The Durk Pearson & Sandy Shaw®
Life Extension NewsTM
Volume 16 No. 7 • August 2013


The Role of COMT in Impatience:

Choosing Between a Small Payoff Right Away or
Waiting for a Larger Payoff Later

A new paper1 reports a reason why people differ in how much they prefer an immediate small payoff rather than waiting for a larger payoff later. This is called the discount rate and, as the researchers note,1 has a large effect on whether one leads a healthy and successful life. They identify disorders such as substance abuse, pathological gambling, overeating, relationship infidelity, and Attention Deficit Disorder as examples of how impulsively choosing short-term rewards can often lead to costly consequences. Their new research1 focused on the effect of COMT (catechol-O-methyltransferase, a gene regulating the enzyme that degrades dopamine, thus controlling the level of dopamine especially in the prefrontal cortex) on the individual’s DD (delay discounting, the tendency to prefer immediate over future rewards

A molecular genetics study in 20072 identified a particular polymorphism (Val158Met) of the COMT gene as being associated with a steeper DD, that is, linked to a stronger preference for immediate as compared to later rewards. “The Val allele (compared to the Met allele) is associated with higher enzymatic activity and thus lower prefrontal cortex dopamine levels.”1 The heritability of DD has been reported in a recent twin study to explain up to 50% of the individual differences in DD.1

These researchers used an EEG technique to determine neural baseline (what the authors called a “neural fingerprint”) to establish a stable resting EEG, which they could use for observing COMT influences on the neural baseline activation. The seventy-three healthy Swiss men (mean age = 25.7 years, SD = 5.0 years) had their EEGs recorded in a protocol of 20 seconds eyes open followed by 40 seconds eyes closed, repeated five times. Only data from the eyes closed condition were analyzed. Then they had buccal epithelial cells collected for DNA.

A greater number of Val alleles was associated with a lower level of baseline activation in the left dorsal prefrontal cortex (DPFC), which in turn leads to a steeper DD (greater preference for immediate as compared to delayed rewards), which the authors called “impatient choice.”

As the paper described in the article before this one explains, EGCG has been found to be a natural inhibitor of COMT, decreasing the degradation of L-Dopa, which increases the availability of L-Dopa to enter the brain to be converted to dopamine. This is consistent with the results of other studies that have reported a reduced risk of Parkinson’s disease in those who drink tea regularly. (Green and white teas contain much higher levels of catechins, including EGCG, as compared to black tea.) It is therefore conceivable that tea drinking may affect delay discounting (DD) of individuals by modulating the activity of COMT to mimic the effects of having a COMT polymorphism that fosters a less impulsive DD.

An increase in EGCG/green/white tea consumption by a population might well have very substantial long-term effects on the general level of prosperity by increasing savings and investment versus immediate consumption gratification. The populations of both China and Japan save and invest a much higher percentage of their incomes than Americans; perhaps their higher levels of tea drinking has something to do with this.

References

  1. Gianotti et al. Why some people discount more than others: baseline activation in the dorsal PFC mediates the link between COMT genotype and impatient choice. Front Neurosci. 6:54. doi: 10.3389/fnins.2012.00054. (May 2012).
  2. Boettiger et al. Immediate reward bias in humans: frontoparietal networks and a role for the catechol-O-methyltransferase 158(Val/Val) genotype. J Neurosci. 27:14383-91 (2007).

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