Possible role for platelet insulin receptors in modulating platelet function in health and diabetes mellitus

Binding studies have shown that human platelets contain binding sites for insulin with a surface density similar to that described for other cells.(1) Evidence for a reduced number and affinity of human platelet membrane insulin binding sites in non-insulin dependent diabetes mellitus (NIDDM) has been provided.(2) However, the influence of insulin and insulin receptors on platelet function has not been completely investigated and clarified. Falcon et al(3) reported phosphorylation of a subunit of the insulin receptor on platelets in response to insulin, but no alterations were detected in cAMP formation or degradation, inositol phosphate formation or phosphorylation of proteins other than the receptor itself. On the other hand Trovati et al(4) found reduced platelet aggregation responses to ADP, PAF, epinephrine, collagen and arachidonate in the presence of 40 µU/ml insulin. Their experience with an euglycemic-hyperinsulinemic clamp provided some further in vivo evidence to support the above mentioned findings. Platelet thromboxane A(2) formation was not altered in the presence of the hormone.