Regulation of cAMP accumulation and activity by distinct phosphodiesterase subtypes in INS-1 cells and human pancreatic β-cells

Abstract

Pancreatic β-cells express multiple phosphodiesterase (PDE) subtypes, but the specific roles for each in β-cell function, particularly in humans, is not clear. We evaluated the cellular role of PDE1, PDE3, and PDE4 activity in the rat insulinoma cell line INS-1 and in primary human β-cells using subtype-selective PDE inhibitors. Using a genetically encoded, FRET-based cAMP sensor, we found that the PDE1 inhibitor 8MM-IBMX, elevated cAMP levels in the absence of glucose to a greater extent than either the PDE3 inhibitor cilostamide or the PDE4 inhibitor rolipram. In 18 mM glucose, PDE1 inhibition elevated cAMP levels to a greater extent than PDE3 inhibition in INS-1 cells, while PDE4 inhibition was without effect. Inhibition of PDE1 or PDE4, but not PDE3, potentiated glucose-stimulated insulin secretion in INS-1 cells. PDE1 inhibition, but not PDE3 or PDE4 inhibition, reduced palmitate-induced caspase-3/7 activation, and enhanced CREB phosphorylation in INS-1 cells. In human β-cells, only PDE3 or PDE4 inhibition increased cAMP levels in 1.7 mM glucose, but PDE1, PDE3, or PDE4 inhibition potentiated cAMP levels in 16.7 mM glucose. Inhibition of PDE1 or PDE4 increased cAMP levels to a greater extent in 16.7 mM glucose than in 1.7 mM glucose in human β-cells. In contrast, elevation of cAMP levels by PDE3 inhibition was not different at these glucose concentrations. PDE1 inhibition also potentiated insulin secretion from human islets, suggesting that the role of PDE1 may be conserved between INS-1 cells and human pancreatic β-cells. Our results suggest that inhibition of PDE1 may be a useful strategy to potentiate glucose-stimulated insulin secretion, and to protect β-cells from the toxic effects of excess fatty acids.

Acute Hemodynamic Effects and Tolerability of Phosphodiesterase-1 Inhibition With ITI-214 in Human Systolic Heart Failure

“…Lastly, PDE1 inhibition has been linked to improved insulin signaling and may have a beneficial impact on diabetes. 40 Its inhibition was also recently found to protect against proteotoxicity in mice with misfolded protein disease. 41 These effects from PDE1 inhibition are potentially relevant to various heart failure syndromes.…”

Identification of Multiple Pancreatic and Extra-Pancreatic Pathways Underlying the Glucose-Lowering Actions of Acacia arabica Bark in Type-2 Diabetes and Isolation of Active Phytoconstituents

“…These studies revealed that the action of A. arabica involved the closure of K-ATP channels, membrane depolarisation, the opening of voltage-dependent calcium channels, the influx of Ca 2+ and the elevation of intracellular Ca 2+ . Stimulatory effects nevertheless persisted in β cells depolarised by tolbutamide or 30 mM KCl, suggesting additional actions such as the activation of adenylate cyclase, which is supported by positive potentiation by the phosphodiesterase inhibitor, IBMX [25].…”

Acute PDE4 Inhibition Induces a Transient Increase in Blood Glucose in Mice

“…Second, PDE4 has been shown to be expressed in the rat insulinoma cell line INS-1 and primary human β-cells. However, PDE1 and PDE3, not PDE4, appear to be the primary regulators of insulin secretion and, as mentioned earlier, increased cAMP signaling resulting from PDE inhibition within β-cells should be promoting insulin release, rather than inhibiting it [ 7 , 45 , 46 , 47 ].…”