Diabetes, Vol 46, Issue 12 1965-1969, Copyright © 1997 by American Diabetes Association
Effect of insulin on GLUT4 cell surface content and turnover rate in human skeletal muscle as measured by the exofacial bis-mannose photolabeling technique
S Lund, GD Holman, JR Zierath, J Rincon, LA Nolte, AE Clark, O Schmitz, O Pedersen and H Wallberg-Henriksson
Medical Department M, Kommunehospitalet, Aarhus University Hospital, Denmark. sl@afdm.aau.dk
Insulin-stimulated glucose transport across the skeletal muscle cell
membrane is a major regulatory step in postprandial glucose disposal. To
estimate the total molar concentration of GLUT4 as well as the turnover
rate of GLUT4 in human vastus lateralis muscles at the cell surface in the
basal state and after insulin exposure, we have applied the sensitive
exofacial bis-mannose photolabeling technique on in vitro incubated human
skeletal muscle strips from healthy subjects. In addition, we have measured
3-O-methylglucose transport in other muscle strips prepared from the same
surgically removed human skeletal muscle biopsies to compare glucose
transport with cell surface level of GLUT4. Maximal in vitro insulin
stimulation (2,400 pmol/l) resulted in a twofold increase compared with
basal in both surface GLUT4 content (0.38 +/- 0.05 vs. 0.19 +/- 0.03 pmol/g
wet muscle wt, P < 0.005) and 3-O-methylglucose transport (1.24 +/- 0.13
vs. 0.63 +/- 0.08 pmol x ml(-1) x h(-1), P < 0.005). The insulin-induced
increment in 3-O-methylglucose transport was strongly correlated with the
insulin-induced increase in cell surface GLUT4 content (r2 = 0.91; P <
0.005). The calculated turnover rate of human skeletal muscle GLUT4
amounted to approximately 8 x 10(4) min(-1) at 35 degrees C and was
unaffected by insulin. In conclusion, maximal in vitro insulin stimulation
of vastus lateralis muscle strips from healthy subjects resulted in a
twofold rise in glucose transport as well as in cell surface content,
whereas the turnover rate of GLUT4 was unaffected by insulin under the
chosen experimental conditions.