Background : This study was to evaluate the change of leukocyte level caused by hyperuricemia and explore the relationship between leukocyte level and hypertension in elderly patients with hyperuricemia.
Methods: A cross-sectional study of serum uric acid level was conducted in 1352 elderly people over 65 years old . The study samples were divided into three categories according to the tertiles of leukocyte: Tertile 1, leukocyte≤5.2 × 10 9 /L; Tertile 2, leukocyte=5.3~6.3 × 10 9 /L; and Tertile 3, leukocyte≥6.4 × 10 9 /L. Multiple logistic regression models were used for modeling relationships between leukocyte, hyperuricemia and hypertension. In vitro, human vascular endothelial cells (HUVECs) were treated by different concentrations of UA (0, 4, 8, 16 mg/dl) for 24 h, then cells were collected. Some cytokines were measured. Reactive oxygen species (ROS) were analyzed with a fluorescence microscope.
Results: The levels of leukocyte were higher in elderly patients with hyperuricemia than without hyperuricemia( P <0.01). In multiple logistic regression, hyperuricemia was an independent risk factor of leukocyte in Tertile 3 (OR=1.657, 95%CI: 1.180～2.328, P =0.004). The prevalences of hypertension were higher in elderly patients with hyperuricemia than without hyperuricemia (77.0% vs 63.5%, χ 2 =11.447, P =0.001). In multiple logistic regression (Model 1), hyperuricemia was an independent risk factor of hypertension (OR=1.536, 95%CI: 1.026～2.302, P =0.037). Leukocyte in Tertile 3 was an independent risk factor of hypertension in Model 2 (OR= 1.333, 95%CI: 1.031~1.724, P =0.028). Expression levels of IL-1β, iNOS and TNF-α were obviously higher in the 8mg/dl UA group and 16mg/dl UA group than that in the control group ( P <0.05). Expression level of eNOS was obviously lower in the 8mg/dl UA group and 16mg/dl UA group than that in the control group ( P <0.05). The production of ROS in the 8mg/dl UA group and in the 16mg/dl UA group were obviously higher than that in the control group ( P <0.05).
Conclusion: The present study demonstrated that hyperuricemia was associated with an increased risk for hypertension. The chronic inflammation caused by hyperuricemia maybe one of important pathogenesis of incident hypertension in patients with hyperuricemia.