Analysis of an Omega 6:3 Balanced Diet Impact on Hibernation Behavior and Cortisol of Captive Arctic Ground Squirrels

Abstract

Arctic Ground Squirrels (AGS) are widely studied in laboratories for their capability to sustain low metabolic rates and temperatures without enduring debilitating bodily harm. A specific range of omega 6 polyunsaturated fatty acids (PUFAs) has been shown to improve captive hibernation by increasing torpor bout length and depth of hibernation across multiple species (Geiser 1993, Frank 2008). To our knowledge, only three studies have investigated the impact of omega 3 fatty acids on hibernation behavior with varying results (Giroud 2018, Frank 2004 and Hill and Florant 2000). Our prior findings show wild AGS plasma have a balanced omega 6 to 3 fatty acid profile (1.3:1), but no one, to our knowledge, has tested the impact of this specific PUFA ratio on captive AGS. We hypothesize that substituting a high omega 6:3 (8:1) diet for a balanced diet (1.3:1) would increase the length of torpor bouts, entrance timing into hibernation and decrease cortisol.Wild juvenile AGS (12 f, 12 m) were evenly distributed to two groups: a balanced omega 6:3 ratio diet (1.3:1) and a control diet of Mazuri rodent chow with an omega 6:3 ratio of (8:1). Animals were fed 47g daily of their diets until first torpor bout and food was withdrawn. Animals were instrumented with abdominal temperature I‐buttons in early August. White adipose tissue (WAT) and plasma were sampled longitudinally at fall (early August at the time of surgery) and winter (mid‐December at time of euthanasia). Animals were euthanized in three stages of the torpor bout cycle: early torpor, late torpor, and full arousal.WAT was analyzed a modified lipid dense tissue protocol using solid phase extraction. Cortisol was measured using RIA. Early August levels of cortisol were 1.4× higher in the animals supplemented with the balanced omega 6:3 diet (p<0.0001). Preliminary temperature data indicates that the balanced diet and control diet AGS do not significantly differ in the number of hibernation days, entrance timing into hibernation or torpor bout length. Additionally, preliminary data indicates a significant increase in body weight of females on a balanced omega 6:3 diet during fall (p<0.013) and winter (p<0.049).Preliminary data indicates the balanced diet does not negatively impact hibernation behavior. The unexpected increase in cortisol in the balanced omega 6:3 ratio fed diet may reflect normal physiological levels rather than stress. Cortisol functions as a stress indicator, but also enhances fat deposition, which is an essential task prior to hibernation.Support or Funding InformationThis work was supported by NIH 20GM103395, UL1GM118991, TL4GM118992, or RL5GM118990. This work was performed in conformance with the FASEB Statement of Principles for animals used in research.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.