515.2 - Pharmacologic or Genetic PDE4 Inactivation Reduces Obesity and Improves Glucose Handling in Mice

Daniel Irelan (University of South Alabama College of Medicine), Abigail Boyd (University of South Alabama College of Medicine), Ileana Aragon (University of South Alabama College of Medicine), Edward Fiedler (University of South Alabama College of Medicine), Wito Richter (University of South Alabama College of Medicine)

Purpose:  Type 4 cyclic nucleotide phosphodiesterases (PDE4s) comprise a group of four isoenzymes (PDE4A to D) that hydrolyze the second messenger cAMP. Non/PAN-selective PDE4 inhibitors exert potent anti-inflammatory properties and are approved for the treatment of COPD and psoriasis, but are also associated with significant side effects, including nausea, emesis and weight loss. Here, we explored the idea that the weight loss associated with PAN-PDE4 inhibitor use may be pursued as a desirable therapeutic outcome in the treatment of obesity-related metabolic syndromes. As a first step, we tested whether treatment of mice with a PAN-PDE4 inhibitor would replicate clinical data and reduce ageing- and/or high-fat diet-induced obesity in the animals. As each of the four PDE4 subtypes plays unique physiological roles, targeting individual PDE4s is a promising approach to improve the tolerability of PDE4 inhibitor therapy. To this end, we determined the metabolic phenotypes of individual PDE4 subtypes in mice.

Methods: Body and tissue weights, food and water consumption, glucose and insulin tolerance, serum insulin and glucagon levels, and locomotor activity and exercise capacity were assessed in aged mice, as well as in young mice fed a high-fat diet. To delineate the role of PDE4s, the phenotypes of mice genetically deficient (KO) in each of the four individual PDE4 subtypes, PDE4A to PDE4D, were compared to their wildtype littermates, and mice treated with the PAN-PDE4 inhibitor Roflumilast were compared to solvent controls.

Results: Treatment with the PAN-PDE4 inhibitor Roflumilast reduced high-fat diet-induced obesity in mice, as reflected by reduced body weight and white fat pads, without lowering food consumption or increasing physical activity (unchanged locomotor activity and exercise capacity) suggesting that the weight-loss effect of PDE4 inhibition observed in clinical trials is replicated in the mouse. Genetic ablation of PDE4B or PDE4D in mice replicated the effects of PAN-PDE4 inhibition by reducing body- and adipose tissue weights in mice, whereas ablation of PDE4A or PDE4C had no effect. Reduced adiposity as a result of PDE4 inactivation was associated with improved glucose handling and insulin sensitivity, while serum levels of insulin and glucagon were unchanged. These data suggest that PDE4 inactivation does not act via pancreatic hormone release but acts in downstream target tissues to enhance glucose utilization.

Conclusions: Inactivation of PDE4s represents a promising approach to tackle obesity and associated metabolic abnormalities such as elevated blood glucose levels. Targeting PDE4B and/or PDE4D with subtype-selective PDE4 inhibitors appears sufficient to mediate these therapeutic benefits and may be free of the adverse effects associated with the PAN-PDE4 inhibitors available to date.

The work was supported in part by funds from the NIH (HL076125, HL141473, HL066299) and a Research Development grant from the University of South Alabama College of Medicine.