The Aging Gut-Brain Axis: Effects of Dietary Polyphenols and Metal Exposure

Diet provides essential metals, which are required for the growth, development, and well-functioning of the body. Nonetheless, some natural and human activities add toxic heavy metals to the diet, consequently introducing them to our bodies, resulting in several disorders and death. The intestine, the metabolism and absorption site of metals, uptakes them through transporters, active processes, and passive processes. It harbors Enteric nervous system (ENS), connecting directly to central nervous system (CNS) and the micro-organisms acting as an endocrine organ, thus regulating the movement of metals into the host. Gut microbes mediate the uptake of essential metals and prohibit toxic metals. However, the imbalance in their concentration manifests into various neurodegenerative diseases via gut involving Firmicutes/Bacteriodetes ratio, Akkermansia, Bifidobacteria, Escherichia, Enterococcus, Bacteroides, and Clostridium. Most importantly, with population aging, the incidence of neurodegenerative disorders is rapidly flourishing, marking the need for novel theranostic approaches to overcome it. Several research have demonstrated the significance of gut microbial homeostasis and its influence on brain functions, often termed as gut-brain axis, necessary for the sustainment of overall health and well-being of the human body. This review presents the novel diagnostic potential of microbes for specific disorders and dietary metals in combination with the therapeutic approach. Furthermore, they propose its utilization as a theranostic tool to investigate the links between mentioned dietary metals and neurological illnesses via the gut.