Obese zebrafish

Obese zebrafish

The zebrafish is a freshwater fish belonging to the minnow family. Native to the Himalayan region, it is a popular aquarium “tropical” fish although it is not native to the tropics. The zebrafish is also an important and widely used subject in scientific research. Zebrafish can reproduce by the thousands and live for just a few months. Zebrafish are emerging as an important model system to study obesity and metabolic disease. They have remarkable similarities in fat metabolism to animals like humans. According to a recent review zebrafish can develop obesity and non‐alcoholic fatty liver disease (NAFLD) by gene manipulation, diet manipulation and modification of the composition of intestinal bacteria. (1)

One of the major advantages of zebrafish is the simplicity and efficiency of manipulation of gene expression. Moreover, zebrafish larvae are see-through. Genetically manipulated zebrafish larvae can express fluorescent proteins in specific cell types, which are then easily detected in the transparent larvae, enabling monitoring of obesity development and progression.

Response to starvation and refeeding have also been studied in zebrafish larvae. It was observed that, when fish were starved for 4 days, fat depots were reduced in all locations. At 7 days of starvation all fat materials were dissolved. Refeeding for 4 days was sufficient to re‐establish fat depots in the same locations as before starvation just like in humans.

In humans, different studies have demonstrated that non‐alcoholic fatty liver disease is less common in women than in men and its prevalence is lower in women of reproductive age. Overfed fertile female zebrafish developed less of this disease compared to overfed old females and all males. Only when food was continuously made available, on a day and night basis, did obesity consistently develop.

Recently, a model of type 2 diabetes in zebrafish has been established. Remarkably, this model of diabetes is also responsive to the antidiabetic drugs like metformin used in people.

It has been shown that the bacteria that live in our guts may have big influences on our size and shape. The relative ease of sterile experimental conditions, compared to mouse model experiments, make germ‐free zebrafish an attractive tool for studying gut bugs. Then we can watch as we add back one by one the germs and see what happens.

We can learn a lot from our cousins of God’s creation, the zebrafish.

1. Faillaci F et al. Obese zebrafish: A small fish for a major human health condition. Animal Models and Experimental Medicine First published: 21 November 2018 https://doi.org/10.1002/ame2.12042