Background: Fecal bile acid and neutral sterol excretion are the obligate endpoints of the reverse cholesterol transport pathway (RCT). In studies in mice, no evidence was found for a relation between HDL-cholesterol (HDL-c) levels and fecal sterol excretion. In this study, we have evaluated this relationship in patients with isolated low HDL-c versus controls.
Results: Fecal sterol excretion was studied in 12 subjects with familial hypoalphalipoproteinemia (FHA) and 11 healthy controls. Compared to the controls (8.9+/-6.3mg/kg/day), neutral sterol excretion was significantly lower in the FHA group (4.0+/-2.4mg/kg/day). Fecal bile acid excretion showed a similar pattern. Across the groups, a strong positive correlation between HDL-c and fecal neutral sterol excretion was found (r=0.53; p=0.01).
Conclusions: Isolated low HDL-c levels in humans are associated with reduced fecal sterol excretion suggesting that in humans HDL regulates the final step in the RCT pathway at low HDL-c levels.