Uric Acid Impairs Insulin Signaling by Promoting Enpp1 Binding to Insulin Receptor in Human Umbilical Vein Endothelial Cells

Insight into small-molecule inhibitors targeting extracellular nucleotide pyrophosphatase/phosphodiesterase1 for potential multiple human diseases

Extracellular nucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1) has been identified as a type II transmembrane glycoprotein. It plays a crucial role in various biological processes, such as bone mineralization, cancer cell proliferation, and immune regulation. Consequently, ENPP1 has garnered attention as a promising target for pharmacological interventions. Despite its potential, the development of clinical-stage ENPP1 inhibitors for solid tumors, diabetes, and silent rickets remains limited. However, there are encouraging findings from preclinical trials involving small molecules exhibiting favorable therapeutic effects and safety profiles. This perspective aims to shed light on the structural properties, biological functions and the relationship between ENPP1 and diseases. Additionally, it focuses on the structure-activity relationship of ENPP1 inhibitors, with the intention of guiding the future development of new and effective ENPP1 inhibitors.

Association between Glycosylated Hemoglobin and Serum Uric Acid: A US NHANES 2011-2020

Background

Serum uric acid (SUA) and glycosylated hemoglobin (HbA1c) were closely related to the body's metabolism. This study aimed to investigate the relationship between HbA1c and SUA in adults.

Methods

This study selected 7293 participants aged ≥20 from 2011 to 2020 in the National Health and Nutrition Examination Survey (NHANES). The multivariate linear regression model was used to test the association between HbA1c and SUA. Subgroup analysis was performed according to age, gender, race, and body mass index (BMI). This study solved the relationship between HbA1c and SUA by fitting a smooth curve. Finally, the inflection point in the nonlinear relationship was calculated by the recursive algorithm, and the relationship between HbA1c and SUA on both sides of the inflection point was analyzed by the two-segment piecewise linear regression model.

Results

All 7293 participants found a negative correlation between HbA1c and SUA by completely adjusting the model (β = -7.93 and 95% CI: -9.49--6.37). In addition, when this study was stratified by gender, age, race, and BMI status, this negative correlation was still statistically significant. In the subgroup analysis, we found that the relationship between the two had different results due to gender differences. In men, HbA1c had a significant negative correlation with SUA. However, in women, the HbA1c value was positively correlated with SUA before 6.8%, and the HbA1c value was negatively correlated with SUA after 6.8%, which indicates that the relationship between HbA1c and SUA in women has changed in prediabetes and diabetes.

Conclusion

This study shows that HbA1c is positively correlated with SUA in American adults before 7%. There is a negative correlation after the HbA1c value of 7%.

A Possible Therapeutic Application of the Selective Inhibitor of Urate Transporter 1, Dotinurad, for Metabolic Syndrome, Chronic Kidney Disease, and Cardiovascular Disease

The reabsorption of uric acid (UA) is mainly mediated by urate transporter 1 (URAT1) and glucose transporter 9 (GLUT9) in the kidneys. Dotinurad inhibits URAT1 but does not inhibit other UA transporters, such as GLUT9, ATP-binding cassette transporter G2 (ABCG2), and organic anion transporter 1/3 (OAT1/3). We found that dotinurad ameliorated the metabolic parameters and renal function in hyperuricemic patients. We consider the significance of the highly selective inhibition of URAT1 by dotinurad for metabolic syndrome, chronic kidney disease (CKD), and cardiovascular disease (CVD). The selective inhibition of URAT1 by dotinurad increases urinary UA in the proximal tubules, and this un-reabsorbed UA may compete with urinary glucose for GLUT9, reducing glucose reabsorption. The inhibition by dotinurad of UA entry via URAT1 into the liver and adipose tissues increased energy expenditure and decreased lipid synthesis and inflammation in rats. Such effects may improve metabolic parameters. CKD patients accumulate uremic toxins, including indoxyl sulfate (IS), in the body. ABCG2 regulates the renal and intestinal excretion of IS, which strongly affects CKD. OAT1/3 inhibitors suppress IS uptake into the kidneys, thereby increasing plasma IS, which produces oxidative stress and induces vascular endothelial dysfunction in CKD patients. The highly selective inhibition of URAT1 by dotinurad may be beneficial for metabolic syndrome, CKD, and CVD.

What is the relationship between serum uric acid level and insulin resistance?: A case-control study

Diabetes, arises from either an absolute or relative insufficiency of insulin or insulin resistance of peripheral tissues. For assessing long-term blood glucose concentration and insulin resistance, the utilization of glycosylated hemoglobin (HbA1c) and the Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) is widespread. Insulin resistance can lead to hyperuricemia by reducing the kidney ability to excrete urate, thus increasing sodium reabsorption. The aim of this study was to investigate the possible relationship between serum uric acid levels and insulin resistance. This was a retrospective case-control study. A total of 2530 applications in 2-year time were included in the study. Patient, known hypertension status, fasting plasma glucose, insulin, uric acid, HDL, low-density lipoprotein (LDL), triglyceride/Tg, HbA1c laboratory values and Tg/HDL ratio were examined. A statistically significant difference existed in the median uric acid values between the insulin-resistant and insulin-sensitive groups (P < .001). Additionally, a weak positive statistical correlation was identified between uric acid and HOMA-IR values (R = 0.299; P < .001) and uric acid and Tg/HDL values (R = 0.357; P < .001). This study concludes that there is a positive correlation between serum uric acid levels and insulin resistance.

Sex-related differences for uric acid in the prediction of cardiovascular events in essential hypertension. A population prospective study

BACKGROUND

Uric acid (UA) is an independent prognostic factor for cardiovascular events, but there are no data demonstrating a different risk profile between women and men. Thus, we tested whether UA is associated with a possible sex-related difference in fatal and non-fatal cardiovascular events.

METHODS

In this prospective population-based study we enrolled 1,650 never-treated Caucasian hypertensive outpatients referred to Catanzaro University Hospital (Italy). Inclusion criteria were newly diagnosed hypertensive patients, aged 20 years or more. Exclusion criteria were secondary form of hypertension, previous cardiovascular events, rheumatic and non-rheumatic valvular heart disease, prosthetic valves, cardiomyopathies, type-2 diabetes, chronic kidney disease, malignant diseases, gout arthritis and secondary forms of hyperuricemia, liver diseases, peripheral vascular diseases, and heart failure. Anthropometric, clinical, and biochemical parameters were measured. UA prognostic role was investigated by Cox regression analyses. Receiver-operating characteristic curve analyses and area under the curve were used to determine the predictive validity and the optimal cut-off point of UA. We investigated following endpoints: coronary events (fatal and nonfatal myocardial infarction, unstable angina, coronary revascularization procedures, coronary death); fatal and nonfatal stroke; all-cause mortality and major adverse cardiovascular events (MACE).

RESULTS

We enrolled 830 males and 820 females aged 52.2 ± 11.3 years. During 9.5 ± 3.1 years follow-up, there were 424 new clinical events (2.71%): 250 coronary (1.59%), 118 (0.75%) cerebrovascular, and 56 (0.40%) deaths. Comparison between groups demonstrated a higher and significant difference in incidence rate in females for MACE (3.08 vs 2.33%, P = 0.001), coronary (1.82 vs 1.36%, P = 0.014) and cerebrovascular events (0.93 vs 0.57%, P = 0.006). UA at multiple Cox regression analysis resulted a strong and significant predictor of coronary events (HR = 1.493;95% CI 1.375-1.621), cerebrovascular events (HR = 1.256;95% CI 1.109-1.423), MACE (HR = 1.415;95% CI 1.328- 53 1.508), and all-cause mortality (HR = 1.469;95% CI 1.237-1.745) in the whole population and in both groups with a HR higher in females. The best estimated cut-off values of uric acid for males and females predicted these endpoints equally well, but it was always lower in females than males.

CONCLUSIONS

We demonstrate, that UA operates with a sex-related impact and best cut-off value in predicting cardiovascular outcomes and all-cause mortality, reflecting a possible sex difference in disease pathophysiology.

Diabetes mellitus as a risk factor and comorbidity in gout

INTRODUCTION

Metabolic disorders are a public health issue because of the complications they cause, but they are also a major risk factor for the onset of gout.

Mechanistic insights of soluble uric acid-induced insulin resistance: Insulin signaling and beyond

Hyperuricemia is a metabolic disease caused by purine nucleotide metabolism disorder. The prevalence of hyperuricemia is increasing worldwide, with a growing trend in the younger populations. Although numerous studies have indicated that hyperuricemia may be an independent risk factor for insulin resistance, the causal relationship between the two is controversial. There are few reviews, however, focusing on the relationship between uric acid (UA) and insulin resistance from experimental studies. In this review, we summarized the experimental models related to soluble UA-induced insulin resistance in pancreas and peripheral tissues, including skeletal muscles, adipose tissue, liver, heart/cardiomyocytes, vascular endothelial cells and macrophages. In addition, we summarized the research advances about the key mechanism of UA-induced insulin resistance. Moreover, we attempt to identify novel targets for the treatment of hyperuricemia-related insulin resistance. Lastly, we hope that the present review will encourage further researches to solve the chicken-and-egg dilemma between UA and insulin resistance, and provide strategies for the pathogenesis and treatment of hyperuricemia related metabolic diseases.

Uric Acid Induces a Proatherothrombotic Phenotype in Human Endothelial Cells by Imbalancing the Tissue Factor/Tissue Factor Pathway Inhibitor Pathway

BACKGROUND

 Several evidence show that elevated plasma levels of uric acid (UA) are associated with the increased risk of developing atherothrombotic cardiovascular events. Hyperuricemia is a risk factor for endothelial dysfunction (ED). ED is involved in the pathophysiology of atherothrombosis since dysfunctional cells lose their physiological, antithrombotic properties. We have investigated whether UA might promote ED by modulating the tissue factor (TF)/TF pathway inhibitor (TFPI) balance by finally changing the antithrombotic characteristics of endothelial cells.

METHODS

 Human umbilical vein endothelial cells were incubated with increasing doses of UA (up to 9 mg/dL). TF gene and protein expressions were evaluated by real-time polymerase chain reaction (PCR) and Western blot. Surface expression and procoagulant activity were assessed by FACS (fluorescence activated cell sorting) analysis and coagulation assay. The mRNA and protein levels of TFPI were measured by real-time PCR and Western blot. The roles of inflammasome and nuclear factor-κB (NF-κB) as possible mechanism(s) of action of the UA on TF/TFPI balance were also investigated.

RESULTS

 UA significantly increased TF gene and protein levels, surface expression, and procoagulant activity. In parallel, TFPI levels were significantly reduced. The NF-κB pathways appeared to be involved in modulating these phenomena. Additionally, inflammasome might also play a role.

CONCLUSION

 The present in vitro study shows that one of the mechanisms by which high levels of UA contribute to ED might be the imbalance between TF/TFPI levels in endothelial cells, shifting them to a nonphysiological, prothrombotic phenotype. These UA effects might hypothetically explain, at least in part, the relationship observed between elevated plasma levels of UA and cardiovascular events.

Interaction of sex and diabetes on the association between hemoglobin glycation index, hemoglobin A1c and serum uric acid

BACKGROUND

Hemoglobin glycation index (HGI), which is calculated by blood glucose and hemoglobin A1c(HbA1c), reflects the individual discrepancy in HbA1c. This study aimed to investigate the association between HGI/HbA1c and serum uric acid(SUA) stratified by sex and diabetes.

METHODS

The study recruited 33772 participants who underwent physical examinations between April 2016 and August 2021 in Beijing Chao-Yang Hospital. A random subsample of 3000 subjects was utilized to calculate the formula of HGI and data of the remaining 30772 participants were used for analysis. HGI and HbA1c were categorized according to quartiles (Q1, Q2, Q3, Q4), using Q1 as the reference. We used multiple linear regression and restricted cubic splines for data analysis.

RESULTS

30772 participants with a mean age of 44.4 years old were included in the analysis, 48.6% (N = 14944) of which were female and 7.7% (N = 2363) with diabetes. Associations of HGI, HbA1c and SUA were modified by sex and diabetes. The relationship between SUA levels and HGI was positive in women without diabetes, with one unit increase in HGI associating with an 11.3 μmol/L increase in SUA (P < 0.001) after adjusting for other confounders. On average, each one-unit increase in HbA1c was associated with a 14.3 μmol/L decrease in SUA in women with diabetes, a 14.9 μmol/L decrease in SUA in men with diabetes, and a 16.5 μmol/L increase in SUA in women without diabetes (all P < 0.001). The SUA levels in men without diabetes showed a bell-shaped relation with HbA1c, increasing as the HbA1c rose to around 5.7% and then falling with a further increase of HbA1c (P < 0.001).

CONCLUSIONS

SUA levels were inversely correlated with HbA1c in diabetic patients, also in men with prediabetes (HbA1c ≥ 5.7%), but positively correlated with HbA1c and HGI in women without diabetes. Glycemic control may help to reduce the risk of hyperuricemia in non-diabetes women.

The Insulin Receptor: An Important Target for the Development of Novel Medicines and Pesticides

The insulin receptor (IR) is a transmembrane protein that is activated by ligands in insulin signaling pathways. The IR has been considered as a novel therapeutic target for clinical intervention, considering the overexpression of its protein and A-isoform in multiple cancers, Alzheimer’s disease, and Type 2 diabetes mellitus in humans. Meanwhile, it may also serve as a potential target in pest management due to its multiple physiological influences in insects. In this review, we provide an overview of the structural and molecular biology of the IR, functions of IRs in humans and insects, physiological and nonpeptide small molecule modulators of the IR, and the regulating mechanisms of the IR. Xenobiotic compounds and the corresponding insecticidal chemicals functioning on the IR are also discussed. This review is expected to provide useful information for a better understanding of human IR-related diseases, as well as to facilitate the development of novel small-molecule activators and inhibitors of the IR for use as medicines or pesticides.

Evaluation of the prognostic ability of serum uric acid for elderly acute coronary syndrome patients with diabetes mellitus: a prospective cohort study

OBJECTIVES

This study evaluated the prognostic power of serum uric acid (UA) in predicting adverse events in elderly acute coronary syndrome (ACS) patients with diabetes mellitus (DM).

METHODS

The analysis involved 718 ACS patients ‍>80 years old whose general clinical data and baseline blood biochemical indicators were collected prospectively from January 2006 to December 2012. These patients were classified into two groups based on DM status, and then followed up after discharge. The Kaplan-Meier method was used for major adverse cardiac event (MACE) rates and all-cause mortality. Multivariate Cox regression was performed to analyze the relationship between UA level and long-term clinical prognosis. Receiver operating characteristic (ROC) curves were analyzed to predict the cutoff value of UA in elderly ACS patients with DM. There were 242 and 476 patients in the DM and non-DM (NDM) groups, respectively, and the follow-up time after discharge was 40‒120 months (median, 63 months; interquartile range, 51‒74 months).

RESULTS

The all-cause mortality, cardiac mortality, and MACE rates in both DM and NDM patients were higher than those in the control group (P=0.001). All-cause mortalities, cardiac mortalities, and MACE rates in DM patients with moderate and high UA levels were significantly higher than those in the NDM group (P=0.001). Long-term survival rates decreased significantly with increased UA levels in the ACS groups (P=0.001). UA (odds ratio (OR)=2.106, 95% confidence interval (CI)=1.244‒3.568, P=0.006) was found to be an independent risk factor for all-cause mortality and MACE in elderly ACS patients with DM. The cutoff value of UA was 353.6 μmol/L (sensitivity, 67.4%; specificity, 65.7%).

CONCLUSIONS

Serum UA level is a strong independent predictor of long-term all-cause death and MACE in elderly ACS patients with DM.

Hyperuricemia-induced endothelial insulin resistance: the nitric oxide connection

Hyperuricemia, defined as elevated serum concentrations of uric acid (UA) above 416 µmol L^-1, is related to the development of cardiometabolic disorders, probably via induction of endothelial dysfunction. Hyperuricemia causes endothelial dysfunction via induction of cell apoptosis, oxidative stress, and inflammation; however, it's interfering with insulin signaling and decreased endothelial nitric oxide (NO) availability, resulting in the development of endothelial insulin resistance, which seems to be a major underlying mechanism for hyperuricemia-induced endothelial dysfunction. Here, we elaborate on how hyperuricemia induces endothelial insulin resistance through the disruption of insulin-stimulated endothelial NO synthesis. High UA concentrations decrease insulin-induced NO synthesis within the endothelial cells by interfering with insulin signaling at either the receptor or post-receptor levels (i.e., proximal and distal steps). At the proximal post-receptor level, UA impairs the function of the insulin receptor substrate (IRS) and phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) in the insulin signaling pathway. At the distal level, high UA concentrations impair endothelial NO synthase (eNOS)-NO system by decreasing eNOS expression and activity as well as by direct inactivation of NO. Clinically, UA-induced endothelial insulin resistance is translated into impaired endothelial function, impaired NO-dependent vasodilation, and the development of systemic insulin resistance. UA-lowering drugs may improve endothelial function in subjects with hyperuricemia.

Serum uric acid is positively associated with the prevalence of nonalcoholic fatty liver in non-obese type 2 diabetes patients in a Chinese population

AIMS

To investigate whether SUA is independently associated with NAFLD in non-obese type 2 diabetic patients in a Chinese population.

METHODS

A cross-sectional study was carried out among 400 non-obese type 2 diabetic inpatients. Patients were stratified according to SUA levels and presence/absence of NAFLD. The clinical and laboratory features were collected retrospectively. Multivariate logistic regression analysis was conducted to estimate odds ratios of SUA for NAFLD.

RESULTS

The levels of SUA were significantly higher in patients with NAFLD than those without NAFLD. SUA was positively associated with the risk factors of NAFLD such as BMI, serum insulin and lipids. The odds of NAFLD were increasingly higher from the second to the fourth quartile of SUA as compared to the lowest quartile. After adjustment for age, gender, BMI and other metabolic components, the odds of NAFLD remained significantly increased for quartile 4.

CONCLUSIONS

SUA levels are strongly and independently associated with the prevalence of NAFLD. SUA may be used as a useful predictor to stratify the higher risks for NAFLD of non-obese type 2 diabetes patients.

Uric Acid and Vascular Damage in Essential Hypertension: Role of Insulin Resistance

Increased levels of uric acid (UA) have been shown to be correlated with many clinical conditions. Uric acid may adversely affect the insulin signalling pathway inducing insulin resistance (IR). Several studies report the association between arterial stiffness (AS), an early indicator of atherosclerosis, and UA. The purpose of the present study was to evaluate the association between UA and AS, considering the potential role of IR. We enrolled 1114 newly diagnosed, never-treated hypertensive patients. Insulin resistance was assessed by the homeostatic model assessment (HOMA) index. Arterial stiffness was evaluated as the measurement of the carotid–femoral pulse wave velocity (PWV). The study cohort was divided into subgroups, according to increasing tertiles of UA. The mean values of UA were 5.2 ± 1.6 mg/dL in the overall population. Pulse wave velocity was linearly correlated with UA (p < 0.0001), HOMA (p < 0.0001), high sensitivity C-reactive protein (p < 0.0001), systolic blood pressure (p < 0.0001) and LDL cholesterol (p = 0.005). Uric acid was the strongest predictor of PWV and was associated with the highest risk for increased AS. The interaction analysis showed that the joint effect of increased UA and HOMA was significantly higher than that expected in the absence of interaction under the additive model, indicating that the two biomarkers synergically interacted for promoting vascular damage. Our data showed that UA interacted with IR to increase AS in a large cohort of newly diagnosed, never-treated hypertensive patients.

Integrated omics analysis reveals the alteration of gut microbe-metabolites in obese adults

Obesity, a risk to health, is a global problem in modern society. The prevalence of obesity was approximately 13% among world's adult population. Recently, several reports suggested that the interference of gut microbiota composition and function is associated with metabolic disorders, including obesity. Gut microbiota produce a board range of metabolites involved in energy and glucose homeostasis, leading to the alteration in host metabolism. However, systematic evaluation of the relationship between gut microbiota, gut metabolite and host metabolite profiles in obese adults is still lacking. In this study, we used comparative metagenomics and metabolomics analysis to determine the gut microbiota and gut-host metabolite profiles in six normal and obese adults of Chinese origin, respectively. Following the functional and pathway analysis, we aimed to understand the possible impact of gut microbiota on the host metabolites via the change in gut metabolites. The result showed that the change in gut microbiota may result in the modulation of gut metabolites contributing to glycolysis, tricarboxylic acid cycle and homolactic fermentation. Furthermore, integrated metabolomic analysis demonstrated a possible positive correlation of dysregulated metabolites in the gut and host, including l-phenylalanine, l-tyrosine, uric acid, kynurenic acid, cholesterol sulfate and glucosamine, which were reported to contribute to metabolic disorders such as obesity and diabetes. The findings of this study provide the possible association between gut microbiota-metabolites and host metabolism in obese adults. The identified metabolite changes could serve as biomarkers for the evaluation of obesity and metabolic disorders.

Distinct uric acid trajectories are associated with incident diabetes in an overweight Chinese population

AIM

To explore uric acid (UA) trajectories in different body mass index (BMI) populations and to determine their associations with incident diabetes.

METHODS

A total of 4566 adults without diabetes in 2011 were enrolled. All participants underwent a medical examination every year until 2016, and were classified into three subgroups based on BMI: non-obese (BMI<24kg/m²); overweight (BMI ≥24kg/m² but<28kg/m²); and obese (BMI ≥28kg/m²). Distinct UA trajectories were identified through group-based trajectory modelling (GBTM). Cox proportional-hazards models were applied to evaluate the associations between UA trajectories and risk of incident diabetes.

RESULTS

UA trajectories were identified in the three BMI subgroups: 'low' (42.4% in non-obese, 22.1% in overweight, 22.0% in obese); 'moderate' (32.5%, 41.1%, 34.8%); 'moderate-high' (18.6%, 29.5%, 30.8%); and 'high' (6.5%, 7.3%, 12.4%). After a 5-year follow-up, 170 (3.7%) participants had developed diabetes. The prevalence of new-onset diabetes increased progressively with the higher UA trajectories in the BMI groups (P values<0.05). Whereas compared with the low trajectory, a significant association between a high UA trajectory and incidence of diabetes was observed only in the overweight population [hazard ratio (HR): 6.95, 95% confidence interval (CI): 1.90-25.45], with no significant associations found in either the non-obese (HR: 0.67, 95% CI: 0.13-3.52) or obese (HR: 0.40, 95% CI: 0.06-2.64) populations, in the fully adjusted model.

CONCLUSION

Higher UA trajectories are significantly associated with an increased risk of incident diabetes, thereby suggesting that monitoring UA trajectories over time may assist in the identification of prediabetes and diabetes, particularly in the overweight population.

Soluble Uric Acid Is an Intrinsic Negative Regulator of Monocyte Activation in Monosodium Urate Crystal-Induced Tissue Inflammation

Although monosodium urate (MSU) crystals are known to trigger inflammation, published data on soluble uric acid (sUA) in this context are discrepant. We hypothesized that diverse sUA preparation methods account for this discrepancy and that an animal model with clinically relevant levels of asymptomatic hyperuricemia and gouty arthritis can ultimately clarify this issue. To test this, we cultured human monocytes with different sUA preparation solutions and found that solubilizing uric acid (UA) by prewarming created erroneous results because of UA microcrystal contaminants triggering IL-1β release. Solubilizing UA with NaOH avoided this artifact, and this microcrystal-free preparation suppressed LPS- or MSU crystal-induced monocyte activation, a process depending on the intracellular uptake of sUA via the urate transporter SLC2A9/GLUT9. CD14⁺ monocytes isolated from hyperuricemic patients were less responsive to inflammatory stimuli compared with monocytes from healthy individuals. Treatment with plasma from hyperuricemic patients impaired the inflammatory function of CD14⁺ monocytes, an effect fully reversible by removing sUA from hyperuricemic plasma. Moreover, Alb-creERT2;Glut9 ^lox/lox mice with hyperuricemia (serum UA of 9-11 mg/dl) showed a suppressed inflammatory response to MSU crystals compared with Glut9 ^lox/lox controls without hyperuricemia. Taken together, we unravel a technical explanation for discrepancies in the published literature on immune effects of sUA and identify hyperuricemia as an intrinsic suppressor of innate immunity, in which sUA modulates the capacity of monocytes to respond to danger signals. Thus, sUA is not only a substrate for the formation of MSU crystals but also an intrinsic inhibitor of MSU crystal-induced tissue inflammation.

Hyperuricemia and Cardiovascular Disease

Purine metabolism in the circulatory system yields uric acid as its final oxidation product, which is believed to be linked to the development of gout and kidney stones. Hyperuricemia is closely correlated with cardiovascular disease, metabolic syndrome, and chronic kidney disease, as attested by the epidemiological and empirical research. In this review, we summarize the recent knowledge about hyperuricemia, with a special focus on its physiology, epidemiology, and correlation with cardiovascular disease. This review also discusses the possible positive effects of treatment to reduce urate levels in patients with cardiovascular disease and hyperuricemia, which may lead to an improved clinical treatment plan.

Mendelian randomization study of serum uric acid levels and diabetes risk: evidence from the Dongfeng-Tongji cohort

OBJECTIVE

Limited Mendelian randomization (MR) studies have assessed the causal relationship between serum uric acid levels and diabetes risk. Here we investigated causality between the serum uric acid concentration and diabetes risk in Chinese population.

RESEARCH DESIGN AND METHODS

The observational analysis, based on the Dongfeng-Tongji prospective cohort (n=15 195) we tested the association of serum uric acid levels with incident diabetes risk. In the instrumental variable analysis, we examined the association of the genetic risk score (GRS) of serum uric acid with diabetes risk in case-control design (2539 cases and 4595 controls) via MR analysis.

RESULTS

During a mean (SD) follow-up of 4.5 (0.5) years, 1156 incident diabetes cases were identified. Compared with those in the lowest quintile of serum uric acid levels, the HRs of incident diabetes were 1.19 (95% CI 0.96 to 1.48), 1.12 (95% CI 0.90 to 1.40), 1.38 (95% CI 1.12 to 1.70), and 1.51 (95% CI 1.23 to 1.87) for Q2, Q3, Q4 and Q5, respectively (P-trend <0.001). The GRS was strongly associated with serum uric acid levels (β=0.17, 95% CI 0.15 to 0.19; P=2.81×10^-67). However, no significant association was observed between the GRS and diabetes risk (OR=1.01, 95 CI 0.95 to 1.06; P=0.75).

CONCLUSIONS

Even though serum uric acid levels were significantly associated with increased incident diabetes risk, the results did not provide evidence for a causal relationship between them.

Uraemic syndrome of chronic kidney disease: altered remote sensing and signalling

Uraemic syndrome (also known as uremic syndrome) in patients with advanced chronic kidney disease involves the accumulation in plasma of small-molecule uraemic solutes and uraemic toxins (also known as uremic toxins), dysfunction of multiple organs and dysbiosis of the gut microbiota. As such, uraemic syndrome can be viewed as a disease of perturbed inter-organ and inter-organism (host-microbiota) communication. Multiple biological pathways are affected, including those controlled by solute carrier (SLC) and ATP-binding cassette (ABC) transporters and drug-metabolizing enzymes, many of which are also involved in drug absorption, distribution, metabolism and elimination (ADME). The remote sensing and signalling hypothesis identifies SLC and ABC transporter-mediated communication between organs and/or between the host and gut microbiota as key to the homeostasis of metabolites, antioxidants, signalling molecules, microbiota-derived products and dietary components in body tissues and fluid compartments. Thus, this hypothesis provides a useful perspective on the pathobiology of uraemic syndrome. Pathways considered central to drug ADME might be particularly important for the body's attempts to restore homeostasis, including the correction of disturbances due to kidney injury and the accumulation of uraemic solutes and toxins. This Review discusses how the remote sensing and signalling hypothesis helps to provide a systems-level understanding of aspects of uraemia that could lead to novel approaches to its treatment.

Serum uric acid as a risk factor of all-cause mortality and cardiovascular events among type 2 diabetes population: Meta-analysis of correlational evidence

AIMS

To explore the association between serum uric acid (SUA) level and the risk of cardiovascular complications and all-cause mortality rates among individuals with type 2 diabetes.

METHODS

Web of Science and PubMed database were searched for studies reported associations between SUA level and cardiovascular complications and all-cause mortality among individuals with type 2 diabetes. Hazard ratios (HRs) were independently extracted by two investigators and synthesized through meta-analysis across selected studies.

RESULTS

6 (n = 11,750 patients), 4 (n = 3044 patients) and 2 studies (n = 7792 patients) were identified reporting associations between SUA level and all-cause mortality, coronary heart disease (CHD) and stroke respectively. HR for all-cause mortality, CHD, and stroke per 59 μmol/l increase was 1.06 (95% CI: 1.03, 1.09), 1.09 (95% CI: 0.94, 1.26) and 1.19 (95% CI: 1.08, 1.31), respectively.

CONCLUSIONS

Overall, the SUA level was associated with a higher risk of all-cause mortality and stroke. We found no significant association between SUA level and CHD among type 2 diabetes population.

Urate-lowering therapy alleviates atherosclerosis inflammatory response factors and neointimal lesions in a mouse model of induced carotid atherosclerosis

Hyperuricemia (HU) is a cause of gout. Clinical studies show a link between HU and cardiovascular disease. However, the role of soluble serum urate (SU) on atherosclerosis development remains elusive. We aimed to use a new HU mouse model [Uricase/Uox knockout (KO)] to further investigate the relationship between HU and atherosclerosis. A mouse model by perivascular collar placement of induced carotid atherosclerosis was established in male Uox-KO mice. The Uox-KO mice had elevated SU levels and enhanced levels of atherosclerosis inflammatory response proteins. In contrast, Uox-KO mice with carotid atherosclerosis showed severe neointimal changes in histology staining consistent with increases in intimal area and increases in proliferating cell nuclear antigen (PCNA)- and F4/80-positive cells. Allopurinol reduced neointimal areas induced by the perivascular collar in hyperuricemic mice, accompanied by decreased expression of PCNA- and F4/80-positive cells. Urate-lowering treatment alleviated atherosclerosis inflammatory response factors and reactive oxygen species (ROS) intensities in both collar placement Uox-KO mice and urate-stimulated human umbilical vein endothelial cells (HUVECs). In vitro results using HUVECs showed ROS was induced by urate and ROS induction was abrogated using antioxidants. These data demonstrate that urate per se does not trigger atherosclerosis intima lesions in male mice. Urate worsens carotid neointimal lesions induced by the perivascular collar and urate-lowering therapy partially abrogates the effects. The current study warrants clinical studies on the possible benefits of urate-lowering therapy in atherosclerosis patients with HU.

Effects of Uric Acid on Diabetes Mellitus and Its Chronic Complications

With the deepening of the researches on uric acid, especially in the study of metabolic diseases, uric acid has been found to be closely related to obesity, metabolic syndrome, nonalcoholic fatty liver disease, diabetes, and other metabolic diseases. Uric acid causes a series of pathophysiological changes through inflammation, oxidative stress, vascular endothelial injury, and so on and thus subsequently promotes the occurrence and development of diseases. This review confirmed the positive correlation between uric acid and diabetes mellitus and its chronic complications through the pathogenesis and clinical studies aspects.

Roles of hyperuricemia in metabolic syndrome and cardiac-kidney-vascular system diseases

Uric acid is the final product of purine metabolism. Hyperuricemia is defined as a condition where the level of uric acid exceeds the normal range. The most well-known disease induced by hyperuricemia is gout. However, many studies have reported that hyperuricemia also plays important roles in cardiac-kidney-vascular system diseases and metabolic syndrome. Although hyperuricemia has been known for a long time, its pathophysiology remains poorly understood. In this review, we highlight studies on advanced pathological mechanisms for injuries induced by hyperuricemia, summarize epidemiological studies on hyperuricemia and its associated diseases, and take a brief look at hyperuricemia prevention.

Higher serum levels of uric acid are associated with a reduced insulin clearance in non-diabetic individuals

AIMS

Decreased insulin clearance has been reported to be associated with insulin resistance-related disorders and incident type 2 diabetes. The aim of this study was to evaluate whether higher levels of uric acid (UA), a known risk factor of type 2 diabetes, are associated with a reduced insulin clearance.

METHODS

440 non-diabetic individuals were stratified in tertiles according to serum UA levels. Insulin clearance and skeletal muscle insulin sensitivity were assessed by euglycemic hyperinsulinemic clamp. Hepatic insulin resistance was estimated by the liver IR index.

RESULTS

Subjects with higher levels of UA displayed an unfavorable metabolic phenotype with a worse lipid profile, increased levels of 2-h post-load glucose levels, fasting, and 2-h post-load insulin levels, hsCRP, liver IR index, and lower levels of eGFR and skeletal muscle insulin sensitivity, in comparison to individuals with lower UA levels. Moreover, subjects with higher UA concentrations exhibited decreased levels of insulin clearance even after adjustment for age, gender, BMI, eGFR, and skeletal muscle insulin sensitivity. In a multivariate regression analysis model including several confounding factors, UA concentration was an independent predictor of insulin clearance (β = - 0.145; P = 0.03). However, when liver IR index was included in the model, the independent association between UA levels and insulin clearance was not retained. Accordingly, in a mediation analysis, liver IR index was a mediator of the negative effects of UA levels on insulin clearance (t = - 2.55, P = 0.01).

CONCLUSIONS

Higher serum levels of UA may affect insulin clearance by impairing hepatic insulin sensitivity.