Marília Seelaender

HMB supplementation: clinical and athletic performance-related effects and mechanisms of action

Amino acids such as leucine and its metabolite α-ketoisocaproate (KIC), are returning to be the focus of studies, mainly because of their anti-catabolic properties, through inhibition of muscle proteolysis and enhancement of protein synthesis. It is clear that these effects may counteract catabolic conditions, as well as enhance skeletal muscle mass and strength in athletes. Moreover, beta-hydroxy-beta-methylbutyrate (HMB) has been shown to produce an important effect in reducing muscle damage induced by mechanical stimuli of skeletal muscle. This review aims to describe the general scientific evidence of KIC and HMB supplementation clinical relevance, as well as their effects (e.g., increases in skeletal muscle mass and/or strength), associated with resistance training or other sports. Moreover, the possible mechanisms of cell signaling regulation leading to increases and/or sparing (during catabolic conditions) of skeletal muscle mass are discussed in detail based on the recent literature.

Endurance training induces depot-specific changes in IL-10/TNF-α ratio in rat adipose tissue

White adipose tissue (WAT) is the source of pro- and anti-inflammatory cytokines and recently, it has been recognized as an important source of interleukin 10 (IL-10). Acute physical exercise is known to induce an anti-inflammatory cytokine profile, however, the effect of chronic physical exercise on the production of IL-10 by WAT has never been examined. We assessed IL-10 and TNF-alpha concentration in WAT of rats engaged in endurance training. Animals were randomly assigned to either a sedentary control group (S, n=7) or an endurance trained group (T, n=8). Trained rats ran on a treadmill 5 days/wk for 8 wk (55-65% VO(2max)). Detection of IL-10 and TNF-alpha protein and mRNA expression, as well as the gene expression of PPAR-gamma, and immunocytochemistry to detect mononuclear phagocytes were carried out. A reduction in absolute retroperitoneal adipose tissue (RPAT) weight in T (44%; p<0.01), when compared with S was observed. IL-10 concentration was increased (1.5-fold, p<0.05), to a higher extent than that of TNF-alpha (66%, p<0.05) in the mesenteric adipose tissue (MEAT) of the trained group, while no change related to training was observed in RPAT. In MEAT, IL-10/TNF-alpha ratio was increased in T, when compared with S (30%; p<0.05). PPAR-gamma gene expression was increased in T (1.1-fold; p<0.01), when compared with S in the same adipose depot. No monocyte infiltration was found. In conclusion, exercise training induced increased IL-10 expression in the mesenteric depot, resulting in a modified IL-10/TNF-alpha ratio. We also conclude that WAT presents a depot-specific response to endurance training regarding the studied aspects.

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 H2O2 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 CO2 from the oxidation of [U‐14C]‐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. Copyright

Regulation of inflammation in the adipose tissue in cancer cachexia: effect of exercise

The paraneoplastic syndrome of cachexia is considered a degenerative chronic inflammatory disease, being deeply related to the increase of pro‐inflammatory factors, especially tumour necrosis factor alpha (TNF‐α). It is known that the adipose tissue is affected by cachexia and contributing with the secretion of pro‐inflammatory factors which reach the adjacent tissues and the circulation. The effect of pro‐inflammatory factors is balanced by the effect of anti‐inflammatory factors, such as interleukin 10 (IL‐10). The IL‐10/TNF‐α ratio has been recently postulated as a marker for the assessment of the degree of inflammation, which correlates with disease‐associated morbidity and mortality. In order to counteract inflammation in chronic disease, our group has currently adopted chronic endurance exercise in models of cancer cachexia and chronic heart failure. Since it is clear that white adipose tissue is strongly implicated in the secretion of both pro‐ and anti‐inflammatory factors in disease, we chose to address its contribution to cachexia‐related inflammation and the effect of endurance training on the capacity of cytokine expression and secretion by this tissue. Our results show an enhancement of IL‐10 adipose tissue content, and increased IL‐10/TNF‐α ratio induced by endurance training. The mechanisms are discussed. Copyright

Chronic exercise decreases cytokine production in healthy rat skeletal muscle

Skeletal muscle is the source of pro‐ and anti‐inflammatory cytokines, and recently, it has been recognized as an important source of interleukin‐6 (IL‐6). Acute physical exercise is known to induce a pro‐inflammatory cytokine profile in the plasma. However, the effect of chronic physical exercise in the production of pro‐ and anti‐inflammatory cytokines by the skeletal muscle has never been examined. We assessed IL‐6, TNF‐α, IL‐1β and IL‐10 levels in the skeletal muscle of rats submitted to endurance training. Animals were randomly assigned to either a sedentary group (S, n = 7) or an endurance exercise trained group (T, n = 8). Trained rats ran on a treadmill for 5 days week−1 for 8 weeks (60% VO2max). Detection of IL‐6, TNF‐α, IL‐1β and IL‐10 protein expression was carried out by ELISA. We found decreased expression of IL‐1β, IL‐6, TNF‐α and IL‐10 (28%, 27%, 32% and 37%, respectively, p < 0.05) in the extensor digital longus (EDL) from T, when compared with S. In the soleus, IL‐1β, TNF‐α and IL‐10 protein levels were similarly decreased (34%, 42% and 50%, respectively, p < 0.05) in T in relation to S, while IL‐6 expression was not affected by the training protocol. In conclusion, exercise training induced decreased cytokine protein expression in the skeletal muscle. These data show that in healthy rats, 8‐week moderate‐intensity aerobic training down regulates skeletal muscle production of cytokines involved in the onset, maintenance and regulation of inflammation, and that the response is heterogeneous according to fibre composition. Copyright

Both adiponectin and interleukin-10 inhibit LPS-induced activation of the NF-κB pathway in 3T3-L1 adipocytes.

Adiponectin and interleukin 10 (IL-10) are adipokines that are predominantly secreted by differentiated adipocytes and are involved in energy homeostasis, insulin sensitivity, and the anti-inflammatory response. These two adipokines are reduced in obese subjects, which favors increased activation of nuclear factor kappa B (NF-κB) and leads to elevation of pro-inflammatory adipokines. However, the effects of adiponectin and IL-10 on NF-κB DNA binding activity (NF-κBp50 and NF-κBp65) and proteins involved with the toll-like receptor (TLR-2 and TLR-4) pathway, such as MYD88 and TRAF6 expression, in lipopolysaccharide-treated 3T3-L1 adipocytes are unknown. Stimulation of lipopolysaccharide-treated 3T3-L1 adipocytes for 24h elevated IL-6 levels; activated the NF-κB pathway cascade; increased protein expression of IL-6R, TLR-4, MYD88, and TRAF6; and increased the nuclear activity of NF-κB (p50 and p65) DNA binding. Adiponectin and IL-10 inhibited the elevation of IL-6 levels and activated NF-κB (p50 and p65) DNA binding. Taken together, the present results provide evidence that adiponectin and IL-10 have an important role in the anti-inflammatory response in adipocytes. In addition, inhibition of NF-κB signaling pathways may be an excellent strategy for the treatment of inflammation in obese individuals.

Endotoxin levels correlate positively with a sedentary lifestyle and negatively with highly trained subjects.

IntroductionA sedentary lifestyle increases the risk of developing cardiovascular disease, obesity, and diabetes. This phenomenon is supported by recent studies suggesting a chronic, low-grade inflammation status. Endotoxin derived from gut flora may be key to the development of inflammation by stimulating the secretion of inflammatory factors. This study aimed to examine plasma inflammatory markers and endotoxin levels in individuals with a sedentary lifestyle and/or in highly trained subjects at rest. Methods: Fourteen male subjects (sedentary lifestyle n = 7; highly trained subjects n = 7) were recruited. Blood samples were collected after an overnight fast (~12 h). The plasmatic endotoxin, plasminogen activator inhibitor type-1 (PAI-1), monocyte chemotactic protein-1 (MCP1), ICAM/CD54, VCAM/CD106 and lipid profile levels were determined.ResultsEndotoxinemia was lower in the highly trained subject group relative to the sedentary subjects (p < 0.002). In addition, we observed a positive correlation between endotoxin and PAI-1 (r = 0.85, p < 0.0001), endotoxin and total cholesterol (r = 0.65; p < 0.01), endotoxin and LDL-c (r = 0.55; p < 0.049) and endotoxin and TG levels (r = 0.90; p < 0.0001). The plasma levels of MCP-1, ICAM/CD54 and VCAM/CD106 did not differ.ConclusionThese results indicate that a lifestyle associated with high-intensity and high-volume exercise induces favorable changes in chronic low-grade inflammation markers and may reduce the risk for diseases such as obesity, diabetes and cardiovascular diseases.

Adipose tissue in Walker 256 tumour-induced cachexia: possible association between decreased leptin concentration and mononuclear cell infiltration

The adipose tissue (AT) is severely affected by cachexia, a paraneoplastic syndrome, which increases the morbidity and mortality of cancer. There is, however, a heterogeneous response to the condition, according to the AT depot. As plasma leptin concentration has been often reported to vary in cachexia, we have measured (species specific radioimmunoassay) the local concentration of leptin in three AT depots: retroperitoneal (RPAT), epididymal (EAT) and mesenteric (MES) of Walker 256 tumour-bearing rats. A reduced concentration of leptin (P<0.0001) was found in all the depots and in the plasma of the cachectic rats, compared with controls already from day 4 after tumour cell injection. The presence of a cell infiltrate was observed in all AT obtained from the tumour-bearing animals. Ultrastructural analysis, along with immunocytochemistry for RT1B (indicating the presence of MHCII) and using antibody against mononuclear phagocytes, showed the cells to be macrophages. The profile of TNFα and PGE2 secretion by the infiltrate was investigated (commercial kits). There was increased production of both factors by the cells of all AT (P<0.05) compared with peritoneal macrophages obtained from the cachectic rats, while the cells isolated from MES showed the highest synthesis of TNFα. The results suggest a possible modulation of the chronic locally produced TNFα and PGE2 upon leptin synthesis by the AT of the cachectic rats.

Adipose tissue inflammation and cancer cachexia: Possible role of nuclear transcription factors

Cancer cachexia is a multifaceted syndrome whose aetiology is extremely complex and is directly related to poor patient prognosis and survival. Changes in lipid metabolism in cancer cachexia result in marked reduction of total fat mass, increased lipolysis, total oxidation of fatty acids, hyperlipidaemia, hypertriglyceridaemia, and hypercholesterolaemia. These changes are believed to be induced by inflammatory mediators, such as tumour necrosis factor-α (TNF-α) and other factors. Attention has recently been drawn to the current theory that cachexia is a chronic inflammatory state, mainly caused by the hosts reaction to the tumour. Changes in expression of numerous inflammatory mediators, notably in white adipose tissue (WAT), may trigger several changes in WAT homeostasis. The inhibition of adipocyte differentiation by PPARγ is paralleled by the appearance of smaller adipocytes, which may partially account for the inhibitory effect of PPARγ on inflammatory gene expression. Furthermore, inflammatory modulation and/or inhibition seems to be dependent on the IKK/NF-κB pathway, suggesting that a possible interaction between NF-κB and PPARγ is required to modulate WAT inflammation induced by cancer cachexia. In this article, current literature on the possible mechanisms of NF-κB and PPARγ regulation of WAT cells during cancer cachexia are discussed. This review aims to assess the role of a possible interaction between NF-κB and PPARγ in the setting of cancer cachexia as well as its significant role as a potential modulator of chronic inflammation that could be explored therapeutically.

Effect of endurance training upon lipid metabolism in the liver of cachectic tumour-bearing rats

The syndrome of cancer cachexia is accompanied by several alterations in lipid metabolism, and the liver is markedly affected. Previous studies showed that moderate exercise training may prevent liver fat accumulation through diminished delivery of lipids to the liver, increased hepatic oxidation and increased incorporation of triacylglycerol (TAG) into very low density lipoprotein (VLDL). Our aim was to examine the influence of moderate intensity training (8 weeks) upon TAG content, VLDL assembly and secretion, apolipoprotein B (apoB) and microsomal transfer protein (MTP) gene expression in the liver of cachectic tumour‐bearing rats. Animals were randomly assigned to a sedentary control (SC), sedentary tumour‐bearing (ST) or exercise‐trained control (EC) or to an exercise trained tumour‐bearing (ET) group. Trained rats ran on a treadmill (60% VO2max) for 60 min day−1, 5 day week−1, for 8 weeks. TAG content and the rate of VLDL secretion (followed for 3 h), as well as mRNA expression of apoB and MTP, and total cholesterol, VLDL‐TAG, VLDL‐cholesterol, high density lipoprotein cholesterol (HDL‐cholesterol) and tumour weight were evaluated. VLDL‐cholesterol showed a decrease in ST (p < 0.05) in relation to SC. Serum TAG, VLDL‐TAG and tissue TAG content were all increased in ST (p < 0.01), when compared with SC. ST showed a lower rate of VLDL secretion (p < 0.05) and reduced expression of apoB (p < 0.001) and MTP (p < 0.001), when compared with SC. These parameters were restored to control values (p < 0.05) when the animals were submitted to the exercise training protocol. Tumour weight decreased 10‐fold after training (p < 0.001). It is possible to affirm, therefore, that endurance training promoted the re‐establishment of lipid metabolism in cachectic tumour‐bearing animals, especially in relation to VLDL secretion and assembly. Copyright