One week of bed rest leads to substantial muscle atrophy and induces whole-body insulin resistance in the absence of skeletal muscle lipid accumulation.

Abstract

Short (<10 days) periods of muscle disuse, often necessary for recovery from illness or injury, lead to various negative health consequences. The present study investigated mechanisms underlying disuse-induced insulin resistance, taking into account muscle atrophy. Ten healthy, young males (age: 23±1 y, BMI: 23.0±0.9 kg·m(-2)) were subjected to one week of strict bed rest. Prior to and after bed rest, lean body mass (DXA) and quadriceps cross-sectional area (CSA; CT) were assessed, and VO2peak and leg strength were determined. Whole-body insulin sensitivity was measured using a hyperinsulinemic-euglycemic clamp. Additionally, muscle biopsies were collected to assess muscle lipid (fraction) content and various markers of mitochondrial and vascular content. Bed rest resulted in 1.4±0.2 kg lean tissue loss and a 3.2±0.9% decline in quadriceps CSA (both P<0.01). VO2peak and 1RM declined by 6.4±2.3 (P<0.05) and 6.9±1.4% (P<0.01), respectively. Bed rest induced a 29±5% decrease in whole-body insulin sensitivity (P<0.01). This was accompanied by a decline in muscle oxidative capacity, without alterations in skeletal muscle lipid content or saturation level, markers of oxidative stress, or capillary density. In conclusion, one week of bed rest substantially reduces skeletal muscle mass and lowers whole-body insulin sensitivity, without affecting mechanisms implicated in high-fat diet-induced insulin resistance.