Introduction
The research discussed in the presented paper is linked to the onset time and progression of Huntington’s disease (HD). In their article, de Diego-Balaguer et al. (2016) consider the genetic factors that may affect one’s cognitive, behavioral, motor, and functional degradation. In particular, they choose to focus on “the Val158Met polymorphism of the catechol-O-methyltransferase (COMT) gene” since this gene is connected to the degradation of dopamine (de Diego-Balaguer et al., 2016, p. e0161106).
According to the authors, the main gap in current knowledge is the lack of understanding of possible roles that the COMT may play in the evolution of the disease. Although studies show such data about HD as the connection between the condition’s onset and repeats of CAG (cytosine, adenine, guanine), they do not reveal any relations between COMT polymorphism and the evolution of HD. These findings can impact drug therapy for HD and help The scholars to find new ways of treating patients using their genetic information. The authors attempt to examine the impact that COMT polymorphism can have on the motor, cognitive, functional, and behavioral decline of patients with HD.
Results
It should be noted that the scholars divide their research into multiple analyses to confirm previous studies and test new hypotheses. First of all, they examine the connection between CAG repeats and the patients’ age of onset. In this case, data analysis is performed to see whether the previous research is correct in establishing a link between the two mentioned above factors. De Diego-Balaguer et al. (2016) use the number of repeats as an independent variable and the age of onset as a dependent one to employ a linear regression model.
Moreover, they also calculate the expected age of onset, using a specific formula “expected age = (21.54 + exp (9.556–0.146*CAG))” to support the correlation (de Diego-Balaguer et al., 2016, p. e0161106). As a result, they confirm that the number of CAG repeats affects the age of onset, showing that the documented age and the predicted age calculations largely overlap.
The second main portion of the calculations is devoted to the tests that determine patients’ HD progression. Here, the authors perform a longitudinal analysis to compare how people with different polymorphism samples, namely Val/Val, Met/Met, and Met/Val, change during their visits to the clinic. The scholars employ the Unified Huntington’s Disease Rating Scale (UHDRS) for this purpose, assessing the participants during the first and the following visits.
The independent variable is the specific gene, and the dependent variable is the patients’ UHDRS score. De Diego-Balaguer et al. (2016) discover that the progression of HD is steeper for people with Met/Met HD gene, while Val/Val and Met/Val HD gene carriers do not experience changes as quickly. However, this difference is noticeable in motor and cognitive domains while being insignificant in functional and behavioral ones. Therefore, people with the Met/Met gene often outperform those with other genes in the first ten years of the disease while scoring lower in the later phases.
Discussion
The investigation of the links between CAG, COMT polymorphism, and people’s HD progression yields multiple conclusions. First of all, the scholars confirm the connection between the number of CAG repeats and the age of HD’s onset. They compare their findings to previous studies and point out the similarities in outcomes, solidifying this concept. Second, the authors show the significance of the effect that COMT polymorphism has on one’s cognitive abilities. They conclude that the differences in people’s Val/Val, Met/Met, and Met/Val genes are vital for pharmacology since they observe varying degrees of the degradation processes in the cognitive and motor spheres.
They point out that polymorphism may determine patients’ response to medications such as entacapone but not levodopa, thus showing some specific needs of patients with different alleles. de Diego-Balaguer et al. (2016) propose new ideas for future treatments that may be passed on people’s specific genotypes. Overall, the findings explored in the article serve as one of the implications for personalized therapy options.
Reference
de Diego-Balaguer, R., Schramm, C., Rebeix, I., Dupoux, E., Durr, A., Brice, A.,… Bachoud-Lévi, A.-C. (2016). COMT Val158Met polymorphism modulates Huntington’s disease progression. PloS One, 11(9), e0161106.