Dean Larner

11β-HSD1 is the major regulator of the tissue-specific effects of circulating glucocorticoid excess

Significance Glucocorticoids are widely prescribed for their anti-inflammatory properties but have Cushingoid side effects that contribute significantly to patient morbidity and mortality. Here we present data to demonstrate that the adverse side-effect profile associated with exogenous active glucocorticoid (GC) administration (including glucose intolerance, hyperinsulinemia, hypertension, hepatic steatosis, increased adiposity, and myopathy) is prevented by global deletion of 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) in mice. This study not only defines a significant shift in our understanding of the physiological and molecular mechanisms underpinning the adverse side effects associated with GC use but also raises the possibility of targeting 11β-HSD1 as a novel adjunctive therapy in the treatment of Cushing syndrome. The adverse metabolic effects of prescribed and endogenous glucocorticoid (GC) excess, Cushing syndrome, create a significant health burden. We found that tissue regeneration of GCs by 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1), rather than circulating delivery, is critical to developing the phenotype of GC excess; 11β-HSD1 KO mice with circulating GC excess are protected from the glucose intolerance, hyperinsulinemia, hepatic steatosis, adiposity, hypertension, myopathy, and dermal atrophy of Cushing syndrome. Whereas liver-specific 11β-HSD1 KO mice developed a full Cushingoid phenotype, adipose-specific 11β-HSD1 KO mice were protected from hepatic steatosis and circulating fatty acid excess. These data challenge our current view of GC action, demonstrating 11β-HSD1, particularly in adipose tissue, is key to the development of the adverse metabolic profile associated with circulating GC excess, offering 11β-HSD1 inhibition as a previously unidentified approach to treat Cushing syndrome.

Remote control of glucose homeostasis in vivo using photopharmacology

Photopharmacology describes the use of light to precisely deliver drug activity in space and time. Such approaches promise to improve drug specificity by reducing off-target effects. As a proof-of-concept, we have subjected the fourth generation photoswitchable sulfonylurea JB253 to comprehensive toxicology assessment, including mutagenicity and maximum/repeated tolerated dose studies, as well as in vivo testing in rodents. Here, we show that JB253 is well-tolerated with minimal mutagenicity and can be used to optically-control glucose homeostasis in anesthetized mice following delivery of blue light to the pancreas. These studies provide the first demonstration that photopharmacology may one day be applicable to the light-guided treatment of type 2 diabetes and other metabolic disease states in vivo in humans.

Male 11β-HSD1 Knockout Mice Fed Trans-Fats and Fructose Are Not Protected From Metabolic Syndrome or Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) defines a spectrum of conditions from simple steatosis to nonalcoholic steatohepatitis (NASH) and cirrhosis and is regarded as the hepatic manifestation of the metabolic syndrome. Glucocorticoids can promote steatosis by stimulating lipolysis within adipose tissue, free fatty acid delivery to liver and hepatic de novo lipogenesis. Glucocorticoids can be reactivated in liver through 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) enzyme activity. Inhibition of 11β-HSD1 has been suggested as a potential treatment for NAFLD. To test this, male mice with global (11β-HSD1 knockout [KO]) and liver-specific (LKO) 11β-HSD1 loss of function were fed the American Lifestyle Induced Obesity Syndrome (ALIOS) diet, known to recapitulate the spectrum of NAFLD, and metabolic and liver phenotypes assessed. Body weight, muscle and adipose tissue masses, and parameters of glucose homeostasis showed that 11β-HSD1KO and LKO mice were not protected from systemic metabolic disease. Evaluation of hepatic histology, triglyceride content, and blinded NAFLD activity score assessment indicated that levels of steatosis were similar between 11β-HSD1KO, LKO, and control mice. Unexpectedly, histological analysis revealed significantly increased levels of immune foci present in livers of 11β-HSD1KO but not LKO or control mice, suggestive of a transition to NASH. This was endorsed by elevated hepatic expression of key immune cell and inflammatory markers. These data indicate that 11β-HSD1-deficient mice are not protected from metabolic disease or hepatosteatosis in the face of a NAFLD-inducing diet. However, global deficiency of 11β-HSD1 did increase markers of hepatic inflammation and suggests a critical role for 11β-HSD1 in restraining the transition to NASH.

Vitamin D-deficiency and sex-specific dysregulation of placental inflammation

To investigate an immunomodulatory role for vitamin D in pregnancy we used mice raised on vitamin D-sufficient (SUFF), or -deficient (DEF) diets. At embryonic day 14, pregnant mice received intraperitoneal injection of lipopolysaccharide (LPS) or vehicle for 24h, with age-matched non-pregnant mice as controls. In non-pregnant mice, 6 serum analytes (IL-1β, IL-18, MDC/CCL22, MIP-1α/CCL3, EGF, IgA) were lower in DEF mice. In pregnant DEF mice only GH was higher. In non-pregnant mice LPS induced 28 analytes, with 5 (IL-18, IP-10/CXCL10, MCP-1/CCL2, MIP-1β/CCL4, MIP-3β/CCL19) being highest in DEF mice. In pregnant SUFF mice 16 serum analytes increased with LPS, and 6 of these (IP-10/CXCL10, MCP-1/CCL2, SAP, TIMP-1, VCAM-1, vWF) were higher and 1 (GCP-2/CXCL6) lower in DEF mice. Parallel analysis of placental mRNAs showed elevated mRNA for Il-6, Ccl2 and Cxcl10 in placentae from male and female fetuses in LPS-DEF mice. However, LPS-induced expression of Ifnγ, Tnfα, and Cxcl6 was only observed in female placentae from DEF mice. LPS-DEF mice also showed smaller litter sizes relative to control SUFF mice. Numbers of female fetuses per dam were significantly lower for DEF mice with or without LPS challenge. LPS had no effect on numbers of male fetuses from DEF mothers, but significantly decreased male fetuses from SUFF mothers. These data indicate that vitamin D is an important component of anti-inflammatory immune responses during pregnancy, with the placenta and fetal sex playing pivotal roles in this process.

Regulation of Renal and Extrarenal 1α-Hydroxylase

Abstract The aim of this chapter is to describe the mechanisms associated with the regulation and function of the vitamin D-activating enzyme, 25-hydoxyvitamin D (25(OH)D)-1α-hydroxylase (1α-OHase) in two distinct settings. The first sections of the chapter will detail the pathways and key regulatory factors associated with renal expresssion of 1α-OHase and how this supports circulating levels of the active hormonal form of vitamin D, 1,25-dihydroxyvitamin D (1,25(OH) 2 D), and the endocrine actions of 1,25(OH) 2 D. The latter sections of the chapter will document how 1α-OHase is regulated outside the kidney. Numerous extrarenal sites have been reported to express 1α-OHase and the tissue-specific impact of this localized capacity to generate 1,25(OH) 2 D is documented in other chapters throughout the rest of the book. However, perhaps the most well-documented examples of extrarenal 1α-OHase expression and activity are the innate immune system and skin keratinocytes. The current chapter will therefore focus on these tissues to illustrate the specific pathways associated with the regulation of 1α-OHase outside the kidney. The overall aim of the chapter will be to describe the wide array of mechanisms that regulate synthesis of 1,25(OH) 2 D, the clinical implications of these mechanisms, and their translational potential.

11β-HSD1 Modulates the Set Point of Brown Adipose Tissue Response to Glucocorticoids in Male Mice.

Glucocorticoids (GCs) are potent regulators of energy metabolism. Chronic GC exposure suppresses brown adipose tissue (BAT) thermogenic capacity in mice, with evidence for a similar effect in humans. Intracellular GC levels are regulated by 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) activity, which can amplify circulating GC concentrations. Therefore, 11β-HSD1 could modulate the impact of GCs on BAT function. This study investigated how 11β-HSD1 regulates the molecular architecture of BAT in the context of GC excess and aging. Circulating GC excess was induced in 11β-HSD1 knockout (KO) and wild-type mice by supplementing drinking water with 100 μg/mL corticosterone, and the effects on molecular markers of BAT function and mitochondrial activity were assessed. Brown adipocyte primary cultures were used to examine cell autonomous consequences of 11β-HSD1 deficiency. Molecular markers of BAT function were also examined in aged 11β-HSD1 KO mice to model lifetime GC exposure. BAT 11β-HSD1 expression and activity were elevated in response to GC excess and with aging. 11β-HSD1 KO BAT resisted the suppression of uncoupling protein 1 (UCP1) and mitochondrial respiratory chain subunit proteins normally imposed by GC excess. Furthermore, brown adipocytes from 11β-HSD1 KO mice had elevated basal mitochondrial function and were able to resist GC-mediated repression of activity. BAT from aged 11β-HSD1 KO mice showed elevated UCP1 protein and mitochondrial content, and a favorable profile of BAT function. These data reveal a novel mechanism in which increased 11β-HSD1 expression, in the context of GC excess and aging, impairs the molecular and metabolic function of BAT.

Brown tumors of primary hyperparathyroidism may be a source of extrarenal 1,25-dihydroxyvitamin D production

Primary hyperparathyroidism (PHPT) is classically characterized by hypercalcemia and an elevated or inappropriately normal parathyroid hormone (PTH) concentration. Associated biochemical indices include a serum phosphorus concentration in the lower range of normal [1], total alkaline phosphatase activity in the upper range of normal [2], low 25-hydroxyvitamin D (25(OH)D) levels [3], and 1,25dihydroxyvitamin D (1,25(OH)2D) levels that are in the upper range of normal or frankly elevated [4]. PTH facilitates the 1α-hydroxylase enzymatic conversion of 25(OH) D to 1,25(OH)2D, a property that helps to account for the classic depiction of 25(OH)D and 1,25(OH)2D D levels in PHPT [5]. Other diseases associated with overproduction of 1,25(OH)2D include sarcoidosis and tuberculosis in which macrophages in the associated granulomas have acquired the 1α-hydroxylase activity. In lymphomas as well, 1,25 (OH)2D-mediated hypercalcemia has been shown to be associated with abnormal synthesis of 1,25(OH)2D by macrophages in the lymphomatous tissue [6]. Today, in parts of the world where calcium is measured routinely, most patients with PHPT lack the overt renal and skeletal manifestations of PHPT which include osteitis fibrosa cystica, a skeletal feature of PHPT characterized by marked radiographic demineralization, fibrosis, brown tumors, and cysts. Histologically, the brown tumors consist of giant cells and fibroblastic stroma. The presentation of such bone lesions is now considered to be an unusual manifestation of PHPT in countries where asymptomatic PHPT has become the predominant presentation of the disease. Thus, the elevated 1,25(OH)2D level in the usual form of PHPT seen today is appropriately assumed to be of renal origin. However, in the case of PHPT associated with brown tumors, it is possible that the macrophages contained therein could contribute to excessive extrarenal production of 1,25 (OH)2D levels. We report an unusual case of a patient with PHPT who was evaluated for a lytic lesion in the maxilla that was shown to be a brown tumor and to be an additional source of 1,25(OH)2D.