Stress-related genetic components in attention-deficit/hyperactivity disorder (ADHD): Effects of the SERPINA6 and SERPINA1 genetic markers in a family-based brazilian sample

SERPINA6 and SERPINA1 were recently identified as the main genes associated with plasma cortisol concentration in humans. Although dysregulation in the Hypothalamus-Pituitary-Adrenal (HPA) axis has been observed in Attention Deficit/Hyperactivity Disorder (ADHD), the molecular mechanisms underlying this relationship are still unclear. Evaluation of the SERPINA6/SERPINA1 gene cluster in ADHD may provide relevant information to uncover them. We tested the association between the SERPINA6/SERPINA1 locus, including 95 single nucleotide polymorphisms (SNPs), and ADHD, using data from a Brazilian clinical sample of 259 ADHD probands and their parents. The single SNP association was tested using binary logistic regression, and we performed Classification and Regression Tree (CART) analysis to evaluate genotype combinations' effects on ADHD susceptibility. We assessed SNPs' regulatory effects through the Genotype-Tissue Expression (GTEx) v8 tool, and performed a complementary look-up analysis in the largest ADHD GWAS to date. There was a suggestive association between ADHD and eight variants located in the SERPINA6 region and one in the intergenic region between SERPINA6 and SERPINA1 after correction for multiple tests (p < 0.032). CART analysis showed that the combined effects of genotype GG in rs2144833 and CC in rs10129500 were associated with ADHD (OR = 1.78; CI95% = 1.24-2.55). The GTEx assigned the SNPs as eQTLs for genes in different tissues, including SERPINA6, and the look-up analysis revealed two SNPs associated with ADHD. These results suggest a shared genetic component between cortisol levels and ADHD. HPA dysregulation/altered stress response in ADHD might be mediated by upregulation of corticosteroid binding globulin (CBG, encoded by SERPINA6) expression.

Associations Between CYP17A1 and SERPINA6/A1 Polymorphisms, and Cardiometabolic Risk Factors in Black South Africans

Research in European and Asian populations has reported associations between single nucleotide polymorphisms (SNPs) in CYP17A1 and SERPINA6/A1 and circulating glucocorticoid concentrations, and some key cardiometabolic risk factors. This study aimed to investigate these associations in black South African adults, who are disproportionally affected by the metabolic syndrome and its related cardiometabolic risk factors. The dataset included black South African adults (n = 4,431; 56.7% women) from the AWI-Gen study, genotyped on the H3A genotyping array and imputed using the African reference panel at the Sanger imputation service. From the imputed data, 31 CYP17A1 SNPs and 550 SERPINA6/A1 SNPs were extracted. The metabolic syndrome and its components were defined using the 2009 harmonized guidelines. Serum glucocorticoid concentrations were measured in a subset of 304 men and 573 women, using a liquid chromatography-mass spectrometry method. Genetic associations were detected using PLINK. Bonferroni correction was used to control for multiple testing. A SNP at SERPINA6/A1, rs17090691 (effect allele G), was associated with higher diastolic blood pressure (BP) in all adults combined (p = 9.47 × 10-6). Sex-stratified analyses demonstrated an association between rs1051052 (effect allele G), another SERPINA6/A1 SNP, and higher high-density lipoprotein (HDL) cholesterol concentrations in women (p = 1.23 × 10-5). No association was observed between these variants and glucocorticoids or between any of the CYP17A1 SNPs and metabolic outcomes after adjusting for multiple testing. Furthermore, there were no associations between any of the SNPs tested and the metabolic syndrome. This study reports novel genetic associations between two SNPs at SERPINA6/A1 and key cardiometabolic risk factors in black South Africans. Future replication and functional studies in larger populations are required to confirm the role of the identified SNPs in the metabolic syndrome and assess if these associations are mediated by circulating glucocorticoids.

High-throughput profiling of the circulating proteome suggests sexually dimorphic corticosteroid signaling following ischemic stroke

Increasing evidence suggests that there are innate differences between sexes with respect to stroke pathophysiology; however, the molecular mechanisms underlying these differences remain unclear. In this investigation, we employed a shotgun approach to broadly profile sex-associated differences in the plasma proteomes of a small group of male ( n = 6) and female ( n = 4) ischemic stroke patients. Peripheral blood was sampled during the acute phase of care, and liquid chromatography electrospray ionization mass spectrometry was used to quantify plasma proteins. We observed widespread differences in plasma composition, as 77 out of 294 detected proteins were significantly differentially expressed between sexes. Corticosteroid-binding globulin (CBG), a negative acute-phase reactant that inversely regulates levels of bioactive free cortisol, was the most dramatically differentially regulated, exhibiting 16-fold higher abundance in plasma from women relative to men. Furthermore, functional annotation analysis revealed that the remaining differentially expressed proteins were significantly enriched for those involved in response to corticosteroid signaling. Plasma CBG levels were further examined in an additional group of male ( n = 19) and female ( n = 28) ischemic stroke patients, as well as a group of male ( n = 13) and female ( n = 18) neurologically normal controls. CBG levels were significantly reduced in male stroke patients relative to male controls; however, no differences were observed between female stroke patients and female controls, suggesting that women may exhibit an attenuated cortisol response to stroke. Collectively, our findings reinforce the idea that there are sex-associated differences in stroke pathophysiology and suggest that cortisol signaling should be investigated further as a potential molecular mediator.

Polygenic risk score of SERPINA6/SERPINA1 associates with diurnal and stress-induced HPA axis activity in children

PURPOSE

Corticosteroid-binding globulin (CBG) transports glucocorticoids in blood. Variation in genes SERPINA6 encoding for CBG, SERPINA2 and SERPINA1 (serpin family A member 6, 2, and 1) have been shown to influence morning plasma cortisol and CBG in adults. However, association of this genetic variation with diurnal and stress-induced salivary cortisol remain unknown. This study aims to investigate the effect of genetic variation in SERPINA6/2/1 loci on diurnal and stress-induced salivary cortisol in children.

METHODS

We studied 186, 8-year-old children with genome-wide genotyping. We generated weighted polygenic risk score (PRS) based on 6 genome-wide significant SNPs (rs11621961, rs11629171, rs7161521, rs2749527, rs3762132, rs4900229) derived from the CORNET meta-analyses. Salivary cortisol was measured across one day and in response to the Trier Social Stress Test for Children (TSST-C).

RESULTS

Mixed models, adjusted for covariates, showed that the PRS x sampling time interactions associated with diurnal (P < 0.001) and stress-induced (P = 0.009) salivary cortisol. In the high PRS group (dichotomized at median) the diurnal salivary cortisol pattern decreased less from awakening to bedtime than in the low PRS group (standardized estimates of sampling time -0.64 vs. -0.73, P < 0.0001 for both estimates). In response to stress, salivary cortisol increased in the high PRS group while it remained unchanged in the low PRS group (standardized estimates of sampling time 0.12, P = 0.015 vs. -0.06, P = 0.16). These results were mainly driven by minor alleles of rs7161521 (SERPINA6) and rs4900229 (SERPINA1).

CONCLUSIONS

Genetic variation in SERPINA6/2/1loci may underpin higher hypothalamic-pituitary-adrenocortical axis activity in children.

The role of corticosteroid-binding globulin in the evaluation of adrenal insufficiency

Cortisol is a hydrophobic molecule that is largely bound to corticosteroid-binding globulin (CBG) in the circulation. In the assessment of adrenal insufficiency, many clinicians measure a total serum cortisol level, which assumes that CBG is present in normal concentrations and with a normal binding affinity for cortisol. CBG concentration and affinity are affected by a number of common factors including oral contraceptive pills (OCPs), fever and infection, as well as rare mutations in the serine protease inhibitor A6 (SERPINA6) gene, and as such, total cortisol levels might not be the ideal way to assess adrenal function in all clinical circumstances. This paper reviews the limitations of immunoassay and liquid chromatography-tandem mass spectrometry (LC-MS/MS) in the measurement of total cortisol, the challenges of measuring free serum cortisol directly as well as the difficulties in calculating an estimated free cortisol from total cortisol, CBG and albumin concentrations. Newer approaches to the evaluation of adrenal insufficiency, including the measurement of cortisol and cortisone in the saliva, are discussed and a possible future role for these tests is proposed.