A study published in the Journal of Neuroscience found that a version of a gene coding for a receptor for the brain chemical dopamine was 66% more common among people who lived to be 90 or older than among a group of younger people who were otherwise similar. The variant leads to a weaker response to the neurotransmitter, lowering the activity of the dopamine system that is responsible for generating feelings of pleasure, desire and reward, as well as for regulating movement.
Graduate student Vanessa Ridaura and colleagues at the Center for Genome Sciences and Systems Biology, University of Washington School of Medicine reported in the September 6 issue of Science that mice lacking bacterial colonies of their own that received gut bacteria from obese humans put on more weight and accumulated more fat than mice that were given bacteria from the guts of lean humans.
To directly test the influence of the human gut microbiome on obesity, the investigators sampled microbes living in the guts of human fraternal and identical twins, one of whom was lean while the other, obese. They introduced these microbes into germ-free mice fed low-fat mouse chow, as well as diets representing different levels of saturated fat and fruit and vegetable consumption typical of the U.S. diet. Increased total body and fat mass, as well as obesity-associated metabolic phenotypes, were transmissible with uncultured fecal communities and with their corresponding fecal bacterial culture collections.