Insulin action on muscle protein kinetics and amino acid transport during recovery after resistance exercise.

Abstract

We have determined the individual and combined effects of insulin and prior exercise on leg muscle protein synthesis and degradation, amino acid transport, glucose uptake, and alanine metabolism. Normal volunteers were studied in the postabsorptive state at rest and about 3 h after a heavy leg resistance exercise routine. The leg arteriovenous balance technique was used in combination with stable isotopic tracers of amino acids and biopsies of the vastus lateralis muscle. Insulin was infused into a femoral artery to increase the leg insulin concentrations to high physiologic levels without substantively affecting the whole-body level. Protein synthesis and degradation were determined as rates of intramuscular phenylalanine utilization and appearance, and muscle fractional synthetic rate (FSR) was also determined. Leg blood flow was greater after exercise than at rest (P<0.05). Insulin accelerated blood flow at rest but not after exercise (P<0.05). The rates of protein synthesis and degradation were greater during the postexercise recovery (65+/-10 and 74+/-10 nmol x min(-1) x 100 ml(-1) leg volume, respectively) than at rest (30+/-7 and 46+/-8 nmol x min(-1) x 100 ml(-1) leg volume, respectively; P<0.05). Insulin infusion increased protein synthesis at rest (51+/-4 nmol x min(-1) x 100 ml(-1) leg volume) but not during the postexercise recovery (64+/-9 nmol x min(-1) x 100 ml(-1) leg volume; P<0.05). Insulin infusion at rest did not change the rate of protein degradation (48+/-3 nmol x min(-1) 100 ml(-1) leg volume). In contrast, insulin infusion after exercise significantly decreased the rate of protein degradation (52+/-9 nmol x min(-1) x 100 ml(-1) leg volume). The insulin stimulatory effects on inward alanine transport and glucose uptake were three times greater during the postexercise recovery than at rest (P<0.05). In contrast, the insulin effects on phenylalanine, leucine, and lysine transport were similar at rest and after exercise. In conclusion, the ability of insulin to stimulate glucose uptake and alanine transport and to suppress protein degradation in skeletal muscle is increased after resistance exercise. Decreased amino acid availability may limit the stimulatory effect of insulin on muscle protein synthesis after exercise.

Assessment of skeletal muscle proteolysis and the regulatory response to nutrition and exercise

“…Additionally, some research suggests that protein consumption may attenuate muscle proteolysis, as physiologic hyperinsulinemia and amino acid administration were observed to lower resting and post-resistance exercise kinetic measures of muscle protein degradation and 3-methylhistidine excretion (57)(58)(59)(60).…”

Role of insulin in the regulation of human skeletal muscle protein synthesis and breakdown: a systematic review and meta-analysis

“…Other data From the articles reviewed, 15 studies used three-pool data [21,25,28,[30][31][32][33][34][35]. Two-pool data from ten of these studies were included in the meta-analysis, which by and large reported similar results with quantitatively different displays.…”

“…Two-pool data from ten of these studies were included in the meta-analysis, which by and large reported similar results with quantitatively different displays. All five studies that exclusively reported three-pool data showed that insulin improved NB protein acquirement [25,[33][34][35]. The increment in NB in these studies was primarily driven by either a reduction in MPB [34] or an increase in MPS [25,[33][34][35].…”

The Effect of a Carbohydrate and Protein Supplement on Resistance Exercise Performance, Hormonal Response, and Muscle Damage

“…Research indicates that insulin acts both through increasing rates of protein synthesis and by decreasing rates of protein breakdown to reduce muscle damage following resistance exercise (1,3,26). Biolo et al (3) have shown that insulin is strongly anabolic postexercise and can reduce muscle protein breakdown.…”