Effects of age and axial length on choroidal stratified structure in normal eyes

To quantify the choroidal structures of normal eyes by optical coherence tomography (OCT)-based binarization and evaluate the relationships among age, refractive power, and ocular axial length. This was a retrospective observational study. One hundred and eighty nine eyes of 189 subjects without ocular diseases were examined by enhanced depth imaging (EDI)-OCT. A choroidal OCT horizontal image with a width of 1500 μm centered on the fovea was binarized. The lumen, stroma, and total choroidal area in the choriocapillaris (CC), Sattler's layer (SL), and Haller's layer (HL) were measured, and the ratio of the luminal area to total choroidal area (L/C ratio) was calculated. Multiple regression analysis was performed for choroidal parameters in each choroidal layer and for age, refractive power, and ocular axial length. Multiple regression analysis showed that an older age was significantly correlated with a lower choroidal area and the L/C ratio in all choroidal layers (each P < 0.05). A Long axial length was significantly associated with lower SL and HL (P < 0.05), but not with refractive power. In the choroid of normal eyes, age-related decreases in the choroidal area and L/C ratio were associated with all choroidal layers, and elongation of the axial length was associated with thinning of SL and HL.

Choroidal vascular structures in diabetic patients: a meta-analysis

PURPOSE

Choroidal vascular structures are likely to be affected in diabetic patients. The aim of this study was to conduct a meta-analysis of choroidal vascular structures in diabetic eyes with no diabetic retinopathy (NDR) and healthy control eyes, which was systematically evaluated by various factors involving the measurements.

METHODS

This study identified clinical data from publications in PubMed and web of science until May 2020. Independent retrospective or prospective clinical studies comparing NDR and healthy control eyes regarding choroidal vascular structures were extracted. Five related studies were enrolled, cumulating in a total of 282 diabetic eyes and 511 control eyes examined in this study. Heterogeneity was statistically quantified by I2 statistics, and meta-analysis was performed using a random effects model. This study included 2 different algorisms of binarization determining the ratio of luminal areas in total choroidal areas, both of which were consolidated and called "choroidal vascular ratio."

RESULTS

Meta-analysis clearly showed that the choroidal vascular ratio was significantly lower in NDR eyes than in healthy control eyes (weighted mean difference =  - 2.16; 95%CI: - 3.19 to - 1.13; P < 0.005). Similar results were obtained in sub-analysis based on adjustment of serum HbA1c levels and duration of diabetes.

CONCLUSIONS

The choroidal vascular ratio of NDR eyes was significantly lower than that of healthy control eyes. The ratio might contribute to a better understanding of the pathophysiology involved in the development of diabetic retinopathy, although there was some heterogeneity in primary analysis studies.

Alteration of choroidal vascular structure in diabetic macular edema

PURPOSE

The aim of this study was to analyze choroidal structures in healthy subjects and patients with/without diabetic macular edema (DME).

METHODS

This was a retrospective observation case control study. Four hundred and two eyes of patients with diabetes mellitus (DM), and 124 age-matched eyes of healthy subjects were enrolled in this study. DM patients were divided into 3 groups: presence of central-involved (CI) DME (n = 81) and nonCI-DME/non-DME (n = 321), based on OCT findings. Central choroidal thickness (CCT) and total choroidal, luminal, and stromal areas were determined using EDI-OCT and a binarization method, respectively. The luminal area expressed as a ratio of the total choroidal area was defined as the L/C ratio.

RESULTS

DM eyes showed a significantly lower L/C ratio than control eyes, whereas there was no significant difference in CCT or total choroidal, luminal, or stromal areas. There was no significant difference between CI-DME and non-DME groups in HbA1c, blood pressure, dyslipidemia, or renal function. CCT and total choroidal, luminal, and stromal areas were significantly greater in the CI-DME group than non-DME group (each P < 0.05).

CONCLUSIONS

These results suggest that CCT was thickened in the presence of DME, associated with both increased luminal and stromal areas, which might be related to the pathology of DME.

Probing Protein Glycation by Chromatography and Mass Spectrometry: Analysis of Glycation Adducts

Glycation is a non-enzymatic post-translational modification of proteins, formed by the reaction of reducing sugars and α-dicarbonyl products of their degradation with amino and guanidino groups of proteins. Resulted early glycation products are readily involved in further transformation, yielding a heterogeneous group of advanced glycation end products (AGEs). Their formation is associated with ageing, metabolic diseases, and thermal processing of foods. Therefore, individual glycation adducts are often considered as the markers of related pathologies and food quality. In this context, their quantification in biological and food matrices is required for diagnostics and establishment of food preparation technologies. For this, exhaustive protein hydrolysis with subsequent amino acid analysis is the strategy of choice. Thereby, multi-step enzymatic digestion procedures ensure good recoveries for the most of AGEs, whereas tandem mass spectrometry (MS/MS) in the multiple reaction monitoring (MRM) mode with stable isotope dilution or standard addition represents “a gold standard” for their quantification. Although the spectrum of quantitatively assessed AGE structures is continuously increases, application of untargeted profiling techniques for identification of new products is desired, especially for in vivo characterization of anti-glycative systems. Thereby, due to a high glycative potential of plant metabolites, more attention needs to be paid on plant-derived AGEs.

Recent advances in detection of AGEs: Immunochemical, bioanalytical and biochemical approaches

Advanced glycation end products (AGEs) are a cohort of heterogeneous compounds that are formed after the nonenzymatic glycation of proteins, lipids and nucleic acids. Accumulation of AGEs in the body is implicated in various pathophysiological conditions like diabetes, cardiovascular diseases and atherosclerosis. Numerous studies have reported the connecting link between AGEs and the various complications associated with diseases. Hence, detection and measurement of AGEs becomes centrally important to understand and manage the menace created by AGEs inside the body. In recent years, an increasing number of immunotechniques as well as bioanalytical techniques have been developed to efficiently measure the levels of AGEs, but most of them are still far away from being clinically consistent, as relative disparity and ambiguity masks their standardization. This article is designed to critically review the recent advances and the emerging techniques for detection of AGEs. It is an attempt to summarize the major techniques that exist currently for the detection of AGEs both qualitatively and quantitatively. This review primarily focuses on the detection and quantification of AGEs which are formed in vivo. Immunochemical approach though costly but most effective and accurate method to measure the level of AGEs. Literature review suggests that detection of autoantibody targeting AGEs is a promising way that can be utilized for detection of AGEs. Future research efforts should be dedicated to develop this method in order to push forward the clinical applications of detection of AGEs.

Neurite regeneration in adult rat retinas exposed to advanced glycation end-products and regenerative effects of neurotrophin-4

The purpose of this study was to determine the effect of low concentrations of advanced glycation end-products on neurite regeneration in isolated rat retinas, and to determine the effects of neurotrophin-4 on regeneration in advanced glycation end-products exposed retinas. Retinal explants of 4 adult Sprague-Dawley rats were cultured on collagen gel and were incubated in; (1) serum-free control culture media, (2) glucose-advanced glycation end-products-bovine serum albumin media, (3) glycolaldehyde-advanced glycation end-products-bovine serum albumin media, (4) glyceraldehyde-advanced glycation end-products-bovine serum albumin media, (5) glucose-advanced glycation end-products+neurotrophin-4 media, (6) glycolaldehyde-advanced glycation end-products+neurotrophin-4 media, or (7) glyceraldehyde-advanced glycation end-products+neurotrophin-4 supplemented culture media. After 7 days, the number of regenerating neurites from the explants was counted. Then, explants were fixed, cryosectioned, and stained for TUNEL. The ratio of TUNEL-positive cells to all cells in the ganglion cell layer was determined. Immunohistochemical examinations for the active-form of caspase-9 and apoptosis-inducing factor were performed. In retinas incubated with advanced glycation end-products containing media, the number of regenerating neurites were fewer than in retinas without advanced glycation end-products, and the number of TUNEL-positive cells and caspase-9- and apoptosis-inducing factor-immunopositive cells was significantly higher than in control media. Neurotrophin-4 supplementation increased the numbers of regenerating neuritis, and the number of TUNEL-positives, caspase-9-, and apoptosis-inducing factor-immunopositive cells were significantly fewer than that in advanced glycation end-products without neurotrophin-4 media. Low doses of advanced glycation end-products impede neurite regeneration in the rat retinas. Neurotrophin-4 significantly enhances neurite regeneration in retinas exposed to advanced glycation end-products.