Plasma and urine uric acid levels: heritability estimates and correlation with IQ

Tunable Coffee Ring Formation on Polycarbonate Nanofiber Film for Sensitive SERS Detection of Phenylalanine in Urine

A new method based on the coffee ring effect was developed for improving the sensitivity, simplicity, and robustness of surface-enhanced Raman scattering (SERS) in determining trace levels of analytes. In this method, a polyvinylpyrrolidone (PVP)-stabilized silver colloidal (AgC) solution was first prepared and mixed with a sample solution. Following deposition of the mixture solution on a solid substrate with a rough surface, a coffee ring was formed once the solvent had evaporated. The formation of a coffee ring not only concentrated the analyte but also reduced the space between silver nanoparticles (AgNPs) to strengthen the hotspot effect, thereby considerably improving SERS sensitivity. To strengthen the coffee ring effect further, the surface roughness of the solid support and PVP content of the AgC solution were investigated. The results indicated that an increase in surface roughness reduced the size of the coffee rings, whereas the addition of PVP not only stabilized the AgNPs but also improved the compactness of the coffee rings. When applying the proposed method to determine the phenylalanine (Phe) level in urine for rapid screening of the phenylketonuria disorder, strong chemical interference from uric acid (UA), which is a major component in urine, was observed. To minimize the interference from UA, ZnO powder was applied to the urine sample to adsorb UA prior to SERS detection. After cleaning by using ZnO, the SERS signals of Phe were revealed for quantitative purposes. Under the optimized conditions, both the sensitivity and reproducibility of SERS measurement considerably improved. Quantitative analyses revealed that the developed method is highly feasible for the rapid determination of Phe in real samples.

Genetic association and functional analysis of rs7903456 in FAM35A gene and hyperuricemia: a population based study

Recent studies have identified SNP rs7903456 of FAM35A to be associated with gout. Because of the close connections between hyperuricemia and gout, we hypothesized that the effect of rs7903456 on gout might be mediated by hyperuricemia or its related quantitative trait, uric acid level. We investigated the association between 31 SNPs of FAM35A, including rs7903456, and hyperuricemia based on 2,773 hyperuricemia patients and controls. We fitted a simple model for each of these 31 SNPs to screen the candidate SNP for further analyses. Moreover, we selected potential confounders and fitted a multivariate model to investigate the adjusted effects of the targeted SNPs. Both disease status of hyperuricemia and blood uric acid level were considered as the main phenotype. We have identified rs7903456 to be associated with hyperuricemia and uric acid level. The significant signal was identified between rs7903456 and uric acid level after adjusted by several potential confounders. Our findings showed that the T allele of rs7903456 could increase the uric acid level by ~10 mmol/L on average after adjusting several biochemical and clinical variables. Our findings indicated that the previously identified effects of rs7903456 on gout might partly be mediated by its effect on uric acid levels.

Blood Uric Acid Level and IQ: A Study in Twin Families

Applying newly devised model, heritability (VA/VP) of plasma uric acid level, corrected for age and sex and standardized, was estimated at 0.8 in families consisting of twin parents, spouses and children. Correlation between spouses due to common genotype (ρ) was approximately 0.1, and variance due to common familial environment (VEC/Vp) was -0.3. Analysis of families of selected twin children and their parents resulted in two estimates of heritability: approximately 0.7 and 0.3, ρ being 0.34 and 0.04, and VEC/Vp being 0.04 and 0.34, respectively. Regression of IQ (y) on corrected and standardized plasma uric acid level (x) in the twin children was y = 5.56x + 123, correlation being 0.334 (p < 0.025). The result indicates a genetic basis of blood uric acid level, which may have resulted from polymorphisms in purine metabolism pathway, end product of which is uric acid in man. The significant correlation between plasma uric acid level and IQ suggests a contribution of partly common gene loci to the two quantitative traits.

Association of serum uric acid level with muscle strength and cognitive function among Chinese aged 50-74 years

AIM

Previous studies have shown that uric acid (UA) has strong anti-oxidant properties, and that high circulating levels of UA are prospectively associated with improved muscle function and cognitive performances in elderly Caucasians. We carried out a replication study in elderly Chinese using cross-sectional design.

METHODS

Data from 2006 individuals aged 50-74 years who participated in a population-based cross-sectional survey in Qingdao, China, were analyzed. Hand grip strength was measured in kilograms by using an electronic dynamometer. The sit-to-stand (STS) test time was used to represent lower limb strength. The Mini-Mental State Examination (MMSE) was used to estimate the participants' cognitive function. Lifestyle, comorbidities and laboratory measures were considered as potential confounders. Multiple linear regression models and binary logistic regression were fitted to find the association of UA with strength measures and cognitive performances.

RESULTS

Participants were grouped according to UA tertiles (<257.75 mmol/L, ≥ 257.75 and ≤ 359.00 mmol/L, >359.00 mmol/L). Hand grip strength significantly increased across UA tertiles (26.4 ± 8.5 kg; 30.1 ± 10.5 kg; 35.0 ± 11.4 kg; P<0.001), and prevalence of cognitive disorder declined across UA tertiles (7.9%, 4.9%, 3.1%; P=0.012). After adjusting for potential confounders, high UA level remained significantly associated with high grip strength (P=0.023) and decreased risk of cognitive disorder with an OR of 1.002 (95% CI 1.000-1.004; P=0.022). However, UA level was not significantly associated with STS time (P=0.780).

CONCLUSIONS

Our findings suggested that notwithstanding the associated increased risk of cardiovascular disease, UA might play a protective role in aging-associated decline in muscle strength and cognitive function.

Variation in the uric acid transporter gene (SLC2A9) and memory performance

Understanding human cognitive ageing is important to improve the health of an increasing elderly population. Serum uric acid levels have been linked to many ageing illnesses and are also linked to cognitive functioning, though the direction of the association is equivocal. SLC2A9, a urate transporter, influences uric acid levels. This study first tested four SLC2A9 SNPs, previously associated with uric acid levels, in approximately 1000 Scots: the Lothian Birth Cohort 1936 (LBC1936). These participants were tested on general cognitive ability at ages 11 and 70. At age 70, they took a battery of diverse cognitive tests. Two replication cohorts were investigated. First, the LBC1921, who were tested on general cognitive ability at age 11. At ages 79 (n = 520), 83 (n = 281) and age 87 (n = 177), they completed cognitive ability test batteries. Second, the Edinburgh Type 2 Diabetes Study (ET2DS) were tested for cognitive abilities aged between 60 and 75 years (n = 1066). All analyses were adjusted for age, gender, body mass index and either childhood cognitive ability test score (LBC) or vocabulary-a measure of prior cognitive ability in ET2DS. Significant associations were detected with SLC2A9 and a general memory factor in LBC1936 and other individual cognitive ability tests (lowest P = 0.0002). The association with logical memory replicated in LBC1921 at all ages (all P < 0.05). These associations were not replicated in ET2DS (all P > 0.1). If the positive associations withstand, then this study could suggest that higher uric acid levels may be associated with increased performance on memory-related tasks.

Uric acid nephrolithiasis: proton titration of an essential molecule?

PURPOSE OF REVIEW

The majority of uric acid nephrolithiasis in humans occurs in the absence of frank hyperuricosuria and is primarily a disease of excessively low urinary pH. Uric acid is substantially less soluble than urate salts so in low urine pH urate is protonated, thus favoring precipitation even under what is considered physiologic concentrations of total urinary uric acid/urate. This commentary examines the rationales behind the existence of uric acid in urine and body fluids in vertebrate evolution.

RECENT FINDINGS

The purpose of uric acid in arthropod, avian and reptilian species is to enable nitrogen excretion in solid state without loss of water. The re-emergence of uric acid in higher primates as an end product of metabolism is intriguing since urea functions perfectly well as a nitrogenous waste. Uric acid must purvey important physiologic functions in primate biology. Numerous roles of uric acid as an antioxidant, immune signaling molecule, and a defender of circulatory integrity have recently been proposed.

SUMMARY

There is little doubt that uric acid serves multiple important functions in higher primates. It is also conceivable, however, that this important molecule when present in the wrong concentration or context can lead to undesirable phenotypes.

Relationship between blood uric acid level and personality traits

The present study deals with the relationship between blood uric acid level and human behavior. Subjects were 37 MZ and 7 DZ twins aged from 18 to 45 years. In males, blood uric acid level increased with age, while it decreased with age in females. Blood uric acid level was corrected and standardized using regression lines separately for males and females. The distribution of standardized uric acid level corresponded well with the theoretical curve of normal distribution. The intraclass correlation coefficient for standardized uric acid level was r = 0.370 (P less than 0.05) for the 37 MZ twins, but not significant for the 7 DZ twins. These findings suggest that blood uric acid level is genetically controlled. By the analysis of 12 personality traits in YG (Yatabe-Guilford) character test, it was revealed that "General activity" was more controlled by genetically than environmentally. In the evaluation of the correlation between standardized uric acid level and the YG 12 personality traits, significant correlation was observed in "Lack of agreeableness" and "Rhathymia". Since these two personality traits include the factor of "activity", it is concluded that the plasma uric acid level and activity in a broader sense are under genetic control. This conclusion is consistent with the generally accepted view that persons with high uric acid level are more active and energetic than those with low level.

Inheritance and alcohol as factors influencing plasma uric acid levels

Variation in plasma uric acid levels in 206 pairs of male and female twins, aged from 18 to 34 years, was consistent with a simple model including only individual environmental and additive genetic effects and a heritability of h2 = 0.73. Individual environmental variation was estimated to be approximately the same as variation of individuals measured on two occasions. Correlations of DZ pairs were also consistent with sex-linked genetic effects. In men there was a significant genetic correlation with weekly alcohol consumption and as much as 18% of the variation in uric acid levels could be accounted for by genetic variation in alcohol consumption.

Uric acid provides an antioxidant defense in humans against oxidant- and radical-caused aging and cancer: a hypothesis

During primate evolution, a major factor in lengthening life-span and decreasing age-specific cancer rates may have been improved protective mechanisms against oxygen radicals. We propose that one of these protective systems is plasma uric acid, the level of which increased markedly during primate evolution as a consequence of a series of mutations. Uric acid is a powerful antioxidant and is a scavenger of singlet oxygen and radicals. We show that, at physiological concentrations, urate reduces the oxo-heme oxidant formed by peroxide reaction with hemoglobin, protects erythrocyte ghosts against lipid peroxidation, and protects erythrocytes from peroxidative damage leading to lysis. Urate is about as effective an antioxidant as ascorbate in these experiments. Urate is much more easily oxidized than deoxynucleosides by singlet oxygen and is destroyed by hydroxyl radicals at a comparable rate. The plasma urate levels in humans (about 300 microM) is considerably higher than the ascorbate level, making it one of the major antioxidants in humans. Previous work on urate reported in the literature supports our experiments and interpretations, although the findings were not discussed in a physiological context.