Energetic Demands Research Articles

Habitat degradation has species-specific effects on the stress response of coral reef fishes

Coral reefs are one of the world's most threatened ecosystems, with transition from coral- to algal-dominated habitats becoming increasingly common. While habitat degradation in other ecosystems can lead to heightened stress among individuals, thereby increasing energetic demands and reducing fitness, the effects of habitat degradation on stress and metabolic performance of coral reef fish is unknown. Therefore, we investigated whether cortisol levels (an indicator of stress), metabolic performance, behaviour, and growth, were influenced by habitat quality in three fish species with varying degrees of reliance on live coral. We reared newly-settled fishes (Pomacentrus amboinensis, P. moluccensis and Dascyllus aruanus) for three weeks in one of three habitat treatments: live coral, dead coral covered in turf algae and cyanobacteria, or a combination of the two. After three weeks we quantified each individuals metabolic performance, cortisol concentration, morphology, and habitat use. Pomacentrus moluccensis had higher cortisol concentrations in the dead coral treatment, compared to the live coral, whereas there was no difference in cortisol levels among habitat treatments for P. amboinensis or D. aruanus. Overall, metabolic performance (aerobic scope, standard and maximum metabolic rate) showed no consistent response to habitat treatments. Regarding morphology, we only found D. aruanus to be impacted, with individuals from the live coral treatment having a significantly higher mass than individuals from the dead coral treatment. Behavioural space-use analysis revealed that D. aruanus and P. moluccensis spent more time away from their habitats in the dead coral treatments, whereas the space-use of P. amboinensis was unaffected by habitat degradation. Understanding how coral loss affects stress levels and fitness of reef fishes is critical to predict future reef fish communities. This study highlights that vulnerability of reef fish to coral reef degradation is species-specific, and related to their reliance on live coral. These changes may provide a mechanistic explanation to observed population declines following coral loss and indicate that remaining individuals have reduced fitness potentially compromising the subsistence of future populations.

Unveiling a novel signalling pathway involving NRF2 and PGAM5 in regulating the mitochondrial unfolded protein response in stressed cardiomyocytes

The mitochondrial unfolded protein response (UPRmt) is a conserved signalling pathway that initiates a specific transcriptional programme to maintain mitochondrial and cellular homeostasis under stress. Previous studies have demonstrated that UPRmt activation has protective effects in the pressure-overloaded human heart, suggesting that robust UPRmt stimulation could serve as an intervention strategy for cardiovascular diseases. However, the precise mechanisms of UPRmt regulation remain unclear. In this study, we present evidence that the NRF2 transcription factor is involved in UPRmt activation in cardiomyocytes during conditions of mitochondrial stress. Silencing NRF2 partially reduces UPRmt activation, highlighting its essential role in this pathway. However, constitutive activation of NRF2 via inhibition of its cytosolic regulator KEAP1 does not increase levels of UPRmt activation markers, suggesting an alternative regulatory mechanism independent of the canonical KEAP1-NRF2 axis. Further analysis revealed that NRF2 likely affects UPRmt activation through its interaction with PGAM5 at the mitochondrial membrane. Disruption of PGAM5 in cardiomyocytes subjected to mitochondrial stress reduces the interaction between PGAM5 and NRF2, enhancing nuclear translocation of NRF2 and significantly upregulating the UPRmt in an NRF2-dependent manner. This NRF2-regulated UPRmt amplification improves mitochondrial respiration, reflecting an enhanced capacity for cardiomyocytes to meet elevated energetic demands during mitochondrial stress. Our findings highlight the therapeutic potential of targeting the NRF2-PGAM5-KEAP1 signalling complex to amplify the UPRmt in cardiomyocytes for cardiovascular and other diseases associated with mitochondrial dysfunction. Future studies should aim to elucidate the mechanisms via which NRF2 enhances the protective effects of UPRmt, thereby contributing to more targeted therapeutic approaches.

Allocation and use of body energy reservoirs in striped dolphins and Blainville's beaked whales: Snowball effect in negative energetic balance

AbstractClimate change, overfishing, and other anthropogenic activities can negatively impact the energetic balance and body condition of cetaceans. Still, cetaceans must meet their energetic demands for survival, which are more expensive to maintain in the marine environment. The resilience of cetaceans to negative energy balance periods is unknown. We analyzed where striped dolphins, a medium‐sized dolphin with shallow‐intermediate diving habits, and Blainville's beaked whales, a larger odontocete with an extreme diving profile, store their energy reserves and how they use that energy. We performed dissections of body mass compartments of fresh dead adults of similar total body lengths but different body masses, determined the lipid and protein content of blubber and muscle, and calculated oxygen stores and the aerobic dive limit. Proteins in muscle were the largest source of energy stores for both species, followed by lipids in the blubber and muscle. Both species catabolized blubber and muscle simultaneously when losing body mass to avoid impairing other important functions. When these functions are impaired, a cascade of increased field metabolic rate and decreased energy intake may occur, decreasing their resilience to environmental challenges and making them more susceptible to diseases, ultimately resulting in death by starvation.

Endurance in Long-Distance Swimming and the Use of Nutritional Aids.

Long-distance swimmers exert energetic, physiological, and neuromuscular demands that must be matched with adequate body composition to improve their performance in long-distance swimming. This review aims to compile all available information on energetic and physiological demands, optimal body composition, nutrition, and ergogenic supplements in long-distance swimming. This will provide an understanding of the specific challenges and needs of this sport and will help swimmers and coaches design more effective training and nutrition plans to optimise performance and achieve their goals. Databases such as Web of Science, SciELO Citation Index, MEDLINE (PubMed), Current Contents Connect, KCI-Korean Journal Database, and Scopus were searched for publications in English using keywords such as swimming, endurance, energy demands, physiological demands, nutrition, body composition, and ergogenic aids, individually or in combination. There is convincing evidence that several physical indicators, such as propulsive surface area, technical, such as stroke rate, and functional, such as hydration strategies, are related to swimming performance and body composition. Each athlete may have a specific optimal body fat level that is associated with improved sporting performance. The nutritional needs of open water swimmers during competition are quite different from those of pool swimmers. Swimmers with an adequate physique have a high body muscle mass and moderately related anaerobic strength both on land and in the water. These general and specific strength capacities, which are given by certain anthropometric and physiological characteristics, are seen throughout the work, as well as ergogenic and nutritional strategies, which have an important impact on long-distance swimming performance.

Cross-talk between tissues is critical for intergenerational acclimation to environmental change in Acanthochromis polyacanthus

Organisms’ responses to environmental changes involve complex, coordinated responses of multiple tissues and potential parental influences. Here using a multi-tissue approach we determine how variation in parental behavioural tolerance and exposure to elevated CO2 influences the developmental and intergenerational molecular responses of their offspring in the coral reef fish Acanthochromis polyacanthus to future ocean acidification (OA) conditions. Gills and liver showed the highest transcriptional response to OA in juvenile fish regardless of parental OA conditioning, while the brain and liver showed the greatest intergenerational acclimation signals. Developmentally induced signals of OA, such as altered neural function in the brain, were restored to control levels after intergenerational exposure. Intergenerational CO2 exposure also enabled the offspring to adjust their metabolic processes, potentially allowing them to better meet the energetic demands of a high CO2 environment. Furthermore, offspring of OA-exposed parents differentially expressed a new complement of genes, which may facilitate intergenerational acclimatory responses. A genetic component of intergenerational plasticity also played a crucial role, with the parental behavioural phenotype largely determining the offspring’s transcriptional signals. Overall, our results reveal tissue-specific transcriptional changes underlying intergenerational plastic responses to elevated CO2 exposure, enhancing understanding of organismal acclimation to OA throughout the whole body.

Energetic and Neuromuscular Demands of Unresisted, Parachute- and Sled-Resisted Sprints in Youth Soccer Players: Differences Between Two Novel Determination Methods.

The aim of this study was to analyze the differences in terms of (1) muscle activation patterns; (2) metabolic power (MP) and energy cost (EC) estimated via two determination methods (i.e., the Global Positioning System [GPS] and electromyography-based [EMG]); and (3) the apparent efficiency (AE) of 30-m linear sprints in seventeen elite U17 male soccer players performed under different conditions (i.e., unloaded sprint [US], parachute sprint [PS], and four incremental sled loads [SS15, SS30, SS45, SS60, corresponding to 15, 30, 45 and 60 kg of additional mass]). In a single testing session, each participant executed six trials (one attempt per sprint type). The results indicated that increasing the sled loads led to a linear increase in the relative contribution of the quadriceps (R2 = 0.98) and gluteus (R2 = 0.94) and a linear decrease in hamstring recruitment (R2 = 0.99). The MP during the US was significantly different from SS15, SS30, SS45, and SS60, as determined by the GPS and EMG approaches (p-values ranging from 0.01 to 0.001). Regarding EC, significant differences were found among the US and all sled conditions (i.e., SS15, SS30, SS45, and SS60) using the GPS and EMG methods (all p ≤ 0.001). Moreover, MP and EC determined via GPS were significantly lower in all sled conditions when compared to EMG (all p ≤ 0.001). The AE was significantly higher for the US when compared to the loaded sprinting conditions (all p ≤ 0.001). In conclusion, muscle activation patterns, MP and EC, and AE changed as a function of load in sled-resisted sprinting. Furthermore, GPS-derived MP and EC seemed to underestimate the actual neuromuscular and metabolic demands imposed on youth soccer players compared to EMG.

Human iPSC-derived MSCs induce neurotrophic effects and improve metabolic activity in acute neuronal injury models.

Mesenchymal stromal cell (MSC) therapy has regenerative potentials to treat various pathological conditions including neurological diseases. MSCs isolated from various organs can differentiate into specific cell types to repair organ damages. However, their paracrine mechanisms are predicted to predominantly mediate their immunomodulatory, pro-angiogenic, and regenerative properties. While preclinical studies highlight the significant potential of MSC therapy in mitigating neurological damage from stroke and traumatic brain injury, the variability in clinical trial outcomes may stem from the inherent heterogeneity of somatic MSCs. Accumulating evidence has demonstrated that induced pluripotent stem cells (iPSCs) are an ideal alternative resource for the unlimited expansion and biomanufacturing of MSCs. Thus, we investigated how iPSC-derived MSCs (iMSCs) influence properties of iPSC-derived neurons. Our findings demonstrate that the secretome from iMSCs possesses neurotrophic effects, improving neuronal survival and promoting neuronal outgrowth and synaptic activity in vitro Additionally, the iMSCs enhance metabolic activity via mitochondrial respiration in neurons, both in vitro and in mouse models. Glycolytic pathways also increased following the administration of iMSC secretome to iPSC-derived neurons. Consistently, in vivo experiments showed that intravenous administration of iMSCs compensated for the elevated energetic demand in male mice with irradiation-induced brain injury by restoring synaptic metabolic activity during acute brain damage. 18F-FDG PET imaging also detected an increase in brain glucose uptake following iMSC administration. Together, our results highlight the potential of iMSC-based therapy in treating neuronal damage in various neurological disorders, while paving the way for future research and potential clinical applications of iMSCs in regenerative medicine.Significance Statement Regenerative biotherapeutics using MSCs have emerged as a promising intervention for treating various neurological diseases. Our study explored the potential beneficial effects of human iPSC-derived MSCs (iMSCs) on neurons. We demonstrated that molecules secreted into the culture medium by iMSCs enhance regenerative capabilities by improving neuronal survival, growth, and metabolic activity, as well as synaptic functions, in human iPSC-derived neurons. Mouse experiments also suggested the potential of iMSC therapy to mitigate synaptic mitochondrial dysfunction and enhance brain glucose uptake during acute radiation-induced brain injury, steps that contribute to restoring normal neuronal function. Our results highlight that iMSCs may be a promising alternative cell product for treating neuronal damage, overcoming the inconsistent efficacy of somatic MSCs due to cell variability.

Sex differences in positional behavior of chimpanzees (Pan troglodytes schweinfurthii) living in the dry and open habitat of Issa Valley, Tanzania.

Many early fossil hominins are associated with savanna-mosaic paleohabitats, and high sexual dimorphism that may reflect differences in positional behavior between sexes. However, reconstructions of hominin behavior and the selective pressures they faced in an open habitat are limited by a lack of studies of extant apes living in contemporary, analogous habitats. Here, we describe adult chimpanzee positional behavior in the savanna-mosaic habitat of the Issa Valley, Tanzania, to test whether Issa chimpanzees show larger sex-differences in positional behavior than their forest-dwelling counterparts. We quantified and compared adult locomotor and postural behavior across sexes (6 females, 7 males) in the riparian forest (closed) and miombo woodland (open) vegetation types at Issa Valley (13,743 focal observations). We then compared our results to published data of chimpanzee communities living in more forested habitats. Issa females and males both spent less time arboreally in open vegetation and showed similar locomotor and postural behavior on the same substrates, notably using a high level of suspensory locomotion when arboreal. Females were, however, more arboreal than males during locomotor behavior, as well as compared with females from other communities. Issa males behaved similarly to males from other communities. Results suggest that open habitats do not elicit less arboreal behaviors in either sex, and may even select for suspensory locomotion to effectively navigate an open canopy. An open habitat may, however, increase sex differences in positional behavior by driving female arboreality. We suggest this is because of higher energetic demands and predator pressures associated with open vegetation, which are likely exaggerated for reproducing females. These results have implications for the interpretation of how sexual dimorphism may influence reconstructions of hominin positional behavior.

Training volume and total energy expenditure of an Olympic and Ironman world champion: approaching the upper limits of human capabilities.

Research on world-class athletes in endurance events, such as cycling Grand Tours, has reported extreme levels of total energy expenditure. However, it has been argued that over extended periods, such as months, sustained energy expenditure is capped at approximately 2.5 times the basal metabolic rate. Triathlon is particularly notable for its high energetic demands due to its multimodal nature, requiring athletes to maintain high training volumes. In this case study, we analyzed the total energy expenditure of world-class triathlete Kristian Blummenfelt using doubly labelled water over two specific periods, along with three years of training data. Total energy expenditure ranged from 7,019-8,506 kcal/day, while energy intake ranged from 4,899 to 6,360 kcal/day. The annual training volumes for the years 2020-2022 were 1,480, 1,350 and 1,308 hours, respectively, following a pyramidal intensity distribution. Approximately 53% of the entire three-year period matched with the doubly labeled water measurement periods in terms of training volume, indicating that the recorded total energy expenditure is representative of the majority of the observed data. Hence, the greater part of the three-year period likely exceeds the proposed metabolic ceiling for sustained total energy expenditure. This not only questions the validity of the current metabolic limits but also suggests a new perspective on what is physiologically achievable in world-class athletes.

The mitochondrial citrate carrier SLC25A1 regulates metabolic reprogramming and morphogenesis in the developing heart

The developing mammalian heart undergoes an important metabolic shift from glycolysis towards mitochondrial oxidation that is critical to support the increasing energetic demands of the maturing heart. Here, we describe a new mechanistic link between mitochondria and cardiac morphogenesis, uncovered by studying mitochondrial citrate carrier (SLC25A1) knockout mice. Slc25a1 null embryos displayed impaired growth, mitochondrial dysfunction and cardiac malformations that recapitulate the congenital heart defects observed in 22q11.2 deletion syndrome, a microdeletion disorder involving the SLC25A1 locus. Importantly, Slc25a1 heterozygous embryos, while overtly indistinguishable from wild type, exhibited an increased frequency of these defects, suggesting Slc25a1 haploinsuffiency and dose-dependent effects. Mechanistically, SLC25A1 may link mitochondria to transcriptional regulation of metabolism through epigenetic control of gene expression to promote metabolic remodeling in the developing heart. Collectively, this work positions SLC25A1 as a novel mitochondrial regulator of cardiac morphogenesis and metabolic maturation, and suggests a role in congenital heart disease.

Early life adversity has sex-dependent effects on survival across the lifespan in rhesus macaques.

Exposure to early life adversity is linked to detrimental fitness outcomes across taxa. Owing to the challenges of collecting longitudinal data, direct evidence for long-term fitness effects of early life adversity from long-lived species remains relatively scarce. Here, we test the effects of early life adversity on male and female longevity in a free-ranging population of rhesus macaques (Macaca mulatta) on Cayo Santiago, Puerto Rico. We leveraged six decades of data to quantify the relative importance of 10 forms of early life adversity for 6599 macaques. Individuals that experienced more early life adversity died earlier than those that experienced less adversity. Mortality risk was highest during early life, defined as birth to 4 years old, but heightened mortality risk was also present in macaques that survived to adulthood. Females and males were affected differently by some forms of adversity, and these differences might be driven by varying energetic demands and dispersal patterns. Our results show that the fitness consequences of early life adversity are not uniform across individuals but vary as a function of the type of adversity, timing and social context, and thus contribute to our limited but growing understanding of the evolution of early life sensitivities.This article is part of the discussion meeting issue 'Understanding age and society using natural populations'.

Physical Activity and Pregnancy Norms Among Daasanach Semi-Nomadic Pastoralist Women in Northern Kenya.

In subsistence populations, high physical activity is typically maintained throughout pregnancy. Market integration shifts activity patterns to resemble industrialized populations, with more time allocated to sedentary behavior. Daasanach semi-nomadic pastoralists living in northern Kenya face lifestyle heterogeneity due to the emergence of a market center. We investigate how Daasanach women manage the energetic demands of pregnancy with subsistence labor tasks and how market integration relates to variation in energetic demands, physical activity, and coping strategies. We conducted nine focus group discussions with 72 pregnant women. We also deployed wrist-worn fitness trackers with 21 pregnant women in two community types: central or peripheral to the market center to capture variation in market integration. Data from focus group discussions were analyzed using thematic analysis. We used multiple linear regression to examine the relationship between gestational age and physical activity. We identified themes of increased fatigue, diet restrictions, and assistance with labor tasks during pregnancy. Gestational age negatively predicted mean daily steps, with a decrease of 1160 ± 437 steps per day with each consecutive pregnancy month. Stratified by community type, gestational age only negatively predicted mean daily steps for peripheral communities, with a decrease of 1443 ± 629 steps per day with each consecutive pregnancy month. Results suggest that physical activity differs with market integration early, but not late, in pregnancy. Daasanach women cope with the energetic demands of pregnancy by reducing physical activity late in pregnancy and receiving assistance with labor tasks from family and neighbors.

Center of mass mechanics during locomotion in the arboreal squirrel monkey (Saimiri sciureus) as a function of speed and substrate.

It is thought that the magnitude of center of mass (COM) oscillations can affect stability and locomotor costs in arboreal animals. Previous studies have suggested that minimizing collisional losses and maximizing pendular energy exchange are effective mechanisms to reduce muscular input and energy expenditure during terrestrial locomotion. However, few studies have explored whether these mechanisms are used in an arboreal context, where stability and efficiency often act as tradeoffs. This study explores three-dimensional center of mass mechanics in an arboreal primate-the squirrel monkey (Saimiri sciureus)-moving quadrupedally at various speeds on instrumented arboreal and terrestrial supports. Using kinetic data, values of energy recovery, center of mass mechanical work and power, potential and kinetic energy congruity, and collision angle and fraction were calculated for each stride. Saimiri differed from many other mammals by having lower energy recovery. Although few differences were observed in center of mass mechanics between substrates at low or moderate speeds, as speed increased, center of mass work was done at a much greater range of rates on the pole. Collision angles were higher, while collision fractions and energy recovery values were lower on the pole, indicating less moderation of collisional losses during arboreal versus terrestrial locomotion. These data support the idea that the energetic demands of arboreal and terrestrial locomotion differ, suggesting that arboreal primates likely employ different locomotor strategies compared to their terrestrial counterparts-an important factor in the evolution of arboreal locomotion.

Exhaustive stress causes a rapid immunological response in the humoral and cellular haemolymph compartments of the pale octopus (Octopus pallidus)

Cephalopods are economically and ecologically important species across the world, yet information linking physiological stress and associated immunological responses is limited in the current literature. Here, the effects of exhaustive exercise in a holobenthic octopus species, Octopus pallidus, were examined by evaluating immunological parameters. In whole haemolymph, the pH and refractive index were measured. To assess the cellular function of the haemolymph, the total count, cell vitality and phagocytosis capacity of the haemocytes were also measured. To assess enzymatic function, activities of the phenoloxidase system and lysozyme were quantified in the plasma and cellular components of the haemolymph. Overall, exhaustive exercise led to rapid changes in the haemolymph with a significant decrease in the pH and phagocytosis capacity though the number of cells and cell vitality were not affected. Exercise also triggered the increase of activated phenoloxidase (PO-like) activity and the decrease of the inactive zymogen prophenoloxidase (ProPO-like), total PO-like and lysozyme activity in plasma and an increase in total PO-like activity in the hemocyte compartment. These responses indicated that a realistic energetic demand had substantial, rapid impact on immune function. These results also provide an important baseline to understand the immune physiology of cephalopods that will further efforts to identify the mechanisms underlying the impacts of stressors.

Survival strategies of Bar-tailed Godwit in tropical sand beaches: Straight-line and zigzag foraging techniques

The near-threatened Bar-tailed Godwit (Limosa lapponica) makes the longest non-stop endurance flights among shorebirds. They are regular winter visitors to the Kadalundi-Vallikkunnu Community Reserve and adjoining sand beaches along the west coast of India. The research investigates their foraging strategies within sand beaches, observed over six years (2016–2022). Extensive field observations across major sand beaches documented two distinct modes of continuous stitching behaviour; a straight-line mode and a zigzag mode. Despite predation pressure and human disturbances, Bar-tailed Godwits achieved high prey capture rates, likely due to the abundance of benthic invertebrates. The study also revealed the prevalence of this behaviour and its association with rate of prey consumption, particularly focusing on the availability of Cosmonotus crabs, the dominant prey species. The zigzag pattern, was associated with higher prey capture rates, suggesting an adaptive response to prey distribution. Our findings suggest that, this unique foraging strategy allows Bar-tailed Godwits to optimize prey capture while conserving time and energy, especially in resource-scarce environments. Furthermore, the implications of these behaviours are discussed in the context of prey availability, nutrient content, and the energetic demands of long-distance migration, shedding light on to the adaptive mechanisms employed by shorebirds in challenging habitats.

Mitochondrial Dysfunction as a Potential Mechanism Mediating Cardiac Comorbidities in Parkinson’s Disease

Individuals diagnosed with Parkinson’s disease (PD) often exhibit heightened susceptibility to cardiac dysfunction, reflecting a complex interaction between these conditions. The involvement of mitochondrial dysfunction in the development and progression of cardiac dysfunction and PD suggests a plausible commonality in some aspects of their molecular pathogenesis, potentially contributing to the prevalence of cardiac issues in PD. Mitochondria, crucial organelles responsible for energy production and cellular regulation, play important roles in tissues with high energetic demands, such as neurons and cardiac cells. Mitochondrial dysfunction can occur in different and non-mutually exclusive ways; however, some mechanisms include alterations in mitochondrial dynamics, compromised bioenergetics, biogenesis deficits, oxidative stress, impaired mitophagy, and disrupted calcium balance. It is plausible that these factors contribute to the increased prevalence of cardiac dysfunction in PD, suggesting mitochondrial health as a potential target for therapeutic intervention. This review provides an overview of the physiological mechanisms underlying mitochondrial quality control systems. It summarises the diverse roles of mitochondria in brain and heart function, highlighting shared pathways potentially exhibiting dysfunction and driving cardiac comorbidities in PD. By highlighting strategies to mitigate dysfunction associated with mitochondrial impairment in cardiac and neural tissues, our review aims to provide new perspectives on therapeutic approaches.

Age, sex, and temperature shape off-territory feeder use in black-capped chickadees.

Spatial ecology tends to focus on average movement patterns within animal groups; however, recent studies highlight the value of considering movement decisions both within and among individuals. We used a marked population of black-capped chickadees (Poecile atricapillus), to assess the causes and consequences of within- and among-individual differences in chickadee space use. Individuals that used feeders in addition to their most-visited "core feeder" were defined as engaging in off-territory feederuse. We found that females were more likely than males to visit off-territory feeders as ambient temperatures decrease and energetic demands increase. This may be due to sex-related differences in dominance, where males which are the dominant sex in chickadees, have priority access to feeders, while females must increase their foraging areas to meet higher energetic demand. We also found that independent of temperature, adult males were less likely than juvenile males and both juvenile and adult females to forage off-territory. We suggest that this may be due to age-specific benefits of space use in males, where un-paired juvenile males may increase feeder exploration to gain information about potential mates. Finally, we found that chickadees that had a higher propensity to visit off-territory feeders were less likely to survive to the next fall. Overall, our results suggest that dominance hierarchies and individual energetics impact within- and among-individual variation in off-territory feeder use. We provide suggestions for future studies to further investigate fitness-related consequences of within- and among-individual variation in space use.

Integration of Mitoflash and Time-Series Transcriptomics Facilitates Energy Dynamics Tracking and Substrate Supply Analysis of Floral Thermogenesis in Lotus.

The high biosynthetic and energetic demands of floral thermogenesis render thermogenic plants the ideal systems to characterize energy metabolism in plants, but real-time tracking of energy metabolism in plant cells remains challenging. In this study, a new method was developed for tracking the mitochondrial energy metabolism at the single mitochondria level by real-time imaging of mitochondrial superoxide production (i.e., mitoflash). Using this method, we observed the increased mitoflash frequencies in the receptacles of Nelumbo nucifera Gaertn. at the thermogenic stages. This increase, combined with the higher expression of antioxidant response-related genes identified through time-series transcriptomics at the same stages, shows us a new regulatory mechanism for plant redox balance. Furthermore, we found that the upregulation of respiratory metabolism-related genes during the thermogenic stages not only correlates with changes in mitoflash frequency but also underscores the critical roles of these pathways in ensuring adequate substrate supply for thermogenesis. Metabolite analysis revealed that sugars are likely one of the substrates for thermogenesis and may be transported over long distances by sugar transporters. Taken together, our findings demonstrate that mitoflash is a reliable tool for tracking energy metabolism in thermogenic plants and contributes to our understanding of the regulatory mechanisms underlying floral thermogenesis.

Lipid Droplets Big and Small: Basic Mechanisms That Make Them All.

Lipid droplets (LDs) are dynamic storage organelles with central roles in lipid and energy metabolism. They consist of a core of neutral lipids, such as triacylglycerol, which is surrounded by a monolayer of phospholipids and specialized surface proteins. The surface composition determines many of the LD properties, such as size, subcellular distribution, and interaction with partner organelles. Considering the diverse energetic and metabolic demands of various cell types, it is not surprising that LDs are highly heterogeneous within and between cell types. Despite their diversity, all LDs share a common biogenesis mechanism. However, adipocytes have evolved specific adaptations of these basic mechanisms, enabling the regulation of lipid and energy metabolism at both the cellular and organismal levels. Here, we discuss recent advances in the understanding of both the general mechanisms of LD biogenesis and the adipocyte-specific adaptations controlling these fascinating organelles.

Sperm Metabolism.

Bioenergetics plays a crucial role in sperm functions, including motility, capacitation-related protein modifications, oocyte recognition and interaction, all of which are essential for fertilization. Sperm metabolism is recognized as flexible, responding to environmental cues and energetic demands during ejaculation, the journey along the female tract, and until fertilization. Recent studies suggest that sperm metabolic functions are relevant beyond fertilization and may influence zygote and embryo development, impacting paternal-derived effects on offspring development and health. In recent years, sperm metabolic functions and homeostasis have gained increasing interest in male reproduction research. Given the crucial implications of sperm metabolism on fertility-related processes, this field is of interest not only in human male fertility but also in livestock research, semen conservation, and assisted reproductive techniques. Newly developed assessment tools are allowing a better understanding of sperm metabolism under different conditions and identifying species-specific peculiarities. This review aims to discuss the current knowledge of mammalian sperm metabolism, focusing on species-specific features, changes during the sperm journey, and potential contributions to translational research and reproductive biotechnologies. Furthermore, we propose future perspectives on sperm bioenergetics research.