Vascular endothelial growth factor in exercising humans under different environmental conditions

AhR regulates VEGF expression by promoting STAT1 transcriptional activity, thereby affecting endothelial angiogenesis in acute limb ischemia

BACKGROUND

Angiogenesis has great potential in the treatment of acute limb ischemia (ALI). Here, we aimed to investigate the effect and mechanism of Aryl hydrocarbon receptor (AhR) on angiogenesis in ALI.

METHODS

The ALI mouse model was constructed by femoral artery ligation, and the cell ischemia injury was induced by Hypoxia/serum deprivation. The laser doppler perfusion imaging was executed to detect the limb blood flow velocity. The tube formation assay was performed to evaluate angiogenesis. The cell viability was measured by 3-(45)-dimethylthiahiazo(-z-y1)-35-di-phenytetrazoliumromide. The cell migration was detected by wound healing assay. Hematoxylin-eosin, immunohistochemistry, immunofluorescence, dual-luciferase reporter gene assay, and Chromatin immunoprecipitation assay were conducted.

RESULTS

In ALI models, AhR expression was increased and translocated from cytoplasm to nucleus. Besides, necrosis and inflammatory infiltration were also increased in gastrocnemius tissues of model mice. In addition, AhR loss (LV-sh-AhR) promoted cell viability, angiogenesis, and migration, and also elevated the levels of vascular endothelial growth factor (VEGF), Tie2, and Ang2 in HUVEC models with Hypoxia/serum deprivation injury. Meanwhile, the interaction between AhR and signal transducer and activator of transcription 1 (STAT1), as well as STAT1 and VEGF, has also been confirmed. Co-transfection of LV-sh-AhR and LV-STAT1 suppressed cell viability, angiogenesis, and migration of injured HUVECs. Furthermore, injection of AAV2/9-shAhR in vivo also promoted angiogenesis, which was consistent with the in vitro experimental results.

CONCLUSIONS

In ALI models, activated AhR was translocated to the nucleus and down-regulated VEGF expression by promoting the transcriptional activity of STAT1, thereby inhibiting endothelial angiogenesis.

Altitude, Exercise, and Skeletal Muscle Angio-Adaptive Responses to Hypoxia: A Complex Story

Hypoxia, defined as a reduced oxygen availability, can be observed in many tissues in response to various physiological and pathological conditions. As a hallmark of the altitude environment, ambient hypoxia results from a drop in the oxygen pressure in the atmosphere with elevation. A hypoxic stress can also occur at the cellular level when the oxygen supply through the local microcirculation cannot match the cells’ metabolic needs. This has been suggested in contracting skeletal myofibers during physical exercise. Regardless of its origin, ambient or exercise-induced, muscle hypoxia triggers complex angio-adaptive responses in the skeletal muscle tissue. These can result in the expression of a plethora of angio-adaptive molecules, ultimately leading to the growth, stabilization, or regression of muscle capillaries. This remarkable plasticity of the capillary network is referred to as angio-adaptation. It can alter the capillary-to-myofiber interface, which represent an important determinant of skeletal muscle function. These angio-adaptive molecules can also be released in the circulation as myokines to act on distant tissues. This review addresses the respective and combined potency of ambient hypoxia and exercise to generate a cellular hypoxic stress in skeletal muscle. The major skeletal muscle angio-adaptive responses to hypoxia so far described in this context will be discussed, including existing controversies in the field. Finally, this review will highlight the molecular complexity of the skeletal muscle angio-adaptive response to hypoxia and identify current gaps of knowledges in this field of exercise and environmental physiology.

The Effects of Acute Hypoxia on Tissue Oxygenation and Circulating Alarmins in Healthy Adults

The binding of high-mobility group box-1 (HMGB-1) to the membrane receptor for advanced glycation end-products (mRAGE) is a key early mediator of non-infectious inflammation and its triggers include ischaemia/hypoxia. The effects of acute hypoxia on soluble RAGE (sRAGE) are unknown. Fourteen healthy adults (50 % women; 26.6±3.8 years) were assessed at baseline normoxia (T0), followed by four time-points (T90, 95, 100 and 180 min) over three hours of continuous normobaric hypoxia (NH, 4,450 m equivalent) and again 60 min after return to normoxia (T240). A 5-min exercise step test was performed during NH at T90. Plasma concentrations of HMGB-1, sRAGE VCAM-1, ICAM-1, VEGF IL-8 and IL-13 were measured using venous blood. Arterial and tissue oxygen saturations were measured using pulse oximetry (SpO2) and near-infrared spectroscopy (StO2), respectively. NH led to a significant reduction in SpO2, StO2, sRAGE and VEGF, which was compounded by exercise, before increasing to baseline values with normoxic restoration (T240). NH-exercise led to a paired increase in HMGB-1. sRAGE inversely correlated with HMGB-1 (r=-0.32; p=0.006), heart rate (r=-0.43; p=0.004) but was not linked to SpO2 or StO2. In conclusion, short-term NH leads to a fall in sRAGE and VEGF concentrations with a transient rise post NH-exercise in HMGB-1.

Exercise-Induced Neuroplasticity: A Mechanistic Model and Prospects for Promoting Plasticity

Aerobic exercise improves cognitive and motor function by inducing neural changes detected using molecular, cellular, and systems level neuroscience techniques. This review unifies the knowledge gained across various neuroscience techniques to provide a comprehensive profile of the neural mechanisms that mediate exercise-induced neuroplasticity. Using a model of exercise-induced neuroplasticity, this review emphasizes the sequence of neural events that accompany exercise, and ultimately promote changes in human performance. This is achieved by differentiating between neuroplasticity induced by acute versus chronic aerobic exercise. Furthermore, this review emphasizes experimental considerations that influence the opportunity to observe exercise-induced neuroplasticity in humans. These include modifiable factors associated with the exercise intervention and nonmodifiable factors such as biological sex, ovarian hormones, genetic variations, and fitness level. To maximize the beneficial effects of exercise in health, disease, and following injury, future research should continue to explore the mechanisms that mediate exercise-induced neuroplasticity. This review identifies some fundamental gaps in knowledge that may serve to guide future research in this area.

Experimental study of survival of pedicled perforator flap with flow-through and flow-end blood supply

BACKGROUND

Flap viability after transfer depends on blood flow from the arterial blood supply below the fascia. This study evaluated survival of a pedicle flap with a perforator lateral branch and flow-through blood supply, compared with that of a flap with a flow-end blood supply and perforator terminal branch.

METHODS

Forty Sprague-Dawley rats, 20 in each group, were assigned to transfer of a superficial epigastric artery pedicle island flap with a flow-through or flow-end configuration of blood supply. Laser Doppler imaging was used to evaluate flap perfusion 2 h, 3 days and 5 days after surgery. The rats were killed on day 5, and lead oxide-gelatine-enhanced flap angiography and histology with haematoxylin and eosin staining was performed. Dorsal midline tissue was excised for quantification of vascular endothelial growth factor by western blot assay.

RESULTS

On day 5 after surgery, the flow-through group exhibited a significantly greater mean(s.d.) flap survival area (97·8(3·5) versus 80·8(10·2) per cent; P = 0·003), microvascular density (303(19) versus 207(41) per mm(2) ; P < 0·001) and perfusion (8·64(0·14) versus 5·95(0·14) perfusion units; P < 0·001) than the flow-end group. The flow-through group exhibited more angiosomes connected by dilated vascular anastomoses between the skin and subcutaneous fasciae.

CONCLUSION

The flow-through blood supply improved pedicle perforator flap survival. Surgical relevance Perforator flap failure is mainly the result of impaired blood supply, as a flow-end blood configuration is nourished only by the perforator terminal branch of the artery. This work showed that the flow-through blood supply nourished by the perforator lateral branch improved flap survival, with dilatation of collateral vascular anastomoses and increased neoangiogenesis. The use of a flow-through configuration improves perforator flap survival and could therefore minimize morbidity resulting from flap necrosis.

Physical exercise-induced adult neurogenesis: a good strategy to prevent cognitive decline in neurodegenerative diseases?

Cumulative evidence has indicated that there is an important role for adult hippocampal neurogenesis in cognitive function. With the increasing prevalence of cognitive decline associated with neurodegenerative diseases among the ageing population, physical exercise, a potent enhancer of adult hippocampal neurogenesis, has emerged as a potential preventative strategy/treatment to reduce cognitive decline. Here we review the functional role of adult hippocampal neurogenesis in learning and memory, and how this form of structural plasticity is altered in neurodegenerative diseases known to involve cognitive impairment. We further discuss how physical exercise may contribute to cognitive improvement in the ageing brain by preserving adult neurogenesis, and review the recent approaches for measuring changes in neurogenesis in the live human brain.

An aryl hydrocarbon receptor induces VEGF expression through ATF4 under glucose deprivation in HepG2

Background

Aryl hydrocarbon receptor (AhR) not only regulates drug-metabolizing enzyme expression but also regulates cancer malignancy. The steps to the development of malignancy include angiogenesis that is induced by tumor microenvironments, hypoxia, and nutrient deprivation. Vascular endothelial growth factor (VEGF) plays a central role in the angiogenesis of cancer cells, and it is induced by activating transcription factor 4 (ATF4).

Results

Recently, we identified that glucose deprivation induces AhR translocation into the nucleus and increases CYP1A1 and 1A2 expression in HepG2 cells. Here, we report that the AhR pathway induces VEGF expression in human hepatoblastoma HepG2 cells under glucose deprivation, which involves ATF4. ATF4 knockdown suppressed VEGF expression under glucose deprivation. Moreover, AhR knockdown suppressed VEGF and ATF4 expression under glucose deprivation at genetic and protein levels.

Conclusions

The AhR-VEGF pathway through ATF4 is a novel pathway in glucose-deprived liver cancer cells that is related to the microenvironment within a cancer tissue affecting liver cancer malignancy.

No correlation between plasma levels of vascular endothelial growth factor or its soluble receptor and acute mountain sickness

Increased plasma levels of vascular endothelial growth factor (VEGF) due to lower levels of its soluble receptor (sFlt-1) had been suggested to cause vasogenic brain edema and thereby to cause the symptoms of acute mountain sickness (AMS). We tested this hypothesis after active ascent to high altitude. Plasma was collected from 31 subjects at low altitude (100 m) before (LA1) and after (LA2) 4 weeks of aerobic exercise training in normobaric hypoxia or normoxia, and one night after ascent to high altitude (4559 m). Training modalities (hypoxia or normoxia) did not influence VEGF- and sFlt-1-levels. Therefore, data of both training groups were analyzed together. After one night at 4559 m, 18 subjects had AMS (AMS+), 13 had no AMS (AMS-). In AMS+ and AMS-, VEGF was 110 ± 75 (SD) pg/ml vs. 104 ± 82 (p = 0.74) at LA1, 63 ± 40 vs. 73 ± 50 (p = 0.54) at LA2, and 88 ± 62 vs. 104 ± 81 (p = 0.54) at 4559 m, respectively. Corresponding values for sFlt-1 in AMS+ and AMS- were 81 pg/ml ± 13.1 vs. 82 ± 17 (p = 0.97), 79 ± 11 vs. 80 ± 16 (p = 0.92) and 139 ± 28 vs. 135 ± 31 (p = 0.70), respectively. Absolute values or changes of VEGF were not correlated and those of sFlt-1 slightly correlated with AMS scores. These data provide no evidence for a role of plasma VEGF and sFlt-1 in the pathophysiology of AMS. They do, however, not exclude paracrine effects of VEGF in the brain.

Vascular endothelial growth factor and acute mountain sickness

Study Objective:

Despite causing significant morbidity throughout the mountainous regions of the world, the pathophysiology of acute mountain sickness (AMS) remains poorly understood. This study aims to improve the understanding of altitude illness by determining if vascular endothelial growth factor (VEGF) plays a role in the development of AMS. The purpose of this study was to determine if elevated plasma VEGF correlates with increased symptoms of AMS at high altitude.

Patients and Methods:

This is a prospective study of a cohort of healthy climbers on Denali (Mount McKinley) in Alaska at 14, 200 feet. Baseline demographics, medications, rates of ascent, and AMS scores were recorded. Pulse oximetry measurements and venous blood samples were obtained. Comparisons were made between mountaineers with and without AMS.

Results:

Seventy-two climbers were approached for participation in the study; 21 (29%) refused. Of the 51 climbers participating in the study, 14 subjects (27.5%) had symptoms of AMS and 37 subjects (72.5%) were free of symptoms of AMS. Plasma VEGF levels were 79.14 pg/dl (SD: 121.44) and 57.57pg/dl (SD: 102.71) in the AMS and non-AMS groups, respectively. These results were nonsignificant. Similarly, comparison of sex, age, rate of ascent, pulse oximetry values, or history of altitude illness did not reveal significant differences between the AMS and non-AMS groups.

Conclusion:

This study does not provide evidence in support of the theory that plasma VEGF correlates with symptoms of AMS.

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.

Effects of short-term vibration and hypoxia during high-intensity cycling exercise on circulating levels of angiogenic regulators in humans

This study aimed to investigate the biological response to hypoxia as a stimulus, as well as exercise- and vibration-induced shear stress, which is known to induce angiogenesis. Twelve male cyclists (27.8 ± 5.4 yr) participated in this study. Each subject completed four cycle training sessions under normal conditions (NC) without vibration, NC with vibration, normobaric hypoxic conditions (HC) without vibration, and HC with vibration. Each session lasted 90 min, and sessions were held at weekly intervals in a randomized order. Five blood samples (pretraining and 0 h post-, 0.5 h post-, 1 h post-, and 4 h posttraining) were taken from each subject at each training session. Hypoxia was induced by a normobaric hypoxic chamber with an altitude of 2,500 m. The mechanical forces (cycling with or without vibration) were induced by a cycling ergometer. The parameters VEGF, endostatin, and matrix metalloproteinases (MMPs) were analyzed using the ELISA method. VEGF showed a significant increase immediately after the exercise only with exogenously induced vibrations, as calculated with separate ANOVA analysis. Endostatin increased after training under all conditions. Western blot analysis was performed for the determination of endostatin corresponding to the 22-kDa cleavage product of collagen XVIII. This demonstrated elevated protein content for endostatin at 0 h postexercise. MMP-2 increased in three of the four training conditions. The exception was NC with vibration. MMP-9 reached its maximum level at 4 h postexercise. In conclusion, the results support the contention that mechanical stimuli differentially influence factors involved in the induction of angiogenesis. These findings may contribute to a broader understanding of angiogenesis.

A single bout of exercise activates matrix metalloproteinase in human skeletal muscle

The aims of this study were 1) to characterize changes in matrix metalloproteinase (MMP), endostatin, and vascular endothelial growth factor (VEGF)-A expression in skeletal muscle in response to a single bout of exercise in humans; and 2) to determine if any exchange of endostatin and VEGF-A between circulation and the exercising leg is associated with a change in the tissue expression or plasma concentration of these factors. Ten healthy males performed 65 min of cycle exercise, and muscle biopsies were obtained from the vastus lateralis muscle at rest and immediately and 120 min after exercise. In the muscle biopsies, measurements of mRNA expression levels of MMP-2, MMP-9, MMP-14, and tissue inhibitor of metalloproteinase; VEGF and endostatin protein levels; and MMP activities were performed. Femoral arterial and venous concentrations of VEGF-A and endostatin were determined before, during, and 120 min after exercise. A single bout of exercise increased MMP-9 mRNA and activated MMP-9 protein in skeletal muscle. No measurable increase of endostatin was observed in the skeletal muscle or in plasma following exercise. A concurrent increase in skeletal muscle VEGF-A mRNA and protein levels was induced by exercise, with no signs of peripheral uptake from the circulation. However, a decrease in plasma VEGF-A concentration occurred following exercise. Thus 1) a single bout of exercise activated the MMP system without any resulting change in tissue endostatin protein levels, and 2) the increased VEGF-A protein levels are due to changes in the skeletal muscle tissue itself. Other mechanisms are responsible for the observed exercise-induced decrease in VEGF-A in plasma.

Acute hypoxia decreases plasma VEGF concentration in healthy humans

Vascular endothelial growth factor (VEGF) is known to be upregulated by hypoxia in vitro. However, in vivo data about VEGF regulation in chronic hypoxic diseases are conflicting. We investigated the effects of hypoxia on plasma VEGF concentration in healthy subjects. To control known confounders, such as insulin, glucose concentrations, or exercise, hypoxic effects on VEGF were studied during experimentally clamping glucose concentrations at rest. In a double-blind crossover study design, we induced hypoxia for 30 min by decreasing oxygen saturation to 75% (vs. normoxic control) in 14 healthy men. Plasma VEGF concentration was determined at baseline, immediately after hypoxia had ended, and after a further 150 min. Levels of its soluble (s)Flt-1 receptor were assessed at baseline and at the end of the clamp. In parallel, catecholamine and cortisol levels were monitored. To investigate potential effects of glucose administration on the release of VEGF, we performed a third session, reducing glucose infusion for 30 min while serum insulin was held stable thereby inducing hypoglycemia. Hypoxia decreased VEGF levels compared with the normoxic control (P<0.05). VEGF concentrations increased during hypoglycemia (P<0.02) but were comparable to the normoglycemic control at the end of the clamp (P>0.80). sFlt-1 receptor concentration remained unchanged during hypoxia and hypoglycemia compared with control (both P>0.4). Epinephrine concentration (P<0.01) increased upon hypoxia, whereas norepinephrine and cortisol did not change. Contrary to in vitro studies, in healthy humans hypoxia decreases plasma VEGF concentration, suggesting that systemic VEGF concentration may be differently regulated than the expression on cellular basis.

Pathogenesis of high altitude pulmonary edema: does alveolar epithelial lining fluid vascular endothelial growth factor exacerbate capillary leak?

Vascular endothelial growth factor (VEGF) is a potent mediator of capillary leak if it gains access to its receptors on the capillary endothelium. We have observed that there are high levels of VEGF compartmentalized in the alveolar epithelial lining fluid of normal humans at levels 500-fold greater than plasma. The potential for high altitude to result in compromise of alveolar epithelial tight junctions and experimental animal studies in which pulmonary edema is induced when VEGF is overexpressed in the alveolar epithelium, suggest a mechanism. We hypothesize that when the epithelial barrier is compromised at high altitude the normally high level of VEGF in the alveolar epithelial fluid has access to the pulmonary endothelium, where it acutely alters permeability, markedly exacerbating the high permeability pulmonary edema that characterizes high altitude pulmonary edema. If correct, this paradigm opens the possibility of testing available anti-VEGF therapies to treat this potentially fatal disorder.

Circulating plasma levels of vascular endothelial growth factor in patients with sleep disordered breathing

INTRODUCTION

Cellular vascular endothelial growth factor (VEGF) expression is increased in response to regional hypoxia, however, contradictory results were reported on the effects of systemic hypoxemia on circulating VEGF levels. This study investigated plasma concentrations of VEGF in patients with a variable degree of overnight hypoxemia due to sleep disordered breathing (SDB).

METHODS

VEGF levels were assessed by ELISA in non-activated (VEGFbl) and thrombin stimulated platelet rich plasma (VEGFprp) of 45 patients with SDB: Group 1 patients with obstructive sleep apnea and an apnea-hypopnea index (AHI) > 15/h; Group 2 subjects with an AHI < 5/h; Group 3 patients on CPAP treatment for sleep apnea.

RESULTS

39 patients were included in the final analysis. Patients in Group 1 had a higher %time of sleep with SaO2 <90% and a significantly lower mean and minimum overnight oxygen saturation than subjects in Group 2 and patients in Group 3 (P<0.05). Despite significant differences in overnight oxygenation, VEGFbl and VEGFprp concentrations were not significantly different between the three study groups. However, plasma levels of VEGFbl were significantly higher (P = 0.02) in SDB patients with arterial hypertension (n = 19; VEGFbl: 14.0+/-3.3 pg/ml) than in those without arterial hypertension (n = 20; VEGFbl: 10.9+/-5.2 pg/ml). There were no relationships between VEGF levels and polysomnographic oxygenation parameters. In univariate analysis we observed significant relationships for VEGFbl with BMI (C: 0.393; P<0.05) and serum fibrinogen (C: 0.399; P<0.05).

CONCLUSIONS

Circulating plasma VEGF levels in patients with sleep disordered breathing may be unrelated to night time hypoxemia (257 Words).

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.

Interleukin-6 and Tumor Necrosis Factor-α in Patients with Obstructive Sleep Apnea-Hypopnea Syndrome

BACKGROUND

In previous studies, significantly elevated levels of vascular endothelial growth factor (VEGF) have been reported in patients with severe obstructive sleep apnea-hypopnea syndrome (OSAHS). On the other hand, plasma tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) have been significantly higher in mild sleep apneics than in normal controls. However, this study included a small number of patients and milder cases of OSAHS.

OBJECTIVES AND METHODS

To assess the involvement of IL-6 and TNF-alpha in VEGF increases in patients with severe OSAHS, serum levels of IL-6 and TNF-alpha were determined in patients with severe OSAHS (n=110) and compared to those of controls (n=45) using an enzyme-linked immunosorbent assay.

RESULTS

No significant increase in IL-6 or TNF-alpha was detected in the present study cohort. However, the body mass index was significantly correlated with the severity of the apnea-hypopnea index.

CONCLUSIONS

These data suggest that the elevation in VEGF is not directly related to IL-6 or TNF-alpha levels. However, the question of whether VEGF is the cause or the result of OSAHS remains to be determined. Further studies are needed to clarify the role of IL-6 and TNF-alpha in the pathogenesis of OSAHS, in which obesity should be entered as an independent factor.

Exercise increases endostatin in circulation of healthy volunteers

Background

Physical inactivity increases the risk of atherosclerosis. However, the molecular mechanisms of this relation are poorly understood. A recent report indicates that endostatin, an endogenous angiostatic factor, inhibits the progression of atherosclerosis, and suggests that reducing intimal and atherosclerotic plaque tissue neovascularization can inhibit the progression atherosclerosis in animal models. We hypothesize that exercise can elevate the circulatory endostatin level. Hence, exercise can protect against one of the mechanisms of atherosclerosis.

Results

We examined treadmill exercise tests in healthy volunteers to determine the effect of exercise on plasma levels of endostatin and other angiogenic regulators. Oxygen consumption (VO₂) was calculated. Plasma levels of endostatin, vascular endothelial growth factor (VEGF), and basic fibroblast growth factor (bFGF) were determined using ELISA. The total peak VO₂ (L) in 7 male subjects was 29.5 ± 17.8 over a 4–10 minute interval of exercise. Basal plasma levels of endostatin (immediately before exercise) were 20.3 ± 3.2 pg/ml, the plasma levels increased to 29.3 ± 4.2, 35.2 ± 1.8, and 27.1 ± 2.2 ng/ml, at 0.5, 2, and 6 h, respectively, after exercise. There was a strong linear correlation between increased plasma levels of endostatin (%) and the total peak VO₂ (L) related to exercise (R² = 0.9388; P < 0.01). Concurrently, VEGF levels decreased to 28.3 ± 6.4, 17.6 ± 2.4, and 26.5 ± 12.5 pg/ml, at 0.5, 2, and 6 h, respectively, after exercise. There were no significant changes in plasma bFGF levels in those subjects before and after exercise.

Conclusions

The results suggest that circulating endostatin can be significantly increased by exercise in proportion to the peak oxygen consumption under physiological conditions in healthy volunteers. These findings may provide new insights into the molecular links between physical inactivity and the risk of angiogenesis dependent diseases such as atherosclerosis.

Vascular endothelial growth factor mRNA expression and arteriovenous balance in response to prolonged, submaximal exercise in humans

Angiogenesis, the growth of new blood vessels from existing ones, occurs in the skeletal muscle as an adaptive response to exercise that satisfies the increased requirement of this tissue for oxygen delivery and metabolic processes. Of the factors that have been identified to regulate this process, the endothelial cell mitogen vascular endothelial growth factor (VEGF) has been proposed to play a key role. The aim of this study was to measure the skeletal muscle VEGF mRNA content and arteriovenous protein balance across the working leg in response to a single bout of prolonged, submaximal exercise. Seven physically active males completed 3 h of two-legged kicking ergometry. Muscle biopsies were collected from the vastus lateralis muscle from both working legs, and blood samples were collected from one femoral artery and femoral vein before, during, and in recovery from exercise. We show that the exercise stimulus elicited a decrease in VEGF protein arteriovenous balance across the exercising leg (P = 0.007), and a ninefold elevation in skeletal muscle VEGF mRNA expression (P < 0.001). The changes in VEGF protein balance and mRNA content were most pronounced 1 h after the cessation of exercise. In conclusion, these findings demonstrate that submaximal exercise, suitable for humans with low CV fitness, induces a decrease in VEGF arteriovenous balance that is likely to be of clinical significance in promoting angiogenic effects.

Vascular endothelial growth factor in the cerebrospinal fluid of infants who died of sudden infant death syndrome: evidence for antecedent hypoxia

OBJECTIVES

Recurrent hypoxemia has been proposed as an important pathophysiological mechanism underlying sudden infant death syndrome (SIDS). However, conflicting results emerged when xanthines were used as markers for hypoxia. The vascular endothelial growth factor (VEGF) gene is highly sensitive to changes in tissue partial oxygen tension, and changes in genomic and protein expression occur even after changes in oxygenation within the physiologic range.

METHODS

For determining whether hypoxia precedes SIDS, VEGF levels were measured using an enzyme-linked immunosorbent assay in the cerebrospinal fluid (CSF) of 51 SIDS infants and in 33 additional control infants who died of an identifiable cause. In addition, 6 rats that had a chronically implanted catheter in the lateral ventricle were exposed to a short hypoxic challenge, and VEGF concentrations were measured in CSF at various time points for 24 hours. Another set of 6 rats were killed with a pentobarbital overdose, and VEGF CSF levels were obtained at different time points after death.

RESULTS

Mean VEGF concentrations in CSF were 308.2 +/- 299.1 pg/dL in the SIDS group and 85.1 +/- 82.9 pg/dL in those who died of known causes. Mean postmortem delay averaged 22 hours for both groups. In rat experiments, hypoxic exposures induced time-dependent increases in VEGF, peaking at 12 hours and returning to baseline at 24 hours. Postmortem duration in the animals was associated with gradual increases in VEGF that reached significance only at 36 hours.

CONCLUSIONS

We conclude that VEGF CSF concentrations are significantly higher in infants who die of SIDS. We postulate that hypoxia is a frequent event that precedes the sudden and unexpected death of these infants.

Levels of vascular endothelial growth factor are elevated in patients with obstructive sleep apnea--hypopnea syndrome

To better understand how humans adapt to hypoxia, the levels of hemoglobin (Hb), serum erythropoietin (Epo), and vascular endothelial growth factor (VEGF) were measured in 106 patients with severe obstructive sleep apnea-hypopnea syndrome. The results indicated that temporal hypoxic stimulation increases Hb. Furthermore, a minor increase in Epo and a substantial increase in VEGF were found. The induction in patients with severe sleep apnea was greater than that reported in other types of hypoxia. (Blood. 2001;98:1255-1257)

Plasma vascular endothelial growth factor in acute mountain sickness

STUDY OBJECTIVES

To investigate the hypothesis that an increase in circulating vascular endothelial growth factor (VEGF) occurs in mountaineers at high altitude, particularly in association with acute mountain sickness (AMS) and/or low hemoglobin oxygen saturation.

DESIGN

: Collection of medical histories, AMS scores, plasma samples, and arterial oxygen saturation (SaO(2)) measurements from mountaineers at 1,500 feet (sea level) and at 14,200 feet.

SETTING

Mount McKinley ("Denali"), AK.

PARTICIPANTS

Sixty-six mountaineers.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

Plasma VEGF at 14,200 feet was not increased in any group. In fact, plasma VEGF was significantly lower in subjects who did not develop AMS (53 +/- 7.9 pg/mL; mean +/- SEM; n = 47) compared to control subjects at sea level (98.4 +/- 14.3 pg/mL; n = 7; p = 0.005). Plasma VEGF at 14, 200 feet for subjects with AMS (62 +/- 12 pg/mL; n = 15) did not differ significantly from subjects at 14,200 feet without AMS, or from control subjects at sea level. Of a small number of subjects with paired specimens at sea level and at base camp (n = 5), subjects who exhibited a decrease in plasma VEGF at 14,200 feet were those who did not develop AMS. Neither SaO(2), prior AMS, AMS symptom scores, or acetazolamide use were correlated with plasma VEGF.

CONCLUSIONS

Subjects at high altitude who do not develop AMS have lower plasma VEGF levels compared to control subjects at sea level. Plasma VEGF at high altitude is not elevated in association with AMS or hypoxia. Sustained plasma VEGF at altitude may reflect a phenotype more susceptible to AMS.

Increase in immune activation, vascular endothelial growth factor and erythropoietin after an ultramarathon run at moderate altitude

The present study was performed to investigate the effects of exhaustive long lasting exercise at moderate altitude on the time course of serum immunomodulatory peptides, vascular endothelial growth factor (VEGF) and serum erythropoietin (EPO). Thirteen well trained runners participated at the Swiss Alpine Marathon of Davos (distance 67 km, altitude difference 2300 m). Interleukin-6 was significantly elevated in the first 2h after the run. In contrast, tumor necrosis factor-alpha and both soluble tumor necrosis factor-a receptors I and II were increased after exercise termination and showed sustained serum concentrations the following days. Neopterin, a serum marker for the activation of the cellular immune system, was increased until day two after the run. Immediately after the run VEGF was significantly elevated and further increased 2.4-fold until day five post exercise (p = 0.005). EPO was also increased after exercise but reached its maximum 2 h after the run (2-fold increase; p = 0.004) and decreased thereafter. The main findings of our study are that prolonged strenuous exercise at moderate altitude induced a significant long lasting increase in serum VEGF and EPO which was accompanied by an activation of the immune system.