141 research outputs found
Lactate Shuttles in Neuroenergetics—Homeostasis, Allostasis and Beyond
No full textUnderstanding brain energy metabolism—neuroenergetics—is becoming increasingly important as it can be identified repeatedly as the source of neurological perturbations. Within the scientific community we are seeing a shift in paradigms from the traditional neurocentric view to that of a more dynamic, integrated one where astrocytes are no longer considered as being just supportive, and activated microglia have a profound influence. Lactate is emerging as the “good guy,” contrasting its classical “bad guy” position in the now superseded medical literature. This review begins with the evolution of the concept of “lactate shuttles”; goes on to the recent shift in ideas regarding normal neuroenergetics (homeostasis)—specifically, the astrocyte–neuron lactate shuttle; and progresses to covering the metabolic implications whereby homeostasis is lost—a state of allostasis, and the function of microglia. The role of lactate, as a substrate and shuttle, is reviewed in light of allostatic stress, and beyond—in an acute state of allostatic stress in terms of physical brain trauma, and reflected upon with respect to persistent stress as allostatic overload—neurodegenerative diseases. Finally, the recently proposed astrocyte–microglia lactate shuttle is discussed in terms of chronic neuroinflammatory infectious diseases, using tuberculous meningitis as an example. The novelty extended by this review is that the directionality of lactate, as shuttles in the brain, in neuropathophysiological states is emerging as crucial in neuroenergetic
Cerebrospinal Fluid Amino Acid Profiling of Pediatric Cases with Tuberculous Meningitis
No full textBackground: In Africa, tuberculosis is generally regarded as persisting as one of the most devastating infectious diseases. The pediatric population is particularly vulnerable, with infection of the brain in the form of tuberculous meningitis (TBM) being the most severe manifestation. TBM is often difficult to diagnose in its early stages because of its non-specific clinical presentation. Of particular concern is that late diagnosis, and subsequent delayed treatment, leads to high risk of long-term neurological sequelae, and even death. Using advanced technology and scientific expertise, we are intent on further describing the biochemistry behind this devastating neuroinflammatory disease, with the goal of improving upon its early diagnosis.Method: We used the highly sensitive analytical platform of gas chromatography-mass spectrometry (GC-MS) to analyze amino acid profiles of cerebrospinal fluid (CSF) collected from a cohort of 33 South African pediatric TBM cases, compared to 34 controls.Results: Through the use of a stringent quality assurance procedure and various statistical techniques, we were able to confidently identify five amino acids as being significantly elevated in TBM cases, namely, alanine, asparagine, glycine, lysine, and proline. We found also in an earlier untargeted metabolomics investigation that alanine can be attributed to increased CSF lactate levels, and lysine as a marker of lipid peroxidation. Alanine, like glycine, is an inhibitory neurotransmitter in the brain. Asparagine, as with proline, is linked to the glutamate-glutamine cycle. Asparagine is associated with the removal of increased nitrites in the brain, whereas elevated proline coincides with the classic biochemical marker of increased CSF protein in TBM. All five discriminatory amino acids are linked to ammonia due to increased nitrites in TBM.Conclusion: A large amount of untapped biochemical information is present in CSF of TBM cases, of which amino acid profiling through GC-MS has potential in aiding in earlier diagnosis, and hence crucial earlier treatment
Miniaturized 1H-NMR method for analyzing limited-quantity samples applied to a mouse model of Leigh disease
No full textIntroduction
The analysis of limited-quantity samples remains a challenge associated with mouse models, especially for multi-platform metabolomics studies. Although inherently insensitive, the highly specific characteristics of nuclear magnetic resonance (NMR) spectroscopy make it an advantageous platform for global metabolite profiling, particularly in mitochondrial disease research.
Objectives
Show method equivalency between a well-established standard operating protocol (SOP) and our novel miniaturized 1H-NMR method.
Method
The miniaturized method was performed in a 2 mm NMR tube on a standard 500 MHz NMR spectrometer with a 5 mm triple-resonance inverse TXI probe at room temperature.
Results
Firstly, using synthetic urine spiked with low (50 µM), medium (250 µM) and high (500 µM) levels (n = 10) of nine standards, both the SOP and miniaturized method were shown to have acceptable precision (CV 0.95), except for taurine. Furthermore, statistical equivalence was shown using the two one-sided test. Secondly, pooled mouse quadriceps muscle extract was used to further confirm method equivalence (n = 3), as well as explore the analytical dynamics of this novel approach by analyzing more-concentrated versions of samples (up to 10× concentration) to expand identification of metabolites qualitatively, with quantitative linearity. Lastly, we demonstrate the new technique’s application in a pilot metabolomics study using minute soleus muscle tissue from a mouse model of Leigh syndrome using Ndufs4 KO mice.
Conclusion
We demonstrate method equivalency, supporting our novel miniaturized 1H-NMR method as a financially feasible alternative to cryoprobe technology—for limited-quantity biological samples in metabolomics studies that requires a volume one-tenth of the SO
Tuberculous meningitis in infants and children: Insights from nuclear magnetic resonance metabolomics
No full textTuberculous meningitis (TBM) is a prevalent form of central nervous system tuberculosis (CNS-TB) and the most severe common form of bacterial meningitis in infants and children below the age of 13 years, especially in the Western Cape Province of South Africa. Research to identify markers for timely and accurate diagnosis and treatment outcomes remains high on the agenda for TBM, in respect of which the field of metabolomics is as yet largely unexploited. However, the national Department of Science and Technology (DST) recently established several biotechnology platforms at South African institutions, including one for metabolomics hosted at North-West University. We introduce this national platform for nuclear magnetic resonance (NMR) metabolomics by providing an overview of work on TBM. We focus on selected collaborative multidisciplinary approaches to this disease and conclude with the outcomes of an untargeted NMR metabolomics study of cerebrospinal fluid from TBM patients. This study enabled the formulation of a conceptual shuttle representing the unique metabolic plasticity of CNS metabolism towards the energy requirements for the microglia-driven neuroinflammatory responses, of which TBM is one example. From insights generated by this explorative NMR metabolomics investigation, we propose directions for future in-depth research strategies to address this devastating disease. In our view, the timely initiative of the DST, the operational expertise in metabolomics now available and the potential for involving national and international networks in this field of research offers remarkable opportunities for the future of metabolomics in South Africa and for an ever greater understanding of disease mechanisms
(1)H NMR spectral identification of medication in cerebrospinal fluid of pediatric meningitis
No full textItem does not contain fulltex
Metabolomics reveals the depletion of intracellular metabolites in HepG2 cells after treatment with gold nanoparticles
No full textStudies on the safety of gold nanoparticles (GNPs) are plentiful due to their successful application in drug delivery and treatment of diseases in trials. Cytotoxicity caused by GNPs has been studied on the physiological and biochemical level; yet, the effect of GNPs (particularly gold nano-spheres) on the metabolome of living organisms remains understudied. In this investigation, metabolomics was used to comprehensively study the metabolic alterations in HepG2 cells caused by GNPs; and to investigate the role of representative GNP coatings. GNPs were synthesized, coated and characterized before use on HepG2 cell cultures. Cells were treated for 3 h with citrate-, poly-(sodiumsterene sulfunate)-, and poly-vinylpyrrolidone (PVP)-capped GNPs, respectively. The internalization of the different GNPs and their effect on mitochondrial respiration and the metabolome were studied. Results indicated that the PVP-capped GNPs internalized more and also caused a more observable effect on the metabolome. Conversely, it was the citrate- and poly-(sodiumsterene sulfunate) coated particles that influenced ATP production in addition to the metabolomic changes. A holistic depletion of intracellular metabolites was observed regardless of GNP coating, which hints to the binding of certain metabolites to the particle
A hypothetical astrocyte-microglia lactate shuttle derived from a 1H NMR metabolomics analysis of cerebrospinal fluid from a cohort of South African children with tuberculous meningitis
No full textTuberculosis meningitis (TBM) is the most
severe form of extra-pulmonary tuberculosis and is particularly
intense in small children; there is no universally
accepted algorithm for the diagnosis and substantiation of
TB infection, which can lead to delayed intervention, a
high risk factor for morbidity and mortality. In this study a
proton magnetic resonance (1H NMR)-based metabolomics
analysis and several chemometric methods were applied to
data generated from lumber cerebrospinal fluid (CSF)
samples from three experimental groups: (1) South African
infants and children with confirmed TBM, (2) non-meningitis
South African infants and children as controls, and
(3) neurological controls from the Netherlands. A total of
16 NMR-derived CSF metabolites were identified, which
clearly differentiated between the controls and TBM cases
under investigation. The defining metabolites were the
combination of perturbed glucose and highly elevated
lactate, common to some other neurological disorders. The
remaining 14 metabolites of the host’s response to TBM
were likewise mainly energy-associated indicators. We
subsequently generated a hypothesis expressed as an
‘‘astrocyte–microglia lactate shuttle’’ (AMLS) based on the
host’s response, which emerged from the NMR-metabolomics
information. Activation of microglia, as implied
by the AMLS hypothesis, does not, however, present a
uniform process and involves intricate interactions and
feedback loops between the microglia, astrocytes and
neurons that hamper attempts to construct basic and linear
cascades of cause and effect; TBM involves a complex
integration of the responses from the various cell types
present within the CNS, with microglia and the astrocytes
as main player
Facile immobilization of glucose oxidase onto gold nanostars with enhanced binding affinity and optimal function
No full textGold nanoparticles provide a user-friendly and efficient surface for immobilization of enzymes and proteins. In this paper, we present a novel approach for enzyme bioconjugation to gold nanostars (AuNSs). AuNSs were modified with l-cysteine (Cys) and covalently bound to N-hydroxysulfosuccinimide (sulfo-NHS) activated intermediate glucose oxidase (GOx) to fabricate a stable and sensitive AuNSs–Cys–GOx bioconjugate complex. Such a strategy has the potential for increased attachment affinity without protein adsorption onto the AuNSs surface. Good dispersity in buffer suspension was observed, as well as stability in high ionic environments. Using the AuNSs–Cys–GOx bioconjugates showed greater sensitivity in the measuring of low concentrations of glucose based on plasmonic and colorimetric detection. Such a novel approach for enzyme immobilization can lead to AuNSs–Cys–GOx bioconjugate complexes that can be used as catalytic nanodevices in nanobiosensors based on oxidases in biomedical application
Metabolic risks at birth of neonates exposed in utero to HIV-antiretroviral therapy relative to unexposed neonates: an NMR metabolomics study of cord blood
No full textIntroduction
Antiretroviral therapy (ART) for HIV-infected pregnant women is highly effective in preventing mother-to-child transmission (PMTCT) of the virus, but deleterious metabolic and mitochondrial observations in infants born to HIV-infected women treated with ART during pregnancy are periodically reported.
Objectives
This study addresses the concern of HIV-ART-induced metabolic perturbations through a metabolomics study of cord blood collected during transitional neonatal hypoglycaemia following birth from newborns either exposed or unexposed to fetal HIV-ART.
Methods
Proton magnetic resonance spectra from cord blood of 11 in utero HIV-ART-exposed and 14 unexposed newborns, as well as serum from 8 control infants, generated 114 spectral bins which were used to identify significant metabolites by means of univariate and multivariate statistical analyses.
Results
The metabolite profiles differed significantly between that from the unexposed newborns and that from infants—interpreted to characterize the state of transitional neonatal hypoglycaemia (low glucose and high lactic acid and ketone bodies). Quantitative analysis of potential ATP generation showed no meaningful difference in the global metabolite profiles of HIV-ART-exposed and unexposed neonates, but Volcano plot analysis, affirmed by odds ratios, indicated that exposure to HIV-ART affected the plasma 3-hydroxybutyric acid and hypoxanthine concentrations.
Conclusions
The metabolite profile for transitional neonatal hypoglycaemia indicated that HIV-ART did not compromise the exposed neonates to the energy stress of allostasis experienced at birth. Increased hypoxanthine and 3-hydroxybutyric acid indicates metabolic stress at birth in some of the newborns exposed to HIV-ART and raises a concern about unrecognized prolonged allostasis with potential neurological consequences for these infant
A diagnostic biomarker profile for fibromyalgia syndrome based on an NMR metabolomics study of selected patients and controls
No full textBackground:
Fibromyalgia syndrome (FMS) is a chronic pain syndrome. A plausible pathogenesis of the disease is
uncertain and the pursuit of measurable biomarkers for objective identification of affected individuals is a continuing
endeavour in FMS research. Our objective was to perform an explorative metabolomics study (1) to elucidate the
global urinary metabolite profile of patients suffering from FMS, and (2) to explore the potential of this metabolite
information to augment existing medical practice in diagnosing the disease.
Methods:
We selected patients with a medical history of persistent FMS (
n
= 18), who described their recent state of
the disease through the Fibromyalgia Impact Questionnaire (FIQR) and an in-house clinical questionnaire (IHCQ). Three
control groups were used: first-generation family members of the patients (
n
= 11), age-related individuals without any
indications of FMS or related conditions (
n
= 10), and healthy young (18
–
22 years) individuals (
n
=20).All
subjects were female and the biofluid under investigation was urine. Correlation analysis of the FIQR showed
the FMS patients represented a well-defined disease gro
up for this metabolomics study. Spectral analyses of
urine were conducted using a 500 MHz
1
H nuclear magnetic resonance (NMR) spectrometer; data processing
and analyses were performed using Matlab, R, SPSS and SAS software.
Results and discussion:
Unsupervised and supervised multivariate analyses distinguished all three control groups and
the FMS patients, and significant increases in metabolites related to the gut microbiome (hippuric, succinic and lactic
acids) were observed. We have developed an algorithm f
or the diagnosis of FMS consisting of three metabolites
—
succinic acid, taurine and creatine
—
that have a good level of diagnostic accurac
y (Receiver Operating Characteristic
(ROC) analysis
—
area under the curve 90%) and on the pain and fatigue symptoms for the selected FMS patient group.
Conclusion:
Our data and comparative analyses indicated an altere
d metabolic profile of patients with FMS, analytically
detectable within their urine. Validation studies may substantiate urinary metabolites to supplement information from
medical assessment, tender-point measurements and FIQR questionnaires for an improved objective diagnosis of FM
- …
