The Selective Phosphodiesterase-5 Inhibitor Tadalafil Induces Microvascular and Metabolic Effects in Type 2 Diabetic Postmenopausal Females

Objective: The objective of the study was to explore the acute in vivo effects of the selective phosphodiesterase-5 inhibitor tadalafil on local microcirculation and regional metabolism in skeletal muscle and adipose tissue (AT). Design, Setting, and Participants: We studied eight postmenopausal female patients with type 2 diabetes (T2D) and eight nondiabetic controls (Ctrl) in the postabsorptive state and 180 min after the administration of tadalafil 10 mg. Intramuscular and sc microdialysis were combined with measurements of forearm (FBF) and AT blood flow as well as with arterial and deep venous blood sampling. Muscle capillary recruitment, as ascertained by the permeability surface area product for glucose (PSglu), forearm glucose uptake (FGU), interstitial lactate, and glycerol concentrations, was measured. Results: When compared with Ctrl, T2D patients exhibited lower (P = 0.01) PSglu but similar FGU and FBF. After tadalafil, PSglu (P = 0.01) and muscle interstitial-arterial (I-A) lactate concentration gradient (P = 0.01) increased significantly in both groups, whereas FBF, FGU, and I-A glycerol remained unchanged. In AT, tadalafil did not significantly affect local blood flow, whereas the sc interstitial (I) lactate and I-A lactate concentrations increased (P = 0.01), and the I-A glycerol decreased in both groups. Finally, in multivariate analysis the PSglu was a strong and independent predictor of muscle glucose disposal (beta: 0.737 and 0.963, P < 0.05, in Ctrl and T2D, respectively). Conclusions: Tadalafil emerges as an acutely acting modulator of microvascular recruitment and glucose metabolism in skeletal muscle and adipose tissue. We suggest that selective phosphodiesterase-5 blockade may provide a path forward to new therapeutics in the setting of insulin resistance. (J Clin Endocrinol Metab 98: 245-254, 2013)