Nutritional Treatment for Traumatic Brain Injury

Elovanoids, a Novel Class of Lipid Mediators, Are Neuroprotective in a Traumatic Brain Injury Model in Rats

BACKGROUND

In the United States, traumatic brain injury (TBI) contributes significantly to mortality and morbidity. Elovanoids (ELVs), a novel class of homeostatic lipid mediators we recently discovered and characterized, have demonstrated neuroprotection in experimental stroke models but have never been tested after TBI.

METHODS

A moderate fluid-percussion injury (FPI) model was used on male rats that were treated with ELVs by intravenous (IV) or intranasal (IN) delivery. In addition, using liquid chromatography-mass spectrometry (LC-MS/MS), we examined whether ELVs could be detected in brain tissue after IN delivery.

RESULTS

ELVs administered intravenously 1 h after FPI improved behavior on days 2, 3, 7, and 14 by 20, 23, 31, and 34%, respectively, and preserved hippocampal CA3 and dentate gyrus (DG) volume loss compared to the vehicle. Whole-brain tractography revealed that ELV-IV treatment increased corpus callosum white matter fibers at the injury site. In comparison to treatment with saline on days 2, 3, 7, and 14, ELVs administered intranasally at 1 h and 24 h after FPI showed improved neurological scores by 37, 45, 41, and 41%. T2-weighted imaging (T2WI) abnormalities, such as enlarged ventricles and cortical thinning, were reduced in rats treated by ELV-IN delivery compared to the vehicle. On day 3, ELVs were detected in the striatum and ipsilateral cortex of ELV-IN-treated rats.

CONCLUSION

We have demonstrated that both ELV-IN and ELV-IV administration offer high-grade neuroprotection that can be selectively supplied to the brain. This discovery may lead to innovative therapeutic targets for secondary injury cascade prevention following TBI.

Impact of increasing one-carbon metabolites on traumatic brain injury outcome using pre-clinical models

Traumatic brain injury is a major cause of death and disability worldwide, affecting over 69 million individuals yearly. One-carbon metabolism has been shown to have beneficial effects after brain damage, such as ischemic stroke. However, whether increasing one-carbon metabolite vitamins impacts traumatic brain injury outcomes in patients requires more investigation. The aim of this review is to evaluate how one-carbon metabolites impact outcomes after the onset of traumatic brain injury. PubMed, Web of Science, and Google Scholar databases were searched for studies that examined the impact of B-vitamin supplementation on traumatic brain injury outcomes. The search terms included combinations of the following words: traumatic brain injury, dietary supplementation, one-carbon metabolism, and B-vitamins. The focus of each literature search was basic science data. The year of publication in the literature searches was not limited. Our analysis of the literature has shown that dietary supplementation of B-vitamins has significantly improved the functional and behavioral recovery of animals with traumatic brain injury compared to controls. However, this improvement is dosage-dependent and is contingent upon the onset of supplementation and whether there is a sustained or continuous delivery of vitamin supplementation post-traumatic brain injury. The details of supplementation post-traumatic brain injury need to be further investigated. Overall, we conclude that B-vitamin supplementation improves behavioral outcomes and reduces cognitive impairment post-traumatic brain injury in animal model systems. Further investigation in a clinical setting should be strongly considered in conjunction with current medical treatments for traumatic brain injury-affected individuals.

Thiamine use is associated with better outcomes for traumatic brain injury patients

Background

Traumatic brain injury (TBI) is a global health concern that often leads to poor prognosis. We designed this study to explore whether thiamine use is associated with a better prognosis of TBI.

Methods

TBI patients selected from the Medical Information Mart for Intensive Care-III database were included in the study. Univariate and multivariate Cox regression analyses were performed to examine the relationship between thiamine use and mortality in TBI patients. Propensity score matching (PSM) was utilized to generate balanced cohorts of the non-thiamine use group and the thiamine use group. Subgroup analysis was performed in the cohort after PSM to verify the association between thiamine use and mortality in TBI patients across different stratifications.

Results

The incidence of thiamine use in TBI was 18.3%. The thiamine use group had a lower 30-day mortality rate (p < 0.001), a longer length of ICU stay (p < 0.001), and a longer length of hospital stay (p < 0.001) than the non-thiamine use group, both in the primary cohort before PSM and the cohort after PSM. A multivariate Cox regression analysis confirmed that thiamine use was independently associated with mortality (OR = 0.454, p < 0.001) after adjusting for confounding effects. In the cohort after PSM, the subgroup analysis showed that thiamine use is associated with lower mortality in TBI patients with a Glasgow Coma Scale (GCS) score of < 13, but it is not associated with mortality in TBI patients whose GCS score is ≥13.

Conclusion

Thiamine supplementation is effective in improving the outcome of TBI, except in cases of mild TBI. The optimal thiamine supplementation strategy for TBI is worthwhile to be explored in future studies.

Non-pharmacological interventions for traumatic brain injury

Heterogeneity and variability of symptoms due to the type, site, age, sex, and severity of injury make each case of traumatic brain injury (TBI) unique. Considering this, a universal treatment strategy may not be fruitful in managing outcomes after TBI. Most of the pharmacological therapies for TBI aim at modifying a particular pathway or molecular process in the sequelae of secondary injury rather than a holistic approach. On the other hand, non-pharmacological interventions such as hypothermia, hyperbaric oxygen, preconditioning with dietary adaptations, exercise, environmental enrichment, deep brain stimulation, decompressive craniectomy, probiotic use, gene therapy, music therapy, and stem cell therapy can promote healing by modulating multiple neuroprotective mechanisms. In this review, we discussed the major non-pharmacological interventions that are being tested in animal models of TBI as well as in clinical trials. We evaluated the functional outcomes of various interventions with an emphasis on the links between molecular mechanisms and outcomes after TBI.

Phosphodiesterase-5 (PDE-5) Inhibitors as Therapy for Cerebrovascular Dysfunction in Chronic Traumatic Brain Injury

Multiple phase III randomized controlled trials (RCTs) for pharmacologic interventions in traumatic brain injury (TBI) have failed despite promising results in experimental models. The heterogeneity of TBI, in terms of pathomechanisms and impacted brain structures, likely contributes to these failures. Biomarkers have been recommended to identify patients with relevant pathology (predictive biomarkers) and confirm target engagement and monitor therapy response (pharmacodynamic biomarkers). Our group focuses on traumatic cerebrovascular injury as an understudied endophenotype of TBI and is validating a predictive and pharmacodynamic imaging biomarker (cerebrovascular reactivity; CVR) in moderate-severe TBI. We aim to extend these studies to milder forms of TBI to determine the optimal dose of sildenafil for maximal improvement in CVR. We will conduct a phase II dose-finding study involving 160 chronic TBI patients (mostly mild) using three doses of sildenafil, a phosphodiesterase-5 (PDE-5) inhibitor. The study measures baseline CVR and evaluates the effect of escalating sildenafil doses on CVR improvement. A 4-week trial of thrice daily sildenafil will assess safety, tolerability, and clinical efficacy. This dual-site 4-year study, funded by the Department of Defense and registered in ClinicalTrials.gov (NCT05782244), plans to launch in June 2023. Biomarker-informed RCTs are essential for developing effective TBI interventions, relying on an understanding of underlying pathomechanisms. Traumatic microvascular injury (TMVI) is an attractive mechanism which can be targeted by vaso-active drugs such as PDE-5 inhibitors. CVR is a potential predictive and pharmacodynamic biomarker for targeted interventions aimed at TMVI. (Trial registration: NCT05782244, ClinicalTrials.gov ).

Human umbilical cord-derived mesenchymal stem cells-harvested mitochondrial transplantation improved motor function in TBI models through rescuing neuronal cells from apoptosis and alleviating astrogliosis and microglia activation

Each year, traumatic brain injury (TBI) causes a high rate of mortality throughout the world and those who survive have lasting disabilities. Given that the brain is a particularly dynamic organ with a high energy consumption rate, the inefficiency of current TBI treatment options highlights the necessity of repairing damaged brain tissue at the cellular and molecular levels, which according to research is aggravated due to ATP deficiency and reactive oxygen species surplus. Taking into account that mitochondria contribute to generating energy and controlling cellular stress, mitochondrial transplantation as a new treatment approach has lately reduced complications in a number of diseases by supplying healthy and functional mitochondria to the damaged tissue. For this reason, in this study, we used this technique to transplant human umbilical cord-derived mesenchymal stem cells (hUC-MSCs)-derived mitochondria as a suitable source for mitochondrial isolation into rat models of TBI to examine its therapeutic benefit and the results showed that the successful mitochondrial internalisation in the neuronal cells significantly reduced the number of brain cells undergoing apoptosis, alleviated astrogliosis and microglia activation, retained normal brain morphology and cytoarchitecture, and improved sensorimotor functions in a rat model of TBI. These data indicate that human umbilical cord-derived mesenchymal stem cells-isolated mitochondrial transplantation improves motor function in a rat model of TBI via rescuing neuronal cells from apoptosis and alleviating astrogliosis and microglia activation, maybe as a result of restoring the lost mitochondrial content.

The Brain–Gut Axis in Traumatic Brain Injury: Implications for Nutrition Support

Purpose of Review

Early enteral nutrition improves outcomes following traumatic brain injury (TBI). This can prove difficult due to TBI-induced feeding intolerance secondary to disruption of the brain-gut axis, a network composed of central nervous system (CNS) input, autonomic signaling, and immunologic regulation that controls gut and CNS homeostasis. Here, we discuss the pathophysiology of brain–gut axis dysregulation and outline nutrition strategies in patients with TBI.

Recent Findings

Feeding intolerance following TBI is multifactorial; complex signaling between the CNS, sympathetic nervous system, parasympathetic nervous system, and enteric nervous system that controls gut homeostasis is disrupted within hours post-injury. This has profound effects on the immune system and gut microbiome, further complicating post-TBI recovery. Despite this disruption, calorie and protein requirements increase considerably following TBI, and early nutritional supplementation improves survival following TBI. Enteral nutrition has proven more efficacious than parenteral nutrition in TBI patients and should be initiated within 48 hours following admission. Immune-fortified nutrition reduces CNS and gut inflammation and may improve outcomes in TBI patients.

Summary

Although autonomic dysregulation of the brain–gut axis results in feeding intolerance following TBI, early enteral nutrition is of paramount importance. Enteral nutrition reduces post-TBI inflammation and enhances immunologic and gut function. When feasible, enteral nutrition should be initiated within 48 hours following injury.

Correlation between vitamin D and cognitive function in patients with traumatic brain injury in China

OBJECTIVE

This study investigated changes in vitamin D levels in traumatic brain injury (TBI) patients and the relationship between vitamin D levels and cognitive function.

METHODS

Thirty-five TBI patients in our hospital were randomly selected, and baseline data were collected. 25-Hydroxyvitamin D (25(OH)D) plasma levels were determined within a month of hospitalization, and awareness and cognitive function were assessed using the Glasgow Coma Scale (GCS) and the Mini Mental State Examination (MMSE), respectively, on the day of blood collection. The data were statistically analyzed.

RESULTS

The MMSE and GCS scores were positively correlated (p < 0.05); higher MMSE scores were associated with higher GCS scores. Moreover, the total score was positively correlated with directional ability, memory, and attention, suggesting high internal consistency of the MMSE score, but no significant correlation with other indicators was observed. 25(OH)D was positively correlated with the injury site (p < 0.05), suggesting that frontal damage has a significant impact on the plasma level of 25(OH)D.

CONCLUSION

The plasma vitamin D level in TBI patients may indicate frontal lobe damage. The overall plasma level of 25(OH)D in TBI patients was not significantly correlated with cognitive function, but the incidence of cognitive impairment was higher with 25(OH)D level between 10 and 30 ng/ml.

Current and Potential Pharmacologic Therapies for Traumatic Brain Injury

The present article reviewed the pharmacologic therapies of traumatic brain injury (TBI), including current and potential treatments. Pharmacologic therapies are an essential part of TBI care, and several agents have well-established effects in TBI care. In the acute phase, tranexamic acid, antiepileptics, hyperosmolar agents, and anesthetics are the mainstay of pharmacotherapy, which have proven efficacies. In the post-acute phase, SSRIs, SNRIs, antipsychotics, zolpidem and amantadine, as well as other drugs, have been used to manage neuropsychological problems, while muscle relaxants and botulinum toxin have been used to manage spasticity. In addition, increasing numbers of pre-clinical and clinical studies of pharmaceutical agents, including potential neuroprotective nutrients and natural therapies, are being carried out. In the present article, we classify the treatments into established and potential agents based on the level of clinical evidence and standard of practice. It is expected that many of the potential medicines under investigation will eventually be accepted as standard practice in the care of TBI patients.

Protective effects of Derinat, a nucleotide-based drug, on experimental traumatic brain injury, and its cellular mechanisms

Traumatic brain injury is the most common cause of death and disability in young people including sport athletes and soldiers, people under 45 years of age in the industrialized countries, representing a growing health problem in developing countries, as well as in aging communities. Treatment of the latter is a serious challenge for modern medicine. This type of injury leads to many kinds of disorders and, quite often, to disability. These issue require development of new methods for brain trauma treatment. The new approach to brain trauma treatment was studied in murine experiments. In particular, sodium salt of deoxyribonucleic acid (DNA) was used. This preparation is a drug known as a mixture of peptides with immunomodulatory effect which is widely used for different kinds of therapy. Derinat, a sodium salt of DNA, isolated from the caviar of Russian sturgeon, is a proven immunomodulator for treatment of diseases associatd with reactive oxygen species (ROS), including brain ischemia-reperfusion (IR) injury. Here we show that treatment with Derinat exert neuroprotective, anti-oxidative, and anti-inflammatory effects in experimental model of traumatic brain injury (TBI) in rats. Intraperitoneal injection of Derinat several times over 3 days after TBI showed less pronounced damage of the injured brain area. Immunohistochemical study showed that the Derinat-induced morphological changes of microglia in cerebral cortex and hippocampus 7 days after TBI. TBI-induced accumulation of 8-oxoguanine (8-oxoG), the marker of oxidative damage, was significantly attenuated by Derinat administration, both on 7th and 14th day after TBI. To investigate cellular mechanism of anti-inflammatory effects, the primary cultures of murine microglia supplied with ATP (50 M and 1 mM), as a substance released at injured site, were used to mimic the in vitro inflammatory response. Derinate treatment caused an increase of glial levels of mRNAs encoding neurotrophic factor (GDNF) and nerve growth factor (NGF) in the presence of ATP, whereas tissue plasminogen activator (tPA) mRNA was inhibited by ATP with or without Derinat. Interleukin-6 (IL-6) mRNA expression was not affected by ATP but was increased by Derinat. Both mRNA and protein levels of ATP-induced TNFα production were significantly inhibited by Derinat. These results partially contribute to understanding mechanisms of immunomodulatory effects of DNA preparations in traumatic brain injury.

Sports Related Brain Injury and Neurodegeneration in Athletes

Sports deserve a special place in human life to impart healthy and refreshing wellbeing. However, sports activities, especially contact sports, renders athlete vulnerable to brain injuries. Athletes participating in a contact sport like boxing, rugby, American football, wrestling, and basketball are exposed to traumatic brain injuries (TBI) or concussions. The acute and chronic nature of these heterogeneous injuries provides a spectrum of dysfunctions that alters the neuronal, musculoskeletal, and behavioral responses of an athlete. Many sports-related brain injuries go unreported, but these head impacts trigger neurometabolic disruptions that contribute to long-term neuronal impairment. The pathophysiology of post-concussion and its underlying mechanisms are undergoing intense research. It also shed light on chronic disorders like Parkinson's disease, Alzheimer's disease, and dementia. In this review, we examined post-concussion neurobehavioral changes, tools for early detection of signs, and their impact on the athlete. Further, we discussed the role of nutritional supplements in ameliorating neuropsychiatric diseases in athletes.

Effects of time-of-day on the concentration of defined excitatory and inhibitory amino acids in the cerebrospinal fluid of rats: a microdialysis study

Amino acid neurotransmitters are responsible for many physiological and pathological processes, and their cerebral concentrations respond to external influences such as the light-dark cycle and to the synthesis, release, and recapture rhythms and form part of the biochemical relationships derived from excitatory-inhibitory (E/I), glutamine-glutamate sum (GLX), glutamatergic processing (glutamine-glutamate ratio) and excitotoxic indexes. The changes in these variables during a 24-h period (1 day) are important because they allow organisms to adapt to external stimuli and form part of physiological processes. Under pathological conditions, the damage produced by acute events may depend on diurnal variations. Therefore, it is important to analyze the extracellular levels of amino acids as well as the above-mentioned indexes over a 24-h period. We focused on determining the cerebrospinal fluid levels of different amino acid neurotransmitters, and the E/I, GLX, glutamatergic processing and excitotoxic indexes, determined by microdialysis over a 24-h cycle. Our results showed significant changes during the 24-h light/dark cycle. Specifically, we found increments in the levels of glutamate (325%), GABA (550%), glutamine (300%), glycine (194%), alanine (304%) and the GLX index (263%) throughout the day, and the maximum levels of glutamate, glutamine, glycine, and alanine were obtained during the last period of the light period. In conclusion, the concentration of some amino acid neurotransmitters and the GLX index show variations depending on the light-dark cycle.

Microglia: A Potential Drug Target for Traumatic Axonal Injury

Traumatic axonal injury (TAI) is a major cause of death and disability among patients with severe traumatic brain injury (TBI); however, no effective therapies have been developed to treat this disorder. Neuroinflammation accompanying microglial activation after TBI is likely to be an important factor in TAI. In this review, we summarize the current research in this field, and recent studies suggest that microglial activation plays an important role in TAI development. We discuss several drugs and therapies that may aid TAI recovery by modulating the microglial phenotype following TBI. Based on the findings of recent studies, we conclude that the promotion of active microglia to the M2 phenotype is a potential drug target for the treatment of TAI.

Nutritional Considerations and Strategies to Facilitate Injury Recovery and Rehabilitation

Nutritional interventions are not commonly a standard of care in rehabilitation interventions. A nutritional approach has the potential to be a low-cost, high-volume strategy that complements the existing standard of care. In this commentary, our aim is to provide an evidence-based, practical guide for athletes with injuries treated surgically or conservatively, along with healing and rehabilitation considerations. Injuries are a normal and expected part of exercise participation. Regardless of severity, an injury typically results in the athlete's short- or long-term removal from participation. Nutritional interventions may augment the recovery process and support optimal healing; therefore, incorporating nutritional strategies is important at each stage of the healing process. Preoperative nutrition and nutritional demands during rehabilitation are key factors to consider. The physiological response to wounds, immobilization, and traumatic brain injuries may be improved by optimizing macronutrient composition, caloric consumption, and nutrient timing and using select dietary supplements. Previous research supports practical nutrition recommendations to reduce surgical complications, minimize deficits after immobilization, and maximize the chance of safe return to play. These recommendations include identifying the individual's caloric requirements to ensure that energy needs are being met. A higher protein intake, with special attention to evenly distributed consumption throughout the day, will help to minimize loss of muscle and strength during immobilization. Dietary-supplement strategies may be useful when navigating the challenges of appropriate caloric intake and timing and a reduced appetite. The rehabilitation process also requires a strong nutritional plan to enhance recovery from injury. Athletic trainers, physical therapists, and other health care professionals should provide basic nutritional recommendations during rehabilitation, discuss the timing of meals with respect to therapy, and refer the patient to a registered dietitian if warranted. Because nutrition plays an essential role in injury recovery and rehabilitation, nutritional interventions should become a component of standard-of-care practice after injury. In this article, we address best practices for implementing nutritional strategies among patients with athletic injuries.

A Pilot Study Assessing the Impact of rs174537 on Circulating Polyunsaturated Fatty Acids and the Inflammatory Response in Patients with Traumatic Brain Injury

Traumatic brain injury (TBI) is a leading cause of death and disability in persons under age 45. The hallmark secondary injury profile after TBI involves dynamic interactions between inflammatory and metabolic pathways including fatty acids. Omega-3 polyunsaturated fatty acids (PUFAs) such as docosahexaenoic acid (DHA) have been shown to provide neuroprotective benefits by minimizing neuroinflammation in rodents. These effects have been less conclusive in humans, however. We postulate genetic variants influencing PUFA metabolism in humans could contribute to these disparate findings. Therefore, we sought to (1) characterize the circulating PUFA response and (2) evaluate the impact of rs174537 on inflammation after TBI. A prospective, single-center, observational pilot study was conducted to collect blood samples from Level-1 trauma patients (N = 130) on admission and 24 h post-admission. Plasma was used to quantify PUFA levels and inflammatory cytokines. Deoxyribonucleic acid was extracted and genotyped at rs174537. Associations between PUFAs and inflammatory cytokines were analyzed for all trauma cases and stratified by race (Caucasians only), TBI (TBI: N = 47; non-TBI = 83) and rs174537 genotype (GG: N = 33, GT/TT: N = 44). Patients with TBI had higher plasma DHA levels compared with non-TBI at 24 h post-injury (p = 0.013). The SNP rs174537 was associated with both PUFA levels and inflammatory cytokines (p < 0.05). Specifically, TBI patients with GG genotype exhibited the highest plasma levels of DHA (1.33%) and interleukin-8 (121.5 ± 43.3 pg/mL), which were in turn associated with poorer outcomes. These data illustrate the impact of rs174537 on the post-TBI response. Further work is needed to ascertain how this genetic variant directly influences inflammation after trauma.

Repetitive, mild traumatic brain injury results in a progressive white matter pathology, cognitive deterioration, and a transient gut microbiota dysbiosis

Traumatic brain injury (TBI) is often accompanied by gastrointestinal and metabolic disruptions. These systemic manifestations suggest possible involvement of the gut microbiota in head injury outcomes. Although gut dysbiosis after single, severe TBI has been documented, the majority of head injuries are mild, such as those that occur in athletes and military personnel exposed to repetitive head impacts. Therefore, it is important to determine if repetitive, mild TBI (rmTBI) will also disrupt the gut microbiota. Male mice were exposed to mild head impacts daily for 20 days and assessed for cognitive behavior, neuropathology and disruptions in the gut microbiota at 0, 45 or 90 days after injury. Deficits in recognition memory were evident at the late post-injury points. Brains show an early increase in microglial activation at the 0-day time point that persisted until 90 days post-injury. This was compounded by substantial increases in astrocyte reactivity and phosphorylated tau at the 90-day time point. In contrast, changes in the microbial community were minor and transient, and very few differences were observed in mice exposed to rmTBI compared to controls. While the progressive emergence of white matter damage and cognitive alterations after rmTBI resembles the alterations observed in athletes and military personnel exposed to rmTBI, these changes could not be linked to systematic modifications in the gut microbiota.

Nutrition Therapy, Glucose Control, and Brain Metabolism in Traumatic Brain Injury: A Multimodal Monitoring Approach

The goal of neurocritical care in patients with traumatic brain injury (TBI) is to prevent secondary brain damage. Pathophysiological mechanisms lead to loss of body mass, negative nitrogen balance, dysglycemia, and cerebral metabolic dysfunction. All of these complications have been shown to impact outcomes. Therapeutic options are available that prevent or mitigate their negative impact. Nutrition therapy, glucose control, and multimodality monitoring with cerebral microdialysis (CMD) can be applied as an integrated approach to optimize systemic immune and organ function as well as adequate substrate delivery to the brain. CMD allows real-time bedside monitoring of aspects of brain energy metabolism, by measuring specific metabolites in the extracellular fluid of brain tissue. Sequential monitoring of brain glucose and lactate/pyruvate ratio may reveal pathologic processes that lead to imbalances in supply and demand. Early recognition of these patterns may help individualize cerebral perfusion targets and systemic glucose control following TBI. In this direction, recent consensus statements have provided guidelines and recommendations for CMD applications in neurocritical care. In this review, we summarize data from clinical research on patients with severe TBI focused on a multimodal approach to evaluate aspects of nutrition therapy, such as timing and route; aspects of systemic glucose management, such as intensive vs. moderate control; and finally, aspects of cerebral metabolism. Research and clinical applications of CMD to better understand the interplay between substrate supply, glycemic variations, insulin therapy, and their effects on the brain metabolic profile were also reviewed. Novel mechanistic hypotheses in the interpretation of brain biomarkers were also discussed. Finally, we offer an integrated approach that includes nutritional and brain metabolic monitoring to manage severe TBI patients.

Effects of probiotics combined with early enteral nutrition on endothelin-1 and C-reactive protein levels and prognosis in patients with severe traumatic brain injury

OBJECTIVE

To investigate the effects of probiotics combined with early enteral nutrition on levels of endothelin-1 (ET-1), C-reactive protein (CRP), and inflammatory factors, and on the prognosis of patients with severe traumatic brain injury (TBI).

METHODS

We enrolled 76 adults with severe TBI. The patients were divided randomly into two equal groups administered enteral nutrition with and without probiotics, respectively. Demographic and clinical data including age, sex, Glasgow Coma Scale score, Sequential Organ Failure Score, Acute Physiology, Chronic Health Score, hospitalization, mortality, and infections were recorded.

RESULTS

Serum levels of inflammatory factors gradually decreased with increasing treatment time in both groups. However, ET-1 at 15 days, and interleukin (IL)-6, IL-10, tumor necrosis factor (TNF)-α, and CRP at 7 and 15 days decreased significantly more in the combined treatment group. Hospitalization duration and pulmonary infection rates were also significantly reduced in the combined compared with the enteral nutrition alone group. GCS scores at 15 days were significantly lower in the combined compared with the enteral nutrition group.

CONCLUSION

Probiotics combined with early enteral nutrition could reduce serum levels of ET-1, CRP, and IL-6, IL-10, and TNF-α, and could thus improve the recovery of patients with severe TBI.

Assessment of cerebrovascular dysfunction after traumatic brain injury with fMRI and fNIRS

Traumatic cerebral vascular injury (TCVI) is a frequent, but under-recognized, endophenotype of traumatic brain injury (TBI).  It likely contributes to functional deficits after TBI and TBI-related chronic disability, and represents an attractive target for targeted therapeutic interventions. The aim of this prospective study is to assess microvascular injury/dysfunction in chronic TBI by measuring cerebral vascular reactivity (CVR) by 2 methods, functional magnetic resonance imaging (fMRI) and functional Near InfraRed Spectroscopy (fNIRS) imaging, as each has attractive features relevant to clinical utility. 42 subjects (27 chronic TBI, 15 age- and gender-matched non-TBI volunteers) were enrolled and underwent outpatient CVR testing by 2 methods, MRI-BOLD and fNIRS, each with hypercapnia challenge, a neuropsychological testing battery, and symptom survey questionnaires. Chronic TBI subjects showed a significant reduction in global CVR compared to HC (p < 0.0001). Mean CVR measures by fMRI were 0.225 ± 0.014 and 0.183 ± 0.026 %BOLD/mmHg for non-TBI and TBI subjects respectively and 12.3 ± 1.8 and 9.2 ± 1.7 mM/mmHg by fNIRS for non-TBI versus TBI subjects respectively. Global CVR measured by fNIRS imaging correlates with results by MRI-BOLD (R = 0.5). Focal CVR deficits seen on CVR maps by fMRI are also observed in the same areas by fNIRS in the frontal regions. Global CVR is significantly lower in chronic TBI patients and is reliably measured by both fMRI and fNIRS, the former with better spatial and the latter with better temporal resolution.  Both methods show promise as non-invasive measures of CVR function and microvascular integrity after TBI.

Psychopharmacology of traumatic brain injury

The pathophysiology of traumatic brain injury (TBI) can be highly variable, involving functional and/or structural damage to multiple neuroanatomical networks and neurotransmitter systems. This wide-ranging potential for physiologic injury is reflected in the diversity of neurobehavioral and neurocognitive symptoms following TBI. Here, we aim to provide a succinct, clinically relevant, up-to-date review on psychopharmacology for the most common sequelae of TBI in the postacute to chronic period. Specifically, treatment for neurobehavioral symptoms (depression, mania, anxiety, agitation/irritability, psychosis, pseudobulbar affect, and apathy) and neurocognitive symptoms (processing speed, attention, memory, executive dysfunction) will be discussed. Treatment recommendations will reflect general clinical practice patterns and the research literature.

Effects of Vitamin D3 on the NADPH Oxidase and Matrix Metalloproteinase 9 in an Animal Model of Global Cerebral Ischemia

Decreased blood flow in the brain leads to a rapid increase in reactive oxygen species (ROS). NADPH oxidase (NOX) is an enzyme family that has the physiological function to produce ROS. NOX2 and NOX4 overexpression is associated with aggravated ischemic injury, while NOX2/4-deficient mice had reduced stroke size. Dysregulation of matrix metalloproteinases (MMPs) contributes to tissue damage. The active form of vitamin D3 expresses neuroprotective, immunomodulatory, and anti-inflammatory effects in the CNS. The present study examines the effects of the vitamin D3 pretreatment on the oxidative stress parameters and the expression of NOX subunits, MMP9, microglial marker Iba1, and vitamin D receptor (VDR), in the cortex and hippocampus of Mongolian gerbils subjected to ten minutes of global cerebral ischemia, followed by 24 hours of reperfusion. The ischemia/reperfusion procedure has induced oxidative stress, changes in the expression of NOX2 subunits and MMP9 in the brain, and increased MMP9 activity in the serum of experimental animals. Pretreatment with vitamin D3 was especially effective on NOX2 subunits, MMP9, and the level of malondialdehyde and superoxide anion. These results outline the significance of the NOX and MMP9 investigation in brain ischemia and the importance of adequate vitamin D supplementation in ameliorating the injury caused by I/R.

Supplements, nutrition, and alternative therapies for the treatment of traumatic brain injury

Studies using traditional treatment strategies for mild traumatic brain injury (TBI) have produced limited clinical success. Interest in treatment for mild TBI is at an all time high due to its association with the development of chronic traumatic encephalopathy and other neurodegenerative diseases, yet therapeutic options remain limited. Traditional pharmaceutical interventions have failed to transition to the clinic for the treatment of mild TBI. As such, many pre-clinical studies are now implementing non-pharmaceutical therapies for TBI. These studies have demonstrated promise, particularly those that modulate secondary injury cascades activated after injury. Because no TBI therapy has been discovered for mild injury, researchers now look to pharmaceutical supplementation in an attempt to foster success in human clinical trials. Non-traditional therapies, such as acupuncture and even music therapy are being considered to combat the neuropsychiatric symptoms of TBI. In this review, we highlight alternative approaches that have been studied in clinical and pre-clinical studies of TBI, and other related forms of neural injury. The purpose of this review is to stimulate further investigation into novel and innovative approaches that can be used to treat the mechanisms and symptoms of mild TBI.

The bidirectional gut-brain-microbiota axis as a potential nexus between traumatic brain injury, inflammation, and disease

As head injuries and their sequelae have become an increasingly salient matter of public health, experts in the field have made great progress elucidating the biological processes occurring within the brain at the moment of injury and throughout the recovery thereafter. Given the extraordinary rate at which our collective knowledge of neurotrauma has grown, new insights may be revealed by examining the existing literature across disciplines with a new perspective. This article will aim to expand the scope of this rapidly evolving field of research beyond the confines of the central nervous system (CNS). Specifically, we will examine the extent to which the bidirectional influence of the gut-brain axis modulates the complex biological processes occurring at the time of traumatic brain injury (TBI) and over the days, months, and years that follow. In addition to local enteric signals originating in the gut, it is well accepted that gastrointestinal (GI) physiology is highly regulated by innervation from the CNS. Conversely, emerging data suggests that the function and health of the CNS is modulated by the interaction between 1) neurotransmitters, immune signaling, hormones, and neuropeptides produced in the gut, 2) the composition of the gut microbiota, and 3) integrity of the intestinal wall serving as a barrier to the external environment. Specific to TBI, existing pre-clinical data indicates that head injuries can cause structural and functional damage to the GI tract, but research directly investigating the neuronal consequences of this intestinal damage is lacking. Despite this void, the proposed mechanisms emanating from a damaged gut are closely implicated in the inflammatory processes known to promote neuropathology in the brain following TBI, which suggests the gut-brain axis may be a therapeutic target to reduce the risk of Chronic Traumatic Encephalopathy and other neurodegenerative diseases following TBI. To better appreciate how various peripheral influences are implicated in the health of the CNS following TBI, this paper will also review the secondary biological injury mechanisms and the dynamic pathophysiological response to neurotrauma. Together, this review article will attempt to connect the dots to reveal novel insights into the bidirectional influence of the gut-brain axis and propose a conceptual model relevant to the recovery from TBI and subsequent risk for future neurological conditions.

Impact of diet-derived signaling molecules on human cognition: exploring the food-brain axis

The processes that define mammalian physiology evolved millions of years ago in response to ancient signaling molecules, most of which were acquired by ingestion and digestion. In this way, evolution inextricably linked diet to all major physiological systems including the nervous system. The importance of diet in neurological development is well documented, although the mechanisms by which diet-derived signaling molecules (DSMs) affect cognition are poorly understood. Studies on the positive impact of nutritive and non-nutritive bioactive molecules on brain function are encouraging but lack the statistical power needed to demonstrate strong positive associations. Establishing associations between DSMs and cognitive functions like mood, memory and learning are made even more difficult by the lack of robust phenotypic markers that can be used to accurately and reproducibly measure the effects of DSMs. Lastly, it is now apparent that processes like neurogenesis and neuroplasticity are embedded within layers of interlocked signaling pathways and gene regulatory networks. Within these interdependent pathways and networks, the various transducers of DSMs are used combinatorially to produce those emergent adaptive gene expression responses needed for stimulus-induced neurogenesis and neuroplasticity. Taken together, it appears that cognition is encoded genomically and modified by epigenetics and epitranscriptomics to produce complex transcriptional programs that are exquisitely sensitive to signaling molecules from the environment. Models for how DSMs mediate the interplay between the environment and various neuronal processes are discussed in the context of the food-brain axis.

Nursing Management of Adults with Severe Traumatic Brain Injury: A Narrative Review

Effective nursing management strategies for adults with severe traumatic brain injury (STBI) are still a remarkable issue and a difficult task for neurologists, neurosurgeons, and neuronurses. A list of justified indications and scientific rationale for nursing management of these patients are continuously evolving. The objectives of the study are to analyze the pertinently available research and clinical studies that demonstrate the nursing management strategies for adults with STBI and to synthesize the available evidence based on the review. A comprehensive literature search was made in following databases such as Google Scholar, Cochrane, J-Gate, ProQuest, and ScienceDirect for retrieving the related studies. In the included studies, data were extracted and evaluated according to the objective. Narrative analysis was adopted to write this review. Patients with STBI have poor prognosis and require quality care for maximizing patients' survival. With a thorough knowledge and discernment of care of such patients, nurses can improve these patients' neurological outcomes.

Omega-3 polyunsaturated fatty acid supplementation attenuates microglial-induced inflammation by inhibiting the HMGB1/TLR4/NF-κB pathway following experimental traumatic brain injury

Background

Microglial activation and the subsequent inflammatory response in the central nervous system play important roles in secondary damage after traumatic brain injury (TBI). High-mobility group box 1 (HMGB1) protein, an important mediator in late inflammatory responses, interacts with transmembrane receptor for advanced glycation end products (RAGE) and toll-like receptors (TLRs) to activate downstream signaling pathways, such as the nuclear factor (NF)-κB signaling pathway, leading to a cascade amplification of inflammatory responses, which are related to neuronal damage after TBI. Omega-3 polyunsaturated fatty acid (ω-3 PUFA) is a commonly used clinical immunonutrient, which has antioxidative and anti-inflammatory effects. However, the effects of ω-3 PUFA on HMGB1 expression and HMGB1-mediated activation of the TLR4/NF-κB signaling pathway are not clear.

Methods

The Feeney DM TBI model was adopted to induce brain injury in rats. Modified neurological severity scores, brain water content, and Nissl staining were employed to determine the neuroprotective effects of ω-3 PUFA supplementation. Assessment of microglial activation in lesioned sites and protein markers for proinflammatory, such as tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, interferon (IFN)-γ, and HMGB1 were used to evaluate neuroinflammatory responses and anti-inflammation effects of ω-3 PUFA supplementation. Immunofluorescent staining and western blot analysis were used to detect HMGB1 nuclear translocation, secretion, and HMGB1-mediated activation of the TLR4/NF-κB signaling pathway to evaluate the effects of ω-3 PUFA supplementation and gain further insight into the mechanisms underlying the development of the neuroinflammatory response after TBI.

Results

It was found that ω-3 PUFA supplementation inhibited TBI-induced microglial activation and expression of inflammatory factors (TNF-α, IL-1β, IL-6, and IFN-γ), reduced brain edema, decreased neuronal apoptosis, and improved neurological functions after TBI. We further demonstrated that ω-3 PUFA supplementation inhibited HMGB1 nuclear translocation and secretion and decreased expression of HMGB1 in neurons and microglia in the lesioned areas. Moreover, ω-3 PUFA supplementation inhibited microglial activation and the subsequent inflammatory response by regulating HMGB1 and the TLR4/NF-κB signaling pathway.

Conclusions

The results of this study suggest that microglial activation and the subsequent neuroinflammatory response as well as the related HMGB1/TLR4/NF-κB signaling pathway play essential roles in secondary injury after TBI. Furthermore, ω-3 PUFA supplementation inhibited TBI-induced microglial activation and the subsequent inflammatory response by regulating HMGB1 nuclear translocation and secretion and also HMGB1-mediated activation of the TLR4/NF-κB signaling pathway, leading to neuroprotective effects.

Lactate supplementation in severe traumatic brain injured adults by primed constant infusion of sodium L-lactate

Carbohydrate fuel augmentation following traumatic brain injury may be a viable treatment to improve recovery when cerebral oxidative metabolism of glucose is depressed. We performed a primed constant sodium L-lactate infusion in 11 moderate to severely brain injured adults. Blood was collected before and periodically during the infusion study. We quantified global cerebral uptake of glucose and lactate and other systemic metabolites associated with energy metabolism. Our hypothesis was that cerebral lactate uptake, as measured by the arteriovenous difference of lactate (AVDlac), would increase in severely injured TBI patients in the neurocritical care unit. Infusion of sodium L-lactate changed net cerebral lactate release, where the arteriovenous difference of lactate is negative, to net cerebral lactate uptake. Results from a mixed effects model of AVDlac with the fixed effects of infusion time, arterial lactate concentration, arterial glucose concentration and arteriovenous difference of glucose shows that doubling arterial lactate concentration (from .92 to 1.84 mM) results in an increase in AVDlac from -.078 mM to .090 mM. We did not detect changes in systemic glucose during the course of the infusion study and observed significant changes in alanine (30% [20 39]), glutamine (34% [24 43]), acetate (87% [60 113]), valine (40% [28 51]), and leucine (24% [16 32]) from baseline levels. Further studies are required to establish the impact of lactate supplementation on cerebral and systemic flux of lactate, on gluconeogenesis, and on the impact on cerebral energetics following injury. © 2017 Wiley Periodicals, Inc.

Protective Effects of Chinese Herbal Medicine Rhizoma drynariae in Rats After Traumatic Brain Injury and Identification of Active Compound

Traumatic brain injury (TBI) is a leading cause of death and disability in the USA. Effective therapeutic strategies for TBI are needed, and increasing attention is turning toward traditional herbal medicine. Rhizoma drynariae is a traditional Chinese medicine that has immunomodulatory and anti-inflammatory effects. Here, using the controlled cortical impact model of TBI in rats, we examined whether oral administration of R. drynariae can reduce TBI-induced brain injury in rats. We also identified the likely active compound among its four major phytochemicals in decoction. We found that post-treatment with R. drynariae decreased brain lesion volume, improved neurologic and cognitive function, and reduced anxiety- and depression-like behaviors. These changes were accompanied by reduced blood levels of IL-6 and increased IL-10. R. drynariae treatment also reversed the TBI-induced decrease in blood monocyte numbers and percentage of blood CD3 and CD4 T lymphocytes while inhibiting microglial/macrophage activation. Furthermore, by using ultra performance liquid chromatography and comparing retention times with authentic standards, we identified eriodictyol as the putative active compound of R. drynariae extract in the blood of rats with TBI. These novel findings indicate that the traditional Chinese herbal medicine R. drynariae protects brain against TBI-induced brain injury, possibly via immune-promoting, anti-inflammatory, and neuroprotective effects. Eriodictyol could be its active compound.

Hypoaminoacidemia Characterizes Chronic Traumatic Brain Injury

Individuals with a history of traumatic brain injury (TBI) are at increased risk for a number of disorders, including Alzheimer's disease, Parkinson's disease, and chronic traumatic encephalopathy. However, mediators of the long-term morbidity are uncertain. We conducted a multi-site, prospective trial in chronic TBI patients (∼18 years post-TBI) living in long-term 24-h care environments and local controls without a history of head injury. Inability to give informed consent was exclusionary for participation. A total of 41 individuals (17 moderate-severe TBI, 24 controls) were studied before and after consumption of a standardized breakfast to determine if concentrations of amino acids, cytokines, C-reactive protein, and insulin are potential mediators of long-term TBI morbidity. Analyte concentrations were measured in serum drawn before (fasting) and 1 h after meal consumption. Mean ages were 44 ± 15 and 49 ± 11 years for controls and chronic TBI patients, respectively. Chronic TBI patients had significantly lower circulating concentrations of numerous individual amino acids, as well as essential amino acids (p = 0.03) and large neutral amino acids (p = 0.003) considered as groups, and displayed fundamentally altered cytokine-amino acid relationships. Many years after injury, TBI patients exhibit abnormal metabolic responses and altered relationships between circulating amino acids, cytokines, and hormones. This pattern is consistent with TBI, inducing a chronic disease state in patients. Understanding the mechanisms causing the chronic disease state could lead to new treatments for its prevention.

Vitamins and nutrients as primary treatments in experimental brain injury: Clinical implications for nutraceutical therapies

With the numerous failures of pharmaceuticals to treat traumatic brain injury in humans, more researchers have become interested in combination therapies. This is largely due to the multimodal nature of damage from injury, which causes excitotoxicity, oxidative stress, edema, neuroinflammation and cell death. Polydrug treatments have the potential to target multiple aspects of the secondary injury cascade, while many previous therapies focused on one particular aspect. Of specific note are vitamins, minerals and nutrients that can be utilized to supplement other therapies. Many of these have low toxicity, are already FDA approved and have minimal interactions with other drugs, making them attractive targets for therapeutics. Over the past 20 years, interest in supplementation and supraphysiologic dosing of nutrients for brain injury has increased and indeed many vitamins and nutrients now have a considerable body of the literature backing their use. Here, we review several of the prominent therapies in the category of nutraceutical treatment for brain injury in experimental models, including vitamins (B2, B3, B6, B9, C, D, E), herbs and traditional medicines (ginseng, Gingko biloba), flavonoids, and other nutrients (magnesium, zinc, carnitine, omega-3 fatty acids). While there is still much work to be done, several of these have strong potential for clinical therapies, particularly with regard to polydrug regimens. This article is part of a Special Issue entitled SI:Brain injury and recovery.

Systematic Review of Traumatic Brain Injury and the Impact of Antioxidant Therapy on Clinical Outcomes

BACKGROUND

Traumatic brain injury (TBI) is an acquired brain injury that occurs when there is sudden trauma that leads to brain damage. This acute complex event can happen when the head is violently or suddenly struck or an object pierces the skull or brain. The current principal treatment of TBI includes various pharmaceutical agents, hyperbaric oxygen, and hypothermia. There is evidence that secondary injury from a TBI is specifically related to oxidative stress. However, the clinical management of TBI often does not include antioxidants to reduce oxidative stress and prevent secondary injury.

AIMS

The purpose of this article is to examine current literature regarding the use of antioxidant therapies in treating TBI. This review evaluates the evidence of antioxidant therapy as an adjunctive treatment used to reduce the underlying mechanisms involved in secondary TBI injury.

METHODS

A systematic review of the literature published between January 2005 and September 2015 was conducted. Five databases were searched including CINAHL, PubMed, the Cochrane Library, PsycINFO, and Web of Science.

FINDINGS

Critical evaluation of the six studies that met inclusion criteria suggests that antioxidant therapies such as amino acids, vitamins C and E, progesterone, N-acetylcysteine, and enzogenol may be safe and effective adjunctive therapies in adult patients with TBI. Although certain limitations were found, the overall trend of using antioxidant therapies to improve the clinical outcomes of TBI was positive.

LINKING EVIDENCE TO ACTION

By incorporating antioxidant therapies into practice, clinicians can help attenuate the oxidative posttraumatic brain damage and optimize patients' recovery.

The Relationship Between Creatine and Whey Protein Supplements Consumption and Anesthesia in Rats

Background:

Because the trend of pharmacotherapy is toward controlling diet rather than administration of drugs, in our study we examined the probable relationship between Creatine (Cr) or Whey (Wh) consumption and anesthesia (analgesia effect of ketamine). Creatine and Wh are among the most favorable supplements in the market. Whey is a protein, which is extracted from milk and is a rich source of amino acids. Creatine is an amino acid derivative that can change to ATP in the body. Both of these supplements result in Nitric Oxide (NO) retention, which is believed to be effective in N-Methyl-D-aspartate (NMDA) receptor analgesia.

Objectives:

The main question of this study was whether Wh and Cr are effective on analgesic and anesthetic characteristics of ketamine and whether this is related to NO retention or amino acids’ features

Materials and Methods:

We divided 30 male Wistar rats to three (n = 10) groups; including Cr, Wh and sham (water only) groups. Each group was administered (by gavage) the supplements for an intermediate dosage during 25 days. After this period, they became anesthetized using a Ketamine-Xylazine (KX) and their time to anesthesia and analgesia, and total sleep time were recorded.

Results:

Data were analyzed twice using the SPSS 18 software with Analysis of Variance (ANOVA) and post hoc test; first time we expunged the rats that didn’t become anesthetized and the second time we included all of the samples. There was a significant P-value (P < 0.05) for total anesthesia time in the second analysis. Bonferroni multiple comparison indicated that the difference was between Cr and Sham groups (P < 0.021).

Conclusions:

The data only indicated that there might be a significant relationship between Cr consumption and total sleep time. Further studies, with rats of different gender and different dosage of supplement and anesthetics are suggested.

Subacute complications during recovery from severe traumatic brain injury: frequency and associations with outcome

BACKGROUND

Medical complications after severe traumatic brain injury (S-TBI) may delay or prevent transfer to rehabilitation units and impact on long-term outcome.

OBJECTIVE

Mapping of medical complications in the subacute period after S-TBI and the impact of these complications on 1-year outcome to inform healthcare planning and discussion of prognosis with relatives.

SETTING

Prospective multicentre observational study. Recruitment from 6 neurosurgical centres in Sweden and Iceland.

PARTICIPANTS AND ASSESSMENTS

Patients aged 18-65 years with S-TBI and acute Glasgow Coma Scale 3-8, who were admitted to neurointensive care. Assessment of medical complications 3 weeks and 3 months after injury. Follow-up to 1 year. 114 patients recruited with follow-up at 1 year as follows: 100 assessed, 7 dead and 7 dropped out.

OUTCOME MEASURE

Glasgow Outcome Scale Extended.

RESULTS

68 patients had ≥1 complication 3 weeks after injury. 3 weeks after injury, factors associated with unfavourable outcome at 1 year were: tracheostomy, assisted ventilation, on-going infection, epilepsy and nutrition via nasogastric tube or percutaneous endoscopic gastroscopy (PEG) tube (univariate logistic regression analyses). Multivariate analysis demonstrated that tracheostomy and epilepsy retained significance even after incorporating acute injury severity into the model. 3 months after injury, factors associated with unfavourable outcome were tracheostomy and heterotopic ossification (Fisher's test), infection, hydrocephalus, autonomic instability, PEG feeding and weight loss (univariate logistic regression). PEG feeding and weight loss at 3 months were retained in a multivariate model.

CONCLUSIONS

Subacute complications occurred in two-thirds of patients. Presence of a tracheostomy or epilepsy at 3 weeks, and of PEG feeding and weight loss at 3 months, had robust associations with unfavourable outcome that were incompletely explained by acute injury severity.

Death following traumatic brain injury in Drosophila is associated with intestinal barrier dysfunction

Traumatic brain injury (TBI) is a major cause of death and disability worldwide. Unfavorable TBI outcomes result from primary mechanical injuries to the brain and ensuing secondary non-mechanical injuries that are not limited to the brain. Our genome-wide association study of Drosophila melanogaster revealed that the probability of death following TBI is associated with single nucleotide polymorphisms in genes involved in tissue barrier function and glucose homeostasis. We found that TBI causes intestinal and blood–brain barrier dysfunction and that intestinal barrier dysfunction is highly correlated with the probability of death. Furthermore, we found that ingestion of glucose after a primary injury increases the probability of death through a secondary injury mechanism that exacerbates intestinal barrier dysfunction. Our results indicate that natural variation in the probability of death following TBI is due in part to genetic differences that affect intestinal barrier dysfunction.

DOI:http://dx.doi.org/10.7554/eLife.04790.001

Traumatic brain injury (TBI) caused by a violent blow to the head or body and the resultant collision of the brain against the skull is a major cause of disability and death in humans. Primary injury to the brain triggers secondary injuries that further damage the brain and other organs, generating many of the detrimental consequences of TBI. However, despite decades of study, the exact nature of these secondary injuries and their origin are poorly understood. A better understanding of secondary injuries should help to develop novel therapies to improve TBI outcomes in affected individuals.

To obtain this information, in 2013 researchers devised a method to inflict TBI in the common fruit fly, Drosophila melanogaster, an organism that is readily amenable to detailed genetic and molecular studies. This investigation demonstrated that flies subjected to TBI display many of the same symptoms observed in humans after a brain injury, including temporary loss of mobility and damage to the brain that becomes worse over time. In addition, many of the flies die within 24 hr after brain injury.

Now Katzenberger et al. use this experimental system to investigate the secondary injuries responsible for these deaths. First, genetic variants were identified that confer increased or decreased susceptibility to death after brain injury. Several of the identified genes affect the structural integrity of the intestinal barrier that isolates the contents of the gut—including nutrients and bacteria—from the circulatory system. Katzenberger et al. subsequently found that the breakdown of this barrier after brain injury permits bacteria and glucose to leak out of the intestine. Treating flies with antibiotics did not increase survival, whereas reducing glucose levels in the circulatory system after brain injury did. Thus, Katzenberger et al. conclude that high levels of glucose in the circulatory system, a condition known as hyperglycemia, is a key culprit in death following TBI.

Notably, these results parallel findings in humans, where hyperglycemia is highly predictive of death following TBI. Similarly, individuals with diabetes have a significantly increased risk of death after TBI. These results suggest that the secondary injuries leading to death are the same in flies and humans and that further studies in flies are likely to provide additional new information that will help us understand the complex consequences of TBI. Important challenges remain, including understanding precisely how the brain and intestine communicate, how injury to the brain leads to disruption of the intestinal barrier, and why elevated glucose levels increase mortality after brain injury. Answers to these questions could help pave the way to new therapies for TBI.

DOI:http://dx.doi.org/10.7554/eLife.04790.002