Figure of mouse brain tissue from the substantia nigra; cells that are stained are dopamine producing.
Parkinson’s disease (PD) is a neurodegenerative disease, which means that the damage in the brain begins several decades before the symptoms appear. In PD, approximately 60% of a specific cell type in the brain dies before symptoms appear. The cells that die are dopamine-producing cells. Dopamine is a neurotransmitter, which is a chemical in the brain that help cells communicate with each other. Dopamine cells within the substantia nigra, an area of the brain, die in PD. In the figure above you can see dopamine-producing cells. PD was first described in 1817 by James Parkinson, and although the exact cause of PD still remains unknown, researchers and clinicians know that changes in our DNA play an important role. There is also an environmental component–for example, exposure to herbicides like paraquat induce PD in people. Another example of an environmental contributor is nutrition.
Nutrition, specifically B-vitamins, have been implicated in the onset and progression of PD. Folic acid is an example of a B-vitamin, and it is well known for its role in preventing neural tube defects during early brain development. Additionally, folic acid also helps to lower levels of a chemical called homocysteine. High levels of homocysteine are present in PD patients who take levodopa (L-DOPA), a pharmaceutical drug that helps replenish dopamine in the brain. The breakdown of L-DOPA in the body requires methyl groups generated from folic acid, and this in turn increases levels of homocysteine.
Methylenetetrahydrofolate reductase (MTHFR) is a protein that breaks down folic acid to generate methyl groups, and people with reduced levels of this protein are reportedly more affected by PD. In a recent research study from our group we use a mouse model with reduced levels of MTHFR to study how the paraquat model of PD impacts onset and progression.
Our study found that reduced levels of MTHFR result in motor impairments in PD mice, and these impairments are characteristic of PD. Additionally, the PD mice were sick and had higher levels of inflammation in the substantia nigra. There were also high levels of oxidative stress, which is an imbalance of reactive oxygen and antioxidant production within a brain region closely connected to the substantia nigra. Higher levels of oxidative stress have been implicated in several neurodegenerative diseases. In terms of targeting oxidative stress through pharmaceuticals, there has not been much progress. Food stuffs such as red wine, green tea, and blueberries have been reported ro reduce levels of oxidative stress through their antioxidant properties, but more investigation is required.
Nutrition is an important aspect of health. It is well documented that not all older adults absorb as many nutrients compared to their younger counterparts due to several factors, one being inflammation in the stomach. These recent research findings presented in this blog along with others suggest that adequate nutrition should be a component of health care for patients with PD.