Rise In Energy Expenditure Research Articles

Investigation of a new solar-wind energy-based heat pump dryer for food waste drying based on different weather conditions

To date, many studies endeavors have been undertaken regarding the provision of energy necessary for heat pump drying systems utilizing renewable energy resources. Conversely, the contemporary heat pump dryers require both electricity and heat concurrently, whilst the sporadic availability of a particular renewable energy source throughout the day necessitates the utilization of a combination of multiple renewable sources as a prospective remedy to these predicaments. The present research aims to assess the practicability of integrating photovoltaic and thermal collectors with wind turbines for the purpose of meeting the energy demands of a food waste drying system. A study was conducted to evaluate the performance of a dryer with a fixed weight of 100 kg and a moisture removal rate of 71.42 kg/h under varying climatic conditions in the cities of St. Petersburg, Yekaterinburg, Yakutsk and Khabarovsk, Russia. The investigation took into account four key factors, specifically energy, exergy, economy, and environment, over a period of one year. The thermodynamic outcomes derived from economic considerations indicate that an increase in dryer usage leads to a decrease in energy efficiency and a rise in energy expenditure. According to the empirical data, the optimum utilization of the dryer was recorded in Khabarovsk urban center as a consequence of the favorable climatic milieu which facilitated an efficacious moisture extraction rate of 51850.92 kg/year. Conversely, the city of Yakutsk demonstrated the lowest utilization frequency of the dryer, attributable to the unfavorable atmospheric conditions which hindered an effective moisture extraction rate, recording a minimal usage frequency of 27996.64 kg/year. The production of clean electricity and avoidance of natural gas for heating purposes in the cities of Khabarovsk and Yakutsk resulted in the attainment of the most pronounced decreases in carbon dioxide emissions, as indicated by the recorded figures of 47.53 tons and 25.32 tons, respectively. Consequently, following an economic evaluation pertaining to optimal repayment time, based on an interest rate of 0.03 %, the cities of St. Petersburg, Yekaterinburg, Yakutsk and Khabarovsk demonstrate repayment periods of 12.9, 12.6, 18, and 9.6 years, respectively.

Abstract P208: The Impact Of Circadian Misalignment On Energy Metabolism And Substrate Oxidation In Adults With Adequate Sleep

Background: Circadian misalignment (CM), the mismatch between timing of behaviors and internal body clock, increases cardiometabolic risk, but the mechanisms are not fully understood. Population studies in night shift workers and intervention studies attempting to replicate CM have often been confounded by differences in energy intake, sleep duration and timing, and eating window duration. We aimed to investigate the effects of CM, induced by delaying mealtimes relative to wake time, independent of sleep timing and duration as well as duration of eating window, on energy expenditure (EE) and substrate oxidation. We hypothesized that CM would reduce EE and increase respiratory quotient (RQ) relative to meals closer to wake time (circadian alignment [CA]). Methods: We used a 2-phase, randomized, crossover study. Men and women (age 20-49 y) were studied under controlled feeding conditions (CA and CM). Each phase included a 10-h eating window at 0900-1900 h (CA) or 1300-2300 h (CM) with fixed mealtimes. Bedtimes were set at 2400-0800 h. Minute-by-minute EE, RQ, and substrate oxidation were obtained over 23 h in a metabolic chamber on d 3-4 and 14-15. Post-meal EE, RQ, and substrate oxidation were calculated as the average of 2-h, 1-h, and 30 min data collections following breakfast, dinner, and snack, respectively. Data were analyzed using a linear mixed effects model including condition, day, and day-by-condition interaction as main predictor variables, and phase as an adjusting covariate. As an exploratory aim, sex-by-condition interaction was also included in the model. Results: Three men and 4 women completed both study phases (age 37.6±8.8 y, BMI 30.8±3.2 kg/m 2 ). EE did not differ between CM and CA. Post-meal RQ for breakfast (p=0.06), dinner (p<0.001), and snack (p<0.001) were higher in CM vs CA. Glucose oxidation after dinner (p<0.001) and snack (p<0.01) were higher in CM vs CA. There were sex-by-condition interactions on EE and glucose oxidation after breakfast (both p=0.06) and dinner (p<0.05), and on EE after snack (p<0.01). In general, CA resulted in greater rise in EE and lesser reduction in glucose oxidation following meals in men compared to women. Conclusion: Delaying mealtimes by 4 h, independent of sleep duration, timing, or diet composition, shifts nutrient metabolism towards greater carbohydrate and lower fat oxidation. Sex may influence the effect of CM on energy metabolism and should be considered in investigations of cardiometabolic risk associated with shift work and late-night eating.

Trends in spontaneous physical activity and energy expenditure among adults in a respiratory chamber, 1985 to 2005.

Fidgeting, a type of spontaneous physical activity (SPA), has substantial thermogenic potential. This research aims to examine secular trends in SPA and energy expenditure (EE) inside a respiratory chamber. From 1985 to 2005, healthy adults (n=678; mean age: 28.8 years; men: 60%; 522 Indigenous American, 129 White, and 27 Black) had a 24-hour stay in the respiratory chamber equipped with radar sensors. Body composition, glucose tolerance, fasting insulin, insulin action (hyperinsulinemic-euglycemic clamp), and insulin secretion (intravenous glucose tolerance test) were measured as covariates. SPA, adjusted for age, sex, race, and body composition, declined (r=-0.30, p<0.0001), with a concomitant rise in the energy cost of SPA (r=0.30, p<0.0001). The 24-hour EE adjusted for covariates increased (r=0.31, p<0.0001), which was reflected in increases in EE during sleep (r=0.18, p<0.0001) and during the awake, fed condition (r=0.28, p<0.0001). The secular trends in SPA or 24-hour EE were unchanged with adjustment for measures related to glucose metabolism. Secular trend analyses showed a decline in fidgeting. However, this decline in SPA was partially counterbalanced by an increase in energy cost of this activity and a rise in EE. Nevertheless, our results support public health efforts to promote small but sustained changes in these behaviors.

Energetic response of Atlantic surfclam Spisula solidissima to ocean acidification

In this study, we assessed the Atlantic surfclam (Spisula solidissima) energy budget under different ocean acidification conditions (OA). During 12 weeks, 126 individuals were maintained at three different ρCO2 concentrations. Every two weeks, individuals were sampled for physiological measurements and scope for growth (SFG). In the high ρCO2 treatment, clearance rate decreased and excretion rate increased relative to the low ρCO2 treatment, resulting in reduced SFG. Moreover, oxygen:nitrogen (O:N) excretion ratio dropped, suggesting that a switch in metabolic strategy occurred. The medium ρCO2 treatment had no significant effects upon SFG; however, metabolic loss increased, suggesting a rise in energy expenditure. In addition, a significant increase in food selection efficiency was observed in the medium treatment, which could be a compensatory reaction to the metabolic over-costs. Results showed that surfclams are particularly sensitive to OA; however, the different compensatory mechanisms observed indicate that they are capable of some temporary resilience.

1798-P: Chronic Administration of a Long-Acting Glucagon Analogue Results in Enhanced Insulin Secretory Activity in a Directly-Observed Murine Model

Aims: GLP-1 (GLP-1R) and glucagon (GCGR) receptor co-agonists are in development to treat type 2 diabetes. The effect of chronic GCGR agonism on weight loss is well-documented, but its direct influence on islet function remains poorly understood. We investigated the effects of a long-acting glucagon analogue G778 on pancreatic islet calcium dynamics. Methods: C57Bl/6 (n=9 per group) mice with diet-induced obesity (DIO) received daily subcutaneous injections of G778 100nmol/kg or saline (and calorie restricted to achieve weight matching) for 40 days. All mice had syngeneic islets with beta-cell specific expression of the calcium fluorophore GCaMP6f implanted in the anterior chamber of the eye, providing a direct, longitudinal readout of beta-cell function in vivo using confocal microscopy. Such islets were tested in vitro to measure the effects of G778 on whole islet calcium dynamics. Another experiment measured the effects of G778 administration on oxygen consumption in a CLAMS system. Results: G778 produced a small but significant rise in energy expenditure (EE) in mice. At 40 days, there was non-significant difference in body weight loss between the saline and G778-treated groups (0.9g ±1.1 vs. 3.4g ±0.7 p=0.07), but a marked improvement in glucose tolerance in mice treated long term with the glucagon analogue (15 min glucose on a 2mg/kg IPGTT 15.9 mmol/L vs. 9.2 mmol/L p&amp;lt;0.001). Islet readouts over the course of the experiment revealed that glucagon receptor agonism was able to restore calcium activity of islets in DIO mice in vivo. In vitro findings confirmed that G778 promoted calcium waves of longer duration and heightened connectivity above 7mM glucose (p=0.05). Summary: Our data suggest that the glucagon element of a glucagon/GLP-1 analogue contributes to weight-loss partly through an elevation in EE but also has independent effects on insulin secretory function, promoting more robust and sustained beta-cell calcium responses. Disclosure K. Suba: None. Y.S. Patel: None. A. Martin Alonso: None. R. Scott: None. J.S. Minnion: None. I. Leclerc: Consultant; Spouse/Partner; Sun Pharmaceutical Industries Ltd. Research Support; Spouse/Partner; Servier. B. Owen: None. W. Distaso: None. T.M. Tan: None. K. Murphy: None. S. Bloom: None. G.A. Rutter: Consultant; Self; Sun Pharmaceutical Industries Ltd. Research Support; Self; Servier, Sun Pharmaceutical Industries Ltd. V. Salem: None. Funding Diabetes UK (15/0005317)

Estimated energy requirements increase across pregnancy in healthy women with dichorionic twins

Estimated energy requirement (EER) has not been defined for twin pregnancy. This study was designed to determine the EER of healthy women with dichorionic-diamniotic (DCDA) twin pregnancies. We aimed to estimate energy deposition from changes in maternal body protein and fat; to measure resting energy expenditure (REE), physical activity level (PAL), and total energy expenditure (TEE) throughout pregnancy and postpartum; and to define the EER based on the sum of TEE and energy deposition for twin gestation. This is a prospective study of 20 women with DCDA twin gestations. Maternal EER, energy deposition, REE, TEE, and PAL were obtained during the first, second, and third trimesters of pregnancy and immediately postpartum. A mixed-effects linear regression model for repeated measures with random intercept was used to test for the effects of BMI groups and time. Gains in total body protein (mean±SD: 2.1±0.7 kg) and fat mass (5.9±2.8 kg) resulted in total energy deposition of 67,042±25,586 kcal between 0 and 30-32 weeks of gestation. REE increased 26% from 1392±162 to 1752±172 kcal/d across the 3 trimesters, whereas TEE increased 17% from 2141±283 to 2515±337 kcal/d. Physical activity decreased steadily throughout pregnancy. Reductions in physical activity did not compensate for the rise in REE and energy deposition, thus requiring an increase in dietary energy intake as pregnancy progressed. EER increased 29% from 2257±325 kcal/d in the first trimester to 2941±407 kcal/d in the second trimester, and stayed consistent at 2906±350 kcal/d in the third trimester. Increased energy intake, on average ∼700 kcal/d in the second and third trimesters when compared with the first trimester, is required to support gestational weight gain and the rise in energy expenditure of DCDA twin pregnancies.

RAAAF's office landscape The End of Sitting: Energy expenditure and temporary comfort when working in non-sitting postures.

An earlier study suggested that the activity-inviting office landscape called “The End of Sitting”, designed by Rietveld Architecture Art Affordances (RAAAF), should be considered as an alternative working environment to prevent sedentary behavior. The End of Sitting lacks chairs and tables but consists instead of a myriad of sloped surfaces at different heights that afford workers to stand, lean or recline at different locations. In this study, we assessed the impact of four of its workspaces on physical intensity, temporary comfort and productivity of office work and compared the outcomes with sitting and standing behind a desk. Twenty-four participants worked for 10 minutes in each of the six test conditions. Energy expenditure, measured by indirect calorimetry, and heart rate were recorded. Questionnaires were used to assess the perceived comfort. The number of words found in the word search test was counted as a measure of productivity. The majority of The End of Sitting workspaces led to a significant increase in energy expenditure compared with sitting behind a desk (ps < .05). Average MET values ranged from 1.40 to 1.58 which is a modest rise in energy expenditure compared to sitting (1.32 METs) and not significantly different from standing (1.47 METs). The scores on the general comfort scale indicated that some workspaces were less comfortable than sitting (ps < .05), but the vast majority of participants reported that at least one of The End of Sitting workspaces was equally or more comfortable than sitting. No differences in productivity between the test conditions were found. Further long-term studies are required to assess the behavioral adaptations, productivity and the level of comfort when using The End of Sitting as a permanent office.

Extracorporeal Carbon Dioxide Removal Enhanced by Lactic Acid Infusion in Spontaneously Breathing Conscious Sheep

The authors studied the effects on membrane lung carbon dioxide extraction (VCO2ML), spontaneous ventilation, and energy expenditure (EE) of an innovative extracorporeal carbon dioxide removal (ECCO2R) technique enhanced by acidification (acid load carbon dioxide removal [ALCO2R]) via lactic acid. Six spontaneously breathing healthy ewes were connected to an extracorporeal circuit with blood flow 250 ml/min and gas flow 10 l/min. Sheep underwent two randomly ordered experimental sequences, each consisting of two 12-h alternating phases of ALCO2R and ECCO2R. During ALCO2R, lactic acid (1.5 mEq/min) was infused before the membrane lung. Caloric intake was not controlled, and animals were freely fed. VCO2ML, natural lung carbon dioxide extraction, total carbon dioxide production, and minute ventilation were recorded. Oxygen consumption and EE were calculated. ALCO2R enhanced VCO2ML by 48% relative to ECCO2R (55.3 ± 3.1 vs. 37.2 ± 3.2 ml/min; P less than 0.001). During ALCO2R, minute ventilation and natural lung carbon dioxide extraction were not affected (7.88 ± 2.00 vs. 7.51 ± 1.89 l/min, P = 0.146; 167.9 ± 41.6 vs. 159.6 ± 51.8 ml/min, P = 0.063), whereas total carbon dioxide production, oxygen consumption, and EE rose by 12% each (223.53 ± 42.68 vs. 196.64 ± 50.92 ml/min, 215.3 ± 96.9 vs. 189.1 ± 89.0 ml/min, 67.5 ± 24.0 vs. 60.3 ± 20.1 kcal/h; P less than 0.001). ALCO2R was effective in enhancing VCO2ML. However, lactic acid caused a rise in EE that made ALCO2R no different from standard ECCO2R with respect to ventilation. The authors suggest coupling lactic acid-enhanced ALCO2R with active measures to control metabolism.

Abstract P125: Aerobic Exercise Training Reduces Postprandial Thermogenesis in Older Women

Introduction: Thermic effect of food is a component of total daily energy expenditure (TDEE). Some literature suggests lower postprandial rise in energy expenditure predicts future weight gain. It is also known that other components of TDEE, resting metabolic rate (RMR) and free-living physical activity energy expenditure, are prone to change in response to exercise training. However, most studies estimate thermic effect of food as a proportion of TDEE and thus have not evaluated whether changes in postprandial thermogenesis occur in response to exercise training. The objective of this study was to determine whether postprandial thermogenesis changed after completing aerobic exercise training in older women. Hypothesis: We hypothesize that the postprandial thermogenesis decreases in sedentary older women who complete 16-week aerobic exercise training. Methods: Sedentary older women (n = 47; age = 65.1 ± 4.3 years) completed 16-week moderate-intensity aerobic exercise training. RMR and 5-hour postprandial thermogenesis following ingesting the same meal, before and at the end of training, was measured via indirect calorimetry. The meal consisted of approximately 40% of each woman’s RMR at baseline. Postprandial thermogenesis was calculated as area under the curve. TDEE was also measured using doubly labelled water before and at the end of training. Results: After exercise training, RMR and TDEE did not change (p &gt; 0.05 for both). Total postprandial thermogenesis (from 287 ±36 to 276 ± 40 kcal for 5 hours, p = 0.008) and postprandial thermogenesis in the first hour (from 69.9±8.7 to 66.3±8.1 kcal, p = 0.05) decreased significantly. The ratios of total and first-hour postprandial thermogenesis to TDEE also decreased (p = 0.026 and 0.013, respectively). Conclusion: Postprandial thermogenesis following the same meal reduced after aerobic training in older women. This adaptive change may contribute to an individual’s ability to defend the body’s energy store.

Mild Cold Exposure Modulates Fibroblast Growth Factor 21 (FGF21) Diurnal Rhythm in Humans: Relationship between FGF21 Levels, Lipolysis, and Cold-Induced Thermogenesis

Cold exposure stimulates fibroblast growth factor 21 (FGF21) secretion in animals, enhancing the cold-induced thermogenesis (CIT) response through browning of white adipose tissue. In humans, the effects of cold exposure on circulating FGF21 levels are unknown. Our objective was to evaluate the effects of mild cold exposure on circulating FGF21 and its relationship with CIT and lipolysis in humans. We conducted a randomized, single-blind, crossover intervention study at the National Institutes of Health Clinical Center. Participants were healthy adults. Subjects were exposed to a 12-h exposure to 24 or 19 C in a whole-room indirect calorimeter. Energy expenditure, plasma FGF 21, nonesterified fatty acid, and adipose tissue microdialysis glycerol concentrations were evaluated. At 24 C, plasma FGF21 exhibited a diurnal rhythm, peaking at 0800 h [110 (59-178) pg/ml], and progressively dropped to a nadir at 1700 h [41 (21-71) pg/ml, P < 0.0001] before rising at 1900 h [60 (11-81) pg/ml, P < 0.0001]. Exposure at 19 C lessened the diurnal reduction of FGF21 observed at 24 C from 0800-1700 h and augmented overall FGF21 levels by 37 ± 45% (P = 0.01). The change in area under the curve plasma FGF21 between 19 and 24 C correlated positively with the change in area under the curve adipose microdialysate glycerol (R(2) = 0.35, P = 0.04) but not with nonesterified fatty acid. Cold-induced increase in FGF21 predicted greater rise in energy expenditure during cold exposure (β = 0.66, P = 0.027), independent of age, gender, fat mass, and lean mass. Mild cold exposure increased circulating FGF21 levels, predicting greater lipolysis and CIT. A small reduction in environmental temperature is sufficient to modulate FGF21 diurnal rhythm in humans, which may mediate cold-induced metabolic changes similar to those in animals.

Adipogenesis: From Stem Cell to Adipocyte

Excessive caloric intake without a rise in energy expenditure promotes adipocyte hyperplasia and adiposity. The rise in adipocyte number is triggered by signaling factors that induce conversion of mesenchymal stem cells (MSCs) to preadipocytes that differentiate into adipocytes. MSCs, which are recruited from the vascular stroma of adipose tissue, provide an unlimited supply of adipocyte precursors. Members of the BMP and Wnt families are key mediators of stem cell commitment to produce preadipocytes. Following commitment, exposure of growth-arrested preadipocytes to differentiation inducers [insulin-like growth factor 1 (IGF1), glucocorticoid, and cyclic AMP (cAMP)] triggers DNA replication and reentry into the cell cycle (mitotic clonal expansion). Mitotic clonal expansion involves a transcription factor cascade, followed by the expression of adipocyte genes. Critical to these events are phosphorylations of the transcription factor CCATT enhancer-binding protein β (C/EBPβ) by MAP kinase and GSK3β to produce a conformational change that gives rise to DNA-binding activity. "Activated" C/EBPβ then triggers transcription of peroxisome proliferator-activated receptor-γ (PPARγ) and C/EBPα, which in turn coordinately activate genes whose expression produces the adipocyte phenotype.

Brown Adipose Tissue, Whole‐Body Energy Expenditure, and Thermogenesis in Healthy Adult Men

Brown adipose tissue (BAT) can be identified by (18)F-fluorodeoxyglucose (FDG)-positron emission tomography (PET) in adult humans. Thirteen healthy male volunteers aged 20-28 years underwent FDG-PET after 2-h cold exposure at 19°C with light-clothing and intermittently putting their legs on an ice block. When exposed to cold, 6 out of the 13 subjects showed marked FDG uptake into adipose tissue of the supraclavicular and paraspinal regions (BAT-positive group), whereas the remaining seven showed no detectable uptake (BAT-negative group). The BMI and body fat content were similar in the two groups. Under warm conditions at 27°C, the energy expenditure of the BAT-positive group estimated by indirect calorimetry was 1,446 ± 97kcal/day, being comparable with that of the BAT-negative group (1,434 ± 246kcal/day). After cold exposure, the energy expenditure increased markedly by 410 ± 293 (P < 0.05) and slightly by 42 ± 114kcal/day (P = 0.37) in the BAT-positive and -negative groups, respectively. A positive correlation (P < 0.05) was found between the cold-induced rise in energy expenditure and the BAT activity quantified from FDG uptake. After cold exposure, the skin temperature in the supraclavicular region close to BAT deposits dropped by 0.14°C in the BAT-positive group, whereas it dropped more markedly (P < 0.01) by 0.60°C in the BAT-negative group. The skin temperature drop in other regions apart from BAT deposits was similar in the two groups. These results suggest that BAT is involved in cold-induced increases in whole-body energy expenditure, and, thereby, the control of body temperature and adiposity in adult humans.

Deletion of the gene encoding MyD88 protects from anorexia in a mouse tumor model

The anorexia–cachexia syndrome, characterized by a rise in energy expenditure and loss of body weight that paradoxically are associated with loss of appetite and decreased food intake, contributes significantly to the morbidity and mortality in cancer. While the pathophysiology of cancer anorexia–cachexia is poorly understood, evidence indicates that pro-inflammatory cytokines are key mediators of this response. Although inflammation hence is recognized as an important component of cancer anorexia–cachexia, the molecular pathways involved are largely unknown. We addressed this issue in mice carrying a deletion of the gene encoding MyD88, the key intracellular adaptor molecule in Toll-like and interleukin-1 family receptor signaling. Wild-type and MyD88-deficient mice were transplanted subcutaneously with a syngenic methylcholanthrene-induced tumor (MCG 101) and daily food intake and body weight were recorded. Wild-type mice showed progressively reduced food intake from about 5 days after tumor transplantation and displayed a slight body weight loss after 10 days when the experiment was terminated. In contrast, MyD88-deficient mice did not develop anorexia, and displayed a positive body weight development during the observation period. While the MyD88-deficient mice on average developed somewhat smaller tumors than wild-type mice, this did not explain the absence of anorexia, because anorexia was seen in wild-type mice with similar tumor mass as non-anorexic knock-out mice. These data suggest that MyD88-dependent mechanisms are involved in the metabolic derangement during cancer anorexia–cachexia and that innate immune signaling is important for the development of this syndrome.

Slow Wave Sleep: Does it Matter?

Sleep is a behavior observed in all living organisms and is necessary for survival. In rodents, total sleep deprivation results in a large rise in energy expenditure and consequent weight loss, despite increased food intake and — unless sleep deprivation is halted — it leads to death, usually in 2–3 weeks.1 Death associated with chronic sleep deprivation has also been reported in other species.2 In humans, the rare hereditary condition, fatal familial insomnia, which is associated with a progressive inability to sleep, invariably leads to death, with a time course of between 8 and 72 months.3,4 In the absence of a disorder, total sleep deprivation does not occur over prolonged periods of time. This attests to the homeostatic drive for sleep; beyond a few days, heroic measures must be taken to keep humans awake. Although less dramatic, the effects of sleep disturbances may be of more practical use in helping us to understand the consequences of normally occurring voluntary sleep loss and sleep loss associated with sleep disorders. In a recent large study of working adult Americans, 16% of respondents reported sleeping less than 6 hours per night on work days.5 Chronic sleep restriction is associated with an increase in sleep propensity — even in inconvenient and dangerous situations — a deterioration of daytime performance, including memory, and a number of physiologic consequences, including adverse effects on endocrine functions and immune responses6 and an increase in the risk of obesity and diabetes.7 In order to understand the consequences and effects of sleep disturbances and how these may be ameliorated, it is important to be able to analyze the neurobiology of sleep. Today, sleep is characterized using polysomnography. Using this technique, it has been shown that sleep consists of two distinct components: rapid eye movement (REM) sleep and nonREM (NREM) sleep. Standardized methods for characterizing normal sleep were first published in 1968 by Allan Rechtschaffen and Anthony Kales.8 REM sleep is characterized by rapid eye movements and a low-amplitude, mixed-frequency EEG.8 It accounts for approximately 18–22% of total sleep time, with the percentage of REM sleep decreasing slightly with age in adults.9 NREM sleep is characterized by the presence of K complexes, sleep spindles, and slow wave activity (SWA), and is arbitrarily divided into four stages of sleep by Rechtschaffen and Kales, with stage 1 considered “light sleep” and stages 3 and 4 considered “deep sleep.”8 Stage 3 sleep has been defined as an epoch of sleep containing more than 20% SWA, while stage 4 sleep has been defined as an epoch of sleep containing more than 50% SWA.8 Together, NREM sleep stages 3 and 4 are often known as slow wave sleep (SWS). SWS is thought, by some investigators, to play an important role in cerebral restoration and recovery in humans10,11 and to be involved in the maintenance and consolidation of sleep.12 However, the exact nature and role of SWS are not clearly understood and there is still much to learn about SWS generation and its physiologic functions. Some of the key questions that need to be answered are: What is the relationship between SWS and other sleep parameters, such as sleep continuity, sleep duration, daytime sleep propensity, and daytime functioning? Does SWS vary with respect to age, sex, race, or basal sleep duration? What are the neurophysiologic and neuroanatomic origins of SWS? Does SWS have unique functions? Is it possible to influence SWS with pharmacologic agents and what are the consequences of doing so? Many of these important questions are addressed in the following articles, which were first presented at a satellite symposium entitled “Slow Wave Sleep (SWS): Does it Matter?” held at the 22nd Annual Meeting of the Associated Professional Sleep Societies (APSS) in Baltimore on June 10, 2008. In these articles, the authors review what is currently known about SWS. In his article, Derk-Jan Dijk discusses the nature of SWA and SWS and how they are regulated, before going on to evaluate the factors affecting SWS and the correlation of SWS with sleep continuity, sleep propensity, and daytime functioning. Giulio Tononi then delves deeper into the electrophysiologic nature of SWA, its regulation, and the relationship between SWA and synaptic strength, before Matthew Walker outlines evidence supporting a role for SWS in memory processing. Finally, James Walsh examines the impact of hypnotic agents on SWS and the consequences of enhancing SWS. Against this background, the question of whether SWS truly has a restorative and refreshing role will be considered, together with the suggestion that enhancing SWS may be of benefit to patients who experience insomnia in its many forms.

The relationship between heart rate and energy expenditure in Alpine, Angora, Boer and Spanish goat wethers consuming different quality diets at level of intake near maintenance or fasting

Six Alpine (AL; 38.4 ± 3.0 kg), Angora (AN; 23.1 ± 2.7 kg), Boer (BO; 40.8 ± 4.5 kg) and Spanish (SP; 33.6 ± 2.2 kg) wethers (1.5 yr of age) were used to determine the effects of time of the day and potential interactions between time, genotype and diet quality on energy expenditure (EE), heart rate (HR) and EE:HR when fed near maintenance and fasting. The experiment consisted of four simultaneous crossovers, with 21 d for adaptation before measures. Diets were 60% concentrate (CON: 15% CP) and ground alfalfa hay (FOR: 23% CP), offered in two meals at 8:00 and 16:00 h. Energy expenditure was determined from O 2 consumption and production of CO 2 and CH 4 over 2-day periods in fed and fasting states (total 4-day fasting period). Fasting EE was higher during the day than night, with values generally highest at 16:00–17:00 h. Animal within breed affected EE, HR and EE:HR ( P < 0.05). The diurnal pattern in EE varied with diet ( P < 0.05), although total daily EE was not different between diets. Before the morning meal, there were a number of hours during which EE was greater for CON than for FOR. However, at both meals the rise in EE was considerably greater for FOR versus CON, lasting for 3–4 h. The same general pattern in HR was observed, although the period of time when there was a dietary difference after the afternoon meal was shorter. For both fed and fasted goats, EE:HR differed among hours of the day ( P < 0.05). EE:HR tended ( P < 0.09) to differ between diets (5.99 and 6.21 for CON and FOR, respectively) and to be affected ( P < 0.09) by an interaction between breed and diet (AL: 5.84 and 6.38; AN: 5.91 and 5.73; BO: 6.05 and 6.58; and SP: 6.17 and 6.15 kJ/(kg BW 0.75 × day):heart beats/min) for CON and FOR, respectively. In conclusion, for use of HR to predict EE by goats, it appears desirable to determine the ratio of EE:HR with a diet similar to that consumed during prediction and over an extended period of time.

Metabolic changes in malnutrition

This paper is concerned with malnutrition caused by inadequate intake of all the major nutrients rather than deficiency diseases relating to a single micronutrient. Three common situations are recognised: young children in third world countries with protein-energy malnutrition; adults in the same countries who are chronically adapted to subsisting on marginally inadequate diets; and patients who become malnourished as a result of chronic diseases. In all these situations infectious diseases are often also present, and this complicates the interpretation of biochemical and physiological observations. The metabolic response to starvation is primarily concerned with maintaining a supply of water-soluble substrates to supply energy to the brain. Thus there is an initial rise in metabolic rate, reflecting gluconeogenic activity. As fasting progresses, gluconeogenesis is suppressed to minimise muscle protein breakdown and ketones become the main fuel for the brain. With chronic underfeeding the basal metabolic rate per cell appears to fall, but the mechanistic basis for this is not clear. The main adaptation to chronic energy deficiency is slow growth and low adult body size, although the reduction in energy requirement achieved by this is partially offset by the preservation of the more metabolically active organs at the expense of muscle, which has a lower metabolic rate. The interaction between malnutrition and the metabolic response to trauma has been studied using an animal model. The rise in energy expenditure and urinary nitrogen excretion following surgery were significantly attenuated in malnourished rats, suggesting that malnutrition impairs the ability of the body to mobilise substrates to support inflammatory and reparative processes. However, the healing process in wounded muscle remained unimpaired in malnutrition, suggesting that this process has a high biological priority.

Seasonal changes in physiological responses and energy expenditure of sheep maintained on semi-arid pasture

A study on the energy expenditure of sheep was carried out at the Central Sheep and Wool Research Institute, India during August 1995 to July 1996 by conducting two experiments: one on tracheal cannulated rams maintained on stall-feeding in autumn 1995 (Expt 1) followed by year-round grazing on silvipasture (Cenchrus ciliaris pasture interspersed with fodder trees) over three seasons: monsoon, winter and summer, 1995/96 (Expt 2). Physiological responses and energy expenditure measurement of housed and grazing sheep were recorded at 06.00, 14.00 and 22.00 h for 5 consecutive days in each season. Tracheostomized sheep harness with meteorological balloon were used for collection of expired air and measurement of energy expenditure. Rectal temperature (RT) of sheep at 06.00 h was similar in all the seasons except for a significant (P&lt;0·05) lower value in monsoon. The rise of RT from 06.00 to 14.00 h in grazing animals was 1·6 °C, higher than that in housed sheep (0·9 °C). Skin temperature (ST) was least in winter and highest at 14.00 h in the monsoon and autumn seasons. Respiration rate (RR) showed a marked rise at 14.00 h in all the seasons. The heart rate (HR) of grazing sheep was higher, irrespective of season, at 14.00 h. At 06.00 and 22.00 h, the heart rate was higher in winter and summer than in the monsoon season. Overall energy expenditure (EE) was 4·85 MJ/24 h during winter which increased to 5·85 MJ/24 h in summer and 6·70 MJ/24 h in the monsoon. The mean rise in energy expenditure per °C rectal temperature in all the seasons was 338 kJ/kg W0·75. Comparable mean values per 10 °C ambient temperature and 10 °C black globe temperature were 404 and 173. The increase in energy expenditure of grazing compared to housed sheep in monsoon, winter and summer was 78, 15 and 33 % respectively. The mean value was +43%.

Effects on energy utilization of a beta3-adrenergic agonist in rats fed on a cafeteria diet.

The antiobesity potential of a new beta3-adrenergic agonist (Trecadrine) was assessed in a cafeteria model of obesity through body composition, thermogenesis and oxygen consumption indicators. Animals fed on a cafeteria diet for 75 days increased body weight and fat content, while muscle mass as a percentage of body weight was reduced in relation to control fed rats. In addition, in vitro brown adipose tissue (BAT) and white adipose tissue (WAT) oxygen consumption was increased in these obese animals as compared with controls. Trecadrine administration reduced weight gain, BAT and WAT stores as well as the respiratory quotient, which was accompanied by an increase in WAT and BAT oxygen consumption and rectal temperature. Moreover, muscle mass as a percentage of body weight maintained the same values as non-obese animals, while an increase in absolute muscle weight was found in Trecadrine-treated obese rats. However, liver weights and in vitro oxygen consumption remained unaltered after cafeteria feeding and Trecadrine administration. Since chronic administration of Trecadrine had no effect on food intake, the stimulation of thermogenesis and oxygen consumption by the beta3-adrenergic agonist in white and brown adipose tissue are apparently responsible for the rise in energy expenditure as well as for the lower weight gain and fat deposition in obese treated rats. Thus, Trecadrine exhibits some promise as a potential treatment for obesity.

Leptin and thermogenesis in humans.

We examined changes in serum leptin concentrations and thermogenesis in 12 healthy men (39 +/- 2 years, BMI 22.8 +/- 0.3 kg m-2) during a 4 h euglycaemic hyperinsulinaemia performed on a control day and after a day of competitive marathon runs. As compared with the control day, after the marathon, baseline FFA concentration (543 +/- 0.73 vs. 955 +/- 96 mumol L-1, P < 0.05), lipid oxidation rate (0.8 +/- 0.1 vs. 1.2 +/- 0.1 mg kg-1 min-1, P < 0.01) and energy expenditure (5.2 +/- 0.1 vs. 5.5 +/- 0.1 kJ min-1, P < 0.01) were elevated. Baseline serum leptin concentrations were similar on the control and postexercise days and increased during insulin infusion by 35-45% on both days (P < or = 0.01). Baseline serum leptin concentration correlated directly with serum insulin (r = 0.65, P < 0.05) and cortisol (r = 0.64, P < 0.05), and inversely with serum growth hormone concentration (r = -0.66, P < 0.05). In the postexercise study, the rise in energy expenditure during insulin clamp correlated with serum leptin concentration as determined before (r = 0.61, P < 0.05) or at the end of insulin infusion (r = 0.55, P < 0.05). Thus, in healthy individuals with normal body weight: (1) hyperinsulinaemia increases serum leptin concentrations; (2) a rise in energy expenditure correlates with serum leptin concentration. These data suggest that leptin is involved in the regulation of energy expenditure in humans.

Correlation between amino acid induced changes in energy expenditure and protein metabolism in humans

The relationship between energy expenditure and protein metabolism during amino acid (AA) administration wasevaluated in normal humans. A balanced AA solution was infused for 180 min at five different rates: 20 (study I), 40 (study II) , 80 (study III) , 160 (study IV), and 240 mg · m 2 −1 · min −1 (study V), on separate days, in seven normal, overnight-fasted subjects (age 25 ± 2 y; height 172 ± 5 cm; weight 68 ± 4 kg). Indirect calorimetry and [I- 14C] leucine infusion techniques were employed. Basal total plasma AA concentration averaged 1827 ± 121 μmol/L and increased to 2192 ± 142, 2576 ± 158, 3677 ± 195, 5638 ± 237, and 7185 ± 261 μmol/L in studies I–V, respectively. Basal energy expenditure averaged 0.60 ± 0.02 kcal· M 2 −1· min −1 and increased slightly in studies I and II (to 0.62 ± 0.03, 0.63 ± 0.02, respectively), and significantly in studies III–V (to 0.65 ± 0.03, 0.70 ± 0.04, and 0.77 ± 0.05 kcal· m 2 −1 · min −1, respectively; all P < 0.01 versus basal; P < 0.05−0.01 for each study versus preceding study). Basal nonoxidative leucine disposal (NOLD), an index of protein synthesis, averaged 73 ± 3 μmol·m 2 −1·min −1 and increased, albeit not significantly, in studies I and II (to 75 ± 5, 76 ± 4, respectively). In contrast, a significant increase in NOLD was observed in studies III–V (to 87 ± 7, 103 ± 7, and 127 ± 9 μmol · ml 2 −1· min −1, respectively; all P < 0.01 versus basal; P < 0.05−0.01 for each study versus preceding study). Basal respiratory quotient averaged 0.81 ± 0.02 and did not change significantly in studies I–V (0.80 ± 0.02, 0.79 ± 0.02, 0.80 ± 0.03, 0.82 ± 0.02 and 0.82 ± 0.03, respectively). The thermic effect of AA administration, calculated as percent of the AA energy infused, was constant and averaged 24 ± 4, 19 ± 3, 17 ± 4, 17 ± 3, and 18 ± 3% in studies I–V, respectively. When AA-induced increase in protein synthesis was plotted with the increment in energy expenditure, a positive correlation was obtained ( r = 0.792, P < 0.001). In summary, during AA administration ( 1) the absolute rise in energy expenditure is dose-dependent and does not show evidence of achieving a plateau; ( 2) it is positively correlated with AA-induced protein synthesis; and ( 3) the thermic effect is not dependent upon the AA dose administered. The data provide a quantitative assessment of AA-induced thermogenesis in normal humans and the energy needs associated with an acute stimulation of protein synthesis.