Hepatic glutamine metabolism during endotoxemia in neonatal rats

Royal Australasia of Surgeons Guest Lecture. Necrotizing enterocolitis: prevention, treatment, and outcome

Necrotizing enterocolitis (NEC) remains a very serious disease, particularly in premature infants. This review describes various aspects of the diagnosis and treatment of the disease. The pathogenesis of NEC is not completely understood, and risk factors include formula enteral feeding and bacterial involvement. Prevention of the disease is desirable, and the most robust evidence is linked to the protective effet of human milk and probiotics. The medical and surgical management has not changed significantly in the last 20 years. Insertions of peimary peritoneal drainage in comparison with laparotomy remain controversial, and this uncertainty stimulated the development of two randomized controlled trials. Neither definitely demonstrated an advantage of either periotneal drainage or laparotomy over the other. The advantage offered by a stoma compared to primary intestinal anastomosis is currently investigated in a multicenter randomized controlled trial (STAT Trial). The mortality of the disease remains high, and new therapeutic interventions are needed. Novel forms of treatment that can improve the outcome of this disease are currently under investigation. These include whole-body moderately controlled hypothermia and administration of amniotic fluid stem cells.

Bench-to-bedside review: Neonatal sepsis-redox processes in pathogenesis

The present review is aimed at elucidating the neonatal 'sepsis redox cycle' - the cascade of inflammatory and redox events involved in the pathogenesis of sepsis in neonates. While adult and neonatal sepses share some common features, there are some substantial differences: higher mortality rates occur in adult sepsis and worse long-term effects are evident in neonatal sepsis survivors. Such epidemiological data may be explained by the lower ability of IL6 and IL8 to activate NF-κB-regulated transcription in neonatal sepsis in comparison to TNF-α, which is involved in the mechanisms of adult sepsis. The activation of NF-κB in neonatal sepsis is further promoted by hydrogen peroxide and results in mitochondrial dysfunction and energy failure as septic neonates experience decreased O₂ consumption as well as lower heat production and body temperature in comparison to healthy peers. In neonates, specific organs that are still under development are vulnerable to sepsis-provoked stress, which may lead to brain, lung, and heart injury, as well as vision and hearing impairments. In the light of the processes integrated here, it is clear that therapeutic approaches should also target specific steps in the neonatal 'sepsis redox cycle' in addition to the current therapeutic approach that is mainly focused on pathogen eradication.

Impaired energy metabolism during neonatal sepsis: the effects of glutamine

Neonatal sepsis is an important cause of morbidity and mortality as a result of multiple organ system failure, particularly in neonates requiring total parenteral nutrition. Suitable therapies and support are needed both to prevent sepsis and to prevent multiple organ failure. After bacterial infection, pro-inflammatory cytokines trigger the antimicrobial activity of macrophages and neutrophils, resulting in production of reactive species such as H2O2, NO, superoxide and peroxynitrite. However, excess production can lead to host tissue damage. Incubation of either hepatocytes or heart mitochondria from neonatal rats with these reactive species, or with cytokines, leads to impairment of mitochondrial oxidative function, and in an animal model of neonatal sepsis similar results to thein vitrofindings have been demonstrated. Recentin vivostudies, using indirect calorimetry of suckling rat pups, show that during endotoxaemia there is a profound hypometabolism, associated with hypothermia. Having determined that cellular oxidative function may be impaired during sepsis, it is of great importance to try to identify therapeutic measures. Much interest has been shown in glutamine, which may become essential during sepsis. It has been shown that hepatic glutamine is rapidly depleted during endotoxaemia. When hepatocytes from endotoxaemic rats were incubated with glutamine, there was a restoration of mitochondrial structure and metabolism.In vivo, intraperitoneal injection of glutamine into endotoxic suckling rats partially reversed hypometabolism, markedly reduced the incidence of hypothermia and improved clinical status. These results suggest that glutamine has a beneficial effect during sepsis in neonates.

Glutamine and acute illness

This is a literature review over a time period of the past 2 years concerning glutamine in clinical nutrition. Emphasis is put upon studies of glutamine in clinical settings, but a brief overview of the large range of literature over the role of glutamine in various experimental settings is also included. The most interesting concept for the past 2 years is the suggestion to use plasma glutamine concentration at admission to the intensive care unit as a prognostic marker and as a possible indicator for indication of glutamine supplementation.

Glutamine in pediatrics: where next?

OBJECTIVE

We reviewed the literature and examined the issues surrounding the use of glutamine in pediatrics and neonatology.

METHODS

We reviewed the literature using Medline, Embase, Current Contents, and International Pharmaceutical Abstracts. Additional information was obtained from bibliographic citations and personal communications.

RESULTS

Evidence showed that glutamine levels are affected in a number of life stages and conditions. Useful, indicative studies are emerging but many fail to demonstrate significant differences. The problems of researching in this patient population were demonstrated.

CONCLUSION

A need for a great deal of further research in this area, including larger multicenter trials, clearly emerged.