Brown adipose tissue (BAT) plays a central role in thermogenesis by coupling fatty acid oxidation to heat production. Efficient BAT thermogenic activity requires enhanced glycolytic flux, which in turn depends on continuous regeneration of cytosolic NAD+ to sustain glyceraldehyde-3-phosphate dehydrogenase activity. This regeneration is mediated by three main pathways: lactate dehydrogenase, the glycerol-3-phosphate shuttle (GPSh), and the malate-aspartate shuttle (MASh). We previously showed that inhibition of the mitochondrial pyruvate carrier increases energy expenditure in brown adipocytes via MASh activation. However, the specific contribution of MASh to BAT energy metabolism remains poorly defined. Here, we show that MASh is functional and directly regulates lipid metabolism in BAT. Enzymatic activities of cytosolic and mitochondrial malate dehydrogenases and glutamic-oxaloacetic transaminases in BAT were comparable to those in the liver. Using a reconstituted system of isolated BAT mitochondria and cytosolic MASh enzymes, we demonstrated that extra-mitochondrial NADH is efficiently reoxidized in a glutamate-dependent manner via MASh. Genetic silencing of the mitochondrial carriers critical to MASh, namely the oxoglutarate carrier (Ogc) and aspartate-glutamate carrier (Aralar1), had no apparent effects on respiratory rates. However, silencing either Ogc or Aralar1 led to the accumulation of small lipid droplets and impaired norepinephrine-induced lipolysis. Taken together, our data indicate a novel role of MASh in regulating BAT lipid homeostasis with potential implications to body energy expenditure and thermogenesis.

The fruit fly Drosophila melanogaster is a valuable model for studying cellular and metabolic processes conserved with mammals. Using its embryonic Schneider S2 cell line, a widely employed system for heterologous protein expression, we investigated how cell growth progression and short-term slight temperature changes affect mitochondrial physiology via high-resolution respirometry. We assessed five mitochondrial bioenergetic parameters and two coupling parameters at 2nd (early) and 7th (late) days of culture, and at two temperatures (26°C and 28°C). We observed that culture time is the overwhelming driver of cell density variation, while temperature effect is only modest. Importantly, a modest 2°C increase, combined with progression to the late growth phase, synergistically enhanced basal, OXPHOS, and leak respiration, while only marginally affecting coupling efficiency. Notably, spare and maximal respiratory capacities rose disproportionately with either cell growth or mild temperature increase, suggesting mitochondrial biogenesis and functional remodeling. These findings reveal that minor, short-term temperature shifts can elicit rapid mitochondrial acclimation that enhances bioenergetic capacity and metabolic flexibility without compromising efficiency. Such responses exemplify mitochondrial plasticity to environmental and developmental cues and may inform strategies to modulate mitochondrial physiology across biological and biomedical contexts.

Mitochondria are the central hubs of energy metabolism, integrating carbohydrate, lipid, and amino acid oxidation to produce ATP through the tricarboxylic acid cycle and oxidative phosphorylation. These organelles also regulate energy homeostasis via redox signaling and substrate exchange between cellular compartments. Mitochondrial redox shuttles maintain the balance between cytosolic and mitochondrial NAD(P)H pools by transferring reducing equivalents across membranes. Among these, the glycerol-phosphate shuttle (GPSh) connects glycolysis with mitochondrial oxygen consumption, regenerating cytosolic NAD+ while transferring electrons into the electron transport system. Although GPSh ensures continuous glycolytic flux, its lower energy yield may favor heat dissipation over ATP synthesis. In the present work, we investigated how substrate utilization shapes energy coupling and thermogenesis in Drosophila melanogaster flight muscle using chip calorimetry. Calorimetric assays revealed that G3P oxidation generated significantly more heat than complex I substrates, demonstrating its high thermogenic potential. When glucose was supplied to intact flight muscles, inhibition of the GPSh with iGP1 decreased heat generation by 85

The fruit fly Drosophila melanogaster is a valuable model for studying cellular and metabolic processes conserved with mammals. Using its embryonic Schneider S2 cell line, commonly used for heterologous protein expression, we investigated how culture duration and slight temperature changes affect mitochondrial physiology via high-resolution respirometry. We assessed five mitochondrial bioenergetic parameters and two coupling parameters at early and late growth phases, and at two temperatures (26°C and 28°C). We observed that a moderate temperature increase coupled with late growth phase synergistically enhanced basal, OXPHOS, and leak respiration, with only minor impacts on mitochondrial coupling efficiency. Notably, spare and maximal respiratory capacities increased disproportionately with either cell growth progression or moderate temperature rise, suggestive of enhanced mitochondrial biogenesis. These results demonstrate that small temperature increases and cell maturation activate mitochondrial bioenergetic capacity through mechanisms consistent with mitochondrial biogenesis and functional remodeling. Such adaptations improve cellular metabolic resilience while maintaining energy conversion efficiency. These findings deepen understanding of mitochondrial plasticity in response to environmental and developmental signals. They may inform strategies to optimize mitochondrial physiology in various biological contexts, including aging, metabolic diseases, and stress adaptation. ### Competing Interest Statement The authors have declared no competing interest. * Abbreviations : ADP : adenosine diphosphate; ATP : adenosine triphosphate; AA : antimycin A; BSA : bovine serum albumin; ETS : electron transport system; FADH₂ : flavin adenine dinucleotide (reduced); FBS : fetal bovine serum; FCCP : carbonyl cyanide p-(trifluoromethoxy)phenylhydrazone; FCR : flux control ratio; NADH : nicotinamide adenine dinucleotide (reduced); OCR : oxygen consumption rate; OXPHOS : oxidative phosphorylation; S2 : Drosophila melanogaster Schneider-2 cell line; SEM : standard error of the mean. Coordenação de Aperfeicoamento de Pessoal de Nível Superior, Finance Code 001 Conselho Nacional de Desenvolvimento Científico e Tecnológico, 308629/2021-3 Fundação de Amparo à Pesquisa do Estado de São Paulo, 2021/06711-2

The coronavirus disease 2019 (COVID-19) pandemic has triggered a global health crisis, with over 700 million confirmed cases and at least 7 million deaths reported by early 2024. Children are less vulnerable to severe SARS-CoV-2 infection than adults and typically experience milder respiratory symptoms. However, a rare but significant complication, known as multisystem inflammatory syndrome in children (MIS-C), can develop weeks after infection, characterized by a spectrum of inflammatory symptoms. This study employed whole-exome sequencing and over-representation analysis to identify genetic variants of potential clinical significance related to MIS-C or severe COVID-19 in a group of children with acute respiratory distress syndrome (ARDS), all of whom were unvaccinated for COVID-19. We observed the enrichment of potentially pathogenic genetic variants in genes related to carbohydrate metabolism, particularly glycogen breakdown, in severe COVID-19 pediatric patients, and in genes related to cholesterol and lipoprotein metabolism in MIS-C patients. These findings offer insights into the genetic underpinnings of MIS-C and severe COVID-19, suggesting potential genes and biological pathways for further research.

The coronavirus disease 2019 (COVID-19) pandemic has triggered a global health crisis, with over 700 million confirmed cases and at least 7 million deaths reported by early 2024. Children are less vulnerable to severe SARS-CoV-2 infection than adults and typically experience milder respiratory symptoms. However, a rare but significant complication, known as multisystem inflammatory syndrome in children (MIS-C), can develop weeks after infection, characterized by a spectrum of inflammatory symptoms. This study employed whole-exome sequencing and over-representation analysis to identify distinct pathogenic genetic variants related to MIS-C or severe COVID-19 in a group of children with acute respiratory distress syndrome (ARDS), all of whom were unvaccinated for COVID-19. We observed an enrichment of pathogenic variants in genes related to carbohydrate metabolism, particularly glycogen breakdown, in severe COVID-19 pediatric patients, and in genes related to cholesterol and lipoprotein metabolism in MIS-C patients. These findings offer insights into the genetic underpinnings of MIS-C and severe COVID-19, suggesting potential genes and biological pathways for further research.

Drosophila melanogaster is undoubtedly one of the most useful model organisms in biology. Initially used in solidifying the principles of heredity, and establishing the basic concepts of population genetics and of the synthetic theory of evolution, it can currently offer scientists much more: the possibility of investigating a plethora of cellular and biological mechanisms, from development and function of the immune system to animal neurogenesis, tumorigenesis and beyond. Extensive resources are available for the community of Drosophila researchers worldwide, including an ever-growing number of mutant, transgenic and genomically-edited lines currently carried by stock centers in North America, Europe and Asia. Here, we provide evidence for the importance of stock centers in sustaining the substantial increase in the output of Drosophila research worldwide in recent decades. We also discuss the challenges that Brazilian Drosophila scientists face to keep their research projects internationally competitive, and argue that difficulties in importing fly lines from international stock centers have significantly stalled the progression of all Drosophila research areas in the country. Establishing a local stock center might be the first step towards building a strong local Drosophila community that will likely contribute to all areas of life sciences research.

Aedes aegypti females are natural vectors of important arboviruses such as dengue, zika, and yellow fever. Mosquitoes activate innate immune response signaling pathways upon infection, as a resistance mechanism to fight pathogens and limit their propagation. Despite the beneficial effects of immune activation for insect vectors, phenotypic costs ultimately affect their fitness. However, the underlying mechanisms that mediate these fitness costs remain poorly understood. Given the high energy required to mount a proper immune response, we hypothesized that systemic activation of innate immunity would impair flight muscle mitochondrial function, compromising tissue energy demand and flight activity. Here, we investigated the dynamic effects of activation of innate immunity by intra-thoracic zymosan injection on A. aegypti flight muscle mitochondrial metabolism. Zymosan injection significantly increased defensin A expression in fat bodies in a time-dependent manner that compromised flight activity. Although oxidant levels in flight muscle were hardly altered, ATP-linked respiratory rates driven by mitochondrial pyruvate+proline oxidation were significantly reduced at 24 h upon zymosan injection. Oxidative phosphorylation coupling was preserved regardless of innate immune response activation along 24 h. Importantly, rotenone-sensitive respiration and complex I-III activity were specifically reduced 24 h upon zymosan injection. Also, loss of complex I activity compromised ATP-linked and maximal respiratory rates mediated by mitochondrial proline oxidation. Finally, the magnitude of innate immune response activation negatively correlated with respiratory rates, regardless of the metabolic states. Collectively, we demonstrate that activation of innate immunity is strongly associated with reduced flight muscle complex I activity with direct consequences to mitochondrial proline oxidation and flight activity. Remarkably, our results indicate a trade-off between dispersal and immunity exists in an insect vector, underscoring the potential consequences of disrupted flight muscle mitochondrial energy metabolism to arbovirus transmission.

Heme is a prosthetic group of proteins involved in vital physiological processes. It participates, for example, in redox reactions crucial for cell metabolism due to the variable oxidation state of its central iron atom. However, excessive heme can be cytotoxic due to its prooxidant properties. Therefore, the control of intracellular heme levels ensures the survival of organisms, especially those that deal with high concentrations of heme during their lives, such as hematophagous insects. The export of heme initially attributed to the feline leukemia virus C receptor (FLVCR) has recently been called into question, following the discovery of choline uptake by the same receptor in mammals. Here, we found that RpFLVCR is a heme exporter in the midgut of the hematophagous insect Rhodnius prolixus, a vector for Chagas disease. Silencing RpFLVCR decreased hemolymphatic heme levels and increased the levels of intracellular dicysteinyl-biliverdin, indicating heme retention inside midgut cells. FLVCR silencing led to increased expression of heme oxygenase (HO), ferritin, and mitoferrin mRNAs while downregulating the iron importers Malvolio 1 and 2. In contrast, HO gene silencing increased FLVCR and Malvolio expression and downregulated ferritin, revealing crosstalk between heme degradation/export and iron transport/storage pathways. Furthermore, RpFLVCR silencing strongly increased oxidant production and lipid peroxidation, reduced cytochrome c oxidase activity, and activated mitochondrial biogenesis, effects not observed in RpHO-silenced insects. These data support FLVCR function as a heme exporter, playing a pivotal role in heme/iron metabolism and maintenance of redox balance, especially in an organism adapted to face extremely high concentrations of heme.

Heme is a prosthetic group of proteins involved in vital physiological processes in aerobic organisms. It participates in redox reactions crucial for cell metabolism due to the variable oxidation state of its central iron atom. However, excessive heme can be cytotoxic due to its prooxidant properties. Therefore, the control of intracellular heme levels ensures the survival of organisms, especially those that deal with high concentrations of heme during their lives, such as hematophagous insects. The feline leukemia virus C receptor (FLVCR) is a membrane protein responsible for heme transport in mammalian cells. In our study, we found that RpFLVCR serves as a heme exporter in the midgut of the hematophagous insect Rhodnius prolixus , a vector for Chagas disease. Silencing RpFLVCR decreased hemolymphatic heme levels and increased the levels of intracellular dicysteinyl-biliverdin, a product of R. prolixus heme degradation, indicating heme retention inside midgut cells. FLVCR silencing led to increased expression of heme oxygenase (HO), ferritin, and mitoferrin mRNAs while downregulating the iron importers Malvolio 1 and 2. In contrast, HO gene silencing increased FLVCR and Malvolio expression and downregulated ferritin, revealing crosstalk between heme degradation/export and iron transport/storage pathways. Furthermore, RpFLVCR silencing strongly increased oxidant production and lipid peroxidation, reduced cytochrome c oxidase activity and activated mitochondrial biogenesis, effects not observed in RpHO-silenced insects. These data support FLVCR function as a heme exporter, playing a pivotal role in heme/iron metabolism and maintenance of redox balance, especially in an organism adapted to face extremely high concentrations of heme.

Background:Brazil has been severely impacted by COVID-19 pandemics that is aggravated by the absence of a scientifically-driven coordinated informative campaign and the interference in public health management, which ultimately affected health measures to avoid SARS-CoV2 spread. The decentralization and resultant conflicts in disease control activities produced different protection behaviours and local government measures. In the present study, we investigated how political partisanship and socio-economic factors determined the outcome of COVID-19 at the local level in Brazil. Methods:A retrospective study of COVID-19 deaths was carried out using mortality databases between Feb 2020, and Jun 2021 for the 5570 Brazilian municipalities. Socio-economic parameters including city categories, income and inequality indexes, health service quality and partisanship, assessed by the result of the second round of the 2018 Brazilian presidential elections, were included. Regression tree analysis was carried out to identify the statistical significance and conditioning relationships of variables. Findings:Municipalities that supported then-candidate Jair Bolsonaro in the 2018 elections were those that had the worst COVID-19 mortality rates, mainly during the second epidemic wave of 2021. This pattern was observed even considering structural inequalities among cities. Interpretation:In general, the first phase of the pandemic hit large and central cities hardest, while the second wave mostly impacted Bolsonarian municipalities, where scientific denialism among the population was stronger. Negative effects of partisanship towards the right-wing on COVID-19 outcomes counterbalances favourable socioeconomic indexes in affluent Brazilian cities. Our results underscore the fragility of public health policies which were undermined by the scientific denialism of right-wing supporters in Brazil. Funding:International joint laboratories of Institute de Recherche pour le Développement, a partnership between the University of Brasília and the Oswaldo Cruz Foundation (LMI-Sentinela - UnB - Fiocruz - IRD), Coordination for the Improvement of Higher Education Personnel (CAPES), National Council for Scientific and Technological Development (CNPq).

Aims: Lung cancer is the leading cause of cancer death worldwide, and tobacco smoking is a recognized major risk factor for lung tumor development. We analyzed the effect of tobacco-specific nitrosamines (TSNAs) on human lung adenocarcinoma metabolic reprogramming, an emergent hallmark of carcinogenesis. Results: A series of in vitro and in vivo bioenergetic, proteomic, metabolomic, and tumor biology studies were performed to analyze changes in lung cancer cell metabolism and the consequences for hallmarks of cancer, including tumor growth, cancer cell invasion, and redox signaling. The findings revealed that nicotine-derived nitrosamine ketone (NNK) stimulates mitochondrial function and promotes lung tumor growth in vivo. These malignant properties were acquired from the induction of mitochondrial biogenesis induced by the upregulation and activation of the beta-2 adrenergic receptors (beta 2-AR)-cholinergic receptor nicotinic alpha 7 subunit (CHRNA alpha 7)-dependent nitrosamine canonical signaling pathway. The observed NNK metabolic effects were mediated by TFAM overexpression and revealed a key role for mitochondrial reactive oxygen species and Annexin A1 in tumor growth promotion. Conversely, ectopic expression of the mitochondrial antioxidant enzyme manganese superoxide dismutase rescued the reprogramming and malignant metabolic effects of exposure to NNK and overexpression of TFAM, underlining the link between NNK and mitochondrial redox signaling in lung cancer. Innovation: Our findings describe the metabolic changes caused by NNK in a mechanistic framework for understanding how cigarette smoking causes lung cancer. Conclusion: Mitochondria play a role in the promotion of lung cancer induced by tobacco-specific nitrosamines.

Scientists are facing enormous pressures posed by growing scientific communities and stagnant/reduced funding. In this scenario, mechanisms of knowledge achievement and management, as well as how recruitment, progression and evaluation are carried out should be reevaluated. We argue here that knowledge has become a profitable commodity and, as a consequence, excessive academic quantification, individual output assessment problems and abusive editorial market strategies have reached unsustainable levels. We propose to reinforce existing guidelines and to establish new ones to overcome these issues. Our proposal, the Initiative for Responsible Scientific Assessment (IRSA), has the main goal to strengthen and expand previous movements in the scientific community to promote higher quality research assessment, focused on better Science.

Leprosy is a much-feared incapacitating infectious disease caused by Mycobacterium leprae or M lepromatosis, annually affecting roughly 200,000 people worldwide. During host-pathogen interaction, M leprae subverts the immune response, leading to development of disease. Throughout the last few decades, the impact of energy metabolism on the control of intracellular pathogens and leukocytic differentiation has become more evident. Mitochondria play a key role in regulating newly-discovered immune signaling pathways by controlling redox metabolism and the flow of energy besides activating inflammasome, xenophagy, and apoptosis. Likewise, this organelle, whose origin is probably an alphaproteobacterium, directly controls the intracellular pathogens attempting to invade its niche, a feature conquered at the expense of billions of years of coevolution. In the present review, we discuss the role of reduced host cell mitochondrial activity during M leprae infection and the consequential fates of M leprae and host innate immunity. Conceivably, inhibition of mitochondrial energy metabolism emerges as an overlooked and novel mechanism developed by M leprae to evade xenophagy and the host immune response.

The adult females of Aedes aegypti mosquitoes are facultative hematophagous insects but they are unable to feed on blood right after pupae emergence. The maturation process that takes place during the first post-emergence days, hereafter named hematophagic and gonotrophic capacitation, comprises a set of molecular and physiological changes that prepare the females for the first gonotrophic cycle. Notwithstanding, the molecular bases underlying mosquito hematophagic and gonotrophic capacitation remain obscure. Here, we investigated the molecular and biochemical changes in adult Ae. aegypti along the first four days post-emergence, prior to a blood meal. We performed a RNA-Seq analysis of the head and body, comparing male and female gene expression time courses. A total of 811 and 203 genes were differentially expressed, respectively in the body and head, and both body parts showed early, mid, and late female-specific expression profiles. Female-specific up-regulation of genes involved in muscle development and the oxidative phosphorylation pathway were remarkable features observed in the head. Functional assessment of mitochondrial oxygen consumption in heads showed a gradual increase in respiratory capacity and ATP-linked respiration as a consequence of induced mitochondrial biogenesis and content over time. This pattern strongly suggests that boosting oxidative phosphorylation in heads is a required step towards blood sucking habit. Several salivary gland genes, proteases, and genes involved in DNA replication and repair, ribosome biogenesis, and juvenile hormone signaling were up-regulated specifically in the female body, which may reflect the gonotrophic capacitation. This comprehensive description of molecular and biochemical mechanisms of the hematophagic and gonotrophic capacitation in mosquitoes unravels potentially new targets for vector control.

Flight dispersal represents a key aspect of the evolutionary and ecological success of insects, allowing escape from predators, mating, and colonization of new niches. The huge energy demand posed by flight activity is essentially met by oxidative phosphorylation (OXPHOS) in flight muscle mitochondria. In insects, mitochondrial ATP supply and oxidant production are regulated by several factors, including the energy demand exerted by changes in adenylate balance. Indeed, adenylate directly regulates OXPHOS by targeting both chemiosmotic ATP production and the activities of specific mitochondrial enzymes. In several organisms, cytochrome c oxidase (COX) is regulated at transcriptional, post-translational, and allosteric levels, impacting mitochondrial energy metabolism, and redox balance. This review will present the concepts on how COX function contributes to flying insect biology, focusing on the existing examples in the literature where its structure and activity are regulated not only by physiological and environmental factors but also how changes in its activity impacts insect biology. We also performed in silico sequence analyses and determined the structure models of three COX subunits (IV, VIa, and VIc) from different insect species to compare with mammalian orthologs. We observed that the sequences and structure models of COXIV, COXVIa, and COXVIc were quite similar to their mammalian counterparts. Remarkably, specific substitutions to phosphomimetic amino acids at critical phosphorylation sites emerge as hallmarks on insect COX sequences, suggesting a new regulatory mechanism of COX activity. Therefore, by providing a physiological and bioenergetic framework of COX regulation in such metabolically extreme models, we hope to expand the knowledge of this critical enzyme complex and the potential consequences for insect dispersal.

Background: Brazil has been severely impacted by COVID-19 pandemics that is aggravated by the absence of a scientifically-driven coordinated campaign. The decentralization and resultant conflicts in disease control activities produced different protection behaviours and local government measures. In the present study, we investigated how political partisanship and socio-economic factors determined the outcome of COVID-19 at the local level in Brazil.Methods: A retrospective study of COVID-19 deaths was carried out using mortality databases between Feb 2020, and Jun 2021 for the 5570 Brazilian municipalities. Socio-economic parameters including city categories, income and inequality indexes, health service quality and partisanship, assessed by the result of the second round of the 2018 Brazilian presidential elections, were included. Regression tree analysis was carried out to identify the statistical significance and conditioning relationships of variables.Findings: Municipalities that supported then candidate Jair Bolsonaro in 2018 elections were those that had the worst COVID-19 mortality rates, mainly during the second epidemic wave of 2021. This pattern was observed even considering structural inequalities among cities.Interpretation: In general, the first phase of the pandemic hit large and central cities hardest, while the second wave mostly impacted Bolsonarian municipalities, where scientific denialism among the population was stronger. Negative effects of partisanship towards the right wing on COVID-19 outcomes counterbalances favorable socioeconomic indexes in affluent Brazilian cities. Our results underscore the fragility of public health policies which were undermined by the scientific denialism of right-wing supporters in Brazil.Funding: International joint laboratories of Institute de Recherche pour le Développement,partnership between the University of Brasília and the Oswaldo Cruz Foundation (LMI-Sentinela- UnB - Fiocruz - IRD), Coordination for the Improvement of Higher Education Personnel(CAPES), National Council for Scientific and Technological Development (CNPq).Declaration of Interest: None to declare.