Steroid-binding proteins in primate plasma.

We used immunological techniques to compare the serum corticosteroid-binding globulins (CBG) and testosterone-estradiol-binding globulins (TeBG) of Old World primates (man, chimpanzee, cynomologus, and rhesus), New World monkeys (squirrel and owl), and prosimians (galago and lemur). Four different antihuman TeBG antisera could not differentiate human and chimpanzee TeBG and recognized the galago and lemur TeBG as similar as well as the rhesus and cynomologus TeBG, as similar. Western blots of serum subjected to sodium dodecyl sulfate gel electrophoresis, with detection by an anti-TeBG antiserum, showed similar patterns of distribution of the two molecular species of TeBG for all of the New World primates and the owl monkey. The abundance of the two TeBG species was reversed in squirrel monkey serum, while lemur and galago displayed only a single band. Four different antihuman CBG antisera grouped together the CBGs of human and chimpanzee, rhesus and cynomologus, and lemur and galago. The squirrel monkey has a CBG with a markedly decreased affinity for cortisol; all four antisera perceived its CBG as much more immunologically distant from the human protein than that of the owl monkey. Indeed, three of the four antisera grouped squirrel monkey CBG with that of the prosimians, while one antiserum saw squirrel monkey CBG as even more distant from the human protein than the CBG of the primitive primates, the prosimians.

Plasma cortisol transport and primate evolution.

Primates have diverged into three major evolutionary groups: prosimians, Old World primates, and New World primates; the last group is distinguished by high circulating cortisol concentrations and resistance to the action of glucocorticoids. We have studied a large spectrum of primate species within these groups to characterize the phylogenetic relationships of cortisol-binding globulin (CBG) among them. The CBG in each species was found to be glycosylated, as judged from lectin interactions, and to exhibit an electrophoretic mobility similar to that of human CBG. Although the CBG affinity for cortisol differed among species, the effects of changes in temperature on the CBG affinity were similar. Strikingly, the CBG-binding capacity of plasma in the New World primates was 1/10th to 1/100th those in the Old World primates and prosimians, while the CBG-binding affinity for cortisol was lower. The reduced capacity and affinity of CBG result in a markedly higher fraction of unbound plasma cortisol in the New World primates than in the Old World primates or the prosimian species examined. This evolutionary pattern of CBG may be a compensatory mechanism for the target organ resistance to glucocorticoids that characterizes the New World monkeys.

Transport of steroid hormones: interaction of 70 drugs with testosterone-binding globulin and corticosteroid-binding globulin in human plasma.

This report describes the binding of 70 synthetic compounds to both testosterone-binding globulin (TeBG) and corticosteroid-binding globulin (CBG). The ability of each compound to displace [3H]testosterone from TeBG and [3H]cortisol from CBG adsorbed from a plasma pool onto a solid phase matrix of Concanavalin A-Sepharose was determined under equilibrium conditions at physiological pH and temperature. From these data, the association constants of the compounds for binding to both TeBG and CBG were calculated and used to predict whether endogenous steroid transport would be altered by the therapeutic administration of the drug. Computer simulation predicted that by interacting with TeBG, therapeutic levels of danazol, methyltestosterone, fluoxymesterone, and norgestrel could displace 83%, 48%, 43%, and 16%, respectively, of the concentration of testosterone bound to TeBG in a normal man. Similarly, by interacting with CBG, therapeutic levels of prednisolone could decrease the concentration of cortisol bound to CBG by approximately 32% in both men and women, and despite relatively low affinity binding to TeBG (5 X 10(5) M-1), prednisolone could also displace small amounts of testosterone from TeBG. These results indicate that binding to steroid transport proteins should be considered among the in vivo effects of drugs on endogenous steroid hormone levels.

Hormonal changes in normal men under marginally negative energy balance.

Six men were confined to a metabolic unit for 105 days. Their assigned work and energy intake were varied throughout six metabolic periods in order to create either a marginally negative (-15%) or an equilibrated energy balance. They were fed a defined diet providing a constant amount of protein. At each metabolic period, T4, T3, reverse T3(rT3), free T3, free reverse T3, thyroid-stimulating hormone, cortisol, cortisol-binding globulin, testosterone, and testosterone/estradiol-binding globulin were measured. Free urinary cortisol was measured daily. Results show that serum thyroid hormones are sensitive to marginal changes in energy intake, expenditure, and balance. The ratio T4/T3 appears to be more sensitive to the balance itself, with the ratio T3/rT3 being more sensitive to the intake and expenditure level at which this balance is established. Regulations of T3 and rT3 production are probably distinct. Urinary cortisol did not show any variation that could be related to the energy balance. However, daily urinary cortisol was correlated to daily urinary nitrogen excretion. No change in serum testosterone was found.

Effects of moderate physical training on prednisone-induced protein wasting: a study of whole-body and bone protein metabolism.

This study investigated the possibility of preventing prednisone-induced protein wasting by regular physical activity. Eight healthy untrained volunteers took prednisone (30 mg/d for nine days), once after a 4-week exercise program that consisted of jogging 2.5 miles four times a week, and once without exercise. Whole body protein turnover was measured from the 15N enrichment plateau of urinary ammonia during ingestion of 15N glycine at hourly intervals. Whole-body protein synthesis and breakdown were derived from nitrogen flux, nitrogen intake, and urinary nitrogen elimination. Muscle myofibrillar protein breakdown was explored by measuring urinary 3-methylhistidine excretion. Bone protein metabolism was studied by measuring serum bone GLA protein (BGP), a specific marker of bone protein synthesis, and urinary elimination of hydroxyproline, an index of bone resorption. Whole-body protein turnover was significantly increased by exercise and prednisone (+19% and +17%, respectively); this effect was related to increased protein synthesis during exercise training (+27%, P less than .01) and to increased protein breakdown during prednisone administration without exercise (+21%, P less than .05). In contrast, values of protein turnover, synthesis, and breakdown were not different from control when the subjects took prednisone after training. Urinary excretion of 3-methylhistidine was decreased (-15%, P less than .05) at the end of the prednisone administration period but was identical to the control value when the subjects took prednisone in association with exercise. In contrast, serum BGP was significantly decreased by prednisone, with or without exercise (-35%, P less than .001). These data suggest that moderate exercise training can prevent, at least in part, the protein loss induced by prednisone.(ABSTRACT TRUNCATED AT 250 WORDS)

Improved clinical status and length of care with low-fat nutrition support in burn patients.

BACKGROUND: The optimal amount and type of fat in the nutrition support of burned patients have not been determined. The aim of this study was to test low-fat nutritional solutions, with or without fish oil, on protein metabolism, morbidity, and length of care in severely burned adults. METHODS: In a prospective randomized clinical trial, 43 patients were assigned to one of the following groups: control (35% fat), low-fat solution (ie, 15% of total calories as fat), low-fat with fish oil, given for 30 days. Nitrogen balance, urinary 3-methylhistidine excretion, urinary cortisol, and clinical status were measured daily. Corticosteroid-binding globulin and total and free serum cortisol were measured every 3 days. RESULTS: Compared with controls, patients on low-fat support had fewer cases of pneumonia: 3/24 vs 7/13 (p = .02), better respiratory and nutrition status, and shorter time to healing: 1.2 vs 1.8 days/% burned area (p = 0.01). There was no difference in nitrogen balance between groups, and 3-methylhistidine excretion was higher and serum free cortisol was lower in log-fat--fed patients than in controls. There was no difference between the two low-fat groups in any of the parameters measured. CONCLUSIONS: This study showed that low-fat nutrition support decreases infectious morbidity and shortens length of stay in burn patients. Fish oil does not seem to add clinical benefit to low-fat solutions. In addition, this study provides the first evidence that nutrition intervention modulates cortisol-binding globulin and the concentration of free circulating cortisol after a severe stress.

Extended clinical utility of a sensitive and reliable radioimmunoassay of thyroid-stimulating hormone.

We have developed a radioimmunoassay for thyroid-stimulating hormone (TSH) that is sufficiently sensitive to permit reliable measurement of subnormal serum TSH levels. We report our evaluation of the utility of this radioimmunoassay in the diagnosis and management of thyroid disease. In 59 normal subjects, the mean serum TSH level was 1.49 +/- 0.10 microU/ml (mean +/- SEM) with the range 0.5 to 4.5 microU/ml. In patients without pituitary-hypothalamic lesions, the serum TSH level accurately reflected thyroid status, being subnormal in 29 hyperthyroid patients, supranormal in 26 hypothyroid patients, and normal in 31 euthyroid patients being treated for nonthyroid conditions. In patients being treated for either hyperthyroidism or hypothyroidism, the serum TSH level appeared to be a sensitive indicator of thyroid status, and its return to normal appeared to be a useful therapeutic criterion. We conclude that improving the sensitivtity and reliability of the serum TSH radioimmunoassay greatly extends its clinical applications.

Decreased corticosteroid-binding globulin in burn patients: relationship with interleukin-6 and fat in nutritional support.

OBJECTIVES: To analyze the effect of low-fat nutritional solutions, with or without fish oil, on serum interleukin (IL)-6, and to explore the relationships between IL-6, corticosteroid-binding globulin (CBG; the main cortisol carrier in plasma), and protein metabolism in severely burned adult patients. DESIGN: Randomized, double-blind study with control and low fat-fed groups. SETTING: Burn center of Hôtel-Dieu Hospital of Montréal. PATIENTS: Thirty-seven men and women with thermal burn injury over >20% of body surface area and no other known medical condition. INTERVENTIONS: Within 24 hrs after admission, nutritional support was started through a gastroenteral tube inserted under endoscopic guidance. The goal for energy intake was calculated using the Curreri formula, and was adjusted with biweekly measurements of resting energy expenditure. Patients were randomly assigned to one of the following groups: control (35% of energy as fat); low fat 1 (15% of energy as fat); and low fat 2 (50% of fat in the form of fish oil). MEASUREMENTS AND MAIN RESULTS: Tumor necrosis factor (TNF)-alpha and TNF-beta, IL-6, CBG, and cortisol free fraction were measured every 3 days for 28 days. Nitrogen balance and urinary 3-methylhistidine excretion were measured daily. IL-6 concentrations were high in all patients, with the highest value (460 +/- 111 units/mL) observed on day 4. Concentrations of IL-6 were higher in control patients than in low fat-fed patients between days 13 and 28, but not between days 1 and 13. Multivariate analysis showed that IL-6, total body surface area burned, and sepsis scores were independent predictors of CBG between days 1 and 13 (n = 170; p<.00001). High IL-6 concentrations were predictors of low CBG concentrations and high cortisol free fractions. There was no relationship between IL-6, nitrogen balance, and 3-methylhistidine excretion. TNF-alpha and TNF-beta activity measurements by biological assay showed no correlation with other factors measured. CONCLUSIONS: a) Low-fat feeding, with or without fish oil, does not change the early production of IL-6 after burn injury; b) serum IL-6 is negatively correlated with CBG, which supports the hypothesis that this cytokine inhibits hepatic CBG production; and c) IL-6 does not appear to directly influence protein metabolism in burn patients.