Polyphenol-rich bilberry ameliorates total cholesterol and LDL-cholesterol when implemented in the diet of Zucker diabetic fatty rats

• Published in: The review of diabetic studies Vol. 10; no. 4; pp. 270 - 282
• Main Authors: Brader, Lea, Overgaard, Ann, Christensen, Lars P, Jeppesen, Per B, Hermansen, Kjeld
• Format: Journal Article
• Language: English
• Published: Belgium SBDR - Society for Biomedical Diabetes Research 01.01.2013
• Subjects: Animals; Blood Glucose - metabolism; Cholesterol - metabolism; Diabetes Mellitus, Type 2 - diet therapy; Diabetes Mellitus, Type 2 - genetics; Diabetes Mellitus, Type 2 - metabolism; Humans; Liver - metabolism; Liver X Receptors; Male; Obesity - diet therapy; Obesity - genetics; Obesity - metabolism; Original Data; Orphan Nuclear Receptors - genetics; Orphan Nuclear Receptors - metabolism; Plant Extracts - analysis; Plant Extracts - metabolism; Polyphenols - analysis; Polyphenols - metabolism; Rats; Rats, Zucker; Vaccinium myrtillus - chemistry; Vaccinium myrtillus - metabolism
• ISSN: 1613-6071; 1614-0575
• DOI: 10.1900/rds.2013.10.270

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. 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. 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. 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). 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.