Metabolic Rate Research Articles

Dietary sugar kelp consumption inhibits adipose tissue inflammation and fibrosis in male mouse model of diet-induced obesity

We previously demonstrated that consumption of U.S.-grown sugar kelp (Saccharina latissima) prohibits inflammation and fibrosis in the liver and white adipose tissue in male diet-induced obesity (DIO) mice. This study investigated whether sugar kelp can elicit similar benefits in female DIO mice. Male and female C57BL/6J mice were fed a low-fat (LF) control, a high-fat/high-sucrose/high-cholesterol (HF) control, or HF containing 6% sugar kelp (HF-Kelp) for 16 weeks. Body weight gain, serum triglyceride and total lipids, and glucose intolerance were decreased in male HF-Kelp compared with HF control. Furthermore, sugar kelp decreased gonadal white adipose tissue (gWAT) weight with smaller adipocytes and total body fat in males. In gWAT, male HF-Kelp exhibited less inflammation and fibrosis than the HF control, confirmed by histological analysis. Moreover, HF-Kelp increased physical activity only in males. Gut microbiome analysis showed sugar kelp elevated observed species and altered beta diversity in both males and females, suggesting changes in the gut microbiome may contribute to the effects of sugar kelp on gWAT inflammation and fibrosis. Therefore, our results demonstrate that sugar kelp consumption prevents obesity-induced inflammation and fibrosis in WAT in male mice, which is attributed, at least in part, to modest increases in metabolic rates, energy expenditure, and physical activity, and also modulating the gut microbiota.

Density-mediated metabolic rate in Daphnia magna interacting with temperature

ABSTRACT Zooplankton change metabolic function as a physiological response to crowding. Unclear is whether zooplankton physiological responses also change according to species and measurement conditions, and whether the physiological responses to crowding are also changed by temperature. Further investigation is essential to unravel the intricate interplay between crowding-induced stress, energy allocation strategies, and behavioral adaptations. In this study, we determined the metabolic rates of cladoceran Daphnia magna at 3 different densities (1, 10, and 20 individuals [ind.] per 50 mL) at 2 temperatures (10 and 20 °C) using a highly accurate optical oxygen meter. We aimed to clarify how crowding and temperature together affect metabolic rate. At both temperatures, metabolic rates of D. magna in the 2 crowded treatments were significantly lower than those in a single treatment, and as temperature decreased the rate of metabolic decrease slowed. Q 10 values varied from 1.63 for the 20 ind. per 50 mL treatment to 2.29 for the 1 ind. per 50 mL treatment, suggesting that the slowing of metabolic rates due to crowding is slightly less pronounced at lower temperatures and may be linked to reduced food consumption.

Resting energy expenditure differs among individuals with different levels of perceived thermal sensitivity: A cross-sectional study.

Metabolic rate has been used in thermophysiological models for predicting the thermal response of humans. However, only a few studies have investigated the association between an individual's trait-like thermal sensitivity and resting energy expenditure (REE), which resulted in inconsistent results. This study aimed to explore the association between REE and perceived thermal sensitivity. The REE of healthy adults was measured using an indirect calorimeter, and perceived thermal intolerance and sensation in the body were evaluated using a self-administered questionnaire. In total, 1567 individuals were included in the analysis (women = 68.9%, age = 41.1 ± 13.2 years, body mass index = 23.3 ± 3.3 kg/m2, REE = 1532.1 ± 362.4 kcal/d). More women had high cold intolerance (31.8%) than men (12.7%), and more men had high heat intolerance (23.6%) than women (16.1%). In contrast, more women experienced both cold (53.8%) and heat (40.6%) sensations in the body than men (cold, 29.1%; heat, 27.9%). After adjusting for age, fat-free mass, and fat mass, lower cold intolerance, higher heat intolerance, and heat sensation were associated with increased REE only in men (cold intolerance, P for trend = .001; heat intolerance, P for trend = .037; heat sensation, P = .046), whereas cold sensation was associated with decreased REE only in women (P = .023). These findings suggest a link between the perceived thermal sensitivity and REE levels in healthy individuals.

Periodic open and closed resonators as a biosensor using two computational methods

The volatile particles and molecules in our dry exhaled breath can reveal enormous information about the health of any person, such as the person’s respiratory and metabolic functioning. Beyond the carbon dioxide level is an indicator of life, it provides important health-related data like people’s metabolic rate. This study considers periodic open and closed resonators for measuring carbon dioxide concentration in dry exhaled breath. Transfer matrix and green methods are used to simulate the interaction between acoustic waves and the proposed sensor. The band gaps using the green method coincide with the transmittance spectra by the transfer matrix. The suggested sensor recorded a sensitivity of 5.3Hz.m-1.s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$5.3 Hz.{m}^{-1}.s$$\\end{document}, a figure of merit of 10,254 m-1.s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${m}^{-1}.s$$\\end{document}, a detection limit of 5×10-6m.s-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$5\ imes {10}^{-6} m.{s}^{-1}$$\\end{document}, and a quality factor of 3×106\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$3\ imes {10}^{6}$$\\end{document}. Furthermore, the efficiency shows that the proposed design is appropriate as a diagnostic sensor for different diseases such as chronic obstructive pulmonary. Besides, cylindrical-adapted sensors are urgently needed in medicine, industry, and biology because they can simultaneously be used for fluid transport and detection.

Acclimation to warming but not hypoxia alters thermal tolerance and metabolic sensitivity in an estuarine crustacean

Coastal species are challenged by multiple anthropogenic stressors. Plasticity may buffer the effects of environmental change, but investigation has largely been restricted to single-stressor performance. Multistressor studies have often been short-term and relatively less is known about the consequences of plasticity under one stressor for performance under another. Here, we aimed to test for the effects of thermal or hypoxic acclimation on thermal tolerance in the amphipod Gammarus chevreuxi. Animals were chronically exposed to raised temperature or hypoxia prior to determination of upper thermal limits and routine metabolic rate (RMR). Warm acclimation increased all metrics of thermal tolerance, but hypoxic acclimation had no effect. Different responses to the two stressors was also observed for the thermal sensitivity of RMR. Consequently, this species possesses the ability to increase thermal tolerance via plasticity in response to chronic warming but increasing duration of hypoxic episodes will not confer cross-tolerance to a warming environment.

#2458 Factors associated with cytomegalovirus infection in kidney transplant patients: analysis from a nationwide registry data

Abstract Background and Aims Cytomegalovirus (CMV) has had a significant impact on solid organ transplantation. It can affect allograft function and increase patient morbidity and mortality. We have made several efforts to prevent CMV infection after kidney transplantation (KT), but we have not yet been able to prevent it satisfactorily. Drugs were used as preventive therapy or preemptive therapy, but they did not completely prevent the diseases. Therefore, it will be possible to reduce CMV infection by taking actions against factors that can easily cause CMV infection. We investigated factors that make CMV infection more likely and explored the effects of CMV infection using The Korean Organ Transplantation Registry (KOTRY) datasets. Method We used the data from the KOTRY datasets. A total of 7545 KT recipients were analysed. Results The mean age of the subjects was 49.7 ± 11.5 years (range, 19-80). Among the 7545 subjects, 58.6% were male. Three hundred and twenty-four (4.2%) subjects had CMV infection (CMV group). There were 4827 (64%) living donors, 2717 (36%) cadaveric donors, and 1338 (17.3%) ABO incompatible donors. Of the total, 95% were transplanted from positive to positive CMV IgG, and 1.9% were from positive to negative. Although preventive treatment is performed in the second cases, in most cases preemptive therapy is performed. The age was 49.6 ± 11.5 in the no CMV group and 51.4 ± 12.6 in the CMV group (P = 0.013). There was no difference in sex, weight and BMI in both cases. The causes of end stage renal disease were glomerulonephritis, DM, and hypertension in that order, and there was no difference in the rates of diabetes and hypertension between the two groups. There was no difference in the desensitization rate at 24% in the no CMV group and 23% in the CMV group. At the time of discharge after surgery, the tacrolimus dose was 6.4 mg/d±3.6 in the no CMV group and 6.3 ± 3.8 mg/d in the CMV group (P = 0.89). Tacrolimus concentration (C0) was 8.0 ± 2.6 ng/ml in the no CMV group and 8.9 ± 2.4 ng/ml in the CMV group. It was higher in the CMV group (P = 0.002). When divided into 3 tertiles based on C0, the break points were 6.7 and 8.9 ng/ml. There was a higher incidence of CMV in the third tertile group compared to the first and second tertiles, but there was no difference between the first and second groups. When the metabolic rate (tacrolimus concentration divided by dose) was divided into three groups, CMV occurred more frequently in the group with the lower metabolic rate, at 3.9% in the group with the lowest tertile and 2.3% in the highest tertile (P = 0.046). At 6 months, tacrolimus dose was 4.3 ± 2.4 mg/d in the no CMV group and 3.9 ± 2.3 mg/d in the CMV group, which was lower in the CMV group (P = 0.005). Tacrolimus concentration was 6.8 ± 2.4 ng/ml in the no CMV group and 6.4 ± 2.3 ng/ml in the CMV group, which was lower in the CMV group (P = 0.004). There was no difference according to metabolic rate. At discharge (62.5 ± 25.7 vs. 54.5 ± 26.5), at 6 month (56.0 ± 22.3 vs. 47.9 ± 19.0), and at 1 year (57.2 ± 20.0 vs. 48.8 ± 19.6 mL/min/1.73 m2), eGFR in the No CMV group was higher than that in the CMV group (P < 0.005). One thousand two hundred and sixty-four (16.8%) patients showed acute rejection within 1 year. Acute rejection occurred within 1 year in 36.4% of the CMV group and 15.9% of the no CMV group (P < 0.001). Delayed graft function occurred in 4.6% of the CMV group and 5.5% of the no CMV group (P < 0.001). Conclusion CMV was more common in older people, those with higher tacrolimus concentrations, and those with lower tacrolimus metabolic rates. The risk increases when the concentration exceeds 8.9 ng/ml, and after reducing the dose, the dose and concentration were lower in the CMV group at 6 month and 1 year. Although the dose was later reduced in the CMV group, more acute rejections occurred within 1 year, which suggests that CMV infection can trigger rejections. Delayed graft function occurred less frequently in the CMV group, which may be related to the higher concentration of tacrolimus.

#1215 Association between dietary magnesium intake and incident chronic kidney disease

Abstract Background and Aims Recent studies suggest a close association between low serum magnesium levels and kidney injury. However, whether dietary magnesium intake relates with kidney function is not well known. In this study, the relationship of dietary magnesium intake with the development of chronic kidney disease (CKD) was evaluated. Method This observational prospective study screened 210,965 European adults aged 40-70 who underwent dietary questionnaire from April 2009 to June 2012 in UK Biobank cohort. Participants with underlying CKD (baseline eGFR < 60 mL/min/1.73 m² or urine albumin-to-creatinine ratio >30 mg/g/Cr) or implausible energy intake (reported energy intake < 1.1 × basal metabolic rate [BMR] or 2.5 × BMR) were excluded. Dietary magnesium intake was assessed through online 24-hour recall dietary questionnaire and adjusted for energy intake using residual method. The participants were categorized into quartile according to energy-adjusted dietary magnesium intake. Primary outcome was incident CKD diagnosed through ICD-10 and OPCS-4 codes. Incident CKD defined as eGFR < 60 mL/min/1.73 m² was also assessed as an additional primary outcome in the sub-cohort with primary care creatinine follow-up data. Results A total of 114,916 participants was included in the final analysis. The median age was 57.0 (IQR, 50.0-63.0) years and 56.8% were female. Median magnesium intake amount per person was 345.6 (IQR, 296.8-402.5) mg/day. During a 1,095,128.6 person-year follow-up, CKD outcome occurred in 3,337 patients. Incidence of CKD was progressively lower in patients with higher magnesium intake (3.2%, 2.9%, 2.8%, and 2.7% in Q1-4, respectively). Cox regression analysis revealed that the hazard ratios (HRs) for incident CKD decreased in a stepwise manner towards higher magnesium intake quartiles (2Q: HR, 0.89; 95% CI, 0.81-0.98; 3Q: HR, 0.87; 95% CI, 0.0.79-0.95; 4Q: HR, 0.84; 95% CI, 0.76-0.92) relative to 1Q (P for trend < 0.001). This association was maintained even after adjustments were made for confounding factors. Similar results were observed with eGFR-defined CKD outcome (2Q: adjusted HR [AHR], 0.75; 95% CI, 0.64-0.89; 3Q: AHR, 0.73; 95% CI, 0.61-0.87; 4Q: AHR, 0.70; 95% CI, 0.58-0.85) relative to 1Q (P for trend < 0.001). Conclusion Higher intake of dietary magnesium may relate with lower risk of incident CKD in adults with normal kidney function.

Influence of temperature on the photoperiodic time measurement and on the maternal induction of diapause in Trichogramma telengai: the separation of the two effects

Thermal effects on photoperiodic time measurement and accumulation of inductive photoperiods have been studied in many insect species whereas the influence of temperature on the last step of the photoperiodic response, the induction of diapause, received less attention from researchers. We investigated thermal modification of the maternal photoperiodic response in Trichogramma telengai (Hymenoptera: Trichogrammatidae). Even a single long-night photoperiod experienced by females of this minute egg parasitoid immediately before oviposition causes a substantial increase in larval diapause incidence in the progeny. This feature allows separation of the thermal effects on different steps of the diapause-inducing photoperiodic response. Laboratory experiments showed that the temperature of the last scotophase (when the final decisive photoperiodic time measurement occurs) caused an inverted U-shaped diapause-inducing response similar to that observed in some other long-day insects. The temperature of the last photophase (when progeny diapause is induced) had a positive linear effect that has not been reported for the induction of winter diapause in any long-day insect. Most probably, such a thermal response is not a specific seasonal adaptation but a direct consequence of the influence of temperature on the rate of metabolism.

House cricket males reared at different perceived acoustic population densities differ in adult behaviour but not physiology

Abstract If environments stay relatively constant over an individual's lifetime, a juvenile that accurately perceives environmental conditions, like population density, may adjust adult traits to better match their environment, thereby increasing success. While previous studies have explored how adult exposure to population density affects physiological and behavioural plasticity, the influence of juvenile density experience on adult traits is less studied. Using the common house cricket, Acheta domesticus, we explored whether perceived acoustic population density during development affected adult physiology and behaviour. We simulated high‐ and low‐densities using live ambient male song. Upon maturation, we measured metabolic (resting respiration) rate, reproductive investment (testes and accessory gland masses), calling song characteristics and aggressive behaviours from pairwise contests between males from different densities. Male rearing density did not affect resting metabolic rates or reproductive organ masses. However, high‐density males had significantly faster, longer chirps, with more pulses—known to be preferred by females—and higher dominant frequency. Low‐density males won more aggressive contests and sang the aggressive song more. Initiation of aggressive behaviours or song and singing more aggressive song were the only other significant predictors of contest outcome. These results suggest that males may plastically adjust calling song characteristics and aggressive behaviour, but not physiology, based on perceived density during development. We hypothesize that alternative mating tactics—that is, territory guarding versus attractive song production—may underlie these observed patterns. Overall, our study highlights the significant influence of early‐life biotic environments on adult behavioural decisions to enhance success in diverse environments.

Convergent accelerated evolution of mammal-specific conserved non-coding elements in hibernators

Mammals maintain their body temperature, yet hibernators can temporarily lower their metabolic rate as an energy-saving strategy. It has been proposed that hibernators evolved independently from homeotherms, and it is possible that the convergent evolution of hibernation involved common genomic changes among hibernator-lineages. Since hibernation is a seasonal trait, the evolution of gene regulatory regions in response to changes in season may have been important for the acquisition of hibernation traits. High-frequency accumulation of mutations in conserved non-coding elements (CNEs) could, in principle, alter the expression of neighboring genes and thereby contribute to the acquisition of new traits. To address this possibility, we performed a comparative genomic analysis of mammals to identify accelerated CNEs commonly associated with hibernation. We found that accelerated CNEs are common to hibernator-lineages and could be involved with hibernation. We also found that common factors of genes that located near accelerated CNEs and are differentially expressed between normal and hibernation periods related to gene regulation and cell-fate determination. It suggests that the molecular mechanisms controlling hibernation have undergone convergent evolution. These results help broaden our understanding of the genetic adaptations that facilitated hibernation in mammals and may offer insights pertaining to stress responses and energy conservation.

Modeling oxygen transport in the brain: An efficient coarse-grid approach to capture perivascular gradients in the parenchyma.

Recent progresses in intravital imaging have enabled highly-resolved measurements of periarteriolar oxygen gradients (POGs) within the brain parenchyma. POGs are increasingly used as proxies to estimate the local baseline oxygen consumption, which is a hallmark of cell activity. However, the oxygen profile around a given arteriole arises from an interplay between oxygen consumption and delivery, not only by this arteriole but also by distant capillaries. Integrating such interactions across scales while accounting for the complex architecture of the microvascular network remains a challenge from a modelling perspective. This limits our ability to interpret the experimental oxygen maps and constitutes a key bottleneck toward the inverse determination of metabolic rates of oxygen. We revisit the problem of parenchymal oxygen transport and metabolism and introduce a simple, conservative, accurate and scalable direct numerical method going beyond canonical Krogh-type models and their associated geometrical simplifications. We focus on a two-dimensional formulation, and introduce the concepts needed to combine an operator-splitting and a Green's function approach. Oxygen concentration is decomposed into a slowly-varying contribution, discretized by Finite Volumes over a coarse cartesian grid, and a rapidly-varying contribution, approximated analytically in grid-cells surrounding each vessel. Starting with simple test cases, we thoroughly analyze the resulting errors by comparison with highly-resolved simulations of the original transport problem, showing considerable improvement of the computational-cost/accuracy balance compared to previous work. We then demonstrate the model ability to flexibly generate synthetic data reproducing the spatial dynamics of oxygen in the brain parenchyma, with sub-grid resolution. Based on these synthetic data, we show that capillaries distant from the arteriole cannot be overlooked when interpreting POGs, thus reconciling recent measurements of POGs across cortical layers with the fundamental idea that variations of vascular density within the depth of the cortex may reveal underlying differences in neuronal organization and metabolic load.

Multiple factor assessment for determining resting metabolic rate in young adults

Existing formulas cannot fully explain the variation of resting metabolic rate (RMR). This study aims to examine potential influencing factors beyond anthropometric measurements and develop more accurate equations using accessible parameters. 324 healthy adults (230 females; 18–32 years old) participated in the study. Height, fat-free mass (FFM), fat mass (FM) and RMR were measured. Menstrual cycle, stress levels, living habits, and frequency of consuming caffeinated foods were collected. Measured RMR were compared with predictive values of the new equations and previous 11 equations. Mean RMR for men and women was 1825.2 ± 248.8 and 1345.1 ± 178.7 kcal/day, respectively. RMR adjusted for FFM0.66FM0.066 was positively correlated with BMI. The multiple regression model showed that RMR can be predicted in this population with model 1 (with FFM, FM, age, sex and daily sun exposure duration) or model 2 (with weight and height replacing FFM and FM). The accuracy was 75.31% in the population for predictive model 1 and 70.68% for predictive model 2. The new equations had overall improved performance when compared with existing equations. The predictive formula that consider daily sun exposure duration improve RMR prediction in young adults. Additional investigation is required among individuals in the middle-aged and elderly demographic.

Metabolic rate of two invasive Ponto‐Caspian goby species and their native competitors in the context of global warming

Abstract In connection with the expansion of alien gobies in European waters, a question arises whether this process can be enhanced or inhibited by global warming. The gobies are of Ponto‐Caspian origin, where the climate is warmer than in invaded European areas. Therefore, they are likely to cope physiologically with climate warming better than native species. Our aim was to identify differences in metabolic traits under elevated summer temperature between the invasive gobies and their native counterparts. Using a laboratory respirometer, we compared the effect of elevated summer temperature (25 vs. 17°C) on the metabolic responses of fish in two species pairs consisting of an invasive goby versus its native counterpart from the same ecological guild: the invasive racer goby Babka gymnotrachelus versus native European bullhead Cottus gobio, and the invasive monkey goby Neogobius fluviatilis versus native gudgeon Gobio gobio. The paired species share functional traits, including morphological characteristics, despite belonging to different fish families. After 4 weeks of acclimation, standard metabolic rate (SMR), maximum metabolic rate (MMR) and aerobic scope (AS = MMR–SMR) of the fish were determined. We found that SMR increased under elevated temperature irrespective of species, yet it was always lower in the gobies than in natives. The MMR of the racer goby was lower than that of the bullhead across all temperatures, whereas no differences in MMR were found between the gudgeon and monkey goby. On the one hand, the elevated temperature did not affect the AS of the racer goby and bullhead. However, the AS of the racer goby was consistently lower than that of the bullhead across all temperatures. On the other, elevated temperature caused a decrease in AS in both the monkey goby and gudgeon. However, this temperature‐induced change in AS was higher in the gudgeon than in the monkey goby. In terms of AS, the invaders did not always outperform the natives at higher temperatures. However, the invaders had lower living costs by maintaining a lower SMR. These results suggest that invasion by gobies may be facilitated by global warming, which is likely to increase their occurrence and effect on local fish communities in freshwater temperate systems.

Post-drought leads to increasing metabolic rates in the surface waters of a natural tropical lake

Post-drought leads to increasing metabolic rates in the surface waters of a natural tropical lake

Hypoxia-induced downregulation of RNA m6A protein machinery in the naked mole-rat heart

Naked mole-rats, Heterocephalus glaber, are champion hypoxia-tolerant rodents that live under low oxygen conditions in their subterranean burrows. Detrimental effects of low oxygen can be mitigated through metabolic rate depression (MRD), metabolic reorganization, and global downregulation of nonessential cellular processes. Recent research has progressively implicated epigenetic modifications – rapid, reversible changes to gene expression that do not alter the DNA sequence itself – as major players in implementing and maintaining MRD. N6-adenosine (m6A) methylation is the most prevalent mammalian RNA modification and is responsible for pre-mRNA processing and mRNA export from the nucleus. Hence, m6A -mediated conformational changes alter the cellular fate of transcripts. The present study investigated the role of m6A RNA methylation responses to 24 h of hypoxia exposure in H. glaber cardiac tissue. Total protein levels of m6A writers/readers/erasers, m6A demethylase activity, and total m6A quantification were measured under normoxic vs. hypoxic conditions in H. glaber heart. While there was no change in either demethylase activity or total m6A content, many proteins of the m6A pathway were downregulated during hypoxia. Overall, m6A may not be a signature hypoxia-responsive characteristic in H. glaber heart, but downregulation of the protein machinery involved in m6A cycling points to an alternate biological involvement. Further research will explore other forms of RNA modifications and other epigenetic mechanisms to determine the controls on hypoxia endurance in this subterranean mammal.

Wildfire smoke reduces lake ecosystem metabolic rates unequally across a trophic gradient

Wildfire smoke covers entire continents, depositing aerosols and reducing solar radiation fluxes to millions of freshwater ecosystems, yet little is known about impacts on lakes. Here, we quantified trends in the spatial extent of smoke cover in California, USA, and assessed responses of gross primary production and ecosystem respiration to smoke in 10 lakes spanning a gradient in water clarity and nutrient concentrations. From 2006 − 2022, the maximum extent of medium or high-density smoke occurring between June-October increased by 300,000 km2. In the three smokiest years (2018, 2020, 2021), lakes experienced 23 − 45 medium or high-density smoke days, characterized by 20% lower shortwave radiation fluxes and five-fold higher atmospheric fine particulate matter concentrations. Ecosystem respiration generally declined during smoke cover, especially in low-nutrient, cold lakes, whereas responses of primary production were more variable. Lake attributes and seasonal timing of wildfires will mediate the effects of smoke on lakes.

We need to talk about the role of zooplankton in marine food webs.

Zooplankton are the key intermediary between primary production and the fish community and a cornerstone of marine food webs, but they are often poorly represented in models that tend to focus on fish, charismatic top predators, or ocean biogeochemistry. In this study, we use an intermediate complexity end-to-end food web model of the North Sea with explicit two-way coupling of zooplankton to phytoplankton and higher trophic levels to ask whether this matters. We vary the metabolic rate of omnivorous zooplankton (OZ) as a proxy for uncertainties in our understanding and modeling of zooplankton form and function, and moving beyond previous studies we look at the impacts on the food web in concert with climate warming and fishing. We consider impacts on food web state and time to recover the relevant unfished state after fishing ceases. We also consider potential impacts on pelagic and demersal fishing fleets if we assume that they are constrained by the requirement to allow recovery to an unfished state within a certain period of time as a way of ensuring consistency with Good Environmental Status as required by EU and UK legislation. We find that all three aspects considered are highly sensitive to changes in the treatment of zooplankton, with impacts being larger than for warming of 2 or 4°C across most food web functional groups, particularly for apex predators. We call for a programme of research aimed at improving our understanding of zooplankton ecology and its relationship to the wider food web, and we recommend that improved representations of zooplankton are incorporated in future modeling studies as a priority.

Deficits in brain glucose transport among younger adults with obesity.

Obesity is associated with alterations in eating behavior and neurocognitive function. In this study, we investigate the effect of obesity on brain energy utilization, including brain glucose transport and metabolism. A total of 11 lean participants and 7 young healthy participants with obesity (mean age, 27 years) underwent magnetic resonance spectroscopy scanning coupled with a hyperglycemic clamp (target, ~180 mg/dL) using [1-13C] glucose to measure brain glucose uptake and metabolism, as well as peripheral markers of insulin resistance. Individuals with obesity demonstrated an ~20% lower ratio of brain glucose uptake to cerebral glucose metabolic rate (Tmax/CMRglucose) than lean participants (2.12 ± 0.51 vs. 2.67 ± 0.51; p = 0.04). The cerebral tricarboxylic acid cycle flux (VTCA) was similar between the two groups (p = 0.64). There was a negative correlation between total nonesterified fatty acids and Tmax/CMRglucose (r = -0.477; p = 0.045). We conclude that CMRglucose is unlikely to differ between groups due to similar VTCA, and, therefore, the glucose transport Tmax is lower in individuals with obesity. These human findings suggest that obesity is associated with reduced cerebral glucose transport capacity even at a young age and in the absence of other cardiometabolic comorbidities, which may have implications for long-term brain function and health.

No evidence for a signal in mammalian basal metabolic rate associated with a fossorial lifestyle.

A vast array of challenging environments are inhabited by mammals, such as living in confined spaces where oxygen levels are likely to be low. Species can exhibit adaptations in basal metabolic rate (BMR) to exploit such unique niches. In this study we use 801 species to determine the relationship between BMR and burrow use in mammals. We included pre-existing data for mammalian BMR and 16 life history traits. Overall, mammalian BMR is dictated primarily by environmental ambient temperature. There were no significant differences in BMR of terrestrial, semi-fossorial and fossorial mammals, suggesting that species occupying a subterranean niche do not exhibit baseline metabolic costs on account of their burrowing lifestyle. Fossorial mammals likely show instantaneous metabolic responses to low oxygen in tunnels, rather than exhibit adaptive long-term responses in their BMR.

Basal forebrain volume and metabolism in carriers of the Colombian mutation for autosomal dominant Alzheimer's disease.

We aimed to study atrophy and glucose metabolism of the cholinergic basal forebrain in non-demented mutation carriers for autosomal dominant Alzheimer's disease (ADAD). We determined thelevel of evidence for or against atrophy and impaired metabolism of the basal forebrain in 167 non-demented carriers of the Colombian PSEN1 E280A mutation and 75 age- and sex-matched non-mutation carriers of the same kindred using a Bayesian analysis framework. We analyzed baseline MRI, amyloid PET, and FDG-PET scans of the Alzheimer's Prevention Initiative ADAD Colombia Trial. We found moderate evidence against an association of carrier status with basal forebrain volume (Bayes factor (BF10) = 0.182). We found moderate evidence against a difference of basal forebrain metabolism (BF10 = 0.167). There was only inconclusive evidence for an association between basal forebrain volume and delayed memory and attention (BF10 = 0.884 and 0.184, respectively), and between basal forebrain volume and global amyloid load (BF10 = 2.1). Our results distinguish PSEN1 E280A mutation carriers from sporadic AD cases in which cholinergic involvement of the basal forebrain is already detectable in the preclinical and prodromal stages. This indicates an important difference between ADAD and sporadic AD in terms of pathogenesis and potential treatment targets.