A mother`s nutritional or psychological stress during pregnancy and breast-feeding may prompt changes in her infant`s genes that increase the child`s risk of obesity later in life, according to a new study in mice.
Ruijun Han at the University of Minnesota and Georgetown University and her colleagues also found that only female offspring rapidly put on weight.
The team focused on the behaviour of neuropeptide Y (NPY), a neurotransmitter found in the brain and autonomic nervous system that is associated with appetite stimulation and the storage of energy as fat.
Building on prior research in the field, the team undertook two studies, one involving mice and the other involving mouse embryonic stem cells.
In the first study, the researchers sought to determine if prenatal and postnatal stress exerted long-term effects on the activation of NPY and its Y2 receptor (Y2R) that would result in the creation of fat cells and the promotion of obesity.
First, they exposed pregnant mice to stress by feeding them a low-protein diet. The team found that this diet caused low birth weight in the offspring.
Female offspring of the mice stressed during pregnancy and lactation grew faster after weaning when they were fed a high-fat diet, and within 2 months, they developed abdominal fat, prediabetes (impaired glucose tolerance) and increased upregulation of Y2R in their fat tissue.
Surprisingly, the same changes were not observed in male offspring, which appeared to grow normally.
"This indicates that maternal stress during pregnancy and lactation could induce gender-specific abdominal obesity and impaired glucose metabolism associated with increased plasma NPY and fat Y2R," said Han.
In the second study, the researchers exposed mice embryonic stem cells to a stress hormone, epinephrine, which helped the cells differentiate into fat cells and also generated NPY.
The cells also decreased DNA methylation in the NPY promoter region, through an epigenetic (non-genetic) process that alters expression of this peptide in cells so that the cells "remember" their type.
The researchers, however, cautioned more work was needed to see if stress produces the same effects in humans.
The findings were presented at the Experimental Biology meeting (EB 2011) in Washington, D.C.