Prognostic significance of the wall to lumen ratio of retinal arterioles evaluated by adaptive optics

OBJECTIVE

Microvascular structural alterations may be considered an important form of hypertension-mediated organ damage. An increased media-to-lumen ratio of subcutaneous small arteries evaluated with locally invasive techniques (micromyography) predicts the development of cardiovascular (CV) events. However, it is not known whether retinal arteriole structural alterations evaluated with a noninvasive approach (Adaptive Optics) may have a prognostic significance.

DESIGN AND METHODS

Two-hundred and thirty-seven subjects (mean age 58.7 ± 16.1 years, age range 13-89 years; 116 males) were included in the study: 65 normotensive subjects (27.4 %) and 172 patients with essential hypertension or primary aldosteronism (72.6 %). All subjects underwent a non-invasive evaluation of retinal arteriolar wall-to-lumen ratio (WLR) by Adaptive Optics. Subjects were re-evaluated after an average follow-up time of 4.55 years in order to assess the occurrence of clinical events (non CV and/or CV death or events).

RESULTS

Fifty-four events occurred in the study population:26 were cardio-cerebrovascular events (ischemic or hemorragic stroke, atrial fibrillation, heart failure, coronary artery disease, peripheral artery disease, cardiac valvular disease) while the remaining were deaths for any cause, or neoplastic diseases. Subjects with events were older and had a WLR of retinal arterioles significantly greater than those without events. The event-free survival was significantly worse in those with a baseline WLR above the median value of the population (0.28) according to Kaplan-Mayer survival curves and multivariate analysis (Cox's proportional hazard model). The evidence was confirmed after restricting the analysis to CV events.

CONCLUSIONS

Structural alterations of retinal arterioles evaluated by Adaptive Optics may predict total and CV events.

Modulation of heme oxygenase/carbon monoxide system affects the inhibitory neurotransmission involved in gastrointestinal motility of streptozotocin-treated diabetic rats

Alterations in gastrointestinal motility of diabetic patients have been linked to degenerative changes induced by glucose abnormalities in the peripheral nervous system. The heme oxygenase/carbon monoxide (HO/CO) signalling represents one of the non-adrenergic/non-cholinergic (NANC) neurotransmission pathways involved in regulation of physiological peristalsis. To investigate the role of HO/CO system in intestinal motility under diabetic conditions, the response to electrical field stimulation (EFS) and western blot analysis of HO/CO pathway components were studied on duodenum longitudinal smooth muscle strips isolated from streptozotocin (STZ)-treated diabetic rats (65 mg kg(-1), i.p.) and respective controls (CTRL), 6 weeks after the onset of diabetes. When compared to CTRL, the ability of CO releasing molecule (CORM-3) (100-400 micromol L(-1)) to enhance NANC relaxation was significantly impaired in STZ-treated rats (P < 0.05). Conversely, in vitro incubation with the HO inhibitor ZnPPIX (10 micromol L(-1), 60 min) significantly reduced EFS-induced relaxation in CTRL (P < 0.05), but not in STZ-treated rats. Interestingly, the ability of ZnPPIX to inhibit EFS-induced relaxation was partially restored in STZ-treated rats co-administered in vivo with the HO-1 inducer cobalt protoporphyrin IX (CoPPIX) (0.5 mg per 100 g body weight weekly). Expression of inducible HO-1 protein was increased in homogenates from STZ-treated rats (vs CTRL, P < 0.01), and further increased in STZ-treated rats receiving CoPPIX (P < 0.05). Taken together, our data underline the essential role of HO/CO system in regulation of inhibitory NANC neurotransmission in the duodenum and suggest that dysregulation of HO/CO activity may represent one mechanism by which gastrointestinal motility is altered in diabetes.