Inhibition of pro-atherogenic trimethylamine production by human gut bacteria is not determined by varying chlorogenic acid content in highbush blueberries

Cardiovascular diseases (CVDs) account for ∼32% of all deaths worldwide, and atherosclerosis-related conditions are the leading cause of death in the United States. Elevated blood levels of trimethylamine N- oxide (TMAO), a gut microbiota-derived metabolite, are linked to increased risk of atherosclerosis.

TMAO is produced when gut bacteria metabolize dietary quaternary amines to trimethylamine (TMA), which is converted to TMAO in the liver. With no FDA-approved drugs available to reduce TMA or TMAO, dietary interventions present the most promising strategy. Chlorogenic acid (CGA), a phenolic abundant in blueberries, inhibits TMA production. Blueberries may thus be a TMA- (and TMAO)- lowering food. CGA content in highbush blueberries varies depending on cultivar, growth conditions, and storage conditions; it remains unclear whether these variations in CGA levels influence the TMA- lowering activity of different blueberry varieties. We investigated the impact of highbush blueberry CGA content on the inhibition of choline-d ₉ conversion to TMA-d ₉ in our ex vivo-in vitro human fecal fermentation model. We tested blueberry skins (to avoid interferences from sugar-rich pulp) from 20 genetically distinct highbush blueberry genotypes, chosen based on their high and low CGA content.

CGA levels in whole berries ranged from 2.6-146 mg/100 g fresh weight (FW), while CGA concentrations in blueberry skins ranged from 0.14-9.7 mg/g. No significant differences were observed in TMA-d ₉ production among the 4 highest and 4 lowest CGA genotypes in kinetic curves or area under the curve (AUC) values. However, significant differences were observed between all genotypes compared to controls, with ∼19.4.% reduction in TMA-d ₉ AUCs compared to blank digesta, indicating that phenolic- rich skin provides similar TMA-lowering benefits across blueberry varieties. This suggests that the CGA content of genotypes is not a crucial factor for lowering TMA. Preliminary evidence suggests that fiber is also not the primary driver of the inhibitory activities of blueberry skins. Future studies, including rodent and human studies, are needed to confirm this in vitro study and understand why blueberries may inhibit TMA and potentially TMAO, as in vitro studies have limitations, and the mechanism of TMA production remains unclear.