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Clostridioides difficile infection (CDI) is a major cause of nosocomial diarrhea that is deemed a global health threat. C. difficile strain BI/NAP1/027 has contributed to the increase in the mortality, severity of CDI outbreaks and recurrence rates (rCDI). Updated CDI treatment guidelines suggest vancomycin and fidaxomicin as initial first-line therapies that have initial clinical cure rates of over 80%. Unacceptably high recurrence rates of 15-30% in patients for the first episode and 40% for the second recurrent episode are reported. Alternative treatments for rCDI include fecal microbiota transplant and a human monoclonal antibody, bezlotoxumab, that can be used in patients with high risk of rCDI. Various emerging potential therapies with narrow spectrum of activity and little systemic absorption that are in development include 1) Ibezapolstat (formerly ACX-362E), MGB-BP-3, and DS-2969b-targeting bacterial DNA replication, 2) CRS3213 (REP3123)-inhibiting toxin production and spore formation, 3) ramizol and ramoplanin-affecting bacterial cell wall, 4) LFF-571-blocking protein synthesis, 5) Alanyl-L-Glutamine (alanylglutamine)-inhibiting damage caused by C. difficile by protecting intestinal mucosa, and 6) DNV3837 (MCB3681)-prodrug consisting of an oxazolidinone-quinolone combination that converts to the active form DNV3681 that has activity in vitro against C. difficile. This review article provides an overview of these developing drugs that can have potential role in the treatment of rCDI and in lowering recurrence rates.

Objective. Allergic asthma is a chronic inflammatory disease, which seriously affects the life quality of patients, especially children. Alanylglutamine is a nutritional supplement with potential protective and anti-inflammatory effects, but its function in allergic asthma remains elusive. In this study, we focused on the investigations of the roles and functional mechanism of Alanylglutamine in asthma. Methods. Ovalbumin (OVA) induction was utilized to establish a mouse asthma model. 16S rDNA sequencing was performed to compare the diversity of intestinal microorganisms under different treatments. Gas chromatography was utilized to screen the intestinal microbe-short-chain fatty acids in the stool. The lung tissue was extracted to determine signaling pathways, including AMPK, NF-κB, mTOR, STAT3, IKKβ, TGF-β, and IL-1β through Western blot or RT-qPCR. Results. It was observed that Alanylglutamine reduced the cytokine in OVA-induced allergic asthma mice. H&E staining showed obvious pneumonia symptoms in the asthma group, while Alanylglutamine alleviated the inflammatory infiltration. Alanylglutamine reversed gut microbiota compositions in OVA-induced allergic asthma mice and enhanced the butyric acid level. The protective role of Alanylglutamine may be associated with the gut microbiota-butyric acid-GPR43 pathway in asthma mice. In contrast to the OVA group, Alanylglutamine activated the protein expression of P-AMPK/AMPK and inhibited the protein expression of P-mTOR/mTOR, P-P65/P65, P-STAT3/STAT3, P-IKKβ/IKKβ, TGF-β, and IL-1β, with similar effects from butyric acid. Conclusion. The results indicated that Alanylglutamine might be beneficial for asthma, and its effect was achieved through the regulation on microbiota and the derived metabolites. The therapeutic effects might be associated with AMPK, NF-κB, mTOR, and STAT3 signaling pathways. These findings will help identify effective therapeutic direction to alleviate allergic inflammation of the lungs and airways.

Objectives Alanylglutamine (AG) is a dipeptide that fuels enterocytes and has a coadjuvant role during gut healing. The current study aimed to investigate the potential ulcer-healing effect of AG in indomethacin-induced gastropathy. Methods Animals (n = 10 rats/group) were randomly allocated into 5 groups. Gastric ulcerated rats were administered AG, AG + dexamethasone, or pantoprazole after indomethacin exposure. Results Comparable to pantoprazole, AG inhibited H-KATPase pump, and elevated the pH of gastric juice. Moreover, the dipeptide increased the serum/mucosal contents of glucagon-like peptide-1 (GLP-1), pS473-Akt, and cyclin-D1. On the contrary, AG abated serum tumor necrosis factor-α and gastric mucosal content of pS45-β catenin, pS9-GSK3β, pS133-CREB, pS536-NF-κB, H2O2, claudin-1, and caspase-3. The administration of dexamethasone before AG hampered its effect on almost all the measured parameters. Conclusions AG confers its antiulcerogenic/antisecretory potentials by repressing the proton pump to increase the gastric juice pH via boosting p-CREB, p-Akt, p-GSK-3β, and GLP-1. Also, it inhibits apoptosis through suppressing nuclear factor-kappa B/tumor necrosis factor-α/H2O2/claudin-1 cue. This trajectory contributes to loosen the tight junction priming AG-mediated GLP-1/β-catenin/cyclin-D1 that results in pronounced increase in gastric mucosa proliferation. Therefore, the crosstalk between multiple pathways orchestrates the action of AG against gastric ulceration.

Differences in plasma L-glutamine (L-Gln) concentrations from ingestion of different formulations of L-Gln were examined in 8 men (26.8 ± 4.2 years old, 181.1 ± 10.9 cm, 85.8 ± 15.4 kg). Subjects reported to the laboratory on 4 separate occasions and randomly consumed 1 of 4 drinks containing 60 mg/kg of L-Gln; 89 mg/kg of Sustamine (L-alanylglutamine [AlaGln]; Kyowa Hakko Europe GmbH, Düsseldorf, Germany), which contained an equivalent L-Gln dose as consumed in L-Gln); 200 mg/kg of an enzymatically hydrolyzed wheat protein (HWP) with an L-Gln content of 31 mg/kg; or a control that consisted only of water. It was hypothesized that the AlaGln trial would increase plasma glutamine concentrations greater than the other experimental trials. Ingestion of L-Gln, AlaGln, and HWP resulted in significant increases in the plasma L-Gln concentration, peaking at 0.5, 0.5, and 0.75 hours, respectively. The corresponding mean peak increases were 179 ± 61, 284 ± 84, and 134 ± 36 μmol/L, respectively. Concentrations returned to baseline in all subjects by 2 hours after L-Gln and HWP and by 4 hours after AlaGln. Mean areas under the plasma concentration curve, calculated between 0 and 4 hours, were 127 ± 61, 284 ± 154, and 151 ± 63 μmol∙h∙L⁻¹ for L-Gln, AlaGln, and HWP, respectively. When allowance was made for the lower L-Gln dose administered as HWP, the peak plasma concentration and area under the plasma concentration curve were approximately the same as for AlaGln. The results suggest a greater transfer from the gut to plasma of L-Gln when supplied as AlaGln and possibly also as HWP compared with when the same dose was provided as the free amino acid.

We aim to demonstrate that low dose growth hormone (GH) administered in i.v. pulses every 3h is able to normalize IGF-I levels in subjects with prolonged critical illness, after multiple trauma. We also ask whether it is possible to control glycaemia during such a treatment and how alanylglutamine (AG) supplementation influences plasma glutamine concentration.We used a prospective double-blind (group 1 vs. 2), randomized trial with an open-label control arm (group 3). Thirty multiple trauma patients (median age: 36, 42, 46 years) were randomized on day 4 after trauma to receive (group 1, n=10) i.v. AG supplementation (0.3 g/kg day from day 4 till 17) and i.v. GH (0.05 mg/kg day divided into 8 boluses, maximum dose at 3 AM, administered on days 7-17) or AG and placebo (group 2, n=10). Group 3 (n=10) received isocaloric isonitrogenous (proteins 1.5 g/kg day) nutrition without AG. Glycaemia was controlled by i.v. insulin infusion according to a routine protocol.GH treatment caused an increase of IGF-I (from median 169 on day 4 to 493 ng/ml on day 17), IGFBP-3 (from 2.4 to 3.2 microg/ml) and a fall in IGFBP-1 (from 11.5 to 3.1 microg/ml), whilst in both groups 2 and 3 these indices remained unchanged. At the end of the study (day 17) IGF-I and IGFBP-1 differed significantly among groups (p=0.008 resp. p=0.010, Kruskal-Wallis). Plasma glutamine remained below the normal range through the study in all groups (median: 0.18-0.30 mM), but had a tendency to rise in group 2 in contrast with a fall in groups 1 and 3 (NS). Group 1 required more insulin (p0.01) than did the control group but median glycaemia was only 0.4-0.5 mM higher in group 1 (6.5 mM) than in groups 2 and 3 (6.1 resp. 6.0 mM).GH (0.05 g/kg day) administered in i.v. pulses is able to normalize IGF-I levels in subjects with prolonged critical illness after trauma. During this treatment, the standard dose of AG prevents worsening of plasma glutamine deficiency and glucose control is possible using routine algorithms, but it requires higher insulin doses.

Sustamine™ (SUS) is a dipeptide composed of alanine and glutamine (AlaGln). Glutamine has been suggested to increase muscle protein accretion; however, the underlying molecular mechanisms of glutamine on muscle protein metabolism following resistance exercise have not been fully addressed. In the present study, 2-month-old rats climbed a ladder 10 times with a weight equal to 75 % of their body mass attached at the tail. Rats were then orally administered one of four solutions: placebo (PLA-glycine = 0.52 g/kg), whey protein (WP = 0.4 g/kg), low dose of SUS (LSUS = 0.1 g/kg), or high dose of SUS (HSUS = 0.5 g/kg). An additional group of sedentary (SED) rats was intubated with glycine (0.52 g/kg) at the same time as the ladder-climbing rats. Blood samples were collected immediately after exercise and at either 20 or 40 min after recovery. The flexor hallucis longus (FHL), a muscle used for climbing, was excised at 20 or 40 min post exercise and analyzed for proteins regulating protein synthesis and degradation. All supplements elevated the phosphorylation of FOXO3A above SED at 20 min post exercise, but only the SUS supplements significantly reduced the phosphorylation of AMPK and NF-kB p65. SUS supplements had no effect on mTOR signaling, but WP supplementation yielded a greater phosphorylation of mTOR, p70S6k, and rpS6 compared with PLA at 20 min post exercise. However, by 40 min post exercise, phosphorylation of mTOR and rpS6 in PLA had risen to levels not different than WP. These results suggest that SUS blocks the activation of intracellular signals for MPB, whereas WP accelerates mRNA translation.

We evaluated the nutritional status of pigs that received glutamine after orthotopic liver transplantation. After transplantation, one group of pigs received an oral diet (group I,n=5), one group received conventional total parenteral nutrition (group II,n=4), and one group received alanylglutamine supplemented parenteral nutrition (group III,n=7). We compared nutritional status, graft liver function, and ileal mucosal thickness in the three groups. There were no significant differences in nutritional parameters or serum chemistries among the groups. In terms of ileal integrity, mucosal thickness was reduced after liver transplantation in group II, whereas it was relatively well preserved in group III. The level of endotoxin in the portal venous blood was significantly lower in group III, than in group II on the 7th day after liver transplantation. Parenteral alanyl-glutamine appears to have beneficial effects in preserving the integrity of the ileal mucosa when oral intake of nutrients may not be feasible. This could prevent bacterial translocation in the portal vein.

Introduction: The supplementation of alanyl-glutamine dipeptide in critically ill patients necessitating total parenteral nutrition (TPN) improves clinical outcomes, reducing mortality, infection rate, and shortening intensive care unit (ICU) hospital lengths of stay (LOSs), as compared to standard TPN regimens.Methods: A Discrete Event Simulation model that incorporates outcomes rates from 200 Italian ICUs for over 60,000 patients, alanyl-glutamine dipeptide efficacy data synthesized by means of a Bayesian random effects meta-analysis, and national cost data has been developed to evaluate the alternatives from the cost perspective of the hospital. Simulated clinical outcomes are death and infection rates in ICU, death rate in general ward, and hospital LOSs. Sensitivity analyses are performed by varying all uncertain parameter values in a plausible range.Results: The internal validation process confirmed the accuracy of the model in replicating observed clinical data. Alanyl-glutamine dipeptide on average results more effective and less costly than standard TPN: reduced mortality rate (24.6% ± 1.6% vs. 34.5% ± 2.1%), infection rate (13.8% ± 2.9% vs. 18.8% ± 3.9%), and hospital LOS (24.9 ± 0.3 vs. 26.0 ± 0.3 days) come at a lower total cost per patient (23,409 ± 3,345 vs. 24,161 ± 3,523 Euro).Treatment cost is completely offset by savings on ICU and antibiotic costs. Sensitivity analyses confirmed the robustness of these results.Conclusions: Alanyl-glutamine dipeptide is expected to improve clinical outcomes and to do so with a concurrent saving for the Italian hospital.

Using in vivo and in vitro techniques, the mechanism by which intestinal mucosa obtains glutamine from luminal oligopeptides was investigated in humans. The rate of hydrolysis by mucosal brush border membrane was more than threefold greater for alanylglutamine than for glycylglutamine. Despite this difference, rates of dipeptide and amino acid disappearance during intestinal perfusion were greater from test solutions containing glycylglutamine than alanylglutamine. Furthermore, rates of intraluminal appearance of products of hydrolysis during the infusion of two dipeptides were similar and less than 5% of the disappearance rate of the parent dipeptide. In contrast to free glutamine, uptake of peptide-bound glutamine by brush border membrane vesicles was not inhibited by deletion of sodium or addition of free amino acids to the incubation medium but was inhibited by other oligopeptides and stimulated by a proton gradient. Inhibition constants for the saturable uptake of glycylglutamine and alanylglutamine by vesicles were not significantly different, suggesting similar affinities for the peptide transporter. It is concluded that in human intestine the predominant mechanism for assimilation of glutamine-dipeptides is absorption as intact dipeptide rather than hydrolysis.

The effects of total parenteral nutrition containing alanylglutamine (Ala-Gln) on tumor growth and cellular immune response were examined in rats inoculated Yoshida sarcoma cells subcutaneously. Rats given Ala-Gln-enriched solution intravenously showed a positive nitrogen balance and the increased function of alveolar macrophages. Studies on in vitro effect of Ala-Gln on immune cells in control rats showed a significant increase in phagocytic activity of alveolar macrophages and in blastogenic response of splenocytes, respectively. In vitro experiment of Gln or Ala-Gln addition to culture medium showed a remarkable enhancement of incorporation of(3)H-thymidine into Yoshida sarcoma cells, but in vivo administration of Ala-Gln containing solution did not accelerate the growth of the same tumor as measured by changes in the weight and volume. These results suggest that Ala-Gln infusion does not stimulate tumor growth due to maintenance of some immune-enhancing effect by Gln liberated from Ala-Gln in tumor-bearing hosts.

We examined the effects of interleukin-1 beta (IL-1), tumor necrosis factor (TNF), and alanylglutamine (Ala-Gln) infusion on the plasma concentrations and interorgan fluxes of taurine and taurine precursors, including methionine and serine, using chronically catheterized awake dogs. In the first study, the dogs received 5 micrograms/kg/h of either human recombinant IL-1 or TNF intravenously for 2 h. Taurine fluxes in the liver and gut were calculated by blood flows and arteriovenous differences during infusion and for 2 h after discontinuation of the cytokine infusions. The 2 h continuous infusions of TNF and IL-1 resulted in 60 and 90% increases, respectively, in the arterial plasma taurine concentration. Hepatic taurine flux changed from uptake to release after 2 h of continuous IL-1 infusion. In the second study, we investigated whether Ala-Gln infusion affects taurine metabolism under normal and stress conditions. The dogs were given a constant 2 h intravenous infusion of IL-1 or saline. Ala-Gln (6 mumol/kg/min) was infused simultaneously during the second hour. Plasma concentrations and fluxes, across the liver, gut, and lung, of taurine and taurine precursors were studied. IL-1 administration increased the plasma concentration, hepatic release, and lung uptake of taurine. Ala-Gln infusion did not affect either plasma concentrations or organ fluxes of taurine. These data suggest that cytokines play a role in taurine metabolism under stress conditions.

The present study was designed to investigate organ metabolism of intravenously (IV) infused (100 mumol.h-1.kg-1) alanylglutamine and its amino acid constituents in a group of healthy subjects. The dipeptide clearance (mumol/min) by kidney (51 +/- 3) was significantly (P less than .01) greater than the clearance by either splanchnic organs (19 +/- 6) or skeletal muscle (21 +/- 8). Infusion of alanylglutamine significantly (P less than .01) increased arterial plasma concentrations of free alanine (260 +/- 31 v 330 +/- 38 mumol/L) and free glutamine (620 +/- 66 v 764 +/- 65 mumol/L) when compared with the baseline period. Concurrently, splanchnic uptake of alanine and glutamine increased and muscle release of alanine ceased. However, muscle release of glutamine remained unaffected. Renal balances of alanine and glutamine changed from neutral to negative (net release) and from positive (net uptake) to neutral, respectively. Infusion of a corresponding mixture of alanine and glutamine had similar effects on arterial plasma concentrations and splanchnic and muscle balances of alanine and glutamine, but had no effect on renal balances of these amino acids. From these studies in man, we conclude that kidney predominates over other organs in clearance of alanylglutamine from plasma and that this may account for the different effect of infusion of alanine and glutamine in free and peptide forms on renal fluxes of these amino acids.

Skeletal muscle protein catabolism following trauma has until recently not been possible to counteract by intravenous nutritional means. The obligatory loss of nitrogen with concomitant reduction of skeletal muscle protein synthesis is also accompanied by a decrease of muscle free glutamine, the extent of which is proportional to the muscle protein catabolism. Serving as a human model of surgical trauma, patients undergoing elective cholecystectomy were given total parenteral nutrition including additions of either glutamine or its analogs (ornithine-alpha-ketoglutarate, alpha-ketoglutarate, or alanylglutamine) during 3 postoperative days. The polyribosome concentration and the intracellular glutamine concentration in skeletal muscle, as well as nitrogen balance, showed a less pronounced skeletal muscle catabolism in these groups than when conventional total parenteral nutrition was given. It is concluded that a support of either glutamine or its carbon skeleton, alpha-ketoglutarate, counteracts the postoperative fall of muscle free glutamine and of muscle protein synthesis. Furthermore, statistical correlations could be shown between the changes of muscle glutamine and muscle protein synthesis and the postoperative nitrogen losses.

In this study we investigated the influence of an infusion of alpha-ketoglutarate (A-KG) on the glutamine metabolism of (1) intensive care units patients and on (2) organ balances of anaesthetized dogs. We compared (3) the effect of an equimolar infusion of A-KG, glutamine and alanylglutamine, respectively on peripheral glutamine balances

In this review, new knowledge about the potential use of glutamine containing dipeptides as substrates in the frame of parenteral nutrition is presented. Using chemical and biotechnological methods, the stable and highly soluble peptide l -alanyl- l -glutamine (Ala-Gln) can be synthesized in high yields. Studies in experimental rats and dogs demonstrate the effective utilization of intravenously supplied Ala-Gln and the rapid provision of free glutamine for maintenance of the intracellular muscle-free glutamine pool in catabolic situations. Subsequent studies in healthy volunteers provide firm evidence that the infused Ala-Gln is rapidly eliminated from plasma ( t 1 2 : 3.8 minutes ), associated by a prompt equimolar increase in the concentrations of free alanine and glutamine. Bolus injection and continuous infusion of the peptide was not accompanied by any side effects, and no complaints by the subjects were noted. These results may indicate a safe and efficient use of Ala-Gln as source of free glutamine in parenteral nutrition.

In this study we administered an infusion of alanylglutamine (10 mumol/kg.min) for 60 minutes to postoperative anaesthetized dogs with catheters placed in the portal and hepatic veins. Arterial plasma levels of alanylglutamine were 83 +/- 27 mumol/L 20 minutes after the onset of the infusion and remained constant throughout the infusion period. Plasma levels of glutamine and alanine approximately doubled compared with preinfusion levels, indicating a release of these amino acids from the dipeptide. The halflife of alanylglutamine, calculated after bolus injection of 2 g, was 1.7 +/- 0.5 minutes. Alanylglutamine was extracted from the liver and the gut (0.9 +/- 0.3 and 0.5 +/- 0.1 mumol/kg.min, respectively). In the basal period (without infusion of alanylglutamine), a glutamine uptake by the liver and the intestine was found. Alanine was taken up by the liver and released from the gut. The infusion of alanylglutamine significantly increased the hepatic uptake of glutamine and alanine (from 0.8 +/- 0.2 to 3.8 +/- 0.6 and from 3.0 +/- 0.4 to 7.5 +/- 0.7 mumol/kg.min respectively; P less than .01) and did not significantly change the intestinal uptake of glutamine and the release of alanine. We conclude that the infusion of alanylglutamine markedly influences the hepatic metabolism of glutamine and alanine, probably via the increased arterial and portal levels of glutamine and alanine.

1. The present study examined the effect of an infusion of the dipeptide alanylglutamine or of the corresponding amino acids alanine and glutamine in equimolar amounts (10 μmol min−1 kg−1) on the canine hindlimb exchange of alanine and glutamine in the post-operative anaesthetized dog. In contrast to glutamine, the dipeptide alanylglutamine is stable in aqueous solution and therefore would be a suitable substrate for parenteral nutrition. 2. The infusion of alanylglutamine increased (a) the arterial concentration of alanylglutamine to a plateau level (120 ± 9.5 μmol/l, mean ± sem) 20 min after start of the infusion, (b) the mean arterial alanine concentration from 761 ± 42 to a plateau of 1500–1700 μmol/l (P > 0.01) and (c) the arterial glutamine concentration from 407 ± 51 to a plateau of 1050–1500 μmol/l (P > 0.01). Alanine and glutamine levels were slightly higher (14% and 26%, respectively, NS) in the group receiving the equimolar amount of alanine and glutamine. 3. Infusion of alanylglutamine for 1 h abolished the net efflux of glutamine (from −0.80 ± 0.1 to −0.03 ± 0.2 μmol min−1 kg−1; P >0.05) and invoked a net influx of alanine (from −0.50 ± 0.19 to + 0.27 ± 0.14 μmol min−1 kg−1; P > 0.01). These changes were similar to those achieved when the two amino acids were infused. 4. This study demonstrates that during short-term administration of alanylglutamine or of the corresponding amino acids the nitrogen release from the hindlimb of the anaesthetized post-operative dog via alanine and glutamine is reduced.

The instability of the amino acid glutamine prompted us to investigate substitute compounds appropriate for culture conditions. The effect of two glutamine-containing dipeptides, alanylglutamine (Ala-Gln) and glycylglutamine (Gly-Gln), on the growth behavior of a hematopoietic cell line in culture (K562) was investigated. Growth rates and [3H]thymidine incorporation rates of cells cultivated in sterile-filtrated media, containing glutamine (Gln) or Ala-Gln or Gly-Gln, were not statistically different. Although heart-sterilization of media containing Gln caused approximately 95% decomposition of the Gln, both dipeptides remained unaltered. Consequently, cell growth was drastically decreased when autoclaved free Gln-containing media were used, but growth was unaffected in the presence of autoclaved dipeptides. Both Ala-Gln and Gly-Gln have an advantage over free Gln as growth factors for cell culture due to the stability of the dipeptides during both autoclaving and storage; the biological activity, however, is comparable.

Due to its instability, glutamine is not included in solutions for parenteral solution. This problem can be obviated by providing glutamine as acetyl-, glycyl-, or alanylglutamine. Using an organ balance technique in conscious dogs, we investigated metabolism of these three sources of glutamine. Liver, gut, kidney, and muscle participated in clearance of glycyl- and alanylglutamine from plasma, but among these organs only kidney cleared acetylglutamine. Furthermore, there was a large urinary excretion for acetylglutamine (38 +/- 6% of amount infused) but only a trace amount for either dipeptide. The infusion of glutamine-dipeptides resulted in similar increases in blood level of free glutamine. The main source of this increase appeared to be hydrolysis of dipeptides by kidney and release of free glutamine to circulation. During the infusion of both dipeptides, glutamine balance (free and dipeptide forms) was always positive (net uptake) across liver, gut, and kidney but was neutral across muscle. Liver or gut glutamine balances were not significantly different during the infusion of dipeptides, but kidney glutamine balance was twofold greater during the infusion of glycyl- than alanylglutamine. We conclude that among these three sources of glutamine, acetylglutamine is least desirable for use in parenteral nutrition. Glycylglutamine may be preferable over alanylglutamine if the objective is to target glutamine for kidney.

In this study we investigated the effect of a total parenteral nutrition supplemented with synthetic dipeptides on plasma and muscle amino acid metabolism in four patients with acute pancreatitis. We infused an amino acid solution containing alanylglutamine, glycylglutamine, glycylvaline, glycylisoleucine, glylcylleucine, and glycyltyrosine for a period of five days in daily dosages of 10.3, 22.1, 68.8, 37.2, 42.5, and 15.7 mmol, respectively. The plasma levels remained below 100 mumol/L for all infused dipeptides. The plasma concentrations of alanylglutamine were not measurable. Mean peptide urine excretion remained below 5%, with the exception of glycylglutamine (8.5% +/- 5.1%). Arteriovenous concentration differences of the dipeptides across the leg were not significantly different from zero, indicating that the infused dipeptides have no important role in the nitrogen exchange of skeletal muscle. A marked intracellular glutamine deficiency in skeletal muscle was found in all four patients (5.1 +/- 0.6 mmol/L v 19.5 +/- 0.8 in healthy subjects) before infusion. Intracellular glutamine concentration was significantly higher after the infusion period (5.1 +/- 0.7 v 9.5 +/- 1.8 mmol/L, P greater than .05), but no normalization of the intracellular glutamine levels was achieved by the infusion of the two glutamine-containing peptides. We conclude that peptides are well metabolized as substrates for parenteral nutrition in catabolic patients. Furthermore, the infusion of glutamine peptides caused a significant increase in intracellular glutamine levels; however, the dosage of glutamine peptides was too low to normalize the muscular glutamine concentrations.

In a recent study we showed that the growth behavior of a hematopoietic cell line (K 562) in culture was the same when using glutamine-containing dipeptides or glutamine as substrate. In this article we study the growth behavior of different tumor cells, originating from the hematopoietic system (K 562), stomach (Kato III), pancreas (Panc 1), and breast (T 47 D), to test the biological activity as preclinical in vitro screening system. We compared L-glutamine (GLN), N-acetyl-L-glutamine (ACE-GLN), L-alanyl-L-glutamine (ALA-GLN), and glycyl-L-glutamine (GLY-GLN). Cell proliferation was measured with the incorporation of [3H] thymidine or the MTT assay (cleavage of 3-(4,5-dimethyldiazol-2-yl)-2-5-diphenyl tetrazolium bromide by mitochondria). In all investigated cell types cell growth was stimulated when using glutamine-containing dipeptides or ACE-GLN instead of a glutamine-free media (not significant for T 47 D). However, GLN or ALA-GLN was advantageous to GLY-GLN or ACE-GLN when measuring cell proliferation with the MTT-assay up to 72 hours. However, alanylglutamine does not enhance proliferation, compared with free glutamine.