) and diabetic (N = 12). The two groups of patients were further tested by a rapid intravenous glucose injection, a tolbutamide test, an insulin sensitivity test and an oral amino acid load. Fasting levels of plasma growth hormone (GH) were normal in all subjects but one. Approximately 1/3 of the GH responses during testing periods were abnormal, being either absent during hypoglycaemia or following amino acid ingestion, or paradoxically increased during hyperglycaemia. No correlation was found between the degree of carbohydrate intolerance and the levels of plasma GH. There was no gross alteration of tissue sensitivity to exogenous insulin. The beta-cell response to tolbutamide, amino acid and intravenous glucose were comparable in patients with a normal or a diabetic OGTT. In both groups, the rates of decrease of blood glucose following tolbutamide or intravenous glucose were also similar and within the normal range. During OGTT, the diabetic group had a delayed insulin release and a low insulinogenic index. It is concluded that in gonadal dysgenesis the intolerance to an oral carbohydrate load is frequently associated with, but unrelated to, anomalies of the GH secretion. In diabetic subjects, the process of insulin secretion loses its normal sensitivity to the oral glucose stimulus while remaining unaltered and similiar to that of non-diabetic subjects in response to tolbutamide, amino acid and intravenous glucose.