Evaluation of glucose transport and its regulation by insulin in human monocytes using flow cytometry.
BACKGROUND
We investigated the effects of insulin on glucose transport in human monocytes using flow cytometry, a method with several advantages over previously used techniques. We hypothesized that monocytes could be used as tools to study insulin action at the cellular level and facilitate the investigation of mechanisms that lead to insulin resistance.


METHODS
Blood was withdrawn from 38 healthy subjects. The expression of glucose transporter (GLUT) isoforms in plasma membrane and the rates of glucose transport were determined with and without insulin (10 to 1,000 mU/L). Anti-CD14 phycoerythrin monoclonal antibody was used for monocyte gating. GLUT isoforms were determined after staining cells with specific antisera to GLUT1, GLUT3, and GLUT4. Glucose transport was monitored with 6-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-6-deoxyglucose (NBDG).


RESULTS
Insulin increased the uptake of NBDG (median effective dose 20 mU/L) and the expression of GLUT3 and GLUT4 isoforms in the plasma membrane (median effective doses 20 and 35 mU/L, respectively) but had no effect on GLUT1. Maximal effects were always reached at 100 mU/L of insulin.


CONCLUSIONS
Monocytes may be a valid model system to study the effects of insulin on glucose transport. Further, flow cytometry is suitable for this investigation and can be used as an alternative to radiotracer methods.
Dimitriadis
George
G
2nd Department of Internal Medicine, Research Institute and Diabetes Center, Athens University Medical School, University General Hospital Attikon, Haidari, Greece. gdim@internet.gr
Maratou
Eirini
E
Boutati
Eleni
E
Psarra
Katherina
K
Papasteriades
Chryssa
C
Raptis
Sotirios A
SA
D009327:4-Chloro-7-nitrobenzofurazan / Q000031:analogs & derivatives / Q000378:metabolism; D000328:Adult; D005434:Flow Cytometry / Q000379:methods*; D005944:Glucosamine / Q000031:analogs & derivatives / Q000378:metabolism; D005947:Glucose / Q000378:metabolism*; D051272:Glucose Transporter Type 1; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D009000:Monocytes / Q000378:metabolism*; D009004:Monosaccharide Transport Proteins / Q000378:metabolism; D020033:Protein Isoforms / Q000378:metabolism; D015203:Reproducibility of Results
D051272:Glucose Transporter Type 1; D007328:Insulin; D009004:Monosaccharide Transport Proteins; D020033:Protein Isoforms; C495677:SLC2A1 protein, human; C045400:6-deoxy-N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)aminoglucose; D009327:4-Chloro-7-nitrobenzofurazan; D005947:Glucose; D005944:Glucosamine