EFFECT OF COFFEE LIPIDS (CAFESTOL AND KAHWEOL) ON REGULATION OF CHOLESTEROL-METABOLISM IN HEPG2 CELLS

We studied the effect of the coffee diterpene alcohols, cafestol and k ahweol, on cholesterol metabolism in HepG2 cells. Uptake of I-125-tyra mine cellobiose-labeled LDL was decreased by 15% to 20% (P<.05) after 18 hours of preincubation with cafestol (20 mu g/mL), whereas 25-hydro xy-cholesterol reduced uptake by 55% to 65% (P<.05). Degradation of LD L in the presence of cafestol was decreased by 20% to 30% (P<.05) unde r the same conditions. The effect of cafestol (20 mu g/mL) on uptake a nd degradation of LDL was greatest (35% to 40%, P<.05) after 6 and 10 hours of preincubation, respectively. Furthermore, the effect of cafes tol was also dependent on its concentration, and a significant decreas e in the LDL uptake (19%) was observed at 10 mu g/mL (P<.05). Specific binding of LDL was reduced by 17% (P<.05) and 60% (P<.05) after prein cubation with cafestol (20 mu g/mL) and 25-hydroxycholesterol (5 mu g/ mL) for 6 hours, respectively, compared with control cells. Analysis o f LDL binding showed that cafestol reduced the number of binding sites for LDL on the cell surface (capacity) by 35% (P<.05). In contrast, n o significant effect on the level of mRNA for the LDL receptor was obs erved after incubation with cafestol, whereas 25-hydroxycholesterol re duced the mRNA level for the LDL receptor by 40% to 50% (P<.05). A fus ion gene construct consisting of a synthetic sterol regulatory element -1 (SRE-1) promoter for the human LDL receptor coupled to the reporter gene for chloramphenicol acetyltransferase (CAT) was transfected into HepG2 cells. No change was observed in CAT activity in SRE-1-transfec ted cells after incubation with cafestol, whereas 25-hydroxycholestero l reduced CAT activity by 30% to 40% (P<.05). Incorporation of [C-14]a cetate into unesterified cholesterol and 3-hydroxy-3-methylglutaryl co enzyme A (HMG-CoA) reductase activity were unaffected in cells incubat ed with cafestol as well as the cafestol-kahweol mixture compared with control cells. Moreover, cafestol and the cafestol-kahweol mixture di d not promote increased incorporation of radiolabeled [C-14]oleic acid into cholesteryl esters after short-term incubation compared with con trol cells. On the other hand, 25-hydroxycholesterol caused a 70% to 9 0% reduction of cholesterol synthesis (P<.05) and HMG-CoA reductase ac tivity (P<.05), decreased HMG-CoA reductase mRNA level by 70% to 80% ( P<.05), and promoted a twofold increase in cholesterol esterification (P<.05). Finally, no effect of the coffee diterpenes on bile acid form ation was observed. These results suggest that cafestol (and kahweol) may reduce the activity of hepatic LDL receptors and thereby cause ext racellular accumulation of LDL.