Sialic acid (SA) is a key component of gangliosides and neural cell adhesion molecules important during neurodevelopment. Human milk contains SA in the form of sialyllactose (SL) an abundant oligosaccharide. To better understand the potential role of dietary SL on neurodevelopment, the effects of varying doses of dietary SL on brain SA content and neuroimaging markers of development were assessed in a newborn piglet model. Thirty-eight male pigs were provided one of four experimental diets from 2 to 32 days of age. Diets were formulated to contain: 0 mg SL/L (CON), 130 mg SL/L (LOW), 380 mg SL/L (MOD) or 760 mg SL/L (HIGH). At 32 or 33 days of age, all pigs were subjected to magnetic resonance imaging (MRI) to assess brain development. After MRI, pig serum and brains were collected and total, free and bound SA was analyzed. Results from this study indicate dietary SL influenced (p = 0.05) bound SA in the prefrontal cortex and the ratio of free SA to bound SA in the hippocampus (p = 0.04). Diffusion tensor imaging indicated treatment effects in mean (p < 0.01), axial (p < 0.01) and radial (p = 0.01) diffusivity in the corpus callosum. Tract-based spatial statistics (TBSS) indicated differences (p < 0.05) in white matter tracts and voxel-based morphometry (VBM) indicated differences (p < 0.05) in grey matter between LOW and MOD pigs. CONT and HIGH pigs were not included in the TBSS and VBM assessments. These findings suggest the corpus callosum, prefrontal cortex and hippocampus may be differentially sensitive to dietary SL supplementation.

Objectives: Previous studies have shown that dietary prebiotics have the potential to improve memory, alter social behavior, and reduce anxiety-like behaviors in rodents. The present research sought to expand upon such results and describe the effects of feeding prebiotics early in life on cognition and neurochemistry using a translational piglet model. Methods: Pigs were provided customized milk replacer containing 2 g/L each of polydextrose (PDX) and galactooligosaccharide (PDX/GOS) or 0 g/L (Control) from postnatal day (PND) 2-33. Beginning on PND 25, pigs were tested on the novel object recognition (NOR), novel location recognition (NLR), and backtest tasks to measure recognition memory and response to restraint stress. At study conclusion pigs were euthanized and intestine, blood, and brain tissues were collected and analyzed. Results: PDX/GOS-fed pigs demonstrated recognition memory on the NOR task (P < 0.001) whereas Control pigs did not (P = 0.184). Additionally, PDX/GOS-fed pigs visited the novel and sample objects more frequently (all P < 0.05) while spending less time per visit exploring the sample object (P = 0.028) than Control pigs. Volatile fatty acids (VFAs) were decreased in the ascending colon (P < 0.012), whereas butyrate tended to be higher in blood (P = 0.080) and lower in the hippocampus (P = 0.061) of PDX/GOS-fed pigs. PDX/GOS-fed pigs exhibited lower serotonin (P = 0.016) in the hippocampus. Conclusion: These findings suggest that early life consumption of PDX/GOS supports recognition memory as measured by NOR while modulating the concentrations of VFAs in the colon, blood, and brain, as well as hippocampal serotonin. GRAPHICAL ABSTRACT

Human milk contains a unique profile of oligosaccharides (OS) and preliminary evidence suggests they impact brain development. The objective of this study was to assess the impact of bovine and/or human milk oligosaccharides (HMO) (2′-fucosyllactose and Lacto-N-neotetraose) on cognition, brain development, and hippocampal gene expression. Beginning on postnatal day (PND) 2, male pigs received one of four milk replacers containing bovine milk oligosaccharides (BMOS), HMO, both (BMOS + HMO), or neither. Pigs were tested on the novel object recognition task using delays of 1- or 48-h at PND 22. At PND 32–33, magnetic resonance imaging procedures were used to assess structural brain development and hippocampal tissue was collected for analysis of mRNA expression. Pigs consuming only HMO exhibited recognition memory after a 1-h delay and those consuming BMOS + HMO exhibited recognition memory after a 48-h delay. Both absolute and relative volumes of cortical and subcortical brain regions were altered by diet. Hippocampal mRNA expression of GABRB2, SLC1A7, CHRM3, and GLRA4 were most strongly affected by diet. HMO and BMOS had distinct effects on brain structure and cognitive performance. These data suggest different mechanisms underlie their influence on brain development.

Sialic acid (SA) is an integral component of gangliosides and signaling molecules in the brain and its dietary intake may support cognitive development. We previously reported that feeding sialyllactose, a milk oligosaccharide that contains SA, alters SA content and diffusivity in the pig brain. The present research sought to expand upon such results and describe the effects of feeding sialyllactose on recognition memory and sleep/wake activity using a translational pig model. Pigs were provided ad libitum access to a customized milk replacer containing 0 g/L or 380 g/L of sialyllactose from postnatal day (PND) 2–22. Beginning on PND 15, pigs were fitted with accelerometers to track home-cage activity and testing on the novel object recognition task began at PND 17. There were no significant effects of diet on average daily body weight gain, average daily milk intake, or the gain-to-feed ratio during the study (all p ≥ 0.11). Pigs on both diets were able to display recognition memory on the novel object recognition task (p < 0.01), but performance and exploratory behavior did not differ between groups (all p ≥ 0.11). Total activity and percent time spent sleeping were equivalent between groups during both day and night cycles (all p ≥ 0.56). Dietary sialyllactose did not alter growth performance of young pigs, and there was no evidence that providing SA via sialyllactose benefits the development of recognition memory or gross sleep-related behaviors.

Mounting evidence suggests that dietary oligosaccharides promote brain development. This study assessed the capacity of oligofructose (OF) alone or in combination with 2′-fucosyllactose (2′-FL) to alter recognition memory, structural brain development, and hippocampal gene expression. Beginning on postnatal day (PND) 2, male pigs received one of three milk replacers formulated to contain OF, OF + 2′-FL, or no oligosaccharides (CON). Pigs were tested on the novel object recognition task using delays of 1 or 48 h at PND 22. At PND 32–33, magnetic resonance imaging (MRI) procedures were used to assess structural brain development and hippocampal tissue was collected for analysis of mRNA expression. Pigs that consumed the OF diet demonstrated increased recognition memory after a 1 h delay, whereas those consuming diets containing OF + 2′-FL displayed increased recognition memory after a 48 h delay. Pigs fed OF or OF + 2′-FL exhibited a larger relative volume of the olfactory bulbs compared with CON pigs. Provision of OF or OF + 2′-FL altered gene expression related to dopaminergic, GABAergic, cholinergic, cell adhesion, and chromatin remodeling processes. Collectively, these data indicate that dietary OF and OF + 2′-FL differentially improve cognitive performance and affect olfactory bulb structural development and hippocampal gene expression.