Scientists from the Harvard Medical School have discovered that some blind cavefish have adapted to varying cycles of starvation and over-eating. These adaptations have led to mutations in a specific gene called MC4R. This is the same gene that can mutate in some obese people, especially those with insatiable appetites.
The likely gene mutation at play stems from the observation that people have different metabolisms. This leads to different people gaining weight and others not, even when people eat similar amounts of the same types of food.
The reason for studying cavefish is due to their variable eating habits. Cavefish live in deep, dark caves in Mexico. The blind fish have adapted to going for prolonged periods without food because they can store large amounts of fat and then burn this very slowly, over a period of several months.
When food does become available, cavefish eat vast quantities in order to prepare for the future when food is scarce once again. Despite long periods of being overweight, the cavefish are not affected by any ill-health related effects.
Analysis has found the cavefish to have mutations in the gene MC4R. This gene is, in people, normally regulated by leptin (the appetite-suppressing hormone). By mutating the gene in mice, researchers have found that mice with the mutated gene quickly become obese and they are also continually hungry. It is likely that similar things happen in people.
So, whereas the gene mutation in the cavefish works to the fish’s advantage, in people, the same mutation can cause obesity and related ill-health effects like type 2 diabetes.
Longer term it is hoped that this knowledge will help in the battle against obesity and that some form of metabolic control drug can be administered to help people with the mutated gene to supress their hunger instinct.
The research findings have been published in the journal PNAS. The paper is titled “Melanocortin 4 receptor mutations contribute to the adaptation of cavefish to nutrient-poor conditions.”
