Energy Expenditure (energy + expenditure)

Distribution by Scientific Domains
Distribution within Medical Sciences

Kinds of Energy Expenditure

  • daily energy expenditure
  • increase energy expenditure
  • total energy expenditure

  • Selected Abstracts

    Effort/gains dynamics in heterogeneous networks

    L. Mamatas
    Abstract We investigate the behaviour of TCP(,, ,) protocols in the presence of wireless networks. We seek an answer to strategic issues of maximizing energy and bandwidth exploitation, without damaging the dynamics of multiple-flow equilibrium. We take a fresh perspective on protocol design: What is the return of the effort that a protocol expends? Can we achieve more gains with less effort? We study first the design assumptions of TCP(,, ,) protocols and discuss the impact of equation-based modulation of , and , on protocol efficiency. We introduce two new measures to capture protocol behaviour: the ,Extra Energy Expenditure' and the ,Unexploited Available Resource Index'. We confirm experimentally that, in general, smoothness and responsiveness constitute a tradeoff; however, we show that this tradeoff does not graft its dynamics into a conservative/aggressive behaviour, as it is traditionally believed. We uncover patterns of unjustified tactics; our results suggest that an adaptive congestion control algorithm is needed to integrate the dynamics of heterogeneous networks into protocol behaviour. Copyright © 2007 John Wiley & Sons, Ltd. [source]

    Cardiac basal metabolism: energetic cost of calcium withdrawal in the adult rat heart

    ACTA PHYSIOLOGICA, Issue 3 2010
    P. Bonazzola
    Abstract Aim:, Cardiac basal metabolism upon extracellular calcium removal and its relationship with intracellular sodium and calcium homeostasis was evaluated. Methods:, A mechano-calorimetric technique was used that allowed the simultaneous and continuous measurement of both heat rate and resting pressure in arterially perfused quiescent adult rat hearts. Using pharmacological tools, the possible underlying mechanisms related to sodium and calcium movements were investigated. Results:, Resting heat rate (expressed in mW g,1dry wt) increased upon calcium withdrawal (+4.4 ± 0.2). This response was: (1) unaffected by the presence of tetrodotoxin (+4.3 ± 0.6), (2) fully blocked by both, the decrease in extracellular sodium concentration and the increase in extracellular magnesium concentration, (3) partially blocked by the presence of either nifedipine (+2.8 ± 0.4), KB-R7943 (KBR; +2.5 ± 0.2), clonazepam (CLO; +3.1 ± 0.3) or EGTA (+1.9 ± 0.3). The steady heat rate under Ca2+ -free conditions was partially reduced by the addition of Ru360 (,1.1 ± 0.2) but not CLO in the presence of EGTA, KBR or Ru360. Conclusion:, Energy expenditure for resting state maintenance upon calcium withdrawal depends on the intracellular rise in both sodium and calcium. Our data are consistent with a mitochondrial Ca2+ cycling, not detectable under normal calcium diastolic levels. The experimental condition here analysed, partially simulates findings reported under certain pathological situations including heart failure in which mildly increased levels of both diastolic sodium and calcium have also been found. Therefore, under such pathological conditions, hearts should distract chemical energy to fuel processes associated with sodium and calcium handling, making more expensive the maintenance of their functions. [source]

    Exercise intensity-dependent regulation of peroxisome proliferator-activated receptor , coactivator-1, mRNA abundance is associated with differential activation of upstream signalling kinases in human skeletal muscle

    Brendan Egan
    Skeletal muscle contraction increases intracellular ATP turnover, calcium flux, and mechanical stress, initiating signal transduction pathways that modulate peroxisome proliferator-activated receptor , coactivator-1, (PGC-1,)-dependent transcriptional programmes. The purpose of this study was to determine if the intensity of exercise regulates PGC-1, expression in human skeletal muscle, coincident with activation of signalling cascades known to regulate PGC-1, transcription. Eight sedentary males expended 400 kcal (1674 kj) during a single bout of cycle ergometer exercise on two separate occasions at either 40% (LO) or 80% (HI) of,. Skeletal muscle biopsies from the m. vastus lateralis were taken at rest and at +0, +3 and +19 h after exercise. Energy expenditure during exercise was similar between trials, but the high intensity bout was shorter in duration (LO, 69.9 ± 4.0 min; HI, 36.0 ± 2.2 min, P < 0.05) and had a higher rate of glycogen utilization (P < 0.05). PGC-1, mRNA abundance increased in an intensity-dependent manner +3 h after exercise (LO, 3.8-fold; HI, 10.2-fold, P < 0.05). AMP-activated protein kinase (AMPK) (2.8-fold, P < 0.05) and calcium/calmodulin-dependent protein kinase II (CaMKII) phosphorylation (84%, P < 0.05) increased immediately after HI but not LO. p38 mitogen-activated protein kinase (MAPK) phosphorylation increased after both trials (,2.0-fold, P < 0.05), but phosphorylation of the downstream transcription factor, activating transcription factor-2 (ATF-2), increased only after HI (2.4-fold, P < 0.05). Cyclic-AMP response element binding protein (CREB) phosphorylation was elevated at +3 h after both trials (,80%, P < 0.05) and class IIa histone deacetylase (HDAC) phosphorylation increased only after HI (2.0-fold, P < 0.05). In conclusion, exercise intensity regulates PGC-1, mRNA abundance in human skeletal muscle in response to a single bout of exercise. This effect is mediated by differential activation of multiple signalling pathways, with ATF-2 and HDAC phosphorylation proposed as key intensity-dependent mediators. [source]

    Energy expenditure in very low birth weight newborns: a comparison between small and appropriate-for-gestational-age

    ACTA PAEDIATRICA, Issue 5 2010
    MEL Moreira
    Abstract Aims:, To compare resting energy expenditure (REE) in small- and appropriate-for-gestational-age very low birth weight newborns after reaching corrected at-term age. Methods:, Observational study that included all clinically stable very low birth weight newborns admitted to a neonatal intensive care unit. The newborns were classified as small-for-gestational-age (SGA) and appropriate-for-gestational-age (AGA). Resting energy expenditure was measured using indirect calorimetry when the newborns reached at-term age. Results:, A total of 51 newborns, of which 23 were SGA and 28 AGA, were included. There was no statistically significant difference in REE between the two groups, although the observed levels were higher than the reference values. Conclusion:, There is no statistical difference in resting expenditure energy between SGA and AGA infants when they reached term. The higher energy expenditure found in both groups may be explained by other factors related to prematurity and its complications and requires further investigation. [source]

    Physical activity levels and estimated energy expenditure in overweight and normal-weight 11-year-old children

    ACTA PAEDIATRICA, Issue 2 2010
    M Soric
    Abstract Aim:, To objectively evaluate physical activity and energy expenditure in overweight and normal-weight 11-year-old children. Methods:, The final sample consisted of 91 children (32 overweight and 59 normal-weight children), mean age (SD) = 11.3 (0.2) years. Energy expenditure and physical activity were assessed during two weekdays and two weekend days using a multiple-sensor body monitor (SenseWear Armband; BodyMedia Inc., Pittsburgh, PA, USA). Results:, Time spent in physical activity was higher in normal-weight compared with overweight children (p = 0.002). The highest level of physical activity was noted in normal-weight boys [mean (SD) = 258 (114) min/day] and the lowest in overweight girls [mean (SD) = 136 (59) min/day] (p = 0.002). In contrast, energy expended during physical activity did not differ between normal-weight and overweight children (2.6 and 2.7 MJ/day, respectively, p = 0.89). The average decrease in physical activity at weekends was 39 min in overweight children (from 166 to 127 min/day) and 27 min in their normal-weight counterparts (from 230 to 203 min/day). Conclusion:, Overweight children engaged in less physical activity of both moderate and vigorous intensity compared with their normal-weight peers. Both overweight and normal-weight children were less active at weekends than on weekdays. Initiatives aiming to increase physical activity of overweight children at weekends are warranted. [source]

    The validity of the Computer Science and Applications activity monitor for use in coronary artery disease patients during level walking

    Ulf Ekelund
    Summary The principal aim of the present study was to examine the validity of the Computer Science and Applications (CSA) activity monitor during level walking in coronary artery disease (CAD) patients. As a secondary aim, we evaluated the usefulness of two previously published energy expenditure (EE) prediction equations. Thirty-four subjects (29 men and five women), all with diagnosed CAD, volunteered to participate. Oxygen uptake (VO2) was measured by indirect calorimetry during walking on a motorized treadmill at three different speeds (3·2, 4·8 and 6·4 km h,1). Physical activity was measured simultaneously using the CSA activity monitor, secured directly to the skin on the lower back (i.e. lumbar vertebrae 4,5) with an elastic belt. The mean (±SD) activity counts were 1208 ± 429, 3258 ± 753 and 5351 ± 876 counts min,1, at the three speeds, respectively (P<0·001). Activity counts were significantly correlated to speed (r=0·92; P<0·001), VO2 (ml kg,1 min,1; r=0·87; P<0·001) and EE (kcal min,1; r=0·85, P<0·001). A stepwise linear regression analysis showed that activity counts and body weight together explained 75% of the variation in EE. Predicted EE from previously published equations differed significantly when used in this group of CAD patients. In conclusion, the CSA activity monitor is a valid instrument for assessing the intensity of physical activity during treadmill walking in CAD patients. Energy expenditure can be predicted from body weight and activity counts. [source]

    Hypocretin/orexin and energy expenditure

    ACTA PHYSIOLOGICA, Issue 3 2010
    J. A. Teske
    Abstract The hypocretins or orexins are endogenous neuropeptides synthesized in discrete lateral, perifornical and dorsal hypothalamic neurones. These multi-functional neuropeptides modulate energy homeostasis, arousal, stress, reward, reproduction and cardiovascular function. This review summarizes the role of hypocretins in modulating non-sleep-related energy expenditure with specific focus on the augmentation of whole body energy expenditure as well as hypocretin-induced physical activity and sympathetic outflow. We compare the efficacy of hypocretin-1 and 2 on energy expenditure and evaluate whether the literature implicates hypocretin signalling though the hypocretin-1 and -2 receptor as having shared and or functionally specific physiological effects. Thus far data suggest that hypocretin-1 has a more robust stimulatory effect relative to hypocretin-2. Furthermore, hypocretin-1 receptor predominantly mediates behaviours known to influence energy expenditure. Further studies on the hypocretin-2 receptor are needed. [source]

    Forearm and leg amino acid metabolism in the basal state and during combined insulin and amino acid stimulation after a 3-day fast

    ACTA PHYSIOLOGICA, Issue 3 2009
    J. Gjedsted
    Abstract Aim:, Fasting is characterized by a progressive loss of protein, but data on protein kinetics are unclear and few have studied the effects of re-feeding. The present study was designed to test the hypothesis that a combined infusion of insulin and amino acids after fasting would induce compensatory increases in protein synthesis and reductions in protein breakdown at the whole body level and in muscle. Methods:, We included 10 healthy male volunteers and studied them twice: (1) in the post-absorptive state and (2) after 72 h of fasting. Amino acid kinetics was measured using labelled phenylalanine and tyrosine, whole body energy expenditure was assessed and urea nitrogen synthesis rates were calculated. Results:, After fasting we observed an increase in arterial blood concentration of branched chain amino acids and a decrease in gluconeogenic amino acids (P < 0.05). Isotopically determined whole body, forearm and leg phenylalanine fluxes were unaltered apart from a 30% decrease in phenylalanine-to-tyrosine conversion (2.0 vs. 1.4 ,mol kg,1 h,1, P < 0.01). During infusion of insulin and amino acids, amino acid concentrations increased. Conclusion:, Our data indicate that after a 72-h fast basal and insulin/amino acid-stimulated regional phenylalanine fluxes in leg and forearm muscle are unaltered. During fasting concentrations of gluconeogenic amino acids decrease and hepatic and/or renal phenylalanine-to-tyrosine conversion decreases. Thus, as opposed to glucose and lipid metabolism, fasting does not induce insulin resistance as regards amino acid metabolism. [source]

    Physiological functions of glucose-inhibited neurones

    ACTA PHYSIOLOGICA, Issue 1 2009
    D. Burdakov
    Abstract Glucose-inhibited neurones are an integral part of neurocircuits regulating cognitive arousal, body weight and vital adaptive behaviours. Their firing is directly suppressed by extracellular glucose through poorly understood signalling cascades culminating in opening of post-synaptic K+ or possibly Cl, channels. In mammalian brains, two groups of glucose-inhibited neurones are best understood at present: neurones of the hypothalamic arcuate nucleus (ARC) that express peptide transmitters NPY and agouti-related peptide (AgRP) and neurones of the lateral hypothalamus (LH) that express peptide transmitters orexins/hypocretins. The activity of ARC NPY/AgRP neurones promotes food intake and suppresses energy expenditure, and their destruction causes a severe reduction in food intake and body weight. The physiological actions of ARC NPY/AgRP cells are mediated by projections to numerous hypothalamic areas, as well as extrahypothalamic sites such as the thalamus and ventral tegmental area. Orexin/hypocretin neurones of the LH are critical for normal wakefulness, energy expenditure and reward-seeking, and their destruction causes narcolepsy. Orexin actions are mediated by highly widespread central projections to virtually all brain areas except the cerebellum, including monosynaptic innervation of the cerebral cortex and autonomic pre-ganglionic neurones. There, orexins act on two specific G-protein-coupled receptors generally linked to neuronal excitation. In addition to sensing physiological changes in sugar levels, the firing of both NPY/AgRP and orexin neurones is inhibited by the ,satiety' hormone leptin and stimulated by the ,hunger' hormone ghrelin. Glucose-inhibited neurones are thus well placed to coordinate diverse brain states and behaviours based on energy levels. [source]

    Lithium and KB-R7943 effects on mechanics and energetics of rat heart muscle

    ACTA PHYSIOLOGICA, Issue 1 2002
    P. Bonazzola
    ABSTRACT The role of calcium influx on energy expenditure during cardiac contraction was studied. For this purpose, the described ability of lithium and KB-R 7943 (KBR) to diminish Ca entry through Na,Ca exchanger (Ponce-Hornos & Langer, J Mol Cell Cardiol 1980, 12, 1367, Satoh et al., Circulation 2000, 101, 1441) were used. In isolated contractions (contractions elicited after at least 5 min of rest) LiCl 45 mmol L,1 decreased pressure developed and pressure,time integral from 42.3 ± 2.7 and 14.5 ± 1.2 to 32.1 ± 3.4 mN mm,2 and 8.3 ± 0.9 mN mm,2 s, respectively. A similar effect was observed in regular contractions (at 0.16 Hz stimulation). The presence of KBR (5 ,mol L,1) in the perfusate induced a slight but not significant decrease in pressure developed and pressure,time integral in steady-state contractions. As it was previously described, the heat involved in a heart muscle contraction can be decomposed into several components (H1, H2, H3 and H4), but only one (H3) was associated with force generation. While H3 decreased with lithium in both types of contractions, H3/PtI ratio remained unaltered, indicating that the economy for pressure maintenance was unaffected. To further investigate the role of Ca entry on force development, a condition in which the contraction is mainly dependent on extracellular calcium was studied. An ,extra' stimulus applied 200 ms after the regular one in a muscle stimulated at 0.16 Hz induces a contraction with this characteristic (Marengo et al., Am J Physiol 1999, 276, H309). Lithium induced a strong decrease in pressure,time integral and H3 associated with this contraction (43 and 45%, respectively) with no change in H3/PtI ratio. Lithium also reduced (53%) an energy component (H2) associated with Ca cycling. The use of KBR showed qualitatively similar results [i.e. a 33% reduction in pressure,time integral associated with the extrasystole (ES) with no changes in H3/PtI ratio and a 30% reduction in the H2 component]. Li and KBR effects appear to be additive and in the presence of 45 mmol L,1 Li and 5 ,mol L,1 KBR the extrasystole was abolished in 77%. Lithium and KBR effects particularly for the extrasystole can be explained through the inhibition of Ca entry via Na,Ca exchange giving support to the participation of the Na,Ca exchanger in the Ca influx from the extracellular space. In addition, the results also suggest the possibility of an effect of Li on an additional Ca sensitive locus (different than the Na,Ca exchanger). In this connection, in isolated contractions lithium decreased the energy release fraction related to mitochondrial processes (H4) increasing the economy of the overall cardiac contraction. [source]

    Low-fat oxidation may be a factor in obesity among men with schizophrenia

    J.-K. Sharpe
    Objective:, Obesity associated with atypical antipsychotic medications is an important clinical issue for people with schizophrenia. The purpose of this project was to determine whether there were any differences in resting energy expenditure (REE) and respiratory quotient (RQ) between men with schizophrenia and controls. Method:, Thirty-one men with schizophrenia were individually matched for age and relative body weight with healthy, sedentary controls. Deuterium dilution was used to determine total body water and subsequently fat-free mass (FFM). Indirect calorimetry using a Deltatrac metabolic cart was used to determine REE and RQ. Results:, When corrected for FFM, there was no significant difference in REE between the groups. However, fasting RQ was significantly higher in the men with schizophrenia than the controls. Conclusion:, Men with schizophrenia oxidised proportionally less fat and more carbohydrate under resting conditions than healthy controls. These differences in substrate utilisation at rest may be an important consideration in obesity in this clinical group. [source]

    Neurophysiology of hunger and satiety

    Pauline M. Smith
    Abstract Hunger is defined as a strong desire or need for food while satiety is the condition of being full or gratified. The maintenance of energy homeostasis requires a balance between energy intake and energy expenditure. The regulation of food intake is a complex behavior. It requires discrete nuclei within the central nervous system (CNS) to detect signals from the periphery regarding metabolic status, process and integrate this information in a coordinated manner and to provide appropriate responses to ensure that the individual does not enter a state of positive or negative energy balance. This review of hunger and satiety will examine the CNS circuitries involved in the control of energy homeostasis as well as signals from the periphery, both hormonal and neural, that convey pertinent information regarding short-term and long-term energy status of the individual. © 2008 Wiley-Liss, Inc. Dev Disabil Res Rev 2008;14:96,104. [source]

    Thiazolidinediones and the preservation of ,-cell function, cellular proliferation and apoptosis

    Michael Decker
    The thiazolidinediones (TZDs) or glitazones are pharmaceutical agents that have profound effects on energy expenditure and conservation. They also exert significant anti-inflammatory effects and influence cell proliferation and cell death. The drugs are primarily used in clinical practice in the treatment of patients with type 2 diabetes mellitus, a disorder of insulin resistance that occurs when the pancreatic ,-cells are unable to produce adequate amounts of insulin to maintain euglycaemia. Loss of pancreatic ,-cell function in type 2 diabetes is progressive and often precedes overt diabetes by 10 years or more, as was shown by the United Kingdom Prospective Diabetes Study. Any therapeutic or preventive approach that would limit or reverse loss of ,-cell function in diabetes would have profound effects on the morbidity associated with this widespread disease. Evidence suggesting a potential role of TZDs in preserving ,-cell function in type 2 diabetes as well as the ability of these agents to exert anti-inflammatory and proapoptotic anticancer effects, and their ability to promote cellular proliferation in various organs is reviewed. [source]

    Subnormal energy expenditure: a putative causal factor in the weight gain induced by treatment of hyperthyroidism

    R. Jacobsen
    Aims:, To examine the causes of weight gain occurring as an adverse effect of treatment of hyperthyroidism. Methods:, We measured 24-h energy expenditure (EE), body composition and spontaneous physical activity (SPA) in eight patients before and 1 year after treatment of hyperthyroidism was initiated, and eight controls. Results:, One year after initiation of treatment thyrotropin was normalized, thyroid hormones had fallen to the lower end of the reference range and fat mass had increased by 3.5 kg (p < 0.001). Twenty-four hour EE adjusted for fat-free mass (FFM) was 15% higher in hyperthyroid patients before treatment than in controls (p = 0.003), and treatment decreased 24-h EE by 1.9 MJ/day (p = 0.001). After treatment, 24-h EE, adjusted for FFM, was similar to the controls. Multiple regression analyses showed that the suppressed EE could partly be attributed to an iatrogenic suppression of thyroid hormones, resulting in lower sleeping EE. Twenty-four hour SPA was normal in the hyperthyroid state, but decreased after treatment by 21% (p = 0.045), to a level not significantly different, but still below that of the controls. Conclusions:, The study suggests that weight gain during treatment of hyperthyroidism might be due to subnormal levels of EE and SPA caused by a suppression of the thyroid hormone to a level in the lower end of the normal range. [source]

    Self glucose monitoring and physical exercise in diabetes

    G. Pugliese
    Abstract Cardiorespiratory fitness, which is determined mainly by the level of physical activity, is inversely related to mortality in the general population as well as in subjects with diabetes, the incidence of which is also increased by low exercise capacity. Exercise is capable of promoting glucose utilization in normal subjects as well as in insulin-deficient or insulin-resistant diabetic individuals. In diabetic subjects treated with insulin or insulin secretagogues, exercise may also result in complications, with too much insulin causing hypoglycaemia and not enough insulin leading to hyperglycaemia and possibly ketoacidosis; both complications may also occur several hours after exercise. Therefore, self-monitoring of blood glucose before, during (for exercise duration of more than 1 h) and after physical exercise is highly recommended, and also carbohydrate supplementation may be required. In the Italian Diabetes Exercise Study (IDES), measurement of blood glucose and systolic and diastolic blood pressure levels before and after supervised sessions of combined (aerobic + resistance) exercise in type 2 diabetic subjects with the metabolic syndrome showed significant reductions of these parameters, though no major hypoglycaemic or hypotensive episode was detected. The extent of reduction of blood glucose was related to baseline values but not to energy expenditure and was higher in subjects treated with insulin than in those on diet or oral hypoglycaemic agents (OHA). Thus, supervised exercise training associated with blood glucose monitoring is an effective and safe intervention to decrease blood glucose levels in type 2 diabetic subjects. Copyright © 2009 John Wiley & Sons, Ltd. [source]

    Nutrition in patients with Type 2 diabetes: are low-carbohydrate diets effective, safe or desirable?

    DIABETIC MEDICINE, Issue 7 2005
    R. L. Kennedy
    Abstract Low-carbohydrate diets have been around for over 100 years. They have become very popular recently but the scientific basis for their use remains to be fully established. This article reviews the recent trials that have been published and also what is known about the effects of low-carbohydrate, high-protein diets on energy expenditure and body composition. Although many controversies remain, there is now mounting evidence that these diets can lead to effective weight loss and may thus be a useful intervention for patients who have, or are at risk of, diabetes. The practical aspects of using these diets as a short- to medium-term intervention are discussed. [source]

    Neuropeptides and appetite control

    DIABETIC MEDICINE, Issue 8 2002
    J. P. H. Wilding
    Abstract Obesity is important in the aetiology of type 2 diabetes, and presents a major barrier to its successful prevention and management. Obesity develops when energy intake exceeds energy expenditure over time. A complex system has evolved to maintain energy homeostasis, but this is biased towards weight gain. Meal size is controlled by a series of short-term hormonal and neural signals that derive from the gastrointestinal tract, such as cholecystokinin whereas others may initiate meals, such as the recently discovered hormone, ghrelin. Other hormones such as insulin and leptin, together with circulating nutrients, indicate long-term energy stores. All these signals act at several central nervous system (CNS) sites but the pathways converge on the hypothalamus, which contains a large number of peptide and other neurotransmitters that influence food intake. As energy deficit is most likely to compromise survival, it is not surprising that the most powerful of these pathways are those that increase food intake and decrease energy expenditure when stores are depleted. When energy stores are low, production of leptin from adipose tissue, and thus circulating leptin concentrations fall, leading to increased production of hypothalamic neurotransmitters that strongly increase food intake, such as neuropeptide Y (NPY), galanin and agouti-related protein (AGRP) and decreased levels of ,-melanocyte-stimulating hormone (,-MSH), cocaine and amphetamine-regulated transcript (CART) and neurotensin that reduce food intake and increase energy expenditure. The finding that mutations in leptin and POMC lead to severe early onset obesity in bumans has highlighted the importance of these peptides in humans. This new understanding may eventually lead to new treatments for obesity that will be of particular benefit in the prevention and treatment of type 2 diabetes. Diabet. Med. 19, 619,627 (2002) [source]

    Stearoyl-CoA desaturase: a new therapeutic target of liver steatosis

    Pawel Dobrzyn
    Abstract Stearoyl-CoA desaturase (SCD) is the rate limiting enzyme catalyzing the biosynthesis of monounsaturated fatty acids, mainly oleate and palmitoleoate, which are used as substrates for the synthesis of triglycerides, wax esters, cholesterol esters, and phospholipids. Recent studies have shown that SCD1, the main SCD isoform expressed in liver, is a key player in the regulation of lipid metabolism. SCD1 deficient mice have increased energy expenditure, reduced body adiposity, increased insulin sensitivity and are resistant to diet-induced obesity and liver steatosis. SCD1 was found to be specifically repressed during leptin-mediated weight loss and leptin-deficient ob/ob mice lacking SCD1 showed markedly reduced adiposity, despite higher food intake. In addition, SCD1 deficiency completely corrects the hypometabolic phenotype and hepatic steatosis of ob/ob mice, and attenuates fasting-induced liver steatosis in peroxisome proliferator-activated receptor-, , deficient mice. Consequently, increased SCD activity has been found in humans and animals which accumulate significant amounts of lipids in liver, whereas SCD1 deficiency ameliorates both high-fat diet induced and genetically induced hepatic steatosis. Much evidence indicates that the direct anti-steatotic effect of SCD1 deficiency stems from increased fatty acid oxidation and reduced lipid synthesis. In this review we discuss our current understanding of the role of SCD1 in regulation of hepatic lipid partitioning and test the hypothesis that pharmacological manipulation of SCD might be of benefit in the treatment of non-alcoholic fatty liver disease. Drug Dev. Res. 67:643,650, 2006. © 2006 Wiley-Liss, Inc. [source]

    Targeting of the central histaminergic system for treatment of obesity and associated metabolic disorders

    Kjell Malmlöf
    Abstract There is currently a need for effective pharmacological therapies for treatment of obesity. In this communication, the involvement of the neurotransmitter histamine in the regulation of food intake is reviewed, together with results obtained in animals with pharmacologically increased brain histamine levels. A survey of the literature reveals that histaminergic circuits, arising from nerve cell bodies in the tuberomammillary nucleus and projecting into the paraventricular nucleus, the arcuate nucleus, and the ventromedial hypothalamus, are strongly involved in regulation of food intake and possibly also energy expenditure. Current literature also suggests the histaminergic circuits connect to other neuronal pathways involved in the regulation of energy balance and body weight. Studies performed in rodents demonstrate that H3 receptor antagonists increase hypothalamic histamine and decrease food intake, which result in decreased body weight. Lipid oxidation is increased and, at higher doses, body fat is also decreased. These changes are associated with lower circulating levels of insulin during an oral glucose challenge suggesting an increase in insulin sensitivity. The effects on food intake have also been confirmed in pigs and rhesus monkeys. It can thus be concluded that results obtained with H3 antagonist in animals warrant future clinical studies to evaluate whether this principle is effective in the treatment of human obesity. Drug Dev. Res. 67:651,665, 2006. © 2006 Wiley-Liss, Inc. [source]

    The impact of prolonged fasting during aestivation on the structure of the small intestine in the green-striped burrowing frog, Cyclorana alboguttata

    ACTA ZOOLOGICA, Issue 1 2005
    Rebecca L. Cramp
    Abstract The effects of short-term fasting and prolonged fasting during aestivation on the morphology of the proximal small intestine and associated organs were investigated in the green-striped burrowing frog, Cyclorana alboguttata (Anura: Hylidae). Animals were fasted for 1 week while active or for 3,9 months during aestivation. Short-duration fasting (1 week) had little effect on the morphology of the small intestine, whilst prolonged fasting during aestivation induced marked enteropathy including reductions in intestinal mass, length and diameter, longitudinal fold height and tunica muscularis thickness. Enterocyte morphology was also affected markedly by prolonged fasting: enterocyte cross-sectional area and microvillous height were reduced during aestivation, intercellular spaces were visibly reduced and the prevalence of lymphocytes amongst enterocytes was increased. Mitochondria and nuclei were also affected by 9 months of aestivation with major disruptions to mitochondrial cristae and increased clumping of nuclear material and increased infolding of the nuclear envelope. The present study demonstrates that the intestine of an aestivating frog responds to prolonged food deprivation during aestivation by reducing in size, presumably to reduce the energy expenditure of the organ. [source]

    Flow energy and channel adjustments in rills developed in loamy sand and sandy loam soils

    Jovan R. Stefanovic
    Abstract The storms usually associated with rill development in nature are seldom prolonged, so development is often interrupted by interstorm disturbances, e.g. weathering or tillage. In laboratory simulated rainfall experiments, active rill development can be prolonged, and under these conditions typically passes through a period of intense incision, channel extension and bifurcation before reaching quasi-stable conditions in which little form change occurs. This paper presents laboratory experiments with coarse textured soils under simulated rainfall which show how channel adjustment processes contribute to the evolution of quasi-stability. Newly incised rills were stabilized for detailed study of links between rill configuration and flow energy. On a loamy sand, adjustment towards equilibrium occurred due to channel widening and meandering, whereas on a sandy loam, mobile knickpoints and chutes, pulsations in flow width and flow depth and changes in stream power and sediment discharge occurred as the channel adjusted towards equilibrium. The tendency of rill systems towards quasi-stability is shown by changes in stream power values which show short-lived minima. Differences in energy dissipation in stabilized rills indicate that minimization of energy dissipation was reached locally between knickpoints and at the downstream ends of rills. In the absence of energy gradients in knickpoints and chutes, stabilized rill sections tended toward equilibrium by establishing uniform energy expenditure. The study confirmed that energy dissipation increased with flow aspect ratio. In stabilized rills, flow acceleration reduced energy dissipation on the loamy sand but not on the sandy loam. On both soils flow deceleration tended to increase energy dissipation. Understanding how rill systems evolve towards stability is essential in order to predict how interruptions between storms may affect long-term rill dynamics. This is essential if event-based physical models are to become effective in predicting sediment transport on rilled hillslopes under changing weather and climatic conditions. Copyright © 2008 John Wiley and Sons, Ltd. [source]

    Minimizing energy expenditure facilitates vertebrate persistence on oceanic islands

    ECOLOGY LETTERS, Issue 5 2002
    Brian K. McNab
    Abstract The characteristics of terrestrial vertebrates on oceanic islands are examined. They often include a reduced body size, a tolerance of conspecifics, flightlessness, a reduced basal rate of metabolism, and a propensity to enter torpor. On oceanic islands ectotherms frequently replace endotherms. These changes reduce the energy expenditure and resource requirements of vertebrates. Such reductions are permitted by the absence of mammalian predators and facilitate the survival of island endemics in the face of a restricted resource base and a variable environment through an increase in population size. Some insular species increase body size, but this occurs only when the resource base is large, due either to a fortuitously abundant resource, or to the absence of other species that exploit normally abundant resources. Some questions are posed to guide future work. They examine of the characteristics that permit species to disperse over water barriers, the conditions that require a reduction in resource use, the rapidity of response by immigrants to island conditions, whether supertramps show physiological differentiation with respect to island distance or size, and whether island size is absolute or relative to the size of the immigrants. [source]

    Maternal Effort is State Dependent: Energetic Limitation or Regulation?

    ETHOLOGY, Issue 4 2008
    Anke Rehling
    Many small altricial rodents have a postpartum oestrus and are often simultaneously pregnant and lactating. Negative influences of concurrent pregnancy and lactation on both lactational performance and the litter in utero are commonly observed and have been interpreted as resulting from high simultaneous energetic demands of gestation and lactation. We studied these effects in the precocial guinea-pig (Cavia aperea f. porcellus) that, like many altricial rodents, has a postpartum oestrus, but in which the peaks of energy expenditure on lactation and gestation are widely separated. This life history allowed to investigate whether physiological regulation other than by energetic limitations may be responsible for allocation conflicts arising when lactation and gestation overlap. By comparing simultaneously pregnant and lactating females with lactating non-pregnant females, we show that females in the former group nurse less and wean earlier than females of the latter group. In a comparison of litter size, litter mass, and pup mortality of females that had not been lactating during pregnancy with females that had been simultaneously pregnant and lactating, we show that the latter do not reduce investment in the following litter. In our study, energetic constraints on ad libitum fed females are unlikely and we therefore suggest that the results must be explained by regulatory constraints on lactational effort. We point out that this explanation has not been excluded for the effects observed in altricial small mammals. [source]

    Growth hormone and changes in energy balance in growth hormone deficient adults

    D. Deepak
    ABSTRACT Background, Adults with growth hormone deficiency (AGHD) have an adverse body composition with an increased prevalence of obesity. It is not known whether growth hormone replacement (GHR) results in alterations in energy intake (EI) and/or energy expenditure (EE). The aim of the study was to investigate the effects of GHR on EI and EE. Materials and methods, Nineteen hypopituitary adults (14 males, 5 females, mean age 46·2 years) with severe GHD (peak GH response to glucagon , 9 mU L,1) were studied. All patients self-injected recombinant human GH starting with 0·3 mg s.c. daily. The following were measured before and following 6 months of stable maintenance of GHR: food intake during a test meal, appetite ratings, resting EE (indirect calorimetry) and voluntary physical activity (accelerometry). Results, GHR nearly doubled voluntary physical activity (mean activity units 3319 vs. 1881, P = 0·007) and improved quality of life score (mean score 9·1 vs. 16·5, P < 0·0001). Subjects reported higher fasting hunger ratings (mean 64·8 vs. 49·6, P = 0·02) but ad libitum energy intake remained unchanged. Eating behavioural traits were favourably altered with lower disinhibition (mean 6·0 vs. 7·2, P = 0·02) and lower susceptibility to hunger ratings (4·6 vs. 6·8, P = 0·001) after GHR. Additionally, GHR did not result in significant changes in resting EE, body weight and body mass index. Conclusions, GHR in AGHD significantly improves voluntary physical activity and quality of life. Following GHR, subjects experience greater ,state' (physiological) hunger, reductions in eating disinhibition and hunger susceptibility, but no effects on calorie intake or macronutrient choice were detected. [source]

    Developmental programming of obesity in mammals

    P. D. Taylor
    Converging lines of evidence from epidemiological studies and animal models now indicate that the origins of obesity and related metabolic disorders lie not only in the interaction between genes and traditional adult risk factors, such as unbalanced diet and physical inactivity, but also in the interplay between genes and the embryonic, fetal and early postnatal environment. Whilst studies in man initially focused on the relationship between low birth weight and risk of adult obesity and metabolic syndrome, evidence is also growing to suggest that increased birth weight and/or adiposity at birth can also lead to increased risk for childhood and adult obesity. Hence, there appears to be increased risk of obesity at both ends of the birth weight spectrum. Animal models, including both under- and overnutrition in pregnancy and lactation lend increasing support to the developmental origins of obesity. This review focuses upon the influence of the maternal nutritional and hormonal environment in pregnancy in permanently programming appetite and energy expenditure and the hormonal, neuronal and autocrine mechanisms that contribute to the maintenance of energy balance in the offspring. We discuss the potential maternal programming ,vectors' and the molecular mechanisms that may lead to persistent pathophysiological changes resulting in subsequent disease. The perinatal environment, which appears to programme subsequent obesity, provides a potential therapeutic target, and work in this field will readily translate into improved interventional strategies to stem the growing epidemic of obesity, a disease which, once manifest, has proven particularly resistant to treatment. [source]

    Is water temperature an adequate predictor of recruitment success in cyprinid fish populations in lowland rivers?

    FRESHWATER BIOLOGY, Issue 4 2003
    A. D. Nunn
    SUMMARY 1. Higher than average ambient water temperature in the first year of life may be responsible for strong cohorts of adult cyprinid fish. Whilst temperature explains much of the variation in year-class strength (YCS), however, it is not the only influential factor as high temperature does not inevitably yield strong year-classes. Furthermore, years in which a strong year-class is prevalent in one species do not necessarily result in strong year-classes in other coexisting species, suggesting other biotic and abiotic factors are important in regulating recruitment success. 2. The relationships between water temperature, river discharge, the position of the Gulf Stream, 0-group fish growth and recruitment success (YCS) were examined in three cyprinid fish species in an English lowland river, using a 15-year data set. 3. Mean length of 0-group fish at the end of the summer was positively correlated with water temperature (cumulative degree-days >12 °C) and negatively correlated with river discharge (cumulative discharge-days above basal discharge rate). Water temperature was negatively correlated with river discharge. 4. YCS was positively correlated with mean 0-group fish length at the end of the summer and with the position of the North Wall of the Gulf Stream. 5. 'Critical periods' (i.e. periods in the first summer of life when fish may be more susceptible to increases in river discharge) were difficult to discern because of interannual variations in river discharge relative to the timing of fish hatching. YCS of roach and chub was most strongly correlated with discharge in the period from June to September inclusive, while YCS of dace was most significantly correlated with discharge in August. 6. River discharge (rather than water temperature) may be the key factor in determining YCS, either directly (through discharge-induced mortality) or indirectly (via reduced growth at lower water temperatures, discharge-associated increases in energy expenditure or reduced food availability). It could be that, in effect, water temperature determines potential YCS while discharge determines realised YCS. [source]

    Intraspecific variation in avian pectoral muscle mass: constraints on maintaining manoeuvrability with increasing body mass

    FUNCTIONAL ECOLOGY, Issue 2 2007
    Summary 1Within a single year, long-distance migrants undergo a minimum of four cycles of fuel storage and depletion because their migrations have at least one stopover. Each cycle includes an almost twofold change in body mass (mb). Pervasive predation threats beg the question whether escape flight abilities keep up with such large changes in mb. 2We derive aerodynamic predictions how pectoral muscle mass (mpm) should change with mb to maintain constant relative flight power. 3We tested these predictions with data on red knot Calidris canutus, a long-distance migrating wader that breeds in arctic tundra and winters in temperate and tropical coastal areas. We focused on the subspecies C. c. islandica. 4mpm varied with mb in a piecewise manner. In islandica knots with mb , 148 g, the slope (1·06) was indistinguishable from the prediction (1·25). In heavy knots (mb > 148 g) the slope was significantly lower (0·63), yielding a mpm 0·81 times lower than predicted at pre-departure weights (210 g). 5Manoeuvrability tests showed that above 160 g, knots were increasingly unable to make a 90° angle turn. This is consistent with mpm being increasingly smaller than predicted. 6Relatively low mpm enables savings on mass and hence flight costs, and savings on overall energy expenditure. We predict that reduced escape flight ability at high mb will be compensated by behavioural strategies to minimize predation risk. [source]

    Measuring metabolic rate in the field: the pros and cons of the doubly labelled water and heart rate methods

    FUNCTIONAL ECOLOGY, Issue 2 2004
    P. J. Butler
    Summary 1Measuring the metabolic rate of animals in the field (FMR) is central to the work of ecologists in many disciplines. In this article we discuss the pros and cons of the two most commonly used methods for measuring FMR. 2Both methods are constantly under development, but at the present time can only accurately be used to estimate the mean rate of energy expenditure of groups of animals. The doubly labelled water method (DLW) uses stable isotopes of hydrogen and oxygen to trace the flow of water and carbon dioxide through the body over time. From these data, it is possible to derive a single estimate of the rate of oxygen consumption () for the duration of the experiment. The duration of the experiment will depend on the rate of flow of isotopes of oxygen and hydrogen through the body, which in turn depends on the animal's size, ranging from 24 h for small vertebrates to up to 28 days in Humans. 3This technique has been used widely, partly as a result of its relative simplicity and potential low cost, though there is some uncertainty over the determination of the standard error of the estimate of mean . 4The heart rate (fH) method depends on the physiological relationship between heart rate and . 5If these two quantities are calibrated against each other under controlled conditions, fH can then be measured in free-ranging animals and used to estimate . 6The latest generation of small implantable data loggers means that it is possible to measure fH for over a year on a very fine temporal scale, though the current size of the data loggers limits the size of experimental animals to around 1 kg. However, externally mounted radio-transmitters are now sufficiently small to be used with animals of less than 40 g body mass. This technique is gaining in popularity owing to its high accuracy and versatility, though the logistic constraint of performing calibrations can make its use a relatively extended process. [source]

    Geographical variation in the size of body organs in seabirds

    FUNCTIONAL ECOLOGY, Issue 3 2000
    G. M. Hilton
    Abstract 1.,The size of body organs shows adaptive temporal variation in many animal species. The variation in the size of body organs was examined to see if it is also a component of local adaptation to geographical variation in ecological conditions. 2.,Major body organs were measured in five species of Icelandic seabirds, sampled from two areas where birds experience slightly different ecological conditions. Between-area differences in ecological conditions were consistent among the study species, allowing tests of the generality of ecological effects on organ size. 3.,All major body organs showed geographical size variation. Livers and kidneys were larger in locations where daily energy expenditure was expected to be higher; small intestines were heavier where food was of lower energy density; stomachs were heavier where food was less digestible; heart and flight muscle were larger where flight costs were greater. 4.,It is concluded that adaptive variation in organ size may be an important means by which animals optimize exploitation of their local environment, and may be a proximate factor in intraspecific life-history and metabolic variations between geographically separate populations. [source]

    Obesity and metabolic syndrome in histone demethylase JHDM2a-deficient mice

    GENES TO CELLS, Issue 8 2009
    Takeshi Inagaki
    Histone H3 lysine 9 (H3K9) methylation is a crucial epigenetic mark of heterochromatin formation and transcriptional silencing. Recent studies demonstrated that most covalent histone lysine modifications are reversible and the jumonji C (JmjC)-domain-containing proteins have been shown to possess such demethylase activities. However, there is little information available on the biological roles of histone lysine demethylation in intact animal model systems. JHDM2A (JmjC-domain-containing histone demethylase 2A, also known as JMJD1A) catalyses removal of H3K9 mono- and dimethylation through iron and ,-ketoglutarate dependent oxidative reactions. Here, we demonstrate that JHDM2a also regulates metabolic genes related to energy homeostasis including anti-adipogenesis, regulation of fat storage, glucose transport and type 2 diabetes. Mice deficient in JHDM2a (JHDM2a,/,) develop adult onset obesity, hypertriglyceridemia, hypercholesterolemia, hyperinsulinemia and hyperleptinemia, which are hallmarks of metabolic syndrome. JHDM2a,/, mice furthermore exhibit fasted induced hypothermia indicating reduced energy expenditure and also have a higher respiratory quotient indicating less fat utilization for energy production. These observations may explain the obesity phenotype in these mice. Thus, H3K9 demethylase JHDM2a is a crucial regulator of genes involved in energy expenditure and fat storage, which suggests it is a previously unrecognized key regulator of obesity and metabolic syndrome. [source]