Glucosamine induces insulin resistance in vivo by affecting GLUT 4 translocation in skeletal muscle. Implications for glucose toxicity.

Abstract

Glucosamine (Glmn), a product of glucose metabolism via the hexosamine pathway, causes insulin resistance in isolated adipocytes by impairing insulin-induced GLUT 4 glucose transporter translocation to the plasma membrane. We hypothesized that Glmn causes insulin resistance in vivo by a similar mechanism in skeletal muscle. We performed euglycemic hyperinsulinemic clamps (12 mU/kg/min + 3H-3-glucose) in awake male Sprague-Dawley rats with and without Glmn infusion at rates ranging from 0.1 to 6.5 mg/ kg/min. After 4 h of euglycemic clamping, hindquarter muscles were quick-frozen and homogenized, and membranes were subfractionated by differential centrifugation and separated on a discontinuous sucrose gradient (25, 30, and 35 % sucrose). Membrane proteins were solubilized and immunoblotted for GLUT 4. With Glmn, glucose uptake (GU) was maximally reduced by 33± 1 %, P < 0.001. The apparent Glmn dose to reduce maximal GU by 50% was 0.1 mg/kg/ min or 1/70th the rate of GU on a molar basis. Control galactosamine and mannosamine infusions had no effect on GU. Relative to baseline, insulin caused a 2.6-fold increase in GLUT 4 in the 25% membrane fraction (f), P < 0.01, and a 40% reduction in the 35%f, P < 0.05, but had no effect on GLUT 4 in the 30%f, P = NS. Addition of Glmn to insulin caused a 41% reduction of GLUT 4 in the 25%f, P < 0.05, a 29% fall in the 30%f, and prevented the reduction of GLUT 4 in the 35%f. The 30%f membranes were subjected to a second separation with a 27 and 30% sucrose gradient. Insulin mobilized GLUT 4 away from the 30%f, P < 0.05, but not the 27%f. In contrast, Glmn reduced GLUT 4 in the 27%f, P < 0.05, but not the 30%f. Thus, Glmn appears to alter translocation of an insulin-insensitive GLUT 4 pool. Coinfusion of Glmn did not alter enrichment of the sarcolemmal markers 5'-nucleotidase, Na+/ K+ATPase, and phospholemman in either 25, 30, or 35%f. Thus, Glmn completely blocked movement of GLUT 4 induced by insulin. Glmn is a potent inducer of insulin resis-

Acute glucosamine-induced insulin resistance in muscle in vivo is associated with impaired capillary recruitment

“…Indeed the incorporation of labelled glucosamine into GLUT4-containing vesicles was increased by glucosamine infusion [46]. The finding that glucosamine inhibited the translocation of both an insulin-sensitive and an insulin-insensitive pool of GLUT4 [45] implies that glucosamine can act directly on GLUT 4 translocation. This is further supported by studies demonstrating that exercise-stimulated glucose uptake is also impaired by glucosamine [47].…”

“…Alternatively, the haemodynamic effects of insulin may result from increased glucose uptake and subsequent release of a metabolic vasodilator, in which case the blunted haemodynamic actions may be secondary to the impairment of metabolism by glucosamine. In this regard it has been suggested that the insulin resistance induced by glucosamine is caused by an impaired translocation of GLUT4 to the plasma membrane [45]. This has been proposed to result from glycosylation of proteins involved in the translocation and docking of GLUT4 to the plasma membrane [45].…”

“…In this regard it has been suggested that the insulin resistance induced by glucosamine is caused by an impaired translocation of GLUT4 to the plasma membrane [45]. This has been proposed to result from glycosylation of proteins involved in the translocation and docking of GLUT4 to the plasma membrane [45]. Indeed the incorporation of labelled glucosamine into GLUT4-containing vesicles was increased by glucosamine infusion [46].…”

Glucosamine activates the plasminogen activator inhibitor 1 gene promoter through Sp1 DNA binding sites in glomerular mesangial cells.

“…Although high glucose-induced insulin resistance was blocked by inhibition of GFA, this did not occur in the case of glucosamine, which promotes flux through the hexosamine pathway distal to this enzyme (17). Similarly, infusion of glucosamine into rats or overexpression of GFA in cultured cells or in trans-genic mice was found to result in insulin resistance (18)(19)(20)(21). Of interest, infusion of glucose, free fatty acids, uridine, or glucosamine into rats, each of which elevated levels of UDP-GlcNAc, increased leptin gene expression in muscle (22).…”

Dysfunction of Retinal Cell and Optic Nerve by Continuous Cerebroventricular Infusion of Glucosamine

“…In vivo experiments have revealed that glucosamine infusion induces insulin resistance in normoglycemic rats (Rosseti et al, 1995). This is accompanied by attenuating insulin-induced GLUT-4 translocation to the cell surface in skeletal muscle (Baron et al, 1995). It has also been reported that glucosamine infusion influences insulin sensitivity in skeletal muscle, adipose tissue, heart muscle and liver (Virkamaki et al, 1997).…”