Date of Award

8-2014

Level of Access Assigned by Author

Campus-Only Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Food and Nutrition Sciences

Advisor

Dorothy J. Klimis-Zacas

Second Committee Member

Rodney J. Bushway

Third Committee Member

Robert Gundersen

Abstract

The goal of this project was to investigate the ability of a wild blueberry-enriched diet to improve parameters related to the pathogenesis of metabolic syndrome in the obese Zucker rat (OZR), which is a valid experimental model for this condition.

Fifty-two of OZR, and 52 lean littermate controls (LZR), were placed on either an 8% freeze-dried wild-blueberry enriched diet, or an isocaloric blueberry-free control diet, for a total of eight weeks. Rats were placed on the experimental diets between 8 and 16 weeks of age, when they start developing the metabolic abnormalities that are characteristic of metabolic syndrome. The effects of wild blueberries were evaluated on plasma lipids, plasma markers of glucose metabolism; plasma markers of inflammation; expression of genes related to the inflammatory response, lipid and glucose metabolism both in the liver and the abdominal adipose tissue; and ex vivo response of the aortic vessel to vasoconstricting and vasorelaxing stimuli.

Wild blueberry consumption resulted in a significant reduction in circulating levels of markers of inflammatory status, as well as a down-regulation of their expression both in the abdominal adipose tissue and the liver. Wild blueberry diet had a positive impact on lipid profile, with significant reductions in serum triglyceride and total cholesterol concentrations. It also positively affected the expression of key enzymes and transcription factors involved in lipid and cholesterol metabolism, including sterol regulatory element binding proteins and peroxisome proliferator-activated receptors. Consumption of wild blueberries improved several markers of glucose and insulin metabolism, including plasma glycated hemoglobin, resistin and retinol binding protein 4 concentrations. Finally, the wild blueberry diet modulated the aortic biomechanical function of the OZR by partially restoring the impaired phenylephrine-induced constrictor responses, and attenuating the exaggerated response to acetylcholine-induced vasorelaxation.

In conclusion, regular consumption of dietary achievable amounts of wild blueberries was able to decrease markers of inflammation, improve blood lipid profile, modulate vasoreactivity, and affect the expression of genes involved in the inflammatory response, lipid and glucose metabolism, and endothelial function in the OZR model of metabolic syndrome.

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