The new results are contrary to earlier studies in adult rats which established a link between exposure to a high fat diet (HFD) and increased anxiety behaviour.However the new research, which examined the influence of maternal HFD on several measures of anxiety behaviour and gene development in adolescent offspring, found that the offspring of rats perinatally exposed to HFD exhibited reduced levels of anxiety - and this was especially the case in females.
“The data suggests that adolescence constitutes an additional period when the effects of developmental programming may modify mental health trajectories,” the authors said.
Anxiety levels are controlled by corticosteroids (like glucocorticoid receptors - GR) in the limbic regions of the brain that control the body’s ability to reduce or increase inflammation and stress levels (the amygdala and hippocampus). Previous studies on adult rats identified increased anxiety when exposed to a HFD, as well as increased inflammation.
The new latest datacould suggest 'a developmental shift' between adolescence and adulthood in the effects of HFD on anxiety, said the team.
HFD offspring less anxious
Ten adult female rats (or dams) were placed on a HFD consisting of 60% fat, 20% protein and 20% carbohydrate and another 10 were exposed to the control house chow diet (CHD) comprising 3.5% fat, 28.5% protein, and 58% carbohydrate.
The rats started the diet four weeks before mating and throughout pregnancy and lactation and were subjected to three behavioural tests to gauge their responses to potentially stressful scenarios.
Results revealed a greater abundance of GR in the hippocampus among HFD-exposed male and female offspring compared to CHD offspring - with levels were significantly higher in females.
“Adolescent analysis of corticosteroid receptors revealed that hippocampal GR expression was increased in HFD-exposed offspring, particularly in females, which supports our behavioral results indicating decreased anxiety among HFD-exposed offspring,” said the report.
There were no significant differences in GR gene activity in the amygdala of HFD-exposed adolescents.
Faster weight gain
Dams-fed HFD gained more weight than CHD dams throughout gestation. There was no difference in body weight of the pups from either group at birth but those from HFD dams put on weight faster than CHD pups prior to weaning.
However by the time the ‘pups’ reached adolescent there was no discernible difference in body weight between the groups.
The researchers added: “This suggests our findings are attributable to perinatal HFD exposure rather than differences in current body weight.”
Publishing date July 11, 2014 DOI: 10.1016/j.neuroscience.2014.04.012
“Maternal high-fat diet alters anxiety behavior and glucocorticoid signaling in adolescent offspring”
Authors: A. Sasaki, W. de Vega, S. Sivanathan, S. St-Cyr, P. O. McGowan