Journal Article

Loss of the insulin receptor in murine megakaryocytes/platelets causes thrombocytosis and alterations in IGF signalling

Samantha F. Moore, Christopher M. Williams, Edward Brown, Thomas A. Blair, Matthew T. Harper, Richard J. Coward, Alastair W. Poole and Ingeborg Hers

in Cardiovascular Research

Published on behalf of European Society of Cardiology

Volume 107, issue 1, pages 9-19
Published in print July 2015 | ISSN: 0008-6363
Published online April 2015 | e-ISSN: 1755-3245 | DOI: https://dx.doi.org/10.1093/cvr/cvv132

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Aims

Patients with conditions that are associated with insulin resistance such as obesity, type 2 diabetes mellitus, and polycystic ovary syndrome have an increased risk of thrombosis and a concurrent hyperactive platelet phenotype. Our aim was to determine whether insulin resistance of megakaryocytes/platelets promotes platelet hyperactivation.

Methods and results

We generated a conditional mouse model where the insulin receptor (IR) was specifically knocked out in megakaryocytes/platelets and performed ex vivo platelet activation studies in wild-type (WT) and IR-deficient platelets by measuring aggregation, integrin αIIbβ3 activation, and dense and α-granule secretion. Deletion of IR resulted in an increase in platelet count and volume, and blocked the action of insulin on platelet signalling and function. Platelet aggregation, granule secretion, and integrin αIIbβ3 activation in response to the glycoprotein VI (GPVI) agonist collagen-related peptide (CRP) were significantly reduced in platelets lacking IR. This was accompanied by a reduction in the phosphorylation of effectors downstream of GPVI. Interestingly, loss of IR also resulted in a reduction in insulin-like growth factor-1 (IGF-1)- and insulin-like growth factor-2 (IGF-2)-mediated phosphorylation of IRS-1, Akt, and GSK3β and priming of CRP-mediated platelet activation. Pharmacological inhibition of IR and the IGF-1 receptor in WT platelets recapitulated the platelet phenotype of IR-deficient platelets.

Conclusions

Deletion of IR (i) increases platelet count and volume, (ii) does not cause platelet hyperactivity, and (iii) reduces GPVI-mediated platelet function and platelet priming by IGF-1 and IGF-2.

Keywords: Platelets; Insulin; Glycoprotein VI; IGF; Insulin resistance

Journal Article.  5862 words.  Illustrated.

Subjects: Cardiovascular Medicine

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