Zebrafish is a small tropical freshwater fish, named for their zebra-like stripes. Though tiny, this little fish plays a big role in biomedical research. It might surprise you that humans share about 70% of their genes with zebrafish. This makes the fish a powerful model for studying health and disease.

Meet the zebrafish

Zebrafish develop remarkably fast. Within 48 hours of fertilization, they have a beating heart, blood flow, and early brain and gut structures. The female releases her eggs into the water to be fertilized by the males, which lets researchers examine and adjust genes as the embryo develops. Zebrafish larvae are transparent until they grow into adults. Besides being cool, this allows researchers to watch cells and organs develop. It’s an incredible window into living biology.

In our lab, we are using zebrafish to study the fascinating connection between the gut microbiome and cardiovascular health. We found that zebrafish have a shared core gut microbiome like humans and rodents do, and they can also produce short chain fatty acids— beneficial molecules made by our gut bacteria.

Looking at the gut

Think of our gut microbiome as a thriving rainforest with diverse species living in balance. Trillions of microbes—bacteria, viruses and fungi—all work together to keep us healthy. When the delicate balance of different kinds of bacteria in the gut is disturbed by diet, stress and diseases, it can contribute to health problems such as high blood pressure.

High blood pressure is the most common and preventable risk factor for heart disease, which is the leading cause of death in the U.S. Nearly half of the U.S. adult population live with high blood pressure, yet only one in four adults have their blood pressure under control with medication. We show that in rats with high blood pressure, there is an imbalance in gut bacteria, and serotonin levels disrupt the communication between the gut and the brain. Our research team thinks fixing this miscommunication could help manage high blood pressure.

Boosting brain-gut communication

Some gut bacteria can talk to our brain through serotonin—the same chemical that regulates mood and sleep. This is where the zebrafish comes in. We are studying how specific gut bacteria can improve the communication between the gut and the brain, specifically through the vagus nerve, which acts like a telephone line that carries messages back and forth.

Using editing tools like CRISPRR, a green fluorescent protein glows under the microscope when a specific serotonin receptor in our zebrafish is activated by the gut bacteria, which lets us see the gut-brain communication in real time. We are trying to find out if a specific gut bacterium can boost the intensity of the green signal by activating serotonin receptors on the vagus nerve. The brighter the glow, the stronger the gut-brain signal is, which then tells us how well the gut bacteria communicate with the brain.

Our findings may help pave the way for more personalized, microbiome-based therapies to manage high blood pressure and overall health, while using simpler animal models to answer big research questions.