GLUT4 glucose transporter content and glucose transport capacity are closely correlated in skeletal muscle. In this study, we tested the hypothesis that a rapid increase in GLUT4 expression occurs as part of the early adaptive response of muscle to exercise and serves to enhance glycogen storage. Rats exercised by swimming had a approximately 2-fold increase in GLUT4 mRNA and a 50% increase in ...

Systemic glucose homeostasis is profoundly influenced by adipose cell function. Here we investigated GLUT4 dynamics in living adipose cells from human subjects with varying BMI and insulin sensitivity index (Si) values. Cells were transfected with hemagglutinin (HA)-GLUT4-green fluorescent protein (GFP)/mCherry (red fluorescence), and were imaged live using total internal reflection fluorescenc...

The aminopeptidase vp165 is one of the major polypeptides enriched in GLUT4-containing vesicles immuno-isolated from adipocytes. In the present study we have confirmed and quantified the high degree of colocalisation between GLUT4 and vp165 using double label immuno-electron microscopy on vesicles isolated from adipocytes and heart. The percentage of vp165-containing vesicles that also containe...

Glucose transporter 4 (GLUT4) is responsible for the uptake of glucose into muscle and adipose tissues. Under resting conditions, GLUT4 is dynamically retained through idle cycling among selective intracellular compartments, from whence it undergoes slow recycling to the plasma membrane (PM). This dynamic retention can be released by command from intracellular signals elicited by insulin and ot...

Insulin stimulates glucose transport by recruiting the GLUT4 glucose transporter to the plasma membrane. Here we use total internal reflection fluorescence microscopy to show that two trafficking motifs of GLUT4, a FQQI motif and a TELE-based motif, target GLUT4 to specialized vesicles that accumulate adjacent to the plasma membrane of unstimulated adipocytes. Mutations of these motifs redistri...

Hyperglycemia and hyperinsulinemia are cardinal features of acquired insulin resistance. In adipose cell cultures, high glucose and insulin cause insulin resistance of glucose uptake, but because of altered GLUT4 expression and contribution of GLUT1 to glucose uptake, the basis of insulin resistance could not be ascertained. Here we show that GLUT4 determines glucose uptake in L6 myotubes stabl...

The effects of exercise training on systolic blood pressure (BP), insulin sensitivity, and plasma membrane GLUT4 protein content in spontaneously hypertensive (SHR) and normotensive Wistar-Kyoto (WKY) rats were compared. 16 SHR and 16 WKY male rats, aged 6 months, were randomized into sedentary and trained (treadmill running, 5 days/week, 60 min/day for 10 weeks) groups (n=8/group). At baseline...

Ojuka EO, Goyaram V, Smith JA. The role of CaMKII in regulating GLUT4 expression in skeletal muscle. Am J Physiol Endocrinol Metab 303: E322–E331, 2012. First published April 10, 2012; doi:10.1152/ajpendo.00091.2012.—Contractile activity during physical exercise induces an increase in GLUT4 expression in skeletal muscle, helping to improve glucose transport capacity and insulin sensitivity. An ...

Insulin stimulates glucose uptake into adipocytes by promoting the translocation of the glucose transporter isoform 4 (GLUT4) from intracellular vesicles to the plasma membrane. In 3T3-L1 adipocytes GLUT4 resides both in an endosomal pool, together with transferrin receptors, and in a unique pool termed 'GLUT4 storage vesicles' (GSVs), which excludes endosomal proteins. The trafficking of GLUT4...

Previous studies have shown that chronic salt overload increases insulin sensitivity, while chronic salt restriction decreases it. In the present study we investigated the influence of dietary sodium on 1) GLUT4 gene expression, by No the n and Western blotting analysis; 2) in vivo GLUT4 protein translocation, by measuring the GLUT4 protein in plasma membrane and microsome, before and after ins...