SODIUM INTAKE MODULATES RETINAL MICROCIRCULATION IN HEALTHY INDIVIDUALS BUT NOT IN CKD AND DKD

Objective: Excess sodium consumption may lead to endothelial dysfunction and disrupted autoregulation, which can lead to sodium-mediated hypertensive organ damage and cardiovascular disease. Retinal microcirculation is not subject to autonomic innervation and represents a marker of cerebrovascular health. The effect of sodium on ocular microcirculation and its relationship with BP remain unknown. This randomized crossover study investigated the effect of sodium on ocular vessel density and its association with BP in three groups with different vascular health conditions. Design and method: Chronic kidney disease (CKD) patients (KDIGO stage G2/3A-A3), type 2 diabetic kidney disease (T2DKD) patients (KDIGO stage G2/3A-A2) and healthy controls (HC) followed both a 7-day low-sodium control diet (<50 mmol/d) and high-sodium diet (>200 mmol/d) in random order. After each diet, 24-h BP measurements (Mobil-O-graph, IEM) and regional ocular vessel densities (VD) of the right eye by optical coherence tomography angiography (RTVue XR Avanti, Optovue) were assessed. Results: We included 23 CKD patients (mean age, 48 yrs; median proteinuria 0.7 g/d; mean eGFR 60 ml/min/1.73m2), 13 DKD patients (mean age, 65 yrs; median proteinuria 0.3 g/d; mean eGFR 62 ml/min/1.73m2) and 16 HC (41 yrs). BP was well-controlled in all groups. Dietary salt interventions were equally successful in the CKD, DKD, and HC groups. After HSD, mean (SD) systolic BP increased in CKD and DKD by 10 (9; p<0.01) and 13 (11; p<0.01) mmHg, respectively, compared to 3 (6.0; p=0.10) mmHg in HC. DKD participants had significantly lower VD compared to CKD and HC participants at LSD. Upon HSD, superficial whole-image VD showed a significant increase (p=0.03) in HC, while CKD and DKD patients showed no response. Comparing the three groups, the VD change was significantly different in HC as compared to both CKD and DKD (p=0.04). Additionally, the regression analysis indicates a negatively correlation between superficial VD and BP change (r=-0.36, R2=0.128, p=0.01). Conclusions: The higher BP responsiveness to high salt in CKD and DKD as compared to HC was accompanied with absent autoregulation of the ocular microcirculation, potentially reflecting an early sign of cerebrovascular disease.