The influence of diet on gut bacteria offers new clues for the treatment of Parkinson's disease

The influence of diet on gut bacteria offers new clues for the treatment of Parkinson's disease

A current oneNpj Parkinson's diseaseStudy examines the relationship between diet and gut microbiome composition to identify functional pathways that impact patients with Parkinson's disease (PD).

Diet and PD risk

PD is one of the most common neurodegenerative diseases associated with aging. Common symptoms associated with Parkinson's disease include progressive motor impairment as well as non-motor symptoms such as gastrointestinal (GI) dysfunction, depression, constipation and cognitive impairment. Specific nonmotor symptoms may manifest in the prodromal stage decades before clinical diagnosis.

Previous studies have shown that diet plays a crucial role in the incidence and progression of Parkinson's disease. For example, those who adhere to a high-quality diet as measured by the Alternative Mediterranean Diet Score (aMED) and the Alternative Healthy Eating Index (AHEI) have a lower risk of Parkinson's disease, while lower values ​​of the Healthy Eating Index (HEI) - 2015 have been associated with chronic constipation and hyposmia in PD patients.

A link between cognitive impairment and low fiber intake has previously been found. In addition, many patients diagnosed with Parkinson's disease at a relatively young age report higher sugar consumption.

Poor diet and aging alter the composition of the gut microbiome, causing the concentration of beneficial bacteria to decrease and harmful bacteria to increase. Insufficient synthesis of essential nutrients in the gut microbiome and increased toxin levels can lead to neurodegeneration and neuroinflammation.

PD patients typically have lower levels of putative short-chain fatty acid (SCFA)-producing bacteria, such as:CoprococcusAndButyricicicoccus,as well as higher values ​​ofAkkermansia,inflammatory bacteria. Importantly, SCFAs have anti-inflammatory properties that affect the enteric nervous system, modulate inflammation in the central nervous system, and support normal microglial development.

To date, few studies have examined the role of diet in the development and progression of Parkinson's disease. Therefore, further research is needed to investigate this association and ultimately use these findings to develop appropriate interventions to alleviate gastrointestinal symptoms in Parkinson's disease.

About the study

The current study examined the association between diet and gut microbial diversity, composition, abundance, and predicted metagenome in Parkinson's disease patients. To this end, a cross-sectional analysis was performed on a subset of PD patients from the Parkinson's Environment and Gene (PEG) study, in which 832 PD patients were recruited between 2001–2007 (PEG1) and 2011–2017 (PEG2).

Patients were recruited who had been diagnosed with Parkinson's disease within the past three to five years, had been a resident of California for at least five years, and had no other neurological disease or terminal illness. Stool samples were collected from patients who had re-exposure between 2017 and 2020 (PEG-Gut).

A total of 85 participants met all eligibility criteria and were included in the current analysis. The study cohort completed the Diet History Questionnaire II (DHQ II) to assess diet. Diet quality was measured using the HEI-2015, with total scores ranging from zero to 100 points.

Study results

Most study participants were men of European descent, non-smokers, overweight and well-educated. Interestingly, most PD patients developed constipation in the tertile with the lowest HEI score.

Consistent with previous reports, the current study confirmed the benefits of a high-quality diet for maintaining a healthy gut in Parkinson's patients. A healthy diet leads to a reduction in suspected inflammatory bacteria, which are abundant in Parkinson's patients compared to healthy individuals.

Adherence to a high-quality diet with a high HEI increased the abundance of SCFA-producing bacteria, such as:Coprococcus1, Ruminococcaceae, Butyricoccus, NK4A214 group,Hydrogenoanaerobacterium,Rombousia,NegativibacillusAndRuminococcaceae UCG-003in PD patients. These bacteria synthesize butyrate, which reduces inflammation, thereby providing energy to the intestinal epithelial cells and strengthening the intestinal epithelium.

Those who reported higher added sugar consumption had lower levelsRomboutsia ButyricoccusAndCoprococci 1. Increased concentration of amyloid-producing bacteria,Klebsiellawere also observed.

PD patients often have elevated levels of proinflammatory cytokines in the serum and colon, which is due to systemic inflammation that could ultimately activate microglia. Activation of microglia is inherently linked to the progression of Parkinson's disease.

Mechanistically, a healthy diet reduces taurine degradation, lipopolysaccharide biosynthesis, circulating lipopolysaccharide numbers, and systemic inflammation in PD. A healthy diet in PD patients also increases the Ruminococcaceae family genera in the intestine, which supports taurine metabolism and reduces taurine degradation.

Conclusions

The current study showed that a healthy diet could be extremely beneficial for PD patients as it could reduce both motor and non-motor symptoms and delay disease progression. In addition, a healthy diet increases the concentration of putative anti-inflammatory butyrate-producing bacteria and reduces the number of putative pro-inflammatory bacteria in Parkinson's patients.

Therefore, the study results highlight the importance of adhering to a high-quality diet from the initial diagnosis of Parkinson's disease, as this could help maintain a healthy microbiome and delay disease progression. However, it is important to note that maintaining a healthy diet can become increasingly difficult as the disease progresses.

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