Objective: The purpose of this review was to systematically assess the extent of current knowledge of Glucose Tranporter-4 (GLUT-4) expression in monocytes in humans to address its potential use as a non-invasive and reliable model to investigate the relationships between insulin signalling, GLUT-4 expression and insulin action in vivo.
Method: Electronic database searches were performed with the keywords 'monocyte', 'leukocyte' and 'white blood cells', and the terms 'GLUT', 'glucose transporter' and 'SLC2A4' (solute carrier family 2 member 4). Studies were examined for robustness of design and outcomes by consensus of three reviewers.
Results: Six cross-sectional or observational studies met the criteria for review. Insulin-stimulated GLUT-4 expression in monocytes from subjects likely to have impaired insulin sensitivity appeared blunted relative to healthy subjects.
Conclusion: The available results provide evidence that monocyte GLUT-4 translocation does occur in response to acute insulin exposure, and may be sensitive to the relative state of insulin resistance of the individual. However, due to the limited quantity and robustness of published data, the ultimate utility of monocyte GLUT-4 expression as an index of whole body insulin responsiveness and the clinical relevance of this methodology is unresolved at this time.