Electroretinographic evidence suggesting that the type 2 diabetic retinopathy of the sand rat Psammomys obesus is comparable to that of humans

Abstract

PurposeType 2 diabetic retinopathy is the main cause of acquired blindness in adults. The aim of this work was to examine the retinal function of the sand rat Psammomys obesus as an animal model of diet-induced type 2 diabetes when subjected to a hypercaloric regimen.Materials and methodsHyperglycemia was induced in Psammomys obesus by high caloric diet (4 kcal/g). The visual function of control (n = 7) and diabetic (n = 7) adult rodents were followed up during 28 consecutive weeks with full-field electroretinogram(ERG) recordings evoked to flashes of white light according to the standard protocol of the International Society for Clinical Electrophysiology of Vision protocol (ISCEV).ResultsTwenty-eight weeks following the induction of diabetes, results revealed significantly reduced and delayed photopic and scotopic ERG responses in diabetic rats compared to control rats. More specifically, we noted a significant decrease in the amplitude of the dark-adapted 0.01ERG (62%), a- and b-wave amplitudes of the dark-adapted 3.0 ERG (33.6%, 55.1%) and the four major oscillatory potentials components (OP1-OP4) (39.0%, 75.2%, 54.8% and 53.7% respectively). In photopic conditions, diabetic rats showed a significant decrease in a- and b-wave (30.4%, 43.4%), photopic negative response (55.3%), 30 Hz flicker (63.7%), OP1-OP4(51.6%, 61.8%, 68.3% and 47.5% respectively) and S-cone (34.7%). Significantly delayed implicit times were observed for all ERG components in the diabetic animals. Results obtained are comparable to those characterizing the retinal function of patients affected with advanced stage of diabetic retinopathy.ConclusionPsammomys obesus is a useful translational model to study the pathophysiology of diabetic retinopathy in order to explore new therapeutic avenues in human patients.

Functional alterations of retinal neurons and vascular involvement progress simultaneously in the Psammomys obesus model of diabetic retinopathy

“…In a previous manuscript (Dellaa et al, 2018), we reported ERG findings in P . obesus that had been affected with diabetes for 7 months.…”

“…In contrast (Kohzaki et al, 2008), showed unaffected b‐waves 11 weeks after STZ injection in Sprague–Dawley rats. No difference was detected in the photopic b/a‐wave ratio during 6 months of the experiment in P. obesus , this fact shows that a‐ and b‐waves are similarly decreased (Dellaa et al, 2018).…”

“…Although DR in the diet‐induced diabetes of P. obesus was previously described (Dellaa et al, 2018; T. Saidi et al, 2011). However, its onset and progression were never reported.…”

“…ERGs were recorded using a Metrovision system (France) following 15 days, 1, 2, 3, 4, 5, 6, and 7 months after the onset of diabetes according to a method previously described by us (Dellaa et al, 2016; Dellaa et al, 2018). The animals were anesthetized with an intraperitoneal injection of ketamine (120 mg/kg), the pupils dilated with tropicamide (25 mg/5 ml; UNIMED, Tunisia) and the cornea anesthetized with eye drops of 0.5% Alcaine (Bausch & Lomb, France).…”

“…In a previous manuscript (Dellaa et al, 2018), we reported ERG findings in P. obesus that had been affected with diabetes for 7 months. This study revealed a significant decrease of all ERG components in both scotopic and photopic conditions.…”