Higher Basal Metabolic Rate Research Articles

Effect of Selection for High Activity-Related Metabolism on Membrane Phospholipid Fatty Acid Composition in Bank Voles.

Endothermy, high basal metabolic rates (BMRs), and high locomotor-related metabolism were important steps in the evolution of mammals. It has been proposed that the composition of membrane phospholipid fatty acids plays an important role in energy metabolism and exercise muscle physiology. In particular, the membrane pacemaker theory of metabolism suggests that an increase in cell membrane fatty acid unsaturation would result in an increase in BMR. We aimed to determine whether membrane phospholipid fatty acid composition of heart, liver, and gastrocnemius muscles differed between lines of bank voles selected for high swim-induced aerobic metabolism-which also evolved an increased BMR-and unselected control lines. Proportions of fatty acids significantly differed among the organs: liver was the least unsaturated, whereas the gastrocnemius muscles were most unsaturated. However, fatty acid proportions of the heart and liver did not differ significantly between selected and control lines. In gastrocnemius muscles, significant differences between selection directions were found: compared to control lines, membranes of selected voles were richer in saturated C18:0 and unsaturated C18:2n-6 and C18:3n-3, whereas the pattern was reversed for saturated C16:0 and unsaturated C20:4n-6. Neither unsaturation index nor other combined indexes of fatty acid proportions differed between lines. Thus, our results do not support the membrane pacemaker hypothesis. However, the differences between selected and control lines in gastrocnemius muscles reflect chain lengths rather than number of double bonds and are probably related to differences in locomotor activity per se rather than to differences in the basal or routine metabolic rate.

Similarity of Crocodilian and Avian Lungs Indicates Unidirectional Flow Is Ancestral for Archosaurs

Patterns of airflow and pulmonary anatomy were studied in the American alligator (Alligator mississippiensis), the black caiman (Melanosuchus niger), the spectacled caiman (Caiman crocodilus), the dwarf crocodile (Osteolaemus tetraspis), the saltwater crocodile (Crocodylus porosus), the Nile crocodile (Crocodylus niloticus), and Morelet's crocodile (Crocodylus moreletii). In addition, anatomy was studied in the Orinoco crocodile (Crocodylus intermedius). Airflow was measured using heated thermistor flow meters and visualized by endoscopy during insufflation of aerosolized propolene glycol and glycerol. Computed tomography and gross dissection were used to visualize the anatomy. In all species studied a bird-like pattern of unidirectional flow was present, in which air flowed caudad in the cervical ventral bronchus and its branches during both lung inflation and deflation and craniad in dorsobronchi and their branches. Tubular pathways connected the secondary bronchi to each other and allowed air to flow from the dorsobronchi into the ventrobronchi. No evidence for anatomical valves was found, suggesting that aerodynamic valves cause the unidirectional flow. In vivo data from the American alligator showed that unidirectional flow is present during periods of breath-holding (apnea) and is powered by the beating heart, suggesting that this pattern of flow harnesses the heart as a pump for air. Unidirectional flow may also facilitate washout of stale gases from the lung, reducing the cost of breathing, respiratory evaporative water loss, heat loss through the heat of vaporization, and facilitating crypsis. The similarity in structure and function of the bird lung with pulmonary anatomy of this broad range of crocodilian species indicates that a similar morphology and pattern of unidirectional flow were present in the lungs of the common ancestor of crocodilians and birds. These data suggest a paradigm shift is needed in our understanding of the evolution of this character. Although conventional wisdom is that unidirectional flow is important for the high activity and basal metabolic rates for which birds are renowned, the widespread occurrence of this pattern of flow in crocodilians indicates otherwise. Furthermore, these results show that air sacs are not requisite for unidirectional flow, and therefore raise questions about the function of avian air sacs.

Evolution of basal metabolic rate in bank voles from a multidirectional selection experiment.

A major theme in evolutionary and ecological physiology of terrestrial vertebrates encompasses the factors underlying the evolution of endothermy in birds and mammals and interspecific variation of basal metabolic rate (BMR). Here, we applied the experimental evolution approach and compared BMR in lines of a wild rodent, the bank vole (Myodes glareolus), selected for 11 generations for: high swim-induced aerobic metabolism (A), ability to maintain body mass on a low-quality herbivorous diet (H) and intensity of predatory behaviour towards crickets (P). Four replicate lines were maintained for each of the selection directions and an unselected control (C). In comparison to C lines, A lines achieved a 49% higher maximum rate of oxygen consumption during swimming, H lines lost 1.3 g less mass in the test with low-quality diet and P lines attacked crickets five times more frequently. BMR was significantly higher in A lines than in C or H lines (60.8, 56.6 and 54.4 ml O2 h(-1), respectively), and the values were intermediate in P lines (59.0 ml O2 h(-1)). Results of the selection experiment provide support for the hypothesis of a positive association between BMR and aerobic exercise performance, but not for the association of adaptation to herbivorous diet with either a high or low BMR.

A strong response to selection on mass-independent maximal metabolic rate without a correlated response in basal metabolic rate.

Metabolic rates are correlated with many aspects of ecology, but how selection on different aspects of metabolic rates affects their mutual evolution is poorly understood. Using laboratory mice, we artificially selected for high maximal mass-independent metabolic rate (MMR) without direct selection on mass-independent basal metabolic rate (BMR). Then we tested for responses to selection in MMR and correlated responses to selection in BMR. In other lines, we antagonistically selected for mice with a combination of high mass-independent MMR and low mass-independent BMR. All selection protocols and data analyses included body mass as a covariate, so effects of selection on the metabolic rates are mass adjusted (that is, independent of effects of body mass). The selection lasted eight generations. Compared with controls, MMR was significantly higher (11.2%) in lines selected for increased MMR, and BMR was slightly, but not significantly, higher (2.5%). Compared with controls, MMR was significantly higher (5.3%) in antagonistically selected lines, and BMR was slightly, but not significantly, lower (4.2%). Analysis of breeding values revealed no positive genetic trend for elevated BMR in high-MMR lines. A weak positive genetic correlation was detected between MMR and BMR. That weak positive genetic correlation supports the aerobic capacity model for the evolution of endothermy in the sense that it fails to falsify a key model assumption. Overall, the results suggest that at least in these mice there is significant capacity for independent evolution of metabolic traits. Whether that is true in the ancestral animals that evolved endothermy remains an important but unanswered question.

Decreased basic metabolic rate may reflect pituitary secretion disturbance in elite female athlete

To evaluate the relationship between basal metabolic rate, energy balance and hormones level in young female athletes with menstrual disorders. Thirty-three well-trained young female athletes, aged 18.4 ± 2.9 years, with menstrual disorders due to hypothalamic-pituitary dysfunction, participated in the study. Evaluation of nutritional status was based on analyses of body composition using the BIA method (fat mass [FM], fat-free mass [FFM]). Basal metabolic rate (BMR) was assessed with a portable indirect calorimeter. Serum luteinizing hormone (LH), folliculate-stimulating hormone (FSH), estradiol (E2), TSH, testosterone (T), prolactin (PRL) and sex-hormone binding globulin (SHBG) and leptin levels were measured. Total energy expenditure (TEE) was evaluated using the HR-Flex method. Dietary records for 7 consecutive days were used to evaluate the athletes’ energy and nutrient intakes. Depending on the measured BMR value and comparing with the Harris-Benedict equation, female athletes were assigned to one of the two groups: LBMR group with low BMRs and HBMR group with high BMRs. Serum leptin (P < 0.016) and LH levels (P < 0.003) were significantly lower in the LBMR group. In the LBMR athletes, a tendency towards negative energy balance was observed (P < 0.032). Significant correlations were found between BMR and LH level (P < 0.021) and between LH and leptin levels (P < 0.001) in the entire sample. Decreased BMR may reflect pituitary secretion disturbance in elite female athlete. Évaluer un lien entre le taux métabolique de base, l’équilibre énergétique et taux d’hormones chez les jeunes athlètes féminines présentant des troubles menstruels. Trente-trois jeunes athlètes féminines bien entraînées avec troubles menstruels à cause d’un dysfonctionnement hypothalamo-hypophysaire, âgées de 18,4 ± 2,9 ans, ont participé à l’étude. L’évaluation nutritionnelle était fondée sur des analyses de la composition corporelle mesurée à l’aide de méthode BIA (masse grasse [FM], masse maigre [FFM]). Le taux métabolique de base (TMB) a été mesuré à l’aide d’un calorimètre indirect portable. Les taux sériques de : hormone lutéinisante (LH), hormone folliculostimulante (FSH), oestradiol (E2), TSH, testostérone (T), prolactine (PRL) et globuline se liant aux hormones sexuelles (SHBG), ainsi que leptine ont été mesurés. La dépense énergétique totale (DET) a été mesurée à l’aide de méthode HR-Flex. Afin d’évaluer les apports énergétiques et nutritionnels des athlètes, nous avons utilisé des dossiers diététiques pendant 7 jours consécutifs. Selon les TMB mesurés et après avoir comparé des valeurs à l’aide d’une équation Harris-Benedict, des athlètes féminines ont été assignées à l’un des deux groupes : groupe LBMR avec un TMB bas et groupe HBMR avec un TMB haut. Le taux sérique de leptine (p < 0,016) et les taux de LH (p < 0,003) étaient sensiblement inférieurs dans le groupe LBMR. La tendance vers l’équilibre énergétique négatif a été observée dans le groupe LBMR (p < 0,032). Rapporté à l’ensemble de l’échantillon, des corrélations significatives entre le TMB et le taux de LH (p < 0,021) et entre les taux de LH et leptine (p < 0,001) ont été trouvées. Le TMB réduit chez les athlètes féminines d’élite peut indiquer un problème de la sécrétion hypophysaire.

Does metabolic rate predict risk‐taking behaviour? A field experiment in a wild passerine bird

Summary Individuals often show consistent differences in risk‐taking behaviours; behaviours that increase resource acquisition at the expense of an increased risk of mortality. Recently, basal metabolic rate (BMR) has been suggested as a potentially important state variable underlying adaptive individual differences in a range of behaviours, including risk‐taking. We tested the relationship between BMR and risk‐taking in free‐living great tits (Parus major) using experimental manipulations of perceived predation risk. We compared the latency of individuals to return to feeders following control (human) and predator (model sparrowhawk, Accipiter nisus) disturbances at fixed feeder locations. We predicted that if variation in risk‐taking is shaped by energetic constraints, high BMR individuals should return to feeders sooner following both disturbance types and show smaller changes in risk‐taking as a function of predation danger. Higher BMR tended to be associated with lower risk‐taking following control disturbances but greater risk‐taking following predator disturbances, resulting in a significant interaction between BMR and treatment. Within‐individual changes in risk‐taking as a function of ambient temperature (a proxy for within‐individual changes in energetic constraints) mirrored these results. Lower temperatures tended to be associated with lower risk‐taking following control disturbances, but greater risk‐taking following predator disturbances, resulting in a significant interaction between temperature and treatment. The effects of BMR and temperature on variation in risk‐taking as a function of perceived predation danger were qualitatively similar, suggesting that energetic constraints play a role in shaping risk‐taking. However, the hypothesized mechanism (energetic requirements directly influence the optimal expression of risk‐taking behaviour) is insufficient to account for the observed negative relationship between energetic constraint and risk‐taking following control disturbances. We conclude that variation in risk‐taking is associated with differences in energetic constraints, including BMR and temperature, but that the relationship is context‐specific, here high vs. low perceived predation risk. Further studies are needed to elucidate potential mechanisms that could generate context‐specific relationships between energetic constraints and risk‐taking.

Sarcolipin overexpression in mice increases their endurance exercise capacity (1162.2)

Sarcolipin (SLN) is a transmembrane protein that interacts with Sarco(endo)plasmic Reticulum Calcium ATPase (SERCA) and is expressed in cardiac and skeletal muscle. SLN is known to inhibit Vmax of SERCA, but its role in muscle physiology is yet to be fully understood. We have shed some light on this front, by showing that SLN knock out (SLN KO) mice are highly sensitive to acute cold and are prone to develop obesity when fed a high fat diet. Moreover, we showed that the SLN KO mice can be rescued from hypothermia by over expression of the SLN transgene; suggesting that SLN is essential for heat generation and increasing metabolic rate. The aim of this study was to further explore how SLN affects muscle function and metabolism; by the use of SLN over expression (SLN OE) mouse model, which expresses SLN in all skeletal muscles up to 10 fold higher than in wild type (WT) mice. Here, we show that SLN OE mice have a higher basal metabolic rate (by indirect calorimetry) than WT mice. The SLN OE mice also have a significantly higher endurance capacity (treadmill running) than their WT littermates. Isolated muscle studies using Tissue Oxygen bath system, show that SLN OE muscle has similar force frequency response as WT muscle, but is more resistant to develop fatigue and consumes more oxygen. Analysis of muscle oxidative metabolic markers and oxygraph measurements using isolated mitochondria; suggest an increased oxidative capacity in the SLN OE muscle compared to WT. Although skeletal muscle can increase metabolic rate up to hundred fold, a decline in the rate of ATP production is a major reason for muscle fatigue during prolonged physical activity. Hence, these results indicate that SLN enhances muscle’s ability to hydrolyze substrates and generate ATP in times of increased energy demand, which in turn increases endurance capacity.Grant Funding Source: Supported by NIH

Thermal energetics of the New-Guinean moss-forest rat (Rattus niobe) in comparison with other tropical murid rodents

The thermal energetics of rodents from cool, wet tropical highlands are poorly known. Metabolic rate, body temperature and thermal conductance were measured in the moss-forest rat, Rattus niobe (Rodentia), a small murid endemic to the highlands of New Guinea. These data were evaluated in the context of the variation observed in the genus Rattus and among tropical murids. In 7 adult R. niobe, basal metabolic rate (BMR) averaged 53.6±6.6mLO2h−1, or 103% of the value predicted for a body mass of 42.3±5.8g. Compared to other species of Rattus, R. niobe combines a low body temperature (35.5±0.6°C) and a moderately low minimal wet thermal conductance cmin (5.88±0.7mLO2h−1°C−1, 95% of predicted) with a small size, all of which lead to reduced energy expenditure in a constantly cool environment. The correlations of mean annual rainfall and temperature, altitude and body mass with BMR, body temperature and cmin were analyzed comparatively among tropical Muridae. Neither BMR, nor cmin or body temperature correlated with ambient temperature or altitude. Some of the factors which promote high BMR in higher latitude habitats, such as seasonal exposure to very low temperature and short reproductive season, are lacking in wet montane tropical forests. BMR increased with rainfall, confirming a pattern observed among other assemblages of mammals. This correlation was due to the low BMR of several desert adapted murids, while R. niobe and other species from wet habitats had a moderate BMR.

Evolution of mitochondrial DNA and its relation to basal metabolic rate

Energy metabolism is essential for the survival of animals, which can be characterized by maximum metabolic rate (MMR) and basal metabolic rate (BMR). Because of the crucial roles of mitochondria in energy metabolism, mitochondrial DNA (mtDNA) has been subjected to stronger purifying selection in strongly locomotive than weakly locomotive birds and mammals. Although maximum locomotive speed (an indicator of MMR) showed a negative correlation with the evolutionary rate of mtDNA, it is unclear whether BMR has driven the evolution of mtDNA. Here, we take advantage of the large amount of mtDNA and BMR data in 106 mammals to test whether BMR has influenced the mtDNA evolution. Our results showed that, in addition to the locomotive speed, mammals with higher BMR have subjected to stronger purifying selection on mtDNA than did those with lower BMR. The evolution of mammalian mtDNA has been modified by two levels of energy metabolism, including MMR and BMR. Our study provides a more comprehensive view of mtDNA evolution in relation to energy metabolism.

Mice divergently selected for high and low basal metabolic rates evolved different cell size and organ mass

Evolution of metabolic rates of multicellular organisms is hypothesized to reflect the evolution of their cell architecture. This is likely to stem from a tight link between the sizes of cells and nuclei, which are expected to be inversely related to cell metabolism. Here, we analysed basal metabolic rate (BMR), internal organ masses and the cell/nucleus size in different tissues of laboratory mice divergently selected for high/low mass-corrected BMR and four random-bred mouse lines. Random-bred lines had intermediate levels of BMR as compared to low- and high-BMR lines. Yet, this pattern was only partly consistent with the between-line differences in cell/nucleus sizes. Erythrocytes and skin epithelium cells were smaller in the high-BMR line than in other lines, but the cells of low-BMR and random-bred mice were similar in size. On the other hand, the size of hepatocytes, kidney proximal tubule cells and duodenum enterocytes were larger in high-BMR mice than other lines. All cell and nucleus sizes were positively correlated, which supports the role of the nucleus in cell size regulation. Our results suggest that the evolution of high BMR involves a reduction in cell size in specialized tissues, whose functions are primarily dictated by surface-to-volume ratios, such as erythrocytes. High BMR may, however, also incur an increase in cell size in tissues with an intense transcription and translation, such as hepatocytes.

High basal metabolic rate does not elevate oxidative stress during reproduction in laboratory mice

Increased oxidative stress (OS) has been suggested as a physiological cost of reproduction. However, previous studies reported ambiguous results, with some even showing a reduction of oxidative damage during reproduction. We tested whether the link between reproduction and OS is mediated by basal metabolic rate (BMR), which has been hypothesized to affect both the rate of radical oxygen species production and antioxidative capacity. We studied the effect of reproduction on OS in females of laboratory mice divergently selected for high (H-BMR) and low (L-BMR) BMR, previously shown to differ with respect to parental investment. Non-reproducing L-BMR females showed higher oxidative damage to lipids (quantified as the level of malondialdehyde in internal organ tissues) and DNA (quantified as the level of 8-oxodG in blood serum) than H-BMR females. Reproduction did not affect oxidative damage to lipids in either line; however, it reduced damage to DNA in L-BMR females. Reproduction increased catalase activity in liver (significantly stronger in L-BMR females) and decreased it in kidneys. We conclude that the effect of reproduction on OS depends on the initial variation in BMR and varies between studied internal organs and markers of OS.

Milk output and composition in mice divergently selected for basal metabolic rate.

From an evolutionary perspective, the high basal metabolic rate (BMR) of homeotherms is hypothesised to be a by-product of natural selection for effective parental care. We estimated daily milk output during two consecutive lactation bouts in mice divergently selected for high/low BMR and applied a cross-fostered design to control for potential differences in the between-line suckling abilities of nursed juveniles. Additionally, to remedy the potential limitation imposed by the ability of mother mice to dissipate excess heat, we exposed them to an ambient temperature of 17°C during the most energetically demanding second week of lactation. We found that the mice selected for high BMR produced significantly more milk in a 24 h period in both reproductive bouts. The milk samples obtained from the high BMR females had lower protein concentration and did not differ with respect to fat. However, the concentration of the primary milk carbohydrate – lactose – was higher. Although all the above between-line differences were statistically significant, their magnitude was too small to unambiguously ascribe them as stemming from a positive genetic correlation between the physiological traits underlying BMR and lactation performance. Nevertheless, our study lends such support at least at the level of phenotypic variation.

Metabolism, thermoregulation and evaporative water loss in the Chaotung Vole (Eothenomys olitor) in Yunnan-Kweichow Plateau in summer

Proper adjustment of thermoregulatory mechanisms ensures the survival of mammals when they are subjected to seasonal changes in their natural environment. To understand the physiological and ecological adaptations of Eothenomys olitor, we measured their metabolic rate, thermal conductance, body temperature (Tb) and evaporative water loss at a temperature range of 5–30°C in summer. The thermal neutral zone (TNZ) of E. olitor was 20–27.5°C, and the mean body temperature was 35.81±0.15°C. Basal metabolic rate (BMR) was 2.81±0.11mlO2/gh and mean minimum thermal conductance (Cm) was 0.18±0.01mlO2/gh°C. Evaporative water loss (EWL) in E. olitor increased when the ambient temperature increased. The maximal evaporative water loss was 6.74±0.19mgH2O/gh at 30°C. These results indicated that E. olitor have relatively high BMR, low body temperature, low lower critical temperature, and normal thermal conductance. EWL plays an inportant role in temperature regulation. These characteristics are closely related to the living habitat of the species, and represent its adaptive strategy to the climate of the Yunnan-Kweichow Plateau, a low-latitude, high-altitude region where annual temperature fluctuations are small, but daily temperature fluctuations are greater.

Basal metabolic rate is positively correlated with parental investment in laboratory mice

The assimilation capacity (AC) hypothesis for the evolution of endothermy predicts that the maternal basal metabolic rate (BMR) should be positively correlated with the capacity for parental investment. In this study, we provide a unique test of the AC model based on mice from a long-term selection experiment designed to produce divergent levels of BMR. By constructing experimental families with cross-fostered litters, we were able to control for the effect of the mother as well as the type of pup based on the selected lines. We found that mothers with genetically determined high levels of BMR were characterized by higher parental investment capacity, measured as the offspring growth rate. We also found higher food consumption and heavier visceral organs in the females with high BMR. These findings suggested that the high-BMR females have higher energy acquisition abilities. When the effect of the line type of a foster mother was controlled, the pup line type significantly affected the growth rate only in the first week of life, with young from the high-BMR line type growing more rapidly. Our results support the predictions of the AC model.

Evolutionary implications of the divergent long bone histologies of Nothosaurus and Pistosaurus (Sauropterygia, Triassic)

BackgroundEosauropterygians consist of two major clades, the Nothosauroidea of the Tethysian Middle Triassic (e.g., Nothosaurus) and the Pistosauroidea. The Pistosauroidea include rare Triassic forms (Pistosauridae) and the Plesiosauria of the Jurassic and Cretaceous. Long bones of Nothosaurus and Pistosaurus from the Muschelkalk (Middle Triassic) of Germany and France and a femur of the Lower Jurassic Plesiosaurus dolichodeirus were studied histologically and microanatomically to understand the evolution of locomotory adaptations, patterns of growth and life history in these two lineages.ResultsWe found that the cortex of adult Nothosaurus long bones consists of lamellar zonal bone. Large Upper Muschelkalk humeri of large-bodied Nothosaurus mirabilis and N. giganteus differ from the small Lower Muschelkalk (Nothosaurus marchicus/N. winterswijkensis) humeri by a striking microanatomical specialization for aquatic tetrapods: the medullary cavity is much enlarged and the cortex is reduced to a few millimeters in thickness. Unexpectedly, the humeri of Pistosaurus consist of continuously deposited, radially vascularized fibrolamellar bone tissue like in the Plesiosaurus sample. Plesiosaurus shows intense Haversian remodeling, which has never been described in Triassic sauropterygians.ConclusionsThe generally lamellar zonal bone tissue of nothosaur long bones indicates a low growth rate and suggests a low basal metabolic rate. The large triangular cross section of large-bodied Nothosaurus from the Upper Muschelkalk with their large medullary region evolved to withstand high bending loads. Nothosaurus humerus morphology and microanatomy indicates the evolution of paraxial front limb propulsion in the Middle Triassic, well before its convergent evolution in the Plesiosauria in the latest Triassic. Fibrolamellar bone tissue, as found in Pistosaurus and Plesiosaurus, suggests a high growth rate and basal metabolic rate. The presence of fibrolamellar bone tissue in Pistosaurus suggests that these features had already evolved in the Pistosauroidea by the Middle Triassic, well before the plesiosaurs radiated. Together with a relatively large body size, a high basal metabolic rate probably was the key to the invasion of the Pistosauroidea of the pelagic habitat in the Middle Triassic and the success of the Plesiosauria in the Jurassic and Cretaceous.

TT Mutant Homozygote ofKruppel-like Factor 5Is a Key Factor for Increasing Basal Metabolic Rate and Resting Metabolic Rate in Korean Elementary School Children

We investigated the contribution of genetic variations of KLF5 to basal metabolic rate (BMR) and resting metabolic rate (RMR) and the inhibition of obesity in Korean children. A variation of KLF5 (rs3782933) was genotyped in 62 Korean children. Using multiple linear regression analysis, we developed a model to predict BMR in children. We divided them into several groups; normal versus overweight by body mass index (BMI) and low BMR versus high BMR by BMR. There were no differences in the distributions of alleles and genotypes between each group. The genetic variation of KLF5 gene showed a significant correlation with several clinical factors, such as BMR, muscle, low-density lipoprotein cholesterol, and insulin. Children with the TT had significantly higher BMR than those with CC (p = 0.030). The highest muscle was observed in the children with TT compared with CC (p = 0.032). The insulin and C-peptide values were higher in children with TT than those with CC (p= 0.029 vs. p = 0.004, respectively). In linear regression analysis, BMI and muscle mass were correlated with BMR, whereas insulin and C-peptide were not associated with BMR. In the high-BMR group, we observed that higher muscle, fat mass, and C-peptide affect the increase of BMR in children with TT (p < 0.001, p < 0.001, and p = 0.018, respectively), while Rohrer's index could explain the usual decrease in BMR (adjust r2 = 1.000, p < 0.001, respectively). We identified a novel association between TT of KLF5 rs3782933 and BMR in Korean children. We could make better use of the variation within KLF5 in a future clinical intervention study of obesity.

Inflammatory challenge increases measures of oxidative stress in a free-ranging, long-lived mammal

Oxidative stress - the imbalance between reactive oxygen species (ROS) and neutralising antioxidants - has been under debate as the main cause of ageing in aerobial organisms. The level of ROS should increase during infection as part of the activation of an immune response, leading to oxidative damage to proteins, lipids and DNA. Yet, it is unknown how long-lived organisms, especially mammals, cope with oxidative stress. Bats are known to carry a variety of zoonotic pathogens and at the same time are, despite their high mass-specific basal metabolic rate, unusually long lived, which may be partly the result of low oxidative damage of organs. Here, we asked whether an immune challenge causes oxidative stress in free-ranging bats, measuring two oxidative stress markers. We injected 20 short-tailed fruit bats (Carollia perspicillata) with bacterially derived lipopolysaccharide (LPS) and 20 individuals with phosphate-buffered saline solution (PBS) as a control. Individuals injected with LPS showed an immune reaction by increased white blood cell count after 24 h, whereas there was no significant change in leukocyte count in control animals. The biological antioxidant potential (BAP) remained the same in both groups, but reactive oxygen metabolites (ROMs) increased after treatment with LPS, indicating a significant increase in oxidative stress in animals when mounting an immune reaction toward the inflammatory challenge. Control individuals did not show a change in oxidative stress markers. We conclude that in a long-lived mammal, even high concentrations of antioxidants do not immediately neutralise free radicals produced during a cellular immune response. Thus, fighting an infection may lead to oxidative stress in bats.

Defining a molecular portrait of physical fitness

To most individuals, the concept of fitness tends to conjure up mental images of physical attributes such as muscular definition or low bodyweight. However, while physical fitness (e.g., body weight, adiposity) is an important component of overall health, there are many “unseen” physiological and biological fitness alterations to the human body that have a far-reaching impact on health and wellness. Over the years, there have been many studies investigating the physiological implications, benefits, and consequences of physical fitness [1]. There are a number of important physiological adaptations, which occur with increasing aptitude in physical fitness. These adaptations include, but are not limited to, greater cardiorespiratory capacity/efficiency, denser bone structure, higher basal metabolic rates, and lower levels of adiposity [2–4]. Furthermore, each adaptation is linked to improved mortality and reduced risk of acute and chronic illnesses. However, though mostly beneficial, these unseen physiological fitness changes may be so varied depending on the individual that they can cause challenges for healthcare providers [5, 6]. Prevention and management of disease, as well as therapeutic dosing, are directly affected by the fitness level of an individual. Therefore, defining the fitness status of an individual at a molecular level, not just by determining physical parameters of fitness, should result in better healthcare and enhanced well-being of an individual. For example, although therapeutic dosing is, in general, determined based on the total body weight of an individual, studies have demonstrated that more physically fit individuals, with more lean mass and less adiposity, can clear pharmaceuticals faster than sedentary individuals with the same total body weight [7, 8]. Dosage decision making may be better tailored to an individual's need in the future by taking into account his/her fitness level. In that regard, the availability of molecular markers of fitness should allow for more precise therapeutic dosing as compared to the traditional method of basing it on total body weight. The ability to rapidly determine the aptitude and the level of physical fitness, through molecular screening methods, has implications in many different fields, those ranging from healthcare [2, 5, 6, 9] to athletics [3] and to the military [10, 11]. To this end, it is necessary to discover and investigate molecular markers which are robust, can be observed at either elevated or lowered levels after short or prolonged exercise(s) regimes or during sedentary periods, and are accurate indicators of the physical fitness and lifestyle of an individual. Furthermore, it will also be necessary to develop point-of-care devices and corresponding analytical methods to make analysis of these molecular markers as simple and cost effective as possible. The aim of this article is to provide information that guides in the selection, detection, and future usage of molecular markers of physical fitness.

The physiology of the honey possum, Tarsipes rostratus, a small marsupial with a suite of highly specialised characters: a review

Field and laboratory studies of the iconic nectarivorous and 'pollenivorous' honey possum, Tarsipes rostratus, are reviewed with the aim of identifying aspects of its physiology that are as yet poorly understood and needed to implement management strategies for its long-term conservation. Dietary specialisations include the loss of teeth, a modified gut with a high rate of passage, exceptionally low minimum nitrogen requirements, an apparently high basal metabolic rate and a permanently polyuric kidney. In contrast, its reproductive physiology is plesiomorphic, combining aspects such as a post-partum oestrus, embryonic diapause, photoperiodicity and extended maternal care that are usually separate characteristics of other marsupial groups. In common with a number of other marsupials, the honey possum has the potential for trichromatic colour vision and has been the subject of several studies attempting to correlate visual quality with ecological realities. Field physiological studies have established its high rates of nectar and pollen intake needed to maintain energy balance and highlight the need for a constant intake from floral sources. Early allometric studies suggesting that the honey possum's relatively low reproductive rate may be linked to a diet limited in protein have not been supported and nitrogen intakes in the field exceed by a factor of 10 the animal's basic requirements for balance. Measurements of rates of protein turnover in field-caught lactating females suggest that they divert nitrogen from the protein pool to milk production by reducing rates of degradation, rather than by increasing rates of synthesis of protein. Although not yet an endangered species, the honey possum's habitat has been drastically reduced since European occupation of Australia and future-targeted research on the animal's unique physiology and habitat linkage is needed that can be translated into effective management practices. Only then will its long-term survival be assured.

Effect of Dietary Restriction on Immune Response of Laboratory Mice Divergently Selected for Basal Metabolic Rate

To study whether dietary restriction (DR; 70% of ad lib. feeding)-elicited immunosuppression results from the trade-off between the costs of mounting an immune response and the metabolic costs of maintenance, we subjected mice from two divergent lines selected for high basal metabolic rate (H-BMR) and low BMR (L-BMR) to 4 wk of DR and then challenged them with keyhole limpet hemocyanin (KLH) antigen. Those line types differ genetically with respect to BMR and to the mass of metabolically expensive internal organs, which are larger in H-BMR mice. In mice of both line types, DR resulted in a significant reduction of body mass, an immune response, and the downsizing of spleen, lymph nodes, thymus, heart, and kidneys but not small intestines. DR resulted in a greater reduction of the spleen and lymph nodes in mice of the H-BMR line type, whereas the thymus was more affected in L-BMR line type. In contrast, immunization resulted in an increase of liver mass in DR mice of both line types. A comparison of the results of current and earlier studies on the same mouse line types suggests that metabolic trade-offs involving the costs of an immune response are more apparent when animals are forced to increase energy demands (e.g., by cold exposure) compared to when energy demands are decreased through DR. Our findings also suggest that divelrgent selection on BMR resulted in between-line-type differences in T-cell- and B-cell-mediated types of an immune response. More generally, our results indicate that production of a wide repertoire of antibodies is not correlated with high BMR.