Abstract BACKGROUND Adrenal insufficiency is primarily treated with replacement of cortisol, which is the predominant circulating glucocorticoid. Human adrenals also secrete corticosterone and emerging evidence suggests this may be a safer glucocorticoid replacement therapy. However, little is known about corticosterone in humans, particularly related to its metabolism. METHODS To investigate the secretion and metabolism of corticosterone in comparison with cortisol, we: 1) investigated the diurnal rhythm of circulating cortisol/ corticosterone in 7 healthy volunteers; 2) quantified A-ring reduction of both hormones in human hepatic cytosol and 3) measured glucocorticoid metabolites in vivo in 24 healthy men; 4) determined the pharmacokinetics of corticosterone via intravenous infusion of 2,2,4,6,6,17α,21,21-[ 2 H] 8 -corticosterone; 5) assessed the response of corticosterone and cortisol to 1mcg ACTH in 279 healthy volunteers. RESULTS The natural diurnal rhythm of corticosterone closely mirrored that of cortisol, and accounted for ∼3% of total circulating glucocorticoid concentrations. Daily corticosterone production, as measured through urinary steroid profiling, was approximately 10-fold lower than cortisol, and corticosterone demonstrated substantially greater metabolism by both 5α- and 5β-reductase than cortisol. In keeping with greater metabolism, the half-life of corticosterone was 28.5 ± 3.3 minutes. Finally, corticosterone demonstrated a greater relative rise in response to ACTH than cortisol, particularly in men, revealing sex-specific differences. CONCLUSIONS Corticosterone is a dynamic glucocorticoid with faster metabolism and greater response to stimulation than cortisol in humans. These data raise the possibility of distinct roles for these two glucocorticoids and highlight important pharmacokinetic differences with implications for the therapeutic potential of corticosterone replacement in humans.

We previously published the DexFEM trial, which showed that in women with heavy menstrual bleeding (HMB), oral dexamethasone reduces menstrual blood loss. Here, we report a pharmacodynamic analysis exploring the likely mechanism for this effect. We studied oral dosing with dexamethasone during the mid-luteal phase of two menstrual cycles (1.5 mg daily, 5 days) in five women with HMB (six recruited aged 41–50 years, one withdrew before treatment). Steroid hormones were profiled in serum and endometrium by liquid chromatography-tandem mass spectrometry (LC-MS/MS). We found that following oral dosing, dexamethasone reached the endometrium and that, compared to the preceding control cycle, cortisol (active), cortisone (inactive) and intermediate 11-deoxycortisol were reduced in all samples assessed, both endometrial (n = 4) and serum (n = 5). Concentrations of androgens, androstenedione and testosterone were reduced in serum but not in all tissue samples. This proof-of-concept pharmacodynamic study supports the inference that dexamethasone is effective in HMB by altering endometrial glucocorticoid concentrations.

Corticosteroid binding globulin (CBG; SERPINA6) binds >85% of circulating glucocorticoids but its influence on their metabolic actions is unproven. Targeted proteolytic cleavage of CBG by neutrophil elastase (NE; ELANE) significantly reduces CBG binding affinity, potentially increasing 'free' glucocorticoid levels at sites of inflammation. NE is inhibited by alpha-1-antitrypsin (AAT; SERPINA1). Using complementary approaches in mice and humans to manipulate NE or AAT, we show high-fat diet (HFD) increases the NE:AAT ratio specifically in murine visceral adipose tissue, an effect only observed in males. Notably, HFD-fed male mice lacking NE have reduced glucocorticoid levels and action specifically in visceral adipose tissue, with improved glucose tolerance and insulin sensitivity, independent of systemic changes in free glucocorticoids. The protective effect of NE deficiency is lost when the adrenals are removed. Moreover, human asymptomatic heterozygous carriers of deleterious mutations in SERPINA1 resulting in lower AAT levels have increased adipose tissue glucocorticoid levels and action. However, in contrast to mice, humans present with systemic increases in free circulating glucocorticoid levels, an effect independent of HPA axis activation. These findings show that NE and AAT regulate local tissue glucocorticoid bioavailability in vivo, providing crucial evidence of a mechanism linking inflammation and metabolism.

BACKGROUND AND PURPOSE:Plasma glucocorticoids increase acutely after MI, thereafter tissue levels are amplified selectively within cells expressing 11-ßhydroxysteroid dehydrogenase type 1 (11-ßHSD1) that regenerates active glucocorticoids from circulating metabolites. Glucocorticoids initially protect cardiomyocytes and prevent excessive inflammation after MI but can also suppress wound repair leading to functional decline. We investigate 11-ßHSD1 inhibition after MI to prevent deterioration of cardiac function and its impact on wound repair. EXPERIMENTAL APPROACH:Adult female Gottingen mini-pigs underwent percutaneous balloon MI/reperfusion and were randomised to receive either oral 11-ßHSD1 inhibitor AZD8329 (n = 11) or vehicle (n = 9), from 2 until 27 days later, with concurrent administration of relevant therapeutic intervention (anti-platelet, statin and ACE inhibitor). KEY RESULTS:AZD8329 treatment increased plasma accumulation of cortisone substrate showing successful 11-ßHSD1 inhibition. Gadolinium-enhanced magnetic resonance imaging (MRI) showed equivalent infarct size in both groups prior to commencing treatment. Twenty-eight days after MI cardiac function and left ventricle area were preserved in the AZD8329 treated group relative to vehicle. There was no impact of 11-ßHSD1 inhibitor on neovascularisation or infarct area. Mass spectrometry imaging revealed AZD8329 binding to the healing infarct and altered regulation of extracellular matrix processing was highlighted by birefringence microscopy and proteomic analysis. CONCLUSIONS AND IMPLICATIONS:Pharmacological inhibition of 11-ßHSD1 after MI prevents deterioration of cardiac function and detrimental remodelling. 11-ßHSD1 inhibitors have safely reached Phase 2 clinical trials in diabetes and dementia, and could be repurposed as an addition to standard care after MI to prevent the development of heart failure.

Approximately one in every 800 children is born with the severe aneuploid condition of Down syndrome (DS), a trisomy of chromosome 21. Low blood pressure (hypotension) is a common condition associated with DS and can have a significant impact on exercise tolerance and quality of life. Little is known about the factors driving this hypotensive phenotype, therefore therapeutic interventions are limited. Carbonyl reductase 1 (CBR1) is an enzyme contributing to the metabolism of prostaglandins, glucocorticoids, reactive oxygen species and neurotransmitters, encoded by a gene (CBR1) positioned on chromosome 21 with the potential to affect blood pressure. Utilising telemetric blood pressure measurement of genetically modified mice, we tested the hypothesis that CBR1 influences blood pressure and that its overexpression contributes to hypotension in DS by evaluating possible contributing mechanisms in vitro. In a mouse model of DS (Ts65Dn), which exhibits hypotension, CBR1 activity was increased and pharmacological inhibition of CBR1 ed to increased blood pressure. Mice heterozygous null for Cbr1 had reduced CBR1 enzyme activity and elevated blood pressure. Further experiments indicate that the underlying mechanisms include alterations in both sympathetic tone and prostaglandin metabolism. We conclude that CBR1 activity contributes to blood pressure homeostasis and inhibition of CBR1 may present a novel therapeutic opportunity to correct symptomatic hypotension in DS.

Glucocorticoids modulate glucose homeostasis, acting on metabolically active tissues such as liver, skeletal muscle, and adipose tissue. Intracellular regulation of glucocorticoid action in adipose tissue impacts metabolic responses to obesity. ATP-binding cassette family C member 1 (ABCC1) is a transmembrane glucocorticoid transporter known to limit the accumulation of exogenously administered corticosterone in adipose tissue. However, the role of ABCC1 in the regulation of endogenous glucocorticoid action and its impact on fuel metabolism has not been studied. Here, we investigate the impact of Abcc1 deficiency on glucocorticoid action and high-fat-diet (HFD)-induced obesity. In lean male mice, deficiency of Abcc1 increased endogenous corticosterone levels in skeletal muscle and adipose tissue but did not impact insulin sensitivity. In contrast, Abcc1-deficient male mice on HFD displayed impaired glucose and insulin tolerance, and fasting hyperinsulinaemia, without alterations in tissue corticosterone levels. Proteomics and bulk RNA sequencing revealed that Abcc1 deficiency amplified the transcriptional response to an obesogenic diet in adipose tissue but not in skeletal muscle. Moreover, Abcc1 deficiency impairs key signalling pathways related to glucose metabolism in both skeletal muscle and adipose tissue, in particular those related to OXPHOS machinery and Glut4. Together, our results highlight a role for ABCC1 in regulating glucose homeostasis, demonstrating diet-dependent effects that are not associated with altered tissue glucocorticoid concentrations.

Background and Purpose: Plasma glucocorticoids (GCs) increase acutely after myocardial infarction (MI), thereafter tissue levels are amplified selectively within cells expressing 11βHydroxysteroid Dehydrogenase type 1 (11βHSD1) that regenerates active GCs from circulating metabolites. GCs initially protect cardiomyocytes and prevent excessive inflammation after MI but can also suppress subsequent wound repair leading to functional decline. The present study aimed to investigate the potential of pharmacological 11βHSD1 inhibition after MI to prevent deterioration of cardiac function and its impact on wound repair. Experimental Approach: Adult female Gottingen mini-pigs underwent percutaneous balloon MI/reperfusion and were randomised to receive either oral 11βHSD1 inhibitor AZD8329 (n=11), or vehicle (n=9), from 2 until 27 days later, with concurrent administration of clinically relevant therapeutic intervention (anti-platelet, statin and ACE inhibitor). Key Results: AZD8329 treatment increased plasma accumulation of cortisone substrate consistent with successful 11βHSD1 inhibition. Gadolinium-enhanced MRI showed equivalent infarct size in both groups prior to commencing treatment. 28 days after MI cardiac function and LV area were preserved in the AZD8329 treated group relative to vehicle. There was no impact of 11βHSD1 inhibitor on neovascularisation or infarct area. Mass spectrometry imaging revealed AZD8329 binding to the healing infarct and altered regulation of extracellular matrix (ECM) processing was highlighted by birefringence microscopy and proteomic analysis. Conclusions and Implications: Pharmacological inhibition of 11βHSD1 after MI prevents deterioration of cardiac function and detrimental remodelling. 11βHSD1 inhibitors have safely reached phase 2 clinical trials in diabetes and dementia and could be repurposed as an addition to standard care after MI to prevent the development of heart failure. ### Competing Interest Statement BRW and SPW are inventors on patents relating to 11βHSD1 inhibitors which are owned by the University of Edinburgh and licensed to Actinogen Biomedical which is developing an 11βHSD1 inhibitor for use in brain disorders. BRW is also a consultant for Actinogen Biomedical. AF is a full-time employee of AZ and may hold company shares and AW was a full-time employee of AZ at the time of the research and may hold company shares. None of the other authors have declared a conflict of interest.

Abstract Disclosure: L.D. Boyle: None. M. Nixon: None. C.M. Underhill: None. L.A. Hill: None. N.Z. Homer: None. M. Magennis: None. R. Andrew: None. G.L. Hammond: None. J.G. Lewis: None. R.H. Stimson: None. B.R. Walker: None. Background: Corticosteroid Binding Globulin (CBG) binds >85% of plasma cortisol, modulating its biological activity. Proteolytic cleavage by neutrophil elastase (NE) reduces CBG binding capacity, proposed to increase free cortisol availability to inflamed tissues. Genetic variation at the locus spanning SERPINA1 (encoding alpha-1 antitrypsin, AAT, the endogenous inhibitor of NE) and SERPINA6 (CBG) altered morning total plasma cortisol. We hypothesised that AAT deficiency increased CBG cleavage and hence free plasma cortisol, resulting in amplified tissue cortisol delivery and increased HPA axis negative feedback. We tested this in recall-by-genotype studies of people who are heterozygous for inactivating mutations in SERPINA1. Methods: 16 asymptomatic carriers of deleterious SERPINA1 single nucleotide polymorphisms (rs17580 & rs28929474) and 16 age-, gender- and BMI-matched controls were recruited from the Generation Scotland Biobank. To quantify in vivo whole body glucocorticoid appearance and clearance rates, and estimate tissue cortisol uptake, we performed arterio-venous plasma sampling across abdominal adipose and skeletal muscle during steady-state 9,11,12,12-[2H]4-cortisol tracer infusion. To assess endogenous negative feedback, participants underwent combined receptor antagonist stimulation of the HPA axis (‘CRASH’) testing using RU486 and spironolactone, or placebo in a double blind randomised crossover design. Total cortisol (LC-MS/MS), free cortisol (isotopic dilution & ultrafiltration), CBG binding capacity (radioligand displacement), CBG concentration and AAT (ELISA) were measured in plasma. Tissue cortisol (LC-MS/MS) and glucocorticoid-dependent transcripts (qPCR) were measured in adipose biopsy samples collected at end of study. Results: AAT was ∼30% lower in AAT+/- (p=0.0002 vs control). Plasma CBG concentration, binding capacity and total cortisol were similar between groups. However, plasma free cortisol fraction was higher in AAT+/- subjects (16.1 +/- 0.2 vs 13.9 +/- 0.04 %, p<0.0001). Adipose tissue from AAT+/- subjects displayed increased cortisol levels and increased glucocorticoid-responsive transcripts PER1 and LPL compared to controls. Consistent with release from CBG, total and free cortisol release across skeletal muscle was increased in AAT+/- subjects vs controls. The rate of appearance of 9,12,12-[2H]3-cortisol was reduced in AAT+/- (p=0.03 vs control), consistent with decreased whole body 11β-HSD1 activity. CRASH testing did not reveal additional differences between groups. Discussion: Subclinical AAT deficiency is associated with a higher free cortisol fraction and increased tissue glucocorticoid exposure. Although consistent with the hypothesis of local tissue-mediated control of glucocorticoid exposure via the NE/AAT/CBG axis, these findings were not accompanied by measurable changes in CBG. Presentation: 6/3/2024

Background and Purpose: Glucocorticoids are powerful anti-inflammatory drugs, but are associated with many side-effects. Topical application in atopic dermatitis leads to skin thinning, metabolic changes, and adrenal suppression. 5 alpha-Tetrahydrocorticosterone (5 alpha THB) is a potential selective anti-inflammatory with reduced metabolic effects. Here, the efficacy and side-effect profile of 5 alpha THB were compared with hydrocortisone in preclinical models of irritant dermatitis.Experimental Approach: Acute irritant dermatitis was invoked in ear skin of male C57BL/6 mice with a single topical application of croton oil. Inflammation was assessed as oedema via ear weight following treatment with 5 alpha THB and hydrocortisone. Side-effects of 5 alpha THB and hydrocortisone were assessed following chronic topical steroid treatment (28 days) to non-irritated skin. Skin thinning was quantified longitudinally by caliper measurements and summarily by qPCR for transcripts for genes involved in extracellular matrix homeostasis; systemic effects of topical steroid administration also were assessed. Clearance of 5 alpha THB and hydrocortisone were measured following intravenous and oral administration.Key Results: 5 alpha THB suppressed ear swelling in mice, with ED50 similar to hydrocortisone (23 mu g vs. 13 mu g). Chronic application of 5 alpha THB did not cause skin thinning, adrenal atrophy, weight loss, thymic involution, or raised insulin levels, all of which were observed with topical hydrocortisone. Transcripts for genes involved in collagen synthesis and stability were adversely affected by all doses of hydrocortisone, but only by the highest dose of 5 alpha THB (8x ED50). 5 alpha THB was rapidly cleared from the systemic circulation.Conclusions and Implications: Topical 5 alpha THB has potential to treat inflammatory skin conditions, particularly in areas of delicate skin.

Objective: Outcomes are poor for patients with congenital adrenal hyperplasia (CAH), in part due to the supraphysiological glucocorticoid doses required to control adrenal androgen excess. Hydrocortisone (ie, cortisol) is the recommended glucocorticoid for treatment of CAH. However, the other endogenous glucocorticoid in humans, corticosterone, is actively transported out of metabolic tissues such as adipose tissue and muscle, so we hypothesized that corticosterone could control adrenal androgens while causing fewer metabolic adverse effects than hydrocortisone. Methods: Thirteen patients (8 female, 5 male) with CAH due to 21-hydroxylase deficiency completed a randomized placebo-controlled crossover study comparing 5 h intravenous infusions of either hydrocortisone, corticosterone or placebo. 6-6[H-2](2)-glucose and 1,1,2,3,3-[H-2](5)-glycerol were infused to measure glucose and glycerol kinetics, and blood samples were collected throughout. Subcutaneous abdominal adipose tissue biopsies were obtained at the end of each infusion. Results: During the infusion, corticosterone and hydrocortisone similarly reduced ACTH, 17 alpha-hydroxyprogesterone, androstenedione, and testosterone (in females only) compared with placebo. Despite achieving circulating corticosterone concentrations similar to 2.5-fold higher than hydrocortisone, by T + 300 min hydrocortisone but not corticosterone increased glucose and insulin concentrations and reduced 6-6-[H-2](2)-glucose clearance compared with placebo. Hydrocortisone increased mRNA levels of the glucocorticoid regulated transcript PER1 in adipose to a greater extent than corticosterone. Conclusions: Corticosterone acutely controls biochemical markers of androgen excess similarly to hydrocortisone but without inducing markers of glucocorticoid "toxicity" in CAH. These data demonstrate proof of concept that corticosterone may be a safer glucocorticoid replacement than current medications, although further research is required to assess the longer-term effects of corticosterone replacement.

While acute post-myocardial infarction (MI) survival has improved thanks to early intervention, the myocardium still sustains damage that increases the risk of heart failure. Adrenal glucocorticoids (GCs) protect cardiomyocytes immediately after MI, but inhibition of GC regeneration within the heart by 11β-hydroxysteroid dehydrogenase 1 (11βHSD1) during infarct repair prevents subsequent deterioration of ventricular structure and function. In the 11βHSD1-knockout mouse this outcome is associated with enhancement of peri-infarct neovascularisation and prevention of infarct expansion. Here, we tested the hypothesis that pharmacological 11βHSD1 inhibition after MI can preserve function in a translational pig model and investigated the role of neovascularisation. MI was induced in female minipigs via temporary coronary occlusion. A standard clinical therapy (SCT, n =9) group received statin, anti-platelet, βadrenoreceptor antagonist and ACE inhibitor immediatley after MI, and a 11βHSD1i group (n=11) received SCT +11βHSD1 inhibitor (50mg/kg) from 48h after MI until the end of the study. Prior to 11βHSD1i treatment, short-axis cine and late gadolinium-enhanced MRI showed no difference in either infarct mass (4.2±0.4g SCT vs 4.0±0.6g 11βHSD1i) or ejection fraction (EF; 60.6±2.9% SCT vs 56.6±1.8% 11βHSD1i). However, by 28 days after MI, while EF was reduced in SCT pigs to 48±4%, it was maintained in pigs given additional 11βHSD1i treatment (57.9±1.8%, p <0.05 vs SCT). Infarct mass did not differ between the two treatments, suggesting that inhibition of infarct expansion did not account for the improvement in function, this was confirmed by a similar area of infarct collagen in histological analysis. Angiogenesis, represented by an increase in CD31 +ve capillaries, was not enhanced in the infarct or the border zone (BZ) after 11βHSD1i treatment, relative to SCT. While vessel maturation (αSMA +ve vessels) was improved in the infarct compared to the remote myocardium, there was no difference between the two groups. Proteomic pathway analysis of the BZ indicated extracellular matrix organisation as the main pathway regulated by 11βHSD1i compared to SCT. In conclusion, 11βHSD1i after MI successfully preserves cardiac function and structure but the mechanism is independent of scar size reduction or enhanced neovascularisation. Instead, the beneficial effects of 11βHSD1i are likely to result from favourable regulation of collagen processing during scar formation.

Abstract Disclosure: L.D. Boyle: None. M. Nixon: None. C.M. Underhill: None. L.A. Hill: None. N.Z. Homer: None. M. Magennis: None. R. Andrew: None. G.L. Hammond: None. J.G. Lewis: None. R.H. Stimson: None. B.R. Walker: None. Background Corticosteroid Binding Globulin (CBG) binds >85% of plasma cortisol, modulating its biological activity. Proteolytic cleavage by neutrophil elastase (NE) reduces CBG binding capacity, proposed to increase free cortisol availability to inflamed tissues. Genetic variation at the locus spanning SERPINA1 (encoding alpha-1 antitrypsin, AAT, the endogenous inhibitor of NE) and SERPINA6 (CBG) altered morning total plasma cortisol. We hypothesised that AAT deficiency increased CBG cleavage and hence free plasma cortisol, resulting in amplified tissue cortisol delivery and increased HPA axis negative feedback. We tested this in recall-by-genotype studies of people who are heterozygous for inactivating mutations in SERPINA1. Methods 16 asymptomatic carriers of deleterious SERPINA1 single nucleotide polymorphisms (rs17580 & rs28929474) and 16 age-, gender- and BMI-matched controls were recruited from the Generation Scotland Biobank. To quantify in vivo whole body glucocorticoid appearance and clearance rates, and estimate tissue cortisol uptake, we performed arterio-venous plasma sampling across abdominal adipose and skeletal muscle during steady-state 9,11,12,12-[2H]4-cortisol tracer infusion. To assess endogenous negative feedback, participants underwent combined receptor antagonist stimulation of the HPA axis (‘CRASH’) testing using RU486 and spironolactone, or placebo in a double blind randomised crossover design. Total cortisol (LC-MS/MS), free cortisol (isotopic dilution & ultrafiltration), CBG binding capacity (radioligand displacement), CBG concentration and AAT (ELISA) were measured in plasma. Tissue cortisol (LC-MS/MS) and glucocorticoid-dependent transcripts (qPCR) were measured in adipose biopsy samples collected at end of study. Results AAT was ∼30% lower in AAT+/- (p=0.0002 vs control). Plasma CBG concentration, binding capacity and total cortisol were similar between groups. However, plasma free cortisol fraction was higher in AAT+/- subjects (16.1 +/- 0.2 vs 13.9 +/- 0.04 %, p<0.0001). Adipose tissue from AAT+/- subjects displayed increased cortisol levels and increased glucocorticoid-responsive transcripts PER1 and LPL compared to controls. Consistent with release from CBG, total and free cortisol release across skeletal muscle was increased in AAT+/- subjects vs controls. The rate of appearance of 9,12,12-[2H]3-cortisol was reduced in AAT+/- (p=0.03 vs control), consistent with decreased whole body 11β-HSD1 activity. CRASH testing did not reveal additional differences between groups. Discussion Subclinical AAT deficiency is associated with a higher free cortisol fraction and increased tissue glucocorticoid exposure. Although consistent with the hypothesis of local tissue-mediated control of glucocorticoid exposure via the NE/AAT/CBG axis, these findings were not accompanied by measurable changes in CBG. Presentation: 6/3/2024

11β-Hydroxysteroid dehydrogenase 1 (11βHSD1) is a drug target to attenuate adverse effects of chronic glucocorticoid excess. It catalyses intracellular regeneration of active glucocorticoids in tissues including brain, liver and adipose tissue (coupled to hexose-6-phosphate dehydrogenase, H6PDH). 11βHSD1 activity in individual tissues is thought to contribute significantly to glucocorticoid levels at those sites, but its local contribution vs glucocorticoid delivery via the circulation is unknown. Here, we hypothesised that hepatic 11βHSD1 would contribute significantly to the circulating pool. This was studied in mice with Cre-mediated disruption of Hsd11b1 in liver ( Alac -Cre) vs adipose tissue ( aP2 -Cre) or whole-body disruption of H6pdh . Regeneration of [9,12,12- 2 H 3 ]-cortisol (d3F) from [9,12,12- 2 H 3 ]-cortisone (d3E), measuring 11βHSD1 reductase activity was assessed at steady state following infusion of [9,11,12,12- 2 H 4 ]-cortisol (d4F) in male mice. Concentrations of steroids in plasma and amounts in liver, adipose tissue and brain were measured using mass spectrometry interfaced with matrix-assisted laser desorption ionisation or liquid chromatography. Amounts of d3F were higher in liver, compared with brain and adipose tissue. Rates of appearance of d3F were ~6-fold slower in H6pdh −/− mice, showing the importance for whole-body 11βHSD1 reductase activity. Disruption of liver 11βHSD1 reduced the amounts of d3F in liver (by ~36%), without changes elsewhere. In contrast disruption of 11βHSD1 in adipose tissue reduced rates of appearance of circulating d3F (by ~67%) and also reduced regenerated of d3F in liver and brain (both by ~30%). Thus, the contribution of hepatic 11βHSD1 to circulating glucocorticoid levels and amounts in other tissues is less than that of adipose tissue.

Cystatin C (CyC), a secreted cysteine protease inhibitor, has unclear biological functions. Many patients exhibit elevated plasma CyC levels, particularly during glucocorticoid (GC) treatment. This study links GCs with CyC's systemic regulation by utilizing genome-wide association and structural equation modeling to determine CyC production genetics in the UK Biobank. Both CyC production and a polygenic score (PGS) capturing predisposition to CyC production were associated with increased all-cause and cancer-specific mortality. We found that the GC receptor directly targets CyC, leading to GC-responsive CyC secretion in macrophages and cancer cells. CyC-knockout tumors displayed significantly reduced growth and diminished recruitment of TREM2+ macrophages, which have been connected to cancer immunotherapy failure. Furthermore, the CyC-production PGS predicted checkpoint immunotherapy failure in 685 patients with metastatic cancer from combined clinical trial cohorts. In conclusion, CyC may act as a GC effector pathway via TREM2+ macrophage recruitment and may be a potential target for combination cancer immunotherapy.

Searchable abstracts of presentations at key conferences in endocrinology ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

Children with diabetes may display cognitive alterations although vascular disorders have not yet appeared. Variations in glucose levels together with relative insulin deficiency in treated type 1 diabetes have been reported to impact brain function indirectly through dysregulation of the hypothalamus–pituitary–adrenal axis. We have recently shown that enhancement of glucocorticoid levels in children with type 1 diabetes is dependent not only on glucocorticoid secretion but also on glucocorticoid tissue concentrations, which is linked to 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) activity. Hypothalamus–pituitary–adrenal axis dysfunction and memory alteration were further dissected in a juvenile rat model of diabetes showing that excess 11β-HSD1 activity within the hippocampus is associated with hippocampal-dependent memory deficits. Here, to investigate the causal relationships between diabetes, 11β-HSD1 activity and hippocampus-dependent memory deficits, we evaluated the beneficial effect of 11β-HSD1 inhibition on hippocampal-related memory in juvenile diabetic rats. We also examined whether diabetes-associated enhancement of hippocampal 11β-HSD1 activity is due to an increase in brain glucose concentrations and/or a decrease in insulin signalling. Diabetes was induced in juvenile rats by daily i.p. injection of streptozotocin for 2 consecutive days. Inhibition of 11β-HSD1 was obtained by administrating the compound UE2316 twice daily by gavage for 3 weeks, after which hippocampal-dependent object location memory was assessed. Hippocampal 11β-HSD1 activity was estimated by the ratio of corticosterone/dehydrocorticosterone measured by LC/MS. Regulation of 11β-HSD1 activity in response to changes in glucose or insulin levels was determined ex vivo on acute brain hippocampal slices. The insulin regulation of 11β-HSD1 was further examined in vivo using virally mediated knockdown of insulin receptor expression specifically in the hippocampus. Our data show that inhibiting 11β-HSD1 activity prevents hippocampal-related memory deficits in diabetic juvenile rats. A significant increase (53.0±9.9