(555.18) Effect of Hyperinsulinemia on Cerebral Autoregulation and Myogenic Control of Cerebral Blood Flow in Healthy Young Adults

Poster Board Number: E78

Brian Shariffi (University of Missouri), Iman Lloyd (University of Missouri), Jadee Wagner (University of Missouri), Jennifer Harper (University of Missouri), Neil McMillan (University of Missouri), James Smith (University of Missouri), Camila Manrique-Acevedo (University of Missouri), Jaume Padilla (University of Missouri), Jacqueline Limberg (University of Missouri)

Objective: Hyperinsulinemia has marked vasodilatory effects within the skeletal muscle vasculature in healthy young adults; however, the magnitude of insulin-stimulated cerebrovascular vasodilation is less clear. Differences between circulations may be due to a greater importance of the cerebral circulation to maintain a constant level of blood flow (i.e., cerebral autoregulation) during hyperinsulinemia. We hypothesized cerebral autoregulation would increase during hyperinsulinemia. Autoregulatory mechanisms, such as myogenic control, play important roles in mediating cerebral vasomotor responses. Thus, we further sought to examine the contribution of the myogenic mechanism to the control of cerebral blood flow during hyperinsulinemia.

Methods:  Middle cerebral artery blood velocity (MCAv) and femoral artery blood velocity (FAV) were measured with Doppler ultrasound and femoral artery blood flow (FBF) was calculated in 17 healthy adults (11M/6F, 28±2 yrs, 24±1 kg/m2) at baseline and following a hyperinsulinemic (40 mU/m2 body surface area/min), euglycemic infusion. Finger plethysmography was used to assess mean blood pressure (MBP). Normalized transfer function gain between changes in MBP and MCAv were estimated in the 0.02-0.07 Hz (very low frequency, VLF) and 0.07–0.20 Hz (low frequency, LF) ranges using the Welch method. Interactions between MBP and MCAv or FAV were determined using cross-correlation analyses.

Results: Intravenous insulin infusion increased plasma insulin concentrations (6±1 to 50±3 μIU/mL, plt;0.01) with blood glucose maintained at baseline levels (p=0.33). There was a significant increase in FBF (121±15 to 151±19 mL/min, p=0.03) during hyperinsulinemia, with no change in MCAv (61±4 to 59±4 cm/s, p=0.28) or MBP (86±2 to 89±2 mmHg, p=0.10). There was no effect of hyperinsulinemia on normalized transfer function gain in the VLF (p=0.25) or LF ranges (p=0.46). Hyperinsulinemia had no effect on the association between MBP and MCAv (p=0.15) or FAV (p=0.82). 

Conclusions:  Hyperinsulinemia in healthy young adults elicits peripheral vasodilation, but no change in MCAv. Contrary to our hypothesis, the sensitivity of the cerebrovascular circulation to changes in MBP (i.e., cerebral autoregulation) is not altered during systemic hyperinsulinemia in healthy adults. Furthermore, the contribution of the myogenic mechanism to the control of blood flow in the peripheral and cerebral circulations is unaffected by hyperinsulinemia. Whether these results translate to disease states (e.g., diabetes) and the implications for cerebrovascular health warrant further exploration.

Support or Funding Information

Funding: Margaret W. Mangel Faculty Research Catalyst Fund (JP, JKL), NIH HL137769 (JP), NIH HL130339 (JKL)

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Funding: lt;/bgt;Margaret W. Mangel Faculty Research Catalyst Fund (JP, JKL), NIH HL137769 (JP), NIH HL130339 (JKL)