Induction of hyperglycaemia in zebrafish (Danio rerio) leads to morphological changes in the retina

Abstract

Diabetes affects over 16 million Americans yearly, resulting in hyperglycaemia and microvascular complications, including retinopathy, neuropathy and nephropathy. Animal models have been developed to examine the immunological aspects of type 1 diabetes and the pathogenic mechanisms associated with diabetic retinopathy, but the methods of diabetes induction raise concerns regarding these models. Zebrafish (Danio rerio) have been used extensively to study developmental processes and mutant zebrafish strains have been used to examine vision disease present in humans. In this paper, we have induced hyperglycaemia in zebrafish by alternately immersing the fish in glucose solution or water. Eyes from untreated fish or fish exposed to alternating glucose/water solutions for 28 days were dissected, sectioned and stained to visualise cell bodies in the retina. In untreated fish retinas, the inner plexiform layer (IPL) and inner nuclear layer (INL) were approximately the same thickness, whereas in fish repeatedly exposed to glucose solutions the IPL was approximately 55% the thickness of the INL. Both the IPL and INL were significantly reduced in retinas of treated fish, compared to untreated fish, similar to that seen in other animal models of diabetes and in diabetic patients. These results suggest that zebrafish may be used as an animal model in which to study diabetic retinopathy.

The Effects Induced Hyperglycemia on Adrenal Cortex Function in the Giant Danio Devario Aequipinnatus Embryos

“…Zebrafish have similar metabolic regulation of glucose as that found in mice and human, [60] and the Giant Danio is phylogenetically closer to Danio rerio [14]. Effects of induced hyperglycemia stress resulted in positive correlation between the %glucose solution and the cortisol level, as well as the incubation time and the cortisol level as seen previously in other model systems, consistent with onset of adrenal cortex function and steroidogenesis [32]. In conclusion, the present study demonstrated that hyperglycemic effects on adrenal cortex function and steroidogenesis in the freshwater fish Giant Danio Devario aequipinnatus embryos.…”

“…These data demonstrate that hyperglycemia can reliably be produced in the Giant Danio Devario aequipinnatus embryos, as has previously shown in Danio rerio species by [32,40]. The induced hypergylcemia in adult rainbow trout through manipulation of food source and stocking conditions [41].…”

“…To induce hyperglycaemia initially, the embryos were treated in a 0.0%, 0.3%, 0.6%, 0.9%, 1.2%, 1.5%, and 1.8% glucose solution, as it readily take up substances from the water [32]. The average glucose measurement for all embryo samples incubated for 24 h, 48 h, 72 h in stock aquaria water ranged from 65 to >600 mg/ dl.…”

Zebrafish—on the move towards ophthalmological research

“…IPL and INL layers were shown to be significantly reduced in treated zebrafish, with the thickness of the IPL approximately 55% of the INL. 96 This study provided some support to the idea that zebrafish can be utilized to model DR. This finding was confirmed by another study where visual impairment was evident after inducing hyperglycaemia in zebrafish.…”

“…95 Hyperglycaemic zebrafish are shown to have similar retinal structure abnormalities as seen in diabetic patients. 96 Hyperglycaemia can be induced in adult zebrafish by immersing alternately in glucose solution and water over 28 days followed by retinal examination. IPL and INL layers were shown to be significantly reduced in treated zebrafish, with the thickness of the IPL approximately 55% of the INL.…”