Lipoprotein markers associated with disability from multiple sclerosis.

Altered lipid metabolism is a feature of chronic inflammatory disorders. Increased plasma lipids and lipoproteins have been associated with multiple sclerosis (MS) disease activity. Our objective was to characterise the specific lipids and associated plasma lipoproteins increased in MS and to test for an association with disability. Plasma samples were collected from 27 RRMS patients (median EDSS, 1.5, range 1-7) and 31 healthy controls. Concentrations of lipids within lipoprotein sub-classes were determined from NMR spectra. Plasma cytokines were measured using the MesoScale Discovery V-PLEX kit. Associations were tested using multivariate linear regression. Differences between the patient and volunteer groups were found for lipids within VLDL and HDL lipoprotein sub-fractions (p < 0.05). Multivariate regression demonstrated a high correlation between lipids within VLDL sub-classes and the Expanded Disability Status Scale (EDSS) (p < 0.05). An optimal model for EDSS included free cholesterol carried by VLDL-2, gender and age (R2 = 0.38, p < 0.05). Free cholesterol carried by VLDL-2 was highly correlated with plasma cytokines CCL-17 and IL-7 (R2 = 0.78, p < 0.0001). These results highlight relationships between disability, inflammatory responses and systemic lipid metabolism in RRMS. Altered lipid metabolism with systemic inflammation may contribute to immune activation.

Abnormal frontostriatal connectivity in adolescent-onset schizophrenia and its relationship to cognitive functioning.

BACKGROUND: Adolescent-onset schizophrenia (AOS) is associated with cognitive impairment and poor clinical outcome. Cognitive dysfunction is hypothesised, in part, to reflect functional dysconnectivity between the frontal cortex and the striatum, although structural abnormalities consistent with this hypothesis have not yet been demonstrated in adolescence. OBJECTIVE: To characterise frontostriatal white matter (WM) tracts in relation to cognition in AOS. DESIGN: A MRI volumetric and diffusion tensor imaging study. PARTICIPANTS: Thirty-seven AOS subjects and 24 age and sex-matched healthy subjects. OUTCOME MEASURES: Using probabilistic tractography, cortical regions with the highest connection probability for each striatal voxel were determined, and correlated with IQ and specific cognitive functions after co-varying for age and sex. Fractional anisotropy (FA) from individual tracts was a secondary measure. RESULTS: Bayesian Structural Equation modeling of FA from 12 frontostriatal tracts showed processing speed to be an intermediary variable for cognition. AOS patients demonstrated generalised cognitive impairment with specific deficits in verbal learning and memory and in processing speed after correction for IQ. Dorsolateral prefrontal cortex connectivity with the striatum correlated positively with these measures and with IQ. DTI voxel-wise comparisons showed lower connectivity between striatum and the motor and lateral orbitofrontal cortices bilaterally, the left amygdalohippocampal complex, right anterior cingulate cortex, left medial orbitofrontal cortex and right dorsolateral prefrontal cortex. CONCLUSIONS: Frontostriatal dysconnectivity in large WM tracts that can explain core cognitive deficits are evident during adolescence. Processing speed, which is affected by alterations in WM connectivity, appears an intermediary variable in the cognitive deficits seen in schizophrenia.

Age independently affects myelin integrity as detected by magnetization transfer magnetic resonance imaging in multiple sclerosis.

BACKGROUND: Multiple sclerosis (MS) is a heterogeneous disorder with a progressive course that is difficult to predict on a case-by-case basis. Natural history studies of MS have demonstrated that age influences clinical progression independent of disease duration. OBJECTIVE: To determine whether age would be associated with greater CNS injury as detected by magnetization transfer MRI. MATERIALS AND METHODS: Forty MS patients were recruited from out-patient clinics into two groups stratified by age but with similar clinical disease duration as well as thirteen controls age-matched to the older MS group. Images were segmented by automated programs and blinded readers into normal appearing white matter (NAWM), normal appearing gray matter (NAGM), and white matter lesions (WMLs) and gray matter lesions (GMLs) in the MS groups. WML and GML were delineated on T2-weighted 3D fluid-attenuated inversion recovery (FLAIR) and T1 weighted MRI volumes. Mean magnetization transfer ratio (MTR), region volume, as well as MTR histogram skew and kurtosis were calculated for each region. RESULTS: All MTR measures in NAGM and MTR histogram metrics in NAWM differed between MS subjects and controls, as expected and previously reported by several studies, but not between MS groups. However, MTR measures in the WML did significantly differ between the MS groups, in spite of no significant differences in lesion counts and volumes. CONCLUSIONS: Despite matching for clinical disease duration and recording no significant WML volume difference, we demonstrated strong MTR differences in WMLs between younger and older MS patients. These data suggest that aging-related processes modify the tissue response to inflammatory injury and its clinical outcome correlates in MS.

Age-related adaptations of brain function during a memory task are also present at rest.

Several studies have demonstrated age-related regional differences in the magnitude of the BOLD signal using task-based fMRI. It has been suggested that functional changes reflect either compensatory or de-differentiation mechanisms, both of which assume response to a specific stimulus. Here, we have tested whether ageing affects both task-based and resting brain function, and the extent to which functional changes are mediated by reductions in grey matter (GM) volume. Two groups, of 22 healthy younger and 22 older volunteers, underwent an imaging protocol involving structural and functional MRI, both during a memory task and at rest. The two groups had similar socio-demographical characteristics and cognitive performance. Image analysis revealed both structural and functional differences. Increased BOLD signal in older relative to younger volunteers was mainly observed in the frontal lobes, both during the task and at rest. Functional changes in the frontal lobes were largely located in brain regions spared from GM loss, and adding GM covariates to the fMRI analysis did not significantly alter the group differences. Our results are consistent with the suggestion that, during normal ageing, the brain responds to neuronal loss by fine-tuning connections between spared neurons. Longitudinal studies will be necessary to fully test this hypothesis.

Reproducibility of sodium MRI measures of articular cartilage of the knee in osteoarthritis.

OBJECTIVE: To determine the stability and reproducibility of the sodium magnetic resonance imaging (MRI) signal measured in the articular cartilage of the knee in both healthy volunteers and osteoarthritis (OA) patients. DESIGN: This was a prospective Research Ethics Committee approved study that acquired sodium and proton MRI data from 15 subjects with OA (three males, age 64 ± 10) and five healthy controls age and sex matched over the group. Each subject underwent standing planar radiographs of their knees for radiological scoring as well as symptomatological assessment questionnaires. In two MRI sessions on the same day, high resolution double-echo steady state (DESS) and 3D short echo time sodium MRI images of the most diseased knee were acquired and co-registered in each session. A blinded reader (LT) manually delineated the articular cartilage into four discrete regions, and two combined regions, on the DESS images. These regions were applied to the sodium images, and a median sodium signal from each reported. Within-subject and between-subject coefficients of variation were estimated and intraclass correlation coefficients for the healthy control group, OA subject group, and all pooled subjects group were calculated. RESULTS: Within-subject variability of sodium MRI at 3T was 3.2% overall, and 2.0% in healthy age-matched volunteers compared to a reproducibility of 3.6% on OA subjects. CONCLUSIONS: The reproducibility of sodium MRI was similar in both healthy controls and OA subjects. Researchers piloting techniques in healthy controls thus may expect a similar reproducibility in a controlled trial involving subjects with American College of Rheumatology (ACR)-defined OA of the knee.

Pragmatic study of orlistat 60 mg on abdominal obesity.

BACKGROUND/OBJECTIVES: It is well established that combining a reduced calorie, low-fat diet with the lipase inhibitor orlistat results in significantly greater weight loss than placebo plus diet. This weight loss is accompanied by changes in adipose tissue (AT) distribution. As 60 mg orlistat is now available as an over-the-counter medication, the primary objective of this study was to determine whether 60 mg orlistat is effective as a weight loss option in a free-living community population with minimal professional input. METHODS: AT and ectopic lipid content were measured using magnetic resonance imaging and (1)H MR spectroscopy, respectively, in 27 subjects following 3 months treatment with orlistat 60 mg and a reduced calorie, low-fat diet. RESULTS: Significant reductions in intra-abdominal AT (-10.6%, P=0.023), subcutaneous (-11.7% P<0.0001) and pericardial fat (-9.8%, P=0.034) volumes and intrahepatocellular lipids (-43.3%, P=0.0003) were observed. These changes in body fat content and distribution were accompanied by improvements in plasma lipids and decreases in blood pressure and heart rate. CONCLUSION: These findings suggest that over-the-counter 60 mg orlistat, in combination with the type of advice a subject could expect to be given when obtaining 60 mg orlistat in a community setting, does indeed result in potentially clinically beneficial changes in body composition and risk factors for metabolic diseases.

Pharmacological differentiation of opioid receptor antagonists by molecular and functional imaging of target occupancy and food reward-related brain activation in humans.

Opioid neurotransmission has a key role in mediating reward-related behaviours. Opioid receptor (OR) antagonists, such as naltrexone (NTX), can attenuate the behaviour-reinforcing effects of primary (food) and secondary rewards. GSK1521498 is a novel OR ligand, which behaves as an inverse agonist at the µ-OR sub-type. In a sample of healthy volunteers, we used [(11)C]-carfentanil positron emission tomography to measure the OR occupancy and functional magnetic resonance imaging (fMRI) to measure activation of brain reward centres by palatable food stimuli before and after single oral doses of GSK1521498 (range, 0.4-100 mg) or NTX (range, 2-50 mg). GSK1521498 had high affinity for human brain ORs (GSK1521498 effective concentration 50 = 7.10 ng ml(-1)) and there was a direct relationship between receptor occupancy (RO) and plasma concentrations of GSK1521498. However, for both NTX and its principal active metabolite in humans, 6-ß-NTX, this relationship was indirect. GSK1521498, but not NTX, significantly attenuated the fMRI activation of the amygdala by a palatable food stimulus. We thus have shown how the pharmacological properties of OR antagonists can be characterised directly in humans by a novel integration of molecular and functional neuroimaging techniques. GSK1521498 was differentiated from NTX in terms of its pharmacokinetics, target affinity, plasma concentration-RO relationships and pharmacodynamic effects on food reward processing in the brain. Pharmacological differentiation of these molecules suggests that they may have different therapeutic profiles for treatment of overeating and other disorders of compulsive consumption.

Greater white and grey matter changes associated with early cannabis use in adolescent-onset schizophrenia (AOS).

BACKGROUND: Cannabis use is associated with a higher risk of schizophrenia, however, its specific long-term effect on the structure of the brain of adolescent-onset schizophrenic patients remains unclear. AIMS: To study cognitive and structural (grey and white matter) changes in patients with adolescent-onset schizophrenia (AOS) with early cannabis use (CAN+ve) (more than 3 times/week for at least 6 months) and without cannabis use (CAN-ve) versus controls. METHOD: An optimised voxel-based morphometry (VBM) and diffusion tensor imaging (DTI) MRI study of 32 adolescents with DSM IV schizophrenia-16 CAN+ve and 16 CAN-ve, and 28 healthy adolescents. RESULTS: Compared to CAN-ve subjects, CAN+ve subjects showed GM density loss in temporal fusiform gyrus, parahippocampal gyrus, ventral striatum, right middle temporal gyrus, insular cortex, precuneus, right paracingulate gyrus, dorsolateral prefrontal cortex, left postcentral gyrus, lateral occipital cortex and cerebellum. Similar group comparison showed decreased fractional anisotropy (FA) in particular in brain stem, internal capsule, corona radiata, superior and inferior longitudinal fasciculus in CAN+ve patients. No cognitive differences were apparent between CAN+ve and CAN-ve subjects, and both were impaired relative to controls. CONCLUSION: Cannabis use in early adolescence increases WM and GM deficits in AOS, but does not appear to increase the cognitive deficit associated with this illness.

Polarity and timing-dependent effects of transcranial direct current stimulation in explicit motor learning.

Transcranial direct current stimulation (tDCS) is attracting increasing interest as a therapeutic tool for neurorehabilitation, particularly after stroke, because of its potential to modulate local excitability and therefore promote functional plasticity. Previous studies suggest that timing is important in determining the behavioural effects of brain stimulation. Regulatory metaplastic mechanisms exist to modulate the effects of a stimulation intervention in a manner dependent on prior cortical excitability, thereby preventing destabilization of existing cortical networks. The importance of such timing dependence has not yet been fully explored for tDCS. Here, we describe the results of a series of behavioural experiments in healthy controls to determine the importance of the relative timing of tDCS for motor performance. Application of tDCS during an explicit sequence-learning task led to modulation of behaviour in a polarity specific manner: relative to sham stimulation, anodal tDCS was associated with faster learning and cathodal tDCS with slower learning. Application of tDCS prior to performance of the sequence-learning task led to slower learning after both anodal and cathodal tDCS. By contrast, regardless of the polarity of stimulation, tDCS had no significant effect on performance of a simple reaction time task. These results are consistent with the idea that anodal tDCS interacts with subsequent motor learning in a metaplastic manner and suggest that anodal stimulation modulates cortical excitability in a manner similar to motor learning.

A knowledge-driven interaction analysis reveals potential neurodegenerative mechanism of multiple sclerosis susceptibility.

Gene-gene interactions are proposed as an important component of the genetic architecture of complex diseases, and are just beginning to be evaluated in the context of genome-wide association studies (GWAS). In addition to detecting epistasis, a benefit to interaction analysis is that it also increases power to detect weak main effects. We conducted a knowledge-driven interaction analysis of a GWAS of 931 multiple sclerosis (MS) trios to discover gene-gene interactions within established biological contexts. We identify heterogeneous signals, including a gene-gene interaction between CHRM3 (muscarinic cholinergic receptor 3) and MYLK (myosin light-chain kinase) (joint P=0.0002), an interaction between two phospholipase C-ß isoforms, PLCß1 and PLCß4 (joint P=0.0098), and a modest interaction between ACTN1 (actinin alpha 1) and MYH9 (myosin heavy chain 9) (joint P=0.0326), all localized to calcium-signaled cytoskeletal regulation. Furthermore, we discover a main effect (joint P=5.2E-5) previously unidentified by single-locus analysis within another related gene, SCIN (scinderin), a calcium-binding cytoskeleton regulatory protein. This work illustrates that knowledge-driven interaction analysis of GWAS data is a feasible approach to identify new genetic effects. The results of this study are among the first gene-gene interactions and non-immune susceptibility loci for MS. Further, the implicated genes cluster within inter-related biological mechanisms that suggest a neurodegenerative component to MS.

Differential effects of the APOE genotype on brain function across the lifespan.

Increasing age and carrying an APOE ε4 allele are well established risk factors for Alzheimer's disease (AD). The earlier age of onset of AD observed in ε4-carriers may reflect an accelerated aging process. We recently reported that APOE genotype modulates brain function decades before the appearance of any cognitive or clinical symptoms. Here we test the hypothesis that APOE influences brain aging by comparing healthy ε4-carriers and non-carriers, using the same imaging protocol in distinct groups of younger and older healthy volunteers. A cross-sectional factorial design was used to examine the effects of age and APOE genotype, and their interaction, on fMRI activation during an encoding memory task. The younger (N=36; age range 20-35; 18 ε4-carriers) and older (35 middle-age/elderly; age range 50-78 years; 15 ε4-carriers) healthy volunteers taking part in the study were cognitively normal. We found a significant interaction between age and ε4-status in the hippocampi, frontal pole, subcortical nuclei, middle temporal gyri and cerebellum, such that aging was associated with decreased activity in e4-carriers and increased activity in non-carriers. Reduced cerebral blood flow was found in the older ε4-carriers relative to older non-carriers despite preserved grey matter volume. Overactivity of brain function in young ε4-carriers is disproportionately reduced with advancing age even before the onset of measurable memory impairment. The APOE genotype determines age-related changes in brain function that may reflect the increased vulnerability of ε4-carriers to late-life pathology or cognitive decline.

Network analysis detects changes in the contralesional hemisphere following stroke.

Changes in brain structure occur in remote regions following focal damage such as stroke. Such changes could disrupt processing of information across widely distributed brain networks. We used diffusion MRI tractography to assess connectivity between brain regions in 9 chronic stroke patients and 18 age-matched controls. We applied complex network analysis to calculate 'communicability', a measure of the ease with which information can travel across a network. Clustering individuals based on communicability separated patient and control groups, not only in the lesioned hemisphere but also in the contralesional hemisphere, despite the absence of gross structural pathology in the latter. In our highly selected patient group, lesions were localised to the left basal ganglia/internal capsule. We found reduced communicability in patients in regions surrounding the lesions in the affected hemisphere. In addition, communicability was reduced in homologous locations in the contralesional hemisphere for a subset of these regions. We interpret this as evidence for secondary degeneration of fibre pathways which occurs in remote regions interconnected, directly or indirectly, with the area of primary damage. We also identified regions with increased communicability in patients that could represent adaptive, plastic changes post-stroke. Network analysis provides new and powerful tools for understanding subtle changes in interactions across widely distributed brain networks following stroke.

Regional differences in neurovascular coupling in rat brain as determined by fMRI and electrophysiology.

Increases in neuronal activity induce local increases in cerebral perfusion. However, our understanding of the processes underlying this neurovascular coupling remains incomplete and, particularly, how these vary across the brain. Recent work supports an important role for astrocytes in neurovascular coupling, in large part via activation of their metabotropic glutamate receptors (mGluR). Here, using a combination of functional magnetic resonance imaging (fMRI) and electrophysiology we demonstrate regional heterogeneity in the mechanisms underlying neurovascular coupling. Direct electrical stimulation of the rat hindpaw sensorimotor cortex induces blood oxygenation level dependent (BOLD) and cerebral blood volume (CBV) fMRI responses in several anatomically distinct cortical and subcortical structures. Following intraperitoneal administration of the type 5 mGluR antagonist, MPEP, both BOLD and CBV responses to cortical stimulation were significantly reduced, whilst the local field potential (LFP) responses remained largely constant. Spatially, the degree of reduction in fMRI responses varied between cortical and subcortical regions (primary cortex approximately 18% vs. striatum approximately 66%), and also between primary and secondary cortical areas ( approximately 18% vs. approximately 55%). Similarly, greater decreases in response amplitude were seen in the contralateral secondary cortex ( approximately 91%) and ipsilateral striatum (approximately 70%), compared to the primary cortex (approximately 44%). Following MPEP, a negative component of the BOLD and CBV responses became more apparent, suggesting that different mechanisms mediate vasodilatory and vasoconstrictory responses. Interestingly, under baseline conditions the quantitative relationship between fMRI and LFP responses in cortical and subcortical regions was markedly different. Our data indicate that coupling between neuronal and fMRI responses is neither empirically nor mechanistically consistent across the brain.

Focal and diffuse cortical degenerative changes in a marmoset model of multiple sclerosis.

BACKGROUND: Degenerative features, such as neuronal, glial, synaptic and axonal loss, have been identified in neocortical and other grey matter structures in patients with multiple sclerosis, but mechanisms for neurodegeneration are unclear. Cortical demyelinating lesions are a potential cause of this degeneration, but the pathological and clinical significance of these lesions is uncertain as they remain difficult to identify and study in vivo. In this study we aimed to describe and quantify cellular and subcellular pathology in the cortex of myelin oligodendrocyte glycoprotein-induced marmoset experimental autoimmune encephalomyelitis using quantitative immunohistochemical methods. RESULTS: We found evidence of diffuse axonal damage occurring throughout cortical grey matter with evidence for synaptic loss and gliosis and a 13.6% decrease in neuronal size and occurring in deep cortical layers. Evidence of additional axonal damage and a 29.6-36.5% loss of oligodendrocytes was found in demyelinated cortical lesions. Leucocortical lesions also showed neuronal loss of 22.2% and a 15.8% increase in oligodendrocyte size. CONCLUSIONS: The marmoset experimental autoimmune encephalomyelitis model, therefore, shows both focal and generalized neurodegeneration. The generalized changes cannot be directly related to focal lesions, suggesting that they are either a consequence of diffusible inflammatory factors or secondary to remote lesions acting through trans-synaptic or retrograde degeneration.

Longitudinal changes in grey and white matter during adolescence.

Brain development continues actively during adolescence. Previous MRI studies have shown complex patterns of apparent loss of grey matter (GM) volume and increases in white matter (WM) volume and fractional anisotropy (FA), an index of WM microstructure. In this longitudinal study (mean follow-up=2.5+/-0.5 years) of 24 adolescents, we used a voxel-based morphometry (VBM)-style analysis with conventional T1-weighted images to test for age-related changes in GM and WM volumes. We also performed tract-based spatial statistics (TBSS) analysis of diffusion tensor imaging (DTI) data to test for age-related WM changes across the whole brain. Probabilistic tractography was used to carry out quantitative comparisons across subjects in measures of WM microstructure in two fiber tracts important for supporting speech and motor functions (arcuate fasciculus [AF] and corticospinal tract [CST]). The whole-brain analyses identified age-related increases in WM volume and FA bilaterally in many fiber tracts, including AF and many parts of the CST. FA changes were mainly driven by increases in parallel diffusivity, probably reflecting increases in the diameter of the axons forming the fiber tracts. FA values of both left and right AF (but not of the CST) were significantly higher at the end of the follow-up than at baseline. Over the same period, widespread reductions in the cortical GM volume were found. These findings provide imaging-based anatomical data suggesting that brain maturation in adolescence is associated with structural changes enhancing long-distance connectivities in different WM tracts, specifically in the AF and CST, at the same time that cortical GM exhibits synaptic "pruning".

Modulation of movement-associated cortical activation by transcranial direct current stimulation.

Transcranial direct current stimulation (tDCS) is currently attracting increasing interest as a tool for neurorehabilitation. However, local and distant effects of tDCS on motor-related cortical activation patterns remain poorly defined, limiting the rationale for its use. Here we describe the results of a functional magnetic resonance imaging (MRI) experiment designed to characterize local and distant effects on cortical motor activity following excitatory anodal stimulation and inhibitory cathodal stimulation. Fifteen right-handed subjects performed a visually cued serial reaction time task with their right hand in a 3-T MRI scanner both before and after 10 min of 1-mA tDCS applied to the left primary motor cortex (M1). Relative to sham stimulation, anodal tDCS led to short-lived activation increases in the M1 and the supplementary motor area (SMA) within the stimulated hemisphere. The increase in activation in the SMA with anodal stimulation was found also when directly comparing anodal with cathodal stimulation. Relative to sham stimulation, cathodal tDCS led to an increase in activation in the contralateral M1 and dorsal premotor cortex (PMd), as well as an increase in functional connectivity between these areas and the stimulated left M1. These increases were also found when directly comparing cathodal with anodal stimulation. Significant within-session linear decreases in activation occurred in all scan sessions. The after-effects of anodal tDCS arose primarily from a change in the slope of these decreases. In addition, following sham stimulation compared with baseline, a between-session decrease in task-related activity was found. The effects of cathodal tDCS arose primarily from a reduction of this normal decrease.

Neurochemical effects of theta burst stimulation as assessed by magnetic resonance spectroscopy.

Continuous theta burst stimulation (cTBS) is a novel transcranial stimulation technique that causes significant inhibition of synaptic transmission for

Short-term adaptation to a simple motor task: a physiological process preserved in multiple sclerosis.

Short-term adaptation indicates the attenuation of the functional MRI (fMRI) response during repeated task execution. It is considered to be a physiological process, but it is unknown whether short-term adaptation changes significantly in patients with brain disorders, such as multiple sclerosis (MS). In order to investigate short-term adaptation during a repeated right-hand tapping task in both controls and in patients with MS, we analyzed the fMRI data collected in a large cohort of controls and MS patients who were recruited into a multi-centre European fMRI study. Four fMRI runs were acquired for each of the 55 controls and 56 MS patients at baseline and 33 controls and 26 MS patients at 1-year follow-up. The externally cued (1 Hz) right hand tapping movement was limited to 3 cm amplitude by using at all sites (7 at baseline and 6 at follow-up) identically manufactured wooden frames. No significant differences in cerebral activation were found between sites. Furthermore, our results showed linear response adaptation (i.e. reduced activation) from run 1 to run 4 (over a 25 minute period) in the primary motor area (contralateral more than ipsilateral), in the supplementary motor area and in the primary sensory cortex, sensory-motor cortex and cerebellum, bilaterally. This linear activation decay was the same in both control and patient groups, did not change between baseline and 1-year follow-up and was not influenced by the modest disease progression observed over 1 year. These findings confirm that the short-term adaptation to a simple motor task is a physiological process which is preserved in MS.