Total Metabolic Rate Research Articles

Tissue-specific glucose partitioning and fat content in prediabetes and type 2 diabetes: whole-body PET/MRI during hyperinsulinemia.

To obtain direct quantifications of glucose turnover, volumes and fat content of several tissues in the development of type 2 diabetes (T2D) using a novel integrated approach for whole-body imaging. Hyperinsulinemic-euglycemic clamps and simultaneous whole-body integrated [18F]FDG-PET/MRI with automated analyses were performed in control (n = 12), prediabetes (n = 16) and T2D (n = 13) subjects matched for age, sex and BMI. Whole-body glucose uptake (Rd) was reduced by approximately 25% in T2D vs control subjects, and partitioning to brain was increased from 3.8% of total Rd in controls to 7.1% in T2D. In liver, subcutaneous AT, thigh muscle, total tissue glucose metabolic rates (MRglu) and their % of total Rd were reduced in T2D compared to control subjects. The prediabetes group had intermediate findings. Total MRglu in heart, visceral AT, gluteus and calf muscle was similar across groups. Whole-body insulin sensitivity assessed as glucose infusion rate correlated with liver MRglu but inversely with brain MRglu. Liver fat content correlated with MRglu in brain but inversely with MRglu in other tissues. Calf muscle fat was inversely associated with MRglu only in the same muscle group. This integrated imaging approach provides detailed quantification of tissue-specific glucose metabolism. During T2D development, insulin-stimulated glucose disposal is impaired and increasingly shifted away from muscle, liver and fat toward the brain. Altered glucose handling in the brain and liver fat accumulation may aggravate insulin resistance in several organs.

Body Composition in Elite Soccer Players from Youth to Senior Squad.

There is a strong relationship between body composition and performance in male soccer players. This study aimed to display an optimal body height and weight, and body composition profile of male soccer players for four competitive age groups. This cross-sectional study included four groups: U-15 (n = 152), U-17 (n = 154), U-19 (n = 61), and seniors (n = 27). Body height and weight were measured under standard conditions, and the bioelectrical impedance analyzer (BIA) analyzed body composition. On average, soccer players in the U-15 group had significantly lower body height, weight, body mass index, skeletal muscle mass, fat-free mass, total body water and basal metabolic rate than U-17, U-19 and seniors, but a higher percentage of body fat than U-17 and U-19, p < 0.05. In addition, the results show significant non-linear increases in body height, weight and body composition as the age of soccer players increases, with the exception of the percentage of body fat mass, which tends to significantly decrease with age. The main findings of this study are that body fat mass remains stable and similar across all age groups, including in the senior squad.

Comparison of Body Compositions Evaluated with Bioelectrical Impedance Analysis (BIA) with Metabolic, Hormonal and Anthropometric Measurements in PCOS Patients

Aim: In this study, it was aimed to compare the body composition parameters measured by BIA(Bioelectrical Impedance Analysis) and the metabolic, anthropometric and hormonal parameters of the PCOS patients with the healthy control group and to examine the effect of PCOS on body composition parameters. It is aimed to give a better direction to PCOS follow-up and treatment. Material and Method: 23 non-obese PCOS patients were involved to this prospective study. PCOS diagnosis was made according to the Rotterdam Consensus. Antropometric, metabolic and hormonal parameters were measured. Body compositions were measured by BIA. Results: When the relationship between body composition parameters and metabolic and hormonal values were examined, significant correlations were found. There was a negative correlation between AUC-insulin levels and SHBG while a significant positive correlation between free testosterone in hirsute women with PCOS. There was a significant negative correlation between free testosterone level increase and body fat ratio while a significant positive correlation between SHBG and body fat ratio. There was a significant negative correlation between DHEAS and BMI and the hip circumference. When the relationship between body composition and antropometric parameters were examined, a significant positive correlation was found between BMI and body fat ratio, total body water and basal metabolic rate in women with PCOS. Conclusion: In this study, significant correlations were found between body compositions and hormonal, metabolic and anthropometric parameters in patients with PCOS. Based on these findings, we believe that BIA can play an important role in outpatient follow-up of patients with PCOS.

Aminopeptidase-N modulation assists lean mass anabolism during refuelling in the white-throated sparrow.

Songbirds meet the extreme metabolic demands of migration by burning both stored fat and protein. However, catabolizing these endogenous tissues for energy leads to organ atrophy, and reductions in gastrointestinal tissue can be as great as 50% of the pre-flight mass. Remarkably, during stopover refuelling birds quickly regain digestive mass and performance. Aminopeptidase-N (APN) is a brush-border enzyme responsible for late-stage protein digestion and may critically assist tissue reconstruction during the stopover, thus compensating for reduced gut size. We hypothesized that birds recovering from a fast would differentially upregulate APN activity relative to disaccharidases to rapidly process and assimilate dietary protein into lean mass. We fasted 23 wild-caught migratory white-throated sparrows (Zonotrichia albicollis) for 48 h to mimic mass reductions experienced during migratory flight and measured intestinal APN activity before the fast, immediately after the fast, and during recovery at 24 h and 48 h post-fast. Total fat mass, lean mass and basal metabolic rate were measured daily. We show that fasted birds maintain APN activity through the fast, despite a 30% reduction in intestine mass, but during refuelling, APN activity increases nearly twofold over pre-fasted individuals. This suggests that dynamically regulating APN may be necessary for rapid protein reconstruction during the stopover.

Effect of hypoxia and air-breathing restricted on respiratory physiology of air-breathing loach (Paramisgurnus dabryanus).

This aim of this study was to determine the respiratory physiology response in the gill and gut of Paramisgurnus dabryanus under different breathing treatment patterns. The experimental design included the following three conditions: a control group without any stress treatments, an inhibited group with intestinal respiration inhibited, and an air-exposed group with gill respiration inhibited. The results indicated that the total static metabolic rate in the air-exposed group (188.92 ± 13.67 mg h-1 kg-1) was much higher than that of the other group after 7 days, decreased significantly after the first day of recovery (81.64 ± 7.85 mg h-1 kg-1). The air metabolic rate in the air-exposed group increased significantly after 7 days (P < 0.05). There was no significant difference among the groups. Histological observation on the gill and hindgut of P. dabryanus showed that the gill filament area of inhibited group became larger, while the gill structure of air exposed group showed some damage. The number of capillariesin the hindgut mucosal epithelial in air-exposed group showed a rapidly increase (P < 0.05). Likewise, the gas diffusion distance (1.24 ± 0.36 μm) became significantly shorter (P < 0.05). Lactate dehydrogenase activity of gill in the air-exposed group (846.68 ± 88.78 U mg-1 protein) significantly increased after 7 days whereas succinate dehydrogenase (1.02 ± 0.21 U mg-1 protein) and Na+/K+ ATPase (0.57 ± 0.20 U mg-1 protein) activity decreased significantly (P < 0.05). However, there was no significant change in the hindgut. After recovery, there was no significant difference in lactate dehydrogenase, succinate dehydrogenase, and Na+/K+ ATPase activity in the gill or hindgut in groups. P. dabryanus had a high viability in air-exposed condition. When recovery occurred under normoxic conditions, the physical levels of respiration returned back to the normal level quickly.

Microplastic Consumption and Its Effect on Respiration Rate and Motility of Calanus helgolandicus From the Marmara Sea

Consumption rates of polystyrene microplastics (beads of 6, 12, and 26 μm diameter) and their effects on energy metabolism and motor activity of the copepodCalanus helgolandicusliving in the Marmara Sea were investigated. All sizes of microplastic particles were actively consumed and excreted via fecal pellets, however, copepods displayed a significant preference for beads sized 6 μm. In a mixture of algae and microplastics beads of 6 μm, microplastics consumption rates linearly (r2= 0.78,n= 154) increased 800 times from 50.8 ± 17.3 to 8,612 ± 5,972 beads ind–1day–1with an increase in bead concentration from 10 to 44,000 beads ml–1. The total and basal metabolic rates as well as time spent swimming forC. helgolandicus, decreased 1.7, 1.8 and about 3-fold, respectively after 7–8 days exposure to microplastic treatments, which was similar to the metabolism and activity of starving animals in filtered water. In copepods consuming microplastics, all vital parameters decreased on the first day of exposure, indicating either accelerated starvation, probably due to increased losses of energy and biological matter in the formation of fecal pellets and/or traumatic/toxic effects of the polystyrene beads on the copepods. Our data from laboratory experiments indicate that the presence of large concentrations of microplastics in water, even when mixed with algae, lowered energy metabolism levels ofC. helgolandicus.

Ecophysiological and behavioural responses to salinity and temperature stress in cyclopoid copepod Oithona davisae with comments on gender differences

The gender differences in reaction to salinity (3-50) and temperature (6-26°C) stress were studied in the thermophilic cyclopoid copepod Oithona davisae, introduced in the brackish temperate Black Sea since 2001. Both females and males possessed similar salinity tolerance ranges (6–40) irrespective of the salinity change rate, and females displayed a striking osmotic control upon sharp (18-40 and 40-18) salinity shocks. By contrast, the temperature response of males and females were different. Torpidity was recorded at a temperature below 10°C in males collected both in warm and cold seasons, as well as in summer-autumn females whilst in females grown up at the beginning of winter the locomotor parameters were high even at 6°С. The total metabolic rate of summer-autumn and winter females was determined by the level of basal metabolic rate and energy expenditures due to motor activity. In winter females that maintained high activity at low temperature, the total and basal metabolic rates, differing by 2.3 times at all temperatures within the range of 8–28°C, varied in accordance with the temperature coefficient Q10 of about 2, whereas in summer-autumn females at low temperatures total metabolic rate decreased to the basal level. The plasticity of both males and female to wide ranges in abiotic conditions provide an adaptive strategy to sustain the spreading of O. davisae in diverse environments.

Serum cholesterol levels and APOEε4 status potentiate metabolic decline in non‐demented individuals

AbstractBackgroundEpidemiological investigations have shown that midlife elevated total serum cholesterol levels increase the risk of Alzheimer’s disease (AD). However, observational studies in late‐life subjects suggested that high cholesterol levels reduce the risk of dementia. Since hypometabolism is a pivotal marker of AD progression, understanding the impact of peripheral cholesterol levels over the brain’s metabolic state in older adults has become crucial to clarify these seemingly conflicting findings. Therefore, whether high serum cholesterol levels accelerate brain metabolic decline in older subjects remains a key question to be answered. Here, we investigated whether total serum cholesterol levels are associated with cerebral metabolic decline. We hypothesized that elevated total serum cholesterol levels accelerate metabolic decline in AD‐related brain regions.MethodWe evaluated 499 cognitively unimpaired and mild cognitive impaired elderly subjects (age&gt;55 years) from Alzheimer's Disease Neuroimaging Initiative (ADNI) with available total serum cholesterol measurements at baseline and longitudinal [18F]FDG‐PET scans. Voxel‐wise general linear modelling was used to assess the baseline association between total serum cholesterol levels and cerebral metabolic rate for glucose (CMRglc), as well as cholesterol’s impact over the 2‐year’s rate of metabolic decline. Age, gender, BMI, cholesterol treatment and diagnostic group were set as covariates for adjustment. APOEε4 genotype was used as both, a covariate or an interaction factor.ResultNo significant associations were observed at baseline. We found a negative correlation between cholesterol levels and the 2‐year CMRglc variation rates in brain regions affected in early stages of AD, which was driven by the interaction with APOEε4 status (Figure 1). Regions affected include the right precuneus (peak t(491) = ‐3.93, p&lt;0.0001) and the right posterior cingulate gyrus (peak t(491) = ‐4.12, p&lt;0.0001). Associations were greater in the right hemisphere.ConclusionOur results support the concept that the interaction of higher serum cholesterol levels with APOEε4 genotype accelerate metabolic decline in AD‐related brain regions. These findings complement cross‐sectional studies postulating that, even among older adults, serum cholesterol levels, in association with the APOEε4 status, might be related to brain functional changes similar to those observed in the development of AD.

Quantitative and simultaneous measurement of oxygen consumption rates in rat brain and skeletal muscle using 17 O MRS imaging at 16.4T.

Oxygen-17 (17 O) MRS imaging, successfully used in the brain, is extended by imaging the oxygen metabolic rate in the resting skeletal muscle and used to determine the total whole-body oxygen metabolic rate in the rat. During and after inhalations of 17 O2 gas, dynamic 17 O MRSI was performed in rats (n = 8) ventilated with N2 O or N2 at 16.4 T. Time courses of the H217 O concentration from regions of interest located in brain and muscle tissue were examined and used to fit an animal-adapted 3-phase metabolic model of oxygen consumption. CBF was determined with an independent washout method. Finally, body oxygen metabolic rate was calculated using a global steady-state approach. Cerebral metabolic rate of oxygen consumption was 1.97 ± 0.19 μmol/g/min on average. The resting metabolic rate of oxygen consumption in skeletal muscle was 0.32 ± 0.12 μmol/g/min and >6 times lower than cerebral metabolic rate of oxygen consumption. Global oxygen consumed by the body was 24.2 ± 3.6 mL O2 /kg body weight/min. CBF was estimated to be 0.28 ± 0.02 mL/g/min and 0.34 ± 0.06 mL/g/min for the N2 and N2 O ventilation condition, respectively. We have evaluated the feasibility of 17 O MRSI for imaging and quantifying the oxygen consumption rate in low metabolizing organs such as the skeletal muscle at rest. Additionally, we have shown that CBF is slightly increased in the case of ventilation with N2 O. We expect this study to be beneficial to the application of 17 O MRSI to a wider range of organs, although further validation is advised.

Inferring the Effect of Species Interactions on Trait Evolution.

Models of trait evolution form an important part of macroevolutionary biology. The Brownian motion model and Ornstein–Uhlenbeck models have become classic (null) models of character evolution, in which species evolve independently. Recently, models incorporating species interactions have been developed, particularly involving competition where abiotic factors pull species toward an optimal trait value and competitive interactions drive the trait values apart. However, these models assume a fitness function rather than derive it from population dynamics and they do not consider dynamics of the trait variance. Here, we develop a general coherent trait evolution framework where the fitness function is based on a model of population dynamics, and therefore it can, in principle, accommodate any type of species interaction. We illustrate our framework with a model of abundance-dependent competitive interactions against a macroevolutionary background encoded in a phylogenetic tree. We develop an inference tool based on Approximate Bayesian Computation and test it on simulated data (of traits at the tips). We find that inference performs well when the diversity predicted by the parameters equals the number of species in the phylogeny. We then fit the model to empirical data of baleen whale body lengths, using three different summary statistics, and compare it to a model without population dynamics and a model where competition depends on the total metabolic rate of the competitors. We show that the unweighted model performs best for the least informative summary statistic, while the model with competition weighted by the total metabolic rate fits the data slightly better than the other two models for the two more informative summary statistics. Regardless of the summary statistic used, the three models substantially differ in their predictions of the abundance distribution. Therefore, data on abundance distributions will allow us to better distinguish the models from one another, and infer the nature of species interactions. Thus, our framework provides a conceptual approach to reveal species interactions underlying trait evolution and identifies the data needed to do so in practice. [Approximate Bayesian computation; competition; phylogeny; population dynamics; simulations; species interaction; trait evolution.]

Effects of seawater salinity and pH on cellular metabolism and enzyme activities in biomineralizing tissues of marine bivalves

Molluscan shell formation is a complex energy demanding process sensitive to the shifts in seawater CaCO3 saturation due to changes in salinity and pH. We studied the effects of salinity and pH on energy demand and enzyme activities of biomineralizing cells of the Pacific oyster (Crassostrea gigas) and the hard-shell clam (Mercenaria mercenaria). Adult animals were exposed for 14 days to high (30), intermediate (18), or low (10) salinity at either high (8.0-8.2) or low (7.8) pH. Basal metabolic cost as well as the energy cost of the biomineralization-related cellular processes were determined in isolated mantle edge cells and hemocytes. The total metabolic rates were similar in the hemocytes of the two studied species, but considerably higher in the mantle cells of C. gigas compared with those of M. mercenaria. Cellular respiration was unaffected by salinity in the clams’ cells, while in oysters’ cells the highest respiration rate was observed at intermediate salinity (18). In both studied species, low pH suppressed cellular respiration. Low pH led to an upregulation of Na+/K+ ATPase activity in biomineralizing cells of oysters and clams. Activities of Ca2+ ATPase and H+ ATPase, as well as the cellular energy costs of Ca2+ and H+ transport in the biomineralizing cells were insensitive to the variation in salinity and pH in the two studied species. Variability in cellular response to low salinity and pH indicates that the disturbance of shell formation under these conditions has different underlying mechanisms in the two studied species.

Retinal capillary oximetry with visible light optical coherence tomography

Assessing oxygen saturation (sO2) remains challenging but is nonetheless necessary for understanding retinal metabolism. We and others previously achieved oximetry on major retinal vessels and measured the total retinal oxygen metabolic rate in rats using visible-light optical coherence tomography. Here we extend oximetry measurements to capillaries and investigate all three retinal vascular plexuses by amplifying and extracting the spectroscopic signal from each capillary segment under the guidance of optical coherence tomography (OCT) angiography. Using this approach, we measured capillary sO2 in the retinal circulation in rats, demonstrated reproducibility of the results, validated the measurements in superficial capillaries with known perfusion pathways, and determined sO2 responses to hypoxia and hyperoxia in the different retinal capillary beds. OCT capillary oximetry has the potential to provide new insights into the retinal circulation in the normal eye as well as in retinal vascular diseases.

Association Between Body Composition and Frailty in Elder Inpatients.

PurposeThe study aimed to investigate the association between body composition and frailty in elder inpatients.Patients and MethodsThis is a cross-sectional study including 656 elder inpatients (275 females and 381 males) aged ≥65 years, from department of geriatrics of Zhejiang Hospital between January 2018 and March 2019. Sociodemographic, health-related data and anthropometric measurements were evaluated. Body composition was assessed by bioimpedance analysis (BIA), mainly including skeletal muscle mass, body fat mass, total body water, fat-free mass,percent body fat, basal metabolic rate. Frailty was assessed by Clinical Frailty Scale (CFS). Univariate logistic regression was used to analyze the association between body composition and frailty.ResultsFrailty was present in 43.9% of the participants. Frail inpatients showed higher waist circumference, body fat mass and percent body fat, non-frail inpatients showed greater upper arm circumference, calf circumference, skeletal muscle mass, total body water, fat-free mass and basal metabolic rate. Subjects with underweight (body mass index (BMI)<18.5 kg/m2; odds ratio (OR), 95% confidence interval (CI)=4.146 (1.286–13.368) P=0.017) and those with high waist circumference (OR 95% CI=1.428 (0.584–3.491) P<0.001), body fat mass (OR, 95% CI=1.143 (0.892–1.315) P<0.001) presented a higher risk of frailty compared to normal subjects. Skeletal muscle mass (OR; 95% CI=0.159 (0.064–0.396) P<0.001) was a protective factor for frailty.ConclusionFrailty in elder Chinese inpatients was characterized by a body composition phenotype with underweight, high waist circumference, low skeletal muscle mass and high body fat mass. Underweight, abdominal obesity and sarcopenic obesity may, therefore, be targets for intervention of frailty.

Relationship of Body Adiposity with Platelet Function in Obese and Non-obese Individuals.

BackgroundAdiposity is firmly linked to a higher incidence of various cardiovascular and metabolic morbidities, including diabetes, hypertension, and thromboembolism. This research study was aimed to verify the association of increased adiposity and hyperreactivity of platelets in obese and non-obese individuals.MethodsThis cross-sectional study was conducted on 42 subjects aged 18 years and above. Subjects were divided into obese and non-obese groups based on their body mass index (BMI). The data was collected through self-administered questionnaires. All participants underwent body composition analysis. Blood samples were collected from all subjects and taken to the Pharmacology Department for the preparation of platelet-rich plasma (PRP) and poor platelet plasma (PPP). Platelet aggregation was induced by arachidonic acid and was monitored with a Bio/Data multichannel aggregation profiler (Bio/Data Corp., Horsham, PA, USA).ResultsSignificant differences were observed in most parameters, such as fat mass, body fat percentage, free fat mass (FFM), the percentage of trunk fat, total body water, waist-hip ratio (WHR), and basal metabolic rate (BMR) of obese and non-obese subjects. The average percent of platelet aggregation in obese and non-obese subjects was 56.33 ± 15.62 and 59.38 ± 12.62, respectively. The average area under the curve (AUC) for platelet aggregation for both groups was 339.33 ± 191.55 and 342 ± 146.68, respectively. Platelet function was not significantly different and didn’t positively correlate with most parameters of the body composition, except WHR, which positively correlated with AUC for platelet function. ConclusionThere was no significant direct correlation between adiposity and platelet activation in obese subjects. However, a significant positive correlation of AUC for platelet aggregation with WHR was observed (resistance (r)-value: 0.307, p < 0.05). These findings suggest that WHR could be an effective determinant to assess the risk of thromboembolism in obese individuals.

Do small precocial birds enter torpor to conserve energy during development?

Precocial birds hatch feathered and mobile, but when they become fully endothermic soon after hatching, their heat loss is high and they may become energy depleted. These chicks could benefit from using energy-conserving torpor, which is characterised by controlled reductions of metabolism and body temperature (Tb). We investigated at what age the precocial king quail Coturnix chinensis can defend a high Tb under a mild thermal challenge and whether they can express torpor soon after achieving endothermy to overcome energetic and thermal challenges. Measurements of surface temperature (Ts) using an infrared thermometer showed that king quail chicks are partially endothermic at 2-10 days, but can defend high Tb at a body mass of ∼13 g. Two chicks expressed shallow nocturnal torpor at 14 and 17 days for 4-5 h with a reduction of metabolism by >40% and another approached the torpor threshold. Although chicks were able to rewarm endogenously from the first torpor bout, metabolism and Ts decreased again by the end of the night, but they rewarmed passively when removed from the chamber. The total metabolic rate increased with body mass. All chicks measured showed a greater reduction of nocturnal metabolism than previously reported in quails. Our data show that shallow torpor can be expressed during the early postnatal phase of quails, when thermoregulatory efficiency is still developing, but heat loss is high. We suggest that torpor may be a common strategy for overcoming challenging conditions during development in small precocial and not only altricial birds.

Determinants of basal metabolic rate in Indian obese patients

AimTo study and investigate the association of basal metabolic rate with body composition parameters such as fat percentage, fat-free mass, total body water and body mass index in obese subjects. MethodsThis was a cross-sectional study of 60 obese subjects. Body composition variables were recorded using TANITA TBF 300 to analyse fat percentage (FAT%), fat-free mass (FFM), total body water (TBW) and basal metabolic rate (BMR). Anthropometric measurements of each obese subjects included age, height, weight, body mass index (BMI), waist and hip circumference and waist-hip ratio. ResultsThe mean age was 38.41 years, height 163.9 cm, weight 86.02 kg with a BMI 32.35 ± 3.86 kg/m2 for 60 obese subjects participating in the current study. Fat% was 48.33 ± 10.56, TBW was 32.96 ± 9.40 kg, FFM was 44.73 ± 13.61 kg, and BMR was 1465 ± 252.7 Kcal. Waist circumference, hip circumference and waist-hip ratio were 96.27 ± 12.33 cm, 116.8 ± 15.04 cm, 0.83 ± 0.10, respectively. BMR has a significant correlation with age, FAT%, FFM, TBW and BMI and anthropometric characteristics like height, weight, waist circumference and waist hip ratio. ConclusionAge, FAT%, FFM, TBW, BMI and anthropometric characteristics like weight, waist circumference and waist hip ratio are significant contributors to BMR. Hence, these factors are important determinants of basal metabolic rate.

Exergy Analysis of the Heart with a Stenosis in the Arterial Valve.

In the past decade, several articles have proposed the use of an exergy perspective to analyze physiological systems of the human body under different physical conditions. Such a perspective focuses on the exergy transformations and the efficiency of the biological processes. This may aid the medical field in assessments of a patient’s physical health by means of an index (exergy efficiency) based on the quality of the energy conversion in a given process within the human heart. As a follow-up, a model was developed to describe the evolution of the transvalvular pressure gradient in the aortic valve as a function of stenosis severity. This model was created using physiological data from 40 patients available in the literature, as well as 32 operating points from different bileaflet aortic valve prosthesis. A linear regression results in values around 14.0 kPa for the pressure gradient in the most severe case, evolving from 1.0 kPa for a healthy scenario. The thermodynamic model assesses the irreversibilities associated with energy conversion processes related to metabolism: exergy destroyed at the valves, exergy increased in the flow, and the power of the heart. Results indicate that destroyed exergy reaches values of 10 W (almost 10% of total basal metabolic rate of the whole body). Exergy efficiency is 15% for a healthy heart, decreasing as a function of the severity of the stenosis to values lower than 5%.

Whether warming magnifies the toxicity of a pesticide is strongly dependent on the concentration and the null model

How global warming changes the toxicity of contaminants is a research priority at the intersection of global change biology and ecotoxicology. While many pesticides are more toxic at higher temperatures this is not always detected. We studied whether deviations from this general pattern can be explained by concentration-dependent interaction effects and by testing the interaction against the inappropriate null model. We exposed larvae of the mosquito Culex pipiens to three concentrations of the pesticide chlorpyrifos (absence, low and high) in the absence and presence of 4 °C warming. Both the low and high chlorpyrifos concentration were lethal and generated negative sublethal effects: activity of acetylcholinesterase (AChE) and total fat content decreased, and oxidative damage to lipids increased, yet growth rate increased. Warming was slightly lethal, yet had positive sublethal effects: growth rate, total fat content and metabolic rate increased, and oxidative damage decreased. For four out of seven response variables the independent action model identified the expected synergistic interaction between chlorpyrifos and warming. Notably, for three variables (survival, AChE and fat content) this was strongly dependent on the chlorpyrifos concentration, and for two of these (AChE and fat content) not associated with a significant interaction in the general(ized) linear models. For survival and fat content, warming only potentiated chlorpyrifos (CPF) toxicity at the low CPF concentration, while the opposite was true for AChE. Our results highlight that taking into account concentration-dependence and appropriate null model testing is crucial to improve our understanding of the toxicity of contaminants in a warming world.

Physical Activity Level Using Doubly-Labeled Water in Relation to Body Composition and Physical Fitness in Preschoolers.

Background and objectives: There is a lack of studies investigating associations of physical activity level (PAL) and activity energy expenditure (AEE) using the doubly-labeled water (DLW) method with body composition and physical fitness in young children. Thus, we aimed to examine cross-sectional associations of PAL and AEE with body composition indices and physical fitness components in Swedish preschool children. Materials and methods: PAL was calculated as total energy expenditure measured using DLW divided by the predicted basal metabolic rate in 40 children aged 5.5 (standard deviation 0.2) years. AEE was calculated as total energy expenditure minus basal metabolic rate and the thermic effect of food, and divided by fat-free mass. Body composition was assessed using the 3-component model by combining measurements based on isotope dilution and air-displacement plethysmography. Physical fitness (muscular strength, motor fitness, and cardiorespiratory fitness) was evaluated using the PREFIT test battery. Multiple linear regression models were conducted. Results: PAL and AEE were negatively associated with body mass index, percent body fat, and fat mass index (PAL: standardized β −0.35, −0.41, and −0.45, all p < 0.036; AEE: standardized β −0.44, −0.44, and −0.47, all p < 0.006, respectively). Furthermore, PAL and AEE were positively associated with the standing long jump test (PAL: standardized β 0.37, p = 0.017; AEE: standardized β 0.38, p = 0.014). There were no statistically significant associations found regarding PAL or AEE with fat-free mass index or any other physical fitness test. Conclusions: Greater PAL and AEE at the age 5.5 were significantly associated with body fatness and improved lower-body muscular strength. Therefore, increasing physical activity, and thus energy expenditure, at young ages may be beneficial for preventing overweight/obesity. However, further studies with larger sample sizes are needed to confirm the results.

Resting regional brain activity correlates of verbal learning deficit in major depressive disorder

Memory deficits are reported in major depressive disorder (MDD). Prefrontal cortical and mesiotemporal cortical (MTC)/subcortical regions are involved in the Buschke Selective Reminding Task (SRT), a verbal list-learning task. To determine whether depression-related changes in resting brain metabolism explain (in part) the deficits in SRT performance found in MDD, statistical correlation maps were calculated between SRT total recall score (TR) and relative regional cerebral metabolic rate for glucose (rCMRglu), measured by [18F]-flourodeoxyglucose (FDG) positron emission tomography (PET), in unmedicated, depressed MDD patients (N = 29). Subsequently, to explore hypothesized loss of top-down control in MDD, we compared the correlations between rCMRglu of SRT-relevant regions of the dorsolateral prefrontal cortex (dlPFC) and amygdala in a larger cohort of MDD (N = 60; 29 inclusive) versus healthy controls (HC) (N = 43). SRT performance of patients is on average 0.5 standard deviation below published normative mean. TR and rCMRglu positively correlate in bilateral dorsomedial PFC, dlPFC, dorsal anterior cingulate; negatively correlate in bilateral MTC/subcortical regions, and cerebellum. rCMRglu in dlPFC correlates negatively with that in amygdala in HC but not in MDD. Depression-related changes present in FDG-PET measured resting brain activity may be in part responsible for memory deficit found in MDD.