Phosphodiesterase 5 Inhibitor Improves Insulin Sensitivity by Regulating Adipose Tissue Macrophage Polarization in Diet-Induced Obese Mice.

Background: Obesity is a rapidly increasing global health issue, which is associated with glucose and insulin resistance. Phosphodiesterase type 5 (PDE5) inhibitors (PDE5i) are known for their ability to enhance blood flow and vascular stability and are widely used to treat conditions such as erectile dysfunction, pulmonary hypertension, heart failure, and cancer. However, studies investigating the role of PDE5i in alleviating obesity and metabolic diseases remains unclear. Therefore, we investigated the effects of PDE5i on obesity and metabolic disorders in diet-induced obese mice and its underlying mechanisms.

Methods: PDE5i was administered to high-fat diet (HFD)-fed C57BL/6J mice for 6 to 7 weeks. Body weight and food intake were measured weekly, and baseline metabolic rates, physical activity, and glucose and insulin tolerance tests were assessed during PDE5i administration. Macrophages and T-cells in the gonadal white adipose tissue (gWAT) were analyzed by flow cytometry. Vascular stability and blood flow in gWAT were analyzed via immunostaining and in vivo live imaging. RAW264.7 cells and bone marrow-derived macrophages were used to determine immunoregulatory effects of PDE5i.

Results: In HFD-fed mice, PDE5i administration significantly enhanced systemic insulin sensitivity and AKT phosphorylation in gWAT. PDE5i reduced the M1/M2 ratio of gWAT macrophages of obese mice. These phenomena were associated with enhanced blood flow to the gWAT. In vitro experiments revealed that PDE5i suppressed lipopolysaccharide-induced proinflammatory cytokine production and increased the mRNA expression of genes associated with M2 polarization.

Conclusion: PDE5i plays a role in regulating adipose tissue inflammation and thus holds promise as a therapeutic agent for metabolic enhancement.