Elevation of plasma epinephrine concentrations inhibits proteolysis and leucine oxidation in man via beta-adrenergic mechanisms.

Abstract

The role of elevated plasma epinephrine concentrations in the regulation of plasma leucine kinetics and the contribution of ,8-receptors were assessed in man. Epinephrine (50 ng/kg per min) was infused either alone or combined with propranolol (f,-blockade) into groups of six subjects fasted overnight; leucine flux, oxidation, and net plasma leucine forearm balance were determined during 180 min. Constant plasma insulin and glucagon concentrations were maintained in all studies by infusing somatostatin combined with insulin and glucagon replacements. Plasma leucine concentrations decreased from baseline during epinephrine infusion by 27±5 gmol/liter (P < 0.02) due to a 22±6% decrease in leucine flux (P < 0.05 vs. controls receiving saline) and to an increase in the metabolic clearance rate of leucine (P < 0.02). Leucine oxidation decreased by 36±8% (P < 0.01 vs. controls). fl-Blockade abolished the effect of epinephrine on leucine flux and oxidation. Net forearm release of leucine increased during epinephrine (P < 0.01), suggesting increased muscle proteolysis; the fall of total body leucine flux was therefore due to diminished proteolysis in nonmuscle tissues, such as splanchnic organs. Nonoxidative leucine disappearance as a parameter of protein synthesis was not significantly influenced by epinephrine. Plasma glucose and FFA concentrations increased via f,-adrenergic mechanisms (P < 0.001). The results suggest that elevation of plasma epinephrine concentrations similar to those observed in severe stress results in redistribution of body proteins and exerts a whole body protein-sparing effect; this may counteract catabolic effects of other hormones during severe stress.

Effects of Adiposity and 30 Days of Caloric Restriction Upon Protein Metabolism in Moderately vs. Severely Obese Women

“…Though increment of change in these hormones did not correlate with changes in leucine kinetics, there are some published reports supporting a relationship between these hormones and protein turnover. It has been shown that epinephrine is anti-proteolytic (37, 38) which is supportive of its negative correlation with protein turnover in this study. Additionally, we have previously shown the positive correlation of insulin with protein turnover (39) and conditions of high insulin without suppressed amino acids are considered to be anabolic (40, 41).…”

Effects of adrenaline on lactate, glucose, lipid and protein metabolism in the placebo controlled bilaterally perfused human leg

“…1998). Studies employing somatostatin and subsequent insulin administration to control insulin levels (Kraenzlin et al. 1989, Castellino et al.…”

“…1990), i.e. an overall neutral impact, but one study also observed increased forearm leucine release (Kraenzlin et al. 1989).…”

Acute β-adrenergic stimulation does not alter mitochondrial protein synthesis or markers of mitochondrial biogenesis in adult men

“…It has been recorded that long-term intake of ␤-AR agonists has anabolic effects on skeletal muscle (9). Also, anabolic effects of ␤-AR stimulation (180 min of 50 ng⅐ kg Ϫ1 ⅐min Ϫ1 epinephrine) on WBPT and isolated limbs were reported in healthy males (22,54). In contrast, ␤-AR stimulation is part of the stress response and contributes to increased protein breakdown, as suggested by improved protein retention following ␤-AR blockade in hyper-catabolic burn victims (15).…”

“…Our measures of protein synthesis included skeletal muscle subfractions and whole body protein turnover (WBPT). WBPT can be altered with ␤-AR stimulation and was included to provide a more complete evaluation of protein turnover (22). On the basis of the previous report in mice (30), we hypothesized that 1) ␤-AR stimulation would increase mRNA content of PGC-1␣ and downstream gene targets, and 2) during the recovery period from ␤-AR stimulation, there would be an increase in whole body protein turnover (WBPT), myofibrillar protein synthesis (MyPS), and mitochondrial protein synthesis (MiPS).…”