Uric Acid, Vascular Stiffness, and Chronic Kidney Disease: Is There a Link?

Chronic kidney disease: Which role for xanthine oxidoreductase activity and products?

The present review explores the role of xanthine oxidoreductase (XOR) in the development and progression of chronic kidney disease (CKD). Human XOR is a multi-level regulated enzyme, which has many physiological functions, but that is also implicated in several pathological processes. The main XOR activities are the purine catabolism, which generates uric acid, and the regulation of cell redox state and cell signaling, through the production of reactive oxygen species. XOR dysregulation may lead to hyperuricemia and oxidative stress, which could have a pathogenic role in the initial phases of CKD, by promoting cell injury, hypertension, chronic inflammation and metabolic derangements. Hypertension is common in CKD patients and many mechanisms inducing it (upregulation of renin-angiotensin-aldosterone system, endothelial dysfunction and atherosclerosis) may be influenced by XOR products. High XOR activity and hyperuricemia are also risk factors for obesity, insulin resistance, type 2 diabetes and metabolic syndrome that are frequent CKD causes. Moreover, CKD is common in patients with gout, which is characterized by hyperuricemia, and in patients with cardiovascular diseases, which are associated with hypertension, endothelial dysfunction and atherosclerosis. Although hyperuricemia is undoubtedly related to CKD, controversial findings have been hitherto reported in patients treated with urate-lowering therapies.

Association between insulin resistance and left ventricular hypertrophy in asymptomatic, Black, sub-Saharan African, hypertensive patients: a case-control study

Background

Conflicting information exists regarding the association between insulin resistance (IR) and left ventricular hypertrophy (LVH). We described the associations between obesity, fasting insulinemia, homeostasis model assessment of insulin resistance (HOMA-IR), and LVH in Black patients with essential hypertension.

Methods

A case–control study was conducted at the Centre Médical de Kinshasa (CMK), the Democratic Republic of the Congo, between January and December 2019. Cases and controls were hypertensive patients with and without LVH, respectively. The relationships between obesity indices, physical inactivity, glucose metabolism and lipid disorder parameters, and LVH were assessed using linear and logistic regression analyses in simple and univariate exploratory analyses, respectively. When differences were observed between LVH and independent variables, the effects of potential confounders were studied through the use of multiple linear regression and in conditional logistic regression in multivariate analyses. The coefficients of determination (R²), adjusted odds ratios (aORs), and their 95% confidence intervals (95% CIs) were calculated to determine associations between LVH and the independent variables.

Results

Eighty-eight LVH cases (52 men) were compared against 132 controls (81 men). Variation in left ventricular mass (LVM) could be predicted by the following variables: age (19%), duration of hypertension (31.3%), body mass index (BMI, 44.4%), waist circumference (WC, 42.5%), glycemia (20%), insulinemia (44.8%), and HOMA-IR (43.7%). Hypertension duration, BMI, insulinemia, and HOMA-IR explained 68.3% of LVM variability in the multiple linear regression analysis. In the logistic regression model, obesity increased the risk of LVH by threefold [aOR 2.8; 95% CI (1.06–7.4); p = 0.038], and IR increased the risk of LVH by eightfold [aOR 8.4; 95 (3.7–15.7); p < 0.001].

Conclusion

Obesity and IR appear to be the primary predictors of LVH in Black sub-Saharan African hypertensive patients. The comprehensive management of cardiovascular risk factors should be emphasized, with particular attention paid to obesity and IR. A prospective population-based study of Black sub-Saharan individuals that includes the use of serial imaging remains essential to better understand subclinical LV deterioration over time and to confirm the role played by IR in Black sub-Saharan individuals with hypertension.

Uric acid fluctuation had no effect on renal function among gout patients

BACKGROUND AND AIMS

To investigate the effects of serum uric acid (SUA) level and its fluctuation on renal dysfunction in gout patients.

METHODS AND RESULTS

Data on gout patients was collected from Huzhou city electronic medical record system data sharing platform, and information about relevant diagnoses, prescriptions, biochemical indexes and imaging characteristics was extracted. The gout patients with baseline normal renal function were enrolled in this analysis, and the estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73 m² was defined as renal dysfunction. The generalized estimating equation and Cox regression analysis were used. A total of 1009 patients with gout were enrolled. Compared with the reference group (normal baseline SUA with endpoint SUA to be < 6 mg/dL), endpoint SUA ≥ 10 mg/dL was associated with an increased risk of renal dysfunction (baseline normal SUA group: HR [95% CI] = 3.28 [1.21, 8.91]; baseline high SUA group: HR [95% CI] = 3.01 [1.43, 6.35]). Subgroup analysis of 771 SUA stable gout patients demonstrated that SUA levels at 8-10 (excluding 10), and ≥10 mg/dL were significantly associated with an increased risk for renal dysfunction, with HR [95%CI] to be 1.99 [1.05, 3.77], and 2.98 [1.38, 6.43], respectively.

CONCLUSION

Regardless of the baseline SUA level, SUA >10 mg/dL was a significant risk factor for renal dysfunction. SUA between 6 and 10 mg/dL was a potential risk factor for renal dysfunction. No significant correlation of SUA fluctuation and renal function was found.

Gender difference in the relationship between uric acid and pulse pressure among Korean adults

Hyperuricemia is associated with cardiovascular disease, but the relationship between uric acid (UA) and pulse pressure (PP) is unclear. Therefore, the present study assesses the relationship between UA and PP among Korean adults. Data from 6,310 subjects (2,800 men and 3,510 women) in the seventh Korean National Health and Nutrition Examination Survey (2016) were analyzed. After adjusting for related variables, the odds ratios (ORs) of hyperuricemia (UA ≥ 7.0 mg/dL in men or ≥ 6.0 mg/dL in women) in the high PP group (PP > 65.0 mmHg) in overall populations (OR, 1.563; 95% confidence interval [CI], 1.144-2.136) and women (OR, 1.631; 95% CI, 1.046-2.544) were significantly higher than those in normal PP, but not in men (OR, 1.309; 95% CI, 0.840-2.040). In conclusion, uric acid was positively associated with pulse pressure in women, but not in men.

Role of hypertension in progression of chronic kidney disease in children

PURPOSE OF REVIEW

Hypertension is an independent risk factor for progression of chronic kidney disease (CKD) in children. Children with early CKD develop hypertension secondary to renal disease. This review aims to highlight recent advances that help us better understand the current role of hypertension in progression of CKD in children.

RECENT FINDINGS

There is increasing evidence that children with CKD who have hypertension develop early atherosclerosis and cardiac adaptive changes. Emerging data from pediatric research in CKD show that elevated blood pressure is associated with the presence of abnormal subclinical markers of cardiovascular disease including increased carotid intima-media thickness, pulse wave velocity and left ventricular mass index. There is also some evidence that these early cardiovascular changes are reversible. Twenty-four hour ambulatory blood pressure monitoring (ABPM) is recommended in children with CKD by the American Academy of Pediatrics to diagnose hypertension.

SUMMARY

Hypertension is associated with subclinical cardiovascular disease in children with CKD. Early diagnosis of hypertension by ABPM and identification of subclinical cardiovascular changes provide a window for intervention, which may reverse early cardiovascular disease, thereby delaying dialysis and improving cardiovascular morbidity and mortality.

Biochemical and Clinical Impact of Organic Uremic Retention Solutes: A Comprehensive Update

In this narrative review, the biological/biochemical impact (toxicity) of a large array of known individual uremic retention solutes and groups of solutes is summarized. We classified these compounds along their physico-chemical characteristics as small water-soluble compounds or groups, protein bound compounds and middle molecules. All but one solute (glomerulopressin) affected at least one mechanism with the potential to contribute to the uremic syndrome. In general, several mechanisms were influenced for each individual solute or group of solutes, with some impacting up to 7 different biological systems of the 11 considered. The inflammatory, cardio-vascular and fibrogenic systems were those most frequently affected and they are one by one major actors in the high morbidity and mortality of CKD but also the mechanisms that have most frequently been studied. A scoring system was built with the intention to classify the reviewed compounds according to the experimental evidence of their toxicity (number of systems affected) and overall experimental and clinical evidence. Among the highest globally scoring solutes were 3 small water-soluble compounds [asymmetric dimethylarginine (ADMA); trimethylamine-N-oxide (TMAO); uric acid], 6 protein bound compounds or groups of protein bound compounds [advanced glycation end products (AGEs); p-cresyl sulfate; indoxyl sulfate; indole acetic acid; the kynurenines; phenyl acetic acid;] and 3 middle molecules [β₂-microglobulin; ghrelin; parathyroid hormone). In general, more experimental data were provided for the protein bound molecules but for almost half of them clinical evidence was missing in spite of robust experimental data. The picture emanating is one of a complex disorder, where multiple factors contribute to a multisystem complication profile, so that it seems of not much use to pursue a decrease of concentration of a single compound.

The problem of cardio-renal diseases in patients with gout

BACKGROUNDS

Although evidence is mounting on the role of hyperuricemia in cardio-renal disease, continuing doubt remains as to whether hyperuricemia can be considered a major causal cardiovascular risk factor. In addition, available data suggest that treatment may be beneficial, even in the absence of overt gout, when hyperuricemia accompanies other clinical conditions, such as urate deposition, advanced chronic kidney disease, or cardiovascular risk factors.

METHODS AND RESULTS

Analysis of the literature suggests there would be sufficient evidence warranting clinical trials to determine whether lowering uric acid levels would be clinically beneficial in the prevention or treatment of cardiovascular and renal diseases.

CONCLUSION

Under a practical profile, it becomes progressively more important to investigate the possibility of reducing serum uric acid levels in the general population below the level of 5.0 mg/dL.

A sensitive and accurate method to simultaneously measure uric acid and creatinine in human saliva by using LC-MS/MS

AIM

To establish a method to simultaneously measure uric acid (UA) and creatinine (Cr) in human saliva.

MATERIALS & METHODS

By using HPLC-MS/MS, we developed and validated a fast, sensitive and accurate method to simultaneously determine UA and Cr in human saliva. The determination range for Cr and UA is of 10-5000 ng/ml with the R2 for both calibration curves over 0.999. The accuracy, precision and recovery of Cr and UA were all acceptable. By using the established method, the Cr and UA levels in saliva from 28 healthy volunteers were measured as 2.9 ± 0.8 µM and 46.8 ± 18.2 µM, respectively.

CONCLUSION

This method can simultaneously determine Cr and UA in saliva for clinical and translational study.