Dose response effect of plasma free fatty acid on insulin mediated capillary recruitment, glucose uptake and glycocalyx modulation

There is strong support for the notion that free fatty acids (FFAs) are an
important link between obesity, insulin resistance and type 2 diabetes. Recent
finding suggest also a role for the microcirculation in the insulin mediated
glucose disposal in peripheral tissues. In this study we will examine insulin
mediated glucose disposal under different levels of FFAs and look at the
endothelial glycocalyx, a highly hydrated mesh on the endothelium. We
hypothesize that insulin mediates capillary blood volume by glycocalyx
modulation and that FFA interfere with this process.

In the current study we want to obtain fundamental insight in the role of
insulin-mediated glycocalyx modulation as well as the effect of FFAs on this
mechanism. We propose that increased levels of FFA degrade the glycocalyx and
result in an impaired insulin mediated increase in capillary blood volume. This
will concurrently result in decreased glucose disposal.

Ten lean male subjects will be studied 3 times after an overnight fast. Micro-
and macrovasculature will be studied in a hyperinsulinemic euglycemic clamp
combined with each visit a different level of FFAs. After a period of one week
subjects will undergo the second study using the same protocol as in the first
study (but with a different level of FFA).
All studies will be performed in healthy volunteers and a pilot study will be
performed for power analysis. All volunteers will undergo a hyperinsulinemic
euglycemic clamp. Within this clamp they will be faced with three levels of
FFA: normal, postprandial and diabetic levels.

1. Clamp with FFAs: placebo, postprandial en diabetic levels through Intralipid
infusion.
2. Hyperinsulinemic clamp after 4 hours of FFA clamp
3. Capillary volume measurements: infusion of haes 6% arterially and venous
sampling. Before and after hyperinsulinemic clamp.
4. Flow mediated dilation (FMD) brachial artery (non invasive). Before FFA
clamp and before hyperinsulinemic clamp.
5. Veneuze plethysmografie: non-invasieve method to determine arterial flow.
6. Sidestream Darkfield (SDF) beeldvorming. During the entire protocol every
hour a 5 minute recording of the sublingual microcirculation is made.

Although the protocol is extensive there is only a minimal risk involved. The
arterial line will be inserted by trained personel aswell as the venous
catheters. Infusio of Intralipid is by using heparin heparine minimized in
dose and a hyperinsulinemic euglycemisc clamp is a low risk procedure.