Single nucleotide polymorphisms and type of steroid impact the functional response of the human glucocorticoid receptor

Genetic variability in exon 1 of the glucocorticoid receptor gene NR3C1 is associated with postoperative complications

Patients undergoing major surgery experience postoperative inflammation, which may contribute to postoperative morbidity. Endogenous glucocorticoids (GCs) are an essential part of the stress response, but this response varies between individuals, which may in turn affect clinical outcome and specifically postoperative inflammation. Exon 1 of the NR3C1 gene, encoding the GC receptor (GR), contains an established region of differential regulation. DNA methylation patterns in this region have been found to differ between individuals. The present study investigated the methylation status and genotype in the cytosine‑phosphate‑guanine (CpG) island in exon 1 of NR3C1 in 24 patients [Median age 65.5 (range 42‑81) years, 11 male, 13 female] who underwent major abdominal (12 pancreatic, 12 hepatic) surgery and explored its association with postoperative complications. DNA was extracted from peripheral blood leukocytes and underwent targeted bisulfite sequencing of the CpG island. Complications were graded according to the Clavien‑Dindo classification and 14 out of 24 patients had postoperative complications. Multifactorial and partial least square analyses were used to analyse the data. A homogenous demethylated pattern was observed in all patients and no single CpG methylation was associated with postoperative complications. Four SNPs were significantly associated with higher Clavien‑Dindo scores. Genetic variability in the chromosome 5:143,402,505‑143,405,805 region of exon 1 of the GR gene NR3C1, but not DNA methylation, was associated with more severe postoperative complications in patients having major abdominal surgery. These results indicated that the patients' response to GCs may be of clinical importance for inflammatory conditions.

Functional characterization of canine wild type glucocorticoid receptor and an insertional mutation in a dog

Background

Glucocorticoids, among the most widely utilized drugs in veterinary medicine, are employed to treat a wide variety of diseases; however, their use often induces adverse events in dogs. The efficacy of glucocorticoids usually depends on dosage, although differences in sensitivity to glucocorticoids in individual animals have been reported. Glucocorticoids bind to the cytoplasmic glucocorticoid receptor (GR), which is expressed in almost all cells. These receptors are key factors in determining individual sensitivity to glucocorticoids. This study examined individual differences in glucocorticoid sensitivity in dogs, focusing on reactivity of the GR to prednisolone.

Results

We first molecularly cloned the GR gene from a healthy dog. We discovered a mutant GR in a dog suspected to have iatrogenic Cushing syndrome. The mutant GR had extra nucleotides between exons 6 and 7, resulting in a truncated form of GR that was 98 amino acids shorter than the wild-type dog GR. The truncated GR exhibited very low reactivity to prednisolone, irrespective of concentration.

Conclusions

We have identified the truncated form of canine GR in a dog with iatrogenic Cushing syndrome. This truncated form showed the very less sensitivity to glucocorticoid in vitro, unfortunately, we could not elucidate its clinical significance. However, our data is a first report about the function of canine GR, and will facilitate the analysis of canine glucocorticoid sensitivity.

Treatment with Synthetic Glucocorticoids and the Hypothalamus-Pituitary-Adrenal Axis

Chronic glucocorticoid (GC) treatment represents a widely-prescribed therapy for several diseases in consideration of both anti-inflammatory and immunosuppressive activity but, if used at high doses for prolonged periods, it can determine the systemic effects characteristic of Cushing's syndrome. In addition to signs and symptoms of hypercortisolism, patients on chronic GC therapy are at risk to develop tertiary adrenal insufficiency after the reduction or the withdrawal of corticosteroids or during acute stress. This effect is mediated by the negative feedback loop on the hypothalamus-pituitary-adrenal (HPA) axis, which mainly involves corticotropin-release hormone (CRH), which represents the most important driver of adrenocorticotropic hormone (ACTH) release. In fact, after withdrawal of chronic GC treatment, reactivation of CRH secretion is a necessary prerequisite for the recovery of the HPA axis. In addition to the well-known factors which regulate the degree of inhibition of the HPA during synthetic GC therapy (type of compound, method of administration, cumulative dose, duration of the treatment, concomitant drugs which can increase the bioavailability of GCs), there is a considerable variation in individual physiology, probably related to different genetic profiles which regulate GC receptor activity. This may represent an interesting basis for possible future research fields.

A novel human glucocorticoid receptor SNP results in increased transactivation potential

Glucocorticoids are one of the most widely used therapeutics in the treatment of a variety of inflammatory disorders. However, it is known that there are variable patient responses to glucocorticoid treatment; there are responders and non-responders, or those that need higher dosages. Polymorphisms in the glucocorticoid receptor (GR) have been implicated in this variability. In this study, ninety-seven volunteers were surveyed for polymorphisms in the human GR-alpha (hGRα), the accepted biologically active reference isoform. One isoform identified in our survey, named hGR DL-2, had four single nucleotide polymorphisms (SNPs), one synonymous and three non-synonymous, and a four base pair deletion resulting in a frame shift and early termination to produce a 743 amino acid putative protein. hGR DL-2 had a decrease in transactivation potential of more than 90%. Upon further analysis of the individual SNPs and deletion, one SNP, A829G, which results in a lysine to glutamic acid amino acid change at position 277, was found to increase the transactivation potential of hGR more than eight times the full-length reference. Furthermore, the hGRα-A829G isoform had a differential hyperactive response to various exogenous steroids. Increasing our knowledge as to how various SNPs affect hGR activity may help in understanding the unpredictable patient response to steroid treatment, and is a step towards personalizing patient care.

The effect of perioperative administration of glucocorticoids on pulmonary complications after transthoracic oesophagectomy: a systematic review and meta-analysis

BACKGROUND

Severe pulmonary complications occur frequently following transthoracic oesophagectomy. An exaggerated immunological response is probably a main driving factor, and this might be prevented by perioperative administration of a glucocorticoid.

OBJECTIVE

To determine the clinical benefits and harms of perioperative glucocorticoid during transthoracic oesophagectomy, using pulmonary complications as the primary outcome. Mortality, anastomotic leakage rate and infection were secondary outcomes.

METHODS

A systematic review of interventional trials with a meta-analysis of randomised controlled trials (RCTs).

RESULTS

The search retrieved seven RCTs and four interventional nonrandomised studies. In total, 367 patients received perioperative glucocorticoid and 415 patients did not. A meta-analysis of the RCTs showed no significant effect of glucocorticoid. For pulmonary complications, the pooled risk ratio was 0.69 [95% confidence interval (CI) 0.26 to 1.79], for anastomotic leakage 0.61 (95% CI 0.23 to 1.61) and for infections 1.09 (95% CI 0.41 to 2.93). A subgroup analysis of RCTs that used weight-dependent dosing within 30 min preoperatively showed a pooled risk ratio of 0.28 (95% CI 0.10 to 0.77) for pulmonary complications compared with placebo.

CONCLUSION

In this meta-analysis, perioperative administration of glucocorticoid did not affect the risk of pulmonary complications after transthoracic oesophagectomy, nor did it cause adverse effects. A subgroup analysis showed that a weight-dependent dose of methylprednisolone 10 to 30 mg kg within 30 min preoperatively might be the most promising dosing regimen for further research.

Comprehensive overview of the structure and regulation of the glucocorticoid receptor

Glucocorticoids are among the most prescribed drugs worldwide for the treatment of numerous immune and inflammatory disorders. They exert their actions by binding to the glucocorticoid receptor (GR), a member of the nuclear receptor superfamily. There are several GR isoforms resulting from alternative RNA splicing and translation initiation of the GR transcript. Additionally, these isoforms are all subject to several transcriptional, post-transcriptional, and post-translational modifications, all of which affect the protein's stability and/or function. In this review, we summarize recent knowledge on the distinct GR isoforms and the processes that generate them. We also review the importance of all known transcriptional, post-transcriptional, and post-translational modifications, including the regulation of GR by microRNAs. Moreover, we discuss the crucial role of the putative GR-bound DNA sequence as an allosteric ligand influencing GR structure and activity. Finally, we describe how the differential composition and distinct regulation at multiple levels of different GR species could account for the wide and diverse effects of glucocorticoids.

Cortisol metabolism in critical illness: implications for clinical care

PURPOSE OF REVIEW

Critical illness is uniformly characterized by elevated plasma cortisol concentrations, traditionally attributed exclusively to increased cortisol production driven by an activated hypothalamic pituitary adrenal axis. However, as plasma adrenocorticotropic hormone (ACTH) concentrations are often not elevated or even low during critical illness, alternative mechanisms must contribute.

RECENT FINDINGS

Recent investigations revealed that plasma clearance of cortisol is markedly reduced during critical illness, explained by suppressed expression and activity of the main cortisol metabolizing enzymes in liver and kidney. Furthermore, unlike previously inferred, cortisol production rate in critically ill patients was only moderately increased to less than double that of matched healthy subjects. In the face of low-plasma ACTH concentrations, these data suggest that other factors drive hypercortisolism during critical illness, which may suppress ACTH by feedback inhibition. These new insights add to the limitations of the current diagnostic tools to identify patients at risk of failing adrenal function during critical illness. They also urge to investigate the impact of lower hydrocortisone doses than those hitherto used.

SUMMARY

Recent novel insights reshape the current understanding of the hormonal stress response to critical illness and further underline the need for more studies to unravel the pathophysiology of adrenal (dys)functioning during critical illness.

Endocrine responses to critical illness: novel insights and therapeutic implications

CONTEXT

Critical illness, an extreme form of severe physical stress, is characterized by important endocrine and metabolic changes. Due to critical care medicine, survival from previously lethal conditions has become possible, but many patients now enter a chronic phase of critical illness. The role of the endocrine and metabolic responses to acute and prolonged critical illness in mediating or hampering recovery remains highly debated.

EVIDENCE ACQUISITION

The recent literature on changes within the hypothalamic-pituitary-thyroid axis and the hypothalamic-pituitary-adrenal axis and on hyperglycemia in relation to recovery from critical illness was critically appraised and interpreted against previous insights. Possible therapeutic implications of the novel insights were analyzed. Specific remaining questions were formulated.

EVIDENCE SYNTHESIS

In recent years, important novel insights in the pathophysiology and the consequences of some of these endocrine responses to acute and chronic critical illness were generated. Acute endocrine adaptations are directed toward providing energy and substrates for the vital fight-or-flight response in a context of exogenous substrate deprivation. Distinct endocrine and metabolic alterations characterize the chronic phase of critical illness, which seems to be no longer solely beneficial and could hamper recovery and rehabilitation.

CONCLUSIONS

Important novel insights reshape the current view on endocrine and metabolic responses to critical illness and further clarify underlying pathways. Although many issues remain unresolved, some therapeutic implications were already identified. More work is required to find better treatments, and the optimal timing for such treatments, to further prevent protracted critical illness, to enhance recovery thereof, and to optimize rehabilitation.