Metabolic Profiling of Maternal and Pup Serum using Near‐Infrared Spectroscopy Identifies Distinct Patterns for Nematode Infection and Dietary Protein Deficiency

Abstract

BackgroundRecent advances in Near‐Infrared (NIR) spectroscopy make it a suitable and inexpensive candidate technique for the analysis of biological fluids and the determination of metabolic profiles. However, few have applied this methodology to study diet and/or infection induced NIR spectral changes in serum that are experienced by nematode infected mice and their offspring.ObjectivesThis study explored the possibility that NIR spectral analysis could: 1) identify metabolomic differences in lactating mice (n = 22) that were subjected to two levels of dietary protein (PD 6% and PS 24%) and two doses of nematode infection, uninfected (UN) and infected (IN) and 2) determine if these differences were similarly reflected in the serum of their nursing pups. Maternal serum and serum pooled from the pups in each litter (n = 25) were collected on day 21 postpartum.MethodsA 4‐way comparison of the four experimental groups (PS‐UN, PS‐IN, PD‐UN and PD‐IN) was conducted for both dams and pups using 8 NIR spectral regions: 1650–1700nm (Region 1), 1701–1750nm (Region 2), 1850–1899nm (Region 3), 2050–2099nm (Region 4), 2100–2130nm (Region 5), 2130–2200nm (Region 6), 2275–2310nm (Region 7) and 2311–2370nm (Region 8). Experimental group differences were determined with a Kruskal‐Wallis test. Post hoc tests were performed using the Bonferroni correction. In all instances a value of P<0.05 was considered statistically significant.ResultsSignificant differences were found in lactating dams between diets for three ratios: Region 1:2, Region 1:7 and Region 2:7, reflecting a diet effect that was only observed in the infected dams, infection per‐se did not produced differences in maternal serum. In contrast to lactating dams, both maternal PD and infection were reflected in pup serum. The PS‐UN pups showed a very distinct pattern, with lower absorbance values than for the other 3 experimental groups (PS‐IN, PD‐IN. PD‐UN). Moreover, the NIR spectral profile of PS‐UN pups differed from PS‐IN pups in Region 1:4 and Region 3:6 and the profile of PS‐IN pups differed from PD‐IN pups in a single ration Region 2:6. Infection resulted in differences for one single region, Region 5, and six (6) spectral region ratios: Region 1:4, Region 2:3, Region 2:3, Region 3:5, Region 3:6, Region 6:7, Region 7:8 whereas protein deficiency resulted in differences for 2 ratios: Region 2:6 and Region 2:7.ConclusionThese results demonstrate that NIR spectral regions, despite their small absorbance in the studied region, change between healthy and unhealthy mice suffering a chronic nematode (H.bakeri) infection, as well as a single nutrient deficiency, such as PD. These results show that metabolomic responses of the neonate to either maternal gastrointestinal nematode infection and/or maternal dietary protein deficiency differ, implying that the nursing pups, who were not directly exposed to either condition, continue to alter their metabolism throughout the duration of the maternal exposure to both stressors. The long‐term consequences of these adaptations require further exploration.Support or Funding InformationNSERC, CIHR, SENACYT