Potential Contribution of Microbiome In Neurodegenerative Diseases: Alzheimer's Disease

Alzheimer’s Disease (AD) is characterized by a slowly progressive decline of cognition and memory and is the most frequent cause of dementia. HM contribute to the regulation of multiple neuro-chemical and neuro-metabolic pathways. The pathological features of AD include amyloid beta peptide (Aβ) deposition, neuronal tangle formation and granulovacuolar degeneration. Aβ protein is a normal part of the innate immune system, the body's first-line defense against infection. However recent report shows that Ab expression protects against fungal and bacterial infections in mouse, nematode, and cell culture models of AD.   However, recent research has shown that these proteins are also expressed on bacterial and fungal cell surfaces and might contribute to immune response.  In addition to commensal microbes there are other pathogens like Chlamydophila pneumoniae, Toxoplasma gondii, HIV- associated neurocognitive disorders (HAND, Viroids, Hepatitis, Cytomegalovirus have been suspected to be involved in AD.  Microbes are proposed to be involved in pathophysiology of neurodegenerative disease through their ability to produce relevant neurotransmitter level, immune modulation due to excess inflammation and translocation to brain from the site of infection trough blood or lymphatic system. Here we elaborated on the emerging ideas showing the contribution of the gut microbiome to human neurological diseases with special emphasis on AD. The evidences outlined in this review may prove useful in designing further studies for taxonomic and functional profiling of microbiota in patients with AD leading to new advanced therapeutic inventions.