For a long time it has been known that hypertension is associated with resistance to insulin-induced glucose disposal in type II diabetes mellitus, obesity, and essential hypertension. Furthermore, recent studies have demonstrated that in these conditions, resistance to insulin-induced glucose disposal is associated with resistance to normal vasodilatory effect of insulin possibly contributing to elevated vascular smooth muscle tone. However, little information is known about the mechanisms underlying this important alteration. Consequently, the long-term objectives of this proposal are to determine the pathophysiology of hypertension in insulin-resistance states and to devise rational therapies for these conditions. More precisely, the objectives of these studies are focused on determining how insulin inhibits agonist- stimulated contraction at the level of the individual canine vascular smooth muscle cells. The proposal is divided into four different (interrelated) objectives. The studies included in the first line of investigation are designed to test the hypothesis that physiological concentration of insulin inhibits AII, 5-HT and NE-induced contraction of individual VSM cells from canine femoral artery. These studies are performed in such a manner that will allow to determine the dose-response relationship of insulin necessary to inhibit the vasoconstrictor effects induced by vasopressor substances. This objective is closely related to hypothesis 2 which intends to determine if the inhibition produced by insulin on vasoconstrictor substances is accompanied by a proportional attenuation of the agonist-evoked Ca2+ transients. The experiments are conducted in vascular smooth muscle cells from adult mongrel dogs in which shortening of the length of the cells and intracellular Ca2+ transients are measured with FURA II after 4-9 days of culture. These studies are closely interrelated to the studies included in hypothesis 3 which attempts to determine if insulin's attenuation of the agonist- induced Ca2+ transient is caused, in part, by decreased Ca2+ influx due to relative hyperpolarization of the cell secondary to stimulation of Na+K+ pump activity. It is further suggested that the stimulation of Na+ pump activity is due in part to increased Na+ secondary to stimulation of Na+H+ exchange activity by insulin. This rather complex hypothesis is divided into four sections. In the first, they intend to define the extent to which the stimulation of Na+-K+ pump activity produced by insulin results in a relative hyperpolarization of the agonist- stimulated cell. In the second section, there are studies to see that the insulin-induced relative hyperpolarization of the agonist-stimulated cells inhibits Ca+ influx; such an effect will be responsible for insulin's attenuation of the Ca2+ transient. In the third and fourth section, there are studies to find out if insulin stimulates Na+-H+ exchange activity and if insulin's stimulation of Na+-H+ exchange activity increases Na+ which is partly responsible for the insulin increase in Na+-K+ pump activity. Finally, in hypothesis 4, there are studies to determine if insulin stimulates Na+-H+ exchange activity by lowering pH. Under these conditions, pH could be lowered by an increased lactic acid production secondary to insulin-stimulated glucose uptake and a subsequent rise in aerobic glycolysis.
| Yang, Ming; Kahn, Andrew M (2006) Insulin-stimulated NADH/NAD+ redox state increases NAD(P)H oxidase activity in cultured rat vascular smooth muscle cells. Am J Hypertens 19:587-92 |
| Yang, Ming; Foster, Estrella; Kahn, Andrew M (2005) Insulin-stimulated NAD(P)H oxidase activity increases migration of cultured vascular smooth muscle cells. Am J Hypertens 18:1329-34 |
| Kahn, Andrew M; Allen, Julius C; Zhang, Sui (2002) Insulin increases NADH/NAD+ redox state, which stimulates guanylate cyclase in vascular smooth muscle. Am J Hypertens 15:273-9 |
| Kahn, A M; Allen, J C; Seidel, C L et al. (2000) Protein kinase C mediates insulin-inhibited Ca2+ transport and contraction of vascular smooth muscle. Am J Hypertens 13:383-8 |
| Kahn, A M; Husid, A; Song, T (1997) Relationship between insulin and hemodialysis-associated hypotension. Curr Opin Nephrol Hypertens 6:1-5 |
