The metabolic role of IL-6 produced during exercise: is IL-6 an exercise factor?

Melatonin supplementation ameliorates oxidative stress and inflammatory signaling induced by strenuous exercise in adult human males

Strenuous exercise induces inflammatory reactions together with high production of free radicals and subsequent muscle damage. This study was designed to investigate for the first time and simultaneously whether over-expression of inflammatory mediators, oxidative stress, and alterations in biochemical parameters induced by acute exercise could be prevented by melatonin. This indoleamine is a potent, endogenously produced free radical scavenger and a broad-spectrum antioxidant; consequently, it might have positive effects on the recovery following an exercise session. The participants were classified into two groups: melatonin-treated men (MG) and placebo-treated individuals (controls group, CG). The physical test consisted in a constant run that combined several degrees of high effort (mountain run and ultra-endurance). The total distance of the run was 50 km with almost 2800 m of ramp in permanent climbing and very changeable climatic conditions. Exercise was associated with a significant increase in TNF-α, IL-6, IL-1ra (in blood), and also an increase in 8-hydroxy-2'-deoxyguanosine (8-OHdG) and isoprostane levels (in urine), and indicated the degree of oxidative stress and inflammation induced. Oral supplementation of melatonin during high-intensity exercise proved efficient in reducing the degree of oxidative stress (lower levels of lipid peroxidation, with a significant increase in antioxidative enzyme activities); this would lead to the maintenance of the cellular integrity and reduce secondary tissue damage. Data obtained also indicate that melatonin has potent protective effects, by preventing over-expression of pro-inflammatory mediators and inhibiting the effects of several pro-inflammatory cytokines. In summary, melatonin supplementation before strenuous exercise reduced muscle damage through modulation of oxidative stress and inflammation signaling associated with this physical challenge.

N-acetylcysteine supplementation controls total antioxidant capacity, creatine kinase, lactate, and tumor necrotic factor-alpha against oxidative stress induced by graded exercise in sedentary men

Aim of this study was to evaluate the effects of short-term (7 days) N-acetylcysteine (NAC) at 1,200 mg daily supplementation on muscle fatigue, maximal oxygen uptake (VO_2max), total antioxidant capacity (TAC), lactate, creatine kinase (CK), and tumor necrotic factor-alpha (TNF-α). Twenty-nine sedentary men (13 controls; 16 in the supplement group) from a randomized control were included. At before and after supplementation, fatigue index (FI) was evaluated in the quadriceps muscle, and performed a graded exercise treadmill test to induce oxidative stress, and as a measure of VO_2max. Blood samples were taken before exercise and 20 minutes after it at before and after supplementation, to determine TAC, CK, lactate, and TNF-α levels. Results showed that FI and VO_2max increased significantly in the supplement group. After exercise decreased the levels of TAC and increased lactate, CK, and TNF-α of both groups at before supplementation. After supplementation, lactate, CK, and TNF-α levels significantly increased and TAC decreased after exercise in the control group. Whereas the TAC and lactate levels did not change significantly, but CK and TNF-α increased significantly in the supplement group. Therefore, this results showed that NAC improved the muscle fatigue, VO_2max, maintained TAC, controlled lactate production, but had no influence on CK and TNF-α.

Vascular effects of exercise: endothelial adaptations beyond active muscle beds

Endothelial adaptations to exercise training are not exclusively conferred within the active muscle beds. Herein, we summarize key studies that have evaluated the impact of chronic exercise on the endothelium of vasculatures perfusing nonworking skeletal muscle, brain, viscera, and skin, concluding with discussion of potential mechanisms driving these endothelial adaptations.

Effects of Tai Chi Chuan on insulin and cytokine levels in a randomized controlled pilot study on breast cancer survivors

BACKGROUND

Tai Chi Chuan (TCC) is an integrative medicine mind-body practice with a physical activity component that has positive effects on aerobic capacity, muscular strength, and quality of life among cancer survivors, similar to the effects elicited by other modes of moderate-intensity exercise. Inflammatory cytokines and insulin and insulin-related signaling molecules may contribute to weight gain and affect cancer recurrence rates and survival; exercise can curb cancer- and treatment-related weight gain, increase survival, and reduce levels of insulin and inflammatory cytokines. Despite knowing the beneficial effects of conventional exercise interventions on these mediators, little is known about the physiologic effects of TCC on these pathways in breast cancer survivors.

METHODS

We assessed the effects of a 12-week, moderately intense, TCC intervention (n = 9) compared with a non-physical activity control (n = 10) consisting of psychosocial support therapy (PST), on levels of insulin, insulin-like growth factor (IGF)-1, insulin growth factor-like binding protein (IGFBP)-1, IGFBP-3, and cytokines interleukin (IL)-6, IL-2, and interferon (IFN)-γ in breast cancer survivors.

RESULTS

Levels of insulin are significantly different in TCC and PST groups; levels remained stable in the TCC group but increased in the PST control group (P = .099). Bivariate analysis revealed novel and significant correlations (all r > 0.45, all P ≤ .05) of both decreased fat mass and increased fat-free mass with increased IL-6 and decreased IL-2 levels.

CONCLUSIONS

This pilot study shows that TCC may be associated with maintenance of insulin levels and changes in cytokine levels that may be important for maintenance of lean body mass in breast cancer survivors.

Effects of 3T3 adipocytes on interleukin-6 expression and insulin signaling in L6 skeletal muscle cells

OBJECTIVE

Central adiposity and inflammation play key roles in the development of insulin resistance through the effects of pro-inflammatory adipokines such as IL-6, but the effect of infiltrating adipocytes in skeletal muscle tissues is not known. Communications between muscle cells and fat cells may contribute to the inflammatory response associated with insulin resistance.

METHODS

In this study we used a co-culture system of skeletal muscle (L6) and adipocyte (3T3-L1) cell lines to study expression of the inflammatory cytokine IL-6 and changes in insulin signaling. This model could mimic the adipocytes infiltrating myocytes that is commonly seen in obese patients.

RESULTS

When plated alone the L6 cells express IL-6 mRNA and secrete IL-6 protein, both of which are increased when the cells are challenged with the bacterial lipopolysaccharide (LPS). In contrast, the 3T3-L1 cells had very little expression of IL-6 mRNA or protein. Co-culture of 3T3-L1 pre-adipocytes with L6 cells, at a density ratio of 1:10, respectively, increased IL-6 expression significantly and decreased insulin-stimulated Akt phosphorylation. To examine the role of IL-6 in insulin sensitivity we incubated the L6 cells with IL-6. A brief challenge of L6 cells with IL-6 enhanced insulin-stimulated Akt phosphorylation. In contrast, incubation of the L6 cells with IL-6 for 96h markedly decreased insulin-stimulated Akt phosphorylation.

CONCLUSION

The enhanced IL-6 mRNA expression and IL-6 release in L6 myocytes co-cultured with 3T3-L1 cells indicate an important interaction between adipocytes and myocytes. This observation may shed some light on the long-standing enigma of obesity-induced insulin resistance where infiltration of the skeletal muscle by preadipocytes/adipocytes is evident.

Secreted proteins from adipose tissue and skeletal muscle - adipokines, myokines and adipose/muscle cross-talk

White adipose tissue and skeletal muscle are the largest organs in the body and both are composed of distinct cell types. The signature cell of adipose tissue is the adipocyte while myocytes are the defining cell of skeletal muscle. White adipocytes are major secretory cells and this is increasingly apparent also for myocytes. Both cells secrete a range of bioactive proteins, generally termed adipokines in the case of adipocytes and myokines for muscle cells. There has, however, been some confusion over nomenclature and we suggest that the name myokine is restricted to a protein that is secreted from myocytes, while the term adipokine should be used to describe all proteins secreted from any type of adipocyte (white, brown or brite). These definitions specifically exclude proteins secreted from other cells within adipose tissue and muscle, including macrophages. There is some commonality between the myokines and adipokines in that both groups include inflammation-related proteins - for example, IL-6, Il-8 and MCP-1. Adipokines and myokines appear to be involved in local autocrine/paracrine interactions within adipose tissue and muscle, respectively. They are also involved in an endocrine cross-talk with other tissues, including between adipose tissue and skeletal muscle, and this may be bi-directional. For example, IL-6, secreted from myocytes may stimulate lipolysis in adipose tissue, while adipocyte-derived IL-6 may induce insulin resistance in muscle.

Bimodal effect on pancreatic β-cells of secretory products from normal or insulin-resistant human skeletal muscle

OBJECTIVE

Type 2 diabetes is characterized by insulin resistance with a relative deficiency in insulin secretion. This study explored the potential communication between insulin-resistant human skeletal muscle and primary (human and rat) β-cells.

RESEARCH DESIGN AND METHODS

Human skeletal muscle cells were cultured for up to 24 h with tumor necrosis factor (TNF)-α to induce insulin resistance, and mRNA expression for cytokines was analyzed and compared with controls (without TNF-α). Conditioned media were collected and candidate cytokines were measured by antibody array. Human and rat primary β-cells were used to explore the impact of exposure to conditioned media for 24 h on apoptosis, proliferation, short-term insulin secretion, and key signaling protein phosphorylation and expression.

RESULTS

Human myotubes express and release a different panel of myokines depending on their insulin sensitivity, with each panel exerting differential effects on β-cells. Conditioned medium from control myotubes increased proliferation and glucose-stimulated insulin secretion (GSIS) from primary β-cells, whereas conditioned medium from TNF-α-treated insulin-resistant myotubes (TMs) exerted detrimental effects that were either independent (increased apoptosis and decreased proliferation) or dependent on the presence of TNF-α in TM (blunted GSIS). Knockdown of β-cell mitogen-activated protein 4 kinase 4 prevented these effects. Glucagon-like peptide 1 protected β-cells against decreased proliferation and apoptosis evoked by TMs, while interleukin-1 receptor antagonist only prevented the latter.

CONCLUSIONS

Taken together, these data suggest a possible new route of communication between skeletal muscle and β-cells that is modulated by insulin resistance and could contribute to normal β-cell functional mass in healthy subjects, as well as the decrease seen in type 2 diabetes.

Exercise-induced liver chemokine CXCL-1 expression is linked to muscle-derived interleukin-6 expression

The chemokine CXC ligand-1 (CXCL-1) is a small cytokine that elicits effects by signalling through the chemokine receptor CXCR2. CXCL-1 has neutrophil chemoattractant activity, is involved in the processes of angiogenesis, inflammation and wound healing, and may possess neuroprotective effects. The aim of this study was to unravel the mechanisms whereby CXCL-1 is regulated by exercise inmice. After a single bout of exercise, CXCL-1 protein increased in serum(2.4-fold), and CXCL-1 mRNA in muscle (6.5-fold) and liver (41-fold). These increases in CXCL-1 were preceded by increases in serum interleukin-6 (IL-6) and muscle IL-6 mRNA. In contrast, exercise-induced regulation of liver CXCL-1 mRNA expression was completely blunted in IL-6 knockout mice. Based on these findings, we examined the possible existence of a muscle-to-liver axis by overexpressing IL-6 in muscles. This resulted in increases in serum CXCL-1 (5-fold) and liver CXCL-1 mRNA expression (24-fold) compared with control. Because IL-6 expression and release are known to be augmented during exercise in glycogen-depleted animals, CXCL-1 and IL-6 expression were examined after exercise in overnight-fasted mice.We found that fasting significantly augmented serum CXCL-1, and CXCL-1 expression in liver and muscle. Taken together, these data indicate that liver is the main source of serum CXCL-1 during exercise in mice, and that the CXCL-1 expression in the liver is regulated by muscle-derived IL-6.

Vaspin and visfatin/Nampt are interesting interrelated adipokines playing a role in the pathogenesis of type 2 diabetes mellitus

Recently, vaspin and visfatin/Nampt have been identified as interesting novel adipokines having insulin-sensitizing and insulin-mimetic effects, respectively. However, the relationship between them has not been elucidated; and their circulating levels in type 2 diabetes mellitus (T2DM) have not been adequately studied. Therefore, this study was designed to investigate whether their levels are altered in Egyptian T2DM patients and to study the correlation of these novel adipokines with each other and with insulin resistance, interleukin-6 (IL-6), and other biochemical parameters. The levels of vaspin, visfatin/Nampt, IL-6, insulin, and other parameters were measured in nonobese and obese T2DM patients together with matched healthy nondiabetic control subjects. Vaspin, visfatin/Nampt, and IL-6 levels were measured by enzyme-linked immunosorbent assay, whereas insulin levels were measured by chemiluminescence technique. Vaspin and visfatin/Nampt levels were found to be significantly elevated in nonobese (1.62 ± 0.22 and 25.9 ± 3.44 ng/mL, respectively) and obese T2DM patients (2.76 ± 0.38 and 45.4 ± 4.60 ng/mL, respectively) compared with control subjects (0.42 ± 0.05 and 9.37 ± 1.98 ng/mL, respectively) at P < .01. In addition, vaspin and visfatin/Nampt levels were found to be significantly positively correlated with each other and with other biochemical parameters. In conclusion, both vaspin and visfatin/Nampt might play an important role in the pathogenesis of T2DM. In addition, the 3 adipokines--vaspin, visfatin/Nampt, and IL-6--are significantly interrelated with each other. Other possible mechanisms of action for vaspin should be considered besides the inhibition of unknown substrate proteases.

Exercise induces a marked increase in plasma follistatin: evidence that follistatin is a contraction-induced hepatokine

Follistatin is a member of the TGF-β super family and inhibits the action of myostatin to regulate skeletal muscle growth. The regulation of follistatin during physical exercise is unclear but may be important because physical activity is a major intervention to prevent age-related sarcopenia. First, healthy subjects performed either bicycle or one-legged knee extensor exercise. Arterial-venous differences were assessed during the one-legged knee extensor experiment. Next, mice performed 1 h of swimming, and the expression of follistatin was examined in various tissues using quantitative PCR. Western blotting assessed follistatin protein content in the liver. IL-6 and epinephrine were investigated as drivers of follistatin secretion. After 3 h of bicycle exercise, plasma follistatin increased 3 h into recovery with a peak of 7-fold. No net release of follistatin could be detected from the exercising limb. In mice performing a bout of swimming exercise, increases in plasma follistatin as well as follistatin mRNA and protein expression in the liver were observed. IL-6 infusion to healthy young men did not affect the follistatin concentration in the circulation. When mice were stimulated with epinephrine, no increase in the hepatic mRNA of follistatin was observed. This is the first study to demonstrate that plasma follistatin is increased during exercise and most likely originates from the liver. These data introduce new perspectives regarding muscle-liver cross talk during exercise and during recovery from exercise.

Exercise-associated hyponatremia: the influence of pre-exercise carbohydrate status combined with high volume fluid intake on sodium concentrations and fluid balance

To evaluate the effect of hydration and carbohydrate (CHO) status on plasma sodium, fluid balance, and regulatory factors (IL-6 & ADH) during and after exercise; 10 males completed the following conditions: low CHO, euhydrated (fluid intake = sweat loss) (LCEH); low CHO, dehydrated (no fluid) (LCDH); high CHO, euhydrated (HCEH); and high CHO, dehydrated (HCDH). Each trial consisted of 90-min cycling at 60% VO(2) max in a 35°C environment followed by 3-h rehydration (RH). During RH, subjects received either 150% of sweat loss (LCDH & HCDH) or an additional 50% of sweat loss (LCEH and HCEH). Blood was analyzed for glucose, IL-6, ADH, and Na(+). Post-exercise Na(+) was greater (p < 0.001) for LCDH and HCDH (141.7 + 0.72 and 141.6 + 0.4 mM) versus LCEH and HCEH (136.4 + 0.6 and 135.9 + 0.3 mM). Post-exercise IL-6 was similar in all conditions, and post-exercise ADH was greater (p = 0.01) in dehydrated versus euhydrated conditions. The rate of urine production was greater in HCEH (7.59 + 3.0 mL/min) compared to all other conditions (3.86 + 2.2, 5.29 + 3.1, and 2.96 + 1.1 mL/min for LCDH, LCEH, and HCDH, respectively). Despite CHO and hydration manipulations, no regulatory effects of IL-6 and ADH on plasma [Na(+)] were observed. With euhydration during exercise and additional fluid consumed during recovery, a high-CHO status increased urinary output during recovery, and it decreased the frequency of hyponatremia (Na(+) < 135 mM). Therefore, a high-CHO status may provide some protection against exercise-associated hyponatremia.

Effect of oat bran on time to exhaustion, glycogen content and serum cytokine profile following exhaustive exercise

The aim of this study was to evaluate the effect of oat bran supplementation on time to exhaustion, glycogen stores and cytokines in rats submitted to training. The animals were divided into 3 groups: sedentary control group (C), an exercise group that received a control chow (EX) and an exercise group that received a chow supplemented with oat bran (EX-O). Exercised groups were submitted to an eight weeks swimming training protocol. In the last training session, the animals performed exercise to exhaustion, (e.g. incapable to continue the exercise). After the euthanasia of the animals, blood, muscle and hepatic tissue were collected. Plasma cytokines and corticosterone were evaluated. Glycogen concentrations was measured in the soleus and gastrocnemius muscles, and liver. Glycogen synthetase-α gene expression was evaluated in the soleus muscle. Statistical analysis was performed using a factorial ANOVA. Time to exhaustion of the EX-O group was 20% higher (515 ± 3 minutes) when compared with EX group (425 ± 3 minutes) (p = 0.034). For hepatic glycogen, the EX-O group had a 67% higher concentrations when compared with EX (p = 0.022). In the soleus muscle, EX-O group presented a 59.4% higher glycogen concentrations when compared with EX group (p = 0.021). TNF-α was decreased, IL-6, IL-10 and corticosterone increased after exercise, and EX-O presented lower levels of IL-6, IL-10 and corticosterone levels in comparison with EX group. It was concluded that the chow rich in oat bran increase muscle and hepatic glycogen concentrations. The higher glycogen storage may improve endurance performance during training and competitions, and a lower post-exercise inflammatory response can accelerate recovery.

Interleukin-6 signaling in liver-parenchymal cells suppresses hepatic inflammation and improves systemic insulin action

The contribution of interleukin (IL)-6 signaling in obesity-induced inflammation remains controversial. To specifically define the role of hepatic IL-6 signaling in insulin action and resistance, we have generated mice with hepatocyte-specific IL-6 receptor (IL-6R) alpha deficiency (IL-6Ralpha(L-KO) mice). These animals showed no alterations in body weight and fat content but exhibited a reduction in insulin sensitivity and glucose tolerance. Impaired glucose metabolism originated from attenuated insulin-stimulated glucose transport in skeletal muscle and fat. Surprisingly, hepatic IL-6Ralpha-disruption caused an exaggerated inflammatory response during euglycemic hyperinsulinemic clamp analysis, as revealed by increased expression of IL-6, TNF-alpha, and IL-10, as well as enhanced activation of inflammatory signaling such as phosphorylation of IkappaBalpha. Neutralization of TNF-alpha or ablation of Kupffer cells restored glucose tolerance in IL-6Ralpha(L-KO) mice. Thus, our results reveal an unexpected role for hepatic IL-6 signaling to limit hepatic inflammation and to protect from local and systemic insulin resistance.

Effects of resistance training on the inflammatory response

Resistance training (RT) is associated with reduced risk of low grade inflammation related diseases, such as cardiovascular disease and type 2 diabetes. The majority of the data studying cytokines and exercise comes from endurance exercise. In contrast, evidence establishing a relationship between RT and inflammation is more limited. This review focuses on the cytokine responses both following an acute bout, and after chronic RT. In addition, the effect of RT on low grade systemic inflammation such as individuals at risk for type 2 diabetes is reviewed. Cytokines are secreted proteins that influence the survival, proliferation, and differentiation of immune cells and other organ systems. Cytokines function as intracellular signals and almost all cells in the body either secrete them or have cytokine receptors. Thus, understanding cytokine role in a specific physiological situation such as a bout of RT can be exceedingly complex. The overall effect of long term RT appears to ameliorate inflammation, but the specific effects on the inflammatory cytokine, tumor necrosis factor alpha are not clear, requiring further research. Furthermore, it is critical to differentiate between chronically and acute Interleukin-6 levels and its sources. The intensity of the RT and the characteristics of the training protocol may exert singular cytokine responses and as a result different adaptations to exercise. More research is needed in the area of RT in healthy populations, specifically sorting out gender and age RT acute responses. More importantly, studies are needed in obese individuals who are at high risk of developing low grade systemic inflammatory related diseases. Assuring adherence to the RT program is essential to get the benefits after overcoming the first acute RT responses. Hence RT could be an effective way to prevent, and delay low grade systemic inflammatory related diseases.

Oxidative stress and inflammatory parameters after an Ironman race

OBJECTIVE

The aim of the present study was to investigate oxidative stress markers and inflammatory response in triathletes after an Ironman race (IR).

DESIGN

Descriptive research.

PARTICIPANTS

Eighteen well-trained male triathletes (mean age, 34.7 +/- 2.15 years; weight, 69.3 +/- 1.9 kg; height, 1.81 +/- 0.58 cm) participated in the study.

SETTING

Ironman Triathlon (3.8-km swim, 180-km cycle, 42.2-km run). Mean environmental conditions ranged from 20 to 25 degrees C and from 79% to 85% relative humidity.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

Before the race and up to 20 minutes after completing the full race, the weights and heights of volunteers were measured and a 10 mL blood sample was drawn from an antecubital vein. Aliquots of washed/lysed red blood cells and plasma/serum samples were stored at -80 degrees C. Lipid peroxidation, protein carbonylation, superoxide dismutase and catalase activities, and cytokines levels [tumor necrosis factor alpha (TNF-alpha), interleukin (IL)-6, IL-10, and IL-1ra] were determined.

RESULTS

After the IR, the results showed a significant increase in TBARS levels (prerace = 1.15 +/- 0.11; postrace = 1.98 +/- 0.27), lipid hydroperoxide content (prerace = 0.75 +/- 0.03; postrace = 1.46 +/- 0.18), protein carbonylation (prerace = 0.67 +/- 0.12; postrace = 2 0.15 +/- 0.60), superoxide dismutase (prerace = 2.67 +/- 0.62; postrace = 3.97 +/- 1.48), and catalase (prerace = 1.48 +/- 0.18; postrace = 2.84 +/- 0.39). TNF-alpha, IL-6, and IL-10 were not detected at basal conditions, but all markers were significantly increased after the IR (TNF-alpha: prerace = ND and postrace = 67.47 +/- 10.34; IL-6: prerace = ND and postrace = 55.41 +/- 3.45; IL-10: prerace = ND and postrace = 122.53 +/- 9.69; IL-1ra: prerace = 127.79 +/- 25.65 and postrace = 259.51 +/- 32.9).

CONCLUSIONS

An Ironman race provokes significant alterations in oxidative stress and inflammatory parameters. Thus, more studies with other markers and different designs are needed to elucidate the cellular alterations induced by an IR.

Serum biomarkers as signals for risk and severity of work-related musculoskeletal injury

Work-related musculoskeletal disorders (MSDs) have accounted for a significant proportion of work injuries and workers' compensation claims in industrialized nations since the late 1980s. Despite epidemiological evidence for the role of repetition and force in the onset and progression of work-related MSDs, complete understanding of these important occupational health problems requires further elucidation of the underlying pathogenesis. Results from several clinical and experimental studies indicate that pathological and/or adaptive tissue changes occur as a consequence of performing repetitive and/or forceful tasks. Here, we review evidence of these tissue changes as revealed by the testing of serum biomarkers. Biomarkers of inflammation (inflammatory cytokines and C-reactive protein), cell stress or injury (malondialdehyde and creatine kinase), and collagen synthesis and degradation (collagen I carboxy-terminal propeptide and type-I collagen cross-linked C-telopeptide, respectively) and their association with MSDs will be reviewed.

Suppression of exercise-induced neutrophilia and lymphopenia in athletes by cystine/theanine intake: a randomized, double-blind, placebo-controlled trial

BACKGROUND

Intense exercise induces increased blood neutrophil counts and decreased lymphocyte counts, and leads to inflammation and immunosuppression. It was previously reported that cystine and theanine (CT) supplementation by long-distance runners before a training camp suppressed the changes of these blood parameters observed in un-supplemented control subjects after the camp. The purpose of the present study was to determine the effects of CT supplementation on the inflammatory response and immune state before and after intense endurance exercise in long-distance runners at a training camp.

METHODS

Sixteen long-distance runners were allocated to one of two groups given CT supplements (700 mg cystine + 280 mg theanine daily) or placebo (8 in each group) for 7 days prior to and during a 9-day training camp. Daily run training averaged 19.9 km/day prior to the camp and 28.6 km/day during the camp. On the initial and final days of the camp, blood samples were collected before and after 15 km morning interval running workouts (1000 m x 15 times) and analyzed for neutrophil and lymphocyte counts and myoglobin.

RESULTS

The relative change in exercise-induced blood neutrophil count (% of pre-exercise values) was significantly lower in the CT group than in the placebo group (163.3 +/- 43.2% vs. 200.4 +/- 19.6%, p = 0.044) on the initial day of camp, but not on the last day. The decline in lymphocyte count (% of pre-exercise values) was significantly less in the CT group than in the placebo group (60.2 +/- 19.2% vs. 36.2 +/- 12.0%, p = 0.010) on the initial day of camp, but not on the last day. In blood myoglobin, there was a trend toward lower % of pre-exercise values in the CT group (p < 0.09) on both measurement days.

CONCLUSION

CT supplementation significantly attenuated the increase in neutrophil count and the reduction in lymphocyte count induced by intense endurance exercise. These results suggest that CT supplementation may suppress the exercise-induced fluctuation of the blood immunocompetent cells and may help to reduce the alteration of the immune state.

C2C12 myoblasts release micro-vesicles containing mtDNA and proteins involved in signal transduction

Micro-vesicles can be released by different cell types and operate as 'safe containers' mediating inter-cellular communication. In this work we investigated whether cultured myoblasts could release exosomes. The reported data demonstrate, for the first time, that C2C12 myoblasts release micro-vesicles as shown by the presence of two exosome markers (Tsg101 and Alix proteins). Using real-time PCR analysis it was shown that these micro-vesicles, like other cell types, carry mtDNA. Proteomic characterization of the released micro-vesicle contents showed the presence of many proteins involved in signal transduction. The bioinformatics assessment of the Disorder Index and Aggregation Index of these proteins suggested that C2C12 micro-vesicles mainly deliver the machinery for signal transduction to target cells rather than key proteins involved in hub functions in molecular networks. The presence of IGFBP-5 in the purified micro-vesicles represents an exception, since this binding protein can play a key role in the modulation of the IGF-1 signalling pathway. In conclusion, the present findings demonstrate that skeletal muscle cells release micro-vesicles, which probably have an important role in the communication processes within skeletal muscles and between skeletal muscles and other organs. In particular, the present findings suggest possible new diagnostic approaches to skeletal muscle diseases.

Calcineurin activates interleukin-6 transcription in mouse skeletal muscle in vivo and in C2C12 myotubes in vitro

Expression of the cytokine interleukin-6 (IL-6) by skeletal muscle is hugely increased in response to a single bout of endurance exercise, and this appears to be mediated by increases in intracellular calcium. We examined the effects of endurance exercise on IL-6 mRNA levels and promoter activity in skeletal muscle in vivo, and the role of the calcium-activated calcineurin signaling pathway on muscle IL-6 expression in vivo and in vitro. IL-6 mRNA levels in the mouse tibialis anterior (TA) were increased 2-10-fold by a single bout of treadmill exercise or by 3 days of voluntary wheel running. Moreover, an IL-6 promoter-driven luciferase transgene was activated in TA by both treadmill and wheel-running exercise and by injection with a calcineurin plasmid. Exercise also increased muscle mRNA expression of the calcineurin regulatory gene MCIP1, as did treatment of C(2)C(12) myotubes with the calcium ionophore A23187. Cotransfection of C(2)C(12) myotubes with a constitutively active calcineurin construct significantly increased while cotransfection with the calcineurin inhibitor CAIN inhibited activity of a mouse IL-6 promoter-reporter construct. Cotransfection with a myocyte enhancer-factor-2 (MEF-2) expression construct increased basal IL-6 promoter activity and augmented the effects of calcineurin cotransfection, while cotransfection with the MEF-2 antagonist MITR repressed calcineurin-activated IL-6 promoter activity in vitro. Surprisingly, cotransfection with a dominant-negative form of another calcineurin-activated transcription factor, nuclear factor activator of T cells (NFAT), greatly potentiated both basal and calcineurin-stimulated IL-6 promoter activity in C(2)C(12) myotubes. Mutation of the MEF-2 DNA binding sites attenuated, while mutation of the NFAT DNA binding sites potentiated basal and calcineurin-activated IL-6 promoter activity. Finally, CREB and C/EBP were necessary for basal IL-6 promoter activity and sufficient to increase IL-6 promoter activity but had minimal roles in calcineurin-activated IL-6 promoter activity. Together, these results suggest that IL-6 transcription in skeletal muscle cells can be activated by a calcineurin-MEF-2 axis which is antagonized by NFAT.

Gene expression profile of mouse masseter muscle after repetitive electrical stimulation

PURPOSE

To examine gene expression profile changes in the mouse masseter muscle tissue after repetitive electrical stimulation by using a DNA microarray technique.

METHODS

Nine male ICR mice aged 10 weeks were used. Each anesthetized mouse was secured on a platform in a supine position and the masseter muscle tissues on both sides were exposed. Bipolar electrodes were set on the right masseteric fascia to electrically stimulate the masseter muscle (8 V, 10 Hz, 20 ms) for 30 min. After cessation of stimulation bilateral masseter muscle tissues were sampled at 0 h (n=3), 1h (n=3), 2h (n=3). Total RNA was isolated from the homogenized muscle tissues and purified mRNA samples (50 microg) were processed and hybridized with microarray slides. Probe arrays were then scanned and analyzed to calculate the signal density. Gene expression profiles were compared at each time point between the right (stimulation side) and left (control side) masseter. When the gene expression levels were different more than 2-fold, the difference was regarded as positive.

RESULTS

Of the 6400 genes assessed, 1733 genes were up-regulated and 515 genes were down-regulated in the stimulation side at least once during the experimental time course. These up- or down-regulated genes were associated with autoimmune/inflammatory disease (28/114), cardiovascular disease (17/61), neuroscience (12/50), apoptosis (27/93), diabetes/obesity (9/28), signal transduction (66/250) and others. 28 genes were up-regulated and 25 genes were down-regulated at all time points.

CONCLUSIONS

Dramatic gene expression changes were induced by the repetitive electrical muscle stimulation in mouse masseter.

Pancreatic islet inflammation in type 2 diabetes: from alpha and beta cell compensation to dysfunction

Evidence in support of the concept of local pancreatic islet inflammation as a mechanism of beta cell failure in type 2 diabetes is accumulating. Observations in human islets from type 2 diabetic patients and rodent models of the disease indicate the increased presence of IL-1 driven cytokines and chemokines in pancreatic islets, concomitant with immune cell infiltration. Inflammation is the body's protective response to harmful stimuli and tissue damage. However, under chronic stress (e.g. metabolic stress in obesity and type 2 diabetes) the body's own defensive response may become deleterious to tissue function. Here, we summarize the current evidence that islet inflammation is a feature of type 2 diabetes, and discuss its role with respect to alpha and beta cell compensation and eventual beta cell failure.

Identification of secreted proteins associated with obesity and type 2 diabetes in Psammomys obesus

OBJECTIVE

Skeletal muscle produces a variety of secreted proteins that have important roles in intercellular communication and affects processes such as glucose homoeostasis. The objective of this study was to develop a novel Signal Sequence Trap (SST) in conjunction with cDNA microarray technology to identify proteins secreted from skeletal muscle of Psammomys obesus that were associated with obesity and type 2 diabetes (T2D).

DESIGN

Secreted proteins that were differentially expressed between lean, normal glucose tolerant (NGT), overweight and impaired glucose tolerant (IGT) and obese, T2D P. obesus were isolated using SST in conjunction with cDNA microarray technology. Subsequent gene expression was measured in tissues from P. obesus by real-time PCR (RT-PCR).

RESULTS

The SST yielded 1600 positive clones, which were screened for differential expression. A total of 91 (approximately 6%) clones were identified by microarray to be differentially expressed between NGT, IGT and T2D P. obesus. These clones were sequenced to identify 51 genes, of which only 27 were previously known to encode secreted proteins. Three candidate genes not previously associated with obesity or type 2 diabetes, sushi domain containing 2, collagen and calcium-binding EGF domains 1 and periostin (Postn), as well as one gene known to be associated, complement component 1, were shown by RT-PCR to be differentially expressed in skeletal muscle of P. obesus. Further characterization of the secreted protein Postn revealed it to be predominantly expressed in adipose tissue, with higher expression in visceral compared with subcutaneous adipose depots.

CONCLUSION

SST in conjunction with cDNA microarray technology is a powerful tool to identify differentially expressed secreted proteins involved in complex diseases such as obesity and type 2 diabetes. Furthermore, a number of candidate genes were identified, in particular, Postn, which may have a role in the development of obesity and type 2 diabetes.

Effect of prior exercise on postprandial lipemia and markers of inflammation and endothelial activation in normal weight and overweight adolescent boys

Postprandial lipemia (PPL) is associated with impaired endothelial function and inflammation. Acute exercise reduces PPL in adults. This investigation examined the effect of an acute bout of exercise on postprandial changes in triglycerides (TG), glucose, insulin, inflammation [white blood cell count (WBC), interleukin-6 (IL-6) tumor necrosis factor-alpha, C-reactive protein (CRP)] and endothelial activation [soluble intercellular adhesion molecule-1 (sICAM-1), vascular adhesion molecule-1 (sVCAM-1)] following a high-fat meal in adolescents. Ten normal weight (NW) (BMI, 20.9 +/- 1.7 kg m(-2); 15.6 +/- 0.7 years) and eight overweight (OW) (BMI, 28.3 +/- 3.6 kg m(-2); 15.9 +/- 0.4 years) adolescent boys underwent two 6-h oral fat tolerance tests (OFTT) separated by 7-10 days. On the evening prior to each OFTT, subjects either rested or completed a treadmill exercise bout (65% V(O)(2max); 600 kcal expended). Exercise reduced (P < 0.01) the postprandial TG area under the curve by approximately 20% in the NW and OW groups. The postprandial glucose and insulin response did not differ between the control and exercise trials or between the NW and OW groups. Circulating leukocytes and plasma IL-6 levels increased (P < 0.01) in the NW and OW groups 6 h following the OFTT in both experimental conditions. There were no changes in CRP, sVCAM-1 or sICAM-1 following the OFTT and there were no differences between experimental condition or NW and OW groups. In conclusion, a moderate exercise bout prior to a high-fat meal effectively reduces postprandial TG concentrations to a similar degree in both NW and OW adolescents, but does not reduce the concomitant postprandial increase in WBC or IL-6.

The effect of a brief sprint interval exercise on growth factors and inflammatory mediators

Exercise training efficiency depends on the intensity, volume, duration, and frequency of training, as well as on the athlete's ability to tolerate it. Recent efforts to quantify the effects of aerobic exercise training on hormonal response have suggested that exercise leads to simultaneous changes of antagonistic mediators. The effects of anaerobic exercise on these mediators are not known. Therefore, the aim of the present study was to evaluate the effects of a brief sprint interval session on the balance between anabolic (growth hormone [GH]--> insulin-like growth factor [IGF]-I axis) and catabolic hormones (cortisol), and circulating inflammatory cytokines such as interleukin (IL)-6. Twelve healthy elite junior handball players (17-20 years) participated in the study. Exercise consisted of a 4 x 250-m run on a treadmill, at a constant intensity of 80% of the personal maximal speed. Each run was separated by 3 minutes of rest. Blood samples were collected before, immediately after each 250-m run, and 1 hour after the last run. Exercise led to significant increases in GH (0.3 +/- 0.2 to 5.1 +/- 2.2 ngxml, p < 0.05), IGF binding protein (IGFBP)-3 (4191 +/- 2.48 to 4875 +/- 301 ngxml, p < 0.05), IL-6 (1.3 +/- 0.2 to 2.1 +/- 0.3 pgxml, p < 0.002), testosterone, and testosterone/cortisol ratio, and to a significant decrease in IGFBP-1 levels. Levels of IL-6 remained elevated 1 hour after the end of exercise. Exercise had no significant effects on IGF-I and cortisol levels. Changes in the GH-IGF-I axis and testosterone/cortisol ratio after the brief sprint interval exercise suggested exercise-related anabolic adaptations. The increase in IL-6 may indicate its important role in muscle tissue repair after anaerobic exercise. Changes in the anabolic-catabolic hormonal balance and in inflammatory mediators can be used as an objective tool to gauge the training intensity of different types of anaerobic exercises and training periods.

Developing biologically-based assessment tools for physical therapy management of neck pain

SYNOPSIS

Neck pain is a common and episodic condition that is treated using a spectrum of interventions known to be moderately effective but is associated with a significant incidence of chronic pain. Recently, there has been increased focus on defining biological aspects of neck pain. Studies have indicated that neurophysiological, biomechanical, and motor control abnormalities are present and may be useful either in prognosis or classification. We review some of these findings in the context of our own work defining biological markers that may form the basis for clinical tests that can be used for prognosis, classification, or outcome evaluation in patients with neck pain. We have identified abnormalities in neurophysiology using quantitative sensory testing (vibration, touch, and current perception) and response to cold provocation that are related to neck disability. We have identified altered muscle biochemistry by measuring circulating muscle proteins in a lumbar surgery model and are now applying those methods to whiplash injury. We have incorporated capnography into treatment to address central physiological changes present in some patients by monitoring and training CO2 levels. We have developed an innovative new test, the Neck Walk Index, that captures abnormal control of head movement during slow gait as a means of differentiating patients with neck pain from either unaffected controls or individuals with other pathologies. We have used time-varying 3-dimensional joint orientation kinematics to assess deficits in motor control during an upper extremity reach task, the results showing that poor coordination and control of the shoulder girdle leads to shoulder guarding and inconsistencies in elbow joint movement. Despite some promising early results, future research is needed to determine how these measures help clinicians to diagnose, evaluate, and forecast future outcome for patients who present with neck pain.

LEVEL OF EVIDENCE

Diagnosis, level 5.

Muscle as an endocrine organ: focus on muscle-derived interleukin-6

Skeletal muscle has recently been identified as an endocrine organ. It has, therefore, been suggested that cytokines and other peptides that are produced, expressed, and released by muscle fibers and exert paracrine, autocrine, or endocrine effects should be classified as "myokines." Recent research demonstrates that skeletal muscles can produce and express cytokines belonging to distinctly different families. However, the first identified and most studied myokine is the gp130 receptor cytokine interleukin-6 (IL-6). IL-6 was discovered as a myokine because of the observation that it increases up to 100-fold in the circulation during physical exercise. Identification of IL-6 production by skeletal muscle during physical activity generated renewed interest in the metabolic role of IL-6 because it created a paradox. On one hand, IL-6 is markedly produced and released in the postexercise period when insulin action is enhanced but, on the other hand, IL-6 has been associated with obesity and reduced insulin action. This review focuses on the myokine IL-6, its regulation by exercise, its signaling pathways in skeletal muscle, and its role in metabolism in both health and disease.

Short-term beta-adrenergic regulation of leptin, adiponectin and interleukin-6 secretion in vivo in lean and obese subjects

AIM

Adipose tissue and skeletal muscle are endocrine organs, secreting substances that have been implicated in obesity-related disorders. This study examined short-term beta-adrenergic regulation of circulating leptin, adiponectin and interleukin-6 (IL-6) concentrations and secretion from abdominal subcutaneous adipose tissue and muscle (IL-6) in vivo in lean and obese subjects.

METHODS

Systemic concentrations and net fluxes of leptin, adiponectin and IL-6 across abdominal subcutaneous adipose tissue and forearm skeletal muscle (IL-6) were assessed before and during beta-adrenergic stimulation (intravenous isoprenaline infusion) in 13 lean and 10 obese men.

RESULTS

Basal circulating leptin concentrations were higher in the obese (p < 0.001), while circulating adiponectin (p = 0.45) and IL-6 concentrations (p = 0.41) were not different between groups. beta-Adrenergic stimulation decreased leptin concentrations in both groups (p < 0.01), but did not reduce net abdominal subcutaneous adipose tissue leptin release. Increased leptin clearance and/or decreased leptin secretion from other fat depots may explain the reduction in leptin concentrations. Adiponectin concentrations remained unchanged during beta-adrenergic stimulation in both groups. beta-Adrenergic stimulation increased IL-6 concentration, which was more pronounced in the obese (p = 0.01 vs. lean). This cannot be explained by increased IL-6 release per unit abdominal subcutaneous adipose tissue and muscle but might be because of the increased fat mass and fat-free mass at whole-body level.

CONCLUSIONS

Short-term beta-adrenergic stimulation decreases leptin concentrations, which cannot be explained by reduced net leptin release from abdominal subcutaneous adipose tissue, while it elevates IL-6 concentration partly by increased release from this fat depot and muscle. Finally, beta-adrenergic stimulation has no short-term regulatory role in adiponectin secretion.

Exercise and brain health--implications for multiple sclerosis: Part II--immune factors and stress hormones

Part I of this review addressed the possible modulatory role of exercise on neuronal growth factors to promote brain health in neurodegenerative diseases such as multiple sclerosis (MS), which is characterized by varied patterns of inflammation, demyelination and axonal loss. Part II presents evidence that supports the potential neuroprotective effect of exercise on the modulation of immune factors and stress hormones in MS. Many current therapies used to attenuate MS progression are mediated, at least in part, through alterations in the relative concentrations of pro- and anti-inflammatory cytokines. Exercise-induced alterations in local and systemic cytokine production may also benefit immune function in health and disease. Exercise immunomodulation appears to be mediated by a complex interaction of hormones, cytokines and neural factors that may favorably influence immune variables in MS. The promising interplay between exercise and brain health in MS deserves further investigation.

Response of plasma IL-6 and its soluble receptors during submaximal exercise to fatigue in sedentary middle-aged men

The pleiotropic cytokine interleukin-6 (IL-6) has been demonstrated to increase during exercise. Little is known regarding the response of the soluble IL-6 receptors (sIL-6R and sgp130) during such exercise. The aim of the current study was to investigate the response of plasma IL-6, sIL-6R and sgp130 during fatiguing submaximal exercise in humans. Twelve participants underwent an incremental exercise test to exhaustion and one week later performed a submaximal exercise bout (96 +/- 6% lactate threshold) to volitional exhaustion. Blood samples taken at rest and immediately post exercise were analyzed for IL-6, sIL-6R and sgp130. IL-6 increased (P < 0.01) by 8.4 +/- 8.9 pg ml(-1) (75.7%) during the exercise period. sIL-6R and sgp130 also increased (P < 0.05) by 2.7 +/- 3.9 ng ml(-1) (9.6%) and 37.7 +/- 55.6 ng ml(-1) (9.6%), respectively. The current study is the first investigation to demonstrate that alongside IL-6, acute exercise stress results in an increase in both sIL-6R and sgp130.

Dietary ALEs are a risk to human health--NOT!

Advanced lipoxidation end-products (ALEs) are formed by reaction of protein with lipid-derived reactive peroxyl and carbonyl compounds produced during food processing and cooking. There is concern that ALEs may induce damage in the gastrointestinal tract, affecting gut health, or enter the body and promote vascular inflammation and tissue damage. However, there is no direct evidence that ALE-proteins are a source of damage in the intestines or that they are transported into the circulation and cause pathology. Modification of proteins by ALEs impedes their digestion, and reactive ALEs released by gastrointestinal proteases would react with proteins or peptides in the gut, limiting their absorption. There are also potent enzymatic mechanisms for detoxifying ALEs or their precursors prior to their entry into the circulation. If ALEs gain access to the circulation, a battery of protective enzymes in tissue provides a second level of defense. These enzymes may be induced in intestinal epithelia and liver by low doses of ALEs, and adaptive responses would provide enhanced protection against future exposure to ALEs. Overall, except in persons with compromised organ function, e. g., vascular, hepatic, or renal diseases, there is little evidence that food ALEs will have any significant pathological effects.

Cytokine response to strenuous exercise in athletes and non-athletes--an adaptive response

Exercise and physical strenuous activity have been demonstrated to increase the serum TNF-alpha and IL-6. Regular physical training is expected to attenuate such a response. This study was undertaken to understand the impact of regular exercise training on IL-6 and TNF-alpha in athletes and non-athletes. Ten athletes, who have been on regular training for the past 6 months, and 10 age- and sex-matched subjects (non-athlete group) who had no practice of regular exercise, were recruited. Both were subjected to undergo the same frequency level of strenuous exercise. Blood samples were collected; one before strenuous exercise and the other after the exercise. Plasma cytokines, IL-6 and TNF-alpha, were estimated using Sandwich ELISA method. All participants in the study were male with the athletes' age being 18.00+/-1.3years (mean+/-SD) and the non-athletes were aged 20.00+/-0.6years (mean+/-SD). Majority of the athletes and non-athletes demonstrated a rise in IL-6 and a fall in TNF-alpha levels. Further, the athletes showed a lesser magnitude of change in the cytokine levels following a longer duration of exercise than non-athletes. Athletes appear to have an attenuated cytokine response. Regular physical training has been demonstrated to attenuate the immune response to exercise in either direction.

State of the Art Reviews: Health Benefits Related to Exercise in Patients With Chronic Low-Grade Systemic Inflammation

Today, there is substantial evidence to suggest that regular exercise has health-promoting effects, which are beyond its effect on weight control. Regular exercise offers protection against all-cause mortality, and there is evidence from randomized intervention studies that physical training is effective as a treatment in patients with chronic heart diseases, type 2 diabetes, and symptoms related with the metabolic syndrome. Chronic diseases such as cardiovascular disease and type 2 diabetes are associated with chronic low-grade systemic inflammation. This review focuses on the anti-inflammatory effects of exercise that are mediated by muscle-derived cytokines (myokines). It is suggested that myokines may be involved in mediating the health-beneficial effects of exercise and that these in particular are involved in the protection against chronic diseases associated with low-grade inflammation.

Physical Activity, Growth, and Inflammatory Mediators in BMI-Matched Female Adolescents

PURPOSE

Physical inactivity is deleterious to health, but it has been difficult to determine the extent to which these effects are attributable to abnormal body composition or to factors related to physical activity alone. To begin to gauge independent effects of physical activity on health risk, we matched by BMI two groups of normal-weight adolescent females, one physically active (all participants in high school sports), and one sedentary.

METHODS

Thirty-seven sedentary and 37 physically active adolescent females (mean 15.5 yr) were matched for age and BMI percentile (mean = 58.8). Comparisons included fitness, body composition and bone mineralization (by DEXA), circulating inflammatory cytokines, growth factors, bone-turnover markers, leptin, and adiponectin.

RESULTS

Compared with the normal-weight sedentary girls, active girls had significantly (P < 0.05) higher fitness level (peak VO2 35.5 +/- 5.2 vs 24.4 +/- 4.1 mL.kg(-1).min(-1)), lean body mass (43.2 +/- 4.4 vs 38.7 +/- 3.6 kg), bone mineralization (spinal BMD z-scores 0.04 +/- 0.88 vs -0.41 +/- 0.85), and lower percent body fat (25.4 +/- 04.6 vs 29.7 +/- 03.7%). Additionally, active girls had lower inflammatory cytokines levels (e.g., TNF-alpha 1.7 +/- 1.3 vs 2.6 +/- 2.2 pg.mL(-1)), and leptin (17.4 +/- 11.2 vs 24.7 +/- 14.7 ng.mL(-1)), and higher bone-turnover markers (e.g. osteocalcin 12.6 +/- 7.6 vs 7.8 +/- 3.0 U.L(-1)), IGFBP-3 (6416 +/- 21280 vs 4247 +/- 1082 ng.mL(-1)), and adiponectin levels (11919 +/- 3935 vs 9305 +/- 2843 ng.mL(-1)).

CONCLUSION

The normal-weight, physically active group was fitter and had greater lean body mass, stronger bones, and lower levels of inflammatory markers than did the normal-weight, sedentary group. In adolescent girls, the choice of a lifestyle involving high school sports is characterized by a circulating mediator and body composition pattern that, if sustained, is associated with generally lower long-term risk of cardiovascular disease and osteoporosis.

Inflammatory process in type 2 diabetes: The role of cytokines

Population-based studies have shown strong relationship between inflammatory markers and metabolic disturbances, obesity, and atherosclerosis, whereas inflammation has been considered as a "common soil" between these clinical entities and type 2 diabetes (T2D). The accumulation of macrophages in adipose tissue (AT), the common origin of macrophages and adipocytes, the prevalent presence of peripheral mononuclear cells, and apoptotic beta cells by themselves seem to be the sources of inflammation present in T2D, since they generate the mediators of the inflammatory processes, namely cytokines. The main cytokines involved in the pathogenesis of T2D are interleukin-1beta (IL-1beta), with an action similar to the one present in type 1 diabetes, tumor necrosis factor-alpha (TNF-alpha), and IL-6, considered as the main regulators of inflammation, leptin, more recently introduced, and several others, such as monocyte chemoattractant protein-1, resistin, adiponectin, with either deleterious or beneficial effects in diabetic pathogenesis. The characterization of these molecules targeted diabetes treatment beyond the classical interventions with lifestyle changes and pharmaceutical agents, and toward the determination of specific molecular pathways that lead to low grade chronic inflammatory state mainly due to an immune system's unbalance.

Role of myokines in exercise and metabolism

During the past 20 yr, it has been well documented that exercise has a profound effect on the immune system. With the discovery that exercise provokes an increase in a number of cytokines, a possible link between skeletal muscle contractile activity and immune changes was established. For most of the last century, researchers sought a link between muscle contraction and humoral changes in the form of an "exercise factor," which could mediate some of the exercise-induced metabolic changes in other organs such as the liver and the adipose tissue. We suggest that cytokines and other peptides that are produced, expressed, and released by muscle fibers and exert either paracrine or endocrine effects should be classified as "myokines." Since the discovery of interleukin (IL)-6 release from contracting skeletal muscle, evidence has accumulated that supports an effect of IL-6 on metabolism. We suggested that muscle-derived IL-6 fulfils the criteria of an exercise factor and that such classes of cytokines should be named "myokines." Interestingly, recent research demonstrates that skeletal muscles can produce and express cytokines belonging to distinctly different families. Thus skeletal muscle has the capacity to express several myokines. To date the list includes IL-6, IL-8, and IL-15, and contractile activity plays a role in regulating the expression of these cytokines in skeletal muscle. The present review focuses on muscle-derived cytokines, their regulation by exercise, and their possible roles in metabolism and skeletal muscle function and it discusses which cytokines should be classified as true myokines.

The biology of obesity

Obesity is a multidisciplinary area, the ‘biology’ of which encompasses: (1) the fundamental mechanisms of energy balance and its regulation; (2) the biological basis for the development of obesity; (3) adipose tissue function; (4) the biological description of the obese state; (5) the pathological consequences of obesity; (6) the physiological basis for treatment strategies. At a mechanistic level, important developments in recent years include the identification of novel neuroendocrine factors in the control of appetite (such as cocaine- and amphetamine-regulated transcript, the orexins, the endocannabinoids) and the discovery of new peripheral signals (such as leptin, ghrelin). Despite the identification of additional uncoupling proteins (UCP2, UCP3), mitochondrial uncoupling in brown adipose tissue through UCP1 remains the only major mechanism for adaptive thermogenesis. White adipose tissue (WAT) has now moved centre stage in energy balance and obesity research, and there are three main reasons: (1) it is the organ which defines obesity; (2) it is the source of a critical endocrine signal in the control of body weight; (3) it secretes a range of diverse protein factors, termed adipokines, some of which are directly implicated in the pathologies associated with obesity. WAT is now recognised as a key endocrine organ, communicating both with the brain and peripheral tissues through the adipokines. Obesity is characterised by mild inflammation, and WAT may be the main locus of the inflammatory state, producing cytokines, chemokines, acute-phase proteins and angiogenic factors. It has been suggested that inflammation in obesity is principally an adaptive response to hypoxia in clusters of adipocytes within the expanding adipose mass.

Physical activity and health, novel concepts and new targets: report from the 12th Conference of the International Research Group on the Biochemistry of Exercise

The present paper is the introductory paper to a series of brief reviews representing the proceedings of a recent conference on ‘The biochemical basis for the health effects of exercise’ organized by the International Research Group on the Biochemistry of Exercise in conjunction with the Nutrition Society. Here the aim is to briefly review and highlight the main innovations presented during this meeting. The following topics were covered during the meeting: exercise signalling pathways controlling fuel oxidation during and after exercise; the fatty acid transporters of skeletal muscle; mechanisms involved in exercise-induced mitochondrial biogenesis in skeletal muscle; new methodologies and insights in the regulation of fat metabolism during exercise; muscle hypertrophy: the signals of insulin, amino acids and exercise; adipose tissue–liver–muscle interactions leading to insulin resistance. In these symposia state-of-the-art knowledge on how physical exercise exerts its effects on health was presented. The fast-growing number of identified pathways and processes involved in the health effects of physical exercise, which were discussed during the meeting, will help to develop tailored physical-activity regimens in the prevention of inactivity-induced deterioration of health.

An exercise intervention without weight loss decreases circulating interleukin-6 in lean and obese men with and without type 2 diabetes mellitus

Obesity and type 2 diabetes mellitus (T2DM) have been associated with a state of chronic low-grade inflammation. We examined the effect of exercise without weight loss on circulating inflammatory biomarkers in previously sedentary lean men and obese men with and without T2DM. Middle-aged men (8 lean, 8 obese, and 8 obese with T2DM) performed 60 minutes of aerobic exercise 5 times per week for 12 weeks without a reduction in body weight. Subjects underwent a hyperinsulinemic-euglycemic clamp before and after the 12-week exercise program to assess insulin sensitivity. Circulating interleukin-6 (IL-6), plasminogen activator inhibitor-1 (PAI-1), and C-reactive protein concentrations were measured by sandwich enzyme-linked immunosorbent assay before and after the exercise intervention. Body fat was measured using magnetic resonance imaging, and waist circumference was recorded for each subject pre- and postexercise intervention. Waist circumference and plasma IL-6 concentrations were significantly lower (P < .05) after exercise training despite no change in body weight or insulin sensitivity. There were no correlations between insulin sensitivity and IL-6. Fasting plasma PAI-1 concentration was significantly lower in the lean group compared with the obese group both pre- and postexercise intervention (P < .05). There were no changes in C-reactive protein or PAI-1 concentrations after exercise training. A 12-week exercise intervention led to reductions in waist circumference and fasting IL-6 concentrations in previously sedentary lean and obese men with or without T2DM, demonstrating significant changes in clinically relevant diabetes-related parameters despite no change in body weight.

A musculoskeletal model of low grade connective tissue inflammation in patients with thyroid associated ophthalmopathy (TAO): the WOMED concept of lateral tension and its general implications in disease

Background

Low level connective tissue inflammation has been proposed to play a role in thyroid associated ophthalmopathy (TAO). The aim of this study was to investigate this postulate by a musculoskeletal approach together with biochemical parameters.

Methods

13 patients with TAO and 16 controls were examined. Erythrocyte levels of Zn, Cu, Ca²⁺, Mg, and Fe were determined. The musculoskeletal evaluation included observational data on body posture with emphasis on the orbit-head region. The angular foot position in the frontal plane was quantified following gait observation. The axial orientation of the legs and feet was evaluated in an unloaded supine position. Functional propioceptive tests based on stretch stimuli were done by using foot inversion and foot rotation.

Results

Alterations in the control group included neck tilt in 3 cases, asymmetrical foot angle during gait in 2, and a reaction to foot inversion in 5 cases. TAO patients presented facial asymmetry with displaced eye fissure inclination (mean 9.1°) as well as tilted head-on-neck position (mean 5.7°). A further asymmetry feature was external rotation of the legs and feet (mean 27°). Both foot inversion as well as foot rotation induced a condition of neuromuscular deficit. This condition could be regulated by gentle acupressure either on the lateral abdomen or the lateral ankle at the acupuncture points gall bladder 26 or bladder 62, respectively. In 5 patients, foot rotation produced a phenomenon of moving toes in the contra lateral foot. In addition foot rotation was accompanied by an audible tendon snapping. Lower erythrocyte Zn levels and altered correlations between Ca²⁺, Mg, and Fe were found in TAO.

Conclusion

This whole body observational study has revealed axial deviations and body asymmetry as well as the phenomenon of moving toes in TAO. The most common finding was an arch-like displacement of the body, i.e. eccentric position, with foot inversion and head tilt to the contra lateral side and tendon snapping. We propose that eccentric muscle action over time can be the basis for a low grade inflammatory condition. The general implications of this model and its relations to Zn and Se will be discussed.

The anti-inflammatory effect of exercise: its role in diabetes and cardiovascular disease control

Chronic low-grade systemic inflammation is a feature of chronic diseases such as cardiovascular disease and type 2 diabetes. Regular exercise offers protection against all-cause mortality, primarily by protection against atherosclerosis and insulin resistance and there is evidence that physical training is effective as a treatment in patients with chronic heart diseases and type 2 diabetes. Regular exercise induces anti-inflammatory actions. During exercise, IL-6 (interleukin-6) is produced by muscle fibres. IL-6 stimulates the appearance in the circulation of other anti-inflammatory cytokines such as IL-1ra (interleukin-1 receptor antagonist) and IL-10 (interleukin-10) and inhibits the production of the pro-inflammatory cytokine TNF-alpha (tumour necrosis factor-alpha). In addition, IL-6 enhances lipid turnover, stimulating lipolysis as well as fat oxidation. It is suggested that regular exercise induces suppression of TNF-alpha and thereby offers protection against TNF-alpha-induced insulin resistance. Recently, IL-6 was introduced as the first myokine, defined as a cytokine, that is produced and released by contracting skeletal muscle fibres, exerting its effects in other organs of the body. Myokines may be involved in mediating the beneficial health effects against chronic diseases associated with low-grade inflammation such as diabetes and cardiovascular diseases.