Scientists have explained the link between overeating and brain function
Scientists from the Department of Anthropology and the School of Biomedical Sciences at Kent State University, Ohio, have investigated the innervation of neuropeptide Y in the brain nucleus.The biologists studied the innervation of neuropeptide Y in the brain nucleus and its role in brain evolution and implications for human health, particularly in relation to addiction and eating disorders.
The researchers suggest that the combination of elevated neuropeptide Y (NPY) and dopamine (DA) in the human adjoining nucleus (NAc) may have improved brain development. However, this same configuration may also have made humans exceptionally vulnerable to eating disorders and substance abuse.
NPY plays a role in the reward system, emotional behavior, and has been linked to increased alcohol consumption, drug abuse, and fat intake. The NAc brain region is central to motivation and action, exhibiting one of the highest densities of NPY in the brain and is of great interest to researchers investigating brain-related promoters of addiction.
The researchers used postmortem brain samples from 74 individuals, including humans, monkeys and primate apes. The data show that human brains are characterized by much denser innervation of NPY in the NAc, measured by axon length to neuron density, compared to other primates.
In addition, humans and chimpanzees have higher NPY in the dorsal striatum compared to gorillas and monkeys. When the researchers examined the density of cortical NPY-ir (NPY-immunoreactive) neurons in Brodmann's area 22, they found no significant differences between human and non-human primate species.
The report emphasizes that the human brain is different among primates, is significantly larger relative to body mass, and has a higher basal metabolic rate. This requires a constant supply of potential energy stores (such as fat and glycogen) and higher body fat mass in humans than in other primates.
The scientists concluded that the shift in NAc function, possibly driven by increased fat intake, has a deep evolutionary origin and possibly contributes to the unique response of the human reward pathway to various stimuli. This same pathway makes current modern humans more susceptible to reward dependence than other primates.