Serum amyloid A, C-reactive protein, and retinal microvascular changes in hypertensive diabetic and nondiabetic individuals: an Anglo-Scandinavian Cardiac Outcomes Trial (ASCOT) substudy

Abstract

Objective: To study the association of the inflammatory markers serum amyloid A (SAA) and C-reactive protein (CRP) with retinal microvascular parameters in hypertensive individuals with and without type 2 diabetes.

Research design and methods: This cross-sectional analysis was a substudy in 711 patients (159 with and 552 without diabetes) of the Anglo-Scandinavian Cardiac Outcomes Trial (ASCOT) based on digital 30-degree images of superior and inferior temporal retinal fields.

Results: SAA was associated with arteriolar length-to-diameter ratio positively in nondiabetic patients (P(trend)= 0.028) but negatively in diabetic patients (P(trend)= 0.005). The difference was unlikely to be a chance finding (P = 0.007 for interaction). Similar results were found for the association of SAA with arteriolar tortuosity (P = 0.05 for interaction). Associations were less pronounced for CRP and retinal parameters.

Conclusions: Inflammatory processes are differentially involved in retinal microvascular disease in diabetic compared with nondiabetic hypertensive individuals.

Figure 1

Association of SAA and CRP (categorized in tertiles) with arteriolar L:D ratio (A and C) and with arteriolar tortuosity (B and D). Ranges for tertiles 1, 2, and 3 (t1, t2, and t3, respectively) for SAA were 0.6–2.4, 2.5–3.9, and 4.0–92.6 mg/l, respectively, for diabetic individuals and 0.6–2.0, 2.1–3.6, and 3.7–162.0 mg/l for nondiabetic individuals. The corresponding values for CRP were 0.1–1.0, 1.0–2.7, and 2.8–49.8 mg/l for diabetic individuals and 0.1–1.0, 1.0–2.4, and 2.4–65.2 mg/l for nondiabetic individuals. P values for trend are derived from multiple linear regression analysis models adjusted for age, sex, BMI, smoking status, and antihypertensive and lipid-lowering treatment in the ASCOT and represent the association between inflammatory markers and retinal parameters over the entire range of SAA or CRP. *P < 0.05 for comparison with t1.