Changes in Muscle Mass and Composition by Exercise and Hypoxia as Assessed by DEXA in Mice

Abstract

Background and Objective: Skeletal muscle is critical for overall health and predicts quality of life in several chronic diseases, thus quantification of muscle mass and composition is necessary to understand how interventions promote changes in muscle quality. The purpose of this investigation was to quantify changes in muscle mass and composition in two distinct pre-clinical models of changes in muscle quality using a clinical dual X-ray absorptiometry (DEXA), validated for use in mice. Materials and Methods: Adult C57Bl6 male mice were given running wheels (RUN; muscle hypertrophy) or placed in hypobaric hypoxia (HH; muscle atrophy) for four weeks. Animals received weekly DEXA and terminal collection of muscle hind limb complex (HLC) and quadriceps weights and signaling for molecular regulators of muscle mass and composition. Results: HH decreased total HLC muscle mass with no changes in muscle composition. RUN induced loss of fat mass in both the quadriceps and HLC. Molecular mediators of atrophy were upregulated in HH while stimulators of muscle growth were higher in RUN. These changes in muscle mass and composition were quantified by a clinical DEXA, which we described and validated for use in pre-clinical models. Conclusions: RUN improves muscle composition while HH promotes muscle atrophy, though changes in composition in hypoxia remain unclear. Use of the widely available clinical DEXA for use in mice enhances translational research capacity to understand the mechanisms by which atrophy and hypertrophy promote skeletal muscle and overall health.

The Effects of a Western Diet vs. a High-Fiber Unprocessed Diet on Health Outcomes in Mice Offspring

“…The offspring weights were measured immediately post sacrifice. For the DEXA measures, the mice were subjected to anesthesia (isoflurane), bound to a plastic sheet, and scanned; the measures were in grams and documented as ‘lean mass’ and ‘fat mass’ totals [ 53 ]. The dams underwent DEXA scans prior to copulation and prior to sacrifice.…”

Hypoxia as a Double-Edged Sword to Combat Obesity and Comorbidities

“…A combination of exercise and hypoxic exposure is proposed to be a promising complementary treatment for obesity [ 232 , 233 , 234 ] as exercise effectively ameliorates obesity and improves systemic metabolism [ 235 , 236 , 237 ]. Mackenzie et al [ 238 ] showed that when patients with type II diabetes, overweight, or obesity underwent a 60-min exercise test under hypoxic conditions (an inhaled oxygen fraction of 0.146), the glucose tolerance and peripheral insulin sensitivity were improved within the following 4 h as compared with patients who underwent normoxia exercise.…”