Influence of nutrition therapy on the intestinal microbiome

Enhanced exclusive enteral nutrition delivery during the first 7 days is associated with decreased 28-day mortality in critically ill patients with normal lactate level: a post hoc analysis of a multicenter randomized trial

BACKGROUND AND AIMS

Exclusive enteral nutrition (EN) is often observed during the first week of ICU admission because of the extra costs and safety considerations for early parenteral nutrition. This study aimed to assess the association between nutrition intake and 28-day mortality in critically ill patients receiving exclusive EN.

METHODS

This is a post hoc analysis of a cluster-randomized clinical trial that assesses the effect of implementing a feeding protocol on mortality in critically ill patients. Patients who stayed in the ICUs for at least 7 days and received exclusive EN were included in this analysis. Multivariable Cox hazard regression models and restricted cubic spline models were used to assess the relationship between the different doses of EN delivery and 28-day mortality. Subgroups with varying lactate levels at enrollment were additionally analyzed to address the potential confounding effect brought in by the presence of shock-related hypoperfusion.

RESULTS

Overall, 1322 patients were included in the analysis. The median (interquartile range) daily energy and protein delivery during the first week of enrollment were 14.6 (10.3-19.6) kcal/kg and 0.6 (0.4-0.8) g/kg, respectively. An increase of 5 kcal/kg energy delivery was associated with a significant reduction (approximately 14%) in 28-day mortality (adjusted hazard ratio [HR] = 0.865, 95% confidence interval [CI]: 0.768-0.974, P = 0.016). For protein intake, a 0.2 g/kg increase was associated with a similar mortality reduction with an adjusted HR of 0.868 (95% CI 0.770-0.979). However, the benefits associated with enhanced nutrition delivery could be observed in patients with lactate concentration ≤ 2 mmol/L (adjusted HR = 0.804 (95% CI 0.674-0.960) for energy delivery and adjusted HR = 0.804 (95% CI 0.672-0.962) for protein delivery, respectively), but not in those > 2 mmol/L.

CONCLUSIONS

During the first week of critical illness, enhanced nutrition delivery is associated with reduced mortality in critically ill patients receiving exclusive EN, only for those with lactate concentration ≤ 2 mmol/L.

TRIAL REGISTRATION

ISRCTN12233792, registered on November 24, 2017.

Whole Model Path Planning-Guided Multi-Axis and Multi-Material Printing of High-Performance Intestinal Implantable Stent

The problems of step effects, supporting material waste, and conflict between flexibility and toughness for 3D printed intestinal fistula stents are not yet resolved. Herein, the fabrication of a support-free segmental stent with two types of thermoplastic polyurethane (TPU) using a homemade multi-axis and multi-material conformal printer guided with advanced whole model path planning is demonstrated. One type of TPU segment is soft to increase elasticity, and the other is used to achieve toughness. Owing to advancements in stent design and printing, the obtained stents present three unprecedented properties compared to previous three-axis printed stents: i) Overcoming step effects; ii) Presenting comparable axial flexibility to a stent made of a single soft TPU 87A material, thus increasing the feasibility of implantation; and iii) Showing equivalent radial toughness to a stent made of a single hard TPU 95A material. Hence, the stent can resist the intestinal contractive force and maintain intestinal continuity and patency. Through implanting such stents to the rabbit intestinal fistula models, therapeutic mechanisms of reducing fistula output and improving nutritional states and intestinal flora abundance are revealed. Overall, this study develops a creative and versatile method to improve the poor quality and mechanical properties of medical stents.

Multidisciplinary nutritional management improves nutritional and hospitalized outcomes of patients with esophageal cancer undergoing chemoradiotherapy: A randomized control trial

BACKGROUND

This study aimed to investigate the effects of multidisciplinary whole-course nutrition management on the nutritional status and complications during the course of treatment in patients with esophageal cancer (EC) undergoing chemoradiotherapy.

METHODS

A total of 36 EC patients undergoing chemoradiotherapy were divided into a control group (n = 18) and an intervention group (n = 18). Participants in the control group were given routine nutritional support, whereas those in the intervention group were provided whole-course nutrition management from the nutrition support team. Nutrition-related indicators, that is, serum albumin level (ALB), hemoglobin (Hb), and C reactive protein were assessed before, during, and after treatment in both groups. The incidence of complications (e.g., lymphocytopenia, radiation esophagitis, and myelosuppression), clinical outcomes, length of hospital stay, and hospital costs were also recorded. Differences between the 2 groups were tested using the Mann-Whitney U and chi-square tests.

RESULTS

The ALB and Hb levels of the patients in the control group decreased significantly [ALB: -2.6 (-5.6, 0), P = .01; Hb: -12.0 (-27.0, -2.0), P = .04] and C reactive protein increased [8.9 (2.9, 14.9), P = .02] compared to those before treatment, while the indicators of participants in the intervention group did not change (P > .05). The incidence of grade ≥ II lymphocytopenia was higher in the control group than that in the intervention group (33.3% vs 61.1%, P = .03). Moreover, compared with the control group, the average length of hospital stay decreased by 12 days [47 (40, 50) vs 35 (23, 40), P = .001], and in-patient expenses decreased by 20,504 CNY in the intervention group (P = .004).

CONCLUSION

Multidisciplinary whole-course nutrition management can maintain the nutritional status of patients with EC undergoing chemoradiotherapy. This may lower the incidence of complications, shorten hospital stays, and reduce in-patient expenses.

Nutritional modulation of the gut microbiome in allogeneic hematopoietic stem cell transplantation recipients

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) represents a potentially curative strategy for many oncological and non-oncological diseases, but it is associated with marked morbidity and mortality. The disruption of gut microbiota (GM) eubiosis has been linked to major allo-HSCT complications, including infections and acute graft vs. host disease (aGvHD), and correlates with mortality. This increasing knowledge on the role of the GM in the allo-HSCT procedure has led to fascinating ideas for modulating the intestinal ecosystem in order to improve clinical outcomes. Nutritional strategies, either by changing the route of nutritional supplementation or by administering specific molecules, are increasingly being considered as cost- and risk-effective methods of modulating the GM. Nutritional support has also emerged in the past several years as a key feature in supportive care for allo-HSCT recipients, and deterioration of nutritional status is associated with decreased overall survival and higher complication rates during treatment. Herein we provide a complete overview focused on nutritional modulation of the GM in allo-HSCT recipients. We address how pre transplant diet could affect GM composition and its ability to withstand the upsetting events occurring during transplantation. We also provide a complete overview on the influence of the route of nutritional administration on the intestinal ecosystem, with a particular focus on the comparison between enteral and parenteral nutrition (PN). Moreover, as mounting evidence are showing how specific components of post-transplant diet, such as lactose, could drastically shape the GM, we will also summarize the role of prebiotic supplementation in the modulation of the intestinal flora and in allo-HSCT outcomes.

Comparison of the effects of different calorie amounts of enteral nutrition in hypercatabolism associated with ghrelin-POMC in endotoxemic rats

Background

Hypercatabolism often occurs in critically ill patients, and it increases infection rates and mortality in these patients. Enteral nutrition (EN) is commonly used in case of hypercatabolism. However, the effect of amount of calories in EN on hypercatabolism remains unexplored.

Objective

Here, we compared the effect of low-calorie, medium-calorie and high-calorie EN on hypercatabolism in the acute phase of endotoxemia, which is associated with gastrointestinal hormones and hypothalamic neuropeptide proopiomelanocortin (POMC).

Methods

Overall 84 adult male Sprague–Dawley rats were used for research. A set of rats were divided into 5 groups, Control (NS) and lipopolysaccharide (LPS) groups were fed a standard chow diet; LPS + L (LPS + 40 kcal/kg/day EN), LPS + M (LPS + 80 kcal/kg/day EN) and LPS + H (LPS + 120 kcal/kg/day EN) groups received EN through a gastric tube for 3 days. Another set of rats were used for parallel control experiment and divided into 5 groups: NS + F (saline + fasting) and LPS + F (LPS + fasting) groups were given no food, NS + L (saline + 40 kcal/kg/day EN), NS + M (saline + 80 kcal/kg/day EN) and NS + H (saline + 120 kcal/kg/day EN) groups received EN through a gastric tube for 3 days. Hypercatabolism was evaluated by assessing skeletal muscle protein synthesis and atrophy, insulin resistance, and corticosterone levels. Moreover, serum inflammatory factors, gastrointestinal hormones, hypothalamic ghrelin, growth hormone secretagogue receptor-1α, hypothalamic neuropeptide, and intestinal injury indicators were detected.

Results

Low-calorie EN effectively increased serum and hypothalamic ghrelin possibly due to slight intestinal barrier damage, thereby decreasing hypothalamic POMC expression; consequently, it alleviated rat insulin resistance, reduced blood cortisol levels and muscle atrophy, and improved the survival rate of rats in the acute phase of endotoxemia. Interestingly, with an increase in calories in enteral nutrition, the aforementioned effects did not increase.

Conclusions

Low-calorie EN could effectively increase gastrointestinal hormone ghrelin by reducing intestinal damage and suppressing POMC expression to ameliorate hypercatabolism when compared with medium-calorie and high-calorie EN. Therefore Low-calorie EN may be preferred for providing EN in the acute stage of endotoxemia.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12986-022-00663-7.

Loss of Health Promoting Bacteria in the Gastrointestinal Microbiome of PICU Infants with Bronchiolitis: A Single-Center Feasibility Study

The feasibility of gastrointestinal (GI) microbiome work in a pediatric intensive care unit (PICU) to determine the GI microbiota composition of infants as compared to control infants from the same hospital was investigated. In a single-site observational study at an urban quaternary care children's hospital in Western Michigan, subjects less than 6 months of age, admitted to the PICU with severe respiratory syncytial virus (RSV) bronchiolitis, were compared to similarly aged control subjects undergoing procedural sedation in the outpatient department. GI microbiome samples were collected at admission (n = 20) and 72 h (n = 19) or at time of sedation (n = 10). GI bacteria were analyzed by sequencing the V4 region of the 16S rRNA gene. Alpha and beta diversity were calculated. Mechanical ventilation was required for the majority (n = 14) of study patients, and antibiotics were given at baseline (n = 8) and 72 h (n = 9). Control subjects' bacterial communities contained more Porphyromonas, and Prevotella (p = 0.004) than those of PICU infants. The ratio of Prevotella to Bacteroides was greater in the control than the RSV infants (mean ± SD-1.27 ± 0.85 vs. 0.61 ± 0.75: p = 0.03). Bacterial communities of PICU infants were less diverse than those of controls with a loss of potentially protective populations.

Nutrition support for critically ill patients

Nutrition support is an important aspect of the management of critically ill patients. This review highlights the emerging evidence on critical care nutrition and focuses on the pathophysiologic interplay between critical illness, the gastrointestinal tract, and nutrition support and the evidence on the best route, dose, and timing of nutrition. Although indirect calorimetry is recommended to measure energy expenditure, predictive equations are commonly used but are limited by their inaccuracy in individual patients. The current evidence supports early enteral nutrition (EN) in most patients, with a gradual increase in the daily dose over the first week. Delayed EN is warranted in patients with severe shock. According to recent trials, parenteral nutrition seems to be as effective as EN and may be started if adequate EN is not achieved by the first week of critical illness. A high protein dose has been recommended, but the best timing is unclear. Immuno-nutrition should not be routinely provided to critically ill patients. Patients receiving artificial nutrition should be monitored for metabolic derangements. Additional adequately powered studies are still needed to resolve many unanswered questions.

Re-examining chemically defined liquid diets through the lens of the microbiome

Trends in nutritional science are rapidly shifting as information regarding the value of eating unprocessed foods and its salutary effect on the human microbiome emerge. Unravelling the evolution and ecology by which humans have harboured a microbiome that participates in every facet of health and disease is daunting. Most strikingly, the host habitat has sought out naturally occurring foodstuff that can fulfil its own metabolic needs and also the needs of its microbiota, each of which remain inexorably connected to one another. With the introduction of modern medicine and complexities of critical care, came the assumption that the best way to feed a critically ill patient is by delivering fibre-free chemically defined sterile liquid foods (that is, total enteral nutrition). In this Perspective, we uncover the potential flaws in this assumption and discuss how emerging technology in microbiome sciences might inform the best method of feeding malnourished and critically ill patients.

Anorexia Nervosa-What Has Changed in the State of Knowledge about Nutritional Rehabilitation for Patients over the Past 10 Years? A Review of Literature

Anorexia nervosa (AN) is a psycho-metabolic disorder with a high risk of somatic complications such as refeeding syndrome (RFS) and carries the highest mortality rate of all psychiatric illnesses. To date, the consensus on the care for patients with AN has been based on recommendations for a combination of alimentation and psychotherapy. It is important to establish an initial caloric intake that will provide weight gain and minimize the risk of complications in the treatment of undernourished patients. Research over the past few years suggests that current treatment recommendations may be too stringent and should be updated. The aim of this paper is to systematize the current reports on nutritional rehabilitation in AN, to present the results of studies on the safe supplementation of patients and its potential impact on improving prognosis and the healing process. This review of literature, from 2011-2021, describes the changing trend in the nutritional protocols used and the research on their efficacy, safety, and long-term effects. In addition, it presents previous reports on the potential benefits of introducing vitamin, pro-and prebiotic and fatty acid supplementation.

Holistic perspective of the role of gut microbes in diabetes mellitus and its management

The gut microbiota (GM) plays a role in the development and progression of type 1 and type 2 diabetes mellitus (DM) and its complications. Gut dysbiosis contributes to the pathogenesis of DM. The GM has been shown to influence the efficacy of different antidiabetic medications. Intake of gut biotics, like prebiotics, probiotics and synbiotics, can improve the glucose control as well as the metabolic profile associated with DM. There is some preliminary evidence that it might even help with the cardiovascular, ophthalmic, nervous, and renal complications of DM and even contribute to the prevention of DM. More large-scale research studies are needed before wide spread use of gut biotics in clinical practice as an adjuvant therapy to the current management of DM.

Nutrition in the Neurocritical Care Unit: a New Frontier

PURPOSE OF REVIEW

This review presents the most current recommendations for providing nutrition to the neurocritical care population. This includes updates on initiation of feeding, immunonutrition, and metabolic substrates including ketogenic diet, cerebral microdialysis (CMD) monitoring, and the microbiome.

RECENT FINDINGS

Little evidence exists to support differences in feeding practices among the neurocritical care population. New areas of interest with limited data include use of immunonutrition, pre/probiotics for microbiome manipulation, ketogenic diet, and use of CMD catheters for substrate utilization monitoring.

SUMMARY

Acute neurologic injury incites a cascade of adrenergic and neuroendocrine events resulting in a pro-inflammatory and hypercatabolic state, which is associated with an increase in morbidity and mortality. Nutritional support provides substrates to mitigate the damaging effects of hypermetabolism. Despite this practice, studies on feeding delivery outcomes remain inconsistent. Guidelines suggest use of early enteral nutrition using standard polymeric formulas. Population heterogeneity, variability in interventions, complexities of the metabolic and inflammatory responses, and paucity of nutrition research in patients requiring neurocritical care have led to controversies in the field. It is imperative that more pragmatic and reproducible research be conducted to better understand underlying pathophysiology and develop interventions that may improve outcomes.

Nutritional Support in Malnourished Children With Compromised Gastrointestinal Function: Utility of Peptide-Based Enteral Therapy

This review focuses on nutritional support in malnourished children with compromised gastrointestinal function addressing the interplay between malnutrition and gastrointestinal dysfunction, and the specific role of peptide-based enteral therapy in pediatric malnutrition. Malnutrition is associated with impaired gut functions such as increased intestinal permeability, malabsorption, and diarrhea, while pre-existing functional gastrointestinal disorders may also lead to malnutrition. Presence of compromised gastrointestinal function in malnourished children is critical given that alterations such as malabsorption and increased intestinal permeability directly interfere with efficacy of nutritional support and recovery from malnutrition. Appropriate nutritional intervention is the key step in the management of malnutrition, while alterations in gastrointestinal functions in malnourished children are likely even in those with mild degree malnutrition. Therefore, nutritional therapy in children with compromised gastrointestinal function is considered to involve gut-protective interventions that address the overlapping and interacting effects of diarrhea, enteropathy and malnutrition to improve child survival and developmental potential in the long-term. Peptide-based enteral formulas seem to have clinical applications in malnourished children with compromised gastrointestinal function, given their association with improved gastrointestinal tolerance and absorption, better nitrogen retention/ balance, reduced diarrhea and bacterial translocation, enhanced fat absorption, and maintained/restored gut integrity as compared with free amino acid or whole-protein formulas.

Applications of gut microbiota in patients with hematopoietic stem-cell transplantation

Studies of the gut microbiota (GM) have demonstrated the close link between human wellness and intestinal commensal bacteria, which mediate development of the host immune system. The dysbiosis, a disruption of the microbiome natural balance, can cause serious health problems. Patients undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT) may cause significant changes in GM due to their underlying malignancies and exposure to extensive chemotherapy and systemic antibiotics, which may lead to different disorders. There are complex and multi-directional interactions among intestinal inflammation, GM and immune reactivity after HSCT. There is considerable effect of the human intestinal microbiome on clinical course following HSCT. Some bacteria in the intestinal ecosystem may be potential biomarkers or therapeutic targets for preventing relapse and improving survival rate after HSCT. Microbiota can be used as predictor of mortality in allo-HSCT. Two different strategies with targeted modulation of GM, preemptive and therapeutic, have been used for preventing or treating GM dysbiosis in patients with HSCT. Preemptive strategies include enteral nutrition (EN), prebiotic, probiotic, fecal microbiota transplantation (FMT) and antibiotic strategies, while therapeutic strategies include FMT, probiotic and lactoferrine usages. In this review, we summarize the advance of therapies targeting GM in patients with HSCT.

Nutrition and the gut microbiome during critical illness: A new insight of nutritional therapy

Changes in the microbiome in response to environmental influences can affect the overall health. Critical illness is considered one of the major environmental factors that can potentially influence the normal gut homeostasis. It is associated with pathophysiological effects causing damage to the intestinal microbiome. Alteration of intestinal microbial composition during critical illness may subsequently compromise the integrity of the intestinal epithelial barrier and intestinal mucosa absorptive function. Many factors can impact the microbiome of critically ill patients including ischemia, hypoxia and hypotension along with the iatrogenic effects of therapeutic agents and the lack of enteral feeds. Factors related to disease state and medication are inevitable and they are part of the intensive care unit (ICU) exposure. However, a nutritional intervention targeting gut microbiota might have the potential to improve clinical outcomes in the critically ill population given the extensive vascular and lymphatic links between the intestines and other organs. Although nutrition is considered an integral part of the treatment plan of critically ill patients, still the role of nutritional intervention is restricted to improve nitrogen balance. What is dismissed is whether the nutrients we provide are adequate and how they are processed and utilised by the host and the microbiota. Therefore, the goal of nutrition therapy during critical illness should be extended to provide good quality feeds with balanced macronutrient content to feed up the entire body including the microbiota and host cells. The main aim of this review is to examine the current literature on the effect of critical illness on the gut microbiome and to highlight the role of nutrition as a factor affecting the intestinal microbiome-host relationship during critical illness.

Reconsidering ventilator-associated pneumonia from a new dimension of the lung microbiome

Complex microbial communities that reside in the lungs, skin and gut are now appreciated for their role in maintaining organ, tissue and immune homoeostasis. As lungs are currently seen as an ecosystem, the shift in paradigm calls for the consideration of new algorithms related to lung ecology in pulmonology. Evidence of lung microbiota does not solely challenge the traditional physiopathology of ventilator-associated pneumonia (VAP); indeed, it also reinforces the need to include molecular techniques in VAP diagnosis and accelerate the use of immunomodulatory drugs, including corticosteroids, and other supplements such as probiotics for VAP prevention and/or treatment. With that stated, both microbiome and virome, including phageome, can lead to new opportunities in further understanding the relationship between health and dysbiosis in VAP. Previous knowledge may be, however, reconsidered at a microbiome scale.

The microbiome and nutrition in critical illness

PURPOSE OF REVIEW

The present review aims to describe the relationship between nutrition and the gut microbiome in critical illness.

RECENT FINDINGS

Critical illness disrupts not only cells of human origin but also the intestinal microbiome, with a decrease in bacterial diversity and transformation into a pathobiome. Under basal conditions, nutrition profoundly alters microbial composition with significant salutatory effects on human health. In critical illness, enteral nutrition is recommended and has theoretical (but not proven) advantages towards improved inner microbial health and diminution of bacterial translocation. Dietary supplements such as probiotics and fiber have been shown to improve microbial derangements in health. However, their impact on the microbiome in critical illness is unclear and although they may have some beneficial effects on patient-centric outcomes, they do not alter mortality. The precise mechanisms of how nutrition and dietary supplements modulate the gut microbiome remain to be determined.

SUMMARY

Nutrition and supplements such as probiotics appear to play a significant role in modulating the microbiome in health, yet the relationship in critical illness is unclear. Further investigation is required to determine the mechanistic determinants of the impact of nutrition on the microbiome in critical illness and the potential clinical implications of this.

Insights into the role of intestinal microbiota in hematopoietic stem-cell transplantation

The gut microbiota (GM) is able to modulate the human immune system. The development of novel investigation methods has provided better characterization of the GM, increasing our knowledge of the role of GM in the context of hematopoietic stem-cell transplantation (HSCT). In particular, the GM influences the development of the major complications seen after HSCT, having an impact on overall survival. In fact, this evidence highlights the possible therapeutic implications of modulation of the GM during HSCT. Insights into the complex mechanisms and functions of the GM are essential for the rational design of these therapeutics. To date, preemptive and curative approaches have been tested. The current state of understanding of the impact of the GM on HSCT, and therapies targeting the GM balance is reviewed herein.

Rationale for and Design of the Study of Early Enteral Dextrose in Sepsis: A Pilot Placebo-Controlled Randomized Clinical Trial

BACKGROUND

Sepsis is characterized by life-threatening organ dysfunction caused by a dysregulated host response to infection and affects over 1 million Americans annually. Loss of glycemic control in sepsis is associated with increased morbidity and mortality, and novel approaches are needed to promote euglycemia and improve outcomes in sepsis. Recent studies from our laboratory demonstrate that early low-level enteral dextrose infusion in septic mice attenuates the systemic inflammatory response and improves glycemic control by inducing intestine-derived incretin hormone secretion.

AIM

The aim of the Study of Early Enteral Dextrose in Sepsis (SEEDS) is to test the effect of a 24-hour enteral dextrose infusion in critically ill septic patients as a therapeutic agent to decrease systemic inflammation and promote euglycemia.

METHODS

SEEDS is a single-center, double-blind, randomized, controlled trial that will enroll 60 septic patients admitted to the intensive care units at the University of Pittsburgh Medical Center Health System in Pittsburgh. Participants will be randomized 1:1 to receive enteral dextrose (n = 30) or water (placebo, n = 30) infusion for 24 hours. The primary outcome is the circulating interleukin-6 level measured after the 24-hour infusion compared between dextrose and placebo groups. Secondary outcomes include postinfusion circulating insulin, incretin, and other proinflammatory cytokine levels, as well as incidence of hyperglycemia and hypoglycemia during the infusion period.

DISCUSSION

This trial will characterize the effects of early enteral dextrose on endogenous endocrine pathways and the systemic inflammatory response in sepsis. The results of this trial will inform future larger interventional studies of early enteral nutrients in critically ill patients with sepsis.

Gut integrity in critical illness

Background

The gut is hypothesized to be the “motor” of critical illness. Under basal conditions, the gut plays a crucial role in the maintenance of health. However, in critical illness, all elements of the gut are injured, potentially worsening multiple organ dysfunction syndrome.

Main body

Under basal conditions, the intestinal epithelium absorbs nutrients and plays a critical role as the first-line protection against pathogenic microbes and as the central coordinator of mucosal immunity. In contrast, each element of the gut is impacted in critical illness. In the epithelium, apoptosis increases, proliferation decreases, and migration slows. In addition, gut barrier function is worsened via alterations to the tight junction, resulting in intestinal hyperpermeability. This is associated with damage to the mucus that separates the contents of the intestinal lumen from the epithelium. Finally, the microbiome of the intestine is converted into a pathobiome, with an increase in disease-promoting bacteria and induction of virulence factors in commensal bacteria. Toxic factors can then leave the intestine via both portal blood flow and mesenteric lymph to cause distant organ damage.

Conclusion

The gut plays a complex role in both health and critical illness. Here, we review gut integrity in both health and illness and highlight potential strategies for targeting the intestine for therapeutic gain in the intensive care unit.

The gut microbiome in anorexia nervosa: relevance for nutritional rehabilitation

Rapidly accumulating evidence supports the important role of gut microbiome in the regulation of mood, behaviour, appetite, gastrointestinal symptomology, and nutrient metabolism. These are all core features frequently altered in individuals with anorexia nervosa (AN). Current treatment recommendations for AN support the use of high-calorie diets as an essential part of nutritional rehabilitation, commonly achieved by elevating the fat content of the diet. However, in contrast to this approach, there is accumulating evidence suggesting the importance of balanced, high-fibre diets on the gut microbiome. Studies have demonstrated profound differences in the microbial composition of underweight people with AN and those of normal- or overweight individuals. Specific alterations vary widely between studies. It is thus far unclear to what extent the observed differences are brought on by iatrogenic effects of nutritional rehabilitation or the disorder itself. To date, only two studies have investigated the changes in the intestinal microbiota during nutritional rehabilitation and corresponding weight restoration. These studies suggest that the gut microbiome of AN patients was different to healthy controls both prior and following nutritional rehabilitation, though it is noted that these states were associated with lower and higher nutritional intakes, respectively. There is a clear need for further investigation regarding the effects of nutritional rehabilitation on the gut microbiome. Such research would provide insights into the potential role of gut microbiome in modulating the pathophysiology of AN and inform future treatment strategies.

The wound environment, microbial virulence and postoperative infection: Practical lessons for the surgeon

For the practicing surgeon, the development of a postoperative wound infection represents a major complication that can be both costly and disabling. As a result, surgeons apply multiple methods of prevention including skin decontamination, use of antibiotics, irrigation with or without antiseptics and meticulous use of technique. In elective surgery, however, most wound infections cannot be predicted. In this review we discuss emerging concepts in wound infection pathogenesis and include a discussion on how the wound environment may directly activate bacteria to express a more harmful or virulent phenotype. Based on these emerging concepts, we provide the practicing surgeon with molecular level evidence to explain why some methods of wound infection protection may be useful while others are not.

Dietary Protein and Muscle in Aging People: The Potential Role of the Gut Microbiome

Muscle mass, strength, and physical function are known to decline with age. This is associated with the development of geriatric syndromes including sarcopenia and frailty. Dietary protein is essential for skeletal muscle function. Resistance exercise appears to be the most beneficial form of physical activity for preserving skeletal muscle and a synergistic effect has been noted when this is combined with dietary protein. However, older adults have shown evidence of anabolic resistance, where greater amounts of protein are required to stimulate muscle protein synthesis, and response is variable. Thus, the recommended daily amount of protein is greater for older people. The aetiologies and mechanisms responsible for anabolic resistance are not fully understood. The gut microbiota is implicated in many of the postulated mechanisms for anabolic resistance, either directly or indirectly. The gut microbiota change with age, and are influenced by dietary protein. Research also implies a role for the gut microbiome in skeletal muscle function. This leads to the hypothesis that the gut microbiome might modulate individual response to protein in the diet. We summarise the existing evidence for the role of the gut microbiota in anabolic resistance and skeletal muscle in aging people, and introduce the metabolome as a tool to probe this relationship in the future.

The role of nutritional support in the physical and functional recovery of critically ill patients: a narrative review

The lack of benefit from randomised controlled trials has resulted in significant controversy regarding the role of nutrition during critical illness in terms of long-term recovery and outcome. Although methodological caveats with a failure to adequately appreciate biological mechanisms may explain these disappointing results, it must be acknowledged that nutritional support during early critical illness, when considered alone, may have limited long-term functional impact.This narrative review focuses specifically on recent clinical trials and evaluates the impact of nutrition during critical illness on long-term physical and functional recovery.Specific focus on the trial design and methodological limitations has been considered in detail. Limitations include delivery of caloric and protein targets, patient heterogeneity, short duration of intervention, inappropriate clinical outcomes and a disregard for baseline nutritional status and nutritional intake in the post-ICU period.With survivorship at the forefront of critical care research, it is imperative that nutrition studies carefully consider biological mechanisms and trial design because these factors can strongly influence outcomes, in particular long-term physical and functional outcome. Failure to do so may lead to inconclusive clinical trials and consequent rejection of the potentially beneficial effects of nutrition interventions during critical illness.