Reactive Carbonyls and Polyunsaturated Fatty Acids Produce a Hydroxyl Radical-like Species

Abstract

The pattern of oxidized amino acids in aortic proteins of nonhuman primates suggests that a species resembling hydroxyl radical damages proteins when blood glucose levels are high. However, recent studies argue strongly against a generalized increase in diabetic oxidative stress, which might instead be confined to the vascular wall. Here, we describe a pathway for glucosestimulated protein oxidation and provide evidence of its complicity in diabetic microvascular disease. Low density lipoprotein incubated with pathophysiological concentrations of glucose became selectively enriched in ortho-tyrosine and meta-tyrosine, implicating a hydroxyl radical-like species in protein damage. Model system studies demonstrated that the reaction pathway requires both a reactive carbonyl group and a polyunsaturated fatty acid, involves lipid peroxidation, and is blocked by the carbonyl scavenger aminoguanidine. To explore the physiological relevance of the pathway, we used mass spectrometry and high pressure liquid chromatography to quantify oxidation products in control and hyperglycemic rats. Hyperglycemia raised levels of ortho-tyrosine, meta-tyrosine, and oxygenated lipids in the retina, a tissue rich in polyunsaturated fatty acids. Rats that received aminoguanidine did not show this increase in protein and lipid oxidation. In contrast, rats with diet-induced hyperlipidemia in the absence of hyperglycemia failed to exhibit increased protein and lipid oxidation products in the retina. Our observations suggest that generation of a hydroxyl radicallike species by a carbonyl/polyunsaturated fatty acid pathway might promote localized oxidative stress in tissues vulnerable to diabetic damage. This raises the possibility that antioxidant therapies that specifically inhibit the pathway might delay the vascular complications of diabetes.

Advanced glycation end-products and methionine sulphoxide in skin collagen of patients with type 1 diabetes

“…Our findings are for skin collagen and do not address the effects of diabetes and its complications on intracellular oxidative stress [33]. Also, the data do not define the potential effects of localised oxidative stress in complication-prone microenvironments, as suggested by increased ortho-and meta-tyrosine in the diabetic retina [34]. Finally, this cross-sectional study cannot reveal whether the increased rates of AGE and MetSO accumulation are a cause or an effect (or neither) of the complications.…”

Rosiglitazone reduces renal and plasma markers of oxidative injury and reverses urinary metabolite abnormalities in the amelioration of diabetic nephropathy

“…To determine whether elevated oxidative stress correlated with DN and functional measures of kidney damage in this diabetic model, we quantified levels of proteinbound o,oЈ-dityrosine and HODE, highly sensitive markers of protein oxidation and lipid peroxidation, respectively (39), in plasma and renal cortex from five animals in each group. Dityrosine levels were significantly increased in the plasma of diabetic animals (Fig.…”

“…HODEs were quantified by reverse-phase C 18 HPLC analysis of triphenylphosphinereduced lipid extracts after base hydrolysis, as described previously (39). Briefly, analyses for HODE were performed on a Jasco HPLC system equipped with a reverse-phase column (Ultrasphere; 250 ϫ 4.6 mm, particle size 5 m, Beckman).…”

Food restriction and refeeding in lambs influence muscle antioxidant status

“…It is now well known that the level of carbonyl groups in proteins is increased by many metabolic alterations such as aging in rats (Reznick and Packer, 1994) or humans (Fano et al, 2001) exercise (Leeuwenburgh and Heinecke, 2001), and various diseases (Himmelfarb et al, 2000;Pennathur et al, 2005). However, the effects of the diet on protein oxidation and carbonyl contents in the literature show variable results.…”