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

Abstract

■ AbstractBACKGROUND: 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, bilberryenriched, 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.

Action mechanism and cardiovascular effect of anthocyanins: a systematic review of animal and human studies

“…The results point to a possible heart protective effect of AMFJ, once it has in its composition phenolic compounds that might have antioxidant action, for example, the anthocyanins. Hypolipidemic and of oxidative stress effects were also shown in other studies [159, 160]. …”

Vaccinium myrtillus L. Fruits as a Novel Source of Phenolic Compounds with Health Benefits and Industrial Applications - A Review

“…Cardiovascular diseases remain one of the leading causes of death and they are, therefore, a primary focus of research and treatment [75]. Several studies have shown that the intake of berry fruits was associated with a reduced risk of cardiovascular diseases.…”

Effects of Bilberry Supplementation on Metabolic and Cardiovascular Disease Risk

“…However, no effects on HDL cholesterol, glucose metabolism or blood pressure were observed. The authors concluded that the effect of bilberries on hypercholesterolemia could probably be attributed to their high anthocyanin content [94]. Likewise, in a study in alloxan-induced diabetic rats, supplementation with bilberry powder (2 g/day) for four weeks increased insulin and reduced total cholesterol, LDL cholesterol, VLDL cholesterol and TG levels, and prevented HDL cholesterol decline [95].…”