Absolutely - the chemicals that microbes make in the gut pass into your blood stream and from there access the entire body. There are mechanisms the body uses to ensure these chemicals are detoxified (phase I and phase II metabolism in the liver) and that they are excreted if they reach too high a concentration.

More locally, the enteroendocrine cells (https://en.wikipedia.org/wiki/Enteroendocrine_cell) that line the gut translate much of the internal nutrient state of the gut up to the brain to tell you things about if you should eat, etc.

There is a lot of research on how we could alter satiety by finding the right language that these cells use. There are approved drugs on the market that mimic the activity of these cells (incretin mimetics) to reduce appetite/weight control.