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Antioxidant Level Related to CAD in Type 1 Diabetes
Among people with type 1 diabetes, a greater potential capacity to respond to oxidative stress may mitigate the future development of coronary artery disease (CAD), a new study suggests.
The findings were published online August 6 in Diabetes Careby Tina Costacou, PhD, and colleagues from the department of epidemiology, University of Pittsburgh, Pennsylvania.
Currently in clinical practice, physicians assess an individual’s risk factors (eg, oxidative stress) for a pathologic condition (eg, heart disease) to make inferences about the likelihood of developing this condition. But these new data suggest that individual risk may be better evaluated by simultaneously assessing factors representing risk and those representing protection from or resistance to that risk, she noted.
Thus, although 2 individuals may have similarly high levels of oxidative stress, there may be differences in the [plasma] concentration of antioxidant vitamins between the 2 that may put them in different risk categories, with one individual potentially requiring vitamin supplementation while the second need not use supplements.
Thus, in the future, it might be possible to tailor antioxidant therapy to specific at-risk subgroups.
Oxidant vs Antioxidant
The new data come from participants with type 1 diabetes in the prospective longitudinal Pittsburgh Epidemiology of Diabetes Complications study. All had initial assessments between 1986 and 1988, at which point they had a mean age of 28 years and mean diabetes duration of 19 years.
Of a total 658 patients, 356 did not have CAD at baseline and had at least 3 stored samples of blood and 24-hour or overnight urine obtained periodically over the subsequent 20 years. These people were assessed for urinary isoprostane (IsoP) levels — a biomarker of oxidative stress — and plasma levels of the antioxidant vitamins α-tocopherol and γ-tocopherol as a way of gauging the potential to respond to oxidative stress.
Concentrations of α-tocopherol increased over time, paralleling the use of vitamin supplements in the population, while γ-tocopherol and urinary IsoP levels didn’t change.
Over the 20-year follow-up, 24.7% of the 356 individuals with no baseline CAD had a coronary event. In models accounting for CAD predictors such as age, diabetes duration, blood pressure, lipid levels, and kidney function, there was a significant inverse association between α-tocopherol concentration and subsequent CAD (P = .02) and a borderline significant direct relationship between urinary IsoP and CAD (P = .06). These associations persisted regardless of glycemic control or subsequent CAD status.
Measures of γ-tocopherol, on the other hand, did not appear to be independently associated with later CAD (P = .54).
And “interestingly,” the ratio of α-tocopherol to urinary IsoP was strongly inversely related to the later development of CAD (P = .003), Dr. Costacou and colleagues note.
Clinical Implications: Will Antioxidants Work in Some?
The authors note that although many studies have failed to find a protective effect of antioxidant vitamin supplementation in the prevention of CAD, secondary-prevention trials have yielded more encouraging results for vitamin-E (α-tocopherol) supplementation.
It may be that antioxidants provide protection against CAD events in those who already have a CAD diagnosis or perhaps in individuals who are genetically susceptible.
Indeed, Dr. Costacou told Medscape Medical News that a previous study of patients with type 2 diabetes found that those with a particular genotype have a higher risk of heart disease and that supplementation with vitamin E can reduce that risk by 53% (Arterioscler Thromb Vasc Biol. 2008;28:341-347).
“Given further supporting data, perhaps one day it may be possible to better classify a person’s disease risk and individualize a treatment regimen. At present, though, we can’t make any inferences on where the balance between oxidative stress and antioxidant levels lies or what type or dosage of vitamin supplementation may best to reduce the risk or prevent disease,” she told Medscape Medical News.
Diabetes Care. Published online August 6, 2013. Abstract
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