Systemic vs. local cytokine and leukocyte responses to unilateral wrist flexion exercise

Effect of chronic stress on tumorigenesis and development

Chronic stress activates the sympathetic nervous system (SNS) and hypothalamic-pituitary-adrenal (HPA) axis to aggravates tumorigenesis and development. Although the importance of SNS and HPA in maintaining homeostasis has already attracted much attention, there is still a lot remained unknown about the molecular mechanisms by which chronic stress influence the occurrence and development of tumor. While some researches have already concluded the mechanisms underlying the effect of chronic stress on tumor, complicated processes of tumor progression resulted in effects of chronic stress on various stages of tumor remains elusive. In this reviews we concluded recent research progresses of chronic stress and its effects on premalignancy, tumorigenesis and tumor development, we comprehensively summarized the molecular mechanisms in between. And we highlight the available treatments and potential therapies for stressed patients with tumor.

The Systemic Effects of Exercise on Regulators of Muscle and Bone in Girls and Women

PURPOSE

To assess the systemic effects of an acute bout of moderate-intensity exercise on factors that are known to regulate muscle and bone growth in prepubertal girls and women.

METHODS

A total of 12 prepubertal girls (8-10 y) and 12 women (20-30 y) cycled at 60% maximal oxygen uptake for 1 hour followed by 1 hour recovery. Blood samples were collected at rest, mid-exercise, end of exercise, mid-recovery, and end of recovery. Plasma was analyzed for interleukin-6, chemokine ligand 1, fibroblast growth factor-2, total insulin growth factor-1 (IGF-1), and free IGF-1 using enzyme-linked immunosorbent assays assays.

RESULTS

Both groups had similar concentrations of systemic factors at baseline with the exception of free IGF-1, which was higher in girls (P = .001). Interleukin-6 response was lower in girls versus women (P = .04), with a difference of +105.1% at end of exercise (P < .001), +113.5% at mid-recovery (P = .001), and +93.2% at end of recovery (P = .02). Girls and women exhibited significant declines in chemokine ligand 1, fibroblast growth factor-2, and total IGF-1 during recovery.

CONCLUSION

Compared with women, an acute bout of moderate-intensity exercise in girls elicits a lower inflammatory response, suggesting that other mechanisms may be more important for driving the anabolic effects of exercise on muscle and bone in girls.

Acute effect of passive cycle-ergometry and functional electrical stimulation on nitrosative stress and inflammatory cytokines in mechanically ventilated critically ill patients: a randomized controlled trial

Early mobilization is beneficial for critically ill patients because it reduces muscle weakness acquired in intensive care units. The objective of this study was to assess the effect of functional electrical stimulation (FES) and passive cycle ergometry (PCE) on the nitrous stress and inflammatory cytometry in critically ill patients. This was a controlled, randomized, open clinical trial carried out in a 16-bed intensive care unit. The patients were randomized into four groups: Control group (n=10), did not undergo any therapeutic intervention during the study; PCE group (n=9), lower-limb PCE for 30 cycles/min for 20 min; FES group (n=9), electrical stimulation of quadriceps muscle for 20 min; and FES with PCE group (n=7), patients underwent PCE and FES, with their order determined randomly. The serum levels of nitric oxide, tumor necrosis factor alpha, interferon gamma, and interleukins 6 and 10 were analyzed before and after the intervention. There were no differences in clinical or demographic characteristics between the groups. The results revealed reduced nitric oxide concentrations one hour after using PCE (P<0.001) and FES (P<0.05), thereby indicating that these therapies may reduce cellular nitrosative stress when applied separately. Tumor necrosis factor alpha levels were reduced after the PCE intervention (P=0.049). PCE and FES reduced nitric oxide levels, demonstrating beneficial effects on the reduction of nitrosative stress. PCE was the only treatment that reduced the tumor necrosis factor alpha concentration.

Cell adhesion molecules and exercise

Background

An extensive systematic review was undertaken in the current literature in order to explore the role of different types and intensities of exercise in cell adhesion molecules (CAMs), one of the markers of vascular inflammation, endothelial dysfunction, and atherosclerosis.

Methods

Twenty-eight qualifying studies were extensively reviewed to examine the effects of different intensities (low-to-moderate vs. high) and types (aerobic vs. resistance) of exercise on intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and selectins.

Results

Low-to-moderate intensity aerobic exercise favorably decreased CAMs in a variety of subject populations, while CAMs momentarily increased immediately following high-intensity aerobic exercise, which then returned to the pre-exercise level within several hours post-exercise. Resistance exercise, regardless of its intensity, did not significantly influence CAMs.

Conclusion

It is evident that the responses of CAMs are dependent upon the type and intensity of exercise performed. The most common, favorable outcome was a decrease in CAMs following low-to-moderate intensity aerobic exercise, while high-intensity aerobic exercise showed a short-lived, momentary increase in CAMs, which returned to the pre-exercise level within a few hours post-exercise. Resistance exercise, regardless of its intensity, neither significantly increased nor decreased CAMs. Future studies should focus more on the role of exercise in both soluble and membrane-bound CAMs as well as proinflammatory cytokines related to atherosclerosis in order to develop specific exercise programing that can effectively improve vascular inflammation and endothelial health.

Exercise-induced changes in stress hormones and cell adhesion molecules in obese men

Purpose

The current study examined the relationship between exercise-induced changes in stress hormones (epinephrine, norepinephrine, and cortisol) and vascular inflammatory markers (soluble intracellular adhesion molecule-1 [sICAM-1], soluble endothelial selectin [sE-selectin], and soluble vascular adhesion molecule-1 [sVCAM-1]) in obese men over a 24-hour period following exercise at lower and higher intensity.

Patients and methods

Fifteen physically inactive, obese, college-aged men performed a single bout of cycling exercise at lower and higher intensities (lower intensity: 50% of maximal heart rate, and higher intensity: 80% of maximal heart rate) in random order. Overnight fasting blood samples were collected at baseline, immediately postexercise (IPE), 1-hour PE (1-h PE), and 24-hour PE. Changes in stress hormones and inflammatory markers were analyzed with a repeated-measures analysis of variance using Bonferroni multiple comparisons and a linear regression analysis (p<0.05).

Results

sICAM-1, sVCAM-1, epinephrine, and norepinephrine did not change over time, while sE-selectin was significantly lower at 1-h PE (10.25±1.07 ng/mL, p=0.04) than at baseline (12.22±1.39 ng/mL). Cortisol and sICAM-1 were negatively related at 1-h PE following lower-intensity exercise (r²=0.34, p=0.02), whereas cortisol and sVCAM-1 were positively related at IPE following higher-intensity exercise (r²=0.36, p=0.02).

Conclusion

Regardless of intensity, an acute bout of aerobic exercise may lower sE-selectin in sedentary obese men. Responses of cortisol are dependent on exercise intensity, and cortisol may be a key stress hormone playing a major role in regulating sICAM-1 and sVCAM-1.

Experimental intermittent ischemia augments exercise-induced inflammatory cytokine production

Acute exercise-induced inflammation is implicated in mediating the beneficial adaptations to regular exercise. Evidence suggests that reduced oxygen and/or blood flow to contracting muscle alters cytokine appearance. However, the acute inflammatory responses to hypoxic/ischemic exercise have been documented with inconsistent results and may not accurately reflect the ischemia produced during exercise in patients with ischemic cardiovascular diseases. Therefore, we determined the extent to which local inflammation is involved in the response to ischemic exercise. Fourteen healthy males performed unilateral isometric forearm contractions for 30 min with and without experimental ischemia. Blood was drawn at baseline, 5 and 10 min into exercise, at the end of exercise, and 30, 60, and 120 min after exercise. Oxygen saturation levels, as measured by near-infrared spectroscopy, were reduced by 10% and 41% during nonischemic and ischemic exercise, respectively. Nonischemic exercise did not affect cytokine values. Ischemia enhanced concentrations of basic fibroblast growth factor, interleukin (IL)-6, IL-10, tumor necrosis factor-alpha, and vascular endothelial growth factor during exercise, but IL-8 was not influenced by ischemic exercise. In conclusion, the present study demonstrates that ischemic, small-muscle endurance exercise elicits local inflammatory cytokine production compared with nonischemic exercise.

NEW & NOTEWORTHY We demonstrate that ischemic, small-muscle endurance exercise elicits local inflammatory cytokine production compared with nonischemic exercise. The present study advances our knowledge of the inflammatory response to exercise in a partial ischemic state, which may be relevant for understanding the therapeutic effects of exercise training for people with ischemic cardiovascular disease-associated comorbidities.

Oxidative stress and immune system analysis after cycle ergometer use in critical patients

OBJECTIVE:

The passive cycle ergometer aims to prevent hypotrophy and improve muscle strength, with a consequent reduction in hospitalization time in the intensive care unit and functional improvement. However, its effects on oxidative stress and immune system parameters remain unknown. The aim of this study is to analyze the effects of a passive cycle ergometer on the immune system and oxidative stress in critical patients.

METHODS:

This paper describes a randomized controlled trial in a sample of 19 patients of both genders who were on mechanical ventilation and hospitalized in the intensive care unit of the Hospital Agamenom Magalhães. The patients were divided into two groups: one group underwent cycle ergometer passive exercise for 30 cycles/min on the lower limbs for 20 minutes; the other group did not undergo any therapeutic intervention during the study and served as the control group. A total of 20 ml of blood was analysed, in which nitric oxide levels and some specific inflammatory cytokines (tumour necrosis factor alpha (TNF-α), interferon gamma (IFN-γ) and interleukins 6 (IL-6) and 10 (IL-10)) were evaluated before and after the study protocol.

RESULTS:

Regarding the demographic and clinical variables, the groups were homogeneous in the early phases of the study. The nitric oxide analysis revealed a reduction in nitric oxide variation in stimulated cells (p=0.0021) and those stimulated (p=0.0076) after passive cycle ergometer use compared to the control group. No differences in the evaluated inflammatory cytokines were observed between the two groups.

CONCLUSION:

We can conclude that the passive cycle ergometer promoted reduced levels of nitric oxide, showing beneficial effects on oxidative stress reduction. As assessed by inflammatory cytokines, the treatment was not associated with changes in the immune system. However, further research in a larger population is necessary for more conclusive results.

Arterial adaptations to training among first time marathoners

BACKGROUND

Exercise training favorably alters arterial anatomy in trained limbs, though the simultaneous effects on passively trained arteries are unclear. Thus, brachial (non-trained limb), popliteal (trained limb) and carotid total wall thickness (TWT), wall-to-lumen ratios (W:L), intima-media thickness (IMT) and lumen diameters (LD) were compared between experimental (n = 14) and control (n = 11) participants before and after the experimental participants participated in marathon training.

METHODS

Arterial dimensions were measured with B-mode ultrasonography. Initial and final testing of VO2max and running speed at 3.5 mmol lactate were measured in the experimental group.

RESULTS

VO2max was unchanged by training, but running speed at 3.5 mmol lactate increased by 5 % (p = .008). Time by group interactions were observed for the brachial and popliteal measures (p < 0.05), but not the carotid. No changes were observed in the control group. Prior to the intervention the experimental group had larger LD in the brachial (p = .002) and popliteal arteries (p = .007) than controls; no other pre-testing differences were found. Following training, TWT declined in the brachial (pre = .99 ± .16 mm; post = .84 ± .10 mm; p = .007) and popliteal (pre = .96 ± .09 mm; post = .86 ± .11 mm; p = .005) arteries, characterized by a 0.07 mm decrease in brachial IMT (p = .032) and a non-significant 0.03 mm reduction in popliteal IMT. LD increased in the brachial (pre = 3.38 ± .35 mm; post = 3.57 ± .41 mm; p = .015) and popliteal (pre = 4.73 ± .48 mm; post = 5.11 ± .72 mm; p = .002) arteries.

CONCLUSIONS

These data suggest that exercise-induced alterations in arterial dimensions occur in trained and non-trained limbs, and that adaptations may be dose dependent.

The evolving concept of physiological ischemia training vs. ischemia preconditioning

Ischemic heart diseases are the leading cause of death with increasing numbers of patients worldwide. Despite advances in revascularization techniques, angiogenic therapies remain highly attractive. Physiological ischemia training, which is first proposed in our laboratory, refers to reversible ischemia training of normal skeletal muscles by using a tourniquet or isometric contraction to cause physiologic ischemia for about 4 weeks for the sake of triggering molecular and cellular mechanisms to promote angiogenesis and formation of collateral vessels and protect remote ischemia areas. Physiological ischemia training therapy augments angiogenesis in the ischemic myocardium by inducing differential expression of proteins involved in energy metabolism, cell migration, protein folding, and generation. It upregulates the expressions of vascular endothelial growth factor, and induces angiogenesis, protects the myocardium when infarction occurs by increasing circulating endothelial progenitor cells and enhancing their migration, which is in accordance with physical training in heart disease rehabilitation. These findings may lead to a new approach of therapeutic angiogenesis for patients with ischemic heart diseases. On the basis of the promising results in animal studies, studies were also conducted in patients with coronary artery disease without any adverse effect in vivo, indicating that physiological ischemia training therapy is a safe, effective and non-invasive angiogenic approach for cardiovascular rehabilitation. Preconditioning is considered to be the most protective intervention against myocardial ischemia-reperfusion injury to date. Physiological ischemia training is different from preconditioning. This review summarizes the preclinical and clinical data of physiological ischemia training and its difference from preconditioning.

Circulating angiogenic biomolecules at rest and in response to upper-limb exercise in individuals with spinal cord injury

OBJECTIVE

Individuals with spinal cord injury (SCI) show structural and functional vascular maladaptations and muscle loss in their lower limbs. Angiogenic biomolecules play important roles in physiological and pathological angiogenesis, and are implicated in the maintenance of muscle mass. This study examined the responses of angiogenic molecules during upper-limb aerobic exercise in patients with SCI and in able-bodied (AB) individuals.

METHODS

Eight SCI patients with thoracic lesions (T6-T12, ASIA A) and eight AB individuals performed an arm-cranking exercise for 30 minutes at 60% of their VO2max. Plasma concentrations of vascular endothelial growth factor (VEGF-A165), VEGF receptor 1 (sVEGFr-1), VEGF receptor 2 (sVEGFr-2), metalloproteinase 2 (MMP-2), and endostatin were measured at rest, after exercise, and at 1.5 and 3.0 hours during recovery.

RESULTS

The two-way analysis of variance showed non-significant main effects of "group" and significant main effects of "time/exercise" for all angiogenic biomolecules examined (P < 0.01-0.001). The arm-cranking exercise significantly increased plasma concentrations of VEGF, sVEGFr-1, sVEGFr-2, MMP-2, and endostatin in both groups (P < 0.001-0.01). The magnitude of the increase was similar in both patients with SCI and AB individuals, as shown by the non-significant group × time interaction for all angiogenic parameters.

CONCLUSIONS

Upper-limb exercise (arm-cranking for 30 minutes at 60% of VO2max) is a sufficient stimulus to trigger a coordinated circulating angiogenic response in patients with SCI. The response of angiogenic molecules to upper-limb aerobic exercise in SCI appears relatively similar to that observed in AB individuals.

Exercise and type 1 diabetes (T1DM)

Physical exercise is firmly incorporated in the management of type 1 diabetes (T1DM), due to multiple recognized beneficial health effects (cardiovascular disease prevention being preeminent). When glycemic values are not excessively low or high at the time of exercise, few absolute contraindications exist; practical guidelines regarding amount, type, and duration of age-appropriate exercise are regularly updated by entities such as the American Diabetes Association and the International Society for Pediatric and Adolescent Diabetes. Practical implementation of exercise regimens, however, may at times be problematic. In the poorly controlled patient, specific structural changes may occur within skeletal muscle fiber, which is considered by some to be a disease-specific myopathy. Further, even in well-controlled patients, several homeostatic mechanisms regulating carbohydrate metabolism often become impaired, causing hypo- or hyperglycemia during and/or after exercise. Some altered responses may be related to inappropriate exogenous insulin administration, but are often also partly caused by the "metabolic memory" of prior glycemic events. In this context, prior hyperglycemia correlates with increased inflammatory and oxidative stress responses, possibly modulating key exercise-associated cardio-protective pathways. Similarly, prior hypoglycemia correlates with impaired glucose counterregulation, resulting in greater likelihood of further hypoglycemia to develop. Additional exercise responses that may be altered in T1DM include growth factor release, which may be especially important in children and adolescents. These multiple alterations in the exercise response should not discourage physical activity in patients with T1DM, but rather should stimulate the quest for the identification of the exercise formats that maximize beneficial health effects.

Brachial artery modifications to blood flow-restricted handgrip training and detraining

Low load resistance training with blood flow restriction (BFR) can increase muscle size and strength, but the implications on the conduit artery are uncertain. We examined the effects of low-load dynamic handgrip training with and without BFR, and detraining, on measures of brachial artery function and structure. Nine male participants (26 ± 4 yr, 178 ± 3 cm, 78 ± 10 kg) completed 4 wk (3 days/wk) of dynamic handgrip training at 40% 1 repetition maximum (1RM). In a counterbalanced manner, one forearm trained under BFR (occlusion cuff at 80 mmHg) and the other under nonrestricted (CON) conditions. Brachial artery function [flow-mediated dilation (FMD)] and structure (diameter) were assessed using Doppler ultrasound. Measurements were made before training (pretraining), after training (posttraining), and after 2-wk no training (detraining). Brachial artery diameter at rest, in response to 5-min ischemia (peak diameter), and ischemic exercise (maximal diameter) increased by 3.0%, 2.4%, and 3.1%, respectively, after BFR training but not after CON. FMD did not change at any time point in either arm. Vascular measures in the BFR arm returned to baseline after 2 wk detraining with no change after CON. The data demonstrate that dynamic low-load handgrip training with BFR induced transient adaptations to conduit artery structure but not function.

Exercise-mediated changes in conduit artery wall thickness in humans: role of shear stress

Episodic increases in shear stress have been proposed as a mechanism that induces training-induced adaptation in arterial wall remodeling in humans. To address this hypothesis in humans, we examined bilateral brachial artery wall thickness using high-resolution ultrasound in healthy men across an 8-wk period of bilateral handgrip training. Unilaterally, shear rate was attenuated by cuff inflation around the forearm to 60 mmHg. Grip strength, forearm volume, and girth improved similarly between the limbs. Acute bouts of handgrip exercise increased shear rate ( P < 0.005) in the noncuffed limb, whereas cuff inflation successfully decreased exercise-induced increases in shear. Brachial blood pressure responses similarly increased during exercise in both the cuffed and noncuffed limbs. Handgrip training had no effect on baseline brachial artery diameter, blood flow, or shear rate but significantly decreased brachial artery wall thickness after 6 and 8 wk (ANOVA, P < 0.001) and wall-to-lumen ratio after week 8 (ANOVA, P = 0.005). The magnitude of decrease in brachial artery wall thickness and wall-to-lumen ratio after exercise training was similar in the noncuffed and cuffed arms. These results suggest that exercise-induced changes in shear rate are not obligatory for arterial wall remodeling during a period of 8 wk of exercise training in healthy humans.

Modification of angiogenic factors by regular and acute exercise during pregnancy

This cross-sectional study examined mechanisms through which exercise might alter preeclampsia risk by estimating the effects of acute and chronic exercise on angiogenic markers in healthy pregnant women with different amounts of regular exercise participation. Serum-soluble fms-like tyrosine kinase-1 (sFlt-1), placental growth factor (PlGF), and soluble endoglin (sEng) were measured before and after 20 min of moderate-intensity cycle ergometry in normotensive, nonsmoking pregnant (16 active, 9 inactive, 34.1 ± 1.6 wk gestation) and nonpregnant (15 active, 12 inactive, midlate luteal phase) women. Inactive women did not regularly exercise at an intensity that was sufficient to cause sweating. Active women exercised for at least 3 h/wk. Inactive pregnant women had significantly lower PlGF concentrations [median (interquartile range): 268 (159, 290) vs. 278 (221, 647) pg/ml, P = 0.014] and higher sFlt-1 [5,180 (4,540, 5,834) vs. 4,217 (2,014, 5,481) pg/ml, P = 0.005] and sEng concentrations [9.1 (7.7, 16.7) vs. 7.8 (6.5, 10.1) ng/ml, P = 0.025] than active pregnant women. This effect of regular exercise participation was not observed in nonpregnant women. Acute exercise in pregnancy was not associated with antiangiogenic changes that might contribute to preeclampsia; rather, there was a small, but statistically significant, increase in PlGF following acute exercise in active pregnant women [278 (221, 647) vs. 335 (245, 628) pg/ml, P = 0.014]. sFlt-1 increased significantly following acute exercise in inactive nonpregnant women [90 (86, 100) vs. 106 (101, 116) pg/ml, P = 0.012], but not in active nonpregnant women. Regular exercise during pregnancy is associated with higher serum PlGF and lower sFlt-1 and sEng concentrations in late gestation, a difference that is unlikely to have predated the pregnancy.

Effect of local cold-pack application on systemic anabolic and inflammatory response to sprint-interval training: a prospective comparative trial

We evaluated the effect of cold ice-pack application following a brief sprint-interval training on the balance between anabolic mediators [growth hormone (GH), insulin-like growth factor-I (IGF-I), testosterone], catabolic markers (cortisol, IGFBP-1), and circulating pro [Interlukin-6 (IL-6) and IL-1β]- and anti-inflammatory cytokines [IL-1 receptor antagonist (IL-1ra)]. Twelve males, elite junior handball players performed 4 × 250 m treadmill run, at 80% of each individual’s maximal speed, followed by a rest period with and without local cold-pack application. Pre, immediately post, and 60-min post-exercise blood samples were drawn. Exercise was associated with a significant increase in IL-6, GH, IGFBP-3, and testosterone levels. Local cold-pack application was associated with significant decreases in IL-1β, IL-1ra, IGF-I, and IGFBP-3 and a greater increase of IGFBP-1 during recovery. Local ice therapy immediately following sprint-interval training was associated with greater decreases in both pro- and anti-inflammatory cytokines and anabolic hormones supporting some clinical evidence for possible negative effects on athletic performance.

Effect of ischaemic exercise training of a normal limb on angiogenesis of a pathological ischaemic limb in rabbits

The present study was designed to test the hypothesis that local exercise of a normal limb can promote angiogenesis in a pathological ischaemic limb. New Zealand White rabbits underwent left femoral artery ligation (Lig) and electrode implantation on the right sciatic nerve. The rabbits were randomly assigned to four groups: (i) Lig-N group, which did not receive ES (electrical stimulation); (ii) Lig-High group, which received high-intensity ES (2.5 mA, 40Hz for 1 ms) on the right hindlimb; (iii) Lig-Low group, which received low-intensity ES (0.3 mA, 40Hz for 1 ms) on the right hindlimb; (iv) Double-Lig-High group, which underwent femoral artery ligation on both hindlimbs and received high-intensity ES (2.5 mA, 40Hz for 1 ms) on the right hindlimb. The ES procedure included 5 min of stimulation, followed by 5 min of rest, and was repeated eight times a day for 4 weeks. Collateral circulation was examined grossly by angiography, resting blood flow was measured using the microspheres technique, and capillary supply was evaluated by immunohistochemistry. VEGF (vascular endothelial growth factor) mRNA and protein were analysed by real-time RT (reverse transcription)–PCR and Western blotting respectively. Collateral blood flow in all of the major muscles of the left hindlimb in the Lig-High group was highest among the four groups (P<0.01). Capillary supply (P<0.001), VEGF mRNA (P<0.01) and VEGF protein (P<0.01) in the gastrocnemius muscle increased remarkably in the Lig-High group; no statistically significant difference was observed among the other three groups. In conclusion, angiogenesis associated with an up-regulation of VEGF expression in pathological ischaemic limb may be facilitated by 4 weeks of physiological ischaemic exercise training in a normal limb.

Acute resistance exercise increases skeletal muscle angiogenic growth factor expression

AIMS

Both aerobic and resistance exercise training promote skeletal muscle angiogenesis. Acute aerobic exercise increases several pro-angiogenic pathways, the best characterized being increases in vascular endothelial growth factor (VEGF). We hypothesized that acute resistance exercise also increases skeletal muscle angiogenic growth factor [VEGF and angiopoietin (Ang)] expression.

METHODS

Seven young, sedentary individuals had vastus lateralis muscle biopsies and blood drawn prior to and at 0, 2 and 4 h post-resistance exercise for the measurement of VEGF; VEGF receptor [KDR, Flt-1 and neuropilin 1 (Nrp1)]; Ang1 and Ang2; and the angiopoietin receptor--Tie2 expression. Resistance exercise consisted of progressive knee extensor (KE) exercise to determine one repetition maximum (1-RM) followed by three sets of 10 repetitions (3 x 10) of KE exercise at 60-80% of 1-RM.

RESULTS

Resistance exercise significantly increased skeletal muscle VEGF mRNA and protein and plasma VEGF protein at 2 and 4 h. Resistance exercise increased KDR mRNA and Tie2 mRNA at 4 h and Nrp1 mRNA at 2 and 4 h. Skeletal muscle Flt-1, Ang1, Ang2 and Ang2/Ang1 ratio mRNA were not altered by resistance exercise.

CONCLUSIONS

These findings suggest that acute resistance exercise increases skeletal muscle VEGF, VEGF receptor and angiopoietin receptor expression. The increases in muscle angiogenic growth factor expression in response to acute resistance exercise are similar in timing and magnitude with responses to acute aerobic exercise and are consistent with resistance exercise promoting muscle angiogenesis.

Effect of training on the response of plasma vascular endothelial growth factor to exercise in patients with peripheral arterial disease

Expansion of the capillary network, or angiogenesis, occurs following endurance training. This process, which is reliant on the presence of VEGF (vascular endothelial growth factor), is an adaptation to a chronic mismatch between oxygen demand and supply. Patients with IC (intermittent claudication) experience pain during exercise associated with an inadequate oxygen delivery to the muscles. Therefore the aims of the present study were to examine the plasma VEGF response to acute exercise, and to establish whether exercise training alters this response in patients with IC. In Part A, blood was collected from patients with IC (n=18) before and after (+20 and +60 min post-exercise) a maximal walking test to determine the plasma VEGF response to acute exercise. VEGF was present in the plasma of patients (45.11+/-29.96 pg/ml) and was unchanged in response to acute exercise. Part B was a training study to determine whether exercise training altered the VEGF response to acute exercise. Patients were randomly assigned to a treatment group (TMT; n=7) that completed 6 weeks of high-intensity treadmill training, or to a control group (CON; n=6). All patients completed a maximal walking test before and after the intervention, with blood samples drawn as for Part A. Training had no effect on plasma VEGF at rest or in response to acute exercise, despite a significant increase in maximal walking time in the TMT group (915+/-533 to 1206+/-500 s; P=0.009) following the intervention. The absence of a change in plasma VEGF may reflect altered VEGF binding at the endothelium, although this cannot be confirmed by the present data.

Alterations in IGF-I affect elderly: role of physical activity

The growth hormone–insulin-like growth factor I (IGF-I) axis is an important physiological regulator muscle for development. Although there is evidence that aging muscle retains the ability to synthesize IGF-I, there is also evidence that aging may be associated with attenuation of the ability of exercise to induce an isoform of IGF-I that promotes satellite cell proliferation. However, it is clear that overexpression of IGF-I in the muscle can protect against age-related sarcopenia. Strength training appears to be the intervention of choice for the prevention and treatment of sarcopenia. IGF-I has been implicated in the loss of the muscle with age, and IGF-I expression levels change as a consequence of strength training in older adults. However, it seems that advancing age, rather than declining serum levels of IGF-I, appears to be a major determinant of life-time changes in body composition in women and men. We concluded that resistive exercise is a significant determinant of muscle mass and function. Elevated levels of IGF-I have been found in physically active compared to sedentary individuals. Recent work suggests that IGF-I as a mediator plays an important role in muscle hypertrophy and angiogenesis, both of which characterize the anabolic adaptation of muscles to exercise.

Inactivity and Inflammation in the Critically Ill Patient

Bed rest is a commonly prescribed activity restriction among patients in the ICU. Although bed rest may promote rest, recovery and safety, inactivity related to bed rest also may lead to complications and adverse outcomes. The biological mechanisms that lead to immediate and long-term sequelae from bed rest have not been elucidated. It may be the inflammatory factors common to critical illness combined with bed rest lead to a positive feedback loop, contributing to inflammatory disequilibrium. This disequilibrium has a profound affect on muscles. Muscle decay has serious and long-term adverse outcomes on survivors of critical illness. Mobility therapy may improve inflammatory disequilibrium and preserve muscles, leading to improved functional outcome. Investigations in the laboratory, in healthy people and among patients with systemic inflammatory disease, suggest that activity does not exacerbate inflammation. Clinically, exercise is beneficial to patients with various chronic inflammatory diseases. Further study is needed to best understand the role, duration, and frequency of activity in promoting recovery for critically ill patients.

Exercise training prevents the inflammatory response to hypoxia in cremaster venules

Systemic hypoxia produces microvascular inflammation in several tissues, including skeletal muscle. Exercise training (ET) has been shown to reduce the inflammatory component of several diseases. Alternatively, ET could influence hypoxia-induced inflammation by improving tissue oxygenation or increasing mechanical antiadhesive forces at the leukocyte-endothelial interface. The effect of 5 wk of treadmill ET on hypoxia-induced microvascular inflammation was studied in the cremaster microcirculation of rats using intravital microscopy. In untrained rats, hypoxia (arterial Po2 = 32.3 ± 2.1 Torr) increased leukocyte-endothelial adherence from 2.3 ± 0.4 to 10.2 ± 0.3 leukocytes per 100 μm of venule ( P < 0.05) and was accompanied by extravasation of FITC-labeled albumin after 4 h of hypoxia (extra-/intravascular fluorescence intensity ratio = 0.50 ± 0.07). These responses were attenuated in ET (leukocyte adherence was 1.5 ± 0.4 during normoxia and 1.8 ± 0.7 leukocytes per 100 μm venule after 10 min of hypoxia; extra-/intravascular fluorescence intensity ratio = 0.11 ± 0.02; P < 0.05 vs. untrained) despite similar reductions of arterial (32.4 ± 1.8 Torr) and microvascular Po2 (measured with an oxyphor-quenching method) in both groups. Shear rate decreased during hypoxia to similar extents in ET and untrained rats. In addition, circulating blood leukocyte count was similar in ET and untrained rats. The effects of ET on hypoxia-induced leukocyte-endothelial adherence remained up to 4 wk after discontinuing training. Thus ET attenuated hypoxia-induced inflammation despite similar effects of hypoxia on tissue Po2, venular shear rate, and circulating leukocyte count.

Increase in interstitial interleukin-6 of human skeletal muscle with repetitive low-force exercise

Interleukin (IL)-6, which is released from muscle tissue during intense exercise, possesses important metabolic and probably anti-inflammatory properties. To evaluate the IL-6 response to low-intensity exercise, we conducted two studies: 1) a control study with insertion of microdialysis catheters in muscle and determination of interstitial muscle IL-6 response over 2 h of rest and 2) an exercise study to investigate the IL-6 response to 20 min of repetitive low-force exercise. In both studies, a microdialysis catheter (cutoff: 3,000 kDa) was inserted into the upper trapezius muscle of six male subjects, and the catheters were perfused with Ringer-acetate at 5 μl/min. Venous plasma samples were taken in the exercise study. The insertion of microdialysis catheters into muscle resulted in an increase in IL-6 from 8 ± 0 to 359 ± 171 and 484 ± 202 pg/ml after 65 and 110 min, respectively ( P < 0.001). Similarly, in the exercise study, IL-6 increased to 289 ± 128 pg/ml after a 55-min rest ( P < 0.001). During the subsequent repetitive low-force exercise, muscle IL-6 further increased to 1,246 ± 461 pg/ml and reached 2,132 ± 477 pg/ml after a 30-min recovery (all P < 0.001). In contrast to this, plasma IL-6 did not significantly change in response to exercise. We conclude that upper extremity, low-intensity exercise results in a substantial increase in IL-6 in the interstitium of the stabilizing trapezius muscle, whereas no change is seen for plasma IL-6.

Attenuation of T-lymphocyte demargination and adhesion molecule expression in response to moderate exercise in physically fit individuals

The effects of physical fitness on leukocyte demargination and cellular adhesion molecule (CAM) responses to moderate exercise were examined. We assessed leukocyte subsets and CAM expression before, immediately after, and 10 min after a 20-min treadmill exercise at 65-70% peak oxygen consumption in fit vs. nonfit individuals. Physical fitness was determined by peak oxygen consumption during a treadmill test. Catecholamine levels were determined by radioenzymatic assay, and enumeration of cells and detection of CAM expression were assessed by flow cytometry. As expected, exercise led to significant increases in numbers of leukocyte subsets, regardless of fitness level (P < 0.01). Values returned to near resting levels 10 min after exercise. More importantly, physically fit individuals showed attenuated responses to the moderate-exercise challenge in numbers of CD3(+), CD4(+), CD8(+), memory (CD45RO(+)) CD4, and naive (CD45RA(+)62L(+)) CD4 and CD8 lymphocytes. Postexercise human leukocyte antigen-DR absent memory CD4(+) cell numbers were also lower in fit subjects. Increases in CD62L-expressing CD4(+) and CD8(+) lymphocytes and CD11a- expressing lymphocytes after exercise were also attenuated in fit individuals compared with nonfit individuals (P < 0.05). Catecholamine levels increased to a similar extent (P < 0.01) in both fitness groups. The findings suggest that physical fitness attenuates demargination of selected lymphocyte subsets in response to moderate exercise. Although the differences in plasma catecholamine responses were not significant between the groups, a possible mediating role of the sympathetic system remains to be further investigated. Being physically fit may offset exaggerated immune cell responses to stress.

Circulating plasma VEGF response to exercise in sedentary and endurance-trained men

The skeletal muscle capillary supply is an important determinant of maximum exercise capacity, and it is well known that endurance exercise training increases the muscle capillary supply. The muscle capillary supply and exercise-induced angiogenesis are regulated in part by vascular endothelial growth factor (VEGF). VEGF is produced by skeletal muscle cells and can be secreted into the circulation. We investigated whether there are differences in circulating plasma VEGF between sedentary individuals (Sed) and well-trained endurance athletes (ET) at rest or in response to acute exercise. Eight ET men (maximal oxygen consumption: 63.8 ± 2.3 ml·kg-1·min-1; maximum power output: 409.4 ± 13.3 W) and eight Sed men (maximal oxygen consumption: 36.3 ± 2.1 ml·kg-1·min-1; maximum power output: 234.4 ± 13.3 W) exercised for 1 h at 50% of maximum power output. Antecubital vein plasma was collected at rest and at 0, 2, and 4 h postexercise. Plasma VEGF was measured by ELISA analysis. Acute exercise significantly increased VEGF at 0 and 2 h postexercise in ET subjects but did not increase VEGF at any time point in Sed individuals. There was no difference in VEGF between ET and Sed subjects at any time point. When individual peak postexercise VEGF was analyzed, exercise did increase VEGF independent of training status. In conclusion, exercise can increase plasma VEGF in both ET athletes and Sed men; however, there is considerable variation in the individual time of the peak VEGF response.

Exercise but not prostanoids enhance levels of vascular endothelial growth factor and other proliferative agents in human skeletal muscle interstitium

In the present study we examined whether exercise and prostanoids have an effect on the muscle interstitial concentration of vascular endothelial growth factor (VEGF) and on the proliferative effect of muscle interstitial fluid. Dialysate from resting and exercising human skeletal muscle, obtained either during control conditions or during cyclooxygenase inhibition, was examined for its content of VEGF and for its effect on endothelial cell proliferation. Microdialysis probes with high (960 kDa) and low (5 kDa) molecular-mass cut-off membranes were placed in the vastus lateralis muscle of healthy young males. The subjects performed one-legged knee extensions (20 W). The concentration of VEGF in the 960 kDa dialysate was greater (P < 0.05) during exercise compared to at rest (67 +/- 28 vs. 230 +/- 22 pg ml-1). The rate of endothelial cell proliferation was 2.7-fold higher (P < 0.05) with the 960 kDa dialysate from resting muscle than with perfusate and was 5.8-fold higher (P < 0.05) than the perfusate value with dialysate from exercising muscle. VEGF was not enhanced with exercise in the 5 kDa dialysate, yet the exercise dialysate induced a 1.9-fold higher (P < 0.05) proliferation than the resting dialysate. Cyclooxygenase inhibition did not affect the VEGF concentration or the proliferating effect of the dialysates (P > 0.05). This study demonstrates for the first time that VEGF is present in the interstitium of human skeletal muscle and that exercise enhances the interstitial concentration of VEGF and of other, as yet unidentified, angiogenic compounds. Products of cyclooxygenase do not appear to have an effect on the release of VEGF or other proliferative agents in human skeletal muscle.