Stéphane Blanc

One for all and all for one: the energetic benefits of huddling in endotherms

Huddling can be defined as “an active and close aggregation of animals”. It is a cooperative group behaviour, permitting individuals involved in social thermoregulation to minimize heat loss and thereby lower their energy expenditure, and possibly allowing them to reallocate the saved energy to other functions such as growth or reproduction. Huddling is especially important in the case of animals faced with high heat loss due to a high surface‐to‐volume ratio, poor insulation, or living in cold environments. Although numerous experimental studies have focused on the huddling behaviour of a wide range of species, to our knowledge, this is the first attempt to review the various implications of this widely used behavioural strategy.

Resveratrol prevents the wasting disorders of mechanical unloading by acting as a physical exercise mimetic in the rat

Long‐term spaceflight induces hypokinesia and hypodynamia, which, along microgravity per se, result in a number of significant physiological alterations, such as muscle atrophy, force reduction, insulin resistance, substrate use shift from fats to carbohydrates, and bone loss. Each of these adaptations could turn to serious health deterioration during the long‐term spaceflight needed for planetary exploration. We hypothesized that resveratrol (RES), a natural polyphenol, could be used as a nutritional countermeasure to prevent muscle metabolic and bone adaptations to 15 d of rat hindlimb unloading. RES treatment maintained a net protein balance, soleus muscle mass, and soleus muscle maximal force contraction. RES also fully maintained soleus mitochondrial capacity to oxidize palmitoyl‐carnitine and reversed the decrease of the glutathione vs. glutathione disulfide ratio, a biomarker of oxidative stress. At the molecular level, the protein content of Sirt‐1 and COXIV in soleus muscle was also preserved. RES further protected whole‐body insulin sensitivity and lipid trafficking and oxidation, and this was likely associated with the maintained expression of FAT/CD36, CPT‐1, and peroxisome proliferator‐activated receptor‐γ coactivator‐1α (PGC‐1α) in muscle. Finally, chronic RES supplementation maintained the bone mineral density and strength of the femur. For the first time, we report a simple countermeasure that prevents the deleterious adaptations of the major physiological functions affected by mechanical unloading. RES could thus be envisaged as a nutritional counter‐measure for spaceflight but remains to be tested in humans.—Momken, I., Stevens, L., Bergouignan, A., Desplanches, D., Rudwill, F., Chery, I., Zahariev, A., Zahn, S., Stein, T. P., Sebedio, J. L., Pujos‐Guillot, E., Falempin, M., Simon, C., Coxam, V., Andrianjafiniony, T., Gauquelin‐Koch, G., Picquet, F., Blanc, S. Resveratrol prevents the wasting disorders of mechanical unloading by acting as a physical exercise mimetic in the rat. FASEB J. 25, 3646–3660 (2011). www.fasebj.org

Resveratrol suppresses body mass gain in a seasonal non-human primate model of obesity

BackgroundResveratrol, a natural polyphenolic compound, was shown to protect rodents against high-fat-diet induced diabesity by boosting energy metabolism. To the best of our knowledge, no data is yet available on the effects of resveratrol in non-human primates. Six non-human heterotherm primates (grey mouse lemurs, Microcebus murinus) were studied during four weeks of dietary supplementation with resveratrol (200 mg/kg/day) during their winter body-mass gain period. Body mass, spontaneous energy intake, resting metabolic rate, spontaneous locomotor activity and daily variations in body temperature were measured. In addition, the plasma levels of several gut hormones involved in satiety control were evaluated.ResultsResveratrol reduced the seasonal body-mass gain by concomitantly decreasing energy intake by 13% and increasing resting metabolic rate by 29%. Resveratrol supplementation inhibited the depth of daily torpor, an important energy-saving process in this primate. The daily amount of locomotor activity remained unchanged. Except for an increase in the glucose-dependent insulinotropic polypeptide, a gut hormone known to promote mobilization of fat stores, no major change in satiety hormone plasma levels was observed under resveratrol supplementation.ConclusionsThese results suggest that in a non-human primate, resveratrol reduces body-mass gain by increasing satiety and resting metabolic rate, and by inhibiting torpor expression. The measured anorectic gut hormones did not seem to play a major role in these observations.

The grey mouse lemur: a non-human primate model for ageing studies.

The use of non-human primate models is required to understand the ageing process and evaluate new therapies against age-associated pathologies. The present article summarizes all the contributions of the grey mouse lemur Microcebus murinus, a small nocturnal prosimian primate, to the understanding of the mechanisms of ageing. Results from studies of both healthy and pathological ageing research on the grey mouse lemur demonstrated that this animal is a unique model to study age-dependent changes in endocrine systems, biological rhythms, thermoregulation, sensorial, cerebral and cognitive functions.

Validity of combining heart rate and uniaxial acceleration to measure free-living physical activity energy expenditure in young men.

Combining accelerometry (ACC) with heart rate (HR) monitoring is thought to improve activity energy expenditure (AEE) estimations compared with ACC alone to evaluate the validity of ACC and HR used alone or combined. The purpose of this study was to estimate AEE in free-living conditions compared with doubly labeled water (DLW). Ten-day free-living AEE was measured by a DLW protocol in 35 18- to 55-yr-old men (11 lean active; 12 lean sedentary; 12 overweight sedentary) wearing an Actiheart (combining ACC and HR) and a RT3 accelerometer. AEE was estimated using group or individual calibration of the HR/AEE relationship, based on an exercise-tolerance test. In a subset (n = 21), AEE changes (ΔAEE) were measured after 1 mo of detraining (active subjects) or an 8-wk training (sedentary subjects). Actiheart-combined ACC/HR estimates were more accurate than estimates from HR or ACC alone. Accuracy of the Actiheart group-calibrated ACC/HR estimates was modest [intraclass correlation coefficient (ICC) = 0.62], with no bias but high root mean square error (RMSE) and limits of agreement (LOA). The mean bias of the estimates was reduced by one-third, like RMSE and LOA, by individual calibration (ICC = 0.81). Contrasting with group-calibrated estimates, the Actiheart individual-calibrated ACC/HR estimates explained 40% of the variance of the DLW-ΔAEE (ICC = 0.63). This study supports a good level of agreement between the Actiheart ACC/HR estimates and DLW-measured AEE in lean and overweight men with varying fitness levels. Individual calibration of the HR/AEE relationship is necessary for AEE estimations at an individual level rather than at group scale and for ΔAEE evaluation.

Regulation of energy balance during long-term physical inactivity induced by bed rest with and without exercise training.

BACKGROUND Short-term physical inactivity affects energy balance and is considered conducive to weigh gain. Long-term effects are unknown. OBJECTIVE The objective of the study was to use a bed-rest model to determine the long-term effects of physical inactivity on energy balance regulation and test the effect of exercise training on energy balance adjustment to physical inactivity. DESIGN Sixteen lean women were divided into two groups (n = 8 each): a control group subjected to a strict 60-d bed rest and an exercise group subjected to a combined aerobic/resistive exercise training concomitantly to bed rest. Body composition, spontaneous energy intake, hunger, total energy expenditure (TEE), and fasting gut hormones were measured. RESULTS Based on bed-rest-induced body composition changes, the control group were in slight negative energy balance (-0.4 +/- 0.4 MJ/d; P = 0.01 vs. zero), essentially due to muscle atrophy (P < 0.001 vs. zero). The stable fat mass (P = 0.19 vs. zero), and the matching between spontaneous energy intake and TEE indicated, however, a stable energy balance. Hunger and gut hormones remained unchanged during the bed rest. In the exercise group, TEE was 24% higher than in the control group (P = 0.004). Unexpectedly, desire to consume food (P = 0.025) decreased and spontaneous energy intake (P = NS) was not stimulated, promoting a negative energy balance (-1.1 +/- 0.5 MJ/d, P = 0.0003 vs. zero). CONCLUSIONS Energy balance is regulated during 2 months of physical inactivity, contrasting with short-term experiments. Conversely, exercise-induced energy expenditure in bed-resting subjects who have no spontaneous physical activity did not induce hunger and promoted a negative energy balance, suggesting a potential role of nonexercise physical activities in energy balance regulation.

Total Energy Expenditure and Body Composition in Two Free-Living Sympatric Lemurs

Background Evolutionary theories that account for the unusual socio-ecological traits and life history features of group-living prosimians, compared with other primates, predict behavioral and physiological mechanisms to conserve energy. Low energy output and possible fattening mechanisms are expected, as either an adaptive response to drastic seasonal fluctuations of food supplies in Madagascar, or persisting traits from previously nocturnal hypometabolic ancestors. Free ranging ring-tailed lemurs (Lemur catta) and brown lemurs (Eulemur sp.) of southern Madagascar have different socio-ecological characteristics which allow a test of these theories: Both gregarious primates have a phytophagous diet but different circadian activity rhythms, degree of arboreality, social systems, and slightly different body size. Methodology and Results Daily total energy expenditure and body composition were measured in the field with the doubly labeled water procedure. High body fat content was observed at the end of the rainy season, which supports the notion that individuals need to attain a sufficient physical condition prior to the long dry season. However, ring-tailed lemurs exhibited lower water flux rates and energy expenditure than brown lemurs after controlling for body mass differences. The difference was interpreted to reflect higher efficiency for coping with seasonally low quality foods and water scarcity. Daily energy expenditure of both species was much less than the field metabolic rates predicted by various scaling relationships found across mammals. Discussion We argue that low energy output in these species is mainly accounted for by low basal metabolic rate and reflects adaptation to harsh, unpredictable environments. The absence of observed sex differences in body weight, fat content, and daily energy expenditure converge with earlier investigations of physical activity levels in ring-tailed lemurs to suggest the absence of a relationship between energy constraints and the evolution of female dominance over males among lemurs. Nevertheless, additional seasonal data are required to provide a definitive conclusion.

Does Protein Supplementation Prevent Muscle Disuse Atrophy and Loss of Strength

Recently there has been much interest in the use of dietary amino acids supplements to decrease the losses in muscle mass and strength observed after space flight or during aging using bed rest analogs. This interest persists even if the results have been mixed. Of the six published amino acid supplementation studies, three showed benefit, three did not. A recent study re-evaluating protein requirements in humans suggests that the official RDA is 41% underestimated. Interestingly, the three studies that showed benefits fed their test subjects a baseline protein level around the old RDA for protein. The three that did not show benefit gave the subjects a baseline protein intake higher than the new RDA. We suggest that the positive effects observed on protein metabolism might just reflect the benefits of adequate protein intake achieved during bed rest rather than a protective effect against bed-rest induced disuse. In conclusion, the efficiency of amino acid countermeasures for preventing the loss in protein mass during space flight or bed rest needs to be seriously questioned. These results extend to clinical situations such as serious illness and progress of aging in which physical inactivity is a significant component of the loss in muscle function.

Activity energy expenditure is a major determinant of dietary fat oxidation and trafficking, but the deleterious effect of detraining is more marked than the beneficial effect of training at current recommendations

BACKGROUND Previous studies suggested that physical activity energy expenditure (AEE) is a major determinant of dietary fat oxidation, which is a central component of fat metabolism and body weight regulation. OBJECTIVE We tested this hypothesis by investigating the effect of contrasted physical activity levels on dietary saturated and monounsaturated fatty acid oxidation in relation to insulin sensitivity while controlling energy balance. DESIGN Sedentary lean men (n = 10) trained for 2 mo according to the current guidelines on physical activity, and active lean men (n = 9) detrained for 1 mo by reducing structured and spontaneous activity. Dietary [d31]palmitate and [1-¹³C]oleate oxidation and incorporation into triglyceride-rich lipoproteins and nonesterified fatty acid, AEE, and muscle markers were studied before and after interventions. RESULTS Training increased palmitate and oleate oxidation by 27% and 20%, respectively, whereas detraining reduced them by 31% and 13%, respectively (P < 0.05 for all). Changes in AEE were positively correlated with changes in oleate (R² = 0.62, P < 0.001) and palmitate (R² = 0.66, P < 0.0001) oxidation. The d31-palmitate appearance in nonesterified fatty acid and very-low-density lipoprotein pools was negatively associated with changes in fatty acid translocase CD36 (R² = 0.30), fatty acid transport protein 1 (R² = 0.24), and AcylCoA synthetase long chain family member 1 (ACSL1) (R² = 0.25) expressions and with changes in fatty acid binding protein expression (R² = 0.33). The d31-palmitate oxidation correlated with changes in ACSL1 (R² = 0.39) and carnitine palmitoyltransferase 1 (R² = 0.30) expressions (P < 0.05 for all). Similar relations were observed with oleate. Insulin response was associated with AEE (R² = 0.34, P = 0.02) and oleate (R² = 0.52, P < 0.01) and palmitate (R² = 0.62, P < 001) oxidation. CONCLUSION Training and detraining modified the oxidation of the 2 most common dietary fats, likely through a better trafficking and uptake by the muscle, which was negatively associated with whole-body insulin sensitivity.

Dietary palmitate and linoleate oxidations, oxidative stress, and DNA damage differ according to season in mouse lemurs exposed to a chronic food deprivation.

This study investigated the extent to which the increase in torpor expression in the grey mouse lemur, due to graded food restriction, is modulated by a trade-off between a whole body sparing of polyunsaturated dietary fatty acids and the related oxidative stress generated during daily torpor. We measured changes in torpor frequency, total energy expenditure (TEE), linoleate (polyunsaturated fatty acid) and palmitate (saturated fatty acid) oxidation, hexanoyl-lysine (HEL; the product of linoleate peroxidation), and 8-hydroxydeoxyguanosine (8OHdG; a marker of DNA damage). Animals under summer-acclimated long days (LD) or winter-acclimated short days (SD) were exposed to a 40% (LD40 and SD40) and 80% (LD80 and SD80) 35-day calorie restriction (CR). During CR, all groups reduced their body mass, but LD80 animals reached survival-threatened levels at day 22 and were then excluded from the CR trial. Only SD mouse lemurs increased their torpor frequency with CR and displayed a decrease in their TEE adjusted for fat-free mass. After CR, SD40 mouse lemurs shifted the dietary fatty acid oxidation toward palmitate and spared linoleate. Such a shift was not observed in LD animals and during severe CR, during which oxidation of both dietary fatty acids was increased. Concomitantly, HEL increased in both LD40 and SD80 groups, whereas DNA damage was only seen in SD80 food-restricted animals. HEL correlated positively with linoleate oxidation confirming in vivo the substrate/product relationship demonstrated in vitro, and negatively with TEE adjusted for fat-free mass, suggesting higher oxidative stress associated with increased torpor expression. This suggests a seasonal-dependant, cost-benefit trade-off between maximizing torpor propensity and minimizing oxidative stress that is associated with a shift toward sparing of dietary polyunsaturated fatty acids that is dependent upon the expression of a winter phenotype.