The intricate relationship between diet, gut microbiota, and neurodegenerative diseases like Alzheimer’s and Parkinson’s is gaining significant attention in scientific studies. Understanding how the gut influences the central nervous system sheds light on potential avenues for mitigating the progression of these debilitating conditions.
Gut Microbiota’s Impact on the Central Nervous System:
The human gut harbors a multitude of bacteria crucial for physiological functions and immunity. Bacterial populations vary from the stomach to the colon, with common bacteria including Firmicutes, Bacteroidetes, Proteobacteria, and Actinobacteria. Heterogeneity in gut microbial composition arises from factors such as diet, drugs, hormones, physical activity, antibiotics, age, and exposure to toxic substances.
Maintaining a healthy gut microbiome is vital for homeostasis, supporting gut-barrier integrity, and metabolizing nutrients. Short-chain fatty acids (SCFAs) produced by these microbes contribute to reducing systemic inflammation. Dysbiosis in gut microbial composition is linked to various health issues, including obesity, diabetes, hypertension, colon cancer, non-alcoholic steatohepatitis, and Crohn’s disease.
Gut-Brain Axis Mechanisms:
The bidirectional interaction between intestinal microbiota and the central nervous system occurs through the gut-brain axis. Gut microbiota members can produce neurotransmitters influencing the gut-brain axis, along with modulating the immune system, affecting tryptophan metabolism, altering microbiota composition, and synthesizing specific metabolites.
The enteric nervous system (ENS) plays a role in modulating gastrointestinal functions through mechanisms linked to sympathetic and parasympathetic signaling. Enteroendocrine cells, activated by signals from gut microbiota, synthesize circulatory hormones that impact central nervous system (CNS) cells by crossing the blood-brain barrier.
Gut Microbiota’s Role in Neurodegenerative Diseases:
Several studies have explored the impact of gut microbes on neurodegenerative diseases like Alzheimer’s and Parkinson’s. Gut bacteria synthesize metabolites associated with immune and metabolic changes, influencing disease progression. Heterogeneity in gut microbial composition was observed in fecal samples from Parkinson’s patients, showcasing specific bacterial abundance variations.
Metabolites such as trimethylamine N-oxide (TMAO), amyloid curli, short-chain fatty acids (SCFAs), secondary bile acids (BAs), and lipopolysaccharides (LPS) have been associated with immune and metabolic changes driving neurodegenerative diseases.
Dietary Intervention and Neurodegenerative Diseases:
Tailored diets, such as the ketogenic diet (KD), the Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) diet, and the Dietary Approaches to Stop Hypertension (DASH) diet, show promise in positively impacting the course of neurodegenerative diseases.
The KD, with its increased fat consumption and reduced carbohydrate intake, has demonstrated anti-inflammatory effects and positive cognitive functions. The Mediterranean diet, rich in vitamins, omega-3 fatty acids, polyphenols, and carotenoids, is associated with anti-inflammatory effects that prevent cognitive disorders and dementia.
While dietary interventions can positively affect the course of Alzheimer’s and Parkinson’s diseases, it’s crucial to consider potential disadvantages, such as reduced bacterial species diversity associated with the KD. Combining dietary intervention with a proper gut microbial composition and diversity holds potential for enhancing the overall well-being of individuals facing these neurodegenerative challenges.