Endogenous Urate Production Augments Plasma Antioxidant Capacity in Healthy Lowland Subjects Exposed to High Altitude

Serum urate levels and neurodegenerative outcomes: a prospective cohort study and mendelian randomization analysis of the UK Biobank

BACKGROUND

Previous studies on the associations between serum urate levels and neurodegenerative outcomes have yielded inconclusive results, and the causality remains unclear. This study aimed to investigate whether urate levels are associated with the risks of Alzheimer's disease and related dementias (ADRD), Parkinson's disease (PD), and neurodegenerative deaths.

METHODS

This prospective study included 382,182 participants (45.7% men) from the UK Biobank cohort. Cox proportional hazards models were used to assess the associations between urate levels and risk of neurodegenerative outcomes. In the Mendelian randomization (MR) analysis, urate-related single-nucleotide polymorphisms were identified through a genome-wide association study. Both linear and non-linear MR approaches were utilized to investigate the potential causal associations.

RESULTS

During a median follow-up period of 12 years, we documented 5,400 ADRD cases, 2,553 PD cases, and 1,531 neurodegenerative deaths. Observational data revealed that a higher urate level was associated with a decreased risk of ADRD (hazard ratio [HR]: 0.93, 95% confidence interval [CI]: 0.90, 0.96), PD (HR: 0.87, 95% CI: 0.82, 0.91), and neurodegenerative death (HR: 0.88, 95% CI: 0.83, 0.94). Negative linear associations between urate levels and neurodegenerative events were observed (all P-values for overall < 0.001 and all P-values for non-linearity > 0.05). However, MR analyses yielded no evidence of either linear or non-linear associations between genetically predicted urate levels and the risk of the aforementioned neurodegenerative events.

CONCLUSION

Although the prospective cohort study demonstrated that elevated urate levels were associated with a reduced risk of neurodegenerative outcomes, MR analyses found no evidence of causality.

Impaired sensitivity to thyroid hormones is associated with hyperuricemia in a Chinese euthyroid population

Objective

Impaired sensitivity to thyroid hormones has been reported as a common metabolic disorder, and it remains poorly understood whether it interplays with uric acid (UA) metabolism as an established risk factor for cardiovascular diseases (CVDs). We aimed to investigate the relationship between thyroid hormone sensitivity and elevated UA in a Chinese euthyroid population.

Methods

A total of 15,955 euthyroid subjects were included in this study. Thyroid hormone sensitivity indices were calculated, including the thyroid feedback quantile-based index (TFQI), the Chinese-referenced parametric TFQI (PTFQI), the TSH index (TSHI), and the thyrotropin thyroxine resistance index (TT4RI), and the FT3/FT4 ratio. Linear and logistic regression analyses were performed to detect the association between thyroid hormone sensitivity and elevated UA.

Results

Subjects with reduced sensitivity to thyroid hormones had increased UA levels in both genders (p for trend < 0.001). Logistic and linear regression analyses showed that higher TFQI, PTFQI, TSHI, and TT4RI were positively associated with elevated UA levels, but negatively associated with the FT3/FT4 ratio. The odds ratio (OR) of the highest versus the first quartile of TFQI was 1.20 (1.05, 1.38) in men and 1.80 (1.46, 2.23) in women (p < 0.001). PTHQI, TSHI, and TT4RI obtained similar results in both genders. Conversely, the highest quartile of the FT3/FT4 ratio was negatively correlated with elevated UA levels [men: OR 0.78 (0.68,0.89), women: OR 0.66 (0.53,0.81)].

Conclusion

Impaired sensitivity to thyroid hormones was associated with elevated UA levels in euthyroid subjects. Our findings shed light on the role of thyroid hormone sensitivity in UA metabolism.

Research Progress on the Relationship between Dietary Patterns and Hyperuricemia

As the final metabolite of purine metabolism, uric acid is critically associated with human health. The serum uric acid level is regulated by diet and the metabolic capacity of the human body. The impaired control of uric acid metabolism and excretion is associated with the increased level of serum uric acid, which ultimately results in hyperuricemia. Hyperuricemia is the "fourth-highest" after hypertension, hyperglycemia, and hyperlipidemia. With progress made in the relationship between diet and hyperuricemia, different dietary patterns and lifestyles have been discussed, such as exercise, the amount intake of meat, seafood, supplements with omega-3 fatty acids, sugar-sweetened soft drinks and energy drinks, and lower-fat-containing foods as well as drinking beer, wine, and spirits in the present article. This study demonstrated that a lower risk of hyperuricemia is substantially correlated with higher baseline adherence to MeDiet, and plant polyphenols can combat hyperuricemia by blocking xanthine oxidase.

Differential Effects of High-Altitude Exposure on Markers of Oxidative Stress, Antioxidant Capacity and Iron Profiles

High altitude (HA) exposure may stimulate significant physiological and molecular changes, resulting in HA-related illnesses. HA may impact oxidative stress, antioxidant capacity and iron homeostasis, yet it is unclear how both repeated exposure and HA acclimatization may modulate such effects. Therefore, we assessed the effects of weeklong repeated daily HA exposure (2,900m to 5,050m) in altitude-naïve individuals (n=21, 13 females, mean ± SD, 25.3 ± 3.7 years) to mirror the working schedule of HA workers (n=19, all males, 40.1 ± 2.1 years) at the Atacama Large Millimeter Array (ALMA) Observatory (San Pedro de Atacama, Chile). Markers of oxidative stress, antioxidant capacity and iron homeostasis were measured in blood plasma. Levels of protein oxidation (p<0.001) and catalase activity (p=0.023) increased and serum iron (p<0.001), serum ferritin (p<0.001) and transferrin saturation (p<0.001) levels decreased with HA exposure in both groups. HA workers had lower levels of oxidative stress, and higher levels of antioxidant capacity, iron supply and hemoglobin concentration as compared to altitude-naïve individuals. Upon a second week of daily HA exposure, changes in levels of protein oxidation, glutathione peroxidase and nitric oxide metabolites were lower as compared to the first week in altitude-naïve individuals. These results indicate that repeated exposure to HA may significantly alter oxidative stress and iron homeostasis, and the degree of such changes may be dependent on if HA is visited naïvely or routinely. Further studies are required to fully elucidate differences in HA-induced changes in oxidative stress and iron homeostasis profiles amongst visitors of HA.

Vitreous Humor Proteome: Targeting Oxidative Stress, Inflammation, and Neurodegeneration in Vitreoretinal Diseases

Oxidative stress is defined as an unbalance between pro-oxidants and antioxidants, as evidenced by an increase in reactive oxygen and reactive nitrogen species production over time. It is important in the pathophysiology of retinal disorders such as diabetic retinopathy, age-related macular degeneration, retinal detachment, and proliferative vitreoretinopathy, which are the focus of this article. Although the human organism's defense mechanisms correct autoxidation caused by endogenous or exogenous factors, this may be insufficient, causing an imbalance in favor of excessive ROS production or a weakening of the endogenous antioxidant system, resulting in molecular and cellular damage. Furthermore, modern lifestyles and environmental factors contribute to increased chemical exposure and stress induction, resulting in oxidative stress. In this review, we discuss the current information about oxidative stress and the vitreous proteome with a special focus on vitreoretinal diseases. Additionally, we explore therapies using antioxidants in an attempt to rescue the body from oxidation, restore balance, and maximize healthy body function, as well as new investigational therapies that have shown significant therapeutic potential in preclinical studies and clinical trial outcomes, along with their goals and strategic approaches to combat oxidative stress.

OxInflammation at High Altitudes: A Proof of Concept from the Himalayas

High-altitude locations are fascinating for investigating biological and physiological responses in humans. In this work, we studied the high-altitude response in the plasma and urine of six healthy adult trekkers, who participated in a trek in Nepal that covered 300 km in 19 days along a route in the Kanchenjunga Mountain and up to a maximum altitude of 5140 m. Post-trek results showed an unbalance in redox status, with an upregulation of ROS (+19%), NOx (+28%), neopterin (+50%), and pro-inflammatory prostanoids, such as PGE₂ (+120%) and 15-deoxy-delta12,14-PGJ₂ (+233%). The isoprostane 15-F_2t-IsoP was associated with low levels of TAC (−18%), amino-thiols, omega-3 PUFAs, and anti-inflammatory CYP450 EPA-derived mediators, such as DiHETEs. The deterioration of antioxidant systems paves the way to the overload of redox and inflammative markers, as triggered by the combined physical and hypoxic stressors. Our data underline the link between oxidative stress and inflammation, which is related to the concept of OxInflammation into the altitude hypoxia fashion.

Data-Independent Acquisition Mass Spectrometry of the Human Lens Enhances Spatiotemporal Measurement of Fiber Cell Aging

The ocular lens proteome undergoes post-translational and progressive degradation as fiber cells age. The oldest fiber cells and the proteins therein are present at birth and are retained through death. Transparency of the lens is maintained in part by the high abundance Crystallin family proteins (up to 300 mg/mL), which establishes a high dynamic range of protein abundance. As a result, previous data-dependent analysis (DDA) measurements of the lens proteome are less equipped to identify the lowest abundance proteins. To probe more deeply into the lens proteome, we measured the insoluble lens proteome of an 18-year-old human with DDA and data-independent analysis (DIA) methods. By applying more recent library-free DIA search methods, 5,161 protein groups, 50,386 peptides, and 4,960 deamidation sites were detected: significantly outperforming the quantity of identifications in using DDA and pan-human DIA library searches. Finally, by segmenting the lens into multiple fiber cell-age-related regions, we uncovered cell-age-related changes in proteome composition and putative function.

High-altitude hypoxia induced reactive oxygen species generation, signaling, and mitigation approaches

Homeostasis between pro-oxidants and anti-oxidants is necessary for aerobic life, which if perturbed and shifted towards pro-oxidants results in oxidative stress. It is generally agreed that reactive oxygen species (ROS) production is accelerated with mountainous elevation, which may play a role in spawning serious health crisis. Exposure to increasing terrestrial altitude leads to a reduction in ambient O₂ availability in cells producing a series of hypoxic oxidative stress reactions and altering the redox balance in humans. Enormous literature on redox signaling drove research activity towards understanding the role of oxidative stress under normal and challenging conditions like high-altitude hypoxia which grounds for disturbed redox signaling. Excessive ROS production and accumulation of free radicals in cells and tissues can cause various pulmonary, cardiovascular, and metabolic pathophysiological conditions. In order to counteract this oxidative stress and maintain the balance of pro-oxidants and anti-oxidants, an anti-oxidant system exists in the human body, which, however, gets surpassed by elevated ROS levels, but can be strengthened through the use of anti-oxidant supplements. Such cumulative studies of fundamentals on a global concept like oxidative stress and role of anti-oxidants can act as a foundation to further smoothen for researchers to study over health, disease, and other pathophysiological conditions. This review highlights the interconnection between high altitude and oxidative stress and the role of anti-oxidants to protect cells from oxidative damages and to lower the risk of altitude-associated sickness.

Uric acid released from poly(ε-caprolactone) fibers as a treatment platform for spinal cord injury

Spinal cord injury (SCI) is characterized by a primary mechanical phase of injury, resulting in physical tissue damage, and a secondary pathological phase, characterized by biochemical processes contributing to inflammation, neuronal death, and axonal demyelination. Glutamate-induced excitotoxicity (GIE), in which excess glutamate is released into synapses and overstimulates glutamate receptors, is a major event in secondary SCI. GIE leads to mitochondrial damage and dysfunction, release of reactive oxygen species (ROS), DNA damage, and cell death. There is no clinical treatment that targets GIE after SCI, and there is a need for therapeutic targets for secondary damage in patients. Uric acid (UA) acts as an antioxidant and scavenges free radicals, upregulates glutamate transporters on astrocytes, and preserves neuronal viability in in vitro and in vivo SCI models, making it a promising therapeutic candidate. However, development of a drug release platform that delivers UA locally to the injured region in a controlled manner is crucial, as high systemic UA concentrations can be detrimental. Here, we used the electrospinning technique to synthesize UA-containing poly(ɛ-caprolactone) fiber mats that are biodegradable, biocompatible, and have a tunable degradation rate. We optimized delivery of UA as a burst within 20 min from uncoated fibers and sustained release over 2 h with poly(ethylene glycol) diacrylate coating. We found that both of these fibers protected neurons and decreased ROS generation from GIE in organotypic spinal cord slice culture. Thus, fiber mats represent a promising therapeutic for UA release to treat patients who have suffered a SCI.

Evaluation of Serum Interleukin 6, Tumor Necrosis Factor-Alpha, and Interferon-Gamma Levels in Relation to Body Mass Index and Blood Pressure in HIV Seropositive Pregnant Women Coinfected with Malaria

Malaria and HIV are leading causes of morbidity and mortality, particularly in sub-Saharan Africa. Both diseases are highly endemic and have a wide geographic overlap with severe impact on pregnancy. This was a case-control study designed to evaluate the levels of interleukin -6 (IL-6), tumor necrosis factor-alpha (TNF-α), and interferon-gamma (IFN-γ) and their relationship with some anthropometric indices such as body mass index (BMI) and blood pressure in HIV-malaria coinfected women attending antenatal clinic at Nnamdi Azikiwe University Teaching Hospital (NAUTH), Nnewi, Nigeria. 122 pregnant women and 30 nonpregnant women (control) aged between 18 and 42 years were recruited for the study. Screening of HIV antibodies was done using a national algorithm. Peripheral malaria was determined using rapid detection and the Giemsa stain technique. Cytokines were assayed using the enzyme-linked immunosorbent assay technique. HIV-malaria coinfected pregnant women showed significantly higher levels of IL-6, IFN-γ, TNF-α, and blood pressure with reduced BMI value compared with HIV seronegative pregnant and nonpregnant control participants (p ≤ 0.001, respectively). The findings indicated significant cytokine imbalance which suggests an active inflammatory process and reduced cellular immunity. The increased BMI and blood pressure level observed indicate overweight and possible hypertension which could subsequently lead to preeclampsia and other adverse pregnancy outcomes.

Hyperuricaemia and gout in cardiovascular, metabolic and kidney disease

During the last century, there has been an increasing prevalence of hyperuricaemia noted in many populations. While uric acid is usually discussed in the context of gout, hyperuricaemia is also associated with hypertension, chronic kidney disease, hypertriglyceridaemia, obesity, atherosclerotic heart disease, metabolic syndrome, and type 2 diabetes. Here we review the connection between hyperuricaemia and cardiovascular, kidney and metabolic diseases. Contrary to the popular view that uric acid is an inert metabolite of purine metabolism, recent studies suggest serum uric acid may have a variety of pro-inflammatory, pro-oxidative and vasoconstrictive actions that may contribute to cardiometabolic diseases. Hyperuricaemia is a predictive factor for the development of hypertension, metabolic syndrome, type 2 diabetes, coronary artery disease, left ventricular hypertrophy, atrial fibrillation, myocardial infarction, stroke, heart failure and chronic kidney disease. Treatment with uric acid-lowering therapies has also been found to improve outcomes in patients with hypertension and kidney disease, in some but not all studies. In conclusion, uric acid is emerging as a potentially treatable risk factor for cardiometabolic diseases, and more clinical trials investigating the potential benefit of lowering serum uric acid are recommended in individuals with hyperuricaemia with and without deposition and concomitant hypertension, metabolic syndrome or chronic kidney disease.

Effect of high-altitude trekking on blood pressure and on asymmetric dimethylarginine and isoprostane production: Results from a Mount Ararat expedition

The study aimed at exploring the mechanisms behind blood pressure and heart rate changes upon acute altitude exposure utilizing urinary excretion of biochemical factors involved in cardiovascular regulation. The study was conducted on 12 lowlander native male mountain climbers, living at sea level, exposed to altitudes ranging from 1800 to 5147 m above sea level over 4 days, during their ascent to Mount Ararat (Turkey). Blood pressure (measured by oscillometric method), heart rate, and blood oxygen saturation (SpO₂ ) were recorded at rest (on awakening before food intake), in hypoxic conditions at 4200 m and at sea level before and after the altitude expedition. In the same study conditions (ie before-during-after the expedition), first-voided urinary samples were collected and assayed for 8-iso-prostaglandin F_2α (8-iso-PGF_2α ) and asymmetric dimethylarginine (ADMA) determination. Heart rate, and systolic and diastolic blood pressures were higher (P < .05) at high altitude than at the sea level. Furthermore, both urinary 8-iso-PGF_2α and ADMA were significantly elevated (P < .01) at high altitude and returned to normal levels soon after returning to sea level. A 4-day exposure to high-altitude hypoxia induced a temporary increase in blood pressure and heart rate, confirming previous findings. Blood pressure increase at high altitude was associated with significantly enhanced production of biochemical mediators such as 8-iso-PGF2α, catecholamines, and ADMA, although we could not demonstrate a direct link between these parallel significant changes probably due to the forcefully limited sample size of our study, carried out in challenging environmental conditions at very high altitude.

The Protective Effects of Increasing Serum Uric Acid Level on Development of Metabolic Syndrome

BACKGROUND

It has not been determined whether changes in serum uric acid (SUA) level are associated with incident metabolic syndrome (MetS). The aim of the current study was to investigate the relationship between changes in SUA level and development of MetS in a large number of subjects.

METHODS

In total, 13,057 subjects participating in a medical health check-up program without a diagnosis of MetS at baseline were enrolled. Cox proportional hazards models were used to test the independent association of percent changes in SUA level with development of MetS.

RESULTS

After adjustment for age, systolic blood pressure, body mass index, fat-free mass (%), estimated glomerular filtration rate, smoking status, fasting glucose, triglyceride, low density lipoprotein cholesterol, high density lipoprotein cholesterol, and baseline SUA levels, the hazard ratios (HRs) (95% confidence intervals [CIs]) for incident MetS in the second, third, and fourth quartiles compared to the first quartile of percent change in SUA level were 1.055 (0.936 to 1.190), 0.927 (0.818 to 1.050), and 0.807 (0.707 to 0.922) in male (P for trend <0.001) and 1.000 (0.843 to 1.186), 0.744 (0.615 to 0.900), and 0.684 (0.557 to 0.840) in female (P for trend <0.001), respectively. As a continuous variable in the fully-adjusted model, each one-standard deviation increase in percent change in SUA level was associated with an HR (95% CI) for incident MetS of 0.944 (0.906 to 0.982) in male (P=0.005) and 0.851 (0.801 to 0.905) in female (P<0.001).

CONCLUSION

The current study demonstrated that increasing SUA level independently protected against the development of MetS, suggesting a possible role of SUA as an antioxidant in the pathogenesis of incident MetS.

Successful treatment of obesity and insulin resistance via ketogenic diet status post Roux-en-Y

This is a single case of a 65-year-old American woman who presented with substantial weight gain and insulin resistance (IR) post-Roux-en-Y gastric bypass (RYGB) surgery. Before RYGB, she had reached 340 lbs (155 kg) and a body mass index (BMI) of 56.6 kg/m2 The surgery resulted in a 70 lbs (32 kg) weight loss, bringing her BMI, per cent total weight loss (%TWL) and per cent excess weight loss (%EWL) to 44.9 kg/m2, 20.6% and 36.8%, respectively. Unfortunately, her BMI would return to 53.6 kg/m2, nearly her pre-RYGB BMI. It was then she sought the guidance of a primary care physician with expertise in nutrition and medical management of obesity, who placed her on a ketogenic diet. One year later, she had lost 102 lbs (46.4 kg), resulting in a BMI, %TWL and %EWL of 36.6 kg/m2, 31.7%, and 63.1%, respectively, also further resulting in significant improvements of her inflammatory biomarkers. This case presentation will explore current literature, covering the effects of obesity on IR, pre-diabetes and other disease-provoking inflammatory biomarkers.

Parasitological and biochemical studies on cutaneous leishmaniasis in Shara'b District, Taiz, Yemen

BACKGROUND

The leishmaniasis is a group of diseases caused by intracellular haemoflagellate protozoan parasites of the genus Leishmania. Leishmaniasis has diverse clinical manifestations; cutaneous leishmaniasis (CL) is the most common form of leishmaniasis which is responsible for 60% of disability-adjusted life years. CL is endemic in Yemen. In Shara'b there is no reference study available to identify the prevalence of endemic diseases and no investigation has been conducted for diagnosing the diseases.

METHODS

This study was conducted in villages for CL which collected randomly. The study aimed at investigating the epidemiological factors of CL in Shara'b by using questioner. Symptoms of lesions in patients suffering from CL, confirmed by laboratory tests, gave a new evidence of biochemical diagnosis in 525 villagers aged between 1 and 60 years old. Venous bloods were collected from 99 patients as well as from 51 control after an overnight fast.

RESULTS

The percentage prevalence of CL was found 18.8%. The prevalence rate of infection among males (19.3%) was higher than females (18.40%). Younger age group (1-15) had a higher prevalence rate (20.3%) than the other age groups. Furthermore, the population with no formal education had the higher rate of infection (61% of the total). A significant increase of serum malondialdehyde (P < 0.001) in CL patients was obtained. The highest level of MDA may be due to over production of ROS and RNS results in oxidative stress and the acceleration of lipid peroxidation in CL patients.

CONCLUSIONS

There were high prevalence rates of CL in Shara'b. The patient who had CL has been found with many changes in some biochemical levels. This study provides a clear indication on the role of MDA as an early biochemical marker of peroxidation damage occurring during CL. Increased uric acid, and catalase activity was provided of free radical.

Effects of Tibetan turnip (Brassica rapa L.) on promoting hypoxia-tolerance in healthy humans

ETHNOPHARMACOLOGICAL RELEVANCE

Tibetan turnip (Brassica rapa L.), widely distributed in Tibet region, is an edible and medical plant with effects of "tonic and anti-hypoxia" "heat-clearing and detoxification" and "alleviating fatigue" according to traditional Tibetan medical books.

AIM OF THE STUDY

This research systematically studied the effects of Tibetan turnip on promoting hypoxia-tolerance in humans and the mechanisms.

MATERIALS AND METHODS

A 7-d, self-control and single-blind human feeding trial was conducted among 27 healthy subjects with 8 males and 10 females in feeding group fed with 7.5g turnip powder 2 times daily while 4 males and 5 females in control group fed with 7.5g radish powder twice a day. Subjects were required to undergo a hypoxia tolerance test (7.1% O₂) and a cardiopulmonary function evaluation (Bruce treadmill protocol) before (1st day) and after (9th day) the trial. Simultaneously, the anti-oxidative activities (SOD, CAT, GSH-Px, MDA), routine and biochemical analyses of blood samples were evaluated.

RESULTS

The females' SpO₂ increased significantly by 6.4% at the end of the hypoxia tolerance test after taking turnips (p<0.05), and the hypoxia symptoms in most of the subjects were alleviated as well. The anaerobic threshold, peak O₂ pulse and peak VO₂/kg were significantly improved after 7-d turnip consumption during the Bruce treadmill test (p<0.05). As for the blood analysis, anti-oxidative activities were boosted effectively after the 7-d treatments. Moreover, mean corpuscular hemoglobin concentration (MCHC) in the males of feeding group increased significantly (p<0.05). However, little changes of all variables were observed in the control group.

CONCLUSIONS

Consumption of Tibetan turnips for 7 days likely contributed to the hypoxia tolerance in healthy humans, which could be due to its abilities of improving oxygen uptake and delivery, enhancing body antioxidant capacity and increasing MCHC. However, further studies with larger samples and double-blind design are warranted, and future studies covering more diverse populations (unhealthy, athletic) would be also considered. Moreover, researches on identifying Tibetan turnip's active compounds are desired as well.

Anaemia in kidney disease: harnessing hypoxia responses for therapy

Improved understanding of the oxygen-dependent regulation of erythropoiesis has provided new insights into the pathogenesis of anaemia associated with renal failure and has led to the development of novel therapeutic agents for its treatment. Hypoxia-inducible factor (HIF)-2 is a key regulator of erythropoiesis and iron metabolism. HIF-2 is activated by hypoxic conditions and controls the production of erythropoietin by renal peritubular interstitial fibroblast-like cells and hepatocytes. In anaemia associated with renal disease, erythropoiesis is suppressed due to inadequate erythropoietin production in the kidney, inflammation and iron deficiency; however, pharmacologic agents that activate the HIF axis could provide a physiologic approach to the treatment of renal anaemia by mimicking hypoxia responses that coordinate erythropoiesis with iron metabolism. This Review discusses the functional inter-relationships between erythropoietin, iron and inflammatory mediators under physiologic conditions and in relation to the pathogenesis of renal anaemia, as well as recent insights into the molecular and cellular basis of erythropoietin production in the kidney. It furthermore provides a detailed overview of current clinical experience with pharmacologic activators of HIF signalling as a novel comprehensive and physiologic approach to the treatment of anaemia.

Cigarette smoking and hyperglycemia increase renal response to low levels of cadmium in welders: cystatin C as a sensitive marker

The present study was undertaken to investigate the utility of cystatin C (CysC) as an early biomarker of cadmium (Cd)-induced renal injury. The study was carried out on 50 adult male individuals divided into five groups of 10 individuals as follows: control, welders, smoker welders, diabetic welders, and smoker diabetic welders. The results indicated that plasma levels of CysC, creatinine, urea, and uric acid were significantly higher in welders compared to control individuals. In addition, the levels of whole blood Cd, lipid peroxidation, and protein oxidation products as well as erythrocyte osmotic fragility were significantly higher in welders compared to control individuals. In contrast, the levels of plasma albumin and whole blood glutathione were significantly decreased in welders compared to control individuals. The alterations of the measured parameters were enhanced in the presence of smoking and hyperglycemia besides exposure to welding fumes. These results suggest that CysC can be used as a sensitive biomarker of the early stages of Cd-induced renal injury.

Immunomodulatory activities of Yoyo bitters: recommended dose precipitated inflammatory responses in male Wistar rats

This study investigated the immunomodulatory capabilities of the sub-chronic administration of Yoyo bitters in male Wistar rats. Eighteen rats weighing 86.2 +/- 4.43 g were randomly picked into three equal groups. The rats were acclimatized for 14 days, after which 0.308 and 0.462 mL kg(-1) b.wt. of Yoyo bitters were administered once daily to groups B and C respectively for 56 days, while group A received distilled water. The feed intake, body weight, blood glucose, interleukin 2 (IL-2), interleukin 6 (IL-6), tumour necrosis factor alpha (TNF-alpha), haematological parameters, serum lipid profile and uric acid, liver reduced glutathione and malodialdehyde were determined. The feed intake, body weight and blood glucose concentrations were reduced (p < 0.05) at the doses. No changes were recorded in the concentration of serum IL-2 (p > 0.05), but IL-6 decreased (p < 0.05) in group B and increased (p < 0.05) in group C, while TNF-alpha were increased (p < 0.05) dose dependent. The haematological parameters were decreased at all the doses (p < 0.05), except the ESR, WBC and lymphocytes that were increased (p < 0.05) and platelets in group C (p < 0.05). The serum total cholesterol, TAG, LDL-C and atherogenic index were decreased (p < 0.05) and HDL-C increased (p < 0.05) in group B only. Serum uric acid was reduced (p < 0.05) in group B, but increased in group C with the concentration of liver MDA (p < 0.05). The study, therefore, established that a dose lower than the manufacturer's recommended dose presented the desired immunomodulatory activities and the habitual use of Yoyo bitters at the adult recommended dose calls for caution.

The kidney in hyperuricemia and gout

PURPOSE OF REVIEW

Gout is a painful inflammatory arthritis associated with hyperuricemia, with a prevalence of almost 10 million in the USA. Reduced renal excretion of urate is the underlying hyperuricemic mechanism in the vast majority of gout patients; most of the genes that affect serum urate level (SUA) encode urate transporters or associated regulatory proteins. Acquired influences can also modulate SUA and renal urate excretion, sometimes precipitating acute gout. Coincidentally, the prevalence of renal comorbidities in gout - hypertension, chronic kidney disease (CKD), and nephrolithiasis - is very high.

RECENT FINDINGS

Recent advances in genetics and molecular physiology have greatly enhanced the understanding of renal reabsorption and secretion of filtered urate. Moreover, baseline SUA appears to be set by the net balance of absorption and secretion across epithelial cells in the kidney and intestine. There have also been substantial advances in the management of gout in patients with CKD.

SUMMARY

The stage is set for an increasingly molecular understanding of baseline and regulated urate transport by the kidney and intestine. The increasing prevalence of gout with CKD will be balanced by an expanding spectrum of therapeutic options for this important disease.

Retinal vessel tortuosity in response to hypobaric hypoxia

PURPOSE

Retinal vascular tortuosity is associated with retinopathy of differing etiologies, including hypertension, diabetes, and hypoxia. However, detailed understanding of the underlying pathophysiology is lacking. The aim of this study was to map changes in tortuosity associated with hypoxia at high altitude, and to determine the influence of sildenafil and an antioxidant preparation on altitude-induced tortuosity.

METHODS

We measured the tortuosity of retinal vessels using a semi-automated method in 35 young, healthy subjects exposed to hypobaric hypoxia for 7 days at 5200 m, and compared the measurements to those from the same vessels at sea level. These subjects simultaneously took part in a randomized double-blind placebo-controlled trial of sildenafil and antioxidant. Comparison of tortuosity between these subgroups was performed.

RESULTS

High altitude was associated with the development of retinal tortuosity in individual vessels. A nonsignificant trend suggests this is limited by prophylaxis with sildenafil or antioxidant.

CONCLUSIONS

Retinal vessel tortuosity increases rapidly at high altitude. We suggest that retinal vessel tortuosity at altitude may result from increased sheer stress causing elongation of vessel segments and that this might be limited by agents that act to preserve nitric oxide dependent vasodilation.

TRIAL REGISTRATION NUMBERS

NCT00664001, NCT00627965.

Uric acid for diagnosis and risk stratification in suspected myocardial infarction

BACKGROUND

Hypoxia precedes cardiomyocyte necrosis in acute myocardial infarction (AMI). We therefore hypothesized that uric acid - as a marker of oxidative stress and hypoxia - might be useful in the early diagnosis and risk stratification of patients with suspected AMI.

MATERIALS AND METHODS

In this prospective observational study, uric acid was measured at presentation in 892 consecutive patients presenting to the emergency department with suspected AMI. The final diagnosis was adjudicated by two independent cardiologists. Patients were followed 24 months regarding mortality. Primary outcome was the diagnosis of AMI, secondary outcome was short- and long-term mortality.

RESULTS

Uric acid at presentation was higher in patients with AMI than in patients without (372 μM vs. 336 μM; P < 0·001). The diagnostic accuracy of uric acid for AMI as quantified by the area under the receiver operating characteristic curve (AUC) was 0·60 (95%Cl 0·56-0·65). When added to cardiac troponin T (cTnT), uric acid significantly increased the AUC of cTnT from 0·89 (95%Cl 0·85-0·93) to 0·92 (95%Cl 0·89-0·95, P = 0·020 for comparison). Cumulative 24-month mortality rates were 2·2% in the first, 5·4% in the second and the third and 15·6% in the fourth quartile of uric acid (P < 0·001 for log-rank). Uric acid predicted 24-month mortality independently. Adding uric acid to TIMI and GRACE risk score improved their prognostic accuracy as shown by an integrated discrimination improvement of 0·04 (P = 0·007) respective 0·02 (P = 0·021).

CONCLUSIONS

Uric acid, an inexpensive widely available biomarker, improves both the early diagnosis and risk stratification of patients with suspected AMI.

High plasma uric acid concentration: causes and consequences

High plasma uric acid (UA) is a precipitating factor for gout and renal calculi as well as a strong risk factor for Metabolic Syndrome and cardiovascular disease. The main causes for higher plasma UA are either lower excretion, higher synthesis or both. Higher waist circumference and the BMI are associated with higher insulin resistance and leptin production, and both reduce uric acid excretion. The synthesis of fatty acids (tryglicerides) in the liver is associated with the de novo synthesis of purine, accelerating UA production. The role played by diet on hyperuricemia has not yet been fully clarified, but high intake of fructose-rich industrialized food and high alcohol intake (particularly beer) seem to influence uricemia. It is not known whether UA would be a causal factor or an antioxidant protective response. Most authors do not consider the UA as a risk factor, but presenting antioxidant function. UA contributes to > 50% of the antioxidant capacity of the blood. There is still no consensus if UA is a protective or a risk factor, however, it seems that acute elevation is a protective factor, whereas chronic elevation a risk for disease.

CYBA and GSTP1 variants associate with oxidative stress under hypobaric hypoxia as observed in high-altitude pulmonary oedema

HAPE (high-altitude pulmonary oedema) is characterized by pulmonary hypertension, vasoconstriction and an imbalance in oxygen-sensing redox switches. Excess ROS (reactive oxygen species) contribute to endothelial damage under hypobaric hypoxia, hence the oxidative-stress-related genes CYBA (cytochrome b-245 α polypeptide) and GSTP1 (glutathione transferase Pi 1) are potential candidate genes for HAPE. In the present study, we investigated the polymorphisms -930A/G and H72Y (C/T) of CYBA and I105V (A/G) and A114V (C/T) of GSTP1, individually and in combination, in 150 HAPE-p (HAPE patients), 180 HAPE-r (HAPE-resistant lowland natives) and 180 HLs (healthy highland natives). 8-Iso-PGF2α (8-iso-prostaglandin F2α) levels were determined in plasma and were correlated with individual alleles, genotype, haplotype and gene-gene interactions. The relative expression of CYBA and GSTP1 were determined in peripheral blood leucocytes. The genotype distribution of -930A/G, H72Y (C/T) and I105V (A/G) differed significantly in HAPE-p compared with HAPE-r and HLs (P≤0.01). The haplotypes G-C of -930A/G and H72Y (C/T) in CYBA and G-C and G-T of I105V (A/G) and A114V (C/T) in GSTP1 were over-represented in HAPE-p; in contrast, haplotypes A-T of -930A/G and H72Y (C/T) in CYBA and A-C of I105V (A/G) and A114V (C/T) in GSTP1 were over-represented in HAPE-r and HLs. 8-Iso-PGF2α levels were significantly higher in HAPE-p and in HLs than in HAPE-r (P=2.2×10(-16) and 1.2×10(-14) respectively) and the expression of CYBA and GSTP1 varied differentially (P<0.05). Regression analysis showed that the risk alleles G, C, G and T of -930A/G, H72Y (C/T), I105V (A/G) and A114V (C/T) were associated with increased 8-iso-PGF2α levels (P<0.05). Interaction between the two genes revealed over-representation of most of the risk-allele-associated genotype combinations in HAPE-p and protective-allele-associated genotype combinations in HLs. In conclusion, the risk alleles of CYBA and GSTP1, their haplotypes and gene-gene interactions are associated with imbalanced oxidative stress and, thereby, with high-altitude adaptation and mal-adaptation.

Predictive value of 8 genetic loci for serum uric acid concentration

AIM

To investigate the value of genomic information in prediction of individual serum uric acid concentrations.

METHODS

Three population samples were investigated: from isolated Adriatic island communities of Vis (n=980) and Korcula (n=944), and from general population of the city of Split (n=507). Serum uric acid concentration was correlated with the genetic risk score based on 8 previously described genes: PDZK1, GCKR, SLC2A9, ABCG2, LRRC16A, SLC17A1, SLC16A9, and SLC22A12, represented by a total of 16 single-nucleotide polymorphisms (SNP). The data were analyzed using classification and regression tree (CART) and general linear modeling.

RESULTS

The most important variables for uric acid prediction with CART were genetic risk score in men and age in women. The percent of variance for any single SNP in predicting serum uric acid concentration varied from 0.0%-2.0%. The use of genetic risk score explained 0.1%-2.5% of uric acid variance in men and 3.9%-4.9% in women. The highest percent of variance was obtained when age, sex, and genetic risk score were used as predictors, with a total of 30.9% of variance in pooled analysis.

CONCLUSION

Despite overall low percent of explained variance, uric acid seems to be among the most predictive human quantitative traits based on the currently available SNP information. The use of genetic risk scores is a valuable approach in genetic epidemiology and increases the predictability of human quantitative traits based on genomic information compared with single SNP approach.

Common variants in SLC17A3 gene affect intra-personal variation in serum uric acid levels in longitudinal time series

AIM

To investigate whether intra-personal variation in serum uric acid concentration is influenced by genes that were described to be associated with serum uric acid levels in cross-sectional studies.

METHODS

The study included 92 participants from the isolated community of the Croatian island of Vis. For each participant, two uric acid concentration measurements were available, one from 2002 and one from 2003. Changes in uric acid concentration were correlated with a set of 8 genes known to affect it: PDZK1, GCKR, SLC2A9, ABCG2, LRRC16A, SLC17A3, SLC16A9, and SLC22A12.

RESULTS

Thirteen participants (14%) had uric acid concentration change greater than 130 micromol/L. Greater variability of uric acid concentration was recorded in women (coefficient of variation 49% vs 12% in men). Two SNPs belonging to SLC17A3 gene (rs9393672 and rs942379) yielded significant association with serum uric acid concentration changes in women. These two single-nucleotide polymorphisms (SNP) explained 0.2%-1.3% of variance for 2002 or 2003 uric acid measurement and 1.1%-1.8% of variance for the average value of these two measurements.

CONCLUSIONS

Repeated measurements offer a possibility to enrich the percent of explained variance and contribute to the understanding of the "missing heritability" concept. Although a number of genes have been shown to affect serum uric acid concentration, SLC17A3 seems to have a major role in determination of serum uric acid repeated measurements variation.

Hyperuricaemia and the metabolic syndrome in type 2 DM

BACKGROUND

Elevated serum uric acid levels (SUA) have been associated with an increased risk of cardiovascular diseases and the metabolic syndrome (MetS) and are often reported to be higher in females than in males. The aim of this report is to determine the prevalence and clinical correlates of hyperuricaemia and also to evaluate associations with the MetS in people with type 2 diabetes mellitus (DM).

METHODS

This was a cross-sectional study conducted in people with type 2 DM in Lagos, Nigeria. Hyperuricaemia was defined by cut-off values of > 7 mg/dl for men and > 6 mg/dl for women. The diagnosis of MetS was made using the new definition by the American Heart Association and other related bodies. Clinical and biochemical parameters were compared between subjects with hyperuricaemia and normouricaemia. Statistical analysis included usage of Student's t test, Pearson correlation coefficients, multivariate regression analysis and chi square.

RESULTS

601 patients with type 2 DM aged between 34-91 years were recruited for the study. The prevalence rates of hyperuricaemia and the MetS were 25% and 60% respectively. The frequency of occurrence of hyperuricaemia was comparable in both genders (59% vs 41%, p = 0.3). Although, the prevalence of the MetS in subjects with hyperuricaemia and normouricaemia was comparable (61 vs 56%, p = 0.1), a higher proportion of hyperuricaemic subjects had 3 or more components of the Mets compared with normouricaemic subjects. Possible predictors of hyperuricaemia include central obesity, smoking and elevated serum triglycerides (TG). SUA levels were found to be positively and significantly associated with serum TG (r = 0.2, p = 0.0001) and total cholesterol (r = 13, p = 0.001).

CONCLUSION

The prevalence of hyperuricaemia in subjects with type 2 DM is comparable in both genders and possible predictors of hyperuricaemia are potentially modifiable. SUA is positively and significantly associated with serum TG and total cholesterol.

Voltammetric determination of dopamine in the presence of uric acid using a 2-hydroxy-1-(1-hydroxynaphthyl-2-azo)- naphthalin-4-sulfonic acid modified glassy carbon electrode

A polymerized film of 2-hydroxy-1-(1-hydroxynaphthyl-2-azo)- naphthalin-4-sulfonic acid (HHNANSA) was prepared at the surface of a glassy carbon electrode by electropolymerization. The modified electrode was used for the simultaneous determination of dopamine (DA) and uric acid (UA). The electrochemical behaviors of the compounds at the surface of the modified electrode were studied using cyclic voltammetry, chronoamperometry, and square wave voltammetry (SWV). The experimental results indicated that the modified electrode exhibited an efficient electrocatalytic activity towards the oxidation of DA and UA, with a peak separation of about 140 mV at pH 5.0. Using chronoamperometry, the catalytic reaction rate constant was measured and found to equal to 1.23 ? 104 mol-1 L s-1. At pH 5.0, the catalytic peak currents linearly depended on the DA and/or UA concentrations in the range of 1.0 - 300 ?mol L-1 DA (two linear segments with different slopes) and 6.7 - 20 ?mol L-1 UA, using SWV. The detection limits for DA and UA were 0.25 ?mol L-1 and 1.17 ?mol L-1, respectively. The RSD % for 40.0 and 140.0 ?mol L-1 DA were 1.9 % and 2.2 %, respectively, whereas for 10.0 and 20.0 ?mol L-1 UA, they were 1.8 % and 1.2 %, respectively. The modified electrode showed good sensitivity, selectivity, and stability. It was successfully applied for the determination of DA and UA in real samples, such as drugs and urine.

Enhanced leukocyte HIF-1alpha and HIF-1 DNA binding in humans after rapid ascent to 4300 m

Hypoxia plays a crucial role in the pathogenesis of a multitude of diseases and clinical conditions such as cancer, diabetes, cardiovascular disease, stroke, pulmonary disease, inflammation, organ transplant, and wound healing. Investigations into the role of hypoxia-inducible transcription factor (HIF) in disease development have been conducted with the basic premise that HIF is activated in vivo during hypoxia in humans, yet this basic physiologic premise has never verified. Thus, we hypothesized that HIF-1 DNA binding would be enhanced in vivo in humans in response to acute global hypoxia. Fourteen human subjects were exposed to normoxia (1600 m) and hypoxia (4300 m, approximately 12% O(2)) in a hypobaric hypoxic chamber (8 h). HIF-1 DNA binding and HIF-1alpha protein were evaluated in circulating leukocytes. Oxidative markers were evaluated by plasma metabolomics using nuclear magnetic resonance and by urinary 15-F(2t)-isoprostane concentrations. Leukocyte HIF-1 DNA binding was increased (p=0.007) and HIF-1alpha was greater during hypoxia compared to normoxia. Circulating total glutathione was reduced by 35% (p=0.001), and lactate and succinate were increased by 29 and 158%, respectively (p=0.007 and 0.001), as were urinary 15-F(2t)-isoprostanes (p=0.037). HIF-1 DNA binding and HIF-1alpha were elevated in vivo in leukocytes of healthy human subjects exposed to 12% oxygen, in association with plasma and urinary markers of hypoxic stress.

Different adaptation patterns of antioxidant system in natives and sojourners at high altitude

Comparative studies on the adaptation pattern of antioxidant status among high altitude natives and acclimatized sojourners are very scanty. The aim of the present study was to compare the differences in antioxidant profile between two groups of active male volunteers, i.e. native highlanders (HAN, n=66) in their natural hypoxic environment with that of sojourners (SOJ, n=81) from sea level (SL) after 4 weeks of stay at an altitude of 4560m. Blood samples of SOJ were collected at SL and HA. Same was collected from HAN once at HA. HAN had significantly higher SOD activity and significantly lower catalase, GPX and GR activities than SOJ at HA. Ratio of GSH/GSSG was also significantly higher in HAN than SOJ at HA. In SOJ, antioxidant profile showed an upregulation after HA stay but it was not effective to reduce the levels of oxidative stress markers. Therefore, it can be stated that lifelong exposure to hypoxia has beneficial adaptive effects on antioxidant system in HAN. Similarly, acclimatization to HA also has beneficial preconditioning effects on antioxidant system in SOJ, but, may not be sufficient to ameliorate oxidative stress completely. Transient increase in metabolic rate due to hypoxia may be a causative factor for excess free radical generation among sojourners at HA.

Oral antioxidant supplementation does not prevent acute mountain sickness: double blind, randomized placebo-controlled trial

BACKGROUND

Acute mountain sickness may be caused by cerebrovascular fluid leakage due to oxidative damage to the endothelium. This may be reduced by oral antioxidant supplementation.

AIM

To assess the effectiveness of antioxidant supplementation for the prevention of acute mountain sickness (AMS).

DESIGN

A parallel-group double blind, randomized placebo-controlled trial.

METHODS

The study was conducted in a university clinical research facility and a high altitude research laboratory. Eighty-three healthy lowland volunteers ascended to 5200 m on the Apex 2 high altitude research expedition. The treatment group received a daily dose of 1 g l-ascorbic acid, 400 IU of alpha-tocopherol acetate and 600 mg of alpha-lipoic acid (Cultech Ltd., Wales, UK) in four divided doses. Prevalence of AMS was measured using the Lake Louise Consensus score sheet (LLS). Secondary outcomes were AMS severity measured using a novel visual analogue scale, arterial oxygen saturation and pulmonary artery systolic pressure (PASP).

RESULTS

Forty-one subjects were allocated to the antioxidant group, and 42 to the placebo group. There was no difference in AMS incidence or severity between the antioxidant and placebo groups using the LLS at any time at high altitude. At the pre-determined comparison point at Day 2 at 5200 m, 69% of the antioxidant group (25/36) and 66% of the placebo group (23/35) had AMS using the LLS criteria (P = 0.74). No differences were observed between the groups for PASP, oxygen saturation, presence of a pericardial effusion or AMS assessed by VAS.

CONCLUSION

This trial found no evidence of benefit from antioxidant supplementation at high altitude.

TRIAL REGISTRATION NUMBER

NCT00664001.

Change in serum uric acid between baseline and 1-year follow-up and its associated factors in male subjects

A number of cross-sectional analysis studies have been conducted to determine the relationships between serum uric acid and related variables or clinical manifestations. However, few data related to changes in serum uric acid within the same cohort population at two separate periods of time have been reported. In this study, we investigated the changes in serum uric acid in a population from baseline to 1-year follow-up and examined the associations with related parameters and medical conditions. A total of 1,437 eligible male subjects who underwent 2 medical examinations at a health promotion center at an interval of approximately 12 months were enrolled in this study. Data were obtained from routine physical assessments such as blood pressure, height, waist circumference, blood analyses for liver function, renal function, lipid profile, and electrolytes, along with standardized questionnaires including self-reported data. In this population, serum uric acid was significantly increased at 1-year follow-up compared with the baseline level (5.94 +/- 1.20 vs 5.99 +/- 1.22, p = 0.003). Changes of some confounders such as total bilirubin, creatinine, BUN, phosphorus, total cholesterol, and triglyceride were significantly associated with changes in serum uric acid. Among them, serum creatinine may be the most influential in determining the serum uric acid level (odds ratio = 21.691, 95%CI = 5.110-92.086). A change of serum uric acid over 1 year did not seem to affect changes in the clinical status for some medical conditions including hypertension, diabetes mellitus, cardiovascular disease, and metabolic syndrome. This analysis showed that a change in serum creatinine level between baseline and 1-year follow-up might be the most potent factor affecting a change in serum uric acid in healthy, male subjects. Changes of serum uric acid did not show any meaningful impact on the development of hypertension, heart failure, diabetes mellitus, and metabolic syndrome in this 1-year follow-up study.