Characterization of milk oligosaccharide and sialic acid content and their influence on brain sialic acid in a lean mouse model for gestational diabetes

Abstract

Oligosaccharides and sialic acids (Sia) are bioactive components in milk that contribute to newborn development and health. Hyperglycemia in pregnancy (HIP) can have adverse effects on both mother and infant. HIP is associated with low-grade systemic inflammation. Inflammation influenced glycan composition, particularly of Sia-containing structures. We hypothesize that HIP and high-fat diet influence milk oligosaccharide composition, particularly sialylated oligosaccharides. Furthermore, we propose that milk Sia content influences pup brain Sia content. To test these hypotheses we (i) characterize mouse milk oligosaccharides and Sia concentrations in mouse milk of a GDM mouse model with dietary fat intake intervention; and (ii) determine Sia levels in offspring brains. The concentrations of oligosaccharides and Sia in mouse milk and offspring's brains were quantified using UPLC-FLD analysis. Analyses were performed on surplus samples from a previous study, where HIP was induced by combining high-fat diet (HF) feeding and low-dose streptozotocin injections in C57Bl/6NTac female mice. The previous study described the metabolic effects of HIP on dams and offspring. We detected 21 mouse milk oligosaccharides, including 9 neutral and 12 acidic structures using UPLC-MS. A total of 8 structures could be quantified using UPLC-FLD. Maternal HIP and HF diet during lactation influenced sialylated oligosaccharide concentrations in mouse milk and total and free sialic acid concentrations. Sia content in offspring brain was associated with total and free Neu5Gc in mouse milk of dams, but no correlations with HIP or maternal diet were observed.

Keywords: Brain; Gestational diabetes mellitus (GDM); Mouse milk; Oligosaccharides; Pre-gestational diabetes (PDM); Sialic acids (sia).

Graphical abstract

Fig. 1

Animals study design. Seven groups were developed in this study, including LF, HF-LF, HF–HF, PDM-LF, PDM-HF, GDM-LF, and GDM-HF. In total, mouse milk (n = 51) was collected from dams (n = 51) and the brain tissue (n = 121) was collected from offspring (n = 121). There are 7 GDM-LF and 7 GDM-HF dams recovered at PN 15.

Fig. 2

UHPLC profiles of oligosaccharides in (a) human milk. (b) Mouse milk.

Fig. 3

(a) The concentration of oligosaccharides in LF (HF-LF, GDM-LF, PDM-LF) and HF (HF–HF, GDM-HF, PDM-HF) groups. (b) The concentration of oligosaccharides in control (LF, HF), GDM (LF, HF), and PDM (LF, HF) groups. Blue points = low-fat diet during lactation, red points = high-fat diet during lactation. One-way ANOVA followed by Tukey's multiple comparison test (LF) or Kruskal Wallis followed by Dunn's multiple comparison test (HF) were used. *p < 0.05, **p < 0.01.

Fig. 4

(a) The concentration of total Sia (Neu5Ac, Neu5Gc, Kdn) in mouse milk. (b) The concentration of free Sia (Neu5Ac, Neu5Gc, Kdn) in mouse milk. (c) The percentage of free and bound Sia in total milk Sia. Os, oligosaccharides. (d) The concentration of total Sia (Neu5Ac, Neu5Gc, Kdn) in mouse brain. Blue points = male pups, red points = female pups. (e) The percentage of total Neu5Ac, Neu5Gc, and Kdn in mouse brain Sia.

Fig. 5

(a) The concentration of total milk Sia (Neu5Ac, Neu5Gc, Kdn) in LF (HF-LF, HIP-LF) and HF (HF–HF, HIP–HF) groups. (b) The concentration of free milk Sia (Neu5Ac, Neu5Gc, Kdn) in LF (HF-LF, HIP-LF) and HF (HF–HF, HIP–HF) groups. (c) The concentration of total milk Sia in control (LF, HF) and HIP (LF, HF) groups. (d) The concentration of free milk Sia in control (LF, HF) and HIP (LF, HF) groups. Blue points = low-fat diet during lactation, red points = high-fat diet during lactation. Black points = PDM mice. One-way ANOVA followed by Tukey's multiple comparison test (Total Sia, Neu5Ac, Neu5Gc) or Kruskal Wallis followed by Dunn's multiple comparison test (Free Sia, Neu5Ac, Neu5Gc, Kdn, total Kdn) were used. *p < 0.05, **p < 0.01.

Fig. 6

(a) The concentration of total brain Sia (Neu5Ac, Neu5Gc, Kdn) in LF (HF-LF, HIP-LF) and HF (HF–HF, HIP–HF) groups. (b) The concentration of total brain Sia (Neu5Ac, Neu5Gc, Kdn) in control (LF, HF) and HIP (LF, HF) groups. Blue points = low-fat diet during lactation, red points = high-fat diet during lactation. Kruskal Wallis followed by Dunn's multiple comparison test was used. *p < 0.05