Maternal Liver Metabolic Response to Chronic Vitamin D Deficiency Is Determined by Mouse Strain Genetic Background

Abstract

Background Liver metabolite levels have the potential to be key biomarkers of systemic metabolic dysfunction and overall health. However, for most conditions we do not know the extent to which genetic differences regulate susceptibility to metabolic responses. This limits our ability to detect and diagnose effects in heterogeneous populations. Objective Here, we investigated the extent to which naturally occurring genetic differences regulate maternal liver metabolic response to vitamin D deficiency, particularly during perinatal periods when such changes can adversely affect maternal and fetal health. Methods We used a panel of eight inbred Collaborative Cross mouse strains, each with a different genetic background (72 dams, 3–6 per treatment group, per strain). We identified robust maternal liver metabolic responses to vitamin D depletion before and during gestation and lactation using a vitamin D deficient (0 IU/kg vitamin D3, VDD) or sufficient diet (1000 IU/kg vitamin D3, VDS). We then identified VDD-induced metabolite changes influenced by strain genetic background. Results We detected a significant VDD effect by OPLS-DA (Q2 = 0.266, pQ2 = 0.002), primarily, altered levels of 78 metabolites involved in lipid, amino acid, and nucleotide metabolism (VIP ≥ 1.5). Metabolites in unsaturated fatty acid and glycerophospholipid metabolism pathways were significantly enriched (FDR < 0.05). VDD also significantly altered levels of putative markers of uremic toxemia, acylglycerols, and dipeptides. The extent of metabolic response to VDD was strongly dependent on genetic strain, ranging from robustly responsive to nonresponsive. Two strains (CC017/Unc and CC032/GeniUnc) were particularly sensitive to VDD, however, each strain altered different pathways. Conclusions These novel findings demonstrate that maternal VDD induces different liver metabolic effects in different genetic backgrounds. Strains with differing susceptibility and metabolic response to VDD represent unique tools to identify causal susceptibility factors and further elucidate the role of VDD-induced metabolic changes in maternal and/or fetal health for ultimately translating findings to human populations.

Genetic regulation of homeostatic immune architecture in the lungs of Collaborative Cross mice

“…In our CC-F1 population, we found ~83% of the variation in their abundance attributable to genetic effects, yet we found no loci associated with this population. The power to map genetic effects is determined by many factors, including the number of loci impacting the disease, and also the gene-environment interactions impacting these cell types (Xue et al, 2020). Our study was designed to minimize environmental variation, such as nutrition, cage and housing effects.…”

Integrative phenotypic and genomic analyses reveal strain-dependent responses to acute ozone exposure and their associations with airway macrophage transcriptional activity

“…Of note, these strains also exhibit statistically significant differences in BAL neutrophilia and injury after exposure to 1 ppm for 3 hours, indicating that similar genetic architecture may contribute to responses along the concentration-response curve (Supplemental Figure 8). Though these strains have been included in previously published studies (84,85), minimal experimental evidence exists to indicate specific functional differences between the two that might account for their divergent responses to O3 exposure. In a study that screened severity of Zika virus infections across 35 CC strains, CC017/Unc was among the strains with low plasma viral load (two days post-infection), whereas CC003/Unc had twice as many plasma viral copies (84).…”

Early life exposure to vitamin D deficiency impairs molecular mechanisms that regulate liver cholesterol biosynthesis, energy metabolism, inflammation, and detoxification

“…Untargeted profiling of whole liver metabolites was performed using mass spectrometry (Metabolon, Inc (37).) as previously described (38). In brief, four distinct mass spectrometry platforms were utilized in order to capture metabolites across a wide range of varying chemical properties: 1) RP/UPLC-MS/MS with acidic positive ion mode electrospray ionization (ESI) for hydrophilic compounds, 2) RP/UPLC-MS/MS with acidic positive ion mode ESI for hydrophobic compounds, 3) RP/UPLC-MS/MS with basic negative ion mode ESI, and 4) HILIC/UPLC-MS/MS with negative ion mode ESI (38).…”

“…as previously described (38). In brief, four distinct mass spectrometry platforms were utilized in order to capture metabolites across a wide range of varying chemical properties: 1) RP/UPLC-MS/MS with acidic positive ion mode electrospray ionization (ESI) for hydrophilic compounds, 2) RP/UPLC-MS/MS with acidic positive ion mode ESI for hydrophobic compounds, 3) RP/UPLC-MS/MS with basic negative ion mode ESI, and 4) HILIC/UPLC-MS/MS with negative ion mode ESI (38). Metabolites were identified based on their spectrum properties, which included criteria such as m/z and retention time/index.…”

“…All data underwent extensive quality control by Metabolon, Inc. to account for sample and instrument variability, including interday differences in instrument tuning. To account for these differences while also maintaining appropriate sample variation, raw data were median normalized (38). Samples with measurements that fell below the limit of quantitation were imputed to the limit of quantitation.…”