Abstract 12656: Phosphodiesterase 4 (PDE4) Inhibition Induces Weight Loss and Improves Insulin Resistance via cAMP-EPAC-AMPK Mediated Reprogramming of Macrophages
Objective: Recent evidence suggests an important role for cAMP-dependent pathways in modulation of innate immune function. Phosphodiesterase 4 (PDE4) is widely expressed in innate immune cells such as macrophages/dendritic cells with potent anti-inflammatory effects on pharmacologic inhibition of the enzyme. We investigated the importance of PDE4 in diet-induced obesity (DIO) and hypothesized that PDE4 inhibition will improve insulin sensitivity and reduce inflammation.
Methods and Results: PDE4 was upregulated in both visceral and subcutaneous (SubQ) white adipose tissue (WAT) in DIO mice (12 weeks of high-fat diet, HFD, 60% fat) compared to normal-chow diet (NCD) mice (↑4∼10-folds, p<0.01). The degree of expression was correlated with macrophage infiltration in stromal vascular fraction from WAT (CD11b+F4/80+ cells, r=0.56, p<0.05). Treatment with Roflumilast (3mg/kg/day), a high affinity inhibitor of PDE4 (IC50 0.39 nM) versus vehicle control (n=6∼10 in each group) for 21 days concomitant with HFD, resulted in rapid and substantial weight loss (↓45.8% fat content), enhanced thermogenesis [(∼20% higher oxygen consumption and heat production, 0.7∼1.1°C higher core body temperature in a cold environment (4°C)], brown adipose reprogramming, improvement in insulin resistance (HOMA-IR ↓ from 0.69±0.04 to 0.44±0.01, p<0.01) and hepatic steatosis. These changes were paralleled by increased alternative macrophage activation (Altf), reduced inflammation in WAT [↑CD206 and CD301 by flow cytometry with ↓ TNF/IL-6 gene expression] and activation of thermogenic genes in brown adipose tissue. In-vitro treatment of mouse bone marrow-derived macrophages (BMDM) promoted Altf and increased expression of tyrosine hydroxylase (↑2.5 folds) and catecholamines secretion. Additional experiments with agents that augment/reduce intracellular cAMP/EPAC/AMPK revealed an essential role for this cascade in Altf activation and catecholamine release.
Conclusions: PDE4 antagonism improves obese diabetic symptoms through convergent pathways involving Altf activation and enhancing thermogenesis via cAMP dependent modulation of macrophage catecholamine release.
Author Disclosures: C. Wu: None. A. Maiseyeu: None. J.A. Deiuliis: None. J. Zhong: None. X. Rao: None. Z. Ying: None. V. Bagalkot: None. S. Rajagopalan: None.
- © 2015 by American Heart Association, Inc.