Myogenic Response in Retinal Arterioles During Acute Hyperinsulinemia

Abstract

 

Purpose:

 

To study the influence of acute hyperinsulinemia on the myogenic response in large retinal arterioles from healthy persons.

 

Methods:

 

Seven healthy persons were examined in a double-blinded randomized study in the morning and in the afternoon on two days separated with at least one month. On all study days the blood insulin level was controlled using clamp technique with infusion of somatostatin, insulin and glucose to either a level of normoinsulinemia (infusion of insulin 0,1Mu/kg/min) or hyperinsulinemia (infusion of insulin 0,9 Mu/kg/min).In one of the healthy persons normoinsulinemia was maintained during the first study day, whereas on the second study day normoinsulinemia in the morning was followed by hyperinsulinemia in the afternoon. The last healthy person was examined with the insulinemia pattern in the reverse order.On all study days of all patients the following were measured during both the morning and the afternoon. The retinal arteriolar diameter as measured by a retinal vessel analyzer (RVA) before and during isometric exercise induced by lifting a hand weight of 2 kg, mean arterial blood pressure, intraocular pressure, and retinal thickness using OCT. The measurements were compared using paired t-tests.

 

Results:

 

The results are given in table 1.No significant difference was found between any of the studied parameters during normoinsulinemia and during hyperinsulinemia.

 

Conclusions:

 

Acute elevation of the blood insulin level does not change the myogenic response in retinal arterioles. This suggests that insulin does not have a direct effect of on the regulation of retinal arteriolar smooth muscle tone.  

 

Keywords: blood supply • diabetic retinopathy • retina