Study in Keralam sheds light on link between gut bacteria, Parkinson’s disease

Trillions of bacteria living in the human gut may play a role in Parkinson’s disease, a brain disorder that causes tremors, stiffness, and slowed movement, according to a new study involving patients from Keralam.

Researchers from the Cochin University of Science and Technology (CUSAT) and the Sree Chitra Tirunal Institute for Medical Sciences and Technology (SCTIMST), Thiruvananthapuram, found significant differences between the gut bacteria of Parkinson’s patients and those of healthy individuals. The findings were published online in npj Parkinson’s Disease, an international scientific journal.

Parkinson’s disease occurs when nerve cells in the brain that produce dopamine, a chemical that helps control movement, gradually die. Scientists have long suspected that the gut and brain communicate continuously, and that an imbalance in gut bacteria could contribute to inflammation affecting the brain. Studies have shown that non-motor symptoms, including constipation and other gastrointestinal problems, can appear years before the tremors begin in Parkinson’s patients.

The study involved 65 Parkinson’s patients attending SCTIMST’s Comprehensive Care Centre for Movement Disorders and 65 healthy individuals, most of whom were the patients’ spouses. Spouses were included as healthy individuals for comparison, as they were more likely to share similar diets and living conditions.

Metagenomic sequencing

Researchers analysed stool samples using metagenomic sequencing (16S rRNA gene amplicon sequencing), a technique that identifies the bacteria present and helps assess their potential functions in the gut. They found higher levels of bacteria potentially associated with inflammation and lower levels of beneficial bacteria that produce short-chain fatty acids, which help maintain the gut lining healthy and regulate the immune system, in Parkinson’s patients.

The researchers suggest that the shift in bacterial communities could weaken the gut barrier and allow inflammation to spread.

“The study found that differences in the abundances of these bacteria were strongly associated with disease severity and other clinical features of Parkinson’s disease,” said Baby Chakrapani P. S., scientist and director of the Centre for Neuroscience at CUSAT and a co-author of the study. “The findings also suggest that gut bacteria may be linked to disease progression through their influence on processes involving dopamine, glutamate, and GABA, chemicals that play important roles in brain function.”

Funded by the Indian Council of Medical Research (ICMR), the study was conducted by scientist Aneesa P. A. under the supervision of Mr. Chakrapani and Dr. Syam Krishnan of SCTIMST.

Gut bacterial composition is influenced by factors such as diet, age, sex, and lifestyle. Differences in these factors, as well as genetics, could explain why studies in different populations have reported inconsistent associations between particular bacteria and Parkinson’s disease.

According to the researchers, this is the first study in an Indian population to integrate gut microbiome composition with its functional role in Parkinson’s disease. The findings could help future research into simple tests for early diagnosis of the disease and treatments aimed at restoring gut health.