Daily Rhythms of Core Temperature and Locomotor Activity Indicate Different Adaptive Strategies to Cold Exposure in Adult and Aged Mouse Lemurs Acclimated to a Summer-Like Photoperiod

Daily variations in core temperature (Tc) within the normothermic range imply thermoregulatory processes that are essential for optimal function and survival. Higher susceptibility towards cold exposure in older animals suggests that these processes are disturbed with age. In the mouse lemur, a long-day breeder, we tested whether aging affected circadian rhythmicity of Tc, locomotor activity (LA), and energy balance under long-day conditions when exposed to cold. Adult (N?=?7) and aged (N?=?5) mouse lemurs acclimated to LD14/10 were exposed to 10–day periods at 25 and 12°C. Tc and LA rhythms were recorded by telemetry, and caloric intake (CI), body mass changes, and plasma IGF-1 were measured. During exposure to 25°C, both adult and aged mouse lemurs exhibited strong daily variations in Tc. Aged animals exhibited lower levels of nocturnal LA and nocturnal and diurnal Tc levels in comparison to adults. Body mass and IGF-1 levels remained unchanged with aging. Under cold exposure, torpor bout occurrence was never observed whatever the age category. Adult and aged mouse lemurs maintained their Tc in the normothermic range and a positive energy balance. All animals exhibited increase in CI and decrease in IGF-1 in response to cold. The decrease in IGF-1 was delayed in aged mouse lemurs compared to adults. Moreover, both adult and aged animals responded to cold exposure by increasing their diurnal LA compared to those under Ta?=?25°C. However, aged animals exhibited a strong decrease in nocturnal LA and Tc, whereas cold effects were only slight in adults. The temporal organization and amplitude of the daily phase of low Tc were particularly well preserved under cold exposure in both age groups. Sexually active mouse lemurs exposed to cold thus seemed to prevent torpor exhibition and temporal disorganization of daily rhythms of Tc, even during aging. However, although energy balance was not impaired with age in mouse lemurs after cold exposure, aging was associated with lower LA and Tc during the night and delayed decrease in IGF-1. This might reflect that adaptive strategies to cold exposure differ with age in mouse lemurs acclimated to a summer-like photoperiod.     

Effects of age on thermoregulatory responses during cold exposure in a nonhuman primate, Microcebus murinus

Cold resistance appears altered with aging. Among existing hypotheses, the impaired capacity in response to cold could be related to an altered regulation of plasma IGF-1 concentration. The combined effects of age and cold exposure were studied in a short-living primate, the gray mouse lemur (Microcebus murinus), which adjusts its energy balance using a daily torpor phase, to avoid high energy cost of normothermia maintenance. Changes in body mass, core temperature, locomotor activity, and caloric intake were monitored under 9-day exposures to 25 degrees C and 12 degrees C in captive animals in winter conditions. Short-term (after 2 days) and long-term (after 9 days) cold-induced changes in IGF-1 levels were also evaluated. In thermoneutral conditions (25 degrees C), general characteristics of the daily rhythm of core temperature were preserved with age. At 12 degrees C, age-related changes were mainly characterized by a deeper hypothermia and an increased frequency of torpor phases, associated with a loss of body mass. A short-term cold-induced decrease in plasma IGF-1 levels was observed. IGF-1 levels returned to basal values after 9 days of cold exposure. No significant effect of age could be evidenced on IGF-1 response. However, IGF-1 levels of cold-exposed aged animals were negatively correlated with the frequency of daily torpor. Responses exhibited by aged mouse lemurs exposed to cold revealed difficulties in the maintenance of normothermia and energy balance and might involve modulations of IGF-1 levels.     

The Influence of Shc Proteins and Aging on Whole Body Energy Expenditure and Substrate Utilization in Mice

While it has been proposed that Shc family of adaptor proteins may influence aging by regulating insulin signaling and energy metabolism, the overall impact of Shc proteins on whole body energy metabolism has yet to be elucidated. Thus, the purpose of this study was to determine the influence of Shc proteins and aging on whole body energy metabolism in a mouse model under ambient conditions (22°C) and acute cold exposure (12°C for 24 hours). Using indirect respiration calorimetry, we investigated the impact of Shc proteins and aging on EE and substrate utilization (RQ) in p66 Shc−/− (ShcKO) and wild-type (WT) mice. Calorimetry measurements were completed in 3, 15, and 27 mo mice at 22°C and 12°C. At both temperatures and when analyzed across all age groups, ShcKO mice demonstrated lower 24 h total EE values than that of WT mice when EE data was expressed as either kJ per mouse, or adjusted by body weight or crude organ mass (ORGAN) (P≤0.01 for all). The ShcKO mice also had higher (P<0.05) fed state RQ values than WT animals at 22°C, consistent with an increase in glucose utilization. However, Shc proteins did not influence age-related changes in energy expenditure or RQ. Age had a significant impact on EE at 22°C, regardless of how EE data was expressed (P<0.05), demonstrating a pattern of increase in EE from age 3 to 15 mo, followed by a decrease in EE at 27 mo. These results indicate a decline in whole body EE with advanced age in mice, independent of changes in body weight (BW) or fat free mass (FFM). The results of this study indicate that both Shc proteins and aging should be considered as factors that influence energy expenditure in mice.     

The Relationship between Running Velocity and the Energy Cost of Turning during Running

Ball game players frequently perform changes of direction (CODs) while running; however, there has been little research on the physiological impact of CODs. In particular, the effect of running velocity on the physiological and energy demands of CODs while running has not been clearly determined. The purpose of this study was to examine the relationship between running velocity and the energy cost of a 180°COD and to quantify the energy cost of a 180°COD. Nine male university students (aged 18–22 years) participated in the study. Five shuttle trials were performed in which the subjects were required to run at different velocities (3, 4, 5, 6, 7, and 8 km/h). Each trial consisted of four stages with different turn frequencies (13, 18, 24 and 30 per minute), and each stage lasted 3 minutes. Oxygen consumption was measured during the trial. The energy cost of a COD significantly increased with running velocity (except between 7 and 8 km/h, p = 0.110). The relationship between running velocity and the energy cost of a 180°COD is best represented by a quadratic function (y = −0.012+0.066x +0.008x², [r = 0.994, p = 0.001]), but is also well represented by a linear (y = −0.228+0.152x, [r = 0.991, p<0.001]). These data suggest that even low running velocities have relatively high physiological demands if the COD frequency increases, and that running velocities affect the physiological demands of CODs. These results also showed that the energy expenditure of COD can be evaluated using only two data points. These results may be useful for estimating the energy expenditure of players during a match and designing shuttle exercise training programs.     

Effects of Slow Deep Breathing at High Altitude on Oxygen Saturation,Pulmonary and Systemic Hemodynamics

Slow deep breathing improves blood oxygenation (Sp_O2) and affects hemodynamics in hypoxic patients. We investigated the ventilatory and hemodynamic effects of slow deep breathing in normal subjects at high altitude. We collected data in healthy lowlanders staying either at 4559 m for 2–3 days (Study A; N = 39) or at 5400 m for 12–16 days (Study B; N = 28). Study variables, including Sp_O2 and systemic and pulmonary arterial pressure, were assessed before, during and after 15 minutes of breathing at 6 breaths/min. At the end of slow breathing, an increase in Sp_O2 (Study A: from 80.2±7.7% to 89.5±8.2%; Study B: from 81.0±4.2% to 88.6±4.5; both p<0.001) and significant reductions in systemic and pulmonary arterial pressure occurred. This was associated with increased tidal volume and no changes in minute ventilation or pulmonary CO diffusion. Slow deep breathing improves ventilation efficiency for oxygen as shown by blood oxygenation increase, and it reduces systemic and pulmonary blood pressure at high altitude but does not change pulmonary gas diffusion.     

Acute Effects of Capsaicin on Energy Expenditure and Fat Oxidation in Negative Energy Balance

Background

Addition of capsaicin (CAPS) to the diet has been shown to increase energy expenditure; therefore capsaicin is an interesting target for anti-obesity therapy.

Aim

We investigated the 24 h effects of CAPS on energy expenditure, substrate oxidation and blood pressure during 25% negative energy balance.

Methods

Subjects underwent four 36 h sessions in a respiration chamber for measurements of energy expenditure, substrate oxidation and blood pressure. They received 100% or 75% of their daily energy requirements in the conditions ‘100%CAPS’, ‘100%Control’, ‘75%CAPS’ and ‘75%Control’. CAPS was given at a dose of 2.56 mg (1.03 g of red chili pepper, 39,050 Scoville heat units (SHU)) with every meal.

Results

An induced negative energy balance of 25% was effectively a 20.5% negative energy balance due to adapting mechanisms. Diet-induced thermogenesis (DIT) and resting energy expenditure (REE) at 75%CAPS did not differ from DIT and REE at 100%Control, while at 75%Control these tended to be or were lower than at 100%Control (p = 0.05 and p = 0.02 respectively). Sleeping metabolic rate (SMR) at 75%CAPS did not differ from SMR at 100%CAPS, while SMR at 75%Control was lower than at 100%CAPS (p = 0.04). Fat oxidation at 75%CAPS was higher than at 100%Control (p = 0.03), while with 75%Control it did not differ from 100%Control. Respiratory quotient (RQ) was more decreased at 75%CAPS (p = 0.04) than at 75%Control (p = 0.05) when compared with 100%Control. Blood pressure did not differ between the four conditions.

Conclusion

In an effectively 20.5% negative energy balance, consumption of 2.56 mg capsaicin per meal supports negative energy balance by counteracting the unfavorable negative energy balance effect of decrease in components of energy expenditure. Moreover, consumption of 2.56 mg capsaicin per meal promotes fat oxidation in negative energy balance and does not increase blood pressure significantly.

Trial Registration

Nederlands Trial Register; registration number NTR2944     

Vagus Nerve Stimulation Increases Energy Expenditure: Relation to Brown Adipose Tissue Activity

Background

Human brown adipose tissue (BAT) activity is inversely related to obesity and positively related to energy expenditure. BAT is highly innervated and it is suggested the vagus nerve mediates peripheral signals to the central nervous system, there connecting to sympathetic nerves that innervate BAT. Vagus nerve stimulation (VNS) is used for refractory epilepsy, but is also reported to generate weight loss. We hypothesize VNS increases energy expenditure by activating BAT.

Methods and Findings

Fifteen patients with stable VNS therapy (age: 45±10yrs; body mass index; 25.2±3.5 kg/m²) were included between January 2011 and June 2012. Ten subjects were measured twice, once with active and once with inactivated VNS. Five other subjects were measured twice, once with active VNS at room temperature and once with active VNS under cold exposure in order to determine maximal cold-induced BAT activity. BAT activity was assessed by 18-Fluoro-Deoxy-Glucose-Positron-Emission-Tomography-and-Computed-Tomography. Basal metabolic rate (BMR) was significantly higher when VNS was turned on (mean change; +2.2%). Mean BAT activity was not significantly different between active VNS and inactive VNS (BAT SUV^Mean; 0.55±0.25 versus 0.67±0.46, P = 0.619). However, the change in energy expenditure upon VNS intervention (On-Off) was significantly correlated to the change in BAT activity (r = 0.935, P<0.001).

Conclusions

VNS significantly increases energy expenditure. The observed change in energy expenditure was significantly related to the change in BAT activity. This suggests a role for BAT in the VNS increase in energy expenditure. Chronic VNS may have a beneficial effect on the human energy balance that has potential application for weight management therapy.

Trial Registration

The study was registered in the Clinical Trial Register under the ClinicalTrials.gov Identifier {"type":"clinical-trial","attrs":{"text":"NCT01491282","term_id":"NCT01491282"}}NCT01491282.     

DCM-Related Tropomyosin Mutants E40K/E54K Over-Inhibit the Actomyosin Interaction and Lead to a Decrease in the Number of Cycling Cross-Bridges

Two DCM mutants (E40K and E54K) of tropomyosin (Tm) were examined using the thin-filament extraction/reconstitu­tion technique. The effects of the Ca²⁺, ATP, phos­phate (Pi), and ADP concentrations on isometric tension and its transients were studied at 25°C, and the results were com­pared to those for the WT protein. Our results indicate that both E40K and E54K have a significantly lower T _HC (high Ca²⁺ ten­sion at pCa 4.66) (E40K: 1.21±0.06 T _a, ±SEM, N = 34; E54K: 1.24±0.07 T _a, N = 28), a significantly lower T _LC (low- Ca²⁺ tension at pCa 7.0) (E40K: 0.07±0.02 T _a, N = 34; E54K: 0.06±0.02 T _a, N = 28), and a significantly lower T _act (Ca²⁺ activatable tension) (T _act = T _HC–T_LC, E40K: 1.15±0.08 T _a, N = 34; E54K: 1.18±0.06 T _a, N = 28) than WT (T _HC = 1.53±0.07 T _a, T _LC = 0.12±0.01 T _a, T _act = 1.40±0.07 T _a, N = 25). All tensions were normalized to T _a ( = 13.9±0.8 kPa, N = 57), the ten­sion of actin-filament reconstituted cardiac fibers (myocardium) under the standard activating conditions. The Ca²⁺ sensitivity (pCa₅₀) of E40K (5.23±0.02, N = 34) and E54K (5.24±0.03, N = 28) was similar to that of the WT protein (5.26±0.03, N = 25). The cooper­a­tivity increased significantly in E54K (3.73±0.25, N = 28) compared to WT (2.80±0.17, N = 25). Seven kinetic constants were deduced using sinusoidal analysis at pCa 4.66. These results enabled us to calculate the cross-bridge distribution in the strongly attached states, and thereby deduce the force/cross-bridge. The results indicate that the force/cross-bridge is ∼15% less in E54K than WT, but remains similar to that of the WT protein in the case of E40K. We conclude that over-inhibition of the actomyosin interaction by E40K and E54K Tm mutants leads to a decreased force-generating ability at systole, which is the main mechanism underlying the early pathogenesis of DCM.     

Aerobic Capacity,Activity Levels and Daily Energy Expenditure in Male and Female Adolescents of the Kenyan Nandi Sub-Group

The relative importance of genetic and socio-cultural influences contributing to the success of east Africans in endurance athletics remains unknown in part because the pre-training phenotype of this population remains incompletely assessed. Here cardiopulmonary fitness, physical activity levels, distance travelled to school and daily energy expenditure in 15 habitually active male (13.9±1.6 years) and 15 habitually active female (13.9±1.2) adolescents from a rural Nandi primary school are assessed. Aerobic capacity () was evaluated during two maximal discontinuous incremental exercise tests; physical activity using accelerometry combined with a global positioning system; and energy expenditure using the doubly labelled water method. The of the male and female adolescents were 73.9±5.7 ml^. kg^−1. min⁻¹ and 61.5±6.3 ml^. kg^−1. min⁻¹, respectively. Total time spent in sedentary, light, moderate and vigorous physical activities per day was 406±63 min (50% of total monitored time), 244±56 min (30%), 75±18 min (9%) and 82±30 min (10%). Average total daily distance travelled to and from school was 7.5±3.0 km (0.8–13.4 km). Mean daily energy expenditure, activity-induced energy expenditure and physical activity level was 12.2±3.4 MJ^. day⁻¹, 5.4±3.0 MJ^. day⁻¹ and 2.2±0.6. 70.6% of the variation in was explained by sex (partial R² = 54.7%) and body mass index (partial R² = 15.9%). Energy expenditure and physical activity variables did not predict variation in once sex had been accounted for. The highly active and energy-demanding lifestyle of rural Kenyan adolescents may account for their exceptional aerobic fitness and collectively prime them for later training and athletic success.     

Age-related effects on the biological clock and its behavioral output in a primate

In humans, activity rhythms become fragmented and attenuated in the elderly. This suggests an alteration of the circadian system per se that could in turn affect the expression of biological rhythms. In primates, very few studies have analyzed the effect of aging on the circadian system. The mouse lemur provides a unique model of aging in non-human primates. To assess the effect of aging on the circadian system of this primate, we recorded the circadian and daily rhythms of locomotor activity of mouse lemurs of various ages. We also examined age-related changes in the daily rhythm of immunoreactivities for vasoactive intestinal polypeptide (VIP) and arginine-vasopressin (AVP) in suprachiasmatic nucleus neurons (SCN), two major peptides of the biological clock. Compared to adult animals, aged mouse lemurs showed a significant increase in daytime activity and an advanced activity onset. Moreover, when maintained in constant dim red light, aged animals exhibited a shortening of the free-running period compared to adult animals. In adults, AVP immunoreactivity (ir) peaked during the second part of the day, and VIP ir peaked during the night. In aged mouse lemurs, the peaks of AVP ir and VIP ir were significantly shifted with no change in amplitude. AVP ir was most intense at the beginning of the night; whereas, VIP ir peaked at the beginning of the daytime. A weakened oscillator could account for the rhythmic disorders often observed in the elderly. Changes in the daily rhythms of AVP ir and VIP ir may affect the ability of the SCN to transmit rhythmic information to other neural target sites, and thereby modify the expression of some biological rhythms.     

Daily Energy Expenditure,Cardiorespiratory Fitness and Glycaemic Control in People with Type 1 Diabetes

Objective

Encouraging daily physical activity improves cardiorespiratory fitness and many cardiovascular risk factors. However, increasing physical activity often creates a challenge for people with type 1 diabetes, because of difficulties maintaining euglycemia in the face of altered food intake and adjustments to insulin doses. Our aim was to examine the triangular relationship between glucose control measured by continuous glucose monitoring system (CGMS), objective measures of total daily energy expenditure (TEE) recorded by a multi-sensory monitoring device, and cardiorespiratory fitness (CRF), in free-living subjects with type 1 diabetes.

Research Design and Methods

Twenty-three individuals (12 women) with type 1 diabetes who were free from micro- and macrovascular complications were recruited. TEE and glucose control were monitored simultaneously for up to 12 days, using a multi-sensory device and CGMS respectively. CRF was recorded as V02 max from a maximal treadmill test with the Bruce protocol.

Results

Subjects (mean±SD) were aged 37±11 years, with BMI = 26.5±5.1 kg.m⁻², HbA_1c = 7.7±1.3% (61±14 mmol/mol) and V02 max (ml.min⁻¹.kg⁻¹)  = 39.9±8.4 (range 22.4 – 58.6). TEE (36.3±5.5 kcal.kg⁻¹.day⁻¹) was strongly associated with CRF(39.9±8.4 ml.min⁻¹.kg⁻¹) independently of sex (r = 0.63, p<0.01). However, neither TEE (r = −0.20, p = 0.36) nor CRF (r = −0.20, p = 0.39; adjusted for sex), were significantly associated with mean glycaemia measured by CGMS.

Conclusion

Higher levels of energy expenditure (due to a more active lifestyle) are associated with increased cardiorespiratory fitness, but not necessarily better glycaemic control. Since increased levels of energy expenditure and good glycaemic control are both needed to protect against diabetes-related complications our data suggest they need to be achieved independently.     

Perinatal Lead (Pb) Exposure Results in Sex-Specific Effects on Food Intake,Fat, Weight,and Insulin Response across the Murine Life-Course

Developmental lead (Pb) exposure has been associated with lower body weight in human infants and late onset obesity in mice. We determined the association of perinatal Pb exposure in mice with changes in obesity-related phenotypes into adulthood. Mice underwent exposure via maternal drinking water supplemented with 0 (control), 2.1 (low), 16 (medium), or 32 (high) ppm Pb-acetate two weeks prior to mating through lactation. Offspring were phenotyped at ages 3, 6, and 9 months for energy expenditure, spontaneous activity, food intake, body weight, body composition, and at age 10 months for glucose tolerance. Data analyses were stratified by sex and adjusted for litter effects. Exposed females and males exhibited increased energy expenditure as compared to controls (p<0.0001 for both). In females, horizontal activity differed significantly from controls (p = 0.02) over the life-course. Overall, food intake increased in exposed females and males (p<0.0008 and p<0.0001, respectively) with significant linear trends at 9 months in females (p = 0.01) and 6 months in males (p<0.01). Body weight was significantly increased in males at the medium and high exposures (p = 0.001 and p = 0.006). Total body fat differed among exposed females and males (p<0.0001 and p<0.0001, respectively). Insulin response was significantly increased in medium exposure males (p<0.05). Perinatal Pb exposure at blood lead levels between 4.1 µg/dL and 32 µg/dL is associated with increased food intake, body weight, total body fat, energy expenditure, activity, and insulin response in mice. Physiological effects of developmental Pb exposure persist and vary according to sex and age.     

Teeth,Sex, and Testosterone: Aging in the World's Smallest Primate

Mouse lemurs (Microcebus spp.) are an exciting new primate model for understanding human aging and disease. In captivity, Microcebus murinus develops human-like ailments of old age after five years (e.g., neurodegeneration analogous to Alzheimer''s disease) but can live beyond 12 years. It is believed that wild Microcebus follow a similar pattern of senescence observed in captive animals, but that predation limits their lifespan to four years, thus preventing observance of these diseases in the wild. Testing whether this assumption is true is informative about both Microcebus natural history and environmental influences on senescence, leading to interpretation of findings for models of human aging. Additionally, the study of Microcebus longevity provides an opportunity to better understand mechanisms of sex-biased longevity. Longevity is often shorter in males of species with high male-male competition, such as Microcebus, but mouse lemurs are sexually monomorphic, suggesting similar lifespans. We collected individual-based observations of wild brown mouse lemurs (Microcebus rufus) from 2003–2010 to investigate sex-differences in survival and longevity. Fecal testosterone was measured as a potential mechanism of sex-based differences in survival. We used a combination of high-resolution tooth wear techniques, mark-recapture, and hormone enzyme immunoassays. We found no dental or physical signs of senescence in M. rufus as old as eight years (N = 189, ages 1–8, mean = 2.59±1.63 SE), three years older than captive, senescent congeners (M. murinus). Unlike other polygynandrous vertebrates, we found no sex difference in age-dependent survival, nor sex or age differences in testosterone levels. While elevated male testosterone levels have been implicated in shorter lifespans in several species, this is one of the first studies to show equivalent testosterone levels accompanying equivalent lifespans. Future research on captive aged individuals can determine if senescence is partially a condition of their captive environment, and studies controlling for various environmental factors will further our understanding of senescence.     

Shortened seasonal photoperiodic cycles accelerate aging of the diurnal and circadian locomotor activity rhythms in a primate

The gray mouse lemur (Microcebus murinus), a prosimian primate, exhibits seasonal rhythms strictly controlled by photoperiodic variations. Previous studies indicated that longevity can be altered by long-term acceleration of seasonal rhythms, providing a model for assessing various aspects of aging. To assess the effect of aging and accelerated aging on the circadian system of this primate, we compared the circadian rhythm of the locomotor activity in adult mouse lemurs (2-4.5 years, n = 9), aged mouse lemurs (5-9 years, n = 10), and adult mouse lemurs that had been exposed from birth to a shortened seasonal photoperiodic cycle (2-4.5 years, n = 7). Compared to adult animals, aged mouse lemurs showed a significant increase in intradaily variability and an advanced activity onset. Aging was characterized by a decrease in amplitude, with both a decrease in nocturnal activity and an increase in daytime activity. When maintained in constant dim red light, aged animals exhibited a shortening of the free-running period (22.8 +/- 0.1 h) compared to adult animals (23.5 +/- 0.1 h). A 3- to 5-year exposure to an accelerated seasonal photoperiodic rhythm ("annual" duration of 5 months) in accelerated mouse lemurs produced disturbances of the locomotor activity rhythm that resembled those of aged mouse lemurs, whether animals were studied in entrained or in free-running conditions. The present study demonstrated a weakened and fragmented locomotor activity rhythm during normal aging in this primate. Increasing the number of expressed seasonal cycles accelerated aging of parameters related to circadian rhythmicity in adult animals.     

The Grey Mouse Lemur Uses Season-Dependent Fat or Protein Sparing Strategies to Face Chronic Food Restriction

During moderate calorie restriction (CR) the heterotherm Microcebus murinus is able to maintain a stable energy balance whatever the season, even if only wintering animals enter into torpor. To understand its energy saving strategies to respond to food shortages, we assessed protein and energy metabolisms associated with wintering torpor expression or summering torpor avoidance. We investigated body composition, whole body protein turnover, and daily energy expenditure (DEE), during a graded (40 and 80%) 35-day CR in short-days (winter; SD40 and SD80, respectively) and long-days (summer; LD40 and LD80, respectively) acclimated animals. LD40 animals showed no change in fat mass (FM) but a 12% fat free mass (FFM) reduction. Protein balance being positive after CR, the FFM loss was early and rapid. The 25% DEE reduction, in LD40 group was mainly explained by FFM changes. LD80 animals showed a steady body mass loss and were excluded from the CR trial at day 22, reaching a survival-threatened body mass. No data were available for this group. SD40 animals significantly decreased their FM level by 21%, but maintained FFM. Protein sparing was achieved through a 35 and 39% decrease in protein synthesis and catabolism (protein turnover), respectively, overall maintaining nitrogen balance. The 21% reduction in energy requirement was explained by the 30% nitrogen flux drop but also by torpor as DEE FFM-adjusted remained 13% lower compared to ad-libitum. SD80 animals were unable to maintain energy and nitrogen balances, losing both FM and FFM. Thus summering mouse lemurs equilibrate energy balance by a rapid loss of active metabolic mass without using torpor, whereas wintering animals spare protein and energy through increased torpor expression. Both strategies have direct fitness implication: 1) to maintain activities at a lower body size during the mating season and 2) to preserve an optimal wintering muscle mass and function.     

Predictive Validity and Classification Accuracy of ActiGraph Energy Expenditure Equations and Cut-Points in Young Children

Objectives

Evaluate the predictive validity of ActiGraph energy expenditure equations and the classification accuracy of physical activity intensity cut-points in preschoolers.

Methods

Forty children aged 4–6 years (5.3±1.0 years) completed a ∼150-min room calorimeter protocol involving age-appropriate sedentary, light and moderate-to vigorous-intensity physical activities. Children wore an ActiGraph GT3X on the right mid-axillary line of the hip. Energy expenditure measured by room calorimetry and physical activity intensity classified using direct observation were the criterion methods. Energy expenditure was predicted using Pate and Puyau equations. Physical activity intensity was classified using Evenson, Sirard, Van Cauwenberghe, Pate, Puyau, and Reilly, ActiGraph cut-points.

Results

The Pate equation significantly overestimated VO₂ during sedentary behaviors, light physical activities and total VO₂ (P<0.001). No difference was found between measured and predicted VO₂ during moderate-to vigorous-intensity physical activities (P = 0.072). The Puyau equation significantly underestimated activity energy expenditure during moderate-to vigorous-intensity physical activities, light-intensity physical activities and total activity energy expenditure (P<0.0125). However, no overestimation of activity energy expenditure during sedentary behavior was found. The Evenson cut-point demonstrated significantly higher accuracy for classifying sedentary behaviors and light-intensity physical activities than others. Classification accuracy for moderate-to vigorous-intensity physical activities was significantly higher for Pate than others.

Conclusion

Available ActiGraph equations do not provide accurate estimates of energy expenditure across physical activity intensities in preschoolers. Cut-points of ≤25counts⋅15 s⁻¹ and ≥420 counts⋅15 s⁻¹ for classifying sedentary behaviors and moderate-to vigorous-intensity physical activities, respectively, are recommended.     

Twenty-Four Hour Total and Dietary Fat Oxidation in Lean,Obese and Reduced-Obese Adults with and without a Bout of Exercise

Background

It has been hypothesized that obese and reduced-obese individuals have decreased oxidative capacity, which contributes to weight gain and regain. Recent data have challenged this concept.

Objective

To determine (1) whether total and dietary fat oxidation are decreased in obese and reduced-obese adults compared to lean but increase in response to an acute exercise bout and (2) whether regular physical activity attenuates these metabolic alterations.

Design

We measured 24-hr total (whole-room calorimetry) and dietary fat (¹⁴C-oleate) oxidation in Sedentary Lean (BMI = 21.5±1.6; n = 10), Sedentary Obese (BMI = 33.6±2.5; n = 9), Sedentary Reduced-Obese (RED-SED; BMI = 26.9±3.7; n = 7) and in Physically Active Reduced-Obese (RED-EX; BMI = 27.3±2.8; n = 12) men and women with or without an acute exercise bout where energy expended during exercise was not replaced.

Results

Although Red-SED and Red-EX had a similar level of fatness, aerobic capacity and metabolic profiles were better in Red-EX only compared to Obese subjects. No significant between-group differences were seen in 24-hr respiratory quotient (RQ, Lean: 0.831±0.044, Obese: 0.852±0.023, Red-SED: 0.864±0.037, Red-EX: 0.842±0.039), total and dietary fat oxidation. A single bout of exercise increased total (+27.8%, p<0.0001) and dietary (+6.6%, p = 0.048) fat oxidation across groups. Although exercise did not impact RQ during the day, it decreased RQ during sleep (p = 0.01) in all groups. Red-EX oxidized more fat overnight than Red-SED subjects under both resting (p = 0.036) and negative energy balance (p = 0.003) conditions, even after adjustment for fat-free mass.

Conclusion

Obese and reduced-obese individuals oxidize as much fat as lean both under eucaloric and negative energy balance conditions, which does not support the hypothesis of reduced oxidative capacity in these groups. Reduced-obese individuals who exercise regularly have markers of metabolic health similar to those seen in lean adults. Both the acute and chronic effects of exercise were primarily observed at night suggesting an important role of sleep in the regulation of lipid metabolism.     

Personality,Metabolic Rate and Aerobic Capacity

Personality traits and cardiorespiratory fitness in older adults are reliable predictors of health and longevity. We examined the association between personality traits and energy expenditure at rest (basal metabolic rate) and during normal and maximal sustained walking. Personality traits and oxygen (VO₂) consumption were assessed in 642 participants from the Baltimore Longitudinal Study of Aging. Results indicate that personality traits were mostly unrelated to resting metabolic rate and energy expenditure at normal walking pace. However, those who scored lower on neuroticism (r =  −0.12) and higher on extraversion (r = 0.11), openness (r = 0.13), and conscientiousness (r = 0.09) had significantly higher energy expenditure at peak walking pace. In addition to greater aerobic capacity, individuals with a more resilient personality profile walked faster and were more efficient in that they required less energy per meter walked. The associations between personality and energy expenditure were not moderated by age or sex, but were in part explained by the proportion of fat mass. In conclusion, differences in personality may matter the most during more challenging activities that require cardiorespiratory fitness. These findings suggest potential pathways that link personality to health outcomes, such as obesity and longevity.     

Effects of Easy-to-Use Protein-Rich Energy Bar on Energy Balance,Physical Activity and Performance during 8 Days of Sustained Physical Exertion

Background

Previous military studies have shown an energy deficit during a strenuous field training course (TC). This study aimed to determine the effects of energy bar supplementation on energy balance, physical activity (PA), physical performance and well-being and to evaluate ad libitum fluid intake during wintertime 8-day strenuous TC.

Methods

Twenty-six men (age 20±1 yr.) were randomly divided into two groups: The control group (n = 12) had traditional field rations and the experimental (Ebar) group (n = 14) field rations plus energy bars of 4.1 MJ•day⁻¹. Energy (EI) and water intake was recorded. Fat-free mass and water loss were measured with deuterium dilution and elimination, respectively. The energy expenditure was calculated using the intake/balance method and energy availability as (EI/estimated basal metabolic rate). PA was monitored using an accelerometer. Physical performance was measured and questionnaires of upper respiratory tract infections (URTI), hunger and mood state were recorded before, during and after TC.

Results

Ebar had a higher EI and energy availability than the controls. However, decreases in body mass and fat mass were similar in both groups representing an energy deficit. No differences were observed between the groups in PA, water balance, URTI symptoms and changes in physical performance and fat-free mass. Ebar felt less hunger after TC than the controls and they had improved positive mood state during the latter part of TC while controls did not. Water deficit associated to higher PA. Furthermore, URTI symptoms and negative mood state associated negatively with energy availability and PA.

Conclusion

An easy-to-use protein-rich energy bars did not prevent energy deficit nor influence PA during an 8-day TC. The high content of protein in the bars might have induced satiation decreasing energy intake from field rations. PA and energy intake seems to be primarily affected by other factors than energy supplementation such as mood state.     

Relationship between mitochondrial haplogroup and seasonal changes of physiological responses to cold

Background

Physiological responses to cold exhibit individual variation that can be affected by various factors, such as morphological characteristics, seasonal changes, and lifestyle; however, the genetic factors associated with this variation remain unclear. Recent studies have identified mtDNA as a potential genetic factor affecting cold adaptation. In addition, non-shivering thermogenesis (NST), a process closely related to mitochondrial dynamics, has also been suggested as an important factor affecting human response to cold. The present study aimed to clarify the relationship between mitochondrial haplogroup and NST during periods of mild cold exposure.

Methods

Seventeen healthy university students (D: n = 8, non-D: n = 9) participated in the present study during summer and winter. A climate chamber was programmed so that ambient temperature inside dropped from 28°C to 16°C over the course of an 80-minute period. Physiological parameters were recorded throughout the course of the experiments.

Results

Increases in VO₂ were significantly greater during periods of cold exposure in winter than they were during periods of cold exposure in summer, and individuals from the D group exhibited greater winter values of ΔVO₂ than individuals from the non-D group.T_re was significantly lower during periods of rest and cold exposure in winter; however, no significant difference was observed between T_re values of individuals in the D and non-D groups. In addition, although T¯dist was significantly lower during periods of rest in winter than it was during those same periods in summer, no significant seasonal differences in values of T¯dist were observed during periods of cold exposure.

Conclusions

Results of the present study indicated that NST was greater in winter, and that the D group exhibited greater NST than the non-D group during winter. Despite the differences between groups in NST, no significant differences in rectal and skin temperatures were found between groups in either season. Therefore, it was supposed that mitochondrial DNA haplogroups had a greater effect on variation in energy expenditure involving NST than they had on insulative responses. Future studies are necessary in order to investigate more multiple candidate genes related to human cold adaptation and to elucidate the relationship between gene polymorphism and physiological polytypism.