This small grant application has been prepared by a new investigator in order to obtain the preliminary data necessary to prepare a competitive RO1 grant application on endothelial cell dysfunction in insulin resistant-states. The objective of this application is to identify the regulatory mechanisms involved in insulin-stimulated Na+/Mg2+ exchange activity in cells from normal and diabetic patients. Our long-term goal is to define the cellular mechanisms that lead to insulin resistance and diabetes. The central hypothesis for the proposed research is that low levels of Mg2+ attenuate the intracellular signal generated following insulin binding to its receptor or antagonize binding of insulin to the receptor. This hypothesis is based on preliminary findings obtained in human microvascular endothelial cells and red blood cells. We propose to test our central hypothesis and accomplish the overall objectives of this proposal through the following specific aims:
Aim 1 : Identify the role of insulin in cellular Mg2+ regulation in human microvascular endothelial cells. On the basis of our preliminary data, we hypothesize that insulin regulates cellular Mg2+ levels via activation of the exchanger, which in turn regulates nitric oxide production in human endothelial cells. We will characterize the intracellular signaling pathways that are downstream of PI3-kinase activation and modulate the activity of the exchanger as well as nitric oxide production in these cells Aim 2: Identify the mechanisms for insulin-regulated Na+/Mg2+ exchange activity in ex vivo human red cells from normal subjects. Erythrocytes have been used as ex vivo models of what may occur in target tissue of insulin resistance's pathophysiology. We hypothesize that the insulin receptor is functionally coupled to the exchanger in human red cells via PI3-kinase activation. Therefore, our studies are designed to characterize PI3-kinase activity as well as phosphorylated Akt levels in erythrocytes upon activation with insulin.
Aim 3 : Identify the mechanisms for regulation of Na+/Mg2+ exchange activity in ex vivo human red cells from Type 2 diabetes mellitus patients. We hypothesize that elevated Na+/Mg2+ exchange activity in the red cells of diabetic patients in comparison to normal subjects explains the low cellular Mg2+ levels observed in patients with diabetes. This suggests an uncoupling between the insulin receptor and the exchanger in these patients. Therefore, we hypothesize that PI3-kinase activity is altered in diabetic red cells when compared to normal. We will compare PI3-kinase activity and phosphorylated Akt levels in erythrocytes from normal and diabetic subjects. We expect that these studies will identify novel cellular mechanisms underlying insulin resistance as well as characterize cellular Mg2+ regulatory mechanisms.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Small Research Grants (R03)
Project #
5R03DK064841-03
Application #
6921956
Study Section
Diabetes, Endocrinology and Metabolic Diseases B Subcommittee (DDK)
Program Officer
Hyde, James F
Project Start
2003-09-20
Project End
2007-08-31
Budget Start
2005-09-01
Budget End
2007-08-31
Support Year
3
Fiscal Year
2005
Total Cost
$173,000
Indirect Cost
Name
Brigham and Women's Hospital
Department
Type
DUNS #
030811269
City
Boston
State
MA
Country
United States
Zip Code
02115
Baudrand, R; Lian, C G; Lian, B Q et al. (2014) Long-term dietary sodium restriction increases adiponectin expression and ameliorates the proinflammatory adipokine profile in obesity. Nutr Metab Cardiovasc Dis 24:34-41
Romero, Jose R; Youte, Rodeler; Brown, Edward M et al. (2013) Parathyroid hormone ablation alters erythrocyte parameters that are rescued by calcium-sensing receptor gene deletion. Eur J Haematol 91:37-45
Guo, Christine; Ricchiuti, Vincent; Lian, Bill Q et al. (2008) Mineralocorticoid receptor blockade reverses obesity-related changes in expression of adiponectin, peroxisome proliferator-activated receptor-gamma, and proinflammatory adipokines. Circulation 117:2253-61
Pang, Jian L; Ricupero, Dennis A; Huang, Su et al. (2006) Differential activity of kaempferol and quercetin in attenuating tumor necrosis factor receptor family signaling in bone cells. Biochem Pharmacol 71:818-26
Zee, Robert Y L; Romero, Jose R; Gould, Jessica L et al. (2006) Polymorphisms in the advanced glycosylation end product-specific receptor gene and risk of incident myocardial infarction or ischemic stroke. Stroke 37:1686-90
Tfelt-Hansen, Jacob; Ferreira, Ana; Yano, Shozo et al. (2005) Calcium-sensing receptor activation induces nitric oxide production in H-500 Leydig cancer cells. Am J Physiol Endocrinol Metab 288:E1206-13
Rivera, Alicia; Ferreira, Ana; Bertoni, Danielle et al. (2005) Abnormal regulation of Mg2+ transport via Na/Mg exchanger in sickle erythrocytes. Blood 105:382-6
Romero, Jose R; Rivera, Alicia; Lanca, Vasco et al. (2005) Na+/Ca2+ exchanger activity modulates connective tissue growth factor mRNA expression in transforming growth factor beta1- and Des-Arg10-kallidin-stimulated myofibroblasts. J Biol Chem 280:14378-84