Characteristics of the participants according to SUA quartiles
We identified 1,947 patients with T2DM with a mean age of 49.6 ± 11.9 years. The population studied herein was stratified into quartiles according to SUA levels. The baseline demographic and medical characteristics for SUA quartiles are provided in Table 1. The cut-off SUA values for Q1, Q2, Q3, and Q4 were <242, 242–293, 293–353, and ≥353 µmol/L, respectively. When analyzed by quartiles of SUA levels, the patients with higher uric acid levels were more likely to be male, smokers, drinker, and younger (all P < 0.001). With respect to metabolic parameters, the patients in the higher uric acid quartiles exhibited higher levels of systolic blood pressure (SBP) and diastolic blood pressure (DBP), BMI, CRP, creatinine, insulin, ACR, TG, and TC than those in the lower uric acid quartiles (all P < 0.05). By contrast, the patients with higher uric acid levels displayed shorter duration of diabetes and lower levels of HbA1C and HDL-C than those with lower uric acid levels (all P < 0.05). However, no difference in CIMT and CAP was observed between the SUA quartile groups.
Correlation between SUA and other parameters
Partial correlation analysis revealed close correlation between SUA levels and BMI, HbA1C, ACR, creatinine, eGFR, SBP, DBP, TC, TG, and HDL-C among various metabolic features after adjusting for age, gender, and duration of diabetes (Table 2). Remarkably, SUA levels gradually increased with increasing number of MetS components. The mean values of SUA concentrations significantly increased for those with one, two, three, four, and five components of MetS; the mean values were 244.3 ± 62.7, 266.9 ± 75.5, 298.7 ± 92.5, 322.2 ± 94.3, and 337.7 ± 98.2 μmol/L, respectively (P < 0.001, Fig. 1a). Furthermore, the prevalence of MetS was higher with increasing SUA quartiles; 57.10%, 72.80%, 80.20%, and 87.90% for Q1, Q2, Q3, and Q4, respectively (P < 0.001 for trend, Fig. 1b).
Comparison of MetS and CAP between the SUA quartile groups
As presented in Table 3, the OR for MetS was higher with increasing SUA quartiles after adjusting for age and gender (OR: 5.132, 95% CI: 3.63–7.25, P < 0.001 for trend). In the highest uric acid quartile, the OR was 2.91 (95% CI: 1.54–5.51, P = 0.003 for trend) for MetS after further adjusting for alcohol drinking, smoking, duration of diabetes, self-reported CVD, BMI, CRP, HbA1C, FBG, eGFR, TC, and LDL-C. A comparison of CAP between the SUA quartile groups after adjusting for multiple potential confounders is given in Table 3. However, no significant differences were observed in the prevalence of CAP across the four groups.
Association between SUA quartiles and other MetS components
The associations of the SUA quartiles with different MetS components in all patients with T2DM are summarized in Table 4. After controlling for multiple confounding factors, the SUA quartiles were found to be independently associated with increased prevalence of hypertension in T2DM populations. The OR for hypertension increased with increasing SUA quartiles. In the highest SUA quartile, the OR was 2.13 (95% CI: 1.34–3.38, P = 0.015) for hypertension. Similarly, in the highest SUA quartile, the OR was 3.45 (95% CI: 2.25–5.28, P < 0.001) for overweight/obesity (BMI ≥ 25 kg/m2). Dyslipidemia was defined as TC ≥ 6.2 mmol/L, or TG = 1.7 mmol/L or greater, or HDL-C < 1.03 mmol/L in men or < 1.30 mmol/L in women. In our patients with T2DM, after controlling for confounding factors, the SUA quartiles were still independently associated with increased prevalence of dyslipidemia. In the highest SUA quartile, the OR for dyslipidemia (TG ≥ 1.7 mmol/L) was 2.71 (95% CI: 1.73–4.25, P < 0.001), and the OR for dyslipidemia (TC ≥ 6.2 mmol/L) was 2.51 (95% CI: 1.17–5.38, P = 0.013). However, no significant differences were found in the prevalence of dyslipidemia (HDL-C abnormality) across the four SUA quartile groups.