Modulation of glucose uptake in adipose tissue by nitric oxide-generating compounds

There is increasing evidence that endogenous nitric oxide (NO) influences adipogenesis, lipolysis and insulin-stimulated glucose uptake. We investigated the effect of NO released from S-nitrosoglutathione (GSNO) and S-nitroso-N-acetylpenicillamine (SNAP) on basal and insulin-stimulated glucose uptake in adipocytes of normoglycaemic and streptozotocin (STZ)-induced diabetic rats. GSNO and SNAP at 0.2, 0.5, and 1 mM brought about a concentration-dependent increase in basal and insulin-stimulated 2-deoxyglucose uptake in adipocytes of normoglycaemic and STZ-induced diabetic rats. SNAP at 1.0 mM significantly elevated basal 2-deoxyglucose uptake (115.8 +/- 10.4%) compared with GSNO at the same concentration (116.1 +/- 9.4%; P < 0.05) in STZ-induced diabetic rats. Conversely, SNAP at concentrations of 10 mM and 20 mM significantly decreased basal 2-deoxyglucose uptake by 50.0 +/- 4.5% and 61.5 +/- 7.2% respectively in adipocytes of STZ-induced diabetic rats (P < 0.05). GSNO at concentrations of 10 mM and 20 mM also significantly decreased basal 2-deoxyglucose uptake by 50.8 +/- 6.4% and 55.2 +/- 7.8% respectively in adipocytes of STZ-induced diabetic rats (P < 0.05). These observations indicate that NO released from GSNO and SNAP at 1 mM or less stimulates basal and insulin-stimulated glucose uptake, and at concentrations of 10 mM and 20 mM inhibits basal glucose uptake. The additive effect of GSNO or SNAP, and insulin observed in this study could be due to different mechanisms and warrants further investigation.