Glucose transport in adipose tissue

Based on the well-known extraction equation and the histology of subcutaneous adipose tissue, transport of glucose from capillary to microdialysis probe is described. Results are evaluated of previous studies by our group and others. Arguments are presented for a simple scheme in which the mean capillary concentration of a solute (i.e. glucose.) is the driving force for diffusion of glucose from capillary to a microdialysis probe. Insertion effects can be explained by a lower glucose concentration around the probe due to an inflammation reaction (12-18 h) and by a slow increase in the number of functioning capillaries around the probe due to wound healing (4-6 days). (C) 2004 Elsevier B.V. All rights reserved.</p

Determination of time delay between blood and interstitial adipose tissue glucose concentration change by microdialysis in healthy volunteers

For the development and use of subcutaneous glucose sensors it is important to know the time lag between changes in blood glucose and subcutaneous interstitial glucose concentration. To determine the time lag we inserted a microdialysis probe into the abdominal subcutaneous adipose tissue of healthy volunteers (n = 19) and performed oral glucose tolerance tests (n=39) over a 7-day period. After correction for the microdialysis system time lag, we compared the change In dialysate glucose concentration with the capillary blood glucose concentration, We found no significant delay time between a change in capillary blood glucose concentration and subcutaneous interstitial fluid glucose concentration using the Mann-Whitney test. The substantial interindividual variation of glucose recovery and the changing recovery in time makes it difficult to draw unambiguous conclusions about the exact physiological time lag, Based on the present experimental findings and theoretical calculations of glucose transport in adipose tissue, the physiological lag time is short and negligible compared to the system delay time of a glucose sensor

Glucose transport in adipose tissue

Based on the well-known extraction equation and the histology of subcutaneous adipose tissue, transport of glucose from capillary to microdialysis probe is described. Results are evaluated of previous studies by our group and others. Arguments are presented for a simple scheme in which the mean capillary concentration of a solute (i.e. glucose.) is the driving force for diffusion of glucose from capillary to a microdialysis probe. Insertion effects can be explained by a lower glucose concentration around the probe due to an inflammation reaction (12-18 h) and by a slow increase in the number of functioning capillaries around the probe due to wound healing (4-6 days). (C) 2004 Elsevier B.V. All rights reserved

How minimally invasive is microdialysis sampling? A cautionary note for cytokine collection in human skin and other clinical studies.

It is common to refer to microdialysis as a minimally invasive procedure, likening it to insertion of an artificial capillary. While a comparison of this type allows the process to be easily visualized by those outside the field, it tends to provide a false impression of the localized perturbation of the tissue space that is caused by catheter insertion. With the increased acceptance of microdialysis sampling as a viable in vivo sampling method, many researchers have begun to use the technique to explore inflammatory and immune-mediated diseases in the skin and other organs. Unfortunately, many of the molecules of interest, particularly chemokines and cytokines, are known to be generated during the inflammatory response to wounding and the subsequent cellular events leading to wound repair. With more than 11,000 reports citing the use of microdialysis sampling, only a few researchers have sought to assess the tissue damage that is incurred by probe insertion. For this reason, caution is warranted when collecting these molecules and inferring a role for them in clinical disease states. This commentary seeks to remind the research community of the confounding effects that signaling molecules related to the wounding response will have on clinical studies. Proper controls must be incorporated into all studies in order to assess whether or not particular molecules are truly related to the disease state under investigation or have been generated as part of the tissue response to the wound incurred by microdialysis catheter implantation