Pharmacogenetics of Ageing and Neurodegeneration

Genetic manipulations and dietary restriction in model organisms have proven that lifespan extension is achievable. Moreover these same interventions can protect against age-related diseases and improve general healthiness. Therefore, current efforts are being put forward to identify drugs that mimic healthy lifespan. Lithium has been documented to be able to extend the lifespan of the worm Caenorhabditis elegans, reduce mortality in Drosophila and a recent report has suggested that lithium concentrations in drinking water correlate with reduced mortality for all causes in a human population. The main objective of the project presented here was to determine the anti-ageing properties of lithium using the fruit fly and to determine the mechanism by which lithium exerts its broad health benefits and anti-ageing properties. My results showed that lithium extended lifespan independent of sex and genetic background. Lithium treated flies were also resistant to multiple stressors and showed reduced triglyceride levels. Lithium did not modify fecundity and it further extended lifespan of DR flies. The pro-longevity effects seemed to also be independent of the nutrient sensing network as it could further extend lifespan of flies with reduced signalling though the insulin/IGF-1 and the mechanistic target of rapamycin (mTOR) network. I performed transcriptional and translational microarrays in lithium treated flies and found out that lithium up-regulated a transcriptional response to stress regulated by the transcription factor cap’n’collar/NRF-2 and down-regulated functional categories implicated in mitochondrial complex I. By performing epistasis experiments I found out that lithium and shaggy, the fly homologue of GSK-3, regulate ageing by acting in the same molecular pathway. However, shaggy seemed to modulate ageing in a tissue-specific manner. The combination of lithium and genetic manipulations of shaggy revealed a very complex regulation of ageing and neurodegeneration. I also explored the nature of neurodegeneration induced by over-expression of Aβ1-42 and found out that some of the changes induced by Aβ1-42 impact general physiology and not only neurons. For example, our results suggest that altered metabolism is a prominent feature of the toxicity of Aβ1-42 in Drosophila

Agephagy – Adapting Autophagy for Health During Aging

Autophagy is a major cellular recycling process that delivers cellular material and entire organelles to lysosomes for degradation, in a selective or non-selective manner. This process is essential for the maintenance of cellular energy levels, components, and metabolites, as well as the elimination of cellular molecular damage, thereby playing an important role in numerous cellular activities. An important function of autophagy is to enable survival under starvation conditions and other stresses. The majority of factors implicated in aging are modifiable through the process of autophagy, including the accumulation of oxidative damage and loss of proteostasis, genomic instability and epigenetic alteration. These primary causes of damage could lead to mitochondrial dysfunction, deregulation of nutrient sensing pathways and cellular senescence, finally causing a variety of aging phenotypes. Remarkably, advances in the biology of aging have revealed that aging is a malleable process: a mild decrease in signaling through nutrient-sensing pathways can improve health and extend lifespan in all model organisms tested. Consequently, autophagy is implicated in both aging and age-related disease. Enhancement of the autophagy process is a common characteristic of all principal, evolutionary conserved anti-aging interventions, including dietary restriction, as well as inhibition of target of rapamycin (TOR) and insulin/IGF-1 signaling (IIS). As an emerging and critical process in aging, this review will highlight how autophagy can be modulated for health improvement

Loss of PLA2G6 leads to elevated mitochondrial lipid peroxidation and mitochondrial dysfunction

© 2015 The Author.The PLA2G6 gene encodes a group VIA calcium-independent phospholipase A2 beta enzyme that selectively hydrolyses glycerophospholipids to release free fatty acids. Mutations in PLA2G6 have been associated with disorders such as infantile neuroaxonal dystrophy, neurodegeneration with brain iron accumulation type II and Karak syndrome. More recently, PLA2G6 was identified as the causative gene in a subgroup of patients with autosomal recessive early-onset dystonia-Parkinsonism. Neuropathological examination revealed widespread Lewy body pathology and the accumulation of hyperphosphorylated tau, supporting a link between PLA2G6 mutations and Parkinsonian disorders. Here we show that knockout of the Drosophila homologue of the PLA2G6 gene, iPLA2-VIA, results in reduced survival, locomotor deficits and organismal hypersensitivity to oxidative stress. Furthermore, we demonstrate that loss of iPLA2-VIA function leads to a number of mitochondrial abnormalities, including mitochondrial respiratory chain dysfunction, reduced ATP synthesis and abnormal mitochondrial morphology. Moreover, we show that loss of iPLA2-VIA is strongly associated with increased lipid peroxidation levels. We confirmed our findings using cultured fibroblasts taken from two patients with mutations in the PLA2G6 gene. Similar abnormalities were seen including elevated mitochondrial lipid peroxidation and mitochondrial membrane defects, as well as raised levels of cytoplasmic and mitochondrial reactive oxygen species. Finally, we demonstrated that deuterated polyunsaturated fatty acids, which inhibit lipid peroxidation, were able to partially rescue the locomotor abnormalities seen in aged flies lacking iPLA2-VIA gene function, and restore mitochondrial membrane potential in fibroblasts from patients with PLA2G6 mutations. Taken together, our findings demonstrate that loss of normal PLA2G6 gene activity leads to lipid peroxidation, mitochondrial dysfunction and subsequent mitochondrial membrane abnormalities. Furthermore we show that the iPLA2-VIA knockout fly model provides a useful platform for the further study of PLA2G6-associated neurodegeneration

A Drosophila

Glucocerebrosidase (GBA1) mutations are associated with Gaucher disease (GD), an autosomal recessive disorder caused by functional deficiency of glucocerebrosidase (GBA), a lysosomal enzyme that hydrolyzes glucosylceramide to ceramide and glucose. Neuronopathic forms of GD can be associated with rapid neurological decline (Type II) or manifest as a chronic form (Type III) with a wide spectrum of neurological signs. Furthermore, there is now a well-established link between GBA1 mutations and Parkinson's disease (PD), with heterozygote mutations in GBA1 considered the commonest genetic defect in PD. Here we describe a novel Drosophila model of GD that lacks the two fly GBA1 orthologs. This knock-out model recapitulates the main features of GD at the cellular level with severe lysosomal defects and accumulation of glucosylceramide in the fly brain. We also demonstrate a block in autophagy flux in association with reduced lifespan, age-dependent locomotor deficits and accumulation of autophagy substrates in dGBA-deficient fly brains. Furthermore, mechanistic target of rapamycin (mTOR) signaling is downregulated in dGBA knock-out flies, with a concomitant upregulation of Mitf gene expression, the fly ortholog of mammalian TFEB, likely as a compensatory response to the autophagy block. Moreover, the mTOR inhibitor rapamycin is able to partially ameliorate the lifespan, locomotor, and oxidative stress phenotypes. Together, our results demonstrate that this dGBA1-deficient fly model is a useful platform for the further study of the role of lysosomal-autophagic impairment and the potential therapeutic benefits of rapamycin in neuronopathic GD. These results also have important implications for the role of autophagy and mTOR signaling in GBA1-associated PD

Plasma irisin is elevated in type 2 diabetes and is associated with increased E-selectin levels

BACKGROUND: Irisin is a hormone released mainly from skeletal muscle after exercise which increases adipose tissue energy expenditure. Adipocytes can also release irisin after exercise, acting as a local adipokine to induce white adipose tissue to take on a brown adipose tissue-like phenotype, suggesting that irisin and its receptor may represent a novel molecular target for the treatment of obesity and obesity-related diabetes. Previous reports provide conflicting evidence regarding circulating irisin levels in patients with type 2 diabetes (T2DM). METHODS: This study investigated plasma irisin concentrations in 79 T2DM individuals, assessing potential associations with measures of segmental body composition, markers of endothelial dysfunction and peripheral blood mononuclear cell telomere length (TL). RESULTS: Resting, overnight-fasted plasma irisin levels were significantly higher in this group of T2DM patients compared with levels we previously reported in healthy volunteers (p < 0.001). Moreover, plasma irisin displayed a positive correlation with body mass index (p = 0.04), body fat percentage (p = 0.03), HbA1c (p = 0.03) and soluble E-selectin (p < 0.001). A significant negative association was observed between plasma irisin and visceral adiposity (p = 0.006) in T2DM patients. Multiple regression analysis revealed that circulating soluble E-selectin levels could be predicted by plasma irisin (p = 0.004). Additionally, cultured human umbilical vein endothelial cells (HUVEC) exposed to 200 ng/ml irisin for 4 h showed a significant fourfold increase in E-selectin and 2.5-fold increase in ICAM-1 gene expression (p = 0.001 and p = 0.015 respectively), and there was a 1.8-fold increase in soluble E-selectin in conditioned media (p < 0.05). CONCLUSION: These data suggest that elevated plasma irisin in T2DM is associated with indices of adiposity, and that irisin may be involved in pro-atherogenic endothelial disturbances that accompany obesity and T2DM. Accordingly, irisin may constitute a potentially novel therapeutic opportunity in the field of obesity and cardiovascular diabetology

Lawson criterion for ignition exceeded in an inertial fusion experiment

For more than half a century, researchers around the world have been engaged in attempts to achieve fusion ignition as a proof of principle of various fusion concepts. Following the Lawson criterion, an ignited plasma is one where the fusion heating power is high enough to overcome all the physical processes that cool the fusion plasma, creating a positive thermodynamic feedback loop with rapidly increasing temperature. In inertially confined fusion, ignition is a state where the fusion plasma can begin "burn propagation" into surrounding cold fuel, enabling the possibility of high energy gain. While "scientific breakeven" (i.e., unity target gain) has not yet been achieved (here target gain is 0.72, 1.37 MJ of fusion for 1.92 MJ of laser energy), this Letter reports the first controlled fusion experiment, using laser indirect drive, on the National Ignition Facility to produce capsule gain (here 5.8) and reach ignition by nine different formulations of the Lawson criterion

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals &lt;1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data