The global burden of cancer attributable to risk factors, 2010-19 : a systematic analysis for the Global Burden of Disease Study 2019

Background Understanding the magnitude of cancer burden attributable to potentially modifiable risk factors is crucial for development of effective prevention and mitigation strategies. We analysed results from the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2019 to inform cancer control planning efforts globally. Methods The GBD 2019 comparative risk assessment framework was used to estimate cancer burden attributable to behavioural, environmental and occupational, and metabolic risk factors. A total of 82 risk-outcome pairs were included on the basis of the World Cancer Research Fund criteria. Estimated cancer deaths and disability-adjusted life-years (DALYs) in 2019 and change in these measures between 2010 and 2019 are presented. Findings Globally, in 2019, the risk factors included in this analysis accounted for 4.45 million (95% uncertainty interval 4.01-4.94) deaths and 105 million (95.0-116) DALYs for both sexes combined, representing 44.4% (41.3-48.4) of all cancer deaths and 42.0% (39.1-45.6) of all DALYs. There were 2.88 million (2.60-3.18) risk-attributable cancer deaths in males (50.6% [47.8-54.1] of all male cancer deaths) and 1.58 million (1.36-1.84) risk-attributable cancer deaths in females (36.3% [32.5-41.3] of all female cancer deaths). The leading risk factors at the most detailed level globally for risk-attributable cancer deaths and DALYs in 2019 for both sexes combined were smoking, followed by alcohol use and high BMI. Risk-attributable cancer burden varied by world region and Socio-demographic Index (SDI), with smoking, unsafe sex, and alcohol use being the three leading risk factors for risk-attributable cancer DALYs in low SDI locations in 2019, whereas DALYs in high SDI locations mirrored the top three global risk factor rankings. From 2010 to 2019, global risk-attributable cancer deaths increased by 20.4% (12.6-28.4) and DALYs by 16.8% (8.8-25.0), with the greatest percentage increase in metabolic risks (34.7% [27.9-42.8] and 33.3% [25.8-42.0]). Interpretation The leading risk factors contributing to global cancer burden in 2019 were behavioural, whereas metabolic risk factors saw the largest increases between 2010 and 2019. Reducing exposure to these modifiable risk factors would decrease cancer mortality and DALY rates worldwide, and policies should be tailored appropriately to local cancer risk factor burden. Copyright (C) 2022 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 license.Peer reviewe

Determining crystal structures through crowdsourcing and coursework

We show here that computer game players can build high-quality crystal structures. Introduction of a new feature into the computer game Foldit allows players to build and real-space refine structures into electron density maps. To assess the usefulness of this feature, we held a crystallographic model-building competition between trained crystallographers, undergraduate students, Foldit players and automatic model-building algorithms. After removal of disordered residues, a team of Foldit players achieved the most accurate structure. Analysing the target protein of the competition, YPL067C, uncovered a new family of histidine triad proteins apparently involved in the prevention of amyloid toxicity. From this study, we conclude that crystallographers can utilize crowdsourcing to interpret electron density information and to produce structure solutions of the highest quality

Global burden of 288 causes of death and life expectancy decomposition in 204 countries and territories and 811 subnational locations, 1990–2021: a systematic analysis for the Global Burden of Disease Study 2021

BACKGROUND Regular, detailed reporting on population health by underlying cause of death is fundamental for public health decision making. Cause-specific estimates of mortality and the subsequent effects on life expectancy worldwide are valuable metrics to gauge progress in reducing mortality rates. These estimates are particularly important following large-scale mortality spikes, such as the COVID-19 pandemic. When systematically analysed, mortality rates and life expectancy allow comparisons of the consequences of causes of death globally and over time, providing a nuanced understanding of the effect of these causes on global populations. METHODS The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2021 cause-of-death analysis estimated mortality and years of life lost (YLLs) from 288 causes of death by age-sex-location-year in 204 countries and territories and 811 subnational locations for each year from 1990 until 2021. The analysis used 56 604 data sources, including data from vital registration and verbal autopsy as well as surveys, censuses, surveillance systems, and cancer registries, among others. As with previous GBD rounds, cause-specific death rates for most causes were estimated using the Cause of Death Ensemble model-a modelling tool developed for GBD to assess the out-of-sample predictive validity of different statistical models and covariate permutations and combine those results to produce cause-specific mortality estimates-with alternative strategies adapted to model causes with insufficient data, substantial changes in reporting over the study period, or unusual epidemiology. YLLs were computed as the product of the number of deaths for each cause-age-sex-location-year and the standard life expectancy at each age. As part of the modelling process, uncertainty intervals (UIs) were generated using the 2·5th and 97·5th percentiles from a 1000-draw distribution for each metric. We decomposed life expectancy by cause of death, location, and year to show cause-specific effects on life expectancy from 1990 to 2021. We also used the coefficient of variation and the fraction of population affected by 90% of deaths to highlight concentrations of mortality. Findings are reported in counts and age-standardised rates. Methodological improvements for cause-of-death estimates in GBD 2021 include the expansion of under-5-years age group to include four new age groups, enhanced methods to account for stochastic variation of sparse data, and the inclusion of COVID-19 and other pandemic-related mortality-which includes excess mortality associated with the pandemic, excluding COVID-19, lower respiratory infections, measles, malaria, and pertussis. For this analysis, 199 new country-years of vital registration cause-of-death data, 5 country-years of surveillance data, 21 country-years of verbal autopsy data, and 94 country-years of other data types were added to those used in previous GBD rounds. FINDINGS The leading causes of age-standardised deaths globally were the same in 2019 as they were in 1990; in descending order, these were, ischaemic heart disease, stroke, chronic obstructive pulmonary disease, and lower respiratory infections. In 2021, however, COVID-19 replaced stroke as the second-leading age-standardised cause of death, with 94·0 deaths (95% UI 89·2-100·0) per 100 000 population. The COVID-19 pandemic shifted the rankings of the leading five causes, lowering stroke to the third-leading and chronic obstructive pulmonary disease to the fourth-leading position. In 2021, the highest age-standardised death rates from COVID-19 occurred in sub-Saharan Africa (271·0 deaths [250·1-290·7] per 100 000 population) and Latin America and the Caribbean (195·4 deaths [182·1-211·4] per 100 000 population). The lowest age-standardised death rates from COVID-19 were in the high-income super-region (48·1 deaths [47·4-48·8] per 100 000 population) and southeast Asia, east Asia, and Oceania (23·2 deaths [16·3-37·2] per 100 000 population). Globally, life expectancy steadily improved between 1990 and 2019 for 18 of the 22 investigated causes. Decomposition of global and regional life expectancy showed the positive effect that reductions in deaths from enteric infections, lower respiratory infections, stroke, and neonatal deaths, among others have contributed to improved survival over the study period. However, a net reduction of 1·6 years occurred in global life expectancy between 2019 and 2021, primarily due to increased death rates from COVID-19 and other pandemic-related mortality. Life expectancy was highly variable between super-regions over the study period, with southeast Asia, east Asia, and Oceania gaining 8·3 years (6·7-9·9) overall, while having the smallest reduction in life expectancy due to COVID-19 (0·4 years). The largest reduction in life expectancy due to COVID-19 occurred in Latin America and the Caribbean (3·6 years). Additionally, 53 of the 288 causes of death were highly concentrated in locations with less than 50% of the global population as of 2021, and these causes of death became progressively more concentrated since 1990, when only 44 causes showed this pattern. The concentration phenomenon is discussed heuristically with respect to enteric and lower respiratory infections, malaria, HIV/AIDS, neonatal disorders, tuberculosis, and measles. INTERPRETATION Long-standing gains in life expectancy and reductions in many of the leading causes of death have been disrupted by the COVID-19 pandemic, the adverse effects of which were spread unevenly among populations. Despite the pandemic, there has been continued progress in combatting several notable causes of death, leading to improved global life expectancy over the study period. Each of the seven GBD super-regions showed an overall improvement from 1990 and 2021, obscuring the negative effect in the years of the pandemic. Additionally, our findings regarding regional variation in causes of death driving increases in life expectancy hold clear policy utility. Analyses of shifting mortality trends reveal that several causes, once widespread globally, are now increasingly concentrated geographically. These changes in mortality concentration, alongside further investigation of changing risks, interventions, and relevant policy, present an important opportunity to deepen our understanding of mortality-reduction strategies. Examining patterns in mortality concentration might reveal areas where successful public health interventions have been implemented. Translating these successes to locations where certain causes of death remain entrenched can inform policies that work to improve life expectancy for people everywhere. FUNDING Bill & Melinda Gates Foundation

Validation of a System xc– Functional Assay in Cultured Astrocytes and Nervous Tissue Samples

Disruption of the glutamatergic homeostasis is commonly observed in neurological diseases and has been frequently correlated with the altered expression and/or function of astrocytic high-affinity glutamate transporters. There is, however, a growing interest for the role of the cystine-glutamate exchanger system xc– in controlling glutamate transmission. This exchanger is predominantly expressed in glial cells, especially in microglia and astrocytes, and its dysregulation has been documented in diverse neurological conditions. While most studies have focused on measuring the expression of its specific subunit xCT by RT-qPCR or by Western blotting, the activity of this exchanger in tissue samples remains poorly examined. Indeed, the reported use of sulfur- and carbon-radiolabeled cystine in uptake assays shows several drawbacks related to its short radioactive half-life and its relatively high cost. We here report on the elaborate validation of a method using tritiated glutamate as a substrate for the reversed transport mediated by system xc–. The uptake assay was validated in primary cultured astrocytes, in transfected cells as well as in crude synaptosomes obtained from fresh nervous tissue samples. Working in buffers containing defined concentrations of Na+, allowed us to differentiate the glutamate uptake supported by system xc– or by high-affinity glutamate transporters, as confirmed by using selective pharmacological inhibitors. The specificity was further demonstrated in primary astrocyte cultures from transgenic mice lacking xCT or in cell lines where xCT expression was genetically induced or reduced. As such, this assay appears to be a robust and cost-efficient solution to investigate the activity of this exchanger in physiological and pathological conditions. It also provides a reliable tool for the screening and characterization of new system xc– inhibitors which have been frequently cited as valuable drugs for nervous disorders and cancer

AMPKα1 Deficiency in Astrocytes from a Rat Model of ALS Is Associated with an Altered Metabolic Resilience

Alterations in the activity of the regulator of cell metabolism AMP-activated protein kinase (AMPK) have been reported in motor neurons from patients and animal models of amyotrophic lateral sclerosis (ALS). Considering the key role played by astrocytes in modulating energy metabolism in the nervous system and their compromised support towards neurons in ALS, we examined whether a putative alteration in AMPK expression/activity impacted astrocytic functions such as their metabolic plasticity and glutamate handling capacity. We found a reduced expression of AMPK mRNA in primary cultures of astrocytes derived from transgenic rats carrying an ALS-associated mutated superoxide dismutase (hSOD1G93A). The activation of AMPK after glucose deprivation was reduced in hSOD1G93A astrocytes compared to non-transgenic. This was accompanied by a lower increase in ATP levels and increased vulnerability to this insult, although the ATP production rate did not differ between the two cell types. Furthermore, soliciting the activity of glutamate transporters was found to induce similar AMPK activity in these cells. However, manipulation of AMPK activity did not influence glutamate transport. Together, these results suggest that the altered AMPK responsiveness in ALS might be context dependent and may compromise the metabolic adaptation of astrocytes in response to specific cellular stress

Receptor density influences ligand-induced dopamine D2L receptor homodimerization

Chronic treatments with dopamine D2 receptor ligands induce fluctuations in D2 receptor density. Since D2 receptors tend to assemble as homodimers, we hypothesized that receptor density might influence constitutive and ligand-induced homodimerization. Using a nanoluciferase-based complementation assay to monitor dopamine D2L receptor homodimerization in a cellular model enabling the tetracycline-controlled expression of dopamine D2L receptors, we observed that increasing receptor density promoted constitutive dopamine D2L receptor homodimerization. Receptor full agonists promoted homodimerization, while antagonists and partial agonists disrupted dopamine D2L receptor homodimers. High receptor densities enhanced this inhibitory effect only for receptor antagonists. Taken together, our findings indicate that both receptor density and receptor ligands influence dopamine D2L receptor homodimerization, albeit excluding any strict correlation with ligands’ intrinsic activity and highlighting further complexity to dopaminergic pharmacology

Pharmacological evidence for the concept of spare glutamate transporters

Through the efficient clearance of extracellular glutamate, high affinity astrocytic glutamate transporters constantly shape excitatory neurotransmission in terms of duration and spreading. Even though the glutamate transporter GLT-1 (also known as EAAT2/SLC1A2) is amongst the most abundant proteins in the mammalian brain, its density and activity are tightly regulated. In order to study the influence of changes in the expression of GLT-1 on glutamate uptake capacity, we have developed a model in HEK cells where the density of the transporter can be manipulated thanks to a tetracycline-inducible promoter. Exposing the cells to doxycycline concentration-dependently increased GLT-1 expression and substrate uptake velocity. However, beyond a certain level of induction, increasing the density of transporters at the cell surface failed to increase the maximal uptake. This suggested the progressive generation of a pool of spare transporters, a hypothesis that was further validated using the selective GLT-1 blocker WAY-213613 of which potency was influenced by the density of the transporters. The curve showing inhibition of uptake by increasing concentrations of WAY-213613 was indeed progressively rightward shifted when tested in cells where the transporter density was robustly induced. As largely documented in the context of cell-surface receptors, the existence of ‘spare’ glutamate transporters in the nervous tissue and particularly in astrocytes could impact on the consequences of physiological or pathological regulation of these transporters

AMPK Modulates the Metabolic Adaptation of C6 Glioma Cells in Glucose-Deprived Conditions without Affecting Glutamate Transport

Energy homeostasis in the central nervous system largely depends on astrocytes, which provide metabolic support and protection to neurons. Astrocytes also ensure the clearance of extracellular glutamate through high-affinity transporters, which indirectly consume ATP. Considering the role of the AMP-activated protein kinase (AMPK) in the control of cell metabolism, we have examined its implication in the adaptation of astrocyte functions in response to a metabolic stress triggered by glucose deprivation. We genetically modified the astrocyte-like C6 cell line to silence AMPK activity by overexpressing a dominant negative mutant of its catalytic subunit. Upon glucose deprivation, we found that C6 cells maintain stable ATP levels and glutamate uptake capacity, highlighting their resilience during metabolic stress. In the same conditions, cells with silenced AMPK activity showed a reduction in motility, metabolic activity, and ATP levels, indicating that their adaptation to stress is compromised. The rate of ATP production remained, however, unchanged by AMPK silencing, suggesting that AMPK mostly influences energy consumption during stress conditions in these cells. Neither AMPK modulation nor prolonged glucose deprivation impaired glutamate uptake. Together, these results indicate that AMPK contributes to the adaptation of astrocyte metabolism triggered by metabolic stress, but not to the regulation of glutamate transport