Change in blood-brain barrier permeability during pediatric diabetic ketoacidosis treatment

Metabolomics in severe traumatic brain injury: a scoping review

BACKGROUND

Diagnosis and prognostication of severe traumatic brain injury (sTBI) continue to be problematic despite years of research efforts. There are currently no clinically reliable biomarkers, though advances in protein biomarkers are being made. Utilizing Omics technology, particularly metabolomics, may provide new diagnostic biomarkers for sTBI. Several published studies have attempted to determine the specific metabolites and metabolic pathways involved; these studies will be reviewed.

AIMS

This scoping review aims to summarize the current literature concerning metabolomics in sTBI, review the comprehensive data, and identify commonalities, if any, to define metabolites with potential clinical use. In addition, we will examine related metabolic pathways through pathway analysis.

METHODS

Scoping review methodology was used to examine the current literature published in Embase, Scopus, PubMed, and Medline. An initial 1090 publications were identified and vetted with specific inclusion criteria. Of these, 20 publications were selected for further examination and summary. Metabolic data was classified using the Human Metabolome Database (HMDB) and arranged to determine the 'recurrent' metabolites and classes found in sTBI. To help understand potential mechanisms of injury, pathway analysis was performed using these metabolites and the Kyoto Encyclopedia of Genes and Genomes (KEGG) Pathway Database.

RESULTS

Several metabolites related to sTBI and their effects on biological pathways were identified in this review. Across the literature, proline, citrulline, lactate, alanine, valine, leucine, and serine all decreased in adults post sTBI, whereas both octanoic and decanoic acid increased. Hydroxy acids and organooxygen compounds generally increased following sTBI, while most carboxylic acids decreased. Pathway analysis showed significantly affected glycine and serine metabolism, glycolysis, branched-chain amino acid (BCAA) metabolism, and other amino acid metabolisms. Interestingly, no tricarboxylic acid cycle metabolites were affected.

CONCLUSION

Aside from a select few metabolites, classification of a metabolic profile proved difficult due to significant ambiguity between study design, sample size, type of sample, metabolomic detection techniques, and other confounding variables found in sTBI literature. Given the trends found in some studies, further metabolomics investigation of sTBI may be useful to identify clinically relevant metabolites.

Tryptophan, kynurenine pathway, and diabetic ketoacidosis in type 1 diabetes

Diabetic ketoacidosis (DKA) is a serious complication of complete insulin deficiency and insulin resistance in Type 1 diabetes (T1D). This results in the body producing high levels of serum ketones in an attempt to compensate for the insulin deficiency and decreased glucose utilization. DKA's metabolic and immunologic dysregulation results in gradual increase of systemic and cerebral oxidative stress, along with low grade systemic and cerebral inflammation and the development of pretreatment subclinical BE. During treatment the early progression of oxidative stress and inflammation is hypothesized to advance the possibility of occurrence of crisis of clinical brain edema (BE), which is the most important cause of morbidity and mortality in pediatric DKA. Longitudinal neurocognitive studies after DKA treatment show progressive and latent deficits of cognition and emphasize the need for more effective DKA treatment of this long-standing conundrum of clinical BE, in the presence of systemic osmotic dehydration, metabolic acidosis and immune dysregulation. Candidate biomarkers of several systemic and neuroinflammatory pathways prior to treatment also progress during treatment, such as the neurotoxic and neuroprotective molecules in the well-recognized tryptophan (TRP)/kynurenine pathway (KP) that have not been investigated in DKA. We used LC-MS/MS targeted mass spectrometry analysis to determine the presence and initiation of the TRP/KP at three time points: A) 6-12 hours after initiation of treatment; B) 2 weeks; and C) 3 months following DKA treatment to determine if they might be involved in the pathogenesis of the acute vasogenic complication of DKA/BE. The Trp/KP metabolites TRP, KYN, quinolinic acid (QA), xanthurnenic acid (XA), and picolinic acid (PA) followed a similar pattern of lower levels in early treatment, with subsequent increases. Time point A compared to Time points B and C were similar to the pattern of sRAGE, lactate and pyruvic acid. The serotonin/melatonin metabolites also followed a similar pattern of lower quantities at the early stages of treatment compared to 3 months after treatment. In addition, glutamate, n-acetylglutamate, glutamine, and taurine were all lower at early treatment compared to 3 months, while the ketones 3-hydroxybutaric acid and acetoacetate were significantly higher in the early treatment compared to 3 months. The two major fat metabolites, L-carnitine and acetyl-L-carnitine (ALC) changed inversely, with ALC significantly decreasing at 2 weeks and 3 months compared to the early stages of treatment. Both anthranilic acid (AA) and 3-OH-anthranilic acid (3OH-AA) had overall higher levels in the early stages of treatment (A) compared to Time points (B and C). Interestingly, the levels of AA and 3OH-AA early in treatment were higher in Caucasian females compared to African American females. There were also differences in the metabolite levels of QA and kynurenic acid (KA) between genders and between races that may be important for further development of custom targeted treatments. We hypothesize that the TRP/KP, along with the other inflammatory pathways, is an active participant in the metabolic and immunologic pathogenesis of DKA's acute and chronic insults.

Leptin receptor deficiency induces early, transient and hyperglycaemia-independent blood-brain barrier dysfunction

Diabetes mellitus (DM) significantly increases susceptibility to central nervous system (CNS) pathologies, including stroke, vascular dementia, cognitive deficits and Alzheimer’s disease. Previous studies (mostly using the streptozotocin model) suggested that blood-brain barrier (BBB) disruption is involved in these conditions. Here, we examined the integrity of brain capillaries and BBB permeability in Lepr^db/db obesity-related diabetic mice. Surprisingly, significant BBB leakage was observed only in young mice at the pre-hyperglycemic stage. Thorough examination of barrier permeability at later diabetic stages showed no evidence for significant BBB leakage during the hyperglycemic state. Electron microscopy imaging of mice with short-term hyperglycaemia supported normal BBB permeability but indicated other stress-related changes in capillary ultrastructure, such as mitochondrial degeneration. Based on our study with this mouse genetic model of obesity-related DM, we suggest that previously reported hyperglycaemia-induced BBB leakage is most likely not the underlying mechanism of DM-related CNS pathologies. Finally we propose that BBB hyper-permeability might be an early and transient phenomenon while stress-related endothelial pathologies do correlate with a short-term diabetic state.

Subclinical cerebral edema in diabetic ketoacidosis in children

Subclinical cerebral edema in diabetic ketoacidosis tends to manifest with subtle neurological symptoms including headache, lethargy, or disorientation and a Glasgow Coma Scale of 14-15. Treatment of subclinical cerebral edema with hyperosmolar therapy for persistent symptoms is associated with good outcomes.

Management of Diabetic Ketoacidosis with Dengue Hemorrhagic Fever

Viral hemorrhagic fever is one of the most important emerging infectious diseases. Some viral hemorrhagic fevers include dengue, hantavirus, Ebola infection, and yellow fever. Dengue virus infection results in a wide spectrum of clinical diseases, including dengue hemorrhagic fever, characterized by the transient period of plasma leakage and hemorrhagic tendency. Vascular instability ranges from mild to fatal shock, and hemorrhage varies from none to life-threatening. Infection is the predominant precipitating factor for diabetic ketoacidosis. In addition to insulin administration, successful management of diabetic ketoacidosis requires fluid resuscitation. We herein report an adult patient with diabetic ketoacidosis complicated with dengue hemorrhagic fever who developed leakage syndrome. Early recognition of leakage and appropriate fluid management was critical in the diabetic ketoacidosis management of this case.

Optic Nerve and Cerebral Edema in the Course of Diabetic Ketoacidosis

In the recent years we have been observing an increased incidence of type 1 diabetes in children and adolescents. This leads to a more frequent acute complication of type 1 diabetes among children with hyperglycemia. The most common of these is diabetic ketoacidosis (DKA), while cerebral edema is the most dangerous. In children with DKA, cerebral edema most often presents with clinical symptoms but may also appear in the so-called "subclinical" form. That is why the search continues for new methods of assessing and monitoring cerebral edema in the course of DKA treatment. Ultrasonographic optic nerve sheath diameter (US ONSD) assessment is performed in various clinical scenarios when cerebral edema is suspected. It is most often performed in adult patients but increasingly often in children. US ONSD assessment is useful in the treatment of DKA in children with type 1 diabetes. This manuscript provides an overview of research results available in PubMed and other available databases on the course of treatment of DKA in children with type 1 diabetes.

Fluid management in pediatric patients with DKA and rates of suspected clinical cerebral edema

OBJECTIVE

To compare outcomes of diabetic ketoacidosis (DKA) 6 yrs before and 6 yrs after changing rehydration fluids from ½ normal saline to Lactated Ringer's and decreasing the total intended fluid volume administered in the first 24 hrs from 3500 mL/m(2) /d to ≤ 2500 mL/m(2) /d at Texas Children's Hospital (TCH) in response to recommendations by the ESPE, LWPES, and ISPAD in 2004.

SUBJECTS/METHODS

A retrospective cohort study was conducted in which 1868 admissions for DKA were identified and reviewed. The cohort was divided into two groups: Group A, 1998-2004, and Group B, 2004-2010. Subjects with suspected clinical cerebral edema and adverse outcomes were identified.

RESULTS

Although not statistically significant, there was an equal number (n = 3) of adverse outcomes (death or neurological damage) in each group despite more than double the admissions in Group B (1264) compared with those in Group A (604). Overall, the incidence of suspected clinical cerebral edema was more than double for those admissions in which fluid resuscitation was initiated at an outside hospital (OSH) vs. at TCH (13.6 vs. 5.3%, p < 0.001).

CONCLUSIONS

Decreasing the intended fluid rate during the initial 24 hrs to 2500 mL/m(2) /d and increasing the IV fluid sodium content did not significantly decrease the incidence of adverse outcomes in children with DKA. However, children transferred from an OSH had a higher incidence of suspected clinical cerebral edema. Thus, we need to more readily share our management protocols with the emergency rooms of local referring hospitals to potentially decrease the incidence of suspected clinical cerebral edema and adverse outcomes in children transferred with DKA.

Biomarkers and genetics of brain injury risk in diabetic ketoacidosis: A pilot study

Diabetic ketoacidosis (DKA) is the primary cause of death for children with diabetes, especially when complicated by cerebral edema. Central nervous system (CNS) involvement is common, however the mechanism of, and predictors of CNS dysfunction/injury are largely unknown. In this observational pilot study, blood was collected from pediatric DKA patients at three time points (consent, 12 hr and 24 hr after beginning treatment), to test genetic markers, ribonucleic acid expression and plasma biomarkers reflecting inflammation (tumor necrosis factor-alpha [TNF-α], interleukin-6 [IL-6]) and cerebral dysfunction and/or possible injury (S100β, glial fibrillary acidic protein [GFAP]). Thirty patients were enrolled in the study. The average age was 11.3 yr, 73% were new onset diabetes and 53% were female. Forty percent exhibited abnormal mentation (Glasgow Coma Scale <15), consistent with CNS dysfunction. IL-6 and TNF-α were elevated in plasma, suggesting systemic inflammation. GFAP was measurable in 45% of patients and correlated positively with GCS. Only two patients had detectable levels of S100β. In conclusion, children with DKA often present with evidence of acute neurologic dysfunction or injury. We have demonstrated the feasibility of exploring genetic and biochemical markers of potential importance in the pathophysiology of CNS dysfunction and/or possible injury in DKA. We have identified IL-6, TNF-α and GFAP as potentially important markers for further exploration. A larger, follow-up study will help to better understand the extent and type of CNS injury in DKA as well as the mechanism underlying this dysfunction/injury.

Effects of metabolic acidosis on intracellular pH responses in multiple cell types

Metabolic acidosis (MAc), a decrease in extracellular pH (pHo) caused by a decrease in [HCO3 (-)]o at a fixed [CO2]o, is a common clinical condition and causes intracellular pH (pHi) to fall. Although previous work has suggested that MAc-induced decreases in pHi (ΔpHi) differ among cell types, what is not clear is the extent to which these differences are the result of the wide variety of methodologies employed by various investigators. In the present study, we evaluated the effects of two sequential MAc challenges (MAc1 and MAc2) on pHi in 10 cell types/lines: primary-cultured hippocampal (HCN) neurons and astrocytes (HCA), primary-cultured medullary raphé (MRN) neurons, and astrocytes (MRA), CT26 colon cancer, the C2C12 skeletal muscles, primary-cultured bone marrow-derived macrophages (BMDM) and dendritic cells (BMDC), Ink4a/ARF-null melanocytes, and XB-2 keratinocytes. We monitor pHi using ratiometric fluorescence imaging of 2',7'-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein while imposing MAc: lowering (pHo) from 7.4 to 7.2 by decreasing [HCO3 (-)]o from 22 to 14 mM at 5% CO2 for 7 min. After MAc1, we return cells to the control solution for 10 min and impose MAc2. Using our definition of MAc resistance [(ΔpHi/ΔpHo) ≤ 40%], during MAc1, ∼70% of CT26 and ∼50% of C2C12 are MAc-resistant, whereas the other cell types are predominantly MAc-sensitive. During MAc2, some cells adapt [(ΔpHi/ΔpHo)2 < (ΔpHi/ΔpHo)1], particularly HCA, C2C12, and BMDC. Most maintain consistent responses [(ΔpHi/ΔpHo)2 ≅ (ΔpHi/ΔpHo)1], and a few decompensate [(ΔpHi/ΔpHo)2>(ΔpHi/ΔpHo)1], particularly HCN, C2C12, and XB-2. Thus, responses to twin MAc challenges depend both on the individual cell and cell type.

Diabetes Mellitus and Blood-Brain Barrier Dysfunction: An Overview

A host of diabetes-related insults to the central nervous system (CNS) have been clearly documented in type-1 and -2 diabetic patients as well as experimental animal models. These host of neurological disorders encompass hemodynamic impairments (e.g., stroke), vascular dementia, cognitive deficits (mild to moderate), as well as a number of neurochemical, electrophysiological and behavioral alterations. The underlying causes of diabetes-induced CNS complications are multifactorial and are relatively little understood although it is now evident that blood-brain barrier (BBB) damage plays a significant role in diabetes-dependent CNS disorders. Changes in plasma glucose levels (hyper- or hypoglycemia) have been associated with altered BBB transport functions (e.g., glucose, insulin, choline, amino acids, etc.), integrity (tight junction disruption), and oxidative stress in the CNS microcapillaries. Last two implicating a potential causal role for upregulation and activation of the receptor for advanced glycation end products (RAGE). This type I membrane-protein also transports amyloid-beta (Aβ) from the blood into the brain across the BBB thus, establishing a link between type 2 diabetes mellitus (T2DM) and Alzheimer's disease (AD, also referred to as "type 3 diabetes"). Hyperglycemia has been associated with progression of cerebral ischemia and the consequent enhancement of secondary brain injury. Difficulty in detecting vascular impairments in the large, heterogeneous brain microvascular bed and dissecting out the impact of hyper- and hypoglycemia in vivo has led to controversial results especially with regard to the effects of diabetes on BBB. In this article, we review the major findings and current knowledge with regard to the impact of diabetes on BBB integrity and function as well as specific brain microvascular effects of hyper- and hypoglycemia.

Change in mean transit time, apparent diffusion coefficient, and cerebral blood volume during pediatric diabetic ketoacidosis treatment

OBJECTIVES

Cerebral edema is a devastating complication of pediatric diabetic ketoacidosis. We examined measures describing potential causes of whole brain and regional brain edema (mean transit time, apparent diffusion coefficient, and relative cerebral blood volume) during treatment of diabetic ketoacidosis in children.

DESIGN

Prospective observational study.

SETTING

Regional children's hospital.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

After Institutional Review Board approval, children admitted with diabetic ketoacidosis (pH <7.3, HCO3 <15 mEq/L, glucose >300 mg/dL, and ketosis) underwent two serial paired contrast-enhanced (gadolinium) and diffusion magnetic resonance imaging scans. Change in whole brain and regional (frontal lobe, occipital lobe, and basal ganglia) mean transit time, apparent diffusion coefficient, and relative cerebral blood volume between the two time periods (12-24 hrs) and (36-72 hrs) after start of insulin treatment (time 0) were determined. Thirteen children (median age, 10.3 ± 1.1 yrs; 7 female) with diabetic ketoacidosis were examined. Overall, whole brain and regional mean transit time decreased from time 1 (first magnetic resonance imaging after time 0) to time 2 (second magnetic resonance imaging after time 0) by 51% ± 59% (p = .01), without differences between the brain regions examined. Whole brain apparent diffusion coefficient increased by 4.7% ± 3.4% (p = .001), without differences between the brain regions examined. There was no change in relative cerebral blood volume for the whole brain and for the three brain regions examined.

CONCLUSIONS

In this study, whole brain mean transit time decreased and apparent diffusion coefficient increased, suggesting a vasogenic process between the two study periods during diabetic ketoacidosis treatment.