Investigation of the retinal metabolic function in type 1 diabetic Akita mice

Abstract

Purpose : Diabetic retinopathy (DR) is the leading cause of vision loss in working-age adults. Understanding the retinal metabolic response to circulating high glucose levels in diabetic patients is critical for development of new therapeutic strategies to treat DR. Measuring retinal metabolic function using the Seahorse analyzer is a promising technique to investigate the effect of hyperglycemia on retinal glycolysis and mitochondrial respiration. Here, we analyzed the retinal metabolic function in young and old diabetic and control mice. We also compared the expression of key glycolytic enzymes between the two groups.

Methods : The Seahorse XF analyzer was used to measure the metabolic function of retina explants from young (7 months) and old (14 months) type 1 diabetic Akita (Ins2^Akita/+) mice and their control littermates. Rate-limiting glycolytic enzymes were analyzed in retina lysates from the two age groups. Furthermore, retina metabolic function and glycolysis enzyme expression were measured in an acute retinal ischemia-reperfusion (IR) injury model that is routinely used to model the ischemic phase of DR.

Results : Retinas from young adult Akita mice showed a decreased glycolytic response as compared to controls. However, this was not observed in the older mice. Western blotting analysis showed decreased expression of the glycolytic enzyme PFKFB3 (6-Phosphofructo-2-kinase/fructose-2, 6-bisphosphatase, isoform 3) in the young Akita mice retinas. Measurement of the oxygen consumption rate showed no difference in retinal mitochondrial respiration between Akita and WT littermates under normal glucose conditions despite evident mitochondrial fragmentation as examined by electron microscopy. However, Akita mice retinas at both 7 and 14 months showed decreased mitochondrial respiration under glucose-free conditions. Retinal metabolic function and glycolysis enzymes expression did not change in the IR injury model.

Conclusions : This is the first study to our knowledge to examine glycolytic enzyme expression and retinal metabolic function under diabetic conditions. Diabetic retinas display a decreased glycolytic response during the early course of diabetes which is accompanied by a reduction in PFKFB3. Diabetic retinas exhibit decreased mitochondrial respiration under glucose deprivation. Further investigation of the retinal metabolic function in response to hyperglycemia will help elucidate the pathophysiology underlying DR.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.