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

Metabolic crosstalk and therapeutic interplay between diabetes and hyperuricemia

Hyperuricemia and diabetes mellitus (DM) are prevalent metabolic disorders with high comorbidity, imposing a substantial global public health burden. Their coexistence is not merely additive but synergistic, exacerbating metabolic dysregulation through mechanisms such as insulin resistance and β-cell apoptosis, ultimately establishing a vicious cycle. Both disorders induce acute and chronic damage to vital organs, particularly the cardiovascular, renal systems. Hyperuricemia aggravates diabetic complications, notably diabetic cardiomyopathy, nephropathy and retinopathy via oxidative stress, inflammation, and metabolic dysregulation.Current urate-lowering therapies (ULTs), such as xanthine oxidase inhibitors and urate transporter 1 (URAT1, also known as SLC22A12) antagonists, demonstrate potential benefits in ameliorating diabetic complications but face challenges including safety concerns and dose adjustments. Similarly, several glucose-lowering drugs also exhibit the benefits of improving hyperuricemia. This review summarizes the metabolic crosstalk and therapeutic interplay between hyperuricemia and DM, examines the pathogenic role of uric acid in diabetic complications, and discusses the benefits and challenges of existing ULTs and glucose-lowering drugs in disrupting this cycle of metabolic dysregulation and concurrent organ damage. We hope our findings deepen the comprehension of the intricate metabolic crosstalk between glucose and urate homeostasis, providing novel therapeutic insights for patients with comorbid DM and hyperuricemia.

Mechanistic evaluation of ertugliflozin in patients with type 2 diabetes and heart failure

The effect of sodium-glucose cotransporter-2 (SGLT2) inhibitor ertugliflozin on fluid volume and kidney function was assessed in patients with type 2 diabetes and heart failure. Thirty-four participants were randomized in this double-blind, placebo-controlled, parallel-group, multicenter study. Physiologic measurements were obtained under clamped euglycemia at baseline, 1 week, and 12 weeks of treatment. The primary outcome was the proximal tubular natriuretic effect of ertugliflozin versus placebo, measured by fractional excretion of lithium (FELi). Ertugliflozin did not increase FELi or total FENa at 1 week or 12 weeks. Ertugliflozin increased both mean 24-h urinary sodium excretion (47.5 ± 22.1 mmol/day vs. placebo, p = 0.032) and urinary volume (p = 0.009) at 1 week, which was attenuated at Week 12. Reductions in extracellular fluid (-1.9 ± 0.8 L, p = 0.01), estimated plasma volume (-11.9 ± 13.9%, p = 0.02), and supine mean arterial pressure (-6.6 ± 2.7 mmHg, p = 0.02) were significant at Week 12. Compared to placebo, ertugliflozin acutely increased circulating angiotensinogen and angiotensin-converting enzyme (ACE) levels, as well as urine adenosine and ACE2 activity (p < 0.05). Changes in other neurohormones, sympathetic activity, kidney, and systemic hemodynamics did not differ compared to placebo. Our findings suggest that SGLT2 inhibition shifts systemic volume toward a state of euvolemia, potentially lowering the risk of worsening heart failure.

Uric acid in diabetic microvascular complications: Mechanisms and therapy

Uric acid (UA) is mainly synthesized in the liver, intestine, and vascular endothelium and excreted by the kidney (70 %) and intestine (30 %). Hyperuricemia (HUA) occurs when UA production exceeds excretion. Many studies have found that elevated UA is associated with diabetic microvascular complications (DMC), including diabetic retinopathy (DR), diabetic nephropathy (DN), and diabetic peripheral neuropathy (DPN). In addition, too high or too low UA levels will promote the occurrence and development of chronic diseases, but the relationship between UA and diabetic microvascular complications (DMC) is not clear. Therefore, the rational treatment of UA in patients with diabetes is essential. In this review, we summarize and discuss the mechanism and treatment of UA and DMC and may provide potential advice for rational drug selection.

Effect of hyperglycemia and empagliflozin on markers of cardiorenal injury and inflammation in patients with type 1 diabetes

AIMS

To investigate the effect of hyperglycemia and empagliflozin on cardiorenal injury and inflammation in patients with uncomplicated type 1 diabetes (T1D).

METHODS

Serum cardiac (sST2, Gal-3, cTnT), kidney injury (KIM-1, NGAL), inflammatory (sTNFR1, sTNFR2), and hemodynamic (NT-proBNP, EPO) markers were assessed post-hoc in two separate T1D cohorts. The glycemic clamp trial (NCT02344602) evaluated 49 adults with T1D and 27 controls under euglycemic and acute hyperglycemic conditions. The crossover BETWEEN trial (NCT02632747) investigated empagliflozin 25 mg plus ramipril for 4 weeks compared to placebo-ramipril for 4 weeks in 30 adults with T1D.

RESULTS

In the glycemic clamp study, hyperglycemia acutely increased levels of NT-proBNP (p = 0.0003) and sTNFR2 (p = 0.003). BETWEEN participants treated with empagliflozin exhibited a paradoxical subacute rise in NT-proBNP (p = 0.0147) compared to placebo, independent of hematocrit. Individuals with higher baseline levels of sST2 and sTNFR1 had greater empagliflozin-associated reductions in systolic blood pressure and greater activation of renin-angiotensin-aldosterone system (RAAS) mediators, whereas those with higher baseline levels of KIM-1 and sTNFR1 had greater glomerular filtration rate (GFR) dip.

CONCLUSION

The protective mechanisms of SGLT2 inhibition on blood pressure, RAAS activation, and renal hemodynamics are apparent in the subset of people with uncomplicated T1D with adverse cardiorenal and inflammatory markers.

Uric Acid Is Not Associated With Cardiovascular Health in Youth With Type 1 Diabetes: SEARCH for Diabetes in Youth Study

CONTEXT

Uric acid's role in cardiovascular health in youth with type 1 diabetes is unknown.

OBJECTIVE

Investigate whether higher uric acid is associated with increased blood pressure (BP) and arterial stiffness over time in adolescents and young adults with type 1 diabetes and if overweight/obesity modifies this relationship.

METHODS

Longitudinal analysis of data from adolescents and young adults with type 1 diabetes from 2 visits (mean follow up 4.6 years) in the SEARCH for Diabetes in Youth multicenter prospective cohort study from 2007 to 2018. Our exposure was uric acid at the first visit and our outcome measures were the change in BP, pulse wave velocity (PWV), and augmentation index between visits. We used multivariable linear mixed-effects models and assessed for effect modification by overweight/obesity.

RESULTS

Of 1744 participants, mean age was 17.6 years, 49.4% were female, 75.9% non-Hispanic White, and 45.4% had a follow-up visit. Mean uric acid was 3.7 mg/dL (SD 1.0). Uric acid was not associated with increased BP, PWV-trunk, or augmentation index over time. Uric acid was marginally associated with PWV-upper extremity (β = .02 m/s/year, 95% CI 0.002 to 0.04). The magnitude of this association did not differ by overweight/obesity status.

CONCLUSION

Among adolescents and young adults with type 1 diabetes, uric acid was not consistently associated with increased BP or arterial stiffness over time. These results support findings from clinical trials in older adults with diabetes showing that lowering uric acid levels does not improve cardiovascular outcomes.

The correlation between serum uric acid and diabetic kidney disease in adult-onset type 1 diabetes patients in China

BACKGROUND/AIM

To assess the correlation between serum uric acid (UA) level and diabetic kidney disease among adult-onset Type 1 diabetes mellitus (T1DM) patients in China.

METHODS

A total of 184 patients with adult-onset T1DM between January 2014 and December 2016 were recruited, with demographics and medical data collected. Comparisons were performed between according to different serum UA gender-specific quartiles. Relationship between serum UA level with urinary ACR and eGFR was also assessed.

RESULTS

Median urinary ACR and eGFR were 21.55 [10.79, 45.02] mg/g and 113.86 [88.43, 143.61] ml/min/1.73 m2, respectively. The median UA was 257.4 (208.2-334.8) μmol/L. Participants with higher serum UA levels had higher urinary ACR and lower eGFR than those with lower UA (P < 0.05). Higher serum UA level was significantly associated with higher urinary ACR in Spearman's correlational analysis (P = 0.006) and multiple stepwise regression analysis (P = 0.013). The association between serum UA and urinary ACR was not linear, but showed a curve correlation, which also showed in the sensitivity analysis. Serum UA in the upper gender-specific quartile, was associated with lower eGFR (P < 0.001) and showed an independent negative correlation with eGFR in multiple stepwise regression analysis (P < 0.001).

CONCLUSIONS

The serum UA level was negatively correlated with eGFR and had a curve correlation with urinary ACR in adult-onset T1DM patients of China.

The correlation between serum uric acid and diabetic kidney disease in type 1 diabetes patients in Anhui, China

BACKGROUND/AIM

To assess the correlation between serum uric acid (UA) level and diabetic kidney disease (DKD) in Type 1 diabetes (T1DM) patients in Anhui, China.

METHODS

A total of 231 patients diagnosed with T1DM in our hospital were enrolled between January 2014 and December 2016. Urinary albumin-creatinine ratio (ACR) in patients with hyperuricemia was compared with those without hyperuricemia. The relationship between serum UA level and urinary ACR was examined by Spearman's correlational analysis and multiple stepwise regression analysis. The binary logistic multivariate regression analysis was performed to analyze the correlated factors for type 1 DKD.

RESULTS

The average serum UA levels were 257.7 [215.0, 338.0]μmol/L. The median levels of urinary ACR were significantly higher in patients with hyperuricemia than those without hyperuricemia. In multiple stepwise regression analysis, Serum UA levels were positively correlated with the urinary ACR. The logistic multivariate regression analysis showed that hyperuricemia (OR: 5.24, 95% CI: 1.40-19.65, P = 0.014) had an independent positive correlation with DKD in T1DM patients, and the odds of Serum UA to DKD were both elevated as the serum UA levels rose no matter whether adjustment for traditional confounders. The area under the receiver operating characteristic curve was 0.62 (95% CI: 0.55-0.70) in assessing the discrimination of the serum UA level for DKD in T1DM patients.

CONCLUSIONS

In Chinese patients with T1DM, the serum UA level is positively correlated with urinary ACR and DKD. The correlation between Serum UA and DKD gradually increases with serum UA levels. Serum UA level is not a good predictor for DKD in T1DM patients. Serum UA may directly contribute to initiating DKD, while it has little direct but an indirect effect on an already established DKD in T1DM patients.

Renal and Vascular Effects of Combined SGLT2 and Angiotensin-Converting Enzyme Inhibition

BACKGROUND

The cardiorenal effects of sodium-glucose cotransporter 2 inhibition (empagliflozin 25 mg QD) combined with angiotensin-converting enzyme inhibition (ramipril 10 mg QD) were assessed in this mechanistic study in patients with type 1 diabetes with potential renal hyperfiltration.

METHODS

Thirty patients (out of 31 randomized) completed this double-blind, placebo-controlled, crossover trial. Recruitment was stopped early because of an unexpectedly low proportion of patients with hyperfiltration. Measurements were obtained after each of the 6 treatment phases over 19 weeks: (1) baseline without treatment, (2) 4-week run-in with ramipril treatment alone, (3) 4-week combined empagliflozin-ramipril treatment, (4) a 4-week washout, (5) 4-week combined placebo-ramipril treatment, and (6) 1-week follow-up. The primary end point was glomerular filtration rate (GFR) after combination treatment with empagliflozin-ramipril compared with placebo-ramipril. GFR was corrected for ramipril treatment alone before randomization. At the end of study phase, the following outcomes were measured under clamped euglycemia (4 to 6 mmol/L): inulin (GFR) and para-aminohippurate (effective renal plasma flow) clearances, tubular sodium handling, ambulatory blood pressure, arterial stiffness, heart rate variability, noninvasive cardiac output monitoring, plasma and urine biochemistry, markers of the renin-angiotensin-aldosterone system, and oxidative stress.

RESULTS

Combination treatment with empagliflozin-ramipril resulted in an 8 mL/min/1.73 m² lower GFR compared with placebo-ramipril treatment (P=0.0061) without significant changes to effective renal plasma flow. GFR decrease was accompanied by a 21.3 mL/min lower absolute proximal fluid reabsorption rate (P=0.0092), a 3.1 mmol/min lower absolute proximal sodium reabsorption rate (P=0.0056), and a 194 ng/mmol creatinine lower urinary 8-isoprostane level (P=0.0084) relative to placebo-ramipril combination treatment. Sodium-glucose cotransporter 2 inhibitor/angiotensin-converting enzyme inhibitor combination treatment resulted in additive blood pressure-lowering effects (clinic systolic blood pressure lower by 4 mm Hg [P=0.0112]; diastolic blood pressure lower by 3 mm Hg [P=0.0032]) in conjunction with a 94.5 dynes × sex/cm⁵ lower total peripheral resistance (P=0.0368). There were no significant changes observed to ambulatory blood pressure, arterial stiffness, heart rate variability, or cardiac output with the addition of empagliflozin.

CONCLUSIONS

Adding sodium-glucose cotransporter 2 inhibitor treatment to angiotensin-converting enzyme inhibitor resulted in an expected GFR dip, suppression of oxidative stress markers, additive declines in blood pressure and total peripheral resistance. These changes are consistent with a protective physiologic profile characterized by the lowering of intraglomerular pressure and related cardiorenal risk when adding a sodium-glucose cotransporter 2 inhibitor to conservative therapy.

REGISTRATION

URL: https://www.

CLINICALTRIALS

gov; Unique identifier: NCT02632747.

Arterial Stiffness and Type 1 Diabetes: The Current State of Knowledge

The most common cause of mortality among people with type 1 diabetes is cardiovascular diseases. Arterial stiffness allows predicting cardiovascular complications, cardiovascular mortality, and all-cause mortality. There are different ways to measure arterial stiffness; the gold standard is pulse wave velocity. Arterial stiffness is increased in people with type 1 diabetes compared to healthy controls. It increases with age and duration of type 1 diabetes. Arterial stiffness among people with type 1 diabetes positively correlates with systolic blood pressure, obesity, glycated hemoglobin, waist circumference, and waist to hip ratio. It has a negative correlation with the estimated glomerular filtration rate, high-density lipoprotein, and the absence of carotid plaques. The increased arterial stiffness could result from insulin resistance, collagen increase due to inadequate enzymatic glycation, and endothelial and autonomic dysfunction. The insulin-induced decrease in arterial stiffness is impaired in type 1 diabetes. There are not enough proofs to use pharmacotherapy in the prevention of arterial stiffness, but some of the medicaments got promising results in single studies, for example, renin-angiotensin-aldosterone system inhibitors, statins, and SGLT2 inhibitors. The main strategy of prevention of arterial stiffness progression remains glycemic control and a healthy lifestyle.

Uric Acid in Inflammation and the Pathogenesis of Atherosclerosis

Hyperuricemia is a common metabolic syndrome. Elevated uric acid levels are risk factors for gout, hypertension, and chronic kidney diseases. Furthermore, various epidemiological studies have also demonstrated an association between cardiovascular risks and hyperuricemia. In hyperuricemia, reactive oxygen species (ROS) are produced simultaneously with the formation of uric acid by xanthine oxidases. Intracellular uric acid has also been reported to promote the production of ROS. The ROS and the intracellular uric acid itself regulate several intracellular signaling pathways, and alterations in these pathways may result in the development of atherosclerotic lesions. In this review, we describe the effect of uric acid on various molecular signals and the potential mechanisms of atherosclerosis development in hyperuricemia. Furthermore, we discuss the efficacy of treatments for hyperuricemia to protect against the development of atherosclerosis.

Acute effects of hypouricemia on endothelium, oxidative stress, and arterial stiffness: A randomized, double-blind, crossover study

We hypothesized acute moderate and drastic reductions in uric acid concentration exert different effects on arterial function in healthy normotensive and hypertensive adults. Thirty-six adults (aged 58 [55;63] years) with or without primary hypertension participated in a three-way, randomized, double-blind, crossover study in which [placebo] and [febuxostat] and [febuxostat and rasburicase] were administered. Febuxostat and rasburicase reduce the uric acid concentration by xanthine oxidoreductase inhibition and uric acid degradation into allantoin, respectively. Endothelial function was assessed in response to acetylcholine, sodium nitroprusside, heating (with and without nitric oxide synthase inhibition) using a laser Doppler imager. Arterial stiffness was determined by applanation tonometry, together with blood pressure, renin-angiotensin system activity, oxidative stress, and inflammation. Uric acid concentration was 5.1 [4.1;5.9], 1.9 [1.2;2.2] and 0.2 [0.2;0.3] mg/dL with [placebo], [febuxostat] and [febuxostat-rasburicase] treatments, respectively (p < 0.0001). Febuxostat improved endothelial response to heat particularly when nitric oxide synthase was inhibited (p < 0.05) and reduced diastolic and mean arterial pressure (p = 0.008 and 0.02, respectively). The augmentation index decreased with febuxostat (ANOVA p < 0.04). Myeloperoxidase activity profoundly decreased with febuxostat combined with rasburicase (p < 0.0001). When uric acid dropped, plasmatic antioxidant capacity markedly decreased, while superoxide dismutase activity increased (p < 0.0001). Other inflammatory and oxidant markers did not differ. Acute moderate hypouricemia encompasses minor improvements in endothelial function, blood pressure, and arterial stiffness. Clinical Trial Registration: NCT03395977, https://clinicaltrials.gov/ct2/show/NCT03395977.

Discoveries from the study of longstanding type 1 diabetes

Award programmes that acknowledge the remarkable accomplishments of long-term survivors with type 1 diabetes have naturally evolved into research programmes to determine the factors associated with survivorship and resistance to chronic complications. In this review, we present an overview of the methodological sources of selection bias inherent in survivorship research (selection of those with early-onset diabetes, incidence-prevalence bias and bias from losses to follow-up in cohort studies) and the breadth and depth of literature focusing on this special study population. We focus on the learnings from the study of longstanding type 1 diabetes on discoveries about the natural history of insulin production loss and microvascular complications, and mechanisms associated with them that may in future offer therapeutic targets. We detail descriptive findings about the prevalence of preserved insulin production and resistance to complications, and the putative mechanisms associated with such resistance. To date, findings imply that the following mechanisms exist: strategies to maintain or recover beta cells and their function; activation of specific glycolytic enzymes such as pyruvate kinase M2; modification of AGE production and processing; novel mechanisms for modification of renin-angiotensin-aldosterone system activation, in particular those that may normalise afferent rather than efferent renal arteriolar resistance; and activation and modification of processes such as retinol binding and DNA damage checkpoint proteins. Among the many clinical and public health insights, research into this special study population has identified putative mechanisms that may in future serve as therapeutic targets, knowledge that likely could not have been gained without studying long-term survivors.

Allopurinol and Renal Outcomes in Adults With and Without Type 2 Diabetes: A Retrospective, Population-Based Cohort Study and Propensity Score Analysis

OBJECTIVES

Elevated uric acid (UA) is common in diabetes and is implicated in the pathogenesis of chronic kidney disease (CKD). Lowering UA with allopurinol may delay CKD progression. We assessed the association between allopurinol and renal outcomes in older adults both with and without diabetes, and whether this differed by diabetes status.

METHODS

We conducted a population-based, retrospective cohort study of older adults ≥66 years of age with a gout flare using administrative data from Ontario, Canada. The primary outcome was doubling of creatinine or kidney failure. Secondary outcomes were a composite of death or kidney failure, decline in estimated glomerular filtration rate by >30%, death and kidney failure. New allopurinol users were compared with nonusers using Cox proportional hazards models and inverse probability of treatment weighting (IPTW). An interaction between allopurinol use and presence or absence of diabetes was assessed.

RESULTS

Among 5,937 older adults with a gout flare (1,911 with diabetes), 1,304 (22%) were newly treated with allopurinol. Median follow-up time was 1.11 (interquartile range, 0.33 to 3.21) years for allopurinol users and 3.38 (interquartile range, 1.42 to 4.43) years for nonusers. There was no association between allopurinol use and the primary outcome (IPTW-adjusted hazard ratio, 0.97; 95% confidence interval, 0.72 to 1.31), and this did not differ by diabetes status. Allopurinol use was not associated with any of the secondary outcomes.

CONCLUSIONS

Allopurinol use was not associated with renal outcomes in older adults with or without diabetes. This supports the interpretation of UA as a biomarker of CKD risk rather than a modifiable target for prevention or treatment of CKD.

Renal physiology of glucose handling and therapeutic implications

The rationale for using sodium-glucose cotransporter 2 (SGLT2) inhibitors in patients with type 2 diabetes (T2D) has evolved over the last decade. Due to the effects on glucosuria and body weight loss, SGLT2 inhibitors were originally approved for glycemic control in T2D. Since glucosuria is attenuated in chronic kidney disease (CKD) Stages 3–5, initial regulatory approval for SGLT2 inhibitor use was limited to patients with T2D and preserved estimated glomerular filtration rate. Over time, however, it has become increasingly apparent that these therapies have a variety of important pharmacodynamic and clinical effects beyond glycemic lowering, including antihypertensive and antialbuminuric properties, and the ability to reduce glomerular hypertension. Importantly, these sodium-related effects are preserved across CKD stages, despite attenuated glycemic effects, which are lost at CKD Stage 4. With the completion of cardiovascular (CV) outcome safety trials—EMPA-REG OUTCOME, CANVAS Program and DECLARE TIMI-58—in addition to reductions in CV events, SGLT2 inhibition consistently reduces hard renal endpoints. Importantly, these CV and renal effects are independent of glycemic control. Subsequent data from the recent CREDENCE trial—the first dedicated renal protection trial with SGLT-2 inhibition—demonstrated renal and CV benefits in albuminuric T2D patients, pivotal results that have expanded the clinical importance of these therapies. Ongoing trials will ultimately determine whether SGLT2 inhibition will have a role in renal protection in other clinical settings, including nondiabetic CKD and type 1 diabetes.

The association between serum uric acid level and the risk of cognitive impairment after ischemic stroke

Post-stroke cognitive impairment (PSCI) is a severe complication of stroke. Predicting PSCI is difficult because some risk factors for stroke, such as blood glucose level and blood pressure, are affected by many other elements. Although recent studies have shown that high serum uric acid (UA) levels are associated with cognitive dysfunction and may be a risk factor for PSCI, its impact remains unclear. Accordingly, the present study aimed to explore the association between serum UA level and PSCI. In total, 274 patients who experienced acute cerebral infarction, confirmed between January 2016 and December 2018, were enrolled. Baseline data and biological indicators were recorded. According to the Montreal Cognitive Assessment (MoCA) scores, patients were divided into two groups: PSCI and non-PSCI. Logistic regression analysis was used to determine possible risk factors for PSCI. Results demonstrated that serum UA levels were significantly higher in the PSCI group than in the non-PSCI group. Multivariable logistic analysis revealed that age, years of education, and UA level were independent risk factors for PSCI. PSCI patients were subdivided according to serum UA level: high and low. Hypertension history and homocysteine (Hcy) levels differed significantly between the high and low UA level groups. Further analysis revealed that a history of hypertension and Hcy demonstrated a certain correlation (r = 0.163, 0.162; P < 0.05), suggesting that serum UA level was an independent risk factor for PSCI. These findings indicate that serum UA level was correlated with PSCI in post-stroke patients and is anticipated to be used in clinical practice to reduce the incidence of PSCI.

Early Endothelial Dysfunction in Type 1 Diabetes Is Accompanied by an Impairment of Vascular Smooth Muscle Function: A Meta-Analysis

Background: A large yet heterogeneous body of literature exists suggesting that endothelial dysfunction appears early in type 1 diabetes, due to hyperglycemia-induced oxidative stress. The latter may also affect vascular smooth muscles (VSM) function, a layer albeit less frequently considered in that pathology. This meta-analysis aims at evaluating the extent, and the contributing risk factors, of early endothelial dysfunction, and of the possible concomitant VSM dysfunction, in type 1 diabetes. Methods: PubMed, Web of Sciences, Cochrane Library databases were screened from their respective inceptions until October 2019. We included studies comparing vasodilatory capacity depending or not on endothelium (i.e., endothelial function or VSM function, respectively) in patients with uncomplicated type 1 diabetes and healthy controls. Results: Fifty-eight articles studying endothelium-dependent function, among which 21 studies also assessed VSM, were included. Global analyses revealed an impairment of standardized mean difference (SMD) (Cohen's d) of endothelial function: -0.61 (95% CI: -0.79, -0.44) but also of VSM SMD: -0.32 (95% CI: -0.57, -0.07). The type of stimuli used (i.e., exercise, occlusion-reperfusion, pharmacological substances, heat) did not influence the impairment of the vasodilatory capacity. Endothelial dysfunction appeared more pronounced within macrovascular than microvascular beds. The latter was particularly altered in cases of poor glycemic control [HbA_1c > 67 mmol/mol (8.3%)]. Conclusions: This meta-analysis not only corroborates the presence of an early impairment of endothelial function, even in response to physiological stimuli like exercise, but also highlights a VSM dysfunction in children and adults with type 1 diabetes. Endothelial dysfunction seems to be more pronounced in large than small vessels, fostering the debate on their relative temporal appearance.

Standardization of measurement procedures for serum uric acid: 8-year experience from Category 1 EQA program results in China

Background Serum uric acid is a critical clinical indicator, and results without equivalence among laboratories cause troubles for disease diagnosis and patient management. External quality assessment (EQA) is a common tool for enhancing harmonization/standardization, therefore, the National Center for Clinical Laboratories in China has initiated a category 1 EQA for serum uric acid measurement since 2010 for evaluating its process of standardization. Methods Commutable EQA samples with target values assigned by reference measurement procedures were sent to participant laboratories. Both concentrations were measured 15 times in 3 days then means and intra-laboratory coefficient of variations (CVs) were reported. Biological variation criteria were used for analysis with CLIA88 criteria as a comparison. Results A total of 1250 laboratories participated in EQA programs from 2010 to 2017, pass rates calculated according to desirable specifications in biological variation database were on a rise overall and inter-laboratory mean bias and CVs were on a decrease. Homogeneous systems showed better inter-laboratory CVs and pass rates than heterogeneous systems. For the mostly used measurement systems; Abbott, Beckman, Roche Modular, Siemens and Hitachi showed desirable performances other than Roche Cobas, according to biological variation criteria. Conclusions Our study provides reliable information on the standardization of measurement procedures for serum uric acid for manufacturers and laboratories. Further improvements for standardization are still needed to make laboratories more patient-centered.

The Impact of Sotagliflozin on Renal Function, Albuminuria, Blood Pressure, and Hematocrit in Adults With Type 1 Diabetes

OBJECTIVE

In people with type 2 diabetes, sodium-glucose cotransporter 2 inhibitors (SGLT2i) reduce cardiovascular risk and progression of diabetic kidney disease. Our aim was to determine whether sotagliflozin (SOTA), a dual SGLT1i and SGLT2i, had favorable effects on clinical biomarkers suggestive of kidney protection in adults with type 1 diabetes.

RESEARCH DESIGN AND METHODS

In this 52-week pooled analysis, 1,575 adults enrolled in the inTandem1 and inTandem2 trials were randomized to SOTA 200 mg, 400 mg, or placebo in addition to optimized insulin therapy. Changes in cardiorenal biomarkers were assessed.

RESULTS

At 52 weeks, in response to SOTA 200 and 400 mg, the placebo-corrected least squares mean change from baseline in estimated glomerular filtration rate was -2.0 mL/min/1.73 m² (P = 0.010) and -0.5 mL/min/1.73 m² (P = 0.52), respectively. Systolic blood pressure difference was -2.9 and -3.6 mmHg (P < 0.0001 for both); diastolic blood pressure changed by -1.4 (P = 0.0033) and -1.6 mmHg (P = 0.0008). In participants with baseline urinary albumin-to-creatinine ratio (UACR) ≥30 mg/g, UACR decreased by 23.7% (P = 0.054) and 18.3% (P = 0.18) for SOTA 200 and SOTA 400 mg, respectively, versus placebo. Increases in serum albumin and hematocrit and reductions in uric acid were observed throughout 52 weeks with both SOTA doses.

CONCLUSIONS

SOTA was associated with short- and long-term renal hemodynamic changes, which were similar to those seen with SGLT2i in type 2 diabetes. Further investigation around cardiorenal effects of SOTA in people with type 1 diabetes is justified.

Plasma uric acid and renal haemodynamics in type 2 diabetes patients

Aim

Increased plasma uric acid (PUA) concentrations are associated with chronic kidney disease in type 2 diabetes (T2D) patients. The mechanisms involved remain unclear. We investigated the relation between PUA and (intra)renal haemodynamics in T2D patients without overt kidney disease.

Methods

Eighty‐eight white men and women with T2D were included (age 64 (58–68) years; body mass index 30.9 (28.3–33.6) kg/m²; glycated haemoglobin 7.1 (6.8–7.6)%). Plasma UA and fractional excretion of UA were measured, while glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were assessed by inulin and PAH‐clearance techniques, respectively. Effective renal vascular resistance was calculated (ERVR). Renal afferent and efferent arteriolar resistances and glomerular hydrostatic pressure were estimated. Relationships between PUA and fractional excretion of UA and (intra)renal haemodynamic parameters were evaluated by multivariable linear regression analyses.

Results

Plasma UA concentrations were at the higher end of the normal range in most participants: 342 ± 68 μmol/L or 5.7 ± 1.1 mg/dL (mean ± SD). In multivariable analyses, PUA concentrations were negatively associated with GFR (r = −0.471; P = 0.001), ERPF (r = −0.436; P = 0.003) and glomerular hydrostatic pressure (r = −0.427; P = 0.003). In contrast, PUA concentrations had a positive correlation with ERVR (r = 0.474; P = 0.001), but not with efferent vascular resistance. Fractional excretion of UA was not related to renal haemodynamics.

Conclusion

Plasma UA was negatively associated to GFR, ERPF but positively related to ERVR in T2D patients without overt renal impairment. Plasma UA‐related increase in ERVR may be related to increased arterial afferent tone, which may put the kidney at risk for renal damage through ischaemia.

This paper, which explored the relationship between plasma uric acid (UA) and renal haemodynamics in patients with type 2 diabetes without overt kidney disease showed that higher plasma UA is associated with lower glomerular filtration rate and effective renal plasma flow but higher effective renal vascular resistance, which may contribute to glomerular dysfunction due to impairment in kidney perfusion.

Elevated Serum Uric Acid Is Associated With Greater Risk for Hypertension and Diabetic Kidney Diseases in Obese Adolescents With Type 2 Diabetes: An Observational Analysis From the Treatment Options for Type 2 Diabetes in Adolescents and Youth (TODAY) Study

OBJECTIVE

Elevated serum uric acid (SUA) is increasingly recognized as a risk factor for kidney disease in adults with diabetes, but data in youth are limited. We hypothesized that elevated SUA predicts development of elevated urinary albumin excretion (UAE) and hypertension over time in teens with type 2 diabetes (T2D).

RESEARCH DESIGN AND METHODS

Serum creatinine, cystatin C, SUA, and the urine albumin-to-creatinine ratio (UACR) were assessed in 539 obese youth, ages 12-17 years, with T2D duration <2 years at baseline in the Treatment Options for Type 2 Diabetes in Adolescents and Youth (TODAY) study. Estimated glomerular filtration rate (eGFR) was calculated using creatinine and cystatin C. Hypertension was defined as systolic or diastolic blood pressure ≥130/80 mmHg and elevated UAE as UACR ≥30 mg/g. Cox proportional hazards models evaluated the relationship between SUA and outcome variables longitudinally over an average follow-up of 5.7 years, adjusting for age, sex, race/ethnicity, BMI, HbA_1c, eGFR, ACE inhibitor/angiotensin receptor blocker use, and TODAY treatment group assignment.

RESULTS

At baseline, hyperuricemia (≥6.8 mg/dL) was present in 25.6% of participants, hypertension in 18.7%, and elevated UAE in 6.1%. During follow-up of up to 7 years, hypertension developed in 37.4% and UAE in 18.0%. Higher baseline SUA increased the risk of incident hypertension (hazard ratio [HR] 1.19, 95% CI 1.03-1.38, per 1 mg/dL increase in SUA) and elevated UAE (HR 1.24, 95% CI 1.03-1.48) in adjusted models.

CONCLUSIONS

Hyperuricemia was common in youth with T2D. Higher baseline SUA independently increased the risk for onset of hypertension and elevated UAE. Research is needed to determine whether SUA-lowering therapies can impede development of diabetic kidney disease and hypertension in T2D youth.

Association between uric acid, renal haemodynamics and arterial stiffness over the natural history of type 1 diabetes

AIMS

To examine the relationship between normal plasma uric acid (PUA) levels, renal haemodynamic function, arterial stiffness and plasma renin and aldosterone over a wide range of type 1 diabetes (T1D) durations in adolescents, young adults and older adults.

MATERIALS AND METHODS

PUA, glomerular filtration rate (GFR), effective renal plasma flow (ERPF), vascular stiffness parameters (aortic augmentation index [AIx], carotid AIx, carotid femoral pulse wave velocity [cfPWV]), and plasma renin and aldosterone were measured during a euglycaemic clamp in people with T1D: 27 adolescents (mean ± SD age 16.8 ± 1.9 years), 52 young adults (mean ± SD age 25.6 ± 5.5 years) and 66 older adults (mean ± SD age 65.7 ± 7.5 years).

RESULTS

PUA was highest in patients with the longest T1D duration: 197 ± 44 μmol/L in adolescents versus 264 ± 82 μmol/L in older adults (P < 0.001). Higher PUA correlated with lower GFR only in older adults, even after correcting for age, glycated haemoglobin and sex (β = -2.12 ± 0.56; P = 0.0003), but not in adolescents or young adults. Higher PUA correlated with lower carotid AIx (β = -1.90, P = 0.02) in adolescents. In contrast, PUA correlated with higher cfPWV (P = 0.02) and higher plasma renin (P = 0.01) in older adults with T1D.

CONCLUSIONS

The relationship between higher PUA with lower GFR, increased arterial stiffness and renin angiotensin aldosterone system (RAAS) activation was observed only in older adults with longstanding T1D. T1D duration may modify the association between PUA, renal haemodynamic function and RAAS activation, leading to renal vasoconstriction and ischaemia. Further work must determine whether pharmacological PUA-lowering prevents or reverses injurious haemodynamic and neurohormonal sequelae of longstanding T1D, thereby improving clinical outcomes.

Renal Hemodynamic Function and RAAS Activation Over the Natural History of Type 1 Diabetes

RATIONALE & OBJECTIVE

The renin-angiotensin-aldosterone system (RAAS) is associated with renal and cardiovascular disease in diabetes. Unfortunately, early RAAS blockade in patients with type 1 diabetes mellitus (T1DM) does not prevent the development of complications. We sought to examine the role of hyperfiltration and RAAS activation across a wide range of T1DM duration to better understand renal hemodynamic status in patients with T1DM.

STUDY DESIGN

Post hoc analysis of blood samples.

SETTING & PARTICIPANTS

148 Canadian patients with T1DM: 28 adolescents (aged 16.2±2.0 years), 54 young adults (25.4±5.6 years), and 66 older adults (65.7±7.5 years) studied in a clinical investigation unit.

EXPOSURE

Angiotensin II infusion (1ng/kg/min; a measure of RAAS activation) during a euglycemic clamp.

OUTCOMES

Glomerular filtration rate measured using inulin clearance, effective renal plasma flow measured using para-aminohippurate, afferent (R_A) and efferent (R_E) arteriolar resistances, and glomerular hydrostatic pressure estimated using the Gomez equations.

RESULTS

In a stepwise fashion, glomerular filtration rate, effective renal plasma flow, and glomerular hydrostatic pressure were higher, while renal vascular resistance and R_A were lower in adolescents versus young adults versus older adults. R_E was similar in adolescents versus young adults but was higher in older adults. Angiotensin II resulted in blunted renal hemodynamic responses in older adults (renal vascular resistance increase of 3.3% ± 1.6% vs 4.9% ± 1.9% in adolescents; P<0.001), suggesting a state of enhanced RAAS activation.

LIMITATIONS

Homogeneous study participants limit the generalizability of findings to other populations. Studying older adult participants with T1DM may be associated with a survivorship bias.

CONCLUSIONS

A state of relatively low RAAS activity and predominant afferent dilation rather than efferent constriction characterize early adolescents and young adults with T1DM. This state of endogenous RAAS inactivity in early T1DM may explain why pharmacologic blockade of this neurohormonal system is often ineffective in reducing kidney disease progression in this setting. Older adults with long-standing T1DM who have predominant afferent constriction and RAAS activation may experience renoprotection from therapies that target the afferent arteriole. Further work is required to understand the potential role of non-RAAS pharmacologic agents that target R_A in patients with early and long-standing T1DM.

Therapeutic value of stimulating the nitrate-nitrite-nitric oxide pathway to attenuate oxidative stress and restore nitric oxide bioavailability in cardiorenal disease

Cardiovascular disorders including hypertension and associated renal disease are major health problems affecting more than 1.5 billion people worldwide. Apart from nonmodifiable factors such as ageing, family history and gender, both sedentary lifestyle and unhealthy dietary habits are considered as major risk factors. The disorders are interrelated suggesting common pathological pathways. Mechanistically, oxidative stress and compromised function of the nitric oxide synthase (NOS) system leading to endothelial dysfunction and reduction in nitric oxide (NO) bioavailability have been widely implicated and associated with development and progression of disease. New strategies that correct this redox imbalance and increase NO bioactivity may have major clinical implications. The inorganic anions, nitrate and nitrite, are endogenously formed by oxidization of NOS-derived NO, but there are also high amounts of nitrate in our daily diet. In this regard, accumulated evidence over the past two decades demonstrates that these anions can be recycled back to NO and other bioactive nitrogen oxides, thus offering an attractive alternative strategy for therapeutic exploitation. In this review, we describe how dietary stimulation of the nitrate-nitrite-NO pathway affects cardiovascular and renal functions in health and disease via modulation of oxidative stress and NO bioavailability. Clinical studies addressing potential effects on the renal system are still limited, but blood pressure-lowering effects of nitrate supplementation have been demonstrated in healthy and hypertensive subjects as well as in patients with chronic kidney disease. However, larger clinical studies are warranted to reveal whether chronic nitrate treatment can slow-down the progression of cardiorenal disease and associated complications.

A causal link between oxidative stress and inflammation in cardiovascular and renal complications of diabetes

Chronic renal and vascular oxidative stress in association with an enhanced inflammatory burden are determinant processes in the development and progression of diabetic complications including cardiovascular disease (CVD), atherosclerosis and diabetic kidney disease (DKD). Persistent hyperglycaemia in diabetes mellitus increases the production of reactive oxygen species (ROS) and activates mediators of inflammation as well as suppresses antioxidant defence mechanisms ultimately contributing to oxidative stress which leads to vascular and renal injury in diabetes. Furthermore, there is increasing evidence that ROS, inflammation and fibrosis promote each other and are part of a vicious connection leading to development and progression of CVD and kidney disease in diabetes.