Date of Award

1-1-2011

Document Type

Campus Access Dissertation

Department

Exercise Science

First Advisor

J Mark Davis

Abstract

Fatigue or persistent tiredness is a common complaint among older adults associated with funcional decline and multiple adverse health outcomes. Mitochondrial dysfunction and chronic inflammation have been recognized as potential biological mechanisms in contributing to fatigue in the elderly. Since the past decade, efforts to understand the molecular basis of disease prevention, health promotion and exercise performance enhancement by certain nutraceuticals have intensified. Quercetin, known as a natural polyphenolic flavonoid substance found in variety of human foods, possesses multiple biological properties, in particular, the ability to stimulate mitochondrial biogenesis and reduce inflammation, form the basis for potential benefits to fatigue resistance and overall well-being in older adults. Previous studies in our laboratory have shown that short-term quercetin supplementation enhances voluntary physical activity and endurance performance in mice, and increases aerobic capacity in young humans. The purpose of this pilot study was to examine the effects of short-term quercetin supplementation on habitual physical activity, exercise performance, cognitive function and mental well-being, as well as to investigate the influence of quercetin on skeletal muscle mitochondrial biogenesis and systemic inflammation in healthy older adults.

Eighteen adults aged between 60 and 89 years participated in the study. In a double-blind, randomized, crossover design, participants received either 1000 mg of quercetin daily dissolved in Tang or placebo (Tang) for 14 days with a 2-week washout period between treatments. Quercetin supplement was well tolerated with excellent compliance and no reported adverse effects. In comparison to placebo, quercetin feedings significantly increased steps taken per day (P = 0.02), along with trends for significant improvements in minutes of low (P = 0.08) and moderate (P = 0.11) intensity of physical activity. Moderate increases (d > 0.80) were noted for gene expression of PGC-1α, citrate synthase and cytochrome c in skeletal muscle. No differences were found between quercetin and placebo conditions in peak oxygen uptake, Short Physical Performance Battery score, cognitive performance, self-rated quality of life, fatigue, and depression as well as inflammatory markers including plasma C-reactive protein and Interleukin-6. These novel data suggest that short-duration quercetin supplementation can promote physical activity in healthy older adults, and the effect might be partially attributed to the increased mitochondrial biogenesis in skeletal muscle, which plays an important role to reduce fatigue. Overall, the results of this study provide additional evidence to support dietary flavonoid quercetin as a possible safe and effective nutritional strategy for disease prevention and health promotion in the elderly population.

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