Enteral versus parenteral nutrition: comparison of energy metabolism in healthy subjects.

Continuous respiratory exchange measurements were performed on 10 healthy young women for 1 h before, 3 h during, and 3 h after either parenteral (iv) or intragastric (ig) administration of a nutrient mixture (52% glucose, 18% amino acid, and 30% lipid energy) infused at twice the postabsorptive resting energy expenditure (REE). REE rose from 0.98 +/- 0.02 (iv) and 0.99 +/- 0.02 kcal/min (ig) postabsorptively to 1.13 +/- 0.03 (iv) and 1.13 +/- 0.02 kcal/min (ig), resulting in nutrient-induced thermogenesis of 10 +/- 0.6 and 9.3 +/- 0.9%, respectively, when related to the metabolizable energy. The respiratory quotient rose from preinfusion values of 0.81 +/- 0.02 (iv) and 0.80 +/- 0.01 (ig) to 0.86 +/- 0.01 (iv) and 0.85 +/- 0.01 (ig). After nutrient administration the respiratory quotient fell significantly to below the preinfusion values. Plasma glucose and insulin concentrations rose during nutrient administration but were higher during the intravenous route. It is concluded that, although the response time to intragastric administration was delayed, the thermic effects and overall substrate oxidations were comparable during intravenous or intragastric administration, albeit, at lower plasma glucose and insulin concentrations via the intragastric route.

Uncovering a role for micro-RNAs in sleep homeostasis and energy metabolism

Micro-RNAs (miRNAs) are key, post-transcriptional regulators of gene expression and have been implicated in almost every cellular process investigated thus far. However, their role in sleep, in particular the homeostatic aspect of sleep control, has received little attention. We here assessed the effects of sleep deprivation on the brain miRNA transcriptome in the mouse. Sleep deprivation affected miRNA expression in a brain-region specific manner. The forebrain expression of the miRNA miR-709 was affected the most and in situ analyses confirmed its robust increase throughout the brain, especially in the cerebral cortex and the hippocampus. The hippocampus was a major target of the sleep deprivation affecting 37 miRNAs compared to 52 in the whole forebrain. Moreover, independent from the sleep deprivation condition, miRNA expression was highly region-specific with 45% of all expressed miRNAs showing higher expression in hippocampus and 55% in cortex. Next we demonstrated that down-regulation of miRNAs in Com/c2o-expressing neurons of adult mice, through a conditional and inducible Dicer knockout mice model (cKO), results in an altered homeostatic response after sleep deprivation eight weeks following the tamoxifen-induced recombination. Dicer cKO mice showed a larger increase in the electro-encephalographic (EEG) marker of sleep pressure, EEG delta power, and a reduced Rapid Eye Movement sleep rebound, compared to controls, highlighting a functional role of miRNAs in sleep homeostasis. Beside a sleep phenotype, Dicer cKO mice developed an unexpected, severe obesity phenotype associated with hyperphagia and altered metabolism. Even more surprisingly, after reaching maximum body weight 5 weeks after tamoxifen injection, obese cKO mice spontaneously started losing weight as rapidly as it was gained. Brain transcriptome analyses in obese mice identified several obesity-related pathways (e.g. leptin, somatostatin, and nemo-like kinase signaling), as well as genes involved in feeding and appetite (e.g. Pmch, Neurotensin). A gene cluster with anti-correlated expression in the cerebral cortex of post-obese compared to obese mice was enriched for synaptic plasticity pathways. While other studies have identified a role for miRNAs in obesity, we here present a unique model that allows for the study of processes involved in reversing obesity. Moreover, our study identified the cortex as a brain area important for body weight homeostasis. Together, these observations strongly suggest a role for miRNAs in the maintenance of homeostatic processes in the mouse, and support the hypothesis of a tight relationship between sleep and metabolism at a molecular - Les micro-ARNS (miARNs) sont des régulateurs post-transcriptionnels de l'expression des gènes, impliqués dans la quasi-totalité des processus cellulaires. Cependant, leur rôle dans la régulation du sommeil, et en particulier dans le maintien de l'homéostasie du sommeil, n'a reçu que très peu d'attention jusqu'à présent. Dans cette étude, nous avons étudié les conséquences d'une privation de sommeil sur l'expression cérébrale des miARNs chez la souris, et observé des changements dans l'expression de nombreux miARNs. Dans le cerveau antérieur, miR-709 est le miARN le plus affecté par la perte de sommeil, en particulier dans le cortex cérébral et l'hippocampe. L'hippocampe est la région la plus touchée avec 37 miARNs changés comparés à 52 dans le cerveau entier. Par ailleurs, indépendamment de la privation de sommeil, certains miARNs sont spécifiquement enrichis dans certaines aires cérébrales, 45% des miARNs étant surexprimés dans l'hippocampe contre 55% dans le cortex. Dans une seconde étude, nous avons observé que la délétion de DICER, enzyme essentielle à la biosynthèse des miARNs, et la perte subséquente des miARNs dans les neurones exprimant la protéine CAMK2a altère la réponse homéostatique à une privation de sommeil, 8 semaines après l'induction de la recombinaison génétique par le tamoxifen. Les souris sans Dicer (cKO) ont une plus large augmentation de l'EEG delta power, le principal marqueur électro-encéphalographique du besoin de sommeil, comparée aux contrôles, ainsi qu'un rebond en sommeil paradoxal plus petit. De façon surprenante, les souris Dicer cKO développent une obésité rapide, sévère et transitoire, associée à de l'hyperphagie et une altération de leur métabolisme énergétique. Après avoir atteint un pic maximal d'obésité, les souris cKO entrent spontanément dans une période de perte de poids rapide. L'analyse du transcriptome cérébral des souris obèses nous a permis d'identifier des voies associées à l'obésité (leptine, somatostatine et nemo-like kinase), et à la prise alimentaire (Pmch, Neurotensin), tandis que celui des souris post-obèses a révélé un groupe de gènes liés à la plasticité synaptique. Au-delà des nombreux modèles d'obésité existant chez la souris, notre étude présente un modèle unique permettant d'étudier les mécanismes sous-jacent la perte de poids. De plus, nous avons mis en évidence un rôle important du cortex cérébral dans le maintien de la balance énergétique. En conclusion, toutes ces observations soutiennent l'idée que les miARNs sont des régulateurs cruciaux dans le maintien des processus homéostatiques et confortent l'hypothèse d'une étroite relation moléculaire entre le sommeil et le métabolisme.

Total energy expenditure and patterns of activity in 8-10-year-old obese and nonobese children.

Total energy expenditure (TEE) and patterns of activity were measured by means of a heart rate (HR)-monitoring method in a group of 8-10-year-old children including 13 obese children (weight, 46 +/- 10 kg; fat mass: 32 +/- 9%) and 16 nonobese children (weight, 31 +/- 5 kg; fat mass, 18 +/- 5%). Time for sleeping was not statistically different in the two groups of children (596 +/- 33 vs. 582 +/- 43 min; p = NS). Obese children spent more time doing sedentary activities (400 +/- 129 vs. 295 +/- 127 min; p < 0.05) and less time in nonsedentary activities (449 +/- 126 vs. 563 +/- 135 min; p < 0.05) than nonobese children. Time spent in moderate or vigorous activity-i.e., time spent at a HR between 50% of the maximal O2 uptake (peak VO2) and 70% peak VO2 (moderate) and at a HR > or = 70% peak VO2 (vigorous)-was not statistically different in obese and nonobese children (88 +/- 69 vs. 52 +/- 35 min and 20 +/- 21 vs. 16 +/- 13 min, respectively; p = NS). TEE was significantly higher in the obese group than in the nonobese group (9.46 +/- 1.40 vs. 7.51 +/- 1.67 MJ/day; p < 0.01). The energy expenditure for physical activity (plus thermogenesis) was significantly higher in the obese children (3.98 +/- 1.30 vs. 2.94 +/- 1.39 MJ/day; p < 0.05). The proportion of TEE daily devoted to physical activity (plus thermogenesis) was not significantly different in the two groups, as shown by the ratio between TEE and the postabsorptive metabolic rate (PMR): 1.72 +/- 0.25 obese vs 1.61 +/- 0.28 non-obese. In conclusion, in free-living conditions obese children have a higher TEE than do nonobese children, despite the greater time devoted to sedentary activities. The higher energy cost to perform weight-bearing activities as well as the higher absolute PMR of obese children help explain this apparent paradox.

Energy cost of glucose storage in human subjects during glucose-insulin infusions.

The effect of graded levels of hyperinsulinemia on energy expenditure, while euglycemia was maintained by glucose infusion, was examined in 22 healthy young male volunteers by using the euglycemic insulin clamp technique in combination with indirect calorimetry. Insulin was infused at five rates to achieve steady-state hyperinsulinemic plateaus of 62 +/- 4, 103 +/- 5, 170 +/- 10, 423 +/- 16, and 1,132 +/- 47 microU/ml. Total body glucose uptake during each of the five insulin clamp studies was 0.41, 0.50, 0.66, 0.74, and 0.77 g/min, respectively. Glucose storage (calculated from the difference between total body glucose uptake minus total glucose oxidation) was 0.25, 0.29, 0.43, 0.49, and 0.52 g/min for each group, respectively, and represented over 60-70% of total glucose uptake. The net increment in energy expenditure after intravenous glucose was 0.08, 0.10, 0.14, 0.17, and 0.23 kcal/min, respectively. Throughout the physiological and supraphysiological range of insulinemia, there was a significant relationship (r = 0.95, P less than 0.001) between the increment in energy expenditure and glucose storage, indicating an energy cost of 0.45 kcal/g glucose stored. However, at each level of hyperinsulinemia, the theoretical value for the energy cost of glucose storage (assuming that all of the glucose is stored in the form of glycogen) could account for only 45-63% of the actual increase in energy expenditure that was measured by indirect calorimetry. These results indicate that factors in addition to glucose storage as glycogen must be responsible for the increase in energy expenditure that accompanies glucose infusion.

Energy consumption of European and African shrews

Is the extremely high oxygen consumption of shrews due to an unusually high basal metabolism? In an attempt to answer this long-standing question, we have measured the oxygen consumption of 13 species of shrews of different origin: from Europe - Sorex araneus, S. Minutus, Neomys fodiens, Crocidura russula, and Suncus etruscus; from Africa - Crocidura bottegi, C. bicolor, C. jouvenetae; C. poensis, C. theresae, C. Wimmeri, C. flavescens, and C. giffardi, The measurements, taken over a period of 20-30 minutes, were made in small, closed-system chambers at 25°C. The metabolic rat our shrews of the subfamily Soricinae lies between the eman and minimum values of the Soricini (M=126.2 W0.52 cal/h and M=82.6 W0.53 cal/h, respectively), as recorded in the literature. Zhe average for the African Crocidurinae is much lower (M= 43.6 W0.67). The metabolic rate of the European Croccidura russula agrees with that of the African species. Thus, the Crocidurinae are characterized by a relatively low metabolic rate; the Soricinae, and in particular the tribe of the Soricini, by an extremely high metabolic rate. The tribes Neomyini and Blarinini occupy an intermediate position. These differences are also to be found at the level of the basal metabolism. This main difference between the two sub-families can most likely be explained by evolution in geographical isolation under differential climatic conditions: the Crocidurinae having evolved in tropical Africa and the Soricinae in temperate Eurasia

New measurements of energy expenditure and physical activity in chronic kidney disease.

The accurate estimation of total daily energy expenditure (TEE) in chronic kidney patients is essential to allow the provision of nutritional requirements; however, it remains a challenge to collect actual physical activity and resting energy expenditure in maintenance dialysis patients. The direct measurement of TEE by direct calorimetry or doubly labeled water cannot be used easily so that, in clinical practice, TEE is usually estimated from resting energy expenditure and physical activity. Prediction equations may also be used to estimate resting energy expenditure; however, their use has been poorly documented in dialysis patients. Recently, a new system called SenseWear Armband (BodyMedia, Pittsburgh, PA) was developed to assess TEE, but so far no data have been published in chronic kidney disease patients. The aim of this review is to describe new measurements of energy expenditure and physical activity in chronic kidney disease patients.

High fat versus high carbohydrate nutritional supplementation: a one year trial in stunted rural Gambian children.

OBJECTIVE: The study tests the hypothesis that a low daily fat intake may induce a negative fat balance and impair catch-up growth in stunted children between 3 and 9y of age. DESIGN: Randomized case-control study. SETTING: Three rural villages of the West Kiang District, The Gambia. SUBJECTS: Three groups of 30 stunted but not wasted children (height for age z-score < or = -2.0, weight for height z-score > or = -2.0) 3-9 y of age were selected by anthropometric survey. Groups were matched for age, sex, village, degree of stunting and season. INTERVENTION: Two groups were randomly assigned to be supplemented five days a week for one year with either a high fat (n = 29) or a high carbohydrate biscuit (n = 30) each containing approximately 1600 kJ. The third group was a non supplemented control group (n = 29). Growth, nutritional status, dietary intake, resting energy expenditure and morbidity were compared. RESULTS: Neither the high fat nor the high carbohydrate supplement had an effect on weight or height gain. The high fat supplement did slightly increase adipose tissue mass. There was no effect of supplementation on resting energy expenditure or morbidity. In addition, the annual growth rate was not associated with a morbidity score. CONCLUSIONS: Results show that neither a high fat nor a high carbohydrate supplement given during 12 months to stunted Gambian children induced catch-up growth. The authors suggest that an adverse effect of the environment on catch-up growth persists despite the nutritional interventions.

Creation of an Age-Adjusted, Dual-Energy X-ray Absorptiometry-Derived Trabecular Bone Score Curve for the Lumbar Spine in Non-Hispanic US White Women.

The trabecular bone score (TBS, Med-Imaps, Pessac, France) is an index of bone microarchitecture texture extracted from anteroposterior dual-energy X-ray absorptiometry images of the spine. Previous studies have documented the ability of TBS of the spine to differentiate between women with and without fractures among age- and areal bone mineral density (aBMD)-matched controls, as well as to predict future fractures. In this cross-sectional analysis of data collected from 3 geographically dispersed facilities in the United States, we investigated age-related changes in the microarchitecture of lumbar vertebrae as assessed by TBS in a cohort of non-Hispanic US white American women. All subjects were 30 yr of age and older and had an L1-L4aBMDZ-score within ±2 SD of the population mean. Individuals were excluded if they had fractures, were on any osteoporosis treatment, or had any illness that would be expected to impact bone metabolism. All data were extracted from Prodigy dual-energy X-ray absorptiometry devices (GE-Lunar, Madison, WI). Cross-calibrations between the 3 participating centers were performed for TBS and aBMD. aBMD and TBS were evaluated for spine L1-L4 but also for all other possible vertebral combinations. To validate the cohort, a comparison between the aBMD normative data of our cohort and US non-Hispanic white Lunar data provided by the manufacturer was performed. A database of 619 non-Hispanic US white women, ages 30-90 yr, was created. aBMD normative data obtained from this cohort were not statistically different from the non-Hispanic US white Lunar normative data provided by the manufacturer (p = 0.30). This outcome thereby indirectly validates our cohort. TBS values at L1-L4 were weakly inversely correlated with body mass index (r = -0.17) and weight (r = -0.16) and not correlated with height. TBS values for all lumbar vertebral combinations decreased significantly with age. There was a linear decrease of 16.0% (-2.47 T-score) in TBS at L1-L4 between 45 and 90 yr of age (vs. -2.34 for aBMD). Microarchitectural loss rate increased after age 65 by 50% (-0.004 to -0.006). Similar results were obtained for other combinations of lumbar vertebra. TBS, an index of bone microarchitectural texture, decreases with advancing age in non-Hispanic US white women. Little change in TBS is observed between ages 30 and 45. Thereafter, a progressive decrease is observed with advancing age. The changes we observed in these American women are similar to that previously reported for a French population of white women (r(2) > 0.99). This reference database will facilitate the use of TBS to assess bone microarchitectural deterioration in clinical practice.

Macronutrients and energy balance in obesity.

Energy balance is the difference between metabolizable energy intake and total energy expenditure. Energy intake is difficult to measure accurately; changes in body weight, for example, are not a good measure of the adequacy of energy intake, because fluctuations in body weight are common even if the overall trend is toward weight loss. It is now customary to assess energy requirements indirectly from total energy expenditure. Total energy expenditure consists of basal metabolism, postprandial thermogenesis, and physical activity. Energy expenditure is related to both body weight and body composition. A reduction in total energy expenditure accompanies weight loss, because basal metabolic rate decreases with the loss of lean tissue mass. Similarly, with weight gain, there is an increase in basal metabolic rate, because lean tissue mass grows to support the increase in fat tissue mass. Excess energy intake over energy expenditure causes weight gain and an accompanying increase in total energy expenditure. Following a period of adaptation, total energy expenditure will match energy intake and body weight will stabilize at a higher level. This same relationship holds for weight loss. Respiratory quotient (measured in steady state) is an indication of the proportion of energy expenditure derived from fat and carbohydrate oxidation. Over long periods of time, fat balance is equivalent to energy balance, as an excess of fat intake over fat oxidation causes fat storage.

Social isolation causers mortality by disrupting energy homeostrasis in ants

Social deprivation can have negative effects on the lives of social animals, including humans, yet little is known about the mechanisms by which social withdrawal affects animal health. Here we show that in the carpenter ant Camponotus fellah, socially isolated workers have a greatly reduced life span relative to ants kept in groups of ten individuals. By using a new tracking system, we found that social isolation resulted in important behavioral changes and greatly increased locomotor activity. The higher activity of single ants and their increased propensity to leave the nest to move along the walls suggested that the increased mortality of isolated ants might stem from an imbalance of energy income and expenditure. This view was supported by the finding that while isolated ants ingested the same amount of food as grouped ants, they retained food in the crop, hence preventing its use as an energy source. Moreover, the difference in life span between single and grouped individuals vanished when ants were not fed. This study thus underlines the role of social interactions as key regulators of energy balance, which ultimately affects aging and health in a highly social organism.