Uric acid: Its relationship to renal hemodynamics and the renal renin-angiotensin system

Hyperuricemia and its related diseases: mechanisms and advances in therapy

Hyperuricemia, characterized by elevated levels of serum uric acid (SUA), is linked to a spectrum of commodities such as gout, cardiovascular diseases, renal disorders, metabolic syndrome, and diabetes, etc. Significantly impairing the quality of life for those affected, the prevalence of hyperuricemia is an upward trend globally, especially in most developed countries. UA possesses a multifaceted role, such as antioxidant, pro-oxidative, pro-inflammatory, nitric oxide modulating, anti-aging, and immune effects, which are significant in both physiological and pathological contexts. The equilibrium of circulating urate levels hinges on the interplay between production and excretion, a delicate balance orchestrated by urate transporter functions across various epithelial tissues and cell types. While existing research has identified hyperuricemia involvement in numerous biological processes and signaling pathways, the precise mechanisms connecting elevated UA levels to disease etiology remain to be fully elucidated. In addition, the influence of genetic susceptibilities and environmental determinants on hyperuricemia calls for a detailed and nuanced examination. This review compiles data from global epidemiological studies and clinical practices, exploring the physiological processes and the genetic foundations of urate transporters in depth. Furthermore, we uncover the complex mechanisms by which the UA induced inflammation influences metabolic processes in individuals with hyperuricemia and the association with its relative disease, offering a foundation for innovative therapeutic approaches and advanced pharmacological strategies.

Analysis of risk factors for changes of renal artery resistance indexes in gout patients by ultrasound colour Doppler

Objectives

Gout may disturb renal hemodynamics by promoting uric acid deposition; however, this relationship has not been elucidated with adequate clinical evidence. In this study, we measured the renal artery resistance index (ARI) in patients with gout to identify the risk factors and establish predictive models for elevated renal ARI in these patients.

Methods

Renal artery ultrasound examination was performed in 235 primary gout patients and 50 healthy controls (HCs); subsequently, their renal interlobar ARI (RIARI), renal segmental ARI (RSARI) and overall intrarenal ARI (OIARI) were recorded. Each ARI > 0.7 was considered elevated.

Results

RIARI, RSARI and OIARI were higher in patients with gout than in HCs (all P < 0.001). Nineteen (8.1%), 24 (10.2%) and 18 (7.7%) patients had elevated RIARI, RSARI and OIARI scores, respectively. Multivariate logistic regression analyses disclosed that: age ≥ 60 years (P = 0.000), abnormal beta2 microglobulin (β2MG) (P = 0.028), and abnormal high-density lipoprotein cholesterol (HDLC) (P = 0.030) were independently associated with elevated RIARI; age ≥ 60 years (P = 0.000), and abnormal β2MG (P = 0.013) were independently related to elevated RSARI; abnormal total protein (TP) (P = 0.014) were independently linked with elevated OIARI in gout patients. Consequently, predictive models for elevated ARI were established using nomograms based on the aforementioned independent risk factors, which showed a satisfactory value for estimating elevated RIARI [area under the curve (AUC):0.929], RSARI (AUC: 0.926) and OIARI (AUC: 0.660) in patients with gout, as validated by receiver operating characteristic curves.

Conclusion

Renal ARI were elevated in patients with gout, whose independent risk factors included older age and abnormal β2MG, HDLC and TP levels.

Serum uric acid predicts the development of atherosclerosis in women but not in men: A ten-year cohort study in China

BACKGROUND AND AIM

Atherosclerosis is becoming a significant health burden. Serum uric acid (SUA) is the final enzymatic product of purine metabolism and can contribute to the development of atherosclerosis. The aim of this study was to explore the possible predictive value of SUA in the development of atherosclerosis in a healthy Chinese population.

METHODS AND RESULTS

In this study, a total of 11,222 healthy subjects with no carotid plaque at baseline were enrolled and divided into sex-specific groups, and then the occurrence of carotid plaque during the follow-up time was documented. The association between carotid plaque and SUA levels was examined using Cox proportional-hazards regression models. The mean SUA level was 5.35 ± 1.41 mg/dL. A total of 2,911 individuals (25.94%) developed carotid plaque during the follow-up time, including 1,071 females and 1,840 males. After adjusting for potential confounding factors, the hazard ratio (HR) and 95% confidence interval (95% CI) in women for the occurrence of carotid plaque associated with SUA levels were 1.163 (1.017-1.330), but no significant correlation was found in men, as the HR was 1.050 (0.965-1.143).

CONCLUSION

Our results indicate that SUA levels predict the development of carotid plaque independent of traditional risk factors only in women.

Mutual effect of homocysteine and uric acid on arterial stiffness and cardiovascular risk in the context of predictive, preventive, and personalized medicine

Background

Arterial stiffness is a major risk factor and effective predictor of cardiovascular diseases and a common pathway of pathological vascular impairments. Homocysteine (Hcy) and uric acid (UA) own the shared metabolic pathways to affect vascular function. Serum uric acid (UA) has a great impact on arterial stiffness and cardiovascular risk, while the mutual effect with Hcy remains unknown yet. This study aimed to evaluate the mutual effect of serum Hcy and UA on arterial stiffness and 10-year cardiovascular risk in the general population. From the perspective of predictive, preventive, and personalized medicine (PPPM/3PM), we assumed that combined assessment of Hcy and UA provides a better tool for targeted prevention and personalized intervention of cardiovascular diseases via suppressing arterial stiffness.

Methods

This study consisted of 17,697 participants from Beijing Health Management Cohort, who underwent health examination between January 2012 and December 2019. Brachial-ankle pulse wave velocity (baPWV) was used as an index of arterial stiffness.

Results

Individuals with both high Hcy and UA had the highest baPWV, compared with those with low Hcy and low UA (β: 30.76, 95% CI: 18.36-43.16 in males; β: 53.53, 95% CI: 38.46-68.60 in females). In addition, these individuals owned the highest 10-year cardiovascular risk (OR: 1.49, 95% CI: 1.26-1.76 in males; OR: 7.61, 95% CI: 4.63-12.68 in females). Of note, males with high homocysteine and low uric acid were significantly associated with increased cardiovascular risk (OR: 1.30, 95% CI: 1.15-1.47), but not the high uric acid and low homocysteine group (OR: 1.02, 95% CI: 0.90-1.16).

Conclusions

This study found the significantly mutual effect of Hcy and UA on arterial stiffness and cardiovascular risk using a large population and suggested the clinical importance of combined evaluation and control of Hcy and UA for promoting cardiovascular health. The adverse effect of homocysteine on arteriosclerosis should be addressed beyond uric acid, especially for males. Monitoring of the level of both Hcy and UA provides a window opportunity for PPPM/3PM in the progression of arterial stiffness and prevention of CVD. Hcy provides a novel predictor beyond UA of cardiovascular health to identify individuals at high risk of arterial stiffness for the primary prevention and early treatment of CVD. In the progressive stage of arterial stiffness, active control of Hcy and UA levels from the aspects of dietary behavior and medication treatment is conducive to alleviating the level of arterial stiffness and reducing the risk of CVD. Further studies are needed to evaluate the clinical effect of Hcy and UA targeted intervention on arterial stiffness and cardiovascular health.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13167-022-00298-x.

Evaluation of renal microperfusion in hyperuricemic nephropathy by Contrast-Enhanced Ultrasound imaging

Diagnostic tools for the early detection of renal injury caused by hyperuricemia are still lacking. Here, we investigated whether contrast-enhanced ultrasound (CEUS) could be used as a diagnostic tool for hyperuricemic nephropathy (HN). In the HN rat model, CEUS detected a significant decline in renal cortical perfusion compared with that in control rats. Peak intensity (PI) values correlated significantly with serum KIM-1 levels and fibrosis scores in HN rats. An early decline in PI values was also observed in chronic kidney disease (CKD) stage 1 patients with HN compared with the controls (61.1±4.52 dB versus 65.80±7.10 dB) and correlated with renal function in the patients with HN. In contrast, an increase in time to reach PI values was detected in HN patients with stage 1 CKD (15.14±1.75 s versus 14.52±4.75 s) and was more pronounced in CKD stage 4 patients (67.32±3.29 s). CEUS was able to detect abnormal renal perfusion in early CKD with HN, which correlated with renal function decline, suggesting that CEUS could be used as a noninvasive tool for assessing renal function in patients with HN.

Hyperuricemia Associated with Low Skeletal Muscle in the Middle-Aged and Elderly Population in China

BACKGROUND

Previous studies have presented inconsistent results on the relationship between serum uric acid and skeletal muscle mass (SMM). We aimed to explore whether a higher serum uric acid level was associated with low SMM in the Chinese population.

METHODS

We performed a cross-sectional analysis of 6595 subjects aged 45 years or older. They were tested for fasting blood glucose, total cholesterol, triglycerides, high-density lipoprotein-cholesterol, low-density lipoprotein-cholesterol, uric acid, blood urea nitrogen, creatinine, and estimated glomerular filtration rate. SMM was accessed by dual-energy x-ray absorptiometry using two approaches: weight-adjusted appendicular skeletal muscle mass (ASM)% and ASM/BMI (body mass index (kg/m²)). Low SMM was defined as a cut-off point of ASM/BMI<0.789 for men and<0.512 for women.

RESULTS

Compared with their normal group, patients with hyperuricemia had lower ASM% (29.33±2.33 vs 30.03±2.34 for males and 24.71±1.99 vs 25.19±2.07 for females, P<0.01) and ASM/BMI (0.83±0.10 vs 0.85±0.10 for male and 0.60±0.07 vs 0.62±0.07 for female), with a higher prevalence of the associated low SMM in both sexes (35.2 vs 26.5% for male and 10.5 vs 5.9% for female, P<0.01). Pearson analysis showed that ASM% and ASM/BMI were negatively correlated with SUA (male: ASM/BMI, r=-0.097, ASM%, r=-0.146; female: ASM/BMI, r=-0.151, ASM%, r=-0.157; all P<0.001). Logistic regression analysis showed a positive association of hyperuricemia with adjusted risk of low SMM association.

CONCLUSIONS

In a middle-aged and elderly Chinese population, hyperuricemia is independently and positively associated with low SMM and can vary by age and gender.

Diffusional kurtosis imaging of kidneys in patients with hyperuricemia: initial study

BACKGROUND

At present, there remains a lack of a reliable indicator for monitoring renal function in patients with hyperuricemia.

PURPOSE

This study aimed to evaluate the feasibility of diffusion kurtosis imaging in the assessment of renal function in patients with hyperuricemia.

MATERIAL AND METHODS

A total of 75 male participants, including 25 with asymptomatic hyperuricemia, 25 with gouty arthritis, and 25 age-matched male healthy controls, were enrolled in this study. Diffusion kurtosis imaging data were acquired to derive axial (Ka), radial (Kr), and mean kurtosis (MK), fractional anisotropy, axial (Da), radial (Dr), and mean diffusivity (MD) for comparisons among the three groups. They were also correlated with estimated glomerular filtration rate (eGFR).

RESULTS

The MK values of the renal cortex and medulla and Kr value of the renal medulla in patients with asymptomatic hyperuricemia and gouty arthritis significantly increased compared with those in the controls (P < 0.05). Patients with gouty arthritis showed significant higher cortical and medullary Ka values compared with the other two groups (P < 0.05). The cortical Kr values of the asymptomatic hyperuricemia and gouty arthritis patients were significantly higher than that of the controls (P < 0.05). The medullary fractional anisotropy value showed a significant difference between the control and gouty arthritis groups (P < 0.05). No correlation was found between any diffusion kurtosis imaging parameters and eGFR value.

CONCLUSION

Diffusion kurtosis imaging is feasible in the assessment of the early changes of renal cortex and medulla in patients with hyperuricemia.

Intravoxel incoherent motion imaging of the kidney: The application in patients with hyperuricemia

BACKGROUND

Hyperuricemia is an independent risk factor for onset and progression of kidney disease. However, there remains a lack of a reliable and noninvasive biomarker to identify and monitor the changes of renal function in patients with hyperuricemia.

PURPOSE

To assess the utility of intravoxel incoherent motion (IVIM) parameters in identifying the early changes of renal function in patients with hyperuricemia.

STUDY TYPE

Retrospective case-control study.

POPULATION

Eighty-four male participants, including asymptomatic hyperuricemia (AH, 27 cases), gouty arthritis (GA, 31 cases), and 26 age-matched healthy controls.

FIELD STRENGTH/SEQUENCE

3.0T; intravoxel incoherent motion (IVIM).

ASSESSMENT

Differences in the IVIM parameters among the three groups were assessed. Pure molecular diffusion (D value); perfusion-related diffusion (D* value); pseudodiffusion fraction (f value); apparent diffusion coefficient (ADC value); estimated glomerular filtration rate (eGFR). Also, they were correlated with eGFR.

STATISTICAL TESTS

Bonferroni test, Tamhane's T₂ method, and Pearson correlation analysis.

RESULTS

The D values in renal cortex and medulla significantly decreased from the control, AH to GA groups (P < 0.05). The GA patients had a significantly lower cortical f value than the controls and AH patients (P < 0.05). The medullary f values in the AH and GA patients were significantly lower than that in the controls (P < 0.05). Also, the cortical and medullary ADC values had similar results across the three groups (P < 0.05), except for the comparison between the AH and GA groups (P = 0.668, P = 0.111, respectively). No significant correlation was found between any IVIM parameters with eGFR.

DATA CONCLUSION

IVIM imaging may be helpful for detecting the early changes of renal function induced by hyperuricemia. The D value could be the most sensitive IVIM-derived parameter in the assessment of renal function in patients with hyperuricemia in this study.

LEVEL OF EVIDENCE

3 Technical Efficacy Stage: 3 J. Magn. Reson. Imaging 2020;51:833-840.

Uric acid and cardiovascular disease

Uric acid (UA) is an end product of purine metabolism in humans and great apes. UA acts as an antioxidant and it accounts for 50% of the total antioxidant capacity of biological fluids in humans. When present in cytoplasm of the cells or in acidic/hydrophobic milieu in atherosclerotic plaques, UA converts into a pro-oxidant agent and promotes oxidative stress and through this mechanism participates in the pathophysiology of human disease including cardiovascular disease (CVD). Most epidemiological studies but not all of them suggested the existence of an association between elevated serum UA level and CVD, including coronary heart disease (CHD), stroke, congestive heart failure, arterial hypertension and atrial fibrillation as well as an increased risk for mortality due to CVD in general population and subjects with confirmed CHD. Evidence available also suggests an association between elevated UA and traditional cardiovascular risk factors, metabolic syndrome, insulin resistance, obesity, non-alcoholic fatty liver disease and chronic kidney disease. Experimental and clinical studies have evidenced several mechanisms through which elevated UA level exerts deleterious effects on cardiovascular health including increased oxidative stress, reduced availability of nitric oxide and endothelial dysfunction, promotion of local and systemic inflammation, vasoconstriction and proliferation of vascular smooth muscle cells, insulin resistance and metabolic dysregulation. Although the causality in the relationship between UA and CVD remains unproven, UA may be pathogenic and participate in the pathophysiology of CVD by serving as a bridging mechanism mediating (enabling) or potentiating the deleterious effects of cardiovascular risk factors on vascular tissue and myocardium.

Renal and Vascular Effects of Uric Acid Lowering in Normouricemic Patients With Uncomplicated Type 1 Diabetes

Higher plasma uric acid (PUA) levels are associated with lower glomerular filtration rate (GFR) and higher blood pressure (BP) in patients with type 1 diabetes (T1D). Our aim was to determine the impact of PUA lowering on renal and vascular function in patients with uncomplicated T1D. T1D patients (n = 49) were studied under euglycemic and hyperglycemic conditions at baseline and after PUA lowering with febuxostat (FBX) for 8 weeks. Healthy control subjects were studied under normoglycemic conditions (n = 24). PUA, GFR (inulin), effective renal plasma flow (para-aminohippurate), BP, and hemodynamic responses to an infusion of angiotensin II (assessment of intrarenal renin-angiotensin-aldosterone system [RAAS]) were measured before and after FBX treatment. Arterial stiffness, flow-mediated dilation (FMD), nitroglycerin-mediated dilation (GMD), urinary nitric oxide (NO), and inflammatory markers were measured before and after FBX treatment. Gomez equations were used to estimate arteriolar afferent resistance, efferent resistance (R_E), and glomerular hydrostatic pressure (P_GLO). FBX had a modest systolic BP-lowering effect in T1D patients (112 ± 10 to 109 ± 9 mmHg, P = 0.049) without impacting arterial stiffness, FMD, GMD, or NO. FBX enhanced the filtration fraction response to hyperglycemia in T1D patients through larger increases in R_E, P_GLO, and interleukin-18 but without impacting the RAAS. FBX lowered systolic BP and modulated the renal R_E responses to hyperglycemia but without impacting the RAAS or NO levels, suggesting that PUA may augment other hemodynamic or inflammatory mechanisms that control the renal response to hyperglycemia at the efferent arteriole. Ongoing outcome trials will determine cardiorenal outcomes of PUA lowering in patients with T1D.

ARISTOLOCHIA BRACTEOLATE RETZ. ATTENUATES HYPERURICEMIA IN A METABOLIC ARTHRITIS RAT MODEL

Background:

The leaves of Aristolochia bracteolata Retz. has been documented in the folk medicine literature for its anti-arthritic activity. The target of the research envisaged was to elucidate the activity of A. bracteolata extract on hyperuricemic condition in arthritis rat model.

Materials and Methods:

Dried and powdered plant leaves were extracted using ether and chloroform. Potassium oxonate was injected intra-articularly to produce arthritis. The hyperuricemic effect, of A. bracteolate was analyzed by studying levels of uric acid in serum as well as in urine of arthritis induced rats. Effects of plant extracts were also studied on BUN (blood urea nitrogen) levels and fraction of uric acid excreted.

Results:

Results indicate that administration of A. bracteolata presented substantial change in uric acid concentration, augmented by potassium oxonate administration in rats. The reduction in levels of uric acid levels was nearly same as allopurinol. The investigation also revealed that the primary plant extract has nephroprotective effect by enhancing the production of Prostaglandin E₂ and Interleukin-1. Histological studies of rat kidney slices indicated the safety of the present plant extract.

Conclusion:

The crude extract of A. bracteolate can be used to reduce hyperuricemia in metabolic arthritis produced in rat model, without inducing any potential damaging effects.

U-shaped relationship between serum uric acid levels and intrarenal hemodynamic parameters in healthy subjects

Hyperuricemia has been reported to affect renal hemodynamics. In a recent study, both low and high levels of serum uric acid (SUA) were found to be associated with loss of kidney function. The goal of this study was to evaluate the relationship between SUA levels and intrarenal hemodynamic parameters in healthy subjects, using plasma clearance of para-aminohippurate (C_PAH) and inulin (C_in). Renal and glomerular hemodynamics were evaluated by simultaneous measurements of C_PAH and C_in in 48 healthy subjects (54.6 ± 13.4 yr). Intrarenal hemodynamic parameters, including efferent and afferent (R_a) arteriolar resistance, were calculated using Gómez's formulas. Relationships of SUA levels with these intrarenal hemodynamic parameters were examined. In quadratic regression analysis, SUA levels had a significant inverse U-shaped relationship with C_in (P < 0.0001, R² = 0.350) and C_PAH (P = 0.0093, R² = 0.188) and a U-shaped relationship with R_a (P = 0.0011, R² = 0.262). In multiple regression analysis with normal (3.5-6.0 mg/dl) and mildly low or high (<3.5 or >6.0 mg/dl) SUA levels entered as dummy variables of zero and one, respectively, mildly low or high SUA levels were significantly and independently associated with R_a (β = 0.230, P = 0.0403) after adjustment for several factors (R² = 0.597, P < 0.0001). Both mild hyperuricemia and mild hypouricemia are significantly associated with increased R_a, although weakly. The increase in R_a in subjects with mild hyperuricemia or hypouricemia may be related to renal hemodynamic abnormalities, possibly leading to a decline in renal function.

An Analysis of Anthropometric Indicators and Modifiable Lifestyle Parameters Associated with Hypertensive Nephropathy

The surge in prevalence of chronic noncommunicable diseases like hypertension and chronic kidney disease has been linked with modifiable lifestyle practices and increased body fat. This study sought to compare the association between different modifiable lifestyle practices, adiposity indices, renal function parameters, and hypertension as well as the predictive implications for levels of these parameters in target cardiac organ damage among an urban Ghanaian hypertensive population. Using a hospital-based case-control study design, 241 Ghanaian indigenes from the Kumasi metropolis were recruited for this study. The case group was made up of 180 hypertensives and 61 normotensives served as controls. In addition to sociodemographic data, standard haemodynamic, anthropometric, renal function, and cardiac organ damage assessments were done. The prevalence of chronic kidney disease (CKD) ranged from 13.3% to 16.6% depending on the equation used in estimating the glomerular filtration rate (eGFR). Percentage cluster distribution by chronic kidney disease was observed to be significantly tilted toward the upper quartiles (3rd and 4th) of the haemodynamic parameters measured. Chronic kidney disease was significantly higher among self-reported smokers and alcoholic hypertensives. In this urban population, adiposity was associated with hypertension and renal insufficiency. Chronic kidney disease was associated with hypertension and cardiac abnormalities.

Hyperuricemia: A Biomarker of Renal Hemodynamic Impairment

BACKGROUND

Many epidemiological, clinical, and experimental reports have demonstrated an association between serum uric acid concentration and a variety of cardiovascular and renal diseases, particularly in hypertension. At present, there seems to be no resolution to the question whether this relationship is causal or coincidental.

SUMMARY

This discussion examines a number of biological, pathophysiological, fundamental, and clinical relationships between serum uric acid concentration and several of these disorders. To this end, discussion and review provide some specific insight conclusions and recommendations related to their clinical relevance.

KEY MESSAGES

We suggest that, in most instances (especially in patients with essential hypertension), the increase in serum uric acid concentration is coincidental, serving as a useful biomarker that relates the magnitude of circulating plasma uric acid concentration with the extent of impaired cardiovascular and renal function. Moreover, the value of certain pharmaceutical agents affecting the serum uric acid level should be considered carefully by taking into consideration the associated pathophysiological derangements.

Cyclic GMP-dependent protein kinase II is necessary for macrophage M1 polarization and phagocytosis via toll-like receptor 2

Cyclic GMP-dependent protein kinase II (cGKII; PRKG2) phosphorylates a variety of biological targets and has been identified as a gout-susceptible gene. However, the regulatory role of cGKII in triggering gout disease has yet to be clarified. Thus, we plan to explore the specific function of cGKII in macrophages related to gout disease. By using cGKII gene knockdown method, we detected macrophage M1/M2 polarization, phagocytosis, and their responses to stimulation by monosodium urate (MSU). cGKII was highly expressed in M1 phenotype, but not in M2, and cGKII knockdown significantly inhibited macrophage M1 polarization by decreasing M1 chemokine markers (CXCL10 and CCL2) and downregulating phagocytosis function. We further identified that cGKII-associated phagocytosis was mediated by upregulating toll-like receptor 2 (TLR2) expression, but not by TLR4. Mimicking gout condition by MSU treatments, we found that MSU alone induced cGKII and TLR2 expression with increased M1 polarization markers and phagocytosis activity. It means that cGKII knockdown significantly inhibited this MSU-induced cGKII-TLR2-phagocytosis axis. Our study showed that cGKII plays a key role in M1 polarization, especially in TLR2-mediated phagocytosis under MSU exposure. The findings provide evidence for the possible role of cGKII as an inflammation exciter in gout disease.

KEY MESSAGE

Gout-susceptible gene cGKII is necessary for macrophage M1 polarization. cGKII regulates M1 phagocytosis function via TLR2. Monosodium urate treatments increase cGKII expression and related function. This study reveals the role of cGKII in enhancing gouty inflammatory responses.

Association between serum uric acid, hypertension, vascular stiffness and subclinical atherosclerosis: data from the Brisighella Heart Study

OBJECTIVE

Serum uric acid (SUA) levels correlate with many recognized cardiovascular risk factors, including age, male sex, hypertension, diabetes mellitus, hypertriglyceridemia, obesity, and insulin resistance. The aim of our study was to verify in a large well characterized population sample the relationship between SUA values, hypertension, arterial stiffness and subclinical atherosclerosis.

METHODS

For this study, we selected 248 men and 371 women adult patients enrolled in the last Brisighella Heart Study population survey for which a full set of data were available and not consuming antihypertensive, antidiabetic, lipid-lowering and uric acid-lowering drugs. SUA and other available variables were related to blood pressure level, carotid-femoral pulse wave velocity (cfPWV) and carotid intima-media thickness (cIMT).

RESULTS

Hypertension prevalence was strongly related to SUA quartiles: we found significant differences between the 2nd (23.0%) and the 3rd quartiles (36.4%; P vs. 2nd < 0.05), and between the 3rd and the 4th quartile (56.3%; P vs. 3rd < 0.05). Similarly, the metabolic syndrome prevalence increased significantly at 39.5% in the 3rd SUA quartile (P < 0.05 vs. 2nd) and at 58.9% in the 4th quartile (P < 0.05 vs. 3rd). Intima-media thickness gradually and significantly rose along quartiles of SUA (P for trend < 0.0001), in particular, it was 0.86  mm in the 1st quartile, 0.90 in the 2nd, 0.94 in the 3rd, and 0.97 in the last quartile, with significant differences between each quartiles (all P < 0.05). In multivariate regression analyses, SUA resulted to be significantly associated to hypertension and metabolic syndrome prevalence, and IMT. Even if a significant association between SUA and cfPWV was found in univariate analysis (P = 0.002), when adjusting for age, the trend became nonsignificant (0.20).

CONCLUSION

In the studied population sample, after adjustment for a large number of parameters, SUA appears to be significantly correlated to hypertension and IMT, but not to aortic stiffness.

Serum uric acid level in newly diagnosed essential hypertension in a Nepalese population: a hospital based cross sectional study

OBJECTIVE

To develop the missing link between hyperuricemia and hypertension.

METHODS

The study was conducted in Department of Biochemistry in collaboration with Nephrology Unit of Internal Medicine Department. Hypertension was defined according to blood pressure readings by definitions of the Seventh Report of the Joint National Committee. Totally 205 newly diagnosed and untreated essential hypertensive cases and age-sex matched normotensive controls were enrolled in the study. The potential confounding factors of hyperuricemia and hypertension in both cases and controls were controlled. Uric acid levels in all participants were analyzed.

RESULTS

Renal function between newly diagnosed hypertensive cases and normotensive healthy controls were adjusted. The mean serum uric acid observed in newly diagnosed hypertensive cases and in normotensive healthy controls were (290.05±87.05) μmol/L and (245.24±99.38) μmol/L respectively. A total of 59 (28.8%) participants of cases and 28 (13.7%) participants of controls had hyperuricemia (odds ratio 2.555 (95% CI: 1.549-4.213), P<0.001).

CONCLUSIONS

The mean serum uric acid levels and number of hyperuricemic subjects were found to be significantly higher in cases when compared to controls.

Survival impact of serum uric acid levels in children and adolescents

Evidence is limited on the association between hyperuricaemia and mortality in children and adolescents. This study was to investigate this association in the paediatric population. The study included children and adolescents who had undergone serum uric acid (SUA) measurement at the Chang Gung Memorial Hospital between 1997 and 2008. The survival status and cause of death of the included were ascertained by examining the National Death Registry of Taiwan. Hyperuricaemia was defined as a SUA level greater than 7.0 mg/dL. We included 13,241 patients (male, n = 7,454; female, n = 5,787) of mean age 14.3 ± 4.9 years. During the 82,800 person-years of follow-up, 455 deaths were identified, which corresponded to a crude mortality rate of 5.50 deaths per 1,000 person-years. Compared with individuals with a SUA <6.0 mg/dL, those with a SUA of 6.0-8.9, 9.0-11.9 and ≥12 mg/dL had an age- and sex-adjusted HR (95% CI) of 1.02 (0.82-1.26), 1.48 (1.08-2.02) and 4.73 (2.67-8.37). After adjustment for age, sex and history of diabetes mellitus and hypertension, hyperuricaemia was found to be associated with a HR (95% CI) of 1.38 (1.13-1.69; p < 0.001) for all-cause mortality. Hyperuricaemia was associated with an increased risk of mortality due to cardiovascular diseases (HR, 5.0; 95% CI 1.79-13.94; p = 0.001) and kidney diseases (11.71; 3.13-43.78; p < 0.001). Paediatric patients with hyperuricaemia were at increased risk of mortality, especially due to kidney and cardiovascular diseases.

Anti-hyperuricemic and nephroprotective effects of Smilax china L

ETHNOPHARMACOLOGICAL RELEVANCE

Smilax china L., popularly known as "Jin Gang Ten", has been widely used as a traditional herbal medicine for the treatment of gout, rheumatoid arthritis and other diseases for a long time in China.

AIM OF STUDY

The present study was carried out to investigate the effect of Smilax china L. on hyperuricemia and renal dysfunction in induced hyperuricemic animals.

MATERIALS AND METHODS

Five fractions (petroleum ether, chloroform, ethyl acetate, n-butanol and residual ethanol fraction) of Smilax china L. were orally administered to potassium oxonate-induced hyperuricemic mice for three days. The xanthine oxidase inhibitory activities and modes of action of nine compounds isolated from ethyl acetate fraction (EAF) were then examined in vitro. Finally, different dosages of EAF were administered to 10% fructose-induced hyperuricemic rats.

RESULTS

EAF (250 mg/kg) exhibited stronger anti-hyperuricemic activity in hyperuricemic mice compared with the other four fractions. Caffeic acid, resveratrol, rutin and oxyresveratrol isolated from EAF showed different inhibitory activities on xanthine oxidase in vitro, with the IC(50) values of 42.60, 37.53, 42.20 and 40.69 μM, respectively, and exhibited competitive or mixed inhibitory actions. Moreover, EAF (125, 250 and 500 mg/kg) markedly reversed the serum uric acid level (p<0.05, p<0.01 and p<0.001, respectively), fractional excretion of urate (p<0.05, p<0.01 and p<0.01, respectively) and blood urea nitrogen (p<0.05, p<0.01 and p<0.01, respectively) to their normal states, and prevented the renal damage against tubulointerstitial pathologies in hyperuricemic rats.

CONCLUSION

These findings show that Smilax china L. exhibits anti-hyperuricemic and nephroprotective activity in hyperuricemic animals.

Fibrinogen, Hematocrit, Platelets in Mild Kidney Dysfunction and the Role of Uric Acid: An Italian Male Population Study

Aim: To examine the relationship between some blood parameters and mild kidney dysfunction. Participants and Methods: A total of 719 Italian men aged 42 to 74 years from a population-based survey carried out in the town of Bollate (Milan). General linear models were used to examine the variations in plasma fibrinogen, hematocrit, platelet counts, mean platelet volume, and uric acid across levels of kidney function (estimated on the basis of glomerular filtration rate [GFR]), adjusting for age, education, smoking, alcohol consumption, physical activity (evaluated as TV watching, engaging in sport practice, and walking/cycling), waist circumference, arm muscle area, high-density lipoprotein (HDL)-cholesterol, triglycerides, hypertension, diabetes, cardiovascular disease history, and nonsteroid anti-inflammatory, diuretic, and antihypertensive drug use. Results: Plasma fibrinogen and hematocrit levels increased, and platelet counts and mean platelet volume significantly decreased as GFR fell to <80 or <70 mL/min per 1.73 m2; stratified analysis revealed an association with serum uric acid levels. Alterations compatible with an increased cardiovascular risk were particularly evident among the participants with higher uric acid levels, whereas those indicative of platelet dysfunction were found among participants with lower levels. Conclusions: Parameters affecting hemostasis and blood viscosity are altered when kidney function is only slightly reduced, and the patterns of these relationships seem to be influenced by the levels of serum uric acid, whose easy and inexpensive measurement could have prognostic value.

Hypertensive renal vascular disease and cardiovascular endpoints

PURPOSE OF REVIEW

Hypertension involves the entire cardiovascular system, and hypertensive vascular disease may promote and exacerbate cardiac and renal dysfunction. We discuss the coexistence of cardiorenal disease as a manifestation of vascular involvement in hypertension, and the relationship of biomarkers of renal vascular involvement in hypertension with cardiovascular endpoints.

RECENT FINDINGS

Markers of renal dysfunction, especially microalbuminuria, have been considered recently as potent predictors of cardiovascular morbidity and mortality in all explored populations, including hypertensive individuals. Microalbuminuria, per se, is related to vascular injury and to the increased glomerular permeability of albumin as a direct manifestation of renal vascular involvement in hypertension, a systemic vascular disease. Left ventricular hypertrophy in hypertension develops even before proteinuria or impairment of renal function. Factors including anemia, inflammation and hyperuricemia are either induced or exacerbated by renal vascular disease, and each of these may exert additional influence in determining the increased incidence of cardiovascular events with progressive renal dysfunction.

SUMMARY

The development and progression of vascular disease is the primary determinant in the progressive cardiac and renal dysfunction observed in hypertension and, therefore, is the underlying mechanism of the overall clinical manifestations of cardiorenal disease. Commonly used biomarkers of renal and vascular function are important tools for determination of the progression and, hence, management of hypertensive disease and its complications.