Ciclagem da massa corporal em camundongos

A obesidade está associada com a inflamação crônica atribuída à liberação de citocinas e adipocinas, à homeostase desregulda da glicemia e à dislipidemia. Intervenções nutricionais são frequentemente acompanhadas por episódios repetidos de perda e recuperação do peso, fenômeno conhecido como efeito sanfona ou ciclagem da massa corporal. Foram avaliados os efeitos da ciclagem da massa corporal sobre os parâmetros: eficiência alimentar, massa corporal (MC), perfil lipídico, metabolismo de carboidratos, indíce de adiposidade corporal, marcadores inflamatórios, esteatose hepática e triglicerídeo (TG) hepático em camundongos C57BL/6 machos que ciclaram a massa corporal duas ou três vezes consecutivas pela alternância de dieta hiperlipídica (high-fat, HF) e dieta padrão (standard-chow,SC). Após cada ciclo de dieta HF, os animais ficavam cada vez mais pesados e, após cada ciclo de dieta SC, os animais perdiam cada vez menos peso. A ciclagem da massa corporal provocou flutuação nas reservas de gordura e nos lipídeos sanguíneos. O colesterol total dos animais, após mudança da dieta HF para dieta SC, apresentou redução dos seus valores, assim como os TG plasmáticos. No teste oral de tolerância à glicose, após o perído de ingestão da dieta HF, os animais apresentaram intolerância à glicose e, após a troca para dieta SC, os animais continuaram com intolerância à glicose. Em relação as adipocinas e citocinas, a leptina, resistina e o fator de necrose tumoral (TNF) alfa séricos aumentaram após o ciclo da dieta HF e diminuíram após a troca por dieta SC. Ao contrário, a adiponectina sérica diminuiu após dieta HF e aumentou após troca por dieta SC. A IL-6 aumentou após ingestão da dieta HF, porém após a troca para dieta SC, a IL-6 permaneceu elevada. Enquanto o MCP-1 não variou durante as trocas de dietas. A expressão da adiponectina no tecido adiposo diminuiu após a dieta HF e os valores permaneceram reduzidos mesmo após a troca para dieta SC. As expressões da leptina e IL-6 no tecido adiposo aumentaram após dieta HF e continuaram aumentados mesmo após a troca para dieta SC. Da mesma forma, a esteatose hepática e os TG hepáticos não reduziram após a mudança da dieta HF para dieta SC. Tanto a dieta HF, como a ciclagem da massa corporal são relevantes para o remodelamento do tecido adiposo e provoca repercussões nos lipídios séricos, na homeostase da glicose, na secreção de adipocinas e provoca acúmulo de gordura no fígado. A troca para dieta SC e redução da MC não são capazes de normalizar a secreção de adipocinas no tecido adiposo e nem das citocinas pró-inflamatórias que permaneceram aumentadas. A esteatose hepática e os TG hepáticos também não são recuperados com a troca para dieta SC e redução da massa corporal. Estes resultados indicam que a ciclagem da MC cria um ambiente inflamatório, que é agraado com adipocinas alteradas, intolerância à glicose e acúmulo de gordura no fígado

Association entre la dépression et les comportements reliés aux habitudes de vie et aux soins du diabète dans la population diabétique du Québec

Les personnes atteintes de diabète sont plus à risque de développer la dépression, un fardeau additionnel dans leurs activités quotidiennes. Notre étude auprès d’adultes diabétiques résidant au Québec vise à en déterminer les caractéristiques lorsque la dépression fait partie du tableau clinique. Hypothèse 1: Les adultes québécois atteints de diabète et de dépression (dépression majeure et mineure) seront plus prédisposés à avoir des indicateurs reliés aux habitudes de vie, aux soins du diabète et à l’efficacité personnelle vis-à-vis du contrôle du poids et de la quantité d’aliments consommés, moins favorables que les sujets diabétiques sans dépression. Hypothèse 2: Chez les Québécois atteints de diabète de type 2, l’association entre la dépression et l’obésité sera affectée par les indicateurs de la Variation Cyclique du Poids (VCP) et de l’efficacité personnelle. Hypothèse 3: Chez les Québécois atteints de diabète de type 2, ceux qui auront développé ou maintenu une dépression au cours de 12 mois, seront plus susceptibles de détériorer les indicateurs reliés à leurs habitudes de vie et à leur efficacité personnelle. Des personnes diabétiques au Québec ont été recrutées à l’aide d’un sondage téléphonique. Des adultes, hommes et femmes, âgés de 18 à 80 ans étaient éligibles à participer. La dépression était déterminée par le questionnaire PHQ-9 « Patient Health Questionnaire-9 ». Au total, 3 221 individus ont été contactés au départ de l’étude; 2 003 ont participé à l’étude (93% type 2)et 1 234 ont participé au suivi de 12 mois. La prévalence de dépression mineure et majeure était de 10,9% et 8,7%, respectivement. Cinquante-trois pourcent des sujets avec dépression majeure avaient deux ou trois indicateurs malsains (tabagisme, inactivité ou obésité), 33% des sujets avaient une dépression mineure et 21% des sujets étaient non déprimés. Les résultats des analyses de régression logistique ont révélé que les sujets dépressifs étaient plus susceptibles d’être de sexe féminin, moins instruits, non mariés,sédentaires, fumeurs, percevaient plus souvent avoir une faible maîtrise du contrôle de la quantité d’aliments ingérés et tendaient davantage à mesurer leur glycémie au moins une fois par jour (p<0,05). Chez les patients avec le diabète de type 2, l’association entre la dépression et l’obésité a été affectée par les variables de la VCP et d’efficacité personnelle. Une année après le début de l’étude, 11,5% des sujets ont développé une dépression et 10% ont maintenu leur état dépressif. Les sujets ayant développé une dépression ou persisté dans leur état de dépression étaient plus susceptibles d’avoir été inactifs au début de l’étude ou d’être restés inactifs au suivi de 12 mois, et d’avoir maintenu une perception d’un faible contrôle de leur poids corporel et de la quantité d’aliments ingérés. Cependant, les changements de statut de dépression n’étaient pas associés à des changements de l’indice de masse corporelle. En conclusion, l’inactivité physique et une faible efficacité personnelle sont des facteurs importants dans le développement et la persistance de la dépression chez les patients diabétiques et méritent d’être considérés dans le traitement.

A role for skeletal muscle stearoyl-CoA desaturase 1 in control of thermogenesis

An enhanced metabolic efficiency for accelerating the recovery of fat mass (or catch-up fat) is a characteristic feature of body weight regulation after weight loss or growth retardation and is the outcome of an "adipose-specific" suppression of thermogenesis, i.e., a feedback control system in which signals from the depleted adipose tissue fat stores exert a suppressive effect on thermogenesis. Using a previously described rat model of semistarvation-refeeding in which catch-up fat results from suppressed thermogenesis per se, we report here that the gene expression of stearoyl-coenzyme A desaturase 1 (SCD1) is elevated in skeletal muscle after 2 wk of semistarvation and remains elevated in parallel to the phase of suppressed thermogenesis favoring catch-up fat during refeeding. These elevations in the SCD1 transcript are skeletal muscle specific and are associated with elevations in microsomal ^9 desaturase enzyme activity, in the ^9 desaturation index, and in the relative content of SCD1-derived monounsaturates in several lipid fractions extracted from skeletal muscle. An elevated skeletal muscle SCD1, by desaturating the products of de novo lipogenesis and diverting them away from mitochondrial oxidation, would inhibit substrate cycling between de novo lipogenesis and lipid oxidation, thereby leading to a state of suppressed thermogenesis that regulates the body’s fat stores.—Mainieri, D., Summermatter, S., Seydoux, J., Montani, J. P., Rusconi, S., Russell, A. P., Boss, O., Buchala, A. J., Dulloo, A. G. A role for skeletal muscle stearoyl-CoA desaturase 1 in control of thermogenesis.

Thrifty metabolism that favors fat storage after caloric restriction: a role for skeletal muscle phosphatidylinositol-3-kinase activity and AMP-activated protein kinase

Energy conservation directed at accelerating body fat recovery (or catch-up fat) contributes to obesity relapse after slimming and to excess fat gain during catch-up growth after malnutrition. To investigate the mechanisms underlying such thrifty metabolism for catch-up fat, we tested whether during refeeding after caloric restriction rats exhibiting catch-up fat driven by suppressed thermogenesis have diminished skeletal muscle phosphatidylinositol-3-kinase (PI3K) activity or AMP-activated protein kinase (AMPK) signaling—two pathways required for hormone-induced thermogenesis in ex vivo muscle preparations. The results show that during isocaloric refeeding with a low-fat diet, at time points when body fat, circulating free fatty acids, and intramyocellular lipids in refed animals do not exceed those of controls, muscle insulin receptor substrate 1-associated PI3K activity (basal and in vivo insulin-stimulated) is lower than that in controls. Isocaloric refeeding with a high-fat diet, which exacerbates the suppression of thermogenesis, results in further reductions in muscle PI3K activity and in impaired AMPK phosphorylation (basal and in vivo leptin-stimulated). It is proposed that reduced skeletal muscle PI3K/AMPK signaling and suppressed thermogenesis are interdependent. Defective PI3K or AMPK signaling will reduce the rate of substrate cycling between de novo lipogenesis and lipid oxidation, leading to suppressed thermogenesis, which accelerates body fat recovery and furthermore sensitizes skeletal muscle to dietary fat-induced impairments in PI3K/AMPK signaling.—Summermatter, S., Mainieri, D., Russell, A. P., Seydoux, J., Montani, J. P., Buchala, A., Solinas, G., Dulloo, A. G. Thrifty metabolism that favors fat storage after caloric restriction: a role for skeletal muscle phosphatidylinositol-3-kinase activity and AMP-activated protein kinase.

Plant secondary compounds and soil microbial processes in carbon and nitrogen cycling in relation to tree species

The aim of this study was to explore soil microbial activities related to C and N cycling and the occurrence and concentrations of two important groups of plant secondary compounds, terpenes and phenolic compounds, under silver birch (Betula pendula Roth), Norway spruce (Picea abies (L.) Karst) and Scots pine (Pinus sylvestris L.) as well as to study the effects of volatile monoterpenes and tannins on soil microbial activities. The study site, located in Kivalo, northern Finland, included ca. 70-year-old adjacent stands dominated by silver birch, Norway spruce and Scots pine. Originally the soil was very probably similar in all three stands. All forest floor layers (litter (L), fermentation layer (F) and humified layer (H)) under birch and spruce showed higher rates of CO2 production, greater net mineralisation of nitrogen and higher amounts of carbon and nitrogen in microbial biomass than did the forest floor layers under pine. Concentrations of mono-, sesqui-, di- and triterpenes were higher under both conifers than under birch, while the concentration of total water-soluble phenolic compounds as well as the concentration of condensed tannins tended to be higher or at least as high under spruce as under birch or pine. In general, differences between tree species in soil microbial activities and in concentrations of secondary compounds were smaller in the H layer than in the upper layers. The rate of CO2 production and the amount of carbon in the microbial biomass correlated highly positively with the concentration of total water-soluble phenolic compounds and positively with the concentration of condensed tannins. Exposure of soil to volatile monoterpenes and tannins extracted and fractionated from spruce and pine needles affected carbon and nitrogen transformations in soil, but the effects were dependent on the compound and its molecular structure. Monoterpenes decreased net mineralisation of nitrogen and probably had a toxic effect on part of the microbial population in soil, while another part of the microbes seemed to be able to use monoterpenes as a carbon source. With tannins, low-molecular-weight compounds (also compounds other than tannins) increased soil CO2 production and nitrogen immobilisation by soil microbes while the higher-molecular-weight condensed tannins had inhibitory effects. In conclusion, plant secondary compounds may have a great potential in regulation of C and N transformations in forest soils, but the real magnitude of their significance in soil processes is impossible to estimate.

Bacterial roles in the formation of high-molecular-weight dissolved organic matter in estuarine and coastal waters: Evidence from lipids and the compound-specific isotopic ratios

High-molecular-weight dissolved organic matter (HMW-DOM, > 1,000 Daltons) is actively involved in the global biogeochemical cycling of many elements, but its carbon sources and detailed formation pathways are still not well understood. In this study, we measured bulk stable carbon and nitrogen isotopic ratios, lipid composition, and compound-specific carbon isotopic ratios of HMW-DOM samples collected from four U.S. estuaries (Boston Harbor/Massachusetts Bay, Delaware/Chesapeake Bay, San Diego Bay, and San Francisco Bay). Analytical results show (1) a fraction of HMW-DOM (lipid associated) in estuarine and coastal waters is derived from bacteria and phytoplankton; (2) this fraction of HMW-DOM is formed by various release processes of bacterial membrane components and bacterial reworking of phytoplankton-derived material; (3) this fraction of HMW-DOM is generally present in all samples from different coastal systems despite variable organic matter inputs and environmental conditions, suggesting an important bacterial role in HMW-DOM formation.

Variability in radiocarbon ages of biochemical compound classes of high molecular weight dissolved organic matter in estuaries

High molecular weight dissolved organic matter (HMW-DOM, > 1000 Da) represents a major fraction (> 30%) of dissolved organic carbon (DOC) in the ocean and thus plays an important role in the global biogeochemical cycling of carbon and many other elements. Its organic sources and formation mechanisms, however, are still not well understood especially in estuarine and coastal regions where multiple natural and anthropogenic sources contribute to total HMW-DOM. In this paper we report our measurements of natural radiocarbon (C-14) abundances and stable carbon isotope (C-13) compositions of the major biochemical compound classes: amino acids, carbohydrates and lipids separated from eight HMW-DOM samples collected from five US estuaries as part of our on-going study of sources, distribution and transport of chromophoric dissolved organic matter (CDOM) in estuarine and coastal waters. Distinct differences in both C-14 and C-13 values were found among the bulk HMW-DOM samples as well as the individual compound classes. Radiocarbon ages of the major compound classes varied by as much as 27,000 years in a single sample. The calculated average radiocarbon ages of the compound fractions of HMW-DOM indicate that the total lipid fraction is very "old", while the acid-insoluble fraction is slightly younger. Total amino acid and carbohydrate fractions, however, have relatively modern apparent C-14 ages. The significant variability in C-14 ages among the compound classes indicates not only multiple organic carbon sources but also different formation and turnover pathways controlling the cycling of different biochemical components of HMW-DOM in estuarine and coastal waters. (c) 2006 Elsevier Ltd. All rights reserved.

The effects of static and diurnally-cycling temperature acclimations on thermal tolerances of rainbow trout, Salmo gairdneri

:ofiedian lethal temperatures ( LT50' s ) were determined for rainbow trout, Salmo gairdnerii, acclimated for a minimum of 21 days at 5 c onstant temperatures between 4 and 20 0 C. and 2 diel temperature fluctuations ( sinewave curves of amplitudes ± 4 and ± 7 0 C. about a mean temperature of 12 0 C. ) . Twenty-four-, 48-, and 96-hour LT50 estimates were c alculated f ollowing standard flow-through aquatic bioassay techniques and probi t transformation of mortality data. The phenomenon of delayed thermal mortality was also investigated. Shifts in upper incipient lethal temperature occurred as a result of previous thermal conditioning. It was shown that increases in constant acclimation temperature result in proportional l inear increases in thermal tolerances. The increase i n estimated 96-hour LT50's was approximately 0.13 0 c. X 1 0 C:1 between 8 and 20 0 C. The effect of acclimation to both cyclic temperature regimes was an increase in LT50 to values between the mean and maximum constant equivalent daily temperatures of the cycles. Twenty-four-, 48-, and 96-hour LT50 estimates of both cycles corresponded approximately to the LT50 values of the 16 0 C. c onstant temperature equivalent . This increase i n thermal tolerance was further demonstrated by the delayed thermal mortality experiments . Cycle amplitudes appeared to i nfluence thermal resistance through alterations in initi al mortality since mortality patterns characteristic of base temperature acclimations re-appeared after approximately 68 hours exposure to test temperatures for the 12 + 4 0 C. group, whereas mortality patterns stabilized and remained constant for a period greater than 192 hours with the larger therma l cycle ( 12 + 7 0 C. ). NO s ignificant corre lations between s pecimen weight and time-to-death was apparent. Data are discussed in relation to the establishment of thermal criteria for important commercial and sport fishes , such as the salmonids , as is the question whether previously reported values on lethal temperature s may have been under estimated.

Trends in children`s physical activity and weight status in high and low socio-economic status areas of Melbourne, Victoria, 1985-2001

Objective:
To examine trends in active transport to and from school, in school sport and physical education (PE), and in weight status among children from high and low socio-economic status (SES) areas in Melbourne, Victoria, between 1985 and 2001.

Methods:
Cross-sectional survey data and measured height and weight from 1985 (n=557) and 2001 (n=926) were compared for children aged between 9–13 years within high and low SES areas.

Results:
From 1985 to 2001, the frequency of walking to or from school declined (4.38±4.3 vs. 3.61 ± 3.8 trips/wk, p<0.001), cycling to or from school also declined (1.22±2.9 vs. 0.36±1.5 trips/wk, p<0.001), and the frequency of PE lessons declined (1.64±1.1 vs. 1.18±0.9 lessons/wk, p<0.001). However, the frequency of school sport increased (0.9±1.22 vs. 1.24±0.8 sessions/wk, p<0.001). In 1985, 11.7% of children were overweight or obese compared with 28.7% in 2001 (p<0.001). Apart from walking to school and school sport, there were greater relative declines in cycling to school and PE, and increases in overweight and obesity among children attending schools in low SES areas compared with those attending schools in high SES areas.

Conclusions:
Declines in active school transport and PE have occurred at the same time as increases in overweight and obesity among Australian children.

Implications:
Promoting active school transport and maintaining school sport and PE should be important public health priorities in Australia. Current inequities in school sport and PE and in prevalence of overweight and obesity by area-level SES also need to be addressed.

Myocardial dysfunction induced by food restriction is related to calcium cycling and beta-adrenergic system changes

Food restriction (FR) has been shown to promote myocardial dysfunction in rats. The aim of this study was to verify the participation of calcium and beta-adrenergic system on myocardial mechanical alteration in rats submitted to FR. Myocardial performance was studied in isolated left ventricular papillar muscle from young Wistar-Kyoto rats (WKY) submitted to FR or to control diet. The groups subjected to FR were fed 50% less food than the control group for 90 days. Mechanical function was studied in isometric contraction at post-rest contraction of 30 seconds (PRC), calcium chloride concentration 5.20 mM, and beta-adrenergic stimulation with isoproterenol 10(-6) M. FR decreased the body weight, and left and right ventricular weight. In basal condition (1.25 MM of calcium) time to peak tension (TPT) and time from peak tension to 50% relaxation (RT50) were greater in the FR group. Muscle function was. The same in both PRC groups. TPT decrease in both high calcium groups, more in FR rats; RT50 dropped only in FR animals. TPT decreased in both Isoproterenol groups, more intensely in the FR group. This result suggests that food restriction impairs myocardial performance and these changes may be attributed to alterations in the intracellular calcium cycling and beta-adrenergic system. (C) 2003 Elsevier B.V. All rights reserved.

Effect of the aerobic capacity on the validity of the anaerobic threshold for determination of the maximal lactate steady state in cycling

The maximal lactate steady state (MLSS) is the highest blood lactate concentration that can be identified as maintaining a steady state during a prolonged submaximal constant workload. The objective of the present study was to analyze the influence of the aerobic capacity on the validity of anaerobic threshold (AT) to estimate the exercise intensity at MLSS (MLSS intensity) during cycling. Ten untrained males (UC) and 9 male endurance cyclists (EC) matched for age, weight and height performed one incremental maximal load test to determine AT and two to four 30-min constant submaximal load tests on a mechanically braked cycle ergometer to determine MLSS and MLSS intensity. AT was determined as the intensity corresponding to 3.5 mM blood lactate. MLSS intensity was defined as the highest workload at which blood lactate concentration did not increase by more than 1 mM between minutes 10 and 30 of the constant workload. MLSS intensity (EC = 282.1 ± 23.8 W; UC = 180.2 ± 24.5 W) and AT (EC = 274.8 ± 24.9 W; UC = 187.2 ± 28.0 W) were significantly higher in trained group. However, there was no significant difference in MLSS between EC (5.0 ± 1.2 mM) and UC (4.9 ± 1.7 mM). The MLSS intensity and AT were not different and significantly correlated in both groups (EC: r = 0.77; UC: r = 0.81). We conclude that MLSS and the validity of AT to estimate MLSS intensity during cycling, analyzed in a cross-sectional design (trained x sedentary), do not depend on the aerobic capacity.

Effect of Cycling Exercise at Different Pedal Cadences on Subsequent Muscle Strength

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Krill as a central node for iron cycling in the Southern Ocean

[EN] In order to establish the potential role of Antarctic krill (Euphausia superba) in the recycling of bioactive elements, we have quantified the release of iron, phosphate, and ammonia by these organisms along the Antarctic Peninsula sector of the Southern Ocean. The experimental results suggested that the presence of krill has a significant impact on ambient iron concentrations, as large amounts of this trace element were released by the krill (22–689 nmol Fe g Dry Weight−1 h−1, equivalent to 0.2 to 4.3 nmol Fe L−1 d−1). Half of this iron release occurred within the first hour of the experiment, and differences in iron and phosphate release rates (3.1 to 14.0 μmol PO43− g DW−1 h−1) seemed to reflect differences in food availability. These results identify krill as a major node in iron cycling in the Southern Ocean, potentially influencing iron residence time in the upper water column of this region.

Effect of transcutaneous electrical muscle stimulation and passive cycling movements on blood pressure and removal of urea and phosphate during hemodialysis

BACKGROUND: Intradialytic exercise has been described to improve blood pressure stability and dialysis efficacy. However, comorbid conditions in the dialysis population often preclude the widespread use of active intradialytic exercise. Therefore, we investigated the effect of intradialytic transcutaneous muscle stimulation (TEMS) and passive cycling movements (PCMs) on blood pressure and dialysis efficacy in patients. STUDY DESIGN: Prospective, controlled, randomized, crossover investigation. SETTING ; PARTICIPANTS: Ten patients were randomly allocated to TEMS, PCMs, or no intervention (NI) for 9 consecutive dialysis sessions. INTERVENTION: Participants were studied with NI, PCMs using a motor-driven ergometer, and bilateral TEMS of the leg musculature. Individual dialysis prescriptions were unchanged during the investigation. OUTCOMES ; MEASUREMENTS: The effect of TEMS and PCMs on blood pressure and dialysis efficacy in patients was assessed. RESULTS: Mean blood pressure increased from 121/64 +/- 21/15 mm Hg with NI to 132/69 +/- 21/15 mm Hg (P < 0.001) during sessions with PCMs and 125/66 +/- 22/16 mm Hg (P < 0.05) during sessions with TEMS. Urea and phosphate removal during dialysis were significantly (P < 0.001) greater with TEMS (19.4 +/- 3.7 g/dialysis and 1,197 +/- 265 mg/dialysis) or PCMs (20.1 +/- 3.4 g/dialysis and 1,172 +/- 315 mg/dialysis) than with NI (15.1 +/- 3.9 g/dialysis and 895 +/- 202 mg/dialysis). Body weight, ultrafiltration, Kt/V, and increases in hemoglobin and albumin levels during dialysis did not differ among the NI, PCMs, and TEMS groups. LIMITATIONS: The study design does not allow extension of the findings to prolonged treatment. CONCLUSION: Future studies during longer observation periods will have to prove the persistence of these acute findings. Both TEMS and PCMs deserve future investigations in dialysis patients because they increase intradialytic blood pressure and facilitate urea and phosphate removal when applied short term.