Polyphenols in Cocoa Powder Improve Cholesterol Balance

Polyphenols present in cocoa powder and dark chocolate exert a positive effect on cholesterol metabolism by enhancing the production of apo A-1, the main protein component of HDL (high-density lipoprotein) and inhibiting the production of apo B, the main protein component of LDL (low-density lipoprotein).

Cocoa powder is rich in polyphenols, such as catechins and procyanidins, and has been shown to inhibit LDL oxidation and atherogenesis in a variety of models. Human studies have also shown that daily intake of cocoa increases plasma HDL and decreases LDL levels. However, the mechanisms responsible for these effects of cocoa on cholesterol metabolism had not been fully elucidated.

In the current study, investigators at Meiji Seika Kaisha, Ltd. (Saitama, Japan) used liver (HepG2) and intestinal (Caco2) cells growing in tissue culture to study the effect of cocoa polyphenols on cellular lipoprotein metabolism. The investigators incubated the cell cultures for 24 hours in the presence of cacao polyphenols such as (-)-epicatechin, (+)-catechin, procyanidin B2, procyanidin C1, and cinnamtannin A2. The concentration of apolipoproteins in the cell culture media was quantified using an enzyme-linked immunoassay, and the mRNA expression was quantified by RT (real time)-PCR.

Results published in the January 12, 2011, online edition of the Journal of Agricultural and Food Chemistry revealed that cacao polyphenols increased apolipoprotein A1 protein levels and mRNA expression while slightly decreasing apolipoprotein B protein and mRNA expression in both HepG2 and Caco2 cells. In addition, cacao polyphenols increased sterol regulatory element binding proteins (SREBPs) and activated LDL receptors in HepG2 cells.

Increased apo A-1 and decreased apo expression were the result of up-regulation of mature form SREBPs and increased LDL receptor activity induced by the cacao polyphenols. This observation allowed the investigators to conclude that, "We have therefore identified the mechanism responsible for the elevation in HDL cholesterol associated with daily cocoa intake. As cholesterol metabolism is known to be regulated by several different mechanisms, it is possible that cacao polyphenols may act on multiple pathways as a regulatory receptor agonist or ligand, similar to other plant polyphenols.”

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