Jac Kee Low

Bio: Jac Kee Low is an academic researcher from Deakin University. The author has contributed to research in topics: Kidney transplantation & Randomized controlled trial. The author has an hindex of 12, co-authored 29 publications receiving 679 citations. Previous affiliations of Jac Kee Low include Mental Health Research Institute & Monash University, Clayton campus.

Deletion of Abca7 increases cerebral amyloid-β accumulation in the J20 mouse model of Alzheimer's disease.

Abstract: ATP-binding cassette transporter A7 (ABCA7) is expressed in the brain and has been detected in macrophages, microglia, and neurons. ABCA7 promotes efflux of lipids from cells to apolipoproteins and can also regulate phagocytosis and modulate processing of amyloid precursor protein (APP) to generate the Alzheimer's disease (AD) amyloid-β (Aβ) peptide. Genome-wide association studies have indicated that ABCA7 single nucleotide polymorphisms confer increased risk for late-onset AD; however, the role that ABCA7 plays in the brain in the AD context is unknown. In the present study, we crossed ABCA7-deficient (A7(-/-)) mice with J20 amyloidogenic mice to address this issue. We show that ABCA7 loss doubled insoluble Aβ levels and thioflavine-S-positive plaques in the brain. This was not related to changes in APP processing (assessed by analysis of full-length APP and the APP β C-terminal fragment). Apolipoprotein E regulates cerebral Aβ homeostasis and plaque load; however, the apolipoprotein E concentration was not altered by ABCA7 loss. Spatial reference memory was significantly impaired in both J20 and J20/A7(-/-) mice compared with wild-type mice; however, there were no cognitive differences between J20 and J20/A7(-/-) mice. There were also no major differences detected in hippocampal or plaque-associated microglial/macrophage markers between J20 and J20/A7(-/-) mice, whereas the capacity for bone marrow-derived macrophages derived from A7(-/-) mice to take up oligomeric Aβ was reduced by 51% compared with wild-type mice. Our results suggest that ABCA7 plays a role in the regulation of Aβ homeostasis in the brain and that this may be related to altered phagocyte function.

Interventions to improve medication adherence in adult kidney transplant recipients: a systematic review

Abstract: Background In kidney transplantation, adherence to immunosuppressive therapy is paramount for long-term graft survival. This systematic review aimed to assess the effectiveness of interventions to improve medication adherence in adult kidney transplantation. Methods Eight electronic databases were searched from inception to November 2013. Only primary intervention studies, which reported measurement of adherence to immunosuppressive medications after kidney transplantation, were included. The quality of all studies was assessed using the Consolidated Standards of Reporting Trials and Transparent Reporting of Evaluations with Non-randomized Designs checklists. A synthesis was undertaken to tease out the domains targeted by interventions: (i) educational/cognitive, (ii) counselling/behavioural, (iii) psychologic/affective and (iv) financial support. For each study, key information, such as population, location, methods of measurements, comparison group, type of intervention and outcomes, were extracted and tabulated. Results Twelve intervention studies were identified. Quality of studies ranged from 16.0 to 80.5%. Effective interventions were implemented for 3, 6 and 12 months. Medication adherence rates were greatly enhanced when multidimensional interventions were implemented whereas one-off feedback from a nurse and financial assistance programmes offered little improvement. Dose administration aids when used in conjunction with self-monitoring also improved adherence. The number of patients who had a drug holiday (at least 1-day interval without a dose) was higher in a once-daily regimen than a twice-daily regimen. Conclusions The findings of this review suggest an intervention targeting behavioural risk factors or a combination of behavioural, educational and emotional changes is effective in enhancing medication adherence. Effectiveness of an intervention may be further enhanced if patients are encouraged to participate in the development process.

Chronic cannabidiol treatment improves social and object recognition in double transgenic APPswe/PS1∆E9 mice.

Abstract: Patients suffering from Alzheimer’s disease (AD) exhibit a decline in cognitive abilities including an inability to recognise familiar faces. Hallmark pathological changes in AD include the aggregation of amyloid-β (Aβ), tau protein hyperphosphorylation as well as pronounced neurodegeneration, neuroinflammation, neurotoxicity and oxidative damage. The non-psychoactive phytocannabinoid cannabidiol (CBD) exerts neuroprotective, anti-oxidant and anti-inflammatory effects and promotes neurogenesis. CBD also reverses Aβ-induced spatial memory deficits in rodents. Thus we determined the therapeutic-like effects of chronic CBD treatment (20 mg/kg, daily intraperitoneal injections for 3 weeks) on the APPswe/PS1∆E9 (APPxPS1) transgenic mouse model for AD in a number of cognitive tests, including the social preference test, the novel object recognition task and the fear conditioning paradigm. We also analysed the impact of CBD on anxiety behaviours in the elevated plus maze. Vehicle-treated APPxPS1 mice demonstrated impairments in social recognition and novel object recognition compared to wild type-like mice. Chronic CBD treatment reversed these cognitive deficits in APPxPS1 mice without affecting anxiety-related behaviours. This is the first study to investigate the effect of chronic CBD treatment on cognition in an AD transgenic mouse model. Our findings suggest that CBD may have therapeutic potential for specific cognitive impairments associated with AD.

Diet-induced adaptive thermogenesis requires neuropeptide FF receptor-2 signalling.

Abstract: Excess caloric intake results in increased fat accumulation and an increase in energy expenditure via diet-induced adaptive thermogenesis; however, the underlying mechanisms controlling these processes are unclear. Here we identify the neuropeptide FF receptor-2 (NPFFR2) as a critical regulator of diet-induced thermogenesis and bone homoeostasis. Npffr2−/− mice exhibit a stronger bone phenotype and when fed a HFD display exacerbated obesity associated with a failure in activating brown adipose tissue (BAT) thermogenic response to energy excess, whereas the activation of cold-induced BAT thermogenesis is unaffected. NPFFR2 signalling is required to maintain basal arcuate nucleus NPY mRNA expression. Lack of NPFFR2 signalling leads to a decrease in BAT thermogenesis under HFD conditions with significantly lower UCP-1 and PGC-1α levels in the BAT. Together, these data demonstrate that NPFFR2 signalling promotes diet-induced thermogenesis via a novel hypothalamic NPY-dependent circuitry thereby coupling energy homoeostasis with energy partitioning to adipose and bone tissue.

The amyloid hypothesis of Alzheimer's disease at 25 years

Abstract: Despite continuing debate about the amyloid β‐protein (or Aβ hypothesis, new lines of evidence from laboratories and clinics worldwide support the concept that an imbalance between production and clearance of Aβ42 and related Aβ peptides is a very early, often initiating factor in Alzheimer9s disease (AD). Confirmation that presenilin is the catalytic site of γ‐secretase has provided a linchpin: all dominant mutations causing early‐onset AD occur either in the substrate (amyloid precursor protein, APP) or the protease (presenilin) of the reaction that generates Aβ. Duplication of the wild‐type APP gene in Down9s syndrome leads to Aβ deposits in the teens, followed by microgliosis, astrocytosis, and neurofibrillary tangles typical of AD. Apolipoprotein E4, which predisposes to AD in > 40% of cases, has been found to impair Aβ clearance from the brain. Soluble oligomers of Aβ42 isolated from AD patients9 brains can decrease synapse number, inhibit long‐term potentiation, and enhance long‐term synaptic depression in rodent hippocampus, and injecting them into healthy rats impairs memory. The human oligomers also induce hyperphosphorylation of tau at AD‐relevant epitopes and cause neuritic dystrophy in cultured neurons. Crossing human APP with human tau transgenic mice enhances tau‐positive neurotoxicity. In humans, new studies show that low cerebrospinal fluid (CSF) Aβ42 and amyloid‐PET positivity precede other AD manifestations by many years. Most importantly, recent trials of three different Aβ antibodies (solanezumab, crenezumab, and aducanumab) have suggested a slowing of cognitive decline in post hoc analyses of mild AD subjects. Although many factors contribute to AD pathogenesis, Aβ dyshomeostasis has emerged as the most extensively validated and compelling therapeutic target.

Using mice to model Alzheimer's dementia: an overview of the clinical disease and the preclinical behavioral changes in 10 mouse models.

Abstract: The goal of this review is to discuss how behavioral tests in mice relate to the pathological and neuropsychological features seen in human Alzheimer’s disease (AD), and present a comprehensive analysis of the temporal progression of behavioral impairments in commonly used AD mouse models that contain mutations in amyloid precursor protein. We provide a brief overview of neuropathological changes seen in AD brain, and some of the clinical neuropsychological assessments used to measure cognitive deficits. This is followed by a critical assessment of behavioral tasks that are used in AD mice to model the cognitive changes seen in humans. Behavioral tests discussed include spatial memory tests (Morris water maze, radial arm water maze, Barnes maze), associative learning tasks (passive avoidance, fear conditioning), alternation tasks (Y-Maze/T-Maze), recognition memory tasks (Novel Object Recognition), attentional tasks (3 & 5 choice serial reaction time), set-shifting tasks, and reversal learning tasks. We discuss the strengths and weaknesses of each of these tests, and how they may correlate with clinical assessments in humans. Finally, the temporal progression of both cognitive and non-cognitive deficits in ten AD mouse models (PDAPP, TG2576, APP23, TgCRND8, J20, APP/PS1, TG2576 + PS1(M146L), APP/PS1 KI, 5xFAD and 3xTg-AD) are discussed. Mouse models of AD and the behavioral tasks used in conjunction with those models are immensely important in contributing to our knowledge of disease progression, and are useful tools to study AD pathophysiology and the resulting cognitive deficits. However, investigators need to be aware of the potential weaknesses of the available preclinical models in terms of their ability to model cognitive changes observed in human AD. It is our hope that this review will assist investigators in selecting an appropriate mouse model, and accompanying behavioral paradigms to investigate different aspects of AD pathology and disease progression.

Eliminating microglia in Alzheimer’s mice prevents neuronal loss without modulating amyloid-β pathology

Abstract: In addition to amyloid-β plaque and tau neurofibrillary tangle deposition, neuroinflammation is considered a key feature of Alzheimer's disease pathology. Inflammation in Alzheimer's disease is characterized by the presence of reactive astrocytes and activated microglia surrounding amyloid plaques, implicating their role in disease pathogenesis. Microglia in the healthy adult mouse depend on colony-stimulating factor 1 receptor (CSF1R) signalling for survival, and pharmacological inhibition of this receptor results in rapid elimination of nearly all of the microglia in the central nervous system. In this study, we set out to determine if chronically activated microglia in the Alzheimer's disease brain are also dependent on CSF1R signalling, and if so, how these cells contribute to disease pathogenesis. Ten-month-old 5xfAD mice were treated with a selective CSF1R inhibitor for 1 month, resulting in the elimination of ∼80% of microglia. Chronic microglial elimination does not alter amyloid-β levels or plaque load; however, it does rescue dendritic spine loss and prevent neuronal loss in 5xfAD mice, as well as reduce overall neuroinflammation. Importantly, behavioural testing revealed improvements in contextual memory. Collectively, these results demonstrate that microglia contribute to neuronal loss, as well as memory impairments in 5xfAD mice, but do not mediate or protect from amyloid pathology.