Patients with AD had less density of retinal microvascular networks than controls. Our findings suggest the presence of retinal microvascular dysfunction in AD.

The microbiota of the human lower intestinal tract helps maintain healthy host physiology, for example through nutrient acquisition and bile acid recycling, but specific positive contributions of the oral microbiota to host health are not well established. Nitric oxide (NO) homeostasis is crucial to mammalian physiology. The recently described entero-salivary nitrate-nitrite-nitric oxide pathway has been shown to provide bioactive NO from dietary nitrate sources. Interestingly, this pathway is dependent upon oral nitrate-reducing bacteria, since humans lack this enzyme activity. This pathway appears to represent a newly recognized symbiosis between oral nitrate-reducing bacteria and their human hosts in which the bacteria provide nitrite and nitric oxide from nitrate reduction. Here we measure the nitrate-reducing capacity of tongue-scraping samples from six healthy human volunteers, and analyze metagenomes of the bacterial communities to identify bacteria contributing to nitrate reduction. We identified 14 candidate species, seven of which were not previously believed to contribute to nitrate reduction. We cultivated isolates of four candidate species in single- and mixed-species biofilms, revealing that they have substantial nitrate- and nitrite-reduction capabilities. Colonization by specific oral bacteria may thus contribute to host NO homeostasis by providing nitrite and nitric oxide. Conversely, the lack of specific nitrate-reducing communities may disrupt the nitrate-nitrite-nitric oxide pathway and lead to a state of NO insufficiency. These findings may also provide mechanistic evidence for the oral systemic link. Our results provide a possible new therapeutic target and paradigm for NO restoration in humans by specific oral bacteria.

Purpose To investigate the changes of the retinal microvascular network and microcirculation in high myopia. Design A cross-sectional, matched, comparative clinical study. Participants Twenty eyes of twenty subjects with non-pathological high myopia (28 ± 5 Years) with a refractive error of −6.31 ± 1.23 Diopters (mean ± standard deviation) and twenty eyes of twenty age- and gender-matched control subjects (30 ± 6 years) with a refractive error of −1.40 ± 1.00 Diopters were recruited. Methods Optical coherence tomography angiography (OCTA) was used to image the retinal microvascular network, which was later quantified by fractal analysis (box counting, Dbox, representing vessel density) in both superficial and deep vascular plexuses. The retinal function imager (RFI) was used to image the retinal microvessel blood flow velocity (BFV). The BFV and microvascular density in the myopia group were corrected for ocular magnification using Bennett’s formula. Results The density of both superficial and deep microvascular plexuses was significantly decreased in the myopia group in comparison to the controls (P < 0.05). The decrease of the microvessel density of the annular zone (0.6 – 2.5 mm), measured as Dbox, was 2.1% and 2.9% in superficial and deep vascular plexuses, respectively. The microvessel density reached a plateau from 0.5 mm to 1.25 mm from the fovea in both groups, but that in myopic group was about 3% lower than the control group. No significant differences were detected between the groups in retinal microvascular BFV in either arterioles or venules (P > 0.05). Microvascular densities in both superficial (r = −0.45, P = 0.047) and deep (r = −0.54, P = 0.01) vascular plexuses were negatively correlated with the axial lengths in the myopic eye. No correlations were observed between BFV and vessel density (P > 0.05). Conclusions Retinal microvascular decrease was observed in the high myopia subjects, whereas the retinal microvessel BFV remained unchanged. The retinal microvascular network alteration may be attributed to ocular elongation that occurs with the progression of myopia. The novel quantitative analyses of the retinal microvasculature may help to characterize the underlying pathophysiology of myopia and enable early detection and prevention of myopic retinopathy.

PurposeTo characterize age-related alterations in the retinal microcirculation, microvascular network, and microstructure in healthy subjects.MethodsSeventy-four healthy subjects aged from 18 to 82 years were recruited and divided into four age groups (G1 with age <35 years, G2 with age 35 ∼ 49 years, G3 with age 50 ∼ 64 years, and G4 with age ≥65 years). Custom ultra-high resolution optical coherence tomography (UHR-OCT) was used to acquire six intraretinal layers of the macula. OCT angiography (OCTA) was used to image the retinal microvascular network. The retinal blood flow velocity (BFV) was measured using a Retinal Function Imager (RFI).ResultsCompared to G1, G2 had significant thinning of the retinal nerve fiber layer (RNFL) (P < 0.05), while G3 had thinning of the RNFL and ganglion cell and inner plexiform layer (GCIPL) (P < 0.05), in addition to thickening of the outer plexiform layer (OPL) and photoreceptor layer (PR) (P < 0.05). G4 had loss in retinal vessel density, thinning in RNFL and GCIPL, and decrease in venular BFV, in addition to thickening of the OPL and PR (P < 0.05). Age was negatively related to retinal vessel densities, the inner retinal layers, and venular BFV (P < 0.05). By contrast, age was positively related to OPL and PR (P < 0.05).ConclusionsDuring aging, decreases in retinal vessel density, inner retinal layer thickness, and venular BFV were evident and impacted each other as observed by simultaneous changes in multiple retinal components.