Resilience to periodic disturbances and the long-term genetic stability in Acropora coral

Climate change is restructuring natural ecosystems. The direct impacts of these events on biodiversity and community structure are widely documented, but the impacts on the genetic variation of populations remains largely unknown. We monitored populations of Acropora coral on a remote coral reef system in northwest Australia for two decades and through multiple cycles of impact and recovery. We combined these demographic data with a temporal genetic dataset of a common broadcast spawning corymbose Acropora to explore the spatial and temporal patterns of connectivity underlying recovery. Our data show that broad-scale dispersal and post-recruitment survival drive recovery from recurrent disturbances, including mass bleaching and mortality. Consequently, genetic diversity and associated patterns of connectivity are maintained through time in the broader metapopulation. The results highlight an inherent resilience in these globally threatened species of coral and showcase their ability to cope with multiple disturbances, given enough time to recover is permitted.

Region-specific changes in brain activity and memory after continuous positive airway pressure therapy in obstructive sleep apnea: a pilot high-density electroencephalography study

STUDY OBJECTIVES

Limited channel electroencephalography (EEG) investigations in obstructive sleep apnea (OSA) have revealed deficits in slow wave activity (SWA) and spindles during sleep and increased EEG slowing during resting wakefulness. High-density EEG (Hd-EEG) has also detected local parietal deficits in SWA (delta power) during NREM. It is unclear whether effective continuous positive airway pressure (CPAP) treatment reverses regional SWA deficits, and other regional sleep and wake EEG abnormalities, and whether any recovery relates to improved overnight memory consolidation.

METHODS

A clinical sample of men with moderate-severe OSA underwent sleep and resting wake recordings with 256-channel Hd-EEG before and after 3 months of CPAP. Declarative and procedural memory tasks were administered pre- and post-sleep. Topographical spectral power maps and differences between baseline and treatment were compared using t-tests and statistical nonparametric mapping (SnPM).

RESULTS

In 11 compliant CPAP users (5.2 ± 1.1 hours/night), total sleep time did not differ after CPAP but N1 and N2 sleep were lower and N3 was higher. Centro-parietal gamma power during N3 increased and fronto-central slow spindle activity during N2 decreased (SnPM < 0.05). No other significant differences in EEG power were observed. When averaged specifically within the parietal region, N3 delta power increased after CPAP (p = 0.0029) and was correlated with the change in overnight procedural memory consolidation (rho = 0.79, p = 0.03). During resting wakefulness, there were trends for reduced delta and theta power.

CONCLUSIONS

Effective CPAP treatment of OSA may correct regional EEG abnormalities, and regional recovery of SWA may relate to procedural memory improvements in the short term.

Blood-Based Transcriptomic Biomarkers Are Predictive of Neurodegeneration Rather Than Alzheimer's Disease

Alzheimer's disease (AD) is a growing global health crisis affecting millions and incurring substantial economic costs. However, clinical diagnosis remains challenging, with misdiagnoses and underdiagnoses being prevalent. There is an increased focus on putative, blood-based biomarkers that may be useful for the diagnosis as well as early detection of AD. In the present study, we used an unbiased combination of machine learning and functional network analyses to identify blood gene biomarker candidates in AD. Using supervised machine learning, we also determined whether these candidates were indeed unique to AD or whether they were indicative of other neurodegenerative diseases, such as Parkinson's disease (PD) and amyotrophic lateral sclerosis (ALS). Our analyses showed that genes involved in spliceosome assembly, RNA binding, transcription, protein synthesis, mitoribosomes, and NADH dehydrogenase were the best-performing genes for identifying AD patients relative to cognitively healthy controls. This transcriptomic signature, however, was not unique to AD, and subsequent machine learning showed that this signature could also predict PD and ALS relative to controls without neurodegenerative disease. Combined, our results suggest that mRNA from whole blood can indeed be used to screen for patients with neurodegeneration but may be less effective in diagnosing the specific neurodegenerative disease.

Hippocampal Neuronal Integrity and Functional Connectivity Within the Default Mode Network in Mild Cognitive Impairment: A Multimodal Investigation

Background: In older people with mild cognitive impairment (MCI), the relationship between early changes in functional connectivity and in vivo changes in key neurometabolites is not known. Two established correlates of MCI diagnosis are decreased N-acetylaspartate (NAA) in the hippocampus, indicative of decreased neuronal integrity, and changes in the default mode network (DMN) functional network. If and how these measures interrelate is yet to be established, and such understanding may provide insight into the processes underpinning observed cognitive decline. Objectives: To determine the relationship between NAA levels in the left hippocampus and functional connectivity within the DMN in an aging cohort. Methods: In a sample of 51 participants with MCI and 30 controls, hippocampal NAA was determined using magnetic resonance spectroscopy, and DMN connectivity was quantified using resting-state functional MRI. The association between hippocampal NAA and the DMN functional connectivity was tested within the MCI group and separately within the control group. Results: In the DMN, we showed a significant inverse association between functional connectivity and hippocampal NAA in 20 specific brain connections for patients with MCI. This was despite no evidence of any associations in the healthy control group or group differences in either of these measures alone. Conclusions: This study suggests that decreased neuronal integrity in the hippocampus is associated with functional change within the DMN for those with MCI, in contrast to healthy older adults. These results highlight the potential of multimodal investigations to better understand the processes associated with cognitive decline. Impact statement This study measured activity within the default mode network (DMN) and quantified N-acetylaspartate (NAA), a measure of neuronal integrity, within the hippocampus in participants with mild cognitive impairment (MCI) and healthy controls. In participants with MCI, NAA levels were inversely associated with connectivity between specific regions of the DMN, a relationship not evident in healthy controls. This association was present even in the absence of group differences in DMN connectivity or NAA levels. This research illustrates the possibility of using multiple magnetic resonance modalities for more sensitive measures of early cognitive decline to identify and intervene earlier.

Safety of higher doses of melatonin in adults: A systematic review and meta-analysis

Melatonin is commonly used for sleep and jetlag at low doses. However, there is less documentation on the safety of higher doses, which are being increasingly used for a wide variety of conditions, including more recently COVID-19 prevention and treatment. The aim of this review was to investigate the safety of higher doses of melatonin in adults. Medline, Scopus, Embase and PsycINFO databases from inception until December 2019 with convenience searches until October 2020. Randomised controlled trials investigating high-dose melatonin (≥10 mg) in human adults over 30 years of age were included. Two investigators independently abstracted articles using PRISMA guidelines. Risk of bias was assessed by a committee of three investigators. 79 studies were identified with a total of 3861 participants. Studies included a large range of medical conditions. The meta-analysis was pooled data using a random effects model. The outcomes examined were the number of adverse events (AEs), serious adverse events (SAEs) and withdrawals due to AEs. A total of 29 studies (37%) made no mention of the presence or absence of AEs. Overall, only four studies met the pre-specified low risk of bias criteria for meta-analysis. In that small subset, melatonin did not cause a detectable increase in SAEs (Rate Ratio = 0.88 [0.52, 1.50], p = .64) or withdrawals due to AEs (0.93 [0.24, 3.56], p = .92), but did appear to increase the risk of AEs such as drowsiness, headache and dizziness (1.40 [1.15, 1.69], p < .001). Overall, there has been limited AE reporting from high-dose melatonin studies. Based on this limited evidence, melatonin appears to have a good safety profile. Better safety reporting in future long-term trials is needed to confirm this as our confidence limits were very wide due to the paucity of suitable data.

Brain oxidative stress and cognitive function in older adults with diabetes and pre-diabetes who are at risk for dementia

AIMS

Diabetes is an established risk factor for dementia. This study aimed to examine the relationship between various cognitive domains, brain oxidative stress and markers of diabetes in older adults at risk for dementia.

METHODS

Older adults at risk for dementia underwent comprehensive neuropsychological and medical assessment. At risk was defined as those with subjective and/or objective cognitive impairment. Pre-diabetes and type 2 diabetes were defined using American Diabetes Association definitions for fasting blood glucose and HbA1c. Brain oxidative stress as indicated by glutathione (GSH) was assessed via magnetic resonance spectroscopy in the anterior cingulate cortex.

RESULTS

One-hundred and forty-seven older adults completed a neuropsychological assessment and fasting blood sample with 63 also undergoing magnetic resonance spectroscopy. Those with pre-diabetes/diabetes according to FBG had impaired memory retention, set-shifting and response inhibition, compared to those with normal blood glucose. In contrast, there were no significant differences in any cognitive outcome using the HbA1c definition. Increasing glucose and HbA1c levels were associated with reduced GSH concentration in the anterior cingulate.

CONCLUSIONS

This study demonstrates that in older adults at risk for dementia, having pre-diabetes or diabetes is associated with impaired memory and executive dysfunction. It also highlights the potential role of oxidative stress as a pathophysiological mechanism that may underpin the link between diabetes and cognitive dysfunction.

Rest-activity functioning is related to white matter microarchitecture and modifiable risk factors in older adults at-risk for dementia

STUDY OBJECTIVES

Growing evidence demonstrates pronounced alterations in rest-activity functioning in older adults at-risk for dementia. White matter degeneration, poor cardiometabolic functioning, and depression have also been linked to a greater risk of decline; however, limited studies have examined the white matter in relation to rest-activity functioning in at-risk older adults.

METHODS

We investigated associations between nonparametric actigraphy measures and white matter microarchitecture using whole-brain fixel-based analysis of diffusion-weighted imaging in older adults (aged 50 years or older) at-risk for cognitive decline and dementia. The fixel-based metrics assessed were fiber density, fiber cross-section, and combined fiber-density, and cross-section. Interactions between rest-activity functioning and known clinical risk factors, specifically body mass index (BMI), vascular risk factors, depressive symptoms and self-reported exercise, and their association with white matter properties were then investigated.

RESULTS

Sixty-seven older adults were included (mean = 65.78 years, SD = 7.89). Lower relative amplitude, poorer 24-h synchronization and earlier onset of the least active 5-h period were associated with reductions in markers of white matter atrophy in widespread regions, including cortico-subcortical and cortical association pathways. Preliminary evidence was also found indicating more pronounced white matter alterations in those with lower amplitude and higher BMI (β = 0.25, 95% CI [0.05, 0.46]), poorer 24-h synchronization and more vascular risk factors (β = 0.17, 95% CI [-0.02, 0.36]) and earlier onset of inactivity and greater depressive symptoms (β = 0.17, 95% CI [0.03, 0.30]).

CONCLUSIONS

These findings highlight the complex interplay between rest-activity rhythms, white matter, and clinical risk factors in individuals at-risk for dementia that should be considered in future studies.

Poorer Theory of Mind in Amnestic Mild Cognitive Impairment Is Associated with Decreased Functional Connectivity in the Default Mode Network

BACKGROUND

Older adults living with amnestic mild cognitive impairment (aMCI) not only demonstrate impairments in Theory of Mind (ToM), relative to adults with non-amnestic MCI (naMCI), but are also at a higher risk of developing dementia.

OBJECTIVE

Our primary objective was to ascertain whether default mode network (DMN) functional connectivity was differentially associated with ToM abilities between MCI subgroups.

METHODS

Using functional magnetic resonance imaging, we investigated alterations in resting-state functional connectivity within the brain's DMN in a sample of 43 older adults with aMCI (n = 19) and naMCI (n = 24), previously reported to demonstrate poorer ToM abilities.

RESULTS

Compared to naMCI, the aMCI subgroup revealed a significant association between poorer ToM performance and reduced functional connectivity between the bilateral temporal pole (TempP) and the left lateral temporal cortex (LTC) (LTC_L-TempP_L: b = -0.06, t(33) = -3.53, p = 0.02; LTC_L-TempP_R: b = -0.07,t(33) = -3.20, p = 0.03); between the right TempP and the dorsal medial prefrontal cortex (dMPFC) (b = -0.04, t(33) = -3.02, p = 0.03) and between the left and right TempP (b = -0.05, t(33) = -3.26, p = 0.03). In the naMCI subgroup, the opposite relationship was present between the bilateral TempP and the left LTC (Combined correlation: r = -0.47, p = 0.02), however, not between the right TempP and the dMPFC (r = -0.14, p = 0.51) or the left and right TempP (r = -0.31, p = 0.14).

CONCLUSION

Our findings suggest that alterations in functional connectivity within the DMN involving temporal and frontal lobe regions are associated with ToM deficits in aMCI.

Altered heart rate variability during sleep in mild cognitive impairment

STUDY OBJECTIVES

Cardiovascular autonomic dysfunction, as measured by short-term diurnal heart rate variability (HRV), has been reported in older adults with mild cognitive impairment (MCI). However, it is unclear whether this impairment also exists during sleep in this group. We, therefore, compared overnight HRV during sleep in older adults with MCI and those with subjective cognitive impairment (SCI).

METHODS

Older adults (n = 210) underwent overnight polysomnography. Eligible participants were characterized as multi-domain MCI or SCI. The multi-domain MCI group was comprised of amnestic and non-amnestic subtypes. Power spectral analysis of HRV was conducted on the overnight electrocardiogram during non-rapid eye movement (NREM), rapid eye movement (REM), N1, N2, N3 sleep stages, and wake periods. High-frequency HRV (HF-HRV) was employed as the primary measure to estimate parasympathetic function.

RESULTS

The MCI group showed reduced HF-HRV during NREM sleep (p = 0.018), but not during wake or REM sleep (p > 0.05) compared to the SCI group. Participants with aMCI compared to SCI had the most pronounced reduction in HF-HRV across all NREM sleep stages-N1, N2, and N3, but not during wake or REM sleep. The naMCI sub-group did not show any significant differences in HF-HRV during any sleep stage compared to SCI.

CONCLUSIONS

Our study showed that amnestic MCI participants had greater reductions in HF-HRV during NREM sleep, relative to those with SCI, suggesting potential vulnerability to sleep-related parasympathetic dysfunction. HF-HRV, especially during NREM sleep, may be an early biomarker for dementia detection.

Obesity and Oxidative Stress in Older Adults At Risk for Dementia: A Magnetic Resonance Spectroscopy Study

OBJECTIVE

This study aimed to investigate the relationship between obesity and oxidative stress in older adults at risk for dementia. It also aimed to explore the influence of physical activity on the relationship between obesity and oxidative stress in this at risk cohort.

METHODS

Older adults at risk for dementia underwent comprehensive medical, neuropsychological, and psychiatric assessment. At risk was defined as participants with subjective or mild cognitive impairment. Glutathione was assessed by magnetic resonance spectroscopy in the left hippocampus and the anterior and posterior cingulate cortex. Body mass index (BMI) was calculated and classified as healthy (BMI <25 kg/m2) or overweight/obese (BMI ≥25 kg/m2).

RESULTS

Sixty-five older adults (mean age=66.2 y) were included for analysis. The overweight/obese group had significantly greater glutathione in the hippocampus compared with the healthy weight group (t=-2.76, P=0.008). No significant difference in glutathione was observed between groups in the anterior or posterior cingulate. In the overweight/obese group, a higher BMI was associated with a diabetes diagnosis and lower total time engaging in physical activity (r=-0.36, P=0.025), however, glutathione did not correlate with activity levels across groups.

CONCLUSION

This study demonstrates that changes in in vivo markers of oxidative stress are present in overweight/obese older adults at risk for dementia. Future research should explore the relationship with diabetes and the longitudinal relationship between BMI and oxidative stress, and response to therapeutic interventions.

Feasibility of 3-month melatonin supplementation for brain oxidative stress and sleep in mild cognitive impairment: protocol for a randomised, placebo-controlled study

INTRODUCTION

Melatonin has multiple proposed therapeutic benefits including antioxidant properties, synchronisation of the circadian system and lowering of blood pressure. In this protocol, we outline a randomised controlled trial to assess the feasibility, acceptability and tolerability of higher dose (25 mg) melatonin to target brain oxidative stress and sleep disturbance in older adults with mild cognitive impairment (MCI).

METHODS AND ANALYSIS

The study design is a randomised double-blind, placebo-controlled, parallel group trial. Forty individuals with MCI will be recruited from the Healthy Brain Ageing Clinic, University of Sydney and from the community, and randomised to receive either 25 mg oral melatonin or placebo nightly for 12 weeks. The primary outcomes are feasibility of recruitment, acceptability of intervention and adherence to trial medication at 12 weeks. Secondary outcomes will include the effect of melatonin on brain oxidative stress as measured by magnetic resonance spectroscopy, blood pressure, blood biomarkers, mood, cognition and sleep. Outcomes will be collected at 6 and 12 weeks. The results of this feasibility trial will inform a future conclusive randomised controlled trial to specifically test the efficacy of melatonin on modifiable risk factors of dementia, as well as cognition and brain function. This will be the first trial to investigate the effect of melatonin in the population with MCI in this way, with the future aim of using this approach to reduce progression to dementia.

ETHICS AND DISSEMINATION

This protocol has been approved by the Sydney Local Health District Ethics Committee (X18-0077). This randomised controlled trial will be conducted in compliance with the protocol published in the registry, the International Conference for Harmonisation on Good Clinical Practice and all other applicable regulatory requirements. The findings of the trial will be disseminated via conferences, publications and media, as applicable. Participants will be informed of results of the study at the conclusion of the trial. Eligible authors will include investigators who are involved in the conception and design of the study, the conduct of the trial, the analysis of the results, and reporting and presentation of study findings.

TRIAL REGISTRATION NUMBER

Australian and New Zealand Clinical Trials Registry (ANZCTRN 12619000876190).

PROTOCOL VERSION

V.8 15 October 2020.

Nocturnal Hypoxemia Is Associated with Altered Parahippocampal Functional Brain Connectivity in Older Adults at Risk for Dementia

BACKGROUND

Obstructive sleep apnea is associated with an increased risk of developing mild cognitive impairment and dementia. Intermittent nocturnal hypoxemia in obstructive sleep apnea is associated with brain changes in key regions that underpin memory.

OBJECTIVE

To determine whether older adults with severe nocturnal hypoxemia would exhibit reduced functional connectivity within these regions, with associated deficits in memory.

METHODS

Seventy-two participants 51 years and over underwent polysomnography with continuous blood oxygen saturation recorded via oximetry. The oxygen desaturation index (ODI, 3% dips in oxygen levels per hour) was the primary outcome measure. ODI was split into tertiles, with analyses comparing the lowest and highest tertiles (N = 48). Thirty-five of the 48 participants from these two tertiles had mild cognitive impairment. Participants also underwent resting-state fMRI and comprehensive neuropsychological, medical, and psychiatric assessment.

RESULTS

The highest ODI tertile group demonstrated significantly reduced connectivity between the left and right parahippocampal cortex, relative to the lowest ODI tertile group (t(42) = -3.26, p = 0.041, beta = -1.99).The highest ODI tertile group also had poorer working memory performance. In the highest ODI tertile group only, higher left-right parahippocampal functional connectivity was associated with poorer visual memory recall (between-groups z = -2.93, p = 0.0034).

CONCLUSIONS

Older adults with severe nocturnal hypoxemia demonstrate impaired functional connectivity in medial temporal structures, key regions involved in sleep memory processing and implicated in dementia pathophysiology. Oxygen desaturation and functional connectivity in these individuals each relate to cognitive performance. Research is now required to further elucidate these findings.

Actigraphy-recorded sleep efficiency and hippocampal volume are related to visual and verbal rate of forgetting in older adults

This study aimed to determine if older adults "at-risk" for dementia (those with MCI or SMC) exhibit accelerated long-term forgetting (ALF) and whether rate of forgetting (RoF) is associated with sleep efficiency, hippocampal volume and demographic/clinical features. Forty-nine "at-risk" participants and eighteen controls underwent examination. Memory was assessed using the Scene Memory Task (SMT) and WMS-III Logical Memory (LM) subtest. Tests were administered at baseline, 24 hours and 2 weeks. While our study did not find ALF in those "at-risk" for dementia, on the SMT, RoF over 24 hours and 2 weeks was negatively correlated with sleep efficiency. For LM, RoF at 2 weeks was moderately associated with left hippocampal volume. Neither visual or verbal RoF was correlated with demographic or clinical variables (age, MMSE, IQ, GDS-15). While ALF was not observed in this sample, our results suggest that visual and verbal forgetting have differential predictors.

Objective measurement of sleep in mild cognitive impairment: A systematic review and meta-analysis

Older adults with mild cognitive impairment (MCI) are at-risk of developing dementia, particularly Alzheimer's disease. While some research suggests that alterations in sleep architecture may mediate cognitive decline, the nature and magnitude of changes to sleep macro- (sleep stages) and micro-architecture (electroencephalography (EEG) oscillations) in MCI is not yet clear. This study aimed to systematically review and meta-analyse case-control studies objectively measuring sleep in MCI. A systematic search was conducted using PubMed, Scopus, Web of Science, Embase and Psycinfo databases and after review, a total of 10 studies met inclusion criteria. Of these, all reported sleep macro-architecture and four reported micro-architecture outcomes. A combined total of 430 participants (209 with and 221 without MCI) underwent objective sleep assessments in the included full text articles. Findings show that compared to healthy controls, those with MCI have pronounced changes in sleep macro-architecture with greater wake after sleep onset, reduced total sleep time, lower sleep efficiency, longer sleep onset latency, longer rapid eye movement sleep (REM) latency, reduced REM sleep, greater N1 sleep, and worse severity of hypoxemia. Pooling of sleep micro-architecture EEG measures was not possible due to limited studies, however reduced spindles in non-REM sleep and greater EEG slowing in REM sleep were reported.

Arterial stiffness relates to executive dysfunction in later life

Cardiovascular disease in older people is often linked with cognitive impairment, particularly in domains of executive function and processing speed. Our aims examined whether carotid-femoral pulse wave velocity (PWV) related to subtle changes of executive function and processing speed. Fifty-six individuals with subjective mood and/or cognitive concerns underwent PWV and neuropsychological assessments of processing speed (Trail Making Test Part A) and executive functioning (Delis Kaplan Executive Function System Stroop Task; Trail Making Test Part B, TMT-B). Individuals with high PWV (≥12.0m/s) had poorer performance on TMT-B, compared to low PWV (<12.0m/s), and a moderate negative correlation (r = -0.38, p = .004) between PWV and TMT-B performance. Our results confirm that in older adults at-risk for cognitive decline, early markers of CVD are associated with subtle decrements in rapid set-shifting (executive function), supporting efforts towards early detection of CVD as a secondary prevention strategy for older individuals with cognitive decline.

Structural brain correlates of obstructive sleep apnoea in older adults at risk for dementia

This study aimed to investigate associations between obstructive sleep apnoea (OSA) and cortical thickness in older adults with subjective and objective cognitive difficulties, who are considered "at-risk" for dementia.83 middle-aged to older adults (51-88 years) underwent neuropsychological testing, polysomnography assessment of OSA and a structural magnetic resonance imaging brain scan. A principal components analysis was performed on OSA measures. Cortical thickness and subcortical volumes were compared to extracted components of "oxygen desaturation" and "sleep disturbance".Oxygen desaturation was significantly related to reduced cortical thickness in the bilateral temporal lobes (left: r=-0.44, p<0.001; right: r=-0.39, p=0.003). Conversely, sleep disturbance was associated with increased thickness in the right postcentral gyrus (r=0.48, p<0.001), pericalcarine (r=0.50, p=0.005) and pars opercularis (r=0.46, p=0.009) and increased volume of the hippocampus and amygdala. Decreased thickness in the bilateral temporal regions was associated with reduced verbal encoding (r=0.28, p=0.010).Given the clinical significance of this sample in terms of dementia prevention, these changes in grey matter reveal how OSA might contribute to neurodegenerative processes in older adults.

Current sleep disturbance in older people with a lifetime history of depression is associated with increased connectivity in the Default Mode Network

BACKGROUND

The present study investigated Default Mode Network (DMN) functional connectivity in subjects with a lifetime history of major depression, comparing those with and without current sleep disturbance. Controls were included to assess DMN abnormalities specific to depression.

METHODS

A total of 93 adults aged 50 years and over were recruited from the Healthy Brain Ageing Clinic at the Brain and Mind Centre, Sydney, Australia. The sample comprised two groups, including 22 controls and 71 participants with a lifetime history of DSM-IV major depression (with depressive episode current or remitted). 52 of those with a lifetime history of depression also met criteria for Mild Cognitive Impairment (MCI). Participants underwent resting-state fMRI along with comprehensive psychiatric, neuropsychological, and medical assessment. Subjective sleep quality was assessed via the Pittsburgh Sleep Quality Index (PSQI). Sleep disturbance was defined as a PSQI score > 5. A total of 68% (n = 48) of cases with a lifetime history of depression met criteria for sleep-disturbance. DMN functional connectivity was assessed via ROI-to-ROI analyses.

RESULTS

Relative to controls, those with lifetime major depression demonstrated significantly increased functional connectivity between the ventromedial prefrontal cortex and the temporal pole. Within the depression group (n = 48), those with current sleep disturbance had significantly increased connectivity between the anterior medial prefrontal cortex and both the parahippocampal cortex and the hippocampal formation, relative to those without sleep disturbance (n = 23). These results were present after controlling for MCI diagnosis.

CONCLUSIONS

Current sleep disturbance together with depression is associated with distinct abnormalities in DMN functioning incorporating regions responsible for self-reflection and declarative memory processes. Impaired sleep is associated with increased connectivity between these regions. Future studies may augment these findings with complementary imaging techniques including cortical thickness and diffusion tensor imaging, as well as high density electroencephalogram recording.

Effect of the Mediterranean diet on cognition and brain morphology and function: a systematic review of randomized controlled trials

Background

Observational studies of the Mediterranean diet suggest cognitive benefits, potentially reducing dementia risk.

Objective

We performed the first published review to our knowledge of randomized controlled trials (RCTs) investigating Mediterranean diet effects on cognition or brain morphology and function, with an additional focus on intervention diet quality and its relation to "traditional" Mediterranean dietary patterns.

Design

We searched 9 databases from inception (final update December 2017) for RCTs testing a Mediterranean compared with alternate diet for cognitive or brain morphology and function outcomes.

Results

Analyses were based on 66 cognitive tests and 1 brain function outcome from 5 included studies (n = 1888 participants). The prescribed Mediterranean diets varied considerably between studies, particularly with regards to quantitative food advice. Only 8/66 (12.1%) of individual cognitive outcomes at trial level significantly favored a Mediterranean diet for cognitive performance, with effect sizes (ESs) ranging from small (0.32) to large (1.66), whereas 2 outcomes favored controls. Data limitations precluded a meta-analysis. Of 8 domain composite cognitive scores from 2 studies, the 3 (Memory, Frontal, and Global function) from PREDIMED (PREvención con DIeta MEDiterránea) were significant, with ESs ranging from 0.39 to 1.29. A posttest comparison at a second PREDIMED site found that the Mediterranean diet modulates the effect of several genotypes associated with dementia risk for some cognitive outcomes, with mixed results. Finally, the risk of low-plasma brain-derived neurotrophic factor was reduced by 78% (OR = 0.22; 95% CI: 0.05, 0.90) in those who consumed a Mediterranean diet compared to control diet at 3 y in this trial. There was no benefit of the Mediterranean diet for incident cognitive impairment or dementia.

Conclusions

Five RCTs of the Mediterranean diet and cognition have been published to date. The data are mostly nonsignificant, with small ESs. However, the significant improvements in cognitive domain composites in the most robustly designed study warrant additional research.

Episodic memory in depression: the unique contribution of the anterior caudate and hippocampus

BACKGROUND

Learning and memory impairments in older adults with depression are linked to hippocampal atrophy. However, other subcortical regions may also be contributing to these deficits. We aimed to examine whether anterior caudate nucleus volume is significantly reduced in older adults with depression compared to controls; whether anterior caudate volume is associated with performance on tasks of episodic learning and memory, and if so, whether this association is independent of the effects of the hippocampus.

METHOD

Eighty-four health-seeking participants meeting criteria for lifetime major depressive disorder (mean age = 64.2, s.d. = 9.1 years) and 27 never-depressed control participants (mean age = 63.9, s.d. = 8.0 years) underwent neuropsychological assessment including verbal episodic memory tests [Rey Auditory Verbal Learning Test and Logical Memory (WMS-III)]. Magnetic resonance imaging was conducted, from which subregions of the caudate nucleus were manually demarcated bilaterally and hippocampal volume was calculated using semi-automated methods.

RESULTS

Depressed subjects had smaller right anterior caudate (RAC) (t = 2.3, p = 0.026) and poorer memory compared to controls (t = 2.5, p < 0.001). For depressed subjects only, smaller RAC was associated with poorer verbal memory (r = 0.3, p = 0.003) and older age (r = -0.46, p < 0.001). Multivariable regression showed that the RAC and hippocampus volume uniquely accounted for 5% and 3% of the variance in memory, respectively (β = 0.25, t = 2.16, p = 0.033; β = 0.19, t = 1.71, p = 0.091).

CONCLUSIONS

In older people with depression, the anterior caudate nucleus and the hippocampus play independent roles in mediating memory. While future studies examining this structure should include larger sample sizes and adjust for multiple comparisons, these findings support the critical role of the striatum in depression.

Association of Anterior Cingulate Glutathione with Sleep Apnea in Older Adults At-Risk for Dementia

STUDY OBJECTIVES

Sleep disordered breathing (SDB) is common in older adults and is strongly associated with cognitive decline, with increasing evidence suggesting that it may represent a risk factor for dementia. Given that SDB is characterized by intermittent episodes of hypoxemia during sleep, it is possible that cognitive impairment may relate to cerebral oxidative stress. This study aimed to examine the relationship between nocturnal markers of hypoxemia and proton magnetic resonance spectroscopy ((1)H-MRS) markers of oxidative stress within the anterior cingulate cortex (ACC) of the brain.

METHODS

Twenty-four older adults (mean age = 67.9 y) at-risk for dementia were recruited from our Healthy Brain Ageing Research Clinic. At-risk was defined as participants seeking help for assessment and/or intervention for cognitive decline, including those with subjective and/or objective cognitive complaints. This could occur in the context of prior depression or risk factors (e.g., vascular) for dementia. All participants underwent psychiatric, medical and neuropsychological assessment followed by overnight polysomnography. In addition, participants underwent (1)H-MRS to derive levels of ACC metabolite glutathione (GSH) reported as a ratio to creatine (GSH/Cr).

RESULTS

Increased levels of GSH/Cr were associated with lower oxygen desaturation (r = -0.54, P = 0.007) and more severe apnea-hypopnea index scores during rapid eye movement sleep (r = 0.42, P = 0.050). In addition, ACC GSH/Cr correlated with poorer executive functioning (i.e., response inhibition: r = -0.49, P = 0.015; set shifting: r = -0.43, P = 0.037).

CONCLUSIONS

Markers of nocturnal hypoxemia and SDB are associated with cerebral oxidative stress in older people at-risk for dementia, suggesting a potential mechanism by which SDB may contribute to brain degeneration, cognitive decline, and dementia. Further work focused on utilizing this biomarker for the early identification and treatment of this possible modifiable risk factor in older persons is now warranted.

Hippocampal volume in older adults at risk of cognitive decline: the role of sleep, vascular risk, and depression

BACKGROUND AND OBJECTIVES

Decreased hippocampal volume in older adults is associated with neurodegenerative and psychiatric diseases. Several modifiable risk factors have been associated with the size of this structure, however the relative contribution of these factors to hippocampal atrophy is unclear. This study aimed to examine the relationship between modifiable risk factors and hippocampal volume in older adults at risk of cognitive decline.

METHODS

Two hundred and eighteen participants (mean age = 67.3 years, MMSE = 28.6) with mood and/or memory complaints underwent clinical and neuropsychological assessment, and magnetic resonance imaging. Measures of depression, global cognitive functioning, exercise, vascular health, cognitive reserve, sleep, and memory were collected. Hippocampal volumes were derived using image segmentation as implemented by FMRIB Software Library.

RESULTS

Smaller hippocampal volumes were strongly associated with poorer verbal learning and memory as well as diagnoses of either multiple or amnestic mild cognitive impairment. Based on univariate correlations, multivariable regressions were performed (controlling for age and total intracranial volume) to determine which modifiable risk factors were associated with hippocampal volume. For the left hippocampus, poor sleep efficiency and greater than five years untreated depressive illness remained significant predictors. For the right hippocampus, diabetes and low diastolic blood pressure significant predictors.

CONCLUSIONS

Although their contribution is small, lower sleep efficiency, low blood pressure, diabetes, and untreated depression are associated with reduced hippocampal volumes. Studies exploring the impact of early intervention for these risk factors on hippocampal integrity are warranted.

Spectroscopic markers of memory impairment, symptom severity and age of onset in older people with lifetime depression: Discrete roles of N-acetyl aspartate and glutamate

BACKGROUND

Glutamate (Glu) and N-acetyl aspartate (NAA) are markers of excitatory processes and neuronal compromise respectively. Increased Glu and decreased NAA concentrations have been implicated in the pathophysiology of depression and cognitive impairment respectively.

OBJECTIVE

To determine the relationship between NAA, Glu, memory and key clinical features in older people with lifetime depression compared to comparison subjects.

METHOD

Thirty-five health-seeking older adults (mean age=63.57 years), with a lifetime depression diagnosis, and 21 age-matched healthy comparison subjects (mean age=65.48 years) underwent neuropsychological testing, psychiatric assessment and proton magnetic resonance spectroscopy from which Glu and NAA were measured (reported as a ratio to creatine).

RESULTS

Compared to comparison subjects, the depressed subjects showed poorer verbal learning and memory retention. Hippocampal NAA and Glu did not differ significantly between groups. However, in comparison subjects, lower levels of hippocampal Glu were associated with poorer memory retention (r=0.55, p=0.018). In the depressed subjects, lower levels of hippocampal NAA were related to poorer verbal learning (r=0.44, p=0.008) and memory retention (r=0.41, p=0.018). Greater hippocampal Glu was associated with more severe depressive symptoms (r=0.35, p=0.039) and an earlier age of illness onset (r=-0.37, p=0.031).

LIMITATIONS

This is a cross sectional study with a heterogeneous group of depressed subjects.

CONCLUSION

Our findings highlight that hippocampal neurometabolites are entwined with both clinical and cognitive features associated with depression in older adults and further suggest that differential mechanisms may underpin these features.

Mild Cognitive Impairment Subtypes in Older People With Depressive Symptoms: Relationship With Clinical Variables and Hippocampal Change

AIMS

To examine the rates and clinical characteristics of mild cognitive impairment (MCI) in older people with depressive symptoms and to determine the relative contribution of hippocampal volume and MCI to memory change.

METHOD

One hundred and fifty-two participants with lifetime Major Depression and remitted or mild symptoms and 28 healthy controls underwent psychiatric and neuropsychological assessments. Magnetic resonance imaging was also conducted in a subset of the patients (n = 81) and healthy controls (n = 18).

RESULTS

MCI was diagnosed in 75.7% of the patients and was associated with increasing age, medical burden, vascular risk factors, later age of depression onset and smaller hippocampi. Multiple regression showed that both hippocampal volume and MCI diagnosis mediate memory performance in depression.

CONCLUSIONS

MCI occurs in older adults with a history of depression and is not simply due to symptom severity. Memory change is linked to underlying hippocampal atrophy in this patient group.

Oxidative stress and depressive symptoms in older adults: A magnetic resonance spectroscopy study

Major depression is common in older adults and associated with greater health care utilisation and increased risk of poor health outcomes. Oxidative stress may be implicated in the pathophysiology of depression and can be measured via the neurometabolite glutathione using proton magnetic resonance spectroscopy ((1)H-MRS). This study aimed to examine the relationship between glutathione concentration and depressive symptom severity in older adults 'at-risk' of depression. In total, fifty-eight older adults considered 'at-risk' of depression (DEP) and 12 controls underwent (1)H-MRS, medical and neuropsychological assessments. Glutathione was measured in the anterior cingulate cortex (ACC), and calculated as a ratio to creatine. Depressive and anxiety symptoms were assessed using the Hospital Anxiety and Depression Scale (HADS). Compared to controls, DEP patients had increased glutathione/creatine ratios in the ACC (t=2.7, p=0.012). In turn, these increased ratios were associated with greater depressive symptoms (r=0.28, p=0.038), and poorer performance on a verbal learning task (r=-0.28, p=0.040). In conclusion, depressive symptoms in older people are associated with increased glutathione in the ACC. Oxidative stress may be pathophysiologically linked to illness development and may represent an early compensatory response. Further research examining the utility of glutathione as a marker for depressive symptoms and cognitive decline is now required.

The Beyond Ageing Project Phase 2--a double-blind, selective prevention, randomised, placebo-controlled trial of omega-3 fatty acids and sertraline in an older age cohort at risk for depression: study protocol for a randomized controlled trial

BACKGROUND

Late-life depression is associated with high rates of morbidity, premature mortality, disability, functional decline, caregiver burden and increased health care costs. While clinical and public health approaches are focused on prevention or early intervention strategies, the ideal method of intervention remains unclear. No study has set out to evaluate the role of neurobiological agents in preventing depressive symptoms in older populations at risk of depression.

METHODS/DESIGN

Subjects with previously reported sub-threshold depressive symptoms, aged 60 to 74 years, will be screened to participate in a single-centre, double-blind, randomised controlled trial with three parallel groups involving omega-3 fatty acid supplementation or sertraline hydrochloride, compared with matching placebo. Subjects will be excluded if they have current depression or suicide ideation; are taking antidepressants or any supplement containing omega-3 fatty acid; or have a prior history of stroke or other serious cerebrovascular or cardiovascular disease, neurological disease, significant psychiatric disease (other than depression) or neurodegenerative disease. The trial will consist of a 12 month treatment phase with follow-up at three months and 12 months to assess outcome events. At three months, subjects will undergo structural neuroimaging to assess whether treatment effects on depressive symptoms correlate with brain changes. Additionally, proton spectroscopy techniques will be used to capture brain-imaging markers of the biological effects of the interventions. The trial will be conducted in urban New South Wales, Australia, and will recruit a community-based sample of 450 adults. Using intention-to-treat methods, the primary endpoint is an absence of clinically relevant depression scores at 12 months between the omega-3 fatty acid and sertraline interventions and the placebo condition.

DISCUSSION

The current health, social and economic costs of late-life depression make prevention imperative from a public health perspective. This innovative trial aims to address the long-neglected area of prevention of depression in older adults. The interventions are targeted to the pathophysiology of disease, and regardless of the effect size of treatment, the outcomes will offer major scientific advances regarding the neurobiological action of these agents. The main results are expected to be available in 2017.

TRIAL REGISTRATION

Australian and New Zealand Clinical Trials Registry ACTRN12610000032055 (12 January 2010).

Cluster analysis reveals abnormal hippocampal neurometabolic profiles in young people with mood disorders

While numerous studies have employed magnetic resonance spectroscopy (MRS) to determine in vivo neurometabolite levels associated with mood disorders the findings in both unipolar depression and bipolar disorder have been mixed. Data-driven studies may shed new light on this literature by identifying distinct subgroups of patients who may benefit from different treatment strategies. The objective of the present study was to utilize hierarchical cluster analysis in order to generate new hypotheses with respect to neurometabolic profiling of mood disorder. Participants were 165 young persons (18-30 yrs) with a mood disorder and 40 healthy controls. Neurometabolite levels were recorded via proton-MRS ((1)H MRS). The ratios (relative to creatine) of glutamate (GLU), N-acetyl aspartate (NAA) and myo-inositol (MI) measured within the hippocampus. Self-reported and clinician rated symptoms as well as cognition were also measured. The unipolar depression (N=90) and bipolar disorder (N=75) groups did not significantly differ (from each other or controls) in their levels of GLU, NAA or MI. Cluster analyses derived four subgroups of patients who were distinguished by all three metabolites. There was a pattern of positive association between NAA and GLU, whereby clusters were abnormally increased (clusters 1, 2) or normal (cluster 4) or abnormally decreased (cluster 3) in these neurometabolites. These findings suggest that there are neurometabolic abnormalities in subgroups of young people with mood disorder, which may occur despite diagnostic similarities. Such evidence highlights that the underlying neurobiology of mood disorder is complex and MRS may have unique utility in delineating underlying neurobiology and targeting treatment strategies.

Delayed circadian phase is linked to glutamatergic functions in young people with affective disorders: a proton magnetic resonance spectroscopy study

BACKGROUND

While the association between affective disorders and sleep and circadian disturbance is well established, little is known about the neurobiology underpinning these relationships. In this study, we sought to determine the relationship between a marker of circadian rhythm and neuronal integrity (N-Acetyl Aspartate, NAA), oxidative stress (glutathione, GSH) and neuronal-glial dysfunction (Glutamate + Glutamine, Glx).

METHODS

Fifty-three young adults (age range 15-33 years, mean = 21.8, sd = 4.3) with emerging affective disorders were recruited from a specialized tertiary referral service. Participants underwent clinical assessment and actigraphy monitoring, from which sleep midpoint was calculated as a marker of circadian rhythm. Proton magnetic resonance spectroscopy was performed in the anterior cingulate cortex (ACC). The metabolites NAA, GSH and Glx were obtained, and expressed as a ratio to Creatine.

RESULTS

Neither NAA or GSH were associated with sleep midpoint. However, higher levels of ACC Glx were associated with later sleep midpoints (rho = 0.35, p = 0.013). This relationship appeared to be independent of age and depression severity.

CONCLUSIONS

This study is the first to demonstrate that delayed circadian phase is related to altered glutamatergic processes. It is aligned with animal research linking circadian rhythms with glutamatergic neurotransmission as well as clinical studies showing changes in glutamate with sleep interventions. Further studies may seek to examine the role of glutamate modulators for circadian misalignment.

Sleep quality in healthy older people: relationship with ¹H magnetic resonance spectroscopy markers of glial and neuronal integrity

The hippocampus and thalamus assume a significant role in the overnight consolidation of memories, a process that is negatively impacted by sleep disruption. Emerging evidence suggests that disturbances of sleep in older people may co-occur with underlying neurobiological changes. This study sought to assess glial and neuronal integrity in these regions in relation to subjective sleep disturbance in a healthy older sample. Forty-three healthy older people (mean age = 70, SD = 5.0) were assessed clinically and medically and screened for cognitive and depressive symptoms, as well as sleep disturbance. Single voxel hippocampal and thalamus metabolite ratios of N-acetyl aspartate (NAA) and myo-inositol (mI) with total creatine (Cr + PCr) were measured using magnetic resonance spectroscopy at 3-Tesla. Higher hippocampal mI/Cr + PCr ratios were significantly correlated with poorer self-reported sleep quality (r = .42, p < .01) and less sleep efficiency (r = -0.42, p < .01) as recorded by the Pittsburgh Sleep Quality Index (Buysse, Reynolds, Monk, Berman, & Kupfer, 1989). No other significant correlations were observed within the hippocampus or within the thalamus. These results indicate that in healthy older people, subjective sleep disturbance may be associated with glial alterations in the hippocampus. Future research is now needed to examine these associations with respect to objective sleep measures and overnight memory consolidation.

Cognitive impairment with and without depression history: an analysis of white matter microstructure

BACKGROUND

Mild cognitive impairment (MCI) and late-life depression are clinical syndromes that often co-occur and may represent an early manifestation of neurodegenerative disease. The present study examined white matter microstructure in patients with MCI with and without a history of major depression compared with healthy controls.

METHODS

Older adults with MCI and no history of major depression (MCI), adults with MCI and euthymic major depression (MCI-MD) and healthy controls underwent comprehensive medical, psychiatric and neuropsychological assessments. Participants also underwent diffusion tensor imaging, which was analyzed using tract-based spatial statistics. White matter hyperintensity (WMH) burden and medical burden were also quantified.

RESULTS

We enrolled 30 participants in the MCI group, 36 in the MCI-MD group and 22 in the control group. Compared with controls, participants in the MCI group had significantly reduced fractional anisotropy (FA) in the corpus callosum, superior longitudinal fasciculus (SLF), corona radiata and posterior thalamic radiation. Participants in the MCI-MD group had significantly reduced FA in the corpus callosum, internal capsule, external capsule, corona radiata, posterior thalamic radiation, sagittal striatum, fornix, SLF, uncinate fasciculus and right cingulum compared with controls. No significant differences in FA were observed between the MCI and MCI-MD groups. Participants in the MCI-MD group had greater medical burden (p = 0.020) and WMH burden than controls (p = 0.013).

LIMITATIONS

Study limitations include the cross-sectional design and antidepressant medication use.

CONCLUSION

To our knowledge, this study is the first to compare white matter microstructure in patients with MCI with and without a history of major depression and suggests that a common underlying structural white matter change may underpin cognitive impairment in both MCI groups. Further research is needed to delineate the pathophysiological mechanisms underlying these microstructural changes.

Deficits in episodic memory retrieval reveal impaired default mode network connectivity in amnestic mild cognitive impairment

Amnestic mild cognitive impairment (aMCI) is believed to represent a transitional stage between normal healthy ageing and the development of dementia. In particular, aMCI patients have been shown to have higher annual transition rates to Alzheimer's Disease (AD) than individuals without cognitive impairment. Despite intensifying interest investigating the neuroanatomical basis of this transition, there remain a number of questions regarding the pathophysiological process underlying aMCI itself. A number of recent studies in aMCI have shown specific impairments in connectivity within the default mode network (DMN), which is a group of regions strongly related to episodic memory capacities. However to date, no study has investigated the integrity of the DMN between patients with aMCI and those with a non-amnestic pattern of MCI (naMCI), who have cognitive impairment, but intact memory storage systems. In this study, we contrasted the DMN connectivity in 24 aMCI and 33 naMCI patients using seed-based resting state fMRI. The two groups showed no statistical difference in their DMN intra-connectivity. However when connectivity was analysed according to performance on measures of episodic memory retrieval, the two groups were separable, with aMCI patients demonstrating impaired functional connectivity between the hippocampal formation and the posterior cingulate cortex. We provide evidence that this lack of connectivity is driven by impaired communication from the posterior cingulate hub and does not simply represent hippocampal atrophy, suggesting that posterior cingulate degeneration is the driving force behind impaired DMN connectivity in aMCI.

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First trial to explore Default Mode Network (DMN) connectivity between MCI and naMCI

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Amnestic and nonamnestic MCI groups show similar overall DMN intra-connectivity.

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aMCI patients have connectivity deficits related to impaired memory retention.

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Impaired DMN connectivity is driven by deficits in posterior cingulate cortex.

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Alzheimer’s disease pathology likely evolves from PCC to hippocampus

Colorimetric assay to quantify macromolecule diffusion across endothelial monolayers

Endothelial "capillary leak", the loss of vascular integrity in response to noxious stimuli, is characterized by extravasation of protein-richfluidfrom capillary lumen into surrounding tissue interstitium. This increase in vascular permeability, in response to inflammatory mediators, correlates with endothelial cell contraction and the formation of intercellular gaps within the monolayer. However, in vivo assessment of paracellular solute flow between endothelial cells may be complicated by multiple uncontrolled parameters. In vitro examinations of endothelial barrier leak have relied on electrical impedence or macromolecule diffusion techniques to determine the details pertinent to capillary barrier function. In this report, a simple, sensitive, nonradioactive, colorimetric assay to quantify the leak of a labeled protein marker across endothelial monolayers is described. This procedure avoids the hazards of radioisotope labels and the technical limitations of electrical resistance technology.

Thrombin-mediated permeability of human microvascular pulmonary endothelial cells is calcium dependent

BACKGROUND

In response to inflammation, endothelial cytoskeleton rearrangement, cell contraction, and intercellular gap formation contribute to a loss of capillary barrier integrity and resultant interstitial edema formation. The intracellular signals controlling these events are thought to be dependent on intracellular calcium concentration ([Ca2+]i). We hypothesized that, in human pulmonary microvascular endothelial cells, a thrombin-induced increase in permeability to albumin would be dependent on Ca2+i and subsequent actin cytoskeleton rearrangements.

METHODS

Human lung microvascular endothelial cells, grown on 0.4 micromol/L pore membranes, were activated with 10 nmol/L human thrombin in Hank's balanced salt solution/0.5% fetal bovine serum. Select cultures were pretreated (45 minutes) with 4 micromol Fura-2/AM to chelate Ca2+i. Permeability was assessed as diffusion of bovine serum albumin/biotin across the monolayer. Similarly treated cells were stained with rhodamine-phalloidin to demonstrate actin cytoskeletal morphology. Separately, cells loaded 2 micromol Fura-2/AM were assessed at OD340/380nm after thrombin exposure to detect free Ca2+i.

RESULTS

Intracellular Ca2+ levels increased 15-fold (2 seconds) and fell to baseline (10 minutes) after thrombin. Permeability increased 10-fold (30 minutes), and a shift from cortical to actin stress fiber morphology was observed. Chelation of Ca2+i diminished permeability to baseline and reduced the percentage of cells exhibiting stress fiber formation.

CONCLUSION

Thrombin stimulates pulmonary capillary leak by affecting the barrier function of activated pulmonary endothelial cells. These data demonstrate a thrombin-stimulated increase in monolayer permeability, and cytoskeletal F-actin stress fibers were, in part, regulated by endothelial Ca2+i. This early, transient rise in Ca2+i likely activates downstream pathways that more directly affect the intracellular endothelial structural changes that control vascular integrity.

A simple high-performance liquid chromatography assay for the major cisapride metabolite, norcisapride, in human urine

A simple high-performance liquid chromatography assay using fluorescence detection for the major metabolite of the gastric prokinetic drug cisapride, norcisapride, is presented. Analysis is performed using an Alltech Platinum EPS C8 column with a mobile phase made up of methanol and 0.02M sodium dihygrogen phosphate (45:55, v/v) containing triethylamine (1 g/L). Complete resolution is achieved among norcisapride, the internal standard (metoclopramide), and endogenous urinary components. The assay is linear over the range 50-2000 ng/mL with a mean recovery of 71.2% across the analytical range following solvent extraction with toluene-isoamyl alcohol (95:5, v/v). Intraday coefficients of variation (precision) determined at 200 and 1000 ng/mL are 6.0 and 9.8%, respectively, and interday coefficients of variation are 8.8 and 6.6%, respectively. Intra- and interassay accuracy (as mean relative error) determined at the same concentrations is within 10% in all cases. An analysis of urine samples from a healthy volunteer following the administration of a single 10-mg oral dose of cisapride is shown.