Infusion of dipeptides as nutritional substrates for glutamine, tyrosine, and branched-chain amino acids in patients with acute pancreatitis

Melatonin ameliorates multiorgan injuries induced by severe acute pancreatitis in mice by regulating the Nrf2 signaling pathway

Severe acute pancreatitis (SAP) is a complicated inflammatory reaction that impacts the pancreas, often resulting in damage to numerous organs. This disorder encompasses a range of processes such as inflammation, oxidative stress, and pancreatitis. The hormone melatonin (MT) is primarily secreted by the pineal gland and plays a crucial role in mitigating inflammation, countering the harmful effects of free radicals, and regulating oxidative stress. The aim of this research was to investigate the potential protective impact and the underlying mechanism of melatonin in mice afflicted with SAP. The biochemical and histological assessments unequivocally demonstrated that melatonin effectively inhibited necrosis, infiltration, edema and cell death in pancreatic tissues, thereby suppressing acute pancreatitis. Notably, melatonin also alleviated the consequent harm to distant organs, notably the lungs, liver, and kidneys. Furthermore, both preventive and therapeutic administration of melatonin prompted nuclear factor E2-related factor 2 (Nrf2) activation followed by Nrf2 target gene expression. Nrf2 initiates the activation of antioxidant genes, thereby providing defense against oxidative stress. Conversely, Nrf2 reduction may contribute to impaired antioxidant protection in SAP. The beneficial impact of Nrf2 on antioxidants was absent in Nrf2-knockout mice, leading to the accumulation of LDH and exacerbation of cell death. This deterioration in both pancreatitis and injuries in distant organs intensified significantly. The results indicate that melatonin has an enhanced ability to protect against multiorgan damage caused by SAP, which is accomplished through the increase in Nrf2 expression. Additionally, Nrf2 initiates the activation of antioxidant genes that offer defense against cell death.

Two new mixed copper(ii)–dipeptide complexes of N,N-donor heterocycle ligands: studies on their non-covalent DNA binding, chemical nuclease, antioxidant and anticancer activities

Two novel mononuclear mixed ligand copper(ii)-dipeptide complexes have been synthesized. The DNA interactions of the complexes were investigated. In addition, the antioxidant and antitumor activities of the complexes were evaluated.

Physicochemical properties of the ternary complexes of Pt(ii) with uracil and small peptide moieties: an experimental and computational study

Interactions of Pt(Ura)(GL) with DNA.

Efficacy of parenteral nutrition supplemented with glutamine dipeptide to decrease hospital infections in critically ill surgical patients

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.

Appearance of individual amino acid concentrations in arterial blood during steady-state infusions of different amino acid formulations to ICU patients in support of whole-body protein metabolism

BACKGROUND

Previous work has demonstrated a relationship between arterial amino acid concentrations and uptake of amino acids across peripheral tissues in healthy volunteers, as well as in chronically and acutely ill patients. The aim of the present study was to evaluate whether different amino acid profiles in commercially available amino acid formulations are translated into significantly different arterial amino acid concentrations presumably high enough to promote protein metabolism in intensive care unit (ICU) patients.

METHODS

Nonprotein calories (60% glucose: 40% lipid) were simultaneously and constantly infused over 72 hours. Different free amino acid solutions were infused at random to each patient for 24 hours in order to determine the appearance of steady-state arterial concentrations of individual amino acids. Basal metabolic and nutrition states were defined after a 12-hour infusion period with glucose in each patient. Healthy volunteers receiving a standardized oral meal served as reference subjects in measurements of venous amino acid concentrations after normal oral food intake.

RESULTS

The sum of all amino acids in arterial plasma increased significantly during steady-state infusions of all the free amino acid solutions vs basal state in ICU patients. Only glutamine, taurine, and tyrosine did not increase at all vs basal state during steady-state infusions of the 3 formulations. Alanine, arginine, citrulline, glycine, histidine, serine, methionine, phenylalanine, valine, and ornithine showed different concentration among the amino acid solutions during infusions. Healthy volunteers had significantly higher overall concentrations of amino acids in both fasted and fed state compared with ICU patients, which indicates that free amino acid solutions remain a limiting component in artificial nutrition to patients to promote arterial amino acid concentrations in the artificially fed state.

CONCLUSIONS

It appears important to continue further improvement of composition profile in solutions of free amino acids to promote adequate uptake across organ beds in promotion of protein balance in artificially nourished patients.

The effect of graded intake of glycyl-L-tyrosine on phenylalanine and tyrosine metabolism in parenterally fed neonates with an estimation of tyrosine requirement

Although tyrosine is considered indispensable during the neonatal period, its poor solubility has limited its inclusion in parenteral amino acid solutions to less than 1% of total amino acids. Dipeptides of tyrosine are highly soluble, have been shown to be well used and safe in animal models and humans, and, therefore, may be used as an effective means of providing tyrosine in the parenterally fed neonate. The goal of the present study was to determine the tyrosine requirement of the parenterally fed neonate receiving graded intakes of glycyl-L-tyrosine as a source of tyrosine. Thirteen infants receiving adequate energy (340 +/- 38 kJ. kg(-1).d(-1)) and protein (2.4 +/- 0.4 g.kg(-1).d(-1)) were randomized to receive parenteral nutrition with one of five graded levels of glycyl-L-tyrosine. The mean requirement and safe level of intake were estimated using a 1-(13)C-phenylalanine tracer and linear regression cross-over analysis that identified a break point in the response of label appearance in breath CO(2) (F(13)CO(2)) and phenylalanine oxidation to graded tyrosine intake. Based on the mean estimates of whole-body phenylalanine oxidation, the tyrosine mean requirement and safe level of intake were found to be 74 mg.kg(-1). d(-1) and 94 mg.kg(-1).d(-1), respectively. This represents 3.1 and 3.9% of total amino acids, respectively, considerably higher than levels found in present commercially available pediatric amino acid solutions. These data raise concern regarding the adequacy of aromatic amino acid intake in the parenterally fed neonate.

Addition of tyrosyl-arginine to parenteral nutrition is anabolic in unstressed rats

To determine whether the addition of tyrosine and arginine (Arg), as tyrosyl-arginine (TyrArg), to parenteral nutrition (PN) can promote anabolism, rats were assigned to: 1) PN (1.20 MJ. kg body weight [BW](-1) x d(-1) and 1.22 gN x kgBW(-1) x d(-1); PN control group, n = 5), 2) PN plus TyrArg (2.6 mmol. kgBW(-1) x d(-1); TyrArg group, n = 6), or 3) PN plus Arg (2.6 mmol. kgBW(-1). d(-1); Arg group, n = 5). Results from these three groups were compared with an unoperated chow-fed reference group (chow control group, n = 5). The BW gain during PN and the proportion of lipid in the total body after 14 d of PN was greater for the TyrArg group than for the PN group (P<0.01). Although the differences in weight gain, body water, lipid, and protein between the TyrArg and Arg groups were not significant, the mean weight gain throughout PN was greater in the TyrArg group than in the Arg group. The proportion of protein in the small intestine, colon, and gastrocnemius muscle was greater in the TyrArg and Arg groups than in the PN group (P<0.01). A distinct requirement for tyrosine has not been demonstrated in this model, and additional studies in stressed animals are required. In contrast, arginine had tissue-specific anabolic activity.

Nutrition in acute pancreatitis

Pancreatitis is a common disorder. Numerous factors have been implicated in the pathogenesis of acute and chronic pancreatitis, but the exact mechanisms of these conditions are still poorly understood. Depending on the cause of the disorder, patients who have pancreatitis are usually not malnourished and are able to eat within 5 to 7 days of disease onset. In these patients, nutritional support is unnecessary. However, severe disease induces a catabolic state similar to that seen in trauma and sepsis, resulting in rapid weight loss and increased morbidity and mortality. Thus, vigorous nutritional support may be useful in the treatment of severe pancreatitis. Studies have shown that parenteral and enteral nutritional support are well tolerated and can maintain or improve nutritional status in patients with pancreatitis. This article reviews nutritional assessment and therapy in pancreatitis.

Glutamine

Glutamine is the most abundant free amino acid in the circulation. It is a primary fuel for rapidly dividing cells and plays a key role in the transport of nitrogen between organs. Although glutamine is absent from conventional regimens aimed at nutritional support, glutamine deficiency can occur during periods of metabolic stress; this has led to the reclassification of glutamine as a conditionally essential amino acid. Experiments with various animal models have demonstrated that the provision of glutamine can result in better nitrogen homoeostasis, with conservation of skeletal muscle. There is also considerable evidence that glutamine can enhance the barrier function of the gut. This review concludes by discussing the clinical evidence that supports the inclusion of stable forms of glutamine in solutions of nutrients.

Glutamine peptide-supplemented long-term total parenteral nutrition: effects on intracellular and extracellular amino acid patterns, nitrogen economy, and tissue morphology in growing rats

Glutamine (GLN) is a nonessential amino acid that is not included in current regimens for parenteral nutrition because of its chemical instability. This study tested the hypothesis that GLN supplementation during long-term total parenteral nutrition (TPN) (3 weeks) would enhance GLN availability, thereby improving nitrogen economy and growth in a growing rat model: Standard TPN delivering 300 kcal/kg per day (lipid:carbohydrate = 1.1) including 2.1 g of nitrogen per kilogram per day in an all-in-one solution was compared with an isonitrogenous, isocaloric, and isovolemic TPN regimen with 0.29 g of nitrogen per kilogram per day substituted by GLN derived from the dipeptides glycyl-GLN and alanyl-GLN (TPN GLN). Enterally fed controls were included. Analysis was confined to nonbacteremic animals with negative blood culture, in which extracellular and intracellular amino acid concentrations including GLN, nitrogen balance, serum protein concentrations, growth, and histologic sections of liver and small-bowel mucosa (light and scanning electron microscopy) were evaluated. Hepatic intracellular GLN concentrations were significantly lower, in animals receiving GLN-free TPN (11.7 +/- 1.6 nmol/mg fat-free dry and solid tissue mass, n = 9) compared with both GLN-supplemented TPN (16.0 +/- 3.0, n = 7) and enteral feeding (18.2 +/- 1.8, n = 6) (p < .001). Corresponding results were found for intracellular GLN concentrations in skeletal muscle (TPN standard 12.5 +/- 3.1, TPN GLN 14.7 +/- 3.1, enteral control 17.3 +/- 2.3, p < .05), intestinal mucosa, and spleen as well as for plasma concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)

Use of the soluble peptide gamma-L-glutamyl-L-tyrosine to provide tyrosine in total parenteral nutrition in rats

Limited solubility restricts amounts of tyrosine (Tyr) in amino acid solutions used in total parenteral nutrition (TPN). Excess phenylalanine (Phe) is included in TPN for conversion to Tyr by liver Phe hydroxylase. However, this conversion is limited, especially in infants. We have confirmed that infants receiving TPN have low Tyr concentrations and high Phe/Tyr ratios in plasma compared with published values for enterally fed neonates. Tyr is important in the synthesis of proteins and other biomolecules, including catecholamines in the brain. We tested the soluble peptide gamma-glutamyl-tyrosine (Glu(Tyr)) as a possible precursor of Tyr in TPN. Groups of five rats were given infusions of TPN containing an amino acid mixture simulating a commercial formulation (group A), TPN in which Glu(Tyr) was substituted for half the Phe in the group A solution) (group B), or saline (group C). Control animals (group C) were fed rodent chow. Blood was sampled at 0 time and daily for 4 days. Brains were collected at 96 hours, and aromatic amino acids in plasma and brains were measured by high-performance liquid chromatography. Throughout the experiment, plasma of animals in group A had significantly elevated Phe and reduced Tyr concentrations compared with control values; plasma concentrations in groups B and C were similar. In groups A and B, brain Tyr levels were 31% and 63% of control values, respectively. In group B, Glu(Tyr) was not detected in brains. These data suggest that supplementing current TPN mixtures with Glu(Tyr), which is stable in solution, can produce normal plasma Tyr concentrations and Phe/Tyr ratios and improve the supply of Tyr to the brain.

Dipeptides in parenteral nutrition: from basic science to clinical applications

The use of intravenous dipeptides shows great promise as an avenue for the provision of amino acids that may otherwise be difficult to deliver via nutrient infusions. The physical/chemical properties and metabolism of numerous dipeptides have now been explored in experimental and human studies. It has been found that these agents have the capacity to spare nitrogen and support serum protein levels in a fashion equivalent to that of intravenous free amino acids. An additional benefit is the ability to deliver certain amino acids that are relatively unstable or poorly soluble in aqueous solutions. These various aspects of intravenous dipeptides are considered in this review.

The potential use of parenteral dipeptides in clinical nutrition

The metabolic effects of intravenous peptides have undergone extensive investigation in recent years. Dipeptide solutions provide a mechanism for the provision of selected amino acids that may be conditionally indispensable under certain clinical conditions. In particular, amino acids such as cystine, glutamine, and tyrosine may be difficult to provide in their free form, but their availability can be increased substantially when they are supplied in the form of a dipeptide. Animal and human studies have demonstrated that parenteral dipeptides are cleared rapidly from the plasma compartment and favorably influence nitrogen equilibrium in healthy volunteers and catabolic patients. Certain dipeptides offer the potential for tailoring tissue-specific nutrition therapy. It seems likely that parenteral peptides will offer a major change in the delivery of intravenous nutrients.