The protective effect of HDL is mostly attributed to their metabolic function in reverse cholesterol transport (RCT), a process whereby excess cellular cholesterol is taken up from peripheral cells, processed in HDL particles, and later delivered to the liver for further metabolism and biliary secretion. Mechanistically, the purinergic P2Y₁₃ ADP-receptor is involved in hepatic HDL endocytosis (i.e., uptake of both HDL protein + lipid moieties), which is considered an important step of RCT. Accordingly, chow-fed P2Y₁₃ knockout (P2Y₁₃^-/-) mice exhibit lower hepatic HDL uptake, which translates into a decrease of hepatic free cholesterol content and biliary cholesterol and phospholipid secretion.

The aim of this study was to determine the effect of high cholesterol diet (HCD) in P2Y₁₃^-/- mice, in order to mimic high dietary cholesterol intake, which is a major cause of dyslipidemia in humans. As previously reported with chow-diet, HCD did not affect plasma lipid levels in P2Y₁₃^-/- compared with control mice but decreased hepatic free and esterified cholesterol content (p < 0.05, P2Y₁₃^-/- versus control). Interestingly, biliary lipid secretion and macrophages-to-feces RCT were more dramatically impaired in P2Y₁₃^-/- mice fed a HCD than chow-diet. HCD did not enhance atherosclerosis in P2Y₁₃^-/- compared with control mice.

This study demonstrates that high dietary cholesterol intake accentuated the metabolic phenotype of P2Y₁₃^-/- mice, with impaired hepatobiliary RCT. Although other animal models might be required to further evaluate the role of P2Y₁₃ receptor in atherosclerosis, P2Y₁₃ appears a promising target for therapeutic intervention aiming to stimulate RCT, particularly in individuals with lipid-rich diet.