Effects of resistance training frequency on body composition and metabolics and inflammatory markers in overweight postmenopausal women.

The present study aimed to determine the importance of resistance training frequency on body composition and metabolics and inflammatory markers in sedentary overweight postmenopausal women (PW). Thirty subjects finished the resistance training-protocol (60% to 80% of 1-RM) and had all the evaluations (anthropometry, strength, food intake and biochemistry) done. Groups were assembled according to the week-frequency of attended sessions (G1-1 day/wk, N.=9; G2-2 days/wk, N.=11 and G3-3 days/wk, N.=10). The strength-training protocol resulted in similar changes on body composition and strength gains in all groups. However, the plasma markers responses differed among groups with G1 showing an increase of both CRP and glucose, with G2 increasing CRP and G3 keeping the baseline values. The results suggest that resistance exercise increases strength and muscle mass independently of the frequency. Moreover, highest resistance training frequency (3 days/week) prevented the rise of plasma glucose and CRP profile after 16 weeks of training in sedentary overweight PW.

Sagital abdominal diameter, but not waist circumference is strongly associated with glycemia, triacilglycerols and HDL-C levels in overweight adults.

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 onehundred twelve adults (M=27, F=85) aging 54.0±11.2 yrs and average body mass index (BMI) of 30.5±9.0 kg/m². 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 cholesterol/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).

Accuracy of sagittal abdominal diameter as predictor of abdominal fat among Brazilian adults: a comparation with waist circumference.

AIM: We aim was to compare the sagittal abdominal diameter (SAD) with waist circumference (WC) as a predictor of central obesity among adults and to identify the sensitivity and specificity of the best cut-off point for SAD. METHODS: A cross-sectional study of 266 Brazilians adults (euthrophic and overweight), aged 31-84 years old, of which 89 men and 177 women, was carried out. Anthropometric measurements such as SAD, weight, height, waist and hip circumferences, waist and hip ratio, body mass index, body fat percentage were performed. Receiver Operating Characteristics (ROC) curve was used to identify the sensitivity and specificity of the best cut off point for SAD as a predictor of central obesity. Statistical analysis were considered significant with a value of p < 0.05. RESULTS: The SAD measurement was positively correlated with WC for both genders, although stronger among overweight and obesity women (r = 0.71; p < 0.001 and r = 0.79; p < 0.001, respectively) than men. ROC curves identified the best cut-off points for SAD of 23.1 cm and 20.1 cm for men and women (96% and 85% sensitivity, 86% and 84% specificity, respectively). CONCLUSION: SAD measurement may be used as an anthropometric tool to identify central obesity among women for presenting adequate sensitivity and specificity.

Bioelectric impedance overestimates the body fat in overweight and underestimates in Brazilian obese women: a comparison with Segal equation 1.

INTRODUCTION: Overweight and obesity are risk factors to appearance of cardiovascular diseases and anthropometry is important as clinical tool for planning and health policymaking at population level. Thus, aim of this work was to compare the simple body fat percentage (%BF) obtained straight by bioeletric impedance (BIA) to the one obtained by the equation of Segal et al (1988), which uses the BIA resistance value, overweight among adult women. METHODS: This study conducted with 86 adult women (50.5±11.0 years old). Body weight and height were measured and estimated the body mass index (BMI). %BF was assessed by BIA (Biodynamics® model 450) and Segal equation. RESULTS: %BF derived from BIA (38.0±4.6%) and Segal et al (1988) (38.7±8.1%) were similar (p=0.85). However, when the women were distributed, in two groups based on their BMI, overweight (n=40; BMI=27.3±1.2 kg/m²) and obesity (n=46; BMI= 36.2±5.1 kg/m²), the two methods presented results significant different (p=0.000). The %BF of overweight women was 34.6±3.6% by BIA and 30.3±2.1% when estimated by Segal equation. In obese women, the %BF was 41.0±3.0% and 46.0±2.6%, respectively. CONCLUSION: BIA overestimated %BF in overweight (+14.2%; +3.0 kg) and underestimated in obese (-10.9%;-4.4 kg) women.

The lactate minimum test protocol provides valid measures of cycle ergometer VO(2)peak.

AIM: The aim of the present study was to investigate the validity of the Lactate Minimum Test (LMT) for the determination of peak VO(2) on a cycle ergometer and to determine the submaximal oxygen uptake (VO(2)) and pulmonary ventilation (VE) responses in an incremental exercise test when it is preceded by high intensity exercise (i.e., during a LMT). METHODS: Ten trained male athletes (triathletes and cyclists) performed 2 exercise tests in random order on an electromagnetic cycle ergometer: 1). Control Test (CT): an incremental test with an initial work rate of 100 W, and with 25 W increments at 3-min intervals, until voluntary exhaustion; 2). LMT: an incremental test identical to the CT, except that it was preceded by 2 supramaximal bouts of 30-sec (approximately 120% VO(2)peak) with a 30-sec rest to induce lactic acidosis. This test started 8 min after the induction of acidosis. RESULTS: There was no significant difference in peak VO(2) (65.6+/-7.4 ml x kg(-1) x min(-1); 63.8 +/- 7.5 ml x kg(-1) x min(-1) to CT and LMT, respectively). However, the maximal power output (POmax) reached was significantly higher in CT (300.6+/-15.7 W) than in the LMT (283.2+/-16.0 W). VO(2) and VE were significantly increased at initial power outputs in LMT. CONCLUSION: Although the LMT alters the submaximal physiological responses during the incremental phase (greater initial metabolic cost), this protocol is valid to evaluate peak VO(2), although the POmax reached is also reduced.

Whole-body protein turnover in malnourished patients with child class B and C cirrhosis on diets low to high in protein energy.

The purpose of this study was to determine the rate of whole-body protein turnover in moderately and severely alcoholic, malnourished, cirrhotic patients fed with different amounts of protein or energy. Six male patients (Child classes B and C) and four age- and sex-matched healthy control subjects were studied for 18 d in fasting and feeding states; a single oral dose of [(15)N]glycine was used as a tracer and urinary ammonia was the end product. The kinetic study showed that patients had higher protein catabolism while fasting (patients: 3.14 +/- 1.2 g of lean body mass/9 h; controls: 1.8 +/- 0.3 g of lean body mass/9 h; P < 0.02). Although not statistically significant, protein catabolism (grams of lean body mass/9 h) was lower with the hyperproteic/hyperenergetic diet when compared with fasting. Nitrogen retention was consistent with the lower protein-catabolism rate; a statistically significant increase in nitrogen balance was observed when patients were fed with the hyperproteic/hyperenergetic diet compared with fasting (4.3 +/- 3.2 g of nitrogen/d and -2.2 +/- 1.9 g of nitrogen/d, respectively; P < 0.01). These data indicate that Child class B and C cirrhotic patients are hypercatabolic and that long-term nutritional intervention with a hyperproteic/hyperenergetic diet is likely needed to improve their clinical and nutritional status.

[Causes of malnutrition in post-gastrectomy patient]. / Causas da desnutrição pós-gastrectomia.

BACKGROUND: The stomach through its mechanical and chemical processes has an unique role in the food processing and bioavailability. Hence gastrectomy has predictable and modifiable nutritional consequences depending upon its knowledge and the post-surgery therapies. OBJECTIVE: To point out the impact of gastrectomy on the nutritional status focusing on both mechanical and chemical actions of stomach on intaked foods. RESULTS: The protein-energy malnutrition and consequent body-weight loss follow reversely the remainer gastric volume and post-operatory length and have anorexy and intestinal malabsorption as their main causes. Lower food intake is probably due to either emotional factors or chemical mediators acting centrally on hypothalamus. The diarrhea may be due to either increased peristalsis or bacterial overgrowth both aggravated by exocrine-pancreas deficiency and gallbladder overflow. The intestinal malabsorption leading to fecal losses of fat and or nitrogen as well as lower utilization of dietary calcium and liposoluble vitamins. The gastrectomy-related anemia is consequent to lower secretion of both HCl and intrinsic factor leading to a decreased solubilization of iron and lower absorption of vitamin B12, respectively. CONCLUSION: Body-weight loss and anemia are the protein-energy malnutrition findings often found in these patients whose severity and lasting depend upon the type of surgery, post-surgery length and received nutritional care, being strongly recommended a supervisioned dietary care.

[Nutritional consequences of metabolic impairment of macronutrients in chronic liver disease]. / Conseqüências nutricionais das alterações metabólicas dos macronutrientes na doença hepática crônica.

Liver chronic pathologies often courses with metabolic abnormalities of macronutrients leading to or aggravating a protein-energy malnutrition status. This review raised the major pathophysiological mechanisms related to the protein-energy malnutrition in chronic liver patients. By large the reduced dietary intake is the most accepted cause particularly among alcoholic patients. Moreover during the treatment prevails the iatrogenic anorexia by unpalatable (restricted) diets interpolated with long-lasting fastings of hospitalized patients. Intestinal fat malabsorption is a common finding whereas hypermetabolism can be found associated with an acute alcoholism. Hypoglycemia or insulin resistance, hypertriglyceridemia and liver steatosis are common findings as well as lower plasma proteins along with higher levels of ammonia, aromatic and sulphur amino acids leading to neurological outcomes. The knowledge of these metabolic changes allow proper dietary interventions toward reduced morbi-mortality of those patients.

Comparison of omega-3 fatty acids and sulfasalazine in ulcerative colitis.

Fish oil omega-3 fatty acids exert antiinflammatory effects on patients with ulcerative colitis. However, a comparative study in patients with mild to moderate ulcerative colitis receiving only sulfasalazine or omega-3 fatty acids has not been performed. We sought to detect changes in the inflammatory disease activity with the use of either fish oil omega-3 fatty acids or sulfasalazine in patients with ulcerative colitis. Ten patients (five male, five female; mean age = 48 +/- 12 y) with mild to moderate active ulcerative colitis were investigated in a randomized cross-over design. They received either sulfasalazine (2 g/d) or omega-3 fatty acids (5.4 g/d) for 2 m.o. Disease activity was assessed by clinical and laboratory indicators, sigmoidoscopy, histology, and whole-body protein turnover (with 15N-glycine). Treatment with omega-3 fatty acids resulted in greater disease activity as detected by a significant increase in platelet count, erythrocyte sedimentation rate, C-reactive protein, and total fecal nitrogen excretion. No major changes in protein synthesis and breakdown were observed during either treatment. In conclusion, treatment with sulfasalazine is superior to treatment with omega-3 fatty acids in patients with mild to moderate active ulcerative colitis.

[The impact of alcohol and chronic liver disease of micronutrients metabolism]. / Implicações do alcoolismo e da doença hepática crônica sobre o metabolismo de micronutrientes.

Liver disease, alcohol and malnutrition are combinations usually associated with micronutrient impairment. Chronic liver disease courses with lower storage and activation of vitamin-coenzymes related to their malabsorption. Alcohol worsens the picture by reducing food intake, increasing micronutrients utilization and decreasing their absorption secondary to either intestinal or pancreatic injuries. Other concurrent causes would be drug treatments, urinary losses, protein deficiency and oxidative stress. As consequences the clinical signs are anemia, liver steatosis, oxidative stress and immunosuppression.

[Mechanism of action and control in the digestion of proteins and peptides in humans]. / Mecanismos de ação e controle da digestão de proteínas e peptídios em humanos.

This review aims to report the major control mechanisms of protein and peptides digestion of special interest in human patients. Regarding protein assimilation its digestive process begins at the stomach with some not so indispensable actions comparatively to those of duodenal/jejunal lumen. However even the intestine processes are partially under gastric secretion control. Proteolytic enzyme activities are related to protein structure and amino acid constituents, tertiary and quartenary structures need HCl denaturation prior to enzymatic hydrolysis. Thereafter the exopeptidases are guided by either NH2 (aminopeptidases) or COOH (carboxypeptidases) terminals of the molecule while endopeptidases are oriented by the specific amino acids constituents of the peptide. Both dietary and luminal secreted proteins and polypeptides undergo to either limited or complete proteolysis resulting basic or neutral free-amino acids (40%) or dioctapeptides. The brush border peptidases continue to degrade oligopeptide to di-tripeptides and neutral free-amino acids. Some peptides are uptaked by the enterocytes whose cytosolic peptidases complete the hydrolysis. Hence the digestive products flowing in the portal vein are mainly free-amino acids from either luminal or cytosolic hydrolysis and some di-tripeptides intactly absorbed. Both mechanical and chemical processes of digestion are under neural (vagal), neuroendocrinal (acetilcholine), endocrinal (gastrin, secretin and cholecystokinin) or paracrinal (histamine) controls. The gastric phase (hydrochloric acid and pepsinogen secretions) is activated by gastrin, histamine and acetilcholine which respond to both dietary-amino acids (tryptophan and phenylalanine) and mechanic distention of stomach. The pancreatic secretion is stimulated by either cephalic or gastric phases and has influence on the intestinal phase of digestion. The intestinal types of cells S and I release secretin and cholecystokinin respectively in response of acid quimo (cells S) or amino acids and peptides (cells I) in the lumen. Secretin stimulates the releasing of water, bicarbonate and enteropeptidases whereas cholecystokinin acts on pancreatic enzymes.

[Mechanisms of absorption of amino acids and oligopeptides. Control and implications in human diet therapy]. / Mecanismos de absorção de aminoácidos e oligopeptídios. Controle e implicações na dietoterapia humana.

The mechanisms involved in the absorption of amino acids and oligopeptides are reviewed regarding their implications in human feedings. Brush border and basolateral membranes are crossed by amino acids and di-tripeptides by passive (facilitated or simple diffusion) or active (Na+ or H+ co-transporters) pathways. Active Na(+)-dependent system occurs mainly at brush border and simple diffusion at basolateral, both membranes have the passive facilitated transport. Free-amino acids use either passive or active transport systems whereas di-tripeptides do mainly active (H+ co-transporter). Brush border have distinctive transport system for amino acids and di-tripeptides. The former occurs mainly by active Na+ dependently whereas the later is active H(+)-dependent with little affinity for tetra or higher peptides. Free amino acids are transported at different speed by saturable, competitive carriers with specificity for basic, acidic or neutral amino acids. Di and tripeptides have at least two carriers both electrogenic and H(+)-dependent. The basolateral membrane transport of amino acids is mostly by facilitated diffusion while for di-tripeptides it is an active anion exchange associated process. The main regulation of amino acids and di-tripeptide transport is the presence o substrate at the mucosal membrane with higher the substrate higher the absorption. Di and tripeptides are more efficiently absorbed than free amino acids which in turns are better absorbed than oligopeptides. So di-tripeptides result in better N-retention and is particularly useful in cases of lower intestinal absorption capacity. The non-absorbed peptides are digested and fermented by colonic bacteria resulting short-chain fatty acids, dicarboxylic acids, phenolic compounds and ammonia. Short-chain fatty acid provides energy for colonocytes and bacteria and the ammonia not fixed by bacteria returns to the liver for ureagenesis.

[Use of proteic metabolism (15N-glycine) in the early detection of disease exacerbation in patients with non-specific ulcerative colitis]. / Utilização do metabolismo protéico (15N-glicina) na detecção precoce de agravamento da atividade da doença em pacientes portadores de retocolite ulcerativa inespecífica.

Disease activity was assessed in 10 (five males and five females) ulcerative colitis patients through the following parameters: clinical, laboratory, sigmoidoscopic and histological. Protein metabolism was also assessed with 15N-glycine and urinary ammonia as end product. Only one patient had exacerbation of the disease two months after the study started. This patient presented in the beginning of the study protein synthesis and breakdown of 4.51 and 3.47 g protein/kg/day, respectively, values higher than all other patients, showing an hypermetabolic state, suggesting an increase of the disease activity. However, this increase was not detected by others indicators and indexes utilized. These data allow to suggest the hypothesis that protein metabolism predicts precociously the exacerbation of disease activity in ulcerative colitis patients.

[Is the metabolic response self-limited in head trauma? Analysis of acute phase proteins and glycemia]. / A resposta metabólica ao trauma cranioencefálico é autolimitada? Análise das proteínas de fase aguda e glicemia.

There are many reports supporting a self-limitation mechanism involved with hypermetabolic response after severe cranial injury. It was proposed a study with severe head injury patients, in three stages of the evolution. The first 7 days after admission (moment 1-M1), the second three days latter (M2) and the last 7 days after the first (M3). Among male patients with severe head injury, attended between January 1992 and December 1993 in University Hospital of Botucatu, UNESP, were selected 28 male patients, with Glasgow severity scale between 4 and 6, with pO2 < 70 mm Hg, weighting 60 kg or more. Among these patients, 6 finished the study, including analysis of the excretion of N, acute phase proteins, glycemia, triglycerides and amine nitrogen. During the study there were no changes in nitrogen balance and there was a decrease in protein C-reative. Glycemia tends to fall within two weeks after injury. The authors make some considerations about possible mechanisms involved in brain modulation associated with the period of dependence of hypermetabolism and hypercatabolism after closed brain injury. There are some evidences that the brain responds to head trauma with a gobal non specific way, which tends to be reorganized beyond the first two weeks after lesion. The study does not show any influence of the type and severity of head trauma.

Plasma levels of transthyretin and retinol-binding protein in Child-A cirrhotic patients in relation to protein-calorie status and plasma amino acids, zinc, vitamin A and plasma thyroid hormones.

Transthyretin and retinol-binding protein are sensitive markers of acute protein-calorie malnutrition both for early diagnosis and dietary evaluation. A preliminary study showed that retinol-binding protein is the most sensitive marker of protein-calorie malnutrition in cirrhotic patients, even those with the mild form of the disease (Child A). However, in addition to being affected by protein-calorie malnutrition, the levels of these short half-life-liver-produced proteins are also influenced by other factors of a nutritional (zinc, tryptophan, vitamin A, etc) and non-nutritional (sex, aging, hormones, renal and liver functions and inflammatory activity) nature. These interactions were investigated in 11 adult male patients (49.9 +/- 9.2 years of age) with alcoholic cirrhosis (Child-Pugh grade A) and with normal renal function. Both transthyretin and retinol binding protein were reduced below normal levels in 55% of the patients, in close agreement with their plasma levels of retinol. In 67% of the patients (4/6), the reduced levels of transthyretin and retinol-binding protein were caused by altered liver function and in 50% (3/6) they were caused by protein-calorie malnutrition. Thus, the present data, taken as a whole, indicate that reduced transthyretin and retinol-binding protein levels in mild cirrhosis of the liver are mainly due to liver failure and/or vitamin A status rather than representing an isolated protein-calorie malnutrition indicator.

[Protein-energy malnutrition as a consequence of the hospitalization of gastroenterologic patients]. / Conseqüências nutricionais (protéico-energéticas) da hospitalização de pacientes gastroenterológicos.

The effects of the clinical and dietetics in patient managements on the protein-energy status of hospitalized patients were retrospectively (four yr) investigated in 243 adult (49 +/- 16 yr), male (168) and female (75) patients suffering from chronic liver diseases (42%), intestinal diseases with diarrhea (14%), digestive cancers (11%), chronic pancreatitis (10%), stomach and duodenum diseases (7%), acute pancreatitis (7%), primary protein-energy malnutrition (3%), esophagus diseases (3%), intestinal diseases with constipation 14 (2%) and chronic alcoholism (2%). The protein-energy nutritional status assessed by combinations of anthropometric and blood parameters showed 75% of protein energy malnutrition at the hospital entry mostly (4/5) in severe and moderate grades. The overall average of hospitalization was 20 +/- 15 days being the shortest (13 +/- 5,7 days) for esophagus diseases and the longest (28 +/- 21 days) for the intestinal diseases with diarrhea patients which also received mostly (42%) of the enteral and/or parenteral feedings followed by acute pacreatitis (41%) and digestive cancers (31%) patients. When compared to the entry the protein-energy malnutrition rate at the discharge decreased only 5% despite the increasing of 30% found on the protein-energy intake. The main improvement of the protein-energy nutritional status were attained to those patients showing protein-energy malnutrition milder degrees at the entry which belonged mostly to primary protein-energy malnutrition, acute pancreatitis and intestinal diseases with diarrhea diseases. The later two groups showed protein-energy nutritional status improvement only after the second week of hospitalization. The digestive cancers patients had their protein-energy nutritional status worsened throughout the hospitalization whereas it happened only in the first week for the intestinal diseases with diarrhea and chronic liver diseases patients, improving thereafter up to the discharge. The protein-energy nutritional status improvement found in few patients could be attributed to some complementary factors such as theirs mild degree of protein-energy malnutrition at entry and/or non-invasive propedeutics and/or enteral-parenteral feddings and/or longer hospitalization staying. The institutional causes for the unexpected lack of nutritional responses by the patients were probably the high demand for the few available beds which favour the hospitalization of the most severed patients and the university-teaching pressure for the high rotation of the available beds. Both often resulting in early discharging. In persisting the current physical area and attendance demand one could suggest an aggressive support early at the entry preceding and/or accompanying the more invasive propedeutical procedures.

Protein-energy status and 15N-glycine kinetic study of child a cirrhotic patients fed low- to high-protein energy diets.

In five male cirrhotic patients (Child A) and in four age- and sex-matched healthy control subjects, whole-body protein turnover was measured using a single oral dose of 15N-glycine as a tracer and urinary ammonia as end product. Subjects were studied in the fasting and feeding state, with different levels of protein and energy intake. The patients were underweight and presented lower plasma transthyretin and retinol-binding protein levels. When compared with controls, the kinetic studies showed patients to be hypometabolic in the fasting (D0) state and with the control diet [D1 = (0.85 g of protein/ 154 kJ) x kg-1.day-1]. However, when corrected by body weight, the kinetic differences between groups disappeared, whereas the N-retention in the feeding state showed better results for the patients due mainly to their efficient breakdown decrease. When fed high-level protein or energy diets [D1 = (0.9 g protein/195 kJ) and D3 = (1.56 g protein/158 kJ) x kg-1.day-1], the patients showed D0 = D1 = D2 < D3 for N-flux and (D0 = D1) < D3 (D2 is intermediary) for protein synthesis. Thus, the present data suggest that the remaining mass of the undernourished mild cirrhotic patients has fairly good protein synthesis activity and also that protein, rather than energy intake, would be the limiting factor for increasing their whole-body protein synthesis.

Proliferating cell nuclear antigen (PCNA) in non-Hodgkin's lymphomas: correlation with working formulation and Kiel classification in formalin-fixed paraffin-embedded material.

PCNA is a 36-KD proliferating cell nuclear antigen associated with the cell cycle. The immunocytochemical detection of PCNA represents a useful tool for the study of tumor proliferation activity. This study documents the detection of PCNA, using antibody PC 10 in formalin-fixed, paraffin-embedded tissue, and correlates the proliferative activity of the non-Hodgkin's lymphomas (NHL) with histological grading assessed by the International Working Formulation (WF) and Kiel classification. In 92 cases of NHLs we found a strong correlation between the PCNA index and lymphoma grading. Statistically significant differences were also found between the proliferative index (PI) in low and high grade lymphomas according to the Kiel classification (t = 9.519; p < 0.001) and between low, intermediate and high grade lymphomas according to the WF classification (F = 79.01; p < 0.001). In the Kiel classification the mean of low grade lymphomas was 39.5% and of high grade 75.7%. In the WF the average of low grade lymphomas was 29.7%, intermediate 53.1% and high 75.1%. Although the differences among the groups had been significant, we found variations inside each histological subgroup in both classifications. The intermediate lymphomas were the most heterogeneous group, with PI inside the same histologic subtypes coincident with low and high grade lymphomas. Since PCNA may be used as a marker of cell proliferation in clinical studies to estimate the biological aggressiveness of lymphomas, its determination in intermediate grade NHL could be very useful to evaluate individual cases in this group and determine prognosis and probably the appropriate therapy.

Controle do fornecimento e da utilizaçäo de substratos energéticos no encéfalo / Control of supply and use of energy substrates in the encephalon

Correspondendo a apenas 2 por cento do peso corpóreo, o cérebro apresenta taxa matabólica superior à maioria dos demais orgäos e sistemas . A maior parte do consumo energético encefálico ocorre no transporte iônico para manutençäo do potencial de membrana celular. Praticamente desprovido de estoques, os substratos energéticos para o encéfalico säo fornecidos necessariamente pela circulaçäo sanguínea. O suprimento desses substratos sofre também a açäo seletiva da barreira hemato-encefálica (BHE). O principal substrato, que é a glicose, tem uma demanda de 150g/dia (0,7mMg/min). A metabolizaçäo 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 sanguíneos desta encontram-se elevados. Quando oxidado, o lactato chega a responder por 21 por cento do consumo cerebral de O2. Em situaçöes de isquemia e inflamaçäo 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 produçäo cerebral de succinil CoA e GTP. Quanto aos demais substratos, embora apresentem condiçöes metabólicas, näo existem demonstraçöes consistentes de que o cerébro produza energia a partir dos ácidos graxos sistêmicos, mesmo em situaçöes de hipoglicemia. De maneira análoga, etanol e glicerol säo considerados apenas a nível de experimentaçäo. A utilizaçäo dos aminoácidos é dependente da sua captaçäo, limitada tanto pela baixa concentraçäo sanguínea, como pela seletividade da BHE. A maior captaçäo ocorre para os de cadeia ramificada e destes, a valina. A menor captaçäo é a de aminoácidos sintetizados no cérebro (aspartato, gluconato e alanina). Todos podem ser oxidados a CO2 e H2O. Entretanto, mesmo com o consumo de glicose reduzido a 50 por cento, a contribuiçäo energética dos aminoácidos näo ultrapassa a 10 por cento. Para manter o suprimento adequado de glicose e oxigênio, o fluxo sanguíneo cerebral é da ordem de 800 ml/min (15 por cento do débito cardíaco). O consumo de O2 pelo cérebro á equivalente a 20 por cento do total consumido pelo corpo. Esses mecanismos, descritos como controladores da utilizaçäo de substratos energéticos pelos cérebro, sofrem a influência da idade apenas no período perinatal, com a oxidaçäo do lactato na fase pré-latente e dos corpos cetônicos, no início da amamentaçäo

Metabolismo da glicose cerebral no trauma crânio-encefálico: uma avaliaçäo / Cerebral glucose metabolism in craniocerebral trauma: an evaluation

Os autores apresentam revisäo geral da distribuiçäo e metabolizaçäo da glicose, com ênfase para os distúrbios que ocorrem no trauma crânio-encefálico, como hiperglicemia que ocorre na fase aguda. Finalizando, säo feitos comentários sobre as possíveis consequências desses conhecimentos sobre os procedimentos atuais, que aconselham a restriçäo na oferta de glicose a pacientes com catabolismo acentuado e que necessitam poupar o contigente de proteína corporal