Perioperative application of l-alanyl-l-glutamine in cardiac surgery: effect on the polarized T cell cytokine expression

The Preventive Role of Glutamine Supplementation in Cardiac Surgery-Associated Kidney Injury from Experimental Research to Clinical Practice: A Narrative Review

Acute kidney injury represents a significant threat in cardiac surgery regarding complications and costs. Novel preventive approaches are needed, as the therapeutic modalities are still limited. As experimental studies have demonstrated, glutamine, a conditionally essential amino acid, might have a protective role in this setting. Moreover, the levels of glutamine after the cardiopulmonary bypass are significantly lower. In clinical practice, various trials have investigated the effects of glutamine supplementation on cardiac surgery with encouraging results. However, these studies are heterogeneous regarding the selection criteria, timing, dose, outcomes studied, and way of glutamine administration. This narrative review aims to present the potential role of glutamine in cardiac surgery-associated acute kidney injury prevention, starting from the experimental studies and guidelines to the clinical practice and future directions.

Glutamine promotes antibiotic uptake to kill multidrug-resistant uropathogenic bacteria

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Impact of Immunonutrition on T Cell Activation: A Randomized Control Study in Cardiac Surgery Patients

Background.

Cardiac surgery provokes an intense inflammatory response that can cause an immunosuppressive state and adverse postoperative outcomes. We recently showed that postoperative immunonutrition with glutamine in “fragile” low-risk cardiac surgery patients was associated with a significantly increased level of CD3+ and CD4+ T cells. In order to clarify the biological relevance and clinical importance of these findings, we investigated whether an increase in the CD4+ T cell level was caused by changes in the systemic inflammatory response (caused by surgery or infection) and if it was associated with their activation status.

Methods.

A randomized control study of low operative risk but “fragile” cardiac surgery patients was performed. Patients were randomized into immunonutrition (IN) and control groups (C). The IN group received normal daily meals plus special immune nutrients for 5 days postoperatively, while the C group received only normal daily meals. Laboratory parameters were investigated before surgery and on the sixth postoperative day and the groups were compared accordingly. The expression of the CD69+ marker was investigated to determine T cell activation status. Serum concentrations of cytokines (interleukin-10 (IL-10), tumor necrosis factor α (TNF-α) and interleukin-6 (IL-6)) and C-reactive protein (CRP) were determined to assess the systemic inflammatory response, while procalcitonin (PCT) levels were evaluated to confirm or deny possible bacterial infection.

Results.

Fifty-five patients were enrolled in the study. Twenty-seven (49.1%) were randomized in the IN group. Results show that on the sixth postoperative day, the CD4+CD69+ and CD8+CD69+ counts did not differ between the IN and C groups, accordingly 0.25 [0.16–0.50] vs 0.22 [0.13-0.41], p=0.578 and 0.13 [0.06–0.3] vs 0.09 [0.05–0.14], p=0.178. Also, statistically significant differences were not observed in the cytokine levels (IN and C groups: TNF-α 8.13 [7.32–10.31] vs 8.78 [7.65–11.2], p=0.300; IL-6 14.65 [9.28–18.95] vs 12.25 [8.55–22.50], p=0.786; IL-10 5.0 [5.0–5.0] vs 5.0 [5.0–5.0], p=0.343 respectively), which imply that an elevated T cell count is not associated with the systemic inflammatory response. Also, PCT (IN and C groups: 0.03 [0.01–0.09] vs 0.05 [0.03–0.08], p=0.352) and CRP (IN and C groups 62.7 [34.2–106.0] vs 63.7 [32.9–91.0], p=0.840) levels did not differ between the two groups. Moreover, low levels of PCT indicated that the increase in T cell count was not determined by bacterial infection.

Conclusions.

Our findings showed that CD4+ T cell levels were associated with neither the systemic inflammatory response nor bacterial infection. Secondly, increases in T cells are not accompanied by their activation status. These results suggest a hypothesis that a higher postoperative T cell concentration may be associated with postoperative immunonutrition in low-risk cardiac surgery patients with intact cellular vitality, i.e. “fragile”. However, immunonutrition alone did not affect T cell activation status.

The efficacy of early postoperative enteral immunonutrition on T-lymphocyte count: A randomised control study in low-risk cardiac surgery patients

BACKGROUND

Patients undergoing cardiac surgery have a pronounced immune response that leads to a reduction in cellular immunity. Immune-modulating nutritional supplements are considered to be beneficial for patients undergoing major surgery. However, due to the lack of studies in the cardiac surgery population, the effect of immunonutrition remains unclear in this patient group.

OBJECTIVE

Our purpose was to research the efficacy of early postoperative enteral immunonutrition on T-lymphocyte count in the cardiac surgery population.

METHODS

This was a randomised control study of low operative risk adult patients, who underwent elective cardiac surgery. These patients were randomised into immunonutrition and control groups. The immunonutrition group was supplemented with immune nutrients for five postoperative days. The counts of T-lymphocytes, as well as the counts for the CD4+ and CD8+ cell subpopulations were determined on the day of surgery and on the sixth postoperative day.

RESULTS

Fifty-five patients were enrolled in the study, the mean age was 69.7 ± 6.3 years, 28 (50.9%) of them were males, the median operative risk was 1.75%. Twenty-seven (49.1%) were randomised into the immunonutrition group. The control and the immunonutrition groups were similar before the intervention. The counts of the CD3+ T cells and CD4+ T cells on the sixth postoperative day were significantly higher in the immunonutrition group compared to the control group with 1.42 ± 0.49 vs. 1.12 ± 0.56 (∗10⁹/l), p = 0.035 and 1.02 ± 0.36 vs. 0.80 ± 0.43 (∗10⁹/l), p = 0.048, respectively. Regression analysis was performed to determine the efficacy of the immunonutrition on the counts of the CD3+ and CD4+ T cells; CD3+ T and CD4+ T cell counts were increased to 0.264 (∗10⁹/l), p = 0.039 and 0.232 (∗10⁹/l), p = 0.021, respectively.

CONCLUSIONS

Early postoperative immunonutrition increases the count of the CD3+ and CD4+ T cells in cardiac surgical patients. Clinical trials identifier number: NCT04047095.

Glutamine effects on heat shock protein 70 and interleukines 6 and 10: Randomized trial of glutamine supplementation versus standard parenteral nutrition in critically ill children

BACKGROUND & AIMS

To determine whether glutamine (Gln) supplementation would have a role modifying both the oxidative stress and the inflammatory response of critically ill children.

METHODS

Prospective, randomized, double-blind, interventional clinical trial. Selection criteria were children requiring parenteral nutrition for at least 5 days diagnosed with severe sepsis or post major surgery. Patients were randomly assigned to standard parenteral nutrition (SPN, 49 subjects) or standard parenteral nutrition with glutamine supplementation (SPN + Gln, 49 subjects).

RESULTS

Glutamine levels failed to show statistical differences between groups. At day 5, patients in the SPN + Gln group had significantly higher levels of HSP-70 (heat shock protein 70) as compared with the SPN group (68.6 vs 5.4, p = 0.014). In both groups, IL-6 (interleukine 6) levels showed a remarkable descent from baseline and day 2 (SPN: 42.24 vs 9.39, p < 0.001; SPN + Gln: 35.20 vs 13.80, p < 0.001) but only the treatment group showed a statistically significant decrease between day 2 and day 5 (13.80 vs 10.55, p = 0.013). Levels of IL-10 (interleukine 10) did not vary among visits except in the SPN between baseline and day 2 (9.55 vs 5.356, p < 0.001). At the end of the study, no significant differences between groups for PICU and hospital stay were observed. No adverse events were detected in any group.

CONCLUSIONS

Glutamine supplementation in critically-ill children contributed to maintain high HSP-70 levels for longer. Glutamine supplementation had no influence on IL-10 and failed to show a significant reduction of IL-6 levels.

Nutritional Effect of Oral Supplement Enriched in ω-3 Fatty Acids, Arginine, RNA on Immune Response and Leukocyte-platelet Aggregate Formation in Patients Undergoing Cardiac Surgery

The aim of the present study was to investigate the influence of a supplement enriched in ω-3 fatty acids on immune responses and platelet–leukocyte complex formation in patients undergoing cardiac surgery. Patients in the supplement group (n = 7) took a supplement enriched in ω-3 fatty acids (Impact^®) in addition to a hospital diet for five successive days before surgery; those in the control group (n = 7) took only hospital diet and did not take Impact^®. Blood samples in both groups were collected at same time points. Before surgery, samples were collected five days before surgery, at the start of supplementation (baseline), and the end of supplementation (postoperative day (POD)-0). After surgery, samples were collected on POD-1 and POD-7. The expression of human leukocyte antigen (HLA)-DR, the ratio of CD4-/CD8-positive cells, the production of interferon (IFN)-γ by CD4-positive cells, plasma levels of cytokines, and leukocyte–platelet aggregates were measured. Before surgery (POD-0), the supplement caused significant increases in HLA-DR expression, CD4/CD8 ratio, and plasma levels of IFN-γ; these levels were significantly higher compared to those in the control group (P < 0.05, respectively). After surgery (POD-1), all values dramatically decreased in comparison with those of POD-0; however, the values in the supplement group were significantly higher compared to their respective markers in the control group (P < 0.05, respectively). Significant differences of HLA-DR expression and CD4/CD8 ratio persisted through POD-7. Before surgery (POD-0), plasma levels of interleukin (IL)-10 in the supplement group decreased significantly compared with those in the control group (P < 0.05). After surgery (POD-1), plasma levels of IL-10 in both the control and supplement groups increased; these levels in the supplement group were significantly lower than those in the control group (P < 0.05). Significant decreases in the percentage of leukocyte–platelet aggregates were found after supplementation; the difference between the supplement and the control groups was found on POD-0 and POD-1 (P < 0.05, respectively). In conclusion, the dietary supplement increased HLA-DR expression, the CD4/CD8 ratio, and the production of IFN-γ by CD4-positive cells; conversely, the levels of IL-10 and the formation of leukocyte–platelet aggregates before and after surgery were suppressed. These beneficial effects may decrease the incidence of complications after surgery.

L-Glutamine or L-alanyl-L-glutamine prevents oxidant- or endotoxin-induced death of neonatal enterocytes

This study tested the hypothesis that L-glutamine (Gln) or L-alanyl-L-glutamine (Ala-Gln) prevents oxidant- or endotoxin-induced death of neonatal enterocytes. Enterocytes of neonatal pigs rapidly hydrolyzed Ala-Gln and utilized Gln. To determine whether Gln or Ala-Gln has a cytoprotective effect, IPEC-1 cells were cultured for 24 h in Gln-free Dulbecco's modified Eagle's-F12 Ham medium containing 0, 0.5, 2.0 or 5.0 mM Gln or Ala-Gln, and 0, 0.5 mM H(2)O(2) or 30 ng/ml lipopolysaccharide (LPS). Without Gln or Ala-Gln, H(2)O(2)- or LPS-treated cells exhibited almost complete death. Gln or Ala-Gln at 0.5, 2 and 5 mM dose-dependently reduced H(2)O(2)- or LPS-induced cell death by 14, 54 and 95%, respectively, whereas D: -glutamine, alanine, glutamate, ornithine, proline, glucosamine or nucleosides had no effect. To evaluate the effectiveness of Gln or Ala-Gln in vivo, 7-day-old piglets received one-week oral administration of Gln or Ala-Gln (3.42 mmol/kg body weight) twice daily and then a single intraperitoneal injection of LPS (0.1 mg/kg body weight); piglets were euthanized in 24 and 48 h to analyze intestinal apoptotic proteins and morphology. Administration of Gln or Ala-Gln to LPS-challenged piglets increased Gln concentrations in small-intestinal lumen and plasma, reduced intestinal expression of Toll-like receptor-4, active caspase-3 and NFkB, ameliorated intestinal injury, decreased rectal temperature, and enhanced growth performance. These results demonstrate a protective effect of Gln or Ala-Gln against H(2)O(2)- or LPS-induced enterocyte death. The findings support addition of Gln or Ala-Gln to current Gln-free pediatric amino acid solutions to prevent intestinal oxidative injury and inflammatory disease in neonates.