Endothelial Dysfunction and Aging---Effects of Caloric Restriction (Cr) and Estrogen

  • Lau, Ying-Tung (PI)

Project: National Science and Technology CouncilNational Science and Technology Council Academic Grants

Project Details

Abstract

Endothelial dysfunction, defined as imbalance of endothelial-derived vasorelaxants and constrictors, is responsible for most cardiovascular diseases. This is considered recently as an imbalance between bioavailable NO (nitric oxide) and oxidative stress (O2 .- neutralizes NO rapidly). Both aging and male gender (or estrogen deficiency) are risks factors for cardiovascular diseases that involve both endothelial dysfunction and oxidative stress. We thus hypothesize that caloric restriction (CR) and estrogen/estrogen receptor (ER) provide vascular protection via reducing oxidative stress to enhance available NO and thus ameliorates endothelial dysfunction associated with aging and gender difference. CR (reducing food intake to 50-70% of ad lib level) increases lifespan and reduces risk factor for cardiovascular diseases. However, neither direct correlational study between endothelial improvement and CR-induced benefits during aging nor mechanistic investigation of the CR-induced vascular protection is available. There has been no study on gender difference of CR (during aging) either. The first part of our proposal aims to explore these issues. Although estrogen via ER confers vascular protection in general, the responsible ER subtype (ERα or ERβ) is not clear and whether different mechanism(s) is involved for endothelial protection for different ER subtype is unknown. The second part of our proposal thus will examine these questions in ovariectomyzed (OVX) rats and the findings will also be useful for the understanding of the CR studies. Our proposal consists of both physiological/functional determination of CR-, gender-, estrogen (and agonists for ERα or ERβ)-induced vascular effects, particularly the endothelial NO/O2 .- balance; and biochemical analysis (mRNA/protein of target molecules, see below) of endothelial cells (EC) obtained by laser capture microdissection (LCM) or whole aortic tissue derived from CR-or estrogen-treated rats. The physiological parameters examined will include endothelium-dependent relaxation (EDR), endothelium-derived NO (EDNO), vascular production of NO and O2 .- (via lucigenin-enhanced chemiluminesence or LEC), as well as blood analysis of glucose, cholesterol, insulin, and other important markers of metabolic/vascular events. The biochemical analysis of molecular targets will consist of vascular sources of NO and O2 .- as well as antioxidant enzymes, including mRNA/protein of endothelial NO synthase (eNOS), inducible NOS (iNOS), BH4 synthase for cofactor BH4 (tetrahydrobiopterin), and heat shock protein (HSP-90) as positive regulators for NO production; NADPH oxidase (NADPH Ox), xanthine oxidase (XO) and uncoupled eNOS (low BH4) for O2 .- production and thus negative regulator for NO production; antioxidant enzyme activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) as negative regulator for O2 .- production. Quantative analysis of these molecular targets under various experimental conditions (CR or control, male or female, OVX or sham, and specific ERα or ERβ agonist/antagonist) can be compared with physiological determinants (EDR, NO/ROS production, etc.) to allow a mechanistic investigation of endothelial functions. For the aging study, rats of both genders under CR treatment for 2, 8, or 20 months will be studied. For the ER study, sham, OVX, OVX supplemented with E2 or specific ERα/ERβ agonist-treated rats will be studied. The results will clarify NO/O2 .- mechanisms involved in endothelial dysfunction during two natural processes, namely, aging and gender difference. These findings also will provide functional test for important difference of beneficial effects of CR in different genders with mechanistic analysis.

Project IDs

Project ID:PC9706-0159
External Project ID:NSC95-2320-B182-030-MY3
StatusFinished
Effective start/end date01/08/0831/07/09

Keywords

  • endothelial dysfunction
  • caloric restriction
  • estrogen receptor
  • nitric oxide,oxidative stress
  • aging.

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