Title : Long-term effect of early undernutrition on social transmission of food preferences in rats
Abstract:
The brain nucleus involve in learning flavors and food preferences appear early in life and continue through adulthood. Epigenetic factors like undernutrition can alter the brain process involved in food preferences. In the other hand, undernutrition is a public health problem of undeveloped countries and predispose to neurodegenerative disease. Olfactory recognition deficits serve as clinical marker to differentiate Alzheimer's disease (AD) subjects from healthy aging groups and olfactory dysfunction in AD can present as impairment in olfactory recognition, emerging during early stages of the disease. The social transmission of food preferences (STFP) is a test of associative olfactory learning not previously used to investigate the effects of early undernutrition in adult rats. This study analyzed how the undernutrition interfere with changes in social interaction, olfactory perception; make a decision and olfactory memory in Male Wistar rats. The rats were divided into two groups randomly control group (CG) and undernourished groups (UG). UG received different percentages of a balanced diet during pregnancy. After birth, by alternating two lactating dams between litters every 12h, one with ligated nipples. Weaning was at 25 days old, followed by an ad-lib diet until post-natal day 90. Before the STFP, the rats were fasted 12h. These procedures included a three-stage protocol: odor exposure, social interaction and preference test. Odor exposure, the demonstrator rats (DR) was exposed to powdered food mixed with a cue spice cinnamon (CI); after that during social interaction, the DR interacted with the observer rats (OR) during 30 minutes; and finally, in the preference test the OR was exposed a two-choice test of powered food with CI and a novel spice cocoa (CO). Results: DR in both groups ingest the necessary amount of CI to be considered in the next stage. During social interaction, in the UG the social transmission is disrupted in OR as evidenced by the significant prolonged latency to initiate social interaction, reduced frequency and duration of head contacts, but increased duration of muzzle investigation directed to DR (p≤0.05). In the preference phase, the OR undernourished prolonged the latency for explore both stimuli contrasted with CG, the underfed OR decreased the frequency of visits for COC but increased the time to explore COC comparing with CIN (p <0.05) in contrast with CG. Finally, during the immediate preference testing, rats of both groups had a clear preference for food containing CI. The results suggest that UG rats during interaction needed increased the time expose to olfactory information in the breath of the DEM to obtain the olfactory cue and encoded. Furthermore, alterations on make a decision during the preference phase could be associated with alterations in olfactory process. Undernutrition do not alter the olfactory short-term memory in STFP. This is a robust and relevant response because the crucial role in survival. Further studies are needed to evaluate the olfactory recognition in undernourished subjects to support like a measure that could be integrated in subclinical early detection of patients at nutritional risk and prone to AD.
