Atherosclerotic Plaques Are Formed Late in Life

Researchers at the Karolinska Institutet (Stockholm, Sweden) and Uppsala University (Sweden) collected atherosclerotic plaques removed during carotid stenosis surgery in 29 well-characterized, symptomatic patients (average age 68 years, 55% male). The patients were admitted for surgery due to carotid lesions that partly obstructed blood flow to the brain, causing symptoms of transischemic attack (TIA). The researchers then used accelerator mass spectrometry (AMS) to determine the age of the plaques by measuring Carbon-14 (14C) residues, which prevailed in the atmosphere following the extensive atomic bomb tests in the 1950's and 1960's.

The researchers were surprised to find that the average age of the plaques was less than 10 years, and all but two plaques had formed within 5–15 years prior to surgery; another striking finding was that the variation of plaque age was low, suggesting that in most people plaque formation occurs during a relative short and late time span in life, lasting between three and five years. The age of plaques was also found to be associated to blood levels of insulin, and plaques with lower age (formed more recently) were found to be more unstable than older plaques, and therefore more likely to cause clinical complications. If the data is proven true, the growth of atherosclerotic lesions may be interrupted to prevent clinical manifestation, such as TIA and stroke, even in late stages of life. The study was published early online on April 7, 2011, in PLoS ONE.

"The correlation between low plaque age, higher insulin levels and instability is also consistent with our findings of gene activity, where younger plaques were characterized with higher activity of genes related to immune responses and oxidative phosphorylation,” said lead author associate professor Johan Björkegren, MD, of the department of medical biochemistry and biophysics at the Karolinska Institutet. "However, our study is small and need to be replicated in future, larger clinical studies before we can determine the exact roles of biological age for plaque stability and associated clinical events.”

Extensive nuclear tests in the 1950s and 1960s led to a rapid increase in atmospheric concentrations of 14C, which since then has steadily been declining. The declination curve can now be used to date biological materials synthesized over the last five to six decades. Through isolation of 14C from any biological sample using AMS, it is possible to map that content on to the declination curve, thus determining the year of synthesis.

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Karolinska Institutet
Uppsala University