11 research outputs found
Variability in Glucocorticoid Sensitivity: The role of the glucocorticoid receptor
The adrenal glands are paired organs localized superomedially to the kidneys. Each gland is
composed of a cortex and a medulla which are embryologically and functionally distinct. The
cells in the medulla are the principal site of adrenaline production in the body. In the adrenal
cortex, the adrenal steroids are synthesized. The cortex is composed of three histologically
different zones, the zona glomemlosa, which is the outermost portion, the zona fasciculata and
the zona reticularis, which is the innermost part. The adrenal cortex produces aldosterone,
which is the principal mineralocorticoid, the glucocorticoid cortisol and the adrenal androgens.
All steroid honnones produced by the adrenal cortex, are derived from cholesterol. About 80%
of the cholesterol used for steroid synthesis is provided by circulating plasma lipoproteins (1-
3). The cells of steroidogenic tissues can also synthesize cholesterol de novo from acetate or
mobilize intracellular cholesteryl ester pools (1-3). A series of enzymatic steps convert
cholesterol into steroids with glucocorticoid, mineralocorticoid or androgen activity
Clinical aspects of glucocorticoid sensitivity
Recent studies demonstrate that primary (hereditary) abnormalities in the glucocorticoid receptor gene make 6.6% of the normal population relatively 'hypersensitive' to glucocorticoids, while 2.3% are relatively 'resistant.' These abnormalities might explain why some individuals develop severe adverse effects during low dose glucocorticoid therapy, while others do not develop side effects even during long-term therapy with a much higher dose. Awareness of this heterogeneity in glucocorticoid sensitivity in the normal population might eventually allow the prediction of a 'safe' dose of glucocorticoid in individual patients. 'Resistance' to the beneficial clinical effects of glucocorticoid therapy in part of the patients with severe rheumatoid arthritis and asthma is probably rarely related to generalized primary (hereditary) glucocorticoid resistance. In the majority of patients this 'resistance' seems to be acquired and localized to the sites of inflammation, where it reflects high local cytokine production, which interferes with glucocorticoid action. Recognition of localized, acquired glucocorticoid resistance is of great importance indicating as alternative drug therapy with other immune-modulating drugs like cyclosporin and methotrexate. Chronic high dose glucocorticoid treatment in such patients is ineffective in alleviating symptomatology, while generalized side effects occur, reflecting the patient's normal systemic sensitivity to these drugs
Differential hormone-dependent transcriptional activation and -repression by naturally occurring human glucocorticoid receptor variants
The molecular mechanisms underlying primary glucocorticoid resistance or
hypersensitivity are not well understood. Using transfected COS-1 cells as
a model system, we studied gene regulation by naturally occurring mutants
of the glucocorticoid receptor (GR) with single-point mutations in the
regions encoding the ligand-binding domain or the N-terminal domain
reflecting different phenotypic expression. We analyzed the capacity of
these GR variants to regulate transcription from different promoters,
either by binding directly to positive or negative glucocorticoid-response
elements on the DNA or by interfering with protein-protein interactions.
Decreased dexamethasone (DEX) binding to GR variants carrying mutations in
the ligand-binding domain correlated well with decreased capacity to
activate transcription from the mouse mammary tumor virus (MMTV) promoter.
One variant, D641V, which suboptimally activated MMTV promoter-mediated
transcription, repressed a PRL promoter element containing a negative
glucocorticoid-response element with wild type activity. DEX-induced
repression of transcription from elements of the intercellular adhesion
molecule-1 promoter via nuclear factor-kappaB by the D641V variant was
even more efficient compared with the wild type GR. We observed a general
DEX-responsive AP-1-mediated transcriptional repression of the
collagenase-1 promoter, even when receptor variants did not activate
transcription from the MMTV promoter. Our findings indicate that different
point mutations in the GR can affect separate pathways of gene regulation
in a differential fashion, which can explain the various phenotypes
observed
Five patients with biochemical and/or clinical generalized glucocorticoid resistance without alterations in the glucocorticoid receptor gene
Cortisol resistance (CR) is a rare disease characterized by a generalized
reduced sensitivity of end-organs to the actions of glucocorticoids (GCs)
Interperson variability but intraperson stability of baseline plasma cortisol concentrations, and its relation to feedback sensitivity of the hypothalamo-pituitary-adrenal axis to a low dose of dexamethasone in elderly individuals
In the present study, we investigated whether the negative feedback action
of glucocorticoids (GCs) on the hypothalamo-pituitary-adrenal (HPA) axis
changes with age. We performed a 1-mg dexamethasone (DEX) suppression test
in 216 healthy elderly individuals. To investigate individual variability
of feedback sensitivity in more detail, 2.5 yr later a 0.25-mg DEX
suppression test was carried out in 164 of the same individuals. We
investigated whether there was an effect of age or gender on both basal
and post-DEX cortisol levels, as well as on the concentration of DEX.
Furthermore, we examined whether the reactions to the two doses of DEX
differed, and whether indications for an intraperson stability of baseline
cortisol levels could be found. Neither the pre- nor the post-1-mg DEX
plasma cortisol concentrations showed a correlation with age, and there
were no differences between men and women. The same was true for the pre-
and post-0.25-mg DEX cortisol concentrations. In reaction to 1 mg DEX,
over 90% of the subjects investigated showed a cortisol suppression to
levels below 50 nmol/L. After the administration of 0.25 mg DEX, there was
a much wider range in post-DEX cortisol concentrations. After the
administration of 1 mg DEX, there was a significant correlation between
liver function parameters and plasma DEX concentrations in males, and
there was a correlation between body mass index and plasma DEX
concentration in females. Plasma DEX concentrations after the
administration of 1 mg and 0.25 mg DEX were closely correlated within
subjects (P < 0.001). There was an intraindividual stability of serum
cortisol levels determined at an interval of 2.5 yr. Furthermore, the
individuals with the highest baseline cortisol concentrations also had the
highest post-0.25-mg DEX cortisol concentrations, indicating a close
relationship between basal cortisol levels and the feedback sensitivity of
the HPA axis to a low dose of DEX. These observations suggest a genetic
influence on the set point of the HPA axis. Aging does not seem to lead to
a change in HPA activity as measured by early morning total cortisol
levels. Also, no changes in the sensitivity of the feedback system to DEX
were observed with age. DEX metabolism is influenced by liver function (in
males) and by body mass index (in females)
Decreased ligand affinity rather than glucocorticoid receptor down-regulation in patients with endogenous Cushing's syndrome
OBJECTIVE: Glucocorticoids (GCs) serve a variety of important functions
throughout the body. The synthesis and secretion of GCs are under the
strict influence of the hypothalamo-pituitary-adrenal axis. The mechanisms
of action of GCs are mediated by the intracellular glucocorticoid receptor
(GR). Over the years, many studies have been performed concerning th
A polymorphism in the glucocorticoid receptor gene may be associated with and increased sensitivity to glucocorticoids in vivo
We investigated whether a polymorphism at nucleotide position 1220,
resulting in an asparagine-to-serine change at codon 363 in the
glucocorticoid receptor (GR) gene is associated with an altered
sensitivity to glucocorticoids. In a group of 216 elderly persons, 13
heterozygotes for the N363S polymorphism were identified by PCR/single
strand conformation polymorphism analysis. In 2 dexamethasone (DEX)
suppression tests (DSTs), using 1 and 0.25 mg DEX, the circulating
cortisol and insulin concentrations were compared between N363S carriers
and controls. In the 1-mg DST, there were no differences between N363S
carriers and controls, with respect to adrenal suppression, but there was
a significantly higher (P < 0.05) insulin response in N363S carriers. In
the 0.25-mg DST, a significantly larger (P < 0.05) cortisol suppression
and higher (P < 0.05) insulin response were seen in N363S carriers.
Comparison of blood pressure, body mass index (BMI), and bone mineral
density (BMD) between the N363S carriers and controls showed that N363S
carriers had a higher (P < 0.05) BMI but normal blood pressure. There was
an obvious trend towards lower age-, BMI-, and sex-adjusted BMD in the
lumbar spine in N363S carriers. GR characteristics measured in 41 controls
and 9 N363S carriers in peripheral mononuclear leucocytes showed no
differences between N363S carriers and controls, with respect to GR number
and ligand binding affinity. However, there was a trend towards greater
sensitivity to DEX in the carriers' lymphocytes, in a mitogen-induced cell
proliferation assay. In transfection assays, the capacity of the codon 363
variant to activate mouse mammary tumor virus promotor-mediated
transcription in COS-1 cells was unaltered, when compared with the
wild-type GR. We conclude that in 6.0% of our study population, a
polymorphism in codon 363 of the GR gene was found. Individuals carrying
this polymorphism seemed healthy at clinical examination but had a higher
sensitivity to exogenously administered glucocorticoids, with respect to
both cortisol suppression and insulin response. Life-long exposure to the
mutated allele may be accompanied by an increased BMI and a lowered BMD in
the lumbar spine but does not affect blood pressure
Human adrenocorticotropin-secreting pituitary adenomas show frequent loss of heterozygosity at the glucocorticoid receptor gene locus
Corticotropinomas are characterized by a relative resistance to the
negative feedback action of cortisol on ACTH secretion. In this respect
there is a similarity with the clinical syndrome of cortisol resistance.
As cortisol resistance can be caused by genetic abnormalities in the
glucocorticoid receptor (GR) gene, we investigated whether the
insensitivity of corticotropinomas to cortisol is also caused by de novo
mutations in the GR gene. We screened for the GR gene in leukocyte and
tumor DNA from 22 patients with Cushing's disease for mutations using
PCR/single strand conformation polymorphism analysis. In a previous study,
we identified 5 polymorphisms in the GR gene in a normal population. These
polymorphisms were used as markers for the possible occurrence of loss of
heterozygosity (LOH) at the GR gene locus. Except for 1 silent point
mutation, we did not identify novel mutations in the GR gene in leukocytes
or corticotropinomas from these patients. Of the 22 patients, 18 were
heterozygous for at least 1 of the polymorphisms. In 6 of these patients,
LOH had occurred in the tumor DNA. Of 21 patients examined for LOH on
chromosome 11q13, only 1, with a corticotroph carcinoma, showed allelic
deletion. As controls we studied 28 pituitary tumors of other subtypes (11
clinically nonfunctioning, 8 prolactinomas, and 9 GH-producing adenomas)
and found evidence for LOH in only 1 prolactinoma. In six patients LOH was
found at the GR gene locus (chromosome 5) in DNA derived from adenoma
cells. Our observations indicate for the first time that LOH at the GR
gene locus is a relatively frequent phenomenon in pituitary adenomas of
patients with Cushing's disease. This might explain the relative
resistance of the adenoma cells to the inhibitory feedback action of
cortisol on ACTH secretion. The specificity of the GR LOH to
corticotropinomas supports this concept. Somatic mutations of the GR are
not a frequent cause of relative cortisol resistance in these cells
A polymorphism in the glucocorticoid receptor gene, which decreases sensitivity to glucocorticoids in vivo, is associated with low insulin and cholesterol levels
We investigated whether a polymorphism in codons 22 and 23 of the
glucocorticoid (GC) receptor gene [GAGAGG(GluArg) --> GAAAAG(GluLys)] is
associated with altered GC sensitivity, anthropometric parameters,
cardiovascular risk factors