Defective P2Y purinergic receptor function: A possible novel mechanism for impaired glucose transport

Abstract

Extracellular ATP is an ubiquitous mediator that regulates several cellular functions via specific P2 plasma membrane receptors (P2Rs), for which a role in modulating intracellular glucose metabolism has been recently suggested. We have investigated glucose uptake in response to P2Rs stimulation in fibroblasts from type 2 diabetic (T2D) patients and control subjects. P2Rs expression was evaluated by RT-PCR; intracellular calcium release by fluorometry; glucose transporter (GLUT1) translocation by immunoblotting and chemiluminescence; glucose uptake was measured with 2-deoxy-D-[1-(3)H]glucose (2-DOG) and ATP by luminometry. Cells from T2D patients, in contrast to those from healthy controls, showed no increase in glucose uptake after ATP stimulation; extracellular ATP caused, however, a similar GLUT1 recruitment to the plasma membrane in both groups. P2Rs expression did not differ between fibroblasts from diabetic and healthy subjects, but while plasma membrane depolarization, a P2X-mediated response was similar in both groups, no evident intracellular calcium increase was detectable in the cells from the former group. The calcium response in fibroblasts from diabetics was restored by co-incubation with apyrase or hexokinase, suggesting that P2YRs in those cells were normally expressed but chronically desensitised. In support to this finding, fibroblasts from T2D subjects secreted a two-fold larger amount of ATP compared to controls. Pre-treatment with apyrase or hexokinase also restored ATP stimulated glucose uptake in fibroblasts from diabetic subjects. These results suggest that extracellular ATP plays a role in the modulation of glucose transport via GLUT1, and that the P2Y-dependent GLUT1 activation is deficient in fibroblasts from T2D individuals. Our observations may point to additional therapeutic targets for improving glucose utilization in diabetes.

International Union of Pharmacology LVIII: Update on the P2Y G Protein-Coupled Nucleotide Receptors: From Molecular Mechanisms and Pathophysiology to Therapy

“…Thus, they are a candidate target for the design of innovative antidiabetic drugs (Solini et al, 2003).…”

Pathophysiology and Therapeutic Potential of Purinergic Signaling

“…P2Y purinoceptors appear to be impaired in fibroblasts from type 2 diabetic patients, which results in reduced glucose uptake via the glucose transporter GLUT 1, suggesting that P2Y receptors may be candidate targets for the design of innovative antidiabetic drugs (Solini et al, 2003). Hormone-specific defects in insulin regulation of ATPase that may contribute to their insulin resistance are seen in non-insulin-dependent diabetic rats (Levy et al, 1994).…”

P2X receptors regulate adenosine diphosphate release from hepatic cells

“…The gated ion channel, P2X7 receptor, has also been shown to activate both the immune and inflammatory responses [25,26]. Fibroblasts from type 2 diabetic patients show 2-3-fold increase in ATP secretion [27] and enhanced inflammatory and cytotoxic responses through the P2X7 receptor [28].…”