Excretion of thromboxane A2 and prostacyclin metabolites during treadmill exercise in patients with intermittent claudication

Intestinal permeability is increased in patients with intermittent claudication

PURPOSE

Intermittent claudication can be regarded as repeated ischemia reperfusion injury, which can induce a generalized increase in vascular permeability, including in intestine. The lactulose mannitol test (L/M test) was performed in patients with intermittent claudication to evaluate the change in intestinal permeability when they were forced to walk.

METHODS

The L/M test was performed in 11 patients with intermittent claudication and 11 control subjects without intermittent claudication. The test was performed at rest and after exercise. Patients walked on a treadmill until they stopped because of pain. The control subjects were forced to walk as far as 200 m on a treadmill. The L/M test was repeated in the patients after successful arterial reconstruction. Then the patients were instructed to walk the same distance at the same speed as they had before surgery.

RESULTS

In patients, the mean L/M ratio after exercise was significantly higher than the mean L/M ratio when they were at rest (0.068 +/- 0.053 vs 0.022 +/- 0.009, P <.05). In control subjects, however, no significant difference was observed between the mean L/M ratios after exercise and at rest. The mean L/M ratio after exercise, decreased from 0.068 +/- 0.053 to 0.018 +/- 0. 016 after successful arterial reconstruction (P <.05) in patients.

CONCLUSION

Intestinal permeability, determined by means of the L/M test, significantly increased in patients with intermittent claudication after exercise, and it diminished after arterial reconstruction. The L/M test is, consequently, a new noninvasive method to reflect ischemia in lower limbs during exercise.

Upright posture and maximal exercise increase platelet aggregability and prostacyclin production in healthy male subjects

BACKGROUND

It is well accepted that heavy physical exertion can trigger the onset of myocardial infarction, but the mechanism is uncertain. As platelet and endothelial function play an important role in thrombotic events, platelet and prostacyclin responses to maximal treadmill exercise were studied.

METHODS/RESULTS

The study subjects were 40 healthy men, mean (SEM) age 29 (5) years. Platelet aggregation was measured on a four channel aggregometer. Plasma 6-keto-prostaglandin F1alpha was analysed using an enzyme immunoassay technique. Upright posture and exercise produced an increase in platelet aggregability, as indicated by a fall in the threshold concentration of adrenaline (epinephrine) from 7.6 (1.5) microM at rest to 4.3 (1.0) microM after exercise (p = 0.002). The collagen lag time became significantly shorter with exercise (from 79.1 (3.1) seconds at rest to 71.9 (2.6) seconds after exercise, p = 0.003). Exercise was also associated with a 55% increase in plasma 6-keto-prostaglandin F1alpha (from 38.1 (75%CI 29.0 to 46.5) pg/ml at rest to 59.2 (47.3 to 66.8) pg/ml after exercise, p<0.001).

CONCLUSIONS

In healthy male subjects, upright posture and maximal exercise increased platelet aggregability but this increase was counteracted by an increase in prostacyclin production. In patients with endothelial dysfunction, a reduced prostacyclin response to exercise may promote a transient prothrombotic imbalance that may trigger cardiovascular disease onset.

Biochemical and inflammatory changes in the exercising claudicant

Intermittent claudication is an early manifestation of atherosclerosis in the leg. The prognosis for the claudicating limb is reasonably good, but patients have excess cardiovascular morbidity and mortality rates compared with a control population. Increasing evidence suggests that the calf pain experienced when walking followed by rest generates a low-grade inflammatory response. The cumulative effects of these individual events may have an adverse effect on the progression of atherosclerosis. A review of the literature was performed to identify studies measuring the exercise-induced inflammatory response in claudicants and to try to identify the role of cumulative inflammatory changes in the progression of atherosclerosis. The effect of exercise training on these markers is briefly explored. Walking until the onset of calf pain (ischaemia) followed by rest (reperfusion) results in the generation of oxygen-derived free radicals, neutrophil activation and a generalized increase in vascular permeability. Baseline levels of chronic inflammatory markers such as acute-phase proteins are elevated in claudicants compared with controls, suggesting that the transient acute inflammatory response has longer-term consequences. Therapeutic exercise training appears to lead to an attenuation of these inflammatory markers. Intermittent claudication can be considered as part of an inflammatory disease process. However, the concerns that exercise training might potentiate the vascular inflammatory response appear to be unjustified, although further work is needed to clarify this. Exercise training should therefore be considered as an important treatment option for claudication.

The evidence for exercise-induced inflammation in intermittent claudication: should we encourage patients to stop walking?

OBJECTIVES

To review clinical and experimental evidence that exercise to the onset of calf pain in patients with intermittent claudication results in an inflammatory response, and to consider whether repeated inflammatory events induced by therapeutic exercise training may lead to progression of atherosclerosis.

METHODS

A literature search was performed to identify studies measuring biochemical markers of exercise-induced ischaemia-reperfusion injury in patients with intermittent claudication. Current theories of atherogenesis were reviewed and the use of acute-phase proteins as potential markers of vascular disease explored.

RESULTS

Exercise to the onset of calf pain results in an inflammatory response with free radical formation, neutrophil activation and systemic vascular endothelial damage. Acute-phase proteins such as C-reactive protein and serum amyloid A protein have exciting potential use as stable biochemical markers of disease in claudication.

CONCLUSIONS

Further studies are needed to determine the effect of long-term exercise training on exercise-induced inflammation in claudication. Early work suggests, in fact, that exercise attenuates this inflammatory response. If this were confirmed then it would support the clinical impression that exercise training is beneficial in terms of symptomatic improvement and cardiovascular health in patients with intermittent claudication.

Reduction by indobufen of neutrophil activation in peripheral arterial occlusive disease

We evaluated the effectiveness of indobufen administration in reducing neutrophil activation in a clinical model of ischemia-reperfusion. Thirty stable patients with intermittent claudication due to occlusive peripheral arterial disease of the leg were randomly assigned to two groups. Patients in group I were treated with indobufen [200 mg orally twice daily (p.o. b.i.d.) for a week]; patients in group II received a placebo. Both groups of patients were submitted to standardized treadmill exercise until onset of claudication. Plasma levels of thromboxane B2 (TxB2) and 6-keto-prostaglandin F1alpha(6-k-PGF1alpha) neutrophil filterability, and neutrophil activation (by nitro-blue tetrazolium test) were assessed in blood samples from the femoral vein draining the ischemic leg. The values were obtained at rest and 5, 30, and 60 min after onset of claudication. Urinary albumin excretion was measured at rest and 1 h after onset of claudication. Plasma levels of TxB2 and 6-k-PGF1alpha increased significantly in the placebo group 5 min after onset of claudication, whereas only a slight nonsignificant increase was observed in the indobufen-treated group at the same timepoint.

Systemic responses in patients with intermittent claudication after treadmill exercise

The effect of 5 min treadmill exercise was investigated in claudicant patients and healthy controls; systemic neutrophil count, plasma thromboxane and von Willebrand's factor (a marker for endothelial injury) were measured. Median (interquartile range (i.q.r.)) resting neutrophil count was 5.6 (5.2-6.0) x 10(6) cells l-1 in claudicants and 2.8 (2.6-3.2) x 10(6) l-1 in controls (P < 0.05); this increased in those with claudication to 7.1 (6.2-7.7) x 10(6) l-1 immediately after exercise (P < 0.05). The resting plasma thromboxane level was 32.1 (25.0-60.0) pg ml-1 in claudicants and rose to 135.0 (104.0-141.3) pg ml-1 15 min after exercise, compared with a rise from 25.0 (22.0-33.5) to 55.5 (33.0-67.0) pg ml-1 in controls (P < 0.05). The resting serum von Willebrand's factor level was 127 (110-135) units dl-1 in claudicants compared with 60 (48-71) units dl-1 in controls; this difference persisted after exercise (P < 0.01). In patients with claudication, the level of von Willebrand's factor increased to 150 (140-156) units dl-1 60 min after exercise (P < 0.05). Free radical scavenging capacity was also investigated by measuring the plasma antioxidant activity of glutathione peroxidase and its essential non-metal cofactor selenium. Scavenging capacity was lower in claudicant patients whose median (i.q.r.) glutathione peroxidase activity (change in absorbance per min per ml plasma) was 2.84 (2.39-3.61) versus 3.24 (3.06-3.79) in controls (P < 0.05). Similarly, plasma concentrations of selenium were lower in claudicants at a median (i.q.r.) of 75.0 (58.0-81.0) micrograms l-1 compared with 88.0 (75.0-92.5) micrograms l-1 in controls (P < 0.05). Exercise in claudicant patients leads to neutrophilia and thromboxane production with subsequent endothelial injury. The antioxidant activity of glutathione peroxidase is reduced in patients with claudication and may allow the unopposed action of free radicals to damage endothelium.

Neutrophils may contribute to the morbidity and mortality of claudicants

Peripheral arterial occlusive disease is a common cause of morbidity in middle-aged men; 5 per cent of those aged over 50 years suffer from intermittent claudication. While claudication itself is not fatal, claudicants have a mortality rate approximately three times that of non-claudicating men of the same age, mainly from cardiovascular disease. This review examines the evidence for involvement of the neutrophil in this increased mortality and describes the possible pathogenesis. It also discusses how treatment of claudication may modify neutrophil behaviour, reducing subsequent mortality and morbidity rates.

Role of the leucocyte in the pathogenesis of vascular disease

The leucocyte plays a key role in the local and systemic tissue injury that results from peripheral arterial disease and chronic venous insufficiency. Despite the apparent dissimilarities between limb ischaemia and chronic venous ulceration, in both diseases macrovascular abnormalities lead to microvascular leucocyte trapping and activation. Activated leucocytes adhere to and damage adjacent endothelium by expressing adhesion molecules and releasing harmful moieties such as proteases and free radicals. Subsequent loss of endothelial integrity and the migration of activated leucocytes outwith the circulation leads to destruction of surrounding tissue. Leucocytes and their products are also involved in the systemic manifestations of ischaemia such as multiple organ failure and coagulopathy. An overview of leucocyte biology as it pertains to peripheral arterial and venous disease is presented. The opportunities for novel therapeutic interventions based on a better understanding of this biology are also discussed.

Effect of surgery on the systemic inflammatory response to intermittent claudication

The hypothesis that intermittent claudication initiates a systemic inflammatory response was investigated by studying the effect of exercise on markers of neutrophil activation and vascular permeability in 25 claudicants and 10 controls. Urinary albumin excretion, previously demonstrated to reflect vascular permeability, increased significantly after exercise in claudicants and was associated with decreased neutrophil filterability and increased serum lysozyme activity. No similar exercise-induced changes were seen in controls or in claudicants after successful arterial bypass surgery. These results suggest that intermittent claudication is associated with potentially deleterious systemic manifestations that are surgically reversible.