δ‐Opioid receptors stimulate GLUT1‐mediated glucose uptake through Src‐ and IGF‐1 receptor‐dependent activation of PI3‐kinase signalling in CHO cells

Abstract

BACKGROUND AND PURPOSEAlthough opioids have been reported to affect glucose homeostasis, relatively little is known on the role of d-opioid receptors. We have investigated the regulation of glucose transport by human d-opioid receptors expressed in Chinese hamster ovary cells. EXPERIMENTAL APPROACHThe uptake of [ ]-2-deoxy-D-glucose uptake that occurred without a change in plasma membrane GLUT1 -required the coupling to Gi/Go proteins -was independent of cAMP and extracellular signal-regulated protein kinases, and was suppressed by blockade of Src and insulin-like growth factor-1 receptor (IGF-1R) tyrosine kinases. Inhibition of phosphatidylinositol 3-kinase (PI3K) by wortmannin or LY294002 and by PI3Ka, but not g, isoform-selective inhibitors greatly reduced the d-opioid receptor stimulation of glucose uptake. Moreover, the response was attenuated by overexpressing a dominant-negative kinase-deficient Akt form and by chemical inhibition of Akt. Stimulation of d-opioid receptors increased protein kinase Cz/l (PKCz/l) phosphorylation and a selective PKCz/l inhibitor slightly reduced opioid stimulation of glucose uptake.

δ-Opioid Receptors Stimulate the Metabolic Sensor AMP-Activated Protein Kinase through Coincident Signaling with Gq/11-Coupled Receptors

“…9B). As reported previously (Olianas et al, 2011), DOR activation by SNC 80 (100 nM) increased glucose uptake by 140 Ϯ 8% (p Ͻ 0.001, n ϭ 6) (Fig. 9C).…”

“…We have recently reported that in CHO/DOR cells, activation of DOR stimulate GLUT1-dependent glucose uptake through a mechanism involving transactivation of insulin-like growth factor1 (IGF1) receptor tyrosine kinase and phosphatidylinositol 3-kinase (PI3K) pathway (Olianas et al, 2011). There is evidence for the occurrence in different cell types of a crosstalk between AMPK and insulin receptor signaling (Towler and Hardie, 2007), and it has been reported that AMPK may regulate PI3K activity (Jakobsen et al, 2001;Tao et al, 2010).…”

“…Because DORs have been reported to affect energy homeostasis (Evans et al, 2001;Olianas et al, 2011), initially it was important to determine the effects of DOR stimulation on intracellular AMP/ATP ratio. AMP levels in CHO cells were too low to be accurately measured with HPLC analysis.…”

“…Similar to AMPK, DORs have been reported to stimulate glucose uptake in skeletal muscle and transfected cells (Evans et al, 2001;Olianas et al, 2011) and to exert neuroprotective effects under hypoxic and ischemic insults (Bofetiado et al, 1996;Zhang et al, 2002). Moreover, it has been shown that DOR agonists increase food intake by acting on distinct brain areas, including the hypothalamus (Glass et al, 1999).…”

“…The measurement of 2-deoxy-D-glucose uptake by CHO/DOR cells was performed as described previously (Olianas et al, 2011). In brief, confluent cell monolayers were incubated in serum-free Ham's F12 medium for 12 h and treated with the agents or the corresponding vehicles as specified in the figure legends.…”