Abstract 292 – Evaluating hemoglobin A1c for use as a nutritional and reproductive biomarker for free-ranging polar bears (Ursus maritimus)

Sarah Teman, Erin Curry, Todd Atwood, Emily Virgin, Karyn Rode, Louisa Rispoli,
Victoria Hope, Kristin Laidre

For polar bears (Ursus maritimus), access to prey is important for nutritional health and
reproductive success. Polar bears in Alaska and western Canada’s southern Beaufort Sea (SB)
have been adversely affected by the loss of sea ice habitat needed to hunt their seal prey.
Springtime foraging is critical for SB bears to gain mass prior to the summer sea-ice retreat,
when access to seals is reduced, and is especially significant for adult females (AF) with cubs-of-
the-year (COY), as they recently emerged from a maternal den and underwent a months-long
fast. During spring field research, it is visually difficult to discern whether a female observed
without cubs was nonreproductive or had denned and experienced litter loss (LL); however,
fasting can be used to infer LL. The current method to assess fasting, the urea-to-creatinine
(UC) ratio, references a temporal window of at least 1-2 weeks. By contrast, hemoglobin A1c
(HbA1c) is a measure of average blood glucose over recent months and may have value as a
longer-term indicator of fasting or nutritional stress. Our objective was to evaluate HbA1c in
fasted vs. non-fasted polar bears. We hypothesized that fasted AF would have greater HbA1c
due to insulin resistance during fasting. We validated a commercial ELISA kit (Human
Hemoglobin A1c: Abcam) using whole blood samples from zoo polar bears. Assay validation
included assessing parallelism between the sample and standard curve, linearity of dilution, and
spike-and-recovery. We compared HbA1c between SB bears that recently fasted (spring-
captured [SC] AF with COY; n=30) to those that did not fast (SC AF with 1- or 2-year-old cubs;
n=36). Preliminary results indicate no difference in HbA1c between the groups (non-fasted:
1.92x106 ± 9.7x104 ng/mL vs. fasted: 1.94x106 ± 1.3x105 ng/mL; Welch’s t-test: p= 0.90). To
our knowledge, this is the first validation of HbA1c for ursids. This study may enhance our
understanding of insulin resistance in fasting polar bears.