Divergent metabolic regulation of autophagy and mTORC1-early events in Alzheimer's disease?

© 2017 Shafei, Harris and Conway. Alzheimer's disease (AD) is a progressive disease associated with the production and deposition of amyloid β-peptide (Aβ) aggregates and neurofibrillary tangles, which lead to synaptic and neuronal damage. Reduced autophagic flux has been widely associated with the accumulation of autophagic vacuoles (AV), which has been proposed to contribute to aggregate build-up observed in AD. As such, targeting autophagy regulation has received wide review, where an understanding as to how this mechanism can be controlled will be important to neuronal health. The mammalian target of rapamycin complex 1 (mTORC1), which was found to be hyperactive in AD brain, regulates autophagy and is considered to be mechanistically important to aberrant autophagy in AD. Hormones and nutrients such as insulin and leucine, respectively, positively regulate mTORC1 activation and are largely considered to inhibit autophagy. However, in AD brain there is a dysregulation of nutrient metabolism, linked to insulin resistance, where a role for insulin treatment to improve cognition has been proposed. Recent studies have highlighted that mitochondrial proteins such as glutamate dehydrogenase and the human branched chain aminotransferase protein, through metabolism of leucine and glutamate, differentially regulate mTORC1 and autophagy. As the levels of the hBCAT proteins are significantly increased in AD brain relative to aged-matched controls, we discuss how these metabolic pathways offer new potential therapeutic targets. In this review article, we highlight the core regulation of autophagy through mTORC1, focusing on how insulin and leucine will be important to consider in particular with respect to our understanding of nutrient load and AD pathogenesis

Hypoxia modulates the stem cell population and induces EMT in the MCF-10A breast epithelial cell line

A common feature among pre-malignant lesions is the induction of hypoxia through increased cell propagation and reduced access to blood flow. Hypoxia in breast cancer has been associated with poor patient prognosis, resistance to chemotherapy and increased metastasis. Although hypoxia has been correlated with factors associated with the latter stages of cancer progression, it is not well documented how hypoxia influences cells in the earliest stages of transformation. Using the immortalized MCF-10A breast epithelial cell line, we used hypoxic culture conditions to mimic reduced O2 levels found within early pre-malignant lesions and assessed various cellular parameters. In this non-transformed mammary cell line, O2 deprivation led to some changes not immediately associated with cancer progression, such as decreased proliferation, cell cycle arrest and increased apoptosis. In contrast, hypoxia did induce other changes more consistent with an increased metastatic potential. A rise in the CD44+CD24-/low-labeled cell sub-population along with increased colony forming capability indicated an expanded stem cell population. Hypoxia also induced cellular and molecular changes consistent with an epithelial-to-mesenchymal transition (EMT). Furthermore, these cells now exhibited increased migratory and invasive abilities. These results underscore the contribution of the hypoxic tumour microenvironment in cancer progression and dissemination

Differential expression of the BCAT isoforms between breast cancer subtypes

© 2020, The Author(s). Background: Biological characterisation of breast cancer subtypes is essential as it informs treatment regimens especially as different subtypes have distinct locoregional patterns. This is related to metabolic phenotype, where altered cellular metabolism is a fundamental adaptation of cancer cells during rapid proliferation. In this context, the metabolism of the essential branched-chain amino acids (BCAAs), catalysed by the human branched-chain aminotransferase proteins (hBCAT), offers multiple benefits for tumour growth. Upregulation of the cytosolic isoform of hBCAT (hBCATc), regulated by c-Myc, has been demonstrated to increase cell migration, tumour aggressiveness and proliferation in gliomas, ovarian and colorectal cancer but the importance of the mitochondrial isoform, hBCATm has not been fully investigated. Methods: Using immunohistochemistry, the expression profile of metabolic proteins (hBCAT, IDH) was assessed between breast cancer subtypes, HER2 + , luminal A, luminal B and TNBC. Correlations between the percentage and the intensity of protein expression/co-expression with clinical parameters, such as hormone receptor status, tumour stage, lymph-node metastasis and survival, were determined. Results: We show that hBCATc expression was found to be significantly associated with the more aggressive HER2 + and luminal B subtypes, whilst hBCATm and IDH1 associated with luminal A subtype. This was concomitant with better prognosis indicating a differential metabolic reliance between these two subtypes, in which enhanced expression of IDH1 may replenish the α-ketoglutarate pool in cells with increased hBCATm expression. Conclusion: The cytosolic isoform of BCAT is associated with tumours that express HER2 receptors, whereas the mitochondrial isoform is highly expressed in tumours that are ER + , indicating that the BCAT proteins are regulated through different signalling pathways, which may lead to the identification of novel targets for therapeutic applications targeting dysregulated cancer metabolism

Voltammetric behaviour of hydrogen peroxide at a silver electrode fabricated from a rewritable digital versatile disc (DVD) and its determination in water samples

In this study we investigated the possibility of applying Ag electrodes manufactured from recordable rewritable digital versatile discs (DVD-RW) for the voltammetric determination of hydrogen peroxide. The calibration plot was linear from 0.087 mM to 3.41 mM hydrogen peroxide with a sensitivity of 58.7 μA mM-1 over this range. A corresponding detection limit of 78.35 μM, based on a signal-to-noise-ratio of 3 was recorded. No interferences were observed by 500 mg L-1 chloride, 50 mg L-1 nitrate, 700 mg L-1 sulphate or 700 mg L-1 carbonate which are found in swimming pool water at these concentrations. Using the multiple standard addition method a percentage recovery of 90.67% with a coefficient of variation of 4.69% (n = 5) was found for a representative swimming pool water concentration of 1.2 mM hydrogen peroxide. Therefore, the performance data suggests that the method is reliable at the concentrations examined in this study and that a rapid, simple, economical and precise method of monitoring hydrogen peroxide in swimming pool and aquaculture applications is possible. © 2013 The Royal Society of Chemistry

The role of hBCATc in breast cancer progression through IGF-1 and insulin signalling cascades

Introduction and Aims:Breast cancer remains the leading cause of cancer mortality in women globally, despite advances in the development of targeted therapies. Driven by oncogenic signals, cancer cells undergo metabolic reprogramming, upregulating metabolite transporters and shuttling nutrients to promote proliferation and migration. The expression of key metabolic enzymes involved in BCAA metabolism (hBCATc and hBCATm), isocitrate dehydrogenase (IDH1 and IDH2) and serine metabolism (PHGDH) have been demonstrated to be upregulated in breast cancer. However, the expression patterns and the role of these metabolic proteins in breast cancer tumourigenesis remains to be elucidated. This research hypothesises that these metabolic pathways converge in tumour cells, whereby particular metabolic pathways are favoured differentially between breast cancer subtypes, which could lead to the identification of novel therapeutic targets. In breast cancer insulin/IGF-1 signalling has been demonstrated to contribute to tumourigenesis through the activation of growth signalling effectors which is mediated by two chief pathways: Akt/mTOR and RAS/MAPK. As nutrient levels of BCAAs particularly leucine, substrates of hBCAT, regulate the mTOR pathway hBCAT was hypothesised to play a role in the regulation of proliferation and migration of triple-negative breast cancer (TNBC) cells through the IGF-1 and insulin signalling pathways. Methods:Using immunohistochemistry, the expression profile of the metabolic proteins was assessed between breast cancer subtypes. The impact of hBCATc expression on proliferation, migration, invasion, apoptosis and modulation of PI3K/Akt and RAS/MAPK signalling was assessed using molecular biological investigations, Western blot and confocal analysis. Results and discussion:Using serial sections, hBCATm was found to be significantly associated with IDH1 expression, indicating that these two metabolic pathways are activated concomitantly. Expression of hBCATm and IDH1 correlated with luminal A breast cancer and smaller breast tumours, indicating better prognosis. Differentially, hBCATc expression was found to be significantly associated with the more aggressive HER2+ and TNBC subtypes. For the first time, knockdown of hBCATc was demonstrated to significantly reduce insulin and IGF-1-mediated proliferation, migration and invasion in TNBC cells. An analysis of this pathway showed that when overexpressed hBCATc regulates proliferation through the PI3K/Akt/mTO axis, whilst simultaneously attenuating the Ras/MAPK pathway, indicating that hBCATc acts as a conduit between these two pathways. Overexpression of hBCATc ultimately led to the increase in FOXO3a, Nrf2 and GRP78, which play fundamental roles in cell proliferation, cell survival and protein folding. Therefore, hBCATc has been demonstrated to provide TNBC cells with metabolic plasticity to alter dependence on the RAS/MAPK and PI3K/Akt/mTOR signalling cascades, in response to IGF-1/insulin, to promote tumour survival and progression

Altered phobic reactions in frontotemporal dementia: A behavioural and neuroanatomical analysis

Introduction: Abnormal behavioural and physiological reactivity to emotional stimuli is a hallmark of frontotemporal dementia (FTD), particularly the behavioural variant (bvFTD). As part of this repertoire, altered phobic responses have been reported in some patients with FTD but are poorly characterised. Methods: We collected data (based on caregiver reports) concerning the prevalence and nature of any behavioural changes related to specific phobias in a cohort of patients representing canonical syndromes of FTD and Alzheimer's disease (AD), relative to healthy older controls. Neuroanatomical correlates of altered phobic reactivity were assessed using voxel-based morphometry. Results: 46 patients with bvFTD, 20 with semantic variant primary progressive aphasia, 25 with non-fluent variant primary progressive aphasia, 29 with AD and 55 healthy age-matched individuals participated. Changes in specific phobia were significantly more prevalent in the combined FTD cohort (15.4% of cases) and in the bvFTD group (17.4%) compared both to healthy controls (3.6%) and patients with AD (3.5%). Attenuation of phobic reactivity was reported for individuals in all participant groups, however new phobias developed only in the FTD cohort. Altered phobic reactivity was significantly associated with relative preservation of grey matter in left posterior middle temporal gyrus, right temporo-occipital junction and right anterior cingulate gyrus, brain regions previously implicated in contextual decoding, salience processing and reward valuation. Conclusion: Altered phobic reactivity is a relatively common issue in patients with FTD, particularly bvFTD. This novel paradigm of strong fear experience has broad implications: clinically, for diagnosis and patient well-being; and neurobiologically, for our understanding of the pathophysiology of aversive sensory signal processing in FTD and the neural mechanisms of fear more generally.Alzheimer's Research UK (ARUK) Brain Research Trust Wolfson Foundation Alzheimer's Society Leonard Wolfson Experimental Neurology Centre Medical Research Council UK (MRC) NIHR UCLH/UCL Biomedical Research Centre Chilean Government (CONICYT PFCHA/Becas Chile) 2017e76180041 Pauline Ashley Action on Hearing Loss-Dunhill Medical Trust Fellowship PA_23 MRC PhD studentships Wellcome Trust Medical Research Council UK (MRC) MR/M018288/1 Medical Research Council UK (MRC) MR/M008525/1 NIHR Rare Disease Translational Research Collaboration BRC149/NS/M