Uric acid modulates vascular endothelial function through the down regulation of nitric oxide production

Effects of allopurinol on exercise-induced muscle damage: new therapeutic approaches?

Intensive muscular activity can trigger oxidative stress, and free radicals may hence be generated by working skeletal muscle. The role of the enzyme xanthine oxidase as a generating source of free radicals is well documented and therefore is involved in the skeletal muscle damage as well as in the potential transient cardiovascular damage induced by high-intensity physical exercise. Allopurinol is a purine hypoxanthine-based structural analog and a well-known inhibitor of xanthine oxidase. The administration of the xanthine oxidase inhibitor allopurinol may hence be regarded as promising, safe, and an economic strategy to decrease transient skeletal muscle damage (as well as heart damage, when occurring) in top-level athletes when administered before a competition or a particularly high-intensity training session. Although continuous administration of allopurinol in high-level athletes is not recommended due to its possible role in hampering training-induced adaptations, the drug might be useful in non-athletes. Exertional rhabdomyolysis is the most common form of rhabdomyolysis and affects individuals participating in a type of intense exercise to which they are not accustomed. This condition can cause exercise-related myoglobinuria, thus increasing the risk of acute renal failure and is also associated with sickle cell trait. In this manuscript, we have reviewed the recent evidence about the effects of allopurinol on exercise-induced muscle damage. More research is needed to determine whether allopurinol may be useful for preventing not only exertional rhabdomyolysis and acute renal damage but also skeletal muscle wasting in critical illness as well as in immobilized, bedridden, sarcopenic or cachectic patients.

The cross-sectional association between uric acid and atherosclerosis and the role of low-grade inflammation: the CODAM study

OBJECTIVES

The aims of this study were to investigate (i) associations between uric acid and prevalent cardiovascular disease (CVD), ankle-arm blood pressure index (AAIx) and carotid intima-media thickness (CIMT) in the total population and in predefined subgroups according to glucose metabolism status and (ii) the extent to which these associations are explained by low-grade inflammation.

METHODS

Cross-sectional analyses were conducted among 530 individuals [60.6% men, mean age 58.9 years (s.d. 6.9), 52.6% normal glucose metabolism (NGM)] at increased risk of CVD from the Cohort of Diabetes and Atherosclerosis Maastricht study. A low-grade inflammation score was computed by averaging the z-scores of eight inflammation markers [CRP, TNF-α, IL-6, IL-8, serum amyloid A, intercellular adhesion molecule 1 (ICAM-1), ceruloplasmin and haptoglobin].

RESULTS

After adjustment for traditional CVD risk factors, plasma uric acid (per s.d. of 81 μmol/l) was associated with CVD in individuals with NGM [odds ratio (OR) = 1.66, 95% CI 1.06, 2.58] but not with disturbed glucose metabolism (DGM) (OR = 0.81, 95% CI 0.55, 1.19, P interaction = 0.165). Uric acid was associated with CIMT in the total population (β = 0.024, 95% CI 0.007, 0.042) and slightly more strongly in individuals with NGM (β = 0.030, 95% CI 0.006, 0.054) than DGM (β = 0.018, 95% CI -0.009, 0.044, P interaction = 0.443). There was no association between uric acid and AAIx in any group (P interaction = 0.058). Uric acid was associated with low-grade inflammation in the total population (β = 0.074, 95% CI 0.013, 0.134, P interaction = 0.737). Adding low-grade inflammation to the models did not attenuate any of the associations.

CONCLUSION

The associations for uric acid with CIMT, and with CVD in NGM only, were not explained by low-grade inflammation. A difference in the strength of the associations between individuals with NGM and DGM was suggested.

Allopurinol prevents cardiac and skeletal muscle damage in professional soccer players

Xanthine oxidase (XO), a free radical-generating enzyme, is involved in tissue damage produced during exhaustive exercise. Our aim was to test whether allopurinol, a powerful inhibitor of XO, may be effective in preventing exercise-induced tissue damage in soccer players. Twelve soccer players were randomized into two experimental groups. One received allopurinol, before a match of the premier Spanish Football League, and the other placebo. Allopurinol prevented the exercise-induced increase in all the markers of skeletal muscle damage analyzed: creatine kinase, lactate dehydrogenase, aspartate aminotransferase, and myoglobin. Creatine kinase-MB isoenzyme and highly sensitive troponin T, specific biomarkers of myocardial injury, increased significantly in the placebo but not in the allopurinol-treated group after the football match. We also found that the exercise-induced lipid peroxidation, as reflected by malondialdehyde measurements, was prevented after allopurinol administration. However, inhibition of XO did not prevent the increment in the activity of alanine aminotransferase found after the match. No changes in the serum gamma glutamyltransferase activity was found after the match on either the placebo and the allopurinol groups. These two enzymes were determined as biomarkers of liver injury. Allopurinol represents an effective and inexpensive pharmacological agent to prevent tissue damage in soccer players.

Hyperuricemia and Risk of Atrial Fibrillation

The association between SUA levels and AF is currently poorly known. We reviewed the literature on the association with AF and hyperuricemia.The association between SUA level and AF has been demonstrated. SUA levels are associated with an increased risk for future AF in both sexes. And elevated SUA levels strongly correlate with an increased incidence of AF in patients with type 2 diabetes mellitus. Moreover, hyperuricemia was in connection with endothelial dysfunction, oxidative stress, systemic inflammatory markers, insulin resistance and LA size.

Free radicals and sprint exercise in humans

Sprint exercise ability has been critical for survival. The remarkably high-power output levels attained during sprint exercise are achieved through strong activation of anaerobic, and to a lesser extent, aerobic energy supplying metabolic reactions, which generate reactive oxygen and nitrogen species (RONS). Sprint exercise may cause oxidative stress leading to muscle damage, particularly when performed in severe acute hypoxia. However, with training oxidative stress is reduced. Paradoxically, total plasma antioxidant capacity increases during the subsequent 2 h after a short sprint due to the increase in plasma urate concentration. The RONS produced during and immediately after sprint exercise play a capital role in signaling the adaptive response to sprint. Antioxidant supplementation blunts the normal AMPKα and CaMKII phosphorylation in response to sprint exercise. However, under conditions of increased glycolytic energy turnover and muscle acidification, as during sprint exercise in severe acute hypoxia, AMPKα phosphorylation is also blunted. This indicates that an optimal level of RONS-mediated stimulation is required for the normal signaling response to sprint exercise. Although RONS are implicated in fatigue, most studies convey that antioxidants do not enhance sprint performance in humans. Although currently controversial, it has been reported that antioxidant ingestion during training may jeopardize some of the beneficial adaptations to sprint training.

The association between hyperuricemia, left atrial size and new-onset atrial fibrillation

BACKGROUND

Although hyperuricemia was associated with several cardiovascular diseases, the role of uric acid (UA) in left atrial (LA) remodeling and new-onset atrial fibrillation (AF) has not been fully explored. The goal of the present study is to investigate the relationship between UA, LA diameter and the development of AF in the large-scale cohort.

METHODS

The study consisted of 2 parts. First, we investigated the association between serum UA and LA diameter in a single-center database (n = 3043). Second, we studied and compared the risk of new-onset AF among patients with and without hyperuricemia in the nationwide longitudinal cohort in Taiwan (n = 122,524).

RESULTS

Elevated serum level of UA was associated with an increased systemic inflammation, and insulin resistance. The LA diameter was significantly correlated with serum UA (r = 0.341, p value < 0.001). The linear correlation between LA dimension and UA level remained significant after the adjustment for clinical, biochemical and echocardiographic variables. In the nationwide cohort, there were 2339 patients (1.9% of the study population) developing AF during the follow-up of 6.3 ± 3.0 years. The AF occurrence rate was higher in patients with hyperuricemia than those without it (2.1% versus 1.7%; p value < 0.001). Hyperuricemia was a significant risk factor of new-onset AF with a hazard ratio of 1.191 (95% confidence interval = 1.098-1.292, p value < 0.001) in the multivariate Cox regression analysis.

CONCLUSIONS

Hyperuricemia was associated with a larger LA size and may be a novel risk factor for the development of AF.