Snapshot Issue 20 March 2006

CYP1A2 protein

For many of us, the taste of coffee is good. So we indulge in it. Yet since the 1970s, the scientific community has managed to make us feel guilty about it by presenting us with an unending list of its possible ravages: from heart disease, bladder cancer and birth defects to high blood pressure, insulin level unsteadiness, reduced fertility and bone fragility. Coffee supporters – on the other hand – can conjure up just as impressive a list of its benefits: ranging from alertness, increased mental performance and mild antidepressant qualities to a reduced risk of colorectal as well as liver cancer and a lower incidence in not only Parkinson’s disease and type 2 diabetes but also Alzheimer’s disease… So who are we to believe?

Sipping a cup of coffee spells sipping down probably about two thousand different chemical entities. And knowing which chemical has an effect on what part of us remains for the most part obscure. However, light is being shed on the ways of caffeine. Caffeine is broken down by an enzyme in our liver – cytochrome P4501A2, or CYP1A2 – and if it is not eliminated from the bloodstream, blood vessels tend to constrict thus favoring myocardial infarction. Vessels are kept dilated by way of adenosine and it may be that caffeine blocks the adenosine receptors.

What is more, it has recently been discovered that the effects of caffeine can be detrimental to some, while they are not to others… How? It all has to do with two common variants of CYP1A2: CYP1A2*1F and CYP1A2*1A. Individuals who carry CYP1A2*1F are slow in metabolizing caffeine. As a result, caffeine lingers in the blood longer and the carriers are more exposed to heart disease. Those who carry CYP1A2*1A, on the other hand, get rid of caffeine fairly fast and are, consequently, less prone to heart conditions. Surprisingly, the two variants’protein sequences are untouched since their polymorphism resides in the non-coding region of the gene. The difference observed in caffeine breakdown could then be due, for instance, to the binding of different regulatory proteins to CYP1A2*1F, which would affect its expression levels and, in turn, its activity.

So? Should we all rush to the doctor’s to find out which variant we carry? No. As always, the message is always the same: more often than not, a little of anything is not bad. Just enjoy your cup of coffee.

Cytochrome P450 1A2, Homo sapiens (human): P05177

L'édition française de cette chronique est disponible dans l'Instantanés du mois de Prolune.

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