Diabetic photoreceptors: Mechanisms underlying changes in structure and function

Abstract

Based on clinical findings, diabetic retinopathy (DR) has traditionally been defined as a retinal microvasculopathy. Retinal neuronal dysfunction is now recognized as an early event in the diabetic retina before development of overt DR. While detrimental effects of diabetes on the survival and function of inner retinal cells, such as retinal ganglion cells and amacrine cells, are widely recognized, evidence that photoreceptors in the outer retina undergo early alterations in diabetes has emerged more recently. We review data from preclinical and clinical studies demonstrating a conserved reduction of electrophysiological function in diabetic retinas, as well as evidence for photoreceptor loss. Complementing in vivo studies, we discuss the ex vivo electroretinography technique as a useful method to investigate photoreceptor function in isolated retinas from diabetic animal models. Finally, we consider the possibility that early photoreceptor pathology contributes to the progression of DR, and discuss possible mechanisms of photoreceptor damage in the diabetic retina, such as enhanced production of reactive oxygen species and other inflammatory factors whose detrimental effects may be augmented by phototransduction.

miRNA-124 Prevents Rat Diabetic Retinopathy by Inhibiting the Microglial Inflammatory Response

“…Both in patient and animal models, the detrimental influence of hyperglycemia on the inner retinal neuronal viability and function is described. Yet, the impact of hyperglycemia on photoreceptor function remains controversial [30][31][32][33]. In our study, we noted the impaired functions of Müller glia/bipolar cells and photoreceptors in 4-month diabetic rats, which is consistent with the observations of others [34][35][36][37].…”

Association of Intravenous Fluorescein Angiography and Adaptive Optics Imaging in Diabetic Retinopathy: A Prospective Case Series

“…Nonetheless, the loss of photoreceptors in the human diabetic retina remains controversial. 22 There is a paucity of evidence demonstrating photoreceptor death in diabetic patients, although it is possible that S-cones may be selectively lost in patients with DR. 23 A previous cross-sectional study on 29 young adults and adolescents with type 1 diabetes and no DR found that these diabetic eyes had no significant difference in cone density on AO imaging compared with healthy controls. 24 In another study by Zaleska-Żmijewska et al, 11 cone density at 2° eccentricities was significantly lower in eyes with mild and moderate NPDR compared with healthy controls.…”

Effect of retinol and α-tocopherol supplementation on photoreceptor and retinal ganglion cell apoptosis in diabetic rats model

“…This reduces oxygen reserve in photoreceptors, and even a minor disruption of oxygen flow in diabetes can result in severe hypoxia. The creation of acellular capillaries, capillary blockage, and capillary dropout can contribute to retinal hypoxia, hence, the vascular pathology of DR [3].…”

“…The loss of photoreceptors in the diabetic retina is still debatable, and various optical coherence tomography (OCT) studies in diabetic patients show that the thickness of the inner retina, including the nerve fiber, retinal ganglion cell, and inner plexiform layers, decreases with the duration of diabetes [3]. In a diabetic animal model study, the outer nuclear layer thickness is frequently reduced, specifically in models of type 1 disease with early-onset.…”