Metabolismo da glicose cerebral no trauma crânio-encefálico: uma avaliação

Os autores apresentam revisão geral da distribuição e metabolização da glicose, com ênfase para os distúrbios que ocorrem no trauma crânio-encefálico, como a hiperglicemia que ocorre na fase aguda. Finalizando, são feitos comentários sobre as possíveis conseqüências desses conhecimentos sobre os procedimentos atuais, que aconselham a restrição na oferta de glicose a pacientes com catabolismo acentuado e que necessitam poupar o contingente de proteína corporal.The authors give a general overview on the cerebral glucose metabolism, with special reference to brain injury, including intake, blood-brain barrier properties for glucose transport, oxidative metabolism and energetic needs during the head trauma. The evidences of the presence of ischemia and hypoxia in those situations and the relationships with the cerebral glucose metabolism are discussed. They point to the several explanations for hyperglicemia present up to 10 days after admission in brain injury, relating to the energetic needs at different phases of head trauma recovery. Some considerations are made about the lack of evidences on increase in glucose consumption or lactate production when hyperglycemia occurs in association with brain damage and ischemia caused by head trauma. The brain capacity to compensate metabolic disturbances is discussed. Some questions are made about current indications for restriction of glucose infusion in pacients who are in catabolic phase and need to spare their body protein pool. At the same way, the polemic about previous hyperglycemia and cerebral injury is revised. Some considerations are made about the moment to introduct increases in glucose administration

Controle do fornecimento e da utilização de substratos energéticos no encéfalo

Correspondendo a apenas 2% do peso corpóreo, o cérebro apresenta taxa metabólica superior à maioria dos demais órgãos e sistemas. A maior parte do consumo energético encefálico ocorre no transporte iônico para manutenção do potencial de membrana celular. Praticamente desprovido de estoques, os substratos energéticos para o encéfalo são fornecidos necessariamente pela circulação sanguínea.O suprimento desses substratos sofre também a ação seletiva da barreira hemato-encefálica (BHE). O principal substrato, que é a glicose, tem uma demanda de 150 g/dia (0,7 mM/g/min). A metabolização intracelular parece ser controlada pela fosfofrutoquinase. A manose e os produtos intermediários do metabolismo (frutose 1,6 bifosfato, piruvato, lactato e acetato) podem substituir, em parte, a glicose, quando os níveis sangüíneos desta encontram-se elevados. Quando oxidado, o lactato chega a responder por 21% do consumo cerebral de Ov em situações de isquemia e inflamação infecciosa, o tecido cerebral passa de consumidor a produtor de lactato. Os corpos cetônicos também podem reduzir as necessidades cerebrais de glicose desde que oferecidos em quantidades suficientes ao encéfalo. Entretanto, devem ser considerados como um substrato complementar e nunca alternativo da glicose, pois comprometem a produção cerebral de succinil CoA e GTP. Quanto aos demais substratos, embora apresentem condições metabólicas, não existem demonstrações consistentes de que o cérebro produza energia a partir dos ácidos graxos sistêmicos, mesmo em situações de hipoglicemia. de maneira análoga, etanol e glicerol são considerados apenas a nível de experimentação. A utilização dos aminoácidos é dependente da sua captação, limitada tanto pela baixa concentração sangüínea, como pela seletividade da BHE. A maior captação ocorre para os de cadeia ramificada e destes, a valina. A menor captação é a de aminoácidos sintetizados no cérebro (aspartato,gluconato e alanina). Todos podem ser oxidados a CO, e H(2)0. Entretanto, mesmo com o consumo de glicose reduzido a 50%, a contribuição energética dos aminoácidos não ultrapassa 10%. Para manter o suprimento adequado de glicose e oxigênio, o fluxo sangüíneo cerebral é da ordem de 800 ml/min (15% do débito cardíaco). O consumo de O, pelo cérebro é equivalente a 20% do total consumido pelo corpo. Esses mecanismos, descritos como controladores da utilização de substratos energéticos pelo cérebro, sofrem a influência da idade apenas no período perinatal, com a oxidação do lactato na fase pré-latente e dos corpos cetônicos, no início da amamentação.Altrough accounting for 2% of body weight, brain has one of the greatest metabolic rates compared with other organs and systems. The energy metabolic consum is expended mainly in the maintenance of ionic gradient, essential to neuronal activity. Brain receives energy substrates from circulation, with interference of blood brain barrier (BBB). Glucose is the main substrate and has a metabolic rate so high as 150 g/day (0,7 mM/G/min). At cellular level, metabolism of glucose seems to be controlled by phosphofructokynase. If the cellular level were high enough, manose and other products like fructose 1,6 biphosphate, pyruvate, lactate and acetate can be used in the place of glucose. Lactate, when oxyded, consums at least 21 % of the cerebral needs of 0,. In ischemia and inflammatory infections, brain tissue produces lactate instead of use it. Ketone bodies reduce cerebral needs of glucose; in view of the disturbances that occur in cerebral production of succinyl CoA and guanosine 3 phosphate (GTP), they must be considered as complementary substrate but not as an alternative one. Although they can be metabolized, there are no evidences that brain could produce energy from systemic free fatty acids, even when hypoglicemia is present. Ethanol and glycerol are considered only at experimental level. Brain uptake of aminoacids occur better for long chain aminoacids, specially valine. The aminoacids that are synthetised in the brain (aspartate,gluconate and alanine) show the lower absortion rates. All aminoacids should be oxided to CO, and H,0. Even when glucose consum is reduced to 30%, aminoacid accounts for only 10% of the energetic expenditure of the brain. To maintain cerebral glucose and oxygen supply to the brain , blood flow must be at least 800 ml/min. The regulation of supply and consumption of energy substrate by the brain is changed in few situations. Among them, are included the oxidation of lactate immediately before milk diet early in development and utilization of ketone bodies at the beginning of lactation. This review includes a brief discussion about the relevance of glucose as the main energy substrate for cerebral tissue in different ages and ischemia or hypoxia

Sagital Abdominal Diameter, But Not Waist Circumference Is Strongly Associated With Glycemia, Triacilglycerols And Hdl-c Levels In Overweight Adults [diámetro Abdominal Sagital, Pero No La Circunferencia De La Cintura Se Asocia Fuertemente Con La Glucemia, Triacilglycerols Y Hdl-c En Adultos Con Sobrepeso]

Aim: To correlate the sagittal abdominal diameter (SAD) and waist circumference (WC) with metabolic syndrome-associated abnormalities in adults. Methods: This cross-sectional study included one-hundred twelve adults (M = 27, F = 85) aging 54.0 ± 11.2 yrs and average body mass index (BMI) of 30.5 ± 9.0 kg/m 2. The assessment included blood pressure, plasma and anthropometric measurements. Results: In both men and female, SAD and WC were associated positively with body fat% (r = 0.53 vs r = 0.55), uric acid (r = 0.45 vs r = 0.45), us-PCR (r = 0.50 vs r = 0.44), insulin (r = 0.89 vs r = 0.75), insulin resistance HOMA-IR (r = 0.86 vs r = 0.65), LDL-ox (r = 0.51 vs r = 0.28), GGT (r = 0.70 vs r = 0.61), and diastolic blood pressure (r = 0.35 vs r = 0.33), and negatively with insulin sensibility QUICKI (r = -0.89 vs r = -0.82) and total choles-terol/TG ratio (r = -0.40 vs r = -0.22). Glycemia, TG, and HDL-c were associated significantly only with SAD (r = 0.31; r = 39, r = -0.43, respectively). Conclusion: Though the SAD and WC were associated with numerous metabolic abnormalities, only SAD correlated with dyslipidemia (TG and HDL-c) and hyperglycemia (glycemia).26511251129Fuller, N.J., Jebb, S.A., Laskey, M.A., Coward, W.A., Ella, M., Four-component model for the assessment of body composition in humans: Comparison with alternative methods, and evaluation of the density and hydration of fat-free mass (1992) Clin Sci, 82 (6), pp. 687-693Biaggi, R.R., Vollman, M.W., Nies, M.A., Brener, C.E., Flakoll, P.L., Levenhagen, D.K., Comparison of air-displacement plethysmography with hydrostatic weighing and bioelectrical impedance analysis for the assessment of body composition in healthy adults (1999) Am J Clin Nutr, 69 (5), pp. 898-903Risérus, U., Arnlov, J., Brismar, K., Zethelius, B., Berglund, L., Vessby, B., Sagittal abdominal diameter is a strong anthropometric marker of insulin resistance and hyperproinsulinemia in obese men (2004) Diabetes Care, 27 (8), pp. 2041-2046Öhrvall, M., Berglund, L., Vessby, B., Sagittal abdominal diameter compared with other anthropometric measurements in relation to cardiovascular risk (2000) Int J Obes, 24 (4), pp. 497-501Petersson, H., Daryani, A., Riserus, U., Sagittal abdominal diameter as a marker of inflammation and insulin resistance among immigrant women from the Middle East and native Swedish women: A cross-sectional study (2007) CardDiabetol, 6, pp. 1-7Brekke, H.K., Lenner, R.A., Taskinen, M.R., Mansson, J.E., Funahashi, T., Matsuzawa, Lifestyle modification improves risk factors in type 2 diabetes relatives (2005) Diabetes Res Clin Prac, 68 (1), pp. 18-28Pimentel, G.D., Portero-Mclellan, K.C., Oliveira, E.R., Spada, A.P., Oshiiwa, M., Zemdegs, J.C., Long-term nutrition education reduces several risk factors for type 2 diabetes mellitus in Brazilians with impaired glucose tolerance (2010) Nutr Res, 30 (3), pp. 186-190Albert, K.G., Zimmet, P., Shaw, J., The metabolic syndrome-a new worldwide definition (2005) Lancet, 366 (9491), pp. 1059-1062Grundy, S.M., Hypertriglyceridemia, insulin resistance, and the metabolic syndrome (1992) Am J Cardiol, 83 (9 B), pp. 25-29Nordhamn, K., Sodergren, E., Olsson, E., Karlstrom, B., Vessby, B., Berglund, L., Reliability of anthropometric measurements in overweight and lean subjects: Consequences for correlations between anthropometric and other variables (2000) Int J Obes, 24 (5), pp. 652-657Schoen, R.E., Thaete, F.L., Sankey, S.S., Weissfeld, J.L., Kuller, L.H., Sagittal diameter in comparison with single slice CT as a predictor of total visceral adipose tissue volume (1998) Int J Obes RelatMetab Disord, 22 (4), pp. 338-342Frenhani, P.B., Pimentel, G.D., Portero-Mclellan, K.C., Burini, R.C., Sagittal abdominal diameter as a predictor of visceral abdominal fat, insulin resistance, dyslipidemia and inflammation in overweight Brazilian adults (2008) Clin Nutr Suppl, 3 (SUPPL. 1), p. 126. , AbstractHeyward, V.H., Stolarczyk, L.M., Avaliagao da composigao corporal aplicada (2000) Led, , Barueri: Sao PauloSegal, K.R., van Loan, M., Fitzgerald, P.I., Hodgdon, J.A., van Itallie, T.B., Lean body mass estimation by bioeletrical impedance analysis: A four-site cross-validation study (1988) Am J Clin Nutr, 47 (1), pp. 7-14Friedewald, T., Levy, R.I., Frederickson, D.S., Estimation of the concentration of low-density lipoprotein cholesterol in plasma, without use of the preparative ultracentrifuge (1972) Clin Chem, 18 (6), pp. 499-502Tsimihodimos, V., Gazi, I., Kostara, C., Tselepis, A.D., Elisaf, M., Plasma lipoproteins and triacylglycerol are predictors of small, dense LDL particles (2007) Lipids, 42 (5), pp. 403-409Levy, J., Mattews, D.R., Hermans, M.P., Correct homeostasis model assessment (HOMA) evaluation uses the computer program (1998) Diabetes Care, 21 (12), pp. 2191-2192Clasey, J.L., Bouchard, C., Teates, C.D., Riblett, J.E., Thorner, M.O., Hartman, M.L., The use of anthropometric and dual-energy X-ray absorptiometry (DXA) measures to estimate total abdominal and abdominal visceral fat in men and women (1999) Obes Tfes, 7 (3), pp. 256-264Piernas Sanchez, C.M., Morales Falo, E.M., Zamora Navarro, S., Garaulet Aza, M., Study and classification of the abdominal adiposity throughout the application of the two-dimensional predictive equation Garaulet et al., in the clinical practice (2010) Nutr Hosp, 25 (2), pp. 270-274Koenig, W., Sund, M., Frohlich, M., Fischer, H.G., d Lówel, H., Dóring, A., C-Reactive protein, a sensitive marker of inflammation, predicts future risk of coronary heart disease in initially healthy middle-aged men: Results from the MONICA (Monitoring Trends and Determinants in Cardiovascular Disease) Augsburg Cohort Study, 1984 to 1992 (1999) Circulation, 99 (2), pp. 237-242Tracy, R.P., Lemaitre, R.N., Psaty, B.M., Ives, D.G., Evans, R.W., Cushman, M., Relationship of C-reactive protein to risk of cardiovascular disease in the elderly. Results from the Cardiovascular Health Study and the Rural Health Promotion Project (1997) ArteriosclerThromb Vase Biol, 17 (6), pp. 1121-1127Valsamakis, G., Chetty, R., Anwar, A., Banerjee, A.K., Barnett, A., Kumar, S., Association of simple anthropometric measures of obesity with visceral fat and the metabolic syndrome in male Caucasian and Indo-Asian subjects (2004) Diabet Med, 21 (12), pp. 1339-1345Pimentel, G.D., Portero-Mclellan, K.C., Maesta, N., Corrente, J.E., Burini, R.C., Accuracy of sagittal abdominal diameter as predictor of abdominal fat among Brazilian adults: A compara-tion with waist circumference (2010) NutrHosp, 25 (4), pp. 656-661Lo ́pez de la Torre, M., Bellido, D., Soto, A., Carreira, J., Hernandez Mijares, A., Standardisation of the waist circumference (WC) for each range of body mass index (BMI) in adult outpatients attended to in Endocrinology and Nutrition departments (2010) Nutr Hosp, 25 (2), pp. 262-26

Comparison Between Anaerobic Threshold Determined By Ventilatory Variables And Blood Lactate Response In Cyclists [comparação Entre Limiar Anaeróbio Determinado Por Variáveis Ventilatórias E Pela Resposta Do Lactato Sanguíneo Em Ciclistas]

Many investigations have shown that the coincidence between the ventilatory thresholds and those thresholds using the lactate response does not happen all of the time, suggesting that there is no relationship between the cause-effect between these phenomena. Thus, the present study had as main purpose to compare and correlate the Oxygen consumption (V̇O2), the power (W), and the heart rate (HR) values attained using protocols to determine the Ventilatory Threshold (VT) and the Individual Anaerobic Threshold (IAT). The sampling was constituted by eight State and National level cyclists (age: 27.88 ± 8.77 years; body mass: 65.19 ± 4.40 kg; height: 169.31 ± 5,77 cm). The IAT was determined starting from a three minutes 50 W warm up with progressive increases of 50 W.3min-1 up to achieving the voluntary exhaustion, when the blood was collected in the last 20 seconds of each phase, and during the recovering period. In order to determine the VT, it was used the same protocol used to determine the IAT, but without performing the blood collection. The VT was identified through the changes in the pulmonary ventilation, as well as of the ventilatory equivalent of the O2 and CO2. The t-Student test showed no significant statistical difference in any of the attained variables. The associations found were high and significant. The V̇O2 (ml.kg-1.min.-1), P (W), and HR (bpm) corresponding to the VT and IAT, as well as the associations between variables were respectively: 48.00 ± 3.82 vs. 48.08 ± 3.71 (r = 0.90); 256.25 ± 32.04 vs. 246.88 ± 33.91 (r = 0.84); 173.75 ± 9.18 vs. 171.25 ± 12.02 (r = 0.97). According to the results attained, it can be concluded that the IAT and the VT produce similar V̇O2, W, and HR values, favoring the adoption of the VT because it is a non-invasive method to determine the anaerobic threshold in cyclists.12134e38eJacobs, I., Blood lactate. 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Historical remarks on the development of the aerobic-anaerobic threshold up to 1966 (1985) Int J Sports Med, 6, pp. 109-116Stegmann, H., Kindermann, W., Schnabel, A., Lactate kinetics and individual anaerobic threshold (1981) Int J Sports Med, 2, pp. 160-165Coen, B., Schwarz, L., Urhausen, A., Kindermann, W., Control of training in middle-and long-distance running by means of the individual anaerobic threshold (1991) Int J Sports Med, 12, pp. 519-524McLellan, T.M., Cheung, K.S., Jacobs, I., Incremental test protocol, recovery mode and the individual anaerobic threshold (1991) Int J Sports Med, 12, pp. 190-195McLellan, T.M., Cheung, K.S., A comparative evaluation of the individual anaerobic threshold and the critical power (1992) Med Sci Sports Exerc, 24, pp. 543-550Urhausen, A., Coen, B., Weiler, B., Kindermann, W., Individual anaerobic threshold and maximum lactate steady state (1993) Int J Sports Med, 14, pp. 134-139Urhausen, A., Weiler, B., Coen, B., Kindermann, W., Plasma catecholamines during endurance exercise of different intensities as related to the individual anaerobic threshold (1994) Eur J Appl Physiol Occup Physiol, 69, pp. 16-20Beneke, R., Anaerobic threshold, individual anaerobic threshold, and maximal lactate steady state in rowing (1995) Med Sci Sports Exerc, 27, pp. 863-867Bourgois, J., Vrijens, J., Metabolic and cardiorespiratory responses in young oarsmen during prolonged exercise tests on a rowing ergometer at power outputs corresponding to two concepts of anaerobic threshold (1998) Eur J Appl Physiol Occup Physiol, 77, pp. 164-169Baldari, C., Guidetti, L., A simple method for individual anaerobic threshold as predictor of max lactate steady state (2000) Med Sci Sports Exerc, 32, pp. 1798-1802Guidetti, L., Musulin, A., Baldari, C., Physiological factors in middleweight boxing performance (2002) J Sports Med Phys Fitness, 42, pp. 309-314Stegmann, H., Kindermann, W., Comparison of prolonged exercise tests at the individual anaerobic threshold and the fixed anaerobic threshold of 4 mmol.l(-1) lactate (1982) Int J Sports Med, 3, pp. 105-110Bourgois, J., Vrijens, J., The Conconi test: A controversial concept for the determination of the anaerobic threshold in young rowers (1998) Int J Sports Med, 19, pp. 553-559Dickhuth, H.H., Yin, L., Niess, A., Rocker, K., Mayer, F., Heitkamp, H.C., Ventilatory, lactate-derived and catecholamine thresholds during incremental treadmill running: Relationship and reproducibility (1999) Int J Sports Med, 20, pp. 122-127McNaughton, L., Wakefield, G., Fasset, R., Bentley, D., A comparison of lactate kinetics, minute ventilation and acid-base balance as measure of the anaerobic threshold (2001) Journal of Human Moviment Studies, 41, pp. 247-261Hughes, E.F., Turner, S.C., Brooks, G.A., Effects of glycogen depletion and pedaling speed on anaerobic threshold" (1982) J Appl Physiol, 52, pp. 1598-1607Yoshida, T., Effect of dietary modifications on lactate threshold and onset of blood lactate 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(1992) J Sports Sci, 10, pp. 309-323Ribeiro, J.P., Hughes, V., Fielding, R.A., Holden, W., Evans, W., Knuttgen, H.G., Metabolic and ventilatory responses to steady state exercise relative to lactate thresholds (1986) Eur J Appl Physiol Occup Physiol, 55, pp. 215-221Yamamoto, Y., Miyashita, M., Hughson, R.L., Tamura, S., Shinohara, M., Mutoh, Y., The ventilatory threshold gives maximal lactate steady state (1991) Eur J Appl Physiol Occup Physiol, 63, pp. 55-59Wyatt, F.B., Comparison of lactate and ventilatory threshold to maximal oxygen consumption: A meta analysis (1999) Journal of Strength and Conditioning Research, 13, pp. 67-71Ahmaidi, S., Hardy, J.M., Varray, A., Collomp, K., Mercier, J., Prefaut, C., Respiratory gas exchange indices used to detect the blood lactate accumulation threshold during an incremental exercise test in young athletes (1993) Eur J Appl Physiol Occup Physiol, 66, pp. 31-36Dickstein, K., Barvik, S., Aarsland, T., Snapinn, S., Karlsson, J., A comparison of methodologies in detection of the anaerobic threshold (1990) Circulation, 81, pp. II38-II46Davis, J.A., Frank, M.H., Whipp, B.J., Wasserman, K., Anaerobic threshold alterations caused by endurance training in middle-aged men (1979) J Appl Physiol, 46, pp. 1039-1046Beaver, W.L., Wasserman, K., Whipp, B.J., A new method for detecting anaerobic threshold by gas exchange (1986) J Appl Physiol, 60, pp. 2020-2027Simon, J., Young, J.L., Blood, D.K., Segal, K.R., Case, R.B., Gutin, B., Plasma lactate and ventilation thresholds in trained and untrained cyclists (1986) J Appl Physiol, 60, pp. 777-781Davis, J.A., Anaerobic threshold: Review of the concept and directions for future research (1985) Med Sci Sports Exerc, 17, pp. 6-21Stone, M.H., Sands, W.A., Stone, M.E., The downfall of sports science in the United States (2004) Strength Cond J, 26, pp. 72-7