Reduced resting skeletal muscle protein synthesis is rescued by resistance exercise and protein ingestion following short-term energy deficit

Abstract

Postabsorptive rates of MPS were 27% lower in ED than EB (P Ͻ 0.001), but REX stimulated MPS to rates equal to EB. Ingestion of 15 and 30 g of protein after REX in ED increased MPS ϳ16 and ϳ34% above resting EB (P Ͻ 0.02). p70 S6K Thr 389 phosphorylation increased above EB only with combined exercise and protein intake (ϳ2-7 fold, P Ͻ 0.05). In conclusion, short-term ED reduces postabsorptive MPS; however, a bout of REX in ED restores MPS to values observed at rest in EB. The ingestion of protein after REX further increases MPS above resting EB in a dose-dependent manner. We conclude that combining REX with increased protein availability after exercise enhances rates of skeletal muscle protein synthesis during short-term ED and could in the long term preserve muscle mass. body composition; fat-free mass; myofibrillar protein synthesis; weight loss ENERGY DEFICIT (ED) can be achieved through reduced energy intake and/or increased energy expenditure and subsequently leads to loss of fat mass (FM). A reduction in FM is a goal for improved health (19, 33); however, when achieved by energy restriction alone, it typically results in the concomitant weight loss comprised of ϳ25% fat-free mass (FFM) (52), of which skeletal muscle is the main component (37,39). Given that the quality and quantity of skeletal muscle is a major determinant of whole body metabolic rate and functional capacity throughout the lifespan (25), nutritional and exercise strategies to prevent or minimize loss of FFM while losing fat mass are crucial.Pasiakos et al. (41) reported a 19% reduction in basal rates of mixed-muscle protein synthesis in young healthy males and females after 10 days of ED (ϳ500 kcal/day). In contrast, a more recent study from Pasiakos et al. (40) found no decrease in rates of resting muscle protein synthesis after 30 days of moderate ED. If a potential decrease in basal rates of muscle protein synthesis was not accompanied by a concomitant reduction in muscle protein breakdown, then ED would presumably result in a marked loss of skeletal muscle protein. Indeed, prolonged ED-induced body weight loss can be comprised of up to 60% FFM (40). In contrast, exercise has been shown to attenuate the loss of lean body tissue that typically occurs with periods of ED alone (50). However, it is currently unknown whether the anabolic effects of resistance exercise (REX) are attenuated during periods of ED.Provision of dietary amino acids increases skeletal muscle protein synthesis, an effect that is enhanced by prior REX (3, 36). To date, only one study has examined whether skeletal muscle exhibits "anabolic resistance" to exercise and protein ingestion following short-term ED (40). However, in that investigation, rates of mixed-muscle protein synthesis and not myofibrillar protein synthesis (MPS; i.e., the contractile protein fraction of muscle) were measured. Furthermore, there was no examination of the impact of exercise, and the cohort under investigation was comprised mainly of males. Hence, the primary aim of the current study was...

Effects of skeletal muscle energy availability on protein turnover responses to exercise

“…However, the magnitude to which energy deficit affects post-REX MPS responses has received little attention. Recently, we showed that REX undertaken subsequent to a 5 day, moderate (∼500 kcal day −1 ) energy deficit, which lowered resting MPS by 27% compared with resting energy balance, only increased MPS to the rate originally observed at rest when subjects were in energy balance (Areta et al, 2014). Post-exercise whey protein provision in graded amounts of either 15 or 30 g augmented MPS and prolonged mTOR phosphorylation in a dose-responsive manner, demonstrating that the energy deficit-induced repression of MPS is relieved with a larger supply of exogenous amino acids.…”

“…As MPS is energetically expensive, it is hardly surprising that periods of energy deficit attenuate resting-, fasted- (Areta et al, 2014;Murphy et al, 2015;Pasiakos et al, 2010) and feedinginduced MPS (Murphy et al, 2015;Pasiakos et al, 2013). However, the magnitude to which energy deficit affects post-REX MPS responses has received little attention.…”

Modulation of autophagy signaling with resistance exercise and protein ingestion following short-term energy deficit

“…Fifteen (8 males, 7 females) young, healthy, resistance-trained subjects [male: age 27 Ϯ 5 yr, body mass (BM) 82.7 Ϯ 6.6 kg, leg press 1-repetition maximum (1-RM) 300 Ϯ 70 kg; female: age 28 Ϯ 4 yr, BM 70.3 Ϯ 7 kg, 1-RM 200 Ϯ 28 kg; values are means Ϯ SD] were recruited in a previous study (2). Subjects were advised of any possible risks associated with the study prior to providing written informed consent.…”

“…Periods of energy deficit (ED) are associated with losses of lean body mass (35), and we (2) and others (44) have demonstrated that short-term ED through dietary restriction reduces postabsorptive rates of MPS compared with energy balance (EB). The protein degradation signaling pathways underlying this increased MPB response are not well characterized, although increased mRNA expression of ubiquitin proteasomal system (UPS) markers have been reported following short-term ED (9,10).…”

A 7-day high protein hypocaloric diet promotes cellular metabolic adaptations and attenuates lean mass loss in healthy males

“…During hypocaloric diet-induced weight loss approximately 20e30% of mass lost is lean mass (LM) [1], increasing dietary protein is one method which has been demonstrated to attenuate skeletal muscle atrophy in a hypocaloric state [35]. The manipulation of carbohydrate intake as a regulator of weight maintenance/loss is well documented demonstrating improved lipid profile and fat oxidation [2,12].…”