When Is It Appropriate to Use Glutamine in Critical Illness?

Intestinal Mucosal Immune Barrier: A Powerful Firewall Against Severe Acute Pancreatitis-Associated Acute Lung Injury via the Gut-Lung Axis

The pathogenesis of severe acute pancreatitis-associated acute lung injury (SAP-ALI), which is the leading cause of mortality among hospitalized patients in the intensive care unit, remains incompletely elucidated. The intestinal mucosal immune barrier is a crucial component of the intestinal epithelial barrier, and its aberrant activation contributes to the induction of sustained pro-inflammatory immune responses, paradoxical intercellular communication, and bacterial translocation. In this review, we firstly provide a comprehensive overview of the composition of the intestinal mucosal immune barrier and its pivotal roles in the pathogenesis of SAP-ALI. Secondly, the mechanisms of its crosstalk with gut microbiota, which is called gut-lung axis, and its effect on SAP-ALI were summarized. Finally, a number of drugs that could enhance the intestinal mucosal immune barrier and exhibit potential anti-SAP-ALI activities were presented, including probiotics, glutamine, enteral nutrition, and traditional Chinese medicine (TCM). The aim is to offer a theoretical framework based on the perspective of the intestinal mucosal immune barrier to protect against SAP-ALI.

Effectiveness and mechanism study of glutamine on alleviating hypermetabolism in burned rats

OBJECTIVES

This study aimed to explore the effects of glutamine on hypermetabolic reactions in burned rats and its underlying mechanism.

METHODS

Fifty-five Sprague-Dawley rats were randomly divided into three groups, namely, the control (C), burned (B), and burned + glutamine (B + G) groups. Rats in the glutamine treatment group were supplemented with 1 g glutamine per kg body weight. Changes in body weight and resting energy expenditure in all groups were observed daily. Blood glucose and glucose tolerance level were measured on days 1, 3, 7, 10 and 14 after burn injury. On days 7 and 14 after injury, the rats were sacrificed, and the weight and protein content of the skeletal muscle were measured. Moreover, the level of glutamine, inflammatory mediator, nicotinamide adenine dinucleotide phosphate (NADPH), glutathione, and the activity of glutamine metabolic enzymes were measured.

RESULTS

The hypermetabolic reaction after burn injury was significantly inhibited by glutamine administration, and the range of variations in the resting energy expenditure and body weight indicators was narrowed remarkably (P < 0.05 or 0.01), whereas the weight and protein content of the skeletal muscle returned to normal (P < 0.05 or 0.01). Glutamine could increase glutaminase activity in various tissues, promote the utilization of glutamine, and appropriately reduce the degree of organ damage and inflammatory response (P < 0.05 or 0.01). Furthermore, glutamine could promote the synthesis of the reducing substances NADPH and glutathione (P < 0.05 or 0.01).

CONCLUSIONS

Glutamine administration effectively reduces hypermetabolic reactions by promoting NADPH synthesis, inhibiting oxidative stress, and improving glutamine utilization after burn injury.

Metabolic engineering of Escherichia coli for efficient production of L-alanyl-L-glutamine

BACKGROUND

L-Alanyl-L-glutamine (AQ) is a functional dipeptide with high water solubility, good thermal stability and high bioavailability. It is widely used in clinical treatment, post-operative rehabilitation, sports health care and other fields. AQ is mainly produced via chemical synthesis which is complicated, time-consuming, labor-intensive, and have a low yield accompanied with the generation of by-products. It is therefore highly desirable to develop an efficient biotechnological process for the industrial production of AQ.

RESULTS

A metabolically engineered E. coli strain for AQ production was developed by over-expressing L-amino acid α-ligase (BacD) from Bacillus subtilis, and inactivating the peptidases PepA, PepB, PepD, and PepN, as well as the dipeptide transport system Dpp. In order to use the more readily available substrate glutamic acid, a module for glutamine synthesis from glutamic acid was constructed by introducing glutamine synthetase (GlnA). Additionally, we knocked out glsA-glsB to block the first step in glutamine metabolism, and glnE-glnB involved in the ATP-dependent addition of AMP/UMP to a subunit of glutamine synthetase, which resulted in increased glutamine supply. Then the glutamine synthesis module was combined with the AQ synthesis module to develop the engineered strain that uses glutamic acid and alanine for AQ production. The expression of BacD and GlnA was further balanced to improve AQ production. Using the final engineered strain p15/AQ10 as a whole-cell biocatalyst, 71.7 mM AQ was produced with a productivity of 3.98 mM/h and conversion rate of 71.7%.

CONCLUSION

A metabolically engineered strain for AQ production was successfully developed via inactivation of peptidases, screening of BacD, introduction of glutamine synthesis module, and balancing the glutamine and AQ synthesis modules to improve the yield of AQ. This work provides a microbial cell factory for efficient production of AQ with industrial potential.

Seven Deadly Sins of Nutrition Therapy in Critically Ill Patients

This article presents 7 nutrition steps that, if not followed by the clinical staff, may be metaphorically considered as "7 deadly sins" of nutrition therapy. In this review, we suggest approaches that must be avoided or accomplished to increase compliance with the "Ten Commandments" of good nutrition practice in the intensive care setting. Multiple aggressive and simultaneous sets of therapies are implemented in the intensive care setting, which include nutrition and metabolic support as important components in these therapies. "Sins" should be remembered as a mnemonic device for nutrition standard care in the intensive care unit; this incorporates nutrition adequacy and protocol adherence.

Therapeutic benefits of glutamine: An umbrella review of meta-analyses

Glutamine may be an essential amino acid in patients with catabolic disease, as it has been demonstrated that circulating glutamine levels drop during critical illness and following major surgery; this may result in an increase in secondary infection risk, recovery time and mortality rates. However, there is much discrepancy in the literature with regards to randomized controlled studies, and therefore, the present study is an umbrella review of published meta-analyses, conducted to examine the effectiveness of glutamine's role as a therapeutic agent. A search using PubMed, Cochrane Library and CINAHL from January 1st, 1980 to December 31st, 2016 was conducted using the following strategy: 'Glutamine AND (meta-analysis OR systematic review)' and publications were retrieved, which provided quantitative statistical analysis of pooled treatment effects on the relative risks of infectious complications, mortality and length of stay in hospital. A total of 22 meta-analyses were entered into the current umbrella review. As displayed in Tables I, II and III, these analyses are split into three groups, based on different parameters. Of the 19 meta-analyses investigating the effects of infectious complications, 15 identified statistically significant reductions in complications, with relative risks ranging between 0.42 and 0.93. In addition, 12 of the 18 meta-analyses analyzing the length of hospital stays presented statistically significant reductions in the length of stay, with reductions ranging between 0.19 to 4.73 days. Only 4 of the 15 meta-analyses studying mortality effects identified statistically significant reductions in mortality with relative risks ranging between 0.64 and 1.28. Statistically significant heterogeneity was observed in 16 of 22 meta-analyses, and publication bias was observed in five of 11 meta-analyses. Glutamine supplementation for critically ill or surgical patients through parenteral or enteral routes appears to reduce the rate of hospital acquired infectious complications and shortening of the length of stay in hospital. Furthermore, glutamine supplementation appeared to reduce the rate of in-patient mortality, but the majority of meta-analyses did not reach statistical significance. However, researchers must appreciate the positive results with caution in light of the fact that there exists statistically significant heterogeneity for the majority of meta-analyses, and statistically significant publication bias in almost half.