And what’s new.
Imagine swallowing a pill about the size of a standard vitamin tablet, which when excreted tells you how your diet has affected various aspects of your well being, right from letting you know whether your mild depressive episode was caused by actual symptoms beyond your immediate control, or as a result of that Double Cheese Pizza you consumed with a large soda at 2:00AM binge-watching your favourite TV show? Imagine being diagnosed with severe clinical depression, Obesity, IBS, Crohn’s disease, what-have-you, and have an app tell you whether constituents of the gut might have played a role in it, without the need for painful, invasive and expensive surgeries? Imagine, as a woman, having access to the ever changing hormonal landscape of your body, in a new and informative way, by observing the diversity of your gut bacteria? Diversity is always good, be it gender, nationality, race, religion, or bacteria within the gut. But that is an article for another time.
Scientists have known for a while now, that the nutrients obtained through food regulate moods in some way, and that the enteroendocrine system or the “Second Brain” is responsible for this. Initially, it was thought that the enteroendocrine cells communicate with the nervous system by releasing hormones in response to the food or bacteria that they sense, which then modulates behaviour. Researchers have recently demonstrated experiments to show that this connection is more direct. Using 3D imaging techniques, the authors observed the presence of tiny microvilli and a foot–like extension on the enteroendocrine cells, similar to dendrites and axons of neurons in the brain. They were also able to show that the cells interacted with each other through real physical synapses, much like neurons of the brain, and not through the release of hormones as previously thought.
Better imaging technology, new materials that are biocompatible, and miniaturisation of electronics are some improvements that are helping with a mechanistic and interpretive function of the microbiome. This article aims to briefly describe ongoings in the world of ingestible pills -what is sensed in the gut using existing technologies, and novel sensing methods that are being developed. Ingestible pills have already been consumed by more than half a million people worldwide. The sensors within them can measure physical parameters like temperature and pressure, or chemical and biochemical parameters like gas, which are direct byproducts of bacterial activity from the food we consume.
Known parameters that can be measured, vary based on which region of the gut is being sensed. For example, Saliva in the mouth provides information about the metabolism of the body, and acts as a biomarker for diseases like HIV and Cancer. Swallowed food passes through the oesophagus, which connects the mouth to the stomach. If you’ve ever had acid reflux, the burning chest pain you feel occurs in the oesophagus, where to test for inflammation or lacerations in severe cases, doctors use techniques like Endoscopy to access the oesophagus wall. The next organ is the stomach, followed by the small intestine. The presence of bacteria like H.Pylori in the stomach is associated with stomach cancers. pH levels, balance of electrolytes, metabolites and bacterial counts are useful parameters to monitor. Primary sensing targets of the small intestine include concentration of electrolytes, gases, and bacteria counts which help in identifying overgrowth of bacteria, etc. Finally, any remaining biological products move to the colon, where the quality of mucosa, nutrient absorption, and chemical analysis of certain compounds indicates the presence of wounds, infections, or even cancer. About 1.5kg of the ~2kg of bacteria hosted in the body lives in the colon. The use of ingestible pills would be effective replacements for colonoscopies, endoscopies, and other methods of current access into the gut.