RETINOPATHY IN GALACTOSEMIC DOGS CONTINUES TO PROGRESS AFTER CESSATION OF GALACTOSEMIA

Background: Progression of diabetic retinopathy in human subjects and animal models is difficult to halt promptly by intensified insulin therapy and strict glycemic control. Objective: To learn whether this resistance to arrest is peculiar to diabetes and insulin therapy or is a characteristic of hyperglycemia itself, we have determined the effect of intervention on diabetic-like retinopathy in a nondiabetic animal model, the galactose-fed dog. Methods: Dogs were given a 30% galactose diet, At the end of 24 months, the dogs were divided into two groups, one of which continued to receive the galactose diet, while the second immediately began receiving the diet minus galactose. All animals were killed after 60 months of study. Results: Consumption of the galactose-rich diet resulted, as expected, in galactosemia evident by elevated hemoglobin Ai, plasma nonenzymatically glycated protein, and erythrocyte polyol concentrations, each of which decreased to normal levels following withdrawal of dietary galactose. Retinopathy was found to be equivocal at the end of 24 months of the galactose diet and subsequently progressed significantly despite cessation of the galactose diet. Conclusion: The fact that retinopathy did not halt promptly at intervention is consistent with previous data from diabetic dogs and suggests that the vascular lesions may be due to sequelae of excessive tissue aldohexose that are not promptly corrected by correction of the aldohexose level.