Adipocyte-Specific Glucocorticoid Inactivation Protects Against Diet-Induced Obesity

Erin E. Kershaw 1 Nicholas M. Morton 0 Harveen Dhillon 1 Lynne Ramage 0 Jonathan R. Seckl 0 Jeffrey S. Flier 1 0 Endocrinology Unit, Molecular Medicine Center, University of Edinburgh, Western General Hospital, Edinburgh, U.K. Division of Endocrinology and Metabolism, Department of Medicine, Beth Israel Deaconess Medical Center , 330 Brookline Ave., Boston, MA 02215 1 Division of Endocrinology and Metabolism, Department of Medi- cine, Beth Israel Deaconess Medical Center, Harvard Medical School , Boston, Massachusetts; and the Local glucocorticoid (GC) action depends on intracellular GC metabolism by 11-hydroxysteroid dehydrogenases (11HSDs). 11HSD1 activates GCs, while 11HSD2 inactivates GCs. Adipocyte-specific amplification of GCs through transgenic overexpression of 11HSD1 produces visceral obesity and the metabolic syndrome in mice. To determine whether adipocytespecific inactivation of GCs protects against this phenotype, we created a transgenic model in which human 11HSD2 is expressed under the control of the murine adipocyte fatty acid binding protein (aP2) promoter (aP2-h11HSD2). Transgenic mice have increased 11HSD2 expression and activity exclusively in adipose tissue, with the highest levels in subcutaneous adipose tissue, while systemic indexes of GC exposure are unchanged. Transgenic mice resist weight gain on high-fat diet due to reduced fat mass accumulation. This improved energy balance is associated with decreased food intake, increased energy expenditure, and improved glucose tolerance and insulin sensitivity. Adipose tissue gene expression in transgenic mice is characterized by decreased expression of leptin and resistin and increased expression of adiponectin, peroxisome proliferator-activated receptor , and uncoupling protein 2. These data suggest that reduction of active GCs exclusively in adipose tissue is an important determinant of a favorable metabolic phenotype with respect to energy homeostasis and the metabolic syndrome. Diabetes 54:1023-1031, 2005 - Gcose homeostasis, insulin sensitivity, lipid lucocorticoids (GCs) play a critical role in multiple metabolic processes, including glumetabolism, and adipogenesis. GC excess, whether endogenous (Cushings syndrome) or exogenous, promotes visceral obesity, insulin resistance, dyslipidemia, and hypertension (1). A similar constellation of metabolic abnormalities is associated with idiopathic obesity and defines the much more prevalent metabolic syndrome (1, 2). While subtle alterations in the hypothalamicpituitary-adrenal axis have been reported in idiopathic obesity and the metabolic syndrome, no clear role for increased circulating GCs has been established (3). GC action in target tissues, however, not only depends on circulating GC concentrations and cellular GC receptor (GR) expression but also on tissue-specific intracellular GC metabolism by 11-hydroxysteroid dehydrogenases (11HSDs) (4). 11HSDs act at the prereceptor level to catalyze the interconversion of hormonally active 11hydroxylated GCs (cortisol in human and corticosterone in mice) and their hormonally inactive 11-keto metabolites (cortisone in humans and 11-dehydrocorticosterone [11DHC] in mice) (5). Two isoforms of 11HSD have been identified. 11HSD1 is a low-affinity NADPH-dependent reductase expressed primarily in GC target tissues, such as liver, adipose tissue, and the central nervous system, where it amplifies local GC action. 11HSD2 is a highaffinity NAD-dependent dehydrogenase expressed primarily in mineralocorticoid target tissues, such as kidney, where it potently decreases local GC action, thus ensuring that only the nonsubstrate aldosterone can access intrinsically nonselective mineralocorticoid receptors (6,7). Evidence is rapidly accumulating to support a role for 11HSD1 in the pathogenesis of visceral obesity and the metabolic syndrome. 11HSD1 is decreased in liver and enhanced in mesenteric adipose tissue (MAT) in several models of rodent obesity, including leptin-resistant Leprfa/ Leprfa rats (8,9) and leptin-deficient Lepob/Lepob mice (10). Several studies have shown that 11HSD1 activity and expression in subcutaneous adipose tissue (SCAT) are positively correlated with obesity and insulin resistance in both men and women (1117). In addition, polymorphic variability at the 11HSD1 locus is associated with increased waist-to-hip ratio in adults (18) and with body composition and insulin resistance in children (19). As such, 11HSD1 has been proposed as a novel therapeutic target for the treatment of obesity and the metabolic syndrome. Indeed, pharmacologic inhibition of 11HSD1 in obese rodents improves glucose tolerance, insulin sensitivity, and lipid profiles (20 22). While such treatment is associated with alterations in hepatic gene expression, adipose tissue has not been evaluated (20,21). Similarly, mice with targeted disruption of 11HSD1 in all tissues have reduced weight gain on high-fat diet (HFD), attenuated gluconeogenic response to fasting, improved glucose tolerance and insulin sensitivity, and atheroprotective lipid profiles, despite having modestly elevated serum corticosterone levels (2325). This favorable metabolic phenotype is associated with improved GC-related metabolic functions in both liver (24) and adipose tissue (25). Nevertheless, both pharmacologic inhibition and targeted gene deletion of 11HSD1 affect all tissues, and, hence, the relative contribution of any individual tissue to overall metabolic phenotype is unclear. Transgenic mouse models have provided insight into the role of 11HSD1 in individual tissues. Mice with adipocyte-specific overexpression of 11HSD1 driven by the murine adipocyte fatty acid binding protein (aP2) promoter develop visceral obesity and the metabolic syndrome (10,26). In contrast, mice with liver-specific overexpression of 11HSD1 driven by the human apolipoprotein E promoter develop insulin resistance, dyslipidemia, and hypertension without obesity (27). These data suggest that GC amplification in adipose tissue, more than liver, contributes to overall energy balance. Whether 11HSD1 in adipose tissue contributes to the other features of the metabolic syndrome, independent of liver, is unknown. Furthermore, the phenotypic consequences of inhibition or absence of GC regeneration by 11HSD1 exclusively in adipose tissue has not been explored. We hypothesized that a reduction of active GCs exclusively in adipose tissue is an important determinant of a favorable metabolic phenotype with respect to energy homeostasis and features of the metabolic syndrome. To test this hypothesis, we generated an animal model of adipocyte-specific GC inactivation through ectopic overexpression of h11HSD2 under the control of the murine aP2 promoter. RESEARCH DESIGN AND METHODS Generation of the aP2-h11HSD2 construct and transgenic mice. A 5.4-kb fragment corresponding to position 5.4 to 21 of the murine aP2 promoter (provided by B.M. Spiegelman) was ligated to a 1.9-kb fragment (...truncated)