This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Keaney, J. F. Articles by Loscalzo, J. Search for Related Content PubMed PubMed Citation Articles by Keaney, J. F., Jr Articles by Loscalzo, J. Related Collections Chronic ischemic heart disease Oxidant stress Platelets

(Circulation. 1999;99:189-191.)
© 1999 American Heart Association, Inc.

Editorials

Diabetes, Oxidative Stress, and Platelet Activation

John F. Keaney, Jr, MD; Joseph Loscalzo, MD, PhD

Correspondence to John F. Keaney, Jr, MD, Whitaker Cardiovascular Institute, Boston University School of Medicine, 715 Albany St, W507, Boston, MA 02118.

Key Words: Editorials • diabetes • platelets • hyperglycemia • oxidation

Diabetes mellitus is a major source of morbidity in developed countries and, among its comorbid conditions, atherosclerosis is perhaps the most important. Since the availability of insulin, up to three fourths of all deaths among diabetics can be directly attributed to coronary artery disease (CAD).¹ In adult patients with diabetes, the risk of CAD is 3- to 5-fold greater in than nondiabetics despite controlling for other known CAD risk factors.¹ In patients with IDDM, up to one third will die of CAD by the age of 50 years.² A number of known risk factors for CAD, such as hypertension, central obesity, and dyslipidemia, are more common in diabetics than in the general population.¹ Despite this prevalence of risk factors, no more than 25% of the excess CAD risk in diabetes can be accounted for by known risk factors.² Thus diabetes represents a major contributing factor to the CAD burden in the developed world, and most of the excess attributed risk of CAD in diabetics cannot be readily quantified with the use of traditional risk factor analysis.

Diabetes is associated with a variety of metabolic abnormalities, principle among which is hyperglycemia. The relation between hyperglycemia and CAD is the subject of considerable debate because serum glucose does not consistently predict the existence of CAD.² Presumably, this confusion stems from the reliance on a single blood glucose measurement, as recent prospective data have clearly established a link between a marker for chronic average glucose levels (HbA_1C) and cardiovascular morbidity and mortality.³ There is considerable controversy with respect to the precise mechanism by which hyperglycemia may contribute to the development of CAD in diabetes. Established sequelae of hyperglycemia, such as cytotoxicity, increased extracellular matrix production, and vascular dysfunction, have all been implicated in the pathogenesis of diabetes-induced vascular disease.¹

Among the sequelae of hyperglycemia, excess oxidative stress has captured considerable attention as a potential mechanism for the increased vascular disease in diabetics. The established association between atherosclerosis and lipid peroxidation within the vascular wall⁴ has led to a renewed interest in the oxidative stress of hyperglycemia as a potential mechanism for diabetic vascular disease. Early evidence to support the association of oxidative stress and hyperglycemia was largely indirect. For example, the plasma from diabetic subjects contains increased levels of thiobarbituric acid-reactive substances⁵ and lipid hydroperoxides,⁶ two markers of lipid peroxidation. A major problem with such studies is assay specificity because the determination of thiobarbituric acid-reactive substances or lipid hydroperoxides in biological samples is prone to artifact.⁷

The molecular mechanism of biological oxidation by glucose was first identified in 1912 by Louis Maillard.⁸ This French chemist described a brown color that formed from heating solutions of carbohydrates and amines and termed this process the "reaction du Maillard." The Maillard reaction accounts for the glucose-dependent, nonenzymatic covalent modification of proteins that accompanies hyperglycemic states. Initially, the Maillard reaction involves the combination of the aldehyde group of glucose in the open-chain form with amine groups on proteins to form a Schiff base followed by Amadori rearrangement to form fructoselysine. This reversible glycosylation of amino groups, or glycation, underlies the formation of HbA_1C, the well-recognized marker of chronic glycemic control in diabetes mellitus, and is not of any direct pathophysiological significance for the complications of diabetes. By contrast, the final stage of the Maillard reaction involves the irreversible oxidation, or glycoxidation, of fructoselysine to yield a host of advanced glycation end products (AGEs) such as N-(carboxymethyl)lysine, pentosidine, and pyrroline, the formation of which correlate directly with the vascular and renal complications of diabetes mellitus.⁹ These carbohydrate-derived protein oxidation products are readily quantified with gas chromatography/mass spectroscopy and are more abundant in diabetics than in age-matched control subjects.⁹

Unlike the quantitation of AGEs and AGE-modified proteins, the quantitation of lipid peroxidation in the setting of hyperglycemia has been more problematic. Recently, a novel class of prostanoid-like compounds has been described by Morrow and Roberts (for review, see Reference 10¹⁰ ). These compounds, known collectively as F₂-isoprostanes, are specific nonenzymatic oxidation products of arachidonic acid that form in situ on esterified phospholipids and are subsequently released in the free form, presumably through the action of phospholipases.¹⁰ In the quantification of oxidative stress, the determination of F₂-isoprostanes has proven quite useful as a marker of lipid peroxidation both in vitro and in vivo. Pathological conditions known to involve a heightened state of oxidative stress, such as carbon tetrachloride poisoning and smoking, are characterized by increased production of F₂-isoprostanes.¹⁰ With respect to diabetes, Gopaul and colleagues¹¹ have found that plasma levels of esterified 8-epi-PGF₂, a prototypical F₂-isoprostane, are 3-fold higher in patients with NIDDM than in normal control subjects, unequivocally demonstrating an association between NIDDM and increased lipid peroxidation. However, the precise role of enhanced lipid peroxidation, or F₂-isoprostanes in particular, in the vascular pathology associated with diabetes mellitus remains to be determined.

In this issue of Circulation, Davì and colleagues have provided an important first step in understanding the implications of lipid peroxidation and increased production of 8-epi-PGF₂ in diabetic vascular disease.¹² Using a specific radioimmunoassay, these investigators found that urinary excretion of 8-epi-PGF₂ in NIDDM and IDDM patients was essentially twice that of healthy age-matched control subjects. This increase in 8-epi-PGF₂ was significantly correlated with increased platelet activation as determined by urinary levels of TXB₂, the major metabolite of thromboxane A₂, and with blood glucose in NIDDM patients. On the basis of prior studies indicating that 8-epi-PGF₂ amplifies agonist-induced platelet aggregation,¹³ Davì and colleagues concluded that increased lipid peroxidation in NIDDM leads to the formation of 8-epi-PGF₂, which, in turn, leads to platelet activation. In support of this hypothesis, the authors found that reducing 8-epi-PGF₂ formation through improved metabolic control or vitamin E supplementation also reduced platelet activation as reflected by a reduction in urinary excretion of TXB₂. Importantly, they also showed that by inhibiting platelet function with aspirin or indobufen, there was no change in the 8-epi-PGF₂ levels, indicating that the oxidative stress in these diabetics was likely to be a cause and not a consequence of platelet activation. Taken together, these data indicate that increased lipid peroxidation in NIDDM has important implications for vascular disease in diabetes.

Despite the accumulating evidence for increased lipid peroxidation in diabetes, the source of this oxidative stress in not known. Both plasma¹¹ and urinary¹² levels of 8-epi-PGF₂ are increased in patients with NIDDM. With regard to urinary 8-epi-PGF₂ excretion, a similar finding was observed for IDDM patients as well.¹² These concordant observations between NIDDM and IDDM patients would tend to implicate hyperglycemia as the culprit metabolic derangement, since this is a major common feature of both patient populations. Consistent with this notion, Davì and colleagues found that improved metabolic control of NIDDM patients significantly reduced urinary 8-epi-PGF₂ levels by 32%.¹² Reports that improved glycemic control by pancreatic islet transplantation reduces vascular oxidative stress and reverses antioxidant enzyme upregulation in rats with streptozotocin-induced diabetes are consistent with hyperglycemia as a source of oxidative stress.¹⁴ Taken together, these data suggest that the extent of metabolic control has a profound influence on the degree of oxidative stress in patients with diabetes.

In addition to AGE formation by oxidation of fructoselysine, there are a number of other putative mechanisms that link hyperglycemia to oxidative stress. Among the most direct is the autoxidation of glucose. Monosaccharides with an -hydroxyaldehyde structure, like glucose, are subject to enediol rearrangement that results in the formation of an enediol radical ion.¹⁵ The formation of this radical anion has two important implications. First, this species is capable of reduced molecular oxygen to form superoxide anion which, under certain circumstances, may contribute to the oxidation of lipids¹⁶ or the activation of platelets.¹⁷ Second, the dicarbonyl products formed by this pathway are quite reactive and may modify adjacent lysine groups to form AGEs such as N-(carboxymethyl)lysine directly. These reactions derived from glucose enolization are, however, dependent on transition metal ions,¹⁵ and the availability of free, redox-active transition metal ions in vivo is controversial. Recent data demonstrating glycation-induced ceruloplasmin fragmentation and free copper release offer one possible mechanism for a source of extracellular transition metals.¹⁸ As an alternative mechanism of AGE-mediated oxidative stress, AGEs have also been shown to induce cellular lipid peroxidation through interacting with their specific surface receptor (RAGE),¹⁹ and this effect can be attenuated by vitamin E.²⁰

Regardless of the mechanism for the synthesis of AGEs, several features of AGE action have direct bearing on the findings of Davì and colleagues.¹² In addition to their role in lipid peroxidation, AGEs enhance the aggregation of human platelets ex vivo.²¹ AGE-modified albumin has also been shown to induce monocyte tissue factor expression and procoagulant activity.²² Thus AGE formation on proteins and lipids appears to contribute to both lipid peroxidation and platelet activation and may therefore contribute to the findings of Davì and colleagues.

Although there is considerable evidence at hand for increased lipid peroxidation in diabetes, arguments for a more generalized increase in oxidative stress are not secure. In vitro, glycoxidation of collagen results in the simultaneous formation of AGEs as well as the protein oxidation products ortho-tyrosine and methionine sulfoxide.²³ Diabetic patients demonstrate an increase in AGE formation compared with age-matched control subjects⁹ but no increase in the noncarbohydrate-derived protein oxidation products ortho-tyrosine and methionine sulfoxide.²³ These data underscore the need for further investigation into the precise molecular nature of oxidative stress in diabetes mellitus and the impact of such stress on diabetic vascular complications.

Footnotes

The opinions expressed in this editorial are not necessarily those of the editors or of the American Heart Association. From Evans Department of Medicine and Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, Mass.

References

1. Bierman EL. George Lyman Duff Memorial Lecture: Atherogenesis in diabetes. Arterioscler Thromb. 1992;12:647–656.[Free Full Text]
   
2. Pyorala K, Laasko M, Uusitupa M. Diabetes and atherosclerosis: an epidemiologic view. Diabetes Metab Rev. 1987;3:463–524.[Medline] [Order article via Infotrieve]
   
3. Singer DE, Nathan DM, Anderson KM, Wilson PWF, Evans JC. Association of HbA_1C with prevalent cardiovascular disease in the original cohort of the Framingham Heart Study. Diabetes. 1992;41:202–209.[Abstract]
   
4. Witztum JL, Steinberg D. Role of oxidized low density lipoprotein in atherogenesis. J Clin Invest. 1991;88:1785–1792.
   
5. Nishigaki I, Hagihara M, Tsunekawa H, Maseki M, Yagi K. Lipid peroxide levels of serum lipoprotein fractions of diabetic patients. Biochem Med. 1981;25:373–378.[Medline] [Order article via Infotrieve]
   
6. Nourooz-Zadeh J, Tajaddini-Sarmadi J, McCarthy S, Betteridge DJ, Wolff SP. Elevated levels of authentic plasma hydroperoxides in NIDDM. Diabetes. 1995;44:1054–1058.[Abstract]
   
7. Janero DR. Malondialdehyde and thiobarbituric acid-reactivity as diagnostic indices of lipid peroxidation and peroxidative tissue injury. Free Radic Biol Med. 1990;9:515–540.[Medline] [Order article via Infotrieve]
   
8. Maillard LC. Action des adices amines sur les sucres: formation des melanoidines par voie methodique. C R Hebd Seances Acad Sci. 1912;154:66–68.
   
9. McCance DR, Dyer DG, Dunn JA, Bailie KE, Thorpe SR, Baynes JW, Lyons TJ. Maillard reaction products and their relation to the complications of diabetes. J Clin Invest. 1993;91:2470–2478.
   
10. Roberts LJ II, Morrow JD. The generation and actions of isoprostanes. Biochim Biophys Acta. 1997;1345:121–135.[Medline] [Order article via Infotrieve]
    
11. Gopaul NK, Anggard EE, Mallet AI, Betteridge DJ, Wolff SP, Nourooz-Zadeh J. Plasma 8-epi-PGF₂ levels are elevated in individuals with non-insulin dependent diabetes mellitus. FEBS Lett. 1995;368:225–229.[Medline] [Order article via Infotrieve]
    
12. Davì G, Ciabottoni G, Consoli A, Messetti A, Falco A, Santarone S, Pennese E, Vitacolonna E, Bucciarelli T, Costantini F, Capani F, Patrono C. In vivo formation of 8-iso-prostaglandin F₂ and platelet activation in diabetes mellitus. effects of improved metabolic control. Circulation. 1999;99:224–229.[Abstract/Free Full Text]
    
13. Pratico D, Smyth EM, Violi F, FitzGerald GA. Local amplification of platelet function by 8-epi- PGF₂ is not mediated by thromboxane receptor isoforms. J Biol Chem. 1996;271:14916–14924.[Abstract/Free Full Text]
    
14. Pieper GM, Jordan M, Dondlinger LA, Adams MB, Roza AM. Peroxidative stress in diabetic blood vessels: reversal by pancreatic islet transplantation. Diabetes. 1995;44:884–889.[Abstract]
    
15. Wolff SP, Dean RT. Glucose autoxidation and protein modification: their potential role of autoxidative glycosylation in diabetes. Biochem J. 1987;245:243–250.[Medline] [Order article via Infotrieve]
    
16. Keaney JF Jr, Frei B. Antioxidant protection of low-density lipoprotein and its role in the prevention of atherosclerotic vascular disease. In: Frei B, ed. Natural Antioxidants in Human Health and Disease. San Diego, Calif: Academic Press; 1994:303–352.
    
17. Salvemini D, de Nucci G, Sneddon JM, Vane JR. Superoxide anions enhance platelet adhesion and aggregation. Br J Pharmacol. 1989;97:1145–1150.[Medline] [Order article via Infotrieve]
    
18. Islam KN, Takahashi M, Higashiyama S, Myint T, Uozumi N. Fragmentation of ceruloplasmin following non-enzymatic glycation reaction. J Biochem. 1995;118:1054–1060.[Abstract/Free Full Text]
    
19. Yan SD, Schmidt AM, Anderson GM, Zhang J, Brett J, Zou YS, Pinsky D, Stern D. Enhanced cellular oxidant stress by the interaction of advanced glycation end products with their receptors/binding proteins. J Biol Chem. 1994;269:9889–9897.[Abstract/Free Full Text]
    
20. Reckelhoff JF, Kanji V, Racusen LC, Schidt AM, Yan SD, Morrow J, Roberts LJ II, Salahudeen AK. Vitamin E ameliorates enhanced renal lipid peroxidation and accumulation of F₂-isoprostanes in aging kidneys. Am J Physiol. 1998;274:R767–R774.[Abstract/Free Full Text]
    
21. Hangaishi M, Taguchi J, Ikari Y, Umezu M, Watanabe T, Miyata T, Kurokawa K, Kimura T, Ohno M. Advanced glycation end products enhanced the aggregation of human platelets in vitro. Circulation. 1997;96(suppl I):I-665.
    
22. Khechai F, Ollivier V, Bridey F, Amar M, Hakim J, de Prost D. Effect of advanced glycation end product-modified albumin on tissue factor expression by monocytes. Arterioscler Thromb Vasc Biol. 1997;17:2885–2990.[Abstract/Free Full Text]
    
23. Wells-Knecht MC, Lyons TJ, McCance DR, Thorpe SY, Baynes JW. Age-dependent increase in ortho-tyrosine and methionine sulfoxide in human skin collagen is not increased in diabetes. J Clin Invest. 1997;100:839–846.[Medline] [Order article via Infotrieve]
    

This article has been cited by other articles:

				A. B. Pai and T. A. Conner Oxidative Stress and Inflammation in Chronic Kidney Disease: Role of Intravenous Iron and Vitamin D Journal of Pharmacy Practice, June 1, 2008; 21(3): 214 - 224. [Abstract] [PDF]

				J. Mehilli, A. Kastrati, H. Schuhlen, A. Dibra, F. Dotzer, N. von Beckerath, H. Bollwein, J. Pache, J. Dirschinger, P. P. Berger, et al. Randomized Clinical Trial of Abciximab in Diabetic Patients Undergoing Elective Percutaneous Coronary Interventions After Treatment With a High Loading Dose of Clopidogrel Circulation, December 14, 2004; 110(24): 3627 - 3635. [Abstract] [Full Text] [PDF]

				R. Ferrara, G. Guardigli, and R. Ferrari Myocardial metabolism: the diabetic heart Eur. Heart J. Suppl., January 1, 2003; 5(suppl_B): B15 - B18. [Abstract] [PDF]

				A. Nitenberg, S. Ledoux, P. Valensi, R. Sachs, J.-R. Attali, and I. Antony Impairment of Coronary Microvascular Dilation in Response to Cold Pressor-Induced Sympathetic Stimulation in Type 2 Diabetic Patients With Abnormal Stress Thallium Imaging Diabetes, May 1, 2001; 50(5): 1180 - 1185. [Abstract] [Full Text]

				J. A. Beckman, A. B. Goldfine, M. B. Gordon, and M. A. Creager Ascorbate Restores Endothelium-Dependent Vasodilation Impaired by Acute Hyperglycemia in Humans Circulation, March 27, 2001; 103(12): 1618 - 1623. [Abstract] [Full Text] [PDF]

				S. B. King III and E. Mahmud Will Blocking the Platelet Save the Diabetic? Circulation, December 21, 1999; 100(25): 2466 - 2468. [Full Text] [PDF]

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Keaney, J. F. Articles by Loscalzo, J. Search for Related Content PubMed PubMed Citation Articles by Keaney, J. F., Jr Articles by Loscalzo, J. Related Collections Chronic ischemic heart disease Oxidant stress Platelets