Effect of Oral Vitamin C Supplementation on High-Altitude Hyperuricemia in Young Men Initially Migrating to High Altitude: A Pilot Study

Intermittent high altitude hypoxia induced liver and kidney injury leading to hyperuricemia

About 140 million people worldwide live at an altitude above 2500 m. Studies have showed an increase of the incidence of hyperuricemia among plateau populations, but little is known about the possible mechanisms. This study aims to assess the effects of high altitude on hyperuricemia and explore the corresponding mechanisms at the histological, inflammatory and molecular levels. This study finds that intermittent hypobaric hypoxia (IHH) exposure results in an increase of serum uric acid level and a decrease of uric acid clearance rate. Compared with the control group, the IHH group shows significant increases in hemoglobin concentration (HGB) and red blood cell counts (RBC), indicating that high altitude hyperuricemia is associated with polycythemia. This study also shows that IHH exposure induces oxidative stress, which causes the injury of liver and renal structures and functions. Additionally, altered expressions of organic anion transporter 1 (OAT1) and organic cation transporter 1 (OCT1) of kidney have been detected in the IHH exposed rats. The adenosine deaminase (ADA) expression levels and the xanthione oxidase (XOD) and ADA activity of liver of the IHH exposure group have significantly increased compared with those of the control group. Furthermore, the spleen coefficients, IL-2, IL-1β and IL-8, have seen significant increases among the IHH exposure group. TLR/MyD88/NF-κB pathway is activated in the process of IHH induced inflammatory response in joints. Importantly, these results jointly show that IHH exposure causes hyperuricemia. IHH induced oxidative stress along with liver and kidney injury, unusual expression of the uric acid synthesis/excretion regulator and inflammatory response, thus suggesting a potential mechanism underlying IHH-induced hyperuricemia.

Prevalence of High-Altitude Polycythemia and Hyperuricemia and Risk Factors for Hyperuricemia in High-Altitude Immigrants

Song Zhen, Anxin Zhang, Jie Luo, Guanghai Xiong, Haibo Peng, Rang Zhou, Yuanfeng Li, Hongqiang Xu, Zhen Li, Wei Zhao, and Haoxiang Zhang. Prevalence of high-altitude polycythemia and hyperuricemia and risk factors for hyperuricemia in high-altitude immigrants. High Alt Med Biol. 24:132-138, 2023. Background: Few studies have investigated the epidemiology of chronic mountain sickness (CMS) in high-altitude immigrants. This study evaluated the prevalence of polycythemia and hyperuricemia (HUA) and risk factors for HUA in high-altitude immigrants. Methods: A cross-sectional study was conducted with 7,070 immigrants 15-45 years of age living on the Tibetan Plateau between January and December 2021. Information from routine physical examinations was obtained from each participant. Binary logistic regression analysis was performed to determine the correlation of several risk factors for HUA. Results: The prevalence of high-altitude polycythemia (HAPC) and HUA was 25.8% (28.7% in males and 9.4% in females) and 54.2% (59.9% in males and 22.5% in females), respectively. The highest prevalence of HAPC in males and females was observed in participants 26-30 and 21-25 years of age, respectively. The highest prevalence of HUA in both males and females was observed in participants 26-30 years of age. Binary logistic regression analysis showed that age, sex, and hemoglobin (Hb) concentration were risk factors for HUA, among which age was a negative factor and male sex and Hb concentration were positive factors. Conclusions: Immigrants are more susceptible to HAPC and HUA. The high prevalence of CMS of immigrants may be associated with Hb concentration, age, and sex.

Serum Metabolomics Identifies Dysregulated Pathways and Potential Metabolic Biomarkers for Hyperuricemia and Gout

OBJECTIVE

To systematically profile metabolic alterations and dysregulated metabolic pathways in hyperuricemia and gout, and to identify potential metabolite biomarkers to discriminate gout from asymptomatic hyperuricemia.

METHODS

Serum samples from 330 participants, including 109 with gout, 102 with asymptomatic hyperuricemia, and 119 normouricemic controls, were analyzed by high-resolution mass spectrometry-based metabolomics. Multivariate principal components analysis and orthogonal partial least squares discriminant analysis were performed to explore differential metabolites and pathways. A multivariate methods with Unbiased Variable selection in R (MUVR) algorithm was performed to identify potential biomarkers and build multivariate diagnostic models using 3 machine learning algorithms: random forest, support vector machine, and logistic regression.

RESULTS

Univariate analysis demonstrated that there was a greater difference between the metabolic profiles of patients with gout and normouricemic controls than between the metabolic profiles of individuals with hyperuricemia and normouricemic controls, while gout and hyperuricemia showed clear metabolomic differences. Pathway enrichment analysis found diverse significantly dysregulated pathways in individuals with hyperuricemia and patients with gout compared to normouricemic controls, among which arginine metabolism appeared to play a critical role. The multivariate diagnostic model using MUVR found 13 metabolites as potential biomarkers to differentiate hyperuricemia and gout from normouricemia. Two-thirds of the samples were randomly selected as a training set, and the remainder were used as a validation set. Receiver operating characteristic analysis of 7 metabolites yielded an area under the curve of 0.83-0.87 in the training set and 0.78-0.84 in the validation set for distinguishing gout from asymptomatic hyperuricemia by 3 machine learning algorithms.

CONCLUSION

Gout and hyperuricemia have distinct serum metabolomic signatures. This diagnostic model has the potential to improve current gout care through early detection or prediction of progression to gout from hyperuricemia.

Association between Oral vitamin C supplementation and serum uric acid: A meta-analysis of randomized controlled trials

INTRODUCTION

Results from recent trials assessing the effect of oral vitamin C supplementation on serum uric acid (SUA) have been inconsistent.

OBJECTIVES

The purpose of this study was to explore the association between oral vitamin C supplementation and serum uric acid.

METHODS

PUBMED, EMBASE, CNKI, Web of Science, and CENTRAL of Cochrane library databases were searched to identify relevant articles published up to February 2020. Heterogeneity was evaluated using I-square (I²) statistics. Random-effects model was used to pool weighted mean differences (WMD) and 95 % confidence interval (CI) as summary effect sizes.

RESULTS

The total sixteen eligible randomized controlled trials (RCTs) containing 1,013 participants were included in this meta-analysis. The pooled findings showed that vitamin C supplementation had a significant effect of lowering SUA. The subgroup analyses showed that the effect of vitamin C supplementation on SUA has positive association with mean age of participants <65 years old, the use of placebo or blank control, duration of trials <1 month and high-quality studies. In addition, sensitivity analysis showed that the results of this study were stable. Both Egger's test and Begg's test demonstrated that no evidence of significant publication bias.

CONCLUSIONS

The results of present meta-analysis have demonstrated that vitamin C supplementation could make a reduction of SUA. The use of placebo, duration of intervention, age of the subjects and study quality have an impact on the effect of oral vitamin C, but the baseline of SUA not.

Natural and synthetic antioxidants targeting cardiac oxidative stress and redox signaling in cardiometabolic diseases

Cardiometabolic diseases (CMDs) are metabolic diseases (e.g., obesity, diabetes, atherosclerosis, rare genetic metabolic diseases, etc.) associated with cardiac pathologies. Pathophysiology of most CMDs involves increased production of reactive oxygen species and impaired antioxidant defense systems, resulting in cardiac oxidative stress (OxS). To alleviate OxS, various antioxidants have been investigated in several diseases with conflicting results. Here we review the effect of CMDs on cardiac redox homeostasis, the role of OxS in cardiac pathologies, as well as experimental and clinical data on the therapeutic potential of natural antioxidants (including resveratrol, quercetin, curcumin, vitamins A, C, and E, coenzyme Q10, etc.), synthetic antioxidants (including N-acetylcysteine, SOD mimetics, mitoTEMPO, SkQ1, etc.), and promoters of antioxidant enzymes in CMDs. As no antioxidant indicated for the prevention and/or treatment of CMDs has reached the market despite the large number of preclinical and clinical studies, a sizeable translational gap is evident in this field. Thus, we also highlight potential underlying factors that may contribute to the failure of translation of antioxidant therapies in CMDs.

Role of Vitamin C in Prophylaxis and Treatment of Gout-A Literature Review

Gout, known as “the disease of the kings”, is the most frequent type of arthritis. It results from sustained hyperuricemia that leads to monosodium urate crystal deposition in joint structures and soft tissue. Environmental factors such as diet affect the incidence of gout; there is a known relationship between the occurrence of an acute attack of gout and the consumption of alcohol and meat; and a low purine diet is a widely recognized nonpharmacological method of supplementing the treatment and preventing recurrence of arthritis. This review aims to summarize the current knowledge about the role of vitamin C in prevention and treatment of gout. A PubMed/Medline database search on the role of vitamin C in purine metabolism was done. Reports from in vitro and animal studies seem to be promising and to allow explanation of the physiological relationship between vitamin C and uric acid. Most epidemiological studies indicate a significant correlation between high vitamin C intake and lower serum uric acid levels. Despite promising observations, there are few observational and interventional studies, and their results do not clearly define the benefits of a high daily intake of vitamin C in preventing the development and recurrence of gout.

Dietary Vitamin E Intake Was Inversely Associated with Hyperuricemia in US Adults: NHANES 2009-2014

INTRODUCTION

Current evidence on the association between dietary vitamin E intake and hyperuricemia risk is limited and conflicting.

OBJECTIVE

The aim of the study was to assess the association of dietary vitamin E intake with hyperuricemia in US adults.

METHODS

We conducted a cross-sectional study using data from the National Health and Nutrition Examination Survey, 2009-2014. Dietary vitamin E intake was evaluated through two 24-h dietary recall interviews. Logistic regression and restricted cubic spline models were used to examine the association between dietary vitamin E intake and hyperuricemia.

RESULTS

Overall, 12,869 participants were included. The prevalence of hyperuricemia was 19.35%. After adjustment for age, gender, BMI, race, educational level, smoking status, alcohol consumption, physical activity, total daily energy intake, total cholesterol, protein intake, glomerular filtration rate, serum Cr, use of uric acid drugs, and drug abuse, the odds ratio (95% confidence interval) of hyperuricemia for the highest tertile of dietary vitamin E intake was 0.77 (0.63-0.96) compared with that of the lowest tertile. In men, dietary vitamin E intake and hyperuricemia were negatively correlated. In stratified analyses by age (20-39, 40-59, and ≥60 years), dietary vitamin E intake was inversely associated with hyperuricemia only among participants aged ≥60 years. Dose-response analyses showed that dietary vitamin E intake was inversely associated with hyperuricemia in a nonlinear manner.

CONCLUSION

Dietary vitamin E intake was negatively correlated with hyperuricemia in US adults, especially among males and participants aged ≥60 years.