Sarcolipin expression in human skeletal muscle: influence of energy balance and exercise

Abstract

Sarcolipin (SLN) is a SERCAs uncoupling protein associated with exercise performance and lower adiposity in mice. To determine SLN protein expression in human skeletal muscle and its relationship with adiposity, resting energy expenditure (REE), and performance, SLN was assessed by Western blot in 199 biopsies from two previous studies. In one study, 15 overweight volunteers underwent a pre‐test followed by four days of caloric restriction and exercise (45min one‐arm cranking + 8h walking), and three days on a control diet. Muscle biopsies were obtained from the trained and non‐exercised deltoid, and vastus lateralis (VL). In another study, 16 men performed seven sessions of 4‐6x30‐sec all‐out sprints on the cycle ergometer with both limbs, and their VL and triceps brachii biopsied pre‐ and post‐training. SLN expression was two‐fold and 44% higher in the VL than in the deltoids and triceps brachii, respectively. SLN was associated neither with adiposity nor REE, and was not altered by a severe energy deficit (5,500 kcal/d). SLN and cortisol changes after the energy deficit were correlated (r=0.38, P=0.039). SLN was not altered by low‐intensity exercise in the overweight subjects, whereas it was reduced after sprint training in the other group. The changes in SLN with sprint training were inversely associated with the changes in gross efficiency (r=‐0.59, P=0.016). No association was observed between aerobic or anaerobic performance and SLN expression. In conclusion, sarcolipin appears to play no role in regulating the fat mass of men. Sprint training reduces sarcolipin expression, which may improve muscle efficiency.