Original Data

Polyphenol-Rich Bilberry Ameliorates Total Cholesterol and LDL-Cholesterol when Implemented in the Diet of Zucker Diabetic Fatty Rats

Lea Brader¹, Ann Overgaard¹, Lars P. Christensen², Per B. Jeppesen¹, Kjeld Hermansen¹

Manuscript submitted November 10, 2013; resubmitted December 10, 2013; accepted December 22, 2013.

Keywords: bilberry, blackcurrant, anthocyanins, cholesterol, insulin sensitivity, blood pressure, type 2 diabetes, obesity

Abstract

BACKGROUND: Bilberries and blackcurrants are nutrient sources rich in bioactive components, including dietary fibers, polyphenols, and anthocyanins, which possess potent cardiovascular protective properties. Few studies investigating the cardio-protective effects of natural components have focused on whole bilberries or blackcurrants. OBJECTIVE: The aim of this trial was to investigate whether a diet enriched with bilberries or blackcurrants has beneficial effects on glucose metabolism, lipid profile, blood pressure, and expression of genes related to glucose and lipid metabolism. METHODS: Male Zucker Diabetic Fatty (ZDF) rats (n = 48) were randomly assigned to either a control, bilberry-enriched, blackcurrant-enriched, or fiber-enriched diet for 8 weeks ad libitum. Real-time quantitative PCR analysis was performed on liver, adipose, and muscle tissue. Berry polyphenol content was determined by HPLC and LC-MS analysis. RESULTS: Bilberry enrichment reduced total (-21%, p = 0.0132) and LDL-cholesterol (-60%, p = 0.0229) levels, but increased HDL-cholesterol to a lesser extent than in controls. This may partly be due to the altered hepatic liver X receptor-α expression (-24%, p < 0.001). Neither bilberries nor blackcurrants influenced glucose metabolism or blood pressure. Nevertheless, transcriptional analysis implied a better conservation of hepatic and adipocyte insulin sensitivity by bilberry enrichment. Anthocyanins constituted 91% and 87% of total polyphenol content in bilberries and blackcurrants, respectively. However, total anthocyanin content (3441 mg/100 g) was 4-fold higher in bilberries than in blackcurrants (871 mg/100 g). CONCLUSIONS: Bilberry consumption ameliorated total and LDL-cholesterol levels, but not HDL-cholesterol levels in ZDF rats. Neither bilberry nor blackcurrant enrichment delayed the development of diabetes or hypertension. Thus, in rats, bilberries may be valuable as a dietary preventive agent against hypercholesterolemia, probably by virtue of their high anthocyanin content.

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