Variations in the neonatal environment modulate adult behavioral and brain responses to palatable food withdrawal in adult female rats

"Comfort-foods" chronic intake has different behavioral and neurobiological effects in male rats exposed or not to early-life stress

The ability of "comfort-food" (CF) diet to revert long-term effects of early-life stress (ELS) is less well known. The objective of this study was to verify if the chronic exposure to CF diet in animals submitted to ELS could relief the stress response at behavioral, neuroendocrine, and neurobiochemical levels, via differences in glucocorticoid receptors expression in brain areas involved in the stress response. From the second day of life, litters of Wistar rats and their mothers were submitted to the reduced nesting material protocol (ELS). In adult life, ELS and a control group were exposed chronically to two diet schemes: standard rat chow only or both "CF" diet, containing fat (34%) and sugar (20%) and a diet similar to the standard diet. Anxiety-like behavior, neuroendocrine response stress, leptin, GR, SOCS-3, pSTAT3, and the abdominal fat were evaluated. The anxiety-like behavior results showed that ELS group when exposed to comfort food were not different from the others groups. Chronic exposure to CF diet induced an anxiety-like behavior in the control group. Groups chronically exposed to CF diet had lower levels of corticosterone over time independent of the neonatal group. The ELS group exposed to the "CF" diet had higher levels of hippocampal GR, lower levels of hypothalamic SOCS-3 and greater accumulation of abdominal fat. Chronic CF diet consumption is able to reduce corticosterone levels independent of the neonatal history, but is associated with anxiety-like behavior in animals without previous history of trauma. Metabolic disturbances like increased adiposity and altered SOCS-3 seem to be a result of multiple insults (neonatal trauma followed by chronic CF diet). We highlight that the Control-chow and ELS-chow data were previously published, and are included in this study for comparative analysis.

Intrauterine Growth Restriction Modifies the Accumbal Dopaminergic Response to Palatable Food Intake

Intrauterine growth restriction (IUGR) associates with increased preference for palatable foods and altered insulin sensitivity. Insulin modulates the central dopaminergic response and changes behavioral responses to reward. We measured the release of dopamine in the accumbens during palatable food intake in IUGR rats both at baseline and in response to insulin. From pregnancy day 10 until birth, gestating Sprague-Dawley rats received either an ad libitum (Control), or a 50% food restricted (FR) diet. In adulthood, palatable food consumption and feeding behavior entropy was assessed using an electronic food intake monitor (BioDAQ®), and dopamine response to palatable food was measured by chronoamperometry recordings in the nucleus accumbens (NAcc). FR rats eat more palatable foods during the dark phase, and their eating pattern has a higher entropy compared to control rats. There was a delayed dopamine release in the FR group in response to palatable food and insulin administration reverted this delayed effect. Western blot showed a decrease in suppressor of cytokine signaling 3 protein (SOCS3) in the ventral tegmental area (VTA) and an increase in the ratio of phospho-tyrosine hydroxylase to tyrosine hydroxylase (pTH/TH) in the NAcc of FR rats. Administration of insulin also abolished this latter effect in FR rats. FR rats showed metabolic alterations and a delay in the dopaminergic response to palatable foods. This could explain the increased palatable food intake and behavioral entropy found in FR rats. IUGR may lead to binge eating, obesity and its metabolic consequences by modifying the central dopaminergic response to sweet food.