Effect Of Intravenous Amino Acids Research Articles

Effects of Intravenous Amino Acids on Anesthesia-Induced Hypothermia in Ovariectomized Rats

A decrease in core temperature during general anesthesia is attenuated by infusion of an intravenous amino acid mixture. The purpose of the present study was to investigate the influence of physical and endocrine changes caused by ovariectomy on the inhibitory effect of amino acid infusion on anesthesia-induced hypothermia. Sprague-Dawley female rats were divided into a sham-operated (Sham) group and an ovariectomized (OVX) group. Saline solution or an amino acid mixture solution was infused for 180 min during sevoflurane anesthesia, and the rectal temperature was measured (4 groups). Intraperitoneal white adipose tissue mass, bilateral gastrocnemius weight and plasma insulin levels were measured. In the Sham rats, no inhibitory effect of the amino acid mixture on anesthesia-induced hypothermia was found, while in the OVX rats, hypothermia was significantly decreased. The intraperitoneal fat weight/body weight ratio was significantly higher in the OVX rats than in the Sham rats, but the gastrocnemius weight/body weight ratio was not significantly different. After amino acid infusion, the plasma insulin level was significantly higher in the OVX rats than in the Sham rats. In conclusion, our findings suggest that, in rats, ovarian function or female hormone affects protein turnover mediated by increase in insulin secretion and, thus, decreases the inhibitory effect of an infusion of amino acid mixture on anesthesia-induced hypothermia.

Epidural Analgesia Enhances the Postoperative Anabolic Effect of Amino Acids in Diabetes Mellitus Type 2 Patients Undergoing Colon Surgery

It has been suggested that diabetes mellitus type 2 amplifies the endocrine-metabolic stress response to surgery, and patients become more catabolic during the postoperative period. The aim of this study, conducted in patients with diabetes mellitus type 2 scheduled to undergo elective colorectal surgery, was to determine whether the anabolic effects of intravenous amino acids are more pronounced when receiving perioperative epidural analgesia compared with patient-controlled analgesia with intravenous morphine. Twelve patients were randomly assigned to receive either epidural analgesia or patient-controlled analgesia with intravenous morphine for perioperative pain control. Protein and glucose kinetics were measured before surgery and on the second postoperative day using L-[1-C]leucine and [6,6H2]glucose infusion during a fasted and a fed (amino acid infusion) state. Preoperative parameters for glucose and protein kinetics were comparable in the fasted state for both groups. Postoperative amino acid infusion increased glucose concentration slightly (P = 0.124) and suppressed the endogenous rate of appearance of glucose (P < 0.0001) and glucose clearance (P < 0.0001) regardless of analgesia technique. The rate of appearance of leucine (P = 0.002), leucine oxidation (P < 0.0001), and protein synthesis (P = 0.026) increased, whereas net protein breakdown was decreased (P = 0.002), leading to a positive protein balance (P < 0.0001) in both groups. The increase in protein balance was greater in the epidural group compared with the patient-controlled analgesia group (P = 0.027). Diabetic patients receiving an amino acid infusion after surgery achieved a positive protein balance without hyperglycemia. This anabolic effect was greater in patients receiving epidural analgesia compared with patient-controlled analgesia with intravenous morphine.

Effect of intravenous amino acids on protein kinetics in preterm infants

To summarize recent findings of the effects of intravenous amino acids on protein kinetics in low-birth-weight infants and to describe the potential cellular mechanism for these observations. Amino acids administered intravenously for 3-5 h in infants have been shown to suppress whole-body proteolysis. Recent data in low-birth-weight infants show that an increase in the dose of amino acid caused a suppression of proteolysis, and a decrease in the rate of glutamine and urea synthesis. These responses returned to basal state, however, when the amino acid infusion continued for 20-24 h. Supplementation with glutamine sustained the suppression of proteolysis after 3-5 days. Plasma insulin concentration did not change during the amino acid infusion. Data from studies in adults and from in vitro studies suggest that the amino acids impact protein breakdown and synthesis via the mammalian target of rapamycin pathway, stimulating initiation of translation and suppressing autophagic proteolysis. Intravenous amino acids, by increasing extracellular amino acid concentration, transiently stimulate protein synthesis and suppress protein breakdown. These effects return to basal state when the amino acid infusions are prolonged. The mechanism of this adaptive response remains to be determined.

Effect of intravenous amino acids on glutamine and protein kinetics in low-birth-weight preterm infants during the immediate neonatal period

Glutamine may be a conditionally essential amino acid in low-birth-weight (LBW) preterm neonates. Exogenously administered amino acids, by providing anaplerotic carbon into the tricarboxylic acid cycle, could result in greater cataplerotic efflux and glutamine de novo synthesis. The effect of dose and duration of amino acid infusion on glutamine and nitrogen (N) kinetics was examined in LBW infants in the period immediately after birth. Preterm neonates (<32 weeks gestation, birth weights 809-1,755 g) were randomized to initially receive either 480 or 960 micromol x kg(-1) x h(-1) of an intravenous amino acid solution for 19-24 hours, followed by a higher or lower amino acid load for either 5 h or 24 h. Glutamine de novo synthesis, leucine N, phenylalanine, and urea kinetics were determined using stable isotopic tracers. An increase in amino acid infusion from 480 to 960 micromol x kg(-1) x h(-1) for 5 h resulted in decreased glutamine de novo synthesis in every neonate (384.4 +/- 38.0 to 368.9 +/- 38.2 micromol x kg(-1) x h(-1), P < 0.01) and a lower whole body rate of proteolysis (P < 0.001) and urea synthesis (P < 0.001). However, when the increased amino acid infusion was extended for 24 h, glutamine de novo synthesis increased (369.7 +/- 92.6 to 483.4 +/- 97.5 micromol x kg(-1) x h(-1), P < 0.001), whole body rate of proteolysis did not change, and urea production increased. Decreasing the amino acid load resulted in a decrease in glutamine rate of appearance (R(a)) and leucine N R(a), but had no effect on phenylalanine R(a). Acutely stressed LBW infants responded to an increase in amino acid load by transiently suppressing whole body rate of glutamine synthesis, proteolysis, and oxidation of protein. The mechanisms of this transient effect on whole body protein/nitrogen metabolism remain unknown.

Effect of Intravenous Amino Acids on Protein Metabolism of Preterm Infants during the First Three Days of Life

Twenty-three preterm infants with respiratory distress syndrome (mean birth weight 1.07 kg, SD 0.24 kg) were randomly assigned to receive glucose alone or glucose with amino acids (1.5 g.kg-1.d-1) i.v. beginning on the 1st d of life. Blood ammonia and serum urea, CO2 content, sodium, potassium, chloride, and ionized calcium concentrations were normal and did not differ between treatment groups. Nitrogen balance was significantly greater in the group that received amino acids [88 (SD 54) versus -135 (SD 45) mg.kg-1.d-1]. In 12 infants (seven, glucose-only; five, glucose and amino acids), leucine kinetic studies were also performed on the 3rd d of life. These 12 infants received a 4-h primed constant infusion of L-[1-13C]leucine. Blood and breath were collected and analyzed for [1-13C]ketoisocaproate and 13CO2, respectively. Leucine turnover and oxidation were calculated. Both leucine turnover and oxidation were significantly higher in the group receiving amino acids than in the glucose-only group [241 (SD 38) versus 164 (SD 25) mumol.kg-1.h-1 and 71 (SD 22) versus 40 (SD 17) mumol.kg-1.h-1, respectively]. In addition, the calculated rate of protein synthesis was higher in the group receiving amino acids [6.9 (SD 1.1) versus 5.0 (SD 1.2) g.kg-1.d-1]. These data indicate that the i.v. administration of amino acids (1.5 g.kg-1.d-1) to ill preterm infants beginning on the 1st d of life improves whole-body protein balance as a result of increased protein synthesis.

The Effect of Intravenous Amino Acids on Intragastric pH During Continuous Intragastric pH-Monitoring

The present study was undertaken to determine the onset and duration of gastric acid stimulation by amino acids measured by continuous intragastric pH-monitoring. A 3-hour intravenous infusion of 250 ml of an amino acid solution (Vamin 18) was given to 20 healthy volunteers. The results were compared with data obtained during basal conditions and during a 3-hour intravenous infusion of a 5% glucose solution. One hour after starting the amino acid infusion the decrease in intragastric pH-levels reached statistical significance (p less than 0.02). This increased intragastric acidity lasted for one hour after stopping the amino acid infusion. Serum gastrin levels remained unchanged. These results indicate that continuous intragastric pH-monitoring is capable of demonstrating stimulation of gastric acidity during and for one hour after an amino acid infusion. These findings may be important for patients on parenteral nutrition.

Intravenous Amino Acids and Stimulation of Gastric Acid Secretion in Infants

To determine the immediate, short-term effect of intravenous amino acids on gastric acid secretion in infants, we measured acid secretion by continuous aspiration of gastric contents in nine enterally fed, chronically ill infants who required intravenous supplements. On day 1, basal acid output was 25 +/- 15 mumol/kg/h (mean +/- SD), and postpentagastrin maximal acid output was 91 +/- 59 mumol/kg/h. On day 2 basal acid output was 24 +/- 16 mumol/kg/h. Acid output was measured for 4 h following addition of amino acids to the intravenous solution. The rate of amino acid infusion was 0.15 g/kg/h. The infusion of intravenous amino acids resulted in an immediate and sustained twofold increase in acid secretion. Hourly totals of amino acid-stimulated acid output were 51 +/- 38, 44 +/- 37, 46 +/- 30, and 47 +/- 31 mumol/kg/h in hours 1-4, respectively. These results were significantly different from basal acid output (p less than 0.01) during the last 2 h of amino acid infusion. Serum gastrin concentration was not significantly different before and after the amino acid infusion (87 +/- 63 pg/ml vs. 105 +/- 56 pg/ml). We conclude that amino acids infused at a rate typical for parenteral nutrition stimulate gastric acid secretion in infants.

Intravenous Amino Acids and Stimulation of Gastric Acid Secretion in Infants

SummaryTo determine the immediate, short‐term effect of intravenous amino acids on gastric acid secretion in infants, we measured acid secretion by continuous aspiration of gastric contents in nine enterally fed, chronically ill infants who required intravenous supplements. On day 1, basal acid output was 25 ± 15 μmol/kg/h (mean ± SD), and postpentagastrin maximal acid output was 91 ± 59 μmol/kg/h. On day 2 basal acid output was 24 ± 16 μmol/kg/h. Acid output was measured for 4 h following addition of amino acids to the intravenous solution. The rate of amino acid infusion was 0.15 g/kg/h. The infusion of intravenous amino acids resulted in an immediate and sustained twofold increase in acid secretion. Hourly totals of amino acid‐stimulated acid output were 51 ± 38, 44 ± 37, 46 ± 30, and 47 ± 31 μmol/kg/h in hours 1–4, respectively. These results were significantly different from basal acid output (p &lt; 0.01) during the last 2 h of amino acid infusion. Serum gastrin concentration was not significantly different before and after the amino acid infusion (87 ± 63 pg/ml vs. 105 ± 56 pg/ml). We conclude that amino acids infused at a rate typical for parenteral nutrition stimulate gastric acid secretion in infants.

Effect of intravenous amino acids on the canine gastric mucosa

A mixture of synthetic L-amino acids (Aminoplex 14) was infused intravenously over 4 hours in five dogs each prepared with a gastric fistula and a denervated fundic pouch. Acid and pepsin outputs from the innervated gastric mucosa (gastric fistula) increased significantly after 90 minutes' infusion of amino acid. Acid output from the denervated fundic mucosa (Heidenhain pouch) was estimated by a method of intragastric titration and increased significantly only in response to intravenous amino acid infusion when the pouch was subjected to distention with 100 ml of perfusate. Blood glucose, serum gastrin, hematocrit and serum osmolality levels did not change throughout the experiments. Bolus intravenous injection of either atropine (0.15 mg/kg) or cimetidine (10 mg/kg) blocked the acid secretory response to intravenous amino acids. It is concluded that intravenous amino acids stimulate the innervated gastric mucosa to secrete both acid and pepsin. The secretory response from denervated mucosa is only obtained in the presence of fundic pouch distention. The gastric secretory response is susceptible to both atropine and histamine H 2 antagonist blockade.

EFFECTS OF AMINO ACIDS ON RENAL GLUCOSE REABSORPTION IN THE DOG

The effects of intravenous amino acids on maximal renal tubular reabsorption of glucose were studied in dogs by clearance techniques. L-Lysine, glycine, and L-alanine caused a significant depression of glucose reabsorption whereas L-aspartic acid and L-leucine did not. These results support other evidence that there is a relationship between the transport mechanisms for a variety of substances such as simple sugars, amino acids, and phosphate in the kidney. The effects, however, are probably not competitive but may depend on some indirect action on net transport such as altered membrane permeability or intracellular osmotic pressure. Incidentally, it was noted that L-aspartic acid, L-lysine, glycine, and L-alanine infused along with glucose resulted in significantly less elevation in plasma glucose concentration than that observed when the same amount of glucose was infused alone. The effects of amino acids on plasma glucose confirm earlier reports that mixtures of amino acids depress elevated blood sugar levels. These effects were found to occur with basic, acidic, and neutral amino acids. The method of action of amino acids in influencing plasma glucose has not been determined, but it may be similar to known effects of leucine, which is thought to induce hypoglycemia, particularly in sensitive individuals, by increasing insulin output.

Effect of Intravenous Amino Acids on Plasma Non-Esterified Fatty Acids.

(1) The effect of infusing an amino acid mixture (protein hydrolysate) on plasma NEFA, venous glucose level, and capillary-venous glucose difference, was studied in 6 healthy volunteer subjects. In every instance, plasma NEFA levels fell precipitously during amino acid infusion, and capillary-venous glucose differences increased concurrently. Similar results were obtained when a single amino acid, L-arginine, was infused in 2 normal subjects. (2) The results suggest that NEFA-lowering effects of parenterally administered amino acids may have been mediated entirely or in part via an induced increase in rate of glucose utilization.