Data confirming a role for PDE5 in adipocyte biology in vitro have been recently reported.
However, a better understanding of the complex role of PDE5 in fat metabolism and whole body
homeostasis requires the use of transgenic animal models either lacking or overexpressing
PDE5 in adipose tissue. This will clarify the role of PDE5 in adipose expansion and
metabolism, and also in glucose homeostasis and vascular function in vivo. Analysis of
expression and activity of PDE5 in different sites of human adipose tissue (i.e. visceral vs.
subcutaneous), and also in different metabolic conditions (i.e. high-fat diet vs. low calorie
intake) could reveal if PDE5 can be considered to be a reliable 'marker' of metabolic
dysfunction of the adipocyte. Importantly, chronic treatment with the PDE5 inhibitor
sildenafil in a mouse model of diet-induced insulin resistance caused a significant
improvement in insulin sensitivity . Also, in humans chronic exposure to tadalafil confirmed
an improvement of insulin sensitivity in men with erectile dysfunction. However, the efficacy
of long-term treatment with PDE5i awaits demonstration in human metabolic diseases such as
obesity and insulin resistance.
The primary purpose of the study is to investigate the effects of tadalafil taken once a day
on body composition in men with sexual distress and/or erectile dysfunction.