Scott P. Webster

Intrahippocampal glucocorticoids generated by 11β-HSD1 affect memory in aged mice

11Beta-hydroxysteroid dehydrogenase type 1 (11β-HSD1) locally amplifies active glucocorticoids within specific tissues including in brain. In the hippocampus, 11β-HSD1 messenger RNA increases with aging. Here, we report significantly greater increases in intrahippocampal corticosterone (CORT) levels in aged wild-type (WT) mice during the acquisition and retrieval trials in a Y-maze than age-matched 11β-HSD1−/− mice, corresponding to impaired and intact spatial memory, respectively. Acute stress applied to young WT mice led to increases in intrahippocampal CORT levels similar to the effects of aging and impaired retrieval of spatial memory. 11β-HSD1−/− mice resisted the stress-induced memory impairment. Pharmacologic inhibition of 11β-HSD1 abolished increases in intrahippocampal CORT levels during the Y-maze trials and prevented spatial memory impairments in aged WT mice. These data provide the first in vivo evidence that dynamic increases in hippocampal 11β-HSD1 regenerated CORT levels during learning and retrieval play a key role in age- and stress-associated impairments of spatial memory.

Elevated hepatic 11β-hydroxysteroid dehydrogenase type 1 induces insulin resistance in uremia

Significance Prevalence of chronic kidney disease (CKD) has reached epidemic proportions in the Western world in recent decades. Abnormally elevated blood insulin and impaired insulin action (insulin resistance) are common complications of CKD, and are associated with increased cardiovascular-related deaths in CKD patients. Therefore, novel therapies are required to treat insulin resistance in CKD. Abnormally elevated levels of glucocorticoids can cause insulin resistance. Here we demonstrate a crucial role for the enzyme 11β-hydroxysteroid dehydrogenase type 1 (11βHSD1) predominantly in liver, which is essential for glucocorticoid production, in causing insulin resistance in CKD. Additionally, 11βHSD1 inhibition corrected insulin resistance in CKD rodent models. Taken together, this is strong evidence that selective inhibition of 11βHSD1 is a promising therapeutic target for treatment of insulin resistance in CKD. Insulin resistance and associated metabolic sequelae are common in chronic kidney disease (CKD) and are positively and independently associated with increased cardiovascular mortality. However, the pathogenesis has yet to be fully elucidated. 11β-Hydroxysteroid dehydrogenase type 1 (11βHSD1) catalyzes intracellular regeneration of active glucocorticoids, promoting insulin resistance in liver and other metabolic tissues. Using two experimental rat models of CKD (subtotal nephrectomy and adenine diet) which show early insulin resistance, we found that 11βHSD1 mRNA and protein increase in hepatic and adipose tissue, together with increased hepatic 11βHSD1 activity. This was associated with intrahepatic but not circulating glucocorticoid excess, and increased hepatic gluconeogenesis and lipogenesis. Oral administration of the 11βHSD inhibitor carbenoxolone to uremic rats for 2 wk improved glucose tolerance and insulin sensitivity, improved insulin signaling, and reduced hepatic expression of gluconeogenic and lipogenic genes. Furthermore, 11βHSD1−/− mice and rats treated with a specific 11βHSD1 inhibitor (UE2316) were protected from metabolic disturbances despite similar renal dysfunction following adenine experimental uremia. Therefore, we demonstrate that elevated hepatic 11βHSD1 is an important contributor to early insulin resistance and dyslipidemia in uremia. Specific 11βHSD1 inhibitors potentially represent a novel therapeutic approach for management of insulin resistance in patients with CKD.

11β-Hydroxysteroid dehydrogenase type 1 contributes to the balance between 7-keto- and 7-hydroxy-oxysterols in vivo

Graphical abstract

β-Cell-Specific Glucocorticoid Reactivation Attenuates Inflammatory β-Cell Destruction

Progression and severity of type 1 diabetes is dependent upon inflammatory induction of nitric oxide production and consequent pancreatic β-cell damage. Glucocorticoids (GCs) are highly effective anti-inflammatory agents but have been precluded in type 1 diabetes and in islet transplantation protocols because they exacerbated insulin resistance and suppressed β-cell insulin secretion at the high-doses employed clinically. In contrast, physiological-range elevation of GC action within β-cells ameliorated lipotoxic β-cell failure in transgenic mice overexpressing the intracellular enzyme 11β-hydroxysteroid dehydrogenase type 1 (MIP-HSD1tg/+ mice). Here, we tested the hypothesis that elevated β-cell 11beta-HSD1 protects against the β-cell destruction elicited by streptozotocin (STZ), a toxin that dose-dependently mimics aspects of inflammatory and autoimmune β-cell destruction. MIP-HSD1tg/+ mice exhibited an episodic protection from the severe hyperglycemia caused by a single high dose of STZ associated with higher and sustained β-cell survival, maintained β-cell replicative potential, higher plasma and islet insulin levels, reduced inflammatory macrophage infiltration and increased anti-inflammatory T regulatory cell content. MIP-HSD1tg/+ mice also completely resisted mild hyperglycemia and insulitis induced by multiple low-dose STZ administration. In vitro, MIP-HSD1tg/+ islets exhibited attenuated STZ-induced nitric oxide production, an effect reversed with a specific 11beta-HSD1 inhibitor. GC regeneration selectively within β-cells protects against inflammatory β-cell destruction, suggesting therapeutic targeting of 11beta-HSD1 may ameliorate processes that exacerbate type 1 diabetes and that hinder islet transplantation.

Quantification of 11β-hydroxysteroid dehydrogenase 1 kinetics and pharmacodynamic effects of inhibitors in brain using mass spectrometry imaging and stable-isotope tracers in mice

Graphical abstract Figure. No caption available. ABSTRACT 11&bgr;‐Hydroxysteroid dehydrogenase 1 (11&bgr;‐HSD1; EC 1.1.1.146) generates active glucocorticoid hormones. Small molecule inhibitors have been developed to target 11&bgr;‐HSD1 for the treatment of dementia; these must enter brain subregions, such as the hippocampus, to be effective. We previously reported mass spectrometry imaging measurement of murine tissue steroids, and deuterated steroid tracer infusion quantification of 11&bgr;‐HSD1 turnover in humans. Here, these tools are combined to assess tissue pharmacokinetics and pharmacodynamics of an 11&bgr;‐HSD1 inhibitor that accesses the brain. [9,11,12,12‐2H]4‐Cortisol was infused (1.75 mg/day) by minipump for 2 days into C57Bl6 mice (male, age 12 weeks, n = 3/group) after which an 11&bgr;‐HSD1 inhibitor (UE2316) was administered (25 mg/kg oral gavage) and animals culled immediately or 1, 2 and 4 h post‐dosing. Mice with global genetic disruption of Hsd11B1 were studied similarly. Turnover of d4‐cortisol to d3‐cortisone (by loss of the 11‐deuterium) and regeneration of d3‐cortisol (by 11&bgr;‐HSD1‐mediated reduction) were assessed in plasma, liver and brain using matrix assisted laser desorption ionization coupled to Fourier transform cyclotron resonance mass spectrometry. The tracer d4‐cortisol was detected in liver and brain following a two day infusion. Turnover to d3‐cortisone and on to d3‐cortisol was slower in brain than liver. In contrast, d3‐cortisol was not detected in mice lacking 11&bgr;‐HSD1. UE2316 impaired d3‐cortisol generation measured in whole body (assessed in plasma; 53.1% suppression in rate of appearance in d3‐cortisol), liver and brain. Differential inhibition in brain regions was observed; active glucocorticoids were suppressed to a greater in extent hippocampus or cortex than in amygdala. These data confirm that the contribution of 11&bgr;‐HSD1 to the tissue glucocorticoid pool, and the consequences of enzyme inhibition on active glucocorticoid concentrations, are substantial, including in the brain. They further demonstrate the value of mass spectrometry imaging in pharmacokinetic and pharmacodynamic studies.

Kynurenine 3-monooxygenase (KMO) is a critical regulator of renal ischemia-reperfusion injury

Acute kidney injury (AKI) following ischemia-reperfusion injury (IRI) has a high mortality and lacks specific therapies. Here, we report that mice lacking kynurenine 3-monooxygenase (KMO) activity (Kmonull mice) are protected against AKI after renal IRI. This advances our previous work showing that KMO blockade protects against acute lung injury and AKI in experimental multiple organ failure caused by acute pancreatitis. We show that KMO is highly expressed in the kidney and exerts major metabolic control over the biologically-active kynurenine metabolites 3-hydroxykynurenine, kynurenic acid and downstream metabolites. In experimental AKI induced by unilateral kidney IRI, Kmonull mice had preserved renal function, reduced renal tubular cell injury, and fewer infiltrating neutrophils compared to wild-type (Kmowt) control mice. Together, these data confirm that flux through KMO contributes to AKI after IRI, and supports the rationale for KMO inhibition as a therapeutic strategy to protect against AKI during critical illness.