Resistance of retinal inflammatory mediators to suppress after reinstitution of good glycemic control: novel mechanism for metabolic memory.
Diabetic retinopathy resists arrest of its progression after reestablishment of good glycemic control that follows a profound period of poor glycemic control. The objective of this study was to elucidate the role of inflammation in the resistance of retinopathy to arrest after termination of hyperglycemia. Streptozotocin-diabetic rats were (a) maintained either in poor glycemic control [PC group; glycated hemoglobin (GHb)>11%] or in good glycemic control (GC group; GHb<7%) for 12 months or (b) allowed to be in poor glycemic control for 6 months followed by good glycemic control for 6 additional months. At 12 months, retina was analyzed for pro-inflammatory mediators. Twelve months of PC increased retinal interleukin 1beta (IL-1beta) mRNA by 2-fold and its protein expression by 25% compared with the values obtained from normal rat retina. Tumor necrosis factor alpha (TNF-alpha) was elevated approximately 3-fold (both mRNA and protein), and the receptors for IL-1beta and TNF-alpha were increased by 40% each. The concentrations of intercellular cell adhesion molecule 1 and vascular cell adhesion molecule 1 were elevated by 40% and 150%, respectively, and inducible nitric oxide synthase transcripts were elevated by 6-fold. Six months of good glycemic control that followed 6 months of poor glycemic control failed to reverse the elevations in IL-1beta, TNF receptor type I, and intercellular cell adhesion molecule 1 but had some beneficial effects on TNF-alpha, inducible nitric oxide synthase, and vascular cell adhesion molecule 1, however these mediators remained significantly elevated. However, the GC group showed no significant change in the retinal pro-inflammatory mediators compared with the normal rats. Failure to reverse retinal inflammatory mediators supports their important role in the resistance of retinopathy to arrest after cessation of hyperglycemia.
Chan
Pooi-See
PS
Kresge Eye Institute, Wayne State University, Detroit, MI 48201, USA.
Kanwar
Mamta
M
Kowluru
Renu A
RA
D000818:Animals; D001835:Body Weight / Q000187:drug effects; D015815:Cell Adhesion Molecules / Q000235:genetics / Q000378:metabolism; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000378:metabolism; D003921:Diabetes Mellitus, Experimental / Q000188:drug therapy / Q000503:physiopathology*; D003930:Diabetic Retinopathy / Q000503:physiopathology*; D018450:Disease Progression; D005786:Gene Expression Regulation; D006442:Glycated Hemoglobin / Q000032:analysis; D006943:Hyperglycemia / Q000503:physiopathology; D018836:Inflammation Mediators / Q000378:metabolism*; D007336:Insulin, Isophane / Q000627:therapeutic use; D008297:Male; D052247:Nitric Oxide Synthase Type II / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011917:Rats, Inbred Lew; D018121:Receptors, Cytokine / Q000235:genetics / Q000378:metabolism; D012160:Retina / Q000201:enzymology / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction
D015815:Cell Adhesion Molecules; D051546:Cyclooxygenase 2; D006442:Glycated Hemoglobin; D018836:Inflammation Mediators; D007336:Insulin, Isophane; D052247:Nitric Oxide Synthase Type II; D012333:RNA, Messenger; D018121:Receptors, Cytokine