Age-related metabolic changes in the upper brainstem tegmentum by MR spectroscopy

Dopaminergic neuron metabolism: relevance for understanding Parkinson's disease

BACKGROUND

Dopaminergic neurons from the substantia nigra pars compacta (SNc) have a higher susceptibility to aging-related degeneration, compared to midbrain dopaminergic cells present in the ventral tegmental area (VTA); the death of dopamine neurons in the SNc results in Parkinson´s disease (PD). In addition to increased loss by aging, dopaminergic neurons from the SNc are more prone to cell death when exposed to genetic or environmental factors, that either interfere with mitochondrial function, or cause an increase of oxidative stress. The oxidation of dopamine is a contributing source of reactive oxygen species (ROS), but this production is not enough to explain the differences in susceptibility to degeneration between SNc and VTA neurons.

AIM OF REVIEW

In this review we aim to highlight the intrinsic differences between SNc and VTA dopamine neurons, in terms of gene expression, calcium oscillations, bioenergetics, and ROS responses. Also, to describe the changes in the pentose phosphate pathway and the induction of apoptosis in SNc neurons during aging, as related to the development of PD.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Recent work showed that neurons from the SNc possess intrinsic characteristics that result in metabolic differences, related to their intricate morphology, that render them more susceptible to degeneration. In particular, these neurons have an elevated basal energy metabolism, that is required to fulfill the demands of the constant firing of action potentials, but at the same time, is associated to higher ROS production, compared to VTA cells. Finally, we discuss how mutations related to PD affect metabolic pathways, and the related mechanisms, as revealed by metabolomics.

Cactus flour (Opuntia ficus-indica) reduces brain lipid peroxidation and anxious-like behavior in old Wistar rats

The aim of this research was to evaluate the effect of cactus flour on the anxious-like behavior and cerebral lipid peroxidation in elderly rats (18 months of life). The rats were divided into four groups (n=10). control (CG) - received the AIN-93M ration. P5%. P10% and P15%. treated with the AIN-93M ration with the addition of 5, 10 and 15% of cactus flour respectively. In the elevated plus maze (EPM) groups P5%, P10% and P15% remained longer in the open arms. P15% remained longer in this region and less time in the closed arms. No significant differences were observed between the groups regarding the time the rats remained in the center of the apparatus. P5%. P10% and P15% performed a greater number of head dips. Regarding the open field animals P5%. P10% and P15% performed a greater number of rearing and stayed for a longer time in the center of the apparatus with P15% being the group that remained for the longest time when compared to the other groups. There was no difference in locomotion and grooming. As for the light-dark box. P15% spent more time in the light part. less time in the dark part and performed a smaller number of transitions. P5%. P10% and P15% had the lowest concentrations of brain lipid peroxidation. Our data demonstrated that consumption of cactus flour by rats promoted anxiolytic effects and minimized brain lipid peroxidation in aging. Given the above, it can be deduced that cactus pear can contribute to the prevention and/or treatment of anxiety in the aging phase.Due to its concentrations of mono and polyunsaturated fatty acids, soluble fibers and antioxidant contents such as vitamin E and selenium.

Broccoli Sprouts Promote Sex-Dependent Cardiometabolic Health and Longevity in Long-Evans Rats

Antioxidants and anti-inflammatory compounds are potential candidates to prevent age-related chronic diseases. Broccoli sprouts (BrSp) are a rich source of sulforaphane-a bioactive metabolite known for its antioxidant and anti-inflammatory properties. We tested the effect of chronic BrSp feeding on age-related decline in cardiometabolic health and lifespan in rats. Male and female Long-Evans rats were fed a control diet with or without dried BrSp (300 mg/kg body weight, 3 times per week) from 4 months of age until death. Body weight, body composition, blood pressure, heart function, and glucose and insulin tolerance were measured at 10, 16, 20, and 22 months of age. Behavioral traits were also examined at 18 months of age. BrSp feeding prolonged life span in females, whereas in males the positive effects on longevity were more pronounced in a subgroup of males (last 25% of survivors). Despite having modest effects on behavior, BrSp profoundly affected cardiometabolic parameters in a sex-dependent manner. BrSp-fed females had a lower body weight and visceral adiposity while BrSp-fed males exhibited improved glucose tolerance and reduced blood pressure when compared to their control counterparts. These findings highlight the sex-dependent benefits of BrSp on improving longevity and delaying cardiometabolic decline associated with aging in rats.

Whole Body Vibration Improves Spatial Memory, Anxiety-Like Behavior, and Motor Performance in Aged Male and Female Rats

Aging is a progressive process leading to functional decline in many domains. Recent studies have shown that physical exercise (PE) has a positive influence on the progression of age-related functional decline, including motor and brain functions. Whole body vibration (WBV) is a form of passive stimulation by mechanical vibration platforms, which offers an alternative for PE interventions, especially for aged individuals. WBV has been demonstrated to mimic the beneficial effects of PE on the musculoskeletal system, as well on the central nervous system. However, preclinical data with aged rodents are very limited. Hence, the purpose of this experiment was to investigate the effects of a 5-week WBV intervention with an aged animal model on memory functions, anxiety-related behavior, and motor performance. The 18-month old male (N = 14) and female (N = 14) Wistar rats were divided into two groups, namely, vibration and pseudo-vibration. Animals underwent a 5-week WBV intervention protocol with low intensity (frequency of 30 Hz and amplitude of 50–200 μm) stimulation. After 5 weeks, the following cognitive and motor tests were administered: open-field, novel and spatial object recognition, grip-hanging, and balance-beam. WBV-treated rats showed a decrease in their anxiety level in the open field test compared with those in the pseudo-treated controls. In addition, WBV-treated male animals showed significantly increased rearing in the open-field test compared to their pseudo controls. Spatial memory was significantly improved by WBV treatment, whereas WBV had no effect on object memory. Regarding motor performance, both grip strength and motor coordination were improved by WBV treatment. Our results indicate that WBV seems to have comparable beneficial effects on age-related emotional, cognitive, and motor decline as what has been reported for active PE. No striking differences were found between the sexes. As such, these findings further support the idea that WBV could be considered as a useful alternative for PE in case active PE cannot be performed due to physical or mental issues.

Current Methods of Magnetic Resonance for Noninvasive Assessment of Molecular Aspects of Pathoetiology in Multiple Sclerosis

Multiple sclerosis (MS) is an autoimmune disease with expanding axonal and neuronal degeneration in the central nervous system leading to motoric dysfunctions, psychical disability, and cognitive impairment during MS progression. The exact cascade of pathological processes (inflammation, demyelination, excitotoxicity, diffuse neuro-axonal degeneration, oxidative and metabolic stress, etc.) causing MS onset is still not fully understood, although several accompanying biomarkers are particularly suitable for the detection of early subclinical changes. Magnetic resonance (MR) methods are generally considered to be the most sensitive diagnostic tools. Their advantages include their noninvasive nature and their ability to image tissue in vivo. In particular, MR spectroscopy (proton 1H and phosphorus 31P MRS) is a powerful analytical tool for the detection and analysis of biomedically relevant metabolites, amino acids, and bioelements, and thus for providing information about neuro-axonal degradation, demyelination, reactive gliosis, mitochondrial and neurotransmitter failure, cellular energetic and membrane alternation, and the imbalance of magnesium homeostasis in specific tissues. Furthermore, the MR relaxometry-based detection of accumulated biogenic iron in the brain tissue is useful in disease evaluation. The early description and understanding of the developing pathological process might be critical for establishing clinically effective MS-modifying therapies.

From fetus to older age: A review of brain metabolic changes across the lifespan

INTRODUCTION

The knowledge of metabolic changes across the lifespan is poorly understood. Thus we systematically reviewed the available literature to determine the changes in brain biochemical composition from fetus to older age and tried to explain them in the context of neural, cognitive, and behavioural changes.

METHODS

The search identified 1262 articles regarding proton magnetic resonance spectroscopy (1H MRS) examinations through December 2017. The following data was extracted: age range of the subjects, number of subjects studied, brain regions studied, MRS sequence used, echo time, MR system, method of statistical analysis, metabolites analyzed, significant differences in metabolites concentrations with age as well as the way of presentation of the results.

RESULTS

82 studies that described brain metabolite changes with age were identified. Reports on metabolic changes related to healthy aging were analyzed and discussed among six basic age groups: fetuses, infants, children, adolescents, adults, and the elderly as well as between groups and during the whole lifetime.

DISCUSSION

The results presented in the reviewed papers provide evidence that normal aging is associated with a number of metabolic changes characteristic for every period of life. Therefore, it can be concluded that the age matching is essential for comparative studies of disease states using 1H MRS.

Detection of Normal Aging Effects on Human Brain Metabolite Concentrations and Microstructure with Whole-Brain MR Spectroscopic Imaging and Quantitative MR Imaging

BACKGROUND AND PURPOSE

Knowledge of age-related physiological changes in the human brain is a prerequisite to identify neurodegenerative diseases. Therefore, in this study whole-brain (1)H-MRS was used in combination with quantitative MR imaging to study the effects of normal aging on healthy human brain metabolites and microstructure.

MATERIALS AND METHODS

Sixty healthy volunteers, 21-70 years of age, were studied. Brain maps of the metabolites NAA, creatine and phosphocreatine, and Cho and the tissue irreversible and reversible transverse relaxation times T2 and T2' were derived from the datasets. The relative metabolite concentrations and the values of relaxation times were measured with ROIs placed within the frontal and parietal WM, centrum semiovale, splenium of the corpus callosum, hand motor area, occipital GM, putamen, thalamus, pons ventral/dorsal, and cerebellar white matter and posterior lobe. Linear regression analysis and Pearson correlation tests were used to analyze the data.

RESULTS

Aging resulted in decreased NAA concentrations in the occipital GM, putamen, splenium of the corpus callosum, and pons ventral and decreased creatine and phosphocreatine concentrations in the pons dorsal and putamen. Cho concentrations did not change significantly in selected brain regions. T2 increased in the cerebellar white matter and decreased in the splenium of the corpus callosum with aging, while the T2' decreased in the occipital GM, hand motor area, and putamen, and increased in the splenium of the corpus callosum. Correlations were found between NAA concentrations and T2' in the occipital GM and putamen and between creatine and phosphocreatine concentrations and T2' in the putamen.

CONCLUSIONS

The effects of normal aging on brain metabolites and microstructure are region-dependent. Correlations between both processes are evident in the gray matter. The obtained data could be used as references for future studies on patients.

Evaluation of normal changes in pons metabolites due to aging using turbo spectroscopic imaging

BACKGROUND AND PURPOSE

To date, MRS study of both normal and pathologic brains have focused mainly on the supratentorial regions; few studies have investigated the infratentorial regions. However, the pons, an important structure of the brain, is associated with many neurodegenerative diseases and is often damaged by brain trauma. For MRS study of pontine disease, one must obtain MRS reference data on normal metabolite levels in the pons, including data on how these levels vary with age. The aim of this study was to analyze normal, age-related, metabolic changes in the pons by using turbo spectroscopic imaging.

MATERIALS AND METHODS

Seventy-eight healthy subjects with ages ranging from 5 days to 78 years were included in this study. NAA/Cr, Cho/Cr, and Cho/NAA ratios were measured by using turbo spectroscopic imaging. The 78 cases were divided into 4 groups by age: 0-5, 6-20, 21-50, and older than 50 years. The metabolite levels were compared with observed age-related changes among the groups.

RESULTS

The normal mean pontine metabolite ratios obtained for the combined age groups were NAA/Cr, 2.44 ± 0.45 (mean); Cho/Cr, 1.93 ± 0.25; and Cho/NAA, 0.83 ± 0.28. Statistically significant differences were found in the NAA/Cr between the 0- to 5- and 6- to 20-year-old groups, and among the 6- to 20-, 21- to 50-, and older than 50-year-old groups. A statistically significant difference was found in Cho/Cr between the 0- to 5- and 6- to 20-year-old subjects; however, no differences were found among the 6- to 20-, 21- to 50-, and older than 50-year-old groups. Statistically significant differences in Cho/NAA were also found among the 4 age groups. The NAA/Cr at birth was low, it rose rapidly at 0-5 years, reaching a peak at approximately 10-20 years, and then gradually decreased. The Cho/Cr decreased rapidly at 0-5 years, then continued to decline, and was stable after 20 years of age.

CONCLUSIONS

Turbo spectroscopic imaging is a good method for analyzing normal changes in the pons metabolites during growth, maturation, and aging.

Age related changes in metabolite concentrations in the normal spinal cord

Magnetic resonance spectroscopy (MRS) studies have previously described metabolite changes associated with aging of the healthy brain and provided insights into normal brain aging that can assist us in differentiating age-related changes from those associated with neurological disease. The present study investigates whether age-related changes in metabolite concentrations occur in the healthy cervical spinal cord. 25 healthy volunteers, aged 23-65 years, underwent conventional imaging and single-voxel MRS of the upper cervical cord using an optimised point resolved spectroscopy sequence on a 3T Achieva system. Metabolite concentrations normalised to unsuppressed water were quantified using LCModel and associations between age and spinal cord metabolite concentrations were examined using multiple regressions. A linear decline in total N-Acetyl-aspartate concentration (0.049 mmol/L lower per additional year of age, p = 0.010) and Glutamate-Glutamine concentration (0.054 mmol/L lower per additional year of age, p = 0.002) was seen within our sample age range, starting in the early twenties. The findings suggest that neuroaxonal loss and/or metabolic neuronal dysfunction, and decline in glutamate-glutamine neurotransmitter pool progress with aging.

Effects of normal aging and SCN1A risk-gene expression on brain metabolites: evidence for an association between SCN1A and myo-inositol

Previously reported MRS findings in the aging brain include lower N-acetylaspartate (NAA) and higher myo-inositol (mI), total creatine (Cr) and choline-containing compound (Cho) concentrations. Alterations in the sodium channel voltage gated type I, alpha subunit SCN1A variant rs10930201 have been reported to be associated with several neurological disorders with cognitive deficits. MRS studies in SCN1A-related diseases have reported striking differences in the mI concentrations between patients and controls. In a study on 'healthy aging', we investigated metabolite spectra in a sample of 83 healthy volunteers and determined their age dependence. We also investigated a potential link between SCN1A and mI. We observed a significantly negative association of NAA (p = 0.004) and significantly positive associations of mI (p ≤ 0.001), Cr (p ≤ 0.001) and Cho (p = 0.034) with age in frontal white matter. The linear association of Cho ends at the age of about 50 years and is followed by an inverted 'U'-shaped curve. Further, mI was higher in C allele carriers of the SCN1A variant rs10930201. Our results corroborated the age-related changes in metabolite concentrations, and found evidence for a link between SCN1A and frontal white matter mI in healthy subjects.

In vivo glutamate measured with magnetic resonance spectroscopy: behavioral correlates in aging

Altered availability of the brain biochemical glutamate might contribute to the neural mechanisms underlying age-related changes in cognitive and motor functions. To investigate the contribution of regional glutamate levels to behavior in the aging brain, we used an in vivo magnetic resonance spectroscopy protocol optimized for glutamate detection in 3 brain regions targeted by cortical glutamatergic efferents-striatum, cerebellum, and pons. Data from 61 healthy men and women ranging in age from 20 to 86 years were used. Older age was associated with lower glutamate levels in the striatum, but not cerebellum or pons. Older age was also predictive of poorer performance on tests of visuomotor skills and balance. Low striatal glutamate levels were associated with high systolic blood pressure and worse performance on a complex visuomotor task, the Grooved Pegboard. These findings suggest that low brain glutamate levels are related to high blood pressure and that changes in brain glutamate levels might mediate the behavioral changes noted in normal aging.

Absence of age-related prefrontal NAA change in adults with autism spectrum disorders

Atypical trajectory of brain growth in autism spectrum disorders (ASDs) has been recognized as a potential etiology of an atypical course of behavioral development. Numerous neuroimaging studies have focused on childhood to investigate atypical age-related change of brain structure and function, because it is a period of neuron and synapse maturation. Recent studies, however, have shown that the atypical age-related structural change of autistic brain expands beyond childhood and constitutes neural underpinnings for lifelong difficulty to behavioral adaptation. Thus, we examined effects of aging on neurochemical aspects of brain maturation using 3-T proton magnetic resonance spectroscopy ((1)H-MRS) with single voxel in the medial prefrontal cortex (PFC) in 24 adult men with non-medicated high-functioning ASDs and 25 age-, IQ- and parental-socioeconomic-background-matched men with typical development (TD). Multivariate analyses of covariance demonstrated significantly high N-acetylaspartate (NAA) level in the ASD subjects compared with the TD subjects (F=4.83, P=0.033). The low NAA level showed a significant positive correlation with advanced age in the TD group (r=-0.618, P=0.001), but was not evident among the ASD individuals (r=0.258, P=0.223). Fisher's r-to-z transformation showed a significant difference in the correlations between the ASD and TD groups (Z=-3.23, P=0.001), which indicated that the age-NAA relationship was significantly specific to people with TD. The current (1)H-MRS study provided new evidence that atypical age-related change of neurochemical aspects of brain maturation in ASD individuals expands beyond childhood and persists during adulthood.

Age-related changes in brain energetics and phospholipid metabolism

Evidence suggests that mitochondria undergo functional and morphological changes with age. This study aimed to investigate the relationship of brain energy metabolism to healthy aging by assessing tissue specific differences in metabolites observable by phosphorus ((31)P) MRS. (31)P MRSI at 4 Tesla (T) was performed on 34 volunteers, aged 21-84, screened to exclude serious medical and psychiatric diagnoses. Linear mixed effects models were used to analyze the effects of age on phosphorus metabolite concentrations, intracellular magnesium and pH estimates in brain tissue. A significant age associated decrease in brain pH (-0.53% per decade), increase in PCr (1.1% per decade) and decrease in PME (1.7% per decade) were found in total tissue, with PCr effects localized to the gray matter. An increase in beta NTP as a function of age (1% per decade) approached significance (p = 0.052). There were no effects demonstrated with increasing age for intracellular magnesium, PDE or inorganic phosphate. This study reports the effects of healthy aging on brain chemistry in the gray matter versus white matter using (31)P MRS measures of high energy phosphates, pH and membrane metabolism. Increased PCr, increased beta NTP (reflecting ATP) and reduced pH may reflect altered energy production with healthy aging. Unlike some previous studies of aging and brain chemistry, this study examined healthy, non-demented and psychiatrically stable older adults and specifically analyzed gray-white matter differences in brain metabolism.

Metabonomic characterization of aging and investigation on the anti-aging effects of total flavones of Epimedium

A liquid chromatography coupled with mass spectrometry (LC/MS) based metabonomics approach was applied to characterize the aging of rats, and the anti-aging effect of total flavones of Epimedium (TFE), a traditional Chinese medicine, has also been investigated. Serum samples collected from 4, 10, 18 and 24 month-old rats and TFE-administered rats have been profiled by LC/MS. Thirty age-related endogenous metabolites were discovered by partial least squares (PLS) and Hotelling's T(2) control chart, among which 25 metabolites were structurally identified by MS(n) analysis and ten of them were further confirmed via authentic chemicals. All important age-related metabolites, such as unsaturated fatty acids, saturated fatty acids, nucleotides, carnosine, ergothioneine and amino acids, displayed age-related changes, and most of them were reset to a younger level after TFE administration. This study indicated that aging could be characterized by changes of lipid metabolisms and accumulation of free radicals. The anti-aging effects of TFE might due to the intervention on lipid metabolism and its property of anti-oxidation.

A systematic review of brain metabolite changes, measured with 1H magnetic resonance spectroscopy, in healthy aging

BACKGROUND

(1)H MR spectroscopy (MRS) can identify metabolite abnormalities in age-related, neurological diseases. However, there is little information on how metabolites change with healthy aging.

METHODS

We systematically reviewed the literature on MRS, from 1980 to 2006, for studies where healthy young subjects (<60 years) were compared to healthy older subjects (>60 years). We extracted metabolite data reported as "no change", "increase" or "decrease" for each metabolite by brain region and, where data were available, meta-analysed mean metabolite concentrations (mM) for young versus old subjects.

RESULTS

Eighteen studies met the inclusion criteria (total n=703 subjects, 284 >60 years old). Most data came from the frontal region, and reported "no change" in older subjects; however, a meta-analysis revealed a decrease in frontal NAA (p=0.05) and increases in parietal choline (p=0.003) and creatine (p<0.001).

DISCUSSION

These data suggest that NAA may decrease and choline and creatine increase with age. Therefore, more data are needed from older subjects to characterise age effects better and ratios in older subjects should be interpreted with caution.

Brain lithium, N-acetyl aspartate and myo-inositol levels in older adults with bipolar disorder treated with lithium: a lithium-7 and proton magnetic resonance spectroscopy study

OBJECTIVES

We investigated the relationship between brain lithium levels and the metabolites N-acetyl aspartate (NAA) and myo-inositol (myo-Ino) in the anterior cingulate cortex of a group of older adults with bipolar disorder (BD).

METHODS

This cross-sectional assessment included nine subjects (six males and three females) with bipolar I disorder and currently treated with lithium, who were examined at McLean Hospital's Geriatric Psychiatry Research Program and Brain Imaging Center. The subjects' ages ranged from 56 to 85 years (66.0 +/- 9.7 years) and all subjects had measurements of serum and brain lithium levels. Brain lithium levels were assessed using lithium magnetic resonance spectroscopy. All subjects also had proton magnetic resonance spectroscopy to obtain measurements of NAA and myo-Ino.

RESULTS

Brain lithium levels were associated with higher NAA levels [df = (1, 8), Beta = 12.53, t = 4.09, p < 0.005] and higher myo-Ino levels [df = (1, 7), F = 16.81, p < 0.006]. There were no significant effects of serum lithium levels on any of the metabolites.

CONCLUSION

Our findings of a relationship between higher brain lithium levels and elevated NAA levels in older adult subjects with BD may support previous evidence of lithium's neuroprotective, neurotrophic, and mitochondrial function-enhancing effects. Elevated myo-Ino related to elevated brain lithium levels may reflect increased inositol monophosphatase (IMPase) activity, which would lead to an increase in myo-Ino levels. This is the first study to demonstrate alterations in NAA and myo-Ino in a sample of older adults with BD treated with lithium.

Low striatal glutamate levels underlie cognitive decline in the elderly: evidence from in vivo molecular spectroscopy

Glutamate (Glu), the principal excitatory neurotransmitter of prefrontal cortical efferents, potentially mediates higher order cognitive processes, and its altered availability may underlie mechanisms of age-related decline in frontally based functions. Although animal studies support a role for Glu in age-related cognitive deterioration, human studies, which require magnetic resonance spectroscopy for in vivo measurement of this neurotransmitter, have been impeded because of the similarity of Glu's spectroscopic signature to those of neighboring spectral brain metabolites. Here, we used a spectroscopic protocol, optimized for Glu detection, to examine the effect of age in 3 brain regions targeted by cortical efferents--the striatum, cerebellum, and pons--and to test whether performance on frontally based cognitive tests would be predicted by regional Glu levels. Healthy elderly men and women had lower Glu in the striatum but not pons or cerebellum than young adults. In the combined age groups, levels of striatal Glu (but no other proton metabolite also measured) correlated selectively with performance on cognitive tests showing age-related decline. The selective relations between performance and striatal Glu provide initial and novel, human in vivo support for age-related modification of Glu levels as contributing to cognitive decline in normal aging.

Liver Triglyceride Content in HIV-1-Infected Patients on Combination Antiretroviral Therapy Studied with 1H-MR Spectroscopy

Objective

To carry out an exploratory evaluation of liver triglyceride content in HIV-1-infected patients receiving highly active antiretroviral therapy (HAART) using proton magnetic resonance spectroscopy and to study how both the treatment itself and the biochemical and physiological variables in which the treatment causes alterations are related to liver fat content.

Methods

Intracellular hepatic triglyceride content was determined in 29 HIV-1-infected patients on their first HAART regime by means of localized water-unsuppressed single voxel proton spectra. Other measurements were body mass index, waist-to-hip ratio, lipodystrophy assessment and a detailed blood biochemical analysis. The relationship between intracellular hepatic triglycerides and relevant descriptive, treatment and biochemical variables was studied by correlation and regression analysis.

Results

Intrahepatic triglycerides were detected in 58.6% of the patients and 13.8% showed a triglyceride content compatible with liver steatosis. Many variables (body mass index, waist-to-hip ratio, cumulative exposure to PIs, lactate, insulin, insulin resistance measured by the homeostasis model assessment method [HOMA-R index], pH, total triglycerides, high density lipoprotein cholesterol and very low density lipoprotein [VLDL] cholesterol) correlated individually with the amount of triglycerides. Stepwise multiple regression analysis showed that the combination of insulin or HOMA-R index and VLDL cholesterol accounted for up to 50.2% of the triglyceride liver variance. A positive relationship was found between the concomitant presence of the metabolic syndrome components (insulin resistance, dyslipidaemia and central obesity) and intrahepatic triglyceride content.

Conclusions

The study showed that intrahepatic triglyceride deposit appears to be a frequent feature of HIV-1-infected patients receiving HAART. A coherent multifactorial combination of biochemical and physiological factors associated with the deposit suggested that cumulative exposure to PIs might be a possible trigger event.

The Role of Quantitative Neuroimaging Indices in the Differentiation of Ischemia From Demyelination: An Analytical Study With Case Presentation

BACKGROUND AND PURPOSE

Differentiation of acute and subacute ischemic stroke lesions from acute demyelinating lesions of multiple sclerosis (MS) may not be possible on conventional magnetic resonance imaging (MRI). Both lesion types enhance on T1 with gadolinium (Gd) contrast and both are hyperintense on diffusion-weighted imaging (DWI). This study is an analysis of two quantitative MR indices: (1) calculated apparent diffusion coefficients (ADCs) and (2) T2 relaxation times (T2R) as means toward differentiating acute ischemic lesions from acute demyelinating lesions. Chronic ischemic and demyelinating lesions were evaluated for comparison as well.

METHODS

The MRI of nine patients with both acute and chronic ischemic lesions and six patients with both acute and chronic demyelinating lesions were analyzed for ADC and T2Rs. The indices were measured by manually placing regions of interest (ROIs) at the anatomic center of the acute lesion. Acute ischemic lesions were chosen by their hyperintensity on DWI and hypointensity on ADC mapping. Acute demyelinating lesions were selected by peripheral contrast enhancement after the administration of Gd. Computation of the ADC involved the diffusion coefficient on a region by region basis as follows: D = -(b(0)/b(1000))ln(S(b1000)/S(b0)), where S(b1000) is the signal intensity on DWI and S(b0) is the signal intensity on T2 with diffusion sensitivities of b(0) and b(1000), respectively. Computation of the T2R was made as follows: T2R = (TE(T2)--TE(PD))/(ln SI(PD)--ln SI(T2)), where TE is the echo time of the different pulse sequences, SI is signal intensity on the different echo sequences, and PD represents proton density sequence.

RESULTS

Twenty-nine acute ischemia, 27 acute demyelination, 28 chronic ischemia, and 43 chronic demyelination image sets were analyzed. The differences between ADC(acute infarct) (0.760) versus ADC(acute plaque) (1.106) were significant (p < 0.02). The differences between T2R(acute infarct) (235.5) versus T2R(acute plaque) (170.5) were also significant (p < 0.02).

CONCLUSIONS

ADC in combination with T2R is a useful tool to differentiate acute ischemic from acute demyelinating lesions. The use of these neuroimaging indices along with magnetic resonance spectroscopy metabolite ratios is then demonstrated in elucidating the pathophysiological mechanism for a case of delayed posttraumatic bilateral internuclear ophthalmoplegia.

Differential aging of the brain: patterns, cognitive correlates and modifiers

Deciphering the secret of successful aging depends on understanding the patterns and biological underpinnings of cognitive and behavioral changes throughout adulthood. That task is inseparable from comprehending the workings of the brain, the physical substrate of behavior. In this review, we summarize the extant literature on age-related differences and changes in brain structure, including postmortem and noninvasive magnetic resonance imaging (MRI) studies. Among the latter, we survey the evidence from volumetry, diffusion-tensor imaging, and evaluations of white matter hyperintensities (WMH). Further, we review the attempts to elucidate the mechanisms of age-related structural changes by measuring metabolic markers of aging through magnetic resonance spectroscopy (MRS). We discuss the putative links between the pattern of brain aging and the pattern of cognitive decline and stability. We then present examples of activities and conditions (hypertension, hormone deficiency, aerobic fitness) that may influence the course of normal aging in a positive or negative fashion. Lastly, we speculate on several proposed mechanisms of differential brain aging, including neurotransmitter systems, stress and corticosteroids, microvascular changes, calcium homeostasis, and demyelination.