Alaska Backcountry Expeditionary Hunting Promotes Sustained Muscle Protein Synthesis

INTRODUCTION

We have previously described negative energy balance (ie, -9.7±3.4 MJ/d) and weight loss (Δ-1.5 ± 0.7 kg) influenced by high levels of energy expenditure (ie, 17.4±2.6 MJ/d) during remote expeditionary hunting in Alaska. Despite negative energy balance, participants retained skeletal muscle. The purpose of this pilot study was to measure skeletal muscle protein synthesis and examine molecular markers of skeletal muscle protein metabolism under similar conditions of physical and nutrient stress.

METHODS

The "virtual biopsy method" was used to evaluate integrated fractional synthetic rates (FSRs) of muscle protein from blood samples in 4 participants. Muscle biopsies were taken to measure molecular markers of muscle protein kinetics (ie, FSTL1, MEF2, MYOD1, B2M, and miR-1-3p, -206, -208b, 23a, and 499a) using real-time polymerase chain reaction.

RESULTS

Our findings in 4 participants (2 females [28 and 62 y of age; 66.2 and 71.8 kg body weight; 25.5 and 26.7 kg/m2 body mass index] and 2 males [47 and 56 y of age; 87.5 and 91.4 kg body weight; 26.1 and 28.3 kg/m2 body mass index]) describe mean muscle FSRs of serum carbonic anhydrase (2.4%) and creatine kinase M-type (4.0%) and positive increments in molecular regulation.

CONCLUSIONS

Preservation of skeletal muscle under conditions of physical and nutrient stress seems to be supported by positive inflection of skeletal muscle FSR and molecular activation.

Essential amino acid enriched meal replacement improves body composition and physical function in obese older adults: A randomized controlled trial

BACKGROUND

Older adults are threatened by the risk of muscle atrophy and excess accumulation of adipose tissue. The objective of this study was to determine whether an essential amino acid enriched meal replacement would reduce excess fat and foster skeletal muscle retention, potentially improving physical function in this cohort.

METHODS

Using a double blind, randomized controlled trial, we compared the influence of an experimental meal replacement enriched with essential amino acids (EMR) to a commercially available, widely used meal replacement (Optifast®) provided once/day (q.d.) for four weeks on body composition, skeletal muscle and physical function in obese older participants. Twenty-eight individuals completed either EMR (n = 13) or Optifast® (n = 15) supplementation protocols. Measurements of body composition, thigh skeletal muscle cross-sectional area (CSA), blood panels, intrahepatic lipid, and physical function were completed pre- and post-supplementation.

RESULTS

Body fat mass, visceral fat mass and volume, and intrahepatic lipid were reduced with EMR but not with Optifast®. Thigh muscle CSA increased (Δ 2.4 ± 3.0 cm²) with EMR but not Optifast® (Δ -1.8 ± 6.0 cm²). There was a significant increase in the distance covered during the 6-min walk test with EMR (Δ 23 ± 27 m) but no change in Optifast® (Δ 11 ± 37 m).

CONCLUSIONS

Beneficial alterations in fat and muscle support the use of EMR-based meal replacements in obese older adults.

CLINICAL TRIAL REGISTRATION

ISRCTN registry under Reference Number ISRCTN15814848.

Equivalent servings of free-range reindeer promote greater net protein balance compared to commercial beef

Wild game consumption has been associated with health benefits but the acute influence on human protein metabolism remains unknown. We compared feeding-induced responses of equivalent amounts of free-range reindeer (FR) and commercial beef (CB) on protein kinetics using stable isotope methodology. Seven participants (age: 40 ± 14 years; body mass index: 24 ± 3 kg/m2) completed two randomised studies, ingesting 2 oz of FR or CB. L-[ring 2H5]phenylalanine & L-[ring 2H2]tyrosine were delivered via primed, continuous intravenous infusion. Blood samples were collected during the basal period and following consumption of FR or CB. Feeding-induced changes in whole-body protein synthesis (PS), protein breakdown (PB), and net protein balance (NB) were determined via plasma sample isotope enrichment analysis by gas chromatography-mass spectrometry; plasma essential amino acid (EAA) concentrations were determined by liquid chromatography-electrospray ionisation-mass spectrometry. Plasma post-prandial EAA concentrations were higher with FR compared to CB (P < 0.05). The acute feeding-induced PS response was not different, but PB was reduced and contributed to a superior level of NB (P < 0.00001) in FR compared to CB. Our results demonstrate that FR may influence more favourable protein metabolism than CB. These data support potential health benefits of wild game onf whole-body protein.Abbreviations: BMI: body mass index; DIAAS: digestible indispensable amino acid score; CB: commercial beef; EAA: essential amino acids; FR: free-range reindeer; Ra: rate of appearance; UAF: University of Alaska Fairbanks; USDA: USA Department of Agriculture.

Alaska backcountry expeditionary hunting promotes rapid improvements in metabolic biomarkers in healthy males and females

We have previously reported negative energy balance and health benefits during an Alaska backcountry expeditionary hunting (ABEH) immersion in two males. The purpose of our present study was to increase the number of participants, include females, and evaluate macronutrient intake and serum lipids. Four men (age: 46 ± 6 year, BMI: 26 ± 1 kg/m2 ) and three women (age: 46 ± 11 year, BMI: 25 ± 3 kg/m2 ) were recruited. Doubly labeled water methodology and dietary recall were utilized to assess energy expenditure and energy intake, respectively. Data were collected during pre- and post-ABEH visits. Body composition was measured using dual-energy x-ray absorptiometry and the cross-sectional area of skeletal muscle in the upper leg (XT), and intrahepatic lipid (IHL) was determined using magnetic resonance imaging and/or spectroscopy (MRI/MRS). Blood parameters were measured by LabCorp. Paired T-tests were used for statistical analysis. Data are reported as mean ± SD and considered significant at p < 0.05. Total energy intake was 7.7 ± 3.4 MJ/day and total energy expenditure was 17.4 ± 2.6 MJ/day, resulting in a negative energy balance of -9.7 ± 3.4 MJ/day. Protein intake(grams)/body weight(kilograms)/day was 1.0 ± 0.4. There were reductions in body weight (Δ-1.5 ± 0.7 kg), BMI (Δ-0.3 ± 0.2 kg/m2 ), fat mass (Δ-1.7 ± 0.9 kg), and IHL (Δ-0.3 ± 0.3% water peak). There were no changes in lean tissue mass (Δ0.6 ± 1.4 kg) or XT (Δ-1.3 ± 3.3 cm2 ). There were significant reductions in total cholesterol (Δ-44 ± 35 mg/dl), LDL-cholesterol (Δ-25 ± 14 mg/dl), VLDL-cholesterol (Δ-7 ± 7 mg/dl), and triglycerides (Δ-35 ± 33 mg/dl). The ABEH immersion resulted in considerable negative energy balance and provided comprehensive benefits in metabolic health without any reduction in skeletal muscle.

Negative Energy Balance Does Not Alter Fat-Free Mass During the Yukon Arctic Ultra-The Longest and the Coldest Ultramarathon

Purpose: The objective of this study was to determine alterations in caloric balance, body composition, metabolites, and cytokines in athletes participating in the Yukon Arctic Ultra.

Methods: Ten participants traveling on foot in the 2017 692-km event were recruited for the study. Measurements and samples were obtained at pre-event, 278 km (C1), 384 km (C2), and post-event. Body composition measurements were obtained using bioelectrical impedance analysis. Accelerometer devices were utilized to provide an estimation of caloric expenditure and dietary recalls provided assessments of caloric intake. Blood serum samples were collected, processed, and analyzed using enzyme-linked immunosorbent assays or nuclear magnetic resonance. Results were analyzed using linear mixed model, presented as means ± SD, and considered significant at p < 0.05.

Results: Participants (8 males, 2 females; age: 37 ± 10 years; body mass index: 24.4 ± 2.5 kg/m²) were recruited. Four males and one female completed the entire event in 260 ± 19 h. Caloric intake/expenditure was 4,126 ± 1,115 kcal/day and 6,387 ± 781 kcal/day, respectively, indicating a caloric deficit of 2,261 ± 1,543 kcal/day. Total mass, body mass index, and fat mass were reduced at each time point of the event. Fat-free mass (FFM) was unchanged throughout the event. Follistatin was increased at C1 (1,715 ± 876 pg/ml) in comparison to baseline. Acetoacetate increased significantly at post-event (6.1 ± 1.5 mg/ml).

Conclusions: Despite a pronounced caloric deficit and sustained activity under extreme cold conditions, FFM was preserved with an increase in serum follistatin and acetoacetate. Future studies should be directed at the role of nutrient strategies and/or training methods on the retention of FFM under these conditions.

The energy requirements and metabolic benefits of wilderness hunting in Alaska

The purported healthy aspects of subsistence foods have led to the popularity of the Paleo diet. There has been very little focus, surprisingly, on health benefits derived from the nomadic nature of humans during the Paleolithic era. The purpose of our study was to examine total energy expenditure (TEE), total energy intake (TEI), body composition, blood lipids, and intrahepatic lipid in humans during a 12-day Alaskan backcountry expeditionary hunting (ABEH) immersion. Four healthy men (age: 42 ± 3 year, BMI: 27 ± 1 kg/m2 ) were recruited for the study. TEE was measured using the doubly labeled water method and a food diary was utilized to assess TEI. Body composition was measured using dual energy X-ray absorptiometry (DXA); cross-sectional area of the thigh (XT) and intrahepatic lipid (IHL) were measured using molecular imaging. Blood samples were collected for the measurement of blood lipids. DXA, XT, IHL, and blood data were collected pre- and immediately post-ABEH. Results were analyzed using paired t-tests and considered significant at P < 0.05. TEE and TEI averaged 18.1 ± 1.2 and 9.1 ± 2.5 MJ/day, respectively, indicating substantial negative energy balance (-9.0 ± 1.3 MJ/day). There was a reduction in percent body fat (∆-3.3 ± 0.2%), total fat mass (∆-3.3 ± 0.4 kg), and visceral fat volume (Δ-261 ± 188 cm3 ). Lean tissue mass and XT was unchanged. There was a decrease in IHL (Δ-0.5 ± 0.1% water peak), and a trend (P = 0.055) toward reduction in LDL-cholesterol. We conclude that constancy of physical activity during negative energy balance may provide metabolic benefits above and beyond variations in diet that exist with the hunter-gatherer lifestyle.

Metabolic Responses to the Yukon Arctic Ultra: Longest and Coldest in the World

Purpose

The Yukon Arctic Ultra is considered the longest and coldest ultraendurance event in the world. Cold exposure and exercise has been reported to influence circulating levels of myokines, adipokines, and hepatokines that may influence considerable alterations in the regulation of metabolism. The purpose of the study was to evaluate the influence of the Yukon Arctic Ultra (430-mile event) on potential activators of brown fat, metabolites, and body composition in healthy individuals.

Methods

Eight male and female participants (mean ± SEM: age, 44 ± 3 yr; body mass index, 23.4 ± 0.9) were recruited for participation. Blood samples were collected at pre-event, mid-event, and post-event checkpoints.

Results

The temperature during the event ranged from −45°C to −8°C. Because of these extremely challenging conditions, 50% of the participants withdrew from competition by the 300-mile mark, and those that surpassed 300 miles lost a significant (P = 0.002; P = 0.01) amount of body weight (76 ± 5 kg to 73 ± 4 kg) and fat mass (13 ± 1 kg to 12 ± 3 kg), respectively. With respect to serum irisin, there was a trend (P = 0.06) toward significance from pre-event (1033 ± 88 ng·mL⁻¹), mid-event (1265 ± 23 ng·mL⁻¹) to post-event (1289 ± 24 ng·mL⁻¹). Serum meteorin-like and fibroblast growth factor-21 remained stable throughout the event. There were no changes in creatinine, acetoacetate, acetate, and valine. Serum lactate decreased (P = 0.04) during the event.

Conclusions

The influence of cold exposure and extreme physical exertion may promote substantial increases in serum irisin, and specific alterations in substrate metabolism that largely preserve skeletal muscle and physiological resilience.