Insulin regulation of vascular smooth muscle calcium metabolism and Ca2+ATPase gene expression

Author

Young-Cheul Kim

Date of Award

5-1995

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Human Ecology

Major Professor

Michael B. Zemel

Committee Members

Gerald L. Vaughan, Jay Whelan, James W. Bailey

Abstract

Recent evidence suggests that hypertension in insulin resistant states may result from impaired insulin regulation of vascular smooth muscle cell (VSMC) Ca²⁺transport. Insulin has previously been shown to attenuate vasoconstrictor героnses to pressor agonists and accelerate vascular smooth muscle (VSM) relaxation and VSM Ca²⁺ efflux. To further determine the cola of insulin in regulating VSMC Ca²⁺, quiescent A7r5 cultured VSMC and human VSMC loaded with fura 2-AM were incubated with or without 10^-7 or 10^-8 insulin for 1 hour, intracellular Ca²⁺ ([Ca²⁺]i) responses to and rates of recovery from angiotensin II (AII) (200 nM) and arginine vasopressin (AVP) were studied fluorometrically in stirred suspension. Insulin caused an increase in the peak [Ca²⁺]i response to AII (Peak/baseline × 100 = 469 ± 96 versus 288 ± 74, p < 0.05) and a decrease in the peak Ca²⁺ response to AVP (288 ± 50 versus 389 ± 33, p < 0.025). However, insulin also caused a marked increase in the rate of [Ca²⁺]i recovery to baseline after stimulation with both AII (77.3 ± 13.8 versus 30.6 ± 6 nM/min, p < 0.03) and AVP (p<0.05), such that the cumulative exposure to elevated [Ca²⁺]i after stimulation with either agonist (i.e., area under the [Ca²⁺]i response curve) was reduced with insulin treatment. Insulin also caused comparable effects on Ca²⁺ recovery in the human cells but was without significant effect on peak Ca²⁺ responses to AVP. It is concluded that accelerated removal of cytosolic Ca²⁺ after agonist stimulation is likely to contribute to insulin attenuation of vasoconstrictor responses and acceleration of vascular relaxation. To evaluate the linkage between this insulin-regulation of VSMC [Ca²⁺]i and classical actions of insulin (i.e. glucose transport and metabolism), cultured VSMCs were incubated in the presence or absence of insulin in a medium containing either pyruvate, glucose, 3-O-methylglucose (3-O-MG) or 2- deoxyglucose (2-DG). Insulin caused a 87% increase in [Ca²⁺]i recovery rate following stimulation with AVP (p<0.01) and caused a marked increase in both plasmalemma and sarcoplasmic reticulum Ca²⁺-ATPase gene expression in the presence of glucose. Comparable increases in both [Ca²⁺]i recovery and Ca²⁺-ATPase expression were found when glucose was replaced by 2-deoxyglucose. In contrast, no stimulation was found in either the glucose-free or 3-O-methylglucose-containing medium. Since both glucose analogues are transported, but only 2-DG is phosphorylated. this indicates that glucose transport and metabolism to glucose-6-phosphate is essential for insulin regulation of VSMC [Ca²⁺]i, possibly via a glucose-6-phosphate-dependent carbohydrate response element in the Ca²⁺-ATPase gene.

Recommended Citation

Kim, Young-Cheul, "Insulin regulation of vascular smooth muscle calcium metabolism and Ca2+ATPase gene expression. " PhD diss., University of Tennessee, 1995.
https://trace.tennessee.edu/utk_graddiss/10011