This study is testing if a supplement called **tributyrin** can help with memory, thinking, and movement problems in people with Parkinson's Disease (PD) who have memory issues or dementia. Tributyrin is a type of short-chain fatty acid, which are naturally found in our bodies and are important for brain health. In this study, researchers will compare tributyrin to a placebo, which is a fake pill with no medicine, to see if tributyrin really helps.

Participants will take tributyrin three times a day for about 80-100 days. They will visit the clinic for tests on their thinking, movement, and have brain imaging scans like MRI and PET before and after taking the supplement. This will help researchers see if there are any improvements or side effects.

**Key Points:**

• Study duration is 80-100 days with multiple clinic visits.
• Participants will take a supplement 3 times daily.
• Researchers will compare effects of tributyrin to a placebo.