A tracer bolus method for investigating glutamine kinetics in humans.
ABSTRACT: Glutamine transport between tissues is important for the outcome of critically ill patients. Investigation of glutamine kinetics is, therefore, necessary to understand glutamine metabolism in these patients in order to improve future intervention studies. Endogenous glutamine production can be measured by continuous infusion of a glutamine tracer, which necessitates a minimum measurement time period. In order to reduce this problem, we used and validated a tracer bolus injection method. Furthermore, this method was used to measure the glutamine production in healthy volunteers in the post-absorptive state, with extra alanine and with glutamine supplementation and parenteral nutrition. Healthy volunteers received a bolus injection of [1-13C] glutamine, and blood was collected from the radial artery to measure tracer enrichment over 90 minutes. Endogenous rate of appearance (endoRa) of glutamine was calculated from the enrichment decay curve and corrected for the extra glutamine supplementation. The glutamine endoRa of healthy volunteers was 6.1±0.9 µmol/kg/min in the post-absorptive state, 6.9±1.0 µmol/kg/min with extra alanyl-glutamine (p?=?0.29 versus control), 6.1±0.4 µmol/kg/min with extra alanine only (p?=?0.32 versus control), and 7.5±0.9 µmol/kg/min with extra alanyl-glutamine and parenteral nutrition (p?=?0.049 versus control). In conclusion, a tracer bolus injection method to measure glutamine endoRa showed good reproducibility and small variation at baseline as well as during parenteral nutrition. Additionally, we showed that parenteral nutrition including alanyl-glutamine increased glutamine endoRa in healthy volunteers, which was not attributable to the alanine part of the dipeptide.
Project description:INTRODUCTION: Glutamine rate of appearance (Ra) may be used as an estimate of endogenous glutamine production. Recently a technique employing a bolus injection of isotopically labeled glutamine was introduced, with the potential to allow for multiple assessments of the glutamine Ra over time in critically ill patients, who may not be as metabolically stable as healthy individuals. Here the technique was used to evaluate the endogenous glutamine production in critically ill patients in the fed state with and without exogenous glutamine supplementation intravenously. METHODS: Mechanically ventilated patients (n?=?11) in the intensive care unit (ICU) were studied on two consecutive days during continuous parenteral feeding. To allow the patients to be used as their own controls, they were randomized for the reference measurement during basal feeding without supplementation, before or after the supplementation period. Glutamine Ra was determined by a bolus injection of 13C-glutamine followed by a period of frequent sampling to establish the decay-curve for the glutamine tracer. Exogenous glutamine supplementation was given by intravenous infusion of a glutamine containing dipeptide, L-alanyl-L-glutamine, 0.28 g/kg during 20 hours. RESULTS: A 14% increase of endogenous glutamine Ra was seen at the end of the intravenous supplementation period as compared to the basal measurements (P?=?0.009). CONCLUSIONS: The bolus injection technique to measure glutamine Ra to estimate the endogenous production of glutamine in critically ill patients was demonstrated to be useful for repetitive measurements. The hypothesized attenuation of endogenous glutamine production during L-alanyl-L-glutamine infusion given as a part of full nutrition was not seen.
Project description:BACKGROUND:Nosocomial infections are an important cause of morbidity and mortality in the surgical intensive care unit (SICU). Clinical benefits of glutamine-supplemented parenteral nutrition may occur in hospitalized surgical patients, but efficacy data in different surgical subgroups are lacking. The objective was to determine whether glutamine-supplemented parenteral nutrition differentially affects nosocomial infection rates in selected subgroups of SICU patients. METHODS:This was a double-blind, randomized, controlled study of alanyl-glutamine dipeptide-supplemented parenteral nutrition in SICU patients requiring parenteral nutrition and SICU care after surgery for pancreatic necrosis, cardiac, vascular, or colonic surgery. Subjects (n = 59) received isocaloric/isonitrogenous parenteral nutrition, providing 1.5 g/kg/d standard glutamine-free amino acids (STD-PN) or 1.0 g/kg/d standard amino acids + 0.5 g/kg/d glutamine dipeptide (GLN-PN). Enteral feedings were advanced as tolerated. Nosocomial infections were determined until hospital discharge. RESULTS:Baseline clinical/metabolic data were similar between groups. Plasma glutamine concentrations were low in all groups and were increased by GLN-PN. GLN-PN did not alter infection rates after pancreatic necrosis surgery (17 STD-PN and 15 GLN-PN patients). In nonpancreatic surgery patients (12 STD-PN and 15 GLN-PN), GLN-PN was associated with significantly decreased total nosocomial infections (STD-PN 36 vs GLN-PN 13, P < .030), bloodstream infections (7 vs 0, P < .01), pneumonias (16 vs 6, P < .05), and infections attributed to Staphylococcus aureus (P < .01), fungi, and enteric Gram-negative bacteria (each P < .05). CONCLUSIONS:Glutamine dipeptide-supplemented parenteral nutrition did not alter infection rates following pancreatic necrosis surgery but significantly decreased infections in SICU patients after cardiac, vascular, and colonic surgery.
Project description:Glutamine supplementation in specific groups of critically ill patients results in favourable clinical outcome. Enhancement of citrulline and arginine synthesis by glutamine could serve as a potential mechanism. However, while receiving optimal enteral nutrition, uptake and enteral metabolism of glutamine in critically ill patients remain unknown. Therefore we investigated the effect of a therapeutically relevant dose of L-glutamine on synthesis of L-citrulline and subsequent L-arginine in this group. Ten versus ten critically ill patients receiving full enteral nutrition, or isocaloric isonitrogenous enteral nutrition including 0.5?g/kg L-alanyl-L-glutamine, were studied using stable isotopes. A cross-over design using intravenous and enteral tracers enabled splanchnic extraction (SE) calculations. Endogenous rate of appearance and SE of glutamine citrulline and arginine was not different (SE controls versus alanyl-glutamine: glutamine 48 and 48%, citrulline 33 versus 45%, and arginine 45 versus 42%). Turnover from glutamine to citrulline and arginine was not higher in glutamine-administered patients. In critically ill nonseptic patients receiving adequate nutrition and a relevant dose of glutamine there was no extra citrulline or arginine synthesis and glutamine SE was not increased. This suggests that for arginine synthesis enhancement there is no need for an additional dose of glutamine when this population is adequately fed. This trial is registered with NTR2285.
Project description:Background Trauma patients are characterised by alterations in the immune system, increased exposure to infectious complications, sepsis and potentially organ failure and death. Glutamine supplementation to parenteral nutrition has been proven to be associated with improved clinical outcomes. However, glutamine supplementation in patients receiving enteral nutrition and its best route are still controversial. Previous trials have been limited by a small sample size, use of surrogate outcomes or a limited period of supplementation. The aim of this trial is to investigate if intravenous glutamine supplementation to trauma patients receiving enteral nutrition is associated with improved clinical outcomes in terms of decreased organ dysfunction, infectious complications and other secondary outcomes. Methods/design Eighty-eight critically ill patients with multiple trauma receiving enteral nutrition will be recruited in this prospective, triple-blind, block-randomised, placebo-controlled clinical trial to receive either 0.5 g/kg/day intravenous undiluted alanyl-glutamine or intravenous placebo by continuous infusion (24 h/day). Both groups will be receiving the same standard enteral nutrition protocol and the same standard intensive care unit care. Supplementation will continue until discharge from the intensive care unit, death or a maximum duration of 3 weeks. The primary outcome will be organ-dysfunction evaluation assessed by the pattern of change in sequential organ failure assessment score over a 10-day period. The secondary outcomes are: the changes in total sequential organ failure assessment score on the last day of treatment, infectious complications during the ICU stay, 60-day mortality, length of stay in the intensive care unit and body-composition analysis. Discussion This study is the first trial to investigate the effect of intravenous alanyl-glutamine supplementation in multiple trauma patients receiving enteral nutrition on reducing severity of organ failure and infectious complications and preservation of lean body mass. Trial registration number This trial is registered at http://www.clinicaltrials.gov. NCT01240291.
Project description:Complete parenteral nutrition solutions contain mixed amino acid products providing all nine essential amino acids and a varying composition of nonessential amino acids. Relatively little rigorous comparative efficacy research on altered parenteral nutrition amino acid composition has been published in recent years.Limited data from randomized, double-blind, adequately powered clinical trials to define optimal doses of total or individual amino acids in parenteral nutrition are available. An exception is the growing number of studies on the efficacy of glutamine supplementation of parenteral nutrition or given as a single parenteral agent. Parenteral glutamine appears to confer benefit in selected patients; however, additional data to define optimal glutamine dosing and the patient subgroups who may most benefit from this amino acid are needed. Although some promising studies have been published, little data are available in the current era of nutrition support on the clinical efficacy of altered doses of arginine, branched chain amino acids, cysteine, or taurine supplementation of parenteral nutrition.Despite routine use of parenteral nutrition, surprisingly little clinical efficacy data are available to guide total or specific amino acid dosing in adult and pediatric patients requiring this therapy. This warrants increased attention by the research community and funding agencies to better define optimal amino acid administration strategies in patient subgroups requiring parenteral nutrition.
Project description:Caesarean-delivered preterm pigs were fed 3 d of parenteral nutrition followed by 2 d of enteral formula feeding. Antibiotics (n=11) or control saline (n=13) were given twice daily from birth to tissue collection at d 5. NEC-lesions and intestinal structure, function, microbiology and immunity markers were recorded. We used Affymetrix microarrays to investigate gene expression in intestinal tissues of preterm piglets treated with antibiotics or control saline. Twenty-four preterm piglets were delivered by caesarean section on day 105 of gestation from two healthy sows. All piglets were initially provided with parenteral nutrition via a vascular catheter, combined with small amounts of minimal enteral nutrition. On day three, all parenteral nutrition was stopped and total enteral nutrition was given through an oro-gastric feeding tube. Piglets were allocated into controls ( n=13) and an intervention group receiving oral and systemic broad-spectrum antibiotics ( n=11). To assure high systemic and intra luminal MIC values antibiotics were given both orally and intramuscularly. All antibiotics were given directly after feeding with an oral bolus and control pigs were given corresponding amounts of saline. On day five, all piglets were euthanized, and small intestinal tissue collected.
Project description:BACKGROUND:Enteral nutrition (EN) is a ubiquitous intervention in ICU patients but there is uncertainty regarding the optimal dose, timing and importance for patient-centered outcomes during critical illness. Our research group has previously found an improved protein balance during normocaloric versus hypocaloric parenteral nutrition in neurosurgical ICU patients. We now wanted to investigate if this could be demonstrated in a general ICU population with established enteral feeding, including patients on renal replacement therapy. METHODS:Patients with EN >80% of energy target as determined by indirect calorimetry were randomized to or 50% or 100% of current EN rate. After 24 hours, whole-body protein kinetics were determined by enteral and parenteral stable isotope tracer infusions. Treatment allocation was then switched, and tracer investigations repeated 24 hours later in a crossover design with patients serving as their own controls. RESULTS:Six patients completed the full protocol. During feeding with 100% EN all patients received >1.2 g/kg/day of protein. Mean whole-body protein balance increased from -6.07 to 2.93 µmol phenylalanine/kg/h during 100% EN as compared to 50% (p = 0.044). The oxidation rate of phenylalanine was unaltered (p = 0.78). CONCLUSIONS:It is possible to assess whole-body protein turnover using a stable isotope technique in critically ill patients during enteral feeding and renal replacement therapy. Our results also suggest a better whole-body protein balance during full dose as compared to half dose EN. As the sample size was smaller than anticipated, this finding should be confirmed in larger studies.
Project description:Background:Hematopoietic stem cell transplantation (HSCT) patients need parenteral nutrition because of nausea, vomiting, and mucositis caused by conditioning regimens. The demand for glutamine increases during the HSCT period. We evaluated the effects of glutamine-containing parenteral nutrition on the clinical outcomes of HSCT patients. Methods:In this retrospective analysis, we reviewed HSCT patients from Seoul National University from August 2013 to July 2017. Depending on their glutamine supplementation status, 91 patients were divided into 2 groups: glutamine group (N=44) and non-glutamine group (N=47). We analyzed the rate of weight change, infection (clinically/microbiologically documented), complications (duration of mucositis and neutropenia, acute graft versus host disease), and 100-days mortality in each group. Results:Regarding the clinical characteristics of the patients, there were no significant differences between the 2 groups except that there was a larger proportion of myeloablative conditioning regimen in the glutamine group (P=0.005). In the glutamine group, the average number of days of glutamine use, parenteral nutrition, and mucositis was 7.6±1.4, 14.6±9.9, and 13.3±9.5, respectively. Furthermore, multivariate analysis revealed odds ratios of 0.37 (95% CI, 0.14-0.96; P=0.042) and 0.08 (95% CI, 0.01-0.98; P=0.048) for clinically documented infection and 100-days mortality, respectively, in the glutamine group. Conclusion:Results showed that the glutamine group had less clinically documented infection and 100-days mortality than the non-glutamine group, but the other outcomes did not show significant differences. The extended duration of glutamine supplementation according to the period of total parenteral nutrition and mucositis should be considered.
Project description:The purpose of this study was to define an optimal injection protocol for 5-10 min duration navigator-based coronary MR angiography using an intravascular gadolinium-based contrast agent (GBCA), which is better suited for steady-state coronary MR angiography than conventional GBCAs.Using projections from pharmacokinetic models of the intravascular concentration of gadofosveset, a dual-injection protocol was formulated and tested on 14 healthy human subjects. Modified Look-Locker inversion recovery (MOLLI) sequences were used for T1 mapping at 3 Tesla to evaluate the concentration of tracer in the aorta over the scanning interval.Pharmacokinetic models for a bolus plus slow infusion technique at a 5, 10, and 15 min steady state intravascular concentration was compared to single bolus curves. The 70 %/30 % bolus/slow infusion technique resulted in the highest intravascular concentration over a 5 min scan duration. Similarly, the 60 %/40 % bolus/slow infusion technique was projected to be ideal for image acquisition duration of 5-10 min. These models were confirmed with T1 maps on normal volunteers. Arterial-venous mixing of contrast was achieved within 90 s of the beginning of the bolus.Gadofosveset injection is optimized for the lowest intravascular T1 time for 5-10 min duration MR angiography by bolus injection of 60-70 % of the total dose followed by slow infusion of the remainder of the total dose. This protocol achieves rapid and prolonged steady state intravascular concentrations of the GBCA that may be useful for prolonged image acquisition, such as required for navigator-based coronary MR angiography at 3 Tesla.ClinicalTrials.gov identifier: NCT01130545 NCT01130545 , registered as of May 25, 2010.
Project description:In vivo 13C magnetic resonance spectroscopy (MRS) enables the investigation of cerebral metabolic compartmentation while, e.g. infusing 13C-labeled glucose. Metabolic flux analysis of 13C turnover previously yielded quantitative information of glutamate and glutamine metabolism in humans and rats, while the application to in vivo mouse brain remains exceedingly challenging. In the present study, 13C direct detection at 14.1 T provided highly resolved in vivo spectra of the mouse brain while infusing [1,6-13C2]glucose for up to 5 h. 13C incorporation to glutamate and glutamine C4, C3, and C2 and aspartate C3 were detected dynamically and fitted to a two-compartment model: flux estimation of neuron-glial metabolism included tricarboxylic acid cycle (TCA) flux in astrocytes (Vg = 0.16 ± 0.03 µmol/g/min) and neurons (VTCAn = 0.56 ± 0.03 µmol/g/min), pyruvate carboxylase activity (VPC = 0.041 ± 0.003 µmol/g/min) and neurotransmission rate (VNT = 0.084 ± 0.008 µmol/g/min), resulting in a cerebral metabolic rate of glucose (CMRglc) of 0.38 ± 0.02 µmol/g/min, in excellent agreement with that determined with concomitant 18F-fluorodeoxyglucose positron emission tomography (18FDG PET).We conclude that modeling of neuron-glial metabolism in vivo is accessible in the mouse brain from 13C direct detection with an unprecedented spatial resolution under [1,6-13C2]glucose infusion.