A simplified micro-method for quantification of fecal excretion of neutral and acidic sterols for outpatient studies in humans.

A simple and precise micro-method for measurement of daily fecal excretion of neutral and acidic sterols has been developed which utilizes sitostanol (24-ethyl-5 alpha-cholestane-3 beta-ol) as fecal flow and recovery marker. Extractions of sterols were performed from 50 microliters of fecal homogenate (feces-water 1:1), and analyses of neutral and acidic sterols were carried out by gas-liquid chromatography. The method is sensitive, precise, and easy to perform; the intra-assay variability yielded coefficients of variations of 1.9% and 3.5% (n = 6) for neutral and acidic sterols, respectively. The results from this method were compared with those obtained with the standard fecal flow marker chromic oxide. The correlation coefficients between the two markers were compared in 16 subjects and were 0.938 and 0.998 for excretion of neutral sterols and acidic sterols, respectively. Comparison of the fecal excretion of neutral and acidic sterols in 12 subjects determined from frozen samples and aliquots (approximately 1 g) sent by ordinary mail to the laboratory (transport time 1 to 5 days) gave identical results using sitostanol as fecal flow marker (818 +/- (SEM) 85 mg/day vs. 838 +/- 89 mg/day for neutral sterols and 417 +/- 59 mg/day vs. 414 +/- 60 mg/day for acidic sterols). The new micro-method is ideally suited for research laboratories in need of a simple, accurate, inexpensive, and high through-put method for measuring daily fecal excretion of neutral and acidic sterols, as well as total cholesterol synthesis, and can be performed on an outpatient basis.