Reduction of Hepatic and Adipose Tissue Glucocorticoid Receptor Expression With Antisense Oligonucleotides Improves Hyperglycemia and Hyperlipidemia in Diabetic Rodents Without Causing Systemic Glucocorticoid Antagonism

Abstract

Glucocorticoids (GCs) increase hepatic gluconeogenesis and play an important role in the regulation of hepatic glucose output. Whereas systemic GC inhibition can alleviate hyperglycemia in rodents and humans, it results in adrenal insufficiency and stimulation of the hypothalamic-pituitary-adrenal axis. In the present study, we used optimized antisense oligonucleotides (ASOs) to cause selective reduction of the glucocorticoid receptor (GCCR) in liver and white adipose tissue (WAT) and evaluated the resultant changes in glucose and lipid metabolism in several rodent models of diabetes. Treatment of ob/ob mice with GCCR ASOs for 4 weeks resulted in ϳ75 and ϳ40% reduction in GCCR mRNA expression in liver and WAT, respectively. This was accompanied by ϳ65% decrease in fed and ϳ30% decrease in fasted glucose levels, a 60% decrease in plasma insulin concentration, and ϳ20 and 35% decrease in plasma resistin and tumor necrosis factor-␣ levels, respectively. Furthermore, GCCR ASO reduced hepatic glucose production and inhibited hepatic gluconeogenesis in liver slices from basal and dexamethasone-treated animals. In db/db mice, a similar reduction in GCCR expression caused ϳ40% decrease in fed and fasted glucose levels and ϳ50% reduction in plasma triglycerides. In ZDF and high-fat diet-fed streptozotocin-treated (HFD-STZ) rats, GCCR ASO treatment caused ϳ60% reduction in GCCR expression in the liver and WAT, which was accompanied by a 40 -70% decrease in fasted glucose levels and a robust reduction in plasma triglyceride, cholesterol, and free fatty acids. No change in circulating corticosterone levels was seen in any model after GCCR ASO treatment. To further demonstrate that GCCR ASO does not cause systemic GC antagonism, normal Sprague-Dawley rats were challenged with dexamethasone after treating with GCCR ASO. Dexamethasone increased the expression of GCresponsive genes such as PEPCK in the liver and decreased circulating lymphocytes. GCCR ASO treatment completely inhibited the increase in dexamethasoneinduced PEPCK expression in the liver without causing any change in the dexamethasone-induced lymphopenia. These studies demonstrate that tissue-selective GCCR antagonism with ASOs may be a viable therapeutic strategy for the treatment of the metabolic syndrome.

Diabetes impairs hippocampal function through glucocorticoid-mediated effects on new and mature neurons

“…Similar results were observed following treatment with the glucocorticoid receptor antagonist RU486 in the Zucker (fa/fa) rat, with no effect of antiglucocorticoid treatment on fed glucose levels 19 . In contrast, treatment with antisense oligonucleotides directed against the glucocorticoid receptor restored normal fasting glucose levels in Zucker diabetic rats 20 . Taken together, these results suggest that inhibiting the actions of corticosterone by various methods will influence fasting, but not fed glucose levels in animal models of type 2 diabetes.…”

Reduction of hepatic glucocorticoid receptor and hexose-6-phosphate dehydrogenase expression ameliorates diet-induced obesity and insulin resistance in mice

“…In rodents, increased hepatic GR mRNA induces activation of the key hepatic gluconeogenic enzyme phosphoenolpyruvate carboxykinase (PEPCK) leading to hyperglycemia and insulin resistance in diabetic db/db mice and obese Zucker rats (Jenson et al 1996, Stafford et al 2001, Liu et al 2005. Pharmacological evidence further validates that selective inactivation of GR improves insulin resistance and obesity in these diabetic animals and patients with Cushing's syndrome (Okada et al 1992, Sartor & Cutler 1996, Watts et al 2005. Moreover, specific inactivation of hepatic GR reduces elevated glucose output and reduces hyperglycemia and insulin resistance in diabetic models (Opherk et al 2004).…”

Glucocorticoids, metabolism and metabolic diseases

“…These effects are accompanied by a down-regulation of gluconeogenic enzyme genes upon GR ablation [50], suggesting a causal role of the GR for the induction of gluconeogenesis under insulin-resistant, diabetic conditions. Indeed, liver-specific GR antagonism by antisense oligonucleotides or synthetic compounds is sufficient to cause substantial improvement of hyperglycemia and dyslipidemia in animal models of type II diabetes [51][52][53][54]. Also, the GR itself has been found to be over-expressed in hepatocytes of diabetic rodent models, in particular in its nuclear, active fraction [55,56], further substantiating the notion that the GC-GR axis plays a critical role in determining hepatic glucose output via its regulatory function for the promoter activity of gluconeogenic enzyme genes.…”