Alaska Backcountry Expeditionary Hunting Promotes Exceptional Rates Of Muscle Protein Synthesis

Abstract

Our Alaskan Backcountry Expeditionary Hunting (ABEH) paradigm represents an 8-14 day unscripted, remote expedition in the uninhabited Brooks Range. Despite negative energy balance (i.e., -9.7 ± 3.4 MJ/day) and significant weight loss (Δ-1.5 ± 0.7 kg) largely influenced by high levels of energy expenditure (i.e., 17.4 ± 2.6 MJ/day), participants retained skeletal muscle as determined by magnetic resonance imaging and lean tissue mass as indicated by dual energy x-ray absorptiometry. Preliminary evidence from these investigations demonstrated an increase in skeletal muscle follistatin-like protein 1, potentially enhancing the anabolism of skeletal muscle. PURPOSE: To determine integrated rates of skeletal muscle protein synthesis throughout the ABEH paradigm that may be relevant to skeletal muscle preservation. METHODS: The use of the virtual biopsy method was employed via 2H2O dosing and liquid chromatography/tandem mass spectrometry analysis to evaluate fractional synthetic rates (FSR) of muscle proteins in four participants (2 females [28 and 62 yr; 66.2 and 71.8 kg; 25.5 and 26.7 kg/m2] and 2 males [47 and 56 yr; 87.5 and 91.4 kg; 26.1 and 28.3 kg/m2]). RESULTS: As an indicator of skeletal muscle synthesis, mean FSR of serum carbonic anhydrase and creatine kinase M-type was 2.4% per day (range: 1.3-5.1% per day) and 4.0% per day (range: 1.4-8.2% per day), respectively. CONCLUSION: Our preliminary findings suggest that the ABEH-induced alterations in skeletal muscle FSR in our cohort are ~four-fold higher than reported in young individuals at baseline and ~ two-fold higher than after 3 weeks of exhaustive sprint interval training. Therefore, chronic mechanical overload may promote a sustained increase in the FSR of skeletal muscle despite limited nutritional provisions and negative energy balance. Research was supported by Pristine Ventures, Inc. Funding was also provided by an Institutional Development Award (IDeA) from the National Institute of General Medical Sciences of the National Institutes of Health under grant number 2P20GM103395 and Sloan Foundation Fellowship to Mr. Brandon Kowalski. The content is solely the responsibility of the authors and does not necessarily reflect the official views of the NIH and/or the Sloan Foundation.