DOI

10.17077/etd.dwiww2ov

Document Type

Thesis

Date of Degree

Spring 2017

Degree Name

MS (Master of Science)

Degree In

Health and Human Physiology

First Advisor

Amy Lynn Sindler

First Committee Member

Diana Zepeda-Orozco

Second Committee Member

Melissa Bates

Abstract

Age-related increases in arterial stiffness are mediated in part by mitochondrial dysfunction. Sirtuin 3 (SIRT3) is a mitochondrial NAD+-dependent deacetylase that regulates mitochondrial function. SIRT3 deficiency contributes to physiological dysfunction in a variety of pathological conditions. Here, we tested the hypothesis that age-associated arterial stiffness, assessed by aortic pulse wave velocity (PWV), would be accompanied with decreased renal and aortic SIRT3 expression and activity due to decreased NAD+ levels. We further tested whether boosting NAD+ concentration with nicotinamide riboside (NR), a NAD+ precursor, for 6 months would reverse the effects of aging. Old (~26 mo, n = 9) C57BL/6 male mice had higher PWV vs. young (6 mo, n = 10) (448 ± 14 vs 382 ± 13, p < 0.005), which was associated with reduced arterial SIRT3 protein (0.365 ± 0.088 AU’s vs 1.000 ± 0.000); p < 0.05). Furthermore, SIRT3 deficient male mice demonstrated higher PWV compared to age-matched control mice (480 ± 21 n = 6 vs. 391 ±12 n = 7, p < 0.005). Aortic SIRT3 protein was negatively correlated with PWV (r=-0.7798, p < 0.005). Old mice also exhibited reduced kidney SIRT3 protein (0.73 ± 0.10 AU’s) compared to young controls (1.00 ± 0.00; p = 0.0192) and reduced NAD+ (918.6 ± 50.5 pmol/mg vs. young 1302.0 ± 56.6 pmol/mg, p = 0.0036). Old mice supplemented with NR had increased NAD+ concentration in kidney tissue (1303.0 ± 90.2 pmol/mg) however, had no effect on normalizing age-associated arterial stiffness (402 ± 18 old with NR vs 418 ± 15 old; p = 0.78). Here we show for that SIRT3 protein correlates with aortic stiffness and may be required for the maintenance of healthy arteries and for the first time that supplementation with NR, a commercially available supplement, ameliorates age-associated decreases in renal NAD+ demonstrating therapeutic potential in kidney disease.

Public Abstract

During the 20th Century the United States saw a change in the leading causes of death, with a shift from infectious diseases such as tuberculosis, pneumonia, and influenza to chronic diseases associated with aging such as cardiovascular disease (Centers for Disease Control). Recent research has unveiled Sirtuin 3 (SIRT3), a protein that requires NAD+ as a substrate, as a major player in age-related diseases throughout the body. The goal of this thesis was to measure SIRT3 protein and NAD+ levels in young and old male mice, and to determine if aging causes changes that has meaningful impact on vascular function, such aortic stiffness, which is both a risk factor and predictor of cardiovascular diseases. Finally, we investigated whether increasing NAD+ with a recently discovered form of vitamin B3, nicotinamide riboside, could increase NAD+ concentration in tissue and reverse age-related aortic stiffening.

We found that SIRT3 was associated with increased aortic stiffness perhaps due to age-related decreases in NAD+. Furthermore, mice deficient in SIRT3 had increased aortic stiffness compared to their age-matched counterparts, indicating that SIRT3 plays a role in maintenance of healthy arteries. Long term NR supplementation increased NAD+ concentration in kidney tissue in old mice, but did not have an effect on age associated arterial stiffness. We show here for the first time that supplementation with NR restores NAD+ levels in the kidney with aging, indicating therapeutic potential in kidney disease.

Keywords

arterial stiffness, Kidney Disease, Nicotinamide Riboside, SIRT3

Pages

x, 40 pages

Bibliography

Includes bibliographical references (pages 35-40).

Copyright

Copyright © 2017 Alexander Lee Brodjeski

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