Posttraumatic skeletal muscle proteolysis: The role of the hormonal environment

Abstract

To investigate the role of hormones as mediators of net skeletal muscle proteolysis following injury, healthy normal male volunteers received a continuous 76-hour infusion of the 3 "stress" hormones: hydrocortisone, glucagon, and epinephrine. As a control, each subject received a saline infusion during another 4-day period. Ten paired studies were conducted. Diets were constant and matched on both occasions. Triple hormone infusion achieved hormone concentrations similar to those seen following mild-moderate injury. After 72 hours of infusion, skeletal muscle intracellular glutamine concentrations were lower in the hormone studies than in the control group (N = 4). Free amino acid concentrations in arterial whole blood and forearm amino acid effiux were little affected by hormonal infusion. Thus, alteration of the hormonal environment by the triple hormone infusion was not a sufficient stimulus to induce all of the changes in skeletal muscle proteolysis observed in critical illness. Since studies utilizing neurohormonal blockade have shown diminished net muscle proteolysis, the stress hormones appear to be necessary but not sufficient for the protein catabolic response to injury.

Urinary Cortisol and Catecholamine Excretion after Burn Injury in Children

“…Large increases in cortisol levels have also been shown to increase net protein breakdown of skeletal muscle (19) and increase efflux of intracellular amino acids (17). Increases in catecholamines lead to a hyperdynamic circulation (34), loss of lean body mass (35), and increased lipolysis (25), principally in the periphery leading to increases in fatty deposition of the liver (36). However, little is known about the magnitude of increase in either catecholamines or cortisol or indeed when they return to more normal levels.…”

The Catabolic Effects of Prolonged Inactivity and Acute Hypercortisolemia Are Offset by Dietary Supplementation

“…Nevertheless, although previous acute studies have provided a cocktail of hormones (e.g. hydrocortisone, glucagon, and epinephrine) to more closely represent the variety of hormonal changes associated with injury (37,38), it appears that hypercortisolemia is primarily responsible for increased muscle protein catabolism (1,39).…”

Gene expression profiles and protein balance in skeletal muscle of burned children after β-adrenergic blockade

“…Typical features of the response include increased body temperature, recruitment of neutrophils, changes in lipid metabolism, increased gluconeogenesis, and stimulation of protective pathways such as coagulation and complement activation, hormonal changes, and increased muscle catabolism (32). These changes lead to increased energy expenditure and futile substrate cycling, with depletion of nutritional and functional fat and protein stores (5,30). Protein catabolism is increased after a severe burn, leading to a breakdown of functional structural proteins that results in the loss of lean muscle mass (10,21).…”