Uric acid and cardiovascular risk: What genes can say

Large-scale cross-ancestry genome-wide meta-analysis of serum urate

Hyperuricemia is an essential causal risk factor for gout and is associated with cardiometabolic diseases. Given the limited contribution of East Asian ancestry to genome-wide association studies of serum urate, the genetic architecture of serum urate requires exploration. A large-scale cross-ancestry genome-wide association meta-analysis of 1,029,323 individuals and ancestry-specific meta-analysis identifies a total of 351 loci, including 17 previously unreported loci. The genetic architecture of serum urate control is similar between European and East Asian populations. A transcriptome-wide association study, enrichment analysis, and colocalization analysis in relevant tissues identify candidate serum urate-associated genes, including CTBP1, SKIV2L, and WWP2. A phenome-wide association study using polygenic risk scores identifies serum urate-correlated diseases including heart failure and hypertension. Mendelian randomization and mediation analyses show that serum urate-associated genes might have a causal relationship with serum urate-correlated diseases via mediation effects. This study elucidates our understanding of the genetic architecture of serum urate control.

Tools for assessing quality and risk of bias in Mendelian randomization studies: a systematic review

BACKGROUND

The use of Mendelian randomization (MR) in epidemiology has increased considerably in recent years, with a subsequent increase in systematic reviews of MR studies. We conducted a systematic review of tools designed for assessing risk of bias and/or quality of evidence in MR studies and a review of systematic reviews of MR studies.

METHODS

We systematically searched MEDLINE, Embase, the Web of Science, preprints servers and Google Scholar for articles containing tools for assessing, conducting and/or reporting MR studies. We also searched for systematic reviews and protocols of systematic reviews of MR studies. From eligible articles we collected data on tool characteristics and content, as well as details of narrative description of bias assessment.

RESULTS

Our searches retrieved 2464 records to screen, from which 14 tools, 35 systematic reviews and 38 protocols were included in our review. Seven tools were designed for assessing risk of bias/quality of evidence in MR studies and evaluation of their content revealed that all seven tools addressed the three core assumptions of instrumental variable analysis, violation of which can potentially introduce bias in MR analysis estimates.

CONCLUSION

We present an overview of tools and methods to assess risk of bias/quality of evidence in MR analysis. Issues commonly addressed relate to the three standard assumptions of instrumental variables analyses, the choice of genetic instrument(s) and features of the population(s) from which the data are collected (particularly in two-sample MR), in addition to more traditional non-MR-specific epidemiological biases. The identified tools should be tested and validated for general use before recommendations can be made on their widespread use. Our findings should raise awareness about the importance of bias related to MR analysis and provide information that is useful for assessment of MR studies in the context of systematic reviews.

The Interaction Between Dietary Fructose and Gut Microbiota in Hyperuricemia and Gout

With the worldwide epidemics of hyperuricemia and associated gout, the diseases with purine metabolic disorders have become a serious threat to human public health. Accumulating evidence has shown that they have been linked to increased consumption of fructose in humans, we hereby made a timely review on the roles of fructose intake and the gut microbiota in regulating purine metabolism, together with the potential mechanisms by which excessive fructose intake contributes to hyperuricemia and gout. To this end, we focus on the understanding of the interaction between a fructose-rich diet and the gut microbiota in hyperuricemia and gout to seek for safe, cheap, and side-effect-free clinical interventions. Furthermore, fructose intake recommendations for hyperuricemia and gout patients, as well as the variety of probiotics and prebiotics with uric acid-lowering effects targeting the intestinal tract are also summarized to provide reference and guidance for the further research.

The Role of IL-6 and ET-1 in the Diagnosis of Coronary MicroVascular Disease in Women

BACKGROUND

Microvascular angina is a common clinical entity, with about a three-fold higher frequency in women. The pathogenesis of microvascular angina has not been much studied, but inflammation and endothelial dysfunction have been incriminated as the main mechanisms of this disease. Methoss: Our purpose was to analyze whether certain inflammatory markers, i.e., interleukin 6 (IL-6) and endothelin 1 (ET-1), can play a role in the diagnosis of microvascular angina in women.

RESULTS

Ninety women with ischemic heart disease were divided into two groups, based on their affliction with either microvascular or macrovascular disease. In general, the levels of IL6 and ET1 were similar between the two groups. Analyzing these marker levels according to the number of coronary lesions, we obtained an increased IL6 value that was similar for patients with microvascular angina, one-vessel, and two-vessel coronary disease, but significantly lower than in women with three-vessel coronary lesions. Also, in microvascular angina, IL6 level was correlated with the NYHA IV functional class. Unexpectedly, the level of ET1 was correlated with left ventricular systolic dysfunction.

CONCLUSIONS

In women with an increased suspicion of microvascular angina, in whom microvascular dysfunction cannot be tested invasively, IL-6 level, unlike the ET-1 level, might be considered a diagnostic marker of this disease.

Major Left Bundle Branch Block and Coronary Heart Disease-Are There Any Differences between the Sexes?

Left bundle branch block is not a benign pathology, and its presence requires the identification of a pathological substrate, such as ischemic heart disease. Left bundle branch block appears to be more commonly associated with normal coronary arteries, especially in women. The objectives of our study were to describe the particularities of left bundle branch block in women compared to men with ischemic heart disease. Result: We included seventy patients with left bundle branch block and ischemic heart disease, with a mean age of 67.01 ± 8.89 years. There were no differences in the profile of risk factors, except for smoking and uric acid. The ventricular depolarization (QRS) duration was longer in men than women (136.86 ± 8.32 vs. 132.57 ± 9.19 msec; p = 0.018) and also men were observed to have larger left ventricular diameters. Left bundle branch block duration was directly associated with ventricular diameters and indirectly associated with left ventricular ejection fraction value, especially in women (R = −0.52, p = 0.0012 vs. R = −0.50, p = 0.002). In angiography, 80% of women had normal epicardial arteries compared with 65.7% of men; all these patients presented with microvascular dysfunction. Conclusion: The differences between the sexes were not so obvious in terms of the presence of risk factors; instead, there were differences in electrocardiographic, echocardiographic, and angiographic aspects. Left bundle branch block appears to be a marker of microvascular angina and systolic dysfunction, especially in women.

Uric Acid and Hypertension: Prognostic Role and Guide for Treatment

The relationship between serum uric acid (SUA) and hypertension has been a subject of increasing interest since the 1870 discovery by Frederick Akbar Mahomed. Several epidemiological studies have shown a strong association between high SUA levels and the presence or the development of hypertension. Genetic analyses have found that xanthine oxidoreductase (XOR) genetic polymorphisms are associated with hypertension. However, genetic studies on urate transporters and Mendelian randomization studies failed to demonstrate a causal relationship between SUA and hypertension. Results from clinical trials on the role of urate-lowering therapy in the management of patients with hypertension are not uniform. Our study sought to analyze the prognostic and therapeutic role of SUA in the hypertensive disease, from uric acid (UA) biology to clinical trials on urate-lowering therapies.

Hyperuricemia and Hypertension, Coronary Artery Disease, Kidney Disease: From Concept to Practice

Since the publication of the Framingham Heart Study, which suggested that uric acid should no longer be associated with coronary heart disease after additional adjustment for cardiovascular disease risk factors, the number of publications challenging this statement has dramatically increased. The aim of this paper was to review and discuss the most recent studies addressing the possible relation between sustained elevated serum uric acid levels and the onset or worsening of cardiovascular and renal diseases. Original studies involving American teenagers clearly showed that serum uric acid levels were directly correlated with systolic and diastolic pressures, which has been confirmed in adult cohorts revealing a 2.21-fold increased risk of hypertension. Several studies involving patients with coronary artery disease support a role for serum uric acid level as a marker and/or predictor for future cardiovascular mortality and long-term adverse events in patients with coronary artery disease. Retrospective analyses have shown an inverse relationship between serum uric acid levels and renal function, and even a mild hyperuricemia has been shown to be associated with chronic kidney disease in patients with type 2 diabetes. Interventional studies, although of small size, showed that uric acid (UA)-lowering therapies induced a reduction of blood pressure in teenagers and a protective effect on renal function. Taken together, these studies support a role for high serum uric acid levels (>6 mg/dL or 60 mg/L) in hypertension-associated morbidities and should bring awareness to physicians with regards to patients with chronic hyperuricemia.

A U-shaped association between serum uric acid with all-cause mortality in normal-weight population

BACKGROUND

It is uncertain how serum uric acid (SUA) associated with all-cause mortality among people with normal weight, hence was explored in this study.

METHODS

We enrolled participants from 1999 to 2006 National Health and Nutrition Examination Survey (NHANES) that had mortality status through 31 December 2015. We estimated adjusted hazard ratios (HRs) and 95% confidence intervals (CI) for all-cause mortality using Cox proportional hazard models, and propensity score analyses were performed. We also performed restricted cubic splines to demonstrate the nonlinear relationship, and used subgroup analysis to examine the effect modification.

RESULTS

We enrolled 6169 participants (2905 men and 3264 women, mean age 42.3 ± 21.4 years) and 1060 (17.2%) cases of all-cause mortality occurred during the mean follow-up of 11.9 years. When using the lowest quartile of SUA as referent, the multivariable HRs for all-cause mortality increased in not parallel with the quartiles of SUA (HRs were 0.92 (95%CI: 0.68, 1.23), 1.10 (95%CI: 0.82, 1.47), and 1.08 (95%CI: 0.80, 1.45) from the second to the fourth quartiles, respectively. When treating SUA as continuous variable, the HRs for all-cause mortality were 1.07 (95%CI: 1.00, 1.15; P = 0.046), 1.03 (95%CI: 0.94, 1.12; P = 0.518) and 1.15 (95%CI: 1.01, 1.31; P = 0.032) in all population, male and female subjects, respectively. Elevated SUA was associated with all-cause mortality and the propensity scores analysis showed the similar results. Subgroup analysis showed SUA was an independent risk of all-cause mortality in female (HR1.17, 95%CI: 1.05, 1.31, P = 0.005), people aged <60 years (HR1.18, 95%CI: 1.03, 1.35, P = 0.018), non-diabetic population (HR1.10, 95%CI: 1.02, 1.18, P = 0.017) and people with eGFR<90 (HR1.10, 95%CI: 1.02, 1.19, P = 0.016). Smoothing spline plots suggested the optimal SUA for the lowest risk of all-cause mortality was approximately 4.7 mg/dl.

CONCLUSION

In normal-weight population, SUA was seemed to be a U-shaped relationship with all-cause mortality.

Serum uric acid and risk of cardiovascular mortality: a systematic review and dose-response meta-analysis of cohort studies of over a million participants

Background

Cardiovascular disease (CVD) is the leading cause of death worldwide. Some studies have suggested anassociation between serum uric acid levels and cardiovascular mortality; however, the results have not been summarized in a meta-analysis.

Methods

A comprehensive search of all related studies until April 2018was performed in MEDLINE/PubMed and Scopus databases DerSimonianand Laird random-effects models were used to combine hazard ratios (HRs) with 95% confidence intervals (CIs). Dose-response analysis was also carried out.

Results

Thirty-two studies containing forty-four arms with 1,134,073 participants reported association between uric acid and risk of CVD mortality were included in our analysis. Pooled results showed a significant positive association between uric acid levels and risk of CVD mortality (HR 1.45, 95% CI 1.33–1.58, I² = 79%). Sub-group analysis showed this relationshipwasstronger in women compared to men. Moreover, there was a significant non-linear association between uric acid levels and the risk of CVD mortality (r = 0.0709, p = 0.001).

Conclusion

Our analysis indicates a positive dose-response association between SUA and CVD mortality risk.

Influence of Genetic and Non-Genetic Risk Factors for Serum Uric Acid Levels and Hyperuricemia in Mexicans

Risk of hyperuricemia is modified by genetic and environmental factors. Our aim was to identify factors associated with serum uric acid levels and hyperuricemia in Mexicans. A pilot Genome-wide association study GWAS was performed in a subgroup of participants (n = 411) from the Health Workers Cohort Study (HWCS). Single nucleotide polymorphisms (SNPs) associated with serum uric acid levels were validated in all the HWCS participants (n = 1939) and replicated in independent children (n = 1080) and adult (n = 1073) case-control studies. The meta-analysis of the whole HWCS and replication samples identified three SLC2A9 SNPs: rs1014290 (p = 2.3 × 10⁻⁶⁴), rs3775948 (p = 8.2 × 10⁻⁶⁴) and rs11722228 (p = 1.1 × 10⁻¹⁷); and an ABCG2 missense SNP, rs2231142 (p = 1.0 × 10⁻¹⁸). Among the non-genetic factors identified, the visceral adiposity index, smoking, the metabolic syndrome and its components (waist circumference, blood pressure, glucose and hyperlipidemia) were associated with increased serum uric acid levels and hyperuricemia (p < 0.05). Among the female HWCS participants, the odds ratio for hyperuricemia was 1.24 (95% CI, 1.01–1.53) per unit increase in soft drink consumption. As reported in other studies, our findings indicate that diet, adiposity and genetic variation contribute to the elevated prevalence of hyperuricemia in Mexico.

Uromodulin in a Pathway Between Decreased Renal Urate Excretion and Albuminuria

BACKGROUND

The mechanism explaining the inverse association between renal urate and albumin excretion remains unclear. First, we evaluated the impact of candidate variants in the main urate transporter genes (i.e., SLC2A9, SLC22A12, ABCG2) on the association between fractional excretion of uric acid (FEUA) and urinary albumin/creatinine ratio (uACR). Second, we examined uromodulin and sodium excretion as mediators of the association between FEUA and uACR.

METHODS

We performed cross-sectional analysis of 737 French Canadians from the CARTaGENE cohort, a random sample of the Quebec population aged 40-69 years (a total of 20,004 individuals). Individuals with available genotyping and urinary data were obtained from a sub-study including gender-matched pairs with high and low Framingham Risk Score and vascular rigidity index. We further excluded individuals with an estimated glomerular filtration rate <60 ml/min/1.73 m2, glycosuria, and use of confounding medication. A spot urine sample was analyzed. Genotyping was performed using the Illumina Omni2.5-8 BeadChips. Genetic variants were analyzed using an additive model.

RESULTS

Final analyses included 593 individuals (45.5% of men; mean age 54.3 ± 8.6). We observed an antagonistic interaction between rs13129697 variant of the SLC2A9 gene and FEUA tertiles on uACR (P = 0.002). Using the mediation analysis, uromodulin explained 32%, fractional excretion of sodium (FENa) 44%, and uromodulin together with FENa explained 70% of the inverse relationship between FEUA and uACR. Bootstrapping process confirmed the role of both mediators.

CONCLUSIONS

Our data suggest that the association of albuminuria with decreased renal urate excretion may be modified by the transporter SLC2A9, and mediated by uromodulin and sodium handling.

How should we manage asymptomatic hyperuricemia?

The definition of asymptomatic hyperuricemia remains unclear, as no consensus exists about the serum urate cutoff or the relevance of ultrasound findings. Comorbidities associated with hyperuricemia have increased in frequency over the past two decades. Hyperuricemia (and/or gout) may be a cause or a consequence of a comorbidity. Whereas epidemiological studies suggest that hyperuricemia may be linked to cardiovascular, metabolic, and renal comorbidities, Mendelian randomization studies have not provided proof that these links are causal. Discrepancies between findings from observational studies and clinical trials preclude the development of recommendations about the potential benefits of urate-lowering therapy (ULT) in individual patients with asymptomatic hyperuricemia. The risk/benefit ratio of ULT is unclear. The risk of developing gout, estimated at 50%, must be weighed against the risk of cutaneous and cardiovascular side effects of xanthine oxidase inhibitors. The need for optimal comorbidity management, in contrast, is universally accepted. Medications for comorbidities that elevate urate levels should be discontinued and replaced with medications that have the opposite effect. Therapeutic lifestyle changes, weight loss as appropriate, and sufficient physical activity are useful for improving general health. Whether ULT has beneficial effects on comorbidities will be known only when well-powered interventional trials with relevant primary endpoints are available.