Uric Acid
URIC ACID: THE OXIDANT–ANTIOXIDANT PARADOX
Uric acid, despite being a major antioxidant in the human plasma, both correlates and predicts development of obesity, hypertension, and cardiovascular disease, conditions associated with oxidative stress. While one explanation for this paradox could be that a rise in uric acid represents an attempted protective response by the host, we review the evidence that uric acid may function either as an antioxidant (primarily in plasma) or pro-oxidant (primarily within the cell). We suggest that it is the pro-oxidative effects of uric acid that occur in cardiovascular disease and may have a contributory role in the pathogenesis of these conditions.
Uric acid, despite being a major antioxidant in the human plasma, both correlates and predicts development of obesity, hypertension, and cardiovascular disease, conditions associated with oxidative stress. While one explanation for this paradox could be that a rise in uric acid represents an attempted protective response by the host, we review the evidence that uric acid may function either as an antioxidant (primarily in plasma) or pro-oxidant (primarily within the cell). We suggest that it is the pro-oxidative effects of uric acid that occur in cardiovascular disease and may have a contributory role in the pathogenesis of these conditions.
The Role of Uric Acid as an Antioxidant in Selected Neurodegenerative Disease Pathogenesis: A Short Review
Uric acid, a potent antioxidant for humans, birds, reptiles, and some primate species, is the end-product of purine degradation that is formed in the xanthine/hypoxanthine reactions catalyzed by xanthine oxidase. Associated with the evolutionary loss of urate oxidase (the enzyme that oxidizes uric acid resulting in the formation of allantoin) and resulting increase in concentrations of uric acid is a prolonged life span. Uric acid is known to scavenge peroxynitrite and other free radicals that can cause an imbalance of oxidants leading to oxidative stress. Uric acid also has a role in protecting DNA from single-strand breaks caused by free radicals in the body leading to a protective effect in neurodegenerative diseases. The brain is particularly vulnerable to oxidative stress as it is considered an ‘expensive tissue’ with a particularly high metabolic rate and comparatively increased utilization of oxygen. Brain tissue is also high in unsaturated lipids, which makes it more susceptible to free radical damage. Oxidative stress is thus linked to the pathogenesis of neurodegenerative diseases and also ischemic brain injury. In this review, we summarize the function of uric acid in alleviating oxidative damage and providing protection to neural cells during injury and disease.
Uric acid, a potent antioxidant for humans, birds, reptiles, and some primate species, is the end-product of purine degradation that is formed in the xanthine/hypoxanthine reactions catalyzed by xanthine oxidase. Associated with the evolutionary loss of urate oxidase (the enzyme that oxidizes uric acid resulting in the formation of allantoin) and resulting increase in concentrations of uric acid is a prolonged life span. Uric acid is known to scavenge peroxynitrite and other free radicals that can cause an imbalance of oxidants leading to oxidative stress. Uric acid also has a role in protecting DNA from single-strand breaks caused by free radicals in the body leading to a protective effect in neurodegenerative diseases. The brain is particularly vulnerable to oxidative stress as it is considered an ‘expensive tissue’ with a particularly high metabolic rate and comparatively increased utilization of oxygen. Brain tissue is also high in unsaturated lipids, which makes it more susceptible to free radical damage. Oxidative stress is thus linked to the pathogenesis of neurodegenerative diseases and also ischemic brain injury. In this review, we summarize the function of uric acid in alleviating oxidative damage and providing protection to neural cells during injury and disease.
Vitamin C Intake and the Risk of Gout in Men – A Prospective Study
During the 20 years of follow-up, we documented 1,317 confirmed incident cases of gout. Compared with men with vitamin C intake < 250mg/day, the multivariate relative risk (RR) of gout was 0.83 (95% confidence interval [CI], 0.71 to 0.97) for total vitamin C intake 500–999 mg/day, 0.66 (0.52 to 0.86) for 1,000–1,499 mg/day, and 0.55 (0.38 to 0.80) for ≥ 1500 mg/day (P for trend < 0.001). The multivariate RR per 500mg increase in total daily vitamin C intake was 0.83 (95% CI, 0.77 to 0.90). Compared with men who did not use supplemental vitamin C, the multivariate RR of gout was 0.66 (95% CI, 0.49 to 0.88) for supplemental vitamin C intake 1,000–1,499 mg/day and 0.55 (0.36 to 0.86) for ≥ 1500 mg/day (P for trend < 0.001).
During the 20 years of follow-up, we documented 1,317 confirmed incident cases of gout. Compared with men with vitamin C intake < 250mg/day, the multivariate relative risk (RR) of gout was 0.83 (95% confidence interval [CI], 0.71 to 0.97) for total vitamin C intake 500–999 mg/day, 0.66 (0.52 to 0.86) for 1,000–1,499 mg/day, and 0.55 (0.38 to 0.80) for ≥ 1500 mg/day (P for trend < 0.001). The multivariate RR per 500mg increase in total daily vitamin C intake was 0.83 (95% CI, 0.77 to 0.90). Compared with men who did not use supplemental vitamin C, the multivariate RR of gout was 0.66 (95% CI, 0.49 to 0.88) for supplemental vitamin C intake 1,000–1,499 mg/day and 0.55 (0.36 to 0.86) for ≥ 1500 mg/day (P for trend < 0.001).
Vitamin C does not lower uric acid levels in gout patients, study finds
Despite previous studies touting its benefit in moderating gout risk, new research reveals that vitamin C, also known ascorbic acid, does not reduce uric acid (urate) levels to a clinically significant degree in patients with established gout. Vitamin C supplementation, alone or in combination with allopurinol, appears to have a weak effect on lowering uric acid levels in gout patients, according to the results of a new study.
Despite previous studies touting its benefit in moderating gout risk, new research reveals that vitamin C, also known ascorbic acid, does not reduce uric acid (urate) levels to a clinically significant degree in patients with established gout. Vitamin C supplementation, alone or in combination with allopurinol, appears to have a weak effect on lowering uric acid levels in gout patients, according to the results of a new study.
Gout and Vitamin C? Yes Vitamin C is good for gout, but there's a small caution
Rapid changes in uric acid levels can trigger a gout attack. This rapid change can be brought about by many factors in addition to mega doses of Vitamin C, including by drug medications that lower uric acid. (It's why doctors prescribe prophylatic medicines such as Colchicine or NSAIDS, along with uric acid lowering medicines). People who are susceptible to gout must consider these rapid changes.
Such a rapid change concerned the authors of one study in the 1970’s who also examined the link between gout and Vitamin C. They recorded that mega doses of Vitamin C (4,000 mg and 8,000 mg daily) reduced uric acid levels significantly, and by more than in the 2005 study. i.e. the same conclusion as Dr. Robert Atkins. However, as far as Vitamin C induced rapid changes in uric acid levels is concerned, this kind of change has not been reported in any study.
Rapid changes in uric acid levels can trigger a gout attack. This rapid change can be brought about by many factors in addition to mega doses of Vitamin C, including by drug medications that lower uric acid. (It's why doctors prescribe prophylatic medicines such as Colchicine or NSAIDS, along with uric acid lowering medicines). People who are susceptible to gout must consider these rapid changes.
Such a rapid change concerned the authors of one study in the 1970’s who also examined the link between gout and Vitamin C. They recorded that mega doses of Vitamin C (4,000 mg and 8,000 mg daily) reduced uric acid levels significantly, and by more than in the 2005 study. i.e. the same conclusion as Dr. Robert Atkins. However, as far as Vitamin C induced rapid changes in uric acid levels is concerned, this kind of change has not been reported in any study.
