Role of leptin in body temperature regulation and lipid metabolism following splenectomy.

OBJECTIVE: The physiological changes in serum triglycerides and body temperature that are induced by splenectomy are poorly understood. Therefore, the aim of this study was to investigate parameters related to lipid and glucose metabolism, as well as thermoregulation, in splenectomized mice. DESIGN AND METHODS: Splenectomized and sham-operated WT mice (C57Bl/6) and ob/ob mice were randomly divided and treated with a standard or high fat diet, and several metabolic parameters and the body temperature were investigated. RESULTS: Splenectomy induced a significant increase in triglyceride levels regardless of the diet. It was found that the splenectomized WT mice showed greater serum leptin and insulin levels compared with the sham-operated mice. Additionally, the body temperatures of the splenectomized WT mice were greater than the body temperatures of the control animals regardless of diet; this result too was observed without any significant change in the temperature of the splenectomized ob/ob animals. CONCLUSION: The results suggest that splenectomy interferes with serum triglyceride metabolism and body temperature regardless of the fat content in the diet and that leptin is involved in the regulation of body temperature related to splenectomy.

Salivary IL-21 and IgA responses to a competitive match in elite basketball players.

Athletes engaged in strenuous training might experience transient immune suppression that could lead to greater incidence of upper respiratory tract infections (URTI). Since interleukin 21 (IL-21) stimulates immunoglobulin A (IgA) secreting cells and a low level of this immunoglobulin is associated with increased incidence of URTI, the aim of the present study was to investigate the effect of a basketball match on salivary cortisol (sC), salivary IL-21 (sIL-21) and salivary IgA (sIgA) levels. Twenty male basketball players participated in an official game in two teams (10 players in each team). The saliva samples were collected before the warm-up and approximately 10-15 min after the end of the match and were analysed by ELISA methods. sC concentration increased significantly after the match while sIL-21 level was reduced (p < 0.05). In opposition to the study's hypothesis, sIgA level did not change in response to the match. The present findings suggest that a basketball match is sufficiently stressful to elevate sC concentration and attenuates the sIL-21 output without compromising the sIgA level. It is reasonable to speculate that the stability of sIgA acute responses to the match, despite the decrement in sIL-21, indicates that other mechanisms rather than IL-21 stimulating B cell proliferation/differentiation might modulate IgA concentration and secretion rate.

Carbamazepine inhibits angiotensin I-converting enzyme, linking it to the pathogenesis of temporal lobe epilepsy.

We find that a common mutation that increases angiotensin I-converting enzyme activity occurs with higher frequency in male patients suffering from refractory temporal lobe epilepsy. However, in their brains, the activity of the enzyme is downregulated. As an explanation, we surprisingly find that carbamazepine, commonly used to treat epilepsy, is an inhibitor of the enzyme, thus providing a direct link between epilepsy and the renin-angiotensin and kallikrein-kinin systems.

Effect of 12 weeks of resistance exercise on post-exercise hypotension in stage 1 hypertensive individuals.

Post-exercise hypotension (PEH), the reduction of blood pressure (BP) after a single bout of exercise, is of great clinical relevance. As the magnitude of this phenomenon seems to be dependent on pre-exercise BP values and chronic exercise training in hypertensive individuals leads to BP reduction; PEH could be attenuated in this context. Therefore, the aim of the present study was to investigate whether PEH remains constant after resistance exercise training. Fifteen hypertensive individuals (46 ± 8 years; 88 ± 16 kg; 30 ± 6% body fat; 150 ± 13/93 ± 5 mm Hg systolic/diastolic BP, SBP/DBP) were withdrawn from medication and performed 12 weeks of moderate-intensity resistance training. Parameters of cardiovascular function were evaluated before and after the training period. Before the training program, hypertensive volunteers showed significant PEH. After an acute moderate-intensity resistance exercise session with three sets of 12 repetitions (60% of one repetition maximum) and a total of seven exercises, BP was reduced post-exercise (45-60 min) by an average of aproximately -22 mm Hg for SBP, -8 mm Hg for DBP and -13 mm Hg for mean arterial pressure (P<0.05). However, this acute hypotensive effect did not occur after the 12 weeks of training (P>0.05). In conclusion, our data demonstrate that PEH, following an acute exercise session, can indeed be attenuated after 12 weeks of training in hypertensive stage 1 patients not using antihypertensive medication.

Hormonal, metabolic and perceptual responses to different resistance training systems.

AIM: The purpose of the present study was to compare the effect of different resistance training systems (Multiple-set [MS] and Pyramid [P]) on hormonal, metabolic and perceptual markers of internal load. METHODS: Ten healthy men performed two resistance training sessions (MS and P) which consisted of three exercises (bench press, peck deck and decline bench press) with the same total volume of load lifted. The training sessions were performed 14 days apart and allocated in a counter-balanced order. Hormonal (plasma insulin, growth hormone [GH], testosterone and cortisol) and metabolic (blood glucose and lactate) responses were assessed before and after each exercise bout. Session rating of perceived exertion (session RPE) was taken 30-min following each bout. RESULTS: No difference was observed for session-RPE between P and MS bouts (P>0.05). Plasma GH, cortisol and lactate increased significantly after exercise both bouts (P<0.01), but there were no significant changes between MS and P (P>0.05). CONCLUSION: It is concluded that the acute bout of resistance exercise following MS and P systems provide similar training strain when the total volume of load lifted is matched.

Plasma Kallikrein and Angiotensin I-converting enzyme N- and C-terminal domain activities are modulated by the insertion/deletion polymorphism.

Angiotensin I-converting enzyme (ACE) is recognized as one of the main effector molecules involved in blood pressure regulation. In the last few years some polymorphisms of ACE such as the insertion/deletion (I/D) polymorphism have been described, but their physiologic relevance is poorly understood. In addition, few studies investigated if the specific activity of ACE domain is related to the I/D polymorphism and if it can affect other systems. The aim of this study was to establish a biochemical and functional characterization of the I/D polymorphism and correlate this with the corresponding ACE activity. For this purpose, 119 male brazilian army recruits were genotyped and their ACE plasma activities evaluated from the C- and N-terminal catalytic domains using fluorescence resonance energy transfer (FRET) peptides, specific for the C-domain (Abz-LFK(Dnp)OH), N-domain (Abz-SDK(Dnp)P-OH) and both C- and N-domains (Abz-FRK(Dnp)P-OH). Plasma kallikrein activity was measured using Z-Phe-Arg-AMC as substrate and inhibited by selective plasma kallikrein inhibitor (PKSI). Some physiological parameters previously described related to the I/D polymorphism such as handgrip strength, blood pressure, heart rate and BMI were also evaluated. The genotype distribution was II n=27, ID n=64 and DD n=28. Total plasma ACE activity of both domains in II individuals was significantly lower in comparison to ID and DD. This pattern was also observed for C- and N-domain activities. Difference between ID and DD subjects was observed only with the N-domain specific substrate. Blood pressure, heart rate, handgrip strength and BMI were similar among the genotypes. This polymorphism also affected the plasma kallikrein activity and DD group presents high activity level. Thus, our data demonstrate that the I/D ACE polymorphism affects differently both ACE domains without effects on handgrip strength. Moreover, this polymorphism influences the kallikrein-kinin system of normotensive individuals.

Efficient method for obtaining Lep(ob)/Lep(ob)-derived animal models using adipose tissue transplantations.

BACKGROUND: Leptin-deficient mice (Lep(ob)/Lep(ob), also known as ob/ob) are of great importance for studies of obesity, diabetes and other correlated pathologies. Thus, generation of animals carrying the Lep(ob) gene mutation as well as additional genomic modifications has been used to associate genes with metabolic diseases. However, the infertility of Lep(ob)/Lep(ob) mice impairs this kind of breeding experiment. OBJECTIVE: To propose a new method for production of Lep(ob)/Lep(ob) animals and Lep(ob)/Lep(ob)-derived animal models by restoring the fertility of Lep(ob)/Lep(ob) mice in a stable way through white adipose tissue transplantations. METHODS: For this purpose, 1 g of peri-gonadal adipose tissue from lean donors was used in subcutaneous transplantations of Lep(ob)/Lep(ob) animals and a crossing strategy was established to generate Lep(ob)/Lep(ob)-derived mice. RESULTS: The presented method reduced by four times the number of animals used to generate double transgenic models (from about 20 to 5 animals per double mutant produced) and minimized the number of genotyping steps (from 3 to 1 genotyping step, reducing the number of Lep gene genotyping assays from 83 to 6). CONCLUSION: The application of the adipose transplantation technique drastically improves both the production of Lep(ob)/Lep(ob) animals and the generation of Lep(ob)/Lep(ob)-derived animal models.

Carbohydrate supplementation during intense exercise and the immune response of cyclists.

OBJECTIVE: To evaluate the effect of carbohydrate supplementation upon some aspects of the immune function in athletes during intense indoor cycling. METHODS: Twelve male athletes cycled for 20 min at a velocity corresponding to 90% of that obtained at the anaerobic threshold and rested for 20 min. This protocol was repeated six times. The athletes received, during the trial, water ad libitum, or a solution of carbohydrate (95% glucose polymers and 5% fructose) at 10% (w/v), 1 g kg h every 20 min, starting at the 10th minute of the first exercise period, plus extra water ad libitum. RESULTS: Exercise induced a reduction in peripheral blood mononuclear cell proliferation (37%) as well as in the production of cytokines by cultured cells (interleukin-1 (IL-1), interleukin-2 (IL-2), tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma), by 37%, 35%, 26% and 16%, respectively). All of these changes were prevented by the ingestion of a carbohydrate drink by the athletes, except that in IFN-gamma production, which was equally decreased (17%) after the second trial. The concentration of plasma glutamine, an important fuel for immune cells, was decreased in the placebo group but maintained in the group that received carbohydrate. CONCLUSION: Carbohydrate supplementation affects positively the immune response of cyclists by avoiding or minimizing changes in plasma glutamine concentration.

Sub-lethal concentrations of activated complement increase rat lymphocyte glutamine utilization and oxidation while lethal concentrations cause death by a mechanism involving ATP depletion.

Nucleated cells are more resistant to complement-mediated cell death than anucleated cells such as erythrocytes. There are few reports concerning the metabolic response of nucleated cells subjected to sub-lethal complement attack. It is possible that the rate of utilization of specific metabolic fuels by the cell is increased to enhance cell defence. We have measured the maximum activity of hexokinase, citrate synthase, glucose 6-phosphate dehydrogenase and glutaminase in rat mesenteric lymphocytes exposed to sub-lethal concentrations of activated complement (present in zymosan-activated serum, ZAS). These enzymes were carefully selected as they indicate changes of flux in glycolysis, TCA cycle, pentose phosphate pathway and glutaminolysis, respectively. The only enzyme activity to change on exposure of lymphocytes to ZAS was glutaminase, which was enhanced approximately by two-fold. Although rates of both glutamine and glucose utilization were enhanced by exposure to ZAS, only the rate of oxidation of glutamine was increased. Complement kills anucleated cells by simple osmotic lysis. However, it is likely that some nucleated cells will display characteristics of an ordered death mechanism and we have demonstrated that the concentration of lymphocyte ATP is dramatically decreased by activated complement. Nevertheless, the extent of cell death could be significantly reduced by the addition of inhibitors of the nuclear enzyme poly (ADP-ribose) polymerase (PARP). We conclude that glutamine metabolism is not only important for lymphocyte proliferative responses but is also important for cell defence from sub-lethal concentrations of activated complement. The rapid rate of complement-induced lymphocyte death reported here is suggested to be a consequence of over-activation of the nuclear enzyme PARP and ATP depletion.

The effect of BCAA supplementation upon the immune response of triathletes.

INTRODUCTION: Intense long-duration exercise could lead to immune suppression through a decrease in the circulating level of plasma glutamine. The decrease in plasma glutamine concentration as a consequence of intense long-duration exercise was reversed, in some cases, by supplementing the diet of the athletes with branched-chain amino acids (BCAA). To better address this question, we have evaluated some blood parameters (lymphocyte proliferation, the level of plasma cytokines, plasma glutamine concentration, and in vitro production of cytokines by peripheral blood lymphocytes) before and after the São Paulo International Triathlon, as well as the incidence of symptoms of infections between the groups. METHODS: Twelve elite male triathletes of mean age 25.5 +/- 3.2 yr (ranging from 21.4 to 30.1 yr), weighing 74.16 +/- 3.9 kg, swam 1.5 km, cycled 40 km, and ran 10 km (Olympic triathlon) in the São Paulo International Triathlon held in April 1997 and April 1998. In both events, six athletes received BCAA and the others, placebo. RESULTS: Athletes from the BCAA group (BG) presented the same levels of plasma glutamine, before and after the trial, whereas those from the placebo group showed a reduction of 22.8% in plasma glutamine concentration after the competition. Changes in the proliferative response of peripheral blood lymphocytes were accompanied by a reduction in IL-1 production after exercise (22.2%), which was reversed by BCAA supplementation (20.3%), without changes in IL-2 production. DISCUSSION: The data obtained show that BCAA supplementation can reverse the reduction in serum glutamine concentration observed after prolonged intense exercise such as an Olympic triathlon. The decrease in plasma glutamine concentration is paralleled by an increased incidence of symptoms of infections that results in augmented proliferative response of lymphocytes cultivated in the absence of mitogens. The prevention of the lowering of plasma glutamine concentration allows an increased response of lymphocytes to ConA and LPS, as well as an increased production of IL-1 and 2, TNF-alpha, and IFN-gamma, possibly linked to the lower incidence of symptoms of infection (33.84%) reported by the supplemented athletes.

Effect of a moderate intensity exercise training protocol on the metabolism of macrophages and lymphocytes of tumour-bearing rats.

It is commonly accepted that moderate intensity exercise is beneficial to the immune system. We tested the influence of a moderate intensity training protocol (8 weeks) upon immune system function in Wistar tumour-bearing (TB) rats. The metabolism of glucose and glutamine in lymphocytes and macrophages was assessed, together with some functional parameters (hydrogen peroxide production and lymphocyte proliferative response). These substrates were chosen since they represent the most important energetic and synthetic metabolites for these cellular types. The training protocol caused a decrease of 17.4 per cent in the production of H(2)O(2) by macrophages, as well as a decrease in glucose consumption (25 per cent) and lactate production (47.1 per cent), and an increase in the production of labelled CO(2) from the oxidation of [U-(14)C]-glucose, in TB rats. The training protocol was also able to induce changes in the maximal activity of some key enzymes in the metabolism of glucose and glutamine, a reduction of hexokinase (68.8 per cent) activity and an increase in the activity of citrate synthase (10.1 per cent) in TB rats. The training protocol increased the proliferative response of lymphocytes cultivated in the absence of mitogens (75 per cent), of those cultivated in the presence of ConA (38.2 per cent) and in the presence of LPS (45.0 per cent). These cells also showed an increase in the maximal activity of some key enzymes of the glycolytic and glutaminolytic pathways. Our data demonstrated that the training protocol was able to induce an increase in aerobic utilisation of both substrates in lymphocytes and macrophages. The training protocol was also able to prevent several changes in glucose and glutamine metabolism that are normally present in sedentary TB rats. These changes in immune cell metabolism induced by the training protocol were able to increase TB rat survival.

Metabolic response of macrophages to injury promoted by the activated complement system.

In nucleated cells, the swelling promoted by a complement system (CS) attack is not enough to promote cell death, because unlike erythrocytes these cells are able to eliminate cytolytic complement channels from the plasma membrane, by processes that include endocytosis. Several studies have demonstrated that the resistance of nucleated cells to the injury promoted by the CS is related to the cellular metabolism. Despite this, to the present day, no study has clearly related cell survival capacity to injury by the CS to its energetic metabolic status. In macrophages, the challenge imposed by the CS provoked an increase in the total amount of glucose incorporated into fatty acids, including phospholipids and cholesterol; substrates for membrane synthesis. The inhibition of cholesterol synthesis promoted an increase of the cell death rate. These data support the importance of cholesterol metabolism for macrophage resistance to necrosis induced by the activated complement system.