Alterations in cerebral availability of metabolic substrates after severe head injury

Dietary Supplementation With Branched Chain Amino Acids to Improve Sleep in Veterans With Traumatic Brain Injury: A Randomized Double-Blind Placebo-Controlled Pilot and Feasibility Trial

Study Objectives

Traumatic brain injury (TBI) is associated with chronic sleep disturbances and cognitive impairment. Our prior preclinical work demonstrated dietary supplementation with branched chain amino acids (BCAA: leucine, isoleucine, and valine), precursors to de novo glutamate production, restored impairments in glutamate, orexin/hypocretin neurons, sleep, and memory in rodent models of TBI. This pilot study assessed the feasibility and preliminary efficacy of dietary supplementation with BCAA on sleep and cognition in Veterans with TBI.

Methods

Thirty-two Veterans with TBI were prospectively enrolled in a randomized, double-blinded, placebo-controlled trial comparing BCAA (30 g, b.i.d. for 21-days) with one of two placebo arms (microcrystalline cellulose or rice protein, both 30 g, b.i.d. for 21-days). Pre- and post-intervention outcomes included sleep measures (questionnaires, daily sleep/study diaries, and wrist actigraphy), neuropsychological testing, and blood-based biomarkers related to BCAA consumption.

Results

Six subjects withdrew from the study (2/group), leaving 26 remaining subjects who were highly adherent to the protocol (BCAA, 93%; rice protein, 96%; microcrystalline, 95%; actigraphy 87%). BCAA were well-tolerated with few side effects and no adverse events. BCAA significantly improved subjective insomnia symptoms and objective sleep latency and wake after sleep onset on actigraphy.

Conclusion

Dietary supplementation with BCAA is a mechanism-based, promising intervention that shows feasibility, acceptability, and preliminary efficacy to treat insomnia and objective sleep disruption in Veterans with TBI. A larger scale randomized clinical trial is warranted to further evaluate the efficacy, dosing, and duration of BCAA effects on sleep and other related outcome measures in individuals with TBI.

Clinical Trial Registration

[http://clinicaltrials.gov/], identifier [NCT03990909].

UPLC-ESI-IT-TOF-MS metabolomic study of the therapeutic effect of Xuefu Zhuyu decoction on rats with traumatic brain injury

It has been widely reported that Xuefu Zhuyu decoction (XFZYD), a traditional Chinese medicine, is effective in the treatment of traumatic brain injury (TBI). However, the mechanism of the therapeutic process is still not fully understood. Metabolomic technique can be used to explore the mechanisms underlying the treatment of TBI with XFZYD. The purpose of this work was to investigate the metabolic characteristics of blood samples from rats with and without XFZYD treatment and the dynamic changes in metabolite profiles on days 1, 3, 7, 14 and 21 after injury (within the severe phase of TBI) based on untargeted UPLC-ESI-IT-TOF-MS analysis. Pattern recognition, clustering analysis and metabolic pathway analysis were used to analyse the metabolomic data of three groups (a sham-operated group, a TBI model, and an XFZYD-treated TBI model). The results showed that XFZYD reversed the abnormalities in the levels of small-molecule metabolites (such as L-acetylcarnitine, L-tryptophan, indoleacrylic acid, γ-aminobutyric acid, hypotaurine, LysoPC(18:1)(11Z), creatine, L-phenylalanine and L-leucine) in TBI rats through six metabolic pathways (including phenylalanine, tyrosine and tryptophan biosynthesis; phenylalanine metabolism; valine, leucine and isoleucine biosynthesis; taurine and hypotaurine metabolism; tryptophan metabolism; and alanine, aspartate and glutamate metabolism) involved in the therapy process. XFZYD regulated the metabolic disorders of endogenous markers by the possible mechanisms of neuroprotection, energy metabolism, inflammatory response and oxidative stress. This study revealed the holistic and dynamic metabolic changes caused by XFZYD in rats with TBI and provided important research methods and approaches for exploring the multiple metabolites and metabolic pathways involved in the therapeutic effect of XFZYD on TBI.

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.

Traumatic brain injury-induced expression and phosphorylation of pyruvate dehydrogenase: a mechanism of dysregulated glucose metabolism

Dysregulated brain glucose metabolism and lactate accumulation are seen following traumatic brain injury (TBI). The underlying molecular mechanism is poorly understood. Pyruvate dehydrogenase (PDH), the rate-limiting enzyme coupling cytosolic glycolysis to mitochondrial citric acid cycle, plays a critical role in maintaining homeostasis of brain glucose metabolism. PDH activity is maintained by the expression of its E1alpha1 subunit 1 (PDHE1alpha1) and is inhibited by the phosphorylation of PDHE1alpha1 (p-PDHE1alpha1). We hypothesized that PDHE1alpha1 expression and phosphorylation was altered in rat brain following controlled cortical impact (CCI)-induced TBI. Compared to naïve controls (=100%), PDHE1alpha1 protein decreased significantly ipsilateral to CCI (62%, P<0.05; 75%, P<0.05; 57%, P<0.05; and 39%, P<0.01) and contralateral to CCI (77%, 78%, 78% and 36% P<0.01) at 4h, 24h, 3- and 7-day post-CCI, respectively. PDHE1alpha1 protein phosphorylation level also decreased significantly ipsilateral to CCI (31%, P<0.01; 102%, P>0.05; 64%, P<0.05; and 14%, P<0.01) and to contralateral CCI (35%, 74%, P<0.05; 60%, P<0.05; 20%, P<0.01) at 4h, 24h, 3- and 7-day post-CCI, respectively. Similar reduction in PDHE1alpha1 and p-PDHE1alpha1 protein was found in the craniotomy (sham CCI) group. TBI-induced change in PDHE1alpha1 expression and phosphorylation could alter brain PDH activity and glucose metabolism.

Bedside monitoring of cerebral blood flow by transcranial thermo-dye-dilution technique in patients suffering from severe traumatic brain injury or subarachnoid hemorrhage

Bedside measurement of cerebral blood flow (CBF) represents an important feature in monitoring of neurointensive care patients which is hard to establish. Therefore, we adopted a recently described thermo-dye-dilution-based approach for monitoring CBF in patients suffering from severe cerebral insults, that is, traumatic brain injury (TBI) or subarachnoid hemorrhage (SAH). Combined fiberoptic-thermistor catheters were placed in one jugular venous bulb and in the abdominal aorta of 16 patients. Following central venous injection of a 50-mL bolus of precooled indocyanine green (ICG) solution, CBF was determined as a function of the mean transit times of coldness and dye. In addition, measurements of CBF using stable xenon-enhanced computerized tomography (sXe-CT) were simultaneously performed in 10 patients. A total of 272 thermo-dye-dilution measurements yielded 196 valid results, with CBF ranging from 26.2 to 144.8 mL 100 g(-1) min(-1). Reproducibility was fairly good, with the standard deviation within sets of repeated measurements being 6.3 mL 100 g(-1) min(-1) and 9.4 as the mean coefficient of variation. Simultaneously obtained values with sXe-CT displayed a good correlation (r = 0.843, p < 0.01); however, the thermo-dye-dilution method consistently overestimated CBF. Data analysis using the Bland and Altman methodology revealed a large bias of 45.7 mL 100 g(-1) min(-1) with a +/- 2 SD range of 37 mL 100 g(-1) min(-1), indicating a rather poor agreement. The thermo-dye-dilution method proved a reasonably reproducible technique, enabling repeated long-term bedside measurements of CBF in neurointensive care patients with a minimum of time effort. However, a high failure rate was also noted, and consistent overestimation of perfusion was observed in comparison to sXe-CT measurements. Although the thermo-dye-dilution technique has been successfully validated in patients with normal neurovascular function, its applicability for bedside monitoring of CBF appears uncertain in patients suffering from severe TBI or SAH.

[Uses and abuses of hyperventilation in severe traumatic brain injury]

A critical evaluation was done about the guidelines and effects of the hyperventilation maneuver on prevention and treatment of increased intracranial pressure (ICP) that follows severe traumatic brain injury (TBI). The prophylactic use of hyperventilation should be avoided after severe TBI acute phase, unless high venous O2 values are recorded at jugular bulb blood (SjO2), or to allow time when there are evidences of neurologic deterioration with posturing. The lack of cerebrovascular response to hyperventilation to low the ICP means that the blood brain barrier (BBB) function is extensively impaired. Then, hyperventilation may be used as a screening therapeutic test in acute severe TBI, since BBB impairment is the pointer that other available clinical procedures for high ICP control (sedation, paralysis and osmotic diuretics) are not workable. A new pathogenetic hypothesis about traumatic brain edema and its therapeutic approach is presented.

The Brain Trauma Foundation. The American Association of Neurological Surgeons. The Joint Section on Neurotrauma and Critical Care. Hyperventilation

Chronic prophylactic hyperventilation therapy should be avoided during the first 5 days after severe TBI and particularly during the first 24 h. CBF measurements in patients with severe TBI demonstrate that blood flow early after injury is low and strongly suggest that in the first few hours after injury the absolute values approach those consistent with ischemia. These findings are corroborated by AVdO2 and SjO2 and brain tissue O2 measurements. Hyperventilation will reduce CBF values even further, but will not consistently cause a reduction of ICP and may cause loss of autoregulation. The cerebral vascular response to hypocapnia is reduced in those with the most severe injuries (subdural hematomas and diffuse contusions), and there is substantial local variability in perfusion. While the CBF level at which irreversible ischemia occurs has not been clearly established, ischemic cell change has been demonstrated in 90% of those who die following TBI, and there is PET evidence that such damage is likely to occur when CBF drops below 15-20 cc/100 g/min. A prospective randomized clinical trial has determined that outcomes are worse when TBI patients are treated with chronic prophylactic hyperventilation therapy. Within the standard, guideline, and options, specific paCO2 thresholds have been described that are different for each of the three parameters. These individual thresholds were selected based on the preponderance of literature supporting those thresholds in the contexts of the statements which included them. With the exception of the threshold included for the standard in this guideline, it is emphasized that the paCO2 threshold is not as important as the general concept of hyperventilation. The preponderance of the physiologic literature concludes that hyperventilation during the first few days following severe traumatic brain injury, whatever the threshold, is potentially deleterious in that it can promote cerebral ischemia.

Dissociation of cerebral glucose metabolism and level of consciousness during the period of metabolic depression following human traumatic brain injury

Utilizing [18F]fluorodeoxyglucose positron emission tomography (FDG-PET), we studied the correlation between CMRglc and the level of consciousness within the first month following human traumatic brain injury. Forty-three FDG-PET scans obtained on 42 mild to severely head-injured patients were quantitatively analyzed for the determination of regional cerebral metabolic rate of glucose (CMRglc). Reduction of cerebral glucose utilization, defined as a CMRglc of < or =4.9 mg/100 g/min, was present regionally in 88% of the studies. The prevalence of global cortical CMRglc reduction was higher in severely head-injured patients (86% versus 67% mild-moderate), although the absolute magnitude was similar across the injury severity spectrum (mean CMRglc 3.9 +/- 0.6 mg/100 g/min). The level of consciousness, as measured by the Glasgow Coma Scale, correlated poorly with the global cortical CMRglc value (r = 0.08; p = 0.63). With regards to severity of head injury, this correlation was worst for the severely injured (r = -0.11; p = 0.58) and better for the mildly injured patients (r = 0.50; p = 0.07). In most cases, intraparenchymal hemorrhagic lesions were associated with either focal CMRglc reduction or elevation. It is concluded that the etiologies of CMRglc reduction are likely multifactorial given the complex nature of traumatic brain injury and that the reduction of CMRglc represents a fundamental pathobiologic state following head injury that is not tightly coupled to level of consciousness.

Intravenous insulin-like growth factor-I (IGF-I) in moderate-to-severe head injury: a Phase II safety and efficacy trial

The purpose of this study was to determine the effect of insulin-like growth factor-I (IGF-I) on the catabolic state and clinical outcome of head-injured patients. Thirty-three patients between the ages of 18 and 59 years with isolated traumatic head injury and Glasgow Coma Scale (GCS) scores of 4 to 10 were randomized to one of two groups. All patients received standard neurosurgical intensive care plus aggressive nutritional support; the patients in the treatment group also received intravenous therapy with continuous IGF-I (0.01 mg/kg/hour).

During the 14-day dosing period, the control patients lost weight, whereas treated patients gained weight despite a significantly higher measured energy expenditure and lower caloric intake (p = 0.02). Daily glucose concentrations and nitrogen outputs were greater in control patients (p = 0.03) throughout the study period. During Week 1, only treated patients achieved positive nitrogen balance. Fifteen of 17 treated and 13 of 16 control patients survived the 1st week. No deaths occurred in patients whose serum IGF-I concentrations were higher than 350 ng/ml. Dichotomized Glasgow Outcome Scale scores for patients with baseline GCS scores of 5 to 7 improved from poor to good for eight of 12 treated patients but for only three of 11 control patients (p = 0.06). Eight of 11 treated patients with serum IGF-I concentrations that were at least 350 ng/ml achieved moderate-to-good outcome scores at 6 months, compared to only one of five patients with lower concentrations (p < 0.05). These findings indicate that pharmacological concentrations of IGF-I may improve clinical outcome and nitrogen utilization in patients with moderate-to-severe head injury.

Intravenous insulin-like growth factor-I (IGF-I) in moderate-to-severe head injury: a phase II safety and efficacy trial

The purpose of this study was to determine the effect of insulin-like growth factor-I (IGF-I) on the catabolic state and clinical outcome of head-injured patients. Thirty-three patients between the ages of 18 and 59 years with isolated traumatic head injury and Glasgow Coma Scale (GCS) scores of 4 to 10 were randomized to one of two groups. All patients received standard neurosurgical intensive care plus aggressive nutritional support; the patients in the treatment group also received intravenous therapy with continuous IGF-I (0.01 mg/kg/hour). During the 14-day dosing period, the control patients lost weight, whereas treated patients gained weight despite a significantly higher measured energy expenditure and lower caloric intake (p = 0.02). Daily glucose concentrations and nitrogen outputs were greater in control patients (p = 0.03) throughout the study period. During Week 1, only treated patients achieved positive nitrogen balance. Fifteen of 17 treated and 13 of 16 control patients survived the 1st week. No deaths occurred in patients whose serum IGF-I concentrations were higher than 350 ng/ml. Dichotomized Glasgow Outcome Scale scores for patients with baseline GCS scores of 5 to 7 improved from poor to good for eight of 12 treated patients but for only three of 11 control patients (p = 0.06). Eight of 11 treated patients with serum IGF-I concentrations that were at least 350 ng/ml achieved moderate-to-good outcome scores at 6 months, compared to only one of five patients with lower concentrations (p < 0.05). These findings indicate that pharmacological concentrations of IGF-I may improve clinical outcome and nitrogen utilization in patients with moderate-to-severe head injury.

Cerebral hyperglycolysis following severe traumatic brain injury in humans: a positron emission tomography study

Experimental traumatic brain injury studies have shown that cerebral hyperglycolysis is a pathophysiological response to injury-induced ionic and neurochemical cascades. This finding has important implications regarding cellular viability, vulnerability to secondary insults, and the functional capability of affected regions. Prior to this study, posttraumatic hyperglycolysis had not been detected in humans. The characteristics and incidence of cerebral hyperglycolysis were determined in 28 severely head injured patients using [18F]fluorodeoxyglucose-positron emission tomography (FDG-PET). The local cerebral metabolic rate of glucose (CMRG) was calculated using a standard compartmental model. In six of the 28 patients, the global cerebral metabolic rate of oxygen (CMRO2) was determined by the simultaneous measurements of arteriovenous differences of oxygen and cerebral blood flow (xenon-133). Hyperglycolysis, defined as an increase in glucose utilization that measures two standard deviations above expected levels, was documented in all six patients in whom both FDG-PET and CMRO2 determinations were made within 8 days of injury. Five additional patients were found to have localized areas of hyperglycolysis adjacent to focal mass lesions. Within the 1st week following the injury, 56% of patients studied had presumptive evidence of hyperglycolysis. The results of this study indicate that the metabolic state of the traumatically injured brain should be defined differentially in terms of glucose and oxygen metabolism. The use of FDG-PET demonstrates that hyperglycolysis occurs both regionally and globally following severe head injury in humans. The results of this clinical study directly complement those previously reported in experimental brain-injury studies, indicating the capability of imaging a fundamental component of cellular pathophysiology characteristic of head injury.

Changes in cerebral oxygen consumption are independent of changes in body oxygen consumption after severe head injury in childhood

This study examines the relation between cerebral O2 consumption (CMRO2) and the O2 consumption of the rest of the body (BVO2) after severe head injury. Seventy nine serial measurements of whole body O2 consumption, CMRO2, plasma adrenaline, T3, and glucagon concentrations were made in 15 children with severe head injuries receiving neurointensive care. Body O2 consumption was measured with indirect calorimetry and CMRO2 with the Kety-Schmidt technique. There was no evidence of a significant relation between CMRO2 and BVO2. Within each child there were statistically significant positive relations between BVO2 and adrenaline, T3, and glucagon. By contrast, there was only a weak significant positive relation between CMRO2 and T3. In conclusion, CMRO2 and BVO2 seem to be determined independently after severe head injury. Thus therapeutic measures aiming to reduce CMRO2 need to be specific to the brain and it should not be assumed that measures which decrease whole body energy expenditure will necessarily have the same effect on CMRO2.

Early ischaemia after severe head injury. Preliminary results in patients with diffuse brain injuries

Ischaemic brain lesions still have a high prevalence in fatally head injured patients and are the single most important cause of secondary brain damage. The present study was undertaken to explore the acute phase of severely head injured patients in order to detect early ischaemia using Robertson's approach of estimating cerebral blood flow (CBF) from calculated arterio-jugular differences of oxygen (AVDO2), lactates (AVDL), and the lactate-oxygen index (LOI). Twenty-eight cases with severe head injury were included (Glasgow Coma Scale Score below or equal to 8). All patients but one had a non-missile head injury. All the patients had a diffuse brain injury according to the admission CT scan. ICP measured at the time of admission was below 20 mmHg in 17 cases (61%). All patients were evaluated with the ischaemia score (IS) devised in our center to evaluate risk factors for developing ischaemia. Mean time from injury to the first AVDO2/AVDL study was 23.9 +/- 9.9 hours. According to Robertson's criteria, 13 patients (46%) had a calculated LOI (-AVDL/AVDO2) value above or equal to 0.08 and therefore an ischaemia/infarction pattern in the first 24 hours after the accident. Of the 15 patients without the ischaemia/infarction pattern, in three cases the CBF was below the metabolic demands and therefore in a situation of compensated hypoperfusion. No patient in our series had hyperaemia. Comparing different variables in ischaemic and non-ischaemic patients, only arterial haemoglobin and ischaemia score (IS) was significantly different in both groups. The ischaemia score had mean of 4.3 +/- 1.7 in the ischaemic group and 2.7 +/- 1.4 in non-ischaemic patients (p = 0.01). It is concluded that ischaemia is highly prevalent in the early period after severe head injury. Factors potentially responsible of early ischaemia are discussed.

The effect of glucose administration on carbohydrate metabolism after head injury

The role of intravenous infusion of glucose in limiting ketogenesis and the effect of glucose on cerebral metabolism following severe head injury were studied in 21 comatose patients. The patients were randomly assigned to alimentation with or without glucose. Systemic protein wasting, arterial concentrations of energy substrates, and cerebral metabolism of these energy substrates were monitored for 5 days postinjury. Both groups were in negative nitrogen balance, and had wasting of systemic proteins despite substantial protein intake. Blood and cerebrospinal fluid (CSF) glucose concentrations were highest on Day 1, but remained higher than normal fasting levels on all days of study, even in the patients who received no exogenous glucose. Although there were no differences in blood or CSF glucose concentrations in the two groups of patients, the glucose group had higher plasma insulin levels, with a mean +/- standard deviation of 14.8 +/- 7.3 microU/ml compared to 10.3 +/- 4.2 microU/ml in the saline group. The blood concentrations of beta-hydroxybutyrate, acetoacetate, pyruvate, glycerol, and the free fatty acids were higher in the saline group than in the glucose group. Cerebral oxygen consumption was similar in the two groups, while the cerebral metabolism of glucose and of the ketone bodies was dependent on whether glucose was administered. In the glucose group, glucose was the only energy substrate utilized by the brain. In the saline group, the ketone bodies beta-hydroxybutyrate and acetoacetate replaced glucose to the extent of 16% of the brain's total energy production. Cerebral lactate production and CSF lactate concentration were lower in the saline group. These studies suggest that administration of glucose during the early recovery period of severe head injury is a major cause of suppressed ketogenesis, and may increase production of lactic acid by the traumatized brain by limiting the availability of nonglycolytic energy substrates.

Intensive management of severe head injury

Intensive management of patients with severe head injury offers the best hope of minimizing death and functional disability in a young, working population. Secondary neurologic insult can be decreased by cardiorespiratory support and ICP control from the outset. Rapid neurologic assessment, airway management, and support of circulation are the basis of emergency management for head injury. Patients with severe head injury require intensive care management for two major reasons: management of ICP and management of organ system dysfunction. Care should not be withheld because of initially grim (and inaccurate) prognostic assessment. Newer techniques for assessing the adequacy of cerebral circulation may allow refinement of management strategies in the future.