Water-soluble vitamin homeostasis in fasting northern elephant seals (Mirounga angustirostris) measured by metabolomics analysis and standard methods

Abstract

Despite the importance of water-soluble vitamins to metabolism, there is limited knowledge of their serum availability in fasting wildlife. We evaluated changes in water-soluble vitamins in northern elephant seals, a species with an exceptional ability to withstand nutrient deprivation. We used a metabolomics approach to measure vitamins and associated metabolites under extended natural fasts for up to 7 weeks in free-ranging lactating or developing seals. Water-soluble vitamins were not detected with this metabolomics platform, but could be measured with standard assays. Concentrations of measured vitamins varied independently, but all were maintained at detectable levels over extended fasts, suggesting that defense of vitamin levels is a component of fasting adaptation in the seals. Metabolomics was not ideal for generating complete vitamin profiles in this species, but gave novel insights into vitamin metabolism by detecting key related metabolites. For example, niacin level reductions in lactating females were associated with significant reductions in precursors suggesting downregulation of the niacin synthetic pathway. The ability to detect individual vitamins using metabolomics may be impacted by the large number of novel compounds detected. Modifications to the analysis platforms and compound detection algorithms used in this study may be required for improving water-soluble vitamin detection in this and other novel wildlife systems.

Fig. 1

Serum pantothenic acid concentrations of lactating females and weaned pups across their respective fasts. Diagonal fill = early lactation or early fast. No fill = late lactation or late fast. Like letters denote significant differences (p < 0.05).

Fig. 2

Serum ascorbate concentrations of lactating females and weaned pups across their respective fasts. Diagonal fill = early lactation or early fast. No fill = late lactation or late fast. There were no significant differences (p < 0.05) found.

Fig. 3

Serum niacin concentrations of lactating females and weaned pups across their respective fasts. Niacin concentrations varied between fasting groups (p < 0.01). Diagonal fill = early lactation or early fast. No fill = late lactation or late fast. Like letters denote significant differences (p < 0.05).

Fig. 4

Serum vitamin B₁₂ concentrations of lactating females and weaned pups across their respective fasts. Diagonal fill = early lactation or early fast. No fill = late lactation or late fast. Like letters denote significant differences (p < 0.05).