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The Gut-Brain Connection: Gut Health & Parkinson’s Disease

By Jordan Harborth, FNC-P, Nurse Practitioner at Neurology Solutions

The benefit of a healthy gut is demonstrated from the moment we are born and during early development. Research has shown a fetus is extremely sensitive to any change in a mother’s microbiotic makeup. So sensitive, in fact, it can alter the way a baby’s brain develops. During a cesarean section, the baby misses an opportunity to ingest the mother’s bacteria as they travel down the vaginal canal. Studies have shown that those born via cesarean section labor to recover the same diversity in their microbiome as those born vaginally. Our gut microbiome is constantly changing. Throughout life our gut health is constantly exposed to stress, toxins, chemicals, certain diets, and even exercise, which impacts our microbiome, whether for better or worse.

The “Second Brain” – the Gut

Our gut has its own neural network known as the enteric nervous system (ENS). This is a complex system of about 100 million nerves found in the lining of the gut. Microbiota play a dynamic role in our physical and psychological health via the ENS.

The ENS comes from the same tissues as our central nervous system (CNS) during fetal development. Therefore, it has many structural and chemical parallels to the brain. That is why the ENS, or gut, is sometimes called the “second brain”.

The ENS is responsible for regulation of neurotransmitters, hormones and electrical discharges through a pathway of nerves, of which both “brains” communicate back and forth. These pathways include the immune, endocrine and neural pathways.

Parkinson’s disease (PD) & Dementia with Lewy Body (DLB)

Parkinson’s disease and dementia with Lewy bodies (DLB) are both neurodegenerative conditions that affect movement and thinking abilities.

Parkinson’s disease is characterized by tremors, stiffness, slowness of movement, and problems with balance and coordination. As the disease progresses, cognitive and behavioral symptoms such as depression and memory loss can develop.

DLB is a type of dementia that often presents with symptoms similar to those seen in Parkinson’s disease, including movement problems, cognitive decline, and fluctuations in alertness and attention. Visual hallucinations are also a common symptom of DLB.

The key difference between the two conditions is that DLB is primarily a dementia, whereas Parkinson’s disease is primarily a movement disorder, although cognitive symptoms can develop over time in Parkinson’s.

Both Parkinson’s and DLB are caused by the degeneration of dopamine-producing neurons in the brain. However, the underlying causes of are not yet fully understood.

Although research is still somewhat new in regard to the gut-brain connection, there is enough evidence to support the theory that many neurologic diseases may start in the gut.

One interesting note that may support the start of PD and other dopamine-lacking neurologic disorders in the gut is that microbes can produce dopamine and its precursors from dietary substrates, with almost half of the body’s dopamine being generated in the GI tract.

Analyses of bacterial taxa at the phylum level showed patients with DLB had a higher abundance of Synergistota than controls, and patients with PD had a higher abundance of Firmicutes than controls. Patients with full-blown DLB showed a decrease in Proteobacteria compared with controls.

Patients with PD had a reduction of Lachnospiraceae UCG_008 and Prevotella, when compared to controls. Healthy controls had a higher abundance of Lactobacillus, Muribaculaceae, Fusicatenibacter, and Enterorhabdus.

Patients with DLB exhibited a decrease of Clostridium sensu stricto 1 and Fusicatenibacter, and an increase in Synergistes and Lactobacillus, when compared to healthy controls. Patients with prodromal DLB, or early DLB, had a higher abundance of Ruminococcaceae UCG_005, Frisingicoccus, and Lactobacillus than healthy controls. Patients with full-blown DLB had a higher abundance of Eubacterium and Ruminococcaceae UCG_005, and a lower abundance of Fusicatenibacter than patients with PD and healthy controls.

This is interesting as despite the similarity of symptoms between PD and DLB, the results obtained show different gut profiles when compared with controls. The high abundance of some taxa SCFA [short chain fatty acids]-producers in healthy controls compared with PD and DLB patients suggest that these changes could have potential implications on the gut-brain communication, and possibly a protective role in the onset and progression of these neurodegenerative diseases.

Elevated levels of Indican bacteria have been shown to affect the intestinal barrier integrity and permeability. High levels of Indican are an indicator of gut dysbiosis. Dysbiosis is an imbalance in the gut where microbiota is altered from a healthy state, characterized by lower resistance and resilience ability. This causes a shift in immune balance toward an inflammatory phenotype. Studies have shown that patient with PD have significantly higher, almost double, urinary concentrations of Indican compared to healthy controls.

Prebiotics and Probiotics

While the exact causes of neurodegenerative diseases are not fully understood, a growing body of research suggests that the gut microbiome may play a key role in the development of these conditions. In particular, researchers have focused on the impact of prebiotics and probiotics on the gut microbiome and the potential benefits they may offer to prevent or slow the progression of neurodegenerative diseases. One of the mechanisms through which prebiotics and probiotics may be beneficial is by improving gut microbiota diversity and function. The gut microbiota is known to play a critical role in regulating the immune system, and a healthy gut microbiome is associated with reduced inflammation and oxidative stress. These factors are known to contribute to the development of neurodegenerative diseases.

Prebiotics are non-digestible food ingredients that stimulate the growth and activity of beneficial microorganisms in the gut. They are commonly found in fiber-rich foods such as whole grains, fruits, and vegetables. Prebiotics play a key role in maintaining a healthy gut microbiome by providing a food source for beneficial bacteria and promoting the growth of a diverse range of species.

Probiotics, on the other hand, are live microorganisms that are consumed in the form of food supplements or fermented foods. Probiotics can colonize the gut and help to maintain a healthy balance of microorganisms, particularly by suppressing the growth of harmful bacteria. Probiotics have been shown to have a number of beneficial effects on the gut microbiome, including improved gut function, reduced inflammation, and enhanced immune function.

Chronic inflammation is a hallmark of many neurodegenerative diseases, and reducing inflammation has been shown to be a promising therapeutic strategy for these conditions. A study conducted in mice with Alzheimer’s disease found that prebiotics reduced inflammation in the brain and improved memory. Similarly, a study conducted in rats with Parkinson’s disease found that probiotics reduced inflammation and improved motor function.

A Pilot study performed in 2021 evaluating the add on effect of Lactobacillus plantarum PS128 showed promising results in PD. PS128 is a specific probiotic, known as a psychobiotic, which has been demonstrated to improve motor deficits and inhibit neurodegenerative processes in Parkinson’s disease (PD)-model mice. In the Pilot study, patients were given 60 billion colony-forming units of PS128 once per night for 12 weeks. After 12 weeks of PS128 supplementation, the UPDRS motor scores improved significantly in both the OFF and ON states. In addition, PS128 supplementation significantly improved the duration of the ON period and OFF period as well as PDQ-39 values, which include mobility, stigma, activities of daily living and cognition. However, PS128 had no obvious effect on non-motor symptoms of patients with PD.

Prebiotics and probiotics have also been shown to have a positive impact on depression and anxiety, which are common symptoms of neurodegenerative diseases. A study conducted in humans found that daily supplementation with prebiotics resulted in improved mood and reduced symptoms of anxiety and depression. Similarly, a study conducted in mice found that oral administration of probiotics reduced anxiety-like behavior and improved social behavior.

In conclusion, there is growing evidence that prebiotics and probiotics can play a role in preventing and mitigating the symptoms of neurodegenerative diseases. These dietary supplements may improve gut microbiota function, reduce oxidative stress, and reduce inflammation in the brain. While more research is needed to fully understand the mechanisms through which prebiotics and probiotics benefit neurodegenerative diseases, these dietary supplements may offer a promising therapeutic strategy for these conditions.

Works Cited:

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