Robert Kumsta

Sex Specific Associations between Common Glucocorticoid Receptor Gene Variants and Hypothalamus-Pituitary-Adrenal Axis Responses to Psychosocial Stress

BACKGROUNDnAlterations in glucocorticoid (GC) signaling have been associated with a number of psychiatric disorders. Genetic variation of the glucocorticoid receptor (GR) might be one of the factors underlying susceptibility to stress related disease.nnnMETHODSnWe investigated 206 healthy subjects and assessed associations between four common GR gene (NR3C1) polymorphisms (ER22/23EK, N363S, BclI, 9beta) and hypothalamic-pituitary-adrenal (HPA) axis responses to psychosocial stress (Trier Social Stress Test, TSST) and glucocorticoid sensitivity measured by a dexamethasone suppression test (DST).nnnRESULTSnMale 9beta AG carriers displayed the highest adrenocorticotropic hormone (ACTH) and total cortisol TSST responses (for ACTH: main effect genotype p = .02) whereas male BclI GG carriers showed diminished responses. Remarkably, the BclI GG genotype in women (all using oral contraceptives) was associated with the highest total cortisol TSST responses, resulting in a significant sex by genotype interaction (p = .03). Following the DST, male 9beta AG carriers had elevated ACTH levels (sex by genotype interaction p = .03).nnnCONCLUSIONSnWe observed significant sex specific associations between GR gene polymorphisms and HPA axis responses to psychosocial stress as well as GC sensitivity. These findings support the relevance of GR gene polymorphisms in HPA axis regulation. Genetic variations of the GR might constitute a risk factor in development of HPA axis related disorders.

Free cortisol awakening responses are influenced by awakening time

Psychobiological investigations on the hypothalamus-pituitary-adrenal (HPA) axis depend on markers that adequately describe the activity of this system. There is evidence that the free cortisol response to awakening, proposed as a marker for the HPA axis, can be influenced by time of awakening. To further investigate this possible confounder, 24 shift working nurses and 31 female students on a regular sleep-wake cycle collected saliva samples 0, 30, 45 and 60 minutes after awakening. Nurses were investigated on the first and second day of their early (awakening: 04:00-05:30 h), late (awakening: 06:00-09:00 h), and night shift (awakening: 11:00-14:00 h), respectively. Students were studied after taking a short nap on two consecutive weekdays (awakening: 18:45-20:30 h). Mean cortisol levels after awakening increased significantly under all three shift conditions (p<0.01), but decreased in the student sample (p<.05). Within the three shift conditions, cortisol responses following waking in the early shift were more pronounced than in late (p<.01) and night shift (p<.05). The present study shows that in a sample with a large range of awakening times, an impact of this variable on the cortisol awakening response can be observed. The data furthermore strongly suggest that waking up per se is insufficient for adrenocortical stimulation.

Sex-specific association between the 5-HTT gene-linked polymorphic region and basal cortisol secretion

OBJECTIVEnA key regulator of serotonergic neurotransmission is the serotonin transporter (5-HTT) and a common 5HTT gene promoter polymorphism, termed 5HTTLPR, is associated with phenotypes related to anxiety and depression. Furthermore, the serotonergic system influences hypothalamus-pituitary-adrenal (HPA) axis activity, which, in turn, is related to psychiatric diseases.nnnMETHODSnTo explore the association between the 5-HTTLPR and HPA axis regulation we performed a detailed endophenotyping in 216 healthy subjects (all 126 females used oral contraceptives).nnnRESULTSnWhile ACTH and cortisol responses to an established psychosocial stress paradigm (Trier Social Stress Test) were not found to be related to the 5-HTTLPR, we observed a significant and sex-specific association with the cortisol awakening response, which is a reliable marker of basal cortisol secretion, and with ACTH levels after dexamethasone administration. The supplementary inclusion of a 5-HTT A/G polymorphism (rs25531) in the analyses did not substantially modify our results.nnnCONCLUSIONnThese findings support the view that the 5-HTTLPR is associated with a major neuroendocrine stress system. It could be speculated that the sex-specific nature of this association contributes to the distinct gender differences in the vulnerability for depression.

Prenatal psychosocial stress exposure is associated with insulin resistance in young adults

OBJECTIVEnThe objective of the study was to examine the association in humans between maternal psychosocial stress exposure during pregnancy and measures of glucose-insulin metabolism in the adult offspring.nnnSTUDY DESIGNnHealthy young adults whose mothers experienced major stressful life events during their pregnancy (n = 36, prenatal stress, PS group, mean age 25 +/- 5.14 [SD] years) and a comparison group (n = 22, CG, mean age 24 +/- 3.7 [SD] years) underwent an oral glucose tolerance test.nnnRESULTSnGlucose levels were not significantly different across the groups; however, prenatally stressed subjects showed significantly elevated 2-hour insulin (P = .01) and C-peptide levels (P = .03). These differences were independent of other major risk factors for insulin resistance, including birth phenotype (birthweight, length of gestation), a family history of diabetes, gestational diabetes, body mass index, proinflammatory state, and smoking.nnnCONCLUSIONnHigher insulin responses reflect relative insulin resistance in these prenatally stressed young adults. This study is the first to provide evidence for a link in humans between prenatal psychosocial stress exposure and alterations in glucose-insulin metabolic function.

A psychobiological perspective on genetic determinants of hypothalamus-pituitary-adrenal axis activity.

Abstract: From the perspective of psychobiological stress research we present a brief overview of findings documenting a significant impact of genetic factors on the activity of the hypothalamus‐pituitary‐adrenal (HPA) axis. Quantitative genetic studies in twins as well as association studies, primarily on polymorphisms in the glucocorticoid receptor gene, are depicted. Recent findings suggest that the collaboration of psychobiology and molecular genetics is a promising interdisciplinary approach that will significantly contribute to the understanding of the mechanisms underlying the link between stress, the HPA axis, and HPA‐related clinical states.

Influence of prenatal psychosocial stress on cytokine production in adult women.

The aim of the present study was to determine the association between prenatal stress and immune function in human adults. Peripheral blood mononuclear cells (PBMCs) from 34 healthy young women whose mothers experienced major negative life events during their pregnancy (Prenatal Stress, PS group, mean age 25, SD +/- 4.34 years), and from a female comparison group (n = 28, CG, mean age 24 +/- 3.40 years), were stimulated with phytohemagglutinin (PHA), and subsequent cytokine production was measured. A bias for T-helper 2 (Th2) cytokine production due to an overproduction of IL-4 relative to IFN-gamma after PHA stimulation was observed in PS subjects. In addition, IL-6 and IL-10 were also significantly elevated. To the best of our knowledge, this study is the first to suggest a direct association between prenatal stress exposure and alterations in immune parameters in adult women.

Cortisol and ACTH responses to psychosocial stress are modulated by corticosteroid binding globulin levels

The hypothalamus-pituitary-adrenal (HPA) axis is vital for an organisms response to physiological and psychological stress. Cortisol, secreted upon activation of the HPA axis, impacts on physiological systems throughout the organism. Responses to cortisol are influenced and modified by a number of factors, including corticosteroid binding globulin (CBG) levels. A major part of circulating cortisol is bound to CBG and only the unbound fraction is thought to be biologically active. The aim of the present study was to examine the modulating effect of CBG levels on hormonal responses following psychosocial stress in women using oral contraceptives (n=115) and in medication-free men (n=93). In women, CBG levels were negatively associated with ACTH and salivary cortisol and positively with total cortisol levels following the TSST. In men, positive associations were observed between CBG and ACTH and total cortisol levels following the TSST. CBG is an important regulatory element of HPA axis response patterns; therefore, CBG levels have to be taken into account as a potential modifier of ACTH and cortisol responses to psychosocial and pharmacological stimulation. Investigations of the consequences of long-lasting OC intake on the neuroendocrine stress regulation in women might be warranted.

Transcriptional control of the human glucocorticoid receptor: identification and analysis of alternative promoter regions

Glucocorticoid receptor levels are thought to be controlled by multiple alternative first exons. Seven of these exons are located in an upstream CpG island. In this study, we investigated the promoter activity of the intronic regions between these exons, and their susceptibility to CpG methylation and sequence variability. The seven promoters were cloned into luciferase reporter genes, and their activity measured in ten cell lines. CpG islands of 221 donors were genotyped and the effects of these SNPs were investigated in a reporter gene assay. We showed that each of the first exons was independently controlled by a unique promoter located directly upstream. Promoter activities were cell type-specific, and varied considerably between cell types. Irrespective of the cell type, in vitro methylation effectively silenced all reporter constructs. Eleven SNPs were observed within the CpG island of 221 donors, and a new promoter-specific haplotype was revealed. Four of the minor alleles reduced the reporter gene activity, with cell type specific effects. This complexity within the CpG island helps to explain the variable, tissue-specific transcriptional control of the GR, and provides insight into the mechanisms underlying tissue specific deregulation of GR levels.

The glucocorticoid receptor gene exon 1-F promoter is not methylated at the NGFI-A binding site in human hippocampus

Recent research has demonstrated that early life experience, such as variation in maternal care, can have a profound impact on the physiological and endocrine stress response of Rattus norvegicus. Low maternal care resulted in increased methylation of the nerve growth factor-inducible protein A (NGFI-A, EGR1) binding site located in the hippocampal glucocorticoid receptor gene (Nr3c1) exon 17 promoter, leading to decreased Nr3c1 expression, which results in a reduced efficiency of glucocorticoid-mediated negative feedback on hypothalamus–pituitary–adrenal axis activity. The human glucocorticoid receptor gene (NR3C1) has a highly similar 5′ structure compared to the rat, and the human alternative exon 1-F is the orthologue to the rat exon 17. Based upon the evidence from rats, and the high sequence identity of the regulatory sequences, we examined the methylation pattern of the corresponding NGFI-A binding site in the human glucocorticoid receptor exon 1-F specific promoter in post mortem hippocampal tissue. In contrast to the findings in rats, neither of the two CpG motifs within the NGFI-A binding site was methylated in the 32 subjects investigated. These observations might reflect different promoter methylation patterns in humans and rats.

Glucocorticoid receptor gene polymorphisms and glucocorticoid sensitivity of subdermal blood vessels and leukocytes

A considerable variability in the sensitivity to glucocorticoids (GCs) exists between individuals and these differences have been implicated in the etiology of psychiatric diseases such as depression. Glucocorticoid receptor (GR) gene polymorphisms might account in part for variability in GC responsiveness. We assessed the association between four common GR gene (NR3C1) polymorphisms (ER22/23EK, N363S, BclI, 9beta) and markers of glucocorticoid sensitivity in two target tissues (subdermal blood vessels, peripheral leukocytes) in 206 healthy individuals. The BclI GG genotype group showed the least degree of skin blanching, reflecting a lower GC sensitivity of subdermal blood vessels (p=.01). No association between GR genotype and GC sensitivity of peripheral leukocytes was observed. In the same subjects we previously observed an association between GR genotype and GC sensitivity of the pituitary. Polymorphism of the GR gene might constitute a vulnerability or protection factor for stress related disorders and altered GC sensitivity.